Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar

Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4-6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tetheredballoon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2-3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds

Imaging Water Dissociation on TiO₂(110)

Scanning tunneling microscopy has been used to identify the adsorption site of H₂O on TiO₂(110)-(1 x 1) at 150 K, and to monitor the site of the dissociation products at 290 K. Water adsorbs onto the rows of fivefold coordinated Ti atoms at 150 K, dissociating by 290 K to form bridging but not terminal hydroxyls. This points to the involvement of bridging O vacancies in the dissociation pathway

On the Solution of Linear Programming Problems in the Age of Big Data

The Big Data phenomenon has spawned large-scale linear programming problems. In many cases, these problems are non-stationary. In this paper, we describe a new scalable algorithm called NSLP for solving high-dimensional, non-stationary linear programming problems on modern cluster computing systems. The algorithm consists of two phases: Quest and Targeting. The Quest phase calculates a solution of the system of inequalities defining the constraint system of the linear programming problem under the condition of dynamic changes in input data. To this end, the apparatus of Fejer mappings is used. The Targeting phase forms a special system of points having the shape of an n-dimensional axisymmetric cross. The cross moves in the n-dimensional space in such a way that the solution of the linear programming problem is located all the time in an "-vicinity of the central point of the cross.Comment: Parallel Computational Technologies - 11th International Conference, PCT 2017, Kazan, Russia, April 3-7, 2017, Proceedings (to be published in Communications in Computer and Information Science, vol. 753

Destination image in travel magazines: A textual and pictorial analysis of Hong Kong and Macau

Based on the analyses of texts and pictures in the top six outbound travel magazines in Mainland China, this article presents an evaluation of the destination images of Hong Kong and Macau as portrayed in 88 travel articles over a three-year period. The results showed that the projected destination images of Hong Kong and Macau were dominated by attributes related to culture, history, and art and leisure and recreation. Hong Kong was often described by image attributes such as places and attractions, shopping, cuisine and food, hotels, and the creative industries. For Macau, history and heritage, places and attractions, gambling, cuisine and food, and hotels were the most often reported. During the study period, Hong Kong and Macau witnessed several significant changes in the image attributes featured in both texts and pictures. These changes were partly influenced by news and events over the period. In this article, implications for destination marketing organizations and directions for future research were suggested

Online and offline heuristics for inferring hierarchies of repetitions in sequences

Hierarchical dictionary-based compression schemes form a grammar for a text by replacing each repeated string with a production rule. While such schemes usually operate online, making a replacement as soon as repetition is detected, offline operation permits greater freedom in choosing the order of replacement. In this paper, we compare the online method with three offline heuristics for selecting the next substring to replace: longest string first, most common string first, and the string that minimized the size of the grammar locally. Surprisingly, two of the offline techniques, like the online method, run in time linear in the size of the input. We evaluate each technique on artificial and natural sequences. In general, the locally-most-compressive heuristic performs best, followed by most frequent, the online technique, and, lagging by some distance, the longest-first technique

Duration and breaks in sedentary behaviour: Accelerometer data from 1566 community-dwelling older men (British Regional Heart Study)

Background: Sedentary behaviours are increasingly recognised as raising risk of CVD events, diabetes and mortality, independently of physical activity (PA) levels. However, little is known about patterns of sedentary behaviour in older adults. Methods: Cross sectional study of 1566/3137 (50% response) men aged 71-91 years from a UK population-based cohort study. Men wore a GT3x accelerometer over the hip for one week in 2010-11. Mean daily minutes of SB, % of day in sedentary behaviours, sedentary bouts and breaks were calculated and summarized by health and demographic characteristics. Results: 1403 ambulatory men aged 78.4 years (SD 4.6 years) with ≥600 minutes of accelerometer wear on ≥3 days had complete data on covariables. Men spent on average 618 minutes (SD=83), or 72% of their day in sedentary behaviours (<100 counts/minute). On average men accumulated 72 spells of sedentary behaviours per day, with 7 breaks in each sedentary hour. Men had on average 5.1 sedentary bouts of ≥30 minutes, which accounted for 43% of sedentary time, and 1.4 bouts of ≥60 minutes, which accounted for 19% of daily sedentary time. Men who were over 80 years old, obese, depressed and had multiple chronic conditions accumulated more sedentary time and spent more time in longer sedentary bouts. Conclusions: Older men spend nearly three quarters of their day in sedentary behaviours, mostly accumulated in short bouts, although bouts lasting ≥30 minutes accounted for nearly half of the sedentary time each day. Men with medical risk factors were more likely to also display sedentary behaviour

Stochastics theory of log-periodic patterns

We introduce an analytical model based on birth-death clustering processes to help understanding the empirical log-periodic corrections to power-law scaling and the finite-time singularity as reported in several domains including rupture, earthquakes, world population and financial systems. In our stochastics theory log-periodicities are a consequence of transient clusters induced by an entropy-like term that may reflect the amount of cooperative information carried by the state of a large system of different species. The clustering completion rates for the system are assumed to be given by a simple linear death process. The singularity at t_{o} is derived in terms of birth-death clustering coefficients.Comment: LaTeX, 1 ps figure - To appear J. Phys. A: Math & Ge

Study of Turbulent Premixed Flame Propagation using a Laminar Flamelet Model

The laminar flamelet concept in turbulent reacting flows is considered applicable to many practical combustion systems (Linan & Williams 1993). For turbulent premixed combustion, the laminar flamelet regime is valid when turbulent Karlovitz number is less than unity, which is equivalent to stating that the characteristic thickness of the flame is less than that of a Kolmogorov eddy; this is known as the Klimov-Williams criterion (Williams 1985). In such a case, the flame maintains its laminar structure, and the effect of turbulent flow is merely to wrinkle and strain the flame front. The propagating wrinkled premixed flame can then be described as an infinitesimally thin surface dividing the unburnt fresh mixture and the burnt product