Reassessment of Permissible Negative Sequence Current for Power Plant Operation of Taipower

The N3 power plant of Taipower is located in the southern tip of Taiwan and connected to the power pool by four out-linking 345-kV overhead transmission circuits. There are two 951-MW generators. Each generator occupied 11% of the system peak load in 1985 when the generator was in commercial operation. Since Taipower is an isolated system, at the N-2 conditions, those generators were reduced to 75% loading to protect the power system. By the way, to avoid damage of negative sequence current (NSC), the limits of the N3 power plant are stricter than those in the IEEE Standard. However, in 2010, the capacity ratio of each generator in the plant to the system peak load has been reduced to 3% only. To increase the economic benefit of those generators, it is required to reassess the operation limits of NSC. EMTP was used to calculate the levels of NSC from the out-linking transmission circuits. From the results of this study, the effects of NSC could be ignored when the four out-linking circuits are in N-0, N-1, and N-2 conditions. The generators can be operated in full loading under these conditions. The modifications to the NSC limits of the N3 power plant are also suggested.

Efficacy of platinum in advanced triple-negative breast cancer with germline BRCA mutation determined by next generation sequencing

Objective:To compare the efficacy of platinum-and non-platinum-based regimens as first-line treatment for advanced triple-negative breast cancer(TNBC)and analyze the relationship between their efficacy and BRCA gene status.Methods:Retrospectively analyze clinical data of 220 patients diagnosed pathologically with advanced TNBC and treated at the Department of Breast Oncology,Peking University Cancer Hospital from 2013 to 2018 and evaluate the efficacy of chemotherapy.A total of 114 patients had BRCA1/2 gene tested by next generation sequencing(NGS)using peripheral blood,and we analyzed the correlation between their efficacy and BRCA1/2 gene status.Results:Non-platinum-based chemotherapy(NPCT)was administered to 129 and platinum-based chemotherapy(PBCT)to 91 study patients.The clinical benefit rate(CBR)and median progression-free survival(PFS)were not statistically different between NPCT and PBCT groups.The median overall survival(OS)was 30.0 and 22.5 months for PBCT and NPCT group,respectively[P=0.090,hazard ratios(HR)=0.703].BRCA status was assessed in 114 patients,14 of whom had deleterious germline BRCA1/2(g BRCA)mutations(seven in each group).In PBCT group,the CBR was 85.7%and 35.1%for patients with and without deleterious g BRCA mutations,respectively(P=0.039).The median PFS were 14.9 and 5.3 months and median OS were 26.5 and 15.5 months for patients with and without deleterious g BRCA mutations,respectively(P=0.001,P=0.161,respectively).Patients in PBCT group had significantly greater rates of grade 3-4 anemia(5.5%vs.0%)and thrombocytopenia(8.8%vs.0%),whereas palmar-plantar erythrodysesthesia(12.4%vs.0%)and peripheral neuropathy(8.6%vs.1.1%)occurred more frequently in NPCT group.Conclusions:Platinum-based regimens are more effective in patients with deleterious g BRCA mutations,but no difference in patients without BRCA gene mutations,so non-platinum is an option in patients without BRCA gene mutations considering the toxicity and side effect.And we recommend that patients with advanced TNBC should have BRCA gene test.

Loading Sequence Effects on Dragload and Downdrag for Pile Foundation

Negative skin friction (NSF) is one of the important problems when designing a pile foundation. However, the influence of loading sequence on the dragload and downdrag for pile foundation is seldom studied. In this paper, a three-dimensional numerical model was established using FLAC3D. Compared with the results of model test, the established model could be used to study the NSF of pile foundation. The influencing factors were discussed including the length-diameter ratio of pile and the loading sequence of pile head load and surcharge. A case history was analyzed using FLAC3D. The calculated results are in good agreement with the measured results. It is concluded that the dragload and downdrag are remarkably influenced by the loading sequence of pile head load and surcharge. The dragload and downdrag reach the maximum values under the condition of surcharge after pile head load.

