• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.425-432
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• 2011

In tilting pad bearing design process, the selection of the proper configuration type of either a Load-Between-Pad (LBP) or Load-On-Pad (LOP) as well as preload and pivot offset conditions is to be carefully considered. Also the bearing needs to be designed in order to be suited for the rotor-bearing system and operating condition. In this paper, it is observed that the dynamic characteristics in a 5 pad tilting pad bearing for the LBP and the LOP configurations are influenced by the variation of preload and pivot offset. In this context, rotor dynamic analysis of the 5MW industrial gas turbine supported by the tilting pad bearing at the front and roller bearing at the rear is carried out based on the dynamic coefficients of the tilting pad bearing investigated. The result shows that two rigid body critical modes experience various changes according to the influence of the tilting pad bearing uniquely applied to one side of this machine. Mainly, the second critical speed, the rigid body mode of conical shape with high whirling in the tilting pad bearing, is significantly changed by preload and pivot offset regardless of the LBP and LOP configurations. And, the first critical mode, the rigid body mode of conical shape with high whirling in the roller bearing, is sensitively affected by preload applied to the LOP configuration and by the its asymmetric dynamic properties.

• 한국산학기술학회논문지
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• 제18권2호
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• pp.737-742
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• 2017

본 최근 기존의 모습과는 다른 고층건물의 형태가 대도시에서 랜드마크로서 주목을 끌고 있으며 혁신적인 건물형태에 대한 탐색은 건축분야에서 지속적으로 이루어질 것이다. 본 연구에서는 소규모의 구조체에 활용되고 있는 $Isotruss^{(R)}$ 그리드를 건물의 외주골조에 적용하여 구조적 성능을 검토하였다. 구조적 거동을 비교하기 위해 다이아그리드 구조시스템을 준거로 하였다. 동일한 규모의 16층, 32층, 48층 건물을 두가지의 구조시스템으로 설계하였다. 아이소트러스 그리드 구조 부재의 선정은 예비적 설계단계로 생각하여 다이아그리드의 강성에 기준한 설계방법을 이용하였다. 경사기둥의 각도로 아이소트러스 구조는 $59^{\circ}$, 다이아그리드 구조는 $68.2^{\circ}$로 하였다. 횡강성, 철골량, 외부골조의 횡력 부담비율, 기둥의 축력 강도비, 고유 진동수를 비교하였다. 6개의 건물 모델을 해석한 결과 두 구조시스템의 구조적 성능은 유사하나 외주골조의 횡하중 분담율이 아이소트러스 그리드 구조가 93.3%로 다이아그리드 구조의 88.7% 보다 약간 커서 코어 기둥의 배치에 있어 유리하다고 볼 수 있다. 따라서 본 연구에서 제안하는 아이소트러스 그리드 시스템은 입면형태가 독특할 뿐만 아니라 기존의 구조시스템과 동등한 구조적 성능을 보유한 것으로 보인다.

• 한국음향학회지
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• 제35권6호
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• pp.480-490
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• 2016

풍력터빈의 대형화와 경량화에 따라 풍력터빈에 작용하는 동하중에 의한 진동 응답이 크게 발생할 수 있다. 특히 공진에서는 큰 진동 응답이 발생하므로 설계 시 정확한 고유진동수의 예측이 요구된다. 이를 위해 풍력터빈 지지구조와 지반에 대한 연성해석이 요구되는데, 일반적으로 유한요소에 기반한 수치적인 방법이 주로 이용된다. 그러나 유한요소 해석은 파일-지반 모델링 및 연산에 많은 노력과 시간을 요구하므로 초기 설계 단계에서는 활용에 많은 제약이 따른다. 반면, 지반을 선형화한 이론 해석은 모델이 단순하고 연산 시간이 매우 짧으므로, 해석의 신뢰성이 확보된다면 지반-지지구조의 거동 특성을 초기에 예측하는데 유용한 도구가 될 수 있다. 본 논문에서는 이론 해석을 이용해 지반에 인입된 파일에 대한 파일-지반 연성해석을 수행하였다. 해석 시 지반의 변형은 탄성 범위 이내에 있다고 단순화하여 파일은 보로, 지반은 연속체로 모델링하였다. 본 연속체 모델을 이용해 파일 상단에 수평 하중 또는 모멘트가 작용할 때 발생하는 파일의 횡변형을 구하고, 파일의 세장비에 따른 영향계수를 도출하였다. 그리고 이를 유한요소해석을 기반으로 한 문헌의 결과와 비교함으로써 해석 결과의 신뢰도를 평가하였다. 이를 통해 연속체 모델의 해석은 세장비가 큰 파일에 대해서는 유효한 반면 약 3 이하의 낮은 세장비를 가지는 파일에서는 신뢰성이 떨어짐을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제25권6호
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• pp.648-655
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• 2014

