The modified firefly algorithm considering fireflies’ visual range and its application in assembly sequences planning

This paper proposes a modified discrete firefly algorithm (MDFA) to solve the problem of assembly sequence planning. Firstly, to improve the performance of the firefly algorithm (FA), we proposed a MDFA by endowing the fireflies with the capability of changeable visual range. The computing case shows the proposed algorithm is more effective and robust than standard FA, genetic algorithm and particle swarm optimization algorithm. Secondly, a method of how to set parameters for FA and MDFA is proposed. This method is practical in the application of FA to solve discrete problem. Thirdly, to make the sequences more closer to real industrial requirements, a so called process precedence relations (PPR) evaluation function is presented, which not only considering the interference between parts, assembly tools and clamps, but also regarding the assembly order between parts and their reference parts. Finally, the evolution performance of the MDFA is investigated, and the performance of the proposed approach to solve ASP is verified through two cases study.     

Coloured adaptive structured Petri-net Part II: deduction of the structured graph from the pregraph and application — modelling of a flexible workshop

In Part II of this paper, the authors describe the transformation of the pregraph into a structured coloured Petri-net. This step illustrates the different elementary processes as sequential control systems of the workshop and communications and binding types between these processes.     

The prediction technology study of fatigue life for key parts of a tracked vehicle’s suspension system

In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software ADAMS. Node force and stress results of the torsion bar from last step simulation were acquired; taking into account the material characteristics and influential factors, fatigue life of the flexible body of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.     

Coordinating the Operation of a Robot’s Manipulator and Vision System

Russian Engineering Research - The effectiveness of autonomous service robots may be improved by coordinating the operation of the manipulators and the robot’s built-in vision system in the...     

On the Allowance for Direct Piezoelectric Effect when Studying the Pulsed Operation Mode of a Piezoelectric Emitter by d’Alambert’s Method

An emitter in the form of a piezoelectric plate loaded on an aqueous medium is considered. Composite waveforms consisting of two half-periods are considered as electric signals fed to the plate, with one half-period exciting and the other one compensating. The pulsed transducer output signal is studied by D’Alambert’s method (without allowance for direct piezoelectric effect) and the Fourier spectral method. The similarity of the results indicates the correctness of applying d’Alambert’s method and the possibility for using it to assess the shape of signals emitted by the piezotransducer.     

Nanoparticle detachment: a possible link between macro- and nanotribology?

Although particle detachment is a common phenomenon associated with most tribological processes, it seldom occurs that each piece of elemental debris can be considered as the result of a single event. Such an association has been revealed by the systematic study of a specific system, where a pin of graphite is made to rub against thoroughly polished steel. While the discontinuous nature of the transfer film allows a quantitative assessment of the volume of transfer h _e to be made by 3D optical-profilometry, the linear dependence of the rate of particle detachment dh _e/dn (n=number of rubbing cycles) with the logarithm of sliding speed v strongly suggests the existence of a particular type of stick–slip, where each stick may lead to the detachment of a debris particle. The variations in size of these debris with environment as revealed by AFM, further suggest that the global rate of particle detachment is of the form: dh _e/dn=Nx _i , where N is the number of stick–slip events per rubbing cycle, x the proportion of stick events leading to a cohesive rupture, and _i the mean volume of an elemental particle. While this relation is apparently supported by most experimental results, its actual validation can only be made by experiments at the level of single (nanoscale) asperities, carried out under well-controlled experimental conditions.     

Hydraulic components’ matching optimization design and entropy production analysis in a large vertical centrifugal pump

Journal of Mechanical Science and Technology - The large vertical centrifugal pump is the core power equipment for long-distance water division and large-scale irrigation projects. The power of the...     

