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Recommendations for processing atmospheric attenuated backscatter profiles from Vaisala CL31 ceilometers
摘要： Ceilometer lidars are used for cloud base height detection, to probe aerosol layers in the atmosphere (e.g. detection of elevated layers of Saharan dust or volcanic ash), and to examine boundary layer dynamics. Sensor optics and acquisition algorithms can strongly influence the observed attenuated backscatter profiles; therefore, physical interpretation of the profiles requires careful application of corrections. This study addresses the widely deployed Vaisala CL31 ceilometer. Attenuated backscatter profiles are studied to evaluate the impact of both the hardware generation and firmware version. In response to this work and discussion within the CL31/TOPROF user community (TOPROF, European COST Action aiming to harmonise ground-based remote sensing networks across Europe), Vaisala released new firmware (versions 1.72 and 2.03) for the CL31 sensors. These firmware versions are tested against previous versions, showing that several artificial features introduced by the data processing have been removed. Hence, it is recommended to use this recent firmware for analysing attenuated backscatter profiles. To allow for consistent processing of historic data, correction procedures have been developed that account for artefacts detected in data collected with older firmware. Furthermore, a procedure is proposed to determine and account for the instrument-related background signal from electronic and optical components. This is necessary for using attenuated backscatter observations from any CL31 ceilometer. Recommendations are made for the processing of attenuated backscatter observed with Vaisala CL31 sensors, including the estimation of noise which is not provided in the standard CL31 output. After taking these aspects into account, attenuated backscatter profiles from Vaisala CL31 ceilometers are considered capable of providing valuable information for a range of applications including atmospheric boundary layer studies, detection of elevated aerosol layers, and model verification.
关键词： attenuated backscatter,aerosol layers,model verification,atmospheric boundary layer,ceilometer,Vaisala CL31,lidar
更新于2025-09-04 15:30:14
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Spectral analysis of atmospheric composition: application to surface ozone model-measurement comparisons
摘要： Models of atmospheric composition play an essential role in our scientific understanding of atmospheric processes and in providing policy strategies to deal with societally relevant problems such as climate change, air quality and ecosystem degradation. The fidelity of these models needs to be assessed against observations to ensure that errors in model formulations are found and that model limitations are understood. A range of approaches are necessary for these comparisons. Here, we apply a spectral analysis methodology for this comparison. We use the Lomb-Scargle Periodogram, a method similar to a Fourier transform, but better suited to dealing with the gapped data sets typical of observational data. We apply this methodology to long-term hourly ozone observations and the equivalent model (GEOS-Chem) output. We show that the spectrally transformed observational data shows a distinct power spectrum with regimes indicative of meteorological processes (weather, macroweather) and specific peaks observed at the daily and annual timescales together with corresponding harmonic peaks at half, third etc. of these frequencies. Model output shows corresponding features. A comparison between the amplitude and phase of these peaks introduces a new comparison methodology between model and measurements. We focus on the amplitude and phase of diurnal and seasonal cycles and present observational/model comparisons and discuss model performance. We find large biases notably for the seasonal cycle in the mid-latitude northern hemisphere where the amplitudes are generally overestimated by up to 16 ppb, and phases are too late on the order of 1-5 months. This spectral methodology can be applied to a range of model-measurement applications and is highly suitable for Multimodel Intercomparison Projects (MIPs).
关键词： Lomb-Scargle Periodogram,ozone,spectral analysis,GEOS-Chem,model-measurement comparisons,atmospheric composition
更新于2025-09-04 15:30:14
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Constitutive modeling of polarization relaxation behavior in ferroelectrics
摘要： A thermodynamically consistent model is formulated to depict the polarization hysteresis and the rate-dependent behavior of relaxation in ferroelectric materials. On the relaxation condition, the polarization gradually changes with time while the applied electric field is kept constant. The present model introduces internal state variables to represent such irreversible dissipation processes. Based on the first and second laws of thermodynamics, the evolution laws of the internal state variables consisting of constitutive equations are then derived through the definitions of the Helmholtz free energy and a dissipation potential. To verify the applicability of the constitutive model, numerical simulations are compared with experiment in the literature.
