Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

Research Collection School Of Computing and Information Systems

Discipline
Keyword
Publication Year
File Type

Articles 6841 - 6870 of 7016

Full-Text Articles in Entire DC Network

Measurement Of The Fraction Of Hadronic Z Decays Into Charm Quark Pairs, R. Barate, M. Thulasidas Jan 1998

Measurement Of The Fraction Of Hadronic Z Decays Into Charm Quark Pairs, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

The full statistics of hadronic Z decays collected with the ALEPH detector are analysed to measure, by three methods, the ratio, RcRc, of the partial decay width of the Z into cc¯cc¯ quarks to the total hadronic width. One method uses the inclusive pp and p⊥p⊥ spectra of electrons. The other two use a double-tagging technique to measure RcRc independently of the charm-tagging efficiency. In one, the tagging procedure uses the reconstruction of high momentum charmed mesons (D∗+D∗+, D+D+ and \({\rm D^0}$) to detect the charm quarks. In the other, a charm quark is tagged from the D∗D∗'s reconstructed in …


Searches For Charginos And Neutralinos In E+E- Collisions At √S = 161 And 172 Gev, R. Barate, M. Thulasidas Jan 1998

Searches For Charginos And Neutralinos In E+E- Collisions At √S = 161 And 172 Gev, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

The data recorded by the ALEPH detector at centre-of-mass energies of 161, 170, and 172 GeV are analysed for signals of chargino and neutralino production. No evidence of a signal is found, although candidate events consistent with the expectations from Standard Model processes are observed. Limits at 95% C.L. on the production cross sections are derived and bounds on the parameters of the Minimal Supersymmetric Standard Model are set. The lower limit on the mass of the lightest ch is 85.5 GeV/c2GeV/c2 for gaugino-like charginos (μ=−500GeV/c2μ=−500GeV/c2), and 85.0 GeV/c2GeV/c2 for Higgsino-like charginos (M2=500GeV/c2M2=500GeV/c2), for heavy sneutrinos (Mν~≥200GeV/c2Mν~≥200GeV/c2) and tanβ=2–√tan⁡β=2. The …


Study Of B0s Oscillations And Lifetime Using Fully Reconstructed D̄S Decays, R. Barate, M. Thulasidas Jan 1998

Study Of B0s Oscillations And Lifetime Using Fully Reconstructed D̄S Decays, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A search for B0sBs0 oscillations is performed using approximately 4 million Z→qq¯Z→qq¯ events collected by the ALEPH experiment during 1991–1995. B0sBs0 candidates are partially reconstructed by combining tracks with fully reconstructed D−sDs− candidates. The B0sBs0 production flavour is estimated from the sign of the opposite hemisphere charge, a fragmentation kaon in the same hemisphere, or a lepton in the opposite hemisphere. From a total sample of 1620 candidates, with a B0sBs0 purity estimated to be 22%, all values of ΔmsΔms below 3.9 ps−1−1 and between 6.5 and 8.8 ps−1−1 are excluded at 95% CL. From the same sample, the B0sBs0 …


Evaluation Of Information Modeling Methods: A Review, Keng Siau, Matti Rossi Jan 1998

Evaluation Of Information Modeling Methods: A Review, Keng Siau, Matti Rossi

Research Collection School Of Computing and Information Systems

Hundreds of modeling methods are in existence today. Yet practitioners and researchers are zealously "producing" new modeling methods. The "blooming" of modeling methods is not the problem; the lack of standardize techniques for evaluating them is. To further complicate the matter, most of the modeling methods are introduced based on common sense and intuition. Theoretical foundations and empirical evidence are severely lacking. With the current state of affairs, evaluation of modeling methods has become necessary. Comparing modeling methods provides us with the necessary knowledge and understanding on the strengths and weaknesses of each method. This knowledge can also guide us …


Evaluating Information Modeling Methods – A Review, Keng Siau, M. Rossi Jan 1998

Evaluating Information Modeling Methods – A Review, Keng Siau, M. Rossi

Research Collection School Of Computing and Information Systems

Hundreds of modeling methods are in existence today, yet practitioners and researchers are zealously “producing” new modeling methods. The “blooming” of modeling methods is not the problem; the lack of standardized techniques for evaluating them is. To further complicate the matter, most of the modeling methods are introduced based on common sense and intuition. Theoretical foundations and empirical evidence are severely lacking. With the current state of affairs, evaluation of modeling methods has become necessary. Comparing modeling methods provides us with the necessary knowledge and understanding on the strengths and weaknesses of each method. This knowledge can also guide us …


