bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic creeping behaviors between hoisting rope and friction lining in friction transmission
Authors: Guo Yongbo , Zhang Dekun , Feng Cunao , Liu Yuan
Published: January 2017

The creeping behaviors between hoisting rope and friction lining in the process of deep coal mine friction transmission are investigated in this study. Rope tension during the hoist lifting and lowering process is obtained first. Then, the calculation models of creeping area, creeping quantity and creeping velocity are established. The rope tension and creeping quantity are measured by a self-designed experiment device to verify the model validity. Subsequently, effects of the kinematic parameters on creeping behaviors are explored. The results show that increases of the terminal mass ratio, terminal mass, maximum acceleration, maximum speed cause expanding trends of overall ranges of the maximum creeping velocity, respectively. Less creep is beneficial to improve the friction transmission safety, service life of friction lining and good anti-slip properties. The most effective way to decrease the creep is to increase the container weight.
Sparse decomposition based on ADMM dictionary learning for fault feature extraction of rolling element bearing
Authors: Tong Qingbin , Sun Zhanlong , Nie Zhengwei , Lin Yuyi , Cao Junci
Published: January 2017

Sparse decomposition is a novel method for the fault diagnosis of rolling element bearing, whether the construction of dictionary model is good or not will directly affect the results of sparse decomposition. In order to effectively extract the fault characteristics of rolling element bearing, a sparse decomposition method based on the over-complete dictionary learning of alternating direction method of multipliers (ADMM) is presented in this paper. In the process of dictionary learning, ADMM is used to update the atoms of the dictionary. Compared with the K-SVD dictionary learning and non-learning dictionary method, the learned ADMM dictionary has a better structure and faster speed in the sparse decomposition. The ADMM dictionary learning method combined with the orthogonal matching pursuit (OMP) is used to implement the sparse decomposition of the vibration signal. The envelope spectrum technique is used to analyze the results of the sparse decomposition for the fault feature extraction of the rolling element bearing. The experimental results show that the ADMM dictionary learning method can updates the dictionary atoms to better fit the original signal data than K-SVD dictionary learning, the high frequency noise in the vibration signal of the rolling bearing can be effectively suppressed, and the fault characteristic frequency can be highlighted, which is very favorable for the fault diagnosis of the rolling element bearing.
Nonlinear dynamic behavior analysis of a DC/DC converter with an ultra-high frequency Z-source converter
Authors: Li Shan , Cui Sen , Chen Yan , Zheng Yong , Si Wenxu
Published: January 2017

Z-source converters have been used in new energy sources because of their advantages. These converters have attracted considerable attention under high-frequency conditions given their high power density and high conversion efficiency. However, the stability of a system of ultra-high frequency Z-source converters are likely to be affected because of the inappropriate selection of parameters or the interference of weak signals in the process of the system. These factors will render such converters unable to work properly. The chaotic bifurcation behavior of Z-source converters based on peak current control mode is analyzed in this study. A precise discrete iterative mapping model for such converters is established, and the regional stability of a system is determined based on the characteristic value of changes in the Jacobian matrix. Finally, the bifurcation and chaos phenomena in a high-frequency Z-source converter and the accuracy of the aforementioned analysis are verified via experiments. The conclusion drawn from this study does not only can provide a reference for the stable operation of ultra-high frequency Z-source converters, but also presents a theoretical basis for optimizing system parameters and improving control performance.
An objective evaluation of healthy human upper extremity motions
Authors: Linkel Artūras , Griškevičius Julius , Daunoravičienė Kristina
Published: January 2017

This paper presents an investigation of quality evaluation of human upper extremity motions by introducing a new methodology. The VICON motion capturing system was applied to evaluate the kinematics of the upper extremity. The created 3D 5 DOF dynamical model in MATLAB allowed calculating additional movement’s quantitative parameters: the work done and power used during the appropriate motion. Finally, least squares method was applied to define torques by using a 3rd degrees polynomial approximation of mean torque values in the angle domain. The calculated parameters of 23 healthy participants’ motions as well as the investigated method could be used in the future in rehabilitation field to evaluate the quality of upper extremity motion of patients. The Pearson’s correlation coefficient between motion angle and angular velocity amplitudes is 0.49-0.82 and between work done and power of the movement is 0.61-0.99.
Identification of internal damage in ballastless tracks based on Gaussian curvature mode shapes
Authors: Xu Jingmang , Wang Ping , Liu Hao , Hu Zhipeng , Chen Rong
Published: January 2017

In order to solve existing problems of ballastless tracks, such as various kinds of internal damage and detection difficulties, this paper presents a method based on Gaussian curvature mode shapes. The proposed method has been validated according to relevant numerical simulations and laboratory tests (e.g. those performed for detecting interlayer damage of CRTS II plate-type ballastless tracks), and had led to the following conclusion: if no damage exists in ballastless tracks, the Gaussian curvature mode shapes will be smooth and continuous under different order modes of the track slabs and no obvious peaks will be found. According to the numerical simulation, in vertical and bending vibration modes of damaged track slabs (e.g. the second-, third-, fourth-, ninth- and tenth-order), the Gaussian curvature modes have obvious peaks at damaged locations; and the second-, third- and fourth-order Gaussian curvature modes of track slabs have discontinuity points at damaged locations according to the calculation made in the modal test for the scale model of damaged ballastless tracks. Moreover, the method based on Gaussian curvature mode shapes can be used for detecting and locating internal damage of ballastless tracks accurately.
The dynamic characteristics of mechanical structures destruction
Authors: Kaźmierczak Henryk
Published: January 2017

