• Title/Summary/Keyword: Global Minimum Point

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A study on minimum weight design of vertical corrugated bulkheads for chemical tankers

  • Shin, Sang-Hoon;Ko, Dae-Eun
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.2
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    • pp.180-187
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    • 2018
  • Corrugated bulkhead has been adopted for cargo tank bulkheads of commercial vessels such as bulk carriers, product oil carriers and chemical tankers. It is considered that corrugated bulkhead is a preferred structural solution, compared to the flat stiffened bulkhead, due to several advantages such as lower mass, easier maintenance and smaller corrosion problems. Many researches to find the optimum shape of corrugated bulkhead have been mostly carried out for bulk carriers. Compared to corrugated bulkheads of bulk carriers, ones of chemical tankers are more complicated since they are composed of transverse and longitudinal bulkheads, and they are made of higher priced materials. The purpose of this study is the development of minimum weight design method for corrugated bulkhead of chemical tankers. Evolution strategy is applied as an optimization technique. It has been verified from many researches that evolution strategy searches global optimum point prominently by using multi-individual searching technique. Multi-individual searching methods need excessive time if they connect to 3-D finite element model for repetitive structural analyses. In order to resolve this issue, 2-D beam element connected to deck and lower stool is substituted for a corrugated structure in this study. To verify the reliability of the structural responses by idealized 2-D beam model, they have been compared with ones by 3-D finite element model. In this study, optimum design for corrugated bulkhead of 30 K chemical tanker has been carried out, and the results by developed optimum design program have been compared with design data of existing ship. It is found out that optimum design is about 9% lighter than one of existing ship.

The Variations of Stratospheric Ozone over the Korean Peninsula 1985~2009 (한반도 상공의 오존층 변화 1985~2009)

  • Park, Sang Seo;Kim, Jhoon;Cho, Nayeong;Lee, Yun Gon;Cho, Hi Ku
    • Atmosphere
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    • v.21 no.4
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    • pp.349-359
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    • 2011
  • The climatology in stratospheric ozone over the Korean Peninsula, presented in previous studies (e.g., Cho et al., 2003; Kim et al., 2005), is updated by using daily and monthly data from satellite and ground-based data through December 2009. In addition, long-term satellite data [Total Ozone Mapping Spectrometer (TOMS), Ozone Monitoring Instrument (OMI), 1979~2009] have been also analyzed in order to deduce the spatial distributions and temporal variations of the global total ozone. The global average of total ozone (1979~2009) is 298 DU which shows a minimum of about 244 DU in equatorial latitudes and increases poleward in both hemispheres to a maximum of about 391 DU in Okhotsk region. The recent period, from 2006 to 2009, shows reduction in total ozone by 6% relative to the values for the pre-1980s (1979~1982). The long-term trends were estimated by using a multiple linear regression model (e.g., WMO, 1999; Cho et al., 2003) including explanatory variables for the seasonal variation, Quasi-Biennial Oscillation (QBO) and solar cycle over three different time intervals: a whole interval from 1979 to 2009, the former interval from 1979 to 1992, and the later interval from 1993 to 2009 with a turnaround point of deep minimum in 1993 is related to the effect of Mt. Pinatubo eruption. The global trend shows -0.93% $decade^{-1}$ for the whole interval, whereas the former and the later interval trends amount to -2.59% $decade^{-1}$ and +0.95% $decade^{-1}$, respectively. Therefore, the long-term total ozone variations indicate that there are positive trends showing a recovery sign of the ozone layer in both North/South hemispheres since around 1993. Annual mean total ozone (1985~2009) is distributed from 298 DU for Jeju ($33.52^{\circ}N$) to 352 DU for Unggi ($42.32^{\circ}N$) in almost zonally symmetric pattern over the Korean Peninsula, with the latitudinal gradient of 6 DU $degree^{-1}$. It is apparent that seasonal variability of total ozone increases from Jeju toward Unggi. The annual mean total ozone for Seoul shows 323 DU, with the maximum of 359 DU in March and the minimum of 291 DU in October. It is found that the day to day variability in total ozone exhibits annual mean of 5.7% in increase and -5.2% in decrease. The variability as large as 38.4% in increase and 30.3% in decrease has been observed, respectively. The long-term trend analysis (e.g., WMO, 1999) of monthly total ozone data (1985~2009) merged by satellite and ground-based measurements over the Korean Peninsula shows increase of 1.27% $decade^{-1}$ to 0.80% $decade^{-1}$ from Jeju to Unggi, respectively, showing systematic decrease of the trend magnitude with latitude. This study also presents a new analysis of ozone density and trends in the vertical distribution of ozone for Seoul with data up to the end of 2009. The mean vertical distributions of ozone show that the maximum value of the ozone density is 16.5 DU $km^{-1}$ in the middle stratospheric layer between 24 km and 28 km. About 90.0% and 71.5% of total ozone are found in the troposphere and in the stratosphere between 15 and 33 km, respectively. The trend analysis reconfirms the previous results of significant positive ozone trend, of up to 5% $decade^{-1}$, in the troposphere and the lower stratosphere (0~24 km), with negative trend, of up to -5% $decade^{-1}$, in the stratosphere (24~38 km). In addition, the Umkehr data show a positive trend of about 3% $decade^{-1}$ in the upper stratosphere (38~48 km).

