This paper presents a control strategy of demand pulled spare parts inventory. It establishes a spare part demand prognosticating model based on reliability analysis. Through parts reliability data the model gets the...This paper presents a control strategy of demand pulled spare parts inventory. It establishes a spare part demand prognosticating model based on reliability analysis. Through parts reliability data the model gets the reliable life function of spare parts and determines parts demand time, depending on part life at given reliabilities. Moreover, a case study is taken to illuminate the demand prognostication and inventory control of on condition maintenance rotables.展开更多
For the cloud computing system,combined wth the memory function and incomplete matching of the biological immune system,a formal modeling and analysis method of the cloud computing system survivability is proposed by ...For the cloud computing system,combined wth the memory function and incomplete matching of the biological immune system,a formal modeling and analysis method of the cloud computing system survivability is proposed by analyzing the survival situation of critical cloud services.First,on the basis of the SAIR(susceptible,active,infected,recovered)model,the SEIRS(susceptible,exposed,infected,recovered,susceptible)model and the vulnerability diffusion model of the distributed virtual system,the evolution state of the virus is divided into six types,and then the diffusion rules of the virus in the service domain of the cloud computing system and the propagation rules between service domains are analyzee.Finally,on the basis of Bio-PEPA(biological-performance evaluation process algebra),the formalized modeling of the survivability evolution of critical cloud services is made,and the SLIRAS(susceptible,latent,infected,recovered,antidotal,susceptible)model is obtained.Based on the stochastic simulation and the ODEs(ordinary differential equations)simulation of the Bio-PEPA model,the sensitivity parameters of the model are analyzed from three aspects,namely,the virus propagation speed of inter-domain,recovery ability and memory ability.The results showthat the proposed model has high approximate fitting degree to the actual cloud computing system,and it can well reflect the survivable change of the system.展开更多
Due to the lack of pre-recognition and post- prediction in existing survivable systems, a recognition model of survival situations for survivable systems is proposed. First, the survival situation data is clustered in...Due to the lack of pre-recognition and post- prediction in existing survivable systems, a recognition model of survival situations for survivable systems is proposed. First, the survival situation data is clustered into several survival clusters with different service levels based on the Ward method, and then the survival clusters are classified and recognized by means of the error-eliminating decision-making method, which can realize the pre-recognition of the system's survival situation. Secondly, the differentiated survival situation data is used to generate stationary predicting sequences. The autoregressive integrated moving average (ARIMA) model is constructed, and the stability, randomness and reversibility index of the model are verified by the auto- correlation function and partial auto-correlation function. Finally, fuzzy particles and the residual correction for the support vector regression (SVR) model are applied to realize the post-prediction of the survival situation. Compared with traditional decision-making methods, the simulation experiments show that the pre-recognition module can not only cluster the survival situation data and identify the service ranks, but can also recognize the illegal users. According to the prediction of abnormal situations numbers and residual correction, the model can effectively realize the post- prediction of survival situations for survivable systems.展开更多
Three kinds of polymeric materials are taken as example for the verification of linear ex-trapolation method from unified master lines with reduced universal equations on creep and stress relaxation tests. The theoret...Three kinds of polymeric materials are taken as example for the verification of linear ex-trapolation method from unified master lines with reduced universal equations on creep and stress relaxation tests. The theoretical values of long-term mechanical behavior and lifetime for a cured epoxide, polypropylene, poly(methyl-methacrylate), and SBR rubber are directly evaluated with the universal equations on reduced creep compliance and reduced stress relax-ation modulus and are compared with their predicted values by the linear extrapolation from the unified master lines of creep and stress relaxation. The results show that the theoretical values of dimensional stability, bearing ability and lifetime are in an excellent agreement with the predicted values, it shows that the linear extrapolation method is more simple and reliable. The dependences of long-term mechanical behaviors and lifetime on the different aging times are discussed.展开更多
