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1.
The clustering coefficient C of a network, which is a measure of direct connectivity between neighbors of the various nodes, ranges from 0 (for no connectivity) to 1 (for full connectivity). We define extended clustering coefficients C(h) of a small-world network based on nodes that are at distance h from a source node, thus generalizing distance-1 neighborhoods employed in computing the ordinary clustering coefficient C = C(1). Based on known results about the distance distribution Pδ(h) in a network, that is, the probability that a randomly chosen pair of vertices have distance h, we derive and experimentally validate the law Pδ(h)C(h) ≤ c log N / N, where c is a small constant that seldom exceeds 1. This result is significant because it shows that the product Pδ(h)C(h) is upper-bounded by a value that is considerably smaller than the product of maximum values for Pδ(h) and C(h). Extended clustering coefficients and laws that govern them offer new insights into the structure of small-world networks and open up avenues for further exploration of their properties.  相似文献   

2.
Editorial     
This issue of Systemic Practice and Action Research focuses on systemic thinking in China. It results from considerable efforts invested in the project by Gerald Midgley and Jennifer Wilby. I am very grateful to Gerald and Jennifer, who have made available to our readership important research issues that would otherwise remain published only in the Chinese language. Inevitably a huge amount of editorial work is required when assisting people not fluent in the English language so that their papers are raised to a standard suitable for publication in a journal published in English. In addition, Gerald and Jennifer have put together a series of papers that make up an interesting whole that tells an important story. Thanks are extended to Gerald and Jennifer for this contribution.  相似文献   

3.
In this paper, under the constraint that the average distance and the average degree (k) remain approximately constant, we studied a random scale-free network model. We found that, if the network maintains the form of its degree distribution and the maximal degree kc is N-dependent cutoff function kc(N)〈 N, the degree distribution would be approximately power-law with an exponent between 2 and 3. The distribution exponent has little relationship with the average degree, denoted by (k). The diameter constraint can be interpreted as an environmental selection pressure, which could explain the scale-free nature of networks. The numerical results indicate that, under the diameter constraint, the preferential attachment can produce the cutoff function kc(N)〈 N and power-law degree distribution.  相似文献   

4.
In order to tradeoff exploration/exploitation and inspired by cell genetic algorithm a cellshift crossover operator for evolutionary algorithm (EA) is proposed in this paper. The definition domain is divided into n-dimension cubic sub-domains (cell) and each individual locates at an ndimensional cube. Cell-shift crossover first exchanges the cell numbers of the crossover pair if they are in the different cells (exploration) and subsequently shift the first individual from its initial place to the other individual's cell place. If they are already in the same cell heuristic crossover (exploitation) is used. Cell-shift/heuristic crossover adaptively executes exploration/exploitation search with the vary of genetic diversity. The cell-shift EA has excellent performance in terms of efficiency and efficacy on ten usually used optimization benchmarks when comparing with the recent well-known FEP evolutionary algorithm.  相似文献   

5.
In this paper, sequence unique reconstruction refers to the property that a sequence is uniquely reconstructable from all its K-tuples. We propose and study the phase transition behavior of the probability P(K) of unique reconstruction with regard to tuple size K in random sequences (iid model). Based on Monte Carlo experiments, artificial proteins generated from lid model exhibit a phase transition when P(K) abruptly jumps from a low value phase (e.g. 〈 0.1) to a high value phase (e.g. 〉 0.9). With a generalization to any alphabet, we prove that for a random sequence of length L, as L is large enough, P(K) undergoes a sharp phase transition when p ≤ 0.1015 where p = P (two random letters match). Besides, formulas are derived to estimate the transition points, which may be of practical use in sequencing DNA by hybridization. Concluded from our study, most proteins do not deviate greatly from random sequences in the sense of sequence unique reconstruction, while there are some "stubborn" proteins which only become uniquely reconstructable at a very large K and probably have biological implications.  相似文献   

6.
1. Introduction The long-term value of a firm is largelydetermined by the value of the company’scustomer relationships, which result in thefirm’s ‘customer equity’ (Blattberg andDeighton 1996), defined by Rust, Lemon andZeithaml (2000, p.4…  相似文献   

7.
There seems to be a significant gap between the theoretical and the practical aspects ofscheduling problems in the job shop environment. Theoretically, scheduling systems are designed onthe basis of an optimum approach to the scheduling model. However in the practice, the optimum thatis built into the scheduling applications seems to face some challenges when dealing with the dynamiccharacter of a scheduling system, for instance machine breakdown or change of orders. Schedulingsystems have become quite complex in the past few years. Competitive business environments andshorter product life cycles are the imminent challenges being faced by many companies these days.These challenges push companies to anticipate a demand driven supply chain in their businessenvironment. A demand-driven supply chain incorporates the customer view into the supply chainprocesses. As a consequence of this, scheduling as a core process of the demand-driven supply chainmust also reflect the customer view. In addition, other approaches to solving scheduling problems, forinstance approaches based on human factors, prefer the scheduling system to be more flexible in bothdesign and implementation. After discussion of these factors, the authors propose the integration of adifferent set of criteria for the development of“ scheduling systems which not only appears to have abetter flexibility but also increased customer-focus.  相似文献   

