• New & Renewable Energy
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• v.19 no.2
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• pp.31-39
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• 2023

Salinity gradient energy can be generated from a mixture of water streams with different salt concentrations by using reverse electrodialysis (RED). In this study, we evaluated the effect of stack size and number of cell pairs on the energy efficiency and specific energy of the RED process. Additionally, we studied the prementioned parameters to maximize the power density of RED. The performance of the RED stack which used a patterned ion exchange membrane, was evaluated as a function of stack size and feed flow rate. Moreover, it was noted that an increase in stack size increased the ion movement through the ion exchange membrane. Furthermore, an increase in feed flow rate led to a reduction in the concentration variation, resulting in an increase in OCV and power density. The energy efficiency and specific energy for 100 cells in the 10 × 10 cm² stack were the highest at 12% and 0.05 kWh/m³, respectively, while the power density from 0.33 cm/s to 5 × 5 cm² stack was the highest at 0.53 W/m². The study showed that the RED performance can be improved by altering the size of the stack and the number of cell pairs, thereby positively affecting energy efficiency and specific energy.

• Journal of Advanced Navigation Technology
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• v.27 no.4
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• pp.429-435
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• 2023

The increasing complexity of avionics systems has emphasized the portability and reusability of software components. In this paper, a structural design method for IOSS (Input Output Service Segment) and TSS (Transport Service Segment) complying with the FACE (The Future Airborne Capability Environment) standard in the VxWorks 653 operating environment that satisfies ARINC 653 requirements is described. IOSS and TSS operate independently in different partitions to minimize time/space separation and the influence of other software, and to increase portability and reusability, strategy patterns among design patterns are applied. In addition, IOSS provides external interface service by applying distributed IO service structure, and among external interfaces, the ARINC 664 P7 interface of FACE-compliant equipment is placed in TSS to optimize the data movement path.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.1
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• pp.219-232
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• 2023

Mobility services need to change according to the regional characteristics of the target service area. Accordingly, analysis of mobility patterns and characteristics based on Origin-Destination (OD) data that reflect travel behaviors in the target service area is required. However, since conventional methods construct the OD data obtained from the administrative district-based zone system, it is hard to ensure spatial homogeneity. Hence, there are limitations in analyzing the inherent travel patterns of each mobility service, particularly for new mobility service like Demand Responsive Transit (DRT). Unlike the conventional approach, this study applies a data-driven clustering technique to conduct spatial analyses on OD travel patterns of regional mobility services based on reconstructed OD data derived from re-aggregation for original OD distributions. Based on the reconstructed OD data that contains information on the inherent feature vectors of the original OD data, the proposed method enables analysis of the spatial characteristics of regional mobility services, including public transit bus, taxi and DRT.

• Design & Manufacturing
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• v.17 no.4
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• pp.42-51
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• 2023

In this study, we investigated the injection molding technology of thick-walled light guides, which are parts that control the light source of automotive lamps. Through injection molding analysis, the gate position that can minimize product shrinkage and deformation was selected, and a mold reflecting the analysis results was manufactured to evaluate the effect of injection speed and holding pressure on transferability during micro-pattern molding through experiments. When designing an injection mold for products with varying thicknesses, it was found that installing the gate on the side of the thicker part was advantageous for reducing volume shrinkage and deformation. It was found that the effect of shrinkage due to thickness may be greater than the position of the gate on pattern transferability. The pattern transfer error decreased as the injection speed and holding pressure increased, and it was found that increasing the injection speed was relatively effective.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.5
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• pp.1059-1071
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• 2024

The 5G mobile network provides various services to numerous devices and applications, unlike LTE which focuses on smartphones. Features of 5G, such as low latency and massive connectivity, increase the overhead of the control plane(CP, signaling part) and make it difficult to detect abnormal devices due to random traffic patterns. In this paper, we propose a DBSCAN clustering-based detection method to counter signaling attacks, which are a type of 'Denial of Service(DoS)' attack targeting mobile networks. DBSCAN helps to create clusters of various shapes and can address dynamic traffic because the algorithm needs not to depend on past traffic statistics. We also use a real-time traced dataset for experiments to assess usability in real-world scenarios. According to the experiments, our method achieves 99.32% of accuracy and 0.03% of false-positive rates, demonstrating superior performance compared to previous works.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.917-925
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• 2005

In this paper, the quad-band antenna for mobile handsets is proposed and developed. The operating frequency bands include GSM(880 MHz${\~}$960 MHz), GPS(1,575 MHz$\pm$10 MHz), DCS(1,710 MHz${\~}$l,880MHz), and PCS(1,850 MHz${\~}$l,990 MHz). The proposed antenna consists of a feed line, a shorting post, and a radiating element of the feed loop. The multi-band operation is achieved by using the fundamental and higher resonant modes of the radiating element. Based on analysis of the current distribution on the radiator, the resonant frequency of each mode can be adjusted by adding the different sizes of slots on the radiator. The radiator of the feed loop is designed to be symmetrical so that the energy is symmetrically distributed on the radiator, which results in omni-directional radiation pattern. The ground plane under the radiator is removed in order to improve the bandwidth. The measured impedance bandwidths are $10.1\%$ in GSM band(VSWR<2.5), $26.8\%$ in GPS band, and DCS/US-PCS bands(VSWR<2.5), respectively. The maximum gains on the H-plane of the fabricated antenna are measured about -0.37 dBi${\~}$2.55 dBi for all operating frequency bands.

