拉伸螺杆半椭圆表面裂纹应力强度因子

将拉伸螺杆简化为理论应力集中系数Kt不同的带“V”形缺口圆杆,采用裂纹尖端为20节点奇异单元的三维有限元模型,对螺杆半椭圆表面裂纹的应力强度因子进行了计算.给出了具有普遍性意义的螺杆表面裂纹应力强度因子公式.为验证本文计算结果的有效性,还将本文M22×1.5螺杆的应力强度因子计算结果与试验结果进行了对比.     

Geometric and mechanical characterization of ribbed FRP rebars

The paper discusses the advantage of fiber-reinforced polymer (FRP) rebar for application in concrete because of its light weight, high strength, high corrosion resistance and durability. Different options of shaping the wave-like texture of FRP bars for concrete bonding are considered. The diameter measurement problem of ribbed FRP bars is examined, and a proprietary procedure is suggested to determine the equivalent diameter and elastic modulus of ribbed FRP bars. The tensile strength (889–1197 MPa) obtained herein is greater than the longitudinal flexural strength (566–822 MPa), which is due to the ribs, contrary to the case of plain bars. The elastic modulus values obtained (40–61 GPa) are in agreement with the known literature data.     

Application of Bar Adsorptive Microextraction for the Determination of Levels of Tricyclic Antidepressants in Urine Samples

This work entailed the development, optimization, validation, and application of a novel analytical approach, using the bar adsorptive microextraction technique (BAμE), for the determination of the six most common tricyclic antidepressants (TCAs; amitriptyline, mianserin, trimipramine, imipramine, mirtazapine and dosulepin) in urine matrices. To achieve this goal, we employed, for the first time, new generation microextraction devices coated with convenient sorbent phases, polymers and novel activated carbons prepared from biomaterial waste, in combination with large-volume-injection gas chromatography-mass spectrometry operating in selected-ion monitoring mode (LVI-GC-MS(SIM)). Preliminary assays on sorbent coatings, showed that the polymeric phases present a much more effective performance, as the tested biosorbents exhibited low efficiency for application in microextraction techniques. By using BAμE coated with C₁₈ polymer, under optimized experimental conditions, the detection limits achieved for the six TCAs ranged from 0.2 to 1.6 μg L⁻¹ and, weighted linear regressions resulted in remarkable linearity (r² > 0.9960) between 10.0 and 1000.0 μg L⁻¹. The developed analytical methodology (BAμE(C18)/LVI-GC-MS(SIM)) provided suitable matrix effects (90.2–112.9%, RSD ≤ 13.9%), high recovery yields (92.3–111.5%, RSD ≤ 12.3%) and a remarkable overall process efficiency (ranging from 84.9% to 124.3%, RSD ≤ 13.9%). The developed and validated methodology was successfully applied for screening the six TCAs in real urine matrices. The proposed analytical methodology proved to be an eco-user-friendly approach to monitor trace levels of TCAs in complex urine matrices and an outstanding analytical alternative in comparison with other microextraction-based techniques.     

Development and Analysis of the Novel Hybridization of a Single-Flash Geothermal Power Plant with Biomass Driven sCO2-Steam Rankine Combined Cycle

This study investigates the hybridization scenario of a single-flash geothermal power plant with a biomass-driven sCO₂-steam Rankine combined cycle, where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EBSILON^®Professional. A topping sCO₂ cycle is chosen due to its potential for flexible electricity generation. A synergy between the topping sCO₂ and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger, where the waste heat from the topping cycle is utilized in the bottoming cycle. The high-temperature heat addition problem, common in sCO₂ cycles, is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and a biomass-to-electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found to be 2.2 kg/s.     

地表下沉力学模型的建立及应用

针对采动覆岩移动的规律，由弯曲下沉带的挠曲特性，应用薄板挠曲理论，建立地表下沉的最大值力学模型，预测覆岩离层未注浆和注浆条件下地表的下沉值。     

Saint-Venant Torsion of a Two-Phase Circumferentially Symmetric Compound Bar

This work is concerned with the Saint-Venant torsion problem of a two-phase circumferentially symmetric compound prismatic bar. By generalizing a method originally proposed by Packham and Shail [12], we demonstrate that for a particular two-phase configuration, simply or multiply connected, which is invariant with phase interchange, the solutions can be constructed from solutions of two analogous problems with constant material properties. An effective shear modulus is derived in analytic form, which is approximately the harmonic mean of the component shear moduli. We also show that the effective torsional shear modulus is homogeneous for arbitrary configurations. This revised version was published online in August 2006 with corrections to the Cover Date.     

