• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.609-612
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• 2007

The HDD (hard disk drive) using Load/Unload (L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop (CSS). Dynamic L/UL has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. The main design objectives of the L/UL mechanisms are no slider-disk contact or no media damage even with contact during L/UL, and a smooth and short unloading process. In this paper, we focus on lift-off force, pitch static attitude (PSA), roll static attitude (RSA) and dimple point. The "lift-off" force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. PSA and RSA are also very important parameters in L/UL system and stability of slider is mainly determined by PSA and RSA. Dimple point by PSA and RSA is also important indicator. Therefore we find the optimal dimple point of SFF HDD suspension for improving the unloading performance.

• The Journal of Korea Robotics Society
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• v.6 no.1
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• pp.58-68
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• 2011

This paper proposes a technique of indoor localization for mobile robot by so called indoor GPS and EKF. Basically the concept of indoor GPS is similar outdoor GPS, and the indoor GPS gets distances between Anchors and Tag by a ranging method of CSS and then estimates the coordinate by distances and known Anchor positions. After we performed performance test of indoor GPS system in ideal and multipath environment, we configured that the indoor GPS has internal error factors and external error factors. This paper handled a multipath problem belonging to external error factors. At first various direct physical method are introduced to fix the multipath problems, and as expected we got errors corrected considerably. And then the method of selective anchors for indoor GPS is applied. With these two level improvement of indoor GPS performance, EKF(Extended Kalman Filter) is applied to mobile robot in indoor environment. The usefulness of the proposed methods are shown by a series of experiments in a environment giving contaminated data by multipath.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.38-42
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• 2017

This paper introduces the concept of a dual hash function to amplify security in a quantum key distribution system. We show the use of the relationship between quantum error correction and security to provide security amplification. Also, in terms of security amplification, the approach shows that phase error correction offers better security. We describe the process of enhancing security using the universal hash function using the BB84 protocol, which is a typical example of QKD. Finally, the deterministic universal hash function induces the security to be evaluated in the quantum Pauli channel without depending on the length of the message.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1301-1318
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• 2017

In order to utilize the licensed channel of cognitive radio (CR) when the primary user (PU) is detected busy, a benefit-exchange access mode based on cooperative communication is proposed to allow secondary user (SU) to access the busy channel through giving assistance to PU's communication in exchange for some transmission bandwidth. A holistic joint optimization problem is formulated to maximize the total throughput of CR system through jointly optimizing the parameters of cooperative spectrum sensing (CSS), including the local sensing time, the pre-configured sensing decision threshold, the forward power of cooperative communication, and the bandwidth and transmission power allocated to SUs in benefit-exchange access mode and traditional access mode, respectively. To solve this complex problem, a combination of bi-level optimization, interior-point optimization and exhaustive optimization is proposed. Simulation results show that, compared with the tradition throughput maximizing model (TTMM), the proposed holistic joint optimization model (HJOM) can make use of the channel effectively even if PU is busy, and the total throughput of CR obtains a considerable improvement by HJOM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.196-202
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• 2002

In this work, we propose a new type of HDD suspension featuring shape memory alloy (SMA) actuator in order to prevent the contact between the slider and disk. The principal design parameters are obtained from the modal analysis using finite element analysis, and then the dynamic model is established to formulate the control scheme for Non-Contact Start/stop mode drive. Subsequently, a robust H$\_$$\infty$/ control algorithm is designed by integrating experimentally-Obtained SMA actuator dynamics to the proposed HDD suspension system. The controller is empirically realized and control results for the load/unload profiles are presented in time domain. In addition, the contact signal between the slider and disk is measured by the electrical resistance method.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.204-209
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• 2005

Load/Unload(L/UL) technology includes the benefits, that is, increased areal density, reduced power consumption and improved shock resistance contrary to contact-start-stop(CSS). It has been widely used in portable hard disk drive and will become the key technology far developing the small form factor hard disk drive. The main object of L/UL is no slider-disk contact or no media damage. For realizing those, we must consider many design parameters in L/UL system. In this paper, we focus on lift-off force. The 'lift-off' force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. To minimize 'lift-off' force we optimizes the slider and suspension using the integrated optimization frame, which automatically integrates the analysis with the optimization and effectively implements the repetitive works between them. In particular, this study is carried out the optimal design considering the process of modes tracking through the entire optimization processes. As a result, we yield the equation which can easily find a lift-off force and structural optimization for suspension.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.157-164
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• 2009

