scholarly journals A Performance-Enhanced Liquid Metal-Based Microheater with Parallel Ventilating Side-Channels

Micromachines ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 133
Author(s):  
Lunjia Zhang ◽  
Pan Zhang ◽  
Ronghang Wang ◽  
Renchang Zhang ◽  
Zhenming Li ◽  
...  
Keyword(s):  
Liquid Metal ◽  
Mechanical Stability ◽  
Micro Electro Mechanical System ◽  
The Novel ◽  
Heating Channel ◽  
Excellent Performance ◽  
Bending Tests ◽  
Metal Heating ◽  
Flat Surfaces ◽  
Side Channels

Gallium-based liquid metal can be used as a material for microheaters because it can be easily filled into microchannels and electrified to generate Joule heat, but the liquid metal-based microheater will suffer breakage induced by voids forming within the liquid metal when the temperature normally gets higher than 100 °C. To resolve this problem, a novel liquid metal-based microheater with parallel ventilating side-channels is presented. It consists of a liquid-metal heating channel and two parallel ventilating side-channels. The heating channel is connected with the side-channels by small gaps between polydimethylsiloxane (PDMS) posts. Experimental results show that this novel microheater can be heated up to 200 °C without damage. To explain its excellent performance, an experiment is performed to discover the development of the voids within the liquid-metal heating channel, and two reasons are put forward in this work on the basis of the experiment. Afterward pressing and bending tests are conducted to explore the mechanical stability of the novel microheaters. Finally, the microheaters are applied to warm water to show their good flexibility on non-flat surfaces. In consequence, the novel liquid metal-based microheater is believed to be widely applicable to soft micro-electro-mechanical system(MEMS) heating devices.

scholarly journals Mechanical Stability of Hybrid Corrugated Sandwich Plates under Fluid-Structure-Thermal Coupling for Novel Thermal Protection Systems

2020 ◽  
Vol 10 (8) ◽  
pp. 2790
Author(s):  
Wenzheng Zhuang ◽  
Chao Yang ◽  
Zhigang Wu
Keyword(s):  
Mechanical Stability ◽  
Thermal Protection ◽  
Element Model ◽  
Parameter Study ◽  
The Novel ◽  
Thermal Coupling ◽  
Mechanical Instability ◽  
Fluid Structure ◽  
Thermal Protection Systems ◽  
Protection Systems

Hybrid corrugated sandwich (HCS) plates have become a promising candidate for novel thermal protection systems (TPS) due to their multi-functionality of load bearing and thermal protection. For hypersonic vehicles, the novel TPS that performs some structural functions is a potential method of saving weight, which is significant in reducing expensive design/manufacture cost. Considering the novel TPS exposed to severe thermal and aerodynamic environments, the mechanical stability of the HCS plates under fluid-structure-thermal coupling is crucial for preliminary design of the TPS. In this paper, an innovative layerwise finite element model of the HCS plates is presented, and coupled fluid-structure-thermal analysis is performed with a parameter study. The proposed method is validated to be accurate and efficient against commercial software simulation. Results have shown that the mechanical instability of the HCS plates can be induced by fluid-structure coupling and further accelerated by thermal effect. The influences of geometric parameters on thermal buckling and dynamic stability present opposite tendencies, indicating a tradeoff is required for the TPS design. The present analytical model and numerical results provide design guidance in the practical application of the novel TPS.

scholarly journals A Novel 4H-SiC MESFET with a Heavily Doped Region, a Lightly Doped Region and an Insulated Region

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 488
Author(s):  
Hujun Jia ◽  
Mengyu Dong ◽  
Xiaowei Wang ◽  
Shunwei Zhu ◽  
Yintang Yang
Keyword(s):  
Breakdown Voltage ◽  
Direct Current ◽  
Oscillation Frequency ◽  
The Novel ◽  
Saturation Current ◽  
Excellent Performance ◽  
Maximum Oscillation Frequency ◽  
Power Added Efficiency ◽  
Novel Structure ◽  
Heavily Doped

A novel 4H-SiC MESFET was presented, and its direct current (DC), alternating current (AC) characteristics and power added efficiency (PAE) were studied. The novel structure improves the saturation current (Idsat) and transconductance (gm) by adding a heavily doped region, reduces the gate-source capacitance (Cgs) by adding a lightly doped region and improves the breakdown voltage (Vb) by embedding an insulated region (Si3N4). Compared to the double-recessed (DR) structure, the saturation current, the transconductance, the breakdown voltage, the maximum oscillation frequency (fmax), the maximum power added efficiency and the maximum theoretical output power density (Pmax) of the novel structure is increased by 24%, 21%, 9%, 11%, 14% and 34%, respectively. Therefore, the novel structure has excellent performance and has a broader application prospect than the double recessed structure.

