bluuebunny/crossref_metadata_2025_split huggingface dataset:
The long‐run impact of idiosyncratic and common shocks on industry output inGhana
Authors: Adom Philip Kofi , Amakye Kwaku , Barnor Charles , Quartey George 
Published: March 2015

AbstractThis study explores the long‐run impact of idiosyncratic and common shocks on industry output in Ghana while controlling for the effects of investment. In order to deal with the second‐order bias problem, this study employed canonical cointegration and fully modified ordinary least‐squares (OLS) regressions, which are more robust to second‐order bias problems. Different models are, therefore, specified and estimated. Fully modifiedOLSand canonical cointegration are extended in successive steps in order to verify if the inclusion of idiosyncratic and common shocks improves the statistical properties of the model. Secondly, a backward approach, in which idiosyncratic and common shocks are excluded successively, is also adopted. Preliminary findings showed signs of long‐run equilibrium. The a priori expectation and the statistical importance of investment are established in both fully modified OLS and canonical cointegration models. This result is robust using both theBartlett andParzen kernels. However, while the elasticity value for investment is invariant to the model and kernel type used for fully modifiedOLS, the opposite result is found for canonical cointegration. Importantly, the absolute value of the investment elasticity is kept within the limits of 0 and 1. The impacts of idiosyncratic and common shocks are negative and statistically significant in the long run for both fully‐modifiedOLSand canonical cointegration. This result is robust to theBartlett andParzen kernels. Result based on the fully modifiedOLSalso showed that the sizes of the elasticity values for both idiosyncratic and common shocks are sensitive to the model type and kernel type used. Despite the differences in the elasticity values, result for both models are qualitatively similar.
Dynamic panel data approaches for estimating oil demand elasticity
Authors: Javan Afshin , Zahran Nahl 
Published: March 2015

AbstractThis study examines the general relationships between crude oil consumption, real oil price and real GDP using a quarterly time series from 1993 to 2012. Specifically, the long‐term and short‐term GDP and price elasticities of oil consumption per capita were estimated using dynamic panel and pooled data regressions based on Nerlove's oil demand model for 25 countries that represent 75 per cent of global oil demand. Price elasticities were found for most OECD countries. These estimates were low and consistent with previous estimates. According to the study results, the short‐run price elasticity ranged between −0.05 and −0.20 and the long‐run between −0.11 and −0.36. Price elasticities for most non‐OECD countries were either positive or insignificant. Estimates of GDP elasticities varied. The short‐run GDP elasticity was between 0.15 and 1.09, while the long‐run was between 0.21 and 1.54. On average, income elasticity for OECD countries was found to be slightly higher than for non‐OECD countries. Contrary to expectations, we found China's income elasticity to be 0.34 in the short run, but it was 0.76 in the long run.
Energy efficiency in OPEC member countries: analysis of historical trends through the energy coefficient approach
Authors: Al‐Rashed Yazeed , León Jorge 
Published: March 2015

AbstractPeriod‐wise energy coefficients for members of the Organization of the Petroleum Exporting Countries (OPEC) were calculated, showing diverse behaviour among them. Behaviour of aggregate OPEC coefficients reflects the general trend among its member nations. Acceleration of transportation fuel demand fuelled high intensities in the mid‐1970s. An overall economic downturn in the 1980s did not dampen demand growth, but in fact accelerated in the industrial and household, public and commercial (HPC) sectors, thus keeping energy coefficients above 1. Energy coefficients were headed towards unity in the 1990s, before finally settling under 1 in the 2000s. We caution from interpreting these developments as improvements in efficiency, as OPEC member countries have not become ‘post‐industrial’ as more value‐added industries, infrastructure development and stability encourage consumption. Electricity coefficients can be used as a proxy for consumer behavioural efficiency, as the HPC sector is its largest consumer. After the 1990s, almost all OPEC member countries had higher electricity coefficients than energy ones, due to reasons spanning from higher urbanisation and population growth rates, to low electricity prices. This suggests that electricity use in the industrial and HPC sectors will be a major driver of future demand growth for those countries, especially as their service sector grows and their economies diversify.
A VARX modelling of energy intensity interactions between China, the United States, Japan and EU
Authors: Akal Mustafa 
Published: March 2015

