Error Analysis of Three Degree-of-Freedom Changeable Parallel Measuring Mechanism

A three degree-of-freedom (DOF) planar changeable parallel mechanism is designed by means of control of different drive parameters. This mechanism possesses the characteristics of two kinds of parallel mechanism. Based on its topologic structure, a coordinate system for position analysis is set-up and the forward kinematic solutions are analyzed. It was found that the parallel mechanism is partially decoupled. The relationship between original errors and position-stance error of moving platform is built according to the complete differential-coefficient theory. Then we present a special example with theory values and errors to evaluate the error model, and numerical error solutions are gained. The investigations concentrating on mechanism errors and actuator errors show that the mechanism errors have more influences on the position-stance of the moving platform. It is demonstrated that improving manufacturing and assembly techniques can greatly reduce the moving platform error. The small change in position-stance error in different kinematic positions proves that the error-compensation of software can improve considerably the precision of parallel mechanism.

Development of Gesture-Changeable under-actuated Humanoid Robotic Finger

Robotic fingers, which are the key parts of robot hand, are divided into two main kinds： dexterous fingers and under-actuated fingers. Although dexterous fingers are agile, they are too expensive. Under-actuated fingers can grasp objects self-adaptively, which makes them easy to control and low cost, on the contrary, under-actuated function makes fingers feel hard to grasp things agilely enough and make many gestures. For the purpose of designing a new finger which can grasp things dexterously, perform many gestures and feel easy to control and maintain, a concept called ＂gesture-changeable under-actuated＂ （GCUA） function is put forward. The GCUA function combines the advantages of dexterous fingers and under-actuated fingers： a pre-bending function is embedded into the under-actuated finger. The GCUA finger can not only perform self-adaptive grasping function, but also actively bend the middle joint of the finger. On the basis of the concept, a GCUA finger with 2 joints is designed, which is realized by the coordination of screw-nut transmission mechanism, flexible drawstring constraint and pulley-belt under-actuated mechanism. Principle analyses of its grasping and the design optimization of the GCUA finger are given. An important problem of how to stably grasp an object which is easy to glide is discussed. The force analysis on gliding object in grasping process is introduced in detail. A GCUA finger with 3 joints is developed. Many experiments of grasping different objects by of the finger were carried out. The experimental results show that the GCUA finger can effectively realize functions of pre-bending and self-adaptive grasping, the grasping processes are stable. The GCUA finger excels under-actuated fingers in dexterity and gesture actions and it is easier to control and cheaper than dexterous hands, becomes the third kinds of finger.

Scaling in Rate-Changeable Birth and Death Processes with Random Removals

We propose a monomer birth-death model with random removals, in which an aggregate of size k can produce a new monomer at a time-dependent rate I（t）k or lose one monomer at a rate J（t）k, and with a probability P（t） an aggregate of any size is randomly removed. We then anedytically investigate the kinetic evolution of the model by means of the rate equation. The results show that the scaling behavior of the aggregate size distribution is dependent crucially on the net birth rate I（t） - J（t） as well as the birth rate I（t）. The aggregate size distribution can approach a standard or modified scaling form in some cases, but it may take a scale-free form in other cases. Moreover, the species can survive finally only if either I（t） - J（t） ≥ P（t） or [J（t） ＋ P（t） - I（t）]t ≈ 0 at t ≥ 1; otherwise, it will become extinct.

Acute myocardial infarction associated with right bundle branch block and changeable trifascicular block: a case report

Rationale:Acute myocardial infarction in the presence of right bundle branch block.Patient concerns:A 70-year-old,male heavy smoker presented with angina and hypertension.Interventions:Electrocardiography,intravenous nitroglycerin infusion,intravenous streptokinase infusion.Diagnosis:Acute myocardial infarction in the presence of with changeable trifascicular heart block.Outcomes:Dramatic clinical improvement with electrocardiographic ST-segment (whether elevation or reciprocal ST-depression) resolution.Lessons:Acute myocardial infarction may be associated right bundle branch block.Accompanied trifascicular heart block had pre-streptokinase left anterior fascicular block with left axis deviation and post-streptokinase left posterior fascicular block with right axis deviation.

