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Xing Yu,이태영 한국기상학회 2011 Asia-Pacific Journal of Atmospheric Sciences Vol.47 No.2
We have investigated the role of convective parameterization in simulations of heavy precipitation systems at grey-zone (2-10 km)resolutions using an approach similar to that used in “observing system simulation experiment”. Simulations with a 1-km grid serve as benchmark simulations. The impacts of convective parameterization at greyzone resolutions (i.e., 3, 6, and 9 km) are then investigated. This study considers two heavy precipitation systems including one associated with a mesoscale cyclone generated over the Shandong Peninsula on 24-25 July 1991, and the other associated with a cloud cluster occurred on 15-16 July 2009. The present study indicates that convective parameterization does not affect much the simulations of the two heavy precipitation systems with 3-km grid size. However, it significantly affects simulations for grid sizes of 6 and 9 km. Simulations with the Kain-Fritsch scheme produce deficiencies such as relatively small heavy rainfall area, smaller maximum precipitation rate, wider area of weak precipitation, etc. Simulations without convective parameterization have also some negative effects such as the overprediction of area-averaged precipitation rate and others. A modified trigger function in the Kain-Fritsch scheme is found to improve the simulations of the heavy precipitation systems over the Korean Peninsula by reducing excessive trigger of convection, especially for simulations with 6- and 9- km grids.
The gridding of MOS for high resolution forecasting
Xing YU,Seon Ki PARK,Yong-Hee LEE,Kwang-Deuk AHN,Sung-Ho CHOO 한국기상학회 2011 한국기상학회 학술대회 논문집 Vol.2011 No.10-2
As the numerical weather prediction (NWP) models became more accurate, model output statistics (MOS) follow that trend. The Korean Meteorological Adminstration (KMA) descided to import the Unified Model (UM) as a next-generation NWP system since 2007. The KLAPS (Korea Local Analysis and. Prediction System) with 5 km resolution is used as the observation to verify the 12 km UM forecast. Four surface variables are verified – temperature, relative humidy, wind speed and wind direction. The MOS forecast are based on a meta-heuristic algorithm – harmony search (HS) and 80 potential varibles derived from the UM forecasts. The MOS process is as follows: 1) to intepolate the 12 km UM output to the corresponding KLAPS 5 km grids. 2) to derive 80 potential predictants. 3) to minimize the difference between the MOS forecasts and the KLAPS analysis fields. The coefficient tuning process is done by the HS method. The MOS is seperated for 4 seasons, and the traning period is 2007-2009. The UM was initilized twice a day (00 and 12 UTC), and 21 valid forecast times are from 6 to 66 hours. Therefore, there exist 2*21 equations for a given grid and predictor. Statistic scores show that MOS forecasts are superior to the UM forecasts for most grids.
Achalasia: The Current Clinical Dilemma and Possible Pathogenesis
Xingyu Jia,Songfeng Chen,Qianjun Zhuang,Niandi Tan,Mengyu Zhang,Yi Cui,Jinhui Wang,Xiangbin Xing,Yinglian Xiao 대한소화기 기능성질환∙운동학회 2023 Journal of Neurogastroenterology and Motility (JNM Vol.29 No.2
Achalasia is a primary esophageal motility disorder manifested by dysphagia and chest pain that impair patients’ quality of life, and it also leads to chronic esophageal inflammation by food retention and increases the risk of esophageal cancer. Although achalasia has long been reported, the epidemiology, diagnosis and treatment of achalasia are not fully understood. The current clinical dilemma of achalasia is mainly due to its unclear pathogenesis. In this paper, epidemiology, diagnosis treatment, as well as possible pathogenesis of achalasia will be reviewed and summarized. The proposed hypothesis on the pathogenesis of achalasia is that genetically susceptible populations potentially have a higher risk of infection with viruses, triggering autoimmune and inflammation responses to inhibitory neurons in lower esophageal sphincter.
Geometrical Simulation Model for Milling of Carbon Fiber Reinforced Polymers (CFRP)
Xingyu Fu,송경은,Dong Min Kim,Zhengyang Kang,Martin Byung-Guk Jun 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.11
This paper proposes a geometrical 3D milling simulation algorithm for Carbon Fiber Reinforced Polymer (CFRP) milling. In this simulation model, milling tools are simplified into layers of circles while CFRP lami- nates are simplified into layers of Dexel lines, which can realize simulations for various complex milling conditions. Significant geometrical parameters, for ex-ample, cutting angle and cutting length, can be computed with high efficiency. With some geometry-related physical models, the machining results can be pre-dicted for the entire milling process. The effectiveness of this simulation model has been validated by the milling force prediction and the delamination pre-diction. The performance of this simulation model benefits industrial CFRP manufacturing and provides a new method for online or long-time-interval simulation of CFRP machining.
Design and experimental study of a multi-modal piezoelectric energy harvester
Xingyu Xiong,S. Olutunde Oyadiji 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
A multi-modal piezoelectric vibration energy harvester is designed in this article. It consists of a cantilevered base beam and some upper and lower layer beams with rigid masses bonded between the beams as spacers. For a four-layer harvester subjected to random base excitations, relocating the mass positions leads to the generation of up to four close resonance frequencies over the frequency range from 10 Hz to 100 Hz with relative large power output. The harvesters are connected with a resistance decade box and the frequency response functions of the voltage and power on resistive loads are determined. The experimental results are validated with the simulation results using the finite element method. On a certain level of power output, the experimental results show that the multi-modal harvesters can generate a frequency band that is more than two times greater than the frequency band produced by a cantilevered beam harvester.
Effects of Secondary Elements on Vortex-Induced Vibration of a Streamlined Box Girder
Xingyu Chen,Fang Qiu,Haojun Tang,Yongle Li,Xinyu Xu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.1
Box girders are aerodynamically favorable, and the paper presents a study on the vortex-induced vibration (VIV) of this girder type at large angles of attack. Taking a box girder as an example, the form of the guardrails and the position of the maintenance tracks were improved to increase the VIV performance. The aerodynamic mechanism was further investigated according to the change in flow field around the girder. Results showed that the VIV performance of the box girder at positive angles of attack is worse. Improving secondary elements is an effective way to increase the VIV performance. Adding four rectangle bars above the original guardrails could achieve the target by preventing the generation of the vortex and blocking its movement. Moving the maintenance tracks inwards with a reasonable distance could also achieve the target as the flow passes through the girder more smoothly. With the combination of the optimal form of the guardrails and the optimal position of the maintenance tracks, the VIV performance of the bridge is higher. The countermeasures provide reference for the inhibition of the VIV of box girders.
Xingyu Fan,Jun LI,Hong Hao,Zhi-Wei Chen 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.5
This paper proposes using the multi-type sensor vibration measurements, such as from a relative displacement sensors and a traditional accelerometer for the damage detection of shear connectors in composite bridge under moving loads. Hilbert-Huang Transform (HHT) spectra of these responses will be fused with a data fusion approach i.e., Dempster-Shafer method, to detect the damage of shear connectors. Experimental studies on a composite bridge model in the laboratory are conducted to demonstrate the effectiveness and performance of using the proposed approach in detecting the damage of shear connectors in composite bridges. Both undamaged and damaged scenarios are considered. The detection results with the data fusion of multi-type sensor measurements show a more reliable and robust performance and accuracy, avoiding the false identifications.