• Title/Summary/Keyword: bias term

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Evaluating Changes and Uncertainty of Nitrogen Load from Rice Paddy according to the Climate Change Scenario Multi-Model Ensemble (기후변화시나리오 다중모형 앙상블에 따른 논 질소 유출 부하량 변동 및 불확실성 평가)

  • Choi, Soon-Kun;Jeong, Jaehak;Yeob, So-Jin;Kim, Minwook;Kim, Jin Ho;Kim, Min-Kyeong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.62 no.5
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    • pp.47-62
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    • 2020
  • Rice paddy accounts for approximately 52.5% of all farmlands in South Korea, and it is closely related to the water environment. Climate change is expected to affect not only agricultural productivity also the water and the nutrient circulation. Therefore this study was aimed to evaluate changes of nitrogen load from rice paddy considering climate change scenario uncertainty. APEX-Paddy model which reflect rice paddy environment by modifying APEX (Agricultural Policy and Environmental eXtender) model was used. Using the AIMS (APCC Integrated Modeling Solution) offered by the APEC Climate Center, bias correction was conducted for 9 GCMs using non-parametric quantile mapping. Bias corrected climate change scenarios were applied to the APEX-Paddy model. The changes and uncertainty in runoff and nitrogen load were evaluated using multi-model ensemble. Paddy runoff showed a change of 23.1% for RCP4.5 scenario and 45.5% for RCP8.5 scenario compared the 2085s (2071 to 2100) against the base period (1976 to 2005). The nitrogen load was found to be increased as 43.9% for RCP4.5 scenario and 76.0% for RCP8.5 scenario. The uncertainty analysis showed that the annual standard deviation of nitrogen loads increased in the future, and the maximum entropy indicated an increasing tendency. And Duncan's analysis showed significant differences among GCMs as the future progressed. The result of this study seems to be used as a basis for mid- and long-term policies for water resources and water system environment considering climate change.

Improvement of precipitation forecasting skill of ECMWF data using multi-layer perceptron technique (다층퍼셉트론 기법을 이용한 ECMWF 예측자료의 강수예측 정확도 향상)

  • Lee, Seungsoo;Kim, Gayoung;Yoon, Soonjo;An, Hyunuk
    • Journal of Korea Water Resources Association
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    • v.52 no.7
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    • pp.475-482
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    • 2019
  • Subseasonal-to-Seasonal (S2S) prediction information which have 2 weeks to 2 months lead time are expected to be used through many parts of industry fields, but utilizability is not reached to expectation because of lower predictability than weather forecast and mid- /long-term forecast. In this study, we used multi-layer perceptron (MLP) which is one of machine learning technique that was built for regression training in order to improve predictability of S2S precipitation data at South Korea through post-processing. Hindcast information of ECMWF was used for MLP training and the original data were compared with trained outputs based on dichotomous forecast technique. As a result, Bias score, accuracy, and Critical Success Index (CSI) of trained output were improved on average by 59.7%, 124.3% and 88.5%, respectively. Probability of detection (POD) score was decreased on average by 9.5% and the reason was analyzed that ECMWF's model excessively predicted precipitation days. In this study, we confirmed that predictability of ECMWF's S2S information can be improved by post-processing using MLP even the predictability of original data was low. The results of this study can be used to increase the capability of S2S information in water resource and agricultural fields.

Study on Health Predictors of Early Retirement of Middle-aged and Elderly Workers in Korea: Proportional Hazard Model Analysis by Employment Type (중·고령자의 건강 악화가 조기은퇴에 미치는 영향 연구-근로형태 별 비례위험모형 분석)

