• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.607-623
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• 2000

Major trends of ozone concentration variations in Korea were investigated by using observation data from around 100 stations for the period of 1991∼1997. In addition, important regulating those variations were inferred. Three measures such as the number of days exceeding 80ppb, the 95th percentile of daily maxima, and the annual average concentration were used for the analysis of multi-scale ozone concentration variations. Three areas in the southwest (Sosan, Mokpo, and Cheju) of which monitoring has been operated since 1995 showed the highest annual average concentrations over; this was noted because of the high annual average in the Yosu area in the early 1990s. Large increases in annual average concentrations were observed along the relatively cleaner areas connecting Kangnung and Kwangju(northeast to southwest), in contrast to polluted areas connecting Seoul and Pusan(northeast to southeast). Both the number of exceedance days and the daily maximum concentration were nearly constant in the Greater Seoul Area in spite of interannual flucturations associated with year-to-year changes in air temperature. Within the Greater Seoul Area, all three measures usually showed the same trend; they decreased in the middle and west and increased in the east and northeast. All three measures including the number of exceedance days increased largely at Sillim where the average concentration was high but no exceedance days were recorded in the early 1999s, Nationwide ozone concentration variations appear to be determined by the competitive influence of long-range transport and local urban emissions, Within the city including the Greater Seoul Area, changes in emission which accompany changes in population and in the number if vehicles ( in the process of urban development) were found to be important components of ozone concentration variations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.2
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• pp.254-259
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• 2008

Mesh WLANs, which consist of wireless mesh routers connecting each other in a mesh topology and self-operate after their autoconfiguration, have several advantages in convenience, swiftness and flexibility of deployment and operation over existing WLANs the expansions of which are done by connecting the APs with wires. However, many technical issues still remain to be solved. Among them, network performance degradations due to the interference between the adjacent hops in multi-hop mesh WLANs, and the reusability of the existing wireless network protocols are critical problems to be answered. This work evaluates the VoIP support performance of IEEE 802.11a/g-based mesh WLANs with multiple wireless interfaces with simulations. The results show that there exit an unfairness in VoIP packet delay performances among mobile routers located at different hops, and that although the capacity of the admitted calls can be increased by increasing the size of voice packet payload it is far less than the expected one. This suggests that the existing 802.11 MAC protocols have their limitation when applied in mesh networks and their enhancement or even a newer one nay be required.

• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.433-444
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• 2019

Shear studs are often used to connect steel girders and concrete deck to form a composite bridge system. The application of precast concrete deck to steel-concrete composite bridges can improve the strength of decks and reduce the shrinkage and creep effect on the long-term behavior of structures. How to ensure the connection between steel girders and concrete deck directly influences the composite behavior between steel girder and precast concrete deck as well as the behavior of the structure system. Compared with traditional multi-I girder systems, a twin-I girder composite bridge system is more simplified but may lead to additional requirements on the shear studs connecting steel girders and decks due to the larger girder spacing. Up to date, only very limited quantity of researches has been conducted regarding the behavior of shear studs on twin-I girder bridge systems. One convenient way for steel composite bridge system is to cast concrete deck in place with shear studs uniformly-distributed along the span direction. For steel composite bridge system using precast concrete deck, voids are included in the precast concrete deck segments, and they are casted with cast-in-place concrete after the concrete segments are erected. In this paper, several sets of push-out tests are conducted, which are used to investigate the heavier of shear studs within the voids in the precast concrete deck. The test data are analyzed and compared with those from finite element models. A simplified shear stud model is proposed using a beam element instead of solid elements. It is used in the finite element model analyses of the twin-I girder composite bridge system to relieve the computational efforts of the shear studs. Additionally, a parametric study is developed to find the effects of void size, void spacing, and shear stud diameter and spacing. Finally, the recommendations are given for the design of precast deck using void for twin I-girder bridge systems.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.3
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• pp.179-184
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• 2022

In this paper, we are going to study how we can automatically determine the number of convolutional filters for the optimal model without a search algorithm. This paper proposes HSE Block by connecting SE Block proposed in SENet to a convolutional neural network and connecting a convolutional neural network not learned at the bottom. An experiment was conducted to increase the number of filters by one per 3 epoch using two datasets for the HSEBlock model and to increase the number of filters by the value in the filter. Based on this experiment, the model was constructed with multi-layer HSE Block instead of layer HSE Block, and the experiment was carried out using a dataset that was more difficult to learn than the one used in the previous experiment. The effect of HSE Block was verified by conducting an experiment with the number of HSE Blocks set to 2, 3, 4, and 5 on a dataset that is more difficult to learn than before.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.1
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• pp.75-85
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• 2014

Existing car-sharing systems have difficulty meeting the demands of one-way trips and connecting to other sharing systems. Therefore, in this study, a multi-mobility sharing service management system that was able to meet the demands of the one-way and round-way trips and shared diverse transportation modes such as cars (electric car/gasoline car), electric motorcycles and bicycles was developed, and a field study was conducted in Kashiwa-no-ha, Kashiwa City and Nagareyama City, Chiba Prefecture, Japan. As a result of the field test, it was confirmed that this system supplied the one-way demands for 54.9% of total car trips and 43.9% of the user used multiple transportation modes by the common interface. In addition, this system contributed to reduce carbon dioxide emissions by sharing vehicles and using eco-friendly vehicles. The developed sharing system is expected to improve mobility by meeting more various types of traffic demand than existing car sharing systems.

