1997~2000년에 발생된 황사에 관한 연구

정용승,김학성,낫짜가도르지 엘,적데어 디,첸 수잰 한국교원대학교 환경과학연구소 2002 환경연구논문집 Vol.- No.7

Joint monitoring of yellow sand (YS) phenomena occurred from 1997 to 2000 was carried out. It was found that the YS in source regions occurred in any time during the year, while the severe dust storms occurred frequently from March to May after the spring thaw. Wind erosion occurred usually with wind greater than about 8 ms^-1 in the source region in any seasons. However, severe YS phenomenon found to occur with wind greater than 15 ms^-1 at least for 3 hours or more. In source regions, YS occurred over 60∼120 days per year. In Korea, YS was found to occur 8∼12 cases per year with 12-22 YS days. It was recorded that maximum concentrations of TSP were 989∼1396 ㎍ m^-3 with PM10 values of 861∼996 ㎍ m^-3 and with the lowest visibility of 1.4∼1.6km. In Mongolia, however, it was observed that the number of dusty days decreased due to the increase in rainy days.

Comparative Analysis of Logistic Regression, Support Vector Machine and Artificial Neural Network for the Differential Diagnosis of Benign and Malignant Solid Breast Tumors by the Use of Three-Dimensional Power Doppler Imaging

Shou-Tung Chen,Yi-Hsuan Hsiao,Yu-Len Huang,Shou-Jen Kuo,Hsin-Shun Tseng,Hwa-Koon Wu,Dar-Ren Chen 대한영상의학회 2009 Korean Journal of Radiology Vol.10 No.5

Objective: Logistic regression analysis (LRA), Support Vector Machine (SVM) and a neural network (NN) are commonly used statistical models in computeraided diagnostic (CAD) systems for breast ultrasonography (US). The aim of this study was to clarify the diagnostic ability of the use of these statistical models for future applications of CAD systems, such as three-dimensional (3D) power Doppler imaging, vascularity evaluation and the differentiation of a solid mass. Materials and Methods: A database that contained 3D power Doppler imaging pairs of non-harmonic and tissue harmonic images for 97 benign and 86 malignant solid tumors was utilized. The virtual organ computer-aided analysis-imaging program was used to analyze the stored volumes of the 183 solid breast tumors. LRA, an SVM and NN were employed in comparative analyses for the characterization of benign and malignant solid breast masses from the database. Results: The values of area under receiver operating characteristic (ROC) curve, referred to as Az values for the use of non-harmonic 3D power Doppler US with LRA, SVM and NN were 0.9341, 0.9185 and 0.9086, respectively. The Az values for the use of harmonic 3D power Doppler US with LRA, SVM and NN were 0.9286, 0.8979 and 0.9009, respectively. The Az values of six ROC curves for the use of LRA, SVM and NN for non-harmonic or harmonic 3D power Doppler imaging were similar. Conclusion: The diagnostic performances of these three models (LRA, SVM and NN) are not different as demonstrated by ROC curve analysis. Depending on user emphasis for the use of ROC curve findings, the use of LRA appears to provide better sensitivity as compared to the other statistical models. Objective: Logistic regression analysis (LRA), Support Vector Machine (SVM) and a neural network (NN) are commonly used statistical models in computeraided diagnostic (CAD) systems for breast ultrasonography (US). The aim of this study was to clarify the diagnostic ability of the use of these statistical models for future applications of CAD systems, such as three-dimensional (3D) power Doppler imaging, vascularity evaluation and the differentiation of a solid mass. Materials and Methods: A database that contained 3D power Doppler imaging pairs of non-harmonic and tissue harmonic images for 97 benign and 86 malignant solid tumors was utilized. The virtual organ computer-aided analysis-imaging program was used to analyze the stored volumes of the 183 solid breast tumors. LRA, an SVM and NN were employed in comparative analyses for the characterization of benign and malignant solid breast masses from the database. Results: The values of area under receiver operating characteristic (ROC) curve, referred to as Az values for the use of non-harmonic 3D power Doppler US with LRA, SVM and NN were 0.9341, 0.9185 and 0.9086, respectively. The Az values for the use of harmonic 3D power Doppler US with LRA, SVM and NN were 0.9286, 0.8979 and 0.9009, respectively. The Az values of six ROC curves for the use of LRA, SVM and NN for non-harmonic or harmonic 3D power Doppler imaging were similar. Conclusion: The diagnostic performances of these three models (LRA, SVM and NN) are not different as demonstrated by ROC curve analysis. Depending on user emphasis for the use of ROC curve findings, the use of LRA appears to provide better sensitivity as compared to the other statistical models.

