Lyapunov exponent of friction-induced vibration under smooth friction curve

This paper studies the nonlinear behavior of the friction-induced vibration by using spring-mass model subject to the smooth frictionvelocity curve. The nonlinearity and instability of the friction may produce the chaotic vibration depending on the friction curve. In order to show this, the Lyapunov exponents are calculated for a variety of the slope and magnitude in the smooth friction curve. In turn, the dependency of the friction curve on the chaotic attractor is illustrated.     

Experimental study on the life prediction of servo motors through model-based system degradation assessment and accelerated degradation testing

The advent of smart factories has resulted in the frequent utilization of industrial robots within factories to increase production automation and efficiency. Due to the increase in the number of industrial robots, it has become more important to prevent any unexpected breakdowns of the factory. As a result, the lifespan prediction of machinery has become a crucial factor because such failures can be directly associated with factory productivity resulting in significant losses. Most of the failures occur within one of the core components of the robot arm, the servo motor, and thus we will focus on the analysis of the servo motor in this study. However, sensor attachment to such equipment is considered difficult due to the dynamic movement of the robot arm, meaning that internal instrumentation should be utilized during analysis. In addition, no definite measure to determine the degradation of the motor exists, and thus a new degradation index is proposed in this study. Therefore, in this study, the lifespan of the servo motor will be estimated through accelerated degradation testing methods based on a new system degradation assessment method, which estimates the fault of the system using observer-based residuals with encoder data obtained from internal instrumentation.     

A study on piezoelectric energy harvester using kinetic energy of ocean

Electricity generation through fossil fuels has caused environmental pollution. Accordingly, research on new renewable energy (solar, wind, geothermal heat, etc.) to replace fossil fuels and solve this problem is in progress. These devices can consistently generate power. However, they have several drawbacks, such as high installation costs and limitations in possible set-up environments. Therefore, the piezoelectric harvesting technology, which is able to overcome the limitations of existing energy technologies, is actively being studied. The piezoelectric harvesting technology uses the piezoelectric effect, which occurs in crystals that generate voltage when stress is applied. Its advantages include a wider installation base and a lower technological cost. This study investigated a piezoelectric energy-harvesting device based on constant wave motion. This device can harvest power in a constant turbulent flow in the middle of the sea. The components of the device are circuitry, percussion bar, triple layer piezoelectric bender, bearing and rudder. A multiphysical analysis coupled with the structure and piezoelectric elements was also conducted to estimate the device performance. The analysis accuracy was improved by applying the impact energy to the bender calculated based on the shape of the wave in the East Sea. The proposed device’s performance was finally confirmed by experiments.     

Comparison of ablative and compressive mechanical behavior of several PICA-like ablative materials

It is significant to compare the ablative and compressive mechanical behavior of different PICA-like materials in the engineering applications. The plasma wind tunnel ablation tests with high-entropy air and CO_2 atmospheres, and compressive experiments in the ambient and 150℃, were conducted for three kinds of PICA-like materials(CF/PR-Si, CBCF/PR-SiOC and NQF/PR-Si composites). The traditional carbon/phenolic(C/PR) braided composites were also used for comparison. PICA-like materials have the better thermal insulation than traditional C/PR composite, especially for CBCF/PR-SiOC composite. The ablation behavior of CF/PR-Si and CBCF/PR-SiOC PICA-like materials in the CO_2 atmosphere can produce a large amount of SiO_2 in the form of coatings, oxide layers and skeletons on the ablated surface, which are greatly different from that in the air atmosphere.The compressive behavior of PICA-like material is greatly depended on the fiber fabrics, and exhibits the large discrete characteristics. The longer fiber in the PICA-like materials plays the role in maintaining the material integrity, while it may increase the thermal conductivity.     

Physicochemical Property and Fatty Acid Profile of Cephalotaxus fortunei Nut Oils

This paper focused on the main composition of Cephalotaxus fortunei nuts, the physicochemical property of its oils, the fatty acid profiles and the content of alkaloids and tocopherol in the nuts oils. And these elements were compared among three kinds of C. fortunei nuts and their oil. The results showed the C. fortunei nuts contained about 65 % crude oil. Meanwhile, the content of crude protein, crude fiber, moisture, ash and reduced sugar were presented, respectively. The important physicochemical indicators of the crude C. fortunei nuts oils were presented, including specific gravity, refractive index, viscosity, acid value and saponification value, etc. The contents of alkaloids were 0.41 % in NUT1, 0.24 % in NUT2 and 0.31 % in NUT3. The contents of tocopherol were low. The analysis of the fatty acid composition showed that the three kinds of oils were all rich in unsaturated fatty acids, oleic acid and linoleic acid, and the main triacylglycerols were dioleoyl-monolinoleoyl (OLO) and triolein (OOO). This work might help with the exploration of the applications of C. fortunei nuts and its oil.     

丁辛醇罐区尾气焚烧系统的应用及技术改造

中石油四川石化有限公司丁辛醇项目新建一套低压火炬作为其罐区尾气安全放空设施,新建低压火炬保证生产装置正常或事故排放时能够及时、安全、可靠地在低压火炬中排放燃烧,并满足国家现行的有关标准和环保要求。现对其构造、技术特点、流程作一简要叙述;在实际使用过程中还存在一些问题,本文对这些问题及其技术解决方法作一论述。     

一种高效过滤亚微米级细颗粒的新液固过滤技术——表层过滤

论述一种新的可高效过滤液体中亚微米级细颗粒的表层过滤技术,分析了表层过滤技术的特点、过滤模式、表层过滤基本条件和设计计算中所必需的数学模型。介绍了表层过滤技术在我国工业生产上推广应用的概况。     

伸缩式法兰液位检测技术的研究与应用

文章介绍了一种新型检测仪表,该变送器探测杆可根据现场情况变化长度,安装方便,易于检修维护。     

浅析建筑智能化弱电施工管理

由于我国经济水平的与日俱增,同时建筑电气工程的整体水平也在逐步上升,促使建筑智能化弱电施工管理的普及程度越来越高。本文从建筑智能化弱电施工设计为切入点,对施工、设计建设等方面进行了分析,并对其提出注意事项与管理策略。     

Preface

Evolutionary Algorithms(EAs)mimicking the principles of natural evolution can be used as powerful search and optimization methods.These Evolutionary Optimization methods are superior to traditional optimization methods especially in situations where gradient information is not readily available.EAs are generic and robust optimization methods since they do not make any assumption about the underlying search space.This is clearly evident by the success of EAs in a diverse range of real-world applications.T...