Simple Piston Research Articles

Piston detection in segmented telescopes via multiple neural networks coordination of feature-enhanced images

High-precision piston detection within a large capture range is a key for segmented telescopes. In this paper, we propose a simple and efficient piston detection method based on multiple neural networks coordination. By setting a mask with a sparse multi-subpupil configuration at conjugate plane of the segmented mirror, a new dataset that is extremely sensitive to the piston is created. And two kinds of neural networks are built for different stages of detection, which ensures the method is of both large-scale and high-precision. Simulation shows that the piston can be detected in the range of the coherence length of the operating light with a sub-nanometer scale precision by this method. This method is robust and does not require complex hardware. It can be widely applied in segmented and deployable primary mirror telescopes.

A Comparative Study of Conceptual Model Complexity to Describe Water Flow and Nitrate Transport in Deep Unsaturated Loess

AbstractUnderstanding nitrate migration through the deep vadose zone is essential for aquifer vulnerability assessments. The effect of variability of physical properties of the deep vadose zone on nitrate transport has been scarcely explored. Recently, deep nitrate storage profiles were determined in the vadose zone of the Loess Plateau of China. Using these observations along with measured soil properties, this study investigates the effect of loess vertical heterogeneity on water movement and nitrate transport through the deep vadose zone. Models of different complexity were established and calibrated. First, a simple piston flow and nitrate mass balance approach was calibrated to the observed nitrate storage. The results indicate that the total nitrate storage is estimated well, while the estimation of the distribution of nitrate is relatively poor. Subsequently, Richards' equation and the Advection‐Dispersion equation were evaluated. Three different conceptualizations of the numerical models were calibrated against deep vadose zone nitrate and water content observations: (1) one‐layer model assuming homogenous loess vadose zone; (2) a model that considers a hydraulic conductivity (Ks) decay function and (3) a model where the Miller‐Miller scaling factors are prescribed to account for changes of the hydraulic functions with depth. Accounting for the vertical Ks decay in the numerical models improved water flow performances. The study reveals the adequacy of implementing water flow and nitrate transport numerical models together with a simple representation of the vertical loess variability, for simulating nitrate migration in loess deep vadose zone environments.

THE LiCore POWER PLANT SIMULATOR OF THE MOLTEN SALT FAST REACTOR

Molten salt reactors as liquid-fuelled reactors are flexible in terms of operation or design choices, but they are very different in terms of design, operation and safety approach compared to solid-fuelled reactors. Such reactors call for a new definition of their operating procedures and safety approach. Dedicated developments and studies have been performed in the frame of the European SAMOFAR project of Horizon2020 and in parallel in France involving CNRS, CORYS and Framatome to develop a system code called LiCore adapted to such reactors, corresponding to a basic-principle power plant simulator. The neutronic model LiCore, at the centre of the simulator, corresponds to an improved point-kinetics model to take into account the specificities of a MSR, notably the circulation of the delayed neutron precursors out of the core. Coupled to a simple piston model for the fuel motion in the core, this code can perform calculations faster than real time to simulate the behaviour of the fuel circuit. Transient calculations performed with LiCore are presented, together with comparisons first to a simple point-kinetics model and then to 3D calculations with the TFM-OpenFOAM coupled code. Finally, the LiCore code has recently been integrated in the ALICES platform, the integrated simulation toolset designed by CORYS for the development, maintenance and operation of major simulator such as power plant simulators.

Modification and discussion of the Green-Ampt model for an evolving wetting profile

ABSTRACT The Green-Ampt (GA) model has been widely used to evaluate soil water infiltration. While a simple piston profile is commonly used, the wetting profile of a soil changes during infiltration and a quarter-ellipse has been found to better describe its evolution. This study aims to improve the GA model and discuss the model parameters when the quarter-ellipse profile is utilized. The soil column is divided into three zones: saturated, transient and dry. The variable γ is introduced to express the ratio of the saturated zone depth to the wetting front depth. A modified GA model is derived via mathematical methods, but an exact solution is difficult to obtain. Therefore, a simplified (SGA) model is developed via a segmented method. Compared with the measured results, the SGA model is more accurate than the traditional model. Finally, the model parameters are discussed and a value of γ = 0.5 is recommended.