An Interlibrary Loan System On The World Wide Web, Schubert Shou Boon Foo, Ee Peng Lim Jan 1998

An Interlibrary Loan System On The World Wide Web, Schubert Shou Boon Foo, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Inter-Library Loan (ILL) service is one of the services provided by libraries that offers users a way to access library resources beyond their affiliated libraries. Additionally, it allows participating libraries to share and maximize their resources. This work examines the ILL process used by libraries in Singapore and proposes that the existing paper-based manual system be replaced by a Web-based ILL system. Such a Web-based system has been successfully designed and implemented at the Nanyang Technological University. The paper presents an overview of the system requirements and architecture, implementation details and demonstrates the feasibility and advantages of the new system.


An Integrated Web-Based Ill System For Singapore Libraries, Schubert Foo, Ee Peng Lim Jan 1998

An Integrated Web-Based Ill System For Singapore Libraries, Schubert Foo, Ee Peng Lim

Research Collection School Of Computing and Information Systems

The paper proposes an integrated Web-based inter-library loan (ILL) system to replace and enhance the existing manual-based ILL system used by Singapore libraries. It describes the system requirements that must be supported in order to make it a viable and acceptable solution to all participating libraries. Subsequently, it presents the client-server Web-based system architecture, database design and Java development platform that are used to implement the system. The new system exhibits a host of advantages over the manual system including the minimising of human resource by eliminating form-filling and other forms of paper work completely, improving the access and speed …


An Upper Limit On The Τ Neutrino Mass From Three- And Five-Prong Tau Decays, R. Barate, M. Thulasidas Jan 1998

An Upper Limit On The Τ Neutrino Mass From Three- And Five-Prong Tau Decays, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A bound on the tau neutrino mass is established using the data collected from 1991 to 1995 at s√≃mZ with the ALEPH detector. Two separate limits are derived by fitting the distribution of visible energy vs invariant mass in τ−→2π−π+ντ and τ−→3π−2π+(π0)ντ decays. The two results are combined to obtain a 95% confidence level upper limit of 18.2 MeV/c2 on the mass of the tau neutrino.


Studies Of Quantum Chromodynamics With The Aleph Detector, R. Barate, M. Thulasidas Jan 1998

Studies Of Quantum Chromodynamics With The Aleph Detector, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

No abstract provided.


The Effect Of Data Model, System And Task Characteristics On User Query Performance – An Empirical Study, Hock Chan, Keng Siau, Kwok-Kee Wei Dec 1997

The Effect Of Data Model, System And Task Characteristics On User Query Performance – An Empirical Study, Hock Chan, Keng Siau, Kwok-Kee Wei

Research Collection School Of Computing and Information Systems

With the proliferation of end-user computing and empowerment of end users in the organizations, the user-database interface is increasingly being recognized as an important research area. A user-database interface consists of two key components: the data model and the query language. Database management system designers can manipulate these two components to produce an effective database interface to maximize user task performance. However, in order to do this, the designers first need to know the effect of the two components on end users and the interaction effect of the two components. Despite the acknowledgment of user-database interface as a cornerstone in …


Inclusive Production Of Neutral Pions In Hadronic Z Decays, R. Barate, M. Thulasidas Dec 1997

Inclusive Production Of Neutral Pions In Hadronic Z Decays, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

A measurement of the inclusive production of π0 mesons in hadronic Z decays is presented and compared to Monte Carlo model predictions. The analysis is based on approximately 2 million hadronic events recorded with the ALEPH detector at LEP at a centre-of-mass energy of ⊡s = 91.2 GeV. Neutral pions are reconstructed using photons measured in the electromagnetic calorimeter and photons from conversion pairs. The inclusive π0 momentum spectrum is measured in the range 0.025 x p = p/p beam 0 per hadronic Z is found to be 4.80 ± 0.07(stat) ± 0.31(sys). The differential inclusive π0 cross section is …


Updated Measurement Of The Τ Lepton Lifetime, R. Barate, Manoj Thulasidas Nov 1997

Updated Measurement Of The Τ Lepton Lifetime, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

A new measurement of the mean lifetime of the τ lepton is presented. Three different analysis methods are applied to a sample of 90000 τ pairs, collected in 1993 and 1994 with the ALEPH detector at LEP. The average of this measurement and those previously published by ALEPH is ττ = 290.1±1.5±1.1fs.


