基于模块化多电平换流器的高压柔性直流输电系统(modular multilevel converter-based high voltage direct current,MMC-HVDC)常采用双极接线方式以提高系统功率输送能力和可靠性。然而目前对于风电场经柔直外送系统的稳定性研究集中...基于模块化多电平换流器的高压柔性直流输电系统(modular multilevel converter-based high voltage direct current,MMC-HVDC)常采用双极接线方式以提高系统功率输送能力和可靠性。然而目前对于风电场经柔直外送系统的稳定性研究集中于单极接线方式,孤岛直驱风电场与采用不同双极协调控制的双极MMC-HVDC互联系统小信号稳定性问题还有待进一步探究。该文首先考虑频率耦合特性、参考系初相位和直流侧耦合特性的影响,分别建立了采用双U/f下垂控制和定U/f-P/Q控制的双极MMC-HVDC系统交流侧等效SISO阻抗模型,并详细分析了金属回线阻抗和双极间功率均分度对交流阻抗特性的影响。接着对比研究了两种协调控制中共有控制环路和特有控制环路对交流侧负电阻特性及互联系统稳定性的影响规律。最后,孤岛直驱风电场经两种双极协调控制下双极MMC-HVDC外送系统Matlab/Simulink时域仿真结果和硬件在环半实物实时仿真实验结果验证了所提出的小信号阻抗模型的精确性和稳定性分析结论的有效性。展开更多
骨髓增殖性肿瘤(myeloproliferative neoplasms,MPN)导致血细胞增加、血液高凝,是非肝硬化门静脉海绵样变性的重要病因。JAK2V617F基因突变可以帮助诊断MPN。我们报道1例JAK2V617F基因突变阳性的MPN患者发生门静脉海绵样变性(cavernous ...骨髓增殖性肿瘤(myeloproliferative neoplasms,MPN)导致血细胞增加、血液高凝,是非肝硬化门静脉海绵样变性的重要病因。JAK2V617F基因突变可以帮助诊断MPN。我们报道1例JAK2V617F基因突变阳性的MPN患者发生门静脉海绵样变性(cavernous transformation of the portal vein,CTPV)。该例患者脾脏显著肿大,一方面是由于骨髓增殖性疾病本身的原因,另一方面是由于PVCT、门脉高压和脾脏淤血造成,表现为外周血血细胞计数基本在正常范围,亦是血细胞增殖和脾脏对血细胞的处理增加的共同作用的结果。抗凝治疗效果差,而应以预防食管曲张静脉破裂出血(EVB)为主。展开更多
The precondition of realizing feedback controlling DC DC converter to avoid chaotic state is to judge the behavior of the converter and take corresponding measures. In this paper, the output signals under different ci...The precondition of realizing feedback controlling DC DC converter to avoid chaotic state is to judge the behavior of the converter and take corresponding measures. In this paper, the output signals under different circuit parameters of the PWM buck converter have been analyzed. The method of using Fourier descriptor to extract output signals characteristics is put forward and proved to be a gist of identifying and classifying the behavior of DC DC converter. This method can establish a good foundation fo...展开更多
A mine-used multi-function serial signal converter is introduced.This converter is based on Ethernet.The core of this design is embedded microprocessor STM32F107VCT6.Embedded operation system μC/OS-Ⅱ is transplanted...A mine-used multi-function serial signal converter is introduced.This converter is based on Ethernet.The core of this design is embedded microprocessor STM32F107VCT6.Embedded operation system μC/OS-Ⅱ is transplanted into this converter,and light-weight Internet protocal （LwIP） stack is also embedded to realize mutual conversion of serial signals such as meter bus （M-Bus） signal,RS485 signal,RS232 signal and Ethernet signal.Interconnection between all kinds of monitoring system interfaces under coal mine can be formed easily,which can solve compatibility problem between monitoring system and communication system and improve overall performance of safety monitoring system.The designed multi-function serial signal converter is of great value for application,which is worthy to be popularized in coal mine safety production.展开更多
KVPO_(4)F(KVPF)has been extensively investigated as the potential cathode material for potassium-ion batteries(PIBs)owing to its high theoretical capacity,superior operating voltage,and three-dimensional Kt conduction...KVPO_(4)F(KVPF)has been extensively investigated as the potential cathode material for potassium-ion batteries(PIBs)owing to its high theoretical capacity,superior operating voltage,and three-dimensional Kt conduction pathway.Nevertheless,the electrochemical behavior of KVPF is limited by the inherent poor electronic conductivity of the phosphate framework