• Korean Journal of Veterinary Research
• /
• v.44 no.4
• /
• pp.669-676
• /
• 2004

To evaluate the diagnostic accuracy of two commercial ELISA tests (Allied- and CSL-ELISA) for the diagnosis of Mycobacterium paratuberculosis in cattle, Meta-analysis using English language papers published during 1990-2001 was performed. Diagnostic odds ratios (DOR) were analyzed using regression analysis together with summary receiver operating characteristic (ROC) curves. The difference in diagnostic performance between the two ELISA systems was evaluated by using linear regression. Publication bias was assessed by funnel plot and linear regression. The pooled sensitivity and specificity were 44% (95% CI, 38 to 51) and 98% (95% CI, 96 to 99) for the random-effect model. The DOR between studies was heterogeneous. The area under the fitted ROC curve (AUC) was 0.72 for the unweighted and 0.77 for the weighted model. Maximum joint sensitivity and specificity for the unweighted and weighted model from their summary ROC curve were 70% and 75%, respectively. Based on the fitted model, at a specificity of 95%, sensitivity was estimated to be 52% for the unweighted and 57% for the weighted model. From the final multivariable model study characteristic, the country was the only significant variable with an explained component variance of 13.3%. There were no significant differences in discriminatory power, sensitivity, and specificity between the two ELISA tests. The overall diagnostic accuracy of two commercial ELISA tests was moderate, as judged by the AUC, maximum joint sensitivity and specificity, and estimates from the fitted model and clinical usefulness of the tests for screening program is limited because of low sensitivity and heterogeneous of DOR. It is, therefore, recommended to use ELISA tests as a parallel testing with other diagnostic tests together to increase test sensitivity in the screening program.

• Journal of the Korean Magnetics Society
• /
• v.10 no.2
• /
• pp.67-73
• /
• 2000

Top spin valve samples with a structure Ta/NiFe/CoFe/Cu/CoFe/FeMn/Ta were deposited on a Si(100) substrate by changing d.c. magnetron sputtering conditions and the exchange-bias and magnetic properties of samples were investigated. The Exchange field, H$\_$ex/ increased with increase of sputtering power of FeMn from 30 to 150 W and CoFe from 30 to 100 W deposited on the Cu, the increase of H$\_$ex/ was found due to the improvement of preferred orientation of (111) FeMn phase from XRD results. In the case of Cu, H$\_$ex/ decreased with the increase of sputtering pressure ranging from 1 to 5 mTorr. The relationship between exchange field and resistance was investigated, spin valve samples with a large exchange field showed the lower resistance, which was strongly dependent on the good crystallinity and grain size increase as well as lower scattering effects. The Cu thickness was changed from 22 to 38 $\AA$ for Si/Ta/NiFe/CoFe/Cu(t), 30 W/CoFe, 100 W/FeMn, 100 W/Ta spin valve structures, MR ratio of 6.5 % and exchange field of about 190 Oe were obtained for the sample with Cu of 22 $\AA$ thickness. The increase of exchange field with decrease of Cu thickness was explained by FM/AFM spin-spin interaction.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.23 no.4
• /
• pp.153-178
• /
• 2018

