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LiMo 2040 Sustainable urban Living and Mobility Concept-Elevator System
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作者 Hugo Gabele Torben Ossendorf 《Journal of Civil Engineering and Architecture》 2024年第1期1-5,共5页
How can individual mobility in urban areas be maintained alongside scooters and cargo bikes if conventional vehicles are foreseeably no longer allowed to enter city centers?And how can urban living be combined with in... How can individual mobility in urban areas be maintained alongside scooters and cargo bikes if conventional vehicles are foreseeably no longer allowed to enter city centers?And how can urban living be combined with individual mobility in a sustainable and socially acceptable way?LiMo-2040 attempts to provide answers to these questions.It follows a holistic approach according to the criteria:As light,as compact and as simple(cost-effective)as possible.Modular e-vehicle concepts(consisting of vehicle cabin and chassis)are known,but have not yet been thought through to their logical conclusion.The LiMo cabin is not only a vehicle cabin,but also a component of a modern high-rise apartment.It therefore requires no parking space and combines urban living and individual mobility sustainably and cost-effectively.If a vehicle is needed,an app can be used to book a chassis that comes along autonomously and waits until the cabin,including its occupants,travels down a sophisticated rail system,docks and autonomously heads for the desired destination. 展开更多
关键词 MODULAR urban mobility SUSTAINABILITY elevator AUTONOMOUS
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Parameter Study on a Composite Sound-Absorbing Structure Liner in Elevator Shafts
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作者 Ting Qu Bo Wang Hequn Min 《Journal of Renewable Materials》 EI 2023年第9期3433-3446,共14页
With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic ... With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic development.This paper proposed a novel eco-friendly sound absorbing structure(NSAS)liner for noise reduction in elevator shafts.The base layer integrated with the shaft walls is a damping gypsum mortarboard,and a rock wool board and a perforated cement mortarboard are used to compose the NSAS.Based on the acoustic impedance theory of porous materials and perforated panels,the sound absorption theory of the NSAS was proposed;the parameter effects of the rock wool board(flow resistivity,porosity,structure factor)and perforated panel(perforated rates,thickness,density,perforated diameter)on NSAS absorption were discussed theoretically for absorption improvement,and experiments were also conducted.Numerical results showed that the perforation rate,the thickness of the perforated plate,and the porosity,flow resistance,and volume density of the rock wool board played a key issue in the absorption performances of the NSAS.Experiments verified the accuracy of the proposed theoretical model.Wideband sound absorption performance of the NSAS at frequencies between 500–1600 Hz was achieved in both numerical analysis and experiments,and the sound absorption coefficient was improved to 0.72 around 1000 Hz after parameter adjustments.The NSAS proposed in this paper can also be made of other renewable materials with preferable structure strength and still has the potential to broaden the absorption bandwidth.It can provide a reference for controlling the elevator shaft noise. 展开更多
关键词 elevator shafts sound-absorbing liner porous material flow resistivity acoustic impedance
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Two-Dimensional Images of Current and Active Power Signals for Elevator Condition Recognition
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作者 Xunsheng Ji Dazhi Wang Kun Jiang 《Journal of Harbin Institute of Technology(New Series)》 CAS 2023年第2期48-60,共13页
In this paper, an improved two-dimensional convolution neural network(2DCNN) is proposed to monitor and analyze elevator health, based on the distribution characteristics of elevator time series data in two-dimensiona... In this paper, an improved two-dimensional convolution neural network(2DCNN) is proposed to monitor and analyze elevator health, based on the distribution characteristics of elevator time series data in two-dimensional images. The current and effective power signals from an elevator traction machine are collected to generate gray-scale binary images. The improved two-dimensional convolution neural network is used to extract deep features from the images for classification, so as to recognize the elevator working conditions. Furthermore, the oscillation criterion is proposed to describe and analyze the active power oscillations. The current and active power are used to synchronously describe the working condition of the elevator, which can explain the co-occurrence state and potential relationship of elevator data. Based on the improved integration of local features of the time series, the recognition accuracy of the proposed 2DCNN is 97.78%, which is better than that of a one-dimensional convolution neural network. This research can improve the real-time monitoring and visual analysis performance of the elevator maintenance personnel, as well as improve their work efficiency. 展开更多
