顺序控制的二重联结变流器谐波及功率因数分析

通过波形分析和理论计算 ,研究了二重联结顺序控制变流器运行在任意Δα下时 ,网侧的输入电流、基波电流、谐波电流、谐波总畸变率、基波因数、功率因数的变化规律 ,给出了计算公式 ,并与同步控制方式下的功率因数进行了比较 ,提出了减小谐波的控制策略。

单相PFC变换器功率因数的数字分析方法

以临界导通模式(BCM)Boost PFC变换器为研究对象,分析了输入电流的过零畸变现象,并得到了输入电流时域模型以及该模型下功率因数的数字分析方法。制作了一台200W的PFC样机。实验结果显示,基于此数字化功率因数分析方法计算出来的结果和利用功率分析仪测出来的功率因数的相对误差在1%以内。

单相PFC变换器的输入电流统一模型及功率因数的数字分析方法

以临界导通模式(Boundary Conduction Mode,BCM)Boost PFC变换器为研究对象,分析了输入电流的过零畸变现象,并得到了输入电流时域模型。综合平均电流模式Boost PFC变换器的输入电流模型,提出了单相PFC变换器输入电流的统一模型以及该模型下功率因数数字分析方法。相比于传统的功率因数数字分析方法,提出的方法在运算速度和准确度上有了很大的提高。制作了一台200W的BCM Boost PFC变换器样机,样机测试结果验证了提出的分析方法的准确性。

用Excel进行本量利分析

本量利分析法是研究成本、业务量和利润三者之间依存关系的一种方法,有着较高的经济管理运用价值。在以往,我们都是运用手工计算来进行本量利的分析,繁杂的计算严重影响了其广泛深入的应用。利用具有强大数据处理能力的Excel软件,设计本量利分析模型,可以非常方便地进行盈亏临界分析、因素变动分析以及敏感分析。

3.5kW功率因数校正变换器补偿网络的设计

为避免变频空调对电网造成谐波污染,空调电源必须具有较高的功率因数。本文基于3.5kW空调,采用Boost功率因数校正变换器的补偿网络,并对其进行稳定性分析及参数设计。变换器选取UCC28180作为控制芯片,采用平均电流控制模式,根据变换器的小信号模型及所选控制芯片的特性建立了不同环路的传递函数,用Mathcad作出相应的幅频、相频特性曲线,通过分析环路特性曲线的稳定性指标,设计了补偿网络的电路参数,保证了系统的高稳定性及较快的动态响应速度。最后根据计算所得的参数制作了一台额定功率为3.5kW的样机,在不同负载情况下进行了实验。实验结果表明,该变换器控制电路简单可靠、系统稳定性较好,补偿网络设计方法合理,可以作为功率等级为3.5kW及以下电气设备的功率因数校正电路。该研究具有一定的实际应用价值。

浅谈影响配网供电可靠性因素及改进措施

目前,各供电企业对配网的供电可靠性都给予了足够的重视,并进行了大量的工作,收到了实效。本文采用循序渐进、由因及果的方法,通过对配网供电可靠性的介绍,提出了影响配网供电可靠性的主要因素,并从分析影响配网供电可靠性的主要因素入手,进一步论述了提高配网供电可靠性的技术措施与管理措施,它对当前配网安全、稳定、可靠地运行具有一定的指导意义。

影响配网供电可靠性因素及改进措施

随着经济建设的飞速发展,国家各项事业也在逐步的完善之中,电力系统作为我国基础工业中的重要组成部分,其管理是否得当不仅关系到人民日常的工作生活,也关系到国家经济的发展建设,尤其对于配网可靠性的管理,是供电企业的基础也是核心工作任务,任何技术的革新和设备的更换都是为了这一个中心目的,由于各领域对于供电可靠性的迫切需要,现在各供电企业已经对于这一问题给予的高度重视,做了大量的工作,并取得了初步的成效。笔者在电力系统工作多年,结合实际工作经验,对配电可靠性的基础理论作以简要介绍,分析了其影响因素及针对于具体问题的解决措施,并对于提高可靠性的技术方法和管理措施进行了综合的论述。

