• Title/Summary/Keyword: Multiple linear Regression

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INFRARED THERMOGRAPHIC ANALYSIS OF TEMPERATURE RISE ON THE SURFACE OF BUCHANAN PLUGGER (적외선열화상장치를 이용한 Buchanan plugger 표면의 온도상승 분석)

  • Choi, Sung-A;Kim, Sun-Ho;Hwang, Yun-Chan;Youn, Chang;Oh, Byung-Ju;Choi, Bo-Young;Juhng, Woo-Nam;Jeong, Sun-Wa;Hwang, In-Nam;Oh, Won-Mann
    • Restorative Dentistry and Endodontics
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    • v.27 no.4
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    • pp.370-381
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    • 2002
  • This study was performed to evaluate the temperature rise on various position of the Buchanan plugger, the peak temperature of plugger's type and the temperature change by its touching time of heat control spling. The heat carrier system 'System B' (Model 1005, Analytic Technologies, USA) and the Buchanan's plug-gers of F, FM, M and ML sizes are used for this study. The temperature was set to 20$0^{\circ}C$ which Dr. Buchanan's "continuous wave of condensation" technique recommended on digital display and the power level on it was set to 10. In order to apply heat on the Buchanan's pluggers, the heat control spring was touched for 1, 2, 3, 4 and 5 seconds respectively. The temperature rise on the surface of the pluggers were measured at 0.5 mm intervals from tip to 20 mm length of shank using the infrared thermography (Radiation Thermometer-IR Temper, NEC San-ei Instruments, Ltd, Japan) and TH31-702 Data capture software program (NEC San-ei Instruments, Ltd, Japan). Data were analyzed using a one way ANOVA followed by Duncan's multiple range test and linear regression test. The results as follows. 1. The position at which temperature peaked was approximately at 0.5 mm to 1.5 mm far from the tip of Buchanan's pluggers (p<0.001). The temperature was constantly decreased toward the shank from the tip of it (p<0.001). 2. When the pluggerss were heated over 5 seconds, the peak temperature by time of measurement revealed from 253.3$\pm$10.5$^{\circ}C$ to 192.1$\pm$3.3$^{\circ}C$ in a touch for 1 sec, from 218.6$\pm$5.$0^{\circ}C$ to 179.5$\pm$4.2$^{\circ}C$ in a touch for 2 sec, from 197.5$\pm$3.$0^{\circ}C$ to 167.5$\pm$3.7$^{\circ}C$ in a touch for 3 sec, from 183.7$\pm$2.5$^{\circ}C$ to 159.8$\pm$3.6$^{\circ}C$ in a touch for 4 sec and from 164.9$\pm$2.$0^{\circ}C$ to 158.4$\pm$1.8$^{\circ}C$ in a touch for 5 sec. A touch for 1 sec showed the highest peak temperature, followed by, in descending order, 2 sec, 3 sec, 4 sec. A touch for 5 sec showed the lowest peak temperature (p<0.001). 3. A each type of pluggers showed different peak temperatures. The peak temperature was the highest in F type and followed by, in descending order, M type, ML type. FM type revealed the lowest peak temperature (p<0.001). The results of this study indicated that pluggers are designed to concentrate heat at around its tip, its actual temperature does not correlate well with the temperature which Buchanan's "continuous wave of condensation" technique recommend, and finally a quick touch of heat control spring for 1sec reveals the highest temperature rise.

Prediction Equations of Pulmonary Function Parameters Derived from the Forced Expiratory Spirogram for Healthy Adults over 50 years old in rural area (농촌지역 50세 이상 인구의 노력성호기곡선을 이용한 폐활량측정법 검사지표의 추정정상치)

