• 대한방사선기술학회지:방사선기술과학
• /
• 제21권1호
• /
• pp.46-51
• /
• 1998

The absorption coefficient of contrast media was measured in region of diagnostic radiology. Relative values of absorption coefficient was found the largest peak in the range of $60{\sim}70\;kVp$ for barium sulfate and 60 kVp for iodine. Increasing the thickness of contrast media and patient, the values of absorption coefficient was rising. In the Radiograph, desired $70{\sim}80\;kVp$ in the gastrointestinal digestion tract with barium sulfate and the vascular tract is before and behind 65 kVp of exposure.

• 농촌계획
• /
• 제22권2호
• /
• pp.109-119
• /
• 2016

Most of countries are trying to increase the supply of renewable energy as the substitute of the fossil energy for reducing greenhouse gas emissions. However, renewable energy sources account for only about 3.86% of the total Korea primary energy supply. To increase the rate of renewable energy in Korea's energy consumption, various policies for expanding the use of renewable energy should be applied. Also these policies should be consider renewable energy resources distribution and regional inequality. In this study, the potentials of photovoltaic, wind power and bioenergy from rice straw, livestock waste and food waste are calculated and the distribution characteristic and regional inequalities are analyzed using Gini's coefficient and Gini decomposition method. As the results, technical potentials of photovoltaic and wind power of city region(Gu) has more potential rate than theoretical potentials. Livestock waste has the most unequal distribution (Gini's coefficient: 0.617) among renewable resources.

• Current Optics and Photonics
• /
• 제5권3호
• /
• pp.278-288
• /
• 2021

We propose a characterization method for the scattering property of microspheres using spectroscopic optical coherence tomography (OCT). To prove the effectiveness of the proposed method, we prepare solutions of different concentrations using microspheres ranging from 28 to 2300 nm in diameter. Time-frequency analysis is performed on the measured interference spectrum of each solution, and the resulting spectroscopic information is converted into histograms for centroid wavelengths. The histograms present a very sensitive response to changes in the concentration and size of microspheres. We classify them into three categories according to their characteristics. When the histogram of each category is replaced with the corresponding calculated value of the scattering coefficient, each category is mapped to a different scattering-coefficient region. It is expected that the proposed method could be used to investigate the optical characteristics of a biological sample from OCT images, which would be helpful for optical diagnostic and therapeutic applications.

• 한국통신학회논문지
• /
• 제27권6A호
• /
• pp.575-583
• /
• 2002

JBIG2는 2진 영상과 문서 압축을 위한 국제 표준이다. JBIG2 표준은 2진 영상과 문서를 고압축으로 부호화하기 위해 영역 특징에 따라 세 가지 부호화 모드를 제공한다. MMR이나 산술 부호화를 이용하여 비트맵(bitmap)의 부호화를 위한 제너릭 영역(Generic region) 부호화를 한다. 그리고, 텍스트 영역의 부호화를 위해 패턴 매칭(Pattern Matching) 부호화를 하고, 하프톤 영역(Halftone region) 부호화를 위해 하프톤 패턴 부호화(Halftone Pattern Coding)를 한다. 본 논문에서는 JBIG2 부호화를 위해 문서를 라인아트, 하프톤, 텍스트 영역으로 분할한 후 각 영역에 제너릭 영역 부호화, 심벌 매칭 부호화, 하프톤 패턴 부호화를 하는 JBIG2 CODEC을 구현하였다. 문서의 효율적 영역 분할을 위해 윤곽선 추출법을 이용한 영역분할 방법과 웨이브릿 계수분표를 이용한 영역 분할 방법을 함께 적용하여 facsimile 테스트 영상(IEEE-167a)의 경우 2% 정도의 압축률 개선과 주관적 화질의 향상을 얻었다. 또한 임의 모양 하프톤 영역의 부호화를 제안하여 기존 영역 분할 방법에서 인지할 수 없는 임의 모양 하프톤 영역 주변 텍스트의 주관적 화질을 개선하였다.

• Journal of Welding and Joining
• /
• 제11권4호
• /
• pp.70-78
• /
• 1993

An attempt was made to investigate the effect of brazing time on microstructure, microhardness, and corrosion of Zircaloy -4as well as the beryllium diffusion into its sheet. The sheets were coated with beryllium and brazed at $1020^{\circ}C$ for 20-40 minutes in $2{\times}10^{-5}$ torr vacuum atmosphere. 1. Microstructurally the brazed zone was largely divided into three regions: a region of continuous or partially formed of eutectic liquid films along grain boundaries; a region of precipitation in both grains and grain boundaries; a region of elongated wide structure of .alpha.-laths, which was not affected by beryllium. 2. Due to the precipitates, the beryllium-migrated region was hardened and the width of the hardened region increased with increasing brazing time. 3. Beryllium brazed Zircaloy -4 sheets showed a higher corrosion rate than those of as-received and heat-treated at a brazing temperature. 4. Diffusion coefficient of beryllium into Zircaloy -4 at $1020^{\circ}C$ for 30 minutes was $7.67{\times}10^{-7}cm^2/sec.$ It seemed that Be penetrated Zircaloy -4 by forming eutectic liquid films along grain boundaries in the proximity of Be/Zr interface and it, thereafter, diffused into Zircaloy mainly by interstitial solid solution.

