• Title/Summary/Keyword: bias effect

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Forecast and verification of perceived temperature using a mesoscale model over the Korean Peninsula during 2007 summer (중규모 수치 모델 자료를 이용한 2007년 여름철 한반도 인지온도 예보와 검증)

  • Byon, Jae-Young;Kim, Jiyoung;Choi, Byoung-Cheol;Choi, Young-Jean
    • Atmosphere
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    • v.18 no.3
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    • pp.237-248
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    • 2008
  • A thermal index which considers metabolic heat generation of human body is proposed for operational forecasting. The new thermal index, Perceived Temperature (PT), is forecasted using Weather Research and Forecasting (WRF) mesoscale model and validated. Forecasted PT shows the characteristics of diurnal variation and topographic and latitudinal effect. Statistical skill scores such as correlation, bias, and RMSE are employed for objective verification of PT and input meteorological variables which are used for calculating PT. Verification result indicates that the accuracy of air temperature and wind forecast is higher in the initial forecast time, while relative humidity is improved as the forecast time increases. The forecasted PT during 2007 summer is lower than PT calculated by observation data. The predicted PT has a minimum Root-Mean-Square-Error (RMSE) of $7-8^{\circ}C$ at 9-18 hour forecast. Spatial distribution of PT shows that it is overestimated in western region, while PT in middle-eastern region is underestimated due to strong wind and low temperature forecast. Underestimation of wind speed and overestimation of relative humidity have caused higher PT than observation in southern region. The predicted PT from the mesoscale model gives appropriate information as a thermal index forecast. This study suggests that forecasted PT is applicable to the prediction of health warning based on the relationship between PT and mortality.

Regulation of autonomic functions following two high frequency yogic breathing techniques

  • Mondal, Joydeb;Balakrishnan, Ragavendrasamy;Krishnamurthy, Manjunath Nandi
    • CELLMED
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    • v.5 no.1
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    • pp.4.1-4.4
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    • 2015
  • Yoga is an ancient Indian system of life, encompassing various practices including practices for self-discipline and also for regulating the health states of the individual, being practiced for thousands of years. The present study aims at understanding the effect of two high frequency breathing practices over autonomic nervous system. Forty healthy male volunteers of age $21{\pm}2$ years with $9{\pm}3$ months of Yoga practice experience were recruited. The two high frequency Yoga breathing practices, kapalabhati (KB) and bhastrika (BH) were given as interventions randomly on either of the two days to minimise laboratory bias. They were assessed before and immediately after the interventions for heart rate, respiratory rate, heart rate variability (HRV), blood pressure and peripheral oxygen saturation. There was a significant increase in heart rate (p<0.01; p<0.001), systolic blood pressure (p<0.01; p<0.001), NN50 (p<0.01; p<0.001) component of HRV for both KB and BH groups respectively. There was a significant reduction in respiratory rate in both the groups (p<0.001, and p<0.05, BH and KB respectively) immediately following intervention. A significant increase in LF component of HRV and reduction in Diastolic blood pressure and high frequency (HF)component following KB was also observed (p<0.05, for all comparisons). The Mean peripheral oxygen saturation remained unaltered in both the groups (p>0.05).The results suggest that high frequency yoga breathing practices induce physiological arousal immediately as evidenced by increased blood pressure and heart rate. The sympathetic arousal was more following KB session as evidenced by an increased diastolic blood pressure, LF power and a decrease in HF power of HRV as compared to the BH session.

Application of artificial neural networks to predict total dissolved solids in the river Zayanderud, Iran

  • Gholamreza, Asadollahfardi;Afshin, Meshkat-Dini;Shiva, Homayoun Aria;Nasrin, Roohani
    • Environmental Engineering Research
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    • v.21 no.4
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    • pp.333-340
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    • 2016
  • An Artificial Neural Network including a Radial Basis Function (RBF) and a Time Delay Neural Network (TDNN) was used to predict total dissolved solid (TDS) in the river Zayanderud. Water quality parameters in the river for ten years, 2001-2010, were prepared from data monitored by the Isfahan Regional Water Authority. A factor analysis was applied to select the inputs of water quality parameters, which obtained total hardness, bicarbonate, chloride and calcium. Input data to the neural networks were pH, $Na^+$, $Mg^{2+}$, Carbonate ($CO{_3}^{-2}$), $HCO{_3}^{-1}$, $Cl^-$, $Ca^{2+}$ and Total hardness. For learning process 5-fold cross validation were applied. In the best situation, the TDNN contained 2 hidden layers of 15 neurons in each of the layers and the RBF had one hidden layer with 100 neurons. The Mean Squared Error and the Mean Bias Error for the TDNN during the training process were 0.0006 and 0.0603 and for the RBF neural network the mentioned errors were 0.0001 and 0.0006, respectively. In the RBF, the coefficient of determination ($R^2$) and the index of agreement (IA) between the observed data and predicted data were 0.997 and 0.999, respectively. In the TDNN, the $R^2$ and the IA between the actual and predicted data were 0.957 and 0.985, respectively. The results of sensitivity illustrated that $Ca^{2+}$ and $SO{_4}^{2-}$ parameters had the highest effect on the TDS prediction.