降低卫生陶瓷开裂缺陷的有效措施

产品开裂是卫生陶瓷生产中常见的缺陷。在中国美标公司的三个卫生陶瓷厂,开裂是出现频率最高的一种缺陷,故本厂专门成立“降低开裂”的研究项目。经多年科研攻关,该项目因降低缺陷显著和有效降低生产成本而在美标亚太区30多家工厂项目评比中获得冠军奖。开裂缺陷率从16%降低到5%,每年可为公司节约直接成本225万人民币。

Classification analysis of microarray data based on ontological engineering

Background knowledge is important for data mining, especially in complicated situation. Ontological engineering is the successor of knowledge engineering. The sharable knowledge bases built on ontology can be used to provide background knowledge to direct the process of data mining. This paper gives a common introduction to the method and presents a practical analysis example using SVM (support vector machine) as the classifier. Gene Ontology and the accompanying annotations compose a big knowledge base, on which many researches have been carried out. Microarray dataset is the output of DNA chip. With the help of Gene Ontology we present a more elaborate analysis on microarray data than former researchers. The method can also be used in other fields with similar scenario.

Climate change trend and causes of tropical cyclones affecting the South China Sea during the past 50 years

Tropical cyclones(TCs)in the South China Sea(SCS)cause serious disasters and loss every year to the coastal and inland areas of southern China.The types of TCs are usually difficult to forecast,and studies on the understanding of the TCs affecting the SCS are lacking.In this study,the authors use the TC data during 1965–2017 from two best-track datasets to analyse the climatic characteristics in terms of the frequency,the track activity,and the influencing indexes of the TCs affecting the SCS and investigate the possible causes.The results show that,during 1965–2017,there were 535 TCs affecting the SCS,mainly occurring from June to November of each year,with the annual average frequency exhibiting a significant downward trend.Meanwhile,the frequency of the track activity in most areas of the SCS also demonstrate a remarkable decreasing trend but an increase in the Gulf of Tonkin and the Taiwan Strait.The large-scale environmental anomalous westerlies and the decrease of humidity in the mid-and low-level over the northern part of the SCS are likely the main causes for the decrease in frequency and the track activity.In addition,the analysis using the cyclone activity index shows that the influence of the before mentioned TCs in southern China gradually decreases,while the influence of TCs in the SCS show a decreasing trend during past decades.

Botulinum toxin for chronic anal fissure after biliopancreatic diversion for morbid obesity

AIM: To study the effect of botulinum toxin in patients with chronic anal fissure after biliopancreatic diversion (BPD) for severe obesity. METHODS: Fifty-nine symptomatic adults with chronic anal fissure developed after BPD were enrolled in an open label study. The outcome was evaluated clinically and by comparing the pressure of the anal sphincters before and after treatment. All data were analyzed in univariate and multivariate analysis. RESULTS: Two months after treatment, 65.4% of the patients had a healing scar. Only one patient had mild incontinence to flatus that lasted 3 wk after treatment, but this disappeared spontaneously. In the multivariate analysis of the data, two registered months after the treatment, sex (P = 0.01), baseline resting anal pressure (P = 0.02) and resting anal pressure 2 mo after treatment (P < 0.0001) were significantly related to healing rate.CONCLUSION: Botulinum toxin, despite worse results than in non-obese individuals, appears the best alternative to surgery for this group of patients with a high risk of incontinence.

Weekend and nighttime effect on the prognosis of peptic ulcer bleeding

AIM:To evaluate whether weekend or nighttime admission affects prognosis of peptic ulcer bleeding despite early endoscopy.METHODS:Retrospective data collection from four referral centers,all of which had a formal out-of-hours emergency endoscopy service,even at weekends.A total of 388 patients with bleeding peptic ulcers who were admitted via the emergency room between January 2007 and December 2009 were enrolled.Analyzed parameters included time from patients' arrival until endoscopy,mortality,rebleeding,need for surgery and length of hospital stay.RESULTS:The weekday and weekend admission groups comprised 326 and 62 patients,respectively.There were no significant differences in baseline characteristics between the two groups,except for younger age in the weekend group.Most patients (97%) had undergone early endoscopy,which resulted in a low mortality rate regardless of point of presentation (1.8% overall vs 1.6% on the weekend).The only outcome that was worse in the weekend group was a higher rate of rebleeding (12% vs 21%,P = 0.030).However,multivariate analysis revealed nighttime admission and a high Rockall score (≥ 6) as significant independent risk factors for rebleeding,rather than weekend admission.CONCLUSION:Early endoscopy for peptic ulcer bleeding can prevent the weekend effect,and nighttime admission was identified as a novel risk factor for rebleeding,namely the nighttime effect.

