Thermodynamic analysis questions claims of improved cardiac efficiency by dietary fish oil
- Loiselle, Denis, Han, June-Chiew, Goo, Eden, Chapman, Brian, Barclay, Christopher, Hickey, Anthony, Taberner, Andrew
- Authors: Loiselle, Denis , Han, June-Chiew , Goo, Eden , Chapman, Brian , Barclay, Christopher , Hickey, Anthony , Taberner, Andrew
- Date: 2016
- Type: Text , Journal article
- Relation: Journal of General Physiology Vol. 148, no. 3 (2016), p. 183-193
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- Description: Studies in the literature describe the ability of dietary supplementation by omega-3 fish oil to increase the pumping efficiency of the left ventricle. Here we attempt to reconcile such studies with our own null results. We undertake a quantitative analysis of the improvement that could be expected theoretically, subject to physiological constraints, by posing the following question: By how much could efficiency be expected to increase if inefficiencies could be eliminated? Our approach utilizes thermodynamic analyses to investigate the contributions, both singly and collectively, of the major components of cardiac energetics to total cardiac efficiency. We conclude that it is unlikely that fish oils could achieve the required diminution of inefficiencies without greatly compromising cardiac performance.
- Authors: Loiselle, Denis , Han, June-Chiew , Goo, Eden , Chapman, Brian , Barclay, Christopher , Hickey, Anthony , Taberner, Andrew
- Date: 2016
- Type: Text , Journal article
- Relation: Journal of General Physiology Vol. 148, no. 3 (2016), p. 183-193
- Full Text:
- Reviewed:
- Description: Studies in the literature describe the ability of dietary supplementation by omega-3 fish oil to increase the pumping efficiency of the left ventricle. Here we attempt to reconcile such studies with our own null results. We undertake a quantitative analysis of the improvement that could be expected theoretically, subject to physiological constraints, by posing the following question: By how much could efficiency be expected to increase if inefficiencies could be eliminated? Our approach utilizes thermodynamic analyses to investigate the contributions, both singly and collectively, of the major components of cardiac energetics to total cardiac efficiency. We conclude that it is unlikely that fish oils could achieve the required diminution of inefficiencies without greatly compromising cardiac performance.
Pharmaceutical pollution in marine waters and benthic flora of the southern Australian coastline
- Long, Benjamin, Harriage, Samantha, Schultz, Nick, Sherman, Craig, Thomas, Michael
- Authors: Long, Benjamin , Harriage, Samantha , Schultz, Nick , Sherman, Craig , Thomas, Michael
- Date: 2023
- Type: Text , Journal article
- Relation: Environmental chemistry Vol. 19, no. 6 (2023), p. 375-384
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- Description: Environmental context Most human pharmaceutical waste is discharged to the environment. While the presence of pharmaceuticals in freshwater systems is well documented globally, little is known of the impact on marine ecosystems. We measured pharmaceuticals in a marine environment in south-eastern Australia and found pharmaceutical concentrations around 24 000 times higher in benthic flora than in the marine surface waters. We discuss the potential use of seaweeds as biological indicators of pharmaceutical pollution. Rationale Pharmaceuticals are emerging pollutants of concern with a range of adverse consequences for organisms and ecosystems. Their presence in freshwater and estuarine systems has been well documented, but less is known about their prevalence in open ocean, or their uptake by benthic flora. This preliminary survey of the southern Australian coastline sought to measure the concentrations of key pharmaceuticals in both surface waters and benthic flora. Methodology This study used LC-MS/MS to measure the concentration carbamazepine, tramadol and venlafaxine in (1) samples from wastewater treatment plants, (2) ocean surface waters and (3) several species of benthic flora. Surface waters and benthic flora were sampled at two sites near waste water treatment plant (WWTP) discharges, and one site away from any discharge. Results All three pharmaceuticals were detected in surface water samples with their risk assessed (via risk quotient) as medium risk (carbamazepine) or low risk (venlafaxine, tramadol). All three pharmaceuticals were also detected in benthic flora, particularly in brown macroalgae Tramadol was measured at a maximum of 34.7 ng g
- Authors: Long, Benjamin , Harriage, Samantha , Schultz, Nick , Sherman, Craig , Thomas, Michael
- Date: 2023
- Type: Text , Journal article
- Relation: Environmental chemistry Vol. 19, no. 6 (2023), p. 375-384
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- Description: Environmental context Most human pharmaceutical waste is discharged to the environment. While the presence of pharmaceuticals in freshwater systems is well documented globally, little is known of the impact on marine ecosystems. We measured pharmaceuticals in a marine environment in south-eastern Australia and found pharmaceutical concentrations around 24 000 times higher in benthic flora than in the marine surface waters. We discuss the potential use of seaweeds as biological indicators of pharmaceutical pollution. Rationale Pharmaceuticals are emerging pollutants of concern with a range of adverse consequences for organisms and ecosystems. Their presence in freshwater and estuarine systems has been well documented, but less is known about their prevalence in open ocean, or their uptake by benthic flora. This preliminary survey of the southern Australian coastline sought to measure the concentrations of key pharmaceuticals in both surface waters and benthic flora. Methodology This study used LC-MS/MS to measure the concentration carbamazepine, tramadol and venlafaxine in (1) samples from wastewater treatment plants, (2) ocean surface waters and (3) several species of benthic flora. Surface waters and benthic flora were sampled at two sites near waste water treatment plant (WWTP) discharges, and one site away from any discharge. Results All three pharmaceuticals were detected in surface water samples with their risk assessed (via risk quotient) as medium risk (carbamazepine) or low risk (venlafaxine, tramadol). All three pharmaceuticals were also detected in benthic flora, particularly in brown macroalgae Tramadol was measured at a maximum of 34.7 ng g
'Dig a hole and bury the past in it' - Reconciliation and heritage of genocide in Cambodia
- Authors: Long, Colin , Reeves, Keir
- Date: 2009
- Type: Text , Book chapter
- Relation: Places of Pain and Shame - Dealing with 'Difficult Heritage p.
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- Authors: Long, Colin , Reeves, Keir
- Date: 2009
- Type: Text , Book chapter
- Relation: Places of Pain and Shame - Dealing with 'Difficult Heritage p.
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Clustering lifestyle risk behaviors among Vietnamese adolescents and roles of school : a Bayesian multilevel analysis of global school-based student health survey 2019
- Long, Khuong, Ngoc-Anh, Hoang, Phuong, Nguyen, Tuyet-Hanh, Tran, Van Huy, Nguyen
- Authors: Long, Khuong , Ngoc-Anh, Hoang , Phuong, Nguyen , Tuyet-Hanh, Tran , Van Huy, Nguyen
- Date: 2021
- Type: Text , Journal article
- Relation: The Lancet Regional Health - Western Pacific Vol. 15, no. (2021), p.