As resource scarcity, extreme climate change, and pollution levels increase, economic growth must rely on more environmentally friendly and efficient production processes, Fuel cells are an ideal alternative to intern...As resource scarcity, extreme climate change, and pollution levels increase, economic growth must rely on more environmentally friendly and efficient production processes, Fuel cells are an ideal alternative to internal combustion (IC) engines and boilers on the path to greener industries because of their high effi- ciency and environmentally friendly operation, However, as a new energy technology, significant market penetration of fuel cells has not yet been achieved, In this paper, we perform a techno-economic and environmental analysis of fuel cell systems using life cycle and value chain activities, First, we investigate the procedure of fuel cell development and identify what activities should he undertaken according to fuel cell life cycle activities, value chain activities, and end-user acceptance criteria, Next, we present a unified learning of the institutional barriers in fuel cell commercialization, The primary end-user accep- tance criteria are function, cost, and reliability; a fuel cell should outperform these criteria compared with its competitors, such as IC engines and batteries, to achieve a competitive advantage, The repair and maintenance costs of fuel cells (due to low reliability) can lead to a substantial cost increase and decrease in availability, which are the major factors for end-user acceptance, The fuel cell industry must face the challenge of how to overcome this reliability barrier, This paper provides a deeper insight into our work over the years on the main barriers to fuel cell commercialization, and discusses the potential pivotal role of fuel cells in a future low-carbon green economy, It also identifies the needs and points out some direc- tions for this future low-carbon economy, Green energy, supplied with fuel cells, is truly the business mode of the future, Striving for a more sustainable development of economic growth by adopting green public investments and implementing policy initiatives encourages environmentally responsible indus- trial investments.展开更多
Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper ...Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper studies the low-density parity-check(LDPC) coding scheme for improving the reliability of multi-level-cell(MLC) NAND Flash memory in radiation environments. Firstly, based on existing physical experiment works, we introduce a new error model for heavyion irradiations; secondly, we explore the optimization of writing voltage allocation to maximize the capacity of the storage channel; thirdly, we design the degree distribution of LDPC codes that is specially suitable for the proposed model; finally, we propose a joint detection-decoding scheme based on LDPC codes, which estimates the storage channel state and executes an adaptive log-likelihood ratio(LLR) calculation to achieve better performance. Simulation results show that, compared with the conventional LDPC coding scheme, the proposed scheme may almost double the lifetime of the MLC NAND Flash memory in radiation environments.展开更多
Cloud computing is becoming an important solution for providing scalable computing resources via Internet. Because there are tens of thousands of nodes in data center, the probability of server failures is nontrivial....Cloud computing is becoming an important solution for providing scalable computing resources via Internet. Because there are tens of thousands of nodes in data center, the probability of server failures is nontrivial. Therefore, it is a critical challenge to guarantee the service reliability. Fault-tolerance strategies, such as checkpoint, are commonly employed. Because of the failure of the edge switches, the checkpoint image may become inaccessible. Therefore, current checkpoint-based fault tolerance method cannot achieve the best effect. In this paper, we propose an optimal checkpoint method with edge switch failure-aware. The edge switch failure-aware checkpoint method includes two algorithms. The first algorithm employs the data center topology and communication characteristic for checkpoint image storage server selection. The second algorithm employs the checkpoint image storage characteristic as well as the data center topology to select the recovery server. Simulation experiments are performed to demonstrate the effectiveness of the proposed method.展开更多
In this paper, firstly we study the series ma intenance system with two components, obtain its exsistence and uniqueness of a dynamic state nonnegative solution by strongly continuous semigroups of operator s theory. ...In this paper, firstly we study the series ma intenance system with two components, obtain its exsistence and uniqueness of a dynamic state nonnegative solution by strongly continuous semigroups of operator s theory. Then we prove that 0 is the eigenvalue of the system’s host operators, a nd finally we study the eigenvector of the eigenvalue 0.展开更多
