Performance Analysis of Multi-Antenna TD-CDMA Receivers with Estimation and Consideration of the Interference Covariance Matrix

The use of adaptive antennas in cellular mobileradio systems is considered to be one of the mostimportant measures to increase capacity. The consideredadaptive antenna concept is applied to the well-known TD-CDMA mobile radio air interface. TD-CDMA isadopted by ETSI for the UTRA TDD mode and is one of thecandidates considered by ITU for IMT-2000. In thereceivers of a TD-CDMA system the intracell multiple access interference (MAI) is eliminated byjoint detection. This detection algorithm also offersthe advantageous possibility of considering theintercell interference covariance matrix in order toenhance system performance. In this paper, amulti-antenna receiver structure with the capability toestimate the covariance matrix of the received intercellmultiple access interference (MAI) is presented. The benefits of taking into account theinterference covariance matrix both in channelestimation and data detection are shown by simulations.The directional channel models applied in thesimulations are derived from measured channel impulseresponses.     

An analysis and implementation of an efficient in-place bucket sort

Various methods, such as address-calculation sorts, distribution counting sorts, radix sorts, and bucket sorts, use the values of the numbers being sorted to increase efficiency but do so at the expense of requiring additional storage space. In this paper, a specific implementation of bucket sort is presented whose primary advantanges are that (i) linear average-time performance is achieved with an additional amount of storage equal to any fraction of the number of elements being sorted and (ii) no linked-list data structures are used (all sorting is done with arrays). Analytical and empirical results show the trade-off between the additional storage space used and the improved computational efficiency obtained. Computer simulations show that for lists containing 1,000 to 30,000 uniformly distributed positive integers, the sort developed here is faster than both Quicksort and a standard implementation of bucket sort. Furthermore, the running time increases with size at a slower rate. Received 2 May 1995 / 31 July 1996     

Nearest Neighbor Queries in Shared-Nothing Environments

In this paper, we propose an efficient solution to the problem of nearest neighbor query processing in declustered spatial databases. Recently a branch-and-bound nearest neighbor finding (BB-NNF) algorithm has been designed to process nearest neighbor queries in R-trees. However, this algorithm is strictly serial (branch-and-bound oriented) and its performance degrades, during processing of a nearest neighbor query, if applied to a parallel environment, since it does not exploit any kind of parallelization. We develop an efficient query processing strategy for parallel nearest neighbor finding (P-NNF), assuming a shared nothing multi-processor architecture, where the processors communicate via a network. In our method, the relevant sites are activated simultaneously. In order to achieve this goal, statistical information is used. The efficiency measure is the response time of a given query. Experimental results, based on real-life and synthetic datasets, show that the proposed method outperforms the branch-and-bound method by factors.     

SkyGraph: an algorithm for important subgraph discovery in relational graphs

A significant number of applications require effective and efficient manipulation of relational graphs, towards discovering important patterns. Some example applications are: (i) analysis of microarray data in bioinformatics, (ii) pattern discovery in a large graph representing a social network, (iii) analysis of transportation networks, (iv) community discovery in Web data. The basic approach followed by existing methods is to apply mining techniques on graph data to discover important patterns, such as subgraphs that are likely to be useful. However, in some cases the number of mined patterns is large, posing difficulties in selecting the most important ones. For example, applying frequent subgraph mining on a set of graphs the system returns all connected subgraphs whose frequency is above a specified (usually user-defined) threshold. The number of discovered patterns may be large, and this number depends on the data characteristics and the frequency threshold specified. It would be more convenient for the user if “goodness” criteria could be set to evaluate the usefulness of these patterns, and if the user could provide preferences to the system regarding the characteristics of the discovered patterns. In this paper, we propose a methodology to support such preferences by applying subgraph discovery in relational graphs towards retrieving important connected subgraphs. The importance of a subgraph is determined by: (i) the order of the subgraph (the number of vertices) and (ii) the subgraph edge connectivity. The performance of the proposed technique is evaluated by using real-life as well as synthetically generated data sets.     

