• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.123-133
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• 2008

This study evaluated the runoff data collected at 12 stream gauge stations of the Chungjoo dam basin using the IHACRES model. Especially, the geomorphology-related parameters of the IHACRES model could be quantified base on the regionalization technique, which have also been applied many stream gauge stations of the Chungjoo dam basin. Summarizing the results is as follows. (1) The climate-related parameters of the IHACRES model c, $\tau_w{^0}$, and f are found to be estimated and used uniformly over the basin. (2) The geomorphology-related parameters of the IHACRES model $t_q,\;t_s,\;and\;v_s$ are found to be estimated by considering the geomorphological parameters like the basin area, channel length, channel slope, basin slope through the regionalization based on the regression analysis. (3) Using the climate-related parameters applied uniformly over the basin and the geomorphology-related parameters estimated based on the regionalization procedure for each stream gauge station, a total of 12 stream gauge stations have been evaluated with their stream flow measurements. As results, the Sanganmi and Youngwal 1 stream gauge stations have been found to make high quality flow data, but Youngwal, Baekokpo, and Panwoon stations low quality flow data. On the whole, 12 stream gauge stations considered show large differences with their data quality, so a plan for securing more consistent data quality should be prepared imminently.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.226-231
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• 2008

The heat transfer characteristics of a solar high-temperature receiver with heat pipes was investigated by numerical simulation. The concentration ratio of the solar receiver ranges 1000 and the concentrated heat is required to be transported to a certain distance for specific applications. This study deals with internal geometry variation of a solar receiver incorporating high-temperature heat pipe. The isothermal characteristics in the receiver section is of major concern. The diameter of the solar thermal receiver was 120 mm and the length was 400 mm. The angle of receiver end wall was varied between $0^{\circ}$ and $45^{\circ}$. The wall thickness of the heat pipe channel was 4mm and 48 axial channels of the same dimensions were attached to the outer wall of the receiver with even spacing in the circumferential direction. The channels are changed to high-temperature sodium heat pipes. Commercial softwares were employed to deal with the radiative heat transfer inside the receiver cavity and the conduction heat transfer along the channels. The numerical results are compared and analyzed from the view Point of high-temperature solar receiver.

• Fashion & Textile Research Journal
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• v.26 no.3
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• pp.279-288
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• 2024

Fingernail-related content on YouTube is gaining popularity. This study aimed to present a new direction for nail content marketing and video production by identifying the current status of nail-related content on YouTube and factors affecting views. As for the research method, the study used the YouTube website, and the elements under analysis were classified into YouTuber characteristics (verbal characteristics, age group, gender, professional status, and celebrity status) and content characteristics (nail field, editing elements, and content). The results showed that standard language and terminology were generally used, and the proportion of YouTubers in their 30s was high. All nail-related content creators on YouTube were women, and they were found to be experts who worked as nail artists and nail content creators. As for the content characteristics, the proportion of art videos was high, and the video length was found mostly to be between 10 and 20 minutes. The editing elements included images, videos, and subtitles, and sound effects and background music were used frequently. Finally, it was found that the proportion of videos providing nail tips and know-how, product information, and procedures was high. This study identified factors that influence the number of views for nail videos. As a result, the study was able to present video production ideas for newcomers starting a nail-content YouTube channel, and this will be helpful in the development of nail content.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1220-1225
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• 2009

In this paper, a tunable fiber feedback laser based on the use of Sagnac loop filter and fiber Bragg grating (FBG) is proposed. The Sagnac loop filter using a high birefringence fiber provides precise 0.33-nm channel spacing as a multi-wavelength grid filter. Ni-Cr wire wound on the FBG is useful to induce the thermo-optic effect of the fiber. Two types of FBG structures, which have a different length of wire, are demonstrated to show the wavelength shift and separation. To tune FBG by resistant heat, some current is supplied into the wire. When the wavelength matched with one of the cavity modes of Sagnac loop filter, the mode-locked lasing is occurred. The electrical power sensitivity of the resonant wavelength is measured to 1.75pm/mW. This laser configuration can be applied the electrical power system for monitoring the power fluctuation.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.63-69
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• 2011

In this study, we report on the novel lithographic patterning method to fabricate organic thin film field effect transistors (OTFTs) based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30 nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce $Al_2O_3$ film grown via atomic layer deposition method onto pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated micron sized pentacene FETs and measured their electrical characteristics.

