• Title/Summary/Keyword: Difference-in-Differences(DID)

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The Effects of R&D Expenses and patents on the Firm value (특허권과 연구개발비 지출이 기업가치에 미치는 영향)

  • Oh, Sang-Hui
    • Management & Information Systems Review
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    • v.36 no.3
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    • pp.239-254
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    • 2017
  • This study examines the relationship between R&D spending and patent rights, which are suggested by firms as a way to increase their firm value. Specifically, we examine the relationship between research and development costs and patent rights, and see if there are any differences in the influence of two variables on firm value. The period of this study is from 2005 to 2016, and the sample of companies used in the research including the patenting companies is composed of 333 companies in total. The results of the study are as follows. First, the cost of R&D expenditure and capitalized R&D expenditure showed a significant positive correlation with patents. Second, R&D spending did not show a significant relationship with firm value, but patent rights showed a significant positive correlation with firm value. However, firms that spend a large amount of R&D expenditure (RDD), such as research and development expenses, showed a significant positive (+) value and a patent dummy (PATD). Third, in the analysis of the difference between the dummy of research and development and the patent dummy, the enterprise value of a company that invested a lot of patents and research and development expenses was high. The contribution of this study is to examine the relevance of corporate value to R&D investment for patents. On the other hand, there are various variables that can be used as a sample of patents.

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Human Risk Assessment of a Contaminated Site Using Korean Risk-Based Corrective Action (K-RBCA) Software (한국형 소프트웨어를 이용한 유류.중금속 복합오염지역의 인체위해성평가 및 RBCA Tool Kit과의 비교분석)

  • Nam, Taek-Woo;Ryu, Hye-Rim;Kim, Young-Jin;Ko, Seok-Oh;Baek, Ki-Tae;Nam, Kyoung-Phile
    • Journal of Soil and Groundwater Environment
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    • v.16 no.1
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    • pp.32-41
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    • 2011
  • By using a newly developed Korean risk-based corrective action (K-RBCA) software (K-RBCA) and the RBCA Tool Kit, risk assessment was performed on a site that was contaminated with aromatic hydrocarbons and heavy metals. Eight chemicals including benzene, ethylbenzene, xylenes, naphthalene, benz(a) anthracene, benzo(b) fluoranthene, benzo(a) pyrene, and arsenic that exceeded the US EPA Soil Screening Level were chosen as the target pollutants. A conceptual site model was constructed based on the site-specific effective exposure pathways. According to the RBCA Tool Kit the carcinogenic risk of arsenic was larger than $10^{-6}$, which is the generally acceptable carcinogenic risk level. The K-RBCA estimated the same level of carcinogenic risk for arsenic. With the RBCA Tool Kit, the carcinogenic risk of benzo(a) pyrene was estimated to be about $1.3{\times}10^{-6}$. However, with the K-RBCA benzo(a) pyrene did not exhibit any risk. The inconsistency between the softwares was attributed to the different fundamental settings (i.e., medium division) between the two softwares. While the K-RBCA divides medium into surface soil, subsurface soil, and groundwater, the RBCA Tool Kit divides medium into only soil and groundwater. These differences lead to the different exposure pathways used by the two softwares. The K-RBCA considers the exposure pathways in surface soil and subsurface soil separately to estimate risk, however, the RBCA Tool Kit considers the surface soil and subsurface soil as one and uses the integrated exposure pathways to estimate risk. Thus the resulting risk is higher when the RBCA Tool Kit is used than when the K-RBCA is used. The results from this study show that there is no significant difference in the risks estimated by the two softwares, thus, it is reasonable to use the K-RBCA we developed in risk assessment of soil and groundwater. In addition, the present study demonstrates that the assessor should be familiar with the characteristics of a contaminated site and the assumptions used by a risk assessment software when carrying out risk assessment.