关键词 elevator condition CURRENT active power two-dimensional convolution network(2DCNN)
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The Development of Using Elevators in Different Buildings
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作者 Lamis Sayed Abdelkader 《Journal of Mechanics Engineering and Automation》 2019年第2期69-73,共5页
Elevators are one of the most important elements of vertical communication used in buildings.Especially in recent times,where high and high rise buildings have become a modern architectural phenomenon and the spread o... Elevators are one of the most important elements of vertical communication used in buildings.Especially in recent times,where high and high rise buildings have become a modern architectural phenomenon and the spread of architecture has become a feature of the age.Hence,the research discusses the technique of installing elevators in buildings.A general introduction to elevators and their types will be discussed,as well as a historical overview of the beginning of the idea of the elevator and the first buildings that were used.The technique of installing the elevator inside the building explained with the images shown components elevator.Also it will mention several speeds of modern elevators used in buildings,the world’s fastest elevator,ultra-rope technology and the reasons for choosing this technique in elevator components in high-rise buildings which may be used in the space elevator that will connect earth and space.As well it shows features of the wire used in the elevators of the Burj-Khalifa,the highest skyscraper in the world.Then it mentions a number of the most recent and newest elevators in the world,then research results and references. 展开更多
关键词 elevators construction technology HYDRAULIC lifts elevator INSTALLATION the FASTEST elevators.
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Clinical features and surgical treatment of double elevator palsy in young children 被引量:4
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作者 Wen-Ting Luo Tong Qiao +2 位作者 Hai-Yun Ye Si-Hong Li Quan-Li Chen 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2018年第8期1352-1357,共6页
AIM: To describe the clinical features of congenital double elevator palsy(CDEP) and to evaluate various surgical outcomes between the standard Knapp and augmented Knapp procedures, based on improvements in primary ey... AIM: To describe the clinical features of congenital double elevator palsy(CDEP) and to evaluate various surgical outcomes between the standard Knapp and augmented Knapp procedures, based on improvements in primary eye position and ocular motility.METHODS: Twenty-two patients with CDEP at Shanghai Children's Hospital were enrolled from July 2014 to January 2018. The forced duction test(FDT) was negative in 21 patients, aged 8 mo to 12 y(mean 5.4 y). Patients were divided into two treatment groups: 16 patients underwent the standard Knapp procedure(group A), with or without horizontal squint procedure; and 5 patients underwent the augmented Knapp procedure(Foster procedure; group B). One patient underwent inferior rectus recession in the affected eye and superior rectus recession in the sound eye because of a positive FDT. The pre-and postoperative vertical deviations in the primary position and ocular motility were compared in the two groups.RESULTS: Twenty-one eyes of the 22 patients(95%) were aligned within 10 prism diopters(PD), and all patients(100%) reached ≥25% elevation improvement after surgery. The average corrected vertical deviation in group B was statistically better than that of group A. For group A, the vertical deviation in the primary position decreased from 24.75Δ±8.35Δ to 4.56Δ±8.07Δ after surgery, for an improvement of 23.06Δ±6.51Δ(P<0.05). In group B, the decrease was from 35.00Δ±5.00Δ(range 30Δ-40Δ) to 1.00Δ±2.24Δ, for an improvement of 34.00Δ±4.18Δ(P<0.05). There were significant differences between the pre-and postoperative elevation in each group(group A, P<0.05; group B, P<0.05). The average scale of improved elevation in group B(1.80±0.45) was not significantly better than that of group A(1.69±0.87; Z=-0.732, P=0.548). The average follow-up periods lasted 21 mo in group A and 18 mo in group B.CONCLUSION: For vertical deviations <30Δ, the standard Knapp procedure can be chosen. For deviations greater than 30Δ-40Δ, the Foster procedure should be chosen. Because of our early interference, the inferior rectus(IR) muscle did not show mechanical restriction. Monocular elevation deficiency(MED) should be diagnosed early so that complications will be reduced and the procedure will be easier for the surgeon. 展开更多
关键词 monocular elevator deficiency double elevator palsy forced duction test inferior rectus recession standard Knapp procedure augmented Knapp procedure
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Prediction of elevator traffic flow based on SVM and phase space reconstruction 被引量:4
