Optimal cross-sectional area distribution of a high-speed train nose to minimize the tunnel micro-pressure wave

The Integral I occurs frequently in aerodynamics. To cite a particular case, Ward has shown that ifS(x)is the cross-sectional area distribution of a slender body its wave dragDis given to a first approxition by D = qI/(2π), whereqis the kinetic pressure. In this case,S(x)is often defined numerically, and the direct evaluation of I is then complicated by the presence of the logarithmic singularity. Several methods may be employed to avoid this complication. Legendre has recently suggested rewriting I in a non-singular form, which unfortunately is not well suited to numerical work. Here, a method for the evaluation of the unmodified integral is presented.

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Acceleration characteristics of laser ablation Cu plasma in the electrostatic field

The European Physical Journal Applied Physics ◽

10.1051/epjap/2021200349 ◽

2021 ◽

Vol 93 (2) ◽

pp. 20802

Author(s):

Buren Duan ◽

Haonan Zhang ◽

Lizhi Wu ◽

Zuohao Hua ◽

Zijing Bao ◽

...

Keyword(s):

Laser Ablation ◽

Electric Field ◽

Field Intensity ◽

Electrostatic Field ◽

High Speed ◽

Electric Field Intensity ◽

Cross Sectional Area ◽

Sectional Area ◽

Iccd Camera ◽

Cross Sectional

As a new concept of space propulsion system, laser-ablation propulsion has attracted more and more attention due to its characteristics of low power consumption, high specific impulse, variable and controllable thrust. With an aim to further raise up the movement velocity of plasma, we combine the laser with high-voltage electrostatic field to accelerate the Cu plasma induced by laser ablation. To demonstrate the acceleration characteristics of plasma under different electric field intensity, the plasma conductivity, plasma shockwave intensity and plasma plume movement process were tested using parallel electrode plate device, self-made torsion pendulum impulse test bench and high-speed ICCD camera. The results showed that the conductive current and impulse formed by the plasma obviously increased under the applied electric field. The images captured by high-speed ICCD camera showed the plasma cross-sectional area was 0.194 mm2 at 900 ns and 0.217 mm2 at 1600 ns when the electric field intensity was 0 V/mm. With the electric field intensity increased to 30 V/mm, the plasma cross-sectional area elevated to 0.280 mm2 at 900 ns and 0.288 mm2 at 1600 ns. The acquisitions prove that the idea of this paper is feasible and favorable, which provide a theoretical basis for the combination of laser ablation propulsion and electric field.

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Mathematical modeling of aerodynamic processes in railway tunnels on high-speed railways

E3S Web of Conferences ◽

10.1051/e3sconf/202015706017 ◽

2020 ◽

Vol 157 ◽

pp. 06017

Author(s):

Alexander Ledyaev ◽

Vladimir Kavkazskiy ◽

Yan Vatulin ◽

Valeriy Svitin ◽

Oleg Shelgunov

Keyword(s):

Mathematical Modeling ◽

High Speed ◽

Practical Experience ◽

Cross Sectional Area ◽

Geometric Parameters ◽

Sectional Area ◽

Cross Sectional ◽

Optimization Task ◽

Sufficient Degree

The study of aerodynamic processes in railway tunnels on highspeed railways in the absence of practical experience in operation should be carried out with a sufficient degree of accuracy only by mathematical modeling. A multi-factor experiment was performed, which resulted in solving the optimization task of determining the tunnel cross-sectional area, taking into account aerodynamic processes. Based on the analysis of the results, the conclusion is made about the applicability of the method to the prognosis of aerodynamic effects on prospective tunnel structures of high-speed railways and optimization of geometric parameters of the tunnels.

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Optimizing cross-sectional area of tunnel entrance hood for high speed rail

Journal of Wind Engineering and Industrial Aerodynamics ◽

10.1016/j.jweia.2018.11.028 ◽

2019 ◽

Vol 184 ◽

pp. 296-304 ◽

Cited By ~ 4

Author(s):

Sanetoshi Saito

Keyword(s):

High Speed ◽

Cross Sectional Area ◽

Sectional Area ◽

Cross Sectional ◽

High Speed Rail ◽

Tunnel Entrance

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Relation Between Iliopsoas Cross-sectional Area and Kicked Ball Speed in Soccer Players

International Journal of Sports Medicine ◽

10.1055/a-0592-7370 ◽

2018 ◽

Vol 39 (06) ◽

pp. 468-472

Author(s):

Taku Wakahara ◽

Manabu Chiba

Keyword(s):

High Speed ◽

Body Height ◽

Cross Sectional Area ◽

Soccer Players ◽

Iliopsoas Muscle ◽

Sectional Area ◽

Cross Sectional ◽

Ball Speed ◽

Instep Kick ◽

Psoas Major

AbstractThis study aimed to investigate the relationship between the maximal anatomical cross-sectional area (ACSA) of the iliopsoas muscle and ball speed in side-foot and instep kicks. The ACSA of the psoas major and iliacus was measured in 29 male collegiate soccer players by using magnetic resonance imaging. They performed maximal side-foot and instep kicks to a stationary ball. The kicked ball speed was measured with a high-speed camera. Ball speed in the side-foot and instep kicks was significantly correlated with body height (side-foot kick: r=0.650, P<0.001; instep kick: r=0.583, P<0.001). After adjustment for body height, the maximal ACSA of the psoas major was significantly correlated with ball speed in the side-foot kick (r=0.441, P=0.017), but not in the instep kick. The maximal ACSA of the iliacus was not correlated with ball speed in side-foot or instep kicks, even after adjustment for body height. Our results suggest that: 1) body height is a significant determinant of the ball speed in side-foot and instep kicks, and 2) for a given body height, the maximal ACSA of the dominant psoas major is a factor that affects the ball speed in side-foot kick.

