• 한국정밀공학회지
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• 제29권3호
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• pp.279-288
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• 2012

The material removal mechanism in machining is significantly affected by the cutting edge geometry. Its effect becomes even more substantial when the depth of cut is relatively small as compared to the characteristic length which represents the shape and size of the cutting edge. Conventionally, radius or focal length has been employed as the characteristic length with the assumption that the shape of cutting edge is round or parabolic. However, in reality, there could be various ways to determine the radius or focal length even for the same tool edge profile, depending on the region to be considered as cutting edge in the measured profile and the constraints to be set in constructing the best fitted circle or parabola. In this regard, the present study proposes various models to determine the characteristic length in terms of radius or focal length. Their physical compatibility are validated by carrying out 2D orthogonal cutting experiments using inserts with a wide range of characteristic length ($30{\sim}180\;{\mu}m$ in terms of radius) and then by investigating the correlation between the characteristic length and the cutting forces. Such validation is based on the common belief that the larger the characteristic length is, the blunter the cutting edge is and the higher the cutting forces are. Interestingly, the results showed that the correlation is higher for the radius or focal length obtained with a constraint that the center of best fitted circle or the focus of the best fitted parabola should be on the bisectional line of the wedge angle of tool.

• 한국환경복원기술학회지
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• 제8권1호
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• pp.45-51
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• 2005

Total phosphorus(TP) removal was examined in a surface-flow wetland constructed in April 2003 during its initial operating stage from June to November 2003. Its dimensions were 87mL by 14mW. It was a part of a four-wetland-cell treatment system constructed near the Kohung Estuarine Lake located in the southern part of Korea. Effluent from a night soil treatment plant was discharged into the wetland and purified effluent from the wetland was discharged into Sinyang Stream flowing into the Lake. Cattails(Typha angustifolia ) from natural wetlands were cut at about 40 cm height and transplanted into the wetland. An average of 25.0$m^3$/day of effluent flowed from the plant into the wetland. Water depth was maintained about 0.2m and hydraulic detention time was about 5.2 days. Average heights of the cattail stems in June and October 2003 were 47.2 and 164.6cm, respectively. The average number of stems was 10.2 stems/$m^2$ in June 2003 and 18.8 stems/$m^2$ in October 2003. Average temperature of influent and effluent ranged 23.4 and $24.2^{\circ}C$, respectively. The average TP concentrations of influent and effluent were about 1.31, 0.50mg/L, respectively. TP loading rate of influent into the wetland averaged 26.81mg/$m^2$, day and average TP loading rate of effluent was 10.04mg/$m^2$, day. Monthly average TP removal by the wetland during the warm growing season of cattails(June to September) ranged 16.28~19.57mg/$m^2$, day and during the cold senescent period (October to November) ranged 12.62~13.90mg/$m^2$, day. TP removal in the wetland continued during the cold winter months and was primarily done by sedimentation and precipitation of phosphorus rather than phosphorus absorption by cattails and microorganisms.

• 복식문화연구
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• 제16권4호
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• pp.646-660
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• 2008

Korean export of fashion products to the U.S. has fallen off sharply after 2001. Now, Korean fashion companies have to develop higher value-added business. In the U.S., Korean-American fashion companies are taking a primary role in up-stream of the fashion industry. To cut the edge over the U.S. fashion companies, one of the solutions could be to build the business relationship with Korean fashion companies which reflect the recent trend rapidly and have high quality production. On this study, we investigated the marketing strategies of Korean-American fashion companies to seek to start business with Korean fashion companies and make suggestions for Korean fashion companies who want to enter into the U.S. market effectively. To analyze current situation of Korean export to the U.S. and the U.S. fashion industry, we considered various kinds of statistic data, publications and studies. And we performed in-depth interviews with 9 Korean-American fashion companies in LA from $9^{th}$ to $21^{st}$ of July. The results are as follows. first, Korean fashion companies should aim for high-end market with the products of high quality and design. Second, there should be professional agents who manage Korean small-medium fashion companies and connect them with Korean-American fashion companies. Third, Korean fashion companies who want to enter into the retail market of the U.S. have to decide the target market clearly and plan strategic and differentiated merchandising. Fourth, Korean fashion companies can specialize in product developing service like proposing a product or a merchandising line as a package including designs, fabric swatches, trims, production information, etc.

