Background: China is facing with a crisis of the aging population. After the implementation of the latest fertility policy, the research on fertility related issues is urgent. Objective: The objective of this study is...Background: China is facing with a crisis of the aging population. After the implementation of the latest fertility policy, the research on fertility related issues is urgent. Objective: The objective of this study is to explore the fertility values among women of childbearing age and the socio-demographic factors associated with it under the background of three-child policy, which is helpful to cope with the aging of the population. Methods: This study was conducted among 383 women of childbearing age who met the inclusion criteria using a general information questionnaire and the fertility values questionnaire from May to August 2021 in Hunan Province, China. Data were collected on the women’s socio-demographic characteristics and fertility values. The descriptive statistics, t-test and analysis of variance were used for data analysis. Results: The total mean score of the positive values was 43.55 ± 10.10, and that of the negative values was 50.87 ± 13.85. There were significant differences in the scores of the overall positive and negative values, as well as scores of each dimension (p The item mean score of the overall negative values (3.38 ± 0.93) was higher than that of the overall positive values (2.90 ± 0.67). Among the positive values, “emotional value” (4.26 ± 0.93) scored the highest, while “worrying about life changes” (3.88 ± 1.10) scored the highest among the negative values. There were significant differences in both the positive and negative values in terms of age, marital status, and “only-child” women or not (p Conclusion: The fertility values among women of childbearing age in Hunan Province were relatively negative, especially, excessive worries about life change since having a child, which may lead to further declines in fertility levels. Relevant support measures are urgently needed from the government to adapt to the three-child policy.展开更多
A comprehensive understanding of the spatial interaction between the industrial undertaking capability and the position of the global value chain of the 12 East Asian countries is conducive to strengthening regional c...A comprehensive understanding of the spatial interaction between the industrial undertaking capability and the position of the global value chain of the 12 East Asian countries is conducive to strengthening regional cooperation, gaining a say in foreign trade and becoming the dominant player in the global division of labor system. The article reveals the operating rules of the interaction between the industrial undertaking capacity and the global value chain position of East Asian countries by calculating the Global Moran Index(Moran’s I), coupling coordination degree and other indicators. The results show that: in time, the values of industrial undertaking capacity and the positions of global value chain in East Asian countries showed a sustained and stable growth trend, and have a consistent trend of change. Spatially, both of the two indexes had significant positive spatial correlation, with Moran’s I showing an ‘inverted U’pattern, and the spatial aggregation distribution of global value chain position lagged behind the spatial aggregation distribution of industrial undertaking capacity by one year. In terms of spatial coupling coordination, the coupling coordination values of the two indicators show a steady upward trend. Combined with the comparative advantage of each country, this paper provides suggestions for promoting the positions of Chinese and other East Asian industries in the global value chain from the perspectives of enhancing independent innovation capability and upgrading industrial structure.展开更多
"3R" principle circular economy emphasizes the technical operation level,while the theoretical viewpoint on value-increasing of circular economy makes deep analysis based on environmental economics. The view..."3R" principle circular economy emphasizes the technical operation level,while the theoretical viewpoint on value-increasing of circular economy makes deep analysis based on environmental economics. The viewpoint takes for that the evaluation of any circular economic model should consider both the economic value and externalities. If the material units unattached to products in the economic system are circulated with value-increasing as more as possible,more value can be created with lower consumption of resources. The essential principle of circular economy is that the material units within an economic system should go through the multiple production to be circulated with value-increasing,the main purpose of circular economy is that the material units shouldn't attach to waste going out of the system as much as possible in order to reduce pollution emissions,the economic mechanism of circular economy is that the economic value chain should be used to pull the material units of the system to achieve smooth circulation.展开更多
