An Empirical Study on the Relation Between the Critical Angle for Bullet Ricochet and the Properties of Wood

The properties of a bullet, an object, and the incidence angle determine whether the bullet will penetrate, perforate, or ricochet. In this study, the critical angle for ricochet was established for .32 Auto and 9 mm Luger bullets on Abachi, Southern Yellow Pine, Beech, and Ipe wooden boards. Results show that the critical angle differs depending on caliber and wood type. The critical angle is higher for .32 Auto bullets than for 9 mm Luger bullets and increases with increasing wood density and Janka hardness. The established critical angles for ricochet on the lightest and softest wood (Abachi) are 10.4° and 10.3° for .32 Auto and 9 mm Luger, respectively. For the heaviest and hardest wood (Ipe), the angles were 45.0° and 33.4°, respectively. The combined results on the four tested woods show a strong linear relationship between both the density and the hardness and the critical angle for both calibers.     

The Influence of Wood Grain on the Bullet's Ricochet Behavior

When a bullet ricochets from wood, various parameters will influence its behavior. In this study, the influence of the wood grain on the ricochet angle (β) and deflection angle (γ) is assessed. Series of five .32 Auto bullets were fired at different angles of incidence (α) on boards of six wood types. The results confirm the previously shown effect that the mean β‐angles usually exceed α and increase when α increases. Overall, the maximum mean γ occurs when the angle of wood grain (ζ), in relation to the plane of impact, lies between 30° and 75° but differs per combination of wood and α. The results show the inclination of γ toward the left or right, depending on the bullets left or right rotation while also showing that the direction of ζ can enhance or counteract this effect considerably, especially when α is close to the critical ricochet angle.     

The quantitative methods component in social sciences curricula in view of journal content

What level of quantitative methods (or applied statistical analysis) should graduate students in the social sciences be prepared to master, if they are to be competitive in the job market? In the age of information technology, more data, in survey or other form, about any imaginable topic exist than ever before. Empirical analysis on the basis of more advanced quantitative methods becomes more common. This study takes the perspective that graduate students in the social sciences must be prepared to read a literature that makes extensive use of quantitative methods. To quantify this dimension of the literature, top journals in economics, political science, public administration, and sociology are examined for their quantitative complexity.     

What Drives the Relationship Between Early Criminal Involvement and School Dropout?

Objective

We examine the relationship between early criminal involvement and school dropout, and analyze which factors underlie this relationship, making use of administrative data from the Netherlands.

Methods

We start by determining the unconditional correlation between early criminal involvement and school dropout, using a basic ordinary least squares model. As this association is likely to be driven by different factors, we proceed by including an extensive set of observable family and individual characteristics into the estimation model. We further proceed to models that account for the influence of unobservable heterogeneity by estimating school, class, sibling and twin fixed effects.

Results

Criminal involvement is associated with an 11 percentage point higher probability of school dropout. The magnitude of this relationship decreases gradually when we account for larger shares of observed and unobserved heterogeneity. The coefficient in the same-gender twin fixed effects model indicates a 3 percentage point higher probability of school dropout, which is statistically significant at a 10 % level. We also find that the association between criminal involvement and school dropout is stronger if juveniles are involved in severe criminal activities.

Conclusions

We conclude that the observable and unobservable factors for which we account explain around 73 % of the unconditional correlation between criminal involvement and school dropout. The remaining variation likely reflects individual-specific characteristics that are different between same-gender twins. A true treatment effect, if existing, is likely to be relatively small. At the same time, serious criminal behavior appears to causally affect school dropout.

     

Regulatory delay and growth: a cross country analysis

This paper exploits cross country data on regulatory delay for 135 countries. The results from the regression analysis suggest that waiting time stemming from business procedures has a negative impact on economic growth, especially when we take into account possible endogeneity.     

The implementation of Directive 2001/20/EC into Belgian law and the specific provisions on pediatric research

The European Clinical Trial Directive (2001/20/EC) was implemented into the Belgian legal system by the Law of 7 May 2004 concerning experiments on the human person (LEH). Apart from implementing the European Directive, this law also broadens the scope of the Directive from interventional clinical trials to all medical experiments involving human persons. This article offers an overview of the requirements for involving minors in medical experiments that are captured in the LEH, illustrates the process of protocol review by an ethics committee, and discusses the dissimilarities between the LEH and the European Directive.