首页 > 最新文献

Science Journal of Applied Mathematics and Statistics最新文献

英文 中文
Assessing the Impacts of Farm-investment on Farmer’s Quality of Life in Near to Woldia Town, North Wollo Ethiopia 评估农业投资对埃塞俄比亚北沃罗沃尔迪亚镇附近农民生活质量的影响
Pub Date : 2021-07-24 DOI: 10.11648/J.SJAMS.20210903.13
Bantie Getnet, Kinfe Gebrekrstos, Lidet Dereje
In Ethiopia, small scale farmers contribute about 80% of the total population of the country and their land holding and also small, that farmer cannot allow the land to stay follow. Some developing region in the country is not fully benefit from the opportunities that can be generated by farm investment project. The study investigates the quality of life of people in near to Woldia town. The main objective of this study was to assess the impact of farm-investment on farmers’ quality of life in near to Woldia town. The appropriate methodology to meet sample size in this study was obtained by using simple random sampling techniques which gives equal chance to every members of population to be selected as a sample. The data was analyzed by using both descriptive and inferential statistics. And the model used for this study was binary logistic regression used to analysis the inferential statistics. And also chi-square used for testing association between dependent and independent variables like gender, marital status, family income, and occupation. This study also identifies gender, occupation, family income; marital status and educational level have impact on quality of life. Finally, the study recommended that the advantage of investments for farmers such as employment opportunities, construction of different social services like school, health center, and economic development to bring a families good quality of life.
在埃塞俄比亚,小农约占该国总人口的80%,他们的土地拥有量也很小,农民不能让土地跟着走。该国一些发展中地区没有充分受益于农业投资项目可能产生的机会。这项研究调查了沃尔迪亚镇附近居民的生活质量。本研究的主要目的是评估农业投资对沃尔迪亚镇附近农民生活质量的影响。适当的方法,以满足本研究的样本量是通过使用简单的随机抽样技术,使人口的每一个成员都有平等的机会被选为一个样本。采用描述性统计和推理统计对数据进行分析。本研究采用二元逻辑回归模型进行推理统计分析。卡方也用于检验因变量和自变量之间的关联,如性别、婚姻状况、家庭收入和职业。该研究还识别了性别、职业、家庭收入;婚姻状况和受教育程度对生活质量有影响。最后,研究建议,投资对农民的优势,如就业机会,建设不同的社会服务,如学校,卫生中心,和经济发展,给家庭带来良好的生活质量。
{"title":"Assessing the Impacts of Farm-investment on Farmer’s Quality of Life in Near to Woldia Town, North Wollo Ethiopia","authors":"Bantie Getnet, Kinfe Gebrekrstos, Lidet Dereje","doi":"10.11648/J.SJAMS.20210903.13","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210903.13","url":null,"abstract":"In Ethiopia, small scale farmers contribute about 80% of the total population of the country and their land holding and also small, that farmer cannot allow the land to stay follow. Some developing region in the country is not fully benefit from the opportunities that can be generated by farm investment project. The study investigates the quality of life of people in near to Woldia town. The main objective of this study was to assess the impact of farm-investment on farmers’ quality of life in near to Woldia town. The appropriate methodology to meet sample size in this study was obtained by using simple random sampling techniques which gives equal chance to every members of population to be selected as a sample. The data was analyzed by using both descriptive and inferential statistics. And the model used for this study was binary logistic regression used to analysis the inferential statistics. And also chi-square used for testing association between dependent and independent variables like gender, marital status, family income, and occupation. This study also identifies gender, occupation, family income; marital status and educational level have impact on quality of life. Finally, the study recommended that the advantage of investments for farmers such as employment opportunities, construction of different social services like school, health center, and economic development to bring a families good quality of life.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124847958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On Bayesian Estimation of Loss and Risk Functions 损失和风险函数的贝叶斯估计
Pub Date : 2021-06-26 DOI: 10.11648/J.SJAMS.20210903.11
Randhir Singh
Loss functions and Risk functions play very important role in Bayesian estimation. This paper aims at the Bayesian estimation for the loss and risk functions of the unknown parameter of the H(r, theta), (theta being the unknown parameter) distribution The estimation has been performed under Rukhin’s loss function. The importance of this distribution is that it contains some important distributions such as the Half Normal distribution, Rayleigh distribution and Maxwell’s distribution as particular cases. The inverse Gamma distribution has assumed as the prior distribution for the unknown parameter theta. This prior distribution is a Natural Conjugate prior distribution for the unknown parameter because the posterior probability density function of the unknown parameter is also inverse gamma distribution The Rukhin’s loss function involves another loss function denoted by w(theta, delta) he form of w(theta, delta) is important as it changes the estimate. In this paper, three forms of w(theta, delta) have been taken and corresponding estimates have been derived. The three, forms are, the Squared Error Loss Function (SELF) and two different forms of Weighted Squared Error Loss Function (WSELF) namely, the Minimum Expected Loss (MELO) Function and the Exponentially Weighted Minimum Expected Loss (EWMELO) Function have been considered. A criterion of performance of various form of w(theta, delta) has ben defined. It has been proved that among three forms of w(theta, delta), considered here, the form corresponding to EWMELO is most dominant.
