Particle Swarm Optimization for Preemptive Scheduling under Break and Resource-Constraints

This paper introduces a particle swarm optimization (PSO)-based methodology to implement preemptive scheduling under break and resource-constraints (PSBRC) for construction projects. The PSBRC under study allows the preemptive activities to be interrupted in off-working time and not to resume immediately in the next working period because all the limited resources are to be reallocated during a break. The potential solution to the PSBRC, i.e., a set of priorities deciding the order to start the activities or restart the interrupted activities, is represented by the multidimensional particle position. Hence PSO is applied to search for the optimal schedule for the PSBRC, in which a parallel scheme is adopted to transform the particle-represented priorities to a schedule. Computational analyses are presented to verify the effectiveness of the proposed methodology. This paper provides an attempt to make use of preemption and break for the resource-constrained construction project with the objective of minimizing project duration.     

The organization of exhaustive searches in a patchy space by capuchin monkeys (Cebus apella).

Search is a serial exploration of alternatives. Efficient search involves the ability to minimize costs (i.e., time/energy) and to keep track of alternatives already explored. The search abilities of 4 capuchin monkeys (Cebus apella) were evaluated by means of an apparatus featuring a set of suspended baited containers. The experiment featured conditions with different spatial configurations of the search space. Results show that the monkeys were able to search exhaustively 9 containers spatially distributed either as a 3?×?3 matrix or as 3 "patches" of 3 containers each. Search efficiency was higher in a search space suitable to organization in clusters or spatial chunks. In this condition, evidence for principled organization of search trajectories, as opposed to a random walk through the search space, emerges clearly and parallels search efficiency. This suggests that monkeys impose a structure over the search space and, by doing so, reduce the memory demands of the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Permutation-Based Particle Swarm Optimization for Resource-Constrained Project Scheduling

In the light of particle swarm optimization (PSO) which utilizes both local and global experiences during search process, a permutation-based scheme for the resource-constrained project scheduling problem (RCPSP) is presented. In order to handle the permutation-feasibility and precedence-constraint problems when updating the particle-represented sequence or solution for the RCPSP, a hybrid particle-updating mechanism incorporated with a partially mapped crossover of a genetic algorithm and a definition of an activity-move-range is developed. The particle-represented sequence should be transformed to a schedule (including start times and resource assignments for all activities) through a serial method and accordingly evaluated against the objective of minimizing project duration. Experimental analyses are presented to investigate the performances of the permutation-based PSO. The study aims at providing an alternative for solving the RCPSP in the construction field by utilizing the advantages of PSO.     

连续驱动摩擦焊接技术的研究与工程应用

在对摩擦焊接进行分类并简要说明的基础上,对连续驱动摩擦焊接技术的研究发展和应用现状进行了全面梳理和深入剖析,涉及焊接工艺过程特征和主要工艺参数、工艺探索及工艺参数对接头性能的影响、数值分析和模拟及工艺参数优化、异种金属和非金属材料摩擦焊接与工艺创新、实际工程应用和焊接设备等方面。从摩擦焊接技术的潜在应用、核心科学问题、新型摩擦焊接设备的研发、数值分析和模拟、与新兴技术的结合等方面,对连续驱动摩擦焊接技术进行了评述和探讨。      

BCOISOA--BP网络在磨矿粒度软测量中的应用

传统人群搜索(SOA)算法通过计算搜索方向、搜索步长和搜寻更新个体位置三个步骤进行寻优.它的缺点在于计算量大,种群之间信息交流少,导致寻优速度慢.针对人群搜索算法存在的缺点,本文提出二项交叉算子改进人群搜索算法(BCOISOA)对其改进.在计算搜索步长方面,本文采用随机数与最大函数值位置乘积判断子群位置,进而提高全局寻优计算速率.在更新位置方面,本文提出二项交叉算子加强种群之间的联系,避免在更新搜索方向过程中,算法因局部最优而导致过早收敛,进而达到快速、准确寻找最优解的目的.本文将以上二项交叉算子改进人群搜索-BP神经网络算法应用在二段式磨矿过程中,实现磨矿粒度在线软测量.仿真结果表明,与人群搜索算法和粒子群算法进行比较,二项交叉算子改进人群搜索算法收敛速度更快,预测精度最高,满足对磨矿粒度实时检测的要求.      

