• Title/Summary/Keyword: Initial Duration Method

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Blast Analysis of Single Degree of Freedom Plant Structures Considering Static Displacement (정적변위를 고려한 플랜트 구조물의 단자유도 폭발 해석)

  • Lee, Jae-Kyoon;Lee, Seung-Hoon;Kim, Han-Soo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.35 no.5
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    • pp.317-324
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    • 2022
  • In this paper, an analysis method that considers the initial static displacement of structural members using an equivalent single-degree-of-freedom system is presented. Newmark's dynamic analysis algorithm was improved to consider the effect of the initial static displacements of structural members. The effect of the initial static displacement on the maximum response according to the assumed duration of the blast load and natural period of the member was investigated. The effects of positive and negative static displacements on the maximum dynamic responses of structural members subjected to a positively applied blast load were also studied. Modified response charts for the shock-type and pressure-type waves are presented so that static displacements can easily be considered. Using a design example, we demonstrate the significance of the modified response chart that considers the static displacement. Based on the results of this study, the maximum response of a the structural member can be easily obtained whilst considering its initial static displacement. The modified response chart presented in this study can be used for the structural design of plants and military facilities.

A Study on Combustion Characteristic Methane Fuel according to Torch Volume Variation in a Constant Volume Combustion Chamber (정적연소기에서 토치의 체적 변화에 따른 메탄의 연소특성 파악)

  • Kwon, Soon-Tae;Park, Chan-Jun;Ohm, In-Young
    • Journal of the Korean Society of Visualization
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    • v.9 no.1
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    • pp.42-48
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    • 2011
  • Six different size of torch-ignition device were applied in a constant volume combustion chamber for evaluating the effects of torch-ignition on combustion. The torch-ignition device was designed for six different volumes and same orifice size. The combustion pressures were measured to calculate the mass burn fraction and combustion enhancement rate. In addition, the flame propagations were visualized by shadowgraph method for the qualitative comparison. The result showed that the combustion pressure and mass burn fraction were increased when using the torch ignition device. And the combustion duration were decreased. The combustion enhancement rates of torch-ignition cases were improved in comparison with conventional spark ignition. Finally, the visualization results showed that the torch-ignition induced faster burn than conventional spark ignition due to the earlier transition to turbulent flame and larger flame surface, during the initial stage. Finally, the initial flame propagation was affected by torch-ignition volume.

Dynamically Adaptive Finite Element Mesh Generation Schemes

  • Yoon, Chong-Yul;Park, Joon-Seok
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.6
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    • pp.659-665
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    • 2010
  • The finite element method(FEM) is proven to be an effective approximate method of structural analysis if proper element types and meshes are chosen, and recently, the method is often applied to solve complex dynamic and nonlinear problems. A properly chosen element type and mesh yields reliable results for dynamic finite element structural analysis. However, dynamic behavior of a structure may include unpredictably large strains in some parts of the structure, and using the initial mesh throughout the duration of a dynamic analysis may include some elements to go through strains beyond the elements' reliable limits. Thus, the finite element mesh for a dynamic analysis must be dynamically adaptive, and considering the rapid process of analysis in real time, the dynamically adaptive finite element mesh generating schemes must be computationally efficient. In this paper, a computationally efficient dynamically adaptive finite element mesh generation scheme for dynamic analyses of structures is described. The concept of representative strain value is used for error estimates and the refinements of meshes use combinations of the h-method(node movement) and the r-method(element division). The shape coefficient for element mesh is used to correct overly distorted elements. The validity of the scheme is shown through a cantilever beam example under a concentrated load with varying values. The example shows reasonable accuracy and efficient computing time. Furthermore, the study shows the potential for the scheme's effective use in complex structural dynamic problems such as those under seismic or erratic wind loads.

A Study on the Selection of a Bridge Structure Type Using DEA and LCC (DEA기법과 LCC개념을 활용한 교량형식 선정 방법에 관한 연구)

  • Han, Sam-Heui;Kim, Jong-Gil
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.4
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    • pp.101-111
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    • 2013
  • In this study, DEA (Data Envelopment Analysis) was carried out on the four bridges, which have the same extension (L=1,615m), in order to select the most superior, economical method of construction using the LCC concept of each bridge structure in the case of the Ulsan-Pohang double track railway which is scheduled to be constructed. DEA models were analyzed with the CCR model, which was designed for the evaluation of relative efficiency of each model. The initial construction costs, maintenance costs, indirect costs (user costs + indirect loss of social costs), and life cycle costs were used as input variables, and average duration was applied as the output variable. LCC was applied to calculate the input variables, and to get the costs of LCC, 100 years of period and 4.83% of real discount rate were applied, and the costs are classified into initial construction, maintenance, user, and indirect loss of social cost. The analysis results showed that the Method 2 and 3 were evaluated as the most efficient, and the other alternatives were evaluated as the following order; Method 1, the default, and Method 4.

