• 지구물리와물리탐사
• /
• 제7권1호
• /
• pp.45-50
• /
• 2004

This paper describes a method of detecting formation boundaries, and permeable fractures, from frequency-domain Stoneley wave logs. Field data sets were collected between the depths of 330 and 360 m in well EE-4 in the Higashi-Hachimantai geothermal field, using a monopole acoustic logging tool with a source central frequency of 15 kHz. Stoneley wave amplitude spectra were calculated by performing a fast Fourier transform on the waveforms, and the spectra were then collected into a frequency-depth distribution of Stoneley wave amplitudes. The frequency-domain Stoneley wave log shows four main characteristic peaks at frequencies 6.5, 8.8, 12, and 13.3 kHz. The magnitudes of the Stoneley wave at these four frequencies are affected by formation properties. The Stoneley wave at higher frequencies (12 and 13.3 kHz) has higher amplitudes in hard formations than in soft formations, while the wave at lower frequencies (6.5 and 8.8 kHz) has higher amplitudes in soft formations than in hard formations. The correlation of the frequency-domain Stoneley wave log with the logs of lithology, degree of welding, and P-wave velocity is excellent, with all of them showing similar discontinuities at the depths of formation boundaries. It is obvious from these facts that the frequency-domain Stoneley wave log provides useful clues for detecting formation boundaries. The frequency-domain Stoneley wave logs are also applicable to the detection of a single permeable fracture. The procedure uses the Stoneley wave spectral amplitude logs at the four frequencies, and weighting functions. The optimally weighted sum of the four Stoneley wave spectral amplitudes becomes almost constant at all depths, except at the depth of a permeable fracture. The assumptions that underlie this procedure are that the energy of the Stoneley wave is conserved in continuous media, but that attenuation of the Stoneley wave may occur at a permeable fracture. This attenuation may take place at anyone of the four characteristic Stoneley wave frequencies. We think our multispectral approach is the only reliable method for the detection of permeable fractures.

• 한국통신학회논문지
• /
• 제21권5호
• /
• pp.1123-1131
• /
• 1996

Knutsson이 QPS(quadrature polar separable) 필터를 제안한 이후 여러가지 개선된 QPS필터가 발표되고 있으며 질감 영상처리에 응용되고 있다. 이들 필터는 방향각 함수로 Kuntsson의 cosine 함수나 지수감쇠 함수를 이용하고 있으며, 라디엘웨이팅 함수로 FPSS(finite prolate spheroidal sequence)나 점근적 FPSS를 이용하고 있다. 이들 필터는 질감영상 생성이나 방향각평가, 그리고 합성된 질감영상의 영역분할면에서 다른 특성을 나타낸다. 본 논문에서는 2-D QPS 필터를 위한 여러가지 커넬함수를 분석하여 그들의 특성을 고찰하며 푸리에영역내에서 국부조직의 주파수성분과 방향각을 평가한다. 그리고 이들 필터에 의한 질감 영상의 특성추출과 영역분할에 대한 응용상의 문제점에 대해서 고찰한다. 실험결과는 개선된 Knutsson 필터와 점근적 FPSS 필터함수가 합성 질감영샹의 방향각 평가와 영역분할면에서 유용하다는 것을 나타낸다.

• 대한기계학회논문집A
• /
• 제21권8호
• /
• pp.1195-1208
• /
• 1997

Bellows is a component in piping systems which absorbs mechanical deformation with flexibility. Its geometry is an axial symmetric shell which consists of two toroidal shells and one annular plate or conical shell. In order to analyze bellows, this study presents the finite element analysis using a conical frustum shell element. A finite element analysis is developed to analyze various bellows. The validity of the developed program is verified by the experimental results for axial and lateral stiffness. The formula for calculating the natural frequency of bellows is made by the simple beam theory. The formula for fatigue life is also derived by experiments. The shape optimal design problem is formulated using multiple objective optimization. The multiple objective functions are transformed to a scalar function by weighting factors. The stiffness, strength and specified stiffness are considered as the multiple objective function. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, and the manufacturing conditions. Geometric parameters of bellows are the design variables. The recursive quadratic programming algorithm is selected to solve the problem. The results are compared to existing bellows, and the characteristics of bellows is investigated through optimal design process. The optimized shape of bellows is expected to give quite a good guideline to practical design.

