An Arbitrary High Order Well-Balanced ADER-DG Numerical Scheme for the Multilayer Shallow-Water Model with Variable Density

In this work, we present a novel numerical discretization of a variable pressure multilayer shallow water model. The model can be written as a hyperbolic PDE system and allows the simulation of density driven gravity currents in a shallow water framework. The proposed discretization consists in an unlimited arbitrary high order accurate (ADER) Discontinuous Galerkin (DG) method, which is then limited with the MOOD paradigm using an a posteriori subcell finite volume limiter. The resulting numerical scheme is arbitrary high order accurate in space and time for smooth solutions and does not destroy the natural subcell resolution inherent in the DG methods in the presence of strong gradients or discontinuities. A numerical strategy to preserve non-trivial stationary solutions is also discussed. The final method is very accurate in smooth regions even using coarse or very coarse meshes, as shown in the numerical simulations presented here. Finally, a comparison with a laboratory test, where empirical data are available, is also performed.

INTENSIFICATION AND STUDY OF HEAT TRANSFER AND FRICTION IN THE PLATE HEATING SURFACES OF THE KMS-2 AIR HEATER WITH A PRESSURE GRADIENT

A numerical study of heat transfer and friction in the heat exchanger channels in the presence of a variable pressure gradient is performed. The research was carried out in software complexes (Code_Saturne, Salome). The results of the validation of the research method are presented and they showed that the deviation of the numerical simulation results from the calculation data according to the known criterion equations is within the error of generalization of the experimental data by the criterion equations. According to the results of studies at Red=3000, Red=4177, Red=6000, it was found that the average value of the heat transfer coeffi cient of the channel of variable cross-section is up to 20 % higher than for the channel at dp/dx0. At the same time, the thermal-hydraulic effi ciency of the alternating channel (L=117 mm, l=58.5 mm, n=2) in the initial section at x =0...0.08 is lower than in the channel with dp/dx>0 by 26.7 %, and at x =0.08...1 it is higher by 5 ... 15 %, at dp/dx

Development and Evaluation of a Novel Mechatronic Percussion System

<p>While numerous attempts at creating mechatronic percussion systems exist, many have been limited to only playing a single membranophone or idiophone. These systems inherently lack the ability to reproduce the expressive nature of strikes which human players are capable of and often require manual reconfiguration in order to vary the striking location, type of beater or striking angle. The few which are able to pan across multiple instruments often lack the ability to perform expressively. We designed a mechatronic percussion system that provides expressivity through controllable variability of the acoustic properties inherent to percussion instruments. Our system can play across the range of an entire traditional drum kit, whether it is set up in a completely horizontal formation, vertically staggered or includes other percussion instruments. When continuously operating at maximum speed, the system is capable of playing for five hours before one subsystem is at risk of failing. Our system possesses two "wrists", each capable of gripping a variety of beaters. A single wrist can reliably perform single drum strokes at a frequency of 21 Hz, surpassing that of the world's fastest drummer. Operating both wrists results in a striking frequency of 51.9 Hz. The level of force behind each stroke and resultant acoustic quality can be controlled to produce an expressive performance. A unique feature of this system is the use of a compliant grip, applying variable pressure to the beater held and allows for a variety of beater diameters to be incorporated.</p>

Development and Evaluation of a Novel Mechatronic Percussion System

<p>While numerous attempts at creating mechatronic percussion systems exist, many have been limited to only playing a single membranophone or idiophone. These systems inherently lack the ability to reproduce the expressive nature of strikes which human players are capable of and often require manual reconfiguration in order to vary the striking location, type of beater or striking angle. The few which are able to pan across multiple instruments often lack the ability to perform expressively. We designed a mechatronic percussion system that provides expressivity through controllable variability of the acoustic properties inherent to percussion instruments. Our system can play across the range of an entire traditional drum kit, whether it is set up in a completely horizontal formation, vertically staggered or includes other percussion instruments. When continuously operating at maximum speed, the system is capable of playing for five hours before one subsystem is at risk of failing. Our system possesses two "wrists", each capable of gripping a variety of beaters. A single wrist can reliably perform single drum strokes at a frequency of 21 Hz, surpassing that of the world's fastest drummer. Operating both wrists results in a striking frequency of 51.9 Hz. The level of force behind each stroke and resultant acoustic quality can be controlled to produce an expressive performance. A unique feature of this system is the use of a compliant grip, applying variable pressure to the beater held and allows for a variety of beater diameters to be incorporated.</p>

