Effects of anisotropic composite skin on electrothermal anti-icing system

To study the effects of anisotropic thermal conductivity of composite aircraft skin on the heat transfer characteristics of electrothermal anti-icing system, the differential equation of anisotropic heat conduction was established using coordinate transformation of principal anisotropy axis. In addition, it was coupled with the heat and mass transfer model of the runback water film on the anti-icing surface to perform numerical simulation of the electrothermal anti-icing system. The temperature results of the vertical and cylindrical orthotropic thermal conduction in the rectangular and semi-cylindrical composite skin were consistent with those obtained by the traditional orthotropic model, which verified the anisotropic heat conduction model. The temperature distribution of anti-icing surface agreed well with the literature data, which validated the coupled heat and mass model of the runback water flow and the anisotropic skin. The anisotropic thermal conductivity of composite skin would make temperature change more gradual, and the effect was more significant where the curvature of the temperature curve was greater. However, the anti-icing surface of the electrothermal anti-icing system was slightly affected by the anisotropic heat conduction of the multilayered composite skin

Achievable efficiencies for probabilistically cloning the states

We present an example of quantum computational tasks whose performance is enhanced if we distribute quantum information using quantum cloning. Furthermore we give achievable efficiencies for probabilistic cloning the quantum states used in implemented tasks for which cloning provides some enhancement in performance.Comment: 9 pages, 8 figure

An adaptive weighting algorithm for accurate radio tomographic image in the environment with multipath and WiFi interference

Radio frequency device-free localization based on wireless sensor network has proved its feasibility in buildings. With this technique, a target can be located relying on the changes of received signal strengths caused by the moving object. However, the accuracy of many such systems deteriorates seriously in the environment with WiFi and the multipath interference. State-of-the-art methods do not efficiently solve the WiFi and multipath interference problems at the same time. In this article, we propose and evaluate an adaptive weighting radio tomography image algorithm to improve the accuracy of radio frequency device-free localization in the environment with multipath and different intensity of WiFi interference. Field experiments prove that our approach outperforms the state-of-the-art radio frequency device-free localization systems in the environment with multipath and WiFi interference

Evaporation/boiling heat transfer characteristics in an artery porous structure

Nucleate boiling is one of the most efficient and effective heat transfer modes, but is limited by the critical heat flux (CHF). An innovative artery porous structure was proposed in this work to enhance the CHF based on the concept of "phase separation and modulation" by forming individual flow paths for liquid supply and vapor venting while keeping the liquid/vapor interface located in the porous structure. In the experiment, the porous structure was made of sintered copper microparticles, multiple arteries were machined directly on the heated surface, and water was employed as the working fluid. The experimental results were compared with those on a flat surface, and a unique evaporation/boiling curve for the artery porous structure was revealed. The experiment validated the principle proposed here for CHF enhancement, and a maximum heat flux of 416 W/cm2 on a heating area of 0.78 cm2 was achieved without the occurrence of any dryout. Further increase of heat flux was limited only by the design temperature of the electrical heater, and a much higher CHF can be expected. In addition, the effects of pore size, artery depth and contact condition on the evaporation/boiling heat transfer performance in the artery porous structure were also experimentally investigated, which can guide further design optimizations of this novel structure

Does the Volatility of Volatility Risk Forecast Future Stock Returns?

This study investigates whether the forward-looking volatility of aggregate volatility (VOV) risk forecasts future stock returns in the US equity market. We find that stocks with higher sensitivities to changes in VOV constructed from VIX options have higher future returns than those with lower sensitivities. In particular, VOV constructed from deep out-of-the-money put options has the strongest predictive power, and the strongest predictability of VOV betas is found for investment horizons between 10-day to 1-month. Our findings are robust after considering estimation uncertainty of VOV betas and controlling for common pricing factors

Product Market Competition, Labor Mobility, and the Cross-Section of Stock Returns

This is the author accepted manuscript. The final version is available on open access from Oxford University Press via the DOI in this recordThis paper explores the impact of product market competition on the positive relation between labor mobility (LM) and future returns. We develop a production-based model and formalize the intuition that low exposure to systematic risk in a concentrated industry limits LM’s amplifying effect on operating leverage. Therefore, the model predicts a stronger positive relation between LM and expected returns for firms in competitive industries. Consistent with the model’s prediction, we empirically find that LM predicts returns only among firms in competitive industries. This evidence suggests that the intensity of competition in firms’ product market potentially drives the positive LM-return relation

