• 대한시과학회지
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• 제20권4호
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• pp.443-451
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• 2018

목적 : 레이저 각막교정술을 받은 후 자동굴절검사기기의 신뢰성에 대해 알아보고자 한다. 방법 : LASEK 수술 최소 3개월 후 나안 시력이 1.0인 57명(114안, $32.0{\pm}26.91$세) 대상자의 굴절상태를 자동굴절검사기(CANON Full Auto Ref-Keratometer RK-F1, Japan)과 검영기(Streak Retinoscope 18200, WelchAllyn, USA)을 이용하여 구면과 실린더굴절력을 측정하였고, 등가구면굴절력과 함께 비교하였다. 수술 전의 굴절상태를 자동굴절검사기기를 이용하여 측정한 결과에 따라 고도, 중도, 저도 근시로 나누어 다시 비교하여 수술 전 굴절상태에 따른 수술 후 자동굴절검사기의 신뢰성의 영향을 분석하였다. 두 타각적굴절방법을 Bland-Altman(Bland-Altman limits of agreement(LoA))을 이용하여 두 방법의 일치도를 확인하였다. 결과 : 수술 후 자동굴절검사법과 검영법에 의한 구면, 실린더, 등가구면굴절력은 전체 비교에서는 모두 통계적으로 유의한 차이(p<0.01)를 보였으며, 수술 전의 굴절상태 분류로서 고도 근시의 실린더굴절력을 제외한 중도, 저도 근시의 모든 요소에서 유의한 차이(p<0.01)를 보였다. 전체적으로 자동굴절검사법에 의한 굴절력은 특히 구면과 등가구면굴절력에서 0.38D ~ 0.53D의 근시 경향으로 나타났다. 반면 검영법은 평균 약 0.30D의 원시 경향을 보였다. 두 굴절검사법의 비교에서는 평균은 $-0.51{\pm}0.45D$, LoA는 +0.36D ~ -1.39D로 나타나 근시 경향이 강하였으며, 호환성이 있는 것으로 나타났다. 결론 : 호환성 측면에서는 긍정적이지만, 레이저 각막교정수술 후의 근시 퇴행이 있는 수술자들의 자동굴절검사법은 근시 경향을 보이기 때문에 반드시 자각적굴절검사를 통해 안경처방을 해야 할 것으로 보인다.

• 대한기계학회논문집B
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• 제23권8호
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• pp.997-1009
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• 1999

Silica particle formation and growth process including chemical reaction, coagulation and sintering was studied in a counterflow diffusion flame burner. The counterflow geometry provides a one dimensional flow field, along the stagnation point streamline, which greatly simplifies interpretation of the particle growth characteristics. $SiCl_4$ has been used as the source of silicon in hydrogen/oxygen/argon flames. The temperature profiles obtained by calculation showed a good agreement with experiment data. Using one and two dimensional sectional method, aerosol dynamics equation in a flame was solved, and these two results were compared. The two dimensional section method can consider sintering effect and growth of primary particle during synthesis, thus it showed evolution of morphology of non-spherical particles (aggregates) using surface fractal dimension. The effects of flame temperature and chemical loading on particle dynamics were studied. Geometric mean diameter based on surface area and total number concentration followed the trend of experiment results, especially, the change of diameters showed the sintering effect in high temperature environment.

• Journal of Theoretical and Applied Mechanics
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• 제2권1호
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• pp.51-70
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• 1996

This study is generalization of the study of Miles[Physica 11D, 1984, pp.309-323]on the resonant motion of a spherical pendulum, which is equivalent to a particle on a spherical container subject to a linear, horizontal excitation. This study covers an arbitrary shape of container and a more general excitation (horizontal but elliptic motion). The averaging method is applied to reduce the governing equations to an autonomous system with cubic nonlinear terms, under the assumption of small amplitude of the container motion. It is shown that both the container shape and the excitation pattern affect the particle dynamics. Under the linear excitation, the anharmonic motion of the particle is possible only for a certain finite range of the parameter a controling the container shape. Stability of the particle's harmonic motion is also influenced by the excitation pattern; as the excitation trajectory becomes closer to a circle, the particle's motion has a stronger tendency to become stable and to follow the rotational direction of the excitation. Under a circular excitation, the motion is always stable and circular with the same rotational direction as the excitation. Analogy between the present model and that of the surface wave inside a circular is studied quantitatively.

