• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.57-68
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• 2017

Purpose: The purpose of this study was to compare volumetric modulated arc therapy(VMAT) with fixed-field intensity modulated radiation therapy(IMRT) using non-coplanar beam when the shape of target is irregular and the location is adjacent to organ at risk(OAR). Materials and Methods: The subjects of this study were a total of 6 patients who had radiation therapy for whole scalp(2 patients), partial scalp(2 patients), and whole ventricle(2 patients) by True Beam STX(Varian Medical Systems, USA). VMAT plans consisted of coplanar or non-coplanar arcs which can minimize the volume of OAR included in beamlets. All fixed-field IMRT plans consisted of non-coplanar beams using more than 2 angles of Couch. Results: The VMAT and IMRT plans were compared with regard to the maximum dose of both lens, both optic nerves, optic chiasm, and brain stem and the mean dose of both eyeballs and hippocampus. VMAT plans showed higher dose than ncIMRT plans at more than 6 of all OARs in every patient, and the ratio was from 1.1 times to 8.2 times. In case of total scalp and partial scalp, the volume of brain which received more than 20 Gy in the VMAT plans was 2 times larger than the volume in the ncIMRT plans. In case of whole ventricle, there was no significant difference. Target coverage was satisfied in both plans($PTV_{100%}=95%$). The maximum dose in target volume and required monitor unit(MU) of ncIMRT were higher than them of VMAT plans. Conclusion: Even though ncIMRT is less efficient than VMAT with regard to required MU and treatment time, the dose to OARs is much lower than VMAT and PTV Coverage is similar with VMAT. If the shape of target is irregular and location is adjacent to OAR, comparison VMAT plan with ncIMRT plan deserves to be considered.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.5 s.39
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• pp.35-43
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• 2004

Small-scale models have been frequently used for seismic performance tests because of limited testing facilities and economic reasons. However, there are not enough studies on similitude law for analogizing prototype structures accurately with small-scale models, although conventional similitude law based on geometry is not well consistent in the inelastic seismic behavior. When fabricating prototype and small-scale model of reinforced concrete structures by using the same material, added mass is demanded from a volumetric change and scale factor could be limited due to aggregate size. Therefore, it is desirable that different material is used for small-scale models. Thus, a modified similitude law could be derived depending on geometric scale factor, equivalent modulus ratio and ultimate strain ratio. In this study, compressive strength tests are conducted to analyze the equivalent modulus ratio of micro-concrete to normal-concrete. Then, equivalent modulus ratios are divided into multi-phase damage levels, which are basically dependent on ultimate strain level. Therefore, an algorithm adaptable to the pseudodynamic test, considering equivalent multi-phase similitude law based on seismic damage levels, is developed. Test specimens, consisted of prototype structures and 1/5 scaled models as a reinforced concrete column, were designed and fabricated based on the equivalent modulus ratios already defined. Finally quasistatic and pseudodynamic tests on the specimens are carried out using constant and variable modulus ratios, and correlation between prototype and small-scale model is investigated based on their test results. It is confirmed that the equivalent multi-phase similitude law proposed in this study could be suitable for seismic performance tests on small-scale models.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.669-678
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• 1994

