Annealing of Nanocrystalline Silicon Micro-bridges with Electrical Stress

2008 ◽  
Vol 1144 ◽  
Author(s):  
Gokhan Bakan ◽  
Adam Cywar ◽  
Cicek Boztug ◽  
Mustafa Bilal Akbulut ◽  
Helena Silva ◽  
...  
Keyword(s):  
Joule Heating ◽  
Pulse Amplitude ◽  
Nanocrystalline Silicon ◽  
High Amplitude ◽  
Molten Silicon ◽  
Current Time ◽  
Electrical Stress ◽  
Applied Pulse ◽  
Voltage Pulse Amplitude ◽  
Texture Modification

ABSTRACTNanocrystalline silicon (nc-Si) micro-bridges are melted and crystallized through Joule heating by applying high-amplitude short duration voltage pulses. Full crystallization of nc-Si bridges is achieved by adjusting the voltage-pulse amplitude and duration. If the applied pulse cannot deliver enough energy to the bridges, only surface texture modification is observed. On the contrary, if the pulse is not terminated after the entire bridge melts, molten silicon diffuses on to the contact pads and the bridge tapers in the middle. Melting of the bridges can be monitored through current-time (I-t) and voltage-time (V-t) measurements during the electrical stress. Conductance of the bridges is enhanced after the electrical stress.

scholarly journals INVESTIGATION OF OZONE SYNTHESIS IN THE NEGATIVE PULSED CORONA DISCHARGE IN OXYGEN AT THE COMBINED SUPPLY VOLTAGE

2021 ◽  
pp. 74-77
Author(s):  
V.I. Golota ◽  
B.B. Kadolin ◽  
I.A. Paschenko
Keyword(s):  
Corona Discharge ◽  
Bias Voltage ◽  
Voltage Pulse ◽  
Supply Voltage ◽  
Pulse Amplitude ◽  
Pulsed Corona Discharge ◽  
Voltage Pulse Amplitude ◽  
Pulsed Corona ◽  
Ozone Synthesis ◽  
Optimal Bias

The influence of combined supply voltage parameters (bias voltage and voltage pulse amplitude) on efficiency of ozone synthesis in the negative pulsed corona discharge in oxygen was obtained. Pulse overvoltage led to intensification of discharge processes. Bias voltage applied during the discharge channel relaxation essentially increased the efficiency of ozone synthesis. It was established that the “optimal” bias voltage which provides maximum ozone generation doesn’t depend on voltage pulse amplitude, but depends on input oxygen concentration and generated ozone concentration.

scholarly journals The Enhancement of Lump Coal Percentage by High-Pressure Pulsed Hydraulic Fracturing for Sustainable Development of Coal Mines

2019 ◽  
Vol 11 (10) ◽  
pp. 2731 ◽  
Author(s):  
Hao Yan ◽  
Jixiong Zhang ◽  
Nan Zhou ◽  
Junli Chen
Keyword(s):  
High Pressure ◽  
Water Injection ◽  
Low Frequency ◽  
Injection Pressure ◽  
Pulse Amplitude ◽  
High Amplitude ◽  
Hard Coal ◽  
Fracture Width ◽  
Mining Face ◽  
Lump Coal

The enhancement of lump coal percentage (LCP) is of great significance for most aging mines to achieve the production reduction and quality improvement. In order to enhance the LCP of hard coal seam in fully mechanized mining face and prolong the service life of aging mines, this paper puts forward the technological path of LCP enhancement using high-pressure pulsed hydraulic fracturing (HPPHF) based on the detailed analysis of the main factors controlling LCP. By analyzing the correlation between coal fracturing and LCP, the enhancement mechanism of LCP through HPPHF was concluded. Using the extended finite element method, a fluid–solid coupling numerical model of high-pressure pulsed water injection into coal seam was established, and effects of the fracturing method, pulse amplitude, pulse frequency, and water injection pressure on fracturing performance were assessed. Simulation results demonstrate that HPPHF can effectively reduce the required maximum pressure in fracturing, thus providing a higher percentage of coal lumps with lower energy consumption through the repeated pulsed loading of coal masses. Variations in pulsed pressure amplitude and frequency, as well as water injection pressure were positively correlated with fracturing performance. By their effect on the fracturing performance, we found that water injection pressure had the greatest influence, and the pulse amplitude and frequency had similar effects. At the same time, “high amplitude-high frequency” and “high amplitude-low frequency” had characteristics of short initiation time, large initiation pressure, but small fracture width, while “low amplitude-high frequency” and “low amplitude-low frequency” had characteristics of slow initiation speed, low initiation pressure, but large fracture width. Through the field test results in the fully mechanized mining face of Shichangwan Coal Mine, it was found that LCP with a diameter range of 13–100 mm was significantly enhanced by HPPHF. The present study is considered quite instrumental in providing a theoretical foundation for enhancing the LCP of hard coal seams and the sustainable development of coal mine enterprises.

scholarly journals Research on Groove Method to Suppress Stall in Pump Turbine

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3822
Author(s):  
Yong Liu ◽  
Hongjuan Ran ◽  
Dezhong Wang
Keyword(s):  
Characteristic Curve ◽  
Low Frequency ◽  
Pulse Amplitude ◽  
Optimization Method ◽  
High Amplitude ◽  
Pump Turbine ◽  
Structure Flow ◽  
Hydrodynamic Optimization ◽  
Full Consideration ◽  
Pressure Pulse Amplitude