Lubricant Flow and Accumulation on the Slider’s Air-Bearing Surface in a Hard Disk Drive

Lubricant accumulation on the slider’s surface of a hard disk drive (HDD) has a detrimental effect on its read/write performance. Air flow through the slider-disk clearance moves some of the lubricant from the air-bearing surface (ABS) toward the slider’s lateral walls where it accumulates. In this article, we show by numerical simulations that the lubricant accumulation characteristics are strongly dependent on the slider’s flying height, skew angle and ABS design. The lubricant flow on the slider’s surface is quantified numerically. Air shear stress, air pressure and disjoining pressure are used as driving forces in the simulations. The lubricant thickness profile and volume evolution are calculated for two states of the HDD: operating and at rest. In the first state, lubricant is driven by air shear stress toward the trailing edge of the slider where it accumulates on the deposit end. In the second state, lubricant from the deposit end flows back into the ABS driven by the action of disjoining pressure. Lubricant accumulation on the four lateral walls of the slider is taken into account. The lateral walls are unfolded to study the flow using a two-dimensional lubrication model. The effects of flying height, skew angle and slider design on the accumulation removal of lubricant from the ABS are determined for the two states of the drive.     

On‐Line Preconcentration and Analysis of Zinc in Water by Flow Injection‐Knotted Reactor: Application to Geological and Environmental Exploration

Abstract

A preconcentration on‐line system composed of flow injection (FI) and a knotted reactor (KR), associated with inductively coupled plasma atomic emission spectrometry (ICP‐AES) has been used to determine Zn concentrations in river water. The zinc was retained as Zn‐2(5‐bromo‐2‐pyridilazo)5‐diethylaminofenol precipitated complex on the knotted reactor (KR). The limit of detection (0.09 µg L^?1 of Zn) of this method makes it particularly suitable for hydrochemical exploration in geological and environmental projects. This application has been validated in the volcanogenic gold (copper, zinc, lead) deposit of La Carolina in the province of San Luis, Argentina. The Carolina Stream and the Grande River have been sampled for water downstream this deposit. The regional background in river water is 2 µg L^?1. Six times this concentration has been observed at more than 6.5 km from the source, La Carolina mine.     

Design and analysis of a new AUV’s sliding control system based on dynamic boundary layer

The new AUV driven by multi-vectored thrusters not only has unique kinematic characteristics during the actual cruise but also exists uncertain factors such as hydrodynamic coefficients perturbation and unknown interference of tail fluid,which bring difficult to the stability of the AUV’s control system.In order to solve the nonlinear term and unmodeled dynamics existing in the new AUV’s attitude control and the disturbances caused by the external marine environment,a second-order sliding mode controller with double-loop structure that considering the dynamic characteristics of the rudder actuators is designed,which improves the robustness of the system and avoids the control failure caused by the problem that the design theory of the sliding mode controller does not match with the actual application conditions.In order to avoid the loss of the sliding mode caused by the amplitude and rate constraints of the rudder actuator in the new AUV’s attitude control,the dynamic boundary layer method is used to adjust the sliding boundary layer thickness so as to obtain the best anti-chattering effects.Then the impacts of system parameters,rudder actuator’s constraints and boundary layer on the sliding mode controller are computed and analyzed to verify the effectiveness and robustness of the sliding mode controller based on dynamic boundary layer.The computational results show that the original divergent second-order sliding mode controller can still effectively implement the AUV’s attitude control through dynamically adjusting the sliding boundary layer thickness.The dynamic boundary layer method ensures the stability of the system and does not exceed the amplitude constraint of the rudder actuator,which provides a theoretical guidance and technical support for the control system design of the new AUV in real complex sea conditions.     

