Degrees of freedom for the residuals of a principal component analysis — A clarification

Various conflicting proposals for degrees of freedom associated with the residuals of a principal component analysis have been published in the chemometrics-oriented literature. Here, a detailed derivation is given of the ‘standard’ formula from statistics. This derivation intends to be more accessible to chemometricians than, for example, the impeccable, but condensed proof that was published by John Mandel in a relatively unknown paper (J. Res. Nat. Bur. Stand., 74B (1970) 149–154). The derivation is presented in the form of a two-stage recipe that also appears to apply to more complex multiway models like the ones considered by Ceulemans and Kiers (Br. J. Math. Stat. Psych., 59 (2006) 133–150).     

DOES MIGRATION EQUALISE REGIONAL UNEMPLOYMENT RATES? EVIDENCE FROM AUSTRALIA

Whether inter-regional migration equilibrates regional economic performance is a question which has received considerable attention in recent literature. The author examines that question, focusing upon regional unemployment rates and real wages within the context of a 24-hour equation econometric model of the interaction between regional wages, regional unemployment, and inter-regional migration in Australia. Used to solve for steady-state values of wage and unemployment differences, the model determined that the steady state involves non-zero unemployment rate differences and non-zero wage differences. The model is also used to investigate the stability of the equilibrating mechanism and to simulate the effects upon unemployment, migration, and wage rates of a shock to employment growth. The main findings are that inter-regional equilibrating forces are slow and do not help equalize regional unemployment rates or wages.     

Interregional transfers: A political-economy CGE approach

We model the effects of changes in a federal governments inter-regional transfers within the context of a CGE model of a federal system in which regional governments act to maximise the welfare of the residents of their region subject to the effects of their decision on regional economic outcomes. Regional governments are modelled as players in a non-cooperative game. Simulations are conducted with six versions of a small two-region model, each calibrated for a particular Australian state and the rest of the nation. We show that a change in the level of transfers has little influence on per-capita private consumption, government consumption and welfare, and that its main effect is to induce migration from the donor region to the recipient region.Received: 27 June 2001, Accepted: 20 December 2002, JEL Classification: C72, D58, H73, R13, R23The research reported in this article was supported by a SPIRT Grant from the Australian Research Council. We are indebted to Peter Dixon, James Giesecke, Sang-Hee Han, Peter McGregor, Alex Scherini, two anonymous referees, and the Pacific editor for their valuable comments and suggestions. The usual disclaimer applies.     

On the proof of concept of a ‘Smart’ wind turbine rotor blade for load alleviation

The trend with offshore wind turbines is to increase the rotor diameter as much as possible to decrease the costs per kilowatt‐hour. The increasing dimensions have led to the relative increase of the loads on the wind turbine structure. Because of the increasing rotor size and the spatial load variations along the blade, it is necessary to react to turbulence in a more detailed way; each blade separately and at several separate radial distances. In this paper, a proof of concept study is performed to show the feasibility of the load alleviation abilities of a ‘Smart’ blade, i.e. a blade equipped with a number of control devices that locally change the lift profile on the blade, combined with appropriate sensors and feedback controllers. Theoretical and experimental models are developed of a scaled non‐rotating rotor blade which is equipped with two trailing edge flaps and strain sensors to facilitate feedback control. A pitch actuator is used to induce disturbances with a similar character as a gust or turbulence. A feedback controller based on classical loop shaping is designed that minimizes the root bending moment in the flapping direction. We show that with appropriate control techniques, the loads for periodic disturbances and for turbulence generated disturbances can be reduced up to 90 and 55%, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

The effects of fiscal equalisation in a model with endogenous regional governments: an analysis in a two-region numerical model

This paper is concerned primarily with the economic and welfare consequences of federal redistributive grants. We use a model which has two regions, each with households, firms and regional governments as well as a federal government. Private agents are (utility and profit) maximisers and we assume that regional governments are empire-builders in that they choose their expenditure and tax levels so as to maximise total expenditure—the size of their empire. Labour is free to move between regions in response to utility differences and does so until such differences have been eliminated. Inter-regional migration, inter-regional trade flows and federal government redistribution are the main sources of interconnectedness between the two regions. The model is linearised in log-differences and simulated using a calibration based on Australian state-level data. We find that the welfare effect of intergovernmental transfers is trivial but that all other variables of interest change substantially—consumption, employment, prices, taxes, wages, output and government expenditure. Finally, the signs of the effects of a federal transfer are not affected by the empire-building behaviour of regional governments although the magnitude of the effects is generally dampened.     

Model selection in spatio-temporal electromagnetic source analysis

Several methods [model selection procedures (MSPs)] to determine the number of sources in electroencephalogram (EEG) and magnetoencphalogram (MEG) data have previously been investigated in an instantaneous analysis. In this paper, these MSPs are extended to a spatio-temporal analysis if possible. It is seen that the residual variance (RV) tends to overestimate the number of sources. The Akaike information criterion (AIC) and the Wald test on amplitudes (WA) and the Wald test on locations (WL) have the highest probabilities of selecting the correct number of sources. The WA has the advantage that it offers the opportunity to test which source is active at which time sample.     

Cement treated recycled demolition waste as a road base material

To enhance the performance of mix granulate road base courses by cement treatment. The mechanical properties of cement treated mix granulate (CTMG) were studied, which was designed with 65% crushed masonry and 35% crushed concrete by mass. The central composite design was employed to prepare specimens with different levels of cement content and degree of compaction. All specimens were cured in a fog room at 20°C for a specific number of days. The compressive strength and the indirect tensile strength were determined through the monotonic compression and indirect tension tests. Effective prediction models for the mechanical properties of CTMG, in relation to the cement content, the degree of compaction and the curing time, were successfully established for a mix containing 65% crushed masonry and 35% crushed concrete by mass.     

The effects of scaffolding metacognitive activities in small groups

This study examined the effects of scaffolds on triads’ metacognitive activities in complex open learning environments. In an experimental design, two experimental groups receiving scaffolds were compared with a control group. The experimental groups differed in the form of scaffolding messages used: structuring scaffolds vs. problematizing scaffolds. We analyzed the effects of scaffolding and the different forms of scaffolds on the amount of metacognitive activities of triads on the interpersonal plane. The results show that scaffolding has a significant effect on stimulating metacognitive activities; triads receiving scaffolds performed significantly more metacognitive activities on the interpersonal plane. Additionally, scaffolding also has a significant development effect; triads continue to show more metacognitive activities after the scaffolding is ceased. Finally, no significant differences between the two forms of scaffolding were found: triads receiving problematizing scaffolds did not showed more metacognitive activities during or after the scaffolding compared to triads receiving structuring scaffolds.     

Lighting control in office buildings

A demonstration project at an office building of Nederlandse Gasunie in Groningen, Holland, is here described by engineers with TNO-TH in Delft. Five different lighting systems were installed on different floors, most of them controlled automatically on daylight in an inner and outer zone. These systems, when compared with a reference system without automatic control, showed savings between 30 and 40 per cent of lighting energy consumption in relation to the maximum number of lighting hours.