Optimal timing for salvage surgery after definitive radiotherapy in hypopharyngeal cancer

  • Chun, Seok-Joo;Keam, Bhumsuk;Heo, Dae Seog;Kim, Kwang Hyun;Sung, Myung-Whun;Chung, Eun-Jae;Kim, Ji-hoon;Jung, Kyeong Cheon;Kim, Jin Ho;Wu, Hong-Gyun
    • Radiation Oncology Journal
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    • v.36 no.3
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    • pp.192-199
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    • 2018
  • Purpose: Use of radiotherapy combined with chemotherapy is increasing in hypopharyngeal cancer. However, many show residual tumor after radiotherapy. Timing for treatment evaluation and salvage therapy is essential. However, optimal timing for salvage surgery has not been suggested. In this study, we tried to evaluate optimal timing for salvage surgery. Methods and Materials: Patients who were diagnosed with hypopharyngeal squamous cell carcinoma between 2006 and 2015 were retrospectively analyzed. All patients received definitive radiotherapy with or without chemotherapy. Response of all treated patients were analyzed at 1, 3, and 6 months after radiotherapy. Any patients with progression before 6 months were excluded. Results: A total of 54 patients were analyzed. Complete remission (CR) rates at 1 month (CR1), 3 months (CR3) and 6 months (CR6) were 66.7%, 81.5%, and 90.7%, respectively. Non-CR at 1 month (NCR1), 3 months (NCR3), and 6 months (NCR6) showed poor locoregional recurrence-free survival rates (1-year rates of 63.7%, 66.7%, and 0.0%, respectively) compared to CR1, CR3, and CR6 (1-year rates 94.3%, 88.0%, and 91.5%, respectively). Particularly significant differences were seen between CR6 and NCR6 (p < 0.001). Of 10 patients with NCR3, 5 showed CR at 6 months (NCR3/CR6). There was no statistical difference in locoregional recurrence-free survival between CR3 and NCR3/CR6 group (p = 0.990). Conclusion: Our data suggest half of patients who did not show CR at 3 months eventually achieved CR at 6 months. Waiting until 6 months after radiotherapy may be appropriate for avoiding additional salvage therapy.

The Clinical Features and Risk Factors of Seizure After Doxylamine Intoxication (독실라민 중독시 발생할 수 있는 발작의 특성과 위험인자)

  • Song, Beom-Soo;Lee, Ki-Man;Kim, Sun-Wook;You, Je-Sung;Chung, Tae-Nyung;Park, Yoo-Seok;Jung, Sung-Phil;Goo, Hong-Du;Park, In-Cheol
    • Journal of The Korean Society of Clinical Toxicology
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    • v.8 no.2
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    • pp.88-96
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    • 2010
  • Purpose: Doxylamine is antihistamine drug that is used as a hypnotic. It is also used for suicidal attempts because it can be easily purchased at the pharmacy without a prescription. There were many articles about the complications after doxylamine intoxication such as a rhabdomyolysis, but only a few articles have reported on seizure. We reviewed the cases of doxylamine intoxication with seizure that were treated in the emergency department. Methods: We reviewed the medical records of the patients who were over 15 years old and who were intoxicated by doxylamine at 3 emergency medical centers from January 2006 to June 2010. We reviewed the patients' age, gender, the dose of doxylamine ingested, if gastrointestinal decontamination was done, the time from intoxication to hospital arrival, the seizure history, treatment of seizure, the electroencephalography (EEG) results, the brain computed tomography (CT) results and the blood test results. Results: There were 168 patients who were intoxicated by doxylamine during the study period. Twelve patients had a seizure episode. The differences between the patients who developed seizure and the patients who did not were the dose and the serum levels of sodium and creatinine. The only clinically meaningful difference was the amount of doxylamine. The amount of doxylamine ingested (>29 mg/kg) predicted the development of seizure with a sensitivity of 75% and a specificity of 92% on the ROC curve. One patient among the seizure patients expired in the emergency department. Conclusion: In case of doxylamine intoxicated patients, there is close relationship between seizure and ingested amount, so close observation needs to be done for the patients who ingest too much because doxylamine can cause death. Further prospective studies are needed for doxylamine intoxicated patients with a seizure episode.

