Retrieval of Aerosol Microphysical Properties from AERONET Photopolarimetric Measurements

Atmospheric aerosols play an important role in earth climate by scattering and absorbing solar and terrestrial radiation, and indirectly through altering the cloud formation, life- time, and radiative properties. However, accurate quantification of these effects is in no small part hindered by our limited knowledge about the particle size distribution (PSD) and refractive index, the aerosol microphysical properties essentially pertain to aerosol optical and cloud-forming properties. The research goal of this thesis is to obtain the aerosol microphysical properties of both fine and coarse modes from the polarimetric solar radiation measured by the SunPhotometer of the Aerosol Robotic Network (AERONET). We achieve so by (1) developing an inversion algorithm that integrates rigorous radiative transfer model with a statistical optimization approach, (2) conducting a sensitivity study and error budgeting exercise to examine the potential value of adding polarization to the current radiance-only inversion, and (3) performing retrievals using available AERONET polarimetric measurements. The results from theoretical information and error analysis indicate a remarkable increase in information by adding additional polarization into the inversion: an overall increase of 2–5 of degree of freedom for signal comparing with radiance-only measurements. Correspond- ingly, retrieval uncertainty can be reduced by 79% (57%), 76% (49%), 69% (52%), 66% (46%), and 49% (20%) for the fine-mode (coarse-mode) aerosol volume concentration, the effective radius, the effective variance, the real part of refractive index, and single scattering albedo (SSA), respectively, resulting in their retrieval errors of 2.3% (2.9%), 1.3% (3.5%), 7.2% (12%), 0.005 (0.035), and 0.019 (0.068). In real cases, we demonstrate that our retrievals are overall consistent with current AERONET operational inversions, but can offer mode-resolved refractive index and SSA with sufficient accuracy for the aerosol composed by spherical particles. Along with the polarimetric retrieval, we also performed radiance-only retrieval to reveal the improvements by adding polarization in the inversion. The comparison analysis indicates that with polar- ization, retrieval error can be reduced by over 50% in PSD parameters, by 10–30% in the refractive index, and by 10–40% in SSA, which is consistent with the theoretical results. Adviser: Jun Wan

External shocks in a small open economy: an evaluation of monetary policy rules

This paper evaluates several small open economy DSGE models and the impact of external shock spillovers on small open economies. We investigate five small economies (the UK, Australia, Canada, New Zealand and Taiwan) and find that the welfare consequences vary depending on key domestic economic variables, and the best interest-rate rule varies across models. Then we examine the performances of the four types of models, a preferred result has been found in a model which considers the country risk premium, as the best rule could be obtained as long as the selected parameters are calibrated for particular economies

A self-adaptive alarm method for tool condition monitoring based on Parzen window estimation

Tool condition monitoring (TCM) takes an important position in CNC manufacturing processes, especially in damages avoiding of working parts and CNC itself. This paper presents a self-adaptive alarm method using probability density functions estimated with the Parzen window based on current signals, which gives an adaptively and rapidly corresponding alarm when the cutting tool fracture occurs. A CNC with cutting tools was obtained by Guangzhou CNC Company for test purpose, and the relative experiments were done in the state key laboratory. Current signals of the spindle motor and the main feed motor were acquired during the tool life. A probability model estimated with the Parzen window is established for current data fusion to alarm adaptively. At the meantime, the acoustic emission (AE) signals were acquired for comparison purpose. Experimental results show that this technique is flexible and fast enough to be implemented in real time for online tool condition monitoring

Maximal Quantum Fisher Information in a Mach-Zehnder Interferometer without initial parity

Mach-Zehnder interferometer is a common device in quantum phase estimation and the photon losses in it are an important issue for achieving a high phase accuracy. Here we thoroughly discuss the precision limit of the phase in the Mach-Zehnder interferometer with a coherent state and a superposition of coherent states as input states. By providing a general analytical expression of quantum Fisher information, the phase-matching condition and optimal initial parity are given. Especially, in the photon loss scenario, the sensitivity behaviors are analyzed and specific strategies are provided to restore the phase accuracies for symmetric and asymmetric losses.Comment: 10 pages, 3 figure

