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Рассмотрен процесс фильтрации смеси углеводородов (метан–н-бутан) в пористой среде. Показана возможность существования автоколебаний в такой системе. Предложен механизм, объясняющий их возникновение. Разработана одномерная численная модель процесса фильтрации смеси углеводородов. Определены основные параметры, влияющие на свойства автоколебательной системы.

Drift motion of particles floating on standing waves excited parametrically in a container (Faraday wave) was studied experimentally, and particle displacements and drift speeds were analyzed statistically. Particle trajectories were reproduced from video images. It is found that the mean square of the drift speed is described by approximate linear dependence on the squared driving amplitudes, and that the displacements follow a law of fractional Brownian motions. Persistent correlation of the particle displacements and velocity correlations in the longitudinal and transversal directions were also estimated. Drift motion tends to normal Brownian at larger driving amplitudes and larger separtion times.

The aim of this study is to investigate gases discharged from a high-pressure vessel numerically. To simulate this subject more realistically, the viscosity and compressibility of the gas are taken into consideration simultaneously. The methods of the Roe scheme, preconditioning, and dual time-stepping matching the lower–upper symmetric-Gauss–Seidel method are adopted to solve compressible flow problems during gaseous discharge processes. The nonreflecting boundary condition is used to prevent flowfields from being polluted by the reflection of the pressure wave induced by the compressible flow at the boundary. Computing procedures are performed on the compute unified device architecture computation platform, which was recently developed and is a highly effective technology for accelerating computational speed. Results show that the mass flow rate of this work is consistent with the existing experimental work. Because of a sudden expansion at a small opening, the phenomena of an alternating variation of t...

The paper presents a data reduction method for determination of thermal diffusivity in flash method. It is based on non-linear χ 2 fit to a model which takes into consideration heat losses. The advantage of the method is that it does not need a knowledge of base line and is suitable for data disturbed by noise and mains hum. A comparison with some other data reduction methods is given.

A model of simultaneous heat and mass transfer through a porous material is presented to explain transient moisture sorption by paper sheets from humid air. There are three primary resistances to moisture transport: (1) diffusion through an external boundary layer; (2) diffusion through the pore system and, (3) diffusion from the pore system into the fibers. It is found that diffusion through the fiber phase perpendicular to the plane of the sheet is not significant for the moisture content range considered here. The mass transport model is able to predict the results of transverse moisture gradient experiments which show that moisture content gradients in paper are not as large as previously thought during transient periods. The model shows that the sigmoidal temperature response of paper to a linear change of relative humidity is due to non-linearities of the moisture content isotherm and heat of sorption.

For computational fluid dynamics simulations, grid systems are generally used in the Eulerian frame for both structured and unstructured grids and solvers designed for the chosen grid systems. In contrast to the grid-based method, in which the connection information with neighboring grids must be maintained, gridless methods do not require an underlying connectivity in the form of control volumes or elements. Hence, gridless methods are feasible and robust for the problems with moving boundary and/or complicated boundary shapes. In this study, a Eulerian gridless solver is proposed, and its application for simulating two-dimensional unsteady viscous flows in low Reynolds number regions is investigated. The solver utilizes the weighted moving square method to obtain the spatial derivatives of the governing equations and solve the pressure Poisson equation iteratively. Simple remedies to satisfy the boundary conditions in the finite difference method are applied. The fractional step method with the second-order Adams–Bashforth method is used for time integration. Some benchmark problems were solved using the developed solver, and the results were compared with those of other experimental and computational methods. Good agreement with the results of other methods confirmed the validity of the proposed solver.

The Internet of Things (IoT) will bring together billions of devices, denoted as Smart Objects (SOs), in an Internet-like architecture. Typically, SOs are embedded devices with severe constraints in terms of processing capabilities, available memory (RAM/ROM), and energy consumption. SOs tend to be deployed in environments in which the human intervention is not suitable or needs to be minimized (e.g., smart city maintenance). They must adapt to the surrounding environment by self-configuring: to this end, several mechanisms have been proposed (e.g., UPnP, ZeroConf, etc.). In this paper, we focus on IEEE 802.15.4 networks with IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) adaptation layer, where IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) is the routing protocol of choice. In this context, we propose a lightweight RPL-based mechanism to Resource Discovery (RD) and Service Discovery (SD), denoted as DiRPL. In particular, DiRPL exploits the RPL handshake to detect new nodes in the network, resources are then simply discovered with a Constrained Application Protocol (CoAP) request and can thus be published in a local resource directory. A very attractive feature of the proposed DiRPL approach is that it builds on well-defined and well-known standard protocols. The performance of the proposed system is investigated with WisMote nodes deployed inside the Cooja simulator, running the Contiki operating system. Practical application scenarios to large-scale smart city monitoring, such as smart lighting and large-scale water consumption monitoring, are investigated.