Changes in the dynamic state of a mechanical structure, as described by energy-related characteristics of the loads of the vibration nodes in a mechanical system, are a significant indicator of differences or changes taking place in its structure. The authors have outlined a method for analysing the fatigue degradation of mechanical structures described in terms of variations in the dynamic mobility, impedances, their real and imaginary parts and fluctuations in the strength of dynamic stiffness and the strength of the internal damping of structures expressed as a function of degradation time (the number of degrading impulse impacts). Information about the technical condition of the individual material samples have been obtained on the basis of the energy characteristics of power spectral density under degrading dynamic load. The dynamic load power distribution matrix defined as the quotient of vector of vibration rate and transposed forcing action vector. The results were presented in the form of power amplitude estimation of the dynamic stiffness forces and damping forces, changing with the ongoing samples degradation process. The variations are identified over the full scope of destruction ranging from nucleation to dominant fracturing. Such an identification is carried out by the method of experimental modal analysis and by energy-based methods with the use of a mechatronic accelerated testing station. The paper provides definitions of the related measurable measures of the process. The point is illustrated with an overview of selected strength characteristics of modern construction steel.
Influence of tilting rotor on characteristics of fluid-induced vibration for labyrinth seals
Authors: Zhang Wanfu , Zhang Yao , Yang Jiangang , Li Chun
Published: January 2017

Labyrinth seal is a key component for the safe and reliable operation of a turbine unit. This paper sets up a three-dimensional numerical model of a labyrinth seal with a tilting rotor based on a compressor eye seal which was studied by Computational Fluid Dynamics method and a test labyrinth seal. The influence of the tilting rotor on the static and dynamic characteristics of labyrinth seals was investigated. Numerical results demonstrated a good agreement with the published article. Both the radial and tangential fluid-induced forces show an obvious increase when the rotor is in tilting conditions. From an efficiency viewpoint, a bigger tilt angle of the rotor is desirable. And eccentricity existence is not beneficial to the seal performance. The results based on the test seal show the whirl frequency ratio increases with the increasing eccentricity ratio. In case of tilting conditions (δ= 0.05 mm, θ= 0.8 deg), the whirl frequency ratio decreases with the increasing rotational speed. The higher rotational speed will be beneficial to the stability improvement when the rotor is in tilting conditions. The whirl frequency ratio also shows a decrease with the increasing inlet pressure. The higher inlet pressure tends to improve the stability when the rotor is in tilting conditions. All the stiffness coefficients and damping coefficients increase as the tilt angle increases. The whirl frequency ratio also shows an increase with the increasing tilt angle. The tilting rotor tends to reduce the stability when the rotor is in eccentric conditions.
Numerical study on aerodynamic noise performances of axial spacing in a contra-rotating axial fan
Authors: Luan Hengxuan , Weng Liyuan , Luan Yuanzhong , Zhang Yongchao , Chen Peng
Published: January 2017

In order to study the effect of axial spacing on behaviors of aerodynamic performance and aerodynamic noises in a contra-rotating fan, the steady/unsteady Reynolds-averaged Navier-Stokes equations are solved by the numerical method in conjunction with a SST turbulence model, and the effects of axial spacing on performance and aerodynamic characteristics are investigated. Furthermore, BEM is adopted to compute the radiation noise of the contra-rotating fan caused by unsteady pressure fluctuations. The results show that axial spacing is an important factor which can affect the aerodynamic performance of contra-rotating fan. As a whole, the effect of axial spacing on the blade loading of Rotor 2 is significantly greater than that of Rotor 1. For Rotor 2, the smaller axial spacing leads to the large secondary flow loss, and the larger axial spacing leads to the strong mixing loss. With the increase of axial spacing, the radiation noise at the characteristic frequency decreases, but showed different changing degrees. With consideration of the aerodynamic performance and aerodynamic noises of the contra-rotating fan, the optimal comprehensive performance appears at the axial spacing of 0.5 chord.
Gas pipeline structural fatigue life prediction based on vibration signals analysis
Authors: Drożyner Przemysław
Published: January 2017

The problem of fatigue life prediction is still a scientific problem, which solution is necessary for industry, particularly for those branches in which failures threaten serious economic, environmental losses and human life. Petrochemical industry including transmission infrastructure – pipelines is example of such industry. Pipelines are exposed to damage due to various reasons, including vibration. Especially at risk are so called small bore connections (SBC) – a kind of branched connection on mainline piping. The paper presents the results of researches related to the development of a method for predicting a fatigue damage of SBC model. The method is based on measurements of current diagnostic signals (vibrations), without taking into consideration the history of previous loads or frequency analysis of extortions. Some experiments were carried out on originally designed and built the inertial fatigue machine. The experiment showed that it is possible to predict the fatigue strength of the specimen during the operation by observing certain combinations of vibration parameters.
Non-uniform embedding applications for synchronization analysis
Authors: Drulyte Migle , Lukoseviciute Kristina , Ragulskiene Jurate
Published: January 2017

Iterative polynomial model for synchronization of vibrations was proposed. A polynomial was constructed using time delay coordinates. For time delay kernel estimation, a non-uniform embedding was used. Evolutionary optimization algorithms were introduced for non-uniform time delay identification. Performance investigation of proposed method was done for two different vibrations.
Elastic wave simulation based on modal excitation in 3D medium
Authors: Barauskas Rimantas , Nečiūnas Audrius , Patašius Martynas
Published: January 2017