Walking Out of Sadness: the Other Side of Taiwan Cinema

Chen, Ru-Shou Robert 문학과영상학회 2013 문학과영상 Vol.14 No.1

City of Sadness (1989) marks the beginning of an end in the history of Taiwan cinema. For the past 20 years, Taiwan cinema was heavily politicized in which, on one hand, it was embedded with government propaganda, or, on the other hand, it became a tool to explore historical trauma left by the Japanese colonialization and the KMT post-colonial rule. This paper would like to explore another side of Taiwan cinema, which can be tentatively classified as the “youth nostalgia” films. This trend starts with Blue Gate Crossing (2002), in which friendship and sexual awakening were foregrounded to portray the lives of three main characters in their high school days. It then was followed by films such as Eternal Summer (2006), Summer’s Tail (2007), Secret (2007), Wind of September (2008), and recently You’re the Apple of My Eye (2011). The milieu for these films is mainly at the high school campus. The narrative circles around their school life, rites of passage, hetero- and/or homo-sexual relationships among friends. High school years in these films are depicted as good old days. Even the imagery is sometimes tinted with yellowish color to evoke nostalgic feeling. Most important of all, those films are depoliticized to the extent that social law and order, the burdens of Taiwan history, and adult figures are all absent from the narrative. These films signify a new opening for Taiwan cinema to “walk out of sadness.” City of Sadness (1989) marks the beginning of an end in the history of Taiwan cinema. For the past 20 years, Taiwan cinema was heavily politicized in which, on one hand, it was embedded with government propaganda, or, on the other hand, it became a tool to explore historical trauma left by the Japanese colonialization and the KMT post-colonial rule. This paper would like to explore another side of Taiwan cinema, which can be tentatively classified as the “youth nostalgia” films. This trend starts with Blue Gate Crossing (2002), in which friendship and sexual awakening were foregrounded to portray the lives of three main characters in their high school days. It then was followed by films such as Eternal Summer (2006), Summer’s Tail (2007), Secret (2007), Wind of September (2008), and recently You’re the Apple of My Eye (2011). The milieu for these films is mainly at the high school campus. The narrative circles around their school life, rites of passage, hetero- and/or homo-sexual relationships among friends. High school years in these films are depicted as good old days. Even the imagery is sometimes tinted with yellowish color to evoke nostalgic feeling. Most important of all, those films are depoliticized to the extent that social law and order, the burdens of Taiwan history, and adult figures are all absent from the narrative. These films signify a new opening for Taiwan cinema to “walk out of sadness.”

Instantaneous multi-mode identification and analysis of vortex-induced vibration via a mode decomposition method

Chen, Zheng-Shou,Rhee, Shin Hyung Elsevier 2019 Applied ocean research Vol.93 No.-

