bluuebunny/crossref_metadata_2025 huggingface dataset:
Botany.
Authors: Thompson Anthony Keith , Oduro Ibok
Published: September 2021

This chapter covers the taxonomy, molecular taxonomy, genomics, breeding and physiology of yams (Dioscorea spp).
Essays and projects.
Authors: Bren Leon , Lane Patrick
Published: September 2021

This chapter contains essays questions and projects about hydrology and water management which can be enjoyable to do and can add greatly to student's depth of understanding.
A PDE hierarchy for directed polymers in random environments
Authors: Gu Yu , Henderson Christopher
Published: September 2021

For a Brownian directed polymer in a Gaussian random environment, with q(t, ⋅) denoting the quenched endpoint density and

Q

n

(

t
,

x

1

,
…
,

x

n

)

=
E

[

q

(

t
,

x

1

)

…
q

(

t
,

x

n

)

]

,

we derive a hierarchical PDE system satisfied by

{

Q

n

}

n
⩾
1

. We present two applications of the system: (i) we compute the generator of

{

μ

t

(

d
x

)

=
q

(

t
,
x

)

d
x

}

t
⩾
0

for some special functionals, where

{

μ

t

(

d
x

)

}

t
⩾
0

is viewed as a Markov process taking values in the space of probability measures; (ii) in the high temperature regime with d ⩾ 3, we prove a quantitative central limit theorem for the annealed endpoint distribution of the diffusively rescaled polymer path. We also study a nonlocal diffusion-reaction equation motivated by the generator and establish a super-diffusive O(t
2/3) scaling.
Discharge dynamics, plasma kinetics and gas flow effect in argon–acetylene discharges
Authors: Tetard G , Michau A , Prasanna S , Mougenot J , Brault P , Hassouni K
Published: September 2021

We investigated capacitively coupled Ar/C2H2 RF plasmas with a 1D fluid model that couples a 13.56 MHz discharge module, a long timescale chemical module and a flow transport module. A new solution procedure was developed in order to accurately describe the coupling between the short timescale discharge dynamics and the long characteristic time processes that play a major role in the molecular growth of reactive species. The plasma was simulated for different inlet gas configurations and flowrates. We showed that for a showerhead configuration one may distinguish two situations. For short residence time the plasma was strongly electronegative in the very center of the discharge gap and dominated by large hydrocarbon positive and negative ions. In this situation the acetylene conversion, although moderate, lead to a significant molecular growth. For long residence time, although C2H2 underwent a total conversion, the products of the primary C2H2 dissociation process were consumed by surface deposition which reduced drastically the molecular growth in the short gap discharge considered here. Whatever the conditions, we confirmed the key-role of Ar* in the acetylene conversion, ionization kinetics as well as the subsequent molecular growth for neutral and charged species. We also showed that remote feed gas and showerhead configurations predicted similar results at low flowrate. At larger flowrate the two configurations presented some discrepancy. Especially H2 density was much larger for the remote feed gas configuration, which affected the overall plasma behavior. Our results highlight that realistic gas-flow models are essential for an accurate description of acetylene conversion in Ar/C2H2 plasma.
Formation and neutralization of electric charge and current of an ion thruster plume
Authors: Perales-Díaz Jesús , Cichocki Filippo , Merino Mario , Ahedo Eduardo
Published: September 2021

A 3D hybrid model is introduced and applied to the simulation of the xenon plasma plume extraction, formation, and neutralization in a gridded ion thruster. The acceleration voltage is 1100 V and the inflow Xe+ per hole ranges from 0.07 to 0.92 μg s−1. While ions and neutrals are treated with a particle-in-cell formulation, electrons are modeled as two independent isothermal populations: one inside the discharge chamber and one in the plume. The definition of a thermalized potential allows to solve the electron currents in the high-conductivity limit of the Ohm’s law. The space charge neutralization distance is observed to be short and thus essentially independent of the acceleration grid-neutralizer distance, which is varied from 10 to 25 mm axially. However, this position strongly affects the electric current neutralization paths in the near plume for each ion beamlet. Electron inertial forces are shown to be comparable to collisional forces in certain plasma regions. A semi-analytical 1D fluid model of the plume, matched to the hybrid model, allows to complete the far plume expansion down to infinity. Grids with an infinite and finite number of apertures are simulated and compared with each other and with the 1D model. The numerically obtained divergence angle of the ion plume is compared with experimental measurements, observing relative errors of around 7% in the position of the optimal perveance, and smaller than 4% in the divergence angle average value.
Enhancement of isolated attosecond pulse generation by using long gas medium
Authors: Liang Yueying , He Xinkui , Zhao Kun , Teng Hao , Wei Zhiyi
Published: September 2021

