模块化多电平换流器(Modular Multilevel Converters,MMC)具有维护方便,易扩容等优点,在柔性直流输电(High Voltage Direct Current,HVDC)、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容,在实际使用中会产生谐波环流,影响...模块化多电平换流器(Modular Multilevel Converters,MMC)具有维护方便,易扩容等优点,在柔性直流输电(High Voltage Direct Current,HVDC)、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容,在实际使用中会产生谐波环流,影响了模块电容电压波动,降低换流器的安全裕度和经济性。文章首先介绍了MMC组成结构;然后通过建立桥臂瞬时功率方程,分析环流产生机理,并得出桥臂环流中存在二次谐波分量的结论,通过控制直流侧电压与桥臂等效输出电压之间的差值,调节环流中的谐波分量,进而将现阶段国内、外环流抑制方法分为间接环流抑制方法与直接环流抑制方法,并对环流的利用也做了相关阐述。最后对环流抑制存在的问题进行总结与展望。展开更多
We have previously shown that tumor cellsgenetically modified to co-express IL-4 or IL-7 and B7.1have increased immunogenicity and provided vaccinessuperior to single gene transfectants or tumor cells/adjuvant mixture...We have previously shown that tumor cellsgenetically modified to co-express IL-4 or IL-7 and B7.1have increased immunogenicity and provided vaccinessuperior to single gene transfectants or tumor cells/adjuvant mixture.Tumor antigens can be presented eitherdirectly by tumor cells or be indirectly represented byhost APC(cross-priming).Here we asked whether B7.1and IL-7 or IL-4 improved in an additive fashion one pathway of antigen presentation or complemented each other by improving preferentially different pathways of antigen presentation.展开更多
In the animal kingdom there are countless strategies via which males optimize their reproductivesuccess when faced with male-male competition. These male strategies typically fall into two maincategories： pre- and po...In the animal kingdom there are countless strategies via which males optimize their reproductivesuccess when faced with male-male competition. These male strategies typically fall into two maincategories： pre- and post-copulatory competition. Within these 2 categories, a set of behaviors,referred to as reproductive suppression, is known to cause inhibition of reproductive physiologyand/or reproductive behavior in an otherwise fertile individual. What becomes evident when con-sidering examples of reproductive suppression is that these strategies conventionally encompassreproductive interference strategies that occur between members of a hierarchical social group.However, mechanisms aimed at impairing a competitor＇s reproductive output are also present innon-social animals. Yet, current thinking emphasizes the importance of sociality as the primarydriving force of reproductive suppression. Therefore, the question arises as to whether there is anactual difference between reproductive suppression strategies in social animals and equivalentpre-copulatory competition strategies in non-social animals. In this perspective paper we explore abroad taxonomic range of species whose individuals do not repeatedly interact with the same indi-viduals in networks and yet, depress the fitness of rivals. Examples like alteration of male repro-ductive physiology, female mimicry, rival spermatophore destruction, and cementing the rival＇sgenital region in non-social animals, highlight that male pre-copulatory reproductive suppressionand male pre-copulatory competition overlap. Finally, we highlight that a distinction between malereproductive interference in animals with and without a social hierarchy might obscure importantsimilarities and does not help to elucidate why different proximate mechanisms evolved. We there-fore emphasize that male reproductive suppression need not be restricted to social animals.展开更多
An indirect method of measuring the rotor position based on the magnetic reluctance variation is presented in the paper. A single-chip microprocessor 80C196KC is utilized to compensate the phase shift produced by the ...An indirect method of measuring the rotor position based on the magnetic reluctance variation is presented in the paper. A single-chip microprocessor 80C196KC is utilized to compensate the phase shift produced by the process of position signals. At the same time, a DSP (Data Signal Processor) unit is used to realize the speed and current closed-loops of the hybrid stepping motor system. At last, experimental results show the control system has excellent static and dynamic characteristics.展开更多
The bias eliminated least squares （BELS） method, which is known as efficient for unknown parameter estimation of transfer function in the correlated noise case, has been developed and applied effectively to the clos...The bias eliminated least squares （BELS） method, which is known as efficient for unknown parameter estimation of transfer function in the correlated noise case, has been developed and applied effectively to the closed-loop system identification. In this paper, under the general settings, the realizations of the BELS method as a weighted instrumental variables （WlV） method in both direct and indirect closed- loop system identification are established through constructing an appropriate weighting matrix in the WlV method. The constructed structures are similar in both cases, which reveals that all the proof procedures of the two realizations are the same. Thus, the unified realizations of the BELS as the WlV method for the closed-loop system identification can be built. A simulation example is given to validate our theoretical analysis.展开更多
Objective To investigate the effects of E2F-1 gene silencing on multidrug resistance of human gastric cancer SGC7901/DDP cells and its possible mechanisms.Methods Gastric cancer SGC7901/DDP cells were seeded in 6 well...Objective To investigate the effects of E2F-1 gene silencing on multidrug resistance of human gastric cancer SGC7901/DDP cells and its possible mechanisms.Methods Gastric cancer SGC7901/DDP cells were seeded in 6 well plates and divided into three groups:the experimental group,blank control and the negative con-展开更多