Effective slip boundary (ESB) formed on textured surfaces provides a very promising method to control complex separated flow. It is becoming technically feasible due to the rapid development of new materials and other innovative technologies. In this paper, we explore the underlying physical mechanisms and guiding principle of this new control strategy by theory of boundary vorticity dynamics. We illustrate the theory by a numerical study of using textured surface to control separated foil-flow. Unlike traditional control strategy working on existing boundary layers, this new strategy aims at weakening or even eliminating the boundary layer itself by manipulating its origin. Significant ESB control effects are observed on suppressing separation, enhancing lift, and reducing drag at stall angle of attack.

Thermal management systems (TMSs) working for electronics packages under harsh environments like intense thermal radiation are challenging due to external thermal interactions. Thermal insulation protection for TMS is very critical in these harsh conditions. An experimental setup was developed to analyze the effect of insulation protection against thermal irradiation over a pumped liquid-cooling active thermal management system (ATMS) with varying heat dissipation rate (0–4.2 kW/m2), thermal irradiation (0.85–3.80 kW/m2), and coolant temperature (15–25 °C). Three configurations of ATMS are considered in the experimental study: ATMS without thermal insulation protection, ATMSs integrated with Cellulose Fibre Insulation (CFI), and Vacuum Insulation Panel (VIP). The effect of insulation on each parameter in all three ATMS configurations over the temperature of the electronics component, cooling load, and nature of heat flow in ATMS was analyzed. VIP outperformed CFI on achieving a significant reduction in the temperature of electronics systems (35.67%) and cooling load (45.64%) experienced by the ATMS. VIP effectively reduced the impact of temperature and cooling load change in ATMS against change in thermal irradiation. The study concluded that thermal insulation protection was most effective at high thermal irradiation and low heat dissipation rate. Heat Flow Direction Index (HFDI) concept was developed to find the nature of heat transfer direction in ATMS without temperature distribution trend. Heat generation rate and irradiation possess significant influence over the nature of heat flow direction.

The Blasius equation dates back to the early twentieth century and describes the boundary layer caused by a uniform flow over a flat plate. Due to the asymptotic condition on the first derivative of the solution, the problem is not an initial value one. The non-linear nature of the equation has led many authors to exploit approximation strategies to obtain an estimate of the solution. Several papers deal with series expansions, but the solutions are partly numerical and do not converge rapidly everywhere. In the present paper, a strategy is proposed to obtain an approximate solution of the Blasius problem in the closed form, i.e., without the use of series expansions. Motivated by the asymptotic behavior of the second derivative, a parametric definition of the third derivative of the Blasius solution is introduced and successive integrations are performed. By imposing the expected asymptotic conditions, a final approximate solution is obtained. This latter has the notable advantage of possessing the same behavior at 0 and at [Formula: see text] as the analytical solution up to the third derivative. It will also be shown how this result can be extended to the Falkner–Skan problem with non-zero pressure gradient and provide an accurate estimation of the thermal boundary layer over a flat plate under isothermal and adiabatic conditions.

Following the March 2011 earthquake, the nuclear power plants in Japan were affected, and emergency systems were activated. The earthquake caused a tsunami, which hit the east coast of Japan, and caused a loss of all on-site and off-site power at the Fukushima Daiichi, leaving it without any emergency power. In this situation, freshwater and seawater were used by helicopter, fire truck, and concrete pump truck to remove heat. To investigate the effect of 35‰ sea salt solution on reflood heat transfer in a long vertical tube (1600 mm in the heating length), quenching experiments were conducted. We have observed a more enhanced cooling performance in the case of the sea salt solution reflood. Consequently, the cooling performance is enhanced more than nearly 10 s for sea salt solution. The enhancing cause of the cooling performance after the quenching experiments using the sea salt solution were investigated through the macroscopic observation, scanning electron microscopy (SEM), contact angles and SEM-energy dispersive X-ray spectroscopy (EDS) of the inner surface of the test section. The cause of the cooling performance enhancement for the sea salt solution is not related to the enhanced wettability of the liquid film on the heater surface due to the deposition of sea salts but the top quenching by earlier condensation of vapor during sea salt solution reflood.

The Marangoni convection induced by simultaneous temperature and concentration gradient during the evaporation process of the binary liquid mixture was observed by means of the optical shadowgraph technique, and its morphology was presented. In order to investigate effects of temperature and concentration gradient on the Marangoni convection, a transient numerical computation was developed and conducted by combining the Volume of Fluid (VOF) numerical method with the continuum surface tension (CSF) method. The details of the local velocity field and concentration distribution of the Marangoni convection was revealed by the simulation, and the reference time when the Marangoni convection took effect to enhance the mass transfer coefficient was acquired. Meanwhile, the Marangoni convection induced by either the temperature gradient or the concentration gradient in this evaporation process was respectively investigated numerically to survey influence of the thermal effect accompanying in mass transfer on the Marangoni convection.