Regional versus general anesthesia for different categories of caesarean deliveries amongst Chinese women: A retrospective cohort analysis

Purpose: To study anesthetic techniques utilized in various caesarian deliveries, justification for preference of general anesthesia, and failure of regional anesthesia in pregnant Chinese women. Methods: Clinical data for 512 Chinese women who successfully delivered through caesarian section were used in this analysis. Data comprising information on anesthetic techniques used, explanations for choice of general anesthesia, failure of regional anesthesia, and levels of supervision were collected and analyzed. Results: Ninety-four of the enrolled women delivered through caesarian category 1, while 112 women delivered via caesarian category 2. Deliveries in caesarian categories 3 and 4 applied to 84 and 222 women, respectively. General anesthesia was used for 219 women, but this procedure was refused by 106 women, while the physician chose it for 34 women. Thirty-six women opted for general anesthesia, while regional anesthesia was used in 293 women. Ten women needed a change from regional anesthesia to general anesthesia due to inadequate regional block, accelerated delivery, and other reasons. General anesthesia was preferred in 17 % of emergency categories, 40 % of semi-emergency categories, and 43 % of elective categories. Conclusion: Patient awareness, training of health professionals, and multi-disciplinary correspondence will be helpful to caregivers in making consensus decisions with respect to the best anesthesia technique for cesarean delivery

Polarimetric remote sensing in oxygen A and B bands: sensitivity study and information content analysis for vertical profile of aerosols

Theoretical analysis is conducted to reveal the information content of aerosol vertical profile in space-borne measurements of the backscattered radiance and degree of linear polarization (DOLP) in oxygen (O2) A and B bands. Assuming a quasi-Gaussian shape for aerosol vertical profile characterized by peak height H and half width y (at half maximum), the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used to simulate the Stokes fourvector elements of upwelling radiation at the top of atmosphere (TOA) and their Jacobians with respect to H and y. Calculations for different aerosol types and different combinations of H and values show that the wide range of gas absorption optical depth in O2 A and B band enables the sensitivity of backscattered DOLP and radiance at TOA to the aerosol layer at different altitudes. Quantitatively, DOLP in O2 A and B bands is found to be more sensitive to H and y than radiance, especially over the bright surfaces (with large visible reflectance). In many O2 absorption wavelengths, the degree of freedom of signal (DFS) for retrieving H (or y) generally increases with H (and y) and can be close to unity in many cases, assuming that the composite uncertainty from surface and aerosol scattering properties as well as measurements is less than 5%. Further analysis demonstrates that DFS needed for simultaneous retrieval of H and y can be obtained from a combined use of DOLP measurements at ~10–100 O2 A and B absorption wavelengths (or channels), depending on the specific values of H. The higher the aerosol layer, the fewer number of channels for DOLP measurements in O2 A and B bands are needed for characterizing H and . Future hyperspectral measurements of DOLP in O2 A and B bands are needed to continue studying their potential and their combination with radiance and DOLP in atmospheric window channels for retrieving the vertical profiles of aerosols, especially highly scattering aerosols, over land

Optimal measurements to access classical correlations of two-qubit states

We analyze the optimal measurements accessing classical correlations in arbitrary two-qubit states. Two-qubit states can be transformed into the canonical forms via local unitary operations. For the canonical forms, we investigate the probability distribution of the optimal measurements. The probability distribution of the optimal measurement is found to be centralized in the vicinity of a specific von Neumann measurement, which we call the maximal-correlation-direction measurement (MCDM). We prove that for the states with zero-discord and maximally mixed marginals, the MCDM is the very optimal measurement. Furthermore, we give an upper bound of quantum discord based on the MCDM, and investigate its performance for approximating the quantum discord.Comment: 8 pages, 3 figures, version accepted by Phys. Rev.