损失函数和风险函数在贝叶斯估计中起着非常重要的作用。本文针对H(r, theta), (theta为未知参数)分布的未知参数的损失和风险函数的贝叶斯估计,在Rukhin损失函数下进行了估计。这种分布的重要性在于它包含了一些重要的分布,如半正态分布、瑞利分布和麦克斯韦分布作为特殊情况。逆分布被假定为未知参数的先验分布。这个先验分布是未知参数的自然共轭先验分布,因为未知参数的后验概率密度函数也是逆分布。Rukhin的损失函数涉及另一个损失函数,表示为w(θ, δ) w(θ, δ)的形式很重要,因为它改变了估计。本文采用了w(theta, delta)的三种形式,并推导了相应的估计。考虑了三种形式,即平方误差损失函数(SELF)和两种不同形式的加权平方误差损失函数(WSELF),即最小期望损失(MELO)函数和指数加权最小期望损失(EWMELO)函数。定义了各种形式w(θ, δ)的性能准则。已经证明,在这里考虑的w(theta, delta)的三种形式中,与EWMELO相对应的形式是最占优势的。
{"title":"On Bayesian Estimation of Loss and Risk Functions","authors":"Randhir Singh","doi":"10.11648/J.SJAMS.20210903.11","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210903.11","url":null,"abstract":"Loss functions and Risk functions play very important role in Bayesian estimation. This paper aims at the Bayesian estimation for the loss and risk functions of the unknown parameter of the H(r, theta), (theta being the unknown parameter) distribution The estimation has been performed under Rukhin’s loss function. The importance of this distribution is that it contains some important distributions such as the Half Normal distribution, Rayleigh distribution and Maxwell’s distribution as particular cases. The inverse Gamma distribution has assumed as the prior distribution for the unknown parameter theta. This prior distribution is a Natural Conjugate prior distribution for the unknown parameter because the posterior probability density function of the unknown parameter is also inverse gamma distribution The Rukhin’s loss function involves another loss function denoted by w(theta, delta) he form of w(theta, delta) is important as it changes the estimate. In this paper, three forms of w(theta, delta) have been taken and corresponding estimates have been derived. The three, forms are, the Squared Error Loss Function (SELF) and two different forms of Weighted Squared Error Loss Function (WSELF) namely, the Minimum Expected Loss (MELO) Function and the Exponentially Weighted Minimum Expected Loss (EWMELO) Function have been considered. A criterion of performance of various form of w(theta, delta) has ben defined. It has been proved that among three forms of w(theta, delta), considered here, the form corresponding to EWMELO is most dominant.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125043430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
A Comparison of the Lehmann and GLM ROC Models Lehmann和GLM ROC模型的比较
Pub Date : 2021-05-07 DOI: 10.11648/J.SJAMS.20210902.13
Melissa Innerst, J. Tubbs, M. Ghebremichael
Recently, several regression methods have been developed to model the receiver operating characteristic curve (ROC), as a measure of accuracy for potential biomarker use in diagnostic testing and disease detection. In this paper, we investigate the Lehmann ROC regression model and compare it to more commonly used ROC regression methods that are found in the literature. The comparative performance of the methods are evaluated using simulated data from the normal, extreme value, and the Weibull distributions. Theory suggests that the Lehmann method should only work well when using the Weibull distribution. Our simulation results suggest that the performance of these methods is more complicated than the theory might suggest. The methods were demonstrated using data from a study concerning the clinical effectiveness of leukocyte elastase determination in the diagnosis of coronary artery disease (CAD).
最近,已经开发了几种回归方法来模拟受试者工作特征曲线(ROC),作为在诊断测试和疾病检测中潜在生物标志物使用的准确性度量。在本文中,我们研究了Lehmann ROC回归模型,并将其与文献中更常用的ROC回归方法进行比较。使用来自正态分布、极值分布和威布尔分布的模拟数据对方法的比较性能进行了评估。理论表明,莱曼方法只有在使用威布尔分布时才有效。我们的模拟结果表明,这些方法的性能比理论所暗示的要复杂得多。这些方法是用一项关于白细胞弹性酶测定在冠状动脉疾病(CAD)诊断中的临床有效性的研究数据来证明的。
{"title":"A Comparison of the Lehmann and GLM ROC Models","authors":"Melissa Innerst, J. Tubbs, M. Ghebremichael","doi":"10.11648/J.SJAMS.20210902.13","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210902.13","url":null,"abstract":"Recently, several regression methods have been developed to model the receiver operating characteristic curve (ROC), as a measure of accuracy for potential biomarker use in diagnostic testing and disease detection. In this paper, we investigate the Lehmann ROC regression model and compare it to more commonly used ROC regression methods that are found in the literature. The comparative performance of the methods are evaluated using simulated data from the normal, extreme value, and the Weibull distributions. Theory suggests that the Lehmann method should only work well when using the Weibull distribution. Our simulation results suggest that the performance of these methods is more complicated than the theory might suggest. The methods were demonstrated using data from a study concerning the clinical effectiveness of leukocyte elastase determination in the diagnosis of coronary artery disease (CAD).","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"150 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115114238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Estimating the Parameters of (POGE-G) Distribution and Its Application to Egyptian Mortality Rates 估计(POGE-G)分布参数及其在埃及死亡率中的应用
Pub Date : 2021-03-30 DOI: 10.11648/J.SJAMS.20210902.12
A. Mohamed, A. Elghany, Gamalat Elgabry
In this paper, we consider power odd generalized exponential-Gompertz (POGE-G) distribution which is capable of life tables to calculate death rates (failure). Based on simulated data from the PPOGE-G distribution, we consider the problem of estimation of parameters under classical approaches and Bayesian approaches. In this regard, we obtain maximum likelihood (ML) estimates, maximum product of spacing (MPS) and Bayes estimates under squared error loss function. We also compute 95% asymptotic confidence interval and highest posterior density interval estimates. The Monte Carlo simulation will be conduct to study and compare the performance of the various proposed estimators (simulation study indicates that the performance of MPS estimates is better MLE estimates and the performance of Bayes estimates is also better). Finally, application of a real data from the projections of the future population for the total of the Egyptian Arabic Republic for the period 2017-2052, depending on the book which introduced from the central agency for public mobilization and statistics in Feb (2019) from this application it could be said that this distributions can be applied to mortality rate data set. The present paper can also be extended to design of progressive censoring sampling plan and other censoring schemes can also be considered.