New theory of acoustic signal detection in the inner ear – An explanation of bifilar structure of the cochlea

In this work a new theory of acoustic signal detection in the inner ear and an experimental explanation of the causes of bifilar cochlear structure was presented. Our innovative approach describes sound detection in a completely different way from the one currently adopted. It requires analyzing the inner ear system in the form of a bent spiral and assuming that perilymph in such a small system behaves like a non-Newtonian fluid. The necessity of analyzing the system in the form of a bifilar spiral results from the need to compensate the head movements, so far omitted in the analysis. We suggest that the construction and the role of the oval window and the stapes are different than just a simple piston that converts mechanical signals to hydrokinetic ones. Stapes provides uniform distribution of the hydrokinetic signal in the spiral cochlear system, and the conversion of momentum to angular momentum creates a force perpendicular to the vestibular membrane, which causes the effect of its deflection, what has not yet been explained.

Temporal and Topographic Source Effects on Tsunami Generation

AbstractWe present a systematic study of the influence on tsunami waves generated by the uplift of a rectangular plug, of the rise time of the deformation, and of its topographic details (e.g., the presence of a sill). We are motivated by the fact that most simulation codes use an instantaneous deformation of a flat ocean floor as an initial condition of the problem, although Hammack (1973, http://resolver.caltech.edu/CaltechAUTHORS:HAMjfm73) performed pioneering laboratory studies as well as analytical computations featuring variable rise times. Here, we consider three 2‐D source shapes, including a flat seafloor, a simple elevated piston, and additional trapezoidal sill on top of it, all with variable rise times, and simulate the resulting waves using the fully nonlinear smooth particle hydrodynamic model graphics processing unit smooth particle hydrodynamic. We validate our results against Hammack's (1973) laboratory measurements and analytical results. We find that a relatively large sill, with height and width of more than half of the local depth and width of the source, has a profound effect on the spatiotemporal structure of the generated free surface wavefield. Specifically, we show that the maximum water surface elevation over the source region is not always the same as the bottom displacement, as assumed in most tsunami propagation models. Next, we obtain simple scaling relationships to predict the maximum height of the generated tsunami over and outside the source, based on the geometry of the sill and the nondimensional bed rise time. Last, we show that inertial effects may lead to an initial free surface displacement over the generation region greater than the maximum vertical displacement of the displaced seabed.

The features of use of the deadweight piston gauges

The main types of the deadweight piston gauges operated in Ukraine, namely, deadweight piston gauges of gauge and absolute pressure with a simple piston, deadweight piston gauges of gauge pressure with a counter-pressure piston, deadweight piston gauges of gauge and absolute pressure with a differential or complex piston, deadweight piston gauges of differential pressure, pneumatic pressure generators, are considered. Advantages and disadvantages of the mentioned gauge designs are indicated. The list of factors influencing the accuracy of pressure reproduction by piston pressure gauges — the effect of temperature, height difference between the measurement standard and the verified (calibrated) instrument, the effect of deformation of the piston, the dependence of the reproduced pressure on the gravitational acceleration — is provided. Formulas are given for calculating the gravitational acceleration and for determining the corrections. In addition, the features of using the deadweight piston gauges in metrological practice are considered.

Laser-matter interaction in cluster medium in the radiation dominated regime

We study the interaction between laser and cluster medium in high intensity regime 1022-24 W/cm2 using a particle based integral code (EPIC3D). By introducing four targets consisting of the same mass, i.e. same packing fraction, but having different internal structure, we investigate the effect of cluster on the acceleration dynamics comparing with that of thin film. In the radiation pressure dominated regime, the cluster medium exhibits a higher maximum energy than that achieved by the simple piston mechanism due to the additional accerelation by the Coulomb explosion. The optimum cluster radius for ion acceleration is found to exist depending on the laser power irradiated.