Searches For Scalar Top And Scalar Bottom Quarks At Lep2, Barate, R.; Et Al., M. Thulasidas Nov 1997

Searches For Scalar Top And Scalar Bottom Quarks At Lep2, Barate, R.; Et Al., M. Thulasidas

Research Collection School Of Computing and Information Systems

Searches for scalar top and bottom quarks have been performed with data collected by the ALEPH detector at LEP. The data sample consists of 21.7 pb−1 taken at √ s = 161, 170, and 172 GeV and 5.7 pb−1 taken at √ s = 130 and 136 GeV. No evidence for scalar top quarks or scalar bottom quarks was found in the channels ˜t → cχ, ˜t → bℓν˜, and b˜ → bχ. For the channel ˜t → cχ a limit of 67 GeV/c 2 has been set on the scalar top quark mass, independent of the mixing angle between …


Search For The Standard Model Higgs Boson In E+E- Collisions At √S = 161, 170 And 172 Gev, Barate, R.; Et Al., M. Thulasidas Oct 1997

Search For The Standard Model Higgs Boson In E+E- Collisions At √S = 161, 170 And 172 Gev, Barate, R.; Et Al., M. Thulasidas

Research Collection School Of Computing and Information Systems

The reaction e+ e ! HZ is used to search for the Standard Model Higgs boson. The data sample consists of integrated luminosities of 10:9 pb1 , 1:1 pb1 , and 9:5 pb1 collected by the ALEPH experiment at LEP during 1996, at centre-of-mass energies of 161, 170 and 172 GeV, respectively. No candidate events were found, in agreement with the expected background of 0.84 events from all Standard Model processes. This search results in a 95% C.L. lower limit on the Higgs boson mass of 69:4 GeV=c2 . When combined with earlier ALEPH searches performed at energies at and …


Search For Sleptons In E+E- Collisions At Centre-Of-Mass Energies Of 161 Gev And 172 Gev, R. Barate, Manoj Thulasidas Sep 1997

Search For Sleptons In E+E- Collisions At Centre-Of-Mass Energies Of 161 Gev And 172 Gev, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

The data recorded by the ALEPH experiment at LEP at centre–of–mass energies of 161 GeV and 172 GeV were analysed to search for sleptons, the supersymmetric partners of leptons. No evidence for the production of these particles was found. The number of candidates observed is consistent with the background expected from four–fermion processes and γγ–interactions. Improved mass limits at 95% C.L. are reported.


A Measurement Of The Qcd Colour Factors And A Limit On The Light Gluino, Barate, R.; Et Al., M. Thulasidas Sep 1997

A Measurement Of The Qcd Colour Factors And A Limit On The Light Gluino, Barate, R.; Et Al., M. Thulasidas

Research Collection School Of Computing and Information Systems

Using data collected from 1992 to 1995 with the ALEPH detector at LEP, a measurement of the colour factor ratios CA/CF and TF /CF and the strong coupling constant αs = CFαs(MZ)/(2π) has been performed by fitting theoretical predictions simultaneously to the measured differential two-jet rate and angular distributions in four-jet events. The result is found to be in excellent agreement with QCD, {fx4-1} Fixing CA/CF and TF/CF to the QCD values permits a determination of αs(MZ) and ηf, the number of active flavours. With this measurement the existence of a gluino with mass below 6.3 GeV/c2 is excluded at …


Theoretical Foundation For Relationship Construct In Information Modeling – Relation Element Theory, Keng Siau Aug 1997

Theoretical Foundation For Relationship Construct In Information Modeling – Relation Element Theory, Keng Siau

Research Collection School Of Computing and Information Systems

Information modeling is a critical process in software development. One of the key constructs in information modeling is the relationship construct. Though commonly used, the relationship construct is poorly defined and lacks a strong theoretical foundation. The objectives of this research are to define and classify the various relationships based on a theory in linguistic known as the relation element theory. This paper describes the theory, relates the theory to the relationship construct, and discusses the implication of the theory on the relationship construct.


Influence And Consensus In Group Decision Making Environment, Fiona Fui-Hoon Nah, Byungcho Kim Aug 1997

Influence And Consensus In Group Decision Making Environment, Fiona Fui-Hoon Nah, Byungcho Kim

Research Collection School Of Computing and Information Systems

In this research, the effect of expert support on influence and consensus in group decision making is investigated. The results indicate that ESS support diminishes the group members' influence on the group judgment as well as the influence exerted by the most influential group member. On the other hand, explanations support provided by ESS increases consensus in group decision making.


