• Journal of Korea Game Society
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• v.9 no.6
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• pp.179-189
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• 2009

We present a novel shadow culling algorithm for interactive ray tracing. Our approach exploits frame-to-frame coherence instead of preprocessing of building shadow data, so this algorithm is suitable for dynamic ray raying. In this algorithm, shadow processing results are stored to each primitive and used in the next frames. We also present a novel occlusion testing method. This method corrects potential shadow errors in our culling algorithm and requires low overhead. Experiment results show that our algorithm reduced both the traversal cost by 7-19 percent and the intersection cost by 9-24 percent.

• Journal of Communications and Networks
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• v.10 no.1
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• pp.71-78
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• 2008

We propose a sub-band spreading technique for adaptive modulation (AM) in orthogonal frequency division multiplexing (OFDM) systems in order to reduce signaling overheads and to average frequency selective fading channels causing different signal-to-noise ratio (SNR) values for subcarriers in each subband. The conventional sub-band based AM schemes can also reduce signaling overheads and complexity for allocating a resource per sub-band at a time. However, they may suffer from the channel variation in a sub-band when the sub-band size is larger than the channel coherence bandwidth (BW). The sub-band spreading at the transmitter enables the received symbols in each sub-band to have an identical reliability even in a frequency selective fading channel. We rigorously analyze the averaged SNR value at the receiver of the sub-band spreading system and the analyzed average SNR in a sub-band is used for an adaptation criterion. The proposed AM scheme outperforms the conventional sub-band based OFDM scheme without spreading, and it can yield better throughput performance than the conventional subcarrier based AM schemes when we consider the signaling overheads.

• Journal of Biomedical Engineering Research
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• v.32 no.4
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• pp.285-288
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• 2011

In this study, we developed an optical coherence tomography(OCT) using a sweep-source laser whose center wavelength is 1310 nm and a probe of hand-held type. The developed hand-held probe targets to diagnose the middle ear, so it is miniaturized for ease and convenience of control. For the first time, we performed in-vivo clinical experiments on tympanic membrane(TM) perforation patients not reported from previous studies about OCT. The high-resolution sectional images of tympanic membrane perforation can be obtained. There aren't many studies about diagnostic instrument of the middle ear and diagnosis with sectional image of the middle ear, so the developed OCT system and hand-held probe are applicable to tympanic membrane perforation and other pathologic diagnosis in the middle ear.

• Journal of Oriental Neuropsychiatry
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• v.7 no.1
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• pp.137-153
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• 1996

Through the classification of region and kinds of illness about the death of vagrants from 1906 to 1942, the results on the study of vagrants under the rule of Japanese imperialism are followings.1. The statistics about the death of vagrants from 1906 to 1912 have no coherence. So this study excludes that time.2. A mental disease as a cause of death of vagrants is 25.4%. It shows the highest ratio of all the other diseases.3. A mental, nervous disease among the cause of vagrants' death is 15%.4. On outbreak ration of mental disease is 26.7 times in men, 24.6 times in women higher, and on nervous disease 48.1 times in man, 48.9 times in woman higher than Japanese.5. Regional outbreak ratio is higher than Japan. The orders are Chonlabukdo, Chungcheongbukdo, Hwanghaedo, Kangwondo. The above results show that vagrants under the rule of Japanese imperialim is produced by cause of disease. The cause of vagrants' death is also related to social situation at that times. And it accord with the basis of documents. The relation between the death of vagrants and mental, nervous disease are considered to be studied in detailI.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.3
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• pp.82-92
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• 1991

A study on the manufacturing of High Precision Linear Scalr using He-Ne Laser interference Of late, along with the advancement of precision machining technology, the requirement of super precision measurement increases as time goes on, and the accuracy of standard scale which is a basis of precision measurement has been cognized as a criterion of industrial development in a nationl. In this paper, we described on technology by which we could carve scale lines thru optical method under the condition of laboratory by using the coherence of He-Ne two-mode stabilized laser and in turn, put it to practical use as linear scale for the measurement of length. Hence in this research in the case of setting scale interval to 20 ${\mu}m$, we employed super precision scale-carving device associated with Ar laser and acousto optic modulator in lieu of flashing lamp scale-carving device, and we obtained as experimental result superior linear scales carved within the accuracy of ${\pm}$0.3${\mu}m$.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.8
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• pp.1261-1274
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• 1997