• 대한기계학회논문집A
• /
• 제32권7호
• /
• pp.561-568
• /
• 2008

The quality of the automatic transmission shift for a wheel loader has been generally evaluated by driver's perception. However the subjective evaluation of the drivers is not always directly related to the shift quality. It is necessary to set up the method for an objective assessment of the shift quality. In this paper, a quantitative assessment method has been developed for the shift quality of the automatic transmission in a wheel loader. The indices for the evaluation were selected through the various tests like the acceleration and the turbine rpm as well as the subjective evaluation of the driver, and were validated by the correlation between subjective and objective assessments using a psychophysical power law. Based on this method, the shift quality of a wheel loader has been evaluated quantitatively under various shift conditions.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.209-213
• /
• 1997

This paper deals with sensing ability of $2^{nd}$ smart sensor that has a sensing ability of distinguish materials. We have developed new signal processing method that have distinguish different materials. We made the $2^{nd}$ smart sensor for experiment. The second type of smart sensor is HH type. We have developed a new signal processing method that can distinguish among different materials. The estimation method (RSAIIn dex) is developed for $2^{nd}$ smart sensor(HH smart sensor). Experiment and analysis are executed for estimation the new method. We estimated sensing ability of $2^{nd}$ smart sensor with RsA, method. Sensing Ability of the $2^{nd}$ smart sensor were evaluated relatively through a new RsAl method. According to frequency changing, influences of the $2^{nd}$ smart sensor are evaluated through a new recognition index RSAI. Applications of this method are for finding abnormal conditions of objects (automanufacturing), feeling of objects (medical product), robotics, safety diagnosis of structure, etc.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.1268-1271
• /
• 2006

This paper introduces what amount of railway vibration level observed from residential area. Five residential area located near the railway were selected to measure the vibration levels generated by the different types of Korean railway vehicles. Those 3-axis vibration measurements are applied to the frequency-dependent weighting functions recommended by ISO 2631-2, which are used to evaluate the 3-axis combined vibration levels such as peak levels, L 10 levels and root-mean-squared values. These evaluated results are shown to indicate the environmental vibration severity for the different residential area. In addition to those physical vibration measurements, the survey of subjective responses of residents was also carried out by distributing the questionnaire suggested by WHO. The questionnaire includes the subjective scales for assessing the annoyance and the sleep-disturbance caused by the environmental vibration. The statistical analysis results collected from 386 respondents are introduced. The highly annoyed population and the highly sleep-disturbed one are examined to identify the .elation between their subjective scale and their corresponding environmental vibration levels. These attempts are shown to lead to the salient model to relate the environmental vibration level and the subjective responses of Korean residents to annoyance and sleep-disturbance.

• 한국인터넷방송통신학회논문지
• /
• 제16권6호
• /
• pp.103-108
• /
• 2016

오늘날 도시의 규모가 커지고 기능이 복잡해지고 있으며, 다양한 사람들이 다양한 활동을 하며 살아가고 있다. 또한 도시에서의 사람의 삶은 많은 부분에서 주변의 사람과 연관되어 있다. 그리고 도시의 생활은 다양한 인공적인 활동을 하고 있음을 뜻하며, 이에 따른 소리의 발생이 주변사람에게는 소음공해가 되기도 한다. 이러한 이유에서 사람들로 만들어진 인공소음은 특히 서울의 도심 4대문 안의 도로 주변의 소음은 평균 73㏈가 될 정도로 크다. 그리고 도시에 사라는 사람들은 소음공해에 쉽게 노출되며 특히 집회나 시위현장 또는 홍보를 위해 사용되는 확성기들은 상당한 소음을 발생시키며 이는 다른 사람들에게 스트레스를 유발한다. 더욱이, 집회 및 시위에 관한 법률 등에서 지정하는 확성기 사용 및 규제는 있지만 잘 지켜지지 않는 것이 현실이다. 그리고 최근 법령을 -5㏈를 낮추는 등의 법령기준을 강화하였지만, 여전히 스트레스가 되고 있다. 따라서 집회 및 시위현장의 소음의 크기를 제한하고 규제하는 것 뿐만 아니라, 노출되는 시간을 고려하여 피해를 줄이는 것이 더 효과적인 방법이다. 소음으로 인한 스트레스는 짧은 시간만 노출되더라도 오래도록 지속되며, 이러한 환경에 위치한다면, 소음공간에서 빠르게 벗어나는 것을 권장 하는 것도 본 연구에서 제시하는 피해저감 방안이다.