A Study on the Robust Pitch Period Detection Algorithm in Noisy Environments (소음환경에 강인한 피치주기 검출 알고리즘에 관한 연구)

  • Seo Hyun-Soo;Bae Sang-Bum;Kim Nam-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2006.05a
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    • pp.481-484
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    • 2006
  • Pitch period detection algorithms are applied to various speech signal processing fields such as speech recognition, speaker identification, speech analysis and synthesis. Furthermore, many pitch detection algorithms of time and frequency domain have been studied until now. AMDF(average magnitude difference function) ,which is one of pitch period detection algorithms, chooses a time interval from the valley point to the valley point as the pitch period. AMDF has a fast computation capacity, but in selection of valley point to detect pitch period, complexity of the algorithm is increased. In order to apply pitch period detection algorithms to the real world, they have robust prosperities against generated noise in the subway environment etc. In this paper we proposed the modified AMDF algorithm which detects the global minimum valley point as the pitch period of speech signals and used speech signals of noisy environments as test signals.

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Point Cloud-based Automated Building Tilt Measurement (포인트 클라우드 기반 건축물 기울기 측정 자동화)

  • Dayoung Yu;Chaeeun Lee;Sung-Han Sim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.5
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    • pp.84-88
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    • 2023
  • This study proposes an automated tilt measurement method using point cloud for buildings. The proposed method consists of two main steps: 1) exterior wall plane extraction, and 2) edge estimation and angle calculation. To validate the performance of the proposed method, the algorithm is applied to a target building, of which the estimated tilt values are compared with those obtained from a total station, a commonly used tool for tilt measurement. The result shows that most estimated tilt values are within the maximum and minimum ranges of the total station measurement, suggesting that the proposed algorithm provides sufficient measurement accuracy. Furthermore, the proposed method is shown to be automated and reliable as well as free from human-induced errors compared to the total station.

Pitch Period Detection Algorithm Using Rotation Transform of AMDF (AMDF의 회전변환을 이용한 피치 주기 검출 알고리즘)

  • Seo, Hyun-Soo;Bae, Sang-Bum;Kim, Nam-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • v.9 no.2
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    • pp.1019-1022
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    • 2005
  • As recent information communication technology is rapidly developed, a lot of researches related to speech signal processing have been processed. So pitch period is applied as important factor to many application fields such as speech recognition, speaker identification, speech analysis and synthesis. Therefore, many algorithms related to pitch detection have been proposed in time domain and frequency domain and AMDF(average magnitude difference function) which is one of pitch detection algorithms in time domain chooses time interval from valley to valley as pitch period. But, in selection of valley point to detect pitch period, complexity of the algorithm is increased. So in this paper we proposed pitch detection algorithm using rotation transform of AMDF, that taking the global minimum valley point as pitch period and established a threshold about the phoneme in beginning portion, to exclude pitch period selection. and compared existing methods with proposed method through simulation.

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Estimating Join Selectivity of Global XQuery Queries in Distributed Environments (분산 환경에서 전역 XQuery 질의의 조인 선택치 추정 방법)

  • Park, Jong-Hyun;Kang, Ji-Hoon
    • Journal of KIISE:Databases
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    • v.34 no.6
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    • pp.564-571
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    • 2007
  • One of the methods for integrating XML data in distributed environments is using XML view. User can query toward distributed local XML views by using global XQuery queries in XQuery which is a standard query language for searching XML data. The global XQuery queries naturally contain join operations because of integrating and searching distributed heterogeneous data. Since join operations are generally expensive for processing a query, its processing technique is very important for efficient processing of global XQuery queries. Therefore there are some studies on the efficient processing of join operations and one of these studies is that selects minimum join cost by estimating a join selectivity. In case of SQL, there are already some researches for estimating a join selectivity and join cost of global SQL queries. However we can not apply their methods for estimating the selectivity of join operations in SQL queries into XQuery queries because of the structural difference between relational data and XML data. Therefore this paper proposes a method for estimating a selectivity of join operations in XQuery queries using the information of XML views. Our contribution is three threefold. First, we define the difference point for estimating join selectivity between SQL and XQuery. Second, we estimate join selectivity in XQuery queries by referring XML views. Third, we evaluate our estimating method.