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- Description: Background: Adolescence is a vulnerable period for many lifestyle risk behaviors. In this study, we aimed to 1) examine a clustering pattern of lifestyle risk behaviors; 2) investigate roles of the school health promotion programs on this pattern among adolescents in Vietnam. Methods: We analyzed data of 7,541 adolescents aged 13–17 years from the 2019 nationally representative Global School-based Student Health Survey, conducted in 20 provinces and cities in Vietnam. We applied the latent class analysis to identify groups of clustering and used Bayesian 2-level logistic regressions to evaluate the correlation of school health promotion programs on these clusters. We reassessed the school effect size by incorporating different informative priors to the Bayesian models. Findings: The most frequent lifestyle risk behavior among Vietnamese adolescents was physical inactivity, followed by unhealthy diet, and sedentary behavior. Most of students had a cluster of at least two risk factors and nearly a half with at least three risk factors. Latent class analysis detected 23% males and 18% females being at higher risk of lifestyle behaviors. Consistent through different priors, high quality of health promotion programs associated with lower the odds of lifestyle risk behaviors (highest quality schools vs. lowest quality schools; males: Odds ratio (OR) = 0·67, 95% Highest Density Interval (HDI): 0·46 – 0·93; females: OR = 0·69, 95% HDI: 0·47 – 0·98). Interpretation: Our findings demonstrated the clustering of specific lifestyle risk behaviors among Vietnamese in-school adolescents. School-based interventions separated for males and females might reduce multiple health risk behaviors in adolescence. Funding: The 2019 Global School-based Student Health Survey was conducted with financial support from the World Health Organization. The authors received no funding for the data analysis, data interpretation, manuscript writing, authorship, and/or publication of this article. © 2021 The Author(s)
- Authors: Long, Khuong , Ngoc-Anh, Hoang , Phuong, Nguyen , Tuyet-Hanh, Tran , Van Huy, Nguyen
- Date: 2021
- Type: Text , Journal article
- Relation: The Lancet Regional Health - Western Pacific Vol. 15, no. (2021), p.
- Full Text:
- Reviewed:
- Description: Background: Adolescence is a vulnerable period for many lifestyle risk behaviors. In this study, we aimed to 1) examine a clustering pattern of lifestyle risk behaviors; 2) investigate roles of the school health promotion programs on this pattern among adolescents in Vietnam. Methods: We analyzed data of 7,541 adolescents aged 13–17 years from the 2019 nationally representative Global School-based Student Health Survey, conducted in 20 provinces and cities in Vietnam. We applied the latent class analysis to identify groups of clustering and used Bayesian 2-level logistic regressions to evaluate the correlation of school health promotion programs on these clusters. We reassessed the school effect size by incorporating different informative priors to the Bayesian models. Findings: The most frequent lifestyle risk behavior among Vietnamese adolescents was physical inactivity, followed by unhealthy diet, and sedentary behavior. Most of students had a cluster of at least two risk factors and nearly a half with at least three risk factors. Latent class analysis detected 23% males and 18% females being at higher risk of lifestyle behaviors. Consistent through different priors, high quality of health promotion programs associated with lower the odds of lifestyle risk behaviors (highest quality schools vs. lowest quality schools; males: Odds ratio (OR) = 0·67, 95% Highest Density Interval (HDI): 0·46 – 0·93; females: OR = 0·69, 95% HDI: 0·47 – 0·98). Interpretation: Our findings demonstrated the clustering of specific lifestyle risk behaviors among Vietnamese in-school adolescents. School-based interventions separated for males and females might reduce multiple health risk behaviors in adolescence. Funding: The 2019 Global School-based Student Health Survey was conducted with financial support from the World Health Organization. The authors received no funding for the data analysis, data interpretation, manuscript writing, authorship, and/or publication of this article. © 2021 The Author(s)
A new hybrid method combining genetic algorithm and coordinate search method
- Authors: Long, Qiang , Huang, Junjian
- Date: 2012
- Type: Text , Conference proceedings
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- Description: This paper proposed a new hybrid method combining genetic algorithm(GA) and coordinate search method (CSM). Genetic algorithm is good at global exploration but bad at accuracy and local search. Whereas, coordinate search method is good at local exploitation, and its accuracy is reliable when searching in a local area. Thus we combine those two methods in this paper to design a hybrid method called genetic algorithm with coordinate search (GACS). Experimental tests shows that this method are good at both global search and local accuracy. © 2012 IEEE.
- Description: 2003010808
- Authors: Long, Qiang , Huang, Junjian
- Date: 2012
- Type: Text , Conference proceedings
- Full Text:
- Description: This paper proposed a new hybrid method combining genetic algorithm(GA) and coordinate search method (CSM). Genetic algorithm is good at global exploration but bad at accuracy and local search. Whereas, coordinate search method is good at local exploitation, and its accuracy is reliable when searching in a local area. Thus we combine those two methods in this paper to design a hybrid method called genetic algorithm with coordinate search (GACS). Experimental tests shows that this method are good at both global search and local accuracy. © 2012 IEEE.
- Description: 2003010808
Nonsmooth and derivative-free optimization based hybrid methods and applications
- Authors: Long, Qiang
- Date: 2014
- Type: Text , Thesis , PhD
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- Description: "In this thesis, we develop hybrid methods for solving global and in particular, nonsmooth optimization problems. Hybrid methods are becoming more popular in global optimization since they allow to apply powerful smooth optimization techniques to solve global optimization problems. Such methods are able to efficiently solve global optimization problems with large number of variables. To date global search algorithms have been mainly applied to improve global search properties of the local search methods (including smooth optimization algorithms). In this thesis we apply rather different strategy to design hybrid methods. We use local search algorithms to improve the efficiency of global search methods. The thesis consists of two parts. In the first part we describe hybrid algorithms and in the second part we consider their various applications." -- taken from Abstract.
- Description: Operational Research and Cybernetics
- Authors: Long, Qiang
- Date: 2014
- Type: Text , Thesis , PhD
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- Description: "In this thesis, we develop hybrid methods for solving global and in particular, nonsmooth optimization problems. Hybrid methods are becoming more popular in global optimization since they allow to apply powerful smooth optimization techniques to solve global optimization problems. Such methods are able to efficiently solve global optimization problems with large number of variables. To date global search algorithms have been mainly applied to improve global search properties of the local search methods (including smooth optimization algorithms). In this thesis we apply rather different strategy to design hybrid methods. We use local search algorithms to improve the efficiency of global search methods. The thesis consists of two parts. In the first part we describe hybrid algorithms and in the second part we consider their various applications." -- taken from Abstract.
- Description: Operational Research and Cybernetics
A hybrid method combining genetic algorithm and Hooke-Jeeves method for constrained global optimization
- Authors: Long, Qiang , Wu, Changzhi
- Date: 2014
- Type: Text , Journal article
- Relation: Journal of Industrial and Management Optimization Vol. 10, no. 4 (2014), p. 1279-1296
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- Description: A new global optimization method combining genetic algorithm and Hooke-Jeeves method to solve a class of constrained optimization problems is studied in this paper. We first introduce the quadratic penalty function method and the exact penalty function method to transform the original constrained optimization problem with general equality and inequality constraints into a sequence of optimization problems only with box constraints. Then, the combination of genetic algorithm and Hooke-Jeeves method is applied to solve the transformed optimization problems. Since Hooke-Jeeves method is good at local search, our proposed method dramatically improves the accuracy and convergence rate of genetic algorithm. In view of the derivative-free of Hooke-Jeeves method, our method only requires information of objective function value which not only can overcome the computational difficulties caused by the ill-condition of the square penalty function, but also can handle the non-diffierentiability by the exact penalty function. Some well-known test problems are investigated. The numerical results show that our proposed method is eficient and robust.