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作者 唐海燕 齐维贵 丁宝 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2011年第3期111-114,共4页
To make elevator group control system better follow the change of elevator traffic flow (ETF) in order to adjust the control strategy,the prediction method of support vector machine (SVM) in combination with phase spa... To make elevator group control system better follow the change of elevator traffic flow (ETF) in order to adjust the control strategy,the prediction method of support vector machine (SVM) in combination with phase space reconstruction has been proposed for ETF.Firstly,the phase space reconstruction for elevator traffic flow time series (ETFTS) is processed.Secondly,the small data set method is applied to calculate the largest Lyapunov exponent to judge the chaotic property of ETF.Then prediction model of ETFTS based on SVM is founded.Finally,the method is applied to predict the time series for the incoming and outgoing passenger flow respectively using ETF data collected in some building.Meanwhile,it is compared with RBF neural network model.Simulation results show that the trend of factual traffic flow is better followed by predictive traffic flow.SVM algorithm has much better prediction performance.The fitting and prediction of ETF with better effect are realized. 展开更多
关键词 support vector machine phase space reconstruction prediction of elevator traffic flow RBF neural network
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Finding Main Causes of Elevator Accidents via Multi-Dimensional Association Rule in Edge Computing Environment 被引量:2
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作者 Hongman Wang Mengqi Zeng +1 位作者 Zijie Xiong Fangchun Yang 《China Communications》 SCIE CSCD 2017年第11期39-47,共9页
In order to discover the main causes of elevator group accidents in edge computing environment, a multi-dimensional data model of elevator accident data is established by using data cube technology, proposing and impl... In order to discover the main causes of elevator group accidents in edge computing environment, a multi-dimensional data model of elevator accident data is established by using data cube technology, proposing and implementing a method by combining classical Apriori algorithm with the model, digging out frequent items of elevator accident data to explore the main reasons for the occurrence of elevator accidents. In addition, a collaborative edge model of elevator accidents is set to achieve data sharing, making it possible to check the detail of each cause to confirm the causes of elevator accidents. Lastly the association rules are applied to find the law of elevator Accidents. 展开更多
关键词 elevator group accidents APRIORI multi-dimensional association rules data cube edge computing
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Analysis and control of vibration of ropes in a high-rise elevator under earthquake excitation 被引量:1
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作者 Thuan Xuan Nguyen Nanako Miura Akira Sone 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2019年第2期447-460,共14页
In this research, the vibration of elevator ropes, including the main rope and compensation rope are investigated simultaneously in a high-rise elevator system under earthquake excitation. Moreover, the paper presents... In this research, the vibration of elevator ropes, including the main rope and compensation rope are investigated simultaneously in a high-rise elevator system under earthquake excitation. Moreover, the paper presents a new control method to restrain the sway of both ropes. This study considers varying rope lengths during elevator operation which cause other system parameters such as natural frequency, and damping ratio to be time-variant variables. The dynamics of the ropes are analyzed by solving the governing non-stationary, nonlinear equation numerically. In order to mitigate the vibration of ropes in several motion conditions, particularly upwards movement, downward movement, stopped at the lowest position, and stopped at the highest position, an active equipment is installed at the compensation sheave. The stability of the system using the controller is analyzed at four states: without disturbance and static car, without disturbance and mobile car, including disturbance and static car, and including disturbance and mobile car. The efficiency of the controller used for dampening the vibration of elevator ropes is validated by numerical simulation results. 展开更多
关键词 elevator ropes HIGH-RISE elevator VIBRATION CONTROLLER STABILITY
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A PID Sliding Mode Control for Ropeless Elevator Maglev Guiding System 被引量:2
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作者 Hasan Alipour Mohammad Bagher Bana Sharifian Hadi Afsharirad 《Energy and Power Engineering》 2012年第3期158-164,共7页