Negative CT Contrast Agents for the Diagnosis of Malignant Osteosarcoma

© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The current positive computed tomography (CT) contrast agents (PCTCAs) including clinical iodides, present high CT density value (CT-DV). However, they are incapable for the accurate diagnosis of some diseases with high CT-DV, such as osteosarcoma. Because bones and PCTCAs around osteosarcoma generate similar X-ray attenuations. Here, an innovative strategy of negative CT contrast agents (NCTCAs) to reduce the CT-DV of osteosarcoma is proposed, contributing to accurate detection of osteosarcoma. Hollow mesoporous silica nanoparticles, loading ammonia borane molecules and further modified by polyethylene glycol, are synthesized as NCTCAs for the diagnosis of osteosarcoma. The nanocomposites can produce H2 in situ at osteosarcoma areas by responding to the acidic microenvironment of osteosarcoma, resulting in nearly 20 times reduction of CT density in osteosarcoma. This helps form large CT density contrast between bones and osteosarcoma, and successfully achieves accurate diagnosis of osteosarcoma. Meanwhile, The NCTCAs strategy greatly expands the scope of CT application, and provides profound implications for the precise clinical diagnosis, treatment, and prognosis of diseases

Improved Charge Separation and Photovoltaic Performance of BiI3 Absorber Layers by Use of an In Situ Formed BiSI Interlayer

Stable and nontoxic bismuth iodide (BiI3) is emerging as a promising absorber material for solar cell applications as it possesses favorable optical properties such as a narrow bandgap (1.7 eV) and a high absorption coefficient (105 cm–1) in the visible region. Despite these promising features, solar cells employing this material have only achieved power conversion efficiencies in the region of 1% as of yet, which is distant from the theoretical efficiency limit of 28%. It is reasonable to suppose that the relatively low performance of BiI3-based solar cells may originate from very short carrier lifetimes (180–240 ps) in BiI3, which makes efficient separation of mobile charges a crucial factor for the improvement of the photovoltaic performance of this material. Herein, transient optical spectroscopy is employed to show that the use of a bismuth sulfide iodide interlayer between the electron transport layer (ETL) and the bismuth iodide absorber promotes efficient charge separation. On the basis of this knowledge, we report BiI3 solar cells with a power conversion efficiency of 1.21% using a solar cell architecture comprised of ITO/SnO2/BiSI/BiI3/organic HTM/Au

Distributed fault estimation with randomly occurring uncertainties over sensor networks

This paper is concerned with the distributed fault estimation problem for a class of uncertain stochastic systems over sensor networks. The norm-bounded uncertainty enters into the system in a random way governed by a set of Bernoulli distributed white sequence. The purpose of the addressed problem is to design distributed fault estimators, via available output measurements from not only the individual sensor, but also its neighbouring sensors, such that the fault estimation error converges to zero exponentially in the mean square while the disturbance rejection attenuation is constrained to a give level by means of the H∞ performance index. Intensive stochastic analysis is carried out to obtain sufficient conditions for ensuring the exponential stability as well as prescribed H∞ performance for the overall estimation error dynamics. Simulation results are provided to demonstrate the effectiveness of the proposed fault estimation technique in this paper.This work was supported in part by the National Natural Science Foundation of China [ grant number 61329301], [grant number 61422301], [grant number 61374127]; the Outstanding Youth Science Foundation of Heilongjiang Province [grant number JC2015016]; the Alexander von Humboldt Foundation of Germany

Numerical simulation of aircraft thermal anti-icing system based on a tight-coupling method

Considering the influence of surface temperature distribution on air convective heat transfer coefficient, the robust tight-coupling method is firstly developed for aircraft thermal anti-icing simulations under icing conditions. To include the effects of the impinging water droplets on the conjugate heat transfer of thermal anti-icing systems, the Messinger thermodynamic model of runback water film is modified and added to the tightly coupled calculation of the external air flow and the internal solid skin heat conduction. Numerical simulations are carried out on an electro-thermal anti-icing system under both dry air and icing conditions, and the main conclusions below can be drawn. First, convective heat transfer coefficient changes slightly with surface temperature near the leading edge, but is obviously affected by temperature distribution in the downstream area. Second, the anti-icing temperature deviations between the predicted value and the experiment date are acceptable and comparable to the calculation results in the literature, verifying the feasibility and effectiveness of the tight-coupling method. Third, compared with the traditional decoupled loose-coupling method, the robust tight-coupling anti-icing method successfully captures the effect of surface temperature on convective heat transfer coefficient, and predicts higher temperature with lower drop rate on the downstream surfaces