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Layout optimization of workshop equipment based on WITNESS
According to the production order, the engine parts workshop of a company mainly produces four parts: valve hydraulic tappet, camshaft, camshaft gear and bearing cover. With the increasing demand of production, the production capacity brought by the original workshop equipment layout gradually cannot meet the increasing demand. In this paper, based on the WITNESS simulation software, we are preparing to collect the data of engine parts and components production workshop in order to get the data information of each element by simulation, and reasoning the unreasonable parts where the busy rate is too high and put forward several improvement methods. Through WITNESS software simulation, respectively, we can analyse whether there will have improvement and conclude the optimal improvement project. As the busy rate of lathe group and milling machine group of the original workshop layout is more than 80%, while the statistics are less than 60% by using the optimal plan to improve the existing layout, reaching a reasonable busy rate. It can be concluded that it is feasible to solve the problem of high work step busy rate and improve the overall production efficiency of the workshop through reasonable equipment layout optimization.
Journal Article
Practical TLA+ : planning driven development
Learn how to design complex, correct programs and fix problems before writing a single line of code. This book is a practical, comprehensive resource on TLA+ programming with rich, complex examples. Practical TLA+ shows you how to use TLA+ to specify a complex system and test the design itself for bugs. You'll learn how even a short TLA+ spec can find critical bugs. Start by getting your feet wet with an example of TLA+ used in a bank transfer system, to see how it helps you design, test, and build a better application. Then, get some fundamentals of TLA+ operators, logic, functions, PlusCal, models, and concurrency. Along the way you will discover how to organize your blueprints and how to specify distributed systems and eventual consistency. Finally, you'll put what you learn into practice with some working case study applications, applying TLA+ to a wide variety of practical problems: from algorithm performance and data structures to business code and MapReduce. After reading and using this book, you'll have what you need to get started with TLA+ and how to use it in your mission-critical applications. What You'll LearnRead and write TLA+ specificationsCheck specs for broken invariants, race conditions, and liveness bugsDesign concurrency and distributed systemsLearn how TLA+ can help you with your day-to-day production workWho This Book Is ForThose with programming experience who are new to design and to TLA+.
Book
Evaluation of Freeway Traffic Management and Control Measures Based on SUMO
With the rapid increase of freeway traffic volume, traffic congestion has become a normal phenomenon, through scientific freeway management and control measures, the traffic efficiency of the whole road can be effectively improved and the congestion problem can be alleviated. Therefore, this paper takes Shaoxing section of Shanghai-Hangzhou-Ningbo Feeway as the research object, puts forward three active traffic control measures, and uses the traffic simulation software SUMO to simulate and evaluate the effect of the freeway control measures. The results show that emergency lane control measure, ramp metering control measure, and variable speed limit control measure can effectively reduce the delay of freeway in the congested section, and improve road capacity. In this paper, the study of freeway management and control measures under congestion conditions, provides relevant decision support and theoretical guidance for freeway management.
Journal Article
Multi-Dimensional Indexes for the Sustainability Evaluation of an Active Distribution Network
An active distribution network (ADN) differs from a traditional distribution network in many aspects, one of which is the integration of a large amount of distributed generation (DG), especially intermittent photovoltaics (PVs). The integration of intermittent PVs has both pros and cons for the distribution system. As the platform on which new techniques work and the main body of a greener future energy system, the development of an ADN has to be sustainable, need-oriented, and environmentally friendly, and the traditional technical–economic evaluation method cannot meet the requirements and provide advice in the decision-making process. Based on the concept of sustainable development, we used an ADN with the integration of a large number of distributed PVs (DGPVs) as an example and established a multi-dimensional index system to evaluate the sustainable development level (SDI) of the ADN. The analysis was based on a platform we built with consideration of the investment feasibility of the DGPVs’ investors, state and industrial policies, and their interactions with the distribution system. We first compared the development of DGPVs and the SDI of the ADN as the carrier of DGPVs under different state policies, and second, we compared the SDIs of three city ADNs with different solar resources and demand levels, but under the same state policy. The analysis results showed that different integration levels of DGPVs can be set for a city/area ADN with different solar resources and demand to achieve a comparable SDI, and a comprehensive incentive mechanism could be adopted for the development of DGPVs. In this way, the benefits of different parties can be considered at the same time and finally, the coordination of the sustainable development of multi-parties can be achieved.
