• 한국레이저가공학회지
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• 제11권1호
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• pp.32-35
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• 2008

In the remote welding system using $CO_2$ laser, laser beam can be rapidly transferred to a workpiece by moving mirrors of scanner system. So, it makes reducing the cycle time of welding process. We can also use and apply various patterns of weld beads by linear controlled mirrors. But most of the domestic car makers have usually applied use stitch-shaped weld bead. In that case, we don't have the merit of remote welding system efficiently. Therefore, in this paper, we investigated the characteristic of weld strength according to patterns of weld bead on $CO_2$ laser welding. And we also studied the relationship between shape of weld bead and value of tensile load.

• 한국조경학회지
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• 제31권3호
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• pp.74-82
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• 2003

Under the assumption that the temperature of one location is closely related to land use characteristics around that location, this study is carried out to assess the impact of urban land use patterns on air temperature. In order to investigate the relationship, GIS techniques and statistical analyses are utilized, after spatially connecting urban land use data in Seoul Metropolitan Area with atmospheric data observed at Automatic Weather Stations (AWS). The research method is as follows: (1) To find out important land use factors on temperature, simple linear regressions for a specific time period (pilot study) are conducted with urban land use characteristics, (2) To make a final model, multiple regressions are carried out with those factors and, (3) To verify that the final model could be appled to explain temperature variations beyond the period, the model is extensively used for 5 different time periods: 1999 as a whole; summer in 1999; 1998 as a whole; summer in 1998; August in 1998. The results of simple linear regression models in the pilot study show that transportation facilities and open space area are very influential on urban air temperature variations, which explain 66 and 61 percent of the variations, respectively. However, the other land use variables (residential, commercial, and mixed land use) are found to have weak or insignificant relationship to the air temperatures. Multiple linear regression with the two important variables in the pilot study is estimated, which shows that the model explains 75 percent of the variability in air temperatures with correct signs of regression coefficients. Thus, it is empirically shown that an increase in open space and a decrease in transportation facilities area can leads to the decrease in air temperature. After the final model is extensively applied to the 5 different time periods, the estimated models explain 68 ∼ 75 percent of the variations in the temperatures is significant regression coefficients for all explanatory variables. This result provides a possibility that one air temperature model for a specific time period could be a good model for other time periods near to the period. The important implications of this result to lessen high air temperature we: (1) to expand and to conserve open space and (2) to control transportation-related factors such as transportation facilities area, road pavement and traffic congestion.

• 한국환경보건학회지
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• 제42권1호
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• pp.1-9
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• 2016

Objectives: Personal exposure to air pollution is affected by contact over time and by location. The purpose of this study was to determine the relationship between personal exposure to $PM_{2.5}$ and the time-activity patterns of the elderly in urban and rural areas. Methods: A total of 44 elderly participants were recruited for a 24-hour $PM_{2.5}$ personal exposure measurement. Twenty-four were from Seoul (urban area) and 20 were from Asan (rural area). Energy expenditure and spatiotemporal positioning were monitored through $PM_{2.5}$ measurement. Spearman correlation analysis was conducted to determine the relationship between $PM_{2.5}$ and time-activity pattern. Results: Daily average $PM_{2.5}$ personal exposures were $19.1{\pm}9.7{\mu}g/m^3$ in Seoul and $29.1{\pm}16.9{\mu}g/m^3$ in Asan. Although outdoor exposure was higher in Seoul than in Asan, residential indoor exposure was higher in Asan than in Seoul. Higher $PM_{2.5}$ personal exposure in Asan could be explained by longer time in residential indoor environments and higher indoor $PM_{2.5}$ concentrations. Seoul elderly had higher energy expenditure, which may be due to the use of mass transportation. Conclusion: Personal exposure to $PM_{2.5}$ was higher among Asan elderly than Seoul elderly because of high residential indoor concentrations and longer residential time. Lack of energy spent and higher personal exposure to $PM_{2.5}$ might have led to higher risk among the Asan elderly.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.1-10
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• 2017

With the current global need for eco-friendly energies, the large scale use of Electric Vehicles (EVs) is predicted. However, the need to frequently charge EVs to an electrical power system involves risks such as rapid increase of demand power. Therefore, in this paper, we propose a practical smart EV charging scheme considering a Time-of-Use (ToU) price to prevent the rapid increase of demand power and provide load leveling function. For a more practical analysis, we conduct simulations based on the actual distribution system and driving patterns in the Republic of Korea. Results show that the proposed method provides a proper load leveling function while preventing a rapid increase of demand power of the system.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 The Third Asian Fuzzy Systems Symposium
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• pp.134-138
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• 1998

Unification of Kohone SOM(Self-Organizing Maps) neural network with the branch-and-bound algorithm is presented for clustering large set of patterns. The branch-and-bound search technique is employed for designing coarse neural network learning paradaim. Those unification can be use for clustering or calssfication of large patterns. For classfication purposes further usefulness is possible, since only two clusters exists in the SOM neural network of each nodes. The result of experiments show the fast learning time, the fast recognition time and the compactness of clustering.

