Optimal online algorithms for scheduling on two identical machines under a grade of service

INTRODUCTIONWe study the problem of online scheduling on two identical parallel machines with a new feature that service requests from various customers are entitled to many different grade of service (GoS) levels. The goal is to minimize the makespan under the constraint that all requests are satisfied. This problem was first proposed by Hwang et al.(2004) and is motivated by the following scenario. In the service industry, the service providers often have special customers, such as, go…     

高校选课制下自动排考系统的设计和实现

针对选课制环境下,上课和考试对象的动态化、个性化带来的各种复杂的考试安排问题,提出可描述的业务结构和基于自动布局的考试安排的概念、算法、实现方式,特别是具有人机协同架构的基于种子的成长式选优算法的设计和针对自动预案的评估、选择、调整的应用模式的实现,被实践证明取得令人满意的效果。作为实际使用的智能系统,对于高校自动化业务处理,在实用、易用、有效性等方面提供了成功的尝试。     

作业车间调度问题解的不可行性检测算法和快速修复算法

为了判别作业车间调度问题的解的可行性,提出了一种基于图论的启发式判别算法,并通过实例验证了方法的正确性.提出了普适于作业车间调度问题的快速修补新算法,可以对于作业车间调度问题的不可行解进行修正使之变成可行解.判别算法和修补算法在最不利情形下的计算复杂性均为O(n),判别算法在最有利情形下的计算复杂性为O(2 |J|+|...     

柱撑粘土皂石的合成及其表征

用水热法合成了柱撑粘土皂石,用羟基铝与其交联,并对其进行了表征.合成出的柱撑粘土皂石显示出较高的热稳定性,在结构上也与文献报道相符.     

关于建设高校思政课数字化资源库的思考

高校思想政治理论课数字化教学资源库的建设对于促进高校思想政治课教学内容的革新、教学方式的变革和教学模式的创新具有重要意义。建设高校思想政治数字化资源库首先要了解资源库建设的内容并厘清其相互之间的关系,突出重点资源建设;其次,应认真研究如何发挥资源库建设在思想政治理论课教学中的作用。在上述基础上精心设计思想政治理论课数字化资源库建设的方案,为资源库研发、应用、管理提供理论上的支持。     

Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions

This paper proposes an analysis and a direct power control （DPC） design of a wind turbine driven doubly-fed induction generator （DFIG） under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions.     

Parameters optimization and nonlinearity analysis of grating eddy current displacement sensor using neural network and genetic algorithm

A grating eddy current displacement sensor （GECDS） can be used in a watertight electronic transducer to realize long range displacement or position measurement with high accuracy in difficult industry conditions. The parameters optimization of the sensor is essential for economic and efficient production. This paper proposes a method to combine an artificial neural network （ANN） and a genetic algorithm （GA） for the sensor parameters optimization. A neural network model is developed to map the complex relationship between design parameters and the nonlinearity error of the GECDS, and then a GA is used in the optimization process to determine the design parameter values, resulting in a desired minimal nonlinearity error of about 0.11%. The calculated nonlinearity error is 0.25%. These results show that the proposed method performs well for the parameters optimization of the GECDS.     

一种四氮杂希夫碱大环配合物LCo[Co(SCN)6]0.5·H2O的水热法合成与表征

以水热法合成了一个新的大环配合物LCo[Co(SCN)6]0.5.H2O(L为5,12-二甲基-7,14-二苯基-1,4,8,11-四氮杂环十四—4,11—二烯),经元素分析、红外光谱、电子光谱以及摩尔电导等对其结构进行了表征,其中钴(Ⅱ)离子为六配位的八面体构型。     

Application of biomonitoring and support vector machine in water quality assessment

The behavior of schools of zebrafish (Danio rerio) was studied in acute toxicity environments. Behavioral features were extracted and a method for water quality assessment using support vector machine (SVM) was developed. The behavioral parameters of fish were recorded and analyzed during one hour in an environment of a 24-h half-lethal concentration (LC₅₀) of a pollutant. The data were used to develop a method to evaluate water quality, so as to give an early indication of toxicity. Four kinds of metal ions (Cu²⁺, Hg²⁺, Cr⁶⁺, and Cd²⁺) were used for toxicity testing. To enhance the efficiency and accuracy of assessment, a method combining SVM and a genetic algorithm (GA) was used. The results showed that the average prediction accuracy of the method was over 80% and the time cost was acceptable. The method gave satisfactory results for a variety of metal pollutants, demonstrating that this is an effective approach to the classification of water quality.     

Performance evaluation of minimum quantity lubrication by vege- table oil in terms of cutting force, cutting zone temperature, tool wear, job dimension and surface finish in turning AISI-1060 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluid changes the performance of machining operations because of their lubrication, cooling and chip flushing functions, but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication （MQL） has been suggested since a decade ago as a means of addressing the issues of environmental intrusiveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL by vegetable oil on cutting temperature, tool wear, surface roughness and dimen- sional deviation in turning AISI-1060 steel at industrial speed-feed combinations by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip-tool and work-tool interaction.     

汉语语音评分系统的设计与实现

作为语言学习的重要组成部分之一,发音学习是人与人之间互相交流的基础。该文分析了传统语音教学及其评价方式的不足,以梅尔频率倒谱系数作为参数进行特征提取,用隐马尔可夫声学模型和音素后验概率算法将测试语音与标准语音进行比对,从而找出二者之间的差异程度,通过评分机制得到分数。实验结果表明,该系统能提高说话者学习语音的积极性,其评分结果与教师的主观感觉相一致,具有一定的实用性和可操作性。     

Improving educational access of vulnerable children in high HIV prevalence communities of Malawi: The potential of open and flexible learning strategies

Many children in Malawi have poor access to learning and are at risk of exclusion and early dropout. In the context of HIV/AIDS, formal schools need to become more flexible and responsive to children's lives. Introducing an educational model that integrates open and flexible learning strategies with conventional schooling, this paper highlights the potential of such an approach to enhance learning experiences, bring psychosocial benefits and improve retention of vulnerable pupils in high HIV prevalence communities in rural Malawi. This paper also argues that effective innovation requires strategies to create an enabling environment and promote an inclusive philosophy within schools.     

