bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum Dot‐Based Protein Imaging and Functional Significance of Two Mitochondrial Chaperones in Cellular Senescence and Carcinogenesis
Authors: KAUL ZEENIA , YAGUCHI TOMOKO , KAUL SUNIL C. , WADHWA RENU
Published: June 2006

Abstract:  Mortalin/mtHSP70 and HSP60 are heat‐shock proteins that reside in multiple subcellular compartments, mitochondria being the dominant compartment. We present here biochemical evidence for their in vivo and in vitro interactions. By the use of quantum dots (powerful tools used for simultaneous imaging of multiple proteins), we visualized minute differences in the subcellular niche of these two proteins in normal and cancer cells. Knockdown of either of these two by shRNA expression plasmids caused growth arrest of osteosarcoma cells. However, interestingly, whereas an overexpression of mortalin extended in vitro life span of normal fibroblasts (TIG‐1), overexpression of HSP60 was neutral. We demonstrate the minute differences in subcellular distribution of mortalin and HSP60, their involvement in tumorigenesis, and functional distinction in pathways involved in senescence.
Phage‐Displayed Antibodies for the Detection of Glycated Proteasome in Aging Cells
Authors: GONZALEZ‐DOSAL REGINA , SØRENSEN MORTEN DRÆBY , CLARK BRIAN F.C. , RATTAN SURESH I. S. , KRISTENSEN PETER
Published: June 2006

Abstract:  Accumulation of posttranslationally damaged proteins during aging could explain the decline of cell performance with age. Nɛ‐carboxymethyllysine (CML) is the major glycation product on damaged proteins, causing dysfunction and cross‐linking. The proteasome, a multicatalytic degradation complex, is one of the pathways for eliminating damaged proteins, and thus regulating their accumulation within the cell. However, the proteinase activities of the proteasome decline during aging. This may be due to posttranslational modifications of the subunits forming the proteasome complex. Using phage display technology, we have selected 16 single‐chain variable fragments (scFv) recognizing the CML‐modified α7 subunit of the proteasome. Using one of them, Ab3, we have observed a five‐fold increase of CML‐α7 in old human skin fibroblasts in comparison with young fibroblasts and telomerase‐immortalized bone marrow cells (hTERT‐BMCs).
Age‐Dependent Effects of in Vitro Radiofrequency Exposure (Mobile Phone) on CD95+ T Helper Human Lymphocytes
Authors: CAPRI MIRIAM , SALVIOLI STEFANO , ALTILIA SERENA , SEVINI FEDERICA , REMONDINI DANIEL , MESIRCA PIETRO , BERSANI FERDINANDO , MONTI DANIELA , FRANCESCHI CLAUDIO
Published: June 2006

Abstract:  Recent studies on “nonthermal” effects of mobile phone radiofrequency (RF) suggest that RF can interact with cellular functions and molecular pathways. To study the possible RF effects on human lymphocyte activation, we analyzed CD25, CD95, CD28 molecules in unstimulated and stimulated CD4+ e CD8+ T cells in vitro. Peripheral blood mononuclear cells (PBMCs) from young and elderly donors were exposed or sham‐exposed to RF (1,800 MHz, Specific Absorption Rate 2 W/kg) with or without mitogenic stimulation. No significant changes in the percentage of these cell subsets were found between exposed and sham‐exposed lymphocytes in both young and elderly donors. Nevertheless, after RF exposure we observed a slight, but significant, downregulation of CD95 expression in stimulated CD4+ T lymphocytes from elderly, but not from young donors. This age‐related result is noteworthy given the importance of a such molecule in regulation of the immune response.
Effect of Chest X-Rays on the Risk of Breast Cancer Among BRCA1/2 Mutation Carriers in the International BRCA1/2 Carrier Cohort Study: A Report from the EMBRACE, GENEPSO, GEO-HEBON, and IBCCS Collaborators’ Group
Authors: Andrieu Nadine , Easton Douglas F. , Chang-Claude Jenny , Rookus Matti A. , Brohet Richard , Cardis Elisabeth , Antoniou Antonis C. , Wagner Teresa , Simard Jacques , Evans Gareth , Peock Susan , Fricker Jean-Pierre , Nogues Catherine , Veer Laura Van't , Van Leeuwen Flora E. , Goldgar David E.
Published: June 2006

Purpose

Women who carry germline mutations in the BRCA1 and BRCA2 genes are at greatly increased risk of breast cancer (BC). Numerous studies have shown that moderate to high doses of ionizing radiation are a risk factor for BC. Because of the role of the BRCA proteins in DNA repair, we hypothesized that BRCA carriers might be more sensitive to ionizing radiation than women in the general population.

Patients and Methods

A retrospective cohort study of 1,601 female BRCA1/2 carriers was performed. Risk of breast cancer from exposure to chest x-rays, as assessed by questionnaire data, was analyzed using a weighted Cox proportional hazards model.

Results

In this cohort, any reported exposure to chest x-rays was associated with an increased risk of BC (hazard ratio [HR] = 1.54; P = .007). This risk was increased in carrier women aged 40 years and younger (HR = 1.97; P < .001) and in women born after 1949 (HR = 2.56; P < .001), particularly those exposed only before the age of 20 years (HR = 4.64; P < .001).

