A Multi-Dwell Temperature Profile Design for the Cure of Thick CFRP Composite Laminates

This paper develops a multi-objective optimization method for the cure of thick composite laminates. The purpose is to minimize the cure time and maximum temperature overshoot in the cure process by designing the cure temperature profile. This method combines the finite element based thermo-chemical coupled cure simulation with the non-dominated sorting genetic algorithm-II (NSGA-II). In order to investigate the influence of the number of dwells on the optimization result, four-dwell and two-dwell temperature profiles are selected for the design variables. The optimization method obtains successfully the Pareto optimal front of the multi-objective problem in thick and ultra-thick laminates. The result shows that the cure time and maximum temperature overshoot are both reduced significantly. The optimization result further illustrates that the four-dwell cure profile is more e ective than the two-dwell, especially for the ultra-thick laminates. Through the optimization of the four-dwell profile, the cure time is reduced by 51.0% (thick case) and 30.3% (ultra-thick case) and the maximum temperature overshoot is reduced by 66.9% (thick case) and 73.1% (ultra-thick case) compared with the recommended cure profile. In addition, Self-organizing map (SOM) is employed to visualize the relationships between the design variables with respect to the optimization result.

Integral Criterion of the Non-uniformity of Stress Distribution for the Topology Optimization of 2D-Models

The emergence of new technologies for the production of structural elements gives impetus to the development of new technologies for their design, in particular with the involvement of a topology optimization method. The most common algorithm for designing topologically optimal structures is focused on reducing their elastic flexibility at a given volume of material. However, a closer to the engineering design approach is the minimization of the volume of a structural element while limiting the resulting mechanical stresses. In contrast to the classical algorithms of this approach, which limit the values of stresses at certain points, this paper develops an alternative criterion: the formation of the image of a structural element is based on minimizing the integral parameter of stress distribution non-uniformity. The developed algorithm is based on the method of proportional topology optimization, and when mechanical stresses are calculated, the classical relations of the finite element method are used. The above parameter can be interpreted as the ratio of the deviation of the values, ordered in ascending order, of equivalent von Mises stresses in the finite elements of a calculation model from their linear approximation to the corresponding mean value. The search for the optimal result is carried out for the full range of possible values of the averaged "density" of the calculation area, which is associated with a decrease in the amount of input data. The proposed integrated strength criterion provides better uniformity of the optimized topology, allows us to smooth the effect of the local peak values of mechanical stresses, determining a single optimization result that is resistant to calculation errors. The algorithm is implemented in the MatLab software environment for two-dimensional models. The efficiency of the approach is tested on the optimization of a classical beam (mbb-beam), a cantilever beam, and an L-shaped beam. A comparative analysis of the obtained results with those available in the literature is given. It is shown that in the absence of constraint on the average value of the density of a finite element model, the proposed criterion gives a ″less dense″ optimization result compared to the classical one (approximately 40%), while the values of "contrast index" are quite close.

Recombinant Expression and Biochemical Characterization of Levansucrase from Halophilic Bacteria Bacillus licheniformis BK1 and BK2