Effects of Voltage Sag on the Performance of Induction Motor Based on a New Transient Sequence Component Method

Voltage sag is one of the most common power quality disturbances in industry,which causes huge inrush currents in stator windings of induction motors,and adversely impacts the motor secure operation.This paper firstly introduces a 2D Time-Stepping multi-slice finite element method(2D T-S multi-slice FEM)which is used for calculating the magnetic field distribution in induction motors under different sag events.Then the paper deduces the transient analytical expression of stator inrush current based on the classical theory of AC motors and presents a separation method for the positive,negative and zero sequence values based on instantaneous currents.With this method,the paper studies the influences of voltage sag amplitude,phase-angle jump and initial phase angle on the stator positive-and negative-sequence peak currents of 5.5 kW and 55 kW induction motors.This paper further proposes a motor protection method under voltage sag condition with the stator negative-sequence peak currents as the protection threshold,so that the protection false trip can be avoided effectively.Finally,the calculation and analysis results are validated by the comparison of calculated and measured stator peak value of the 5.5 kW induction motor.

The Acquisition of English Negatives by a Portuguese Boy

this study provided the strong evidence that L2 learner's development patterns in syntactic structure is very similar to the pattern of L1 learners.L2 and L1 learner pass the similar gradual route to get the TL negative structure.But L2 learners' acquisitional sequences are not completely rigid.Individual learners may be interfered by other social or psychological factors en route and they may take longer than two years and some never travel the whole distance.

Open-loop Phase Synchronization Method of Positive and Negative Sequences for Three-phase Asymmetric Grid

Currently,a grid-connected inverter is required to inject a dual-sequence current during asymmetric grid sags,which means both positive and negative sequence phases should be tracked.This paper proposes an open-loop phase synchronization(OLS)method of positive and negative sequences for an asymmetric grid based on the moving average filter(MAF),which does not need to separate the positive and negative sequence fundamental components of grid voltage.As a benefit,there is no double-frequency oscillation in the estimated phases at offnominal frequencies since the positive and negative sequence phases are obtained simultaneously.The proposed method not only has the inherent advantages of OLS,but also further improves the dynamic response since the window length of MAF is only 1/6 of the fundamental period.The effectiveness of the proposed OLS is verified by experimental results.

基于双向LSTM与CRF融合模型的否定聚焦点识别

否定表达作为自然语言文本中常见的语言现象,对自然语言处理上层应用,如情感分析、信息抽取等,具有十分重要的意义。否定聚焦点识别任务是更细粒度的否定语义分析,其旨在识别出句子中被否定词修饰和强调的文本片段。该文将该任务作为序列标注问题,提出了一种基于双向长短期记忆网络结合条件随机场(BiLSTMCRF)的否定聚焦点识别模型,其中,BiLSTM网络能够充分利用上下文信息并抓取全局特征,CRF层能够有效学习输出标签之间的前后依赖关系。在*SEM2012评测任务数据集上的实验结果表明,基于BiLSTM-CRF的否定聚焦点识别方法的准确率(accuracy)达到69.58%,与目前最好的系统相比,性能提升了2.44%。

差比序列视角下“不是A但是/只是/而是B”之比较

语言中的某些词或词组可以形成一个差比序列。将不同差比序列项分别嵌入"不是A但是/只是/而是B"框架,对其嵌入条件、语义内涵和否定类别分别加以比较,可从新的视角发现这三个框架深层次的区别与联系。

从普遍语法的角度看ESL否定句习得顺序

研究表明,不同母语的学习者在把英语作为第二语言(ESL)进行习得的过程中,对英语否定句的习得遵循着大致相同的顺序。针对这一问题,从普遍语法的角度提出了ESL否定句习得直接利用普遍语法、间接利用普遍语法、以及不利用普遍语法的三种假设,并结合具体语例对每一种假设进行了分析。

汉语否定与不确定覆盖域检测

自然语言文本中存在大量否定和不确定表述,识别这些信息并将其与确定性内容分离,对自然语言处理的下游应用,如信息抽取、信息检索、情感分析等,都具有十分重要的意义.与英语相比,面向汉语的否定与不确定覆盖域检测研究目前较为匮乏.提出了一个基于双向长短期记忆(bidirectional long short-term memory, BiLSTM)网络和条件随机场(conditional random fields, CRF)的融合模型,将覆盖域检测任务作为序列标注问题,针对给定的否定或不确定关键词,识别其在句子中的语义作用范围.该模型既具有LSTM(long short-term memory)网络能够利用前向与后向上下文信息的特性,同时又能够借助CRF 层获取输出标签之间的依赖关系,这得益于该框架能够有效地对序列信息及长距离上下文依赖信息进行编码的优势.在CNeSp语料集上的实验结果验证了模型的有效性,其中,在金融新闻子数据集上,否定与不确定覆盖域检测准确率分别达到79.16%和76.79%,比目前基于传统机器学习的汉语覆盖域检测方法分别提升了25.06%和34.46%.