Paper describes a simulation of an elastic wave in homogenous isotropic waveguide with generic cross-section using semi-analytical finite element (SAFE) formulation. The wave is considered a travelling displacement field in the waveguide as a result to forcing excitation and is expressed via modes’ superposition. The solutions for modes are obtained solving SAFE governing eigen problem. Attenuation of the medium in SAFE framework differently from prior researchers is simulated via Rayleigh damping. It is shown, that severe damping is not properly supported by the SAFE formulation and revision for properly accepting linear viscosity is needed.
Bending of symmetric cross-ply multilayered plates in hygrothermal environments
Authors: Zenkour Ashraf M. , Alghanmi Rabab A.
Published: January 2017

The bending analysis of symmetric cross-ply laminated plates in a hygrothermal environment is presented. The sinusoidal shear deformation plate theory is used for this purpose. It enables the trial and testing of different through-the-thickness transverse shear-deformation distributions and, among them, strain distributions that do not involve the undesirable implications of the transverse shear correction factors. The governing differential equations for the bending of laminated plates are obtained using various plate theories. Displacement functions that identically satisfy boundary conditions are used to reduce the governing equations to a set of coupled ordinary differential equations with variable coefficients. Numerical results for deflection and stresses are presented. The effect of different types of sinusoidal hygrothermal/thermal loadings is investigated. The influence various parameters such as material anisotropy, aspect ratio, side-to-thickness ratio, thermal expansion coefficients ratio and stacking sequence on the hygrothermally induced response is also investigated. A concluding remark is made.
Vibration and instability analysis of fluid-conveying nanotubes embedded in visco-elastic medium with consideration of surface effect
Authors: Zhen Ya-Xin
Published: January 2017

We establish an analytical model to investigate the surface effects on the vibration and instability of fluid-conveying nanotubes embedded in visco-elastic medium. Based on nonlocal elastic theory and Euler-Bernoulli beam theory, the vibration equation of fluid-conveying nanotubes is established with considering three typical boundary conditions. The effects of both inner and outer surface layers on the nanotubes are taken into consideration and the Kelvin-Voigt model is introduced. The results show that the boundary conditions of system, the damping and elastic coefficient of the surrounding medium, thickness of nanotubes and aspect ratios have significant effects on the dynamic behaviors of the nanotubes. The damping parameter of the visco-elastic foundation causes an obvious reduction of the critical flow velocity. For smaller tube thickness, larger aspect ratio or higher elastic parameter of surrounding foundation, the stability of the nanotubes may be greatly enhanced. This article might be helpful for the design and improvement of nanotubes for fluid-conveying applications embedded in elastic medium in nanoelectromechanical systems and microelectromechanical systems.
Plane wave propagation in a 3D anisotropic half-space under Green-Naghdi theory II
Authors: Chakraborty S. , Mandal S. C. , Das A. K. , Sarkar N. , Lahiri A.
Published: January 2017

In this paper, the theory of coupled thermoelasticity in three dimension is employed for triclinic half-space, subjected to time dependent heat source on the boundary of the space which is traction free and is considered in the context of Green-Naghdi model of type II (thermoelasticity without energy dissipation) of generalized thermoelasticity. Normal mode analysis is used to the non-dimensional coupled equations. Finally, the resulting equations are written in the form of a vector-matrix differential equation which is then solved by eigenvalue approach. Numerical results for the temperature, thermal stresses, and displacements are presented graphically and analyzed. Mathematical results shown in thermoelastic curves were supplemented by tectonic movements of elastic lithospheric plates.
Free vibration analysis of electric-magneto-elastic functionally graded plate with uncertainty
Authors: Xie G. Q. , Tian J. H.
Published: January 2017

Free vibration analysis of electric-magneto-elastic functionally graded plate with uncertain parameters is studied in this paper. The elastic, electric and magnetic parameters are regarded as interval variables. Interval analysis of electric-magneto-elastic functionally graded plate are carried out by introducing the interval algorithm into the dynamic equations. A simply supported electric-magneto-elastic functionally graded plate as a numerical example are provided to the validity of the method.
Application of evolution-based uncertainty design on gear
Authors: Shi Boqiang , Shen Yanhua , Yu Guoqing , Duan Guochen , Liu Ruiyue
Published: January 2017

The evolution of mechanical parameters, a factor affecting the mechanical reliability, has gathered more attention nowadays. However, studies on time varying uncertainty can hardly be found. A new method based on evolution-based uncertainty design (EBUD) is applied to the design of gear in this paper. Considering the wear evolution over the lifetime, a tooth wear’s time-varying uncertainty model based on the continuous-time model and Ito lemma is established. Drift and volatility functions dependent on the drift rate and volatility rate of rotational speed and torque are used to express the time-varying uncertainty of tooth thickness. The method can predict the reliability and provide an instruction in reliability improving, maintenance and repair of the gear system.
A novel Pennes’ bioheat transfer equation with memory-dependent derivative
Authors: Sarkar N.
Published: January 2017

In this paper, a new mathematical model for Pennes’ bioheat equation using the new memory-dependent derivative is established. The one-dimensional thermal behavior in living tissue subject to instantaneous surface heating is investigated. Numerical calculations are performed to study the temperature transients in the skin exposed to instantaneous surface heating. Numerical results are plotted in the form of two-dimensional graphs and discussed. In this novel model, the time delay parameter is a new indicator of bio-heat efficiency in living tissues.
Urine diversion dry toilets in eThekwini Municipality, South Africa: acceptance, use and maintenance through users' eyes
Authors: Mkhize Nosipho , Taylor Myra , Udert Kai M. , Gounden Teddy G. , Buckley Chris A.
Published: January 2017

