Optimation of cooled shields in insulations

A method to optimize the location, temperature, and heat dissipation rate of each cooled shield inside an insulation layer was developed. The method is based on the minimization of the entropy production rate which is proportional to the heat leak across the insulation. It is shown that the maximum number of shields to be used in most practical applications is three. However, cooled shields are useful only at low values of the overall, cold wall to hot wall absolute temperature ratio. The performance of the insulation system is relatively insensitive to deviations from the optimum values of the temperature and location of the cooling shields. Design curves for rapid estimates of the locations and temperatures of cooling shields in various types of insulations, and an equation for calculating the cooling loads for the shields are presented

More than one dynamic crossover in protein hydration water

Studies of liquid water in its supercooled region have led to many insights into the structure and behavior of water. While bulk water freezes at its homogeneous nucleation temperature of approximately 235 K, for protein hydration water, the binding of water molecules to the protein avoids crystallization. Here we study the dynamics of the hydrogen bond (HB) network of a percolating layer of water molecules, comparing measurements of a hydrated globular protein with the results of a coarse-grained model that has been shown to successfully reproduce the properties of hydration water. With dielectric spectroscopy we measure the temperature dependence of the relaxation time of protons charge fluctuations. These fluctuations are associated to the dynamics of the HB network of water molecules adsorbed on the protein surface. With Monte Carlo (MC) simulations and mean--field (MF) calculations we study the dynamics and thermodynamics of the model. In both experimental and model analyses we find two dynamic crossovers: (i) one at about 252 K, and (ii) one at about 181 K. The agreement of the experiments with the model allows us to relate the two crossovers to the presence of two specific heat maxima at ambient pressure. The first is due to fluctuations in the HB formation, and the second, at lower temperature, is due to the cooperative reordering of the HB network

Accumulation variations of selected heavy metals in Barbus xanthopterus in Karoon and Dez Rivers of Khuzestan, Iran

The concentrations of Cd, Pb, Ni and Hg were determined in gill, liver and muscle of Barbus xanthopterus in down streams of Karoon and Dez Rivers during summer 2009. Heavy metal concentrations varied significantly, depending on the types of the tissue in fish species. The levels of heavy metals such as Cd, Pb, Ni and Hg in the Barbus xanthopterus of Karoon River were higher than in Barbus xanthopterus of Dez River (Pliver>muscle. The concentration of Hg in Karoon River was in the sequence liver>gill>muscle but, in Dez River, it was in the sequence liver>muscle>gill. Among heavy metals (Cd, Pb, Ni and Hg), the accumulation of Pb was more than other heavy metals in fish (P<0.05). In both rivers, the accumulation of heavy metals in muscle of fish was higher than the world health organization (WHO) standard

Morphological changes of Bunni (Barbus sharpeyi) larvae in laboratory conditions

In this study, the early development of Bunni (Barbus sharpeyi) larvae was surveyed through morphological changes and measuring total length, standard length, head length, thickness of larvae, eye diameter and snout length. The initial period of the larval life can be divided into 2 phases: endogenous and exogenous food sources. During the first three days of the larvae development, there was a gradual yolk sac reduction until its complete absorption at the end of third day, indicating the necessity of exogenous feeding. From the fourth to eleventh day, the final development of the heart, gill, air bladder, fins and intestine were observed. Total length of newly hatched larvae was 6.26mm and total length of fifteen days larvae was 8.35mm. The larval development of Barbus sharpeyi was similar to other Barbus species

An extended laser flash technique for thermal diffusivity measurement of high-temperature materials

Knowledge of thermal diffusivity data for high-temperature materials (solids and liquids) is very important in analyzing a number of processes, among them solidification, crystal growth, and welding. However, reliable thermal diffusivity versus temperature data, particularly those for high-temperature liquids, are still far from complete. The main measurement difficulties are due to the presence of convection and the requirement for a container. Fortunately, the availability of levitation techniques has made it possible to solve the containment problem. Based on the feasibility of the levitation technology, a new laser flash technique which is applicable to both levitated liquid and solid samples is being developed. At this point, the analysis for solid samples is near completion and highlights of the technique are presented here. The levitated solid sample which is assumed to be a sphere is subjected to a very short burst of high power radiant energy. The temperature of the irradiated surface area is elevated and a transient heat transfer process takes place within the sample. This containerless process is a two-dimensional unsteady heat conduction problem. Due to the nonlinearity of the radiative plus convective boundary condition, an analytic solution cannot be obtained. Two options are available at this point. Firstly, the radiation boundary condition can be linearized, which then accommodates a closed-form analytic solution. Comparison of the analytic curves for the temperature rise at different points to the experimentally-measured values will then provide the thermal diffusivity values. Secondly, one may set up an inverse conduction problem whereby experimentally obtained surface temperature history is used as the boundary conditions. The thermal diffusivity can then be elevated by minimizing the difference between the real heat flux boundary condition (radiation plus convection) and the measurements. Status of an experimental study directed at measuring the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloys are presented. Preliminary measurements showing surface temperature histories are discussed

The comparison of heavy metals Hg, Cd and Pb in the tissues of Liza abu from Karoon and Bahmanshir Rivers, Khuzestan Province

