A queuing network model for the management of berth crane operations

This paper focuses on the optimal management of container discharge/loading at any given berthing point, within a real maritime terminal. Productivity maximization of expensive resources, as rail-mounted berth cranes, should be matched with the vessel requirement of minimizing waiting times with an adequate rate of service completion. To this practical problem, a queuing network model is proposed. Due to its complexity, discrete-event simulation appears as the most appropriate approach to model solution. To get a systematic representation of real constraints and policies of resource allocation and activity scheduling, an event graph (EG)-based methodology has been exploited in simulator design. Alternative policies issued by the operation manager can be inserted in a suitable panel-like view of the queuing network model and then compared by means of simulation, to evaluate the average measures for all berth cranes, such as throughput and completion time. Numerical experiments for simulator validation against real data are encouraging. Some decisions on both straddle carrier assignment to berth cranes and hold assignment and sequencing upon the same crane could be improved by the proposed manager-friendly simulation tool.     

Genericity of Weakly Computable Objects

In computability theory many results state the existence of objects that in many respects lack algorithmic structure but at the same time are effective in some sense. Friedberg and Muchnik’s answer to Post’s problem is one of the most celebrated results in this form. The main goal of the paper is to develop a general result that embodies a large number of these particular constructions, capturing the essential idea that is common to all of them, and expressing it in topological terms. To do so, we introduce the effective topological notions of irreversible function and directional genericity and provide two main results that identify situations when such constructions are possible, clarifying the role of topology in many arguments from computability theory. We apply these abstract results to particular situations, illustrating their strength and deriving new results. This paper is an extended version of the conference paper (Hoyrup 6) with detailed proofs and new results.

     

Genericity of open set reachability for some classes of discrete-time nonlinear systems

Meromorphic discrete-time time-invariant systems are considered. It is proved that the property of open set reachability is generic in parameter space.     

A model for preventive maintenance operations and forecasting

Equipment costs constitute the greatest majority of overall costs for semiconductor manufacturing. Therefore, maintaining high equipment availability has been regarded as one of the major goals in the industry. The ability to forecast correctly equipment preventive maintenance (PM) timing requirements not only can help optimizing equipment uptime but also minimizing negative impacts on manufacturing production efficiency. This research used grey theory and evaluation diagnosis to construct a PM forecasting model for prediction of PM timing of various machines. The results showed significant improvements of PM timing predictions compared to the existing method based on experience and an alternative method proposed by Li and Chang (Semiconductor Manufacturing Technology Workshop 2002: 10–11, pp. 275–277) for the same fab cases. Received: June 2005 / Accepted: December 2005     

灾难救援应急物资敏捷配送模型

应急物资敏捷配送是灾难救援的重要工作之一,为了给灾区快速配送应急物资,构建了包含救灾物资储备库、应急物资配送中心及受灾点三层结构的应急物资敏捷配送体系。建立相应双层优化模型,其中下层模型决策车辆路径安排,上层模型根据下层模型的结果决策应急物资的分配。根据该模型的特点,提出一种改进蚁群算法求解下层模型,并用CPLEX软件求解上层模型。最后以5·12汶川大地震应急救援为例,对优化模型及求解方法进行了验证。     

Genericity and Non-bounding in the Enumeration degrees

The structure of the semi lattice of enumeration degrees hasbeen investigated from many aspects. One aspect is the boundingand non-bounding properties of generic degrees. Copestake provedthat every 2-generic enumeration degree bounds a minimal pairand conjectured that there exists a 1-generic degree that doesnot bound a minimal pair. In this paper we verify this longstandingconjecture by constructing such a degree using an infinite injurypriority argument.     

Hortatory operations in highway traffic management

This article examines two aspects of traffic management for highway networks. First, we introduce the term hortatory operations to describe highway traffic management as a type of human-machine system in which human operators have limited ability to directly control activities in the system. Instead, they must rely heavily on distributing messages of advice and encouragement as a means to achieve smooth traffic behavior. We discuss some of the features of this type of system. Second, we portray traffic management as a process that integrates both quantitative and qualitative information. We then describe the development and testing of a decision-aiding software tool that combines the two types of information. The tool supports traffic management by helping operators differentiate between demand-based and incident-based congestion. The decision aid's performance was investigated using real traffic data. The results of statistical analysis showed that the integrated process had superior performance compared to the “traditional” quantitative analysis running alone     