Do Planktonic Foraminifera Juveniles Bias the Paleoceanographic/Paleoclimatic History Interpretation\ulcorner : Short Report of Year-long Trap Result (부유성 유공충의 유생은 고해양/고기후의 연구에 영향을 미치는가\ulcorner : 1년간의 퇴적물트랩 관찰로부터)

  • Im Chul Shin;Byong-Kwon Park;Hi-Il Yi
    • The Korean Journal of Quaternary Research
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    • v.13 no.1
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    • pp.91-98
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    • 1999
  • The effect of the relative abundances of planktonic foraminifera juveniles on the climatic and oceanographic history interpretations is documented for the first time (as far as we know) by use of the year-long time-series sediment trap samples. Statistical correlation analysis suggests that many climatic and oceanographic variables such as sinking flux (total number) of planktonic foraminifera, relative abundance of some climatic indicator species G. bulloides and N. dutertrei, temperature, and salinity do not show any significant correlations with the relative abundance of planktonic foraminifera juveniles. However, planktonic foraminifera juveniles show moderate correlations with species diversity indices (species richness, Shannon-Wiener index, and Equitability). These indicate that the juveniles do not affect the relative abundances(%) of species compositions but affect the species diversity indices. Based on this one-year trap result, special care is required when we use species diversity indices for the interpretations of paleoceanography when the juveniles are excluded from total planktonic foraminiferal countings.

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On the Effect of Tube Attenuation on Measuring Water Vapor Flux Using a Closed-path Hygrometer (폐회로 습도계를 이용한 수증기 플럭스 관측시관의 감쇠 효과에 관하여)

  • Hong Jinkyu;Kim Joon;Choi Taejin;Yun Jin-il;Tanner Bert
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.2 no.3
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    • pp.80-86
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    • 2000
  • Eddy covariance method is widely used in measuring vertical fluxes of mass and energy between the atmosphere and the biosphere. In this method, scalar concentration is measured with either open-path or closed-path sensors. For the latter, fluctuations of scalar concentration are attenuated as the sample travels through a long tube, resulting in flux loss. To quantify this tube attenuation, water vapor concentrations measured with both closed-path and open-path sensors were analyzed. Our statistical analysis showed that the power spectral density obtained from the closed-path sensor was different from that from the open-path sensor in the frequency range of > 0.5 Hz. The loss of water vapor flux due to tube attenuation was < 5% during midday. At nighttime, however, the flux loss increased significantly because of the low wind speeds and the weak turbulence sources. Theoretical calculation for the tube attenuation showed a small bias in high frequency range probably because of the interaction of sticky water vapor with a tube wall.

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Performance Analysis of the KOMPSAT-1 Orbit Determination Using GPS Navigation Solutions (GPS 항행해를 이용한 아리랑 1호의 궤도결정 성능분석 연구)

  • Kim, Hae-Dong;Choi, Hae-Jin;Kim, Eun-Kyou
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.4
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    • pp.43-52
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    • 2004
  • In this paper, the performance of the KOMPSAT-1 orbit determination (OD) accuracy at the ground station was analyzed by using the flight data. The Bayesian least squares estimation was used for the orbit determination and the assessment of the orbit accuracy was evaluated based on orbit overlap comparisons. We also compared the result from OD using GPS navigation solutions with NORAD TLE and the result from OD using range data. Furthermore, the effect of observation type and OBT drift on the accuracy was investigated. As a consequence, It is shown that the OD accuracy using only GPS position data is on the order of 5m RMS (Root Mean Square) with 4 hrs arc overlap for the 30hr arc and the GPS velocity data is not proper as a observation for the OD due to its inferior quality. The significant deterioration of the accuracy due to the critical clock bias was not founded by means of the comparison of OD result from other observations.

An analysis of consumer choice between the Internet and TV home shopping channels (인터넷 및 TV 홈쇼핑 채널 간의 소비자 선호 결정 요인)

  • Lee, Gwang-Hoon
    • Journal of Distribution Research
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    • v.12 no.4
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    • pp.27-47
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    • 2007
  • Using survey data and the Heckit model that adequately controls the sample selection bias, we analyze shoppers expenditure through two major emerging shopping channels: Internet shopping and TV home shopping channels. Age, Internet experience, daily Internet usage, the number of computers are factors that affect the ratio of consumers' expenditure through Internet shopping relative to the expenditure through TV home shopping. Shopping frequency which represents the shoppers' incentives to reduce transaction costs also has a positive effect on the proportion of shoppers' expenditure through the Internet shopping. Shoppers' perceptions of convenience, reliability, speed, and diversity are also shown to affect shoppers' relative expenditure ratio through Internet shopping. In contrast, shoppers' perception of prices does not seem to affect their purchasing behavior.