Conclusion

In our series of BRCA carriers, we detected a relatively large effect on BC risk with a level of radiation exposure that is at least an order of magnitude lower than in previously studied medical radiation–exposed cohorts. Although part of this increase may be attributable to recall bias, the observed patterns of risk in terms of age at exposure and attained age are consistent with those found in previous studies. If confirmed, the results have important implications for the use of x-ray imaging in young BRCA1/2 carriers.
Principal component analysis for Riemannian manifolds, with an application to triangular shape spaces
Authors: Huckemann Stephan , Ziezold Herbert
Published: June 2006

Classical principal component analysis on manifolds, for example on Kendall's shape spaces, is carried out in the tangent space of a Euclidean mean equipped with a Euclidean metric. We propose a method of principal component analysis for Riemannian manifolds based on geodesics of the intrinsic metric, and provide a numerical implementation in the case of spheres. This method allows us, for example, to compare principal component geodesics of different data samples. In order to determine principal component geodesics, we show that in general, owing to curvature, the principal component geodesics do not pass through the intrinsic mean. As a consequence, means other than the intrinsic mean are considered, allowing for several choices of definition of geodesic variance. In conclusion we apply our method to the space of planar triangular shapes and compare our findings with those of standard Euclidean principal component analysis.
On the total length of the random minimal directed spanning tree
Authors: Penrose Mathew D. , Wade Andrew R.
Published: June 2006

In Bhatt and Roy's minimal directed spanning tree construction for a random, partially ordered set of points in the unit square, all edges must respect the ‘coordinatewise’ partial order and there must be a directed path from each vertex to a minimal element. We study the asymptotic behaviour of the total length of this graph with power-weighted edges. The limiting distribution is given by the sum of a normal component away from the boundary plus a contribution introduced by the boundary effects, which can be characterized by a fixed-point equation, and is reminiscent of limits arising in the probabilistic analysis of certain algorithms. As the exponent of the power weighting increases, the distribution undergoes a phase transition from the normal contribution being dominant to the boundary effects being dominant. In the critical case in which the weight is simple Euclidean length, both effects contribute significantly to the limit law.
Slepian models for the stochastic shape of individual Lagrange sea waves
Authors: Lindgren Georg
Published: June 2006

Gaussian wave models have been successfully used since the early 1950s to describe the development of random sea waves, particularly as input to dynamic simulation of the safety of ships and offshore structures. A drawback of the Gaussian model is that it produces stochastically symmetric waves, which is an unrealistic feature and can lead to unconservative safety estimates. The Gaussian model describes the height of the sea surface at each point as a function of time and space. The Lagrange wave model describes the horizontal and vertical movements of individual water particles as functions of time and original location. This model is physically based, and a stochastic version has recently been advocated as a realistic model for asymmetric water waves. Since the stochastic Lagrange model treats both the vertical and the horizontal movements as Gaussian processes, it can be analysed using methods from the Gaussian theory. In this paper we present an analysis of the stochastic properties of the first-order stochastic Lagrange waves model, both as functions of time and as functions of space. A Slepian model for the description of the random shape of individual waves is also presented and analysed.
Fractional Laplace motion
Authors: Kozubowski T. J. , Meerschaert M. M. , Podgórski K.
Published: June 2006

Fractional Laplace motion is obtained by subordinating fractional Brownian motion to a gamma process. Used recently to model hydraulic conductivity fields in geophysics, it might also prove useful in modeling financial time series. Its one-dimensional distributions are scale mixtures of normal laws, where the stochastic variance has the generalized gamma distribution. These one-dimensional distributions are more peaked at the mode than is a Gaussian distribution, and their tails are heavier. In this paper we derive the basic properties of the process, including a new property called stochastic self-similarity. We also study the corresponding fractional Laplace noise, which may exhibit long-range dependence. Finally, we discuss practical methods for simulation.
Stability of spatial queueing systems
Authors: Bordenave C.
Published: June 2006

In this paper, we analyze a queueing system characterized by a space-time arrival process of customers served by a countable set of servers. Customers arrive at points in space and the server stations have space-dependent processing rates. The workload is seen as a Radon measure and the server stations can adapt their power allocation to the current workload. We derive the stability region of the queueing system in the usual stationary ergodic framework. The analysis of this stability region gives some counter-intuitive results. Some specific subclasses of policy are also studied. Wireless communications networks is a natural field of application for the model.
Sufficient conditions for stability of longest-queue-first scheduling: second-order properties using fluid limits
Authors: Dimakis Antonis , Walrand Jean
Published: June 2006

We consider the stability of the longest-queue-first scheduling policy (LQF), a natural and low-complexity scheduling policy, for a generalized switch model. Unlike that of common scheduling policies, the stability of LQF depends on the variance of the arrival processes in addition to their average intensities. We identify new sufficient conditions for LQF to be throughput optimal for independent, identically distributed arrival processes. Deterministic fluid analogs, proved to be powerful in the analysis of stability in queueing networks, do not adequately characterize the stability of LQF. We combine properties of diffusion-scaled sample path functionals and local fluid limits into a sharper characterization of stability.
Decay rates for quasi-birth-and-death processes with countably many phases and tridiagonal block generators
Authors: Motyer Allan J. , Taylor Peter G.
Published: June 2006

