特高压换流站晶闸管控制单元回检信号异常问题分析

晶闸管是特高压换流站运行的核心设备,晶闸管控制单元是晶闸管级的关键元件。针对某特高压换流站运行过程中频繁发生监控后台报晶闸管故障并反复复归问题,分析了晶闸管故障现象和判定逻辑,并进行了TCE回检信号光功率的测试。根据测试结果,明确是晶闸管控制单元回检信号光功率不足导致回检信号异常。阀控系统上报晶闸管故障,及时排除了晶闸管级元件的安全隐患,保障了特高压换流站的安全稳定运行。

煤层底板突水危险性的PNN预测模型研究及应用

为准确有效地预测煤层底板突水的危险性,在分析大量观测实例数据的基础上,选取底板含水层水压、煤层采高、隔水层厚度、断层落差、煤层倾角和断层距工作面距离等6项指标作为影响煤层底板突水的初始特征指标。针对指标之间具有相关性的问题,利用主成分分析(PCA)法提取6项特征指标的主成分,将其作为概率神经网络(PNN)的输入向量,建立基于PCA的煤层底板突水危险性的PNN预测模型。选取21组煤矿实测数据作为学习样本,用于训练模型。采用回代估计法对模型回检。利用学习好的模型,预测另外4组矿井突水数据样本。结果表明,该方法有效降低了指标数据相关性,实现了降维,使PNN模型工作复杂度减弱。将该模型应用于工程实例中,所得预测结果准确率为100%。

岩溶塌陷倾向性等级的KPCA-SVM预测模型

为了快速、有效地预测岩溶塌陷倾向性等级,在统计分析大量观测实例的基础上,选取岩性系数、岩体结构系数、地下水系数、覆盖层系数、地形地貌系数和环境条件系数作为特征指标。利用核主成分分析(KPCA)方法在高维空间提取岩溶塌陷影响因子的主成分,将获取的主成分作为支持向量机(SVM)的特征向量,建立基于KPCA的岩溶塌陷倾向性等级的SVM预测模型。将12组观测数据作为学习样本对模型进行训练。采用回代估计法进行回检,误判率为0。利用训练好的模型对2组待判样本进行预测。结果表明:经KPCA后指标个数减少,相关性降低,SVM运算的复杂度降低。用该模型所得预测结果的准确率为100%。

一起换相失败导致直流闭锁故障分析及其阀控策略优化研究

文章研究了直流输电系统中针对换相失败的阀控策略,指出现有控制策略在临界条件下存在极控系统检测不到交流低电压信号,VBE无法闭锁回检信号的检测而造成跳闸的隐患。通过详细分析网内交流系统故障导致换流站直流换相失败而闭锁的故障过程,进一步验证现有阀控策略的隐患。文章最后针对采样回路进行优化。

Regression-Based Method of Acoustic Detection

Based on the signal detection theory. a target detection method with the regression calculation which is easily achieved by computer software or hardware was developed in order to insure the acoustic detection system working with high detection possibility and under the condition of low signal to noise ratio. Meanwhile. the physical implication of detection formula wsa discussed and computer result was shown.

HPLC Determination of Captopril in Human Plasma with Pre-column Derivation and Solid-phase Extraction and Studies on Its Pharmacokinetic and Relative Bioavailability

A new pre-column derivation HPLC method with solid-phase extraction to determine captopril in human plasma was established. Derivation products were extracted by a solid-phase extraction method after the reagent, p-a-dibromoacetophenone(p-BPB), was added in the plasma samples. The samples were analyzed in a VP-ODS column with UV-detector. The calibration curve of captopril was linear within the range of 5~1000 ngmL-1 with r=0.9987, the recovery of this method was 98.652.04%, within day and between day RSD were no more than 3.4% and 8.4% respectively. To study the pharmacokinetics and the relative bioavailability of captopril tablets, two formulations of captopril tablets were given to 18 healthy male volunteers according to a randomized 2-way cross-over design with a 1-week washout period. The respective AUC0~6 , Cmax and Tmax values of the two formulations were 424.5125.7 and 439.4113.3 mghL-1; 505.9244.6 and 504.8172.2 mgL-1; 0.6620.181 and 0.5280.176 h. Results from statistics analysis showed that there were no significant difference between the AUC0~6 , Cmax and Tmax values of the two formulations, The relative bioavailability of tablets I with respect to II was 96.114.6% from AUC0~6 measurement. Bioequivalance was observed between the two tablets.

