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The working principle of the motor can cause unbalanced magnetic pull (UMP) between stator and rotor unavoidably. Previous research about nonlinear vibration excited by UMP was focused on the rotor supported by traditional mechanical bearings or gas bearings. However, the magnetic levitation rotor is particular due to the low rigidity provided by the active magnetic bearing (AMB). UMP amplifies rotor vibration in the resonant zone and further excites the nonlinear electromagnetic force, thus producing different vibration phenomena. The paper calculates rotor orbit, spectra analysis, and time-history plot with numerical methods and studies the influence of the rotation speed, eccentricity, key control parameters, and UMP on rotor dynamics in detail. Results illustrate displacement response spectra of the magnetic levitation rotor are quite different from previous research results. The appearing frequency components are inducted by universal formulas in this paper. Furthermore, research shows a slight adjustment of the control parameters affect significantly harmonic components and vibration characteristics. The research results have practical reference significance for fault diagnosis, feature recognition, and controller optimization of the AMB-rotor system.

Background:Triple-negative breast cancer (TNBC) is a high-risk breast cancer subtype, which accounts for 15% to 20% of all breast cancers and generally has a poor prognosis. TNBC patients have high recurrence post-surgery and high risk of metastasis to other organs. The tumor microenvironment (TME) plays important roles in the carcinogenesis, development, and metastasis of tumors. Methods: This study aimed to investigate the effects of immune and stromal cell-related genes on TNBC prognosis. The ESTIMATE algorithm was used to calculate the immune/stromal scores of TNBC samples from the GEO database. The samples were divided into high- and low- score groups and the differential expression genes were identified using the limma package within R. Functional enrichment and protein-protein interaction (PPI) network analyses revealed that these genes are primarily involved in immune responses. Results:Survival analysis in both GSE21653 and KM-plotter website showed that 36 genes were significantly related to disease-free survival (DFS) of TNBC. Another survival analysis by R package survival in GSE58812 indicated that 14 genes of 36 were greatly interrelated to DFS of TNBC. Moreover, the expression levels of some of these genes were verified through immunohistochemical staining and RT-qPCR. Finally, four genes importantly associated with TNBC prognosis were identified with Cox-LASSO analysis. Time-dependent receiver-operating characteristic (ROC) analysis displayed an area under the curve (AUC) of 0.95 for one-year survival rate, indicating the four genes performed very well for prognosis prediction. Conclusions:In conclusion, we identified four genes, including BIRC3, CD8A, GNLY and TRIM22, that are possibly associated with the TME and are potential prognostic and therapeutic markers of TNBC.

In order to study the windage losses caused by the friction between fluid and rotor surface in high speed rotating machines, a series of rundown experiments are performed in a vacuum chamber. By means of an evacuation method, the windage losses are extracted by subtraction operation between specified pressure and near absolute vacuum. The windage losses separated with existing separation models for large gap are compared to the extracted values with evacuation method and the results show big disagreements. For this reason, a modified separation model considering the skin effect and gas state is presented for rotating electrical machines simultaneously including both large and small gap. Using the modified separation model, the results show good agreements with the extracted values. In contrast to the evacuation method, the new model provides a way to quickly assess windage losses in electrical machines, where vacuuming is not obligatory any more.

High temperature superconducting (HTS) magnetic bearing can operate in the harsh environment of low temperature and negative pressure with low loss and self-stability. Therefore, it has been gradually applied in flywheel energy storage, cryogenic liquid pump, cold compressor and some other cryogenic rotating machinery. The load-carrying performance of HTS magnetic bearing is affected by the cooling temperature of HTS directly. In this paper, the linear model is used to modify the temperature dependence to evaluate the influence of cooling temperature on load-carrying performance quantitatively, and the results are analyzed and displayed from the aspects of maximum levitation force, levitation stiffness and hysteresis effect. The research results of this paper have practical significance for the design and safe operation of HTS levitation system.

Active control of flexible rotors is a challenging issue in modern industries. This paper focuses on the synthesis of a mixed sensitivity robust controller for a linear parameter-varying (LPV) system. The objective is to control rotor vibration, especially when the rotor is passing the first two bending critical speeds. In the formulation of the problem for the controller, weighting functions are proposed based on the relationship between the desired shape of the open-loop transfer function and sensitivity functions of the closed-loop system. Recent research has highlighted the efficiency of mixed sensitivity robust controllers in stabilizing a wide range of magnetic bearing systems. Here, the method is extended to control the vibration of a piezoelectric bearing system. The experimental rotor features two unbalance-exited resonances within its operating range. Experimental results demonstrate good performance of the vibration reduction and the effectiveness of the design method.

In this paper, a type of mutual inductance sensor based on the PCB technology is proposed for cryogenic radial displacement measurement. Firstly, the feasibility of the scheme is analyzed from the aspects of the low temperature usability of materials and components, and the temperature sensitivity of the sensor. Then the experiments at low temperature (77 K) and room temperature are carried out with a simple and effective setup. The experimental results show that the sensitivity has no obvious change from room temperature to low temperature, and the linearity remains at a good level. However, the standard deviation and repeatability of the measurement are affected by external factors. Generally speaking, this paper verifies the feasibility of applying this sensor to micro displacement measurement at low temperature, which lays a foundation for the development of more mature displacement sensor for HTS bearing.

A high pressure hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect at room temperature is studied here. In the apparatus, a helium-gas-filled alfa-type Stirling refrigerator uses Gd sheets as the regenerator and the regenerator is put in a magnetic field varying from 0 to 1.4 T, which is provided by a Halbach-type rotary permanent magnet assembly. With an operating pressure of 5.5 MPa and a frequency of 2.5 Hz, a no-load temperature of 273.8 K was reached in 9 minutes, which is lower than that of 277.6 K for pure Stirling cycle. For the hybrid operation, cooling powers of 40.3 W and 56.4 W were achieved over temperature spans of 15 K and 12 K, respectively. For the latter case, the cooling power improves by 28.5% if compared with that exploiting only the Stirling cycle refrigeration effect.

Condensation heat transfer and pressure drop of R170 were studied experimentally in a horizontal tube with inner diameter of 4 mm. The tests were conducted at saturation pressures from 1 MPa to 2.5 MPa, mass fluxes from 100 kg (m2∙s)−1 to 250 kg (m2∙s)−1 and average heat fluxes from 55.3 kW m−2 to 96.3 kW m−2 over the entire vapor quality range. The effects of vapor quality, mass flux and saturation pressure on condensation heat transfer and pressure drop were examined and analyzed. The experimental data were compared with various well-known correlations of condensation heat transfer coefficient and pressure drop. The comparison results showed that Koyama et al. correlation agreed with the experimental heat transfer coefficient with a mean absolute relative deviation less than 25%, and the Yan and Lin correlation can accurately predict the experimental pressure drop with a mean absolute relative deviation less than 18%.

HIAF-BRing, the main synchrotron accelerator of the High Intensity Heavy-Ion Accelerator Facility, requires an average pressure lower than 1 × 10−9 Pa and the magnetic field increase rate no less than 12 T/s to fulfill radioactive beam physics and high energy density physics experiments. To reduce the eddy current effect and the gap size of dipoles compared to the thin-wall stainless steel vacuum chamber with reinforced ribs, a new design of ceramic-lined vacuum chamber with wall thickness 0.3 mm has been proposed by IMP. In order to effectively reduce the beam impedance and the desorption rate of ceramic materials, Au coating on ceramic (Yttria stabilized zirconia) by magnetron sputtering has been carried out. The adhesive force of Au film is 28.1 MPa measured by scratch test while the crystalline size of Au particle is in the range of 15.7–21.4 nm by X-ray diffraction (XRD). The longitudinal impedances of four types of round-ring-lined 0.6-m-long straight stainless-steel tubes and the ultimate pressure of the new designed vacuum chamber (uncoated vs Au-coated) have been measured to verify the feasibility of this method.

Cold compressors are the core components needed for the development of a facility for large-capacity refrigeration at superfluid helium temperature. The compressor impeller operates at extremely low temperature and low pressure which involves a performance penalty due to heat transfer from the warm side of the machine to the cold side and thus affects the recycle of the cold exergy downstream. To investigate the heat transfer effect on cold compressor performance, a conjugate heat transfer analysis is performed with commercial CFD solver and is then validated with the experimental data tested at different rotation speed. Then a series of configurations of different thermal boundaries are analyzed to investigate the influence of heat transfer on performance. The simulated results show that the external heat transfer has a negative impact on pressure distribution. The helium gas inside the impeller flow domain is more sensitive to external heat leakage comparing with that inside the diffuser flow. More than that, the mass flow leakage through blade tip clearance is highly affected by the external heat transfer, which counts for the performance degradation.

Large-scale helium cryo-refrigerator is widely used in superconducting systems, nuclear fusion engineering, and scientific researches, etc., however, its energy efficiency is quite low. First, a 2 kW at 20.0 K helium Brayton cryo-refrigerator is built, and a series of tests have been systematically conducted to investigate the performance of the cryo-refrigerator. It is found that maximum heat conductance proportion (90.7%) appears in the heat exchangers of cold box rather than those of heat reservoirs, which is the main characteristic of the helium Brayton cryo-refrigerator/cycle different from the air Brayton refrigerator/cycle. Other three characteristics also lie in the configuration of refrigerant helium bypass, internal purifier and non-linearity of specific heat of helium. Second, a model of helium Brayton cryo-refrigerator/cycle is presented according to finite-time thermodynamics. The assumption named internal purification temperature depth (PTD) is introduced, and the heat capacity rate of whole cycle is divided into three different regions in accordance with the PTD: room temperature region, upper internal purification temperature region and lower one. Analytical expressions of cooling capacity and COP are obtained, and we found that the expressions are piecewise functions. Further, comparison between the model and the experimental results for cooling capacity of the helium cryo-refrigerator shows that error is less than 7.6%. The PTD not only helps to achieve the analytical formulae and indicates the working temperature of internal purifier, but also reflects the heat conductance distribution of heat exchangers in the cold box. Last, effects of the PTD on cooling capacity and COP of the helium cryo-refrigerator are investigated. In a word, this study provides a better understanding of energy conversion and utilization of the cycle and helps to optimize it.

In order to meet the training needs of Partial Discharge (PD) detection personnel, a PD detection training simulator is developed. The composition of the system and the functions of the modules are described, then the three-dimensional graphic engine based on Open Scene Graph (OSG) and the way of scene organization based on hierarchical tree are introduced, moreover, the methods of fault simulation and detection instrument simulation based on algorithm component library are presented. Application shows that the system can provide various detection schemes, and it is an ideal training tool for the detection personnel.

The Roman pots of the TOTEM experiment at LHC will be equipped with edgeless silicon micro-strip detectors. A detector package consists of 10 detector planes cooled at - 15 ∘ C in vacuum. The detector resolution is 20 μ m , the overall alignment precision has to be better than 30 μ m . The detector planes are composed of a kapton hybrid glued on a substrate made of low expansion alloy, CE07 with 70% Si and 30% Al. An evaporative cooling system based on the fluorocarbon C 3 F 8 with oil-free compressors has been adopted. The throttling of the fluid is done locally through capillaries. A thermo-mechanical prototype has been assembled. The results fully match the requirements and the expectations of calculations. They show a low thermal gradient on the cards and a uniform temperature distribution over the 10 planes.

An application of CFD model for the simulation of a strongly swirling and high speed flow in the vortex tube is presented in this paper. A partly modified standard K-ε turbulent model has been used to investigate the flow characteristics and energy separation effect in the vortex tube. It is found that there is an obvious energy separation effect in the vortex tube and the numerical solutions of the flow and temperature fields agree well with the experiments. More detailed flow features are obtained by the CFD calculation. Based on the validated numerical model, the influence of the cold flow fraction on the energy separation effect is also investigated and compared with experimental results.

The phase space method is used in studying a thermo-acoustic heat engine in this paper. The maximum Lyapunov exponent is used to quantify the phase space that is reconstructed from the pressure signal of the thermo-acoustic heat engine. For quantifying the system change, the maximum Lyapunov exponents of the reconstructed pressure phase space trails are calculated. The plot of the maximum Lyapunov exponents versus time is attained. Good agreement between the plot and the evolving process of the real physical phenomenum indicates that the maximum Lyapunov exponents can reflect the state changes of the thermo-acoustic heat engine.

The purpose of this paper is to investigate the stability of oscillation modes in a thermoacoustic Stirling prime mover, which is a combination of looped tube and resonator. Two modes, with oscillation frequencies of 76 and 528 Hz, have been observed, stabilities of which are widely different. The stability of the high frequency mode (HFM) is affected by low frequency mode (LFM) strongly. Once the LFM is excited when the HFM is present, the HFM will be gradually slaved and suppressed by the LFM. The details of the transition from HFM to LFM have been described. The two stability curves of the two modes have been measured. Mean pressure Pm is an important control parameter influencing the mode stability in the tested system.

Thermodynamic mechanism of thermoacoustic self-excited oscillation is analyzed in this paper. The law of minimizing entropy flow is obtained basing on the fundamentals of finite-time thermodynamics. The results obtained here show that the thermoacoustic self-excited oscillation, which is a non-isentropic oscillation with power-output corresponding to a limit cycle in the phase space takes place when hot temperature Th exceeds a threshold value [Formula: see text]. The effect of nonlinear terms on the system will lead to the second harmonic wave.

The work proposes a simple and feasible calculation method––network model method to calculate temperature differences generated in thermo-driven thermoacoustic refrigerator (TAR). The theoretical calculation model is first built. The network model is given and used to make numerical calculations under different conditions including heat-pump stack positions in TAR, different oscillating pressure ratios (PR), plate spacings and different stack geometries. Theoretically calculated results show that the former two factors make significant influence on temperature differences, the influence of stack spacing on temperature difference has relation with PR, and cooling effect of pin-array stack is superior to that of parallel plate stack under other same conditions. Furthermore, theoretically calculated results and experimentally measured data are in good agreement at small acoustic pressure amplitude.

A traveling wave thermoacoustic engine consisting of a loop tube with a resonator has been tested. The onset characteristic together with the transition of oscillation mode from traveling wave to standing wave and the periodic shifting between modes in this system are investigated experimentally. The process of self-sustained thermoacoustic oscillation in this heat engine is described and analyzed through phase space distribution reconstructed from the time series of acoustic signal.

Hydrocarbons have high thermodynamic performances, belong to the group of natural refrigerants, and they are the main components in mixture Joule-Thomson low temperature refrigerators (MJTR). New evaluations of nucleate boiling contribution and nucleate boiling suppression factor in flow boiling heat transfer have been proposed for hydrocarbons. A forced convection heat transfer enhancement factor correlation incorporating liquid velocity has also been proposed. In addition, the comparisons of the new model and other classic models were made to evaluate its accuracy in heat transfer prediction.

A traveling wave thermoacoustic-driven system with a designed resonant frequency of 200 Hz has been established. Nonlinear thermoacoustic phenomena, such as the oscillation onset temperature and shifts of the resonant frequency, are presented. Experimental investigations have been conducted by changing wire-screen mesh size, working gases, and mean pressures, and the effects have been noted on temperature profiles, oscillation modes, frequency jumps, and pressure amplitudes. The analysis indicates that the relative penetration depth ratio (δv/rh) plays an important role with these nonlinear phenomena.

In helium refrigeration system, high-speed centrifugal cold compressor is utilized to pumped gaseous helium from saturated liquid helium tank at low temperature and low pressure for producing superfluid helium or sub-cooled helium. Stall and surge are common unsteady flow phenomena in centrifugal cold compressors which severely limit operation range and impact efficiency reliability. In order to obtain the installed range of cold compressor, unsteady flow in the case of low mass flow or high pressure ratio is investigated by the CFD. From the results of the numerical analysis, it can be deduced that the pressure ratio increases with the decrease in reduced mass flow. With the decrease of the reduced mass flow, backflow and vortex are intensified near the shroud of impeller. The unsteady flow will not only increase the flow loss, but also damage the compressor. It provided a numerical foundation of analyzing the effect of unsteady flow field and reducing the flow loss, and it is helpful for the further study and able to instruct the designing.

In this paper, an experimental study on two-phase flow patterns (evaporation) for propane in a horizontal smooth tube is presented. The tests were conducted at various saturation pressures from 0.2 MPa to 0.4 MPa for different mass velocities from 70 kg/(m 2 s) to 180 kg/(m 2 s) and two heat fluxes (20.16 kW/m 2 and 37.1 kW/m 2 ) in the entire ranges of vapour qualities. Several flow pattern maps were compared with the experimental flow pattern data, especially for the intermittent/annular (I/A) transition line. Finally, a transition equation of intermittent/annular flow for propane was modified with an improved flow pattern map.