Oxygen and hydrogen isotopic variations between adjacent drips in three caves at increasing elevation in a temperate coastal rainforest, Vancouver Island, Canada

The interpretation of speleothem paleoenvironmental records requires understanding of spatial–temporal variations in vadose drip water chemistry and isotopic composition. This study reports on intra- and inter-cave differences in δD, δ18O and electrical conductivity, using 18 monthly water samples from three adjacent drips (<20m apart) in each of three caves at increasing elevation (0, 550, and 740m ASL) on very steep ground at the head of Tahsis Inlet fjord on the Pacific coast of Vancouver Island, British Columbia.All drips showed isotopic seasonal signals, despite varied patterns of drip hydrology. There was overlap in isotopic ranges (at 1 SD) between all three caves, in contrast with the expected δ18O depletion of −0.15 to −0.5‰/100m of ascent observed in standard precipitation. The isotopic seasonality was approximated with sine curves, and compared to a GNIP data set from Victoria ∼300km to the south. The δD and δ18O drip isotopes lagged the Victoria record by 155±26days and 165±50days respectively. The longest lag was at the slowest drip (sea level), while the shortest lag (87days for δ18O, 550m ASL) implies a short residence time, paradoxically from the drip with the highest mean electrical conductivity. Vadose residence time was less than one climatic year, reflecting a combination of negligible matrix porosity in the host rock and super-humid climatic conditions. Beneath the epikarst, drip hydrology was evidently by simple piston flow.Phase-shifted drip isotope records showed excellent agreement with sea level mean monthly air temperatures at the Tahsis meteorological station over the study period. The δD and δ18O drip amplitudes were damped on average 74% and 73% respectively compared to the Victoria data. The drips at 740m ASL are tightly aligned to the global mean meteoric water line (GMWL) and 18O-depleted; the drips at 550m ASL and at sea level plot along the GMWL, or between it and the Victoria LMWL, with the exception of the slowest drip (sea level) which displays some seasonal evaporitic enrichment.The findings quantify substantial intra- and inter-cave variation of δD and δ18O in drips having a wide range of drip type and volume of flow, sufficient to mute the altitudinal isotopic lapse rate in this local coastal rainforest environment.

The Concept of Single Use Piston Break Safety Syringe

A syringe is a simple piston pump consisting of a plunger that fits tightly in a tube. The plunger can be pulled and pushed along inside a cylindrical tube (the barrel), allowing the syringe to take in and expel a liquid or gas through an orifice at the open end of the tube. The open end of the syringe may be fitted with a hypodermic needle, a nozzle, or tubing to help direct the flow into and out of the barrel. Syringes are often used to administer injections, apply compounds such as glue or lubricant, and measure liquids. The reuse and abuse of syringe has led to cross-infection of diseases; thus, the need of single use safety syringe arises. Single use safety syringe is able to prevent the abuse of syringe. Many inventions have been produced; the most common are through-push retract breakable safety syringe, rotary plunger retractable safety syringe and release-ring breakable safety syringe. A new type of single use safety syringe Piston Break Safety Syringe is discussed in this paper. The new Piston Break Safety Syringe has similar design with the widely used safety syringe; hence, it makes it easier to be adapted by the users due to its similarity, since no extra training is required. The cost should be equivalently low due to the similarity in size, design and number of components.

Precipitation input and antecedent soil moisture effects on mercury mobility in soil—laboratory experiments with an enriched stable isotope tracer

AbstractTerrestrial soils are net mercury (Hg) sinks, but leaching of Hg from upland environments constitutes an important source to downstream wetlands and water bodies. Broadly, hydrology is instrumental in facilitating Hg transport within, and export from watersheds but the relative influences of specific hydrological factors such as antecedent soil moisture and precipitation in controlling the transport of Hg through upland soils are not well understood. The purpose of this research was to elucidate the relative controls of these hydrological factors using a full factorial laboratory experiment involving the application of an enriched stable Hg isotope tracer to intact soil cores. Antecedent soil moisture and precipitation input depth were statistically significant, mutually exclusive controls on tracer Hg mobility. Neither factor however had a strongly significant influence on the mobility of ambient Hg. Tracer Hg mobility was enhanced with larger precipitation events as well as from initially drier soils and appeared to move via simple piston flow. The majority (&gt;99.5%) of added tracer Hg was sorbed to soil organic matter in the surface 3 cm, regardless of the hydrological treatment combinations. Overall, these results suggest that tracer and ambient Hg are differentially controlled by hydrological conditions. Changes in hydrology may have little impact on ambient Hg mobilization in sandy loam soils. If tracer Hg is broadly representative of contemporary soil Hg stocks, extreme precipitation events among otherwise drier conditions could enhance the export of contemporary Hg from upland systems. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Mechanically Automated Light Weight WAstage REmover [MALWWARE

