Offsetting Losses: Bargaining Power and Rebel Attacks on Peacekeepers

Abstract

Many naturally occurring materials, such as wood and bone, have intricate porous microstructures and high stiffness and toughness to density ratios. Here, the influence of pores in a material on crack dynamics in brittle fracture is investigated. A dynamic phase field finite element model is used to study the effects of pores with respect to crack path, crack propagation velocity and energy release rate in a strip specimen geometry with circular pores. Four different ordered pore distributions are considered, as well as randomly distributed pores. The results show that the crack is attracted by the pores; this attraction is stronger when there is more energy available for crack growth. Crack propagation through pores also enables higher crack propagation velocities than are normally seen in strip specimens without pores (i.e. homogeneous material), without a corresponding increase in energy release rate. It is further noticed that as the porosity of an initially solid material increases, the crack tip is increasingly likely to become shielded or arrested, which may be a key to the high relative strength often exhibited by naturally occurring porous materials. We also find that when a pore is of the same size as the characteristic internal length then the pore does not localise damage. Since the characteristic internal length only regularises the damage field and not the strain end kinetic energy distributions, crack dynamics are still affected by small pores.

Obstruction and intimidation of peacekeepers: How armed actors undermine civilian protection efforts

“…Recent research has begun to address what explains violent attacks on peacekeepers (Fjelde, Hultman & Lindberg Bromley, 2016;Salverda, 2013). However, little attention has been given to other types of resistance against peace missions, such as the intimidation and obstruction of peacekeepers.…”

“…In addition, a body of research has begun to emerge which shows that the effectiveness of peacekeeping missions depends on the relationship between the local actors and the peacekeeping mission (Gippert, 2017;Whalan, 2013). Some recent studies focus on the determinants of rebel violence against peacekeepers (Fjelde, Hultman & Lindberg Bromley, 2016;Salverda, 2013), but strategies of armed actors involving threats and impeding the access of peacekeepers have not yet received any scholarly attention. Our understanding of resistance against peacekeepers would be incomplete if we only look at killing of peacekeepers and ignore non-lethal intimidation and obstruction because these non-lethal types of resistance can undermine the effectiveness of peacekeepers.…”

UN Peacekeeping and Protection from Sexual Violence

“…The presence of peacekeepers could exacerbate these challenges as the conflicting parties want to secure as strong positions as possible, should the conflict come to an end and/or a settlement (cf. Fjelde, Hultman, and Lindberg Bromley 2016). This might spur more violence and a more complex situation for peacekeepers to manage.…”

Predictive Peacekeeping: Strengthening Predictive Analysis in UN Peace Operations

“…Moreover, there be might variables closely related to attacks on peacekeepers that can serve as early warning indicators. For instance, Fjelde et al (2016) find that, on the country level, peacekeepers are very likely to be attacked by rebel groups when the balance of power turns against these rebels in their struggle against governments. If information analysts can uncover what explains violence against peacekeepers on the local level through machine learning, then peacekeepers can be alerted when there is a higher risk of being attacked.…”