Xiaodi Xu, Shanchao Sun, Yang Fei, Liubin Niu, Xinyu Tian, Zaitian Ke, Peng Dai and Zhiming Liang
This article aims to predict the rapid track geometry change in the short term with a higher detection frequency, and realize the monitoring and maintenance of the railway state.
Abstract
Purpose
This article aims to predict the rapid track geometry change in the short term with a higher detection frequency, and realize the monitoring and maintenance of the railway state.
Design/methodology/approach
Firstly, the ABA data needs to be filtered to remove the DC component to reduce the drift due to integration. Secondly, the quadratic integration in frequency domain for concern components of the vertical and lateral ABA needs to be done. Thirdly, the displacement in lateral of the wheelset to rail needs to be calculated. Then the track alignment irregularity needs to be calculated by the integration of lateral ABA and the lateral displacement of the wheelset to rail.
Findings
By comparing with a commercial track geometry measurement system, the high-speed railway application results in different conditions, after removal of the influence of LDWR, identified that the proposed method can produce a satisfactory result.
Originality/value
This article helps realize detection of track irregularity on operating vehicle, reduce equipment production, installation and maintenance costs and improve detection density.
Details
Keywords
Yat Hung Chiang and Eddie W.L. Cheng
– This paper aims to explore the use of the data envelopment analysis (DEA), Cobb-Douglas and translog production function methods in estimating contractors’ efficiency.
Abstract
Purpose
This paper aims to explore the use of the data envelopment analysis (DEA), Cobb-Douglas and translog production function methods in estimating contractors’ efficiency.
Design/methodology/approach
In this paper, the DEA, translog and Cobb-Douglas methods were used to estimate the technical efficiency of 23 contractors in Hong Kong from 2003 to 2009. For this research, four input and three output variables were identified.
Findings
The results suggest that the efficiency scores obtained from the DEA method were significantly different from those obtained from the translog and Cobb-Douglas methods, while the efficiency scores from the translog method were similar to those from the Cobb-Douglas method. The DEA method further reveals that the company had poor utilisation of its resources over the past few years. On the output side, the current ratio was too small, implying that the company suffered from excess current liabilities relative to its current assets.
Research limitations/implications
Application of efficiency measurement in the built environment is still in its infancy. The current research, therefore, calls for more research to be undertaken to establish the applied literature base for the construction industry.
Practical implications
The DEA method helps the inefficient company explore ways to improve the utilisation of the inputs as well as the process and to maximise the outputs.
Originality/value
Knowing the relative performance of contractors helps understand their competitiveness in the construction industry. By estimating their technical efficiency, contractors can improve the conditions for enhancing performance.
Details
Keywords
Satoru Tanaka and Shuya Hayashi
This paper examines the economic forces which may lead to government-assisted or -facilitated bid-rigging (kansei-dango) in public procurement in Japan, and considers their…
Abstract
This paper examines the economic forces which may lead to government-assisted or -facilitated bid-rigging (kansei-dango) in public procurement in Japan, and considers their implications. A public official may often worry about situations where his/her procurement project will not be successfully implemented. Based on a simplified theoretical treatment and on case studies of kansei-dango, it is argued that the desire to avert the risk of unsuccessful procurement resulting from the "experience goods" status of procured goods and/or services may be one reason for bid-rigging. Based on this understanding of kansei-dango, we discuss some implications for policies to restrain this type of corruption.
This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder…
Abstract
This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.
Details
Keywords
THE new DataSYS 700 Series multi‐dimensional measurement system from Gould is a complete data‐acquisition and measurement system based on state‐of‐the‐art digital storage…
Abstract
THE new DataSYS 700 Series multi‐dimensional measurement system from Gould is a complete data‐acquisition and measurement system based on state‐of‐the‐art digital storage oscilloscope technology.
Xushan Zhao, Yuanxun Wang, Haiou Zhang, Runsheng Li, Xi Chen and Youheng Fu
This paper aims to summarize the influence law of hybrid deposited and micro-rolling (HDMR) technology on the bead morphology and overlapping coefficient. A better bead topology…
Abstract
Purpose
This paper aims to summarize the influence law of hybrid deposited and micro-rolling (HDMR) technology on the bead morphology and overlapping coefficient. A better bead topology positively supports the overlapping deposited in multi-beads between layers while actively assisting the subsequent layer's deposition in the wire and arc additive manufacturing (WAAM). Hybrid-deposited and micro-rolling (HDMR) additive manufacturing (AM) technology can smooth the weld bead for improved surface quality. However, the micro-rolling process will change the weld bead profile fitting curve to affect the overlapping coefficient.
Design/methodology/approach
Weld bead contours for WAAM and HDMR were extracted using line lasers. A comparison of bead profile curves was conducted to determine the influence law of micro-zone rolling on the welding bead contour and fitting curve. Aiming at the optimized overlapping coefficient of weld bead in HDMR AM, the optimal HDMR overlapping coefficient curve was proposed which varies with the reduction based on the best surface flatness. The mathematical model for overlapping in HDMR was checked by comparing the HDMR weld bead contours under different rolling reductions.
Findings
A fitting function of the bead forming by HDMR AM was proposed based on the law of conservation of mass. The change rule of the HDMR weld bead overlapping spacing with the degree of weld bead rolling reduction was generated using the flat-top transition calculation for this model. Considering the damming-up impact of the first bead, the overlapping coefficient was examined for its effect on layer surface flatness.
Originality/value
Using the predicted overlapping model, the optimal overlapping coefficients for different rolling reductions can be achieved without experiments. These conclusions can encourage the development of HDMR technology.
