• 한국대기환경학회지
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• 제16권5호
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• pp.539-544
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• 2000

A simple analytic model is proposed here to analyze the concentration deficit field caused by a large area of vegetated area. With non-dimensional deposition velocity chosen as small parameter, the regular perturbation method is exploited to derive the mass balance equation and the dynamic equations for the concentration deficit field, Analytic solutions to those equations are obtained in a closed form for several cases of interest, assuming that the concentration field is stationary and the plume can be nicely approximated as Gaussian for a point source. The results suggest that quite a negligible fraction (less than 1%) of the gaseous air pollutants emitted into the air is removed by the vegetated area of which width is 4 km in wind-wise direction, the typical dimension of the Restricted Development Zones around the metropolitan regions in South Korea.

• 한국정밀공학회지
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• 제19권2호
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• pp.195-202
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• 2002

An automated process planning system for cold forging of non-axisymmetric parts of comparatively simple shape was developed in this study. Programs for the system have been written with Visual LISP in the AutoCAD using a personal computer and are composed of four main modules such as input module, shape cognition and shape expression module, material diameter determination module and process planning module. The design rules and knowledges for the system are extracted from the plasticity theories, handbook, relevant reference and empirical knowledge of field experts. Generally, in forging, only front view is needed for expression of axisymmetric parts, but non-axisymmetric parts need front and plane view. At the plane, this system cognizes the external shape of non-axisymmetric, parts - number of sides of regular polygon and radius of a circle circumscribing the polygon of n sides. At the front view, the system perceives diameter of axisymmetric portions and height of primitive geometries such as polygon, cylinder, cone, concave, convex, etc.

• 천문학논총
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• 제30권2호
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• pp.583-584
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• 2015

In this paper, the numerical results concerning different orbits of a 3D axisymmetric non-rotating galactic potential are presented. We use $Paczy{\acute{n}}ski^{\prime}s$ gravitational potential with different birth velocity distributions for the isolated old Neutron Star (NS) population. We note some smooth non-constant segments corresponding to regular orbits as well as the characterization of their chaoticity. This is strongly related to the effect of different kick velocities due to supernovae mass-loss and natal kicks to the newly-formed NS. We further confirm that the dynamical motion of the isolated old NSs in the gravitational field becomes obvious, with some significant diffraction in the symmetry of their orbital characteristics.

• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.125-130
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• 1989

In the present study, we described a test to explore the function of optokinetic system which subjected to a full visual field stimulation using two different stimulus images patterns. Our results were interesting in a point of view that the stimulation image pattern had non- neglisible influence on the optokinetic response and that in a bidimensionnel image such as the randomly distributed spots images pattern the linearity of system was assured upto the stimulus velocity of about 50 deg/sec for normal subject. As for measuring human optokinetic after nystagmus, the regular stripes pattern was rather desirable than the randomly distributed spots pattern in this study.

• 대한수학회보
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• 제60권1호
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• pp.83-91
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• 2023

A ring R is called a UN ring if every non unit of it can be written as product of a unit and a nilpotent element. We obtain results about lifting of conjugate idempotents and unit regular elements modulo an ideal I of a UN ring R. Matrix rings over UN rings are discussed and it is obtained that for a commutative ring R, a matrix ring M_n(R) is UN if and only if R is UN. Lastly, UN group rings are investigated and we obtain the conditions on a group G and a field K for the group algebra KG to be UN. Then we extend the results obtained for KG to the group ring RG over a ring R (which may not necessarily be a field).

• Journal of Radiation Protection and Research
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• 제24권4호
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• pp.215-223
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• 1999

PWR 원전 증기발생기 수실의 방사선장 특성과 그곳에서 작업하는 종사자의 유효선량을 몬테칼로 시뮬레이션으로 평가하였다. 선원항으로는 고리1호기 증기발생기 방사화물 분석결과가 사용되었으며 유효선량 평가에는 MCNP4A코드와 MIRD형 성별 수학적 인형 모의피폭체가 사용되었다. 수실 내부 방사선장은 U튜브 영역에서 내려오는 방사선이 지배적이었으며 극각에 대해 근사적으로 코사인 분포를 나타내었다 유효선량률은 표준성인과 체격이 작은 성인(이 목적으로 15세 모의피폭체가 사용되었다.)의 경우 각각 36.22$mSvh^{-1}$와 37.06$mSvh^{-1}$로서 체격의 영향은 경미했다. 한편, 모의피폭체의 머리, 가슴 및 하복부에 해당하는 위치에서 평가된 조사선량률과 에너지스펙트럼에 대해 ICRU47에서 주어진 주위선량당량 환산계수를 이용해 평가한 등가선량률은 각각 119, 71, 및 58 $mSvh^{-1}$로 나타났다. 따라서 개인선량계 판독에서 얻는 심부선량 또는 유효선량은 앞서 계산한 유효선량률의 2배 정도가 될 것으로 보인다. 이 사실은 일반적인 개인선량계의 경사입사 방사선에 대한 과대/과소 평가 특성과 함께 비정규, 고선량률 방사선장에 종사하는 작업자의 선량계측 계획 및 결과의 해석에 매우 신중해야 함을 알려준다.

