• Steel and Composite Structures
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• v.21 no.6
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• pp.1227-1250
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• 2016

Most of the research work has been conducted on K-joints under static loading. Very limited information is available in consideration of fatigue strength of K-joints with concrete-filled chord. This paper aims to describe experimental and numerical investigations on stress concentration factors (SCFs) of concrete-filled circular chord and square braces K-joints under balanced axial loading. Experiment was conducted to study the hot spot stress distribution along the intersection of chord and braces in the two specimens with compacting concrete filled in the chord. The test results of stress distribution curves of two specimens were reported. SCFs of concrete-filled circular chord and square braces K-joints were lower than those of corresponding hollow circular chord and square brace K-joints. The corresponding finite element analysis was also conducted to simulate stress distribution along the brace and chord intersection region of joints. It was achieved that experimental and finite element analysis results had good agreement. Therefore, an extensive parametric study was carried out by using the calibrated finite element model to evaluate the effects of main geometric parameters and concrete strength on the behavior of concrete-filled circular chord and square braces K-joints under balanced axial loading. The SCFs at the hot spot locations obtained from ABAQUS were compared with those calculated by using design formula given in the CIDECT for hollow SHS-SHS K-joints. CIDECT Design Guide was generally quite conservative for predicting SCFs of braces and was dangerous for predicting SCFs of chord in concrete-filled circular chord and square braces K-joints. Finally SCF formulae were proposed for circular chord and square braces K-joints with concrete-filled in the chord under balanced axial loading. It is shown that the SCFs calculated from the proposed design equation are generally in agreement with the values derived from finite element analysis, which were proved to be reliable and accurate.

• The Research Journal of the Costume Culture
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• v.31 no.2
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• pp.141-160
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• 2023

Controlling fashion waste throughout the entire product lifecycle is critical in a circular economy. This study explored the possibility of establishing a public recycling system for fashion waste. Since consumer interests and participation are essential, theoretical research, social-text analysis, and quantitative research were conducted to identify consumers' perceptions of the public recycling of fashion waste and circular fashion. Data were collected via an online survey among women in their 20-30's living in Korea, and 304 samples were used for data analysis. The results were as follows. First, consumers' perceptions of recycling fashion waste were composed of recycling difficulty, the need for public recycling, and the need for EPR. Circular fashion perception comprised favor, environment protection, attractiveness, economics, quality and hygiene risks, and lack of diversity. Second, the reuse-recycle attitude and need for EPR affected the favor of all types of circular fashion products. Third, environmental concerns impacted attractiveness, and the favor significantly affected the purchase intention of all types of circular fashion products. In particular, quality and hygiene risk negatively affected the purchase intention of used-fashion products, while attractiveness positively impacted the purchase intention of upcycled-fashion products. The results implied that discussing the public recycling system of fashion waste and EPR policy is imperative. The results also showed the need to classify different types of circular fashion products, such as used, upcycled, and regenerated fashion items, to examine consumers' perceptions. In addition, the recycling of the fashion waste scale developed in this study could be used for further research.

• Geomechanics and Engineering
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• v.31 no.3
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• pp.237-248
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• 2022

Nowadays, more and more subway tunnels were planed and constructed underneath the ground of urban cities to relieve the congested traffic. Potential damage may occur in existing tunnel if the new tunnel is constructed too close. So far, previous studies mainly focused on the tunnel-tunnel interactions with circular shape. The difference between circular and horseshoe shaped tunnel in terms of deformation mechanism is not fully investigated. In this study, three-dimensional numerical parametric studies were carried out to explore the effect of different tunnel shapes on the complicated tunnel-tunnel interaction problem. Parameters considered include volume loss, tunnel stiffness and relative density. It is found that the value of volume loss play the most important role in the multi-tunnel interactions. For a typical condition in this study, the maximum invert settlement and gradient along longitudinal direction of horseshoe shaped tunnel was 50% and 96% larger than those in circular case, respectively. This is because of the larger vertical soil displacement underneath existing tunnel. Due to the discontinuous hoop axial stress in horseshoe shaped tunnel, significant shear stress was mobilized around the axillary angles. This resulted in substantial bending moment at the bottom plate and side walls of horseshoe shaped tunnel. Consequently, vertical elongation and horizontal compression in circular existing tunnel were 45% and 33% smaller than those in horseshoe case (at monitored section X/D = 0), which in latter case was mainly attributed to the bending induced deflection. The radial deformation stiffness of circular tunnel is more sensitive to the Young's modulus compared with horseshoe shaped tunnel. This is because of that circular tunnel resisted the radial deformation mainly by its hoop axial stress while horseshoe shaped tunnel do so mainly by its flexural rigidity. In addition, the reduction of soil stiffness beneath the circular tunnel was larger than that in horseshoe shaped tunnel at each level of relative density, indicating that large portion of tunneling effect were undertaken by the ground itself in circular tunnel case.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.2
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• pp.55-64
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• 2017

