• 한국터널지하공간학회 논문집
• /
• 제24권6호
• /
• pp.553-581
• /
• 2022

TBM (Tunnel Boring Machine)이 터널 산업에 도입된 이후로 안전성과 친환경의 이점으로 TBM의 사용이 전 세계적으로 증가하였다. 암반 및 토사 지반을 굴착하는 TBM 터널에서의 주요 비용 중 하나는 손상되거나 마모된 커터의 교체로 볼 수 있다. 커터의 교체는 시간과 비용에 큰 영향을 끼치는 작업이며 TBM 가동률과 굴진율을 크게 감소시킬 수 있다. 따라서 커터의 수명을 정확하게 평가하는 것은 공기와 비용의 측면에서 매우 중요하다. 그러나 복합 지반을 포함하여 토사 구간, 암반구간에서 커터 마모에 대한 예측은 매우 복잡하고 명확하지 않다. 이에 따라 커터 마모에 대한 다양한 예측 모델이 개발 및 도입되었지만 이러한 불확실성으로 인해 가변적인 결과를 나타낸다. 본 연구에서는 커터 마모 예측 모델을 제시하기 보다는 커터 교체의 설계 및 시공 사례 연구를 소개하고 분석했다. 커터는 지반 조건, TBM 장비 및 운전의 영향을 많이 받으므로 불확실성과 한계를 감안하면 신뢰성 있는 예측 모델을 제안하는 것은 매우 어렵기 때문에 오히려 실제 사례를 분석하고 이에 대한 자료 공유가 더 실용적이다. 커터 교체에 대한 예측과 결과 간의 차이를 확인하고 심도 있게 분석하였다.

• 대한기계학회논문집A
• /
• 제26권5호
• /
• pp.924-931
• /
• 2002

Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• 대한기계학회논문집A
• /
• 제26권5호
• /
• pp.939-951
• /
• 2002

We propose a new multiscale Galerkin method based on interpolation wavelets for two-dimensional Poisson's and plane elasticity problems. The major contributions of the present work are: 1) full multiresolution numerical analysis is carried out, 2) general boundaries are handled by a fictitious domain method without using a penalty term or the Lagrange multiplier, 3) no special integration rule is necessary unlike in the (bi-)orthogonal wavelet-based methods, and 4) an efficient adaptive scheme is easy to incorporate. Several benchmark-type problems are considered to show the effectiveness and the potentials of the present approach. is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• 한국수산과학회지
• /
• 제43권6호
• /
• pp.642-647
• /
• 2010

This study examined the antimicrobial activity of Myagropsis yendoi (MY). The antimicrobial activity of ethanol and aqueous MY extracts were measured using a paper disc assay. The MY ethanol extract had the best antimicrobial activity. It inhibited the growth of Candida tropicalis and Gram-positive bacteria such as Bacillus subtilis, Listeria innocua, L. monocytogenes, and Staphylococcus aureus at 4 mg/mL. The minimum inhibitory concentration (MIC) of the MY ethanol extract ranged from 0.1 to 0.5%. The MY ethanol extract inhibited the growth of B. subtilis and L. innocuaat concentrations of 0.15% and 0.1%, respectively. The antimicrobial activity of the MY ethanol extract was not affected by heating at $121^{\circ}C$ for 15 min or pH 2.10. Therefore, the main substances responsible for the antimicrobial activity of the MY ethanol extract are believed to be stable with changing heat and pH.