本文考虑幂奇广义指数- gompertz (POGE-G)分布,该分布能够用生命表计算死亡率(失效率)。基于PPOGE-G分布的模拟数据,研究了经典方法和贝叶斯方法下的参数估计问题。在这方面,我们得到了误差平方损失函数下的最大似然估计(ML)、最大间距积(MPS)和贝叶斯估计。我们还计算了95%渐近置信区间和最高后验密度区间估计。将进行蒙特卡罗仿真来研究和比较各种提出的估计器的性能(仿真研究表明MPS估计的性能优于MLE估计,贝叶斯估计的性能也优于MLE估计)。最后,根据公共动员和统计中央机构(2019年2月)从这一应用中介绍的书籍,应用了2017-2052年期间阿拉伯埃及共和国未来人口总数预测的实际数据,可以说,这种分布可以应用于死亡率数据集。本文也可推广到渐进式滤波采样方案的设计,并可考虑其它滤波方案。
{"title":"Estimating the Parameters of (POGE-G) Distribution and Its Application to Egyptian Mortality Rates","authors":"A. Mohamed, A. Elghany, Gamalat Elgabry","doi":"10.11648/J.SJAMS.20210902.12","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210902.12","url":null,"abstract":"In this paper, we consider power odd generalized exponential-Gompertz (POGE-G) distribution which is capable of life tables to calculate death rates (failure). Based on simulated data from the PPOGE-G distribution, we consider the problem of estimation of parameters under classical approaches and Bayesian approaches. In this regard, we obtain maximum likelihood (ML) estimates, maximum product of spacing (MPS) and Bayes estimates under squared error loss function. We also compute 95% asymptotic confidence interval and highest posterior density interval estimates. The Monte Carlo simulation will be conduct to study and compare the performance of the various proposed estimators (simulation study indicates that the performance of MPS estimates is better MLE estimates and the performance of Bayes estimates is also better). Finally, application of a real data from the projections of the future population for the total of the Egyptian Arabic Republic for the period 2017-2052, depending on the book which introduced from the central agency for public mobilization and statistics in Feb (2019) from this application it could be said that this distributions can be applied to mortality rate data set. The present paper can also be extended to design of progressive censoring sampling plan and other censoring schemes can also be considered.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"17 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133408611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Analyzing the Economic Development Using Partial Least Square Structural Model: A Case of Narok, Kenya 用偏最小二乘结构模型分析经济发展——以肯尼亚纳罗克为例
Pub Date : 2021-03-17 DOI: 10.11648/J.SJAMS.20210902.11
Otieno Okumu Kevin, Samuel Muthiga Nganga
After the establishment of the Narok County government and the transition from the central system of government into the Devolved system of governance, majority of the residents of Narok County had much anticipation in terms of developments that will take place as a result of governance being brought close to them. The study was checking economic development changes that has taken place in Narok Town the Headquarter of Narok County since the establishment of the Narok County Government. The objective was to access how the introduction of county government has impacted on the economic development by investigating its impact on the various key indicators of the economic development such as health, trade, and infrastructure. The study used a sample of 320 residents drawn at random from all parts of the town, the samples was surveyed using a written survey instrument and their opinion on the state of various economic indicators was captured and used to develop a structural equation model using SmartPLS 3 software, in order to use in examining the economic development status of Narok Town. The study fits a significant model that can tell the whereabouts of the economic status of the Town presently and in future. It was concluded that the county government has not done much in terms of economic development since the introduction of County government because the rural areas in the county are still struggling to catch up with the indicators of economic development. It was also evidenced that the impact of County government on trade is good compared to its impact on health and infrastructure.