The work described is concerned with the way micron-size particles attached to a surface are resuspended when exposed to a turbulent flow. An improved version of the Rock'n'Roll model (Reeks and Hall, 2001) is developed where this model employs a stochastic approach to resuspension involving the rocking and rolling of a particle about surface asperities arising from the moments of the fluctuating drag forces acting on the particle close to the surface. In this work, the model is improved by using values of both the streamwise fluid velocity andacceleration close to the wall obtained from Direct Numerical Simulation (DNS) of turbulentchannel flow. Using analysis and numerical calculations of the drag force on a sphere near a wall in shear flow (O'Neill (1968) and Lee and Balachandar (2010)) these values are used to obtain the joint distribution of the moments of the fluctuating drag force and its time derivative acting on a particle attached to a surface. In so doing the influence of highly non-Gaussian forces (associated with the sweeping and ejection events in a turbulent boundary layer) on short and long term resuspension rates is examined for a sparse monolayer coverage of particles, along with the dependence of the resuspension upon the timescale of the particle motion attached to the surface, the ratio of the rms/ mean of the removal force and the distribution of adhesive forces. Model predictions of the fraction resuspended are compared with experimental results., 31 pages 21 figures

An overview is given regarding experimental activities in the field of hypersonic flow. After a brief introduction into the history of hypersonic ground based facilities modern high-enthalpy wind tunnels are described including their capabilities and flow diagnostic techniques. After the HERMES technology program came to an end in Europe, an ESA technology program, called Manned-Space-Transportation Program (MSTP) has been initiated among several institutions in Europe to preserve the knowledge in hypersonics. Besides of the ESA activities 3 Sonderforschungsbereiche (centers of excellence) exist at German universities. These centers are related to hypersonic flow research; they are supported by the Deutsche Forschungsgemein-schaft DFG

Based on the novel structural online control policy (SOCP) deadlock handling method presented in our previous work, we have shown that for a specific group of use cases it is possible to relax the requirements of the method, providing an improvement in its performance. In the present work, a new type of deadlock-free zone was introduced which enabled the method to improve its efficiency for both bidirectional as well as unidirectional and mixed path systems. For bidirectional systems, a beneficial outcome was obtained by approaching the global problem solution using sequentially solved local problems. For unidirectional and mixed systems, on the other hand, this paper introduces a condition that allows verification of the feasibility of performing process reservations in a staged manner. The fulfillment of this condition means that there is a possibility of obtaining higher efficiency of the transportation system. The effectiveness of the proposed approaches has been verified by simulations. Their results were compared with the results of the original method resulting in a significant improvement.

In the field of modern bidding, electronic bidding leads a new trend of development, convenience and efficiency and other significant advantages effectively promote the reform and innovation of China’s bidding field. Nowadays, most systems require a strong and trusted third party to guarantee the integrity and security of the system. However, with the development of blockchain technology and the rise of privacy protection, researchers has begun to emphasize the core concept of decentralization. This paper introduces a decentralized electronic bidding system based on blockchain and smart contract. The system uses blockchain to replace the traditional database and uses chaincode to process business logic. In data interaction, encryption techniques such as zero-knowledge proof based on graph isomorphism are used to improve privacy protection, which improves the anonymity of participants, the privacy of data transmission, and the traceability and verifiable of data. Compared with other electronic bidding systems, this system is more secure and efficient, and has the nature of anonymous operation, which fully protects the privacy information in the bidding process.

Fluorite is an important industrial mineral composed of calcium and fluorine (CaF2). This mineral is widely distributed through different deposits. However, in most cases, fluorite is tightly associated with gangue, such as calcite and quartz. In this paper, different depressants are tested in the flotation of fluorite in two different laboratory configurations&mdash, cell and column. Quebracho tree (QT) was tested as the main depressant in combination with white dextrin (WD), potato starch (PT), carboxymethyl cellulose (CMC), and sodium hexametaphosphate (SHMP). The optimum pulp pH of the flotation of fluorite was determined as approximately 9.5&ndash, 10. The best results are obtained using a combination of quebracho and white dextrin as depressants, reaching 74% of fluorite grade for modified column flotation and 70.5% for cell flotation. Additionally, the metallurgical recovery obtained higher values when the flotation was carried out in the modified column and using the same combination of depressant agents&mdash, 75% for modified column flotation and 60% for flotation cell.

(1988). ENERGY AND ENVIRONMENTAL POLICIES: ABSOLUTES AND ALTERNATIVES. Heat Transfer Engineering: Vol. 9, No. 1, pp. 5-5.

We investigate the influence of unsteady partial cavitation on the fluid-structure interaction of a freely vibrating hydrofoil section at high Reynolds numbers. We consider an elastically-mounted NACA66 hydrofoil section that is free to vibrate in the transverse flow direction. Cavitating flow dynamics coupled with the transverse vibration are studied at low angles of attack. For the numerical study, we employ a recently developed unified variational fluid-structure interaction framework based on homogeneous mixture-based cavitation with hybrid URANS-LES turbulence modeling. We first validate the numerical implementation against experimental data for turbulent cavitating flow. For freely oscillating hydrofoil, we observe large-amplitude vibrations during unsteady partial cavitating conditions that are absent in the non-cavitating flow. We identify a frequency lock-in phenomenon as the main source of sustained large-amplitude vibration whereby the unsteady lift forces lock into a sub-harmonic of the hydrofoil natural frequency. During cavity collapse and shedding, we find a periodic generation of clockwise vorticity, leading to unsteady lift generation. We determine the origin of this flow unsteadiness near the trailing edge of the hydrofoil via the interplay between the growing cavity and adverse pressure gradient. The flow-induced structural vibration is observed to have a consequent impact on the cavity dynamics. In the frequency lock-in regime, large coherent cavitating structures are seen over the hydrofoil suction surface undergoing a full cavity growth-detachment-collapse cycle. For the post-lock-in regime, cavity length is shorter and the attached cavity is observed to undergo high frequency spatially localized oscillations. In this regime, cavity shedding is primarily limited to the cavity trailing end and frequency of a complete cavity detachment and shedding event is reduced.

