ARMA spectral estimation based on partial autocorrelations

This paper presents a new method for estimating the coefficients of autoregressive moving-average parameters of stationary time series. The method is based on computing the sample autocorrelations of the given time series and fitting an ARMA model so as to approximate the partial autocorrelations in a least-squares sense. When the given time series are characterized by spectral zeroes near the unit circle, they tend to have relatively long sequences of nonzero partial autocorrelations; hence the new method is especially effective in such cases. This paper contains a derivation of all necessary mathematical details, as well as several numerical examples illustrating the performance.     

Freeze concentration of milk and saline solutions in a liquid–solid fluidized bed: Part I. Experimental

Fluidized bed freeze concentration is a novel technique that uses a fluidized bed heat exchanger (FBHE) to concentrate liquids through the process of freeze concentration. Ice formed on the cooled surface of the vertical heat exchanger is removed by particles fluidized inside the FBHE. In this paper, the operating conditions are reported for freeze concentration of saline solutions and milk in FBHE. The operation was tested with equilateral 4 mm and then 5 mm particles at different bed porosities, cooling rates and NaCl and milk concentrations. Experiments with NaCl solutions showed that the 5 mm particles were more aggressive than 4 mm in removing ice from the heat exchanger wall. Whilst particle size was considered responsible for this, the particle shape could have played a major role. A theoretical analysis on effect of FBHE parameters showed the size of particles to exert influence on FBHE performance. The result from experiments with skim milk and whole milk maintained the conclusions formed previously with NaCl experiments with regard to the effect of tested parameters on operational stability. However, the ice formed from milk was more difficult to remove than the ice formed from NaCl solutions. Whole milk showed even more resistance to ice removal. Skim milk was freeze concentrated from 13% to 27% TS content in these experiments. Installing a wash screen further improved the purity of separated ice.     

Towards a Guideline for Design of a Corporate Entrepreneurship Function for Business Development in Medium‐Sized Technology‐Based Companies

The speed with which global high‐technology markets evolve makes companies recognize that an effective innovation process is the best way to guarantee competitiveness. However, when (medium‐sized) companies then wish to set up a corporate entrepreneurship function to enhance business development processes, they can find little material available in literature to assist in such processes. In this article we have described a guideline and some backgrounds for creating a corporate entrepreneurship function to realize business development in a high‐tech context.     

Risk and preventive factors for fatalities in All-terrain Vehicle Accidents in New Zealand

All-Terrain Vehicles (ATVs) have been used in agriculture for a few decades now. Yet despite their invaluable contribution to the productivity of the agricultural industry they are associated with a large number of accidents, many of which result in a severe or fatal outcome. The main objective of this study was to identify the risk factors for ATV-related fatal injuries in order to support the design of effective interventions. Using data held by the Department of Labour, the current study analysed 355 cases of serious harm accidents associated with ATVs including 45 fatalities. The findings suggest that injuries are more likely to occur when accidents involve any of the following: children under the age of 10; four-wheel drive ATVs; driving downhill; driving on a sealed road; driving backwards; or if the ATV rolls sideways. A fatal outcome is more likely to occur when ATV accidents end up with the vehicle rolling over and pinning the driver underneath. Fatalities were also associated with injuries to the head, neck and chest. Being employed; and/or having formal training; and/or having brakes and tyres well maintained on the ATV; and/or having no fluid load on the ATV reduced the risk for fatality. Since the likelihood of a fatal outcome was found to be related to human behaviour and ATV rollover, it is suggested that interventions should mainly address these two issues.     

Thirty-day self-reported risky driving behaviors of ADHD and non-ADHD drivers

The present study aims to compare differences in reported risky driving behaviors of drivers – males and females – having and not having Attention Deficit Hyperactivity Disorder (ADHD), by using a checklist of driving behaviors based on the Driving Behavior Questionnaire (DBQ). Unlike the studies which employ the DBQ by asking the subjects to fill the questionnaire once, in this present study, the participants were asked to report their behaviors on a daily basis for 30 consequent days. The checklist included two factors of risky driving behavior: Violation and Faults. Thirty-eight drivers – 10 males and 9 females with ADHD, and 9 males and 10 females without ADHD (N-ADHD) as control groups – participated in the study. The results showed that the mean of the unsafe behaviors of ADHD was higher, i.e., less safe driving, compared to that of N-ADHD. However, a statistically significant effect was found only between male ADHD and male N-ADHD for the Faults. In order to check the effect of the length of the study, the 30 days duration of the research was divided into three consecutive periods. The reported driving habits of the female ADHD showed safer behaviors than those of the males. Unlike the findings of N-ADHD of both genders, which showed a tendency towards safer driving reports in the three periods, both genders of the ADHD showed higher rates of Faults, i.e., a decrease in safety driving reports, in the three periods. The findings suggest that ADHD drivers differ from the N-ADHD drivers in making driving mistakes, i.e., Faults, due to their lack of sustained attention, but not in making Violations. However, some of the results in the present study were not very strong. Possible explanations for this as well as methodological considerations are discussed, and further research is suggested.