Levansucrase was an extracellular polysacharride (EPS) which has a role in synthesizing levans by transferring fructose moiety from sucrose to acceptor molecules. In the previous study, we have successfully cloned the levansucarese gene from two Bacillus licheniformis strains of BK1 and BK2 labeled as lsbl-bk1 and lsbl-bk2. The present study aims to optimize the expression level of both genes in E. coli expression system and also to obtain the optimum conditions for the recombinant enzymes activity by applying the response surface methodology (RSM). The optimization result found that the highest Lsbl-bk1 production in E. coli expression system was occurred when the recombinant cells grown in the medium containing 0.6% (w/v) NaCl at 42°C, and induced by 0.6 mM IPTG. Different optimum conditions were found for Lsbl-bk2 production. It was achieved when 1.1% (w/v) NaCl added to the production medium and induced by 0.7 mM IPTG at 40°C. RSM optimization result for biochemical characterization of Lsbl-bk1 levansucrase showed the highest specific activity achieved at 56°C and pH 7.5, whereas for the Lsbl-bk2 levansucrase reached the highest specific activity at 50°C and pH 7.5. The addition of Co2+, Ti2+, Mg2+, Ba2+, Zn2+, Fe3+, Ca2+ metal ion to both levansucrases solution did not significantly altered their specific activity, indicating that both levansucrases are not metalo enzymes. Furthermore, the specific activity of levansucrase was also not affected by the addition of 1-25% (w/v) NaCl, suggesting that the variation of ionic strength did not alter the native state of both enzymes. The plot results of levansucrase specific activities toward sucrose concentration showed that both levansucrases follow Michaelis-Menten profile with kcat/KM values ​​about 3.8 and 3.6 s-1/mM respectively. These data indicated that the recombinant levansucrases from halophilic bacteria B. licheniformis BK1 and BK2 are a non metaloenzyme with high affinity and binding rate to sucrose substrate, in which the catalytic efficiency on hydrolysis reactions is relatively low.

Optimasi Pembuatan Daging Tiruan Umbi Porang (Amorphophallus oncophyllus) dan Isolat Protein Kedelai dengan Metode RSM (Response Surface Methodology)

Meat analogue is a form of product which has originated from vegetal component which has a lot of tissue and could replace animal meat. The forming of meat analogue is using the extrusion technique. Primary ingredient which used is isolate soy protein and water, but also it is able to be added by other carbohydrates source such as porang bulb (Amorphophallus oncophyllus) wherewith increase the functional character over the meat analogue. This research is aimed for identify the optimum condition of proper treatment between the water additional formulation, isolate soy protein, porang bulb, therewithal the extrusion time. This reasearch was conducted in 5 phases: (1) determining the water content, isolate soy protein and porang bulb powder extrution time; (2) undertaking the randomization box-behnken model over RSM method. (3) Meat analogue forming based on the related randomization; (4) analysed parameters are; texture, WHC, OHC, protein solubility and organoleptic. The data analysis is using RSM Analyze. The optimization result of porang bulb meat analogue in the formulation of 90% water content, 18 minutes of extrusion time and 50% of used isolate soy protein. Meat analogue character with the optimization result as follows: texture 66,93 g/mm, WHC 304,98%, OHC 60,15%, protein solubility 80,06% and organoleptic 70,6%.

PENGARUH PANJANG BENTANG TERHADAP UKURAN PENAMPANG OPTIMUM BETON PRATEGANG PADA BALOK SEDERHANA DENGAN MENGGUNAKAN ALGORITMA GENETIKA

