• Title/Summary/Keyword: data similarity

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The Chemistry and Origin of Amphibolitic Rocks in the Sobaegsan Metamorphic Belt and the Ogbang and Sangdong Tungsten Mine Areas, Korea (소백산변성대(小白山變成帶)와 옥방(玉房) 및 상동중석광상내(上東重石鑛床內)의 각섬석질암(角閃石質岩)의 지화학(地化學) 및 성인(成因)에 관(關)한 연구(硏究))

  • So, Chil-Sup;Kim, Sang-Myeong
    • Economic and Environmental Geology
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    • v.8 no.3
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    • pp.147-164
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    • 1975
  • 19 amphibolite samples from the Precambrian Sobaegsan metamorphic belt including the Ogbang mine amphibolites were analyzed for 24 elements each, by wet chemical and emission spectroscopic methods. All the chemical data were evaluated by the methods outlined by Evans and Leake(1960) and Leake(1964) and by Shaw and Kudo(1965). The chemical similarity of all the studied rocks analyzed to basic igneous rocks is consistently indicated particularly by trace element abundance and variation trends. Petrography and oxidation ratios were also considered in attempting to determine the nature of the parent rocks. 3 analyses of W-bearing mafic metamorphic rocks from Sangdong area of the Ogcheon geosynclinal zone are also presented and discussed. Geochemical data for these latter rocks have been possibly derived from mafic tuffs deposited in an area of carbonate deposition.

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An Efficient Algorithm for Streaming Time-Series Matching that Supports Normalization Transform (정규화 변환을 지원하는 스트리밍 시계열 매칭 알고리즘)

  • Loh, Woong-Kee;Moon, Yang-Sae;Kim, Young-Kuk
    • Journal of KIISE:Databases
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    • v.33 no.6
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    • pp.600-619
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    • 2006
  • According to recent technical advances on sensors and mobile devices, processing of data streams generated by the devices is becoming an important research issue. The data stream of real values obtained at continuous time points is called streaming time-series. Due to the unique features of streaming time-series that are different from those of traditional time-series, similarity matching problem on the streaming time-series should be solved in a new way. In this paper, we propose an efficient algorithm for streaming time- series matching problem that supports normalization transform. While the existing algorithms compare streaming time-series without any transform, the algorithm proposed in the paper compares them after they are normalization-transformed. The normalization transform is useful for finding time-series that have similar fluctuation trends even though they consist of distant element values. The major contributions of this paper are as follows. (1) By using a theorem presented in the context of subsequence matching that supports normalization transform[4], we propose a simple algorithm for solving the problem. (2) For improving search performance, we extend the simple algorithm to use $k\;({\geq}\;1)$ indexes. (3) For a given k, for achieving optimal search performance of the extended algorithm, we present an approximation method for choosing k window sizes to construct k indexes. (4) Based on the notion of continuity[8] on streaming time-series, we further extend our algorithm so that it can simultaneously obtain the search results for $m\;({\geq}\;1)$ time points from present $t_0$ to a time point $(t_0+m-1)$ in the near future by retrieving the index only once. (5) Through a series of experiments, we compare search performances of the algorithms proposed in this paper, and show their performance trends according to k and m values. To the best of our knowledge, since there has been no algorithm that solves the same problem presented in this paper, we compare search performances of our algorithms with the sequential scan algorithm. The experiment result showed that our algorithms outperformed the sequential scan algorithm by up to 13.2 times. The performances of our algorithms should be more improved, as k is increased.

