bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Contact Characteristics of Small Rough Surfaces Taking Bulk Deformation and Meniscus Force Into Consideration
Authors: Ono Kyosuke , Yamane Masami
Published: June 2007

We numerically investigated the characteristics of contact force, adhesion force, and contact stiffness between a smooth contact pad and a small rough surface, such as a current magnetic disk surface. The computer-generated asperity had an isotropic Gaussian distribution with a small asperity height and high asperity density. We took asperity contact, bulk deformation, and meniscus force of a lubricant layer at contacting asperity into consideration in the calculations. We evaluated the effects of asperity density, contact pad area, asperity radius, root mean square (RMS) asperity height, and lubricant thickness on external and internal contact forces, adhesion force, and contact stiffness as a function of the separation between the contact pad and disk in both approaching and separating processes. We found that contact and adhesion force tend to change suddenly at the start and end of contact and exhibits hysteresis in the approaching and separating processes when asperity density becomes large and RMS asperity height becomes small comparable with current head sliders and magnetic disks. We also found that contact stiffness is governed by bulk deformation and that the contact stiffness and adhesion force can be regarded as constant during contact when the asperity density increases, the RMS asperity height decreases, and the contact area increases.
Rolling Contact Between Rigid Cylinder and Semi-Infinite Elastic Body With Sliding and Adhesion
Authors: Hao S. , Keer L. M.
Published: June 2007

Based on a hybrid superposition of an indentation contact and a rolling contact an analytical procedure is developed to evaluate the effects of surface adhesion during steady-state rolling contact, whereby two analytic solutions have been obtained. The first solution is a Hertz-type rolling contact between a rigid cylinder and a plane strain semi-infinite elastic substrate with finite adhesion, which is a JKR-type rolling contact but without singular adhesive traction at the edges of the contact zone. The second solution is of a rolling contact with JKR singular adhesive traction. The theoretical solution indicates that, when surface adhesion exists, the friction resistance can be significant provided the external normal force is small. In addition to the conventional friction coefficient, the ratio between friction resistance force and normal force, this paper suggests an “adhesion friction coefficient” which is defined as the ratio between friction resistance force and the sum of the normal force and a function of maximum adhesive traction per unit area, elastic constant of the substrate, and contact area that is characterized by the curvature of the roller surface.
Transient Temperature Involving Oscillatory Heat Source With Application in Fretting Contact
Authors: Wen Jun , Khonsari M. M.
Published: June 2007

An analytical approach for treating problems involving oscillatory heat source is presented. The transient temperature profile involving circular, rectangular, and parabolic heat sources undergoing oscillatory motion on a semi-infinite body is determined by integrating the instantaneous solution for a point heat source throughout the area where the heat source acts with an assumption that the body takes all the heat. An efficient algorithm for solving the governing equations is developed. The results of a series simulations are presented, covering a wide range of operating parameters including a new dimensionless frequency ω¯=ωl2∕4α and the dimensionless oscillation amplitude A¯=A∕l, whose product can be interpreted as the Peclet number involving oscillatory heat source, Pe=ω¯A¯. Application of the present method to fretting contact is presented. The predicted temperature is in good agreement with published literature. Furthermore, analytical expressions for predicting the maximum surface temperature for different heat sources are provided by a surface-fitting method based on an extensive number of simulations.
Modeling of Fretting Wear Under Gross Slip and Partial Slip Conditions
Authors: Gallego L. , Nélias D.
Published: June 2007

The paper presents a numerical model to investigate fretting wear either under partial or gross slip conditions. An efficient three-dimensional elastic–static contact model to solve both the normal contact problem and the tangential contact problem is presented. The contact model is validated with analytical solutions for a sphere on flat geometry. A wear law issued from the literature and based on the friction energy is used to simulate surface wear. Numerical friction logs are obtained and the wear rate evolution is found to be highly dependent on the tangential displacement.
Modeling of the Effect of Preferential Texturing on the Interfacial Forces in Sub-5nm Ultralow Flying Head-Disk Interfaces
Authors: Suh Allison Y. , Polycarpou Andreas A.
Published: June 2007

Preferential surface texturing is expected to significantly improve tribological performance of ultralow flying magnetic storage head-disk interfaces (HDIs) by modifying the roughness and reducing the contact area preferentially, thereby reducing the relevant interfacial forces, such as friction, contact, and adhesive forces. Because of the different etch rates in the titanium carbide (top surface) and alumina (bottom surface) portions of the slider air-bearing surface (ABS), during reactive ion etching the surface heights possess a distinct bimodal distribution. In order to accurately and realistically capture the interfacial phenomena of the ultralow flying HDI with a preferentially textured slider ABS, a probability density function was proposed by linking two different Gaussian asperity distributions. The proposed bimodal asperity distribution was then directly incorporated into a previously developed rough surface contact model to calculate the corresponding interfacial forces. The results were then directly compared to a single Gaussian approximation (ignoring the bimodality) as well as a high-order polynomial curve-fit approximation (encompassing the bimodality). Comparative studies revealed that the proposed bimodal distribution method has a main advantage of being able to resolve the top and bottom asperity contributions separately, which is physically more accurate, and thereby providing interfacial force estimates that are more physically accurate. Other simpler methods, by assuming a single continuous distribution over the entire surface, are not able to isolate the top and bottom asperity distributions and thus are more likely to overestimate the interfacial forces in sub-5 nm flying HDIs.
A Comparison of the Tribo-Mechanical Properties of a Wear Resistant Cobalt-Based Alloy Produced by Different Manufacturing Processes
Authors: Yu H. , Ahmed R. , de Villiers Lovelock H.
Published: June 2007

