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The axial bearing does not contain a laminated piece; so its dynamic performance is poor and often does not meet the load requirements. To accurately assess axial bearing performances during the design stage, it is necessary to accurately calculate the dynamic characteristics of the bearing, including amplitude, phase, and other parameters. Traditional studies have generally used the magnetic circuit method (MCM) or the finite element method (FEM) to analyze the dynamic performance of bearings, and few experimental measurements are carried out. Some experiments use a Guess meter to measure the magnetic field at local locations without directly measuring the electromagnetic force. In this paper, the dynamic force of axial bearing is measured by experiments, and the finite element calculation with Ansys Maxwell is carried out to study the influence of the gap, resonance, and other factors on the electromagnetic force. The comparison reveals a significant error in the calculation method using the initial gap because the gap between the stator and rotor changes with the dynamic force in the experiment. In this paper, the calculation method of “analyzing the dynamic performance of the bearing with the actual gap after the DC component is energized as the calculation gap” is proposed, which significantly reduces the calculation error and can ensure that the calculation error of amplitude and phase within 100 Hz is less than 5%. The method is of great significance for the engineering application of axial electromagneticbearings.

Helium gas is used as the coolant in high temperature gas-cooled reactor while its insulation property is not good and brings big challenges to insulation design work. In this paper, breakdown volt...

As one of the key technologies of high-temperature gas-cooled reactor, primary helium circulator–equipped active magnetic bearing provides driving force for primary helium cooling system. However, repetitive periodic vibration produced by rotor imbalance may introduce risks to primary helium circulator (even for high-temperature gas-cooled reactors). First, this article analyzes a periodic component extraction algorithm which is widely used in active magnetic bearing rotor unbalance control methods and points out the problem that the periodic component extraction algorithm occupies numerous computing resources which cannot satisfy the real-time request of active magnetic bearing control system. Then, a novel iterative learning control algorithm based on the iteration before last iteration of system information (iterative learning control-2) and a plug-in parallel control mechanism based on the existing control system are put forward, meanwhile, an integrated independent distributed active magnetic bearing control system is designed to solve the problem. Finally, both the simulation and experiment are carried out, respectively. The corresponding results show that the control method and control system proposed in this article have significant suppression effect on the repetitive periodic vibration of the active magnetic bearing system without degrading the real-time requirement and can provide important technical support for the safe and stable operation of the primary helium circulator in high-temperature gas-cooled reactor.

Nowadays, heavy metal ion pollution in water is becoming more and more common, especially arsenic, which seriously threatens human health. In this work, we used Fe3O4–rGO nanocomposites to modify a glassy carbon electrode and selected square wave voltametric electrochemical detection methods to detect trace amounts of arsenic in water. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that Fe3O4 nanoparticles were uniformly distributed on the rGO sheet, with a particle size of about 20 nm. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) showed that rGO provides higher sensitivity and conductive substrates. Under optimized experimental conditions, Fe3O4–rGO-modified glassy carbon electrodes showed a higher sensitivity (2.15 µA/ppb) and lower limit of detection (1.19 ppb) for arsenic. They also showed good selectivity, stability, and repeatability.

Currently, heavy metal ion contamination in water is becoming more and more common, especially Pb(II), which is a serious threat to human health. In this experiment, MoS2/rGO nanocomposites were used to modify glassy carbon electrodes and square wave voltammetry(SWV) electrochemical detection method was selected to detect trace Pb(II) in water. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that MoS2 nanoparticles were uniformly distributed on the rGO films. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that MoS2/rGO has higher sensitivity and conductivity. After determining the optimal experimental parameters, the MoS2/rGO modified glassy carbon electrodes exhibited high sensitivity (57.57 μA μM−1) and low limit of detection (0.060 μM) for Pb(II) as well as good interference resistance and stability.