• 한국철도학회논문집
• /
• 제17권4호
• /
• pp.223-227
• /
• 2014

제동 패드는 철도차량의 기초제동요소 중 하나이다. 제동 패드는 제동 캘리퍼로부터 압부력을 전달받아 제동디스크와의 마찰력으로 철도차량에 제동작용을 한다. 따라서 제동 패드는 주어진 고압의 압부력을 견뎌야 하므로 제동 패드의 주요 성능평가항목으로 압축강도를 관리한다. 압축강도를 측정하는 규격은 KRS, KRCS, KRT 등이 있다. 이들 규격은 압축강도를 측정하기 위한 시험편의 크기를 $20mm{\times}10mm{\times}15mm$ (가로${\times}$세로${\times}$높이)로 규정하고 있다. 압축강도에 대한 불확도를 줄이기 위하여 불확도 요인을 분석한 결과, 단면의 치수를 변경함으로써 불확도를 줄일 수 있음을 알았다. 새로운 단면치수에 의한 불확도를 평가하여 불확도 감소에 대한 유효성을 입증하였다.

• The Journal of Advanced Prosthodontics
• /
• 제5권2호
• /
• pp.75-83
• /
• 2013

PURPOSE. Maxillofacial silicone elastomer is usually colored intrinsically with color pigments to match skin colors. The purpose of this study was to investigate the color stability of a maxillofacial silicone elastomer, colored with a thermochromic, color changing pigment. MATERIALS AND METHODS. Disc-shaped maxillofacial silicone specimens were prepared and divided into 3 groups: a conventionally colored control group, one group additionally colored with 0.2 wt% thermochromic pigment, and one group with 0.6 wt% thermochromic pigment. Half of the surface of each specimen was covered with an aluminium foil. All of the specimens were exposed to UV radiation in 6 hour cycles over 46 days. In between the UV exposures, half of the specimens were stored in darkness, at room temperature, and the other half was stored in an incubator, at a humidity of 97% and a temperature of $+37^{\circ}C$. Color measurements were made with a spectrophotometer and registered according to the CIELAB $L^*a^*b^*$ color model system. The changes in $L^*$, $a^*$ and $b^*$ values during artificial aging were statistically analyzed by using paired samples t-test and repeated measures ANOVA. P-values <.05 were considered as statistically significant. RESULTS. The UV exposure resulted in visually noticeable and statistically significant color changes in the $L^*$, $a^*$ and $b^*$ values in both of the test groups containing thermochromic pigment. Storage in the incubator lead to statistically significant color changes in the $a^*$ and $b^*$ values of the specimens containing thermochromic pigment, compared to those stored at room temperature. CONCLUSION. The specimens containing thermochromic pigment were very sensitive to UV radiation, and the thermochromic pigment is not suitable, as such, to be used in maxillofacial prostheses.

• 복식문화연구
• /
• 제19권1호
• /
• pp.176-190
• /
• 2011

Today's young generation in digital era has a rich education environment and convenient life, on the other hand, there was negative impact on growth as normal body type because of adverse impact on an excessive study and insufficient exercise, etc. Also, for these people in IT culture generation, using small mobile including computer for long time is becoming main issue as changing factor in posture and body type in terms of spine like their neck disc. This body-typed characteristic reaches to normal adult body type in the process of physical development of adult woman and has least modification in body type. Therefore, despite of early young generation, body suitability of upper body clothes might caused imbalance. So, for intended to early 20s women, to design clothes with consideration on imbalance of body type by bended and curved spine, body type studies about size of upper body and forms are needed. As this researcher measured the body type of early 20s college women in metropolitan area, changes in body type of young generation with use of digital equipment recently were recognized since straight body type was decreased unequally and had characteristic in terms of changes to be bended body type. The changes of these body type should be considered to make clothes. Also, since there are some restrictions on this research objects in terms of local and numbers of measured objects, a broad interpretation of result on this research should be really careful.

• Nuclear Engineering and Technology
• /
• 제55권7호
• /
• pp.2662-2669
• /
• 2023

For the precise measurements of special nuclear materials (SNM) including Pu and Am isotopes, we have used phoswich detector combination of two single crystal scintillators of Gd₃Ga₃Al₂O₁₂:Ce and CsI:Tl. High detection efficiency and sensitivity along with high figure of merit for the discrimination of these phoswich detectors ensures the detection and discrimination of thermal neutrons and gammas from spontaneous fission of Pu and other isotopes in presence of high gamma background. Using this detector, the low energy gammas, which is stopped completely in 1mm thick disc of GGAG, can be also discriminated from high energies gamma and shows linearity in wide range of sample quantities. By changing only the appropriate shielding, the similar setup was used for thermal neutron detection and shows a very good linearity over wide range. The quantity of a test sample was also calculated accurately by using the measured calibrated plot.

