The development and exploration mode of coal resource activities in China result in tremendous waste of resources and ecological environment pollution problems. This article analyzed the use of economic theory of exte...The development and exploration mode of coal resource activities in China result in tremendous waste of resources and ecological environment pollution problems. This article analyzed the use of economic theory of externalities of coal mining activities from the point of environmental economics principles, proposed the ecological compensation connotation of coal mining activities, and analyzed the feasibility of the implementation of ecological compensation from economic viewpoint.展开更多
Local governments have long been ardently pursuing the industrial specialization effect(MAR externalities) and industrial diversification effect(Jacobs externalities). Such a pursuit has resulted in severe distortion ...Local governments have long been ardently pursuing the industrial specialization effect(MAR externalities) and industrial diversification effect(Jacobs externalities). Such a pursuit has resulted in severe distortion of resource allocation and negative effect on sustainability of local economic development. Regarding the effect from both MAR and Jacobs externalities on local economic development existing literature records notable disputes. Therefore, for local economic development, one important issue is which externality(MAR or Jacobs) can better bring the effect into play. By studying a panel data of 283 Chinese cities from 2003 to 2012 and applying dynamic plane data GMM method, this paper conducted a regression analysis of the relationship among industrial agglomeration externalities, city size, and regional economic development. The result indicates that with regard to the whole nation, MAR externalities are conducive to regional economy development whereas Jacobs externalities will, to an extent, restrain regional economic development. As regards eastern, middle, and western regions, MAR externalities are conducive only to the economic development of the eastern region; their effects on middle and western regions are insignificant. Moreover, the interaction item between MAR externalities and city size has a significant negative synergistic effect on national economic development and a certain acceleration effect on eastern region as well as a strong negative synergistic effect on the middle region and an insignificant effect on the western region. The interaction item between Jacobs externalities and city size has a positive synergistic effect on only the middle region and has an insignificant synergistic effect on both eastern and western regions. Capital stock and labor input have significant accelerating effects on GDP growth per capita of Chinese cities, whereas material capital and labor input remain primary driving forces for Chinese local economic development. Furthermore, human capital contributes to accelerating urban economic development, whereas government intervention restrains urban economic development.展开更多
The present study aims to assess the externalities of a ski resort,that is planned to be built at Tzoumerka mountains,in Greece.The research relies on the Contingent Valuation method,which indirectly estimates the eco...The present study aims to assess the externalities of a ski resort,that is planned to be built at Tzoumerka mountains,in Greece.The research relies on the Contingent Valuation method,which indirectly estimates the economic value of environmental and other nonmarket assets,based on the expressed preferences of members of a social group.The investigation was based on primary data.The core idea of questionnaire’s design,is subject to the use of a double WTP(willingness to pay)question,aiming at the monetary assessment of the attitude of the residents,regarding the upcoming infrastructure project,taking into account both its positive and its negative externalities.Depending on the attitude of the survey respondents,they were asked to decide if they wish to offer an amount of money either to promote or to prevent the construction of the ski resort.Parametric and non-parametric models were then applied in order to calculate in economic terms the expressed opinion of the respondents.The primary question to be answered is whether the willingness to build the ski resort holds a higher economic value than the desire to prevent it.According to the results of the survey,the vast majority of residents(92.4%)supported the idea of building the ski resort,projecting their apparent desire for the tourist and economic development of the area.The reinforcement of the construction idea of the project was estimated on average at €378,200.The very low proportion of the participants who disagreed with the project(5%),did not allow the economic assessment of its prevention,leaving room for further research into the application of Contingent Valuation method and its contribution in cost-benefit analysis and decision making,regarding upcoming projects.展开更多
Urban shrinkage is a global phenomenon,and it will coexist with urban growth for many years.At the same time,the network connection between cities continuously improved due to the construction of the transportation an...Urban shrinkage is a global phenomenon,and it will coexist with urban growth for many years.At the same time,the network connection between cities continuously improved due to the construction of the transportation and information networks.However,the relationship between urban network externalities and urban population growth/shrinkage remains unclear.Therefore,based on high-speed railway(HSR)flow data,a spatial econometric model is used to explore the mechanism behind urban population growth and shrinkage from the perspective of network externalities in China.The results indicate that:1)the urban network experiences a certain clubbing effect.Growing cities that are strongly connected are concentrated along China’s main railway lines and the southeastern coastal areas,while shrinking cities that are weakly connected are distributed at the periphery of the network.2)Moreover,the network externality disregards spatial distance and together with the agglomeration externality influences the growth and shrinking of cities.3)Urban economic development still promotes the development of Chinese cities.However,the improvement of the urban economy has a negative cross-regional spillover effect on neighboring cities due to urban competition.4)Lastly,Local spillovers of urban network externalities are positive,while cross-regional ones are negative.Consequently,the government needs to promote the construction of multi-dimensional network connections between cities to promote cities’sustainable development.This study reveals the relationship between urban network externalities and urban development,enriches the theories of network externalities and urban growth/shrinkage,and provides a reference for regional coordinated development.展开更多
