scholarly journals Impact-Initiation Sensitivity of High-Temperature PTFE-Al-W Reactive Materials

Crystals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 30
Author(s):  
Tao Sun ◽  
Yuanfeng Zheng ◽  
Ying Yuan ◽  
Haifu Wang
Keyword(s):  
High Temperature ◽  
Temperature Interval ◽  
High Speed ◽  
Sample Temperature ◽  
Initiation Mechanism ◽  
Reactive Materials ◽  
Impact Initiation ◽  
The Difference ◽  
Sensitivity Changes ◽  
The Impact

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C.

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.

The effect analysis of an engine jet on an aircraft blast deflector

2018 ◽  
Vol 41 (4) ◽  
pp. 990-1001
Author(s):  
Song Ma ◽  
Jianguo Tan ◽  
Xiankai Li ◽  
Jiang Hao
Keyword(s):  
High Temperature ◽  
Flow Field ◽  
High Speed ◽  
Deflection Angle ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aircraft Engine ◽  
Experimental Results ◽  
Exhaust Gases ◽  
The Impact

This paper establishes a novel mathematical model for computing the plume flow field of a carrier-based aircraft engine. Its objective is to study the impact of jet exhaust gases with high temperature, high speed and high pressure on the jet blast deflector. The working condition of the nozzle of a fully powered on engine is first determined. The flow field of the exhaust jet is then numerically simulated at different deflection angle using the three-dimensional Reynolds averaged Navier–Stokes equations and the standard [Formula: see text]-[Formula: see text] turbulence method. Moreover, infra-red temperature tests are further carried out to test the temperature field when the jet blast deflector is at the [Formula: see text] deflection angle. The comparison between the simulation results and the experimental results show that the proposed computation model can perfectly describe the system. There is only 8–10% variation between them. A good verification is achieved. Moreover, the experimental results show that the jet blast deflector plays an outstanding role in driving the high-temperature exhaust gases. It is found that [Formula: see text] may be the best deflection angle to protect the deck and the surrounding equipment effectively. These data results provide a valuable basis for the design and layout optimization of the jet blast deflector and deck.

scholarly journals Comparative Characteristics of Structural-Textural, Mineralogical and Petrochemical Features of Melt Rock Impactites of the Kara Astrobleme. Preliminary Data (Pay-Khoy, Russia)

2021 ◽  
Vol 906 (1) ◽  
pp. 012020
Author(s):  
Alexandr Zubov ◽  
Tatyana Shumilova
Keyword(s):  
High Temperature ◽  
Preliminary Data ◽  
Fundamental Problem ◽  
River Mouth ◽  
Ultrahigh Pressure ◽  
Time Interval ◽  
Impact Melt ◽  
Reported Study ◽  
The Difference ◽  
The Impact

Abstract The Kara astrobleme is one of the largest astroblemes known on land. Its diameter is ~65 km, the age is about 70 million years. The astrobleme is located at the northeastern part of the Pay-Khoy anticlinorium at the Kara River mouth region (Kara Sea coast, Russia). It is a unique object of impact genesis due to the presence of a variety of suevites and melt impactites. Melt rocks are products of the highest degree of impact transformation of target rocks. The diversity of melt rock impactites of the Kara astrobleme and obtaining their complex comparative mineralogical and petrochemical characteristics are important for solving the fundamental problem for studying of the typomorphism of the impactitogenesis products of melt rocks both – the impactites of the Kara astrobleme and other astroblemes in general. In the Kara astrobleme region there are at list two different types of massive melt rocks bodies – a cover melt rock at the Anaroga River (I) studied by previous researchers and an unexplored body of melt rock impactite at the Kara River (II) spatially connected with ultrahigh-pressure high-temperature (UHPHT) glasses just recently discovered. Our preliminary data indicate that the melt rock varieties of the Kara astrobleme have significant differences in texture and structure. The considered melt rocks are mostly composed of a matrix represented by a “mixture” of amorphous and cryptocrystalline masses of predominantly feldspar composition with a subordinate SiO2 content. According to the data of energy dispersive analysis the compositions of the studied melt rocks are similar and have minor deviations within the first percent. The difference in the shape of silicate segregations in melt rocks may indicate that the impact melt could have a high temperature with a shorter time interval for the solidification of melt rock II on the Kara River, in contrast to the massive melt rock I on the Anaroga River, where the impact melt had large volume and, accordingly, was cooled longer at lower temperatures. The data obtained complement the specificity of the Kara melt impactites, which may play a role in complementing the geological model of the Kara astrobleme. The reported study was funded by RFBR, project number 20-35-90065; the analytical equipment has been used at the Center for Collective Use “Geonauka” (IG Komi FRC SC UB RAS, Syktyvkar, Russia); the author expresses his gratitude to Isaenko S.I. for analytical work using Raman spectroscopy; Tropnikov E.M. for help in performing microprobe studies.