A modified predictive control strategy of three-phase grid-connected converters with optimized action time sequence

Due to the excellent dynamic performance,the Finite Control Set Model Predictive Control has been widely used in various types of converters.However,when Finite Control Set Model Predictive Control is adopted,the switching frequency of converters varies significantly with system operating conditions.Consequently,constant-frequency predictive control strategy has been proposed.Two active voltage vectors and a zero voltage vector are selected within each sampling period.The action time sequence is then calculated.Due to the unsymmetrical distribution of current variation rates around zero,the calculated value of the voltage-vector action time will turn up negative.According to common sense,the voltage-vector action time is greater than or equal to zero.The action time is normally forced to zero whenever a negative value is predicted,resulting in the control failure and performance deterioration.To solve this problem,this paper proposes modified strategy.The modified strategy examines the action time calculated out.When negative action time comes out,the modified strategy reselects the active voltage vector accordingly,instead of forcing the action time to be zero.Optimized action time sequence is further determined by minimizing the cost function.The effectiveness of the modified strategy is clearly verified by experimental tests,and analytical remarks are all founded in practical results.

Intelligent power factor compensation equipment of three phase low voltage loads

An intelligent power factor correction scheme is presented for three phase low power factor loads. This new scheme is able to perform individual phase sensing of parameters by monitoring at all times to sense a change in system parameters and affects individual phase correction by applying the exact amount of reactive components needed for each phase, and can also reduce negative sequence current caused by the load to improve system balance. An optimization criterion is used for the proper calculation of reactive power steps in a power compensation installation of capacitor banks. The criterion is enabled by sampling measurements performed on the electrical plant examined within specific interval of time.

Modeling method of sequence admittance for three-phase voltage source converter under unbalanced grid condition

The admittance is a strong tool for stability analysis and assessment of the three-phase voltage source converters(VSCs) especially in grid-connected mode.However, the sequence admittance is hard to calculate when the VSC is operating under unbalanced grid voltage conditions. In this paper, a simple and direct modeling method is proposed for a three-phase VSC taking the unbalanced grid voltage as a new variable for the system.Then coupling in the three-phase system can be calculated by applying the harmonic linearization method. The calculated admittance of three-phase VSCs is verified by detailed circuit simulations.

Gene therapeutic approaches to inhibit hepatitis B virus replication

Acute and chronic hepatitis B virus(HBV) infections remain to present a major global health problem. The infection can be associated with acute symptomatic or asymptomatic hepatitis which can cause chronic inflammation of the liver and over years this can lead to cirrhosis and the development of hepatocellularcarcinomas. Currently available therapeutics for chronically infected individuals aim at reducing viral replication and to slow down or stop the progression of the disease. Therefore, novel treatment options are needed to efficiently combat and eradicate this disease. Here we provide a state of the art overview of gene therapeutic approaches to inhibit HBV replication. We discuss non-viral and viral approaches which were explored to deliver therapeutic nucleic acids aiming at reducing HBV replication. Types of delivered therapeutic nucleic acids which were studied since many years include antisense oligodeoxynucleotides and antisense RNA, ribozymes and DNAzymes, RNA interference, and external guide sequences. More recently designer nucleases gained increased attention and were exploited to destroy the HBV genome. In addition we mention other strategies to reduce HBV replication based on delivery of DNA encoding dominant negative mutants and DNA vaccination. In combination with available cell culture and animal models for HBV infection, in vitro and in vivo studies can be performed to test efficacy of gene therapeutic approaches. Recent progress but also challenges will be specified and future perspectives will be discussed. This is an exciting time to explore such approaches because recent successes of gene therapeutic strategies in the clinic to treat genetic diseases raise hope to find alternative treatment options for patients chronically infected with HBV.

Design of DSTATCOM Controller for Compensating Unbalances

In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due to unequal voltage magnitudes at the fundamental frequency, phase angle deviations or unequal distribution of single phase loads. The voltage unbalance is a major power quality issue, because a small unbalance in the phase voltages can cause a larger unbalance in the phase currents. A completely balanced three-phase three wire system contains only positive sequence components of voltage, current and impedance, whereas unbalanced system contains both positive and negative sequence components of voltages and currents. The negative sequence component of current in the unbalanced system increases the temperature and losses in the equipments. Hence, it is necessary to mitigate this problem by supplying the negative sequence current to the load at the load side and keep the source side balanced. This paper proposes the shunt connected, current injecting Distribution Static Synchronous Compensator (DSTATCOM) with appropriate controller to mitigate the unbalanced load current. The symmetrical components based Hysteresis Current Controller (HCC) is designed for DSTATCOM to diminish the unbalances in a three-phase three-wire system. The performance of the controller is studied by simulating the entire system in the MATLAB/Simulink environment. The DSTATCOM with HCC is found to be better than other controllers because it is suitable for compensating both balanced and unbalanced loads.

