基于Super-Twisting滑模S面的无人机路径跟踪控制

针对小型固定翼无人机在执行任务时跟踪精度低以及容易受外界风影响的问题,设计基于Super-Twisting滑模S面(STSM S-Plane)的路径跟踪控制器,同时采用内外双环控制模式。外环即速度环采用Super-Twisting滑模控制,内环即姿态环采用S面控制。考虑到S面控制求导易导致积分爆炸的问题引入了二阶微分器,并对外界风组成进行建模研究。最后通过空间特殊曲线来验证所设计算法的控制性能。仿真结果表明,所设计的算法可以实现固定翼无人机对期望路径的精确跟踪,并具有良好的鲁棒性和抗干扰性能。

基于改进型Super-twisting的双馈感应发电机直接功率控制

为提高双馈感应发电机(DFIG)直接功率控制的鲁棒性和抗干扰能力,提出一种改进型超螺旋滑模(STSMC)的直接功率控制(DPC)。首先,建立参数摄动下的DFIG最大功率捕获模型和定子磁场定向的双馈感应发电机模型;然后,将非奇异快速终端滑模面(NFTSM)与一种改进型超螺旋(Super-twisting)优化算法结合,设计DFIG直接功率控制器(IST-NFTSMC)。其中所设计的非奇异滑模面能有效避免传统滑模控制(SMC)的奇异现象,且改进超螺旋控制律能有效削弱NFTSMC抖振,提高功率控制精度;最后,通过仿真和实验,与PI控制和传统SMC控制相比,该控制能削弱DFIG功率与电流抖振问题,加快其收敛速度,提高DFIG直接功率控制稳态精度。

Twisted Yangian Y(sp_(2))的单权模

讨论了Twisted Yangian Y(sp_(N))的权模问题,构造了Y(sp_(2))的一类无限维单权模,分类了具有一个一维权空间的Y(sp_(2))单权模.

TFF3依赖TWIST1上调TRIB3促结直肠癌转移的机制

目的探讨TFF3基因过表达对结直肠癌HT29细胞增殖、迁移和侵袭能力的影响,以及与癌转移相关的机制。方法构建TFF3过表达的HT29细胞系,qRT-PCR和Western blot法检测TFF3、TWIST1/TRIB3信号通路及上皮间质转化过程中相关mRNA和蛋白的表达,CCK-8法检测HT29细胞增殖能力,细胞划痕实验和Transwell实验评估细胞迁移和侵袭能力,透射电子显微镜观察TFF3过表达前后细胞形态的变化。结果pIRES2-TFF3质粒转染HT29细胞后,相较于对照组,TFF3 mRNA和蛋白表达水平显著升高(P<0.01),细胞增殖、迁移和侵袭能力显著增强(P<0.01),且TWIST1、TRIB3、Vimentin、Snail的表达也显著上升,而E-cadherin的表达则明显下降(P<0.05)。TFF3过表达后的HT29细胞出现了多种变化,如细胞间连接减少、绒毛脱落、伪足形成,以及形态上梭形细胞增多等。结论TFF3过表达可能通过Twist1/TRIB3信号通路促进结直肠癌细胞的EMT过程,从而提高其转移潜力,加速癌症的恶性进展。

Twisted Yangian Y(sp^(2))的一类单权模

研究了Twisted Yangian Y(g_(N))的权模问题,构造了Y(sp^(2))的一类权空间维数均为2的无限维权模,给出了该权模不可约的充分条件.

