• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.396-403
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• 1999

This experimental study investigates the hysterestic behavior of traditional timber frames subjected to lateral loads. Prototype frames for this study were selected from one of typical national treasures for timber structures in Korea. For simplicity roof structures and braket systems were excluded from specimens and the joint behavior of beam-to-column system were presumed to have crucial effect on their global behavior. The experimental observation showed stiffness degradation and slip after experiencing initial yield and the first cycle at a new larger displacement due to inherent gaps in traditional timber connection and gradual indentation of interfaces, The cyclic behaviors of all specimens were similar to those os modern timber frames with bolt and nail connections. Additional structural members such as an upper beam and clay-filled wall increased the initial stiffness strength and energy dissipation. It is expected that collapse of Korean traditional timber frames under lateral load is mainly caused from P-$\Delta$ effects rather than local member failure.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.95-105
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• 2012

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia ($NH_3$) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and $NH_3$ slip reduction in the SCR system. This paper investigated NOx and $NH_3$ emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and $O_2$ for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate $NH_3$ absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.174-182
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• 2014

Recently, not only common types of hybrid electric vehicle (HEV) such as series or parallel but many other types of HEVs including 4WD hybrid electric vehicle have been developed and released. In this study, analysis of fuel economy and driving performance for 2WD and 4WD HEV are conducted using backward simulation based on dynamic programming. To analyze the characteristics of 4WD HEV, tire slip model based on vehicle dynamics was applied to the backward simulation program. As a result, 2WD HEV shows better fuel economy than 4WD HEV because of relatively simple configuration. However, in a severe road condition, 4WD HEV shows better driving performance that 2WD HEV had about 6% of impossible time to follow the driving cycle though the 4WD HEV had no impossible time.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.632-639
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• 2010

Ground Transportation is one of the most required field that users need positioning information Especially, more precise position can make smart traffic management possible and bring convenience to users. By advanced wireless network, cars can receive the GPS information of reference station in any tim e and any where. Thus land vehicles are possible to process precise positioning. In general, for precise positioning code and phase measurements are used. But receivers provide not only code and phase measurements but also doppler measurements and Doppler is direct measurement of velocity. In this paper, because velocity is very important information required in Ground Transportation, precise positioning for Ground Transportation is studied. For precise positioning RTK(Real-Time Kinematic) was used and double differenced doppler measurements were added, As a Result, positioning error by multipath and cycle slip was soften. However there still remained Positioning error. Thus smoothing technique using doppler measurement in position domain is used for softening positioning error.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.371-382
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• 2004

To improve the precision of relative positioning for GPS single frequency(L1) receiver, we accomplished the GPS data processing using the weighted smoothing techniques. The weighted phase smoothing technique is used to minimize the measurement error of pseudorange and position domain smoothing technique is adopted to make the complement of cycle-slip affection. we also considered some component errors like as ionospheric error, which are related with baseline length, and processed for several baselines (5, 10, 30, 40, and 150 km) to check the coverage area of this algorithm. This paper shows that weighted phase smoothing technique give more stable results after using this technique and the position domain smoothing technique can reduce the errors which are sensitive to the observational environment. Based on the results, we could find out that this algorithm is available for post-time and real-time applications and these techniques can be substitution methods which is able to get the high accuracy and precision without resolving the Integer ambiguity.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.201-211
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• 2019

The particle size and crystallinity of fault gouge generally decreases with slip. Phyllosilicates including talc are known to be present in fault gouge and play an important role in fault weakening. In particular, the coefficient of friction varies depending on the presence of a water molecule on the surface of mineral. The purpose of this study is to investigate the effect of talc on fault weakening by changing the water content and dehydration behavior of talc before and after grinding, which systematically varied particle size and crystallinity using high energy ball mill. Infrared spectroscopy and thermal analysis show that the as-received talc is hydrophobic before grinding and the water molecule is rarely present. After grinding up to 720 minutes, the particle size decreased to around 100 ~300 nm, and in talc, where amorphization proceeded, the water content increased by about 8 wt.% and water molecule would be attached on the surface of talc. As a result, the amount of vaporized water by heating increased after grinding. The dihydroxylation temperature also decreased by ${\sim}750^{\circ}C$ after 720 minutes of grinding at ${\sim}950^{\circ}C$ before grinding due to the decrease of particle size and crystallinity. These results indicate that the hydrophobicity of talc is changed to hydrophilic by grinding, and water molecules attached on the surface, which is thought to lower the coefficient of friction of phyllosilicates. The repeated slip throughout the seismic cycle would consistently lower the coefficient of friction of talc present in fault gouge, which could provide the clue to the weakening of matured fault.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.751-762
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• 2022

