Subcooled and saturated boiling of ammonia–lithium nitrate solution in a plate-type generator for absorption machines

This paper presents the experimental heat transfer evaluation during subcooled and saturated boiling of ammonia–lithium nitrate solution in a fusion plate heat exchanger, acting as a vapor generator under operating conditions representative of single-effect absorption machines. The solution flow rate and outlet temperature were modified in the ranges of 0.041–0.083 kg/s and 78–97 °C, respectively. The region where vapor bubbles begin to arise is estimated using a correlation for the wall superheat required for the onset of nucleate boiling. Results show that subcooled boiling is present in the generator. The initial boiling temperature is about 3.1 °C lower than the saturation temperature. The influence of the heat and mass fluxes on the boiling heat transfer coefficient is analyzed. The paper offers a correlation for the Nusselt number, including the subcooled and saturated boiling regions.     

Highway and Road Probabilistic Safety Assessment Based on Bayesian Network Models

A Bayesian network model is developed, in which all the items or safety related elements encountered when traveling along a highway or road, such as terrain, infrastructure, light signals, speed limit signs, intersections, roundabouts, curves, tunnels, viaducts, and any other safety relevant elements are reproduced. Since human error is the main cause of accidents, special attention is given to modeling the driver behavior variables (driver's tiredness and attention) and to how they evolve with time or travel length. The sets of conditional probabilities of variables given their parents, which permit to quantify the Bayesian network joint probability, are obtained and written as closed formulas, which allow us to identify the particular contribution of each variable to safety and facilitate the computer implementation of the proposed method. In particular, the probabilities of incidents affecting safety are calculated so that a probabilistic safety assessment of the road can be done and its most critical elements can be identified and sorted by importance. This permits the improvement of road safety making adequate corrections to save time and money in the maintenance program by concentrating on the most critical elements and effective investments. Some real examples of a Spanish highway and a conventional road are provided to illustrate the proposed methodology and show its advantages and performance.     

Preservation of functionality of Bifidobacterium animalis subsp. lactis INL1 after incorporation of freeze-dried cells into different food matrices

The aim of this work was to investigate how production and freeze-drying conditions of Bifidobacterium animalis subsp. lactis INL1, a probiotic strain isolated from breast milk, affected its survival and resistance to simulated gastric digestion during storage in food matrices. The determination of the resistance of bifidobacteria to simulated gastric digestion was useful for unveiling differences in cell sensitivity to varying conditions during biomass production, freeze-drying and incorporation of the strain into food products. These findings show that bifidobacteria can become sensitive to technological variables (biomass production, freeze-drying and the food matrix) without this fact being evidenced by plate counts.     

Food and nutrition knowledge in Chilean high school graduates

The purpose of this study was to determine the degree of knowledge on food and nutrition in students graduating from high school in the Metropolitan Area of Santiago. The sample included 272 students of both sexes and type of school (public and private) and from high, medium and low socioeconomic level (SEL), measured through the Graffar Modified Scale. The degree of knowledge on food and nutrition was measured through a test of 48 items based on curriculum program objectives. The test covered three areas: Area 1, Food and Requirements; Area 2, Food, Personal and Environmental Hygiene, and Area 3, Nutritional Physiology. Students showed a good achievement of the food and nutrition objectives that are considered essential for obtaining and adequate nutrition and health status. Students from high SEL registered a significantly higher degree of knowledge on food and nutrition than students from other strata (p less than 0.001). However, sex and type of school had no effect on the degree of food and nutrition knowledge. This study is a contribution to the better understanding of factors affecting the food and nutrition knowledge, and provides good foundations for further studies.     

Sensory evaluation and acceptability study, at the consumer level, of bread supplemented with sweet lupine flour

The purpose of this study was to determine the effect of incorporating sweet lupine flour (SLF) to bread, upon the organoleptic characteristics and acceptability of the product. The substitution levels were 3, 6, 9 and 12%. The sensory evaluation test was done by 25 trained judges using the hedonic scaling method (9 to 1 scoring). Internal and external characteristics of appearance, color, aroma, texture, bitterness and flavor, as well as general acceptability, were measured. Sensory evaluation results of the external characteristics were significant at the 9 and 12% SLF levels for color (p less than 0.05) while the other parameters did not show significant differences. In regard to the internal characteristics, a significant difference for color was found at the 3% level of SLF (p less than 0.05); and at 6, 9 and 12% SLF levels, for appearance (p less than 0.05). The general acceptability was good at all the levels tested, with no significant differences among them. An acceptability study at the consumer level for 9% lupine flour bread was carried out in a group of 90 girls, aged 10-12 years, during a 10-day period. The results showed a very good acceptability of the product (p less than 0.01). The results of this study indicate that the incorporation of 6% SLF to the bread, did not affect adversely its sensory properties. Moreover, the acceptability of bread containing up to 12% SLF was excellent.     

