Nonlinear Hyperbolic Rigid Heat Conductor of the Coleman Type

A one-dimensional nonlinear hyperbolic homogeneous isotropic rigid heat conductor proposed by Coleman is analyzed using the method of weakly nonlinear geometric optics. For such a model the law of conservation of energy, the dissipation inequality, the Cattaneo's equation, and a generalized energy-entropy relation with a parabolic variation of the energy and entropy along the heat-flux axis, are postulated. First, it is shown that the model can be described by a non-homogeneous quasi-linear hyperbolic matrix partial differential equation of the first order for an unknown vector u = (θ, Q) ^T , where θ and Q are the dimensionless absolute temperature and heat-flux fields, respectively. Next, the Cauchy problem for the matrix equation with a weakly perturbed initial condition is formulated, and an asymptotic solution to the problem in terms of the amplitudes σ_α (α = 1, 2) that satisfy a pair of nonlinear first order partial differential equations, is obtained. The Cauchy problem is then solved in a closed form when the initial data are suitably restricted. Numerical examples are included.     

VISCOSITY OF BITUMEN-CRUMB RUBBER BLEND (NEW PAVING MATERIAL)

ABSTRACT

The feasibility of blending scrap tire rubber with Asphalt Ridge and Circle Cliffs (Utah, USA) tar sand bitumens was studied. Viscosity of the blended mixtures was analyzed as a function of composition, and coprocessing variables including processing temperature and time. Coprocessing of tar sand bitumens with crumb rubber at elevated temperatures has been shown to increase the viscosity of the bitumens with the exception of the bitumen-rubber sample prepared at 380°C. Optimum viscosity behavior was exhibited for an oil-extended bitumen blended with crumb rubber at 200°C for 0.5 hours. The viscosity of the bitumen-rubber blend prepared under these conditions met ASTM specifications of a viscosity-graded AC-30 asphalt binder. Viscosity increase was most noticeable at low temperature, providing the benefit of high viscosity at pavement temperatures experienced during summer months without concession of processability at pavement construction temperatures. A difference in viscosity was observed between bitumen modified with whole-tire crumb and tread-rubber crumb, due to the compositional differences that exist between the two materials.     

The use of the MRI technique in the evaluation of water distribution in tumbled porcine muscle

The non-destructive magnetic resonance imaging (MRI) technique was used to study the spatial distribution of water in meat samples without and with brine and the influence of injection curing on water distribution in cured meat. Fresh non-treated porcine ham muscles (m. biceps femoris) were used; muscles injected with curing salt and subjected to half-time tumbling (3 h and 20 min) and full-time tumbling (6 h and 40 min) were studied. A "Lutetia" type 4 tumbler of French manufacture with a helicoidal paddle and a 2000 kg drum capacity was used. Histological examination of fresh non-treated muscles, after brine injection, and during and after the completion of tumbling demonstrated considerable differences. The use of MRI made it possible to estimate the effect of the tumbling procedure on the dynamics of brine migration and binding by muscle proteins. The spatial imaging of the proton density distribution confirmed that with longer meat tumbling times the binding of brine and its uniform distribution in the muscles increased.     

Size-Fractionating Aerosol Generator

An aerosol generator has been developed and evaluated for applications where the aerosol concentration and size distribution need to be tailored to specific needs. In this device, a modified Wright nebulizer generates the primary aerosol whose concentration and, to a limited degree, size distribution are adjusted through selection of the pressure drop and the gas-to-liquid flow rate ratio. Further modification of the size distribution is achieved through virtual and solid-plate impaction so that specific aerosol concentration in specific size ranges can be chosen as the aerosol output.     

The effective crushing distance in axially compressed thin-walled metal columns

This paper examines the effective crushing distance of thin-walled box columns. In contrast to previous work on this subject where a perfectly plastic material was assumed, the hardening property of a material is now taken into account. A simplified theoretical model of a compressed rigid-linearly strain hardening metal strip is studied and a closed-form solution is derived for the crushing distance of unstiffened as well as transversly stiffened box columns. The theoretical predictions are in excellent agreement with experimental data.     

Interdiffusion in M7C3 and M3C phases during diffusion chromizing

The interdiffusion of chromium in M₇C₃ and M₃C carbide cases obtained during diffusion chromizing is discussed. The diffusional characteristics of the two phases are emphasized and are related to the chromium concentration by means of the Matano method using the experimental chromium profiles. The importance of grain boundary diffusion and the influence of the layer morphology on the variation of the interdiffusion coefficient are considered in turn.     

An asymptotic approach to one-dimensional model of nonlinear thermoelasticity at low temperatures and small strains*

A one-dimensional nonlinear homogeneous isotropic thermoelastic model with an elastic heat flow at low temperatures and small strains is analyzed using the method of weakly nonlinear asymptotics. For such a model, both the free energy and the heat flux vector depend not only on the absolute temperature and strain tensor but also on an elastic heat flow that satisfies an evolution equation. The governing equations are reduced to a matrix partial differential equations, and the associated Cauchy problem with a weakly perturbed initial condition is solved. The solution is given in the form of a power series with respect to a small parameter, the coe?cients of which are functions of a slow variable that satisfy a system of nonlinear second-order ordinary differential transport equations. A family of closed-form solutions to the transport equations is obtained. For a particular Cauchy problem in which the initial data are generated by a closed-form solution to the transport equations, the asymptotic solution in the form of a sum of four traveling thermoelastic waves admitting blow-up amplitudes is presented.     

Left ventricular morphology and function in diabetic and nondiabetic hemodialyzed patients

Morbidity in end-stage renal disease (ESRD) diabetic patients is worse than in patients without diabetes mellitus (DM). This study aims to compare clinical, laboratory, and echocardiographic features between the ESRD patients with and without DM. Fifty-eight ESRD patients on dialysis were prospectively divided into two groups according to the presence of DM. Demographic, clinical, laboratory, and echocardiographic features (ejection fraction and wall motion score index) were compared between the two groups. Overall, 20 out of 58 patients (37.8%) with ESRD had DM. There were no significant differences between the patients with DM and those without DM when it comes to age (60.6 ± 10.6 vs. 59.0 ± 10.6 years, P = 0.665), ejection fraction (52.6% ± 12.8% vs. 54.2% ± 12.8%, P = 0.59), and wall motion score index (1.21 ± 0.3 vs.1.15 ± 0.3, P = 0.37). In multivariant analysis of the interventricular septum, posterior wall thickness and left atrium size correlated positively with DM. There was also no statistical difference in myocardial perfusion disturbances on real-time contrast echocardiography between the groups with and without DM (12 (60%) patients vs. 14 patients (36.8%), P = 0.079). Among diabetics 77.8% had significant atherosclerotic changes, while in the group without DM, only 38.1%, P = 0.01. From the laboratory parameters ferritin and high-sensitivity C-reactive protein levels were significantly higher in the group with DM, P = 0.014 and P = 0.026, respectively. Patients with ESRD and DM have significantly bigger left atrial size, thicker left ventricular walls, and higher serum ferritin and high-sensitivity C-reactive protein levels than the patients without DM. The aforementioned features may be possible risk factors for the development of adverse cardiac events in patients on hemodialysis.