Relocation Selection for Poverty Alleviation:Factor Analysis and GIS Modeling

Resettlement is considered a major policy measure in two major Chinese policy programs,the "Great Development of the West" and poverty alleviation in the new century,and the "New Countryside Development".The selection of the target location of resettlement sites for poverty-stricken villages is of critical importance to the success of resettlement projects,yet the selection process is challenged by the need for analyzing a variety of contributing factors,and the need for many rounds of tedious data processing.So in this paper we present an in-depth analysis of the major factors and data processing model concerning mountainous povertystricken villages,which also takes a major part of China's poor villages.Our analysis shows the following factors bear the most importance in resettlement selection:1) topography:candidate areas should have slope less than 25 degrees and altitude less than 2400 meters.2) accessibility:close to market conventions places and transportation facilities.3) farming resources:with abundant land and water resources.4) non-intrusiveness:interests of receiving villages should be considered and negative impact minimized.A simple measure could be having the candidate area 1000 m away from the receiving residents.5) Minimal ecological and political footprint:candidate areas shall not conflict with nature conservation areas or nationally planned key land use projects.6) Social and cultural compatibility:residents will better off if relocated in the same county,considering language,religion,ethnic culture and other factors.Taking Makuadi,Lushui County of Nujiang Prefecture as a case study,we demonstrate how GIS analysis and modeling tools can be used in the selection process of resettlement projects in mountainous areas.

Early graft dysfunction following adult-to-adult livingrelated liver transplantation:Predictive factors and outcomes

AIM:To describe a condition that we define as early graft dysfunction(EGD)which can be identified preoperatively. METHODS:Small-for-size graft dysfunction following living-related liver transplantation(LRLT)is characterized by EGD when the graft-to-recipient body weight ratio(GRBWR)is below 0.8%.However, patients transplanted with GRBWR above 0.8%can develop dysfunction of the graft.In 73 recipients of LRLT(GRBWR>0.8%),we identified 10 patients who developed EGD.The main measures of outcomes analyzed were overall mortality,number of re-transplants and length of stay in days(LOS).Furthermore we analyzed other clinical pre-transplant variables,intraoperative parameters and post transplant data.RESULTS:A trend in favor of the non-EGD group(3-mo actuarial survival 98%vs 88%,P=0.09;3-mo graft mortality 4.7%vs 20%,P=0.07)was observed as well as shorter LOS(13 d vs 41.5 d;P=0.001)and smaller requirement of peri-operative Units of Plasma (4 vs 14;P=0.036).Univariate analysis of pre- transplant variables identified platelet count,serum bilirubin,INR and Meld-Na score as predictors of EGD. In the multivariate analysis transplant Meld-Na score (P=0.025,OR:1.175)and pretransplant platelet count(P=0.043,OR:0.956)were independently associated with EGD. CONCLUSION:EGD can be identified preoperatively and is associated with increased morbidity after LRLT. A prompt recognition of EGD can trigger a timely treatment.

Stability influence factors analysis and construction of a deep beam anchorage structure in roadway roof

Deep beam anchorage structures based on spatial distribution analysis of the cable prestressed field have been proposed for roadway roof support, Stability and other factors that influence deep beam structures are studied in this paper using mechanical calculations, numerical analysis and field measurements, A mechanical model of deep beam structure subjected to multiple loading is established, including analysis of roof support in the return airway of S1203 working face in the Yuwu coal mine, China, The expression of maximum shear stress in the deep beam structure is deduced according to the stress superposition criterion, It is found that the primary factors affecting deep beam structure stability are deep beam thickness, cable pre-tension and cable spacing, The variation of maximum shear stress distribution and prestressed field diffusion effects according to various factors are analyzed using Matlah and FLAC3DTM software, and practical support parameters of the S1203 return airway roof are determined, According to the observations of rock pressure, there is no evidence of roof separation, and the maximum values of roof subsidence and convergence of wall rock are 72 and 48 mm, respectively, The results show that the proposed roof support design with a deep beam structure is feasible and achieves effective control of the roadway roof,

Affecting Factors on Entrepreneurial Oriemation in the Industry

In the present age, entrepreneurship at the organizational level and entrepreneurial orientation at the individual level can be considered as competitive advantage in a new age. This study examines the affecting factors on entrepreneurial orientation in a sample of 248 employees in the industry. This article considered employees＇ entrepreneurial orientation as an dependent variable and emotional and organizational intelligences, as independent variables, which may be effected on entrepreneurial orientation. The results of data analysis by LISREL show that employees＇ willingness to act entrepreneurially increases when they have high emotional and organizational intelligences.

