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Reliability prediction and its validation for nuclear power units in service

Jinyuan SHI,Yong WANG

《能源前沿（英文）》 2016年第10卷第4期页码 479-488 doi: 10.1007/s11708-016-0425-7

摘要： In this paper a novel method for reliability prediction and validation of nuclear power units in service is proposed. The equivalent availability factor is used to measure the reliability, and the equivalent availability factor deducting planed outage hours from period hours and maintenance factor are used for the measurement of inherent reliability. By statistical analysis of historical reliability data, the statistical maintenance factor and the undetermined parameter in its numerical model can be determined. The numerical model based on the maintenance factor predicts the equivalent availability factor deducting planed outage hours from period hours, and the planed outage factor can be obtained by using the planned maintenance days. Using these factors, the equivalent availability factor of nuclear power units in the following 3 years can be obtained. Besides, the equivalent availability factor can be predicted by using the historical statistics of planed outage factor and the predicted equivalent availability factor deducting planed outage hours from period hours. The accuracy of the reliability prediction can be evaluated according to the comparison between the predicted and statistical equivalent availability factors. Furthermore, the reliability prediction method is validated using the nuclear power units in North American Electric Reliability Council (NERC) and China. It is found that the relative errors of the predicted equivalent availability factors for nuclear power units of NERC and China are in the range of –2.16% to 5.23% and –2.15% to 3.71%, respectively. The method proposed can effectively predict the reliability index in the following 3 years, thus providing effective reliability management and maintenance optimization methods for nuclear power units.

关键词： nuclear power units in service reliability reliability prediction equivalent availability factors

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Understanding coupled factors that affect the modelling accuracy of typical planar compliant mechanisms

Guangbo HAO,Haiyang LI,Suzen KEMALCAN,Guimin CHEN,Jingjun YU

《机械工程前沿（英文）》 2016年第11卷第2期页码 129-134 doi: 10.1007/s11465-016-0392-z

摘要：

In order to accurately model compliant mechanism utilizing plate flexures, qualitative planar stress (Young’s modulus) and planar strain (plate modulus) assumptions are not feasible. This paper investigates a quantitative equivalent modulus using nonlinear finite element analysis (FEA) to reflect coupled factors in affecting the modelling accuracy of two typical distributed-compliance mechanisms. It has been shown that all parameters have influences on the equivalent modulus with different degrees; that the presence of large load-stiffening effect makes the equivalent modulus significantly deviate from the planar assumptions in two ideal scenarios; and that a plate modulus assumption is more reasonable for a very large out-of-plane thickness if the beam length is large.

关键词： coupling factors modelling accuracy compliant mechanisms equivalent modulus

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Availability growth models and verification of power equipment

Jinyuan SHI, Jiamin XU

《能源前沿（英文）》 2021年第15卷第2期页码 529-538 doi: 10.1007/s11708-019-0624-0

摘要： The general availability growth models for large scale complicated repairable system such as electric generating units, power station auxiliaries, and transmission and distribution installations are presented. The calculation formulas for the maintenance coefficient, mathematical expressions for general availability growth models, ways for estimating, and fitting on checking the parameters of the model are introduced. Availability growth models for electric generating units, power station auxiliaries, and transmission and distribution installations are given together with verification examples for availability growth models of 320–1000 MW nuclear power units and 1000 MW thermal power units, 200–1000 MW power station auxiliaries, and 220–500 kV transmission and distribution installations. The verification results for operation availability data show that the maintenance coefficients for electric generating units, power station auxiliaries, transmission and distribution installations conform to the power function, and general availability growth models conform to rules of availability growth tendency of power equipment.

关键词： repairable system power equipment electric generating unit power station auxiliary transmission and distribution installation reliability availability availability growth model

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Bridging reliability and operations management for superior system availability: Challenges and opportunities

《工程管理前沿（英文）》页码 391-405 doi: 10.1007/s42524-022-0206-4

摘要： Recently, firms have begun to handle the design, manufacturing, and maintenance of capital goods through a consolidated mechanism called the integrated product-service system. This new paradigm enables firms to deliver high-reliability products while lowering the ownership cost. Hence, holistic optimization models must be proposed for jointly allocating reliability, maintenance, and spare parts inventory across the entire value chain. In the existing literature, these decisions are often made fragmentally, thus resulting in local optimality. This study reviews the extant works pertaining to reliability-redundancy allocation, preventative maintenance, and spare parts logistics models. We discuss the challenges and opportunities of consolidating these decisions under an integrated reliability-maintenance-inventory framework for attaining superior system availability. Specific interest is focused on the new product introduction phase in which firms face a variety of uncertainties, including installed base, usage, reliability, and trade policy. The goal is to call for tackling the integrated reliability-maintenance-inventory allocation model under a nonstationary operating condition. Finally, we place the integrated allocation model in the semiconductor equipment industry and show how the firm deploys reliability initiatives and after-sale support logistics to ensure the fleet uptime for its global customers.