Contemporary costume by the 'Deconstruction' from the outside has shown disclosure, destruction, poverty and analysis. The conclusion of this thesis as follows, 1. The Deconstruction of disclosure by infra disclosed the underwear and inner structure outside, which has deconstructed a fixed idea i.e.'underwear must be in outwear', modesty versus immodesty and disclosure versus concealment. 2. The Deconstruction of destruction originated in punk look has rejected traditional manners and utility, at the same time, it has shown the ambivalence i.e. completeness versus incompleteness, making versus destructing by slashes, rips, fringes. 3. The Deconstruction of poverty has appeared as French avangarde mode, little black dress by Chanel, second hand style by hippy, blue jean, granny look, especially Rei Kawakubo's poor look influenced by Zen Aesthetics and post punk. It has looked like old and worn out dress by doing patchwork, dye, decolor, rip, fray, which has shown the decentring by concealing the body than disclosing, rejecting snobbery. 4. The Deconstruction of analysis, seemingly partial and patched is a violation only of our expectation of clothing's unbroken entity though it has looked like a fragment. The completeness and coherence of it is made more evident by its breach, void, and bond like a poetic language. As the result, disclosed, destructed, poor, and analytical costumes has expressed as an escape from the appearance which traditional aesthetic concept had pursued.

• The Journal of Korean Association of Computer Education
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• v.8 no.2
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• pp.75-83
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• 2005

The problem of adolescents' Internet addiction is getting serious. So, preventive education of Internet addiction that cultivate right Internet use attitude is getting important. The purpose of this study is to offer a suggestion about preventive education of Internet addiction based on characteristics of adolescents' Internet addiction. We analyzed factors affecting Internet addiction by using multidimensional scale of Internet addiction for adolescent. This scale is composed of eleven factors that are mentioned by previous researches. As a result, the significant factors affecting Internet addiction are internet use time, escape from reality, anger-control, depression, family coherence, social competence, impulsivity, self-efficacy. Based on these analysis, we made a suggestion about preventive education of Internet addiction.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.74.2-74.2
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• 2016

It is important to know how well observation errors are removed in the calibration process prior to ensuing scientific research. In mm-VLBI observations, a radio wave suffers from an atmospheric propagation delay due to the rapid change of atmospheric refraction. It makes phases of VLBI correlation output fluctuate rapidly, which essentially decreases the coherence of phases and reduces the integration time. Consequently, it is challenging to achieve a high signal-to-noise ratio and enhance the quality of scientific output. Among the causes of the atmospheric propagation delay, water vapor in the troposphere is the most decisive factor to affect phase errors in the high frequency range (> 10GHz). It is expected to have the non-dispersive characteristic that enables to introduce new calibration strategy, Frequency Phase Transfer (FPT). This new method utilizes low frequency phases to compensate phase errors in high frequency bands. In addition, Korean VLBI Network (KVN) which benefits from the simultaneous 4-channels (22/43/86/129 GHz) observations is ideal to probe FPT performance. In order to evaluate FPT performance of KVN, we present the results of FPT phase analysis and discuss its performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1207-1211
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• 2015

Various laser systems have been widely used in almost all industrial technologies because they have high energy density, directivity and coherence. Recently the clinical application is becoming wider in medical parts such as incurable disease, diagnosis and so on. Generally, ruby laser beam has the greatest efficacy for removing tattoos, freckle and other skin problem. But current medical ruby laser system has the maximum repetition rate of 2Hz and optical output beam energy of 1J. Many medical doctors really want to have a high repetition ruby laser system because that can reduce the operation time. We investigated a new ruby laser system with high repetition rate of 4Hz using double cavities. Furthermore, we develop a new power supply system adopting zero voltage switching(ZVS) to minimize switching loss by LLC resonant converter designed as 2kW class.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.629-631
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• 2015

In this proceedings, preliminary results of the KVN Source-Frequency Phase-Referencing (SFPR) observation of 3C 66A and 3C 66B are presented. The motivation of this work is to measure the core-shift of these 2 sources and study the temporal evolution of the jet opacity. Two more sources were observed as secondary reference calibrators and each source was observed at 22, 43, and 86 GHz simultaneously. Our preliminary results show that after using the observations at the lower frequency to calibrate those at the higher frequency of the same source, the residual visibility phases for each source at the higher frequencies became more aligned, and the coherence time became much longer; also, the residual phases for different sources, within 10 degrees angular separations, follow similar trends. After reference to the nearby calibrator, the SFPRed maps were obtained as well as the astrometric measurements, i.e. the combined coreshift. The measurements were found to be affected by structural blending effects because of the large beamsize of KVN, but this can be corrected with higher resolution maps (e.g. KAVA maps).