• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.7
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• pp.86-94
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• 1998

The rosette-scan seeker is a device mounted on the infrared guided missile. It offers the positions and iamges of target to missiles servo system by scanning a space about target in rosette pattern with a single detector. An instantaneous field of view (IFOV), which is a diameter of a detector moving along the path of the rosette pattern, has the property that its smaller size provide the less interference of background signals and detector noise. If its size is too small to voer the total field of view (TFOV), however, it produces the invisible regions in the TFOV. In this case, the invisible regions cause the performance of the seeker to deteriorate. For full scan-coverage, it is necessary to design the small IFOV without the invisible regions in the TFOV, as possible. In this paper, we propose the new method of designing the smaller IFOV than the conventional method and verify full coverage of the scanned region. By comparing the nose equivalent flux density (NEFD) of the proposed method with the that of the conventional one, we confirm that the former is better than the latter in terms of performance.

• Journal of Power System Engineering
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• v.12 no.5
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• pp.40-47
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• 2008

The turbulent flow characteristics around a small-size axial fan(SSAF) for a refrigerator are strongly dependent upon the operating points. Four operating points such as $\phi$ =0.1, 0.18, 0.25 and 0.32 were adopted in this study to investigate three-dimensional turbulent flow characteristics around the SSAF by using a fiber-optic type Laser Doppler Anemometer(LDA) system. Downstream mean velocity profiles of the SSAF along the radial distance show that axial and tangential velocity components exist predominantly, except $\phi$ = 0.1, and have a maximum value at $r/R{\fallingdotseq}0.8$, but radial velocity component having a relatively small value only turns flow direction to the outside or the central part of the SSAF. The turbulent intensity shows that the radial component exists most greatly after $r/R{\fallingdotseq}0.5$. Downstream turbulent kinetic energy at $\phi$ = 0.25 and 0.32 together has the largest peak value at $r/R{\fallingdotseq}0.9$.

• Progress in Medical Physics
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• v.11 no.1
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• pp.1-18
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• 2000

For wedged photon beams, the variation of the wedge factor with field size was reported by several authors. However, until now such variation with field size had not been explained quantitatively. Therefore, the variation of the wedge factor was investigated by measuring outputs with field sizes increasing from 4 cm $\times$ 4 cm to 25 cm $\times$ 25 cm for open and wedged 6 and 10MV X-ray beams. The relative outputs for wedged fields to 10 cm $\times$ 10 cm have been obtained. The results show the Increase of the wedge factor caused by the change in fluence of high energy Photon beam with field size, up to 8.0% for KD77-6MV X-ray beam. This increase could be explained as a linear function of the irradiated wedge volume except small field size up to about 10 cm. In the cases of the narrow rectangular beam parallel to the wedge direction, the wedge factor decreases slightly with increasing field size up to about 10-15 cm due to a relatively reduced photon fluence from the change of the wedge thickness. We could explain the causes of a wedge factor variation with field size as the fluences of primary photon passed throughout the wedge, contributing to the dose at the central beam axis and that the fluences were affected by the gradient of the wedge with the change of field size. For clinical use, the formula developed to describe the wedge factor variation with field size has been corrected.

• Animal Systematics, Evolution and Diversity
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• v.7 no.2
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• pp.179-188
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• 1991

In order to determine the taxonomic status of Apodemus agrarius chejuensis from Cheju island in Korea, three hundred and eleven samples of eight subspecies of striped field mice (subspecies, agrarius, ningpoensis , pallidior, chevrieri, insulaemus, manchuricus, coreae, and chejuensis of A. agrarius Pallas) in Asia, collected from Turkey , China, Taiwan, , Manchuria, and Koarea, were used. Four external and 27 cranial characters were measured and their measurements were utilized for multivariate analyses such as cluster, principal component, and discriminant analyses. Four forms were revealed . A largest-size from was chejuensis, whereas a large-size form was cheverieri. A medium -size from and a small-size from were coreae and other five subspecies (agrarius , ningpoensis, pallidior, insulaemus, and manchuricus) , respecitvley, but their differences were clinal. A discontinuous gap was revealed between chejuensis (a largest-size from) and six subspecies ( a medium-size from and a small-size form) Although chejuensis appeared to be a distinct species, it is concluded that molecular analyses are necessary in order to describe it as a new species.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.398-407
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• 1999

In the present image processing technique, the concept of the gradient indicator(GI) has been introduced to find out the depth-of-field in sizing large particles ranging from $30{\mu}m$ to $30{\mu}m$ where using of the concept of the normalized contrast value(VC) is not appropriate. The gradient indicator is defined as the ratio of the local value to the maximum possible value of the gray-level gradient in an image frame. The gradient indicator decreases with the increases of the particle size and the distance from the exact focal plane. A particle is considered to be in focus when the value of the gradient indicator at its image boundary stays above a critical value. This critical gradient indicator($GI_{critical}$) is defined as the maximum gradient indicator($GI_{max}$) subtracted by a constant ${\Delta}GI$ which is to account for the particle-size effect. In the present ca.so, the value of ${\Delta}GI$ was set to 0.28 to keep the standard deviation of the measured particles mostly within 0.1. It was also confirmed that, to find the depth-of-field for small particles(${\leq}30{\mu}m$) with the same measurement accuracy, tho concept of the critical normalized contrast($VC_{critical}$) is applicable with 85% of the maximum normalized contrast value($VC_{max}$). Finally, the depth-of-field was checked for the size range between $10{\mu}m$ and $300{\mu}m$ when the both in-focus criteria ($GI_{critical}$ and $VC_{critical}$) were adopted. The change of the depth-of-field with the particle size shows good linearity in both the VC-applicable and the GI-applicable ranges with a reasonable accuracy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1198-1204
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• 2013

