• 한국지반공학회논문집
• /
• 제30권1호
• /
• pp.37-47
• /
• 2014

불포화 수리전도도는 Mualem 모세관 모델에 의하여 이론적으로 함수특성곡선으로부터 적분된다. 하지만 예측된 수리전도도는 포화 부근에서 모관흡수력의 미소한 변화에도 극도로 민감하다. 원활한 형태의 함수특성곡선에 의한 Mualem 수리전도도는 포화 부근에서 급격하게 감소하며, 수리적 거동을 신뢰할 수 있게 모델하지 못하거나 수치해의 안정성을 저해 한다. van Genuchten-Mualem(VGM) 수리전도도를 개선하기 위하여, 낮은 모관흡수력 수준에 있는 임의의 공기함입치이내에서 van Genuchten 함수특성곡선을 수정하였다. 수정 VG 곡선은 대수축에서 임의의 공기함입치에서 포화상태까지 선형화된다. 수정 VG 함수특성곡선은 실제 함수특성거동의 회귀분석에 영향을 끼치지 않으며 원래의 VG 함수특성곡선의 계수를 그대로 사용한다. 수정 VG 곡선을 이용하여, VGM 수리전도도는 임의의 공기합입치를 기준으로 구간별 적분하여 수정되었다. 수정 VGM 수리전도도가 해석적 해로 제안되었으며, 포화부근 영역에서 수리전도도가 급격하게 감소하는 현상이 제거되었다. 실제 사면의 2차원 침투해석을 통하여 VGM 수리전도도와 제안된 모델에 따른 수리거동을 비교하였다. 제안된 모델은 여러 강우조건에 따른 해의 수렴성을 확보하였지만, VGM 수리전도도를 적용하면, 포화부근의 수리전도도가 급격하게 감소하여 강우량이 많은 경우 해가 수렴하지 않았다. 특히 선행강우에 의한 초기 안전율과 집중강우 후 최종 안전율을 크게 평가할 수 있었다. 제안된 수리전도도 모델은 침투해석과 안정해석을 통하여 실제 사면의 붕괴를 재현할 수 있었다.

• 한국대기환경학회지
• /
• 제26권3호
• /
• pp.330-338
• /
• 2010

In this study, removal characteristics of nitrogen oxides $(NO_x)$ from road transport by using peat as the packing media for biodegradation have been investigated in the long term. Physicochemical and biological treatment of peatmixed media eliminates any requirement to use chemical substances and also facilitates the biodegradable actions of microorganism. Safe biodegradation of pollutants, no need to apply additional microbes owing to their active growth, and no generation of secondary pollutants were found in this experiment. It was concluded that average removal efficiencies of nitric oxide (NO) and nitrogen dioxide $(NO_2)$ were 80% and 97% respectively with respect to the linear velocity 35~40 mm/s and 0.3 ppm ozone concentration in the long period operation. Inflow concentration of nitric oxide over 0.05 ppm was suitable when pretreated with ozone. Non-ozone stage was performed with linear velocity 20~100 mm/s and then the average removal efficiency of nitric oxide and nitrogen dioxide were 38% and 94% respectively. Other results showed that the apparent static pressure was raised with increases in applied water content and aerial velocity in mixed media during fan operation.

• 한국소음진동공학회논문집
• /
• 제20권1호
• /
• pp.29-35
• /
• 2010

This paper studies causes of the L-1 blade damage of a low pressure turbine, which was found during the scheduled maintenance, in 500 MW fossil power plants. Many failures of turbine blades are caused by the coupling of aerodynamic forcing with bladed-disk vibration characteristics. In this study the coupled vibration characteristics of the L-1 turbine bladed-disk in a fossil power plant is shown for the purpose of identifying the root cause of the damage and confirming equipment integrity. First, analytic and experimental modal analysis for the bladed-disk at zero rpm as well as a single blade were performed and analyzed in order to verify the finite element model, and then steady stresses, natural frequencies and corresponding mode shapes, dynamic stresses were calculated for the bladed-disk under operation. Centrifugal force and steady steam force were considered in calculation of steady and dynamic stress. The proximity of modes to sources of excitation was assessed by means of an interference diagram to examine resonances. In addition, fatigue analysis was done for the dangerous modes of operation by a local strain approach. It is expected that these dynamic characteristics will be used effectively to identify the root causes of blade failures and to perform prompt maintenance.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권6호
• /
• pp.2473-2476
• /
• 2014

