Stress-strain State and Vibration Frequencies of Blades of the Main Mine Fan Impeller

The paper discusses geometrical characteristics and strength parameters of fan blades equipped with replaceable active part it end ended to improve the fan adjustability owing to replacement or removal of the active part, which allows the fan to maintain a wide range of ventilation modes.

The Hydrodynamic Crisis of Nucleate Boiling in a Horizontal Thin Layer of Dielectric Liquid HFE-7100

The results of an experimental study on critical heat fluxes(CHF)during the nucleate boiling of the HFE-7100 dielectric liquid in horizontal layers of different heights at atmospheric pressure are presented.The existence of a critical layer height has been established.In layers above the critical layer height,a hydrodynamic boiling crisis occurs;in thinner layers,a surface drying crisis occurs.At a layer height equal to the critical value,a dry spot first appears,followed by transition boiling,which gradually spreads to the entire heating surface.In these experiments,the critical layer height was equal to 6 mm.In a layer of liquid with a critical layer height of 6 mm,a two-dimensional Taylor instability was observed in the transition boiling mode when the ratio of the diameter of the"vapor jets"to the distance between them,as well as the void fractions in the layer(-π/16),corresponded to the main provisions of the Zuber theory.The calculation of CHF using the relations of Zuber’s theory,when approaching the crisis from the transition boiling side and taking into account the real geometric dimensions,aligns well with the experimental results.

Comparison of explosive welding of pure titanium/SUS 304 austenitic stainless steel and pure titanium/SUS 821L1 duplex stainless steel

Pure commercial titanium was welded with two types of stainless steel,namely SUS 304 austenitic stainless steel and SUS 821L1 duplex stainless steel.The wavy interface of SUS 821L1 was smaller than that of SUS 304.The vortex zone was observed from both longitudinal and transverse directions,and its composition was analyzed.The interface of Ti/SUS 821L11 was able to bear 401−431 MPa shear load while that of Ti/SUS 304 could withstand 352−387 MPa.The weldability window was used to analyze experimental phenomenon.Furthermore,the smoothed particle hydrodynamics(SPH)numerical simulation method was used to simulate the wavy interface.The trend of wavelength and amplitude change with strength and the stand-offs was consistent with the experimental results.

Experimental and numerical investigations of interface properties of Ti6Al4V/CP-Ti/Copper composite plate prepared by explosive welding

Explosive welding technique is widely used in many industries.This technique is useful to weld different kinds of metal alloys that are not easily welded by any other welding methods.Interlayer plays an important role to improve the welding quality and control energy loss during the collision process.In this paper,the Ti6Al4V plate was welded with a copper plate in the presence of a commercially pure titanium interlayer.Microstructure details of welded composite plate were observed through optical and scanning electron microscope.Interlayer-base plate interface morphology showed a wavy structure with solid melted regions inside the vortices.Moreover,the energy dispersive spectroscopy analysis in the interlayer-base interface reveals that there are some identified regions of different kinds of chemical equilibrium phases of CueTi,i.e.CuTi,Cu_(2)Ti,CuTi_(2),Cu_(4)Ti,etc.To study the mechanical properties of composite plates,mechanical tests were conducted,including the tensile test,bending test,shear test and Vickers hardness test.Numerical simulation of explosive welding process was performed with coupled Smooth Particle Hydrodynamic method,Euler and Arbitrary Lagrangian-Eulerian method.The multi-physics process of explosive welding,including detonation,jetting and interface morphology,was observed with simulation.Moreover,simulated plastic strain,temperature and pressure profiles were analysed to understand the welding conditions.Simulated results show that the interlayer base plate interface was created due to the high plastic deformation and localized melting of the parent plates.At the collision point,both alloys behave like fluids,resulting in the formation of a wavy morphology with vortices,which is in good agreement with the experimental results.

