The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co...The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.展开更多
Rotation sintering, also known as slush molding, is used to manufacture molded skins, such as dashboards or door interior panels for cars. At present, approximately 80% of such molded skins are manufactured using elec...Rotation sintering, also known as slush molding, is used to manufacture molded skins, such as dashboards or door interior panels for cars. At present, approximately 80% of such molded skins are manufactured using electroforms to achieve the complex free-form surfaces, and surface structures, such as leather graining that the industry demands. The manufacture of these electroforms is, however, time-consuming and expensive. This project aims to replace conventional electroforms with laser-drilled molds. Holes in tool molds should be drilled by using laser radiation as part of an automated process. The system consists of a robot with a fiber-laser beam source. A CAx （computer-aided x） process chain has been developed for this purpose in which the CAD （computer-aided design） data of the tool molds are processed, drill hole fields generated, and a machine-specific RC （robot control） program created. Process-specific fundamentals, such as suitable process windows and process control, have been devised to manufacture holes using fiber laser radiation The advantages of the new laser-drilled tool molds may result in substituting them for conventional electroforms, allowing old markets to be re-entered or additional markets to be created and targeted through new molds or lower costs.展开更多
With in-depth development of the Internet of Things(IoT)in various industries,the informatization process of various industries has also entered the fast lane.This article aims to solve the supply chain process proble...With in-depth development of the Internet of Things(IoT)in various industries,the informatization process of various industries has also entered the fast lane.This article aims to solve the supply chain process problem in e-commerce,focusing on the specific application of Internet of Things technology in e-commerce.Warehousing logistics is an important link in today’s e-commerce transactions.This article proposes a distributed analysis method for RFID-based e-commerce warehousing process optimization and an e-commerce supply chain management process based on Internet of Things technology.This article first introduces the advantages and disadvantages of shared IoT identification technology and the IoT resource sharing platform based on the three-layer abstract data model and representational state transfer(REST)style.Combining actual IoT applications and the characteristics of an existing platform,a REST-based IoT resource sharing platform is proposed.Combined with actual projects,a REST-based IoT resource sharing platform was built,and key technology experiments were conducted for verification.Finally,optimizing the e-commerce supply chain management process under Internet of Things technology and explaining the advantages of optimized e-commerce supply chain management are discussed.Research on this subject provides a theoretical basis for the application of the Internet of Things in e-commerce and has practical significance and practical value for managing service capabilities and service levels in e-commerce.展开更多
[Objectives]This study was conducted to investigate the effect of compound fresh-keeping liquid on the browning and quality of fresh-cut yam during the cold chain process.[Methods]Under the simulated cold chain condit...[Objectives]This study was conducted to investigate the effect of compound fresh-keeping liquid on the browning and quality of fresh-cut yam during the cold chain process.[Methods]Under the simulated cold chain condition of 4℃,a uniform design(U6*(64))experiment was carried out to optimize the compound preservative formula,and a better compound preservative formula was obtained using the regression equation.[Results]The compound preservative formula was:AA 0.25%,CA 0.5%,Nisin 0.09%,GSH 0.15%.The compound fresh-keeping liquid effectively delayed the browning of fresh-cut yam and the accumulation of MDA,maintained the content of TSS,inhibited the activity of PAL and delayed the appearance of the maximum activity of POD and POD.[Conclusions]This study provides technical support for the actual extension of the shelf life of fresh-cut yam.展开更多