<P><B>Abstract</B></P> <P>The dynamic characteristics of marine risers/pipes often present serried modes with various frequencies due to high levels of structural flexibility and slenderness, especially when the flow velocity is non-uniformly distributed along the span. Therefore, the vortex-induced vibration (hence VIV) for slender risers/pipes is usually characterized by multi-mode motions. In this paper, by means of a newly developed empirical mode decomposition (EMD) method which contributes to more efficient instantaneous multi-mode identification and analysis, new characteristics of a multi-mode “lock-in” vibration process of a large-scale flexible pipe subject to shear flow were discussed. Because the two-degree vibration along the span can be analyzed simultaneously, the effects of multi-mode VIV were investigated systematically. From the given illustrative examples, it was found that the vibration energy diffusion between the fluid and the structure, and among the participating modes, may be repeatable and reversible, or even irreversible, which causes VIV to be highly intricate. The coexistence of multiple modes, energy transfer, and mode switching/jump is observed when the reduced velocity is relatively high. The multi-dominant mode phenomenon is also found in both cross-flow (CF) and in-line (IL) VIVs. Energy transfers between the CF and IL directions occasionally occur, and CF VIV is apt to dominate the vibration process, because it is superior to IL VIV with the increment of the reduced velocity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> By means of a newly developed empirical mode decomposition (EMD) method, new characteristics of a multi-mode “lock-in” vibration process of a large-scale flexible pipe subject to shear flow were discussed. </LI> <LI> The vibration energy diffusion between the fluid and the structure, and among the participating modes, may be repeatable and reversible, or even irreversible, which causes VIV to be highly intricate. </LI> <LI> The multi-dominant mode phenomenon is found in both cross-flow (CF) and in-line (IL) VIVs. </LI> <LI> In contrast to IL VIV, CF VIV is superior and prone to dominate the vibration process with the increment of the reduced velocity. </LI> <LI> Energy transfers between the CF and IL directions occasionally occur. </LI> </UL> </P>

Numerical investigation of vortex shedding and vortex-induced vibration for flexible riser models

Chen, Zheng-Shou,Kim, Wu-Joan The Society of Naval Architects of Korea 2010 International Journal of Naval Architecture and Oc Vol.2 No.2

The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.

Combination of multiplex reverse transcription recombinase polymerase amplification assay and capillary electrophoresis provides high sensitive and high-throughput simultaneous detection of avian influenza virus subtypes

Shou-Kuan Tsai,Chen-Chih Chen,Han-Jia Lin,Han-You Lin,Ting-Tzu Chen,Lih-Chiann Wang 대한수의학회 2020 Journal of Veterinary Science Vol.21 No.2

The pandemic of avian influenza viruses (AIVs) in Asia has caused enormous economic loss in poultry industry and human health threat, especially clade 2.3.4.4 H5 and H7 subtypes in recent years. The endemic chicken H6 virus in Taiwan has also brought about human and dog infections. Since wild waterfowls is the major AIV reservoir, it is important to monitor the diversified subtypes in wildfowl flocks in early stage to prevent viral reassortment and transmission. To develop a more efficient and sensitive approach is a key issue in epidemic control. In this study, we integrate multiplex reverse transcription recombinase polymerase amplification (RT-RPA) and capillary electrophoresis (CE) for high-throughput detection and differentiation of AIVs in wild waterfowls in Taiwan. Four viral genes were detected simultaneously, including nucleoprotein (NP) gene of all AIVs, hemagglutinin (HA) gene of clade 2.3.4.4 H5, H6 and H7 subtypes. The detection limit of the developed detection system could achieve as low as one copy number for each of the four viral gene targets. Sixty wild waterfowl field samples were tested and all of the four gene signals were unambiguously identified within 6 h, including the initial sample processing and the final CE data analysis. The results indicated that multiplex RT-RPA combined with CE was an excellent alternative for instant simultaneous AIV detection and subtype differentiation. The high efficiency and sensitivity of the proposed method could greatly assist in wild bird monitoring and epidemic control of poultry.

Empirical decomposition method for modeless component and its application to VIV analysis

Chen, Zheng-Shou,Park, Yeon-Seok,Wang, Li-ping,Kim, Wu-Joan,Sun, Meng,Li, Qiang The Society of Naval Architects of Korea 2015 International Journal of Naval Architecture and Oc Vol.7 No.2

Aiming at accurately distinguishing modeless component and natural vibration mode terms from data series of nonlinear and non-stationary processes, such as Vortex-Induced Vibration (VIV), a new empirical mode decomposition method has been developed in this paper. The key innovation related to this technique concerns the method to decompose modeless component from non-stationary process, characterized by a predetermined 'maximum intrinsic time window' and cubic spline. The introduction of conceptual modeless component eliminates the requirement of using spurious harmonics to represent nonlinear and non-stationary signals and then makes subsequent modal identification more accurate and meaningful. It neither slacks the vibration power of natural modes nor aggrandizes spurious energy of modeless component. The scale of the maximum intrinsic time window has been well designed, avoiding energy aliasing in data processing. Finally, it has been applied to analyze data series of vortex-induced vibration processes. Taking advantage of this newly introduced empirical decomposition method and mode identification technique, the vibration analysis about vortex-induced vibration becomes more meaningful.

