Interactions of Space Bodies With Atmospheres of Planets

1997 ◽  
Vol 50 (11) ◽  
pp. 671-688 ◽  
Author(s):  
V. P. Stulov
Keyword(s):  
Numerical Methods ◽  
High Speed ◽  
Gas Flow ◽  
Space Vehicle ◽  
Body Motion ◽  
Modern Theory ◽  
Inviscid Gas ◽  
Meteor Body ◽  
Vehicle Aerodynamics ◽  
The Difference

In this review article, a modern theory of meteor body motion in the atmosphere is described. The theory is based on the results of high-speed aerodynamics. The author understands that such an application is difficult and unusual. The difference between space vehicle aerodynamics and bolide physics is, first of all, in absence of knowledge about shapes of meteoroids and of their physical-mechanical properties. On the other hand, the main aerodynamical laws are the same for vehicles and meteoroids. This permits one to achieve some new developments in meteor physics. In the first section, a simple analytical model for meteor trajectories is developed. The second and fourth sections of the article contain high-speed aerodynamics results: inviscid gas flow past bodies, and convective and radiative heat transfer. The third section is devoted to one of the difficult problems in meteor physics-the theory of meteoroid destruction due to aerodynamical loading. Finally, the fifth section contains some common questions on bolide phenomema. For the solution of meteor physics problems, both analytical and numerical methods are used. As such problems contain a number of determining parameters which are not accurately known, the analytical methods are preferable. The numerical methods are necessary for calculation of complex gasdynamical structures forming during the motion of the meteor bodies in the atmosphere. There are 50 references included at the end of this article.

Case study: Prediction and field tests of railway noise and effects of a low-height noise barrier

2020 ◽  
Vol 68 (4) ◽  
pp. 303-314
Author(s):  
Yuna Park ◽  
Hyo-In Koh ◽  
University of Science and Technology, Transpo ◽  
University of Science and Technology, Transpo ◽  
University of Science and Technology, Transpo ◽  
...  
Keyword(s):  
High Speed ◽  
Field Tests ◽  
Residential Areas ◽  
Railway Systems ◽  
Railway Noise ◽  
Sound Levels ◽  
Noise Barrier ◽  
The Difference ◽  
Reduction Effect ◽  
The Impact

Railway noise is calculated to predict the impact of new or reconstructed railway tracks on nearby residential areas. The results are used to prepare adequate counter- measures, and the calculation results are directly related to the cost of the action plans. The calculated values were used to produce noise maps for each area of inter- est. The Schall 03 2012 is one of the most frequently used methods for the production of noise maps. The latest version was released in 2012 and uses various input para- meters associated with the latest rail vehicles and track systems in Germany. This version has not been sufficiently used in South Korea, and there is a lack of standard guidelines and a precise manual for Korean railway systems. Thus, it is not clear what input parameters will match specific local cases. This study investigates the modeling procedure for Korean railway systems and the differences between calcu- lated railway sound levels and measured values obtained using the Schall 03 2012 model. Depending on the location of sound receivers, the difference between the cal- culated and measured values was within approximately 4 dB for various train types. In the case of high-speed trains, the value was approximately 7 dB. A noise-reducing measure was also modeled. The noise reduction effect of a low-height noise barrier system was predicted and evaluated for operating railway sites within the frame- work of a national research project in Korea. The comparison of calculated and measured values showed differences within 2.5 dB.

scholarly journals Prognostic Assessment of the Performance Parameters for the Industrial Diesel Engines Operated with Microalgae Oil

2021 ◽  
Vol 13 (11) ◽  
pp. 6482
Author(s):  
Sergejus Lebedevas ◽  
Laurencas Raslavičius
Keyword(s):  
Energy Efficiency ◽  
Diesel Engine ◽  
High Speed ◽  
Performance Parameters ◽  
Prognostic Assessment ◽  
High Speed Diesel ◽  
Microalgae Oil ◽  
The Difference ◽  
Smoke Opacity ◽  
Efficiency Indicators

A study conducted on the high-speed diesel engine (bore/stroke: 79.5/95.5 mm; 66 kW) running with microalgae oil (MAO100) and diesel fuel (D100) showed that, based on Wibe parameters (m and φz), the difference in numerical values of combustion characteristics was ~10% and, in turn, resulted in close energy efficiency indicators (ηi) for both fuels and the possibility to enhance the NOx-smoke opacity trade-off. A comparative analysis by mathematical modeling of energy and traction characteristics for the universal multi-purpose diesel engine CAT 3512B HB-SC (1200 kW, 1800 min−1) confirmed the earlier assumption: at the regimes of external speed characteristics, the difference in Pme and ηi for MAO100 and D100 did not exceeded 0.7–2.0% and 2–4%, respectively. With the refinement and development of the interim concept, the model led to the prognostic evaluation of the suitability of MAO100 as fuel for the FPT Industrial Cursor 13 engine (353 kW, 6-cylinders, common-rail) family. For the selected value of the indicated efficiency ηi = 0.48–0.49, two different combinations of φz and m parameters (φz = 60–70 degCA, m = 0.5 and φz = 60 degCA, m = 1) may be practically realized to achieve the desirable level of maximum combustion pressure Pmax = 130–150 bar (at α~2.0). When switching from diesel to MAO100, it is expected that the ηi will drop by 2–3%, however, an existing reserve in Pmax that comprises 5–7% will open up room for further optimization of energy efficiency and emission indicators.

