Integrated Radial-axial Magnetic Bearing with Variable Permanent-Magnet Bias Flux In Situ

Xu Shilei,Li Jiajing,Wang Zhipeng,Sun Jinji,Ren Hongliang 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.4

Bias magnetic fl ux plays a crucial role in the performance of active magnetic bearings. However, the bias fl ux produced by NdFeB or SmCo materials in traditional permanent-magnet (PM) bias bearings cannot be adjusted, resulting in infl exible bearing performance. To improve the controllability of the PM bias fl ux in the integrated radial-axial magnetic bearing (RAMB), this article proposes a new design that uses a low coercivity AlNiCo magnet and equips a magnetization coil. By controlling the current of the magnetization coil, the magnetization state and bias fl ux of the AlNiCo magnet can be adjusted in situ, thereby improving the force characteristics and rotor iron losses of the PM-biased RAMB. The designed RAMB is analyzed and verifi ed by the 3D fi nite element method and the analytical model based on Preisach’s hysteresis theory and magnetic circuit method. The proposed design off ers a new idea for magnetic bearing structure and control.

Characteristics of calcium carbonate fouling on heat transfer surfaces under the action of electric fields

Zhiming Xu,Hongliang Chang,Bingbing Wang,Jingtao Wang,Qi Zhao 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

The present study examined the effect of electric fields in calcium carbonate (CaCO 3 ) scale formation on a heat transfer surface. The effects of electric fields ranging from 0 V to 4000 V on the fouling properties of CaCO 3 were investigated. Results showed that the optimal electric voltage was approximately 500 V, at which the asymptotic value of fouling resistance and the deposited weight were minimal and corresponded to 52.8 % and 61.3 % reductions, respectively, compared with the results recorded at 0 V. At higher voltages of 3000 V or 4000 V, the asymptotic value of fouling resistance and the weight of fouling deposits increased relative to those obtained at 0 V. The scanning electron microscope images of the fouling deposits obtained at 0 V showed mainly aragonites with sharp and needle-like crystal structures. The structure of CaCO 3 fouling changed from aragonites to spherical vaterites as the applied voltage was increased.

Existence and multiplicity of solutions for nonlinear Schr\"{o}dinger-Kirchhoff-type equations

Haibo Chen,Hongliang Liu,Liping Xu 대한수학회 2016 대한수학회지 Vol.53 No.1

In this paper, we consider the following Schr\"{o}dinger-Kirch\-hoff-type equations \[ \left[a+b\left(\int_{\mathbb{R}^{N}}(|\nabla u|^{2}+V(x)|u|^{2})dx\right)\right][-\Delta u+V(x)u]=f(x,u), ~~\mbox{in}~ \mathbb{R}^{N}. \] Under certain assumptions on $V$ and $f$, some new criteria on the existence and multiplicity of nontrivial solutions are established by the Morse theory with local linking and the genus properties in critical point theory. Some results from the previously literature are significantly extended and complemented.

Triaxial Test Research on Mechanical Properties and Permeability of Sandstone with a Single Joint Filled with Gypsum

Jin Yu,Xu Chen,Yan-yan Cai,Hongliang Liu 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.6

In this study, the mechanical properties and permeability variation in single joint rock samples filled with a gypsum layer were investigated. In order to simulate the inclined infilled joint, the solid cylinders were saw-cut at the dip angles of 90°, 60°, 45°, 30° or 0° with respect to the samples’ axes, and then joined together with gypsum. Triaxial compression experiments with permeability measurements were then performed using these prepared samples. The results indicated that the peak strength and failure modes change with the inclined angles. In comparison with the theoretical analysis of rock with a clean joint, infilling has a marked influence on the mechanical properties to some extent. In regards to the initial permeability, the results showed decreases of approximately two orders of magnitude with the increasing of the prefabricated joint angle, and the initial permeability of the samples with a prefabricated joint were all larger than the intact sample. The evolutionary trends of the permeabilities in triaxial compression in the sandstone samples were shown to be varied with a joint filled with gypsum at different angles, due to the fact that the changes of the inner structure are quite different during the loading process.