关键词： Constitutive model,Polarization relaxation,Ferroelectric material,Hysteresis
更新于2025-09-04 15:30:14
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The role of cloud contamination, aerosol layer height and aerosol model in the assessment of the OMI near-UV retrievals over the ocean
摘要： Retrievals of aerosol optical depth (AOD) at 388 nm over the ocean from the Ozone Monitoring Instrument (OMI) two-channel near-UV algorithm (OMAERUV) have been compared with independent AOD measurements. The analysis was carried out over the open ocean (OMI and MODerate-resolution Imaging Spectrometer (MODIS) AOD comparisons) and over coastal and island sites (OMI and AERONET, the AErosol RObotic NETwork). Additionally, a research version of the retrieval algorithm (using MODIS and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) information as constraints) was utilized to evaluate the sensitivity of the retrieval to different assumed aerosol properties.
关键词： MODIS,CALIOP,aerosol layer height,aerosol model,AERONET,OMI,aerosol optical depth,cloud contamination
更新于2025-09-04 15:30:14
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Intrinsic correlation between electronic structure and degradation: from few layers to bulk black phosphorus
摘要： Black phosphorus (BP) has received much attention due to its fascinating properties, such as a high mobility and tunable band gap which covers the band gap lacuna between graphene and transition metal dichalcogenides. However, these advantages have been overshadowed due to the fast degradation of BP in ambient conditions. To overcome this obstacle, the degradation mechanisms should be unveiled with direct observation followed by a thorough analysis. Here, we reveal two sequential degradation processes and layer-dependent degradation rates of BP under dark conditions by scanning Kelvin probe microscopy (SKPM) measurements and theoretical modeling. The layer-dependent degradation is successfully interpreted with the oxidation model based on the Marcus-Gerischer theory (MGT). Under dark conditions, the electron transfer rate from BP to oxygen molecule depends on the number of layers that give different carrier concentrations. The oxidation rate is strongly dependent on the number of layers, and thus carrier concentrations. This suggests the possibility of stability improvement by carrier modulation. This work not only provides a deeper understanding of the degradation mechanism itself but also suggest new strategies for stable BP-based electronics design.
关键词： oxidation model,work function,degradation,black phosphorus,Marcus-Gerischer theory
更新于2025-09-04 15:30:14
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A NEW PHOTOBIOMODULATION TECHNIQUE PRODUCES A NEUROPROTECTIVE EFFECT ON AMYLOID Aβ25-35 PEPTIDE INDUCED TOXICITY IN MICE BY SYNERGISTIC MECHANISMS WHEN APPLIED BOTH ON THE HEAD AND ABDOMEN
摘要： In this work the effect of the weak combined MFs was studied in vivo in heritable animal model of AD: well characterized mice transgenic for mutant APPswe and mutant presenilin 1 (PS1dE9) that cause early onset familial Alzheimer’s disease (AD). Transgenic mice (Tg) and control C3H mice were exposed to the same MF at age of 8 months. Mice were also exposed by MF in two groups at the same time (Tg+MF and C3H+MF). A setup for generating a MF consisted of two pairs of coaxial Helmhollz coils oriented along the geomagnetic ?eld vector. A direct current was supplied to one of the pairs of coils to generate a constant component of MF with induction of 42 mcT. An alternating current signal produced by a programmable sinusoidal current generator was fed to other pair of coils to create a variable component of MF with induction of amplitude of 80 nT. The current signal was the sum of two signals with frequencies of 4.38 and 4.88 Hz. Estimation of amyloid plaque loads was performed by counting amyloid plaques, staining with thio?avine S, of the next brain areas: in the CA1 and CA3 ?elds of the hippocampus and temporal cortex of Tg mice. The effect of MFs on Ab deposits was revealed in Tg mice. That Tg+MF group showed the decreased density of plaques with small and middle sizes in the cortex and with large and middle size in the CA3, the ?eld of the hippocampus. In CA1 ?eld the tendency of the increase of small plaques was observed followed by a decrease of density of plaques with middle sizes. Thus, the data suggest that MFs can be applied for preventive purposes in a group of risk of AD.
