An Experimental Study of the Hyper-parameters Distribution Region and Its Optimization Method for Support Vector Machine with Gaussian Kernel

Zhigang Yan,Yuanxuan Yang,Yunjing Ding 보안공학연구지원센터(IJSIP) 2013 International Journal of Signal Processing, Image Vol.6 No.5

Characteristics of Velocity Ambiguity for CINRAD-SA Doppler Weather Radars

Zhigang Chu,Yan Yin,Songshan Gu 한국기상학회 2014 Asia-Pacific Journal of Atmospheric Sciences Vol.50 No.2

The velocity ambiguity in Doppler weather radars hasinhibited the application of wind field data for long time. One effectivesolution is software-based velocity dealiasing algorithm. In thispaper, in order to better design, optimize and validate velocitydealiasing algorithms for CINRAD-SA, data from operational radarswere used to statistically characterize velocity ambiguity. The analyzedcharacteristic parameters included occurrence rate, and inter-station,inter-type, temporal, and spatial distributions. The results show that14.9% of cloud-rain files and 0.3% of clear-air files from CINRADSAradars are ambiguous. It is also found that echoes of weakconvections have the highest occurrence rate of velocity ambiguitythan any other cloud types, and the probability of ambiguity is higherin winter than in summer. A detailed inspection of the occurrence ofambiguity in various cases indicates that ambiguous points usuallyoccur in areas with an elevation angle of 6.0o, an azimuth of 70o or250o, radial distance of 50-60 km, and height of 5-6 km, and that99.4% of ambiguous points are in the 1st-folding interval. Suggestionsfor performing dealiasing at different locations and different timepoints are provided.

Ratio of PM2.5 to PM10 Mass Concentrations in Beijing and Relationships with Pollution from the North China Plain

Zhigang Li,Xin Yang,Chuanfeng Zhao,Tianyi Fan 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.3

Five years of PM2.5/PM10 ratios and their potential relationships with wind and relative humidity (RH) were analyzed for three areas in Beijing (northwestern mountainous area, urban area and southern suburbs), and these values were compared with those of five other cities, including Tianjin, Dalian, Hangzhou, Shanghai and Guangzhou. In the past five years, both PM2.5 and PM10 mass concentrations have decreased over the three Beijing regions, particularly during winters. The PM2.5/PM10 ratios have distinct seasonal characteristics, with more frequent high ratios in winter than in other seasons. The high ratio frequency decrease is most evident in winter and in the southern Beijing suburbs. This fine particle proportion decrease is related to air pollution control policies, including the national project ‘Coal to Gas’. HighPM2.5/PM10 ratios are linked to heavy pollution levels and low wind speeds, indicating the importance of PM2.5 accumulation during pollution events in Beijing. The higher PM2.5/PM10 ratios in Beijing are also closely related to southerly winds and high humidity, indicating the contribution of anthropogenic pollution transported from the south. Due to similar geographic environments, Tianjin is similar to Beijing in terms of the frequency distribution characteristics of the PM2.5/PM10 ratios. The coastal city of Dalian is further north and not similar to Beijing or Tianjin, owing to a sea breeze influence. Different from Beijing and Tianjin, the southern cities of Hangzhou, Shanghai and Guangzhou show almost no change in the PM2.5/PM10 ratio frequency distribution with increases in wind speed and relative humidity.

Energy efficiency task scheduling for battery level-aware mobile edge computing in heterogeneous networks

Zhigang Xie,Xin Song,Jing Cao,Siyang Xu 한국전자통신연구원 2022 ETRI Journal Vol.44 No.5

This paper focuses on a mobile edge-computing-enabled heterogeneous network. A battery level-aware task-scheduling framework is proposed to improve the energy efficiency and prolong the operating hours of batterypowered mobile devices. The formulated optimization problem is a typical mixed-integer nonlinear programming problem. To solve this nondeterministic polynomial (NP)-hard problem, a decomposition-based taskscheduling algorithm is proposed. Using an alternating optimization technology, the original problem is divided into three subproblems. In the outer loop, task offloading decisions are yielded using a pruning search algorithm for the task offloading subproblem. In the inner loop, closed-form solutions for computational resource allocation subproblems are derived using the Lagrangian multiplier method. Then, it is proven that the transmitted power-allocation subproblem is a unimodal problem; this subproblem is solved using a gradient-based bisection search algorithm. The simulation results demonstrate that the proposed framework achieves better energy efficiency than other frameworks. Additionally, the impact of the battery level-aware scheme on the operating hours of battery-powered mobile devices is also investigated.

Identification of tyrosine 71 as a critical residue for the cytotoxic activity of Clostridium perfringens epsilon toxin towards MDCK cells

Zhigang Jiang,Jitao Chang,Fang Wang,Li Yu 한국미생물학회 2015 The journal of microbiology Vol.53 No.2

Clostridium perfringens epsilon toxin (Etx) is an extremely potent toxin, causing fatal enterotoxaemia in many animals. Several amino acids in domains I and II have been proposed to be critical for Etx to interact with MDCK cells. However, the critical amino acids in domain III remain undefined. Therefore, we assessed the effects of aromatic amino acids in domain III on Etx activity in this study. All of the results indicated that Y71 was critical for the cytotoxic activity ofEtx towards MDCK cells, and this activity was dependent on the existence of an aromatic ring residue in position 71. Additionally, mutations in Y71 did not affect the binding of Etx to MDCK cells, indicating that Y71 is not a receptor binding site for Etx. In summary, we identified an amino acid in domain III that is important for the cytotoxic activity of Etx, thereby providing information on the structure-function relationship of Etx.