Welded head studs are mainly used as shear connectors to bond steel girders and concrete slabs in steel-concrete composite bridges. For welded shear connectors, environmental problems include noise and scattering dust which are generated during the removal of damaged or aged slabs. Therefore, it is necessary to develop demountable shear connectors that can easily replace aged concrete slabs for efficient maintenance and thus for better management of environmental problems and life cycle costs. The buried nut method is commonly studied in relation to bolted shear connectors, but this method is not used in civil structures such as bridges due to low rigidity, low shear resistance, and increased initial slip. In this study, in order to mitigate these problems, a demountable bolted shear connector is proposed in which the buried nut is integrated into the stud column and has a tapered shape at the bottom of an enlarged column shank. To verify the performance of the proposed demountable stud bolts in terms of static shear strength and slip displacement, a horizontal shear test was conducted, with the performance outcomes compared to those of conventional welded studs. It was confirmed that the proposed demountable bolted shear connector is capable of excellent shear performance and that it satisfies the slip displacement and ductility design criteria, meaning that it is feasible as a replacement for existing welding studs.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.353-356
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• 2005

In Taiwan, there are more the one hundred GPS tracking stations maintained by Ministry of the Interior (MOI), Academia Sinica, Central Weather Bureau and Central Geological Survey. In the further, they may be instead of the GPS controlling points after giving the lawful status. In other words, the engineers don't need to survey on the reference points when they are surveying in the field. They only need to download the GPS data via internet and process the observations in their company. The precise coordinates of the unknown points will be obtained. Therefore, the data qualities of the tracking stations are more and more important. In this study, six data quality indexes were adopted as follows: observations, cycle slips, multipath on L1, multipath on L2, clock offset and frequency stability. Besides, the relationships of the indexes and the positioning precision were found. The frequency stability of GPS receiver is the most important index, the cycle slip is the second index and the mutlipath is the third index. According to the results, the auto-analytical system of GPS data quality was established and the tracking stations were monitored. When the receiver got some problem or the station's environment changed, we hope to find and resolve the problems earlier to make sure the high data quality of the tracking stations. Moreover, we try to design a data quality verification to help users and let the engineers have more and more confidence when they use the data of GPS tracking stations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.4
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• pp.337-345
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• 2007

National Geographic Information Institute has installed the first permanent Global Positioning System (GPS) station SUWN in 1995 and, as of today, the number of sites is 14. In this study, we visited all the 14 stations and determined if the site mount and antenna configuration conforms to the international site guidelines published by International GNSS Service and National Geodetic Survey. The environment around each station was also checked for the possibility of causing positioning errors. In addition, the GPS data quality was evaluated using the quality-checking program called TEQC. As a result of site visits, we found that low stations (TABK, CHJU, KWNJ, and WNJU) have unfavorable environment and TEQC results validated it. TEQC results also showed that the GPS receiver change during years 2005-2006 reduced the multipath errors and the number of cycle slips at every station.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.549-557
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• 2019

In this paper, we focus on the real-time detection method of a seismic ionospheric disturbance using Global Navigation Satellite System (GNSS) signal. First, the monitor for the detection of the seismic ionospheric disturbance is studied based on the estimated ionospheric delay using the GNSS signals. And then, the threshold for the automatic detection is computed. Moreover, to discriminate the seismic ionospheric disturbance against the other ionospheric anomalies due to other error sources such as cycle slips, the signatures of the ionospheric perturbation caused by the seismic wave is investigated. Based on the observation, the detection strategy is proposed. Using GPS observations collected from the 47 permanent stations in South Korea and Japan, the proposed real-time detection method is evaluated.