  • Chung, Jongwoo
    • 한국노년학
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    • v.37 no.4
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    • pp.871-891
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    • 2017
  • The purpose of this paper is to reduce the reverse-causality and overestimate bias of analysis on how health affected middle-aged and elderly worker's early retirement. From the Korean Longitudinal Study of Ageing(KLoSA) panel data, I researched 1,049 people who were 45-52 years old in 2006. To eliminate the reverse-causality problem, I used the health data which is surveyed before retirement. To reduce bias, I controlled the health status when retirees worked. The main results are as follows. First, the worsened health still affects the hazard of early retirement, with reducing the endogeneity problem. Second, chronic illness is one of the strong predictors of early retirement to self-employed, and self-reported bad health is the main health predictor of wage workers. These results give two implications; first, the impact magnitude of the health indicator depends on employment type. Each employment type has different flexibility of working hours. It seems that the flexibility can reduce early retirement hazard with health problems. Self-employed, who has more flexibility of working hours can work until they have to stop working due to the serious health problem or doctor's advice. Second, to promote middle-aged and elderly workers to keep working, the long-term health policy which decreases chronic illness is needed.

Ideology, Politics, and Social Science Scholarship on the Responsibility of Intellectuals

  • Koerner, E.F.K.
    • Lingua Humanitatis
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    • v.2 no.2
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    • pp.51-84
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    • 2002
  • The 1990s have seen the publication of many books devoted to Language and Ideology (cf. Joseph & Taylor 1990. for one of the early ones) even though the term 'ideology' itself has remained ill-defined (Woolard 1998). The focus of attention has usually been placed on the particular use of language and often for some kind of 'political' ends, not on linguistic or other scholarship which might have been driven by some sort of ideology, i.e., a bundle of assumptions which themselves were taken as given. At least since Edward Said's 1978 book Orientalism, it has been clear to everyone that scholars construct their conceptualization of things in line with their understanding of the cultural, social, and political world in which they live, and that this often unreflected 'pre-understanding' effects their view of cultures that are different from theirs and more often than not geographically and temporally distant from theirs. This recognition has had a sobering effect no doubt, and Said's book has long since become 'mainstream.' Much more disturbing to the scholarly profession has been the publication of Martin Bernal's Black Athena in 1987, since it went much further, going beyond accusations of colonialism and cultural bias, in suggesting that the Western representation of Classical Greece over the past two hundred years was false and that what had been accepted until now about occidental antiquity must now be seen derived from African-Asiatic cultures of the Near East, notably that of the Ancient Egyptians, and that no other than Socrates should be seen as black man. While we may understand the intellectual climate in the United States that led academics to present 'myth as history' (Lefkowitz 1996), it is obvious that lines of regular scholarly principles of investigation have been crossed (cf Lefkowitz & Rogers 1996). The present paper investigates what may be seen as the ideological underpinnings of such work. After reviewing some recent scholarship in the area of linguistic historiography that have shown that academic work has never been 'value-neutral' (as may have been assumed or has been claimed by some practitioners), it is argued that in effect one must be aware of what Clemens Knobloch has recently termed Resonanzbedarf, i.e., the desire, whether conscious or not, of scholars-and probably scientists, too-to have their work recognized by the educated public and that, in so doing, their discourses tend to pick up on contemporary popular notions. These efforts may be harmless if everyone was to recognize these allusions and adoption of certain lexical. items(buzz words) as props or what Germans call Versatzstiicke, but history tells us that this has not always been the case. Still, as Hutton (1999) has shown, not all scholarship during the Third Reich for example can simply be dismissed as worthless because it was conducted in under a prevailing political ideology. Indeed, in seemingly innocent times, linguists can be shown to frame their argument in a way that makes them appear so utterly superior to their predecessors (cf. Lawson 2001). Upon closer inspection, those discourses turn out to be much like those of scholars in nationalistic environments that have tended to select their 'facts' to prove a particular hypothesis (cf., e.g., Koerner 2001). The article argues for scholars to take a more active role in exploding myths, scientifically unfounded claims, and ideologically driven distortions, especially those that are socially and politically harmful.