scholarly journals INFLUENCE OF ERRORS IN DETERMINATION OF TRACING SLOPE ON THE ACCURACY OF GEODETIC BASE FOR ROUTE

2021 ◽  
pp. 111-117
Author(s):  
Kostiantyn Mamonov ◽  
Svitlana Kamchatnaya ◽  
Yevhen Orel ◽  
Oleksandr Saiapin
Keyword(s):  
High Speed ◽  
Methodological Approach ◽  
Line Length ◽  
Route Length ◽  
The Difference ◽  
Artificial Development ◽  
The Right ◽  
The Impact ◽  
Further Development

The purpose of this article is to study and develop a methodological approach tosolving the problem of accuracy of the geodetic base of the route. For this purpose, the followingtasks are set: mathematical substantiation the dependence of the line length on the ratio of the traceslope and the guide slope; description of the function of optimal use of the guiding slope at highspeed; determination of the impact of errors in the course of the geodetic justification on the routelength. Starting from the determined point and further to the right, artificial development of the lineis required. Because when a trace is planed using level curves, this point can be reached sooner orlater, and in some cases, this point can not be reached not at all, the line length designed accordingto the plan will be slightly different than in the case of tracing with usage the exact data. Thus, theobtained results indicate the following. If the error positions during a high-speed segment are suchthat the ordnance datum of the passage is less than the truth, the route length will be less than thetrue and vice versa. This trivial result indicates that the location of geodetic support points ondifferent sides of the pass is not recommended. It is established that due to the accumulation of errorsin the transmission of coordinates in the working substantiation networks, the conditions of the linedesign and the amount of operating costs change. It is mathematically substantiated that the linelength depends on the depth of the excavation on the pass and the height of the embankment at thepoint, and also on the difference of ordnance datum at these points. The difference between the traceslope and the guiding slope has an inversely proportional effect. In addition, the function of optimaluse of the guide slope at a high-speed segment has the form of a broken line according to its fracturesthe need for artificial development of the route can be established. The influence of errors in the course of the working justification is manifested in the discrepancy between the true and projectedroute length. If this error is not taken into account, it will lead to significant overspending duringbuilding a longer line than necessary. Further development of the problem of increasing the accuracyof tracing and reducing the impact of errors is planned in the direction of creating methods of digitalmodelling and automated programs.

scholarly journals Study on the impact of the Beijing–Shanghai high-speed railway on regional economic equity based on economic performance

2021 ◽  
Author(s):  
Heng Yang ◽  
Qiong Tong ◽  
Pan Zhao
Keyword(s):  
High Speed ◽  
Optimal Allocation ◽  
Research Result ◽  
Difference In Differences ◽  
High Speed Railway ◽  
Regional Economic ◽  
Big Cities ◽  
The Difference ◽  
The Impact ◽  
Economic Equity

AbstractAccording to the panel data of stations along the Beijing–Shanghai high-speed railway (BSHR) from 2008 to 2018, the influence of BSHR on regional economy of cities along the line is analyzed, and the influence of the opening of the BSHR on regional economic equity of cities along the line, through constructing the difference-in-differences model. The research result shows that the opening of the BSHR greatly promotes the growth of the GDP per capita of the site cities along the line and the optimal allocation of resources, such as labor, information and technology, and accelerates the two-way flow of factors of production between big cities and small and medium-sized cities at stations along the high-speed railway, makes high-quality resources from small and medium-sized cities flow to big cities along the line, while some backward resources from big cities gradually tilt toward small- and medium-sized cities along the line. In short, the opening of BSHR promotes the economic growth of the cities along the line, shortens the economic gap between the cities, is conducive to realizing regional economic equity.

scholarly journals Bulk Density Homogenization and Impact Initiation Characteristics of Porous PTFE/Al/W Reactive Materials

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2271 ◽  
Author(s):  
Baoqun Geng ◽  
Haifu Wang ◽  
Qingbo Yu ◽  
Yuanfeng Zheng ◽  
Chao Ge
Keyword(s):  
Bulk Density ◽  
Testing System ◽  
Sintering Process ◽  
Structure Characteristics ◽  
Reactive Materials ◽  
Theoretical Maximum ◽  
Mesoscale Structure ◽  
Impact Initiation ◽  
Different Types ◽  
The Impact

In this research, the bulk density homogenization and impact initiation characteristics of porous PTFE/Al/W reactive materials were investigated. Cold isostatic pressed (CIPed) and hot temperature sintered (HTSed) PTFE/Al/W reactive materials of five different theoretical maximum densities were fabricated via the mixing/pressing/sintering process. Mesoscale structure characteristics of the materials fabricated under different molding pressures were compared while the effect of molding pressures on material bulk densities was analyzed as well. By using the drop weight testing system, effects of the theoretical maximum densities (TMDs), drop heights and molding pressures on the impact initiation characteristics were studied. Quantitatively, characteristic drop heights (H50) for different types of materials were obtained. The two most significant findings of this research are the density homogenization zone and the sensitivity transition zone, which would provide meaningful guides for further design and fabrication of reactive materials.

