• Title/Summary/Keyword: Axial Mode

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Effect of Alloying on the Microstructure and Fatigue Behavior of Fe-Ni-Cu-Mo P/M Steels

  • Bohn, Dmitri A.;Lawley, Alan
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 1997.04a
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    • pp.34-34
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    • 1997
  • The effect of alloying mode and porosity on the axial tension-tension fatigue behavior of a P/M steel of nominal composition Fe-4w/o Ni-1.5w/o Cu-O.5w/o Mo-O.5w/o C has been evaluated. Alloying modes utilized were elemental powder mixing, partial alloying(distaloy) and prealloying by water atomization; in each case the carbon was introduced as graphite prior to sintering. Powder compacts were sintered(1120C/30 min.) in 7Sv/o H2/25v/o N2 to densities in the range 6.77-7.2 g/cm3. The dependence of fatigue limit response on alloying mode and porosity was interpreted in terms of the constituent phases and the pore and fracture morphologies associated with the three alloying modes. For the same nominal composition, the three alloying modes resulted in different sintered microstructures. In the elemental mix alloy and the distaloy, the major constituent was coarse and fine pearlite, with regions of Ni-rich ferrite, Ni-rich martensite and Ni-rich areas. In contrast, the prealloy consisted primarily of martensite by with some Ni-rich areas. From an examination of the fracture surfaces following fatigue testing it was concluded that essentially all of the fracture surfaces exhibited dimpled rupture, characteristic of tensile overload. Thus, the extent of growth of any fatigue cracks prior to overload was small. The stress amplitude for the three alloying modes at 2xl06 was used for the comparison of fatigue strengths. For load cycles <3xl05, the prealloy exhibited optimum fatigue response followed by the distaloy and elemental mix alloy, respectively. At load cycles >2xl06, similar fatigue limits were exhibited by the three alloys. It was concluded that fatigue cracks propagate primarily through pores, rather than through the constituent phases of the microstructure. A decrease in pore SIze improved the S-N behavior of the sintered steel.

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Behaviour of ultra-high strength concrete encased steel columns subject to ISO-834 fire

  • Du, Yong;Zhou, Huikai;Jiang, Jian;Liew, J.Y. Richard
    • Steel and Composite Structures
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    • v.38 no.2
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    • pp.121-139
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    • 2021
  • Ultra-high strength concrete (UHSC) encased steel columns are receiving growing interest in high-rise buildings owing to their economic and architectural advantages. However, UHSC encased steel columns are not covered by the modern fire safety design code. A total of 14 fire tests are conducted on UHSC (120 MPa) encased steel columns under constant axial loads and exposed to ISO-834 standard fire. The effect of load ratio, slenderness, stirrup spacing, cross-section size and concrete cover to core steel on the fire resistance and failure mode of the specimens are investigated. The applicability of the tabulated method in EC4 (EN 1994-1-2-2005) and regression formula in Chinese code (DBJ/T 15-81-2011) to fire resistance of UHSC encased steel columns are checked. Generally, the test results reveal that the vertical displacement-heating time curves can be divided into two phases, i.e. thermal expansion and shortening to failure. It is found that the fire resistance of column specimens increases with the increase of the cross-section size and concrete cover to core steel, but decreases with the increase of the load ratio and slenderness. The EC4 method overestimates the fire resistance up to 186% (220 min), while the Chinese code underestimates it down to 49%. The Chinese code has a better agreement than EC4 with the test results since the former considers the effect of the load ratio, slenderness, cross section size directly in its empirical formula. To estimate the fire resistance precisely can improve the economy of structural fire design of ultra-high strength concrete encased steel columns.

Acoustic Modeling in a Gas Turbine Combustor with Backflow Using a Network Aproach (역류형 가스터빈 연소기에서 네트워크 접근법을 이용한 음향장 모델링)

  • Son, Juchan;Hong, Sumin;Hwang, Jeongjae;Kim, Min Kuk;Kim, Daesik
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.5
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    • pp.18-26
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    • 2021
  • In this work, we have developed a 1D network model aimed at predicting eigenvalues for resonance frequency analysis in a lab-scale industrial gas turbine single nozzle combustion system. Modern industrial gas turbines generally adopt combustors with very complex geometry and flow path to meet various design requirements simultaneously. The current study has developed a network model for combustion systems with backflow at the same axial location. The modeling results of resonance frequencies and mode distributions for a given system using the network model were validated from comparisons with prediction results using a 3D Helmholtz solver.

Design of a Polarization-Switching Patch Antenna Using Parasitic Elements (기생소자를 이용한 편파 전환 패치 안테나 설계)

  • Won Jun Lee
    • Journal of Advanced Navigation Technology
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    • v.28 no.5
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    • pp.720-725
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    • 2024
  • In this paper, we propose a microstrip patch antenna with polarization-switching characteristics using parasitic elements and PIN diodes placed at the sides of the microstrip patch. The proposed antenna is designed by arranging four linear parasitic elements along the sides of a square-shaped microstrip patch, with each parasitic element connected to a PIN diode. By utilizing the open and short circuit characteristics of the PIN diodes based on the applied bias, the electrical length of the parasitic element slots is altered, enabling polarization switching between right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). The proposed antenna resonates at 4.21 GHz, with a return loss of 17.5 dB and a bandwidth of 135 MHz when operating in RHCP mode, and a return loss of 18.4 dB and a bandwidth of 144 MHz when operating in LHCP mode. Additionally, the axial ratios for RHCP and LHCP are 2.53 dB and 2.52 dB, respectively, and the gains are 6.62 dBic and 6.32 dBic, respectively.

