A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power...A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power series expansion developed in resolving the so-called Grandi’s paradox. Comparisons with accurate tabulated values for well-known cases such as the error function are presented using the expansions truncated at various orders.展开更多
The aspiration of all wind turbine designers is to attain Betz’s upper limit, which represents the highest efficiency in wind energy extraction. Majority of working turbines operate slightly below this limit with an ...The aspiration of all wind turbine designers is to attain Betz’s upper limit, which represents the highest efficiency in wind energy extraction. Majority of working turbines operate slightly below this limit with an exception of a few operating in wind tunnels. This study proposes for a comprehensive reevaluation of Betz’s derivation, aiming to establish the gap between a theoretical power limit and a practical limit for realization. There are two common expressions for power coefficient giving the same optimal value of 59%, but they generate different power-coefficient curves when plotted against velocity ratios. This paper presents a new method being referred as “Direct Multiplication Fractional Change” (DMFC) for deriving power-coefficient curves in wind energy, and compares its generated curve with established models. Discrepancies in power-coefficient expressions are identified and harmonized. Three approaches, namely EVAM, LVM, and DMFCM, were used for the numerical derivation of cp in the study, with their evaluation summarized in a table. The study collaborates its findings with a formulated velocity-distance curve, commonly presented as a hypothetical velocity profile in some publications. The results from DMFCM indicate two distinct maxima for the power coefficient. On the front side of the disc, a maximum of 0.5 is achievable in practice, although it is not the highest theoretically. On the rear side, a theoretical maximum of 0.59 is observed, but this value is not attainable in practice. These maxima are separated by their positions along the line of flow relative to the disc. However, this approximation is limited to a streamlined flow model of the rotor disc.展开更多
The electric power industry is undergoing profound transformations driven by big data,posing challenges to the traditional power grid marketing management model.These challenges include neglecting market demands,insuf...The electric power industry is undergoing profound transformations driven by big data,posing challenges to the traditional power grid marketing management model.These challenges include neglecting market demands,insufficient data support,and inadequate customer service.The application of big data technology offers innovative solutions for power grid marketing management,encompassing critical aspects such as data collection and integration,storage management,analysis,and mining.By leveraging these technologies,power grid enterprises can precisely understand customer needs,optimize marketing strategies,and enhance operational efficiency.This paper explores strategies for power grid marketing management based on big data,addressing areas such as customer segmentation and personalized services,as well as market demand forecasting and response.Furthermore,it proposes implementation pathways,including essential elements such as organizational structure and team building,data quality and governance systems,training,and cultural development.These efforts aim to ensure the effective application of big data technology and maximize its value.展开更多
This paper introduces the system structure and work principle of the upgraded real time information system in Wangting Power Plant, and then expounds the realization way and function features of this system on B/S co...This paper introduces the system structure and work principle of the upgraded real time information system in Wangting Power Plant, and then expounds the realization way and function features of this system on B/S computing mode. The results of field application show the new system has good capability, reliability and expandability.展开更多
An alternative method was introduced for voltage sag source location based on S and TT transformed disturbance powers. It is done to avoid the wrong and inconclusive detection of conventional disturbance power method ...An alternative method was introduced for voltage sag source location based on S and TT transformed disturbance powers. It is done to avoid the wrong and inconclusive detection of conventional disturbance power method proposed in the literature. Unlike in the case of the traditional method, the proposed method first transforms the recorded voltage and current during the sag event to some special features before calculating the new version of disturbance powers. The effectiveness of the proposed method has been verified through simulation and actual data from an industrial power system. The results show that the presented method can correctly detect the location of voltage sag source.展开更多
