• 제목/요약/키워드: $D^{-1}$method

검색결과 11,871건 처리시간 0.05초

Preparation and Evaluation of Bupivacaine Microspheres by a Solvent Evaporation Method (II) (용매증발법에 의한 부피바카인 마이크로스피어의 제조 및 평가 (II))

  • 곽손혁;이시범;이종수;이병철;황성주
    • YAKHAK HOEJI
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    • 제45권6호
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    • pp.623-633
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    • 2001
  • Various bupivacaine-loaded microspheres were prepared using poly(d,1-lactide) (PLA) and poly(d,1-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. The effects of process conditions such as drug loading, polymer type and solvent type on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency and yield of PLGA micro- spheres were higher than those of PLA microspheres. The prepared microspheres had an average particle size below 5${\mu}{\textrm}{m}$. The particle size range of microspheres was 1.65~2.24${\mu}{\textrm}{m}$. As a result of SEM, the particle size of PLA microspheres was smaller than that of PLGA microspheres. In morphology studies, microspheres showed a spherical shape and smooth surface in all process conditions. In thermal analysis, bupivacaine-loaded microspheres showed no peaks originating from bupivacaine. This suggested that bupivacaine base was molecular-dispersed in the polymer matrix of microspheres. The release pattern of the drug from microspheres was evaluated for 96 hours. The initial burst release of bupivacaine base decreased with increasing the molecular weight of PLGA, and the drug from microspheres released slowly. In conclusion, bupivacaine-loaded microspheres were successfully prepared from poly(d,1-lactide) and poly (d,1- lactic-co-glycolide) polymers with different molecular weights allowing control of the release rate.

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PULSATIONAL CHARACTERISTICS OF $\delta$ SCUTI VARIABLE HR1170

  • Kim, Seoung-Li;Lee, See-Woo
    • Journal of The Korean Astronomical Society
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    • 제23권1호
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    • pp.1-13
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    • 1990
  • New uvby photoelectric photometry was carried out for a $\delta$ Scuti variable, HR1170. By applying the Fourier method and the linear least square method, three frequencies were derived: $f_1=10.06134c/d$ ($P_1=0.^d0994$). $f_2=11.91754c/d$ ($P_2=0.^d0839$). $f_3=18.96776c/d$ ($P_3=0.^d0527$). From the observed pulsational constants and from the phase difference and amplitude ratios for color(b-y) and magnitude y. three different pulsation modes (n, l) of $f_1(0,0)$, $f_2(1,2)$, $f_3(3,2)$ are deduced, indicating the existence of nonradial mode in HR1170. Some physical parameters indicate that HR1170 is evolving at the stage of H-shell burning.

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Antiferroelectric Liquid Crystal Display with High Image Quality

  • Chang, Young-Joo;Yu, Jeong-Seon;Yoo, Jeong-Geun;Jeong, Dong-Jin;Park, Sung-Chon;Chae, Su-Yong;Yang, Hong-Geun
    • Journal of Information Display
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    • 제3권4호
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    • pp.1-3
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    • 2002
  • The antiferroelectric liquid crystal display (AFLCD) is a unique display that can at demonstrate a moving image perfectly the passive matrix driving scheme. We optimised driving the waveform and introduced a dual-driving method. Also, by improving this driving method and using line inversion method, we realize the AFLC display of high image quality with $160(RGB){\times}240$, 32768 colors, crosstalk free and flicker free contrast ratio is greater than 60:1, and the brightness is above 200 $cd/m^2$.

