• Computers and Concrete
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• v.22 no.1
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• pp.101-116
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• 2018

As one of the most important engineering structures, arch dams are huge constructions built with human hands and have strategical importance. Because of the fact that long construction duration, water supply, financial reasons, major loss of life and material since failure etc., the design of arch dams is very important problem and should be done by expert engineers to determine the structural behavior more accurately. Finite element analyses and non-destructive experimental measurements can be used to investigate the structural response, but there are some difficulties such as spending a long time while modelling, analysis and in-situ testing. Therefore, it is more useful to conduct the research on the laboratory conditions and to transform the obtained results into real constructions. Within the scope of this study, it is aimed to determine the structural behavior of arch dams considering experimentally validated prototype laboratory model using similitude and scaling laws. Type-1 arch dam, which is one of five arch dam types suggested at the "Arch Dams" Symposium in England in 1968 is selected as reference prototype model. The dam is built considering dam-reservoir-foundation interaction and ambient vibration tests are performed to validate the finite element results such as dynamic characteristics, displacements, principal stresses and strains. These results are considered as reference parameters and used to determine the real arch dam response with different scales factors such as 335, 400, 416.67 and 450. These values are selected by considering previously examined dam projects. Arch heights are calculated as 201 m, 240 m, 250 m and 270 m, respectively. The structural response is investigated between the model and prototype by using similarity requirements, field equations, scaling laws etc. To validate these results, finite element models are enlarged in the same scales and analyses are repeated to obtain the dynamic characteristics, displacements, principal stresses and strains. At the end of the study, it is seen that there is a good agreement between all results obtained by similarity requirements with scaling laws and enlarged finite element models.

• Journal of Advanced Navigation Technology
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• v.19 no.4
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• pp.338-344
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• 2015

The national competency standards (NCS) is a systematize and standardize for skills required to perform their job. The NCS has developed a learning module with materialization and standardize by competence unit element, which is the unit of specific job competency. The existing curriculum is material to gab analysis for use in education training with competence unit element. The existing gab analysis has evaluated subjectively by experts. The gab analysis by experts bring up a subject subjective decision, accuracy lack, temporal and spatial inefficiency by psychological factor. This paper is proposed automated evaluation model for problem resolve of subjective evaluation. This paper use index term extraction, term frequency-inverse document frequency for feature value extraction, cosine similarity algorithm for gab analysis between existing curriculum and competence unit element. This paper was presented similarity mapping table between existing curriculum and competence unit element. The evaluation model in this paper should be complemented by an improved algorithm from the structural characteristics and speed.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.23-30
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• 2017

PURPOSES : In this paper, the applicability of DEM to a coarse graining method was evaluated by simulating a series of minicone tests for cement paste. METHODS : First, the fundamental physical quantities that are used in a static liquid bridge model were presented with three basic quantities based on the similarity principle and coarse graining method. Then, the scale factors and surface tensions for six different sizes of particles were determined using the relationship between the physical quantities and the basic quantities. Finally, the determined surface tensions and radii were utilized to simulate the fluidal behavior of cement paste under a minicone test condition, and the final shape of the cement paste with reference DEM particle radii was compared with the final shape of the others. RESULTS : The simulations with adjusted surface tensions for five different radii of particles and surface tension showed acceptable agreement with the simulation with regard to the reference size of the particle, although disagreement increases as the sizes of the particle radii increase. It seems reasonable to increase the particle radii by at least 0.196 cm considering the computational time reduction of 162 min. CONCLUSIONS : The coarse graining method based on the similarity principle is applicable for simulating the behavior of fluidal materials when the behavior of the materials can be described by a static liquid bridge model. However, the maximum particle radius should be suggested by considering not only the scale factor but also the relationship of the particle size and number with the radius of the curve of the boundary geometry.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1085-1089
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• 2015

Text-mining technique in the past had difficulty in realizing the analysis algorithm due to text complexity and degree of freedom that variables in the text have. Although the algorithm demanded lots of effort to get meaningful result, mechanical text analysis took more time than human text analysis. However, along with the development of hardware and analysis algorithm, big data technology has appeared. Thanks to big data technology, all the previously mentioned problems have been solved while analysis through text-mining is recognized to be valuable as well. However, applying text-mining to Korean text is still at the initial stage due to the linguistic domain characteristics that the Korean language has. If not only the data searching but also the analysis through text-mining is possible, saving the cost of human and material resources required for text analysis will lead efficient resource utilization in numerous public work fields. Thus, in this paper, we compare and evaluate the public document classification by handwork to public document classification where word frequency(TF-IDF) in a text-mining-based text and Cosine similarity between each document have been utilized in big data environment.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.257-265
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• 2017

