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1

Experimental investigation on effects of machining parameters on the performance of Ti-6Al-4V micro rotary parts fabricated by LS-WEDT

Sun Y., Gong Y., Cai M., Ma X., Li P.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 2

385--400

EN

The low speed wire electrical discharge turning (LS-WEDT) is firstly proposed to fabricate the Ti-6Al-4V micro rotary workpiece in this study. The surface quality, sub-surface damages and machining efficiency of LS-WEDT process are discussed. The single factor experiments and orthogonal experiments are respectively conducted to analyze effects of speed parameters and peak current on surface roughness (Ra), material removal rate (MRR), surface morphology and the white layer of the TC4 micro rotary workpiece machined by LS-WEDT. Experimental results indicated that the most important factors affecting the Ra and MRR in LS-WEDT respectively are the peak current and feeding speed, and the rotating speed and feeding speed have significant interactive effect on Ra and MRR. Besides, the low feeding speed can cause surface burning and the high rotating speed will elongate craters. Furthermore, the surface oxidation of TC4 workpiece machined by LS-WEDT is far more serious than the surface alloying and Ti3O and Ti6O can be detected on the machined surface. Moreover, the serrated white layer can be observed and gradually becomes continuous and thin with the decrease of peak current. Finally, large amounts of oxygen and less copper elements can be detected on the top of the white layer and longitudinal cracks.

2

Experimental study on surface characteristics and improvement of microelectrode machined by low speed wire electrical discharge turning

Sun Y., Gong Y., Liu Y., Li Q., Zhou Y.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 4

964--977

EN

Electrical discharge machining (EDM) as the nontraditional machining process has a unique superiority in fabricating microelectrodes due to its non-contact removal mechanism. Therefore, the method of LS-WEDT (low speed wire electrical discharge turning) is firstly proposed to fabricate microelectrodes in this study. More importantly, the multiple cutting strategy is introduced to divide the machining process into rough cut (RC), trim cut (TC) and finishing trim cut (FTC). Experimental results showed that the ridges will appear after RC, the spherical droplets congregation phenomenon can be observed after TC and the surface will be covered with refined grains in nano level after FTC, which disclosed the unique surface characteristics of LS-WEDT. After FTC, the microelectrode of 90 μm in diameter and 1000 μm in length is successfully and firstly fabricated by LS-WEDT method, moreover, it has good surface quality with Ra of 0.59 μm and high dimensional precision with surface profile accuracy of 3.22 μm. Additionally, the comparative analysis was made to investigate the LS-WEDTed and LS-WEDMed surface, the discharge craters distributed in LS-WEDTed surface are longer than LS-WEDM. Finally, the surface quality machined by LS-WEDT after FTC is better than LS-WEDM, which is attributed to the point contact and good flushing conditions.

3

Occupational Safety and Health Status of Sanitation Workers in Urban Areas: A Pilot Study From Wuhan, China

Gong Y., Yu J., Zhang X., Liang Y.

International Journal of Occupational Safety and Ergonomics

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2013

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Vol. 19, No. 3

435--442

EN

Sanitation workers' workload increases quickly with rapid urbanization, but there is almost no evidence or policy recommendations for their management in developing countries. This study describes the health status and occupational protection of sanitation workers; it also explores risk factors related to their health status in Wuhan City, China. Three hundred and eighty-five sanitation workers from 54 streets of Wuhan were surveyed. Their prevalence of 2-week illness and arthritis was relatively higher than in the general population in China. Findings related to occupational protection showed that both sanitation workers (users) and their managers (providers) neglected the role of low-cost protection measures, especially masks, soap/hand sanitizer and prejob training (use rate of 7.27%, 26.75% and 43.64%, respectively). High-intensity workload was an important risk factor for 2-week illness, and prejob training was an important protective factor against arthritis.

4

Optimization and validation of a method based on derivatization with methylating agent followed by HPLC-DAD for determining dithiocarbamates residues

Zhou L., Xu J., Luan L., Ma J., Gong Y., Qin D., Pan C.

Acta Chromatographica

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2013

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Vol. 25, no. 4

613--625

EN

Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and L-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.

5

Composite Adaptive Inverse Controller Design for Permanent Magnet Synchronous Motor

Qu Y., Gong Y., Cui Y., Han T.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 7b

365--369

EN

Permanent magnet synchronous motor (PMSM) servo system is a nonlinear, multi-variables strong coupling system. To improve the performance of the PMSM system, a composite adaptive inverse control strategy is proposed. This control strategy adopt improved radial basis function (RBF) neural network and FIR filter as nonlinear filter. The proposed filter is used to identify the system, inverse system and design the adaptive inverse controller. Meanwhile the chaos multi-population particle swarm optimization (CMPSO) algorithm is proposed to training the parameters of the nonlinear filter offline. And then an improved variable step size LMS (IVSLMS) algorithm is used to optimize the parameters online. These algorithm improves the convergence speed and accuracy, further improves the control performance of adaptive inverse control. The results of simulation and experiment indicate that the PMSM servo system has good dynamic, static performance and robustness by using proposed hybrid adaptive inverse control strategy.

PL

W celu poprawy parametrów silnika synchronicznego z magnesami trwałymi PMSM zaproponowano kompozytowa adaptacyjną strategię sterowania. Strategia wykorzystuje sieć neuronową i nieliniowy filtr SOI.

6

Speaker recognition based on the combination of GMM and SVDD

Zhou Y., Zhang X., Wang J., Gong Y., Zhou Y.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 3

329-332

EN

Scare-level combination of subsystems can yield significant performance gains over individual subsystems in speaker recognition. A novel speaker verification method based on support vector data description (SVDD) is proposed to remedy the defect of Gaussian mixture model (GMM) to same extent, and then using the theory of multiple classifier systems (MCS),a new speaker recognition system based on the combination of GMM and SVDD is proposed. Experiments on TlMIT speech database show that the GMM-SVDD model fully utilizes the complementarities of GMM and SVDD to improve the performance obviously in speaker verification, closed-set speaker identification and speaker recognition.

PL

Zaproponowano nowa metodę rozpoznawania głosu bazującą na systemie SVDD jako alternatywę dla modelu GMM. Następnie wykorzystując teorię wielokrotnego systemu klasyfikacji MCS zaproponowano wykorzystanie połączenia systemów GMM i SVDD. Eksperymenty potwierdziły że nowy model GMM-SVOO umożliwia ulepszonę rozpoznawanie głosu.