Optimization of Heat Processing of Farmed Atlantic Cod (Gadus morhua) Muscle with Respect to Cook Loss,Water Holding Capacity,Color, and Texture

Convenience products of fish that are heat processed in-pack are often subjected to a compromise between quality and durability within the framework of required safety. The purpose of this study was to provide knowledge for optimizing pasteurization of cod muscle by quantifying changes in water holding capacity (WHC), cook loss, color, and texture within a wide range of processing times and temperatures. A heat load equivalent to 2 min at 70°C may be applied to the cod while maintaining the WHC above 66%, the cook loss below 5.6%, and keeping hardness and whiteness low, provided that the processing temperature is kept in the range 68 ± 4°C.     

杉木采伐对集水区土壤热状况的影响

土壤作为森林生态系统的子体系 ,是林木扎根并赖以生存的基础 ,也是土壤微生物一切生命活动的场所。因此 ,有关土壤养分、水分及其土壤物理结构特征等方面的研究报告颇多 (王政权等 ,2 0 0 0 ;张合平等 ,1 997)。但是有关森林土壤的热状况 ,以及林木采伐后对土壤热状况影响的研究报导很少 (康文星等 ,1 989;刘煊景等 ,1 993)。本文在获得采伐前连续 3年和采伐后连续 3年的观测数据的基础上 ,就杉木人工林生态系统土壤的热状况各因子之间 ,土壤各组成成分对热状况的单一或组合效应 ,以及皆伐这种人为强烈干扰对土壤热状况的影响进行了剖析。…     

Thermal degradation modeling of flexural strength of wood after exposure to elevated temperatures

Abstract

Wood is being used heavily in single-family residential dwellings. Therefore, it is important to categorize their response when exposed to elevated temperatures for a sustained period of time. An important aspect of structural fire design is to assess postfire residual strength of existing structures. This study addresses this issue by developing models to predict strength degradation of wood after exposure to elevated temperature. The objectives were to (a) study the effect of exposure time on bending strength [Modulus of Rupture (MOR)] of wood at elevated temperatures, (b) interpret any relationships between different temperature and time of exposure using kinetics and a statistical approach, and (c) compare the two approaches. Two hundred thirty-two samples in total were tested in flexure as a function of exposure time and several temperatures. MOR of wood decreased as a function of temperature and exposure time. Rate of degradation was higher at higher temperatures. These results were fit to a simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model with apparent activation energy of 37.4 kJ/mol. A regression-based statistical model was also developed. The kinetics-based model fit the data better with one less parameter and predictions consistently matched the observed values, making the model preferred over the regression approach.     

Plant antifreeze proteins and their expression regulatory mechanism

Low temperature is one of the major limiting environmental factors which constitutes the growth, development,productivity and distribution of plants. Over the past several years, the proteins and genes associated with freezing resistance of plants have been widely studied. The recent progress of domestic and foreign research on plant antifreeze proteins and the identification and characterization of plant antifreeze protein genes, especially on expression regulatory mechanism of plant antifreeze proteins are reviewed in this paper. Finally, some unsolved problems and the trend of research in physiological functions and gene expression regulatory mechanism of plant antifreeze proteins are discussed.     

木材弦向导热系数的理论表达式

分析木材细胞结构形态,以长匣子形作为木材细胞模型,根据材料导热与导电规律的相似性,应用类比推理方法,从欧姆电阻定律推出材料导热的热阻公式;依据该细胞模型和热阻公式推导木材弦向导热系数的理论表达式,从而揭示木材弦向导热系数是木材孔隙率的函数。孔隙率越大的木材,导热系数越小,并实际计算了24种木材的弦向导热系数,与试验值比较,理论值的最大误差12.6%,平均误差小于6.4%。     

Mechanical Performance and Thermology Performance of 20CrMo Steel at High Temperature

Employing the Gleeble-1500D thermal analogue machine and the STA449 synthesis thermal analyzer,the study on hot ductility and parts of thermology performance of 20CrMo steel has been carried out , many consulted foundation data has been obtained, the optimum ductility temperature arrange has been found, contraction of cross sectional area is only 30% between 600 degree and 775 degree, but contraction of cross sectional area is more than 80% between 800 degree and 1 250 degree, contraction of cross sectional area drops to under 60% rapidly between 1 350 degree and melting point,a curve is drawn showing the relationshi Pbetween heat capacity and the variation of temperature for the first time, the counting formulas of the heat capacity are regressed by disjunction. A curve is drawn showing the relationshi Pbetween the coefficient of thermal expansion and the variation of temperature, and their application in continuous casting is discussed herein.     

Influence of Indoor Thermal Environment on Thermal Comfort of Human Body

Analyses the thermal environment parameters from physiological aspect and from psychological aspect respectively. Introduces the conception of thermal comfort of human body from heat balance aspect. Presents some measures to improve indoor thermal environment and advance thermal comfort of human body. Analyses the influence of indoor thermal environment on thermal comfort of human body and some questions on the aspect of this research, also puts forward some advices.     

Phase Transformation Diffusion Bonding of Titanium Alloy to Stainless Steel

Jointing of titanium alloy and stainless steel is very often in the fields like aviation, chemical plants etc. The combination of materials has the advantages of both titanium alloy and stainless steel and will reduce the consumption of titanium resource. The phase transformation diffusion bonding of TA17 titanium alloy to 0CriSNigTi stainless steel are carried out on Gleeble - 1500D. The effcet of maximum thermal cycle temperature, the tensile strength, the fracture surface and microstruture of the joints are investigated. The results show that TiFe and TiFe2 intermetallics and some solid solutions are formed along the interface, when maximum thermal cycle temperature increase, the area proportion of intermetallics in the fracture surface increase, which are detrimental to the mechanical properties of the transition joints.     

Influence of Humidity Distribution on Cross Diffusion Extent in Building Space

The influencing relationship equation of humidity distribution on the characteristics and extent of cross diffusion was proposed based on the non equilibrium thermodynamic theory. With the parameters of temperature, humidity and contaminant gas concentration, a further study on the relationship was employed. It was showed that the temperature grads and the contaminant gas mass grads were less than zero when the humidity grads and additional diffusion coefficient were both positive/negative, otherwise the two grads were more than zero. Moreover, the higher the initial temperature and contaminant gas concentration were, the greater the absolute values of temperature grads and contaminant gas mass grads were, with the same humidity grads and additional diffusion coefficient. Whereas the influence of initial temperature was limited, and that of initial contaminant gas concentration was obvious.     

Performance analysis of a concentrating solar hybrid photovoltaic thermal system

The photovoltaic components of a hybrid photovoltaic thermal (PV/T) system are combined with a solar thermal collector, which generates both thermal and electrical energy simultaneously with a higher integrated efficiency. A three dimensional steady model of the concentrating solar PV/T system which has a plate type metallic thermal collector with a serpentine rectangular channel is developed. The processes of photovoltaic and thermal transformation and heat transfer in the PV/T collector are calculated and simulated. The effects of the optical concentrating ratio, coolant mass flow rate, ambient air velocity and glass cover on both thermal and electrical performance of the collector are presented and discussed.