Most operational uses of wind speed data require measurements at, or estimates generated for, the reference height of 10 m above mean sea level (AMSL). On the Ieodo Ocean Research Station (IORS), wind speed is measured by instruments installed on the lighthouse tower of the roof deck at 42.3 m AMSL. This preliminary study indicates how these data can best be converted into synthetic 10 m wind speed data for operational uses via the Korea Hydrographic and Oceanographic Agency (KHOA) website. We tested three well-known conventional empirical neutral wind profile formulas (a power law (PL); a drag coefficient based logarithmic law (DCLL); and a roughness height based logarithmic law (RHLL)), and compared their results to those generated using a well-known, highly tested and validated logarithmic model (LMS) with a stability function (${\psi}_{\nu}$), to assess the potential use of each method for accurately synthesizing reference level wind speeds. From these experiments, we conclude that the reliable LMS technique and the RHLL technique are both useful for generating reference wind speed data from IORS observations, since these methods produced very similar results: comparisons between the RHLL and the LMS results showed relatively small bias values ($-0.001m\;s^{-1}$) and Root Mean Square Deviations (RMSD, $0.122m\;s^{-1}$). We also compared the synthetic wind speed data generated using each of the four neutral wind profile formulas under examination with Advanced SCATterometer (ASCAT) data. Comparisons revealed that the 'LMS without ${\psi}_{\nu}^{\prime}$ produced the best results, with only $0.191m\;s^{-1}$ of bias and $1.111m\;s^{-1}$ of RMSD. As well as comparing these four different approaches, we also explored potential refinements that could be applied within or through each approach. Firstly, we tested the effect of tidal variations in sea level height on wind speed calculations, through comparison of results generated with and without the adjustment of sea level heights for tidal effects. Tidal adjustment of the sea levels used in reference wind speed calculations resulted in remarkably small bias (<$0.0001m\;s^{-1}$) and RMSD (<$0.012m\;s^{-1}$) values when compared to calculations performed without adjustment, indicating that this tidal effect can be ignored for the purposes of IORS reference wind speed estimates. We also estimated surface roughness heights ($z_0$) based on RHLL and LMS calculations in order to explore the best parameterization of this factor, with results leading to our recommendation of a new $z_0$ parameterization derived from observed wind speed data. Lastly, we suggest the necessity of including a suitable, experimentally derived, surface drag coefficient and $z_0$ formulas within conventional wind profile formulas for situations characterized by strong wind (${\geq}33m\;s^{-1}$) conditions, since without this inclusion the wind adjustment approaches used in this study are only optimal for wind speeds ${\leq}25m\;s^{-1}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.363-363
• /
• 2008

The development of dry etching process for sapphire wafer with plasma has been key issues for the opto-electric devices. The challenges are increasing control and obtaining low plasma induced-damage because an unwanted scattering of radiation is caused by the spatial disorder of pattern and variation of surface roughness. The plasma-induced damages during plasma etching process can be classified as impurity contamination of residual etch products or bonding disruption in lattice due to charged particle bombardment. Therefor, fine pattern technology with low damaged etching process and high etch rate are urgently needed. Until now, there are a lot of reports on the etching of sapphire wafer with using $Cl_2$/Ar, $BCl_3$/Ar, HBr/Ar and so on [1]. However, the etch behavior of sapphire wafer have investigated with variation of only one parameter while other parameters are fixed. In this study, we investigated the effect of pressure and other parameters on the etch rate and the selectivity. We selected $BCl_3$ as an etch ant because $BCl_3$ plasmas are widely used in etching process of oxide materials. In plasma, the $BCl_3$ molecule can be dissociated into B radical, $B^+$ ion, Cl radical and $Cl^+$ ion. However, the $BCl_3$ molecule can be dissociated into B radical or $B^+$ ion easier than Cl radical or $Cl^+$ ion. First, we evaluated the etch behaviors of sapphire wafer in $BCl_3$/additive gases (Ar, $N_2,Cl_2$) gases. The behavior of etch rate of sapphire substrate was monitored as a function of additive gas ratio to $BCl_3$ based plasma, total flow rate, r.f. power, d.c. bias under different pressures of 5 mTorr, 10 mTorr, 20 mTorr and 30 mTorr. The etch rates of sapphire wafer, $SiO_2$ and PR were measured with using alpha step surface profiler. In order to understand the changes of radicals, volume density of Cl, B radical and BCl molecule were investigated with optical emission spectroscopy (OES). The chemical states of $Al_2O_3$ thin films were studied with energy dispersive X-ray (EDX) and depth profile anlysis of auger electron spectroscopy (AES). The enhancement of sapphire substrate can be explained by the reactive ion etching mechanism with the competition of the formation of volatile $AlCl_3$, $Al_2Cl_6$ or $BOCl_3$ and the sputter effect by energetic ions.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.3.1-3.1
• /
• 2010

