• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.249-259
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• 2020

Design criteria for limit state design of underground structures have already been published overseas, and research has been conducted to revise the design method in Korea. In order to estimate the probability of failure under seismic load, the probability variable should be considered in the reliability analysis. In this study, the failure probability of the existing shield tunnel segment lining design was calculated by applying the coefficient of variation (COV) for the earth pressure and the seismic load effect in consideration of the statistical characteristics of the domestic ground properties. Based on the results of calculating the reliability index (β) from the calculated probability of failure and analyzing the reliability index according to the change in the load factor and the results of domestic and foreign research, the target reliability index (β_T) during earthquakes of shield tunnel segment lining is analyzed to be "2.3", it was proposed as the target reliability index for the design of the limit state under seismic load.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.521-528
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• 2010

A product system will be improved continually until requirements are satisfied. It is true that considering alternative designs to improve product system is hard work; it is also true that selecting an adequate design idea that represents the needs of stakeholders concerned and meets effectiveness factors properly is not an easy work, either. In the process of driv-ing an idea and designing, which is called Design Phase, there are lots of existing tools for testing the driven idea in DFSS. But, those kinds of tools do not offer the function that helps to select the technically better design idea among alternative design ideas that have the same evaluation level. Moreover it is inappropriate to select adequate alternative design ideas by just verifying only the evaluation table in pugh matrix, since satisfied deviation val-ues are low when there is a too competitive mass product system in a market. Also, for the IT product with short life cycle, faster and more effective testing tool is needed. Therefore, the 'roduct quality index' is suggested in order to select an appropriate candidate design concept for system development that meets requirements by using 'deality concept' pro-vided by TRIZ. According to the result of this research, it is possible to select technically better idea fast and effectively; it is confirmed by applying the approach to the case of LCD BLU (Back Light Unit).

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.2
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• pp.29-40
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• 2018

Strength design wind loads for the wind resistance design of structures shall be evaluated by the product of wind loads calculated based on the basic wind speed with 100 years return period and the wind load factor 1.3 specified in the provisions of load combinations in Korean Building Code (KBC) 2016. It may be sure that the wind load factor 1.3 in KBC(2016) had not been determined by probabilistic method or empirical method using meteorological wind speed data in Korea. In this paper, wind load factors were evaluated by probabilistic method and empirical method. The annual maximum 10 minutes mean wind speed data at 69 meteorological stations during past 40 years from 1973 to 2012 were selected for this evaluation. From the comparison of the results of those two method, it can be found that the mean values of wind load factors calculated both probability based method and empirical based method were similar at all meteorological stations. When target level of reliability index is set up 2.5, the mean value of wind load factors for all regions should be presented about 1.35. When target level of reliability index is set up 3.0, wind load factor should be presented about 1.46. By using the relationship between importance factor(conversion factor for return period) and wind load factor, the return periods for strength design were estimated and expected wind speeds of all regions accounting for strength design were proposed. It can be found that return period to estimate wind loads for strength design should be 500 years and 800 years in according to target level of reliability index 2.5 and 3.0, respectively. The 500 years basic wind speed map for strength design was suggested and it can be used with a wind load factor 1.0.

• Current Photovoltaic Research
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• v.3 no.3
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• pp.91-96
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• 2015

Optical modeling and characterization of transparent dye-sensitized solar cells (DSC) are presented to design and estimate DSC devices numerically. In order to model the inhomogeneous active layer of DSC, the porous structure of titanium oxide ($TiO_2$) and dye mixture, we prepared films consisting of layer by layer of the DSC's basic materials sequentially, and characterized the optical parameters of the films with the effective refractive index, which was extracted from the transmittance and reflectance measurements in ultra violet to near infra-red range. By using the effective refractive index, we made the optical model for DSC, and demonstrated that the optical model based on effective refractive index can be used to design and evaluate the performance of transparent-type DSC modules.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.10-19
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• 1993

Design optimisation generally necessitates a tool of assessing the economics of designs. This paper proposes a method of assessing the economics of marine electric generating systems. The pay back period(PBP) and the net present valuve(NPV) of the investment for a designed project are properly converted into a economic index. The mechanical factors dominating the easiness in operating the system are also assessed and quantified to form a index which eventually is added to the economic index producing a comprehensive economic index. The method has been tested on a design example and it's validity has been shown.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.5-15
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• 2014

