Traction power systems for electrified railways:evolution,state of the art,and future trends

Traction power systems(TPSs)play a vital role in the operation of electrified railways.The transformation of conventional railway TPSs to novel structures is not only a trend to promote the development of electrified railways toward high-efficiency and resilience but also an inevitable requirement to achieve carbon neutrality target.On the basis of sorting out the power supply structures of conventional AC and DC modes,this paper first reviews the characteristics of the existing TPSs,such as weak power supply flexibility and low-energy efficiency.Furthermore,the power supply structures of various TPSs for future electrified railways are described in detail,which satisfy longer distance,low-carbon,high-efficiency,high-reliability and high-quality power supply requirements.Meanwhile,the application prospects of different traction modes are discussed from both technical and economic aspects.Eventually,this paper introduces the research progress of mixed-system electrified railways and traction power supply technologies without catenary system,speculates on the future development trends and challenges of TPSs and predicts that TPSs will be based on the continuous power supply mode,employing power electronic equipment and intelligent information technology to construct a railway comprehensive energy system with renewable energy.

Research on Intelligent Identification of PD Patterns Based on the Fingerprint Features

Five-electrode configurations were designed to simulate the distribution inhomogeneity of electric field intensities in the air-insulating medium, and the characteristic data waveforms of partial discharge generated by different electrode configurations under the excitation of power frequency AC voltage were carefully collected in this paper. Furthermore, the feature vectors of the corresponding fingerprint, contained in partial discharge data, were extracted by rigorous mathematical algorithms, and the artificial neural network was employed to realize the pattern recognition of partial discharge caused by the inhomogeneity of electric field intensity with different electrode configurations. The results indicate that the J4 value in the space of 7 feature quantities is 1905.6, and the recognition rate is 100% when the hidden layer neuron of the network is 19. However, the J5 value of 9 feature quantities is 1589.9, and the purpose of recognition has been achieved when the number of hidden layer neurons of the network is 6. Increasing the number of hidden layer neurons will only waste computing resources. Of course, PD information collection mode, feature quantity selection, optimal feature space composition, network structure and classification algorithm are the key to realizing PD fault intelligence identification.

Analysis of rail potential and stray current in MVDC railway electrification system

In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction substations(TSSs)are placed much farther and train loads are much heavier than in the conventional DC-RES.Hence,the MVDC-RES brings a drastic change in catenary voltage,TSS spacing,and train loading,which affects rail potential and stray current.In this connection,this work performs some significant quantitative analysis of rail potential and stray current in the MVDC-RES environment.An MVDC simulation model is proposed and different grounding schemes are analyzed for a single-train and two TSSs scenario as well as for a multi-train multi-TSS scenario.According to the simulation and analysis,the maximum values of rail potential and stray current at MVDC-RES distances and the maximum safe distance between adjacent TSSs are determined.

Analysis of the Electric Locomotives Neutral-section Passing Harmonic Resonance

For the further analysis and suppression of the electric locomotives neutral-section passing overvoltage, on the basis of theoretical analysis of the neutral-section passing harmonic resonance conditions, this paper establishes simplified harmonic resonance simulation models of the electric locomotives neutral-section passing using MATLAB/Simulink, and makes the overvoltage simulation analysis of the existing electric locomotives neutral-section passing system in the event of a harmonic resonance. Results show that when the system harmonic resonance occurs, the operating overvoltage of the neutral-section passing is serious intensified by the overvoltage of the harmonic resonance, which will make the voltage of the pantograph collector head exceeding 100kV. This amplitude of the overvoltage will breakdown the air gap, which will be a serious threat to the safety operation of the electric railway. However, this kind of neutral-section passing overvoltage hasn’t cause the attention in the field and theoretical studies, which need more analysis and verification in the further study.

