• Title/Summary/Keyword: time-series

Search Result 7,601, Processing Time 0.048 seconds

Long-term Influence of Mild to Moderate Ischemic Mitral Regurgitation after Off-pump Coronary Artery Bypass Surgery (무심폐기하 관상동맥우회술에서의 중등도의 허혈성 승모판막부전증의 중요성)

  • Hong, Jong-Myeon;Cartier, Raymond
    • Journal of Chest Surgery
    • /
    • v.43 no.3
    • /
    • pp.246-253
    • /
    • 2010
  • Background: Our objective was to review the long-term prognosis of patients with preoperative mild to moderate ischemic mitral regurgitation who underwent off-pump coronary artery bypass grafting. Material and Method: We prospectively followed 1,000 consecutive and systematic off-pump coronary artery bypass grafting patients who were operated on between September 1996 and March 2004; follow-up was achieved for 97%. Sixty-seven patients (6.7%) had mild to moderate ischemic mitral regurgitation at the time of surgery. Operative mortality, actuarial survival and major adverse cardiac event free survival were compared to assess the effect of ischemic mitral regurgitation. Result: Average follow-up was $66{\pm}22$ months. Patients with ischemic mitral regurgitation were older (p<0.001), had lower ejection fractions (p<0.001) and more comorbidities. Significantly more female patients presented with ischemic mitral regurgitation (p=0.002). There was no significant difference in operative mortality and perioperative myocardial infarction in ischemic mitral regurgitation patients (p=0.25). Eight-year survival was decreased in ischemic mitral regurgitation patients ($39.6{\pm}11.8%$ vs $76.7{\pm}2.2$, p<0.001). However, after correcting for risk factors, mild to moderate ischemic mitral regurgitation was not found to be a significant independent risk factor for long-term mortality (p=0.42). Major adverse cardiac event free survival at 8 years was significantly lower in ischemic mitral regurgitation patients ($53.12{\pm}12%$ vs $77{\pm}2%$, p<0.001). After correction for risk factors, ischemic mitral regurgitation remained a significant independent cause of major adverse cardiac events (HR: 2.31), especially congestive heart failure and recurrent myocardial infarction. Conclusion: In our series, patients with preoperative mild to moderate ischemic mitral regurgitation had a higher prevalence of preoperative risk factors than patients without ischemic mitral regurgitation. They had comparable perioperative mortality and morbidity, but, in the long term, were found to be at elevated risk for recurrent cardiac events.

A Study On Design of ZigBee Chip Communication Module for Remote Radiation Measurement (원격 방사선 측정을 위한 ZigBee 원칩형 통신 모듈 설계에 대한 연구)

  • Lee, Joo-Hyun;Lee, Seung-Ho
    • Journal of IKEEE
    • /
    • v.18 no.4
    • /
    • pp.552-558
    • /
    • 2014
  • This paper suggests how to design a ZigBee-chip-based communication module to remotely measure radiation level. The suggested communication module consists of two control processors for the chip as generally required to configure a ZigBee system, and one chip module to configure a ZigBee RF device. The ZigBee-chip-based communication module for remote radiation measurement consists of a wireless communication controller; sensor and high-voltage generator; charger and power supply circuit; wired communication part; and RF circuit and antenna. The wireless communication controller is to control wireless communication for ZigBee and to measure radiation level remotely. The sensor and high-voltage generator generates 500 V in two consecutive series to amplify and filter pulses of radiation detected by G-M Tube. The charger and power supply circuit part is to charge lithium-ion battery and supply power to one-chip processors. The wired communication part serves as a RS-485/422 interface to enable USB interface and wired remote communication for interfacing with PC and debugging. RF circuit and antenna applies an RLC passive component for chip antenna to configure BALUN and antenna impedance matching circuit, allowing wireless communication. After configuring the ZigBee-chip-based communication module, tests were conducted to measure radiation level remotely: data were successfully transmitted in 10-meter and 100-meter distances, measuring radiation level in a remote condition. The communication module allows an environment where radiation level can be remotely measured in an economically beneficial way as it not only consumes less electricity but also costs less. By securing linearity of a radiation measuring device and by minimizing the device itself, it is possible to set up an environment where radiation can be measured in a reliable manner, and radiation level is monitored real-time.