As an important intermediate product, short-chain fatty acids（SCFAs） can be generated after hydrolysis and acidification from waste activated sludge, and then can be transformed to methane during anaerobic digestion...As an important intermediate product, short-chain fatty acids（SCFAs） can be generated after hydrolysis and acidification from waste activated sludge, and then can be transformed to methane during anaerobic digestion process. In order to obtain more SCFA and methane,most studies in literatures were centered on enhancing the hydrolysis of sludge anaerobic digestion which was proved as un-efficient. Though the alkaline pretreatment in our previous study increased both the hydrolysis and acidification processes, it had a vast chemical cost which was considered uneconomical. In this paper, a low energy consumption pretreatment method, i.e. enhanced the whole three stages of the anaerobic fermentation processes at the same time, was reported, by which hydrolysis and acidification were both enhanced, and the SCFA and methane generation can be significantly improved with a small quantity of chemical input. Firstly, the effect of different pretreated temperatures and pretreatment time on sludge hydrolyzation was compared. It was found that sludge pretreated at 100°C for 60 min can achieve the maximal hydrolyzation. Further, effects of different initial p Hs on acidification of the thermal pretreated sludge were investigated and the highest SCFA was observed at initial p H 9.0with fermentation time of 6 d, the production of which was 348.63 mg COD/g VSS（6.8 times higher than the blank test） and the acetic acid was dominant acid. Then, the mechanisms for this new pretreatment significantly improving SCFA production were discussed. Finally,the effect of this low energy consumption pretreatment on methane generation was investigated.展开更多
E-supply chain is the trend of the supply chain ma na gement. However, building E-supply chain depends on business process improvemen t and re-engineering, which becomes one of the important aspects in supply chai n m...E-supply chain is the trend of the supply chain ma na gement. However, building E-supply chain depends on business process improvemen t and re-engineering, which becomes one of the important aspects in supply chai n management. However, the supply chain process re-engineering and improvement is constrained because of lack of integrating operation framework and standards based on information management. We find that the idea of CALS origins from DoD of USA can solve the problems very well. CALS is the abbreviation of "continues acquisition and life- cycle support". It is an information strategy adopted by many developed counties. The final objective of the CALS is that government a nd industry can generate, exchange, manage and use all the digital information t hroughout the lifecycle of a product in virtue of adopting the international and national standards, improving existing business process and introducing advance d technology. The Integrated Digital Environment (IDE) created by CALS provides a brand new operation mode for consumer, contractor and supplier in supply chain . Besides, a series mutual standard is involved in CALS system. These standards and the standardization technology would be applied widely in the supply chain. This study mainly focuses on supply chain process in CALS environment, and puts forward a framework model of supply chain process. Then the study analyzes the c haracteristics of the model, which includes the application of standards and inf ormation technology, and finally discusses on methods to achieve the supply chai n process in CALS environment.展开更多
Through the process analysis of cold chain logistics of agricultural products,we find that cold chain logistics of agricultural products contradict the development model of low-carbon economy to some extent.We apply t...Through the process analysis of cold chain logistics of agricultural products,we find that cold chain logistics of agricultural products contradict the development model of low-carbon economy to some extent.We apply the development idea of low-carbon economy,introduce the thirdparty logistics companies,establish distribution center of cold chain logistics of agricultural products,and strengthen information sharing,to reengineer the process of cold chain logistics of agricultural products in China.The results show that applying low-carbon economy to process reengineering of cold chain logistics of agricultural products,has advantages of increasing added value of products,promoting scale merit and abating lag,plays a role in promoting emission reduction,high efficiency and environmental protection in the process of cold chain logistics of agricultural products in China.展开更多
