• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.9
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• pp.10-17
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• 2007

It opens a new horizon on spintronics for the potential application of MTJ as a universal logic element, to employ the magneto-logic in substitution for the transistor-based logic device. The magneto-logic based on the MTJ element shows many potential advantages, such as high density, and nonvolatility. Moreover, the MTJ element has programmability and can therefore realize the full logic functions just by changing the input signals. This magneto-logic using MTJ elements can embody the reconfigurable circuit to overcome the rigid architecture. The established magneto-logic element has been designed and fabricated on a triple-layer MTJ. We present a novel magneto-logic structure that consists of a single layer MTJ and a current driver, which requires less processing steps with enhanced functional flexibility and uniformity. A 4-bit gray counter is designed to verify the magneto-logic functionality of the proposed single-layer MTJ and the simulation results are presented with the HSPICE macro-model of MTJ that we have developed.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.253-263
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• 2016

Chrysanthemum production would benefit from crop growth simulations, which would support decision-making in crop management. Chrysanthemum is a typical short day plant of which floral initiation and development is sensitive to photoperiod. We developed a model to predict phenological development and leaf appearance of chrysanthemum (cv. Baekseon) using daylength (including civil twilight period), air temperature, and management options like light interruption and ethylene treatment as predictor variables. Chrysanthemum development stage (DVS) was divided into juvenile (DVS=1.0), juvenile to budding (DVS=1.33), and budding to flowering (DVS=2.0) phases for which different strategies and variables were used to predict the development toward the end of each phenophase. The juvenile phase was assumed to be completed at a certain leaf number which was estimated as 15.5 and increased by ethylene application to the mother plant before cutting and the transplanted plant after cutting. After juvenile phase, development rate (DVR) before budding and flowering were calculated from temperature and day length response functions, and budding and flowering were completed when the integrated DVR reached 1.33 and 2.0, respectively. In addition the model assumed that leaf appearance terminates just before budding. This model predicted budding date, flowering date, and leaf appearance with acceptable accuracy and precision not only for the calibration data set but also for the validation data set which are independent of the calibration data set.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.5-15
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• 2012

In this study, a series of CFD (Computational Fluid Dynamics) numerical analyses were performed in order to evaluate the thermal performance of six full-scale closed-loop vertical ground heat exchangers constructed in a test bed located in Wonju. The circulation HDPE pipe, borehole and surrounding ground formation were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the system. Two user-defined functions (UDFs) accounting for the difference in the temperatures of the circulating inflow and outflow fluid and the variation of the surrounding ground temperature with depth were adopted in the FLUENT model. The relevant thermal properties of materials measured in laboratory were used in the numerical analyses to compare the thermal efficiency of various types of the heat exchangers installed in the test bed. The simulation results provide a verification for the in-situ thermal response test (TRT) data. The CFD numerical back-analysis with the ground thermal conductivity of 4 W/mK yielded better agreement with the in-situ thermal response tests than with the ground thermal conductivity of 3 W/mK.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10C
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• pp.967-983
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• 2003

In wireless spread-spectrum communication systems utilizing PN (pseudo noise) sequences, a variety of noise sources from the channel affect the data reception performance. Among them, in this paper we are concerned with the narrowband interference that may arise from the use of the spectral bands overlapped by the existing narrowband users or the intentional jammers as in military communication. The effect of this interference can be reduced to some extent at the receiver with the PN demodulation by processing gain. It is known, however, that when the interferers are strong, the reduction cannot be sufficient and thereby requiring the extra use of narrowband interference cancellers (NIC's) at the receivers. A class of adaptive NIC's are studied here based on different two cost functions. One is the chip mean-squared error (MSE) computed prior to the PN demodulation and used in the conventional cancellers. Since thses conventional cancellers should be operated at the chip rate, the computational requirements are enormous. The other is the symbol MSE computed after the PN demodulation in which case the weights of the NIC's can be updated at a lot lower symbol rate. To compare the performance of these NIC's, we derive a common measure of performance, i.e., the symbol MSE after the PN demodulation. The analytical results are verified by computer simulation. As a result, it is shown that the cancellation capability of the symbol-rate NIC's are similar or better than the conventional one while the computational complexity can be reduced a lot.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.7-15
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• 2012

Semiconductor packages are increasingly moving toward miniaturization, lighter and multi-functions for mobile application, which requires highly integrated multi-stack package. To meet the industrial demand, the package and silicon chip become thinner, and ultra-thin packages will show serious reliability problems such as warpage, crack and other failures. These problems are mainly caused by the mismatch of various package materials and geometric dimensions. In this study we perform the numerical analysis of the warpage deformation and thermal stress of 4-layer stacked FBGA package after EMC molding and reflow process, respectively. After EMC molding and reflow process, the package exhibits the different warpage characteristics due to the temperature-dependent material properties. Key material properties which affect the warpage of package are investigated such as the elastic moduli and CTEs of EMC and PCB. It is found that CTE of EMC material is the dominant factor which controls the warpage. The results of RSM optimization of the material properties demonstrate that warpage can be reduced by $28{\mu}m$. As the silicon die becomes thinner, the maximum stress of each die is increased. In particular, the stress of the top die is substantially increased at the outer edge of the die. This stress concentration will lead to the failure of the package. Therefore, proper selection of package material and structural design are essential for the ultra-thin die packages.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2010.03a
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• pp.40-40
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• 2010

