• 한국지반환경공학회 논문집
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• 제12권1호
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• pp.51-60
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• 2011

전기비저항은 지층의 자세한 이해와 지반의 기본 물성치 획득을 위하여 다양한 측정 장비에 적용되고 있다. 본 연구의 목적은 프로브가 관입되는 동안 온도가 전기비저항에 미치는 영향을 상쇄시켜 보다 정밀한 전기비저항을 평가할 수 있는 온도보상형 전기비저항 프로브(TRP)를 개발하고 적용하는 것이다. 전기비저항 콘의 직경에 따른 온도변화를 분석하기 위하여 두가지 직경(2mm, 5mm)의 콘을 제작하였다. 온도 센서는 전기비저항 프로브와의 전기적 간섭현상을 고려하여 선단부에서 15mm 떨어진 곳에 부착하였다. 또한 모터식 관입기와 전기비저항 프로브 사이의 전기적 교란을 막기 위하여 절연 커넥터를 이용하였다. 직경 30cm의 아크릴 수조에 주문진사를 수중강사법으로 시료를 조성하고 타격에 의해 상대밀도를 증가시키면서 실험을 진행하였다. 실험결과, 관입되는 동안 프로브의 온도가 증가하였으며, 정확한 전기비저항 프로파일을 산정하기 위하여 온도보정이 필요한 것으로 나타났다. 본 연구에서는 온도보상형 전기비저항 프로브(TRP)를 개발하고, 이를 관입실험에 적용하여 정확한 지반조사를 수행하기 위해서는 온도에 대한 영향 및 관입특성을 고려해야 함을 보여준다.

• 대한토목학회논문집
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• 제29권4C호
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• pp.163-174
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• 2009

온도 변화에 의하여 로드셀이나 스트레인 게이지의 결과값이 변하기 때문에 로드셀이나 전기저항식 변형율계를 이용하는 기계적 장치는 주변 온도의 변화에 의하여 영향을 받는다. 본 연구에서는 기존의 전기저항식 변형율계 타입의 콘이 가지는 문제점과 한계를 극복하고 관입과 동시에 연속적으로 온도보상이 가능한 직경 1~7mm의 초소형 광섬유 마이크로콘을 개발하였다. 광섬유는 머리카락 굵기의 작은 직경을 가지고 있어 원하는 크기의 센서를 구성할 수 있고 전기적 신호인 전압을 측정하는 것이 아니라 빛의 파장변화를 감지하여 변형율로 변환하게 되므로 주변 조건에 의한 간섭 영향이 거의 없다. 개발된 콘의 온도보상 효과를 검증하기 위해 외력이 없는 상태에서 콘 주변의 온도를 변화시키는 온도시험을 실시하였다. 주변 온도에 따라 측정전압이 변화되는 전기저항식 변형률계 콘과는 달리 광섬유 센서를 적용한 콘은 일정한 값을 유지하는 것으로 나타났으며 관입과 동시에 지중의 온도변화를 연속적으로 확인할 수 있었다. 또한, 다층지반 콘관입시험에서는 관입되는 동안 교란영역이 적고 분해능이 뛰어나 선단지지력의 변화만으로도 다층지반의 경계를 명확하게 탐지할 수 있는 것으로 분석되었다. 본 연구에서는 광섬유 센서를 이용한 초소형 마이크로콘으로 다층지반을 효과적으로 탐지할 수 있으며 지중의 온도 영향이 고려된 순수한 선단저항력을 획득할 수 있음을 보여준다.

• 대한기계학회논문집B
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• 제21권9호
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• pp.1105-1114
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• 1997

The heat transfer characteristics of free surface water jet impinging normally against a flat uniform heat flux surface were investigated. This deals with the effect of three nozzle configurations (Cone type, Reverse cone type, Vertical circular type) on the local and the average heat transfer. Heat transfer measurements were made for water jet issuing from a nozzle of which exit diameter 8 mm. The experimental conditions investigated are Reynolds number range of 27000 ~ 70000( $V_{O}$=3 ~ 8 m/s), nozzle-to-target plate distances H/D=2 ~ 10, and radial distance from the stagnation point r/D ~ = 0 ~ 7.42. For all jet velocities of H/D=2, the local Nusselt number decreased monotonically with increasing radial distance. However, for H/D from 4 to 10, and for the jet velocity $V_{O}$.geq.7 m/s for Cone type nozzle and $V_{O}$.geq.6 m/s for the other type nozzles, the Nusselt number distributions exhibited secondary peaks at r/D=3 ~ 3.5. For Reverse cone type nozzle and Vertical circular nozzle, the maximum stagnation point heat transfer and the maximum average heat transfer occurs at H/D=8. But for the Cone type nozzle, the maximum stagnation and average heat transfer occurs at H/D=10, 4, respectively. From the optimum nozzle-to-target plate distance, the stagnation and the average heat transfer reveal the following ranking: Reverse cone type nozzle, Vertical circular type nozzle, Cone type nozzle.ozzle.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.213-217
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• 2004