Target reliability index in the limit state design indicated the safety margin and it is important to determine the partial factor. To determine the target reliability index which is needed in the limit state design, the six design and construction case histories of gravel compaction piles (GCP) were investigated. The limit state functions were defined by bulging failure for the major failure mode of GCP. The reliability analysis were performed using the first order reliability method (FORM) and the reliability index was calculated for each ultimate bearing capacity formulation. The reliability index of GCP tended to be penportional to the safety factor of allowable stress design and average value was ${\beta}$=2.30. Reliability level that was assessed by reliability analysis and target reliability index for existing structure foundations were compared and analyzed. As a result, The GCP was required a relatively low level of safety compared with deep and shallow foundations and the currd t reliability level were similar to the target reliability in the reinforced earth retaining-wall and soil-nailing. Therefore the target reliability index of GCP suggested as ${\beta}_T$=2.33 by various literatures together with the computed reliability level in this study.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.296-303
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• 2004

The heat and flow characteristics in a single-phase parallel-flow heat exchanger was examined numerically to obtain its optimal shape. A response surface method was introduced to approximately predict its performance with respect to the design parameters over the design domain. The inflow/outflow angle of the working fluid, the location of inlet/outlet, the protruding height of flat tube and the height of header were chosen as a design parameter The evaluation of the relative importance of the design parameters was performed based on a sensitivity analysis. An efficiency index was used as an evaluation characteristics value to simultaneously consider both the heat transfer and the pressure drop. The efficiency index of the optimum model, compared to that of the base model, was increased by 9.3%.

• 연구논문집
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• s.33
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• pp.89-97
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• 2003

A barrel cam is used as a very important part of an index drive unit. The index drive unit must have an intermittent-rotational motion. The barrel typed cam and roller gear mechanism has the advantages of high reliability to perform a prescribed motion of a follower. This paper proposes a new method for the shape design of the barrel cam and also a CAD program is developed by using the proposed method. As defined in this paper, the relative velocity method for the shape design calculates the relative velocity of the follower versus cam at a center of roller, and then detemines a contact point by using the geometric relationships and the kinematic constraints, where the direction of the relative velocity must be parallel to a common tangential line at the contact point of two independent bodies, i.e. the cam and the follower. Then, the shape of the cam is defined by the coordinate transformation of the trace of the contact points. This paper presents shape design of the barrel cam in order to prove the accuracy of the proposed methods

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.453-462
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• 2019

Mental workload (MWL) is a major consideration for the user interface design in nuclear power plants (NPPs). However, each MWL evaluation method has its advantages and limitations, thus the evaluation and control methods based on multi-index methods are needed. In this study, fuzzy comprehensive evaluation (FCE) theory was adopted for assessment of interface designs in NPP based on operators' MWL. An evaluation index system and membership functions were established, and the weights were given using the combination of the variation coefficient and the entropy method. The results showed that multi-index methods such as performance measures (speed of task and error rate), subjective rating (NASA-TLX) and physiological measure (eye response) can be successfully integrated in FCE for user interface design assessment. The FCE method has a correlation coefficient compared with most of the original evaluation indices. Thus, this method might be applied for developing the tool to quickly and accurately assess the different display interfaces when considering the aspect of the operators' MWL.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4139-4145
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• 2012

This paper shows an antireflection coating design skill for utilization the thin-film silicon solar cell in the future. The reflectivity of each index profile previously suggested as linear, cubic and quintic function has been calculated and compared. Each index profile is applied to the antireflection coating consisting of 6 layers with 180nm thickness. Also we suggest the graded index profile and compare it's reflectivity to the linear, cubic and quintic's ones. As a results we find the reflectivity generally decreases as the order goes to higher. However the reflectivity in the graded index profile shows the higher(lower) value than ones in the linear, cubic and quintic especially in the shorter(longer) wavelength range from 500 nm to below 700 nm(above 700 nm to 800 nm). Therefore we find that the graded index profile structure could be applied for the better antireflection coating design scheme especially for optical device and optical filter in the range of from deep red to infrared.