  • Kim, Won-Young;Kim, Kwang-Hyun;Youn, Boung-Han;Lee, Seung-Uk;Cho, Chul-Hyun;Choi, Jin-Su;Kim, Hun-Nam
    • Tuberculosis and Respiratory Diseases
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    • v.45 no.3
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    • pp.536-545
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    • 1998
  • Background: The studies on prediction equations of pulmonary function parameters for adults in Korea have been performed in a reference population mainly consisted of young and middle ages. So they included a relatively few elderly who conducted pulmonary function test frequently in clinic. We established prediction equations of pulmonary function parameters for healthy adults over 50 years old in rural area and compared this results with those of other studies. Therefore we attempted to consider normative values of pulmonary function tests for elderly in Korea. Method: Five hundred thirty-three women and men over 50 years old in rural area were participated. A "healthy" subgroup of 110 women and 32 men were identified by excluding those who had conditions that negatively influenced pulmonary function. We derived prediction equations for FVC, $FEV_1$ and $FEV_1%$ by multiple linear regression method from their age, heights and weights in each sex. Results: Prediction equations for FVC and $FEV_1$ in each sex were derived as follows Male; FVC (L)=0.02488Height(cm)-0.0269Age(years)+0.493 $FEV_1(L)$=0.01874Weight(kg)-0.0282Age(years)+2.906 Female; FVC(L)=0.02160Height(cm)-0.0192Age(years)-0.0125 $FEV_1(L)$=0.01720Height(cm)-0.0194Age(years)+0.3890 Prediction equations for $FEV_1%$ were not derived because $FEV_1%$ didn't have statistically significant terms. Comparing Predicted values that were calculated by substitution into the equations of various studies of mean values of age, heights and weights from this study, FVC and $FEV_1$ values in men of this study were lower than those of other studies. In women, FVC and $FEV_1$ values of this study were as similar as or lower than those of the study conducted for healthy elderly blacks in U.S.A respectively. Conclusion: We have got prediction equations of pulmonary function parameters which were driven from forced expiratory spirogram in adults over 50 years old in rural area. Predicted values of this study were lower than those of other studies which were conducted in Korea. So we consider that the study for spirometry reference values for elderly Korean using the method compatible with ATS recommendation need to be conducted more frequently forward.

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Physicochemical Characteristics and Varietal Improvement Related to Palatability of Cooked Rice or Suitability to Food Processing in Rice (쌀 식미 및 가공적성에 관련된 이화학적 특성)

  • 최해춘
    • Proceedings of the Korean Journal of Food and Nutrition Conference
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    • 2001.12a
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    • pp.39-74
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    • 2001
  • The endeavors enhancing the grain quality of high-yielding japonica rice were steadily continued during 1980s∼1990s along with the self-sufficiency of rice production and the increasing demands of high-quality rices. During this time, considerably great, progress and success was obtained in development of high-quality japonica cultivars and qualify evaluation techniques including the elucidation of interrelationship between the physicochemical properties of rice grain and the physical or palatability components of cooked rice. In 1990s, some high-quality japonica rice caltivars and special rices adaptable for food processing such as large kernel, chalky endosperm aromatic and colored rices were developed and its objective preference and utility was also examined by a palatability meter, rapid-visco analyzer and texture analyzer. The water uptake rate and the maximum water absorption ratio showed significantly negative correlations with the K/Mg ratio and alkali digestion value(ADV) of milled rice. The rice materials showing the higher amount of hot water absorption exhibited the larger volume expansion of cooked rice. The harder rices with lower moisture content revealed the higher rate of water uptake at twenty minutes after soaking and the higher ratio of maximum water uptake under the room temperature condition. These water uptake characteristics were not associated with the protein and amylose contents of milled rice and the palatability of cooked rice. The water/rice ratio (in w/w basis) for optimum cooking was averaged to 1.52 in dry milled rices (12% wet basis) with varietal range from 1.45 to 1.61 and the expansion ratio of milled rice after proper boiling was average to 2.63(in v/v basis). The major physicochemical components of rice grain associated with the palatability of cooked rice were examined using japonica rice materials showing narrow varietal variation in grain size and shape, alkali digestibility, gel consistency, amylose and protein contents, but considerable difference in appearance and torture of cooked rice. The glossiness or gross palatability score of cooked rice were closely associated with the peak. hot paste and consistency viscosities of viscogram with year difference. The high-quality rice variety “Ilpumbyeo” showed less portion of amylose on the outer layer of milled rice grain and less and slower change in iodine blue value of extracted paste during twenty minutes of boiling. This highly palatable rice also exhibited very fine net structure in outer layer and fine-spongy and well-swollen shape of gelatinized starch granules in inner layer and core of cooked rice kernel compared with the poor palatable rice through image of scanning electronic mcroscope. Gross sensory score of cooked rice could be estimated by multiple linear regression formula, deduced from relationship between rice quality components mentioned above and eating quality of cooked rice, with high Probability of determination. The ${\alpha}$ -amylose-iodine method was adopted for checking the varietal difference in retrogradation of cooked rice. The rice cultivars revealing the relatively slow retrogradation in aged cooked rice were Ilpumbyeo, Chucheongbyeo, Sasanishiki, Jinbubyeo and Koshihikari. A Tongil-type rice, Taebaegbyeo, and a japonica cultivar, Seomjinbyeo, shelved the relatively fast deterioration of cooked rice. Generally, the better rice cultivars in eating quality of cooked rice showed less retrogiadation and much sponginess in cooled cooked rice. Also, the rice varieties exhibiting less retrogradation in cooled cooked rice revealed higher hot viscosity and lower cool viscosity of rice flour in amylogram. The sponginess of cooled cooked rice was closely associated with magnesium content and volume expansion of cooked rice. The hardness-changed ratio of cooked rice by cooling was negatively correlated with solids amount extracted during boiling and volume expansion of cooked rice. The major physicochemical properties of rice grain closely related to the palatability of cooked rice may be directly or indirectly associated with the retrogradation characteristics of cooked rice. The softer gel consistency and lower amylose content in milled rice revealed the higher ratio of popped rice and larger bulk density of popping. The stronger hardness of rice grain showed relatively higher ratio of popping and the more chalky or less translucent rice exhibited the lower ratio of intact popped brown rice. The potassium and magnesium contents of milled rice were negatively associated with gross score of noodle making mixed with wheat flour in half and the better rice for noodle making revealed relatively less amount of solid extraction during boiling. The more volume expansion of batters for making brown rice bread resulted the better loaf formation and more springiness in rice bread. The higher protein rices produced relatively the more moist white rice bread. The springiness of rice bread was also significantly correlated with high amylose content and hard gel consistency. The completely chalky and large gram rices showed better suitability for fermentation and brewing. Our breeding efforts on rice quality improvement for the future should focus on enhancement of palatability of cooked rice and marketing qualify as well as the diversification in morphological and physicochemical characteristics of rice grain for various value-added rice food processings.

