비파괴 기술을 이용한 대구경 수도용 밸브의 상태평가에 관한 연구

이호민,최현용,박수완,오태민,김채민,배철호 대한상하수도학회 2023 상하수도학회지 Vol.37 No.4

In this study, non-destructive technologies that can be applied to evaluate the integrity of valve materials, safety against internal pressure caused by corrosion, and the blocking function of large-diameter water valves during operation without requiring specimen collection or manpower entering the inside of the valve were tested to assess the reliability of the technologies and their suitability for field application. The results showed that the condition of the graphite structure inside the valve body can be evaluated directly through the optical microscope in the field without specimen collection for large-diameter water butterfly valves, and the depth of corrosion inside the valve body can be determined by array ultrasound and the tensile strength can be measured by instrumented indentation test. The reliability of each of these non-destructive techniques is high, and they can be widely used to evaluate the condition of steel or cast iron pipes that are significantly smaller in thickness than valves. Evaluation of blocking function of the valves with mixed gas showed that it can be detected even when a very low flow rate of mixed gas passes through the disk along with the water flow. Finally, as a result of evaluating the field applicability of non-destructive technologies for three old butterfly valves installed in the US industrial water pipeline, it was found that it is possible to check the material and determine the suitability of large-diameter water valves without taking samples, and to determine the corrosion state and mechanical strength. In addition, it was possible to evaluate safety through the measurement results, and it is judged that the evaluation of the blocking function using mixed gas will help strengthen preventive response in the event of an accident.

부비동 내시경수술 후 발생한 기뇌증과 심각한 뇌수막염 치험 1예

이호민,이상민,이정민,이태훈 대한이비인후과학회 부산,울산,경남 지부회 2011 임상이비인후과 Vol.22 No.2

Pneumocephalus represents rare complications in endoscopic sinus surgery. Pneumocephalus following nasal and sinus surgery occurs because of iatrogenic damage to the skull base. Patients with posttraumatic cerebrospinal fluid leakage lasting more than 7 days have at least 8- to 10-fold increase in risk of meningitis. Although treatment regimens for Streptococcus pneumoniae meningitis have improved, the mortality rate remains as high as 25% with neurological sequelae in up to half of survivors. We report a 35-year-old man with pneumocephalus and meningitis as complications of endoscopic sinus surgery. We initially treated the patient by administration of antibiotics and lumbar drain. After controlling inflammation, endoscopic repair of cerebrospinal fluidrhinorrhea with osteomucoperiosteal free flap obtained from the middle turbinate under general anesthesia was done. The patient was followed up without any complication.

분무열분해법에 의해 제조된(Ca, Sr)₂MgSi₂O₇:Eu²⁺ 형광체의 발광 특성

이호민,정경열,정하균,이종흔,Lee, Ho Min,Jung, Kyeong Youl,Jung, Ha-Kyun,Lee, Jong Heun 한국화학공학회 2006 Korean Chemical Engineering Research(HWAHAK KONGHA Vol. No.