Two-phase flow and heat transfer is still an area of intense research and great uncertainty. Even severely restricting ourselves to just annular, internal two-phase flow does not significantly improve our chances of accurately predicting either pressure gradients or heat transfer coefficients for an arbitrary tube geometry or fluid. This article summarizes a series of investigations that aim to identify the fundamental governing physics of internal two-phase flow: a Theory of Everything. The techniques developed to do so have been varied, and novel approaches are presented here. At the macro scale, simultaneous visualization and measurement of pressure gradient have led to interesting observations about the relationship between flow regimes and these fundamental macroscale behaviors. Since the macroscale behaviors are governed, for the most part, by behaviors at the micro scale, a number of techniques have been developed to study this near-wall behavior in quantitative detail. In particular, dye-assisted ...

Hyperthermia has been used as one of the therapies for cancer treatment since the early 1970s. This condition is reached when temperature of a cell (or larger mass) is elevated to 43°C, about 6 degrees above body temperature, causing the destruction of the mass. With fewer complications than chemotherapy and radiation this thermotherapy has been used as an assisting therapy in conjunction with chemo or radiation therapies. Because of nanotechnology and its medical applications, there have been many recent developments in making hyperthermia more effective in treatment of many forms of cancers.

The increased number of women diagnosed with breast cancer in industrialized countries is raising the awareness of possible factors influencing this occurrence. The present work is based on a multi-layer transport model to analyze the concentration of toxins present in the breast ducts. The multi-layer model presented describes the transport of caffeine, cimetidine, aspirin and nicotine during the resting mammary gland period. Additionally, the dermal transport of drugs such as nicotine and aspirin into the resting mammary gland is analyzed. In a unique approach we also present the impact of introducing an external heat flux at the boundaries to increase the diffusion of these particles into the breast ducts. Our model predicts the movement of toxins and/or drugs within the resting mammary glands.

Photonic-crystal surface-emitting lasers (PCSELs) have led to amazing results in overcoming the divergence limitation of semiconductor lasers. However, so far, the physical mechanism behind this promising control of far-field characteristics is still unclear. Here, we perform a theoretical study of the mechanism of the influence of photonic crystal (PhC) geometry on the far field of PCSELs. The perspective from group theory is adopted in our analysis. We explore the function of symmetry in the formation of the far-field pattern (FFP) and clarify the roles played by various PhC parameters in this process. Through our analysis, a symmetry criterion to design PCSELs with single-lobed narrow beams is shown, where an asymmetric in-plane PhC structure, a large vertical confinement factor, and a sufficient number of periods are required. Our results reveal the physical origin of the narrow beam of PCSELs, which can even reach 0.1° with a PhC cavity size of over 1000 μm at a lasing wavelength of 940 nm.

Wave motions in a fluid cylinder rotating about the axis are investigated within the framework of the linear theory. The cylinder is assumed to be fairly long. This makes it possible to restrict attention to the study of the plane oscillation pattern. The fluid is assumed to be ideal and incompressible. The models in which the fluid particles are confined by gravitational (body) or/and capillary forces (surface stress forces) are considered. A mode analysis is carried out and the dispersion relations are constructed. Traveling and steady-state waves on the surface of the fluid cylinder are investigated; qualitative effects ("wave inertia") are established.

The development of miniaturized and more powerful electronic devices and microprocessors has resulted in high heat generation and temperature values in these components. That affects the performance, reliability and lifespan of the devices. In addition, more local hot spots are generated in the components that require even more attention to prevent stress failure and fatigue. As such, the employment of advanced electronics cooling systems is very essential to keep the temperature below the safe temperature. In this work, innovative cooling systems are developed and analyzed employing jet impingement technology, high conductive metal foam, rib structured target surfaces, confined non-uniform small-scale channel, and conductive heat spreader plate. The base of the foam-filled cooling channel is subject to a uniform high heat flux value resembling the electronics device to be cooled. For numerical modeling of thermal transport through foam filled region, the local thermal non-equilibrium model in porous media is utilized resulting in two energy equations for solid and fluid phases. For better understanding of flow and thermal characteristics of jet impingement through the combination of metal foam and rib structured surfaces in confined channels, several effective parameters are studied such as slot and circular jet impingements, the shape and orientation of the ribs, impinging jet velocity, applied heat flux and the thickness of conductive heat spreader plate for hotspot removal. The results show that the fully foam filled channel provides a more efficient cooling in comparison with partially foam filled channel. Furthermore, the results indicate the advantage of utilization of ribs at the stagnation region of the impinging jet, for local thermal treatment of hotspots. The perpendicular cuboid ribs placed at the stagnation zone of the coolant jet impingement provide 13% increase in maximum local Nusselt number while the increase in the pressure drop and required pumping power are as small as 4.2%. Doubling the velocity would result in 35.3% increase in the maximum local Nusselt number, 180% increase in the pressure drop and 460.7% increase in the required pumping power. An increase in the thickness of the conductive heat spreader plate increases the base local temperature but improves local temperature uniformity.