• 한국터널지하공간학회 논문집
• /
• 제23권4호
• /
• pp.233-252
• /
• 2021

본논문은 쉴드 TBM 챔버(Chamber) 내 배토처리 효율성 향상을 위한 연구이다. 현재 국내에서는 TBM 공법을 이용한 시공사례가 증가하는 추세이다. TBM 공법 사용의 증가에 따른 디스크 커터(Disc Cutter), 커터 비트(Cutter bit) 및 세그먼트와 같은 TBM 공법의 연구 또한 증가하는 추세를 보인다. 하지만 챔버와 챔버 내 교반 성능에 대한 연구는 미비한 실정이다. 원활한 배토처리와 굴착토의 거동을 개선하기 위하여 챔버 내 효과적인 믹싱 바 배치에 따른 교반 효율 변화에 대한 연구를 수행하였다. 축소모형 실험은 식별의 용이성을 위하여 색이 다른 플라스틱 소재를 사용하여 지반을 조성하였다. 또한 믹싱 바 배치를 상이하게 하여 4가지 Case로 분류하였으며, 입도분포를 단입도와 다입도로 분류하여 총 8가지의 Case로 실험을 진행하였다. 모든 Case의 커터헤드의 회전속도는 5 RPM으로 동일하며, 실험시간 또한 동일한 조건인 1분 30초로 진행하였다. 교반 효율을 확인하기 위하여 각 Case별 상부, 중부(좌 or 우), 하부 위치의 시료를 채취하여 분석하였다. 축소모형실험 결과 실제 사용되는 Case 1과 Case 1-1보다 새로운 배치방법인 Case 4와 Case 4-1의 교반 효율이 증가하는 양상을 보인다. 그에 따라 챔버 내 믹싱 바 배치를 변경하여 교반 효율을 증가시킬 수 있을 것으로 보이며, 교반 효율증가에 따라 공기 절약에 효과적일 것으로 판단된다. 따라서 본 연구는 국내 쉴드 TBM 공법 활용에 있어 큰 지표로써 작용할 것으로 보인다.

• Journal of Korean Neurosurgical Society
• /
• 제30권4호
• /
• pp.451-455
• /
• 2001

Objectives : There have been several studies documenting the changing level of the conus throughout infancy and childhood, but there is only a little detailed study that documents the range of conus positions in a living adult population, especially in Korean, without spinal deformity. Methods : we made a sequential study of magnetic resonance images of the lumbar spine to determine the variation in position of the conus medullaris in 650 living korean adults population without spinal deformity who checked MRI to identify the cause of low back pain. The study population consisted of patients over the age of 16 years. A T1-weighted, midline, sagittal image was reviewed for identifying the postion of conus. This location was recorded in relation to the upper, middle, or lower third of the adjacent vertebral body or the adjacent intervertebral disc. Results : The study group consisted of 305 men(47%) and 345 women(53%) with a mean age 45.9 years(range, 16-79 years). The conus existed commonly at the middle third of L1(131cases, 20.2%), at the L1-2 intervertebral space(129cases, 19.8%), and the lower third of L1(123cases, 18.9%). The mean position of conus was the lower third of L1(range, middle third of T12 to middle third of L3). Conclusions : The mean position of conus was at the lower third of L1(range, middle third of T12 to middle third of L3). This results was same as that of foreign study. Our results of living korean adult population could allow for safe clinical procedures such as lumbar puncture, spinal anesthesia, and help to explain the differences among observed neurologic injuries from fracture-dislocation at the thoracolumbar junction.