Underactuated spacecraft angular velocity stabilization and three-axis attitude stabilization using two single gimbal control moment gyros

Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.

LINC00609 inhibits A549 cells progression through the regulation of miR-128-3p/RND3 axis

Background:Long-chain non-coding RNA(lncRNA)LINC00609 is a potential tumor suppressor,but the mechanism of action in non-small cell lung cancer(NSCLC)is yet to be understood.Objectives:The effects of LINC00609 on A549 cell proliferation,apoptosis,and cell cycle arrest were investigated.Methods:The LINC00609 levels in NSCLC and normal tissues were analyzed by bioinformatics.Expressions of LINC00609,miR-128-3p,and Rho family GTPase 3(RND3)in NSCLC cells(A549)were determined by qRT-PCR.Bioinformatics analysis predicted target genes and dual-luciferase reporter assays to ensure that LINC00609 targeted miR-128-3p and miR-128-3p targeted RND3.The proliferation of cells was determined using EDU and CCK-8.Flow cytometry was used to evaluate cell apoptosis rate and cell cycle.The western blotting assay identified proteins related to proliferation and apoptosis.Results:In NSCLC tissues,LINC00609 was expressed in low levels,while its high expression was associated with a higher survival rate.LINC00609 affected cell proliferation,apoptosis,cell cycle arrest,and expression of related proteins.Dual-luciferase reporter assay showed that LINC00609 binds specifically to miR-128-3p,and miR-128-3p binds to RND3.MiR-128-3p overexpression could neutralize the effects of LINC00609.A siRNA targeting RND3 could reverse the effect of the miR-128-3p inhibitor.Silencing RND3 resulted in a decrease in apoptosis rate and the number of cells in the S-phase and an increase in the number of cells in the G1-phase.Furthermore,phosphorylation levels of the AKT protein and mTOR protein,and Bcl2 expression,increased;however,the expression of RND3,Bax,and caspase3 decreased.Conclusions:LINC00609 regulated miR-128-3p/RND3 axis to modulate A549 cell proliferation,apoptosis,and cell cycle arrest.In the case of NSCLC,LINC00609 could be a potential target for therapy.

Misalignment Angle Calculation Accuracy Analysis of Three-Axis Stabilized Geostationary Satellite

The most challenging problem of navigation in three-axis stabilized geostationary satellite is accurate calculation of misalignment angles, deduced by orbit measurement error, attitude measurement error, thermal elastic deformation, time synchronization error, and so on. Before the satellite is launched, the misalignment model must be established and validated. But there were no observation data, which is a non-negligible risk of yielding the greatest returns on investment. On the basis of misalignment modeling using landmarks and stars, which is not available between different organizations and is developed by ourselves, experimental data are constructed to validate the navigation processing flow as well as misalignment calculation accuracy. In the condition of using landmarks, the maximum misalignment calculation errors of roll, pitch, and yaw axis are 2, 2, and 104 micro radians, respectively, without considering the accuracy of image edge detection. While in the condition of using stars, the maximum errors of roll, pitch, and yaw axis are 1, 1, and 3 micro radians, respectively, without considering the accuracy of star center extraction. Results are rather encouraging, which pave the way for high-accuracy image navigation of three-axis stabilized geostationary satellite. The misalignment modeling as well as calculation method has been used in the new generation of geostationary meteorological satellite in China, FY-4 series, the first satellite of which was launched at the end of 2016.

海水淡化高压泵与能量回收一体机水润滑轴承-转子系统稳定性

为保障海水淡化高压泵与能量回收一体机的安全稳定运行,对轴颈倾斜时的水润滑转子系统的稳定性展开研究.基于流体动压润滑理论,采用差分法和微扰法,建立考虑四自由度的32动力系数模型,同时求解转子动力学方程,分析不同偏心距、倾斜角、载荷下轴承的动静特性和口环间隙水膜产生的流体动压润滑效应对转子稳定性的影响.求解转子系统特征方程,并通过特征值实部对转子的稳定性进行分析.研究结果表明:倾斜运动对转子稳定性影响较大,四自由度下偏心率和倾斜角的增大使得32个动特性系数有不同程度的增大,从而减小运行过程中转子涡动产生的位移量,同时具有更高的承载能力;口环间隙水膜的动压润滑效应对转子稳定性具有不可忽视的影响,可使得转子的位移响应减小为原来的1/3,达到稳定运行的时间缩短为原来的1/3;一体机转子的极限转速为40000~45000 r/min,当转速超过极限转速时,系统出现正实部的特征值,增大口环宽度和减小口环水膜间隙厚度可增大转子的极限转速.

