bluuebunny/crossref_metadata_2025_split huggingface dataset:
Living mulch persistence in an apple orchard and its effect on the weed flora in temperate climatic conditions
Authors: Żelazny Wiktor Rafał , Licznar‐Małańczuk Maria 
Published: November 2021

AbstractReplacing herbicide fallow with alternative floor management can conserve soil and reduce agrochemical use in an orchard. Increased perennial weed resistance to foliar preparations has recently become an additional motivation to abandon herbicides. This study explores apple tree understory weed flora alteration after introducingFestuca ovinaliving mulch to the rows. Delayed cover crop sowing was tested as a possible approach to address the problem of high perennial weed dominance when a living mulch is introduced in the year of orchard establishment, in addition to reducing competition. The effect of replacing the M.9 dwarfing rootstock with the M.26 and P 60 semi‐dwarfing rootstocks to foster tree competitiveness was also investigated, and the influence of the mulch dominance on apple yield was analysed. Abundant perennial weed flora developed in the living mulch regardless of the mitigation strategy, and one of the cover crop cohorts exhibited unsatisfactory persistence when maintained under trees on P 60. This pattern was attributed to an interactive effect of shadowing by the more vigorous trees and byGlechoma hederaceaandArtemisia vulgarisweeds, which abounded due to insufficient mowing frequency. More intensive tree understory management is recommended, especially in semi‐dwarf orchards, andG. hederaceashould be studied more as a candidate mulch species, potentially superior toF. ovina.
Roof Deformation and Collapse of Stamps With Isolated Grooves: A Contact Mechanics Approach
Authors: Jin Fan , Tang Changyu , Guo Xu , Bai Longteng 
Published: November 2021

Abstract
This paper has revisited the roof deformation and collapse of stamps with isolated grooves based on a contact mechanics approach, with emphasis on establishing the nonadhesive and adhesive contact solutions for surfaces containing a shallow rectangular groove with the effects of applied load and interfacial adhesion taken into account. By solving singular integral equations and using the energy release rate approach, closed-form solutions are derived analytically for the deformed groove shapes, interfacial stress distributions, and equilibrium relations between load and contact size, which reduce to the previously proposed solutions without adhesion or without applied load. Finite element (FE) analysis is performed to validate the nonadhesion solutions, while experiment results of stamp collapse reported in the literature are adopted to examine the adhesion solutions. By introducing the Johnson parameter α to represent a competition between surface energy and elastic strain energy of the groove, four kinds of contact behaviors of the groove roof can be characterized appropriately: nonadhesion, weak adhesion, intermediate adhesion, and strong adhesion. Hysteresis loop and energy loss due to distinct load/unloading paths are revealed in the cases of intermediate and strong adhesion. We have also provided the critical applied pressure to achieve roof collapse and the corresponding equilibrium contact size for full range of α.
Design, analysis and test of a novel cylinder-driven mode applied to microgripper
Authors: Chen Xiaodong , Xie ZM , Tan Huifeng 
Published: November 2021

Abstract
How to enlarge the output displacement is a key issue in the research field of microgrippers. It is difficult to further enlarge the output displacement for the traditional displacement transmission mechanism (DTM). In this research, a two-stage amplification cylinder-driven DTM based on the compliant mechanisms is designed to realize the displacement output expansion. The opening and closing of the clamping jaws is driven by the air cylinder to enlarge the output displacement of the microgripper. According to the analysis of statics model of the mechanism, the relationship between the output displacement of the microgripper and the driving pressure of the cylinder is established. The magnification of the microgripper is obtained using a dynamic model. Moreover, based on the finite element analysis, the mechanical structure parameters are optimized. The microgripper was fabricated by utilizing wire electro discharge machining (WEDM) technique, and then a series of experiments were carried out to obtain the relationship between the displacement and the driving pressure. It is found that the maximum output displacement measured is 1190.4μm under the pressure of 0-0.6 Mpa, corresponding to the magnification of 47.63. Compared with the results of finite element analysis and theoretical calculation, the test results have a discrepancy of 2.39% and 6.62%, respectively. The microgripper has successfully grasped a variety of micro-parts with irregular shapes, and parallel grasping can be achieved, demonstrating the potential application of this design in the field of micromanipulation.
Confined Transducer Geometries to Enhance Sensitivity to Thermal Boundary Conductance in Frequency-Domain Thermoreflectance Measurements
Authors: Warzoha Ronald J. , Wilson Adam A. , Donovan Brian F. , Clark Andy , Cheng Xuemei , An Lu , Lee Ezra , Liu Xiaosong , Feng Gang 
Published: November 2021