• 대한방사선기술학회지:방사선기술과학
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• 제25권1호
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• pp.63-71
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• 2002

The aim of this study Is to develop a simple and fast method which computes in-vivo doses from transmission doses measured doting patient treatment using an ionization chamber. Energy fluence and the dose that reach the chamber positioned behind the patient is modified by three factors: patient attenuation, inverse square attenuation. and scattering. We adopted a straightforward empirical approach using a phantom transmission factor (PTF) which accounts for the contribution from all three factors. It was done as follows. First of all, the phantom transmission factor was measured as a simple ratio of the chamber reading measured with and without a homogeneous phantom in the radiation beam according to various field sizes($r_p$), phantom to chamber distance($d_g$) and phantom thickness($T_p$). Secondly, we used the concept of effective field to the cases with inhomogeneous phantom (patients) and irregular fields. The effective field size is calculated by finding the field size that produces the same value of PTF to that for the irregular field and/or inhomogeneous phantom. The hypothesis is that the presence of inhomogeneity and irregular field can be accommodated to a certain extent by altering the field size. Thirdly, the center dose at the prescription depth can be computed using the new TMR($r_{p,eff}$) and Sp($r_{p,eff}$) from the effective field size. After that, when TMR(d, $r_{p,eff}$) and SP($r_{p,eff}$) are acquired. the tumor dose is as follows. $$D_{center}=D_t/PTF(d_g,\;T_p){\times}(\frac{SCD}{SAD})^2{\times}BSF(r_o){\times}S_p(r_{p,eff}){\times}TMR(d,\;r_{p,eff})$$ To make certain the accuracy of this method, we checked the accuracy for the following four cases; in cases of regular or irregular field size, inhomogeneous material included, any errors made and clinical situation. The errors were within 2.3% for regular field size, 3.0% irregular field size, 2.4% when inhomogeneous material was included in the phantom, 3.8% for 6 MV when the error was made purposely, 4.7% for 10 MV and 1.8% for the measurement of a patient in clinic. It is considered that this methode can make the quality control for dose at the time of radiation therapy because it is non-invasive that makes possible to measure the doses whenever a patient is given a therapy as well as eliminates the problem for entrance or exit dose measurement.

• 소성∙가공
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• 제11권5호
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• pp.405-413
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• 2002

A process planning system for cold forging of non-axisymmetric parts of comparatively simple shape was developed in this study. Programs for the system have been written with Visual LISP in AutoCAD. Shape of the product must be drawn with the solid line and the hidden line, and with the plane and front view, as well. At the plane, the system recognizes the external shape of non-axisymmetric portions - the number of the sides of the regular polygons and the radii of circles inscribing and circumscribing the polygon. At the front view, the system cognizes the diameter of axisymmetric portions and the height of the primitive geometries such as polygon, cylinder, cone, concave, convex, etc. The system perceives that the list developed from the solid line must be formed by the operation of forward extrusion or upsetting, and that the list developed from the hidden line must be formed by the operation of backward extrusion. The system designs the intermediate geometries again by considering clearance between workpiece and die, and then finally the billet diameter, in reverse order from the finished product, on the basis of volume constancy and using the operations, the forming sequence, the number of operations and the intermediate geometries which were already designed. The design rules and knowledges for the system were extracted from the plasticity theories, handbook, relevant reference and empirical knowledge of field experts. Suitability of the process planning was analyzed using SuperForge of FVM simulation package. The results of analysis showed good formability.

• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.1-5
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• 2020

Heart consists of myocardium cells and the electrophysiological activity of the cells generate magnetic fields. By measuring this magnetic field, magnetocardiogram (MCG), functional diagnosis of the heart diseases is possible. Since the strength of the MCG signals is weak, typically in the range of 1-10 pT, we need sensitive magnetic sensors. Conventionally, superconducting quantum interference devices (SQUID)s were used for the detection of MCG signals due to its superior sensitivity to other magnetic sensors. However, drawback of the SQUID is the need for regular refill of a cryogenic liquid, typically liquid helium for cooling low-temperature SQUIDs. Efforts to eliminate the need for the refill in the SQUID system have been done by using cryocooler-based conduction cooling or use of non-cryogenic sensors, or room-temperature sensors. Each sensor has advantage and disadvantage, in terms of magnetic field sensitivity and complexity of the system, and we review the recent trend of MCG technology.

• 복식문화연구
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• 제9권1호
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• pp.19-32
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• 2001

The purpose of this study is to determine aesthetical characteristics of the Korean traditional wedding dress for women by analyzing such dresses'aesthetical senses. For the purpose, the study showed four types of the dress, jukyee, whalot, weonsam and private weonsam and their photographed stimuli to subjects and then obtained data using the seven scale measures of meaning differentiation consisting of 25 pairs of adjective words. Results of the study are described as follows; Aesthetical senses shown in the Korean traditional dressing dress for women included six factors in total, among which attractiveness was found as the main factor, followed by chastity. For the four types of the dress, whalot adpated revelation as its main factor while the remaining three types, or jukyee, weonsam and private weonsam were found having dignity as their main factors. Adjective words which largely accounted for aesthetical senses included uncomfortable, warn, chaste, intellectual, bright, unique, regular, luxurious, classical, ornamental and beautiful suggesting that the Korean traditional wedding dress for women is somewhat unfunctional, but high in attractiveness and aesthetic beauty and has a better classical harmonization of dignity and revelation. Aesthetical senses were most different according to nationality(Korean and Japan) when they were analyzed in terms of nationality, gender and whether of specialization or non-specialization. Japanese people had unique and interesting senses while Korean people, chaste, calm and delicate aesthetical senses. According to gender, men revealed free senses and women, classical ones. According whether of specialization or non-specialization those who specialized in a related field had more unique, straight, regular, luxurious and interesting aesthetical senses that those who did not specialize.