A Study on Image Segmentation Method Based on a Histogram for Small Target Detection (소형 표적 검출을 위한 히스토그램 기반의 영상분할 기법 연구)

  • Yang, Dong Won;Kang, Suk Jong;Yoon, Joo Hong
    • Journal of Korea Multimedia Society
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    • 제15권11호
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    • pp.1305-1318
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    • 2012
  • Image segmentation is one of the difficult research problems in machine vision and pattern recognition field. A commonly used segmentation method is the Otsu method. It is simpler and easier to implement but it fails if the histogram is unimodal or similar to unimodal. And if some target area is smaller than background object, then its histogram has the distribution close to unimodal. In this paper, we proposed an improved image segmentation method based on 1D Otsu method for a small target detection. To overcome drawbacks by unimodal histogram effect, we depressed the background histogram using a logarithm function. And to improve a signal to noise ratio, we used a local average value by the neighbor window for thresholding using 1D Otsu method. The experimental results show that our proposed algorithm performs better segmentation result than a traditional 1D Otsu method, and needs much less computational time than that of the 2D Otsu method.

Wideband Circularly Polarized Microstrip Array Antennal Adopting Sequential Rotation Method Using Shortened Phase Delay (단축된 위상지연을 사용하는 시퀀셜 로테이션 광대역 원형편파 마이크로스트립 배열 안테나)

  • 양태식;이범선
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • 제10권4호
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    • pp.628-635
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    • 1999
  • At center frequency of 11.85 GHz, wideband left-handed circularly polarized microstrip array antenna is designed with the method of sequential ratation based on $2\times2$ radiation elements($0^{\circ}$, $45^{\circ}$, $90^{\circ}$, $135^{\circ}$ phase delay). Its return loss, axial ratio bandwidth, radration pattern, and gain are compared with those adopting sequential rotation based on $1\times2$ radiation elements($0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$phase delay). The $8\times8$ array is manufactured and measured. The results show that 10 dB return loss bandwidth is 10.51~12.74GHz(18.82%) which is 1.57 times wider than the case using $1\times2$ sequential rotation method, 3 dB axial ratio bandwidth is 11.43~12.5 GHz(9.03%) which is 1.25 times as wide as that using $1\times2$ sequential rotation method and the antennal gain is 25.4 dB. The results of mesurements are almost similar to those of simulation.

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A Noise Reduction Method Combined with HMM Composition for Speech Recognition in Noisy Environments

  • Shen, Guanghu;Jung, Ho-Youl;Chung, Hyun-Yeol
    • IEMEK Journal of Embedded Systems and Applications
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    • 제3권1호
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    • pp.1-7
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    • 2008
  • In this paper, a MSS-NOVO method that combines the HMM composition method with a noise reduction method is proposed for speech recognition in noisy environments. This combined method starts with noise reduction with modified spectral subtraction (MSS) to enhance the input noisy speech, then the noise and voice composition (NOVO) method is applied for making noise adapted models by using the noise in the non-utterance regions of the enhanced noisy speech. In order to evaluate the effectiveness of our proposed method, we compare MSS-NOVO method with other methods, i.e., SS-NOVO, MWF-NOVO. To set up the noisy speech for test, we add White noise to KLE 452 database with different SNRs range from 0dB to 15dB, at 5dB intervals. From the tests, MSS-NOVO method shows average improvement of 66.5% and 13.6% compared with the existing SS-NOVO method and MWF-NOVO method, respectively. Especially our proposed MSS-NOVO method shows a big improvement at low SNRs.

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Coding Efficiency Improvement By Applying Rate-Distortion Optimization To 3D-DCT Based Integral Image Compression Method (3D-DCT 기반 집적영상 압축 방법의 율-왜곡 최적화를 통한 부호화 효율 향상 방법)

  • Jeon, Ju-Il;Kang, Hyun-Soo
    • The Journal of the Korea Contents Association
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    • 제12권9호
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    • pp.1-8
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    • 2012
  • In this paper, we propose a rate-distortion optimization method to improve the coding efficiency of the conventional 3D-DCT based compression method using adaptive block mode selection for integral images. In the conventional 3D-DCT based compression method, 3D-DCT blocks of variable block sizes are adaptively selected depending on the characteristics of integral images, and then 3D-DCT is performed. The proposed method applies a rate-distortion optimization to determine the optimal block mode. In addition, we suggest the optimal Lagrangian parameter for integral images. Experimental results show that the proposed method gives bit-rate reduction of about 5%.

