• International Journal of Concrete Structures and Materials
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• 제7권3호
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• pp.183-191
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• 2013

Prestress losses assumed for bridge girder design and deflection analyses are dependent on the concrete modulus of elasticity (MOE). Most design specifications, such as the American Association of State Highways and Transportation Officials (AASHTO) bridge specifications, contain a constant value for the MOE based on the unit weight of concrete and the concrete compressive strength at 28 days. It has been shown in the past that that the concrete MOE varies with the age of concrete. The purpose of this study was to evaluate the effect of a time-dependent and variable MOE on the prestress losses assumed for bridge girder design. For this purpose, three different variable MOE models from the literature were investigated: Dischinger (Der Bauingenieur 47/48(20):563-572, 1939a; Der Bauingenieur 5/6(20):53-63, 1939b; Der Bauingenieur, 21/22(20):286-437, 1939c), American Concrete Institute (ACI) 209 (Tech. Rep. ACI 209R-92, 1992) and CEB-FIP (CEB-FIP Model Code, 2010). A typical bridge layout for the Dallas, Texas, USA, area was assumed herein. A prestressed concrete beam design and analysis program from the Texas Department of Transportation (TxDOT) was utilized to determine the prestress losses. The values of the time dependent MOE and also specific prestress losses from each model were compared. The MOE predictions based on the ACI and the CEB-FIP models were close to each other; in long-term, they approach the constant AASHTO value. Dischinger's model provides for higher MOE values. The elastic shortening and the long term losses from the variable MOE models are lower than that using a constant MOE up to deck casting time. In long term, the variable MOE-based losses approach that from the constant MOE predictions. The Dischinger model would result in more conservative girder design while the ACI and the CEB-FIP models would result in designs more consistent with the AASHTO approach.

• 한국건축시공학회지
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• 제8권5호
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• pp.85-91
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• 2008

Prepacked concrete has recently been used in the special constructions fields such as underwater concrete work, heavy-weight concrete work, underground structure work, partial repair works for damaged reinforced concrete structures. and polymer-modified mortars have been employed as grouting mortars for the prepacked concrete. The purpose of this study is to recommend the optimum mix design of polymer-modified grouting mortars for prepacked concrete. Polymer-modified mortars using SBR and EVA emulsions as admixture of grouting mortars for prepacked concrete are prepared with various mix proportions such as sand-binder ratio, fly ash replacement ratio, polymer-binder ratio. and tested for flowability, viscosity of grouting mortars, bleeding ratio, expansion ratio, flexural and compressive strengths of grouting mortars and compressive and tensile strengths of prepacked concretes. From the test results, it is apparent that polymer-modified mortars can be produced as grouting mortars when proper mix design is chosen. We can design the mix proportions of high strength mortars for prepacked concrete according to the control of mix design factors such as type of polymer, polymer-binder ratio, sand-binder ratio and fly ash replacement ratio. Water-binder ratio of plain mortars for a constant flowability value are in the ranges of 43% to 50%. SBR-modified mortar has a little water-binder ratios compared to those of plain mortar, however, EVA-modified mortar needs a high water-binder ratio due to a high viscosity of polymer dispersion. The expansion and bleeding ratios of grouting mortars are also controlled in the proper value ranges. Polymer-modified grouting mortars have good flexural. compressive and tensile strengths, are not affected with various properties with increasing fly ash replacement to cement and binder-sand ratio. In this study, SBR-modified grouting mortar with a polymer-binder ratio of 10% or less, a fly ash replacement of 10% to cement and a sand-binder ratio of 1.5 is recommended as a grouting mortar for prepacked concrete.

• Journal of Welding and Joining
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• 제27권5호
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• pp.81-87
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• 2009

Recently, extruded aluminium-alloy panels have been used in the car bodies for the purpose of the light-weight of railway vehicles and FSW(Friction Stir Welding), which is superior to the arc weldings, has been applied in the railway vehicles. This paper presents the optimum design of the FSW process on A6005 extruded alloy for railway vehicles to improve its mechanical properties. Rotational speed, welding speed and tilting angle of the tool tip were chosen as design parameters. Three objective functions were determined; maximizing the tensile strength, minimizing the hardness and maximizing the difference between the normalized tensile strength and hardness. The tensile tests and the hardness tests for fifteen FSW experiments were carried out according to the central composite design table. Recursive model functions on three characteristic values, such as the tensile strength, the hardness difference(${\Delta}Hv$) and the difference of normalized tensile strength and ${\Delta}Hv$, were estimated according to the classical response surface analysis methodology. The reliability of each recursive function was verified by F-test using the analysis of variance table. Sensitivity analysis on each characteristic value was done. Finally, the optimum values of three design parameters were found using Sequential Quadratic Programming algorithm.