and unstable electrode/electrolyte interface.To address the above issues,this work proposes an infiltration-calcination method to confine the in-situ grown KVPF into the mesoporous carbon CMK-3(denoted KVPF@CMK-3).The assembled KVPF@CMK-3 nanocomposite features three-dimensional interconnected carbon channels,which not only offer abundant active sites and significantly accelerate K t/electron transport,but also prevent the growth of KVPF nanoparticle agglomerates,hence stabilizing the structure of the material.Additionally,V–F–C bonds are created at the interface of KVPF and CMK-3,which reduce the loss of F and stabilize the electrode interface.Thus,when tested as a cathode material for PIBs,the KVPF@CMK-3 nanocomposite delivers superior reversible capacitiy(103.2 mAh g^(-1) at 0.2 C),outstanding rate performance(90.1 mAh g^(-1) at 20 C),and steady cycling performance(92.2 mAh g^(-1) at 10 C and with the retention of 88.2%after 500 cycles).Moreover,its potassium storage mechanism is further examined by ex-situ XRD and ex-situ XPS techniques.The above synthetic strategy demonstrates the potential of KVPF@CMK-3 to be applied as the cathode for PIBs.展开更多
Microelectronic power converters such as buck and boost converter are required to be tolerant to radiations including electron radiation. This paper examines electron radiation effects on the Ⅰ-Ⅴ characteristics of ...Microelectronic power converters such as buck and boost converter are required to be tolerant to radiations including electron radiation. This paper examines electron radiation effects on the Ⅰ-Ⅴ characteristics of VDMOSFET and its corresponding effects in buck converter. Analysis of the electrical characteristics shows that after irradiation the threshold voltage and drain current for all VDMOSFETs degraded more than two orders of magnitude. The impact of this electrical degradation has been investigated in an application of typical buck converter circuit. The buck converter with n-channel switching transistor shows that after irradiation its output voltage increased with the drain current in the n-channel ZVN4424 A VDMOSFET, while the buck converter with p-channel switching transistor shows its output voltage decreased with the drain current in the p-channel ZVP4424 A VDMOSFET after irradiation.展开更多
This paper describes the development of a timer based voltage to frequency converter(V FC).Timer LM555is used in astable multivibrator mode with two OPTO-LDRs(light dependent resistors)in the circuitry.The frequency o...This paper describes the development of a timer based voltage to frequency converter(V FC).Timer LM555is used in astable multivibrator mode with two OPTO-LDRs(light dependent resistors)in the circuitry.The frequency of timer output waveform which is measured using a digital storage oscillator(DSO)is almost linearly proportional to the applied input voltage.Hence we obtain a linear relationship between the frequency of timer output waveform and the input voltage.Because of its quasi-digital output,the main advantages of this developed converter are linear input-output relationship,small size,easy portabilityand high cost performance.In addition,the timer output waveform can be directly interfaced with personal computer or microprocessor/microcontroller for further processing of the input voltage signal without intervening any analog-to-digital converter(ADC).展开更多