In high temperature reactor pebble-bed modules (HTR-PM), the helium blower is the key equipment which is in the primary loop and drives the helium to exchange the energy. The usage of active magnetic bearing (AMB) is to avoid the lubricating oil leaked and keep the environment of helium pure. However, helium blower test needs to proceed under the condition of helium loop, which is difficult in early construction stage and will result in much more time and money cost. In this paper, we propose and produce a new device to simulate the dynamic force to build a force environment similar to the helium loop. The device called aerodynamic force simulator (AFS) derives from the idea of active magnetic bearing and utilizes electromagnetic force replacing aerodynamic force when helium blower works. Active magnetic bearing commissioning and dropping load test of helium proceed successfully with the utilization of aerodynamic force simulator. Through a series of tests, it is proved that the aerodynamic force simulator is effective and economic, and the design of helium blower and its components is reasonable and reliable.

The high-temperature gas-cooled reactor-pebble bed module (HTR-PM) has been proposed by the Institute of Nuclear and New Energy Technology of Tsinghua University. The helium circulator is equipped in the primary loop of HTR-PM to drive high-temperature helium for energy exchange. The active magnetic bearing (AMB), replaced by the ordinary mechanical bearing, is chosen as the perfect supporting scheme for the helium circulator of HTR-PM. Additionally, the auxiliary bearing is applied in case of AMB failures and has become indispensable to provide mechanical supports and displacement constraints for the rotor. When the rotor drops down, the auxiliary bearing needs to sustain fierce impacts and corresponding thermal growth. While due to the special environment in the primary loop of HTR-PM, oil or grease lubrication can’t be applied in the auxiliary bearing. A new design of unlubricated auxiliary bearing is proposed in this paper. This paper mainly deals with the following two aspects to reveal the rotor drop: dynamic analysis including fatigue life prediction, and corresponding thermal growth. Moreover, dropping experiments are carried out in the HTR-PM helium circulator system. The experimental results can verify the auxiliary bearing capacity to endure the dynamic impact of the dropping rotor, and provide suggestions for the auxiliary bearing type selection. The results in this paper will provide theoretical suggestions for further engineering design and application of the auxiliary bearing in the helium circulator of HTR-PM.

The DC and 50 Hz AC breakdown voltage of helium between two parallel copper electrodes were measured to obtain the base data for insulation design of the electrical equipment working in the high pressure and high temperature helium gas in High Temperature Reactor (HTR). The measurements were performed in the distance of 0.25–0.53 mm, the temperature of 15–180 °C, and the pressure of 0.05–7 MPa. It has been proved that, for both DC and 50 Hz AC, the breakdown voltage increases with the increasing of the pressure, with the increasing of the distance, and with the decreasing of the temperature. The DC breakdown voltage is about 1.4 times of the value of 50 Hz AC or, in other words, is similar to the peak value of 50 Hz AC. The Paschen law, describing the relationship between the breakdown voltage of helium ( U b ) and the product of gas density and electrode distance ( ρd ), was presented for DC and 50 Hz AC respectively, based on the experimental data at high pressure and high temperature. Good linearity is shown in the data. Furthermore, the linear fitting equation was also presented. The slope of Paschen curve about U b - ρd at the range of large ρd is influenced by the collision cross section and the ionization energy of helium atom, and not influenced by the temperature, for DC. Both for DC and 50 Hz AC, the slope of Paschen curve about U b - ρd is about 6 × 10 5 times of the slope of Paschen curve about U b - Pd , where Pd is the product of gas pressure and electrode distance. Both for DC and 50 Hz AC, the breakdown voltage of helium is less than one fifth of the value of air, at 0.1 MPa and room temperature. However, the breakdown voltage of helium at 180 °C and 7 MPa is larger than the value of air at 0.1 MPa and room temperature.

The Active Magnetic Bearing (AMB) technology is introduced in the High Temperature Reactor-Pebble-bed Modules (HTR-PM) demonstration nuclear power plant, which is being constructed in Shandong province, China. The auxiliary bearing is one of the most important components guaranteeing the reliability of the AMB. It also has an important impact on the reliability of the whole reactor system. Compared with the traditional auxiliary bearing, a novel one proposed by the authors has a smaller impact force and the rotor center orbit is much more concentrated during the rotor drop. This paper establishes an analytical model of drop of rolling-sliding integrated auxiliary bearing to analyze the above phenomena. Based on the Hertz contact theory, the complex structure inside the rolling bearing is simplified through a spring damping model. The overall impact model of the rolling-sliding integrated auxiliary bearing is established. Then, according to the structural characteristics of the rolling-sliding integrated auxiliary bearing, the tangential force inside the rolling- sliding integrated auxiliary bearing can be obtained by applying the angular momentum theorem. Finally, a four-degree-of-freedom horizontal rotor drop model is established to analyze and calculate the center orbit and motion state of the rotor. The analytical model is helpful in the selection and design of auxiliary bearing for AMB. In further research this contact model can be used to calculate the center orbit and contact forces in the application of the rolling-sliding integrated auxiliary bearing.