This paper derives the variance of the information content and develops its statistical inference method. We describe the relations between information content and sensitivity, specificity, efficiency, prevalence rate...This paper derives the variance of the information content and develops its statistical inference method. We describe the relations between information content and sensitivity, specificity, efficiency, prevalence rate. If sensitivity, specificity and efficiency are fixed, the closer to 0. 5 the prevalence rate is, the more the information content. If prevalence rate and efficiency are fixed, the closer to each other the sensitivity and specificity are, the more the information content. We compare the power of information content method, efficiecy test, Youden's index test and kappa coefficient method. The information content method has higher power than the other methods in most conditions. It is especially sensitive to the difference between two sensitivities. It comes to conclusion that the information content method has more virtues than the other methods mentioned in this paper.展开更多
AIM:To investigate whether the axial length(AL)/total corneal refractive power(TCRP)ratio is a sensitive and simple factor that can be used for the early diagnosis of Marfan’s syndrome(MFS)in children.METHODS:The rel...AIM:To investigate whether the axial length(AL)/total corneal refractive power(TCRP)ratio is a sensitive and simple factor that can be used for the early diagnosis of Marfan’s syndrome(MFS)in children.METHODS:The relationship between the AL/TCRP ratio and the diagnosis of MFS for 192 eyes in 97 children were evaluate.The biological characteristics,including age,sex,AL,and TCRP,were collected from medical records.Receiver operating characteristic(ROC)curve analysis was performed to investigate whether the AL/TCRP ratio effectively distinguishes MFS from other subjects.The Youden index was used to re-divide the whole population into two groups according to an AL/TCRP ratio of 0.59.RESULTS:Of 96 subjects(mean age 7.46±3.28 y)evaluated,56(110 eyes)had a definite diagnosis of MFS in childhood based on the revised Ghent criteria,41(82 eyes)with diagnosis of congenital ectopia lentis(EL)were included as a control group.AL was negatively correlated with TCRP,with a linear regression coefficient of-0.36(R2=0.08).A significant correlation was found between age and the AL/TCRP ratio(P=0.023).ROC curve analysis showed that the AL/TCRP ratio distinguished MFS from the other patients at a threshold of 0.59.MFS patients were present in 24/58(41.38%)patients with an AL/TCRP ratio of≤0.59 and in 34/39(87.18%)patients with an AL/TCRP ratio of>0.59.CONCLUSION:An AL/TCRP ratio of>0.59 is significantly associated with the risk of MFS.The AL/TCRP ratio should be measured as a promising marker for the prognosis of children MFS.Changes in the AL/TCRP ratio should be monitored over time.展开更多
Wind energy is a clean and sustainable energy, and wind power does not rely on fossil fuels. So there is no fuel price risk, and it, of course, does not include the environmental costs, such as carbon emissions. Becau...Wind energy is a clean and sustainable energy, and wind power does not rely on fossil fuels. So there is no fuel price risk, and it, of course, does not include the environmental costs, such as carbon emissions. Because of these unique advantages, wind power has gradually become an important part of the strategy of sustainable development in China. Now with the growing voices on global greenhouse gas emission reduction, and as a clean and efficient energy, wind power has huge potential in combating climate change, energy security pressures and the needs for energy. Wind power in China began to develop from the 1980s. In the first 20 years, the speed of development was slow; but since 2004, it has had an extremely rapid growth.This paper, in order to study the development mechanism of China＆amp;amp;amp;#39;s wind power industry, investigated and analyzed the status quo of wind power industry in China, and then found that （1） the development trend of wind power industry in China appears exponential growth; （2） China＆amp;amp;amp;#39;s installed capacity of wind power is still smaller than that os some other countries; （3） new subsidy policies bring developing opportunities to wind power industry in China; （4） the sectors of wind power industry are in unbalanced growing; （5） the owners of proposed wind farms are too optimistic though the built wind farm had many problems. In addition, by using the methodology of Game Theory, this paper has also constructed the matrix of pre-assessing risks of China＆amp;amp;amp;#39;s wind power industry to further discuss the potential risk factors within China＆amp;amp;amp;#39;s wind power industry as risk factors of wind farm construction, risk factors of production of wind turbines, risk factors of parts and components manufacturing industry under risk indicators like R＆amp;amp;amp;amp;D, patents, the domestic policy, the international policy, the quality of products and the market regulation, in order to provide a scientific assessment and self-assessment tool for investors or implementers, and also to promote the further development of the wind power industry.展开更多