Single-incision laparoscopic ileostomy is a safe and feasible method of fecal diversion for anastomotic leakage following laparoscopic low anterior resection

  • Hwang, Duk Yeon;Lee, Gyeo Ra;Kim, Ji Hoon;Lee, Yoon Suk
    • Annals of Surgical Treatment and Research
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    • v.95 no.6
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    • pp.319-323
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    • 2018
  • Purpose: Currently, many operations are performed using the single-incision laparoscopic method. Although there have been recent reports on single-incision laparoscopic ileostomy, none have compared this method to conventional laparoscopic ileostomy. This study aimed to assess the safety and feasibility of single-incision laparoscopic ileostomy for anastomotic leakage following laparoscopic low anterior resections. Methods: From April 2012 to April 2017, 38 patients underwent laparoscopic ileostomy (single-incision; 19 patients referred to as group A, conventional laparoscopy; 19 patients referred to as group B) for anastomotic leakage following laparoscopic low anterior resection. We analyzed surgical and clinical outcomes between the 2 groups. Patients in whom a protective ileostomy was carried out during the initial laparoscopic low anterior resection were excluded from this study. Results: No significant differences were observed between the 2 groups in terms of patient demographics and initial operation details. Incisional surgical site infections occurred less in group A than in group B (2 of 19 vs. 9 of 19, P = 0.029). The median ileostomy operation time, amount of intraoperative bleeding, parastomal hernia ratio, hospital stay duration after ileostomy, postoperative pain score were not significantly different between the 2 groups. Conclusion: Single-incision laparoscopic ileostomy is safe and feasible method of fecal diversion for anastomotic leakage following laparoscopic low anterior resection.

A Study on the microstructure and Surge Characteristics of ZnO varistors for distribution Arrester (배전급 피뢰기용 ZnO 바리스터 소자의 미세구조 및 서지 특성에 관한 연구)

  • 김석수;조한구;박태곤;박춘현;정세영;김병규
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.2
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    • pp.190-197
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    • 2002
  • In this thesis, ZnO varistors with various formulation, such as A∼E, were fabricated according to ceramic fabrication method. The microstructure, electrical properties, and surge characteristics of ZnO varistors were investigated according to ZnO varistors with various formulation. In the microstructure, A∼E\`s ZnO varistor ceramics sintered at 1130$\^{C}$ was consisted of ZnO grain(ZnO), spinel phase (Zn$\_$2.33/Sb$\_$0.67/O$\_$4/), Bi-rich phase(Bi$_2$O$_3$) and intergranuler phase, wholly. Lightning impulse residual voltage of A, B, C and E\`s ZnO varistors suited standard characteristics, below 12kV at current of 5kA. On the contrary, D\`s ZnO varistor exhibited high residual voltage as high reference voltage. In the accelerated aging test, leakage current and watt loss of B, C and D\`s ZnO varistors increases abruptly with stress time under the first a.c. stress(115$\^{C}$/3.213kV/300h). Consequently, C varistor exhibited a thermal run away. On the contrary, leakage current and watt loss of A and C\`s ZnO varistors which show low initial leakage current exhibited constant characteristics. After high current impulse test, A\`s ZnO varistor has broken the side of varistor but impulse current flowed. On the contrary, E\`s ZnO Varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After long duration impulse current test, E\`s ZnO varistor exhibited good discharge characteristics which the appearance of varistor was not wrong such as puncture, flashover, creaking and other significant damage. After high current impulse test and long duration impulse current test, E\`s ZnO varistor exhibited very good characteristics which variation rate of residual voltage is 1.4% before and after test.

