Engineering factors in the production of concentrated fruit juices 1. Fluid physical properties of orange juices

This study presents the essential physical properties (boiling-point rise, viscosity, density, specific heat) of orange juices, necessary for the optimization of processing units for concentrated orange juices.
When these physical properties were correlated with the sucrose content of juice, expressed as degrees Brix, in the range 10–65° Brix and compared with those of aqueous sucrose solutions, significant differences were observed in respect of viscosity, specific heat and elevation of boiling point.     

Evaluation of diffusion coefficients in osmotic concentration of bananas (Musa Cavendish Lambert)

The effect of time of exposure, solution concentration and temperature on the osmotic concentration of banana (slices of 11 mm thickness) was studied in aqueous sucrose solutions. the selectivity of the cellular tissues was reduced by steam blanching the banana slices before osmotic treatment. Effective diffusion coefficients for the loss of water and the increase in sucrose content were determined according to Fick's Law applied to a two-dimensional body; calculated on the basis of the concentration of various components in the liquid phase impenetrating the fruit. These coefficients revealed values similar to binary diffusion coefficients for pure sucrose solutions.     

Cryopreservation of <i>Cyrtopodium hatschbachii</i> Pabst (Orchidaceae) immature seeds by encapsulation-dehydration

The aim of the present study was to investigate the efficiency of the encapsulation-dehydration technique for cryopreservation of Cyrtopodium hastchbachii Pabst seeds. Immature seeds of this species were cryopreserved by an encapsulation-dehydration technique. Seeds of five immature pods, 120 days after pollination, were encapsulated in 3% calcium alginate matrix and pretreated in liquid medium supplemented with 0.08 M sucrose (24 h), 0.15 M sucrose (24 h), 0.25 M sucrose (48 h), 0.5 M sucrose (24 h) and 0.75 M sucrose (24 h) in shaker at 60 rpm. Alginate beads were dehydrated 5 h in silicagel and immersed in liquid nitrogen for 12 h. Cryopreserved beads were thawed at 30°C for 1 min, rehydrated using the same liquid mediums [0.75 M sucrose (24 h), 0.5 M sucrose (24 h), 0.25 M sucrose (48 h) and 0.15 M sucrose (24 h)] and cultivated in half strength Murashige & Skoog medium (1962) with the addition of 2 g/L activated charcoal. Sixty four percent of seeds survived and developed into acclimatized plants after being cryopreserved. In this work, the encapsulation-dehydration technique was employed for first time in Cyrtopodium hatschbachii.     

Modelling of multiple-effect falling-film evaporators

The classic mathematical model of multi-effect evaporators operating in forward flow was combined with an accurate estimation of the overall heat transfer coefficient (HTC) in falling-film evaporators. For this correlation developed by Narayanamurthy & Sarma (1977) has been used. It was possible also to estimate the order of magnitude of the fouling factor (Rd). Finally, the design of an orange-juice double-effect falling-film evaporator (DEFFE) system was carried out according to two different strategies.     

掺钕钨酸钆钠晶体生长、结构及光谱特性

采用提拉法生长了尺寸为φ(30～35)mm×80mm的掺钕钨酸钆钠[Nd:NaGd(WO4)2,Nd:NGW]晶体。生长Nd:NGW晶体的最佳工艺参数为:晶体的提拉速率为1～2mm/h,晶体转速为15～18r/min,冷却速率为10℃/h,液面上轴向温度梯度为0.7～1℃/mm。通过热重-差热分析(thermogravimetry-differential thermal analysis,TG-DTA),X射线衍射(X-ray diffraction,XRD)对晶体进行表征。测试了晶体的红外及Raman光谱,分析了晶体的振动模式,并将晶体振动光谱进行归属。由TG-DTA曲线得到晶体熔点为1251.7℃。XRD分析表明:晶体属于四方晶系、白钨矿结构、I41/a空间群,晶胞参数a=0.53213nm,c=1.13070nm。吸收光谱表明:Nd:NGW晶体在805nm附近有较强、较宽的吸收峰,吸收截面积为3.581×10-20cm2,适合于激光二极管泵浦。     

Towards a Knowledge-Based System for Seismic Assessment of Buildings

Aknowledge-based system, whose objectives are to support the procedures which lead to the seismic risk evaluation of buildings and to suggest possible retrofitting, is presented. The system architecture and its principal functions are described, with emphasis on the main part of the system: a model (“artificial world”) which describes the structure and possible behaviors of the building and its environment, at different definition levels, with qualitative and/or quantitative attributes.     

Economic study of tomato paste production

Statistics of tomato production and utilization have been reported to show the recent development of the tomato industry in the EEC countries. In particular, the profitability of tomato paste production has been evaluated and then analysed to assess the influence of the operating costs, EEC payments and market price of tomato paste. The economic balance for a plant capacity of 14 tons of raw tomatoes per hr and 2880 operational hr per year shows profitability of 22% in 1979 and 16% in 1980 owing to inflation and decrease in product demand. The annual cost of raw materials is not only more than 75% of production costs, but is also double the total capital invested. For this reason the tomato industry is compelled to resort to high-interest, short-term loans which further reduce net earnings. Mechanization of crop harvesting, automation of sorting, optimization of evaporation and packaging units and flexibility of plants are needed to maintain interest in tomato paste production in industrialized areas.     

VISCOELASTIC PROPERTIES OF ALGINATE GELS BY OSCILLATORY DYNAMIC TESTS

The response of several mannuronic and guluronic alginate gels to oscillatory tests was studied by varying the alginate concentration (c) from 1.0 to 1.75% w/w. Frequency dependence of the complex shear modulus G* discriminated between the alginate gels in terms of their different orders of the relaxation function α and "gel stiffness" A_α values using Friedrich and Heymann theory (1988). Guluronic alginate gels were approximately 4-5 times stronger than mannuronic ones, their networks exhibiting higher or smaller rates of stress relaxation, respectively. For both alginate types the gel stiffness parameter A_α was found to be a power function of alginate concentration and type (intrinsic viscosity [η], GG block diad frequency, F_GG, and average G-block length, N_G), its sensitivity with respect to c and N_G being greater than that to [η] and F_GG.     

聚乙烯亚胺/氮掺杂纳米TiO2喷墨打印墨水的制备及性能研究

由于纳米二氧化钛（TiO₂）具有无毒、折射率高、化学稳定性高的特点,特别是因存在光生空穴而具有强氧化性,已广泛应用于光催化剂、光电池、电池组、光致/电致变色装置、气敏传感器、薄膜晶体管等光化学产品中。然而,未改性的TiO₂只能吸收波长小于387nm的紫外光,在一定程度上限制了其应用范围。采用氮掺杂技术可以缩小锐钛型TiO₂的带宽,从而提高TiO₂在可见光区的光吸收性和光催化性。如将N-TiO₂分散后用于光催化和光伏研究方面,时间稳定性高的N-TiO₂溶液可用于喷墨打印。