• Korean Journal of Optics and Photonics
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• v.20 no.1
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• pp.6-15
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• 2009

A mobile phone camera consisting of two aspheric lenses is designed, and stray light distribution on the image plane is analyzed. We assume that most of the incident light is absorbed on the inner surfaces of the lens barrel and spacers, only a small fraction of the light is scattered uniformly. Assuming that 10% of the incident light is scattered on the barrel and spacers, the maximum value of stray light is 7.1% of the ideal image intensity. The result of analysis shows that stray light originated mostly from internal reflection on the ribs. The contributions of scattering by the barrel and spacers are relatively small. To reduce the internal reflection, thin absorbing plates are inserted between lenses, and the shapes of spacers are modified. After the redesigning of the lens barrel, the maximum value of stray light is reduced to 1.1% of the ideal image intensity.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1082-1090
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• 2008

In this paper, a general solution for the vibrational energy and intensity distribution through a compliant and dissipative joint between plate structures is derived on the basis of energy flow analysis (EFA). The joints are modeled by four sets of springs and dashpots to show their compliancy and dissipation in all four degrees of freedom. First, for the EFA, the power transmission and reflection coefficients for the joint on coupled plate structures connected at arbitrary angles were derived by the wave transmission approach. In numerical applications, EFA is performed using the derived coefficients for coupled plate structures under various joint properties, excitation frequencies, coupling angles, and internal loss factors. Numerical results of the vibrational energy distribution showed that the developed compliant and dissipative joint model successfully predicted the joint characteristics of practical structures vibrating in the medium-to-high frequency ranges. Moreover, the intensity distribution of a compliant and dissipative joint is described.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.399-407
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• 1998

The infrared reflection coatings with pigment can be used to protect the surfaces of combustible materials exposed to fire. To obtain high reflectivities in the infrared range (0.5-10.mu.m) important to fire, several dielectric pigments, such as titanium dioxide, iron oxide, and silicon, can be synthesized to polymer coatings. The theoretical analysis shows that the coating design with particles diameter in the 1.5 to 2.5.mu.m range and volume fraction in the 0.1 to 0.2 range is estimated to be optimal. In the analysis of the radiation, the dependent scattering, absorption by polymeric binder, and the internal interface reflection are considered. In addition, the temperature distribution in the semi-transparent coating layer and an opaque substrate (PMMA) is also presented.

• Current Optics and Photonics
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• v.4 no.5
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• pp.441-445
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• 2020

A novel design for a Fresnel lens for a solar end-pumped laser is demonstrated in this paper. The new hybrid Fresnel lens includes two parts, inner and outer. The inner part is a twice-total-internal-reflection and vertical-transmission lens. The outer part is a once-total-reflection and vertical-transmission lens. The radius of the Fresnel lens is 600 mm, and its focal length is 750 mm. The concentrating performance of the Fresnel lens is examined using TracePro. The results show that the concentration efficiency has been greatly improved. The total concentration efficiency of the hybrid Fresnel lens reaches 73.2% when the radius of the laser rod is 3 mm. This design can simplify the concentration system of a solar end-pumped solid-state laser.

• International Journal of Advanced Culture Technology
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• v.7 no.4
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• pp.23-31
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• 2019

This study was a quasi-experimental study with a single group pre-posttest design for evaluating the effects and meanings of a global health training program for nursing students. A mixed data collection method utilizing both qualitative and quantitative methods was applied. The qualitative method consisted of reflection journal entry analysis, while the quantitative study evaluated data collected from a self-reported questionnaire. After attending the program, cultural competencies of participants significantly increased than pre-test while global citizenship was not. Through an analysis of reflection journals written during the overseas training period, the meanings of experiences derived after the program were classified into five themes and 12 sub themes, which were, 'improvement of global health leadership', 'experience of barriers in reality', 'improvement of nursing professional value', 'inspiration of a perspective on health equity', and 'internal growth'. The results indicate that global health training program evaluated in this study was meaningful; it provided students with opportunities to experience the nurse's role in diverse global environments and attempted to measure the effects.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.147.2-148
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• 2016

Light management technology is very important for thin film solar cells, which can reduce optical reflection from the surface of thin film solar cells or enhance optical path, increasing the absorption of the incident solar light. Using proper light trapping structures in hydrogenated amorphous silicon (a-Si:H) solar cells, the thickness of absorber layers can be reduced. Instead, the internal electric field in the absorber can be strengthened, which helps to collect photon generated carriers very effectively and to reduce light-induced loss under long-term light exposure. In this work, we introduced a chemical etching technology to make honey-comb textures on glass substrates and analyzed the optical properties for the textured surface such as transmission, reflection and scattering effects. Using ray optics and finite difference time domain method (FDTD) we represented the behaviors of light waves near the etched surfaces of the glass substrates and discussed to obtain haze parameters for the different honey-comb structures. The simulation results showed that high haze values were maintained up to the long wavelength range over 700 nm, and with the proper design of the honey-comb structure, reflection or transmission of the glass substrates can be enhanced, which will be very useful for the multi-junction (tandem or triple junction) thin film a-Si:H solar cells.

