• Tribology and Lubricants
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• 제27권5호
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• pp.264-268
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• 2011

In this study, we examined the friction characteristics of a dimple pattern on a carbon nitride coating. The study was conducted with a hexagonal array 40 ${\mu}m$ dimple pattern on a steel bearing containing a CNx coating. The area density of the dimple patterns were varied between 5% and 25%, the speed was varied from 0.06-0.26 m/s, and the load was varied between 20-100N. In general, we found that as the velocity increased, the friction coefficient increased. Furthermore, the friction coefficient was lowest at a load of 40N. The friction coefficient of the non-coated specimen was 0.025-0.15; on the other hand, the friction coefficient of the coated specimen was 0.002-0.02. Thus, we determined that the coated materials could reduce the friction coefficient by a factor of 7.5.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.585-590
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• 2000

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon. Numeral information was deduced and quantified effective information from the image. Also, pattern recognition of a defected input image was performed by neural network algorithm. Input pattern of various numeral was composed combinationally, and then, it was studied by neural network. Furthermore, possibility of pattern recognition was confirmed on artifical defected input data formed by simulation. Finally, application on unknown input pattern was also examined.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.455-464
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• 1994

The intelligent trajectory control method that controls moving direction and average velocity for a prosthetic arm is proposed by pattern recognition and force estimations using EMG signals. Also, we propose the real time trajectory planning method which generates continuous accelleration paths using 3 stage linear filters to minimize the impact to human body induced by arm motions and to reduce the muscle fatigue. We use combination of MLP and fuzzy filter for pattern recognition to estimate the direction of a muscle and Hogan's method for the force estimation. EMG signals are acquired by using a amputation simulator and 2 dimensional joystick motion. The simulation results of proposed prosthetic arm control system using the EMG signals show that the arm is effectively followed the desired trajectory depended on estimated force and direction of muscle movements.

• 오토저널
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• 제4권2호
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• pp.58-68
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• 1982

It is well known to diesel engineers that the heat release pattern is one of the most important factors affecting engine performance. Thorough research in heat release pattern has materially helped the progress in high-speed diesel engine development . This paper is based on the research conducted at KAIST and Daewoo Heavy Industry last year. The purpose of this paper is to determine the heat release pattern in combustion chamber of MAN M type, the famous low-noise engine. Thermodynamic cycle simulation was performed using Whitehous-Way's heat release pattern with modified coefficients and Annand's heat transfer model. Instantaneous temperature and pressure of gas in cylinder could be determined by the numerical solution of simultaneous equation of mass conservation, equation of energy conservation, and state equation of ideal gas. Calculated results were compared with measured values in some details emphasizing upon the factors affecting rate of heat release. The agreement was fairly good and revealed why M type should have lower burning velocity at the early part of combustion in spite of high injection rate. Additional results by parametric studies were given in relation to fuel injection conditions for further application to engine development.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.240-242
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• 2014

This paper presents the system which can be predicted 3-D underwater radiated noise pattern using submarine hull velocity and can be analyzed the counter detected performance for threats in real time. To verify the developed system the tests were done in a water tank for structure like a submarine. The far field radiated noise pattern predicted using the developed system is compared with the result calculated using the near field measurement system, these results have shown good agreement.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.125-130
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• 1989

In the present study, we described a test to explore the function of optokinetic system which subjected to a full visual field stimulation using two different stimulus images patterns. Our results were interesting in a point of view that the stimulation image pattern had non- neglisible influence on the optokinetic response and that in a bidimensionnel image such as the randomly distributed spots images pattern the linearity of system was assured upto the stimulus velocity of about 50 deg/sec for normal subject. As for measuring human optokinetic after nystagmus, the regular stripes pattern was rather desirable than the randomly distributed spots pattern in this study.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.816-822
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• 2000

In the core of the nuclear power plant of PWR, several cases of fuel failure by unknown causes have been experienced for various fuel types. From the common features of the failure pattern, failure lead time, flow conditions, and flow induced vibration characteristics in nuclear fuel bundles, it is deduced that the fretting wear failure of the fuel rod at the spacer grid position is due to the fluidelastic vibration. In the past, fluidelastic vibration was simulated by quasi -static semi-analytical model, so called the static model, which could not account for the interaction between the rods within a bundle. To overcome this defect and to provide for more flexibilities applicable to the fuel bundle, Tanaka's unsteady model was modified to accomodate the geometrical differences and governing parameter changes during the operations such as the number of rods, pitch to diameter ratio (P/D), spring force, damping coefficient, etc. The critical velocity was calculated by solving the governing equations with the MATLAB code. A comparison between the estimated critical velocity and the test result shows a good agreement. Finally, the level of decrease of the critical velocity due to the reduction in the spring force and reduced damping coefficient due to the radiation exposure is also estimated.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.173-176
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• 2005

This paper proposes a fuzzy correction algorithm that can correct the distorted medical image caused by the scanning nonlinear velocity of the Digital X-ray Scanner System (DX-Scanner) using the Multichannel Ionization Chamber (MIC). In the DX-Scanner, the scanned medical image is distorted for reasons of unsuitable integration time at the nonlinear acceleration period of the AC servo motor during the inspection of patients. The proposed algorithm finds the nonlinear motor velocity modeling through fuzzy system by clustering and reconstructs the normal medical image lines by calculating the suitable moving distance with the velocity of the motor using the modeling, acceleration time and integration time. In addition, several image processing is included in the algorithm. This algorithm analyzes exact pixel lines by comparing the distance of the acceleration period with the distance of the uniform velocity period in every integration time and is able to compensate for the velocity of the acceleration period. By applying the proposed algorithm to the test pattern for checking the image resolution, the effectiveness of this algorithm is verified. The corrected image obtained from distorted image is similar to the normal and better image for a doctor's diagnosis.

• 대한기계학회논문집
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• 제12권3호
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• pp.566-574
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• 1988

본 연구에서는 LDV의 수광계를 비임의 진행방향에 수직한 방향으로 위치시켜 분무액적에 의한 반사 산란성분을 수광하여 검출되는 신호의 가시도에 의해 액적크기 를 측정함과 동시에 도플러변화 주파수로부터 속도를 측정하고, 이 방법의 신뢰도를 충돌식 포진법에 의하여 측정한 결과와 비교하므로써 평가하여, 관측각 90˚의 측방 산란형 LDV에 의한 분무액적의 크기와 속도의 동시측정에 관한 유용성을 살펴보고자 한다.

• 대한산업공학회지
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• 제22권3호
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• pp.337-349
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• 1996

A study was conducted to find the possible relationship between slip distance and dynamic coefficient of friction (DCOF) through the biomechanical study of slips and falls using a broader variety of floors and levels of slipperiness than those used before. Four different floor surfaces covering the full range of floor slipperiness (with and without on oil contaminant) were prepared for ten subjects with each walking at a fixed velocity. The results showed that slip distance and heel velocity had a decreasing trend while stride length had a increasing trend as DCOF increased. The contaminant effect overpowered floor slipperiness effect because a higher DCOF surface with oil contaminant created longer slip distance than the lower DCOF with dry floor. Normal gait pattern and suggested heel velocity (10 to 20 cm/sec) were seen on dry floors but abnormally longer stride length and 5 to 10 times faster heel velocity were found an oily floors. In other words, faster heel velocity (greater than 10 to 20 cm/sec) is recommended to measure DCOF on oily floors because the assumption of normal gait was no longer valid.