This paper proposes an innovative, Eco-friendly, simply operated system for cleaning of light weight wastage materials on municipal roads, which is equipped with cylinders of a typical Internal Combustion engine with mechanical gear trains. With simple piston action, we can remove light weight wastes like dry leaves and thin plastic things. Our conventional and present vacuum cleaners use either Electric power or Gasoline, since it is a kind of polluting our environment in an indirect way. To overcome the disadvantages of conventional systems and to protect our environment, we use a pneumatic system here with the least number of moving parts which are cheaper than present vacuum cleaners. This system does not need either Electrical or Gasoline energy. It is as simple as pushing a wheelchair, so anyone can run this system. We can extend its application to any level. Our system has two operations. Both operations are simultaneous and give more power to the machine.

Large-eddy simulations of turbulent flows in internal combustion engines

Large-eddy simulations (LES) of turbulent spray combustion in internal combustion engines are conducted with a new hybrid Eulerian–Lagrangian methodology. In this methodology, the Eulerian filtered compressible gas equations are solved in a generalized curvilinear coordinate system with high-order finite difference schemes for the turbulent velocity and pressure. However, turbulent mixing and combustion are simulated with the two-phase compressible scalar filtered mass density function (FMDF) and Lagrangian spray models. The LES/FMDF model is used for simulation of in-cylinder turbulent flow and spray mixing and combustion in three flow configurations: (1) a poppet valve in a sudden expansion, (2) a simple piston–cylinder assembly with a stationary valve, and (3) a realistic single-cylinder, direct-injection spark–ignition (DISI) engine. The flow statistics predicted by the LES model are shown to compare well with the available experimental data for (1) and (2). The computed in-cylinder flow for the third configuration shows significant cycle-to-cycle variations. The flow in the DISI engine is also highly inhomogeneous and turbulent during the intake stroke, but becomes much more homogeneous and less turbulent in the compression stroke. Simulations of spray, mixing and combustion in the DISI engine indicate the applicability of the LES/FMDF model to internal combustion engines and other complex combustion systems.

Evaluation of variable mass moment of inertia of the piston–crank mechanism of an internal combustion engine

The current paper presents an original method for evaluating the variable mass moment of inertia of the piston–crank mechanism of an internal combustion engine based on the principle of kinetic energy equality of the real mechanism and its reduced model. The method has been developed to evaluate the variable mass moment of inertia of a 12-cylinder V-engine having a piston–crank mechanism with main and auxiliary connecting rods. In order to study the influence of the piston–crank mechanism configuration on mass moment of inertia variability, the procedure has been also applied on virtual ‘shortened’ variants: 2-cylinder and 6-cylinder V-engines with main and auxiliary connecting rods, and a 6-cylinder in-line engine with simple piston–crank mechanism. The results are compared with values obtained using the usual simple method for determining the approximate constant mass moment of inertia based on Huygens–Steiner theorem. It is shown that there is negligible difference between the constant value obtained by the simple method and the mean value of variable mass moment of inertia evaluated using the proposed model. Variability of mass moment of inertia is relatively small for a large number of cylinders, but it rises with cylinder number reduction. The presented method with appropriate modifications may be applied to any piston–crank mechanism arrangement.

