Investigation of the Ga-Sb-S chalcogenide glass with low thermo-optic coefficient as an acousto-optic material

In this study, two series of Ga_xSb_40-xS₆₀ (x = 4, 6, 8, 10 mol%) and Ga_ySb₃₆S_64-y (y = 3, 5, 6 mol%) glasses were prepared and the relationship between their compositional and acousto-optic (AO) properties was investigated systematically for the first time. In the Ga_ySb₃₆S_64-y system, the AO figure of merit (M₂) increased as the Ga increased, and the maximum M₂ of the Ga₆Sb₃₆S₅₈ glass was 455.78 × 10^?18 s³/g, which is ～301 times greater than that of fused silica and ～2.5 times greater than that of As₂S₃ chalcogenide (ChG) glass at 1550 nm. However, its thermo-optic coefficients (dn/dT) varied greatly (32.1 × 10^?6 °C^?1–57.2 × 10^?6 °C^?1), and acoustic attenuations (α) at 10 MHz were high, from 5.446 dB/cm to 7.274 dB/cm. In the Ga_xSb_40-xS₆₀ glass system, the M₂ value and α at different ultrasonic frequencies gradually decreased with the improvement of Ga. Compared with the Ga_ySb₃₆S_64-y system, the Ga_xSb_40-xS₆₀ glass system had lower α (at 10 MHz) and dn/dT, which are 5.001 dB/cm–5.563 dB/cm and 17.3 × 10^?6 °C^?1–55.6 × 10^?6 °C^?1, respectively. These results provide a significant reference for the further development of novel ChG glasses and help expand their application fields.     

考虑变幂数的畸变动力学相似试验模型设计方法及试验研究

动力学相似理论广泛应用于大型结构的振动试验，其中畸变相似用于解决结构的设计参数不满足等比例缩放时的相似问题，针对畸变相似关系中幂数为定值导致预测精度低的问题，提出考虑变幂数的畸变动力学相似试验模型设计方法。首先，在敏感性分析与中心差分理论推导的幂数表达式的基础上，将中心差分的范围不断扩大得到一组随相似比变化的幂数。采用最小二乘法将这组幂数拟合为关于相似比的函数并建立相似关系。然后，在多盘转子系统的数值算例中将变幂数法与文献中的两种方法进行对比，结果表明，变幂数法的预测精度较文献中的方法有很大提高。最后，通过试验研究验证了数值算例中动力学模型及临界转速求解的正确有效性。相似关系的建立是以模型的临界转速为基础，因此也验证了数值算例中的相似预测结果。     

X-ray photons attenuation characteristics for two tellurite based glass systems at dental diagnostic energies

X-ray photons attenuation characteristics for the two tellarite based glasses Bi₂O₃– B₂O₃– TeO₂– TiO₂ and PbO–ZnO–TeO₂–B₂O₃ have been investigated at dental diagnostic energies (between 30-80 keV) using Geant4 code and WinXcom software. The correlation coefficient (R²) is utilized to evaluate the extent to which Geant4 results are related to the WinXcom data. For the both series, R² is close to 1 for all samples and this implies a perfect degree of association between the Geant4 and WinXcom data. The linear attenuation coefficient is proportionally increased with addition of TeO₂ in both series, which implies that there is a decreasing tendency in the X-ray photon transmission corresponding with an increase in the TeO₂ content in the glasses. The half value layer (HVL) decreases as the density increases and this decreasing is very notable at 70 and 80 keV. The maximum HVL for all samples occurs at 80 keV and this implies that the HVL gradually increases as the energy of the X-ray photons increase. Also, the increment of TO₂ in the glasses (in both systems) leads to reduce the mean free path and BiTeTi6 and PbTeB6 samples have the lowest MFP. The MFP for both systems was compared with three heavy concretes and the comparison revealed that the selected systems can be utilized to fabricate protection masks used during diagnostic radiation of the head or oral cavity.     

A New Time-Aware Collaborative Filtering Intelligent Recommendation System

Aiming at the problem that the traditional collaborative filtering recommendation algorithm does not fully consider the influence of correlation between projects on recommendation accuracy, this paper introduces project attribute fuzzy matrix, measures the project relevance through fuzzy clustering method, and classifies all project attributes. Then, the weight of the project relevance is introduced in the user similarity calculation, so that the nearest neighbor search is more accurate. In the prediction scoring section, considering the change of user interest with time, it is proposed to use the time weighting function to improve the influence of the time effect of the evaluation, so that the newer evaluation information in the system has a relatively large weight. The experimental results show that the improved algorithm improves the recommendation accuracy and improves the recommendation quality.     