BACKGROUND Acute upper gastrointestinal bleeding is a common medical emergency that has a 10%hospital mortality rate.According to the etiology,this disease can be divided into acute varicose veins and nonvaricose vein...BACKGROUND Acute upper gastrointestinal bleeding is a common medical emergency that has a 10%hospital mortality rate.According to the etiology,this disease can be divided into acute varicose veins and nonvaricose veins.Bleeding from esophageal varices is a life-threatening complication of portal hypertension.Portal hypertension is a clinical syndrome defined as a portal venous pressure that exceeds 10 mmHg.Cirrhosis is the most common cause of portal hypertension,and thrombosis of the portal system not associated with liver cirrhosis is the second most common cause of portal hypertension in the Western world.Primary myeloproliferative disorders are the main cause of portal venous thrombosis,and somatic mutations in the Janus kinase 2 gene(JAK2 V617F)can be found in approximately 90% of polycythemia vera,50% of essential thrombocyrosis and 50% of primary myelofibrosis.CASE SUMMARY We present a rare case of primary myelofibrosis with gastrointestinal bleeding as the primary manifestation that presented as portal-superior-splenic mesenteric vein thrombosis.Peripheral blood tests revealed the presence of the JAK2 V617F mutation.Bone marrow biopsy ultimately confirmed the diagnosis of myelofibrosis(MF-2 grade).CONCLUSION In patients with acute esophageal variceal bleeding due to portal hypertension and vein thrombosis without cirrhosis,the possibility of myeloproliferative neoplasms should be considered,and the JAK2 mutation test should be performed.展开更多
A discrete iterative map model of V^2C control boost converter was established to study the dynamical behaviors of the converter. By using parameter space map and bifurcation diagram, the effects of circuit parameters...A discrete iterative map model of V^2C control boost converter was established to study the dynamical behaviors of the converter. By using parameter space map and bifurcation diagram, the effects of circuit parameters on the bifurcation behaviors of V^2C control and current-mode control boost converters were analyzed. The phase portraits and time-domain waveforms of the V^2C control boost converter were obtained by Runge-Kutta algorithm through piecewise smooth switching model. The research results indicate that V^2C control boost converters can evolve into periodic and chaotic behaviors, and show weaker nonlinear behaviors than current-mode control boost converters.展开更多
文摘基于模块化多电平换流器的高压柔性直流输电系统(modular multilevel converter-based high voltage direct current,MMC-HVDC)常采用双极接线方式以提高系统功率输送能力和可靠性。然而目前对于风电场经柔直外送系统的稳定性研究集中于单极接线方式,孤岛直驱风电场与采用不同双极协调控制的双极MMC-HVDC互联系统小信号稳定性问题还有待进一步探究。该文首先考虑频率耦合特性、参考系初相位和直流侧耦合特性的影响,分别建立了采用双U/f下垂控制和定U/f-P/Q控制的双极MMC-HVDC系统交流侧等效SISO阻抗模型,并详细分析了金属回线阻抗和双极间功率均分度对交流阻抗特性的影响。接着对比研究了两种协调控制中共有控制环路和特有控制环路对交流侧负电阻特性及互联系统稳定性的影响规律。最后,孤岛直驱风电场经两种双极协调控制下双极MMC-HVDC外送系统Matlab/Simulink时域仿真结果和硬件在环半实物实时仿真实验结果验证了所提出的小信号阻抗模型的精确性和稳定性分析结论的有效性。
文摘目的 筛选卵巢癌预后不良的分子生物学标志。方法 从GEO数据库获得卵巢癌GSE14001、GSE14407数据集,用在线分析工具GEO2R、Venn筛选得到卵巢癌和正常卵巢组织差异表达基因(DEGs),对DEGs进行富集分析,构建蛋白互作网络(PPI),以及构建网络模块得到关键基因,利用Kaplan Meier plotter网站分析关键基因与卵巢癌患者总生存期之间关系,应用GEPIA数据库分析DEGs在卵巢和卵巢癌组织中表达,应用The Human Protein Atlas数据库获取筛选基因的免疫组化结果,对比它们在卵巢和卵巢癌组织间的表达差异。结果 得到211个DEGs,92个上调和119个下调。差异基因生物学过程主要涉及侧枝发芽的正向调控、乏氧反应、间充质-上皮细胞信号传导;细胞组分主要集中在质膜顶、细胞表面、细胞外外泌体等部位;分子功能主要涉及丝氨酸型内肽酶活性、金属内肽酶活性、受体活性等;信号通路富集于白细胞跨内皮细胞迁移、细胞黏附通路、癌症通路等信号通路。得到35个候选基因,其中14个基因高表达、8个基因低表达与患者总生存期相关(P<0.05)。其中ATP6V1F、GINS1、GINS4基因在卵巢癌组织中在RNA水平和蛋白质水平表达均高于正常组织(P<0.05)。GNB3在卵巢癌组织中RNA水平表达低于正常组织,而在蛋白质水平恰好相反(P<0.05)。结论 ATP6V1F、GINS1、GINS4有可能是卵巢癌预后不良的新分子标志物。