This paper studies the outcomes of independent and interdependent pair-wise contests between economic agents subject to an optimal external decision problem for each pair. The external decision maker like the governme...This paper studies the outcomes of independent and interdependent pair-wise contests between economic agents subject to an optimal external decision problem for each pair. The external decision maker like the government or regulator is faced with the problem of how to devise rules and regulations regarding contests. In this paper, a decision problem is faced under negative and positive externalities. A pair of entities is represented by disjoint convex sets in a small area in a neighborhood. I assume that each entity imposes an equal externality on the other (and the other only) and thus they can be considered to be twins. Among the group of twins in any neighborhood, there is a set of twin pairs such that, for each pair in the set, each twin can impose a strictly negative externality on the other (and the other only), and this is a potential welfare loss which concerns the decision maker. A separating hyper-plane can block the negative externalities between any pair of twins given convexity. However, this can be costly if positive externality from the neighborhood is also blocked by the separation technology. Thus, this paper compares the pair-wise utility from separation to that of non-separation. A simple representation of the decision problem is developed with respect to a single and isolated neighborhood. A complete characterization of the decision problem is obtained with a large number of pair-wise intersecting neighborhoods.展开更多
With the advent of Internet financial innovation,many commercial banks quietly have started to enter into the Ecommercial in order to prevent oligarchs from eroding financial market.From the perspective of industrial ...With the advent of Internet financial innovation,many commercial banks quietly have started to enter into the Ecommercial in order to prevent oligarchs from eroding financial market.From the perspective of industrial division,this paper reveals the nature of a phenomenon that E-commercial enterprises and banks have stepped into each other's field,which E-commerce of banks can give full play to network effects.Then it uses game theory to analyze the motions of banks to involve into E-commerce and the short-term competitive equilibrium of large incumbent Ecommercial enterprises as well.For individual rationality,the dominant strategy of banks and E-commercial enterprises is(enter,counterattack).Considering network externalities,it constructs a competing model on banks and incumbent E-commercial enterprises and simulates competitive trends and balanced results of their behaviors,which illustrates that banks can obtain network effect after choosing E-commerce strategy.展开更多
This paper summarizes my previous work in Lin (2010), in which I use spatial econometrics to analyze air pollution externalities. In Lin (2010), state-by-state source-receptor transfer coefficients that can be used as...This paper summarizes my previous work in Lin (2010), in which I use spatial econometrics to analyze air pollution externalities. In Lin (2010), state-by-state source-receptor transfer coefficients that can be used as a basis for a location- differentiated permit system are estimated. Results affirm the importance of regional transport in determining local ozone air quality, although owing to non-monotonicities in ozone production the externality is not always negative. Because the origin of emissions matters, results also reject a non-spatially differentiated NOx cap and trade program as an appropriate mechanism for reducing ozone smog.展开更多
With the further development of socialist market economy, the mobility of factor markets in China, especially the labor market, is strengthened. Externalities interacts with the agglomeration of productive factors. Un...With the further development of socialist market economy, the mobility of factor markets in China, especially the labor market, is strengthened. Externalities interacts with the agglomeration of productive factors. Under the framework of new economic geography, this article presents a theoretical model involving the endogenous population density affected by urban externalities. Results show that the population density is more concentrated around the center because the degree and extent of interaction between individuals intensifies when the distance from the center decreases. When there are several externalities resources, the aggregation of externalities changes the configuration of spatial factor allocation. These results fit well with the empirical facts about the decreasing density of floating population along the cities of Guangzhou, Dongguan and Shenzhen in Guangdong Province which is situated in the eastern coast of the Pearl River Delta. We fred that under the impacts of externalities released from Hong Kong into the coast, floating population was more concentrated around Shenzhen and Dongguan, which are more adjacent to Hong Kong compared with Guangzhou City.展开更多
This study shows how family firm size affects the extent to which bus and coach operators in Australia interact with and contribute to their community by quantifying the value of eight social externalities and present...This study shows how family firm size affects the extent to which bus and coach operators in Australia interact with and contribute to their community by quantifying the value of eight social externalities and presenting the results, using the number of staff and the number of buses per operator as the denominators. The study highlights how a transaction between the government, as buyer, and the bus operator, as seller of services, can affect an external factor that being community and regional development. The results suggest that the small- and medium-sized family firm bus operators are the governance models most likely to contribute toward achieving community and regional development outcomes, which in turn, highlights the importance placed on the achievement of the non-financial goals of family firms and the socio-emotional wealth of the community in which it is embedded. This study suggests that it is possible that contracting bus-services for social value, rather than just lowest price, would create greater benefit for the community and this would offset any gains in economic efficiency achieved by large and non-family firms.展开更多
