• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.45-51
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• 2005

The distribution of shaft resistance is measured by the static load test with the strain gauge or stress gauge, so that the long-term load distribution must be considered for the pile design. However, the measurement by strain gauge generally assumes the 'zero reading', which is the reading taken at 'zero time' with 'zero' load and the residual stress, which is the negative skin friction(or the negative shaft resistance) caused by the pile construction, is neglected. Therefore, the measured value by strain gauge is different from the true load-distribution because residual stresses were neglected. In this study, the three drilled shafts were constructed, and the strain measurements were carried out just after shaft construction. As a result of this study, it is shown that the true load-distribution of drilled shaft is quite different with known load distribution and the true load-distribution of drilled shaft changed from the negative skin friction to the positive skin according to the load increment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.29-34
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• 2011

In this paper, we propose and analyze the equalizer schemes, zero-forcing (ZF) and minimum mean square error (MMSE) in power line communication (PLC) system for automatic meter reading (AMR). For efficient implementation of AMR system with PLC, effects of impulsive noise and multipath channel should be mitigated. To overcome these effects, the above equalizer schemes are employed. System performance is evaluated in term of bit error rate. From simulation results, it is confirmed that the equalizer can significantly improve bit error rate (BER) performance in PLC system, and MMSE equalizer provides better performance than ZF scheme. The results of this paper can be applied to AMR system as well as various smart grid services using PLC.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.214-220
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• 2012

Deformation behaviour of rock mass around an opening measured during tunnel excavation is very important in order to assess the stability of the tunnel. Unfortunately displacement measured only after the installation of displacement measuring device can be acquired, which results in inevitably excluding the pre-displacement occurred and accumulated before the displacement measuring devices are installed. So it is very important to consider the pre-displacement based on the elapsed time before zero reading after deformation behaviour started. In this study, the accuracy of total estimated displacement depending on the distance between face and measurement position is calculated by statistical non-linear fitting on measurable displacement data. Besides, the influence of the unavoidable measurement error is considered by using Monte-Carlo simulation. As a result, the faster the initial reading started and the smaller the measurement error is, the higher the accuracy of estimating total displacement is obtained.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.587-590
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• 2005

We investigated the input impedance characteristics of UHF-band RFID tag chip for increased reading range. A voltage multiplier designed using 0.4 ${\mu}m$ $zero-V_T$ MOSFET showed that DC output voltage of 2 V can be obtained using standard CMOS process. The input impedance of the voltage multiplier was examined to achieve impedance level for maximum reading distance using analytical and numerical approaches. The input impedance of the voltage multiplier could be varied in a wide range by selecting the size of MOSFET and the number of multiplying stages of the voltage multiplier, and thus, the impedance level required for the tag antenna can be obtained in presence of other tag circuit blocks.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.361-367
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• 2009

The criteria such as ASTM recommends that the zero reading process of CPT must be performed in the same temperature condition with underground in order to reduce the effect of temperature. However, this method can not consider the change of temperature occurred during penetration. In this study, ultra small size temperature sensor with 0.5mm in diameter is manufactured to estimate and compensate the effect of temperature by using FBG sensor. The continuous temperature changes are monitored during cone penetration by using FBG temperature sensor installed in cone penetrometer. The temperature compensated tip resistances show the uniform and similar distributions with depth in different with originally measured tip resistance in cohesive soil. This study verifies that the tip resistances measured by previous zero reading method are affected by the change of underground temperature, and suggests the new temperature compensation technique using by FBG temperature sensor.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.279-284
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• 2005

We investigated the impedance matching characteristics of UHF-band RFID tag antenna and tag chip for increased reading range. A voltage multiplier designed using 0.4 $\mu$m zero-$V_T$ MOSFET showed that DC output voltage of about 2 V can be obtained using standard CMOS process. The input impedance of the voltage multiplier was examined to achieve impedance matching to the RFID tag antenna using analytical and numerical approaches. The input impedance of the voltage multiplier could be varied in a wide range by selecting the size of MOSFET and the number of multiplying stages, and thus can be impedance matched to a tag antenna in presence of other tag circuit blocks. A meander line inductively-coupled RFID tag antenna operating at UHF band also shows the feasibility of impedance matching to tile RFID tag chip.

