• Title/Summary/Keyword: simplified intensity

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Wind tunnel modeling of flow over mountainous valley terrain

  • Li, C.G.;Chen, Z.Q.;Zhang, Z.T.;Cheung, J.C.K.
    • Wind and Structures
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    • v.13 no.3
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    • pp.275-292
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    • 2010
  • Wind tunnel experiments were conducted to investigate the wind characteristics in the mountainous valley terrain with 4 simplified valley models and a 1:500 scale model of an existing valley terrain in the simulated atmospheric neutral boundary layer model. Measurements were focused on the mean wind flow and longitudinal turbulence intensity. The relationship between hillside slopes and the velocity speed-up effect were studied. By comparing the preliminary results obtained from the simplified valley model tests and the existing terrain model test, some fundamental information was obtained. The measured results indicate that it is inappropriate to describe the mean wind velocity profiles by a power law using the same roughness exponent along the span wise direction in the mountainous valley terrain. The speed-up effect and the significant change in wind direction of the mean flow were observed, which provide the information necessary for determining the design wind speed such as for a long-span bridge across the valley. The longitudinal turbulence intensity near the ground level is reduced due to the speed-up effect of the valley terrain. However, the local topographic features of a more complicated valley terrain may cause significant perturbation to the general wind field characteristics in the valley.

Effect of excitation intensity on slope stability assessed by a simplified approach

  • Korzec, Aleksandra;Jankowski, Robert
    • Earthquakes and Structures
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    • v.21 no.6
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    • pp.601-612
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    • 2021
  • The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

3-D Finite Element Mesh Generation of Tires Considering Detailed Tread Pattern (상세 트레드 패턴을 반영한 3차원 타이어 유한요소 격자 생성)

  • Cho, Jin-Rae;Kim, Ki-Whan;Hong, Sang-Il;Kim, Nam-Jeon;Kim, Kee-Woon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.10
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    • pp.1615-1622
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    • 2003
  • Being contacted directly with. ground, the tire tread part is in shape of complex patterns of variable ASDs(anti-skid depth) to satisfy various tire performances. However, owing to the painstaking mesh generation job and the extremely long CPU-time, conventional 3-D tire analyses have been performed by either neglecting tread pattern or modeling circumferential grooves only. As a result, such simplified analysis models lead to considerably poor numerical expectations. This paper addresses the development of a 3-D tire mesh generation considering the detailed tread pattern and shows that the contact pressure and frictional energy distribution of tires considering the detailed pattern become better than those by the simplified tire model.

A study of noise source identification on plate excited structure borne sound by acoustic intensity method (음향인텐시티법에 의한 고체진동 가진판의 소음원 검출에 관한 연구)

  • 오재응;김상헌;홍동표;이찬홍
    • Journal of the korean Society of Automotive Engineers
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    • v.8 no.4
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    • pp.43-55
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    • 1986
  • In the studies of noise reduction, it is important to know the generation mechanism of noise in order to identify the noise source. The relation between the structural vibration and the radiated sound is very complex and so this paper deals with a simplified radiation model that was originally developed as a verification tool for the acoustic intensity measurement procedure. As the first step for the identification of the noise source, this study deals with the noise evaluation by measuring sound pressure. On the next step, the acoustic radiational pattern is determined by the acoustic intensity method and this paper established that the acoustic intensity method is effective on the detection of noise. In the study, furthermore, the method could be used to predict the change in the sound radiational characteristics with the attachment of absorber and could be used in determining the attachment position.

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Efficacy Analysis of Simplified Intensity-modulated Radiotherapy with High or Conventional Dose and Concurrent Chemotherapy for Patients with Neck and Upper Thoracic Esophageal Carcinoma

  • Zhu, Wei-Guo;Zhou, Ke;Yu, Chang-Hua;Han, Ji-Hua;Li, Tao;Chen, Xiao-Fei
    • Asian Pacific Journal of Cancer Prevention
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    • v.13 no.3
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    • pp.803-807
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    • 2012
  • For patients with neck and upper thoracic esophageal carcinoma, it is difficult to control lymph node metastases with conventional dose therapy. In this study, we assessed the feasibility of simplified intensity-modulated radiotherapy (sIMRT) and concurrent chemotherapy for 44 patients and boosted high-dose to metastatic lymph nodes. Three radiation treatment volumes were defined: PGTVnd, with which 68.1Gy was delivered in high dose group (hsIMRT group), and 60Gy in the conventional dose group (csIMRT group); PTV1, featuring 63.9Gy in the hsIMRT group and 60Gy in the csIMRT group; PTV2, with 54Gy given to both groups. The sIMRT plan included 5 equi-angular coplanar beams. All patients received the cisplatin and 5-FU regimen concurrently with radiotherapy. The treatment was completed within six weeks and one case with grade three acute bronchitis was observed in hsIMRT group. For esophageal lesions, 80% complete response (CR) and 20% partial response (PR) rates were found in the hsIMRT group, and 79.2% CR, with 20.8% PR, in the csIMRT group; for lymph node lesions, 75% CR and 25% PR rates were observed in the hsIMRT group, with 45.8% and 37.5% respectively in the csIMRT group (P<0.05). The differences in 1-, 2- and 3-year relapse-free survival rates were all statistically significant (P<0.05). The major toxicity observed in both groups was Grade I~II leucopenia. sIMRT can generate a desirable dose distribution in treatment of neck and upper thoracic esophageal carcinoma with a better short-term efficacy. Boosted high dosing to metastatic lymph nodes can increase the relapse-free survival rate.

