Epidemiology of enuresis in Turkish children

The treatment and favorable outcome of a bitch with uterine torsion and two retained fetuses are described. The condition was corrected surgically by ovariohysterectomy. Complications (i.e., septic shock, peritonitis, and hemostatic abnormalities) were managed with aggressive medical therapy. Torsion of the gravid uterus in dogs is a life-threatening condition which can have a successful outcome if medical complications encountered in the pre- and postoperative periods are treated quickly and effectively.     

MMPP models for multimedia traffic

The paper presents a study on the use of Markov‐Modulated Poisson Processes (MMPP's) for characterizing multimedia traffic with short‐term and long‐term correlation. The applicability of the 2‐state MMPP and a refined moment‐based parameter‐matching technique to model an arbitrary ATM traffic stream in evaluating its queueing performance are examined by simulation. Following a discussion on the limitation of the 2‐state MMPP model, a model using a superposition of N homogeneous 2‐state MMPP to characterize bursty multimedia traffic is presented. The proposed model requires only five parameters which can be estimated from the samples of the traffic counting process by using a pdf‐based matching technique. The introduced pdf‐based parameter‐matching procedure uses the probability density function of the arrival rate and the IDC curve of the traffic samples. An approximation for the probability of loss in MMPP/D/1 queues is also obtained. The versatility and accuracy of the proposed model to characterize bursty multimedia traffic are shown by several case studies and test results. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of water drying conditions on the surface property and morphology of waterborne UV-curable coatings for engineered flooring

UV-curable coatings are widely used on wooden materials such as flooring and furniture, because they have excellent properties, including high hardness, gloss, mar and chemical resistance, and are also environmental friendly, containing no solvents. Recently, waterborne UV-curable coatings have been studied as a viable alternative, since solvents are added to spray applications to lower viscosity. We investigated the effects of water drying conditions on the surface properties and morphology of waterborne UV-curable coatings at the flash-off step. Temperature conditions studied were 22 °C, 50 °C, and 80 °C, with various drying times. We evaluated surface properties such as pendulum hardness, pencil hardness, and adhesion strength. Also observed was surface morphology, comparing surface properties using optical microscopy after drying and UV-curing. Insufficient drying caused cracking, peeling and blistering at the surface of a cured coating. Sufficient drying was very important for the best application and ideal surface morphology of waterborne UV-curable coatings.     

Wear of water walls in a commercial circulating fluidized bed combustor with two gas exits

The tube thickness profiles of water walls, including wing walls, were measured in a large commercial circulating fluidized bed furnace (200 tonnes steam/h, 4.97 m × 9.90 m × 28.98 m high) by means of an ultrasonic thickness gauge in order to investigate tube wastage patterns. Wastage of all water walls, including wing walls, was significant in the transition region just above the refractory lining around the circumference of the combustor, especially at the center of the sidewalls and both sides of the front and rear walls. The lateral wear profile seemed to be influenced mainly by secondary flow, stronger toward the center than in the corners, and somewhat by the wing walls and two gas exits. Wastage of some tubes was also found to be appreciable around the gas exit. The lateral profiles of tube thickness at the gas exit level and other findings indicate asymmetric flows between the two exits.     

Modeling of power supply noise in large chips using the circuit-based finite-difference time-domain method

In this paper, a multilayered on-chip power distribution network consisting of two million passive elements has been modeled using the finite-difference time-domain (FDTD) method. In this method, a branch capacitor has been used. The use of the branch capacitor is important for simulating multilayered power grids. In addition, a method for including the CMOS inverter characteristics into the FDTD simulation has been presented. As an example of the application of this method, an H-tree clock network was simulated to compute the power supply noise distribution across an entire chip. Various scenarios with varying decoupling capacitances, load capacitances, number of clock buffers, and rise times have been analyzed to demonstrate the importance of circuit nonlinearity on power supply noise. Also, a method has been presented for analyzing package and board planes. Based on the methods presented, the interaction between chip and package has been discussed for capturing the resonant behavior that is otherwise absent when each section of the system is analyzed separately.     