Effusion-cooling is the next logical step in gas turbine blade cooling. Research on this topic has been done since the early 1950s, but manufacturing and modelling difficulties have prevented its commercial application so far. Still, there is a multitude of scientific publications about most aspects of this technology. Here, an overview over the publications most relevant for engineering uses is provided, with a focus on its application to gas turbine blades. The topics addressed here include the basic geometric and aerodynamic parameters known from film-cooling, but also the thermal conductivity of the base material, simplified approaches for modelling effusion-cooling and finally the application to blades, which incorporates the combination of impingement- and effusion-cooling as well as influences from operation.

The Madzaringwe Formation in the Vele colliery is one of the coal-bearing Late Palaeozoic units of the Karoo Supergroup, consisting of shale with thin coal seams and sandstones. Maceral group analysis was conducted on seven representative coal samples collected from three existing boreholes—OV125149, OV125156, and OV125160—in the Vele colliery to determine the coal rank and other intrinsic characteristics of the coal. The petrographic characterization revealed that vitrinite is the dominant maceral group in the coals, representing up to 81–92 vol.% (mmf) of the total sample. Collotellinite is the dominant vitrinite maceral, with a total count varying between 52.4 vol.% (mmf) and 74.9 vol.% (mmf), followed by corpogelinite, collodetrinite, tellinite, and pseudovitrinite with a count ranging between 0.8 and 19.4 vol.% (mmf), 1.5 and 17.5 vol.% (mmf), 0.8 and 6.5 vol.% (mmf) and 0.3 and 5.9 vol.% (mmf), respectively. The dominance of collotellinite gives a clear indication that the coals are derived from the parenchymatous and woody tissues of roots, stems, and leaves. The mean random vitrinite reflectance values range between 0.75% and 0.76%, placing the coals in the medium rank category (also known as the high volatile bituminous coal) based on the Coal Classification of the Economic Commission for Europe (UN-ECE) coal classification scheme. The inertinite content is low, ranging between 4 and 16 vol.% (mmf), and it is dominated by fusinite with count of about 1–7 vol.% (mmf). The high amount of inertinite, especially fusinite, with empty cells and semi-fusinite in the coals will pose a threat to coal mining because it aids the formation of dust.

Since the Euro 5 regulation was implemented, increasing numbers of Light-Duty (LD) diesel vehicles are being equipped with Diesel Particulate Filter (DPF). Inherently, if a DPF is filled with soot and Particulate Matter (PM), then the DPF must be regenerated periodically. Therefore, this study investigates how an active regeneration process influences the emissions of gases and the size-resolved particle emissions from LD diesel vehicles. The experimental apparatuses were installed to measure the exhaust gas emissions during regeneration events. Two Fast particle analyzers (DMS-500) were positioned upstream and downstream of the DPF to measure the PN concentration and particle size distribution. X-ray Photoelectron Spectroscopy (XPS) was used to investigate the elemental composition and chemical state information of the collected soot samples during regeneration. The experimental results showed that during an active regeneration, the post-injection rate increased, and the post injection timing was significantly retarded, which caused the peak pressure of the cylinder and the thermal efficiency to decrease and the exhaust temperature to increase. According to the upstream PN results, a large increase in the number of nucleation particles occurred during an active regeneration due to the retarded and increased post-injection process. In contrast, the accumulation mode particles measured downstream of the DPF had a majority of total particles during a regeneration because of the increased exhaust temperature, which caused the nucleation mode particles to be easily oxidized.

We propose an Einstein-aether scalar–tensor cosmological model. In particular, in the scalar–tensor Action Integral, we introduce the aether field with aether coefficients to be functions of the scalar field. This cosmological model extends previous studies on Lorentz-violating theories. For a spatially flat Friedmann–Lemaitre–Robertson–Walker background space, we write the field equations which are of second order with dynamical variables the scale factor and the scalar field. The physical evolution of the field equations depends upon three unknown functions which are related to the scalar–tensor coupling function, the scalar field potential, and the aether coefficient functions. We investigate the existence of analytic solutions for the field equations and the integrability properties according to the existence of linear in the momentum conservation laws. We define a new set of variables in which the dynamical evolution depends only upon the scalar field potential. Furthermore, the asymptotic behavior and the cosmological history are investigated where we find that the theory provides inflationary eras similar to that of scalar–tensor theory but with Lorentz-violating terms provided by the aether field. Finally, in the new variables, we found that the field equations are integrable due to the existence of nonlocal conservation laws for arbitrary functional forms of the three free functions.

