机械化黄酒生产中酵母的生长及控制

机制黄酒始于20世纪50年代,主要采用纯种发酵工艺,酵母菌的生长对酒质影响较大。以85#酵母、生麦曲和苏-16#纯种培养熟麦曲混合曲(9∶1)为糖化发酵剂,采用大罐发酵工艺,探讨糖度变化与酵母生长条件的关系。试验结果表明,机制黄酒最高糖化温度仅31℃左右;酵母接种量以2.5%～3.0%为宜,接种酵母应为稳定期,即培养40h左右的速酿酵母,可有效缩短酵母生长迟缓期;在酵母对数生长期,应保持有充足的糖分提供给酵母营养,一般为50～150g/L;稳定期酵母浓度可达4亿/ml左右,糖度下降速度可达7.5g/L·h,酒精度上升1.75%/h左右;当醪液酒精度达到10%(v/v),糖度4～5g/L,酵母浓度3亿/ml左右时,即进入衰退期;衰退期的酵母不再增殖,当酒精度达18%(v/v)时,出现酵母凝聚现象,发酵液变清,酵母出芽率几乎为零,揭示整个发酵结束。(一平)     

The Open City and the e[ad] School of Architecture and Design

Located in Ritoque on central Chile's Pacific coast, Open City is a unique community established in the 1970s by faculty members from the nearby e[ad] school of architecture at the Pontifical Catholic University of Valparaíso. Here Professor David Jolly Monge , a founding member of the Open City, and Guest-Editors Christian Hermansen Cordua and Michael Hensel describe how the construction of structures on the site offer the collective community and students alike ongoing opportunities for ‘thinking, research and experimentation’.     

Interaction parameter, k12, for non-azeotropic refrigerant mixtures

The interaction parameter, k₁₂, is determined from the experimental equilibrium data obtained by other authors. Vapour-liquid equilibria for binary mixtures of halocarbon refrigerants are predicted using the Redlich-Kwong-Soave equation of state. The mixtures considered are: R14-R23, R23-R12, R13-R12, R13-R11, R13B1-R22, R13B1-R152a, R22-RC318, R12-RC318, R12-R11.     

Mixing rules for the specific heat capacities of several HFC-mixtures

The specific heat capacity at constant pressure (c_p) of some relevant HFCs as replacements for R12, R502 and R22 was measured. The liquids investigated are binary or ternary mixtures of R134a, R152a, R125, R32 and R143a. Empirical functional relations in polynomial forms between the temperature, specific heat capacity and concentration are established and the coefficients of the polynomial correlations are presented. These equations can be used to calculate the c_p-values for the mixtures investigated over the whole concentration range and the predicted properties generally agree with the source data to ca ± 0.1% for the pure substances. The accuracy of the measurements is better than <1% for the pure fluids and <1.5% for the mixtures. Differences between 1 and 2% can occur only at temperatures >40°C and < −50°C.     

电容式MEMS开关中弹性膜应力对驱动电压的影响

详细分析了多种参数对 MEMS电容式开关驱动电压的影响 ,包括材料选取和工艺参数变化 ,并对驱动电压理论值进行计算。利用表面微机械加工技术在硅衬底上实现了电容式开关 ,测试结果表明采用 Al0 .96 Si0 .0 4弹性膜和厚胶牺牲层工艺能获得适中的剩余应力释放 ,微桥应力约为 10 6 N/m2 ,这为获得较低的开关驱动电压提供了可能。对长 1m m的 MEMS开关 ,当弹性膜厚为 0 .5μm,桥高为 3μm、桥宽为 30 μm、桥长为 2 50 μm时获得了 2 5V的驱动电压 ,S参数测试表明该电容式开关 1～ 4 0 GHz频段内的插入损耗低于 1d B。     

The impact of river regulation on the lotic macroinvertebrate communities of the lower rhǒne,France

Channelization and the construction of 12 dams on the Lower Rhǒne during the last 30 years increased the morphological and biological effects of 19th century embanking along the river. These trends were demonstrated on the main channel, i.e. the central axis of the alluvial floodplain, by the synchronic study of the benthic macrofauna of six lowhead hydroelectric impoundments. The variability of the most significant taxa was investigated by an ANOVA, and the data-samples matrix was processed with a Principal Components Analysis in order to analyse the communities organization and their significance. The benthic macroinvertebrate communities of the channel include some lentic potamic species topographically related with this kind of river (metapotamon), as well as eurytopic and pollution-tolerant species. Thus, the Lower Rhǒne has become a slow potamic river, in the same way as other large mid-European rivers. Flow velocity appears to be the most important structural factor in a large regulated river. The homogeneity of the macroinvertebrate communities and the absence of longitudinal typology show that, in a very intensely regulated river, the River Continuum Concept is too theoretical, and the disturbing effects of dams on longitudinal changes and species response to regulation must be taken into account.     