A study on the modeling and analysis of a helicopter’s occupant seat belt for crashworthiness

Abstrac  In this paper, a method of modeling a seat belt on a crew seat during a dynamic seat testing was studied. The body segments of the occupant were modeled with joints that consisted of various stiffness, damping, and friction. Three types of seat belt restraint systems were investigated and an analysis on the injury assessment of the helicopter’s crew under a drop impact was conducted. The effectiveness of the seat belt system for crashworthiness and safety was likewise evaluated. From the impact analysis results, it was determined that the head, neck, and spine of the crew body can be easily damaged in the vertical direction more than the longitudinal direction. Based on the verified model, the human body’s behavior was studied using three point restraint systems. The displacement and injury level of the 12-point restraint system was the smallest. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Young-Shin Lee received a B.S. degree in Mechanical Engi-neering from Younsei University, Korea in 1972. He received master and Ph.D. degree in Mechanical Engineering from Yonsei University, Korea in 1974 and 1980 respectively. He is currently professor and Dean of Industry Graduate School and Director of BK21 Mechatronics Group at Chungnam National University, Korea. Prof. Lee’s research interests are in area of impact mechanics, optimal design, biomechanical analysis and shell structure analysis. Jung-Hyun Lee received a B.S. degree in Mechanical Design Engineering from Chungnam Na-tional University, Korea in 2007. He received master degree in Mechanical Design Engineering from Chungnam National Uni-versity, Korea in 2009. He is currently researcher of Korea Aerospace Research Institute, Korea. Kyu-Hyun Han received a B.S. degree in Mechanical Design Engineering from Hanbat National University, Korea in 2002. He received master degree in Mechanical Design Engineering from Chungnam National University, Korea in 2004. He is currently researcher of Simuline Inc, Korea.     

Leonardo da Vinci’s Friction Experiments: An Old Story Acknowledged and Repeated

Leonardo da Vinci (1452–1519) is universally regarded as a brilliant polymath, designer, astronomer, artist, philosopher, and a visionary engineer of the Renaissance era. Interestingly, due to the delayed discovery of several caches of his notebook pages (as late as the 1960s), his immense contribution to the field of tribology has only recently surfaced. From these salvaged documents, da Vinci’s three notable observations that preceded the development of the laws of friction were uncovered: (1) Friction is independent of apparent contact area, (2) the resistance of friction is directly proportional to applied load, and (3) friction has a consistent value of µ = 0.25. In this work, we have attempted to construct a nearly faithful recreation of Leonardo da Vinci’s apparatus for measuring friction based on his notebook illustrations and investigate the conditions under which Leonardo da Vinci’s experiments produced his findings. Our experiments, performed roughly 500 years later, reproduced Leonardo da Vinci’s findings of friction coefficients with wood of µ = 0.25, but only under conditions of roughly cut and brusquely squared samples of dry wood that were handled and sullied by hand in a fashion typical of wood working but inconsistent with the modern laboratory practice. Thus, our interpretation of Leonardo da Vinci’s findings is that these first tribological studies were actually performed on roughly cut and unpolished samples that had been handled extensively prior to and during testing; Such a procedure of sample preparation is entirely reasonable for the time period and suggests an active, dusty, and dynamic laboratory environment.     

Distribution of Fe and adsorption of NH3in mordenite:a computational study

采用色散校正密度泛函方法(DFT-D2)研究了Fe同晶取代进入丝光沸石骨架中的可能位置及其对NH3分子的吸附。结果表明,Fe优先取代位是T1O6位,然后依次是T2O5,T4O2和T3O1位,且能量差小于0.09 eV,说明Fe可能分布在四种非等价晶体T位,而且电荷平衡质子的位置影响Fe取代位的稳定性。本文还采用DFT和DFT-D2方法计算了NH3分子在每一个Fe取代的T位的吸附能。通过比较发现,DFT低估了NH3的吸附能约0.53 eV,这表明DFT-D2方法对于NH3吸附是很有必要的,且结果与文献相符,T2O5位的Brnsted酸性最强,NH3在Brnsted酸位的吸附比在Lewis酸位的吸附更稳定。     

Note: Non-destructive measurement of thermal effusivity of a solid and liquid using a freestanding serpentine sensor-based 3ω technique

A non-destructive thermal effusivity characterization method described as a freestanding serpentine sensor-based 3ω technique was reported. This freestanding serpentine sensor was fabricated by the mature flexible printed circuit production technique. Expression for the temperature response of the freestanding serpentine sensor with respect to the thermal effusivity of the test sample was presented. The technique was further verified by measuring four kinds of standard samples at room temperature. Experimental results which well agree with reference values demonstrate the new technique is of great application value to thermal effusivity characterization of solids, liquids, and structures to which the conventional 3ω technique is not applicable, e.g., solids with porous surfaces.     

