• The Journal of Engineering Geology
• /
• v.22 no.4
• /
• pp.459-466
• /
• 2012

A difficulty encountered in engineering seismic mapping is that reflection events from shallow discontinuities are commonly overlapped with coherent noise such as air wave, direct waves, head waves, and high-amplitude surface waves. Here, the radial trace transform, a simple geometric re-mapping of a trace gather (x-t domain) to another trace gather (v-t domain), is applied to investigate the rejection effect of coherent linear noises. Two different types of data sets were selected as a representative database: good-quality data for intermediate sounding (hundreds of meters) in a sedimentary basin and very noisy data for shallow (${\leq}50m$) mapping of the weathered zone and bedrock surface. Results obtained with cascaded application of the radial transform and low-cut filtering proved to be as good as, or better than, those produced using f-k filtering, and were especially effective for air wave and direct wave. This simple transform enables better understanding of the characteristics of various types of noise in the RT domain, and can be generally applied to overcoming diffractions and back-scatterings caused by joints, fractures, and faults commonly that are encountered in geotechnical problems.

• The KSFM Journal of Fluid Machinery
• /
• v.16 no.2
• /
• pp.21-26
• /
• 2013

Super-cavitating vehicle which is operating under water speeds up to 100m/s. In this process super-cavitation around body reduces frictional resistance. This paper introduces experimental study on different width of suction path as there is a warhead in the torpedo. Hydraulic performances of turbopump at non-cavitating condition does not display a significant differences depending on different width of suction path. However, cavitation performance of each model shows obvious differences in the same condition of experience. In case of radial inlet, the value of critical NPSH(which indicates 3% head drop) increases about 20% in comparison of axial inlet.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.3
• /
• pp.404-412
• /
• 2008

As a suitable volute configuration in the range of low specific speed, circular casing is suggested in this study. The internal flows in a centrifugal pump with the circular and spiral casings are measured by PIV and analyzed by CFD. The results show that the head and efficiency of the pump by a circular casing of very small radius are almost same as those by the spiral casing. Even at the best efficiency point, the internal flow of the pump by circular casing is asymmetric, and vortex and strong secondary flow occurs in the impeller passage. The radial velocity becomes higher remarkably only near the region of the discharge throat. The flow in the impeller outlet is strongly controlled by the circular casing because the velocity distribution almost does not affected by the position of the impeller blades.

• Clinics in Shoulder and Elbow
• /
• v.9 no.2
• /
• pp.216-221
• /
• 2006

Avulsion of the triceps brachii is an uncommon injury. The usual mechanism of injury is fall onto an outstretched hand but can occur after direct contact injuries. Diagnosis is critical and dependent on history, physical examination, and radiological findings. Rupture of triceps brachii occurs most frequently at the tendo-osseous insertion and may be complete or partial, and could be associated with radial head fracture. Treatments include surgical repair of the complete rupture and immobilization of partial triceps rupture. We report 3 cases of triceps avulsion fractures treated by open surgical repair with literature reviews.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.559-564
• /
• 2001

In order to apply into a compact and reliable centrifugal blood pump, this paper introduces a self-bearing motor in which a rotor is rotated without contact. The rotor is actively controlled in only radial directions, while the axial and tilting motions are passively stable owing to the disk-shape structure of the rotor. A prototype was made in outer-rotor type that is far better in the compactness than inner-rotor type. The prototype could be driven up to 8000 rpm with the rotor vibration under 0.12mm. The maximum cardiac output and pressure head were 9 L/min and over 200 mmHg, respectively. These experimental results show that the proposed self-bearing motor has sufficient performance for application to a real blood pump.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.32B no.12
• /
• pp.1565-1571
• /
• 1995

Misalignment of recording head position results in inter-track interference (ITI), which is a primary factor limiting radial(track) density in current digital magnetic channels. This paper proposes a multi- channel adaptive PRML for digital high-density recording channels, and compares it with the conventional single-channel PRML in the presence of ITI for the per- formance evaluation. Simulation results show that the proposed method removes ITI effectively when heal-misalignment occurs, then improving its performance significantly as compared with the single- channel PRML. As a result, it is confirmed that multi-channel adaptive PRML is well suited for high-density recording in digital magnetic channels.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.915-920
• /
• 1998

본 논문에서는 반구형 헤드(hemi-spherical head)를 가진 압력용기에 비방사형(non-radial) 노즐을 가공할 경우, 개구(opening) 간격이 반구형 헤드의 설계에 미치는 영향을 검토하기 위하여 개구 간격의 변화에 따른 응력분포변화를 분석하였다. ASME 코드는 NB-3222.4(d)의 설계 조건을 만족하는 압력 용기의 혜드에 노즐을 가공할 경우, NB-3338.2(d)에서 개구사이의 최소거리를 제시하고 있다. 본 논문에 서는 ASME 코드가 제시하고 있는 개구사이의 최소거리의 타당성과 설계상 이 요건을 만족하지 못하는 경우에 대하여 분석하고 검토하였다. 해석모델은 한국 표준형원자로의 가압기를 기본모델로하여 개구사이의 간격변화에 따른 응력변화를 검토하고, 설계시 고려하여야할 인자를 분석하였다.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.4
• /
• pp.400-408
• /
• 2009

Optimization of seal geometries can reduce significantly the energetic losses in a hydraulic seal [1], especially for high head runner turbine. In the optimization process, a reliable prediction of the losses is needed and CFD is often used. This paper presents numerical experiments to determine an adequate CFD model for straight, labyrinth and stepped hydraulic seals used in Francis runners. The computation is performed with a finite volume commercial CFD code with a RANS low Reynolds turbulence model. As numerical computations in small radial clearances of hydraulic seals are not often encountered in the literature, the numerical results are validated with experimental data on straight seals and labyrinth seals. As the validation is satisfactory enough, geometrical optimization of hydraulic seals using CFD will be studied in future works.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.558-563
• /
• 2004

Experiments were performed to see the effect of radial tip clearance on a turbopump inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7. Hydraulic and cavitation tests were done for three cases of tip clearance ratio, that is, 0.026, 0.053, and 0.079. With increase in the tip clearance, inducer head and pressure on the inducer tip decreased. Attached cavitation and cavitation surge were found in the cavitation tests. In the attached cavitation one cell rotated at the same rotational speed as that of the inducer. Cavitation performance deteriorated with increase in the tip clearance. The level of casing vibration increased in the cavitation condition and the level was very high when the attached cavitation appeared.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.1 s.34
• /
• pp.19-24
• /
• 2006

Experiments are carried out to investigate the effect of radial tip clearance on a turbopump inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7. Hydraulic and cavitation tests are performed for three cases of tip clearance ratio, that is, 0.026, 0.053, and 0.079. With increase in the tip clearance, inducer head and pressure on the inducer tip decrease. Attached cavitation and cavitation surge are observed in the cavitation tests. In the attached cavitation one cell rotates at the same rotational speed as that of the inducer. Cavitation performance deteriorates with increase in the tip clearance. The level of casing vibration increases in the cavitation condition and the level is very high when the attached cavitation appears.