• Clean Technology
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• v.12 no.3
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• pp.175-181
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• 2006

The feasibility of the use of porous fossil diatoms for indoor air pollution control was investigated via the characterization of physical and chemical properties. The fossil diatoms were observed by SEM(Scanning Electron Microscope). Diatomite had well-distributed pores below 5 nm and relatively large surface area compare to sericite. However, no porosity in sericite was found. Results showed that diatomite had better performance than sericite in respect to porosity and large surface area. But diatomite which is thermally treated at $950^{\circ}C$ has no porosity and low surface area because of combustion of fossil diatoms or calcination of inorganic oxide at high temperature, and has poor adsorption capability of ammonia gas. In conclusion, porous diatomite has relatively high performance to adsorb noxious chemical compounds, such as ammonia gas and VOCs.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.61-66
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• 2001

Defocused Fourier plane holograms are stored in disk-type holographic memories where thin recording media are used, the areal storage density per hologram and the intensity uniformity of the signal beam at the recording plane are studied. As the pixel pitch of the spatial light modulator that represents binary data increases, the storage density per hologram increases if exact Fourier holograms are stored. When defocused Fourier plane holograms are stored, however, we show that there exists an optimal pixel pitch that maximizes the area storage density per hologram in general, to increase the areal storage density per hologram, f/# of the Fourier transform lens that focuses the data image should be as small as possible. In this case, not only the intensity distribution at the recording plane but also the recording area becomes very sensitive to the degree of defocusing. Therefore, even if the exact Fourier plane holograms are stored, the defocusing effect owing to the medium thickness should be taken into account to achieve the maximal areal storage density per hologram.logram.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.9 s.339
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• pp.61-72
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• 2005

This paper proposes a method which efficiently allocates decoupling capacitance to reduce power supply noise at the floorplan level. We observe problems of previous approach that the decoupling capacitance of each module was overestimated and the power supply noises of modules were changed by inserting additional area for decoupling capacitance, and then suggest a new approach. And, we also present a simple heuristic method which can effectively allocate white space modules for decoupling capacitance area within more faster time instead of LP technique. Experimental results show that our approach can reduce the area of decoupling capacitance to average 7.9 percent compared with Zhao's approach in [4]. Therefore both total area and wire length of nniflm result are decreased. Also, we confirm that our approach solves well the problem caused by inserting additional area. In execution time comparison, our approach shows average 11.6 percent improvement.

• Elastomers and Composites
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• v.33 no.3
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• pp.185-192
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• 1998

This study was investigated on the physical properties of synthetic rubber compounds containing silica and silane copuled silica. Surface area and pore volume of silane copuled silica appeared to be low compared with those of pure silica because silane coupling agent blocks the pore of silica surface during silanization reaction. Silica with large surface area and high structure showed the short scorch time$(t_5)$ and rapid cure rate. The silane coupled silica showed the shorter scorch time and more rapid cure rate than pure silica because of the of effect of sulfur in the silane coupling agent(Si 69), The high value of $N_2SA$ minus CTAB com-pared with surface area and structure of silica showed the high 300% modulus. Also, the surface area and structure of silica did not affected the amount of PICO loss that indicate the abrasion resistance but affected the amount of cut and chip loss.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.78-82
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• 2006

현재 치수계획은 선적인 개념의 제방위주 하천대응 치수계획에서 벗어나 면적인 개념의 유역 대응 치수계획으로 전환되고 있다. 이에 유역종합치수계획에서 유역대응 치수계획으로 천변저류지 계획이 수립되고 있지만 계획수립에 대한 표준화된 방법이 제시되어 있지 않은 실정이다. 이에 낙동강 유역종합치수계획을 중심으로 각 유역종합치수계획에서 사용하였던 방법들을 정리하여 천변저류지 수립절차, 분석방법, 홍수조절효과, 운영방안 등에 대해 살펴보고 또한 천변저류지 홍수조절효과 산정에 대한 문제점 및 향후 계획을 제시하여 천변저류지 계획 전반에 대한 수립 방안을 제시하고자 한다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.280-281
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• 2017