Food habits of high school graduates in the metropolitan area of Santiago, Chile

The purpose of this study was to determine the food habits of Chilean high-school graduates, and measure the effect that socioeconomic level (SEL), type of school (public and private school), sex and age exerts on those habits. A random and stratified sample of 283 schoolers, according to type of school, sex and SEL, measured through the Graffar Modified Scale was selected for the study. Food habits were defined by the frequency of consumption of food, expressed as days per week and were compared with the Model Allowance established by the Ministry of Health of Chile. A food habits questionnaire was administered to students by duly trained interviewers, and were defined by the frequency of consumption of food groups. Data were analyzed by the chi-square procedure, analysis of variance and Student's "t" test. In accordance with the results, the most consumed foods (over 90% of students) were meat, poultry, eggs, potatoes, apples, bread, rice, oil and butter or margarine. On the other hand, the most disliked foods (40% and more of students) were fresh cheese, viscera, radish and chickpeas. The high SEL students showed a significantly greater frequency of consumption of dairy products, and of meat products and eggs (p less than 0.001). No differences were found according to type of school, sex and age of students. We conclude, therefore, that SEL exerts a significant effect on food habits, in spite of which they were adequate according to the Model Allowance.     

Modification of the Marching Cubes Algorithm to Obtain a 3D Representation of a Planar Image

Programming and Computer Software - The registration of a 3D model over an image can be seen as the alignment of visual correspondences extracted from these two data. This is a challenging task and...     

An Alternate Double–Single Track Proposal for High‐Speed Peripheral Railway Lines

This article presents alternate double–single track (ADST) lines as an alternative to double‐track lines. The idea consists of using single track where the infrastructure is very expensive (tunnels and viaducts) and double track where it is cheaper (smooth orography) combined with small changes in departure times so that trains may cross in the double‐track segments with no reduction in travel times. The solution is shown to be very efficient for traffic demands between 30 and 40 trains per day and the costs are reduced substantially (close to 40%). A linear programming program is given that (1) decides the optimal sequence of single and double tracks and (2) optimizes the timetables for the optimal or other alternative sequences. The Palencia–Santander line is used to illustrate the proposal and some suggestions are given to use the ADST lines in several countries.     

Proactive,Backward Analysis and Learning in Road Probabilistic Bayesian Network Models

Some probabilistic safety assessment models based on Bayesian networks have been recommended recently for safety analysis of highways and roads. These methods provide a very natural and powerful alternative to traditional approaches, such as fault and event tree based methods. In this article, we present several new and original contributions to complement the inference engine tools of these models to provide new and relevant information about safety and backward analysis on one hand, and to learn the complex multidimensional joint probabilities of all variables, on the other hand. More precisely, we show how standard tools combined with the partitioning technique can be used in new ways to solve three relevant problems (1) to prognosticate the most probable combinations of variables leading to incidents, (2) to perform a backward analysis to identify the causes of accidents, and (3) to learn the model parameters using Bayesian conjugate methods (categorical and Dirichlet families). Finally, some real examples of applications are used to illustrate the proposed methods.     

Ammonia-lithium nitrate absorption chiller with an integrated low-pressure compression booster cycle for low driving temperatures

Single-effect absorption refrigeration hybridized with mechanical vapor compression in a vapor circuit is known as the absorption cycle with an integrated booster compressor. In this study, the compressor is located between the evaporator and the absorber. This paper presents a numerical model of this cycle with ammonia-lithium nitrate solution as the working pair. It is based on UA?ΔT_lm models for separate regions of plate-type heat exchangers. The results are offered as a function of external circuit flow parameters. Different pressure ratios of the compressor were tested for a wide range of hot water driving temperatures (55–95 °C), showing that low values are more beneficial. This cycle allows for working at lower driving temperatures than the single-effect cycle, with low electricity consumption. At the same driving temperature, the capacity is augmented with an increased compressor pressure ratio, thus allowing for demand matching of the cooling. This cycle, operating with hot water at 67 °C with a pressure ratio of 2.0, has the capacity of a single-effect absorption cycle at 94 °C. The electrical COP was found to be higher than that in an ammonia vapor compression cycle for comprehensive working conditions.