The Prediction of DEA based Efficiency Rating for Venture Business Using Multi-class SVM (다분류 SVM을 이용한 DEA기반 벤처기업 효율성등급 예측모형)

  • Park, Ji-Young;Hong, Tae-Ho
    • Asia pacific journal of information systems
    • /
    • v.19 no.2
    • /
    • pp.139-155
    • /
    • 2009
  • For the last few decades, many studies have tried to explore and unveil venture companies' success factors and unique features in order to identify the sources of such companies' competitive advantages over their rivals. Such venture companies have shown tendency to give high returns for investors generally making the best use of information technology. For this reason, many venture companies are keen on attracting avid investors' attention. Investors generally make their investment decisions by carefully examining the evaluation criteria of the alternatives. To them, credit rating information provided by international rating agencies, such as Standard and Poor's, Moody's and Fitch is crucial source as to such pivotal concerns as companies stability, growth, and risk status. But these types of information are generated only for the companies issuing corporate bonds, not venture companies. Therefore, this study proposes a method for evaluating venture businesses by presenting our recent empirical results using financial data of Korean venture companies listed on KOSDAQ in Korea exchange. In addition, this paper used multi-class SVM for the prediction of DEA-based efficiency rating for venture businesses, which was derived from our proposed method. Our approach sheds light on ways to locate efficient companies generating high level of profits. Above all, in determining effective ways to evaluate a venture firm's efficiency, it is important to understand the major contributing factors of such efficiency. Therefore, this paper is constructed on the basis of following two ideas to classify which companies are more efficient venture companies: i) making DEA based multi-class rating for sample companies and ii) developing multi-class SVM-based efficiency prediction model for classifying all companies. First, the Data Envelopment Analysis(DEA) is a non-parametric multiple input-output efficiency technique that measures the relative efficiency of decision making units(DMUs) using a linear programming based model. It is non-parametric because it requires no assumption on the shape or parameters of the underlying production function. DEA has been already widely applied for evaluating the relative efficiency of DMUs. Recently, a number of DEA based studies have evaluated the efficiency of various types of companies, such as internet companies and venture companies. It has been also applied to corporate credit ratings. In this study we utilized DEA for sorting venture companies by efficiency based ratings. The Support Vector Machine(SVM), on the other hand, is a popular technique for solving data classification problems. In this paper, we employed SVM to classify the efficiency ratings in IT venture companies according to the results of DEA. The SVM method was first developed by Vapnik (1995). As one of many machine learning techniques, SVM is based on a statistical theory. Thus far, the method has shown good performances especially in generalizing capacity in classification tasks, resulting in numerous applications in many areas of business, SVM is basically the algorithm that finds the maximum margin hyperplane, which is the maximum separation between classes. According to this method, support vectors are the closest to the maximum margin hyperplane. If it is impossible to classify, we can use the kernel function. In the case of nonlinear class boundaries, we can transform the inputs into a high-dimensional feature space, This is the original input space and is mapped into a high-dimensional dot-product space. Many studies applied SVM to the prediction of bankruptcy, the forecast a financial time series, and the problem of estimating credit rating, In this study we employed SVM for developing data mining-based efficiency prediction model. We used the Gaussian radial function as a kernel function of SVM. In multi-class SVM, we adopted one-against-one approach between binary classification method and two all-together methods, proposed by Weston and Watkins(1999) and Crammer and Singer(2000), respectively. In this research, we used corporate information of 154 companies listed on KOSDAQ market in Korea exchange. We obtained companies' financial information of 2005 from the KIS(Korea Information Service, Inc.). Using this data, we made multi-class rating with DEA efficiency and built multi-class prediction model based data mining. Among three manners of multi-classification, the hit ratio of the Weston and Watkins method is the best in the test data set. In multi classification problems as efficiency ratings of venture business, it is very useful for investors to know the class with errors, one class difference, when it is difficult to find out the accurate class in the actual market. So we presented accuracy results within 1-class errors, and the Weston and Watkins method showed 85.7% accuracy in our test samples. We conclude that the DEA based multi-class approach in venture business generates more information than the binary classification problem, notwithstanding its efficiency level. We believe this model can help investors in decision making as it provides a reliably tool to evaluate venture companies in the financial domain. For the future research, we perceive the need to enhance such areas as the variable selection process, the parameter selection of kernel function, the generalization, and the sample size of multi-class.