This paper aims to compare the tribo-mechanical properties and structure–property relationships of a wear resistant cobalt-based alloy produced via two different manufacturing routes, namely sand casting and powder consolidation by hot isostatic pressing (HIPing). The alloy had a nominal wt % composition of Co–33Cr–17.5W–2.5C, which is similar to the composition of commercially available Stellite 20 alloy. The high tungsten and carbon contents provide resistance to severe abrasive and sliding wear. However, the coarse carbide structure of the cast alloy also gives rise to brittleness. Hence this research was conducted to comprehend if the carbide refinement and corresponding changes in the microstructure, caused by changing the processing route to HIPing, could provide additional merits in the tribo-mechanical performance of this alloy. The HIPed alloy possessed a much finer microstructure than the cast alloy. Both alloys had similar hardness, but the impact resistance of the HIPed alloy was an order of magnitude higher than the cast counterpart. Despite similar abrasive and sliding wear resistance of both alloys, their main wear mechanisms were different due to their different carbide morphologies. Brittle fracture of the carbides and ploughing of the matrix were the main wear mechanisms for the cast alloy, whereas ploughing and carbide pullout were the dominant wear mechanisms for the HIPed alloy. The HIPed alloy showed significant improvement in contact fatigue performance, indicating its superior impact and fatigue resistance without compromising the hardness and sliding∕abrasive wear resistance, which makes it suitable for relatively higher stress applications.
Air-Bearing Effects on Actuated Thermal Pole-Tip Protrusion for Hard Disk Drives
Authors: Juang Jia-Yang , Bogy David B.
Published: June 2007

Flying height (FH) control sliders with thermal actuation have been introduced recently in commercial products for compensating the static FH loss and reducing the risk of head-disk contacts. In the research reported here, we investigated the effects of air-bearing surface (ABS) designs on the thermal actuation. We created a three-dimensional finite element model of an entire slider with a detailed read/write transducer structure and conducted thermal-structural coupled-field analysis using velocity slip and temperature jump boundary conditions to formulate the heat transfer across the head-disk interface when a slider flies over a spinning disk. An iteration procedure was used to obtain the equilibrium solutions. Four ABS designs with distinct features were simulated. We defined five measures of merit, including protrusion rate, actuation efficiency, power consumption, pressure peak, and temperature rise of the sensor to evaluate the performance of thermal actuation. It is found that the effect of the pressure is more significant than that of the FH on the heat conduction from the slider to the disk. The efficiencies of three conventional designs decrease as the FHs are continuously reduced. A new ABS design, called “Scorpion III,” is presented and demonstrates an overall enhancement, including virtually 100% efficiency with significantly less power consumption. Transient thermal analysis showed that it requires ∼1–2ms for the temperature to reach the steady-state values, and there is a trade-off between increasing the actuation bandwidth and decreasing the power consumption.
A Deterministic-Chaos Study of Electron Triboemission Outputs
Authors: Molina G. J. , Furey M. J. , Kajdas C.
Published: June 2007

The authors have carried out extensive measurements of electron triboemission from the scratching of ceramics and semiconductors that are briefly summarized in this paper. Analysis of the frequency-domain distribution of typical triboemission count-pulse outputs suggested that their occurrence is not Poisson’s (e.g., it is not random). This paper presents a study on the hypothesis of deterministic-chaos origin for triboemission data. Electron triboemission outputs from the ceramics alumina, sapphire, silicon nitride, and the semiconductors Si and Ge are analyzed by means of extracting deterministic-chaos metrics. The results suggest that the low-level electron-emission components may be described by multiplicative processes of random initiation, while the superimposed large burst-type components may be of deterministic origin.
Theoretical Analysis of Textured “Damper” Annular Seals
Authors: Arghir M. , Billy F. , Pineau G. , Frěne J. , Texier A.
Published: June 2007