Secure hash function based on chaotic tent map with changeable parameter

A new algorithm for a novel hash function, based on chaotic tent map with changeable parameter, is proposed and analyzed. The one dimensional and piecewise tent map with changeable parameters decided by the position index of blocked messages is chosen, and blocked massages translated into ASCII code values are employed as the iteration time of the chaotic tent map. The final 128-bit hash value is generated by logical XOR operation on intermediate hash values. Theoretical analysis and computer simulation indicate that the proposed algorithm can satisfy the performance requirements of hash function.

Placement Design of Changeable Message Signs on Curved Roadways

This paper presented a fundamental framework for Changeable Message Sign(CMS)placement design along roadways with horizontal curves.This analytical framework determines the available distance for motorists to read and react to CMS messages based on CMS character height,driver's cone of vision,CMS pixel's cone of legibility,roadway horizontal curve radius,and CMS lateral and vertical placement.Sample design charts were developed to illustrate how the analytical framework may facilitate CMS placement design.

Time-resolved multiple imaging by detecting photons with changeable wavelengths

Transporting information is one of the important functions of photons and is also the essential duty of information science. Here, we realize multiple imaging by detecting photons with changeable wavelengths based on time-resolved correlation measurements. In our system, information from multiple objects can be transported. During this process, the wavelength of the photons illuminating the objects is different from the wavelength of the photons detected by the detectors. More importantly, the wavelength of the photons that are utilized to record images can also be changed to match the sensitive range of the used detectors. In our experiment, images of the objects are reconstructed clearly by detecting the photons at wavelengths of 650, 810, and 1064 nm, respectively. These properties should have potential applications in information science.

The Queuing Model of M/M/S/K ＋ M Based on the Impatience and Changeable Service Rate

The work flow of call center is a typical stochastic service system. This article exploites service rate, which is the most controllable artificial factor of call center, and integrates the abandoning rate of impatient customers, models a new-style call center＇s queuing model - the queuing model of M/M/S/K ＋ M based on the impatience and changeable service rate. Then, making use of the traffic forecast result coming from the time series, it models to figure out the numbers of agents per hour, and complete the agents＇ office-hour arrangements in the restriction of some system indexes. Finally, it optimizes the design method by the contrast and analysis of the changeable service rate model and the traditional regular service rate model.

变权理论-梯形云模型融合的金属矿绿色开采评价研究

如何有效评价金属矿山绿色开采水平对于发展绿色矿业非常重要。针对目前金属矿绿色开采评价方法存在评价结果单一、忽略金属矿绿色开采指标数据的随机性和模糊性的问题,研究提出变权理论-梯形云模型融合的金属矿绿色开采评价方法。首先,构建金属矿绿色开采评价指标体系,综合使用组合赋权法和变权理论得到各项指标的变权权重;其次,利用梯形云模型计算每个指标在对应等级下的隶属度,并得出隶属度评价向量;最后,结合变权理论与梯形云模型并按最大隶属度原则实现对金属矿绿色开采情况的评价。此外,以某金属矿山为实例,计算并分析其评价结果。该实例表明此方法对金属矿绿色开采情况进行评价可行,可为金属矿绿色开采评价的问题提供参考。

再论汉代人的国家意识

汉代人的国家意识在带有“公”属性的同时,其一家一姓“皇帝专属”的“私”属性十分浓厚。虽然总体来看,汉代人的强国与爱国意识得到了空前强化,但汉代人的国家意识也具有多层次性、差异性和可变性。理性看待汉代人的国家意识,可为现今中国真正有效、稳固、积极、健康的群体爱国意识的形成及爱国行为的产生提供有价值的历史启示。