Using environmental tracers to assess the extent of river–groundwater interaction in a quarried area of the English Chalk

The Swanscombe area of Kent, SE England represents a typical example of a heavily quarried Chalk area currently undergoing re-development. Because the Chalk is also an important aquifer, a good understanding of groundwater movement is required if environmental impacts are to be minimised and the water resource maximised. In particular, the nature of the relationship between the River Darent and groundwater in the Swanscombe Chalk Block requires better characterisation. Here, ‘environmental tracers’ in the form of ambient concentrations of stable isotopes, chlorofluorocarbons (CFCs), sulphur hexafluoride (SF6) and tritium (3H) are used to investigate this and other aspects of groundwater movement in the vicinity of the quarries. Stable isotopic contrasts indicate little evidence for widespread river infiltration to the regional Chalk aquifer, although stable isotope and 3H data suggest that 20–35% of the abstraction by river-valley public water supply boreholes may be derived from the river. The CFCs, while present at above-modern concentrations in almost all groundwaters, can be used as tracers, indicating basically S–N flowpaths in the area south of the quarries, though sub-karstic conduits associated with areas of Palaeogene cover add a level of uncertainty at the local scale. Simple piston flow residence times based on SF6 range from 1 to 17 a, but the data are probably better interpreted in terms of mixing between varying amounts of modern recharge derived from the south and deeper stored groundwater. The information gained from environmental tracers can therefore contribute to effective resource management.

Echolocating bats emit a highly directional sonar sound beam in the field

Bats use echolocation or biosonar to navigate and find prey at night. They emit short ultrasonic calls and listen for reflected echoes. The beam width of the calls is central to the function of the sonar, but directionality of echolocation calls has never been measured from bats flying in the wild. We used a microphone array to record sounds and determine horizontal directionality for echolocation calls of the trawling Daubenton's bat, Myotis daubentonii, flying over a pond in its natural habitat. Myotis daubentonii emitted highly directional calls in the field. Directionality increased with frequency. At 40 kHz half-amplitude angle was 25°, decreasing to 14° at 75 kHz. In the laboratory, M. daubentonii emitted less intense and less directional calls. At 55 kHz half-amplitude angle was 40° in the laboratory versus 20° in the field. The relationship between frequency and directionality can be explained by the simple piston model. The model also suggests that the increase in the emitted intensity in the field is caused by the increased directionality, focusing sound energy in the forward direction. The bat may increase directionality by opening the mouth wider to emit a louder, narrower beam in the wild.

Can a transmission coefficient be greater than unity?

In studying the sound transmission through panels, it is usual to consider a model based on an infinite panel. The sound transmission coefficient is defined as the ratio of transmitted power to incident power and must, therefore, be less than or equal to unity due to energy conservation. However, it is shown here that, for a finite panel, it is possible to find values of transmission coefficient that are greater than unity at certain frequencies due to the normalisation used for the incident power. This occurs at the fundamental resonance of the fluid-loaded panel. Example results are presented for a simple circular piston and then for a flexible rectangular panel and an explanation for this phenomenon is provided. In effect, the panel is excited by a sound field that is much larger than its own surface and attracts sound power from a wide region of the incident field. This result stands as an interesting test case for calculation methods where the occurrence of transmission coefficients greater than unity should not necessarily be seen as an error in the calculation.

Analysis of piston assembly friction using the indicated mean effective pressure experimental method to validate mathematical models

The piston assembly friction is experimentally measured using the indicated mean effective pressure with detailed accuracy. The experimental results are compared with a relatively less complex piston assembly friction model typical of those used in industry, predicting the individual performance of compression rings, the oil control ring, and the piston skirt. The validation is carried out under fired conditions on a single-cylinder gasoline engine. The experimental results for an SAE 0W20 lubricant without a friction modifier were compared with the predictions. The predicted results correlate very well with the measurements, especially at higher lubricant inlet temperatures. The piston skirt friction was predicted using a simple concentric piston—cylinder model and a more realistic but computationally intensive method incorporating the piston's secondary motion. The results clearly indicate that a relatively less complex model can give realistic results under real engine conditions.

