59,197 research outputs found
A Corrected Proof of the Stochastic Verification Theorem within the Framework of Viscosity Solutions
No full textWe present a full and corrected proof of the stochastic verification theorem that was first obtained by Zhou, Yong, and Li [SIAM J. Control Optim., 35 (1997), pp. 243--253]
The origin of the X-ray-emitting plasma in the eastern edge of the Cygnus Loop
No full textThe Cygnus Loop is interacting with a protrusion of the cavity wall in its eastern edge (the XA region), where the X-ray emission is very bright. The complexity of the environment and the non-linear physical processes of the shock–cloud interaction make the origin of the X-ray emission still not well understood. Our purpose is to understand the physical origin of the X-ray emission in the XA region, addressing, in particular, the role of thermal conduction in the interaction process. We analysed two XMM–Newton data sets, performing image analysis and spatially resolved spectral analysis on a set of homogeneous regions. We applied a recently developed diagnostic tool to compare spectral analysis results with predictions of theoretical models, and to estimate the efficiency of thermal conduction on the X-ray-emitting shocked plasma. We found that the inhomogeneous cavity wall contains both large clumps (the protrusion) and small isolated clumps with different densities. A large indentation bent over to the south is detected. The abundance of the surrounding interstellar medium is ∼0.2 times solar value. We confirmed the important role of thermal conduction in the evolution of X-ray-emitting plasma during shock–cloud interaction
FIGURE 3. Carex daxinensis Y. Y. Zhou & X. F in Notes on Carex (Cyperaceae) from China: three new species
No full textFIGURE 3. Carex daxinensis Y. Y. Zhou & X. F. Jin, sp. nov. (A) habit; (B) staminate scale; (C) pistillate scale; (D) perigynium; (E) achene (drawn by Xiao-Feng Jin from holotype in HTC).Published as part of Zhou, Ying-Ying & Jin, Xiao-Feng, 2014, Notes on Carex (Cyperaceae) from China: three new species, pp. 133-140 in Phytotaxa 164 (2) on page 136, DOI: 10.11646/phytotaxa.164.2.7, http://zenodo.org/record/513266
On the almost intersections of transient Brownian motions
No full textLet {B^d_1 (t )} and {B^d_2 (t )} be independent Brownian motions in R^d starting from 0 and nx
respectively, and let w^d_i (a, b) = {x ∈ R^d : B^d_i (t ) = x for some t ∈ (a, b)}, i = 1, 2. Asymptotic
expressions as n → ∞ for the probability of dist(w^d_1
(n^2 t_1, n^2 t_2), w^d_2 (0, n^2 t_3)) = 4,
respectively for the probability of dist (w^4_1
(n^2 t_1, n^2 t_2),w^4_2 (0, n^2 t_3)) >= 1 are obtained. As an application,
an improvement of a result due to M. Aizenman concerning the intersections of Wiener
sausages in R^4 is presented
Erratum to "A corrected proof of the stochastic verification theorem within the framework of viscosity solutions"
No full textEvaluation of fracture mode classification in flawed red sandstone under uniaxial compression
No full textTo study the classification of fracture modes of rocks during the cracking process, uniaxial compression tests were conducted on intact and flawed red sandstone specimens. Meanwhile, both acoustic emission (AE) and digital image correlation (DIC) technologies were adopted to monitor and record the real-time cracking process of the specimens tested. In this study, the interevent time function F(τ) (AE events rate) was utilized to distinguish the transition from microcracking to macrocracking for the tested specimens. An AE parameter analysis method based on two indices of RA (rise time/amplitude) and AF (AE counts/duration) values was performed to classify the different cracking modes during the loading process. The classification results of the cracking modes coincide with the cracking type of macrocracks captured by the photographic system. Moreover, the adequacy of the crack classification was also evaluated by the kernel density estimation (KDE) function, a nonparametric density estimation method. KDE is used as a parametric model to overcome the randomness found in the data set generated by AE testing and can well identify and visualize the high concentration regions of RA and AF values. A continuous increase of RA values (more than 400 ms/v) can serve as an early warning for the ultimate failure of red sandstone. The results of this present investigation can be applied in the health monitoring of rock engineering
Creep mechanical properties and creep damage model of sandstone considering temperature effect based on acoustic emission
No full textThis work studies the creep mechanical properties and creep damage model of high-temperature heat treated sandstone. Acoustic emission (AE) technology is used to monitor the crack evolution of sandstone in uniaxial compression and creep experiments in real time. The influence of temperature on the mechanical properties of sandstone is analyzed through AE count, cumulative AE count, and AE absolute energy. The relationship between cumulative AE count and axial strain is discussed, and the cumulative AE count increases exponentially with increasing axial strain. Moreover, an appropriate damage evolution equation is established based on the cumulative AE count, and a nonlinear viscoelastic-plastic model capable of describing the decay creep, steady-stage creep, and accelerated creep stages of high-temperature heat treated sandstone is constructed. Through the model validation and parameter inversion, the new creep damage model can be employed to study the creep instability of geotechnical engineering under high temperature environment
An evidence-based framework for designing urban green infrastructure morphology to reduce urban building energy use in a hot-humid climate
No full textUrban green infrastructures (UGIs) play an essential role in reducing urban building energy consumption by cooling surrounding areas and shielding buildings from direct solar radiation heat gain. Although the energy-saving effect of UGIs is widely agreed upon, there is a lack of systematic knowledge about how UGI morphology affects urban building energy consumption. Consequently, an effective method to design UGI morphology to reduce urban building energy consumption in urban design is not available. A grading system was proposed to evaluate the strength of evidence for the findings and conclusions in studies that pertain to the cooling and energy-saving effects of UGI. The evidence-based literature review found that strategically designing the morphology of UGI, including its size, shape, location, connectivity, spatial pattern, and configuration, can effectively reduce the air temperature surrounding the UGI area and building energy demand. This study formulated a morphological design framework for UGI as part of the urban design process to reduce urban building energy consumption. Based on the evidence-based answers to the key questions in the framework, design strategies are provided as visual charts and technical principles. The study includes an urban design case in Nanjing, China, which applied this framework to achieve the goal of urban energy savings
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Drag reduction in a turbulent boundary layer using periodic blowing through one array of streamwise slits
No full textActive drag reduction of a turbulent boundary layer has been experimentally investigated using periodic blowing through one array of streamwise slits. Local skin-friction drag exhibits a strong dependence on control parameters, including the blowing amplitude A+ and frequency f +. A maximum drag reduction of almost 70% has been achieved at x+=33 downstream of the actuators. The near-wall structure under control are measured using smoke-wire flow visualization, hot-wire and PIV techniques. All the results point to a pronounced change in the structure of the boundary layer and a significant increase of the mean energy dissipation rate
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