Influence of the Distribution of Excess Carbide on the Properties of Genuine Damascus Steel

The methods of spectral, x-ray phase and microprobe analysis show that genuine Damascus steel is a high-purity unalloyed high-carbon steel with a high phosphorus content. It is shown that phosphorus in an amount of from 0.1% to 0.2%, having a high liquation coefficient, contributes to the process of segregation of carbon in interdendritic zone in the process of crystallization. Interdendritic zone formed carbon clusters, in the process of forging transform into oblong carbides cementite. The main physical and chemical factors affecting the formation of oblong carbides are revealed. The hardness of carbide layers was determined, which was about 920 HV. The hardness of the troostite matrix was amounted about 475 HV. It is established that the cutting edge of the blade knife of Damascus steel is nothing more than a “micro-saw” consisting of parallel carbide and troostite layers. Tests are conducted on the preservation of the cutting edge sharpness of the blades knife of homogeneous structure of steel У15А (Russian) and the layered structure of genuine Damascus steel Ds15P (Indo-Persian). Found that with little effort cut (to 4 kg) ancient Damascus steel (Ds15P) shows a greater number of cuts than the modern instrument steel У15А. With an increase, force on the cutting edge from 6 kg to 12 kg carbon Tool steel is showed a more number of cutting on the 25% than in genuine Damascus steel. The fatigue crack propagation in the true Layered structure of Damascus steel Ds15P occurs for a greater number of cycles than in a homogeneous structure of the steel У15А. The blade knife of genuine Damascus steel, in terms of fatigue reliability (survivability), has almost 2 times longer service life than the blade knife of the modern carbon tool steel type У15А. It is proved that loss in cutting ability of a genuine Damascus steel compensates increased the reliability (“survivability”) of the blade knife with fatigue loads.

Wootz: Cast Iron or Steel?

It is shown that the excess carbide phase in Wootz is of an unusual nature origin that differs from the excess phase of secondary cementite, ledeburite and primary cementite in iron-carbon alloys. It is revealed that the morphological features of excess cementite in Wootz lie in the abnormal size of excess carbides having the shape of irregular prisms. It is discovered that the faceted angular carbides are formed within the original of metastable ledeburite, so they are called “eutectic carbides”. It was found that angular eutectic carbides in the Wootz formed during long isothermal soaking at the annealing and subsequent deformation of ledeburite structures. It is revealed that carbon takes up 2.25% in Wootz (in the region of white cast iron), while none in its structure of crushed ledeburite. It is shown that the pattern of carbide heterogeneity consists entirely of angular eutectic carbides having an irregular trigonal-prismatic morphology. It is shown that Wootz (Damascus steel) is non-alloy tool steel of ledeburite class, similar with structural characteristics of die steel of ledeburite class and high-speed steel, differing from them only in the nature of excess carbide phase.

Determination of the Fracture Toughness of Optomechanical Devices

Static fracture toughness characteristics are traditionally determined in tests of standard notched specimens using a P-V curve, where P is the load and V is the notch-opening displacement. This curve has a characteristic point Q. At the load PQ corresponding to this point, the crack starts to propagate. For this load, the fracture toughness characteristics are then calculated. In brittle (elastic) fracture, the P-V curve at the onset of crack propagation has an extremum (or a local extremum), from whose ordinate PQ is determined with sufficient accuracy. In ductile and elastic-ductile fracture, P-V curves are monotonically increasing, and PQ is calculated using the 5% secant offset method without taking into account the characteristics of the material, so that the PQ is determined inaccurately. To improve the accuracy of PQ determination, we propose a thermographic method for determining the fracture toughness of metals. This method involves plotting the load P against the temperature change ΔТ over a relatively short period of time at the notch tip. This plot is then transformed to a P-ΔS curve, where ΔS is the specific entropy increment at the notch tip, which is calculated through ΔТ. This thermodynamic diagram has a characteristic step at the beginning of crack propagation, and from the ordinate of this step, PQ can be determined much more accurately. Furthermore, in the thermographic method, the preparation of test specimens can be simplified by replacing the process of growing a fatigue crack at the tip of a notch by making a sharp cut, which provides significant time savings. Statistical processing and comparison of test results of steel 20 specimens using the conventional and thermographic methods have shown the advantages of the thermographic method in accuracy and complexity.