• Journal of the Korean Geophysical Society
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• v.9 no.1
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• pp.1-6
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• 2006

To remove ringing and increase vertical resolution of GRP data, signature deconvolution was applied to GPR data obtained using a 100 MHz antenna in the Soyang Lake. The signature was extracted through stacking reflection signals from the lake bottom. Results of this deterministic deconvolution was compared with those from the conventional Wienner method. Due to increased vertical resolution, both deconvolution methods are able to resolve three or more layers in an apparent single layer on the input data. However, identification of reflection boundaries from ringing is not easy due to poor definition in the output data of the Wienner filter. On the contrary, the signature deconvolution greatly enhances both vertical resolution and definition of reflection boundaries, showing detailed internal stratigraphic features of the three sedimentary layers. Since extraction of signature at various depths is possible, this deconvolution method can be appled effectively to unstationary GPR data.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.69-77
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• 2017

This paper introduces an optical encoder using the reflection in the slit. The digital optical encoder is a sensor to generate a pulse according to the displacement. An optical encoder is composed of 3 parts: light source, slit plate and light-receiving element. In a conventional encoder, one slit produces one signal. The resolution of the digital optical encoder is determined by the number of slits in the encoder plate. The small slit size is most important among the factors that determine the resolution in a generic-type optical encoder. However, a small slit has low productivity and technical difficulties, so analog optical encoders have emerged as an alternative. Nonetheless, this alternative requires additional circuitry and equipment because of the noise and drafts in the analog signals. A new sensor is presented in this paper with a high resolution and a slit of the same size using the reflection in the slit. Then, the path of the light that passes through the slit ccording to the shape was analyzed, and some paths were expressed in the mathematical expressions. In addition, the optical paths were analyzed in the rectangular, octagonal, and circular encoders, and shown the obtained number of signals per slit by using them. Thus, we confirm that this method has the best performance in circle-shaped slits.

• The Journal of Internal Korean Medicine
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• v.30 no.1
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• pp.173-180
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• 2009

Objectives : The aim of this study was to investigate the evaluation of gastrointestinal parasympathetic nerve activity by comparing between HRV and bowel sound parameters in patients with functional dyspepsia. Methods : 62 patients (male 22, female 40) were enrolled. HRV was measured in all patients. and TP (total power), LF (low frequency density: 0.04$\sim$0.15Hz), HF (high frequency density: 0.15$\sim$0.4Hz). and LF/HF ratio were analyzed. HF band is a reflection of parasympathetic activity. and the LF-to-HF ratio is considered a marker of sympathovagal balance. Bowel sounds were recorded at the day after, and postprandial %BS was used to indicate the gastric vagal activity after eating. HRV and bowel sound parameters were compared. and correlation between them was analyzed. Results : There was no difference in LF/HF ratio between patient group and healthy group of other report. According to values of %BS, each patient was classified into a normal (>6 %BS) or hypoactivity (<6 %BS) of gastric vagus nerve group. HF component of the hypoactivity group was not significantly higher than that of the normal group. There was no correlation between HRV and bowel sound parameters. Conclusions : Because no correlation was found between HRV and bowel sound parameters in patients with functional dyspepsia, we concluded that it is not proper to evaluate gastric vagus nerve activity by HRV measurement.

• Economic and Environmental Geology
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• v.17 no.2
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• pp.115-139
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• 1984

The Cu-Pb-Zn-Ag hydrothermal vein-type deposits which comprise the Sambong mine occur within calc-alkaline volcanics of the Cretaceous Gyeongsang Basin. The ore mineralization took place through three distinct stages of quartz (I and II stages) and calcite veins (III stage) which fill the pre-existing fault breccia zones. These stages were separated in time by tectonic fracturing and brecciation events. The reflection variations of one mineral depending on mineralization sequence are considered to be resulted from variation in its chemical composition due to different physico-chemical conditions in the hydrothermal system. The reflection power of sphalerite increases with the content of Fe substituted for Zn. Reflectances of the sphalerite grain are lower on (111) than on (100) surface. The spectral profiles depend on the internal reflection color. Sphalerite, showing green, yellow and reddish brown internal reflection, have the highest reflection power at $544m{\mu}$ (green), $593m{\mu}$ (yellow) and $615m{\mu}$ (red) wavelength, respectively. Chalcopyrite is recognized as biaxial negative from the reflectivity data of randomly oriented grains measured at the most sensitivity at $544m{\mu}$. The microindentation hardness against the Fe content (wt. %) for the sphalerite increases to 8.05% Fe and then decreases toward 9.5% Fe content. Vickers hardness of the sphalerite is considerably higher on surface of (100) than on (111). The relationship between Vickers hardness and crystal orientation of the galena was determined to be $VHN_{(111)}$ > $VHN_{(210)}$ > $VHN_{(100)}$. The softer sulfides have the wider variation of the diagonal length in the indentation. Diagonal length in the indentation is pyrite