• Journal of the Korean GEO-environmental Society
• /
• v.24 no.9
• /
• pp.25-32
• /
• 2023

The Korean Industrial Standards (KS F) have a various regulations for measuring the weight of dried soil and rock. However, if the dried weight is measured in air after drying at 110±5℃ or 105±5℃, a weight singularity occurs, in which the weight decreases and then increases as the measurement time continues. In this study, basaltic rock from Ulleung Island was oven dried at 40 to 110℃. The weight was measured on an electronic scale with a sensitivity of 0.0001g (0.1mg) to find weight singularities. A method to easily determine the dry weight using the weight singularities was presented. As a result of analyses of the singularity of rock specimen according to temperature, the singularities were appeared in the temperature range of 40 to 110℃, and the weight of the singularity was smaller as the heating temperature increased. In particular, the weight singularity duration appeared, and the duration of the singularity was shorter as the heating temperature increased. The results of the convection measurement experiment showed that the cause of the singularity is the convection phenomenon caused by the contact of the heated rock with the air. The weight decrease of oven dried rock occurs when the effect of convection is dominant over the effect of air moisture absorption. Conversely, the weight increase of rock occurs when the effect of air moisture absorption is dominant over the effect of convection.

• Journal of the Korean Society of Radiology
• /
• v.15 no.5
• /
• pp.697-704
• /
• 2021

It is hard to get Filaments which are materials of the 3D printing Fused Deposition Modeling(FDM) method as radiation shielding in Korea. and also related research is insufficient. This study aims to provide basic data for the development of radiation shields using 3D printing by evaluating the physical properties and radiation shielding capabilities of filaments containing metal particles. after selecting five metal filaments containing metal particle reinforcement materials, the radiation shielding rate was calculated according to the Korean Industrial Standard's protective equipment test method to evaluate physical properties such as tensile strength, density, X-ray Diffraction(XRD), and weight measurement using ASTM's evaluation method. In the tensile strength evaluation, PLA + SS was the highest, ABS + W was the lowest, and ABS + W is 3.13 g/cm³ which value was the highest among the composite filaments in the density evaluation. As a result of the XRD, it may be confirmed that the XRD peak pattern of the particles on the surface of the specimen coincides with the pattern of each particle reinforcing material powder metal, and thus it was confirmed that the printed specimen contained powder metal. The shielding effect for each 3D printed composite filament was found to have a high shielding rate in proportion to the effective atomic number and density in the order of ABS + W, ABS + Bi, PLA+SS, PLA + Cu, and PLA + Al. In this study, it was confirmed that the metal particle composite filament containing metal powder as a reinforcing material has radiation shielding ability, and the possibility of using a radiation shielding filament in the future.

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.2
• /
• pp.108-118
• /
• 2009

Statement of problem: Volume stability, microstructure reproducibility and fluidity along with compatibility with dental stone must be in consideration in order to use tissue conditioner as a material for functional impression. There are few studies concerning the influence of time factor in oral condition on surface roughness of the stone and optimal retention period in the oral cavity considering such changes in surface roughness. Purpose: The purpose of this study was to find out the influence of various kinds of tissue conditioner, its powder/liquid ratio and immersion time on surface roughness of the stone. Material and methods: Materials used in this study were the three kinds of tissue conditioners(Coe-Comfort, Visco-Gel, Soft-Liner) and were grouped into three: group R-mixed with standard powder/liquid ratio that was recommended by the manufacturers, group M-mixed with 20% more powder, group L-mixed with 20% less powder. Specimens were made with the size of 20 mm diameter and 2 mm width. Each tissue conditioner specimens were subdivided into 5 groups according to the immersion time(0 hour, 1 day, 3 days, 5 days, 7 days), completely immersed into artificial saliva and were stored under $37^{\circ}C$. Specimens of which the given immersion time elapsed were taken out and were poured with improved stone, making the stone specimens. Surface roughness of the stone specimens was measured by a profilometer. Results: Within the limitation of this study, the following results were drawn. 1. Major influencing factor on surface roughness of the stone model made from tissue conditioner was the retention period(contribution ratio($\rho$)=62.86%, P<.05) of the tissue conditioner in oral cavity to make functional impression. 2. In case of Coe-Comfort, higher mean surface roughness value of the stone model with statistical significance was observed compared to that of Soft-Liner and Visco-Gel as immersion time changes(P<.05). 3. In case of group L(less), higher mean surface roughness value of the stone model with statistical significance was observed compared to that of R(recommended) and M(more) group as immersion time changes(P<.05). Conclusion: We may conclude that as the retention period of time in oral cavity influences surface roughness of the stone model the most and as the kind of tissue conditioner and its P/L ratio may influence also, clinician should well understand the optimal retention period in oral cavity and choose the right tissue conditioner for the functional impression, thus making the functional impression with tissue conditioner usefully.