본 논문에서는 기존의 배풍기 효율을 높이고 크기를 줄이기 위해 임펠러의 속도를 높이는 설계에 관한 연구다. 임펠러 속도는 5500rpm으로 증가시키고 크기는 320mm에서 250mm로 줄였으며 효율과 최대 풍량을 향상키기기 위해 임펠러의 Hub/Tip 비율을 줄이며, 날개각도에 변화를 주는 방식을 제안한다. Hub/Tip 비율이 줄어들면 유량이 통과하는 면적이 넓어지게 되는 효과를 얻게 되고, 임펠러 중심거리에 따른 날개 각도를 변화시키면 풍압과 풍량이 달라지는 효과를 얻게 되어 동일한 rpm으로 회전하는 배풍기의 효율을 높일 수 있다. 설계된 구동용 SRM과 임펠러의 설계에 따른 운전 특성을 시뮬레이션을 통해 해석하고자 한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.38-46
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• 2014

Effects of various parameters on bond property between reinforcing bar and concrete are investigated in many researchers, and various study is on going to improve the bond strength. Properties of interface between reinforcement and concrete is important role in bond property. This study analyzed the interfacial bond mechanism between deformed bar and concrete by finite element analysis (FEA) to evaluate the effect of rib shape. The FEA model in this study is simplified 2D plane stress model. The variables of analysis are selected by rib angle, rib height, rib spacing and relative rib area. From the results of analysis, reinforcing bars with rib angle $30{\sim}60^{\circ}$ showed better bond strength than the others. Bond strength ratio following to the rib height is proportionally increased up to the $0.12d_b$, but rib spacing has little effect on bond strength. The results also indicated that relative rib area can be efficiently represented the properties of deformed shape in reinforcing bars, and zigzagged rib height shape showed excellent bond strength increase.

• Journal of Wetlands Research
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• v.16 no.1
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• pp.113-124
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• 2014

The observed rainfall may be different along with the altitude of rain gauge, resulting in the fact that the characteristics of rainfall events occurred in urban or mountainous areas are different. Due to the mountainous effects, in higher altitude, the uncertainty involved in the rainfall observation gets higher so that the density of rain gauges should be more dense. Basically, a methodology for the rain gauge network evaluation, considering this altitude effect of rain gauges can account for the mountainous effects and becomes an important step for forecasting flash flood and calibrating of the radar rainfall. For this reason, in this study, we suggest a methodology for rain gauge network evaluation with consideration of the rain gauge's altitude. To explore the density of rain gauges at each level of altitude, the Equal-Altitude-Ratio of the density of rain gauges, which is based on the fixed amount of elevation and the Equal-Area-Ratio of the density of rain gauges, which is based on the fixed amount of basin area are designed. After these two methods are applied to a real watershed, it is found that the Equal-Area-Ratio generates better results for evaluation of a rain gauge network with consideration of rain gauge's altitude than the Equal-Altitude-Ratio does. In addition, for comparison between the soundness of rain gauge networks in other watersheds, the Coefficient of Variation (CV) of the rain gauge density by the Equal-Area-Ratio is served as the index for the evenness of the distribution of the rain gauge's altitude. The suggested method is applied to the five large watersheds in Korea and it is found that rain gauges installed in a watershed having less value of the CV shows more evenly distributed than the ones in a watershed having higher value of the CV.

• Phonetics and Speech Sciences
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• v.16 no.2
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• pp.19-27
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• 2024

The Lombard effect is an involuntary response to speakers' experiences in the presence of noise during voice communication. This study aimed to investigate the Lombard effect by comparing the acoustic features of children and adults under different listening conditions. Twelve male children (5-9 years old) and 12 young adult men (24-35 years old) were recruited to produce speech under three different listening conditions (quiet, noise-55 dB, noise-70 dB). Acoustic analyses were then carried out to characterize their acoustic features, such as F0, intensity, duration, and vowel space area, under the three listening conditions. A Lombard effect was observed in the intensity and duration for children and adults who participated in this study under adverse listening conditions. However, we did not observe a Lombard effect in the F0 and vowel space areas of either group. These findings suggest that children can adjust their speech production in challenging listening conditions as much as adults.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.33 no.12
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• pp.32-38
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• 2004

초고층건물의 건설이 증가되고 있지만 건물외파와 출입문의 기밀도가 낮게 유지될 때, 이러한 누설면적과 층별로 구획할 수없는 수직샤프트(계단실 등)와 직렬로 배치될 경우, 필연적으로 발생하게 되는 굴뚝 현상(stack effect)의 발생원인과 차압크기 산정하는 방법 및 예방대책을 소개하고자 한다.