On the relationship between low cloud variability and lower tropospheric stability in the Southeast Pacific

In this study, we examine marine low cloud cover variability in the Southeast Pacific and its association with lower-tropospheric stability (LTS) across a spectrum of timescales. On both daily and interannual timescales, LTS and low cloud amount are very well correlated in austral summer (DJF). Meanwhile in winter (JJA), when ambient LTS increases, the LTS–low cloud relationship substantially weakens. The DJF LTS–low cloud relationship also weakens in years with unusually large ambient LTS values. These are generally strong El Niño years, in which DJF LTS values are comparable to those typically found in JJA. Thus the LTS–low cloud relationship is strongly modulated by the seasonal cycle and the ENSO phenomenon. We also investigate the origin of LTS anomalies closely associated with low cloud variability during austral summer. We find that the ocean and atmosphere are independently involved in generating anomalies in LTS and hence variability in the Southeast Pacific low cloud deck. This highlights the importance of the physical (as opposed to chemical) component of the climate system in generating internal variability in low cloud cover. It also illustrates the coupled nature of the climate system in this region, and raises the possibility of cloud feedbacks related to LTS. We conclude by addressing the implications of the LTS–low cloud relationship in the Southeast Pacific for low cloud feedbacks in anthropogenic climate change

A refined invariant subspace method and applications to evolution equations

The invariant subspace method is refined to present more unity and more diversity of exact solutions to evolution equations. The key idea is to take subspaces of solutions to linear ordinary differential equations as invariant subspaces that evolution equations admit. A two-component nonlinear system of dissipative equations was analyzed to shed light on the resulting theory, and two concrete examples are given to find invariant subspaces associated with 2nd-order and 3rd-order linear ordinary differential equations and their corresponding exact solutions with generalized separated variables.Comment: 16 page

Hot electrons in low-dimensional phonon systems

A simple bulk model of electron-phonon coupling in metals has been surprisingly successful in explaining experiments on metal films that actually involve surface- or other low-dimensional phonons. However, by an exact application of this standard model to a semi-infinite substrate with a free surface, making use of the actual vibrational modes of the substrate, we show that such agreement is fortuitous, and that the model actually predicts a low-temperature crossover from the familiar T^5 temperature dependence to a stronger T^6 log T scaling. Comparison with existing experiments suggests a widespread breakdown of the standard model of electron-phonon thermalization in metals

Unsupervised Diverse Colorization via Generative Adversarial Networks

Colorization of grayscale images has been a hot topic in computer vision. Previous research mainly focuses on producing a colored image to match the original one. However, since many colors share the same gray value, an input grayscale image could be diversely colored while maintaining its reality. In this paper, we design a novel solution for unsupervised diverse colorization. Specifically, we leverage conditional generative adversarial networks to model the distribution of real-world item colors, in which we develop a fully convolutional generator with multi-layer noise to enhance diversity, with multi-layer condition concatenation to maintain reality, and with stride 1 to keep spatial information. With such a novel network architecture, the model yields highly competitive performance on the open LSUN bedroom dataset. The Turing test of 80 humans further indicates our generated color schemes are highly convincible

How does the driver's Perception Reaction Time affect the performances of crash surrogate measures?

© 2015 Kuang et al. With the merit on representing traffic conflict through examining the crash mechanism and causality proactively, crash surrogate measures have long been proposed and applied to evaluate the traffic safety. However, the driver's Perception-Reaction Time (PRT), an important variable in crash mechanism, has not been considered widely into surrogate measures. In this regard, it is important to know how the PRT affects the performances of surrogate indicators. To this end, three widely used surrogate measures are firstly modified by involving the PRT into their crash mechanisms. Then, in order to examine the difference caused by the PRT, a comparative study is carried out on a freeway section of the Pacific Motorway, Australia. This result suggests that the surrogate indicators' performances in representing rear-end crash risks are improved with the incorporating of the PRT for the investigated section

Influence of long-range cation order on relaxor properties of doped Pb(Mg1/3Nb2/3)O3 ceramics

The 1:1 B-site cation order in Pb(Mg1/3Nb2/3)O3 relaxor ferroelectric ceramics was significantly enhanced by doping of minor amounts of La3+, Sc3+, or W6+ (less than 3 at. %) combined with a slow cooling procedure. Transmission electron microscopy examination confirmed the size increase of the cation-ordered regions embedded in a disordered matrix in the samples that were slowly cooled after sintering. The average cation ordering parameter (S) determined from x-ray diffraction data in these partially ordered samples was about 0.3–0.4. The ferroelectric properties and dielectric relaxation were compared in partially ordered and disordered (S=0) samples with the same composition. It was found that typical relaxor behavior was preserved in partially ordered ceramics. Furthermore, the temperature and diffuseness of the characteristic relaxor permittivity peak and the parameters of dielectric relaxation (in particular, the distribution of relaxation times and the Vogel-Fulcher freezing temperature) were practically independent of S. In contrast, the diffuseness of the phase transition from the ferroelectric phase (induced by external electric field) to the ergodic relaxor phase appeared to be much larger in the disordered samples than in the partially ordered ones (this diffuseness was assessed using pyroelectric current and ferroelectric hysteresis loops). These results suggest that cation ordering did not influence the behavior of polar nanoregions which are responsible for the dielectric response in the ergodic relaxor phase but significantly influenced the ferroelectric phase transition. The results are interpreted in terms of different types of polar regions in the disordered matrix and cation-ordered domains