Isolated attosecond pulse generation in argon is theoretically investigated for different gas pressures and medium lengths. The output of attosecond pulse is effectively enhanced by using a longer gas medium with optimized pressure. The peak intensity of the attosecond pulse by using 6 mm gas medium is doubled compared with that of 1–3 mm gas cell, which is usually used in the experiment. Our simulation shows that the distortion of the driving laser waveform and the absorption are the main factors that limit the output of the attosecond pulse for the long gas medium. Optimized generation condition could be found by balancing the medium length and pressure.
Strong-field response time and its implications on attosecond measurement
Authors: Chen Chao , Che Jiayin , Xie Xuejiao , Wang Shang , Xin Guoguo , Chen Yanjun
Published: September 2021

To measure and control the electron motion in atoms and molecules by the strong laser field on the attosecond time scale is one of the research frontiers of atomic and molecular photophysics. It involves many new phenomena and processes and raises a series of questions of concepts, theories, and methods. Recent studies show that the Coulomb potential can cause the ionization time lag (about 100 attoseconds) between instants of the field maximum and the ionization-rate maximum. This lag can be understood as the response time of the electronic wave function to the strong-field-induced ionization event. It has a profound influence on the subsequent ultrafast dynamics of the ionized electron and can significantly change the time–frequency properties of electron trajectory (an important theoretical tool for attosecond measurement). Here, the research progress of response time and its implications on attosecond measurement are briefly introduced.
Shedding vortex simulation method based on viscous compensation technology research
Authors: Zhou Hao , Wang Lei , Huang Zhang-Feng , Ren Jing-Zhi
Published: September 2021

Owing to the influence of the viscosity of the flow field, the strength of the shedding vortex decreases gradually in the process of backward propagation. Large-scale vortexes constantly break up, forming smaller vortexes. In engineering, when numerical simulation of vortex evolution process is carried out, a large grid is needed to be arranged in the area of outflow field far from the boundary layer in order to ensure the calculation efficiency. As a result, small scale vortexes at the far end of the flow field cannot be captured by the sparse grid in this region, resulting in the dissipation or even disappearance of vortexes. In this paper, the effect of grid scale is quantified and compared with the viscous effect through theoretical derivation. The theoretical relationship between the mesh viscosity and the original viscosity of the flow field is established, and the viscosity term in the turbulence model is modified. This method proves to be able to effectively improve the intensity of small-scale shedding vortexes at the far end of the flow field under the condition of sparse grid. The error between the simulation results and the results obtained by using fine mesh is greatly reduced, the calculation time is shortened, and the high-precision and efficient simulation of the flow field is realized.
A new algorithm for reconstructing the three-dimensional flow field of the oceanic mesoscale eddy*
Authors: Yan Chao , Feng Jing , Yang Ping-Lv , Huang Si-Xun
Published: September 2021

A new algorithm for reconstructing the three-dimensional flow field of the oceanic mesoscale eddies is proposed in this paper, based on variational method. Firstly, with the numerical differentiation Tikhonov regularizer, we reconstruct the continuous horizontal flow field on discrete grid points at each layer in the oceanic region, in terms of the horizontal flow field observations. Secondly, benefitting from the variational optimization analysis and its improvemen, we reconstruct a three-dimensional flow field under the constraint of the horizontal flow and the vertical flow. The results of simulation experiments validate that the relative error of the new algorithm is lower than that of the finite difference method in the case of high grid resolution, which still holds in the case of unknown observational errors or in the absence of vertical velocity boundary conditions. Finally, using the reanalysis horizontal data sourcing from SODA and the proposed algorithm, we reconstruct three-dimensional flow field structure for the real oceanic mesoscale eddy.
Decoding the electron dynamics in high-order harmonic generation from asymmetric molecular ions in elliptically polarized laser fields
Authors: Zhang Cai-Ping , Miao Xiang-Yang
Published: September 2021

The high-order harmonic generation from an asymmetric molecular ion is theoretically investigated based on the Born–Oppenheimer model with two-dimensional electron dynamics. It is shown that the harmonic intensity changes periodically in elliptically polarized laser fields. The periodical character is ellipticity-dependent. By establishing the physical image, the periodicity of the harmonic intensity can be ascribed to the contributions of the ground state and the excited state. Furthermore, the electron dynamics from different electronic states can be selected via combining the elliptically polarized laser field with a static electric field. The harmonics dominated either by ground state or excited state are emitted once in an optical cycle in the combined laser field.
Self-adaptive behavior of nunchakus-like tracer induced by active Brownian particles
Authors: Xia Yi-Qi , Feng Guo-Qiang , Shen Zhuang-Lin
Published: September 2021

We design a nunchakus-like tracer and investigate its self-adaptive behavior in an active Brownian particle (ABP) bath via systematically tuning the self-propelled capability and density of ABPs. Specifically, the nunchakus-like tracer will have a stable wedge-like shape in the ABP bath when the self-propelled force is high enough. We analyze the angle between the two arms of the tracer and the velocity of the joint point of the tracer. The angle exhibits a non-monotonic phenomenon as a function of active force. However, it increases with density of ABPs increasing monotonically. A simple linear relationship between the velocity and the self-propelled force is found under the highly active force. In other words, the joint points of the tracer diffuse and the super-diffusive behavior can make the relation between the self-propelled force and the density of ABPs persist longer. In addition, we find that the tracer can flip at high density of ABPs. Our results also suggest the new self-adaptive model research of the transport properties in a non-equilibrium medium.
Characterizing microlensing planetary system OGLE-2014-BLG-0676Lb with adaptive optics imaging*
Authors: Xie Xiao-Jia , Dong Subo , Shvartzvald Yossi , Gould Andrew , Udalski Andrzej , Beaulieu Jean-Philippe , Beichman Charles , Close Laird Miller , B. Henderson Calen , R. Males Jared , Marquette Jean-Baptiste , M. Morzinski Katie , R. Gelino Christopher
Published: September 2021

