Stabilized fiber-optic extrinsic Fabry–Perot sensor system for acoustic emission measurement

A fiber-optic Fabry–Perot (F–P) acoustic emission (AE) sensor system based on an improved double wavelength stabilization technique is described. Without stabilization, the sensor system drifts out of quadrature due to the presence of low-frequency dynamic strains. The stabilization is achieved by using a dense wavelength division multiplexer (DWDM) to generate two quadrature phase-shifted output signals. An optimum model of double wavelength stabilization is established. The filtering wavelengths of DWDM are calculated using an optimization design method. The performance of the developed sensor system was verified by two preliminary tests. One was a test on the stabilization of operating point of fiber-optic F–P sensor, and other was the detection of simulated AE signals generated by the impact and pencil lead breaking. The test results demonstrate that simulated AE signals are successfully detected using this stabilized sensor system, which solves the fade-out problem.     

Model independent control of lightly damped noise/vibration systems

Feedforward control is a popular strategy of active noise/vibration control. In well-damped noise/vibration systems, path transfer functions from actuators to sensors can be modeled by finite impulse response (FIR) filters with negligible errors. It is possible to implement noninvasive model independent feedforward control by a recently proposed method called orthogonal adaptation. In lightly damped noise/vibration systems, however, path transfer functions have infinite impulse responses (IIRs) that cause difficulties in design and implementation of broadband feedforward controllers. A major source of difficulties is model error if IIR path transfer functions are approximated by FIR filters. In general, active control performance deteriorates as model error increases. In this study, a new method is proposed to design and implement model independent feedforward controllers for broadband in lightly damped noise/vibration systems. It is shown analytically that the proposed method is able to drive the convergence of a noninvasive model independent feedforward controller to improve broadband control in lightly damped noise/vibration systems. The controller is optimized in the minimum H2 norm sense. Experiment results are presented to verify the analytical results.     

用计算机辅助测量液体的粘滞系数

主要说明用自制光电门配合计算机辅助测量液体粘滞系数的原理和方法,当小球挡住光电门的光路时,会使光敏管产生一个电脉冲,可以利用计算机声卡配合audition软件捕捉这个脉冲,从而实现小球下落时间的测量,提高实验的精确度。     

水面油污染物差分偏振光谱信号预处理算法研究

采用差分偏振光谱法在3～5μm波段对水面溢油污染物进行被动遥感时,所测差分偏振光谱是含有强大气吸收光谱信号与油污染物目标弱光谱信号的混合谱,这给油污染物光谱特征识别带来了困难。另外,受环境因素以及油膜自身张力影响,水面油膜厚度分布以及油膜表面粗糙度在测量过程中发生变化,从而使得连续测量的差分偏振光谱中油污染物光谱信息含量存在不同。利用这一特点,基于固定点迭代的快速主成分分析算法FastPCA设计了水面溢油污染物差分偏振光谱信号预处理算法。实验结果表明,该算法可以有效地将水面油污染物目标光谱特征信息从具有强大气吸收的混合差分偏振光谱信号中提取出来,通过光谱重构得到油污染物光谱特征信号,可用于进一步的定性、定量分析。     

Metallic state in cubic FeGe beyond its quantum phase transition

We report on results of electrical resistivity and structural investigations on the cubic modification of FeGe under high pressure. The long-wavelength helical order (T(C) = 280 K) is suppressed at a critical pressure p(c) approximately 19 GPa. An anomaly at T(X)(p) and strong deviations from a Fermi-liquid behavior in a wide pressure range above p(c) suggest that the suppression of T(C) disagrees with the standard notion of a quantum critical phase transition. The metallic ground state persisting at high pressure can be described by band-structure calculations if zero-point motion is included. The shortest FeGe interatomic distance display discontinuous changes in the pressure dependence close to the T(C)(p) phase line.     

Low-temperature preparation of anatase titania-coated magnetite

A composite photocatalyst with an anatase titania shell and a magnetite core was prepared in a novel way at low temperature (75 °C at most) by coating photoactive titanium dioxide onto a magnetic Fe₃O₄ core. The photocatalytic activity of the prepared photocatalyst was evaluated by the degradation of model contaminated water of phenol and compared to single-phase titania (either Degussa P25 or prepared titania without magnetic Fe₃O₄). The results showed that the photoactivity was slightly depressed. Then, a remarkable improvement in photoactivity was achieved by modifying the photocatalyst with a SiO₂ layer between the Fe₃O₄ core and TiO₂ shell. The repetitive using of the modified photocatalyst was also investigated, and experimental results illustrated that the photocatalytic-degraded ratio of phenol was still higher than 80% after six cycles.     

光学多普勒层析三维矢量测速方法研究

光学多普勒层析术(ODT)是一种高分辨、非侵入的生物医学成像手段,能同时得到组织的结构信息和组织内血管的流速信息.提出了一种新型的基于相位分辨技术的ODT三维矢量测速方法.在ODT系统样品臂的准直镜和聚焦透镜之间加入窄带相位片,形成三个不同的相位延迟,通过计算多普勒频移和不同相位延迟下的多普勒展宽,可得到毛细管内的三维矢量流场分布.对已知浓度的聚苯乙烯溶液进行了一系列不同角度和不同流速的实验,结果证明这种新型的ODT矢量测速方法可以较精确的实现三维矢量流速的测量.     

Arbitrated Quantum Signature Scheme with Continuous-Variable Coherent States

Motivated by the revealing features of the continuous-variable (CV) quantum cryptography, we suggest an arbitrated quantum signature (AQS) protocol with CV coherent states. It involves three participants, i.e., the signer Alice, the verifier Bob and the arbitrator Charlie who is trustworthy by Alice and Bob. Three phases initializing phase, signing phase and verifying phase are included in our protocol. The security of the signature scheme is guaranteed by the generation of the shared keys via the CV-based quantum key distribution (CV-QKD) and the implementation process of the CV-based quantum teleportation as well. Security analysis demonstrates that the signature can be neither forged by anyone nor disavowed by the receiver and signer. Moreover, the authenticity and integrality of the transmitted messages can be ensured. The paper shows that a potential high-speed quantum signature scheme with high detection efficiency and repetition rate can be realized when compared to the discrete-variable (DV) quantum signature scheme attributing to the well characteristics of CV-QKD.     

High-throughput screening against $$\sim $$6.1 million structurally diverse,lead-like compounds to discover novel ROCK inhibitors for cerebral injury recovery

Rho-associated protein kinase (ROCK) has been recognized as an attractive therapeutic target to promote neurogenesis, neuroregeneration, and neurorecovery after cerebral injury. Here, a high-throughput screening protocol was described to discover novel ROCK inhibitors from a large chemical library containing \(\sim \)6.1 million structurally diverse, lead-like compounds. The protocol employed empirical rules such as ADMET evaluation and chemical similarity analysis to exclude those of drug-unlike candidates, and then molecular docking and binding affinity predictions were performed to suggest few promising candidates with high scores. Consequently, five compounds were successfully identified to have satisfactory activity profile with \(\hbox {IC}_{50}\) values at nanomolar level. In order to elucidate the molecular mechanism of inhibitor binding to target, the complex structures of ROCK kinase domain with the five identified compounds were modeled and examined in detail. A number of polar chemical forces such as hydrogen bonds and cation-\(\pi \) interactions as well as nonpolar contacts such as \(\pi \)–\(\pi \) stacking and hydrophobic forces were revealed at the complex interface, conferring high affinity and strong specificity to inhibitor binding. In addition, several key residues around the kinase active site, including Val90, Lys105, Asn203, and Phe368, were found to play an important role in binding.