• 제어로봇시스템학회논문지
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• 제15권1호
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• pp.82-88
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• 2009

The output of the encoder is a digital pulse, which is also easy to be connected to a digital controller. There are various angular velocity detecting methods of M, T, and M/T. Each of them has its own properties. There is a common limitation that the angular velocity detection period is strongly dependent on the destination velocity magnitude in case of ultimate low range. They have ultimately long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a zero velocity detectable sensor algorithm with the dual encoder system. The sensor algorithm is able to keep detection period moderately at near zero velocity and even detect zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the algorithm validity.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.97-103
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• 2006

A modified one-sided measurement technique is proposed for Rayleigh wave (R-wave) velocity measurement in concrete. The scattering from heterogeneity may affect the waveforms of R-waves in concrete, which may make the R-waves dispersive. Conventional one-sided techniques do not consider the scattering dispersion of R-waves in concrete. In this study, the maximum energy arrival concept is adopted to determine the wave velocity by employing its continuous wavelet transform. Experimental study was performed to show the effectiveness of the proposed method. The present method is applied to monitor the strength development of early-age concrete. A series of experiments were performed on early-age concrete specimens with various curing conditions. Results reveal that the proposed method can be effectively used to measure the R-wave velocity in concrete structures and to monitor the strength development of early-age concrete.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.427-436
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• 2017

Concrete technologists have used ultrasonic pulse velocity test for decades to evaluate the properties of concrete. However, the presented research work focuses on the use of ultrasonic pulse velocity test to study the degradation in steel-concrete bond subjected to increasing loading. A detailed experimental investigation was conducted by testing five identical beam specimens under increasing loading. The loading was increased from zero till failure in equal increments. From the experimentation, it was found that as the reinforced concrete beams were stressed from control unloaded condition till complete failure, the propagating ultrasonic wave velocity reduced. This reduction in wave velocity is attributed to the initiation, development, and propagation of internal cracking in the concrete surrounding the steel reinforcement. Using both direct and semidirect methods of testing, results of reduction in wave velocity with evidence of internal cracking at steel-concrete interface are presented. From the presented results and discussion, it can be concluded that the UPV test method can be successfully employed to identify zones of poor bonding along the length of reinforced concrete beam. The information gathered by such testing can be used by engineers for localizing repairs thereby leading to saving of time, labor and cost of repairs. Furthermore, the implementation strategy along with real-world challenges associated with the application of the proposed technique and area of future development have also been presented.

• 대한기계학회논문집
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• 제10권6호
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• pp.861-869
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• 1986

본 연구에서는 동시확립문제의 속도장해석에 있어서 단면내의 속도분포에 대 한 일체의 가정을 하지 않고 운동량방정식을 직접 해석하여 단면내의 속도분포를 구하 였다. 또한 Prandtl수, 반경비 및 편심도가 열전달특성에 미치는 영향에 대한 해석 도 수행하였다.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.313-323
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• 2020

Non-destructive tests are commonly used in construction industry to access the quality and strength of concrete. However, till date there is no non-destructive testing method that can be adopted to evaluate the bond condition of reinforced concrete beams. In this regard, the presented research work details the use of ultra-sonic pulse velocity test method to evaluate the bond condition of reinforced concrete beam. A detailed experimental research was conducted by testing four identical reinforced concrete beam samples. The samples were loaded in equal increments till failure and ultra-sonic pulse velocity readings were recorded along the length of the beam element. It was observed from experimentation that as the cracks developed in the sample, the ultra-sonic wave velocity reduced for the same path length. This reduction in wave velocity was used to identify the initiation, development and propagation of internal micro-cracks along the length of reinforcement. Using the developed experimental methodology, researchers were able to identify weak spots in bond along the length of the specimen. The proposed method can be adopted by engineers to access the quality of bond for steel reinforcement in beam members. This allows engineers to carryout localized repairs thereby resulting in reduction of time, cost and labor needed for strengthening. Furthermore, the methodology to apply the proposed technique in real-world along with various challenges associated with its application have also been highlighted.