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Convergent Factors Related to Depression of Wage Workers in Korea: Focusing on Gender Differences (한국 임금근로자의 우울과 관련된 융복합적 요인: 성별 차이를 중심으로)

  • Kwon, Young-Sook
    • Journal of the Korean Applied Science and Technology
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    • v.38 no.4
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    • pp.1029-1044
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    • 2021
  • This research was conducted to investigate the prevalence of depression and convergent factors related to depression in male and female wage workers. Using data from the 2014 and 2016 Korea National Health and Nutrition Examination Survey, 3,763 adults (1,888 males, 1,875 females) between the ages of 19 and under 65 were analyzed. Depression was measured by the Patient Health Questionnaire-9 (PHQ-9), and the depression (PHQ-9≥10) of all workers was 4.1% (3.2% for men, 5.0% for women). Multiple logistic regression analysis was performed to evaluate the depressive factors of male and female wage workers. In male workers, work-related characteristics such as employment type and working hours per week were found to be significantly related to depression even after adjusting for socio-demographic characteristics, health-related characteristics, and life style characteristics. However, in female workers, work-related characteristics did not expose a significant relationship, showing a difference from male workers. Therefore it is necessary to develop and implement workplace counselling or mental health promotion programs that take into account the gender characteristics of depression risk factors. Also, as health-related characteristics (diagnosis of depression, suicide plan, perceived stress level, unmet medical services, self-rated health status) were found to be related to depression for both male and female workers, continuous management of these factors is required.

Comparative Review of the Correlation Between Electroneurography, Electromyography, Hematology Tests, or the Heart Rate Variability Test, with an Improvement in the Severity of Bell's Palsy Symptoms

  • Hwang, Ji-Min;Kim, Jun-Yeon;Kim, Ha-Na;Park, Kyeong-Ju;Jo, Min-Gi;Jang, Jun-Yeong;Nam, Sang-Soo;Goo, Bon Hyuk;Kim, Jung-Hyun;Ko, Min Jung;Chae, Sang Yeup;Park, Young Jae
    • Journal of Acupuncture Research
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    • v.38 no.3
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    • pp.192-199
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    • 2021
  • Background: In this retrospective study, we aimed to determine which diagnostic tests were associated with an improvement in Bell's palsy symptoms. Methods: There were 30 patients who visited Kyung Hee University Korean Medicine Hospital from April 1, 2017 to February 29, 2020, and who received East-West collaboration treatment for Bell's palsy. The tests included electroneurography (ENoG), electromyography (EMG), hematology, and heart rate variability (HRV) results which were used to determine if any test correlated with improvement of Bell's palsy symptoms. Results: The initial severity of symptoms did not correlate with the tests performed, with the exception of mean corpuscular hemoglobin concentration (p = 0.013). For both ENoG for oculi degeneration and mean EMG tests, the rate of nerve degeneration showed a significant negative correlation with the improvement of Bell's palsy symptoms. Amongst the HRV test indicators, the square root of the mean of the sum of the squares of differences between the adjacent normal R-R wave interval, the standard deviation of intervals, total power, very low frequency, and high frequency of the wave was negatively correlated with improvement of Bell's palsy symptoms. Similarly, glycosylated hemoglobin Type A1c (HbA1c) and erythrocyte sedimentation rate (ESR) showed a negative correlation with improvement of symptoms of Bell's palsy. With the exception of HbA1c and ESR, the remaining hematology test results showed no significant difference when comparing before and after treatment. Conclusion: ENoG, EMG, HRV test, HbA1c, and ESR negatively correlated with improvements in Bell's palsy symptoms and may determine the prognosis of Bell's palsy.

The Significances of Chest X-ray Findings and Serum IFN-γ, IL-5, ECP as Predictors of Prognosis of Bronchiolitis and Bronchopneumonia in Infants (영아의 세기관지염과 기관지 폐렴의 예후 지표로서 혈청 IFN-γ, IL-5 및 ECP치와 흉부 방사선 소견의 의의)

