Auto-Alignment Non-Contact Optical Measurement Method for Quantifying Wobble Error of a Theodolite on a Vehicle-Mounted Platform

During non-landing measurements of a theodolite, the accuracy of the goniometric readings can be compromised by wobble errors induced by various factors such as wind loads, theodolite driving torque, and the stiffness of the supporting structure. To achieve high-precision non-landing measurements, it is essential to accurately determine and correct the platform wobble errors affecting the azimuth and pitch pointing angles. In this paper, a non-contact optical measurement method is proposed for quantifying platform wobble errors. The method establishes an auto-alignment optical path between an autocollimator and a reflector in the measuring device. By detecting the deviation angle of the CCD image point as the optical path changes, precise measurements of the platform wobble errors can be obtained. Experimental results demonstrate that the measuring device can achieve an auto-alignment optical path within 5 minutes, significantly improving measurement efficiency. Furthermore, after measuring the platform wobble error and applying data correction, the average error in the azimuth pointing angle is reduced from 31.5″ to 9.8″, and the average error in the pitch pointing angle is reduced from 21″ to 9.2″. These results highlight the substantial correction effect achieved by the proposed method

Vestibular dysfunction in Parkinson’s disease: a neglected topic

Dizziness and postural instability are frequently observed symptoms in patient with Parkinson’s disease (PD), potentially linked to vestibular dysfunction. Despite their significant impact on quality of life, these symptoms are often overlooked and undertreated in clinical practice. This review aims to summarize symptoms associated with vestibular dysfunction in patients with PD and discusses vestibular-targeted therapies for managing non-specific dizziness and related symptoms. We conducted searches in PubMed and Web of Science using keywords related to vestibular dysfunction, Parkinson’s disease, dizziness, and postural instability, alongside the reference lists of relevant articles. The available evidence suggests the prevalence of vestibular dysfunction-related symptoms in patients with PD and supports the idea that vestibular-targeted therapies may be effective in improving PD symptoms

Development of MEMS Airflow Volumetric Flow Sensing System with Single Piezoelectric Micromachined Ultrasonic Transducer (PMUT) Array

Compared to conventional ultrasonic flowmeters using multiple transducers, this paper reports, for the first time, an airflow volumetric flowmeter using a signal PMUT array to measure the flow rate in a rectangular pipe. The PMUT around 200 kHz is selected to fit the system requirements. All PMUT elements on this single array are then electrically grouped into transmitter and receiver. In order to minimize the crosstalk signal between transmitter and receiver, a phase shift signal is applied at the transmitter to reduce the amplitude of the crosstalk signal by 87.8%, hence, the resultant high sensing resolution. Based on the analog signal extracted from the single PMUT array, a complete flow sensing system is built by using the cross-correlation method and cosine interpolation, whereby the change in flow rate is reflected by the time of flight difference (dTof) recorded at the receiver. Meanwhile, the acoustic path self-calibration is realized by using multiple echoes. Compared with the previously reported MEMS flowmeters with dual or multiple PMUT devices, this paper proposes a single PMUT array flow sensing system, which is able to measure the flow rate changes up to 4 m3/h. With the implementation of a single device, the problem of ultrasound device/reflector misalignment during system setup is completely eradicated

Homologous Compounds Zn_<i>n</i>In₂O_3<i>+n</i> (<i>n</i> = 4, 5, and 7) Containing Laminated Functional Groups as Efficient Photocatalysts for Hydrogen Production

Strong visible light absorption and high charge mobility are desirable properties for an efficient photocatalyst, yet they are hard to be realized simultaneously in a single semiconductor compound. In this work, we demonstrate that these properties coexist in homologous compounds Zn_<i>n</i>In₂O_3+<i>n</i> (<i>n</i> = 4, 5, and 7) with a peculiar layered structure that combines optical active segment and electrical conductive segment together. Their enhanced visible light absorption originates from tetrahedrally or trigonal-bipyramidally coordinated In atoms in Zn­(In)­O₄₍₅₎ layers which enable p–d hybridization between In 4d and O 2p orbitals so that valence band minimum (VBM) is uplifted with a reduced band gap. Theoretical calculations reveal their anisotropic features in charge transport and functionality of different constituent segments, i.e., Zn­(In)­O₄₍₅₎ layers and InO₆ layers as being for charge generation and charge collection, respectively. Efficient photocatalytic hydrogen evolution was observed in these compounds under full range (λ ≥ 250 nm) and visible light irradiation (λ ≥ 420 nm). High apparent quantum efficiency ∼2.79% was achieved for Zn₄In₂O₇ under full range irradiation, which is almost 5-fold higher than their parent oxides ZnO and In₂O₃. Such superior photocatalytic activities of these homologous compounds can be understood as layer-by-layer packing of charge generation/collection functional groups that ensures efficient photocatalytic reactions

Ultrathin Lanthanum Tantalate Perovskite Nanosheets Modified by Nitrogen Doping for Efficient Photocatalytic Water Splitting

Ultrathin nitrogen-doped perovskite nanosheets LaTa2O6.77N0.15- have been fabricated by exfoliating Dion-Jacobson-type layered perovskite RbLaTa2O6.77N0.15. These nanosheets demonstrate superior photocatalytic activities for water splitting into hydrogen and oxygen and remain active with photon wavelengths as far as 600 nm. Their apparent quantum efficiency under visible-light illumination (lambda >= 420 nm) approaches 1.29% and 3.27% for photocatalytic hydrogen and oxygen production, being, almost 4-fold and 8-fold higher than bulk RbLaTa2O6.77N0.15. Their outstanding performance likely stems from their tiny thickness (single perovskite slab) that essentially removes bulk charge diffusion steps and extends the lifetime of photogenerated charges. Theoretical calculations reveal a peculiar 2D charge transportation phenomenon in RbLaTa2O6.77N0.15; thus, exfoliating RbLaTa2O6.77N0.15 into LaTa2O6.77N0.15- nanosheets has limited impact on charge transportation properties but significantly enhances the surface areas which contributes to more reaction sites