The aim of this paper is to determine the power losses recorded by a PV generator operating under partial shading conditions. These losses are evaluated through two distinct methods. The first method is based on mathe...The aim of this paper is to determine the power losses recorded by a PV generator operating under partial shading conditions. These losses are evaluated through two distinct methods. The first method is based on mathematical modeling, while the second is based on Simulink’s physical model. The losses recorded are considerable and increase as a function of the increase in the percentage of shading up to a limit value where they become constant in the case where an ideal by-pass diode is connected in parallel with the modules. This limit value is non-existent in the case where the bypass diode is not ideal, which in fact corresponds to the real model. However, it emerges that the power losses are minimized in a PV system comprising bypass diodes, in particular in the case where the partial shading is considerable.展开更多
Feature reduction is a key process in pattern recognition. This paper deals with the feature reduction methods for a time-shift invariant feature, power spectrum, in Radar Automatic Target Recognition (RATR) using Hig...Feature reduction is a key process in pattern recognition. This paper deals with the feature reduction methods for a time-shift invariant feature, power spectrum, in Radar Automatic Target Recognition (RATR) using High-Resolution Range Profiles (HRRPs). Several existing feature reduction methods in pattern recognition are analyzed, and a weighted feature reduction method based on Fisher's Discriminant Ratio (FDR) is proposed in this paper. According to the characteristics of radar HRRP target recognition, this proposed method searches the optimal weight vector for power spectra of HRRPs by means of an iterative algorithm, and thus reduces feature dimensionality. Compared with the method of using raw power spectra and some existing feature reduction methods, the weighted feature reduction method can not only reduce feature dimensionality, but also improve recognition performance with low computation complexity. In the recognition experiments based on measured data, the proposed method is robust to different test data and achieves good recognition results.展开更多
China: the future of nuclear powerWang Yonggan: In terms of the highlighted issue ofenergy security, oil is of paramount importance, coal isthe foundation and electricity is the pivot according
With the advent of big data,the demand for computing has been increasing in a very large scale for the past decade,so geographically distributed data centers are erected in the direction of cloud computing development...With the advent of big data,the demand for computing has been increasing in a very large scale for the past decade,so geographically distributed data centers are erected in the direction of cloud computing development. A Lyapunov optimization approach is considered for the problem of minimizing energy cost for distributed Internet data centers( IDCs). By capturing the power cost of servers and cooling systems,the Lyapunov optimization technique is formulated to design a decisive strategy that offers provable power cost minimization and Qo S guarantees. The algorithm performance and effectiveness are validated via simulations driven by real world traces.展开更多
文摘A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power series expansion developed in resolving the so-called Grandi’s paradox. Comparisons with accurate tabulated values for well-known cases such as the error function are presented using the expansions truncated at various orders.
文摘The aspiration of all wind turbine designers is to attain Betz’s upper limit, which represents the highest efficiency in wind energy extraction. Majority of working turbines operate slightly below this limit with an exception of a few operating in wind tunnels. This study proposes for a comprehensive reevaluation of Betz’s derivation, aiming to establish the gap between a theoretical power limit and a practical limit for realization. There are two common expressions for power coefficient giving the same optimal value of 59%, but they generate different power-coefficient curves when plotted against velocity ratios. This paper presents a new method being referred as “Direct Multiplication Fractional Change” (DMFC) for deriving power-coefficient curves in wind energy, and compares its generated curve with established models. Discrepancies in power-coefficient expressions are identified and harmonized. Three approaches, namely EVAM, LVM, and DMFCM, were used for the numerical derivation of cp in the study, with their evaluation summarized in a table. The study collaborates its findings with a formulated velocity-distance curve, commonly presented as a hypothetical velocity profile in some publications. The results from DMFCM indicate two distinct maxima for the power coefficient. On the front side of the disc, a maximum of 0.5 is achievable in practice, although it is not the highest theoretically. On the rear side, a theoretical maximum of 0.59 is observed, but this value is not attainable in practice. These maxima are separated by their positions along the line of flow relative to the disc. However, this approximation is limited to a streamlined flow model of the rotor disc.