We constrain the host-star flux of the microlensing planet OGLE-2014-BLG-0676Lb using adaptive optics (AO) images taken by the Magellan and Keck telescopes. We measure the flux of the light blended with the microlensed source to be K = 16.79 ± 0.04 mag and J = 17.76 ± 0.03 mag. Assuming that the blend is the lens star, we find that the host is a

0.73

−
0.29

+
0.14

M
⊙

star at a distance of

2.67

−
1.41

+
0.77

kpc, where the relatively large uncertainty in angular Einstein radius measurement is the major source of uncertainty. With mass of

M
p

=

3.68

−
1.44

+
0.69

M
J

, the planet is likely a “super Jupiter” at a projected separation of

r
⊥

=

4.53

−
2.50

+
1.49

AU, and a degenerate model yields a similar

M
p

=

3.73

−
1.47

+
0.73

M
J

at a closer separation of

r
⊥

=

2.56

−
1.41

+
0.84

AU. Our estimates are consistent with the previous Bayesian analysis based on a Galactic model. OGLE-2014-BLG-0676Lb belongs to a sample of planets discovered in a “second-generation” planetary microlensing survey and we attempt to systematically constrain host properties of this sample with high-resolution imaging to study the distribution of planets.
Corrigendum: Reaching 30% energy coupling efficiency for a high-density-carbon capsule in a gold rugby hohlraum on NIF (2021 Nucl. Fusion
64 086028)
Authors: Ping Y. , Amendt P. , Baker K. , Smalyuk V.A. , Chen H. , Khan S. , Hartouni E.P. , Ho D. , Jones O. , Landen O.N. , Lemos N. , Lindl J. , Moody J. , Nikroo A. , Rubery M. , Schlossberg D.J. , Stadermann M. , Strozzi D. , Tipton R. , Woodworth B. , Adrian P.J. , Lahmann B. , Frenje J. , Petrasso R. , Kong C. , Rice N. , Wild C.
Published: September 2021

In the published paper titled ‘Reaching 30% energy coupling efficiency for a high-density-carbon capsule in a gold rugby hohlraum on NIF’ (2021 Nucl. Fusion
61 086028), the red shaded areas representing experimental uncertainties did not show up in figures 2 and 3. This corrigendum provides the correct figures 2 and 3.
Overview of coordinated spherical tokamak research in Japan
Authors: Takase Y. , Ejiri A. , Fujita T. , Hanada K. , Idei H. , Nagata M. , Onchi T. , Ono Y. , Tanaka H. , Tsujii N. , Uchida M. , Yasuda K. , Kasahara H. , Murakami S. , Takeiri Y. , Todo Y. , Tsuji-Iio S. , Kamada Y.
Published: September 2021

Spherical tokamak (ST) research in Japan has produced many innovative results: (i) plasma start-up to I
p > 70 kA was achieved by electron cyclotron wave (ECW) with N
∥ = 0.75, while electron heating to T
e > 500 eV was achieved with N
∥ = 0.26 on QUEST. (ii) The radiofrequency (RF)-induced transport model was combined with the x-ray emission model, and extended magnetohydrodynamics equilibrium with kinetic electrons was developed to interpret fast-electron-dominated lower hybrid wave sustained plasmas on TST-2. (iii) Density as high as 30 times the cutoff density was achieved by electron Berstein wave current drive combined with electron beam injection on LATE. (iv) Multiple plasmoids formed by tearing instability in the elongated current sheet were observed, and flux closure and ion heating by plasmoid-mediated fast magnetic reconnection were observed on HIST. (v) Optimization of ECW-assisted inductive start-up with a vertical field with positive decay index was performed on TST-2. (vi) Stabilization of the vertical displacement event by a set of upper and lower helical field coils was demonstrated on TOKASTAR-2. (vii) A 6 h discharge was achieved by cool-down of the center stack cover on QUEST, where the plasma duration limit was consistent with the wall saturation time estimated by modeling. (viii) Extension of ion heating by plasma merging was achieved on TS-3U, TS-4U, UTST, MAST, and ST40.
Classification of the reducible Verma modules over the Jacobi algebra

G2
Authors: Aizawa N , Dobrev V K , Doi S
Published: September 2021

In the present paper we study the representations of the Jacobi algebra. More concretely, we define, analogously to the case of semi-simple Lie algebras, the Verma modules over the Jacobi algebra