• Journal of IKEEE
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• v.23 no.4
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• pp.1288-1294
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• 2019

The channel-achieving property made the polar code show to advantage as an error-correcting code. However, sufficient error-correction performance shows the asymptotic property that is achieved when the length of the code is long. Therefore, efficient architecture is needed to realize the implementation of very-large-scale integration for the case of long input data. Although the most basic fully parallel encoder is intuitive and easy to implement, it is not suitable for long polar codes because of the high hardware complexity. Complementing this, a partially parallel encoder was proposed which has an excellent result in terms of hardware area. Nevertheless, this method has not been completely generalized and has the disadvantage that different architectures appear depending on the hardware designer. In this paper, we propose a hardware design scheme that applies the proposed systematic approach which is optimized for bit-dimension permutations. By applying this solution, it is possible to design a generalized partially parallel encoder for long polar codes with the same intuitive architecture as a fully parallel encoder.

• Journal of radiological science and technology
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• v.32 no.3
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• pp.299-306
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• 2009

Purpose : To compare radiation dose for coronary CT angiography (CTA) obtained with 6 examination protocols such as a retrospectively ECG gated helical scan, a prospectively ECG gated sequential scan, low kVp technique, and cardiac dose modulation technique. Materials and Methods : Coronary CTA was performed by using 6 current clinical protocols to evaluate effective dose and organ dose in primary beam area with anthropomorphic female phantom and glass dosimetric system in 64 channel multi-detector CT. After acquiring topograms of frontal and lateral projection with 80 kVp and 10 mA, main coronary scan was done with 0.35 sec tube rotation time, 40 mm collimation ($0.625\;mm{\times}64\;ea$), small scan field of view (32 cm diameter), 105 mm scan length. Heart beat rate of phantom was maintained 60 bpm in ECG gating. In constant mAs technique 120 kVp, 600 mA was used, and 100 kVp for low kVp technique. In a retrospectively ECG gated helical CT technique 0.22 pitch was used, peak mA (600 mA) was adopted in range of $40{\sim}80%$ of R-R interval and 120mA(80% reduction) in others with cardiac dose modulation. And 210 mAs was used without cardiac dose modulation. In a prospectively ECG gated sequential CT technique data were acquired at 75% R-R interval (middle diastolic phase in cardiac cycle), and 120 msec additional padding of the tube-on time was used. For effective dose calculation region specific conversion factor of dose length product in thorax was used, which was recommended by EUR 16262. Results : The mean effective dose for conventional coronary CTA without cardiac dose modulation in a retrospectively ECG gated helical scan was 17.8 mSv, and mean organ dose of heart was 103.8 mGy. With low kVp and cardiac dose modulation the mean effective dose showed 54.5% reduction, and heart dose showed 52.3% reduction, compared with that of conventional coronary CTA. And at the sequential scan(SnapShot pulse mode) under prospective ECG gating the mean effective dose was 4.9 mSv, this represents an 72.5% reduction compared with that of conventional coronary CTA. And heart dose was 33.8 mGy, this represents 67.4% reduction. In the sequential scan technique under prospective ECG gating with low kVp the mean effective dose was 3.0 mSv, this represents an 83.2% reduction compared with that of conventional coronary CTA. And heart dose was 17.7 mGy, this represents an 82.9% reduction. Conclusion : In coronary CTA at retrospectively ECG gated helical scan, cardiac dose modulation technique using low kVp reduced dose to 50% above compared with the conventional helical scan. And the prospectively ECG gated sequential scan offers substantially reduced dose compared with the traditional retrospectively ECG gated helical scan.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1263-1264
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• 2007