Digital Earth surface maps for radar ground clutter simulation

This paper dwells upon optimizing the azimuth samp-ling interval of digital surface maps used to model radar ground clutter.The resulting equations can be used to find the digital map sampling interval for the required calculation error and modeled power of the simulated signal,which determines the resulting distribution of backscatter intensity.The paper further showcases how the sampling interval could be increased by pre-processing the map.

葡萄糖浓度对THz频段血液光学特性的影响（英文）

无创性血糖检测仍是糖尿病患者护理安全舒适的现实科学任务。本文研究了血糖光学特性与血糖浓度之间的相关性。用时域THz光谱研究了全血在0.3~0.5 THz频率范围内的透射谱。在注射胰岛素后的短时间内,由同一糖尿病患者产生了生物样品。得到了血液光学特性的频散特性。基于频散,给出了血糖浓度与折射率和介电常数的关系式。这项工作是复杂研究的一部分,重点是无创葡萄糖测量技术的发展。记录血糖水平与血液光学参数之间的依赖关系,使得将来可以使用反射光谱技术进行无创血糖水平检测。

Algorithms for automatic measurement of SIS-type hysteretic underdamped Josephson junction’s parameters by current-voltage characteristics

Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction(JJ)can be measured by its current-voltage characteristics(IVCs).Currents and voltages at JJ are commensurate with the intrinsic noise level of measuring instruments.This leads to the need for multiple measurements with subsequent statistical processing.In this paper,the digital algorithms are proposed for the automatic measurement of the JJ parameters by IVC.These algorithms make it possible to implement multiple measurements and check these JJ parameters in an automatic mode with the required accuracy.The complete sufficient statistics are used to minimize the root-mean-square error of parameter measurement.A sequence of current pulses with slow rising and falling edges is used to drive JJ,and synchronous current and voltage readings at JJ are used to realize measurement algorithms.The algorithm performance is estimated through computer simulations.The significant advantage of the proposed algorithms is the independence from current source noise and intrinsic noise of current and voltage meters,as well as the simple implementation in automatic digital measuring systems.The proposed algorithms can be used to control JJ parameters during mass production of superconducting integrated circuits,which will improve the production efficiency and product quality.

Crystal Structures of Tris-dipivaloylmetanates of Tm^3＋ and Yb^3＋

A series of Ln（Ⅲ） dipivaloylmethanates Ln（dpm）3 has been obtained. The crystalstructures of Tm（dpm）3 （1） and Yb（dpm）3 （2） were determined by X-ray analysis at 200（2） K（Pmn2b Z = 2; a = 17.7509（8）, b = 10.5805（4）, c = 9.8380（4） A, V = 1847.7（1） A3 for （1） and a =17.7272（6）, b = 10.5882（3）, c = 9.8440（3） A, V= 1847.7（1） A^3 for （2））. These data complete thestructural evaluation of lanthanoid tris-dipivaloylmethanates. Compounds 1 and 2 are isostructuralto the complexes Ln（dpm）3 （Ln -- Er and Lu）. It is demonstrated that the volatility of tris-dipivaloylmethanates of rare earth elements increases from the complex of Lu to that of La.

Optical measuring systems and technologies for some urgent tasks in industry and science

Modern industry and science take novel optical measuring systems and laser technologies with high resolution and productivity for solving actual tasks,including safety problems for mining,oil,atomic and railway in-dustries.The TDI SIE's results in these trends are presented.

Teacher-Retraining Course Design Renewal

Teacher-retraining course design is considered to be a challenge not only to the course participants but to the course designers as well, especially, when the participants enrolled turn out to have dramatically different professional background and conditions. This article supports the idea that changes to the course design should be made straightaway in response to the trainees＇ specific needs. The context for rural school teacher retraining at Novosibirsk State Technical University in Russia illustrates reasons for making immediate changes necessary as the course progressed, and reaction to them. The article discusses a model for a teacher retraining course in which EFL improvement is the core element.