circ_0003204 regulates the osteogenic differentiation of human adipose-derived stem cells via miR-370-3p/HDAC4 axis

Human adipose-derived stem cells(hASCs)are a promising cell type for bone tissue regeneration.Circular RNAs(circRNAs)have been shown to play a critical role in regulating various cell differentiation and involve in mesenchymal stem cell osteogenesis.However,how circRNAs regulate hASCs in osteogenesis is still unclear.Herein,we found circ_0003204 was significantly downregulated during osteogenic differentiation of hASCs.Knockdown of circ_0003204 by si RNA or overexpression by lentivirus confirmed circ_0003204 could negatively regulate the osteogenic differentiation of hASCs.We performed dual-luciferase reporting assay and rescue experiments to verify circ_0003204 regulated osteogenic differentiation via sponging miR-370-3p.We predicted and confirmed that miR-370-3p had targets in the 3′-UTR of HDAC4 m RNA.The following rescue experiments indicated that circ_0003204 regulated the osteogenic differentiation of hASCs via miR-370-3p/HDAC4 axis.Subsequent in vivo experiments showed the silencing of circ_0003204 increased the bone formation and promoted the expression of osteogenic-related proteins in a mouse bone defect model,while overexpression of circ_0003204 inhibited bone defect repair.Our findings indicated that circ_0003204 might be a promising target to promote the efficacy of hASCs in repairing bone defects.

完全匹配层在矩阵式波动方程SBP-SAT方法应用

数值离散方法和截断边界效果是地震动模拟实现的关键。基于分部求和(summation-by-parts,SBP)和一致逼近(simultaneous approximation term,SAT)的SBP-SAT方法具有较高的稳定性,这使得该方法具备了较高的应用前景和价值。此外,完全匹配层(perfect matching layer,PML)是一种应用广泛用于模拟截断边界的技术,但引入匹配层可能会破坏原始方程的稳定性,特别是在各向异性介质或曲线域模型中。首先基于数理推导,给出弹性波动方程系数矩阵的对称形式。在此基础上,引入多轴完全匹配层(multi-axis perfect matching layer,MPML),并建立相应的匹配层方程。通过本征值分析,我们可以判断阻尼函数对原方程特征根实部的走向和取值范围的影响。然后,我们采用SBP-SAT方法对矩阵对称形式匹配层方程进行离散,并在频域中采用能量法进行稳定性评估。通过对不同模型的数值仿真,表明所提出的离散框架具有整合度高、稳定性好和拓展性强等特点。此外,多轴匹配层可以与SBP-SAT方法结合,可以稳定地模拟曲线域中的波传播。

The Electric-Field Controllable Non-Volatile 35° Rotation of Magnetic Easy Axis in Magnetoelectric CoFeB/(001)-Cut Pb(Mg_(1/3)Nb_(2/3))O_3-25%PbTiO_3 Heterostructure

Using in situ electric-field-modulated anisotropic magnetoresistance measurement, a large reversible and non- volatile in-plane rotation of magnetic easy axis of -35° between the positive and negative electrical poling states is demonstrated in C040Fe40B20//（001）-cut Pb（Mgl/3Nb2/3）O3-25PbTiO3 （PMN-PT）. The specific magneto- electric coupling mechanism therein is experimentally verified to be related to the synchronous in-plane strain rotation induced by 109° ferroelastic domain switching in the （001）-cut PMN-PT substrate.

Stabilization variation of organic conductor surfaces induced by π-π stacking interactions

The structures and stabilization of three crystal surfaces of TCNQ-based charge transfer complexes（CTCs） including PrQ（TCNQ） 2,MPM（TCNQ） 2,and MEM（TCNQ） 2,have been investigated by scanning tunneling microscopy（STM）.The three bulk-truncated surfaces are all ac-surface,which are terminated with TCNQ molecular arrays.On the ac-surface of PrQ（TCNQ） 2,the TCNQ molecules form a tetramer structure with a wavelike row behavior and a 纬 angle of about 18掳 between adjacent molecules.Moreover,the dimer structures are resolved on both ac-surfaces of MPM（TCNQ） 2 and MEM（TCNQ） 2.In addition,the tetramer structure is the most stable structure,while the dimer structures are unstable and easily subject to the STM tip disturbance,which results in changeable unit cells.The main reasons for the surface stabilization variation among the three ac-surfaces are provided by using the ＇蟺-atom model＇.

