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Halogen (F, Cl, Br, and I) concentrations for 129 loess samples from worldwide localities yield geometric means of 517 ± 53 μg/g F, 150 ± 20 μg/g Cl, 1.58 ± 0.16 μg/g Br, 1.16 ± 0.11 μg/g I (2 standard errors). These concentrations, notably for Br and I, are substantially higher than previous estimates for the average upper continental crystalline bedrocks, with enrichment factors of 1.3 +0.7/−0.4 (F), 1.8 +2.4/−0.8 (Cl), 3.8 +1.3/−1.0 (Br), and 39 +71/−16 (I) (95%confidence), documenting enrichment of halogens on the continental surface. These surface halogens are likely sourced from the oceans and may be influenced by climate fluctuations. Halogen ratios (Br/Cl, I/Cl, and Br/I) in loess are similar to those of organic-rich soils/sediments from both terrigenous and marine settings, suggesting that terrigenous and marine organic matter have indistinguishable halogen ratios. The Br/I ratios differ from those in the fine grained matrix of glacial diamictites, indicating that another process (beyond biological influence) is responsible for fractionating halogens in the upper continental crust. Using a mixing model, we calculate that over 80–90 % of loess originates from crystalline bedrocks, while the remainder (<10–20 %) derives from the halogen- and organic-rich sedimentary cover or other sources (e.g., marine aerosols). 

The shape of a foil undergoing a combined pitching heaving motion is critical to its design in applications that demand high efficiency and thrust. This study focuses on understanding of how the shape of a foil affects its propulsive performance. We perform two-dimensional numerical simulations of fluid flows around a flapping foil for different governing parameters in the range of biological swimmers and bio-inspired underwater vehicles. By varying the foil shape using a class-shape transformation method, we investigate a broad range of foil-like shapes. In the study, we also show consistent results with previous studies that a thicker leading-edge and sharper trailing-edge makes for a more efficient foil shape undergoing a flapping motion. In addition, we explain that the performance of the foil is highly sensitive to its shape, specifically the thickness of the foil between the 18th and 50th percent along the chord of the foil. Moreover, we elucidate the flow mechanisms behind variations in performance metrics, particularly focused on constructive interference between the vortices generated at the leading-edge with the trailing-edge vortex, as well as the pressure field differences that lead to higher power consumption in less efficient foil shapes. 

This paper presents the optimal study of a vernier-type axial-flux permanent-magnet (AFPM) machine, which has a high-polarity spoke-type PM rotor, a wound stator with a low number of coils, and a profiled stator. Both stators have profiled teeth to enhance the magnetic interaction between the rotor PM array and stator windings for torque production. Compared to the topology with two wound stators, the studied one has a smaller total axial length and is expected more suitable for applications where the space is limited in axial direction. Both topologies are optimized through 3-dimensional (3D) finite element analysis (FEA) by the combined design of experiments (DOE) based sensitivity analysis and surrogate-assisted multiobjective differential evolution (DE) algorithm. Key factors affecting the two objectives, i.e., total active material cost and total electromagnetic loss, are identified. The optimization results are presented and compared, providing practical guidelines for the optimal design and operation of such machines. The manufacturing aspects and their impacts on the electromagneticperformance are also discussed. 

Slotless and coreless machines with low inductance and low core losses are attractive for high speed and high power density applications. With the increase in fundamental frequency, typical drive implementations using conventional silicon-based devices are performance limited and also produce large current and torque ripples. This paper presents a systematic study of proposed drive configurations implemented with wide bandgap (WBG) devices in order to mitigate such issues for 2-phase very low inductance machines. Two inverter topologies, i.e., a dual H-bridge inverter with maximum redundancy and survivability and a 3-leg inverter for reduced cost, are considered. Feasible modulation schemes are derived based on theoretical analysis and the associated maximum output voltages are identified. Simulation and experimental results are provided to validate the feasibility of drive systems and the effectiveness of analysis. 

Coreless axial-flux permanent-magnet (AFPM) machines may be attractive options for high-speed and high-power density applications due to the elimination of core losses. In order to make full use of the advantages offered by these machines and avoid excessive eddy current losses in windings, advanced technologies for winding conductors need to be employed to suppress the eddy effect, such as the Litz wire and printed circuit board (PCB). In this paper, the best practices for designing Litz wire/PCB windings are discussed and a brief survey of state of the art PCB winding technology is provided. Three coreless AFPM machines are mainly considered. A design optimization procedure based on the multi-objective differential evolution algorithm and 3-dimensional (3D) finite element analysis (FEA) is proposed to take into account the ac winding losses of Litz wires and PCB traces in the machine design stage. Selected designs are being prototyped and will be tested with a customized test fixture. 

Because cloud storage services have been broadly used in enterprises for online sharing and collaboration, sensitive information in images or documents may be easily leaked outside the trust enterprise on-premises due to such cloud services. Existing solutions to this problem have not fully explored the tradeoffs among application performance, service scalability, and user data privacy. Therefore, we propose CloudDLP, a generic approach for enterprises to automatically sanitize sensitive data in images and documents in browser-based cloud storage. To the best of our knowledge, CloudDLP is the first system that automatically and transparently detects and sanitizes both sensitive images and textual documents without compromising user experience or application functionality on browser-based cloud storage. To prevent sensitive information escaping from on-premises, CloudDLP utilizes deep learning methods to detect sensitive information in both images and textual documents. We have evaluated the proposed method on a number of typical cloud applications. Our experimental results show that it can achieve transparent and automatic data sanitization on the cloud storage services with relatively low overheads, while preserving most application functionalities.