• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.2885-2887
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• 1999

초고속 영상 기법의 Echo Planar Imaging과 Spiral Scan Imaging 기법은 자기장의 inhomogeneity에 영향을 많이 받게 된다. 본 논문에서는 자기장의 inhomogeneity를 보정하는 기능인 shimming 기능을 자동으로 실행할 수 있는 알고리즘을 구현하였다. 자기장의 inhomogeneity를 보정하기 위해서 자기장에 생성될 수 있는 spherical harmonic function중 1차에 대해 보정을 시도하였고, 기존의 알고리즘보다 뛰어난 결과를 얻을 수 있었다.

• Smart Structures and Systems
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• v.19 no.3
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• pp.237-241
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• 2017

The present study deals with the propagation of Love wave (a type of surface wave) in crustal layer having temperature dependent inhomogeneity. It is assumed that the inhomogeneity in the crustal layer arises due to linear temperature variation in rigidity and density. The upper boundary of the crustal layer is traction free. Numerical results for Love wave are discussed by plotting analytical curves between phase velocity against wave number and stress against depth in the presence of inhomogeneity and temperature parameters. The effects boundary condition on the Love wave propagation in the crustal layer is also analyzed. The results presented in this study would be useful for seismologists and geologists.

• Progress in Medical Physics
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• v.20 no.4
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• pp.260-268
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• 2009

In this study, we estimated inhomogeneity correction factor in small field. And, we evaluated accuracy of treatment planning and measurement data which applied inhomogeneity correction factor or not. We developed the Inhomogeneity Correction Phantom (ICP) for insertion of inhomogeneity materials. The inhomogeneity materials were 12 types in each different electron density. This phantom is able to adapt the EBT film and 0.125 cc ion chamber for measurement of dose distribution and point dose. We evaluated comparison of planning and measurement data using ICP. When we applied to inhomogeneity correction factor or not, the average difference was 1.63% and 10.05% in each plan and film measurement data. And, the average difference of dose distribution was 10.09% in each measurement film. And the average difference of point dose was 0.43% and 2.09% in each plan and measurement data. In conclusion, if we did not apply the inhomogeneity correction factor in small field, it shows more great difference in measurement data. The planning system using this study shows good result for correction of inhomogeneity materials. In radiosurgery using small field, we should be correct the inhomogeneity correction factor, more exactly.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.57-62
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• 2011

This paper proposed a method which is the three types of magnet model for improving field inhomogeneity of superconducting magnet. The length of coil wire was compared for the optimized current pattern using minimum power methods and field inhomogeneity under the specific simulation condition in case of same magnet field strength about each magnet type field inhomogeneity. Length of wire and field inhomogeneity were compared under the same condition(18 target points, 20cm DSV). According to the simulation results, the smaller target points can reduce the wire length but it can not improve the field inhomogeneity. Length of wire and low field inhomogeneity can not improve in same time. However, small DSV and reducing target points can overcome the these problem. And to conclude, if it processes shimming as reducing target points in case of magnet model which is open to space, about the size of same imaging region it needs a lot of current values(or the length of wire) and decreases field homogeneity but it is useful to get small ROI.

• Progress in Medical Physics
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• v.15 no.3
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• pp.149-155
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• 2004

Purpose: To investigate the effects of tissue inhomogeneity corrections on the dose delivered to prostate cancer patients treated with Intensity-Modulated Radiation Therapy (IMRT). Methods and Materials: For five prostate cancer patients, IMRT treatment plans were generated using 6 MV or 10 MV X-rays. In each plan, seven equally spaced ports of photon beams were directed to the isocenter, neglecting the tissue heterogeneity in the body. The dose at the isocenter, mean dose, maximum dose, minimum dose and volume that received more than 95% of the isocenter dose in the planning target volume ( $V_{p>95%}$) were measured. The maximum doses to the rectum and the bladder, and the volumes that received more than 50, 75 and 90% of the prescribed dose were measured. Treatment plans were then recomputed using tissue inhomogeneity correction maintaining the intensity profiles and monitor units of each port. The prescription point dose and other dosimetric parameters were remeasured. Results: The inhomogeneity correction reduced the prescription point dose by an average 4.9 and 4.0% with 6 and 10 MV X-rays, respectively. The average reductions of the $V_{p>95%}$ were 0.8 and 0.9% with the 6 and 10 MV X-rays, respectively. The mean doses in the PTV were reduced by an average of 4.2 and 3.4% with the 6 and 10 MV X-rays, respectively. The irradiated volume parameters in the rectum and bladder were less decreased; less than 2.1 % (1.2%) of the reduction in the rectum (bladder). The average reductions in the mean dose were 1.0 and 0.5% in the rectum and bladder, respectively. Conclusions: Neglect of tissue inhomogeneity in the IMRT treatment of prostate cancer gives rise to a notable overestimation of the dose delivered to the target, whereas the impact of tissue inhomogeneity correction to the surrounding critical organs is less significant.