Multiple Representation For Understanding Data Structures, Biffah Hancies, Venky Shankararaman, Jose Munoz Aug 1997

Multiple Representation For Understanding Data Structures, Biffah Hancies, Venky Shankararaman, Jose Munoz

Research Collection School Of Computing and Information Systems

In this paper an approach to enhance the learning of abstract computing concepts by novice students is presented. This approach is based on effective use of multiple visual representations, and it was applied within the domain of linear data structures: array, stack, queue and linked list. A prototype computer-based instructional system called MRUDS (Multiple Representation for Understanding Data Structures) was developed and evaluated. It was found from the evaluation that the three presentation modules namely, analogy, representation and algorithm contributed to the students' learning process, each contributing to and reinforcing the effect of the others.


Report On The 5th Ifip International Workshop On Quality Of Service, Oguz Angin, Andrew T. Campbell, Lai Tee Cheok, Raymond Liao, Koon-Seng Lim, Klara Nahrstedt Jul 1997

Report On The 5th Ifip International Workshop On Quality Of Service, Oguz Angin, Andrew T. Campbell, Lai Tee Cheok, Raymond Liao, Koon-Seng Lim, Klara Nahrstedt

Research Collection School Of Computing and Information Systems

This paper presents a summary of the fifth International Workshop on Quality of Service (IWQOS) which was held at Columbia University in May 1997. The goal of this three-day meeting was to foster interaction between researchers active in the area of Quality of Service(QOS) research, to reflect on past experiences and lessons learnt, and to discuss future QOS challenges. To reflect this goal, this year's workshop included a hot program made up of (i) a keynote address on "Programming Telecommunications Networks"; (ii) panels addressing "QOS for Distributed Object Computing Middleware --- Fact or Fiction?" and "Reservations about Reservations"; (iii) a …


Measurement Of The Transverse Spin Correlations In The Decay Z → Τ+Τ-, Barate, R.; Et Al., M. Thulasidas Jul 1997

Measurement Of The Transverse Spin Correlations In The Decay Z → Τ+Τ-, Barate, R.; Et Al., M. Thulasidas

Research Collection School Of Computing and Information Systems

A measurement of the transverse-transverse, CTT, and transverse-normal CTN, τ spin correlations in the decay Z0 → τ+ τ− is presented based on the aplanarity angle of the decay products of both taus. Based on 80 pb−1 of data collected by ALEPH[1] in 1992, 1993 and 1994 on the peak of the Z resonance, the results are: CTT = 1.00 ± 0.14(stat) ± 0.04(syst), CTN =−0.08 ± 0.14(stat) ± 0.02(syst). These values are in agreement with the Standard Model predictions, CTT = 0.989 and CTN = 0.


Measurement Of The Branching Fraction For D0 → K-Π+, R. Barate, M. Thulasidas Jun 1997

Measurement Of The Branching Fraction For D0 → K-Π+, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

The branching fraction for D0 → K−π+ is measured with the statistics collected by ALEPH from 1991 to 1994. The method is based on the comparison between the rate for the reconstructed D∗+→ D0π+, D0 → K−π+ decay chain and the rate for inclusive soft pion production at low transverse momentum with respect to the nearest jet. The result is B(D0 → K−π+0 = (3.90 ± 0.09 ± 0.12)%


Search For The Bc Meson In Hadronic Z Decays, R. Barate, Manoj Thulasidas Jun 1997

Search For The Bc Meson In Hadronic Z Decays, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

A search for the Bc meson decaying into the channels Jψπ+ and Jψℓ+νℓ (ℓ = e or μ) is performed in a sample of 3.9 million hadronic Z decays collected by the ALEPH detector. This search results in the observation of 0 and 2 candidates in each of these channels, respectively, while 0.44 and 0.81 background events are expected. The following 90% confidence level upper limits are derived:Br(Z→BcXBr(Z→qq̄Br(Bc+→Jψπ+)


A Measurement Of Rb Using A Lifetime-Mass Tag, R. Barate, Manoj Thulasidas May 1997

A Measurement Of Rb Using A Lifetime-Mass Tag, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

ALEPH's published measurement of Rb = Γ(Ζ → bb̄)/Γ(Ζ → hadrons) using a lifetime tag is updated using the full LEP 1 data sample. Considerable effort has been devoted to understanding systematic effects. Charm background is better controlled by combining the lifetime tag with a tag based on the b/c hadron mass difference. Furthermore, the algorithm used to reconstruct the event primary vertex is designed so as to reduce correlations between the two hemispheres of an event. The value of Rb is measured to be 0.2167 ± 0.0011 (stat) ± 0.0013 (syst).