• Current Optics and Photonics
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• 제1권4호
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• pp.364-371
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• 2017

Compared to one made of glass, an aluminum mirror features light weight, compact design, low cost, and quick manufacturing. Reflective mirrors and supporting structures can be made from the same material, to improve the athermal performance of the system. With the rapid development of ultraprecise machining technologies, the field of applications for aluminum mirrors has been developed rapidly. However, most of them are rotationally symmetric in shape, and are used for infrared applications. In this paper, the design and manufacture of an off-axis aluminum mirror used for a three-mirror-anastigmat (TMA) optical system at visible wavelengths is presented. An optimized, lightweight design provides a weight reduction of more than 40%, while the surface deformation caused by earth's gravity can meet the required tolerance. The two pieces of an off-axis mirror can be diamond-turned simultaneously in one setup. The centrifugal deformation of the off-axis mirror during single-point diamond turning (SPDT) is simulated through the finite-element method (FEM). The techniques used to overcome centrifugal deformation are thoroughly described in this paper, and the surface error is reduced to about 1% of the original value. After post-polishing, the form error is $1/30{\lambda}$ RMS and the surface roughness is better than 5 nm Ra, which can meet the requirements for visible-light imaging.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.369-372
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• 2000

ESO(Evolutionary Structural Optimization) method is known that elements involved low stress value are removed from the previous model or that elements are added around elements involved high stress level on it and then the optimized model is obtained with required weight. Rejection ratio/addition ratio and evolutionary ratio are predefined and elements having lower/higher stress than reference stress, which average Mises stress on edge elements times rejection ratio, are deleted/added. In this study, when the plate having a cutout is subjected various in-plane load, a cutout shape is optimized using ESO method. ANSYS is used to analyse a finite element model and optimization procedure is made by APDL (ANSYS Parametric Design Language). ESO method is useful in rather than a complex structure optimization as well as a cutout shape optimization.

• Asia pacific journal of information systems
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• 제12권1호
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• pp.1-16
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• 2002

Most of searching systems used by shopping-mall provide too much information for user requirements or fail to provide appropriate items reflecting customer's preference. This paper aims to design and implement the product searching systems based on customer preference which will enable efficient product selection in the internet shopping-mall. The proposed system consists of user/provider interface, searching and model agent, data management system, and model management system. Especially, we construct the searching pattern database to support fast search using association mining method. And this system includes the customer-oriented decision model which shows the highly preferred products. Input weight value per attribute and preference level should be needed to compute priority grade of preference.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.209-217
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• 1994

The present study is concerned with the characteristics of the high speed precision bar cropping. This process is a practical application of High Energy Rate Forming in which the impact energy source is given by internal combustion engine. To enhance the added value of product, the recent forging fields trend toward the near net shape processes through the cold and closed die forging. For the purpose of these processes the precedent process is to obtain the precision billet which has little weight deviation and defect. The accuracy of initial billet by bar cropping depends upon the process parameters and die design technology. Therefore, in order to investigate the effect of process parameters upon product quality, the cropping experiments are carried out according to the various parameters such as billet clearence, billet length, billet material, cropping speed and so on. From these results some criteria of the optimal die design for the product of good quality are suggested.

• Design & Manufacturing
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• 제17권1호
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• pp.27-32
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• 2023

In this paper, we intend to predict the mass of the spiral using CAE and machine learning. First, We generated 125 data for the experiment through a complete factor design of 3 factors and 5 levels. Next, the data were derived by performing a molding analysis through CAE, and the machine learning process was performed using a machine learning tool. To select the optimal model among the models learned using the learning data, accuracy was evaluated using RMSE. The evaluation results confirmed that the Support Vector Machine had a good predictive performance. To evaluate the predictive performance of the predictive model, We randomly generated 10 non-overlapping data within the existing injection molding condition level. We compared the CAE and support vector machine results by applying random data. As a result, good performance was confirmed with a MAPE value of 0.48%.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.338-338
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• 2017