• Journal of the Korean Geophysical Society
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• v.1 no.1
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• pp.51-58
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• 1998

A numerical program has been developed to model 2-D resistivity responses for a pole-pole array configuration in cross-hole resistivity measurements. Apparent resistivity and secondary potential were computed using the program for a cylindrical inhomogeneity in an uniform host medium excited by a point source of current in a borehole. Surprisingly apparent resistivity in the receiver hole turns out to be lower than the one of surrounding medium regardless of the conductivity of cylindrical inhomogeneity. Using only cross-hole data, therefore, it is impossible to interpret the conductivity of inhomogeneity. To overcome this problem, 3-D measurement and interpretation are necessary. If 3-D data acquisition is impossible, inline data should be used to get the information about the conductivity of inhomogeneity.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.117-124
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• 2003

The fracture processes under static tensile loading were simulated using a proposed numerical simulation method, based on finite element method and fracture mechanism, and analyzed to verify an influence of rock inhomogeneity on static tensile strength. Static tensile strengths for the specimen models with different spatial microscopic tensile strength when m=5 and m=50 were estimated. These analyses revealed that the static tensile strength becomes closer to the mean microscopic tensile strength at a higher uniformity coefficient and the scatter of the strength data decreases in increasing the uniformity coefficients. Therefore, it could be concluded that rock inhomogeneity has an effect on static tensile strength.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4112-4119
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• 2023

This study employs the microshear test method to examine the local mechanical properties of narrow-gap welded joints, revealing the mechanical inhomogeneity by evaluating the microshear strength, stress-strain curves, and failure strain. On this basis, the influence of weld joints micromechanical inhomogeneity on the crack tip opening displacement (CTOD) fracture toughness is investigated. From the root weld layer to the cover weld layer, the fracture toughness at the center of the weld seam demonstrates an increasing trend, with the experimental and calculated CTOD values showing a good correspondence. The microproperties of the welded joints significantly impact the load-bearing capacity and fracture toughness. During the deformation process of the "low-matching" microregions, the plastic zone expansion is hindered by the surrounding microregion strength constraints, thus reducing the fracture toughness. In contrast, during the deformation of the "high-matching" microregions, the surrounding microregions absorb some of the loading energy, partially releasing the concentrated stress at the crack tip, which in turn increases the fracture toughness.

• Composites Research
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• v.15 no.3
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• pp.11-17
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• 2002

Cracking of the reinforcements is a significant damage mode in particle or short-fiber reinforced composites because the broken reinforcements lose load carrying capacity. This paper deals with elastic stress distributions and load carrying capacity of intact and cracked ellipsoidal inhomogeneities. Three dimensional finite element analysis has been carried out on intact and broken ellipsoidal inhomogeneities in all infinite body under pure shear. For the intact inhomogeneity, the stress distribution is uniform in the inhomogeneity and non-uniform in the surrounding matrix. On the other hand, for the broken inhomogeneity, the stress in the region near crack surface is considerably released and the stress distribution becomes more complex. The average stress in the inhomogeneity represents its load carrying capacity, and the difference of average stresses between the intact and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The broken inhomogeneity with higher aspect ratio maintains higher load carrying capacity.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.634-636
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• 2007

The texture and microstructure in Cu/Nb added ultra low carbon steels through the different thickness layer were studied after hot rolling. It was found that the two ultra low carbon steels all show the inhomogeneity of hot rolling texture and the Cu-added ultra low carbon steel was far more inhomogeneous than Nb-added one. In the center layer, the strong ${\alpha}\;fibre,\;{\gamma}\;fibre$ textures and the shear textures including 001<110>, 111<112> were founded. Near the surface, the ${\alpha}\;fibre$ texture and the orientation texture caused by a typical plane-strain deformation condition of bcc metals were observed.