Production scheduling of single-stage multi-product batch chemical processes with fixed batch sizes

We address the problem of scheduling a single-stage multi-product batch chemical process with fixed batch sizes. We present a mixed-integer nonlinear programming model to determine the schedule of batches, the batch size, and the number of overtime shifts that satisfy the demand at minimum cost for this process. We introduce a polynomial-time algorithm to solve the problem when the processing times of all batches are identical and the setup and cleaning times are sequence-independent. The solution procedure is based on recognizing that the optimal fixed batch size is a member of a set whose cardinality is polynomial. Given a batch size, the problem may be formulated as an assignment problem. Thus, an optimal solution may be found by iteratively solving a polynomial number of assignment problems. This work was motivated by a pesticide manufacturing company in the design of a new plant where the assumptions of a single bottleneck machine, fixed batch sizes, sequence-independent setup times, and identical batch processing times are all valid. An example is developed for this application.     

Biochemical and technological characteristics of hot chicken meat

In the hot breast and leg muscles of broiler chicken the level of ATP, the 'R' value, the lactic acid content, the pH value, the length of sarcomers, the water and fat retention capacity, the fat emulsion stability, thermal drip, and the extractability of protein fraction were investigated. It was found that in the breast muscles the onset of rigor mortis commenced within 30–60 min, and in the leg muscles as early as 15–30 min after killing of the birds. The deepest rigor mortis occurred between the first and fourth hour, and then gradually declined, sooner in the leg than in the breast muscles. The addition of sodium chloride (2.0–2.5%) to the minced pre-rigor meat not later than 40 min after slaughter, or better, an injection of NaCl brine into intact muscles 15 min after slaughter of birds, preserved their good technological properties.
The tenderness and the thermal drip of hot salted and chilled salted muscles showed no significant differences, but water retention and fat emulsifying capacity were better in the hot salted meat samples. The hot salted and cooked muscles were preferred by the sensory panel to corresponding samples of chilled muscles.
From the hot salted chicken meat more sarcoplasmic and myofibrillar proteins were extracted than from meat salted after chilling. However, after frozen storage the extractability of myofibrillar proteins were higher in the salted chilled meat.     

高熵合金在钎焊和表面工程领域的应用研究进展

随着合金制造水平的提高及性能要求的复杂化,高熵合金逐渐引起极大的关注.目前在材料加工领域内的研究主要集中于钎焊和表面工程两大方向.在钎焊领域,高熵合金可以作为钎焊填充材料应用于高温和低温钎焊,本文归纳了合金高熵化的相关经验参数,阐述了第一性原理计算和相图计算等模拟计算手段在高熵合金填充材料设计领域内的应用;详细介绍了高熵合金钎料在镍基高温合金、陶瓷-金属异种材料、低温封装等连接领域的最新研究进展.同时,分析了工艺参数对高熵合金钎料钎焊接头组织与性能的影响.在表面工程领域,论述了高熵合金薄膜/涂层的应用方向与制备手段,总结了在高温防护涂层、硬质保护层以及其他应用领域的研究进展.同时归纳了高熵合金在钎焊和表面工程领域研究和应用中存在的问题,而未来将在降低钎料熔点、提高焊缝高温力学性能以及发展共晶高熵合金钎料/涂层等领域进一步提高研究水平.     

Emulsifying Properties of Food Proteins: Bovine Mi cellar Casein

The capacity of micellar casein isolated from bovine milk to stabilize oil in water (0:w) emulsions was studied. Emulsion surface area per unit mass of protein, i.e., emulsifying activity (EA), was highest at a protein concentration of 1% and o:w ratio of 1:9. The surface concentration of micellar casein was related to the o:w ratio being highest at an o:w of 4:6. Interfacial surface area decreased at pH 6.7 reflecting micellar stability and improved with increasing pH apparently because of destabilization of the casein micelle. Emulsion stability was high when the EA was high. The apparent viscosity of the emulsions was inversely related to EA.     

Determination of Principal Axes ot Truss Towers

The paper is concerned with the determination of the principal axes of geometrically non linear truss towers by a microcomputer. A knowledge of the principal axes may be used at the planning and design stage to advantageously orient the tower with respect to the dominant wind direction. The principal axes may also be used for the assessment of the truss tower's sensitivity to wind direction. A scale for the evaluation of this sensitivity is proposed in the paper. The sensitivity of a structure to lateral load direction depends on the structure's geometry and topology. An example is presented that shows how sensitivity of a space truss can the affected by the by the modifications of its geometry and topology.     

ON THE OPTIMALITY OF DISKS OF UNIFORM CREEP STRENGTH AGAINST BRITTLE RUPTURE

Axisymmetric rotating disks of uniform brittle rupture under creep conditions are considered. The similarity of deviators, according to the flow theory, and the time hardening hypothesis combined with the Kachanov-Sdobyrev brittle rupture rule are used as the governing equations for the unsteady creep problem. The concept of a fully damaged design method is applied, when the appropriate iteration of the thickness (the decision variable) is introduced such that the local condition of the Kachanov type ( ↓x_i t_r) = 0 (the objective) to be satisfied for each x_i under the constant volume condition (the constraint). In general, the disk of uniform creep strength, with geometry changes neglected, is found either as optimal or non-optimal with respect to the lifetime. In case of non-stationary loading (due to prestressing), and the geometric constraints allowed for, an additional small improvement of the lifetime is obtained when shape corrections are imposed upon the disk of uniform creep rupture strength     

INFLUENCE OF CONSTRUCTION OF POWER LOSSES IN A SUPERCONDUCTING A.C. GENERATOR SCREENING SYSTEM

ABSTRACT

Results of calculations of a power losses in a superconducting a.c. generator screening system during asymmetrical load are given. The main variants of screening system are considered. The influence of the screening system parameters on the power losses in particular shells of the rotor is discussed