Prediction method for steady-state response of local rubbing blade-rotor systems

Qian Zhao,Hongliang Yao,Qi Xu,Bang-chun Wen 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4

Blade-rotor systems frequently encounter the problem of blade-to-case rubbing, which affects their safety and stability. Numericalsimulation can be used to predict the steady-state response of these systems. However, such simulation is frequently computationallyexpensive because of the high dimensions of the dynamic model of a blade-rotor system. To overcome this problem, a new method thatcombines the receptance-based dimension-reduction approach with the incremental harmonic balance (IHB) method is presented in thisstudy. First, a dynamic model of a blade-rotor system is developed using the finite element method, and the number of dimensions of themodel is reduced by the receptance method. Subsequently, the steady-state response is obtained by the improved IHB method to convenientlymanage the large number of super-harmonic components of the local rubbing system. Finally, the precision and efficiency of theproposed method is verified by comparing its results with those obtained by the Newmark-b method. The proposed method is found to beefficient in analyzing local rubbing blade-rotor systems with high dimensions, local nonlinearities, and rich super-harmonics.

Significance of Preoperative Nerve Reconstruction Using Diffusion Tensor Imaging Tractography for Facial Nerve Protection in Vestibular Schwannoma

Yuanlong Zhang,Hongliang Ge,Mingxia Xu,Wenzhong Mei 대한신경외과학회 2023 Journal of Korean neurosurgical society Vol.66 No.2

Objective : The facial nerve trace on the ipsilateral side of the vestibular schwannoma was reconstructed by diffusion tensor imaging tractography to identify the adjacent relationship between the facial nerve and the tumor, and to improve the level of intraoperative facial nerve protection. Methods : The clinical data of 30 cases of unilateral vestibular schwannoma who underwent tumor resection via retrosigmoid approach were collected between January 2019 and December 2020. All cases underwent magnetic resonance imaging examination before operation. Diffusion tensor imaging and anatomical images were used to reconstruct the facial nerve track of the affected side, so as to predict the course of the nerve and its adjacent relationship with the tumor, to compare the actual trace of the facial nerve during operation, verify the degree of coincidence, and evaluate the nerve function (House-Brackmann grade) after surgery. Results : The facial nerve of 27 out of 30 cases could be displayed by diffusion tensor imaging tractography, and the tracking rate was 90% (27/30). The intraoperative locations of facial nerve shown in 25 cases were consistent with the preoperative reconstruction results. The coincidence rate was 92.6% (25/27). The facial nerves were located on the anterior middle part of the tumor in 14 cases, anterior upper part in eight cases, anterior lower part in seven cases, and superior polar in one case. Intraoperative facial nerve anatomy was preserved in 30 cases. Among the 30 patients, total resection was performed in 28 cases and subtotal resection in two cases. The facial nerve function was evaluated 2 weeks after operation, and the results showed grade I in 12 cases, grade II in 16 cases and grade III in two cases. Conclusion : Preoperative diffusion tensor imaging tractography can clearly show the trajectory and adjacent position of the facial nerve on the side of vestibular schwannoma, which is beneficial to accurately identify and effectively protect the facial nerve during the operation, and is worthy of clinical application and promotion.

EXISTENCE AND MULTIPLICITY OF SOLUTIONS FOR NONLINEAR SCHRÖDINGER-KIRCHHOFF-TYPE EQUATIONS

CHEN, HAIBO,LIU, HONGLIANG,XU, LIPING Korean Mathematical Society 2016 대한수학회지 Vol.53 No.1

In this paper, we consider the following $Schr{\ddot{o}}dinger$-Kirchhoff-type equations $\[a+b\({\int}_{{\mathbb{R}}^N}({\mid}{\nabla}u{\mid}^2+V(x){\mid}u{\mid}^2)dx\)\][-{\Delta}u+V(x)u]=f(x,u)$, in ${\mathbb{R}}^N$. Under certain assumptions on V and f, some new criteria on the existence and multiplicity of nontrivial solutions are established by the Morse theory with local linking and the genus properties in critical point theory. Some results from the previously literature are significantly extended and complemented.