More attention should be paid on the interpretation of gene expression data

Molecular profiling of gene expression is important for determining signatures in cancer progression and diagnosis.For this purpose,polymerase chain reactionbased techniques are preferentially used as a feasible and sensitive approach.Nevertheless,when relative quantitative analyses are performed on gene expression,the interpretation of mathematical equations must be carefully done.This letter to the editor is focused on recently published gene expression data in World Journal of Gastroenterology by Ozmen et al demonstrating increased levels of LYVE-1,VEGFR-3 and CD44 genes in gastric cancer samples compared to nonneoplastic gastric tissues.However,there are major concerns about misinterpretation of the gene expression data obtained with the 2-ΔΔCt relative quantitative method.In the study,2-ΔΔCt values calculated for many samples were smaller than 1(2-ΔΔCt < 1) which indicate decreased levels of LYVE-1,VEGFR-3 and CD44 gene expression in the gastric cancer tissues.This unfortunate mistake is an important example showing how a simple error in the interpretation of relative-quantitative gene expression data may result in misleading scientific conclusions.In this letter,a brief explanation of the 2-ΔΔCt method is given.In addition,the importance of technical quality and interpretation in gene expression studies is discussed.

Determining Topographic Shielding from Digital Elevation Models for Cosmogenic Nuclide Analysis:a GIS Approach and Field Validation

Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates. Traditionally, this parameter is measured in the field and uncertainty and/or inconsistency may exist among different investigators. This paper provides an ArcGIS python code to determine topographic shielding factors using digital elevation models （DEMs）. This code can be imported into ArcGIS as a geoprocessing tool with a user-friendly graphical interface. The DEM-derived parameters using this method were validated with field measurements in central Tian Shan. Results indicate that DEM-derived shielding factors are consistent with field-measured values. It provides a valuable tool to save fieldwork efforts and has the potential to provide consistent results for different regions in the world to facilitate the comparison of cosmogenie nuclide results.

Development of the Buddhist-Based Spiritual Health of Thai University Students Instrument

This study contributes to the development of a valid and reliable instrument, Buddhist-based Spiritual Health of Thai University Students Instrument （SHTUSI）. Participants were students from bachelor level of 15 faculties （N = 530）, Prince of Songkla University, Hatyai Campus, Thailand. Content validity was examined by six experts （I-CVI = 1）. Construct validity was evaluated by factor analysis with four latent factors： noble mind, moral living, mindful management, and attentive learning. The reliability coefficient of SHTUSI with 30 items was satisfactory value （Cronbach＇s α = .89）. Each factor has good internal reliability which includes： （1） noble mind （Cronbach＇s α = .86）; （2） moral living （Cronbach＇s a = .78）; （3） mindful management （Cronbach＇s α = .77）; and （4） attentive learning （Cronbach＇s α = .76）. Furthermore, the test-retest reliability was .51 and the concurrent validity was tested by Thai Happiness Indicator with moderate correlation （Pearson＇s r = .574, p 〈 .01）. The finding suggests that the development instrument has adequate validity and reliability.

A novel method for predicting breakthrough time of horizontal wells in bottom water reservoirs

Dimensional analysis and numerical simulations were carried out to research prediction method of breakthrough time of horizontal wells in bottom water reservoir. Four dimensionless independent variables and dimensionless time were derived from 10 influencing factors of the problem by using dimensional analysis. Simulations of horizontal well in reservoir with bottom water were run to find the prediction correlation. A general and concise functional relationship for predicting breakthrough time was established based on simulation results and theoretical analysis. The breakthrough time of one conceptual model predicted by the correlation is very close to the result by Eclipse with less than 2% error. The practical breakthrough time of one well in Helder oilfield is 10 d, and the predicted results by the method is 11.2 d, which is more accurate than the analytical result. Case study indicates that the method could predict breakthrough time of horizontal well under different reservoir conditions accurately. For its university and ease of use, the method is suitable for quick prediction of breakthrough time.