• Journal of the Korean Geophysical Society
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• v.3 no.1
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• pp.1-12
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• 2000

A palaeomagnetic study was carried out on Early through Late Cretaceous sandstones and volcanic sequences (the Songnaedong Formation, Chaeyaksan Volcanics, Konchonri Formation, and Jusasan Andesite it ascending order) from Konchonri area in the northern Milyang subbasin of the Kyongsang Basin, Korea. A high-temperature stable remanence with direction of $d=22.9^{\circ},\;i=59.1^{\circ}\;({\alpha}_{95}=3.0^{\circ})$ has been isolated and a corresponding pole was $71.6^{\circ}N,\;199.6^{\circ}E\;(A_{95}=4.2^{\circ})$. The characteristic high-temperature component resides in both hematite and magnetite. The primary nature of this remanence is confirmed from positive fold and reversals tests, The palaeopole is consistent with those of the Hayang Group in other parts of the Kyongsang Basin. A comparison of the palaeomagnetic pole position from the studied area with the contemporary pole from China west of the Tan-Lu fault presents that Konchonri area has experienced little latitudinal displacement nor vertical-axis block rotation relative to the Chinese blocks since the Cretaceous. Based on the formations indicating dual polarity, radiometric and paleontologic data, the magnetostratigraphic age of the studied sequence from the Songnedong Formation to the Jusasan Andesite ranges from upper Albian to lower Campanian reverse polarity chronozone. On the other hand, volcanic samples of the Chaeyaksan Volcanics and the Jusasan Andesite showed the scattered directions considered in group, even though individual sample showed a stable remanent magnetization in response to thermal demagnetization. It indicates that they have been reworked after acquisition of the stable remanent magnetization.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.7-17
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• 2006

In this paper, we proposed an optical true time-delay (TTD) for planar phased array antennas (PAAs), which is composed of a wavelength-dependent optical true time delay (WDOTTD) followed by a wavelength-independent optical true time delay (WIOTTD). The WDOTTD is a fiber Bragg gratings (FBGs) Prism and the WDOTTD is a fiber delay-lines matrix of which each component consists of a certain length of fiber connected to cross-ports of a 2${\times}$2 MEMS switch. A 10-GHz 2-bit${\times}$4-bit two-dimensional optical TTD has been fabricated by cascading a WDOTTD with a maximum time delay of 810 ps to a WIOTTD of $\pm$50 ps. Time delay and insertion loss for each radiation angle have been measured. Time delay error for the WIOTTD has been measured to be less than $\pm$1 ps. We have also designed a two-dimensional 10-GHz PAA composed of 8${\times}$8 microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation and analyzed.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.94-98
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• 2006

An optical microphone based on a dual-core fiber collimator and a membrane type micromirror serving as an optical head and a reflective diaphragm respectively was implemented. The micromirror diaphragm is suspended by a thin silicon bar linked with a frame, thus it is subject to a displacement induced by acoustic waves. The optical head incorporating two collimators integrated in a single housing gives light to and receives it from the diaphragm, rendering the optical microphone structure simple and compact. This dual-core collimator having a slowing varying beam profile facilitates the initial alignment of the optical head with the diaphragm, especially the distance between them. For the assembled microphone, the static characteristics were investigated tofind the operation point defined as the optimum distance between the head and the diaphragm, and a frequency response with a variation of about $\pm$5 dB for the range of up to 3kHz was achieved.

• Journal of Korean Society of Transportation
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• v.20 no.4
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• pp.151-162
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• 2002

The object of this study is to develop an operating time prediction model for expressways using toll collection data. A Prediction model based on modular neural network model was developed and tested using real data. Two toll collection system(TCS) data set. Seoul-Suwon section for short range and Seoul-Daejeon section for long range, in Kyongbu expressway line were collected and analyzed. A time series analysis on TCS data indicated that operating times on both ranges are in reasonable prediction ranges. It was also found that prediction for the long section was more complex than that for the short section. However, a long term prediction for the short section turned out to be more difficult than that for the long section because of the higher sensitivity to initial condition. An application of the suggested model produced accurate prediction time. The features of suggested prediction model are in the requirement of minimum (3) input layers and in the ability of stable operating time prediction.

• Journal of Korean Society of Transportation
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• v.33 no.5
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• pp.497-507
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• 2015

Nonrecurrent congestion of freeway was primarily caused by incident. The main cause of incident was known as a traffic accident. Therefore, accurate prediction of traffic incident clearance time is very important in accident management. Traffic accident data on freeway during year 2008 to year 2014 period were analyzed for this study. KNN(K-Nearest Neighbor) algorithm was hired for developing incident clearance time prediction model with the historical traffic accident data. Analysis result of accident data explains the level of accident significantly affect on the incident clearance time. For this reason, incident clearance time was categorized by accident level. Data were sorted by classification of traffic volume, number of lanes and time periods to consider traffic conditions and roadway geometry. Factors affecting incident clearance time were analyzed from the extracted data for identifying similar types of accident. Lastly, weight of detail factors was calculated in order to measure distance metric. Weight was calculated with applying standard method of normal distribution, then incident clearance time was predicted. Prediction result of model showed a lower prediction error(MAPE) than models of previous studies. The improve model developed in this study is expected to contribute to the efficient highway operation management when incident occurs.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.3
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• pp.214-224
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• 2004