- Authors: Long, Qiang , Wu, Changzhi
- Date: 2014
- Type: Text , Journal article
- Relation: Journal of Industrial and Management Optimization Vol. 10, no. 4 (2014), p. 1279-1296
- Full Text:
- Reviewed:
- Description: A new global optimization method combining genetic algorithm and Hooke-Jeeves method to solve a class of constrained optimization problems is studied in this paper. We first introduce the quadratic penalty function method and the exact penalty function method to transform the original constrained optimization problem with general equality and inequality constraints into a sequence of optimization problems only with box constraints. Then, the combination of genetic algorithm and Hooke-Jeeves method is applied to solve the transformed optimization problems. Since Hooke-Jeeves method is good at local search, our proposed method dramatically improves the accuracy and convergence rate of genetic algorithm. In view of the derivative-free of Hooke-Jeeves method, our method only requires information of objective function value which not only can overcome the computational difficulties caused by the ill-condition of the square penalty function, but also can handle the non-diffierentiability by the exact penalty function. Some well-known test problems are investigated. The numerical results show that our proposed method is eficient and robust.
Pre-service primary teachers’ perceptions of early childhood philosophy and pedagogy: A case study examination
- Lord, Alison, McFarland, Laura
- Authors: Lord, Alison , McFarland, Laura
- Date: 2010
- Type: Text , Journal article
- Relation: Australian Journal of Teacher Education Vol. 35, no. 3 (2010), p.
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- Description: Abstract: This study examined the experiences of three primary teacher education students participating in early childhood-focused community play sessions, as well as their perceptions of early childhood and primary philosophy and pedagogy. The purpose was to explore perceived differences in primary and early childhood preservice teacher courses, which may then translate to differences in approaches to pedagogy in the field. Three pre-service teachers participated in a weekly community play session on a rural university campus in NSW, Australia. As these students had been educated in primary education pedagogy, a focus group interview was conducted to gain insights to their experiences in the play sessions, which had an early childhood emphasis in theory and practice. Qualitative analysis suggests that these students found several major differences in their early childhood and primary experiences. Themes and properties that emerged included Pedagogy (curriculum, parents, play) and Foundational Knowledge (developmental theory, discontinuity of development). These primary students found the idea of developing curriculum based on observations and interests rather than mandated Syllabus outcomes, challenging. Also, they found the role of play and parent-teacher relationships in early childhood and primary to differ. Students also noted a lack of foundational developmental theory, specifically in the birth-two period, in their teacher education course, and expressed the idea that younger children are discretely different from older children, rather than seeing development as a continuous process. Implications for teacher education courses and children’s transition to school are discussed
- Authors: Lord, Alison , McFarland, Laura
- Date: 2010
- Type: Text , Journal article
- Relation: Australian Journal of Teacher Education Vol. 35, no. 3 (2010), p.
- Full Text:
- Reviewed:
- Description: Abstract: This study examined the experiences of three primary teacher education students participating in early childhood-focused community play sessions, as well as their perceptions of early childhood and primary philosophy and pedagogy. The purpose was to explore perceived differences in primary and early childhood preservice teacher courses, which may then translate to differences in approaches to pedagogy in the field. Three pre-service teachers participated in a weekly community play session on a rural university campus in NSW, Australia. As these students had been educated in primary education pedagogy, a focus group interview was conducted to gain insights to their experiences in the play sessions, which had an early childhood emphasis in theory and practice. Qualitative analysis suggests that these students found several major differences in their early childhood and primary experiences. Themes and properties that emerged included Pedagogy (curriculum, parents, play) and Foundational Knowledge (developmental theory, discontinuity of development). These primary students found the idea of developing curriculum based on observations and interests rather than mandated Syllabus outcomes, challenging. Also, they found the role of play and parent-teacher relationships in early childhood and primary to differ. Students also noted a lack of foundational developmental theory, specifically in the birth-two period, in their teacher education course, and expressed the idea that younger children are discretely different from older children, rather than seeing development as a continuous process. Implications for teacher education courses and children’s transition to school are discussed
Air pollution perception in ten countries during the COVID-19 pandemic
- Lou, Baowen, Barbieri, Diego, Passavanti, Marco, Hui, Cang, Gupta, Akshay, Hoff, Inge, Lessa, Daniela, Sikka, Gaurav, Chang, Kevin, Fang, Kevin, Lam, Louisa, Maharaj, Brij, Ghasemi, Navid, Qiao, Yaning, Adomako, Solomon, Foroutan Mirhosseini, Ali, Naik, Bhaven, Banerjee, Arunabha, Wang, Fusong, Tucker, Andrew, Liu, Zhuangzhuanga, Wijayaratna, Kasunt, Naseri, Sahra, Yu, Lei, Chen, Hao, Shu, Benan, Goswami, Shubham, Peprah, Prince, Hessami, Amir, Abbas, Montasir, Agarwal, Nithin
- Authors: Lou, Baowen , Barbieri, Diego , Passavanti, Marco , Hui, Cang , Gupta, Akshay , Hoff, Inge , Lessa, Daniela , Sikka, Gaurav , Chang, Kevin , Fang, Kevin , Lam, Louisa , Maharaj, Brij , Ghasemi, Navid , Qiao, Yaning , Adomako, Solomon , Foroutan Mirhosseini, Ali , Naik, Bhaven , Banerjee, Arunabha , Wang, Fusong , Tucker, Andrew , Liu, Zhuangzhuanga , Wijayaratna, Kasunt , Naseri, Sahra , Yu, Lei , Chen, Hao , Shu, Benan , Goswami, Shubham , Peprah, Prince , Hessami, Amir , Abbas, Montasir , Agarwal, Nithin
- Date: 2022
- Type: Text , Journal article
- Relation: Ambio Vol. 51, no. 3 (2022), p. 531-545
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- Description: As largely documented in the literature, the stark restrictions enforced worldwide in 2020 to curb the COVID-19 pandemic also curtailed the production of air pollutants to some extent. This study investigates the perception of the air pollution as assessed by individuals located in ten countries: Australia, Brazil, China, Ghana, India, Iran, Italy, Norway, South Africa and the USA. The perceptions towards air quality were evaluated by employing an online survey administered in May 2020. Participants (N = 9394) in the ten countries expressed their opinions according to a Likert-scale response. A reduction in pollutant concentration was clearly perceived, albeit to a different extent, by all populations. The survey participants located in India and Italy perceived the largest drop in the air pollution concentration; conversely, the smallest variation was perceived among Chinese and Norwegian respondents. Among all the demographic indicators considered, only gender proved to be statistically significant. © 2021, The Author(s).