Abstract
Quantifying the resistance to heat flow across well-bonded, planar interfaces is critical in modern electronics packaging architectures, particularly as device length scales are reduced and power demands continue to grow unabated. However, very few experimental techniques are capable of measuring the thermal resistance across such interfaces due to limitations in the required measurement resolution provided by the characterization technique (i.e., Rth &lt; 0.1 mm2·K/W in steady-state configurations) and restrictions on the thermal penetration depth that can be achieved as a result of the heating event that is typically imposed on a sample’s surface (for optical pump-probe thermoreflectance techniques). A recent numerical fitting routine for Frequency-domain Thermoreflectance (FDTR) developed by the authors1 offers a potential avenue to rectify these issues if the transducer’s geometry can be confined. This work utilizes numerical simulations to evaluate the sensitivity of FDTR to a range of thermal boundary resistance (TBR) values as a function of the thermal resistance of adjacent material layers. Experimental measurements are performed across a handful of different material systems to validate our computational results and to demonstrate the the extent to which confined transducer geometries can improve our sensitivyt to the TBR across so-called “buried” interfaces when characterized with FDTR.
Experimental Investigation of Boiling Heat Transfer in a Liquid Chamber With Partially Soluble Nanofluids
Authors: Unno Noriyuki , Yuki Kazuhisa , Kibushi Risako , Nogita Rika , Mitani Atsuyuki 
Published: November 2021

Abstract
Boiling heat transfer (BHT) is a promising technique to remove a high heat flux emitted from next-generation electronic devices. However, critical heat flux (CHF) is a big problem in BHT because it restricts the maximum performance of the cooling devices using BHT. Nanofluid has been widely used to improve the CHF. In this study, the authors investigated the BHT of a compact cooling device at low pressure using a special nanofluid: that is made with partially soluble particles in water. The experimental result found that the CHF with the special nanofluid is 170 W/cm2 and is higher than that with nanofluid made with an insoluble nanoparticle.
Hotspot Cooling Performance for Submerged Confined Two-Phase Jet Impingement Cooling
Authors: Chowdhury Tanvir Ahmed , Putnam Shawn A. 
Published: November 2021

Abstract
Jet impingement can be particularly effective for removing high heat fluxes from local hotspots. Two-phase jet impingement cooling combines the advantage of both the nucleate boiling heat transfer with the single-phase sensible cooling. This study investigates two-phase submerged jet impingement cooling of local hotspots generated by a diode laser in a 100 nm thick Hafnium (Hf) thin-film on glass. The jet/nozzle diameter is ∼1.2 mm and the normal distance between the nozzle outlet and the heated surface is ∼3.2 mm. Novec 7100 is used as the coolant and the Reynolds numbers at the jet nozzle outlet range from 250 to 5000. The hotspot area is ∼ 0.06 mm2 and the applied hotspot-to-jet heat flux ranges from 20 W/cm2 to 220 W/cm2. This heat flux range facilitates studies of both the single-phase and two-phase heat transport mechanisms for heat fluxes up to critical heat flux (CHF). The temporal evolution of the temperature distribution of the laser heated surface is measured using infrared (IR) thermometry. This study also investigates the nucleate boiling regime as a function of the distance between the hotspot center and the jet stagnation point. For example, when the hotspot center and the jet are co-aligned (x/D = 0), the CHF is found to be ∼ 177 W/cm2 at Re ∼ 5000 with a corresponding heat transfer coefficient of ∼58 kW/m2.K. While the CHF is ∼ 130 W/cm2 at Re ∼ 5000 with a jet-to-hotspot offset of x/D ≈ 4.2.
CFD - Based Investigation of Effects of Obstruction in Front of Small Axial Cooling Fan and Deterioration of Supply Flow Rate
Authors: Fukuda Tetsushi , Masuda Yukio , Fukue Takashi , Sugimoto Yasuhiro , Hatakeyama Tomoyuki , Ishizuka Masaru , Koizumi Katsuhiro 
Published: November 2021