8.
The aim of this paper is to explore an explicit use of the concept of sustainability within transport planning. This paper analyses the concept of sustainability based on a practical approach for a sustainable development of Nordhavn, an area of Copenhagen, exemplifying a complex planning problem. An exploration of the application of the concept of sustainability is carried out using elements of Soft Systems Methodology (SSM). This approach indicates a need to separate the use of sustainability considerations regarding the transport planning ‘process’ from the transport planning ‘results’. The two approaches are related to the planning levels presented by Ulrich (Syst Prac 1(4):415–428, 1988). It was chosen to focus on the understanding of a sustainable transport planning process. This focus is addressed by four stakeholder groups interviewed based on the ‘ought to’ mode of Critical Systems Heuristics (CSH). Finally an outline of some of the factors of a sustainable transport planning process is proposed.  相似文献   

9.
1. Introduction In the past decades, the evolutionary perspective has contributed lot to the economics (Arthur and Durlauf et al 1997, Dosi and Nelson 1994, Aruka 2001). The economy is studied as an evolving complex system with many features in complexity such as nonlinear interactions and emergent properties. In reality, the economic system consists of many adaptive agents. They learn from each other, and their values may be influenced by others’ values and actions. These interactions amo…  相似文献   

10.
We consider a continuous review perishable (s,S) inventory system with a service facility consisting of a waiting hall of finite capacity and a single server. We assume two types of customers, ordinary and negative, arrive according to a Markovian Arrival Process (MAP). An ordinary customer joins the queue and a negative customer instead of joining the queue removes one ordinary customer from the queue. The removal rule adopted in this paper is RCE (removal of a customer from the end). The individual customer's unit demand is satisfied after a random time of service which is assumed to have a phase-type distribution. The life time of each item and the lead time of the reorders have been assumed to be independent exponential distributions. The joint probability distribution of the number of customers in the system and the inventory level is obtained for the steady state case. Various stationary system performance measures are computed and the total expected cost rate is calculated. The results are illustrated numerically.  相似文献   

11.
This paper reports on an on-going project on urban sustainability, the Puerto Aura in the region of the Valsequillo Lake in Puebla, Mexico. As part of the project, a simulation model was built to explore the dynamic interaction of the dimensions inherent in sustainable urban development. After reviewing literature on sustainable urban development (SUD) frameworks and tools, we identify key variables that intervene in SUD. We propose a System Dynamics model to simulate the dimensions that intervene in a sustainable development and to anticipate the consequences of the decision making process. The structure and inter-relationships of four sectors in the proposed model are described, the sustainability indicators in each sector explained. Preliminary conclusions are drawn stating that a complete run of the model simulating a 20 years horizon in monthly periods is expected when the full data from the Puerto Aura master plan becomes available.
Alberto Paucar-Caceres (Corresponding author)Email:
  相似文献   

12.
Simulating the supply disruption for the coordinated supply chain   总被引:1,自引:0,他引:1  
There are many disruptive accidents in the supply chain operations system and achieving the coordination of supply chain is main objective for supply chain research. While disruptive accidents have increasingly influenced the coordinated operation of the supply chain, existing research literature on the supply chain coordination is setting in a stationary environment. The answer for how the disruptive accidents affect the coordinated supply chain is given in this paper. Based on the benchmark supply chain which is coordinated by the negative incentive mechanism, we study the impacts of supply disruption on the supply chain system by using simulation approach in which two different distribution function of random variable are used to express the supply disruption. Comparison between these two simulation results and possible coordination mechanism under the supply disruption are proposed. From the perspective of supply chain risk management, we provide the inspiration for the manager.  相似文献   

13.
The author critically examines educational systems design (ESD) through the lens of pragmatism. Examining ESD through a lens of pragmatism draws to the foreground issues related to Banathy's (1991, 1996, 2001) idealized systems design for social and societal systems. The author addresses the complex and dynamic nature of systems design, focusing on the systemic processes in which user-designers are continually challenged to inquire, communicate, and consider choices, and make design decisions concerning the nature of the system being designed. The power of social systems design (SSD) lies in the ability to consider the ideal image of a social and/or societal system, critically and pragmatically in relation to creating a new system that will contribute to the evolutionary betterment of society and a sustainable future for humankind. Following an introduction, the author examines pragmatism. Then the author applies a lens of pragmatism, critically, to examine educational systems design in relation to generating change and creating the ideal educational system. The author then argues the pragmatics of educational systems design, concluding the paper with final reflections on ESD as a process.  相似文献   

14.
1. Introduction Data mining (DM), sometimes referred to as knowledge discovery in database (KDD), is a systematic approach to find underlying patterns, trends, and relationships buried in data. Data mining has drawn much attention from bothresearchers and practitioners due to its wide applications in crucial business decisions. Basically, the research on DM can be classified into two categories: methodologies and technologies. According to Curt (1995), the technology part of DM consists of…  相似文献   

