compression and expansion
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Machines ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 62
Author(s):  
Chuang Wang ◽  
Bingqi Wang ◽  
Mingkun Liu ◽  
Ziwen Xing

Screw machines, mainly including single-screw type and twin-screw type, have gone through significant development and improvement during the past decade. This paper reviews the relevant studies available in the open literature for acquiring insight into and to establish the state of the art of the research and application status of screw machines. The related research on different aspects, which would affect the performance and reliability of screw machines includes rotor profile and geometric characteristics, thermodynamic modelling, vibration and noise, lubrication and wear, control of capacity and built-in volume ratio, and liquid injection technology. In the aspect of thermodynamic modelling, the available methods, i.e., empirical or semi-empirical model, lump model, and 3D CFD model, adopted for the performance prediction and optimal design of screw machines are summarized. Then, the review covers the application status of screw machines in the fields of air compression and expansion, refrigeration and heat pump, organic Rankine cycle (ORC), and other popular applications, with an emphasis on the reported performance and progress in technologies of screw machines. Finally, conclusions and perspectives for future research in the area of screw machines are presented. The review provides readers with a good understanding of the research focus and progress in the field of screw machines.


2022 ◽  
Author(s):  
B. Kodess

Abstract. The structural characteristics of samples of a four-component superconducting material (YBCO) after exposure to X-ray irradiation during a long time are investigated. The effect of X-ray beam processing on angular positions (corresponding parameters of the crystal lattice) and the width of Bragg reflections is established. The phenomenon of oscillatory behavior in the unit cell dimension with long-time irradiation is found. The analysis of the profiles of reflection also demonstrates the presence of reversible changes phase composition with the exposure time. The observed phenomena reflect the presence of a nontrivial and specific process of compression and expansion of the unit cell due to the accumulation and then disengagement outside of ionized oxygen, which is formed under such irradiation exposure on the surface of the samples.


Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 111
Author(s):  
Denis Wittor ◽  
Matthias Hoeft ◽  
Marcus Brüggen

Radio relics are diffuse synchrotron sources that illuminate shock waves in the intracluster medium. In recent years, radio telescopes have provided detailed observations about relics. Consequently, cosmological simulations of radio relics need to provide a similar amount of detail. In this methodological work, we include information on adiabatic compression and expansion, which have been neglected in the past in the modelling of relics. In a cosmological simulation of a merging galaxy cluster, we follow the energy spectra of shock accelerated cosmic-ray electrons using Lagrangian tracer particles. On board of each tracer particle, we compute the temporal evolution of the energy spectrum under the influence of synchrotron radiation, inverse Compton scattering, and adiabatic compression and expansion. Exploratory tests show that the total radio power and, hence, the integrated radio spectrum are not sensitive to the adiabatic processes. This is attributed to small changes in the compression ratio over time.


2021 ◽  
Vol 63 ◽  
pp. 342-358
Author(s):  
Jasobanta Jena ◽  
Sheena Mittal

We investigate the interaction between a singular surface and a strong shock in the self-gravitating interstellar gas clouds with the assumption of spherical symmetry. Using the method of the Lie group of transformations, a particular solution of the flow variables and the cooling–heating function for an infinitely strong shock is obtained. This paper explores an application of the singular surface theory in the evolution of an acceleration wave front propagating through an unperturbed medium. We discuss the formation of an acceleration, considering the cases of compression and expansion waves. The influence of the cooling–heating function on a shock formation is explained. The results of a collision between a strong shock and an acceleration wave are discussed using the Lax evolutionary conditions.   doi:10.1017/S1446181121000328


2021 ◽  
pp. 1-19
Author(s):  
Alexandra N. Scurry ◽  
Daniela M. Lemus ◽  
Fang Jiang

Abstract Reliable duration perception is an integral aspect of daily life that impacts everyday perception, motor coordination, and subjective passage of time. The Scalar Expectancy Theory (SET) is a common model that explains how an internal pacemaker, gated by an external stimulus-driven switch, accumulates pulses during sensory events and compares these accumulated pulses to a reference memory duration for subsequent duration estimation. Second-order mechanisms, such as multisensory integration (MSI) and attention, can influence this model and affect duration perception. For instance, diverting attention away from temporal features could delay the switch closure or temporarily open the accumulator, altering pulse accumulation and distorting duration perception. In crossmodal duration perception, auditory signals of unequal duration can induce perceptual compression and expansion of durations of visual stimuli, presumably via auditory influence on the visual clock. The current project aimed to investigate the role of temporal (stimulus alignment) and nontemporal (stimulus complexity) features on crossmodal, specifically auditory over visual, duration perception. While temporal alignment revealed a larger impact on the strength of crossmodal duration percepts compared to stimulus complexity, both features showcase auditory dominance in processing visual duration.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yiran Ding ◽  
Mengqi Zeng ◽  
Qijing Zheng ◽  
Jiaqian Zhang ◽  
Ding Xu ◽  
...  

AbstractInterlayer spacing is expected to influence the properties of multilayer two-dimensional (2D) materials. However, the ability to non-destructively regulate the interlayer spacing bidirectionally and reversibly is challenging. Here we report the preparation of 2D materials with tunable interlayer spacing by introducing active sites (Ce ions) in 2D materials to capture and immobilize Pt single atoms. The strong chemical interaction between active sites and Pt atoms contributes to the intercalation behavior of Pt atoms in the interlayer of 2D materials and further promotes the formation of chemical bonding between Pt atom and host materials. Taking cerium-embedded molybdenum disulfide (MoS2) as an example, intercalation of Pt atoms enables interlayer distance tuning via an electrochemical protocol, leading to interlayer spacing reversible and linear compression and expansion from 6.546 ± 0.039 Å to 5.792 ± 0.038 Å (~11 %). The electronic property evolution with the interlayer spacing variation is demonstrated by the photoluminescence (PL) spectra, delivering that the well-defined barrier between the multilayer and monolayer layered materials can be artificially designed.