We consider the class of level-independent quasi-birth-and-death (QBD) processes that have countably many phases and generator matrices with tridiagonal blocks that are themselves tridiagonal and phase independent. We derive simple conditions for possible decay rates of the stationary distribution of the ‘level’ process. It may be possible to obtain decay rates satisfying these conditions by varying only the transition structure at level 0. Our results generalize those of Kroese, Scheinhardt, and Taylor, who studied in detail a particular example, the tandem Jackson network, from the class of QBD processes studied here. The conditions derived here are applied to three practical examples.
A simple integer-valued bilinear time series model
Authors: Doukhan P. , Latour A. , Oraichi D.
Published: June 2006

In this paper, we extend the integer-valued model class to give a nonnegative integer-valued bilinear process, denoted by INBL(p,q,m,n), similar to the real-valued bilinear model. We demonstrate the existence of this strictly stationary process and give an existence condition for it. The estimation problem is discussed in the context of a particular simple case. The method of moments is applied and the asymptotic joint distribution of the estimators is given: it turns out to be a normal distribution. We present numerical examples and applications of the model to real time series data on meningitis andEscherichia coliinfections.
Comparative Study of Evaluation of Primary Isoclinic Data by Various Spatial Domain Methods in Digital Photoelasticity
Authors: Ramji M , Gadre V Y , Ramesh K
Published: June 2006

With the advent of PC-based digital image processing systems, automation of parameter estimation based on intensity processing from the entire field has now become simpler. Various methods for obtaining the isoclinic parameter using plane, circular, and mixed polariscopes have been reported in the literature. A comparative study has been conducted on the performance of these methods both qualitatively and quantitatively. The focus of the study is on how these algorithms provide the basic isoclinic data. To illustrate the performance, theoretically simulated and experimentally recorded images for a ring under diametral compression is used. The role of background light intensity and quarter-wave plate mismatch on the experimental evaluation of isoclinic data is brought out.
Creep Failure Behaviour of a 9CrMoNbV Weld Metal with Anisotropy Under a Biaxial Loading State
Authors: Hyde T H , Sun Wei
Published: June 2006

The ‘bulk’ material creep failure behaviour of an anisotropic 9CrMoNbV weld metal, under biaxial loading conditions, was investigated, using creep damage analyses with a ‘unit cell’ model. The model consists of a columnar region and a weaker ‘equiaxed’ (fine-grained and coarse-grained) region. Creep damage analyses were conducted using a single-variable Kachanov-type damage law, for which the material constants were obtained from experimental data. The bulk material creep rupture lives, under a range of biaxial load ratios, were determined, including the effects of a triaxial stress state parameter for the material. The typical failure modes are described and isochronous creep rupture curves and master load loci are presented.
A Crack Initiation Threshold Methodology in Fretting Fatigue
Authors: Araújo J. A , Vivacqua R. C , da Silva Bernardo A. T , Mamiya E. N
Published: June 2006

This work aims to develop a fretting crack initiation threshold methodology based on the application of high cycle fatigue (HCF) multiaxial models. The proposed methodology considers the use of multiaxial stress based models, which define safe and damage zones in an appropriate stress space, associated with a volume-averaging procedure. The methodology proved satisfactory in estimating the fretting fatigue limit of simple experiments using cylindrical contacts and was also able to capture the size effect phenomenon present in such tests.
Passenger Thermal Comfort in Vehicles - A Review
Authors: Walgama C , Fackrell S , Karimi M , Fartaj A , Rankin G W
Published: June 2006

A comprehensive survey is presented of research studies regarding thermal comfort issues in the vehicle passenger compartment environment. The work is classified according to whether it is concerned with the passenger compartment environment or the condition of the passengers and their interaction with the compartment. The review includes factors associated with passenger compartment conditions, such as flow field and temperature field, which affect the thermal comfort of the occupants. The evolution of thermal comfort models is reviewed. Also included are various computational and empirical models for predicting physiological response and the sensation of thermal comfort in the non-uniform transient environment of a vehicle. The use of thermal manikins in these studies is also incorporated. Areas in which additional information is required are identified and comments are made regarding future research directions.
Wheel-Slip Control of a Passenger Vehicle Using an Electrorheological Valve Pressure Modulator
Authors: Choi Seung-Bok , Cho M-S , Wereley N M
Published: June 2006

