Mechanical properties and thermal conductivity of pristine andfunctionalized carbon nanotube reinforced metallic glass composites:A molecular dynamics approach

This work uses the molecular dynamics approach to study the effects of functionalization of carbon nanotubes (CNTs) on the mechanical properties of Cu64Zr36 metallic glass (MG). Three types of functional groups, carboxylic, vinyl and ester were used. The effect of CNT volume fraction (Vf) and the number of functional groups attached to CNT, on the mechanical properties and thermal conductivity of CNT-MG composites was analysed using Biovia Materials Studio. At lower values of Vf (from 0 to 5％), the per-centage increase in Young's modulus was approximately 66％. As the value of Vf was increased further (from 5 to 12％), the rate of increase in Young's modulus was reduced to 16％. The thermal conductivity was found to increase from 1.52 W/mK at Vf=0％to 5.88 W/mK at Vf=12％, thus giving an increase of approximately 286％. Functionalization of SWCNT reduced the thermal conductivity of the SWCNT-MG composites.     

Damage modeling of ballistic penetration and impact behavior of concrete panel under low and high velocities

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete panels. This paper is divided into two parts. The first part consists of numerical modeling of reinforced concrete panel penetrated with a spherical projectile using concrete damage plasticity (CDP) model, while the second part focuses on the comparison of CDP model and Johnson-Holmquist-2 (JH-2) damage model and their ability to describe the behavior of concrete panel under impact loads. The first and second concrete panels have dimensions of 1500 mm × 1500 mm × 150 mm and 675 mm × 675 mm × 200 mm, respectively, and are meshed using 8-node hexahedron solid elements. The impact object used in the first part is a spherical projectile of 150 mm diameter, while in the second part steel projectile of a length of 152 mm is modeled as rigid element. Failure and scabbing characteristics are studied in the first part. In the second part, the com-parison results are presented as damage contours, kinetic energy of projectile and internal energy of the concrete. The results revealed a severe fracture of the panel and high kinetic energy of the projectile using CDP model comparing to the JH-2 model. In addition, the internal energy of concrete using CDP model was found to be less comparing to the JH-2 model.     

WHO IS THE ENEMY?

We examine who benefits when there is a strong leader in place, and who benefits when a situation lacks a proper leader. There are fractious terrorist groups who seek to serve the same people in common cause against a common enemy. The groups compete for rents obtained from the public by engaging in actions against the common enemy. We determine the leadership structure under which each group is better off, as well as the circumstance that the common enemy prefers. We are able to state simple and general conditions for each group and the common enemy to benefit.     

“Government contracting options: A model and application“∗

This paper models and simulates a government‐contractor principal‐agent weapon system repair model. Insights are derived as to how government repair contracts should be constructed so as to induce optimal contractor behavior. The paper's general conclusion is that the best contracting approach combines a lump‐sum payment that does not vary with the number of units repaired, expensive item cost‐sharing, and a contractor‐provided availability guarantee. Provided there is intercontractor competition, this type of contract performs well even if the government is poorly informed about weapon system break patterns or repair costs.     

One more push: Forcing the Dardanelles in March 1915

The historiography of the Gallipoli campaign suggests that the Turks were critically short of ammunition for the Dardanelles coastal defences in March 1915. This theme, established by Winston Churchill, became the basis for a widespread belief that the Royal Navy, after its failure to carry the Dardanelles on 18 March 1915, simply needed one more determined naval push to breakthrough the narrows. The presumed consequence was that the Ottoman Empire, with Constantinople under the guns of the Royal Navy, would have withdrawn from the war. Using modern Turkish sources, the author examines the available quantities, placement, and expenditure of ammunition, and challenges the premise that the Turks were desperately short of heavy shells. The author concludes that the Turks had sufficient remaining ammunition to fiercely contest control of the straits.     

Just How Important Are ‘Hearts and Minds’ Anyway? Counterinsurgency Goes to the Polls

Despite all the talk of ‘hearts and minds’ being the key to counterinsurgency, local public opinion is rarely studied and when it is, it often yields surprising conclusions. Through analyzing polling data from Vietnam, Iraq and Afghanistan, this article shows that public opinion is less malleable, more of an effect rather than a cause of tactical success, and a poor predictor of strategic victory. As a result, modern counterinsurgency doctrine’s focus on winning popular support may need to be rethought.     

‘What Kind of War is This?’

This article explores the nature of the American war in Vietnam in an effort to determine whether it was a response to an indigenous uprising or an external effort by the Communist Party of Vietnam (CPV) to use a wide array of policies and programs to unite North Vietnam and South Vietnam under the party’s leadership. It argues that, although there initially were elements of the South Vietnamese population that rose against the southern leadership, the CPV gained control of their resistance and relegated it to a secondary role in the CPV war effort.