Details
Keywords
He-Nan Bu, Hong-Gen Zhou, Zhu-Wen Yan and Dian-Hua Zhang
In the process of cold rolled strip, there is tight coupling between flatness control and gauge control. The variation of the roll gap caused by the change of bending force will…
Abstract
Purpose
In the process of cold rolled strip, there is tight coupling between flatness control and gauge control. The variation of the roll gap caused by the change of bending force will lead to the change of rolling force. Furthermore, it can cause a deep impact on the control accuracy of strip exit thickness and exit crown. The purpose of this paper is to improve the accuracy of the bending force preset value for cold rolled strip.
Design/methodology/approach
In this paper, the bending force preset control strategy with considering of rolling force was proposed for the first time and the preset objective function of bending force was established on the basis of the two-objective optimization of bending force and rolling force. Meanwhile, the multi-objective intelligent algorithm – INSGA-II – was used to solve the objective function.
Findings
The proposed bending force multi-objective preset model has been tested in a 1,450 mm tandem cold rolling line. The analyzed results of field data show that the deviations of strip exit thickness and exit crown are reduced effectively by using the improved model, and at the same time, more reasonable bending force preset values are obtained, which can enhance the accuracy of flatness preset control.
Originality/value
A preset model of bending force with considering flatness and gauge is proposed in this paper and the multi-objective function of bending force preset is established on the basis of the two-objective optimization of bending force and rolling force. The value lies in proposing a new decoupling method of rolling force and bending force.
Details
Keywords
The purpose of this paper is to develop a directional and roll control system for unmanned combat air vehicle (UCAV) automatic takeoff roll, with the objective of keeping the UCAV…
Abstract
Purpose
The purpose of this paper is to develop a directional and roll control system for unmanned combat air vehicle (UCAV) automatic takeoff roll, with the objective of keeping the UCAV along the runway centerline and keeping the wings level, especially when there is a crosswind.
Design/methodology/approach
The nonlinear model of the UCAV during takeoff roll is established. The model is linearized about the lateral‐directional equilibrium point at different forward speeds. The approximate directional model and roll model are extracted using time‐scale decomposition technique. Then the directional control law and roll control law are developed using gain scheduling approach. Nose wheel steering, differential brake and rudder are used as the primary directional control device at low, medium and high speeds, respectively, according to both the qualitative and quantitative analysis of their control effectiveness at different speeds. A priority matrix is developed to determine the secondary control device which is used if the primary control device fails, thus the directional control system can have a certain degree of fault tolerance.
Findings
This work developed the directional control law and roll control law by using gain scheduling approach. Experimental results verified that the developed directional and roll control system has high robustness and satisfactory fault tolerance: it can guarantee a safe takeoff under a 50 ft/sec crosswind, even if one directional control device fails, which satisfies the relevant criteria in MIL‐HDBK‐1797.
Practical implications
The directional and roll control system developed can be easily applied to practice and can steer the UCAV during takeoff roll safely, which will considerably increase the autonomy of the UCAV.
Originality/value
The paper shows how time‐scale decomposition technique is employed to extract the approximate directional model and roll model, which simplifies model analysis and control law design. A fault‐tolerant directional control system is designed to improve safety during takeoff.
Details
Keywords
This paper reports work undertaken for the rational exploitation of fabric rolls in order to be able to arrange cutting layers of fabric without leftovers or with a minimum and/or…
Abstract
This paper reports work undertaken for the rational exploitation of fabric rolls in order to be able to arrange cutting layers of fabric without leftovers or with a minimum and/or useful leftover. A computer program called “The Optimat Program”, based on theoretical and experimental considerations shown here, has been developed and used for the arrangement of cutting layers from a production fabric for men's jackets. It is concluded that such a program can bring about a considerable saving in materials during the cutting and spreading process in garment manufacture.
Details
Keywords
Lipeng Wang, Zhi Zhang, Qidan Zhu and Xingwei Jiang
This paper aims to propose a novel model predictive control (MPC) with time varying weights to develop a lateral control law in an automatic carrier landing system (ACLS), which…
Abstract
Purpose
This paper aims to propose a novel model predictive control (MPC) with time varying weights to develop a lateral control law in an automatic carrier landing system (ACLS), which minimizes landing risk and improves flight quality.
Design/methodology/approach
First, a nonlinear mathematic model of an F/A-18 aircraft during lateral landing is established. Then the landing model is linearized in the form of state deviations on the equilibrium points. Second, landing risk windows are proposed and a high-dimensional landing risk model is addressed through a back propagation (BP) neural network. The trained samples are acquired based on a pilot behavior model. Third, time varying weights created from the lateral landing risk are introduced into the performance function of MPC. Optimal solution is solved quicker and some state deviations are focused on and eliminated. Fourth, the algebraic inequalities are substituted by the linear matrix inequalities (LMIs), which are easily calculated by the computers.
Findings
On a semi-physical platform, the proposed method compares with a traditional MPC algorithm and a modified MPC with an additional term. The test results indicate that the proposed algorithm brings about an excellent landing performance as well as an ability of eliminating landing risk.
Practical implications
The landing phase of a carrier-based aircraft is one of the most dangerous and complicated stages, and the algorithm proposed by this paper plays a vital role in the lateral landing.
Originality/value
This paper establishes a lateral landing risk model, which considers not only the current landing state but also the future touchdown point. This lateral landing risk is integrated into the time varying weights of the MPC algorithm so that the state deviations and landing risk can be both reduced in the rolling optimization.