Background: Little is known about the cancer screening prevalence and correlates in older adults from different racial backgrounds. In the context of heightened efforts for prevention and early diagnosis, we collected information on screening for two major types of cancers: cervical and breast cancer in order to establish their prevalence estimates and correlates among older South African women who participated in the Study of Global Ageing and Adults Health (SAGE) in 2008. Materials and Methods: We conducted a national population-based cross-sectional study with a multi-stage stratified cluster sample of 3,840 individuals aged 50 years or older in South Africa in 2008. In this analysis, we only considered the female subsample of (n=2202). The measures used included socio-demographic characteristics, health variables, anthropometric and blood pressure measurements. Multivariable regression analysis was performed to assess the association of socio-demographic factors, health variables and cancer screening. Results: Overall, regarding cervical cancer screening, 24.3% ever had a Papanicolaou (PAP) smear test, and regarding breast cancer screening, 15.5% ever had a mammography. In multivariate logistic regression analysis, younger age, higher education, being from the White or Coloured population group, urban residence, greater wealth, and suffering from two or more chronic conditions were associated with cervical cancer screening, and higher education, being from the White or Indian/Asian population group, greater wealth, having a health insurance, and suffering from two or more chronic condtions were associated with breast cancer screening. Conclusions: Cancer screening coverage remains low among elderly women in South Africa in spite of the national guideline recommendations for regular screening in order to reduce the risk of dying from these cancers if not detected early. There is a need to improve accessibility and affordability of early cervical and breast cancer screening for all women to ensure effective prevention and management of cervical and breast cancer.

• Asian Pacific Journal of Cancer Prevention
• /
• 제16권11호
• /
• pp.4629-4631
• /
• 2015

Background: The research was to compare the efficacy and side effects of cisplatin or lobaplatin in combination with mitomycine (MMC) and vincristine in treating patients with cervical squamous carcinoma. Materials and Methods: Cervical squamous carcinoma patients who were pathologically diagnosed with stage Ib-IIb from April 2012 to May 2013 in the general hospital of Chinese People's Libration Amy were enrolled. All patients were confirmed without prior treatment and were randomly divided into two groups, Group A and B. Efficacy and side effects were evaluated after one cycle of chemotherapy. Results: Group A (n=42) were treated with Loubo$^{(R)}$ (Lobaplatin) $50mg/m^2$, MMC $16mg/m^2$ and Vincristine $2mg/m^2$ every 21 days. Group B (n=44) were treated with Cisplatin $100mg/m^2$, MMC $16mg/m^2$ and Vincristine $2mg/m^2$ every 21 days. All 86 patients completed one cycle of chemotherapy with cisplatin or lobaplatin in combination with MMC and vincristine. No difference was observed regardiing short-term effect between two groups. Main side effects were bone marrow suppression and gastrointestinal reactions including decrease of white blood cells, platelet and nausea/vomiting. Grade III-VI liver and kidney impairment was not reported in two groups. In group A the incidence of uterine artery spasm in the process of drug delivery was significantly lower than the group B. Conclusions: Cisplatin or lobaplatin with MMC and Vincristine in the interventional treatment of cervical squamous carcinoma were effective, especially after uterine artery perfusion chemotherapy at tumor reduction and tumor downstaging period. The adverse reactions of concurrent chemotherapy are tolerable, and low physical and mental pressure even more less stimulation of vascular in treatment with lobaplatin. However, the long-term effects of this treatment need further observation.

• 한국세라믹학회지
• /
• 제44권12호
• /
• pp.696-702
• /
• 2007

The family of (Sr,Mg)-doped $LaGaO_3$ compounds, which exhibit high ionic conductivity at $600-800^{\circ}C$ over a wide range of oxygen partial pressure, appears to be promising as the electrolyte for intermediate temperature solid oxide fuel cells. Conventional synthesis routes of (Sr,Mg)-doped $LaGaO_3$ compounds based on solid state reaction have some problems such as the formation of impurity phases, long sintering time and Ga loss during high temperature sintering. Phase stability problem especially, the formation of additional phases at the grain boundary is detrimental to the electrical properties of the electrolyte. From this point of view, we focused to synthesize single phase (Sr,Mg)-doped $LaGaO_3$ electrolyte at the stage of powder synthesis and to apply relatively low heat-treatment temperature using novel synthesis route based on combustion method. The synthesized powder and sintered bulk electrolytes were characterized by XRD, TG-DTA, FT-IR and SEM. AC impedance spectroscopy was used to characterize the electrical transport properties of the electrolyte with the consideration of the contribution of the bulk lattice and grain boundary to the total conductivity. Finally, relationship between synthesis condition and electrical properties of the (Sr, Mg)-doped $LaGaO_3$ electrolytes was discussed with the consideration of phase analysis results.