This paper presents a wheel slip control for the anti-lock brake system (ABS) of a passenger vehicle using a controllable electrorheological (ER) valve pressure modulator. As a first step, the principal design parameters of the ER valve and hydraulic booster are appropriately determined by considering the braking pressure variation during the ABS operation. An electrically controllable pressure modulator is then constructed and its pressure controllability is evaluated empirically. Subsequently, a quarter-car wheel slip model is established and integrated with the governing equation of the pressure modulator. A sliding mode controller to achieve the desired slip rate is then designed and implemented via the hardware-in-the-loop simulation (HILS). Braking control performance and road transition control response are evaluated and presented in the time domain.
Robust Tracking of Vibration Profiles for the Exhaust Durability Test
Authors: Kim Hwa Soo , Lee Ho Sung , Cho Young Man , Kim Han-Jun
Published: June 2006

This paper presents a robust controller for the exhaust durability test that enables precise tracking of the vibration profiles against parameter variations. First, the dynamics between the hydraulic actuator input and the acceleration on the exhaust pipe are unravelled via a nonparametric system identification method to establish the baseline system behaviour. Next, the physics-based modelling leads to a parametric model whose dynamics match those of the nonparametric one under various conditions and, as a result, provide a clue for the root causes of the parameter variations. The structured uncertainties arising from the parameter variations naturally call for a robust control design methodology based on the μ-synthesis. The extensive validation tests show that the proposed robust control system clearly delivers the desired performance of tracking vibration profiles during the exhaust durability test while overcoming parameter variations.
Thermodynamic Simulation of Scroll Compressor/Expander Module in Automotive Fuel Cell Engine
Authors: Yuanyang Zhao , Liansheng Li , Pengcheng Shu
Published: June 2006

Considering the leakage and heat transfer, the mathematical model of the scroll compressor/expander module (CEM) used in the automotive fuel cell systems is developed based on thermodynamics theory. The performance of the scroll CEM is simulated at different rotation speed, operating pressure, inlet temperature, and so on. The simulated results show that the power consumed by the scroll CEM is about 50 per cent of that of just the scroll compressor. However, for different operating pressures, the consumed power of the scroll CEM has the least value at the design point. The power consumed by the scroll CEM decreases about 4.5 per cent when the inlet temperature rises from 0 to 35°C. The flowrate of dry air increases with the rise of the scroll CEM rotation speed. Moreover, it decreases 11.4 per cent when the scroll CEM inlet temperature changes from 0 to 35 °C.
Advanced Protection for Vulnerable Road Users: A Case Study
Authors: Moxey E , Johnson N , McCarthy M G , Galloway L , Parker G A , McLundie W M
Published: June 2006

There is increasing international interest in collision avoidance and more recently in safety systems for ‘vulnerable road users’ (VRUs). Pedestrians and cyclists (VRUs) account for approximately one in four of all road deaths in the European Union. The aim of the ‘advanced protection for vulnerable road users’ (APVRU) project was to develop a sensor system capable of detecting VRUs, distinguishing them from the road environment, tracking their position, and predicting potential impacts with the vehicle. The proposed fusion of sensor data from multiple, short-range, high-accuracy, pulse radar units and a low-resolution passive infrared sensor array served to eliminate the majority of clutter by negating false triangulation combinations, while ensuring that only thermally distinct, moving targets are considered. The intention is that a derivative of the sensor system may eventually provide the technological link between VRU detection and a driver warning, collision avoidance, and/or the activation of a safety system on the vehicle (external airbags). The performance of this preliminary, ‘proof-of-concept’ APVRU system was demonstrated during real-world accident scenarios, impacting with an anthropometric dummy, at speeds, limited by current hardware, up to 25 km/h (15.5 mile/h).
Modal Analysis of In-Use Emissions from Heavy-Duty Diesel Engines: On-Board Measurement
Authors: Krishnamurthy M , Gautam M
Published: June 2006

This paper reports the results of modal analysis performed to determine the episodic nature of events and emissions for engine operation within the not-to-exceed (NTE) zone, for each of the selected routes. West Virginia University developed a portable emissions measurement device called the mobile emissions measurement system to obtain engine operating conditions, vehicle speed, and in-use brake-specific emissions of CO2 and NOx from heavy-duty vehicles, tested on specific routes, which included a mix of highway and city driving patterns. The contribution of each mode to variations in emissions rates has been documented. The average brake-specific emissions of NOx and CO2 show a strong dependence on the driving modes and were the highest when the engine operated in the cruise mode. The amounts of time that the engine spends in the NTE region and also over continuous 30 s windows of NTE operation for the different routes were calculated. Results indicate that longer operation in the NTE region produced higher brake-specific emissions of NOx compared with their shorter operating counterparts. The primary implication of this work is that emission control strategies and policies should be focused on the mode of operation of the vehicle during on-road operation, in addition to existing procedures.
Effects of Compression Ratio on Performance, Combustion, and Emission Characteristics of an HCCI Engine
Authors: Hu Tiegang , Liu Shenghua , Zhou Longbao , Li Wei
Published: June 2006

