Investigation of dynamic characteristics of planetary gear stage in wind turbine considering voltage dip

Jianjun Tan,Caichao Zhu,Chaosheng Song,Xiangyang Xu,Zi Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

The transient variation of electrical parameters makes system loads fluctuate and reduces bearing capacity when the grid voltage dips. This work proposes an electromechanical coupling dynamic model of the wind turbine drivetrain to build a dynamic interconnection between the electric and drivetrain subsystems. The drivetrain subsystem that includes an improved model of the planetary gear stage is developed and validated. This improved model considers the carrier and planet bearing clearances, the connection relationship among the carrier, main shaft, and planets as well as the flexibilities of the main shaft and parallel stage shafts. The influences of the carrier bearing clearances, non-torque load and planet position angle on planet bearing loads are investigated under the low-voltage ride through (LVRT) event. The results indicate that as the LVRT occurs, the planet bearing loads reduce below the minimum requisite with a high, fluctuating system speed; considering the bearing clearances, the impacts occur in the planet bearing in the minimum load zone followed by significant stress variation; the non-torque load suppresses the planet bearing impacts in a limited range of carrier bearing clearance; the planet position angle has a significant effect on the planet bearing impacts because of the asymmetry of load and structure of the planetary gear stage.

A Random Deflected Subgradient Algorithm for Energy-Efficient Real-time Multicast in Wireless Networks

( Guoping Tan ),( Jianjun Liu ),( Yueheng Li ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.10

In this work, we consider the optimization problem of minimizing energy consumption for real-time multicast over wireless multi-hop networks. Previously, a distributed primal-dual subgradient algorithm was used for finding a solution to the optimization problem. However, the traditional subgradient algorithms have drawbacks in terms of i) sensitivity to iteration parameters; ii) need for saving previous iteration results for computing the optimization results at the current iteration. To overcome these drawbacks, using a joint network coding and scheduling optimization framework, we propose a novel distributed primal-dual Random Deflected Subgradient (RDS) algorithm for solving the optimization problem. Furthermore, we derive the corresponding recursive formulas for the proposed RDS algorithm, which are useful for practical applications. In comparison with the traditional subgradient algorithms, the illustrated performance results show that the proposed RDS algorithm can achieve an improved optimal solution. Moreover, the proposed algorithm is stable and robust against the choice of parameter values used in the algorithm.

Chinese Society of Allergy Guidelines for Diagnosis and Treatment of Allergic Rhinitis

Lei Cheng,Jianjun Chen,Qingling Fu,Shaoheng He,Huabin Li,Zheng Liu,Guolin Tan,Zezhang Tao,Dehui Wang,Weiping Wen,Rui Xu,Yu Xu,Qintai Yang,Chonghua Zhang,Gehua Zhang,Ruxin Zhang,Yuan Zhang,Bing Zhou,Do 대한천식알레르기학회 2018 Allergy, Asthma & Immunology Research Vol.10 No.4

Allergic rhinitis (AR) is a global health problem that causes major illnesses and disabilities worldwide. Epidemiologic studies have demonstrated that the prevalence of AR has increased progressively over the last few decades in more developed countries and currently affects up to 40% of the population worldwide. Likewise, a rising trend of AR has also been observed over the last 2-3 decades in developing countries including China, with the prevalence of AR varying widely in these countries. A survey of self-reported AR over a 6-year period in the general Chinese adult population reported that the standardized prevalence of adult AR increased from 11.1% in 2005 to 17.6% in 2011. An increasing number of original articles and imporclinical trials on the epidemiology, pathophysiologic mechanisms, diagnosis, management and comorbidities of AR in Chinese subjects have been published in international peer-reviewed journals over the past 2 decades, and substantially added to our understanding of this disease as a global problem. Although guidelines for the diagnosis and treatment of AR in Chinese subjects have also been published, they have not been translated into English and therefore not generally accessible for reference to non-Chinese speaking international medical communities. Moreover, methods for the diagnosis and treatment of AR in China have not been standardized entirely and some patients are still treated according to regional preferences. Thus, the present guidelines have been developed by the Chinese Society of Allergy to be accessible to both national and international medical communities involved in the management of AR patients. These guidelines have been prepared in line with existing international guidelines to provide evidence-based recommendations for the diagnosis and management of AR in China.