Abstract
This study describes the deterioration of a small axial fan’s supply flow rate in high-density packaging electronic equipment. A cooling fan flow rate can be predicted by its P-Q curve, which shows a relationship between a pressure rise at a fan (ΔP) and a supply flow rate (Q). However, in high-density packaging electronic equipment, the fan performance is affected by the mounting components around the fans, and the accurate prediction of the supply flow rate becomes difficult. This paper tried to do flow visualization around a small axial cooling fan’s impellers when the obstruction was mounted in front of the fan through CFD analysis. A relationship between the supply flow rate by the fan and the flow pattern around the impellers was investigated while changing the distance between the test fan and the obstruction. Through this study, the following results can be obtained. The fan’s flow is stable in the rotating stall region and the higher flow rate operating points regardless of whether or without the obstruction. At the lower flow rate conditions, the formation of a complex unsteady flow is reproduced. As the flow rate decreases, the flow’s separation point becomes closer to the leading edge of the impeller. In the case of obstruction, the change of the flow pattern causes a larger attack angle. As a result, fan performance is degraded.
Measuring the Thermal Contact Resistance Between Cu Foams and Substrates for On-Chip Cooling Applications in Data Centers
Authors: Arrivo Lucas , Schon Steven , Wemhoff Aaron P. 
Published: November 2021

Abstract
Data centers housing high performance computing equipment have large and growing rack densities, which pushes the limits of traditional air cooling technologies because of limited heat transfer coefficients. Therefore, on-chip cooling using so-called cold plates is emerging as a necessary cooling option for high-density electronics. The use of mini-channels or pins fins to enhance internal heat transfer area inside cold plates requires extensive micro-machining that is relatively time consuming and expensive for mass production. As an alternative approach, inserting and bonding pre-manufactured metal foams into hollow bodies are explored as a potentially inexpensive means to enhance the interior heat transfer area of cold plates. One key aspect of the performance of metal foams in cold plates is the thermal contact resistance in the bonding between the foam and the substrate. This project predicts the contact resistance using measurements of different foam types (pure Cu and Cu with oxide), porosities (63%, 80%, 93%, and 95%) and thicknesses (4 mm, 8 mm, and 10 mm). These measurements are carried out with and without the use of thermal interface material (TIM) pads. A theory is proposed and implemented to estimate the contact and foam thermal resistances, but further work is needed to gain confidence in the results. Observations suggest that different thermal behavior is seen for the Cu foams compared to the Cu with oxide foams, and that the use of TIM pads can achieve 10x to 40x reduction in overall thermal resistance for highly porous foams bonded on Cu substrates.
Temperature Cycling Study of Aerosol-Jet Printed Conductive Silver Traces in Printed Electronics
Authors: Zhao Beihan , Riso Christopher , Leslie David , Dasgupta Abhijit , Das Siddhartha , Fleischer Jason , Hines Daniel 
Published: November 2021

Abstract
Aerosol-Jet Printing (AJP) provides a new method for electronic component manufacturing. Understanding the reliability of electronics printed using the AJP process is essential to take full advantage of this technology and realize its industrial potential.
In the current study, we have designed and tested AJP printed samples and conducted failure analysis of those samples that have exhibited early failures. Failures first occurred in the short traces that connect the main traces to the silver pads, due to local stress-raisers caused by local geometric features in the printing geometry. Thermal-Mechanical Finite-Element-Modeling (FEM) has been performed to analyze the cyclic history of thermo-mechanical stress distribution and plastic strain distribution.
Transient Performance and Melt Front Characterization of Phase Change Materials
Authors: Stamps Tyler , Huitink David 
Published: November 2021

