• Journal of the Korean Geotechnical Society
• /
• v.21 no.8
• /
• pp.107-116
• /
• 2005

Generally, when the stability of the geosynthetic reinforced soil slopes is analyzed, the required tensile forces of each reinforcement layers are calculated from total reinforcement forces which are necessary to retain the equilibrium state of slip mass in which the slip surfaces are assumed to be a linear or bilinear. It is assumed that the reinforcement forces are increased or constant with depth. However, according to the instrumented field data and laboratory model test results, the maximum tensile strain of reinforcement in a reinforced soil slope is developed in a certain elevation, not a bottom of the slope. In the concept of reinforced soil, postulated failure surfaces are the traces of the position in which the reinforcement tensile forces are maximum in the layer, and the reinforcement tensile forces are related to the stress state on the postulated failure surface. Therefore, in this study, based on the distribution of normal stress on the slip surface, a new method for the evaluation of required tensile forces is suggested and a number of the instrumented field data are analyzed by newly suggested method. As a result, it is shown that the newly suggested method produces relatively accurate reinforcement tension forces.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2015.10a
• /
• pp.969-972
• /
• 2015

Many studies have been carried out in order to develop a frequency efficient communication system than the current communication system for satisfying the increasing demands of wireless data services in mobile communication systems. If a communication system dramatically improving the frequency utilization efficiency is not developed, service providers must maintain more number of base station equipments to meet the increasing demands of wireless data service. Service provider needs a system or method to reduce maintenance costs. Demands of wireless data service are changed according to time of day, location and so on. Power consumption can be reduced if the supplied power of communication systems is controlled by wireless data traffics. This paper describes the design and implementation of power management system of mobile communication base station's equipment based on smart grid. The proposed power management system controls the supplied power to the mobile communication infrastructures depending on the demand of wireless data. Field test results of the implemented system show the proposed system saves 26% of the power consumption in the base stations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.6
• /
• pp.457-465
• /
• 2014

This paper introduces a test bed for communication protocol schemes of underwater acoustic sensor network, and also shows experimental results obtained from the test bed. As a testing protocol, carrier sense multiple access/collision avoidance (CSMA/CA) is evaluated on underwater acoustic channel. A sensor node is equipped with a DSP control board of ATmega2560 and a commercial underwater modem produced by Benthos. The control board not only manipulates a GPS signal to acquire the information of location and time, but also controls the underwater modem to operate according to the procedure designed for a given testing protocol. Whenever any event takes place such as exchanging control/data packets between underwater modems and acquiring location and timing information, each sensor node reports them through radio frequency (RF) air interface to a central station located on the ground. The four kinds of packets for CSMA/CA, RTS(Request To Send), CTS(Clear to Send), DATA, ACK(Acknowledgement) are designed according to the underwater communication environment and are analyzed through the lake experiment from the point of feasibility of CSMA/CA in underwater acoustic communications.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.6
• /
• pp.999-1012
• /
• 2017

Theoretical, empirical and numerical methods are used to evaluate the rock load due to tunnelling. Theoretical and empirical methods do not consider ground conditions, tunnel shape, and construction conditions. However, through numerical analysis, it is possible to analyze the displacement and stresses around tunnel due to its excavation, and evaluate the rock load considering ground and construction conditions. The stress transfer ratio(e) which is defined as a ratio of the difference between the major and minor principal stresses to major principal stress is used in order to understand the stress transfer effect around the tunnel excavation using numerical analysis results. The loosend area around tunnel periphery was found based on this approach. The difference of rock load from stress transfer effect was found according to the ground grade. From comparison, rock load obtained from stress transfer effect (e = 10%) were somewhat larger than the results obtained from the critical strain method, but smaller than those obtained from theoretical and empirical methods. The stress transfer effect approach considers the ground condition, tunnel shape; therefore, it can be applied to evaluate the rock load in concrete lining design.

• Korean Journal of Environment and Ecology
• /
• v.10 no.1
• /
• pp.66-75
• /
• 1996

To propose basic information for national resource management and planting disign, plant community structure of evergreen broad-leaved forest was investigated. Fifty-two plots(each size 300m$^{2}$) were set up at Ch'omch'alsan area of Chindo, Korea. TWINSPAN and DCA methods were used for classification and ordination analysis. Fifty-two plots were divided into seven groups, which were Quercus variabilis-Carpinus tschonoskii community, Q. glauca community, Castanepsis cuspidata var. sieboldii-Q. stenophylla community, Castanopsis cuspidata var. sieboldii-Camelia japonica community, Q. acuta-Camelia japonica community, Carpinus coreaca-Q spp. community, C. coreana community. Pinus densiflora almost have been selected. Carpinus tschomoskii, Q. variabillis and Q. serrata were to be succeeded by Castanea cuspidata var. sieboldii, Q. stenophylla, Q. acuta and Neolitsea sericea in canopy layer. And Neolitsea sericea, Q. glauca and Camellia japonica was showed high importance values in fertile soil condition. Future restoration plan was necessary for a tourist resort or national forest in warm temperate region. And evergreen broad-leaved plants shall be planted in considering of environmental condition at warm temperate and industrial complex area.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.13 no.4
• /
• pp.1-13
• /
• 2009