A comparative study was conducted on concentration of heavy metals Hg, Cd and Pb in the muscle, liver and gill tissues of Liza abu in winter 2009, in Karoon and Bahmanshir Rivers of Khuzestan province. We used 216 specimens of Liza abu. Metals were extracted from the tissues using wet digestion method and concentration of the heavy metals was measured by Atomic Absorption Spectrophotometer. The highest concentration of Cd, Hg and Pb were measured at 0.540±0.264, 0.029±0.005 and 1.080±0.128mg/Kg dry weight respectively. The lowest concentration of Cd, Hg and Pb were found to be 0.434±0.035, 0.024±0.001 and 0.930±0.036mg/Kg dry weight, respectively. No significant differences in concentration of heavy metals Cd, Hg and Pb in the muscle, liver and gill of Liza abu from the Karoon and Bahmanshir Rivers were detected (P 0.05). Results showed accumulation of Hg and Cd was lower than the FDA standard but accumulation of Pb was higher than the WHO standard

Spawning season and fecundity of Sepia pharaonis In Bushehr coastal waters (Persian Gulf)

Fecundity rate and spawning season for cuttlefish (Sepia pharaonis), a commercially important species in Busheher coastal waters were studied from December 2007 to May 2008. We collected 142 specimens and after their sexuality were 18 males, 3 immatures, 16 first stage pieces, 14 second stage pieces and 91 pieces in third and fourth stages. The assesse d biological characteristics such as: Mantle length, weight of total body, Nidam ental gland, weight of head, weight of ovary and fecundity rate. We recorded 201 .8 plus or minus 6.8mm for mean, 280mm for maximum and 115mm for minimum mantle length. The mean body total weight was 895.8 plus or minus 143g, and the maximum was 2098g, while its mini mum was 241.13g. The mean, maximum and minimum Nidamental gland weight was 41.1 ± 18.6, 126.8, and 0.2g, respectively. For the relationship between mantle length (ML, mm) and fecundity we found the linear regression equation: Fecundity = -6 30.68+5.22ML. The mean, maximum and minimum fecundity rate was 494 plus or minus 131, 1246 and 178, respectively. The results of this study showed spawning season for Sepia pharaonis in the coastal waters of Busheher Province to be from the end of February to the end of June

The embryonic development and formation of Bunnei (Barbus sharpeyi Gunther, 1874)

Understanding the embryogenesis of Bunni is a useful tool for finding the time and suitable environmental conditions for spawning, growth requirements and use of techniques to increase the growth rate and survival. The stages of embryonic development for Bunnei (Barbus sharpeyi) was investigated in 22°C. The reared brood stocks were spawned in captivity condition. The oocytes were spherical, brown and very adhesive. The cleavage was fast and the first division was recorded within 15-20 minutes after fertilization. The blastulation and gastrulation were investigated in 7:40 and 13:10 hours after fertilization with the yolk sac diameter of 1.18±0.061mm (Mean±SD), respectively. The organogenesis was started 21 hours after the fertilization, when the blastopore was closed and notochord was formed. The embryonic stages were continued by appearance the brain, the somites and the melanophores on the yolk sac. The heart was beaten and shown the blood circulation 65 hours after the fertilization. The head, tail and pectoral fins were moved frequently. The embryo reached to pre hatching and final hatching 79:10 and 84:10 hours after fertilization, respectively, and the embryo existed from corion with the length of about 5.29±0/121mm (Mean±SD)

The Role of Pore Structure of SMFs-based Pd Nanocatalysts in Deactivation Behavioral Pattern Upon Acetylene Hydrogenation Reaction

In this research, SMFs panels were applied for further deposition of CNFs, ZnO and Al2O3 to hydro-genate selectively acetylene to ethylene. To understand the role of different structures of the examined supports, the characterization methods of SEM, ASAP, NH3-TPD and N2 adsorption-desorption isotherms were used. Following the characterization of green oil by FTIR, the presence of more unsaturated constitu-ents and then, more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO was confirmed, which in turn, could block the pores mouths. Besides the limited hydrogen transfer, the lowest pore diameters of Al2O3 / SMFs close to the sur-face, supported by N2 adsorption-desorption isotherms could explain the fast deactivation of this catalyst, compared to the other ones. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3521

The Formation of the Intermetallic-Containing Pd2Sn Alloy: The Creation of the Isolated Adsorption Sites

In the current study, tin-promoted Pd / MWNTs synthesized via polyol process were developed. TEM images evidences resulted in the formation of highly-dispersed Pd-Sn nanoparticles. The formation of Pd2Sn structural phase was confirmed by XRD and TPR techniques, composed mainly of intermetallic spe-cies, supported by XPS results. In this research, we applied intermetallic-containing tin-promoted catalysts for the selective hydrogenation reaction of acetylene as the case study. The presence of a discontinuity in the Arrhenius plots could come from the kinetic factor as a result of change in acetylene coverage on Pd metallic ensembles. The intermetallic-containing assembled catalysts led to the good management of cata-lytic performance due to the creation of isolated adsorption sites on the catalyst surface, resulting in the higher ethylene selectivity. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3521