Direct and controlled device integration of graphene oxide on Quartz Crystal Microbalance via electrospray deposition for stable humidity sensing

Integration of advanced and functional materials onto conventional sensing platforms can improve the device performances and even discover new applications. For piezoelectric resonant sensors, an addition of sensing materials can induce damping and hinder a stable device operation. Hence, the development of efficient method for materials integration is important to ensure high-performance and reliable sensor operation. This work presents a direct and precisely controlled integration of graphene oxide (GO) using the electrospray deposition (ESD) onto a 10 MHz Quartz Crystal Microbalance (QCM) for humidity sensing. The proposed ESD method achieves a high mass resolution of a few nanograms. Moreover, the GO uniformly coats across the sensing electrode region as it acts as a ground electrode during ESD. The proposed ESD method also works for a wide range of nanomaterials, such as carbon nanotubes, tin oxide, and silicon carbide micro-and nano-powders. Compared to the conventional drop-casting and dip coating approaches, our method ensures minimal GO agglomeration, resulting in a stable QCM-oscillator operation in a wide range of relative humidity from 11% to 97%. The measurement sensitivity increases with an amount of GO, but less GO results in better noise and detection limit performances. The results shed light on the importance of selecting an optimal amount of sensing materials for stable sensor operations.     

Various density light field image coding based on distortion minimization interpolation

In recent years, the light field (LF) as a new imaging modality has attracted wide interest. The large data volume of LF images poses great challenge to LF image coding, and the LF images captured by different devices show significant differences in angular domain. In this paper we propose a view prediction framework to handle LF image coding with various sampling density. All LF images are represented as view arrays. We first partition the views into reference view (RV) set and intermediate view (IV) set. The RVs are rearranged into a pseudo sequence and directly compressed by a video encoder. Other views are then predicted by the RVs. To exploit the four dimensional signal structure, we propose the linear approximation prior (LAP) to reveal the correlation among LF views and efficiently remove the LF data redundancy. Based on the LAP, a distortion minimization interpolation (DMI) method is used to predict IVs. To robustly handle the LF images with different sampling density, we propose an Iteratively Updating depth image based rendering (IU-DIBR) method to extend our DMI. Some auxiliary views are generated to cover the target region and then the DMI calculates reconstruction coefficients for the IVs. Different view partition patterns are also explored. Extensive experiments on different types LF images also valid the efficiency of the proposed method.     

Strong f-f excitation in titanium silicate: Near-UV LED pumped red phosphors with outstanding temperature sensitivity

Optical thermometry and white light-emitting diodes (WLEDs) are the research hotspots for Eu³⁺ doped phosphors. In this study, a series of Sr₂TiSi₂O₈: Eu³⁺ red phosphors were developed in a solid-state reaction method. The luminescent properties of the Sr₂TiSi₂O₈: Eu³⁺ phosphor illustrate that Sr₂TiSi₂O₈: Eu³⁺ is effectively excited by the NUV LED chip and emit an intense red light with a peak of 618 nm due to the noninversion symmetry coordination of Eu³⁺ in Sr₂TiSi₂O₈. The local coordination environment of Eu³⁺ was investigated in detail using crystallographic data, spectroscopic data and Judd–Ofelt parameters. In addition, the emission intensity of Sr₂TiSi₂O₈:Eu³⁺ is extremely sensitive to temperature. The relative sensitivity of Sr₂TiSi₂O₈:Eu³⁺ is 1.1% k^-1@300 k, which is comparable to other Eu³⁺-activated temperature sensing materials. The possible mechanism of the temperature sensitive quenching characteristics was proposed. The results indicate that Sr₂TiSi₂O₈:Eu³⁺ is a potential temperature sensing material.     

On the application of remote sensing towards the estimation of cultivated land lost to urbanization

In this research work, a 40-km² SPOT-5 High-Resolution Imagery (HRI) of the Warsak locality in district Peshawar, Pakistan, was utilized to approximate the quantity of cultivated land lost to urbanization, due to the construction of new homes and buildings. The imagery from a period of 2005 to 2015 for wheat crop was taken, specifically during the months of March and June when the crop is rich green and golden ripe respectively. eCognition ® program’s Object-Oriented Classification Method (OOCM) was employed for recognition of land versus buildings. Nearest Neighbour (NN), Support Vector Machine (SVM), Decision Trees (DT) and Random Forests (RF) were utilized for the classification process. The results demonstrated that the urbanized area had increased by approximately 28 per cent in the area considered. Moreover, the efficacy of the proposed method is depicted by an accuracy of 97.9 per cent and a Kappa Statistics of 0.975 for the SVM classifier.     

Low-memory and high-performance architectures for the CCSDS 122.0-B-1 compression standard

Two low-memory and high-performance architectures for the CCSDS 122.0-B-1 standard are proposed. They use novel memory organizations to reduce the total memory requirements in order to be implemented in a single FPGA device. The architectures were implemented in radiation-hardened and commercial FPGA devices. Based on the experimental results for the case of Virtex5QV radiation-hardened device, the throughput is 135 MSamples/sec for image with 12 bits/pixel and horizontal resolution up 8192 pixels. Also, the proposed architectures outperform the existing one in terms of the memory requirements and area.     

