• Tuberculosis and Respiratory Diseases
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• v.47 no.3
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• pp.365-373
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• 1999

Background: Despite widespread use of tracheostomy in intensive care unit, it is still controversial to define the best timing from endotracheal intubation to tracheostomy under prolonged mechanical ventilation. Early tracheostomy has an advantage of easy airway maintenance and enhanced patient mobility whereas a disadvantage in view of nosocomial infection and tracheal stenosis. However, there is a controversy about the proper timing of tracheostomy. Methods: We conducted a retrospective study of the 35 medical and 15 surgical ICU patients who had admitted to Ewha Womans University Mokdong Hospital from January 1996 to August 1998 with the observation of APACHE III score, occurrence of nosocomial infections, and clinical outcomes during 28 days from tracheostomy in terms of early (n=25) vs. late (n=25) tracheostomy. We defined the reference day of early and late tracheostomy as 7th day from intubation. Results: The number of patients were 25 each in early and late tracheostomy group. The mean age were $48{\pm}18$ years in early tracheostomy group and $63{\pm}17$ years in late tracheostomy group, showing younger in early tracheostomy group. The median duration of intubation prior to tracheostomy was 3 days and 13 days in early and late tracheostomy groups. Organs that caused primary problem were nervous system in 27 cases(54%), pulmonary 14(28%), cardiovascular 4(8%), gastrointestinal 4(8%) and genitourinary 1(2%) in the decreasing order. Prolonged ventilation was the most common reason for the purpose of tracheostomy in both groups. APACHE m scores at each time of intubation and tracheostomy were slightly higher in late tracheostomy group but not significant statistically. Day to day APACHE III scores were not different between two groups with observation upto 7th day after tracheostomy, Occurrence of nosocomial infections, weaning from mechanical ventilation, and mortality showed no significant difference between two groups with observation of 28 days from tracheostomy. The mortality was increased as the APACHE m score upto 7 days after tracheostomy increased, but there were no increment for the mortality in terms of the time of tracheostomy and the days of ventilator use before tracheostomy, Conclusion: The early tracheostomy seems to have no benefit with respect to severity of illness, nosocomial infection, duration of ventilatory support, and mortality. It suggests that the time of tracheostomy is better to be decided on clinical judgement in each case. And in near future, prospective, randomized case-control study is required to confirm these results.

• Journal of Intelligence and Information Systems
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• v.16 no.4
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• pp.67-84
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• 2010

In terms of business, forecasting is a work of what is expected to happen in the future to make managerial decisions and plans. Therefore, the accurate forecasting is very important for major managerial decision making and is the basis for making various strategies of business. But it is very difficult to make an unbiased and consistent estimate because of uncertainty and complexity in the future business environment. That is why we should use scientific forecasting model to support business decision making, and make an effort to minimize the model's forecasting error which is difference between observation and estimator. Nevertheless, minimizing the error is not an easy task. Case-based reasoning is a problem solving method that utilizes the past similar case to solve the current problem. To build the successful case-based reasoning models, retrieving the case not only the most similar case but also the most relevant case is very important. To retrieve the similar and relevant case from past cases, the measurement of similarities between cases is an important key factor. Especially, if the cases contain symbolic data, it is more difficult to measure the distances. The purpose of this study is to improve the forecasting accuracy of case-based reasoning approach using fuzzy relation and composition. Especially, two methods are adopted to measure the similarity between cases containing symbolic data. One is to deduct the similarity matrix following binary logic(the judgment of sameness between two symbolic data), the other is to deduct the similarity matrix following fuzzy relation and composition. This study is conducted in the following order; data gathering and preprocessing, model building and analysis, validation analysis, conclusion. First, in the progress of data gathering and preprocessing we collect data set including categorical dependent variables. Also, the data set gathered is cross-section data and independent variables of the data set include several qualitative variables expressed symbolic data. The research data consists of many financial ratios and the corresponding bond ratings of Korean companies. The ratings we employ in this study cover all bonds rated by one of the bond rating agencies in Korea. Our total sample includes 1,816 companies whose commercial papers have been rated in the period 1997~2000. Credit grades are defined as outputs and classified into 5 rating categories(A1, A2, A3, B, C) according to credit levels. Second, in the progress of model building and analysis we deduct the similarity matrix following binary logic and fuzzy composition to measure the similarity between cases containing symbolic data. In this process, the used types of fuzzy composition are max-min, max-product, max-average. And then, the analysis is carried out by case-based reasoning approach with the deducted similarity matrix. Third, in the progress of validation analysis we verify the validation of model through McNemar test based on hit ratio. Finally, we draw a conclusion from the study. As a result, the similarity measuring method using fuzzy relation and composition shows good forecasting performance compared to the similarity measuring method using binary logic for similarity measurement between two symbolic data. But the results of the analysis are not statistically significant in forecasting performance among the types of fuzzy composition. The contributions of this study are as follows. We propose another methodology that fuzzy relation and fuzzy composition could be applied for the similarity measurement between two symbolic data. That is the most important factor to build case-based reasoning model.