Evaluation of Spectral Band Adjustment Factor Applicability for Near Infrared Channel of Sentinel-2A Using Landsat-8 (Landsat-8을 활용한 Sentinel-2A Near Infrared 채널의 Spectral Band Adjustment Factor 적용성 평가)

  • Nayeon Kim;Noh-hun Seong;Daeseong Jung;Suyoung Sim;Jongho Woo;Sungwon Choi;Sungwoo Park;Kyung-Soo Han
    • Korean Journal of Remote Sensing
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    • v.39 no.3
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    • pp.363-370
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    • 2023
  • Various earth observation satellites need to provide accurate and high-quality data after launch. To maintain and enhance the quality of satellite data, it is crucial to employ a cross-calibration process that accounts for differences in sensor characteristics, such as the spectral band adjustment factor (SBAF). In this study, we utilized Landsat-8 and Sentinel-2A satellite imagery collected from desert sites in Libya4, Algeria3, and Mauritania2 among pseudo-invariant calibration sites to calculate and apply SBAF, thereby compensating the uncertainties arising from variations in bandwidths. We quantitatively compared the reflectance differences based on the similarity of bandwidths, including Blue, Green, Red, and both the near-infrared (NIR) narrow, and NIR bands of Sentinel-2A. Following the application of SBAF, significant results with reflectance differences of approximately 1% or less were observed for all bands except NIR. In the case of the Sentinel-2A NIR band, it exhibited a significantly larger bandwidth difference compared to the NIR narrow band. However, after applying SBAF, the reflectance difference fell within the acceptable error range (5%) of 1-2%. It indicates that SBAF can be applied even when there is a substantial difference in the bandwidths of the two sensors, particularly in situations where satellite utilization is limited. Therefore, it was determined that SBAF could be applied even when the bandwidth difference between the two sensors is large in a situation where satellite utilization is limited. It is expected to be helpful in research utilizing the quality and continuity of satellite data.

Analysis of Twitter for 2012 South Korea Presidential Election by Text Mining Techniques (텍스트 마이닝을 이용한 2012년 한국대선 관련 트위터 분석)

  • Bae, Jung-Hwan;Son, Ji-Eun;Song, Min
    • Journal of Intelligence and Information Systems
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    • v.19 no.3
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    • pp.141-156
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    • 2013
  • Social media is a representative form of the Web 2.0 that shapes the change of a user's information behavior by allowing users to produce their own contents without any expert skills. In particular, as a new communication medium, it has a profound impact on the social change by enabling users to communicate with the masses and acquaintances their opinions and thoughts. Social media data plays a significant role in an emerging Big Data arena. A variety of research areas such as social network analysis, opinion mining, and so on, therefore, have paid attention to discover meaningful information from vast amounts of data buried in social media. Social media has recently become main foci to the field of Information Retrieval and Text Mining because not only it produces massive unstructured textual data in real-time but also it serves as an influential channel for opinion leading. But most of the previous studies have adopted broad-brush and limited approaches. These approaches have made it difficult to find and analyze new information. To overcome these limitations, we developed a real-time Twitter trend mining system to capture the trend in real-time processing big stream datasets of Twitter. The system offers the functions of term co-occurrence retrieval, visualization of Twitter users by query, similarity calculation between two users, topic modeling to keep track of changes of topical trend, and mention-based user network analysis. In addition, we conducted a case study on the 2012 Korean presidential election. We collected 1,737,969 tweets which contain candidates' name and election on Twitter in Korea (http://www.twitter.com/) for one month in 2012 (October 1 to October 31). The case study shows that the system provides useful information and detects the trend of society effectively. The system also retrieves the list of terms co-occurred by given query terms. We compare the results of term co-occurrence retrieval by giving influential candidates' name, 'Geun Hae Park', 'Jae In Moon', and 'Chul Su Ahn' as query terms. General terms which are related to presidential election such as 'Presidential Election', 'Proclamation in Support', Public opinion poll' appear frequently. Also the results show specific terms that differentiate each candidate's feature such as 'Park Jung Hee' and 'Yuk Young Su' from the query 'Guen Hae Park', 'a single candidacy agreement' and 'Time of voting extension' from the query 'Jae In Moon' and 'a single candidacy agreement' and 'down contract' from the query 'Chul Su Ahn'. Our system not only extracts 10 topics along with related terms but also shows topics' dynamic changes over time by employing the multinomial Latent Dirichlet Allocation technique. Each topic can show one of two types of patterns-Rising tendency and Falling tendencydepending on the change of the probability distribution. To determine the relationship between topic trends in Twitter and social issues in the real world, we compare topic trends with related news articles. We are able to identify that Twitter can track the issue faster than the other media, newspapers. The user network in Twitter is different from those of other social media because of distinctive characteristics of making relationships in Twitter. Twitter users can make their relationships by exchanging mentions. We visualize and analyze mention based networks of 136,754 users. We put three candidates' name as query terms-Geun Hae Park', 'Jae In Moon', and 'Chul Su Ahn'. The results show that Twitter users mention all candidates' name regardless of their political tendencies. This case study discloses that Twitter could be an effective tool to detect and predict dynamic changes of social issues, and mention-based user networks could show different aspects of user behavior as a unique network that is uniquely found in Twitter.