• Steel and Composite Structures
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• v.27 no.1
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• pp.75-87
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• 2018

This paper presents a new method to compute the shear strength of composited structural B-C-W members. These B-C-W members, defined as concrete-filled steel box beams, columns and shear walls, consist of a slender rectangular steel plate box filled with concrete and inserted steel plates connecting the two long-side steel plates. These structural elements are intended to be used in structural members of super-tall buildings and nuclear safety-related structures. The concrete confined by the steel plate acts to be in a multi-axial stressed state: therefore, its shear strength was calculated on the basis of a concrete's failure criterion model. The shear strength of the steel plates on the long sides of the structural element was computed using the von Mises plastic strength theory without taking into account the buckling of the steel plate. The spacing and strength of the inserted plates to induce plate yielding before buckling was determined using elastic plate theory. Therefore, a predictive method to compute the shear strength of composited structural B-C-W members without considering the shear span ratio was obtained. A coefficient considering the influence of the shear span ratio was introduced into the formula to compute the anti-lateral bearing capacity of composited structural B-C-W members. Comparisons were made between the numerical results and the test results along with this method to predict the anti-lateral bearing capacity of concrete-filled steel box walls. Nonlinear static analysis of concrete-filled steel box walls was also conducted by using ABAQUS and the results agreed well with the experimental data.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.8
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• pp.54-60
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• 2008

The bus architecture consists of a master initiating a communication transaction, a slave responding to the transaction, a arbiter selecting a master, a bridge connecting buses and so on. Recently this is more complicated and developed toward multi-bus architecture. In this paper, several cases of multi-shared bus architecture are discussed and in order to decrease the bridge latency, the architecture introducing a memory selector is proposed. Finally, a LCD controller using DMA master is integrated in this bus architecture that is verified due to RTL simulation and FPGA board test. DMA, LCD line buffer and SDRAM controller are normally operated in the timing simulation using ModelSim tool, and the LCD image is confirmed in the real FPGA board containing LCD panel.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.106-113
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• 2017

In this paper, we propose a suitable network topology for the Ethernet based Train Communication Network (TCN) for control system in a autonomous multi-articulated vehicle. We propose a network topology considering the structural constraints such as the number of cables and ports, and the performance constraints such as network response time and maximum throughput. We compare the network performances of star topology and daisy chain topology as well as hybrid topology, which is proposed in previous studies and a compromise between daisy chain and star topology. Here, the appropriate number of nodes in a group is obtained for the configuration of the hybrid topology. We first derive estimates of the network performance through simulation with different topologies, and then, implement the network by connecting the actual devices with each network topology. The performance of each topology is measured using various network performance measurement programs and the superiority of the proposed topology is described through comparison.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.5
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• pp.89-106
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• 2020

This study examines the functionality and landscape design specifics of the outdoor space of representative commercial multi-complexes in Korea in order to overview the design trends of outdoor landscaping trends. Through surveying the composition of outdoor spaces along with their relation to the surrounding landscape, open spaces, and the neighboring communities, this paper identified the change in trends regarding the characteristics of outdoor landscape planning and acknowledged the enhanced public value of outdoor space. This study asserts that the characteristics of outdoor spaces can best be understood by examining the ways in which the outdoor space relates to adjoining commercial multi-complexes and the surrounding landscape. Focusing on the relationships that outdoor space establishes, commercial multi-complexes can be categorized as follows: in/outdoor separated type, in/outdoor semi-open type, surrounding landscape-projected type, and surrounding landscape-combined type. By studying the landscape design specifics of the outdoor space of representative cases of each type, the following has been concluded: First, the amount of outdoor space has expanded in terms of importance and function while serving to assist in various activities and participatory experiences, and no longer merely serves as a backdrop of commercial facilities. Second, with the strengthened connectivity between in/outdoor spaces, the elements of outdoor surroundings are more actively introduced indoors to improve amenities. Through directly connecting certain indoor program spaces with outdoor spaces, commercial multi-complexes tend to provide richer combined experiences. Third, with the expansion of outdoor space functionality, commercial multi-complexes are increasingly recognized as a quasi-public space, making good example of liminal space. In light of the recent case of development plans linked with public open spaces in suburban settings, commercial landscape design shows the possibility of creating an open space that can function as a center for local culture and green networks in the community.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.235-243
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• 2019

Recently, urban inundation was frequently occurred due to the intensive rainfall exceeding marginal capacity of the flood control facility. Furthermore, needs for the underground storage facilities to mitigate urban flood are increasing according to rapidly accelerating urbanization. Thus, in this study, drainage efficiency in drain tunnel connecting to underground storage was investigated from the air-core measurements in the drop shaft against two types of inlet structure. In case of the spiral inlet, the multi-stage structure is introduced at the bottom of the inlet to improve the vortex induction effect at low inflow discharge (multi-stage spiral inlet). The average cross-sectional area of the air-core in the multi-stage spiral inlet is 10% larger than the tangential inlet, and show the highly air emission effect and the highly inflow efficiency at the high inflow discharge. In case of the tangential inlets, the air emission effect decreased after exceeding the maximum inflow discharge, which is required to maintain the inherent performance of the tangential inlet. From the measurements, the empirical formula for the cross-sectional area of the air-core according to locations inside the drop shaft was proposed in order to provide the experimental data available for the inlet model used in experiments.