A Study on Estimating Optimal Tonnage of Coastal Cargo Vessels in Korea (우리나라 연안화물선의 적정선복량 추정에 관한 연구)

  • 이청환;이철영
    • Journal of the Korean Institute of Navigation
    • /
    • v.13 no.1
    • /
    • pp.21-53
    • /
    • 1989
  • In the past twenty years, there has been a rapid increase in the volume of traffic in Korea due to the Korean great growth of the Korean economy. Since transformation provides an infrastructure vital to economic growth, it becomes more and more an integral part of the Korea economy. The importance of coastal shipping stands out in particular, not only because of the expansion limit on the road network, but also because of saturation in the capacity of rail transportation. In spite of this increase and its importance, coastal shipping is falling behind partly because it is givenless emphasis than ocean-going shipping and other inland transportation systems and partly because of overcompetition due to excessive ship tonnage. Therefore, estimating and planning optimum ship tonnage is the first take to develop Korean coastal shipping. This paper aims to estimate the optimum coastal ship tonnage by computer simulation and finally to draw up plans for the ship tonnage balance according to supply and demand. The estimation of the optimum ship tonnage is peformed by the method of Origin -Destimation and time series analysis. The result are as follows : (1) The optimum ship tonnage in 1987 was 358, 680 DWT, which is 54% of the current ship tonnage (481 ships, 662, 664DWT) that is equal to the optimum ship tonnage in 1998. this overcapacity result is in excessive competition and financial difficulties in Korea coastal shipping. (2) The excessive ship tonnage can be broken down into ship types as follows : oil carrier 250, 926 DWT(350%), cement carrier 9, 977 DWT(119%), iron material/machinery carrier 25, 665 DWT(117%), general cargo carrier 17, 416DWT(112%). (3) the current total ship crew of 5, 079 is more than the verified optimally efficient figure of 3, 808 by 1271. (4) From the viewpoint of management strategy, it is necessary that excessive ship tonnage be reduced and uneconomic outdated vessels be broken up. And its found that the diversion into economically efficient fleets is urgently required in order to meet increasing annual rate in the amounts of cargo(23, 877DWT). (5) The plans for the ship tonnage balance according to supply and demand are as follows 1) The establishment of a legislative system for the arrangement of ship tonnage. This would involve; (a) The announcement of an optimum tonnage which guides the licensing of cargo vessels and ship tonnage supply. (b) The establishment of an organization that substantially arrangement tonnage in Korea coastal shipping. 2) The announcement of an optimum ship tonnage both per year and short-term that guides current tonnage supply plans. 3) The settlement of elastic tariffs resulting in the protect6ion of coastal shipping's share from other tonnage supply plans. 4) The settlement of elastic tariffs resulting in the protection of coastal shipping's share from other transportation systems. 4) Restriction of ocean-going vessels from participating in coastal shipping routes. 5) Business rationalization of coastal shipping company which reduces uneconomic outdated vessels and boosts the national economy. If we are to achieve these ends, the followings are prerequisites; I) Because many non-licensed vessels are actually operating and threatening the safe voyage of the others in Korea coastal routes, it is necessary that those ind of vessels be controlled and punished by the authorities. II) The supply of ship tonnage in Korean coastal routes should be predently monitored because most of the coastal vessels are to small to be diverted into ocean-going routes in case of excessive supply. III) Every ship type which is engaged in coastal shipping should be specialized according to the characteristics of its routes as soon possible.

  • PDF

Forecasting Hourly Demand of City Gas in Korea (국내 도시가스의 시간대별 수요 예측)

