• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.575-580
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• 2020

We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC) to detect the fission fragments and reconstruct the fission reaction plane in the experiment of studying nuclear equation of state (nEOS) by means of heavy ion collision (HIC). This experiment put forward high requirements for the performances of PPAC, such as the time resolution, efficiency and position resolution. According to these requirements we designed the PPAC with an active area of 240 mm × 280 mm working at low gas pressure. The results show that time resolution could be less than 300 ps. Position resolution is consistent with the theoretical calculation about 1.35 mm. Detection efficiency could be approaching 100% gradually with the voltage increasing in different gas pressures. The performances of PPAC have also been verified in beam experiment. Each set of anode wires can be accurately separated in the position spectrum. In the beam experiment, we also got the back-to-back correlation of fission fragments which is one of the direct signals characterizing binary decay.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.116-118
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• 2002

It has been noted that Monte Carlo simulations are the most accurate method to calculate dose distributions in any material and geometry. Monte Carlo transport algorithms determine the absorbed dose by following the path of representative particles as they travel through the medium. Accurate Monte Carlo dose calculations rely on detailed modeling of the radiation source. We modeled the effects of beam modifiers such as collimators, blocks, wedges, etc. of our accelerator, Varian Clinac 600C/D to ensure accurate representation of the radiation source using the EGSnrc based BEAM code. These were used in the EGSnrc based DOSXYZ code for the simulation of particles transport through a voxel based Cartesian coordinate system. Because Monte Carlo methods use particle-by-particle methods to simulate a radiation transport, more particle histories yield the better representation of the actual dose. But the prohibitively long time required to get high resolution and accuracy calculations has prevented the use of Monte Carlo methods in the actual clinical spots. Our ultimate aim is to develop a Monte Carlo dose calculation system designed specifically for radiation therapy planning, which is distinguished from current dose calculation methods. The purpose of this study in the present phase was to get dose calculation results corresponding to measurements within practical time limit. We used parallel processing and some variance reduction techniques, therefore reduced the computational time, preserving a good agreement between calculations of depth dose distributions and measurements within 5% deviations.

• Progress in Medical Physics
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• v.26 no.3
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• pp.178-184
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• 2015

The Markus ionization chamber(R) is a small plane parallel ionization chamber widely used in clinical electron beam dosimetry. Plane parallel chambers were recommended for low energy electron dosimetry with the beam quality at $R_{50}<4.0g/cm^2$ (${\bar{E}}{\approx}10MeV$) according to TRS-398 protocol. However, the quality correction factors ($k_{Q,Q_0}$) of the Markus chamber was not presented in TRS-398 protocol for electron beam quality at $R_{50}<2.0g/cm^2$ (${\bar{E}}{\approx}4MeV$). In this study, the $k_{Q,Q_0}$ factors of the Markus chambers (PTW-34045) for beam qualities at $R_{50}=1.0$, 1.4, 2.0, 2.5, 3.0, and $5.0g/cm^2$ were determined by Monte Carlo calculations (DOSRZnrc/EGSnrc) and the dosimetric formalism of quality correction factor. The derived $k_{Q,Q_0}$ values were evaluated using the produced data based on TRS-398 and TG-51 protocols and known values for the Markus chamber.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1324-1333
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• 2010

In this paper, three kinds of beam coupling losses which occur in a quasi-optics circuit for millimeter wave receiver system have been intensively investigated. First, the beam coupling losses which are caused by mismatch of beam waists radii and their positions between those of one and the other have been evaluated. It shows that beam coupling losses due to mismatch of beam waists radii and their positions between two quasi-optics circuits can be minimized if beam waist radius is chosen as larger than 3 times the operation wavelength. Second, the beam coupling losses have been studied when the axis of propagation of one beam is tilted with respect to that of the other beam. It is noted that smaller beam waist radius results in greater tolerance to tilts and angular misalignments. Third, the beam coupling cases in which two beams are offset if their axes of propagation are parallel but one is displaced relative to the other have been investigated. It is confirmed that beam waists radii with larger than 3 times operation wavelength are less sensitive to lateral offsets.

• Journal of radiological science and technology
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• v.21 no.2
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• pp.5-10
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• 1998

In the mammography, X-ray beam quality is one of the most important factors. Using X-ray mammography unit model GE/CGR Senography 600T Senix H.F, Authors studied four subjects. 1. The aluminum attenuation rate in 30 kVp when used with or without compression plate. 2. HVLs at 5 different area of the X-ray field of $26{\sim}32kVp$. 3. HVLs to know the influence of corrected measurement or parallel measurement. 4. Film density with microdensitometer along and cross to the long axis of X-ray tube, in terms of the Heel effect in the X-ray field. The following results were obtained. 1. Beam quality of anode area was harder than cathode area. 2. The dose reduction rate of compression plate was approximately $65.5%{\sim}88.1%$ and the beam quality with compression plate was hardened up to 4kVp accordingly. 3. If the X-ray beam enters the attenuation plate obliquely, HVL was $2.6{\sim}2.9%$ harder than perpendicular to it. 4. Because of heel effect, the film density of cathode area is higher than anode area to film density of 0.5.