A Simplified Estimation of Stress Intensity Factor on the Hertzian Contact (혜르츠접촉하에서 응력확대계수의 간단한 계산법)

  • Jin, Song-Bo;Kim, Seock-Sam
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1999.06a
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    • pp.30-37
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    • 1999
  • 헤르츠 접촉하에 있는 반무한체에서의 표면균열을 살펴보았다. 시편의 응력확대계수 K를 구하기 위해 사용되는 간단화된 방법을 이 논문에 쓰여진 모델에 적용시켰다. 기존에 알려진 결과에 비해 상당히 만족스런 결과를 얻었으며 다른 방법보다 이 방법이 훨씬 더 편리함이 입증되었다.

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Analysis of Unseating Failure of Various Types of Bridge Spans under Seismic Excitations (지진발생시 교량형식에 따른 낙교위험도 분석)

  • 김상효
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1998.04a
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    • pp.123-130
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    • 1998
  • The probability of unseating failure of the bridge spans under earthquakes is investigated. Seismic excitations are simulated as nonstationary processes by combining a stationary process and an intensity function. For computational convenience, a simplified single-degree-of-freedom model is adopted, which retains the dynamic characteristics of the original brige motion in concern. The time history analysis for the developed single degree-of-freedom model are carried out to evaluate the response processes, and the probabilistic characteristics of response displacements are evaluated. The reliability analysis of the bridge against the unseating failure is performed with the statistical information of the maximum displacements of responses.

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SIMPLIFIED APPROACH TO VALUATION OF VULNERABLE EXCHANGE OPTION UNDER A REDUCED-FORM MODEL

  • Huh, Jeonggyu;Jeon, Jaegi;Kim, Geonwoo
    • East Asian mathematical journal
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    • v.37 no.1
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    • pp.79-85
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    • 2021
  • In this paper, we investigate the valuation of vulnerable exchange option that has credit risk of option issuer. The reduced-form model is used to model credit risk. We assume that credit event is determined by the jump of the counting process with stochastic intensity, which follows the mean reverting process. We propose a simple approach to derive the closed-form pricing formula of vulnerable exchange option under the reduced-form model and provide the pricing formula as the standard normal cumulative function.

Photoinduced Anisotropy and Reorientation of Anisotropic Axis in Amorphous $As_2S_3$ Thin Film (비정질 $As_2S_3$ 박막의 광유도 비등방성과 비등방축의 가역성)

  • 김향균
    • Proceedings of the Optical Society of Korea Conference
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    • 1990.02a
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    • pp.162-166
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    • 1990
  • Photoinduced anisotropy (PIA) in amorphous As2S3 (a-As2S3 ) thin film, deposited by vacuum evaporation, is investigated. PIA is induced by linearly polarized Ar+ laser beam (λ=514.5nm) and probed by weak Ar+ laser (λ=514.5nm) and He-Ne laser (λ=632.8nm) beam through the crossed analyzer. Keeping pump beam intensity constantly, rotation of pump beam polarization direction induces reorientation phenomina of anisotropic axis. Introducing directional factor into simplified 3-level system, which is used to analyze photodarkening phenomina, an analytical expression of PIA is derived. Temporal behavior of PIAand its reorientation phenomina are investigated andcompared with theory. In the experiment pump beam intensity is 100mW/$\textrm{cm}^2$ and thickness of a-As2S3 thin film is 3${\mu}{\textrm}{m}$. In those condition, time constant of photoinduced anisotropy obtained by method of least square curve fitting is 4.0$\times$10-2sec-1. The time constant of PIA we obtained is larger than that of photodarkening, 2.8$\times$10-2sec-1.

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Fracture analysis of spot-welds with an edge crack using 2-D hybrid special finite element (이차원 하이브리드 특별 요소을 이용한 균열을 내포하는 용접점의 파단 해석)

  • Yang C. H.;Song J. H.;Huh H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.05a
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    • pp.39-42
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    • 2004
  • In the present paper, a novel systematic method using the 2-D hybrid special finite elements containing an edge crack is employed to study the fracture behaviors of laser beam spot-welds in automotive structures. 2-D hybrid special finite elements each containing an edge crack can assure the high precision especially in the vicinity of crack tips and give a better description of its singularity with only one hybrid element surrounding one crack. Therefore, the numerical modeling of the laser beam spot-welds can be greatly simplified. Some numerical examples are provided to demonstrate the validity and versatility of the proposed method. All the lap-shear, lap-tension and angle clip specimens are analyzed and some useful fracture parameters (such as stress intensity factors, the initial direction of crack growth) are obtained simultaneously.

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