我国发展冻干食品的前景与对策

本文通过对我国冻干食品生产现状，食品资源优势及国外冻干食品市场分析，指出了我轨展冻干食品的前及对策，并预测冻干食品将成为21世纪我国食品的发展方向。     

食品真空冷冻干燥技术的现状及发展前景的探讨

本文综述了真空冷冻干燥技术在食品科学领域中的应用概况和食品用真空冷冻干燥设备的现状。探讨了食品冻干技术今后的发展前景。试图对我国食品冻干技术的发展、新型功能食品的开发和冻干设备水平的提高有所影响     

食品真空冷冻干燥过程工艺参数分析

针对目前国内冻干食品企业制定食品冻干工艺和食品冻工设备设计需要,系统分析了食品真空冷冻干燥过程的主要工艺参数及其之间的关系; 为冻干食品企业制定食品冻干工艺及食品真空冷冻干燥设备工程设计确定技术参数提供参考。     

冻干食品加工过程中的能耗分析

本文分析了冻干食品加工过程中各阶段的能源消耗，并对降低冻干食品加工能耗提出了一些建议，对冻干工程设计及冻干食品生产工艺有一定的参考价值。     

国际市场流行冻干食品

国际市场流行冻干食品真空包装冷冻干燥食品，正在国际市场迅速兴起，并在国内形成发展趋势。冻干食品是指将新鲜食品快速冷冻至零下１８摄氏度，而放入真空器中脱水干燥包装而成食品。冻干食品不仅保持了新鲜食品的色、香、味、形，而且最大限度地保存了食品的维生素，蛋...     

食品冻干技术在兰州开发成功

前景广阔的食品冻干技术最近在兰州中国科学院近代物理研究所开发成功。专家认为,这一实用高技术将为农产品和食品的加工、运输和储藏带来显著经济效益。 食品冻干技术就是把食品快速冷冻后在真空状态下进行脱水.冻干食品作为宇航员独享的宇宙食品正在迅速进入寻常百姓家。有些发达国家冻干食品已占到方便食品的一半。我国食品冻干技术目前还处于起步阶段。有些地方引进的设备价格昂贵,效果不佳。近代物理研究所一批有三十多年工作经验的低温和真空专家,采用国产通用设备把高科技用于新产品开发取得成功,从而降低了成本,为这一技术迅速推广…     

发展我国冻干蔬菜产业大有可为

本文介绍了真空冷冻干燥食品的发展现状、特点及其工艺流程 ,着重讨论了发展冻干食品工业的广阔前景     

食品冷冻干燥技术的研究

随着科学技术进步的经济的发展，人们对食品的要求日趋理性化。传统以保藏为目的的食品加工，满足了人们消费动、植物食品不受季节和地域限制的需求，但加工出来造成的营养成分、生理活性成分的损失，色、香、味的劣变，以及过分依赖添加剂等所引起的安全性等问题，日益被消费者所关注和担忧。随着人们生活水平的提高，及对饮食快捷化、方便化的迫切需求，人们对待“吃”的观念已由过去的吃饱吃好转向注重饮食的快捷与营养及安全并重，使得冻干食品应运而生，并给冻干食品的发展提供了机遇。本文研究了冻干食品的特点和食品冷冻干燥技术的有关技术问题。     

冻干食品最终冻结温度和装载量的计算

本文对冻干食品的最终冻结温度和冻干食品的装载量计算进行介绍。     

国内信息

冻干食品供不应求　　根据国家海关总署、国家商检局统计 ,我国脱水蔬菜出口量每年以 3 0 %速度递增 ,出口量约占世界总产量的 2 /3 ,而冻干蔬菜在国际市场的价格是热风干燥脱水蔬菜的 4倍至 6倍。国际市场冻干食品供不应求 ,而国内尚处于发展初期 ,产量很低 ,目前我国生产的冻     

A hybrid finite difference/helmholtz integral scheme for ultrasonic scattering

Two techniques for analyzing the scattering of elastic waves by flaws are combined in a hybrid model. One is a finite difference scheme for handling the details of the interaction with the flaw, the other is a Helmholtz integral scheme for extending the results into the far field. Results are given for the diffraction coefficients for a semi-infinite thin crack, and for a 270° corner.     