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The Variations of Stratospheric Ozone over the Korean Peninsula 1985~2009 (한반도 상공의 오존층 변화 1985~2009)

  • Park, Sang Seo;Kim, Jhoon;Cho, Nayeong;Lee, Yun Gon;Cho, Hi Ku
    • Atmosphere
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    • v.21 no.4
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    • pp.349-359
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    • 2011
  • The climatology in stratospheric ozone over the Korean Peninsula, presented in previous studies (e.g., Cho et al., 2003; Kim et al., 2005), is updated by using daily and monthly data from satellite and ground-based data through December 2009. In addition, long-term satellite data [Total Ozone Mapping Spectrometer (TOMS), Ozone Monitoring Instrument (OMI), 1979~2009] have been also analyzed in order to deduce the spatial distributions and temporal variations of the global total ozone. The global average of total ozone (1979~2009) is 298 DU which shows a minimum of about 244 DU in equatorial latitudes and increases poleward in both hemispheres to a maximum of about 391 DU in Okhotsk region. The recent period, from 2006 to 2009, shows reduction in total ozone by 6% relative to the values for the pre-1980s (1979~1982). The long-term trends were estimated by using a multiple linear regression model (e.g., WMO, 1999; Cho et al., 2003) including explanatory variables for the seasonal variation, Quasi-Biennial Oscillation (QBO) and solar cycle over three different time intervals: a whole interval from 1979 to 2009, the former interval from 1979 to 1992, and the later interval from 1993 to 2009 with a turnaround point of deep minimum in 1993 is related to the effect of Mt. Pinatubo eruption. The global trend shows -0.93% $decade^{-1}$ for the whole interval, whereas the former and the later interval trends amount to -2.59% $decade^{-1}$ and +0.95% $decade^{-1}$, respectively. Therefore, the long-term total ozone variations indicate that there are positive trends showing a recovery sign of the ozone layer in both North/South hemispheres since around 1993. Annual mean total ozone (1985~2009) is distributed from 298 DU for Jeju ($33.52^{\circ}N$) to 352 DU for Unggi ($42.32^{\circ}N$) in almost zonally symmetric pattern over the Korean Peninsula, with the latitudinal gradient of 6 DU $degree^{-1}$. It is apparent that seasonal variability of total ozone increases from Jeju toward Unggi. The annual mean total ozone for Seoul shows 323 DU, with the maximum of 359 DU in March and the minimum of 291 DU in October. It is found that the day to day variability in total ozone exhibits annual mean of 5.7% in increase and -5.2% in decrease. The variability as large as 38.4% in increase and 30.3% in decrease has been observed, respectively. The long-term trend analysis (e.g., WMO, 1999) of monthly total ozone data (1985~2009) merged by satellite and ground-based measurements over the Korean Peninsula shows increase of 1.27% $decade^{-1}$ to 0.80% $decade^{-1}$ from Jeju to Unggi, respectively, showing systematic decrease of the trend magnitude with latitude. This study also presents a new analysis of ozone density and trends in the vertical distribution of ozone for Seoul with data up to the end of 2009. The mean vertical distributions of ozone show that the maximum value of the ozone density is 16.5 DU $km^{-1}$ in the middle stratospheric layer between 24 km and 28 km. About 90.0% and 71.5% of total ozone are found in the troposphere and in the stratosphere between 15 and 33 km, respectively. The trend analysis reconfirms the previous results of significant positive ozone trend, of up to 5% $decade^{-1}$, in the troposphere and the lower stratosphere (0~24 km), with negative trend, of up to -5% $decade^{-1}$, in the stratosphere (24~38 km). In addition, the Umkehr data show a positive trend of about 3% $decade^{-1}$ in the upper stratosphere (38~48 km).

