工作中电子天平的检定

本文对电子天平这一精密仪器作了基本介绍,以图文结合的方式阐述了天平的检定方法及计算过程。     

Comparison of different peeling systems for kiwifruit (Actinidia deliciosa,cv Hayward)

Galicia (N.W. Spain) produces 60% of Spanish kiwifruit (Actinidia deliciosa) and 5–20% of these are ‘destrío’ fruits, which do not reach market size and the appropriate form. These rejected fruits can be processed into products, thus increasing their added value. The processing of kiwifruit always includes a peeling operation, which can be performed by different systems. The most suitable conditions for caustic peeling and thermal peeling were established. Then, the two peeling systems were compared with manual peeling with the aim of selecting the best system to remove the peel of the ‘destrío’ kiwifruit. The fruits, once harvested, were stored in a cold chamber at 0 °C. Before processing or marketing kiwifruits, it is necessary to remove them from storage in cold chamber and storage at room temperature. In this study, different storage times at room temperature before peeling kiwifruits were also tested. The best system for peeling the kiwifruit was thermal peeling as this system resulted in the lowest weight loss and preserved the green colour characteristic of the kiwifruit. The best time for peeling the kiwifruit was after 8 days of storage at room temperature, after being removed from the cold chamber.     

汽车车身冲压件热成形工艺

对车身热冲压成形的工艺进行了详尽的介绍,并对这种新工艺的优势、缺陷等进行了分析。     

全厂控制回路振荡检测与平台的构建

全厂级别控制回路振荡检测在工业自动化生产中有着重要的意义。在基于互相关函数、转移熵、格兰杰因果关系检验等三种方法的基础上,对仿真数据进行了计算,并且应用MATLAB GUI设计了包含上述三种方法的控制回路振荡源检测平台。通过仿真数据进行振荡源检测,结果初步证明了平台的有效性。     

IC基板传输机器人末端执行器结构拓扑优化设计

在半导体封装基板检测的传输过程中,末端执行器对其快速稳定高效率的传输起着关键作用。在满足设计强度、刚度的条件下,以末端执行器轻量化为目标,建立了末端执行器的三维模型,利用有限元分析软件ANSYS对基板传输机器人末端执行器进行静力学和模态分析,得到末端执行器在最大载荷情况下的应力、应变特性和对应的振型,并对其进行拓扑优化设计,根据拓扑优化结果建立新的末端执行器结构,对新的结构进行强度校核,验证设计方案的有效性。研究结果表明,优化后末端执行器的前四阶固有频率都大于伺服电动机的回转频率(50Hz),质量减少了26.7%,较好地实现了轻量化的目标,同时为后续的相关产品研制提供了一种新的技术方案。     

Microstructure and tensile properties of nanocrystalline (FeNiCoCu)1−xTixAlx high entropy alloys processed by high pressure torsion

In this study, an equal-atomic FeNiCoCu high entropy alloy (HEA) and a Ti and Al added (FeNiCoCu)₈₆Ti₇Al₇ HEA were subjected for high pressure torsion (HPT) up to 10 rotations. Microstructure observation and mechanical properties test revealed that significant grain refinement as well as enhanced strength could be obtained in both HPT processed alloys. The HPT processed FeNiCoCu HEA alloy shows nanocrystalline structure consisting of FCC matrix (grain size ∼100 nm) and FeCo-riched BCC phase. The HPT processed (FeNiCoCu)₈₆Ti₇Al₇ HEA alloy shows nanocrystalline structured FCC matrix (mean grain size ∼50 nm) and refined NiCoTiAl-riched particles (mean particle size ∼0.71 μm). The ultimate tensile strength of the HPT processed FeNiCoCu and (FeNiCoCu)₈₆Ti₇Al₇ alloys are 1402 MPa and 1849 MPa, respectively. The microstructure evolution during HPT and strengthening mechanisms of the HPT processed specimens were discussed.     

Comparisons of buckling-to-weight behavior of cylindrical shells with composite and metallic stiffeners

The present research deals with the study of buckling pressure-to-weight ratio of cylindrical shells with laminated ring stiffeners. The research introduces a strain energy formulation for laminated rings, in which each ring stiffener may be treated individually and the geometrical dimensions and material properties of the stiffeners may be different from one another. In a parametric study, the impacts of various geometrical parameters of rings on the buckling pressure-to-weight ratio of shells for composite and metallic stiffeners are compared. The results show that the buckling-to-weight behavior of the shells with Steel stiffeners generally differs from the shells with stiffeners made of Aluminum, E-glass/epoxy, Graphite/epoxy, or Kevlar49/epoxy.     

Liquid chromatographic determination of caffeine and adrenergic stimulants in food supplements sold in Brazilian e-commerce for weight loss and physical fitness

Methyl-xanthines and adrenergic stimulants, such as caffeine and synephrine, are commonly added to food supplements due to their stimulating and thermogenic effects. In addition, the abusive consumption of food supplements with ergogenic and aesthetic purposes has been observed worldwide. This work describes the study of caffeine, p-synephrine, hordenine, octopamine, tyramine, ephedrine and salicin as stimulants in dietary supplements marketed in Brazil for weight loss and physical fitness claims. A total of 94 different products were acquired from 30 Brazilian websites. Thus, the sampling of marketed supplements was performed in virtual commerce (e-commerce) with claims of weight loss, appetite reduction, fat burning and metabolism acceleration. The developed analytical method involved the separation of the stimulants by HPLC with diode array detection (HPLC-DAD) by using a gradient elution of flow rate (0.7–2.5 ml min^?1) and mobile phase composition (0.1% H₃PO₄/methanol). The validated method was applied to the study of 46 dietary supplements. Caffeine, p-synephrine and ephedrine were found to be present as stimulants in 52% of the studied samples marketed as encapsulated or bulk forms. Caffeine was found to be present in concentrations that represent doses from 25.0 to 1476.7 mg day^–1. Synephrine was found in concentrations that represent doses from 59.1 to 127.0 mg day^–1. Ephedrine was found to be associated with caffeine in one formulation at a concentration representing a 26.1 mg day^–1 dosage.     

Schedule Model for Project Portfolio Based on Design Structure Matrix

To improve the enterprise resource utilization and shorten the cycle of the whole project portfolio,a scheduling model based on Design Structure Matrix ( DSM) is built. By setting the project activity weight index system and calculating the activity weight for the project portfolio,the constraint relationship between project portfolio information and resource utilization,as the two dimensions of the DSM,are fully reflected in the schedule model to determine the order of these activities of project portfolio. A project portfolio example is given to illustrate the applicability and effectiveness of the schedule model.     

Grey Entropy Relation Algorithm of Choosing the Optimum Diagnostic Nodes in Analogue Circuits

Choosing the optimum diagnostic nodes is helpful to increase the accuracy and the efficiency of circuits fault diagnosis. Grey entropy relation algorithm is proposed to choose the optimum diagnostic nodes of analogue circuits in this paper. Analogue circuits are regarded as grey system. Grey relation analysis and grey entropy analysis are combined to grey entropy relation algorithm. Grey entropy relation algorithm is used to quantify the relationship between the diagnostic nodes and fault components. The relevance between the diagnostic nodes and fault components can be evaluated by grey entropy relation degrees. According to the rank order of grey entropy relation degrees, the optimum diagnostic nodes of analogue circuits can be selected objectively and accurately. An example of fault diagnosis is presented to verify the validity of the optimum diagnostic nodes.