Electric field-induced phase transitions in (111)-, (110)-, and (100)-oriented Pb(Mg1∕3Nb2∕3)O3 single crystals

Electric field-induced phase transitions were investigated in (111), (110), and (100) thin platelets of relaxor ferroelectric Pb(Mg1∕3Nb2∕3)O3 single crystals with electric fields applied along the ⟨111⟩, ⟨110⟩, and ⟨100⟩ directions, respectively. Temperature dependences of complex dielectric permittivity, pyroelectric current and dielectric hysteresis loops were investigated. Electric field-temperature (E-T) phase diagrams were proposed for the different directions of the field. Alongside with the high-temperature ergodic relaxor phase and the low-temperature glassy nonergodic relaxor phase existing at E=0, the ferroelectric phase may appear in the diagram at the fields higher than the threshold field (Eth). The temperature of the first-order transition between ergodic relaxor and ferroelectric phases (TC) was located in field cooling and field heating after field-cooling regimes. For the ⟨111⟩ field direction, TC is higher and Eth is lower than for the other directions. For the ⟨100⟩ direction, TC is the lowest and Eth is the highest. The critical point bounding the TC(E) line when the field is applied in ⟨111⟩ direction [ Z. Kutnjak, J. Petzelt and R. Blinc Nature 441 956 (2006)] is not observed in the ⟨110⟩ and ⟨100⟩ directions up to the highest applied field of 7.5 kV∕cm. Extrapolation of experimental data suggests that the critical point for the ⟨110⟩ and ⟨100⟩ directions (if any) can be expected only at much higher fields. In the hysteresis loops experiments performed after zero-field cooling, the lower temperature limit is determined above which a ferroelectric phase can be induced from the frozen glassy state at a given field strength or the polarization of the induced ferroelectric phase can be reversed. This limit is located at much lower temperatures in the (100) platelet than in the (110) or (111) platelets. An additional ferroelectric rhombohedral to ferroelectric orthorhombic phase transition occurs in the (110) platelet at high electric fields (∼20 kV∕cm). The mechanisms of the field-induced transformation from the glassy nonergodic relaxor phase or the ergodic relaxor phase to the ferroelectric phase are discussed

Synergistic interactions between wear and corrosion of Ti-16Mo orthopedic alloy

In this study, corrosion, wear, and tribocorrosion of Ti-16Mo alloy manufactured by powder metallurgy (PM) in phosphate-buffered saline are investigated. The results indicate that the corrosion rate of Ti-16Mo alloy increases about 100 times from 0.00009 mm/yr to 0.00851 mm/yr under the tribocorrosion condition. Also, corrosion accelerates wear loss, and wear increment rate due to the corrosion (4.7715 mm/yr) of Ti-16Mo alloy is about 40% of pure mechanical wear rate (11.78 mm/yr). Compared with as-cast pure Ti (23.70999 mm/yr) and Ti-6Al-4 V (17.12003 mm/yr), Ti-16Mo alloy exhibits the lowest materials loss of 16.56001 mm/yr making it become a promising alloy for bone-tissue applications

Design and performance evaluation of additively manufactured composite lattice structures of commercially pure Ti (CP–Ti)

Ti alloys with lattice structures are garnering more and more attention in the field of bone repair or regeneration due to their superior structural, mechanical, and biological properties. In this study, six types of composite lattice structures with different strut radius that consist of simple cubic (structure A), body-centered cubic (structure B), and edge-centered cubic (structure C) unit cells are designed. The designed structures are firstly simulated and analysed by the finite element (FE) method. Commercially pure Ti (CP–Ti) lattice structures with optimized unit cells and strut radius are then fabricated by selective laser melting (SLM), and the dimensions, microtopography, and mechanical properties are characterised. The results show that among the six types of composite lattice structures, combined BA, CA, and CB structures exhibit smaller maximum von-Mises stress, indicating that these structures have higher strength. Based on the fitting curves of stress/specific surface area versus strut radius, the optimized strut radius of BA, CA, and CB structures is 0.28, 0.23, and 0.30 mm respectively. Their corresponding compressive yield strength and compressive modulus are 42.28, 30.11, and 176.96 MPa, and 4.13, 2.16, and 7.84 GPa, respectively. The CP-Ti with CB unit structure presents a similar strength and compressive modulus to the cortical bone, which makes it a potential candidate for subchondral bone restorations

The effect of Cu content on corrosion, wear and tribocorrosion resistance of Ti-Mo-Cu alloy for load-bearing bone implants

In this study, the effects of Cu content on wear, corrosion, and tribocorrosion resistance of Ti-10Mo-xCu alloy were investigated. Results revealed that hardness of Ti-10Mo-xCu alloy increased from 355.1 ± 15.2 HV to 390.8 ± 17.6 HV by increasing Cu content from 0 % to 5 %, much higher than CP Ti (106.6 ± 15.1 HV) and comparable to Ti64 (389.7 ± 13.9 HV). With a higher Cu content, wear and tribocorrosion resistance of Ti-10Mo-xCu alloys were enhanced, and corrosion resistance showed an initial increase with a subsequent decrease. Wear mechanisms under pure mechanical wear and tribocorrosion conditions of Ti-10Mo-xCu alloys were a combination of delamination, abrasion and adhesion wear