Cognitive function correlations with apolipoprotein Eε4 single nucleotide polymorphism in 1000 elderly patients following general anesthesia A randomized controlled study

BACKGROUND： Cognitive dysfunction occurs in elderly patients following general anesthesia, and this might be associated with genetics. Studies have shown that the ε4 allele gene is closely associated with senile dementia. OBJECTIVE： To compare and analyze the correlations between cognitive dysfunction and single nucleotide polymorphism of apolipoprotein E （ApoE） following inhalation or intravenous anesthesia. DESIGN, TIME AND SETTING： A randomized, controlled study was performed. The patients were recruited from the Department of Anesthesia, Second Affiliated Hospital, Medical College, Xi＇an Jiaotong University, China between May 2005 and December 2008. Genetic analyses were conducted at the Departments of Neuroanatomy and Forensic Medicine, Medical Corlege, Xi＇an Jiaotong University, China. PARTICIPANTS： A total of t 000 patients of ASA I-II grade, without genetic connection, were enrolled in this study, comprising 520 males and 480 females, aged （70.1± 4.6） years and weighing （57.3 ± 7.5） kg. No patients suffered from cognitive dysfunction. METHODS： The patients were equally and randomly divided into intravenous anesthesia and gas anesthesia groups. Total intravenous anesthesia and inhaled anesthesia were used. Genomic DNA from whole blood was extracted. The ApoE gene was amplified by PCR. Restriction fragment length polymorphism of ApoE gene was analyzed. Cognitive function was evaluated by Mini-Mental State Examination （MMSE）. Patients scoring 〈 25 points were diagnosed with cognitive dysfunction. MAIN OUTCOME MEASURES： Correlation of ApoE gene frequency and ApoE ε 4 allele to MMSE scores was measured. RESULTS： MMSE scores in patients from the gas anesthesia group significantly decreased 3 days after surgery, compared with the intravenous anesthesia group. The proportion of patients that scored 〈 25 points was significantly greater in the gas anesthesia group compared with the intravenous anesthesia group 3 days after surgery. Reduced MMSE scores closely correlated with expression of the ApoE ε 4 allele in the gas anesthesia group （odds ratio = 2.83; 95% confidence interval was 1.25-6.39, P 〈 0.05）. However, decreased MMSE scores did not closely correlated with expression of the ApoE ε 4 allele in the intravenous anesthesia group （odds ratio = 0.96; 95% confidence interval was 0.37-2.39, P 〉 0.05）. CONCLUSION： Results demonstrated a correlation between cognitive dysfunction and ApoE single nucleotide polymorphism in elderly patients after gas anesthesia. However, no relationship between cognitive dysfunction and ApoE single nucleotide polymorphism was determined in elderly patients following intravenous anesthesia. Therefore, elderly patients, especially those expressing the ApoE ε4 gene, should be cautiously exposed to gas anesthesia.

Identification of Green-Revertible Yellow 3(GRY3),encoding a 4-hydroxy-3-methylbut-2-enyl diphosphate reductase involved in chlorophyll synthesis under high temperature and high light in rice

Chlorophyll,a green pigment in photosynthetic organisms,is generated by two distinct biochemical pathways,the tetrapyrrole biosynthetic pathway(TBP) and the methylerythritol 4-phosphate(MEP)pathway.MEP is one of the pathways for isoprenoid synthesis in plants,with 4-hydroxy-3-methylbut-2-enyl diphosphate reductase(HDR) catalyzing its last step.In this study,we isolated a greenrevertible yellow leaf mutant gry3 in rice and cloned the GRY3 gene,which encodes a HDR participating in geranylgeranyl diphosphate(GGPP) biosynthesis in chloroplast.A complementation experiment confirmed that a missense mutation(C to T) in the fourth exon of LOC_Os03g52170 causes the gry3 phenotype.Under high temperature and high light,transcript and protein abundances of GRY3 were reduced in the gry3 mutant.Transcriptional expression of chlorophyll biosynthesis,chloroplast development,and genes involved in photosynthesis were also affected.Excessive reactive oxygen species accumulation,cell death,and photosynthetic proteins degradation were occurred in the mutant.The content of GGPP was reduced in gry3 compared with Nipponbare,resulting in a stoichiometric imbalance of tetrapyrrolic chlorophyll precursors.These results shed light on the response of chloroplast biogenesis and maintenance in plants to high-temperature and high-light stress.