Effect of Molybdenum Doping on Oxygen Permeation Properties and Chemical Stability of SrCo0.8Fe0.2O3-δ

The phase composition, microstructure, thermal expansion coefficients, oxygen permeation properties and chemical stability of SrCo0.8Fe0.2O3-δ （SCFM） were investigated and compared with those of SrCo0.8Fe0.2O3-δ（SCF）. Single phase SCFM was successfully prepared by a combined EDTA-citric method. SCFM shows a lower thermal expansion coefficient （24× 10^-6-29× 10^-6/K） than SCF between 500 and 1050 ℃, indicating a more stable structure. SCFM shows a high oxygen permeation flux, although the oxygen flux of SCFM decreases slightly because of Mo dopant. Furthermore, it was demonstrated that the doping of Mo in SCF can prevent the order-disorder transition and improves the chemical stability to CO2.

短b轴ZSM-5分子筛制备方法及应用研究进展

ZSM-5分子筛作为应用最为广泛的催化剂之一,一直是研究关注的重点。由于其沿着b轴直通孔道相比于沿着a轴和c轴的Z形孔道具有更好的扩散性能,其长度的控制对改善分子筛的催化特性具有重要作用。综述了控制ZSM-5分子筛各向生长的主要方法,结构导向法和生长修饰法。对短b轴ZSM-5分子筛在MTP、MTH以及MTG等催化领域的应用进行了具体分析。并指出,特定季铵盐作为结构导向剂制备的片层分子筛,具有均匀良好的自柱撑结构和晶间介孔,由于结构导向剂制备难度较高,采用生长修饰剂部分取代季铵盐更加经济环保。特定生长修饰剂合成难度低且成本低廉,制备的分子筛具有分散或团聚片层结构,新工艺的开发以改善晶间介孔将使其具有更好的扩散性。对片层分子筛厚度和酸性的精准调控、合成机理以及各向长度对催化性能影响的深入研究,以保证高效制备兼顾转化率、选择性以及稳定性的分子筛对短b轴分子筛的发展具有重要意义。

Effect of varying normal stress on stability and dynamic motion of a spring-slider system with rate- and state-dependent friction

Incorporating rate and state friction laws, stability of linearly stable （i.e., with stiffness greater than the critical value） spring-slider systems subjected to triggering perturbations was analyzed under variable normal stress condition, and comparison was made between our results and that of fixed normal stress cases revealed in previous studies. For systems associated with the slip law, the critical mag- nitude of rate steps for triggering unstable slips are found to have a similar pattern to the fixed normal stress case, and the critical velocity steps scale with a/（b - a） when k = kcr for both cases. The rate-step boundaries for the variable normal stress cases are revealed to be lower than the fixed normal stress case by 7 %-16 % for a relatively large ct = 0.56 with （b - a）/a ranging from 0.25 to 1, indicating easier triggering under the variable normal stress condition with rate steps. The difference between fixed and variable normal stress cases decreases when the α value is smaller. In the same slip- law-type systems, critical displacements to trigger instability are revealed to be little affected by the variable normal stress condition. When k 〉 kcr（V,）, a spring-slider system with the slowness law is much more stable than with the slip law,suggesting that the slowness law fits experimental data better when a single state variable is adopted. In stick-slip motions, the variable normal stress case has larger stress drops than the constant normal stress case. The variable normal stress has little effect on the range of slip velocity in systems associated with the slowness law, whereas systems associated with the slip law have a slowest slip velocity immensely smaller than the fixed normal stress case, by ~ 10 orders of magnitude.

Effect of arginine on stability of GST-ZNF191(243-368)

For better understanding the chemical or biological information of ZNF191 （243-368）, we expressed the fusion protein of GST and ZNF191 （243-368）, and used it to obtain the binding DNA sequence of this zinc finger protein. But in the process of expression and purification, we found this fusion protein slowly degradated. For resolving this problem, we simultaneously added charged amino acids L-Arg and L-Glu to the solution of fusion protein, and demonstrated that this method can dramatically increase the stability of this fusion protein. This method can make the fusion protein suitable for the continuous works, especially for situations where high protein concentration and long-term stability without precipitate and degradation of protein are required.

