• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.434-438
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• 2003

The shearing process for the sheet metal is normally used in the precision elements such as semi-conductor components. In these precision elements, the burr formation brings a bad effect on the system assembly and demands the additional de-burring process. In this paper, we have developed the desktop-type precision punching system to investigate the burr formation mechanism and present kinematically Punch-die auto aligning methodology, for the purpose of burr unifomizing and minimizing, between the rectangular shaped punch and die. By using the scanning electron microscope, the aligned punching results are compared with the miss-aligned ones. Also, we measured the relative burr heights using the self-designed laser measuring device for insitu self aligning. Since it is hard to get the perfect, so called, burr-free edges during the shearing process, we introduced the ultrasonic do-burring machine. The de-burring operation was carried out by a novel do-burring method, the reversal flow resistance method, under different machining loads and abrasive types. The final do-burring results show the validity of our punching do-burring system pursuing the burr-free punched elements.

• 대한기계학회논문집B
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• 제31권9호
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• pp.780-789
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• 2007

Lock-on phenomenon in the wake of a circular cylinder is investigated at the Reynolds number of 360 using direct numerical simulation (DNS). To induce lock-on, a streamwise velocity perturbation with a frequency of twice the natural shedding frequency is superimposed on the free stream velocity. The Reynolds stress distributions are investigated to analyze the streamwise force balance acting on the recirculation region and the results are compared with the previous experimental result. When the lock-on occurs, the pressure force on the recirculation region is shown to increase mainly due to the reversal of the Reynolds shear stress distribution, which is consistent with our previous results using PIV measurement. It is also shown that, with the lock-on, the strength of the primary vortices increases whereas that of the secondary vortices decreases significantly. Further, under the lock-on condition the wavelength of the secondary vortices increases by as much as 2.5 times.

• Journal of Chest Surgery
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• 제14권3호
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• pp.302-306
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• 1981

Aorticopulmonary window is a rare anomaly among congenital heart disease. Various terms have been suggested including A-P window, A-P fenestration, fistula, aorticseptal defect etc. The defect lies usually between the left side of the ascending aorta and right wall of the pulmonary artery just anterior to the origin of the right main pulmonary artery. We have experienced one case of aorticopulmonary septal defect which was diagnosed as V5D with pulmonary hypertension in 1 4/12 year old, 7.2 Kg, male patient. Operation was done under the hypothermic cardiopulmonary bypass using 5t. Thomas cardioplegic solution. Vertical right ventriculotomy over the anterior wall of RVOT revealed no defect in the ventricular septum, and incision was extended up to the main pulmonary artery to find the source of massive regurgitation of blood through MPA. Finger tip compression of the aorticopulmanary window was replaced with Foley bag catheter balloon, and the $7{\times}10$ mm aorticoseptal defect located 15mm above the pulmonic valve was sutured continuously wih 3-0 nylon suture during azygos flow of cardiopulmonary cannula which was located distal to the window resulted massive air pumping systemically, and temporary reversal of pumping was tried to minimize cerebral air embolism. Remained procedure was done as usual, and pump off was smooth and uneventful. Postoperatively, patient was attacked frequent opistotonic seizure with no recovery sign mentally and p.hysically. Vital signs were gradually worsen with peripheral cyanosis and oliguria, and cardiac activity was arrested 1485 minutes after operation. Autopsy was performed to find the sutured window and massive edema of the brain.

• 대한전기학회논문지
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• 제45권3호
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• pp.358-364
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• 1996

Recently, much power demand from domestic power consumer is weakening the allowable power reserve margin in summer, especially at midday for one day due to a steep increase of air cooling loads such as air conditioner. Therefore solar airconditioning system can'be considered as one of the best remedies to meet the increase of peak power. Generally in solar air conditioning system, the diode rectifier is used to build up DC link voltage from AC source. The diode rectifier is simple and cheap but it brings out the problems of low power factor and plentiful harmonics at the AC source. Also It can derate the utilization rate of solar energy because the reverse of power flow cannot be made. Hence, in this paper to overcome the peak power problem in summer and to endure good AC input characteristics, solar air conditioning system using the PWM converter is proposed. As results, obtained are the characteristics of the PWM converter such as low distorted current waveform, high power factor and bidirectional power control. And also the stability of proposed system is verified by examining the dynamics of step load change and power reversal testing. (author). refs., figs., tabs.