A Genetic Algorithm-based optimization model for supporting green transportation operations

Green Logistics (GL) has emerged as a trend in the management of the distribution of goods and the collection of end-of-life products. With its focus on maximizing the economic and environmental value by means of recycling and emission control, GL contributes to the sustainable development of industry but also requires a more comprehensive transportation scheme when conducting logistics services. This study is motivated by the practice of delivering and collecting water carboys. In this paper, a Genetic Algorithm-based optimization model (GOM) is proposed for designing a green transportation scheme of economic and environmental cost efficiency in forward and reverse logistics. Two vehicle routing models with simultaneous delivery and pickup (full or partial pickup) are formulated and solved by a Genetic Algorithm. A cost generation engine is designed to perform a comprehensive cost comparison and analysis based on a set of economic and environmental cost factors, so as to examine the impact of the two models and to suggest optimal transportation schemes. The computational experiments show that the overall cost is evidently lower in the full pickup model. Notably, the impact of product cost after recycling and reusing empty carboys on total cost is more significant than the impact of transportation cost and CO₂ emission cost. In summary, the proposed GOM is capable of suggesting a guidance for the logistics service providers, who deal with green operations, to adopt a beneficial transportation scheme so as to eventually achieve a low economic and environmental cost.     

A fuzzy, knowledge-based decision support tool for production operations management

Abstract: Production operations managers frequently have to make decisions based on vague, imprecise knowledge. Any software tool developed to aid their decision making needs to take into account the approximate nature of the information available to them and the inexact knowledge to which individual facts are applied. Much of this knowledge is expressed as vague, linguistic articulations. A convenient framework for dealing with such approximate knowledge is fuzzy logic and fuzzy set theory. As a specific example, a system was developed for providing decision support in the Just-in-Time area of production operations management.     

A plug and play pathway approach for operations management games development

Many researchers have advocated the use of games (and simulations) to enhance students’ learning. Research has shown that in order to promote a deeper understanding of material, students ought to be engaged with what they are doing. However, there are limited interactive games for classroom teaching, especially within the operations management subject area. In light of this, this paper proposes the development of a plug and play interactive game pathway to enhance students learning.     

A distributed data collection and management framework for tracking construction operations

Construction work typically means producing on shifting locations. Moving materials, equipment and men efficiently from place to place, in and in between projects, depends on good coordination and requires specialized information systems. The key to such information systems are appropriate approaches to collect de-centralized sensor readings and to process, and distribute them to multiple end users at different locations both during the construction process and after the project is finished. This paper introduces a framework for the support of such distributed data collection and management to foster real-time data collection and processing along with the provision of opportunities to retain highly precise data for post-process analyses. In particular, the framework suggests a scheme to benefit from exploiting readings from the same sensors in varying levels of detail for informing different levels of decision making: operational, tactical, and strategic. The sensor readings collected in this way are not only potentially useful to track, assess, and analyse construction operations, but can also serve as reference during the maintenance stage. To this extent, the framework contributes to the existing body of knowledge of construction informatics. The operationality of the framework is demonstrated by developing and applying two on site information systems to track asphalt paving operations.     

Genericity in Java: persistent and database systems implications

Lack of parametric polymorphism has been a major obstacle for making Java a viable database programming language. Regrettably, a recently accepted solution for genericity in Java 5.0 has far-reaching negative implications for persistent and database systems because of static and dynamic type violations. Severe implications occur in typical database transactions when processing a variety of database collections. Well-known approaches to persistence in Java, including Java’s own persistence mechanism, do not perform correctly due to incorrect dynamic type information that gets promoted to persistence along with objects. Dynamic checking of types of objects fetched from the persistent store may now lead to unexpected type violations. Further problems occur in reflective transactions as Java Core Reflection now allows dynamic type violations without detecting them or throwing standard exceptions. All of this shows that extending Java with parametric polymorphism has not made Java a more viable database programming language. Both legacy systems, such as those based on the Java binding of the ODMG or JDO, and future Java-related persistent and database technologies will be affected. The source of these problems is in an implementation idiom called type erasure. This paper provides formal proofs of the above implications of type erasure along with specific samples of code in Java 5.0 illustrating these violations. The limitations of the virtual platform and extensions required for persistent systems to solve this problem are also elaborated.     