Use of Electrothermal Explosion and Electro-Thermal Analyser (ETA-100) for the Study the Kinetics of Fast High-Temperature Reactions in SHS-Ceramic Systems

2010 ◽  
Vol 63 ◽  
pp. 203-212
Author(s):  
A.S. Shteinberg ◽  
A.A. Berlin
Keyword(s):  
High Temperature ◽  
Rate Constants ◽  
High Speed ◽  
Dissimilar Materials ◽  
Isothermal Kinetics ◽  
Hard Alloys ◽  
Wide Range ◽  
Static Conditions ◽  
The Impact ◽  
Kinetics Of

Due to the lack of specialty kinetic methods and instruments, the kinetics of fast hightemperature reactions SHS-ceramic systems has not been adequately studied. Recently, we have developed a number of methods of so-called non-isothermal kinetics (NIK) and designed instruments allowing one to obtain information about reactions of ceramic systems in a wide range of practically important temperatures and rates. The use of one of the NIK-methods (called electrothermal analysis based on the phenomena of electro thermal explosion) allows one to study kinetics of SHS of some ceramic materials characterized by the total reaction time ~ 10 μs. In ETE, both samples pressed from reagents powders or cylindrical samples made from tightly rolled foils were studied. The joule heating was accompanied by high-speed scanning of the non-stationary temperature field on its surface. Description and technical characteristics of the specialty device electrothermoanalyzer ETA-100 manufactured by ALOFT are given. Kinetic parameters of fast EM reactions for the temperatures up to 3600 K can be measured by ETE method using ETA-100. New kinetic data for fast high-temperature gasless SHS yielding individual and composite materials (including refractory carbides and borides of transition metals, silicon and boron carbides, some refractory oxides and hard alloys) are presented. At high-speed impact of the samples, the reaction rate constants were found to exceed the combustion rate constants (measured by ETA-100) by many orders of magnitude. It was concluded that the kinetic mechanisms of the corresponding fast reactions in the static conditions and under the impact are dramatically different. It was shown that SHS in ETE mode has a significant potential as a modern practical method to be used for welding of refractory and dissimilar materials, production of coarse superabrasives, etc.

Application of Horizontal Bamboo Bars in Highway Bridge Embankment Backfill

2014 ◽  
Vol 501-504 ◽  
pp. 1424-1428
Author(s):  
Qiang Chen ◽  
Yao Dong Kuang ◽  
Ben Jiao Zhang ◽  
Bin Huang
Keyword(s):  
Effective Treatment ◽  
High Speed ◽  
Impact Load ◽  
Highway Bridge ◽  
Transition Area ◽  
Bridge Abutment ◽  
The Difference ◽  
The Impact ◽  
Highway Embankment

Because the backfill of highway bridge embankment is not dense enough and the located in the hard and soft transition area, the big settlement that threats the safety of driving usually occurs when influenced by the impact load of high-speed vehicles. According to statistic of investigation of the accidents on certain highway, the difference between settlements in bridge abutment and bridge back is around 32mm to 100mm. This kind of big settlement difference is the main reason for bumping and other problems harming the operation of highway. In this paper we experimentally use horizontal bamboo bars used in the construction of side bridge embankment to deal with the continuous backfill settlement, which is effective. Bar pile to treat the settlement of highway embankment backfill is one of the economical, reliable and effective treatment without constructional occupation of driving lanes.

scholarly journals INFLUENCE OF USING TOOLS IN PRE-CLINICAL AND CLINICAL TRAINING OF DENTAL STUDENTS

2021 ◽  
Vol 10 (34) ◽  
Author(s):  
V.S Serikov ◽  
Keyword(s):  
High Speed ◽  
Clinical Training ◽  
Dental Students ◽  
Practical Training ◽  
Psychomotor Skills ◽  
Low Speed ◽  
Self Confidence ◽  
The Difference ◽  
The Impact ◽  
Real Patients

The purpose of this study is to evaluate the impact of using tools in pre - clinical and clinical training of dental students. In this study, the goal was to evaluate the effects of using high-speed and low-speed handpieces by dental students during their preclinical practical training on phantoms and compare them with polyclinic work on real patients. In the course of the study, students were asked to perform first-class black cavities dissection using low-speed and high-speed turbine tips. Thus, the type of tip speed did not affect the theoretical capabilities of students of the faculty of dentistry when testing and preparing carious cavities of class I. However, there were differences in the practical training of dental students and the inability to create the correct tooth cavity, due to the difference in the speed of movement of the boron head of a high-speed turbine tip. The data obtained in the course of the study indicate the need to implement an educational program using real high-speed turbine tips in order to improve the practical training of students of the faculty of dentistry. The use of high-speed tips can strengthen the self-confidence of dental students and ensure the acquisition of cognitive thinking and psychomotor skills from working with phantoms to clinical practice.

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