A large cage system for the purpose of fishes farming in the open sea was influenced by various forces from the ocean environment. The deformation of the cage by these forces affects the safety of the cage itself, as well as that of the cultivated creatures. In this research, theoretical model was established to analyzing dynamic movement influenced by current for cage. Also, to increase the accuracy of calculations, the reduction ratio of flow speed acquired using the flume tank experiment. Applying the reduction ratio of flow speed to the numerical calculation, the calculation values were compared with the measured values in the flume tank experiment using cage model. The results were as follows ; 1. When the flow speed of the flume tank is fixed, the decrease of the velocity of flow which is passed the upper panel side is proportion to the increase of porosity ratio of netting. 2. When the porosity ratio is fixed, the increase of the velocity of flow which is passed the upper panel side is proportion to the increase of velocity of flow. 3. When the porosity ratio and the flow speed of the flume tank are fixed, the decrease of the velocity of flow which is passed the upper panel side is proportion to the increase of attack angle. 4. As a result of comparison between the underwater shape by simulation which is applying the reduction ratio of flow speed from the experiment using plane netting and that by model experiment, it was found out that the result of the simulation was very close to that of model gear within ${\pm}$ 5 % error range.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.1-8
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• 2005

In this paper, CMOS A/D converter with 6bit 2GSPS Nyquist input at 1.8V is designed. In order to obtain the resolution of 6bit and the character of high-speed operation, we present an Interpolation type architecture. In order to overcome the problems of high speed operation, a novel One-zero Detecting Encoder, a circuit to reduce the Reference Fluctuation, an Averaging Resistor and a Track & Hold, a novel Buffered Reference for the improved SNR are proposed. The proposed ADC is based on 0.18um 1-poly 3-metal N-well CMOS technology, and it consumes 145mW at 1.8V power supply and occupies chip area of 977um $\times$ 1040um. Experimental result show that SNDR is 36.25 dB when sampling frequency is 2GHz and INL/DNL is $\pm$0.5LSB at static performance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.9
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• pp.31-39
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• 2011

In this paper, we propose a signal readout system with small area and low power consumption for CNT sensor arrays. The proposed system consists of signal readout circuitry, a digital controller, and UART I/O. The key components of the signal readout circuitry are 64 transimpedance amplifiers (TIA) and SAR-ADC with 11-bit resolution. The TIA adopts an active input current mirror (AICM) for voltage biasing and current amplification of a sensor. The proposed architecture can reduce area and power without sampling rate degradation because the 64 TIAs share a variable gain amplifier (VGA) which needs large area and high power due to resistive feedback. In addition, the SAR-ADC is designed for low power with modified algorithm where the operation of the lower bits can be skipped according to an input voltage level. The operation of ADC is controlled by a digital controller based on UART protocol. The data of ADC can be monitored on a computer terminal. The signal readout circuitry was designed with 0.13${\mu}m$ CMOS technology. It occupies the area of 0.173 $mm^2$ and consumes 77.06${\mu}W$ at the conversion rate of 640 samples/s. According to measurement, the linearity error is under 5.3% in the input sensing current range of 10nA - 10${\mu}A$. The UART I/O and the digital controller were designed with 0.18${\mu}m$ CMOS technology and their area is 0.251 $mm^2$.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.77-87
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• 2004

In this paper a back-propagation neural network model is developed to estimate the preconsolidation pressure of Korean soft soils based on 176 oedometer tests and 63 piezocone test results, which were compiled from 11 sites - western and southern parts of Korea. Only 147 data were used for the training of the neural network and 29 data, which were not used during the training phase, were used for the verification of trained network. Empirical and theoretical models were compared with the developed neural network model. A simple 4-4-9-1 multi-layered neural network has been developed. The cone tip resistance $q_T$ penetration pore pressure $u_2$, total overburden pressure $\sigma_{vo}$ and effective overburden pressure $\sigma'_{vo}$ were selected as input variables. The developed neural network model was validated by comparing the prediction results of the proposed neural network model for the new data which were not used for the training of the model with the measured preconsolidation pressures. It can also predict more precise and reliable preconsolidation pressures than the analytical and empirical model. Furthermore, it can be carefully concluded that neural network model can be used as a generalized model for prediction of preconsolidation pressure throughout Korea since developed model shows good performance for the new data which were not used in both training and testing data.

• Journal of Korean Society of Forest Science
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• v.98 no.6
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• pp.696-702
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• 2009

Yellow poplar (Liriodendron tulipifera L.) is an insect-pollinated tree species with large, perfect flower, and its seed sets average only about 10 percent naturally. In its controlled pollination, pollination bags are usually taken to prevent unwanted pollination, but bagging is an expensive and time-consuming process. Therefore, this study was conducted to determine the need of pollination bag by estimating how much unintended pollination would occur when different cross methods were applied. Five different pollination methods were applied as follows: 1) natural open pollination (i.e. insect pollination) as a reference, 2) self-pollination; no removing reproductive organs with bagging, 3) open pollination; emasculated(removing sepal, petal and stamen) without bagging, 4) controlled pollination; emasculated with bagging and 5) controlled pollination; emasculated without bagging. Very low value of full seed rate (0.2%) was observed in method 3, it was suggested that removing stamen and petal restrict the activity of pollen vectors like bee. Difference in the full seed rate between method 4 and method 5 was not significant (27.9% versus 24.0%, respectively). Consequently, controlled pollination without bagging might be an alternative method for extensive breeding and mass production of seeds in yellow poplar.