In order to improve the influence of the uncertain and dynamic of node enterprise behavior on the performance of supply chain,the method based on stochastic process algebra for description,analysis,validation and eval...In order to improve the influence of the uncertain and dynamic of node enterprise behavior on the performance of supply chain,the method based on stochastic process algebra for description,analysis,validation and evaluation of supply chain business process model is proposed.Firstly,the description of the uncertainty of node enterprise behavior is given using the extended Unified Modeling Language sequence diagram,and mapping rule is defined from the extended Unified Modeling Language sequence diagram to stochastic process algebra.Secondly,on the basis of the acquired stochastic process algebra model,the supply chain business process model is verified with Mobility Workbench.Finally,according to the operational semantics of stochastic process algebra,the continuous-time Markov chain,isomorphic with stochastic process algebra model,is built; and the system performance evaluation of transient status and stable status is respectively conducted in accordance with Markov transfer relations and the current state of system,obtaining the predicted performance value and average performance index value for a specific period of time.The simulation experiments show that the proposed method can accurately describe the stochastic behaviors of supply chain system and interactions among nodes,effectively verify the validity of the model,and objectively and exactly evaluate design of the supply chain.展开更多
This paper presents a digital model for the powder metallurgical(PM)production chain of high-performance sintered gears based on an integrated computational materials engineering(ICME)platform.Discrete and finite elem...This paper presents a digital model for the powder metallurgical(PM)production chain of high-performance sintered gears based on an integrated computational materials engineering(ICME)platform.Discrete and finite element methods(DEM and FEM)were combined to describe the macroscopic material response to the thermomechanical loads and process conditions during the entire production process.The microstructural evolution during the sintering process was predicted on the meso-scale using a Monte-Carlo Model.The effective elastic properties were determined by a homogenization method based on modelling a representative volume element(RVE).The results were subsequently used for the FE modelling of the heat treatment process.Through the development of multi-scale models,it was possible obtain characteristics of the microstructural features.The predicted hardness and residual stress distributions allowed the calculation of the tooth root load bearing capacity of the heat-treated sintered gears.展开更多
在多种合理的无信息先验分布下,基于Markov Chain Monte Carlo方法,提出了一种简单且易于抽样的幂律过程的Bayesian分析方法.所提方法将失效、时间截尾数据统一分析,能快捷地获取幂律过程模型参数的Markov Chain Monte Carlo样本,利用...在多种合理的无信息先验分布下,基于Markov Chain Monte Carlo方法,提出了一种简单且易于抽样的幂律过程的Bayesian分析方法.所提方法将失效、时间截尾数据统一分析,能快捷地获取幂律过程模型参数的Markov Chain Monte Carlo样本,利用该样本不但能直接给出模型参数函数的后验分布,还能给出单样预测和双样预测的分析.一个经典工程数值算例说明了所提方法的可行性、合理性与有效性.该方法具有一定的优越性,可为小子样可靠性增长分析提供一种值得参考的方法.展开更多
Without specifying the structure of a time series,we model the distribution of a multivariate Markov process in discrete time by the corresponding multivariate Markov family and the one-dimensional flows of marginal d...Without specifying the structure of a time series,we model the distribution of a multivariate Markov process in discrete time by the corresponding multivariate Markov family and the one-dimensional flows of marginal distributions.Such models tackle simultaneously temporal dependence and contemporaneous dependence between time series.A specific parametric form of stationary copula,namely skew-t copula,is assumed.Skew-t copulas are capable of modeling asymmetry,skewness,and heavy tails.An empirical study with unfiltered daily returns for three stock indices shows that the skew-t copula Markov model provides a better fit than the skew-Normal copula Markov or t-copula Markov model,and the skew-t copula model without Markov property.展开更多
The paper proposes a process-functional model of transportation mix concrete, which is a structured description of a means of transportation technology mix concrete road at the level of the production process. Range o...The paper proposes a process-functional model of transportation mix concrete, which is a structured description of a means of transportation technology mix concrete road at the level of the production process. Range of activities related to the transportation of concrete mixtures is presented in the form of hierarchically nested processes that are coordinated on the basis of general systems theory. The model is described in a strict sequence: process chain→process step→process link, and all built technological chains consist of indivisible units.展开更多
