Accurate project progress measurement is critical for effective project management. Besides guarantying smooth work progress, it affords project managers the chance to identify early warning signs for peremptory remed...Accurate project progress measurement is critical for effective project management. Besides guarantying smooth work progress, it affords project managers the chance to identify early warning signs for peremptory remedial actions to keep the project on schedule and to budget. However, pertinent barriers can suppress the realization of the benefits of an accurate assessment of construction progress. This study aims to identify, examine and prioritize the critical barriers militating against accurate project progress measurement in the Ghanaian construction industry. Sixteen barriers identified from the literature were administered in a questionnaire survey to professionals with tier one construction firms and consultants. Sixty experienced construction professionals practising with tier-one construction firms and consultancy services took part in the survey. The relative importance index technique was used to rank the factors and correlation in responses of the two parties tested by the Mann-Whitney <em>U</em> statistics. The most critical barriers perceived by the professionals were 1) Reliance on Supervisor’s Judgement, 2) Generic and Non-Systematic Approach, 3) Variable Quality of Data and 4) Intricate Measurement Reports. Other highly ranked barriers include 5) Lack of Timely Information, 6) Laborious Data Gathering and 7) Quality Integration Constraint. The findings underpin the need to minimize dependence on subjective opinions and mere experiences of supervisors for assessment of project progress in this age of information technology. Incorporation of a level of automation into traditional progress methods will not only reduce human errors introduced into manually collected data but facilitate visualization of progress reports. Contiguous to a clear specification of the method of progress measurement in the contract document, a system that conveniently integrates cost, time and scope of work into progress measurement must be pursued. Addressing these identified critical barriers will consolidate current construction progress management practices.展开更多
This review examines the critical risks,barriers,and success factors in achieving sustainable affordable housing(SAH)by addressing environmental,economic,social and technical dimensions of sustainability.The aim of th...This review examines the critical risks,barriers,and success factors in achieving sustainable affordable housing(SAH)by addressing environmental,economic,social and technical dimensions of sustainability.The aim of this study is to identify different critical risks and barriers to the development of the Sustainable Affordable Housing(SAH)CSF framework.The objectives of this research are to define SAH(Sustainable Affordable Housing)and important factors for achieving SAH and to develop SAH Critical Success Factors(CSFs)frameworks.To achieve these objectives,there are two methods for reviewing and analyzing documents,i.e.,systematic review and bibliographic review.The years of publication are limited to 2014 to 2023 in the English language and restricted to open access.A total of 63 articles were retrieved and screened for relevance identified as directly relevant to our topic using the PRISMA systematic review process.The growth pattern aligns strongly with an exponential growth model,as evidenced by a high R^(2) value of 0.9133 indicating a robust correlation and demonstrating the accelerating interest in the field over the past decade.This comprehensive analysis led to the development of the sustainable affordable housing(SAH)critical success framework,providing a structured approach to understanding and implementing critical factors for sustainable and affordable housing initiatives.The findings emphasize the need for integrated policy reforms,innovative construction technologies,and collaborative stakeholder engagement to advance the SAH agenda.Future research directions include conducting longitudinal studies to assess the long-term impacts of SAH policies,comparative analyses of international best practices,and explorations into emerging construction technologies.展开更多
It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on pr...It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further investigated.The results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.展开更多
The critical lengths of an oscillator based on double-walled carbon nanotubes(DWCNTs)are studied by energy minimization and molecular dynamics simulation.Van der Waals(vdW)potential energy in DWCNTs is shown to be cha...The critical lengths of an oscillator based on double-walled carbon nanotubes(DWCNTs)are studied by energy minimization and molecular dynamics simulation.Van der Waals(vdW)potential energy in DWCNTs is shown to be changed periodically with the lattice matching of the inner and outer tubes by using atomistic models with energy minimization method.If the coincidence length between the inner and outer tubes is long enough,the restoring force cannot drive the DWCNT to slide over the vdW potential barrier to assure the DWCNT acts as an oscillator.The critical coincidence lengths of the oscillators are predicted by a very simple equation and then confirmed with energy minimization method for both the zigzag/zigzag system and the armchair/armchair system.The critical length of the armchair/armchair system is much larger than that of the zigzag/zigzag system.The vdW potential energy fluctuation of the armchair/armchair system is weaker than that of the zigzag/zigzag system.So it is easier to slide over the barrier for the armchair/armchair system.The critical lengths of zigzag/zigzag DWCNTbased oscillator are found increasing along with temperature,by molecular dynamics simulations.展开更多
We consider a branching random walk with an absorbing barrier,where the associated one-dimensional random walk is in the domain of attraction of an a-stable law.We shall prove that there is a barrier and a critical va...We consider a branching random walk with an absorbing barrier,where the associated one-dimensional random walk is in the domain of attraction of an a-stable law.We shall prove that there is a barrier and a critical value such that the process dies under the critical barrier,and survives above it.This generalizes previous result in the case that the associated random walk has finite variance.展开更多
文摘Accurate project progress measurement is critical for effective project management. Besides guarantying smooth work progress, it affords project managers the chance to identify early warning signs for peremptory remedial actions to keep the project on schedule and to budget. However, pertinent barriers can suppress the realization of the benefits of an accurate assessment of construction progress. This study aims to identify, examine and prioritize the critical barriers militating against accurate project progress measurement in the Ghanaian construction industry. Sixteen barriers identified from the literature were administered in a questionnaire survey to professionals with tier one construction firms and consultants. Sixty experienced construction professionals practising with tier-one construction firms and consultancy services took part in the survey. The relative importance index technique was used to rank the factors and correlation in responses of the two parties tested by the Mann-Whitney <em>U</em> statistics. The most critical barriers perceived by the professionals were 1) Reliance on Supervisor’s Judgement, 2) Generic and Non-Systematic Approach, 3) Variable Quality of Data and 4) Intricate Measurement Reports. Other highly ranked barriers include 5) Lack of Timely Information, 6) Laborious Data Gathering and 7) Quality Integration Constraint. The findings underpin the need to minimize dependence on subjective opinions and mere experiences of supervisors for assessment of project progress in this age of information technology. Incorporation of a level of automation into traditional progress methods will not only reduce human errors introduced into manually collected data but facilitate visualization of progress reports. Contiguous to a clear specification of the method of progress measurement in the contract document, a system that conveniently integrates cost, time and scope of work into progress measurement must be pursued. Addressing these identified critical barriers will consolidate current construction progress management practices.