Breakdown voltages of helium between needle-plane copper electrodes were measured to obtain the base data for insulation design of the electrical equipment working in high temperature and pressure helium gas in the High Temperature Gas-cooled Reactor (HTGR). The measurements were performed at a gap length between 1.02 mm and 5.30 mm, temperature and pressure varying from 0.01 to 7 MPa and 25–180 °C, respectively. Some abnormal “U-shapes” were found to appear especially at pressure over 3 MPa, which can be explained by the effects of space charge on the corona layer. COMSOL Multiphysics was used to simulate the discharge with a two-dimensional drift–diffusion model. The results agree well with the experimental data on the whole, but the errors rise when the pressure and gap length become very large. Evolutions of the current and particle number densities were also obtained. These breakdown voltages and characteristics of helium discharge is considered much valuable to the insulation design in HTGR.

The 10 MW high-temperature gas-cooled reactor (HTR-10) was constructed by the Institute of Nuclear and New Energy Technology (INET) of Tsinghua University. The auxiliary bearing is utilized in this system to meet particular requirements for the reactor. The main role of the auxiliary bearing is to constrain rotor displacements and also to support the rotor when the rotor drops down, which is caused by the active magnetic bearing (AMB) failure. The auxiliary bearing needs to endure huge impact, rapid angular acceleration and thermal shock. On the one hand, complex geometrical constructions and forces applied on the system bring difficulties and restrictions to establish an appropriate model to reveal the actual dynamic process. On the other hand, large volumes of data obtained from experiments show velocities and displacements of the rotor during the rotor drop process and then can indicate the actual dynamic interactions to a great extent. The research in this paper is based on the test rig of the AMB helium circulator of HTR-10. This paper aims to analyze the dynamic performance and contact forces of the rotor by processing experimental data. A measurement to estimate forces developed due to impacts of the rotor and the auxiliary bearings is presented. It is of great significance and provides certain foundation to elaborate the rotor drop process for the AMB helium circulator of HTR-10.

In this paper, experiments on breakdown voltages of helium gas in a uniform field have been carried out at a separation from 0.25 to 3.02 mm. The pressure and temperature respectively vary from 1 to 7 MPa, 25 °C to 180 °C, which is the working condition for the main helium blower and its Active Magnetic Bearings (AMBs) in the High Temperature Reactor-Pebble-bed Module (HTR-PM). COMSOL Multiphysics and a self-programmed FD-FCT (Finite Difference-Flux Corrected Transport) code with a two-dimensional drift–diffusion plasma model have been used to simulate the breakdown process and the results agree well with the experimental data. This kind of theoretical and experimental work provides valuable references for helium insulation design of electric devices in HTR-PM and other helium gas-cooled reactors. It also helps understand the mechanisms in helium discharge at high temperature and pressure which is quite different from its low counterpart.

The Active Magnetic Bearing (AMB) is used in the High Temperature Reactor- Pebble-bed Modules (HTR-PM) which is being constructed in Shandong province, China. The auxiliary bearing is one of the most important components guaranteeing the reliability of the AMB. A novel rolling-sliding integrated auxiliary bearing is studied through the drop experiment. For comparison, a traditional rolling auxiliary bearing in the same AMB is also studied experimentally. It was found that the rotor center orbit with the novel auxiliary bearing is much simpler and more focused. The impact force with the novel auxiliary bearing during the drop is much less. The drop process with the novel auxiliary bearing is more stable. All these phenomena are due to the fact that the contact point of the rotor with the novel auxiliary bearing is easy to stay at the lowest position of the circular contact surface during drop process.