A complete hydatidiform mole coexisting with a fetus following in vitro fertilization and embryo transfer (IVF-ET) is a rare event. The diagnosis is often not easy because of the morphological similarity to a partial ...A complete hydatidiform mole coexisting with a fetus following in vitro fertilization and embryo transfer (IVF-ET) is a rare event. The diagnosis is often not easy because of the morphological similarity to a partial mole, but important to the treatment. We present a recent case in which STR polymorphism analysis clearly revealed a different genetic origin for the fetal and molar parts. STR polymorphisms on 15 variable number tandem repeat loci and a gender-determination locus, which were detected by polymerase chain reaction, indicating that the cord/placenta and molar tissue were parental and androgenous, respectively. During follow-up, the patient developed persistent gestational trophoblastic tumor (GTT) which was successfully treated with chemotherapy. In this case, STR polymorphism analysis exactly diagnosed a twin pregnancy consisting of a complete hydatidiform mole and a fetus.展开更多
In the last decades, there is a lot of discussion in many scientific fields, about the high importance of water as a basic element for the existence and the maintenance of life, aiming to the right and proper usage of...In the last decades, there is a lot of discussion in many scientific fields, about the high importance of water as a basic element for the existence and the maintenance of life, aiming to the right and proper usage of water in our everyday basic water-needs due to its limited resources and the growing demand. This research deals with simple ways and technological systems applicable in urban residential buildings for the better management of domestic fresh water, as far as its maintenance and sustainability. Main aim of the survey is the effective minimization of urban daily water usage. All measurements of water quantities have estimated in the imperial gallon (1 gallon = 4.546 liter), and in liter (1 liter = 0.2 gallon).展开更多
[Objective] The aim was to provide certain theoretical basis for the protection of broccoli. [Method] Exogenous sodium nitroprusside was used to in the experiment. Under the condition of 20 ℃ and RH 95%, the optimal ...[Objective] The aim was to provide certain theoretical basis for the protection of broccoli. [Method] Exogenous sodium nitroprusside was used to in the experiment. Under the condition of 20 ℃ and RH 95%, the optimal SNP concentration of broccoli was determined. [Result] The exogenous SNP could effectively maintain the quality of broccoli, inhabited the yellowing of broccoli and the increasing of cell membrane permeability, and maintain the soluble solids content, decreased the degradation rate of chlorophyll and delayed the loss of VC. [Conclusion] Exogenous sodium nitroprusside can effectively maintain the quality of broccoli to keep it fresh.展开更多
In this paper, a class of non-autonomous functional integro-differential stochastic equations in a real separable Hilbert space is studied. When the operators A(t) satisfy Acquistapace-Terreni conditions, and with s...In this paper, a class of non-autonomous functional integro-differential stochastic equations in a real separable Hilbert space is studied. When the operators A(t) satisfy Acquistapace-Terreni conditions, and with some suitable assumptions, the existence and uniqueness of a square-mean almost periodic mild solution to the equations are obtained.展开更多
Poplar has gained popularity among farmers of Punjab,Haryana,Western Uttar Pradesh,and the foothills of Uttarakhand and Himachal Pradesh due to their fast growth rate and suitability for industrial uses such as pulp a...Poplar has gained popularity among farmers of Punjab,Haryana,Western Uttar Pradesh,and the foothills of Uttarakhand and Himachal Pradesh due to their fast growth rate and suitability for industrial uses such as pulp and timber production.Integrating poplar trees into agroforestry systems optimizes land resources and economic gains,as successful techniques have been developed to coordinate crop timing and arrangements effectively.Integrating poplar trees with agricultural crops provides additional income streams for farmers and contributes to soil conservation,biodiversity enhancement,and other environmental benefits.Farmers in these regions typically employ effective spacing of 5 m×4 m for block plantation and 1 m×3 m for row plantation.In the present study,a systematic literature review encompassing 137 English-language journal articles was conducted to assess the economic benefits of Poplar using discounted cash flow(DCF)analysis,considering short-rotation poplar(SRC)and very short-rotation poplar(vSRC)plantations alongside annual crops.The findings revealed that increasing canopy density led to a decline in crop yields by 37%,70%,and 99% at canopy densities of 30%,60%,and 90%,respectively,from early spring to harvest.Cost-benefit analysis in Saharanpur district,India,indicated average annual net returns of