Effects of relatedness and number of distractors on attribute judgments in Alzheimer's disease.

Participants made judgments about the relative salience of category exemplars (e.g., fruit: apple or grape) or parts (e.g., plane: wings or seats). Mildly affected Alzheimer's disease (AD) patients were as accurate but slower than normal controls, and their response times increased more for related (e.g., apple, grape, or fig) than unrelated (e.g., apple, gym, bandit) choices as the number of alternatives was increased from 2 to 3. Performance (accuracy and response times) of moderate-severely affected patients was poorer still, but number of distractors and relatedness did not interact. In combination with previous findings (e.g., M. K. Johnson, A. M. Hermann, & J. L. Bonilla, 1995), these results suggest that the reflective processes necessary for deciding among competing alternatives show disruption early in the disease process. Such processing deficits would compound any difficulties arising from a degrading semantic structure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scenario-Based Multi-Objective Genetic Algorithm Optimization of Closed Ball-Milling Circuit of Esfordi Phosphate Plant

The main goal of this article is to demonstrate an approach based on integration of process simulation and Multi-Objective Genetic Algorithm (MOGA) concepts to solve a real grinding circuit optimization problem by finding the best operating condition under which process objectives can be achieved. Esfordi phosphate plant is located near city of Bafgh at Yazd province of Iran and produces 5 Mt of phosphate annually. The fine particles (nearly ?20 µm) in hydrocyclone underflow which contain a high grade of iron are subjected to over grinding. In addition to electrical energy loss, this causes problems in the downstream process, i.e., flotation stage. The main goals of this study were to solve this problem by adjusting operating condition so that (a) hydrocyclone overflow particle size can be increased from 94.2 µm to 100 µm and (b) increase hydrocyclone underflow particle size from 205 to 500 µm. The second process objective will decrease fine particles in hydrocyclone underflow stream. First, plant sampling campaigns were carried out to calibrate ball mill and hydrocyclone models to be used for performing simulation trials. Then, full circuit simulations were done and optimized by MOGA search process to find the best operating condition that produces hydrocyclone overflow and underflow streams with predefined particle sizes simultaneously. The results indicate that there are various solutions that can be recommended for plant testing and performance improvements. The results of plant implementation of one solution for scenario No. 4 showed improved circuit performance and also validated simulator predictions.     

Improving Labor Flow Reliability for Better Productivity as Lean Construction Principle

New management thinking, like that of lean production, has suggested that better labor and cost performance can be achieved by improving the reliability of flows. In this context, lean thinking portrays reliable flows as the timely availability of resources, i.e., materials, information, and equipment. Little attention has been given to labor as a flow. Further, little discussion can be found related to flexible capacity management strategies. Efforts to utilize lean thinking in construction, so far, have generated limited evidence to support the need for more reliable labor flows. This paper investigates the lean principle that more reliable flows lead to better labor performance. Actual data from three bridge construction projects are examined to document the instances of poor flow (resource) reliability and its effect on labor performance. Inefficient labor hours are calculated. The results show that there is strong support that more reliable material, information, and equipment availability contributes to better performance. However, the projects showed considerable deficiencies in the utilization of the labor resource. It is concluded that lean improvement initiatives should focus more on workforce management strategies to improve labor utilization that will lead to better labor performance.     

Iconic Animation for Activity-based Construction Simulation

This paper discusses the development of an animation tool for the activity-based construction (ABC) modeling and simulation system. The tool uses an activity-based network diagram, i.e., ABC simulation model, as the animation background image, and uses precreated two-dimensional (2D) iconic images for simulation entities (e.g., resources). The animation process displays the queuing status and dynamic movements of 2D iconic images on the background. It also distinguishes active and idle states of resources and activities. Dynamic reports are available for selected activities with graphs including the production rate and utilization of involved resources. From visualizing the change of status of a simulation process and dynamic interaction between simulation entities in the process, the user can better understand the dynamic nature of the construction process. Animation provides an avenue to demonstrate how dynamic operations are simulated. It also provides an effective tool for the user to verify a simulation model and to validate the obtained simulation results. Compared to other systems, the ABC animation does not require any extra effort in addition to the ABC simulation model constructed for simulation purposes. Therefore, the presented technology greatly reduces the time and cost for achieving animation. A variety of useful information can be observed through animation, and is illustrated using two construction examples.     

