• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.132-139
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• 2008

To meet demand of big capacity and high speed rotation for washing machine, more stress from bending and twisting are complexly loaded onto the shaft supporting the horizontal drum, causing problems in fracture strength and fatigue life. Also, Vibration occurs due to the frequency of the rotating parts. But, shaft has various design factors such as diameter and distance between bearings according to configuration of shaft, the optimal values can't be easily determined. Using a design of experiment (DOE) based on the FEM (Finite Element Method), which has several advantages such as less computing, high accuracy performance and usefulness, this study was performed investigating the interaction effect between the various design factor as well as the main effect of the each design factor under bending, twist and vibration and proposed optimum design using center composition method among response surface derived from regression equation of simulation-based DOE.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.1
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• pp.1-8
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• 2008

Numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm(NSGA-II) of multi-objective optimization using three-dimensional Navier-Stokes analysis is presented in this work. Reynolds-averaged Navier-Stokes(RANS) equations with ${\kappa}-{\varepsilon}$ turbulence model are discretized with finite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-II and local search strategy with weighted sum approach to refine the result obtained by NSGA-II to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.53-63
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• 2021

Age structure and growth of white croaker Pennahia argentata were estimated an analysis of otoliths. Fish specimens were collected from the Southern Sea of Korea from January to December 2018. A thin section method was used for age determination because otoliths of white croaker are oval in shape and large in size. Otoliths were cut vertically into 0.4-0.5 mm thick sections with an electric saw (Micracut 125). Monthly changes in the marginal index indicated that rings (opaque zone) were formed once a year in August. The estimated von Bertalanffy growth equation estimated by a non-linear regression were L∞=34.71 (1-e0.38(t+0.80)). In the present study, the oldest female was 8 years old and the male was 7 years old.

• Journal of the Korean Society of Clothing and Textiles
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• v.44 no.6
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• pp.1053-1069
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• 2020

This study examined the sales pattern relationship with respect to product attributes to propose sales forecasting for fashion products. We analyzed 537 SKU sales data of T-shirts in the domestic sports brand using SAS program. The sales pattern of fashion products fluctuated and were influenced by exogenous factors; therefore, we removed the influence of exogenous factors found to be price discounts and holiday effects as a result of regression analysis. In addition, it was difficult to predict sales using the sales patterns of the same product since fashion products were released as new products every year. Therefore, the forecasting model was proposed using sales patterns of related product attributes when attributes were considered descriptive variables. We classified sales patterns using K-means clustering in order to explain the relationship between sales patterns and product attributes along with creating a decision tree classifier using attributes as input and sales patterns as output. As a result, the sales patterns of T-shirts were clustered into six types that featured the characteristic shape of peak and slope. It was also associated with the combination of product attributes and their values in regards to the proposed sales pattern prediction model.

• Journal of Hydrogen and New Energy
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• v.32 no.6
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• pp.636-641
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• 2021

Using numerical analysis, various factors influencing the performance development of high-pressure pumps for Dimethyl Ether (DME) engines were identified and the impact of each factor was evaluated using Taguchi method. DME fuels are more compressive than diesel fuels and have the lower heat generation, so it is necessary to increase the size of the plunger and speed (RPM) of the pump as well. In addition, it is necessary to change the shape and design of control valve to control the discharge flow and pressure. In this study, various variables affecting the performance and flow rate increase of high-pressure pumps for DME engines are planned using Taguchi method, and the best design method is proposed using correlation of the most important variables. As a result, we were able to provide the design value needed for a six-liter engine and provide optimal conditions. The best combination factors to optimize the flow rate at RPM 2,000 and diameter plunger with 20 mm. The regression equation can also be used to optimize the flow rate; -8, 13+0, 2552 RPM +54, 17 diam. Plunger.

• Journal of the Korean Society of Visualization
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• v.20 no.2
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• pp.78-85
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• 2022

In these days, the rapid development in prediction technology using artificial intelligent is being applied in a variety of engineering fields. Especially, dimensionality reduction technologies such as autoencoder and convolutional neural network have enabled the classification and regression of high-dimensional data. In particular, pixel level prediction technology enables semantic segmentation (fine-grained classification), or physical value prediction for each pixel such as depth or surface normal estimation. In this study, the pressure distribution of the ship's surface was estimated at the pixel level based on the artificial neural network. First, a potential flow analysis was performed on the hull form data generated by transforming the baseline hull form data to construct 429 datasets for learning. Thereafter, a neural network with a U-shape structure was configured to learn the pressure value at the node position of the pretreated hull form. As a result, for the hull form included in training set, it was confirmed that the neural network can make a good prediction for pressure distribution. But in case of container ship, which is not included and have different characteristics, the network couldn't give a reasonable result.

