Energy and Mass Transfer Phenomena in Natural Draft Cooling Towers

In this paper, the development of natural draft cooling towers diagnostics is presented. Diagnostic method is based on measurements of velocity and temperature fields of the airflow in the entire surface area of cooling tower and the raised phenomenological model of heat and mass transfer in a selected reference vertical segment of cooling tower. Velocity and temperature fields of the airflow were measured with the aid of a remote control mobile robot unit that was developed to enable measurements in an arbitrary measurement point above the spray zones over the entire cooling tower area. Topological structures of the humid air velocity profiles and temperature profiles above the spray zones were obtained at constant integral parameters of a power plant. Measurement results of temperature and mass flow characteristics of the air and water flows in a selected reference vertical segment of cooling tower are presented in the form of phenomenological dependence. Phenomenological dependence links local cooling tower efficiency, geometrical characteristics of spray elements, and air and water flow rates. In the concluding part, both methods are applied together on a selected segment of cooling tower, and local and integral cooling tower efficiency can be determined.     

Suitability of some selected maize hybrids from Serbia for the production of bioethanol and dried distillers' grains with solubles

BACKGROUND: Bioethanol is mostly produced from starchy parts of the corn grain kernel leaving significant amounts of valuable by‐products such as dried distillers' grains with solubles (DDGS) which can be used as a substitute for traditional feedstuff. The suitability of six maize hybrids from Serbia was investigated for bioethanol and DDGS production. The correlation between physical and chemical characteristics of the grain, bioethanol yield and quality of the corresponding DDGS was assessed. RESULTS: All hybrids had very different chemical composition and physical characteristics which could allow various applications. The highest bioethanol yield (94.5% of theoretical) and volumetric productivity (2.01 g l^?1 h^?1) were obtained with hybrid ZP 434 and the lowest with ZP 611k. Regarding chemical composition, all DDGS samples manifested good properties as feed components. Their protein content was higher compared to the kernel. In addition, the samples showed high digestibility and high mineral content, especially of calcium and phosphorus. CONCLUSION: A hybrid ZP 434 was selected as the most promising bioethanol producer. This property is attributed to the highest level of soft endosperm which is more susceptible to starch‐hydrolysing enzymes. A high yield potential per hectare makes it the best candidate for commercial bioethanol production. © 2012 Society of Chemical Industry     

Socio-Economic Demands,Ecological Conditions and the Power of Tradition: Past Woodland Management Decisions in a Central European Landscape

Humans have managed European landscapes, including woodlands, for millennia. Prior to the birth of modern forestry in the eighteenth and nineteenth centuries, there existed two basic management forms for lowland broadleaved woods: coppicing and wood pasture. While the existence and characteristics of these two basic management types are well-known, the reasons why particular woods were coppiced while others pastured are little investigated. As a case-study, we chose two large ancient woods in the southern Moravian region of Central Europe. One was managed as coppice, while the other as wood pasture for most of their histories. The woods are similar in size, location, climate and vegetation. We examined several potential explanations (terrain morphology, soil productivity, abundance of woodland, ownership and economy) for past management decisions in these woods. We found that the links between soil productivity, economic demands and ownership were of key importance. Other factors were less significant, for example woodland abundance played no detectable role in spite of the decreasing availability of woodland resources. We also found that tradition mattered; it took a major shift in ideology to change entire management strategies. In sum, management decisions were driven by a complex network of multiple interactions among the individual factors.     

Photoelectric properties of MISM phthalocyanine structure

Langmuir-Blodgett films have been prepared from copper tetra-4-t-butylphthalocyanine. A voltage dependence of capacitance can be attributed to the presence of a Schottky depletion layer. The barrier potential was determined as l·4eV, and the carrier concentration about 10²⁴m^?3     

A New and Fast HPLC Method for Determination of Rutin, Troxerutin, Diosmin and Hesperidin in Food Supplements Using Fused-Core Column Technology

A new and fast high-performance liquid chromatography (HPLC) method using fused-core column for separation of rutin, troxerutin, diosmin, and hesperidin has been developed and used for determination of these flavonoids in food supplements. Efficient separation of flavonoids and internal standard methylparaben was achieved on the fused-core column Ascentis Express RP-Amide (100?×?3.0 mm), particle size 2.7 μm, with mobile phase acetonitrile/water solution of acetic acid pH?3 (30:70, v/v) at a flow rate of 1.0 mL?min^?1 and at temperature 50 °C. The detection wavelengths were set at 283 nm for hesperidin and at 255 nm for rutin, troxerutin, diosmin, and internal standard methylparaben. Under the optimal chromatographic conditions, good linearity with correlation coefficients in the range (r?=?0.9991–0.9998; n?=?7) for all flavonoids was achieved. Commercial samples of food supplements were extracted with 100 % dimethyl sulfoxide using ultrasound bath for 10 min and then diluted to methanol. A 5-μL sample volume of the filtered solution was directly injected into the HPLC system. Accuracy of the method defined as a mean recovery of flavonoids from food supplement matrix was in the range 96.2–104.4 % for all flavonoids. The intraday method precision was satisfactory, and relative standard deviations of sample analysis including preparation and determination of different food supplements were in the range 0.5–3.5 % for all flavonoids. The developed method has shown high sample throughput during sample preparation process, modern separation approach, and short time (5 min) of analysis.     