文摘骨髓增殖性肿瘤(myeloproliferative neoplasms,MPN)导致血细胞增加、血液高凝,是非肝硬化门静脉海绵样变性的重要病因。JAK2V617F基因突变可以帮助诊断MPN。我们报道1例JAK2V617F基因突变阳性的MPN患者发生门静脉海绵样变性(cavernous transformation of the portal vein,CTPV)。该例患者脾脏显著肿大,一方面是由于骨髓增殖性疾病本身的原因,另一方面是由于PVCT、门脉高压和脾脏淤血造成,表现为外周血血细胞计数基本在正常范围,亦是血细胞增殖和脾脏对血细胞的处理增加的共同作用的结果。抗凝治疗效果差,而应以预防食管曲张静脉破裂出血(EVB)为主。
文摘The precondition of realizing feedback controlling DC DC converter to avoid chaotic state is to judge the behavior of the converter and take corresponding measures. In this paper, the output signals under different circuit parameters of the PWM buck converter have been analyzed. The method of using Fourier descriptor to extract output signals characteristics is put forward and proved to be a gist of identifying and classifying the behavior of DC DC converter. This method can establish a good foundation fo...
文摘A mine-used multi-function serial signal converter is introduced.This converter is based on Ethernet.The core of this design is embedded microprocessor STM32F107VCT6.Embedded operation system μC/OS-Ⅱ is transplanted into this converter,and light-weight Internet protocal （LwIP） stack is also embedded to realize mutual conversion of serial signals such as meter bus （M-Bus） signal,RS485 signal,RS232 signal and Ethernet signal.Interconnection between all kinds of monitoring system interfaces under coal mine can be formed easily,which can solve compatibility problem between monitoring system and communication system and improve overall performance of safety monitoring system.The designed multi-function serial signal converter is of great value for application,which is worthy to be popularized in coal mine safety production.
基金This work was supported by the National Natural Science Foundation of China(22179063).
文摘KVPO_(4)F(KVPF)has been extensively investigated as the potential cathode material for potassium-ion batteries(PIBs)owing to its high theoretical capacity,superior operating voltage,and three-dimensional Kt conduction pathway.Nevertheless,the electrochemical behavior of KVPF is limited by the inherent poor electronic conductivity of the phosphate framework and unstable electrode/electrolyte interface.To address the above issues,this work proposes an infiltration-calcination method to confine the in-situ grown KVPF into the mesoporous carbon CMK-3(denoted KVPF@CMK-3).The assembled KVPF@CMK-3 nanocomposite features three-dimensional interconnected carbon channels,which not only offer abundant active sites and significantly accelerate K t/electron transport,but also prevent the growth of KVPF nanoparticle agglomerates,hence stabilizing the structure of the material.Additionally,V–F–C bonds are created at the interface of KVPF and CMK-3,which reduce the loss of F and stabilize the electrode interface.Thus,when tested as a cathode material for PIBs,the KVPF@CMK-3 nanocomposite delivers superior reversible capacitiy(103.2 mAh g^(-1) at 0.2 C),outstanding rate performance(90.1 mAh g^(-1) at 20 C),and steady cycling performance(92.2 mAh g^(-1) at 10 C and with the retention of 88.2%after 500 cycles).Moreover,its potassium storage mechanism is further examined by ex-situ XRD and ex-situ XPS techniques.The above synthetic strategy demonstrates the potential of KVPF@CMK-3 to be applied as the cathode for PIBs.