AlScN Film Based Piezoelectric Micromechanical Ultrasonic Transducer for an Extended Long-Range Detection

Piezoelectric micromachined ultrasonic transducers (PMUTs) have been widely applied in distance sensing. However, the sensing distance of currently reported miniaturized ultrasonic sensors (e.g., PMUTs or CMUT) is still limited up to a certain range (e.g., &le;5 m) compared to conventional bulk ultrasonic devices. This paper reports a PMUT array design using scandium-doped aluminum nitride (AlScN) as its piezoelectric layer for an extended long-range detection purpose. To minimize air attenuation, our device is resonating at 66 kHz for a high receive sensitivity of 5.7 mV/Pa. The proposed PMUT array can generate a sound pressure level (SPL) as high as 120 dB at a distance of 10 cm without beam forming. This PMUT design is catered for a pin-to-pin replacement of the current commercial bulk ultrasonic ranging sensor and works directly with the conventional range finding system (e.g., TI PGA460). In comparison with the common bulk transducer, the size of our device is 80% smaller. With the identical ranging detection setup, the proposed PMUT array improves the system SNR by more than 5 dB even at a distance as far as 6.8 m. The result of extended sensing distance validates our miniaturized PMUT array as the optimized candidate for most ultrasonic ranging applications. With the progressive development of piezoelectric MEMS, we believe that the PMUT technology could be a game changer in future long-range sensing applications

Bimorph Dual-Electrode ScAlN PMUT with Two Terminal Connections

This paper presents a novel bimorph Piezoelectric Micromachined Ultrasonic Transducer (PMUT) fabricated with 8-inch standard CMOS-compatible processes. The bimorph structure consists of two layers of 20% scandium-doped aluminum nitride (Sc0.2Al0.8N) thin films, which are sandwiched among three molybdenum (Mo) layers. All three Mo layers are segmented to form the outer ring and inner plate electrodes. Both top and bottom electrodes on the outer ring are electrically linked to the center inner plate electrodes. Likewise, the top and bottom center plate electrodes are electrically connected to the outer ring in the same fashion. This electrical configuration maximizes the effective area of the given PMUT design and improves efficiency during the electromechanical coupling process. In addition, the proposed bimorph structure further simplifies the device&rsquo;s electrical layout with only two-terminal connections as reported in many conventional unimorph PMUTs. The mechanical and acoustic measurements are conducted to verify the device&rsquo;s performance improvement. The dynamic mechanical displacement and acoustic output under a low driving voltage (1 Vpp) are more than twice that reported from conventional unimorph devices with a similar resonant frequency. Moreover, the pulse-echo experiments indicate an improved receiving voltage of 10 mV in comparison with the unimorph counterpart (4.8 mV). The validation of device advancement in the electromechanical coupling effect by using highly doped ScAlN thin film, the realization of the proposed bimorph PMUT on an 8-inch wafer paves the path to production of next generation, high-performance piezoelectric MEMS

Synergistic path planning for ship-deployed multiple UAVs to monitor vessel pollution in ports

Traditionally, vessel air emissions are monitored onboard vessels or at fixed points at sea. These methods ineffectively meet the needs of monitoring pollution from vessels travelling. Unmanned aerial vehicles (UAVs) equipped with pollution monitoring sensors are becoming a research focus. However, due to battery capacity constraints, the monitoring scope of UAVs is still not optimal. Thus, using a ship (such as a patrol ship) as a UAV mobile supply base can overcome battery limitations and increase monitoring coverage. This paper investigates the joint routing and scheduling problem of ship-deployed multiple UAVs (SDMU) for the monitoring of pollution from vessels.The artificial bee colony (ABC) algorithm based on simulated annealing is employed to minimize the total monitoring time. The model and solution algorithm are verified by real-time dynamic vessel data from Tianjin Port

Application of Ion mobility Spectrometry and the derived collision Cross Section in the Analysis of Environmental Organic Micropollutants

Ion mobility spectrometry (IMS) is a rapid gas-phase separation technique, which can distinguish ions on the basis of their size, shape, and charge. The IMS-derived collision cross section (CCS) can serve as additional identification evidence for the screening of environmental organic micropollutants (OMPs). In this work, we summarize the published experimental CCS values of environmental OMPs, introduce the current CCS prediction tools, summarize the use of IMS and CCS in the analysis of environmental OMPs, and finally discussed the benefits of IMS and CCS in environmental analysis. An up-to-date CCS compendium for environmental contaminants was produced by combining CCS databases and data sets of particular types of environmental OMPs, including pesticides, drugs, mycotoxins, steroids, plastic additives, per- and polyfluoroalkyl substances (PFAS), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), as well as their well-known transformation products. A total of 9407 experimental CCS values from 4170 OMPs were retrieved from 23 publications, which contain both drift tube CCS in nitrogen (DTCCSN2) and traveling wave CCS in nitrogen (TWCCSN2). A selection of publicly accessible and in-house CCS prediction tools were also investigated; the chemical space covered by the training set and the quality of CCS measurements seem to be vital factors affecting the CCS prediction accuracy. Then, the applications of IMS and the derived CCS in the screening of various OMPs were summarized, and the benefits of IMS and CCS, including increased peak capacity, the elimination of interfering ions, the separation of isomers, and the reduction of false positives and false negatives, were discussed in detail. With the improvement of the resolving power of IMS and enhancements of experimental CCS databases, the practicability of IMS in the analysis of environmental OMPs will continue to improve