Ethanol combined with heparin as a locking solution for the prevention of catheter related blood stream infections in hemodialysis patients: A prospective randomized study

Introduction: Ethanol lock solution has been mainly administered in paediatric and home parenteral nutrition patients in order to prevent catheter related blood stream infections (CRBSI). Its utility in hemodialysis (HD) patients with non‐tunneled‐uncuffed catheter (NTC) has been poorly explored. Methods: We conducted a prospective randomized study in chronic HD patients requiring a newly inserted NTC‐while awaiting for the maturation of an already established arteriovenous fistula (AVF) or arteriovenous graft (AVG) or tunneled‐cuffed catheter insertion. Patients were randomized in two groups: Group A, where the lock solution was ethanol 70% + unfractionated heparin 2000 U/mL and group B, that received only unfractionated heparin 2000 U/mL. Primary end point was CRBSIs whereas exit site infections, thrombotic and bleeding episodes were the secondary end points. Findings: One hundred three HD patients were enrolled in the study (group A, n = 52; group B, n = 51). The median number of catheter days was 32 for group A (range: 23–39) and 34 (range: 27–40) for group B with no statistically significant difference between the two groups. Group A (ethanol + heparin) demonstrated 4/52 episodes (7.69%) of CRBSI whereas Group B (heparin) 11/51 episodes (21.57%) (P = 0.04). CRBSI rates per 1000 catheter days were 2.53/1000 catheter days for group A and 6.7/1000 catheter days for group B (P = 0.04). Mean cumulative infection‐free catheter survival in the ethanol group did not differ significantly compared to the heparin group (log‐rank test = 2.99, P = 0.08). Thrombotic episodes did not differ between the two groups. Discussion: Locking of NTCs in HD patients with ethanol 70% + unfractionated heparin reduces CRBSI rates without increasing the thrombotic episodes.     

Stabilization of linear systems with simultaneous state,actuation, and measurement delays

This paper considers the problem of stabilizing continuous-time linear systems with time delays. Specifically, a fixedorder (i.e. full- and reduced-order) dynamic compensation problem is addressed for systems with simultaneous state, input, and output delays. The principal result involves sufficient conditions for characterizing fixed-order dynamic controllers for delay systems via a system of modified coupled Riccati equations. The controllers obtained are delay independent and hence apply to systems with arbitrary unknown delay.     

框架网格划分对钢筋用量的影响

针对如何节省钢材的问题,提出优化钢筋混凝土框架结构单位面积配筋量的方法.主要技术路线是探索板、梁尺寸及柱数目变化对构件内力分布和配筋量的影响.具体内容是将一个纵、横向长度给定的矩形建筑进行纵向长度均匀网格划分（每个网格线交点设有一根柱子）,每种划分得到n个面积相同的网格.一般随着n的增大板配筋变小,梁与柱的配筋则增加,n将存在一个数值,使板、梁和柱的总体配筋量达到极值.模拟一层钢筋混凝土框架结构,分别对板、梁、柱的配筋进行配筋公式推导,得到n与三个构件配筋体积V的函数关系,并进一步转换成单位面积配筋量m与n的关系.以n为优化变量,利用Matlab获得函数变化及最小值,最后通过具体案例进行了演示.     

Interconnection of geographically distributed wireless mesh testbeds: Resource sharing on a large scale

Creating large scale testbeds for evaluating wireless mesh technologies and protocols, and for testing their ability to support real world applications in realistic environments, is a crucial step towards the ultimate success of the WMN paradigm. In this paper we suggest the hierarchical federation of a planetary scale infrastructure, such as PlanetLab, with a number of local OMF-based wireless testbeds as a viable approach towards this goal. Along such direction, we present an architectural model for integrating at the technical level these two kinds of infrastructures and our initial implementation of such a model. We also present some test case experiments we run on our initial implementation of the integrated architecture, to illustrate how an experiment on peer-to-peer traffic optimization can be executed by combining both wireless nodes of a OMF-based testbed and PlanetLab nodes located across Europe. The possibility of running this kind of experiments in such a hybrid experimental scenario highlighted several real-world issues that are worth to be further investigated.     

Broadband municipal optical networks in Greece: A suitable business model

This paper proposes a business model for the optimal exploitation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe in detail the way that these networks should be managed, operated, maintained and expanded. Taking into consideration that these infrastructures will widely alter the broadband map of Greece, that Greece has currently one of the lowest broadband penetration percentages in Europe and that the proper exploitation strategy of the networks to be deployed could boost the demand for broadband connections and applications, the application of the optimal business model appears to be of vital importance. We describe the proposed business model in detail, including ways for expanding the broadband infrastructures, as well as tackling of viability issues regarding the authority responsible for managing the broadband metropolitan networks.