The effects of the dimethyl ether (DME) homogeneous charge compression ignition (HCCI) engine compression ratio on its performance, combustion, and emission characteristics were studied experimentally on a modified single-cylinder diesel engine. Three kinds of compression ratio, 8, 10.7, and 14, were designed by separately enlarging the volume of the combustion chamber on the piston head. The experimental results indicate that the HCCI engine has a wider stable working region and higher effective thermal efficiency at ε = 10.7. It was also found that an increased compression ratio produces advanced ignition and increased energy release rates. The variety of compression ratio has no effect on NOx and smoke emission and the DME HCCI engine achieves smokeless combustion and zero NOx emission with all the designed compression ratio; CO emission is reduced with an increase of compression ratio at comparable working conditions; HC emission presents a dramatic result, the highest at ε = 10.7 and the lowest at ε = 14.
Study of the Effect of Spark Ignition on Gasoline HCCI Combustion
Authors: Wang Zhi , Wang Jian-Xin , Shuai Shi-Jin , Tian Guo-Hong , An Xinliang , Ma Qing-Jun
Published: June 2006

Homogeneous charge compression ignition (HCCI) has challenges with regard to ignition control. A spark-assisted gasoline HCCI combustion strategy was used to control ignition of HCCI combustion. In this paper, the effects of spark ignition (SI) on HCCI combustion were investigated on a gasoline direct injection (GDI) engine. The experimental results show that SI improves the stability of HCCI combustion at HCCI critical status (HCCI-CS). At the transition from SI to HCCI mode, the transition fluctuations can be smoothed by the SI in SI/HCCI hybrid combustion engine. Local SI can trigger entire HCCI in the cylinder at sub-HCCI-CS. Without SI, misfire occurs at sub-HCCI-CS. The reason is that local high temperature and pressure owing to local heat release from the spark electrode leads to increase of temperature and pressure in the entire cylinder. When the temperature and concentration of mixture are below sub-HCCI-CS, SI has little effect on HCCI ignition.
A Sensitivity Analysis of Design Attributes and Operating Conditions on Tyre Operating Temperatures and Rolling Resistance Using Finite Element Analysis
Authors: Narasimha Rao K V , Kumar R Krishna , Bohara P C
Published: June 2006

The hysteresis characteristics of tyre materials primarily contribute to operating temperatures and rolling resistance. The experimental results of these characteristics measured for different tyres at various operating conditions, pavement surface texture, and tyre wear clearly indicate a complex relationship among various design attributes and operating conditions. It is extremely difficult to develop analytical models that can be used to study these complex relationships and, therefore, one should rely completely on experimental results. However, experimental techniques to study these tyre characteristics are highly expensive and complex. In addition to this, the manufacture of an actual tyre for each design alternative will increase significantly the tyre development cycle and, in addition, have a severe impact on the overall economy. In this study, a three-stage sequential model using finite element (FE) technique is used to determine these characteristics for tyres with smooth and circumferential groove tread profiles. An FE algorithm is developed with Petrov-Galerkin Eulerian technique in cylindrical coordinates and is used to determine three-dimensional tyre-operating temperatures. A sensitivity analysis has been made with various operating conditions and tyre design attributes that will aid tyre designers to realize improved designs with reduced rolling resistance and acceptable temperatures.
Development of a Heavy-Duty Engine Test Cycle Representative of On-Highway Not-To-Exceed Operation
Authors: Krishnamurthy M , Gautam M
Published: June 2006

This paper describes the development of an engine test cycle that is representative of the real-world heavy-duty engine activity in the not-to-exceed (NTE) zone of operation. The test cycle is intended to provide an in-laboratory verification capability to determine if an engine exceeds the in-use emissions standards. By simulating the real-world driving pattern of the vehicle the test cycles provide the most realistic estimation of emission levels in the NTE zone of operation. It is well recognized that traditional laboratory test cycles do not provide an accurate representation of a vehicle's operation on the road under present-day driving conditions. This cycle was developed by collecting and analysing engine activity data and statistical information on heavy-duty vehicle use for different applications under real-world conditions. A test vehicle instrumented with the West Virginia University mobile emissions measurement system (MEMS), a portable on-board tailpipe exhaust emissions measurement system, was used to obtain engine operating conditions, vehicle speed, and in-use brake-specific emissions of CO2 and NO x. The vehicle was tested on specific routes, which included a mix of highway and city driving patterns. The speed and torque points were normalized according to procedures described in the Code of Federal Regulations (CFR) Title 40, Part 1065. A representative transient cycle that was developed has been used to conduct emissions tests on heavy-duty diesel engines, and serves to characterize NO x emissions during the NTE operation. This characterization will aid in-laboratory testing and provide a better understanding of the emissions behaviour during on-road NTE operation, electronic control module calibrations, and engine development. The results indicate that the on-highway NTE cycle called the ‘WVU NTE cycle’ produced emissions results that were within ±1 per cent of those produced during an on-road test.
Study on the Performance and Emissions of a Compression Ignition Engine Fuelled with Fischer-Tropsch Diesel Fuel
Authors: Yongcheng Huang , Longbao Zhou , Shangxue Wang , Shenghua Liu
Published: June 2006