The polarographic analyses or pyridine and some of its derivatives have been reported. Cetylpyridinium bromide （CPB）, a surface-active agent, can be used as a germicide in medicine. Doss et al. have studied its pola...The polarographic analyses or pyridine and some of its derivatives have been reported. Cetylpyridinium bromide （CPB）, a surface-active agent, can be used as a germicide in medicine. Doss et al. have studied its polarographic behaviour in dependence on the capacity of the DME. Dolezil et al., while using CPB to suppress the polarographic oxygen maximum, determined its trace concentrations (10-6～10-5M) indirectly, but the direct polarographic determination of CPB has not yet been reported. The present展开更多
文摘模块化多电平换流器(Modular Multilevel Converters,MMC)具有维护方便,易扩容等优点,在柔性直流输电(High Voltage Direct Current,HVDC)、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容,在实际使用中会产生谐波环流,影响了模块电容电压波动,降低换流器的安全裕度和经济性。文章首先介绍了MMC组成结构;然后通过建立桥臂瞬时功率方程,分析环流产生机理,并得出桥臂环流中存在二次谐波分量的结论,通过控制直流侧电压与桥臂等效输出电压之间的差值,调节环流中的谐波分量,进而将现阶段国内、外环流抑制方法分为间接环流抑制方法与直接环流抑制方法,并对环流的利用也做了相关阐述。最后对环流抑制存在的问题进行总结与展望。
文摘We have previously shown that tumor cellsgenetically modified to co-express IL-4 or IL-7 and B7.1have increased immunogenicity and provided vaccinessuperior to single gene transfectants or tumor cells/adjuvant mixture.Tumor antigens can be presented eitherdirectly by tumor cells or be indirectly represented byhost APC(cross-priming).Here we asked whether B7.1and IL-7 or IL-4 improved in an additive fashion one pathway of antigen presentation or complemented each other by improving preferentially different pathways of antigen presentation.
文摘In the animal kingdom there are countless strategies via which males optimize their reproductivesuccess when faced with male-male competition. These male strategies typically fall into two maincategories： pre- and post-copulatory competition. Within these 2 categories, a set of behaviors,referred to as reproductive suppression, is known to cause inhibition of reproductive physiologyand/or reproductive behavior in an otherwise fertile individual. What becomes evident when con-sidering examples of reproductive suppression is that these strategies conventionally encompassreproductive interference strategies that occur between members of a hierarchical social group.However, mechanisms aimed at impairing a competitor＇s reproductive output are also present innon-social animals. Yet, current thinking emphasizes the importance of sociality as the primarydriving force of reproductive suppression. Therefore, the question arises as to whether there is anactual difference between reproductive suppression strategies in social animals and equivalentpre-copulatory competition strategies in non-social animals. In this perspective paper we explore abroad taxonomic range of species whose individuals do not repeatedly interact with the same indi-viduals in networks and yet, depress the fitness of rivals. Examples like alteration of male repro-ductive physiology, female mimicry, rival spermatophore destruction, and cementing the rival＇sgenital region in non-social animals, highlight that male pre-copulatory reproductive suppressionand male pre-copulatory competition overlap. Finally, we highlight that a distinction between malereproductive interference in animals with and without a social hierarchy might obscure importantsimilarities and does not help to elucidate why different proximate mechanisms evolved. We there-fore emphasize that male reproductive suppression need not be restricted to social animals.
文摘An indirect method of measuring the rotor position based on the magnetic reluctance variation is presented in the paper. A single-chip microprocessor 80C196KC is utilized to compensate the phase shift produced by the process of position signals. At the same time, a DSP (Data Signal Processor) unit is used to realize the speed and current closed-loops of the hybrid stepping motor system. At last, experimental results show the control system has excellent static and dynamic characteristics.
基金Supported by the National Natural Science Foundation of China for Distinguished Young Scholars (Grant No. 60625104)the Ministerial Foundation of China (Grant No. A2220060039)the Fundamental Research Foundation of BIT (Grant No. 1010050320810)
文摘The bias eliminated least squares （BELS） method, which is known as efficient for unknown parameter estimation of transfer function in the correlated noise case, has been developed and applied effectively to the closed-loop system identification. In this paper, under the general settings, the realizations of the BELS method as a weighted instrumental variables （WlV） method in both direct and indirect closed- loop system identification are established through constructing an appropriate weighting matrix in the WlV method. The constructed structures are similar in both cases, which reveals that all the proof procedures of the two realizations are the same. Thus, the unified realizations of the BELS as the WlV method for the closed-loop system identification can be built. A simulation example is given to validate our theoretical analysis.
文摘Objective To investigate the effects of E2F-1 gene silencing on multidrug resistance of human gastric cancer SGC7901/DDP cells and its possible mechanisms.Methods Gastric cancer SGC7901/DDP cells were seeded in 6 well plates and divided into three groups:the experimental group,blank control and the negative con-
文摘The polarographic analyses or pyridine and some of its derivatives have been reported. Cetylpyridinium bromide （CPB）, a surface-active agent, can be used as a germicide in medicine. Doss et al. have studied its polarographic behaviour in dependence on the capacity of the DME. Dolezil et al., while using CPB to suppress the polarographic oxygen maximum, determined its trace concentrations (10-6～10-5M) indirectly, but the direct polarographic determination of CPB has not yet been reported. The present
