电网典型“死区”故障保护动作分析

"死区"故障故障点较难判断,对电力调度员来说是故障处理的难点,如不快速切除该区域内的故障,将严重威胁电力系统的安全稳定运行。文中简要分析了电网中几种常见的"死区"故障现象,提出了"死区"故障的处理方法和预防措施,并举例说明。

计及报装容量阶跃性的中压配电网接线模式研究

将用户报装容量纳入接线模式研究过程,建立了供电能力"死区"模型。对用户报装容量概率分布条件下的线路期望负荷、期望接入用户数进行了分析,并以此为基础提出了计及"死区"影响的线路负载率、变电站出线间隔利用系数和用户平均占用出线间隔数等指标的计算方法。实际算例表明,该方法能够有效降低"死区"造成的不利影响,大幅度提升馈线实际接入能力和电网资源实际利用率,对提高配电网规划建设的经济性具有较强的指导意义。

Self Adjusting Feedforward Compensation Tracking Control for Proportional Valve Controlled Motor

Aim Aiming at the position tracking control for valve controlled motor electrohydraulic proportional servo systems mainly driving the static load torque, the tracking performance was studied in the presence of the variable gain and deadzone. Methods On the basis of conventional composite control with the deadzone compensation method, a comprehensive control approach with the deadzone and self adjusting feedforward compensation was proposed. Results Experimental results showed that the good tracking performance was achieved for the sinusoidal and constant velocity position tracking under a wide variations of load torque. Conclusion The position tracking accuracy for valve controlled motor electrohydraulic proportional servo systems has been solved by using the comprehensive control approach with the deadzone and self adjusting feedforward compensation.

100t钢包吹氩工艺优化数值模拟研究

通过数值模拟,研究了100 t钢包在LF精炼过程中底吹氩气流量对钢包内钢液流动特性、"渣眼"面积及活跃区比例的影响。结果表明,在一定范围内,增大吹氩量有利于增大"渣眼"面积,强化钢水运动,缩小"死区"体积比例,有利于脱硫反应的进行。但当吹氩量超过临界值时,"死区"体积比例缩小幅度降低。100 t钢包最佳吹氩量为300 L/min。

现代露天矿山剥离系统中排土机应用的若干问题

从排土机的分类、主要技术性能参数等方面对排土机在现代露天矿山剥离系统中的现状进行了分析,对排土机排土时初始路堤修筑的方法和步骤、对排土场"死区"的处理方法等问题进行了论述。

北衙金矿JJC10.5×11.0m浸吸槽改造研究

大型选矿设备的使用是实现规模化生产的主要途径之一,但由于大型浸吸槽的传动性能受限和槽内矿浆的流动性欠佳,往往导致浸吸槽"死区"[1]和槽内"矿浆短路"等现象。本文介绍了一种JJC10.5×11m浸吸槽改造的思路和方案,并且在改造后投入生产取得了较好的效果。

Precision Point to Point Control of Proportional Valve Controlled Motor with a Time Varying Load

Aim In accordance with the positioning control for valve controlled motor electrohydraulic proportional servo systems driving the static load torque, the positioning performance was studied in the presence of the time? varying deadzone and gain. Methods The large positioning errors caused by the time varying deadzone were significantly reduced by using the dynamic compensation method for the deadzone; and the large overshoot caused by the time varying gain were dramatically reduced by using the three section intelligent control schemes. Results Experimental results demonstrated that the positioning performance of rapid response, high accuracy and smaller or even no overshoot was achieved under a wide variations of load torque. Conclusion The good positioning performance for valve controlled motor servo systems has been achieved in the presence of the time varying deadzone and gain.

Robust CMOS phase frequency detector for high speed and low jitter charge pump PLL

In order to improve the performance of the existing phase frequency detectors （PFDs）, a systematical analysis of the existing PFDs is presented. Based on the circuit architecture, both classifications and comparisons are made. A new robust CMOS phase frequency detector for a high speed and low jitter charge pump phrase-locked loop （PLL） is designed. The proposed PFD consists of two rising-edge triggered dynamic D flip-flops, two positive-edge detectors and delaying units and two OR gates. It adopts two reset mechanisms to avoid the LIP and DN signals to be logic-1 simultaneously. Thus, any current mismatch of the charge pump circuit will not worsen the performance of the PLL. Furthermore, it has hardly any dead-zone phenomenon in phase characteristic. Simulations with ADS are performed based on a TSMC 0. 18-μm CMOS process with a 1.8-V supply voltage. According to the theoretical analyses and simulation results, the proposed PFD shows a satisfactory performance with a high operation frequency （≈ 1 GHz）, a wide phase-detection range [ ± 2π], a near zero dead-zone （ 〈 0. 1 ps）, high reliability, low phase jitter, low power consumption （ ≈100 μW） and small circuit complexity.

