Search

When nuclear power plants are under accident conditions, normal air-conditioning system will cease for safety considerations. However, the equipment still generates much heat and indoor temperature will rise rapidly, which threatens the personnel safety. Therefore, massive concrete envelopes with cooling fins are expected to absorb the heat passively from the indoor air continuously. The numerical simulations were conducted to study the temperature change and distribution during a 72-hour period. The results show that indoor temperature was 298.37 K at the final hour, with the maximal increase of 6.34 K in the beginning. The massive envelopes with cooling fins can be a reliable and effective way to mitigate the temperature rise under accident conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT Styrene-acrylonitrile copolymer (SAN)/acrylonitrile-styrene-acrylate terpolymer (ASA) blends (75/25, wt/wt) was toughened by blending with impact modifiers including chlorinated polyethylene (CPE), hydrogenated nitrile butadiene rubber (HNBR), and butadiene rubber (BR) and the impact property was tested at four temperatures (-30, −15, 0, and 25 °C). The combination of CPE and HNBR was imported to toughen the SAN/ASA blends, indicating that CPE and HNBR had similar toughening effect at room temperature but HNBR exhibited a better performance at low temperature. When a little HNBR was substituted by BR, the impact strength improved dramatically with the total content of impact modifiers keeping at 30 phr. After 15 phr CPE, 10 phr HNBR and 5 phr BR were employed into blends together, the impact strength reached to a peak of 14 kJ/m2 at −30 °C while the impact strength of the blends individually toughened by 30 phr CPE or 30 phr HNBR was 5 or 12 kJ/m2, respectively. The toughening mechanism showed that the low glass-transition temperature (-108 °C) of BR and the compatibilization between BR and matrix accounted for the improvement of toughness. Simultaneously, scanning electron microscopy, dynamic mechanical analysis, flexural and tensile properties, heat distortion temperature, and Fourier transform infrared spectroscopy were measured. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45364. [ABSTRACT FROM AUTHOR]

The special features inherent in the development of high-temperature deformation and structural evolution in materials are investigated, using a VT22 titanium alloy of the transition class (Ti - 4.74 mass% Al - 5.57 mass% Mo - 5.04 mass% V) subjected to helical rolling + aging as an example. This treatment is found to give rise to an intragrain fine acicular martensite structure with fine inclusions of α-phase particles of size ~1 μm. It is shown that in the alloy undergoing plastic deformation at temperatures approaching the polymorphic transformation temperature, the elongation to failure is in excess of 300%. The high plasticity of the alloy in the conditions considered is likely to be due to vigorous development of phase transformations and intensification of diffusion-controlled processes, including the effects of the evolution of the dislocation structure, growth of subgrains, and formation of new grains in the bulk of the pre-existing ones during plastic deformation. [ABSTRACT FROM AUTHOR]

Previous studies have found that both high temperature and low temperature increase the risk of childhood hand, foot and mouth disease (HFMD). However, little is known about whether temperature variation between neighboring days has any effects on childhood HFMD. A Poisson generalized linear regression model, combined with a distributed lag non-linear model, was applied to examine the relationship between temperature change and childhood HFMD in Hefei, China, from 1st January 2010 to 31st December 2012. Temperature change was defined as the difference of current day's mean temperature and previous day's mean temperature. Late spring and early summer (April-July) were chosen as the main study period due to it having the highest childhood HFMD incidence. There was a statistical association between temperature change between neighboring days and childhood HFMD. The effects of temperature change on childhood HFMD increased below a temperature change of 0 °C (temperature drop). The temperature change has the greatest adverse effect on childhood HFMD at 7 days lag, with 4 % (95 % confidence interval 2-7 %) increase per 3 °C drop of temperature. Male children and urban children appeared to be more vulnerable to the effects of temperature change. Temperature change between adjacent days might be an alternative temperature indictor for exploring the temperature-HFMD relationship. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate a temperature regime ranged from 15 to 30°C on survival, growth, life span and reproductive traits (reproductive period, clutch number, offspring number) of Phallocryptus spinosa from Iran. Newly hatched nauplii (N= 200 and 3 replicates per each treatment) were allocated into containers and maintained at various temperature regimes (at 15, 20, 25 and 30˚C). During trial, the larvae were fed with unicellular algae Dunaliella tertiolecta and Lansy PZ (lipid-enriched yeast). Survival and growth rate of P. spinosa with an interval of 3 days to 18 days were examined. After attaining adulthood, 16 pairs of adult P. spinosa were transferred from all culture vessels into separate containers supplied with 300 ml of brackish water (5 ppt) and similar temperatures to compare their life span and reproductive traits. Based on results obtained, maximum growth at shortest period (13.2±2.0 mm on day 12) was observed at 30°C; whereas, all P. spinosa died before reaching sexual maturity by day 15. Maximum survival (86%) was observed at 15°C; however, minimum growth also was obtained at the same temperature with none of P. spinosa reaching sexual adulthood. On the 18th day, P. spinosa reached sexual adulthood only at 20 and 25°C. Furthermore, a significant difference was observed in most of the reproductive traits especially in total egg production per female at 20°C. Thus, it seems that 20°C is the suitable temperature to rear this fairy shrimp. Future studies should be focused on the feasibility of mass production of this species as a valuable live feed in the aquaculture industry. [ABSTRACT FROM AUTHOR]