Studies on attractive color changing property of dye chromophore and fluorophore have been greatly enjoyed in the related industrial and research fields such as optoelectronics, chemosensor, biosensor and so on. The optical property based on D-$\Pi$-A intramolecular charge transfer (ICT) system of chromophore molecules can be utilized as suitable sensing probes for checking media polarity and determining colorimetric chemosensing effect, especially heavy metal detection. These finding are obtained by absorption and emission properties. In this work, donor-acceptor D-$\Pi$-A type fluorescent dyes were designed and synthesized with the corresponding donor and acceptor groups. The selected donor moieties might be provided prominent amorphous properties which are very useful in designing and synthesizing functional polymers and in fabricating devices. Another reasons to choose are commercial availabilities in high purity and low price. Donor-bridge-acceptor (D-A) type dyes can produce impressive optical-physical properties, yielding them potentially suitable for applications in the synthesis of small functional organic molecules. Small organic functional molecules have unique advantages, such as better solubility, amorphous character, and represent an area of research which needs to be explored and developed. Currently, their applications in metalorganic compounds is rapidly expanding and becoming widespread in self-assembly processes, photoluminescence applications, chiral organocatalysts, and ingrafts with nanomaterials. Colloidal nanoparticles have received great attentions in recent years. The photophysical properties of nanoparticles, particularly in terms of brightness, photostability, emission color purity and broad adsorption range, are very attractive functions in many applications. To our knowledge background, colloidal nanoparticles have been enjoyed their applications in bio-probe research fields. This research interest can be raised by the advantages of the materials such as high photoluminescence quantum yields, sharp emission band, long-term photostability and broad excitation spectra. In recent, the uses of nanoparticles being embedded in a polymer matrix and binded on polymer surface have been explored and their properties such as photo-activation and strong photoluminescence have been proposed. The prepared chromophores and nanoparticles were investigated with absorption and emission properties, solvatochromic behaviors, pH induced color switching effects, chemosensing effects and HOMO/LUMO energy potentials with computer simulation. In addition, synthesized fluorophore dyes and particles were applied onto PE/Aramid fiber fluorescing colorations. And the related details were then discussed.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1021-1030
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• 2010

In the sensor network, many tiny nodes construct Ad-Hoc network using wireless interface. As this type of system consists of thousands of nodes, managing each sensor node in real world after deploying them is very difficult. In order to install the sensor network successfully, it is necessary to verify its software using a simulator beforehand. In fact Sensor network simulators require high fidelity and timing accuracy to be used as a design, implementation, and evaluation tool of wireless sensor networks. Cycle-accurate, instruction-level simulation is the known solution for those purposes. In this paper, we developed an instruction-level sensor network simulator for Telos sensor node as named TeloSlM. It consists of MSP430 and CC2420. Recently, Telos is the most popular mote because MSP430 can consume the minimum energy in recent motes and CC2420 can support Zigbee. So that TeloSlM can provide the easy way for the developers to verify software. It is cycle-accurate in instruction-level simulator that is indispensable for OS and the specific functions and can simulate scalable sensor network at the same time. In addition, TeloSlM provides the GUI Tool to show result easily.

• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.35-48
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL and CRRM. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate and the system service cost.

• Journal of Navigation and Port Research
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• v.32 no.6
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• pp.459-464
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• 2008

In this paper, we present the model-based fuzzy controller for container cranes which effectively performs set-point tracking control of trolley and anti-swaying control under system parameter and disturbance changes. The first part of this paper focuses on the development of Takagi-Sugeno (T-S) fuzzy modeling in a nonlinear container crane system. Parameters of the membership functions are adjusted by a RCGA to have same dynamic characteristics with nonlinear model of a container crane. In the second part, we present a design methodology of the model-based fuzzy controller. Sub-controllers are designed using LQ control theory for each subsystem in fuzzy model and then the proposed controller is performed with the combination of these sub-controllers by fuzzy IF-THEN rules. In the results of simulation, the fuzzy model showed almost similar dynamic characteristics compared to the outputs of the nonlinear container crane model. Also, the model-based fuzzy controller showed not only the fast settling time for the change in parameter and disturbance, but also stable and robust control performances without any steady-state error.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.6
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• pp.747-752
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• 2006

In this paper, the adaptive fuzzy sliding mode controller with two systems is designed. The existing sliding mode controller used to $approximation{\^{u}}(t)$ with discrete sgn function and sat function for keeping the state trajectories on the sliding surface[1]. The proposed controller decrease the disturbance for uncertain control gain and This paper is concerned with an Adaptive Fuzzy Sliding Mode Control(AFSMC) that the fuzzy systems ate used to approximate the unknown functions of nonlinear system. In the adaptive fuzzy system, we adopt the adaptive law to approximate the dynamics of the nonlinear plant and to adjust the parameters of AFSMC. The stability of the suggested control system is proved via Lyapunov stability theorem, and convergence and robustness properties ate demonstrated. Futhermore, fuzzy tuning improve tracking abilities by changing some sliding conditions. In the traditional sliding mode control, ${\eta}$ is a positive constant. The increase of ${\eta}$ has led to a significant decrease in the rise time. However, this has resulted in higher overshoot. Therefore the proposed ${\eta}$ tuning AFSMC improve the performances, so that the controller can track the trajectories faster and more exactly than ordinary controller. The simulation results demonstrate that the performance is improved and the system also exhibits stability.