Multi-Layer Deep Sparse Representation for Biological Slice Image Inpainting

Biological slices are an effective tool for studying the physiological structure and evolutionmechanism of biological systems.However,due to the complexity of preparation technology and the presence of many uncontrollable factors during the preparation processing,leads to problems such as difficulty in preparing slice images and breakage of slice images.Therefore,we proposed a biological slice image small-scale corruption inpainting algorithm with interpretability based on multi-layer deep sparse representation,achieving the high-fidelity reconstruction of slice images.We further discussed the relationship between deep convolutional neural networks and sparse representation,ensuring the high-fidelity characteristic of the algorithm first.A novel deep wavelet dictionary is proposed that can better obtain image prior and possess learnable feature.And multi-layer deep sparse representation is used to implement dictionary learning,acquiring better signal expression.Compared with methods such as NLABH,Shearlet,Partial Differential Equation(PDE),K-Singular Value Decomposition(K-SVD),Convolutional Sparse Coding,and Deep Image Prior,the proposed algorithm has better subjective reconstruction and objective evaluation with small-scale image data,which realized high-fidelity inpainting,under the condition of small-scale image data.And theOn2-level time complexitymakes the proposed algorithm practical.The proposed algorithm can be effectively extended to other cross-sectional image inpainting problems,such as magnetic resonance images,and computed tomography images.

Study on Distribution Coefficient of Traction Return Current in High-Speed Railway

The distribution coefficient of return current network is an important method to decrease the rail potential. In order to resolve the problem of high rail potential in high-speed railway based on EN50122-1 and Pr EN50170 the distribution coefficient of longitudinal traction return current conductors is calculated through changing the interval of transverse connection. Based on field data and theoretical analysis, the parameters of longitudinal traction return current conductors are calculated. Results indicate that the best distance of the transverse connection is 400 m – 600 m.

A power-quality monitoring and assessment system for high-speed railways based on train-network-data center integration

In recent years,with the rapid development of high-speed railways(HSRs),power interruptions or disturbances in traction power supply systems have become increasingly dangerous.However,it is often impossible to detect these faults immediately through single-point monitoring or collecting data after accidents.To coordinate the power quality data of both traction power supply systems(TPSSs)and high-speed trains(HSTs),a monitoring and assessing system is proposed to access the power quality issues on HSRs.By integrating train monitoring,traction substation monitoring and data center,this monitoring system not only realizes the real-time monitoring of operational behaviors for both TPSSs and HSTs,but also conducts a comprehensive assessment of operational quality for train-network systems.Based on a large number of monitoring data,the field measurements show that this real-time monitoring system is effective for monitoring and evaluating a traction-network system.

Survival of patients with gastric cancer surgically treated at the National Cancer Center of China from 2011 to 2018 according to stage at diagnosis

Objective:The postoperative survival rates of patients with gastric cancer at different stages treated at the National Cancer Center(NCC)of China have not been reported.Therefore,we evaluated the survival of patients with gastric cancer who underwent surgery at the NCC from 2011 to 2018 to provide baseline information for further studies.Methods:We identified 7,301 patients with primary gastric carcinoma who underwent surgery at the NCC be-tween January 2011 and May 2018;among these,5,008 patients were enrolled in this study.Follow up was completed on April 30,2020.We analyzed the 5-year survival according to the stage,sex,age,and other clini-copathological features.Results:Five-year survival rates of patients with pTNM stages ⅠA,ⅠB,ⅡA,ⅡB,ⅢA,ⅢB,ⅢC,and Ⅳ treated at the NCC were 94.9%,91.8%,86.5%,76.1%,61.1%,44.2%,29.7%,and 8.1%,respectively,which were similar to those reported in Japan during the same period.Five-year survival rates of patients with ypTNM stages I,II,III,and IV were 93.1%,63.2%,27.2%,and 0.0%,respectively.In multivariable analysis,age,signet ring cell carcinoma,adjuvant chemotherapy,and degree of differentiation were revealed as important prognostic factors.Conclusion:The survival rates of patients with gastric cancer treated at the NCC have been significantly improved,reaching the levels of Japan in the same period.

Pursuing the goal of carbon neutrality in China:path for realization of carbon sequestration in planted forests

Tree plantations are an important forest resource that substantively contributes to climate change mitigation and carbon sequestration.As the area and standing volume of tree plantations in China have increased,issues such as unreasonable structure,low productivity,limited ecological functionality and diminishing ecological stability have occurred,which hinder the ability of tree plantations to enhance carbon sequestration.This study outlined the trajectory of carbon sequestration and its associated benefits in tree plantations by examining the current state of tree plantation establishment and growth,elucidated the strategies for advantages of carbon sequestration and climate change mitigation in planted forests,and summarized the existing problems with tree plantations.This paper underscores the pressing need for concerted efforts to boost carbon sequestration within planted forests and proposes management and development strategies for Chinese tree plantations.In the future,it will be necessary to apply scientific theories to practice and develop multi-objective management optimization models for the high-quality development of tree plantations.This will involve establishing a cohesive national carbon trading market,improving the prediction of carbon sequestration,and identifying priority zones for afforestation and reforestation,to better serve China’s national strategy for achieving peak carbon and carbon neutrality.