Water splitting reaction using photocatalysts is of great interest in the utilization of solar energy [1]. In the present work, visible light-responsive $TiO_2$ thin films (Vis-$TiO_2$) were prepared by a radio frequency magnetron sputtering (RF-MS) deposition method and applied for the separate evolution of $H_2$ and $O_2$ from water as well as the photofuel cell. Special attentions will be focused on the effect of HF treatment of Vis-$TiO_2$ thin films on their photocatalytic activities. Vis-$TiO_2$ thin films were prepared by an RF-MS method using a calcined $TiO_2$ plate and Ar as the sputtering gas. The Vis-$TiO_2$ thin films were then deposited on the Ti foil substrate with the substrate temperature at 873 K (Vis-$TiO_2$/Ti). Vis-$TiO_2$/Ti thin films were immersed in a 0.045 vol% HF solution at room temperature. The effect of HF treatments on the activity of Vis-$TiO_2$/Ti thin films for the photocatalytic water splitting reaction have been investigated. Vis-$TiO_2$/Ti thin films treated with HF solution (HF-Vis-$TiO_2$/Ti) exhibited remarkable enhancement in the photocatalytic activity for $H_2$ evolution from a methanol aqueous solution as well as in the photoelectrochemical performance under visible light irradiation as compared with the untreated Vis-$TiO_2$/Ti thin films. Moreover, Pt-loaded HF-Vis-$TiO_2$/Ti thin films act as efficient and stable photocatalysts for the separate evolution of $H_2$ and $O_2$ from water under visible light irradiation in the presence of chemical bias. Thus, HF treatment was found to be an effective way to improve the photocatalytic activity of Vis-$TiO_2$/Ti thin films. Furthermore, unique separate type photofuel cell was fabricated using a Vis-$TiO_2$ thin film as an electrode, which can generate electrical power under solar light irradiation by using various kinds of biomass derivatives as fuel. It was found that the introduction of an iodine ($I^-/{I_3}^-$) redox solution at the cathode side enables the development of a highly efficient photofuel cell which can utilize a cost-efficient carbon electrode as an alternative to the Pt cathode.

• Progress in Medical Physics
• /
• v.11 no.2
• /
• pp.123-130
• /
• 2000

The performance of an electrometer directly affects on the accuracy and precision in radiation dosimetry. This study is to list of the quality control for maintaining performance and to perform evaluation tests of an electrometer. Performance tests selected include proper polarizing voltages, warm-up and equalization time, leakages, long-term stability, linearity, and effect of ambient conditions. An electrometer connected with a rigid stem ionization chamber was evaluated with a Strontium-90 check device. Bias voltage was measured directly on the input socket. Equalization time is the time required for reaching threshold of charged state after the power is on or the bias voltage is changed. Pre- and post-signal leakages are defined as the accumulation of signal with no exposure and after exposure, respectively. Over three months period, the electrometer's long-term stability was measured by comparison of the temperature-pressure corrected readings. Linearity was expressed as the deviation of readings from multiple short exposures from one continuous exposure. Effect of ambient conditions was expressed as the zero drift of the electrometer over 17-34$^{\circ}C$ temperature ranges. For two nominal values, 300 and 500 volts, measured voltages were lower by 2.5 and 5.8%, respectively. The warm-up time, 20 minutes, was longer than the lamp time by 9 minutes and the equalization time was less than 1 minute. Without exposure, the zero-drift was 0.002 scale-unit in 15 minutes and the leakage after 10 minutes exposure was minimal. The IQ-4 was stable over 99.4% for three-month periods. Deviation from the linearity was 0.9% for measurement scale, 0.000-9.991. Over 17-34$^{\circ}C$ temperature range, the zero-drift was minimal, less than 0.2%. For a clinically-used electrometer, a list for the basic peformance evaluations is proposed. By running this program, the measurement error using an electrometer can be reduced and in turn the improvement in accuracy and precision of radiation dosimetry can be achieved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.1
• /
• pp.29-36
• /
• 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.

• The Journal of Korean Society for School & Community Health Education
• /
• v.3
• /
• pp.15-33
• /
• 2002