- Authors: Lou, Baowen , Barbieri, Diego , Passavanti, Marco , Hui, Cang , Gupta, Akshay , Hoff, Inge , Lessa, Daniela , Sikka, Gaurav , Chang, Kevin , Fang, Kevin , Lam, Louisa , Maharaj, Brij , Ghasemi, Navid , Qiao, Yaning , Adomako, Solomon , Foroutan Mirhosseini, Ali , Naik, Bhaven , Banerjee, Arunabha , Wang, Fusong , Tucker, Andrew , Liu, Zhuangzhuanga , Wijayaratna, Kasunt , Naseri, Sahra , Yu, Lei , Chen, Hao , Shu, Benan , Goswami, Shubham , Peprah, Prince , Hessami, Amir , Abbas, Montasir , Agarwal, Nithin
- Date: 2022
- Type: Text , Journal article
- Relation: Ambio Vol. 51, no. 3 (2022), p. 531-545
- Full Text:
- Reviewed:
- Description: As largely documented in the literature, the stark restrictions enforced worldwide in 2020 to curb the COVID-19 pandemic also curtailed the production of air pollutants to some extent. This study investigates the perception of the air pollution as assessed by individuals located in ten countries: Australia, Brazil, China, Ghana, India, Iran, Italy, Norway, South Africa and the USA. The perceptions towards air quality were evaluated by employing an online survey administered in May 2020. Participants (N = 9394) in the ten countries expressed their opinions according to a Likert-scale response. A reduction in pollutant concentration was clearly perceived, albeit to a different extent, by all populations. The survey participants located in India and Italy perceived the largest drop in the air pollution concentration; conversely, the smallest variation was perceived among Chinese and Norwegian respondents. Among all the demographic indicators considered, only gender proved to be statistically significant. © 2021, The Author(s).
Modeled approaches to estimating blue carbon accumulation with mangrove restoration to support a blue carbon accounting method for Australia
- Lovelock, Catherine, Adame, Fernanda, Butler, Don, Kelleway, Jeffrey, Dittmann, Sabine, Fest, Benedikt, King, Karen, Macreadie, Peter, Mitchell, Katherine, Newnham, Mark, Ola, Anne, Owers, Christopher
- Authors: Lovelock, Catherine , Adame, Fernanda , Butler, Don , Kelleway, Jeffrey , Dittmann, Sabine , Fest, Benedikt , King, Karen , Macreadie, Peter , Mitchell, Katherine , Newnham, Mark , Ola, Anne , Owers, Christopher
- Date: 2022
- Type: Text , Journal article
- Relation: Limnology and Oceanography Vol. 67, no. S2 (2022), p. S50-S60
- Full Text:
- Reviewed:
- Description: The development and refinement of methods for estimating organic carbon accumulation in biomass and soils during mangrove restoration and rehabilitation can encourage uptake of restoration projects for their ecosystem services, including those of climate change mitigation, or blue carbon. To support the development of a blue carbon method for Australia under the Emission Reduction Fund scheme we investigated; (1) whether carbon accumulation data from natural mangroves could be used to estimate carbon accumulation during restoration; (2) modeling mangrove biomass accumulation; and (3) how modeled carbon accumulation could be achieved over heterogeneous sites. First, we assessed carbon accumulation in soil and biomass pools from the global literature, finding that estimating carbon accumulation using data from natural mangroves provided similar estimates as those for restored or rehabilitated mangroves. We assessed mangrove biomass accumulation from global chronosequence studies, which we used to develop regional models for estimating biomass accumulation with restoration in Australia using values from local natural mangroves. Estimating biomass carbon accumulation using site-based means of stand biomass provided similar estimates as values estimated through use of regional means values stratified by elevation; and reduced overestimates of biomass carbon accumulation that were based on regional mean values. Modeling soil carbon accumulation over environmentally heterogeneous project sites can apply a similar approach, stratifying over variation in site elevation. Our analysis provides a strategy for modeling blue carbon pools for an Australian blue carbon method that accommodates regional differences and is based on data from natural mangroves. © 2022 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.
- Authors: Lovelock, Catherine , Adame, Fernanda , Butler, Don , Kelleway, Jeffrey , Dittmann, Sabine , Fest, Benedikt , King, Karen , Macreadie, Peter , Mitchell, Katherine , Newnham, Mark , Ola, Anne , Owers, Christopher
- Date: 2022
- Type: Text , Journal article
- Relation: Limnology and Oceanography Vol. 67, no. S2 (2022), p. S50-S60
- Full Text:
- Reviewed:
- Description: The development and refinement of methods for estimating organic carbon accumulation in biomass and soils during mangrove restoration and rehabilitation can encourage uptake of restoration projects for their ecosystem services, including those of climate change mitigation, or blue carbon. To support the development of a blue carbon method for Australia under the Emission Reduction Fund scheme we investigated; (1) whether carbon accumulation data from natural mangroves could be used to estimate carbon accumulation during restoration; (2) modeling mangrove biomass accumulation; and (3) how modeled carbon accumulation could be achieved over heterogeneous sites. First, we assessed carbon accumulation in soil and biomass pools from the global literature, finding that estimating carbon accumulation using data from natural mangroves provided similar estimates as those for restored or rehabilitated mangroves. We assessed mangrove biomass accumulation from global chronosequence studies, which we used to develop regional models for estimating biomass accumulation with restoration in Australia using values from local natural mangroves. Estimating biomass carbon accumulation using site-based means of stand biomass provided similar estimates as values estimated through use of regional means values stratified by elevation; and reduced overestimates of biomass carbon accumulation that were based on regional mean values. Modeling soil carbon accumulation over environmentally heterogeneous project sites can apply a similar approach, stratifying over variation in site elevation. Our analysis provides a strategy for modeling blue carbon pools for an Australian blue carbon method that accommodates regional differences and is based on data from natural mangroves. © 2022 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.
Changes in vegetation over nine years after rehabilitating a linear feature in Australia's arid zone
- Low, W. A., McNally, A., Davies, B. K., Greenslade, Penelope
- Authors: Low, W. A. , McNally, A. , Davies, B. K. , Greenslade, Penelope
- Date: 2012
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 34, no. 4 (2012), p. 399-414
- Full Text:
- Reviewed:
- Description: A 36-km road built in 1961 between Ayers Rock (Uluru) and the Olgas (Kata Tjuta), Northern Territory, Australia had seriously deteriorated by the 1980s. A newly aligned road, which was ecologically located and avoid sensitive Aboriginal sites, was completed early in 1991. The old road was rehabilitated by deep ripping, filling with imported sand and topsoil and by grading logs and windrows1 over the new surface. This paper reports on the effectiveness of the rehabilitation technique used in reinstating vegetation over 8 years and considers whether this rehabilitation aim was met. Plant colonisation and succession were monitored on 15 paired plots, one in the rehabilitated road and the other in the adjacent undisturbed habitat (with four exceptions) and also on the windrows. Sites at eight creek crossings and those subject to fire and rabbit activity were also monitored. Different landscape units responded in different ways to the rehabilitation. Herbaceous species from imported sand plain fill and top soil eventually dominated the road where they were introduced and were likely to persist in most areas because of local recruitment. The revegetation of the road has stabilised the old road surface as observed by the reduced erosion although succession did not always approach the reference site communities because of a greater resemblance to the Simpson Land System. Over the 8 years of monitoring considerable changes in vegetation occurred and are probably continuing. Only the road sites in the Simpson Land System approached the condition of the adjacent undisturbed vegetation because the vegetation of the other two land systems became closer to that of the Simpson Land System rather than to that of the surrounding vegetation. It is recommended that the introduced Buffel grass, known to alter landscape-level processes by reducing native herbaceous species and increasing risk of high intensity wildfire, which is most evident at creek crossings, should be controlled. Recommendations are made for improved management. © 2012 Australian Rangeland Society.