An efficient pipeline MDC Radix-4 FFT structure is proposed in this paper. Every stages in pipeline FFT structure consists of delay' commutator and butterfly. Proposed butterflies in front and rear stages utilize CORDIC and Common Sub-expression Sharing(CSS) techniques, respectively. It is shown that proposed butterfly structure can reduce the number of adders through sharing common patterns of CSD type coefficients. The Verilog-HDL modeling and Synopsys logic synthesis results that the proposed structure show 48.2% cell area reduction in the complex multiplication part and 22.1% cell area reduction in overall 256-point FFT structure comparison with those of the conventional structures. Consequently, the proposed FFT structure can be efficiently used in various OFDM systems.

• Journal of Nutrition and Health
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• v.50 no.1
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• pp.41-52
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• 2017

Purpose: The objective of the study was to investigate the effects of xylobiose-sugar mixture intake on defecation frequency and constipation symptoms in 31 young women with constipation. Methods: Thirty-one subjects were assigned to two groups, and subjects in each group were administered 10 g of a 7% xylobiose-sugar mixture (Experiment 1: XBS, n = 15) or 10 g of a 7% xylobiose-sugar mixture containing coffee mix (Experiment 2: XBS coffee mix, n = 16) twice per day for 6 weeks. During the study, clinical efficacy was assessed by a daily diary record. The subjects recorded their defecation frequency and fecal characteristics. Results: During pretreatment week, mean defecation frequency of XBS subjects was 2.13 times/week, whereas that of XBS coffee mix subjects was 1.56 times/week. The mean defecation frequencies of XBS and XBS coffee mix subjects increased significantly to 3.73 times/week (p < 0.05) and 3.56 times/week by week 6 (p < 0.05), respectively. After treatment with either XBS or XBS coffee mix, patients presented significant improvements in their amounts of stool, feelings of residual stool leftness, and abdominal pain symptoms (p < 0.05). The total constipation scoring system (CSS) for diagnosing constipation symptoms significantly decreased in the XBS group (10.53 score vs 7.22 score) and in the XBS coffee mix group (10.75 score vs 6.51 score) after 6 weeks. Improvement due to intake of 7% xylobiose-containing sugar seemed to last during the experimental period. Conclusion: The addition of approximately 7% xylobiose to commercially available sweeteners has been shown to improve constipation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.12
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• pp.2792-2799
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• 2012

Multilateration that consists of three or more fixed nodes has been widely used in the field of indoor real time location system(RTLS). However, when one or two among fixed nodes are partially out of communication reachability due to obstruction and unstable node, it is difficult to obtain an efficient location information. In order to improve the challenges of poor ranging measurements and fluctuations in these environment, this paper presents, based on TOF(Time of Flight), a new algorithm which can reduce the inherent ranging measurements errors in the conventional multilateration using a vector prediction algorithm for the displacement estimation of mobile node and Kalman filter for an efficient distance average. Even if a person moves with mobile node and then it fails ranging measurement from some of fixed nodes, the proposed algorithm using a present and previous measurement value can predict the distance between mobile node and fixed node which fails ranging measurement. The experimental results are shown that the proposed system improves the localization accuracy and efficiency compared with conventional method, respectively.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.273-279
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• 2014

In this paper, we propose a novel algorithm for three dimensional positioning system and implement a system over indoor wireless channel. A commercial modules are used for mobile and fixed nodes which are product of German company Nanotron Co. This module adopts chirp spread spreading scheme as modulation method to improve the ranging resolution and the module satisfies the IEEE standard 802.15.4a. The distance computation is based on received signal strength(RSS) levels and trilateration method. A testbed was set up to measure and compare the positioning estimation error of the proposed algorithm. The experiments results showed that the accuracy of location estimation was sufficiently good as much as 1m distance error in a wireless environment in an office building.