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Air Transportation

10.1093/oso/9780198802297.003.0011 ◽

2017 ◽

Cited By ~ 3

Author(s):

Peter Rez

Keyword(s):

High Speed ◽

Energy Use ◽

Air Transportation ◽

Primary Energy ◽

Air Travel ◽

Cross Sectional Area ◽

Sectional Area ◽

Cross Sectional ◽

Transportation Energy ◽

Turbofan Engines

When an airplane is full, the energy used to travel a given distance compares very favourably with driving an economical car. Primary energy use is less since airplane turbofan engines are more efficient than car engines. Even airplanes with propellers driven by petrol engines are more efficient than cars as the engines are operating at near-peak rpm and producing a higher proportion of the rated power. Air travel uses a lot of energy because it makes travelling long distances easy, even if not very comfortable. The airplane is limited by the weight it can carry, which puts a limit on how tightly the passengers can be squeezed together. Given that drag will always be a factor in high-speed transportation, even for ground transportation, energy use can be minimised by reducing the cross-sectional area and squeezing more people into even smaller spaces, such as in the hyperloop.

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Branching Pattern of Pulmonary Arterial Tree in Anesthetized Dogs

Journal of Biomechanical Engineering ◽

10.1115/1.3138616 ◽

1986 ◽

Vol 108 (3) ◽

pp. 289-293 ◽

Cited By ~ 12

Author(s):

Y. H. Liu ◽

E. L. Ritman

Keyword(s):

High Speed ◽

Cross Sectional Area ◽

Arterial Phase ◽

Branching Pattern ◽

Sectional Area ◽

Arterial Tree ◽

Cross Sectional ◽

Lung Inflation ◽

Pulmonary Arterial

The geometry of the pulmonary arterial tree of six adult dogs was measured by a high-speed, volume-scanning, X-ray tomographic technique. After the dogs were anesthetized a catheter was advanced to the right ventricular outlfow tract and 2 mL/kg Renovist contrast agent injected rapidly. During the subsequent pulmonary arterial phase of the angiogram the dogs were scanned. Three-dimensional geometry of the pulmonary arterial tree was measured in terms of vessel segment cross-sectional area, branching angles and interbranch segment lengths along axial pathways. The effect of lung inflation and phase of the cardiac cycle on geometry was shown to be most marked on vessel cross-sectional area. The geometric branching patterns in all dogs were similar. The observed, in-vivo branching pattern behaved somewhat like the branching pattern predicted from optimized models proposed by Murray [4, 5], Zamir [10, 11] and Uylings [7].

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Effect of dentinal surface preparation on bond strength of self-etching adhesive systems

Brazilian Oral Research ◽

10.1590/s1806-83242006000100010 ◽

2006 ◽

Vol 20 (1) ◽

pp. 52-58 ◽

Cited By ~ 4

Author(s):

Patrícia Itocazo Rocha ◽

Alessandra Bühler Borges ◽

José Roberto Rodrigues ◽

César Augusto Galvão Arrais ◽

Marcelo Giannini

Keyword(s):

Bond Strength ◽

High Speed ◽

Testing Machine ◽

Surface Preparation ◽

Surface Treatments ◽

Cross Sectional Area ◽

Sectional Area ◽

Adhesive Systems ◽

Cross Sectional ◽

Low Speed

The aim of this study was to evaluate the effects of dentin surface treatments on the tensile bond strength (TBS) of the self-etching primer Clearfil SE Bond (CSE) and the one-step self-etching One-Up Bond F (OUB). The exposed flat dentin surfaces of twenty-four sound third molars were prepared with diamond bur at high-speed, carbide bur at low-speed or wet ground with #600 grit SiC paper. The adhesive systems were applied to the dentin surfaces and light-cured according to the manufacturers' instructions. A 6-mm high composite crown was incrementally built-up and each increment was light-cured for 40 seconds. After being stored in water (37°C/24 h), the samples were serially sectioned parallel to the long axis, forming beams (n = 20) with a cross-sectional area of approximately 0.8 mm². The specimens were tested in a Universal Testing Machine at 0.5 mm/min. The cross-sectional area was measured and the results (MPa) were analyzed by two-way ANOVA and Tukey Test (p < 0.05). Overall, the groups treated with CSE exhibited the highest TBS for all surface treatments. Dentin surfaces prepared with carbide bur at low speed reduced TBS in the CSE group; however, OUB was not affected by surface treatments. The effect of surface abrasive methods on TBS was material-dependent.

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