- Description: 2003010572
Changes in vegetation over nine years after rehabilitating a linear feature in Australia's arid zone
- Authors: Low, W. A. , McNally, A. , Davies, B. K. , Greenslade, Penelope
- Date: 2012
- Type: Text , Journal article
- Relation: Rangeland Journal Vol. 34, no. 4 (2012), p. 399-414
- Full Text:
- Reviewed:
- Description: A 36-km road built in 1961 between Ayers Rock (Uluru) and the Olgas (Kata Tjuta), Northern Territory, Australia had seriously deteriorated by the 1980s. A newly aligned road, which was ecologically located and avoid sensitive Aboriginal sites, was completed early in 1991. The old road was rehabilitated by deep ripping, filling with imported sand and topsoil and by grading logs and windrows1 over the new surface. This paper reports on the effectiveness of the rehabilitation technique used in reinstating vegetation over 8 years and considers whether this rehabilitation aim was met. Plant colonisation and succession were monitored on 15 paired plots, one in the rehabilitated road and the other in the adjacent undisturbed habitat (with four exceptions) and also on the windrows. Sites at eight creek crossings and those subject to fire and rabbit activity were also monitored. Different landscape units responded in different ways to the rehabilitation. Herbaceous species from imported sand plain fill and top soil eventually dominated the road where they were introduced and were likely to persist in most areas because of local recruitment. The revegetation of the road has stabilised the old road surface as observed by the reduced erosion although succession did not always approach the reference site communities because of a greater resemblance to the Simpson Land System. Over the 8 years of monitoring considerable changes in vegetation occurred and are probably continuing. Only the road sites in the Simpson Land System approached the condition of the adjacent undisturbed vegetation because the vegetation of the other two land systems became closer to that of the Simpson Land System rather than to that of the surrounding vegetation. It is recommended that the introduced Buffel grass, known to alter landscape-level processes by reducing native herbaceous species and increasing risk of high intensity wildfire, which is most evident at creek crossings, should be controlled. Recommendations are made for improved management. © 2012 Australian Rangeland Society.
- Description: 2003010572
Effects of a structured reflective interview on parental reflective functioning : a pilot randomised controlled trial
- Low, Yu, Lewis, Andrew, Serfaty, Irene
- Authors: Low, Yu , Lewis, Andrew , Serfaty, Irene
- Date: 2023
- Type: Text , Journal article
- Relation: Journal of Child and Family Studies Vol. 32, no. 2 (2023), p. 516-529
- Full Text:
- Reviewed:
- Description: The Parental Reflective Interview Procedure was developed as part of an initial assessment interview for an attachment-based intervention for child mental health conditions. This study was a pilot randomised controlled trial that utilised a parallel, single-blind trial design to evaluate the differences in the effects of the Parental Reflective Interview Procedure compared to a diagnostic interview on parental reflective functioning. The control group was administered a structured diagnostic interview (Mini International Neuropsychiatric Interview for Children and Adolescents—Parent Version) and matched for time with clinician. The study sample were 25 parents of clinic-referred children who scored above the clinical cut-off score on the Child Behaviour Checklist. Parental reflective functioning was measured with the Parental Reflective Functioning Questionnaire at baseline and repeated post-intervention, and then again at a two-week follow up. Results showed that the Parental Reflective Interview Procedure produced moderate improvements in parents’ understanding of their children’s mental states and maintenance in their reflections on intergenerational parent-child relationship patterns. The diagnostic interview showed decreases in both these dimensions. The findings suggest that the Parental Reflective Interview Procedure is a promising format for initial assessment when referral indicates difficulty in the parent-child relationship. The interview acts as a good orientation for parents to an intervention focused on parent-child relationship dynamics. Further work refining this interview, its coding and integration into a tailored feedback session is required. © 2023, The Author(s).
- Authors: Low, Yu , Lewis, Andrew , Serfaty, Irene
- Date: 2023
- Type: Text , Journal article
- Relation: Journal of Child and Family Studies Vol. 32, no. 2 (2023), p. 516-529
- Full Text:
- Reviewed:
- Description: The Parental Reflective Interview Procedure was developed as part of an initial assessment interview for an attachment-based intervention for child mental health conditions. This study was a pilot randomised controlled trial that utilised a parallel, single-blind trial design to evaluate the differences in the effects of the Parental Reflective Interview Procedure compared to a diagnostic interview on parental reflective functioning. The control group was administered a structured diagnostic interview (Mini International Neuropsychiatric Interview for Children and Adolescents—Parent Version) and matched for time with clinician. The study sample were 25 parents of clinic-referred children who scored above the clinical cut-off score on the Child Behaviour Checklist. Parental reflective functioning was measured with the Parental Reflective Functioning Questionnaire at baseline and repeated post-intervention, and then again at a two-week follow up. Results showed that the Parental Reflective Interview Procedure produced moderate improvements in parents’ understanding of their children’s mental states and maintenance in their reflections on intergenerational parent-child relationship patterns. The diagnostic interview showed decreases in both these dimensions. The findings suggest that the Parental Reflective Interview Procedure is a promising format for initial assessment when referral indicates difficulty in the parent-child relationship. The interview acts as a good orientation for parents to an intervention focused on parent-child relationship dynamics. Further work refining this interview, its coding and integration into a tailored feedback session is required. © 2023, The Author(s).
A case study of clustering in regional Australia : Public policies and private action
- Lowe, Julian, Thompson, Helen, Lynch, David, Braun, Patrice
- Authors: Lowe, Julian , Thompson, Helen , Lynch, David , Braun, Patrice
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at the 30th annual conference of the Australian and New Zealand Regional Science Association International, Beechworth, Victoria : 26th September, 2006
- Full Text:
- Reviewed:
- Description: The paper starts with an evaluation of a group of ICT organizations in a regional Victorian town and using a range of qualitative and quantitative data evaluates whether there is a cluster emerging and if so what are the processes of clustering that underpin this. Using archival and interview data the paper then examines key events and turning points in the development of what might be identified as a nascent cluster (Rosenfeld, 1997). In the context of current public policy that directly or indirectly supports ‘clustering’, the paper then assesses the effectiveness of public policy versus private action in the development of regional agglomerations of organisations and institutions that may be called clusters.
- Description: E1
- Description: 2003001802
- Authors: Lowe, Julian , Thompson, Helen , Lynch, David , Braun, Patrice
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at the 30th annual conference of the Australian and New Zealand Regional Science Association International, Beechworth, Victoria : 26th September, 2006
- Full Text:
- Reviewed:
- Description: The paper starts with an evaluation of a group of ICT organizations in a regional Victorian town and using a range of qualitative and quantitative data evaluates whether there is a cluster emerging and if so what are the processes of clustering that underpin this. Using archival and interview data the paper then examines key events and turning points in the development of what might be identified as a nascent cluster (Rosenfeld, 1997). In the context of current public policy that directly or indirectly supports ‘clustering’, the paper then assesses the effectiveness of public policy versus private action in the development of regional agglomerations of organisations and institutions that may be called clusters.
