• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.604-610
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• 2008

A 2.4 GHz CMOS RF front-end using for ZigBee application is described The front-end consists of a low noise amplifier and a down-mixer and uses a 2 MHz IF frequency. A common source with resistive feedback and an inductive degeneration are adopted for a low noise amplifier, and a 20 dB gain control step is digitally controlled. A passive mixer for low current consumption is employed. The RF front-end is implemented in 0.18 ${\mu}m$IP6M CMOS process. The measured performance is 4.44 dB NF and -6.5 dBm IIP3 while consuming 3.28 mA current from a 1.8 V supply.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.87-93
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• 2001

As a new type of a linear decorrelating receiver, the Pseudo-Decorrelator was presented for asynchronous code division multiple access systems by the author. In this paper, the concept of the Pseudo-Decorrelator is extended to derive a receiver for WCDMA uplink systems over an additive white Gaussian noise channel. Starting with the analysis of the multiple access components of the decision statistics, a non-square cross-correlation matrix for each bit is obtained. This cross-correlation matrix is then inverted, and the inverted matrix is applied to the decision statistics obtained from a conventional receiver. In this receiver, the detection process can be started after the first three consecutive bits are received. Simulation results are presented for K-user systems over an additive white Gaussian noise channel under the circumstances in which synchronization errors, including time delay errors and carrier phase errors exist. It is shown that the proposed receiver performs better than a conventional receiver and parallel interference canceller.

• Journal of the Korean Chemical Society
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• v.26 no.1
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• pp.1-6
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• 1982

The addition of thiophenol to ${\alpha}$-methylstyrene has been studied MO theoretically using CNDO/2 method. Although overall reaction proceeds in two steps i.e., (1) decomposition of thiophenol to give phenylthiyl radical and (2) addition of the radical to ${\alpha}$-methylstyrene to give a new monomer radical, theoretical results suggested that the phenylthiyl radical formation step, (1), was the dominant process in determining the rate of addition; this was the rationale behind the negative ${\rho}$ value obtained experimentally from the Hammett plots for substituents on the thiyl radicals. The departure from a linear Hammett plot for addition of ${\rho}$-chlorophenylthiyl and m-trifluoromethyl phenylthiyl to ${\rho}$-methoxy-${\alpha}$-methylstyrene could be explained as a result of an increased contribution of the addition step, (2) to the overall reaction rate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.995-1001
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• 2005

Implicit Integration has become a standard approach to efficient cloth animation, and it guarantees the stability of the system so that large steps can be used. Therefore, it is regarded as the best method for the real-time or interactive animation of cloth. Since the implicit method was introduced for stable cloth animation, various cloth animation techniques based on the method have been proposed. It is now possible to generate the real-time animation of cloth model with thousands of mass-point in general PC environments. Although the implicit method guarantees the stability, the implementation of the implicit method is generally more difficult than that of the explicit method. Even worse, it is very difficult to parallelize the computation process of the implicit method. The cloth animation with implicit method can be formalized as a linear system solving. In this paper we propose an stable and efficient cloth animation techniques based on the implicit method. The proposed method can be easily parallelized. Self-collision is another important issue in cloth animation, we also propose an efficient self-collision avoidance techniques.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.549-557
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• 2012

In this paper an on-chip photo energy harvesting system with MPPT(Maximum Power Point Tracking) control is proposed. The ISC(Integrated Solar Cell) is implemented using p-diff/n-well diodes available in CMOS processes. MPPT control is implemented using the linear relationship between the open-circuit voltage of a PV(Photovoltaic) cell and its MPP(Maximum Power Point) voltage such that a small pilot PV cell can track the MPP of a main PV cell in real time. Simulation results show that the designed circuit with the MPPT control delivers the MPP voltage to load even though the load is heavy such that the load circuit can operate properly. The proposed circuit is designed in 0.18um CMOS process. The designed main PV cell and pilot PV cell occupy $8mm^2$ and $0.4mm^2$ respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.247-250
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• 2008

RC6 which has different algorithm of encryption and decryption has been implemented to have the same algorithm between encryption' and decryption though inserting symmetry layer using simple rotate and logical operation. That means the half of whole RC6 round uses encryption algorithm and the rest of it uses decryption one and symmetry layer has been put into the middle of encryption and decryption. The proposed RC6 algorithm has no difference with the original one in the speed of process. However it is quite safe because by inserting symmetry layer the path of high probability which is needed for differential and linear analysis is cut oft so that it is hard to be analyzed. The proposed algorithm can be easily applied to the algorithm which has different encryption and decryption an make it same, and it can be good idea to be used to design a new block cipher algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.521-528
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• 2009