Abstract
Thermal management systems are often over-designed for average use in order to handle spikes in heat generation, which increases the spatial and financial requirements. One way to mitigate this is via the use of phase change materials (PCMs) as thermal buffers and storage media. This paper examines the melt front behavior of a common solid to liquid PCM, paraffin, experimentally and numerically. A 16 cm3 fully enclosed melting chamber was designed and constructed to observe the melt behavior via IR imaging. The chamber applies a constant temperature heat flux to one end of the sample and a constant temperature cold boundary on the other. ARL ParaPower was used for the numerical simulation. This tool models the convection in liquid PCM as an effective thermal conductivity parameter. The MATLAB-based program offers faster computation times than high fidelity commercial FEA tools. The experimental and numerical data are then compared via a custom MATLAB script which identifies the melt front and outputs the position and velocity over time for each test case. It was concluded that ParaPower adequately depicts the melt front behavior under this set of experimental conditions. This work enables future studies using the IR-transparent melt chamber designed herein.
A Hybrid Microporous Copper Structure for High Performance Capillary-Driven Liquid Film Boiling
Authors: Soroush Farid , Liu Tanya , Wu Qianying , Zhang Chi , Asheghi Mehdi , Goodson Kenneth E. , Marco Lorenz , Christian Egger , Martin Rittner 
Published: November 2021

Abstract
Phase change thermal management devices including heat pipes and ultra-thin vapor chambers can remove and spread the excess heat from microprocessors more efficiently compared with the conventional heat sinks. However, the capillary and CHF limits of the evaporator section remained a challenge for high heat flux (&gt; 100 Wcm−2) large area (&gt; 5 × 5 mm2) applications. In this study, a hybrid microporous structure consists of copper wire meshes (CWMs) as the liquid delivery routing and copper inverse opals (CIOs) film as the boiling/evaporation platform is proposed. The feasibility of the approach and the design optimization were studied with extensive modeling and CFD simulations. For the experiment setup, the heater and the RTD sensors are fabricated over a Silicon chip using the conventional micro fabrication processes and the micro porous copper film is deposited based on template-assisted electrodeposition, resulting in CIOs structure with average 5 μm pore size, 1 μm neck, and 15 μm thickness. A copper wire mesh structure (500 μm thickness, 0.5 porosity, 71 μm wire diameter) with 4 × 4 tile openings (1 × 1 mm2 area per tile) was fixed over the CIOs film with mechanical constraints. A flow loop and vapor chamber are designed and fabricated to perform capillary boiling experiments in a saturated environment (liquid water and vapor at ∼100°C). The hybrid microporous structure was able to remove over 75 W from the 5 × 5 mm2 heater area (over 300 W cm−2 heat flux) with 9°C super heat resulting in thermal resistance of 0.03 cm2°CW−1 at the CHF. The findings of this study are largely beneficial for the design and fabrication of high performance evaporator wicks and next-generation heat routing technologies.
Reliable Additive Manufacturing Using Transient Liquid Phase Sintering
Authors: Nave Gilad , Buxbaum Clifton , McCluskey F. Patrick 
Published: November 2021