• Journal of Environmental Impact Assessment
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• v.10 no.1
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• pp.21-37
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• 2001

항공 비디오의 가장 큰 장점은 협각조망범위에 동영상을 제공함으로서 저렴한 경비로 소폭/장거리 지상물체를 감시하는 최적의 원격탐사도구로 알려져 있다. 선형감시에 대한 비디오의 이와 같은 이론적인 장점에 의거하여 하천수질을 모니터링 하기 위한 비디오 샘플링 기법이 본 연구를 통해 제시되었다. 본 연구의 근본적인 의도는 전통적인 샘플링에 기반을항공 비디오의 가장 큰 장점은 협각조망범위에 동영상을 제공함으로서 저렴한 경비로 소폭/장거리 지상물체를 감시하는 최적의 원격탐사도구로 알려져 있다. 선형감시에 대한 비디오의 이와 같은 이론적인 장점에 의거하여 하천수질을 모니터링 하기 위한 비디오 샘플링 기법이 본 연구를 통해 제시되었다. 본 연구의 근본적인 의도는 전통적인 샘플링에 기반을 둔 현장조사의 개념을 디지털 비디오의 해석기법에 연계시키려는 것이었다. 특정 지점에서 시료를 채취하는 현지 샘플링조사와 동일한 방식으로 장거리에 걸친 하천의 수질감시를 위해 원격동영상을 컴퓨터 모니터에 디스플레이 하면서 비디오 샘플지점을 선정하여 수질을 감시하였다. 비디오 샘플링 기법은 하천 색조의 변화실태에 대한 가상현실의 형태로 정보를 제공했다. 다양한 샘플지점에서 나타나는 하천 색조의 변화추세를 가시적으로 파악할 수 있었으며 전통적인 현장 샘플링 방법으로는 추적하는 데 한계가 있는 특정오염원에 기인한 하천수질의 광역적인 변화패턴을 파악하는 데 상당한 가능성을 보여주었다. 이와 같이 영구적으로 보전된 영상기록은 오염 물질의 이동확산 등 수질환경의 광역적인 변화 추이에 대한 시각적인 정보를 제공하고 있어 현장샘플링과 동시에 사용할 경우 하천수질감시에 있어 상당히 유용한 도구가 될 수 있음을 보여주었다. 본 연구를 통해서 제시된 비디오 샘플링 기법이 도로, 철도, 송유관 등 다양한 선형지형지물의 환경감시에 효과적으로 사용될 수 있을 것으로 사료된다. 둔 현장조사의 개념을 디지털 비디오의 해석기법에 연계시키려는 것이었다. 특정 지점에서 시료를 채취하는 현지 샘플링조사와 동일한 방식으로 장거리에 걸친 하천의 수질감시를 위해 원격동영상을 컴퓨터 모니터에 디스플레이 하면서 비디오 샘플지점을 선정하여 수질을 감시하였다. 비디오 샘플링 기법은 하천 색조의 변화실태에 대한 가상현실의 형태로 정보를 제공했다. 다양한 샘플지점에서 나타나는 하천 색조의 변화추세를 가시적으로 파악할 수 있었으며 전통적인 현장 샘플링 방법으로는 추적하는 데 한계가 있는 특정오염원에 기인한 하천수질의 광역적인 변화패턴을 파악하는 데 상당한 가능성을 보여주었다. 이와 같이 영구적으로 보전된 영상기록은 오염 물질의 이동확산 등 수질환경의 광역적인 변화 추이에 대한 시각적인 정보를 제공하고 있어 현장샘플링과 동시에 사용할 경우 하천수질감시에 있어 상당히 유용한 도구가 될 수 있음을 보여주었다. 본 연구를 통해서 제시된 비디오 샘플링 기법이 도로, 철도, 송유관 등 다양한 선형지형지물의 환경감시에 효과적으로 사용될 수 있을 것으로 사료된다.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.1-16
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• 2002

The purposes of this study were to investigate the effects of strength training on the change of ground reaction force for the children with trisomy 21 Down syndrome. The subjects of this study were consisted of eight elementary school students with Down syndrome who participated in the strength training. The strength training was administered by six items such as squat, leg curl, leg extension, toe raise, sit-ups, and hyperextension. For strengthening muscle, each group also was treated by walking for 8 weeks, three times a week, 10-15RM, 3sets, which was based on the principle of progressive overload. For inquiring the effect of strength training, the ground reaction force variables were measured in two phases : before-training and 8 week-after training. The gait of each subject was acquisition using 2 AMTI force platforms set at 100 frequency. The results of this study were as follows: The pattern of vertical, antero-posterior and medio-lateral forces, trajectory of net COP and the timing ratio of reaching the each events were shown variously. So, it is not easy to explain these variables clearly. As the result of strength training, these variables were changed. However, the results of within subjects differ greatly, there was no difference statistically.

• Spatial Information Research
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• v.23 no.4
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• pp.47-56
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• 2015

Recently, there has been an increase in the number of people who use the smart-phone navigation for using various latest functions such as group driving and location sharing. But smart-phone has a limited storage space for one application, since a lot of applications with different purposes are installed in the smart-phone. For this reason, road network data with a large space of memory used for map matching in the device for navigation cannot be stored in the smart-phone for this reason map matching is impossible. Besides, smart-phone which doesn't use the external GPS device, provides inaccurate GPS information, compared to the device for navigation. This is why the smart-phone navigation is hard to provide accurate location determination. Therefore, this study aims to help map matching that is more accurate than the existing device for navigation, by reducing the capacity of road network data used in the device for navigation through format design of a new road network and conversion and using a database of driver's driving patterns. In conclusion, more accurate map matching was possible in the smart-phone by using a storage space more than 80% less than existing device at the intersection where many roads cross, the building forest that a lot of GPS errors occur, the narrow roads close to the highway. It is considered that more accurate location-based service would be available not only in the navigation but also in various applications using GPS information and map in the future Navigation.