• Applied Microscopy
• /
• v.33 no.3
• /
• pp.195-204
• /
• 2003

The Experimental calibration method has been investigated to correct d-spacing estimation and to identify phases in the electron diffraction data acquired by imaging plates. When the diffraction data from the imaging plate was corrected by the d-spacing calibration method with the radial intensity distribution plotting in this experiment, The accuracy of d-spacing estimation was significantly increased in errors of about 0.5%. The experimental calibration equation followed up the first order exponential decay function was derived from the trace of d-spacing deviation between the measured and the calculated values. It was applied to the analysis of d-spacing and the phase identification of the transitional phases formed from [001] gibbsite specimen by electron beam irradiation effect. In this case more accurate phase identification and d-spacing evaluation is possible for the transitional phases whose diffraction patterns are complicatedly superimposed. It is concluded that ${\chi}$-alumina, ${\gamma}$-alumina and ${\sigma}$-alumina are clearly identified as the major transitional phases formed from gibbsite by electron beam irradiation for 120 min.

• Fire Science and Engineering
• /
• v.32 no.2
• /
• pp.1-6
• /
• 2018

The combustion characteristics of cypress wood coated with boric acid (BA) and ammonium pentaborate (APB) were examined using a cone calorimeter according to the ISO 5660-1 standard. As a result, the combined specimens of boric acid and ammonium pentaborate (BA/APB) led to an improved fire performance index due to their synergistic effect. In addition, the total heat release values of the specimen coated with the boron compounds were 6.1~14.1% lower than that of the base specimen. The total smoke release rate (TSR) of the specimens coated with the boron compound decreased throughout the combustion process, except for BA/APB. The maximum concentration of carbon monoxide was reduced by 15.8~25.5%. In general, wood treated with flame retardants has a lower fire hazard.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.692-697
• /
• 2005

A canard type aircraft, which has good wing stall and stall/spin proof characteristics, is being developed. The previous first and second prototypes, having full depth core sandwich type wing and fixed landing gear, was built for test flights. Newly developing Firefly will be equipped with retractable landing gear and conventional foam core sandwich laminate for wing and fuselage. For manufacturing, composite material process has been studied including coupon tests. Wet lay-up onto foam core with glass fabric using lay-up mold has been chosen, and composite material parts are cured under room temperature and atmospheric pressure condition. In general, molded parts show so good surface smoothness and standardized quality that are best in mass production. In this study, we present the mold technology and development status for small aircraft firefly.