Continuing investment under conditions of failure: A laboratory study of the limits to escalation.

100 business students participated in a laboratory experiment designed to test for limiting factors in the process of escalation. Ss were instructed to assume the role of the financial vice-president of a large conglomerate. It was explained that the company had declined in recent years and that management had identified several divisions that might benefit from developmental investment. Ss decided how to spend a developmental budget and typed their decisions into a computer. The computer gave them immediate performance reports. Whichever divisions Ss started out with continued to decline, whereas alternative divisions, if there were alternatives, improved. A questionnaire was administered at the end of the simulation. Commitment and investment alternatives available to the Ss were manipulated. Results support the hypothesized de-escalation process (i.e., although escalation occurs during the 1st stage of investment, a de-escalation process may be typical later on) and show that the availability of alternative investments also limited escalation. A survival analysis of S investments suggested that commitment may not be the dominant process in escalation and de-escalation. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

碱煮过程浸出率预测与优化研究

针对钨碱煮过程WO_3浸出率预测困难的问题,建立了动态机理模型与最小二乘支持向量机(LSSVM)相结合的并联混合模型,在该混合模型的基础上,构建了碱煮过程优化模型,将动态浸出问题转化为带约束的优化问题,并以粒子群优化(PSO)算法对优化模型进行求解。仿真结果表明,混合模型预测精度高,优化模型效果好,提高了WO_3浸出率,降低了浸出成本。     

Resource Optimization Using Combined Simulation and Genetic Algorithms

This paper presents a new approach for resource optimization by combining a flow-chart based simulation tool with a powerful genetic optimization procedure. The proposed approach determines the least costly, and most productive, amount of resources that achieve the highest benefit/cost ratio in individual construction operations. To further incorporate resource optimization into construction planning, various genetic algorithms (GA)-optimized simulation models are integrated with commonly used project management software. Accordingly, these models are activated from within the scheduling software to optimize the plan. The result is a hierarchical work-breakdown-structure tied to GA-optimized simulation models. Various optimization experiments with a prototype system on two case studies revealed its ability to optimize resources within the real-life constraints set in the simulation models. The prototype is easy to use and can be used on large size projects. Based on this research, computer simulation and genetic algorithms can be an effective combination with great potential for improving productivity and saving construction time and cost.     

Simulation Approach to Evaluating Cost Efficiency of Selective Demolition Practices: Case of Hong Kong’s Kai Tak Airport Demolition

This research resorted to the use of construction operations simulation modeling to investigate the cost efficiency of waste-handling practices on the Kai Tak Airport demolition project in Hong Kong. By modeling the site operation of sieving and stockpiling broken concrete, the well-established construction simulation methodology of CYCLONE was contrasted with the newly developed simplified discrete event simulation approach (SDESA). Further, the SDESA model was readily extended to include (1) raw demolition waste collecting and sorting; (2) broken concrete sieving and stockpiling; (3) steel bar recycling; and (4) debris disposal at the landfill. The production rate derived from simulation was indicative of a close match between the simulation model and the actual site system. The resulting simulation model provided a basis for evaluating the cost efficiency of actual site operations and alternative resource provision scenarios being postulated. Through computer simulation, the actual site operation was found smooth and efficient with utilization rates for resources of different types ranging from 79 to 99%. In addition, the cost–time reduction ratios were calculated for four alternatives of resource provisions in comparison with the original base case. The research findings suggested that provided the project budget had satisfied the higher cash flow requirement, doubling the resource provision on site would potentially cut the project duration by half and not increase the total direct cost.     

Visual search for simple targets.