光伏充电系统的设计与研制

根据光伏阵列的输出特性与蓄电池充电特性,设计了一套具有最大功率点跟踪的光伏充电系统。该系统以dsPIC30F5011单片机为控制器,采用Cuk电路为充电主回路,根据蓄电池端电压对蓄电池采用四阶段充电控制策略。在欠电压充电阶段,采用基于PI调节的涓流对蓄电池充电;在快速充电的阶段,使用基于电导增量法的最大功率跟踪算法对蓄电池充电;在过冲与浮充阶段,使用基于PI调节的带有温度补偿的恒压充电。试验结果表明,最大功率点跟踪能快速跟踪外界环境的变化,并稳定工作在最大功率点,提高光伏电池的使用效率;过冲和浮充电压精度高,能延长蓄电池使用寿命。     

Method and application of wavelet shrinkage denoising based on genetic algorithm

INTRODUCTION Most underwater acoustic signals received by sonar are corrupted inevitably by unpredictable noise sources. In most cases, sonar system is adversely influenced by noise so disturbing that target signals cannot be detected and classified correctly so that pre-processing is necessary to reduce the noise as much as possible. Methods of noise reduction based on wavelet transform have been developed extensively in pre-vious literatures (Xu et al., 1994; Sun, 1998), and include wav…     

MCFC燃料电池的非线性建模及基于FGA的模糊控制

1Introduction Moltencarbonatefuelcell(MCFC)isaclearelec tricitygeneratingtechniquewithhighefficiency,which istobeusedwidely.Withoutcombustion,MCFCcon vertschemicalenergycontainedinfuelandoxidantin toelectricenergyviaelectro chemicalreaction.Per formanceof…     

年龄和学习时间对英语语音的影响

人们普遍认为儿童在第二语言学习方面要优于成人,尤其他们在语音方面的特殊能力给人留下深刻印象,这也是从小学开始外语教育的一个普遍依据。实验通过对60个年龄在13-35岁的中国学生所做的语音测试考察年龄和学习时间对英语语音的影响。实验证明年龄是影响语音能力的一个重要因素,在青春期前学习外语的学生更有可能达到标准的语音水平。     

项目驱动教学模式下“模拟护理国际会议”的组织与实施

项目驱动教学模式(PBL)以构建主义理论为基础,是一种以学生为中心的教学方式,有利于学生模拟真实情境,构建知识并转化为应用技能。本文探讨在该教学模式指导下如何组织和实施"模拟护理国际会议",提高涉外护理学生语言能力和专业水平。     

Volatile profile analysis and quality prediction of Longjing tea (Camellia sinensis) by HS-SPME/GC-MS

This study aimed to analyze the volatile chemical profile of Longjing tea, and further develop a prediction model for aroma quality of Longjing tea based on potent odorants. A total of 21 Longjing samples were analyzed by headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Pearson’s linear correlation analysis and partial least square (PLS) regression were applied to investigate the relationship between sensory aroma scores and the volatile compounds. Results showed that 60 volatile compounds could be commonly detected in this famous green tea. Terpenes and esters were two major groups characterized, representing 33.89% and 15.53% of the total peak area respectively. Ten compounds were determined to contribute significantly to the perceived aroma quality of Longjing tea, especially linalool (0.701), nonanal (0.738), (Z)-3-hexenyl hexanoate (−0.785), and β-ionone (−0.763). On the basis of these 10 compounds, a model (correlation coefficient of 89.4% and cross-validated correlation coefficient of 80.4%) was constructed to predict the aroma quality of Longjing tea. Summarily, this study has provided a novel option for quality prediction of green tea based on HS-SPME/GC-MS technique.     

SMART原则下的高中英语写作教学与评价

SMART黄金原则是由Specific(具体的)、Measurable(可衡量的)、Achievable(可实现)、Realistic(可行的)和Time-based and efficiency-oriented(即时有效的)首字母缩写而成。采用该原则检视《普通高中英语课程标准(实验)》的写作内容标准和写作教学与评价建议后,作者建议修订《普通高中英语课程标准(实验)》时要遵循上述原则,进一步制定明确的写作内容标准细则,开发或研制可衡量的英语写作评价工具,设计可实现的操作性强的英语写作任务,构建主体多元和形式多样的英语写作评价体系,指导教师如何进行即时有效的写作评价信息反馈。     

高温后高强高性能混凝土双轴压强度规律与破坏准则

利用大型静动真三轴试验机,进行了常温20℃以及200,300,400,500和600℃高温后高强高性能混凝土在7种应力σ2∶σ3=0∶-1,-0.20∶-1,-0.30∶-1,-0.40∶-1,-0.50∶-1,-0.75∶-1,-1.00∶-1双轴压试验.单双轴压试块尺寸为100 mm×100 mm×100 mm立方体.受压面的减摩垫层为3层塑料薄膜中间夹3层黄油.测得了双轴主压方向的静态强度,剖析了温度和应力比对单、双轴压强度发展趋势的影响规律以及试件破坏形态.试验结果表明:随温度的升高,高温后高强高性能混凝土的单轴压强度并不一定降低;双轴压强度相对于其单轴的提高倍数取决于应力比、不同温度等级后的高强高性能混凝土"脆硬性".提出了修正的带有温度和应力比参数高强高性能混凝土Kupfer-Gerstle破坏准则公式.