• Journal of Intelligence and Information Systems
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• v.19 no.4
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• pp.97-121
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• 2013

With the growing importance of knowledge for sustainable competitive advantages and innovation in a volatile environment, many researches on knowledge sharing have been conducted. However, previous researches have mostly relied on the questionnaire survey which has inherent perceptive errors of respondents. The current research has drawn the relationship among primary participant behaviors towards the participation level in knowledge sharing, basically from online user behaviors on Wikipedia, a representative community for online knowledge collaboration. Without users' participation in knowledge sharing, knowledge collaboration for creating knowledge cannot be successful. By the way, the editing patterns of Wikipedia users are diverse, resulting in different revisiting periods for the same number of edits, and thus varying results of shared knowledge. Therefore, we illuminated the participation level of knowledge sharing from two different angles of number of edits and revisiting period. The behavioral dimensions affecting the level of participation in knowledge sharing includes the article talk for public discussion and user talk for private messaging, and community registration, which are observable on Wiki platform. Public discussion is being progressed on article talk pages arranged for exchanging ideas about each article topic. An article talk page is often divided into several sections which mainly address specific type of issues raised during the article development procedure. From the diverse opinions about the relatively trivial things such as what text, link, or images should be added or removed and how they should be restructured to the profound professional insights are shared, negotiated, and improved over the course of discussion. Wikipedia also provides personal user talk pages as a private messaging tool. On these pages, diverse personal messages such as casual greetings, stories about activities on Wikipedia, and ordinary affairs of life are exchanged. If anyone wants to communicate with another person, he or she visits the person's user talk page and leaves a message. Wikipedia articles are assessed according to seven quality grades, of which the featured article level is the highest. The dataset includes participants' behavioral data related with 2,978 articles, which have reached the featured article level, with editing histories of articles, their article talk histories, and user talk histories extracted from user talk pages for each article. The time period for analysis is from the initiation of articles until their promotion to the featured article level. The number of edits represents the total number of participation in the editing of an article, and the revisiting period is the time difference between the first and last edits. At first, the participation levels of each user category classified according to behavioral dimensions have been analyzed and compared. And then, robust regressions have been conducted on the relationships among independent variables reflecting the degree of behavioral characteristics and the dependent variable representing the participation level. Especially, through adopting a motivational theory adequate for online environment in setting up research hypotheses, this work suggests a theoretical framework for the participation level of online knowledge sharing. Consequently, this work reached the following practical behavioral results besides some theoretical implications. First, both public discussion and private messaging positively affect the participation level in knowledge sharing. Second, public discussion exerts greater influence than private messaging on the participation level. Third, a synergy effect of public discussion and private messaging on the number of edits was found, whereas a pretty weak negative interaction effect of them on the revisiting period was observed. Fourth, community registration has a significant impact on the revisiting period, whereas being insignificant on the number of edits. Fifth, when it comes to the relation generated from private messaging, the frequency or depth of relation is shown to be more critical than the scope of relation for the participation level.

• Journal of Intelligence and Information Systems
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• v.22 no.4
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• pp.45-67
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• 2016