Gel Filtration Chromatography Combined with Bradford Method for Determination of Total Residual Protein in Ferment Antibiotics

Aim A novel method has been developed for evaluation of the levels of total residual protein in antibiotics produced by fermentation using gel filtration chromatography (GFC) combined with Bradford assay based on determination of residual protein in lincomycin hydrochloride. Methods The chromatographic conditions were SuperdexTM peptide column, 0.01 mol*L-1 phosphate buffer solution as mobile phase, and flow rate of 1 mL·min-1. Five hundred microliters of lincomycin hydrochloride solution (3 g of lincomycin hydrochloride dissolved in 10 mL of mobile phase) was injected into the chromatograph and the eluted solution was collected between 6 min and 14.5 min (protein eluted from column within this period), and the residual content of total protein in the eluted solution was assayed using Bradford assay method. Results The average recovery was more than 90% for bovine serum albumin, the calibration equation for the range of 0-12 μg·mL-1 of protein was y=-0.002 4x2+0.064 2x+0.002 9, r2=0.999 9, RSD=0.1%-0.9%, and the LOD and LOQ were 3 and 10 ng·mL-1 of protein, respectively. Conclusion The novel method for determining the residual protein in ferment antibio-tics is simple, rapid, and precise.

Ileoscopy in patients with ileocolonic tuberculosis

AIM: To study the role of retrograde terminal ileoscopy in patients suspected to have ileocolonic tuberculosis. METHODS: A retrospective analysis was performed for patients undergoing colonoscopy for suspected ileocolonic tuberculosis between January 2000 and June 2004, in whom retrograde ileoscopy had been performed. Only patients diagnosed with tuberculosis on the basis of histological findings of either a caseating granuloma or those having non-caseating granuloma or a collection of epithelioid cells at a minimum of one endoscopic lesion (either in the colon or the terminal ileum) on histology with good responses to conventional anti-tuberculous drugs were enrolled for the study. RESULTS: Fifty-three patients were included. The terminal ileum was involved in only 11 patients. Eight of these patients had involvement of the cecum too. Two patients had ileal lesions without cecal involvement; however, lesions were noted in the ascending colon. In one patient the whole colon was normal and only the terminal ileum showed nodularity and ulceration. Histological examination of the ileal biopsies obtained from the ileal lesions showed noncaseating granulomas in five, collection of epithelioid cells in four and nonspecific histology in two patients. Mucosal biopsies obtained from the lesion in the terminal ileum, in the patient in whom mucosal abnormality was observed to be confined to the ileum, showed noncaseating granulomas. In two other patients the ileal biopsies alone showed histological evidence of tuberculosis with biopsies from the colonic lesions showing non-specific inflammatory changes only. CONCLUSION: Retrograde ileoscopy should be performed in all patients undergoing colonoscopy for suspected ileocolonic tuberculosis. In some patients only the terminal ileum may be involved and histological examination may reveal evidence of tuberculosis only from the lesions in the terminal ileum. This approach would lead to additional lesions being picked up andincreasing the chances of well-timed diagnosis of tuberculosis.

