贮藏时间和物流温度对“纽荷尔”脐橙货架寿命和品质的影响

以赣南脐橙主栽品种"纽荷尔"为试材,研究了贮藏时间(30,60,90,120 d)及物流温度(5℃和10℃)对果实货架寿命和品质的影响。研究结果表明:脐橙在冷藏(5℃)条件下,随着贮藏时间的增加,果实品质逐渐下降,并缩短了物流转货架后贮藏寿命,尤其是在果实贮藏超过90 d以后,严重影响了果实货架品质。在贮藏前期,物流温度对脐橙果实货架寿命和品质无显著影响,但5℃物流较10℃物流能显著降低贮藏60 d脐橙货架期果实腐烂率,较好保持脐橙果实TSS、总糖及Vc含量,从而更好维持果实品质,说明适时、适温冷链物流对延长脐橙货架寿命、保持果实品质有很好的作用。

Comparison of Soil Respiration in Two Grass-Dominated Communitiesin the Xil in River Basin: Correlations and Controls

A comparative study of soil respiration was conducted between in a semi-arid steppe community and in a wet meadow community in the Xilin River Basin of Nei Mongol. The seasonal pattern, the climatic controls, and the correlations of soil respiration with plant biomass components, were examined for each community. The main results are reported as follows: (1) The seasonal changes in soil respiration in the two communities had similar dynamic patterns (both being of two peaks), ranging from 312.8 to 1738.9 mg C(.)m(-2).s(-1) and from 354.6 to 2235.6 Mg C.m(-2).s(-1) in the growing season for the steppe plot and the meadow plot respectively. The soil respiration rate of the meadow plot was distinctly higher than that of the steppe plot, with the daily averages being 1349.6 mg C-m(-2).s(-1) and 785.9 mg C-m(-2).s(-1) respectively. (2) The correlation between soil respiration rate and soil moisture was much more significant than with temperature for the steppe community, and being on the contrary for the meadow community, reflecting the different effects of the two climatic factors in different habitats. Based on these regressive relations, the total CO2 efflux rate in the growing season in 2001 was estimated as 142.4 g C/m(2) in the steppe plot, and 236.1 g C/m(2) in the meadow plot. (3) There was no evident relation between the total canopy biomass and CO2 evolution rate, but a significant power function relation between the live canopy biomass and CO2 evolution rate in the meadow plot was detected. In the steppe plot, there existed only a weak relation between soil respiration and either live or total canopy biomass.

Studying creation of bulk elementary excitation by heaters in superfluid helium-II at low temperatures

In this paper, the obtained experimental results concerning creation of bulk elementary excitations （BEEs） in isotopically pure liquid ^4He at low temperatures -60 mK are discussed. Positive rotons＇ （R^＋-rotons） creation by a pulsed heater was studied. Signals were recorded for the following quantum processes： quantum evaporation of ^4He-atoms from the free liquid-helium surface by the BEEs of the liquid helium-Ⅱ, and BEEs reflection from the free surface back into the bulk liquid. Typical signals are shown, and ratios of signal amplitudes are evaluated. For long heater pulses from 5 to 10 μs, appearance of the second atomic cloud consisting of evaporated ^4He-atoms was observed in addition to the first atomic cloud. It is thought that the first atomic cloud of the evaporated helium atoms consists of very fast ^4He-atoms with energies ～35 K evaporated by positive rotons with the special energies ～17 K （～2ER～2×8.6 K with ER representing the roton minimum energy） corresponding to the third non-dispersive Zakharenko wave. The second cloud of slower ^4He-atoms was created by surface elementary excitations （SEEs or ripplons） possessing the special energies ～7.15 K representing the binding energy. It was assumed that such SEEs can be created by phonons incoming to the liquid surface with special energies ～6.2 K corresponding to the first non-dispersive Zakharenko wave which can interact at the liquid surface with the same phonons already reflected from the surface for long heater pulses. Also, some pulsed-heater characteristics were studied in order to better understand the features of such heaters in low temperature experiments.

Determination of Thermal Properties of Cuts and Residue Streams Obtained in the Molecular Distillation Process

A real-time sensing of the molecular distillation process temperature by a FLUKE brand thermograph Ti50 IR FlexCam and thermography technique was realized. After completion of the molecular distillation, three properties of heat transport chain cuts and residues obtained in the process were estimated by Differential Scanning Calorimetry （DSC） （specific heat, enthalpy, thermal conductivity）. These properties are of great importance for improving oil characterization and for future modeling and simulation of the molecular distillation process. The results show that through the method of Differential Scanning Calorimetry, profiles have been obtained from the variation of specific heat, enthalpy and thermal condutivity as a function of temperature for samples of cuts from the distillation （ASTM D-2892） and fractions of distillate and residue from the process of molecular distillation.