Preparation of magnetic carbon spheres derived form 8-quinoliolato Fe (III) complexe and its application in water treatment

Zhigang Jia,Lulu Yang,Jianhong Liu,Qiuze Wang,Rongsun Zhu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Magnetic carbon spheres have been successfully prepared by the synchronous carbonation and activationof the 8-quinoliolato Fe(III) complexe with sphere morphology, which has been synthesized bysolovthermal method. The obtained composite possesses relatively even pore diameter of 3.8 nm, highsurface area of 335.59m2/g with 52.67 wt.% Fe3O4 coated, and a saturation magnetization (Ms) of35.27 emu/g. Dye separationperformance of the magnetic carbon spheres is investigated using methyleneorange and methylene blue as modle. The resluts show that the maxium adsorption capacity formethylene orange and methylene blue is 128.70mgg 1 and 151.29mgg 1, respectively, and the processcan rapidly reach adsorption equilibrium within 5 min, which is important for the application of the aspreparedmagnetic carbon spheres.

A High-Precision Calibration Method for MEMS Gyroscopes

Zhigang Shang,Xiaochuan Ma,Mo Li,Yu Liu 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

MEMS (Micro-Electromechanical Systems) gyroscopes are widely used in many industrial products. However, observations often include many errors because of being not precisely calibrated and effectively compensated. This paper first proposes the idea that the excitation signal is designed using Persistent Excitation Signal Criterion in the modern control theory. The cosine angular velocity signal is selected as the excitation signal and proved to be Persistent Excitation Signal. The calibration scheme and data-acquisition program are proposed. Cross-correlation algorithm is used to solve calibration parameters. In order to verify the effectiveness and stability of the proposed calibration, we conduct simulations and in-depth discussions. Considering the temperature features of MEMS gyroscopes, the temperature control turntable is chosen to generate the excitation signal. Then we take turns to calibrate the parameters by the traditional method and the proposed method. The verification experiment is designed and implemented to verify the accuracy of calibration parameters. The results of the comparison and verification experiment show that the proposed method is an efficient and simple high-precision calibration method.

Synthesis of acetic acid-[(hydrazinylthioxomethyl)thio]-sodium and its application on the flotation separation of molybdenite from galena

Zhigang Yin,Wei Sun,Yuehua Hu,Runqing Liu,Wei Jiang,Chenhu Zhang,Qingjun Guan,Chenyang Zhang 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.52 No.-

A novel organic compound acetic acid-[(hydrazinylthioxomethyl)thio]-sodium was synthesized andcharacterized. Theflotation performance and adsorption mechanism of AHS to galena were investigatedby micro, benchflotation tests, UV spectra, zeta potential, FTIR and XPS measurements. The resultsdemonstrated that AHS exhibited superior depressing power to galena and could be used as selectivedepressant forflotation separation of molybdenite from galena. The results of UV spectra, FTIR, zetapotential and XPS measurements demonstrated that AHS chemisorb on galena surface by formingfivememberedcheat ring with releasing of H ions. Therefore, the possible adsorption mode of AHS on galenasurface was recommended.

Wettability and corrosion of molten sodium carbonate on aluminum-silicon refractory

Zhigang Xu,Yi Xia,Yizhao Mu 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6

The corrosion and infiltration of refractory by chemical waste liquid rich in alkali ions such as potassium and sodiumare the main cause of material damage. Their service life varies with the material systems. In this work, threekinds of aluminum-silicon refractories were prepared by using alumina, mullite, andalusite and clay as raw materials. Staticcrucible method was used to carry out alkali corrosion test at 900 ℃, and Na2CO3 was used as corrosive agent. The phasesand microstructures of the residual crucibles were examined by means of X-ray diffraction (XRD) and scanning electronmicroscope (SEM). The wetting process of molten Na2CO3 on refractory was detected by high temperature contact anglemeasurement system. The corrosion and infiltration resistance of refractories were discussed based on their wettability. Theresults show that corundum-mullite system has weak ability to resist corrosion and infiltration of the molten Na2CO3. Bycontrast, high-purity mullite system has better performance. The mullite transformed from andalusite can improve its infiltrationresistance. The infiltration of molten Na2CO3 into refractory is related to its wetting ability, they both determine thedamage degree of refractories.

A Modularized Equalizer for Supercapacitor Strings in Hybrid Energy Storage Systems

Zhigang Gao,Fenlin Jiang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

In hybrid energy storage systems, supercapacitors are usually connected in series to meet the required voltage levels. Equalizers are effective in prolonging the life of hybrid energy storage systems because they eliminate the voltage imbalance on cells. This study proposes a modularized equalizer, which is based on a combination of a half-bridge inverter, an inductor, and two auxiliary capacitors. The proposed equalizer inherits the advantages of inductor-based equalization systems, but it also offers unique merits, such as low switching losses and an easy-to-use control algorithm. The zero-voltage switching scheme is analyzed, and the power model is established. A fixed-frequency operation strategy is proposed to simplify the control and lower the cost. The switching patterns and conditions for zero-voltage switching are discussed. Simulation results based on PSIM are presented to verify the validity of the proposed equalizer. An equalization test for two supercapacitor cells is performed. An experimental hybrid energy storage system, which consists of batteries and supercapacitors, is established to verify the performance of the proposed equalizer. The analysis, simulation results, and experimental results are in good agreement, thus indicating that the circuit is practical.