Topological design of channels for squeeze flow optimization of thermal interface materials

Performance of thermal interface materials (TIMs) used between a microelectronic device and its associated heat spreader is largely dependent on the bulk thermal conductivity of the TIM, but the bond-line thickness (BLT) of the applied material as well as the interfacial contact resistances are also significant contributors to overall performance. Hierarchically Nested Channels (HNCs), created by modifying the surface topology of the chip or the heatsink with hierarchical arrangements of microchannels in order to improve flow, have been proposed to reduce both the required squeezing force and the final BLT at the interfaces. In the present work, a topological optimization framework that enables the design of channel arrangements is developed. The framework is based on a resistance network approximation to Newtonian squeeze flow. The approximation, validated against finite element (FE) solutions, allows efficient, design-oriented solutions for squeeze flow in complex geometries. A comprehensive design sensitivity analysis exploiting the resistance network approximation is also developed and implemented. The resistance approximation and the sensitivity analysis is used to build an automated optimal channel design framework. A Pareto optimal problem formulation for the design of channels is posed and the optimal solution is demonstrated using the framework.     

Studies on the composition,quality and processing of triticale Part 3. Rheological and baking properties

Studies on rheological and baking properties of 14 promising strains of triticale and two check wheat varieties from India are reported. The farinograms obtained from triticale flours, in general, revealed poor dough development time and lower stability than those from wheat flours. The mean water absorption capacity of triticale flours was 54.3 percent compared to 64.4 percent of wheat flour. The triticale flour produced poor loaf volumes with mean value of 399 cm³ compared to 475 cm³ of wheat flour. Cookie baking tests showed that triticale flours were eminently suited for this purpose because of their soft flour and weaker gluten. Triticale whole meal required much less water for preparation of dough for chapatis and produced red coloured chapatis which tended to stale faster.     

Shastra: multimedia collaborative design environment

A distributed environment that supports multimedia interfaces, Shastra strengthens collaboration in scientific and engineering design. Implemented on a desktop system, it provides an infrastructure for user- and application-level cooperation. We describe the Shastra architecture and tools, then walk through a scenario that shows how it enhances collaborative problem solving     

Nonlinear dynamics of tubes carrying a pulsatile flow

The nonlinear dynamics of a cantilever tube conveying a pulsatile flow and undergoing planar motions is investigated. The mean flow is near its critical value at which the downward vertical position of the tube gets unstable by flutter and executes limit-cycle oscillations. The pulsations in the flow are assumed to be small and harmonic with frequency nearly twice that of the limit cycle. To study the nonlinear dynamics, the method of averaging is utilized and the governing partial differential equation is reduced to a dynamic system on the plane. These two first-order differential equations depend on three parameters and govern the dynamics of the amplitude of motion of the tube. The planar system is studied for its qualitative behaviour using ideas from the local bifurcation theory and a local bifurcation set in the parameter plane is constructed. Using ideas from codimension-two unfolding of singularities, this bifurcation set is further refined. The resulting partial bifurcation set and the associated phase portraits in the various regions of the flowrate-detuning parameter plane show that the averaged equations have constant as well as periodic solutions. The stabifity type and the number of these solutions changes from one region to another. This explains how periodic or 'phase-locked' oscillations of the cantilever tube bifurcate into amplitude-modulated or almost-periodic motions.