纳罗克县政府成立后,从中央政府体制向地方政府体制过渡,纳罗克县的大多数居民对政府离他们更近的治理所带来的发展充满了期待。该研究旨在检查纳罗克县总部纳罗克镇自纳罗克县政府成立以来发生的经济发展变化。目的是通过调查县政府对卫生、贸易和基础设施等经济发展的各种关键指标的影响,了解县政府的引入对经济发展的影响。该研究使用了从城镇所有部分随机抽取的320名居民的样本,使用书面调查工具对样本进行了调查,并使用SmartPLS 3软件捕获了他们对各种经济指标状态的意见,并用于开发结构方程模型,以便用于检查纳罗克镇的经济发展状况。该研究符合一个重要的模型,可以告诉城镇的经济地位,目前和未来的去向。结论是县政府成立以来,县政府在经济发展方面做得并不多,因为县内农村经济发展指标仍在追赶上。还有证据表明,县政府对贸易的影响比其对卫生和基础设施的影响要好。
{"title":"Analyzing the Economic Development Using Partial Least Square Structural Model: A Case of Narok, Kenya","authors":"Otieno Okumu Kevin, Samuel Muthiga Nganga","doi":"10.11648/J.SJAMS.20210902.11","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210902.11","url":null,"abstract":"After the establishment of the Narok County government and the transition from the central system of government into the Devolved system of governance, majority of the residents of Narok County had much anticipation in terms of developments that will take place as a result of governance being brought close to them. The study was checking economic development changes that has taken place in Narok Town the Headquarter of Narok County since the establishment of the Narok County Government. The objective was to access how the introduction of county government has impacted on the economic development by investigating its impact on the various key indicators of the economic development such as health, trade, and infrastructure. The study used a sample of 320 residents drawn at random from all parts of the town, the samples was surveyed using a written survey instrument and their opinion on the state of various economic indicators was captured and used to develop a structural equation model using SmartPLS 3 software, in order to use in examining the economic development status of Narok Town. The study fits a significant model that can tell the whereabouts of the economic status of the Town presently and in future. It was concluded that the county government has not done much in terms of economic development since the introduction of County government because the rural areas in the county are still struggling to catch up with the indicators of economic development. It was also evidenced that the impact of County government on trade is good compared to its impact on health and infrastructure.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115007640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Nonparametric Penalized Spline Model Calibrated Estimator in Complex Survey with Known Auxiliary Information at Both Cluster and Element Levels 复杂测量中辅助信息已知的非参数惩罚样条模型校正估计
Pub Date : 2021-03-10 DOI: 10.11648/J.SJAMS.20210901.13
Nthiwa Janiffer Mwende, A. Islam, Pius Nderitu Kihara
The present study uses penalized splines (p- spline) to estimate the functional relationship between the survey variable and the auxiliary variable in a complex survey design; where a population divided into clusters is in turn subdivided into strata. This study has considered a case of auxiliary information present at two levels; at both cluster and element levels. The study further, applied model calibration technique by penalty function to estimate population total. The calibration problems at both levels have been treated as optimization problems and solving by the method of penalty functions so as to derive the estimators for this study. The reasoning behind the use of model calibration is that if the calibration constraints are satisfied by the auxiliary variable, then the study expects that the fitted values of the variable of interest satisfies such constraints too. This study run a Monte Carlo simulation to assess the finite sample performance of the penalized spline model calibrated estimator under complex survey data. Simulation studies were conducted to compare the efficiency of p-spline model calibrated estimator with Horvitz Thompson estimator (HT) by mean squared error (MSE) criterion. This study shows that the p-spline model-based estimator is generally more efficient than the HT in terms of the mean squared error. The results have also shown that the estimator obtained is unbiased, consistent and very robust because it does not fail in the event the model is misspecified for the data.
本研究使用惩罚样条(p样条)来估计复杂调查设计中调查变量和辅助变量之间的函数关系;一个被划分成集群的人口又被细分成阶层。本研究考虑了辅助信息存在于两个层面的情况;在集群和元素级别。在此基础上,应用罚函数模型标定技术估计种群总数。将这两个层次的标定问题作为优化问题,用罚函数法求解,从而推导出本研究的估计量。使用模型校准的原因是,如果辅助变量满足校准约束,那么研究期望感兴趣变量的拟合值也满足这些约束。本研究运行蒙特卡罗模拟来评估在复杂调查数据下惩罚样条模型校准估计器的有限样本性能。采用均方误差(MSE)准则对p样条模型校正估计器与Horvitz Thompson估计器(HT)的效率进行了仿真研究。本研究表明,基于p样条模型的估计器在均方误差方面通常比HT更有效。结果还表明,所获得的估计量是无偏的,一致的,并且非常稳健,因为它不会在模型对数据的错误指定的情况下失败。
{"title":"Nonparametric Penalized Spline Model Calibrated Estimator in Complex Survey with Known Auxiliary Information at Both Cluster and Element Levels","authors":"Nthiwa Janiffer Mwende, A. Islam, Pius Nderitu Kihara","doi":"10.11648/J.SJAMS.20210901.13","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210901.13","url":null,"abstract":"The present study uses penalized splines (p- spline) to estimate the functional relationship between the survey variable and the auxiliary variable in a complex survey design; where a population divided into clusters is in turn subdivided into strata. This study has considered a case of auxiliary information present at two levels; at both cluster and element levels. The study further, applied model calibration technique by penalty function to estimate population total. The calibration problems at both levels have been treated as optimization problems and solving by the method of penalty functions so as to derive the estimators for this study. The reasoning behind the use of model calibration is that if the calibration constraints are satisfied by the auxiliary variable, then the study expects that the fitted values of the variable of interest satisfies such constraints too. This study run a Monte Carlo simulation to assess the finite sample performance of the penalized spline model calibrated estimator under complex survey data. Simulation studies were conducted to compare the efficiency of p-spline model calibrated estimator with Horvitz Thompson estimator (HT) by mean squared error (MSE) criterion. This study shows that the p-spline model-based estimator is generally more efficient than the HT in terms of the mean squared error. The results have also shown that the estimator obtained is unbiased, consistent and very robust because it does not fail in the event the model is misspecified for the data.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114426827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Constant Stress Partially Accelerated Life Tests for Extended Generalized log Logistic Distribution Based on Type I Censored Competing Risks Data 基于I型删节竞争风险数据的扩展广义对数Logistic分布恒应力部分加速寿命试验
Pub Date : 2021-02-23 DOI: 10.11648/J.SJAMS.20210901.12
Elgabry Gamalat, Rezk Hoda
As a result of technology improvement getting information about products and materials lifetimes under usual conditions. Therefore accelerated life testing or partially accelerated life testing usually are used to truncate the tests survives. The test items under accelerated life testing run under accelerated conditions and partially life tests run under both accelerated and use conditions. The main idea of accelerated life testing that the acceleration element is not unknown or the mathematical model relating the lifetime of the unit and the stress is known or can be assumed. In some cases, neither acceleration factor nor life-stress relations are not unknown. This paper concerned with studying and discussed the constant–stress partially accelerated life test (CPALT) under type I censored (T.I.C) competing risks data. Failure times resulting from T.I.C competing risks data are assumed to follow the Extended generalized log logistic (EGLL) distribution because this model is completely flexible to study positive data. This distribution is applied in various fields, for example lifetime studies, economics, finance and insurance. The maximum likelihood (ML) method is used to estimate the parameters under TIC competing risks data. The simulation algorithm is performed to assess the theoretical results of the maximum likelihood estimates based on TIC competing risks data.