文摘This review examines the critical risks,barriers,and success factors in achieving sustainable affordable housing(SAH)by addressing environmental,economic,social and technical dimensions of sustainability.The aim of this study is to identify different critical risks and barriers to the development of the Sustainable Affordable Housing(SAH)CSF framework.The objectives of this research are to define SAH(Sustainable Affordable Housing)and important factors for achieving SAH and to develop SAH Critical Success Factors(CSFs)frameworks.To achieve these objectives,there are two methods for reviewing and analyzing documents,i.e.,systematic review and bibliographic review.The years of publication are limited to 2014 to 2023 in the English language and restricted to open access.A total of 63 articles were retrieved and screened for relevance identified as directly relevant to our topic using the PRISMA systematic review process.The growth pattern aligns strongly with an exponential growth model,as evidenced by a high R^(2) value of 0.9133 indicating a robust correlation and demonstrating the accelerating interest in the field over the past decade.This comprehensive analysis led to the development of the sustainable affordable housing(SAH)critical success framework,providing a structured approach to understanding and implementing critical factors for sustainable and affordable housing initiatives.The findings emphasize the need for integrated policy reforms,innovative construction technologies,and collaborative stakeholder engagement to advance the SAH agenda.Future research directions include conducting longitudinal studies to assess the long-term impacts of SAH policies,comparative analyses of international best practices,and explorations into emerging construction technologies.
基金Project(51404201)supported by the National Natural Science Foundation of ChinaProject(2011ZX05024-003)supported by the National Science and Technology Major Project of China+1 种基金Project(14ZB0045)supported by the Scientific Project of Sichuan Provincial Education Department,ChinaProject(2015JY0076)supported by Basic Application Research of Science and Technology Department of Sichuan Province,China
文摘It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further investigated.The results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.
基金Supported in part by the National Natural Science Foundation of China(11072108)the Foundation for the Author of National Excellent Doctoral Dissertation of China(201028)+3 种基金the Program for New Century Excellent Talents in University(NCET-11-0832)the Funding of Jiangsu Innovation Program for Graduate Education(CXZZ13-0144)the Funding for Outstanding Doctoral Dissertation in NUAA(BCXJ13-03)the Fundamental Research Funds for the Central Universities of China
文摘The critical lengths of an oscillator based on double-walled carbon nanotubes(DWCNTs)are studied by energy minimization and molecular dynamics simulation.Van der Waals(vdW)potential energy in DWCNTs is shown to be changed periodically with the lattice matching of the inner and outer tubes by using atomistic models with energy minimization method.If the coincidence length between the inner and outer tubes is long enough,the restoring force cannot drive the DWCNT to slide over the vdW potential barrier to assure the DWCNT acts as an oscillator.The critical coincidence lengths of the oscillators are predicted by a very simple equation and then confirmed with energy minimization method for both the zigzag/zigzag system and the armchair/armchair system.The critical length of the armchair/armchair system is much larger than that of the zigzag/zigzag system.The vdW potential energy fluctuation of the armchair/armchair system is weaker than that of the zigzag/zigzag system.So it is easier to slide over the barrier for the armchair/armchair system.The critical lengths of zigzag/zigzag DWCNTbased oscillator are found increasing along with temperature,by molecular dynamics simulations.
基金The authors are very grateful to Professor Mu-Fa Chen for his helpful comments and suggestions.This work was supported by the National Natural Science Foundation of China(Grant Nos.11871103,11371061)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant No.KJQN 201900514).
文摘We consider a branching random walk with an absorbing barrier,where the associated one-dimensional random walk is in the domain of attraction of an a-stable law.We shall prove that there is a barrier and a critical value such that the process dies under the critical barrier,and survives above it.This generalizes previous result in the case that the associated random walk has finite variance.
