• Title/Summary/Keyword: bias effect

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Examining Impact of Weather Factors on Apple Yield (사과생산량에 영향을 미치는 기상요인 분석)

  • Kim, Mi Ri;Kim, Seung Gyu
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.16 no.4
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    • pp.274-284
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    • 2014
  • Crops and varieties are mostly affected by temperature, the amount of precipitation, and duration of sunshine. This study aims to identify the weather factors that directly influence to apple yield among the series of daily measured weather variables during growing seasons. In order to identify them, 1) a priori natural scientific knowledge with respect to the growth stage of apples and 2) pure statistical approaches to minimize bias due to the subject selection of variables are considered. Each result estimated by the Panel regression using fixed/random effect models is evaluated through suitability (i.e., Akaike information criterion and Bayesian information criterion) and predictability (i.e., mean absolute error, root mean square error, mean absolute percentage). The Panel data of apple yield and weather factors are collected from fifteen major producing areas of apples from 2006 to 2013 in Korea for the case study. The result shows that variable selection using factor analysis, which is one of the statistical approaches applied in the analysis, increases predictability and suitability most. It may imply that all the weather factors are important to predict apple yield if statistical problems, such as multicollinearity and lower degree of freedom due to too many explanatory variables used in the regression, can be controlled effectively. This may be because whole growth stages, such as germination, florescence, fruit setting, fatting, ripening, coloring, and harvesting, are affected by weather.

Qu-Ji-Du-Huang-Wan for Essential Hypertension : Systemic Review and Meta-analysis (본태성 고혈압에 대한 기국지황환(杞菊地黄丸)의 효과에 관한 체계적 고찰 및 메타 분석)

  • Han, In Sik;Shin, Ji Hye;Cho, Yoon Young;Park, Hae Mo;Yang, Chang Sop;Jeong, Min Jeong;Jang, Insoo;Sun, Seung Ho
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.31 no.2
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    • pp.118-125
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    • 2017
  • The purpose of this study is to investigate the blood pressure reducing effect of Qi-Ju-Di-Huang-Wan (QJDHW) in adults with essential hypertension by using methods of systemic review and meta-analysis. Major search engines, such as PubMed, EMBASE, Cochrane library, Web of Science, CNKI, CiNii, J-STAGE, KISS, NDSL, RISS, OASIS, DBpia and so on, were used. The search period we used is from the start date of the search engine to October 30, 2016 and no language limits were placed. Randomized controlled trials using QJDHW in adults with essential hypertension were searched and extracted by two independent researchers. Meta-analysis was performed on outcome variables of the total effective rate (TER), systolic blood pressure (SBP) and diastolic blood pressure (DBP). Risk of bias (RoB) of Cochrane was used to assess methodological quality. Thirteen studies were finally selected. We observed that the combined treatment of QJDHW and antihypertensive drug had 3.6 times the odds ratio of TER for blood pressure lowering than a single use of an antihypertensive drug. Additionally, mean differences of SBP and DBP were -8.88 mmHg (95% Confidential Interval (CI) -12.77 mmHg, -5.00 mmHg, P<0.00001), -7.09 mmHg (95% CI -9.93, -4.25, P <0.00001), respectively. Single use of QJDHW did not reduce blood pressure more than an antihypertensive drug. All items of RoB were unclear and the methodological quality was low. Our analysis suggests that the combination of QJDHW and antihypertensive drugs may be more effective in reducing blood pressure than a single antihypertensive drug. But due to low methodological quality, careful interpretation will be needed and systematic long-term clinical trials will be required.

Prognostic Impact of Elevation of Vascular Endothelial Growth Factor Family Expression in Patients with Non-small Cell lung Cancer: an Updated Meta-analysis