scholarly journals Plastic failure zone characteristics and stability control technology of roadway in the fault area under non-uniformly high geostress: A case study from Yuandian Coal Mine in Northern Anhui Province, China

2020 ◽  
Vol 12 (1) ◽  
pp. 406-424 ◽  
Author(s):  
Yaoguang Huang ◽  
Aining Zhao ◽  
Tianjun Zhang ◽  
Weibin Guo
Keyword(s):  
Numerical Methods ◽  
Numerical Solutions ◽  
Stress Test ◽  
Pressure Coefficient ◽  
Stability Control ◽  
Failure Zone ◽  
Plastic Failure ◽  
Comparison Results ◽  
High Geostress ◽  
The Difference

AbstractIn order to explore the effective support method for deep broken roadway, based on the in situ stress test results, the analytical and numerical solutions of the stress and the range of plastic failure zone (PFZ) in a circular roadway subjected to non-uniform loads were obtained using analytical and finite difference numerical methods based on the elastoplastic theory, respectively. Their comparison results show that the analytical and numerical methods are correct and reasonable. Furthermore, the high geostress causes the stress and range of PFZ in roadway roof and floor to increase sharply while those in roadway ribs decrease. Moreover, the greater the difference of horizontal geostress in different horizontal directions is, the larger the range of PFZ in roadway roof and floor is. The shape of PFZ in roadway varies with the ratio of horizontal lateral pressure coefficient in x-direction and y-direction. Finally, according to the distribution characteristics of PFZ and range of PFZ under the non-uniformly high geostress, this paper has proposed a combined support scheme, and refined and optimized supporting parameters. The field monitoring results prove that the roadway deformation and fracture have been effectively controlled. The research results of this paper can provide theoretical foundation as well as technical reference for the stability control of deep broken roadway under non-uniformly high geostress.

scholarly journals Heat Transmission in High Speed Gas Flow (3rd Report)

1952 ◽  
Vol 18 (67) ◽  
pp. 31-35
Author(s):  
Kensuke KAWASHIMO ◽  
Shigebumi AOKI
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Heat Transmission

A Fault Diagnosis Method for the Roller-Marks in Offset Printing Machine Based on Texture Recognition

2012 ◽  
Vol 262 ◽  
pp. 361-366
Author(s):  
Zhuo Fei Xu ◽  
Hai Yan Zhang ◽  
Ling Hui Ren
Keyword(s):  
Fault Diagnosis ◽  
High Speed ◽  
Solution Method ◽  
Offset Printing ◽  
Texture Recognition ◽  
Defect Image ◽  
Diagnosis Method ◽  
The Difference ◽  
Detecting Method ◽  
Printing Machine

Roller-mark is a common problem in offset printing and its solution method is important for printing. A new detecting method of texture analysis was given in this paper. In this study, printing image was acquired with high-speed CCD. Compared the difference between printing image and standard image, a defective image was obtained. Then the reason of roller-marks was given by the texture recognition of defect image. Finally, experiments were taken to prove the feasibility and effectiveness of this new method for the roller-marks diagnosis in the offset printing machine.

Experimental Investigation During Stall and Surge in a Transonic Fan Stage and Rotor-Only Configuration

2006 ◽  
Author(s):  
A. J. Gannon ◽  
G. V. Hobson ◽  
R. P. Shreeve ◽  
I. J. Villescas
Keyword(s):  
High Speed ◽  
Fast Response ◽  
Pressure Measurements ◽  
Post Processing ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
The Difference ◽  
Data Signal ◽  
Transonic Fan ◽  
Casing Pressure

High-speed pressure measurements of a transonic compressor rotor-stator stage and rotor-only configuration during stall and surge are presented. Rotational speed data showed the difference between the rotor-only case and rotor-stator stage. The rotor-only case stalled and remained stalled until the control throttle was opened. In the rotor-stator stage the compressor surged entering a cyclical stalling and then un-stalling pattern. An array of pressure probes was mounted in the case wall over the rotor for both configurations of the machine. The fast response probes were sampled at 196 608 Hz as the rotor was driven into stall. Inspection of the raw data signal allowed the size and speed of the stall cell during its growth to be investigated. Post-processing of the simultaneous signals of the casing pressure showed the development of the stall cell from the point of inception and allowed the structure of the stall cell to be viewed.

