• Journal of Communications and Networks
• /
• 제6권3호
• /
• pp.258-268
• /
• 2004

We demonstrate rotationally invariant space-time (ST) trellis codes with a 4-D rectangular signal constellation for data transmission over fading channels using two transmit antennas. The rotational invariance is a good property to have that may alleviate the task of the carrier phase tracking circuit in the receiver. The transmitted data stream is segmented into eight bit blocks and quadrature amplitude modulated using a 256 point 4-D signal constellation whose 2-D constituent constellation is a 16 point square constellation doubly partitioned. The 4-D signal constellation is simply the Cartesian product of the 2-D signal constellation with it-self and has 32 subsets. The partition is performed on one side into four subsets A, B, C, and D with increased minimum-squared Euclidian distance, and on the other side into four rings, where each ring includes four points of equal energy. We propose both linear and nonlinear ST trellis codes and perform simulations using an appropriate multiple-input multiple-output (MIMO) channel model. The 4-D ST codes constructed here demonstrate about the same frame error rate (FER) performance as their 2-D counterparts, having however the added value of rotational invariance.

• Journal of Astronomy and Space Sciences
• /
• 제29권4호
• /
• pp.389-395
• /
• 2012

The problem of spacecraft attitude control is solved using an adaptive neuro-fuzzy inference system (ANFIS). An ANFIS produces a control signal for one of the three axes of a spacecraft's body frame, so in total three ANFISs are constructed for 3-axis attitude control. The fuzzy inference system of the ANFIS is initialized using a subtractive clustering method. The ANFIS is trained by a hybrid learning algorithm using the data obtained from attitude control simulations using state-dependent Riccati equation controller. The training data set for each axis is composed of state errors for 3 axes (roll, pitch, and yaw) and a control signal for one of the 3 axes. The stability region of the ANFIS controller is estimated numerically based on Lyapunov stability theory using a numerical method to calculate Jacobian matrix. To measure the performance of the ANFIS controller, root mean square error and correlation factor are used as performance indicators. The performance is tested on two ANFIS controllers trained in different conditions. The test results show that the performance indicators are proper in the sense that the ANFIS controller with the larger stability region provides better performance according to the performance indicators.

• 인터넷정보학회논문지
• /
• 제3권2호
• /
• pp.69-77
• /
• 2002

최근 디지털 비디오는 인터넷을 통해 제공되는 매우 중요한 정보 미디어의 하나이며 멀티미디어 분야에서 매우 중요한 역할을 수행하고 있다. 본 논문에서는 웹 상에서 실시간 사용자 인터페이스를 통해 비디오 내용 검색과 브라우징을 제공하는 비디오 브라우징 서비스를 제시한다. 비디오 시퀀스의 장면 분할과 키 프레임 추출을 위해서 RGB 컬러 히스토그램과 $x^2$(카이 스퀘어) 히스토그램을 합성한 효율적인 장면 전환 검출 방법을 제안한다. 이렇게 추출된 키 프레임들은 물리적인 방법과 논리적인 방법에 따라 색인 화된다. 이 시스템은 또한 비디오카세트리코더(VCR)가 갖고 있는 비디오 편집과 검색 기능을 포함한다. 비디오 브라우징을 위하여 날짜, 분야, 그리고 주제의 세 가지 요소가 사용되며, 비디오 브라우징 서비스는 아파치 웹서버에서 MySQL, PHP, 그리고 JMF를 이용하여 구현된다.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
• /
• pp.151-154
• /
• 2001

In this Paper, a new harmonic imaging technique is proposed and evaluated experimentally. In the proposed method, a weighted chin signal with a hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic (2f0) component of a transmitted chirp signal generated in a square-law system. The proposed method uses the compressed 2f0 component to form an image, for which the crosscorrelation term with f0 component should be suppressed below at least -60dB. After experiment, the 6dB pulse width and peak sidelobe level of the compressed 2f0 component were 0.7us and -60dB, respectively. This result shows that the proposed method can successfully eliminate the f0 component with a single transmit-receive event and therefore is more efficient than the conventional pulse inversion (PI) method in terms of frame rate. We also observed that the 2nd harmonic compont starts to decrease for source pressure higher than 210kPa in water, which implies that SNR of the 2nd harmonic imaging using short pulses cnanot be incresed beyond a certain limit.

• 제어로봇시스템학회논문지
• /
• 제18권9호
• /
• pp.854-862
• /
• 2012

The optimal design of batch-storage network by using periodic square wave model provides analytical lot sizing equations for a complex supply chain network characterized as multi-supplier, multi-product, multi-stage, non-serial, multi-customer, cyclic system including recycling and/or remanufacturing. The network structure includes multiple currency flows as well as material flows. The processes are represented by multiple feedstock/product materials with fixed composition which are very suitable for production processes. In this study, transportation processes that carry multiple materials with unknown composition are added and the time frame is changed from single period into multiple periods in order to represent nonperiodic parameter variations. The objective function of the optimization involves minimizing the opportunity costs of annualized capital investments and currency/material inventories minus the benefit to stockholders in the numeraire currency. The expressions for the Kuhn-Tucker conditions of the optimization problem are reduced to a multiperiod subproblem for average flow rates and analytical lot-sizing equations. The multiperiod lot sizing equations are different from single period ones. The effects of corporate income taxes, interest rates and exchange rates are incorporated.

