The j-integral for augmented double cantilever beams and its application to bonded joints

The J-integral for the double cantilever type specimen is obtained explicitly based on the assumption of a beam on the elastic/plastic foundation. The solution agrees with known solutions as special cases. Also discussed is the path independence of the J-integral for the bonded double cantilever joints where the integral path crosses the boundary of two dissimilar materials. Though contrary to some investigator's previous conclusion, the J-integral for bonded joints is found path independent within the framework of the strength of materials.     

Integrating an ultramicroelectrode in an AFM cantilever: combined technology for enhanced information

We present a novel approach to develop and process a microelectrode integrated in a standard AFM tip. The presented fabrication process allows the integration of an electroactive area at an exactly defined distance above of the end of a scanning probe tip and the subsequent remodeling and sharpening of the original AFM tip using a focused ion beam (FIB) technique (See ref 1 for patent information). Thus, the functionality of scanning electrochemical microscopy (SECM) can be integrated into any standard atomic force microscope (AFM). With the demonstrated approach, a precisely defined and constant distance between the microelectrode and the sample surface can be obtained, alternatively to the indirect determination of this distance usually applied in SECM experiments. Hence, a complete separation of the topographical information and the electrochemical signal is possible. The presented technique is a significant step toward electrochemical imaging with submicrometer electrodes as demonstrated by the development of the first integrated frame submicroelectrode.     

Accurate and precise calibration of AFM cantilever spring constants using laser Doppler vibrometry

Accurate cantilever spring constants are important in atomic force microscopy both in control of sensitive imaging and to provide correct nanomechanical property measurements. Conventional atomic force microscope (AFM) spring constant calibration techniques are usually performed in an AFM. They rely on significant handling and often require touching the cantilever probe tip to a surface to calibrate the optical lever sensitivity of the configuration. This can damage the tip. The thermal calibration technique developed for laser Doppler vibrometry (LDV) can be used to calibrate cantilevers without handling or touching the tip to a surface. Both flexural and torsional spring constants can be measured. Using both Euler-Bernoulli modeling and an SI traceable electrostatic force balance technique as a comparison we demonstrate that the LDV thermal technique is capable of providing rapid calibrations with a combination of ease, accuracy and precision beyond anything previously available.     

Deep-learning-based nanowire detection in AFM images for automated nanomanipulation

Atomic force microscope(AFM)-based nanomanipulation has been proved to be a possible method for assembling various nanoparticles into complex patterns and devices.To achieve efficient and fully automated nanomanipulation,nanoparticles on the substrate must be identified precisely and automatically.This work focuses on an autodetection method for flexible nanowires using a deep learning technique.An instance segmentation network based on You Only Look Once version 3(YOLOv3)and a fully convolutional network(FCN)is applied to segment all movable nanowires in AFM images.Combined with follow-up image morphology and fitting algorithms,this enables detection of postures and positions of nanowires at a high abstraction level.Benefitting from these algorithms,our program is able to automatically detect nanowires of different morphologies with nanometer resolution and has over 90%reliability in the testing dataset.The detection results are less affected by image complexity than the results of existing methods and demonstrate the good robustness of this algorithm.     

SFM in acoustic mode and its applications to observation of ferroelectric domain

Ferroelectric domain structures as well as other surface topologies such as grain boundaries and scratches in transparent (PbLa)(ZrTi)O₃ (PLZT) ceramics and BaTiO₃ ceramics have been respectively investigated by scanning probe acoustic microscopy (SPAM). A periodic striation-like domain pattern has been imaged. The observed SPAM domain contrast is related to acoustic signals generated through a local piezoelectric coupling mechanism. The submicron domain structure was confirmed by scanning force microscopy (SFM) in the piezoresponse mode.     