One of reliability measurements of vehicle is estimated by driving mileage but the reliability of component, such as an hydraulic clutch system, is defined from the number of successful operational cycle. Relationship between these reliability measurement variables(mileage and cycle) should be examined first of all in the reliability estimation of components. Relationship between mileage and cycles is commonly known as linear function. However, the gradient depends on the operational environmental condition. Therefore, estimation of mission profile variable should be done with correlation analysis at the same time. In this paper, we derive mission profile variable of an hydraulic clutch system by field vehicle test and suggest the determination process of durability test parameters of CMC(Clutch Master Cylinder) with mission profile variable.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.258-258
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• 2014

Spark discharge in water generates shockwaves which have been utilized to generate mechanical actuation for potential use in pumping application. Discharge pulses of several microseconds generate shockwaves and vapor bubbles which subsequently displace the water for a period of milliseconds. Through the use of a sealed discharge chamber and metal bellow spring, the fluid motion can be used create an oscillating linear actuator. Continuous actuation of the bellow has been demonstrated through the use of high frequency spark discharge. Discharge in water forms a region of high electric field around the electrode tip which leads to the creation of a thermal plasma channel. This process produces fast thermal expansion, vapor and bubble generation, and a subsequent shockwave in the water which creates physical displacement of the water [1]. Previous work was been conducted to utilize the shockwave effect of spark discharge in water for the inactivation of bacteria, removal of mineral fouling, and the formation of sheet metal [2-4]. Pulses ranging from 25 to 40 kV and 600 to 900 A are generated inside of the chamber and the bellow motion is captured using a slow motion video camera. The maximum displacements measured are from 0.7 to 1.2 mm and show that there is a correlation between discharge energy input to the water and the displacement that is generated. Subsequent oscillations of the bellow are created by the spring force of the bellow and vapor in the chamber. Using microsecond shutter speed ICCD imaging, the development of the discharge bubble and spark can be observed and measured.

• Polymer(Korea)
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• v.29 no.4
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• pp.392-398
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• 2005

Self-assembled multilayer thin films of poly(ethylene-alt-maleic anhydride) (PEMAh) and poly(4-vinyl pyridine) (P4VP) were fabricated by layer-by-layer (LbL) sequential adsorption. Fourier transform infrared (FT-IR) spectroscopic analysis of the self-assembled PEMAh/P4VP multilayer films confirms that the driving forces for the multilayer buildup are the intermolecular hydrogen bonding and electrostatic interactions. The linear increase of absorption peak of P4VP at 256 nm with increasing number of PEMAh/P4VP bilayers indicates that the multilayer buildup is an uniform assembling process. We also investigate the effects of polyelectrolyte concenhation variation of the dipping solution and pH variation of the PEMAh solution on the multilayer film formation. Thickness. adsorbed polyelectrolyte mass and surface roughness of the multilayer films were measured by UV-visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy (AFM), respectively.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.3
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• pp.19-28
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• 2001

The purpose of this paper is to examine factors affecting user´s satisfaction in development of natural recreation forest(NRF) in order to answer the research question: What is the magnitude of factors affecting user´s satisfaction in development of NRF. After reviewing the literature, mechanism of outdoor recreation, and development factors in NRF, we constructed the conceptual framework and have formulated the hypothesis of this research. we have obtained data through a questionnaire, which surveyed 625 visitors at 10 of the 72 natural recreation forests in Korea in 1999, We have analyzed the data using the mean difference test, Pearson´s correlation analysis, and multiple linear regression method. We found that 1) all the development factors except recreational resources affecting user´s satisfaction have turned out to be statistically significant at one percent level. The direction of relationship between independent variable and dependent variable is the same as that of dependent variable. 2) in bivariate analysis, the relationships between user´s satisfaction and all the development factors are fairly high and statistically significant. The higher the value of development factors, the higher the degree of user´s satisfaction. 3 in multivariate analysis, such variables as the suitability of activities level of services, atmosphere, and facility have been statistically significant at one percent level, and 4) Their relative contribution of the suitability of various recreational activities, level of atmosphere, and service on dependent variable have been turned out to have 8.167, 4.889, 3.333, and 1.611 times more importance than that of the suitabity of recreational resources, respectively. The research results suggest that a guideline for the creation of marketable NFR and development of use-programs and recreational atmosphere be recommended in the planning and development process of NRF, and excessive investment on facilities is not desirable. The approach and analysis method adopted by this research is highly useful for an evaluation criterion of NRF and development of devices for increasing user´s satisfaction in NRF. It is recommended that more empirical study on individual factors affecting user´s satisfaction be performed in the future.