Fischer-Tropsch (F-T) diesel fuel is characterized by a high cetane number, a near-zero sulphur content, and a very low aromatic level. In the present paper, the performance and emissions of an unmodified single-cylinder direct injection diesel engine operating on F-T diesel fuel are studied and compared with those of conventional diesel fuel operation. The results show that F-T diesel fuel exhibits a slightly longer injection delay and injection duration, displays an 18.7 per cent average shorter ignition delay, and has a lower peak value of premixed burning rate and a higher peak value of diffusion burning rate than conventional diesel fuel. The engine with F-T diesel fuel has a slightly lower peak combustion pressure and a far lower rate of pressure rise, and consequently a lower mechanical load and combustion noise compared with conventional diesel fuel. In addition, the brake specific fuel consumption is lower and the brake fuel conversion efficiency is higher for F-T diesel fuel operation. The CO2, HC, CO, NO x, and smoke emissions with F-T diesel fuel are reduced at all operating conditions when compared with conventional diesel fuel. On average, NO x and smoke emissions are reduced by 16.7 and 40.3 per cent respectively with F-T diesel fuel. The study demonstrates that F-T diesel fuel is an excellent clean alternative fuel for diesel engines.
Effect of Engine Operation Parameters, Fuel Property and Exhaust Gas Treatment on Exhaust Odour in Direct Injection Diesel Engines
Authors: Roy M M
Published: June 2006

This study investigated the effect of engine parameters: injection timing, exhaust gas re-circulation (EGR), engine speed, injection pressure, compression ratio, and others; alternate fuels n-heptane, n-decane and methyl tertiary butyl ether (MTBE); and exhaust gas treatment by catalytic converters, water-washing and air-dilution systems on exhaust odour in direct injection (DI) diesel engines. Engine parameters, injection timing and injection pressure are found most promising for the effective control of odourous emissions. To test the effect of fuel properties on odour, n-heptane, a low boiling point fuel, n-decane a fuel with high cetane number and an oxygenated fuel MTBE are investigated. The fuel n-decane shows a great prospect to reduce exhaust odour. In exhaust gas treatment, a catalytic converter is attempted first. The catalytic converter is very promising in reducing exhaust odour when the engine exhaust temperature is 200 °C or more. This happens when the engine is under load. But at the idling condition of the engine, the exhaust gas temperature is much below of 200 °C (hardly 100–120 °C). In this condition, the use of catalytic converters is ineffective. Here new ideas of water-washing and air-dilution of exhaust gases have been introduced. The water-washing and air-dilution systems are found very effective to reduce odour at the idling condition of the engine.
A Wavelet Packet and Residual Analysis Based Method for Hydraulic Pump Health Diagnosis
Authors: Gao Yingjie , Zhang Qin
Published: June 2006

This paper presents wavelet packet decomposition (WPD) and wavelet coefficient residual analysis based methods for hydraulic pump health diagnosis. A real-time pump health diagnosis system has been created on the basis of this method. This pump diagnosis system would analyse a short sequence of pump discharge pressure signals to detect if the pump was operating under a healthy condition or not. If the pump were operating with defective conditions, a further diagnosis would be implemented to identify the possible cause(s) of the defect(s). Based on the results obtained from a series of random laboratory tests by randomly selecting one of the four testing pumps 8 times, the developed WPD-residual analysis based pump diagnosis system was missing only one out of a total 32 diagnoses, which represented a 96.9 per cent accuracy rate in health diagnosis. Out of 23 fault diagnosing tests, 21 returned a correct diagnosis, resulting in a 91.3 per cent accuracy rate. The study also found that the accuracy rate could be further improved by taking available information from more packets to support fault diagnosis. It is worth pointing out that, while this method was tested against a hydraulic pump, it can also be applied to other equipment.
Steady State Rolling Analysis of a Radial Tyre: Comparison with Experimental Results
Authors: Ghoreishy M H R
Published: June 2006

This research paper is devoted to the description of a finite element model for the numerical study of a radial tyre under steady state rolling condition. The finite element model was developed using the commercial computer software ABAQUS. The simulation started with an axisymmetric model to analyse the tyre under inflation pressure load. Then a full three-dimensional model was generated for the modelling of the tyre under static vertical load. Having obtained the tyre configuration under contact load, a steady state rolling analysis was conducted using a mixed Lagrangian/Eulerian technique. In this stage, a constant ground velocity was assumed and the spinning velocity was changed to find the free rolling speed of the tyre. The computed loaded dimensions of the tyre in both static and dynamic situations were also compared with experimentally measured data for three commercial tyres available on the market. The comparison verified the validity and applicability of the proposed model. In addition, the distributions of pressure and frictional shear stress fields at the contact zone are presented and discussed.
Effect of a Dual-Mass Flywheel on the Impact-Induced Noise in Vehicular Powertrain Systems
Authors: Theodossiades S , Gnanakumarr M , Rahnejat H , Kelly P
Published: June 2006