  • Zheng, Chun-Long;Qiu, Chen;Shen, Mei-Xiao;Qu, Xiao;Zhang, Tie-Hong;Zhang, Ji-Hong;Du, Jia-Jun
    • Asian Pacific Journal of Cancer Prevention
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    • v.16 no.5
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    • pp.1881-1895
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    • 2015
  • Background: The vascular endothelial growth factor family has been implicated in tumorigenesis and metastasis. The prognostic value of each vascular endothelial growth factor family member, particular VEGF/VEGFR co-expression, in patients with non-small lung cancer remains controversial. Materials and Methods: Relevant literature was identified by searching PubMed, EMBASE and Web of Science. Studies evaluating expression of VEGFs and/or VEGFRs by immunohistochemistry or ELISA in lung cancer tissue were eligible for inclusion. Hazard ratios (HRs) and 95% confidence intervals (CIs) from individual study were pooled by using a fixed- or random-effect model, heterogeneity and publication bias analyses were also performed. Results: 74 studies covering 7,631 patients were included in the meta-analysis. Regarding pro-angiogenesis factors, the expression of VEGFA (HR=1.633, 95%CI: 1.490-1.791) and VEGFR1 (HR=1.924, 95%CI: 1.220-3.034) was associated separately with poor survival. Especially, VEGFA over-expression was an independent prognostic factor in adenocarcinoma (ADC) (HR=1.775, 95%CI: 1.384-2.275) and SCC (HR=2.919, 95%CI: 2.060-4.137). Co-expression of VEGFA/VEGFR2 (HR=2.011, 95%CI: 1.405-2.876) was also significantly associated with worse survival. For lymphangiogenesis factors, the expression of VEGFC (HR=1.611, 95%CI: 1.407-1.844) predicted a poor prognosis. Co-expression of VEGFC/VEGFR3 (HR=2.436, 95%CI: 1.468-4.043) emerged as a preferable prognostic marker. Conclusions: The expression of VEGFA (particularly in SCC and early stage NSCLC), VEGFC, VEGFR1 indicates separately an unfavorable prognosis in patients with NSCLC. Co-expression VEGFA/VEGFR2 is comparable with VEGFC/VEGFR3, both featuring sufficient discrimination value as preferable as prognostic biologic markers.

Al2O3 High Dense Single Layer Gas Barrier by Neutral Beam Assisted Sputtering (NBAS) Process

  • Jang, Yun-Seong;Hong, Mun-Pyo
    • Proceedings of the Korean Vacuum Society Conference
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    • 2015.08a
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    • pp.157-157
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    • 2015
  • Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}g/m^2day$. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2day$) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study NBAS process was introduced to deposit enhanced film density single gas barrier layer with a low WVTR. Fig. 1. shows a schematic illustration of the NBAS apparatus. The NBAS process was used for the $Al_2O_3$ nano-crystal structure films deposition, as shown in Fig. 1. The NBAS system is based on the conventional RF magnetron sputtering and it has the electron cyclotron resonance (ECR) plasma source and metal reflector. $Ar^+$ ion in the ECR plasma can be accelerated into the plasma sheath between the plasma and metal reflector, which are then neutralized mainly by Auger neutralization. The neutral beam energy is controlled by the metal reflector bias. The controllable neutral beam energy can continuously change crystalline structures from an amorphous phase to nanocrystal phase of various grain sizes. The $Al_2O_3$ films can be high film density by controllable Auger neutral beam energy. we developed $Al_2O_3$ high dense barrier layer using NBAS process. We can verified that NBAS process effect can lead to formation of high density nano-crystal structure barrier layer. As a result, Fig. 2. shows that the NBAS processed $Al_2O_3$ high dense barrier layer shows excellent WVTR property as a under $2{\times}10^{-5}g/m^2day$ in the single barrier layer of 100nm thickness. Therefore, the NBAS processed $Al_2O_3$ high dense barrier layer is very suitable in the high efficiency OLED application.

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A Study on the Long-run Equilibrium Relationship and Causality between the Prices of Fisheries Products at Different Levels of Distribution -Focused on Hairtail and Squid in Pusan- (수산물의 유통단계별 가격간 장기균형관계와 인과성 분석 -부산지역의 갈치, 오징어를 중심으로-)

  • 강석규;이광진
    • The Journal of Fisheries Business Administration
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    • v.29 no.2
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    • pp.77-96
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    • 1998
  • Fisheries products in Korea generally go through three markets, namely the wholesale market at production site (Market A), the wholesale market at consumption site (Market B), and the retail market (Market C), from producers to end consumers. As the products move from Market A through Market B to Market C, the marginal gap of prices asked in these markets demonstrates an apparent relationship. The producers, middlemen, consumers, and governmental departments concerned may influence the marketing prices of fisheries products. This study employing the cointegration theory tries to investigate whether causality of the price-setting among these markets exists and, if any, what it is. The authors have focused their attention on fisheries markets in Pusan, analyzing the long-run equilibrium relationship and causality between the prices of hairtail and squid among markets at different levels. Data used in this study cover the period f개m August 1984 to December 1997 fer hairtail, and the period from May 1989 to December 1997 for squid. The main findings of the study may be summarized as follows: First, regardless of the price time-series of hairtail and squid in individual market, the first difference is necessary fur satisfying the stationary conditions since each time-series is a first integration. This means homogeneous integration of time-series, which is a requirement of the long-run equilibrium of prices at different markets, is satisfied. Second, the study of the long-run equilibrium relationship between the prices at Market A and Market B shows that a long-run equilibrium relationship does exist for selling prices of the two species at Market A and Market B. Third, the ECM (error correction model ) used here to describe the long- and short-run dynamics of price change demonstrates that, in the case of squid, the price change in Market A will lead to a corresponding price change in Market B in the long-run period. In the short-run, however, the price at Market H is not only influenced by the price change in Market A but influence the price at Market A as well, that is, the Prices between Market A and Market B have a feedback effect. It should be stressed that the limitation in data collection, which cover only two species of hairtail and squid, is likely to cause a sampling bias. Nonetheless, we may conclude that a dynamic relation in the formation of prices does exist in view of the transaction amount of species at different markets. It is believed that the conclusion drawn from this study would not only contribute to a long-lasted debate on the direction of causality of price-setting among academic circle and fishing community, but would provide a useful standard for the policy makers in charge of the price-setting of fisheries products as well.