The framing of this theme would contribute to a better analysis of the benefits of open-air quarrying in Zinder, and should make it possible to understand and measure the socio-environmental externalities of this type...The framing of this theme would contribute to a better analysis of the benefits of open-air quarrying in Zinder, and should make it possible to understand and measure the socio-environmental externalities of this type of activity in an urban environment. The approach method consisted of carrying out surveys combined with field observations and interviews with the various stakeholders as well as the local population. The results obtained made it possible to identify both positive and negative impacts. The positive impacts are above all the advantages derived from these aggregate quarries, in particular, the creation of direct and permanent jobs and the increase in community income. The price of piling up a truck costs around 28,000 CFA ($56 CAN) and that of loading is around 10,000 F CFA ($20 CAN). This has the effect of removing young people (20 - 39 years old) from the circuit of migration outside the region and even the country. The possibility of using the extraction sites by the local population was identified, in terms of profits relating to fish farming, off-season crops, animal drinking and reclaimed plots. The study also noted negative externalities, such as the temptation of young boys to become involved in extractive activities for immediate gains at the expense of school attendance. Added to this is the upheaval in the topography of the urban landscape, pollution and nuisances (noise, visual and olfactory), while the disappearance or clogging of quarry ponds is the cause of frequent flooding in the neighborhoods. In short, corrective measures (e.g. the revegetation of sites) certainly make it possible to minimize the harmful impacts on the urban environment. But, to improve the performance and organizational capacity of the quarrying industry in Niger, even stronger regulation, training and awareness of stakeholders prove to be the necessary measures.展开更多
Ownership/private property and property inheritance are concepts well-established and constitutionally protected in our modern societies.Nevertheless,numerous provisions in the national legal framework enable the stat...Ownership/private property and property inheritance are concepts well-established and constitutionally protected in our modern societies.Nevertheless,numerous provisions in the national legal framework enable the states to expropriate individual private goods under certain severe circumstances through compensation prerequisites.The present manuscript presents a short comparative study of the constitutional articles of many countries,regarding expropriation actions,examines the compensation techniques employed,and interrelates expropriation implementation with economic analysis methods and experimental economics.Furthermore,this paper states that the current Greek expropriate methods consist of an economic disturbance and externality in economic terms.展开更多
High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress aro...High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.展开更多
This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the...This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the excitation frequency aligns with the natural frequency of the pipe,significantly increasing the degree of operational risk.The governing equation of motion based on the Euler-Bernoulli beam is derived for the relative deflection with stationary simply supported ends,with the effects of the external excitations represented by source terms distributed along the pipe length.The fourth-order partial differential equation is solved via the generalized integral transform technique(GITT),with the solution successfully verified via comparison with results in the literature.A comprehensive analysis of the vibration phenomena and changes in the motion state of the pipe is conducted for three classes of external excitation conditions:same frequency and amplitude(SFSA),same frequency but different amplitudes(SFDA),and different frequencies and amplitudes(DFDA).The numerical results show that with increasing gas volume fraction,the position corresponding to the maximum vibration displacement shifts upward.Compared with conditions without external excitation,the vibration displacement of the pipe conveying two-phase flow under external excitation increases significantly.The frequency of external excitation has a significant effect on the dynamic behavior of a pipe conveying two-phase flow.展开更多
The paper presents experimental investigation results of crack pattern change in cement pastes caused by external sulfate attack(ESA).To visualize the formation and development of cracks in cement pastes under ESA,an ...The paper presents experimental investigation results of crack pattern change in cement pastes caused by external sulfate attack(ESA).To visualize the formation and development of cracks in cement pastes under ESA,an X-ray computed tomography(X-ray CT)was used,i e,the tomography system of Zeiss Xradia 510 versa.The results indicate that X-CT can monitor the development process and distribution characteristics of the internal cracks of cement pastes under ESA with attack time.In addition,the C3A content in the cement significantly affects the damage mode of cement paste specimens during sulfate erosion.The damage of ordinary Portland cement(OPC)pastes subjected to sulfate attack with high C3A content are severe,while the damage of sulfate resistant Portland cement(SRPC)pastes is much smaller than that of OPC pastes.Furthermore,a quadratic function describes the correlation between the crack volume fraction and development depth for two cement pastes immermed in sulfate solution.展开更多