Empirical Estimation and Diurnal Patterns of Surface PM2.5 Concentration in Seoul Using GOCI AOD (GOCI AOD를 이용한 서울 지역 지상 PM2.5 농도의 경험적 추정 및 일 변동성 분석)

  • Kim, Sang-Min;Yoon, Jongmin;Moon, Kyung-Jung;Kim, Deok-Rae;Koo, Ja-Ho;Choi, Myungje;Kim, Kwang Nyun;Lee, Yun Gon
    • Korean Journal of Remote Sensing
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    • v.34 no.3
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    • pp.451-463
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    • 2018
  • The empirical/statistical models to estimate the ground Particulate Matter ($PM_{2.5}$) concentration from Geostationary Ocean Color Imager (GOCI) Aerosol Optical Depth (AOD) product were developed and analyzed for the period of 2015 in Seoul, South Korea. In the model construction of AOD-$PM_{2.5}$, two vertical correction methods using the planetary boundary layer height and the vertical ratio of aerosol, and humidity correction method using the hygroscopic growth factor were applied to respective models. The vertical correction for AOD and humidity correction for $PM_{2.5}$ concentration played an important role in improving accuracy of overall estimation. The multiple linear regression (MLR) models with additional meteorological factors (wind speed, visibility, and air temperature) affecting AOD and $PM_{2.5}$ relationships were constructed for the whole year and each season. As a result, determination coefficients of MLR models were significantly increased, compared to those of empirical models. In this study, we analyzed the seasonal, monthly and diurnal characteristics of AOD-$PM_{2.5}$model. when the MLR model is seasonally constructed, underestimation tendency in high $PM_{2.5}$ cases for the whole year were improved. The monthly and diurnal patterns of observed $PM_{2.5}$ and estimated $PM_{2.5}$ were similar. The results of this study, which estimates surface $PM_{2.5}$ concentration using geostationary satellite AOD, are expected to be applicable to the future GK-2A and GK-2B.

Relations of neurological and social cognitions in patients with acute phase and chronic phase before returning to the community (급성기와 지역사회 복귀 전 만성 뇌졸중 환자의 신경학적 인지기능과 사회인지 기능의 관계)

  • Park, Myoung-Ok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.5
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    • pp.549-556
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    • 2017
  • This study investigated the importance of social cognitive intervention and the cognitive rehabilitation intervention by comparing the difference and examining the relationship between neurological cognitive function and social cognitive function of stroke patients in the acute phase and chronic stroke before returning to the community. LOTCA, cartoon intention inference task, and social behavior sequence task were performed on 30 acute stroke inpatients and 30 chronic stroke patients from May 2015 to June 2016. A two sample t test was conducted to examine the differences between the groups. The Pearson's correlations test was performed to examine the correlation among the variables in each group. As a result, there were statistically significant differences between the neurological cognitive function and social cognitive function of acute stroke patients and chronic stroke patients who were undergoing rehabilitation training before returning to the community (p<0.05). A linear relationship was found between the thinking operation and social behavior sequence task in the acute stroke group (r=0.539, p<0.05). In the chronic stroke group, visual perception (r=0.530, p<0.05), visual motor organization (r=0.655, p<0.05) and thinking operation (r=0.534, p<0.05) were correlated with the cartoon intention inference task. In addition, the social behavior sequence task were correlated with visual organization (r=0.534, p<0.05) and thinking operation (r=0.764, p<0.05). As a result of multiple regression analysis, the neurological cognitive functions influencing the social cognitive function in the cartoon task was found to be the thinking operation (B = 0.431) in acute stroke patients and the thinking operation (B=0.272) and visuomotor organization (B = 0.218) in the case of chronic stroke. In addition, the results of the social behavior sequence task revealed the thinking operation (B=0.417) in the acute stroke patients, and thinking operation (B=0.267), visual motor organization(B=0.274) and visual perception(B=151) in chronic stroke patients to be significant. According to this result, there is a difference in the neurological and social cognitive levels between the two groups. Therefore, the social cognition is strongly related to the high level cognitive function as thinking operation of the neurological cognitive function. Therefore, in further research, it would be necessary to determine if there is a change in higher cognitive function in neurological cognitive function after applying a social cognition intervention program for stroke.

