基于遗传禁忌算法的城市公交线网优化研究

针对城市公共交通线网优化问题,利用遗传禁忌算法进行研究.通过对公交线网优化目标函数和关键约束条件的分析,从乘客利益、企业效益及社会环境的角度出发,以公共交通效率最大化为总目标,建立公交线网优化模型.在分析遗传算法和禁忌搜索算法自身的优势与不足的基础上,提出基于遗传禁忌算法的公交线网优化算法,并将其应用于银川市公共交通线网规划中,结果表明该算法科学合理,可操作性强.     

一种基于模式搜索的自学习遗传算法研究

根据自学习遗传算法的原理,设计了基于模式搜索的学习算子.在此基础上与改进的遗传算法结合,提出了一种基于模式搜索的自学习遗传算法.通过对该算法在复杂函数优化情况下与传统遗传算法的对比测试表明,该算法的改进是有效的.     

Accurate 3D reconstruction of subject-specific knee finite element model to simulate the articular cartilage defects

The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00 cm², the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes (⩾1.00 cm²). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.     

A new method based on the non-isothermal kinetic equation to estimate the critical temperature of thermal explosion for energetic materials using non-isothermal DSC

A method for estimating the critical temperature of thermal explosion for energetic materials using differential scanning calorimetry (DSC) measurement is derived from the Semenov’s thermal explosion theory and the non-isothermal kinetic equation based on Harcourt-Esson’s kinetic equation. The result obtained from this method coincides completely with that of the Hu-Yang-Liang-Wu method.     

Numerical simulation of fluid flow caused by buoyancy forces during vacuum arc remelting process

The metallurgical structure and composition of ingots which depend critically on the fluid motion within the molten pool during the vacuum arc remelting (VAR) process have important effect on the subsequent mechanical processes like forging, rolling and welding. In order to determine the fluid motion of molten pool, a 2D finite element model is established using ANSYS10.0 software, combined with the turbulent fluid flow and heat transfer. The fluid motion caused by thermo buoyancy forces is investigated at different VAR processes in the present study. The results indicate that the fluid flows symmetrically along the axis of the molten pool and clockwisely along the circle at the right pool’s profile. It is also shown that the maximum velocity increases with increasing melting rate and a direct proportional relationship exists.     

Chosen ciphertext secure identity-based broadcast encryption in the standard model

To give concurrent consideration both the efficiency and the security (intensity of intractable problem) in the standard model, a chosen ciphertext secure identity-based broadcast encryption is proposed. Against the chosen ciphertext security model, by using identity (ID) sequence and adding additional information in ciphertext, the self-adaptive chosen identity security (the full security) and the chosen ciphertext security are gained simultaneously. The reduction of scheme’s security is the decisional bilinear Diffie-Hellman (BDH) intractable assumption, and the proof of security shows that the proposed scheme is indistinguishable against adaptive chosen ciphertext attacks in the standard model under the decisional BDH intractable assumption. So the security level is improved, and it is suitable for higher security environment.     

“船舶结构与设备”教学优化的探讨

以自身教学实践分析"船舶结构与设备"课程的教学情况,从课程教学重点、教学方法、教师能力、学校等方面进行探讨,提出二手实物教学方法和校企联合培养手段的改革来优化课堂教学效果和学生实践能力。     

沥青路面再生技术的应用及其社会经济效益分析

常规的沥青路面养护维修方式会产生大量的旧沥青路面废弃材料,对环境造成不良影响,不仅增加了工程投资,也造成巨大的资源压力。该文以安徽省干线公路沥青路面再生技术为例,分析了沥青路面厂拌热再生技术、水泥就地冷再生技术、全深式厂拌冷再生技术在安徽省干线公路养护维修中所带来的巨大社会、环境和经济效益。     

CORS系统在航道工程测量中的应用

CORS系统在航道工程测量方面的应用前景十分广阔,该文介绍了CORS系统技术的基本原理,在航道工程测量中的应用以及与常规RTK相比所具有的特点。通过工程实例,展示CORS系统在超长作业区域中体现出的优越性能,阐述了CORS系统发展趋势。     

Verification of a simplified analytical method for predictions of ship groundings over large contact surfaces by numerical simulations

In this paper, a verification is presented of a simplified analytical method for the predictions from numerical simulations of structural performance during ship groundings over seabed obstacles with large contact surfaces and trapezoidal cross-section. This simplified analytical method was developed by Lin Hong and Jørgen Amdahl and calculates grounding characteristics, such as resistance and distortion energy, for double-bottomed ships in shoal grounding accidents. Two finite-element models are presented. One was built for a hold, and the other was built for a hold and a ship hull girder and also considers sectional properties, ship mass, added mass and the hydrodynamic restoring force. The verification was completed by comparing horizontal and vertical resistances and the distortion energy between seven numerical-simulation cases and a set of corresponding cases computed by a simplified analytical method. The results show that the resistances obtained by the simplified analytical method are close to the mean values of the resistance curves obtained by numerical simulations. The comparisons prove that the energy dissipation-prediction capability of the simplified analytical method is valuable. Thus, the simplified analytical method is feasible for assessing ship groundings over seabed obstacles with large contact surfaces and trapezoidal cross-section. Furthermore, studies of the influence of ship motion during groundings ascertained that ship motion affects structural performance characteristics. Resistances are lessened at the end of the grounding due to the reduction of indentations caused by heave and pitch motions of the ship hull girder. Finally, a new method for predicting the structural performance of the time-consuming complete-ship model by applying a combination of normal numerical simulations and ship-motion calculations is proposed and proven.