scholarly journals Understanding Screaming Channels: From a Detailed Analysis to Improved Attacks

2020 ◽  
pp. 358-401
Author(s):  
Giovanni Camurati ◽  
Aurélien Francillon ◽  
François-Xavier Standaert
Keyword(s):  
Spatial Diversity ◽  
Low Noise ◽  
Security Evaluation ◽  
The Novel ◽  
Proof Of Concept ◽  
Wireless Devices ◽  
Side Channels ◽  
Security Evaluations ◽  
The One

Recently, some wireless devices have been found vulnerable to a novel class of side-channel attacks, called Screaming Channels. These leaks might appear if the sensitive leaks from the processor are unintentionally broadcast by a radio transmitter placed on the same chip. Previous work focuses on identifying the root causes, and on mounting an attack at a distance considerably larger than the one achievable with conventional electromagnetic side channels, which was demonstrated in the low-noise environment of an anechoic chamber. However, a detailed understanding of the leak, attacks that take full advantage of the novel vector, and security evaluations in more practical scenarios are still missing. In this paper, we conduct a thorough experimental analysis of the peculiar properties of Screaming Channels. For example, we learn about the coexistence of intended and unintended data, the role of distance and other parameters on the strength of the leak, the distortion of the leakmodel, and the portability of the profiles. With such insights, we build better attacks. We profile a device connected via cable with 10000·500 traces. Then, 5 months later, we attack a different instance at 15m in an office environment. We recover the AES-128 key with 5000·1000 traces and key enumeration up to 223. Leveraging spatial diversity, we mount some attacks in the presence of obstacles. As a first example of application to a real system, we show a proof-of-concept attack against the authentication method of Google Eddystone beacons. On the one side, this work lowers the bar for more realistic attacks, highlighting the importance of the novel attack vector. On the other side, it provides a broader security evaluation of the leaks, helping the defender and radio designers to evaluate risk, and the need of countermeasures.

A Novel Brazing Technique for Aluminum and Other Metals

1993 ◽  
Vol 314 ◽  
Author(s):  
Roland S. Timsit ◽  
B. J. Janeway
Keyword(s):  
Liquid Metal ◽  
Filler Metal ◽  
Surface Film ◽  
The Novel ◽  
Nitrogen Gas ◽  
Metallurgical Bond ◽  
Joint Assembly

AbstractIn the novel brazing technique, the aluminum components in the joint assembly are coated with a powder mix consisting of elemental Si and a potassium fluoroaluminate flux. During brazing at −600°C in nitrogen gas, the flux melts and removes the native Al2O3 surface film from the coated aluminum components. This action allows the silicon to diffuse into the aluminum to generate in-situ a layer of Al-Si filler metal of eutectic composition.The liquid metal then flows into thejoint and yields a metallurgical bond on cooling.This brazing technique maybe exploited with aluminum using intermediary elements other than Si. The technique may also be used for joining other metals.

Enhancement of heat transfer in a square channel by roughened surfaces in rib-elements and turbulent flow manipulation

2017 ◽  
Vol 27 (7) ◽  
pp. 1571-1595 ◽  
Author(s):  
Jian Liu ◽  
Gongnan Xie ◽  
Bengt Ake Sunden ◽  
Lei Wang ◽  
Martin Andersson
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Research Work ◽  
Flow Characteristics ◽  
High Heat ◽  
The Novel ◽  
Content Type ◽  
Flat Surfaces ◽  
Square Channel ◽  
High Heat Transfer

Purpose The purpose of this paper is to augment heat transfer rates of traditional rib-elements with minimal pressure drop penalties. Design/methodology/approach The novel geometries in the present research are conventional cylindrical ribs with rounded transitions to the adjacent flat surfaces and with modifications at their bases. All turbulent fluid flow and heat transfer results are presented using computation fluid dynamics with a validated v2f turbulence closure model. Turbulent flow characteristics and heat transfer performances in square channels with improved ribbed structures are numerically analyzed in this research work. Findings Based on the results, it is found that rounded transition cylindrical ribs have a large advantage over the conventional ribs in both enhancing heat transfer and reducing pressure loss penalty. In addition, cylindrical ribs increase the flow impingement at the upstream of the ribs, which will effectively increase the high heat transfer areas. The design of rounded transition cylindrical ribs and grooves will be an effective way to improve heat transfer enhancement and overall thermal performance of internal channels within blade cooling. Originality/value The novel geometries in this research are conventional cylindrical ribs with rounded transitions to the adjacent flat surfaces and with modifications at their bases. The combination of cylindrical ribs and grooves to manipulate the turbulent flow.