Journal Article
Analysis of the impact of COVID-19 on the coupling of the material flow and capital flow in a closed-loop supply chain
The complex and changeable external social and economic environment has a significant impact on the sustainable development of the closed-loop supply chain. In particular, the occurrence of uncertain emergencies increases the risk of interruption of the closed-loop supply chain, making it insufficient to analyze its complex changes from the perspective of material flow alone. Based on this analysis, the paper constructs a closed-loop supply chain material flow and capital flow coupling system composed of manufacturers, sellers and recyclers to explore the impact of material flow sudden interruption on the closed-loop supply chain system when an uncertain emergency occurs. In this paper, based on the closed-loop supply chain system coupled with logistics and capital flow, a system dynamics simulation model was established by using Vensim simulation software to analyze the impact of COVID-19 epidemic on manufacturers, sellers and recyclers under five scenarios. The results show that when COVID-19 outbreaks occur, the material flow of each main enterprise in the closed-loop supply chain is more easily influenced than the capital flow. At the same time, it can be found that the recyclers in the main enterprises of the closed-loop supply chain are more easily influenced by the material flow. The model constructed in this paper has applicability and can be used for related studies of closed-loop supply chain under other emergencies, but the scene design should be carried out according to the characteristics of emergencies themselves.
Journal Article
Design and Manufacturing of a Low-Cost Prosthetic Foot
Below-knee prosthetics are used to restore the functional activity and appearance of persons with lower limb amputation. This work attempted to design and manufacture a low-cost, novel, comfortable, lightweight, durable, and flexible smart below-knee foot prosthesis prototype. This prosthesis foot was designed according to the natural leg measurement of an adult male patient. The foot is composed of rigid PVC layers interspersed with elastic strips of PTFE, and the axis of the ankle joint is flexible and consists of metal layers and a composite of polymeric damping strips with different mechanical properties, making it flexible and allowing it to absorb shocks and store and release energy. The design, modeling, and simulation of the manufactured prosthetic foot were performed via the ANSYS 18.0 software and the finite element method (FEM), where a large number of parallel and oblique planes and sketches were created. This work included four adult patients weighing 50, 75, 90, and 120 kg with different walking cycles. The results show that the highest equivalent von Mises stress and total deformations for the prosthetic limb occur at the beginning of the walking step, while the highest equivalent elastic strains and strain energy release rates are observed at the end of the walking step, regardless of the weight. This prototype can satisfactorily perform the biomechanical functions of a natural human foot, and it can be produced in attractive sizes, models, and shapes to suit different levels of below-knee amputations for different ages and weights, especially for patients with limited income.
Journal Article
Design, Modeling and Implementation of Digital Twins
A Digital Twin (DT) is a set of computer-generated models that map a physical object into a virtual space. Both physical and virtual elements exchange information to monitor, simulate, predict, diagnose and control the state and behavior of the physical object within the virtual space. DTs supply a system with information and operating status, providing capabilities to create new business models. In this paper, we focus on the construction of DTs. More specifically, we focus on determining (methodologically) how to design, create and connect physical objects with their virtual counterpart. We explore the problem into several phases: from functional requirement selection and architecture planning to integration and verification of the final (digital) models. We address as well how physical components exchange real-time information with DTs, as well as experimental platforms to build DTs (including protocols and standards). We conclude with a discussion and open challenges.
Journal Article
Residual Stresses in Cast Iron Components - Simulated Results Verified by Experimental Measurements
The aim of this work was to investigate how accurately residual stresses can be simulated in a cast component. The reason why this is important is that a simulation that also considers residual stresses can be used to design cast components more weight-and cost-efficient. The verification was done by comparing simulated results with physical measurements on cylinders made of ductile iron. The measurements were performed with two methods, sectioning and hole-drilling. These methods were applied on both as-cast and machined cylinders. The simulations were based on process data from casting trials and material data from the simulation software database. The material data for the heat conductivity of the molding sand was fitted to get a good conformity between measured and simulated temperatures. This was done to ensure that the residual stress simulation used a relevant temperature history. It turned out that the simulation was in good agreement with results from the sectioning measurements of the axial stress while results from the hole-drilling measurements were contradictive. These results were contradictive for both as-cast and machined cylinders. It can therefore be concluded that residual stresses measured by the sectioning method resulted in good conformity with the simulated σz stresses. It was also concluded that the feeders, acting as extra heat sources, affects residual stresses locally and contributes to differences in stresses beneath the feeders, compared to corresponding areas between the feeders. It was also found that the resolution of the mesh needs to be finer to take into account changes in the stresses with increments in depth when using hole drilling method.
Journal Article
Vibration Based Piezoelectric Energy Harvesting - A Review
In this digital race, electronic equipment has been integrated into human beings as a part of their body. Some electronic equipment is connected by wires, while some are self-powered by batteries. Today the ultra-low-power smart electronic gadgets and smart wireless sensor devices need an unlimited battery for enhancing the performance. In a remote area such as forests and hill areas, conventional charging methods of batteries by wire is not possible. Supplying power through wires is difficult. To overcome this, a sustainable solution is energy harvesting. The renewable sources for energy harvesting are light, heat, wind, tidal, motion, and vibration. Researchers have more interest in harvesting energy through mechanical vibration due to its abundant availability. This paper reviews the work about piezoelectric crystals and their role in energy harvesting, simulation software used, energy harvesting circuits and storage devices.
Journal Article