• 한국해양학회지:바다
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• 제7권3호
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• pp.95-99
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• 2002

3.5KHz 천부지층탐사기(Subbottom Profiler)는 10~100m 깊이까지의 천부 해저지층구조를 정밀하게 파악하기 위한 탐사장비이다. 천부지층탐사는 1m 보다 정밀한 해상도를 요하는 탐사이다. 그러나 해상의 파고는 대부분 1m 이상인 경우가 많기 때문에 파도에 의한 너울영항으로 자료의 품질이 크게 저하된다. 본 연구에서는 디지털로 취득된 3.5KHz 천부지층탐사자료에서 너울영향을 제거함으로써 고품질의 지층단면도를 획득할 수 있음을 보였다. 너울 효과를 제거하기 전에 해저면 신호의 진폭이 큰 점을 이용하여 해저면 추출심도를 구하였다. 너울영향을 제거하기 위하여 인접트레이스의 추출심도를 이용한 인접심도 평균법과 고주파 제거 필터링법을 각각 적용한 결과, 두가지 모두 양호한 결과를 도출할 수 있었다. 자료의 상태가 매우 불량한 경우와 심도가 얕아 직접파와 중첩되는 경우 등에서는 해저면 심도추출이 부정확하여 너울영향제거에 어려움이 있다.

• 한국정밀공학회지
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• 제27권8호
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• pp.62-69
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• 2010

Internal lathe machining with a boring bar is weak with respect to vibration because the bar is long and slender. Therefore, it is important to study the dynamic characteristics of a boring bar. The purpose of this study was to identify the effects of overhang and cutting conditions on the dynamic response characteristics of a boring bar. For an efficient experiment, an $L_g(3^3)$ orthogonal array was applied and the results were quantitatively analyzed by ANOVA. Overhang, feed per revolution, and depth of cut were selected as independent variables. Meanwhile, dynamic stiffness, damping ratio, damping coefficient, and acceleration were chosen as dependent variables. The vibration signal was obtained from an accelerometer attached to the boring bar, followed by visualization by a signal analyzer. The effect of overhang was found to have a significant effect on the dynamic stiffness, damping ratio, and damping coefficient, but the other variables did not. As the length of the overhang increased, the dynamic stiffness decreased and the damping ratio increased. In addition, the damping coefficient increased until the length of the overhang was 4D (where D is the shank diameter), after which it remained constant. The acceleration decreased until the overhang length was 4D, and then increased sharply when the overhang was increased further. From these results, the behavioral trend of the damping characteristics changed when its overhang length was 4D. Consequently, there is a critical point that the dynamic characteristics of boring bar change.

• 한국지진공학회논문집
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• 제24권5호
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• pp.219-232
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• 2020

The slip-weakening model developed by Ohnaka and Yamashita is extended over the breakdown zone by equating the scaling relationships for the breakdown zone and the whole rupture area. For the extension, the study uses the relationship between rupture velocity and radiation efficiency, which was derived in the theory of linear elastic fracture mechanics, and the definition of f_max given in the specific barrier model proposed by Papageorgiou and Aki. The results clearly show that the extended scaling relationship is governed by the ratio of rupture velocity to S wave velocity, and the velocity ratio can be determined by the ratio of characteristic frequencies of a Fourier amplitude spectrum, which are corner frequency, f_c, and source-controlled cut-off frequency, f_max, or vice versa. The derived relationship is tested by using the characteristic frequencies extracted from previous studies of more than 130 shallow crustal events (focal depth less than 25 km, M_W 3.0~7.5) that occurred in Japan. Under the assumption of a dynamic similarity, the rupture velocity estimated from f_max/f_c and the modified integral timescale give quite similar scale-dependence of the rupture area to that given by Kanamori and Anderson. Also, the results for large earthquakes show good agreement to the values from a kinematic inversion in previous studies. The test results also indicate the unavailability of the spectral self-similarity proposed by Aki because of the scale-dependent rupture velocity and the rupture velocity-dependent f_max/f_c; however, the results do support the local similarity asserted by Ohnaka. It is also remarkable that the relationship between the rupture velocity and f_max/f_c is quite similar to Kolmogorov's hypothesis on a similarity in the theory of isotropic turbulence.

• 한국기계가공학회지
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• 제20권8호
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• pp.93-98
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• 2021

The complex effects of the machining parameters make it is difficult to control and predict surface roughness. The theoretical surface roughness observed during mechanical machining with a round tool is determined by the tool radius and pitch. However, it was revealed that other parameters, such as the depth of cut and cutting speed, also affect surface roughness. This study adapted the Taguchi method, which can analyze the effects of cutting parameters quantitatively with an efficient number of experiments, to optimize the parameters for better surface roughness. Experiments were designed based on an orthogonal array, and the quantitative effects on the surface roughness were analyzed using the S/N ratio. The surface roughness was affected by all parameters, especially the tool radius. The optimum cutting parameter values obtained in this study showed better surface roughness than the other combinations of the parameters.

