Time-dependent variables

This paper describes a method of evaluation of the single and multistage compressors response to steady and unsteady inlet distortions. It allows also the evaluation of the appearance of unstable regimes and their characterization (rotating stall and surge). It is based on a linearized approach using mean line calculations. The compressor is considered as a series of vaned and vaneless spaces, and the corresponding equations are solved by use of Fourier series for time independent variables and by Laplace’s transform for time-dependent variables. An analogy between the compressor’s response and a servo-mechanism is developed, using Nyquist’s diagram. Results are compared with experimental data which prove the validity of the approach. A parametric study indicates which parameters can be modified to improve the flow stability.

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Effect of Time Dependent Variables on Different Types of PSC Box Girder Bridges.

SAMRIDDHI A Journal of Physical Sciences Engineering and Technology ◽

10.18090/samriddhi.v11i02.6 ◽

2019 ◽

Vol 11 (02) ◽

pp. 123-128

Author(s):

Norine George ◽

Kiran Umachagi ◽

Sunil Kumar Tengli

Keyword(s):

Cross Section ◽

Prestressed Concrete ◽

Cell Types ◽

Time Dependent ◽

Box Girder ◽

Temperature Creep ◽

Dependent Variables ◽

Concrete Box Girder ◽

Girder Bridge ◽

Creep And Shrinkage

Time dependent variables such as temperature gradient, effective temperature, creep, and shrinkage lead to long term deflection in prestressed concrete girders. This in turn effects the serviceability and sustainability of the bridge in the long run. Therefore, research and analysis is of paramount importance before deciding the type of girder to be used. A parametric study was carried out in order to determine the most desirable and efficient type of box girder to be used for a prestressed concrete bridge having a continuous span. Three prestressed concrete box girder bridge models of single, multi-cell rectangular and multi-cell trapezoidal cross section, having similar span, width and depth were taken into consideration. The finite element models were analysed using MIDAS Civil. The behaviour of the box girder cell types under various time dependent properties such as temperature, creep and shrinkage are presented in this paper. The results show that the prestressed concrete box girder bridge of multi-cell rectangular cross section exhibits greater forces and moments due to time dependent variables in comparison to the other two box girder cell types.

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Theoretical Study of Flow Instabilities and Inlet Distortions in Axial Compressors

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/81-gt-211 ◽

1981 ◽

Author(s):

P. Ferrand ◽

J. Chauvin

Keyword(s):

Theoretical Study ◽

Rotating Stall ◽

Time Dependent ◽

Flow Instabilities ◽

Axial Compressors ◽

Independent Variables ◽

Servo Mechanism ◽

Dependent Variables ◽

Multistage Compressors ◽

Method Of Evaluation

This paper describes a method of evaluation of the single and multistage compressors response to steady and unsteady inlet distortions. It allows also the evaluation of the appearance of unstable regimes and their characterization (rotating stall and surge). It is based on a linearized approach using mean line calculations. The compressor is considered as a serie of vaned and vaneless spaces, and the corresponding equations are solved by use of Fourier series for time independent variables and by Laplace’s transform for time dependent variables. An analogy between the compressor’s response and a servo-mechanism is developed, using Nyquist’s diagram. Results are compared with experimental data which prove the validity of the approach. A parametric study indicates which parameters can be modified to improve the flow stability.

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Business Cycles in a Three-sector Growth Model with Portfolio Equilibrium between Land, Gold and Capital

Margin The Journal of Applied Economic Research ◽

10.1177/0973801017753284 ◽

2018 ◽

Vol 12 (2) ◽

pp. 171-196

Author(s):

Wei-Bin Zhang

Keyword(s):

Business Cycles ◽

Environmental Change ◽

Growth Model ◽

Capital Accumulation ◽

Jel Classification ◽

Time Dependent ◽

Tax Rate ◽

Exogenous Shocks ◽

Dependent Variables ◽

Economic Foundation

This study generalises a growth model proposed by Zhang (2016) through allowing all the time-dependent variables to be time-dependent. Zhang’s model deals with dynamic interdependence between capital accumulation and environmental change, with portfolio equilibrium among land, gold and physical wealth in a multi-sector general equilibrium framework. The model explains the dynamics of prices, rents and distribution of land, gold, physical wealth and environmental change on the basis of micro-economic foundation. This article generalises the model to explain business cycles due to different exogenous shocks. We simulate the motion of the economy and conduct comparative dynamic analysis to demonstrate business cycles due to periodic oscillations in the propensity to use gold, the propensity to consume housing, the propensity to consume industrial goods, the propensity to consume agricultural goods, the propensity to save, and the tax rate on the consumption of industrial goods. JEL Classification: O41, D41, E32

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