Treatment with intravenous alteplase in ischaemic stroke patients with onset time between 4.5 and 24 hours(HOPE):protocol for a randomised,controlled,multicentre study

Background While intravenous thrombolysis is recommended for patients who had an acute ischaemic stroke(AIS)within 4.5hours of symptom onset,there are few randomised trials investigating the benefits of thrombolysis beyond this therapeutic window.Aim To determine whether patients who had an AIS selected with the presence of potentially salvageable tissue on CT perfusion at 4.5–24hours after stroke onset(for stroke with unknown onset time,the midpoint of the time last known to be well and symptom recognition time;for wake-up stroke,the midpoint of the time last known to be well or sleep onset and wake up time)will benefit from intravenous thrombolysis.Design HOPE is a prospective,multicentre,randomised,open-label blinded endpoint trial with the stage of phase III.The treatment allocation employs 1:1 randomisation.The treatment arm under investigation is alteplase with standard therapy,the control arm is standard therapy.Eligibility imaging criteria include ischaemic core volume≤70mL,penumbra≥10mL and mismatch≥20%.Study outcomes The primary outcome is non-disabled functional outcome(assessed as modified Rankin Scale score of 0–1 at 90 days).Discussion HOPE is the first trial to investigate whether intravenous thrombolysis with alteplase offers benefits in patients who had an AIS presenting within 4.5–24hours,which has the potential to extend time window and expand eligible population for thrombolysis therapy.

基于H2DCFDA荧光探针的植物活性氧检测方法

活性氧(reactive oxygen species,ROS)是植物体内的一把“双刃剑”。ROS作为信号分子在植物生命活动中发挥关键作用,但ROS过量积累会对生物大分子造成氧化损伤。准确测定ROS含量对于评估植物细胞内的氧化还原状态至关重要。由于植物体内ROS各组分半衰期短且反应活性强,定性定量检测较为困难。因此,选择合适的检测方法以提高检测的时空准确性非常重要。目前,荧光分析法因其具有灵敏度高、选择性好、检出限低和直观性强等优点,受到研究人员的广泛关注。该文详细描述基于流式细胞仪和激光共聚焦显微镜,利用2′,7′-二氯二氢荧光素二乙酸酯(H2DCFDA)荧光探针检测水稻(Oryzasativa)体内ROS水平和时空分布的操作流程及注意事项。该技术也可用于直接检测拟南芥(Arabidopsis thaliana)、玉米(Zea mays)和大豆(Glycine max)等模式植物组织中ROS的水平和分布。

植物核黄素的生物合成及其功能研究进展

核黄素是生物体维持正常代谢所必需的辅酶因子FMN和FAD的合成前体,其在线粒体电子传递链、三羧酸循环、脂肪酸β氧化、支链氨基酸分解代谢、氧化还原稳态、染色质重塑、DNA修复、细胞凋亡和次生代谢产物合成中发挥关键作用。核黄素缺乏会引发机体代谢紊乱和一系列表型缺陷,严重时甚至导致生物体死亡。自然界生命体中仅微生物和植物可以从头合成核黄素,而人和动物需从食物中获取核黄素。目前,微生物中核黄素的合成及其调控机制已研究得比较清晰,而核黄素在植物体内转运和代谢的调控机制尚不清楚。因此,挖掘核黄素缺乏相关突变体对解析植物核黄素生物合成、转运和代谢的分子机制以及其对植物生长发育的调控机理具有重要意义。该文综述了核黄素的生物合成途径及其关键限速酶,重点阐述了核黄素参与的植物生长发育过程,并展望了植物核黄素的研究前景。

Adaptive droop control for better current-sharing in VSC-based MVDC railway electrification system

