• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
• /
• pp.322-325
• /
• 1994

Mareel and Bitmead proved the presence of chaotic signal in random noise by applying dead beat control theory to adaptive mechanism. In this paper robust adaptive theory is proposed. With the property of chaotic signal that has order and law, the proposed theory can enhance the control Performance by applying the recursive algorithm that uses dynamic relation which have small correlation. The performance of proposed algorithm is demonstrated with the computer simulation of position control of electric motor. In this simulation, the adaptive low is adopted to control electric motor and the Presence of chaotic signal in feedback signal is proved by using several method such as time series, fourier spectrum phase portrait method.

• Ocean Systems Engineering
• /
• 제7권3호
• /
• pp.179-193
• /
• 2017

Dynamic response analysis of offshore triceratops with stiffened buoyant legs under impact and non-impact waves is presented. Triceratops is relatively new-generation complaint platform being explored in the recent past for its suitability in ultra-deep waters. Buoyant legs support the deck through ball joints, which partially isolate the deck by not transferring rotation from legs to the deck. Buoyant legs are interconnected using equally spaced stiffeners, inducing more integral action in dispersing the encountered wave loads. Two typical nonlinear waves under very high sea state are used to simulate impact and non-impact waves. Parameters of JONSWAP spectrum are chosen to produce waves with high vertical and horizontal asymmetries. Impact waves are simulated by steep, front asymmetric waves while non-impact waves are simulated using Stokes nonlinear irregular waves. Based on the numerical analyses presented, it is seen that the platform experiences both steady state (springing) and transient response (ringing) of high amplitudes. Response of the deck shows significant reduction in rotational degrees-of-freedom due to isolation offered by ball joints. Weak-asymmetric waves, resulting in non-impact waves cause steady state response. Beat phenomenon is noticed in almost all degrees-of-freedom but values in sway, roll and yaw are considerably low as angle of incidence is zero degrees. Impact waves cause response in higher frequencies; bursting nature of pitch response is a clear manifestation of the effect of impact waves on buoyant legs. Non-impact waves cause response similar to that of a beating phenomenon in all active degrees-of-freedom, which otherwise would not be present under normal loading. Power spectral density plots show energy content of response for a wide bandwidth of frequencies, indicating an alarming behaviour apart from being highly nonlinear. Heave, being one of the stiff degrees-of-freedom is triggered under non-impact waves, which resulted in tether tension variation under non-impact waves as well. Reduced deck response aids functional requirements of triceratops even under impact and non-impact waves. Stiffened group of buoyant legs enable a monolithic behaviour, enhancing stiffness in vertical plane.

• Wind and Structures
• /
• 제25권1호
• /
• pp.1-24
• /
• 2017

This paper presents a 1:25 multi-freedom aero-elastic model for a high lighting pole at the Zhoushan stadium. To validate the similarity characteristics of the model, a free vibration test was performed before the formal test. Beat phenomenon was found and eliminated by synthesis of vibration in the X and Y directions, and the damping ratio of the model was identified by the free decay method. The dynamic characteristics of the model were examined and compared with the real structure; the similarity results were favorable. From the test results, the major along-wind dynamic response was the first vibration component. The along-wind wind vibration coefficient was calculated by the China code and Eurocode. When the peak factor equaled 3.5, the coefficient calculated by the China code was close to the experimental result while Eurocode had a slight overestimation of the coefficient. The wind vibration coefficient during typhoon flow was analyzed, and a magnification factor was suggested in typhoon-prone areas. By analyzing the power spectrum of the dynamic cross-wind base shear force, it was found that a second-order vortex-excited resonance existed. The cross-wind response in the test was smaller than Eurocode estimation. The aerodynamic damping ratio was calculated by random decrement technique and the results showed that aerodynamic damping ratios were mostly positive at the design wind speed, which means that the wind-induced galloping phenomenon is predicted not to occur at design wind speeds.