Monolithic miniaturized quartz microbalance array and its application to chemical sensor systems for liquids

We report on the design, fabrication, and application of novel monolithic miniaturized quartz microbalance (QMB) arrays. Up until now, almost all reported resonator arrays (often designated as "electronic noses" or "electronic tongues", respectively, dependent on their application) are assembled from single QMBs. We fabricate arrays with up to 36 QMBs on a single AT-cut quartz blank. Mass sensitive devices based on AT-cut quartz resonators are suitable as (bio)chemical sensors. A frequency shift caused by mass accumulation on the sensor surface increases theoretically with f/sup 2/, hence the detection limits for the application as chemical sensors should be decreased with increasing frequency. Since the quality factor Q of a quartz crystal decreases with f, the frequency stability is reduced, thus limiting mass sensitivity. The mass sensitivity of resonators with different resonant frequencies was examined by means of electrochemical copper deposition on their surface. Subsequently, the manufactured resonators were coated with different layers (polystyrene, amyl-calix[8]arene, /spl beta/-cyclodextrine). In order to examine the applicability of such coatings as sensitive layers, their sensitivities to toluene in water were investigated. Moreover, arrays with up to four different resonant frequencies on one chip were fabricated for comparing the resonator behavior of the same coating at different frequencies. In another test setup, different layers were sprayed onto an array of microbalances having all the same resonant frequency. This allowed for comparing the different coating behavior under equivalent test conditions. Arrays were tested for viscosity measurement to find an optimum resonant frequency.     

High performance testbed for four-beam infrared interferometric nulling and exoplanet detection

Technology development for a space-based infrared nulling interferometer capable of earthlike exoplanet detection and characterization started in earnest in the last 10 years. At the Jet Propulsion Laboratory, the planet detection testbed was developed to demonstrate the principal components of the beam combiner train for a high performance four-beam nulling interferometer. Early in the development of the testbed, the importance of "instability noise" for nulling interferometer sensitivity was recognized, and the four-beam testbed would produce this noise, allowing investigation of methods for mitigating this noise source. The testbed contains the required features of a four-beam combiner for a space interferometer and performs at a level matching that needed for the space mission. This paper describes in detail the design, functions, and controls of the testbed.     

电化学法制备铁氰化铜/Nafion及其对卡托普利的检测

为对药片中卡托普利的含量进行精确测定,采用电聚合的方法,在玻碳电极表面沉积均匀分布的铁氰化铜/Nafion复合物。用扫描电镜(SEM)和X射线能量色散光谱(EDX)分别对样品的形貌和成分进行表征。利用循环伏安法(CV)研究药物分子卡托普利在该修饰电极上的电化学行为。研究结果显示,该修饰电极对卡托普利具有非常好的电催化性能。一定条件下,卡托普利在6.62×10-5~3.80×10-3mol/L范围内,其氧化峰电流与物质量浓度呈现很好的线性关系,其相关系数是0.996,检出限为5.0×10-6mol/L。该修饰电极具有快速、灵敏和高效的特点,并且可用于卡托普利实际样品的检测。     

Polymer nanocomposite nanomechanical cantilever sensors: material characterization, device development and application in explosive vapour detection

This paper reports an optimized and highly sensitive piezoresistive SU-8 nanocomposite microcantilever sensor and its application for detection of explosives in vapour phase. The optimization has been in improving its electrical, mechanical and transduction characteristics. We have achieved a better dispersion of carbon black (CB) in the SU-8/CB nanocomposite piezoresistor and arrived at an optimal range of 8-9 vol% CB concentration by performing a systematic mechanical and electrical characterization of polymer nanocomposites. Mechanical characterization of SU-8/CB nanocomposite thin films was performed using the nanoindentation technique with an appropriate substrate effect analysis. Piezoresistive microcantilevers having an optimum carbon black concentration were fabricated using a design aimed at surface stress measurements with reduced fabrication process complexity. The optimal range of 8-9 vol% CB concentration has resulted in an improved sensitivity, low device variability and low noise level. The resonant frequency and spring constant of the microcantilever were found to be 22 kHz and 0.4 N m(-1) respectively. The devices exhibited a surface stress sensitivity of 7.6 ppm (mN m(-1))(-1) and the noise characterization results support their suitability for biochemical sensing applications. This paper also reports the ability of the sensor in detecting TNT vapour concentration down to less than six parts per billion with a sensitivity of 1 mV/ppb.     