• 동력기계공학회지
• /
• 제17권3호
• /
• pp.72-81
• /
• 2013

Many articles have been published about a 2-degree of freedom model that includes the lateral and yaw motions for controller synthesis in intelligent transport system applications. In this paper, a 3-degree of freedom linear model that includes the roll motion is developed to design a robust steering controller for lane following maneuvers using ${\mu}$-synthesis. This linear perturbed system includes a set of parametric uncertainties in cornering stiffness and unmodelled dynamics in steering actuators. The state-space model with parametric uncertainties is represented in linear fractional transformation form. Design purpose can be obtained by properly choosing the frequency dependent weighting functions. The objective of this study is to keep the tracking error and steering input energy small in the presence of variations of the cornering stiffness coefficients. Furthermore, good ride quality has to be achieved against these uncertainties. Frequency-domain analyses and time-domain numerical simulations are carried out in order to evaluate these performance specifications of a given vehicle system. Finally, the simulation results indicate that the proposed robust controller achieves good performance over a wide range of uncertainty for the given maneuvers.

• 한국자동차공학회논문집
• /
• 제17권4호
• /
• pp.1-9
• /
• 2009

A simplified model of seat-human body is presented to analyze vibrations of human body on a seat of vehicle. The theoretical model having seven degrees-of-freedom is composed of the inter-connected masses, springs and dampers. Until now, evaluation of ride comfort has been usually performed only through vehicle tests. This study aims to complement shortcomings of conventional vehicle tests in evaluation of ride comfort by using the theoretical model. The acceleration values of the human body are obtained from frequency response functions of the theoretical model. Thereafter, Ride and SEAT indexes are acquired by considering response characteristics of the human body for the 12 axes that are presented in BS 6841. A vehicle test is carried out to measure the acceleration values for the three parts of the human body such as upper body, hip and foot. Ride and SEAT indexes of the vehicle test are also obtained by considering the response characteristics of the human body, of which results are compared with the values from the theoretical model. It is found that the theoretical results are in good agreement with the experimental results.

• International Journal of Automotive Technology
• /
• 제4권4호
• /
• pp.181-191
• /
• 2003

Since the nonlinearity and uncertainties which inherently exist in vehicle system need to be considered in active suspension control law design, this paper proposes a new control strategy for active vehicle suspension systems by using a combined control scheme, i.e., respectively using a genetic algorithm (GA) based self-tuning PID controller and a fuzzy logic controller in two loops. In the control scheme, the PID controller is used to minimize vehicle body vertical acceleration, the fuzzy logic controller is to minimize pitch acceleration and meanwhile to attenuate vehicle body vertical acceleration further by tuning weighting factors. In order to improve the adaptability to the changes of plant parameters, based on the defined objectives, a genetic algorithm is introduced to tune the parameters of PID controller, the scaling factors, the gain values and the membership functions of fuzzy logic controller on-line. Taking a four degree-of-freedom nonlinear vehicle model as example, the proposed control scheme is applied and the simulations are carried out in different road disturbance input conditions. Simulation results show that the present control scheme is very effective in reducing peak values of vehicle body accelerations, especially within the most sensitive frequency range of human response, and in attenuating the excessive dynamic tire load to enhance road holding performance. The stability and adaptability are also showed even when the system is subject to severe road conditions, such as a pothole, an obstacle or a step input. Compared with conventional passive suspensions and the active vehicle suspension systems by using, e.g., linear fuzzy logic control, the combined PID and fuzzy control without parameters self-tuning, the new proposed control system with GA-based self-learning ability can improve vehicle ride comfort performance significantly and offer better system robustness.