Comparison of Myogenous and Arthrogenous Pain Patients of Temporomandibular Disorders using Research Diagnostic Criteria for Temporomandibular Disorders (측두하악장애 연구진단기준(RDC/TMD)를 이용한 측두하악장애의 근육성 동통과 관절성 동통 환자군의 비교)

  • Park, Joo Sun;Kim, Dong Hee;Chung, Jin Woo
    • Journal of Oral Medicine and Pain
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    • v.37 no.4
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    • pp.233-242
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    • 2012
  • The purposes of this study were to compare psychological profiles, to investigate the differences in the clinical characteristics, and to compare treatment outcomes between myogenous pain and arthrogenous pain subgroups of temporomandibular disorder (TMD) based on Research Diagnostic Criteria for Temporomandibular disorders (RDC/TMD). Two hundred and fifty two patients diagnosed as TMD were divided into three groups based on the RDC/TMD axis I diagnostic guidelines; myogenous pain group, arthrogenous pain group, and mixed pain (both myogenous pain and arthrogenous pain) group. RDC/TMD history questionnaire was administered to each patient and depression, somatization, jaw disability, pain intensity, disability days, and graded chronic pain scale were analyzed. Bruxism, clenching, insomnia, headache, and unilateral chewing were assessed in a standardized TMD dysfunction questionnaire and the duration of onset, chronicity of pain, treatment period, the effectiveness of the treatment, and improvement of symptoms also analyzed. Myogenous pain group had higher depression (p=0.002), and somatization scales (p<0.001) than the arthrogenous pain group. Mixed pain group showed higher pain intensity (p=0.008), disability days (p<0.001), graded chronic pain scale (p=0.005), somatization (p<0.001), and depression scores (p=0.002) than the arthrogenous pain group. Jaw disability did not show any significant differences among the three groups (p=0.058). Arthrogenous pain group reported more limitation of mouth opening than myogenous pain group (p=0.007). Duration of onset showed that the arthrogenous pain group had lowest prevalence of chronicity among three groups (p=0.002). Mixed pain group patients showed lowest symptom improvements among three groups (p=0.007). Multiple linear regression analysis results showed that the treatment effectiveness was significantly associated with somatization score (${\beta}$=-0.251, p=0.03).

Total Cholesterol Level and Its Related Factors of the Adult Population in the Rural Area and the Sea-Board Area (농어촌지역 성인들의 총콜레스테롤치 및 관련요인)

  • Bae, Do-Ho;Chun, Byung-Yeol;Kam, Sin;Ahn, Soon-Gi;Jin, Dae-Gu;Kim, Jong-Yeon;Lee, Kyung-Eun;Woo, Kuck-Hyeun
    • Journal of agricultural medicine and community health
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    • v.26 no.2
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    • pp.97-109
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    • 2001
  • To investigate the total cholesterol level and its related factors in the rural and sea-board, 2,840 adults who participated voluntarily were examined during the study period December 1999 to February 2000. The height, weight, and fasting serum total cholesterol were measured. Body mass index was calculated. Information on age, gender, smoking, alcohol, and menopausal status in women were collected using a questionnaire by interviewing method. The mean value of total cholesterol was 191.6mg/ dl in sea- board and 173.6mg/ dl in rural men, respectively, and 206.9mg/ dl and 186.9mg/ dl in sea-board and in rural women. By simple analysis, in men, area, BMI and smoking were significant risk factors(p<0.01). Area(p<0.01), age(p<0.01), BMI(p<0.01), smoking(p<0.05), and menopausal status (p<0.01) were significant. In multiple linear regression analysis, the significant factors for total cholesterol in men were area(sea-board versus rural area; p<0.01), body mass index(the more obese; p<0.01), and smoking (non-smoker versus smoker ; p<0.05). Those in women were area(sea-board versus rural area; p<0.01), body mass index(the more obese; p<0.01), and menopausal status(menopause versus normal; p<0.01). Thus, in both gender, the significant factors related with total cholesterol were area and body mass index, and in addition to those, menopausal status was proved as a significant risk factor in women.