  • Cho, Su Hyun;Lee, Hyun Seung;Lee, Mi Hee;Lee, Joon Sung
    • Clinical and Experimental Pediatrics
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    • v.46 no.3
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    • pp.230-235
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    • 2003
  • Purpose : Lower respiratory tract infections in infant and young children are often due to a virus, especially the Respiratory syncytial(RS) virus. Chest X-ray findings in bronchiolitis and bronchopneumonia are different. The radiographic hallmark of bronchiolitis is pulmonary hyperinflation and similar to that of bronchial asthma. Bronchiolitis is predisposed to later development of bronchial asthma. To evaluate the difference of immuno-pathophysiology between bronchiolitis and bronchopneumonia, we measured $IFN-{\gamma}$(Th1 cytokine), IL-5(Th2 cytokine) and ECP. We also investigated whether X-ray findings in infants with viral infected respiratory disease are useful in predicting the development of asthma. Methods : We measured IL-5, ECP, $IFN-{\gamma}$ levels in serum from 21 infants with bronchiolitis and 21 infants with bronchopneumonia and 16 infants without pulmonary viral diseases. Results : IL-5 levels of bronchiolitis and bronchopneumonia were significantly higher than those of the control(P=0.02, P=0.042). IL-5 levels of bronchiolitis were higher than those of bronchopneumonia but there was no significant difference. $IFN-{\gamma}$ levels of bronchopneumonia were higher than those of bronchiolitis but there was no significant difference. ECP levels of bronchiolitis and bronchopneumonia were higher than those of the control but only those of bronchiolitis were significantly higher than those of the control(P=0.045). IL-5 and ECP levels did not show any significant correlation in bronchiolitis, bronchopneumonia and control groups. Conclusion : We cannot prove the distinct differences in serum Th1/Th2 cytokine profiles between bronchiolitis and bronchopneumonia in infants. These results suggest that the different findings on chest X-ray between bronchiolitis and bronchopneumonia could not be a predictor of later development of asthma.

Ecological Characteristics of Korean Red Pine (Pinus densiflora S. et Z.) Forest on Mt. Nam as a Long Term Ecological Research (LTER) Site (국가장기생태연구 장소로서 구축된 남산 소나무림의 생태적 특성)

  • Lee, Chang-Seok;Cho, Yong-Chan;Shin, Hyun-Cheol;Lee, Choong-Hwa;Lee, Seon-Mi;Seol, Eun-Sil;Oh, Woo-Seok;Park, Sung-Ae
    • Journal of Ecology and Environment
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    • v.29 no.6
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    • pp.593-602
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    • 2006
  • Species composition, spatial distribution of major species, diameter and height classes distribution, and species diversity were .analyzed in the Korean red pine (Pinus densiflora, hereafter referred as pine) forest in the permanent quadrats, which were designed for Long Term Ecological Research (LTER). Collected data were compared with those from the other areas including urban center (Mt. Inwang and Hongneung) and boundary areas (Mts. Acha, Bukhan, Bulam, Cheonggye, Daemo, and Surak), and natural areas (Mts. Seolak, Songni, and Wolak) to clarify the ecological characteristics of pine forest on Mt. Nam. Species composition of pine forest on Mt. Nam showed a similarity with those of urban center but did a little and big differences with those on urban boundary and natural areas, respectively. Such differences that pine forest on Mt. Nam showed, were usually due to Styrax japonicus, Sorbus alnifolia, Oplismenus undulatifolius, Ailanthus altissima, Ageratina altissima and so on, which showed higher coverage there. Predicted from diameter and height classes distribution of tree species, pine forest on Mt. Nam showed a possibility to be replaced by a S. japonica. Considered that this replacer species is not only a sub-tree but also shade intolerant, such successional trend could be interpreted as a sort of retrogressive succession. Those on urban boundary and natural areas showed a difference by displaying probabilities to be maintained as themselves as an edaphic climax or succeeded to oak forests. Species diversity of pine forest on Mt. Nam was lower than those in urban boundary and natural areas due to excessive dominance of several species, which led to different species composition from the other areas. Plants, which produced the differences, were species that flourishes in the polluted industrial area (S. japonica and S. alnifolia), favors the disturbed site (O. undulatifolius), and exotic species (A. altissima and Eupatorium rugosum). Those results reflects that pine forest of Mt. Nam was exposed on severe environmental pollution and excessive human interferences.

