Spirobifluorene-Based Porous Organic Salts: Their Porous Network Diversification and Construction of Chiral Helical Luminescent Structures

Porous organic salts (POSs) are organic porous materials assembled via charge-assisted hydrogen bonds between strong acids and bases such as sulfonic acids and amines. To diversify the network topology of POSs and extend its functions, this study focused on using 4,4′,4′′,4′′′-(9,9′-spirobi[fluorene]-2,2′,7,7′-tetrayl)tetrabenzenesulfonic acid ( spiroBPS ), which is a tetrasulfonic acid comprising a square planar skeleton. The POS consisting of spiroBPS and triphenylmethylamine ( TPMA ) ( spiroBPS/TPMA ) was constructed from the two-fold interpenetration of an orthogonal network with pts topology, which has not been reported in conventional POSs, owing to the shape of the spirobifluorene backbone. Furthermore, combining tris(4-chlorophenyl)methylamine ( TPMA-Cl ) and tris(4-bromophenyl)methylamine ( TPMA-Br ), which are bulkier than TPMA owing to the introduction of halogens at the p-position of the phenyl groups with spiroBPS allows us to construct novel POSs ( spiroBPS/TPMA-Cl and spiroBPS/TPMA-Br ). These POSs were constructed from a chiral helical network with pth topology, which was induced by the steric hindrance between the halogens and the curved fluorene skeleton. Moreover, spiroBPS/TPMA-Cl with pth topology exhibited circularly polarized luminescence (CPL) in the solid state, which has not been reported in hydrogen-bonded organic frameworks (HOFs).     

基于Markov网络的检索模型

基于Markov网络的信息检索模型提出一种贝叶斯网络推广的检索模型,该模型利用词项在文档集中的共现信息来构造Markov网络,通过该索引项子Markov网络来加载附加查询证据源,计算文档与查询之间的相关性概率,由此概率进行文档排序. 实验结果表明,本文提出的Markov网络模型比其他传统的检索方法具有更优的检索性能.     

循环经济生态工业网络稳定性研究

以天津泰达生态工业网络为典型案例,分析了生态工业网络的构建方法、稳定性的表现、影响因素,提出了增加生态工业网络系统稳定性的建议。     

End-to-end availability-dependent pricing of network services

We discuss how a new pricing scheme can be integrated within a communication network. The pricing scheme is based on the availability of end-to-end communications, and is an alternative to congestion pricing, which is not applicable when communication capacity is higher than demand (as happens in most communication backbone networks). We also investigate how, based on this scheme, an optimization algorithm for updating the network topology can be applied. The network update problem is modeled as a combinatorial optimization problem, which is approximately solved using a Genetic Algorithm. The good results obtained in a case study show that the method is robust and can be applied even when end-to-end availability measures can only be computed approximately (in this case, using a Monte Carlo method). This research is part of the PAIR associated research project, supported by the INRIA, France, and has also received the support of ECOS-Sud, under Action U03E02. The participation of Pablo Rodríguez was supported by the French Embassy in Uruguay as part of the French Ministère des Affaires étrangères scientific cooperation program; and by the “Programa de Jóvenes Investigadores” of CSIC, UDELAR, Uruguay.     

A tabu search approach for solving a difficult forest harvesting machine location problem

This paper deals with two main problems in forest harvesting. The first is that of selecting the locations for the machinery to haul logs from the points where they are felled to the roadside. The second consists in designing the access road network connecting the existing road network with the points where machinery is installed. Their combination induces a very important and difficult problem to solve in forest harvesting. It can be formulated as a combination of two difficult optimization problems: a plant location problem and a fixed charge network flow problem. In this paper, we propose a solution approach based on tabu search. The proposed heuristic includes several enhancements of the basic tabu search framework. The main difficulty lies in evaluating neighboring solutions, which involves decisions related to location of machinery and to road network arcs. Hence, the neighborhood is more complex than in typical applications of metaheuristics. Minimum spanning tree algorithms and Steiner tree heuristics are used to deal with this problem. Numerical results indicate that the heuristic approach is very attractive and leads to better solutions than those provided by state-of-the-art integer programming codes in limited computation times, with solution times significantly smaller. The numerical results do not vary too much when typical parameters such as the tabu tenure are modified, except for the dimension of neighborhood.     