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Effect of Various Parameters on Stress Distribution around Holes in Mechanically Fastened Composite Laminates (기계적으로 체결된 복합재료 평판에서 다양한 인자의 영향에 따른 원공 주위의 응력분포)

  • Choi Jae-Min;Chun Heoung-Jae;Byun Joon-Hyung
    • Composites Research
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    • v.18 no.6
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    • pp.9-18
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    • 2005
  • With the wide applications of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joints have become a very important research area because the joints are often the weakest areas in composite structures. This paper presents an analytical study of the stress distributions in mechanically single-fastened and multi-fastened composite laminates. The finite element models which treat the pin and hole contact problem using a contact stress analysis are described. A dimensionless stress concentration factor is used to compare the stress distributions in composite laminates quantitatively In the case of single-pin loaded composite laminate, the effects of stacking sequence, the ratio of a hole diameter and the width of a laminate (W/D ratio), the ratio of hole diameter and distance from edge to hole (E/D ratio), friction coefficient and clamping force are considered. In the case of multi-pin loaded composite laminate, the influence of the number of pins, pitch distance, number of rows, row spacing and hole pattern are considered. The results show that P/D ratio and E/D ratio affect more on stress distributions near the hole boundary than the other factors. In the case of multi-pin loaded composite laminate, the stress concentration in the double column case is better than the other cases of multi-pin loaded composite laminate.

ADVANTAGES OF USING ARTIFICIAL NEURAL NETWORKS CALIBRATION TECHNIQUES TO NEAR-INFRARED AGRICULTURAL DATA

  • Buchmann, Nils-Bo;Ian A.Cowe
    • Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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    • 2001.06a
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    • pp.1032-1032
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    • 2001
  • Artificial Neural Network (ANN) calibration techniques have been used commercially for agricultural applications since the mid-nineties. Global models, based on transmission data from 850 to 1050 nm, are used routinely to measure protein and moisture in wheat and barley and also moisture in triticale, rye, and oats. These models are currently used commercially in approx. 15 countries throughout the world. Results concerning earlier European ANN models are being published elsewhere. Some of the findings from that study will be discussed here. ANN models have also been developed for coarsely ground samples of compound feed and feed ingredients, again measured in transmission mode from 850 to 1050 nm. The performance of models for pig- and poultry feed will be discussed briefly. These models were developed from a very large data set (more than 20,000 records), and cover a very broad range of finished products. The prediction curves are linear over the entire range for protein, fat moisture, fibre, and starch (measured only on poultry feed), and accuracy is in line with the performance of smaller models based on Partial Least Squares (PLS). A simple bias adjustment is sufficient for calibration transfer across instruments. Recently, we have investigated the possible use of ANN for a different type of NIR spectrometer, based on reflectance data from 1100 to 2500 nm. In one study, based on data for protein, fat, and moisture measured on unground compound feed samples, dedicated ANN models for specific product classes (cattle feed, pig feed, broiler feed, and layers feed) gave moderately better Standard Errors of Prediction (SEP) compared to modified PLS (MPLS). However, if the four product classes were combined into one general calibration model, the performance of the ANN model deteriorated only slightly compared to the class-specific models, while the SEP values for the MPLS predictions doubled. Brix value in molasses is a measure of sugar content. Even with a huge dataset, PLS models were not sufficiently accurate for commercial use. In contrast an ANN model based on the same data improved the accuracy considerably and straightened out non-linearity in the prediction plot. The work of Mr. David Funk (GIPSA, U. S. Department of Agriculture) who has studied the influence of various types of spectral distortions on ANN- and PLS models, thereby providing comparative information on the robustness of these models towards instrument differences, will be discussed. This study was based on data from different classes of North American wheat measured in transmission from 850 to 1050 nm. The distortions studied included the effect of absorbance offset pathlength variation, presence of stray light bandwidth, and wavelength stretch and offset (either individually or combined). It was shown that a global ANN model was much less sensitive to most perturbations than class-specific GIPSA PLS calibrations. It is concluded that ANN models based on large data sets offer substantial advantages over PLS models with respect to accuracy, range of materials that can be handled by a single calibration, stability, transferability, and sensitivity to perturbations.

