• 천문학회보
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• 제43권2호
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• pp.39.2-39.2
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• 2018

RR Tel is an interacting binary system in which a hot white dwarf (WD) accretes matter from a Mira variable via gravitational capture of the stellar wind. We present a high-resolution optical spectrum of RR Tel obtained with MIKE at Magellan-Clay telescope, Chile. We find broad emission features at 6825, 7082, 7023, and $7053{\AA}$, which are formed through Raman scattering of far-UV O VI ${\lambda}{\lambda}$ 1032 and $1038{\AA}$, C II ${\lambda}{\lambda}$ 1036 and $1037{\AA}$ with atomic hydrogen. Raman O VI 6825 and 7082 features are characterized by double-peaked profiles indicative of an accretion flow with a characteristic speed ~ 30km/s, whereas the Raman C II features exhibit a single Gaussian profile with FWHM ${\sim}10{\AA}$. Monte Carlo simulations for Raman O VI and C II are performed by assuming that the emission nebula around the WD consists of the inner O VI disk with a representative scale of 1 AU and the outer part with C II sphere. The best fit for Raman profiles is obtained with an asymmetric matter distribution of the O VI disk, the mass loss rate of the cool companion ${\dot{M}}{\sim}2{\times}10^{-6}M_{{\odot}/yr}$ and the wind terminal velocity v~10 km/s. We also find O VI doublet at 3811 and $3834{\AA}$, which are blended with other emission lines. Our profile decomposition shows that the O VI ${\lambda}{\lambda}$ 3811, 3834 doublet have a single Gaussian profile with a width ~ 25 km/s. A comparison of the restored fluxes of C II ${\lambda}{\lambda}$ 1036 and 1037 from Raman C II features with the observed C II ${\lambda}1335$ leads to an estimate of a lower bound of N(CII) > $9.87{\times}10^{13}cm^{-2}$ toward RR Tel, which appears consistent with the presumed distance D ~ 2.6 kpc.

• Journal of Gastric Cancer
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• 제20권4호
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• pp.431-441
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• 2020

Purpose: Various studies have indicated that reduced-port robotic gastrectomies are safe and feasible for treating patients with early gastric cancer. However, there have not been any comparative studies conducted that have evaluated patients with clinically advanced gastric cancer. Therefore, we aimed to compare the perioperative outcomes of D2 lymph node dissections during reduced-port robotic distal subtotal gastrectomies (RRDGs) and conventional 5-port laparoscopic distal subtotal gastrectomies (CLDGs). Materials and Methods: We retrospectively evaluated 118 patients with clinically advanced gastric cancer who underwent minimally invasive distal subtotal gastrectomies with D2 lymph node dissections between February 2016 and November 2019. To evaluate the patient data, we performed a 1:1 propensity score matching (PSM) according to age, sex, body mass index, American Society of Anesthesiologists physical status classification score, and clinical T status. The short-term surgical outcomes were also compared between the two groups. Results: The PSM identified 40 pairs of patients who underwent RRDG or CLDG. The RRDG group experienced a significantly longer operation time than the CLDG group (P<0.001), although the RRDG group had significantly less estimated blood loss (P=0.034). The number of retrieved extraperigastric lymph nodes in the RRDG group was significantly higher than that of the CLDG group (P=0.008). The rate of postoperative complications was not significantly different between the two groups (P=0.115). Conclusions: D2 lymph node dissections can be safely performed during RRDGs and the perioperative outcomes appear to be comparable to those of conventional laparoscopic surgeries. Further studies are needed to compare long-term survival outcomes.

• 대한물리의학회지
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• 제18권1호
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• pp.15-24
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• 2023

PURPOSE: This study examined the effects of lowintensity resistance exercise combined with blood flow restriction on muscle activity and muscle fatigue to determine if such a combination may be an alternative to high-intensity resistance exercise in maintaining the muscle mass and strength and preventing degenerative loss of skeletal muscle and to provide basic data for presenting the effectiveness of exercise. METHODS: The interventions were provided for five weeks, four sessions a week, once a day, 60 minutes a session to Experimental group I (n = 13), in which low-intensity resistance exercise was applied by combining blood flow restriction with the biceps curl and experimental group II (n = 12), in which only high-intensity resistance exercise was applied. As a pre-test, the biceps brachii muscle activity and fatigue were measured by surface electromyography, and the hemodynamic variables, such as blood pressure and heart rate, were measured. The post-test was performed identically to the pre-test and compared and analyzed with the pre-test. RESULTS: A significant difference within-group was observed in the biceps brachii muscle activity and fatigue in experimental group I and only in biceps brachii activity in experimental group II. No significant differences were observed between the two groups. CONCLUSION: Since the low-intensity resistance exercise combined with blood flow restriction has similar effects to high-intensity resistance exercise, it is considered an alternative for improving muscle function in groups unable to perform high-intensity resistance exercise.