Prediction of two-phase pressure gradients of refrigerants in horizontal tubes

Two-phase pressure drop data were obtained for evaporation in two horizontal test sections of 10.92 and 12.00 mm diameter for five refrigerants (R-134a, R-123, R-402A, R-404A and R-502) over mass velocities from 100 to 500 kg/m² s and vapor qualities from 0.04 to 1.0. These data have then been compared against seven two-phase frictional pressure drop prediction methods. Overall, the method by Müller-Steinhagen and Heck (Müller-Steinhagen H, Heck K. A simple friction pressure drop correlation for two-phase flow in pipes. Chem. Eng. Process 1986;20:297–308) and that by Grönnerud (Grönnerud R. Investigation of liquid hold-up, flow-resistance and heat transfer in circulation type evaporators, part IV: two-phase flow resistance in boiling refrigerants. Annexe 1972-1, Bull. de l'Inst. du Froid, 1979) were found to provide the most accurate predictions while the widely quoted method of Friedel (Friedel L. Improved friction drop correlations for horizontal and vertical two-phase pipe flow. European Two-phase Flow Group Meeting, paper E2; June 1979; Ispra, Italy) gave the third best results. The data were also classified by two-phase flow pattern using the Kattan-Thome-Favrat (Kattan N, Thome JR, Favrat D. Flow boiling in horizontal tubes. Part 1: development of a diabatic two-phase flow pattern map. J. Heat Transfer 1998;120:140–7; Kattan N, Thome JR, Favrat D. Flow boiling in horizontal tubes. Part 2; new heat transfer data for five refrigerants. J Heat Transfer 1998;120:148–55; Kattan N, Thome JR, Favrat D. Flow boiling in horizontal tubes. Part 3: development of a new heat transfer model based on flow patterns. J. Heat Transfer 1998;120:156–65) flow pattern map. The best available method for annular flow was that of Müller-Steinhagen and Heck. For intermittent flow and stratified-wavy flow, the best method in both cases was that of Grönnerud. It was observed that the peak in the two-phase frictional pressure gradient at high vapor qualities coincided with the onset of dryout in the annular flow regime.     

Refrigerant charge, pressure drop, and condensation heat transfer in flattened tubes

Horizontal smooth and microfinned copper tubes with an approximate diameter of 9 mm were successively flattened in order to determine changes in flow field characteristics as a round tube is altered into a flattened tube profile. Refrigerants R134a and R410A were investigated over a mass flux range from 75 to 400 kg m⁻² s⁻¹ and a quality range from approximately 10–80%. For a given refrigerant mass flow rate, the results show that a significant reduction in refrigerant charge is possible. Pressure drop results show increases of pressure drop at a given mass flux and quality as a tube profile is flattened. Heat transfer results indicate enhancement of the condensation heat transfer coefficient as a tube is flattened. Flattened tubes with an 18° helix angle displayed the highest heat transfer coefficients. Smooth tubes and axial microfin tubes displayed similar levels of heat transfer enhancement. Heat transfer enhancement is dependent on the mass flux, quality and tube profile.     

Time-dependent behavior of gas absorption in lubricant oil

Gas absorption behavior in liquid with time has been studied by applying a simple mathematical model. The model is based on a one-dimensional mass diffusion process due to the concentration difference in dissolving gas. In order to examine the model validity, selected experimental data in the literature have been analyzed with the present model. The model has faithfully reproduced the experimental transient behavior of dissolving gases, and physically meaningful model parameters, diffusion constant and solubility limit, have been obtained for dissolving gas (water and refrigerant) in various lubricant oils. The validity and the significance of the model are discussed.     

Étude de la stabilité thermique du réseau collagène de la peau par calorimétrie différentielle. Influence d'un traitement cosmétique

Afin d'étudier l'influence d'un traitement cosmétique (crème au collagène) au niveau du derme de rats, nous avons utilisé une technique physico-chimique: la calorimétrie différentielle programmée. Cette méthode renseigne sur la température et l'enthalpie de dénaturation des fibres collagènes du derme.
Nous avons pu mettre en évidence par cette technique un abaissement de plus de 2°C de la température de fin de dénaturation du collagène chez des animaux âgés de 5 mois et ayant subi 4 mois de traitement (entre 1 et 5 mois). En revanche, aucune modification n'est apparue après ce même traitement chez des rats de 9 mois (traités entre 5 et 9 mois).
Par ailleurs, l'étude de l'évolution de ces paramètres thermiques avec l'âge sur des animaux témoins montre que les animaux traités pendant 4 mois par une crème au collagène et âgés de 5 mois possèdent un réseau collagène dont la stabilité thermique étudiée par calorimétrie différentielle est voisine de celle obtenue pour des animaux témoins âgés de 3 mois.
La différence observée pourrait correspondre à des modifications de la structure des fibres collagènes et/ou de la nature et du taux de leurs liaisons de réticulation.
Study of the thermal stability of skin collagen by differential calorimetry. Influence of a cosmetic treatment