Anti‐SOX1 Antibodies in Paraneoplastic Neurological Syndrome

Xuan Sun,Jiping Tan,Hui Sun,Yan Liua,Weiping Guan,Jianjun Jia,Zhenfu Wang 대한신경과학회 2020 Journal of Clinical Neurology Vol.16 No.4

Anti-Sry-like high mobility group box (SOX) 1 antibodies (abs) are partly characterized onconeural autoantibodies (autoabs) due to their correlation with neoplastic diseases. Anti- SOX1 abs are associated with various clinical manifestations, including Lambert-Eaton myasthenic syndrome (LEMS) and paraneoplastic cerebellar degeneration (PCD). However, the clinical characteristics of patients with anti-SOX1 abs have not been described in detail. This review systematically explores the reported patients with anti-SOX1 abs and analyzes these cases for demographic characteristics, clinical features, coexisting neuronal autoabs, neuroimaging findings, treatment, and clinical outcomes. In addition, considering that PCD is the most common paraneoplastic neurological syndrome and that the association between PCD and anti-SOX1 abs remains unclear, we focus on the presence of autoabs in relation to PCD and associated tumors. PCD-associated autoabs include various intracellular autoabs (e.g., anti-Hu, anti-Yo, anti-Ri, and anti-SOX1) and cell-surface autoabs (anti-P/Q-type voltage-gated calcium channel). Commonly involved tumors in PCD are small-cell lung cancer (SCLC), gynecological, and breast tumors. LEMS is the most common clinical symptom in patients with anti- SOX1 abs, followed by PCD, and multiple neuronal autoabs coexist in 47.1% of these patients. SCLC is still the predominant tumor in patients with anti-SOX1 abs, while non-SCLC is uncommon. No consistent imaging feature is found in patients with anti-SOX1 abs, and there is no consensus on either the therapy choice or therapeutic efficacy. In conclusion, the presence of anti-SOX1 abs alone is a potential predictor of an uncommon paraneoplastic neurological disorder, usually occurring in the setting of LEMS, PCD, and SCLC. The detection of anti-SOX1 abs contributes to an early diagnosis of underlying tumors, given the diversity of clinical symptoms and the absence of characteristic neuroimaging features.

Settlement behaviours and control measures of twin-tube curved buildings-crossing shield tunnel

Jianwei Jia,Ruiqi Gao,Defeng Wang,Jianjun Li,Ziwen Song,Jinghui Tan 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.5

Settlement control techniques are critical for the safety of shield tunnel constructions, especially for facing complex situations. In this study, the shield tunnel structure from Huaita east road station to Heping Road station in Xuzhou metro No.3 line (China) is taken as engineering background, which has various complex problems of the upper-soft and lower-hard composite stratum conditions, twin curve shield tunnels, and underpass the foundation of the piled raft. The deformation characteristics of shield tunnelling passing through buildings are explored. Subsequently, comprehensive research methods of numerical simulation and field measurement are adopted to analyzing the effectiveness of settlement control by using the top grouting technique. The results show that the settlement of the buildings has obvious spatial characteristics, and the hysteresis effect can be obviously observed in soil deformation caused by shield construction. Meanwhile, the two shield constructions can cause repeated disturbances, reducing the soil deformation's hysteresis effect. Moreover, the shield tunnel's differential settlement is too large when a single line passes through, and the shield construction of the outer curve can cause more significant disturbance in the tunnel than the inside curve. Notably, the proposed process control parameters and secondary topgrouting method can effectively control the deformation of the shield tunnel, especially for the long-term deformation.