The Effect of Brand Extension of Private Label on Consumer Attitude - a focus on the moderating effect of the perceived fit difference between parent brands and an extended brand - (PL의 브랜드확장이 소비자태도에 미치는 영향에 관한 연구 : 모브랜드 적합도 인식 차이의 조절효과를 중심으로)

  • Kim, Jong-Keun;Kim, Hyang-Mi;Lee, Jong-Ho
    • Journal of Distribution Research
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    • v.16 no.4
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    • pp.1-27
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    • 2011
  • Introduction: Sales of private labels(PU have been growing m recent years. Globally, PLs have already achieved 20% share, although between 25 and 50% share in most of the European markets(AC. Nielson, 2005). These products are aimed to have comparable quality and prices as national brand(NB) products and have been continuously eroding manufacturer's national brand market share. Stores have also started introducing premium PLs that are of higher-quality and more reasonably priced compared to NBs. Worldwide, many retailers already have a multiple-tier private label architecture. Consumers as a consequence are now able to have a more diverse brand choice in store than ever before. Since premium PLs are priced higher than regular PLs and even, in some cases, above NBs, stores can expect to generate higher profits. Brand extensions and private label have been extensively studied in the marketing field. However, less attention has been paid to the private label extension. Therefore, this research focuses on private label extension using the Multi-Attribute Attitude Model(Fishbein and Ajzen, 1975). Especially there are few studies that consider the hierarchical effect of the PL's two parent brands: store brand and the original PL. We assume that the attitude toward each of the two parent brands affects the attitude towards the extended PL. The influence from each parent brand toward extended PL will vary according to the perceived fit between each parent brand and the extended PL. This research focuses on how these two parent brands act as reference points to one another in the consumers' choice consideration. Specifically we seek to understand how store image and attitude towards original PL affect consumer perceptions of extended premium PL. How consumers perceive extended premium PLs could provide strategic suggestions for retailer managers with specific suggestions on whether it is more effective: to position extended premium PL similarly or dissimilarly to original PL especially on the quality dimension and congruency with store image. There is an extensive body of research on branding and brand extensions (e.g. Aaker and Keller, 1990) and more recently on PLs(e.g. Kumar and Steenkamp, 2007). However there are no studies to date that look at the upgrading and influence of original PLs and attitude towards store on the premium PL extension. This research wishes to make a contribution to this gap using the perceived fit difference between parent brands and extended premium PL as the context. In order to meet the above objectives, we investigate which factors heighten consumers' positive attitude toward premium PL extension. Research Model and Hypotheses: When considering the attitude towards the premium PL extension, we expect four factors to have an influence: attitude towards store; attitude towards original PL; perceived congruity between the store image and the premium PL; perceived similarity between the original PL and the premium PL. We expect that all these factors have an influence on consumer attitude towards premium PL extension. Figure 1 gives the research model and hypotheses. Method: Data were collected by an intercept survey conducted on consumers at discount stores. 403 survey responses were attained (total 59.8% female, across all age ranges). Respondents were asked to respond to a series of Questions measured on 7 point likert-type scales. The survey consisted of Questions that measured: the trust towards store and the original PL; the satisfaction towards store and the original PL; the attitudes towards store, the original PL, and the extended premium PL; the perceived similarity of the original PL and the extended premium PL; the perceived congruity between the store image and the extended premium PL. Product images with specific explanations of the features of premium PL, regular PL and NB we reused as the stimuli for the Question response. We developed scales to measure the research constructs. Cronbach's alphaw as measured each construct with the reliability for all constructs exceeding the .70 standard(Nunnally, 1978). Results: To test the hypotheses, path analysis was conducted using LISREL 8.30. The path analysis for verification of the model produced satisfactory results. The validity index shows acceptable results(${\chi}^2=427.00$(P=0.00), GFI= .90, AGFI= .87, NFI= .91, RMSEA= .062, RMR= .047). With the increasing retailer use of premium PLBs, the intention of this research was to examine how consumers use original PL and store image as reference points as to the attitude towards premium PL extension. Results(see table 1 & 2) show that the attitude of each parent brand (attitudes toward store and original pL) influences the attitude towards extended PL and their perceived fit moderates these influences. Attitude toward the extended PL was influenced by the relative level of perceived fit. Discussion of results and future direction: These results suggest that the future strategy for the PL extension needs to consider that positive parent brand attitude is more strongly associated with the attitude toward PL extensions. Specifically, to improve attitude towards PL extension, building and maintaining positive attitude towards original PL is necessary. Positioning premium PL congruently to store image is also important for positive attitude. In order to improve this research, the following alternatives should also be considered. To improve the research model's predictive power, more diverse products should be included in study. Other attributes of product should also be included such as design, brand name since we only considered trust and satisfaction as factors to build consumer attitudes.