Using control and repairing loops to remove production errors is not the only solution to increase the manufacturing yield. The production of errors can also be directly avoided, prevented or eliminated, even as early...Using control and repairing loops to remove production errors is not the only solution to increase the manufacturing yield. The production of errors can also be directly avoided, prevented or eliminated, even as early as in the planning phase. This paper suggests that the idea of Process Signatures can help to achieve Loopless Production. Loopless Production offers an option to guarantee the production quality towards the vision of the zero-defect manufacturing. It is considered that closed loops are used in a production process chain to identify and to correct the unknown and the systematic errors. These errors can actually be avoided through specifically adjusted or optimal arranged production processes. This puts a higher demand on the understanding of processes, which involve various energy-material interactions. This demand can be met via Process Signatures which aims to develop a process-independent description method of effects of processes. A supportive relationship is foreseen between Process Signatures and Loopless Production. The combination of these two ideas shall allow the simplification of the work for the rationalization of process sequences, the streamlining of closed loops as well as the selection of optimal substitute processes.展开更多
A rice mill survey covering diverse rice processing companies in terms of their milling output, type of technology and year of establishment was conducted to understand the current situation of the rice milling indust...A rice mill survey covering diverse rice processing companies in terms of their milling output, type of technology and year of establishment was conducted to understand the current situation of the rice milling industry and to identify enablers and barriers to its growth in Nepal. Coarse rice varieties dominate Nepal’s rice processing industry, with a 42% share by total weight, followed by medium rice (34%) and fine varieties (less than 7%). Polished white rice (<em>Arwa</em>) was the dominant rice type in Nepal in the survey, followed by parboiled and steamed rice. The price and profit margins increased from coarse to fine rice varieties and from <em>Arwa</em> to parboiled and steamed rice. The cost of milling also followed a similar trend. The rice milling industry in Nepal largely influences the adoption or non-adoption of any specific type of rice variety by dictating specific brands in the market and this has important implications for rice research and development. The rice processing industry of Nepal was unable to compete with the Indian rice milling industry because of: 1) low profit margins due to the high cost of rice production and procurement, 2) a lack of economies of scale, 3) a lack of milling technologies for long and extra-long and steamed rice in the country and a lack of investment to modernize rice milling technology, and 4) unavailability of paddy throughout the year locally. Millers were willing to upgrade their rice milling technology to include high throughput parboiling, steamed rice as well as long and extra-long grain rice. This will be a strategic decision in counteracting the ever-increasing rice imports in Nepal. We believe that the findings of the study will be vital for formulating an appropriate rice research, development and rice processing strategy for Nepal to achieve food and nutritional security and the Sustainable Development Goals.展开更多
基金the National Natural Science Foundation of China(52275378).
文摘The final quality of complex conical-section rings depends on co-design of multiple processes in forming process chain.In this study,for a complex aeroengine casing ring with a large slope and a flange on its end,a co-design method of the forming process chain is put forward towards the objective of precision forming,which not only proposes a standard process route composed of multiple processes of upsetting,punching,rectangular ring rolling,loose tooling forging and profiled ring rolling,but also presents co-design methods of dies and blanks for all the processes.For profiled ring rolling,a design method of preformed blank that makes the blank and the target conical-section ring have the same axial volume distribution is proposed.By the method,the axial metal redistribution during the process can be alleviated greatly thus improving the forming stability and precision of the ring.Based on the geometric features of designed preformed blank,design methods of blanks and dies for loose tolling forging,rectangular ring rolling,punching and upsetting are proposed sequentially.In view of the key roles of loose tooling forging(manufacturing the preformed blank)and profiled ring rolling on the final quality of the conical ring parts,inherited FE simulations for these two processes are performed to verify the proposed design methods and determine appropriate design parameter.It is demonstrated that the proposed design method has significant advantages in improving forming precision.Besides,a suggestive value 1.5 of the rolling ratio for profiled ring rolling(a key design parameter)is given based on comprehensive consideration of multiple indicators such as ring roundness,deformation uniformity and forming load.The corresponding industrial experiments performed illustrate that a high forming precision of the conical-section aeroengine casing ring is achieved.