The effect of salinity and temperature on electromagnetic wave attenuation in brine

Ice slurries are typically formed from an aqueous solution of water and salt (NaCl) at 5% salinity. Ice pigs, used in many industry areas, are taken from a bulk ice slurry and used to clear waste or recover product from pipes. Ice fraction is a key property of an ice slurry, since it determines it's ‘thickness’ and therefore cleaning capacity. Electromagnetic wave interrogation has been shown to accurately predict an ice fraction to within an error of ±1.2%. The largest remaining process error comes from inherent salinity variation, which affects the electromagnetic wave attenuation significantly. Increasing electromagnetic wave attenuation with increasing salinity and the effect of temperature, shown to also increase attenuation, is quantified. Calibration methods are proposed, aiming to eliminate the unwanted effect of varying salinity. Analysis on multiple samples showed a 16% reduction in average error, and 9% reduction in maximum error when the calibration method was applied.     

老井复查评价技术在浅层油藏中的研究与应用

本文以靖安地区浅层老井为例,利用钻井、录井、测井、取心等资料,结合现代测井解释评价技术,对受当时技术条件限制被误判的储层进行再分析研究。制定可行的复查评价标准与流程,确定出油下限,优选补孔潜力井,并结合精细地质研究成果筛选建产目标区,达到挖潜增效和滚动增储的双重目的。对老区日后寻找新储量进行勘探开发具有十分重要的意义。     

煤系地层致密砂岩气甜点区地震逐级预测——以鄂尔多斯盆地东南缘下二叠统山西组2~3亚段为例

鄂尔多斯盆地东南部下二叠统山西组2~3亚段(以下简称山2~3亚段)为该盆地重要的天然气勘探目的层,但该亚段储层薄、厚度变化快、非均质性强,储层预测和勘探目标优选难度大。为了准确预测该亚段煤系地层致密砂岩气甜点区、提高天然气勘探成功率,针对该套储层的特征和预测难点,提出了90°相移技术识别河道外形、模型约束波阻抗反演刻画砂体厚度和子波衰减梯度属性识别含气砂体的地震逐级预测技术。研究结果表明:①山2~3亚段上覆5号煤地震强反射层,下伏储层地震反射能量弱,加之为稀疏二维地震测网、井控程度低,致使致密砂岩气甜点区预测难度大;②所提出的技术方法通过地震逐级预测约束,可以有效地刻画河道砂体分布并识别有效含气储层,提高了对勘探开发目标预测的精度;③基于该技术方法指导部署的勘探开发目标实钻效果好,地震预测结果横向分辨率高,真实地反映了河道及河道砂体的变化特征。结论认为,采用该方法可以有效地解决二维地震勘探区煤系地层强非均质性、薄储层致密砂岩气甜点区预测的地质难题。     

基于火箭遥测的地面站接收信号情况预估方法

火箭尾焰造成的信号衰减是地面测量点位选择重点考虑的问题,通常采用传统β角确定火箭尾焰对遥测地面站接收信号的影响程度。针对新型固体火箭发射中β角分析法对遥测地面站接收信号情况预测不准确的问题,文中在分析影响遥测地面站信号接收因素的基础上,提出了一种采用信号衰减方向性预估遥测地面站接收信号情况的模型。通过分析火箭遥测实测飞行姿态、位置以及地面遥测设备实际跟踪信号情况确定了模型参数,并通过实例计算证明了该方法优的优越性。     

高温下Pt-13Rh/Pt热电偶的热电动势衰减机理研究

模拟1400℃富含Pt-Rh的使用环境，研究R型热电偶(Pt-13Rh/Pt)在高温下的衰减机理。分析竹节状缩颈现象的形成原因，讨论引起热电动势衰减的因素。结果表明，在富含气相Pt-Rh的高温环境下，热电偶外瓷珠表面沉积了固态的Pt、Rh，导致绝缘电阻的降低以及实际测温点向低温区转移，最终导致热电动势衰减。     

Process−microstructure−properties relationship in Al−CNTs−Al2O3 nanocomposites manufactured by hybrid powder metallurgy and microwave sintering process

Al−2CNTs−xAl₂O₃ nanocomposites were manufactured by a hybrid powder metallurgy and microwave sintering process. The correlation between process-induced microstructural features and the material properties including physical and mechanical properties as well as ultrasonic parameters was measured. It was found that physical properties including densification and physical dimensional changes were closely associated with the morphology and particle size of nanocomposite powders. The maximum density was obtained by extensive particle refinement at milling time longer than 8 h and Al₂O₃ content of 10 wt.%. Mechanical properties were controlled by Al₂O₃ content, dispersion of nano reinforcements and grain size. The optimum hardness and strength properties were achieved through incorporation of 10 wt.% Al₂O₃ and homogenous dispersion of CNTs and Al₂O₃ nanoparticles (NPs) at 12 h of milling which resulted in the formation of high density of dislocations and extensive grain size refinement. Also both longitudinal and shear velocities and attenuation increase linearly by increasing Al₂O₃ content and milling time. The variation of ultrasonic velocity and attenuation was attributed to the degree of dispersion of CNTs and Al₂O₃ and also less inter-particle spacing in the matrix. The larger Al₂O₃ content and more homogenous dispersion of CNTs and Al₂O₃ NPs at longer milling time exerted higher velocity and attenuation of ultrasonic wave.