Solution approaches for the cutting stock problem with setup cost

In this paper, we study the Cutting Stock Problem with Setup Cost (CSP-S) which is a more general case of the well-known Cutting Stock Problem (CSP). In the classical CSP, one wants to minimize the number of stock items used while satisfying the demand for smaller-sized items. However, the number of patterns/setups to be performed on the cutting machine is ignored. In most cases, one has to find the trade-off between the material usage and the number of setups in order to come up with better production plans. In CSP-S, we have different cost factors for the material and the number of setups, and the objective is to minimize total production cost including both material and setup costs. We develop a mixed integer linear program and analyze a special case of the problem. Motivated by this special case, we propose two local search algorithms and a column generation based heuristic algorithm. We demonstrate the effectiveness of the proposed algorithms on the instances from the literature.     

谈建筑施工企业的成本管理

借鉴先进、科学的管理经验,从全过程、全员、全方位三方面对建筑施工企业的成本管理进行了分析,在此基础上,提出了施工企业的成本管理措施,以期使经济效益最大化,提高企业的竞争力。     

如何实现广义成本管控

广义成本管控是一项跨学科、跨层次、跨领域的开放、延伸、交融的全新成本管控的系统工程;仅局限于人力资源、物力资源和费用开支进行有效控制,仅关注于作业流程、关键设备、消耗指标进行节点管理,仅拘泥于捡芝麻、抱西瓜的思想认知的逐步提高,均不适应高度市场化经济条件下成本管理的新格局。成本管控除了要对可控制、可量化目标进行有效控制外,还要就企业管理全过程所产生的边际成本、机会成本、风险成本以及其他无形成本进行监控,从而形成一种跳出为抓成本而抓成本的新思路;其旨在强调对企业生产经营的各个方面,各个环节以及各个阶段的所有成本进行高效控制,从而形成全员、全方位、宽领域管控成本的理念。     

Effect of Nb on Mechanical Properties of HAZ for High-Nb X80 Pipeline Steels

The mechanical properties of heat affected zone (HAZ) of two commercial high-Nb X80 grade pipeline steels with different alloy elements were investigated using thermal simulation performed on a Gleeble-3500 thermal simulator. The results showed that the high-Nb steels have excellent weldability. Embrittlement regions appear in coarse grain heat affected zone (CGHAZ) and intercritically heat affected zone (ICHAZ); Softening region appears in fine-grain heat affected zone (FGHAZ), and the strength here was even lower than 555 MPa as required in the standard. Meanwhile, with the increase of heat input, the strength and the toughness of HAZ of steel with high Nb, C and lower alloy decrease notably. Therefore, take into account the welding procedure during manufacture of weld pipe, suitable amount of alloy elements, such as Cr, Ni, Cu, Mo and so on, is necessary for high Nb X80 heavy-thick steel plate.     

基于速度反馈控制的自激振动特性研究

工程中自激振动常被作为不利因素而加以抑制,然而在振动能量捕获等振动利用研究中,自激振动也有振幅响应大、抗干扰能力强等优点,利用自激振动作为振动驱动将具有极大的优势。以悬臂梁为研究对象,通过模态参数与测点组合条件,导出了基于速度反馈控制下各阶模态的变化模式,得到了产生自激振动的数值判据,并对单模态进入自激振动以后的非线性极限环现象进行了讨论。通过理论建模、数值仿真和控制实验及数据处理,验证了该研究的正确性。     

Quantifying life safety Part II: Quantification of fire protection systems

In part I of the paper, an assembly building was analyzed in order to compute the failure probabilities, and thus the safety level, of current code-compliant buildings. In this second part, various fire protection systems are modeled within the fire and egress simulations in order to quantify their magnitude of impact. Since all fire protection systems can fail to perform as designed on demand, the potential failure along with its probability is accounted for in an event tree analysis. Comparing the resulting failure probabilities of the performance-based analyses with and without fire protection systems yields information about the magnitude of impact of the fire protection systems on the level of safety and hence allows a direct, objective, and quantitative comparison to other systems and designs. Accounting for the cost of the systems, a direct cost–benefit analysis can be conducted.     

建筑外延

文章将建筑师从事建筑学领域以外的活动分类梳理为四个方向——生活体验、艺术创作、空间运营、媒体传播,发现外延活动的共性所在,并期待其对建筑学本身的影响可以成为值得研究的课题。     

Efficient algorithm for calculating short cycles in Tanner graph based on matrix computation

Loop distribution of Tanner graph affects the BER performance of low-density parity-check codes(LDPC) decoding.To count short cycles in the Tanner graph efficiently,a side by side recursion algorithm based on matrix computation was proposed.Firstly,5 basic graph structures were defined to realize recursive calculate in the implementation process.Compared with previous works,the algorithm provided many methods for counting the same length of cycles.The same result confirmed the correctness of the algorithm.The new algorithm could not only calculate the total number of cycles,but also gave the number each edge participating in fixed-length cycles.Its complexity was proportional to the product of D and square of N,where D was the average degree of variable nodes,and N denoted the code length.For LDPC codes,D was far less than N.For most of the LDPC codes,the calculation for numbers of cycle-length g、g+2、g+4 was only several seconds.     

Grain-level statistical plasticity analysis on strain cycle fatigue of a FCC metal

The micromechanical strain cycle fatigue-life is systematically investigated by the micro-level numerical simulation, compared with symmetrical strain cycle experiments of copper, focusing on the characteristics of polycrystalline aggregation and the mechanism of microscale plastic deformation. A methodology to predict the low-cycle fatigue life by micro-level simulation along with statistical analysis is proposed through the following steps: (1) A crystal plasticity model is developed based on the nonlinear kinematic hardening mechanism of crystal slipping system. This model is applied to the calculations of crystal grain interior stresses and plastic strains. (2) A statistical representative volume element (SRVE) is constructed for a pure copper as a material model which features a polycrystalline Voronoi aggregation consisting of a number of crystal grains. This SRVE can be used for statistical analysis of the material inhomogeneous stresses and strains during cycle loading. (3) The simulations are performed to model the experimental cycle evolution of strain fatigue by using the SRVE under the symmetrical tensile–compressive loading. (4) Statistical and micromechanical analyses are carried out for the inhomogeneous interior stresses and strains of the SRVE of the polycrystalline copper in the low cycle regime. The resulting analysis can render the microscale interpretation and numerical simulation for the low-cycle fatigue evolution accordingly.