One of the problems in increasing rice production is getting lines or varieties that have high adaptability so that able to produce maximum production in a variety of environmental conditions. One strategy that can be done to get adaptive varieties is through the improvement of native varieties. This research was conducted in rain fed paddy field, Aceh province, Indonesia from June to September 2014. The texture of the soil was clay-loam with the soil pH ranged from 6.5-6.7. Five potential progenies of rice from crossing between native Indonesian rice with introduced rice varieties consist of C3, C4, S3, S5, S6 were used in this study. Besides that, one national rice variety Ciherang also used as a comparison. The plants were growth in the plot with the size of $2m{\times}1.4m$ with plant distance was $20cm{\times}20cm$. The fertilizers used in this study were Urea, NPK, and KCl. Randomized block design with 6 rice progenies/variety and 3 replications were used in this study. There were 18 experimental units and each experimental unit had 10 samples for the sources of data. The variables that were observed in this study including plant height at harvesting time, number of productive tiller, the percentage of empty grains and filled grain per panicle, weight of filled grains per hill, weight of filled grain per plot and yield potential per hectare. Analyzed were also conducted for the depth of root penetration, dry-root weight, dry-shoot weight, shoot-root weight ratio and its correlation with the weight of filled grain per hill. The research results show that there was significant difference on plant height at harvesting time, number of productive tillers, the percentage of empty grains and filled grain per panicle, weight of filled grains per hill, weight of filled grain per plot and yield potential per ha (p>0.01) among the treatments. In addition, depth root penetration, dry-root weight, dry-shoot weight, shoot-root weight ratio also had significant difference (p>0.01) among the treatment. The highest plant at harvesting time was found in S6, reaching 129.8 cm and the shortest plants was found in C3 reaching 107.5 cm. The largest number of productive tillers and the highest percentage of filled grains per panicle were found in Ciherang reaching 10.5 tillers and 80.7% respectively. Ciherang also had the heaviest weight of filled grains per hill and per plot reaching 21.1 g and 2.18 kg respectively. Whereas, S6 had the lowest number of tillers and the lowest percentage of filled grain per panicle.. The highest yield potential per ha was found in Ciherang reaching 7.79 tons. Among the progenies, S5 had the highest yield potential reaching 5 tons/Ha. The result also showed significant relationship between shoot-root weight ratio with weight of filled grains per hill. The highest value of shoot-root weight ratio (1.57) in Ciherang is thought had closed relationship with its yield potential.

• Asian-Australasian Journal of Animal Sciences
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• 제24권9호
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• pp.1233-1242
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• 2011

The in vivo digestibility of mulberry leaves (Morus alba) and the effects of the partial replacement of cotton seed with fresh mulberry leaf in rations on the performance of growing Vietnamese cattle was investigated. For the in vivo digestibility trial, twenty castrated rams of Phanrang breed (a local prolific breed) with an initial weight of 23-25 kg, were first assigned to four groups according to weight and then randomly assigned to one of four dietary treatments to determine digestibility of nutrients in mulberry leaves (M. alba), natural Bermuda grass (Cynodon dactylon), elephant grass (Pennisetum purpureum) and buffalo grass (Panicum maximum cv. TD 58). All forages were cut and chopped daily before being offered (at 120% maintenance) to the sheep. In the feeding trial, 20 Laisind (Vietnam yellow cows${\times}$Red Sindhy bulls) crossbred bulls averaged 18 month old and 184 kg were used to investigate the effect of partial replacement of cottonseed in the diet by mulberry leaves on live weight gain and feed conversion rate. The experiment was a randomized complete block design with four levels of fresh mulberry leaves which varied from 0 to 15% of total dietary dry mater and five animals per treatment over an 84 day period. The in vivo digestion trial showed the superior quality of mulberry leaves compared with the grasses. Chemical analysis indicated that mulberry leaves had the highest CP and the lowest NDF contents (22.3 and 31.1% DM, respectively) among the four forages tested. Digestibility of DM and OM of the mulberry leaf (66.4 and 71.8%, respectively) was also the highest but that of CP (58.2%) and NDF (58.4%) was the lowest of the four forages evaluated (p<0.05). Consequently, the ME value and therefore net energy (NE) and unit feed for lactation (UFL) values of the mulberry leaves, which was estimated from chemical composition and digestibility values, were the highest among the forages investigated in the present study. Results of the feeding trial showed no treatment effect on average daily gain (ADG) of the cattle. The values were 554, 583, 565 and 568 g/d for animals in the diets of 0, 5, 10, and 15% mulberry leaves inclusion, respectively. Total DM intake of the animal was not affected by the treatment when expressed as kg/animal/d. However, when adjusted for metabolic weight of the animal the DM intake was reduced (p<0.05) as whole cottonseed was replaced by mulberry leaves in the ration. When the level of mulberry leaves in the ration increased from 5 to 15% of dietary DM at the expense of whole cottonseed, CP and ME intakes of the cattle were significantly decreased (p<0.05) and the feed to gain ratio reduced by 8 to 14% as compared with the control diet (p<0.05). Mulberry leaf is a good feed ingredient for ruminants because of its high level of crude protein and high digestibility of nutrients and energy. Mulberry leaves can be efficiently used as a source of protein supplement to replace cottonseed, a more expensive animal feeds ingredient, in the diet for Vietnamese cattle.