As oil and gas exploration moves into deeper waters,marine risers are subjected to increasingly complex service conditions,including vessel motions,ocean currents,seabed-soil interactions,and internal flow effects.Thi...As oil and gas exploration moves into deeper waters,marine risers are subjected to increasingly complex service conditions,including vessel motions,ocean currents,seabed-soil interactions,and internal flow effects.This work establishes a dynamic behavior model of steel catenary risers(SCRs)with varying curvatures subjected to internal flow and external currents and considers the effects of pipe-soil interactions on the curvature profile.The governing equation is solved via the generalized integral transform technique(GITT),which yields a semi-analytical solution of a high-order nonlinear partial differential equation.Parametric studies are then performed to analyze the effects of varying curvature on the vibration frequency and amplitude of SCRs.The vibration frequency and amplitude increase with the touchdown angle and hang-off angle,although the effect of the hang-off angle is negligible.Additionally,as the curvature increases along the centerline axis,the position of the maximum amplitude of the SCR moves upward.展开更多
BACKGROUND Pain in the back or pelvis or fear of back pain may affect the timing or cocontraction of the core muscles.In both static and dynamic movements,the Sahrmann core stability test provides an assessment of cor...BACKGROUND Pain in the back or pelvis or fear of back pain may affect the timing or cocontraction of the core muscles.In both static and dynamic movements,the Sahrmann core stability test provides an assessment of core muscle activation and a person's ability to stabilize the lumbopelvic complex.Preparatory cues and images can be used to increase the activation of these muscles.To attain optimal movement patterns,it will be necessary to determine what cueing will give the most effective results for core stability.AIM To investigate the effects of external and internal cues on core muscle activation during the Sahrmann five-level core stability test.METHODS Total 68 participants(21.83±3.47 years)were randomly allocated to an external(n=35)or internal cue group(n=33).Participants performed the Sahrmann fivelevel core stability test without a cue as baseline and the five-level stability exercises with an internal or external cue.External cue group received a pressure biofeedback unit(PBU),and the internal cue group received an audio cue.A Delsys Trigno^(TM)surface electromyography unit was used for muscle activation from the rectus abdominis,external oblique,and transverse abdominis/internal oblique muscles.RESULTS Linear mixed effects model analysis showed that cueing had a significant effect on core muscle activation(P=0.001);however,there was no significant difference between cue types(internal or external)(P=0.130).CONCLUSION Both external and internal cueing have significant effects on core muscle activation during the Sahrmann five-level core stability test and the PBU does not create higher muscle activation than internal cueing.展开更多
This study explores whether the current external quality assessment(EQA)level and acceptable bias for basic semen analysis in China are clinically useful.We collected data of semen EQA from Andrology laboratories in t...This study explores whether the current external quality assessment(EQA)level and acceptable bias for basic semen analysis in China are clinically useful.We collected data of semen EQA from Andrology laboratories in the Hunan Province(China)in 2022 and searched for data in the published literature from January2000 to December 2023 in China.On the basis of these data,we analyzed the coefficients of variation and acceptable biases of different quality control materials for basic semen analysis through robust statistics.We compared these findings with quality specifications based on biological variation from optimal,desirable,and minimum levels of bias to seek a unified and more suitable semen EQAbias evaluation standard for China's national conditions.Different sources of semen quality control material exhibited considerable variation in acceptable biases among laboratories,ranging from 8.2%to 56.9%.A total of 50.0% of the laboratories met the minimum quality specifications for progressive motility(PR),whereas 100.0%and 75.0%of laboratories met only the minimum quality specifications for sperm concentration and total motility(nonprogressive[NP]+PR),respectively.The Z value for sperm concentration and PR+NP was equivalent to the desirable performance specification,whereas the Z value for PR was equivalent only to the minimum performance specification.This study highlights the feasibility of operating external quality assessment schemes for basic semen analysis using quality specifications based on biological variation.These specifications should be unified among external quality control(EQC)centers based on biological variation.展开更多
Dear Editor,We aimed to describe the management of the intraoperative injury of the right external iliac artery that occurred during robot-assisted right nephroureterectomy with bladder cuff excision.Surgery was sched...Dear Editor,We aimed to describe the management of the intraoperative injury of the right external iliac artery that occurred during robot-assisted right nephroureterectomy with bladder cuff excision.Surgery was scheduled for suspected urothelial carcinoma of the distal ureter in a 60-year-old woman.The patient involved in the present research signed a dedicated form to consent to the publication of images and/or information about her.Past medical history included Brugada syndrome diagnosed in 2015,and hypercholesterolemia.Past surgical history included one cesarean section only.Family history included ovarian cancer(sister),colorectal cancer(mother),and kidney cancer(father).展开更多
Obesity is a common chronic metabolic disease affecting populations in multiple countries and regions worldwide.Traditional Chinese medicine(TCM)external treatments have garnered increasing attention due to their uniq...Obesity is a common chronic metabolic disease affecting populations in multiple countries and regions worldwide.Traditional Chinese medicine(TCM)external treatments have garnered increasing attention due to their unique therapeutic advantages,such as simplicity of operation,proven efficacy,and minimal side effects.In recent years,research on the application of TCM external treatments in obesity treatment has deepened,involving various methods such as acupuncture,tuina(massage),acupoint catgut embedding,and acupoint herbal patching.This article reviews relevant studies to provide new insights for enhancing clinical efficacy and safety.展开更多
文摘The development and exploration mode of coal resource activities in China result in tremendous waste of resources and ecological environment pollution problems. This article analyzed the use of economic theory of externalities of coal mining activities from the point of environmental economics principles, proposed the ecological compensation connotation of coal mining activities, and analyzed the feasibility of the implementation of ecological compensation from economic viewpoint.