• Advances in concrete construction
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• v.14 no.2
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• pp.139-151
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• 2022

Filling materials poured into precast member joint are subjected to restraint stress by the precast member and joint reinforcement. The induced stress will likely cause cracks at early ages and performance degradation of the entire structure. To prevent these issues and design reasonable joints, it is very important to analyze and evaluate the restrained shrinkage cracks of filling materials at various restraint conditions. In this study, a new time zero-that defines the shrinkage development time of a filling material-is proposed to calculate the accurate amount of shrinkage. The tensile stresses and strengths at different ages were compared through the ring test (AASHTO PP34) to evaluate the crack potential of the restrained filling materials at various restraint conditions. The mixture which contained an expansive additive and a shrinkage reducing agent exhibited high resistance to shrinkage cracking owing to the high-drying shrinkage compensation effect. The high-performance, fiber-reinforced cement composite, and ultra-high-performance, fiber-reinforced cement composite yielded very high resistance to shrinkage and cracking owing to the pull-out property of steel fibers. To this end, multiple nonlinear regression analyses were conducted based on the test results. Accordingly, a modified tensile stress equation that considered both the geometric shape of the specimen and the intrinsic properties of the material is proposed.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.61-69
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• 2022

The function of coolant in machining is to reduce the frictional force in the contact area in between the tool and the material, and to increase the precision by cooling the work-piece and the tool, to make the machining surface uniform, and to extend the tool life. However, cutting oil is harmful to the human body because it uses chlorine-based extreme pressure additives to cause environmental pollutants. In this study, the effect of cutting temperature and surface roughness of titanium alloy for medical purpose (Ti-6Al-7Nb) in eco-friendly ADL slot shape machining was investigated using the response surface analysis method. As the design of the experiment, three levels of cutting speed, feed rate, and depth of cut were designed and the experiment was conducted using the central composite planning method. The regression expressions of cutting temperature and surface roughness were respectively obtained as quadratic functions to obtain the minimum value and optimal cutting conditions. The values from this formula and the experimental values were compared. As a result, this study makes and establishes the basis to prevent environmental pollution caused by the use of coolant and to replace it with ADL (Aerosol Dry Lubricant) machining that uses a very small amount of vegetable oil with high pressure.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1260-1265
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• 2009

Topographical features in South Korea is characterized that 70% of territory is composed of the mountains that can experience intense rainfall during storms in the summer and autumn. Efficient planning and management of landscape becomes utmost important since the cutting slopes in the mountain areas have been increased due to the limited construction areas for the roadway and residential development. This paper proposed an efficient way of slope management for the landslide risk by developing Web-GIS landslide risk management system. By deploying the Logistic Regression Analysis, the system could increase the prediction accuracy that the landslide disaster might be occurred. High resolution survey technology using GPS and Total-Station could extract the exact position and visual shape of the slopes that accurately describe the slope information. Through the proposed system, the prediction of damage areas from the landslide could also make it easy to efficiently identify the level of landslide risks via web-based user interface. It is expected that the proposed landslide risk management system can support the decision making framework during the identification, prediction, and management of the landslide risks.

• International Journal of Advanced Culture Technology
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• v.11 no.4
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• pp.302-309
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• 2023

Wearable devices, attached to the human body, track and enhance users' activities, health, and communication. Therefore, considering ergonomic factors in product design is crucial. However, previous research has somewhat overlooked the importance of integrating ergonomic design elements into a broad spectrum of design factors. This study aims to examine the impact of physical attributes inherent in smart wristbands and smartwatches on the perceived functional value, specifically, perceived usefulness, ease of use, and fit. A survey was conducted among 289 US adults who had experience using smart wristbands or smartwatches. The collected data were analyzed using descriptive statistics, factor analysis, Cronbach's alpha, t-test, MANOVA, and regression analysis in SPSS version 29. The results showed that the shape of the front display significantly influenced perceived ease of use, and the product's weight had a substantial impact on both perceived ease of use and fit. Furthermore, distinct technical features on the front display had varied effects on perceived usefulness, ease of use, and fit. Notably, the presence of activity tracking, alarm, and calendar functionalities led to distinct differences in ease of use and fit. Features such as distance tracking, phone call, social media notifications, text messaging, and time display functions showed significant influences on the perception of fit. These findings provide insights into the physical values of smart wristbands and smartwatches as perceived by users.