• 대한기계학회논문집A
• /
• 제34권8호
• /
• pp.1059-1065
• /
• 2010

본 연구에서는 SMART 원자로의 사류형 원자로냉각재펌프의 축소모형에 대한 수력성능을 예측하기 위하여 설계점을 포함한 다양한 탈설계점에서의 해석을 수행하였다. 계산시간의 효율성을 위하여 임펠러와 디퓨저 각 1개 유로로 이루어진 계산영역을 해석대상으로 선정하였다. 임펠러와 디퓨저간의 정보교환을 위하여 스테이지 기법을 사용하였다. 정상상태 비압축성 유동조건에서 축소모형의 수력성능특성을 파악하기 위하여 해석영역의 입구와 출구에서 압력차를 측정하여 양정, 효율과 축동력을 산출하였다. 수력성능 곡선은 일반적인 사류펌프의 성능특성을 잘 모사하는 것으로 나타났다. 저유량에서의 펌프 내부유동의 복잡한 흐름을 확인 하였다.

• Childhood Kidney Diseases
• /
• 제15권2호
• /
• pp.107-115
• /
• 2011

소아에서 급성 신손상의 흔한 원인들로는 신허혈, 신독성 약물들, 그리고 패혈증 등이 있으며, 신대체요법 시작시의 저혈압, 신대체 요법 동안 승압제의 사용, 그리고 신대체 요법 시작시의 수액 과부하 정도가 환자의 생존(소아 중환자실 퇴원)에 영향을 미치는 요인들로 알려져 있다. 지속적 신대체 요법의 빠른 시작은 급성 신손상을 가진 환자들에게서 사망률과 예후에 나쁜 영향을 미치는 수액 과부하를 감소시키는 것으로 보고되었다. 이에 저자들은 소아 환자에게서 지속적 신대체 요법의 실제 처방과 급성 신손상, 수액 과부하, 그리고 지속적 신대체 요법간의 연관성 및 치료결과를 살펴보고자 한다. 결론적으로, 급성 신손상을 가진 소아의 치료에 있어서 과도한 수액 과부하가 발생하기 전에 빠른 지속적 신대체 요법의 시작이 필요하다고 제시하는 바이다.

• 한국유체기계학회 논문집
• /
• 제8권4호
• /
• pp.27-38
• /
• 2005

The present study investigated the effect of relative position of the blade on blade surface heat transfer. The experiments were conducted in a low speed wind tunnel with a stationary annular turbine cascade. The test section has a single turbine stage composed of sixteen guide vanes and blades. The chord length of the blade is 150 mm and the mean tip clearance of the blade is $2.5\%$ of the blade chord. The Reynolds number based on blade inlet velocity and chord length is $1.5{\times}105$ and mean turbulence intensity is about $3\%$. To investigate the effect of relative position of blade, the blade at six different positions in a pitch was examined. For the detailed mass transfer measurements, a naphthalene sublimation technique was used. In general, complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as a laminar flow separation, relaminarization, flow acceleration, transition to turbulence and tip leakage vortices. The results show that the blade relative position affects those heat transfer characteristics because the distributions of incoming flow velocity and turbulence intensity are changed. Especially, the heat transfer pattern on the near-tip region is significantly affected by the relative position of the blade because the effect of tip leakage vortex is strongly dependent on the blade position. On the pressure side, the effect of blade position is not so significant as on the suction side surface although the position and the size of the separation bubble are changed.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
• /
• pp.140-150
• /
• 2004

In this study, the effect of relative position of the blade for the fixed vane has been investigated on blade surface heat transfer. The experiments were conducted in a low speed stationary annular cascade, and heat transfer of blade was examined for six positions within a pitch. Turbine test section has one stage composed of sixteen guide vanes and blades. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is about $2.5\%$ of the blade chord. For the detailed mass transfer measurements on the blade surfaces, a naphthalene sublimation technique was used. The inlet flow Reynolds number is fixed to $1.5{\times}10^5$. Complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as separation bubble, relaminarization, transition to turbulence and leakage vortices. The distributions of velocity and turbulence intensity change significantly with the relative position due to the blockage effect of the blade. This causes the variation of heat transfer patterns on the blade surface. The results show that the flow near the leading edge get highly disturbed and deflected toward the either side of the blade when the blade leading edge is positioned close to the trailing edge of the vane. Therefore, separation bubble disappears on the pressure side and overall heat transfer on the relaminarization region is increased. But, due to reduced tip gap flow at the upstream region, the effect of leakage flow on the upstream region of the blade surface is weakened. Thus, the heat transfer characteristics significantly change with the blade positions.