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TWO COUNTERMEASURE STRATEGIES TO MITIGATE RANDOM DISRUPTIONS IN CAPACITATED systems

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Journal of systems Science and systems engineering 2010年第2期19卷 210-226页

作者： Niyazi O.BAKIR Alex SAVACHKIN Andrés Uribe-SANCHEZ department of industrial engineering Bilkent University department of industrial and Management systems engineering University of South Florida

We examine a capacitated system exposed to random stepwise capacity disruptions with exponentially distributed interarrival times and tmiformly distributed magnitudes. We explore two countermeasure policies for a risk-neutral decision maker who seeks to maximize the long-nm average reward. A one-phase policy considers implementation of countermeasures throughout the entirety of a disruption cycle. The results of this analysis form a basis for a two-phase model which implements countermeasures during only a fraction of a disruption cycle. We present an extensive numerical analysis as well as a sensitivity study on the fluctuations of some system parameter values.

关键词： Capacity analysis capacitated system lean random disruptions countermeasure policy

MAINTENANCE OF MULTI-STATE PRODUCTION systems DETERIORATED BY RANDOM SHOCKS AND PRODUCTION

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Journal of systems Science and systems engineering 2011年第1期20卷 110-118页

作者： Won Seok YANG Dae E.LIM Kyung C.CHAE department of Business Administration Hannam University department of industrial and systems engineering

We consider the preventive maintenance of a production system that is deteriorated by random shocks and the production process itself. The degree of deterioration is modeled by discrete and finite states. Shocks arrive according to a Poisson process and deteriorate the system by random amounts. The system may deteriorate whenever it produces an item. The system is continuously monitored and repaired if the system state is at or above a predetermined level for maintenance. We analyze the lifetime, product quantity, average cost, and average profit considering revenue from the product and cost due to setup, operation, and repair. Assuming a structure of system parameters and costs, using numerical examples, we investigate the impact of production and shock arrivals on the average profit and the optimal maintenance level that maximizes the average profit. The proposed model is applicable to manufacturing tasks in which machines wear due to production, for example, press processes, milling, turning, punching, and drilling.

关键词： Multi-state deterioration random shock maintenance cost-benefit analysis

Formation of TiN Grid on NiTi by Laser Gas Nitriding for Improving Wear Resistance in Hanks' Solution

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Journal of Materials Science & Technology 2016年第5期32卷 459-464页

作者： C.H.Ng O.K.Chan H.C.Man department of industrial and systems engineering The Hong Kong Polytechnic University

Laser gas nitriding （LGN） is a common surface modification method to enhance the wear resistance of titanium （Ti） alloys, which are known to have poor tribological properties. In the present study, a titanium nitride （TIN） grid network was fabricated on the surface of nickel titanium （NiTi） by LGN. The laser processing parameters were selected to achieve nitriding without surface melting and hence to＇maintain a smooth surface finish. The characteristics of the grid-nitrided samples were investigated by scanningelectron microscopy, X-ray diffractometry, optical microscopy, 2-D profilometry, contact angle measurements and nanoindentation. The wear resistance of the nitrided samples was evaluated using reciprocating wear test against ultra-high-molecular-weight polyethylene （UHMWPE） in Hanks＇ solution. The results indicate that the wear rates of the grid-nitrided samples and the UHMWPE counter-body in the wear pair are both significantly reduced. The decrease in wear rates can be attributed to the combination of a hard TiN grid and a soft NiTi substrate. In Hanks＇ solution, the higher hydrophilicity of the nitrided samples also contributes to the better performance in wear test against hydrophobic UHMWPE.

关键词： Laser Nitriding Surface patterning Titanium alloys Wear

A TWO-LEVEL GENETIC ALGORITHM FOR SCHEDULING IN ASSEMBLY ISLANDS WITH FIXED-POSITION LAYOUTS

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Journal of systems Science and systems engineering 2010年第2期19卷 150-161页

作者： George Q.HUANG department of industrial and Manufacturing systems engineering The University of Hong Kong

This paper focuses on the scheduling problem in assembly islands environment with fixed-position layouts. In such configuration, the product normally remains in one location for its entire manufacturing period while machines, materials and workers are moved to an assembly site called an assembly island. This production layout has some unique features such as moving assembly workers, tools and materials; limited space at assembly site; considerable distance between islands. The authors first give the definition and mathematical model for the scheduling problem and then propose a two-level genetic algorithm to obtain a near optimal solution to minimize the makespan. Experimental results show that this algorithm is effective. The performance analysis of the proposed algorithm indicates that it is more efficient in the airline or shipbuilding industry than in the machine or tool final assembly companies.

