Enhancing nugget size and weldable current range of ultra-high-strength steel using multi-pulse resistance spot welding

ABSTRACT

This paper presents an innovative approach that uses a pulse-profile to improve the welding quality of CP1180 steel in resistance spot welding process. Three pulses with two cooling times were used in the developed multi-pulse welding (MPW) schedule. The experimental results show that the first pulse increases the contact area between the sheets to improve the current flow pattern. The second pulse was designed to extend the sheet-to-sheet contact area and corona bond for preventing rapid nugget growth. Using these designs, the nugget size was maximised through the third pulse. The maximum nugget size using the designed MPW schedule was 18.5% greater than that of the single-pulse welding schedule and the weldable current range was extended by 130%.     

配网工程建设时间控制

时间控制是运用科学的方法、工具,并综合运用现有资源,在规定时间内取得预期效果的一种控制手段。本文从工程时间管理的概念出发,研究了如何运用时间管理方法实现工程施工工期的管理,讨论了时间管理在工程建设中的重要性,为企业配网工程建设时间控制管理提供参考。     

A two stage heuristic algorithm for the integrated aircraft and crew schedule recovery problems

Airline disruptions incurred huge cost for airlines and serious inconvenience for travelers. In this paper, we study the integrated aircraft and crew schedule recovery problem. A two stage heuristic algorithm for the integrated recovery problem is proposed. In the first stage, the integrated aircraft recovery and flight-rescheduling model with partial crew consideration is built. This model is based on the traditional multi-commodity network model for the aircraft schedule recovery problem. The objective of this model also includes minimization of the original crew connection disruption. In the second stage, the integrated crew schedule recovery and flight re-scheduling model with partial aircraft consideration is built. We proposed a new multi-commodity model for the crew schedule recovery. The main advantage of such model is that it is much more efficient to integrate the flight-scheduling and aircraft consideration. New constraints are incorporated to guarantee that the aircraft connections generated in the stage 1 are still feasible. Two stages are run iteratively until no improvement can be achieved. Experimental results show that our method can provide better recovery solutions compared with the benchmark algorithms.     

Efficient reliability analysis of dynamic k-out-of-n phase-AND mission systems

Motivated by real-world applications of satellites and wireless sensor networks, this paper models and evaluates a dynamic k-out-of-n phase-AND mission system (k/n-PAMS). The mission task conducted by a k/n-PAMS involves multiple consecutive phases; the mission is successful as long as the task is successful in any of the phases. Due to factors, such as scheduled maintenance, location changes in task execution during different phases, and resource sharing with other tasks, the total number of available components n for the considered mission task and the required number of working components k may change from phase to phase. In addition, due to varying load and working environments, component failure time distributions are also phase dependent. This paper proposes an analytical modeling approach based on multivalued decision diagrams (MDDs) for assessing reliability of the considered k/n-PAMS. The approach encompasses a new and fast MDD model generation algorithm that considers behaviors of all the mission phases simultaneously based on node labeling. As demonstrated through empirical studies on k/n-PAMSs with different sizes (different numbers of phases and different numbers of system components), the proposed algorithm is more efficient than the traditional phase-by-phase model generation method.     

A framework for improving the efficiency of operational testing through Bayesian adaptive design

When developing a product, it is important to consider product performance from a user perspective. This type of evaluation can be done through operational testing—assessing the ability of representative users to satisfactorily accomplish tasks with the product in operationally representative environments. This process can be expensive and time-consuming, but is critical to understanding whether the product can adequately do the job for which it was designed. We show how an existing design of experiments (DOEs) process for operational testing can be leveraged to construct a Bayesian adaptive design. This design, nested within the larger design created by the DOE process, allows interim analyses to stop testing early for success or futility. Representative simulations are presented to demonstrate how these interim analyses can be used in an operational test setting, and reductions in necessary test events are shown. The application of Bayesian-adaptive design methods will allow future operational testing to be conducted in less time and at less expense, on average, without compromising the ability of the existing process to verify the product meets the user's needs.     

资源约束下的海外工程项目进度风险因素分级研究

目前国内对外承包企业“走出去”步伐日益加快,项目规模、类型、分布有了很大的变化,进度风险日益加剧,受资源约束影响日益显著,承包企业管理难度加大。通过对实施项目的资源种类、重要性、特殊性进行分析,说明资源对海外工程项目实施的重要性。通过文献调研、专家调查等方法,从承包商角度对资源约束下海外项目进度风险因素进行识别、分类,采用层次分析法对各影响因素权重进行分析、排序,建立资源约束下海外项目进度风险影响因素的分级体系,为承包商进行海外工程项目进度风险管理防范提供指导。     

工程项目投资及进度和质量目标的对立统一

就工程项目的三大目标，即投资、进度和质量的关系，从对立和统一两方面进行了深入探讨，详细地阐述了在确定工程项目的控制目标时，应重点关注和控制的几个方面，以帮助人们正确认识和处理三大目标的关系。     

浅谈城市消防安全分级制

引入分级制概念，概述了英国、日本、中国香港和美国的城市消防分级制总体状况，着重介绍了美国在分级时所考虑的特征、对应的扣分值和所涉及的条款，包括供水、消防局、消防通讯、防火安全控制和补充条款环境、气候等因素及应用范围，进而提出了在我国开展消防安全分级制的必要性。     

上海浦东机场二期扩建工程总进度纲要的编制

对上海浦东国际机场二期扩建工程总进度纲要的编制进行了系统的、全面的分析和总结,阐明了总进度纲要编制的指导思想、工作分解结构的定义、进度计划实现的基础工作、主要阶段目标及关键性控制节点确定等的逻辑过程、目的和结果,提出了进度动态控制思想,为二期扩建工程总进度目标的控制和实现提供了科学的、可靠的依据。     

大型复杂工程智能进度计划管理系统设计与实现

以精准建造理论和多层次多阶段进度计划为基本原理,从智能进度计划管理系统的概念入手,分析了该系统的必要性,提出了该系统的基本模块、层次结构、功能结构,并分析了该系统的应用状况;最后从整体角度得出了基于精准建造的智能进度计划管理系统是大型复杂工程项目进度管理的有效方式之一。