由于技术的改进,在通常条件下获得产品和材料寿命的信息。因此,通常采用加速寿命试验或部分加速寿命试验来缩短试验寿命。加速寿命试验项目在加速条件下运行,部分寿命试验在加速和使用条件下运行。加速寿命试验的主要思想是加速度元件不是未知的,或者单元寿命与应力之间的数学模型是已知的或可以假设的。在某些情况下,加速因素和生活压力关系都不是未知的。本文研究和讨论了I型截尾(T.I.C)竞争风险数据下的恒应力部分加速寿命试验(CPALT)。由于该模型在研究正数据时具有完全的灵活性,因此假定由T.I.C竞争风险数据引起的失效时间服从扩展广义对数逻辑(EGLL)分布。这种分布被应用于各个领域,例如终身研究、经济学、金融和保险。采用极大似然(ML)方法估计TIC竞争风险数据下的参数。通过仿真算法对基于TIC竞争风险数据的最大似然估计的理论结果进行了评估。
{"title":"Constant Stress Partially Accelerated Life Tests for Extended Generalized log Logistic Distribution Based on Type I Censored Competing Risks Data","authors":"Elgabry Gamalat, Rezk Hoda","doi":"10.11648/J.SJAMS.20210901.12","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210901.12","url":null,"abstract":"As a result of technology improvement getting information about products and materials lifetimes under usual conditions. Therefore accelerated life testing or partially accelerated life testing usually are used to truncate the tests survives. The test items under accelerated life testing run under accelerated conditions and partially life tests run under both accelerated and use conditions. The main idea of accelerated life testing that the acceleration element is not unknown or the mathematical model relating the lifetime of the unit and the stress is known or can be assumed. In some cases, neither acceleration factor nor life-stress relations are not unknown. This paper concerned with studying and discussed the constant–stress partially accelerated life test (CPALT) under type I censored (T.I.C) competing risks data. Failure times resulting from T.I.C competing risks data are assumed to follow the Extended generalized log logistic (EGLL) distribution because this model is completely flexible to study positive data. This distribution is applied in various fields, for example lifetime studies, economics, finance and insurance. The maximum likelihood (ML) method is used to estimate the parameters under TIC competing risks data. The simulation algorithm is performed to assess the theoretical results of the maximum likelihood estimates based on TIC competing risks data.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122329469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Eco-Epidemiological Modelling and Analysis of Prey-Predator Population 食饵-捕食者种群的生态流行病学建模与分析
Pub Date : 2021-02-23 DOI: 10.11648/J.SJAMS.20210901.11
Abayneh Fentie Bezabih, G. K. Edessa, Koya Purnachandra Rao
In this paper, prey-predator model of five Compartments are constructed with treatment is given to infected prey and infected predator. We took predation incidence rates as functional response type II and disease transmission incidence rates follow simple kinetic mass action function. The positivity, boundedness, and existence of the solution of the model are established and checked. Equilibrium points of the models are identified and Local stability analysis of Trivial Equilibrium point, Axial Equilibrium point, and Disease-free Equilibrium points are performed with the Method of Variation Matrix and Routh Hourwith Criterion. It is found that the Trivial equilibrium point 〖E〗_(o) is always unstable, and Axial equilibrium point 〖E〗_(A) is locally asymptotically stable if βk - (t1+d2) < 0, qp1k - d3(s+k) < 0, & qp3k - (t2+d4)(s+k) < 0 conditions hold true. Global Stability analysis of endemic equilibrium point of the model has been proved by Considering appropriate Liapunove function. In this study, the basic reproduction number of infected prey is obtained to be the following general formula R01=[(qp1-d3)2 kβd3s2]⁄[(qp1-d3){(qp1-d3)2ks(t1+d2 )+rsqp2 (kqp1-kd3-d3s)}] and the basic reproduction number of infected predator population is computed and results are written as the general formula of the form as R02=[(qp1-d3 )(qp3 d3 )k+αrsq(kqp1-kd3-d3s)]⁄[(qp1-d3)2 (t2+d4)k]. If the basic reproduction number is greater than one, then the disease will persist in prey-predator system. If the basic reproduction number is one, then the disease is stable, and if basic reproduction number less than one, then the disease is dies out from the prey-predator system. Finally, simulations are done with the help of DEDiscover software to clarify results.
