Airline planning and scheduling: Models and solution methodologies

The airline industry is a representative industry with high cost and low profitability. Therefore, airlines should carefully plan their schedules to ensure that overall profit is maximized. We review the literature on airline planning and scheduling and focus on mathematical formulations and solution methodologies. Our research framework is anchored on three major problems in the airline scheduling, namely, fleet assignment, aircraft routing, and crew scheduling. General formulation, widely used solution approaches, and important extensions are presented for each problem and integrated problems. We conclude the review by identifying promising areas for further research.     

桁架式火星探测器的着陆缓冲特性分析

着陆缓冲机构是着陆器实现行星探测软着陆的关键部位之一,它的缓冲性能直接关系到着陆器是否能安全地在行星表面实现软着陆。根据某院提供的火星着陆器模型,在三维建模软件中建立着陆器的合理简化模型,为了提高分析着陆器软着陆过程冲击响应的准确性,采用MSC公司的Patran/Dytran有限元软件,用瞬态动力学的方法对着陆器的缓冲性能进行分析。仿真结果与试验数据十分吻合,着陆器的缓冲和传力性能良好。因此,采用拉杆缓冲的桁架式火星着陆器是可行的,仿真结果与试验数据也为今后的火星探测提供了参考。     

超前预留缓冲区交替式相向采掘沿空送巷的应用研究

为了减少工作面推采产生的矿压对沿空送巷的影响,采用预留采掘头面之间的安全缓冲区和合理避开矿压应力区,预留缓冲区交替式相向采掘工艺,实现矿井沿空送巷高效安全生产。     

Revisiting the Parallel Strategy for DOACROSS Loops

Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front...     

相场法模拟GaAs衬底上InGaAs异质结表面形貌

本工作采用相场法模拟GaAs衬底上生长的In_(0.3)Ga_(0.7)As多层异质结构薄膜表面。通过引入多序参量,使用半隐性傅里叶谱方法求解Cahn-Hilliard方程可以求得带缓冲层结构的薄膜表面形貌。计算结果模拟了薄膜生长过程,研究显示,使用In0.15-Ga0.85As缓冲层,厚度从1nm增加到4nm,薄膜表面临界波长从34nm提升到80nm。随着缓冲层的厚度从1nm增加到10nm,使用正弦波表面的模拟结果显示,薄膜表面粗糙度从2.87nm下降到0.43nm,随机叠加波表面的模拟结果也类似,表面粗糙度从1.21nm下降到0.18nm。热力学分析和应变分布分析可以解释缓冲层对薄膜表面形貌演化的作用。该模拟计算方式对设计缓冲层结构有很大的帮助,模拟计算的结果可以与实验相比对。     

Exploring the biomechanics of walking and crowd “flow”

Crowd movement simulation models are generally based on aggregated speed and flow data collected more than 50 years ago. There appears to be no validated modelling capability to include the impact of recent and future changes in population demographics, resulting from an ageing population and increasing obesity rates. New analytical approaches and data gathering are required to successfully model crowd movement and safety for current and future generations. This study carried out (a) a review of the primary components of crowd movement, demographics and analytical techniques, (b) prototype experiments to investigate age-related aspects of space and potential points of contact and (c) a new predictive model for crowd flow analysis based on pedestrian biomechanics and anthropometric data. The model uses the physical space taken up by the biomechanical walking process and the spatial buffer between points of potential contact with other pedestrians to predict the speed of movement at different levels of congestion. The new analytical model was used to predict single file speeds (for people with different demographics in congested space), which compared well with published experimental data. The next steps for model development for wider “flows” and additional experiments to provide data sets for wider demographics are also proposed.     

A resilient buffer allocation scheme in active queue management: a stochastic cooperative game theoretic approach

During the last decade, a plentiful number of active queue management schemes have been proposed, but their main objectives are simply allocating the buffer resource to all flows evenly, or protecting responsive flows from being degraded by unresponsive flows. However, the sending rates of the responsive flows can be determined diversely, and not all unresponsive flows have aggressively high sending rates. Furthermore, it is rational to reserve a portion of the buffer resource for certain privileged traffic. Grounded by these evidences, in this paper, we present a resilient active queue management algorithm, named Prior‐Core‐based Buffer Allocation considering diverse congestion control algorithms, fair‐unresponsive flows, and some privileged traffic. Our approach is based on stochastic cooperative game theory, where the payoffs yielded by cooperation are described by random variables, and the core is defined only over the distribution of these random payoffs; the core in this situation is called the prior‐core. As a result, it is shown that our buffer allocation, yielded by the prior‐core, achieves completely fair allocation for those flows whose requirement does not exceed the fair‐share regardless of the responsiveness, whereas aggressive flows are restricted according to availability of the buffer; all these are verified through ns‐2 simulation experiments. Copyright © 2014 John Wiley & Sons, Ltd.     

A prediction-based dynamic file assignment strategy for parallel file systems

Nowadays, the rapid development of the internet calls for a high performance file system, and a lot of efforts have already been devoted to the issue of assigning nonpartitioned files in a parallel file system with the aim of pursuing a prompt response to requests. Yet most of the existing strategies still fail to bring about an optimal performance on system mean response time metrics, and new strategies which can achieve better performance in terms of mean response time become indispensable for parallel file systems. This paper, while addressing the issue of assigning nonpartitioned files in parallel file systems where the file accesses exhibit Poisson arrival rates and fixed service times, presents an on-line file assignment strategy, named prediction-based dynamic file assignment (PDFA), to minimize the mean response time among disks under different workload conditions, and a comparison of the PDFA with the well-known file assignment algorithms, such as HP and SOR. Comprehensive experimental results show that PDFA is able to improve the performance consistently in terms of mean response time among all algorithms for comparison.     

带缓冲区且产品保修的设备预防性维护建模

论文考虑的是一个完美的生产系统,即生产系统所生产的产品均没有质量问题。为提高设备的可靠性,调整市场需求,提出带缓冲区的设备预防性维护优化建模方法。已经出售的产品,顾客在使用过程中可能会出现故障,基于这个情况,在保修期内会予以免费维修。找出生产系统的运行时间(T)和缓冲区库存量(S),以此为决策变量建立期望成本模型。在此基础上,构造求解最优策略的算法。通过数值算例演示了该模型,通过灵敏度分析确定了最优策略和相关参数的关系。