The first-principles design of ductile refractory alloys

The purpose of this work is to predict elastic and thermodynamic properties of chromium-based alloys based on first-principles calculations and to demonstrate an appropriate computational approach to develop new materials for high-temperature applications in energy systems. In this study, Poisson ratio is used as a screening parameter to identify ductilizing additives to the refractory alloys. The results predict that elements such as Ti, V, Zr, Nb, Hf, and Ta show potential as ductilizers in Cr while Al, Ge, and Ga are predicted to decrease the ductility of Cr. Experimental evidence, where available, validates these predictions. The purpose of this work is to predict elastic and thermodynamic properties of chromium-based alloys based on first-principles calculations and to demonstrate an appropriate computational approach to develop new materials for high-temperature applications in energy systems. In this study, Poisson ratio is used as a screening parameter to identify ductilizing additives to the refractory alloys. The results predict that elements such as Ti, V, Zr, Nb, Hf, and Ta show potential as ductilizers in Cr while Al, Ge, and Ga are predicted to decrease the ductility of Cr. Experimental evidence, where available, validates these predictions.     

The effects of air pollution and climatic factors on atmospheric corrosion of marble under field exposure

The atmospheric corrosion of marble was evaluated in terms of SO₂ concentration as air pollution and climatic factors such as rainfall, relative humidity, temperature and so on under the field exposure. Marble of calcite type (CaCO₃) was exposed to outdoor atmospheric environment with and without a rain shelter at four test sites in the southern part of Vietnam for 3-month, 1- and 2-year periods from July 2001 to September 2003. The thickness loss of marble was investigated gravimetrically. X-ray diffraction and X-ray fluorescent methods were applied to study corrosion products on marble. The corrosion product of marble was only gypsum (CaSO₄ · 2H₂O) and was washed out by rain under the unsheltered exposure condition. It was found that the most substantial factors influencing the corrosion of marble were rainfall, SO₂ concentration in the air and relative humidity. Based on the results obtained, we estimated the dose-response functions for the atmospheric corrosion of marble in the southern part of Vietnam.     

Reaction engineering studies of methane coupling in fluidised-bed reactors

The oxidative coupling of methane has been conducted in 30 and 60mm dia. fluidised-bed reactors. Methane conversions as high as 40% were achieved at isothermal conditions using methane/oxygen mixtures without diluents. At the same contact time the two reactors had similar selectivities to hydrocarbons. At 850°C the hydrocarbon selectivity decreased dramatically with increasing contact time but this effect was much less severe at lower temperatures. Axial gas concentration profiles through the catalyst bed in the 60mm reactor indicated that at 850°C there was a rapid consumption of oxygen and formation of products in the bottom section of the bed followed by a net loss of hydrocarbon in the oxygen-free zone. This loss was due to carbon formation on the catalyst which was circulated back to the oxygen-containing zone of the bed where the carbon was combusted.     

Development of a ground-coupled heat pump system simulation model using g-function approximation for a residential code-compliant tool

This study develops a ground-coupled heat pump (GCHP) simulation model for a residential code-compliant simulation tool. To achieve this, this study proposed the g-function approximation method using polynomial curve-fitting equations. In addition, the residential air-source heat pump (ASHP) simulation model (i.e., RESYS in DOE-2.1e) was modified to include a vertical ground heat exchanger module. To check validity of the new GCHP system model, this study compared the simulation results against the results from the other simulation tools. The results between the programs showed good agreement within 5.3% differences for the annual total site energy use. Using the developed GCHP simulation model, the energy savings for a code-compliant residential building in Houston and Dallas were evaluated in comparison with the ASHP system, and the resultant annual energy savings were about 10% to 15% in the total site energy use and 30% to 40% in the heating plus cooling energy use.     

Enhancement of Mechanical Properties of Extruded Mg–9Al–1Zn–1MM–0.7CaO–0.3Mn Alloy Through Pre-aging Treatment

The effect of pre-aging treatment before extrusion has been investigated in Mg–9.0Al–1.0Zn–1MM–0.7CaO–0.3Mn alloy. The as-cast microstructure consists of α-Mg dendrite with secondary solidification phase particles, (Mg, Al)₂Ca, β-Mg₁₇Al₁₂ and Al₁₁RE₃ at the inter-dendritic region. After extrusion, β-Mg₁₇Al₁₂ precipitates are present, but higher density and more homogeneous distribution in pre-aged alloy. In addition, μm-scale banded bulk β-Mg₁₇Al₁₂ particles are generated during extrusion. Al₁₁RE₃ particles are broken into small particles, and are aligned along the extrusion direction. (Mg, Al)₂Ca particles are only slightly elongated along the extrusion direction, providing stronger particle stimulated nucleation (PSN) effect by severe deformation during extrusion. The mechanical properties can be significantly enhanced by introducing pre-aging treatment, i.e. β-Mg₁₇Al₁₂ precipitates provide grain refining and strengthening effects and (Mg, Al)₂Ca particles provide PSN effect.