基金funded by International Islamic University Malaysia(No.EDW B14-159-1044)
文摘Microelectronic power converters such as buck and boost converter are required to be tolerant to radiations including electron radiation. This paper examines electron radiation effects on the Ⅰ-Ⅴ characteristics of VDMOSFET and its corresponding effects in buck converter. Analysis of the electrical characteristics shows that after irradiation the threshold voltage and drain current for all VDMOSFETs degraded more than two orders of magnitude. The impact of this electrical degradation has been investigated in an application of typical buck converter circuit. The buck converter with n-channel switching transistor shows that after irradiation its output voltage increased with the drain current in the n-channel ZVN4424 A VDMOSFET, while the buck converter with p-channel switching transistor shows its output voltage decreased with the drain current in the p-channel ZVP4424 A VDMOSFET after irradiation.
文摘This paper describes the development of a timer based voltage to frequency converter(V FC).Timer LM555is used in astable multivibrator mode with two OPTO-LDRs(light dependent resistors)in the circuitry.The frequency of timer output waveform which is measured using a digital storage oscillator(DSO)is almost linearly proportional to the applied input voltage.Hence we obtain a linear relationship between the frequency of timer output waveform and the input voltage.Because of its quasi-digital output,the main advantages of this developed converter are linear input-output relationship,small size,easy portabilityand high cost performance.In addition,the timer output waveform can be directly interfaced with personal computer or microprocessor/microcontroller for further processing of the input voltage signal without intervening any analog-to-digital converter(ADC).
文摘BACKGROUND Acute upper gastrointestinal bleeding is a common medical emergency that has a 10%hospital mortality rate.According to the etiology,this disease can be divided into acute varicose veins and nonvaricose veins.Bleeding from esophageal varices is a life-threatening complication of portal hypertension.Portal hypertension is a clinical syndrome defined as a portal venous pressure that exceeds 10 mmHg.Cirrhosis is the most common cause of portal hypertension,and thrombosis of the portal system not associated with liver cirrhosis is the second most common cause of portal hypertension in the Western world.Primary myeloproliferative disorders are the main cause of portal venous thrombosis,and somatic mutations in the Janus kinase 2 gene(JAK2 V617F)can be found in approximately 90% of polycythemia vera,50% of essential thrombocyrosis and 50% of primary myelofibrosis.CASE SUMMARY We present a rare case of primary myelofibrosis with gastrointestinal bleeding as the primary manifestation that presented as portal-superior-splenic mesenteric vein thrombosis.Peripheral blood tests revealed the presence of the JAK2 V617F mutation.Bone marrow biopsy ultimately confirmed the diagnosis of myelofibrosis(MF-2 grade).CONCLUSION In patients with acute esophageal variceal bleeding due to portal hypertension and vein thrombosis without cirrhosis,the possibility of myeloproliferative neoplasms should be considered,and the JAK2 mutation test should be performed.
基金The National Natural Science Foundation of China (No.50677056)the Natural Science Foundations of Jiangsu Province (No.BK2009105)
文摘A discrete iterative map model of V^2C control boost converter was established to study the dynamical behaviors of the converter. By using parameter space map and bifurcation diagram, the effects of circuit parameters on the bifurcation behaviors of V^2C control and current-mode control boost converters were analyzed. The phase portraits and time-domain waveforms of the V^2C control boost converter were obtained by Runge-Kutta algorithm through piecewise smooth switching model. The research results indicate that V^2C control boost converters can evolve into periodic and chaotic behaviors, and show weaker nonlinear behaviors than current-mode control boost converters.