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Toxic Impact Analysis by Exposure Duration of Dog Studies for Pesticides using in Korea (국내 사용농약의 노출 기간이 개의 독성반응에 미치는 영향 분석)

  • Lee, Je Bong;Jeong, Mi-Hye;You, Are-Sun;Hong, Soonsung;Paik, Min-Kyoung;Oh, Jin-Ah;Park, Kyung Hun;Ihm, Yang Bin
    • The Korean Journal of Pesticide Science
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    • v.17 no.4
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    • pp.350-358
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    • 2013
  • Both 13-week and 1-year studies in dog were required for pesticide registration in domestic pesticide control authority. It is raising issue up whether to request 1-year dog study of pesticides using non-food crop. So at this investigation, relevant toxicity test to establish acceptable daily intake (ADI), target organs, difference of no-observed adverse-effect levels (NOAELs) in 13-week and 1-year of 166 active ingredients are analyzed. The data were evaluated to determine if the 13-week dog study and the long term studies in two rodent species (mice and rats) without 1-year dog study were sufficient for the identification of NOAELs and lowest observed adverse effect levels (LOAELs) for the derivation of ADI. Toxicity end points and dose response data from 13 week and 1-year studies were compared. The analysis showed that 68 ADIs of the 166 pesticides were established from dog studies. Major target organs of dog studies were liver in 49 cases, body weight change in 21 cases, cholinesterase inhibition in 16 cases, and alteration in hematology in 14 cases. Similarity of target organ in 13-week and 1-year was 73%. 22 of 40 pesticides had similar critical effects regardless of duration and had NOAELs within a difference of 1.5-fold of each other. For the remaining 18 pesticides, 14 items had lower NOAELs in the 1-year study than 13-week study primarily due to dose selection and spacing. In only 10% of the cases were additional toxic effects identified in the 1-year study that were not observed in the 13-week study.

