Science and Technology Studies Commons^™

An Adaptive Channel Tracking Method For Mimo- Ofdm Systems, Jun Tong, Yaohuan Gong, Shengxian Sun

Faculty of Engineering and Information Sciences - Papers: Part A

The tracking of the time-varying channel is crucial for MIMO-OFDM wireless communication systems. Aiming at doubly-selective fading MIMO channels, we present a novel pilot pattern and the corresponding adaptive channel tracking algorithm. Compared with the traditional pilot patterns, the new pattern has higher frequency efficiency and is more suitable for large transmit arrays. The computational complexity, frequency efficiency and BER performance of the system assisted by the proposed channel tracking scheme are analyzed. Simulation results demonstrate that the proposed scheme can track the timevarying channel effectively

Finite-Element Analysis To Determine Effect Of Monolimb Flexibility On Structural Strength And Interaction Between Residual Limb And Prosthetic Socket, Winson Lee, Ming Zhang, David A. Boone, Bill Contoyannis

Faculty of Engineering and Information Sciences - Papers: Part A

Monolimb refers to a kind of transtibial prostheses having the socket and shank molded into one piece of thermoplastic material. One of its characteristics is that the shank is made of a material that can deform during walking, which can simulate ankle joint motion to some extent. Changes in shank geometry can alter the stress distribution within the monolimb and at the residual limb-socket interface and, respectively, affect the deformability and structural integrity of the prosthesis and comfort perceived by amputees. This paper describes the development of a finite-element model for the study of the structural behavior of monolimbs with …

Finite Element Modeling Of Contact Interface Between Trans-Tibial Residual Limb And Prosthetic Socket, Winson Lee, Ming Zhang, Xiaohong Jia, Jason Cheung

Faculty of Engineering and Information Sciences - Papers: Part A

Finite element method has been identified as a useful tool to understand the load transfer mechanics between a residual limb and its prosthetic socket. This paper proposed a new practical approach in modeling the contact interface with consideration of the friction/slip conditions and pre-stresses applied on the limb within a rectified socket. The residual limb and socket were modeled as two separate structures and their interactions were simulated using automated contact methods. Some regions of the limb penetrated into the socket because of socket modification. In the first step of the simulation, the penetrated limb surface was moved onto the …

Load Transfer Mechanics Between Trans-Tibial Prosthetic Socket And Residual Limb-Dynamic Effects, Xiaohong Jia, Ming Zhang, Winson Lee

Faculty of Engineering and Information Sciences - Papers: Part A

The effects of inertial loads on the interface stresses between trans-tibial residual limb and prosthetic socket were investigated. The motion of the limb and prosthesis was monitored using a Vicon motion analysis system and the ground reaction force was measured by a force platform. Equivalent loads at the knee joint during walking were calculated in two cases with and without consideration of the material inertia. A 3D nonlinear finite element (FE) model based on the actual geometry of residual limb, internal bones and socket liner was developed to study the mechanical interaction between socket and residual limb during walking. To …

Study On The Mechanism Of The Squeeze-Strengthen Effect In Magnetorheological Fluids, Xianzhou Zhang, X L. Gong, P Q. Zhang, Q M. Wang

Faculty of Engineering and Information Sciences - Papers: Part A

Current magnetorheological (MR)fluids have the limitation that their yield stresses are not strong enough to meet some industrial requirements. X. Tang, X. Zhang, and R. Tao [J. App. Phys87, 2634 (2000)] proposed a method to achieve high-efficiency MR fluids by study of squeeze-strengthen effect. But there is little report on its mechanism. This paper aims to investigate this effect through experimental and theoretical approaches. For this purpose, an apparatus is designed to experimentally study the mechanism of this squeeze-strengthen effect. Taking account of a modified magnetic dipole model and the friction effect, a semiempirical model is proposed to explain this …

Smoothing With Mixed Model Software, Long Ngo, M P. Wand

Faculty of Engineering and Information Sciences - Papers: Part A

Smoothing methods that use basis functions with penalization can be formulated as fits in a mixed model framework. One of the major benefits is that software for mixed model analysis can be used for smoothing. We illustrate this for several smoothing models such as additive and varying coefficient models for both S-PLUS and SAS software. Code for each of the illustrations is available on the Internet.