Structural design philosophy expected to be low cost and safe at once. At prestressed concrete structure, concrete allowable stress for bending structural component have to fullfill limit values on tranfer and service condition. Prestressed force determined using moment coeffiecient β method based on allwoable stress. At this structure, to achieve optimum design is not an easy task due to interaction between dimension size and prestressing force value. To determine optimum design criteria, genetics algorithms as one of optimum design method has been used in this paper. Genetics algorithm is a method to find the best solution using organism genetics process based on Darwin theory which solutions with the best fitness value that could be survive as the optimization result. Fitness value is minimum construction cost. Optimization process using genetics algorithm has been worked with computer software assitance Matlab. Simpe beam has been considered as numerical example. Optimization result is optimum design of dimension size and prestressing force. Optimization procedure with beam length (L) 10 m result are beam width (b) 0,40 m, beam height (h) 0,47 m, prestressing force (Fi) value 1344 KN and bulding cost total Rp. 16.651.000,-. Next optimization procedure has been done using different beam length. From this study, the interaction between beam length to optimum dimension size and minimum building cost has been achieved.Keywords : beam length, genetics algoritm, optimum sizing, prestressed concreteAbstrak: Filosofi perencanaan struktur diharapkan ekonomis sekaligus aman. Pada struktur beton prategang, tegangan ijin beton untuk komponen struktur lentur harus memenuhi nilai batas pada saat transfer dan beban layan. Gaya prategang ditentukan dengan menggunakan metode koefisien momen β yang didasarkan pada tegangan ijin. Pada struktur ini, penentuan desain optimum tidak mudah karena adanya keterkaitan antara ukuran penampang dengan besaran gaya prategang yang dibutuhkan. Untuk memperoleh kriteria desain yang optimum digunakan metode optimasi dengan menggunakan algoritma genetika. Algoritma genetika merupakan metode pencarian sesuai dengan proses genetika organisme berdasarkan teori evolusi Darwin, dimana solusi dengan nilai fitness (tujuan) yang tinggi yang mampu bertahan sebagai hasil dari proses optimasi. Nilai fitness (tujuan) adalah memperoleh total harga konstruksi yang paling rendah. Proses optimasi dengan algoritma genetika dikerjakan dengan bantuan software komputer Matlab. Untuk melakukan optimasi digunakan algoritma genetika real. Jenis struktur yang ditinjau adalah balok sederhana. Dari hasil optimasi dengan berbagai panjang bentang diperoleh dimensi balok dan nilai gaya prategang yang optimum. Proses optimasi dengan panjang bentang (L) 10 m, diperoleh lebar balok (b) 0,40 m, tinggi balok (h) 0,47 m, nilai gaya prategang (Fi) sebesar 1344 KN dengan total harga Rp. 16.651.000,-. Proses optimasi selanjutnya dilakukan dengan panjang bentang balok yang bervariasi. Dari hasil penelitian diperoleh hubungan antara panjang bentang balok dengan ukuran penampang optimum serta harga total struktur yang paling rendah.Kata kunci : algoritma genetika, beton prategang, panjang bentang, ukuran penampang optimum

An Approach to Flexible-Robust Optimization of Large-Scale Systems

Though Robust Optimization has proven useful in solving many design problems with uncertainties, it is not suitable for certain problems which have sequential options in the decision making process. In this work, an integration of a Real Option model with the Robust Optimization technique is presented. This approach aims to eliminate the shortcomings of robust optimization for sequential decision making problems. We provide an example of applying this new integrated model to the operational control of a single reservoir of the Oregon-Washington Columbia River system by optimizing the flexibility of the system. Flexibility for an engineering system is the ease with which the system can respond to uncertainty in a manner to sustain or increase its value delivery through decision-making. In this paper, we define flexibility as the amount of water left in the storage reservoir to produce electricity after meeting demand. Real Option analysis is an economic tool which helps to value the multiple courses of actions in a decision: that is to either sell the flexibility or hold it for future use based upon the future value of flexibility. Selling flexibility causes one to lose some future value because one may be forced to repurchase that flexibility from the market at higher prices later due to shortages; Real Options analysis values future purchases to support decision-making. Robust optimization focuses on for selling the flexibility in a daily market and gives an optimal result by maximizing net revenue, considering all the physical and operational constraints of the reservoir to avoid floods or other environmental calamities. Net revenue is defined as cost of selling and cost of future purchase of the flexibility. We provide an optimization result of 27 random inflow scenarios which gives high, medium and low flexibility to allocate using the integrated model. We compare the optimal solutions given by the integrated model with that given by robust optimization. The integrated real option-robust optimization model improves the revenue from allocating flexibility as much as 40 percent over the robust optimization result.

Influence of selected turbulence model on the optimization of a Class-Shape Transformation parameterized airfoil

An airfoil was parameterized using the class-shape transformation technique and then optimized via genetic algorithm. The aerodynamic characteristics of the airfoil were obtained with the use of a CFD software. The automated numerical technique was validated using available experimental data and then the optimization procedure was repeated for few different turbulence models. The obtained optimized airfoils were then compared in order to gain some insight on the influence of the different turbulence models on the optimization result.