G

2

. We study their reducibility and give explicit construction of the reducible Verma modules exhibiting the corresponding singular vectors. Using this information we give a complete classification of the reducible Verma modules. More than this we exhibit their interrelation of embeddings between these modules. These embeddings are illustrated by diagrams of the embedding patterns so that each reducible Verma module appears in one such diagram.
Design of android based Unmanned Surface Vehicles (USV) for oil spill monitoring
Authors: Ardiansyah  , Oktaviano I Z , Sutrisno I , Adhitya R Y , Arfianto A Z , Suharso D D , Suwondo I , Ardhana V Y P , Soeroso H , Mulyodiputro M D
Published: September 2021

In this research, a USV will be developed that can detect oil spills on the waters, so in the future it can overcome the problem of water pollution. To be able to determine the thickness of the oil on the water surface, TEMT6000 and LED sensors are used. The light intensity will be converted into ADC value by the TEMT6000 sensor. Furthermore, on this system USV will be controlled by Android and can monitor water surface conditions. Android applications will be connected to Wemos via wifi. Then Wemos is connected serially with a RF915 and another RF915 will be connected to the microcontroller of the USV. From the results of the USV test, the USV can be controlled via Android by moving forward, backward, turning left and right. The maximum range of RF915 is 493.3 meters. Then the oil spill detection average error is 5.45% and the the average of the success rate is 94.55%.
Analysis of equipment for biaxial material testing
Authors: Hassasroudsari P , Kubec V , Prantl A
Published: September 2021

This paper aims to analyze the operation of the equipment for biaxial testing. The equipment’s stiffness is one of the main factors influencing the magnitude of reaction forces in the device’s guidance, consequently affecting the measurement accuracy. Based on intensive research on the topic of biaxial testing devices, the present paper deals with the analysis and optimization of the equipment’s current design.
Determination of mechanical properties of steam turbine rotor materials
Authors: Rund M , Džugan J , Konopík P , Nesládek M , Kuželka J , Růžička M , Méšt’ánek P
Published: September 2021

Increasing share of renewable energy sources in the electricity production results in a pressure on the thermal power plants to cover the power fluctuation very frequently. The increasing number of the start-ups and shutdowns as well as requirements for prompt ramping and for higher operation temperature has cardinal influence on the lifetime of the steam turbine. This all brings new challenges in to the designing process of the new steam turbines and lifetime analysis of currently operated ones. This paper aims to present experimental work, basic material parameters such as tensile test properties and FATT are determined here. Additionally, advanced material properties are probed by fracture toughness tests, fatigue crack growth tests and stress intensity factor threshold tests under various temperature ranges and cycle asymmetries R. The study is carried out for several steels used for the turbine shafts design.
The use of induction heating in reaction apparatus small tonnage production
Authors: Savina A S , Men’shikov V V , Boldyrev V S , Razvodova A A , Bogatov N A , Zotkin A P
Published: September 2021

Currently, in the planning and further implementation of technological processes that require heating of products to operating temperatures of about 1300 C, the issue of selecting energy-efficient environmentally friendly reactors using various heating methods is an acute issue. This scientific article discusses the effective use of electric and non-electric heating methods. Recommendations on the practical application of these methods are given, based on the final product and the specific features of the technological cycle of a particular enterprise. The question of the compliance of both methods with modern international requirements for the small-tonnage chemistry devices under consideration is considered. On the example of the Scientific Production Association «Lakokraspokrytiye» the main advantages in the application of induction heating in reactors used in technological lines for the production of paints and varnishes and coatings are shown. Examples are given of devices that are currently being developed and implemented in the Scientific Production Association «Lakokraspokrytiye», their basic characteristics are described. The described small-tonnage chemistry devices are widely used in the Russian Federation, CIS countries and Eastern Europe.
Problems with Surface Protection of Welded Joints by Vitreous Enamel Coating
Authors: Sternadelová K , Mohyla P , Kozák J , Krupová H , Krejčí L
Published: September 2021

This work deals with the application of a vitreous enamel coating on welded joints, whereas vitreous enamel being intentionally applied in high thicknesses. As a base material, we used low-carbon steel Kosmalt E 300 T. Two different processes were chosen for pre-treatment-chemical and mechanical. The resulting enamel coating consisted of two successively applied layers of base and cover enamel coating. The thickness and microhardness of the coating were measured. The metallographic analysis was also performed on selected samples. The results show that the high thickness of the enamel coating significantly impairs the useful properties of the product.
Material characterization of Au/Ni nanocatalyst for low-temperature carbon dioxide methanation
Authors: Tomiczek Blażej , Szindler Marek , Pawlyta Miroslawa , Borylo Paulina
Published: September 2021

