Crystallization and thermal expansion behavior of lithium zinc silicate sealing glass

Effect of heat treatment schedule on the crystallization and thermal expansion behavior of a lithium zinc silicate glass system was investigated by differential scanning calorimeter (DSC), X-ray diffraction, and linear thermal expansion test. Two well-defined crystallization exothermic peaks were observed from the DSC trace. According to the apparent activation energies and avrami parameter values calculated from the two crystallization exothermal peaks, the first crystallization exothermal peak was attributed to a combining surface and internal crystallization behavior, while the second one was found to be internal crystallization. Additionally, the phase evolution and the thermal expansion behavior with increasing heat treatment temperature were found to be closely related. Interestingly, it was found in comparison with previous reports that addition of CaO varies the phase composition of the resulting glass–ceramic in an opposite way to K₂O and the deep rooted reason has been discussed which may cast light on the modulation of properties of glass–ceramic involved crystalline phase of quartz or cristobalite. At last, average thermal expansion coefficient of 7.99–15.38×10⁻⁶ K⁻¹ in the temperature range of 25–400 °C has been obtained with different heat treatment schedules.     

Performance optimization of integrated resilience engineering and lean production principles

This paper conducts performance assessment from integrated resilience engineering (IRE) and lean production points of view. This is the first study that evaluates the impact of integrated resilience engineering (IRE) on lean production principles. Second, this study considers integrated impact of lean production by a unique intelligent algorithm. The proposed algorithm is composed of radial basis function (RBF), multi-layer perceptron (MLP) and adaptive neuro-fuzzy inference system (ANFIS). Moreover, the algorithm is capable of handling both crisp and fuzzy data due to the existence of intelligent approach. The proposed algorithm is equipped with verification and validation mechanism through conventional regression, statistical methods and data envelopment analysis. To demonstrate the applicability of the study, a real-world pipe manufacturer is considered as our case study. The results showed that “pull system” and “fault tolerant” among lean and IRE factors, respectively have been implemented inappropriately, while other factors are either suitably executed or ineffective.     

Crystal growth of LiF/LiYF4 eutectic crystals and their luminescent properties

Undoped and 0.5 mol% Ce-doped LiF–LiYF₄ eutectic crystals were grown by the micro-pulling-down method at different growth rates. The SEM images of all the eutectic crystals showed LiF with rod-like structure in the LiYF₄ matrix. The diameter of the rod phase systematically decreased with the increase of the growth rate. The radioluminescence spectra of cerium doped crystal under alpha-ray excitation showed emission peak at 325 nm related to Ce³⁺ 5d-4f transition. The white part in the cathodoluminescence image is considered to be due to Ce³⁺ ion in LiYF₄ phase, according to the scanning electron microscopy (SEM) image in the same region.     

Atomic layer deposition of platinum thin films on anodic aluminium oxide templates as surface-enhanced Raman scattering substrates

Platinum thin films are deposited on anodic aluminium oxide (AAO) templates by atomic layer deposition (ALD). The highly ordered island-like platinum nanostructures formed on the AAO template produce a high Raman scattering signal because of the periodical hexagonal arrangement. As an illustration, dramatic enhancement is achieved using Rhodamine 6G (R6G) as a molecular probe.Field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) show that the gap between the island-like structures is below 10 nm. Owing to activation by the incident laser beam, the localized electromagnetic field on the platinum island surface can be dramatically enhanced by the sub-10 nm regime subsequently amplifying the Raman signal. Finite-difference time-domain (FDTD) calculation matches the experimental phenomena suggesting that the excellent surface-enhanced Raman scattering (SERS) characteristics of the platinum structure arise from the high density and abundance of hot spots. Because the platinum film is inert in air, the SERS enhancing substrate can be used reliably in many trace chemical and biological detection applications.     

Microstructure and texture evolution in fully pearlitic steel during wire drawing

The evolution of morphology of pearlite and crystallographic texture of ferrite matrix in fully pearlitic steels during wire drawing were quantitatively investigated.The study revealed that a fiber structure of the pearlite morphology and a <110> fiber texture of the ferrite matrix begin to take shape and develop gradually with increasing strain.The growth rates of the fiber structure and the <110> texture are different in different regions within the wires with increasing drawing strain.There is a close relationship between the pearlite morphology and the crystalline texture during wire drawing.The pearlite interlamellar spacing(ILS) and thickness of cementite lamellae(T) decrease gradually both in longitudinal and transverse sections.The definition of pearlite colony should be reconsidered for describing microstructure of the wire drawing deformed pearlitic steels.     