The active magnetic bearing (AMB) is introduced to the helium circulator of the 10 MW high temperature gas-cooled reactor (HTR-10). Auxiliary bearing bears huge instantaneous impact load when the AMB fails to work in the helium circulator. The huge load may cause serious damage to the auxiliary bearing. In order to reduce the impact load and protect the AMB and rotor system, a new type of auxiliary bearing with axial buffer shim is presented in this paper. There are two different structures of auxiliary bearing to be studied in the paper. One is the auxiliary bearing with the buffer shim and another one is without the buffer shim. The finite element method and LS-DYNA software are applied to analyze the structure characteristic of the auxiliary bearing. The rotor dropping trajectory and the stress distribution of the auxiliary bearing are analyzed by comparing two different auxiliary bearing structures during the rotor drop. The stress change of the auxiliary bearing in each impact course is mainly studied, and the law of stress variation in impact course is analyzed. Besides, the stress distribution and deformation of two auxiliary bearing is the focus research when impact force is maximum in the paper. Finally, the research shows the auxiliary bearing structure without the buffer shim can bear the huge impact of the rotor drop, and the addition of buffer shim can also reduce the damage of the rotor drop to the auxiliary bearing structure. These researches’ result provides an important reference for the experiment of rotor drop, and has laid a theoretical foundation for the practical application of this structure.

As primary pump of High Temperature Gas-cooled Rector (HTGR), the safety and reliability of primary helium circulator has a direct relationship with heat export in the reactor core. This paper proposed two conceptual design methods, which are structural redundancy design in the axial and radial magnetic bearings (coils), and crossing redundancy design between amplifiers and the redundant bearings (coils), combined with the characteristics of magnetic bearing in the primary helium circulator. Then we built Markov model for the magnetic bearing with redundant structure, which was used to reliability analysis and calculation. Finally, we performed simulation of the redundant magnetic bearings in Matlab/Simulink. The results show that the redundant structure design can greatly improve the reliability of the magnetic bearing system. Therefore, these methods would provide a new approach for further improving the safety and reliability of primary helium circulator.

We propose a semisupervised sparse graph learning (SSGL) method for feature extraction of hyperspectral remote sensing imagery in this paper. The proposed SSGL method aims to build a semisupervised sparse graph that can maximize the class discrimination and preserve the local neighborhood information by combining labeled and unlabeled samples. In our semisupervised sparse graph, we connect labeled samples according to their label information and sparse representation, connect unlabeled samples by sparse representation which set unlabeled training samples set as dictionary. Moreover, by setting sparse connections between labeled sample and unlabeled samples, the label information can be well propagated from labeled samples to unlabeled samples. In this way, the similarity of data points can be well modelled in the spectral feature space, and the data distribution characteristics can be better expressed. Experimental results on real hyperspectral images (HSIs) demonstrate the advantages of our method compared to some related feature extraction methods.

The influences of parameters on the bubble size in aluminum alloy melt during the gas injection foaming process were studied. The four parameters were the orifice diameter (0.4–3.0 mm), the orifice numbers (1 and 4), the gas chamber volume (11–800 cm3), and the gas flux (10–282 L/h). It was found that the bubble size decreased with the decrease of the orifice diameter and the gas chamber volume, and with the increase of the orifice number. The effect of gas flux showed a dual-stage at different gas fluxes: the “metastable large bubble stage” and the “stable bubbling stage”. A modified semiempirical formula and a concept of “effective gas chamber volume,” which is the nominal chamber volume divided by the effective orifice number, were proposed. The bubble size calculated by the modified formula with the effective gas chamber volume agreed well with the experimental data.

With the advantages of frictionless, no need of lubrication, no pollution, low consuming and long life, active magnetic bearing (AMB) is applied in the primary helium circulator of the High Temperature Gas-Cooled Reactor-Pebble bed Module (HTR-PM), which is under construction in Shidao Bay Nuclear Power Plant. Active magnetic bearing is a typical mechatronic system with interconnection of mechanical and electronic components with the function of picking up signals, processing and producing. Displacement sensor is an important component to pick up signals for stability control, and also the most susceptible part to fail due to variation of air temperature and vibration of high rotation speed. However, rotating system can’t run normally if a single sensor fails in AMB without redundancy design. For security considerations, higher reliability is required in some special equipment, especially in primary helium circulator of HTR-PM. Design and implementation of redundant sensors is an effective method. This paper reviewed the present research of fault diagnosis and redundant control of displacement sensors, simulation of coil’s short-circuit and open-circuit fault was made with MATLAB/SIMULINK. Parameters were optimized for fault diagnostic circuit by Multisim. Based on the high reliability demand, redundancy design was applied both on structure and control system in AMB. Schematic drawing and PCB board were finished by Altium Design, and experiments were carried out. The result showed that if the coils of sensor failed, AMB system could still work normally by switching to the redundant sensors automatically.