Dynamic fuzzy criterion model for reservoir operations and a case study

Reservoir operation is a special inventory problem under conditions of uncertain supply and controlled demand. In this paper, we will restrict our attention to reservoir operations. In many cases, the problem which the reservoir manager is concerned with is not to maximize the direct economic benefit, but to operate the reservoir system as normally as possible, i.e., to fulfill the requirement for water demand, recreation, fishing, generating electricity, and ecology, etc., and to avoid flooding, as much as possible. This paper presents a dynamic fuzzy criterion model (DFCM) for reservoir operations. In DFCM, a satisfactory degree function is adopted as a criterion function. The objective is to let the reservoir system be in the highest possible satisfactory state. This model is available to the reservoir system whose parameters are fuzzy or whose economical benefits are very difficult to measure. We obtain the existence, uniqueness, and stability theorems to the equation of DFCM, and prove that the optimal release policy for a reservoir is a bounded critical number policy. Finally, the application of DFCM in Qinhuangdao region water resource system is discussed.     

A real-time food safety management system for receiving operations in distribution centers

Food safety plan is being promoted in the food industry by the Hong Kong Government as a preliminary quality control tool. However, it appears to be a challenging task for Distribution Centers (DC) that handles food inventory since most of them are lack of knowledge and know how technology to manage information in a real time base. This paper proposes a Radio Frequency Identification based Food Operations Assignment System (RFID-FOAS) to help DC facilitates the food safety control activities in receiving areas by generating a proper safety plan. The system has adopted the Radio Frequency Identification (RFID) technology and the Case-Based Reasoning (CBR) technique to facilitate the inventory data-capturing process and assist in formulating decisions, respectively. The developed system aims to help reduce the difficulties in safety plan development using a knowledge-based expert system. The significance and contribution of RFID-FOAS in the context of managing the inventory quality in DC for safety plan development is demonstrated through the adoption of the system in a Hong Kong-based logistics company. The generated results show that the decision-making process of the safety plan development is facilitated. Moreover, the real-time data capturing nature of RFID technology has further improved the efficiency and timeframe requested for the actions. With the support of RFID-FOAS, the data capture system and the decision-making time is minimized. As a result, inventory quality and customer satisfaction level are significantly improved.     

Using UML to model relational database operations

The Unified Modeling Language (UML) is being used as the de-facto standard in the software industry. With the adoption of UML 2.0, the new enhancements allow this version to describe many of the elements found in today's software technology as well as Model Driven Architecture and Service-Oriented Architecture. Although the Object Management Group (OMG) has released several UML Profiles to tailor the language to specific areas, relational database modeling is not fully addressed in these profiles. Many existing software applications involve complex application layer implemented in object-oriented programming languages and at the same time use relational database systems as the back-end data store. Modeling the whole system in a consistent manner will help developers and end users better understand the application. In this work we show how to model relational database operations using UML. Atomic database operations are modeled based on our framework and are used as building blocks to model more complex database operations.     

多面体三向DEXEL模型与布尔运算

提出了一种多面体的DEXEL化算法及一种三向DEXEL模型。与单向DEXEL模型相比,三向DEXEL模型能更精确地表示一个型体。在同一三向DEXEL模型空间,实现并、交、差布尔运算。将三向DEXEL模型用于飞机复合材料零件设计,设计了蜂窝结构、方管、圆管结构。在Java2.0与Java 3D环境下编程,实现并验证了所有算法。     

3D model management for e-commerce

This paper contributes to the efficient visualization and management of 3D content for e-commerce purposes. The main objective of this research is to improve the multimedia management of complex 3D models, such as CAD or BIM models, by simply dragging a CAD/BIM file into a web application. Our developments and tests show that it is possible to convert these models into web compatible formats. The platform we present performs this task requiring no extra intervention from the user. This process makes sharing 3D content on the web immediate and simple, offering users an easy way to create rich accessible multiplatform catalogues. Furthermore, the platform enables users to view and interact with the uploaded models on any WebGL compatible browser favouring collaborative environments. Despite not being the main objective of this work, an interface with search engines has also been designed and tested. It shows that users can easily search for 3D products in a catalogue. The platform stores metadata of the models and uses it to narrow the search queries. Therefore, more precise results are obtained.