• 항공우주시스템공학회지
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• 제15권5호
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• pp.33-42
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• 2021

현대 전투기는 정안정성 완화 개념을 적용하여 기동성과 성능을 향상시키는데, 천음속 비행영역에서는 충격파 형성과 더불어 감속기동 중 발생하는 공력중심 전방이동 현상에 의해 갑작스런 기수 들림이 발생하는 경향을 갖는다. 또한 천음속 중간 받음각 비행영역은 항공기 모델링이 어려워 모델 기반의 제어 방식은 이 문제를 해결하는데 한계를 갖는다. 이번 논문에서는 초음속 경전투기 모델을 이용하여 천음속 영역에서 감속선회 기동 중 모델 기반 증분형 동적 모델역변환 방식의 천음속 피칭모멘트 보상 제어(TPMC)와 모델과 센서를 기반으로 하는 Hybrid 증분형 동적모델 역변환(IDI) 제어의 성능을 분석하였다. 분석 결과, Hybrid 증분형 동적모델 역변환 제어는 천음속 피칭모멘트 보상 제어에 비해 빠른 초기 반응과 동등한 최대 수직가속도 제한 성능을 가지면서 조종사가 예측 가능한 비행성을 제공하여 천음속 중간 받음각 비행영역에서 하중제한 초과 방지 제어기의 성능을 크게 개선하였다.

• 한국대기환경학회지
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• 제33권6호
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• pp.616-625
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• 2017

Measurements using five real-time particle samplers were compared to measurements using three NRM (National Reference Method system) filter-based samplers(Gravimetric method) at Incheon, Korea, between May and August, 2014. The purpose of this study was to suggest the quality assurance/quality control (QA/QC) method of each instrument for use in a real-time continuous particle sampler to measure the mass of airborne particles with an aerodynamic diameter less than $2.5{\mu}m$ ($PM_{2.5}$). Five real-time particle samplers of BAM1020, FH62C_14, TEOM, PM-711 and SPM-613 were evaluated by comparing its measured 23 hr average $PM_{2.5}$ concentrations with those measured with NRM filter-based samplers simultaneously. The parameters(e.g. Inlet heating condition, Slope factor, Film response, Intercept, Background, Span value) of the real-time samplers were optimized respectively by conducting test performance evaluation during 7 days in field sampling. For example, inlet heating temperature of TEOM sampler controls $35{\sim}40^{\circ}C$ to minimize the fluctuation of the real-time measurement data and background value of BAM1020 is the key factor affecting the accuracy of $PM_{2.5}$ mass concentration. We classified the $PM_{2.5}$ concentration according to relative humidity (80%) to identify water absorbed in aerosols by measuring the ${\beta}$-ray samplers(BAM1020, FH62C_14) and TEOM. ${\beta}$-ray samplers were not strongly affected by relative humidity that the difference of the average $PM_{2.5}$ concentration was about 5%. On the other hand, The TEOM sampler overestimated $PM_{2.5}$ mass concentration about 15% at low relative humidity (<80%).

• 한국농공학회논문집
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• 제57권5호
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• pp.51-60
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• 2015

In Korea, 69.4 % of duck farms had utilized conventional plastic greenhouses. In this facilities, there are difficulties in controlling indoor environments for raising duck. High rearing density in duct farms also made the environmental control difficult resulting in getting more stressed making their immune system weaker. Therefore, a facility is needed to having structurally enough solidity and high efficiency on the environmental control. So, new design plans of duck house have recently been conducted by National Institute of Animal Science in Korea. As a study in advance to establish standard, computational fluid dynamics (CFD) was used to estimate the aerodynamic problems according to the designs by means of overall and regional ventilation efficiencies quantitatively and qualitatively. Tracer gas decay (TGD) method was used to calculate ventilation rate according to the structural characteristics of duck houses including installation of indoor circulation fan. The results showed that natural ventilation rate was averagely 164 % higher than typically designed ventilation rate, 1 AER ($min^{-1}$). Meanwhile, mechanically ventilated duck houses made 81.2 % of summer ventilation rate requirement. Therefore, it is urgent to develop a new duck house considering more structural safety as well as higher efficiency of environmental control.

