Thermal analysis of a diesel engine operating with diesel–biodiesel blends

In this paper we study the transient heat conduction in a piston of a diesel engine, subjected to a periodic boundary condition on the surface in contact with the combustion gases. The heat transfer coefficient at the top surface was modeled taking into account the temperature and pressure inside the combustion chamber. Such instantaneous pressure was measured using a special probe for an engine operating with several blends of diesel and biodiesel, and the temperature was obtained through a First Law analysis. The physical properties, including the cetane number were evaluated experimentally for all diesel/biodiesel blends used in this work. An elliptic scheme of numerical grid generation was used, so that the irregular shaped piston in the physical domain was transformed into a cylinder in a computational domain. The timewise variations of the temperature of several points in the piston were examined for different piston materials and various load conditions.     

Clinical Satisfaction and Quality of Ceramic Fixed Dentures

It is known that several factors can affect the clinical success and durability of fixed partial dentures. Therefore, the aim of the present study was to present a literature review about the longevity, clinical success, and quality, as well as, patients' and dental surgeons' satisfaction of ceramic fixed dentures. High rate of patients' satisfaction has been observed in relation to the esthetic of ceramic crowns. In addition, the literature has shown that dental ceramics can be used in several clinical situations with high success rate and longevity. Despite of failures and complications of ceramic restorations, nowadays, with the improvement of mechanical properties of such materials, ceramic crowns present a favorable prognosis and can be used in several clinical situations with high success rate, clinical quality, and great patients' satisfaction.     

Improved energy efficiency of farmers' cooperative litchi drying operation in Northern Thailand

In 2007, Hmong farmers growing litchi in the mountainous region of Northern Thailand started to dry the fruit in response to its declining market price. However, the locally available dryer, although affordable and of a size appropriate for smallholder farmers' cooperatives, showed excessive gas consumption, and this, along with rising fuel costs, imposed a threat to the drying operation. The objective of this study was to test low‐cost, easy‐to‐implement modifications to a locally available convection dryer, to improve its energy efficiency. Experiments were conducted in cooperation with a Hmong farmers' cooperative in Northern Thailand. Insulation of the air ducts and control of the air recirculation rate led to energy cost savings of US$2.45 per dryer‐load. With the modifications required being simple, the investment needed was recovered after only approximately 20 loads, while the energy efficiency of the dryer increased from 33% to 39%.     

Viscoelastic Properties of Tomato Juice: Applicability of the Cox–Merz Rule

Tomato is one of the most important vegetables for the food industry. Rheological characterization of food is important for products, equipments, and unit operations design and evaluation. It is necessary for process optimization and high-quality products assurance. However, the works in literature present variable data, and some rheological characterization, as viscoelastic properties, are still scarce. The present work has evaluated the viscoelastic properties of tomato juice, as well as the applicability of the Cox–Merz rule. Tomato juice has shown dominant elastic properties rather than the viscous ones and could be classified as a weak gel (storage modulus higher then loss modulus). Moreover, due to the low pulp content, it has shown low viscoelastic behavior, with small dependency of oscillatory of the storage modulus. The rheological oscillatory and steady-state shear rheological properties of tomato juice were then correlated by two linear modifications on the Cox–Merz rule. The obtained values are in agreement with those described in the literature for other food products. The obtained data are potentially useful for future studies on food properties and process design.     