It has recently been shown that the mechanical properties of thin, rectangular wooden plates can be tuned by carving them with specific patterns of perforations, effectively realising a 2D wooden mechanical metamaterial. Such a material is of great interest for the construction of musical instruments, as it could allow a new degree of creative control for makers. Furthermore, issues with the shrinking supplies of tone-woods could be alleviated as wood samples that don not meet the desired requirements could simply be altered, instead of being discarded. In this work, we study the effect of the use of these metamaterials in the soundboards of classical guitars. By way of simulations, we evaluate their impact on the modal behaviour and on the sound pressure level of the instrument, as well as on its ability to sustain the load exerted by the strings. Our results show that the metamaterials can tune the instrument’s response without compromising its structural integrity. We thus conclude that the use of wooden mechanical metamaterials in the soundboards of classical guitars is feasible and, in many ways, beneficial, not the least since it opens the door to using non-traditional woods with bespoke density and stiffness.

Sulfane sulfur species are an important type of reactive sulfur species. These compounds have unique reactivity to attach reversibly to other sulfur atoms and exhibit regulatory effects in diverse biological systems. Recent studies have suggested that sulfane sulfurs are involved in signal transduction processes of hydrogen sulfide (H2S). The development of probes for selective, rapid, and sensitive detection of sulfane sulfur is of great significance for studying their physiological and pathological roles in biological systems, especially in plant systems for which physiological research has lagged behind. However, so far there is still a lack of sufficient chemical tools for directly tracking and measuring sulfane sulfur in biological systems, and in particular, the detection of sulfane sulfur in living plant tissues is still challenging. Herein, we report a near-infrared fluorescent probe, SSNIP, for the selective imaging of sulfane sulfur. SSNIP is capable of detecting sulfane sulfur at physiological concentrations in both aqueous buffer and living human cells. Then, with SSNIP, we demonstrate the fluorescent monitoring of endogenous sulfane sulfur in plant tissues such as Arabidopsis thaliana roots for the first time. Furthermore, the application of SSNIP in evaluating the level of sulfane sulfur in Arabidopsis thaliana roots at different growth stages is performed. The results show that the level of sulfane sulfur in Arabidopsis thaliana roots correlates well with their growth stages, which suggests that sulfane sulfurs might act as actual signaling molecules to promote plant growth and root elongation. In addition, it reveals potential applications for the biological and pathological studies of sulfane sulfur, especially in plant physiology.

In the present study, the flow boiling characteristics of R134a/R245fa zeotropic mixtures with three mass fractions (10/90, 30/70 and 70/30 by wt%) in a single rectangular micro-channel and their pure components were experimentally investigated. The flow boiling in micro-channel was visualized from the top view and heated on three sides with the cross-sectional area of 1 mm × 1 mm and length of 106 mm. For each test refrigerant, the visualization results and heat transfer coefficients were obtained under the parametric conditions comprising the heat flux range of 30–120 kW/m 2 and mass flux range of 60–1100 kg/m 2 s at the same evaporating temperature of 18.5 °C. The corresponded outlet vapor quality was in the range of 0–1. Results showed that almost all of the test refrigerants experienced five typical flow patterns. Different bubble coexistence phenomena were observed for the pure and mixed refrigerants, respectively. The hysteresis of flow pattern transition for R134a/R245fa zeotropic mixtures was strongly affected by both of the temperature glide and blending ratio. Based on the comparison with pure components, flow boiling heat transfer characteristics of test zeotropic mixtures were analyzed and discussed in detail by considering the mixture effects. Taking account of capillary and Marangoni effect in confined space, as well as other impact factors, the developed prediction method exhibited satisfactory accuracy in predicting the heat transfer coefficient of zeotropic mixtures.

Abstract An experimental method for determination of aerodynamic loads is presented. It is based on velocity vector field results obtained with Particle Image Velocimetry (PIV). As PIV is an optical measurement technique, the developed method for load determination can be defined as noninvasive. It is shown that the only information needed to estimate the lift and drag forces exerted on a body placed in the flow is a velocity distribution measured around the investigated object. Therefore, PIV results provide sufficient input experimental data to be used. Fundamental fluid mechanics theories were employed to develop algorithms for load estimation. Determination of the lift force is based on velocity circulation calculations. It is obtained by integrating the velocity field along a closed-loop encircling the body. An essential achievement made is the development of a procedure for finding an optimal size of the integration curve used for lift calculations. In the case of the drag force estimation, an analysis of fluid momentum changes has been used. The momentum deficit, within a given control volume containing the analysed aerofoil, is determined and related to the reaction drag force exerted on the body. Additionally, pressure field reconstruction based on velocity data, which enabled an application of small control surfaces and kept the drag estimation error at a satisfactorily low level, was introduced. The developed method was tested and verified with the reference computational fluid dynamics simulation results and applied further to the wind tunnel experimental data. A flow around the standard NACA0012 aerofoil at two flow regimes was investigated (Re=$$0.7\times 10^5$$ 0.7 × 10 5 and Re=$$1.4\times 10^5$$ 1.4 × 10 5 ). Lift and drag coefficient characteristics as a function of the angle of attack were obtained. An exceptional agreement between the experimental and reference numerical lift characteristics was attained (relative differences no larger than 5%). In the case of drag estimation, an acceptable level of similarity was observed (max. discrepancies below 20%). Graphic abstract

