3,607 research outputs found
The fragmentation instability of a black hole with global monopole under GUP
The fragmentation of black hole containing global monopole under GUP
is studied. We focus on that the black hole breaks into two parts. We derive
the entropies of the initial black hole and the broken parts while the
generalization of Heisenberg's uncertainty principle is introduced. We find
that the global monopole black hole keeps stable instead of breaking
because the entropy difference is negative without the generalization. The
fragmentation of the black hole will happen if the black hole entropies are
limited by the GUP and the considerable deviation from the general relativity
leads the case that the mass of one fragmented black hole is extremely small
and the other one is extremely large.Comment: 9 pages, 4 figure
CardioCam: Leveraging Camera on Mobile Devices to Verify Users While Their Heart is Pumping
With the increasing prevalence of mobile and IoT devices (e.g., smartphones, tablets, smart-home appliances), massive private and sensitive information are stored on these devices. To prevent unauthorized access on these devices, existing user verification solutions either rely on the complexity of user-defined secrets (e.g., password) or resort to specialized biometric sensors (e.g., fingerprint reader), but the users may still suffer from various attacks, such as password theft, shoulder surfing, smudge, and forged biometrics attacks. In this paper, we propose, CardioCam, a low-cost, general, hard-to-forge user verification system leveraging the unique cardiac biometrics extracted from the readily available built-in cameras in mobile and IoT devices. We demonstrate that the unique cardiac features can be extracted from the cardiac motion patterns in fingertips, by pressing on the built-in camera. To mitigate the impacts of various ambient lighting conditions and human movements under practical scenarios, CardioCam develops a gradient-based technique to optimize the camera configuration, and dynamically selects the most sensitive pixels in a camera frame to extract reliable cardiac motion patterns. Furthermore, the morphological characteristic analysis is deployed to derive user-specific cardiac features, and a feature transformation scheme grounded on Principle Component Analysis (PCA) is developed to enhance the robustness of cardiac biometrics for effective user verification. With the prototyped system, extensive experiments involving 25 subjects are conducted to demonstrate that CardioCam can achieve effective and reliable user verification with over 99% average true positive rate (TPR) while maintaining the false positive rate (FPR) as low as 4%
Effect of Repeated Thermal Shock on Mechanical Properties of ZrB 2
ZrB2-20 vol.% SiC-10 vol.% h-BN (particles) ceramic composites (ZSB) were fabricated by hot pressing under inert gas protected. ZSB samples with mean size 75 × 55 × 40 mm3 were heated using current heating method and then cooled down to low temperature by circulating water. ZSB samples repeatedly went through thermal shock with 10–50 times under various conditions, respectively. Diverse effects on residual strength of ZSB at different experiment conditions (temperatures, thermal shock times, and heating rates) were investigated. The test results indicated that the residual strength of specimen materials all reached the maximum while the temperature was 1600°C and thermal shock number was less than 50 times. Because ZSB samples could not stand the extremely serious hyperoxidation at very high temperature (1800°C), the residual strength of samples decreased sharply. At 1600°C, when the thermal shock times was 20, ZSB samples’ residual strength reached the maximum, but it decreased to the lowest point while the thermal shock times was 30. So we argued that the sensitive thermal shock number was 30. Finally, we analyzed the influences on samples residual strength generated by different heating rates at the same temperature and thermal shock number; the results showed that when heating rate was equal to cooling rate, the residual strength of specimen materials reached the maximum
Plane Constraints Aided Multi-Vehicle Cooperative Positioning Using Factor Graph Optimization
The development of vehicle-to-vehicle (V2V) communication facil-itates the
study of cooperative positioning (CP) techniques for vehicular applications.
The CP methods can improve the posi-tioning availability and accuracy by
inter-vehicle ranging and data exchange between vehicles. However, the
inter-vehicle rang-ing can be easily interrupted due to many factors such as
obsta-cles in-between two cars. Without inter-vehicle ranging, the other
cooperative data such as vehicle positions will be wasted, leading to
performance degradation of range-based CP methods. To fully utilize the
cooperative data and mitigate the impact of inter-vehicle ranging loss, a novel
cooperative positioning method aided by plane constraints is proposed in this
paper. The positioning results received from cooperative vehicles are used to
construct the road plane for each vehicle. The plane parameters are then
introduced into CP scheme to impose constraints on positioning solutions. The
state-of-art factor graph optimization (FGO) algo-rithm is employed to
integrate the plane constraints with raw data of Global Navigation Satellite
Systems (GNSS) as well as inter-vehicle ranging measurements. The proposed CP
method has the ability to resist the interruptions of inter-vehicle ranging
since the plane constraints are computed by just using position-related data. A
vehicle can still benefit from the position data of cooperative vehicles even
if the inter-vehicle ranging is unavaila-ble. The experimental results indicate
the superiority of the pro-posed CP method in positioning performance over the
existing methods, especially when the inter-ranging interruptions occur.Comment: 14 pages, 16 figures, IEEE trans on IT
Import technology sophistication and high-quality economic development: evidence from city-level data of China
This paper adopts five dimensions and 15 indexes of green development, people’s life, innovation ability, economic vitality and
coordinated development to establish an evaluation system of
high-quality economic development. It uses principal component
analysis to measure the economic high-quality development of
233 prefecture-level cities from 2003 to 2016, and empirically
studies the impact of import sophistication on China’s high-quality economic development. The results show that the increase in
the sophistication of imported technology can significantly promote the high-quality development of the regional economy, and
this effect is applicable to both imported intermediate and final
products. In regions with higher and lower levels of economic
development, eastern areas, and regions with high-quality development above 90% quantiles, the increase in imported technology content can significantly drive the high-quality development
of the local economy. However, it has a great negative impact on
the areas with a high-quality development index below 10%
quantile. The robustness and endogeneity check support the
above viewpoint. Further mechanism analysis shows that the final
product import competition and intermediate product import
spillover play a mediating role in the process of import sophistication affecting the high-quality economic development. The conclusion of this paper has important theoretical value and practical
significance for the use of import trade to achieve high-quality
economic development
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