Designs for Generalized Linear Models With Several Variables and Model Uncertainty

Standard factorial designs sometimes may be inadequate for experiments that aim to estimate a generalized linear model, for example, for describing a binary response in terms of several variables. A method is proposed for finding exact designs for such experiments that uses a criterion allowing for uncertainty in the link function, the linear predictor, or the model parameters, together with a design search. Designs are assessed and compared by simulation of the distribution of efficiencies relative to locally optimal designs over a space of possible models. Exact designs are investigated for two applications, and their advantages over factorial and central composite designs are demonstrated.     

Flow fields in shell-and-tube condensers: comparison of a pure refrigerant and a binary mixture

Detailed 2D CFD calculations for vapour flow field and rate of condensation are carried out for a geometry similar to a real shell-and-tube condenser with 100 tubes, with condensation on the shell-side. The differences in vapour flow behaviour are investigated for pure R22 and for a binary mixture of R32 and R134a, which has a gliding temperature difference of 5.5 K. It is shown that, the flow field for a zeotropic mixture is significantly different from that for a pure fluid. The nature of the mixture flow causes the vapour and condensate to flow counter-currently in part of the condenser. Adjustments of the inlet design turn out to influence the rate of heat transfer by up to 24% for the conditions tested, with greater influence on heat transfer for lower driving forces.     

Monolithic versus hierarchical approach to integrated scheduling in a supply chain

The two approaches, monolithic and hierarchical, with a set of mixed integer programming formulations are proposed and compared for multi-objective integrated scheduling in a customer driven supply chain. The supply chain consists of multiple manufacturers (suppliers) of parts, a single producer of finished products and a set of customers who generate final demand for the products. Each supplier has a number of identical production lines in parallel for the manufacture of parts, and the producer has a flexible assembly line for assembly of products. Given a set of orders, the problem objective is to determine which orders are to be provided with parts by each supplier, find a schedule for the manufacture of parts by each supplier and for the delivery parts from each supplier to the producer, and find a schedule for the assembly of products for each order by the producer, such that a certain performance measure of the supply chain is optimised. The selection of the parts supplier for each order is combined with due date setting for some orders, subject to the suppliers and the producer available capacity. Different objective functions are considered that take into account both customer service level and total manufacturing, delivery and production cost. Numerical examples are presented that are modelled by real-world integrated scheduling in a customer driven supply chain of high-tech products, and some computational results are reported to compare the two approaches.     

A Membrane-Associated Light-Harvesting Model is Enabled by Functionalized Assemblies of Gene-Doubled TMV Proteins

Photosynthetic light harvesting requires efficient energy transfer within dynamic networks of light-harvesting complexes embedded within phospholipid membranes. Artificial light-harvesting models are valuable tools for understanding the structural features underpinning energy absorption and transfer within chromophore arrays. Here, a method for attaching a protein-based light-harvesting model to a planar, fluid supported lipid bilayer (SLB) is developed.  The protein model consists of the tobacco mosaic viral capsid proteins that are gene-doubled to create a tandem dimer (dTMV). Assemblies of dTMV break the facial symmetry of the double disk to allow for differentiation between the disk faces. A single reactive lysine residue is incorporated into the dTMV assemblies for the site-selective attachment of chromophores for light absorption. On the opposing dTMV face, a cysteine residue is incorporated for the bioconjugation of a peptide containing a polyhistidine tag for association with SLBs. The dual-modified dTMV complexes show significant association with SLBs and exhibit mobility on the bilayer. The techniques used herein offer a new method for protein-surface attachment and provide a platform for evaluating excited state energy transfer events in a dynamic, fully synthetic artificial light-harvesting system.     