분무열분해법을 이용하여$(Ca,Sr)_{2-y}MgSi_2O_7:Eu^{2+}{_y}$ 형광체 분말을 제조하고 $Eu^{2+}$의 농도, 후열처리온도 변화 및 Ca/Sr 비에 따른 발광특성을 조사하였다. 또한, Ca/Sr의 비를 변화시켜 발광특성의 변화를 관찰하였다. $Ca_2MgSi_2O_7$나 $Sr_2MgSi_2O_7$ 분말 모두 $1,000^{\circ}C$ 이상의 온도에서 열처리를 했을 때 순수한 정방정계 상이 제조되었다. $Ca_2MgSi_2O_7:Eu^{2+}{_y}$ 녹색 형광체는 $Eu^{2+}(y)$의 농도가 5 mol%, 후열처리 온도가 $1,250^{\circ}C$ 일 때 가장 높은 발광 강도는 보였다. ${(Ca_{1-x},Sr_x)}_{1.95}MgSi_2O_7:{Eu^{2+}}_{0.05}$의 발광 파장은 Sr의 농도가 증가함에 따른 결정장 감소로 인해 524nm에서 456nm로 점진적으로 blue shift 되었다. $Sr_2MgSi_2O_7:Eu^{2+}$는 Sr 자리에 약 10 mol% Ca를 치환시킴으로써 청색 형광체의 발광 강도는 크게 향상되었다. 제조된 분말들은 치밀하지 못하고 다공성 구조를 가져 후열처리 전에는 구형을 유지하였으나 열처리($900{\sim}1,300^{\circ}C$) 후에는 구형의 형상을 잃고 입자들 간의 응집이 발생하였다. $(Ca,Sr)_{2-y}MgSi_2O_7:Eu^{2+}{_y}$ (CMS) phosphor particles were prepared by using a spray pyrolysis process. The luminescent property was optimized by changing the content of Eu and the post-treatment temperature. The luminescence characteristics were also monitored with changing the ratio of Ca to Sr. The pure tetragonal $Ca_2MgSi_2O_7$ or $Sr_2MgSi_2O_7$ particles were obtained when the post-treatment temperature was over $1,000^{\circ}C$. The highest emission intensity of CMS particles were achieved when the concentration (y) of Eu and the treatment temperature were 0.05 and $1,250^{\circ}C$,respectively. The emission wavelength $({\lambda}_{max})$ of ${(Ca_{1-x},Sr_x)}_{1.95}MgSi_2O_7:{Eu^{2+}}_{0.05}$ was gradually shifted from 524 nm to 456 nm with increasing the content of Sr due to the reduction of crystal field strength. The emission intensity and its width of $Sr_2MgSi_2O_7:Eu$ was greatly enhanced by substituting Ca of less than 10 mol% for Sr without any significant peak shift. The morphology of as-prepared particles was spherical, but changed to irregular-shaped one after the post treatment at the temperature range from 900 at $1,300^{\circ}C$.

TDWR을 이용한 미규모에서의 난류 발달 분석

이호민,김경익,조요한 한국기상학회 2006 한국기상학회 학술대회 논문집 Vol.2006 No.-

대구경 상수도관 부식 손상부의 고분자 필러와 복합슬리브 성능 평가

이호민,박정수,박정주,배철호 대한상하수도학회 2023 상하수도학회지 Vol.37 No.4

In this study, the physical properties and fracture characteristics according to the tensile load are evaluated on the materials of the polymeric filler and carbon fiber-based composite sleeve technique. The polymeric filler and the composite sleeve technique are applied to areas where the pipe body thickness is reduced due to corrosion in large-diameter water pipes. First, the tensile strength of the polymeric filler was 161.48~240.43 kgf/cm2, and the tensile strength of the polyurea polymeric filler was relatively higher than that of the epoxy. However, the tensile strength of the polymeric filler is relatively very low compared to ductile cast iron pipes(4,300 kgf/cm2<) or steel pipes(4,100 kgf/cm2). Second, the tensile strength of glass fiber, which is mainly used in composite sleeves, is 3,887.0 kgf/cm2, and that of carbon fiber is up to 5,922.5 kgf/cm2. The tensile strengths of glass and carbon fiber are higher than ductile cast iron pipe or steel pipe. Third, when reinforcing the hemispherical simulated corrosion shape of the ductile cast iron pipe and the steel pipe with a polymeric filler, there was an effect of increasing the ultimate tensile load by 1.04 to 1.06 times, but the ultimate load was 37.7 to 53.7% compared to the ductile cast iron or steel specimen without corrosion damage. It was found that the effect on the reinforcement of the corrosion damaged part was insignificant. Fourth, the composite sleeve using carbon fiber showed an ultimate load of 1.10(0.61T, 1,821.0 kgf) and 1.02(0.60T, 2,290.7 kgf) times higher than the ductile cast iron pipe(1,657.83 kgf) and steel pipe(2,236.8 kgf), respectively. When using a composite sleeve such as fiber, the corrosion damage part of large-diameter water pipes can be reinforced with same level as the original pipe, and the supply stability can be secured through accident prevention.