The nanocatalyst for the carbon oxide methanation process is used, among others, in environmental protection, chemical industry, and renewable energy sources. The use of a suitable catalyst allows a chemical reaction to be carried out between unreacted gaseous substrates. The most frequently studied monometallic catalysts are: Ni, Ru, Rh, Pt, Au, Cu, Fe. Bimetallic nanocatalysts are equally popular. Their catalytic properties differ from those of pure component metals. Numerous studies indicate a positive effect in catalysts containing particles: Au-Ag, Au-Pt, Au-Pd, Pd-Ni, Pd-Cu. A review of the literature indicates that examples of the use of metal nanoparticles of spherical shape deposited on a nickel substrate in the methanation process are known, but so far no attempt has been shown in publications to produce a catalyst based on gold nanoparticles with developed surface in the form of spiky (nanourchins, nanostars) on a nickel base as presented in the article. Gold nanourchins are deposited on a nickel substrate in the form of a nickel molecular mesh. The prepared nanocatalyst has been subjected to structural analysis using a transmission electron microscope (TEM). Scanning Electron Microscopic (SEM) images were taken with a Zeiss Supra 35. Qualitative studies of chemical composition were also performed using the Energy Dispersive Spectrometer (EDS). Based on the TEM results, the appearance of the X-ray diffraction pattern was computer modelled. A nanocatalyst was obtained with a high coverage of the nickel molecular mesh surface with gold nanoparticles not exceeding 50 nm in diameter.
Chemical-mechanical polishing of TRIP steel surface
Authors: Ambrož O , Černík D , Rychlý D , Jozefovič P , Mikmeková Š
Published: September 2021

TRIP steels are mostly used due to their high mechanical properties in the automotive industry. The excellent mechanical properties of these steels are inseparably related to the retained austenite phase (γ) phase. Therefore, accurate knowledge of γ phase volume fraction, size, and distribution within a matrix is crucial for a correct understanding of the structure-properties relationship. This study aims to clarify the effect of the sample preparation technique on the results of phase analysis obtained by an electron back-scattered diffraction (EBSD) method. For EBSD analysis, the TRIP steel specimens were prepared by various techniques, such as mechanical polishing, chemical-mechanical polishing (CMP), and electropolishing. The CMP technique shows the most promising results. Therefore, this work focuses mainly on a methodology for optimizing this technique.
Modelling of inhomogeneous chamber states in rotary positive displacement vacuum pumps
Authors: Pleskun Heiko , Jünemann Timo , Bode Tobias , Brümmer A.
Published: September 2021

Chamber model simulation is a common approach to simulate rotary positive displacement vacuum pumps. Therefore the pump is abstracted into working chambers and connecting clearances, whereby the clearance leakages can be identified as the major loss mechanism in such machines. The clearance mass flow rates are calculated with respect to the thermodynamic states in the adjacent chambers, which are normally considered to be homogeneous. In this work it is shown, that the chamber state is inhomogeneous for rarefied gases due to the movement of the pistons which causes a pressure gradient within the chamber. This effect increases with higher Knudsen numbers, because of the increasingly dominant friction. An efficient way to model these inhomogeneous states with a one-dimensional approach for geometrically abstracted chambers is shown. The approach is applied to chamber model simulations of a screw spindle vacuum pump (SSVP) and the results are compared to simulations with homogeneous chamber states and to measurements.
Optimization of the tip profile of orbiting scroll in an asymmetry suction chamber scroll compressor
Authors: Shuaihui Sun , Zhe Wang , Pengcheng GUO , bo ZHANG , Zhenkai MAO
Published: September 2021

The scroll compressors with asymmetrical suction chamber have large discharge loss, as the pressure in outside chamber is far larger than the discharge pressure when the discharge process begins. It is necessary to optimize the scroll profile around the discharge port to reduce the discharge loss. The theoretical method is to redesign the tip profile to obtain the same volume ratio of outside working chamber with the inner working chamber. However, as it is difficult to predict the discharge loss through the flank gap in discharge chamber, the optimum design cannot be obtained. In this paper, we establish an optimization platform based on the CFD method. The profile of orbiting scroll tip is parametrized with CAD software, then the CFD calculation will be done and the performance parameters will be extracted. The MOST optimization algorithm is used to search the best performance parameters and control the parameterized value of scroll profile. After iterations, the best profile with the modification angle of 66.3° was obtained. Compared to the original model, the volumetric efficiency of the compressor increased by 4.11%; and the isentropic efficiency increased by 4.91%. Afterwards, the flow field are analysed to study the characteristics of the optimized scroll compressor. The results show that the backflow, the secondary vortex in discharge chamber and the discharge mass flow pulsation were reduced, which led to the decrease of the discharge loss and the improvement of the isentropic efficiency.
Flow computation inside a scroll compressor based on open-source code
Authors: Fadiga E , Casari N , Angel B , Picavet A
Published: September 2021

Computational fluid dynamics (CFD) is an essential tool for improving the performance of positive displacement machines, which are commonly adopted in vapour compression applications. The numerical analysis of such machines is characterized by several modelling challenges. Firstly, the relative motion of the wraps and the presence of particularly small gap sizes need to be considered during the implementation of a reliable meshing strategy. In addition to that, the operating conditions are close to the saturated-vapour line, requiring a real gas equation of state for the determination of fluid thermophysical properties.

