• 한국산림과학회지
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• 제111권2호
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• pp.287-301
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• 2022

본 연구는 기계화 목재 생산 작업에 가장 많이 활용되는 크레인 작업의 효율성을 높이기 위하여 엔드이펙터를 직관적으로 수직 또는 수평 제어할 수 있는 크레인 팁 제어방법을 제안하고 제어성능을 확인하기 위해 수행되었다. 실험 변수에 따른 제어성능을 검증하고자 전동실린더를 이용하여 실험실 규모의 크레인을 제작하고, 크레인에 대한 순기구학/역기구학 분석을 통하여 현재 크레인 팁의 위치좌표와 각 목표점에서의 조인트 각도를 출력할 수 있도록 구성하였다. 경로점을 생성하여 제어하는 방법을 이용하였고, LBO(Lateral Boundary Offset)을 이용한 불감대 영역을 설정하도록 하였다. 뱅뱅제어(Bang-bang control)을 이용하여 적정 파라미터를 선정하였고, 경로점의 개수와 LBO 반경은 평균오차와 관계가 있었으며, 실린더의 속도는 소요시간과 관계가 있는 것으로 확인되었다. 경로점의 개수가 증가, LBO 반경이 감소함에 따라 평균오차는 감소하였고, 실린더의 속도가 감소함에 따라 소요시간은 감소하였다. 비례제어를 이용하여 실린더의 속도가 매 제어주기마다 변경될 때에는 소요시간은 큰 폭으로 감소하였지만 실제 제어의 형상은 큰 범위에서 오버슈트와 언더슈트를 반복하며 제어가 이루어졌다. 따라서, 추가적으로 각각의 실린더의 속도를 상대적으로 변경할 수 있는 속도 게인을 적용하여 비례제어를 수행하였고, 10 mm 이내의 범위에서 제어가 이루어짐에 따라 20 ms의 제어주기에서 속도 게인이 적용된 비례제어만을 이용하여 크레인 팁 제어가 가능한 것으로 검증되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.64-64
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• 2009

Atomic force microscopy (AFM) fabrication of oxide patterns is an attractive technique for nanoscale patterns and related device structures, SiC exhibits good performance in high-power, high-frequency, and high-temperature conditions that is comparable to the performance of Si. The AFM fabrication of oxide patterns on SiC is important for electronic applications. However, there has not been much reported investigations on oxidation of SiC using AFM. We achieved the local oxidation of 4H-SiC using the high loading force of ~100 nN, although the oxidation of SiC is generally difficult mainly due to the physical hardness and chemical inactivity. All the experiments were performed using atomic force microscopy (S.I.S. GmbH, Germany) with a Pt/Ir-coated Si tip at ~40% humidity and room temperature. The spring constant and resonance frequency of the tip were around ~3 N/m and ~70 kHz. We fabricated oxide patterns on n-type 4H-SiC ($\sim10^{19}/cm^3$) and n-type Si ($\sim1.9\times10^{16}/cm^3$). In summary, we demonstrated that the oxide patterns can be obtained over the electric field of ${\sim}\times10^7 V/cm$ and the high loading force using the tip as a cathode. The electric field transports the oxyanions (OH-) to the positively biased surface.

• Journal of Korean Neurosurgical Society
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• 제59권6호
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• pp.559-563
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• 2016

Objective : Low back pain, caused intervertebral disc degeneration has been treated by thermal annuloplasty procedure, which is a non-surgical treatement. The theoretical backgrounds of the annuloplasty are thermal destruct of nociceptor and denaturization of collagen fiber to induce contraction, to shrink annulus and thus enhancing stability. This study is about temperature and its distribution during thermal annuloplasty using 1414 nm Nd : YAG laser. Methods : Thermal annuloplasty was performed on fresh human cadaveric lumbar spine with 20 intact intervertebral discs in a $37^{\circ}C$ circulating water bath using newly developed 1414 nm Nd : YAG laser. Five thermocouples were attached to different locations on the disc, and at the same time, temperature during annuloplasty was measured and analyzed. Results : Thermal probe's temperature was higher in locations closer to laser fiber tip and on lateral locations, rather than the in depth locations. In accordance with the laser fiber tip and the depth, temperatures above $45.0^{\circ}C$ was measured in 3.0 mm depth which trigger nociceptive ablation in 16 levels (80%), in accordance with the laser fiber end tip and laterality, every measurement had above $45.0^{\circ}C$, and also was measured temperature over $60.0^{\circ}C$, which can trigger collagen denaturation at 16 levels (80%). Conclusion : When thermal annuloplasty is needed in a selective lesion, annuloplasty using a 1414 nm Nd : YAG laser can be one of the treatment options.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.128.1-128.1
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• 2013

We investigated the correlation between electrical transport and mechanical stress in $Bi_2Te_2Se$ by using a conductive probe atomic force microscopy in an ultra-high vacuum environment. Uniform distribution of measured friction and current were observed over a single quintuple layer terrace, which is an indication of the uniform chemical composition of the surface. By measuring the charge transport of $Bi_2Te_2Se$ surface as a function of the load applied by a tip to the sample, we found that the current density varies with applied load. The variation of current density was explained in light of the combined effect of the changes in the in-plane conductance and spin-orbit coupling that were theoretically predicted. We suppose that the local density of states is modified by tip-induced strain, but topological phase still remains. We exposed a clean topological insulator surface by tip-induced indentation. The surface conductance on the indented $Bi_2Te_2Se$ surface was studied, and the role of surface oxide on the surface conductance is discussed.