关键词： Assembly islands scheduling genetic algorithm

MINIMIZING A LINEAR FRACTIONAL FUNCTION SUBJECT TO A SYSTEM OF SUP-T EQUATIONS WITH A CONTINUOUS ARCHIMEDEAN TRIANGULAR NORM

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Journal of systems Science & Complexity 2009年第1期22卷 49-62页

作者： Pingke LI Edward P.Fitts department of industrial and systems engineering,North Carolina State University,Raleigh,NC 27695-7906,US Shu-Cherng FANG Edward P.Fitts department of industrial and systems engineering,North Carolina State University,Raleigh,NC 27695-7906,USA department of Mathematical Sciences,Tsinghua University,Beijing 100084,China College of Management,Dalian University of Technology,Dalian 116024,China. department of industrial and systems engineering North Carolina State University

This paper shows that the problem of minimizing a linear fractional function subject to asystem of sup-T equations with a continuous Archimedean triangular norm T can be reduced to a 0-1linear fractional optimization problem in polynomial ***,parametrization techniques,e.g.,Dinkelbach's algorithm,can be applied by solving a classical set covering problem in each *** reduction can also be performed on the sup-T equation constrained optimization problems withan objective function being monotone in each variable *** method could be extended aswell to the case in which the triangular norm is non-Archimedean.

关键词： Fractional optimization fuzzy relational equations triangular norms.

Adaptive Pinpoint and Fuel Efficient Mars Landing Using Reinforcement Learning

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IEEE/CAA Journal of Automatica Sinica 2014年第4期1卷 397-411页

作者： Brian Gaudet Roberto Furfaro the Research Engineer Department of Systems and Industrial EngineeringUniversity of Arizona department of systems and industrial engineering Department of Aerospace and Mechanical EngineeringUniversity of Arizona

Future unconstrained and science-driven missions to Mars will require advanced guidance algorithms that are able to adapt to more demanding mission requirements, e.g. landing on selected locales with pinpoint accuracy while autonomously flying fuel-efficient trajectories. In this paper, a novel guidance algorithm designed by applying the principles of reinforcement learning(RL) theory is presented. The goal is to devise an adaptive guidance algorithm that enables robust, fuel efficient,and accurate landing without the need for off line trajectory generation and real-time tracking. Results from a Monte Carlo simulation campaign show that the algorithm is capable of autonomously following trajectories that are close to the optimal minimum-fuel solutions with an accuracy that surpasses that of past and future Mars missions. The proposed RL-based guidance algorithm exhibits a high degree of flexibility and can easily accommodate autonomous retargeting while maintaining accuracy and fuel efficiency. Although reinforcement learning and other similar machine learning techniques have been previously applied to aerospace guidance and control problems(e.g., autonomous helicopter control), this appears, to the best of the authors knowledge, to be the first application of reinforcement learning to the problem of autonomous planetary landing.

关键词： Mars landing guidance reinforcement learning policy iteration Markov decision process

Stochastic resonance in the FitzHugh-Nagumo system driven by bounded noise

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Chinese Physics B 2010年第1期19卷 143-147页

作者：容启亮雷佑铭徐雁 department of industrial and systems engineering Hong Kong Polytechnic University

We investigate stochastic resonance （SR） in the FitzHugh-Nagumo system under combined bounded noise and weak harmonic excitation. Taking a spectral amplification factor as a signal-to-noise ratio, we show numerically that bounded noise can induce SR by adjusting either the intensity of bounded noise or its colour. Moreover, the increase of noise colour can enhance the SR and make the peak of the SR shift toward lower noise intensities, which is more feasible in practice. Since bounded noise is flexible to model random excitation, these findings may have some potential applications in engineering, neuroscience and biology.

关键词： bounded noise FitzHugh-Nagumo system stochastic resonance

Accelerated proportional degradation hazards-odds model in accelerated degradation test

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Journal of systems engineering and Electronics 2015年第2期26卷 397-406页

作者： Tingting Huang Zhizhong Li School of Reliability and systems engineering Beihang University department of industrial engineering Tsinghua University

An accelerated proportional degradation hazards-odds model is proposed. It is a non-parametric model and thus has path- free and distribution-free properties, avoiding the errors caused by faulty assumptions of degradation paths or distribution of degra- dation measurements. It is established based on a link function which combines the degradation cumulative hazard rate function and the degradation odds function through a transformation pa- rameter, and this makes the accelerated proportional degradation hazards model and the accelerated proportional degradation odds model special cases of it. Hypothesis tests are discussed, and the proposed model is applicable when some model assumptions are satisfied. This model is utilized to estimate the reliability of minia- ture bulbs under low stress levels based on the degradation data obtained under high stress levels to validate the effectiveness of this model.

关键词： accelerated proportional degradation hazards(APDH) accelerated proportional degradation odds(APDO) link function non-parametric

Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue engineering Applications

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Nano-Micro Letters 2018年第4期10卷 314-323页

作者： George Z.Tan Yingge Zhou department of industrial Manufacturing and Systems Engineering Texas Tech University

The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.

关键词： Divergence electrospinning 3D nanofiber scaffold Tissue engineering Microstructure gradient