This study was part of the VUNA project aimed to develop an affordable sanitation system that produces a valuable fertiliser, reduces pollution of water resources and promotes health. Urine diversion dry toilets (UDDTs) simplify the on-site hygienisation of faeces and allow for nutrient recovery from urine. Social acceptance is vital for the implementation of the UDDT, because sanitation is only effective if the system not only provides a well-designed toilet and effective waste management, but also offers users a facility that caters to their needs and is sensitive to their cultural lifestyle. This study used qualitative and quantitative methods to investigate acceptance, use and maintenance of UDDTs. Key findings indicate lower levels of acceptance of UDDTs among the elderly, who are accustomed to traditional pit toilets. The users aspire to own a flush toilet, perceived to be indicative of household wealth. A dominant concern was emptying the pit and the quality of the building material. Community interventions are required that will promote acceptance, understanding and encourage proper use and maintenance of the UDDT, and may need some technology modification. There is an urgent need for increased community participation to address users' perceptions, attitudes and behaviour concerning the UDDT.
Evaluation of the information content of long-term wastewater characteristics data in relation to activated sludge model parameters
Authors: Alikhani Jamal , Takacs Imre , Al-Omari Ahmed , Murthy Sudhir , Massoudieh Arash
Published: January 2017

A parameter estimation framework was used to evaluate the ability of observed data from a full-scale nitrification–denitrification bioreactor to reduce the uncertainty associated with the bio-kinetic and stoichiometric parameters of an activated sludge model (ASM). Samples collected over a period of 150 days from the effluent as well as from the reactor tanks were used. A hybrid genetic algorithm and Bayesian inference were used to perform deterministic and parameter estimations, respectively. The main goal was to assess the ability of the data to obtain reliable parameter estimates for a modified version of the ASM. The modified ASM model includes methylotrophic processes which play the main role in methanol-fed denitrification. Sensitivity analysis was also used to explain the ability of the data to provide information about each of the parameters. The results showed that the uncertainty in the estimates of the most sensitive parameters (including growth rate, decay rate, and yield coefficients) decreased with respect to the prior information.
Removal of organic phosphorus and formaldehyde in glyphosate wastewater by CWO and the lime-catalyzed formose reaction
Authors: Xing Bo , Chen Honglin , Zhang Xiaoming
Published: January 2017

Glyphosate (PMG) wastewater with 40–600 mg/L organic phosphorus (OP) and 1–4% CH2O was treated by catalytic wet oxidation (CWO) and the lime-catalyzed formose reaction to remove total phosphorus (TP) and improve biodegradability. Activated carbons (ACs) modified by H2O2 oxidation and thermal treatment with melamine were used as CWO catalysts and characterized by N2 adsorption/desorption and XPS. The CWO experiments were performed in an autoclave reactor at 110–130 °C and 1.0 MPa. The modified AC showed higher catalytic activity than the parent AC due to the introduction of nitrogen-containing functional groups, exhibited over 90% OP removal for various real PMG wastewaters, and had good stability for 20 consecutive CWO runs. The CWO effluents were further treated by lime at 80 °C to remove TP and CH2O. The treated efﬂuents, containing 0.5–12 mg/L TP and 20–60 mg/L CH2O, showed good biodegradability with a BOD5/COD ratio of 0.31–0.41. The combination of CWO and lime is an effective treatment method prior to biological treatment for solving the problems of OP and CH2O encountered by the glyphosate industry.
Kinetic and equilibrium profile of the adsorptive removal of Acid Red 17 dye by surfactant-modified fuller's earth
Authors: Shah Jasmin , Jan Muhammad Rasul , Muhammad Mian , Ara Behisht , Fahmeeda
Published: January 2017

In the present study, fuller's earth (FE) was modified with sodium dodecyl sulfate for removal of Acid Red 17 (AR 17) dye from aqueous solutions. The surfactant-modified FE and FE were characterized by a Fourier transform infrared spectrometer, thermogravimetric analyzer and scanning electron microscope. Batch adsorption experiments were carried out as a function of contact time, pH, initial concentration of AR 17 and adsorbent dosage. About 99.1% adsorption efficiency was achieved within 60 min at adsorbent dose of 0.1 g for initial dye concentration of 1,000 mg L−1 at pH 10. The adsorption data were well fitted with the Dubinin–Radushkevich isotherm model implying physisorption as the major phenomenon for adsorption. The kinetic data were analyzed using four kinetic equations: pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich equations. The rates of adsorption confirmed the pseudo-second-order kinetics with good correlation value (R2 = 0.999). The results indicate that the modified adsorbent can effectively be used for the removal of AR 17 from wastewater with high absorption capacity of 2164.61 mg g−1.
Synthesis and characterization of a novel magnetic biochar from sewage sludge and its effectiveness in the removal of methyl orange from aqueous solution
Authors: Zhang Jing , Liu Mao , Yang Tao , Yang Kai , Wang Hongyu
Published: January 2017

