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Preparation and Characterization of Cellulose Nano-Whiskers Extracted from Microcrystalline Cellulose by Acid Hydrolysis (산 가수분해를 이용하여 microcrystalline cellulose로부터 추출 된 cellulose nano-whisker의 특성분석)

  • Jeong, Hae-Deuk;Yoon, Chang-Rok;Lee, Jong-Hyeok;Bang, Dae-Suk
    • Elastomers and Composites
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    • v.45 no.1
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    • pp.51-57
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    • 2010
  • Cellulose nanowhiskers (CNW) gamered increasing interest for their remarkable reinforcement of polymer composites. In this work, we were to produce cellulose whiskers from commercially available microcrystalline cellulose (MCC) by acid hydrolysis with sulfuric and hydrochloric acids. Electron microscopy found that each acid produced sililar cellulose crystals of diameters ranging from 20 to 30 nm and lengths ranging from 200 to 300 nm. Moreover, all samples showed remarkable flow birefringence through crossed polarization filters. Conductometric titration of CNW suspensions revealed that the sulfuric acid treated sample had a surface charge of between 140.00 mmol/kg and 197.78 mmol/kg due to sulfate groups, while that of the hydrochloric acid treated sample was undetectable. Thermogravimetric analysis showed that the thermal decomposition temperature and apparent activation energy (evaluated by Broido's method at different stages of thermal decomposition.) of H1-CNW - prepared by hydrolysis with hydrochloric acid - was higher than those of S1-CNW and S2-CNW - prepared by hydrolyzing MCC with sulfuric acid.

Acceleration of Anisotropic Elastic Reverse-time Migration with GPUs (GPU를 이용한 이방성 탄성 거꿀 참반사 보정의 계산가속)

  • Choi, Hyungwook;Seol, Soon Jee;Byun, Joongmoo
    • Geophysics and Geophysical Exploration
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    • v.18 no.2
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    • pp.74-84
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    • 2015
  • To yield physically meaningful images through elastic reverse-time migration, the wavefield separation which extracts P- and S-waves from reconstructed vector wavefields by using elastic wave equation is prerequisite. For expanding the application of the elastic reverse-time migration to anisotropic media, not only the anisotropic modelling algorithm but also the anisotropic wavefield separation is essential. The anisotropic wavefield separation which uses pseudo-derivative filters determined according to vertical velocities and anisotropic parameters of elastic media differs from the Helmholtz decomposition which is conventionally used for the isotropic wavefield separation. Since applying these pseudo-derivative filter consumes high computational costs, we have developed the efficient anisotropic wavefield separation algorithm which has capability of parallel computing by using GPUs (Graphic Processing Units). In addition, the highly efficient anisotropic elastic reverse-time migration algorithm using MPI (Message-Passing Interface) and incorporating the developed anisotropic wavefield separation algorithm with GPUs has been developed. To verify the efficiency and the validity of the developed anisotropic elastic reverse-time migration algorithm, a VTI elastic model based on Marmousi-II was built. A synthetic multicomponent seismic data set was created using this VTI elastic model. The computational speed of migration was dramatically enhanced by using GPUs and MPI and the accuracy of image was also improved because of the adoption of the anisotropic wavefield separation.

The study on scheme for train position detection based on GPS/DR (GPS/DR기반의 차상열차위치검지방안 연구)

  • Shin, Kyung-Ho;Joung, Eui-Jin;Lee, Jun-Ho
    • Proceedings of the KSR Conference
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    • 2006.11b
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    • pp.802-810
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    • 2006
  • For a thorough train control, the precise train position detection is necessarily required. The widely used current way for train position detection is the one of using track circuits. The track circuit has a simple structure, and has a high level of reliability. However trains can be detected only on track circuits, which have to be installed on all ground sections, and much amount of cost for its installation and maintenance is needed. In addition, for the track circuit, only discontinuous position detection is possible because of the features of the closed circuit loop configuration. As the recent advances in telecommunication technologies and high-tech vehicle-based control equipments, for the train position detection, the method to detect positions directly from on trains is being studied. Vehicle-based position detection method is to estimate train positions, speed, timing data continuously, and to use them as the control information. In this paper, the features of GPS navigation and DR navigation are analyzed, and the navigation filters are designed by constructing vehicle-based train position detection method by combining GPS navigation and DR navigation for their complementary cooperation, and by using kalman filter. The position estimation performance of the proposed method is also confirmed by simulations.