A Study on the Emotional Reaction to the Interior Design - Focusing on the Worship Space in the Church Buildings - (실내공간 구성요소에 의한 감성반응 연구 - 기독교 예배공간 강단부를 중심으로 -)

  • Lee, Hyun-Jeong;Lee, Gyoo-Baek
    • Archives of design research
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    • v.18 no.4 s.62
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    • pp.257-266
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    • 2005
  • The purpose of this study is to investigate the psychological reaction to the image of the worship space in the church buildings and to quantify its contribution of the stimulation elements causing such reaction, and finally to suggest basic data for realizing emotional worship space of the church architecture. For this, 143 christians were surveyed to analyze the relationship between 23 emotional expressions extracted from the worship space and 32 images of the worship space. The combined data was described with the two dimensional dispersion using the quantification theory III. The analysis found out that 'simplicity-complexity' of the image consisted of the horizontal axis (the x-axis) and 'creativity' of the image the vertical axis(the y-axis). In addition, to extract the causal relationship between the value of emotional reaction and its stimulation elements quantitatively, the author indicated 4 emotional word groups such as simple, sublime for x-axis and typical creative for y-axis based on its similarity by the cluster analysis, The quantification theory I was also used with total value of equivalent emotional words as the standard variance and the emotional stimulation elements of the worship space as the independent variance. 9 specific examples of the emotional stimulation elements were selected including colors and shapes of the wall and the ceiling, shapes and finish of the floor materials, window shapes, and the use of the symbolic elements. Furthermore, 31 subcategories were also chosen to analyse their contribution on the emotional reaction. As a result, the color and finish of the wall found to be the most effective element on the subjects' emotional reaction, while the symbolic elements and the color of the wall found to be the least effective. It is estimated that the present study would be helpful to increase the emotional satisfaction of the users and to approach a spatial design through satisfying the types and purposes of the space.

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The Usefulness Assessment of Verifying Daily Output by Using CHECKMATE$^{TM}$ (CHECKMATE$^{TM}$를 이용한 일일 출력 검증의 유용성 평가)

  • Cho, Han-Sang;Nam, Sang-Soo;Park, Hae-Jin;Kim, Mi-Hwa;Park, An-Tae
    • The Journal of Korean Society for Radiation Therapy
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    • v.23 no.1
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    • pp.51-58
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    • 2011
  • Purpose: In this study, we tried to check the usefulness of two Linear Accelerators, Clinac IX and 21EX (Varian, Palo Alto, CA), which are equipped in Ajou Medical Center. From 2008 to 2010, we evaluated the error range of Absolute Dose based on the daily output, which was measured by CHECKMATE$^{TM}$ (Sun Nuclear, Melbourne, FL). Materials and Methods: For Daily Q.A, photon beams of two linear accelerators, 21EX and IX (6 MV and 10 MV, respectively) were measured daily by using CHECKMATE$^{TM}$ just before the treatment began, while the absolute dose was measured biweekly by using water phantom. We analyzed the data of measured values from the daily Q.A and the absolute dose from 2008 to 2010 for 21EX, and from 2009 to 2010 for IX. We utilized Excel 2007 (Microsoft, USA) to evaluate Average, Standard deviation and Confidence level of the data. Furthermore, in order to check the measured values of CHECKMATE$^{TM}$ and the significance of absolute dose, each error value was compared and analyzed. Results: During the observation period, the output of two equipment's absolute dose increased in process of time and in both 6 MV and 10 MV, there was a similar increasing trend. In addition, the error rate of the measured value of CHECKMATE$^{TM}$ and the value of absolute dose were under 0.34, which means that there is a similarity relationship between the two measured values. After checking that the measured value of CHECKMATE$^{TM}$ increased, We measured the absolute dose to adjust that. When the error range was close to 2~3%, the number of changing the output was four for 21EX and three for IX. Conclusion: As a result of measuring and analyzing the daily output changes for two years by using CHECKMATE$^{TM}$, we could find that there is a significance between the output which we should obey during Q.A, and the measured value of absolute dose within the error tolerance of 2~3%. Thus, the use of CHECKMATE$^{TM}$ can be positively considered for more efficient and reliable daily output verification of linear accelerator. It can also be a good standard for other medical centers to understand the trends of linear accelerator and to refer to for the correction of each output.

