This research evaluated the suitability of stone dust in the design and production of High Perfor-mance Concrete (HPC). HPC mix was designed, tested, costed and a comparison of concrete classes used in the market (Cla...This research evaluated the suitability of stone dust in the design and production of High Perfor-mance Concrete (HPC). HPC mix was designed, tested, costed and a comparison of concrete classes used in the market (Class 25, 30 and 35) done using Cost Benefit Analysis (CBA). The cost benefit was analyzed using Internal Rate of Return (IRR) and Net Present Value (NPV). Laboratory tests established the properties concrete obtained from the design mix. Compressive strength, slump, and modulus of elasticity were tested and analyzed. Structural analysis using BS 8110 was done for a 10 storey office building to establish the structural member sizes. Members obtained from concrete Classes 25, 30, 35 and the new compressive strengths from HPC (Class 80) were obtained and compared. Analysis was done for structural members’ sizes and area freed as a result of de-signing with HPC as well as the steel reinforcement used. To justify the initial cost of HPC if ado- pted, the Cost Benefit Analysis (CBA) was used to estimate increased costs versus income resulting from increased let table space created. The minimum class of concrete used in design was limited to Class 25 N/mm2. The research shows that it is possible to manufacture high strength concrete using locally available stone dust. The stone dust sampled from Mlolongo quarries achieved a characteristic strength of 86.7 N/mm2 at a water cement ratio of 0.32. With the results structural analysis of a 10 storey office structures with columns spaced at 8 meters center to center was de-signed using the four classes and results compared. There was a reduction of columns from 1.2 m wide to 0.65 m wide (over 45%) when concrete class changes from Class 25 to Class 80 creating over 3% of the total space area per floor. Cost benefit analysis using Net Present Value (NPV) and Internal Rate of Return (IRR) presented business case for the use of HPC. With Class 80, the IRR was at 3% and NPV being 8% of the total initial investment. The steel reinforcement increased by 8.64% using Class 30, 11.68% using Class 35 and reduced by 8.37% at Class 80. Further analysis needs to be done to understand the trend of steel reinforcement keeping all the member sizes the same. In this study the member sizes were optimized based on the steel reinforcement and serviceability. This paper provides useful information to design Engineers and Architects and inform future design of multi storey structures.展开更多
Low cost, high performance supercapacitor electrodes were fabricated using coconut waste as precursor. Simple one step pyrolysis is adopted to get the spherical shaped particle where lignocellulosic nature of carbon c...Low cost, high performance supercapacitor electrodes were fabricated using coconut waste as precursor. Simple one step pyrolysis is adopted to get the spherical shaped particle where lignocellulosic nature of carbon converts into porous carbon nanospheres. Three types of coconut wastes, namely, coconut fiber(CF), coconut leaves(CL) and coconut stick(CS) have been studied and compared for their application in supercapacitors. Uniform spherical shape with particle size ranging from 30 to 60 nm for leaves and sticks and20 nm for fibers was obtained. The electrochemical properties of the porous carbon nanospheres were studied using cyclic voltammetry(CV), chronopotentiometry(CP) and electrochemical impedance spectroscopy(EIS). The porous carbon nanospheres derived from all the three biowaste samples show good electrochemical performance for supercapacitor application. Porous carbon nanospheres derived from coconut fiber exhibited maximum specific capacitance of 236 F/g followed by coconut stick and coconut leaves with 208 and 116 F/g respectively at a scan rate of 2 m V/s. Further impedance studies showed a charge transfer resistance of 4.9 for the porous carbon nanospheres derived from coconut fiber, while those from coconut leaves and coconut stick exhibited a slightly higher resistance of 6 and14.2, respectively. The simple eco-friendly approach we have demonstrated for synthesizing coconut waste based carbon nanospheres makes them excellent candidates for future, low-cost, energy storage devices.展开更多
Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwav...Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwave photonics filtering[1–3],arbitrary generation[4–6]and analog to digital conversion[7]。展开更多
Energy performance contracting(EPC)has emerged as a useful project financ-ing and delivery tool for building retrofits,particularly among building owner-ships which have experienced reduced funding for capital project...Energy performance contracting(EPC)has emerged as a useful project financ-ing and delivery tool for building retrofits,particularly among building owner-ships which have experienced reduced funding for capital projects.Through EPC,a contractor(called the EPC contractor or the energy service company)guaran-tees minimum energy savings performance and enables the building owner to finance the project using utility savings over the length of the project(which is typically 12-15 years,or longer).Despite its growing use,there is a dearth of lit-erature regarding a contractor’s risks related to the delivery and execution of EPC building retrofits.This is particularly important as the performance guarantee effec-tively transfers project performance risk from the owner to the EPC contractor.This research proposes a project factors-based risk framework for EPC building retrofits,initially developed through a comprehensive review of relevant literature and project documents and refined through the elicited expertise of 19 highly expe-rienced EPC contracting professionals.A Delphi technique-based expertise elici-tation strategy was used to confirm the findings of the a priori(literature-based)framework and provide additional analysis related to risk causes and control mea-sures as well as relative risk importance.This information was used to construct a refined risk framework which provides insight into the lengthy project performance period during the earliest phases of the project’s life cycle.This has the advantage of providing rapid screening of the project factors that can potentially lead to the greatest project performance risks.展开更多