Researchers' common findings is that there are positive or negative effect of alcohol expectancy on drinking behavior. Therefore we would effectively prevent troublesome drinking of the youth and university students by inquiring and controlling critical factors affecting alcohol expectancy. The purposes of this thesis are, first, to empirically test factors affecting the alcohol expectancy level of elementary schoolchild(potential drinker).; second, to suggest the necessity for development of pre-alcohol prevention programs. On the basis of previous research, eighteen factors included in four categories(general characters, environmental characters, alcohol knowledge, drinking experience) affecting alcohol expectancy level were found out. 623 subjects used in this study were drawn from 8 elementary schools in Daegu, Korea. The empirical results suggested that the alcohol expectancy level of elementary schoolchildren was negative in general. And it was proved that 9 factors were significantly correlated with alcohol expectancy level. To put it concretely(see Fig.), (1) It was proved that schoolchildren with bad environment(live in oneself, displeased drinking feeling) rather than good environment(live with parents, nice drinking feeling) for drinking had more negative alcohol expectancy. (2) Korean traditional culture that partakes of sacrificial food and drink have an influence on the first drinking of most elementary schoolchildren. And it was proved that schoolchildren with this drinking experience rather than any other motives had less negative alcohol expectancy. (3) It was proved that schoolchildren adapting themselves rather than being difficult in school life had more negative alcohol expectancy. And the more knowledge about alcohol or drinking schoolchildren had, the more they had negative alcohol expectancy (4) It was proved that schoolchildren having drinking experience or drinking at present rather than having no drinking experience or not-drinking at present had less negative alcohol expectancy. (5) It was proved that schoolchildren having strong drinking intention rather than having weak or no drinking intention in the future had more positive alcohol expectancy. Based on previous results, guideline for development of pre-alcohol prevention programs can be represented: discriminated programs development on educatee, drinking education programs development increasing the power of self-control about alcohol and drinking, social education or continuing education programs development on drinking, open preschool education to substantially prevent drinking or alcoholism etc. The findings, however, should be interpreted with caution, because this study has several limitations in measurement and sampling as follows. First, selection bias because of limited selection of sampling. It is because the subjects are drawn from only 8 elementary schools in Daegu. Second, less refined measurement ; Therefore, it is necessary to develop more detailed measures on alcohol knowledge, alcohol expectancy level especially. Further researches should be suggested and encouraged with more refined methodologies.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.5 no.1
• /
• pp.109-122
• /
• 2002

The purpose of this investigation is to evaluate the effects of the Nuegra on enhancement of the masculine and physical activities in general through measuring changes of the testosterone, FSH and subjective symptoms like fatigue, insomnia, urinary stream, muscular weakness, libido and erectile dysfunction. Total 168 male subjects were enrolled from 12 urology, internal medicine clinics and general practitioner, During the 6-week investigational period, 2 capsules of Nuegra were given to the subjects right after meal for 4 weeks, and 1 capsule of Nuegra was added each time in subjects with no or minimal effect. Testoster-one and FSH levels were measured at first visit and last visit, for evaluating masculine activities. To avoid bias and standardize the test results, only one clinic was assigned as a central lab, and all blood samples were transferred. General information and subjective symptoms were evaluated at first visit and at 2 weeks interval, week 2, 4 and 6 using VAS (Visual Analogue Scale). The mean age of the subjects were 51.8${\pm}$8.2 years old (range: 36.1-82.1). Based on the subjects who were tested on testosterone and FSH levels at day l and week 6, the means were 4.4${\pm}$1.4 nmol/L (range: 2.6-7.7), 8.6${\pm}$9.6 mIU/mL (range: 0.3-40.4), respectively at day 1. At week 6, the results were 4.9 ${\pm}$1.6 (2.6-8.9 range), 9.4${\pm}$13.1 (1.0-53.9 range), respectively. Marginally significant difference between pre-dose and post-dose was present. Statistically significant differences were revealed in general assessment for subjective symptoms, fatigue, insomnia, erectile dysfunction, etc. In fatigue, response rates were 39.6, 65.4 and 76.4% at week 2, 4 and 6, respectively (P < 0.0001). Response vates for erectile dysfunction were 13.4, 41.2 and 72.7% at week 2, 4, and 6 (P < 0.0001), respectively, Response rates for libido were 13.6, 51.6 and 73.5% at week 2, 4, and 6 (P < 0.0001), respectively. For urinary stream response rates were 26.9, 44.7 and 66.8% at week 2, 4, and 6 (P < 0.0001), respectively. VAS for muscular weakness did not show significant results that response rates were 40, 60 and 80% at week 2, 4, and 6 from 8.2 (P ＝ 0.24), respectively. Response rates for insomnia were 50, 60, 100% at week 2, 4, and 6 (P < 0.0001), respectively. The results shows that Nuegra tends to enhance masculine activities including libido, erectile dysfunction and urinary stream and also effective for improving general conditions especially insomnia, muscular weakness and fatigue. In conclusion, this investigation has demonstrated that Nuegra does not only have tendency to increase masculine activities through increased secretion of the testosterone and FSH but also improve general conditions such as erectile dysfunction, libido, fatigue and muscular power.