The appearance and persistence of impact-induced clonk noise in rear wheel drive light truck drivelines has led to an urgent need for remedial action. The pressure for delivering results within tight schedules and financial constraints has resulted in palliative actions rather than fundamental investigations. It has been speculated that the use of a dual-mass flywheel (DMF) can lead to attenuation of clonk metallic noise, even though its main purpose has been to counter transmission rattle by reducing the input torsional impulse. The present work investigates the effect of DMF on impact-induced clonk noise and its severity through experimentation. Sound measurements in the driveline only reveal a slight reduction in the overall levels of impact-induced noise, but a significant change in its quality - the sharpness associated with the typical metallic content of clonk is absent. The effect is also highlighted by the main frequency content of the response when DMF is employed. The duration of the clonk phenomenon is altered from the case where a traditional single solid-mass flywheel is employed.
Design and Analysis of a Speed-Dependent Torsional Vibration Absorber
Authors: Wu Feng-Tai , Cheng Chih-Chun
Published: June 2006

A novel design of a vibration absorber used in reducing the torsional vibration of a crankshaft is proposed. When a crankshaft is rotating, its natural frequency corresponding to the first torsional mode varies due to the inertia force. The proposed vibration absorber is installed inside the cavity of the front pulley and rotates with the crankshaft. Therefore its natural frequency also varies with the rotating speed. The objective is to design a vibration absorber whose torsional natural frequency not only varies with the rotating speed but also coincides with the varying natural frequency of the rotating crankshaft. Thus it can effectively suppress the torsional vibration of the crankshaft when a vehicle cruises at a varying speed. Results from numerical simulations using the finite element method show that the torsional vibration of the crankshaft can be reduced by more than 45 dB.
Effects of Ageing on the Biomechanical Properties of Rat Articular Cartilage
Authors: Wang L , Kalu D N , Banu J , Thomas J B , Gabriel N , Athanasiou K
Published: June 2006

Previous studies have demonstrated that male Sprague Dawley (SD) rats experience age-related bone loss with the same characteristics as that in ageing men. As articular cartilage, like bone, is a critical component of the health and function of the musculoskeletal system, the authors hypothesized that articular cartilage in the untreated male SD rats could be a suitable model for studying the age-related deterioration of articular cartilage in men. To test this hypothesis, male SD rats were killed at between 6 and 27 months. The right femur of each rat was removed. The effects of ageing on the structural integrity of the distal femoral articular cartilage were studied by biomechanical testing with a creep indentation apparatus. The aggregate modulus, Poisson's ratio, permeability, thickness, and percentage recovery of articular cartilage were determined using finite element/non-linear optimization modelling. No significant differences were observed in these biomechanical properties of the distal femoral articular cartilage as a function of age. Therefore, untreated male SD rats appear to be unsuitable for studying the age-related changes of articular cartilage as they occur in men. However, and more intriguingly, it is also possible that ageing does not affect the biomechanical properties of articular cartilage in the absence of cartilage pathology.
The Role of the Surface Amorphous Layer of Articular Cartilage in Joint Lubrication
Authors: Graindorge S , Ferrandez W , Ingham E , Jin Z , Twigg P , Fisher J
Published: June 2006

Articular cartilage is a complex soft tissue that performs multiple functions in the joint. In particular, the amorphous layer that covers the surface of articular cartilage is thought to play some role in lubrication. This study aimed to characterize the surface amorphous layer (SAL) using a variety of techniques, including environmental scanning electron microscopy, transmission electron microscopy, white light interferometry, and biochemical analysis of its composition. Friction tests were conducted to investigate the role of the SAL in lubrication. A protocol to remove successfully the SAL without damaging the underlying cartilage was developed and the material removed from healthy cartilage was found to contain approximately equal quantities of glycosaminoglycan (GAG), protein, and lipid. Cartilage-on-cartilage friction tests were conducted on fresh, healthy cartilage with and without the SAL, under both dynamic and static operating conditions. Removal of the SAL was not found to change the friction coefficient. However, subsequent staining of specimens indicated that the SAL had replenished during the test following loading. The replenished SAL was characterized and found to contain lipids and sulphated GAGs with undetectable protein. This study revealed experimental evidence of surface layer replenishment in articular cartilage. It was postulated that the surface layer regeneration mechanism was purely mechanical and associated with movement of GAGs and lipids through the cartilage matrix during deformation, since the experimental set-up did not contain any means of biochemical activation.
Explaining Left Ventricular Pressure Dynamics in Terms of LV Passive and Active Elastances
Authors: Zhong Liang , Ghista Dhanjoo N , Ng Eddie Y-K , Lim Soo T , Tan Ru S , Chua Leok P
Published: June 2006

There has been much characterization of the heart as a pump by means of models based on elastance and compliance. The present paper puts forward the new concept of time-varying passive and active elastance. The biomechanical basis of cyclic elastances of the left ventricle (LV) is presented. Elastance is defined in terms of the relationship between ventricular pressure and volume as d P = Ed V + Vd E, where E includes passive elastance, Ep, and active elastance, Ea. By incorporating this concept in LV models to simulate diastolic (filling) and systolic phases, a time-varying expression has been obtained for Ea, and an LV volume dependent expression has been obtained for Ep. It is proposed to use these two elastances Ea and Ep to represent the intrinsic LV properties. The active elastance, Ea, can be used to characterize the LV contractile state and represents LV pressure variation due to LV volume variation (such as during the filling and ejection phases). The passive elastance, Ep, can serve as a measure of LV resistance to filling. Furthermore, it has been demonstrated how the LV pressure dynamics (and LV pressure response to LV volume) can be explained in terms of Ea and Ep.
The Biomechanical Response of Spinal Cord Tissue to Uniaxial Loading
Authors: Oakland R J , Hall R M , Wilcox R K , Barton D C
Published: June 2006