As a microwave near field probe for near field scanning optical microscope(NSOM) system, H-shaped(ridge type) small aperture is proposed and its performances from the viewpoints of the transmission efficiency(transmission cross section) and spatial confinement(beam spot size) are compared with those of the previous narrow rectangular aperture type. While the transmission efficiencies are comparable to each other for the two structures, the transmitted beam spot size for the proposed H-shaped aperture is much smaller than that for the previous rectangular aperture. This strong point of the H-shaped aperture is expected to significantly improve near-field optical applications such as optical data storage, nanolithography and nanomicroscopy. It is also observed that the transmission efficiency can be improved if the coupling aperture is implemented in the type of the transmission cavity.

• Journal of Powder Materials
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• v.20 no.3
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• pp.186-190
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• 2013

The electrochemical performance for the corrosion of zinc anodes according to particle size and shape as anode in Zn/air batteries was study. We prepared five samples of Zn powder with different particle size and morphology. For analysis the particle size of theme, we measured particle size analysis (PSA). As the result, sample (e) had smaller particle size with $10.334{\mu}m$ than others. For measuring the electrochemical performance of them, we measured the cyclic voltammetry and linear polarization in three electrode system (half-cell). For measuring the morphology change of them before and after cyclic voltammetry, we measured Field Emission Scanning Electron Microscope (FE-SEM). From the cyclic voltammetry, as the zinc powder had small size, we knew that it had large diffusion coefficient. From the linear polarization, as the zinc powder had small size, it was a good state with high polarization resistance as anode in Zn/air batteries. From the SEM images, the particle size had increased due to the dendrite formation after cyclic voltammetry. Therefore, the sample (e) with small size would have the best electrochemical performance between these samples.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.1
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• pp.33-39
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• 2010

Purpose: It is very important to confirm conformance of dose distribution that is formed with treatment planning from IMRS or IMRT. It has been a problem dropped accuracy and conformance when the field size is getting smaller because of character of the 2D ion chamber. Verification of MatriXX Phantom dose distribution with a change in the SAD. Dose distribution measurement and analysis to improve the accuracy and should be useful to evaluate the award. Materials and Methods: A use of Novalis linear accelerator 6 MV photon beams. In general, IMRS were 25 patients with small field size. The selected patients were divided into three groups on the basis of the field size. SAD was changed from 80 to 130 cm and field size to determine the dose distribution to the change, each dose was measured using MatriXX Phantom. Analysis of measured values obtained from the program for each patient through the treatment planning system comparison and analysis of the dose distribution and gamma values were expressed. Result: SAD 80, 100, and 120 cm in size in the gamma value to the investigation of patients less than $3\;cm^2$ average 0.939, 0.969, and 0.979, respectively. Patients with more than $5\;cm^2$ 0.962, 0.983, and 0.988, respectively. $5\;cm^2$ or more patients 0.982, 0.990, and 0.992, respectively. Conclusion: The error rate of less than $3\;cm^2$ field size is increased rapidly. If the field size is increased, resolution is increased by 2D ion chambers. It has been approved that it can be credible if it is around $3\;cm^2$ when measuring dose distribution using MatriXX. Adjusting geometric field size by changing SAD is likely to be very useful when you measure dose distribution using MatriXX.

• Journal of Yeungnam Medical Science
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• v.8 no.2
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• pp.114-120
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• 1991

In electron therapy, low melting point alloy is used for shaping of the field. Electron field shaping material affect the output factor as well as the collimator system. The output factors of electron beams for shaped fields from NELAC-1018 were measured using ionization chamber of Farmer type in water phantom. The output factors of electron beams depend on the incident energy, inherent collimator system and the size of shaped field. Obtained results were followings. 1. In the smaller applicator, output varied extremely according to extent of collimator opening. 2. The higher energy, the output is less varied according to treatment field at small field.

• Journal of Communications and Networks
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• v.16 no.5
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• pp.479-484
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• 2014

In this paper, we consider the construction of cyclic and quasi-cyclic structured q-ary low-density parity-check (LDPC) codes over a designated small field. The construction is performed with a pre-defined sliding-window, which actually executes the regular mapping from original field to the targeted field under certain parameters. Compared to the original codes, the new constructed codes can provide better flexibility in choice of code rate, code length and size of field. The constructed codes over small fields with code length from tenths to hundreds perform well with q-ary sum-product decoding algorithm (QSPA) over the additive white Gaussian noise channel and are comparable to the improved spherepacking bound. These codes may found applications in wireless sensor networks (WSN), where the delay and energy are extremely constrained.