Assessment of the relative sensitivity of milk ELISA for detection of Mycobacterium avium ssp. paratuberculosis infectious dairy cows

Milk ELISA are commonly used for detection of Mycobacterium avium ssp. paratuberculosis (MAP) antibodies in dairy cows, due to low cost and quick processing for large numbers of samples. However, low sensitivity and variations from host and environmental factors can impede detection of MAP antibodies at early disease stages. The objectives of our study were to assess the sensitivity of milk ELISA in comparison with fecal tests and to evaluate how detectable antibody concentrations in milk vary with changes in fecal shedding of MAP, cow age, cow parity, days in milk, and time of year. To compare the sensitivity of a commercial milk ELISA with solid and broth fecal culture and with fecal real-time PCR, a longitudinal study was performed for the identification of MAP-infectious animals as determined by prior fecal testing for MAP shedding. In addition, associations between variation in milk MAP ELISA score and changes in fecal MAP shedding, host age, days in milk, and season were evaluated. Monthly milk and fecal samples were collected over 1 yr from 46 cows that were previously shedding MAP in their feces. Sensitivity of milk ELISA was 29.9% (95% CI: 24.8 to 35.1%), compared with 46.7% (40.7 to 52.7%) for fecal solid culture, 55.0% (49.3 to 60.7%) for fecal broth culture, and 78.4% (73.3 to 83.1%) for fecal direct real-time PCR. The effect of stage of lactation could not be separated from the effect of season, with increased milk ELISA scores at greater days in milk in winter. However, unpredictable monthly variations in results were observed among the 3 assays for individual cow testing, which highlights the importance of identifying patterns in pathogen and antibody detection over time in MAP-positive herds.     

FLOW AND HEAT TRANSFER IN RECTANGULAR ENCLOSURES USING A NEW BLOCK-IMPLICIT NUMERICAL METHOD

This work reports a numerical investigation on buoyancy-induced flows occurring in enclosures of small aspect ratio and inclined with respect to the horizontal direction. The numerical method used consists of the control-volume approach and a new block-implicit error-smoothing operator. Governing equations are written in terms of primitive variables and are recast into a general form. In the proposed method, all governing equation are relaxed locally, in contrast with commonly used segregated schemes. The effects of Rayleigh number, aspect ratio, and cavity inclination on temperature and velocity patterns are discussed. It is expected that more advanced parallel computer architectures can benefit from the error-smoothing operator described here.     

Left ventricular mechanical dyssynchrony in patients with different stages of chronic kidney disease and the effects of hemodialysis

Left ventricular (LV) dyssynchrony is a known cause of mortality in patients with heart failure and may possibly play a similar role in patients with chronic kidney disease (CKD) in whom sudden death is one of the most common and as yet not fully explained cause of death. LV synchronicity and its relationship with increased volume load and various biomarkers was analyzed in 145 patients including 53 patients with CKD stages 3 and 4 and in 92 CKD stage 5 patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) using color tissue Doppler imaging and tissue synchronization imaging. The HD patients were evaluated both before and after a single HD session. LV dyssynchrony was defined as a regional difference in time to peak systolic myocardial velocity, between 12 LV segments > 105 milliseconds. LV dyssynchrony was present in 54% of the patients with no difference between CKD 3 and 4 (58%), HD (48%), and PD (51%). LV dyssynchrony was independently associated with LV mass index and increased estimation of LV end‐diastolic pressure. A single HD session resulted in significant changes in LV synchronicity variables—with improvement in 50% of the patients—especially in patients with higher myocardial systolic velocities and lower LV mass index. Abnormalities in LV synchronicity are highly prevalent in CKD patients already prior to dialysis treatment and are associated with LV hypertrophy, LV dysfunction and load conditions, underlining the importance of volume status for LV synchronicity in CKD patients.     

Phenolic foams from wood tar resols

This article investigates resole‐type phenolic foams, in which 40% phenol was substituted with distilled oily fractions from wood tar. Different proportions of blowing agent, hexamethylenetetramine, and stabilizer, a sodium alkyl sulfate surface active agent, were used to produce a series of rigid foams, which were characterized by curing index, density and hardness. The average curing index was about 90% and densities ranged from 480 to 960 kg.m^?3. A fractal dimension (D_f) approach was used to assess the homogeneity of pores within the foams and an average (dimensionless) value of 2.6 was found, indicating a non uniform structure. Compressive strength tests of the foams gave values above 1.0 MPa, which is higher than those for typical phenolic foams. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010