长期不同秸秆还田措施对土壤供磷能力的影响

研究潮土区冬小麦-夏玉米轮作体系下长期不同秸秆还田措施对土壤磷素吸附解吸特性的影响,以期为提高该地区土壤供磷能力提供理论依据。依托山东禹城长期定位试验(始于2007年),研究了秸秆不还田(CK)、小麦秸秆单季还田(W)、玉米秸秆单季还田(M)和小麦玉米秸秆双季还田(D)4个处理对土壤有效磷含量和土壤磷吸附解吸特性的影响。结果发现,与CK相比,3种秸秆还田均显著提高了土壤有效磷含量,W、M和D处理有效磷含量分别增加了47.5%、15.4%和12.2%,而土壤交换性钙含量分别降低了49.1%、30.5%和31.7%。不同秸秆还田措施均对潮土磷吸附特征产生了影响:与CK相比,秸秆还田处理均能显著降低土壤对磷的吸附,W、M和D处理土壤磷平均吸附量分别下降了10.7%、7.5%和5.1%;单季秸秆还田处理W的土壤最大吸磷量(Q_(m))显著低于CK处理,但M和D处理土壤Q_(m)与CK没有显著差异;秸秆还田处理的磷吸附饱和度(DPS)均有所增加,但仅单季秸秆还田处理(W和M处理)的磷吸附饱和度显著高于CK。3种秸秆还田处理均显著提高了土壤磷解吸能力,各处理土壤磷解吸率表现为W>D≈M>CK,而秸秆还田处理均显著降低了土壤磷解吸滞后系数(HI),规律表现为CK>D≈M>W。相关性分析结果显示,土壤交换性钙含量与土壤磷吸附解吸能力显著相关。以上结果说明,在石灰性潮土中,单季和双季秸秆还田均能减少土壤对磷的吸附及增加其对磷的解吸能力,从而提升土壤供磷能力,且小麦单季秸秆还田效果优于其他两个秸秆还田处理。降低土壤中交换性钙对磷的固定可能是秸秆还田提高土壤磷有效性的重要途径。

高速动车组变轨距转向架轮轴结构及联接设计

为实现高速动车组跨国互联互通要求,结合变轨距转向架总体设计方案,提出了高速动车组变轨距转向架关键技术之一的轮轴结构及其联接结构的设计方案。对能够实现车轮轴向滑动且传递扭矩的轮轴及联接结构组成进行了总体介绍,突破传统轮轴配合设计理念,采用在车轮与车轴之间增加滑动轴承和衬套、轮轴分别压装内外齿套结构实现车轮滑动及扭矩传递功能。对车轮、车轴的材料选型和结构设计进行了论述,选取成熟应用的轮轴材质,并设计出全新阶梯状轮毂结构。按照EN和UIC标准,对车轮和车轴进行了强度计算及分析,其静强度和疲劳强度均满足要求。同时为验证轮轴联接可靠性,按照GB/T17855—2017标准,对花键进行齿面接触强度、齿根弯曲强度、齿根剪切强度、齿面耐磨损能力及外花键扭转与弯曲强度计算,计算结果满足运用要求。

高校历史建筑内部空间更新与活化研究——以南京大学鼓楼校区东南楼为例

当下中国的城市建设已从“增量开发”走向“存量更新”。其中,大量历史建筑都普遍存在空间形式单一、使用灵活性差等问题,面临如何在保存特有历史文化价值的前提下,充分活化利用其原有空间的难题。文章以南京大学鼓楼校区东南楼为例,通过对其三层及阁楼层的原有砖木结构进行研究分析,梳理空间关系,进而提出改造方案,通过功能空间转换与复合,以实现在传统建筑外壳下,充分满足当前高校教学多样化的需求,同时在未来可继续适应高校教学需求的变化。从而为高校历史建筑内部空间更新与活化利用提供一种设计思路与参考。

复杂多变工况下高铁轮对轴承故障识别研究

为提升复杂多变工况下轴承故障识别精度,研究了高铁轮对轴承故障识别方法。复杂多变工况下的轮对轴承振动信号经集合经验模态分解后,获得多个IMF分量及剩余分量,计算各分量的排列熵,以此为初始特征集,将朴素贝叶斯算法和最大均值差异(FSBD)方法相结合筛选有效特征,进行源域深度迁移自编码器训练,将输出参数作为目标域深度迁移自编码器的初始参数,检测目标域特征子集,输出故障识别结果。实验结果表明:该方法可实现轮对轴承振动信号的分解,完成初始特征FSI值的计算,选取特征数为150时,轮对轴承故障识别效果最突出,识别精度达到98.5%。