A Constraint Programming model for food processing industry: a case for an ice cream processing facility

This paper presents a Constraint Programming (CP) scheduling model for an ice cream processing facility. CP is a mathematical optimisation tool for solving problems either for optimality (for small-size problems) or good quality solutions (for large-size problems). For practical scheduling problems, a single CP solution model can be used to optimise daily production or production horizon extending for months. The proposed model minimises a makespan objective and consists of various processing interval and sequence variables and a number of production constraints for a case from a food processing industry. Its performance was compared to a Mixed Integer Linear Programming (MILP) model from the literature for optimality, speed, and competence using the partial capacity of the production facility of the case study. Furthermore, the model was tested using different product demand sizes for the full capacity of the facility. The results demonstrate both the effectiveness, flexibility, and speed of the CP models, especially for large-scale models. As an alternative to MILP, CP models can provide a reasonable balance between optimality and computation speed for large problems.     

Analysis of closed loop supply chain using genetic algorithm and particle swarm optimisation

This paper describes a relational database system for semi-generative process planning for sheet metal parts that emulates expert system capabilities. The system integrates a feature-based relational database for the parts, a forward chaining rule-based strategy for machine selection, both global and feature-specific execution of the rules and a graph theoretic cost optimization model for optimal process plan selection. This system, which is currently being developed for a sheet metal fabrication company, suggests that, using the experience of shopfloor personnel, an efficient integration of feature-based process planning and expert system strategies can be accomplished.     

Spherical wave decomposition approach to ultrasonic field calculations

A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically analyzing the diffraction field of a continuous wave transducer of arbitrary size, shape, and frequency. Using the extensively studied circular transducer for comparison, numerical results are shown for an unfocused transducer with uniform velocity excitation as well as for a focused transducer with Gaussian velocity excitation. Data concerning the execution time, program size, and convergence of the method are also presented for its implementation as a design tool on a minicomputer system.     

A Novel Hexahedral Interface Element for Nonlinear Crack Analysis

Existence of a crack in structures would lead to a sudden failure and damage. Establishing a precise analytical model for the cracked element would be a powerful tool to achieve the right answers in the analysis of the structure. The main aim of this article is to formulate a hexahedral interface element for use in nonlinear crack analysis. In this investigation, the kinematics of the discontinuous displacement field along with the virtual work principle, for a body with an internal discontinuity, is utilized. Based on the suggested interpolation functions for the discrete segments, and also the element displacement field, the element stiffness matrix is calculated. The proposed element can be used for modeling of the discrete cracks in three-dimensional problems, such as a concrete dam. Several numerical examples are analyzed for the accuracy test and a few of them are presented here. The results indicated that utilizing sufficient elements yields suitable answers.     

The Stiles–Crawford Effect: spot-size ratio departure in retinitis pigmentosa

The Stiles–Crawford effect of the first kind is the retina’s compensative response to loss of luminance efficiency for oblique stimulation manifested as the spot-size ratio departure from the perfect power coupling for a normal human eye. In a retinitis pigmentosa eye (RP), the normal cone photoreceptor morphology is affected due to foveal cone loss and disrupted cone mosaic spatial arrangement with reduction in directional sensitivity. We show that the flattened Stiles–Crawford function (SCF) in a RP eye is due to a different spot-size ratio departure profile, that is, for the same loss of luminance efficiency, a RP eye has a smaller departure from perfect power coupling compared to a normal eye. Again, the difference in spot-size ratio departure increases from the centre towards the periphery, having zero value for axial entry and maximum value for maximum peripheral entry indicating dispersal of photoreceptor alignment which prevents the retina to go for a bigger compensative response as it lacks both in number and appropriate cone morphology to tackle the loss of luminance efficiency for oblique stimulation. The slope of departure profile also testifies to the flattened SCF for a RP eye. Moreover, the discrepancy in spot-size ratio departure between a normal and a RP eye is shown to have a direct bearing on the Stiles–Crawford diminution of visibility.