In this retrospective study, a total of 275 solid masses were examined for cytopathologic diagnosis. Twenty four percent (67/275) of these cytologic samples were followed by surgical biopsy and histopathologic diagnos...In this retrospective study, a total of 275 solid masses were examined for cytopathologic diagnosis. Twenty four percent (67/275) of these cytologic samples were followed by surgical biopsy and histopathologic diagnosis, allowing for comparisons. On average, the cutaneous and subcutaneous solid masses were recognized when the dogs were aged between 6 and 9 years old. The origins of the solid masses included connective tissue tumors 37.1% (23/62), epithelial tissue tumors 33.9% (21/62), round cell tumors 19.4% (12/62), masses of inflammatory lesions 4.8% (3/62) and lesions due to other causes 4.8% (3/62). The sensitivity and positive predictive value (PPV) of cytopathology in the diagnosis of solid masses were 93% (62/67) and 97% (62/64), respectively. Generally, neo-plasms were over diagnosed by cytopathology as was indicated by the positive predictive value. Both the sensitivity and the PPV of cytopathology comparative to histopathology in the diagnosis of inflammatory processes were 100% (3/3). The inflammatory lesions were eventually confirmed as necrotizing myositis, necro-suppurative cystitis and endocrine inflammatory dermatopathy based on histopathology. Less than 8% (5/67) of samples were incorrectly diagnosed by cytology. The study showed high accuracy between cytological and histopathological examination of solid masses in dogs, and thus a reliable diagnostic tool in patient care.展开更多
Introduction: Helicobacter pylori is a gram-negative bacillus responsible for numerous gastroduodenal pathologies, and this infection is a public health problem. The prevalence of infection with this bacterium remains...Introduction: Helicobacter pylori is a gram-negative bacillus responsible for numerous gastroduodenal pathologies, and this infection is a public health problem. The prevalence of infection with this bacterium remains high in countries with limited resources. Diagnosis relies mainly on numerous invasive and noninvasive methods. The aim of this work was to evaluate the different indirect diagnostic methods using bacterial cultures. Methods: We conducted a cross-sectional and analytical study from January to May 2022 in the gastroenterology departments of Douala General Hospital and Douala Military Hospital. All patients aged 18 years and older who were in the gastroenterology consultation and agreed to participate were included in our study. Sociodemographic, clinical, and paraclinical data were collected. Urease, liquid urea, and culture tests were performed from the specimens obtained by fibroscopy. Serological tests were performed on the blood sample. Results: 101 patients were included, 58 were female and 43 were male, for a sex ratio of 1.3. The mean age was 44.2 ± 16 years. The prevalence of infection was 90.5%, 44.1%, 40.6% and 21.8% for serology, direct microbiological examination, RUT (rapid urea test) and culture, respectively. Comparison of the different tests showed sensitivity and specificity of 67.1% and 64%, respectively, for RUT, 100% and 73.7%, respectively, for direct microbiological examination, and 100% and 14.8%, respectively, for serology. The positive and negative predictive values were 39.5% and 100% for serology, 39% and 85% for RUT, and 55.6% and 100% for direct microbiological examination, respectively. Conclusion: The prevalence of Helicobacter pylori infection depends on the type of test used. Direct examination is more reliable than RUT and serology.展开更多
Task scheduling in cloud computing environments is a multi-objective optimization problem, which is NP hard. It is also a challenging problem to find an appropriate trade-off among resource utilization, energy consump...Task scheduling in cloud computing environments is a multi-objective optimization problem, which is NP hard. It is also a challenging problem to find an appropriate trade-off among resource utilization, energy consumption and Quality of Service(QoS) requirements under the changing environment and diverse tasks. Considering both processing time and transmission time, a PSO-based Adaptive Multi-objective Task Scheduling(AMTS) Strategy is proposed in this paper. First, the task scheduling problem is formulated. Then, a task scheduling policy is advanced to get the optimal resource utilization, task completion time, average cost and average energy consumption. In order to maintain the particle diversity, the adaptive acceleration coefficient is adopted. Experimental results show that the improved PSO algorithm can obtain quasi-optimal solutions for the cloud task scheduling problem.展开更多