- Description: E1
- Description: 2003001802
Small firms and regional towns : Towards a typology
- Authors: Lowe, Julian , Henson, Sam
- Date: 2005
- Type: Text , Conference paper
- Relation: Paper presented at the 2nd National Conference on the Future of Australian Country Towns, Bendigo, Australia : 11th -13th July, 2005
- Full Text:
- Reviewed:
- Description: The dominant forms of enterprise in Small Towns are, not surprisingly, small firms. But are these small firms different to their metropolitan counterparts, and are these differences related to their location in regional towns? In addition, are these regional small firms governed by different rules and principles? Overseas studies, generally focusing on firm start-ups, have identified differences between regional and urban enterprises, but the differences are usually small (Westhead, 1995). The explanatory variables identified vary from study to study but include access to finance, physical resources, employment levels, population density, industry structure, regional externalities, human capital, knowledge spillovers, and resource munificent regions as possible explanations for the variations (Armington & Acs, 2002; Keeble, 1997). In this paper, the basic proposition is that regional firms in Australia may be different, but they are not necessarily disadvantaged. Focusing on issues of firm behaviour and competitiveness the paper presents a typology of firms that attempts to explain the fit between a small firm and its regional location. The typology is illustrated and discussed, using preliminary findings from a qualitative, case-based study of small, Western Victorian firms.
- Description: E1
- Description: 2003001146
- Authors: Lowe, Julian , Henson, Sam
- Date: 2005
- Type: Text , Conference paper
- Relation: Paper presented at the 2nd National Conference on the Future of Australian Country Towns, Bendigo, Australia : 11th -13th July, 2005
- Full Text:
- Reviewed:
- Description: The dominant forms of enterprise in Small Towns are, not surprisingly, small firms. But are these small firms different to their metropolitan counterparts, and are these differences related to their location in regional towns? In addition, are these regional small firms governed by different rules and principles? Overseas studies, generally focusing on firm start-ups, have identified differences between regional and urban enterprises, but the differences are usually small (Westhead, 1995). The explanatory variables identified vary from study to study but include access to finance, physical resources, employment levels, population density, industry structure, regional externalities, human capital, knowledge spillovers, and resource munificent regions as possible explanations for the variations (Armington & Acs, 2002; Keeble, 1997). In this paper, the basic proposition is that regional firms in Australia may be different, but they are not necessarily disadvantaged. Focusing on issues of firm behaviour and competitiveness the paper presents a typology of firms that attempts to explain the fit between a small firm and its regional location. The typology is illustrated and discussed, using preliminary findings from a qualitative, case-based study of small, Western Victorian firms.
- Description: E1
- Description: 2003001146
Growth beyond start-up : Entrepreneurship and firms in transition
- Authors: Lowe, Julian , Henson, Sam
- Date: 2004
- Type: Text , Conference paper
- Relation: Paper presented at the AGSE-Babson Entrepreneurship Research Conference, Hawthorne, Australia : 1st February, 2004
- Full Text:
- Reviewed:
- Description: The paper reports on the preliminary stages of a case-based study of regional, highgrowth SMEs. The study explores the actions, activities and processes undertaken by the firms and their start- up entrepreneurs. A framework for growth is proposed, supporting the notion of the growth process as a complex, multidimensional construct. Tentative suggestions are made about the nature of “distributed entrepreneurship” within a small, rapidly growing firm and the issue of regional impacts is also addressed.
- Description: E1
- Description: 2003000814
- Authors: Lowe, Julian , Henson, Sam
- Date: 2004
- Type: Text , Conference paper
- Relation: Paper presented at the AGSE-Babson Entrepreneurship Research Conference, Hawthorne, Australia : 1st February, 2004
- Full Text:
- Reviewed:
- Description: The paper reports on the preliminary stages of a case-based study of regional, highgrowth SMEs. The study explores the actions, activities and processes undertaken by the firms and their start- up entrepreneurs. A framework for growth is proposed, supporting the notion of the growth process as a complex, multidimensional construct. Tentative suggestions are made about the nature of “distributed entrepreneurship” within a small, rapidly growing firm and the issue of regional impacts is also addressed.
- Description: E1
- Description: 2003000814
A matter of trust : Networks and entrepreneurs
- Lowe, Julian, Braun, Patrice
- Authors: Lowe, Julian , Braun, Patrice
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at Regional Frontiers of Entrepreneurship Research 2006, Auckland, New Zealand : 8th February, 2006 p. 496-509
- Full Text:
- Reviewed:
- Description: This paper discusses elements of inter-entrepreneurial trust in regional networks and clusters in terms of influencing business processes and economic viability in today’s economy. The message that can be extracted from the literature is that competitive advantage strongly depends on interfirm collaboration and that networks with a high degree of trust lead to entrepreneurship and innovation. The paper highlights two local Victorian network studies, one in the grains industry and one in the tourism industry, and explores trust based relations in these regional networks. Contrasting sectoral results indicate that social network cohesion and trust were found to be present in the grains community but were absent in the tourism community. Borrowing from the economics and leadership literature, it is proposed that trust fosters certain types of inter-entrepreneurial networks. A description of these networks and related policy implications conclude the paper.
- Description: E1
- Description: 2003001805
- Authors: Lowe, Julian , Braun, Patrice
- Date: 2006
- Type: Text , Conference paper
- Relation: Paper presented at Regional Frontiers of Entrepreneurship Research 2006, Auckland, New Zealand : 8th February, 2006 p. 496-509
- Full Text:
- Reviewed:
- Description: This paper discusses elements of inter-entrepreneurial trust in regional networks and clusters in terms of influencing business processes and economic viability in today’s economy. The message that can be extracted from the literature is that competitive advantage strongly depends on interfirm collaboration and that networks with a high degree of trust lead to entrepreneurship and innovation. The paper highlights two local Victorian network studies, one in the grains industry and one in the tourism industry, and explores trust based relations in these regional networks. Contrasting sectoral results indicate that social network cohesion and trust were found to be present in the grains community but were absent in the tourism community. Borrowing from the economics and leadership literature, it is proposed that trust fosters certain types of inter-entrepreneurial networks. A description of these networks and related policy implications conclude the paper.
- Description: E1
- Description: 2003001805
Bird responses to targeted revegetation : 40 years of habitat enhancement at Clarkesdale Bird sanctuary, central-western Victoria
- Loyn, Richard, Faragher, J. T., Coutts, D. C., Palmer, Grant
- Authors: Loyn, Richard , Faragher, J. T. , Coutts, D. C. , Palmer, Grant
- Date: 2009
- Type: Text , Journal article
- Relation: Australian Field Ornithology Vol. 26, no. 3 (2009), p. 53-75
- Full Text:
- Reviewed:
- Description: A program of planting Australian shrubs and trees has been conducted in degraded farmland at the Clarkesdale Bird Sanctuary (central-western Victoria) since the 1960s, to address the issue of declining native birds, as perceived by the late landowner Gordon Clarke. The shrubs and trees were selected to attract birds, and included many species that were not native to the region. This form of management is often practised by private landholders (at various scales), but its effects are rarely documented. Bird surveys were conducted for this study between 1999 and 2001 at 27 sites: 11 in native eucalypt forest on ridges and slopes, 13 in planted areas on ridges and slopes, and three in planted areas on river-flats and a small gully (with three supplementary sites in a pine plantation). Total bird abundance and species per count were highest in the planted sites on river-flats and gully, and higher in the planted sites on ridges and slopes than in native forest on similar topography. Honeyeaters (Meliphagidae), Superb Fairy-wrens Malurus cyaneus, open-country birds, seed-eating birds and five insectivorous guilds reached their maximum abundance in planted sites. Barkforaging insectivores, canopy-foraging insectivores, frugivores and a generalist insectivore were marginally more common in native forest than in planted sites. Introduced birds were uncommon. Generalised linear modelling showed that total bird abundance was positively related to the cover of planted native vegetation, native low shrubs and young wattles Acacia spp. and to the presence of indigenous Cherry Ballart Exocarpos cupressiformis. Various guilds showed positive relationships with the cover of planted native vegetation, native low shrubs, young wattles, original old wattles, original old eucalypts and trees with small or large hollows. The planting program has provided new habitat for many native forest birds. A greater challenge is to address the needs of some uncommon species that have declined locally, such as the Brown Treecreeper Climacteris picumnus and Speckled Warbler Chthonicola sagittata.