Adaptive Complex Interpolator for Channel Estimation in Pilot-Aided OFDM System

Guanghui Liu,Liaoyuan Zeng,Hongliang Li,Linfeng Xu,ZhengningWang 한국통신학회 2013 Journal of communications and networks Vol.15 No.5

In an orthogonal frequency division multiplexing system,conventional interpolation techniques cannot correctly balanceperformance and overhead when estimating dynamic longdelaychannels in single frequency networks (SFNs). In this study,classical filter analysis and design methods are employed to derivea complex interpolator for maximizing the resistible echo delay in achannel estimator on the basis of the correlation between frequencydomain interpolating and time domain windowing. The coefficientcomputation of the complex interpolator requires a key parameter,i.e., channel length, which is obtained in the frequency domain witha tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in asimulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channelestimator can not only handle SFN echoes with more than 200 µsdelay but also achieve a bit-error rate performance close to the optimumminimum mean square error method, which significantlyoutperforms conventional channel estimation methods, while preservinga low implementation cost in a short-delay channel.

Robust CFO Acquisition in PN-Padded OFDM Systems

Guanghui Liu,Liaoyuan Zeng,Hongliang Li,Linfeng Xu,ZhengningWang 한국전자통신연구원 2013 ETRI Journal Vol.35 No.4

As an alternative to the traditional pilot-aided orthogonal frequency division multiplexing (OFDM), the time-domain pseudonoise (PN)-padded OFDM provides a higher spectral efficiency. However, the carrier frequency offset (CFO) attenuates peaks of the conventional PN correlation output, which limits the CFO estimation range of the OFDM synchronizer. An improved correlation is proposed in this letter to remove the CFO-induced amplitude attenuation of correlation peaks. For a synchronizer adopting the designed correlator, a larger range of CFO acquisition is obtained through using wider correlation windows with a smaller interval between them. The proposed method of CFO acquisition is verified in a digital terrestrial multimedia broadcast receiver, in which the synchronizer is able to acquire CFOs up to ±320 kHz in the DVB-T F1 channel. Furthermore, the acquisition range can be expanded in more favorable channels.

Ginsenoside Rb1 ameliorates cisplatin-induced learning and memory impairments

Chen Chen,Haifeng Zhang,Hongliang Xu,Yake Zheng,Tianwen Wu 고려인삼학회 2019 Journal of Ginseng Research Vol.43 No.4

Background: Ginsenoside Rb1 (Rb1), a dominant component from the extract of Panax ginseng root,exhibits neuroprotective functions in many neurological diseases. This study was intended to investigatewhether Rb1 can attenuate cisplatin-induced memory impairments and explore the potentialmechanisms. Methods: Cisplatin was injected intraperitoneally with a dose of 5 mg/kg/wk, and Rb1 was administeredin drinking water at the dose of 2 mg/kg/d to rats for 5 consecutive wk. The novel objects recognition taskand Morris water maze were used to detect the memory of rats. Nissl staining was used to examine theneuron numbers in the hippocampus. The activities of superoxide dismutase, glutathione peroxidase,cholineacetyltransferase, acetylcholinesterase, and the levels of malondialdehyde, reactive oxygen species,acetylcholine, tumor necrosis factor-a, interleukin-1b, and interleukin-10 were measured by ELISAto assay the oxidative stress, cholinergic function, and neuroinflammation in the hippocampus. Results: Rb1 administration effectively ameliorates the memory impairments caused by cisplatin in bothnovel objects recognition task and Morris water maze task. Rb1 also attenuates the neuronal loss inducedby cisplatin in the different regions (CA1, CA3, and dentate gyrus) of the hippocampus. Meanwhile, Rb1 isable to rescue the cholinergic neuron function, inhibit the oxidative stress and neuroinflammation incisplatin-induced rat brain. Conclusion: Rb1 rescues the cisplatin-induced memory impairment via restoring the neuronal loss byreducing oxidative stress and neuroinflammation and recovering the cholinergic neuron functions.