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Performance evaluation of Wave observation system using GPS (GPS를 이용한 파고 관측 시스템의 성능 평가)

  • Huh, Yong;Hwang, Chang-Su;Kim, Dae Hyun;Heo, Sin;Kim, Joo-Youn;Lee, Kee-Wook;Hong, Sung-Doo
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.15 no.4
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    • pp.357-362
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    • 2012
  • Despite the Wave observations data is very important information to human life at sea, the technology development and research for wave equipments are lacking. In this study, the wave observation system using GPS was evaluated the quality of wave observation data by comparing of long-term observations. The result of the comparison of the acceleration sensor (Hippy-40) and GPS sensor (Mose-1000), the correlation coefficient of the significant wave height and significant wave periods is 0.997 and 0.990 respectively. Also in case of BIAS, the significant wave height is 0.014 m, the significant wave period is -0.212 sec. It makes no significant differences whether the acceleration sensor (Hippy-40) and GPS sensor (Mose-1000). These results of the wave observation data using GPS quality will be evaluated as very good.

Computational Study on the Hemodynamics of Cardiovascular System Including Short-term Auto-regulation Functions (단기적 자율조절기능을 포함하는 심혈관계 혈류역학 모델링에 관한 수치적 연구)

  • 심은보;정찬일;최한고
    • Journal of Biomedical Engineering Research
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    • v.22 no.5
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    • pp.393-402
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    • 2001
  • A computational model representative of cardiovascular circulation was built using 12 standard lumped compartments. Especially, both the baroreceptor reflex and the cardiopulmonary reflex control model were implemented to explain the auto-regulation of cardiovascular system. Another important aspect of this model is to utilize the impulse-response curve of the nerve system in transferring the impulse error signals to autonomous nerve system. For the verification of this model, we have computed the normal hemodynamic conditions and compared those with the clinical data. Then. hemodynamic shock of 20% hemorrhage to cardiovascular system was simulated to test the effects of the control system model. The results of these two simulations were well matched with the experimental ones. The steady state LBNP simulation was also performed. The transient changes of hemodynamic variables due to ramp increase of bias pressure of LBNP showed good agreement with the physiological experiments. Numerical solution using only the baroreflex model showed relatively a larger deviation from the experimental data. compared with the one using the control model haying both the baroreflex and the cardiopulmonary reflex systems, which shows an important role of the cardiopulmonary reflex system for the simulation of the hemodynamic behavior of the cardiovascular system .

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Examining the factors influencing leaf disease intensity of Kalopanax septemlobus (Thunb. ex Murray) Koidzumi (Araliaceae) over multiple spatial scales: from the individual, forest stand, to the regions in the Japanese Archipelago

  • Sakaguchi, Shota;Yamasaki, Michimasa;Tanaka, Chihiro;Isagi, Yuji
    • Journal of Ecology and Environment
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    • v.35 no.4
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    • pp.359-365
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    • 2012
  • We investigated leaf disease intensity of Kalopanax septemlobus (prickly castor oil tree) caused by the parasitic fungus Mycosphaerella acanthopanacis, in thirty natural host populations in the Japanese Archipelago. The disease intensity observed for individual trees were analyzed using a generalized additive model as a function of tree size, tree density, climatic terms and spatial trend surface. Individual tree size and conspecific tree density were shown to have significant negative and positive effects on disease intensity, respectively. The findings suggest that the probability of disease infection is partly determined by dispersal of infection agents (ascospores) from the fallen leaves on the ground, which can be enhanced by aggregation of host trees in a forest stand. Regional-scale spatial bias was also present in disease intensity; the populations in northern Japan and southern Kyushu were more severely infected by the fungus than those in southwestern Honshu and Shikoku. Regional variation of disease intensity was explained by both climatic factors and a trend surface term, with a latitudinal cline detected, which increases towards the north. Further research should be conducted in order to understand all of the factors generating the latitudinal cline detected in this study.