GA and ICA approaches to job rotation scheduling problem: considering employee’s boredom

This paper presents a new model dealing with the job rotation scheduling problem, which is less studied, focusing on human characteristics such as boredom. Existing literature on conceptualizing boredom shows that researchers evaluate boredom in terms of exposure to the same tasks. We developed it to “exposure to similar tasks” and defined its functionality based on the need of assigning jobs with more similarity to each worker in the smallest period of planning which lowers the external interruption effect on worker’s concentration. To address the imbalance between number of jobs and that of workers in many industrial settings, we developed a multi-period imbalance assignment model. The proposed model is to rotate workers during a given planning horizon such that the total cost including assignment and boring cost will be minimized. The applicability of the model is described by presenting some real cases and validated through solving several randomly produced test problems by using Lingo software. Two search algorithms, genetic algorithm (GA) and imperialist competitive algorithm (ICA), designed to conquer the algorithmic complexity of model and their parameters adjusted using Taguchi’s method were used. The efficiency of algorithms is shown, comparing it with Lingo computation times, and it is shown that ICA solutions have better quality than GA solutions as well.     

Coupling system dynamics and contact behaviour: Modelling bearings subjected to environmental induced vibrations and ‘false brinelling’ degradation

During the last decades the increase in power of mechanical systems and the demand for increasing service life leads mechanical components of a system to work in extreme conditions. Moreover, actual mechanical systems include surfaces in sliding contact that are subjected to wear if exposed to high vibration. In fact, the vibration of components in contact results in large oscillations of the local contact stresses, due to the local deformation of the components at the contact interfaces. To approach correctly tribological problems, the coupling between the scale of the mechanism (system dynamics) and the scale of the contact needs to be accounted for.This paper presents an analysis concerning the influence of the vibrations induced by aircraft engines on the contact stresses of rolling bearings of the bleed system valves. To study the wear, resulting from false brinelling at the contact surfaces between balls and races of the bearings, it is then necessary to determine the forces due to the system vibrations and acting at the bearing connections with the structure. In order to perform a numerical transient analysis of the system dynamics a nonlinear simplified model of the valve (mechanism scale) is developed. The model is validated by comparing the numerical results with experimental tests. The time behaviour of the global forces on the bearings, and the respective displacements between the contact surfaces, are then used as inputs for a finite element model of the bearings (contact scale). The model is used to calculate and analyze the behaviour in time of the local contact constraints between race and balls. This analysis, developed in the framework of a European project, is an example of the proposed general approach to contact problems, by coupling the analysis of the mechanism and contact scales.     

Of mice, cats, and men: is human breast cancer a zoonosis?

Mouse mammary tumor virus (MMTV), a member of the betaretroviridae, is the most common cause of breast cancer (BC) in mice. MMTV is transmitted in mice both in the germline as endogenous proviruses and exogenously as infectious virions. Here, we review a variety of evidence accumulated for six decades that has suggested that a human homologue of MMTV may exist. The findings include recent studies from several independent laboratories that have detected sequences very closely related to MMTV in DNA isolated from human BC tumors. Other laboratories, however, have failed to detect the MMTV-related sequences in human DNA samples, and conclusive evidence for a human mammary tumor virus has been elusive. We also reviewed additional studies, suggesting that betaretroviruses are present in a much wider range of species than previously known, including rodents, felines, and primates. The observation that a subset of cats may be infected with a close homologue of MMTV may be of epidemiological significance for human BC. Cats may become infected by MMTV from mice, and in turn may transmit the virus to humans, possibly after selection for variants with an expanded host range.