The present work presents a theoretical approach for the analysis of textured annular “damper” seals. The data for the seal were extracted from the work of Childs and Fayolle (ASME J. Tribol. 121(1), pp. 42–49). The texture of the stator consists of equally spaced cylindrical holes of an order of magnitude larger than the seal clearance. The main idea of the present work is that the static and dynamic characteristics of the textured annular seal can be predicted by using a slightly modified bulk-flow model. The modifications are introduced by considering the textured seal as being geometrically similar to a straight seal with the same clearance. The presence of the texture is taken into account by considering modified friction laws for the rotor and for the stator, separately. An additional inertia effect due to the texture is also added as a source term to the momentum equations. The modified friction laws and the inertia effect are deduced from a three-dimensional Navier-Stokes analysis of the flow in the textured seal. This computational analysis is carried on for a single texture element extracted from the round-hole pattern of stator by using periodicity boundary conditions. The stiffness and the damping of the annular seal were calculated by using the modified bulk-flow model and results were compared with the experimental data from Childs and Fayolle. The use of the present model shows a net improvement of the predictions for the direct and cross-coupling stiffness and for the cross-coupling damping. The results obtained for the direct damping are still under discussion.
Sirtuin 2 Inhibitors Rescue α-Synuclein-Mediated Toxicity in Models of Parkinson's Disease
Authors: Outeiro Tiago Fleming , Kontopoulos Eirene , Altmann Stephen M. , Kufareva Irina , Strathearn Katherine E. , Amore Allison M. , Volk Catherine B. , Maxwell Michele M. , Rochet Jean-Christophe , McLean Pamela J. , Young Anne B. , Abagyan Ruben , Feany Mel B. , Hyman Bradley T. , Kazantsev Aleksey G.
Published: June 2007

The sirtuins are members of the histone deacetylase family of proteins that participate in a variety of cellular functions and play a role in aging. We identified a potent inhibitor of sirtuin 2 (SIRT2) and found that inhibition of SIRT2 rescued α-synuclein toxicity and modified inclusion morphology in a cellular model of Parkinson's disease. Genetic inhibition of SIRT2 via small interfering RNA similarly rescued α-synuclein toxicity. Furthermore, the inhibitors protected against dopaminergic cell death both in vitro and in a
Drosophila
model of Parkinson's disease. The results suggest a link between neurodegeneration and aging.
Naïve Bayesian Classifier for Rapid Assignment of rRNA Sequences into the New Bacterial Taxonomy
Authors: Wang Qiong , Garrity George M. , Tiedje James M. , Cole James R.
Published: June 2007

The Ribosomal Database Project (RDP) Classifier, a naïve Bayesian classifier, can rapidly and accurately classify bacterial 16S rRNA sequences into the new higher-order taxonomy proposed in Bergey's
Taxonomic Outline of the Prokaryotes
(2nd ed., release 5.0, Springer-Verlag, New York, NY, 2004). It provides taxonomic assignments from domain to genus, with confidence estimates for each assignment. The majority of classifications (98%) were of high estimated confidence (≥95%) and high accuracy (98%). In addition to being tested with the corpus of 5,014 type strain sequences from Bergey's outline, the RDP Classifier was tested with a corpus of 23,095 rRNA sequences as assigned by the NCBI into their alternative higher-order taxonomy. The results from leave-one-out testing on both corpora show that the overall accuracies at all levels of confidence for near-full-length and 400-base segments were 89% or above down to the genus level, and the majority of the classification errors appear to be due to anomalies in the current taxonomies. For shorter rRNA segments, such as those that might be generated by pyrosequencing, the error rate varied greatly over the length of the 16S rRNA gene, with segments around the V2 and V4 variable regions giving the lowest error rates. The RDP Classifier is suitable both for the analysis of single rRNA sequences and for the analysis of libraries of thousands of sequences. Another related tool, RDP Library Compare, was developed to facilitate microbial-community comparison based on 16S rRNA gene sequence libraries. It combines the RDP Classifier with a statistical test to flag taxa differentially represented between samples. The RDP Classifier and RDP Library Compare are available online at
http://rdp.cme.msu.edu/
.
Serum thyroid hormone concentrations and thyroid histomorphology as biomarkers in bowhead whales (Balaena mysticetus)
Authors: Rosa Cheryl , O’Hara Todd M. , Hoekstra Paul F. , Refsal Kent R. , Blake John E.
Published: June 2007

Serum thyroid hormone (TH) concentrations have been used alone or with other measurements to assess health status or effects of toxicant exposure in marine mammals. Histological sections from thyroid glands of the bowhead whale ( Balaena mysticetus L., 1758) were examined in conjunction with serological TH analyses. Serum was assayed for total and free triiodothyronine and total and free thyroxine via radioimmunoassay. Histomorphology of thyroid tissue was assessed by light microscopy and the utilization of an epithelial-follicular index (EFI). Age, sex, or season did not significantly affect serum TH levels. However, TH concentrations in pregnant or lactating females were found to be significantly lower than in the other sex and reproductive groups investigated. The EFI and epithelial height (EH) were greater in spring subadult and adult whales compared with those that were landed in the fall. No correlation was found between serum TH concentrations and serum, blubber, or liver levels of select polychlorinated biphenyl metabolites and organochlorine congeners examined. Low variability in concentrations of the serum THs across age, season, and sex and reproductive groups supports the existence of strong homeostatic mechanisms for maintaining TH concentrations in these presumably healthy animals. Departures from these ranges may indicate a disturbance in these regulatory mechanisms and may be a useful indication of toxicity or other health disorders.
When pigeons in motion lose sight of their food: behaviour on visible displacement tasks revisited
Authors: Krachun C. , Plowright C.M.S.
Published: June 2007