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Development of GPS/IMU/SPR Integrated Algorithm and Performance Analysis for Determination of Precise Car Positioning (정밀 차량 위치결정을 위한 GPS/IMU/SPR 통합 알고리즘 개발 및 성능 분석)

  • Han, Joong-Hee;Kang, Beom Yeon;Kwon, Jay Hyoun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.32 no.2
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    • pp.163-171
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    • 2014
  • Based on the GPS/IMU integration, the car navigation has unstable conditions as well as drastically reduces accuracies in urban region. Nowadays, many cars mounted the camera to record driving states. If the ground coordinates of street furniture are known, the position and attitude of camera can be determined through SPR(Single Photo Resection). Therefore, an estimated position and attitude from SPR can be applied measurements in Kalman filter for updating errors of navigation solutions from GPS/IMU integration. In this study, the GPS/IMU/SPR integration algorithm was developed in loosely coupled modes through extended Kalman filters. Also, in order to analyze performances of GPS/IMU/SPR, simulation tests were conducted in GPS signal reception environments and the GCPs (Ground Control Points) distributions. In fact, the position and attitude gathered from GPS/IMU/SPR integration are more precise than the position and attitude from GPS/IMU integration. When IPs (image points), corresponded to GCPs, were concentrated in the center of image, the position error in the optical axis respectively increased. To understand effects from SPR, we plan to carry additional test on the magnitude of GCP, IP and initial exterior orientation errors.

Impact of Group Delay in RF BPF on Impulse Radio Systems (임펄스 라디오 시스템에서 RF 대역 통과 필터의 군지연 영향 분석)

  • Myoung Seong-Sik;Kwon Bong-Su;Kim Young-Hwan;Yook Jong-Gwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.4 s.95
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    • pp.380-388
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    • 2005
  • This paper presents analysis results of the effects of RF filter characteristics on the system performance of impulse radio. The impulse radio system transmits modulated pulses having very short time duration and information can be extracted in receiver side based on cross-correlation between received and transmitted pulses. Accordingly, the pulse distortion due to in-band group delay variation can cause serious system performance degradation. In general, RF bandpass filters inevitably cause group delay difference to the signal passing through the filter which is proportional to its skirt characteristic due to its resonance phenomenon. For time as well as frequency domain analysis, small signal scattering parameter $S_{21}$ and its Fourier transform are used to characterize output pulse waveform under the condition that the input and output ports are matched. The output pulse waveform of the filter is predicted based on convolution integral between input pulse and filter transfer function, and resulting BER performances in the BPM and PPM based impulse radio system are calculated.

A New Design of the Interrogating Waves for Medical Ultrasonic Imaging Based on Wavelets and Subband Filter Banks: A Simulation Study (의료용 초음파 영상시스템을 위한 Wavelet 과 Subband Filter Bank 에 기반한 새로운 탐침 파형의 설계: A Simulation Study)

  • Yang Yoon Seok
    • Journal of Biomedical Engineering Research
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    • v.25 no.6
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    • pp.431-438
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    • 2004
  • Medical ultrasonic imaging is a useful imaging facility known to be most safe and easy. It enables physicians to observe the inside structures of the bodies, blood flow, and motions of internal organs. Some physical properties of biologic tissues can also be estimated from backscattered sounds. However, the ultrasonic pulses interrogating the living organisms leave their footprints in the returning signals during imaging. Some significant details are buried in the footprints and their overlaps from adjacent particles. These distortions also decrease the quality of the images. Many research efforts have been made to enhance the image quality and to recover the acoustic information in various ways. In this study, a new interrogation method based on the wavelet and subband filter bank is proposed. It adopts the subband wavelet filters satisfying the perfect-reconstruction (PR) conditions as the interrogating pulses to restore the details useful in tissue characterization and to enhance the image quality. The proposed method was applied to two types of simulations of ultrasonic imaging. The results showed its ability to restore the detailsin the simulated interrogation of biologic tissues, and verified the improved image quality in the simulated imaging of general ultrasonic phantom compared with the conventional method.

Study on the Emergency Assessment about Seismic Safety of Cable-supported Bridges using the Comparison of Displacement due to Earthquake with Disaster Management Criteria (변위 비교를 통한 케이블지지교량의 긴급 지진 안전성 평가 방법의 고찰)

  • Park, Sung-Woo;Lee, Seung Han
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.6
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    • pp.114-122
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    • 2018
  • This study presents the emergency assessment method about seismic safety of cable-supported bridges using seismic acceleration sensors installed on the primary structural elements of them. The structural models of bridges are updated iteratively to make their dynamic characteristics to be similar to those of real bridges based on the comparison of their natural frequencies with those of real bridges estimated from acceleration data measured at ordinary times by the seismic acceleration sensor. The displacement at the location of each seismic acceleration sensor is derived by seismic analysis using design earthquake, and the peak value of them is determined as the disaster management criteria in advance. The displacement time history is calculated by the double integration of the acceleration time history which is recorded at each seismic acceleration sensor and filtered by high cut(low pass) and low cut(high pass) filters. Finally, the seismic safety is evaluated by the comparison of the peak value in calculated displacement time history with the disaster management criteria determined in advance. The applicability of proposed methodology is verified by performing the seismic safety assessment of 12 cable-supported bridges using the acceleration data recorded during Gyeongju earthquake.