The share of voltage source converter(VSC)technology is increasing in conventional power systems,and it is penetrating into specific transportation systems such as electric vehicles,railways,and ships.Researchers are identifying feasible methods to improve the performance of railway electrification systems(RESs)by utilizing VSC-based medium-voltage direct current(MVDC)railways.The continuous motion of electric trains makes the catenary resistance a variable quantity,as compared to the traction substation(TSS),and affects the currentsharing behavior of the system.A modified droop control technique is proposed in this paper for VSC-based MVDC RES to provide more effective current-sharing while maintaining catenary voltages above the minimum allowable limit.The droop coefficient is selected through an exponential function based on the ratio between the concerned TSS current and the system average current.This enables small adjustments of droop values in less concerning marginal current deviations,and provides higher droop adjustments for large current deviations.Meanwhile,the catenary voltages are regulated by considering the voltage data at the midpoint between two TSSs,which experiences the lowest voltages owing to the larger distance from the TSSs.The proposed techniques are validated via simulations and experiments.

Adjuvant chemotherapy may be unnecessary for ypT0-2N0 gastric cancer patients after neoadjuvant chemotherapy and curative gastrectomy

To the Editor:Gastric cancer(GC)is the sixth most common type of cancer and the third most common cause of cancer-related deaths worldwide.[1]Due to the lack of typical clinical symptoms in the early stage of GC,most patients have advanced-stage disease at the time of initial treatment and have a poor prognosis.The rate of radical resection is low.Even after radical resection,recurrence or death occurs in 50%to 90%of patients,and the 5-year overall survival(OS)rate is less than 30%.[2]Therefore,various multimodal strategies,which would presumably reduce the risk of cancer recurrence and improve survival,are being explored to eliminate any residual tumors and micro-metastases.Neoadjuvant chemotherapy(NAC)followed by surgery is recommended as the standard of care for patients with localized resectable GC.

Application of CFD-DEM to the study of solid exchange in a dual-leg fluidized bed

The CFD-DEM model was developed to simulate solid exchange behavior between two half beds in a bench-scale two-dimensional dual-leg fluidized bed （DL-FB）. Power spectrum density （PSD） analysis was applied to obtain the dominant frequency （F） of the simulated differential particle number （APLR） between the two half beds. Effects of fluidization velocity （u） and bed material inventory （H） on the solid exchange behavior were studied using the CFD-DEM model. Not only snapshots of the simulated particle flow patterns using the OpenGL code but also the dominant frequency of APLR was similar to the experimental results. The simulation results show that higher fluidization velocity assists the exchange of more particles between the two half beds, but the dispersion of clusters on the bed surface into single particles decreases the cluster exchange frequency. A greater bed material inventory results in more intense cluster exchange. The cluster exchange frequency decreases with an increase of the bed material inventory.

十二指肠残端处理对全腹腔镜胃癌根治术后并发症的影响

目的评估全腹腔镜胃癌手术中十二指肠残端处理对术后并发症的影响。方法建立前瞻性观察队列,纳入2021年12月至2022年12月于中国医学科学院肿瘤医院接受全腹腔镜胃癌根治术的患者,使用直线切割闭合器离断十二指肠,并行BillrothⅡ式或Roux-en-Y式吻合,十二指肠残端处理采用3-0可吸收倒刺线行连续缝合。主要观察患者术后短期并发症发生情况,分级依据Clavien-Dindo分级标准,并于术后第1、3、5、7天留取流经十二指肠残端的引流液,检测总胆红素和淀粉酶。结果本研究共纳入134例患者,其中63例行十二指肠残端加固,71例未行十二指肠残端加固。两组患者在年龄、性别、体质量指数(body mass index,BMI)、美国东部肿瘤协作组(Eastern Cooperative Oncology Group,ECOG)评分、营养风险(Nutritional Risk Screening 2002,NRS 2002)评分、内科合并症、术前新辅助治疗及TNM分期上,两者差异均无统计学意义。两组均以BillrothⅡ吻合方式为主。在手术时间上,十二指肠残端加固组与未加固组相比差异无统计学意义(160.7±38.2 min vs.156.3±36.6 min,P=0.649)。两组患者总体并发症发生率及严重并发症发生率差异无统计学意义,但十二指肠残端未加固组出现2例十二指肠残端瘘,而加固组无十二指肠残端瘘发生。在术后引流液总胆红素和淀粉酶指标方面,加固组在术后第1、3、5、7天引流液总胆红素和淀粉酶中位数均低于未加固组,且在术后第1天引流液总胆红素测定中两组间差异有统计学意义。结论在全腹腔镜胃癌手术中进行十二指肠残端加固可有效降低十二指肠残端瘘的发生。