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60 GHz WPAN LNA and Mixer Using 90 nm CMOS Process (90 nm CMOS 공정을 이용한 60 GHz WPAN용 저잡음 증폭기와 하향 주파수 혼합기)

  • Kim, Bong-Su;Kang, Min-Soo;Byun, Woo-Jin;Kim, Kwang-Seon;Song, Myung-Sun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.1
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    • pp.29-36
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    • 2009
  • In this paper, the design and implementation of LNA and down-mixer using 90 nm CMOS process are presented for 60 GHz band WPAN receiver. In order to extract characteristics of the transistor used to design each elements under the optimum bias conditions, the S-parameter of the manufactured cascode topology was measured and the effect of the RF pad was removed. Measured results of 3-stages cascode type LNA the gain of 25 dB and noise figure of 7 dB. Balanced type down-mixer with a balun at LO input port shows the conversion gain of 12.5 dB within IF frequency($8.5{\sim}11.5\;GHz$) and input PldB of -7 dBm. The size and power consumption of LNA and down-mixer are $0.8{\times}0.6\;mm^2$, 43 mW and $0.85{\times}0.85\;mm^2$, 1.2 mW, respectively.

Analysis of AOD Characteristics Retrieved from Himawari-8 Using Sun Photometer in South Korea (태양광도계 자료를 이용한 한반도 내 Himawari-8 관측 AOD 특성 분석)

  • Lee, Gi-Taek;Ryu, Seon-Woo;Lee, Tae-Young;Suh, Myoung-Seok
    • Korean Journal of Remote Sensing
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    • v.36 no.3
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    • pp.425-439
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    • 2020
  • Through the operations of advanced geostationary meteorological satellite such as Himawari-8 and GK2A, higher resolution and frequency of AOD (Aerosol Optical Depth) data have become available. In this study, we analyzed the characteristics of Himawari-8/AHI (Advanced Himawari Imager) aerosol properties using the recent 4 years (2016~2019) of Sun photometer data observed at the five stations(Seoul National University, Yonsei University, Hankuk University of Foreign Studies, Gwangju Institute of Science and Technology, Anmyon island) which is a part of the AERONET (Aerosol Robotic Network). In addition, we analyzed the causes for the AOD differences between Himawari AOD and Sun photometer AOD. The results showed that the two AOD data are very similar regardless of geographic location, in particular, for the clear condition (cloud amount < 3). However, the quality of Himawari AOD data is heavily degraded compared to that of the clear condition, in terms of bias (0.05 : 0.21), correlation (0.74 : 0.64) and RMSE (Root Mean Square Error; 0.21 : 0.51), when cloud amount is increased. In general, the large differences between two AOD data are mainly related to the cloud amount and relative humidity. The Himawari strongly overestimates the AOD at all five stations when cloud amount and relative humidity are large. However, the wind speed, precipitable water, height of cloud base and Angstrom Exponent have been shown to have no effect on the AOD differences irrespective of geographic location and cloud amount. The results suggest that caution is required when using Himawari AOD data in cloudy conditions.

A Preliminary Quantification of $^{99m}Tc$-HMPAO Brain SPECT Images for Assessment of Volumetric Regional Cerebral Blood Flow ($^{99m}Tc$-HMPAO 뇌혈류 SPECT 영상의 부위별 체적 혈류 평가에 관한 기초 연구)

  • Kwark, Cheol-Eun;Park, Seok-Gun;Yang, Hyung-In;Choi, Chang-Woon;Lee, Kyung-Han;Lee, Dong-Soo;Chung, June-Key;Lee, Myung-Chul;Koh, Chang-Soon
    • The Korean Journal of Nuclear Medicine
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    • v.27 no.2
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    • pp.170-174
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    • 1993
  • The quantitative methods for the assessment of the cerebral blood flow using $^{99m}Tc$-HMPAO brain SPECT utilize the measured count distribution in some specific reconstructed tomographic slice or in algebraic summation of a few neighboring slices, rather than the true volumetric distribution, to estimate the relative regional cerebral blood flow, and consequently produce the biased estimates of the true regional cerebral blood flow. This kind of biases are thought to originate mainly from the arbitrarily irregular shape of the cerebral region of interest(ROI) which are analyzed. In this study, a semi-automated method for the direct quantification of the volumetric regional cerebral blood flow estimate is proposed, and the results are compared to those calculated by the previous planar approaches. Bias factors due to the partial volume effect and the uncertainty in ROI determination are not considered presently for the methodological comparison of planar/volumetric assessment protocol.

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