Laboratory scale study for an area of influence and flowing aspect of groundwater saturated zone was conducted for three sediment grains. On the AMG(Average Modal diameter Grains) 0.34, 1.38, 3.89mm diameter samples, the affected area of the aquifer were 15.2, 37.0, 30.0%/m2 each. Air flow for AMG 0.34mm diameter grain size provides indication of pattern of channelized air flow in saturated zone and expansion state in above saturated zone. For AMG of 1.38, 3.89mm diameter grains, air flow are pervasive air flow, forming a symmetrical cone of influence around the injection point. And also AMG 1.38, 3.89mm diameter samples show onset of collapse and approach to steady state in above saturated zone, respectively. In this study, optimal sites for in situ air sparging, may be grain diameters between about AMC 1.5～2.5mm diameter.

• 한국분무공학회지
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• 제6권2호
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• pp.16-21
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• 2001

This paper describes the macroscopic behavior and atomization characteristics of the high-pressure gasoline swirl injector in direct-injection gasoline engine. The global spray behavior of fuel injector was visualized by shadowgraph technique. The atomization characteristics of gasoline spray such as mean diameter and mean velocity of droplets were measured by the phase Doppler particle analyzer system. The macroscopic visualization and experiment of particle measurement on the fuel spray were investigated at 7 and 10 MPa of injection pressure under different spray cone angle. The results of this work show that the geometry of injector was more dominant over the macroscopic characteristics of spray than the fuel injection pressure and injection duration. As for the atomization characteristics, the increase of injection pressure resulted in the decrease of fuel droplet diameter and the atomization characteristics differed as to the spray cone angle. The most droplets had under $25{\mu}m$ diameter and for the large droplets(upper $40{\mu}m$) as the spray grew the atomization presses were very slow. Comparison results between the measured droplet distribution and the droplet distribution functions revealed that the measured droplet distribution is very closed to the Normal distribution function and Nukiyama-Tanasawa's function.

• 한국군사과학기술학회지
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• 제19권5호
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• pp.638-644
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• 2016

In this research, theoretical study on empirical analysis method to estimate waterdrop's deformation by shock wave is presented. Flow field is calculated using theoretical and empirical relations. Waterdrop's deformation including movement, size, mass, and orientation is modeled using empirical relations derived from existing experimental data. Developed method is applied to specific flight examples with arbitrary flight speed and vehicle's configuration. The flight speed is assumed to Mach number of 2 and 4. The diameter of waterdrop is varied from 1 to 5 mm. Waterdrops along the stagnation line in front of hemispherical nose with the radius of 50 mm and around a cone-shaped side wall with the half angle of 20 degree are considered. It is found that the maximum diameter of the waterdrop is increased up to 2.77 times the initial diameter. The mass is conserved more than 66.7 %. In the case of a cone-shaped side wall, waterdrop's orientation angles defined from the flight direction when the Mach number is 2 and 4 are calculated as 33.0 and 25.6 degree, respectively.

• Mass Spectrometry Letters
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• 제7권1호
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• pp.21-25
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• 2016

Dual-channel nano-electrospray has recently become an ionization technique of great promise especially in biological mass spectrometry. This unique approach takes advantage of the mixing processes that occurs during electrospray. Understanding in more detail the fundamental principles influencing spray formation further study of the origins of the mixing processes: (1) in a Taylor cone region, (2) in charged droplets or (3) in both environments. The dual-channel emitters were made from borosilicate theta-shape glass tubes (O.D. 1.2 mm) and had a tip diameters of less than 4 μm. Electrical contact was achived by deposition of a thin film of an appropriate metal onto the surface of the emitter. The experimental investigation of the Taylor cone formation in a dual-channel electrospray emitter has been carried out by injection of polystyrene beads (diameter 3 μm) at very low concentrations into one of the channels of the non-tapered theta-glass tubes. High-speed camera experiments were set up to visualize the mixing processes in Taylor cone regions for dual-channel emitters. Mass spectra from dual nano-electrospray are presented.