A novel magnetic biochar from sewage sludge (MSBC) using SrFe12O19 as magnetic substrate was successfully synthesized under high-temperature and oxygen-free conditions. Several techniques and methodologies (X-ray diffraction, Fourier transform infrared spectroscopy and vibrating sample magnetometer) were used to determine the surface functional groups and physicochemical properties of MSBC, which showed that the MSBC combined the features of both SrFe12O19 and sludge biochar (SBC). And then the adsorption behavior of methyl orange (MO) from aqueous solution onto the MSBC was investigated. And the influence of variables including pH, initial concentration of MO, adsorbent dosage and contact time was studied in detail. The optimal adsorption amount of MO (149.18 mg·g−1) was obtained with 600 MO mg·L−1, 2 MSBC g·L−1, at pH of 5 for 40 min. The equilibrium data were evaluated using Langmuir and Freundlich isotherms. The Langmuir model better described the absorption of MO. Besides, the kinetic data were analyzed using pseudo-first-order and pseudo-second-order equations, and the pseudo-second order exhibited the better fit for the kinetic studies (R2 = 0.9982). This study showed that MSBC could be utilized as an efficient, magnetically separable adsorbent for the environmental cleanup.
Can DNA sequencing show differences between microbial communities in Polish and Danish wastewater treatment plants?
Authors: Miłobędzka A. , Muszyński A.
Published: January 2017

The microbial populations in the activated sludge of two Polish wastewater treatment plants (WWTPs) were identified and quantified using Illumina sequencing of 16S ribosomal RNA amplicons over a 2-year period. Their dynamics over time were compared to Danish WWTPs (data collected in previous studies by Center for Microbial Communities, Aalborg University). The bacterial communities in Polish and Danish WWTPs were similar to each other, but the microbial diversity in Polish WWTPs was lower. The dominant genera in Polish WWTPs were more abundant than in Danish WWTPs; 30 of them constituted more than half the of activated sludge community. Polish WWTPs showed a higher abundance of bacteria involved in nitrogen and chemical oxygen demand removal (Proteobacteria and Bacteroidetes), while polyphosphate-acculumating bacteria were the dominant bacterial group in Danish plants. The microbial community structures in the examined Polish WWTPs were relatively similar to each other and showed strong seasonal variations which are not normally observed in Danish WWTPs.
Piperine and Its Various Physicochemical and Biological Aspects: A Review
Authors: Chopra Bhawna , Dhingra Ashwani Kumar , Kapoor Ram Prakash , Prasad Deo Nandan
Published: January 2017

Piper nigrumL. is examined as the king of species worldwide by virtue of its principle piperine. In Ayurveda, since from the ancient times, it is known as “Yogvahi”. It is one of the important alkaloids of Pepper fruits (Family Piperaceae) and has been found to have numerous medicinal properties such as antioxidant, antiplatelet, anti-inflammatory, antihypertensive, hepatoprotective, antithyroid, antitumor, antiasthmatic activity and also have significant role as fertility enhancer. The present review discusses the biosynthetic pathway, extraction process, chemistry and various analytical methods of piperine. It also describes the structural modification of piperine and its various effects on biological system. The utility of piperine as a bioenhancer for certain antibacterial- antibiotics and a potent inhibitor of drug metabolism are also discussed. Thus, review provides knowledgeable erudition on the piperine which paves way for further work.
Benefits of using amorphous metallic fibres in concrete slabs-on-grade
Authors: Nayar Sunitha K , Gettu Ravindra
Published: January 2017

The effective utilization of pseudo-ductile materials like Fibre Reinforced Concrete (FRC) depends on the incorporation of suitable material parameters in appropriate design approaches. A design methodology has been developed for slabs-on-grade addressing various failure patterns, and giving a performance requirement as the design output. This opens up the choice of fibres, allowing the use of combinations of fibres to suit the service requirements. In this context, the current study explores the use of hybrid combinations of conventional steel fibres (SF) and a genre of corrosion-resistant amorphous metallic fibres (AMF) that have the ability to significantly enhance the flexural strength of concrete, even at relatively low dosages. It is shown that AMF, when used in combination with SF, results in a synergistic response with respect to toughness; mixes with 15 kg/m3 of SF and 20 kg/m3 of AMF exhibit about 50% higher characteristic flexural strength and more than double the characteristic equivalent flexural strength than the mix with 15 kg/m3 of SF alone, in the concrete considered here. Consequently, when FRC with a hybrid combination of fibres (AMF+SF) was considered in design, a significant reduction in thickness of slab was possible, in comparison to FRC with only SF.
Диффузия межузельного магния в бездислокационном кремнии
Authors: Шуман В.Б. , Лаврентьев А.А. , Астров Ю.А. , Лодыгин А.Н. , Порцель Л.М.
Published: January 2017

Исследовалась диффузия примеси магния в пластины монокристаллического бездислокационного дырочного кремния в диапазоне температур T = 600-800 oC. Источником диффузии служил слой, имплантированный магнием с энергией ионов 150 кэВ при дозах 5·1014 и 2· 1015 см-2. Коэффициент диффузии межузельных донорных центров магния Di при некоторой заданной T пределялся путем измерения глубины p-n-перехода, который формировался в образцах, прошедших термообработку в течение времени t. В результате исследований впервые определена зависимость Di(T). Данные свидетельствуют, что диффузия осуществляется преимущественно по межузельному механизму. DOI: 10.21883/FTP.2017.01.8313
Исследования полупроводникового минерала CuFeS-=SUB=-2-=/SUB=- из гидротермальных отложений океанского рифта методом ЯМР Cu в локальном поле
Authors: Матухин В.Л. , Погорельцев А.И. , Гавриленко А.Н. , Гарькавый С.О. , Шмидт Е.В. , Бабаева С.Ф. , Суханова А.А. , Теруков Е.И.
Published: January 2017