A Leak-Free Head-Out Plethysmography System to Accurately Assess Lung Function in Mice

Mice are a valuable model for elegant studies of complex, systems-dependent diseases, including pulmonary diseases. Current tools to assess lung function in mice are either terminal or lack accuracy. We set out to develop a low-cost, accurate, head-out variable-pressure plethysmography system to allow for repeated, non-terminal measurements of lung function in mice. Current head-out plethysmography systems are limited by air leaks that prevent accurate measures of volume and flow. We designed an inflatable cuff that encompasses the mouse’s neck preventing air leak. We wrote corresponding software to collect and analyze the data, remove movement artifacts, and automatically calibrate each dataset. This software calculates inspiratory/expiratory volume, inspiratory/expiratory time, breaths per minute, enhanced pause, mid-expiratory flow, and end-inspiratory pause. To validate the use, we established our plethysmography system accurately measured tidal breathing, the bronchoconstrictive response to methacholine, sex and age associated changes in breathing, and breathing changes associated with house dust mite sensitization. Our estimates of volume, flow, and timing of breaths are in line with published estimates, we observed dose-dependent decreases in volume and flow in response to methacholine (P < 0.05), increased lung volume and decreased breathing rate with aging (P < 0.05), and that house dust mite sensitization decreased tidal volume and flow (P <0.05) while exacerbating the methacholine induced increases in inspiratory and expiratory time (P < 0.05). We describe an accurate, sensitive, low-cost, head-out plethysmography system that allows for longitudinal studies of pulmonary disease in mice.New & NoteworthyWe describe a variable-pressure head-out plethysmography system that can be used to assess lung function in mice. A balloon cuff that inflates around the mouse’s neck prevents air leak, allowing for accurate measurements of lung volume and air flow. Custom software facilitates system calibration, removes movement artifacts, and eases data analysis. The system was validated by measuring tidal breathing, responses to methacholine, and changes associated with house dust mite sensitization, sex, and aging.Contributions to StudyStephanie Bruggink: development of head-out plethysmography chamber, measurement of breathing, data analysis, prepared manuscriptKyle Kentch: development of head-out plethysmography chamber, programmed software to collect and analyze data, prepared manuscriptJason Kronenfeld: development of tools to analyze data, analysis of dataBenjamin Renquist: development of head-out plethysmography chamber, statistical analysis, prepared manuscript

The Adaptive Damping Technique: Improving the Simulation Accuracy of Hydraulic Transients

Hydraulic surges are transient events frequently observed in various industrial and laboratory flow situations. Understanding surge physics and its accurate numerical prediction is crucial to the safety of flow systems. The maximum accuracy achievable for transient surge simulations is limited by the inefficiencies in the mathematical models used. In this work, we propose a mathematical model that incorporates an adaptive damping technique for the accurate prediction of hydraulic surges. This model also takes the compressibility effects in the liquid during the surge process into account. The novel approach of using the local pressure fluctuation data from the flow to adjust the unsteady friction for controlling the dissipation is introduced in this paper. The adaptive-dissipation is actualized through a unique 'variable pressure wave damping coefficient' function definition. Numerical simulation of three different valve-induced surge experiments demonstrates the reliability and robustness of the mathematical model. Numerical results from the proposed model show an excellent match with the experimental data by closely reproducing both the frequency and the amplitude of transient pressure oscillations. A comparative study explains the improvement in the simulation accuracy achieved by replacing the constant damping coefficient with the proposed variable coefficient. The superiority of the new model with the adaptive damping capability over the similar models in literature and those used in commercial software packages is also well established through this study.