In this article, we have investigated, via numerical simulation, the interaction of two identical balls settling in a vertical square tube filled with a viscoelastic fluid. For two balls released in Oldroyd-B fluids, one on top of the other initially, we have observed two possible scenarios, among others: either the trailing ball catches up the leading one to form a doublet (dipole) or the balls separate with a stable final distance. If the ball density is slightly larger than the fluid density, the two balls form a doublet, either vertical or tilted. If one further increases the ball density, the two balls still form a doublet if the initial distance is small enough, but for larger initial distances at higher elasticity numbers, the balls move away from each other and their distance reaches a stable constant. Factors influencing doublet formation are (possibly among others) the ball density, the ball initial distance, and the fluid elasticity number. When settling in finite extendable nonlinear elastic–Chilcott and Rallison fluids, low values of the coil maximal extension limit enhance ball separation.In this article, we have investigated, via numerical simulation, the interaction of two identical balls settling in a vertical square tube filled with a viscoelastic fluid. For two balls released in Oldroyd-B fluids, one on top of the other initially, we have observed two possible scenarios, among others: either the trailing ball catches up the leading one to form a doublet (dipole) or the balls separate with a stable final distance. If the ball density is slightly larger than the fluid density, the two balls form a doublet, either vertical or tilted. If one further increases the ball density, the two balls still form a doublet if the initial distance is small enough, but for larger initial distances at higher elasticity numbers, the balls move away from each other and their distance reaches a stable constant. Factors influencing doublet formation are (possibly among others) the ball density, the ball initial distance, and the fluid elasticity number. When settling in finite extendable nonlinear elastic–C...

The quantity of heat transmitted from a metal surface to boiling water increases as the temperature difference ΔT is increased, but after the ΔT has reached a certain limit, quantity Q decreases with further increase in ΔT. This turning point is the maximum value of heat transmitted. The existence of this point was actually observed in the experiment. Under atmospheric pressure, ΔT corresponding to the maximum value of heat transfer for water at 100°C falls between 20 degC to 40 degC, and Q is between 1080000 and 1800000 kcal/m2 h (i.e. between 2000 and 3000 kg/m2h, if expressed in constant evaporation rate at 100°C) ; this figure is larger than the maximum value of heat transfer as was previously considered. Also, the minimum value of heat transfer was obtained, and in the Q−ΔT curve for the high temperature region, the burn-out effect is discussed.

Melting and solidification of pure materials, during which liquid convection is driven by buoyancy, or a combination of buoyancy and surface tension forces is considered. A numerical model, which is verified by comparing its predictions with experimental results, is used to show that thermocapillary effects can be of primary influence upon local melting rates in both relatively high and low Pr materials, and it can have a significant impact upon overall solidification. In low Pr materials, overall solidification rates are affected by thermocapillary convection more than overall melting rates. Thermocapillary convection is shown to have a significant influence upon phase change, regardless of the value of the dynamic Bond number considered in this study.

The forced convective heat transfer near a wall or a plate immersed in a packed bed at high temperature is considered in this paper. The non-Darcian effects are considered for the hydrodynamics and heat transfer and dependent scattering theory are taken into account for the radiation transfer. The discrete-ordinale method is used to solve the equation for radiation intensity. It is found from the numerical predictions that radiative heat transfer rate increases with a decrease of the convection-radiation parameter (Bo) or conduction-radiation parameter ( N ) and an increase of the Reynolds number. The effect of radiation on conduction-convection is determined by the sign of the net radiation absorbed by the particles. The radiation properties of the plate and the bed, as well as the direction of heat flux, have obvious influence on heat transfer in packed beds at high temperature.

The results of the research and design of a novel vacuum photosensor with a planar molybdenum blade structure are presented. The advanced prototype implements the principle of an increasing penetrability of the Schottky barrier for the metal&ndash, vacuum interfaces under the action of an external strong electrostatic field. Theoretical and experimental substantiation of the photosensor performance in a wide range of wavelengths (from 430 to 680 nm and from 800 to 1064 nm) beyond the threshold of the classical photoelectric effect is given. The finite element method was applied to calculate distribution of the optical and electrostatic fields inside the photosensor structure. The sensor current-to-light response was studied using the periodic pulsed irradiation with the tunable wavelength. It was shown that the nanoscale localization zones of two types are formed near the surface of the blade tip: the zone of an increased concentration of hot electrons localized inside the molybdenum blade, and the zone with an increased strength of the external electrostatic field localized outside the blade. In general, the mutual positions of these zones may not coincide, whereas the position of the first-type localization zone significantly varies with the changes in the wavelength of the irradiating light. This causes features in the spectrum of the quantum yield of the photosensor such as expressed non-monotonic behavior and occurrence of sharp dips. The design of the photosensor that provides matching of the positions for both types of localization zones was proposed, the manufactured prototypes of the designed device were experimentally studied. In the designed photosensor, the ballistic transport of photoelectrons in the vacuum gap with a strong field provides a possibility for the creation of ultra-fast optoelectronic devices, such as modulators, detectors, and generators.