Roads are the major asset of any country and to conserve them maintenance is essential. The delay of maintenance works can lead the road in the stage of expensive rehabilitation and reconstruction. In Nepal, Departmen...Roads are the major asset of any country and to conserve them maintenance is essential. The delay of maintenance works can lead the road in the stage of expensive rehabilitation and reconstruction. In Nepal, Department of Roads (DoR) is responsible for maintenance of strategic roads of country. The maintenance practice of the road under Department of Road is predominantly based on Strengthen Maintenance Division Process where several maintenance activities like Routine maintenance, Recurrent Maintenance, Periodic Maintenance and Emergency Maintenance are planned and carried out. The maintenance work is based on traditional quantity and unit price based short term maintenance contracts, where maintenance of physical works is outsourced. Client demands the contractor what work is to be done, when to be do it and the extent of the work. The contractor is paid on the basis of a defined output or quantity accomplished, and the schedule of the rates. DoR engineers required full time supervision of work. Pilot based performance based maintenance practice of road started in Nepal in 2003. The study assesses performance road maintenance practices of road maintenance in Nepal on the basis of the framework of cost efficiency, level of service effectiveness and quality of service. The study concluded that implementation of Performance Based Maintenance Contract (PBMC) was not successful in Nepal as Road Asset condition was not maintained to performance standard. One of the reasons is the weak service delivery of contractor alongside weak contract enforcement from the road agency.展开更多
近年来,超高性能混凝土(UHPC)得到了推广应用,但在UHPC生产过程中超量水泥消耗以及UHPC自身耐久性强、寿命长的特点,对UHPC的碳排放水平认识尚不清楚。因此,研究采用生命周期评价(LCA)方法构建了UHPC碳排放定量分析模型,对比分析钢-UHP...近年来,超高性能混凝土(UHPC)得到了推广应用,但在UHPC生产过程中超量水泥消耗以及UHPC自身耐久性强、寿命长的特点,对UHPC的碳排放水平认识尚不清楚。因此,研究采用生命周期评价(LCA)方法构建了UHPC碳排放定量分析模型,对比分析钢-UHPC桥面板与常规钢-混桥面板结构在全生命周期内的碳排放。结果表明:虽然生产阶段UHPC的碳排放量约1 245.84 kg CO_(2)eq/m^(3),是普通混凝土的1.58倍,但从性能上来说,UHPC碳强度是普通混凝土的62.25%,是一种更绿色的建材;在整个生命周期内,与常规钢-混桥面板相比,钢-UHPC桥面板的年均碳排放量下降了35.76%,具有巨大的碳减排潜力,有助于基础设施的可持续性发展;钢-UHPC桥面板方案具有工程比选优势,经济性合理,同时其单位产值碳排放为0.89 t CO_(2)eq/万元,是常规钢-混桥面板的86.41%,具有更好的减碳效果。研究对结果的可靠性和碳减排措施进行了讨论,最后提出了有待进一步研究的内容。展开更多
文摘This research evaluated the suitability of stone dust in the design and production of High Perfor-mance Concrete (HPC). HPC mix was designed, tested, costed and a comparison of concrete classes used in the market (Class 25, 30 and 35) done using Cost Benefit Analysis (CBA). The cost benefit was analyzed using Internal Rate of Return (IRR) and Net Present Value (NPV). Laboratory tests established the properties concrete obtained from the design mix. Compressive strength, slump, and modulus of elasticity were tested and analyzed. Structural analysis using BS 8110 was done for a 10 storey office building to establish the structural member sizes. Members obtained from concrete Classes 25, 30, 35 and the new compressive strengths from HPC (Class 80) were obtained and compared. Analysis was done for structural members’ sizes and area freed as a result of de-signing with HPC as well as the steel reinforcement used. To justify the initial cost of HPC if ado- pted, the Cost Benefit Analysis (CBA) was used to estimate increased costs versus income resulting from increased let table space created. The minimum class of concrete used in design was limited to Class 25 N/mm2. The research shows that it is possible to manufacture high strength concrete using locally available stone dust. The stone dust sampled from Mlolongo quarries achieved a characteristic strength of 86.7 N/mm2 at a water cement ratio of 0.32. With the results structural analysis of a 10 storey office structures with columns spaced at 8 meters center to center was de-signed using the four classes and results compared. There was a reduction of columns from 1.2 m wide to 0.65 m wide (over 45%) when concrete class changes from Class 25 to Class 80 creating over 3% of the total space area per floor. Cost benefit analysis using Net Present Value (NPV) and Internal Rate of Return (IRR) presented business case for the use of HPC. With Class 80, the IRR was at 3% and NPV being 8% of the total initial investment. The steel reinforcement increased by 8.64% using Class 30, 11.68% using Class 35 and reduced by 8.37% at Class 80. Further analysis needs to be done to understand the trend of steel reinforcement keeping all the member sizes the same. In this study the member sizes were optimized based on the steel reinforcement and serviceability. This paper provides useful information to design Engineers and Architects and inform future design of multi storey structures.