• 복식
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• 제65권3호
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• pp.131-150
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• 2015

This article studied the procedures and items used in royal princess weddings by examining "Garyedeungrok(嘉禮謄錄)" which describes Princess Hwasun(和順翁主, 1720-1758)'s wedding in 1732. This was the first wedding by a princess during King Yeongjo(英祖)'s reign. Preparation for the wedding was made based on the previous weddings of royal princesses, but it did not follow the old tradition. The wedding costs were cut down, and it was done in a simpler way than before. However, the simplification of elaborate wedding outfits were not part of this change as ceremonial robes such as No-ui(露衣), Jangsam(長衫) and Chopo(綃袍) were used without much alteration. The wedding ceremony of Princess Hwasun shows the transition process from the royal princess wedding ceremony traditions and rituals in the late 17th century to "Gukhonjeongrye", which emerged and became solidified as a new social norm in the 18th century. A legitimate royal princess and a de facto princess from King's concubine were hardly different when it came to their royal outfitting but the disparity in social status between the two was found in the materials used to make clothes for their respective husbands. Princess Hwasun's wedding procedure shown in "Garyedeungrok" is similar to that of "Gukjo-orye-ui(國朝五禮儀)": Napchae(納采), Nappye(納幣), Chinyeong(親迎), Dongroe(同牢), Hyeongugo(見舅姑), Hyeonsadang(見祠堂), and Seojohyeon(壻朝見). But "Garyedeungrok" deals with the procedures of Gantaek(揀擇), Buma-guanrye(駙馬冠禮), and Seonon(宣醞), which are not included in "Gukjo-orye-ui", and also with the process of preparation for wedding items and the information of related people. However, it is hard to learn about its specific shapes and features because it is often restricted to lists such as a list of clothing. Collecting new materials and an in-depth and succeeding study are required in the future.

• 한국게임학회 논문지
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• 제8권4호
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• pp.17-27
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• 2008

본 연구는 비디오 게임 구조와 플레이어 의식의 순환적 시스템에 대한 밀도 있는 관찰과 분석을 위해 '어드벤처 게임(Adventure Game)'장르로 분석대상을 제한하였다. 어드벤처 게임 고유의 특징적 단위구조인 '퍼즐 시스템'을 분석하였고, 그 경험이 플레이어의 의식에 '완결 욕구'를 발생시켜 몰입과 참여도에 작용하는 메커니즘 연구에 중점을 두었다. 연구과정은 문헌연구와 직접 플레이 등을 통해 어드벤처게임과 그 구성 요소들의 본질적 특성 및 비디오 게임 플레이의 몰입 특성을 살펴보았으며, 어드벤처게임에서의 퍼즐 시스템을 정의하고, 이 시스템 내에서 퍼즐요소와 내러티브 요소가 유기적으로 작용하는 구조 및 플레이 과정을 분석하여 '퍼즐 시스템'과 '완결 욕구'에 대한 가설들을 수립하였다. 가설을 확인하기 위하여 극적인 컷 씬이 포함된 게임과 컷 씬이 제외된 게임단위를 제작하고 실험을 실시하여 차이를 조사하였으며, 게임 난이도의 수준차이와 실패지점의 위치 변화를 유도하여 게임의 해결여부, 실패지점에 따른 플레이어의 완결 욕구와 참여도 변화를 파악하였다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2006년도 학술대회
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• pp.127-132
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• 2006

Quantization in video coding plays an important role in controlling the bit-rate of compressed video bit-streams. It has been used as an important control means to adjust the amount of bit-streams to at]owed bandwidth of delivery networks and storage. Due to the dependent nature of video coding, dependent quantization has been proposed and applied for MPEG-2 video coding to better maintain the quality of reconstructed frame for given constraints of target bit-rate. Since Scalable Video Coding (SVC) being currently standardized exhibits highly dependent coding nature not only between frames but also lower and higher scalability layers where the dependent quantization can be effectively applied, in this paper, we propose a dependent quantization scheme for SVC and compare its performance in visual qualities and bit-rates with the current JSVM reference software for SVC. The proposed technique exploits the frame dependences within each GOP of SVC scalability layers to formulate dependent quantization. We utilize Lagrange optimization, which is widely accepted in R-D (rate-distortion) based optimization, and construct trellis graph to find the optimal cost path in the trellis by minimizing the R-D cost. The optimal cost path in the trellis graph is the optimal set of quantization parameters (QP) for frames within a GOP. In order to reduce the complexity, we employ pruning procedure using monotonicity property in the trellis optimization and cut the frame dependency into one GOP to decrease dependency depth. The optimal Lagrange multiplier that is used for SVC is equal to H.264/AVC which is also used in the mode prediction of the JSVM reference software. The experimental result shows that the dependent quantization outperforms the current JSVM reference software encoder which actually takes a linear increasing QP in temporal scalability layers. The superiority of the dependent quantization is achieved up to 1.25 dB increment in PSNR values and 20% bits saving for the enhancement layer of SVC.