• 복식문화연구
• /
• 제10권5호
• /
• pp.493-503
• /
• 2002

This study examined consumer characteristics and consumers' clothing purchase behavior for each of the four fashion brand types. The ultimate purpose of this study is to suggest the most effective marketing strategy for competitive advantage in fashion brand strategy. The subjects selected for the final analysis are 412 women of age 20 thru 34 in Seoul and areas. The data were analyzed using frequency, percentage, factor analysis, chi-square test, ANOVA, duncan test. The results of our study indicate that it is possible to meaningfully describe and contrast four brand types based on consumer's characteristics and purchase behavior. 1. The clothing brand is classified into four types : Designer brand 10.9%, National brand 27.2%, Middle-price brand 36.2%, Low-price brand 25.7%. 2. There are significant diferences according to four brand types in the demographic traits such as age education and income the average monthly spending on clothing. 3. There are an important discrimination according to tow brand types in their clothing purchase behavior such as information usage, clothing choice criterion and brand choice motivation. 4. Based on the result of this analysis and the review of literature, the brand strategy is suggested that characteristic and products development is efficient way to each brand consumers' purchase need. Therefore each brand which pursue an added value must frame marketing strategy on the basis of the target consumers' sensitivity characteristic according to the fashion consciousness.

• 대한전자공학회논문지
• /
• 제20권4호
• /
• pp.47-54
• /
• 1983

DCT/DPCM 복합 감축방식(hybrid coding)에서 주요 시스템 변수에 따른 성능 변화가 평균 자승오차와 주관검사(subjective test)를 기준으로 해서 연구되었다. 검토된 시스템 변수는 DCT 변환계수의 예측상수, 블록 양자기의 평준화 계수 및 비트배정등이다. 그리고 적응식 감축방식의 특성도 비교 검토되었다. 실험결과로는 영상의 공분체 모델을 근거로 하는 비트 기정 및 적응방식이 실시간 처리에 편리할 뿐만 아니라, 낮은 비트율에서는 매우 유리한 방법임이 확인되었다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2005년도 추계종합학술대회
• /
• pp.123-126
• /
• 2005

STP는 토폴로지 구성방법에 따라 네트워크의 성능이 달라진다. 따라서 효율적인 네트워크 환경을 위하여 최적의 토폴로지를 구성할 필요가 있다. 본 논문은 이더넷에서 스위치들 사이의 효율적인 네트워크 구축을 위한 최적의 토폴로지 구성방법을 제안하였다 루트스위치에서 송신한 프레임을 같은 도메인 안에 있는 스위치들이 프레임을 수신하는 시간을 수학적 모델로 계산하여 최적의 토폴로지 구성 방법을 도출하였다. 그리고 최적의 토폴로지에서의 루트 스위치의 위치에 따른 성능을 분석하였다. 성능 분석 결과 정방형으로 설계된 망에서 루트스위치가 중앙에 위치하게 설계하는 것이 효과적이라는 결론을 얻을 수 있었다.

• 로봇학회논문지
• /
• 제14권4호
• /
• pp.357-362
• /
• 2019

This paper proposes a model and train method that can real-time detect objects and distances estimation based on a monocular camera by applying deep learning. It used YOLOv2 model which is applied to autonomous or robot due to the fast image processing speed. We have changed and learned the loss function so that the YOLOv2 model can detect objects and distances at the same time. The YOLOv2 loss function added a term for learning bounding box values x, y, w, h, and distance values z as 클래스ification losses. In addition, the learning was carried out by multiplying the distance term with parameters for the balance of learning. we trained the model location, recognition by camera and distance data measured by lidar so that we enable the model to estimate distance and objects from a monocular camera, even when the vehicle is going up or down hill. To evaluate the performance of object detection and distance estimation, MAP (Mean Average Precision) and Adjust R square were used and performance was compared with previous research papers. In addition, we compared the original YOLOv2 model FPS (Frame Per Second) for speed measurement with FPS of our model.

• 천문학회보
• /
• 제44권1호
• /
• pp.85.1-85.1
• /
• 2019

Accurate estimation of the masses, the ages, and the chemical abundances of host stars is crucial to understand physical characteristics of exo-planetary systems. In this study, we investigate physical dimensions of 94 planet-hosting stars based on spectroscopic observation and stellar evolutionary computation, From the high resolution echelle spectroscopy of the BOES observation, we have analysed metallicities and alpha-element enhancements of host stars. By combining recent spectro-photometric observations, stellar parameters are calibrated within the frame work of the standard stellar theory. In general, the minimum chi-square estimation can be strongly biased in cases that stellar properties rapidly changes after the terminal age main-sequence. Instead, we adopt a Bayesian statistics considering a priori distribution of stellar parameters during the rapid evolutionary phases. we determine a reliable set of stellar parameters between theoretical model grids. To overcome this statistical bias, (1) we adopt a Bayesian statistics considering a priori distribution of stellar parameters during the rapid evolutionary phases and (2) we construct the fine model grid that covers mass range ($0.2{\sim}3.0M_{\odot}$) with the mass step ${\Delta}M=0.01M_{\odot}$, metallicities Z = 0.0001 ~ 0.04, and the helium and the alpha-element enhancement. In this presentation, we introduce our calibration scheme for several hosting stars.