자계 유도 고상결정화(FESPC)를 이용하여 제작한 다결정실리콘(poly-Si) 박막 트랜지스터(TFT)는 비정질 실리콘 박막 트랜지스터(a-Si:H TFT)보다 뛰어난 전기적 특성과 우수한 안정성을 지닌다. $V_{DS}$ = -0.1 V에서 채널 폭과 길이가 각각 $5\;{\mu}m$, $7\;{\mu}m$인 P형 TFT의 이동도(${\mu}$)와 문턱 전압($V_{TH}$)은 각각 $31.98\;cm^2$/Vs, -6.14 V 이다. FESPC TFT는 일반 poly-Si TFT에 비해 채널 내 결정 경계 숫자가 많아서 상대적으로 열악한 특성을 가진다. 채널 길이 $5\;{\mu}m$인 TFT의 $V_{TH}$는 채널 길이 $18\;{\mu}m$ 소자의 $V_{TH}$보다 1.36V 작지만, 일반적으로 큰 값이다. 이 현상은 채널에 다수의 결정 경계가 존재하고, 수평 전계가 크기 때문이다. 수평 전계가 증가하면, 결정 경계의 전위 장벽 높이가 감소하게 되는데, 이는 DIGBL 효과이다. ${\mu}$의 증가에 따라서, 드레인 전류가 증가하고 $V_{TH}$은 감소한다. 활성화 에너지($E_a$)는 드레인 전압과 결정 경계의 수에 따라 변하는데, 드레인 전압이 크거나 결정 경계의 수가 감소하면 $E_a$는 감소한다. $E_a$가 감소하면 $V_{TH}$가 감소한다. 유리기판 위의 FESPC를 이용한 P형 poly-Si TFT의 $V_{TH}$는 채널의 길이와 $V_{DS}$에 영향을 받는다. 증가한 수평 전계가 결정 경계에서 에너지 장벽을 낮추는 효과를 일으키기 때문이다.

• Journal of KIISE:Databases
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• v.31 no.4
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• pp.422-431
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• 2004

In recent years, different models in data delivery have been explored in mobile computing systems. Particularly, there were a lot of research efforts in the periodic push model where the server repetitively disseminates information without explicit request. However, average waiting time per data operation highly depends on the length of a broadcast cycle and different access pattern among clients may deteriorate the response time considerably. In this case, clients are preferably willing to send a data request to the server explicitly through backchannel in order to obtain optimal response time. We call the broadcast model supporting backchannel as hybrid broadcast. In this paper, we devise a new transaction processing algorithm(O-PreH) in hybrid broadcast environments. The data objects which the server maintains are divided into Push_Data for periodic broadcasting and Pull_Data for on-demand processing. Clients tune in broadcast channel or demand the data of interests according to the data type. Periodic invalidation reports from the server support maintaining transactional consistency. If one or more conflicts are found, conflict orders are determined not to violate the consistency(pre-reordering) and then the remaining operations have to be executed pessimistically. Through extensive simulations, we demonstrate the improved throughput of the proposed algorithm.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.34-39
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• 2017

Typical flow regime of overflow at barrier or weir constructed in mid and small streams becomes as the submerged flow during most flood events. One of major causes of barrier failure has been reported as the levee-scour near the conjuction node between barrier and levee. However, most related design guidelines in Korea have not mentioned about the protection of levee around barrier or weir in detail. Furthermore, most previous researches have focused on the flow characteristics of overflow around several types of weirs but they did not have considered the material properties of levee itself. In this study, local scour near barrier was investigated with different material properties of levee under the submerged overflow condition which is assumed to reenact a flood event. Based on results from Fritz et al. and Mavis et al., a theoretical formula was also proposed in initial stage of laboratory experiments. And hydraulic experiments were carried out for the verification of the proposed formula. Levee was installed in the prismetic trapezoidal open channel and most parts were made of concrete except for movable section in which scour was expected to occur for the efficiency of experimental procedure. Each compaction of movable section in levee was followed by the basis of the KS F 2312. Further, after performing the experiments to find the optimum water content for each sediment, the specific amount of water was injected before flowing water. The difference between the proposed theoretical formula and experiment results was not much but considerable, which might be caused by the effect of compaction. For theoretical approach, it seemed that the formula did not take into account the compaction of levee, thus the correction coefficient for levee compaction determined in the literature was considered. Finally, the formula for the length of scour around barrier or weir was proposed, which can be useful to predict a levee in the reference design of revetment in mid and small streams. As shortly future study, scour length of levee around barrier or weir under different flow conditions such as perfect overflow condition will be studied and it will be able to contribute to suggest the design formula or criteria under all overflow conditions near barrier or weir.