As a result of the rise in processing power demands of today’s personal computers, water cooled pin fin heat sinks are increasingly being employed for the cooling of graphical processing units. Currently, these high performance devices are manufactured through high-cost, high-waste processes. In recent years, a new solution has emerged using the cold gas dynamic spray process, in which pin fins are directly manufactured onto a baseplate by spraying metallic powder particles through a mask. This process allows for a high degree of adaptability to different graphics processing unit shapes and sizes not achievable by any other process to date. One drawback of this process is that, as substrate sensitivity to heat and mechanical residual stresses requires the use of reduced spray parameters, there is reduced deposition efficiency, resulting in a fair portion of the feedstock powder being wasted. This work aims to demonstrate the feasibility of using powder recycling to mitigate this issue and compares coatings sprayed with reclaimed powder to their counterparts sprayed with as-received powder. The work demonstrates that cold gas dynamic spray is a highly flexible and economically competitive process for the production of pin fin heat sinks when using powder recycling even when spray parameters result in reduced deposition efficiency. The benefits of pin fins on heat transfer properties of flat plates used for graphical processing units is briefly addressed and demonstrated

In wireless sensor networks, source nodes usually send their data packets to a single sink following a specific routing protocol. In this way, unicast delivery becomes a dominant means of data transmission through the network. However, if one of links in the route is out of order, a dynamic routing protocol will rule the search by the routers for a new transmission route and thus, more time will be taken with regards to searching for the route. In this paper, a condition in which an emergency occurs is envisioned. Source nodes must send the emergency information packets to the possible sink as soon as possible. Then the multicast delivery should be taken instead of the unicast delivery so as to save more time.

A first generation, one-dimensional predictive model is proposed for designing heat sinks with fractal flow networks. A three-dimensional computational fluid dynamics (CFD) model is analyzed as a means for validating the model and identifying areas for improvement. Two separate CFD models were developed. One was analyzed with conjugate heat transfer whereas the other was not. For the conjugate heat transfer model, heat flux was provided at a single surface, simulating a heat source. Energy addition to the latter model, referred to as the non-conjugate model, was uniform to all surfaces and was developed to assess the assumptions employed in the one-dimensional model. Both CFD models were run with and without variable properties and are compared to results with a series of parallel channels with identical convective surface areas. In all cases, with and without conjugate heat transfer and with and without variable fluid properties, the fractal flow network showed lower maximum surface temperatures than the straight channel network for identical pumping powers. The pumping power, however, was determined assuming constant fluid properties. The variation in fluid viscosity with temperature was determined to have a significant impact on the pressure distribution, which indicates that variable fluid viscosity needs to be included in the one-dimensional model. Also varied in the analyses were heat sink material, heat flux and flow rate. Qualitative results show that temperature variations within the copper substrate are less significant than in the stainless steel substrate. All analyses, including the one-dimensional model, were restricted to laminar flow conditions. / Graduation date: 2002

Wireless Sensor Network (WSN) has become a popular wireless technology in recent years. In WSN, a large number of sensors are used to collect data and forward data hop-by-hop to a sink. Due to the unbalancing of traffic load, some grid nodes may consume more energy and their packet loss ratio may be increased as well. In order to improve above-mentioned shortcomings, in this Thesis, we propose an Adaptive Grid-based Data Collection (AGDC) scheme. Because a mobile sink may move, it is possible the traffic load of primary grid nodes can be changed in WSN. According to the distribution of traffic load, the AGDC can adjust transmission range to allocate one or more temporary grid nodes between two primary grid nodes. Through the added temporary grid nodes, traffic load is evenly dispersed among different grid nodes. We allow the primary grid nodes to use smaller transmission power to save energy and allow the temporary grid nodes to buffer data to reduce packet loss ratio. For the purpose of evaluation, we perform simulation on NS-2. With the proposed AGDC scheme, the transmission range of a primary grid node can be set to an appropriate distance to reduce power consumption and packet loss ratio. Since the packet loss ratio is reduced, the throughput of entire WSN is increased.

No description available.

Thesis (M.S.)--Ohio University, August, 2000. / Title from PDF t.p.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--Oregon State University, . / Printout. Includes bibliographical references (leaves 99-103). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 87-92). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 67-70). Also available on the World Wide Web.