We present a molecular dynamics study of the motion of cylindrical polymer droplets on striped surfaces. We first consider the equilibrium properties of droplets on different surfaces, we show that for small stripes the Cassie-Baxter equation gives a good approximation of the equilibrium contact angle. As the stripe width becomes non-negligible compared to the dimension of the droplets, the droplet has to deform significantly to minimize its free energy, this results in a smaller value of the contact angle than the continuum model predicts. We then evaluate the slip length, and thus the damping coefficient as a function of the stripe width. For very small stripes, the heterogeneous surface behaves as an effective surface, with the same damping as an homogeneous surface with the same contact angle. However, as the stripe width increases, damping at the surface increases until reaching a plateau. Afterwards, we study the dynamics of droplets under a bulk force. We show that if the stripes are large enough the droplets are pinned until a critical acceleration. The critical acceleration increases linearly with stripe width. For large enough accelerations, the average velocity increases linearly with the acceleration, we show that it can then be predicted by a model depending only the size of droplet, viscosity and slip length. We show that the velocity of the droplet varies sinusoidally as a function of its position on the substrate. On the other hand, for accelerations just above the depinning acceleration we observe a characteristic stick-slip motion, with successive pinnings and depinnings.

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The transport of neutral hydrogen atoms in a hydrogen plasma is investigated. An analytical approach based on a polynomial expansion technique is used to solve boundary value problems for half-space and slab plasma. A linear version of the Boltzmann equation is considered to describe the transport of the neutrals. Particular and complete solutions are obtained for specular and diffuse reflections. The numerical results are reported.

Earthquakes are one of the most important and hazardous natural disasters in the world and in our country. They also have lots of characteristics from the point of effects caused by them. For this reason it requires special engineering approach to analyze those effects and to design earthquake resistant structures. Almost all of the life losses caused by the earthquakes are related with improperly designed buildings safety of which are not ensured against severe earthquakes. Structural damages and collapses cause very important economical losses. So, understanding of the characteristics of an earthquake and correct determination of the behavior of buildings under earthquake excitation turn out to be the most important requirement to build earthquake resistant buildings. When we take into consideration the destructive effects of severe earthquakes that happened especially in recent years (Kocaeli 1999, Düzce 1999) one can easily see the importance of knowing the behavior of buildings under earthquake loads. In this study torsional effects that occur during earthquake excitations are analyzed in multi-story reinforced concrete buildings. In that manner the behavior of reinforced concrete structures under earthquake loads are examined and by the way the behaviors of structures having torsional irregularities are enlightened and clarified. Moreover the effects of rigidity, ultimate capacity and ductility on the behavior of structures under ground motion are summarized. Torsional irregularity is a key irregularity in determination of the method to be used in earthquake analysis. Definition of the torsional irregularity of a multi-story reinforced concrete building is explained in accordance with Turkish Earthquake Code and the related principles of computations that have to be followed according to the code are given. Multi-story reinforced concrete buildings are classified according to their plan geometry and the effects of plan geometry on the torsional irregularity are explained. While in certain structures torsional irregularity may happen in very high levels in some structures it may happen so small that can be safely omitted. For that reason buildings forming torsional irregularity are classified and their characteristics and torsional irregularity parameters are given. Shear walls without causing any torsional irregularity on buildings having different plan geometries are shown.

A lateral load carrying system consisting of only shear walls is used generally for structures having 14 storeys or more. It can be seen that the effect of earthquakes in the systems consisting of the shear walls or shear walls-core are very small. For resisting earthquake effects it is proposed to construct shear walls which are perpendicular to each other in plan and having the cross sectional area 1.5% of the building. Unfortunately in this proposal, the effect of number of storeys and the division of shear wall area to the necessary parts is not taken into consideration. In this paper, these factors are considered as, number of storeys, plan area of a storey, earthquake risk zone, material properties and shear wall thickness. The criteria for determination of the dimensions of earthquake shear walls which are suitable for architectural considerations of the building are given. For various storey areas and 10 storeys, the lengths of shear walls which ensure the suggested criteria, having the same length are given in diagrams. It is also shown how to find the length of shear walls under the same conditions if there are more than 10 storeys.