Twist2表达与卵巢癌脉管浸润及预后的相关研究

目的:分析Twist2与卵巢癌患者的预后及脉管浸润之间的关系,探索Twist2在卵巢癌脉管浸润中的作用及机制。方法:利用KM plotter分析卵巢癌患者中Twist2 mRNA的表达与卵巢癌总生存率(OS)、无进展生存率(PFS)、肿瘤进展后生存率(PPS)的相关性。利用癌症基因组学数据库cBioportal分析卵巢癌患者中Twist2与脉管浸润的相关性。体外实验:采用Transwell检测Twist2对卵巢癌CAOV3细胞[空白组、阴性对照组(siNC组)、siTwist2组]侵袭、迁移能力的影响,并利用实时荧光定量多聚核苷酸链式反应(realtime-PCR)及蛋白免疫印迹(Western blot)检测分别从RNA水平及蛋白水平检测下调Twist2表达后CAOV3细胞中Twist2、血管内皮生长因子C(VEGFC)表达的变化。结果:①KM plotter在线数据分析结果示,Twist2高表达的卵巢癌患者与不良预后有关,OS(HR 1.24,95%CI 1.01~1.52)、PFS(HR 1.39,95%CI 1.14~1.70)及PPS(HR 1.37,95%CI 1.08~1.74)差异均有统计学意义(P<0.05);cBioportal分析示,Twist2 mRNA表达与卵巢癌血管浸润(r=0.93,P=0.001)及淋巴管浸润(r=0.89,P=0.009)均呈正相关。②体外实验Transwell检测示,与空白组和siNC组比较,siTwist2组卵巢癌细胞的侵袭及迁移能力显著下降(P<0.05)。Realtime-PCR及Western blot检测示,与空白组和siNC组比较,siTwist2组中Twist2 mRNA及蛋白、VEGFC mRNA及蛋白的表达均明显下降(P<0.05)。结论:卵巢癌中Twist2的表达与肿瘤预后及脉管浸润密切相关,下调Twist2后,细胞迁移及侵袭穿透的细胞数明显减少、VEGFC表达降低,Twist2可能通过VEGFC来诱导肿瘤细胞侵袭转移参与肿瘤脉管浸润,Twist2可能是未来卵巢癌评估预后及靶向治疗的指标之一。

TWIST1通过激活自噬促进肺动脉高压大鼠模型肺血管重塑作用及机制的实验研究

目的探讨Twist相关蛋白1(Twist-related protein 1,TWIST1)对野百合碱(Monocrotaline,MCT)诱导的肺动脉高压(pulmonary arterial hypertension,PAH)大鼠肺血管重塑的影响及机制。方法将50只健康雄性SD大鼠,随机分为5组,即对照组、模型组、二甲基亚砜(Dimethyl sulfoxide,DMSO)溶剂处理的模型组、TWIST1抑制剂Harmine组、自噬抑制剂羟氯喹组。检测右心室收缩压(RVSP),右心室肥厚指数(RVHI)和内膜厚度百分比(MT%)以评估大鼠PAH的发展。采用免疫印迹法检测TWIST1,自噬相关蛋白LC3B以及RND3的蛋白质水平。结果与对照组比较,MCT诱导的PAH大鼠中TWIST1和LC3B表达增加,分别为对照组的2.32±0.22倍和0.87±0.19倍,差异具有统计学意义(t=15.812,11.227,均P<0.001);同时RND3表达下调,为对照组的0.32±0.07倍,差异具有统计学意义(t=-13.003,P<0.001)。给与TWIST1抑制剂Harmine或自噬抑制剂羟氯喹可显著抑制MCT诱导的自噬激活和RND3表达下调,同时降低了MCT诱导的PAH大鼠的RVSP,RVHI和MT%,差异具有统计学意义(t=-24.277~16.636,均P<0.001)。结论TWIST1通过诱导自噬激活促进肺血管重塑,促进PAH的发生发展。

Visualizing the Local Twist Angle Variation within and between Domains of Twisted Bilayer Graphene

Moirésuperlattices in twisted two-dimensional materials have emerged as ideal platforms for engineering quantum phenomena,which are highly sensitive to twist angles,including both the global value and the spatial inhomogeneity.However,only a few methods provide spatial-resolved information for characterizing local twist angle distribution.