Given the recent development of smart devices, users are producing, sharing, and acquiring a variety of information via the Internet and social network services (SNSs). Because users tend to use multiple media simultaneously according to their goals and preferences, domestic SNS users use around 2.09 media concurrently on average. Since the information provided by such media is usually textually represented, recent studies have been actively conducting textual analysis in order to understand users more deeply. Earlier studies using textual analysis focused on analyzing a document's contents without substantive consideration of the diverse characteristics of the source medium. However, current studies argue that analytical and interpretive approaches should be applied differently according to the characteristics of a document's source. Documents can be classified into the following types: informative documents for delivering information, expressive documents for expressing emotions and aesthetics, operational documents for inducing the recipient's behavior, and audiovisual media documents for supplementing the above three functions through images and music. Further, documents can be classified according to their contents, which comprise facts, concepts, procedures, principles, rules, stories, opinions, and descriptions. Documents have unique characteristics according to the source media by which they are distributed. In terms of newspapers, only highly trained people tend to write articles for public dissemination. In contrast, with SNSs, various types of users can freely write any message and such messages are distributed in an unpredictable way. Again, in the case of newspapers, each article exists independently and does not tend to have any relation to other articles. However, messages (original tweets) on Twitter, for example, are highly organized and regularly duplicated and repeated through replies and retweets. There have been many studies focusing on the different characteristics between newspapers and SNSs. However, it is difficult to find a study that focuses on the difference between the two media from the perspective of supply and demand. We can regard the articles of newspapers as a kind of information supply, whereas messages on various SNSs represent a demand for information. By investigating traditional newspapers and SNSs from the perspective of supply and demand of information, we can explore and explain the information dilemma more clearly. For example, there may be superfluous issues that are heavily reported in newspaper articles despite the fact that users seldom have much interest in these issues. Such overproduced information is not only a waste of media resources but also makes it difficult to find valuable, in-demand information. Further, some issues that are covered by only a few newspapers may be of high interest to SNS users. To alleviate the deleterious effects of information asymmetries, it is necessary to analyze the supply and demand of each information source and, accordingly, provide information flexibly. Such an approach would allow the value of information to be explored and approximated on the basis of the supply-demand balance. Conceptually, this is very similar to the price of goods or services being determined by the supply-demand relationship. Adopting this concept, media companies could focus on the production of highly in-demand issues that are in short supply. In this study, we selected Internet news sites and Twitter as representative media for investigating information supply and demand, respectively. We present the notion of News Value Index (NVI), which evaluates the value of news information in terms of the magnitude of Twitter messages associated with it. In addition, we visualize the change of information value over time using the NVI. We conducted an analysis using 387,014 news articles and 31,674,795 Twitter messages. The analysis results revealed interesting patterns: most issues show lower NVI than average of the whole issue, whereas a few issues show steadily higher NVI than the average.

• Journal of Intelligence and Information Systems
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• v.22 no.4
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• pp.123-138
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• 2016

This study investigates intents of acquisitions in information technology industries. Mergers and acquisitions are a strategic decision at corporate-level and have been an important tool for a firm to grow. Plenty of firms in information technology industries have acquired startups to increase production efficiency, expand customer base, or improve quality over the last decades. For example, Google has made about 200 acquisitions since 2001, Cisco has acquired about 210 firms since 1993, Oracle has made about 125 acquisitions since 1994, and Microsoft has acquired about 200 firms since 1987. Although there have been many existing papers that theoretically study intents or motivations of acquisitions, there are limited papers that empirically investigate them mainly because it is challenging to measure and quantify intents of M&As. This study examines the intent of acquisitions by measuring specific intents for M&A transactions. Using our measures of acquisition intents, we compare the intents by four acquisition types: (1) the acquisition where a hardware firm acquires a hardware firm, (2) the acquisition where a hardware firm acquires a software/IT service firm, (3) the acquisition where a software/IT service firm acquires a hardware firm, and (4) the acquisition where a software /IT service firm acquires a software/IT service firm. We presume that there are difference in reasons why a hardware firm acquires another hardware firm, why a hardware firm acquires a software firm, why a software/IT service firm acquires a hardware firm, and why a software/IT service firm acquires another software/IT service firm. Using data of the M&As in US IT industries, we identified major intents of the M&As. The acquisition intents are identified based on the press release of M&A announcements and measured with four categories. First, an acquirer may have intents of cost saving in operations by sharing common resources between the acquirer and the target. The cost saving can accrue from economies of scope and scale. Second, an acquirer may have intents of product enhancement/development. Knowledge and skills transferred from the target may enable the acquirer to enhance the product quality or to expand product lines. Third, an acquirer may have intents of gain additional customer base to expand the market, to penetrate the market, or to enter a foreign market. Fourth, a firm may acquire a target with intents of expanding customer channels. By complementing existing channel to the customer, the firm can increase its revenue. Our results show that acquirers have had intents of cost saving more in acquisitions between hardware companies than in acquisitions between software companies. Hardware firms are more likely to acquire with intents of product enhancement or development than software firms. Overall, the intent of product enhancement/development is the most frequent intent in all of the four acquisition types, and the intent of customer base expansion is the second. We also analyze our data with the classification of production-side intents and customer-side intents, which is based on activities of the value chain of a firm. Intents of cost saving operations and those of product enhancement/development can be viewed as production-side intents and intents of customer base expansion and those of expanding customer channels can be viewed as customer-side intents. Our analysis shows that the ratio between the number of customer-side intents and that of production-side intents is higher in acquisitions where a software firm is an acquirer than in the acquisitions where a hardware firm is an acquirer. This study can contribute to IS literature. First, this study provides insights in understanding M&As in IT industries by answering for question of why an IT firm intends to another IT firm. Second, this study also provides distribution of acquisition intents for acquisition types.

• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.3
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• pp.75-82
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• 2010

This study formed an estimation of the visual characteristics of urban bridges in Yanghwaro in the Gyeongui Railroad Area using a landscape simulation. Existing theses have formerly only suggested directions for design based on visual preference, but there is as yet no research on the practical process of landscape design. As a result, it is difficult to directly apply this to bridge design. This study found a potential bridge site and presented a direction for bridge design in order to improve the image of the surrounding urban landscape by surveying the visual effects and landscape preferences of different bridge types. An urban landscape was produced using a landscape simulation model and was made the background for the survey. Five bridge types--Girder, Arch, Truss, Cable and Suspension--were selected and presented. The shapes of the bridges were selected based on the floor plan. The results of this study are as follows. In a preference analysis, every bridge except Girder was evaluated as a positive influence. When rating the image, 'artificial' was rated significantly higher than other traits when assessing the background image. When the Girder Bridge was introduced, 'stable' and 'orderly' were both rated highly while 'stable', 'beautiful', 'orderly' and 'interesting' were high with the introduction of the Arch Bridge. 'Beautiful', 'stable', and 'orderly' were given a high value in the introduction of the Truss Bridge and every image except 'natural', 'harmony' and 'orderly' were highly rated in the introduction of the Cable Bridge. Further, every image but 'natural' was highly rated with the introduction of the Suspension Bridge. Based on the analysis of the landscape, there is a difference in preference before and after modeling a bridge type, while the bridge itself is an influence when it is the main object of the simulated scene. This study researched only the shape of the bridge as a part of the landscape but other elements such as stability, economics, and construction are also factors in the design of a bridge. Stability, economics, construction and other factors must be considered when selecting a bridge type in the future.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.206-214
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• 2005

Heterogeneously-catalyzed oxidation of aqueous phase trichloroethylene (TCE) over supported metal oxides has been conducted to establish an approach to eliminate ppm levels of organic compounds in water. A continuous flow reactor system was designed to effect predominant reaction parameters in determining catalytic activity of the catalysts for wet TCE decomposition as a model reaction. 5 wt.% $CoO_x/TiO_2$ catalyst exhibited a transient period in activity vs. on-stream time behavior, suggesting that the surface structure of the $CoO_x$ might be altered with on-stream hours; regardless, it is probable to be the most promising catalyst. Not only could the bare support be inactive for the wet decomposition reaction at $36^{\circ}C$, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. Very low TCE conversion appeared for $TiO_2$-supported $NiO_x$ and $CrO_x$ catalysts. Wet oxidation performance of supported Cu and Fe catalysts, obtained through an incipient wetness and ion exchange technique, was dependent primarily on the kinds of the metal oxides, in addition to the acidic solid supports and the preparation routes. 5 wt.% $FeO_x/TiO_2$ catalyst gave no activity in the oxidation reaction at $36^{\circ}C$, while 1.2 wt.% Fe-MFI was active for the wet decomposition depending on time on-stream. The noticeable difference in activity of the both catalysts suggests that the Fe oxidation states involved to catalytic redox cycle during the course of reaction play a significant role in catalyzing the wet decomposition as well as in maintaining the time on-stream activity. Based on the results of different $CoO_x$ loadings and reaction temperatures for the decomposition reaction at $36^{\circ}C$ with $CoO_x/TiO_2$, the catalyst possessed an optimal $CoO_x$ amount at which higher reaction temperatures facilitated the catalytic TCE conversion. Small amounts of the active ingredient could be dissolved by acidic leaching but such a process gave no appreciable activity loss of the $CoO_x$ catalyst.