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Validity of Nursing Diagnoses Related to Difficulty in Respiratory Function (호흡기능장애와 관련된 간호진단의 타당도 조사)

  • 김조자;이원희;유지수;허혜경;김창희;홍성경
    • Journal of Korean Academy of Nursing
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    • v.23 no.4
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    • pp.569-584
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    • 1993
  • This study was done to verify validity of nursing diagnoses related to difficulty in respiratory function. First, content validity was examined by an expert group considering the etiology and the signs / symptoms of three nursing diagnoses - ineffective airway clearance, ineffective breathing pattern, impaired gas exchange. Second, clinical validity was examined by comparing the frequencies of the etiologies and signs / symptoms of the three nursing diagnoses in clinical case studies with the results of the content validity. This study was a descriptive study. The sample consisted of 23 experts (professors, head nurses and clinical instructors) who had had a variety of experiences using nursing diagnoses in clinical practice, and 102 case reports done by senior student nurses of the college of nursing of Y-university. These reports were part of their clinical practice in the ICU. The instrument used for this study was a checklist for etiologies and signs and symptoms based on the literature, Doenges and Moorhouse (1988), Kim, McFarland, McLane (1991), Lee Won Hee et al. (1987), Kim Cho Ja et at. (1988). The data was collected over four month period from May 1992 to Aug. 1992. Data were analyzed using frequencies done with the SPSS / PC+ package. The results of this study are summarized as follows : 1. General Characteristics of the Expert Group A bachelor degree was held by 43.5% and a master or doctoral degree by 56.5% of the expert group. The average age of the expert group was 35.3 years. Their average clinical experience was 9.3 years and their average experience in clinical practice was 5.9 years. The general characteristics of the patients showed that there were more women than men, that the age range was from 1 to over 80. Most of their medical diagnoses were diagnoses related to the respiratory. system, circulation or neurologic system, and 50% or more of them had a ventilator with intubation or a tracheostomy. The number of cases for each nursing diagnoses was : · Ineffective airway clearance, 92 cases. · Ineffective breathing pattern, 18 cases. · Impaired gas exchange, 22 cases. 2. The opinion of the expert group as to the classification of the etiology, and signs and symptoms of the three nursing diagnoses was as follows : · In 31.8% of the cases the classification of etiology was clear. · In 22.7%, the classification of signs and symptoms was clear. · In 17.4%, the classification of nursing interventions was clear. 3. In the expert group 80% or mere agreed to ‘dysp-nea’as a common sign and symptom of the three nursing diagnoses. The distinguishing signs and symptoms of (Ineffective airway clearance) were ‘sputum’, ‘cough’, ‘abnormal respiratory sounds : rales’. The distinguishing sings and symptoms of (Ineffective breathing pattern) were ‘tachypnea’, ‘use of accessory muscle of respiration’, ‘orthopnea’ and for (Impaired gas exchange) it was ‘abnormal arterial blood gas’, 4. The distribution of etiology, and signs and symptoms of the three nursing diagnoses was as follows : · There was a high frequency of ‘increased secretion from the bronchus and trachea’ in both the expert group and the case reports as the etiology of ineffective airway clearance. · For the etiologies for ineffective breathing pat-tern, ‘rain’, ‘anxiety’, ‘fear’, ‘obstructions of the tract, ca and bronchus’ had a high ratio in the ex-pert group and ‘decreased expansion of lung’ in the case reports. · For the etiologies for impaired gas exchanges, ‘altered oxygen -carrying capacity of the blood’ and ‘excess accumulation of interstitial fluid in lung’ had a high ratio in the expert group and ‘altered oxygen supply’ in the case reports. · For signs and symptoms for ineffective airway clearance, ‘dyspnea’, ‘altered amount and character of sputum’ were included by 100% of the expert group. ‘Abnormal respiratory. sound(rate, rhonchi)’ were included by a high ratio of the expert group. · For the signs and symptoms for ineffective breathing pattern. ‘dyspnea’, ‘shortness of breath’ were included by 100% of the expert group. In the case reports, ‘dyspnea’ and ‘tachypnea’ were reported as signs and symptoms. · For the sign and symptoms for impaired gas exchange, ‘hypoxia’ and ‘cyanosis’ had a high ratio in the expert group. In the case report, ‘hypercapnia’, ‘hypoxia’ and ‘inability to remove secretions’ were reported as signs and symptoms. In summary, the similarity of the etiologies and signs and symptoms of the three nursing diagnoses related to difficulty in respiratory function makes it difficult to distinguish among them But the clinical validity of three nursing diagnoses was established through this study, and at last one sign and symp-tom was defined for each diagnosis.