• Journal of Audiology & Otology
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• 제25권1호
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• pp.43-48
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• 2021

Background and Objectives: Conflicting mechanisms have been reported about spontaneous reversal of positional nystagmus during head-roll maneuver in patients with benign paroxysmal positional vertigo (BPPV). The objective of this study is to review the reports about the characteristics and possible mechanisms of reversing positional nystagmus and to present seven new cases. Subjects and Methods: Seven cases (5 males, 2 females; 4 left-sided, 3 right-sided) were recruited among 732 patients with BPPV seen outpatient clinic between 2009 and 2019. Diagnosis of lateral canal canalolithiasis was confirmed when transient geotropic nystagmus was documented during head-roll test. Reversing positional nystagmus was analyzed in each case and clinical characteristics of the patients were documented. Results: The age of patients was ranging between 30 to 64 years (46.44±10.91). Duration of symptoms was short (21.34±19.74). Six of them had a story of head trauma. Initial latency was short. First, intense geotropic nystagmus was observed following provocative head-roll position on the affected side. There was short "silent phase". Then, a longer second-phase of reversed nystagmus was noted. Total duration of nystagmus was 78.40±6.82 seconds. Maximal slow phase velocity was 24.05±6.34 deg/sec. All patients were cured with barbeque maneuver. Conclusions: Ipsilateral reversing positional nystagmus during head-roll maneuver is due to lateral canal canalolithiasis. Mechanism is likely to be due to endolymphatic double flow. Bilateral cases may be due to simultaneous co-existence of canalolithiasis and cupulolithiasis. Longer recording of nystagmus is recommended not to miss the cases with spontaneous direction-changing positional nystagmus.

• 대한청각학회지
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• 제25권1호
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• pp.43-48
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• 2021

Background and Objectives: Conflicting mechanisms have been reported about spontaneous reversal of positional nystagmus during head-roll maneuver in patients with benign paroxysmal positional vertigo (BPPV). The objective of this study is to review the reports about the characteristics and possible mechanisms of reversing positional nystagmus and to present seven new cases. Subjects and Methods: Seven cases (5 males, 2 females; 4 left-sided, 3 right-sided) were recruited among 732 patients with BPPV seen outpatient clinic between 2009 and 2019. Diagnosis of lateral canal canalolithiasis was confirmed when transient geotropic nystagmus was documented during head-roll test. Reversing positional nystagmus was analyzed in each case and clinical characteristics of the patients were documented. Results: The age of patients was ranging between 30 to 64 years (46.44±10.91). Duration of symptoms was short (21.34±19.74). Six of them had a story of head trauma. Initial latency was short. First, intense geotropic nystagmus was observed following provocative head-roll position on the affected side. There was short "silent phase". Then, a longer second-phase of reversed nystagmus was noted. Total duration of nystagmus was 78.40±6.82 seconds. Maximal slow phase velocity was 24.05±6.34 deg/sec. All patients were cured with barbeque maneuver. Conclusions: Ipsilateral reversing positional nystagmus during head-roll maneuver is due to lateral canal canalolithiasis. Mechanism is likely to be due to endolymphatic double flow. Bilateral cases may be due to simultaneous co-existence of canalolithiasis and cupulolithiasis. Longer recording of nystagmus is recommended not to miss the cases with spontaneous direction-changing positional nystagmus.

• 대한임상검사과학회지
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• 제49권3호
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• pp.316-321
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• 2017

빗장밑혈류빼앗김증후군은 좌측 몸쪽부분 빗장밑동맥 혹은 팔머리동맥에 심한 혈관 협착이나 폐색이 원인이 되어 발생한다. 병변이 있는 부위에서는 제한적이며, 불충분한 혈류가 발생하여 반대쪽으로부터 연결혈관을 통해 일부 혈액이 유입될 수 있다. 이러한 현상을 빗장밑혈류빼앗김현상이라고 한다. 이중초음파검사는 빗장밑혈류빼앗김현상을 측정하는데 유용한다. 빗장밑혈류빼앗김현상을 보이는 일부 환자에서는 척추뇌바닥혈류부전 혹은 허혈성 말초동맥질환 증상을 호소한다. 빗장밑혈류빼앗김증후군은 빗장밑혈류빼앗김현상과 더불어 신경학적 증상이 반드시 동반될 경우로 정의할 수 있다. 저자는 팔머리동맥의 심한 협착을 보이는 환자에서 척추동맥과 더불어 바깥목동맥과 전방순환계를 담당하는 온목동맥 및 속목동맥에서 이중초음파검사를 이용한 혈류빼앗김현상이 관찰된 증례를 보고하고자 한다.