A statistically significant research finding should not be defined as a P-value of 0.05 or less, because this definition does not take into account study power. Statistical significance was originally defined by Fishe...A statistically significant research finding should not be defined as a P-value of 0.05 or less, because this definition does not take into account study power. Statistical significance was originally defined by Fisher RA as a P-value of 0.05 or less. According to Fisher, any finding that is likely to occur by random variation no more than 1 in 20 times is considered significant. Neyman J and Pearson ES subsequently argued that Fisher's definition was incomplete. They proposed that statistical significance could only be determined by analyzing the chance of incorrectly considering a study finding was significant(a Type Ⅰ?error) or incorrectly considering a study finding was insignificant(a Type Ⅱ error). Their definition of statistical significance is also incomplete because the error rates are considered separately, not together. A better definition of statistical significance is the positive predictive value of a P-value, which is equal to the power divided by the sum of power and the P-value. This definition is more complete and relevant than Fisher's or Neyman-Peason's definitions, because it takes into account both concepts of statistical significance. Using this definition, a statistically significant finding requires a P-value of 0.05 or less when the power is at least 95%, and a P-value of 0.032 or less when the power is 60%. To achieve statistical significance, P-values must be adjusted downward as the study power decreases.展开更多
Background: Multiplex virus assays are useful in immunocompromised hosts but still challenging in routine clinical settings in terms of their sensitivity, specificity, reproducibility, and time and cost performances. ...Background: Multiplex virus assays are useful in immunocompromised hosts but still challenging in routine clinical settings in terms of their sensitivity, specificity, reproducibility, and time and cost performances. In recent years, we developed a qualitative multiplex virus PCR assay capable of the simultaneous detection of 13 virus species within 3 h. However, because of the multiple and concomitant nature of this virus assay, it should be validated for qualitative reliability. Materials and Methods: As a preclinical examination, this multiplex PCR was able to detect 1.25 × 10<sup>3</sup> copies/mL of 13 synthesized virus genomes and preserved same virus DNAs by the serial dilution method. Blood samples from 40 patients who underwent hematopoietic stem cell transplantation were then examined by multiplex PCR for 13 virus species, followed by quantitative real-time PCR for all 13 virus species as reference PCR when these patients developed symptoms suggestive of viral infection. Results: In 421 cumulative qualitative-quantitative tests, the multiplex PCR certainly detected 1.0 × 103 copies/mL of 5 viruses (CMV, JCV, BKV, HHV-6, ADV) that were frequently detected and thus reasonably analyzed. The positive and negative predictive values of multiplex PCR were 84.2% - 93.3% and 90.7% - 99.0%, respectively, and sensitivity and specificity were 59.0% - 83.3% and 97.2% - 99.2%, respectively, for these 5 viruses. Conclusion: From these performances, the multiplex PCR assay may be acceptable in a routine clinical laboratory setting.展开更多
Digital trade rules and higher positions of enterprises in the global value chain(GVC)are both important topics in the context of high-quality economic development.This paper refers to the data of RTA digital trade ru...Digital trade rules and higher positions of enterprises in the global value chain(GVC)are both important topics in the context of high-quality economic development.This paper refers to the data of RTA digital trade rules concluded by China in the TAPED database in 2000-2014 and the matched data in the WIOD database,the China Customs Import and Export Database and the China Industrial Enterprise Database to investigate the effects of digital trade rules on Chinese enterprises as to their ascending GVC positions.It finds that signing the RTA digital trade rules can steadily and significantly promote the position ascendance;compared with the digitalization rules on trading objects,signing the digitalization rules on trade modes produces greater effects of driving up the positions,which are realized mainly via the three channels of advancing cross-border flow of R&D factors,promoting corporate digital transformation,and improving professional management.Digital trade rules that are horizontally broader and vertically deeper are in greater favor of Chinese enterprises for ascending in the global value chain,which is especially evident among those in digital industry and processing trade.During the negotiations of digital trade rules,it's imperative to pay close attention to the rules on e-commerce cooperation,awareness of e-commerce importance,intellectual property protection,attempts in big data-related trade in goods,and cross-border data flow,so as to secure the core interests of Chinese enterprises in gaining higher positions.This paper offers great policy implications as to how to sign digital trade rules by China in the future and how to select partners in greater support for Chinese enterprises to ascend to the middle and high end of the global value chain.展开更多