USD 346.36 for Poplar-based agrisilviculture,while monoculture yielded USD 140.73 per annum.Furthermore,economic analysis in Yamunanagar and Haridwar districts showed benefit-cost ratios ranging from 2.35 to 3.7.Additionally,Poplar block and boundary plantations were found to sequester significantly more carbon in long-lived biomass,serving as substitutes for fossil fuels(5.45 and 1.84 t ha-1 yr-1)in poplar-based systems with block and boundary plantations.The study suggested expanding spacing between tree rows may mitigate resource competition between plantations and crops.The study inferred that Poplar-based agroforestry may play a crucial role in climate mitigation programs by effectively sequestering atmospheric carbon and offering fuel,fodder,timber,and wood products,thereby alleviating pressure on existing natural forests.展开更多
The method of the phase plane is emploied to investigate the solitary and periodic traveling waves for a class of nonlinear dispersive partial differential equations.By using the bifurcation theory of dynamical system...The method of the phase plane is emploied to investigate the solitary and periodic traveling waves for a class of nonlinear dispersive partial differential equations.By using the bifurcation theory of dynamical systems to do qualitative analysis,all possible phase portraits in the parametric space for the traveling wave systems are obtained.It can be shown that the existence of a singular straight line in the traveling wave system is the reason why smooth solitary wave solutions converge to solitary cusp wave solution when parameters are varied.The different parameter conditions for the existence of solitary and periodic wave solutions of different kinds are rigorously determined.展开更多
In reliability theory and survival analysis, the problem of point estimation based on the censored sample has been discussed in many literatures. However, most of them are focused on MLE, BLUE etc; little work has bee...In reliability theory and survival analysis, the problem of point estimation based on the censored sample has been discussed in many literatures. However, most of them are focused on MLE, BLUE etc; little work has been done on the moment-method estimation in censoring case. To make the method of moment estimation systematic and unifiable, in this paper, the moment-method estimators(abbr. MEs) and modified momentmethod estimators(abbr. MMEs) of the parameters based on type Ⅰ and type Ⅱ censored samples are put forward involving mean residual lifetime. The strong consistency and other properties are proved. To be worth mentioning, in the exponential distribution,the proposed moment-method estimators are exactly MLEs. By a simulation study, in the view point of bias and mean square of error, we show that the MEs and MMEs are better than MLEs and the “pseudo complete sample” technique introduced in Whitten et al.(1988). And the superiority of the MEs is especially conspicuous, when the sample is heavily censored.展开更多
文摘This paper presents a control strategy of demand pulled spare parts inventory. It establishes a spare part demand prognosticating model based on reliability analysis. Through parts reliability data the model gets the reliable life function of spare parts and determines parts demand time, depending on part life at given reliabilities. Moreover, a case study is taken to illuminate the demand prognostication and inventory control of on condition maintenance rotables.
基金The National Natural Science Foundation of China(No.61202458,61403109)the Natural Science Foundation of Heilongjiang Province of China(No.F2017021)Harbin Science and Technology Innovation Research Funds(No.2016RAQXJ036)
文摘For the cloud computing system,combined wth the memory function and incomplete matching of the biological immune system,a formal modeling and analysis method of the cloud computing system survivability is proposed by analyzing the survival situation of critical cloud services.First,on the basis of the SAIR(susceptible,active,infected,recovered)model,the SEIRS(susceptible,exposed,infected,recovered,susceptible)model and the vulnerability diffusion model of the distributed virtual system,the evolution state of the virus is divided into six types,and then the diffusion rules of the virus in the service domain of the cloud computing system and the propagation rules between service domains are analyzee.Finally,on the basis of Bio-PEPA(biological-performance evaluation process algebra),the formalized modeling of the survivability evolution of critical cloud services is made,and the SLIRAS(susceptible,latent,infected,recovered,antidotal,susceptible)model is obtained.Based on the stochastic simulation and the ODEs(ordinary differential equations)simulation of the Bio-PEPA model,the sensitivity parameters of the model are analyzed from three aspects,namely,the virus propagation speed of inter-domain,recovery ability and memory ability.The results showthat the proposed model has high approximate fitting degree to the actual cloud computing system,and it can well reflect the survivable change of the system.
