• 한국통신학회논문지
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• 제41권2호
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• pp.215-221
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• 2016

Data failure in wireless communications considerably affects the reconstruction quality of transmitted data. Traditionally, fascinating trials have been conducted to overcome the data failure intensifying reliable reconstruction of a media. But, none of these efforts neither effective, computationally inexpensive nor simply configurable to reduce the problems of transmitting media or images. In practice, it is necessary to maintain the quality of transmitted image without sacrificing any data, content, or information. So, to deal with dynamic events such as sensor node participation and departure, during transmission, an efficient scheme is important. For this reason, a new robust scheme has been presented in this paper to minimize the limitation of traditional wireless networking. This scheme uses Software-Defined Image Sensor Network (SD-ISN) to ensure scalability and dependability of the sensor network of handling data losses. Finally, a comparison of our proposed SD-ISN with conventional wireless networking has been presented in simulation to test the robustness and effectiveness of our proposed SD-ISN approach.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.452-472
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• 2019

Most existing wavelet-based multiplicative watermarking methods are affected by geometric attacks to a certain extent. A serious limitation of wavelet-based multiplicative watermarking is its sensitivity to rotation, scaling, and translation. In this study, we propose an image watermarking method by using dual-tree complex wavelet transform with a multi-objective optimization approach. We embed the watermark information into an image region with a high entropy value via a multiplicative strategy. The major contribution of this work is that the trade-off between imperceptibility and robustness is simply solved by using the multi-objective optimization approach, which applies the watermark error probability and an image quality metric to establish a multi-objective optimization function. In this manner, the optimal embedding factor obtained by solving the multi-objective function effectively controls watermark strength. For watermark decoding, we adopt a maximum likelihood decision criterion. Finally, we evaluate the performance of the proposed method by conducting simulations on benchmark test images. Experiment results demonstrate the imperceptibility of the proposed method and its robustness against various attacks, including additive white Gaussian noise, JPEG compression, scaling, rotation, and combined attacks.

• Smart Structures and Systems
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• 제31권5호
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• pp.437-454
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• 2023

Real-time hybrid simulation (RTHS), which has the advantages of a substructure pseudo-dynamic test, is widely used to investigate the rate-dependent mechanical response of structures under earthquake excitation. However, time delay in RTHS can cause inaccurate results and experimental instabilities. Thus, this study proposes a model-based adaptive control strategy using a Kalman filter (KF) to minimize the time delay and improve RTHS stability and accuracy. In this method, the adaptive control strategy consists of three parts-a feedforward controller based on the discrete inverse model of a servohydraulic actuator and physical specimen, a parameter estimator using the KF, and a feedback controller. The KF with the feedforward controller can significantly reduce the variable time delay due to its fast convergence and high sensitivity to the error between the desired displacement and the measured one. The feedback control can remedy the residual time delay and minimize the method's dependence on the inverse model, thereby improving the robustness of the proposed control method. The tracking performance and parametric studies are conducted using the benchmark problem in RTHS. The results reveal that better tracking performance can be obtained, and the KF's initial settings have limited influence on the proposed strategy. Virtual RTHSs are conducted with linear and nonlinear physical substructures, respectively, and the results indicate brilliant tracking performance and superb robustness of the proposed method.

• 벤처창업연구
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• 제6권4호
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• pp.21-37
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• 2011

12월 결산 코스닥상장법인을 대상으로 대주주지분과 기업성과의 관계를 규명하기위해 회귀분석을 실시하였다. 회귀분석은 기업성과를 시장성과와 회계성과로 나누어 실시하였다. 시장성과의 경우 회귀분석결과, 대다수의 국내 선행연구가 지지하는 U자형 절충가설이 코스닥상장법인에게는 적용되지 않는 것으로 나타났다. 반면 회계성과의 대용변수인 ROA (Return on Assets)와 대주주 지분율의 관계는 역U자의 형태와 유사한 것으로 나타났다. 보다 정확한 검증을 위해 강건성 검정을 실시하였다. 그 결과, 회계성과로 대주주 지분과 기업성과의 관계를 분석할 경우 대주주 지분율 0-50%구간 까지는 이해일치 가설을 지지하지만 50%이상 구간에서는 대주주 지분율과 회계성과의 관계가 유의하지 않은 것으로 나타났다.