• Journal of Intelligence and Information Systems
• /
• v.24 no.4
• /
• pp.1-32
• /
• 2018

In addition to stakeholders including managers, employees, creditors, and investors of bankrupt companies, corporate defaults have a ripple effect on the local and national economy. Before the Asian financial crisis, the Korean government only analyzed SMEs and tried to improve the forecasting power of a default prediction model, rather than developing various corporate default models. As a result, even large corporations called 'chaebol enterprises' become bankrupt. Even after that, the analysis of past corporate defaults has been focused on specific variables, and when the government restructured immediately after the global financial crisis, they only focused on certain main variables such as 'debt ratio'. A multifaceted study of corporate default prediction models is essential to ensure diverse interests, to avoid situations like the 'Lehman Brothers Case' of the global financial crisis, to avoid total collapse in a single moment. The key variables used in corporate defaults vary over time. This is confirmed by Beaver (1967, 1968) and Altman's (1968) analysis that Deakins'(1972) study shows that the major factors affecting corporate failure have changed. In Grice's (2001) study, the importance of predictive variables was also found through Zmijewski's (1984) and Ohlson's (1980) models. However, the studies that have been carried out in the past use static models. Most of them do not consider the changes that occur in the course of time. Therefore, in order to construct consistent prediction models, it is necessary to compensate the time-dependent bias by means of a time series analysis algorithm reflecting dynamic change. Based on the global financial crisis, which has had a significant impact on Korea, this study is conducted using 10 years of annual corporate data from 2000 to 2009. Data are divided into training data, validation data, and test data respectively, and are divided into 7, 2, and 1 years respectively. In order to construct a consistent bankruptcy model in the flow of time change, we first train a time series deep learning algorithm model using the data before the financial crisis (2000~2006). The parameter tuning of the existing model and the deep learning time series algorithm is conducted with validation data including the financial crisis period (2007~2008). As a result, we construct a model that shows similar pattern to the results of the learning data and shows excellent prediction power. After that, each bankruptcy prediction model is restructured by integrating the learning data and validation data again (2000 ~ 2008), applying the optimal parameters as in the previous validation. Finally, each corporate default prediction model is evaluated and compared using test data (2009) based on the trained models over nine years. Then, the usefulness of the corporate default prediction model based on the deep learning time series algorithm is proved. In addition, by adding the Lasso regression analysis to the existing methods (multiple discriminant analysis, logit model) which select the variables, it is proved that the deep learning time series algorithm model based on the three bundles of variables is useful for robust corporate default prediction. The definition of bankruptcy used is the same as that of Lee (2015). Independent variables include financial information such as financial ratios used in previous studies. Multivariate discriminant analysis, logit model, and Lasso regression model are used to select the optimal variable group. The influence of the Multivariate discriminant analysis model proposed by Altman (1968), the Logit model proposed by Ohlson (1980), the non-time series machine learning algorithms, and the deep learning time series algorithms are compared. In the case of corporate data, there are limitations of 'nonlinear variables', 'multi-collinearity' of variables, and 'lack of data'. While the logit model is nonlinear, the Lasso regression model solves the multi-collinearity problem, and the deep learning time series algorithm using the variable data generation method complements the lack of data. Big Data Technology, a leading technology in the future, is moving from simple human analysis, to automated AI analysis, and finally towards future intertwined AI applications. Although the study of the corporate default prediction model using the time series algorithm is still in its early stages, deep learning algorithm is much faster than regression analysis at corporate default prediction modeling. Also, it is more effective on prediction power. Through the Fourth Industrial Revolution, the current government and other overseas governments are working hard to integrate the system in everyday life of their nation and society. Yet the field of deep learning time series research for the financial industry is still insufficient. This is an initial study on deep learning time series algorithm analysis of corporate defaults. Therefore it is hoped that it will be used as a comparative analysis data for non-specialists who start a study combining financial data and deep learning time series algorithm.