Fire retardant evaluation of carbon nanofiber/graphite nanoplatelets nanopaper-based coating under different heat fluxes

Three types of carbon nanofiber based nanopapers, namely, 1Clay/5CNF/9APP, 1xGnP/5CNF/9APP, and 3xGnP/1CNF/9APP were made and their flame retardant efficiency was compared with thermogravimetric analysis and cone calorimeter test with 50 kW/m² of heat flux. The nanopaper of 3xGnP/1CNF/9APP was selected for experimental study because of its relatively good bonding with underlying structure and flame resistance performance. The fire response of glass fiber reinforced polyester composites with and without the selected nanopaper coating was thoroughly examined with cone calorimeter test using varied heat fluxes. It was found that at higher heat flux, the nanopaper demonstrated better flame retardant efficiency. Specifically, at 100 kW/m² of heat flux, the 1st and 2nd PHRR of the nanopaper-coated sample were more than 32% and 47% lower than the PHRR of control sample, respectively. In order to gain an insight into the pyrolysis process and flame retardation mechanism, the temperature profiles at the middle and back of the samples subjected to different heat fluxes were recorded. At 100 kW/m² of heat flux, the final temperature within the nanopaper-coated sample was roughly 280 ^oC, which is lower than control sample. The degradation rates in flexural moduli of the samples with coupon shape were determined using three-point bending. The three-point bending test results showed when the sample was exposed to 25 kW/m² heat flux for 240 seconds, the flexural modulus of control sample almost reduced to zero, whereas the nanopaper-coated sample still retained a half of its original flexural modulus. Finally, flame retardation mechanism was proposed for the nanopaper-coated composites.     

冲击荷载作用下含水泥质粉砂岩的损伤规律研究

采用分离式霍普金森压杆(SHPB)试验装置,对泥质粉砂岩进行了不同含水状态下的动态力学性能试验,分析了含水率变化对泥质粉砂岩动力特性的影响,并基于连续损伤理论及统计强度理论建立了泥质粉砂岩的动态损伤力学模型,得到了相应的损伤演化规律。研究结果表明,采用基于Weibull分布建立的动态时效损伤模型,其理论拟合曲线与实测曲线具有较好的一致性,损伤参数F0与弹性模量及冲击速度有一定的相关性,弹性模量越大,损伤参数F0也越大,含水率的变化对岩石动力特性具有较大的影响。     

线性调频信号低旁瓣脉压窗函数的优化设计

由于线性调频(LFM)信号的幅度谱不是标准的矩形形状,常用的窗函数有时无法将脉压旁瓣降得足够低,因此提出了LFM 信号低旁瓣脉压窗函数的优化设计方法。首先,将频域窗函数的求解表示为一个最优化问题,即在保证设计窗函数下的脉压主瓣与期望主瓣的差别小于给定值的条件下,使设计窗函数下的脉压旁瓣尽可能低;然后,将问题表示为标准二阶锥规划形式并求解。仿真实例表明,设计窗的脉压旁瓣显著低于海明窗的脉压旁瓣,设计窗脉压主瓣的无约束部分有所展宽,两个窗函数下脉压信噪比相同。     

Tm,Ho声光调Q激光系统理论与实验研究

利用激光速率方程理论,对Tm,Ho激光系统计算预测得出最佳耦合输出透过率和调Q激光脉冲宽度.实验采用Tm, Ho:LuLF为增益介质,三向侧面泵浦,环形腔声光调Q.选用透过率20%和30%的输出镜作对比.在透过率20%耦合输出时,得到调Q激光脉冲能量最大为58.0 mJ,对应光光转换效率为1.45%;在透过率30%耦合输出时,得到调Q激光脉冲能量最大为62.9 mJ,对应光光转换效率1.57%,并且获得了最大动静比48.7%.激光脉冲宽度在注入能量3.25 J时为417.2 ns.与理论计算结果较为一致.     

钢管混凝土拱均匀温差设计取值研究

以一座钢管混凝土桁拱为研究对象,应用经实桥实测温度场验证的有限元方法和三个不同区域实测环境温度,通过对计算合龙温度、有效温度和温差设计取值方法精度的计算以及温度次内力与有限元理论值差异的对比分析,研究了钢管混凝土拱均匀温差设计取值问题。研究表明,福建省地方建设标准《钢管混凝土拱桥技术规程》推荐的计算合龙温度公式可推广至全国其他区域;对于有效温度,可取当地最高气温作为最高有效温度,最低日平均气温或当地最低气温作为最低有效温度。