Behavior of Unsteady Turbulent Starting Round Jets

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Neerav Abani ◽  
Jaal B. Ghandhi
Keyword(s):  
High Speed ◽  
Penetration Rate ◽  
Injection Rate ◽  
Injection Velocity ◽  
Time Varying ◽  
Velocity Change ◽  
Rate Of Penetration ◽  
Round Jets ◽  
The Difference ◽  
Sudden Decrease

Turbulent starting jets with time-varying injection velocities were investigated using high-speed schlieren imaging. Two solenoid-controlled injectors fed a common plenum upstream of an orifice; using different upstream pressures and actuation times, injection-rate profiles with a step increase or decrease in injection velocity were tested. The behavior of the jet was found to be different depending on the direction of the injection-velocity change. A step increase in injection velocity resulted in an increased rate of penetration relative to the steady-injection case, and a larger increase in injection velocity resulted in an earlier change in the tip-penetration rate. The step-increase data were found to be collapsed by scaling the time by a convective time scale based on the tip location at the time of the injection-velocity change and the difference in the injection velocities. A sudden decrease in injection velocity to zero was found to cause a deviation from the corresponding steady-pressure case at a time that was independent of the initial jet velocity, i.e., it was independent of the magnitude of the injection-velocity change. Two models for unsteady injection from the literature were tested and some deficiencies in the models were identified.

First-Principles Theory of Polarization in Ferroelectrics

1992 ◽  
Vol 291 ◽  
Author(s):  
R. Resta ◽  
M. Posternak ◽  
A. Baldereschi
Keyword(s):  
Spontaneous Polarization ◽  
First Principles ◽  
Ferroelectric Materials ◽  
Recent Experimental Data ◽  
Modern Theory ◽  
Rigid Core ◽  
Novel Approach ◽  
Prototype Structure ◽  
Effective Charges ◽  
The Difference

ABSTRACTWe outline a modern theory of the spontaneous polarization P in pyroelectric and ferroelectric materials. Although P itself isnot an observable, the difference ΔP between two crystal states can indeed be measured and calculated. We define P as the difference between the polar structure and a suitably chosen nonpolar prototype structure. We previously proposed and implemented a supercell scheme in order to evaluate P in pyroelectric BeO; here we adopt an approach recently developed by King-Smith and Vanderbilt, where ΔP is obtained from the computation of Berry's phases, with no use of supercells. We apply this novel approach, which is numerically very convenient, in order to revisit our previous work on BeO. We then perform a first-principles investigation of the spontaneous polarization P of KNbO3 in its tetragonal phase, which is a well studied perovskite ferroelectric. Our calculated P value confirms the most recent experimental data. The polarization is linear in the ferroelectric distortion; the Born effective charges show strong variations from nominal ionic values, and a large inequivalence of the 0 ions. Only the highest nine valence-band states (O 2p) contribute to P, while all the other states behave as rigid core states.

Angular Momentum Requirements of the Twisting and Nontwisting Forward 1 1/2 Somersault Dive

1987 ◽  
Vol 3 (1) ◽  
pp. 47-62 ◽  
Author(s):  
Ross H. Sanders ◽  
Barry D. Wilson
Keyword(s):  
Angular Momentum ◽  
High Speed ◽  
Center Of Gravity ◽  
Transverse Axis ◽  
Free Position ◽  
High Speed Cinematography ◽  
The Difference ◽  
Hip Flexion ◽  
Commonwealth Games

This study investigated the in-flight rotation of elite 3m springboard divers by determining the angular momentum requirement about the transverse axis through the divers center of gravity (somersault axis) required to perform a forward 1 1/2 somersault with and without twist. Three elite male divers competing in the 1982 Commonwealth Games were filmed using high-speed cinematography while performing the forward 1 1/2 somersault in the pike position and the forward 1 1/2 somersault with one twist in a free position. The film was digitized to provide a kinematic description of each dive. An inclined axis technique appeared to be the predominant means of producing twist after takeoff from the board. The angular momentum about the somersault axis after takeoff was greater for the forward 1 1/2 somersault with twist than the forward 1 1/2 somersault without twist for all three divers. The difference in angular momentum between the two dives of each diver ranged from 6% to 19%. The most observable difference between the dives during the preflight phases was the degree of hip flexion at takeoff. There was more hip flexion at takeoff in 5132D than 103B for all three divers. This difference ranged from 9° to 18° (mean = 14°).

Sign in / Sign up

Export Citation Format

Share Document