Представлены результаты исследования природных образцов минерала халькопирита CuFeS2 из массивных океанических сульфидных руд Срединно-Атлантического хребта методом ядерного магнитного резонанса 63Cu (ЯМР 63Cu) в локальном поле при комнатной температуре. Значительная ширина обнаруженных резонансных линий в спектре ЯМР 63Cu прямо свидетельствует о большом распределении локальных магнитных и электрических полей в исследованных образцах халькопирита. Это распределение может быть следствием заметного отклонения состава исследованных образцов халькопирита от стехиометрического. Полученные результаты показывают, что импульсный метод ЯМР 63Cu может быть одним из эффективных методов изучения физических свойств глубоководных полиметаллических сульфидов Мирового океана. DOI: 10.21883/FTP.2017.01.8253
Баллистический магнетотранспорт в подвешенном двумерном электронном газе с периодической решeткой антиточек
Authors: Жданов Е.Ю. , Погосов А.Г. , Буданцев М.В. , Похабов Д.А. , Бакаров А.К.
Published: January 2017

Исследовано магнетосопротивление подвешенных полупроводниковых наноструктур с двумерным электронным газом, структурированным периодическими квадратными решeтками антиточек. Показано, что баллистический режим электронного транспорта сохраняется после отрыва образцов от подложки. Проведeн прямой сравнительный анализ соизмеримых осцилляций магнетосопротивления, а также их температурных зависимостей в образцах до и после подвешивания. Обнаружено, что температурные зависимости практически идентичны для неподвешенных и подвешенных образцов, в то время как в нелинейном режиме, обусловленном пропусканием постоянного тока, наблюдаются существенные отличия. Соизмеримые осцилляции в подвешенных образцах оказываются более устойчивыми по отношению к воздействию постоянного тока, что предположительно может быть объяснено усилением электрон-электронного взаимодействия после отрыва наноструктур от высокодиэлектрической подложки. DOI: 10.21883/FTP.2017.01.8259
Двухтоновые нелинейные электростатические волны в квантовой электронно-дырочной плазме полупроводников
Authors: Дубинов А.Е. , Китаев И.Н.
Published: January 2017

Рассмотрены продольные электростатические волны в квантовой электронно-дырочной плазме полупроводников с учетом вырожденности электронов и дырок, а также с учетом обменного взаимодействия. В рамках линейной теории найдено, что дисперсионная кривая продольных волн имеет две ветви --- плазмонную и фононную. Найдено выражение для критической частоты отсечки для плазменных колебаний, а также выражение для скорости звука для акустических колебаний. Показано, что плазменная волна всегда существует в виде суперпозиции двух составляющих, имеющих разный период и длину волны. В рамках нелинейной теории получены два нелинейных решения, одно из которых имеет форму простой суперпозиции двух тонов, а другое --- имеет форму биений. DOI: 10.21883/FTP.2017.01.7871
Время жизни избыточного электрона в порошках Cu-Zn-Sn-Se
Authors: Новиков Г.Ф. , Гапанович М.В. , Гременок В.Ф. , Бочаров К.В. , Tsai W.-T. , Jeng Ming-Jer , Chang Liann-Be
Published: January 2017

Методом время-разрешенной микроволновой фотопроводимости в диапазоне 36 ГГц в интервале температур 200-300 K изучена кинетика гибели носителей тока в порошках Cu-Zn-Sn-Se, полученных ампульным твердофазным методом синтеза. Время жизни избыточных электронов при комнатной температуре оказалось меньше 5 нс. Энергия активации для процесса рекомбинации составила Ea~0.054 эВ. DOI: 10.21883/FTP.2017.01.8274
Атомная и электронная структура поверхности CdTe (111)B-(2sqrt(3)sqrt орт.
Authors: Бекенев В.Л. , Зубкова С.М.
Published: January 2017

Впервые проведены ab initio расчеты атомной и электронной структуры 4 вариантов полярной поверхности CdTe (111)B-(23x4) орт., заканчивающейся Te: идеальной, релаксированной, реконструированной и реконструированной с последующей релаксацией. В приближении слоистой сверхрешетки поверхность моделировали пленкой толщиной 12 атомных слоев и вакуумным промежутком ~16 Angstrem. Для замыкания оборванных связей Cd на противоположной стороне пленки добавляли 24 фиктивных атома водорода с зарядом 1.5 электрона каждый. Ab initio pасчеты проводили с использованием программы Quantum Espresso, основанной на теории функционала плотности. Показано, что релаксация приводит к расщеплению верхних четырех слоев. Для 4 вариантов поверхности рассчитаны и проанализированы зонные структуры, а также полные и послойные плотности электронных состояний. DOI: 10.21883/FTP.2017.01.8226
Рост, cтруктура и морфология поверхности эпитаксиальных пленок CdTe
Authors: Нуриев И.Р. , Мехрабова М.А. , Назаров А.М. , Садыгов Р.М. , Гасанов Н.Г.
Published: January 2017