关键词： system availability product-service integration installed base new product introduction service supply chain reliability-maintenance-inventory optimization

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A modified zone model for estimating equivalent room thermal capacity

Hua CHEN, Xiaolin WANG

《能源前沿（英文）》 2013年第7卷第3期页码 351-357 doi: 10.1007/s11708-013-0254-x

摘要： The zone model has been widely applied in control analysis of heating, ventilation and air conditioning (HVAC) systems to achieve a high building efficiency. This paper proposed a modified zone model which is much simpler in the HVAC system simulation and has the similar accuracy to the complicated simulation model. The proposed model took into consideration the effect of envelop heat reservoir on the room indoor temperature by introducing the thermal admittance of the inner surfaces of the building enclosure. The thermal admittance for the building enclosure was developed based on the building thermal network analytical theory and transfer function method. The efficacy of the proposed model was demonstrated by comparing it with the complicated model — heat balance method (HTB2 program). The predicted results from the proposed model well agreed with those from the complicated simulation. The proposed model can then make the HVAC system dynamic simulation much faster and more acceptable for control design due to its simplicity and efficiency.

关键词： room model thermal network analysis transfer function heating ventilation and air conditioning (HVAC) system simulation

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Analyzing the service availability of mobile cloud computing systems by fluid-flow approximation

Hong-wu LV,Jun-yu LIN,Hui-qiang WANG,Guang-sheng FENG,Mo ZHOU

《信息与电子工程前沿（英文）》 2015年第16卷第7期页码 553-567 doi: 10.1631/FITEE.1400410

摘要： Mobile cloud computing (MCC) has become a promising technique to deal with computation- or data-intensive tasks. It overcomes the limited processing power, poor storage capacity, and short battery life of mobile devices. Providing continuous and on-demand services, MCC argues that the service must be available for users at anytime and anywhere. However, at present, the service availability of MCC is usually measured by some certain metrics of a real-world system, and the results do not have broad representation since different systems have different load levels, different deployments, and many other random factors. Meanwhile, for large-scale and complex types of services in MCC systems, simulation-based methods (such as Monte-Carlo simulation) may be costly and the traditional state-based methods always suffer from the problem of state-space explosion. In this paper, to overcome these shortcomings, fluid-flow approximation, a breakthrough to avoid state-space explosion, is adopted to analyze the service availability of MCC. Four critical metrics, including response time of service, minimum sensing time of devices, minimum number of nodes chosen, and action throughput, are defined to estimate the availability by solving a group of ordinary differential equations even before the MCC system is fully deployed. Experimental results show that our method costs less time in analyzing the service availability of MCC than the Markov- or simulation-based methods.

关键词： Service availability Mobile cloud computing Fluid-flow approximation Ordinary differential equations

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Distribution of background equivalent static wind load on high-rise buildings

Jianguo ZHANG , Ming GU ,

《结构与土木工程前沿（英文）》 2009年第3卷第3期页码 241-248 doi: 10.1007/s11709-009-0036-z

摘要： In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel. Some typical methods proposed in some relative literatures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods, are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use.

