• Computers and Concrete
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• v.23 no.1
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• pp.69-80
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• 2019

Modeling approach for mesoscopic model of concrete depicting mass transportation and physicochemical reaction is important since there is growing demand for accuracy and computational efficiency of numerical simulation. Mesoscopic numerical simulation considering binder, aggregate and Interfacial Transition Zone (ITZ) generally produces huge number of DOFs, which is inapplicable for full structure. In this paper, a three-dimensional multiscale approach describing three-phase structure of concrete was discussed numerically. An effective approach generating random aggregate in polygon based on checking centroid distance was introduced. Moreover, ITZ elements were built by parallel expanding the surface of aggregates on inner side. By combining mesoscopic model including full-graded aggregate and macroscopic model, cases related to diffusivity and thickness of ITZ, volume fraction and grade of aggregate were studied regarding the consideration of multiscale compensation. Results clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of, rebar diameter, concrete cover and exposure period.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.187-197
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• 2023

Today's world is experiencing rapid technological advancement like never before. The ever-changing technology space has overwhelmed citizens with a substantial load of information, which has made it difficult for them to keep up with the technology awareness. This review paper is written to provide information about the Internet of Things in a way that technical along with nontechnical individuals can understand the definition, historical evolution, components, and scope of IoT technology. Relevant literature published between January 2009 and February 2023 was included in this paper. The applications of the Internet of Things in healthcare have been a special focus of this paper as IoT has massive potential in this field and healthcare professionals often face significant issues in keeping their technology knowledge up to date. Moreover, some of the most common issues associated with IoT introduction in healthcare are also discussed in the paper along with some suitable recommendations. Although, IoT can significantly transform our lives and can introduce convenience and efficiency, particularly in the healthcare sector. However, its adoption in healthcare is still a major task due to various challenges presented by the health workforce. Thus, in-depth empirical research is suggested to assist the IoT technology transition.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.444-453
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• 2014

A throttleable rocket engine enables operational possibilities such as the docking of spacecraft, maneuvering in a certain orbit and landing on a planet's surface, altitude control, and entrance to atmosphere-less planets. Thus, throttling methods have long been researched. However, dual-manifold injectors, which represent one throttling method, have been investigated less than others. In this study, dual-manifold and single-manifold injectors were compared to determine the characteristics of dual-manifold injectors. Also, the effects of gas injection were investigated with various F/O ratios. To investigate the characteristics, mass flow rate, spray pattern, spray angle, and droplet size were measured. The spray angle and droplet size were captured by indirect photography. About 30 images were taken to assess the spray patterns and spray angle. Also, 700 images were analyzed to understand the droplet distribution and targeting area, moving to the right from the centerline with 1.11-cm intervals. The droplet size was obtained from an image processing procedure. From the results, the spray angle showed two transition regions, due to swirl momentum in the swirl chamber regardless of the F/O ratio. The droplet size showed similar trends in both dual-manifold and single-manifold injectors except in the low mass flow rate region. In the case of the dual- manifold injector, the spray cone was not fully developed in the low mass flow rate region due to low angular momentum in the swirl chamber.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.825-835
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• 2019

When the tunnel is designed, the ground is classified into several grades and the corresponding support system is applied according to the support pattern table. However, a simple pattern application based on rock grade does not take into account the longitudinal stress transitions occurring at rock grade boundaries. In this study, three-dimensional numerical analysis was performed to estimate the stress change in the longitudinal rock grade change of NATM tunnel, and the influence zone of load transfer was investigated using the influence line and trend line. As a result, the downward change of rock grade in the direction of tunnel excavation occurs in the range of 0.35~0.7D from low-strength rock to high-strength rock around the grade change boundary. It is necessary to apply a downward pattern of about 1.0D to the safety direction in consideration of the influence range of 0.35D to 0.7D.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.465-472
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• 2009

The technologies for improving the capacity of hydrogen storage were investigated and the recent data of hydrogen storage by using various porous carbon materials were summarized. As the media of hydrogen storage, activated carbon, carbon nanotube, expanded graphite and activated carbon fiber were mainly investigated. The hydrogen storage in the carbon materials increased with controlled pore size about 0.6~0.7 nm. In case of catalyst, transition metal and their metal oxide were mainly applied on the surface of carbon materials by doping. Activated carbon is relatively cheap because of its production on a large scale. Carbon nanotube has a space inside and outside of tube for hydrogen storage. In case of graphite, the distance between layers can be extended by intercalation of alkali metals providing the space for hydrogen adsorption. Activated carbon fiber has the high specific surface area and micro pore volume which are useful for hydrogen storage. Above consideration of research, porous carbon materials still can be one of the promising materials for reaching the DOE target of hydrogen storage.