Проведено исследование структуры и морфологии поверхности эпитаксиальных пленок CdTe, выращенных на стеклянных подложках без компенсации и с компенсацией дополнительным источником паров Те в процессе роста. Определены оптимальные условия (Tso=1000-1100 K, Tsu=570-670 K) получения эпитаксиальных пленок с совершенной структурой и чистой, гладкой поверхностью, без включения второй фазы. Установлено, что на стеклянных подложках эпитаксиальные пленки растут плоскостью (111) кубической границентрированной решетки с параметром a=6.481 Angstrem. Регулированием температуры основного и компенсирующего источников получены пленки CdTe c n- и p-типом проводимости. DOI: 10.21883/FTP.2017.01.7947
Циклотронный резонанс дираковских фермионов в квантовых ямах InAs/GaSb/InAs
Authors: Криштопенко С.С. , Иконников А.В. , Маремьянин К.В. , Бовкун Л.С. , Спирин К.Е. , Кадыков А.М. , Marcinkiewicz M. , Ruffenach S. , Consejo C. , Teppe F. , Knap W. , Семягин Б.Р. , Путято М.А. , Емельянов Е.А. , Преображенский В.В. , Гавриленко В.И.
Published: January 2017

Теоретически исследована зонная структура в трехслойных симметричных квантовых ямах InAs/GaSb/InAs, ограниченных барьерами AlSb. Показано, что в зависимости от соотношения толщин слоев InAs и GaSb в системе может реализовываться нормальная зонная структура, бесщелевое состояние с дираковским конусом в центре зоны Бриллюэна и инвертированная зонная структура (двумерный топологический изолятор). Экспериментальные исследования циклотронного резонанса в образцах с бесщелевым зонным спектром, выполненные при различных значениях концентрации электронов, подтверждают существование безмассовых дираковских фермионов в квантовых ямах InAs/GaSb/InAs. DOI: 10.21883/FTP.2017.01.8244
Спин-зависимое туннелирование в гетероструктурах с магнитным слоем
Authors: Денисов К.С. , Рожанский И.В. , Аверкиев Н.С. , Lahderanta E.
Published: January 2017

Предложен механизм создания спиновой поляризации в полупроводниковых гетероструктурах, содержащих квантовую яму и пространственно отделенный от нее слой магнитных примесей. Спиновая поляризация носителей заряда в квантовой яме появляется вследствие спин-зависимой туннельной рекомбинации на примесных состояниях в магнитном слое, при этом возникает быстрый линейный рост степени циркулярной поляризации фотолюминесценции из квантовой ямы. Теоретически рассмотрены две ситуации. В первом случае имеет место резонансное туннелирование на спин-расщепленные подуровни примесного центра, при этом генерация спиновой поляризации происходит в меру разной заселенности резонансных уровней в квантовой яме для противоположных проекций спина. Второй, нерезонансный случай, имеет место, когда спин-расщепленный примесный уровень лежит выше заполненных состояний электронов в квантовой яме и играет роль промежуточного состояния в двухэтапном когерентном процессе спин-зависимой рекомбинации электрона из квантовой ямы с дыркой в примесном слое. Разработанная теория позволила качественно и количественно объяснить кинетику фотовозбужденных электронов в экспериментах по фотолюминесценции с временным разрешением в гетероструктурах на основе InGaAs, легированных слоем Mn. DOI: 10.21883/FTP.2017.01.8291
Формирование и свойства захороненного изолирующего слоя двуокиси кремния в двухслойных структурах "пористый кремний-на-изоляторе"
Authors: Болотов В.В. , Князев Е.В. , Пономарева И.П. , Кан В.Е. , Давлеткильдеев Н.А. , Ивлев К.Е. , Росликов В.Е.
Published: January 2017

Изучен процесс окисления мезопористого кремния в двухслойной структуре "макропористый кремний-мезопористый кремний". Методами электронной микроскопии, эллипсометрии, электрофизическими измерениями исследована морфология и диэлектрические свойства получаемого слоя захороненного диэлектрика. Определено наличие специфического вида дефектов "шипов", возникающих при окислении стенок макропор в макропористом кремнии, границ пересечения фронтов окисления мезопористого кремния. Установлено, что при исходной пористости мезопористого кремния 60% и трехстадийном термическом окислении формируются захороненные слои двуокиси кремния с напряженностью электрического поля пробоя Ebr~ 104-105 В/cм. Показана перспективность применения многослойных структур "пористый кремний-на-изоляторе" в интегрированных химических микро- и наносенсорах. DOI: 10.21883/FTP.2017.01.8246
Исследование параметров наноразмерного слоя в наногетероструктурах на основе полупроводниковых соединений A-=SUP=-II-=/SUP=-B-=SUP=-VI-=/SUP=-
Authors: Караваев М.Б. , Кириленко Д.А. , Иванова Е.В. , Попова Т.Б. , Ситникова А.А. , Седова И.В. , Заморянская М.В.
Published: January 2017

Методами локальной катодолюминесценции и рентгеноспектрального микроанализа проведено комплексное исследование широкозонных наногетероструктур на основе ZnSe, полученных методом молекулярно-пучковой эпитаксии. Было показано, что используемые методы позволяют неразрушающим способом определять глубину залегания, элементный состав и геометрические параметры наноразмерного слоя ZnCdSe. Точность результатов контролировалась методом просвечивающей электронной микроскопии. Методики исследования основаны на возможности варьирования энергии первичного электронного пучка, что приводит к изменению областей генерации характеристического рентгеновского излучения и катодолюминесценции. DOI: 10.21883/FTP.2017.01.8249
Получение гетероструктурных оксидных композиций для перспективных солнечных элементов нового поколения
Authors: Бобков А.А. , Лашкова Н.А. , Максимов А.И. , Мошников В.А. , Налимова С.С.
Published: January 2017