文摘Low cost, high performance supercapacitor electrodes were fabricated using coconut waste as precursor. Simple one step pyrolysis is adopted to get the spherical shaped particle where lignocellulosic nature of carbon converts into porous carbon nanospheres. Three types of coconut wastes, namely, coconut fiber(CF), coconut leaves(CL) and coconut stick(CS) have been studied and compared for their application in supercapacitors. Uniform spherical shape with particle size ranging from 30 to 60 nm for leaves and sticks and20 nm for fibers was obtained. The electrochemical properties of the porous carbon nanospheres were studied using cyclic voltammetry(CV), chronopotentiometry(CP) and electrochemical impedance spectroscopy(EIS). The porous carbon nanospheres derived from all the three biowaste samples show good electrochemical performance for supercapacitor application. Porous carbon nanospheres derived from coconut fiber exhibited maximum specific capacitance of 236 F/g followed by coconut stick and coconut leaves with 208 and 116 F/g respectively at a scan rate of 2 m V/s. Further impedance studies showed a charge transfer resistance of 4.9 for the porous carbon nanospheres derived from coconut fiber, while those from coconut leaves and coconut stick exhibited a slightly higher resistance of 6 and14.2, respectively. The simple eco-friendly approach we have demonstrated for synthesizing coconut waste based carbon nanospheres makes them excellent candidates for future, low-cost, energy storage devices.
文摘Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwave photonics filtering[1–3],arbitrary generation[4–6]and analog to digital conversion[7]。
文摘Energy performance contracting(EPC)has emerged as a useful project financ-ing and delivery tool for building retrofits,particularly among building owner-ships which have experienced reduced funding for capital projects.Through EPC,a contractor(called the EPC contractor or the energy service company)guaran-tees minimum energy savings performance and enables the building owner to finance the project using utility savings over the length of the project(which is typically 12-15 years,or longer).Despite its growing use,there is a dearth of lit-erature regarding a contractor’s risks related to the delivery and execution of EPC building retrofits.This is particularly important as the performance guarantee effec-tively transfers project performance risk from the owner to the EPC contractor.This research proposes a project factors-based risk framework for EPC building retrofits,initially developed through a comprehensive review of relevant literature and project documents and refined through the elicited expertise of 19 highly expe-rienced EPC contracting professionals.A Delphi technique-based expertise elici-tation strategy was used to confirm the findings of the a priori(literature-based)framework and provide additional analysis related to risk causes and control mea-sures as well as relative risk importance.This information was used to construct a refined risk framework which provides insight into the lengthy project performance period during the earliest phases of the project’s life cycle.This has the advantage of providing rapid screening of the project factors that can potentially lead to the greatest project performance risks.
文摘Roads are the major asset of any country and to conserve them maintenance is essential. The delay of maintenance works can lead the road in the stage of expensive rehabilitation and reconstruction. In Nepal, Department of Roads (DoR) is responsible for maintenance of strategic roads of country. The maintenance practice of the road under Department of Road is predominantly based on Strengthen Maintenance Division Process where several maintenance activities like Routine maintenance, Recurrent Maintenance, Periodic Maintenance and Emergency Maintenance are planned and carried out. The maintenance work is based on traditional quantity and unit price based short term maintenance contracts, where maintenance of physical works is outsourced. Client demands the contractor what work is to be done, when to be do it and the extent of the work. The contractor is paid on the basis of a defined output or quantity accomplished, and the schedule of the rates. DoR engineers required full time supervision of work. Pilot based performance based maintenance practice of road started in Nepal in 2003. The study assesses performance road maintenance practices of road maintenance in Nepal on the basis of the framework of cost efficiency, level of service effectiveness and quality of service. The study concluded that implementation of Performance Based Maintenance Contract (PBMC) was not successful in Nepal as Road Asset condition was not maintained to performance standard. One of the reasons is the weak service delivery of contractor alongside weak contract enforcement from the road agency.
文摘近年来,超高性能混凝土(UHPC)得到了推广应用,但在UHPC生产过程中超量水泥消耗以及UHPC自身耐久性强、寿命长的特点,对UHPC的碳排放水平认识尚不清楚。因此,研究采用生命周期评价(LCA)方法构建了UHPC碳排放定量分析模型,对比分析钢-UHPC桥面板与常规钢-混桥面板结构在全生命周期内的碳排放。结果表明:虽然生产阶段UHPC的碳排放量约1 245.84 kg CO_(2)eq/m^(3),是普通混凝土的1.58倍,但从性能上来说,UHPC碳强度是普通混凝土的62.25%,是一种更绿色的建材;在整个生命周期内,与常规钢-混桥面板相比,钢-UHPC桥面板的年均碳排放量下降了35.76%,具有巨大的碳减排潜力,有助于基础设施的可持续性发展;钢-UHPC桥面板方案具有工程比选优势,经济性合理,同时其单位产值碳排放为0.89 t CO_(2)eq/万元,是常规钢-混桥面板的86.41%,具有更好的减碳效果。研究对结果的可靠性和碳减排措施进行了讨论,最后提出了有待进一步研究的内容。
