• 제목/요약/키워드: 파의상

검색결과 110건 처리시간 0.024초

A Study for the Construction of the P and S Velocity Tomogram from the Crosswell Seismic Data Generated by an Impulsive Source (임펄시브 진원에 의한 공대공 탄성파기록으로부터 P파, S파 속도 영상도출에 관한 연구)

  • Lee, Doo-Sung
    • Geophysics and Geophysical Exploration
    • /
    • 제6권3호
    • /
    • pp.138-142
    • /
    • 2003
  • Crosswell seismic data were acquired in three sections crossing a tunnel of 3 different types; one was empty, another was ailed by sand, and the other was filled by rock debris. Both the P- and S-wave first arrivals were picked and the traveltime tomography was conducted to generate the P- and S- wave velocity tomograms on the all three sections. Among six tomograms, only one tomogram shows a low velocity zone that can be interpreted as a tunnel image. The tomogram is the P wave velocity image of a section that crosses an empty tunnel. The result of numerical analysis for the spatial resolution of the traveltime tomography was consistent to this finding.

Effects of Waves and Free-Surface Boundary Conditions on the Flow A Surface-Piercing Flat Plate (수면 관통 평판주위 유동에 미치는 파의 영향 및 자유표면 경계조건에 대한 연구)

  • Choi, Jung-Eun;Stern, F.
    • Journal of the Society of Naval Architects of Korea
    • /
    • 제34권1호
    • /
    • pp.41-49
    • /
    • 1997
  • Computational results from Navier-Stokes equations are presented for the Stokes-wave/flat-plate boundary-layer and wake for small wave steepness(Ak=0.01), including exact and approximate treatments of the viscous free-surface boundary conditions. The macro-scale flow indicate that the variations of the external-flow pressure gradients cause acceleration or deceleration of the streamwise velocity component and alternating direction of the cross flow. Remarkably, the wake displays a greater response, i.e., a bias with regard to favorable as compared to adverse pressure gradients. The micro-scale flow indicates that the free-surface boundary conditions have a profound influence over the boundary layer and near/intermediate wake. Order-of-magnitude estimates are conformed to the computational results. And appreciable errors are introduced through approximations to the free-surface boundary conditions.

  • PDF

A New High Power Factor Correction Diode Rectifier System (새로운 능동형 고역률 다이오드 정류기시스템)

  • 김현정;최세완;원충연;김규식
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • 제8권6호
    • /
    • pp.543-550
    • /
    • 2003
  • Thin paper proposes a new three-phase rectifier that actively shapes the input current sinusoidal by means of two rectifier bridges, each followed by a dc-dc boost converter. The proposed approach draws sinusoidal input current at unity power factor and has output voltage regulation capability The size and weight of magnetic material Is reduced by Incorporating a low KVA three-phase autotransformer and by directly connecting the dc outputs each other without using low frequency interphase transformer(IPT). The operation principle is described along with simple control method, and experimental results on a 1.5KW prototype are provided.

A study on Algorithm Automatically Generating Ray Codes for Ray-tracing (파선코드 자동생성 알고리즘에 관한 연구)

  • Lee, Hee-Il;Cho, Chang-Soo
    • Geophysics and Geophysical Exploration
    • /
    • 제11권4호
    • /
    • pp.361-367
    • /
    • 2008
  • When constructing a synthetic seismogram in the earthquake study or in seismic data interpretation by using a ray-tracing technique, the most troublesome and error-prone task is to define a suite of ray codes for the corresponding rays to trace in advance. An infinite number of rays exist for any arbitrarily located source and receiver in a medium. Missing certain important rays or an inappropriate selection of ray codes in tracing rays may result in wrong interpretation of the earthquake record or seismogram. Automatic ray code generation could be able to eliminate those problems. In this study we have developed an efficient algorithm with which one can generate systematically all the ray codes for the source(s) and receiver(s) arbitrarily located in a model. The result of this work could be used not only in analysing multiples in seismic data processing and interpretation, but also in coda wave study, study on the amplification effects in a basin and phase identification of the waves multiply reflected/refracted in earthquake study.

Analytic Solution to Mild Slope Equation for Transformation of Waves Propagating over an Axi-symmetric Pit (축대칭 함몰지형 위를 진행하는 파의 변형에 관한 완경사 방정식의 해석 해)

  • Jung, Tae-Hwa;Suh, Kyung-Duck
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • 제18권4호
    • /
    • pp.308-320
    • /
    • 2006
  • An analytic solution to the mild-slope equation is derived for waves propagating over an axi-symmetric pit. The water depth inside the pit varies in proportion to a power of radial distance from the pit center. The governing equation is transformed into ordinary differential equations by using separation of variables, and the coefficients of the equations are transformed into explicit forms by using Hunt's (1979) approximate solution. Finally, by using the Frobenius series, the analytic solution is derived. Due to the feature of Hunt's equation, the present analytic solution is accurate in shallow and deep waters, while it is less accurate in intermediate depth water. The validity of the analytic solution is demonstrated by comparison with numerical solutions. The analytic solution is also used to examine the effects of pit geometry and relative depth on wave transformation.

A Study on Safety Blasting Design with Blast Vibration Analysis Urban Area (도심지 미진동 제어 발파에서 진동분석을 통한 안전발파설계에 관한 연구)

  • 안명석;박종남;배상근
    • Explosives and Blasting
    • /
    • 제17권2호
    • /
    • pp.36-44
    • /
    • 1999
  • A study was made on the design of the prediction model concerning blasting vibration in a constraction site, Namgu, Daegu City. The geology in this area consists of hornfels of shale and mud underlain by quartize, of which the main strike of the geological structure is NW direction. Measurements were carried out on the top of the wall concrete water storage tank, which is burried in the ground earth. The attenuation due to the vertical wall of the concrete structure may be experted because of spherical divergency at the bottom corner of the wall by the Huygens principle. For design of blasting prediction model, thus among scaled distance(SD) may be preferable to use in the regression model, since they represents most likely the average ground condition. Judging from the regression results, the cube root method may be more suitable for this area. The SD values for the maximum allowable vibration velocity of 0.5 cm/s, in this area are 22.5, 28.0 and 30.6 for the significance level of 50%, 95% and 99%, respectively.