基于LabVIEW的高速列车变轨轮对性能试验测试系统研究

变轨距轮对技术是解决铁道车辆在轨距不同区间直通运行的一种行之有效的方法,根据某主机厂设计的新型变轨距轮对的变轨原理和技术参数,研制了变轨距轮对综合性能试验台,模拟变轨距轮对解锁/锁紧、变轨、跑合等功能。变轨距轮对的性能直接影响到变轨距转向架的性能,对列车的运行安全起到至关重要的作用。以变轨距轮对为研究对象,针对轮对在变轨过程中的运动状态及性能,进行了测试方法与试验研究。利用上位机软件LabVIEW进行编程控制,通过采集的数据进行分析处理,实时监测轮对运行的状态。试验结果表明,系统能够完成轮对的型式试验性能测试,并且可以有效地监控设备运行状态并能进行故障预警和处理。研究可为变轨距转向架和变轨列车的运行提供技术支持,具有一定的工程应用价值。

高压SVG在煤炭行业复杂多变供电系统中的应用

本文介绍了新风光电子科技股份有限公司生产的高压SVG在充矿能源南屯煤矿复杂多变供电系统的应用情况。介绍了SVG单机并机各种控制方案。结果表明,该高压SVG智能控制系统根据系统的需求,自动调节无功的输出,补偿效果好,补偿精度高。

一种变轨距转向架的方案设计

针对600mm/1067mm轨距变换的变轨距转向架技术市场需求,分析了国内外的变轨距转向架技术进展,对设计的变轨距转向架技术方案进行了系统性的介绍,包括滑移构架滑移变轨技术、独立旋转车轮技术、紧凑一系悬挂技术、电机直驱车轮随动技术等核心技术,填补了我国变轨距转向架的技术空白,为系统性掌握变轨距转向架核心技术奠定了坚实的基础。

单交通路口变相位变周期信号控制

在城市交通控制中,平面交叉路口各方向的交通量在不同时刻是不相同的,针对这特点,利用模糊控制理论,提出一种变相位变周期的控制算法,使得单个平面交叉路口信号控制的相位、周期及绿信比等成为可变的参数。仿真结果表明,与传统信号控制方式相比,变相位变周期的信号控制效果更好。

基于支持向量回归的电力变压器状态评估

为提高电力变压器状态评估的准确性,将变压器健康状态分为5级。鉴于支持向量机对小样本具有良好的拟合能力,而变压器数据具有小样本、贫信息的特点,提出了基于支持向量回归的电力变压器状态评估模型。将变压器的油色谱分析数据和电气实验数据利用半岭模型确定变压器各个参数的分值,评分项目结果作为支持向量机的自变量,通过多层动态自适应优化算法优化了支持向量回归的参数,形成变权重的预测。实例验证了变压器状态评估模型的正确性及可行性,其结果更接近变压器的真实运行状态。

上海滨岸沉积物、上覆水中N含量及时空变化

综合分析了上海滨岸潮滩表层沉积物及上覆水中营养盐N的含量 ,结果显示 ,表层沉积物中NH+ 4 N的含量在 8月、2月及 11月均很高 ,占 5 0 %～ 98% ,在 11月份NH+ 4 N和NO-3 N含量均显著增加 ;在空间分布上 ,长江口南岸无机氮含量普遍高于杭州湾北岸 ,其中NH+ 4 N含量峰值出现在SDK和BLG ,NO-3 N的沿程分布与NH+ 4 N较为一致 ,二者均受到排污及长江入海径流输入的影响。上覆水中在 2月和 8月NO-3 N含量普遍高于NO-2 N和NH+ 4 N ,而在 11月NH+ 4 N的含量则明显增加 ,并超过了NO-3 N ;无机氮沿程分布呈现较大地区差异的特点 ,而且NO-3 N含量普遍高于NH+ 4 N(SDK、WSK、LC除外 ) ,这受污水排放和所在沉积环境等多因素控制。在对比分析从2 0世纪 80年代至 2 0 0 0年近 2 0年间上海滨岸带无机氮含量的变化趋势 ,发现上海滨岸水体及沉积物总体质量在不断下降。其中滨岸水体若以国家海水水质标准进行评价 ,发现各采样点无机氮含量均超过四类海水的标准 ,而且最大超标幅度达到了 9.5 4倍 。