Study Of Muon-Pair Production At Centre-Of-Mass Energies From 20 To 136 Gev With The Aleph Detector, R. Barate, M. Thulasidas May 1997

Study Of Muon-Pair Production At Centre-Of-Mass Energies From 20 To 136 Gev With The Aleph Detector, R. Barate, M. Thulasidas

Research Collection School Of Computing and Information Systems

The total cross section and the forward-backward asymmetry for the process e+e− → μ+μ−(nγ) are measured in the energy range 20–136 GeV by reconstructing the effective centre-of-mass energy after initial state radiation. The analysis is based on the data recorded with the ALEPH detector at LEP between 1990 and 1995, corresponding to a total integrated luminosity of 143.5 pb−1. Two different approaches are used: in the first one an exclusive selection of events with hard initial state radiation in the energy range 20–88 GeV is directly compared with the Standard Model predictions showing good agreement. In the second one, all …


Source-Aware Multidatabase Query Processing, Ee Peng Lim, Yinyan Cao, Roger Hsiang-Li Chiang May 1997

Source-Aware Multidatabase Query Processing, Ee Peng Lim, Yinyan Cao, Roger Hsiang-Li Chiang

Research Collection School Of Computing and Information Systems

We introduce a multidatabase model to represent the information that derives from different local databases. This model, known as Tuple-Source (TS) relational model, accommodates tuples from different local databases by attaching them with their source information in the global relations which are also known as TS-relations. In other words, a source attribute is implicit in every TS-relation. To manipulate the global relations, we have developed the TSSQL query language and implemented a distributed query processor to process such queries. In this paper, we report our distributed query processing architecture and algorithms. Our architecture consists of a query mediator and a …


A Measurement Of Rb Using Mutually Exclusive Tags, R. Barate, Manoj Thulasidas May 1997

A Measurement Of Rb Using Mutually Exclusive Tags, R. Barate, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

A measurement of Rb using ve mutually exclusive hemisphere tags has been performed by ALEPH using the full LEP1 statistics. Three tags are designed to select the decay of the Z0 to b quarks, while the remaining two select Z0 decays to c and light quarks, and are used to measure the tagging eciencies. The result, Rb = 0:2159 0:0009(stat) 0:0011(syst), is in agreement with the electroweak theory prediction of 0:21580:0003.


Distributed Query Processing For Structured And Bibliographic Databases, Ee Peng Lim, Ying Lu Apr 1997

Distributed Query Processing For Structured And Bibliographic Databases, Ee Peng Lim, Ying Lu

Research Collection School Of Computing and Information Systems

To support future digital library systems which draw information from different sources on the internet, we have to provide integrated queries to pre-existing database servers which contain structured, semi-structured and unstructured data. In this paper, we specifically examine the problem of querying both existing structured relational databases and bibliographic databases. By adopting the well-accepted Z39.50 standard protocol to access bibliographic databases in different legacy library systems, we have developed an extended SQL model, known as HarpSQL, to support integrated queries to both SQL databases and bibliographic databases. Using HarpSQL, one can not only query bibliographic databases in an SQL manner, …


Cascade Artmap: Integrating Neural Computation And Symbolic Knowledge Processing, Ah-Hwee Tan Mar 1997

Cascade Artmap: Integrating Neural Computation And Symbolic Knowledge Processing, Ah-Hwee Tan

Research Collection School Of Computing and Information Systems

This paper introduces a hybrid system termed cascade adaptive resonance theory mapping (ARTMAP) that incorporates symbolic knowledge into neural-network learning and recognition. Cascade ARTMAP, a generalization of fuzzy ARTMAP, represents intermediate attributes and rule cascades of rule-based knowledge explicitly and performs multistep inferencing. A rule insertion algorithm translates if-then symbolic rules into cascade ARTMAP architecture. Besides that initializing networks with prior knowledge can improve predictive accuracy and learning efficiency, the inserted symbolic knowledge can be refined and enhanced by the cascade ARTMAP learning algorithm. By preserving symbolic rule form during learning, the rules extracted from cascade ARTMAP can be compared …


A System For Query Comprehension, Hock Chuan Chan, Kwok Kee Wei, Keng Siau Mar 1997

A System For Query Comprehension, Hock Chuan Chan, Kwok Kee Wei, Keng Siau

Research Collection School Of Computing and Information Systems

A major difficulty of query writing is that users do not fully understand queries. A system providing feedback is proposed so as to enable users to better understand their queries. It is a multi-functional rule-based system. In addition to providing an English translation for the query, it pin-points syntax errors, and suggests possible solutions. It also finds likely semantic errors, and provides possible solutions. The system was implemented for a query language based on the entity relationship model. It is expected to lead to better user performance. Empirical testing showed significant improvement in user performance with the feedback system. The …