In this study, a series of numerical simulations was conducted in order to design a truncated mooring line with a static similarity to the prototype. A finite element method based on minimizing the potential energy was utilized to describe the dynamics of mooring lines. The prototype mooring lines considered were installed at a water depth of 1,000 m, whereas the KRISO ocean engineering basin (OEB) in Daejeon has a water depth of 3.2 m, which represents 192 m using a scaling of 1:60. First, an investigation for the design of the truncated mooring line was carried out to match the static characteristics of the KRISO Daejeon OEB environment. Then, the same procedure was performed with the KRISO new deepwater ocean engineering basin (DOEB) that is under construction in Busan. This new facility has a water depth of 15 m, which reflects a real scale depth of 900 m considering the 1:60 scaling factor. A finite element method was used to model the mooring line dynamics. It was found that the targeted truncated mooring line could not be designed under the circumstances of the KRISO OEB with any material properties, whereas several mooring lines were easily matched to the prototype under the circumstances of the KRISO DOEB.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.5
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• pp.445-450
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• 2011

In order to estimate a yacht sail performance, measuring system of aerodynamic forces acting on the yacht sail is constructed and experiments of flexible model sail are carried out at the medium-size subsonic wind tunnel of Chungnam National University. Experimental results for a flexible sail are compared with experimental and numerical results of fixed shape sail. In case of a fixed shape sail, lift and drag coefficients are rarely changed at all velocity conditions. However, those of the flexible sail are decreased as the incoming velocity is increased. These are understandably resulted from shape variations due to the flexible material. Therefore aero-elastic similarity should be more carefully considered in the model test rather than other similarities.

• YAKHAK HOEJI
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• v.42 no.6
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• pp.627-633
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• 1998

Impurity profiling analysis of methamphetamine seized in Korea was investigated for the evidential and intelligent purpose. Samples were extracted with ethylacetate which contai ns internal standard of dioctylsebacate under basic condition and extracts were analyzed by GC-FID. Ephedrine, chloroephedrine & 1,2-dimethyl-3-phenylaziridine were identified impurities in illicit methamphetamine by GC-MS. These impurities revealed that most of abused methamphetamine in Korea were synthesized from ephedrine as a starting material. For the classification of samples. firstly, 24 impurity peaks were selected after inspection of every peak in 50 samples as the specific markers of impurities. Secondly, corresponding peak retention time and area ratio to the internal standard were calculated and database was created with values of 24 peaks by in-house program. Finally, cluster analysis was attempted with the resultant profiles using the STAR plot, which was based on the Euclidian distance for evaluating similarity among samples. A total of 76 samples were divided into 8 different groups within 90% statistical similarity and inter-batch samples showed similar impurity patterns by this procedure. In conclusion, the analysis of impurities is a suitable index for estimation the common or different origin of methamphetamine sample.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.4
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• pp.303-308
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• 2004

We isolated a novel lactic acid bacterium from a Korean traditional fermented food, soybean paste. The newly isolated strain, dubbed RKY2, grew well on glucose, sucrose, galactose, and fructose, but it could not utilize xylose, starch, or glycerol. When the partially amplified 16S rDNA sequence (772 bp) of the strain RKY2 was compared with 10 reference strains, it was found to be most similar to Lactobacillus pentosus JCM $1588^T$, with 99.74% similarity. There-fore, the strain RKY2 was renamed Lactobacillus sp. RKY2, which has been deposited in the Korean Collection for Type Cultures as KCTC 10353BP. Lactobacillus sp. RKY2 was found to be a homofermentative lactic acid bacterium, because its end-product from glucose metabolism was found to be mainly lactic acid. It could produce more than 90 g/L of lactic acid from MRS medium supplemented with 100 g/L of glucose, with 5.2 g $L^-1$ $h^-1$ of productivity and 0.95 g/g of lactic acid yield.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.313-320
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• 2005

Stick-slip friction is one of the material removal mechanisms in tribology. It occurs when the static friction force is larger than the dynamic friction force, and make the friction curve fluctuated. In the friction monitoring of chemical mechanical polishing(CMP), the friction force also vibrates just as stick-slip friction. In this paper, an attempt to show the similarity between stick-slip friction and the friction of CMP was conducted. The prepared hard pa(IC1000/Suba400 stacked/sup TM/) and soft pad(Suba400/sup TM/) were tested with SiO₂ slurry. The friction force was measured by piezoelectric sensor. According to this experiment, it was shown that as the head and table velocity became faster, the stick-slip time shortened because of the change of real contact area. And, the gradient of stick-slip period as a function of head and table speed in soft pad was more precipitous than that of hard one. From these results, it seems that the fluctuating friction force in CMP is stick-slip friction caused by viscoelastic behavior of the pad and the change of real contact area.

• Advances in materials Research
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• v.8 no.3
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• pp.155-177
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• 2019

In this paper, a new displacement based high-order shear deformation theory is introduced for the static response of functionally graded sandwich plate with new definition of porosity distribution taking into account composition and the scheme of the sandwich plate. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory presented is variationally consistent, has strong similarity with classical plate theory in many aspects, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. Material properties of FGM layers are assumed to vary continuously across the plate thickness according to either power-law or sigmoid function in terms of the volume fractions of the constituents. The face layers are considered to be FG across each face thickness while the core is made of a ceramic homogeneous layer. Governing equations are derived from the principle of virtual displacements. The closed-form solution of a simply supported rectangular plate subjected to sinusoidal loading has been obtained by using the Navier method. Numerical results are presented to show the effect of the material distribution, the sandwich plate geometry and the porosity on the deflections and stresses of FG sandwich plates. The validity of the present theory is investigated by comparing some of the present results with other published results.