Efficacy and Safety of Pharmacopuncture and Bee venom Acupuncture for Knee Osteoarthritis: A systematic review and meta-analysis (퇴행성 슬관절염에 대한 약침 및 봉독 요법의 효용성 및 안전성: 체계적 문헌 고찰 및 메타 분석)

  • Lee, Yeon Jae;Jo, Hyo Rim;Kim, Seon Hye;Sung, Won Suk;Kim, Eun Jung
    • The Journal of Korean Medicine
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    • v.41 no.1
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    • pp.55-83
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    • 2020
  • Objectives: The purpose of this study was to evaluate the efficacy and safety of pharmacopuncture and bee venom acupuncture for knee osteoarthritis. Methods: We searched for randomized controlled trials that investigated the effects of pharmacopuncture and bee venom acupuncture on knee osteoarthritis through the electronic databases including Pubmed, EMBASE, Cochrane, CiNii, CNKI, KMBASE, KISS, NDSL, and OASIS. Meta-analysis was performed by Review Manager software and the quality of included studies were assessed by the Cochrane risk of bias tool. Results: A total of 20 articles with 1536 participants were identified. 12 trials about phamacopuncture and 8 trials about bee venom acupuncture showed significant improvement than sham treatment, western medicine treatment, and other Korean medicine treatment such as acupuncture in diverse scales. Six trials reported adverse events. Conclusions: These findings showed certain efficacy and safety of pharmacopuncture and bee venom acupuncture. It would be helpful for patients and Korean medicine doctors in the choice of the treatment for knee osteoarthritis. Well-designed studies with long term follow up and more number of participants should be conducted to strengthen the evidence of the use of pharmacopuncture and bee venom acupuncture.

An analysis of air apollution and daily mortality (대기중 총분진과 사망자수에 관한 분석)

  • Kim, Ho
    • The Korean Journal of Applied Statistics
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    • v.13 no.2
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    • pp.265-274
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    • 2000
  • Relationship between the daily mortality and total suspended particulate(TSP) for the period of 1996-1997 was examined in Seoul, Korea. Generalized additive model was adapted for the analysis to allow the seasonality and long-term time effect in the air pollution and the nonlinear relationships with weather variables such as air temperature and relative humidity. An increase of 100 Ji9/m') TSP corresponds to 0.8-5.2 percent increase of the daily mortality Unidirectional (prospective and retrospective) case-crossover design results in large bias of the estimates. Bidirectional method gives relatively unbiased estimates but the standard errors are larger Case-crossover design should be used with caution in the situation where the data have seasonal trends like air pollution study.

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Effects of Smoking Cessation Intervention among Female Smokers: Systematic Review (여성 흡연자의 금연 중재 효과: 체계적 문헌고찰)

  • Kim, Da Hye;Choe, Yu Hyeon;Ham, Ok Kyung;Im, Boae;Kim, Na Kyeong
    • Journal of Korean Public Health Nursing
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    • v.34 no.2
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    • pp.263-276
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    • 2020
  • Purpose: This paper systematically reviewed the effects of smoking cessation (SC) intervention among female smokers. Methods: A systematic search was performed targeting articles published on eight electronic databases, from January 1, 2010, to February 25, 2020. Nine studies were included in the systematic review. The risk of bias (RoB) tool was used to evaluate the quality of scientific evidence. Results: A randomized controlled trial (RCT) was performed in all nine studies. Interventions were classified as exercise (n=4), cognitive behavioral counseling (n=2), motivational counseling (n=1), group counseling with self-help group (n=1), and pharmacotherapy (n=1). The SC rates were measured using a 7-days point prevalence abstinence in 55.6% of the studies. Exercise studies showed higher SC rates in the experimental groups than control groups after the intervention, but the differences were not significant. Other interventions were employed in two or fewer studies or did not conduct long-term follow-up, thus we were unable to examine effects of these interventions. Conclusion: It is necessary to develop SC programs for female smokers by carefully considering the characteristics of female smokers. Further research will be needed to confirm the effects of SC programs in certain subgroups among females. Also more experimental studies on SC intervention should be carried out with scientific rigor.