Search

The shape of the "freezing tip" formed by the crystallization of water droplets demonstrated remarkable universality - no dependence on the cooling rate and physico-chemical properties of the substrate has been observed. At the same time, the spatial orientation of the freezing cone may be varied. We hypothesized that the orientation of the freezing tip is determined by the direction of heat flux at the base of the sessile droplet. This direction is expected to be changed when the substrate with a low thermal diffusivity is not cooled uniformly.We studied the freezing of water droplets placed on the inclined surface of wedges made from a variety of materials (polymers: Polymethylmethacrylate, Polytetrafluoroethylene, Polyurethane and metal: Titanium), which were cooled from below. The shape of the frozen droplets was controlled in situ.The computational model was suggested for the transient temperature field in the polymer wedge to determine a time variation of the local heat flux under the droplets. A comparison of numerical results and the measurements enabled us to confirm the aforementioned hypothesis relating the orientation of the freezing tips to the direction of the heat flux.It was established that the orientation of the freezing cone axis depends on the location of the frozen droplet on the inclined surface of the wedge. Calculations of the transient temperature field of the wedge confirmed our hypothesis about the physical reason of the various spatial orientations of the freezing cones.

Water condensation was studied on silanized (superhydrophobic) and fluorinated (superoleophobic) micro-rough aluminum surfaces of the same topography. Condensation on superhydrophobic surfaces occurred via film-wise mechanism, whereas on superoleophobic surfaces it was drop-wise. The difference in the pathways of condensation was attributed to the various energy barriers separating the Cassie and Wenzel wetting states on the investigated surfaces. The higher barriers inherent for superoleophobic surfaces promoted the drop-wise condensation. Triple-stage kinetics of growth of droplets condensed on superoleophobic surfaces is reported and discussed., 20 pages, 6 figures

Fluorescent nanomaterials of excellent optical properties have been widely used in fields ranging from bio-imaging, ions detection to solid-state lighting, displays and sensing. Recently, microfluidics have been proven to be an effective way to produce functional materials in nanometer scale with controllable morphology and customized properties in a continuous manner, providing an alternative approach for the synthesis of fluorescent nanomaterials. This review focuses on recent progress in the microfluidic fabrication of fluorescent nanomaterials. Firstly, based on the type of the energy coupling, the existing microfluidic configurations for synthesizing nanomaterials are summarized and categorized. Afterwards, typical examples are shown to demonstrate how fluorescent nanomaterials, including semiconductor nanocrystals, carbon dots, metal nanoparticles, rare earth doped nanophosphors, perovskite nanocrystals, and fluorescent oxide composites, are fabricated. Furthermore, the development directions of microfluidic-based nanofabrication in the future are prospected. Hopefully this review can serve as a guidance for both the scientific and industry research communities interested in this field.

The a priory unknown peculiarities of heat transfer in superheated hydrocarbons with water traces have been studied experimentally. The approach was based on the relative version of the method of controlled pulse heating of a wire probe at constant current mode. The pulse duration was varied in the range of 1–120 ms. A region of probe temperature rise was limited from above by the value of spontaneous boiling-up temperature of a substance. The objects of study were n-hexane, n-decane, and n-hexadecane. The water content was varied in the range from 5 ppm (initial sample) to 35 ppm (watered sample). A sharp increase in the heat transfer intensity for watered sample with respect to that of initial one has been revealed. The observed effect was manifested solely at temperatures close to the values of boiling-up temperature of watered sample.

We present a novel model of transient multiphase flow for gas-liquid mixtures in long pipelines. The study develops a general flexible formulation of a one-dimensional flow for complex multiphase mixtures in the presence of slip and mass exchange. Multi-fluid and drift-flux approaches are combined. The multi-fluid model governs the momentum balance for the fluids, and drift-flux correlations are used for modelling of the slip between individual components. A tree-like graph is introduced to describe the hierarchy of fluids and components within the mixture. The numerical implementation for an arbitrary number of components is based on the extension of the Semi-Implicit Method for Pressure-Linked Equations. Imbalances of equations are selected as criteria for iteration convergence. Specific corrections are discussed, including those proposed for the equilibrium gas-release model.

A Faraday fiber-optic current sensor with suppression of excess noise produced by a low-coherent light source is presented. The sensor is designed to detect short current pulses and represents an in-line interferometer with a sensing element based on a spun highly birefringent fiber. To suppress the excess noise, a two-channel light detection scheme without an additional delay line is applied. It is established that bending birefringence induced in the spun fiber wound on a coil limits the noise suppression. To minimize this effect, a new geometry of the sensing coil is used. The proposed sensor exhibits a 5-fold improvement of the signal-to-noise ratio and the same enhancement of the sensitivity to a value of 0.8A in the 3.5 MHz bandwidth. The minimum duration of the measured current pulse is 200 ns.

Russian Abstract: В настоящем препринте предлагается реконструкция индоевропейской филогении на основе тринадцати 110-словных списков для праязыков ИЕ-подгрупп (протогерманский, протославянский и т. д.) или древних языков соответствующих подгрупп (хеттский, древнегреческий и т. д.). Мы применяем более или менее формальные методы сбора лингвистических данных и последующей обработки (семантическая реконструкция, деривационная дрейфовая элиминация, оптимизация гомоплазий), недавно предложенные или разработанные для настоящего исследования. Мы используем последовательную филогенетическую процедуру и получаем консенсусное дерево, основанное на нескольких алгоритмах (байесовский анализ, максимальная экономность, присоединение соседей, отсутствие применения топологических ограничений). Полученная топология дерева и датировки полностью совместимы с традиционными представлениями экспертов. Нашей главной находкой является мультифуркация внутренней ИЕ клады на четыре ветви ок. 3357-2162 гг. до н.э.: (1) греко-армянскую, (2) албанскую, (3) итало-германо-кельтскую, (4) балто-славяно-индо-иранскую. Предлагаемый сценарий расхождения примиряет друг с другом различные мнения о внутреннем ИЕ ветвлении, высказывавшиеся ранее индоевропеистами. English Abstract: This preprint suggests the reconstruction of Indo-European phylogeny based on thirteen 110-word lists for the proto-languages ​​of the IE subgroups (Proto-German, Proto-Slavonic, etc.) or the ancient languages ​​of the corresponding subgroups (Hittite, Ancient Greek, etc.). We use more or less formal methods for the collection of linguistic data and subsequent processing (semantic reconstruction, derivational drift elimination, optimization of homoplasias) recently proposed or developed for this study. We use a consistent phylogenetic procedure and obtain a consensus tree based on several algorithms (Bayesian analysis, maximum economy, joining of neighbors, lack of application of topological restrictions). The obtained tree topology and dating are fully compatible with the traditional views of experts. Our main finding is the multifurcation of the internal clade AI into four branches approx. 3357-2162 BC: (1) Greek-Armenian, (2) Albanian, (3) Italo-Germanic-Celtic, (4) Balto-Slavic-Indo-Iranian. The proposed scenario of discrepancy reconciles with each other the different opinions on the internal AI branching expressed earlier by the Indo-Europeists.