- Authors: Loyn, Richard , Faragher, J. T. , Coutts, D. C. , Palmer, Grant
- Date: 2009
- Type: Text , Journal article
- Relation: Australian Field Ornithology Vol. 26, no. 3 (2009), p. 53-75
- Full Text:
- Reviewed:
- Description: A program of planting Australian shrubs and trees has been conducted in degraded farmland at the Clarkesdale Bird Sanctuary (central-western Victoria) since the 1960s, to address the issue of declining native birds, as perceived by the late landowner Gordon Clarke. The shrubs and trees were selected to attract birds, and included many species that were not native to the region. This form of management is often practised by private landholders (at various scales), but its effects are rarely documented. Bird surveys were conducted for this study between 1999 and 2001 at 27 sites: 11 in native eucalypt forest on ridges and slopes, 13 in planted areas on ridges and slopes, and three in planted areas on river-flats and a small gully (with three supplementary sites in a pine plantation). Total bird abundance and species per count were highest in the planted sites on river-flats and gully, and higher in the planted sites on ridges and slopes than in native forest on similar topography. Honeyeaters (Meliphagidae), Superb Fairy-wrens Malurus cyaneus, open-country birds, seed-eating birds and five insectivorous guilds reached their maximum abundance in planted sites. Barkforaging insectivores, canopy-foraging insectivores, frugivores and a generalist insectivore were marginally more common in native forest than in planted sites. Introduced birds were uncommon. Generalised linear modelling showed that total bird abundance was positively related to the cover of planted native vegetation, native low shrubs and young wattles Acacia spp. and to the presence of indigenous Cherry Ballart Exocarpos cupressiformis. Various guilds showed positive relationships with the cover of planted native vegetation, native low shrubs, young wattles, original old wattles, original old eucalypts and trees with small or large hollows. The planting program has provided new habitat for many native forest birds. A greater challenge is to address the needs of some uncommon species that have declined locally, such as the Brown Treecreeper Climacteris picumnus and Speckled Warbler Chthonicola sagittata.
On the design of a class of rotary compressors using bayesian optimization
- Lu, Kui, Phung, Truong, Sultan, Ibrahim
- Authors: Lu, Kui , Phung, Truong , Sultan, Ibrahim
- Date: 2021
- Type: Text , Journal article
- Relation: Machines Vol. 9, no. 10 (2021), p.
- Full Text:
- Reviewed:
- Description: The optimization process of compressors is usually regarded as a ‘black-box’ problem, in which the mathematical form underlying the relationship between design parameters and the design objective is impractical and costly to be obtained. To solve the ‘black-box’ problem, Bayesian optimization has been proven as an accurate and efficient method. However, the application of such a method in the design of compressors is rarely discussed, particularly no work has been reported in terms of the positive displacement type compressor. Therefore, this paper aims to introduce the Bayesian optimization to the design of positive displacement compressors through the optimization process of the novel limaçon compressor. In this paper, a two-stage optimization process is presented, in which the first stage optimizes the geometric parameters as per design requirements and the second stage focuses on revealing an optimum setting of port geometries that improves machine performance. A numerical illustration is offered to prove the validity of the presented approach. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- Authors: Lu, Kui , Phung, Truong , Sultan, Ibrahim
- Date: 2021
- Type: Text , Journal article
- Relation: Machines Vol. 9, no. 10 (2021), p.
- Full Text:
- Reviewed:
- Description: The optimization process of compressors is usually regarded as a ‘black-box’ problem, in which the mathematical form underlying the relationship between design parameters and the design objective is impractical and costly to be obtained. To solve the ‘black-box’ problem, Bayesian optimization has been proven as an accurate and efficient method. However, the application of such a method in the design of compressors is rarely discussed, particularly no work has been reported in terms of the positive displacement type compressor. Therefore, this paper aims to introduce the Bayesian optimization to the design of positive displacement compressors through the optimization process of the novel limaçon compressor. In this paper, a two-stage optimization process is presented, in which the first stage optimizes the geometric parameters as per design requirements and the second stage focuses on revealing an optimum setting of port geometries that improves machine performance. A numerical illustration is offered to prove the validity of the presented approach. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Design and optimisation of the limaçon rotary compressor
- Lu, Kui
- Authors: Lu, Kui
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: The limaçon positive displacement machine is characterised by its internal geometry and unique mechanical motion; both based on a mathematical curve known as the limaçon of Pascal. The limaçon technology offers many advantages, such as compact size and double‐acting functionality, and its great potential for fluid processing applications has been proven by a number of patents and innovative designs in engines, expanders, and pumps. However, no commercial application of the limaçon technology in the field of positive displacement compressors has been reported in the literature. This could be attributed to the fact that the potential of the limaçon technology for gas compression has not been established as yet. The process of establishing potential is necessary before funds and resources are dedicated to investing in prototyping and testing. This process entails a considerable amount of modelling, coding and analysis as one must ensure the embodiment is geometrically capable of delivering suction and compression strokes, ports can be arranged to support the workings of these strokes, a number of measurable parameters can be identified as impacting compressor performance and it is possible to calculate a set of parameters which optimise this performance. To achieve this objective, a comprehensive mathematical model of a limaçon machine, implemented as a compressor,was first developed. The model, which is multi‐physical in nature, spans such domains as kinematics, fluid dynamics, characteristics of the port flow, internal leakage due to seal vibration, dynamics of the discharge valve, and thermodynamics. Subsequently, the simulation of the model has been performed to numerically study the operational characteristics of the limaçon compressor and to investigate the effect of various parameters on the compressor performance. It was found that the increase in the operating speed and pressure ratio would lead to negative effects on machine performance, especially on volumetric efficiency. Additionally, the results of simulations indicated that the level of fluid over‐compression is influenced by the characteristics of the discharge valve. To ensure the suitability of limaçon technology for use in positive displacement compressors, a study was undertaken to determine whether such an embodiment lent itself to optimisation efforts. For this purpose, the thorough mathematical model which has been developed to simulate compressor workings was then used for optimisation purposes whereby a Bayesian optimisation procedure was applied. The optimisation procedure was conducted in a two‐stage fashion where the first stage optimises the machine dimensions to meet volumetric requirements specified by the designer; and the second stage focuses on revealing the optimum combination of port geometries that improves machine performance. A numerical illustration was presented to prove the validity of the presented approach, and the results show that considerable improvements in the isentropic and volumetric efficiencies can be attained. Moreover, the optimised design was tested under different operating speeds and pressure ratios to investigate its robustness. It was found that the optimised design can exhibit relatively stable performance when the working conditions vary within a small bandwidth around that used in the optimisation procedure. The limaçon technology has three embodiments, namely the limaçon‐to‐limaçon (L2L), the limaçon‐to‐circular, and the circolimaçon. The circolimaçon embodiment features using circular arcs, rather than limaçon curves, to develop profiles for the rotor and housing. This embodiment simplifies the manufacturing process and reduces the production cost associated with producing a limaçon technology. A feasibility study of the circolimaçon embodiment was conducted by comparing its performance with that of the L2L type device. The machine dimensions and port geometries obtained from the optimisation procedure were used in the comparative study. A nonlinear three‐degree of freedom model was presented to describe the dynamic behaviour of the apex seal during the machine operation. Additionally, the leakage through the seal‐housing gap was formulated by considering the inertia and viscous effects of the flow. The results from the case study suggest that the circolimaçon embodiment exhibits comparable performance to the L2L‐type machine, despite having more significant seal vibrations. Moreover, it was also discovered that the circolimaçon compressor with a small capacity undergoes a lower level of seal dynamics, indicating better machine reliability.