• 감성과학
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• 제24권3호
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• pp.115-124
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• 2021

Non-verbal communication is important in human interaction. It provides a layer of information that complements the message being transmitted. This type of information is not limited to human speakers. In human-robot communication, increasing the animacy of the robotic agent-by using non-verbal cues-can aid the expression of abstract concepts such as emotions. Considering the physical limitations of artificial agents, robots can use light and movement to express equivalent emotional feedback. This study analyzes the effects of LED and motion animation of a spherical robot on the emotion being expressed by the robot. A within-subjects experiment was conducted at the University of Tsukuba where participants were asked to rate 28 video samples of a robot interacting with a person. The robot displayed different motions with and without light animations. The results indicated that adding LED animations changes the emotional impression of the robot for valence, arousal, and dominance dimensions. Furthermore, people associated various situations according to the robot's behavior. These stimuli can be used to modulate the intensity of the emotion being expressed and enhance the interaction experience. This paper facilitates the possibility of designing more affective robots in the future, using simple feedback.

• Progress in Superconductivity
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• 제4권1호
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• pp.19-26
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• 2002

We have earlier developed a 40-channel SQUID system. An important figure of merit of a MEG system is the localization error, within which the underlying current source can be localized. With this system, we investigated the localization error in terms of the standard deviation of the coordinates of the ECDs and the systematic error due to inadequate modeling. To do this, we made localization of single current dipoles from tangential components of auditory evoked fields. Equivalent current dipoles (ECD) at N1m peak were estimated based on a locally fitted spherical conductor model. In addition, we made skull phantom and simulation measurements to investigate the contribution of various errors to the localization error. It was found that the background noise was the main source of the errors that could explain the observed standard deviation. Further, the amount of systematic error, when modeling the head with a spherical conductor, was much less than the standard deviation due to the background noise. We also demonstrated the performance of the system by measuring the evoked fields to grammatical violation in sentence comprehension.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1379-1389
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• 1999

A new technique for control of size and shape of flame-made particles is Introduced. The characteristic sintering time can be controlled Independently of collision time by heating the particles with irradiation of laser because the sintering time strongly depends on temperature. A coflow oxy-hydrogen diffusion flame burner was used for $SiCl_4$ conversion to silica particle. Nanometer sized aggregates irradiated by a high power CW $CO_2$ laser beam were rapidly heated up to high temperatures and then were sintered to approach volume-equivalent spheres. The sphere collides much slower than the aggregate, which results in reduction of sizes of particles maintaining spherical shape. Light scattering of Ar ion laser and TEM observation using a local sampling device were used to confirm the above effects. When the $CO_2$ laser was irradiated at low position from the burner surface, particle generation due to gas absorption of laser beam occurred and thus scattering intensity increased with $CO_2$ laser power. At high irradiation position, scattering intensity decreased with $CO_2$ laser power and TEM image showed a clear mark of evaporation and recondensation of particles for high $CO_2$ laser power. When the laser was irradiated between the above two positions where small aggregates exist, average size of spherical particles obviously decreased to 58% of those without $CO_2$ laser irradiation with the spherical shape. Even for increased carrier gas flow rate by a factor of three, TEM photograph also revealed considerable reduction of particle size.

• 한국광학회지
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• 제19권2호
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• pp.108-115
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• 2008

구면 SELFOC 렌즈와 플라스틱 비구면 렌즈를 사용하여 mobile phone 광학계를 설계하였다. SELFOC 소재는 radial GRIN(gradient index) 분포를 가지며, 이것은 설계에 추가적인 자유도를 제공하므로, 비구면을 구면으로 대치할 수 있다. 두개의 플라스틱 비구면 렌즈로 구성된 통상적인 2P 광학계와 결상특성을 비교 하였다. 이 연구에서는 시판되고 있는 SELFOC 소재를 사용하여 1GRIN 1P 광학계를 설계하였다. 그러나 1GRIN 1P의 성능보다 통상적인 2P 광학계의 성능이 좋았다. 1GRIN 1P 설계에서 성능은 GRIN 소재의 굴절률 구배에 의지하므로 굴절률 구배가 클수록 좋은 성능을 보인다. 그러므로 큰 굴절률 구배를 갖는 가상의 GRIN 소재를 사용하여 광학계를 설계하였다. 현재 시판되는 SELFOC 소재보다 3배 정도 굴절률 구배가 큰 GRIN 소재가 개발된다면, 1GRIN 1P 광학계의 성능이 통상적인 2P 광학계의 성능과 유사하거나 더 좋아 질 것이다.

