Thermomechanical Framework for the Constitutive Modeling of Asphalt Concrete

This study is concerned with the constitutive modeling of asphalt concrete. Unlike most constitutive models for asphalt concrete that do not take into account the evolution of the microstructure of the material, this study incorporates the evolution of the microstructure by using a framework that recognizes that a body’s natural configurations can evolve as the microstructure changes. The general framework, on which this study is based, is cast within a full thermomechanical setting. In this paper, we develop models within the context of a mechanical framework that stems from the general framework for models based on the full thermodynamic framework and the resulting equations represent a nonlinear rate type viscoelastic model. The creep and stress relaxation experiments of Monismith and Secor are used for validating the efficacy of the model, and it is found that the predictions of the theory agree very well with the available experimental results. The advantages of using such a framework are many, especially when one wants to model the diverse mechanical and thermodynamic response characteristics of asphalt and asphalt concrete.     

Using Real-Time Stereo Vision for Mobile Robot Navigation

This paper describes a working vision-based mobile robot that navigates and autonomously explores its environment while building occupancy grid maps of the environment. We present a method for reducing stereo vision disparity images to two-dimensional map information. Stereo vision has several attributes that set it apart from other sensors more commonly used for occupancy grid mapping. We discuss these attributes, the errors that some of them create, and how to overcome them. We reduce errors by segmenting disparity images based on continuous disparity surfaces to reject spikes caused by stereo mismatches. Stereo vision processing and map updates are done at 5 Hz and the robot moves at speeds of 300 cm/s.     

Air/Water Oxygen Transfer in a Biological Aerated Filter

The oxygen-transfer characteristics of an upflow biological aerated filter filled with angular clay media were determined over a wide range of gas and liquid flow rates. Liquid-side, oxygen-transfer coefficients (KLa) were measured using a nitrogen gas stripping method under abiotic conditions and were found to increase as both gas and liquid superficial velocity increases, with values ranging from 12 to 110?h?1 based on empty bed volume. The effect of gas and liquid velocity, wastewater to clean water ratio, and temperature dependence was correlated to within ±20% of the experimental KLa value. Stagnant gas holdup is roughly double in wastewater compared to clean water, but the dynamic gas holdup is the same. The oxygen-transfer coefficient is directly proportional to the dynamic gas holdup. Stagnant gas holdup does not influence the rate of oxygen transfer. The results suggest that dynamic gas holdup largely determines the specific interfacial area (a), whereas the interstitial liquid velocity largely controls the oxygen-transfer coefficient (KL).     

A multiple-scale analysis of grating-assisted couplers

Optical directional couplers with longitudinal periodic perturbations or gratings are analyzed by a multiple-scale solution to the coupled-mode equations. The use of two length scales in the analysis becomes the key to obtaining globally valid analytic solutions, which are shown to be in excellent agreement with the exact numerical solutions. Because of the nonorthogonality of the coupled modes in the structure, two different coupling lengths, a maximum power transfer length and a zero crosstalk length, are predicted for the power exchange. The spectral properties of the coupler are also studied through a generalized multiple scale method     

Assessment of strain gradients affecting the performance of 3-D strain rosettes – relevant to the analysis of cement mantle strains in total hip replacements

A large scale model analysis, using embedded strain gauges, of the strain distribution in the cement mantle surrounding a femoral prosthesis is underway. In order to predict, and so avoid, positions of locally high strain gradients in this model, a finite element and experimental analysis of a similar problem was undertaken. For this purpose, a loose fitting rectangular steel insert inside a surrounding rectangular epoxy sheath was used to model an extreme case of the torsional and bending components of hip joint load. The axial component of joint load was modelled using an axisymmetric finite element model of a tapered shaft. The finite element results were used to determine suitable positions for embedding gauges in the experimental model. Results showed that the finite element analysis failed to adequately model the close sliding fit between the steel insert and epoxy. Altering the experimental model to artificially replicate the finite element contact conditions produced good correlation in bending, with experimental strains agreeing with simple bending theory to within 6%. Satisfactory correlation under torsional loading was not obtained, but strain magnitudes were low. Predicted positions for embedding gauges give conservative results, lessening the possibility of strain gradient induced error in the large scale model test of the cement mantle and prosthesis.     