The pump turbine is prone to stall when running at part-load operation. Stalls would cause a hump-like head characteristic curve, low-frequency high-amplitude pressure pulsation, and surge or resonance in the system. There is a lack of efficient methods for pump turbine stall suppression. The traditional blade hydrodynamic optimization method has limited effect and would influence the other characteristics. As the essence of stall is flow separation, forming a severe backflow vortex, a “Groove Method” is put forward and employed to suppress stall in a pump turbine with the full consideration of the mechanical structure, flow field, and pressure field. Both experiments and calculations are carried out to test the effectiveness of this new method. Furthermore, its deep mechanisms are revealed. This method can weaken the head hump to a certain extent and reduce the pressure pulse amplitude induced by stall. Meanwhile, the performance at the design operating point is not disturbed much.

Effect of anodal and cathodal pulses applied during action potential at a single Ranvier node

1959 ◽  
Vol 197 (6) ◽  
pp. 1247-1254 ◽  
Author(s):  
Hiroshi Ooyama ◽  
Ernest B. Wright
Keyword(s):  
Action Potential ◽  
Refractory Period ◽  
Pulse Amplitude ◽  
Ranvier Node ◽  
Delayed Response ◽  
Positive Pulse ◽  
Applied Pulse ◽  
Single Ranvier Node

An anodal pulse applied during the falling phase of an action potential, if weak, produces a slight enhancement of negativity of the falling phase, but if increased in amplitude produces a split of the action potential into an early and "delayed" response and finally, complete abolition of the falling phase. If the pulse amplitude is increased still more after abolition, a second response is elicited. The latency to this second response following abolition is shorter than the latency to the delayed response, and further increase of the applied pulse amplitude cannot abolish this second response. To obtain abolition of the delayed response it is necessary to apply a considerably stronger anodal pulse near the peak of the spike than later during the falling phase. The reverse is true to obtain the second response. The anodal pulse sufficient to produce anode break excitation during the action potential and elicit the second response is ineffective applied to a resting node membrane. It is postulated that: a) due to an effect of the action potential itself the membrane is being actively depolarized during the early falling phase of the spike and b) the excitability of the node membrane is actually retained both during and following an action potential in the so-called refractory period but requires "resetting" by a positive pulse in order for re-excitation to take place.

Estimation of the Limit State Criterion for Steels C1020 and A 516-55 with V-Notch under Quasistatic Loading Using Acoustic Emission Control

2019 ◽  
Vol 945 ◽  
pp. 585-591
Author(s):  
M.M. Zakirnichnaya ◽  
O.R. Abdulganieva ◽  
D.A. Yudicheva
Keyword(s):  
Acoustic Emission ◽  
Room Temperature ◽  
Oil And Gas ◽  
Limit State ◽  
Maximum Size ◽  
Pulse Amplitude ◽  
High Amplitude ◽  
Low Alloy Steels ◽  
Microcrack Formation ◽  
State Criterion

There is a need to determine the stresses value for responsible designs in the oil and gas refining, petrochemical and chemical industries, at which the defect reaches its maximum size. This stress value can be taken as the limit state criterion for strength calculations of vessels and apparatus. The article presents a technique for determining the limit state criterion for carbonaceous and low-alloy steels using the example of steels C1020 and A 516-55 in the state of delivery. As a limit state criterion it is proposed to use the stress value corresponding to the microcrack formation moment. The studies are based on the uniaxial tension tests results at room temperature of flat samples with V-shaped stress concentrators of 2 mm deep, accompanied by an acoustic emission nondestructive testing method. Based on the obtained pulse amplitude and pulse energy dependences on time in the process of testing and fractographic studies, a technique for estimating acoustic emission signals was developed to determine the microcrack formation moment for test steels. Stress values that can be taken as the limit state criterion for steels C1020 and A 516-55 in the delivery state for strength calculations vessels and apparatus are determined using the developed experimentally technique based on the high-amplitude acoustic emission to low-amplitude signals ratio. With the help of specimen fractures fractographic analysis the legitimacy of using the developed technique is justified. Thus, at room temperature for steel C1020, the stress at which a microcrack begins to form is 420 MPa, for steel A 516-55 it is 455 MPa.

A TEM investigation of silicon nitride whiskers

1987 ◽  
Vol 45 ◽  
pp. 160-161
Author(s):  
Tapan Roy
Keyword(s):  
Silicon Nitride ◽  
High Resolution ◽  
Ceramic Matrix Composites ◽  
High Resolution Electron Microscopy ◽  
Molten Silicon ◽  
Matrix Composites ◽  
Ceramic Fibers ◽  
Resolution Electron ◽  
Point To Point ◽  
Technological University

Ceramic fibers are being used to improve the mechanical properties of metal matrix and ceramic matrix composites. This paper reports a study of the structural and other microstructural characteristics of silicon nitride whiskers using both conventional TEM and high resolution electron microscopy.The whiskers were grown by T. E. Scott of Michigan Technological University, by passing nitrogen over molten silicon in the presence of a catalyst. The whiskers were ultrasonically dispersed in chloroform and picked up on holey carbon grids. The diameter of some whiskers (<70nm) was small enough to allow direct observation without thinning. Conventional TEM was performed on a Philips EM400T while high resolution imaging was done on a JEOL 200CX microscope with a point to point resolution of 0.23nm.

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