• 대한의용생체공학회:의공학회지
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• 제11권1호
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• pp.157-162
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• 1990

In this study, a peripheral auditory model is used as a frequency feature extractor and a recurrent network which has recurrent links on input nodes is constructed in order to show the reliability of the recurrent network as a recognizer by executing recognition tests for 4 Korean place names and syllables. In the case of using the general learning rule, it is found that the weights are diverged for a long sequence because of the characteristics of the node function in the hidden and output layers. So, a refined weight compensation method is proposed and, using this method, it is possible to improve the system operation and to use long data. The recognition results are considerably good, even if time worping and endpoint detection are omitted and learning patterns and test patterns are made of average length of data. The recurrent network used in this study reflects well time information of temporal speech signal.

• International Journal of Computer Science & Network Security
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• 제21권2호
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• pp.193-197
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• 2021

Customers are increasingly attracted towards different e-commerce websites and applications for the purchase of products significantly. This is the reason the sellers are moving to different internet based services to sell their products online. The growth of customers in this sector has resulted in the use of big data analytics to understand customers' behavior in predicting the demand of items. It uses a complex process of examining large amount of data to uncover hidden patterns in the information. It is established on the basis of finding correlation between various parameters that are recorded, understanding purchase patterns and applying statistical measures on collected data. This paper is a document of the bottom-up strategy used to manage the selling price of a first-time product for maximizing profit while selling it online. It summarizes how existing customers' expectations can be used to increase the sale of product and attract the attention of the new customer for buying the new product.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 춘계학술대회 논문집
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• pp.55-60
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• 2007

The purpose of this study is to evaluate the temporal land cover change by gradual urbanization of Gyeongan-cheon watershed. This study used the five land use of Landsat TM satellite images(l987, 1991, 2001, 2004) which were classified by maximum likelihood method. The five land use maps examine its accuracy by error matrix and administrative district statistics. This study analyze land use patterns in the past using time.series Landsat satellite images, and predict 2004 year land use using a CA-Markov combined CA(Cellular Automata) and Markov process, and examine its appropriateness. Finally, predict 2030, 2060 year land use maps by CA-Markov model were constructed from the classified images.

• 한국언론정보학보
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• 제41권
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• pp.145-180
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• 2008

이 연구에서는 인터넷이 일상생활에 도입되면서 전반적인 생활시간 패턴에 변화를 가져온다는 관점에서 연구문제를 설정하였다. 새로운 매체가 등장했을 때 기존의 전통적 매체이용 시간에 대한 대체 혹은 보완 여부에만 주목할 경우, '미디어 고립주의'에 빠질 위험이 있다. 이뿐만 아니라 연구 결과가 일관되지 못하다는 한계점도 지적되어 왔다. 따라서 인터넷 이용 행동이 일상적 활동 영역에 미치는 영향을 거시적으로 살펴볼 수 있도록 하기 위해 2000년과 2005년도의 국민생활시간조사 자료를 통시적으로 분석함으로써 기존 연구(이재현, 2005)에서 제안된 시간 재할당 가설을 검증, 보완하고자 하였다. 먼저 연령대별로 인터넷 이용자와 비이용자 간에 일상적 활동 영역 및 매체 이용 영역에서 나타나는 시간 소비량의 차이를 검정한 후, 유의미한 차이를 보인 활동 영역에 대해서는 로지스틱 회귀분석을 통해 인터넷 이용 유무에 따른 생활시간 이용 패턴의 차이를 종합적으로 살펴보았다. 연구 결과, 2000년도와 인터넷 사용자가 급증한 2005년도의 경우를 비교했을 때 대부분의 연령 집단에서 생활시간 패턴이 재조직화되고 있음을 확인하였으며, 특히 젊은 연령층일수록 시간 재할당 현상이 더 일찍, 더 뚜렷이 나타나는 경향을 보였다.

• 한국경제지리학회지
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• 제10권4호
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• pp.427-443
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• 2007

본 연구의 목적은 현재 서울시를 포함한 수도권 지역에서 가장 높은 수송분담율을 차지하고 있는 지하철망 상 통행흐름의 시 공간적 구조를 밝히고, 그러한 통행흐름과 토지이용의 관계성을 밝히는 것이다. 특히 본 연구에서는 지난 2004년 7월 이후 수도권 대중교통이용자의 대부분이 이용하고 있는 교통카드 통행거래자료 중 매년 주중 하루치의 통행 트랜잭션 데이터베이스에 대하여 데이터마이닝 기법을 적용하여 지난 4년간 수도권 지하철망 상 통행흐름의 위상학적 구조를 비교분석하였다. 또한 하루 중 시간대별 통행흐름의 공간적 특징을 분석하기 위하여 하루를 아침 출근시간대, 낮 시간대, 저녁 퇴근 시간대로 나누어 수도권 지하철망 상의 각 지하철역의 시간대별 출발통행량과 도착통행량을 산출하고, GIS를 이용하여 그 공간적 패턴을 비교한 결과 시간대별로 확연한 차이가 나타남을 확인하였다. 그리고 지하철 통행흐름의 위상학적 구조와 토지이용과의 관계성을 밝히기 위하여 각 지하철역의 시간대별 출발 도착 통행량과 그 지하철역 주변지역의 토지이용상태를 반영하는 지리적 변수들 간의 상관관계분석과 다중회귀분석을 실시하였으며, 분석 결과 시간대별 출발 통행량 및 도착 통행량 관계를 설명하는 선형 대수식을 도출하였다. 함수식의 적합성 판명을 위하여 공선성진단과 이분산성분석을 실시하였다.