基金Under the auspices of National Natural Science Foundation of China(No.41571112)Natural Science Foundation of Zhejiang Province of China(No.LY16D010002)
文摘Local governments have long been ardently pursuing the industrial specialization effect(MAR externalities) and industrial diversification effect(Jacobs externalities). Such a pursuit has resulted in severe distortion of resource allocation and negative effect on sustainability of local economic development. Regarding the effect from both MAR and Jacobs externalities on local economic development existing literature records notable disputes. Therefore, for local economic development, one important issue is which externality(MAR or Jacobs) can better bring the effect into play. By studying a panel data of 283 Chinese cities from 2003 to 2012 and applying dynamic plane data GMM method, this paper conducted a regression analysis of the relationship among industrial agglomeration externalities, city size, and regional economic development. The result indicates that with regard to the whole nation, MAR externalities are conducive to regional economy development whereas Jacobs externalities will, to an extent, restrain regional economic development. As regards eastern, middle, and western regions, MAR externalities are conducive only to the economic development of the eastern region; their effects on middle and western regions are insignificant. Moreover, the interaction item between MAR externalities and city size has a significant negative synergistic effect on national economic development and a certain acceleration effect on eastern region as well as a strong negative synergistic effect on the middle region and an insignificant effect on the western region. The interaction item between Jacobs externalities and city size has a positive synergistic effect on only the middle region and has an insignificant synergistic effect on both eastern and western regions. Capital stock and labor input have significant accelerating effects on GDP growth per capita of Chinese cities, whereas material capital and labor input remain primary driving forces for Chinese local economic development. Furthermore, human capital contributes to accelerating urban economic development, whereas government intervention restrains urban economic development.
文摘The present study aims to assess the externalities of a ski resort,that is planned to be built at Tzoumerka mountains,in Greece.The research relies on the Contingent Valuation method,which indirectly estimates the economic value of environmental and other nonmarket assets,based on the expressed preferences of members of a social group.The investigation was based on primary data.The core idea of questionnaire’s design,is subject to the use of a double WTP(willingness to pay)question,aiming at the monetary assessment of the attitude of the residents,regarding the upcoming infrastructure project,taking into account both its positive and its negative externalities.Depending on the attitude of the survey respondents,they were asked to decide if they wish to offer an amount of money either to promote or to prevent the construction of the ski resort.Parametric and non-parametric models were then applied in order to calculate in economic terms the expressed opinion of the respondents.The primary question to be answered is whether the willingness to build the ski resort holds a higher economic value than the desire to prevent it.According to the results of the survey,the vast majority of residents(92.4%)supported the idea of building the ski resort,projecting their apparent desire for the tourist and economic development of the area.The reinforcement of the construction idea of the project was estimated on average at €378,200.The very low proportion of the participants who disagreed with the project(5%),did not allow the economic assessment of its prevention,leaving room for further research into the application of Contingent Valuation method and its contribution in cost-benefit analysis and decision making,regarding upcoming projects.
基金Under the auspices of the National Natural Science Foundation of China (No.41971167)Fundamental Scientific Research Funds of Central China Normal University (No.CCNU22JC0262022CXZZ005)。
文摘Urban shrinkage is a global phenomenon,and it will coexist with urban growth for many years.At the same time,the network connection between cities continuously improved due to the construction of the transportation and information networks.However,the relationship between urban network externalities and urban population growth/shrinkage remains unclear.Therefore,based on high-speed railway(HSR)flow data,a spatial econometric model is used to explore the mechanism behind urban population growth and shrinkage from the perspective of network externalities in China.The results indicate that:1)the urban network experiences a certain clubbing effect.Growing cities that are strongly connected are concentrated along China’s main railway lines and the southeastern coastal areas,while shrinking cities that are weakly connected are distributed at the periphery of the network.2)Moreover,the network externality disregards spatial distance and together with the agglomeration externality influences the growth and shrinking of cities.3)Urban economic development still promotes the development of Chinese cities.However,the improvement of the urban economy has a negative cross-regional spillover effect on neighboring cities due to urban competition.4)Lastly,Local spillovers of urban network externalities are positive,while cross-regional ones are negative.Consequently,the government needs to promote the construction of multi-dimensional network connections between cities to promote cities’sustainable development.This study reveals the relationship between urban network externalities and urban development,enriches the theories of network externalities and urban growth/shrinkage,and provides a reference for regional coordinated development.