Liquefaction is a significant threat to structures on loose saturated sandy soil deposits in the event of an earthquake, and can often cause catastrophic damage, economic loss, and loss of life. Nevertheless, the Korean peninsula has for a long time been recognized as a safe region with respect to the hazard of liquefaction, as the peninsula is located in a moderate seismicity region, and there have been no reports of liquefaction, with the exception of references in some historical documents. However, some earthquakes that have recently occurred in different parts of the world have led to liquefaction in non-plastic silty soils, a soil type that can be found in many of the western coastal areas of Korea. In this study, we first present procedures for evaluating the liquefaction potential, and calculate the liquefaction potential index (LPI) distribution at two western coastal sites using both piezocone penetration test (CPTu) data and standard penetration test (SPT) data. The LPI is computed by integrating liquefaction potential over a depth of 20m, and provides an estimate of liquefaction-related surface damage. In addition, we compared the LPI values obtained from CPTu and SPT, respectively. Our research found that the CRR values from CPTu were lower than those from the SPT, particularly in the range between 40 and 120 for the corrected tip resistance, (qc1N)CS, from the CPTu, or in the range of CRR less than 0.23, resulting in relatively high LPI values. Moreover, it was observed that the differences in the CRR between the two methods were relatively higher for soils with high fine contents.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.5
• /
• pp.19-35
• /
• 2018

The necessity of predicting the spatial information of the site-specific seismic response, which is essential information for the comprehensive earthquake disaster countermeasures, is increasing for the mid-west urban areas where the earthquake-induced damages can be increased due to frequent occurrence of mid-scale earthquake such as 2016 Gyeongju Earthquake and 2017 Pohang Earthquake. Especially, researches on strategic securing of site survey datasets and understanding the site-specific site response characteristics were conducted for Gyeonggi-do, South Korea. In this study, a GIS-based framework for site-specific assessment of site response and induced vulnerable area in Gyeonggi-do, South Korea was proposed. Geo-Data based on GIS platform was constructed for regional estimation of geotechnical characteristics by collecting borehole and land coverage datasets. And the geo-spatial grid information was developed for deriving spatial distribution of geotechnical layer and site response parameters based on the optimization of the geostatistical interpolation method. Accordingly, base information for Improving earthquake preparedness measures was derived as seismic zonation map with administrative sub-units considering the quantitative site effect of Gyeonggi-do.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.11 s.114
• /
• pp.1050-1057
• /
• 2006

This paper proposes a new predistortion linearizer with amplitude modulator and PFG(Polar Function Generator) using second order harmonic signals. This linearizer consists of PFG that combine with in-phase and quadrature-phase of second harmonic signals and amplitude modulator in main path. The predistorted third order intermodulation distortion(IMD3) signals that are generated by amplitude modulator with fundamental and PFG signals, improve a amplifier nonlinear characteristics. The proposed linearizer and amplifier have been manufactured and tested to operate in cellular base-station transmitting band$(869\sim894MHz)$. The test results show that IMD3 can be removed by more than 22.5 dB in case of CW 2-tone signals ${\Delta}f=1$ MHz, and the adjacent channel power ratio(ACPR) also can be improved by more than 8.4 dB for CDMA IS-95 1FA signals.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.3
• /
• pp.554-561
• /
• 2017

IoT (Internet of Things) devices are often located in environments where indoor or underground, signals are difficult to reach. In addition, the transmission power is low, the base station should be designed to be able to receive signals even at low reception sensitivity. For this reason, a device having a poor channel condition can be transmitted at a low data rate using a low coding rate or repetition. When the coverage class is divided according to the channel condition and the data rate, the packet length may vary from one coverage class to another, and the performance of the slotted aloha random access may be degraded. We will focus on two methods of using shared-resource and seperate resources among multiple slotted aloha methods. In particular, when devices with different coverage classes use shared resources, performance of a device with a bad channel condition may deteriorate. Conversely, when using separate resources for each coverage class, there is a problem that congestion may occur which increases the number of devices that perform random access to one resource area. In this paper, we propose some methods to overcome this problem. This study is mainly focused on MTC devices, and is considered to be a high possibility of future development.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.11 no.5
• /
• pp.623-629
• /
• 2018

Smart Factory is a concept of automatic production system of machines by the fusion of ICT and manufacturing. As a base technology for realizing such a smart factory, there is an increasing interest in a low-power environmentally friendly LED lighting system, and researches on so-called optical ID related application technologies such as communication using a LED and position recognition are actively underway. In this paper, We have proposed a system that can reliably identify logistics location and additional information without being affected by electromagnetic interference such as high voltage, high current, and generator in the plant. Through the basic experiment, we confirmed the applicability of the color ID recognition rate from 98.8% to 93.8% according to the eight color variations in the short distance.