Effect Of Aging And Deformation On The Microstructure And Properties Of Fe-Ni-Ti Maraging Steel, A Shekhter, H I. Aaronson, M K. Miller, S P. Ringer, E V. Pereloma

Faculty of Engineering and Information Sciences - Papers: Part A

The age-hardening behavior of Fe−25.3Ni−1.7 Ti (wt pct) alloy both in undeformed specimens and in specimens cold deformed by 10 or 20 pct prior to aging was studied. The microstructural changes during aging were observed using transmission electron microscopy (TEM) and atom probe analysis and there were related to the mechanical properties as measured by microhardness and shear punch testing. An excellent combination of hardness, strength, and ductility was achieved after only 5 seconds aging at 550°C. We propose that this rapid strengthening is due to a dislocation friction effect arising from the formation of a fine dispersion of Ni−Ti …

Role Of Cr And P Additions In The Development Of Microstructure And Texture In Annealed Low Carbon Steels, E V. Pereloma, I B. Timokhina, A I. Nosenkov, J J. Jonas

Faculty of Engineering and Information Sciences - Papers: Part A

The recrystallisation behaviour of four warm rolled steels was investigated during annealing. The extra-low carbon (ELC) steel displayed the highest rate of recrystallisation, the steels with additions of chromium and phosphorus (LC(Cr)), (LC(Cr,P)) recrystallised at intermediate rates, while the interstitial-free (IF) steel exhibited the lowest rate. The additions of Cr and Cr/P increased the fraction of g-fibre in the annealing textures compared to that present in the ELC steel; this effect was particularly pronounced up to 50 % recrystallisation. After the completion of recrystallisation, the steel textures were characterized by a dominant g-fibre in the IF steel, while in the …

Effect Of Microstructure On The Stability Of Retained Austenite In Transformation-Induced-Plasiticity Steels, I B. Timokhina, P D. Hodgson, E V. Pereloma

Faculty of Engineering and Information Sciences - Papers: Part A

Two Fe-0.2C-1.55Mn-1.5Si (in wt pct) steels, with and without the addition of 0.039Nb (in wt pct), were studied using laboratory rolling-mill simulations of controlled thermomechanical processing. The microstructures of all samples were characterized by optical metallography, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural behavior of phases under applied strain was studied using a heat-tinting technique. Despite the similarity in the microstructures of the two steels (equal amounts of polygonal ferrite, carbide-free bainite, and retained austenite), the mechanical properties were different. The mechanical properties of these transformation-induced-plasticity (TRIP) steels depended not only on the individual behavior of all …

Massive Increase In The Stiffness Of The Human Lens Nucleus With Age: The Basis For Presbyopia?, Karl Robert Heys, Sandra Leigh Cram, Roger J W Truscott

Faculty of Engineering and Information Sciences - Papers: Part A

Purpose: To determine the stiffness of different regions of human lenses as a function of age, and to correlate the biophysical measurements in the lens center with nuclear water content.

Methods: A custom made probe fitted to a dynamic mechanical analyzer was employed to measure stiffness values at 1 mm increments across equatorial sections of individual human lenses. Thermogravimetric analysis was used to determine the percentage water content in the nuclei of human lenses.

Results: There was a pronounced increase in lens stiffness over the age range from 14 to 78. In the nucleus, stiffness values varied almost 1,000 fold …

On A Heat Problem Involving The Perturbed Hardy-Sobolev Operator, Nirmalendu Chaudhuri, Kunnath Sandeep

Faculty of Engineering and Information Sciences - Papers: Part A

No abstract provided.

Mansfield's Imprimitivity Theorem For Arbitrary Closed Subgroups, Astrid An Huef, Iain Raeburn

Faculty of Engineering and Information Sciences - Papers: Part A

No abstract provided.

Cuntz-Krieger Algebras Of Infinite Graphs And Matrices, Iain Raeburn, Wojciech Szymanski

Faculty of Engineering and Information Sciences - Papers: Part A

We show that the Cuntz-Krieger algebras of infinite graphs and infinite {0,1}-matrices can be approximated by those of finite graphs. We then use these approximations to deduce the main uniqueness theorems for Cuntz-Krieger algebras and to compute their K-theory. Since the finite approximating graphs have sinks, we have to calculate the K-theory of Cuntz-Krieger algebras of graphs with sinks, and the direct methods we use to do this should be of independent interest.

