为了研究不同配筋率对混凝土徐变性能的影响,本文对素混凝土、8 mm钢筋混凝土和10 mm钢筋混凝土进行了为期350 d的压缩徐变试验。将非线性黏性元件与经典Burgers模型串联,得到了修正Burgers模型。利用不同配筋率混凝土的徐变试验数据,对CEB-FIB(MC90)模型和修正Burgers模型进行拟合计算,从而得到了混凝土徐变拟合曲线。研究结果表明: 钢筋能够有效地抑制混凝土的徐变,并且随着配筋率的增加,抑制效果进一步增强; 与CEB-FIP(MC90)模型相比,修正Burgers模型的拟合结果更加准确,能更好地预测钢筋混凝土的徐变。修正Burgers模型 徐变 钢筋混凝土 钢筋约束 CEB-FIP模型 Levenberg-Marquardt优化算法 modified Burgers model creep reinforced concrete reinforcing steel CEB-FIP model Levenberg-Marquardt optimization algorithm
为了合理地设计和利用再生混凝土,在再生混凝土均匀化过程中,综合考虑原生骨料界面处较大的孔隙率、砂浆处的孔洞和微裂缝,以及骨料界面效应,同时结合扭转变形原理、Mori-Tanaka方法、微分法和Christensen三相模型,建立了一套可预测骨料界面效应下含初始缺陷再生混凝土弹性模量的模型。计算结果表明,当再生骨料取代率由0%增加到100%(质量分数)时,再生混凝土的弹性模量会降低24.4%,新水泥砂浆和原生骨料弹性模量的下降会导致再生混凝土的弹性模量出现不同程度的降低,预测模型能较好地预测界面效应下含初始缺陷再生混凝土弹性模量,并实现参数化分析。初始缺陷 界面效应 再生混凝土 弹性模量 均匀化方法 三相模型 initial defect interface effect recycled aggregate concrete elastic modulus homogenization method three-phase model
Micro-nano optomechanical accelerometers are widely used in automobile, aerospace, and other industrial applications. Here, we fabricate mechanical sensing components based on an electrically pumped GaN light-emitting diode (LED) with a beam structure. The relationship between the blueshift of the electroluminescence (EL) spectra and the deformation of the GaN beam structure based on the quantum-confined Stark effect (QCSE) of the InGaN quantum well (QW) structure is studied by introducing an extra mass block. Under the equivalent acceleration condition, in addition to the elastic deformation of GaN-LED, a direct relationship exists between the LED’s spectral shift and the acceleration’s magnitude. The extra mass block (gravitational force: ) induced blueshift of the EL spectra is obtained and shows driven current dependency. A polymer sphere (PS; gravitational force: ) is placed at the center of the beam GaN-LED, and a blueshift of 0.061 nm is observed in the EL spectrum under the injection current of 0.5 mA. The maximum sensitivity of the acceleration is measured to be , and the maximum measurable acceleration is calculated to be . It indicates the simultaneous realization of high sensitivity and a broad acceleration measurement range. This work is significant for several applications, including light force measurement and inertial navigation systems with high integration ability.
2023, 11(9): 1583
To date, fluorescence imaging systems have all relied on at least one beam splitter (BS) to ensure the separation of excitation light and fluorescence. Here, we reported multi-layer long pass filter integrated GaN LED. It is considered as the potential source for imaging systems. Experimental results indicate that the GaN LED shows blue emission peaked at 470.3 nm and can be used to excite dye materials. Integrating with a long pass filter (550 nm), the light source can be used to establish a real-time fluorescence detection for dyes that emit light above 550 nm. More interestingly, with this source, a real-time imaging system with signature words written with the dyes, such as ‘N J U P T’, can be converted into CCD images. This work may lead to a new strategy for integrating light sources and BS mirrors to build mini and smart fluorescence imaging systems.GaN LED self-filtering illumination source fluorescence imaging
Chinese Optics Letters
2023, 21(1): 011101
Negative refraction might occur at the interface between a two-dimensional photonic crystal (PhC) slab and a homogeneous medium, where the guiding of the electromagnetic wave along the third dimension is governed by total internal reflection. Herein, we report on the observation of negative refraction in the PhC slab where the vertical guiding is enabled by a bound state in the continuum and essentially beyond the light cone. Such abnormal refraction and guiding mechanism are based on the synchronous crafting of spatial dispersion and the radiative lifetime of Bloch modes within the radiative continuum. Microwave experiments are provided to further validate the numerical proposal in an all-dielectric PhC platform. It is envisioned that the negative refraction observed beyond the light cone might facilitate the development of optical devices in integrated optics, such as couplers, multiplexers, and demultiplexers.
2021, 9(8): 08001592
Microlasers based on high quality (Q) whispering-gallery mode (WGM) resonance are promising low threshold laser sources for bio-sensing and imaging applications. In this Letter, dye-doped polymer microspheres were fabricated by a controlling emulsion solvent evaporation method. WGM lasing with low threshold and high Q factors was realized in an individual microsphere under femtosecond laser pumping. The slight change of environmental relative humidity (RH) can be monitored by measuring the shift of the lasing modes at the exposure of water molecules, which demonstrates the sensitivity is as high as 6 pm/RH%. The results would offer an insight into employing microlasers as sensors.140.2020 Diode lasers 160.2540 Fluorescent and luminescent materials
Chinese Optics Letters
2018, 16(8): 081401