本文建立了五区系的食饵-捕食模型,并给出了被感染猎物和被感染捕食者的处理方法。我们将捕食发生率作为功能反应型,疾病传播发生率遵循简单的动力学质量作用函数。建立并检验了模型解的正性、有界性和存在性。利用变分矩阵法和Routh hour准则对模型的平衡点进行了辨识,并对平凡平衡点、轴向平衡点和无病平衡点进行了局部稳定性分析。发现当βk - (t1+d2) < 0、qp1k - d3(s+k) < 0、qp3k - (t2+d4)(s+k) < 0条件成立时,平凡平衡点〖E〗_(o)总是不稳定的,轴向平衡点〖E〗_(A)局部渐近稳定。通过考虑适当的Liapunove函数,证明了模型局部平衡点的全局稳定性分析。本研究得到受感染捕食者的基本繁殖数为通式R01=[(qp1-d3)2 kβd3s2]⁄[(qp1-d3){(qp1-d3)2ks(t1+d2)+rsqp2 (kqp1-kd3-d3s)}],计算出受感染捕食者种群的基本繁殖数,结果为R02=[(qp1-d3)(qp3 d3) k+αrsq(kqp1-kd3-d3s)]⁄[(qp1-d3)2 (t2+d4)k]形式的通式。如果基本繁殖数大于1,则该疾病将在捕食者-猎物系统中持续存在。如果基本繁殖数为1,则该疾病是稳定的,如果基本繁殖数小于1,则该疾病从捕食者-猎物系统中消失。最后,在DEDiscover软件的帮助下进行了仿真,以澄清结果。
{"title":"Eco-Epidemiological Modelling and Analysis of Prey-Predator Population","authors":"Abayneh Fentie Bezabih, G. K. Edessa, Koya Purnachandra Rao","doi":"10.11648/J.SJAMS.20210901.11","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20210901.11","url":null,"abstract":"In this paper, prey-predator model of five Compartments are constructed with treatment is given to infected prey and infected predator. We took predation incidence rates as functional response type II and disease transmission incidence rates follow simple kinetic mass action function. The positivity, boundedness, and existence of the solution of the model are established and checked. Equilibrium points of the models are identified and Local stability analysis of Trivial Equilibrium point, Axial Equilibrium point, and Disease-free Equilibrium points are performed with the Method of Variation Matrix and Routh Hourwith Criterion. It is found that the Trivial equilibrium point 〖E〗_(o) is always unstable, and Axial equilibrium point 〖E〗_(A) is locally asymptotically stable if βk - (t1+d2) < 0, qp1k - d3(s+k) < 0, & qp3k - (t2+d4)(s+k) < 0 conditions hold true. Global Stability analysis of endemic equilibrium point of the model has been proved by Considering appropriate Liapunove function. In this study, the basic reproduction number of infected prey is obtained to be the following general formula R01=[(qp1-d3)2 kβd3s2]⁄[(qp1-d3){(qp1-d3)2ks(t1+d2 )+rsqp2 (kqp1-kd3-d3s)}] and the basic reproduction number of infected predator population is computed and results are written as the general formula of the form as R02=[(qp1-d3 )(qp3 d3 )k+αrsq(kqp1-kd3-d3s)]⁄[(qp1-d3)2 (t2+d4)k]. If the basic reproduction number is greater than one, then the disease will persist in prey-predator system. If the basic reproduction number is one, then the disease is stable, and if basic reproduction number less than one, then the disease is dies out from the prey-predator system. Finally, simulations are done with the help of DEDiscover software to clarify results.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121682360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Evaluation of Field Pea (Pisum sativum L.) Genotypes for Yield and Yield Attributing Traits at High Land of Arsi, South East Ethiopia 大田豌豆(Pisum sativum L.)的评价埃塞俄比亚东南部Arsi高地产量及产量性状基因型研究
Pub Date : 2020-11-24 DOI: 10.11648/J.SJAMS.20200806.11
Kedir Yimam, Aliyi Robsa, Gizachew Yilma, Temesgen Abo
The production and productivity of field pea in Ethiopia is constrained by low-yielding potential of land race, susceptibility to diseases like powdery mildew and Ascochyta blight/spot as well as a biotic stresses like frost and soil acidity. The field experiment was conducted in 2018/19 main cropping season at two locations using simple lattice design to evaluate the genetic variability and performance of forty nine field pea genotypes for yield ad yield attributing traits. The combined/pooled / analysis of variance revealed highly significant (P≤0.01) to significant (P≤0.05) differences among genotypes observed for all traits under study except for number of seeds pod-1. The seed yield ranged from 1955 to 5997 kg ha-1 with a mean of 3803 kg across the two locations. Two genotypes PDFPT-BEK and P-313-053 were relatively high yielder over the two locations. The genotypic (GCV) and phenotypic (PCV) coefficient of variation (GCV) ranged from (1.07%) to (22.40%) and (1.22%) to (28.18% for days to maturity and grain yield, respectively for combined analyses. The PCV values were relatively greater than GCV in magnitude for all traits, of which significantly higher PCV than GCV values observed for number of pods per plant, Stand count, powdery mildew and ascocayta blight, but insignificant differences between PCV and GCV values observed for days to flowering, days to maturity, plant height, 1000 seed weight, and grain yield. Broad sense heritability ranged from 23.66% to 90.73%. The genetic advance as percentage of mean (GAM) varied from 1.92% to 36.73%. Higher heritability (H2) coupled with high GAM observed for grain yield per ha and Higher heritability (H2) coupled with Moderate or relatively high value of GAM in plant height and seed size. Therefore, improvement of these traits could be done through selection of genotypes based on the phenotypic performance.