Semi-quantitative analysis of the structural evolution of mesophase pitch-based carbon foams by Raman and FTIR spectroscopy

Graphitized carbon foams(GFms)were prepared using mesophase pitch(MP)as a raw material by foaming(450℃),pre-oxidation(320℃),carbonization(1000℃)and graphitization(2800℃).The differences in structure and properties of GFms prepared from different MP precursors pretreated by ball milling or liquid phase extraction were investigated and compared,and semi-quantitative calculations were conducted on the Raman and FTIR spectra of samples at each preparation stage.Semi-quantitat-ive spectroscopic analysis provided detailed information on the structure and chemical composition changes of the MP and GFm de-rived from it.Combined with microscopic observations,the change from precursor to GFm was analyzed.The results showed that ball milling concentrated the distribution of aromatic molecules in the pitch,which contributed to uniform foaming to give a GFm with a uniform pore distribution and good properties.Liquid phase extraction helped remove light components while retaining large aromatics to form graphitic planes with the largest average size during post-treatment to produce a GFm with the highest degree of graphitization and the fewest open pores,giving the best compression resistance(2.47 MPa),the highest thermal conductivity(64.47 W/(m·K))and the lowest electrical resistance(13.02μΩ·m).Characterization combining semi-quantitative spectroscopic ana-lysis with microscopic observations allowed us to control the preparation of the MP-derived GFms.

Preparation of a high-performance synthetic pitch from aromatic hydrocarbons containing N/Cl

The preparation of a synthetic pitch from aromatic monomers could easily regulate structure orientation at the molecu-lar level,which would be useful in fabrication.An isotropic synthetic pitch was prepared by a chlorine-and/or nitrogen-induced sub-stitution polymerization reaction method using aromatic hydrocarbon precursors containing Cl and N,which for this study were chloromethyl naphthalene and quinoline.This method was verified by investigating the structural changes under different synthesis conditions,and the synthesis mechanism induced by aromatics containing Cl was also probed.The result shows that the pyridinic N in quinoline contains a lone pair of electrons,and is an effective active site to induce the polymerization reaction by coupling with aromatic hydrocarbons containing Cl.The reaction between such free radicals causes strong homopolymerization and oligomeriza-tion.A higher reaction temperature and longer reaction time significantly increased the degree of polymerization and thus increased the softening point of the pitch.A linear molecular structure was formed by the Cl substitution reaction,which produced a highly spinnable pitch with a softening point of 258.6℃,and carbon fibers with a tensile strength of 1163.82 MPa were obtained.This study provides a relatively simple and safe method for the preparation of high-quality spinnable pitch.

Retraction:miR-203 suppresses bladder cancer cell growth and targets twist1

Following the publication,concerns have been raised about a number of figures in this article.An unexpected area of similarity was identified in terms of the cellular data,where the results from differently performed experiments were intended to have been shown,although the areas immediately surrounding this area featured comparatively different distributions of cells.In addition,the western blots in this article were presented with atypical,unusually shaped and possibly anomalous protein bands in many cases.

A review of the catalytic preparation of mesophase pitch

Because of its high purity and excellent orientation, mesophase pitch is a superior precursor for high-performance car-bon materials. However, the preparation of top-notch mesophase pitch faces challenges. Catalytic polycondensation at low temperat-ures is more favorable for synthesizing mesophase pitch, because it circumvents the high-temperature free radical reaction of other thermal polycondensation approaches. The reaction is gentle and can be easily controlled. It has the potential to significantly im-prove the yield of mesophase pitch and easily introduce naphthenic characteristics into the molecules, catalytic polycondensation is therefore a preferred method of synthesizing highly spinnable mesophase pitch. This review provides a synopsis of the selective pre-treatment of the raw materials to prepare different mesophase pitches, and explains the reaction mechanism and associated research advances for different catalytic systems in recent years. Finally, how to manufacture high-quality mesophase pitch by using a cata-lyst-promoter system is summarized and proposed, which may provide a theoretical basis for the future design of high-quality pitch molecules.