Effects of macro-parameters on vibration and radiation noise for high speed wheel gear transmission in electric vehicles

Xi Chen,Chaosheng Song,Caichao Zhu,Jianjun Tan,Najeeb Ullah 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

Considering flexible shafts, a coupled dynamic model for the gear transmission system of wheel reducer used in electric vehicle was developed. By combining the acoustics finite element modal for housing in Virtual Lab and the coupled dynamic model for gear transmission system, a simulation method was proposed for the prediction of the radiation noise for the wheel reducer. Then, the effects of different macro geometry gear parameters including pressure angle and helical angle on the dynamic response and radiation noise were investigated under the rated working condition. Results show that the peak-peak value of the transmission error dramatically falls in the starting zone, followed by an upward trend with the increase of the pressure angle for the low speed stage gear pair. The minimum transmission error and vibration acceleration occur when the pressure angle is 17°. The increase of the pressure angle does not affect the sound pressure level at the field point obviously. The design case with 17° pressure angle shows the optimum radiation noise level, which is 4.41dB less than the original model. Compared to the pressure angle, the helix angle has a major influence on the transmission error, vibration acceleration and acoustic radiation noise. With the increase of the helix angle, the time-varying transmission error curve becomes more smooth with a lower peak-peak value. Besides, the increase of helix angle results in lowering the varying and fluctuating trend of both vibration acceleration and acoustic radiation noise. The design case with 24° helix angle shows the prime radiation noise level, which is 7 dB less than the original scheme.

Effects of gear modifications on the dynamic characteristics of wind turbine gearbox considering elastic support of the gearbox

Shuaishuai Wang,Caichao Zhu,Chaosheng Song,Huachao Liu,Jianjun Tan,Houyi Bai 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

The reliability and service life of wind turbines are directly influenced by the dynamic performance of the gearbox under the timevarying wind loads. The control of vibration behavior is essential for the achievement of a 20-year service life. We developed a rigidflexible coupled dynamic model for a wind turbine gearbox. The planet carrier, the housing, and the bedplate are modelled as flexibilities while other components are assumed as rigid bodies. The actual three points elastic supporting are considered and a strip based mesh model is used to represent the engagement of the gear pairs. The effects of gear tooth modifications on the dynamics were investigated. Finally, we conducted a dynamic test for the wind turbine gearbox in the wind field. Results showed that the contact characteristics of gear pairs were improved significantly; the peak-to-peak value of transmission error of each gear pair was reduced; the amplitudes of the vibration acceleration and the structural noise of the wind turbine gearbox were lowered after suitable tooth modification.

Development and supercapacitor application of ionic liquid-incorporated gel polymer electrolyte films

Ravi Muchakayala,Shenhua Song,Jingwei Wang,Youhua Fan,Manjunatha Bengeppagari,Jianjun Chen,Manlin Tan 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.59 No.-

A new gel polymer electrolyte based on 1-methyl-1-propylpyrrolidinium bis(trifluoromethyl sulfonyl)imide ([PMpyr][NTf2]) entrapped in poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) is prepared and optimized for flexible solid state supercapacitor applications. The structural, thermal, electrical and electrochemical properties of the ionic liquid gel polymer electrolyte membranes are studied by different characterization techniques. The transparent gel polymer electrolyte membranes exhibit high amorphicity and excellent thermal stability. The 20PVdF-HFP:80[PMpyr][NTf2] gel polymer electrolyte membrane possesses a high ionic conductivity (1.596 × 10−3 S cm−1) and wide electrochemical stability window (4.7 V) at room temperature. It is used as the electrolyte material for the fabrication of flexible electric double layer supercapacitors (EDLCs) with multiwalled carbon nanotube (MWCNT)-added and unadded activated carbon (AC) electrodes. The performances of flexible EDLCs are evaluated using cyclic voltammetry and galvanostatic charge–discharge measurements. The EDLC with MWCNT-added AC electrodes exhibits apparently higher specific capacitance of electrode (156.64 F g−1), specific energy (30.69 Wh kg−1) and specific power (4.13 kW kg−1) than that with AC electrodes. The cyclic stability of the former is still in a good condition at the 2000th charge–discharge cycle and much better than the latter. The present comparative study indicates that the 20PVdF-HFP:80[PMpyr][NTf2] gel polymer electrolyte is a good candidate for the development of flexible solid-state supercapacitors.