The spinal cord is an integral component of the spinal column and is prone to physical injury during trauma or more long-term pathological insults. The development of computational models to simulate the cord-column interaction during trauma is important in developing a proper understanding of the injury mechanism. Such models would be invaluable in seeking both preventive strategies that reduce the propensity for injury and identifying specific treatment regimes. However, these developments are hampered by the limited information available on the structural and mechanical properties of this soft tissue owing to the difficulty in handling this material in a cadaveric situation. The purpose of the present paper is to report the rapid deterioration in the quality of the tissues once excised, which provides a further challenge to the successful elucidation of the structural properties of the tissue. In particular, the tangent modulus of the tissue is seen to increase sharply over a period of 72 h.
Effect of Lubricant Composition on the Fatigue Properties of Ultra-High Molecular Weight Polyethylene for Total Knee Replacement
Authors: Aurora A , DesJardins J D , Joseph P F , LaBerge M
Published: June 2006

Ultrahigh molecular weight polyethylene (UHMWPE) fatigue is a critical factor affecting the longevity of total knee replacement (TKR) bearings. With the increased need for laboratory studies to mimic near in vivo conditions for accurate characterization of material performance, the present study investigated the role of hyaluronic acid (HA) in testing lubricant on the crack growth response of UHMWPE. It was hypothesized that the change in lubricant viscosity as a result of HA would affect the fatigue life of the polymer. A fracture mechanics approach as per ASTM E 647 was adopted for this study. Surface micrograph and surface chemistry analyses were employed to study the micromechanisms of fatigue failure and protein adsorption of the specimen surfaces. Rheological analysis indicated that the addition of HA to diluted bovine serum increased testing lubricant viscosity. HA concentrations of 2.22, 0.55, and 1.5 g/1 closely matched the viscosity ranges reported for osteoarthritis, rheumatoid arthritic diseased joint fluid, and periprosthetic fluids respectively. Results showed that the addition of HA to standard diluted bovine serum lubricants, in concentrations similar to that of periprosthetic fluid, delayed crack initiation and crack growth during fatigue testing.
Finite Element Analysis of the Long-Term Fixation Strength of Cemented Ceramic Cups
Authors: Janssen D , Stolk J , Verdonschot N
Published: June 2006

Clinical studies have shown that adequate fixation of ceramic cups using bone cement is difficult to achieve. As the cement-ceramic bond strength is low, a satisfactory fixation strength requires a cup design that allows mechanical interlocking, although such a design will probably promote cement cracking and therefore cup loosening in the long term. An investigation has been carried out to establish whether a cemented ceramic cup can be designed in such a way that both a satisfactory initial fixation strength is obtained and cement cracking is reduced to levels found around PE cups functioning well in vivo. By means of finite element analysis, the fatigue loading of three geometrically different cemented acetabular cups, with ceramic and PE material properties, has been simulated, and the severity of the crack patterns produced in the cement has been analysed. Furthermore, the fixation strength has been analysed by simulating a pull-out test prior to and after fatigue testing. All ceramic cups produced much larger amounts of cement damage during fatigue testing than any PE cup, caused by stress concentrations in the cement that were attributable to the high stiffness of the ceramic. Even a completely smooth ceramic cup produced more damage than a sharp-grooved PE cup. Owing to the excessive cement cracking, the fixation strength of the ceramic cups dropped after fatigue loading. It is concluded that cemented ceramic cups have an increased risk of long-term mechanical failure by comparison with PE cups, and that a ceramic cup design that combines sufficient fixation strength with low cement failure may be difficult to achieve.
Selective Laser Sintering of Hydroxyapatite Reinforced Polyethylene Composites for Bioactive Implants and Tissue Scaffold Development
Authors: Hao L , Savalani M M , Zhang Y , Tanner K E , Harris R A
Published: June 2006

Selective laser sintering (SLS) has been investigated for the production of bioactive implants and tissue scaffolds using composites of high-density polyethylene (HDPE) reinforced with hydroxyapatite (HA) with the aim of achieving the rapid manufacturing of customized implants. Single-layer and multilayer block specimens made of HA-HDPE composites with 30 and 40 vol % HA were sintered successfully using a CO2 laser sintering system. Laser power and scanning speed had a significant effect on the sintering behaviour. The degree of particle fusion and porosity were influenced by the laser processing parameters, hence control can be attained by varying these parameters. Moreover, the SLS processing allowed exposure of HA particles on the surface of the composites and thereby should provide bioactive products. Pores existed in the SLS-fabricated composite parts and at certain processing parameters a significant fraction of the pores were within the optimal sizes for tissue regeneration. The results indicate that the SLS technique has the potential not only to fabricate HA-HDPE composite products but also to produce appropriate features for their application as bioactive implants and tissue scaffolds.