상악동에 발생한 기질화 혈종 3례

이호민,이태훈,이정민,김재기 대한비과학회 2013 Journal of rhinology Vol.20 No.1

Organizing hematomas are rare benign tumors and appear as masses that are composed of neovascularization with organizing fibrotic tissue in a hematoma. Although histologically benign, this condition may be clinically progressive. Radiological findings can range from a benign appearance to a more aggressive process, including bony erosion. Organizing hematoma of the maxillary sinus is a rare clinical disease. To our knowledge, only a few cases have previously been published, and most were without bleeding history and disorders. Until now, all of the reports about this lesion have discussed the clinical course, and no previous report has closely considered pathologic findings and pathogenesis. We report three cases of organizing hematoma of the maxillary sinus presenting with an enlarging maxillary sinus mass.

외측 잠김 금속판 고정 후 발생한 원위 대퇴골 불유합에서 시행한 내측 잠김 금속판 고정 및 자가골 이식술의 효과

이호민,김종필,백인화,문한솔,남선교 대한골절학회 2024 대한골절학회지 Vol.37 No.1

Purpose: This study examined the outcomes of additional medial locking plate fixation and autogenous bone grafting in the treatment of nonunions that occurred after initial fixation for distal femoral fractures using lateral locking plates. Materials and Methods: The study involved eleven patients who initially underwent minimally invasive lateral locking plate fixation for distal femoral fractures between January 2008 and December 2020. The initial procedure was followed by additional medial locking plate fixation and autogenous bone grafting for clinically and radiographically confirmed nonunions, while leaving the stable lateral locking plate in situ. A clinical evaluation of the bone union time, knee joint range of motion, visual analog scale (VAS) pain scores, presence of postoperative complications, and functional evaluations using the lower extremity functional scale (LEFS) were performed. Results: In all cases, bone union was achieved in an average of 6.1 months after the secondary surgery. The range of knee joint motion, weight-bearing ability, and VAS and LEFS scores improved at the final follow-up compared to the preoperative conditions. All patients could walk without walking assistive devices and did not experience pain at the fracture site. On the other hand, three patients complained of pain in the lateral knee joint caused by irritation by the lateral locking plate; hence, lateral hardware removal was performed. One patient complained of mild paresthesia at the anteromedial incision site. Severe complications, such as deep infection or metal failure, were not observed. Conclusion: For nonunion with stable lateral locking plates after minimally invasive lateral locking plate fixation of distal femur fractures, additional medial locking plate fixation and autogenous bone grafting, while leaving the lateral locking plate intact, can achieve successful bone union.

관 세척에 따른 색도성 물질의 제거 효과

이호민,최태호,윤현우,김동홍,배철호,Lee, Ho-Min,Choi, Tae-Ho,Yun, Hyun-Woo,Kim, Dong-Hong,Bae, Cheol-Ho 대한상하수도학회 2020 상하수도학회지 Vol.34 No.4

In this study, air scouring cleaning was selected and applied among 5 small blocks (S1~S5) in domestic S cities to analyze the cleaning effect of particles causing discoloration. In order to identify the cleaning effect, 10 locations were selected as water quality investigation point, such as the stagnant or water mains ends. Removal of solids, variation of particle components, weight and concentration were analyzed. And the level of the cleanness of the surface inside water mains using endoscope was investigated. As a result of analysis, the solids discharged after cleaning were mainly sand and gravel, pieces related to pipe materials, and corrosion products. As a result of analyzing the concentrated particles of the filter before and after cleaning, it was found that the change in discoloration on the filter was large. In addition, as a result of comparing the weight and the concentration of the particles, it was found that the particles causing discoloration were significantly removed after cleaning. From the results of the endoscopy, it was confirmed that most of the precipitated and accumulated dark yellow discoloration matters inside water mains were removed through cleaning. Therefore, it seems that the particles causing discoloration in water decreased after cleaning. Therefore, it is expected that, if properly cleaning was applied, matters that cause discoloration can be removed from the water mains, and customer's complaints can also be reduced through water quality improvement.