• Korean Journal of Materials Research
• /
• v.7 no.10
• /
• pp.856-862
• /
• 1997

박막형 CdTe/CdS 태양전지의 배면전극(back contacts)물질로서 Cu도핑된 ZnTe 박막(ZnTe:Cu)을 전착법(electroplating)으로 제조하는 연구를 수행하였다. Sulfate계의 전해질 수용액에서 CdTe 기판과 투명전극으로 코팅된 유리(In$_{2}$O$_{3}$: Sn, ITO)기판 위에 ZnTe 박막을 코팅하는 방법으로써 potentiostat와 기판(cathode), Pt counter electrode, Ag/AgCI 표준전극으로 구성된 장치를 사용하여 pH=2.5-4, T=70-8$0^{\circ}C$, 0.02M $Zn^{2+}$ 1x$10^{-4}$M TeO$_{2}$, 0.2M $K_{2}$SO$_{4}$조건에서 -0.800 Vs~-0.975 V 범위의 전압(V$_{a}$ )에 걸쳐 실험하였다. ITO박막을 기판으로 사용하여 cyclic voltammogram을 작성한 결과 약 -0.50 V 에서 Te환원 peak이 나타났다. Auger electron spectroscopy (AES)로 조성분석한 결과 표면에서 Zn signal이 강하게 나왔고 시편의 두께에 따라 Zn의 signal감소하는 반면 Cd signal은 증가하는 것이 확인되었다. SEM 사진으로부터 ZnTe의 표면이 작은 입자 (0.2$\mu\textrm{m}$ 이하)로 구성되어 있으며 낮은 V$_{a}$ 에서는 입자가 작아지면서 조직이 치밀해짐이 관찰되었다. Optical transmission방법에 의하여 ITO기판위에 입혀진 박막의 밴드갭은 2.5 eV으로 측정되었다. 수용액중의 Cu$_{2+}$와 triethanolamine(TEA)은 산성용액에서 착물형성이 이루어지지 않았으며 1,10-phenanthroline과는 pH=2에서도 착물이 형성되었다.

• Tunnel and Underground Space
• /
• v.26 no.4
• /
• pp.316-326
• /
• 2016

The purpose of this study is to investigate the influence of cleavages on indirect tensile strength (ITS) of the granite. Brazilian disc tests and ring tests with three different hole sizes were performed. 2D DEM (Discrete Element Method) simulation was employed to further understand the failure process during the tests and the mechanism behind. Results show that ITS decreases across hardway, grain and rift cleavage. Measured average ITS from ring tests is about 2.5 ~ 6.4 times of those measured from Brazilian disc tests, and it decreases with increasing ratio of diameters of inner hole and specimen. Failure pattern in ring tests is influenced by both hole size and relative positions of cleavages parallel and perpendicular to the loading direction.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.16 no.1
• /
• pp.29-33
• /
• 1996

The eddy current test(ECT) probe of differential encircling coil type was designed and fabricated, and the optimum condition of ECT was derived for the examination of the irradiated fuel rod. The correlation between ECT test frequency and phase & amplitude was derived by performing the test of the standard rig that includes inner notches, outer notches and through-holes. The defect of through-hole was predicted by ECT at the G33-N2 fuel rod irradiated in the Kori-1 nuclear power reactor. The metallographic examination on the G33-N2 fuel rod was Performed at the defect location predicted by ECT. The result of metallographic examination for the G33-N2 fuel rod was in good agreement with that of ECT. This proves that the evaluation for integrity of irradiated fuel rod by ECT is reliable.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.4
• /
• pp.331-337
• /
• 2009

Space launch vehicles require highly reliable, lightweight structures. It is thus important to monitor the structural health of these components with nondestructive inspections. In this paper, we studied an example of a nondestructive inspection that was partially applied to the manufacture and inspection of a launch vehicle. Ultrasonic tests, X-rays, tapping, and acoustic emissions comprised the inspection method. A payload fairing, high pressure tank, fastener part, and bonding part were used as hardware to be inspected. We proposed a quantitative standard for debonding inspection of the payload fairing and acoustic emission data for the proof test of the high pressure tank. We analyzed the fracture mode of the sandwich fastener part according to frequency changes. We also proposed a standard specimen for ultrasonic inspection of bonds of different materials. The present analyses and results provide data for evaluation of the launch operation sequence to ensure launch vehicles afford high reliability.