心电信号的检测技术与临床应用

心电信号是人类最早研究并应用于医学临床的生物电信号之一，与其他生物电信号相比，它更易于检测并具有较直观的规律性。自1903年心电图发明以来，无论在生物医学方面，还是在工程学方面，心电信号的记录、处理与诊断技术均得到飞速发展，并积累了相当丰富的临床资料。当前，心电信号的处理仍是生物医学工程研究的重要对象之一。本文综述了心电图的基本及最新检测技术，并对心电信号检测的发展趋势作了展望。     

Comparison of strain gage and interferometric detection for measurement and control of piezoelectric actuators

The capability of controllable and repeatable positioning in the subnanometer range is fundamental not only for scanning probe microscope applications, but also for nanotechnology in general. Up to now, piezoceramic actuators have been used for this purpose. However, these actuators are far from being ideal transducers. For precise metrological applications, as well as for general use in scanning probe microscopy, some method has to be implemented to correct creep and nonlinearity of piezoceramic materials. In the present study, two different position measuring systems have been implemented—one based on strain gage detection and the other on interferometry. The corresponding results are presented and the performance of both setups compared.     

Combined fluorescent and interferometric detection of protein on a BioCD

We perform simultaneous interferometric and fluorescent detection of molecular protein layers on a BioCD. The 488 nm excitation wavelength of fluorescein also provides the interferometric detection channel that operates in a common-path in-line configuration in the condition of phase quadrature set by a thermal oxide on silicon. The simultaneous acquisition of both channels enables a direct correlation between bound mass and fluorescent surface density, which we compare in forward- and reverse-phase immunoassays. Scaling mass sensitivities for immunoassays measured in the interferometric and fluorescent channels are 15 pg/mm and 1.5 pg/mm, respectively, when applied to gel-printed periodic antibody patterns detected in the frequency domain from the spinning disc. These sensitivities are limited by the inhomogeneities of the print. While fluorescence is subject to bleaching, the interferometry signal is robust under long-term laser illumination.     

Wavelet tests for the detection of transients in the VIRGO interferometric gravitational wave detector

Here we employ discrete wavelet transforms (DWTs) to develop test statistics for the detection of transients, i.e., signals with a short duration and unknown shape, embedded in Gaussian white noise. Distributions of the test statistics under both the and alternative hypotheses can be easily derived. We test performance on a set of 78 templates provided by theoretical studies on gravitational waves emitted in a supernova explosion where we seek the maximal detection distance of the source generating the signal at which the tests correctly reject the hypothesis. We discuss practical implementation issues and performance assessment methods. We compare results with both matched filtering, an optimal method that requires the prior knowledge of the signal shape, and with the slope filtering, that uses limited prior knowledge on the signal. The wavelet statistics show a good behavior for each of the considered waveforms, unlike other detection methods.     

谐波信号的闭环检测和估计算法及其应用

从联合检测估计的角度讨论了检测器和估计器之间的耦合机制,并就水声目标线谱特征提取问题研究了一种谐波信号的闭环检测和估计算法.该算法通过迭代形式在检测器和估计器之间不断交换信息,用以改善未知参数的先验分布,从而得到较好的检测和估计性能.对海试数据的仿真结果表明,该算法可以有效地提取目标的线谱特征.     

Comparison of linear and rotationally shearing interferometric layouts for extrasolar planet detection from space

We use the point spread function and the modulation transfer function (MTF) as two figures-of-merit to evaluate the performance of the multiaperture interferometric configurations for the detection of a faint planet in the vicinity of its bright star. We design nonredundant interferometric layouts that provide satisfactory coverage of the spatial frequencies of interest. We propose a design incorporating a rotating, rotationally shearing interferometer in a gravity-free environment and compare its performance with the Earth-based, fixed, linear configurations. The side peak of its MTF may be centered on the coordinate associated with a likely planet spatial frequency, resulting in planet signal enhancement and isolation.     