Firms actively participate in the production of the global value chain(GVC),which is an important driving force for economic development.Using a difference-in-difference method,our research shows that industries that ...Firms actively participate in the production of the global value chain(GVC),which is an important driving force for economic development.Using a difference-in-difference method,our research shows that industries that are relatively more human-capital intensive experienced a larger GVC position upgrading after 2003 than they had in prior years.Second,mechanism analysis shows that human capital expansion increases firms’GVC position not only through an imported intermediate input effect but also through an innovation effect.Third,this study shows that increases in the college-educated labor force have a heterogeneous effect on a firm's GVC position across firms’various characteristics.Human capital expansion has the largest positive effect on state-owned firms relative to foreign and domestic private firms.Human capital expansion has also significantly improved the GVC position of firms located in China's eastern and central regions.The findings of this study indicate that it helps upgrading the GVC position of Chinese firms.展开更多
Existence and uniqueness conditions for nonnegative solutions to initial value prob-lems of general sublinear-linear differential equations are obtained.They extend the uniquenesstheorem due to H.Murakami~[6] and the ...Existence and uniqueness conditions for nonnegative solutions to initial value prob-lems of general sublinear-linear differential equations are obtained.They extend the uniquenesstheorem due to H.Murakami~[6] and the main results of H.G.Kaper and M.K.Kwong~[4].展开更多
We investigated the false-negative,true-negative,false-positive,and true-positive predictive values from a general group testing procedure for a heterogeneous population.We show that its false(true)-negative predictiv...We investigated the false-negative,true-negative,false-positive,and true-positive predictive values from a general group testing procedure for a heterogeneous population.We show that its false(true)-negative predictive value of a specimen is larger(smaller),and the false(true)-positive predictive value is smaller(larger)than that from individual testing procedure,where the former is in aversion.Then we propose a nested group testing procedure,and show that it can keep the sterling characteristics and also improve the false-negative predictive values for a specimen,not larger than that from individual testing.These characteristics are studied from both theoretical and numerical points of view.The nested group testing procedure is better than individual testing on both false-positive and false-negative predictive values,while retains the efficiency as a basic characteristic of a group testing procedure.Applications to Dorfman’s,Halving and Sterrett procedures are discussed.Results from extensive simulation studies and an application to malaria infection in microscopy-negative Malawian women exemplify the findings.展开更多
文摘Background: China is facing with a crisis of the aging population. After the implementation of the latest fertility policy, the research on fertility related issues is urgent. Objective: The objective of this study is to explore the fertility values among women of childbearing age and the socio-demographic factors associated with it under the background of three-child policy, which is helpful to cope with the aging of the population. Methods: This study was conducted among 383 women of childbearing age who met the inclusion criteria using a general information questionnaire and the fertility values questionnaire from May to August 2021 in Hunan Province, China. Data were collected on the women’s socio-demographic characteristics and fertility values. The descriptive statistics, t-test and analysis of variance were used for data analysis. Results: The total mean score of the positive values was 43.55 ± 10.10, and that of the negative values was 50.87 ± 13.85. There were significant differences in the scores of the overall positive and negative values, as well as scores of each dimension (p The item mean score of the overall negative values (3.38 ± 0.93) was higher than that of the overall positive values (2.90 ± 0.67). Among the positive values, “emotional value” (4.26 ± 0.93) scored the highest, while “worrying about life changes” (3.88 ± 1.10) scored the highest among the negative values. There were significant differences in both the positive and negative values in terms of age, marital status, and “only-child” women or not (p Conclusion: The fertility values among women of childbearing age in Hunan Province were relatively negative, especially, excessive worries about life change since having a child, which may lead to further declines in fertility levels. Relevant support measures are urgently needed from the government to adapt to the three-child policy.