• 한국초등과학교육학회지:초등과학교육
• /
• 제31권4호
• /
• pp.450-462
• /
• 2012

Gestures are a common phenomenon of human communication. There exists little research concerned with the gestures in science education, and most researches of gestures have focused on individual gestures. However, learning occurs through sociocultural interactions with friends, family, teachers, and others in society. Hence, the purpose of this study was to investigate and identify the types and features of gestures which were made by elementary students to communicate with peers in science discourse. A group of six fourth-graders was observed in eight science discourses where they talked about ideas related to thermal concepts. The data was collected through interviews and questionnaires. The analysis of the data showed that students' gestures in science discourses could be classified into seven types: signal iconic gesture, illustrative iconic gesture, personal deictic gesture, object deictic gesture, beat gesture, emotional metaphoric gesture, and content metaphoric gesture. It was also found that these gestures had functions of repeating, supplementing, and replacing utterance to communicate with others. Students frequently expressed scientific terms metaphorically as everyday terms through their gestures. Gestures were shared, imitated, and transferred in the communication process, and students' gestures also made influence on other students' ideas through these processes.

• 전기학회논문지
• /
• 제60권6호
• /
• pp.1128-1133
• /
• 2011

In a wind farm, a large number of small wind turbine generators (WTGs) operate whilst a small number of a large generator do in a conventional power plant. To maintain high quality and reliability of electrical energy, a wind farm should have equal performance to a thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid, which gives significant effects on the operation of a wind farm and the power system stability. This paper presents an analysis of response of a wind farm during grid fault conditions. During fault conditions, each WTG might produce different frequency components in the voltage. The different frequency components result in the non-fundamental frequencies in the voltage and the current of a wind farm, which is called by "beats". This phenomenon requires considerable changes of control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement of a wind farm. Moreover, it may cause difficulties in protection relays of a wind farm. This paper analyzes the response of a wind farm for various fault conditions using a PSCAD/EMTDC simulator.

• 대한기계학회논문집A
• /
• 제26권9호
• /
• pp.1905-1913
• /
• 2002

Using the finite element method, this study investigates the dynamic time responses of a flexible spinning disk of which axis of rotation is misaligned with the axis of symmetry. The misalignment between the axes of symmetry and rotation is one of the major vibration sources in optical disk drives such as CD-ROM, CD-R, CD-RW and DVD drives. Based upon the Kirchhoff plate theory and the von-Karman strain theory, three coupled equations of motion for the misaligned disk are obtained: two of the equations are for the in-plane motion while the other is for the out-of-plane motion. After transforming these equations into two weak forms for the in-plane and out-of-plane motions, the weak forms are discretized by using newly defined annular sector finite elements. Applying the generalized-$\alpha$ time integration method to the discretized equations, the time responses and the displacement distributions are computed and then the effects of the misalign ment on the responses and the distributions are analyzed. The computation results show that the misalignment has an influence on the magnitudes of the in-plane displacements and it results in the amplitude modulation or the beat phenomenon in the time responses of the out-of-plane displacement.

