• E2M - 전기 전자와 첨단 소재
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• 제9권1호
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• pp.24-29
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• 1996

A composite piezoelectric ceramic transducer is fabricated with three piezoelectric ceramic disk vibrators and two sheets of thin insulator. Its equivalent circuit is derived from the Mason's model of a thickness-driven piezoelectric vibrator. When the electric input near its fundamental resonance frequency is applied to the center vibrator and the output voltages across the left and the right vibrators are connected in series to the resistor loads, the load characteristics at resonance frequencies under the various resistor loads and the frequency characteristics near the resonance frequency without load are investigated. Furthermore, symbolic expressions for input impedances, voltage ratios, resonance frequencies, and bandwidths are derived. The data calculated from those symbolic expressions are agreed well with the measurement data.

• 한국군사과학기술학회지
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• 제16권6호
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• pp.819-827
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• 2013

Compared to legacy frequency hopping communications, future radio communications are required the secure and high data rate, ad-hoc network communication. In this paper, we have designed the network communication structure on the frequency hopping mode, and analyzed the performance of synchronization on the frequency hopping network radio systems. The design results are shown the initial sync. phase of approximately 9 hops and the traffic packet phase of approximately 30 hops. Also, we have simulated the performance on the communication conditions which are carrier bandwidth of 50kHz, user data rate of 64kbps and OQPSK modulation scheme in AWGN. In the simulation, we analyzed the correlation and the performance of synchronization success. The result of simulation show 99% probability for synchronization success at $E_b/N_o$ -4dB.

• 응용통계연구
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• 제33권6호
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• pp.805-812
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• 2020

본 논문은 최근 금융시계열 분야에서 자주 등장하는 고빈도 시계열 변동성 분석을 다루고 있다. 고빈도 시계열 변동성 분석을 위해 차원 축소를 목적으로 하는 함수형 주성분분석을 적용하였으며 이를 수행하는 R의 두 함수를 비교하고 있다. 응용으로서, KOSPI 고빈도 자료에 적용해 보았다.

• 정보저장시스템학회논문집
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• 제11권1호
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• pp.1-5
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• 2015

The selective frequency analysis method is suggested in the holographic data storage system with the nyquist aperture to reduce the size of hologram. The image filter was designed with many different methods to improve the bit error rate caused by the nyquist aperture. In previous the methods of image restoration for HDS, an iteration time and a highly precise point spread function were necessary. In this paper, we describe the optical system with analytic method. Thereby, we expect our result help the researchers to design the filter.

• 소음진동
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• 제7권1호
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• pp.61-69
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• 1997

Despite of the development in the finite element method, it is difficult to get the finite element model describing the dynamic characteristics of the complex structure exactly. Therefore a number of different methods have been developed in order to update the finite element model of a structure using vibration test data. This paper outlines the basic formulation for the frequency response function based updating method. One important advantage of this method is that the intermediate step of performing an eigensolution extraction is unnecessary. Using simulated experimental data, studies are conducted in the case of 10 DOF discrete system. The solution of noisy and incomplete experimental data is discussed. True measured frequency response function data are used for updating the finite element model of a beam and a plate. Its applicability to the joint identification is also considered.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.291-294
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• 1999

This paper presents a GaAs MESMET self oscillating mixer for high efficiency L-band frequency conversion with small chip area consumption. Main circuit topology is consist of cascoded two FET with resonating part. The circuit is designed as unstably nonlinear for limited frequency band. FET with drain shorted to source is used for frequency tuning element. Linear conversion gain of -18.83 ㏈ is achieved with 9mA and 4V consumption. Input 1㏈ compression point is more than 11㏈m. The chip area is 1.4$\times$1.4 mm.

• 대한임베디드공학회논문지
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• 제5권2호
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• pp.57-66
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• 2010

In this paper, we propose an enhanced voice recognition algorithm using adaptive MFCC(Mel Frequency Cepstral Coefficients) and neural network. Though it is very important to extract voice data from the raw data to enhance the voice recognition ratio, conventional algorithms are subject to deteriorating voice data when they eliminate noise within special frequency band. Differently from the conventional MFCC, the proposed algorithm imposed bigger weights to some specified frequency regions and unoverlapped filterbank to enhance the recognition ratio without deteriorating voice data. In simulation results, the proposed algorithm shows better performance comparing with MFCC since it is robust to variation of the environment.

• ETRI Journal
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• 제30권1호
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• pp.21-32
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• 2008

Cognitive radio (CR) has been proposed as an effective technology for flexible use of the radio spectrum. The interference between primary users and CR users, however, becomes a critical problem when they are using adjacent frequency channels with different transmission power levels. In this paper, a robust CR orthogonal frequency division multiplexing (OFDM) architecture, which can effectively suppress interference to nearby primary users and overcome adjacent channel interference (ACI) to the CR user, is proposed. This new approach is characterized by adaptive data repetition for subcarriers under heavy ACI, and adaptive time spreading for subcarriers near the borders of the CR user's spectrum. The data repetition scheme provides extra power gain against the ACI coming from primary users. Time spreading guarantees an acceptable interference level to nearby primary users. By computer simulation, we demonstrate that, under a CR environment, the proposed CR OFDM architecture outperforms conventional OFDM systems in terms of throughput and BER performance.

• 대한전자공학회논문지TC
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• 제46권7호
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• pp.32-38
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• 2009

본 논문에서는 중첩부호화를 사용하여 단일주파수의 Broadcast(BC) 서비스와 Unicast(UC)데이터 서비스를 하나의 주파수 밴드를 통해 제공하는 BC/UC 오버레이 시스템의 성능을 평가한다. 일반적으로 BC 서비스와 UC 데이터 서비스는 별개의 서비스로 여겨져 왔으며 서비스를 위한 주파수 밴드도 다른게 할당 되어왔다. 그러나 주파수 자원의 희소가치가 높아지면서 최근에는 BC 서비스와 UC 데이터서비스를 "중첩"하여 하나의 주파수 밴드를 통해 서비스를 하고자하는 노력이 있었으며 3GPP LTE에서는 중첩부호화 기반의 방송 및 데이터 서비스 오버레이 시스템을 규격에 반영하기에 이르렀다. 본 논문에서는 특히 UC 데이터 서비스의 수율과 BC 서비스의 커버리지를 지표로 중첩부호화를 사용한 BC/UC 서비스 다중화 방식과 주파수 분할의 BC/UC 서비스 다중화 방안을 비교한다.

• 한국통신학회논문지
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• 제39B권6호
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• pp.370-378
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• 2014

잘 알려진 바와 같이 데이터마이닝 (Data Mining)은 대용량의 데이터를 분석하여 필요한 정보를 추출하는데 있어서 매우 중요한 역할을 수행한다. 그중에서 집합에 포함된 원소들의 빈도수 (Frequency)를 알아내는 것은 데이터마이닝에서 기본적으로 지원되어야 하는 필수기능이다. 동시에 사용자가 소유한 다중집합 (혹은 집합) 자체의 공개를 원하지 않는 경우에 대비하여 다중집합의 원소는 공개하지 않고 빈도수만 계산하는 방법이 필요하다. 본 논문에서는 암호학적 도구를 기반으로 사용하여 이러한 조건을 만족하는 기법을 개발하고, 이것의 안전성을 엄밀하게 증명한다. 본 논문에서 제안된 기법은 기존 기법들과 달리 첫째, 시스템 가정이 일반적이고 둘째, 통신/연산 복잡도가 효율적이고 마지막으로 엄밀한 안전성 증명을 제시한다.