• 대한후두음성언어의학회지
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• 제33권3호
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• pp.166-171
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• 2022

Background and Objectives Vocal fold (VF) scar is known to be the most common cause of dysphonia after laryngeal microsurgery (LMS). Steroids reduce postoperative scar formation by inhibiting inflammation and collagen deposition. However, the clinical evidence of whether steroids are helpful in reducing VF scar formation after LMS is still lacking. The purpose of this study is to determine whether intralesional VF steroid injection after LMS helps to reduce postoperative scar formation and voice quality. Materials and Method This study was conducted on 80 patients who underwent LMS for VF polyp, Reinke's edema, and leukoplakia. Among them, 40 patients who underwent VF steroid injection after LMS were set as the injection group, and patients who had similar sex, age, and lesion size and who underwent LMS alone were set as the control group. In each group, stroboscopy, multi-dimensional voice program, Aerophone II, and voice handicap index (VHI) were performed before and 1 month after surgery, and the results were statistically analyzed. Results There were no statistically significant differences in the distribution of sex, age, symptom duration, occupation and smoking status between each group. Both groups consisted of VF polyp (n=21), Reinke's edema (n=11), and leukoplakia (n=9). On stroboscopy, the lesion disappeared after surgery, and the amplitude and mucosal wave were symmetrical on both sides of the VFs in all patients. Acoustic parameters and VHI significantly improved after surgery in all patients. However, there was no significant difference between the injection and control group in most of the results. Conclusion There was no significant difference in the results of stroboscopy, acoustic, aerodynamic, and subjective evaluation before and after surgery in the injection group and the control group.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1487-1501
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• 2011

Recently, fast-growing up railway transportations. Because, regional traffic congestion problem solving and a period of rapid expansion to meet the demand of industries. In addition the government also suggest to new paradigm for the future 'Low Carbon, Green Growth' is presented as a new national vision. To meet the social needs and the time demands, Last of the railway increase very long tunnels and huge deep tunnels. Especially this trend accelerated high speed up in the tunnel, the revision of design criteria and research challenges are being actively improved. Mainly in the tunnel cross-section was under the control of the vehicle train speed 150km/hr by the construction of the vehicle cross-section of the tunnel. More than 200km/hr rail tunnel depending on the vehicle's speed caused the tunnel to the pressure fluctuations will be governed by the aerodynamic changes. Considering the economy to ensure the optimum cross-section of the railway tunnel to the description scheme is selected cross-section of the railway tunnel to determine the size domestic or international railway tunnel for the elements((based on fast Algorithm design criteria, the center line spacing, streetcar line, cross-sectional shape, sectoral issues, such as interface and aerodynamics) based on design practices and to review results. In this study, to propose guidelines depending on the size of a railway tunnel cross section for the size of the determining reasonable factors when designing the railway tunnel and cost-effective standards guidelines.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.125-130
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• 2001

Experimental and analytical researches have been conducted on the twin-fluid atomizers for better droplet breakup during the past decades. But, the studies on the disintegration mechanism still present a great challenge to understand the drop behavior and breakup structure. In an effort to describe the aerodynamic behavior of the sprays issuing from the internal mixing counter-swirling nozzle, the spatial distribution of axial (U) radial (V) and tangential (W) components of droplet velocities are investigated across the radial distance at several axial locations of Z=30, 50, 80, 120 and 170mm, respectively. Experiments were conducted for the liquid flow rates which was kept constant at 7.95 g/s and the air injection pressures were varied from 20 kPa to 140 kPa. Counter-swirling internal mixing nozzles manufactured at angles of $15^{\circ},\;30^{\circ},\;45^{\circ}$ and $60^{\circ}$ the central axis with axi-symmetric tangential-drilled holes was considered. The distributions of velocities and turbulence intensities are comparatively analyzed. PDPA is installed to specify spray flows, which have been conducted along the axial downstream distance from the nozzle exit. Ten thousand of sampling data was collected at each point with time limits of 30 second. 3-D automatic traversing system is used to control the exact measurement. It is observed that the sprays with all swirl angle have the maximum SMD for on air injection pressure of 20 kPa and 140 kPa with centerline, respectively. The nozzle with swirl angle of $60^{\circ}$ has vest performance.