  • Han, Jung-Hee;Lee, Geun-Cheol
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.17 no.2
    • /
    • pp.87-95
    • /
    • 2016
  • This study examined the characteristics of the hourly demand of city gas in Korea and proposed multiple regression models to obtain precise estimates of the hourly demand of city gas. Forecasting the hourly demand of city gas with accuracy is essential in terms of safety and cost. If underestimated, the pipeline pressure needs to be increased sharply to meet the demand, when safety matters. In the opposite case, unnecessary inventory and operation costs are incurred. Data analysis showed that the hourly demand of city gas has a very high autocorrelation and that the 24-hour demand pattern of a day follows the previous 24-hour demand pattern of the same day. That is, there is a weekly cycle pattern. In addition, some conditions that temperature affects the hourly demand level were found. That is, the absolute value of the correlation coefficient between the hourly demand and temperature is about 0.853 on average, while the absolute value of the correlation coefficient on a specific day improves to 0.861 at worst and 0.965 at best. Based on this analysis, this paper proposes a multiple regression model incorporating the hourly demand ahead of 24 hours and the hourly demand ahead of 168 hours, and another multiple regression model with temperature as an additional independent variable. To show the performance of the proposed models, computational experiments were carried out using real data of the domestic city gas demand from 2009 to 2013. The test results showed that the first regression model exhibits a forecasting accuracy of MAPE (Mean Absolute Percentage Error) around 4.5% over the past five years from 2009 to 2013, while the second regression model exhibits 5.13% of MAPE for the same period.

Music Recall Technique for Affect Modification using Stimulative-Sedative Music : Case Study of Anorexia Nervosa (자극성-진정성 음악을 이용한 부적 정서 조절의 음악회상기법 (Music Recall Technique) : 신경성 식욕부진증 환자의 사례 연구)

  • Gill, Su Yeon
    • Journal of Music and Human Behavior
    • /
    • v.2 no.1
    • /
    • pp.1-15
    • /
    • 2005
  • The purpose of this study is to develop Music Recall Technique for affect modification using programmed series of classical music, and further to apply the technique as therapeutic intervention for clients with anorexia nervosa. Music Recall Technique is composed of two sub-technique: first one is 'Music Recall(MR)' which is the way to reproduce of existing music on one's head and mind after listening to the music, and second intervention is 'Creative Music Recall(CMR)' which is the way to modify the exposed musical pieces or newly learned musical pieces. A client with anorexia nervosa with severe anxiety, anger and depression participated in this case study. The MRT is implemented in different stages pertaining to client's level of utilizing the music recall skill for the period of 10 sessions. Situations eliciting negative emotions were identified and music recalling was reinforced for the pertaining situation in order for the negative emotion to be coped and reduced by the end of session time. The client participated for 10 sessions, and was asked to fill out self-report on the affect change using MRT. Visual Analogue Scale was used for pre and post test for each session to measure the self perceived level of negative affect. State-trait anxiety inventory was also used to measure the anxiety level following the implementation of MRT. As results, negative emotions, such as anxiety, anger and depression were modified during stimulative-sedative music recall process. These negative emotions were decreased mostly during stimulative MR, especially, in the beginning process. Each negative affect on negative situation measured by VAS during each and entire session have been decreased. Negative emotion measured by state-trait anxiety inventory, state-trait anger expression inventory, and hopelessness-depression inventory were decreased as well. The results suggest that stimulative music using contemporary classic music was effective in reduction and modification of negative affect such as anxiety, anger and depression. It shows that Music Recall Technique can be a meaningful intervention for affect modification, and further it can be utilized as self-help in the outside of music therapy setting.

  • PDF

Forecasting of Demand for Papers in Korea (한국(韓國)의 지류(紙類) 수요예측(需要豫測)에 관한 연구(硏究))

  • Chung, Il Yong;Chung, Young Gwan
    • Journal of Korean Society of Forest Science
    • /
    • v.65 no.1
    • /
    • pp.80-91
    • /
    • 1984
  • The purposes of this study are to analyze and forecast the domestic demand for papers by regression models with time-series data (1965-81). For the period of 1965-81, the real GNP of Korea grew at annual average increase rate of 8.8 percent. On the other hand, the domestic demand of papers grew at annual average increase rate of 17.9 percent in this period. Especially, the annual average increase rate for board-papers accounted to 25.8 percent. To analyze domestic demand for papers, GNP, per capita GNP, price findex of papers, production activity index of the major papers consuming industries and price index of substitutive goods were selected as independent variables. The expected values of domestic demand for papers were computed by forecasting equations as follows. T-values are in parentheses. ${\ell}nDDP=2.452+1.986{\ell}nPG-0.844{\ell}nPWI$ $(33.397)^*\;(-6.149)^*\;R^2=0.997$ ${\ell}nDDP=6.468+0.827{\ell}nPDA$ $(17.403)^*\;R^2=0.950$ DDP : Domestic demand for papers PG : Real GNP per capita (1,000 won) PWI : Real price index of papers (1980 = 100) PDAV : Production activity index of the major papers consuming industries The results analyzed and forecasted by these models are summarized as follows: The domestic demand for papers had positive correlation toward per capita GNP and production activity index of the major papers consuming industries. Per capita GNP elasticity of the domestic demand for papers was the most elastic among independent variables. The price elasticity of domestic demand for papers had negative sign and inelastic. These were not only statistically significant but theoretically compatible. The domestic demand for papers was projected to be 3,152-4,470 thousand mit in 1991, representing at annual increase rate of 5.0-12.4 percent during the period of 1982-91. Domestic demand for papers per capita was projected to be 69.1-98.0 kg in 1991.