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Red Meat Intake and Risk of Non-Hodgkin Lymphoma: A Meta-Analysis

  • Fallahzadeh, Hosein;Cheraghi, Maria;Amoori, Neda;Alaf, Mehrangiz
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.23
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    • pp.10421-10425
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    • 2015
  • Background: While the incidence of non-Hodgkins lymphoma (NHL) has been rising worldwide, the reasons remain undefined. Recent research has focused on effect of red andf processed meat intake as a risk factor, but with inconclusive results. We therefore conducted a meta-analysis of data published to date, to ascertain the overall association between intake and NHL. Materials and Methods: A published literature search was performed through Pubmed, Cochrane Library, Medline, and Science Citation Index Expanded databases for articles published in English. Pooled odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated using random or fixed effects models. Heterogeneity was assessed using Chi-square and I2 statistics. Dissemination bias was evaluated by funnel plot analysis.We performed a formal meta-analysis using summary measures from these studies. Results: In total, 11 published studies were included in the final analysis. The combined analysis revealed that there was significant association between the red meat and NHL risk (OR=1.10, 95%CI: 1.02 to 1.19, p=0.01). Additionally, there was showed significance association between processed red meat and NHL risk (OR=1.17, 95%CI: 1.06 to 1.29, p=0.001). In subgroup analysis, a statistical significant association was noted between diffuse large B-cell lymphoma (DLBCL) (OR=1.20, 95%CI: 1.04 to 2.37, P=0.01) and red meat intake. Conclusions: In this meta-Analysis, there was evidence for association between consumption of red meat, or processed meat and risk of NHL, particularly with the DLBCL subtype in the red meat case.

Vitamin D Receptor BsmI Polymorphism and Colorectal Cancer Risk: an Updated Analysis

  • Yu, Kun;Yang, Jing;Jiang, Yan;Song, Run;Lu, Qing
    • Asian Pacific Journal of Cancer Prevention
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    • v.15 no.12
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    • pp.4801-4807
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    • 2014
  • Background: Previous studies have investigated the association between the vitamin D receptor (VDR) BsmI polymorphism and colorectal cancer (CRC) susceptibility, but the results were conflicting. The aim of this study is to quantitatively summarize the relationship between this polymorphism and CRC risk. Materials and Methods: Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure (CNKI) and Chinese Biomedicine databases for studies published before November 2013. Summary odds ratios (ORs) and 95% confidence intervals (95%CIs) for VDR BsmI polymorphism and CRC were calculated in a fixed-effects model (the Mantel-Haenszel method) and a random-effects model (the DerSimonian and Laird method) when appropriate. Results: This meta-analysis included 14 case-control studies, which included 10,822 CRC cases and 11,779 controls. Overall, the variant genotype (BB) of the BsmI was associated with a lower CRC risk when compared with the wild-type bb homozygote (OR=0.66, 95%CI: 0.49-0.88). Similarly, a decreased CRC risk was also found in the dominant and recessive models. When stratifying for ethnicity, source of controls, and study sample size, associations were observed among Caucasians, population-based studies and studies with large study sample size (>1000 subjects). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. No publication bias was found in the present study. Conclusions: This updated meta-analysis suggests that the VDR BsmI polymorphism may be associated with a moderate protective effect against CRC.

Correlation Between the “seeing FWHM” of Satellite Optical Observations and Meteorological Data at the OWL-Net Station, Mongolia

  • Bae, Young-Ho;Jo, Jung Hyun;Yim, Hong-Suh;Park, Young-Sik;Park, Sun-Youp;Moon, Hong Kyu;Choi, Young-Jun;Jang, Hyun-Jung;Roh, Dong-Goo;Choi, Jin;Park, Maru;Cho, Sungki;Kim, Myung-Jin;Choi, Eun-Jung;Park, Jang-Hyun
    • Journal of Astronomy and Space Sciences
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    • v.33 no.2
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    • pp.137-146
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    • 2016
  • The correlation between meteorological data collected at the optical wide-field patrol network (OWL-Net) Station No. 1 and the seeing of satellite optical observation data was analyzed. Meteorological data and satellite optical observation data from June 2014 to November 2015 were analyzed. The analyzed meteorological data were the outdoor air temperature, relative humidity, wind speed, and cloud index data, and the analyzed satellite optical observation data were the seeing full-width at half-maximum (FWHM) data. The annual meteorological pattern for Mongolia was analyzed by collecting meteorological data over four seasons, with data collection beginning after the installation and initial set-up of the OWL-Net Station No. 1 in Mongolia. A comparison of the meteorological data and the seeing of the satellite optical observation data showed that the seeing degrades as the wind strength increases and as the cloud cover decreases. This finding is explained by the bias effect, which is caused by the fact that the number of images taken on the less cloudy days was relatively small. The seeing FWHM showed no clear correlation with either temperature or relative humidity.