Availability-based maintenance optimization under unequal inspection period and imperfect repair

Taking the multi-component system as research object, a maintenance optimization model based on the unequal inspection period and imperfect repair is established by considering the requirement of expected availability for improving the system＇s availability. An age reduction factor is used to describe the effect of imperfect repair, and the modelling approach for the unequal inspection period is proposed. Unavailable situations are classified into three kinds of independent cases, and the availability is calculated accordingly. Based on the analysis of the relationship between the unavailable cases and the unequal inspection period, an optimization model under imperfect repair is established to optimize the system＇s expected availability. A case study of a wind turbine is provided, and three key components, i.e. gearbox, generator and spindle, are considered. The optimization results of the unequal inspection period model and the equal inspection period model are compared. The results show that the unequal inspection period model based on availability can update the maintenance plan so as to optimize maintenance activities and improve the system＇s availability.

Blind multiple watermarking algorithm for audio

To make digital watermarking accomplish several goals, a new method for simultaneously embedding multiple watermarks into the same audio signal is proposed. First, the original audio signal is segmented into frames of appointed lengths and all the element watermarks are encoded to achieve a mixed watermark. Then, the binary bits in the mixed watermark are embedded into the audio frames with the echo hiding technique. The watermark extraction can be performed without an original audio signal. Furthermore, in order to enhance the extraction accuracy and the robustness of the proposed algorithm against common signal manipulations, the autocorrelafion of the power cepstrum is utilized to estimate the echo delays in the watermarked audio frames to extract the mixed watermark and the corresponding decoding method is applied to achieve the element watermarks. Computer simulation results indicate that the proposed scheme has great robustness against common signal manipulations of Mp3 compressing, re-sampling, re-quantizing, low-pass filtering and white noise addition.

Effect of infliximab on small bowel stenoses in patients with Crohn's disease

AIM: To assess prospectively small bowel stenoses in Crohn's disease (CD) patients treated with infliximab using Small Intestine Contrast Ultrasonography (SICUS). METHODS: Twenty patients (M 12, age, 42.7 ± 11.8 years), 15 of whom showed obstructive symptoms indicating the presence of small bowel stenosis, and 5 without stenosis, were treated with infliximab (5 mg/kg at wk 0, 2, 6 and 5 mg/kg every 8 wk thereafter) for steroid refractoriness, fistulizing disease, or to avoid high-risk surgery. SICUS was performed at the induction phase and at regular time intervals during the follow-up period of 34.7 ± 16.1 mo (range 7-58). Small bowel stenoses were detected by SICUS, endoscopy and MRI. RESULTS: In no case was progression of stenoses or the appearance of new ones seen. Of the 15 patients with stenosis, 5 stopped treatment after the induction phase (2 for no response, 3 for drug intolerance, one of whom showed complete regression of one stenosis). Among the remaining 10 patients, a complete regression of 8 stenoses (1 stenosis in 5 patients and 3 stenoses in one patient) was observed after 6-22 infliximab infusions. CONCLUSION: In patients with CD treated with infliximab we observed: (a) No progression of small bowel stenosis and no appearance of new ones, (b) Complete regression of 1/22 stenosis after the induction phase and of 8/15 (53.3%) stenosis after 6-22 infusionsduring maintenance therapy.

Retrieval of Electron Return Time from High-order Harmonics Generated in a Mixture of He and Ne Gases

In terms of single-atom induced dipole moment by Lewenstein model, we present the macroscopic high-order harmonic generation from mixed He and Ne gases with different mixture ratios by solving three-dimensional Maxwell＇s equation of harmonic field. And then we show the validity of mixture formulation by Wagner et al. [Phys. Rev. A 76 （2007） 061403（R）] in macroscopic response level. Finally, using/east squares fitting we retrieve the electron return time of short trajectory by formulation in Kanai et al. [Phys. Rev. Lett. 98 （2007） 153904] when the gas jet is put after the laser focus.