  • PDF

The Impact of SSM Market Entry on Changes in Market Shares among Retailing Types (기업형 슈퍼마켓(SSM)의 시장진입이 소매업태간 시장점유율 변화에 미친 영향)

  • Choi, Ji-Ho;Yonn, Min-Suk;Moon, Youn-Hee;Choi, Sung-Ho
    • Journal of Distribution Research
    • /
    • v.17 no.3
    • /
    • pp.115-132
    • /
    • 2012
  • This study empirically examines the impact of SSM market entry on changes in market shares among retailing types. The data is monthly time-series data spanning over the period from January 2000 to December 2010, and the effect of SSM market entry on market shares of retailing types is analyzed by utilizing several key factors such as the number of new SSM monthly entrants, total number of SSMs, the proportion of new SSM entrant that is smaller than $165m^2$ to total new SSM entrants. According to the Korean Standard Industrial Classification codes, the retailing type is classified into 5 groups: department stores, retail sale in other non-specialized large stores(big marts), supermarkets, convenience stores, and retail sale in other non-specialized stores with food or beverages predominating (others). The market shares of retailing types are calculated by the ratio of each retailing type monthly sales to total monthly retailing sales in which total retailing sales is the sum of each retailing type sales. The empirical model controls for the size effects with the number of monthly employees for each retailing type and the macroeconomic effects with M2. The empirical model employed in this study is as follows; $$MS_i=f(NewSSM,\;CumSSM,\;employ_i,\;under165,\;M2)$$ where $MS_i$ is the market share of each retailing type (department stores, big marts), supermarkets, convenience stores, and others), NewSSM is the number of new SSM monthly entrants, CumSSM is total number of SSMs, $employ_i$ is the number of monthly employees for each retailing type, and under165 is the proportion of new SSM entrant that is smaller than $165m^2$ to total new SSM entrants. The correlation among these variables are reported in

    .
    shows the descriptive statistics of the sample. Sales is the total monthly revenue of each retailing type, employees is total number of monthly employees for each retailing type, area is total floor space of each retail type($m^2$), number of store is total number of monthly stores for each retailing type, market share is the ratio of each retailing type monthly sales to total monthly retailing sales in which total retailing sales is the sum of each retailing type sales, new monthly SSMs is total number of new monthly SSM entrants, and M2 is a money supply. The empirical results of the effect of new SSM market entry on changes in market shares among retailing types (department stores, retail sale in other non-specialized large stores, supermarkets, convenience stores, and retail sale in other non-specialized stores with food or beverages predominating) are reported in
    . The dependant variables are the market share of department stores, the market share of big marts, the market share of supermarkets, the market share of convenience stores, and the market share of others. The result shows that the impact of new SSM market entry on changes in market share of retail sale in other non-specialized large stores (big marts) is statistically significant. Total number of monthly SSM stores has a significant effect on market share, but the magnitude and sign of effect is different among retailing types. The increase in the number of SSM stores has a negative effect on the market share of retail sale in other non-specialized large stores(big marts) and convenience stores, but has a positive impact on the market share of department stores, supermarkets, and retail sale in other non-specialized stores with food or beverages predominating (others). This study offers the theoretical and practical implication to these findings and also suggests the direction for the further analysis.