대구경 상수관로의 기존 부분 보수보강 기술 성능평가

이호민,배철호,박정수,정기문 대한상하수도학회 2022 상하수도학회지 Vol.36 No.6

In this study, as the proportion of aged pipelines increases rapidly, in the event of an accident caused by corrosion and structural deterioration of metal pipes, appropriate overlay welding is applied in the field to partially repair it. The size of the base steel plate and the selection of a stable welding method were evaluated, and possible problems caused by the overlay welding were identified, and improvement measures were proposed. For the test, a new steel pipe coated with epoxy lining on the inner surface and polyethylene on the outer surface was subjected to a tensile test by processing the repaired specimen through overlay welding with a steel plate after artificial cracking, and structural safety was evaluated after repair. Furthermore, the influences of the size of the throat and the size of the steel plate were analyzed. As a result of the tensile test by dividing the repaired steel plate overlay into a constraint and non-constraint conditions, the tensile load was concentrated in the welded part and damage occurred in the welded part. It was found that the maximum load leading to breakage increases as the size of the welding throat increases. In addition, it was found that the resistance to load increased slightly as the size of the overlaid steel plate increased, but the effect was not significant, confirming the need for repair in consideration of the site conditions. As a result of evaluating the damage to the coating material on the back side of the welding, it was confirmed that the coating material on the opposite side of the welding burned black(epoxy) or was greatly deformed by heat(polyethylene). Therefore, it is necessary to secure structural stability through repainting, etc. in order to prevent damage to the coating material on the opposite side during overlay welding.

EPANET 기반의 Pressure Driven Analysis 모형 개발 및 적용

이호민,유도근,김동영,김중훈 한국방재학회 2013 한국방재학회논문집 Vol.13 No.4

Hydraulic analysis of water distribution systems (WDS) is divided into two types, one is Demand Driven Analysis (DDA)which applies to a steady state condition and other is Pressure Driven Analysis (PDA) which applies to an abnormal condition. In DDA, it is assumed that available discharge in demand nodes is always equal to the required discharge, and the assumption is suitable for a steady state condition. However, in abnormal conditions such as pipe failure or excess of demand, DDA model may produce unrealistic outputs such as negative pressure, so application of PDA model is required. The Gradient Algorithm used for DDA in EPANET was improved to develop a PDA model based on the Global Gradient Algorithm. Additionally, the developed model was applied to evaluate the emergency water supply plan of a large block system in Yeong Wol. The results showed to 66~100% of the total network demand was available in the emergency scenarios of failure in each reservoir. The developed PDA model is capable to solve negative pressure problem shown in existing DDA model and to analyse evaluation of emergency water supply plan with high reliability. 상수도관망의 수리학적 해석 방법에는 주로 정상상태의 시스템 해석에 사용되는 Demand Driven Analysis (DDA)와 비정상상태 시스템 해석에 사용되는 Pressure Driven Analysis (PDA)가 있다. DDA는 각 절점의 수요량은 모두 공급된다는 가정하에 절점의 압력수두를 계산하는 기법으로, 관망시스템이 정상상태일 경우에는 해석에 무리가 없다. 하지만 비정상상태, 즉 어떠한 원인으로 관망의 수리학적 상태가 변화했을 때에는 DDA로 해석을 할 경우 부압이 발생하는 등 비현실적인 결과를 발생시킬 수 있으며, 따라서 PDA 수리해석의 적용이 필요하다. 본 연구에서는 EPANET의 DDA 수리해석 모형에 포함된Gradient Algorithm을 분석 및 개량하여 Global Gradient Algorithm을 적용한 PDA 수리해석모형을 개발하였다. 또한 개발모형의 적용성 평가를 위해 탑재된 PDA 기능을 이용하여 영월군 대블럭 시스템의 배수지에 문제가 발생한 시나리오에 대하여비상급수계획 분석을 시행하였고, 그 결과 각 배수지의 문제 발생시 66~100%의 비상급수가 가능한 것으로 나타났다. 기존DDA 해석 모형에서 발생한 부압 등의 문제를 해결할 수 있었고, 공급가능 유량을 정량적으로 산정하여 보다 신뢰도 높은 비상급수계획 분석이 가능한 것으로 나타났다.