- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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A reaction-based turn-on fluorescent sensor for the detection of Cu (II) with excellent sensitivity and selectivity: Synthesis, DFT calculations, kinetics and application in real water samples
摘要： A reaction-based turn-on fluorescent chemosensor RhB-Cu, starting from rhodamine B (RhB), for Cu2+ was easily synthesized in two steps. The sensor could selectively detect Cu2+ with a 100-fold fluorescence enhancement among the common metal ions, exhibiting an extremely low detection limit of 4.7 nM. To the best of our knowledge, this was the best record for the detection of Cu2+ with organic fluorescent sensors. There was a 1:1 binding stoichiometry between RhB-Cu and Cu2+ with an association constant of 6.42 × 104 M-1. Noteworthy, it could distinguish Cu2+ from Cu+, which was hard to realize in the previous studies. In addition, the detection mechanism was proposed based on mass spectrometric analysis and density functional theory (DFT) calculations. Kinetic studies were conducted to obtain the activation energy, enthalpy and entropy, so as to elucidate the solvent effect. Interestingly, the kinetic compensation effect (KCE) was uncovered in this work. Finally, RhB-Cu was proved to have the capability to work in real water samples. It would highly contribute to the even better design of fluorescent sensor for Cu2+ in future.
关键词： fluorescent sensor,solvent effect,kinetic compensation effect (KCE),copper,density functional theory (DFT),PET mechanism
更新于2025-10-22 19:38:57
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Spectral correction for handheld optoacoustic imaging by means of near-infrared optical tomography in reflection mode
摘要： In vivo imaging of tissue/vasculature oxygen saturation levels is of prime interest in many clinical applications. To this end, the feasibility of combining two distinct and complementary imaging modalities was investigated: optoacoustics (OA) and near-infrared tomography (NIROT), both operating noninvasively in reflection mode. Experiments were conducted on two optically heterogeneous phantoms mimicking tissue before and after the occurrence of a perturbation. OA imaging was used to resolve submillimetric vessel-like optical absorbers at depths up to 25 mm, but with a spectral distortion in the OA signals. NIROT measurements were utilized to image perturbations in the background and to estimate the light fluence inside the phantoms at the wavelength pair (760 nm, 830 nm). This enabled the spectral correction of the vessel-like absorbers' OA signals: the error in the ratio of the absorption coefficient at 830 nm to that at 760 nm was reduced from 60%-150% to 10%-20%. The results suggest that oxygen saturation (SO2) levels in arteries can be determined with <10% error and furthermore, that relative changes in vessels' SO2 can be monitored with even better accuracy. The outcome relies on a proper identification of the OA signals emanating from the studied vessels.
关键词： fluence compensation,near-infrared optical tomography,blood oxygen saturation,quantitative optoacoustic imaging,optoacoustic signal quantification,multimodal imaging,spectral correction
更新于2025-09-23 15:23:52
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A Phase-Calibration Method for Vector-Sum Phase Shifters Using a Self-Generated LUT
摘要： This paper presents a new self-calibration method for vector-sum phase shifters (PS) to compensate for process variations and achieve reconfigurable operating frequency. The calibration system generates a look-up table for the control voltages of the variable-gain amplifiers of the PS to minimize the rms phase error at a frequency of interest. The calibration system consists of a coupled-line coupler, an amplifier, a power detector (PD), an analog-to-digital converter, and a data processing unit. In this calibration method, first, the amplitudes of IQ vectors are swept and their powers are measured. Then, phase errors are calculated from these power measurements using the cosine formula. Finally, the vector pairs providing the least phase error are chosen for each desired phase shift. The practicality of the proposed system is demonstrated by realizing a self-calibrated X-band 7-b PS fabricated in IHP 0.25-μm SiGe BiCMOS technology, including the on-chip coupler, amplifier, and PD. The calibration system improves the rms phase error by at least 1°, does not degrade the rms gain error, and increases the insertion loss by 1.6 dB. The self-calibrated PS achieves a 2° rms phase error across X-band frequencies. The overall chip size is 2.6 mm2. The power consumption of the PS and the overall system are 110 and 233 mW, respectively. This built-in calibration system mitigates process variation effects, and the performance of the PS can be optimized for any center frequency across X-band.
