Influence of obstruction’s unilateral length on flow and heat transfer performance of micro-channel heat sinks with flow obstructions

As the density and integration of electronic equipment continue to increase, it becomes necessary to build micro-channel heat sinks with more efficient cooling effects to solve the heat removal issue. This paper proposes a series of obstructions established on a smooth water-cooled micro-channel and analyzes the heat transfer and flow performance from the viewpoint of fluid dynamics. By adjusting the unilateral side length of the obstructions, the simulation conducted a comparative analysis between the seven different obstruction shapes and smooth micro-channel heat sinks, focusing on Nusselt number, thermal resistance, and pressure loss across a range of Reynolds numbers. The findings demonstrate that the heat dissipation capacity of micro-channel heat sinks with obstructions is consistently superior to that of the smooth heat sink, and the performance of these heat sinks is affected by the length of unilateral side of the obstructions. With no consideration of pumping power, the paper argues that the heat sink with obstructions, specifically those with a unilateral side length of 0.06 mm, has the best heat dissipation capacity at Reynolds numbers below 460. At this Reynolds number, the Nusselt number increases by 99% and the thermal resistance decreases by 33% compared to a smooth micro-channel heat sink. However, when the pumping power is considered, the heat sink with obstructions whose unilateral sides are the shortest has the best performance due to its minimal pressure loss. While meeting the thermal resistance requirement of 0.033, it requires only one-fourth of the pumping power needed by a heat sink with obstructions whose unilateral sides are longest

Simplify Belief Propagation and Variation Expectation Maximization for Distributed Cooperative Localization

Only a specific location can make sensor data useful. The paper presents an simplify belief propagation and variation expectation maximization (SBPVEM) algorithm to achieve node localization by cooperating with another target node while lowering communication costs in a challenging environment where the anchor is sparse. A simplified belief propagation algorithm is proposed as the overall reasoning framework by modeling the cooperative localization problem as a graph model. The high-aggregation sampling and variation expectation–maximization algorithm is applied to sample and fit the complicated distribution. Experiments show that SBPVEM can obtain accurate node localization equal to NBP and SPAWN in a challenging environment while reducing bandwidth requirements. In addition, the SBPVEM has a better expressive ability than PVSPA, for SBPVEM is efficient in challenging environments

Investigation on cracking performance of UHPC overlaid concrete deck at hogging moment zone of steel-concrete composite girders

The concrete deck at the negative bending moment region of a continuous steel-concrete composite girder bridge is the weakest part of the structure. Introducing ultra-high performance concrete (UHPC) to the hogging region may overcome the shortage and break through the bottleneck. This paper explores the cracking performance of steel-concrete composite girders with concrete slabs topped by a thin layer of UHPC subjected to a negative bending moment.Areal continuous composite girder bridge is briefly introduced as the engineering background, and the cracking characteristic of the concrete deck over the middle piers of the bridge is numerically modeled. Approaches to strengthen the cracking performance of the concrete deck at the hogging region through topping UHPC overlays are proposed. The effectiveness of the approaches is examined by conducting a series of numerical and experimental tests. Numerical results indicate that the normal concrete (NC) deck near the middle forums of the bridge would crack due to the large tensile stress from negative bending moments. Replacing the top concrete with an identical-thick UHPC overlay can increase the cracking resistance of the deck under the moment. As the thickness of the UHPC overlay increased from 6.0 cm to 12.0 cm, the maximum shear stress at the UHPC overlay-to-NC substrate interface under different load combinations was decreased by 56.3%65.3%. Experimental results show that the first-cracking load of the composite beam using an NC-UHPC overlaid slab was 2.1 times that using an NC slab. The application of a UHPC overlaid deck can significantly improve the crack performance of the steel-concrete composite girder bridge