基金The National Natural Science Foundation of China(No.61202458,61403109)the Natural Science Foundation of Heilongjiang Province(No.F2017021)Harbin Science and Technology Innovation Research Funds(No.2016RAQXJ036)
文摘Due to the lack of pre-recognition and post- prediction in existing survivable systems, a recognition model of survival situations for survivable systems is proposed. First, the survival situation data is clustered into several survival clusters with different service levels based on the Ward method, and then the survival clusters are classified and recognized by means of the error-eliminating decision-making method, which can realize the pre-recognition of the system's survival situation. Secondly, the differentiated survival situation data is used to generate stationary predicting sequences. The autoregressive integrated moving average (ARIMA) model is constructed, and the stability, randomness and reversibility index of the model are verified by the auto- correlation function and partial auto-correlation function. Finally, fuzzy particles and the residual correction for the support vector regression (SVR) model are applied to realize the post-prediction of the survival situation. Compared with traditional decision-making methods, the simulation experiments show that the pre-recognition module can not only cluster the survival situation data and identify the service ranks, but can also recognize the illegal users. According to the prediction of abnormal situations numbers and residual correction, the model can effectively realize the post- prediction of survival situations for survivable systems.
基金This work was supported by the National Natural Science Foundation of China (No.50973007).
文摘Three kinds of polymeric materials are taken as example for the verification of linear ex-trapolation method from unified master lines with reduced universal equations on creep and stress relaxation tests. The theoretical values of long-term mechanical behavior and lifetime for a cured epoxide, polypropylene, poly(methyl-methacrylate), and SBR rubber are directly evaluated with the universal equations on reduced creep compliance and reduced stress relax-ation modulus and are compared with their predicted values by the linear extrapolation from the unified master lines of creep and stress relaxation. The results show that the theoretical values of dimensional stability, bearing ability and lifetime are in an excellent agreement with the predicted values, it shows that the linear extrapolation method is more simple and reliable. The dependences of long-term mechanical behaviors and lifetime on the different aging times are discussed.
基金the Ministry of Economic Development and Trade of Government of Alberta for the Campus Alberta Innovation Program (CAIP) Research Chair (RCP-12-001BCAIP)
文摘As resource scarcity, extreme climate change, and pollution levels increase, economic growth must rely on more environmentally friendly and efficient production processes, Fuel cells are an ideal alternative to internal combustion (IC) engines and boilers on the path to greener industries because of their high effi- ciency and environmentally friendly operation, However, as a new energy technology, significant market penetration of fuel cells has not yet been achieved, In this paper, we perform a techno-economic and environmental analysis of fuel cell systems using life cycle and value chain activities, First, we investigate the procedure of fuel cell development and identify what activities should he undertaken according to fuel cell life cycle activities, value chain activities, and end-user acceptance criteria, Next, we present a unified learning of the institutional barriers in fuel cell commercialization, The primary end-user accep- tance criteria are function, cost, and reliability; a fuel cell should outperform these criteria compared with its competitors, such as IC engines and batteries, to achieve a competitive advantage, The repair and maintenance costs of fuel cells (due to low reliability) can lead to a substantial cost increase and decrease in availability, which are the major factors for end-user acceptance, The fuel cell industry must face the challenge of how to overcome this reliability barrier, This paper provides a deeper insight into our work over the years on the main barriers to fuel cell commercialization, and discusses the potential pivotal role of fuel cells in a future low-carbon green economy, It also identifies the needs and points out some direc- tions for this future low-carbon economy, Green energy, supplied with fuel cells, is truly the business mode of the future, Striving for a more sustainable development of economic growth by adopting green public investments and implementing policy initiatives encourages environmentally responsible indus- trial investments.