• 한국항공우주학회지
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• 제43권7호
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• pp.601-608
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• 2015

유연날개의 공력 및 구조 설계값을 설계 변수로 하여 정적 상태에서의 정적 공탄성해석 및 최적화를 수행하였다. 정적 공탄성해석과 최적화를 위해 상용 해석소프트웨어들이 연계된 강건한 다분야 최적설계 시스템을 개발하였다. 최적화 설계변수로는 가로세로비, 테이퍼비, 후퇴각과 날개 위아래 스킨 두께를 설정하였다. 전역적 다목적 최적화를 위해 실수기반 적응영역 다목적 유전자 알고리즘을 적용하였으며 계산시간을 줄이기 위해 메타모델로 서포트벡터회귀 기법을 적용하였다. 유연날개에 대한 파레토 결과 분석을 통해 최대 항속시간과 최소 중량에 대한 최적 결과를 확인하였다.

• 한국항공우주학회지
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• 제32권6호
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• pp.56-63
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• 2004

본 연구에서는 공력 압축성 효과를 고려하여 플랩이 있는 무인기 카나드에 대한 동적 공탄성 해석을 수행하였다. 고려한 해석 모델은 국내에서 개발 후보로 검토된 모델 중 하나인 CRW(Canard-Rotor-Wing) 무인기의 전운동(all-movable) 카나드이다. 초기 설계 데이터를 기반으로 하여 등가구조 날개 모델을 구성하였다. 엄밀한 공탄성 특성해석을 위해 주파수 및 시간영역 해석기법이 모두 적용되었으며, 카나드 및 플랩 연결부의 회전강성 변화에 대한 매개변수 연구를 수행하였다. 플랩이 있는 전운동 조종면의 경우 각 조종축에서의 등가회전강성은 공탄성 안정성에 중요한 설계인자이다. 본 연구를 통하여 설계 초기단계에서 동적공탄성 안정성에 미치는 영향을 파악하였으며 관련 해석결과들을 제시하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.441-447
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• 2002

KSR-III(Korea Sounding Rocket - III), which is being developed by Space Technology R&D Division of KARI(Korea Aerospace Research Institute) will be launched in late 2002. It is a three-stage, liquid propellant rocket which can reach 250 km altitude and will carry out observation of ozone layer and scientific experiments, such as microgravity experiment, and atmospheric measurement. KSR-III is believed to be an intermediate to the launch vehicle capable of carrying a satellite to its orbit. Space Test Department of KARI performed GVT(Ground Vibration Test) fer KSR-III EM at Rocket Test Building of KARI. GVT is very important for predicting the behavior of rocket in its operation, developing flight control program and performing aerodynamic analysis. This paper gives an introduction of rocket GVT configuration and information on test procedures, techniques and results of It. In this test. to simulate free-free condition, test object hung in the air laterally by 4 bungee cords specially devised. For the excitation of test object, pure random signal by two electromagnetic shakers was used and total 22 frequency response functions were achieved. Polyreference parameter estimation was performed to identify the modal parameters with MIMO(Multi-Input-Multi-Output) method. As the result of the test, low frequency mode shapes and modal parameters below 60Hz were identified

• 대한후두음성언어의학회지
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• 제19권1호
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• pp.11-15
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• 2008

Endoscopic laser cordectomy is known as an oncologically sound procedure for T1 and selected T2 glottic carcinoma ; it has comparable local control rate and better long-term laryngeal preservation rate when compared with those of radiotherapy. Even if results of the reported voice outcome studies after surgery or radiotherapy are diverse and controversial, resection deeper than the body layer of the vocal fold (type III, IV, V cordectomy) usually leads to aerodynamic insufficiency during phonation and results in poor voice quality. A keyhole defect or development of synechiae at the anterior commissure after type VI cordecomy may also result in unsatisfactory vocal outcome. However, many advances in phonosurgical techniques are reported to be successfully applied in the reconstruction of glottal defect that is subsequent to endoscopic laser cordectomy. In case of glottal insufficiency, voice restoration can be achieved by means of augmentation of the paraglottic space or medialization of the excavated vocal fold. Injection laryngoplasty with synthetic materials or autologous fat is gaining its popularity for restoring minor glottal volume defect because of its convenience. Laryngeal framework surgery, especially type I thyroplasty with premade implant systems or Gore-Tex, is most frequently used to correct larger glottic volume defect. In case of anterior commissural keyhole defect, additional procedure including laryngofissure may be required. For anterior commissural synechiae, laryngeal keel may be inserted for several weeks or mitomycin-C may be repeatedly applied after the division of adhesive scar to prevent restenosis. In this paper, current concepts and the authors' experiences of phonosurgical reconstruction of vocal function after endoscopic cordectomy will be introduced.