基于同轴图像传感的激光焊接过程质量监测技术

针对激光焊接过程中由于参数不匹配、装配误差等原因造成的焊接过程不稳定等焊接缺陷，基于同轴图像传感技术，建立起一套激光焊接过程中的质量在线监测系统，对焊接过程中的熔池图像进行了采集分析及其熔池特征信息的提取. 结果表明，在激光功率为1 500 W的不等厚不锈钢薄板激光焊接试验条件下，焊接过程中的不稳定、下塌缺陷以及焊偏现象与熔池形状各特征信息变化具有一定的相关性. 结合BP神经网络算法对所提特征信息进行分类、识别，基于LabVIEW软件平台，可实现相应缺陷的自动化识别及报警功能.     

Enhanced Sensitivity in Nanopore Sensing of Cancer Biomarkers in Human Blood via Click Chemistry

Cancer biomarkers are expected to be indicative of the occurrence of certain cancer diseases before the tumors form and metastasize. However, many biomarkers can only be acquired in extremely low concentrations, which are often beyond the limit of detection (LOD) of current instruments and technologies. A practical strategy for nanopore sensing of cancer biomarkers in raw human blood down to the femtomolar level is developed here. This strategy first converts the detection of cancer biomarkers to the quantification of copper ions by conducting a sandwich assay involving copper oxide nanoparticles. The released Cu²⁺ is then taken to catalyze the “click” reaction which ligates a host–guest modified DNA probe. Finally, this DNA probe is subjected to single‐channel recordings to afford the translocation events that can be used to derive the concentrations of the original biomarkers. Due to the amplification effects of nanoparticle loadings and the “click” reaction, the LOD of this strategy can be as low as the subfemtomolar level. Further, the acid treatment step could effectively eliminate the interferences from plasma proteins in raw human blood and make the strategy highly suitable for the detection of cancer biomarkers in clinical samples.     

含齿形裂隙类岩石材料单轴压缩试验研究

为研究含齿形裂隙岩石在单轴压缩下的破坏特征及强度特性，制作了含不同裂隙倾角和起伏角的齿形裂隙类岩石材料试件，并采用岩石力学伺服试验机进行单轴压缩试验。试验结果表明：（1）试件主要产生拉伸、剪切和拉剪复合裂纹，且根据裂纹的扩展路径可划分为A型（拉伸破坏）、B型（剪切破坏）、C型（复合破坏）3种破坏模式，裂隙倾角对试件最终破坏模式影响显著；（2）当裂隙倾角较小时，试件应力—应变曲线为多峰曲线，随着裂隙倾角的增大，曲线呈单峰形式，表现为延性减弱，脆性增强，而裂隙倾角相同但起伏角不同的试件应力—应变曲线大致相同；（3）当裂隙起伏角相同时，试件当量峰值强度随裂隙倾角的增大呈先减小后增大的规律，且裂隙起伏角对试件当量峰值强度的影响小于裂隙倾角。     

Chitosan Microspheres as Carriers for pH‐Indicating Species in Corrosion Sensing

Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material.     

含V型相交裂隙岩体的力学特性及破坏模式试验

为深入了解V型相交裂隙岩体试件的力学特性和裂纹演化规律,采用MTS815电液伺服控制试验机对含不同夹角V型相交裂隙岩体试件进行了常规单轴压缩试验,基于试验结果,详细分析了试件的应力-应变曲线、强度与变形特性、裂纹演化与破坏模式及能量耗散特征。研究结果表明:①裂隙试件的应力-应变曲线进入裂纹萌生与扩展阶段早于完整试件,在峰前出现了明显的应力降现象,在峰后破坏阶段,完整试件表现为应力-应变曲线的快速跌落,而裂隙试件呈现台阶状多阶段性跌落,甚至缓慢水平下降,体现出明显的延性破坏特征;②裂隙试件的峰值应力、弹性模量和峰值应变均有明显减小。峰值强度和弹性模量随裂隙夹角的增加呈先增大后减小的变化趋势。轴向峰值应变主要受裂隙夹角的影响,总体随夹角的增大呈线性减小的趋势;③裂隙的存在能够完全改变岩体试件的破坏模式,随着裂隙夹角的逐渐增加,裂隙试件破坏模式的演化过程为:台阶式张拉-剪切复合破坏(30°)→张拉-八字形剪切复合破坏(60°)→台阶式平行双斜面剪切破坏(90°)。当裂隙夹角为60°时,试件的裂纹演化和破坏模式体现出对加载方向近似的结构对称性特征;④相交裂隙试件单轴压缩破坏的弹性应变能、耗散能、总能量和能量耗散率均较完整试件有大幅度的减小。裂隙试件产生的裂纹数量越多,试件表面的脱落现象越明显,耗散能和能量耗散率也越大。拉-剪复合破坏比单纯剪切破坏要消耗更多的能量。试件的破坏特征和破坏模式能很好地反映试件的能量耗散特性。