This paper describes the continuing effort to develope a single acting free-piston Stirling engine/alternator combination for use of the household cogeneration. Free piston Stirling engines(FPSE) use variations of working gas pressure to drive mechanically unconstrained reciprocating elements. Stirling cycle free-piston engines are driven by the Stirling thermodynamic cycle which is characterized by an externally heated device containing working gas that is continuously re-used in a regenerative, reversible cycle. The ideal cycle is described by two isothermal process connected by two constant volume processes. Heat removed during the constant volume cooling process is internally transferred to the constant volume heating process by mutual use of a thermal storage medium called the regenerator. Since the ideal cycle is reversible, the ideal efficiency is that of Carnot. Free-piston Stirling engine is have no crank and rotating parts to generate lateral forces and require lubrication. The FPSE is typically comprised of two oscillating pistons contained in a common cylinder. The temperature difference across the displacer maintains the oscillations, and the FPSE operate at natural frequency of the mass-spring system. The power is generated from a linear alternator. The purpose of this paper is to describe the design process of the single acting free-piston Stirling engine/alternator. Electrical output of the single acting free-piston Stirling engine/alternator is about 0.95 kW.

• 대한후두음성언어의학회지
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• 제24권2호
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• pp.107-111
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• 2013

Objectives : We developed two-dimensional (2D) scanning videokyomography to evaluate the mucosal wave of whole vocal cords in real time to overcome the limit of preexisting stroboscopy and line scanning videokymography which could not evaluate it. Methods : We implemented a continuous light source with high brightness, a high-definition CMOS camera, and capture board for saving the data. We created the software program to analyze the image data from the system. The test of the functionality of the 2D scanning videokymography camera was performed in one of the authors (P.H.J 32 years old male). Vocal cord images were obtained during normal phonation and falsetto phonation. Images were obtained also during cough, diplophonia. Results : The system made it possible to measure objective parameters, including fundamental frequency, amplitude, regularity, mucosal wave, and phase difference, medial and lateral peak, opening versus closing duration related to vocal fold vibration. Simultaneously, it enabled analysis of the whole mucosal wave of the entire vocal fold in real time. 2D scanning videokymography was also effective for evaluating the dynamic status of the vocal fold when the subject phonated aperiodic voice. Conclusion : In conclusion, 2D scanning videokymography can support the analysis of the whole mucosal wave of the entire vocal cord with objective vocal parameters, overcoming the limitations of stroboscopy and previous line scanning videokymography techniques.

• Journal of Acupuncture Research
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• 제26권3호
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• pp.115-131
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• 2009

Objectives: This survey was done in order to find out how Korean medical doctors derive pattern identification for acupuncture prescriptions in treating low back pain in real clinical practice. Methods : The survey questionnaire was developed by the committee of experts who major in acupuncture & moxibustion or statistics for acupuncture clinical trial protocol development. The questionnaires were distributed via e-mail to 75 members of Korean Acupuncture & moxibustion society from March 26th to April 14th in 2009. 57 members completed answers, and the computerized data were analyzed by SPSS 17.0 statistical program. Results : 1.57 Korean medical doctors selected meridian pattern identification based on the course of the meridians(44.6%), visceral pattern identification(32.1%), pattern identification based on cause of disease(14.3%) as the most commonly used pattern identification methods for acupuncture prescription when treating low back pain patients in real clinical practice. 2. In meridian pattern identification based on the course of the meridians, gallbladder meridian of hypochondriac region(13.0%), bladder meridian of lateral low back region(11.2%), governer vessel of central low back region(11.7%) were selected 3. In visceral pattern identification, yang deficiency of kidney(20.2%), deficiency of kidney(19.3%), liver(16.7%), yin deficiency of kidney(14.0%), violence qi of kidney(8.8%), small intestine(7.9%) were selected. Conclusions : In our e-mail survey, Korean medical doctors answered that Meridian Pattern Identification based on the course of the meridians is the most often used diagnosis method. Visceral pattern identification, pattern identification based on cause of disease, meridian pattern identification based on symptom and pattern identification based on qi-blood-yin-yang theory in order of frequency used, were selected for low back pain diagnosis in real clinical practice.

• Journal of Acupuncture Research
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• 제26권3호
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• pp.59-65
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• 2009

Objectives : This survey was done in order to find out how Korean medical doctors derive pattern identification for acupuncture prescriptions in treating knee pain in real clinical practice. Methods : The survey questionnaire was developed by the committee of experts who major in acupuncture & moxibustion or statistics for acupuncture clinical trial protocol development. The questionnaires were distributed via e-mail to 75 members of Korean Acupuncture & moxibustion society from March 26th to April 14th in 2009. 57 members completed answers, and the computerized data were analyzed by SPSS 17.0 statistical program. Results : 1.54 Korean medical doctors selected meridian pattern identification based on the course of the meridians(52.5%), visceral pattern identification(27.1%), pattern identification based on cause of disease(8.5%) as the most commonly used pattern identification methods for acupuncture prescription when treating knee pain patients in real clinical practice. 2. In meridian pattern identification based on the course of the meridians, liver meridian of the medial knee region(13.2%), bladder meridian of the posterior knee region(12.0%), spleen meridian of the lateral knee region(11.7%), stomach meridian of the anterior knee region(9.8%) and kidney meridian of the medial knee region(8.6%) were selected. 3. In visceral pattern identification, blood stasis of sinews due to liver and kidney deficiency(5.3%), damp joint with yang deficiency of liver and kidney(4.9%), kidney qi deficiency with congealing cold(4.5%), yin deficiency of liver and kidney(4.1%) were selected. Conclusions : In our e-mail survey, Korean medical doctors answered that Meridian Pattern Identification based on the course of the meridians is the most often used diagnosis method. Visceral pattern identification, pattern identification based on cause of disease, pattern identification based on symptom and pattern identification based on qi-blood-yin-yang theory in order of frequency used, were selected for knee pain diagnosis in real clinical practice.