Stabilization control of a bumblebee in hovering and forward flight

Our previous study shows that the hovering and forward flight of a bumblebee do not have inherent stability （passive stability）. But the bumblebees are observed to fly stably. Stabilization control must have been applied. In this study, we investigate the longitudinal stabilization control of the bumblebee. The method of computational fluid dynamics is used to compute the control derivatives and the techniques of eigenvalue and eigenvector analysis and modal decomposition are used for solving the equations of motion. Controllability analysis shows that at all flight speeds considered, although inherently unstable, the flight is controllable. By feedbacking the state variables, i.e. vertical and horizontal velocities, pitching rate and pitch angle （which can be measured by the sensory system of the insect）, to produce changes in stroke angle and angle of attack of the wings, the flight can be stabilized, explaining why the bumblebees can fly stably even if they are passively unstable.

Chemial Bond and Stability of Adsorption of [Au(AsS_3)]^(2-)on the Surface of Kaolinite

Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS 3)] 2- on the surface of kaolinite.The correlation among structure,chemical bond and stability was discussed.Several models were selected with [Au(AsS 3)] 2- in different directions and sites.The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au-O covalent bond,so these models are more stable than those with gold above or under the layer.The models with gold near to [AlO 2(OH) 4] octahedra are more stable than those with gold near to the vacancy without aluminium.These two stable tendencies in kaolinite-[Au(AsS 3)] 2- are stronger than that in kaolinite-Au systems.The interaction between [Au(AsS 3)] 2- and kaolinite is stronger than that between gold and kaolinite,and this interaction is strong enough to form the surface complexes.

SrCo_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ) perovskite stabilized by niobium for oxygen permeation

The effect of Nb doping on the oxygen permeation and stability of SrCo_(0.8)Fe_(0.2)O_(3-δ)(SCFO) was investigated comprehensively.Cubic perovskite phase was formed in SrCo_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ)(SCFNO).The SCFNO with a thickness of 1 mm had a high level of oxygen permeation flux of 1.4 ml.min^(-1).cm^(-2) at 850 ℃ under air/He gradient.The bulk diffusion is the rate-limiting step in overall oxygen permeation mechanism for SCFNO when the thickness is higher than 1.0 mm.The partial substitution of Nb for Co suppresses the transition of oxygen vacancies order/disorder proven by DSC measurement and enhances the phase stability under low oxygen partial pressure.During long-term tests under low oxygen pressure,the SCFNO exhibites structural stability and stable oxygen permeation.It is proved that substitution of Nb for Co is an effective way to improve the properties of SCFO.

Effect of butylphthalide soft capsule on the anti-inflammatory effect and plaque stability in patients with ischemic cerebrovascular disease and carotid atherosclerosis

Objective:To explore the effect of butylphthalide soft capsule on the serum hs-CRP, MMP-9, and TNF-α in patients with ischemic cerebrovascular disease in order to evaluate the the therapeutic effect in the treatment of carotid atherosclerosis.Methods:According to the carotid ultrasound results, the patients were divided into the stable plaque group (control group) and the vulnerable plaque group. The patients in the vulnerable plaque group were randomized into the intervention 1 group and intervention 2 group. The patients in the two subgroups were given bayaspirin and atorvastatin. On this basis, the patients in the intervention 1 group were given butylphthalide soft capsules. The serum hs-CRP, MMP-9, and TNF-αbefore treatment and 6 months after treatment in each group were detected. The color Doppler ultrasound was used to measure and evaluate IMT, Crouse score, and plaque echo change. Results: The serum hs-CRP, MMP-9, and TNF-α levels before treatment between the two subgroups were significantly higher than those in the control group, but the comparison between intervention 1 group and intervention 2 group was not statistically significant. The serum hs-CRP, MMP-9, and TNF-α levels 6 months after treatment in the two subgroups were significantly reduced when compared with before treatment. The serum hs-CRP, MMP-9, and TNF-α levels after treatment in the intervention 1 group were significantly lower than those in the intervention 2 group. IMT 6 months after treatment in the two subgroups was significantly reduced when compared with before treatment. The reduced degree of IMT after treatment in the intervention 1 group was significantly greater than that in the intervention 2 group. Crouse score after treatment in the two subgroups was significantly reduced when compared with before treatment, but the comparison between the two groups was not statistically significant. The unstable plaque number after treatment in the two subgroups was significantly reduced when compared with before treatment. The unstable plaque number after treatment in the intervention 1 group was significantly lower than that in the intervention 2 group.Conclusions:Butylphthalide soft capsule can resist the inflammation, reverse the prolieration of carotid intima, stabilize the vulnerable plaque, and remove the non-atherosclerotic plaque.

