1,720,957 research outputs found
High efficiency single and multi-phase direct liquid jet-impingement cooling for heterogeneous packaging
No full textThe rapid development of high-power heterogeneously integrated chiplet packages for high-performance computing and datacenters has increased the demand for an energy-efficient thermal management strategy with a high heat transfer potential. This study presents a comprehensive experimental evaluation of direct-liquid jet-impingement cooling using both single-phase (deionized water) and two-phase (HFE-7100) working fluids on a 2.5D thermal test vehicle (TTV) replicating a realistic chiplet architecture. The cooling module features a 4 x 4 jet array precisely aligned over high-power logic dies, with secondary crossflow used to cool adjacent memory regions, effectively reducing pressure drop. Furthermore, deep reactive ion etched (DRIE) micro pin-fins were fabricated on the silicon surface, allowing distinct heat transfer enhancements for both single and two-phase cooling regimes, with minimal increase in required pumping power. Single-phase water cooling demonstrated superior thermal performance, achieving a minimum junction-to-fluid thermal resistance of 0.032 K/W while maintaining chip temperatures under 70 degrees C at 1 kW heat loads with a low pumping power of only 1.3 W. In contrast, two-phase jet cooling on the micro pin-finned surface at elevated inlet temperatures up to 45 degrees C achieved a 78 % improvement in energy efficiency compared to single-phase water jet cooling, which was quantified with an exergy-destruction-based metric, with only an 8.7 % higher thermal resistance. By directly comparing working fluids, operating conditions, and surface structuring on a realistic 2.5D chiplet package, this work offers guidance for selecting cooling strategies based on thermal performance, energy efficiency, and reliability. The findings highlight the effectiveness of direct-liquid jet-impingement combined with silicon micro pin-fin structuring as an energy efficient thermal management strategy for high-power heterogeneously integrated packages.
Liquid cooling module incorporating a metal foam and fin hybrid structure for high power insulated gate bipolar transistors (IGBTs)
No full textWe propose a liquid cooling system incorporating a porous medium combined to the multiscale flow manifold. Specifically, this work compares two types of porous media by varying the porosity: the first type only includes a metal foam layer, and the second incorporates an additional circular pin-fin array within the metal foam. The thermohydraulic performances of each type such as the average junction temperature, temperature deviation, flow were investigated using both numerical and experimental approaches. Due to the influence of the additional thermal conductivity matrix by fin structure integration, the second configuration (metal-foam and pin-fin hybrid type) provides a higher thermal performance compared to the first one. The suggested cooling solution with the second configuration could provide a very low thermal resistance (similar to 0.185 K/W) with the pressure drop range between 5 and 15 kPa, which surpasses the performances of the previous-reported direct liquid cooling solutions such as the jet impingement, turbulator, and microchannel. This work will help develop high performance and compact cooling solutions for high power semiconductor applications such as an insulated gate bipolar transistor (IGBT) or a microprocessor.
Artificial neural network (ANN)-based multi-objective optimization of the vapor chamber with liquid supply layer for high heat flux applications
No full textWe developed a multi-objective optimization process using artificial neural networks (ANN) to estimate and enhance the thermal-hydraulic performance of vapor chambers (VCs). A numerical model was employed to evaluate the impact of various components on VC performance, and the resulting data were used to train the ANN model. This approach led to an optimized VC design that significantly reduced thermal resistance while substantially improving critical heat flux (CHF). This improvement was primarily due to the distinct roles of the liquid supply layer (LSL) and the evaporator wick. The optimized VC with liquid supply layer (VC-LSL) exhibited a thermal resistance 1/3 lower and a junction temperature 100 degrees C lower than those of the optimized VC without liquid supply layer (VC-NL) at heat flux of 500 W/cm2. This work demonstrates significant potential for maximizing heat transfer performance by establishing an optimal VC design adaptable to a wide range of heat fluxes.
Optimization framework for energy-efficient and uniform jet impingement cooling for heterogeneous integration packaging
No full textThe imbalance in heat power generated by various types of chips poses an obstacle to the reliability and performance of heterogeneous integration (HI) packaging technology, leading to excessive cooling that reduces the system's energy efficiency. We propose a framework to optimize the impinging nozzle arrangement for energy-efficient uniform jet cooling of HI packages. This framework utilizes a convolutional neural network (CNN)-based surrogate model that learns nozzle arrangements and heating scenarios to predict the temperature non-uniformity of the package. The potential optimal designs predicted by the CNN are used for re-training through an experimentally validated numerical analysis model. Combined with this active learning approach, the proposed hierarchical exploration algorithm accelerates optimization by gradually scaling the design options. The optimization results showed an increase in cooling uniformity by up to 39.5 %, while the cooling COP improved by up to 200 % across the investigated flow rate range (3–8 L/min). The optimized designs were experimentally validated with a maximum error of 4.34 % in average thermal resistance. Our framework achieved up to 45.7 % data savings compared to the random sampling-based approach. Along with a discussion on applying the CNN model to untrained conditions to further enhance optimization efficiency, our work represents a novel approach to broadly address the rapidly evolving diverse heating scenarios of HI, contributing to improved cooling energy efficiency in data centers and enhanced reliability of high-performance processors
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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