• Bulletin of the Korean Space Science Society
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• 1993.10a
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• pp.15-15
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• 1993

Revised Yale Isochrone(Green et al, 1987)과 Lee의 HB simulation data(LEE '||'&'||' Demarque 1990)을 이용하여 Park이 만든 CMD simulation program(Park 1983).에 쌍성을 첨가하면 CMD에 어느 정도의 영향을 나타내게 되는가를 조사하였다. MS, SGB와 RGB는 큰 변화가 없었으나, HB에서는 많은 변화를 나타내었다. 193919 S02401193919 ^x We have observed the emission of HC3N J= 4-3, 5-4 10-9 and 12-11 transitions toward the Sgr B2 central region in an area of 150"XISO" with resolutions of16"-48". The intensities and central velocities of line profiles show significant variations with positions. In contrast to the in tensities of the low J-level transitions which gradually increase from the central source toward the outside region the HC3N emission of the high J-level transition become stronger toward the central radio continuum source MO5. Systematic chainge in the radial velocity of each line profile occurs along north-south direction there are a few peaks in most line profiles, and these indicate that there not multiple velocity components along the line of sight. Distributions of excitation temperah at and column density which were estimated from the excitation calculations show the existence of a small(IxEpc),hot(Tex> SOK) core which contains two tempegatlue peaks at -15" east and north of MDS. The column density of HCaN is (1-3):n1014cm-2. Column density at distant position from MD5 is larger than that in the (:entral region. We have deduced that this hot-core has a mass of 10sR1 which i:s about an order of magnitude larger those obtained by previous studies.previous studies.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.11
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• pp.945-951
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• 2021

The SOQPSK-TG is a modulated signal for aeronautical telemetry with a very good bandwidth efficiency. In this paper, the frequency waveform filter of the SOQPSK-TG is linearly approximated and modeled with a duobinary precoder and a modified frequency waveform filter having a phase transition period of about 1T_b. In combination with the existing precoder, the SOQPSK-TG is modeled by a double duobinary MSK. Comparing the SOQPSK-TG signal and the newly modeled double duobinary MSK signal in time domain and frequency domain, it is confirmed that the two signals are almost identical and there is virtually no performance difference. Moreover, we can attain 0.1 dB BER performance improvement compared to the existing cosine filter when the filter of the IQ-detector is implemented with a cosine sum filter taking into account the change in the modulation index by the new double doubinary precoder.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.585-592
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• 2016

Visualization was done by using $CH^*$ chemiluminescence images and PMT measurements in order to understand the origin of fluctuating pressure and chemical luminosity at about 500 Hz frequency even in stable combustion, which was observed in recent experimental tests, and to find the physical correlation leading to Low Frequency Instability(LFI) in terms of phase angle. In stable combustion, chemical reactions are distributed along the shear layer flow showing a negative coupling(about 180 degree in phase angle) with combustion pressure. However, phase difference is shifted to a positive coupling showing less than 90 degree in unstable case. Also a periodic change in the distribution of chemical reactions is observed along with local flame extinction and the appearance of big scale vortex flow. In the transition to LFI, local flame extinction and small vortex flow start to appear in a row. As seen in the bluff body wake in reactive flow, the periodic appearance of vortex flow seems to share the same physical process of BVK(Bernard Von Karman) instability generation. Thus, the appearance of local extinction in 500 Hz fluctuations is gradually amplified to complete extinctions of about 20 Hz, and it leads into LFI.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.11-17
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• 2010

In this paper, we propose HMM-based upper-body gesture. First, to recognize gesture of space, division about pose that is composing gesture once should be put priority. In order to divide poses which using interface, we used two IR cameras established on front side and side. So we can divide and acquire in front side pose and side pose about one pose in each IR camera. We divided the acquired IR pose image using SVM's non-linear RBF kernel function. If we use RBF kernel, we can divide misclassification between non-linear classification poses. Like this, sequences of divided poses is recognized by gesture using HMM's state transition matrix. The recognized gesture can apply to existent application to do mapping to OS Value.

• KIEAE Journal
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• v.8 no.2
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• pp.11-21
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• 2008

The purpose of this study is to interpret the visual and auditory images and cognitive characteristics about townscapes in Namwon city. It was acquired the survey results about 8 types of verbal interviews and 2 kinds of sketch maps which are based on urban images from 102 Namwon residents. They held in a variety of images of Namwon in their minds such as Jiri mountain, clean environment, sightseeing, special products, urban/building structures, Korean classical music, historical novel, local sports, and emotional images. The nice streets or places which the residents recommended are the places which have abundant natural areas, psychological peace and rest, available space for physical activity, places for performances and events, and regional attractions. The streets or places which they didn't like are decadent places, and areas of crowded traffic. The transition times of visual and auditory scene can be classified with the Saemaul movement in the 1970's(the rural new community movement) and the improvement of the city in the 1990's. The elements of visual images in Namwon city on the basis of the cognitive maps were expressed such elements as paths, districts, nodes, edges, and landmarks. The elements of auditory images, which are on the basis of the concept of the soundscape, included sounds of narrative musical form unique to Korea; p'ansori, sounds of traditional markets, and sounds of nature. It was found that the imageability of visual and auditory images is relatively clear in specific areas in Namwon city.