PAD Spectrometer Based on Wide Tunable Optical Parametric Oscillator for Noninvasive Medical Diagnostics

The gas analyzer based on optical parametric oscillators (OPO) and laser photo - acoustic spectroscopy is demonstrated. The optical parametric oscillators based on fun – out PPLN and bulk crystal AgGaS2 with a two-pass pumping are developed. Wide tunable OPO is pumped by compact nanosecond Nd: YLF laser. Pulse duration is 5 - 7 ns, maximum pulse energy is 1.5 mJ at a frequency of 100-2000 Hz. OPO lasing threshold is 10 - 16 mJ/cm2 at the spectral range 2.2 - 4 μm for fun – out PPLN OPO and 12 - 20 mJ/cm2 at the spectral range 4 - 7.5 μm for AgGaS2 OPO. Absorption spectra of gaseous mixtures (CH4, C3H8, C2H6, C2H4 and CO2) and human’s breath were studied.

Specification and Analysis of Discrete Behavior of Hybrid Systems in the Workbench ISMA

Hybrid systems are important in applications in CAD, real-time software, robotics and automation, mechatronics, aeronautics, air and ground transportation systems, process control, and have recently been at the center of intense research activity in the control theory, computer-aided verification, and artificial intelligence communities. In the past several years, methodologies have been developed to model hybrid systems, to analyze their behavior, and to synthesize controllers that guarantee closed-loop safety and performance specifications. These advances have been complemented by computational tools for the automatic verification and simulation of hybrid systems. Modern technologies of computer simulation tools include preparing, debugging, analysis and calculation of effective program models, meaningful interpretation of research results.

Prediction of the Cyclic Life of Pieces with Macrocracks by Thermographic Method

To improve the accuracy for prediction of cyclic life of pieces with macrocracks we propose to use a new thermographic method. Traditionally this question is solved on the basis Paris formula which connects the speed of crack growth (SCG) with Stress intensity factor K. However parameter K is not identical to the SCG because K doesn’t consider non-linear processes at the top of crack (TC). That is why the using K gives the considerable error. For overcoming this problem we proposed instead of K to connect SCG with another diagnostic parameter, such as ΔS(1c)—increment of specific entropy for cycle (ISE) at the TC, which can be calculated with sufficient accuracy through passive temperature field on the surface of tested object. Parameter ISE can be obtained both simultaneously with building of a kinetic fatigue diagram and on the basis of measuring of temperature under exploitation of piece. In both cases the prediction of cyclic lifetime is much higher than with the help parameter K. Besides parameter ISE allows to follow the crack development inside tested object. This means that suggested parameter ISE is more universal and convenient than traditional parameter K.

The Calculation of the Effective Tensor Coefficient of the Medium for the Objects with Microinclusions

In this paper, several approaches for calculation of the effective tensor coefficient for domains with inclusions have been proposed. The limits of the approaches using are found. The series of numerical experiments are made on the different frequencies, for different inclusions location and boundary conditions for the contrast properties of the matrix and inclusion materials.

Application of artificial neural networks for stress state analysis based on the photoelastic method

The present article proposes an evolutionary development of the photoelasticity method for measuring stresses based on annular photoelastic sensors application along with stress pattern recording with the aid of a digital camera and its recognition using artificial neural networks.The analysis of the modern application of the photoelasticity method for various problems within the theory of strength is presented.The principle of operation of photoelastic sensors based on the photoelasticity effect is considered.Optical patterns in an annular photoelastic sensor are presented for various values of the horizontal stress.The calculation of the stress state of the sensor for the following full-scale experiment has been performed,the estimate of the threshold conditions under which the sensor can be applied has been performed.As a result of a laboratory experiment,a dataset of 1500 isochromatic images has been assembled.A subspecies of a neural network,namely a convolutional neural network,has been applied as a machine learning algorithm.Different combination of models and optimizers have been employed.The application of downhole sensors for continuous monitoring of alterations in the rock mass stress state and the integration of this data into a digital field model based on Internet of Things technologies has been proposed.

STCF conceptual design report (Volume 1): Physics & detector

The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.