The bubble formation at a submerged orifice in the process of aluminum foams produced by gas injection method is investigated. The experimental results show that the increase of the gas flow rate and the orifice diameter can lead to increasing of the bubble size. The large orifice can make the frequency of bubble formation decrease by slowing down the increase of the gas chamber pressure when the gas flow rate increases. The effect of the gas chamber volume on the bubble size can be ignored in the experiment when it expands from 1 to 125 cm3. A theoretical model of bubble formation, expansion, and detachment under constant flow conditions is established to predict the bubble size. The theoretical predictions for air-aluminum melt systems are consistent with the experimental results.

Gene mutation (e.g. substitution, insertion and deletion) and related phenotype information are important biomedical knowledge. Many biomedical databases (e.g. OMIM) incorporate such data. However, few studies have examined the quality of this data. In the current study, we examined the quality of protein single-point mutations in the OMIM and identified whether the corresponding reference sequences align with the mutation positions. Our results show that close to 20% of mutation data cannot be mapped to a single reference sequence. The failed mappings are caused by position conflict, site shifting (peptide, N-terminal methionine) and other types of data error. We propose a preliminary model to resolve such inconsistency in the OMIM database.

With the completion of the human genome project and the development of new methods for gene variant detection, the integration of mutation data and its phenotypic consequences has become more important than ever. Among all available resources, locus-specific databases (LSDBs) curate one or more specific genes' mutation data along with high-quality phenotypes. Although some genotype-phenotype data from LSDB have been integrated into central databases little effort has been made to integrate all these data by a search engine approach. In this work, we have developed disease related unique gene mutation search engine (DRUMS), a search engine for human disease related unique gene mutation as a convenient tool for biologists or physicians to retrieve gene variant and related phenotype information. Gene variant and phenotype information were stored in a gene-centred relational database. Moreover, the relationships between mutations and diseases were indexed by the uniform resource identifier from LSDB, or another central database. By querying DRUMS, users can access the most popular mutation databases under one interface. DRUMS could be treated as a domain specific search engine. By using web crawling, indexing, and searching technologies, it provides a competitively efficient interface for searching and retrieving mutation data and their relationships to diseases. The present system is freely accessible at http://www.scbit.org/glif/new/drums/index.html.

In order to study the effect of repetitive task training combined with neuromuscular electrical stimulation on lower limb function for severe paralysis patients with acute cerebral apoplexy. Chose 36 cases of severe paralysis in patients with acute cerebral apoplexy and devided into treatment group and control group. 18 cases in each group, the control group was given routine rehabilitation therapy. The treatment group was given repetitive task training on the basis of control group. Including sit - stand and stand training. Evaluate the lower limb motor function by the FMA, the walking function by FAC and the activities of daily living by FIM respectively before and after 2 months of treatment.The results were showed that the scores of FMA and FIM were significantly better than before treatment after 2 months (P < 0.05) , and the the scores of FMA and FIM in treatment group were better than control group (P < 0.01). The scores changed of FMA and FIM in treatment group (Δ FMA and Δ FIM scores) were better than control group (P < 0.01).Walking function was better in treatment group than control group as the grade of FAC in treatment group was more higher. So repetitive task training combined neuromuscular electrical stimulation can more effectively improve the lower limb exercise function, walking function and daily life activity for severe paralysis patients with acute cerebral apoplexy.