Large Deviation Results for Generalized Compound Negative Binomial Risk Models

In this paper we extend and improve some results of the large deviation for random sums of random variables. Let {Xn;n 〉 1} be a sequence of non-negative, independent and identically distributed random variables with common heavy-tailed distribution function F and finite mean μ ∈R^＋, {N（n）; n ≥0} be a sequence of negative binomial distributed random variables with a parameter p C （0, 1）, n ≥ 0, let {M（n）; n ≥ 0} be a Poisson process with intensity λ 〉 0. Suppose {N（n）; n ≥ 0}, {Xn; n≥1} and {M（n）; n ≥ 0} are mutually independent. Write S（n） =N（n）∑i=1 Xi-cM（n）.Under the assumption F ∈ C, we prove some large deviation results. These results can be applied to certain problems in insurance and finance.

Phases-Controlled Coordinated Charging Method for Electric Vehicles

When private electric vehicles(EVs),which will be the main part of the EVs’cluster in the future,are plugged in power system by single phase power line,can result to three-phase unbalance problem of distribution network.In this work,a phased-controlled coordinated charging method was put forward to solve this problem.Firstly,the impacts of charging load to distribution network was analyzed based on the equivalent circuit;and then an architecture of the control method and its corresponding optimal control model were introduced.The optimal model is a multi-objective optimization model,which includes minimizing load variance of each phase and minimizing the power asymmetrical degree of three-phase load;lastly,three scenarios considering balance and unbalance cases were envisioned to verify the reasonableness of this control method based on IEEE-37 distribution network.Results show that the phased-controlled coordinated charging method can minimize the load variance as well as the negative sequence current.

A new method of AHP applied to personal credit evaluation

This paper presents a new negative judgment matrix that combines the advantages of the reciprocal judgment matrix and the fuzzy complementary judgment matrix, and then puts forth the properties of this new matrix. In view of these properties, this paper derives a clear sequencing formula for the new negative judgment matrix, which improves the sequencing principle of AHP. Finally, this new method is applied to personal credit evaluation to show its advantages of conciseness and swiftness.

Study Hybrid Compensation Cophase Traction Power Supply System Schemes for High-Speed and Heavy Haul Electrical Railway with V Connection Transformer

In order to solve negative phase sequence problem of V connection transformer in the high speed and heavy haul electrical railway of China, the hybrid compensative co-phase traction power supply system which based on passive and active compensation is proposed. Firstly, There construction and capacity distribution are analyzed, and the compensation current of active equipment is gave;Second, the feature of the hybrid compensative schemes are discussed. In the end, the related simulation results have confirmed the effectiveness of the compensation schemes in this paper.

Fault Ride-Through(FRT)Behavior in VSC-HVDC as Key Enabler of Transmission Systems Using SCADA Viewer Software

The world’s energy consumption and power generation demand will continue to rise.Furthermore,the bulk of the energy resources needed to satisfy the rising demand is far from the load centers.The aforementioned requires long-distance transmission systems and one way to accomplish this is to use high voltage direct current(HVDC)transmission systems.The main technical issues for HVDC transmission systems are loss of synchronism,variation of quadrature currents,amplitude,the inability of station 1(rectifier),and station 2(inverter)to either inject,or absorb active,or reactive power in the network in any circumstances(before a fault occurs,during having a fault in network and after a fault cleared),and the variations of power transfer capabilities.Additionally,faults impact power quality such as voltage dips and power line outage time.This paper presents a method of overcoming the aforementioned technical issues using voltage-source converter(VSC)based HVDC transmission systems with SCADA VIEWER software and dynamic grid simulator.The benefits include having a higher capacity transmission system and proposed best method for control of active and reactive power transfer capabilities.Simulation results obtained using MATLAB validated the experimental results from SCADA Viewer software.The results indicate that the station’s rectifier or inverter can either inject or absorb either active power or reactive power in any circumstance.Also,the reverse power flow under different modes of operation can ride through faults.At a 100.0%power transfer rate,the rectifier injected 775.0 W into the network.At a 0.0%power transfer rate,the rectifier injected 164.0 W into the network.At a-100.0%rated power,the rectifier injected 1264.0 W into the network and direction was also changed.