关键词： high-rise buildings along-wind cross-wind background equivalent static wind load close formulae

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China’s new problems of food security revealed by the Food Equivalent Unit

Huilong LIN,Ruichao LI,Cangyu JIN,Chong WANG,Maohong WEI,Jizhou REN

《农业科学与工程前沿（英文）》 2014年第1卷第1期页码 69-76 doi: 10.15302/J-FASE-2014023

摘要： China's food security has a great influence on the world, and has always been the top priority in China. In recent years, as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing, research based on nutrition security and broad food systems are increasingly needed in today’s China. Thus, not only grain for human consumption, but also animal foods have been integrated into the Food Equivalent, which is used to analyze China’s current agriculture system and reveal the water resource distribution. The results indicated that the average animal food consumption has risen by 78.6%, and now China’s daily supply of animal food per capita has reached about 50% of that in the USA and 80% of that in the South Korea. So there exist an obvious disparity in animal food supply between China and these two countries. It is impossible for the China’s current agricultural system to achieve the level in the USA. Under China’s current agricultural system, the consumption proportion of feed grain had surpassed the consumption of food grain, increased sharply from 33% in 1992 to 67% in 2011. However, the growth potential of total grain output is approaching an upper limit, so the continued growth of feed grain demand exerts great pressure on the China’s food supply. The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security. China’s current “grain farming” cannot meet the demand of increasing nutrition and appropriate resource utilization. The implementation of grassland agriculture appears feasible and necessary for saving feed grain, providing a large number of high-quality animal foods and appropriate water resource utilization.

关键词： food security nutrition security food equivalent unit grassland agriculture China

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Equivalent circuit and characteristic simulation of a brushless electrically excited synchronous wind

Hao WANG, Fengge ZHANG, Tao GUAN, Siyang YU

《机械工程前沿（英文）》 2017年第12卷第3期页码 420-426 doi: 10.1007/s11465-017-0439-9

摘要：

A brushless electrically excited synchronous generator (BEESG) with a hybrid rotor is a novel electrically excited synchronous generator. The BEESG proposed in this paper is composed of a conventional stator with two different sets of windings with different pole numbers, and a hybrid rotor with powerful coupling capacity. The pole number of the rotor is different from those of the stator windings. Thus, an analysis method different from that applied to conventional generators should be applied to the BEESG. In view of this problem, the equivalent circuit and electromagnetic torque expression of the BEESG are derived on the basis of electromagnetic relation of the proposed generator. The generator is simulated and tested experimentally using the established equivalent circuit model. The experimental and simulation data are then analyzed and compared. Results show the validity of the equivalent circuit model.

关键词： wind power brushless electrically excited synchronous generator hybrid rotor equivalent circuit

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Aerobic granular sludge formation based on substrate availability: Effects of flow pattern and fermentation

Quan Yuan, Hui Gong, Hao Xi, Kaijun Wang

《环境科学与工程前沿（英文）》 2020年第14卷第3期 doi: 10.1007/s11783-020-1226-0

摘要： Penetration depth and substrate characters affect AGS formation and performance. The relationship between substrate gradient and particle size affects AGS stability. The fermentation process is proposed as a pretreatment to improve AGS stability. The influences of flow patterns (mixed-flow and plug-flow) and fermentation pretreatment on aerobic granular sludge (AGS) formation with various substrate availability levels were investigated by running four identical laboratory-scale sequencing batch reactors (R1–R4), comparing two anaerobic feeding strategies and three kinds of substrates. R1 achieved faster granulation with a fast influent fill step followed by a modified anaerobic mixed-flow phase, but the AGS showed poorer stability with a cracked structure and a high suspended solids concentration in the effluent. The anaerobic plug-flow feeding mode (with influent fed slowly from the bottom) in R2 provided deeper penetration depth for the substance to reach the core of AGS and accordingly strengthen AGS stability. An acidogenic up-flow sludge bed reactor was introduced as a pretreatment to improve the AGS performance by enhancing glucose pre-fermentation (R4). AGS fed with mixed volatile fatty acids (VFA) after glucose fermentation showed similar performance compared with the reactor fed with acetate in the aspects of stability, structure, size distribution and nitrogen removal efficiency, and 74% similarity in the microbial community. For actual wastewater with low VFA concentrations, fermentation treatment was suggested as a promising pretreatment for stable AGS granulation and operation.

关键词： Anaerobic plug-flow feeding mode Anaerobic mixed-flow mode Fermentation pretreatment Substrate gradient Penetration depth

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Fault classification and reconfiguration of distribution systems using equivalent capacity margin method

K. Sathish KUMAR, T. JAYABARATHI

《能源前沿（英文）》 2012年第6卷第4期页码 394-402 doi: 10.1007/s11708-012-0211-0

摘要： This paper investigates the capability of support vector machines (SVM) for prediction of fault classification and the use of the concept of equivalent capacity margin (ECM) for restoration of the power system. The SVM, as a novel type of machine learning based on statistical learning theory, achieves good generalization ability by adopting a structural risk minimization (SRM) induction principle aimed at minimizing a bound on the generalization error of a model rather than the minimization of the error on the training data only. Here, the SVM has been used as a classification. The inputs of the SVM model are power and voltage values. An equation has been developed for the prediction of the fault in the power system based on the developed SVM model. The next steps of this paper are the restoration and reconfiguration by using the ECM concept, the development of a code, and the testing of the results with various load outages, which have been executed for a 12 load system.