Valley-dependent transport in a mescoscopic twisted bilayer graphene device

We study the valley-dependent electron transport in a four-terminal mesoscopic device of the two monolayer graphene nanoribbons vertically stacked together, where the intersection forms a bilayer graphene lattice with a controllable twist angle. Using a tight-binding lattice model, we show that the longitudinal and transverse conductances exhibit significant valley polarization in the low energy regime for small twist angles. As the twist angle increases, the valley polarization shifts to the high energy regime. This arises from the regrouping effect of the electron band in the twisted bilayer graphene region. But for relatively large twist angles, no significant valley polarization is observed. These results are consistent with the spectral densities of the twisted bilayer graphene.

Twisted Integration of Complex Oxide Magnetoelectric Heterostructures via Water‑Etching and Transfer Process

Manipulating strain mode and degree that can be applied to epitaxial complex oxide thin films have been a cornerstone of strain engineering.In recent years,lift-off and transfer technology of the epitaxial oxide thin films have been developed that enabled the integration of heterostructures without the limitation of material types and crystal orientations.Moreover,twisted integration would provide a more interesting strategy in artificial magnetoelectric heterostructures.A specific twist angle between the ferroelectric and ferromagnetic oxide layers corresponds to the distinct strain regulation modes in the magnetoelectric coupling process,which could provide some insight in to the physical phenomena.In this work,the La_(0.67)Sr_(0.33)MnO_(3)(001)/0.7Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.3PbTiO_(3)(011)(LSMO/PMN-PT)heterostructures with 45.and 0.twist angles were assembled via water-etching and transfer process.The transferred LSMO films exhibit a fourfold magnetic anisotropy with easy axis along LSMO<110>.A coexistence of uniaxial and fourfold magnetic anisotropy with LSMO[110]easy axis is observed for the 45°Sample by applying a 7.2 kV cm^(−1)electrical field,significantly different from a uniaxial anisotropy with LSMO[100]easy axis for the 0°Sample.The fitting of the ferromagnetic resonance field reveals that the strain coupling generated by the 45°twist angle causes different lattice distortion of LSMO,thereby enhancing both the fourfold and uniaxial anisotropy.This work confirms the twisting degrees of freedom for magnetoelectric coupling and opens opportunities for fabricating artificial magnetoelectric heterostructures.

Investigating the occurrence and predictability of pitch angle scattering events at ADITYA-Upgrade tokamak with the electron cyclotron emission radiometer

This paper describes the experimental analysis and preliminary investigation of the predictability of pitch angle scattering(PAS) events through the electron cyclotron emission(ECE)radiometer signals at the ADITYA-Upgrade(ADITYA-U) tokamak. For low-density discharges at ADITYA-U, a sudden abnormal rise is observed in the ECE signature while other plasma parameters are unchanged. Investigations are done to understand this abrupt rise that is expected to occur due to PAS. The rise time is as fast as 100 μs with a single step and/or multiple step rise in ECE radiometer measurements. This event is known to limit the on-axis energy of runaway electrons. Being a repetitive event, the conditions of its repetitive occurrence can be investigated, thereby exploring the possibility of it being triggered and surveyed as an alternate runaway electron mitigation plan. Functional parameterization of such events with other discharge parameters is obtained and the possibility to trigger these events is discussed.PREDICT code is used to investigate the possible interpretations for the PAS occurrence through modeling and supporting the ECE observations. The trigger values so obtained experimentally are set as input criteria for PAS occurrence. Preliminary modeling investigations provide reliable consistency with the findings.

On the effect of pitch and yaw angles in oblique impacts of smallcaliber projectiles

A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.