AbstractThis study attempts to predict energy intensity interactions between China, the United States, Japan and EU by developing a restricted VARX model by proposing energy intensities of the countries interact with each others, and gross domestic product (GDP) levels per capita and Organization of Petroleum Exporting Countries (OPEC) oil‐based current energy prices affect energy intensities of the countries based upon the direction of group causalities. There exist significant causal interactions between energy intensities of the countries up to lag five either increasing efficiency or not. China's current GDP level affects its own energy use and EU's energy intensity positively, on the other way; EU's current GDP level affects only China's energy intensity while Japan's current GDP level only affects its own energy intensity negatively, ceteris paribus. It is found that OPEC oil‐based current energy prices only affect the United States' energy intensity but not others' energy intensity, ceteris paribus, for the period of 1971–2009. Evaluating cumulative effects of energy intensities of all countries, it is found that each country has experienced higher energy intensity and consumed energy less efficiently even there have been existing new technology‐embodied equipments used and alternative energy sources developed in energy consumption for the years.
Parameter-Dependent Lyapunov Functions in the Robust Control of Discrete Linear Repetitive Processes Using Previous Pass-Windowed Information
Authors: Cichy Błażej , Galkowski Krzysztof , Rogers Eric 
Published: March 2015

Abstract
The variables in multidimensional systems are functions of more than one indeterminate, and such systems cannot be controlled by standard systems theory. This paper considers a subclass of these systems that operate over a subset of the upper-right quadrant of the two-dimensional (2D) plane in the discrete domain with a specified recursive structure known as repetitive processes. Physical examples of such processes are known and also their representations can be used in the analysis of other classes of systems, such as iterative learning control. This paper gives new results on the use of the parameter-dependent Lyapunov functions for stability analysis and controls law design of a subclass of repetitive processes that arise in application areas. These results aim to eliminate or reduce the effects of model parameter uncertainty.
An Axial Turbobrake
Authors: Goodisman M. I. , Oldfield M. L. G. , Kingcombe R. C. , Jones T. V. , Ainsworth R. W. , Brooks A. J. 
Published: March 2015

The Axial Turbobrake (Patent applied for) is a novel turbomachine which can be used to absorb power generated by test turbines. Unlike a compressor there is no pressure recovery through the turbobrake. This simplifies the aerodynamic design and enables high stage loadings to be achieved. The blades used have high turning two dimensional profiles.
This paper describes a single stage axial turbobrake, which is driven by the exhaust gas of the test turbine and is isolated from the turbine by a choked throat. In this configuration no fast acting controls are necessary as the turbobrake operates automatically with the turbine flow.
Tests on a 0.17 scale model, show that the performance is close to that predicted by a simple two-dimensional theory, and demonstrate that the turbobrake power absorption can be controlled and hence matched to that typically produced by the first stage of a modern highly loaded transonic turbine. A full size axial turbobrake will be used in a short duration rotating turbine experiment in an Isentropic Light Piston Tunnel at RAE Pyestock.
Design Method for Subsonic and Transonic Cascade With Prescribed Mach Number Distribution
Authors: Léonard O. , Van Den Braembussche R. A. 
Published: March 2015

An iterative procedure for blade design, using a Time Marching procedure to solve the unsteady Euler equations in the blade-to-blade plane is presented. A flow solver, which performs the analysis of the flow field for a given geometry, is transformed into a design method. This is done by replacing the classical slip condition (no normal velocity component) by other boundary conditions, in such a way that the required pressure or Mach number distribution may be imposed directly on the blade. The unknowns are calculated on the blade wall using the so-called compatibility relations.
Since the blade shape is not compatible with the required pressure distribution, a non-zero velocity component normal to the blade wall evolves from the new flow calculation. The blade geometry is then modified by resetting the wall parallel to the new flow field, using a transpiration technique, and the procedure is repeated until the calculated pressure distribution has converged to the required one.
Examples for both subsonic and transonic flows are presented and show a rapid convergence to the geometry required for the desired Mach number distribution. An important advantage of the present method is the possibility to use the same code for the design and the analysis of a blade.
Improved Gas Turbine Reliability and Availability With Static Starting Equipment
Authors: Denesdi L. , Wittwer M. 
Published: March 2015

Either a conventional motor starting system or a static starting system can be used to accelerate a large gas turbine from standstill to self-sustaining speed. In the motor-starting configuration, the gas turbine rotor is accelerated by a cranking electromotor. In a static starting configuration, a current with a variable frequency is supplied to the generator stator. The synchronous generator then operates — during the start-up — as a synchronous motor, accelerating the gas turbine rotor. The static starting system has a “soft start” capability, i.e., the power required for start-up increases gradually, without surging.
This paper outlines the operating principle of the static starting method. A comparative analysis of the reliability and availability of the conventional motor starting and static starting configurations is presented.
Preliminary Experience With an Expert System Providing Initial Centrifugal Compressor Sizing for Performance Prediction and Analysis
Authors: Schoonmaker Peter M. 
Published: March 2015