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The Effect of Body Mass Index, Fat Percentage, and Fat-free Mass Index on Pulmonary Function Test -With Particular Reference to Parameters Derived from Forced Expiratory Volume Curve- (신체질량지수 및 체지방률, 그리고 제지방지수가 폐기능 검사에 미치는 영향 -노력성 호기곡선을 중심으로-)

  • Park, Ji Young;Pack, Jong Hae;Park, Hye Jung;Bae, Seong Wook;Shin, Kyeong Cheol;Chung, Jin Hong;Lee, Kwan Ho
    • Tuberculosis and Respiratory Diseases
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    • v.54 no.2
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    • pp.210-218
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    • 2003
  • Background : Sex specific cross sectional reference values for the lung function indices usually employ a linear model with a term for age and height. The purpose of this study was to determine the effects of the body mass index (BMI), the fat percentage of the body mass and the fat-free mass index (FFMI) on the forced expiratory volume curve. Methods : Between January 2000 and December 2001, a total of 300 subjects, 150 men and 150 women (mean age : $45{\pm}13$ years), with a normal lung function were enrolled in the study sample. This study measured the $FEV_1$, FVC and $FEF_{25-75%}$ from the forced expiratory volume curve by a spirometer and the body composition by a bioelectrical impedance method in all subjects. Multiple regression analysis was used in order to examine the effects of the body composition on the parameters derived from the forced expiratory volume curve. Results : After adjusting for age, the BMI and Fat percentage improved the descriptions of the FVC (p<0.05, $r^2=0.491$) and $FEV_1$ (p<0.05, $r^2=0.654$) in women. In contrast, the FFMI contributed significantly to the FVC (p<0.05, $r^2=0.432$) and $FEV_1$ (p<0.05, $r^2=0.567$) in men. The $FEF_{25-75%}$ correlated with the fat percentage in women (p<0.05, $r^2=0.337$). Conclusion : These results suggest that the BMI, the fat percentage and the FFMI are significant determinants of the forced expiratory volume curve. The plmonary function test, when considering the BMI, the fat percentage and the FFMI, might be useful in clinical applications.

AGE ESTIMATION USING PANORAMIC RADIOGRAPHS OF DEVELOPING PERMANENT TEETH (발육중인 영구치의 파노라마 방사선 사진 계측을 이용한 연령 추정)

  • Choi, Eun-Young;Choi, Nam-Ki;Kim, Seon-Mi;Yang, Kyu-Ho
    • Journal of the korean academy of Pediatric Dentistry
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    • v.34 no.2
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    • pp.215-221
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    • 2007
  • The aim of this study was to test whether metric measurements of crown length, root length and apex width during tooth development could be a better basis for correlation with age than the classical methods based on subjective estimations of various stages of tooth development. Panoramic radiographs of 120 children, aged 7 to 9 years, were collected from the department of the pediatric dentistry of Chonnam National University Hospital, Korea. The methods of Mornstad was used to estimate age. The structures measured were crown length root length and apex width in panoramic radiographic. The results were as follows : 1. In the boys, it showed higher correlation between lower 2nd molar crown length, lower 1st molar root length or lower 1st permolar apical width and age. In the girls, it showed higher correlation between lower 2nd premolar crown length, lower 2nd molar root length or lower 1st molar apical width and age. 2. With the aid of a multiple regression model, a linear relationship between some of these distances and age was shown. Boy(months) = 43.958 + lower 2nd molar crown length ${\times}$ 4.392 + lower 1st molar root length ${\times}$ 2.255 - lower 1st permolar apical width ${\times}$ 2.046, Girl(months) = 75.213 + lower 2nd premolar crown length ${\times}$ 3.910 lower 2nd molar root length ${\times}$ 2.280 - lower 1st molar apical width ${\times}$ 6.217 Age was estimated in boys and girls using the mathematic model ; the mean difference between chronological and estimated ages was $-2.1{\pm}6.8$ months for boys and $6.1{\pm}6.2$ months for girls. Therefore, it seems to be more accurate and easier than the earlier methods.

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