• 수면정신생리
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• 제29권1호
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• pp.4-8
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• 2022

Obesity hypoventilation syndrome (OHS) is defined as the triad of obesity (body mass index, [BMI] ≥ 30 kg/m²), daytime hypercapnia (PaCO2 ≥ 45 mm Hg), and sleep breathing disorder, after excluding other causes for hypoventilation. As the obese population increases worldwide, the prevalence of OHS is also on the rise. Patients with OHS have poor quality of life, high risk of frequent hospitalization and increased cardiopulmonary mortality. However, most patients with OHS remain undiagnosed and untreated. The diagnosis typically occurs during the 5th and 6th decades of life and frequently first diagnosed in emergency rooms as a result of acute-on-chronic hypercapnic respiratory failure. Due to the high mortality rate in patients with OHS who do not receive treatment or have developed respiratory failure, early recognition and effective treatment is essential for improving outcomes. Positive airway pressure (PAP) therapy including continuous PAP (CPAP) or noninvasive ventilation (NIV) is the primary management option for OHS. Changes in lifestyle, rehabilitation program, weight loss and bariatric surgery should be also considered.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.43-44
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• 2023

This study evaluated the mechanical and electrical properties of low-cement mortar using a large amount of industrial by-products to reduce carbon emissions from the cement industry. As types of industrial by-products, blast furnace slag and fly ash, which are representative materials, were used, and ultra-high fly ash was mixed and evaluated to solve the problem of initial strength loss. In addition, in order to evaluate the electrical properties, 1% of MWCNT was incorporated relative to the powder mass. As experimental items, the compressive strength was measured on the 1st, 3rd, 7th and 28th days of age, and the rate of change in electrical resistance was measured on the 28th day of age. As a result of the experiment, the initial strength of the test specimen mixed with blast furnace slag and fly ash was significantly lower than that of 100% cement, and the specimen mixed with blast furnace slag showed strength equal to that of cement at 28 days of age. As an electrical characteristic, the electrical resistance was reduced when the load was loaded, and this reason is judged to be the effect of improving the conductivity as the connection between CNTs is narrowed by the compressive load.

• 한국구조물진단유지관리공학회 논문집
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• 제13권1호통권53호
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• pp.97-105
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• 2009

건설산업에서 혼합콘크리트의 개발 및 사용은 내구성 측면에서의 공극구조개선 및 투수성 감소등의 확장 연구를 통해 나날이 증가하고 있는 실정이다. 한편, 콘크리트내의 균열은 투수성, 염해 침투속도 및 압축강도등을 결정하는 중요한 인자이며, 이는 철근의 부식과도 밀접한 관련을 가지는 것으로 알려져 있다. 더욱이 콘크리트 구조물의 피복두께에 균열이 발생한 경우, 이를 통해 철근 부식이 가속화됨은 주지의 사실이다. 최근에 콘크리트내의 침투를 고려한 균열효과와 관련하여 다수의 연구가 수행되어져 온 것이 사실이며, 그에 따라 내구성을 고려한 균열 혼합콘크리트의 사용수명 평가에 관한 연구도 필요한 것이 사실이다. 본 연구에서는 0.3mm의 균열을 변수로 두고, OPC, 30% PFA, 60% GGBS 및 10% SF의 결합재를 혼입하여 사용한 혼합콘크리트보의 부식평가를 자연 및 인공 환경조건에 맞추어 반전지전위측정시험, 갈바닉전류측정시험, 무게감량법등으로 측정 및 비교분석하였다.

• Journal of the Korean Wood Science and Technology
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• 제36권1호
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• pp.45-53
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• 2008

건축 내장재 중 바닥재의 연소거동을 살펴보기 위해 열류량 $50kWm^{-2}$의 콘 칼로리미터를 이용하여 측정하였다. 7종의 국산 바닥재를 이용하여 각각의 연소 거동을 최대 열방출률과 전체 열방출량 그리고 평균 열방출률을 통해서 살펴보았다. 실험한 결과 중밀도섬유판(MDF) 바닥재가 다른 바닥재에 비해 높은 열 방출 특성을 나타났다. 또한 MDF 바닥재는 연소 시 질량의 감소가 다른 바닥재보다 더 큰 것을 확인할 수 있었다. 연소 시 발생하는 가스 발생량을 측정하였는데, PE계 섬유판(PE fiberboard flooring)과 PVC계 plastic resin sheet에서 높은 일산화탄소와 이산화탄소의 발생량을 확인할 수 있었다. 비광소멸면적을 통해서 가스 평균 방출량을 살펴보면 일산화탄소나 이산화탄소와 같은 경향을 나타났다. 바닥재의 가스유해성 평가는 쥐의 행동 정지시간을 기준으로 측정하였다. 측정 결과 MDF 바닥재에서 유해성이 높은 것으로 측정되었다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.40-44
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• 2003