In traditional visible displacement tasks, animals view an object as it is moved out of their sight, but either the object moves behind an occluder or an occluder moves in front of it. Here we present a more ecologically realistic visible displacement task for pigeons ( Columba livia (Gmelin, 1789)) in which it was the animal that occluded the object, a food dish in this case, by virtue of its own motion. In a branched maze, pigeons had visual access to food, which they would lose from view as they moved through the maze. A within-subject design was used whereby the task was presented first in descending order of difficulty (i.e., decreasing memory load owing to the opening of (i) gaps and (ii) windows in the walls of the maze), and followed 10 months later by an ascending order. When the food was visible at all times through windows and gaps, pigeons would make turns in the maze that would bring them closer to the food (i.e., they chose the shortest route above chance levels). In general, they failed to do so when the food was lost from view, but there was one exception at the end of the study (the second time that there were gaps but no windows): there was a significant tendency for the last two turns that brought the bird out of the maze to be the shortest route to the food. The pigeons may have learned to take advantage of opportunities to lighten their memory load.
Male body size varies with latitude in a temperate lizard
Authors: Howes Briar J. , Lougheed Stephen C.
Published: June 2007

To examine the evolution of sexual size dimorphism (SSD), interspecific studies are often performed to generate hypotheses for the origin and maintenance of SSD. Although these methods are invaluable to our understanding of the evolution of SSD, they often quantify SSD for a species based on few populations. We found a significant sex-specific latitudinal cline in Plestiodon fasciatus (L., 1758) (=  Eumeces fasciatus (L., 1758)), a species that was previously considered to be monomorphic for body size. Male body size significantly increased with increasing latitude, whereas female body size was relatively constant. Our findings argue for the importance of increased understanding and appreciation of intraspecific variation in SSD. We suggest that a more integrated approach to SSD be employed, where both intraspecific and interspecific variation is considered. We provide a foundation for posing hypotheses of the causes and consequences of SSD in P. fasciatus and perhaps other members of the species group.
Assessment of the Vascular Effects of PC6 (Neiguan) Using the Second Derivative of the Finger Photoplethysmogram in Healthy and Hypertensive Subjects
Authors: Rivas-Vilchis José F. , Hernández-Sánchez Fernando , González-Camarena Ramón , Suárez-Rodríguez Luis D. , Escorcia-Gaona Ricardo , Cervantes-Reyes Jorge A. , Román-Ramos Rubén
Published: June 2007

Indices obtained from the second derivative of the digital volume pulse waveform have been proposed to characterize vascular aging, arterial rigidity, and the effects of vasoactive drugs. The purpose of this study was to assess the effects of manual needling of PC6 on SDDVP indices in healthy and untreated hypertensive subjects. AI, B:A, and D:A indices, based on the height of the wave components of SDDVP, in 40 healthy subjects and 25 untreated hypertensive subjects were compared. DVP was obtained by measuring infrared light transmission through the finger. For each subject, 20-min-long DVP registration was obtained. PC6 was stimulated unilaterally by manual needling for 5 min (1–6 min). In each subject, pre-acupuncture DVP indices were compared to those of during acupuncture (1 vs. 4 min) and post-acupuncture (1 vs. 18 min). In healthy subjects, AI was significantly improved when comparing the pre- to the post-acupuncture values. In hypertensive subjects, the SDDVP indices improved significantly as follows: the AI index when the value of pre-acupuncture comparing to that of during acupuncture and post-acupuncture values; B:A and D:A indices when the pre-comparing to post-acupuncture values. There were significant differences between healthy and hypertensive subjects in AI, B:A, and D:A at baseline and in B:A in the during acupuncture period; there were no significant differences at post-acupuncture. These results indicate that manual needling of PC6 produced acute effects on vascular pathophysiology. Moreover, PC6 needling produced changes in SDDVP indices related to both large artery stiffness and the reflected wave originating in small arteries.
PERFORMANCE MEASUREMENT IN MILITARY PROVISIONS: THE CASE OF RETAIL STORES OF TAIWAN'S GENERAL WELFARE SERVICE MINISTRY
Authors: YANG CHYAN , WANG JAMES TSUNG-CHENG , LU WEN-MIN
Published: June 2007

This paper aims to explore the operating efficiency and the benchmark-learning roadmap of the military retail stores for Taiwan's General Welfare Service Ministry (GWSM). This study also presents an extension to the data envelopment analysis (DEA) method, by incorporating the traditional DEA, stratification DEA, attractiveness measure, and progress measure for assessing the performance of 31 retail stores of GWSM. The assessment can assist the Ministry of National Defense to improve the operational management of GWSM and to help the military retail stores on better delivering and efficient service to soldiers, veterans, and their dependents. The potential applications and strengths of DEA in assessing the military retail stores are highlighted.
DYNAMIC PARAMETER DESIGN BY ANT COLONY OPTIMIZATION AND NEURAL NETWORKS
Authors: CHANG HSU-HWA , CHEN YAN-KWANG , CHEN MU-CHEN
Published: June 2007

Parameter design is the most important phase in the development of new products and processes, especially in regards to dynamic systems. Statistics-based approaches are usually employed to address dynamic parameter design problems; however, these approaches have some limitations when applied to dynamic systems with continuous control factors. This study proposes a novel three-phase approach for resolving the dynamic parameter design problems as well as the static characteristic problems, which combines continuous ant colony optimisation (CACO) with neural networks. The proposed approach trains a neural network model to construct the relationship function among response, inputs and parameters of a dynamic system, which is then used to predict the responses of the system. Three performance functions are developed to evaluate the fitness of the predicted responses. The best parameter settings can be obtained by performing a CACO algorithm according to the fitness value. The best parameter settings that are obtained are no longer restricted to the values of control factor levels. The proposed approach is demonstrated with two illustrative examples. Results show that the proposed approach outperforms the Taguchi method.
ON THE CONSTRUCTION OF GAP FUNCTIONS FOR VARIATIONAL INEQUALITIES VIA CONJUGATE DUALITY
Authors: ALTANGEREL LKHAMSUREN , BOŢ RADU IOAN , WANKA GERT
Published: June 2007

In this paper, we deal with the construction of gap functions for variational inequalities by using an approach which bases on the conjugate duality. Under certain assumptions we also investigate a further class of gap functions for the variational inequality problem, the so-called dual gap functions.
EXTENSION OF THE FREQUENCY-RANGE OF INTERFEROMETERS FOR THE "MAGNETIC" COMPONENTS OF GRAVITATIONAL WAVES?
Authors: CORDA CHRISTIAN
Published: June 2007

Recently, with an enlightening treatment, Baskaran and Grishchuk have shown the presence and importance of the so-called "magnetic" components of gravitational waves (GW's), which have to be taken into account in the context of the total response functions of interferometers for GW's propagating from arbitrary directions. In this paper the analysis of the response functions for the magnetic components is generalized in its full frequency dependence, while in the work of Baskaran and Grishchuk the response functions were computed only in the approximation of wavelength much larger than the linear dimensions of the interferometer. It is also shown that the response functions to the magnetic components grow at high frequencies, differently from the values of the response functions to the well-known ordinary components that decrease at high frequencies. Thus the magnetic components could in principle become the dominant part of the signal at high frequencies. This is important for a potential detection of the signal at high frequencies and confirms that the magnetic contributions must be taken into account in the data analysis. More, the fact that the response functions of the magnetic components grow at high frequencies shows that, in principle, the frequency-range of Earth-based interferometers could extend to frequencies over 10000 Hz.
A METHOD FOR ESTIMATING FRACTAL DIMENSION OF TREE CROWNS FROM DIGITAL IMAGES
Authors: ZHANG DONGSHENG , SAMAL ASHOK , BRANDLE JAMES R.
Published: June 2007

A new method for estimating fractal dimension of tree crowns from digital images is presented. Three species of trees, Japanese yew (Taxus cuspidata Sieb & Zucc), Hicks yew (Taxus × media), and eastern white pine (Pinus strobus L.), were studied. Fractal dimensions of Japanese yew and Hicks yew range from 2.26 to 2.70. Fractal dimension of eastern white pine range from 2.14 to 2.43. The difference in fractal dimension between Japanese yew and eastern white pine was statistically significant at 0.05 significance level as was the difference in fractal dimension between Hicks yew and eastern white pine. On average, the greater fractal dimensions of Japanese yew and Hicks yew were possibly related to uniform foliage distribution within their tree crowns. Therefore, fractal dimension may be useful for tree crown structure classification and for indexing tree images.
MODIFIED NEAREST NEIGHBOR METHOD FOR MULTISTEP AHEAD TIME SERIES FORECASTING
Authors: ABBAS SYED RAHAT , ARIF MUHAMMAD
Published: June 2007

Multistep ahead time series forecasting has become an important activity in various fields of science and technology due to its usefulness in future events management. Nearest neighbor search is a pattern matching algorithm for forecasting, and the accuracy of the method considerably depends on the similarity of the pattern found in the database with the reference pattern. Original time series is embedded into optimal dimension. The optimal dimension is determined by using autocorrelation function plot. The last vector in the embedded matrix is taken as the reference vector and all the previous vectors as candidate vectors. In nearest neighbor algorithm, the reference vector is matched with all the candidate vectors in terms of Euclidean distance and the best matched pattern is used for forecasting. In this paper, we have proposed a hybrid distance measure to improve the search of the nearest neighbor. The proposed method is based on cross-correlation and Euclidean distance. The candidate patterns are shortlisted by using cross-correlation and then Euclidean distance is used to select the best matched pattern. Moreover, in multistep ahead forecasting, standard nearest neighbor method introduces a bias in the search which results in higher forecasting errors. We have modified the search methodology to remove the bias by ignoring the latest forecasted value during the search of the nearest neighbor in the subsequent iteration. The proposed algorithm is evaluated on two benchmark time series as well as two real life time series.
INTERNET ANOMALY DETECTION BASED ON STATISTICAL COVARIANCE MATRIX
Authors: JIN SHUYUAN , YEUNG DANIEL S. , WANG XIZHAO
Published: June 2007