Synchronizationof Synthetic Facial Image Sequences and Synthetic Speech for Virtual Reality (가상현실을 위한 합성얼굴 동영상과 합성음성의 동기구현)

  • 최장석;이기영
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.35S no.7
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    • pp.95-102
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    • 1998
  • This paper proposes a synchronization method of synthetic facial iamge sequences and synthetic speech. The LP-PSOLA synthesizes the speech for each demi-syllable. We provide the 3,040 demi-syllables for unlimited synthesis of the Korean speech. For synthesis of the Facial image sequences, the paper defines the total 11 fundermental patterns for the lip shapes of the Korean consonants and vowels. The fundermental lip shapes allow us to pronounce all Korean sentences. Image synthesis method assigns the fundermental lip shapes to the key frames according to the initial, the middle and the final sound of each syllable in korean input text. The method interpolates the naturally changing lip shapes in inbetween frames. The number of the inbetween frames is estimated from the duration time of each syllable of the synthetic speech. The estimation accomplishes synchronization of the facial image sequences and speech. In speech synthesis, disk memory is required to store 3,040 demi-syllable. In synthesis of the facial image sequences, however, the disk memory is required to store only one image, because all frames are synthesized from the neutral face. Above method realizes synchronization of system which can real the Korean sentences with the synthetic speech and the synthetic facial iage sequences.

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Clinical characteristics and progress of Kawasaki disease patients who had early treatment with intravenous immune globulin (가와사끼병에서 면역글로불린 조기 투여군의 임상적 특성 및 치료 경과)

  • Park, So-Yoon;Lee, Young Hwan
    • Clinical and Experimental Pediatrics
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    • v.50 no.10
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    • pp.1005-1010
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    • 2007
  • Purpose : To determine the optimal time of high dose intravenous immune globulin (IVIG) treatment, we analysed the clinical characteristics and progress of a group of Kawasaki disease patients who had early treatment with IVIG. Method : A retrospective study was conducted of 188 patients with Kawasaki disease who were admitted to Yeungnam University Medical Center from January 2000 to December 2005. All patients were treated with a high dose IVIG and high dose aspirin for the initial acute phase treatment. The early treatment group consisted of 94 patients who received treatment before 5 days of fever, and the conventional group consisted of 94 patients who were treated on or after day 5. The patients' sex, age, laboratory findings, total duration of fever, duration of fever after initial IVIG, need for additional IVIG and coronary artery status were noted. Result : There were no significant differences between the two groups in sex ratio and age. No significant differences were noted in the level of WBC count, ESR, CRP, serum albumin, LDH, total duration of fever and coronary abnormality. But the value of ALT($151.8{\pm}17.3$ vs. $81.9{\pm}13.4$, P=0.002), duration of fever after initial IVIG ($3.8{\pm}0.5days$ vs. $2.1{\pm}0.2days$, P=0.003), and rate of additional IVIG (15.9% vs. 6.3%, P=0.037) were significantly higher in the early treatment group. There was no significant difference in initial dose of IVIG, but dosage of aspirin was lower in early treatment group (P=0.037). Conclusion : There is no evidence that early treatment of IVIG has greater efficacy in preventing cardiac sequelae than conventional treatment. In addition, early treatment is likely to result in a greater requirement for additional IVIG treatment.

A Study on the Phonemic Segmentation of an Initial Affricate (초성파찰음의 음소분류에 관한 연구)

  • Kim, Ki-Woon;Lee, Ki-Young;Bae, Chul-Soo;Choi, Kap-Seok
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.33-36
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    • 1988
  • In this paper, the starting point of affricate is detected from the first predictor coefficient of a 12-pole linear predictive coding (LPC) analysis and phonemic segmentation is done through measuring short time energy and zero crossing rate. By this segmentation method, the duration of an aspirate can be mearsured in order to detect an aspirate or not.

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Vibration Reduction Effects of Stay Cable Due to Friction Damper (마찰댐퍼에 의한 사장 케이블의 진동저감 효과)

  • Kim, Hyung Ku;Yhim, Sung Soon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.2
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    • pp.54-61
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    • 2013
  • Stay cable has a strong axial rigidity due to large initial tension and, on the other hand, it has a weak laterally flexural rigidity. Wind loads or traffic loads cause the cables to vibrate significantly and affect the mechanical properties and the performance of cables of cable-stayed bridge (CSB). Therefore, the development of vibration reduction design is an urgent task to control the vibration vulnerable long-span bridges. As Friction damper (FD) shows to reduce the amplitude and duration time of vibration of cable of CSB from measured date in field test, friction damper can be considered that it is effective device significantly to reduce the amplitude and duration time in vibration of cable of CSB under traffic load, wind load and so on. Vibration characteristics of cable can change according to manufacturing method and type of established form. Nevertheless, analysis method in this study can present the design of friction damper for vibration reduction of cable of cable-stayed bridge from now on.