• 한국인터넷방송통신학회논문지
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• 제22권6호
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• pp.149-154
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• 2022

GaN 소자는 고출력 및 고선형성 특성을 가지므로 레이더 수신기에서 저잡음 증폭기로 활용되어 리미터 없이 구현될 수 있으며, 이로 인해 잡음지수를 개선하고 면적을 줄일 수 있다. 본 논문에서는 Ka-대역 레이더용 수신기에 적용하기 위한 GaN 저잡음 증폭기를 기술하였다. 설계된 저잡음 증폭기는 150-nm GaN HEMT 공정으로 제작되었으며, 목표주파수 내에서 패키징 손실을 포함하여 >23 dB 이득, <6.5 dB의 잡음지수 특성을 보였다. 고입력 부하시험시 이득 및 잡음 저하가 있었으나, 반복시험시 추가적인 성능저하는 나타나지 않았다. 부하시험 후 잡음지수 및 S-파라미터 측정을 통해 GaN 저잡음 증폭기에서 ~40 dBm 펄스 입력 전력을 견딜 수 있음을 확인하였다.

• 한국콘텐츠학회논문지
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• 제17권12호
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• pp.92-103
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• 2017

본 연구는 스포츠브랜드와 스포츠 스타의 개성이 브랜드 애착과 브랜드 충성도에 미치는 영향과 차이를 비교분석 하였다. 이를 위해 부산, 경상 지역의 대학교의 대학생들을 대상으로 설문조사를 실시하였으며, 총 316부를 본 연구의 유효표본으로 선정하여 분석하였다. 자료 분석방법으로는 SPSS 18.0 version을 이용하여 빈도분석, 탐색적 요인분석, 신뢰도분석, 상관관계분석, 대응표본 t-test, 다중회귀분석을 실시하였다. 연구결과, 첫째, 스포츠브랜드 개성 중 흥미, 세련, 강인 순으로 브랜드 애착에 유의한 영향을 미쳤다. 둘째, 스포츠브랜드 개성 중 흥미, 세련, 강인 순으로 행동적 충성도에 유의한 영향을 미쳤으며, 강인, 흥미, 능력 순으로 태도적 충성도에 영향을 미쳤다. 셋째, 스포츠 스타 개성 중 흥미, 신뢰, 세련 순으로 브랜드 애착에 유의한 영향을 미쳤다. 넷째, 스포츠 스타 개성 중 흥미, 신뢰, 능력 순으로 행동적, 태도적 충성도에 유의한 영향을 미쳤다. 다섯째, 스포츠브랜드 개성과 스포츠 스타 개성의 차이검증을 분석한 결과 모든 요인에서 평균값의 차이가 통계적으로 유의한 것으로 나타났다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.92-97
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• 2000

An AMR(Adaptive Multi-Rate) speech coding algorithm has been adopted as a standard speech codec for IMT-2000. It is based on the algebraic CELP, and consists of eight speech coding modes having the bit rate from 4.75 kbit/s to 12.2 kbit/s. It also contains the VAD(Voice Activity Detector), SCR (Source Controlled Rate) operation, and error concealment scheme for robustness in a radio channel. The bit rate of AMR is changed on a frame basis depending on the channel condition. In this paper, we introduced AMR speech coding algorithm and performed the real-time implementation using TMS320C6201, i.e., a Texas Instrument's fixed-point DSP. With the ANSI C source code released from ETSI and 3GPP, we convert and optimize the program to make it run in real time using the C compiler and assembly language. It is verified that the decoded result of the implemented speech codec on the DSP is identical with the PC simulation result using ANSI C code for test sequences. Also, actual sound input/output test using microphone and speaker demonstrates its proper real-time operation without distortions or delays.

• 한국전산유체공학회지
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• 제13권1호
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• pp.7-13
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• 2008

Several high resolution schemes such as OSHER, MUSCL, SMART, GAMMA, WACEB and CUBISTA are comparatively studied with respect to the accurate capturing of fluid interfaces throughout the application to two typical test cases of a translation test and a collapsing water column problem with a return wave. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method and an interface capturing method, which is based on the finite-volume technique and fully conservative. The calculated results show that SMART scheme gives the best performance with respect to accuracy and robustness.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
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• pp.1862-1863
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• 2006

In this paper, A new tuning method for IMC-PID controller is proposed with the identification using the relay method from closed-loop transfer function. It is considered a second-order plus delay time(SOPDT) model and selected a third-order plus delay time transfer function model as a target function. The filter function is derived from the suitable target function to satisfy the design specifications. A robustness test was done to verify the robust-stability.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권10호
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• pp.671-677
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• 2004

This paper presents the design of a now controller for the read/write head of a hard disk drive. The general controller for seeking is the time-optimal control. However if we use only the time optimal control law, this could be vulnerable to chattering effect. To solve this problem, we propose a modified controller design algorithm in this paper. The proposed controller consists of bang-bang control for seeking and sliding-mode control for tracking. Moreover, to test the robustness and stability of control system, a bounded disturbance is selected to maximize a severity index. Simulation results show the superiority of the proposed controller through comparison with time optimal VSC(variable structure control).