Intrusion detection is an important part of assuring the reliability of computer systems. Different intrusion detection approaches vary with different patterns used and different intrusions addressed. However, what patterns are effective in constructing a detection system is still a challenge. This paper attempts to apply the traditional covariance matrix concept to the detection of multiple known and unknown network anomalies. With respect to the initiation of typical flood-based network intrusions, the proposed approach takes the measure of covariance matrix to reflect the changes of sequential correlativity of the network traffic when flood-based attacks happen. The differences among covariance matrices of network samples collected in temporal sequences of fixed and equal length are directly evaluated to detect multiple network anomalies. Extensive experiments on the subset of KDDCUP 1999 dataset show that the covariance matrix, as a new pattern, can be directly utilized to construct an effective detection system for flood-based attacks. It also points out that utilizing the covariance matrix in the detection of flood-based attacks can achieve higher performance over traditional approaches.
AUTONOMY-ORIENTED SOCIAL NETWORKS MODELING: DISCOVERING THE DYNAMICS OF EMERGENT STRUCTURE AND PERFORMANCE
Authors: ZHANG SHIWU , LIU JIMING
Published: June 2007

A social network is composed of social individuals and their relationships. In many real-world applications, such a network will evolve dynamically over time and events. A social network can be naturally viewed as a multiagent system if considering locally-interacting social individuals as autonomous agents. In this paper, we present an Autonomy-Oriented Computing (AOC) based model of a social network, and study the dynamics of the network based on this model. In the AOC model, the profile of agents, service-based interactions, and the evolution of the network are defined, and the autonomy of the agents is emphasized. The model can reveal dynamic relationships among global performance, local interaction (partner selection) strategies, and network topology. The experimental results show that the agent network forms a community with a high clustering coefficient, and the performance of the network is dynamically changing along with the formation of the network and the local interaction strategies of the agents. In this paper, the performance and topology of the agent network are analyzed, and the factors that affect the performance and evolution of the agent network are examined.
MINING NON-REDUNDANT ASSOCIATION RULES BASED ON CONCISE BASES
Authors: XU YUE , LI YUEFENG
Published: June 2007

Association rule mining has many achievements in the area of knowledge discovery. However, the quality of the extracted association rules has not drawn adequate attention from researchers in data mining community. One big concern with the quality of association rule mining is the size of the extracted rule set. As a matter of fact, very often tens of thousands of association rules are extracted among which many are redundant, thus useless. In this paper, we first analyze the redundancy problem in association rules and then propose a reliable exact association rule basis from which more concise nonredundant rules can be extracted. We prove that the redundancy eliminated using the proposed reliable association rule basis does not reduce the belief to the extracted rules. Moreover, this paper proposes a level wise approach for efficiently extracting closed itemsets and minimal generators — a key issue in closure based association rule mining.
A PROGRESSIVE CLUSTERING ALGORITHM TO GROUP THE XML DATA BY STRUCTURAL AND SEMANTIC SIMILARITY
Authors: NAYAK RICHI , TRAN TIEN
Published: June 2007

Since the emergence in the popularity of XML for data representation and exchange over the Web, the distribution of XML documents has rapidly increased. It has become a challenge for researchers to turn these documents into a more useful information utility. In this paper, we introduce a novel clustering algorithm PCXSS that keeps the heterogeneous XML documents into various groups according to their similar structural and semantic representations. We develop a global criterion function CPSim that progressively measures the similarity between a XML document and existing clusters, ignoring the need to compute the similarity between two individual documents. The experimental analysis shows the method to be fast and accurate.
SUBSEQUENCE COUNTING AS A MEASURE OF SIMILARITY FOR SEQUENCES
Authors: WANG HUI
Published: June 2007

The longest common subsequence is a well known and popular method for measuring similarity between sequences. It advocates the use of information contained in the longest common subsequence as an indication of similarity. In this paper we consider the count of all common subsequences as a measure of sequence similarity with the view that all common information is captured. This measure is inspired and derived from a generic similarity measure, neighborhood counting metric. The close connection of the neighborhood counting metric with probability and the Bayes classifier helps gain an insight from the probabilistic perspective into the all-common subsequences measure. We design algorithms to calculate this measure and we also carry out an experiment in the framework of k-nearest neighbors on a gene sequence classification task. The experiment shows that the all-common subsequences measure and the longest common subsequence measure have little difference for small k values, but differ significantly for large k values. The performance of the all-common subsequences measure remains steady as k gets larger, but the performance of the longest common subsequence measure drops sharply as k gets larger. Such a property may be useful for those tasks where we are interested not only in the nearest neighbor, but also in the first k nearest neighbors. The main contribution of this paper is a suite of algorithms for finding all common subsequences.
SEQUENTIAL PATTERN MINING AND NONMONOTONIC REASONING FOR INTELLIGENT INFORMATION AGENTS
Authors: LAU RAYMOND Y. K. , LI YUEFENG , WU SHENG-TANG , ZHOU XUJUAN
Published: June 2007