During wintertime 1990/91 fogwater and rime ice was collected on a polyethylene plate of0.25 m 2 sho~y after sampling aerosol in eight size classes. Fog water deposition reaches up to 15. ml/m h. For elements analysed in aerosol and ter samples as well deposition velocities due to wet deposition range between 10 −4 and 10 −2 m/s.

In order to meet the ever-increasing 5G and beyond Radio Access Network (RAN) densification demands, Fiber-Wireless transport networks are expected to play a key role in accelerating 5G deployment by providing the essential RAN flexibility, while at the same time avoiding costly fiber-trenching. Due to the inefficiency of the Radio-and-Fiber (R&F) networks for application in dense RAN topologies, Analog-Radio-over-Fiber (A-RoF) technology is regarded as a key enabling solution, since it greatly simplifies the remote antenna while offering very high spectral efficiency. For this type of dense A-RoF network, new and efficient Medium-Transparent-Medium Access Control (MT-MAC) protocols are required that can concurrently arbitrate optical and wireless resources, while at the same time offering the necessary Quality-of-Service (QoS) for correct operation of the combined Fronthaul/Midhaul/Backhaul segments present in 5G disaggregated RANs. In this paper, we propose a QoS-enabled MT-MAC (qMT-MAC) protocol that can combine Fronthaul/Midhaul/Backhaul flows under the same framework, while satisfying the strict delay and jitter requirements set by the relevant standards. Results show that qMT-MAC concurrently achieves the delay and jitter requirements for combined Fronthaul/Midhaul/Backhaul traffic even when loads approach the network’s capacity, while attested enhanced prioritization policies can offer up to a 64% delay reduction over State-of-the-Art MT-MAC protocols.

Generasi muda memiliki peran sentral sebagai pemimpin yang membawa perubahan pada masa depan Indonesia. Sebagai calon pemimpin masa depan, generasi muda dituntut terampil berbicara di depan publik untuk menyampaikan gagasan secara efektif. Permasalahan yang dihadapi oleh para siswa adalah kesulitan berbicara di depan publik karena kendala teknis maupun emosional dan sekolah tidak memberikan materi tentang berbicara di depan publik. Kegiatan PkM bertujuan agar para siswa lebih mengasah keterampilan berbicara di depan publik (public speaking skills) sehingga mereka lebih percara diri untuk bebricara di depan publik. Manfaat lain dari workshop public speaking skills adalah sebagai keunggulan bersaing bagi para siswa. Workshop diberikan kepada 23 siswa SMK Strada Daan Mogot secara daring dan luring sesuai ketentuan pihak sekolah. Di akhir kegiatan dilakukan uji keterampilan public speaking. Hasil workshop menunjukkan bahwa tujuan workshop tercapai sesuai rencana yaitu dengan hasil evaluasi yang menunjukkan rasa percaya diri yang lebih baik dan nilai kemampuan siswa berbicara di depan publik adalah baik dan baik sekali.Abstract: The younger generation has a central role as leaders who bring about change in the future of Indonesia. As future leaders, young people are required to be skilled in public speaking to convey ideas effectively. The problems faced by the students were difficulty speaking in public due to technical and emotional problems and the school did not provide material on public speaking. The PkM activity aims to make students hone their public speaking skills. Another benefit of public speaking skills training is as a competitive advantage for students. The training was given to 23 students of SMK Strada Daan Mogot online and onsite according to the school's regulations. At the end of the activity, a public speaking skill test was conducted. The results of the training showed that the training objectives were achieved, with the evaluation results which showed better self-confidence and the value of students' ability to speak in public was good and very good.

“Wasan” is the collective name given to a set of mathematical texts written in Japan in the Edo period (1603–1867). These documents represent a unique type of mathematics and amalgamate the mathematical knowledge of a time and place where major advances where reached. Due to these facts, Wasan documents are considered to be of great historical and cultural significance. This paper presents a fully automatic algorithmic process to first detect the kanji characters in Wasan documents and subsequently classify them using deep learning networks. We pay special attention to the results concerning one particular kanji character, the “ima” kanji, as it is of special importance for the interpretation of Wasan documents. As our database is made up of manual scans of real historical documents, it presents scanning artifacts in the form of image noise and page misalignment. First, we use two preprocessing steps to ameliorate these artifacts. Then we use three different blob detector algorithms to determine what parts of each image belong to kanji Characters. Finally, we use five deep learning networks to classify the detected kanji. All the steps of the pipeline are thoroughly evaluated, and several options are compared for the kanji detection and classification steps. As ancient kanji database are rare and often include relatively few images, we explore the possibility of using modern kanji databases for kanji classification. Experiments are run on a dataset containing 100 Wasan book pages. We compare the performance of three blob detector algorithms for kanji detection obtaining 79.60% success rate with 7.88% false positive detections. Furthermore, we study the performance of five well-known deep learning networks and obtain 99.75% classification accuracy for modern kanji and 90.4% for classical kanji. Finally, our full pipeline obtains 95% correct detection and classification of the “ima” kanji with 3% False positives.