The eddy effect of the magnetic thrust bearing (MTB) is researched by the finite element analysis (FEA). The active magnetic bearing (AMB) is an advanced bearing, used in HTR-PM. The alternating current in the bearing windings will decrease the electromagnetic force and cause phase lag, especially in the MTB which has no lamination structure. According to the calculation in this paper, simple sinusoidal current has large eddy effect. The force decreases obviously and the phase lag is large. However, the current containing direct part and sinusoidal part, which is closer to actual current, has less eddy effect. That is to say, because of the direct part in the current, the eddy effect of the sinusoidal part decreases.Copyright © 2014 by ASME

HTGR, short for high temperature gas cooled reactor, has gained a lot of attention in nuclear industry. Gas helium, 7MPa in pressure, is used as primary coolant of HTR-PM in where there are a lot of electrical equipment. Insulating property of helium is worse than that of air according to Paschen curves and there are very few articles or related standards about insulating property of high pressure gas helium, which makes the electrical equipment structure design lack of basis. In this study, an experimental platform for testing insulating performance is designed, based on which the experiments of testing the withstanding voltages of penetration assemblies and the breakdown voltages of parallel plane electrodes at different pressures are carried out. The results show that for both the penetration assemblies and the parallel plane, their breakdown voltages in helium are far lower than in air under the same condition of 15°C /0.1MPa. For the penetration assemblies, their insulating properties in helium at 150°C/7MPa are better than those in air at 15°C/0.1MPa.Copyright © 2014 by ASME

The active magnetic bearing (AMB) is a new kind of high-performance bearing which suspends the rotor with controlled electromagnetic force. It was chosen to support the rotor of the helium blower in HTR-PM instead of conventional bearings. The power losses in the active magnetic bearings compose of three components: copper loss, iron loss and windage loss. In this paper, the iron loss, which composes of the eddy current loss and the hysteresis loss, is researched. The power loss of silicon steel lamination (35H300) was measured. Experimental data was taken over a range of 50Hz to 25,000Hz (sinusoidal current) for several magnetic field intensities. According to the experimental data, the eddy current loss and hysteresis loss increase with the frequency. And the hysteresis loss in the silicon steel lamination occupies the major part when the frequency of current is low, however the growth rate of eddy current is much faster than that of the hysteresis loss. And the FEM calculation of power loss in the magnetic bearing, which rotor and stator are made from silicon steel lamination (35H300), is also presented. The result shows the core loss of magnetic bearing also follow the separation theory. We can separate the core loss of magnetic bearing into two parts: hysteresis loss and eddy current loss. It will be very useful to calculate the power loss in the magnetic bearing.Copyright © 2014 by ASME

The method to design the interference fit for the rotor components of the active magnetic bearing (AMB) was proposed. The rotor components include the thrust collar, the radial bearing rotor components and the sensor rotor components. Four main influencing factors and the machining accuracy are considered during the designing, such as the centrifugal force, the loadings, the thermal expansion coefficient, the electromagnetic force, and the coupling surface roughness. Some calculation examples were presented. These examples are base on the AMB of a helium blower, which is going to be applied in the High Temperature Reactor-Pebblebed Modules (HTR-PM) in Rongcheng City, Shandong province. Both the analytical calculation and the finite element analysis were carried out, and then were compared. The method of design based on the simple analytic formula was proved to be available.

High-temperature gas-cooled reactor-pebble bed module (HTR-PM) of China, based on the technology and experience of the 10MW high-temperature gas-cooled reactor (HTR-10), is currently in the design and experiment phase. The helium blower is the key equipment in the first loop of the HTR-PM. Active magnetic bearings (AMBs) are replacing ordinary bearings as the perfect sustaining assembly for the helium blower because they have several advantages: they are free of contact, do not require lubrication, are not subject to the contamination of wear, have endurance, and control performance very well. So the AMB is the appropriate supporting assembly. The rotor’s length of the helium blower is about 3.3 m, its weight is about 4000 kg and the rotating speed is 4000 r/min. The maximal radial load of the upper AMB or the lower AMB is about 1950kg, and the maximal axial load is about 4500kg. So the axial and radial AMBs must have enough carrying capacity to support the rotor. It is difficult to design the AMB in limited space. Many factors may restrict the AMB design, for example, clearance between AMB and rotor, electric current, and environment temperature, etc. In this paper, design of magnetic field will be analyzed. Heat loss of AMB will be discussed. The designing scheme of magnetic field will offer the important theoretical base for AMB design of the helium blower of HTR-PM.