基金supported by the National Basic Research Project of China(973)(2013CB329006)National Natural Science Foundation of China(NSFC,91538203)the new strategic industries development projects of Shenzhen City(JCYJ20150403155812833)
文摘Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper studies the low-density parity-check(LDPC) coding scheme for improving the reliability of multi-level-cell(MLC) NAND Flash memory in radiation environments. Firstly, based on existing physical experiment works, we introduce a new error model for heavyion irradiations; secondly, we explore the optimization of writing voltage allocation to maximize the capacity of the storage channel; thirdly, we design the degree distribution of LDPC codes that is specially suitable for the proposed model; finally, we propose a joint detection-decoding scheme based on LDPC codes, which estimates the storage channel state and executes an adaptive log-likelihood ratio(LLR) calculation to achieve better performance. Simulation results show that, compared with the conventional LDPC coding scheme, the proposed scheme may almost double the lifetime of the MLC NAND Flash memory in radiation environments.
基金supported by Beijing Natural Science Foundation (4174100)NSFC(61602054)the Fundamental Research Funds for the Central Universities
文摘Cloud computing is becoming an important solution for providing scalable computing resources via Internet. Because there are tens of thousands of nodes in data center, the probability of server failures is nontrivial. Therefore, it is a critical challenge to guarantee the service reliability. Fault-tolerance strategies, such as checkpoint, are commonly employed. Because of the failure of the edge switches, the checkpoint image may become inaccessible. Therefore, current checkpoint-based fault tolerance method cannot achieve the best effect. In this paper, we propose an optimal checkpoint method with edge switch failure-aware. The edge switch failure-aware checkpoint method includes two algorithms. The first algorithm employs the data center topology and communication characteristic for checkpoint image storage server selection. The second algorithm employs the checkpoint image storage characteristic as well as the data center topology to select the recovery server. Simulation experiments are performed to demonstrate the effectiveness of the proposed method.
文摘In this paper, firstly we study the series ma intenance system with two components, obtain its exsistence and uniqueness of a dynamic state nonnegative solution by strongly continuous semigroups of operator s theory. Then we prove that 0 is the eigenvalue of the system’s host operators, a nd finally we study the eigenvector of the eigenvalue 0.
基金Supported by Production and Rresearch Projects of Guangdong Province (2007B090400140)
文摘A complete hydatidiform mole coexisting with a fetus following in vitro fertilization and embryo transfer (IVF-ET) is a rare event. The diagnosis is often not easy because of the morphological similarity to a partial mole, but important to the treatment. We present a recent case in which STR polymorphism analysis clearly revealed a different genetic origin for the fetal and molar parts. STR polymorphisms on 15 variable number tandem repeat loci and a gender-determination locus, which were detected by polymerase chain reaction, indicating that the cord/placenta and molar tissue were parental and androgenous, respectively. During follow-up, the patient developed persistent gestational trophoblastic tumor (GTT) which was successfully treated with chemotherapy. In this case, STR polymorphism analysis exactly diagnosed a twin pregnancy consisting of a complete hydatidiform mole and a fetus.
文摘In the last decades, there is a lot of discussion in many scientific fields, about the high importance of water as a basic element for the existence and the maintenance of life, aiming to the right and proper usage of water in our everyday basic water-needs due to its limited resources and the growing demand. This research deals with simple ways and technological systems applicable in urban residential buildings for the better management of domestic fresh water, as far as its maintenance and sustainability. Main aim of the survey is the effective minimization of urban daily water usage. All measurements of water quantities have estimated in the imperial gallon (1 gallon = 4.546 liter), and in liter (1 liter = 0.2 gallon).
基金Supported by National Vegetable Industry System Construction
文摘[Objective] The aim was to provide certain theoretical basis for the protection of broccoli. [Method] Exogenous sodium nitroprusside was used to in the experiment. Under the condition of 20 ℃ and RH 95%, the optimal SNP concentration of broccoli was determined. [Result] The exogenous SNP could effectively maintain the quality of broccoli, inhabited the yellowing of broccoli and the increasing of cell membrane permeability, and maintain the soluble solids content, decreased the degradation rate of chlorophyll and delayed the loss of VC. [Conclusion] Exogenous sodium nitroprusside can effectively maintain the quality of broccoli to keep it fresh.