Resols hardened by Methyl Formate—a Contribution to raising Occupational and Environmental Standards in the Foundry

The introduction of some advanced methods of mould and core production may well have an adverse effect on the health and well-being of the operator, or lead to a deterioration in the internal and external environment of the foundry. In this presentation the authors discuss the use of sands bonded with an alkaline phenolic resin, hardened by methylformate vapour. Points examined include chemical changes during thermal destruction of the sand binder during pouring, solidification and cooling of the casting, and during the subsequent reclamation of the sand. It is concluded that this particular process offers a number of environmental advantages in addition to its production attributes.     

The psychology of thinking before the cognitive revolution: Otto Selz on problems, schemas, and creativity.

Otto Selz has been hailed as one of the most important precursors of the cognitive revolution, yet surprisingly few studies of his work exist. He is often mentioned in the context of the Würzburg School of the psychology of thinking and sometimes in the context of Gestalt psychology. In this paper, it is argued that Selz’s emphasis on the role of problems and schemas in the direction of thought processes and creativity sets him apart from the program of the Würzburg School. On the other hand, by developing a theory of thinking that is exclusively at the intentional level, Selz also differs from psychologists that take physics as a model for psychology, such as the Gestalt psychology of Wolfgang K?hler. Special emphasis is given in this paper to Selz’s use of the concept of problem or task and the concept of the schema. It is further argued that the concept of the schema is the result of Selz’s adaptation of the theory of relations as developed by the philosopher Meinong. The paper begins with a sketch of Selz’s life that ended so tragically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low IFT gas–oil gravity drainage in fractured carbonate porous media

This paper addresses a study of gas–oil gravity drainage in fractured carbonate rock subjected to gas injection in low interfacial tension. The purpose of the experiments described in the paper was to investigate gas injection in fractured carbonate reservoirs in both secondary and tertiary cases (after water injection), focusing on gravity drainage using equilibrium gas followed by re-pressurization. Gas injection experiments were performed on 20 cm long and low permeable outcrop chalk core surrounded with a fracture established with a novel experimental set-up in reservoir conditions. The core was saturated with binary mixture live oil consisting of C₁ and C₇ of a known composition, while the fracture was filled with sealing material to obtain a homogeneous saturation. After core initialization, the sealing material was removed by increasing the temperature to higher than its melting point and displaced by live oil. Gas was then injected into the fracture and gravity drainage experiments were performed in low interfacial tension (< 0.5 mN/m) where the IFT between the phases were measured experimentally by selecting the proper pressure and temperature.Experiments were performed at different pressures and reversibility of the effect of the interfacial tension was checked by re-pressurization process. The oil recovered from the bottom side of the block was measured versus time.Based on the results of this study, the recovery of oil showed a significant increase by re-pressurization in gravity drainage process. It was also clear that low IFT gravity drainage is capable to recover a significant amount of oil in fractured reservoirs even after water injection.     

Reduction rules for reset/inhibitor nets

Reset/inhibitor nets are Petri nets extended with reset arcs and inhibitor arcs. These extensions can be used to model cancellation and blocking. A reset arc allows a transition to remove all tokens from a certain place when the transition fires. An inhibitor arc can stop a transition from being enabled if the place contains one or more tokens. While reset/inhibitor nets increase the expressive power of Petri nets, they also result in increased complexity of analysis techniques. One way of speeding up Petri net analysis is to apply reduction rules. Unfortunately, many of the rules defined for classical Petri nets do not hold in the presence of reset and/or inhibitor arcs. Moreover, new rules can be added. This is the first paper systematically presenting a comprehensive set of reduction rules for reset/inhibitor nets. These rules are liveness and boundedness preserving and are able to dramatically reduce models and their state spaces. It can be observed that most of the modeling languages used in practice have features related to cancellation and blocking. Therefore, this work is highly relevant for all kinds of application areas where analysis is currently intractable.     

Apparent fracture toughness of low-carbon steel CSN 411353 as related to stress corrosion cracks

The occurrence of cracks in structural components indicates a certain threat to their reliable operation, because these cracks can grow during operation and reach critical sizes, leading to fracture. The fracture resistance of a structural component is given by the fracture toughness of the material, determined on standardized specimens with a precycled fatigue crack, and the constraint. The fracture toughness itself depends also on the environment. There is enough evidence that in the conditions of the environment assisted cracking the fracture toughness can be significantly reduced by hydrogen mechanism. Our research results have confirmed this and have demonstrated a considerable reduction in the stress corrosion fracture toughness as compared to that related to fatigue cracks. This should be taken into account when assessing the integrity of structural components with stress corrosion cracks. This paper presents experimental results concerned with the stress corrosion fracture toughness of specimens from a DN150 gas line pipe made of low-C steel CSN 411353.