In this paper, three different controllers are proposed and simulated for maglev guiding systems to have convenient and smooth elevator motion. The proposed controllers are PID, sliding mode, and PID sliding mode cont... In this paper, three different controllers are proposed and simulated for maglev guiding systems to have convenient and smooth elevator motion. The proposed controllers are PID, sliding mode, and PID sliding mode controllers. The advantages and disadvantages of the proposed controllers are discussed. Although, PID controller is fast, its response affected considerably by external disturbances. Unlike PID, the sliding mode controller is so robust, but its transient is unsuitable based on application conditions. However, an acceptable controller for ropeless elevator guiding system should guaranty the passengers safety and convenient. Consequently, the response of the system should be fast, robust, and without considerable overshoots and oscillations. These required advantages are compromised in the proposed parallel PID sliding mode controller. The affectivity of the introduced controllers for maglev guiding system is investigated through conducted simulations in MATLAB/Simulink environment. The obtained results illustrate that PID sliding mode controller is a so fast and robust controller for a ropeless elevator maglev guiding system. 展开更多
关键词 GUIDING System Linear Ropeless elevator NON-LINEAR Control PID SLIDING MODE CONTROLLER
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Multi-objective Optimization of Multi-Agent Elevator Group Control System Based on Real-time Particle Swarm Optimization Algorithm 被引量:3
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作者 Yanwu Gu 《Engineering(科研)》 2012年第7期368-378,共11页
In order to get a globally optimized solution for the Elevator Group Control System (EGCS) scheduling problem, an algorithm with an overall optimization function is needed. In this study, Real-time Particle Swarm Opti... In order to get a globally optimized solution for the Elevator Group Control System (EGCS) scheduling problem, an algorithm with an overall optimization function is needed. In this study, Real-time Particle Swarm Optimization (RPSO) is proposed to find an optimal solution to the EGCS scheduling problem. Different traffic patterns and controller mechanisms for EGCS are analyzed. This study focuses on up-peak traffic because of its critical importance to modern office buildings. Simulation results show that EGCS based on Multi-Agent Systems (MAS) using RPSO gives good results for up-peak EGCS scheduling problem. Besides, the elevator real-time scheduling and reallocation functions are realized based on RPSO in case new information is available or the elevator becomes busy because it is unavailable or full. This study contributes a new scheduling algorithm for EGCS, and expands the application of PSO. 展开更多
关键词 MULTI-AGENT SYSTEM elevator Group Control SYSTEM REAL-TIME Particle SWARM Optimization Up-Peak Traffic
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Intelligent Decisions Modeling for Energy Saving in Lifts:An Application for Kleemann Hellas Elevators 被引量:2
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作者 Vasilios Zarikas Nick Papanikolaou +1 位作者 Michalis Loupis Nick Spyropoulos 《Energy and Power Engineering》 2013年第3期236-244,共9页
The present work proposes a methodological approach for modeling decisions regarding energy reduction in an elevator. This is achieved with the integration of existing as well as acquired knowledge, in a decision modu... The present work proposes a methodological approach for modeling decisions regarding energy reduction in an elevator. This is achieved with the integration of existing as well as acquired knowledge, in a decision module implemented in the electronics of an elevator. So far, elevators do not exploit information regarding their recent usage. In the developed system decisions are driven based on information arising from monitoring the use of the elevator. Monitoring provides various records of usage which consequently are used to predict elevator’s future usage and to adapt accordingly its functioning. Till now, there are only elevators that encompass in their electronics algorithms with if then rules in order to control elevator’s functioning. However, these if then rules are based only on good practice knowledge of similar elevators installed in similar buildings. Even this knowledge which unavoidably is associated with uncertainty is not encoded in a mathematically consisted way in the algorithms. The design, the implementation and a first pilot evaluation study of an elevator’s intelligent decision module are presented. The study concludes that the presented application sufficiently reduces energy consumption through properly controlled functioning. 展开更多
关键词 elevators ENERGY Consumption Reduction ENERGY Engineering APPLIED BAYESIAN NETWORKS APPLIED DECISION NETWORKS APPLIED Influence DIAGRAMS APPLIED Intelligent Decisions Fuzzy Rules
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Elevator Simulation电梯仿真软件的应用 被引量:2
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作者 曹嘉佳 《机电工程技术》 2019年第12期211-212,共2页