基金Under the auspices of China’s National Social Science Research Grant(No.16BTJ025)。
文摘A comprehensive understanding of the spatial interaction between the industrial undertaking capability and the position of the global value chain of the 12 East Asian countries is conducive to strengthening regional cooperation, gaining a say in foreign trade and becoming the dominant player in the global division of labor system. The article reveals the operating rules of the interaction between the industrial undertaking capacity and the global value chain position of East Asian countries by calculating the Global Moran Index(Moran’s I), coupling coordination degree and other indicators. The results show that: in time, the values of industrial undertaking capacity and the positions of global value chain in East Asian countries showed a sustained and stable growth trend, and have a consistent trend of change. Spatially, both of the two indexes had significant positive spatial correlation, with Moran’s I showing an ‘inverted U’pattern, and the spatial aggregation distribution of global value chain position lagged behind the spatial aggregation distribution of industrial undertaking capacity by one year. In terms of spatial coupling coordination, the coupling coordination values of the two indicators show a steady upward trend. Combined with the comparative advantage of each country, this paper provides suggestions for promoting the positions of Chinese and other East Asian industries in the global value chain from the perspectives of enhancing independent innovation capability and upgrading industrial structure.
文摘"3R" principle circular economy emphasizes the technical operation level,while the theoretical viewpoint on value-increasing of circular economy makes deep analysis based on environmental economics. The viewpoint takes for that the evaluation of any circular economic model should consider both the economic value and externalities. If the material units unattached to products in the economic system are circulated with value-increasing as more as possible,more value can be created with lower consumption of resources. The essential principle of circular economy is that the material units within an economic system should go through the multiple production to be circulated with value-increasing,the main purpose of circular economy is that the material units shouldn't attach to waste going out of the system as much as possible in order to reduce pollution emissions,the economic mechanism of circular economy is that the economic value chain should be used to pull the material units of the system to achieve smooth circulation.
文摘In this retrospective study, a total of 275 solid masses were examined for cytopathologic diagnosis. Twenty four percent (67/275) of these cytologic samples were followed by surgical biopsy and histopathologic diagnosis, allowing for comparisons. On average, the cutaneous and subcutaneous solid masses were recognized when the dogs were aged between 6 and 9 years old. The origins of the solid masses included connective tissue tumors 37.1% (23/62), epithelial tissue tumors 33.9% (21/62), round cell tumors 19.4% (12/62), masses of inflammatory lesions 4.8% (3/62) and lesions due to other causes 4.8% (3/62). The sensitivity and positive predictive value (PPV) of cytopathology in the diagnosis of solid masses were 93% (62/67) and 97% (62/64), respectively. Generally, neo-plasms were over diagnosed by cytopathology as was indicated by the positive predictive value. Both the sensitivity and the PPV of cytopathology comparative to histopathology in the diagnosis of inflammatory processes were 100% (3/3). The inflammatory lesions were eventually confirmed as necrotizing myositis, necro-suppurative cystitis and endocrine inflammatory dermatopathy based on histopathology. Less than 8% (5/67) of samples were incorrectly diagnosed by cytology. The study showed high accuracy between cytological and histopathological examination of solid masses in dogs, and thus a reliable diagnostic tool in patient care.
文摘Introduction: Helicobacter pylori is a gram-negative bacillus responsible for numerous gastroduodenal pathologies, and this infection is a public health problem. The prevalence of infection with this bacterium remains high in countries with limited resources. Diagnosis relies mainly on numerous invasive and noninvasive methods. The aim of this work was to evaluate the different indirect diagnostic methods using bacterial cultures. Methods: We conducted a cross-sectional and analytical study from January to May 2022 in the gastroenterology departments of Douala General Hospital and Douala Military Hospital. All patients aged 18 years and older who were in the gastroenterology consultation and agreed to participate were included in our study. Sociodemographic, clinical, and paraclinical data were collected. Urease, liquid urea, and culture tests were performed from the specimens obtained by fibroscopy. Serological tests were performed on the blood sample. Results: 101 patients were included, 58 were female and 43 were male, for a sex ratio of 1.3. The mean age was 44.2 ± 16 years. The prevalence of infection was 90.5%, 44.1%, 40.6% and 21.8% for serology, direct microbiological examination, RUT (rapid urea test) and culture, respectively. Comparison of the different tests showed sensitivity and specificity of 67.1% and 64%, respectively, for RUT, 100% and 73.7%, respectively, for direct microbiological examination, and 100% and 14.8%, respectively, for serology. The positive and negative predictive values were 39.5% and 100% for serology, 39% and 85% for RUT, and 55.6% and 100% for direct microbiological examination, respectively. Conclusion: The prevalence of Helicobacter pylori infection depends on the type of test used. Direct examination is more reliable than RUT and serology.