Quantitatively analyzed published data based on searching for simple targets (e.g., alphanumeric data, colors, and familiar shapes). Relationships were investigated for search time and scanning rate with the number of nontarget stimuli in an array, the number of possible targets, and the total amount of displayed information. On other grounds, a general relationship about time-controlled processes was postulated (i.e., that the rate of performance of a time-controlled process is an increasing function of the maximum stimulus, or information load, up to a limit). With this postulate, search performance (both as a function of the number of elements to be searched and the number of possible targets) can be accounted for in terms of a sequential information processing model. Results also suggest a maximum scanning capacity of 50 elements/sec, or 5.6 bits/sec of total information. Other factors suggested as important are the relative emphasis put on speed or accuracy; the dimensionality of the target (i.e., whether it differs from nontarget elements in 1 or more than 1 way); and the cognitive, or psychological, homogeneity of stimulus array. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How does feature-based attention affect visual processing?

Five experiments are reported from which it is concluded that attending on the basis of a stimulus feature (e.g., red) does not directly affect the sensory quality of stimuli that possess that feature. Feature-based attention was manipulated in a visual search task by providing information about the probability that the target would possess a given feature (e.g., "The target has a 1.0 probability of being red when present.") Feature-based attention failed to aid performance under "data-limited" conditions (i.e., those under which performance was primarily affected by the quality of the stimulus) but did affect performance under conditions that were not data limited (Experiments 1-3). If attending to a feature had affected the sensory quality of stimuli, performance should have been aided under all conditions. Experiments 4 and 5 provided converging support for this conclusion.     

Long-term priming of neighbours biases the word recognition process: Evidence from a lexical decision task.

The role of orthographically similar words (i.e., neighbours) in the word recognition process has been studied extensively using short-term priming paradigms (e.g., Colombo, 1986). Here we demonstrate that long-term effects of neighbour priming can also be obtained. Experiment 1 showed that prior study of a neighbour (e.g., TANGO) increased later lexical decision performance for similar words (e.g., MANGO), but decreased performance for similar pseudowords (e.g., LANGO). Experiment 2 replicated this bias effect and showed that the increase in lexical decision performance due to neighbour priming is selectively due to words from a relatively sparse neighbourhood. Explanations of the bias effect in terms of lexical activation and episodic memory retrieval are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integrated Simulation System for Construction Operation and Project Scheduling

Simulation modeling is important in predicting the productivity of construction operations and the performance of project schedules. It would be desirable if operation and project models are vertically integrated in practice. However, existing discrete event simulation systems do not allow integrating operation and project models. This paper introduces an integrated simulation system named “Construction Operation and Project Scheduling” (COPS). COPS analyzes the productivity of construction operations as well as the performance of a project schedule individually and jointly. It creates operation models, maintains these models in its operation model library, conducts sensitivity analysis with different resource combinations, finds the optimal resource combination that satisfies the user’s requirements relative to hourly production and hourly cost of the operation, feeds this information into a project schedule, and executes stochastic simulation-based scheduling. A case study is presented to demonstrate this integrated simulation system.     

Working in the sky: A diary study on work engagement among flight attendants.

This study aims to gain insight in the motivational process of the Job Demands-Resources (JD-R) model by examining whether daily fluctuations in colleague support (i.e., a typical job resource) predict day-levels of job performance through self-efficacy and work engagement. Forty-four flight attendants filled in a questionnaire and a diary booklet before and after consecutive flights to three intercontinental destinations. Results of multilevel analyses revealed that colleague support had unique positive effects on self-efficacy and work engagement. Self-efficacy did not mediate the relationship between support and engagement, but work engagement mediated the relationship between self-efficacy and (in-role and extra-role) performance. In addition, colleague support had an indirect effect on in-role performance through work engagement. These findings shed light on the motivational process as outlined in the JD-R model, and suggest that colleague support is an important job resource for flight attendants helping them reach their work-related goals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do Multielement Visual Tracking and Visual Search Draw Continuously on the Same Visual Attention Resources?

Multielement visual tracking and visual search are 2 tasks that are held to require visual-spatial attention. The authors used the attentional operating characteristic (AOC) method to determine whether both tasks draw continuously on the same attentional resource (i.e., whether the 2 tasks are mutually exclusive). The authors found that observers can search and track within the same trial significantly better than would be predicted if the 2 tasks were mutually exclusive. In fact, the AOC for tracking and search is similar to that for tracking and auditory monitoring. The results of additional experiments support an attention-switching account for this high level of dual-task performance in which a single attentional resource is efficiently switched between the tracking and search. The results provide important constraints for architectures of visual selective attention and the mechanisms of multielement tracking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)