文摘This paper studies the outcomes of independent and interdependent pair-wise contests between economic agents subject to an optimal external decision problem for each pair. The external decision maker like the government or regulator is faced with the problem of how to devise rules and regulations regarding contests. In this paper, a decision problem is faced under negative and positive externalities. A pair of entities is represented by disjoint convex sets in a small area in a neighborhood. I assume that each entity imposes an equal externality on the other (and the other only) and thus they can be considered to be twins. Among the group of twins in any neighborhood, there is a set of twin pairs such that, for each pair in the set, each twin can impose a strictly negative externality on the other (and the other only), and this is a potential welfare loss which concerns the decision maker. A separating hyper-plane can block the negative externalities between any pair of twins given convexity. However, this can be costly if positive externality from the neighborhood is also blocked by the separation technology. Thus, this paper compares the pair-wise utility from separation to that of non-separation. A simple representation of the decision problem is developed with respect to a single and isolated neighborhood. A complete characterization of the decision problem is obtained with a large number of pair-wise intersecting neighborhoods.
基金National Natural Science Foundation of China(No.71501094)National Social Science Foundation of China(No.15BJY160)
文摘With the advent of Internet financial innovation,many commercial banks quietly have started to enter into the Ecommercial in order to prevent oligarchs from eroding financial market.From the perspective of industrial division,this paper reveals the nature of a phenomenon that E-commercial enterprises and banks have stepped into each other's field,which E-commerce of banks can give full play to network effects.Then it uses game theory to analyze the motions of banks to involve into E-commerce and the short-term competitive equilibrium of large incumbent Ecommercial enterprises as well.For individual rationality,the dominant strategy of banks and E-commercial enterprises is(enter,counterattack).Considering network externalities,it constructs a competing model on banks and incumbent E-commercial enterprises and simulates competitive trends and balanced results of their behaviors,which illustrates that banks can obtain network effect after choosing E-commerce strategy.
文摘This paper summarizes my previous work in Lin (2010), in which I use spatial econometrics to analyze air pollution externalities. In Lin (2010), state-by-state source-receptor transfer coefficients that can be used as a basis for a location- differentiated permit system are estimated. Results affirm the importance of regional transport in determining local ozone air quality, although owing to non-monotonicities in ozone production the externality is not always negative. Because the origin of emissions matters, results also reject a non-spatially differentiated NOx cap and trade program as an appropriate mechanism for reducing ozone smog.
基金This paper was supported by National Natural Science Foundation of China (Grant No. 40341008)
文摘With the further development of socialist market economy, the mobility of factor markets in China, especially the labor market, is strengthened. Externalities interacts with the agglomeration of productive factors. Under the framework of new economic geography, this article presents a theoretical model involving the endogenous population density affected by urban externalities. Results show that the population density is more concentrated around the center because the degree and extent of interaction between individuals intensifies when the distance from the center decreases. When there are several externalities resources, the aggregation of externalities changes the configuration of spatial factor allocation. These results fit well with the empirical facts about the decreasing density of floating population along the cities of Guangzhou, Dongguan and Shenzhen in Guangdong Province which is situated in the eastern coast of the Pearl River Delta. We fred that under the impacts of externalities released from Hong Kong into the coast, floating population was more concentrated around Shenzhen and Dongguan, which are more adjacent to Hong Kong compared with Guangzhou City.
文摘This study shows how family firm size affects the extent to which bus and coach operators in Australia interact with and contribute to their community by quantifying the value of eight social externalities and presenting the results, using the number of staff and the number of buses per operator as the denominators. The study highlights how a transaction between the government, as buyer, and the bus operator, as seller of services, can affect an external factor that being community and regional development. The results suggest that the small- and medium-sized family firm bus operators are the governance models most likely to contribute toward achieving community and regional development outcomes, which in turn, highlights the importance placed on the achievement of the non-financial goals of family firms and the socio-emotional wealth of the community in which it is embedded. This study suggests that it is possible that contracting bus-services for social value, rather than just lowest price, would create greater benefit for the community and this would offset any gains in economic efficiency achieved by large and non-family firms.