• 한국군사과학기술학회지
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• 제8권4호
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• pp.120-129
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• 2005

To analyze a blast effect of developed explosives, three different kinds of aluminized tastable explosives and melted cast explosive TNT were used. Conventional explosive TNT was used as a reference. Each tested explosive charge of 340mm diameter spherical type was initiated at the charge center with DXD-65(${\sim}750g$) booster and RP-87 EBW detonator. Thirteen piezo type pressure sensors were located at a range from 4 to 50m away from the charge. From the blast wave profiles, we calculated a peak blast pressure and impulse of the explosion. The calculated pressures and in pulses were converted to TNT Equivalent Weight(TEW) factor by the scaling ]aw method. The average TEW factors based on the blast pressure of TX-01, TX-02, TX-03, TX-04 were 1.298, 1.05, 1.266, 1.274 and the average TEW factors based on impulse were 1.504, 1.686, 1.640, 1.679. From the results, we concluded that TEW factors based on blast pressure and based on impulse of aluminized explosives were superior to TNT. This results are owing to the high contents of aluminum in formulations.

• 한국안광학회지
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• 제20권3호
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• pp.263-276
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• 2015

목적: 구면렌즈와 원주렌즈를 시험테에 중첩하였을 때 합성굴절력의 신뢰도를 알아보고자 하였다. 방법: 마이너스 구면 시험렌즈와 원주 시험렌즈의 굴절력, 중심두께 및 주변부두께를 측정하였으며 구면 시험렌즈와 원주 시험렌즈를 장입순서를 바꿔가며 시험테에 중첩되었을 때의 굴절력을 자동렌즈미터로 측정하여 합성굴절력 계산값과 비교 평가하였다. 결과: 시험렌즈의 중심부와 주변부의 두께증감이 도수의 증감과 상관성을 보이지 않았으며 79개 시험렌즈 중 3개의 시험렌즈에서 국제기준규격(ISO-9801)에서 벗어난 굴절력이 측정되었다. 정점간거리를 보정하는 굴스트랜드 공식 굴절력값이 얇은 렌즈 공식 굴절력값보다 실측값과의 오차가 적었으나, 여전히 실측값과는 통계적으로 유의한 차이가 있었다. 굴절력의 크기는 원주렌즈와 구면렌즈의 위치와 상관없이 평균적으로 얇은 렌즈 공식 굴절력값 > 실측 굴절력값 > 굴스트랜드 공식 굴절력값 순으로 나타났다. 구면렌즈가 안쪽, 원주렌즈가 바깥쪽에 장입되었을 경우에는 굴스트랜드 공식에 대입하였을 때 원주굴절력만 오차가 발생하지만 원주렌즈가 안쪽, 구면렌즈가 바깥쪽에 장입되었을 때는 구면굴절력과 원주굴절력 모두에서 오차가 나타났다. 실측값의 등가구면굴절력을 비교하였을 때 구면렌즈가 시험테의 안쪽, 원주렌즈가 시험테의 바깥쪽에 장입된 경우가 정확도가 더 높았으며 과교정의 우려가 작았다. 결론: 본 연구 결과 시험렌즈테에 렌즈를 중첩하였을 때의 합성굴절력은 정점간거리 외에도 중첩되는 렌즈의 두께와 광학중심 등의 영향을 받으며 구면렌즈와 원주렌즈의 중첩 순서에 따라 굴절력에 차이가 있으므로 이에 대한 기준의 정립이 필요함을 제안한다.

• 대한간호학회지
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• 제35권2호
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• pp.390-398
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• 2005

Purpose: This study was aimed at providing basic data for developing a nursing intervention program which enables systematic and correct visual acuity care by discovering out visual acuity conditions, prevalence rate of myopia, and the factors related to myopia with Preschool children. Method: The subjects of this study consisted of 519 children between 3 and 6 years of age from 12 kindergartens in Seoul which were selected through multiple cluster sampling. Myopia was defined as the spherical equivalent (SE) of more than -0.5 diopters (D) in the right eye. The data was analyzed by t-test, 2-test, ANOVA, and logistic regression by using the SAS program. Result: The prevalence rate of myopia was $8.7\%$. the odds ratio of child myopia when one parent had myopia was 2.2 times higher than when neither parent had myopia. The odds ratio of child myopia when reading more than three books per week was 0.27 times higher than reading less than three books. Conclusion: Myopia should be continuously and intensively managed from the age of 3.