基金partially been sponsored by the National Science Foundation of China(No.61572355,61272093,610172063)Tianjin Research Program of Application Foundation and Advanced Technology under grant No.15JCYBJC15700
文摘Task scheduling in cloud computing environments is a multi-objective optimization problem, which is NP hard. It is also a challenging problem to find an appropriate trade-off among resource utilization, energy consumption and Quality of Service(QoS) requirements under the changing environment and diverse tasks. Considering both processing time and transmission time, a PSO-based Adaptive Multi-objective Task Scheduling(AMTS) Strategy is proposed in this paper. First, the task scheduling problem is formulated. Then, a task scheduling policy is advanced to get the optimal resource utilization, task completion time, average cost and average energy consumption. In order to maintain the particle diversity, the adaptive acceleration coefficient is adopted. Experimental results show that the improved PSO algorithm can obtain quasi-optimal solutions for the cloud task scheduling problem.
文摘A statistically significant research finding should not be defined as a P-value of 0.05 or less, because this definition does not take into account study power. Statistical significance was originally defined by Fisher RA as a P-value of 0.05 or less. According to Fisher, any finding that is likely to occur by random variation no more than 1 in 20 times is considered significant. Neyman J and Pearson ES subsequently argued that Fisher's definition was incomplete. They proposed that statistical significance could only be determined by analyzing the chance of incorrectly considering a study finding was significant(a Type Ⅰ?error) or incorrectly considering a study finding was insignificant(a Type Ⅱ error). Their definition of statistical significance is also incomplete because the error rates are considered separately, not together. A better definition of statistical significance is the positive predictive value of a P-value, which is equal to the power divided by the sum of power and the P-value. This definition is more complete and relevant than Fisher's or Neyman-Peason's definitions, because it takes into account both concepts of statistical significance. Using this definition, a statistically significant finding requires a P-value of 0.05 or less when the power is at least 95%, and a P-value of 0.032 or less when the power is 60%. To achieve statistical significance, P-values must be adjusted downward as the study power decreases.
文摘Background: Multiplex virus assays are useful in immunocompromised hosts but still challenging in routine clinical settings in terms of their sensitivity, specificity, reproducibility, and time and cost performances. In recent years, we developed a qualitative multiplex virus PCR assay capable of the simultaneous detection of 13 virus species within 3 h. However, because of the multiple and concomitant nature of this virus assay, it should be validated for qualitative reliability. Materials and Methods: As a preclinical examination, this multiplex PCR was able to detect 1.25 × 10<sup>3</sup> copies/mL of 13 synthesized virus genomes and preserved same virus DNAs by the serial dilution method. Blood samples from 40 patients who underwent hematopoietic stem cell transplantation were then examined by multiplex PCR for 13 virus species, followed by quantitative real-time PCR for all 13 virus species as reference PCR when these patients developed symptoms suggestive of viral infection. Results: In 421 cumulative qualitative-quantitative tests, the multiplex PCR certainly detected 1.0 × 103 copies/mL of 5 viruses (CMV, JCV, BKV, HHV-6, ADV) that were frequently detected and thus reasonably analyzed. The positive and negative predictive values of multiplex PCR were 84.2% - 93.3% and 90.7% - 99.0%, respectively, and sensitivity and specificity were 59.0% - 83.3% and 97.2% - 99.2%, respectively, for these 5 viruses. Conclusion: From these performances, the multiplex PCR assay may be acceptable in a routine clinical laboratory setting.