Standard Performance Measurements of GE AdvanceTM Positron Emission Tomography (GE AdvanceTM 양전자방출단층촬영기의 표준 성능평가)

  • Jeong, Ha-Kyu;Kim, Hee-Joung;Son, Hye-Kyung;Bong, Jung-Kyun;Jung, Hai-Jo;Jeon, Tae-Joo;Kim, Jae-Sam;Lee, Jong-Doo;Yoo, Hyung-Sik
    • The Korean Journal of Nuclear Medicine
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    • v.35 no.2
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    • pp.100-112
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    • 2001
  • Purpose: The purpose of this study was to establish optimal imaging acquisition conditions for the GE AdvanceTM PET imaging system by performing the acceptance tests designed by National Electrical Manufacturers Association (NEMA) protocol and General Electric Medical Systems (GEMS) test procedures. Materials and Methods: Performance tests were carried out with 18FDG radioactivity source and phantoms by using a standard acquisition mode. Transaxial resolution and scatter traction tests were performed with a line source and axial resolution with a point source, respectively. A cylindrical phantom made of polymethylmethacrylate (PMMA) was used to measure sensitivity, count rate losses and randoms, uniformity correction, and attenuation inserts were added to measure remaining tests. The test results were acquired in a diagnostic acquisition mode and analyzed mainly on high sensitivity mode. Results: Transaxial resolution and axial resolution were measured as average of 4.65 mm and 3.98 mm at 0 cm, and 6.02 mm and 6.71 mm at 20 cm on high sensitivity mode, respectively. Average scatter fraction was 9.87%, and sensitivity was 225.8kcps/μCi/cc of trues. Activity at 50% deadtime was 4.6μCi/cc, and the error of count rate correction at that activity was from 1.49% to 3.83%. Average nonuniformity for total slice w3s 8.37%. The accuracy of scatter correction was -0.95%. The accuracies of attenuation correction were 5.68% for air, 0.04% for water and -6.51% for polytetrafluoroethylene (PTFE). Conclusion: The results satisfied most acceptance criteria, indicating that the GE AdvanceTM PET system can be optimally used for clinical applications.

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Evaluation of usefulness of the Gated Cone-beam CT in Respiratory Gated SBRT (호흡동조 정위체부방사선치료에서 Gated Cone-beam CT의 유용성 평가)

  • Hong sung yun;Lee chung hwan;Park je wan;Song heung kwon;Yoon in ha
    • The Journal of Korean Society for Radiation Therapy
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    • v.34
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    • pp.61-72
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    • 2022
  • Purpose: Conventional CBCT(Cone-beam Computed-tomography) caused an error in the target volume due to organ movement in the area affected by respiratory movement. The purpose of this paper is to evaluate the usefulness of accuracy and time spent using the Gated CBCT function, which reduces errors when performing RGRT(respiratory gated radiation therapy), and to examine the appropriateness of phase. Materials and methods: To evaluate the usefulness of Gated CBCT, the QUASARTM respiratory motion phantom was used in the Truebeam STxTM. Using lead marker inserts, Gated CBCT was scaned 5 times for every 20~80% phase, 30~70% phase, and 40~60% phase to measure the blurring length of the lead marker, and the distance the lead marker moves from the top phase to the end of the phase was measured 5 times. Using Cedar Solid Tumor Inserts, 4DCT was scanned for every phase, 20-80%, 30-70%, and 40-60%, and the target volume was contoured and the length was measured five times in the axial direction (S-I direction). Result: In Gated CBCT scaned using lead marker inserts, the axial moving distance of the lead marker on average was measured to be 4.46cm in the full phase, 3.11cm in the 20-80% phase, 1.94cm in the 30-70% phase, 0.90cm in the 40-60% phase. In Fluoroscopy, the axial moving distance of the lead marker on average was 4.38cm and the distance on average from the top phase to the beam off phase was 3.342cm in the 20-80% phase, 3.342cm in the 30-70% phase, and 0.84cm in the 40-60% phase. Comparing the results, the difference in the full phase was 0.08cm, the 20~80% phase was 0.23cm, the 30~70% phase was 0.10cm, and the 40~60% phase was 0.07cm. The axial lengths of ITV(Internal Target Volume) and PTV(Planning Target Volume) contoured by 4DCT taken using cedar solid tumor inserts were measured to be 6.40cm and 7.40cm in the full phase, 4.96cm and 5.96cm in the 20~80% phase, 4.42cm and 5.42cm in the 30~70% phase, and 2.95cm and 3.95cm in the 40~60% phase. In the Gated CBCT, the axial lengths on average was measured to be 6.35 cm in the full phase, 5.25 cm in the 20-80% phase, 4.04 cm in the 30-70% phase, and 3.08 cm in the 40-60% phase. Comparing the results, it was confirmed that the error was within ±8.5% of ITV Conclusion: Conventional CBCT had a problem that errors occurred due to organ movement in areas affected by respiratory movement, but through this study, obtained an image similar to the target volume of the setting phase using Gated CBCT and verified its usefulness. However, as the setting phase decreases, the scan time was increases. Therefore, considering the scan time and the error in setting phase, It is recommended to apply it to patients with respiratory coordinated stereotactic radiation therapy using a wide phase of 30-70% or more.