埃塞俄比亚大田豌豆的产量和生产力受到土地品种的低产量潜力、对白粉病和Ascochyta疫病/斑疹等疾病的易感性以及霜冻和土壤酸度等生物胁迫的制约。本试验于2018/19年主要种植季在两个地点进行,采用简单格设计对49个大田豌豆基因型的产量和产量归因性状的遗传变异和表现进行了评价。综合/汇总/方差分析显示,除pod-1种子数外,各基因型间差异均极显著(P≤0.01)至显著(P≤0.05)。种子产量在1955 ~ 5997公斤/公顷之间,两个地点的平均产量为3803公斤/公顷。两个基因型PDFPT-BEK和P-313-053在两个地点的产量相对较高。组合分析结果表明,籽粒产量和生育期基因型变异系数(GCV)和表型变异系数(PCV)分别为(1.07% ~ 22.40%)和(1.22% ~ 28.18%)。各性状的PCV值均相对大于GCV值,其中单株荚果数、林分数、白粉病和子囊疫病的PCV值显著高于GCV值,而开花天数、成熟天数、株高、千粒重和籽粒产量的PCV值与GCV值差异不显著。广义遗传力为23.66% ~ 90.73%。遗传进步率(GAM)在1.92% ~ 36.73%之间变化。较高遗传力(H2)配较高GAM的每公顷产量,较高遗传力(H2)配中等或较高GAM的株高和种子大小。因此,这些性状的改良可以通过基于表型表现的基因型选择来实现。
{"title":"Evaluation of Field Pea (Pisum sativum L.) Genotypes for Yield and Yield Attributing Traits at High Land of Arsi, South East Ethiopia","authors":"Kedir Yimam, Aliyi Robsa, Gizachew Yilma, Temesgen Abo","doi":"10.11648/J.SJAMS.20200806.11","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20200806.11","url":null,"abstract":"The production and productivity of field pea in Ethiopia is constrained by low-yielding potential of land race, susceptibility to diseases like powdery mildew and Ascochyta blight/spot as well as a biotic stresses like frost and soil acidity. The field experiment was conducted in 2018/19 main cropping season at two locations using simple lattice design to evaluate the genetic variability and performance of forty nine field pea genotypes for yield ad yield attributing traits. The combined/pooled / analysis of variance revealed highly significant (P≤0.01) to significant (P≤0.05) differences among genotypes observed for all traits under study except for number of seeds pod-1. The seed yield ranged from 1955 to 5997 kg ha-1 with a mean of 3803 kg across the two locations. Two genotypes PDFPT-BEK and P-313-053 were relatively high yielder over the two locations. The genotypic (GCV) and phenotypic (PCV) coefficient of variation (GCV) ranged from (1.07%) to (22.40%) and (1.22%) to (28.18% for days to maturity and grain yield, respectively for combined analyses. The PCV values were relatively greater than GCV in magnitude for all traits, of which significantly higher PCV than GCV values observed for number of pods per plant, Stand count, powdery mildew and ascocayta blight, but insignificant differences between PCV and GCV values observed for days to flowering, days to maturity, plant height, 1000 seed weight, and grain yield. Broad sense heritability ranged from 23.66% to 90.73%. The genetic advance as percentage of mean (GAM) varied from 1.92% to 36.73%. Higher heritability (H2) coupled with high GAM observed for grain yield per ha and Higher heritability (H2) coupled with Moderate or relatively high value of GAM in plant height and seed size. Therefore, improvement of these traits could be done through selection of genotypes based on the phenotypic performance.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129207542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Modeling and Predicting Corona Contagion Dynamics in China, USA, Brazil & Ethiopia 中国、美国、巴西和埃塞俄比亚的冠状病毒传染动力学建模与预测
Pub Date : 2020-09-29 DOI: 10.11648/J.SJAMS.20200805.13
T. Tulu, I. Leong, Zunyou Wu
The COVID-19 pandemic is a global pandemic of coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS CoV 2). The outbreak was first identified in Wuhan, China, in December 2019. In this article, we investigate the problem of modelling the trend of the current Coronavirus disease 2019 pandemic in China, USA, Ethiopia and Brazil along time. Two different models were developed using Bayesian Markov chain Monte Carlo simulation methods. The models fitted included Poisson autoregressive as a function of a short-term dependence only and Poisson autoregressive as a function of both a short-term dependence and a long-term dependence. The models can be employed to understand the contagion dynamics of the COVID-19, which can heavily impact health, economy and finance. The result indicates whether disease has an upward/downward trend, and where about every country is on that trend, all of which can help the public decision-makers to better plan health policy interventions and take the appropriate actions to control the spreading of the virus.