In this work, a commercial scroll compressor has been simulated at three different operating conditions. The geometrical modelling, meshing strategy and compression process have been obtained thanks to a set of libraries built in OpenFOAM-v2006. The results have been compared with experimental data of the pressure evolution in the compression chambers. Furthermore, a complete fluid flow analysis is presented to assess the capabilities of the developed tool when applied to a compressor operating with R410a.
Mechanical and deformation characteristics of rotary compressor discharge valve
Authors: Hu YS , Xu J , Yang O X , Gao J , Zhang X Y , Hu Y P
Published: September 2021

The discharge valve plays an important role in the rotary compressor. For better understanding the mechanical characteristics of discharge valve in the process of movement, a mechanical model considering the coupling effect with limiter is established. Some major parameters, i.e., displacement, stress, stiffness and elastic force, are obtained to characterize the mechanical properties of the discharge valve. Two cases of valve component are calculated by the mechanical model, and the results indicated that the profile of limiter has an important influence on the movement of discharge valve. In order to verify the accuracy of the model, finite element method and high-speed photography are used. The comparison results show the calculation error of valve stiffness obtained by the model is within 3.9% compared with the finite element method results, and the valve motion is consistent with the high-speed photography results. Based on the above analysis, the profile of limiter in one valve component is optimized. The initial winding displacement of the valve is advanced from 2.115 mm to 1.453 mm after the optimization of limiter profile, which exhibits better limiting effect.
Development of the Universal Modelling Method mathematical model and the practice of its application
Authors: Galerkin Y.B. , Solovyeva O.A. , Drozdov A.A. , Semenovskiy V.B.
Published: September 2021

We present the latest improvements to the Universal Modelling Method for optimal gas-dynamic design of centrifugal compressors. The calculation of the gas velocity at the inlet to the impeller blade cascade was corrected. The flow restructuring scheme at the inlet to the impeller blade cascade has been refined. In accordance with this, the mathematical model of the non-incidence gas inlet to an impeller has been improved. A new approach to modelling the velocity diagram on the blade surfaces is proposed, based on the flow parameters corresponding to the non-incidence flow inlet. A mathematical model with quasi-three-dimensional approach to calculating losses in 3D impellers has been developed. The method of gas-dynamic functions is applied to the calculation of flow parameters in control sections. The new mathematical model was identified based on the test results of model stages and compressors. The mathematical model showed a 0.525% error in modelling efficiency of stages with 2D impellers for the design flow rate. For stages with 3D impellers, the modelling error is 0.889%. To verify the new model, the characteristics of 11 low-flow-rate model stages were calculated. The efficiency modelling error for the design flow rate is 1.08%. A series of model stages with a range of design flow rates coefficient 0.15–0.015 and design loading factor of 0.5 was designed. Four of these model stages were tested on the Gas dynamics of turbomachines laboratory ECC-55 test rig. The measured gas-dynamic characteristics confirmed those declared in the design.
Dynamic modelling and experimental validation of Coupled Vane Compressor
Authors: Shakya P , Ooi K T
Published: September 2021

The newly developed Coupled Vane Compressor (CVC) consists of a unique feature that is a couple of vanes cut through the rotor diametrically. Theoretically, this allows the rotor of any diameter which can accommodate the coupled vanes, to be able to operate CVC. Thus, unlike other rotary compressors, CVC design is mostly free of geometrical constraints imposed on the size of its rotor, making it one of the most compact compressors. Nevertheless, CVC suffers from frictional losses similar to other rotary compressors and therefore, studies of dynamic forces acting in CVC is of great interest. In this paper, dynamic forces acting on its components and frictional losses occurring due to rubbing of various components were studied and analysed. Unlike in other vane compressors, in which frictional losses are mostly due to the rubbing of vane tips against cylinder wall and vane sides against vane slot in the rotor, in CVC, the loss also occurs due to rubbing between the coupled vanes. A CVC prototype of 44 cm3 was developed and the compressor power consumption was experimentally studied in an open-type test circuit using air as an operating fluid. The predicted and measured power consumed by CVC were compared and the predicted results were found to have maximum discrepancy of ±15% with the measured results.
Effects of Lubricating oil on the performance of a Four-Intersecting-Vane Rotary Expander
Authors: Murthy A A , Norris S , Subiantoro A
Published: September 2021

Lubrication plays an important aspect in machinery. It seals internal leakage gaps, reduces friction and cools components. The present investigation is intended to test the effects of lubrication to an expander’s performance. Polyester lubricating oil grades (Grade 48 and Grade 68) were tested at various operating conditions. The expander prototype is of the rotary mechanism with four vanes comprising two intersecting bars. An experimental test rig was designed and built. The pressure diagram as function of rotational angle was recorded by six pressure transducers arranged in the working chamber, based on which the features of the expansion process of the four-intersecting-vane rotary expander were analysed. To start with, the working fluid was compressed air, but the eventual intended application is in a vapour compression refrigeration system. The experimental study revealed that the rotary vane expander worked steadily at different operating conditions. The experimental results showed that the expander flow rate was generally lower with a thinner oil (POE grade 46), whereas the volumetric efficiency increased from 23.2% to 27.2%. The adiabatic efficiency decreased from 22.5% to 18.1% with a higher viscosity lubricating oil (POE grade 68).
Application of LDV and PIV techniques for flow measurements in the suction port of a screw compressor
Authors: Nouri J. M. , Guerrato D. , Stosic N. , Yan Y.
Published: September 2021