套管式换热器内部非对称流动现象研究

使用数值模拟和物理验证两种方法,研究了套管式换热器内稳态的流场和温度场,分析了换热器内部流动“死区”和换热能效。通过实验验证了数学模型的合理性,基于此进行了数值计算,主要结论为换热器存在垂直弯头的情况下,管道内流动速度并非对管道中心线呈完全对称,在转弯处会产生速度“死区”;改进后的换热器一定程度上减弱了流动“死区”,套管内流动速度更加均匀,换热能效比有显著提升。

微型计算机半桥式开关电源中功率晶体管损坏分析及维修对策

本文简述了微机开关电源的工作原理,分析了造成开关电源功率晶体管损坏的原因和机理,根据笔者的工作经验,提出了维修开关电源的对策和方法.

测三极管特性的改进电路

指出了电子线路基础实验教材中所给出的测三极管特性的电路所存在的问题 。

Gastric cancer incidence and mortality in Zhuanghe,China,between 2005 and 2010

AIM： To investigate the incidence and mortality of gastric cancer （GC） in Zhuanghe region, northeast China and the influencing factors for their changing trends.METHODS： All new cancer cases and deaths registered from 2005 to 2010 in Zhuanghe County were reviewed. The annual GC cases, constituent ratio, crude rates,age-standardized rates, their sex and age distribution and temporal trends were assessed. The method of annual percentage change （APC） was used to estimate the trends of GC.RESULTS： Altogether 2634 new cases of GC and 1722 related deaths were registered, which accounted for 21.04% and 19.13% of all cancer-related incidence and deaths, respectively. The age-standardized incidence rate steadily decreased from 57.48 in 2005 to 44.53 in 2010 per 10^5 males, and from 18.13 to 14.70 per 10s females, resulting in a APC of -5.81% for males and -2.89% for females over the entire period. The magnitude of APC in GC mortality amounted to -11.09% and -15.23%, respectively, as the agestandardized mortality rate steadily decreased from 42.08 in 2005 to 23.71 in 2010 per 10^5 males, and from 23.86 to 10.78 per 10^5 females. Females had a significantly lower incidence （a male/female ratio 2.80, P 〈 0.001） and mortality （a male/female ratio 2.30, P 〈 0.001）. In both genders, the peak incidence and mortality occurred in the 80-84 years age group. The age-standardized mortality/incidence ratio also decreased from the peak of 0.73 in 2005 to 0.53 in 2010 for males, and from 1.32 to 0.73 for females.CONCLUSION： Encouraging declines of incidence and mortality of GC were observed in Zhuanghe region between 2005 and 2010, possibly due to the economic development and efficient GC control strategies.

Stability analysis and stabilization of wireless networked control systems based on deadband control scheduling

The stability analysis and stabilization problems of the wireless networked control systems(WNCSs) with signal transmission deadbands were considered. The deadbands were respectively set up at the sensor to the controller and the controller to the actor sides in the WNCS, which were used to reduce data transmission, furthermore, to decrease the network collision and node energy consumption. Under the consideration of time-varying delays and signal transmission deadbands, the model for the WNCS was presented. A novel Lyapunov functional which took full advantages of the network factors was exploited. Meanwhile, new stability analysis and stabilization conditions for the WNCS were proposed, which described the relationship of the delay bounds, the transmission deadband bounds and the system stability. Two examples were used to demonstrate the effectiveness of the proposed methods. The results show that the proposed approach can guarantee asymptotical stability of the system and reduce the data transmission effectively.