Effective bandwidths for the multi-type UAS channel

The Uniform Arrival and Service (UAS) model is one of several appropriate to modelling traffic offered to a multi-service communication channel. We exhibit, via asymptotics and a range of specific examples, that it is possible to assign a notionaleffective bandwidth to each source, dependent not only on its mean bandwidth but also on its burstiness and on the channel. The effective bandwidth can be calculated quickly and efficiently using the results of Anick, Mitra and Sondhi and reduces the multi-service network to the more familar, and well understood, form of a traditional circuit-switched network.This research was carried out while the authors were supported by the SERC under Grant GR/E 83009 and Christ's College, Cambridge respectively.     

How to compute least infeasible flows

It is well-known how to use maximum flow to decide when a flow problem with demands, lower bounds, and upper bounds is infeasible. Less well-known is how to compute a flow that is least infeasible. This paper considers many possible ways to define “least infeasible” and shows how to compute optimal flows for each definition. For each definition it also gives a dual characterization in terms of cuts, a polynomial routine for recognizing that type of least infeasible flow, and relates that definition to dual cut canceling min-cost flow network algorithms. This research was partially supported by an NSERC Operating Grant, an NSERC Grant for Research Abroad, and a UBC Killam Faculty Study Leave Fellowship. Parts of this research were done while the author was visiting Laboratoire ARTEMIS IMAG at Université Joseph Fourier de Grenoble, France.     

Shortest paths algorithms: Theory and experimental evaluation

We conduct an extensive computational study of shortest paths algorithms, including some very recent algorithms. We also suggest new algorithms motivated by the experimental results and prove interesting theoretical results suggested by the experimental data. Our computational study is based on several natural problem classes which identify strengths and weaknesses of various algorithms. These problem classes and algorithm implementations form an environment for testing the performance of shortest paths algorithms. The interaction between the experimental evaluation of algorithm behavior and the theoretical analysis of algorithm performance plays an important role in our research. This work was done while Boris V. Cherkassky was visiting Stanford University Computer Science Department and supported by the NSF and Powell Foundation grants mentioned below. Andrew V. Goldberg was supported in part by ONR Young Investigator Award N00014-91-J-1855, NSF Presidential Young Investigator Grant CCR-8858097 with matching funds from AT&T, DEC, and 3M, and a grant from Powell Foundation. Corresponding author. This work was done while Tomasz Radzik was a Postdoctoral Fellow at SORIE, Cornell University, and supported by the National Science Foundation, the Air Force Office of Scientific Research, and the Office of Naval Research, through NSF grant DMS-8920550, and by the Packard Fellowship of éva Tardos.     

Real-time Capturing and Measurement of Traffic Flow Based on WinPcap

In order to understand how a network is being used or whether it is being abused, an administrator needs to inspect the flow of the traffic and ＂infers＂ the intent of the users and applications. So the network traffic measurement and analysis are crucial to network monitoring, reliable DDoS detecting and attack source locating as well. In this paper, we discuss the principle of real-time network traffic measurement and analysis through embedding a traffic measurement and analysis engine into IP packet-decoding module, and emphasize the implementation of visualizing the real-time network traffic, which are helpful to network monitoring and network traffic modeling.     

Deterministic global optimization in isothermal reactor network synthesis

The reactor network synthesis problem involves the simultaneous determination of the structure and operating conditions of a reactor system to optimize a given performance measure. This performance measure may be the yield of a given product, the selectivity between products, or the overall profitability of the process. The problem is formulated as a nonlinear program (NLP) using a superstructure based method in which plug flow reactors (PFRs) in the structure are modeled using differential-algebraic equations (DAEs). This formulation exhibits multiple local minima. To overcome this, a novel deterministic global optimization method tailored to the special structure and characteristics of this problem will be presented. Examples of isothermal networks will be discussed to show the nature of the local minima and illustrate various components of the proposed approach.