Role of intravenously administered hyoscine butyl bromide in retrograde terminal ileoscopy: A randomized, double-blinded, placebo-controlled trial

AIM： To evaluated the role of hyoscine butyl bromide in facilitating retrograde ileoscopy. METHODS： Retrograde terminal ileoscopy was attempted in 200 consecutive patients undergoing colonoscopy. After intubation of the cecum and visualization of the ileocecal valve, butyl bromide injection or normal saline was given intravenously to the patients in a double blind random fashion. The pulse rate and oxygen saturation were measured continuously. After completion of the procedure, endoscopists were then asked to score the ease of intubation and the ease of visualization of the terminal ileum on a visual scale of 1 to 10. The patients were also asked to score the pain after receiving hyoscine butyl bromide injection on a score of 1 to 10. RESULTS： Terminal ileoscopy could be performed in 188 patients. The mean （SD） visual analogue score for the ease of intubation of the cecum was 7.4 （0.65） in the injection group and 5.9 （0.8） in the placebo group （P 〈 0.001）. The mean （SD） length of ileum visualized in the injection group was 14.4 （3.3） cm and 10.4 （2.7） cm in the placebo group （P 〈 0.001）. The mean （SD） visual analogue score for ease of visualization of the terminal ileum was 7.5 （0.69） in the injection group and 5.9 （0.7） in the placebo group （P 〈 0.001）. The pain score experienced by the patients was 6.5 （0.7） in the injection group and 6.7 （0.69） in the placebo group （P 〈 0.008）. Although the pulse rate increased significantly in patients receiving the drug, no statistically significant difference was noted in the oxygen saturation between the two groups either before or after administration of the drug. No complications were observed in either of the groups. CONCLUSION： Hyoscine butyl bromide injection is a useful adjunct in helping the intubation and visualization of terminal ileum during colonoscopy.

Expression of matrix metalloproteinases and tissue inhibitor metalloproteinases increases in X-irradiated rat ileum despite the disappearance of CD8a T cells

AIM： To investigate their expression and activity in the rat ileum after exposure to ionizing radiation along with that of the cellular effectors and molecular mediators involved in the regulation of MMPs. METHODS： Rats were exposed to a single 10-Gy dose of X-rays delivered to the abdomen. A combination of methods, such as zymography, immunohistochemistry and real time reverse transcriptase-polymerase chain reaction, were used to localize and quantify MMPs and the molecules involved in MMP activating and inhibitory pathways （plasmin/ plasminogen, TIMPs）, CD^8＋, as well as inflammatory （interleukin （IL）-1β, IL-8, tumor necrosis factor-s, TNF-α） and fibrogenic mediators （transforming growth factor- β1-3） within ileal tissue at 1, 3, and 7 d after irradiation. RESULTS： A marked increase in MMP-2 and -14 mRNA and protein levels associated with an increased activity of MMP-2 was observed in irradiated ileal tissue. MMP-2 and -14 expression was mainly observed in inflammatory, epithelial, and mesenchymal cells, whereas a slight increase in MMP-3 expression was detected in the few infiltrating macrophages at d i after irradiation. Conversely, MMP-1, -7, and -9 mRNA levels were not found to be affected by abdominal irradiation. Irradiation was found to induce disappearance of CD^8＋ cells. Furthermore, we have observed that TNF-α and IL-1β protein levels increased 6 h after irradiation, whereas those of IL-8 only increased after 3 d and was concomitant with neutrophil infiltration. In addition, the expressions of molecules involved in MMP activating and inhibitory pathways （urokinase-type plasminogen activator andtissue-type plasminogen activator; TIMP-1, TIMP-2, and plasminogen activator-inhibitor-i） were found to be increased after abdominal irradiation. CONCLUSION： This study showed that abdominal irradiation induces an acute remodeling of the ileum associated with an increased expression of MMPs and TIMPs that do not involve CD^8＋ T cells but involve mesenchymal and epithelial cells, although to a lesser extent, and probably even soluble inflammatory and fibrogenic mediators.