Accurate Parked Vehicle Detection using GMM-based 3D Vehicle Model in Complex Urban Environments (가우시안 혼합모델 기반 3차원 차량 모델을 이용한 복잡한 도시환경에서의 정확한 주차 차량 검출 방법)

  • Cho, Younggun;Roh, Hyun Chul;Chung, Myung Jin
    • The Journal of Korea Robotics Society
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    • 제10권1호
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    • pp.33-41
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    • 2015
  • Recent developments in robotics and intelligent vehicle area, bring interests of people in an autonomous driving ability and advanced driving assistance system. Especially fully automatic parking ability is one of the key issues of intelligent vehicles, and accurate parked vehicles detection is essential for this issue. In previous researches, many types of sensors are used for detecting vehicles, 2D LiDAR is popular since it offers accurate range information without preprocessing. The L shape feature is most popular 2D feature for vehicle detection, however it has an ambiguity on different objects such as building, bushes and this occurs misdetection problem. Therefore we propose the accurate vehicle detection method by using a 3D complete vehicle model in 3D point clouds acquired from front inclined 2D LiDAR. The proposed method is decomposed into two steps: vehicle candidate extraction, vehicle detection. By combination of L shape feature and point clouds segmentation, we extract the objects which are highly related to vehicles and apply 3D model to detect vehicles accurately. The method guarantees high detection performance and gives plentiful information for autonomous parking. To evaluate the method, we use various parking situation in complex urban scene data. Experimental results shows the qualitative and quantitative performance efficiently.

STUDY ON STATISTICAL ESTIMATION OF IRRADIANT CONTRAST (통계적 방법을 이용한 적외선 신호 대비값 계산 방법 연구)

  • Han, K.I.;Choi, J.H.;Ha, N.K.;Jang, H.S.;Lee, S.H.;Kim, D.G.;Kim, T.K.
    • Journal of computational fluids engineering
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    • 제22권1호
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    • pp.37-42
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    • 2017
  • Infrared signals are frequently used to detect objects exposed to wide variety of environmental conditions. Detection by infrared signature is accomplished by distinguishing objects by using the IR radiant contrast between objects and the background. There are several methods of estimating the IR radiant contrast. The inverse distance weighting method, which is one of the IR radiant contrast estimation method using the effect of distance from objects, is known to be an effective way to analyze radiant contrast for complex backgrounds. However this method has a disadvantage of requiring a long calculation time. In this study we propose a statistical method of estimating the IR radiant contrast by using randomly selected pixels of arbitrary number among background pixels to reduce calculation time. Some measured IR images in MWIR and LWIR regions are used to test the applicability of the method proposed and we found that the proposed method is very effective in determining the IR radiant contrast showing very rapid estimation with minar accuracy loss.

Study on D2D Relay based Interconnection Network of HAM Radio and Wi-Fi for Securing Communication Performance in Satellite Wireless Package Systems (이동단말용 위성 통신 무선 패키지 시스템을 위한 D2D Relay 기반 HAM Radio와 Wi-Fi Network 결합망의 통신 성능 확보 연구)

  • Hwang, Yu Min;Cha, Jae Sang;Kim, Jin Young
    • Journal of Satellite, Information and Communications
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    • 제10권1호
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    • pp.12-16
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    • 2015
  • In this paper, we introduce a wireless package system based on the amateur radio HR(HAM Radio) and satellite communication as a novel wireless disaster communication system and have configured a interference scenario receiving interference from adjacent base stations and D2D groups in the disaster network. In such interference scenarios, we propose a frequency re-allocation method to avoid interference and communicate with disaster networks by securing the channel capacity required between D2D terminals. As a result of computer simulation, we can find the proposed method has improved BED performance of a gain of 1.5dB and overall system throughput than conventional methods.