基于CCD的三峡升船机船厢行程检测研究

提出了一种适合三峡升船机船厢行程测量的光学测试系统和方法。该系统采用特制的条形码与线阵CCD的像元对应的测量方法作为系统的总体测量方案，对系统的检测原理、光学系统以及数据处理进行了研究，对物距变化的修正与补偿部分，提出了几种有效和可行的方法，并对实验结果进行了误差分析，全程精度可达5mm以内，研制的系统解决了升船机大行...     

Flexible white top-emitting organic light-emitting diode with a MoO_x roughness improvement layer

In this paper, an MoOx film is deposited on a polyethylene terephthalate （PET） substrate as a buffer layer to improve the surface roughness of the flexible PET substrate. With an optimized MoOx thickness of 100 nm, the surface roughness of the PET substrate can be reduced to a very small value of 0.273 nm （much less than 0.585 nm of the pure PET）. Flexible white top-emitting organic light-emitting diodes （TEOLEDs） with red and blue dual phosphorescent emitting layers are constructed based on a low-reflectivity Sm/Ag semi-transparent cathode. The flexible white emission exhibits the best luminance and current injection characteristics with the 100-nm-thick MoOx buffer layer and this result indicates that a smooth substrate is beneficial to the enhancement of device electrical and electroluminescence performances. However, the white TEOLED with a 50-nm-thick MoOx buffer layer exhibits a maximum current efficiency of 4.64 cd/A and a power efficiency of 1.9 lm/W, slightly higher than those with a 100-nm MoOx buffer layer, which is mainly due to an obvious intensity enhancement but limited current increases in 50-nm MoOx-based white TEOLED. The change amplitudes of the Commission International de l’Eclairage （CIE） chromaticity coordinates are less than （0.016, 0.005） for all devices in a wide luminance range over 100 cd/m2, indicating an excellent color stability in our white flexible TEOLEDs. Additionally, the flexible white TEOLED with an MoOx buffer layer shows excellent flexibility to withstand more than 500 bending times under a curvature radius of approximately 9 mm. Research demonstrates that it is mainly attributed to the high surface energy of the MoOx buffer layer, which is conducible to the improvement of the surface adhesion to the PET substrate and the Ag anode.     

应变率对光圆钢筋与混凝土“粘结-滑移”行为影响的实验研究

为研究应变率对钢筋与混凝土界面粘结性能的影响,利用高速拉伸试验机进行了光圆钢筋的动态拔出实验。通过合理设计加载夹具和测试方法,得到不同应变率下光圆钢筋的“粘结-滑移”全程曲线。实验结果表明:随着应变率的增大,钢筋-混凝土界面的粘结强度显著提高,且界面失效形式由拔出失效为主转变为混凝土试件的破裂破坏为主;粘结强度的动态增强因子(fDIF)随应变率的增长斜率明显可以分为低应变率和高应变率两个区段。低应变率下,fDIF 增长较为缓慢;而高应变率下,fDIF快速增长;转变应变率约为33 s^-1。     

Experiments on transonic limit-cycle-flutter of a flexible swept wing

The aeroelastic behavior of wing models is nonlinear particularly in the transonic speed range. The interaction between aerodynamic and structural forces can lead to the occurrence of Limit-Cycle Oscillations (LCOs). If in addition the wing model is flexible and backward swept, the kinematic coupling between bending and torsion makes the situation even more complex.In the research project “Aerostabil” such a wing was investigated, which was equipped with pressure transducers in three sections and accelerometers. The experiments were performed in the adaptive test section of the transonic wind tunnel TWG in Göttingen. Already Dietz et al. (2003) have reported about experimental details and preliminary results. Based on these data Bendiksen (2008) studied numerically LCO-flutter behavior using a very similar, theoretical model (G-wing) and Stickan et al. (2014) used the original data as a LCO flutter test case. The influence of flexibility on the steady aerodynamics of the wing was described in Schewe & Mai (2018). In this paper now the flutter experiments with the same flexible model were analyzed systematically in the transonic range 0.84 <Ma <0.89 and for six angles of attack from 1.46°to 2.7°. Maps of stability, LCO amplitudes and instantaneous pressure distributions are presented. It was found that unstable regions are islands, whose extent depends on the angle of attack. A LCO test case, already treated in the literature is examined in more detail. The analysis of the time functions showed that during LCO-flutter the motion induced aerodynamic sectional lift forces particularly in the outer wing are asymmetric and thus acting as amplitude limiter. The reason for the asymmetry lies in the shock/boundary layer interaction. The test case, containing the stages of built-up and the transition to the limit cycle provides an excellent opportunity for improving our knowledge about LCOs and for code validation purposes.