The BOD removal characteristics of submerged biofilters filled with three kinds of filter media respectively were experimentally examined with constant temperature, pH value and variable BOD loading and recirculation ratio. Obtained results are as follows; 1. The BOD removal ratio decreases with the increasing $BOD_5$ volumetric loading rate, and the loading rate for the BOD removal over 90% is lower thean $1.6kg{\cdot}BOD_5/m^3{\cdot}d$ for the plastic media of Netring and cubic wire meshes. This is a much large value than $0.3{\sim}0.8kg{\cdot}BOD_5/m^3{\cdot}d$ for conventional activated sludge process. The required submerged biofilter volume is found to be much samller than that of conventional activated sludge process. 2. The decreasing order of BOD removal is Netring (random plastic media), cubic wire meshes (plastic module), and then gravel (stone media). This is mainly due to the media characteristics such as void ratio, specific surface area and media shapes. 3. The $BOD_5$ removal rate increases with the recircuration ration, but the rate of increases becomes samaller as the recirculation ratio increases over 20. When $BOD_5$ loading is $1.8kg{\cdot}BOD_5/m^3{\cdot}d$, the required recirculation rationto obtain 90% $BOD_5$ removal is about 20 for Netring and it was about 30 for cubic wire meshes. 4. Reynold's Number increases with recirculation ratio, and the Reynold's Numbers corresponding to the recircuration ratio of 10~50 are less than 52, showing laminar up flows in the filter. The settled and effluent sludges increase with increase of Reynol's Number, and there are the definite Reynold's Numbers at which the settling sludge concentrations become nearly constant respectively in each filters. 5. In this submerged biofilter system, small volume of sludge hopper can be substituted for a separated settling tank.

• Geotechnical Engineering
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• v.8 no.1
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• pp.19-28
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• 1992

Recently, testing equipment which can run resonant column test altogether with the torsional shear test at the very highly controlled condition was developed at the University of Texas at Austin(U.S.A). With this equipment, the effects of high amplitude pre-straining vibrations on the dynamic properties of clean sands were studied. Tests showed the following results. Low amplitude shear modulus was gradually increased with little void ratio change as the number of high amplitude vibration cycles increased. Variation of volumetric strain with confining pressure for the pre -strained specimen under vibration was smaller than that of fresh specimen. Also the slope of the diagram for shear modulus and confining pressure relationship of the prestrained specimen was smaller than that of fresh specimens. These results agreed well with the analytical results.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.3 no.2
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• pp.65-71
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• 2017

To assess the effects of filter and reconstruction of Cu-64 PET data on Siemens scanner, the various reconstruction algorithm with various filters were assessed in terms of spatial resolution, non-uniformity (NU), recovery coefficient (RC), and spillover ratio (SOR). Image reconstruction was performed using filtered backprojection (FBP), 2D ordered subset expectation maximization (OSEM), 3D reprojection algorithm (3DRP), and maximum a posteriori algorithms (MAP). For the FBP reconstruction, ramp, butterworth, hamming, hanning, or parzen filters were used. Attenuation or scatter correction were performed to assess the effect of attenuation and scatter correction. Regarding spatial resolution, highest achievable volumetric resolution was $3.08mm^3$ at the center of FOV when MAP (${\beta}=0.1$) reconstruction method was used. SOR was below 4% for FBP when ramp, Hamming, Hanning, or Shepp-logan filter were used. The lowest NU (highest uniform) after attenuation & scatter correction was 5.39% when FBP (parzen filter) was used. Regarding RC, 0.9 < RC < 1.1 was obtained when OSEM (iteration: 10) was used when attenuation and scatter correction were applied. In this study, image quality of Cu-64 on Siemens Inveon PET was investigated. This data will helpful for the quantification of Cu-64 PET data.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.146-154
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• 1995

I n this paper, an experimental research was carried out to investigate the confinement effect of spiral reinforcements in concrete column specimens subjected to t.he concentric axial corn pressive loads. Main variables were the compressive strengths of concrete of 27.2, 62.4 and 81.2 MPa, and the spacings of spirals of 120, 60, 40, 30, 25 and 20mm. and the yield strengths of spir als of 451 and 1375MPa, respectively. For the same volumetric ratio and yield strength of spir als, it was shown that the strength increment of confined concrete was almost same regardless of the strength of unconfined concrete, however, the axial stram at maximum stress was decreas ed with increasing of the compressive strength of unconfined concrete.