文摘Rotation sintering, also known as slush molding, is used to manufacture molded skins, such as dashboards or door interior panels for cars. At present, approximately 80% of such molded skins are manufactured using electroforms to achieve the complex free-form surfaces, and surface structures, such as leather graining that the industry demands. The manufacture of these electroforms is, however, time-consuming and expensive. This project aims to replace conventional electroforms with laser-drilled molds. Holes in tool molds should be drilled by using laser radiation as part of an automated process. The system consists of a robot with a fiber-laser beam source. A CAx （computer-aided x） process chain has been developed for this purpose in which the CAD （computer-aided design） data of the tool molds are processed, drill hole fields generated, and a machine-specific RC （robot control） program created. Process-specific fundamentals, such as suitable process windows and process control, have been devised to manufacture holes using fiber laser radiation The advantages of the new laser-drilled tool molds may result in substituting them for conventional electroforms, allowing old markets to be re-entered or additional markets to be created and targeted through new molds or lower costs.
文摘With in-depth development of the Internet of Things(IoT)in various industries,the informatization process of various industries has also entered the fast lane.This article aims to solve the supply chain process problem in e-commerce,focusing on the specific application of Internet of Things technology in e-commerce.Warehousing logistics is an important link in today’s e-commerce transactions.This article proposes a distributed analysis method for RFID-based e-commerce warehousing process optimization and an e-commerce supply chain management process based on Internet of Things technology.This article first introduces the advantages and disadvantages of shared IoT identification technology and the IoT resource sharing platform based on the three-layer abstract data model and representational state transfer(REST)style.Combining actual IoT applications and the characteristics of an existing platform,a REST-based IoT resource sharing platform is proposed.Combined with actual projects,a REST-based IoT resource sharing platform was built,and key technology experiments were conducted for verification.Finally,optimizing the e-commerce supply chain management process under Internet of Things technology and explaining the advantages of optimized e-commerce supply chain management are discussed.Research on this subject provides a theoretical basis for the application of the Internet of Things in e-commerce and has practical significance and practical value for managing service capabilities and service levels in e-commerce.
基金Natural Science Foundation of Guangxi(2017GXNSFAA198082)Guangxi Aquatic Vegetable Fresh-keeping and Processing Engineering Research Center Project(GXSSSCBXYJGZX1912)。
文摘[Objectives]This study was conducted to investigate the effect of compound fresh-keeping liquid on the browning and quality of fresh-cut yam during the cold chain process.[Methods]Under the simulated cold chain condition of 4℃,a uniform design(U6*(64))experiment was carried out to optimize the compound preservative formula,and a better compound preservative formula was obtained using the regression equation.[Results]The compound preservative formula was:AA 0.25%,CA 0.5%,Nisin 0.09%,GSH 0.15%.The compound fresh-keeping liquid effectively delayed the browning of fresh-cut yam and the accumulation of MDA,maintained the content of TSS,inhibited the activity of PAL and delayed the appearance of the maximum activity of POD and POD.[Conclusions]This study provides technical support for the actual extension of the shelf life of fresh-cut yam.
基金supported by the National Science Foundation of China (Grant no. 51408419)the National Key Technology Research and Development Program of China (Grant nos. 2014BAL02B02-03 and 2014BAC29B01)the Key Program for International S&T Cooperation Projects of China (Grant no. 2012DFG91380)
文摘As an important intermediate product, short-chain fatty acids（SCFAs） can be generated after hydrolysis and acidification from waste activated sludge, and then can be transformed to methane during anaerobic digestion process. In order to obtain more SCFA and methane,most studies in literatures were centered on enhancing the hydrolysis of sludge anaerobic digestion which was proved as un-efficient. Though the alkaline pretreatment in our previous study increased both the hydrolysis and acidification processes, it had a vast chemical cost which was considered uneconomical. In this paper, a low energy consumption pretreatment method, i.e. enhanced the whole three stages of the anaerobic fermentation processes at the same time, was reported, by which hydrolysis and acidification were both enhanced, and the SCFA and methane generation can be significantly improved with a small quantity of chemical input. Firstly, the effect of different pretreated temperatures and pretreatment time on sludge hydrolyzation was compared. It was found that sludge pretreated at 100°C for 60 min can achieve the maximal hydrolyzation. Further, effects of different initial p Hs on acidification of the thermal pretreated sludge were investigated and the highest SCFA was observed at initial p H 9.0with fermentation time of 6 d, the production of which was 348.63 mg COD/g VSS（6.8 times higher than the blank test） and the acetic acid was dominant acid. Then, the mechanisms for this new pretreatment significantly improving SCFA production were discussed. Finally,the effect of this low energy consumption pretreatment on methane generation was investigated.