Computational study on unconventional superconductivity and mechanical properties of novel antiferrromagnetic (Ca,Sr,Ba)Fe2Bi2 compounds

2019 ◽  
Vol 33 (28) ◽  
pp. 1950341
Author(s):  
D. S. Jayalakshmi ◽  
M. Sundareswari ◽  
E. Viswanathan ◽  
D. Hemanand ◽  
Venkat Pranesh
Keyword(s):  
Free Energy ◽  
Transport Theory ◽  
Mechanical Stability ◽  
Computational Study ◽  
Anisotropy Constant ◽  
Coupling Factor ◽  
The Novel ◽  
Electron Phonon Coupling ◽  
Constant Relaxation Time ◽  
Electron Transport Properties

The ab initio calculation is performed to investigate about the structural and the electron transport properties of the experimentally reported (parent) compounds viz., BaFe2As2, SrFe2As2, CaFe2As2 and the novel compounds which are anticipated from our computational work namely BaFe2Bi2, SrFe2Bi2, CaFe2Bi2 with different magnetic order. The space group of the reported compounds is I4/mmm (139) and belong to ThCr2Si2 type. The formation energies of the reported compounds are compared in the anti-ferromagnetic (AFM), nonmagnetic (NM) and ferromagnetic (FM) orders. From the comparison, it reveals that the anti-ferro magnetism is the stabled state for the reported compounds. At ambient temperature with constant relaxation time, the resistivity, power factor, Seebeck coefficient and electrical conductivity are computed by using BoltzTraP transport theory code. To explain the superconducting nature of the novel compounds the transition temperature (T[Formula: see text]), electron–phonon coupling factor and Debye temperature are calculated and presented. The mechanical stability of the compounds is examined by using Young’s, bulk and shear modulus, anisotropy constant and Poisson’s ratio which are calculated by using Tetra-elastic code. The Mechanical Temperament of these compounds is analyzed by using Pugh’s ratio. The ELATE tool is used to visualize the elastic properties of these compounds. The thermodynamical stability of the compounds is examined by using Gibbs free energy, vibrational Helmholtz free energy and entropy which are calculated by using Gibbs2 code. All the properties of the theoretically predicted (novel) compounds are analyzed and compared with their parent (experimentally reported) compounds.

The Properties And Performance Of Micro-Tubular (Less Than 1mm Od) Anode Supported SOFC's For APU-Applications

2008 ◽  
Vol 1106 ◽  
Author(s):  
Jung-Hoon Song ◽  
Brycen Roy ◽  
Kevin Galloway ◽  
Nigel Sammes ◽  
Toshio Suzuki
Keyword(s):  
Mechanical Properties ◽  
Solid Oxide Fuel Cells ◽  
Mechanical Test ◽  
Impedance Measurement ◽  
Future Generation ◽  
Cell Performance ◽  
The Novel ◽  
Excellent Performance ◽  
And Performance ◽  
Anode Support

AbstractMicro tubular solid oxide fuel cells (SOFCs) have many desirable advantages compared to general SOFC. Recently, microtubualr SOFC are now studied to apply into APU system in a future generation vehicles. In this study, electrochemical and mechanical properties of the micro tubular SOFCs (less than 1 mm O.D.) have been characterized. Electrochemical characterization showed the excellent performance of MT SOFC with the power density of 1 W/cm2 at 600°C. Impedance measurement indicated that the contribution of contact resistance on the cell performance was still high and there were many possibilities to improve the cell performance. Mechanical test of the MT-SOFC using burst testing apparatus indicated the mechanical properties were mainly dependent on porosity and wall thickness, i.e. physical properties of anode support. This study examined the properties of micro-tubular SOFC using the novel characterization method for APU application.