• Journal of Bio-Environment Control
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• v.27 no.3
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• pp.222-230
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• 2018

This study aimed to determine effects of light-emitting diodes on plant growth, leaf morphology and cell elongation of two cultivars ('World-star' and 'Sushiro') of Spinacia oleracea. Plants were grown in a NFT system for 25 days after transplanting (DAT) under the LEDs [White (W), Red and Blue (RB, ratio 2:1), Blue (B), Red (R) LED] under the same light intensity and photoperiod ($130{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 12 hours). The 'World-star' variety was significantly higher in shoot fresh and dry weights, leaf number, and leaf area than the 'Sushiro' variety. For the 'World-star' variety, the two treatments of mixed light (RB) and red light (R) showed a 35% higher shoot dry weight than that of blue light (B) and white light (W) at 25 DAT. In the 'Sushiro' variety, mixed light (RB) treatment, which had the highest shoot fresh and dry weights, showed 40% higher than the white light (W) treatment, which had the lowest shoot fresh and dry weights. Both varieties showed leaf epinasty symptom at 21 DAT only in both mixed light (RB) and red light (R), and red light (R) treatment showed significantly higher symptom than mixed light (RB), indicating the leaf epinasty is associated with red light. Microscopic observations of the cell size in the leaf center and edge parts showed that the cell density of leaf edge under the red light (R) was lower than that in leaf center, supporting previous reports that suggest an association of the cell size difference between the leaf center and edge with the leaf epinasty occurrence. Since the blue light (B) plays a role in alleviating the epinasty symptom caused by the red light (R), it seems necessary to identify the appropriate mixing ratio of the two light sources. In addition, the World-star variety seems to be more suitable for the cultivation of plant factory using LED light sources.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.371-380
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• 2018

Aim of this study was to investigate the effects of different nutrient solutions and various light qualities generated by LED on the growth and glucosinolates contents of watercress (Nasturtium officinale) grown under hydroponics for 3 weeks. The seeds of watercress were sown on crushed rockwool media and raised them for two weeks. They were transplanted in a semi-DFT (deep flow technique) hydroponics system. A controlled-environment room was maintained at $20{\pm}1^{\circ}C$ and $16{\pm}1^{\circ}C$ temperatures and $65{\pm}10%$ and $75{\pm}10%$ relative humidity (day and night, respectively), with a provided photosynthetic photon flux density (PPFD) of $180{\pm}10{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ and a photoperiod of 16/8h. To find out the best kinds of nutrient solutions for growing watercress, Otsuka House 1A (OTS), Horticultural Experiment Station in Korea (HES), and Netherland's Proefstaion voor Bloemisterij en Gasgroente (PBG) were adapted with initial EC of $1.0-1.3dS{\cdot}m^{-1}$ and pH of 6.2, irradiating PPFD with fluorescent lamps (Ex-1). Either monochromatic (W10 and R10) or mixed LEDs (R5B1, R3B1, R2B1G1, and W2B1G1) were irradiated with a differing ratio of each LED's PPFD to understanding light quality on the growth and glucosinolates contents of watercress (Ex-2). Although significant difference in the shoot growth of watercress was not found among three nutrient solutions treatments, but the root fresh weight increased by 13.7% and 55.1% in PBG and OTS compared to HES, respectively. OTS increased the gluconasturtiin content by 96% and 65% compared to PBG and HES. Compared with the white light (W10), the red light (R10) showed a 101.3% increase in the shoot length of watercress. Increasing blue light portion positively affected plant growth. The content of total glucosinolates in watercress was increased by 144.5% and 70% per unit dry weight in R3B1 treatment compared with R2B1G1 and W10 treatments, respectively. The growth and total glucosinolates contents of the watercress were highest under R3B1 among six light qualities.

• Progress in Medical Physics
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• v.17 no.1
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• pp.47-53
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• 2006

The accuracy of the dosimetry in the Cyberknife system is accomplishing important role from all processes of the stereotactic radiosurgery. In this study, we estimated relative output factors for Cyberknife. All measurements were peformed by six different detectors: diode detector, X-Omat V film, Gafchromic EBT film, 0.015 cc, 0.125 cc and 0.6 cc ionization chamber The diode detector and three ionization chambers peformed using water phantom at 80 cm SSD and 1.5 cm depth. When the film measurements were peformed, the water phantom was replaced with a solidwater phantom. Each collimator normalized with respect to the output factor of the largest collimator (60 mm). For the collimators over than 30 mm, the output factors from the different detectors showed a good agreement within 0.5% except 0.6 cc ion chamber For the collimators less than 15 mm, there were substantial differences In the output factors among different detectors. That is, the value of output factor for the 5 mm collimator of a diode and Gafchromic film was each $0.656{\pm}0.009$ and $0.777{\pm}0.013$. In the ion chamber and diode detector, those difference were due to the presence of large dose gradients and lack of electronic equilibrium in narrow megavoltage x-ray beams Therefore, the Gafchromic EBT film were considered more accurate than the others detectors.