15.
It is only the observable part of the real world that can be stored in data. For such incomplete and ill-structured data, data crystallizing aims at presenting the hidden structure among events including unobservable events. This is realized by data crystallization, where dummy items, corresponding to potential existence ofunobservable events, are inserted to the given data. These dummy items and their relations with observable events are visualized by applying KeyGraph to the data with dummy items, like the crystallization of snow where dusts are involved in the formation of crystallization of water molecules. For tuning the granularity level of structure to be visualized, the tool of data crystallization is integrated with human's process of understanding significant scenarios in the real world. This basic method is expected to be applicable for various real world domains where previous methods of chance-discovery lead human to successful decision making. In this paper, we apply the data crystallization with human-interactive annealing (DCHA) to the design of products in a real company. The results show its effect to industrial decision making.  相似文献   

16.
With increasingly intense competition between enterprises, the realization of advanced supply chain management has become an exquisite premise for the survival of firms. Procurement management is an important means to reduce costs and to enhance the competitive advantage. By exploiting the single period newsvendor model, this paper analyses and compares the benefit mechanisms of e-procurement and traditional procurement to quantify the effect of the Internet on supply chain procurement management in a neutral e-market. This work was partly supported by the National Natural Science Foundation of China under Grant No. 70125004 and 70572050. Guangshu Chang is a lecturer of Zhengzhou Institute of Aeronautics. He received his master degree from Zhengzhou University in 2000. His research interests include e-commerce, supply chain management and quality management. Jichao Xu is a professor of Zhengzhou Institute of Aeronautics. His research interests include quality management and quality engineering. Jianfeng Yang is a PhD student of Management School, Northwestern Polytechnical University. His research interest includes quality management. Jinfeng He is a PhD student of Management School, Northwestern Polytechnical University. Her research interest includes quality management. Li Zhang is a PhD student of Management School, Northwestern Polytechnical University. Her research interest includes quality management.  相似文献   

17.
Roadmapping, originated from industry as a strategic planning tool, is attracting increasing applications in academy. Based on the recognition that roadmapping is a knowledge creation process, this paper analyzes what kind of support is needed or helpful for establishing a creative environment for roadmapping in academy and reviews various types of such support from the perspective of i-system methodology. As case studies of such support, this paper further introduces roadmapping pratices in Janpan Advanced Institute of Science and Technology.  相似文献   

18.
1. Introduction As an important application field of the data clustering technologies (Jain and Murty et al. 1999), text clustering is unsupervised partitioning of a collection of textual documents into self-similar groups so that any item is more similar with another item in the same group thanwith an item outside the group. Such groups are called clusters, which are run-timely formed during the clustering process, instead of being pre-defined as in the case of text categorization, which comm…  相似文献   

19.
In several rural areas in Colombia there is a serious lack of water quality supply. Thereby the problematic situation is understood as complex one that involves stakeholders with pluralistic interests, multiple variables and requires the development of sustainable and suitable solutions. In order to address this issue, this paper proposes an integration of engineering design framework (CDIO) with a systemic approach. Particularly the approach emphasizes on systemic elements such as autonomy, systems within systems, cooperation between stakeholders and cause effect relations; it also proposes a previous observing phase for engineering design framework. Thus the proposed systemic framework aims to generate projects that improve living conditions in rural communities and promote the production of knowledge between the stakeholders to ensure sustainability in the long term. To illustrate the proposal, this work contains a case study that discusses a project carried out by a research team—Ingenieros Sin Fronteras Colombia—in a rural district near to Colombia’s capital. The experience, which involved and benefited 16 families in the community, provided strong evidence to support the proposed framework. The paper concludes with a discussion about the replication of this proposal in other contexts.  相似文献   

20.
This paper analyses Chinese manufacturing performance from a multilateral perspective in 1980–2004. The PPPs, relative price levels, labor productivity and ULCs in multilateral comparison are used to explore Chinese manufacturing competitiveness. The PPPs are based on the benchmark year 1997. These results are compared to the previous estimates based on the 1987 benchmark. The findings are as follows: the PPPs derived by the different approaches in the base year 1997 in Chinese manufacturing are approximately 3.7 yuan/international $. Since the middle 1980s, China’s relative price level has been the lowest among all five countries and declined during the period of time. Its ULC has also been declining with some fluctuation. In the 1980s, there was “no catch-up rapid growth” in its labor productivity. However, after 1992, a beginning has been made with catch up distinctly, though from a very low level. This work was supported by the National Natural Science Foundation of China under Grant 70173029, 70571004 and 70531010. Ruoen Ren Professor of School of Economics & Management in Beihang University received Ph.D. in Economics in Renmin University of China in 1987. As one who enjoys the Government Special Allowance, he specializes in the study of international competitiveness, macroeconomics analysis, input-output table research, and credit risk management etc. His primary academic achievements are as follows: ICP in China, ICOP in China, KLEMS in China, Credit risk management in China commercial bank. In addition to his teaching and research at school, he is a chief economist in China Development Bank, a member in Science & Technical committee in Ministry of Education, and an executive director in China’s Input-output Association, etc. Haitao Zheng Doctorial candidate of School of Economics & Management in Beihang University, majors in the study on international competitiveness and insurance actuary. Meanwhile, he is an Associate of Society of Chinese Actuary.  相似文献   

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