- Description: Doctor of Philosophy
- Authors: Lu, Kui
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text:
- Description: The limaçon positive displacement machine is characterised by its internal geometry and unique mechanical motion; both based on a mathematical curve known as the limaçon of Pascal. The limaçon technology offers many advantages, such as compact size and double‐acting functionality, and its great potential for fluid processing applications has been proven by a number of patents and innovative designs in engines, expanders, and pumps. However, no commercial application of the limaçon technology in the field of positive displacement compressors has been reported in the literature. This could be attributed to the fact that the potential of the limaçon technology for gas compression has not been established as yet. The process of establishing potential is necessary before funds and resources are dedicated to investing in prototyping and testing. This process entails a considerable amount of modelling, coding and analysis as one must ensure the embodiment is geometrically capable of delivering suction and compression strokes, ports can be arranged to support the workings of these strokes, a number of measurable parameters can be identified as impacting compressor performance and it is possible to calculate a set of parameters which optimise this performance. To achieve this objective, a comprehensive mathematical model of a limaçon machine, implemented as a compressor,was first developed. The model, which is multi‐physical in nature, spans such domains as kinematics, fluid dynamics, characteristics of the port flow, internal leakage due to seal vibration, dynamics of the discharge valve, and thermodynamics. Subsequently, the simulation of the model has been performed to numerically study the operational characteristics of the limaçon compressor and to investigate the effect of various parameters on the compressor performance. It was found that the increase in the operating speed and pressure ratio would lead to negative effects on machine performance, especially on volumetric efficiency. Additionally, the results of simulations indicated that the level of fluid over‐compression is influenced by the characteristics of the discharge valve. To ensure the suitability of limaçon technology for use in positive displacement compressors, a study was undertaken to determine whether such an embodiment lent itself to optimisation efforts. For this purpose, the thorough mathematical model which has been developed to simulate compressor workings was then used for optimisation purposes whereby a Bayesian optimisation procedure was applied. The optimisation procedure was conducted in a two‐stage fashion where the first stage optimises the machine dimensions to meet volumetric requirements specified by the designer; and the second stage focuses on revealing the optimum combination of port geometries that improves machine performance. A numerical illustration was presented to prove the validity of the presented approach, and the results show that considerable improvements in the isentropic and volumetric efficiencies can be attained. Moreover, the optimised design was tested under different operating speeds and pressure ratios to investigate its robustness. It was found that the optimised design can exhibit relatively stable performance when the working conditions vary within a small bandwidth around that used in the optimisation procedure. The limaçon technology has three embodiments, namely the limaçon‐to‐limaçon (L2L), the limaçon‐to‐circular, and the circolimaçon. The circolimaçon embodiment features using circular arcs, rather than limaçon curves, to develop profiles for the rotor and housing. This embodiment simplifies the manufacturing process and reduces the production cost associated with producing a limaçon technology. A feasibility study of the circolimaçon embodiment was conducted by comparing its performance with that of the L2L type device. The machine dimensions and port geometries obtained from the optimisation procedure were used in the comparative study. A nonlinear three‐degree of freedom model was presented to describe the dynamic behaviour of the apex seal during the machine operation. Additionally, the leakage through the seal‐housing gap was formulated by considering the inertia and viscous effects of the flow. The results from the case study suggest that the circolimaçon embodiment exhibits comparable performance to the L2L‐type machine, despite having more significant seal vibrations. Moreover, it was also discovered that the circolimaçon compressor with a small capacity undergoes a lower level of seal dynamics, indicating better machine reliability.
- Description: Doctor of Philosophy
Geometric design of the limaçon rotary compressor using bayesian optimization
- Lu, Kui, Sultan, Ibrahim, Phung, Truong
- Authors: Lu, Kui , Sultan, Ibrahim , Phung, Truong
- Date: 2022
- Type: Text , Conference paper
- Relation: 3rd International Conference on Energy and Power, ICEP 2021, Chiang Mai, Thailand, 18-20 November 2021, AIP Conference Proceedings 2681 Vol. 2681
- Full Text:
- Reviewed:
- Description: In the design of positive displacement compressors, the mathematical relationship between design parameters and design objectives is usually impractical and costly to be extracted, making the optimization process becomes a 'black-box' problem. In the available literature, the Bayesian optimization method, compared to other optimization techniques, has been proven as an accurate and efficient method to solve the 'black-box' problem. However, the application of such a method in the design of the rotary compressor has not been discussed in published papers. Hence, the current study is intended to employ Bayesian optimization to geometric design a class of positive displacement compressors, which is known as the limaçon compressor. In this paper, the geometric characteristics of the limaçon compressor are presented, and a function, which incorporates volumetric and geometric aspects, is employed to evaluate the optimization process and to reveal the optimum design scenario as per design requirements. A case study is offered to prove the validity of the presented approach. © 2022 American Institute of Physics Inc.. All rights reserved.
- Authors: Lu, Kui , Sultan, Ibrahim , Phung, Truong
- Date: 2022
- Type: Text , Conference paper
- Relation: 3rd International Conference on Energy and Power, ICEP 2021, Chiang Mai, Thailand, 18-20 November 2021, AIP Conference Proceedings 2681 Vol. 2681
- Full Text:
- Reviewed:
- Description: In the design of positive displacement compressors, the mathematical relationship between design parameters and design objectives is usually impractical and costly to be extracted, making the optimization process becomes a 'black-box' problem. In the available literature, the Bayesian optimization method, compared to other optimization techniques, has been proven as an accurate and efficient method to solve the 'black-box' problem. However, the application of such a method in the design of the rotary compressor has not been discussed in published papers. Hence, the current study is intended to employ Bayesian optimization to geometric design a class of positive displacement compressors, which is known as the limaçon compressor. In this paper, the geometric characteristics of the limaçon compressor are presented, and a function, which incorporates volumetric and geometric aspects, is employed to evaluate the optimization process and to reveal the optimum design scenario as per design requirements. A case study is offered to prove the validity of the presented approach. © 2022 American Institute of Physics Inc.. All rights reserved.