• Journal of Mechanical Science and Technology
• /
• 제20권12호
• /
• pp.2230-2241
• /
• 2006

This paper presents a sole application of boundary element method to the conjugate heat transfer problem of thermally developing laminar flow in a thick walled pipe when the fluid velocities are fully developed. Due to the coupled mechanism of heat conduction in the solid region and heat convection in the fluid region, two separate solutions in the solid and fluid regions are sought to match the solid-fluid interface continuity condition. In this method, the dual reciprocity boundary element method (DRBEM) with the axial direction marching scheme is used to solve the heat convection problem and the conventional boundary element method (BEM) of axisymmetric model is applied to solve the heat conduction problem. An iterative and numerically stable BEM solution algorithm is presented, which uses the coupled interface conditions explicitly instead of uncoupled conditions. Both the local convective heat transfer coefficient at solid-fluid interface and the local mean fluid temperature are initially guessed and updated as the unknown interface thermal conditions in the iterative solution procedure. Two examples imposing uniform temperature and heat flux boundary conditions are tested in thermally developing region and compared with analytic solutions where available. The benchmark test results are shown to be in good agreement with the analytic solutions for both examples with different boundary conditions.

• 한국농공학회논문집
• /
• 제58권1호
• /
• pp.61-71
• /
• 2016

This study performed the physical and mechanical experiment on the samples of costal marine clays individually collected in western and southern regions to identify the characteristics of western and southern costal marine clay. Based on the experiment result, the characteristics of costal marine clay is identified undrained shear strength. Based on the experiment result on the physical and mechanical characteristics of costal marine clays, the regression is presented that can analyze the mechanical characteristics of undrained shear strength in costal marine clay of Korea, region of Korea and western-southern region. The correlation of uniaxial compressive strength and undrained shear strength was suitable for use of western-southern region correlation equation. The test result of Jeonnam Yeosu area compares with prediction results of previous researchers formula and western-southern region formula. Prediction results appear highest reliability on the 0.827 of coefficient of determination in the prediction results of the western-southern region formula.

• 대한기계학회논문집B
• /
• 제28권5호
• /
• pp.535-544
• /
• 2004

The heat (mass) transfer characteristics in the tip-leakage flow region of a high-turning first-stage turbine rotor blade has been investigated by employing the naphthalene sublimation technique. The heat transfer data in the tip-leakage flow area for the tip clearance-to-span ratio, h/s, of 2.0% are compared with those in endwall three-dimensional flow region without tip clearance (h/s : 0.0 %). The result shows that the thermal load in the tip-leakage flow region for h/s = 2.0% is more severe than that in the endwall flow region for h/s : 0.0%. The thermal loads even at the leading and trailing edges for h/s = 2.0% are found larger than those for h/s = 0.0%. The tip-leakage flow results in heat transfer augmentations near the tip on both pressure and suction sides in comparison with the mid-span results.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1985년도 추계학술대회 논문집
• /
• pp.21-23
• /
• 1985

By adding La$_2$O$_3$ to optical multicomponent glass composition, after making mother glass and core fiber that enable to enlarge the infrared transmittance region, then surveyed the optical properties. Through thermal analysis of the glass abstained by melt-quenching after selecting stable basic composition on devitrification and replace SiO$_2$ by 4-12wt% La$_2$O$_3$. As La$_2$O$_3$ increases up to l2wt% transition temperature, refractive index, density, deformation temperature increased, whereas thermal expansion coefficient decreased. As a result of inspectig transmittance in UV/VIS/IR region, visable region indicated the decrease of transmittance by increasing the La$_2$O$_3$ and transmittance region was enlarged by increasing the La$_2$O$_3$ in IR region. Also, fabricate core fiber at 820$^{\circ}C$ and severy the optical loss we could fact that La$_2$O$_3$ composition added 12wt% showed the minimum optical loss.

• Water Engineering Research
• /
• 제3권3호
• /
• pp.163-176
• /
• 2002

In this study, laboratory experiments have been performed to investigate characteristics of the velocity fields and turbulence for non-buoyant plane jet in the vicinity of the jet nozzle using PIV system. The experimental results show that, in the transition region, the lateral velocity profile is in good agreement with Gaussian distribution. However, the coefficient of Gaussian distribution, $\K_{u,}$, decreases with longitudinal distance in the transition region. The existing theoretical equation for the centerline velocity tends to overestimate the measured data in the transition region. A new equation for the centerline velocity derived by incorporating varying $k_{u}$ gives better agreement with the measured data than the previous equation. The results of the turbulence characteristics show peak values are concentrated on the shear layers. The Reynolds shear stress profile shows the positive peak in the upper layer and negative peak in the lower layer. The turbulent kinetic energy also provides double peaks at the shear layers. The peak of the Reynolds shear stress and the turbulent kinetic energy increases until x/B=8, and then it decreases afterwards.s.