文摘The framing of this theme would contribute to a better analysis of the benefits of open-air quarrying in Zinder, and should make it possible to understand and measure the socio-environmental externalities of this type of activity in an urban environment. The approach method consisted of carrying out surveys combined with field observations and interviews with the various stakeholders as well as the local population. The results obtained made it possible to identify both positive and negative impacts. The positive impacts are above all the advantages derived from these aggregate quarries, in particular, the creation of direct and permanent jobs and the increase in community income. The price of piling up a truck costs around 28,000 CFA ($56 CAN) and that of loading is around 10,000 F CFA ($20 CAN). This has the effect of removing young people (20 - 39 years old) from the circuit of migration outside the region and even the country. The possibility of using the extraction sites by the local population was identified, in terms of profits relating to fish farming, off-season crops, animal drinking and reclaimed plots. The study also noted negative externalities, such as the temptation of young boys to become involved in extractive activities for immediate gains at the expense of school attendance. Added to this is the upheaval in the topography of the urban landscape, pollution and nuisances (noise, visual and olfactory), while the disappearance or clogging of quarry ponds is the cause of frequent flooding in the neighborhoods. In short, corrective measures (e.g. the revegetation of sites) certainly make it possible to minimize the harmful impacts on the urban environment. But, to improve the performance and organizational capacity of the quarrying industry in Niger, even stronger regulation, training and awareness of stakeholders prove to be the necessary measures.
文摘Ownership/private property and property inheritance are concepts well-established and constitutionally protected in our modern societies.Nevertheless,numerous provisions in the national legal framework enable the states to expropriate individual private goods under certain severe circumstances through compensation prerequisites.The present manuscript presents a short comparative study of the constitutional articles of many countries,regarding expropriation actions,examines the compensation techniques employed,and interrelates expropriation implementation with economic analysis methods and experimental economics.Furthermore,this paper states that the current Greek expropriate methods consist of an economic disturbance and externality in economic terms.
基金financially supported by the National Natural Science Foundation of China(Nos.52175284 and 52474396)the National Key Research and Development Program of China(No.2022YFB3404201)。
文摘High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.
基金financially supported by the Key Research and Development Program of Shandong Province(Grant Nos.2022CXGC020405,2023CXGC010415 and 2025TSGCCZZB0238)the National Natural Science Foundation of China(Grant No.52171288)the financial support from CNPq,FAPERJ,ANP,Embrapii,and China National Petroleum Corporation(CNPC).
文摘This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the excitation frequency aligns with the natural frequency of the pipe,significantly increasing the degree of operational risk.The governing equation of motion based on the Euler-Bernoulli beam is derived for the relative deflection with stationary simply supported ends,with the effects of the external excitations represented by source terms distributed along the pipe length.The fourth-order partial differential equation is solved via the generalized integral transform technique(GITT),with the solution successfully verified via comparison with results in the literature.A comprehensive analysis of the vibration phenomena and changes in the motion state of the pipe is conducted for three classes of external excitation conditions:same frequency and amplitude(SFSA),same frequency but different amplitudes(SFDA),and different frequencies and amplitudes(DFDA).The numerical results show that with increasing gas volume fraction,the position corresponding to the maximum vibration displacement shifts upward.Compared with conditions without external excitation,the vibration displacement of the pipe conveying two-phase flow under external excitation increases significantly.The frequency of external excitation has a significant effect on the dynamic behavior of a pipe conveying two-phase flow.
基金Funded by Chinese National Natural Science Foundation of China(No.U2006224)。
文摘The paper presents experimental investigation results of crack pattern change in cement pastes caused by external sulfate attack(ESA).To visualize the formation and development of cracks in cement pastes under ESA,an X-ray computed tomography(X-ray CT)was used,i e,the tomography system of Zeiss Xradia 510 versa.The results indicate that X-CT can monitor the development process and distribution characteristics of the internal cracks of cement pastes under ESA with attack time.In addition,the C3A content in the cement significantly affects the damage mode of cement paste specimens during sulfate erosion.The damage of ordinary Portland cement(OPC)pastes subjected to sulfate attack with high C3A content are severe,while the damage of sulfate resistant Portland cement(SRPC)pastes is much smaller than that of OPC pastes.Furthermore,a quadratic function describes the correlation between the crack volume fraction and development depth for two cement pastes immermed in sulfate solution.
基金financially supported by the National Natural Science Foundation of China(Grant No.52201312).