Investigation on the seismic performance of T-shaped column joints

  • Chen, Changhong;Gong, He;Yao, Yao;Huang, Ying;Keer, Leon M.
    • Computers and Concrete
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    • v.21 no.3
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    • pp.335-344
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    • 2018
  • More and more special-shaped structural systems have been widely used in various industrial and civil buildings in order to satisfy the new structural system and the increasing demand for architectural beauty. With the popularity of the special-shaped structure system, its seismic performance and damage form have also attracted extensive attention. In the current research, an experimental analysis of six groups of (2/3 scale) T-shaped column joints was conducted to investigate the seismic performance of T-shaped column joints. Effects of the beam cross section, transverse stirrup ratio and axial compression ratio on bearing capacity and energy dissipation capacity of column joints were obtained. The crack pattern of T-shaped column joints under low cyclic load was presented and showed a reversed "K" mode. According to the crack configurations, a tensile-shear failure model to determine the shear bearing capacity and crack propagation mechanisms is developed.

Sensitivity-based Damage detection in deep water risers using modal parameters: numerical study

  • Min, Cheonhong;Kim, Hyungwoo;Yeu, Taekyeong;Hong, Sup
    • Smart Structures and Systems
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    • v.15 no.2
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    • pp.315-334
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    • 2015
  • A main goal of this study is to propose a damage detection technique to detect and localize damages of a top-tensioned riser. In this paper, the top-tensioned finite element (FE) model is considered as an analytical model of the riser, and a vibration-based damage detection method is proposed. The present method consists of a FE model updating and damage index method. In order to accomplish the goal of this study, first, a sensitivity-based FE model updating method using natural frequencies and zero frequencies is introduced. Second, natural frequencies and zero frequencies of the axial mode on the top-tensioned riser are estimated by eigenvalue analysis. Finally, the locations and severities of the damages are estimated from the damage index method. Three numerical examples are considered to verify the performance of the proposed method.

Eccentrically compressive behaviour of RC square short columns reinforced with a new composite method

  • Zhang, Fan;Lu, Yiyan;Li, Shan;Zhang, Wenlong
    • Steel and Composite Structures
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    • v.27 no.1
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    • pp.95-108
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    • 2018
  • A new composite reinforced method, namely self-compacting concrete filled circular CFRP-steel jacketing, was proposed in this paper. Experimental tests on eight RC square short columns reinforced with the new composite reinforced method and four RC square short columns reinforced with CFS jackets were conducted to investigate their eccentrically compressive behaviour. Nine reinforced columns were subjected to eccentrically compressive loading, while three reinforced columns were subjected to axial compressive loading as reference. The parameters investigated herein were the eccentricity of the compressive loading and the layer of CFRP. Subsequently, the failure mode, ultimate load, deformation and strain of these reinforced columns were discussed. Their failure modes included the excessive bending deformation, serious buckling of steel jackets, crush of concrete and fracture of CFRP. Moreover, these reinforced columns exhibited a ductile failure globally. Both the eccentricity of the compressive loading and the layer of CFRP had a significant effect on the eccentrically compressive behaviour of reinforced columns. Finally, formulae for the evaluation of the ultimate load of reinforced columns were proposed. The theoretical formulae based on the ultimate equilibrium theory provided an effective, acceptable and safe method for designers to calculate the ultimate load of reinforced columns under eccentrically compressive loading.

Investigations on the influence of radial confinement in the impact response of concrete

  • Al-Salloum, Yousef;Alsayed, Saleh;Almusallam, Tarek;Ibrahim, S.M.;Abbas, H.
    • Computers and Concrete
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    • v.14 no.6
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    • pp.675-694
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    • 2014
  • Annular and solid concrete specimens with different aspect ratios and static unconfined compressive strengths were studied for impact loading using SHPB test setup. Numerical simulations in LSDYNA were also carried out and results were validated. The stress-strain curves obtained under dynamic loading were also compared with static compressive tests. The mode of failure of concrete specimen was a typical ductile failure at high strain rates. In general, the dynamic increase factor (DIF) of thin solid specimens was higher than thick samples. In the numerical study, the variation of axial, hydrostatic and radial stresses for solid and annular samples was studied. The core phenomenon due to confinement was observed for solid samples wherein the applied loads were primarily borne by the innermost concrete zone rather than the outer peripheral zone. In the annular samples, especially with large diameter inside hole, the distribution of stresses was relatively uniform along the radial distance. Qualitatively, only a small change in the distribution of stresses for annular samples with different internal diameters studied was observed.