Influence of the filling gas mixture on the interruption capability of medium voltage load break switches

In today’s medium voltage switchgear SF6 is commonly used as insulating and arc quenching medium. Because of its high potential impact on the environment a substitution with an environmentally friendly alternative is pursued. In this paper the influence of the mixing ratio of carbon dioxide nitrogen mixtures as filling gas on the interruption capability in medium voltage load break switches is investigated. The interruption capability is regarded by means of the thermal interruption performance as well as the dielectric recovery of a model load break switch. The model load break switch allows an axial arc blowing with variable pressure and uses an exchangeable nozzle system.

Rice Straw as a Natural Sorbent in a Filter System as an Approach to Bioremediate Diesel Pollution

Rice straw, an agricultural waste product generated in huge quantities worldwide, is utilized to remediate diesel pollution as it possesses excellent characteristics as a natural sorbent. This study aimed to optimize factors that significantly influence the sorption capacity and the efficiency of oil absorption from diesel-polluted seawater by rice straw (RS). Spectroscopic analysis by attenuated total reflectance infrared (ATR-IR) spectroscopy and surface morphology characterization by variable pressure scanning electron microscopy (VPSEM) and energy-dispersive X-ray microanalysis (EDX) were carried out in order to understand the sorbent capability. Optimization of the factors of temperature pre-treatment of RS (90, 100, 110, 120, 130 or 140 °C), time of heating (10, 20, 30, 40, 50, 60 or 70 min), packing density (0.08, 0.10, 0.12, 0.14 or 0.16 g cm−3) and oil concentration (5, 10, 15, 20 or 25% (v/v)) was carried out using the conventional one-factor-at-a-time (OFAT) approach. To eliminate any non-significant factors, a Plackett–Burman design (PBD) in the response surface methodology (RSM) was used. A central composite design (CCD) was used to identify the presence of significant interactions between factors. The quadratic model produced provided a very good fit to the data (R2 = 0.9652). The optimized conditions generated from the CCD were 120 °C, 10 min, 0.148 g cm−3 and 25% (v/v), and these conditions enhanced oil sorption capacity from 19.6 (OFAT) to 26 mL of diesel oil, a finding verified experimentally. This study provides an improved understanding of the use of a natural sorbent as an approach to remediate diesel pollution.

Revisiting decompression sickness risk and mobility in the context of the SmartSuit, a hybrid planetary spacesuit

Gas pressurized spacesuits are cumbersome, cause injuries, and are metabolically expensive. Decreasing the gas pressure of the spacesuit is an effective method for improving mobility, but reduction in the total spacesuit pressure also results in a higher risk for decompression sickness (DCS). The risk of DCS is currently mitigated by breathing pure oxygen before the extravehicular activity (EVA) for up to 4 h to remove inert gases from body tissues, but this has a negative operational impact due to the time needed to perform the prebreathe. In this paper, we review and quantify these important trade-offs between spacesuit pressure, mobility, prebreathe time (or risk of DCS), and space habitat/station atmospheric conditions in the context of future planetary EVAs. In addition, we explore these trade-offs in the context of the SmartSuit architecture, a hybrid spacesuit with a soft-robotic layer that, not only increases mobility with assistive actuators in the lower body, but it also applies some level of mechanical counterpressure (MCP). The additional MCP in hybrid spacesuits can be used to supplement the gas pressure (i.e., increasing the total spacesuit pressure), therefore reducing the risk of DCS (or reduce prebreathe time). Alternatively, the MCP can be used to reduce the gas pressure (i.e., maintaining the same total spacesuit pressure), therefore increasing mobility. Finally, we propose a variable pressure concept of operations for the SmartSuit spacesuit. Our framework quantifies critical spacesuit and habitat trade-offs for future planetary exploration and contributes to the assessment of human health and performance during future planetary EVAs.