Analysis of risk factors for polypoid lesions of gallbladder among health examinees

AIM: To investigate the prevalence and risk factors of polypoid lesions of gallbladder (PLG) among the health examinees in the Shanghai region, China. METHODS: A total of 11 816 subjects who underwent health examinations in our hospital between August 2010 and February 2011 were analyzed retrospectively. Among them, there were 7174 men and 4642 women. PLG was diagnosed by the real-time ultrasonography. Those with the body mass index (BMI) ≥ 28 were considered to be obese. Blood biochemical indices were detected with the fully automatic biochemical analyzer and hepatitis B surface antigen (HBsAg) was tested by the automated enzyme immunoassay. The correlations between the prevalence of PLG and age, sex, BMI, serum cholesterol (T-Cho), triglycerides (TG),blood sugar, HBsAg, high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), gallstone and fatty liver were investigated. After univariate analysis of 11 variables, stepwise logistic regression analysis was performed to explore the risk factors of PLG. RESULTS: There was a significant difference in sex, T-Cho, HBsAg, HDL-C, LDL-C and fatty liver between the PLG-positive group and the PLG-negative group (332/163 vs 6842/4479, P = 0.003; 22/473 vs 295/11 026, P =0.013; 92/403 vs 993/10 328, P = 0.001; 47/448 vs 332/10 989, P = 0.001; 32/463 vs 381/10 940, P = 0.001; 83/412 vs 3260/8061, P = 0.001). No significant difference was found in the age, BMI, TG, blood sugar and gallstone between the two groups (47.3 ± 26 vs 45.1 ± 33, P = 0.173; 59/436 vs 1097/10 224, P = 0.102; 52/443 vs 982/10 339, P = 0.158; 17/478 vs 295/11 026, P = 0.26; 24/471 vs 395/10 926, P = 0.109). Logistic regression analysis showed that the sex, HBsAg and HDL-C were independent risk factors for the development of PLG in a descending order of HDL-C > HBsAg > sex. CONCLUSION: In healthy people, the male gender, positive HBsAg, and low HDL-C confer higher risks of PLG development.

Multi-mode controller IC for soft-switched flyback converter with high efficiency over the entire load range

This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with valley switching (CCMVS) is employed to realize soft switching so as to reduce turn-on loss of power switch as well as conducted electromagnetic interference (EMI). At light load, the converter operates in discontinuous conduction mode (DCM) with valley switching and adaptive off-time control (AOT) to limit the switching frequency range and maintain load regulation. At extremely light load or in standby mode, burst mode operation is adopted to provide low power consumption through reducing both switching frequency and static power dissipation of the controller. The multi-mode control is implemented by an oscillator whose pulse duration is adjusted by output feedback. An accurate valley switching control circuit guarantees the minimum turn-on voltage drop of power switch. The pro-totype of the controller IC was fabricated in a 1.5-μm BiCMOS process and applied to a 310 V/20 V, 90 W flyback DC/DC converter circuitry. Experimental results showed that all expected functions were realized successfully. The flyback converter achieved a high efficiency of over 80% from full load down to 2.5 W, with the maximum reaching 88.8%, while the total power consumption in standby mode was about 300 mW.

Log-normal censored regression model detecting prognostic factors in gastric cancer:A study of 3018 cases

AIM:To investigate the efficiency of Cox proportional hazard model in detecting prognostic factors for gastric cancer.METHODS:We used the log-normal regression model to evaluate prognostic factors in gastric cancer and compared it with the Cox model.Three thousand and eighteen gastric cancer patients who received a gastrectomy between 1980 and 2004 were retrospectively evaluated.Clinic-pathological factors were included in a log-normal model as well as Cox model.The akaike information criterion (AIC) was employed to compare the efficiency of both models.Univariate analysis indicated that age at diagnosis,past history,cancer location,distant metastasis status,surgical curative degree,combined other organ resection,Borrmann type,Lauren's classification,pT stage,total dissected nodes and pN stage were prognostic factors in both log-normal and Cox models.RESULTS:In the final multivariate model,age at diagnosis,past history,surgical curative degree,Borrmann type,Lauren's classification,pT stage,and pN stage were significant prognostic factors in both log-normal and Cox models.However,cancer location,distant metastasis status,and histology types were found to be significant prognostic factors in log-normal results alone.According to AIC,the log-normal model performed better than the Cox proportional hazard model (AIC value:2534.72 vs 1693.56).CONCLUSION:It is suggested that the log-normal regression model can be a useful statistical model to evaluate prognostic factors instead of the Cox proportional hazard model.