There are many problems in turbomachinery which do not lend themselves to numerical analysis. One such area is the preliminary design of centrifugal compressor stages. It seems likely that expert systems technology and object-oriented programming techniques will be able to make some impact on this class of problems. This paper presents the results of the first phase of a project designed to test this assumption.
This paper describes a simple methodology for establishing the initial parameters of centrifugal compressor stages up to a pressure ratio of 5.0. The method combines heuristic rules and empirical relationships, with some very simple optimization routines. It requires very little input from the user other than aerodynamic performance requirements. Phase 1 of this project uses this methodology to estimate the initial geometry of a centrifugal compressor impeller.
Convective Transport Phenomena on the Suction Surface of a Turbine Blade Including the Influence of Secondary Flows Near the Endwall
Authors: Chen P. H. , Goldstein R. J. 
Published: March 2015

A naphthalene sublimation technique is employed to study the mass transfer distribution on the suction (convex) surface of a simulated turbine blade. Comparison with a heat transfer study shows good agreement in the general trends in the region of two-dimensional flow on the blade.
Near the endwall, local convective coefficients on the suction surface are obtained at 4608 locations from two separate runs. The secondary flows in the passage significantly affect the mass transfer rate on the suction surface and their influence extends to a height of 75% of the chord length, from the endwall, in the trailing edge region. The mass transfer rate in the region near the endwall is extremely high due to small but intense vortices. Thus, a large variation in the mass transfer distribution occurs on the suction surface, from a mass transfer Stanton number of 0.0005 to a maximum of 0.01. In the two-dimensional flow region, the mass transfer distributions at two different Reynolds number are presented.
Principles of the ITS Ceramic Research Combustor Design: Segmented Flame Tube and Staged Combustion
Authors: Pfeiffer A. , Schulz A. , Wittig S. 
Published: March 2015

At the Institute for Thermal Turbomachinery in Karlsruhe a small research combustor was developed to investigate the applicability of high temperature loaded ceramic components under near ideal engine conditions. The design concept includes film evaporation of the liquid fuel and staged combustion with variable air supply. The combustor liner is segmented and consists of ceramic elements. For the prediction of the failure probability the newly developed fracture statistic code CERITS was used.
The key features of the combustor and the test facility are described and preliminary experimental results of the first test phase are reported with emphasis on emission measurements and durability of the ceramic components. The determining parameters under consideration are thermal power, air/fuel ratio and the temperature of the preheated inlet air.
The Efficiencies of Single-Stage Centrifugal Compressors for Aircraft Applications
Authors: Rodgers C. 
Published: March 2015

The thrust of most recent advances in single– and two–stage centrifugal compressor technology by the aerospace community has been motivated by interest in increasing airbreathing propulsion system power density, and improving specific fuel consumption with higher stage pressure ratios. Advances in the last decade have made it appropriate to review the major design parameters influencing the efficiency levels of single–stage centrifugal compressors for aircraft applications.
A simple efficiency correlation was derived for advanced single–stage centrifugal compressors. It was based upon four critical parameters:
• Inlet Specific Speed
• Impeller Tip Diameter
• Inducer Tip Relative Mach Number
• Exit Discharge Mach Number
The correlation was shown to predict attainable state–of–the–art efficiencies within a band width of ± 2 % points. This was considered acceptable for preliminary compressor and engine design work.
Theory of Finite Disturbances in a Centrifugal Compression System With a Vaneless Radial Diffuser
Authors: Moore F. K. 
Published: March 2015

A previous small-perturbation analysis of circumferential waves in centrifugal compression systems, assuming inviscid flow, is first shown to be consistent with observations that narrow diffusers are more stable than wide ones, when boundary-layer displacement effect is included.
Then, a previous analysis for finite-strength transients containing both surge and rotating stall in axial machines is adapted for a centrifugal compression system. Under certain assumptions, and except for a new second-order swirl, the diffuser velocity field, including resonant singularities, can be carried over from the previous inviscid, linear analysis.
Nonlinear transient equations are derived and applied in a simple example to show that throttling through a resonant value of flow coefficient must occur in a sudden surge-like drop, accompanied by a transient rotating wave. This “inner” solution is superseded by an “outer” surge response on a longer time scale. Numerical results are shown for various parametric choices relating to throttle schedule and the characteristic slope.
Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage
Authors: Zeschky J. , Gallus H. E. 
Published: March 2015

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data includes the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution.
The formation of the tip clearance vortex and the passage vortices is presented, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.
Rotating Stall Flow and Dangerous Blade Excitation of Centrifugal Compressor Impeller: Part 1 — Phenomenon of Large-Number Stall Cells
Authors: Seidel U. , Chen J. , Haupt U. , Hasemann H. , Jin D. , Rautenberg M. 
Published: March 2015