关键词： BiCMOS,vector-sum phase shifter,look-up table,Self-calibration,process compensation,phase shifter,SiGe
更新于2025-09-23 15:23:52
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Hybrid Camera Array-Based UAV Auto-Landing on Moving UGV in GPS-Denied Environment
摘要： With the rapid development of Unmanned Aerial Vehicle (UAV) systems, the autonomous landing of a UAV on a moving Unmanned Ground Vehicle (UGV) has received extensive attention as a key technology. At present, this technology is confronted with such problems as operating in GPS-denied environments, a low accuracy of target location, the poor precision of the relative motion estimation, delayed control responses, slow processing speeds, and poor stability. To address these issues, we present a hybrid camera array-based autonomous landing UAV that can land on a moving UGV in a GPS-denied environment. We first built a UAV autonomous landing system with a hybrid camera array comprising a fisheye lens camera and a stereo camera. Then, we integrated a wide Field of View (FOV) and depth imaging for locating the UGV accurately. In addition, we employed a state estimation algorithm based on motion compensation for establishing the motion state of the ground moving UGV, including its actual motion direction and speed. Thereafter, according to the characteristics of the designed system, we derived a nonlinear controller based on the UGV motion state to ensure that the UGV and UAV maintain the same motion state, which allows autonomous landing. Finally, to evaluate the performance of the proposed system, we carried out a large number of simulations in AirSim and conducted real-world experiments. Through the qualitative and quantitative analyses of the experimental results, as well as the analysis of the time performance, we verified that the autonomous landing performance of the system in the GPS-denied environment is effective and robust.
关键词： GPS-denied environment,moving UGV,UAV autonomous landing,hybrid camera array,motion compensation
更新于2025-09-23 15:23:52
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Open-path Halon 1301 NDIR sensor with temperature compensation
摘要： Halon 1301 (bromotrifluoromethane) is a kind of fire extinguishing agent in aviation industry. Volume concentration measurement of Halon 1301 is necessary in the design of aircraft fire protection systems. In this research, an open-path Halon 1301 non-dispersive infrared (NDIR) sensor has been developed for in-situ measurement, a novel cavity-type absorption module was designed to get fast response and more compact structure. Experiment results show that measurement was remarkably affected by temperature. Therefore, temperature compensation algorithm was also studied in this thesis, which was proven to be effective within the range of 25 oC-105 oC.
关键词： non-dispersive infrared (NDIR),mid-infrared absorption spectrum,Halon 1301,temperature compensation,concentration measurement
更新于2025-09-23 15:23:52
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Defect analysis of TiO2 doped with ytterbium and nitrogen by ab initio calculations
摘要： Different defects are studied in the network of anatase TiO2 to improve the utilization of the material for photoelectrochemical applications. With the ab initio calculations, defect-induced TiO2 models with different doping concentrations and oxidation states of Yb and N dopants are studied. Oxygen-deficient systems are modeled, and the interaction of oxygen vacancy with the Yb and N dopant in the bulk of TiO2 is elucidated. Yb 4f states are coupled with the O 2p states reducing the band gap and shifting the absorption edge of the TiO2 toward visible regime. Increasing Yb doping concentration reduced the band gap, and the 2.08% Yb doping concentration is considered as an optimal Yb doping. Comparing the band structures of mono-doped and codoped samples, Yb, N codoping reduced the band gap while creating isolated states in the forbidden region. Compensated and non-compensated systems of Yb- and/or N-doped TiO2 models are studied. Charge compensation in Yb, N-codoped TiO2 stabilized the system, reduced the band gap without having isolated states and provided broader absorption band. The Ti16?xYbxNyO31?y, x = 2, y = 1, model provided minimum structure modification with the suitable band structure for photoelectrochemical applications explaining the experimental results for the synergistic effect of Yb, N codoping in TiO2.