The application of LDV and PIV systems to measure the flow variation in the suction port of a new designed optical screw compressor has been found to be very successful. Time-resolved mean velocity measurements were made over a time window of 1° (Δθ) at a rotor speed of 1000 rpm, a pressure ratio of 1 and a gas temperature of 55°C. The LDV investigation on the suction port has shown a very stable and slow flow with almost no influence of the rotor motions everywhere except close to rotors at Z=-10mm where the rotor motions start to show its influence and formed a more complex flow with a wavy axial flow profile. The PIV results confirmed flow trend measured by LDV and showed no influence of rotors’ movement on the mean flow structure. The PIV results within the vertical plane also showed relatively strong horizontal stream flow vectors upstream of the inlet suction port and became almost vertically downwards at the inlet port. Despite the current success, further improvements have been recommended to give better optical accessibility as close as possible to the rotors entrance.
Theoretical study on the leakage characteristics of Disc-Seal Single Screw Pump used in oily sludge waste heat source absorption refrigeration system
Authors: Wang Z L , Shi H W , Wang S Y , Wang Z M , Hao M M , Wang J
Published: September 2021

The disc-seal single screw pump (DSSP) used in the field of oily sludge transport has a huge advantage. However, there is no research on the leakage characteristics of the DSSP at present, which makes its application limited. Therefore, the mathematical calculation model of leakage amount of each leakage channel was established in this paper according to the geometric model of the leakage channel. By using this mathematical model, the influence rule of working parameters on the leakage characteristics was analyzed. The results show that the total leakage amount per unit time of the DSSP varies periodically with the rotation of the screw, and the total leakage per unit time of the DSSP will increase with the increase of outlet pressure and screw rotation velocity. When the dynamic viscosity coefficient of the medium increases, the corresponding leakage will be reduced, in which the transmission medium dynamic viscosity is the main factor affecting the total leakage of the DSSP. The study of the leakage characteristics of the DSSP can provide a theoretical basis for the optimal design of its structure in the future.
Automatically reconfigurable optical data center network with dynamic bandwidth allocation
Authors: Xue Xuwei , Prifti Kristif , Pan Bitao , Chen Sai , Guo Xiaotao , Yan Fulong , Zhang Shaojuan , Wang Yu , Xie Chongjin , Calabretta Nicola
Published: September 2021

The rapid increasing traffic in data centers (DCs) puts tremendous pressure to the present multi-tier network architectures and electrical switching techniques. Switching traffic in the optical domain featuring ultra-high bandwidth, therefore, has been intensively investigated to build the high capacity data center networks (DCNs). To handle the variable traffic pattern in DCs, the network reconfigurability with adaptable optical bandwidth allocation is of key importance to flexibly assign the optical bandwidth. To this end, we propose and experimentally evaluate a software-defined networking enabled reconfigurable optical DCN with dynamic bandwidth allocation in this work, based on novel optical top of racks exploiting a wavelength selective switch. Experimental assessments show that the proposed solution can automatically reallocate the optical bandwidth in real-time to adapt the dynamic traffic pattern. Compared with the conventional optical DCN with static bandwidth provision, the end-to-end latency performance of the reconfigurable scheme with adaptable bandwidth allocation improves of 58.3% and the average packet loss decreases one order of magnitude. Moreover, the reconfigurable optical DCN features deterministic latency performance, with much lower time variations of packets delivery completion. Based on the experimental parameters, the simulation platform is also built to validate the good scalability of the proposed reconfigurable DCN. Numerical results illustrate the negligible performance degradation (11%) as the network scales from 2560 to 40 960 servers.
Daily Physical Activity, Sedentary Behavior and Alcohol Use in At-Risk College Students
Authors: West Ashley B , Bomysoad Rachel N , Russell Michael A , Conroy David E
Published: September 2021

Background

The college years present an opportunity to establish health behavior patterns that can track across adulthood. Health behaviors tend to cluster synergistically however, physical activity and alcohol have shown a positive association.

Purpose

This study applied a multi-method approach to estimate between- and within-person associations between daily physical activity, sedentary behavior and alcohol use among polysubstance-using college students.

Methods

Participants were screened for recent binge drinking and either tobacco or cannabis use. They wore an activPAL4 activity monitor and a Secure Continuous Remote Alcohol Monitor continuously in the field for 11 days, and completed daily online questionnaires at the beginning of each day to report previous day physical activity, sedentary behavior, and alcohol consumption.

Results

Participants (N = 58, Mage = 20.5 years, 59% women, 69% White) reported meeting national aerobic physical activity guidelines (75%) and drinking 2–4 times in the past month (72%). On days when participants reported an hour more than usual of daily sedentary behavior, they reported drinking for less time than usual (γ = −.06). On days when participants took 1,000 more steps than usual, the longest episode of continuous transdermal alcohol detection was shorter (γ = −.03).