Effect of Perturbations in Coriolis and Centrifugal Forces on the Non-Linear Stability of <i>L</i>₄in the Photogravitational Restricted Three Body Problem

Effect of perturbations in Coriolis and centrifugal forces on the non-linear stability of the libration point L4 in the restricted three body problem is studied when both the primaries are axis symmetric bodies (triaxial rigid bodies) and the bigger primary is a source of radiation. Moser’s conditions are utilized in this study by employing the iterative scheme of Henrard for transforming the Hamiltonian to the Birkhoff’s normal form with the help of double D’Alembert’s series. It is found that L4 is stable for all mass ratios in the range of linear stability except for the three mass ratios μc1, μc2 and μc3, which depend upon the perturbations ε1 and ε1 in the Coriolis and centrifugal forces respectively and the parameters A1,A2,A3 and A4 which depend upon the semi-axes a1,b1,c1;a2,b2,c2 of the triaxial rigid bodies and p, the radiation parameter.

Effects of shear-thinning/thickening nature on the stability of Couette-like flow with uniform crossflow

The linear stability of wall-injected pressure- driven Couette-like flow in power-law fluids is studied. Previous study on this kind of flow for Newtonian fluids by Nicoud and Angilella [Phys. Rev. E 56, 3000 （1997）] was extended to power-law fluids to understand the effects of shear-thinning/thickening nature on the flow stability. A related expression between the critical crossflow Reynolds number for Newtonian fluids and that for power-law fluids is obtained as the streamwise Reynolds number is large enough based on numerical computations, and verified theoretically in the case of a limiting condition with the power-law index.

Morphological stability analysis of vesicles with mechanical-electrical coupling effects

Using a recently established liquid crystal model for vesicles, we present a theoretical method to analyze the morphological stability of liquid crystal vesicles in an electric field. The coupled mechanical-electrical effects associated with elastic bending, osmotic pressure, surface tension, Max- well pressure, as well as flexoelectric and dielectric proper- ties of the membrane are taken into account. The first and second variations of the free energy are derived in a com- pact form by virtue of the surface variational principle. The former leads to the shape equation of a vesicle embedded in an electric field, and the latter allows us to examine the stabil- ity of a given vesicle morphology. As an illustrative exam- ple, we analyze the stability of a spherical vesicle under a uniform electric field. This study is helpful for understanding and revealing the morphological evolution mechanisms of vesicles in electric fields and some associated phenomena of cells.

人冠状动脉内SDF-1/CXCR4轴表达水平与斑块稳定性的相关性

目的 探讨基质细胞衍生因子(SDF)-1/CXCR4轴在人冠状动脉斑块稳定及猝死中的作用及相关性,并寻找其可能参与的信号通路。方法 收集尸检案例的冠脉标本77例,其中非冠心病猝死但明确诊断为冠心病患者24例(CHD组),冠状动脉粥样硬化性心脏病猝死者25例(SCD组),以非冠心病猝死并无动脉粥样硬化者28例为对照组。运用苏木素-伊红(HE)染色检测血管内膜厚度、坏死核心厚度、纤维帽厚度、血管腔面积分数;利用免疫组织化学技术、Western印迹检测冠脉内膜SDF-1、CXCR4及核转录因子(NF)-κB p65蛋白的表达量,分析其表达与斑块结构与其稳定性的关系。结果 与对照组比较,病变各组内膜厚度增高、纤维帽变厚、血管狭窄程度显著增高(P<0.05);病灶内SDF-1、CXCR4蛋白表达水平与内膜厚度、坏死区厚度及血管腔面积分数呈显著正相关(P<0.05)。与对照组比较,病变各组CXCR4与NF-κB p65通路蛋白的表达量显著升高(P<0.05),并呈显著正相关关系(r=0.918,P<0.001)。结论 人冠状动脉粥样硬化病灶内SDF-1/CXCR4轴的表达升高可能通过调节NF-κB相关信号通路从而影响斑块结构稳定性。