Improving the gas barrier and mechanical properties of a-SiO x films synthesized at low temperature by using high energy and hydrogen flow rate control

: Herein, we report effect of variation of hydrogen flow rate on properties of Si:H films synthesized using PE-CVD method. Raman spectroscopy analysis show increase in crystalline volume fraction and crystallite size implying that hydrogen flow in PECVD promote the growth of crystallinity in nc-Si:H films with an expense of reduction in deposition rate. FTIR spectroscopy analysis indicates that hydrogen content in the film increases with increase in hydrogen flow rate and hydrogen is predominantly incorporated in Si-H2 and (Si-H2)n bonding configuration. The optical band gap determined using E04 method and Tauc method (ETauc) show increasing trend with increase in hydrogen flow rate and E04 is found higher than ETauc over the entire range of hydrogen flow rate studied. We also found that the defect density and Urbach energy also increases with increase in hydrogen flow rate. Photosensitivity (Photo /Dark) decreases from  103 to  1 when hydrogen flow rate increased from 30 sccm to 100 sccm and can attributed to amorphous-to-nanocrystallization transition in Si:H films. The results obtained from the present study demonstrated that hydrogen flow rate is an important deposition parameter in PE-CVD to synthesize nc-Si:H films.

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Continuous separation of particles using a microfluidic device equipped with flow rate control valves

Journal of Chromatography A ◽

10.1016/j.chroma.2006.05.020 ◽

2006 ◽

Vol 1127 (1-2) ◽

pp. 214-220 ◽

Cited By ~ 50

Author(s):

Yuushi Sai ◽

Masumi Yamada ◽

Masahiro Yasuda ◽

Minoru Seki

Keyword(s):

Microfluidic Device ◽

Flow Rate ◽

Rate Control ◽

Continuous Separation ◽

Control Valves ◽

Flow Rate Control

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Variable Powder Flow Rate Control in Laser Metal Deposition Processes

ASME 2008 Dynamic Systems and Control Conference, Parts A and B ◽

10.1115/dscc2008-2112 ◽

2008 ◽

Author(s):

Lie Tang ◽

Jianzhong Ruan ◽

Robert G. Landers ◽

Frank Liou

Keyword(s):

Transport System ◽

Flow Rate ◽

Rate Control ◽

Metal Deposition ◽

Powder Flow ◽

Laser Metal Deposition ◽

Motion System ◽

Powder Flow Rate ◽

Deposition Processes ◽

Flow Rate Control

This paper proposes a novel method, called Variable Powder Flow Rate Control (VPFRC), for the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to adjust the powder flow rate to maintain a uniform powder deposition per unit length even when disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the powder delivery system motor and the powder transport system (i.e., five–meter pipe, powder dispenser, and cladding head) are constructed. A general tracking controller is then designed to track variable powder flow rate references. Since the powder flow rate at the nozzle exit cannot be directly measured, it is estimated using the powder transport system model. The input to this model is the DC motor rotation speed, which is estimated on–line using a Kalman filter. Experiments are conducted to examine the performance of the proposed control methodology. The experimental results demonstrate that the VPFRC method is successful in maintaining a uniform track morphology, even when the motion system accelerates and decelerates.

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Feasibility Study on the Use of a Voice Coil Motor Direct Drive Flow Rate Control Valve

ASME 2009 Dynamic Systems and Control Conference, Volume 1 ◽

10.1115/dscc2009-2631 ◽

2009 ◽

Cited By ~ 1

Author(s):

Shuai Wu ◽

Richard Burton ◽

Zongxia Jiao ◽

Juntao Yu ◽

Rongjie Kang

Keyword(s):

Neural Network ◽

Flow Control ◽

Flow Rate ◽

Rate Control ◽

Network Flow ◽

Voice Coil Motor ◽

Direct Drive ◽

Hydraulic Test ◽

Servo Valve ◽

Flow Rate Control

This paper considers the feasibility of a new type of voice coil motor direct drive flow control servo valve. The proposed servo valve controls the flow rate using only a direct measurement of the spool position. A neural network is used to estimate the flow rate based on the spool position, velocity and coil current. The estimated flow rate is fed back to a closed loop controller. The feasibility of the concept is established using simulation techniques only at this point. All results are validated by computer co-simulation using AMESim and Simulink. A simulated model of a VCM-DDV (Voice Coil Motor-Direct Drive Valve) and hydraulic test circuit are built in an AMESim environment. A virtual digital controller is developed in a Simulink environment in which the feedback signals are received from the AMESim model; the controller outputs are sent to the VCM-DDV model in AMESim (by interfacing between these two simulation packages). A LQR (Linear Quadratic Regulator) state feedback and nonlinear compensator controller for spool position tracking is considered as this is the first step for flow control. A flow rate control loop is subsequently included via a neural network flow rate estimator. Simulation results show that this method could control the flow rate to an acceptable degree of precision, but only at low frequencies. This kind of valve can find usage in open loop hydraulic velocity control in many industrial applications.

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EXPERIMENTAL INVESTIGATION OF ENHANCEMENT IN EFFICIENCY OF CENTRIFUGAL PUMP BY REDUCTION IN CAVITATION OF PUMP

International Journal of Engineering Applied Sciences and Technology ◽

10.33564/ijeast.2021.v05i10.042 ◽

2021 ◽

Vol 5 (10) ◽

Author(s):

Gaffar G. Momin

Keyword(s):

Experimental Investigation ◽

Centrifugal Pump ◽

Flow Rate ◽

Rate Control ◽

Flowing Liquid ◽

Discharge Flow ◽

Pump Performance ◽

Cavitation Phenomenon ◽

Discharge Flow Rate ◽

Flow Rate Control

Cavitation phenomenon is basically a process formation of bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure and it is the most challenging fluid flow abnormalities leading to detrimental effects on both the centrifugal pump discharge characteristics as well as physical characteristics. In this low pressure zones are the first victims of cavitation. Due to cavitation pitting of impeller occurs and wear of internal walls of pumps occurs due to which there is creation of vibrations and noize are there. Due to this there is bad performance of centrifugal pump is there. Firstly, description of the centrifugal pump with its various parts are described after that pump characteristics and its important parameters are presented and discussed. Passive discharge (flow rate) control methods are utilized for improvement of flow rate and mechanical and volumetric and overall efficiency of the pump. Mechanical engineers is considering an important phenomenon which is known as Cavitation due to which there is decrease in centrifugal pump performance. There is also effect on head of the pump which is getting reduced due to cavitation phenomenon. In present experimental investigation the cavitation phenomenon is studied by starting and running the pump at various discharges and cavitating conditions of the centrifugal pump. Passive discharge (flow rate) control is realized using three different impeller blade leading edge angles namely 9.5 degrees, 16.5 degrees .and 22.5 degrees for reduction in the cavitation and increase the of the centrifugal pump performance at different applications namely, domestic, industrial applications of the centrifugal pump.

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