Amperometric ultramicrosensors for peroxynitrite detection and its application toward single myocardial cells

The research studied the concentration variation of peroxynitrite anion (O=N-O-O-) released from cultured neonatal myocardial cells induced by ischemia/reperfusion and studied the protective effect of melatonin on the injury. For this purpose, amperometry peroxynitrite ultramicrosensors (UMS) were fabricated and constructed by electropolymerizing inorganic macromolecular film of tetraaminophthalocyanine manganese(II) and coating chemically with poly(4-vinylpyridine). Under optimum conditions, the UMS showed high selectivity and sensitivity to peroxynitrite determination with a calculated detection limit of 1.8 x 10(-8) mol/L (S/N of 3). The detection of peroxynitrite was based on electrocatalytic reduction of peroxynitrite. The mechanism of catalysis was also discussed. The UMS should be promising for in vivo measurement of peroxynitrite without interference or fouling. Peroxynitrite released from myocardial cells both in the ischemic period and in the reperfusion period was measured directly. This approach may lead to important information for myocardial cells on the mechanism of injury and prospective treatments of medicine such as melatonin.     

一种悬臂弯曲加载表面裂纹扩展试样及其应用

介绍了一种带有上下对称圆弧的板状试样,试样上圆弧几何中心预制有半椭圆表面裂纹,这种设计能够较好地模拟压力容器具有表面裂纹时的特点.利用这种试样,可以完成悬臂弯曲加载恒总应变控制下的低周疲劳表面裂纹扩展速率试验,获得表面裂纹扩展长度和深度的关系,最终建立表面和深度裂纹扩展速率与总应变的函数关系.据此,可为含有表面裂纹体的压力容器低周疲劳剩余使用寿命评估提供依据.     

Dynamic modeling and vibration analysis of piezoelectric microcantilever in AFM application

Piezoelectric microcantilevers (MCs) are widely used in common piezoelectric micro-electromechanical systems. These systems are used in ultraprecise scanning and characterization applications. Given the widespread use of this type of MCs in nanotechnology, their vibrating motion problem has recently become a matter of interest. Accurate vibration analysis and studying their vibrating behavior can play a key role in increasing their measurement accuracy and optimal design. For this purposes, first, the differential equation of motion of MCs is solved using modal superposition method by using Runge–Kutta in time domain and finite element methods. The extended Fourier amplitude sensitivity test statistical method is used to conduct sensitivity analysis on the main parameters of the vibrating motion to determine the effects of each interaction coefficient on the motion of the MC. Results showed that the numerical finite element method and modal superposition method based on the non-uniform beam model have acceptable accuracy in calculating resonance amplitude and natural frequency of this kind of MC. The results of the sensitivity analysis indicate the high sensitivity of the first vibrating mode to force coefficient, which means that this mode is suitable for topography of the sample surface and the nanoparticle.     

Synthesis of porous nanododecahedron Co3O4/C and its application for nonenzymatic electrochemical detection of nitrite

Porous nanododecahedron of Co₃O₄/C has been synthesized by calcination of the ZIF-67 in air at 400 °C and then be used as electrode material for fabricating a highly sensitive and low overpotential sensor of nitrite ion (NO₂^?). The structure and morphology characterization show that ZIF-67 behaves as an ideal sacrificial template for preparing Co₃O₄/C with regular shape. The two components of Co₃O₄ and carbon are uniformly distributed in the composite. Electrochemical analysis shows that the excellent electrocatalysis performance toward the oxidation of NO₂^? is based on the synergy of Co₃O₄ and carbon in the nanocomposite. At NO₂^? concentration from 2 nM to 8 mM, a fast response time within 3 s is revealed and 1.21 nM of detection limit is achieved. The sensor is also reliable to analysis of NO₂^? existed in the real samples of soil leaching liquid and macrophage supernate.     

Porous polypyrrole/polymethylmethacrylate composite film prepared by vapor deposition polymerization of pyrrole and its application for ammonia detection

A simple method has been developed to fabricate porous polypyrrole/polymethyl methacrylate composite films. The synthesis procedures include the vapor deposition polymerization of pyrrole on the composite films of polymethyl methacrylate and ferric hydroxide bis(1,4-bis(2-ethylhexyl) sulfosuccinate), successively, washing the obtained composite films with methanol. Scanning electron microscopic and microscopic Raman spectral studies indicated that the pores had an average size of about 5 μm and they were uniformly dispersed in the whole films. The electrical conductivities of the composite films were measured to be in the range of 10^− 3 to 10^− 2 S cm^− 1. The porous composite films showed electroactivity, and the sensors based on them exhibited high sensitivity and fast response to ammonia gas.