The Efficient Edge Detection using Genetic Algorithms and Back-Propagation Network (유전자와 역전파 알고리즘을 이용한 효율적인 윤곽선 추출)

  • Park, Chan-Lan;Lee, Woong-Ki
    • The Transactions of the Korea Information Processing Society
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    • v.5 no.11
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    • pp.3010-3023
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    • 1998
  • GA has a fast convergence speed in searching the one point around optimal value. But it's convergence time increase in searching the region around optimal value because it has no regional searching mechanism. BP has the tendency to converge the local minimum because it has global searching mechanism. To overcome these problems, a method in which a genetic algorithm and a back propagation are applied in turn is proposed in this paper. By using a genetic algorithm, we compute optimal synaptic strength and offset value. And then, these values are fed to the input of the back propagation. This proposed method is superior to each above method in improving the convergence speed.

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A Study on the Flexibility in Exporting Korean Apparel Products (한국의류제품 수출의 유연성(flexibility)에 관한 연구)

  • 김용주
    • Journal of the Korean Society of Costume
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    • v.34
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    • pp.37-56
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    • 1997
  • The Korean Apparel industry has played an significant role for the econom-ic development in Korea which is mainaly due to the apparel exports to the world market. However the Koran apparel industry has confronted drastic changes in domestic and also in international market for the last several years. Korean apparel products have lost price competitiveness in international market because domestic labor costs have increased so fast and al-so newcomers such as China or other Asian countries have emerged as compet-itive producers. Furthermore domestic market has been saturated with the Korean apparel manufacturers and also with the foreign retailers. Therefore the Korean apparel industry should establish market-ing strategies in order to regain competitiveness. This study aims to analyze the factors for non-price competitiveness of Korean apparel industry and propose the way to regain competitiveness form the buyers' point of view. The present study utilize the survey data for the internet database which is established by the Cotton Incorporated. The results show that the Korean apparel industry is not competitive in terms of non-price factors such as minimum orders terms of payment preproduction stage use of new technolo-gy and lead times. These factors are not directly related to the price of product which is suggested to the buyers. However these are flexibility factors which play important roles in decision making process of buyers because they can reduce risks in uncertain business environment. Therefore the Korean apparel industry should establish global marketing strate-gies which can enhance non-price competitiveness as well as price competitiveness.

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Analysis of Joule-heat Characteristics according to the DC-link Capacitor Film Geometrics (DC-link Capacitor필름 형상에 따른 Joule-heat특성 분석)

  • Jeon, Yong Won;Kim, Young Shin;Jeon, Euy Sik
    • Journal of the Semiconductor & Display Technology
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    • v.19 no.1
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    • pp.42-48
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    • 2020
  • As global warming accelerates, eco-friendly electric cars are being developed to reduce carbon dioxide emissions, and power conversion inverters are used to drive motors. Among inverter components, DC-link capacitor is heated by high current usage, which causes problems such as performance and life-saving of inverter. Although metal cases with good thermal performance have been used to solve this problem, it is difficult to apply them in practice due to insulation problems with other parts. In this paper, the Heat-Generation influence factor of DC-link capacitor is analyzed. Variables on heat-generation are set at 3 levels for film width, inductance, and film thickness. Box-Behnken to 13 tests using the design and minimal deviations, e.g. through the experiment three times by each level. The surface of the film k type by attaching the sensor current is measured temperature. Capacitance was set to a minimum level of 200 ㎌ and had a frequency of 16 kHz with Worst case, ambient temperature of 85℃ and a ripple current of 50 Ams was applied. The temperature at the measurement point was collected in the data logger after sampling at 1 minute intervals for 2 hours after saturation with the ambient temperature. This experiment confirmed that setup factors are correlated with heat-generation.

A Study on the Holiday Effect of Purchase Interval of Mobile Phone in Chinese Online B2C Market

  • Kwak, Youngsik;Hong, Jaewon;Nam, Yongsik;Nam, Yoonjung
    • Journal of the Korea Society of Computer and Information
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    • v.24 no.6
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    • pp.205-210
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    • 2019
  • The purpose of this study is to demonstrate empirically whether replacement intervals of mobile phones sold in China online B2C are influenced by purchase points such as holidays. If there is a holiday effect, it is expected that the product replacement interval or interpurchase interval will be short compared to the usual one at holiday time. In order to verify this positively, at TMall, one of the largest B2C sites in China, we explored 5,132 replacement cycle intervals and the point of purchase at which one of the sales records of an agent dealing with all multinational mobile phones had minimum two purchase records. As a result, there was a buyer who had shorter replacement period than usual in holiday season. There was no statistically significant difference in the intervals of interchange between holidays. Based on the results, it was found that the mobile phone vendors were aware that purchasing was occurring due to the holiday.