  • PDF

[ $PFC^{3D}$ ] Modeling of Stress Wave Propagation Using The Hopkinson's Effect ($PFC^{3D}$ 상에서의 홉킨슨 효과를 이용한 응력파의 전파모델링)

  • Choi Byung-Hee;Ryu Chang-ha
    • Explosives and Blasting
    • /
    • 제23권3호
    • /
    • pp.27-42
    • /
    • 2005
  • An explosion modeling technique was developed by using the spherical discrete element code, $PFC^{3D}$, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a $PFC^{3D}$ particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). The stress wave propagation modeling was conducted by simulating the experimental approach based on the Hopkinson's effect combined with the spatting phenomenon that had previously been developed to determine the dynamic tensile strength of Inada granite. As a result, the stress wave velocity obtained by the proposed modeling technique was 4167 m/s, which is merely $3\%$ lower than the actual wave velocity of 4300 m/s for an Inada granite.

The Error Performance of PSK Satellite Communication System with a Soft Limiter Type Transponder in Jamming Environments (소프트리미터형 중계기를 장치한 PSK 위성통신 시스템의 Jamming 환경하에서의 오율특성)

  • 강영흥;조성언;조성준
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • 제16권11호
    • /
    • pp.1084-1094
    • /
    • 1991
  • Upon introducing satellite communication system to korea, one of the important problems to copy with is the effect from the probable intentional interference i. e. jamming. In this paper, we have considered the M any PSK signal and the soft limiter type, which contains hard limiter, nonhnear satellite transponder in environments of uplink tone or noise jamming plus Gaussian noise and downlink Gaussian noise. Using the derived error rate equation, we have evaluated numerically the error performance of BPSK and QPSK system, and shown in figures in terms of upink and downink earner to jamming rater(CJR) and limiting level. From the results we have known that tone jamming effect on the error performance in BPSK and QPSK signals in nonlinear satelhie shnnel become less with increasing the uplink CNR and with decreasing the liniting level. And in a tone jamming, the limiting level affects hardly on the error performance of both BPSK and QPSK signals. When limiting leveri is zero, BPSK and QPSK signals show the best error rate performance.

  • PDF

Laboratory study of $CO_2$ migration in water-saturated anisotropic sandstone, based on P-wave velocity imaging (P-파 속도 영상화에 근거한 물로 포화된 이방성 사암에서의 $CO_2$ 이동에 관한 실험 연구)

  • Xue, Ziqiu;Lei, Xinglin
    • Geophysics and Geophysical Exploration
    • /
    • 제9권1호
    • /
    • pp.10-18
    • /
    • 2006
  • We measured the changes in P-wave velocity that occur when injecting $CO_2$ in gaseous, liquid, and supercritical phases into water-saturated anisotropic sandstones. P-wave velocities were measured in two cylindrical samples of Tako Sandstone, drilled along directions normal and parallel to the bedding plane, using a piezo-electric transducer array system. The velocity changes caused by $CO_2$ injection are typically -6% on average, with maximum values about -16% for the case of supercritical $CO_2$ injection. P-wave velocity tomograms obtained by the differential arrival-time method clearly show that $CO_2$ migration behaviour is more complex when $CO_2$ flows normal to the bedding plane than when it flows parallel to bedding. We also found that the differences in P-wave velocity images were associated both with the $CO_2$ phases and with heterogeneity of pore distribution in the rocks. Seismic images showed that the highest velocity reduction occurred for supercritical $CO_2$ injection, compared with gaseous or liquid $CO_$ injection. This result may justify the use of the seismic method for $CO_2$ monitoring in geological sequestration.

Surgical Angioplasty of Left Main and Proximal Left Anterior Descending Coronary Artery (좌주관상동맥및 좌전하챙지기시부의 수술적 혈관 성형술)

  • 이원용;김응중
    • Journal of Chest Surgery
    • /
    • 제29권8호
    • /
    • pp.861-866
    • /
    • 1996
  • Surgical angioplasty of isolated stenosis of the left main coronary artery(LMCA) restores a more physiologic flow to the myocardium, allows percutdneous transluminal coronary angioplasty (PTCA) of distal coronary stenoses at a later stage, and is a less time consuming and convenient procedure than the conventional coronary artery bypass grafting(CABG) . Between Jul. 1994 and Dec. 1995, 7 surgical angioplasty had been performed. LMCA stenoses involved ostium in 2 patients, middle third in 3, and dis- tal third in 2. In 2 patients, the origin of left anterior descending coronary artery was involved in conjunction with LMCA. T e additional coronary artery stenoses were found in 2 cases. One patient was emergently operated after coronary angiography following his cardiac arrest. LMCA was approached anteriorly in all patients. The pulmonary artery was transected in 3 patients for a better exposure. The onlay patch consisted or autologous or bovine pericardium. There was no postoperative myocardial infarction or mortality. Left ventricular functions were well preserved in all patients. Postoperative coronary angiography revealed widely patent LMCA in 5 cases, and mild narrowing of distal anastomotic sites in 2 cases. Provided that well defined indications are followed correctly, surgical angioplasty can be a safe alternative to conventional CABG.

  • PDF