Рассматриваются перспективы создания солнечных элементов на основе оксидов металлов с объемным гетеропереходом, при этом ZnO был сформирован методом гидротермального синтеза. Представлены результаты синтеза наностержней оксида цинка на различных затравочных слоях. Отмечена значительная роль операции формирования зародышевого слоя. Показана возможность управления структурой массивов наностержней посредством использования поверхностно-активного вещества. Полученные ограненные наностержни перспективны для получения солнечных элементов нового поколения. DOI: 10.21883/FTP.2017.01.8356
Оптимизация параметров источников питания, возбуждаемых beta-излучением
Authors: Булярский С.В. , Лакалин А.В. , Абанин И.Е. , Амеличев В.В. , Светухин В.В.
Published: January 2017

Представлены результаты экспериментальных исследований и расчетов эффективности преобразования энергии источников beta-излучения Ni-63 в электрическую с помощью кремниевых p-i-n-диодов. Все вычисления выполнены с учетом распределения beta-электронов по энергиям. Получено выражение для напряжения холостого хода преобразователя с учетом распределения электронов высоких энергий в области пространственного заряда p-i-n-диода. Показаны пути оптимизации параметров преобразователя за счет совершенствования технологии изготовления диодов, оптимизации толщины активного слоя излучателя и i-области полупроводникового преобразователя. Вычислено распределение потерь на преобразование источника и приемника излучения, а также потерь при входе электронов высоких энергий в полупроводник. Экспериментальные значения эффективности преобразования 0.4-0.7% хорошо согласуются с расчетными параметрами. DOI: 10.21883/FTP.2017.01.8223
Влияние "объема" активной среды на излучательные свойства лазерных гетероструктур с выходом излучения через подложку
Authors: Некоркин С.М. , Звонков Б.Н. , Байдусь Н.В. , Дикарева Н.В. , Вихрова О.В. , Афоненко А.А. , Ушаков Д.В.
Published: January 2017

Исследованы излучательные свойства лазерных структур InGaAs/GaAs/InGaP с вытеканием излучения через подложку в зависимости от числа квантовых ям в активной области и лазерных диодов на их основе. Установлено, что наличие 6-8 квантовых ям в активной области является оптимальным с точки зрения наблюдаемых значений порогового тока и выходной оптической мощности лазеров. DOI: 10.21883/FTP.2017.01.8258
Аноды для литий-ионных аккумуляторов на основе p-Si с самоорганизующимися макропорами
Authors: Преображенский Н.Е. , Астрова Е.В. , Павлов С.И. , Воронков В.Б. , Румянцев А.М. , Жданов В.В.
Published: January 2017

Практическое применение технологии электрохимического травления монокристаллического кремния для изготовления микроструктурированных анодов сдерживает их себестоимость. Предлагаемый подход позволит сократить издержки за счет: снижения требований к качеству исходного материала путем замены n-Si на p-Si, исключения операций по формированию затравочных центров и многократного использования кремниевой подложки. В работе проведены исследования процесса образования неупорядоченных макропор в p-Si (100) с удельным сопротивлением 10-20 Ом·см в 4%-м растворе плавиковой кислоты в диметилформамиде и определен вклад в него химического растворения кремния. Получены зависимости от плотности тока для скорости анодирования, морфологии пористых слоев, эффективной валентности, числа пор на единицу поверхности и средних значений диаметра пор. Разработана технология формирования пористых слоев толщиной ~50 мкм и пористостью ~70%, сочетающая возможность последовательного отделения нескольких мембран от одной и той же подложки. Исследованы электрохимические характеристики анодов, изготовленных из этих мембран, и проведено 120+ циклов испытаний при токе заряда/разряда 0.2 А/г в режиме ограничения зарядной емкости величиной 1000 мА·ч/г. DOI: 10.21883/FTP.2017.01.8314
Влияние двух- и трехслойных просветляющих покрытий на формирование фототоков в многопереходных солнечных элементах на основе A-=SUP=-III-=/SUP=-B-=SUP=-V-=/SUP=-
Authors: Мусалинов С.Б. , Анзулевич А.П. , Бычков И.В. , Гудовских А.С. , Шварц М.З.
Published: January 2017

Представлены результаты моделирования методом матриц переноса двухслойного, TiO2/SiO2, и трехслойного, TiO2/Si3N4/SiO2, просветляющих покрытий для многопереходных гетероструктурных солнечных элементов InGaP/GaAs/Ge. Экспериментально получено и оптимизировано двухслойное просветляющее покрытие TiO2/SiO2. С использованием экспериментальных спектральных зависимостей квантового выхода фотоответа солнечного элемента InGaP/GaAs/Ge и оптических характеристик просветляющих покрытий, полученных при моделировании, определены значения плотностей фототоков отдельных каскадов трехпереходного солнечного элемента для условий облучения AM1.5D (1000 Вт/м2), а также для случая отсутствия потерь на отражение. В рамках моделирования показано, что оптимизированное трехслойное просветляющее покрытие TiO2/Si3N4/SiO2 дает выигрыш в величине плотности фототока на 2.3 мА/см2 (AM1.5D) для Ge-субэлемента по сравнению с рассматриваемым вариантом двухслойного просветляющего покрытия TiO2/SiO2, обеспечивая тем самым рост коэффициента заполнения вольт-амперной характеристики и выходной электрической мощности многопереходного солнечного элемента. DOI: 10.21883/FTP.2017.01.8355