Indirect heat integration across plants using hot water circles

Total site heat integration(TSHI) provides more opportunities for energy saving in industry clusters. Some design methods including direct integration using process streams and indirect integration using intermediate-fluid circuits, i.e., steam, dowtherms and hot water, have been proposed during last few decades. Indirect heat integration is preferred when the heat sources and sinks are separated in independent plants with rather long distance. This improves energy efficiency by adaption of intermediate fluid circle which acts as a utility provider for plants in a symbiotic network. However, there are some significant factors ignored in conventional TSHI, i.e. the investment of pipeline, cost of pumping and heat loss. These factors simultaneously determine the possibility and performance of heat integration. This work presents a new methodology for indirect heat integration in low temperature range using hot water circuit as intermediate-fluid medium. The new methodology enables the targeting of indirect heat integration across plants considering the factors mentioned earlier. An MINLP model with economic objective is established and solved. The optimization results give the mass flow rate of intermediate-fluid, diameter of pipeline, the temperature of the circuits and the matches of heat exchanger networks(HENS) automatically. Finally, the application of this proposed methodology is illustrated with a case study.

Parametric Optimization of Organic Rankine Cycle with R245fa/R601a as Working Fluid

In order to select the appropriate working fluids and optimize parameters for medium-temperature geothermally-powered organic Rankine cycle(ORC), R245 fa is mixed with R601 a at geothermal water temperature of 110 ℃. Based on thermodynamics, the characteristics of mixture and its influence on the performance of ORC under different evaporating temperatures and composition proportions are analyzed. Results show that the zeotropic mixture R245fa/R601a(0.4/0.6) has the highest performance. When the evaporating temperature reaches 67 ℃, the outlet temperature of geothermal water is 61 ℃, the net power output is the highest and the thermal efficiency is about 9%.

Convection and Phase-Separation Behavior of Binary Mixture under Microwave Irradiation

When the temperature of a thin layer of a solution is vertically controlled, Rayleigh-Bemard convection is observed. When a binary isobutyric acid aqueous solution is used as the binary mixture, phase separation is simultaneously induced at the approximate critical solution temperature. In this study, these behaviors of phase separation and convection were observed under microwave irradiation. When the microwave power was higher, coalescence of fine droplets after the initial phase separation was accelerated and the coalescence size decreased. However, the solution became more unsteady because of smaller interfacial tension or greater heat generated by the radiation. Finally, in cases of higher microwave power, a steady convection pattern could not exist for a prolonged period because the water-rich phase was more active toward microwave irradiation, and the vertical temperature gradient became disordered.

Differences in sensitivity of native and exotic fish species to changes in river temperature

This paper describes the effects that temperature changes in the Rhine river distributaries have on native and exotic fish diversity. Site-specific potentially affected fractions （PAFs） of the regional fish species pool were derived using species sensitivity distributions （SSDs） for water temperature. The number of fish species in the river distributaries has changed remarkably over the last century. The number of native rheophilous species declined up until 1980 due to anthropogenic disturbances such as commercial fishing, fiver regulation, migration barriers, habitat deterioration and water pollution. In spite of progress in river re- habilitation, the native rheophilous fish fauna has only partially recovered thus far. The total number of species has strongly in- creased due to the appearance of more exotic species. After the opening of the Rhine-Main-Danube waterway in 1992, many fish species originating from the Ponto-Caspian area colonized the Rhine basin. The yearly minimum and maximum river tempera- tures at Lobith have increased by circa 4 ~C over the period 1908-2010. Exotic species show lower PAFs than native species at both ends of the temperature range. The interspecific variation in the temperature tolerance of exotic fish species was found to be large. Using temporal trends in river temperature allowed past predictions of PAFs to demonstrate that the increase in maximum river temperature negatively affected a higher percentage of native fish species than exotic species. Our results support the hy- pothesis that alterations of the river Rhine＇s temperature regime caused by thermal pollution and global wanning limit the full recovery of native fish fauna and facilitate the establishment of exotic species which thereby increases competition between native and exotic species. Thermal refuges are important for the survival of native fish species under extreme summer or winter temperature conditions