文摘As oil and gas exploration moves into deeper waters,marine risers are subjected to increasingly complex service conditions,including vessel motions,ocean currents,seabed-soil interactions,and internal flow effects.This work establishes a dynamic behavior model of steel catenary risers(SCRs)with varying curvatures subjected to internal flow and external currents and considers the effects of pipe-soil interactions on the curvature profile.The governing equation is solved via the generalized integral transform technique(GITT),which yields a semi-analytical solution of a high-order nonlinear partial differential equation.Parametric studies are then performed to analyze the effects of varying curvature on the vibration frequency and amplitude of SCRs.The vibration frequency and amplitude increase with the touchdown angle and hang-off angle,although the effect of the hang-off angle is negligible.Additionally,as the curvature increases along the centerline axis,the position of the maximum amplitude of the SCR moves upward.
文摘BACKGROUND Pain in the back or pelvis or fear of back pain may affect the timing or cocontraction of the core muscles.In both static and dynamic movements,the Sahrmann core stability test provides an assessment of core muscle activation and a person's ability to stabilize the lumbopelvic complex.Preparatory cues and images can be used to increase the activation of these muscles.To attain optimal movement patterns,it will be necessary to determine what cueing will give the most effective results for core stability.AIM To investigate the effects of external and internal cues on core muscle activation during the Sahrmann five-level core stability test.METHODS Total 68 participants(21.83±3.47 years)were randomly allocated to an external(n=35)or internal cue group(n=33).Participants performed the Sahrmann fivelevel core stability test without a cue as baseline and the five-level stability exercises with an internal or external cue.External cue group received a pressure biofeedback unit(PBU),and the internal cue group received an audio cue.A Delsys Trigno^(TM)surface electromyography unit was used for muscle activation from the rectus abdominis,external oblique,and transverse abdominis/internal oblique muscles.RESULTS Linear mixed effects model analysis showed that cueing had a significant effect on core muscle activation(P=0.001);however,there was no significant difference between cue types(internal or external)(P=0.130).CONCLUSION Both external and internal cueing have significant effects on core muscle activation during the Sahrmann five-level core stability test and the PBU does not create higher muscle activation than internal cueing.
基金supported by the Hunan Province Municipal Natural Science Foundation(2022JJ30018)the Hunan Province Health Commission Science Foundation(B202301037899)to WNL。
文摘This study explores whether the current external quality assessment(EQA)level and acceptable bias for basic semen analysis in China are clinically useful.We collected data of semen EQA from Andrology laboratories in the Hunan Province(China)in 2022 and searched for data in the published literature from January2000 to December 2023 in China.On the basis of these data,we analyzed the coefficients of variation and acceptable biases of different quality control materials for basic semen analysis through robust statistics.We compared these findings with quality specifications based on biological variation from optimal,desirable,and minimum levels of bias to seek a unified and more suitable semen EQAbias evaluation standard for China's national conditions.Different sources of semen quality control material exhibited considerable variation in acceptable biases among laboratories,ranging from 8.2%to 56.9%.A total of 50.0% of the laboratories met the minimum quality specifications for progressive motility(PR),whereas 100.0%and 75.0%of laboratories met only the minimum quality specifications for sperm concentration and total motility(nonprogressive[NP]+PR),respectively.The Z value for sperm concentration and PR+NP was equivalent to the desirable performance specification,whereas the Z value for PR was equivalent only to the minimum performance specification.This study highlights the feasibility of operating external quality assessment schemes for basic semen analysis using quality specifications based on biological variation.These specifications should be unified among external quality control(EQC)centers based on biological variation.
文摘Dear Editor,We aimed to describe the management of the intraoperative injury of the right external iliac artery that occurred during robot-assisted right nephroureterectomy with bladder cuff excision.Surgery was scheduled for suspected urothelial carcinoma of the distal ureter in a 60-year-old woman.The patient involved in the present research signed a dedicated form to consent to the publication of images and/or information about her.Past medical history included Brugada syndrome diagnosed in 2015,and hypercholesterolemia.Past surgical history included one cesarean section only.Family history included ovarian cancer(sister),colorectal cancer(mother),and kidney cancer(father).
基金Supported by National Natural Science Foundation of China(82174525)Natural Science Foundation of Jilin Province(YDZJ202301ZYTS469)+1 种基金Science and Technology Research Project of Jilin Provincial Department of Education in 2022(JJKH20230966KJ)2023 Jilin College Student Innovation and Entrepreneurship Training Project(S202310199043).
文摘Obesity is a common chronic metabolic disease affecting populations in multiple countries and regions worldwide.Traditional Chinese medicine(TCM)external treatments have garnered increasing attention due to their unique therapeutic advantages,such as simplicity of operation,proven efficacy,and minimal side effects.In recent years,research on the application of TCM external treatments in obesity treatment has deepened,involving various methods such as acupuncture,tuina(massage),acupoint catgut embedding,and acupoint herbal patching.This article reviews relevant studies to provide new insights for enhancing clinical efficacy and safety.