Evaluation of cathode quality and damage of aluminium electrolytic cell based on non-destructive technology

To evaluate the quality and damage condition of the electrolyzer,wave velocity detection technology and impact echo technology were used to detect the cathode part of the electrolyzer.The experimental results show that wave velocity is linearly related to the porosity,and there is also a linear relationship between wave velocity and the square root of reciprocal density in cathode carbon blocks(CCBs)before installation into electrolyzer.Combined with detection results of wave velocity and voltage drop,the large-size CCBs with relatively good quality can be found.Through the impact echo technology on cathode steel rods(CSRs),the results of the on-site detection show that the damage condition of CSRs can be effectively evaluated,and the damage location of CSRs can be determined.This study proposes a novel and quantifiable method for the evaluation of cathode quality and damage,which provides a reference for prolonging the service life of the electrolyzer.

Diagnosis of uremia patients based on color space

Since traditional nail diagnosis is susceptible to objective factors such as illumination,medical experience,etc.,a nail diagnosis system of traditional Chinese medicine which combines objective nail image acquisition with information analysis is proposed and applied to the clinical research of nail diagnosis of uremia patients.Fifteen nail pictures of uremic patients were collected and segmented.The color information of nails was extracted.The relationship between the hemoglobin values of uremic patients and the values of color space before and after maintenance hemodialysis was analyzed by correlation analysis and multiple regression analysis.The experimental results show that the hemoglobin value of uremic patients have certain correlations with multiple color channels;before and after dialysis,there are significant changes in multiple channels;and the related multiple regression equation is established.

Colorectal cancer screening behavior and willingness:An outpatient survey in China

AIM： To identity the factors influencing colorectal cancer （CRC） screening behavior and willingness among Chinese outpatients.METHODS： An outpatient-based face-to-face survey was conducted from August 18 to September 7, 2010 in Changhai Hospital. A total of 1200 consecutive patients aged ≥ 18 years were recruited for interview. The patient＇s knowledge about CRC and screening was pre-measured as a predictor variable, and other pre- dictors included age, gender, educational level, month- ly household income and health insurance status. The relationship between these predictors and screening behavior, screening willingness and screening approach were examined using Pearson＇s 2 test and logistic regression analyses.RESULTS： Of these outpatients, 22.5% had undergone CRC screening prior to this study. Patients who had participated in the screening were more likely to have good knowledge about CRC and screening （OR： 5.299, 95% CI： 3.415-8.223）, have health insurance （OR： 1.996, 95% CI： 1.426-2.794） and older in age. Higher income, however, was found to be a barrier to the screening （OR： 0.633, 95% CI： 0.467-0.858）. An analysis of screening willingness showed that 37.5% of the patients would voluntarily participated in a screen at the recommended age, but 41.3% would do so under doctor＇s advice. Screening willingness was positively correlated with the patient＇s knowledge sta- tus. Patients with higher knowledge levels would like to participate in the screening （OR： 4.352, 95% CI： 3.008-6.298）, and they would select colonoscopy as a screening approach （OR： 3.513, 95% CI： 2.290-5.389）. However, higher income level was, again, a bar- rier to colonoscopic screening （OR： 0.667, 95% CI： 0.505-0.908）. CONCLUSION： Patient＇s level of knowledge and in-ome should be taken into consideration when conducting a feasible CRC screening.