2021 ◽  
Vol 13 (2) ◽  
pp. 255
Author(s):  
Hari Subagio ◽  
Evron Asrial ◽  
Yusnaini Yusnaini ◽  
Nurul Rosana ◽  
Gatut Bintoro ◽  
...  

Highlight ResearchThe mortality of lobster seeds by predators in the first year is 96.0-99.4%It takes technology to catch seeds before being eaten by predatorsApplication of sound wave-based attractor technology to lobstersDo lobsters have the ability to hear sound waves?The lobster's sense of hearing begins to function from the puerulus stage AbstractIndonesia is a country that produces abundant lobster seeds (puerulus), however, there is a paradox, where natural mortality in the first year since entering the settlement phase can reach 96.0-99.4%. The use of lobster resources, especially in the puerulus stage, for cultivation, is very strategic. Therefore, it is necessary to improve puerulus fishing technology. In the capture fisheries sector, the use of the sense of hearing in fish resources has been carried out to increase catch productivity, by utilizing sound wave-based attractors’ technology. For lobster resources, to what extent is this technology applicable? Underwater sound waves are a phenomenon of compression and expansion of a medium as sound energy passes through it. This aspect of the study is still new and very prospective. The purpose of this review article is to answer some basic questions: Can lobsters be able to hear sounds that come from their surroundings, since when do lobsters sense of hearing begin to function, and anatomically what kind of auditory organs are in lobsters. The results of the review conclude as follows: lobsters have senses that are able to perceive or listen to sound waves (sound) from their surrounding environment, this ability has been possessed by lobsters since they were in the postlarva or puerulus stage. Anatomically, the organs that act as the sense of hearing in lobsters are: receptors on the body surface, chordotonal organs and statocyst organs.


Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2684
Author(s):  
Xiuxiu Lyu ◽  
Yujie Zhu ◽  
Chi Zhang ◽  
Xiangyu Hu ◽  
Nikolaus A. Adams

In this paper, a Lagrangian-Eulerian (LE) two-way coupling model is developed to numerically study the cavitation bubble cloud. In this model, the gas-liquid mixture is treated directly as a continuous and compressible fluid and the governing equations are solved by methods in Eulerian descriptions. An isobaric closure exhibiting better consistency properties is applied to evaluate the pressure of gas-liquid mixture. The dispersed gas/vapor bubbles are tracked in a Lagrangian fashion, and their compression and expansion are described by a modified Rayleigh-Plesset equation, which considers the close-by flow properties other than these of the infinity for each bubble. The performance of the present method is validated by a number of benchmark tests. Then, this model is applied to study how the bubble cloud affects the shape and propagation of a pressure wave when the pressure pulse travels through. In the end, a three-dimensional simulation of a vapor cloud’s Rayleigh collapse is carried out, and the induced extreme pressure is discussed in detail. The total bubble number’s influence on the extreme collapse pressure and the size distribution of bubbles during the collapse are also analyzed.


2021 ◽  
pp. 1-17
Author(s):  
J. JENA ◽  
S. MITTAL

Abstract We investigate the interaction between a singular surface and a strong shock in the self-gravitating interstellar gas clouds with the assumption of spherical symmetry. Using the method of the Lie group of transformations, a particular solution of the flow variables and the cooling–heating function for an infinitely strong shock is obtained. This paper explores an application of the singular surface theory in the evolution of an acceleration wave front propagating through an unperturbed medium. We discuss the formation of an acceleration, considering the cases of compression and expansion waves. The influence of the cooling–heating function on a shock formation is explained. The results of a collision between a strong shock and an acceleration wave are discussed using the Lax evolutionary conditions.


2021 ◽  
Author(s):  
Houda Hachem ◽  
Ramla Gheith ◽  
Fethi Aloui

Abstract By developing our proper CFD code under Fortran, the performances of a Stirling engine are studied in unsteady laminar regime and closely linked to the properties of its regenerator. However, it is responsible about the maximum part of losses in the Stirling engine. These losses depend on geometric and physical properties of the material constituting the regenerator. Thus, finding the suitable regenerator material that generates the greatest heat exchange and the lowest pressure drop is a good solution to reduce sources of irreversibility and ameliorate the global performances of the Stirling engine. The aim of this paper is to describe oxillatory flow and heat transfer inside porous regenerator materials and to determine the most suitable regenerator material. Brinkman-Forchheimer-Lapwood extended Darcy model is assumed to simulate momentum transfer within the porous regenerator. And the oscillatory flow is described by the Navier-Stockes compressible equations. The local thermal equilibrium of the gas and the matrix is taken into account for the modelling of the porous regenerator. The governing equations with the appropriate boundary conditions are solved by the control volume based finite element method (CVFEM). A numerical code on the software Fortran is elaborated to evaluate flow and heat transfer characteristics inside regenerator. Results showed that the fluid flow and heat transfer between the compression and expansion phases were varied significantly. It was shown that the superior comprehensive performance of the regenerator makes it possible to improve the performance of Stirling engines.


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