Purpose Recently, with the spread of SPECT/CT, various image correction methods can be applied quickly and accurately, which enabled us to expect quantitative accuracy as well as image quality improvement. Among them, the Collimator Detector Response(CDR) recovery is a correction method aiming at resolution recovery by compensating the blurring effect generated from the distance between the detector and the object. The purpose of this study is to find out quantitative change depending on the change in detection distance in SPECT/CT images with CDR recovery applied. Materials and Methods In order to find out the error of acquisition count depending on the change of detection distance, we set the detection distance according to the obit type as X, Y axis radius 30cm for circular, X, Y axis radius 21cm, 10cm for non-circular and non-circular auto(=auto body contouring, ABC_spacing limit 1cm) and applied reconstruction methods by dividing them into Astonish(3D-OSEM with CDR recovery) and OSEM(w/o CDR recovery) to find out the difference in activity recovery depending on the use of CDR recovery. At this time, attenuation correction, scatter correction, and decay correction were applied to all images. For the quantitative evaluation, calibration scan(cylindrical phantom, $^{99m}TcO_4$ 123.3 MBq, water 9293 ml) was obtained for the purpose of calculating the calibration factor(CF). For the phantom scan, a 50 cc syringe was filled with 31 ml of water and a phantom image was obtained by setting $^{99m}TcO_4$ 123.3 MBq. We set the VOI(volume of interest) in the entire volume of the syringe in the phantom image to measure total counts for each condition and obtained the error of the measured value against true value set by setting CF to check the quantitative accuracy according to the correction. Results The calculated CF was 154.28 (Bq/ml/cps/ml) and the measured values against true values in each conditional image were analyzed to be circular 87.5%, non-circular 90.1%, ABC 91.3% and circular 93.6%, non-circular 93.6%, ABC 93.9% in OSEM and Astonish, respectively. The closer the detection distance, the higher the accuracy of OSEM, and Astonish showed almost similar values regardless of distance. The error was the largest in the OSEM circular(-13.5%) and the smallest in the Astonish ABC(-6.1%). Conclusion SPECT/CT images showed that when the distance compensation is made through the application of CDR recovery, the detection distance shows almost the same quantitative accuracy as the proximity detection even under the distant condition, and accurate correction is possible without being affected by the change in detection distance.

• Proceedings of the IEEK Conference
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• 2000.11d
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• pp.5-8
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• 2000

In this paper, a technique to estimate the circular object's center and radius under noisy condition is described. The technique is based on Davies'Hough transform approach to circular object location but more robust to noise and faster to estimate the circle by using an area of cumulated points.

• Journal of the Chungcheong Mathematical Society
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• v.21 no.1
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• pp.61-69
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• 2008

For a real subextension of some cyclotomic function field with a non-cyclic Galois group order $l^2$, l being a prime different from the characteristic of function field, we compute the index of the Sinnott group of circular units.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2851-2856
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• 2007

Flow patterns in the presence of two identical nearby circular cylinders at =100 were numerically studied. We considered all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. Eight distinct flow patterns were identified based on vorticity contours and streamlines, which are Base-Bleed, Biased-Base-Bleed, Shear- Layer-Reattachment, Induced-Separation, Vortex-Impingement, Flip-Flopping, Modulated Periodic, and Synchronized-Vortex-Shedding. Collecting all the numerical results, we propose a general flow pattern diagram for flows past the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use this diagram to distinguish flow patterns in the presence of two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.

• Structural Engineering and Mechanics
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• v.24 no.4
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• pp.411-427
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• 2006

The Discrete Element Method, DEM, is increasingly used in fracture studies of non-homogeneous continuous media, such as rock and concrete. A 2D circular rigid DEM formulation, developed to model concrete, has been adopted. A procedure developed to generate aggregate particles with a given aspect ratio and shape is presented. The aggregate particles are modelled with macroparticles formed by a group of circular particles that behave as a rigid body. Uniaxial tensile and compression tests performed with circular and non-circular aggregates, with a given aspect ratio, have shown similar values of fracture toughness when adopting uniform strength and elastic properties for all the contacts. Non-circular aggregate assemblies are shown to have higher fracture toughness when different strength and elastic properties are set for the matrix and for the aggregate/matrix contacts.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.1
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• pp.52-57
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• 2005

This paper describes a fabrication method of a circular diaphragm using boron etching stop method. It will be applied to acoustic transducers such as microphones or microspeakers and so on. The sensitivity is expected to be increased with the circular diaphragm through the simulation results to compare with a general rectangular diaphragm. The borondoped layer which is doped with solid source is sufficient for achieving an etching stop in 20 wt% TMAH, and the thickness is about $7.4{\mu}m$. The diameter of the circular silicon nitride diaphragm was measured to be 2 mm with $1{\mu}m$ thickness. The fabrication of piezoelectric acoustic devices was completed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.4
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• pp.305-312
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• 1989

Laminal natural convection heat transfer in the annulus between isothermal horizontal non-circular cylinders is studied by solving the Navier-Stokes and energy equation using an elliptic numerical procedure. Results are obtained to determine the effects of the diameter ratio($D_o/D_i$) and Rayleigh number on heat transfer. The diameter ratio is varied from 1.5 to 13.0 at Pr=0.7, H/L=1.5 and $10^3{\leqslant}Ra_L{\leqslant}4{\times}10^4$. It is found that the diameter ratio causes a more significant on the local heat transfer coefficient of lower semi-circular cylinder and plate than upper semi-circular cylinder. The mean Nusselt number increases as the diameter ratio and Rayleigh number increase, and is higher than that of the circular annulus with a same wetted perimeter.