Drafting a composite indicator of validity for regulatory models and legal systems

The aim of this paper is to lay the groundwork for the creation of a composite indicator of the validity of regulatory systems. The composite nature of the indicator implies a) that its construction is embedded in the long-standing theoretical debate and framework of legal validity; b) that it formally contains other sub-indicators whose occurrence is essential to the determination of validity. The paper suggests, in other words, that validity is a second-degree property, i.e., one that occurs only once the justice, efficiency, effectiveness, and enforceability of the system have been checked

A model for the Statistical Distribution of Road Vehicle Vibrations

This paper presents the initial results of a study aimed at improving the method by which the vibrations produced by transport vehicles are characterised and simulated. More specifically, this paper focuses on the rigid body vibrations generated by road transport vehicles in the context of distribution of packaged goods and produce. The research uses a variety of vibration data, collected from various vehicle types and routes in Spain and Australia with high-capacity vibration recorders. Vehicles used range from small transport vehicles to large truck-trailers with both airbags and steel spring suspensions while the routes travelled include suburban streets, main roads and motorways. The paper discusses the significance and limitations of the average power spectral density (PSD) and explains why the average PSD is not always adequate as the sole descriptor of road vehicle vibrations as the process generally tends to be non-stationary and non-Gaussian. The paper adopts an alternative analysis method, based on the statistical distribution of the moving root-mean-square (RMS) vibrations, as a supplementary indicator of overall ride quality. The measured data was used to compute the statistical distribution of each vibration record, the shape of which was compared for the entire set of records. The suitability of various mathematical models, based on the Weibull and Rayleigh distributions were investigated for describing the probability distribution function (PDF) of road vehicle vibration RMS time history. The paper proposes a single mathematical model that can accurately describe the statistical character of the random vibrations generated by road vehicles in general. It shows that the model can also effectively describe the statistical parameters of the process namely the mean, median, standard deviation, skewness and kurtosis

Effect of Initial Pre-compression of Corrugated Paperboard Cushions on Shock Attenuation Characteristics in Repetitive Impacts

The use of paper as a cushioning material is motivated by its environmental advantage over polymeric materials such as expanded polystyrene. Various studies have been conducted to investigate the capability of corrugated paperboard (CPB) to act as cushioning materials for protective packaging. The studies have normally focused on performance of cushions and effects of climatic conditions on the shock attenuation in the fi rst drop. However, no information is available to show that CPB can be engineered to produce a cushioning element with good shock attenuation in repetitive impacts. This study investigates the deterioration of the shock attenuation characteristics of CPB cushions in consecutive impacts. A series of cushion-test style experiments on multilayer cushion pads made entirely from CPB were conducted. Each cushion was fi rst subjected to 20 impacts, followed by simulated warehousing in a climatic chamber, and then the additional 15 impacts. The effect of initial pre-compression strain introduced in the process of making cushion pads is discussed and demonstrated. The performance of cushions was judged not only by the maximum acceleration of shocks. Entire recorded shock pulses and calculated corresponding shock response spectra were analysed and are presented as 3D maps in order to reveal trends that occur when a cushion is subjected to multiple drops. The paper shows that the level of pre-compression has an important effect on the degree of deterioration of cushion performance after multiple drops. As an example, the maximum acceleration for a pad pre-compressed to 95% strain increased by less than 20% between the 1st and the 35th drop. In contrast, for 80% pre-compression, the increase was 300%. It was found that the selection of optimum static stress should be made in conjunction with the expected number of impacts in order to optimize the cushion performance