Conclusions

Daily physical activity and sedentary behavior were negatively associated with time-based measures of alcohol use with the lowest risk on days characterized by both activity and sedentary behavior. Intensive longitudinal monitoring of time-based processes can provide new insights into risk in multiple behavior change and should be prioritized for future work.
Longitudinal Pathways to Influenza Vaccination Vary With Socio-Structural Disadvantages
Authors: Fayaz Farkhad Bita , Karan Alexander , Albarracín Dolores
Published: September 2021

Background

Although influenza vaccination can prevent influenza-related deaths, uptake remains low, particularly in disadvantaged populations.

Purpose

A theoretical model of psychological pathways to vaccination accounting for the direct and moderating role of socio-structural factors was tested. The study sought to understand the joint contributions of psychological (i.e., knowledge, attitudes, and intention) and socio-structural factors (i.e., income, education, and insurance) to influenza vaccination, prospectively.

Methods

A nationally representative empaneled sample of over 3,000 U.S. adults answered questions about vaccination knowledge, attitudes, and intentions, as well as actual vaccination across five timepoints from September 2018 to May 2019. Socio-structural factors were examined as moderators.

Results

Findings revealed strong positive associations between knowledge and attitudes, attitudes and intentions, as well as intentions and subsequent vaccination. Importantly, health insurance moderated the associations between attitudes and intentions and between intentions and vaccination, such that those without insurance had weaker associations between attitudes and intentions and between intentions and vaccination. In addition, education moderated the path from knowledge to attitude and from intentions to vaccination, such that people with lower educational attainment had weaker associations between knowledge and attitudes and between intentions and vaccination.

Conclusions

Socio-structural factors act as barriers to the influence of knowledge on attitudes, attitudes on intentions, and intentions on behavior. Future research needs to be mindful of the specific paths disrupted by social disadvantages and examine ways to intervene to decrease those effects.
Gene flow, barriers, speciation and hybridization inParoliniaspecies (Brassicaceae) endemic to Gran Canaria
Authors: González-Pérez Miguel Ángel , Caujapé-Castells Juli
Published: September 2021

Oceanic islands are natural laboratories where evolutionary processes can be studied more readily. In the present work we use nuclear microsatellites to quantitatively assess the roles of hybridization, colonization, gene flow and geographical barriers in four Parolinia spp. endemic to Gran Canaria in connection with known geological events throughout the dynamic geological ontogeny of the island. Our genetic analyses show that these Parolinia spp. share 69% of all alleles detected and display low genetic divergence among populations, suggesting a close genetic relationship and recent differentiation. This close relationship is more evident between Parolinia platypetala and Parolinia ornata, which were included in the same genetic pool in the STRUCTURE analysis, and probably represent the early stages of an incipient speciation process, as suggested by the absence of gene flow barriers between them. NEWHYBRIDS, STRUCTURE and MIGRATE analyses unequivocally suggest frequent past migration and hybridization from P. ornata to P. filifolia, but contemporary migration is low overall. Despite the overall genetic closeness among the Parolinia spp. assessed, microsatellites dispelled doubts regarding the appropriate name/s for two taxonomically conflicting populations. In line with the predictions of the surfing syngameon hypothesis, ancestral hybridization, vicariance and dispersal events linked to the complex ontogeny of the island may have been key factors to shape the current genetic diversity and structure of Parolinia in Gran Canaria.
Resting-State fMRI Functional Connectivity Strength Predicts Local Activity Change in the Dorsal Cingulate Cortex: A Multi-Target Focused rTMS Study
Authors: Feng Zi-Jian , Deng Xin-Ping , Zhao Na , Jin Jing , Yue Juan , Hu Yun-Song , Jing Ying , Wang Hong-Xiao , Knösche Thomas R , Zang Yu-Feng , Wang Jue
Published: September 2021

Previous resting state functional magnetic resonance imaging (RS-fMRI) studies suggested that repetitive transcranial magnetic stimulation (rTMS) can modulate local activity in distant areas via functional connectivity (FC). A brain region has more than one connection with the superficial cortical areas. The current study proposed a multi-target focused rTMS protocol for indirectly stimulating a deep region, and to investigate 1) whether FC strength between stimulation targets (right middle frontal gyrus [rMFG] and right inferior parietal lobule [rIPL]) and effective region (dorsal anterior cingulate cortex [dACC]) can predict local activity changes of dACC and 2) whether multiple stimulation targets can focus on the dACC via FC. A total of 24 healthy participants received rTMS with two stimulation targets, both showing strong FC with the dACC. There were four rTMS conditions (>1 week apart, 10 Hz, 1800 pulses for each): rMFG-target, rIPL-target, Double-targets (900 pulses for each target), and Sham. The results failed to validate the multi-target focused rTMS hypothesis. But rMFG-target significantly decreased the local activity in the dACC. In addition, stronger dACC-rMFG FC was associated with a greater local activity change in the dACC. Future studies should use stronger FC to focus stimulation effects on the deep region.