Assignments of meaning in epidemiology

Epidemiology works in a public domain, gathering the results of surveys and trials into forms of knowledge which are made available to many stakeholders. Health policy makers, lawyers, the media, medical technology companies, and those who use and deliver health services all have legitimate interests in epidemiology. There is unfortunately no common language in which each of these stakeholders can express their interest in the outcomes of epidemiological studies. The largest and most important gap exists between those who use computational data and those who use cultural and linguistic models to generate their explanations. Methods have been described, however, which allow the identification of all legitimate stakeholders before epidemiological studies are undertaken. Identifying the stakeholders, however, will serve no purpose unless there is a prior commitment by epidemiologists to respect both reductionist and narrative accounts of truth.     

Automatic composition techniques for video production

Video production involves the process of capturing, editing and composing video segments for delivery to a consumer. A composition must yield a coherent presentation of an event or narrative. This process can be automated if appropriate domain-specific metadata are associated with video segments and composition techniques are established. Automation leads to the support of dynamic composition and customization for applications such as news on demand. In this paper, we present techniques to achieve dynamic, real-time and cohesive video composition and customization. We also identify metrics for evaluating our techniques with respect to existing manually produced video-based news. The results of such an evaluation show that the quality of automatic composition is comparable to-and in some cases, better than-broadcast news video composition. The results also validate the assertions on which the automatic composition techniques are based     

An automated fluorescent PCR method for detection of shiga toxin-producing Escherichia coli in foods

An automated fluorescence-based PCR system (a model AG-9600 AmpliSensor analyzer) was investigated to determine whether it could detect Shiga toxin-producing Escherichia coli (STEC). The AmpliSensor PCR assay involves amplification-mediated disruption of a fluorogenic DNA signal duplex (AmpliSensor) that is homologous to conserved target sequences in a 323-bp amplified fragment of Shiga toxin genes stx1, stx2, and stxe. Using the Amplisensor assay, we detected 113 strains of STEC belonging to 50 different serotypes, while 18 strains of non-Shiga-toxin-producing E. coli and 68 strains of other bacteria were not detected. The detection limits of the assay were less than 1 to 5 CFU per PCR mixture when pure cultures of five reference strains were used and 3 CFU per 25 g of food when spiked ground beef samples that were preenriched overnight were used. The performance of the assay was also evaluated by using 53 naturally contaminated meat samples and 48 raw milk samples. Thirty-two STEC-positive samples that were confirmed to be positive by the culture assay were found to be positive when the AmpliSensor assay was used. Nine samples that were found to be positive when the PCR assay was used were culture negative. The system described here is an automated PCR-based system that can be used for detection of all serotypes of STEC in food or clinical samples.     

GP documentation of obesity: what does it achieve?

BACKGROUND: Obesity is a major and increasing health problem in the United Kingdom, and, until recently, the government health promotion package for general practice reimbursed general practitioners for documenting obesity. Despite poor evidence for effectiveness of interventions in primary care, documentation of obesity could possibly improve patient awareness and knowledge, or provide public health information. AIM: To assess patient perception of obesity and its health risk, and the accuracy of estimating obesity using patient information. METHOD: Subjects were consecutive attenders to a general practitioner (GP) at a single urban practice in the South and West Region. Outcome measures were 'measured' body mass index (BMI) calculated from measured weight and height, 'estimated' BMI using patient information, and patient perception of obesity and the health risks of obesity. RESULTS: There is good correlation between 'estimated' and 'measured' BMI (intraclass correlation 0.91). Estimated BMI is lower than measured BMI (mean 0.77 lower), and the difference increases with age and level of BMI: for BMIs of < 20, 20-24.99, 25-29.99, and > or = 30 the mean differences (estimated-measured) were -0.06, -0.46, -0.98 and -1.72 respectively. Estimated obesity (BMI > 30) is reasonably sensitive (70%), specific (99%), and predictive (93% positive predictive value) of measured obesity (kappa 0.78). All obese subjects are aware that they are overweight, and most of them (78%, 95% confidence interval 66-88%) are aware that their weight is a health risk. CONCLUSION: Obese patients attending GPs' surgeries are likely to know if they are overweight, or could easily estimate from their knowledge of height and weight that they were overweight with reasonable accuracy. Obese subjects also know that their weight carries health risks. Thus, measurement of obesity in the general population is not likely to improve risk assessment or patient knowledge significantly. Without evidence for effective intervention or improved decision-making in primary care, reimbursement guidelines linked to the documentation of obesity in the population are probably an inefficient use of resources.