2019冠状病毒病大流行是由严重急性呼吸综合征冠状病毒2 (SARS CoV 2)引起的2019年冠状病毒病全球大流行,于2019年12月在中国武汉首次发现。本文研究了中国、美国、埃塞俄比亚和巴西当前冠状病毒病2019大流行趋势的建模问题。采用贝叶斯马尔可夫链蒙特卡罗仿真方法建立了两种不同的模型。拟合的模型包括泊松自回归(仅作为短期依赖的函数)和泊松自回归(作为短期依赖和长期依赖的函数)。这些模型可用于了解COVID-19的传染动态,这可能严重影响卫生、经济和金融。结果表明疾病是否有上升/下降趋势,以及每个国家在这一趋势中的位置,所有这些都可以帮助公共决策者更好地规划卫生政策干预措施并采取适当行动来控制病毒的传播。
{"title":"Modeling and Predicting Corona Contagion Dynamics in China, USA, Brazil & Ethiopia","authors":"T. Tulu, I. Leong, Zunyou Wu","doi":"10.11648/J.SJAMS.20200805.13","DOIUrl":"https://doi.org/10.11648/J.SJAMS.20200805.13","url":null,"abstract":"The COVID-19 pandemic is a global pandemic of coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS CoV 2). The outbreak was first identified in Wuhan, China, in December 2019. In this article, we investigate the problem of modelling the trend of the current Coronavirus disease 2019 pandemic in China, USA, Ethiopia and Brazil along time. Two different models were developed using Bayesian Markov chain Monte Carlo simulation methods. The models fitted included Poisson autoregressive as a function of a short-term dependence only and Poisson autoregressive as a function of both a short-term dependence and a long-term dependence. The models can be employed to understand the contagion dynamics of the COVID-19, which can heavily impact health, economy and finance. The result indicates whether disease has an upward/downward trend, and where about every country is on that trend, all of which can help the public decision-makers to better plan health policy interventions and take the appropriate actions to control the spreading of the virus.","PeriodicalId":422938,"journal":{"name":"Science Journal of Applied Mathematics and Statistics","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114089984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
期刊
Science Journal of Applied Mathematics and Statistics
全部 Acc. Chem. Res. ACS Applied Bio Materials ACS Appl. Electron. Mater. ACS Appl. Energy Mater. ACS Appl. Mater. Interfaces ACS Appl. Nano Mater. ACS Appl. Polym. Mater. ACS BIOMATER-SCI ENG ACS Catal. ACS Cent. Sci. ACS Chem. Biol. ACS Chemical Health & Safety ACS Chem. Neurosci. ACS Comb. Sci. ACS Earth Space Chem. ACS Energy Lett. ACS Infect. Dis. ACS Macro Lett. ACS Mater. Lett. ACS Med. Chem. Lett. ACS Nano ACS Omega ACS Photonics ACS Sens. ACS Sustainable Chem. Eng. ACS Synth. Biol. Anal. Chem. BIOCHEMISTRY-US Bioconjugate Chem. BIOMACROMOLECULES Chem. Res. Toxicol. Chem. Rev. Chem. Mater. CRYST GROWTH DES ENERG FUEL Environ. Sci. Technol. Environ. Sci. Technol. Lett. Eur. J. Inorg. Chem. IND ENG CHEM RES Inorg. Chem. J. Agric. Food. Chem. J. Chem. Eng. Data J. Chem. Educ. J. Chem. Inf. Model. J. Chem. Theory Comput. J. Med. Chem. J. Nat. Prod. J PROTEOME RES J. Am. Chem. Soc. LANGMUIR MACROMOLECULES Mol. Pharmaceutics Nano Lett. Org. Lett. ORG PROCESS RES DEV ORGANOMETALLICS J. Org. Chem. J. Phys. Chem. J. Phys. Chem. A J. Phys. Chem. B J. Phys. Chem. C J. Phys. Chem. Lett. Analyst Anal. Methods Biomater. Sci. Catal. Sci. Technol. Chem. Commun. Chem. Soc. Rev. CHEM EDUC RES PRACT CRYSTENGCOMM Dalton Trans. Energy Environ. Sci. ENVIRON SCI-NANO ENVIRON SCI-PROC IMP ENVIRON SCI-WAT RES Faraday Discuss. Food Funct. Green Chem. Inorg. Chem. Front. Integr. Biol. J. Anal. At. Spectrom. J. Mater. Chem. A J. Mater. Chem. B J. Mater. Chem. C Lab Chip Mater. Chem. Front. Mater. Horiz. MEDCHEMCOMM Metallomics Mol. Biosyst. Mol. Syst. Des. Eng. Nanoscale Nanoscale Horiz. Nat. Prod. Rep. New J. Chem. Org. Biomol. Chem. Org. Chem. Front. PHOTOCH PHOTOBIO SCI PCCP Polym. Chem.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
0
微信
客服QQ
Book学术公众号 扫码关注我们
反馈
×
意见反馈
请填写您的意见或建议
请填写您的手机或邮箱
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
现在去查看 取消
×
提示
确定
Book学术官方微信
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术
文献互助 智能选刊 最新文献 互助须知 联系我们:info@booksci.cn
Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。
Copyright © 2023 Book学术 All rights reserved.
ghs 京公网安备 11010802042870号 京ICP备2023020795号-1