  • PDF
  • Effect of PE Film Mulching and Irrigation Method on the Growth, Yield and Antioxidant Activity for Potatoes Grown in Winter Season at Saemangeum Reclaimed Land (새만금 간척지에서 감자 겨울재배시 비닐멀칭 및 관수방법이 생육, 수량 및 괴경의 항산화 활성에 미치는 영향)

    • Choi, Weon-Young;Cho, Kwang-Min;Kim, Sun;Jeong, Jae-Hyeok;Lee, Su-Hwan;Lee, Kyeong-Bo;Lee, Geon-Hwi;Park, Ki-Hun
      • KOREAN JOURNAL OF CROP SCIENCE
      • /
      • v.60 no.1
      • /
      • pp.63-69
      • /
      • 2015
    • This study was conducted to measure the effect of PE film mulching and irrigation methods on the growth, yield and antioxidant activity of potatoes tubers, in order to examine the possibility of cultivating potatoes in winter season in vinyl greenhouse on the reclaimed tidal land with weak ground inside the sea wall currently completed. The test was conducted on the sandy loam soil (Munpo series), and its salt concentration was 0.42% at the time of planting. The emergence speed per kind of PE film mulching was in the order of black > coloration > transparent > green color, with the black color showing the fastest speed. The temperature change during a day per kind of PE film mulching was in the order of transparent > coloration > green > black color. As for the salt concentration in the soil for each different way of water management, the salt concentration in the treatment of drip irrigation with 1 week interval was lower than that drip irrigation with 2 weeks interval. As for the growth of above-aerial part, plant length was higher, number of tiller and leaves were more and dry weight of above-aerial part was larger in the treatment of drip irrigaton with 1 week interval than drip irrigation with 2 weeks interval. As for the yield of potatoes depending on each way of water management, the yield in the treatment of drip irrigation with 1 week interval was more than drip irrigation with 2 weeks interval. The yield for each different kind of PE film mulching in the weekly drip-irrigation management section was in the order of transparent ${\geq}$ black ${\geq}$ coloration ${\geq}$ green color. In both of total phenol content and DPPH free radical activity experiments, the content and activity were higher with pear color vinyl treatment.

    Field Tests for Assessing the Bioremediation Feasibility of a Trichloroethylene-Contaminated Aquifer (관측정 자연표류 실험을 통한 트리클로로에틸렌(Trichloroethylene) 오염 지하수의 생물학적 복원 타당성 연구)

    • Kim Young;Kim Jin-Wook;Ha Chul-Yoon;Kim Nam-Hee;Hong Kwang-Pyo;Kwon Soo-Yul;Ahn Young-Ho;Ha Joon-Su;Park Hoo-Won
      • Journal of Soil and Groundwater Environment
      • /
      • v.10 no.3
      • /
      • pp.38-45
      • /
      • 2005
    • The feasibility of stimulating in situ aerobic cometabolic activity of indigenous microorganisms was investigated in a trichloroethylene (TCE)-contaminated aquifer. A series of single-well natural drift tests (SWNDTs) was conducted by injecting site groundwater amended with a bromide tracer and combinations of toluene, oxygen, nitrate, ethylene and TCE into an existing monitoring well and by sampling the same well over time. Three field tests, Push-pull Transport Test, Drift Biostimulation Test, and Drift Surrogate Activity Test, were performed in sequence. Initial rate of toluene degradation was much faster than the rate of bromide dilution resulting from natural groundwater drift, indicating stimulation of indigenous toluene-oxidizing microorganisms. Transformation of ethylene, a surrogate probing overall activity of TCE transformation, was also observed, and its transformation results in the production of ethylene oxide, suggesting that some tolueneoxidizing microorganisms stimulated may express a orthomonooxygenase enzyme. Also in situ transformation of TCE was confirmed by greater retardation of TCE than bromide after the stimulation of toluene-oxidizing microorganisms. These results indicate that, in this environment, toluene and oxygen additions stimulated the growth and aerobic cometabolic activity of indigenous microorganisms expressing orthomonooxygenase enzymes. The simple, low-cost field test method presented in this study provides an effective method for conducting rapid field assessments and pilot testing of aerobic cometabolism, which has previously hindered application of this technology to groundwater remediation.


    (34141) Korea Institute of Science and Technology Information, 245, Daehak-ro, Yuseong-gu, Daejeon
    Copyright (C) KISTI. All Rights Reserved.