文摘E-supply chain is the trend of the supply chain ma na gement. However, building E-supply chain depends on business process improvemen t and re-engineering, which becomes one of the important aspects in supply chai n management. However, the supply chain process re-engineering and improvement is constrained because of lack of integrating operation framework and standards based on information management. We find that the idea of CALS origins from DoD of USA can solve the problems very well. CALS is the abbreviation of "continues acquisition and life- cycle support". It is an information strategy adopted by many developed counties. The final objective of the CALS is that government a nd industry can generate, exchange, manage and use all the digital information t hroughout the lifecycle of a product in virtue of adopting the international and national standards, improving existing business process and introducing advance d technology. The Integrated Digital Environment (IDE) created by CALS provides a brand new operation mode for consumer, contractor and supplier in supply chain . Besides, a series mutual standard is involved in CALS system. These standards and the standardization technology would be applied widely in the supply chain. This study mainly focuses on supply chain process in CALS environment, and puts forward a framework model of supply chain process. Then the study analyzes the c haracteristics of the model, which includes the application of standards and inf ormation technology, and finally discusses on methods to achieve the supply chai n process in CALS environment.
文摘Through the process analysis of cold chain logistics of agricultural products,we find that cold chain logistics of agricultural products contradict the development model of low-carbon economy to some extent.We apply the development idea of low-carbon economy,introduce the thirdparty logistics companies,establish distribution center of cold chain logistics of agricultural products,and strengthen information sharing,to reengineer the process of cold chain logistics of agricultural products in China.The results show that applying low-carbon economy to process reengineering of cold chain logistics of agricultural products,has advantages of increasing added value of products,promoting scale merit and abating lag,plays a role in promoting emission reduction,high efficiency and environmental protection in the process of cold chain logistics of agricultural products in China.
基金Sponsored by the National High-Tech.R&D Program for CIMS,China(Grant No.2007AA04Z146)
文摘In order to improve the influence of the uncertain and dynamic of node enterprise behavior on the performance of supply chain,the method based on stochastic process algebra for description,analysis,validation and evaluation of supply chain business process model is proposed.Firstly,the description of the uncertainty of node enterprise behavior is given using the extended Unified Modeling Language sequence diagram,and mapping rule is defined from the extended Unified Modeling Language sequence diagram to stochastic process algebra.Secondly,on the basis of the acquired stochastic process algebra model,the supply chain business process model is verified with Mobility Workbench.Finally,according to the operational semantics of stochastic process algebra,the continuous-time Markov chain,isomorphic with stochastic process algebra model,is built; and the system performance evaluation of transient status and stable status is respectively conducted in accordance with Markov transfer relations and the current state of system,obtaining the predicted performance value and average performance index value for a specific period of time.The simulation experiments show that the proposed method can accurately describe the stochastic behaviors of supply chain system and interactions among nodes,effectively verify the validity of the model,and objectively and exactly evaluate design of the supply chain.
基金Supported by the German Research Foundation DFG(Project-ID:390621612)within the Cluster of Excellence Inter-net of Production(IoP).
文摘This paper presents a digital model for the powder metallurgical(PM)production chain of high-performance sintered gears based on an integrated computational materials engineering(ICME)platform.Discrete and finite element methods(DEM and FEM)were combined to describe the macroscopic material response to the thermomechanical loads and process conditions during the entire production process.The microstructural evolution during the sintering process was predicted on the meso-scale using a Monte-Carlo Model.The effective elastic properties were determined by a homogenization method based on modelling a representative volume element(RVE).The results were subsequently used for the FE modelling of the heat treatment process.Through the development of multi-scale models,it was possible obtain characteristics of the microstructural features.The predicted hardness and residual stress distributions allowed the calculation of the tooth root load bearing capacity of the heat-treated sintered gears.