• Imaging Science in Dentistry
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• 제44권3호
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• pp.229-236
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• 2014

Purpose: To investigate the prevalence of bifid and trifid mandibular canals using cone-beam computed tomography (CBCT) images, and to measure their length, diameter, and angle. Materials and Methods: CBCT images of 500 patients, involving 755 hemi-mandibles, were used for this study. The presence and type of bifid mandibular canal was evaluated according to a modified classification of Naitoh et al. Prevalence rates were determined according to age group, gender, and type. Further, their diameter, length, and angles were measured using PACSPLUS Viewer and ImageJ 1.46r. Statistical analysis with chi-squared and analysis of variance (ANOVA) tests was performed. Results: Bifid and trifid mandibular canals were found in 22.6% of the 500 patients and 16.2% of the 755 sides. There was no significant difference between genders and among age groups. The retromolar canal type accounted for 71.3% of the identified canals; the dental canal type, 18.8%; the forward canal type, 4.1%; and the trifid canal type, 5.8%. Interestingly, seven cases of the trifid canal type, which has been rarely reported, were observed. The mean diameter of the bifid and trifid mandibular canals was 2.2 mm and that of the main mandibular canal was 4.3 mm. Their mean length was 16.9 mm; the mean superior angle was $149.2^{\circ}$, and the mean inferior angle was $37.7^{\circ}$. Conclusion: Bifid and trifid mandibular canals in the Korean population were observed at a relatively high rate through a CBCT evaluation, and the most common type was the retromolar canal. CBCT is suggested for a detailed evaluation of bifid and trifid mandibular canals before mandibular surgery.

• Imaging Science in Dentistry
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• 제47권1호
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• pp.39-44
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• 2017

Purpose: Insufficient knowledge of the anatomy of the maxillary sinuses prior to sinus graft surgery may lead to perioperative or postoperative complications. This study sought to characterize the position of the posterior superior alveolar artery (PSAA) within the maxillary sinuses using cone-beam computed tomography (CBCT). Materials and Methods: A total of 300 patients with edentulous posterior maxillae, including 138 females and 162 males with an age range of 33-86 years, who presented to a radiology clinic between 2013 and 2015 were enrolled in this retrospective cross-sectional study. The distance from the inferior border of the PSAA to the alveolar crest according to the residual ridge classification by Lekholm and Zarb, the distance from the PSAA to the nasal septum and zygomatic arch, and the diameter and position of the PSAA were all assessed on patients' CBCT scans. The data were analyzed using the Mann-Whitney test and the t-test. Results: The PSAA was detected on the CBCT scans of 87% of the patients; it was located beneath the sinus membrane in 47% of cases and was intraosseous in 47% of cases. The diameter of the artery was between 1 and 2 mm in most patients (72%). The mean diameter of the artery was $1.29{\pm}0.39mm$, and the mean distances from the PSAA to the zygomatic arch, nasal septum, and alveolar crest were $22.59{\pm}4.89mm$, $26.51{\pm}3.52mm$, and $16.7{\pm}3.96mm$, respectively. Conclusion: The likelihood of detecting the PSAA on CBCT scans is high; its location is intraosseous or beneath the sinus membrane in most patients. Determining the exact location of the PSAA on CBCT scans preoperatively can help prevent it from being damaged during surgery.

• Journal of Biosystems Engineering
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• 제20권3호
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• pp.245-249
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• 1995

In this study power requirements to saw shoots with circular saw were determined by measuring and analyzing the required maximum torque to provide the information for the mechanization of Korean pine cone harvest. Two levels of feed rate of shoots, 10.4mm/s and 20.8mm/s, three levels of sawing speed 5.8㎧, 11.6㎧, and 17.4㎧, and 14 levels of shoot diameter from 7.7 to 18.1mm were used as variables. 1) The maximum torques were significantly affected by all three variables. The average maximum torque, 18.2 N-cm for feed rate of 20.Bmm/s was greater as much as 80% of 10.1 N-cm for feed rate of 10.4mm/s. 2) As the sawing speed was increased from 5.8㎧ to 11.6㎧ and 17.4㎧, the maximum torques were decreased to 14.8N-cm, 8.5N-cm, and 7.IN-cm, respectively when the feed rate was 10.4mm/s. The maximum torque ranged from 4.5 to 19.3N-cm as shoot diameter increased from 7.7 to 18.1mm. The minimum power requirements to saw shoots of 18.1mm with circular saw was 30W for the feed rate of 10.4mm/s. 3) The maximum torques were 28.6N-cm, 14.6N-cm, and 11.4N-cm when sawing speeds were 5.8㎧, 11.6㎧, and 17.4㎧, respectively when the feed rate was 20.8mm/s and these torques were increased as much as 93%, 36%, and 61% of those for the feed rate of 10.4mm/s. The maximum torque increased from 9.7N-cm to 30.7N-cm as shoot diameter increased from 7.7 to 18.1mm. The minimum power requirements to saw shoots of 18.1mm was 54W which was 1.8 times of 30W for the feed rate of 10.4mm/s.