基金Major Project of National Social Science Fund of China"Research on China's Standards Governance and Reconstruction of Global Trade Rules"(17ZDA099)Youth Project of National Natural Science Foundation of China"Research on the Division of Labor Pattern,Functional Upgrading Effect,and Policy Optimization of China's Embedding into the Global Value Chain"(72203058).
文摘Digital trade rules and higher positions of enterprises in the global value chain(GVC)are both important topics in the context of high-quality economic development.This paper refers to the data of RTA digital trade rules concluded by China in the TAPED database in 2000-2014 and the matched data in the WIOD database,the China Customs Import and Export Database and the China Industrial Enterprise Database to investigate the effects of digital trade rules on Chinese enterprises as to their ascending GVC positions.It finds that signing the RTA digital trade rules can steadily and significantly promote the position ascendance;compared with the digitalization rules on trading objects,signing the digitalization rules on trade modes produces greater effects of driving up the positions,which are realized mainly via the three channels of advancing cross-border flow of R&D factors,promoting corporate digital transformation,and improving professional management.Digital trade rules that are horizontally broader and vertically deeper are in greater favor of Chinese enterprises for ascending in the global value chain,which is especially evident among those in digital industry and processing trade.During the negotiations of digital trade rules,it's imperative to pay close attention to the rules on e-commerce cooperation,awareness of e-commerce importance,intellectual property protection,attempts in big data-related trade in goods,and cross-border data flow,so as to secure the core interests of Chinese enterprises in gaining higher positions.This paper offers great policy implications as to how to sign digital trade rules by China in the future and how to select partners in greater support for Chinese enterprises to ascend to the middle and high end of the global value chain.
基金This research was financially supported by the Key Research Institutes of Humanities and Social of the Ministry of Education of China(No.17JJD790014)the Major Program of the National Social Science Foundation of China(Nos.13&ZD167 and 17ZDA114)。
文摘Firms actively participate in the production of the global value chain(GVC),which is an important driving force for economic development.Using a difference-in-difference method,our research shows that industries that are relatively more human-capital intensive experienced a larger GVC position upgrading after 2003 than they had in prior years.Second,mechanism analysis shows that human capital expansion increases firms’GVC position not only through an imported intermediate input effect but also through an innovation effect.Third,this study shows that increases in the college-educated labor force have a heterogeneous effect on a firm's GVC position across firms’various characteristics.Human capital expansion has the largest positive effect on state-owned firms relative to foreign and domestic private firms.Human capital expansion has also significantly improved the GVC position of firms located in China's eastern and central regions.The findings of this study indicate that it helps upgrading the GVC position of Chinese firms.
文摘Existence and uniqueness conditions for nonnegative solutions to initial value prob-lems of general sublinear-linear differential equations are obtained.They extend the uniquenesstheorem due to H.Murakami~[6] and the main results of H.G.Kaper and M.K.Kwong~[4].
基金supported by National Natural Science Foundation of China (Grant Nos.11801102,11861017)Beijing Natural Science Foundation (Z180006)the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health.
文摘We investigated the false-negative,true-negative,false-positive,and true-positive predictive values from a general group testing procedure for a heterogeneous population.We show that its false(true)-negative predictive value of a specimen is larger(smaller),and the false(true)-positive predictive value is smaller(larger)than that from individual testing procedure,where the former is in aversion.Then we propose a nested group testing procedure,and show that it can keep the sterling characteristics and also improve the false-negative predictive values for a specimen,not larger than that from individual testing.These characteristics are studied from both theoretical and numerical points of view.The nested group testing procedure is better than individual testing on both false-positive and false-negative predictive values,while retains the efficiency as a basic characteristic of a group testing procedure.Applications to Dorfman’s,Halving and Sterrett procedures are discussed.Results from extensive simulation studies and an application to malaria infection in microscopy-negative Malawian women exemplify the findings.