With the explosive growth of information available on the Internet, more effective data mining and data reasoning mechanism is required to process the sheer volume of information. Belief revision logic offers the expressive power to represent information retrieval contexts, and it also provides a sound inference mechanism to model the nonmonotonicity arising in changing retrieval contexts. Contextual knowledge for information retrieval can be extracted via efficient sequential pattern mining. We present a pattern taxonomy extraction model which efficiently performs the task of discovering descriptive frequent sequential patterns by pruning the noisy associations. This paper illustrates a novel approach of integrating the sequential data mining method into the belief revision based adaptive information agents to improve the agents' learning autonomy and prediction power. Initial experiments show that our belief revision logic and sequential pattern mining based intelligent information agents outperform the vector space model based information agents. Our work opens the door to the development of next generation of intelligent information agents to alleviate the information overload problem.
MODEL NET: A REPRESENTATION OF THE STATIC STRUCTURE OF MODELBASE
Authors: QI CHANGSONG , SUN JIGUI
Published: June 2007

Model net proposed in this paper is a kind of directed graph used to represent and analyze the static structure of a modelbase. After the formal definition of the model net was given, a construction algorithm is introduced. Then, two simplification algorithms are put forward to show how this approach can reduce the computational complexity of model composition for a specific decision problem. In succession, a model composition algorithm is worked out based on the simplification algorithms. As a result, this algorithm is capable of finding out all the candidate composite models for a specific decision problem. Finally, several advantages of the model net are discussed briefly.
HARDNESS AND APPROXIMATION OF OCTILINEAR STEINER TREES
Authors: MÜLLER-HANNEMANN MATTHIAS , SCHULZE ANNA
Published: June 2007

Given a point set K of terminals in the plane, the octilinear Steiner tree problem is to find a shortest tree that interconnects all terminals and edges run either in horizontal, vertical, or ±45° diagonal direction. This problem is fundamental for the novel octilinear routing paradigm in VLSI design, the so-called X-architecture.

As the related rectilinear and the Euclidian Steiner tree problem are well-known to be NP-hard, the same was widely believed for the octilinear Steiner tree problem but left open for quite some time. In this paper, we prove the NP-completeness of the decision version of the octilinear Steiner tree problem.

We also show how to reduce the octilinear Steiner tree problem to the Steiner tree problem in graphs of polynomial size with the following approximation guarantee. We construct a planar graph of size [Formula: see text] which contains a (1 + ε)–approximation of a minimum octilinear Steiner tree for every ε > 0 and n = |K|. Hence, we can apply any α–approximation algorithm for the Steiner tree problem in graphs (for planar graphs, Borradaile et al. very recently presented a polynomial time approximation scheme) and achieve an (α + ε)–approximation bound for the octilinear Steiner tree problem. This approximation guarantee also holds for the more difficult case where the Steiner tree has to avoid blockages (obstacles bounded by octilinear polygons).
FRACTAL IMAGE COMPRESSION ALGORITHMS BASED ON POSSIBILITY THEORY
Authors: YANG RUI , YANG XIAOYUAN , LI B.
Published: June 2007

Two fractal image compression algorithms based on possibility theory are originally presented in this paper. Fuzzy sets are used to represent the edge character of each image block, and two kinds of membership function are designed. A fuzzy integrated judgement model is also proposed. The model generates an accurate value for each edge block, which would be a label during the search process. The edge possibility distribution function and the edge necessity level are designed to control the quantity of the blocks to be searched. Meanwhile the pre-restriction is proposed, the average intensity value at different locations is used to be a necessary condition before the MSE computations. It is shown by our experiments that the encoding times of our two algorithms, compared to that of Jacquin's approach, are reduced to 60%–70% and 10%–20%, respectively.
INTERVAL-VALUED REPRESENTABILITY OF QUALITATIVE DATA: THE CONTINUOUS CASE
Authors: BOSI GIANNI , CAMPIÓN MARIA JESÚS , CANDEAL JUAN CARLOS , INDURÁIN ESTEBAN
Published: June 2007

In the framework of the representability of ordinal qualitative data by means of interval-valued correspondences, we study interval orders defined on a nonempty set X. We analyse the continuous case, that corresponds to a set endowed with a topology that furnishes an idea of continuity, so that it becomes natural to ask for the existence of quantifications based on interval-valued mappings from the set of data into the real numbers under preservation of order and topology. In the present paper we solve a continuous representability problem for interval orders. We furnish a characterization of the representability of an interval order through a pair of continuous real-valued functions so that each element in X has associated in a continuous manner a characteristic interval or equivalently a symmetric triangular fuzzy number.
EVALUATING GOVERNMENT WEBSITES BASED ON A FUZZY MULTIPLE CRITERIA DECISION-MAKING APPROACH
Authors: BÜYÜKÖZKAN GÜLÇIN , RUAN DA
Published: June 2007

This paper presents a framework of website quality evaluation for measuring the performance of government websites. Multiple criteria decision-making (MCDM) is a widely used tool for evaluating and ranking problems containing multiple, usually conflicting criteria. In line with the multi-dimensional characteristics of website quality, MCDM provides an effective framework for an inter-websites comparison involving the evaluation of multiple attributes. It thus ranks different websites compared in terms of their overall performance. This paper models the inter-website comparison problem as an MCDM problem, and presents a practical and selective approach to deal with it. In addition, fuzzy logic is applied to the subjectivity and vagueness in the assessment process. The proposed framework is effectively illustrated to rate Turkish government websites.
PERFORMANCE EVALUATION OF FUZZY SINGLE LAYER WEIGHTLESS NEURAL NETWORK
Authors: AL-ALAWI RAIDA
Published: June 2007