Abstract
Additive manufacturing is rapidly revolutionizing the way products are designed and built. Its advantages in terms of mobile manufacturing, mass customization, part reduction, waste reduction, and just-in-time sparing are causing it to be considered for many electronics applications. Many of these applications require high thermal and electrical conductivity and high strength in harsh environments. Such applications would benefit greatly from additive manufacturing of metals. However, the number of metal systems that can be successfully manufactured this way is small, with some of the highest conductivity metals (e.g. Cu, Ag) being particularly difficult. Two ways of depositing metals dominate the market. The first is direct ink writing (DIW). The other common technique is laser sintering, including direct metal laser sintering (DMLS). While the DIW process is fine in principle, the inks typically used are not optimized for harsh applications, and produce a voided and porous layer that limits the thermal and electrical conductivity. Laser sintering must be done in vacuum and requires that the laser raise the temperature of the powder to around 500°C which can result in damage to the substrate. Furthermore, this process is expensive, lacks mobility, and consumes significant energy.
This paper will discuss a new form of metal additive manufacturing that addresses the shortcomings of current direct writing and laser sintering approaches by making use of the transient liquid phase sintering process. During the TLPS process, low melting point semimetal powder of Indium will be melted at a temperature of 300°C. This liquid will then surround and diffuse with high melting temperature metal powders forming intermetallic compounds at the solid-liquid interface. These intermetallics possess a higher melting point than the low temperature semimetal. The paper will demonstrate the use of this technique to make reliable 2D lines and 3D structures. It will also discuss the deposition and sintering process and its effect on the adhesion strength, thermal conductivity, and electrical resistivity of the resulting structures.
Enhanced Processability and Thermal Fatigue Reliability With Low Melting Point SnBi Solder Alloy LMPA-Q
Authors: Vandevelde Bart , Nawghane Chinmay , Labie Riet , Lauwaert Ralph , Werkhoven Daniel 
Published: November 2021

Abstract
SnBi based solder alloys become an interesting alternative for standard SnAgCu as they can be used to solder components at much lower temperature. The typically 50°C lower solder reflow temperature is less damaging for PCB and components, and also prevents hot tear and head-in-pillow failures for large fine pitch BGA components. A reasonable concern for these low-melting temperature solders is the thermal cycling reliability performance, in particular for harsh conditions such as automotive products. In this work, thermal cycling testing and failure analysis have been performed on 9 × 9 mm size QFN components and large chip components (2010 and 2512) which are typically sensitive to thermal fatigue. The results are benchmarked to standard SAC alloy. Also the process advantages from the low temperature solder alloys are depicted in this paper. Finally, the effect of Pb contamination on this SnBi based solder is investigated.
Optimizing Closed-Loop Liquid Cooling Solution for Extreme High Power Multi-Packages
Authors: Panigrahy Arunima , Subrahmanyam Prabhakar , Pang Ying-Feng , Sahan Ridvan , Xia Amy 
Published: November 2021

Abstract
Current technological developmental efforts for high performing liquid assisted air-cooling solution (LAAC) is presented in this research. The roadmap needs of high-power packages such as client, datacenter and graphics product segments are addressed. Systematic evaluation and qualification process for developing cost effective LAAC solutions to provide cooling capabilities for multiple socketed packages are also discussed. This effort includes qualifying high performing heat exchanger (finned radiator) and cold plate with different fin designs. Thermal simulations were conducted and correlated with experimental data. The concept of power density approach is introduced for predicting the cooling capability of newly developed LAAC solution for different lidded package form factors. The paper presents supporting data of performance evaluation from graphics segment that extends the solution capability to data center segment. The technology developed here will address the increasing cooling capability needed for future products with high power dissipation and multiple socket cooling configuration.
Microchannel Heat Sink for Thermal Management of Concentrated Photovoltaic Cells
Authors: Varghese Dinumol , Sefelnasr Ahmed , Sherif Mohsen , Alnaimat Fadi , Mathew Bobby 
Published: November 2021

Abstract
This article conceptualizes a single-phase microchannel heat sink for thermal management of concentrated photovoltaic cells; details of the model-based parametric study that is carried out on the heat sink is also detailed in this article. The heat sink consists of multiple serpentine microchannels. The mathematical model consists of continuity equation, Navier-Stokes equations and energy equations. Fluent module of Ansys Workbench is used for solving the model. The performance of the device is quantified in terms two metrics such as thermal resistance and pumping power. Studies are done for Reynolds number ranging from 100 to 1250. It is observed that increase in Reynolds number decreases the thermal resistance while increasing the pumping power irrespective of the geometric parameters of the heat sink. Decrease in hydraulic diameter of the microchannel reduces the thermal resistance while increasing the pumping power. Increase in the length segment of the serpentine microchannel increases and decreases the thermal resistance and pumping power, respectively. With increase in the offset width of the serpentine microchannel the thermal resistance and pumping power decreases and increases, respectively.