Sound field modelling using SimulUS

The motivation behind developing the SimulUS beam model was as a tool for the rapid visualisation of ultrasonic fields generated by phased array transducers (both linear and matrix). However, it is possible to model single crystal transducers by defining a 1 by 1 matrix. The present work was carried out using the version released in December of 2005 and was part of a larger validation programme in TWI involving other models. The core of the model is based on Huygen’s discretisation method of evaluating the free field ahead of the sound radiator (Section 2). SimulUS operates principally in the continuous wave (1) mode but a pulse wave expression is incorporated. The model is primarily designed for rapid visualisations of the sound field but it can be used as a pulse wave modelling package. The computing requirements are less intensive when the input waveform is of a single frequency (continuous wave). Hence, in this paper, the evaluation of the performance of SimulUS in its primary continuous wave mode is presented. SimulUS was envisioned for use in applications such as: q Technique development – such that the operator can rapidly evaluate the suitability of a particular setup for the inspection task. q Probe design – confident design of, in particular, phased array probes such that the designer can ensure that the parameters are correctly specified to achieve optimised field properties for the application. q Training – allowing students to understand the basics of phased array ultrasonics and conventional ultrasonics through an interactive learning approach; where the effects of varying the crystal size, pitch, frequency etc on the ultrasonic field generated by the transducer can be understood and even the effects of failed elements modelled. 2. Principles of ultrasonic field models Ultrasonic field models have been developed utilising various different theories. In essence, they are all required to evaluate the sound pressure field ahead of a transducer. As well as SimulUS, two other successful models will be described to illustrate the different approaches that have been taken in the past; both models are well established and have been extensively validated within industry and by research organisations. The models developed in the Non-Destructive Testing Applications Centre (NDTAC) of the Central Electricity Generating Board (CEGB) were based on an analytical approximation to the pressure distribution over the sound radiator. The CIVA model, developed by Commissariat a l’energie Atomique (CEA), is a semi-analytical model using a theory for electromagnetic wave propagation that was adapted for simulating the elastodynamic propagation of sound waves (2) . The sound field ahead of the probe face can be described using Huygen’s principle, which uses elementary waves of the same frequency which originate at discrete points on the radiating surface (3) . These waves then undergo interference effects in front of the radiating surface and their summation, as derived by Fresnel, gives the strength of the field at any point ahead of the probe. The solution depends on noting that at any given point ahead of the radiator, Huygens’ elementary waves from discrete points have taken different paths. Since the sound pressure has an inverse relationship to actual distance travelled from the origin, the path difference dictates actual pressure contributions from each elementary wave at the point of interest. This method of evaluating the resultant pressure contribution is known as zone construction. For each elementary contribution, the path difference is converted to an angular measurement along with the change in pressure at the given distance; vector addition is used to evaluate the pressure and phase at any given point ahead of the radiator. This method can be used effectively for evaluating the pressure values along the beam axis and off axis with modifications to the element configuration. This forms the basis of the SimulUS model where the contribution of wavelets from sources on the transducer is summed on the calculation plane. The NDTAC beam model is an analytical model that was developed to form part of a larger systematic approach to the modelling of ultrasonic inspections. The model was designed to generate the sound fields created by single crystal probes. It is a modified version of the simple piston oscillator model of a single crystal. The Fresnel integral approach to evaluate pressure values at a general point ahead of the probe face is computationally intensive. The NDTAC model was envisaged as a module in a systematic approach to evaluating defect interaction; since the beam model needed to be run several times, it needed to be computationally less intensive while providing sufficient accuracy in the prediction of pressure values ahead of the probe. Hence, the NDTAC model suggests an approximation for the amplitude profile over the radiating face such that the evaluation of the field ahead can be performed analytically as opposed to resorting to numerical methods (4)

Effect of Axially Symmetric Magnetic Fields for Dynamics of Low-Current DC Vacuum Arc Plasma

In this paper, effects of four types of axially symmetric magnetic fields on the dynamics of low-current dc vacuum arc plasma, which is less than 30 A, were examined. Arcs were ignited by the opening of the butt contacts made of zinc. In the axial magnetic field, the arc plasma was restricted within a column, and the arc voltage rose with increasing gap length. When a magnet was arranged behind the cathode, the cathode spot rotated in the opposite direction to the Lorentz force (-J times B) on the edge of the circular-rod cathode. On the other hand, when a magnet was arranged behind the anode, the arc plasma was constricted on the anode side, and the lifetimes of the arcs became longer, although the arc voltage rose with increasing gap length. The compression effect of the axial component of the magnetic field was analyzed by introducing a simple magnetic piston model, and the experimental diameters of the arc column showed a good agreement with the model.