文摘The electric power industry is undergoing profound transformations driven by big data,posing challenges to the traditional power grid marketing management model.These challenges include neglecting market demands,insufficient data support,and inadequate customer service.The application of big data technology offers innovative solutions for power grid marketing management,encompassing critical aspects such as data collection and integration,storage management,analysis,and mining.By leveraging these technologies,power grid enterprises can precisely understand customer needs,optimize marketing strategies,and enhance operational efficiency.This paper explores strategies for power grid marketing management based on big data,addressing areas such as customer segmentation and personalized services,as well as market demand forecasting and response.Furthermore,it proposes implementation pathways,including essential elements such as organizational structure and team building,data quality and governance systems,training,and cultural development.These efforts aim to ensure the effective application of big data technology and maximize its value.
文摘This paper introduces the system structure and work principle of the upgraded real time information system in Wangting Power Plant, and then expounds the realization way and function features of this system on B/S computing mode. The results of field application show the new system has good capability, reliability and expandability.
基金the financial support from the Universiti Kebangsaan Malaysia under the research grant UKM-DLP-2011-059
文摘An alternative method was introduced for voltage sag source location based on S and TT transformed disturbance powers. It is done to avoid the wrong and inconclusive detection of conventional disturbance power method proposed in the literature. Unlike in the case of the traditional method, the proposed method first transforms the recorded voltage and current during the sag event to some special features before calculating the new version of disturbance powers. The effectiveness of the proposed method has been verified through simulation and actual data from an industrial power system. The results show that the presented method can correctly detect the location of voltage sag source.
文摘This paper derives the variance of the information content and develops its statistical inference method. We describe the relations between information content and sensitivity, specificity, efficiency, prevalence rate. If sensitivity, specificity and efficiency are fixed, the closer to 0. 5 the prevalence rate is, the more the information content. If prevalence rate and efficiency are fixed, the closer to each other the sensitivity and specificity are, the more the information content. We compare the power of information content method, efficiecy test, Youden's index test and kappa coefficient method. The information content method has higher power than the other methods in most conditions. It is especially sensitive to the difference between two sensitivities. It comes to conclusion that the information content method has more virtues than the other methods mentioned in this paper.
基金Supported by the National Natural Science Foundation of China(No.81770908)the Shanghai Science and Technology Commission(Scientific Innovation Project,No.20Y11911000)。
文摘AIM:To investigate whether the axial length(AL)/total corneal refractive power(TCRP)ratio is a sensitive and simple factor that can be used for the early diagnosis of Marfan’s syndrome(MFS)in children.METHODS:The relationship between the AL/TCRP ratio and the diagnosis of MFS for 192 eyes in 97 children were evaluate.The biological characteristics,including age,sex,AL,and TCRP,were collected from medical records.Receiver operating characteristic(ROC)curve analysis was performed to investigate whether the AL/TCRP ratio effectively distinguishes MFS from other subjects.The Youden index was used to re-divide the whole population into two groups according to an AL/TCRP ratio of 0.59.RESULTS:Of 96 subjects(mean age 7.46±3.28 y)evaluated,56(110 eyes)had a definite diagnosis of MFS in childhood based on the revised Ghent criteria,41(82 eyes)with diagnosis of congenital ectopia lentis(EL)were included as a control group.AL was negatively correlated with TCRP,with a linear regression coefficient of-0.36(R2=0.08).A significant correlation was found between age and the AL/TCRP ratio(P=0.023).ROC curve analysis showed that the AL/TCRP ratio distinguished MFS from the other patients at a threshold of 0.59.MFS patients were present in 24/58(41.38%)patients with an AL/TCRP ratio of≤0.59 and in 34/39(87.18%)patients with an AL/TCRP ratio of>0.59.CONCLUSION:An AL/TCRP ratio of>0.59 is significantly associated with the risk of MFS.The AL/TCRP ratio should be measured as a promising marker for the prognosis of children MFS.Changes in the AL/TCRP ratio should be monitored over time.