Tribology in Full View

MRS Bulletin ◽  
2008 ◽  
Vol 33 (12) ◽  
pp. 1168-1173 ◽  
Author(s):  
Laurence D. Marks ◽  
Oden L. Warren ◽  
Andrew M. Minor ◽  
Arno P. Merkle
Keyword(s):  
Contact Mechanics ◽  
Mechanical Stability ◽  
Fundamental Problem ◽  
Interface Problem ◽  
The Novel ◽  
Sensors And Actuators ◽  
Force Sensitivity ◽  
Transmission Electron ◽  
New Information

AbstractFor many years, a fundamental problem in contact mechanics, both tribology and indentation problems, has been the inability to see what is taking place—the buried-interface problem. Over the past few years, there have been developments whereby it has become possible to perform contact mechanics experimentsin situwithin a transmission electron microscope. These new experiments have been enabled by both the miniaturization of sensors and actuators and improvements in their mechanical stability and force sensitivity. New information is now becoming available about the nanoscale processes of sliding, wear, and tribochemical reactions, as well as microstructural evolution during nanoindentation such as dislocation bursts and phase transformations. This article provides an overview of some of these developments, in terms of both the advances in technical instrumentation and some of the novel scientific insights.

scholarly journals A Photolabile Fe Catalyst for Light-Triggered Alkyd Paint Curing

2021 ◽  
Author(s):  
Johan Bootsma ◽  
Wesley R Browne ◽  
Jitte Flapper ◽  
Bas de Bruin
Keyword(s):  
Transition Metal ◽  
The Novel ◽  
Excellent Performance ◽  
Neutral Complex ◽  
Drying Time ◽  
Alkyd Paint ◽  
Active Complex ◽  
Spectral Changes ◽  
Fe Catalyst ◽  
Wide Range

In search for cobalt replacements for alkyd paint curing we show that the photo-active complex [(Cp)Fe(C<sub>6</sub>H<sub>6</sub>)]+ (Cp = cyclopentadienyl) acts as a latent catalytic drier that allows for photochemical control over the onset of curing, without the need for anti-skinning agents such as the volatile MEKO normally used to prevent curing during paint storage. The highly soluble neutral complex [(Cp)Fe(Ch)] (Ch = cyclohexadienyl) readily converts to the photo-active complex [(Cp)Fe(C<sub>6</sub>H<sub>6</sub>)]<sup>+</sup> upon oxidation in alkyd, allowing the latter to be dosed in a wide range of concentrations. Infrared and Raman studies show similar spectral changes of the alkyd paint matrix as have been observed in alkyd curing mediated by the known commercial cobalt- and manganese-based driers Durham NUODEX® Cobalt 10 Neo and NUODEX® DryCoat. The new [(Cp)Fe(Ch)] / [(Cp)Fe(C<sub>6</sub>H<sub>6</sub>)]<sup>+</sup> system performs equally well as both commercial paint driers in terms of drying time, and outperforms NUODEX® DryCoat by showing a hardness development (increase) similar to the cobalt-based drier. Based on an observed light-dark on/off effect and EPR studies we propose that photolysis of [(Cp)Fe(C<sub>6</sub>H<sub>6</sub>)]+ generates short-lived active Fe<sup>II</sup> species, explaining the excellent latency. The novel alkyd curing system [(Cp)Fe(Ch)] / [(Cp)Fe(C<sub>6</sub>H<sub>6</sub>)]<sup>+</sup> presented herein is the first example of an intrinsically latent paint curing catalyst that is: (1) based on an abundant and harmless transition metal (Fe), (2) doesn’t require any anti-skinning agents, and (3) shows excellent performance in terms of drying times and hardness development. <br>

scholarly journals Maize brace root biomechanics are determined by geometry within a genotype and material properties between genotypes

2019 ◽  
Author(s):  
Lindsay Erndwein ◽  
Elahe Ganji ◽  
Ashley N. Hostetler ◽  
Adam Stager ◽  
Megan L. Killian ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Zea Mays ◽  
Material Properties ◽  
Growth Stage ◽  
Yield Loss ◽  
Mechanical Stability ◽  
Bending Tests ◽  
Bending Modulus ◽  
Root Biomechanics

ABSTRACTCrop plants are susceptible to yield loss by mechanical failure, which is called lodging. In maize (Zea mays), aerial nodal brace roots impart mechanical stability to plants, with previous studies showing that the lowest whorl of brace roots contributes the most. The features of brace roots that determine their contribution to mechanical stability are poorly defined. Here we tested the hypothesis that brace root mechanical properties vary between whorls, which may influence their contribution to mechanical stability. 3-point bending tests were used to determine that brace roots from the lowest whorl have the highest structural mechanical properties regardless of growth stage, and that these differences are largely due to brace root geometry within a genotype. Analysis of the brace root bending modulus determined that differences between genotypes are attributable to both geometry and material properties. These results support the role of brace root biomechanics to determine the brace root contribution to mechanical stability.HIGHLIGHTBrace root biomechanics vary within and between genotypes. These results support the importance of biomechanics to define the contribution of brace roots to mechanical stability.

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