Coastal eutrophication, land use changes and Ceratium furca (Dinophyceae) blooms in Pago Pago Harbor, American Samoa 2007-2009

The bloom forming dinoflagellate, Ceratium furca, has been linked with coastal eutrophication worldwide in tropical and subtropical locations. During the summer of 2007, an unusual 6-month long bloom of C. furca was observed in Pago Pago Harbor, Tutuila Island, American Samoa. Incidents of dinoflagellate blooms in this area have not been previously reported. The bloom was first reported in May and dissipated in November 2007. In February-March 2009, a similar C. furca bloom was observed. During both blooms, no fish mortality events were reported. Maximum cell counts were observed on September 20, 2007 at 9 200 cell/mL. At this time, total nitrogen was measured at 1.2 mg/L while total phosphate was below detection limits. Changes in land use practices may have been the primary driver of these blooms. Intense fertilization of athletic fields coupled with ineffective management strategies is hypothesized to have a direct link to the increase in nutrients found in the Pago Pago Harbor and may have been the trigger for the initialization of these blooms. During 2008, the fields were not used due to an infestation of the fire ant, Solenopsis geminata. Once controlled, the fields were opened again in 2009 and fertilizers were applied in January, a month before the bloom was observed.

Role of body mass index in colon cancer patients in Taiwan

AIM： To determine the effect of body mass index （BMI） on the characteristics and overall outcome of colon cancer in Taiwan. METHODS： From January 1995 to July 2003, 2138 patients with colon cancer were enrolled in this study. BMI categories （in kg/m2） were established according to the classification of the Department of Health of Tai- wan. Postoperative morbidities and mortality, and survival analysis including overall survival （OS）, disease- free survival （DFS）, and cancer-specific survival （CSS） were compared across the BMI categories.27 kg/m2） patients. Being female, apparently anemic, hypoalbuminemic, and having body weight loss was more likely among underweight patients than among the other patients （P 〈 0.001）. Underweight patients had higher mortality rate （P = 0.00.7） and lower OS （P 〈 0.001） and DFS （P = 0.002） than the other pa- tients. OS and DFS did not differ significantly between normal-weight, overweight, and obese patients, while CSS did not differ significantly with the BMI category. CONCLUSION： In Taiwan, BMI does not significantly affect colon-CSS. Underweight patients had a higher rate of surgical mortality and a worse OS and DFS than the other patients. Obesity does not predict a worse survival.

Compensation of Dead-Time Effect of Speed Sensorless Vector Control System

The key of speed sensorless vector control system lies in the accurate orientation of magnetic field. In some field-oriented algorithms, the integrator of observers and the dead-time effect bring in system errors during the estimation of field position. In this paper, a saturated feedback integrator is used, and the dead-time effect is compen- sated by current positive feedback. Experiments were carried out on the hardware platform of MCK2407, with chip TMS320LF2407 from TI Company. The results show that the prooosed method is simole and effective, and the accuracy of field position is improved.

Determinants of invasive strategy in elderly patients with non-ST elevation myocardial infarction

Background Knowledge gaps across literature prevent current guidelines from providing the profile of elderly patients most likely to derive benefit fi^om invasive strategy （IS） in non ST-elevation myocardial infarction （NSTEMI）. Furthermore, the benefit of IS in a real-world elderly population with NSTEMI remains unclear. The aims of this study were to determine factors that lead the cardiologist to opt for an IS in elderly patients with NSTEMI, and to assess the impact of IS on the 6-month all-cause mortality. Methods This multicenter prospective study enrolled all consecutive patients aged 〉 75 years old who presented a NSTEMI and were hospitalized in cardiology intensive care unit between February 2014 and February 2015. Patients were compared on the basis of reperfusion strategy （invasive or conservative） and living status at six months, in order to determine multivariate predictors of the realization of an IS and multivariate predictors of 6-month mor- tality. Results A total of 141 patients were included; 87 （62%） underwent an IS. The strongest independent determinants of IS were younger age [odds ratio （OR）： 0.85, 95%-confidence interval （CI）： 0.78-0.92; P 〈 0.001） and lower ＂Cumulative Illness Rating Scale-Geriatric＂ number of categories score （OR： 0.83, 95%CI： 0.73-0.95; P = 0.002）. IS was not significantly associated with 6-month survival （OR： 0.80, 95%CI： 0.27-2.38; P = 0.69）. Conclusions In real-world elderly patients with NSTEMI, younger patients with fewer comorbidities profited more often from an IS. However, IS did not modify 6-month all-cause mortality.