A Study on the Difference of Strategies for Conflict Resolution between Rural Residents and Urban-to-Rural Migrants (게임이론에 근거한 농촌원주민과 귀농·귀촌인 간 갈등해결 전략차이 연구)

  • Kim, Tae-kyun;Park, Sang-hyeok
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.14 no.2
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    • pp.151-163
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    • 2019
  • In recent years, as the population of ear and aged villages has increased, the problem of conflict between rural residents and urban-to-rural migrants has been widespread. For successful rural community, such conflict resolution is more important than anything else. However, if we look at previous studies. It is true that there are many studies that focus on people who are not rural residents or urban-to-rural migrants. This study was conducted to find out the difference of strategies for conflict resolution between rural residents and urban-to-rural migrants. This study derives the factors of conflict based on the contents of previous studies, To see the difference, five strategies were used from the response strategies that were used in the 'Computer Prisoner's Dilemma Contest' held by Axelrod (2009). I would like to know what kind of strategies of rural residents and urban-to-rural migrants. All analyzes were done using SPSS 22.0 for Windows, and the results of each conflict resolution analysis showed that the indigenous conflicts were low All. Among the causes of conflict, the highest level of conflict was caused by the 'rural residents who did not understand urban culture'. The strategy is the most used, followed by tit for tat Strategy, and all-c strategy, in that order. However, It is not uncommon for employers to use a work-type strategy, and it can be seen that the strategy changes depending on the cause. As can be seen from the above results, The conflict resolution strategies are almost similar strategies. It can be seen that conflict resolution strategy is used differently according to personality. The purpose of this study is to investigate the differences in conflicts in the rural areas. In particular, it is meaningful to examine the choice of solution strategies based on game theory through reviewing prior research and eliciting actual conflict factors in the field. Successful rural settlement can be achieved not through stakeholder competition but through mutual cooperation by gaining cooperation to the other side. Mutual cooperation is more profitable than betrayal in various conflict situations. The secret to maintaining and communicating smoothly is not to use the other person to fill his or her selfish interests, but to reject it for profit, but to draw cooperation from the other party.

Weed Competition and Herbicide Response of Rice under the Foggy Condition II. Growth and Weed Competition of Rice (안개조건하(條件下)에서 벼(Oryza sativa L.)의 잡초경합(雜草競合)과 제초제(除草劑) 반응차이(反應差異)에 관(關)한 연구(硏究) II. 벼의 생장(生長)과 잡초경합(雜草競合))

  • Guh, Ja-Ock;Lee, Min-Soo;Kuk, Yong-In;Chon, Sang-Uck
    • Korean Journal of Environmental Agriculture
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    • v.14 no.2
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    • pp.221-231
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    • 1995
  • The objectives of the present study were to find out the differences in growth and weed competition of rice under the foggy and non-foggy condition, and finally, the fundamental data for the establishment of the paddy weed control system under the locational foggy regions. The research was carried out on tin trays ($0.12m^2$) in greenhouse equipped with an Auto Foggy System(SAE KI RTN Co.). The results are summarized as follows: Exp. I. Difference in rice growth under the foggy and non-foggy condition. 1. While the plant height was not affected, the number of tillers was decreased by the foggy condition. The ratio of the number of effective tiller, however, became higher under the foggy condition. 2. Due to the fog present, the heading rate was decreased and heading time was delayed. 3. The foggy condition did not affect the dry weight of rice straw whether they were grown under the foggy or non-foggy condition. However, yield components such as the number of ears, the number of grains per ear, thousand kernel weight and percentage of ripeness were reduced. Particularly, weights of perfect brown and unpolished rice were also decreased. Exp. II. Effect of the duration of competition between weed and rice grown under the foggy condition on the growth of rice plant. 1. There was no difference in the height of rice grown under a different duration of competition. There was a clear tendency that the number of tillers of rice grown under the foggy condition was decreased as the duration of competition was decreased. 2. When the duration of competition was longer than 60 days, the heading rate was decreased and the initiation of heading was also delayed by 2-4 days. 3. Under the foggy condition, the duration of competition for more than 40 days affected dry weight of rice straw and the difference in yield was greatest in the non-competition and competition for more than 40 days.

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