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Expiration-Day Effects: The Korean Evidence (주가지수 선물과 옵션의 만기일이 주식시장에 미치는 영향: 개별 종목 분석을 중심으로)

  • Choe, Hyuk;Eom, Yun-Sung
    • The Korean Journal of Financial Management
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    • v.24 no.2
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    • pp.41-79
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    • 2007
  • This study examines the expiration-day effects of stock index futures and options in the Korean stock market. The so-called 'expiration-day effects', which are the abnormal stock price movements on derivatives expiration days, arise mainly from cash settlement. Index arbitragers have to bear the risk of their positions unless they liquidate their index stocks on the expiration day. If many arbitragers execute large buy or sell orders on the expiration day, abnormal trading volumes are likely to be observed. If a lot of arbitragers unwind positions in the same direction, temporary trading imbalances induce abnormal stock market volatility. By contrast, if some information arrives at market, the abnormal trading activity must be considered a normal process of price discovery. Stoll and Whaley(1987) investigated the aggregate price and volume effects of the S&P 500 index on the expiration day. In a related study, Stoll and Whaley(1990) found a similarity between the price behavior of stocks that are subject to program trading and of the stocks that are not. Thus far, there have been few studies about the expiration-day effects in the Korean stock market. While previous Korean studies use the KOSPI 200 index data, we analyze the price and trading volume behavior of individual stocks as well as the index. Analyzing individual stocks is important for two reasons. First, stock index is a market average. Consequently, it cannot reflect the behavior of many individual stocks. For example, if the expiration-day effects are mainly related to a specific group, it cannot be said that the expiration of derivatives itself destabilizes the stock market. Analyzing individual stocks enables us to investigate the scope of the expiration-day effects. Second, we can find the relationship between the firm characteristics and the expiration-day effects. For example, if the expiration-day effects exist in large stocks not belonging to the KOSPI 200 index, program trading may not be related to the expiration-day effects. The examination of individual stocks has led us to the cause of the expiration-day effects. Using the intraday data during the period May 3, 1996 through December 30, 2003, we first examine the price and volume effects of the KOSPI 200 and NON-KOSPI 200 index following the Stoll and Whaley(1987) methodology. We calculate the NON-KOSPI 200 index by using the returns and market capitalization of the KOSPI and KOSPI 200 index. In individual stocks, we divide KOSPI 200 stocks by size into three groups and match NON-KOSPI 200 stocks with KOSPI 200 stocks having the closest firm characteristics. We compare KOSPI 200 stocks with NON-KOSPI 200 stocks. To test whether the expiration-day effects are related to order imbalances or new information, we check price reversals on the next day. Finally, we perform a cross-sectional regression analysis to elaborate on the impact of the firm characteristics on price reversals. The main results seem to support the expiration-day effects, especially on stock index futures expiration days. The price behavior of stocks that are subject to program trading is shown to have price effects, abnormal return volatility, and large volumes during the last half hour of trading on the expiration day. Return reversals are also found in the KOSPI 200 index and stocks. However, there is no evidence of abnormal trading volume, or price reversals in the NON-KOSPI 200 index and stocks. The expiration-day effects are proportional to the size of stocks and the nearness to the settlement time. Since program trading is often said to be concentrated in high capitalization stocks, these results imply that the expiration-day effects seem to be associated with program trading and the settlement price determination procedure. In summary, the expiration-day effects in the Korean stock market do not exist in all stocks, but in large capitalization stocks belonging to the KOSPI 200 index. Additionally, the expiration-day effects in the Korean stock market are generally due, not to information, but to trading imbalances.

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