基金supported by National Key Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of China in the 11th Five-Year Plan(Grant No.2007BAC03A12)
文摘Wind energy is a clean and sustainable energy, and wind power does not rely on fossil fuels. So there is no fuel price risk, and it, of course, does not include the environmental costs, such as carbon emissions. Because of these unique advantages, wind power has gradually become an important part of the strategy of sustainable development in China. Now with the growing voices on global greenhouse gas emission reduction, and as a clean and efficient energy, wind power has huge potential in combating climate change, energy security pressures and the needs for energy. Wind power in China began to develop from the 1980s. In the first 20 years, the speed of development was slow; but since 2004, it has had an extremely rapid growth.This paper, in order to study the development mechanism of China＆amp;amp;amp;#39;s wind power industry, investigated and analyzed the status quo of wind power industry in China, and then found that （1） the development trend of wind power industry in China appears exponential growth; （2） China＆amp;amp;amp;#39;s installed capacity of wind power is still smaller than that os some other countries; （3） new subsidy policies bring developing opportunities to wind power industry in China; （4） the sectors of wind power industry are in unbalanced growing; （5） the owners of proposed wind farms are too optimistic though the built wind farm had many problems. In addition, by using the methodology of Game Theory, this paper has also constructed the matrix of pre-assessing risks of China＆amp;amp;amp;#39;s wind power industry to further discuss the potential risk factors within China＆amp;amp;amp;#39;s wind power industry as risk factors of wind farm construction, risk factors of production of wind turbines, risk factors of parts and components manufacturing industry under risk indicators like R＆amp;amp;amp;amp;D, patents, the domestic policy, the international policy, the quality of products and the market regulation, in order to provide a scientific assessment and self-assessment tool for investors or implementers, and also to promote the further development of the wind power industry.
文摘The aim of this paper is to determine the power losses recorded by a PV generator operating under partial shading conditions. These losses are evaluated through two distinct methods. The first method is based on mathematical modeling, while the second is based on Simulink’s physical model. The losses recorded are considerable and increase as a function of the increase in the percentage of shading up to a limit value where they become constant in the case where an ideal by-pass diode is connected in parallel with the modules. This limit value is non-existent in the case where the bypass diode is not ideal, which in fact corresponds to the real model. However, it emerges that the power losses are minimized in a PV system comprising bypass diodes, in particular in the case where the partial shading is considerable.
基金Partially supported by the National Natural Science Foundation of China (No.60302009)the National Defense Advanced Research Foundation of China (No.413070501).
文摘Feature reduction is a key process in pattern recognition. This paper deals with the feature reduction methods for a time-shift invariant feature, power spectrum, in Radar Automatic Target Recognition (RATR) using High-Resolution Range Profiles (HRRPs). Several existing feature reduction methods in pattern recognition are analyzed, and a weighted feature reduction method based on Fisher's Discriminant Ratio (FDR) is proposed in this paper. According to the characteristics of radar HRRP target recognition, this proposed method searches the optimal weight vector for power spectra of HRRPs by means of an iterative algorithm, and thus reduces feature dimensionality. Compared with the method of using raw power spectra and some existing feature reduction methods, the weighted feature reduction method can not only reduce feature dimensionality, but also improve recognition performance with low computation complexity. In the recognition experiments based on measured data, the proposed method is robust to different test data and achieves good recognition results.
文摘China: the future of nuclear powerWang Yonggan: In terms of the highlighted issue ofenergy security, oil is of paramount importance, coal isthe foundation and electricity is the pivot according
基金Supported by the National Natural Science Foundation of China(No.61502255)the Inner Mongolia Provincial Natural Science Foundation(No.2014BS0607)the Science Research Project for Inner Mongolia College(No.NJZY14064)
文摘With the advent of big data,the demand for computing has been increasing in a very large scale for the past decade,so geographically distributed data centers are erected in the direction of cloud computing development. A Lyapunov optimization approach is considered for the problem of minimizing energy cost for distributed Internet data centers( IDCs). By capturing the power cost of servers and cooling systems,the Lyapunov optimization technique is formulated to design a decisive strategy that offers provable power cost minimization and Qo S guarantees. The algorithm performance and effectiveness are validated via simulations driven by real world traces.