• Earthquakes and Structures
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• v.2 no.1
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• pp.89-107
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• 2011

In this paper a simple mathematical model is presented for estimating the natural frequencies and corresponding mode shapes of a tall building with outrigger-belt truss system. For this purposes an equivalent continuum system is analyzed in which a tall building structure is replaced by an idealized cantilever continuum beam representing the structural characteristics. The equivalent system is comprised of a cantilever shear beam in parallel to a cantilever flexural beam that is constrained by a rotational spring at outrigger-belt truss location. The mathematical modeling and the derivation of the equation of motion are given for the cantilevers with identically paralleled and rotational spring. The equation of motion and the associated boundary conditions are analytically obtained by using Hamilton's variational principle. After obtaining non-trivial solution of the eigensystem, the resulting is used to determine the natural frequencies and associated mode shapes of free vibration analysis. A numerical example for a 40 story tall building has been solved with proposed method and finite element method. The results of the proposed mathematical model have good adaptation with those obtained from finite element analysis. Proposed model is practically suitable for quick evaluations during the preliminary design stages.

• Coupled systems mechanics
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• v.12 no.4
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• pp.297-313
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• 2023

This paper deals with delamination analysis of non-linear viscoelastic multilayered beam subjected to bending in the plane of the layers. For this purpose, first, a non-linear viscoelastic model is presented. In order to take into account the non-linear viscoelastic behaviour, a non-linear spring and a non-linear dashpot are assembled in series with a linear spring connected in parallel to a linear dashpot. The behaviours of the non-linear spring and dashpot are described by applying non-linear stress-strain and stress-rate of strain relationships, respectively. The constitutive law of the model is derived. Due to the non-linear spring and dashpot, the constitutive law is non-linear. This law is used for describing the time-dependent mechanical behaviour of the beam under consideration. The material properties involved in the constitutive law vary along the beam length due to the continuous material inhomogeneity of the layers. Solution of the strain energy release rate for the delamination is obtained by analyzing the balance of the energy with considering of the non-linear viscoelastic behaviour. The strain energy release rate is found also by using the complementary strain energy for verification. A parametric study is carried-out by using the solution obtained. The solutions derived and the results obtained help to understand the time-dependent delamination of non-linear viscoelastic beams under loading in the plane of layers.

• Structural Engineering and Mechanics
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• v.90 no.2
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• pp.143-157
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• 2024

Cold-formed steel (CFS) I sections are increasingly being used as load-bearing components in building constructions, and such I sections frequently incorporate web holes to facilitate service installation. The economical and structural advantages of these elements have prompted many researchers to investigate the behavior of such structures. Despite numerous studies on the buckling stability of castellated beams, there is a notable absence of experimental investigation into oval castellated beams with stiffeners. This study examines the local buckling of cold-formed steel castellated I-beams stiffened with oval constellations through experimental and numerical analysis. Four specimens are fabricated with and without stiffeners, including parallel, perpendicular, and intersecting types attached to the web portion of the beam, along with cross stiffeners for the oval-shaped openings at the beam ends. Additionally, a numerical model is developed to predict the behavior of castellated beams with oval openings up to failure, considering both material and geometric nonlinearities. Codal analysis is performed using the North American specification for cold-formed steel AISI S-100 and the Australian/New Zealand design code AS/NZS 4600. The anticipated outcomes from numerical analysis, experimental research, and codal analysis are compared and presented. It will be more helpful to the preliminary designers.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.3 s.192
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• pp.47-54
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• 2007

This paper describes the development of the intelligent gripper with two 3-axis force sensor that can measure forces Fx, Fy, Fz simultaneously, for stably grasping an unknown object. In order to grasp an unknown object using an intelligent gripper softly, it should measure the force in the gripping direction and the force in the gravity direction, and perform the force control using the measured farces. Thus, the intelligent gripper should be composed of 3-axis force sensor that can measure forces Fx, Fy, Fz at the same time. In this paper, the intelligent gripper with two 3-axis force sensor was manufactured and its characteristic test was carried out. The fabricated gripper could grasp an unknown object stably. Also, the sensing element of 3-axis force sensor was modeled and designed with five parallel-plate beams, and 3-axis force sensor for the intelligent gripper was fabricated. The characteristic test of the made sensor was carried out.

• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.93-101
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• 2007

The purpose of this study was to analyze the research trends of artistic gymnastics on the kinetics. This study analyzed the 76 published papers in the Journal of Korean Alliance for Health, Physical Education, Recreation & Dance and Korean Journal of Sport Biomechanics between 1995 and 2006. Papers were split into two groups for analysis, 1995-1999 and 2000-2006, and classified according to research methods, areas, and main topics. Conclusions are as follow. First, method of research were kinematical research(80.3%), kinetic(17.1%), and EMG research(2.6%). Second, areas of research were hi-bar(31.6%), vault(23.7%), parallel bars(21.1%), floor exercise(13.2%), rings(3.9%), balance beam(3.9%), uneven bars(2.6%). Last, main topic of research were focused on vault Tsukahara skill(13.9%), hi-bar flight skill(11.4%), parallel bars support skill(10.1%), hi-bar dismount skill(8.9%), floor exercise salto skill(8.9%).