• Journal of The Korean Association For Science Education
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• v.17 no.2
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• pp.127-137
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• 1997

The purpose of this study was to assess elementary student's ability of measuring length, area, and volume and reading metric scales. The findings of this study were as follows. All students were successful in measuring without scale, regardless of grades. But they were less successful in measuring the task using standard and nonstandard scales. Especially, in measuring area, lower grade students were not able to perform the task using nonstandard instruments, but higher grade students were able to perform the task. Measuring area using grade paper was least successful for sixth graders. In measuring volume, students under fifth grade read the upper scale when using graduated cylinder. In measuring by direct comparison, students were more successful in measuring length than in measuring area and volume using given material. The use of given nonstandard material was successful for 4th, 5th, and 6th grade students. In measuring using metric scale, lower grade students did not pay attention to the zero of the scale, but just read the end point. Higher grade students considered both zero and end points.

• Journal of IKEEE
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• v.8 no.2 s.15
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• pp.195-206
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• 2004

In an RFID system, it is desirable to have both the reader and the transponder tuned to the same resonant frequency for efficient data transmission between them. Any difference in frequency will decrease the transponder coil voltage or the internal power supply voltage and will increase the possibility of zero modulation in the reader coil, which results in the reduction of the reading distance. In this paper, the phenomena caused by the frequency mismatch are theoretically analyzed and mathematically modelled. Several schemes to compensate for the frequency mismatch are also mentioned. The derived equations and analyzed theory on the data transmission between the reader and the transponder will be helpful to the development of RFID systems for many applications.

• Journal of The Korean Association For Science Education
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• v.19 no.3
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• pp.367-376
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• 1999

When 37 7th-graders learned science in cooperative learning environments, their small-group processes were audio/video taped. The verbal behaviors that appeared in cooperative learning processes were categorized, and the relationships between verbal behaviors and academic achievement were investigated. Students' verbal behaviors were classified into learning behaviors and management behaviors. Learning behaviors were further coded into giving help. reading problem, and asking help. Giving help was the most frequent behavior among the categories. In studying zero-order correlation between verbal behaviors and academic achievement, giving help and reading problem were found to have positive relationships with academic achievement. Giving specific content, which is a subcategory of giving help. showed the closest correlation with academic achievement. In studying partial correlation between verbal behaviors and the improvement of academic achievement, only application subtest score. which demands higher-order thinking, was positively related with some verbal behaviors including giving specific content.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.619-628
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• 2012

The ZigBee network has been considered to monitor electricity usage of home appliances in the smart grid network. ZigBee, however, may suffer from a coexistence problem with wireless local area network (WLAN). In this paper, to resolve the coexistence problem between ZigBee network and WLAN, we propose a new protocol constructing a cognitive smart grid network for supporting monitoring of home appliances. In the proposed protocol, home appliances first estimates the transmission timing and channel information of WLAN by reading request to send/clear to send (RTS/CTS) frames of WLAN. Next, based on the estimated information, home appliances transmit a data at the same time as WLAN transmission. To manage the interference between WLAN and smart grid network, we propose a cognitive beamforming algorithm. The beamforming algorithm is designed to guaranteeing zero interference to WLAN while satisfying a required rate for smart metering. We also propose an energy efficient rate adaptation algorithm. By slowing down the transmission rate while satisfying an imperceptible impact of quality of service (QoS) of the receiver, the home appliance can significantly save transmit power. Numerical results show that the proposed multiple antenna technique provides reliable communications for smart metering with reduced power comparing to the simple transmission technique.