Estimation Of Diffusion Coefficients, Lateral Shear Stress, And Velocity In Open Channels With Complex Geometry, Shu-Qing Yang, Jian-Xing Yu, Yuan-Zhan Wang

Faculty of Engineering and Information Sciences - Papers: Part A

The lateral distributions of depth-averaged apparent shear stress, depth mean velocity, and diffusion coefficients are essential in certain quantitative analysis for sediment transport and environmental studies. An analytical method for the computation of these parameters is presented. A mathematical relationship between these parameters, based on the concept of surplus energy transport through a minimum relative distance developed by Yang and Lim [1997], is established, the depth-averaged apparent shear stress is determined from the boundary shear stress, depth mean velocity is obtained by considering the influence of nonuniform shear velocity and the free surface in 3-D channels, and the diffusion coefficients …

A Note On Devaney's Definition Of Chaos, Joseph Tonien

Faculty of Engineering and Information Sciences - Papers: Part A

Devaney defines a function to be chaotic if it satisfies three conditions: transitivity, having dense set of periodic points and sensitive dependence on initial conditions. Banks et al prove that if the function is continuous then the third conditioin is implied from the first two and therefore is redundant. However, if the function is not assumed to be continuous, then it is not known if the third condition is redundant or not.

In this note, without assuming the function is continuous, we prove that the third condition is redundant if the underlying topological space is not precompact.

Linear Code Implies Publicf-Key Traitor Tracing With Revocation, Joseph Tonien, Rei Safavi-Naini

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper, we show that the linear-coded Kurosawa–Desmedt scheme can be modified to allow revocation of users, that is to show a revocation scheme can be derived from a linear code.

Energy Injection By Distributed Generation For Improvement In Feeder-Voltage Profile, Kashem M. Muttaqi, Gerard Ledwich

Faculty of Engineering and Information Sciences - Papers: Part A

No abstract provided.

Code Compression Based On Operand-Factorization For Vliw Processors, Montserrat Ros, Peter Sutton

Faculty of Engineering and Information Sciences - Papers: Part A

Code compression techniques have been devised as a way of battling large code. Code compression algorithms usually require specific techniques to maintain the integrity of the program and ensure its functionality. RISC processors have been the main focus for code compression techniques but VLIW (Very Long Instruction Word) processors are now being considered in this area.

A Hamming Distance Based Vliw/Epic Code Compression Technique, Montserrat Ros, Peter Sutton

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents and reports on a VLIW code compression technique based on vector Hamming distances [19]. It investigates the appropriate selection of dictionary vectors such that all program vectors are at most a specified maximum Hamming distance from a dictionary vector. Bit toggling information is used to restore the original vector. A dictionary vector selection method which considered both vector frequency as well as maximum coverage achieved better results than just considering vector frequency or vector coverage independently. This method was found to outperform standard dictionary compression on TI TMS320C6x program code by an average of 8%, giving compression …

Improving Adaboost For Classification On Small Training Sample Sets With Active Learning, Lei Wang, Xuchun Li, Eric Sung

Faculty of Engineering and Information Sciences - Papers: Part A

Recently, AdaBoost has been widely used in many computer vision applications and has shown promising results. However, it is also observed that its classification performance is often poor when the size of the training sample set is small. In certain situations, there may be many unlabelled samples available and labelling them is costly and time-consuming. Thus it is desirable to pick a few good samples to be labelled. The key is how. In this paper, we integrate active learning with AdaBoost to attack this problem. The principle idea is to select the next unlabelled sample base on it being at …

Synchrotron Radiation Based Experimental Determination Of The Optimal Energy For Cell Radiotoxicity Enhancement Following Photoelectric Effect On Stable Iodinated Compounds, S Corde, A Joubert, J F. Adam, A M. Charvet, J F. Le Bas, F Esteve, H Elleaume, J Balosso

Faculty of Engineering and Information Sciences - Papers: Part A

This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml1 of iodine radiological contrast agent or cells pre-exposed with 10 mM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with …

What Prevent B2b Ecommerce Adoption In Developing Countries?: A Socio-Cultural Perspective, Savanid Vatanasakdakul, William Tibben, Joan Cooper

Faculty of Engineering and Information Sciences - Papers: Part A

It is widely believed that B2B e-commerce will help firms in developing countries to reduce cost and to improve their access to global market. Yet, developing countries are still some way from success in their adoption of B2B e-commerce. This paper explores social and cultural perspectives that impact on B2B e-commerce adoption in developing countries. Interviews were conducted with key informants from various industries in Thailand. Some common problems related to social and cultural issues faced by industries are presented. It was found that even though B2B e-commerce was implemented in many firms, its use was still very limited. Firms …

Design-Side Considerations: A Reaction To Duem, Robert B. K. Brown

Faculty of Engineering and Information Sciences - Papers: Part A

Evaluation of a system's usability is a difficult task, but a new method, DUEM, addresses several of the issues. Any evaluation conducted after the fact however has limited effect, so further work is required at the design end of the lifecycle. Early-Phase elicitation tools, such as i*, may form the basis for new design tools which simplify software development, improve usability and ensure greater system success. Informing such design tools with the principles of the latest Activity Theory-based usability evaluation methods, such as DUEM should facilitate easier testing. As an added benefit, such a design method can form the first …