文摘在多种合理的无信息先验分布下,基于Markov Chain Monte Carlo方法,提出了一种简单且易于抽样的幂律过程的Bayesian分析方法.所提方法将失效、时间截尾数据统一分析,能快捷地获取幂律过程模型参数的Markov Chain Monte Carlo样本,利用该样本不但能直接给出模型参数函数的后验分布,还能给出单样预测和双样预测的分析.一个经典工程数值算例说明了所提方法的可行性、合理性与有效性.该方法具有一定的优越性,可为小子样可靠性增长分析提供一种值得参考的方法.
文摘Without specifying the structure of a time series,we model the distribution of a multivariate Markov process in discrete time by the corresponding multivariate Markov family and the one-dimensional flows of marginal distributions.Such models tackle simultaneously temporal dependence and contemporaneous dependence between time series.A specific parametric form of stationary copula,namely skew-t copula,is assumed.Skew-t copulas are capable of modeling asymmetry,skewness,and heavy tails.An empirical study with unfiltered daily returns for three stock indices shows that the skew-t copula Markov model provides a better fit than the skew-Normal copula Markov or t-copula Markov model,and the skew-t copula model without Markov property.
文摘The paper proposes a process-functional model of transportation mix concrete, which is a structured description of a means of transportation technology mix concrete road at the level of the production process. Range of activities related to the transportation of concrete mixtures is presented in the form of hierarchically nested processes that are coordinated on the basis of general systems theory. The model is described in a strict sequence: process chain→process step→process link, and all built technological chains consist of indivisible units.
文摘Using control and repairing loops to remove production errors is not the only solution to increase the manufacturing yield. The production of errors can also be directly avoided, prevented or eliminated, even as early as in the planning phase. This paper suggests that the idea of Process Signatures can help to achieve Loopless Production. Loopless Production offers an option to guarantee the production quality towards the vision of the zero-defect manufacturing. It is considered that closed loops are used in a production process chain to identify and to correct the unknown and the systematic errors. These errors can actually be avoided through specifically adjusted or optimal arranged production processes. This puts a higher demand on the understanding of processes, which involve various energy-material interactions. This demand can be met via Process Signatures which aims to develop a process-independent description method of effects of processes. A supportive relationship is foreseen between Process Signatures and Loopless Production. The combination of these two ideas shall allow the simplification of the work for the rationalization of process sequences, the streamlining of closed loops as well as the selection of optimal substitute processes.
文摘A rice mill survey covering diverse rice processing companies in terms of their milling output, type of technology and year of establishment was conducted to understand the current situation of the rice milling industry and to identify enablers and barriers to its growth in Nepal. Coarse rice varieties dominate Nepal’s rice processing industry, with a 42% share by total weight, followed by medium rice (34%) and fine varieties (less than 7%). Polished white rice (<em>Arwa</em>) was the dominant rice type in Nepal in the survey, followed by parboiled and steamed rice. The price and profit margins increased from coarse to fine rice varieties and from <em>Arwa</em> to parboiled and steamed rice. The cost of milling also followed a similar trend. The rice milling industry in Nepal largely influences the adoption or non-adoption of any specific type of rice variety by dictating specific brands in the market and this has important implications for rice research and development. The rice processing industry of Nepal was unable to compete with the Indian rice milling industry because of: 1) low profit margins due to the high cost of rice production and procurement, 2) a lack of economies of scale, 3) a lack of milling technologies for long and extra-long and steamed rice in the country and a lack of investment to modernize rice milling technology, and 4) unavailability of paddy throughout the year locally. Millers were willing to upgrade their rice milling technology to include high throughput parboiling, steamed rice as well as long and extra-long grain rice. This will be a strategic decision in counteracting the ever-increasing rice imports in Nepal. We believe that the findings of the study will be vital for formulating an appropriate rice research, development and rice processing strategy for Nepal to achieve food and nutritional security and the Sustainable Development Goals.