Achieving timely percutaneous reperfusion for rural ST-elevation myocardial infarction patients by direct transport to an urban PCI-hospital

Backgrounds ST-elevation myocardial infarction （STEMI） guidelines recommend reperfusion by primary percutaneous coronary in- tervention （PCI） ≤ 90 min from time of first medical contact （FMC）. This strategy is challenging in rural areas lacking a nearby PCI-capable hospital. Recommended reperfusion times can be achieved for STEMI patients presenting in rural areas without a nearby PCI-capable hospital by ground transportation to a central PCI-capable hospital by use of protocol-driven emergency medical service （EMS） STEMI field triage protocol. Methods Sixty STEMI patients directly transported by EMS from three rural counties （Nassau, Camden and Charlton Counties） within a 50-mile radius of University of Florida Health-Jacksonville （UFHJ） from 01/01/2009 to 12/31/2013 were identified from its PCI registry. The STEMI field triage protocol incorporated three elements： （1） a cooperative agreement between each of the rural emergency medical service （EMS） agency and UFHJ; （2） performance of a pre-hospital ECG to facilitate STEMI identification and laboratory activation; and （3） direct transfer by ground transportation to the UFHJ cardiac catheterization laboratory. FMC-to-device （FMC2D）, door-to-device （D2D）, and transit times, the day of week, time of day, and EMS shift times were recorded, and odds ratio （OR） of achieving FMC2D times was calculated. Results FMC2D times were shorter for in-state STEMIs （81 ± 17 vs. 87± 19 min）, but D2D times were similar （37 ± 18 vs. 39 ± 21 min）. FMC2D 〈 90 min were achieved in 82.7% in-state STEMIs compared to 52.2% for out-of-state STEMIs （OR = 4.4, 95% CI： 1.24-15.57; P = 0.018）. FMC2D times were homogenous after adjusting for weekday vs. weekend, EMS shift times. Nine patients did not meet FMC2D ≤ 90 min. Six were within 10 min of target; all patient achieved FMC2D 〈 120 min. Conclusions Guideline-compliant FMC2D ≤90 min is achievable for rural STEMI patients within a 50 mile radius of a PCI-capable hospital by use of protocol-driven EMS ground transportation. As all patients achieved a FMC2D time 〈 120 min, bypass of non-PCI capable hospitals may be reasonable in this situation.

The perceptions on good death of the older adults in the semi-urban community:A qualitative study

Objective This study aimed to explore the perceptions of good death of the older adults living in Bang Nang Li Sub-District,Amphawa District,Samut Songkhram Province,Thailand.Method The data of the study was collected using in-depth interviews between October 2019 to January 2020.The data collected a total of 14 older adults who had firsthand experience in caring for terminally ill patients were recruited for the study.Content analysis was employed to analyze qualitative data.Results The results of this study revealed the perceptions of good death which were categorized into three main themes and eight sub-themes,including 1)death without suffering(not suffering from life support devices,dying with care);2)natural death(death with the end of life expectancy,death with illness or ailments);and 3)death without the worries(preparation for death,spiritual and belief practice toward preparation for death,family and property management before death,death among family members and at their familiar place).Conclusion The findings of this research provided the insight to clarify the understanding of the perceptions on a good death of older adults.The findings can be used to support the practice and management of nursing education and health care providers who have to be involved in palliative care for terminally ill older adults.

Adamantinoma of the pelvic bone, a difficult diagnosis with fatal outcome

Adamantinoma is a primary low grade malignant bone tumor that is predominantly located in the mid-portion of the tibia. The tumor is of interest for two reasons： first, there still exists considerable dispute as to the origin of the lesion and recent reports reveal that the condition is more malignant than had previously been supposed. Although cases of adamanti- noma located to the axial skeleton have been reported, this is the first case of adamantinoma located to pelvic bone in Iran. Here we present the clinical, radiological ＆ histopathological features of a 19 year-old male with painful lesion located to the right pelvic bone which was morphologically and immunohistochemically diagnosed as adamantinoma. In general, metastasis is seen in 15%-20% of patients. The spread can occur to regional nodes, lung and infrequently to skeleton, liver and brain . Several weeks after surgery, our patient＇s condition gradually worsened. A CT-scan of abdomen revealed widespread liver metastasis and the patient died due to acute liver failure. This case demonstrates that the mortality rate from adamantinoma is not always low.