A new structure of rotating stall with unusual large-number stall cells (up to 7) has been detected experimentally in a high performance single stage centrifugal compressor system with backswept impeller and vaned diffusers. The number of stall cells is firstly identified by a phase analysis of pressure signals obtained from fast response dynamic transducers located at different circumferential positions on the shroud wall, and then verified by comparing the resulting frequencies of blade vibration with that measured from blade mounted strain gages. Up to 6 transducers in one radial position have been used for more certainty of the phase analysis. For the case of intermittent stall patterns, the frequency analysis of pressure and blade vibration signals is performed separately for sections with different characters of oscillation to avoid the smearing effect if signals of the whole pattern are averaged. As a result, the large-number stall cells, numbered 4–7, were determined in the speed range of 12000–14000 rpm, and in the higher speeds of 15000–16000 rpm right after the occurrence of normal stall cells of 2, when the flow rate is slightly reduced along the constant speed line.
For the large-number stall cell case, the measured blade vibration strain has reached such a high level that is already beyond the tolerance of blade material. Moreover, frequencies of blade excitation are always in the vincinity of resonance. These two features, which are not observed for the normal stall cell case and for the excitation of broadband character, show a particular danger of this phenomenon to the compressor operation.
Comparative Evaluation of Combustion Codes for Low-Btu Gas Applications
Authors: Yang Tah-Teh , Agrawal Ajay K. 
Published: March 2015

Four computer codes (PHOENICS, PCGC, FLUENT and INTERN) representing a spectrum of existing combustion modeling capabilities were evaluated for low-Btu gas applications. In particular, the objective was to identify computer code(s) that can be used effectively for predictions of (a) the flow field to yield efficient combustion, (b) the temperature field to ensure structural integrity and (c) species concentrations to meet environmental emission standards in a gas turbine combustor operating on low-Btu coal gas. Detailed information on physical models, assumptions, limitations and operational features of various codes was obtained through a series of computational runs of increasing complexity and grouped as (a) experimental validation, (b) code comparison and (c) application to coal gas combustion.
INTERN is not suitable for the present application since it has been tailored to model combustion process of premixed hydrocarbon fuels. FLUENT is easy to use and has detailed combustion models (in Version 3), however, it is not favored here because the user is unable to alter, modify or change the existing model(s). While PCGC-2 has the most comprehensive models for combustion, it is not user friendly and is inherently limited to axisymmetric geometry. PCGC-3 is expected to overcome these drawbacks. Built in combustion models in PHOENICS are similar to those in FLUENT. However, the user can implement advanced models on PHOENICS leading to a flexible and powerful combustion code.
Separating Hydrogen From Coal Gasification Gases With Alumina Membranes
Authors: Egan B. Z. , Fain D. E. , Roettger G. E. , White D. E. 
Published: March 2015

Synthesis gas produced in coal gasification processes contains hydrogen, along with carbon monoxide, carbon dioxide, hydrogen sulfide, water, nitrogen, and other gases, depending on the particular gasification process. Development of membrane technology to separate the hydrogen from the raw gas at the high operating temperatures and pressures near exit gas conditions would improve the efficiency of the process.
Tubular porous alumina membranes with mean pore radii ranging from about 9 to 22 A have been fabricated and characterized. Based on the results of hydrostatic tests, the burst strength of the membranes ranged from 800 to 1600 psig, with a mean value of about 1300 psig. These membranes were evaluated for separating hydrogen and other gases.
Tests of membrane permeabilities were made with helium, nitrogen, and carbon dioxide. Measurements were made at room temperature in the pressure range of 15 to 589 psi. In general, the relative gas permeabilities correlated qualitatively with a Knudsen flow mechanism; however, other gas transport mechanisms such as surface adsorption may also be involved.
Efforts are under way to fabricate membranes having still smaller pores. At smaller pore sizes, higher separation factors are expected from molecular sieving effects.
Advanced Ducted Engines Nacelle Aerodynamics and Integration Testing
Authors: McCall J. E. , Tracksdorf Peter , Heinig Klaus 
Published: March 2015

Future aircraft engine development may lead to Advanced Ducted Engines (ADE) which have a bypass ratio significantly higher than present turbofans. The increases in bypass ratio will dictate larger diameter nacelles and an increasing importance of the nacelle aerodynamics and wing integration aerodynamics.
A series of isolated wind tunnel tests was therefore designed and conducted by PWA and MTU to investigate inlet, nozzle and reverser aerodynamics. Additional installed testing was done in cooperation with MBB and BAe. Key features of the tests are noted and significant results are discussed.