关键词： animal model,weak combined magnetic fields,Alzheimer’s disease,amyloid-b
更新于2025-09-04 15:30:14
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Enhanced Dickson voltage multiplier rectenna by developing analytical model for radio frequency harvesting applications
摘要： Radio frequency (RF) energy harvesting has experienced a rapid development recently because of the increasing number of RF transmitter sources. This article illustrates a novel analytical model for the voltage multiplier rectifier at 900 MHz. The model proposes a method of deriving the output characteristics of the rectifying circuits in terms of two main parameters; voltage and current. The design consists of seven stages of Dickson voltage multiplier rectifier. A Schottky diode HSMS 285C was used in the design. Equations for the model were developed. These equations were used to extract the values of output voltage and current. A simulation was optimized using advanced design systems. The system was correspondingly fabricated and tested for input power range of 1 × 10?5-1 × 10?1 W. Experimental results show that an output voltage of 5.45 V and current of 1.26 × 10?5 A are achieved at 10 dBm using a 10 kΩ load, achieving an efficiency of 37.82%.
关键词： analytical model,Dickson voltage multiplier rectifier,RF harvesting,rectenna
更新于2025-09-04 15:30:14
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Correlation between the structure and structural relaxation data for (GeSe2)y(Sb2Se3)1-y glasses
摘要： Combined calorimetric and structural study, employing the techniques of differential scanning calorimetry and Raman spectroscopy, was performed to describe the enthalpy relaxation processes in the (GeSe2)y(Sb2Se3)1-y chalcogenide glasses. The full glass forming compositional region (y = 0.3–0.9) was explored. The enthalpy relaxation was described in terms of the phenomenological Tool-Narayanaswamy-Moynihan model. Compositional evolution of the glass transition temperatures and relaxation activation energies was explained based on the changing average bond energies and overall interconnectivity of the glassy matrices. Resemblance between the activation energies of the relaxation processes and viscous flow was confirmed for all studied glasses. Non-linearity and non-exponentiality of the enthalpy relaxation were found to be invariant with composition. The structural relaxation kinetics as well as kinetic fragilities determined for the present (GeSe2)y(Sb2Se3)1-y glassy system were very similar to the results obtained earlier for the (GeS2)y(Sb2S3)1-y glasses, which can be attributed to the similarly constrained topology of the pseudo-binary compositional lines.
关键词： Enthalpy relaxation,Raman spectroscopy,TNM model,Ge-Sb-Se glasses,DSC
更新于2025-09-04 15:30:14
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Complex Systems Design & Management (Proceedings of the Ninth International Conference on Complex Systems Design & Management, CSD&M Paris 2018) || A Domain Model-Centric Approach for the Development of Large-Scale Office Lighting Systems
摘要： The high-tech system industry faces many challenges, such as continuously increasing system complexity, scale and customer demands. We address these challenges using a domain model-centric approach. This approach focuses on clear and formal system specifications, connected to a chain of automatic transformations for system analysis, including virtual prototyping, and system synthesis, e.g. code generation. We have applied the approach to the development of large-scale office lighting systems in order to reduce development effort and handle the complexity of system control.
关键词： virtual prototyping,system complexity,code generation,domain model-centric approach,large-scale office lighting systems
更新于2025-09-04 15:30:14
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Scalable heliostat calibration system (SHORT) - Calibrate a whole heliostat field in a single night
摘要： Efficient operation of a solar plant requires precise control of the solar field, in order to achieve the desired flux on the receiver. In order to do so, accurate knowledge about the relation between heliostat axis encoder values and the actual orientation of the reflective surface is essential. Such information is gained from heliostat calibration, making it an essential part of plant operation. Being able to perform such a calibration frequently allows maintaining high efficiency of the solar field, by compensating for drift or other deviations which can occur over time.Such a solution is imperative for using small sized heliostats, where the solar field potentially containstens or even hundreds of thousands of them.Even for whatever heliostat such a calibration allowsa more precise control on their aiming point leading to a better plant performance. The presented solution addresses this withan automatic procedure, which is able to calibrate a full solar field during one night by using cameras and artificial targets within the solar field. The method has been successfully tested at the Plataforma Solar de Almeria (PSA), showing that a beam accuracy of about 0.6 mrad can be achieved.
关键词： heliostat calibration,artificial targets,solar field,kinematic model,camera
更新于2025-09-04 15:30:14