基金Acknowledgement This article is funded by the National Natural Science Foundation of China (11161052), Guangxi Natural Science Foundation of China (201 ljjA10044) and Guangxi Education Hall Project (201012MS183)
文摘In this paper, a class of non-autonomous functional integro-differential stochastic equations in a real separable Hilbert space is studied. When the operators A(t) satisfy Acquistapace-Terreni conditions, and with some suitable assumptions, the existence and uniqueness of a square-mean almost periodic mild solution to the equations are obtained.
文摘Poplar has gained popularity among farmers of Punjab,Haryana,Western Uttar Pradesh,and the foothills of Uttarakhand and Himachal Pradesh due to their fast growth rate and suitability for industrial uses such as pulp and timber production.Integrating poplar trees into agroforestry systems optimizes land resources and economic gains,as successful techniques have been developed to coordinate crop timing and arrangements effectively.Integrating poplar trees with agricultural crops provides additional income streams for farmers and contributes to soil conservation,biodiversity enhancement,and other environmental benefits.Farmers in these regions typically employ effective spacing of 5 m×4 m for block plantation and 1 m×3 m for row plantation.In the present study,a systematic literature review encompassing 137 English-language journal articles was conducted to assess the economic benefits of Poplar using discounted cash flow(DCF)analysis,considering short-rotation poplar(SRC)and very short-rotation poplar(vSRC)plantations alongside annual crops.The findings revealed that increasing canopy density led to a decline in crop yields by 37%,70%,and 99% at canopy densities of 30%,60%,and 90%,respectively,from early spring to harvest.Cost-benefit analysis in Saharanpur district,India,indicated average annual net returns of USD 346.36 for Poplar-based agrisilviculture,while monoculture yielded USD 140.73 per annum.Furthermore,economic analysis in Yamunanagar and Haridwar districts showed benefit-cost ratios ranging from 2.35 to 3.7.Additionally,Poplar block and boundary plantations were found to sequester significantly more carbon in long-lived biomass,serving as substitutes for fossil fuels(5.45 and 1.84 t ha-1 yr-1)in poplar-based systems with block and boundary plantations.The study suggested expanding spacing between tree rows may mitigate resource competition between plantations and crops.The study inferred that Poplar-based agroforestry may play a crucial role in climate mitigation programs by effectively sequestering atmospheric carbon and offering fuel,fodder,timber,and wood products,thereby alleviating pressure on existing natural forests.
基金National Natural Science Foundation of China(No.19731003,No.19961003)Yunnan Provincial Natural Science Foundation of China(No.1999A0018M,No.2000A0002M)
文摘The method of the phase plane is emploied to investigate the solitary and periodic traveling waves for a class of nonlinear dispersive partial differential equations.By using the bifurcation theory of dynamical systems to do qualitative analysis,all possible phase portraits in the parametric space for the traveling wave systems are obtained.It can be shown that the existence of a singular straight line in the traveling wave system is the reason why smooth solitary wave solutions converge to solitary cusp wave solution when parameters are varied.The different parameter conditions for the existence of solitary and periodic wave solutions of different kinds are rigorously determined.
基金This research is partially supported by National Science Foundation of China (No. 69971016).
文摘In reliability theory and survival analysis, the problem of point estimation based on the censored sample has been discussed in many literatures. However, most of them are focused on MLE, BLUE etc; little work has been done on the moment-method estimation in censoring case. To make the method of moment estimation systematic and unifiable, in this paper, the moment-method estimators(abbr. MEs) and modified momentmethod estimators(abbr. MMEs) of the parameters based on type Ⅰ and type Ⅱ censored samples are put forward involving mean residual lifetime. The strong consistency and other properties are proved. To be worth mentioning, in the exponential distribution,the proposed moment-method estimators are exactly MLEs. By a simulation study, in the view point of bias and mean square of error, we show that the MEs and MMEs are better than MLEs and the “pseudo complete sample” technique introduced in Whitten et al.(1988). And the superiority of the MEs is especially conspicuous, when the sample is heavily censored.