• 한국정밀공학회지
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• 제24권9호
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• pp.76-85
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• 2007

An optical rotary encoder is easy to implement for automatic control applications. In particular, the output of the encoder has a digital form pulse, which is also easy to be connected to a popular digital controller. By using the encoder, there are various angular velocity detecting methods, M-, T-, and M/T-method. Each of them has a property of its own. They have common limitation that the angular velocity detection period is strongly subject to the destination velocity magnitude in case of ultimate low range. They have ultimate long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a dual encoder system with two encoders of normal resolution. The dual encoder system is able to keep detection period moderately at near zero velocity and even detects zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the dual encoder system validity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.56.2-56
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• 2001

For the improvement of minimum sensing angular velocity of ring laser gyro, the influence of a low-scattering mirror application to laser resonator was investigated. Super polishing technique was employed for the fine mirror substrates of less than 1-${\AA}$-rms roughness. Mirror coating using ion-beam sputtering coating machine produced low-scattering mirror less than 30-ppm scattering. As a result of the mirror application to ring laser, the minimum sensing angular velocity of the gyro was improved down to about 0.1 deg/sec.

• 한국패류학회지
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• 제30권3호
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• pp.273-279
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• 2014

The mass mortalities have been occurring of Korean scallop Patinopecten yessoensis from 1997's to now in Korea east sea. Cages behavior and interference effect (common name; curtain effect) between scallop cages were investigated in culture grounds on the eastern coastal waters of Korea for understand to mechanism of rising about mass mortalities of Korean scallop quickly. The first experiment was carried out in circulating water channel to assess inclination angel from relationship between velocity and cages interval, velocity with culture cages position. An angle of inclination of scallop culture cages were 94.6 to 92.3 degree under a several velocity which were from 0.1 m/s and 131.9 to 118.1 degree under 0.5 m/s with cages interval were 1 m, 94.3 to 91.0 degree under velocity is 0.1 m/s and 133.2 to 122.4 degree under 0.5 m/s with cages interval were 1.5 m and 94.6 to 96.4 degree under velocity is 0.1 m/s and 131.7 to 131.8 under 0.5 m/s with cages interval were 2 m. The second experiment was designed to prove the tank test. Velocities were measured inside and outside of the scallop culture ground at eastern sea of Korea. The velocity of inside of the culture was the slowest as 0.1m/s. In this result, interference between former cage and after cage was occurred.

• Physical Therapy Rehabilitation Science
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• 제13권3호
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• pp.304-314
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• 2024

Objective: This study aimed to investigate the association of explosive strength with muscle mass and muscle function measured using traditional methods such as peak torque (PT) and joint angular velocity (PAV). Design: Cross-sectional study Methods: Twenty-nine healthy adults (14 males and 15 females) participated in this study. Body mass index and appendicular skeletal muscle index (ASMI) were measured using bioelectrical impedance analysis. The explosive strength of the knee extensors was evaluated by measuring the rate of torque development (RTD) and rate of velocity development (RVD). RTD was analyzed by dividing it into early (0-50 ms) and late (100-200 ms) muscle contraction phases. In addition, PT and PAV were measured as traditional methods for assessing muscle function. Results: According to regression analysis, PAV accounts for 24.7% and 66.9% of the variance of RTD 0-50 (p=0.006) and RVD (p<0.001), respectively. On the other hand, ASMI (p=0.035) and isometric PT (p=0.001) explained 49.2% of the RTD 100-200. Conclusions: Early RTD is mainly predicted by PAV, which is thought to be a result of muscle fiber type. Therefore, PAV presents the possibility of an alternative method to evaluate explosive performance. Late RTD seems to be related to ASMI or isometric PT. The findings of this study are expected to contribute to musculoskeletal rehabilitation and evaluation in that they revealed factors contributing to early and late muscle contraction.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.154-154
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• 2021

Since the development of Bubble Image Velocimetry (BIV) technique as the complementary technique of Particle Image Velocimetry (PIV), the application of digital imaging technique in the field of hydraulic and coastal engineering increased rapidly. BIV works very well in multi-phase flow (air-water) flows where the PIV technique doesn't. However, the velocity field obtained from BIV technique often resulted in a velocity vector on the outside of the flow (false velocity) since the Field of View (FOV) usually not only cover the air-water flow but also the area outside the flow. In this study, a simple technique of post processing velocity field was developed. This technique works based on the average of the pixel value in the interrogation area. An image of multi-phase flow of wave overtopping was obtained through physical experiment using BIV technique. The velocity calculation was performed based on the similar method in PIV. A velocity masking technique developed in this study then applied to remove the false velocity vector. Result from non-masking, manually removed and auto removed false velocity vector were presented. The masking technique show a similar result as manually removed velocity vector. This method could apply in a large number of velocity field which is could increase the velocity map post-processing time.