• 한국IT서비스학회지
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• 제12권3호
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• pp.111-126
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• 2013

As the gaps become narrower in interconnection fee and volume rate, the MNOs began to introduce flat pricing for unlimited voice traffic competitively in Korea wireless telecommunication market : 'unlimited talks within intra-network' by the 1st operator, followed by the 3rd operator's 'unlimited talks over all networks'. As a result, subscribers tip in toward the third ranked operator and could bring a substantial change to steadfast market structure over the last decade in Korea. This paper aims to develop a simple economic model to analyze competition with flat pricing for unlimited voice traffic, and to check whether the pricing can be appropriate for the MNOs. The results show that MNOs already step in the necessary conditions to launch flat pricing for voice traffic. It also predicts that the MNOs compete with unlimited talk over all networks and set a single fee in an equilibrium. At present, the MNOs run virtually identical pricing for unlimited talk over all networks, considering their differentiation with respect to service quality, coverage and brand preference.

• 마이크로전자및패키징학회지
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• 제24권3호
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• pp.77-81
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• 2017

Pulse electroplating of Ni-P alloy was studied to fulfill the material requirement to the advanced vertical probe tip in wafer probe card. The major concerns are for the electrical conductivity and yield strength. Plating parameters such as current density, duty cycle and solution components were examined to obtain the nanocrystal structure and proper percentage of phosphorus, leading to how to control the nanocrystal grain growth and precipitation of $Ni_3P$ after heat treatment. Among the parameters, the amount of phosphorus acid was the main factor affecting on the grain size and sheet resistance, and the amount of 0.1 gram was appropriate. Since hardness in Ni-P alloy is increased by as-plated nanocrystal structure plus precipitation of $Ni_3P$, the concentration of P less than 15 at% was better choice for the grain coarsening without minus in hardness value. The following heat treatment made grain growth and dispersion of precipitates adjustable to meet the target limit of resistance of $100m{\Omega}$ and hardness number of over 1000Hv. The Ni-P alloy will be a candidate for the substitute of the conventional probe tip material.

• 대한기계학회논문집A
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• 제24권1호
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• pp.69-78
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• 2000

The one-parameter singular expression for stresses and displacements near a crack tip has been widely thought to be sufficiently accurate over a reasonable re ion for any geometry and loading conditions. In many cases, however subsequent terms of the series expansion are quantitatively significant, and so we now consider the evaluation of such terms and their effect on the predicted crack growth direction. For this purpose the problem of a cracked orthotropic plate subjected to a biaxial load is analysed. It is assumed that the material is ideal homogeneous anisotropic. BY considering the effect of the load applied parallel to the plane of the crack, the distribution of stresses and displacements at the crack tip is reanalyzed. In order to determine values for the angle of initial crack extension we employ the normal stress ratio criterion.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.191-197
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• 1998

The recent results of the engine development performed in this you on Turbogreen 1200, the first industrial gas turbine engine developed in Korea, are presented. In order to improve the engine performance and structural stability from the first prototype engine, several variants of the engine and major components such as combustor and rotor assembly have been developed and tested. This paper shows these results especially focused on the engine test and performance analysis, in which test system, instrumentation and data processing are discussed as well. The engine performance and its trend give relatively good coincidence with the design ones. At design power of 1.2MW, the thermal efficiency of the engine is estimated over $25\%$ which is below the design target of $27.2\%$. This gap of efficiency is caused mainly by large tip clearance between turbine blades and casing. Considering high design efficiency superior to those of other competitive engines in this power class, Turbogreen 1200 would have a strong competition in its performance if the design efficiency is achieved by further developments such as tip clearance control, which are very possible and natural in final mass production of the developed gas turbine engine.

• The Plant Pathology Journal
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• 제24권2호
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• pp.112-117
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• 2008

Pre-infection behavior of Fusarium circinatum on stems of pine species was investigated with scanning electron microscopy. Two-year-old stems of Pinus densiflora and p. rigida were inoculated with the fungal conidial suspension and subjected to $25^{\circ}C$ for up to 16 hr. Most microconidia germinated 12 hr after inoculation on pine stems. Conidia produced germ tubes from either one or both ends of microconidia. Germ tubes grew over the stem surface and appeared to enter host tissues through natural openings on pine stems. Surface cracks in the cork were entrance sites of germ tubes of F. circinatum. In addition, host cell wall cracks were often found at the tip of germ tubes. The cuticle appeared to be eroded either at the tip of germ tubes or around germlings. Germ tubes also produced appressoria-like structures, exhibiting swollen tips of germ tubes on the stem surface. There seems to be no significant differences in the pre-infection behavior of F. circinatum on stems between the two pine species.

• Structural Engineering and Mechanics
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• 제65권6호
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• pp.699-706
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• 2018

In the present contribution, fracture resistance of U-notched GPPS members under mixed mode I/III loading conditions is assessed by using the Averaged Strain Energy Density (ASED) criterion. This criterion has been founded based on the ASED parameter averaged over a well-defined control volume embracing the notch edge. The validation of the theoretical criterion predictions is evaluated through comparing with the results of a series of mixed mode I/III fracture tests conducted on rectangular-shaped GPPS specimens weakened by a single edge U-notch. A recently developed apparatus for mixed mode I/III fracture experiments is employed for measuring the fracture loads of the specimens. The test samples are fabricated with different notch tip radii with the aim of evaluating the influence of this major feature of the U-notched components on the mixed mode I/III fracture behavior. It is shown that the onset of brittle fracture in U-notched GPPS specimens under various combinations of tension and out-of-plane shear can well be predicted by means of the ASED criterion.