Soil-borne infectious disease including Pythium aphanidermatum and Rhizoctonia solani causes severe damage to plants, such as cucumber. This soil-borne infectious disease was not controlled effectively by chemical pesticide. Since these diseases spread through the soil, chemical agents are usually ineffective. Instead, biological control, including antagonistic microbe can be used as a preferred control method. An efficient method was developed to select an antagonistic strain to be used as a biological control agent strain. In this new method, surface tension reduction potential of an isolate was included in the ‘decision factor’ in addition to the other factors, such as growth rate, and pathogen inhibition rate. Considering these 3 decision factors by a statistical method, an isolate from soil was selected and was identified as Bacillus sp. GB16. In the pot test, this strain showed the best performance among the isolated strains. The lowest disease incidence rate and fastest seed growth was observed when Bacillus sp. GB16 was used. Therefore this strain was considered as plant growth promoting rhizobacteria (PGPR). The action of surface tension reducing component was deduced as the enhancement of wetting, spreading, and residing of antagonistic strain in the rhizosphere. This result showed that new selection method was significantly effective in selecting the best antagonistic strain for biological control of soil-borne infectious plant pathogen. The antifungal substances against P. aphanidermatum and R. solani were partially purified from the culture filtrates of Bacillus sp. GB16. In this study, lipopeptide possessing antifungal activity was isolated from Bacillus sp. GB16 cultures by various purification procedures and was identified as a surfactin-like lipopeptide based on the Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), high performance liquid chromatography mass spectroscopy (HPLC-MS), and quadrupole time-of-flight (Q-TOF) ESI-MS/MS data. The lipopeptide, named GB16-BS, completely inhibited the growth of Pythium aphanidermatum, Rhizoctonia solani, Penicillium sp., and Botrytis cineria at concentrations of 10 and 50 mg/L, respectively. A novel method to prevent the foaming and to provide oxygen was developed. During the production of surface active agent, such as lipopeptide (surfactin), large amount of foam was produced by aeration. This resulted in the carryover of cells to the outside of the fermentor, which leads to the significant loss of cells. Instead of using cell-toxic antifoaming agents, low amount of hydrogen peroxide was added. Catalase produced by cells converted hydrogen peroxide into oxygen and water. Also addition of corn oil as an oxygen vector as well as antifoaming agent was attempted. In addition, Ca-stearate, a metal soap, was added to enhance the antifoam activity of com oil. These methods could prevent the foaming significantly and maintained high dissolved oxygen in spite of lower aeration and agitation. Using these methods, high cell density, could be achieved with increased lipopeptide productivity. In conclusion to produce an effective biological control agent for soil-borne infectious disease, following strategies were attempted i) effective screening of antagonist by including surface tension as an important decision factor ii) identification of antifungal compound produced from the isolated strain iii) novel oxygenation by $H_2O_2-catalase$ with vegetable oil for antifungal lipopeptide production.

• 공업화학
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• 제31권5호
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• pp.575-580
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• 2020

본 연구에서는 열 안정성 염 제거장치가 추가된 아민 재생 공정을 모사하고, 폐수 량, 열 안정성 염 제거 량, MDEA(methyl diethanolamine) 손실량을 고려한 최적 운전조건 도출 전략을 제시하였다. 산성 가스를 흡수 및 탈거하는 아민 재생공정에서 열 안정성 염은 공정 장비 및 아민 용액의 흡수 효율을 저해한다. 열 안정성 염 제거 방법 중 하나인 이온교환수지법은 NaOH와 같은 강 염기성 용액을 사용하여 중화반응을 통해 염을 제거시키는 방법이다. 공정 모델링 과정에서 산성 가스의 탈거 과정은 Radfrac 모델을 사용했고, 반응의 평형상수는 Gibbs 자유에너지를 사용하여 계산하였다. 탈거된 아민 용액의 일부는 열 안정성 염 제거 장치로 들어가게 되고, 제거 장치는 중화반응을 이용한 Rstoic 모델을 사용하였다. 실제 운전데이터와 시뮬레이션 결과를 비교하여 검증하였고, 제거 장치로 들어가는 질량 유량을 조절하여 사례연구를 하고 최적 운전 조건을 제시하였다.

• Advances in nano research
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• 제16권2호
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• pp.127-140
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• 2024

Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young's modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness.