多级离心泵叶轮与流道式导叶的匹配特性

本文对多级离心泵设计了流道式导叶,采用Spalart-Allmaras湍流模型对设计结果进行数值模拟。通过对流道式导叶几何结构的调整,探讨了叶轮-导叶间隙、导叶进口方式及级间密封对离心泵流动性能的影响。经过分析得到了以下结论:导叶进口直径为叶轮出口直径的1.027倍时与叶轮匹配较好;导叶进口宽度的减小在小流量工况下存在优势;对导叶进口进行斜切处理可以有效消除密封通道对水泵造成的影响,同时提高了大流量工况下的水力性能,设计点效率提高0.65%,扬程提高1.30%,分析结果为离心泵流道式导叶与叶轮匹配设计提供理论指导。

基于NREC的新型氧气风机设计与流场分析

为了得到节能高效的新型氧气离心风机,利用NREC软件进行全三维结构设计。通过三元流设计理论得到高效率叶轮,其中第一级和第二级转子效率均可达到88%以上,再通过NREC内部的蜗壳设计模块得到高效率蜗壳。利用NUMECA的Fine\open对设计结果进行数值模拟,风机整机效率在设计点工况下可达到82%以上,远超于同类型风机,流场均匀,且具有较宽广且平坦的工作特性,同时使风机的电能消耗大幅降低,减少污染物排放,实现节能环保。本课题的研究可为节能高效的氧气风机设计提供理论参考。

Altered amplitude of low-frequency fluctuations and default mode network connectivity in high myopia:a resting-state fMRI study

AIM:To analyze changes in amplitude of low-frequency fluctuations(ALFFs)and default mode network(DMN)connectivity in the brain,using resting-state functional magnetic resonance imaging(rs-fMRI),in high myopia(HM)patients.METHODS:Eleven patients with HM(HM group)and 15 age-and sex-matched non-HM controls(non-HM group)were recruited.ALFFs were calculated and compared between HM group and non-HM group.Independent component analysis(ICA)was conducted to identify DMN,and comparisons between DMNs of two groups were performed.Region-of-interest(ROI)-based analysis was performed to explore functional connectivity(FC)between DMN regions.RESULTS:Significantly increased ALFFs in left inferior temporal gyrus(ITG),bilateral rectus gyrus(REC),bilateral middle temporal gyrus(MTG),left superior temporal gyrus(STG),and left angular gyrus(ANG)were detected in HM group compared with non-HM group(all P<0.01).HM group showed increased FC in the posterior cingulate gyrus(PCC)/precuneus(preCUN)and decreased FC in the left medial prefrontal cortex(mPFG)within DMN compared with nonHM group(all P<0.01).Compared with non-HM group,HM group showed higher FC between mPFG and bilateral middle frontal gyrus(MFG),ANG,and MTG(all P<0.01).In addition,HM patients showed higher FC between PCC/(preCUN)and the right cerebellum,superior frontal gyrus(SFG),left pre CUN,superior frontal gyrus(SFG),and medial orbital of the superior frontal gyrus(ORB supmed;all P<0.01).CONCLUSION:HM patients show different ALFFs and DMNs compared with non-HM subjects,which may imply the cognitive alterations related to HM.

A line laser detection screen design and projectile echo power calculation in detection screen area

A line laser with high power as the background light source for the design of a new photoelectric detection target is proposed in this paper, aiming to improve the detection ability of the traditional photoelectric detection target under low background illumination. The laser emitted pulse waveform function and the laser echo pulse response function were used to establish the mathematical model of the reflected echo power of projectile in the detection area and derive the calculation function of minimum detectable echo power in the line laser detection screen, according to information of the line laser emitted power, incident angle of projectile, duration time and detection distance of projectile passing through the line laser detection screen. Calculations and experimental results showed that the design method of line laser detection screen and calculation model of laser echo power are reasonable, and the detection ability of line laser detection screen is obviously higher than that of traditional photoelectric detection screen, especially in low background illumination;at the same time, the designed line laser detection screen was used to combine a six line laser detection screen intersection test system, based on live ammunition for shooting. The test system is stable and able to obtain the dynamic parameters of the flying projectile, verifying that the design of the line laser detection screen in new photoelectric detection target can be suitable for shooting range test applications.

半开式离心叶轮轴向力数值计算及平衡方法

使用NUMECA/Fine turbo对一台5.2kg/s,压比2.5的半开式离心压气机进行轴向力计算,发现使用不带叶轮背部空腔的模型求解,NUMECA的监测器读出的轴向推力是错误的。同时,带轮盘空腔模型计算时默认的旋转域和旋转壁面也将得到错误的轴向力。文中给出了正确的轴向力求解方法,并以此进行了轴向力平衡设计的验证计算。模型原始轴向推力正确值应该在9000N以上,通过平衡后降低至5000N以下,满足实验台推力轴承8000N的承受上限。实验过程中轴承振动和温度均没有升高,证明轴向力平衡方案有效。

High-confinement ultra-wideband bandpass filter using compact folded slotline spoof surface plasmon polaritons

A novel bandpass filter(BPF)based on spoof surface plasmon polaritons(SSPPs)using a compact folded slotline structure is proposed and experimentally demonstrated.The proposed novel SSPPs structure compared with a conventional plasmonic waveguide with slot line SSPPs unit structure at the same size,the considerable advantages in much lower asymptotic frequency with tight field confinement,which enable the proposed filter to be more miniaturization.A high-efficient mode conversion structure is designed to transition from TE-mode to SSPPs-mode by gradient slotline lengths.The low-frequency stop-band can be committed with microstrip to slotline evolution on both sides of the dielectric,while the high-frequency cutoff band is realized by the proposed SSPPs structure.The influence of dispersion relation,electric field distribution,surface current,and structural parameters on the transmission characteristics of the proposed BPF are analyzed by finite difference time domain(FDTD).To validate the design concept,the prototype of the miniaturized SSPPs BPF has been manufactured and measured.The experimental results show high performance of the fabricated sample,in which the working in a range of 0.9 GHz-5.2 GHz with the relative bandwidth is 142%,the insertion loss less than 0.5 dB,the reflection coefficient less than-10 dB,and the group delay is less than one ns.This works provides a mirror for realizing the miniaturization of waveguides,and the application and development of high-confinement SSPPs functional devices in the microwave and THz regimes.

Ultra-wideband surface plasmonic bandpass filter with extremely wide upper-band rejection

An ultra-wideband bandpass filter(BPF)with a wide out-of-band rejection based on a surface plasmonic waveguide(SPW)slotline with ring grooves is designed and analyzed.A paired microstrip-to-slotline transition is designed for quasiTEM to TM mode conversion by using a microstrip line with a circular pad and the slotline with the same circular slot.The mode conversion between the TM and the surface plasmon polariton(SPP)mode is realized by using a gradient slotline with ring grooves and an impedance matching technique.The upper cut-off frequencies of the passband can be adjusted by using these proposed SPP units,while the lower frequencies of the passband are created by using the microstrip-toslotline transitions to give an ultra-wideband BPF.The dispersion curves of SPP units,electric field distribution,and the transmission spectra of the proposed ultra-wideband bandpass filter are all calculated and analyzed by the finite-difference time-domain(FDTD)method.The simulated results show that the presented filter has good performance including a wide3-dB bandwidth of 149%from 0.57 GHz to 3.93 GHz,an extremely wide 40-dB upper-band rejection from 4.2 GHz to18.5 GHz,and low loss and high selectivity in the passband.To prove the design validity,a prototype of the BPF has been manufactured and measured,showing a reasonable agreement with simulation results.The unique features of the proposed BPF may make it applicable for integrated circuit and plasmonic devices in microwave or THz frequency ranges.

Estimation of lunar FeO abundance based on imaging by LRO Diviner

Understanding the abundance and distribution characteristics of FeO on the surface of the Moon is important for investigating its evolution. The current high resolution maps of the global FeO abundance are mostly produced with visible and near infrared reflectance spectra. The Christiansen Feature （CF） in mid-infrared has strong sensitivity to lunar minerals and correlates to major elements composing minerals. This paper investigates the possibility of mapping global FeO abundance using the CF values from the Diviner Lunar Radiometer Experiment aboard the Lunar Reconnaissance Orbiter （LRO） mission. A high correlation between the CF values and FeO abundances from the Apollo samples was found. Based on this high correlation, a new global map （±60°） of FeO was produced using the CF map. The results show that the global FeO average is 8.2 wt.%, the highland average is 4.7 wt.%, the global modal abundance is 5.4 wt.% and the lunar mare mode is 15.7 wt.%. These results are close to those derived from data provided by Clementine, the Lunar Prospector Gamma Ray Spectrometer （LP-GRS） and the Chang＇e-1 Interference Imaging Spectrometer （IIM）, demonstrating the feasibility of estimating FeO abundance based on the Diviner CF data. The near global FeO abundance map shows an enrichment of lunar major elements.

Effect of Thymosin Injection combined with entecavir therapy on the viral load, liver fibrosis and immune response of patients with compensated liver cirrhosis

Objective: To study the effect of Thymosin Injection combined with entecavir therapy on the viral load, liver fibrosis and immune response of patients with compensated liver cirrhosis. Methods: Patients who were diagnosed with chronic hepatitis b complicated by compensated liver cirrhosis in our hospital between March 2015 and January 2017 were selected and randomly divided into two groups, observation group received Thymosin Injection combined with entecavir therapy, and control group received entecavir therapy. The viral load, liver function injury indexes, liver fibrosis indexes, immune cytokines and immune cell apoptosis molecules were measured 24 weeks after treatment. Results: 24 weeks after treatment, HBV-DNA copy number in peripheral blood as well as ALT, AST, TBIL, HA, PC-III, LN, C-IV, IL-4, IL-10, TGF-β1, IL-17 and IL-22 levels in serum of observation group was significantly lower than those of control group, and peripheral blood FAS, CYCS, CASP8, CASP9 and CASP3 mRNA expression were significantly lower than those of control group. Conclusion:Thymosin Injection combined with entecavir therapy can reduce viral load, improve liver function, inhibit liver fibrosis and regulate immune function in patients with compensated liver cirrhosis.

Argo温度数据的ConvGRU模型预测分析

Argo(Array for Real-time Geostrophic Oceanography)是海洋环境信息的重要来源之一,可通过自动剖面浮标、卫星定位和数据同化等技术获取大范围全球海洋上层之间的海温剖面资料。本文利用ConvGRU(Convolutional Gate Recurrent Unit)作为Argo温度的预测模型,以西北太平洋部分海域为研究区域,选取2004-2018年Argo数据作为训练数据,对2019年的0 m、50 m、100 m、200 m和300 m不同深度位置水平剖面进行了预测分析。研究结果表明:ConvGRU模型对Argo温度数据的变化趋势具有较好的模拟能力;预测模型的训练集和验证集的RMSE(root mean squared error)均值分别为0.0462℃和0.0463℃,MAE(mean absolute error)均值分别为0.0442℃和0.0450℃,其Acc(accuracy)都在99%以上;对于预测评估,RE(relative error)的误差范围为0.0228~0.0427,预测变化的空间特性与真实值的吻合程度较高。

Three-dimensional numerical simulation of a vertical axis tidal turbine using the two-way fluid structure interaction approach

The objective of this study was to develop, as well as validate the strongly coupled method (two-way fluid structural interaction (FSI)) used to simulate the transient FSI response of the vertical axis tidal turbine (VATT) rotor, subjected to spatially varying inflow. Moreover, this study examined strategies on improving techniques used for mesh deformation that account for large displacement or deformation calculations. The blade's deformation for each new time step is considered in transient two-way FSI analysis, to make the design more reliable. Usually this is not considered in routine one-way FSI simulations. A rotor with four blades and 4-m diameter was modeled and numerically analyzed. We observed that two-way FSI, utilizing the strongly coupled method, was impossible for a complex model; and thereby using ANSYS-CFX and ANSYS-MECHANICAL in work bench, as given in ANSYS-WORKBENCH, helped case examples 22 and 23, by giving an error when the solution was run. To make the method possible and reduce the computational power, a novel technique was used to transfer the file in ANSYS-APDL to obtain the solution and results. Consequently, the results indicating a two-way transient FSI analysis is a time- and resource-consuming job, but with our proposed technique we can reduce the computational time. The ANSYS STRUCTURAL results also uncover that stresses and deformations have higher values for two-way FSI as compared to one-way FSI. Similarly, fluid flow CFX results for two-way FSI are closer to experimental results as compared to one-way simulation results. Additionally, this study shows that, using the proposed method we can perform coupled simulation with simple multi-node PCs (core i5).

Effects of Stress Level and Stress State on Creep Ductility:Evaluation of Different Models

The last few decades have witnessed an increasing emphasis on the development of strain-based ap- proach for predicting the creep life or damage of components operating at elevated temperatures. Creep ductility, as a key parameter in this approach, may vary with a number of factors including strain rate, state of stress, operating temperature, material microstructure, etc. The present paper, however, is focused on reviewing the state-of-the-art understanding of the effects of stress level and stress state on the creep ductility. Mechanisms involving the void growth and coalescence are presented to describe the role of stress level in the variation of uniaxial creep ductility. The prediction capacity of existing empirical duc- tility models is also assessed in light of uniaxial test data. On the other hand, a vast body of multiaxial creep test data, collected from open literature, is utilized to examine the influence of the state of stress on the creep ductility. Then, a variety of multiaxial ductility factor models are introduced and evaluated with the available experimental data. Finally, a brief discussion on the dependence of creep ductility on the stress triaxiality and Lode parameter, predicted by numerical methods, is provided.