Empirical mode decomposition based on Fourier transform and band-pass filter

Chen, Zheng-Shou,Rhee, Shin Hyung,Liu, Gui-Lin The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.2

A novel empirical mode decomposition strategy based on Fourier transform and band-pass filter techniques, contributing to efficient instantaneous vibration analyses, is developed in this study. Two key improvements are proposed. The first is associated with the adoption of a band-pass filter technique for intrinsic mode function sifting. The primary characteristic of decomposed components is that their bandwidths do not overlap in the frequency domain. The second improvement concerns an attempt to design narrowband constraints as the essential requirements for intrinsic mode function to make it physically meaningful. Because all decomposed components are generated with respect to their intrinsic narrow bandwidth and strict sifting from high to low frequencies successively, they are orthogonal to each other and are thus suitable for an instantaneous frequency analysis. The direct Hilbert spectrum is employed to illustrate the instantaneous time-frequency-energy distribution. Commendable agreement between the illustrations of the proposed direct Hilbert spectrum and the traditional Fourier spectrum was observed. This method provides robust identifications of vibration modes embedded in vibration processes, deemed to be an efficient means to obtain valuable instantaneous information.

Effect of bidirectional internal flow on fluid.structure interaction dynamics of conveying marine riser model subject to shear current

Chen, Zheng-Shou,Kim, Wu-Joan The Society of Naval Architects of Korea 2012 International Journal of Naval Architecture and Oc Vol.4 No.1

This article presents a numerical investigation concerning the effect of two kinds of axially progressing internal flows (namely, upward and downward) on fluid.structure interaction (FSI) dynamics about a marine riser model which is subject to external shear current. The CAE technology behind the current research is a proposed FSI solution, which combines structural analysis software with CFD technology together. Efficiency validation for the CFD software was carried out first. It has been proved that the result from numerical simulations agrees well with the observation from relating model test cases in which the fluidity of internal flow is ignorable. After verifying the numerical code accuracy, simulations are conducted to study the vibration response that attributes to the internal progressive flow. It is found that the existence of internal flow does play an important role in determining the vibration mode (/dominant frequency) and the magnitude of instantaneous vibration amplitude. Since asymmetric curvature along the riser span emerges in the case of external shear current, the centrifugal and Coriolis accelerations owing to up- and downward internal progressive flows play different roles in determining the fluid.structure interaction response. The discrepancy between them becomes distinct, when the velocity ratio of internal flow against external shear current is relatively high.

FSI Analysis of TLP Tether System for Floating Wind Turbine

Zheng-Shou Chen,Wu-Joan Kim,Jae-Hoon Yoo 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.1

ANSYS multi-physics software was applied to solve the coupled dynamic problem related to a full-scale TIP foundation for floating wind turbines. In this coupled dynamics simulation, the forced oscillation imposed on the tethers' top resulting from the sway of the wind turbine platform and the self-excited vortex-induced vibration (VIV) along the tether span have been taken into account. The stability of this tensioned tether system has been validated in the form of separate static and dynamic analyses. The dynamic characteristics of the tensioned tether linked to the floating wind turbine were analyzed by the resultant modal form and its corresponding vortex shedding pattern. The calculated result shows that even a slight forced oscillation imposed on the tethers' top leads to the VIV amplification and enhances the risk of instability in the case of low pretension. It is also found that the "synchronization" would be aggravated when the top tension decreases and the "2P" vortex shedding mode takes place. The increased top tension imposed on the tethers contributes to the stability of the tensioned legs by diminishing the oscillation amplitude markedly.