• 수면정신생리
• /
• 제9권1호
• /
• pp.24-33
• /
• 2002

목 적 : 폐쇄성 수면무호흡증(이하 수면무호흡증) 환자에서 고혈압이 흔히 병발되나 지속적 상기도 양압술(이하 양압술)에 따른 고혈압 해소 정도는 연구방법에 따라 상이한 결과를 보이고 있다. 이에 저자들은 지속적-비관혈적 혈압 측정법을 이용하여 기초 혈압치가 다양한 수면무호흡증 환자군에서 양압술을 적용하면서 야간 수면중 혈압 및 심박 동수 반응에 양압술이 미치는 영향을 연구하고자 하였다. 또한 양압술에 의한 혈역학적 변화에 영향을 줄 수 있는 요인들을 찾고자 하였다. 방 법 : 연구대상으로는 수면무호흡증의 임상 증상을 지니고 있으며 기초 측정일의 야간 수면다원검사 결과 호흡장애지수가 5이상인 환자 10명(평균연령 52.2$\pm$12.4세, 남자 9명, 여자 1명)을 선택하였다. 양압술을 시행하지 않은 상태인 기초 측정일과 양압술을 시행한 양압술 시행일 모두에서 야간 수면다원기록과 동시에 지속적-비관혈적 혈압측정기($Finapres^{(R)}$)를 사용하여 매 박동(beat-to-beat)시의 수축기 혈압, 이완기 혈압, 그리고 심박동수를 측정하였다. 또한 매 2초마다 혈중산소포화도($SaO_2$)를 측정하였다. 기초 측정일과 양압술 시행일 두 군간에 혈역학적 및 호흡기적 변인들의 평균치를 비교하였다. 기초 측정일 값에서 양압술 시행일 값을 뺀 수축기 혈압 델타값 및 이완기 혈압 델타값 각각과 기초 측정일의 측정치들(수축기 혈압, 이완기 혈압, 그 각각의 혈압 변이도, 심박동수 및 심박동수 변이도, 혈중산소포화도 평균치, 그리고 호흡장애지수), 양압술 시행일의 측정치들(양압술 처방압력 및 총 각성시간 분율), 연령, 그리고 비만도 간의 상관관계를 분석하였다. 결 과 : 1) 혈중 산소포화도의 평균치와 호흡장애지수가 기초 측정일에 비해 양압술 시행일에서 각각 증가(p<.01) 및 감소(p<.01)하였으나, 혈역학적 변인을 포함한 다른 비교 변인들에서는 차이가 없었다. 2) 기초 측정일의 혈압에서 양압술 시행일의 혈압을 뺀 델타값들을 분석한 결과 기초 측정일의 혈압치와 대상군의 연령에 따라 혈압 반응이 차별적으로 나타났다. 수축기 혈압 델타값과 기초 측정일의 수축기 혈압간에 유의한 정적 상관관계를 보였으나(p<.01), 이완기 혈압 델타값과 기초 측정일의 이완기 혈압간에는 각성기(p<.01)를 제외한 다른 수면단계에서 유의한 상관관계가 없었다. 렘수면단계를 제외한 모든 수면단계에서 이완기 혈압의 델타값과 연령 사이에 유의한 역 상관관계가 있었지만(p<.05), 수축기 혈압의 델타값과 연령 간에는 유의한 상관관계가 없었다. 3) 수축기 혈압 델타값 및 이완기 혈압델타값 각각과 기초 측정일의 측정치들, 양압술 시행일의 측정치들, 그리고 비만도 간의 상관관계를 분석한 결과, 이완기 혈압 델타값과 양압술 시행일의 각성시간 분율간의 유의한 정적 상관관계(p<.01) 외에는 유의한 상관관계가 없었다. 결 론 : 양압술 적용에 따라 수축기 혈압 델타값과 이완기 혈압 델타값이 기초 측정일의 수축기 혈압치와 대상군의 연령에 따라 각각 증가 또는 감소하였다. 따라서, 본 연구는 양압술에 따른 혈압 반응은 단순 감소로 나타나는 것이 아니라 여러 변인의 조건에 따라 차별적 혈압 반응 양상으로 나타나는 복합적인 현상이며 앞으로 좀더 세밀하게 연구되어야 할 대상임을 시사한다.

• 한국감성과학회:학술대회논문집
• /
• 한국감성과학회 2000년도 추계학술대회 논문집
• /
• pp.81-87
• /
• 2000

Beat-to-beat changes in heart period (heart period variability, HPV) are mediated by fluctuations in autonomic activity. Spectral analysis is used to quantify such fluctuations in the range of 0.15-0.40 Hz (high frequency, HF), which are influenced primarily by parasympathetic factors. These fluctuations are often referred to as RSA (respiratory sinus arrhythmia), the physiological phenomenon extracted by spectral analysis and other methods including histograms of heart rate ( HR), deviations of HR etc. Respiratory sinus arrhythmia indexing with peak-to-valley method suggested by Grossman et at., (1981) yields a simple range statistic and is quantified on breath-by-breath basis, thus being quite sensitive and less dependent on recording time as compared to spectral analysis. It is strongly recommended to use at least 1 min epoch to asses HF component of HPV and at least 2 min fer low frequency (LF) of HPV and even 5 min far valid clinical assessment. Peak-to-valley statistic is limited to RSA index only, but has its pragmatic advantages. Most important is possibility of its application far relatively small epoch analysis. We used short periods (20,30, 40 sec only) and off-line analysis of RSA using ECG and respiration curve this method of assessment and proved that this method is more practically effective. The RSA index was not so far dependent on respiration pattern differences and reflected actual vagal control of HR and were accompanied by low HR under some high stress conditions and in an aversive affective visual stimulation experiments. Another factor that might modulate cardiac chronotropic response is the interaction of sympathetic and parasympathetic inputs on sino-atrial (SA) node level, because responses to vagal influences are known to be proportional to ongoing sympathetic activity, that is so called accentuated antagonism. Since sympathetic outflow (increment of influences on SA) under negative emotions or stress was high in almost all physiological responses, vagal effects on HR could be therefore potentiated, leading to masking of output cardiac response seen in HPV, In the case of moderate sympathetic activation, on the other hand, autonomic interactions in cardiac control appear to be minimal. Thus RSA index appears to be an effective alternative method to assess and measure spectral HPV.