Effect of Rigid Pitch Motion on Flexible Vibration Characteristics of a Wind Turbine Blade

Adynamic pitch strategy is usually adopted to improve the aerodynamic performance of the blade of awind turbine.The dynamic pitch motion will affect the linear vibration characteristics of the blade.However,these influences have not been studied in previous research.In this paper,the influences of the rigid pitch motion on the linear vibration characteristics of a wind turbine blade are studied.The blade is described as a rotating cantilever beam with an inherent coupled rigid-flexible vibration,where the rigid pitch motion introduces a parametrically excited vibration to the beam.Partial differential equations governing the nonlinear coupled pitch-bend vibration are proposed using the generalized Hamiltonian principle.Natural vibration characteristics of the inherent coupled rigid-flexible system are analyzed based on the combination of the assumed modes method and the multi-scales method.Effects of static pitch angle,rotating speed,and characteristics of harmonic pitch motion on flexible natural frequencies andmode shapes are discussed.It shows that the pitch amplitude has a dramatic influence on the natural frequencies of the blade,while the effects of pitch frequency and pith phase on natural frequencies are little.

Wafer-scale 30°twisted bilayer graphene epitaxially grown on Cu_(0.75)Ni_(0.25)(111)

Twisted bilayer graphene(TBG) has been extensively studied because of its novel physical properties and potential application in electronic devices.Here we report the synthesis and characterization of 300 TBG naturally grown on Cu_(0.75)Ni_(0.25)(111) film and investigate the electronic structure by angle-resolved photoemission spectroscopy.Compared with other substrates,our TBG with a wafer scale is acquired with a shorter growth time.The Fermi velocity and energy gap of Dirac cones of TBG are comparable with those of a monolayer on Cu_(0.85)Ni_(0.15)(111).The signature of moré lattices has not been observed in either the low-energy electron diffraction patterns or the Fermi surface map within experimental resolution,possibly due to different Cu and Ni contents in the substrates enhancing the different couplings between the substrate and the first/second layers and hindering the formation of a quasiperiodic structure.

Tubular Heat Enhancement Using Twisted Tape Inserts with Large Holes

Heat augmentation techniques play a vital role in the heating and cooling processes in industries,including solar collectors and many applications that utilize heat exchangers.Several studies are based on inserting fillers inside the tubes to enhance heat transfer.This investigation considered the effects of twisted tapes with large holes on a tubular heat exchanger’s(HX)heat transmission,pressure drop,and thermal boosting factor.In the experimental section,counter-swirl flow generators used twisted tapes with pairs of 1.0 cm-diameter holes and changes in porosity(Rp)at 1.30%and 2.70%.In the experiments,air was utilized as a working fluid in a tube with a circular cross-section.The turbulent flow was considered,with Reynolds numbers(Re)domain from 4800 to 9500,and a boundary condition with a uniform wall heat flux was constructed.The findings expound that when the number of holes rose,the Nusselt number(Nu),the factor of friction(f),and the thermal enhancement factor(η)all increased as well.Additionally,as the friction factor increased,the Nusselt number of the tape-equipped tube was noticeably higher.Additionally,it was discovered that the friction factor was between 70%and 94%lower than the values of the tube without tape,while the(Nu)was between 87%and 97%higher than the conventional tube values.The maximum value ofηis 89%.According to the experimental results,empirical correlations for Nu,f,andηwere also generated.

基于改进Super-Twisting算法和电流预测的PMSM调速控制

针对永磁同步电机传统PI控制器存在响应速度慢、控制精度低、鲁棒性差等问题,该文提出一种改进调速控制方案。首先,将全局快速积分型终端滑模理论与广义Super-Twisting算法相结合,基于Anti-Windup原理设计改进广义Super-Twisting积分终端滑模速度控制器,并采用新型分段指数函数优化控制律;其次,设计改进扩展扰动观测器对系统未知扰动进行前馈补偿;最后,在电流环引入无差拍电流预测控制器,进一步改善系统的动态响应。仿真结果表明,所提出的改进控制方案能够有效提高调速系统的动态控制性能、控制精度和鲁棒性。