关键词： support vector machines (SVM) structural risk minimization (SRM) equivalent capacity margin (ECM) restoration fault classification

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Meta-analysis of the risk factors of breast cancer concerning reproductive factors and oral contraceptive

Qiong DAI MD, Bei LIU MD, Yukai DU MM,

《医学前沿（英文）》 2009年第3卷第4期页码 452-458 doi: 10.1007/s11684-009-0080-z

摘要： The authors performed a meta-analysis of case-control studies that addressed whether reproductive factors and oral contraceptive use were associated with breast cancer by searching the MEDLINE, PubMed, Proquest, Embase, ScienceDirect, African Healthline, BMJ Health Intelligence and Chinese Periodical net databases for all English-language and Chinese-language papers published from January 1, 1997 to December 31, 2007. A total of 15 studies calculating pool ORs indicated that menopausal age >50yr [odds ratio (OR), 1.39; 95% confidence interval (CI), 1.22―1.57] and oral contraceptive use (OR, 2.12*, “*”: summary OR was adjusted; 95% CI, 1.24―3.62) were correlated with the increase in breast cancer risk while the summary OR based on number of full-term pregnancies ≥1 (OR, 0.63*; 95% CI, 0.60―0.68) and breast-feeding (OR, 0.76; 95% CI, 0.64―0.90) indicated no association with breast cancer risk. The correlation was statistically significant. Menopausal age >50yr and oral contraceptive use are positively correlated with an increase in breast cancer risk while breast-feeding and number of full-term pregnancies ≥1 are protective factors.

关键词： meta-analysis breast cancer risk factors reproductive factors oral contraceptive use

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医院中子照射器I型堆热中子束流孔道等效平面源的模拟计算

朱养妮,江新标,赵柱民,张良,周永茂

《中国工程科学》 2012年第14卷第8期页码 56-59

摘要：

采用蒙特卡罗程序MCNP模拟计算了医院中子照射器I型堆（IHNI-1）热中子束流孔道出口处的等效平面源。对B堆芯进行了临界搜索计算，模拟计算了热中子束流孔道及出口处中子、γ的束流参数，应用等效平面源模型建立了BNCT等效中子、γ平面源。为人体头颅等效模型剂量分布的快速计算提供了较为可靠的平面源。

关键词：医院中子照射器I型堆热中子束流孔道等效中子平面源等效γ平面源

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Risk factors of prognosis after acute kidney injury in hospitalized patients

null

《医学前沿（英文）》 2017年第11卷第3期页码 393-402 doi: 10.1007/s11684-017-0532-9

摘要：

The risk factors, especially laboratory indicators, of prognosis after acute kidney injury (AKI) remain unclear. We conducted a retrospective survey of Chinese People’s Liberation Army General Hospital from January 1, 2012 to December 31, 2012 according to the AKI diagnosis standard issued by Kidney Disease Improving Global Outcomes. The epidemiological features and factors influencing hospital mortality and renal function recovery were evaluated through logistic regression analysis. Among 77 662 cases of hospitalized patients, 1387 suffered from AKI. The incidence rate and mortality of AKI were 1.79% and 14.56%, respectively. Multivariate logistic regression analysis revealed that high AKI stage, age greater than 80 years, neoplastic disease, low cardiac output, increased white blood cell count, and decreased platelet count and serum albumin levels were the risk factors affecting the mortality of AKI patients. Conversely, body mass index between 28 and 34.9 was a protective factor. Increased AKI stage, tumor disease, post-cardiopulmonary resuscitation, and RRT were the risk factors of renal function recovery upon discharge. In addition to traditional risk factors, white blood cell count, platelet count, albumin, and BMI were the predictors of the mortality of AKI patients. No laboratory indicators were found to be the risk factors of renal function recovery in AKI patients.

关键词： acute kidney injury risk factors prognosis