目前高职院校机电专业已经把电梯作为一个典型的工业案例引入到学生的PLC课堂中,但多数院校主要是通过单部电梯的实验箱模型来完成实践操作,这种电梯的实验箱具有一定的局限性,只是单部的运动,而现实生活中更多是多部电梯接收复杂的信号... 目前高职院校机电专业已经把电梯作为一个典型的工业案例引入到学生的PLC课堂中,但多数院校主要是通过单部电梯的实验箱模型来完成实践操作,这种电梯的实验箱具有一定的局限性,只是单部的运动,而现实生活中更多是多部电梯接收复杂的信号,同时运动载客。为了让实验案例更加接近实际生活应用,引入了Elevator Simulation电梯仿真软件,通过以太网通信连接编程计算机与电梯仿真模型机,在计算机上引入博途V14软件进行编程控制,通过Elevator Simulation电梯仿真软件对电梯进行仿真调试,不仅提高了学生的操作能力,更提升了学生的工程创造能力。 展开更多
关键词 PLC课堂 elevator Simulation电梯仿真软件 高职院校
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Protection of Elevators against Lightning
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作者 Zhang Jinsong Zhao Xi 《Meteorological and Environmental Research》 CAS 2018年第5期44-46,共3页
In the thunderstorm process on August 3,2016,among the nine elevators in a housing estate in the middle of Neijiang City,six elevators were damaged by lightning. In this study,the impact of lightning stroke on elevato... In the thunderstorm process on August 3,2016,among the nine elevators in a housing estate in the middle of Neijiang City,six elevators were damaged by lightning. In this study,the impact of lightning stroke on elevators was analyzed firstly,and then measures to protect elevators against lightning were proposed,which provides a practical basis for the improvement of protection of elevators against lightning. 展开更多
关键词 elevators LIGHTNING PROTECTION Measures
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Educational Research on a Water Elevator
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作者 Antonio Agoncillo Ahmad Alahmad +8 位作者 Shayea Aldughaiem Saud Almutairi Ali Alnaser Mohammad Alrasheed Ahed Dashtti Kimberly Duran Michael Vartanians David Boyajian Tadeh Zirakian 《Journal of Civil Engineering and Architecture》 2018年第12期890-895,共6页
This project involves modeling a water elevator in order to study its behavior and relate its mechanical advantages to various fluid mechanics properties. The reason that this small scale water elevator was constructe... This project involves modeling a water elevator in order to study its behavior and relate its mechanical advantages to various fluid mechanics properties. The reason that this small scale water elevator was constructed was to get a better understanding of such real world applications. As developing engineers, students have to grasp how to implement the theory they learn in the classroom. The properties of the water elevator were described with the energy equation, conservation of mass, volumetric flow rate, and hydrostatic pressure. After conducting various tests, theoretical and experimental values were compared and an analysis of the data was assembled allowing for the development of a more thorough understanding of fluid mechanics. 展开更多
关键词 elevator EXPERIMENTATION THEORY engineering EDUCATIONAL research PROJECT based LEARNING
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Tianjin Otis Elevator Co., Ltd.
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作者 Xiao Qiang, Staff Reporter 《China's Foreign Trade》 1995年第3期44-45,共2页
It is difficult to imagine that many of the modern buildings in China adopt elevators produced by the Tianjin Otis Elevator Co., Ltd.——one of the 500 largest foreign-funded enterprises nationwide and ranking 27th am... It is difficult to imagine that many of the modern buildings in China adopt elevators produced by the Tianjin Otis Elevator Co., Ltd.——one of the 500 largest foreign-funded enterprises nationwide and ranking 27th among the 100 largest machinery enterprises. It is also the largest foreign-funded enterprise in Tianjin. Founded in February 1984, 展开更多
关键词 Tianjin Otis elevator Co LTD US HIGH
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Analysis of the Causes of Elevator Operation Resonance in Elevator Inspection
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作者 Yuzhe Jia 《Journal of World Architecture》 2019年第1期1-5,共5页
Generally speaking,there are two reasons for elevator operation resonance to occur.One is because the quality of the hardware facilities is not up to standard,resulting in a mismatch between the operations of the vari... Generally speaking,there are two reasons for elevator operation resonance to occur.One is because the quality of the hardware facilities is not up to standard,resulting in a mismatch between the operations of the various components in the elevator operation;the other is caused by irregular installation,use and maintenance of the elevator.The installation of each component between the elevators should cooperate with each other to perfectly cooperate to complete the operation of the elevator.If not,there will be big problems.While using the elevator to replace the traditional ladder,we must also understand the cause of the elevator operation resonance,and study the corresponding countermeasures to reduce the accident caused by the elevator operation resonance. 展开更多
关键词 elevator operation RESONANCE TRACTION MACHINE
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Research of Maintenance Task Interval Optimization of Elevator Hydraulic Actuation System
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作者 CHEN Rui WANG Yiping SUN Tieyuan 《International Journal of Plant Engineering and Management》 2019年第3期169-179,共11页