• 터널과지하공간
• /
• 제23권1호
• /
• pp.42-53
• /
• 2013

천공 작업 시 드릴비트 버튼의 타격 속도와 타격 간격은 천공효율을 높이는데 있어 매우 중요한 요소이다. 따라서 본 연구에서는 버튼의 타격 속도 및 간격에 따른 암반 파쇄성능을 분석하기 위하여 홉킨스바 시험기를 이용한 타격시험을 수행하였다. 먼저, 버튼의 타격속도에 따른 암석파쇄 현상을 분석하기 위하여 단일타격 시험을 수행하였고, 수치해석을 통해 단일 타격 시험에 대한 암석의 파쇄과정을 모사하였다. 다음으로 버튼의 타격 간격에 따른 천공효율을 예측하기 위하여 타격 후 설정된 거리만큼 암석 시료를 이동시키고 재차 타격하는 방식으로 다중타격 시험을 수행하였다. 타격시험 후 암석의 천공부피는 레이저 스캐너를 이용하여 측정하였으며, 타격에너지와 천공부피를 통해 천공성능을 계산하였다. 이러한 시험 결과를 바탕으로 직경 102 mm 드릴비트의 1회 타격 시 천공성능을 예측하였다.

• 패션비즈니스
• /
• 제1권1호
• /
• pp.71-83
• /
• 1997

The purpose of this study is to analyze the present fashion phenomenon by considering the types of street fashion, the center of avant-grade modern fashion, that shows the origination background and special feature concretely. The times was defined through the 1980's from World War II that street style originated, so the range of study was the 1990's when the street style was influenced by that of the past and was revived. The ways of study were to analyze the records of ideology, art and music connected with the street style from World War II to the present when it has risen. The summary of result is as follows. (1) In the 1940's, Zooties was the jet of desire suppressed by African-Americans that couldn't receive favors socially and economically and Hipsters pursued reformative bebop that made up of soft Jazz. In the 1950's, Modernists were running after Cool Jazz to the minimum. In the 1970's, Funk appered in the sexual desire and erotic strength, and was surfaced from Negro Getto. In the 1980's B-boys & Flygirls showed the street style by the scribble art of slum in the New York. As mentioned above, In the 1990's, Acid Jazz influenced by the Jazz of Negro has been the fashion added to the tradition of musical form that come from eclecticism of Jazz tended Neo-Jazz. (2) In the 1940's, Western style dreamed the country life because of rapid urbanization. In the 1950's, Beat obtained the feeling of liberation from the dissolute life and activity. In the 1960's, Psychedelics showed the freedom affected by the Pop-art and Op-art, and Hippies pursued the true individuality as 'love & peace' life style and the return to nature. In the 1990's, Grunge look influenced by the above has been fashion that shows the practical use of second-hand clothing or patchwork contrary to elitism. (3) In the 1940's, Caribbean style appered in the typical textile color with the center of West Indies. In the 1960's, Rude boys showed the magnificence and difficulty of Jamaica, and Rastafarians had a tendency to come back to the ancient civilization of America. In the 1970's, Two-tone was the simple clothing for harmonizing among human races. In the 1990's, Jamaica look influenced by the above has been the Lege fashion introduced to a high fashion, appearing in the special bright color, applique, unique hair style, and so on. (4) In the 1950's, Sufers pursued natural rhythm, getting out of everything. In the 1970' s, Skaters enjoyed the speed on the paved road. In the 1980's, Casuals emphasized the spirit of cooperation of young-things. In the 1990's, Casual look Influenced by the above has been the fashion that forms the activity, function and strong spirit of cooperation by pursuing comfortable life and sports in the tension of life and variety of modern society. (5) It was hard for Bikers to adjust themselves in society after the war. In the 1950's, Coffee bar cowboys were the reckless running boys in the leather jacket. In the 1960's, Rockers created the group originality as disobedient outsiders and Greasers imitated Rolling Stones. In the 1980's, Punks resisted the viewpoint of the old generation in offensive fashion. In the 1990's, Cyberpunk influenced by the above has pursued the classless structure, electronic music and metallic clothing that forebodes gloomily as the computer generation of ultra-modern science times. Accordingly, in understanding a complex modern fashion phenomenon, it was analyzed that the street styles of the past, from World War II to the 1980's, were reflected in that of the 1990's dividing into the five types in a word, namely Acid Jazz, Grunge look, Jamaica look, Casual look and Cyberpunk.