• Steel and Composite Structures
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• 제48권2호
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• pp.207-233
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• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• 한국산림과학회지
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• 제36권1호
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• pp.9-25
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• 1977

소나무 천연집단(天然集團)의 변이(變異)를 조사(調査)하기 위(爲)해 1971년(年), 1975년(年)에 각각(各各) 3개집단(個集團)을 조사(調査)한데 이어 1976년(年)에 강원도(江原道)의 이제군(麟蹄郡) 기린면(麒麟面) 진동리(鎭東里)(집단(集團) 7)와 정선군(旌善郡) 임계면(臨溪面) 약천리(藥川里) (집단(集團) 8) 그리고 삼척군(三陟郡) 하장면(下長面) 한소리(汗沼里)(집단(集團) 9)에서 각각(各各) 1개집단(個集團)(한 집단(集團)에서 20주(株))씩의 임분(林分)을 택(擇)하였으며 외형적(外形的)으로 우량(優良)하다고 생각되는 임목개체(林木個體)를 대상(對象)으로 조사(調査)하였다. 대상임목(對象林木)은 외부(外部) 형태학적(形態學的) 특성(特性), 침엽(針葉)의 특성(特性), 재질(材質)의 특성(特性)이 조사분석(調査分析)되었고 그 결과(結果)는 다음과 같이 요약(要約)된다. 1. 3개집단(個集團)의 평균임령(平均林齡)은 50~63년간(年間)에 있고 성장(成長)은 비슷하였다. 직관(直觀)으로 판단(判斷)할 때 삼척집단(三陟集團)이 우량수형(優良樹型)을 가진 것으로 생각되었다. 지하고율(枝下高率)은 정선집단(旌善集團)이 0.53으로 가장 높은 값이었고 수관지수(樹冠指數)는 0.91로서 불량(不良)하다고 생각되었다. 삼척집단(三陟集團)은 세지성(細枝性)이라는 점(點)과 분지각(分枝角)이 가장 예각(銳角)이란 점(點)에 있어서 바람직했다. 수관장(樹冠長)은 모두 비슷했다. 2. 지하고대(地下高對) 수고(樹高) 그리고 수관지수(樹冠指數)의 빈도분포(頻度分布)를 보면 집단간(集團間)에 차이(差異)가 있는 것으로 사료(思料)되었다. 3. 거치밀도(鋸齒密度)는 3개집단(個集團) 모두 약 27로서 집단간(集團間) 유의차(有意差)는 없었고 개체간차(個體間差)가 큰 것으로 나타났다. 특히 높은 밀도(密度)를 가지는 개체(個體)(40이상(以上)의 것)가 있었다. 기공열수(氣孔列數)와 수지도수(樹指道數)에 있이거도 집단간차이(集團間差異)는 없었고 개체간차이(個團間差異)는 컸다. 4. 수지도지수(樹指道指數)(R.D.I.)에 있어서는 집단(集團)8이 0.074로서 다른 두집단(集團)의 2-3배(倍)의 값을 보였다. 5. 10년단위(年單位) 평균(平均) 연륜폭(年輪幅)의 성장과정(成長過程)은 초기(初期)(30년(年)까지)에는 집단간(集團間)의 차이(差異)가 있었으나 그 이후(以後)가 되면서 같은 값에 접근(接近)했다. 6. 평균추재졸(平均秋材卒)에 있어서는 집단간(集團間)의 차이(差異)가 없었으나 Range에 있어서 차이(差異)가 있었다. 가령 집단(集團)8은 23~30인데 집단(集團)9는 16~36으로 7 : 20의 차(差)를 나타내고 있다. 7. 목재비중(木材比重)은 평균치(平均値)에 있어서 집단간(集團間)의 차이(差異)가 없었고 Range에 있어서도 그러하였다. 수령(樹齡)의 증가(增加)에 따라 비중(比重)은 증가(增加)하나 그 증감(增減)의 과정(過程)은 집단(集團)에 따라 차이(差異)가 있다. 8. 가도관장(假導管長)은 집단간차이(集團間差異)가 없고 Range 또한 비슷하고 수령(樹齡)의 증가(增加)에 따라 그 길이가 증가(增加)하고 있었다. 증가경향(增加傾向)의 집단간차이(集團間差異)가 없었다.