In order to solve the best maintenance interval problem of the elevator hydraulic actuation systems on civil aircraft, a method based on reliability and cost minimum is introduced in this paper. The estimation of syst... In order to solve the best maintenance interval problem of the elevator hydraulic actuation systems on civil aircraft, a method based on reliability and cost minimum is introduced in this paper. The estimation of system reliability is presented by using two-parameter Weibull distributions. The parameters are estimated by using Weibull probability statistical analysis and the practical operational data. Then, the maintenance optimization model isformulated where the objective function is to minimize the expected schedule maintenance cost in a time unit. The results of numerical example show that the proposed model could scheme the optimal maintenance intervals for the considered system when the parameters are given. This research has certain significance in theoryand engineering practice. 展开更多
关键词 elevator HYDRAULIC ACTUATION SYSTEM maintenance INTERVAL minimum COST Weibull
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Design of New Elevator Pressure Guide Plate and Its Test Device
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作者 Qihang Xu Shaoke Chen 《Mechanical Engineering Science》 2019年第1期7-13,共7页
Pressure guide plate plays a certain role in the safe operation of elevator.Based on understanding the respective performance of new and old pressure guide plates,this paper analyses the problems existing in the origi... Pressure guide plate plays a certain role in the safe operation of elevator.Based on understanding the respective performance of new and old pressure guide plates,this paper analyses the problems existing in the original pressure guide plate.It also conducts stress analysis according to the function of pressure guide plate on elevator,and designs a new type of pressure guide plate combined with technological capability and equipment.According to the stress characteristics,a test device is designed and a comparative test is made between the new type of pressure guide plate and the old in order to test the reliability of the new type of pressure guide plate.The test proves that the new pressure guide plate of elevator can meet the requirements of product use and safe operation of elevator products. 展开更多
关键词 PRESSURE GUIDE PLATE Test DEVICE GUIDE RAILS elevator
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Fault Prediction of Elevator Door System Based on PSO-BP Neural Network
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作者 Penggao Wen Meng Zhi +1 位作者 Guangyao Zhang Shengmao Li 《Engineering(科研)》 2016年第11期761-766,共7页
Nowadays, the elevator has become an indispensable means of indoor transportation in people’s life, but in recent years this kind of traffic tools has caused many casualties because of the gate system fault. In order... Nowadays, the elevator has become an indispensable means of indoor transportation in people’s life, but in recent years this kind of traffic tools has caused many casualties because of the gate system fault. In order to ensure the safe and reliable operation of the elevator, the failure of elevator door system was predicted in this paper. Against the fault type of elevator door system: elevator door opened, excessive vibration when elevator door opened or closed, elevator door did not open or closed when reached the specified level. Three fault types were used as the output of the prediction model. There were 8 reasons for the failure, used them as input. A model based on particle swarm optimization (PSO) and BP neural network was established, using MATLAB to emulation;the results showed that: PSO-BP neural network algorithm was feasible in the fault prediction of the elevator door system. 展开更多
关键词 elevator Door System Gate System Fault Fault Prediction PSO-BP Neural Network
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Einstein’s Elevator in Cosmology
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作者 Rainer Burghardt 《Journal of Modern Physics》 2016年第16期2347-2356,共11页
The metrics of gravitational and cosmological models are brought into canonical form in comoving coordinates. The FWR curvature parameter k is read from this and it is shown that k=0 does not correlate to a flat model... The metrics of gravitational and cosmological models are brought into canonical form in comoving coordinates. The FWR curvature parameter k is read from this and it is shown that k=0 does not correlate to a flat model, but for a spatially positively curved geometry in which reference systems which are in free fall exist. This also corresponds to Einstein’s elevator principle. Moreover, we will show that our subluminal cosmos is associated with the R<sub>h</sub>=ct model of Melia, assuming that k=0 is related to a free-falling system in the sense described above. 展开更多
关键词 COSMOLOGY Einstein’s elevator Canonical Form of the Metric
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