The paper evaluates the performance of a neuro-fuzzy pattern classification system based on the weightless neural network architecture. The system utilizes a Single Layer Weightless Neural Network (SLWNN) to extract the features vector that measures the similarity of the input pattern to the different classification groups. In contrast to the traditional crisp Winner-Takes-All (WTA) classification scheme used by SLWNN, our system uses a Fuzzy Inference System (FIS) for classification. The network is trained by a hybrid learning scheme that combines a single pass learning phase for training the SLWNN followed by a supervised learning phase for extracting a set of fuzzy rules suitable to classify the training set. The FIS learns fuzzy rules from the feature vectors generated by the SLWNN for the set of training patterns. The recognition of handwritten numerals is employed as a test-bed to demonstrate the effectiveness of the proposed neuro-fuzzy system. Experimental results show that the performance of the proposed system surpasses the performance of the traditional SLWNN.
INTERVAL METHODS IN KNOWLEDGE REPRESENTATION
Authors: Kreinovich Vladik
Published: June 2007

This section is maintained by Vladik Kreinovich. Please send your abstracts (or copies of papers that you want to see reviewed here) to vladik@utep.edu, or by regular mail to: V. Kreinovich, Department of Computer Science, University of Texas, El Paso, TX 79968, USA.
EFFECTIVE OPTIMIZATION ALGORITHMS FOR FRAGMENT-ASSEMBLY BASED PROTEIN STRUCTURE PREDICTION
Authors: DERONNE KEVIN W. , KARYPIS GEORGE
Published: June 2007

Despite recent developments in protein structure prediction, an accurate new fold prediction algorithm remains elusive. One of the challenges facing current techniques is the size and complexity of the space containing possible structures for a query sequence. Traditionally, to explore this space fragment assembly approaches to new fold prediction have used stochastic optimization techniques. Here, we examine deterministic algorithms for optimizing scoring functions in protein structure prediction. Two previously unused techniques are applied to the problem, called the Greedy algorithm and the Hill-climbing (HC) algorithm. The main difference between the two is that the latter implements a technique to overcome local minima. Experiments on a diverse set of 276 proteins show that the HC algorithms consistently outperform existing approaches based on Simulated Annealing optimization (a traditional stochastic technique) in optimizing the root mean squared deviation between native and working structures.
EFFICIENT COMPUTATION OF MINIMUM RECOMBINATION WITH GENOTYPES (NOT HAPLOTYPES)
Authors: WU YUFENG , GUSFIELD DAN
Published: June 2007

A current major focus in genomics is the large-scale collection of genotype data in populations in order to detect variations in the population. The variation data are sought in order to address fundamental and applied questions in genetics that concern the haplotypes in the population. Since, almost all the collected data is in the form of genotypes, but the downstream genetics questions concern haplotypes, the standard approach to this issue has been to try to first infer haplotypes from the genotypes, and then answer the downstream questions using the inferred haplotypes. That two-stage approach has potential deficiencies, giving rise to the general question of how well one can answer the downstream questions using genotype data without first inferring haplotypes, and giving rise to the goal of computing the range of downstream answers that would be obtained over the range of possible inferred haplotype solutions. This paper provides some tools for the study of those issues, and some partial answers. We present algorithms to solve downstream questions concerning the minimum amount of recombination needed to derive given genotypic data, without first fixing a choice of haplotypes. We apply these algorithms to the goal of finding recombination hotspots, obtaining as good results as a published method that first infers haplotypes; and to the case of estimating the minimum amount of recombination needed to derive the true haplotypes underlying the genotypic data, obtaining weaker results compared to first inferring haplotypes using the program PHASE.
AN ITERATIVE ALGORITHM TO QUANTIFY FACTORS INFLUENCING PEPTIDE FRAGMENTATION DURING TANDEM MASS SPECTROMETRY
Authors: YU CHUNGONG , LIN YU , SUN SHIWEI , CAI JINJIN , ZHANG JINGFEN , BU DONGBO , ZHANG ZHUO , CHEN RUNSHENG
Published: June 2007

In protein identification by tandem mass spectrometry, it is critical to accurately predict the theoretical spectrum for a peptide sequence. To date, the widely-used database searching methods adopted simple statistical models for predicting. For some peptide, these models usually yield a theoretical spectrum with a significant deviation from the experimental one. In this paper, in order to derive an improved predicting model, we utilized a non-linear programming model to quantify the factors impacting peptide fragmentation. Then, an iterative algorithm was proposed to solve this optimization problem. Upon a training set of 1803 spectra, the experimental result showed a good agreement with some known principles about peptide fragmentation, such as the tendency to cleave at the middle of peptide, and Pro's preference of the N-terminal cleavage. Moreover, upon a testing set of 941 spectra, comparison of the predicted spectra against the experimental ones showed that this method can generate reasonable predictions. The results in this paper can offer help to both database searching and de novo methods.