Myth Or Fact: Is Open Source Software More Secure Than Closed Source Software?, Daniel Saffioti, Gene Awyzio, Robert B. K. Brown

Faculty of Engineering and Information Sciences - Papers: Part A

This paper examines one aspect of quality that organizations look for when selecting software, namely security. Studies over time have indicated that security; scalability, interoperability and flexibility are important however the major issue has always been support. This has led to the sometimes inflexible concept of Standard Operating Environments (SOEs) within organisations. Whilst SOEs provide many benefits to an organisation they can leave them vulnerable to several large security risks. CERT statistics show that security incidents have increased six fold since 2000 [1]. This paper will examine trends in both open and closed software development for a number of platforms …

A Review Of Routing Protocols For Mobile Ad Hoc Networks, Mehran Abolhasan, Tadeusz Wysocki, Eryk Dutkiewicz

Faculty of Engineering and Information Sciences - Papers: Part A

The 1990s have seen a rapid growth of research interests in mobile ad hoc networking. The infrastructureless and the dynamic nature of these networks demands new set of networking strategies to be implemented in order to provide efficient end-to-end communication. This, along with the diverse application of these networks in many different scenarios such as battlefield and disaster recovery, have seen MANETs being researched by many different organisations and institutes. MANETs employ the traditional TCP/IP structure to provide end-to-end communication between nodes. However, due to their mobility and the limited resource in wireless networks, each layer in the TCP/IP model …

A Systematic Study Of Radio-Induced X-Ray Cavities In Clusters, Groups, And Galaxies, L Birzan, D A. Rafferty, B R. Mcnamara, M W. Wise, Paul E. J Nulsen

Faculty of Engineering and Information Sciences - Papers: Part A

We present an analysis of 16 galaxy clusters, one group, and one galaxy drawn from the Chandra Data Archive. These systems possess prominent X-ray surface brightness depressions associated with cavities or bubbles that were created by interactions between powerful radio sources and the surrounding hot gas. The central galaxies in these systems harbor radio sources with luminosities ranging between ∼2 × 10 38 and 7 × 10 44 ergs s -1. The cavities have an average radius of ∼10 kpc, and they lie at an average projected distance of ∼20 kpc from the central galaxy. The minimum energy associated with …

Summability For Nonunital Spectral Triples, Adam C. Rennie

Faculty of Engineering and Information Sciences - Papers: Part A

This paper examines the issue of summability for spectral triples for the class of nonunital algebras. For the case of (p, -) summability, we prove that the Dixmier trace can be used to define a (semifinite) trace on the algebra of the spectral triple. We show this trace is well-behaved, and provide a criteria for measurability of an operator in terms of zeta functions. We also show that all our hypotheses are satisfied by spectral triples arising from eodesically complete Riemannian manifolds. In addition, we indicate how the Local Index Theorem of Connes-Moscovici extends to our nonunital setting.

Maple+Grtensorii Libraries For Cosmology, Dumitru N. Vulcanov, Valentina-Mira Wheeler

Faculty of Engineering and Information Sciences - Papers: Part A

The article mainly presents some results in using MAPLE platform for com- puter algebra (CA) and GrTensorII package in doing calculations for theoretical and numerical cosmology.

An Investigation Into The Effects Of Heat Transfer On The Motion Of A Spherical Bubble, P J Harris, H Al-Awadi, Wee King Soh

Faculty of Engineering and Information Sciences - Papers: Part A

This paper investigates the effect of heat transfer on the motion of a spherical bubble in the vicinity of a rigid boundary. The effects of heat transfer between the bubble and the surrounding fluid, and the resulting loss of energy from the bubble, can be incorporated into the simple spherical bubble model with the addition of a single extra ordinary differential equation. The numerical results show that for a bubble close to an infiniterigid boundary there are significant differences in both the radius and Kelvin impulse of the bubble when the heat transfer effects are included.

The Limiting Ideal Theory For Shear-Index Cohesionless Granular Materials, Grant Cox, James Hill

Faculty of Engineering and Information Sciences - Papers: Part A

To model cohesionless granular flow using continuum theory, the usual approach is to assume the cohesionless Coulomb-Mohr yield condition. However, this yield condition assumes that the angle of internal friction is constant, when according to experimental evidence for most powders the angle of internal friction is not constant along the yield locus, but decreases for decreasing normal stress component σ from a maximum value of π/2. For this reason, we consider here the more general yield function which applies for shear-index granular materials, where the angle of internal friction varies with σ. In this case, failure due to frictional slip …