关键词： Doping concentration,Point defects,Charge compensation,Ytterbium
更新于2025-09-23 15:23:52
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[Micro/Nano Technologies] Micro Electro Mechanical Systems Volume 2 || Micro Thermal Flow Sensor
摘要： Measurement of ?uid mechanics is very important in various ?elds, and ?ow sensors have been widely applied to execute accurate and ef?cient measurements. Compared with other sensing principle, thermal ?ow sensors are based on convective heat transfer and take merits of simple structure and easy use and thus offer a practical solution for various ?uidics applications. In this chapter, we describe mainly hot-?lm anemometer fabricated on polyimide substrate. Hot-?lm or hot-wire anemometer utilizes a thermal element that serves as both a joule heater and a temperature sensor. We introduce the principle of thermal ?ow sensing, design and fabrication of the micro hot-?lm ?ow sensor, the measurement methodology, and application cases by using the micro hot-?lm ?ow sensors.
关键词： Flow sensor,Temperature compensation,Micro anemometer,Hot ?lm,Measurement principle
更新于2025-09-23 15:23:52
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Deformation sensing and electrical compensation of smart skin antenna structure with optimal fiber Bragg grating strain sensor placements
摘要： Skin antenna structure is a kind of multifunctional composite structure in which printed antennas are integrated. This paper proposes a new smart skin antenna structure with embedded fiber Bragg grating (FBG) strain sensors. Utilizing the measured strains from limited FBG strain sensors, the deformation shapes are reconstructed by using a strain–displacement transformation, and the deteriorated radiation patterns caused by the deformations are compensated by using a strain-electromagnetic coupling mode which is derived and validated for the first time in the paper. Moreover, a two-step sensor placement method considering the information redundancy is proposed to determine optimal FBG strain sensor locations. The comparisons show that the two-step sensor placement method is advantageous in terms of the sensor distribution and computational cost. The fabrication process of the smart skin antenna structure was presented, and an experimental system with optimal sensor placements was developed. The measured results demonstrate that the reconstructed shapes agree well with the real ones, and that the deteriorated radiating patterns were almost completely restored to the desired ones. The proposed smart skin antenna structure which can provide the electromagnetic receiving-sending, structural deformation monitoring and electrical correction functions has a potential application prospect in the future mobile vehicle.
关键词： Fiber Bragg grating,Deformation sensing,Electrical compensation,Smart skin antenna,Optimal sensor placement
更新于2025-09-23 15:23:52
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Monodimensional enlargement of resolved field of view in line scan cameras by a single doubly symmetric mirror
摘要： The geometry of the sensed and thus optically relevant area in the image plane of line scan cameras suggests that improvement of the overall system is possible, by joint design of optics and electronics. By a technique named Linear Fovea (LF) proposed in this paper, the optical contrast along the Line-of-Interest (LOI) in the image plane i.e. the location of the opto-electronic sensor, is optimized at the expense of contrast elsewhere. In the LF method, employing a single doubly symmetric surface, the resolved ?eld of view (RFOV) as the merit function, is maximized, by ?nding appropriate Zernike coe?cients describing that surface. The technique is applied on a proof-of-concept single mirror telescope and both MTF analysis and standard target imaging simulation are performed. Results show that by this technique, the RFOV can be doubled, or alternatively the illumination can be increased 2.5 times keeping RFOV unchanged. Furthermore, a rather uniform response is kept along the LOI.
关键词： Foveated imaging,Aberration compensation,Lens design,Wide ?eld angle lenses,Free form optics,Line scan cameras
更新于2025-09-23 15:23:52
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Arbitrarily accurate variable rotations on the Bloch sphere by composite pulse sequences
摘要： Composite pulse sequences, which produce arbitrary prede?ned rotations of a two-state system at an angle θ on the Bloch sphere, are presented. The composite sequences can contain arbitrarily many pulses and can compensate experimental errors in the pulse amplitude and duration to any desired order. A special attention is devoted to two classes of π/2 sequences—symmetric and asymmetric—the phases of which are given by simple formulas in terms of rational multiples of π for any number of constituent pulses. This allows one to construct arbitrarily accurate π/2 composite rotations. These π/2 composite sequences are used to construct three classes of arbitrarily long composite θ sequences by pairing two π/2 composite sequences, one of which is shifted by a phase π ? θ with respect to the other one.
关键词： Bloch sphere,quantum control,composite pulses,error compensation,pulse sequences
更新于2025-09-23 15:23:52