CO 2 bubble nucleation on the microrough poly(ε-caprolactone) surface has been investigated using a density functional theory approach. For the considered system, the effect of chemical and morphologic characteristics of poly(ε-caprolactone) on the solubility, surface tension, interfacial density distribution, nucleation free-energy barrier, and critical nucleus radius have been calculated to interpret the nucleation mechanism. All calculations are performed with the universal force field parameters. Some results have been examined by the available experimental data. According to the free-energy barrier and critical radius, the nucleation number with respect to pressure has been estimated under the instant depressurization. As a result, this work provides a theoretical explanation of bubble formation mechanism of polymer foaming at low temperature. [ABSTRACT FROM AUTHOR]

Abstract: It requires more energy to maintain a narrow indoor temperature range than a broader range, in which the building may be allowed to float with reduced conditioning for longer periods of time. A narrow range should presumably be preferable to the building occupants to justify its increased energy cost. At what widths are temperature ranges detected, preferred, or judged unacceptable? Three databases of occupant satisfaction in buildings are used to examine the acceptability of three classes of temperature range currently employed in the ISO and European standards, and proposed for the ASHRAE standard. These are alternatively identified as class A, B, and C, or category I, II, and III, but their specifications are identical. The A class (I category) is found to confer no relative satisfaction benefit to individuals or to realistic building occupancies. In addition, the differences in B and C class satisfaction are small. [Copyright &y& Elsevier]

Abstract: This paper examines optimal control strategies of variable air volume air conditioning system. The control strategies included a base control strategy of fixed temperature set point and two advanced strategies for insuring comfort and indoor air quality (IAQ). The first advanced control adjusts the fresh air supply rate and the supply air temperature to maintain the temperature set point in each zone while assuring indoor air quality. The second strategy controls the fresh air rate and the supply air temperature to maintain an acceptable thermal comfort and IAQ in each zone. The optimization problem for each control strategy is formulated based on the cost of energy consumption and constrained by system and thermal space transient models. The optimization problem is solved using genetic algorithm. The optimization scheme/model is applied to a case study for a building floor in Beirut weather. The thermal space and system component models were validated for the base strategy using Visual DOE 4.0 software [Architectural Energy Cooperation, San Francisco, USA; 2005 〈www.archenergy.com〉]. Energy savings up to 30.4% were achieved during the summer season of four months with the optimized advanced strategies when compared with the conventional base strategy while comfort and IAQ were satisfied. [Copyright &y& Elsevier]

Abstract: In this study, the potential saving of cooling energy by elevated air speed which can offset the impact of increased room air temperature on occupants’ comfort, as recommended in the present standards (ASHRAE 55 2004, ISO 7730 2005 and EN 15251 2007), was quantified by means of simulations with EnergyPlus software. Fifty-four cases covering six cities (Helsinki, Berlin, Bordeaux, Rome, Jerusalem and Athens), three indoor environment categories I, II and III (according to standard EN 15251 2007) and three air velocities (<0.2, 0.5 and 0.8m/s) were simulated. The required cooling/heating energy was calculated assuming a perfectly efficient HVAC system. A cooling energy saving between 17 and 48% and a reduction of the maximum cooling power in the range 10–28% has been obtained. The results reveal that the required power input of the fan is a critical factor for achieving energy saving at elevated room temperature. Under the assumptions of this study, the energy saving may not be achieved with the methods for air speed increase, such as ceiling, standing, tower and desk fans widely used today when the power consumption of the fan is higher than 20W. [Copyright &y& Elsevier]

In this work, we explore the temperature control of heterogeneous reactive distillation. By heterogeneous reactive distillation, we mean a two-liquid phase exists in the reflux drum and a decanter is used to separate the aqueous product from the organic reflux. Process characteristics of n-butyl propionate are explored and a systematic procedure is proposed for the design of butyl propionate reactive distillation. The control structure design procedure consists of the following steps: (1) setting the control objective, (2) selection of manipulated variables, (3) determination of temperature-control trays, (4) finding controller settings for regulatory control, and (5) providing feedforward compensation for production rate variation. Because specifications on the bottoms product have to be met and stoichiometric balance has to be maintained, we have a 2 x 2 control problem with two obvious inputs: reboiler duty and feed ratio. The reactive distillation exhibits unique temperature sensitivities and the nonsquare relative gain successfully identifies temperature-control trays, which results in an almost one-way decoupled system. Therefore, decentralized PI controllers are used at the regulatory level. As a result of the unique feature of a kinetically controlled distillation column, maintaining constant tray temperatures does not imply the same quality specification. Feedforward temperature compensation is necessary to maintain the desired product composition. The proposed design procedure is further extended to butyl acetate reactive distillation, where a similar process behavior is observed, and good control performance can be achieved using simple temperature control. [ABSTRACT FROM AUTHOR]