• KSBB Journal
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• v.14 no.1
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• pp.24-30
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• 1999

The fed-bach simultaneous saccharification and fermentation (SSF) of newspaper to ethanol with Brettanomyces custersii was studied. The initial substrate concentration for the effective fed-batch SSF was 8% (w/v). The initial optimum enzyme concentration was 30 FPU/g cellulose for cellulase and the optimum volumetric ratio of $\beta$-glucosidase to cellulase was 0.1. When 4% (w/v) of ball-milled newspaper was supplemented intermittently at time intervals, considering the mixing of newspaper slurry, the fed-batch SSF showed higher ethanol concentration (26.80 g/L) and two times higher ethanol production yield based on enzyme than the batch SSF.

• Architectural research
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• v.7 no.1
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• pp.39-48
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• 2005

Main objective of this research is to evaluate performance of high-strength concrete (HSC) columns for ductility and strength. Eight one-third scale columns with compressive strength of 69 MPa were subjected to a constant axial load corresponding to 30 % of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement (${\rho}_s=1.58$, 2.25 %), tie configuration (Type H, Type C and Type D) and tie yield strength ($f_{yh}=549$ and 779 MPa). Test results show that the flexural strength of every column exceeds the calculated flexural capacity based on the equivalent concrete stress block used in the current design code. Columns with 42 % higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behaviour, showing a displacement ductility factor (${\mu}_{{\Delta}u}$) of 3.69 to 4.85, and a curvature ductility factor (${\mu}_{{\varphi}u}$) of over 10.0. With an axial load of 30 % of the axial load capacity, it is recommended that the yield strength of transverse reinforcement be held equal to or below 549 MPa.

• Journal of Korean Neurosurgical Society
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• v.51 no.2
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• pp.120-123
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• 2012

Objective : Percutaneous vertebroplasty (PVP) is usually carried out under three-dimensional (2D) fluoroscopic guidance. However, operative complications or bone cement distribution might be difficult to assess on the basis of only 2D radiographic projection images. We evaluated the feasibility of performing an intraoperative and postoperative examination in patients undergoing PVP by using three-dimensional (3D) reconstructive C-arm. Methods : Standard PVP procedures were performed on 14 consecutive patients by using a Siremobil Iso-$C^{3D}$ and a multidetector computed tomography machine. Post-processing of acquired volumetric datasets included multiplanar reconstruction (MPR) and surface shaded display (SSD). We analyzed intraoperative and immediate postoperative evaluation of the needle trajectory and bone cement distribution. Results : The male : female ratio was 2 : 12; mean age of patients, 70 (range, 77-54) years; and mean T score, -3.4. The mean operation time was 52.14 min, but the time required to perform and post-process the rotational acquisitions was 7.76 min. The detection of bone cement distribution and leakage after PVP by using MPR and SSD was possible in all patients. However, detection of the safe trajectory for needle insertion was not possible. Conclusion : 3D rotational image acquisition can enable intra- or post-procedural assessment of vertebroplasty procedures for the detection of bone cement distribution and leakage. However, it is difficult to assess the safe trajectory for needle insertion.

• Geomechanics and Engineering
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• v.14 no.5
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• pp.459-466
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• 2018

By conducting uniaxial loading cycle tests on the coal rock with outburst proneness, the dilatation characteristics at different loading rates were investigated. Under uniaxial loading and unloading, the lateral deformation of coal rock increased obviously before failure, leading to coal dilatation. Moreover, the post-unloading recovery of the lateral deformation was rather small, suggesting the onset of an accelerated failure. As the loading rate increased further, the ratio of the stress at the dilatation critical point to peak-intensity increased gradually, and the pre-peak volumetric deformation decreased with more severe post-peak damage. Based on the laboratory test results, the lateral deformation of the coals at different depths in the #1302 isolated coal pillars, Yangcheng Coal Mine, was monitored using wall rock displacement meter. The field monitoring result indicates that the coal lateral displacement went through various distinct stages: the lateral displacement of the coals at the depth of 2-6 m went through an "initial increase-stabilize-step up-plateau" series. When the coal wall of the working face was 24-18 m away from the measuring point, the coals in this region entered the accelerated failure stage; as the working face continued advancing, the lateral displacement of the coals at the depth over 6 m increased steadily, i.e., the coals in this region were in the stable failure stage.