Molecular and Ecological Analyses of Microbial Community Structures in Biofilms of a Full-Scale Aerated Up-Flow Biobead Process

  • Ju, Dong-Hun;Choi, Min-Kyung;Ahn, Jae-Hyung;Kim, Mi-Hwa;Cho, Jae-Chang;Kim, Tae-Sung;Kim, Tae-San;Seong, Chi-Nam;Ka, Jong-Ok
    • Journal of Microbiology and Biotechnology
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    • v.17 no.2
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    • pp.253-261
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    • 2007
  • Molecular and cultivation techniques were used to characterize the bacterial communities of biobead reactor biofilms in a sewage treatment plant to which an Aerated Up-Flow Biobead process was applied. With this biobead process, the monthly average values of various chemical parameters in the effluent were generally kept under the regulation limits of the effluent quality of the sewage treatment plant during the operation period. Most probable number (MPN) analysis revealed that the population of denitrifying bacteria was abundant in the biobead #1 reactor, denitrifying and nitrifying bacteria coexisted in the biobead #2 reactor, and nitrifying bacteria prevailed over denitrifying bacteria in the biobead #3 reactor. The results of the MPN test suggested that the biobead #2 reactor was a transition zone leading to acclimated nitrifying biofilms in the biobead #3 reactor. Phylogenetic analysis of 16S rDNA sequences cloned from biofilms showed that the biobead #1 reactor, which received a high organic loading rate, had much diverse microorganisms, whereas the biobead #2 and #3 reactors were dominated by the members of Proteobacteria. DGGE analysis with the ammonia monooxygenase (amoA) gene supported the observation from the MPN test that the biofilms of September were fully developed and specialized for nitrification in the biobead reactor #3. All of the DNA sequences of the amoA DGGE bands were very similar to the sequence of the amoA gene of Nitrosomonas species, the presence of which is typical in the biological aerated filters. The results of this study showed that organic and inorganic nutrients were efficiently removed by both denitrifying microbial populations in the anaerobic tank and heterotrophic and nitrifying bacterial biofilms well-formed in the three functional biobead reactors in the Aerated Up-Flow Biobead process.

Network-adaptive H.264 Video Streaming over IEEE 802.11e (IEEE 802.11e에서 네트워크 적응적인 H.264 비디오 스트리밍)

  • Lee, Sun-Hun;Chung, Kwang-Sue
    • Journal of Broadcast Engineering
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    • v.13 no.1
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    • pp.6-16
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    • 2008
  • An instable wireless channel condition causes more packet losses and retransmissions due to interference, fading, station mobility, and so on. Therefore video streaming service over a wireless networks is a challenging task because of the changes in the wireless channel conditions and time-constraints characteristics of the video streaming services. To provide efficient video streaming over a wireless networks, QoS-enhanced MAC protocol, IEEE 802.11e, is standardized recently. Tn this paper, we propose a new network-adaptive H.264 video streaming mechanism in the IEEE 802.11e wireless networks. To improve the quality of video streaming services, video stream has to adapt to the changes in the wireless channel conditions. The wireless channel conditions are estimated by the packet loss probability and informed to the application layer by the cross-layering. According to the wireless channel information, the video streaming application filters out the low-priority data. This adaptation mechanism efficiently uses system resources because it drops the low-priority data in advance. Therefore, our cross-layer design can provide improved video streaming services to the end-user. Through the implementation and performance evaluation, we prove that the proposed mechanism improves the QoS of the video streaming by providing the smoothed playback.

Accurate Camera Calibration Method for Multiview Stereoscopic Image Acquisition (다중 입체 영상 획득을 위한 정밀 카메라 캘리브레이션 기법)

  • Kim, Jung Hee;Yun, Yeohun;Kim, Junsu;Yun, Kugjin;Cheong, Won-Sik;Kang, Suk-Ju
    • Journal of Broadcast Engineering
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    • v.24 no.6
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    • pp.919-927
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    • 2019
  • In this paper, we propose an accurate camera calibration method for acquiring multiview stereoscopic images. Generally, camera calibration is performed by using checkerboard structured patterns. The checkerboard pattern simplifies feature point extraction process and utilizes previously recognized lattice structure, which results in the accurate estimation of relations between the point on 2-dimensional image and the point on 3-dimensional space. Since estimation accuracy of camera parameters is dependent on feature matching, accurate detection of checkerboard corner is crucial. Therefore, in this paper, we propose the method that performs accurate camera calibration method through accurate detection of checkerboard corners. Proposed method detects checkerboard corner candidates by utilizing 1-dimensional gaussian filters with succeeding corner refinement process to remove outliers from corner candidates and accurately detect checkerboard corners in sub-pixel unit. In order to verify the proposed method, we check reprojection errors and camera location estimation results to confirm camera intrinsic parameters and extrinsic parameters estimation accuracy.