• 터널과지하공간
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• 제22권3호
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• pp.163-172
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• 2012

국내 대단면 지하 석회석광산 갱내에서 디젤장비의 사용이 증가함에 따라 배출 오염물질 및 열방출로 인한 작업환경의 악화 문제가 심각해지고 있다. 본 연구에서는 적정 소요환기량의 확보를 통한 갱내 환경의 최적화를 위한 기초연구로 갱내 환기망내 기류분포와 디젤장비의 배출가스 농도분포를 측정하고, 지하 심부화와 기계화에 따른 온 습도 변화를 고려하여 갱내 소요환기량을 추정하였다. 배기팬의 용량 부족 및 갱도 관리의 문제로 인하여 갱내 다수의 지점에서 기류정체가 심하고, 주요 갱도에서의 기류방향이 장비의 이동에 따른 순간적인 변화가 크며 계절별 변화 또한 큰 편이다. 디젤 배출가스인 CO의 경우 적재작업시 규제농도 50 ppm을 자주 초과하였으며, $NO_2$의 경우 천공 및 적재작업동안 대부분 규제농도 3 ppm을 초과하였다. 광산보안법규를 적용하여 구한 갱내 소요환기량에 비하여 실제 환기량이 심각하게 부족하였으며 자연환기력의 영향에 따라 환기량 부족문제는 외부 온도가 낮은 겨울철이 상대적으로 덜 심각하였다.

• 한국지반공학회논문집
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• 제33권12호
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• pp.7-20
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• 2017

본 연구에서는 전단특성 및 유변학적 정수를 모두 산정할 수 있는 직접전단실험 장비를 이용하여 조립토와 세립토에 대하여 전단강도 및 유변학적 특성에 대한 입도분포의 영향을 조사하고자 하였다. 최대입경 0.075mm의 세립토와 최대입경이 0.425mm이고, 세립분 함량이 17%인 조립토를 건조상태와 액성한계상태로 조성하여, 산사태 분류기준에 따라 재활성 산사태(reactivated landslide) 혹은 붕괴직후 토석류 속도에 해당하는 전단속도에 대하여 전단강도를 산정하였다. 또한, 유변학적 특성 평가를 위해 액성한계상태로 조성된 조립토와 세립토에 대하여 서로 다른 세 가지의 전단변형률속도로 반복적으로 전단하며 잔류전단강도를 측정하였다. 측정된 잔류전단강도와 전단변형률속도와의 관계를 통해 빙햄모델의 소성 점도와 항복응력을 산정하였다. 건조 및 액성한계상태에서 조성된 시료에 대하여 첨두전단강도에서 산정한 점착력의 경우, 세립토에서 조립토보다 더 크게 산정되었으며, 내부마찰각은 조립토에서 더 크게 산정되었다. 유변학 정수의 경우, 소성 점도와 항복응력이 조립토보다 세립토에서 더 큰 것으로 나타났다. 본 연구는 재활성 산사태 혹은 붕괴직후 토석류의 거동예측에 효과적으로 활용될 것으로 기대된다.

• 생명과학회지
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• 제23권2호
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• pp.157-166
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• 2013

본 연구는 Sprague-Dawley계 숫쥐에서 출생 초기 에탄올에의 노출에 의한 성장 후 뇌혈류 자가조절의 변동을 관찰하고 이러한 변동에 대한 nociceptin의 관여를 관찰하고자 하였다. 실험동물에게 에탄올 2.5 g/kg을 생후 6, 7 및 8일의 3일 동안 2시간 간격으로 1일 2회 피하 주사하였다. 주령 4, 8 및 12주 시기에 단계적 출혈에 의한 저혈압 및 혈액 재주입에 의한 혈압 상승시의 평균동맥혈압의 변동에 따른 국소 뇌혈류 변동을 laser-Doppler flowmetry 방법으로 측정하였고, 경막과 대뇌피질에서 nociceptin-유사 면역반응력의 발현을 면역조직화학법으로 측정하였다. 출생 초기 에탄올 투여는 4, 8 및 12주령 모두에서 국소 뇌혈류 자가조절 기능을 거의 소실시켰다. 에탄올 투여 전에 nociceptin을 전처치한 군에서는 모든 연령군에서 국소 뇌혈류 자가조절 기능이 보존되었으나, nociceptin 수용체 선택적 경쟁적 길항제인 [$Nphe^1$]nociceptin(1-13)$NH_2$를 전처치한 군에서는 보존되지 아니하였다. 출생 초기 에탄올 투여에 의하여 경막 내 nociceptin-유사 면역반응력이 모든 연령군에서 현저히 증가하였고, 7-nitroindazole (7-NINA) 전처치뿐만 아니라 aminoguanidine 전처치에 의하여 모든 주령에서 유의하게 억제되었다. 출생 초기 에탄올 투여에 의하여 대뇌피질 내 nociceptin-유사 면역반응력이 모든 연령군에서 현저히 증가하였고, 7-NINA 전처치와 aminoguanidine 전처치에 의하여 모든 주령에서 유의하게 억제되었다. 모든 실험군의 동맥혈가스분석 결과는 실험 전, 중 및 후에 유의한 차이를 보이지 아니하였다. 이상의 결과로 보아 출생 초기 에탄올 투여는 성장 후 뇌혈류 자가조절에 변동을 초래하고, 이에 대한 보상기전으로서 nociceptin의 발현이 증가하는데, 여기에는 nitric oxide가 깊이 관여하는 것으로 생각된다.