Transient Marangoni convection in hanging evaporating drops

Abstract. A combined experimental and numerical analysis has been carried out to study Marangoni effects during the evaporation of droplets. The experiments are performed with pendant drops of silicone oils (with different viscosities) and hydrocarbons. The temperature of the disk sustaining the drop is rapidly increased or decreased in order to study transient heating or cooling processes. The velocity field in the droplet is evaluated monitoring the motion of tracers in the meridian plane, using a laser sheet illumination system and a video camera. Surface temperature distributions of the drops are detected by infrared thermocamera. The numerical model is based on axisymmetric Navier-Stokes equations, taking into account the presence of Marangoni shear stresses and evaporative cooling at the liquid-air interface. Marangoni flows cause a larger, more uniform surface temperature, increasing heat transfer from disk to droplet, as well as evaporation rate. When Marangoni effects are negligible, larger surface temperature differences occur along the drop surface and heat transfer is relatively small. The role of Marangoni and buoyancy flows in silicone oils with different viscosities and hydrocarbons is discussed and correlations are presented between experimental and numerical results. Keywords: Viscosity of liquids; diffusive momentum transport, Evaporation and condensation, Surface tension and related phenomena, Flows in ducts, channels, nozzles, and conduit

Buoyancy and surface tension-driven convection around a bubble

A combined experimental and numerical analysis has been carried out to study the behavior of a bubble under a horizontal heated surface. In this configuration, the interaction between buoyancy and surface tension driven convection produces complex fluid dynamic structures. An instability occurs in the form of an oscillatory three-dimensional fluctuation of the thermal and velocity field when a critical temperature difference is exceeded. The structure of this flow regime has been investigated with transient three-dimensional simulations carried out for normal gravity and zero gravity conditions. The velocity field around the bubble has been experimentally analyzed with a ``laser sheet'' technique for the flow visualization and a Wollaston prism interferometer has been utilized to capture the oscillatory temperature field. Good correlations are shown between experimental and numerical results. Keywords: Thermal convection, Buoyancy-driven instabilities, Surface-tension-driven instability, Interaction

Temperature uniformity in cross-flow double-layered microchannel heat sinks

An in-house finite element method (FEM) procedure is used to carry out a numerical study on the thermal behavior of cross-flow double-layered microchannel heat sinks with an unequal number of microchannels in the two layers. The thermal performance is compared with those yielded by other more conventional flow configurations. It is shown that if properly designed, i.e., with several microchannels in the top layer smaller than that in the bottom layer, cross-flow double-layered microchannel heat sinks can provide an acceptable thermal resistance and a reasonably good temperature uniformity of the heated base with a header design that is much simpler than that required by the counter-flow arrangement

Molecular diagnosis of grapevine fleck virus

A digoxigenin-labelled riboprobe was developed for the detection of grapevine fleck virus (GFkV) in infected tissues of grapevine leaves, roots and canes. The probe was GFkV-specific and was successfully used for virus identification both with dot spot assays, using alkali-treated crude sap, and tissue blot assays, using cross and longitudinal sections of leaf petioles. Primers designed for the amplification by reverse transcription-polymerase chain reaction of a viral genome fragment 243 nucleotides in size, gave also positive and repeatable results. These newly developed molecular-based detection tools extend the range of available procedures for the sensitive identification of GFkV in naturally infected hosts

Guest Editorial: Special section on emerging trends and computing paradigms for testing, reliability and security in future VLSI systems

With the rapid advancement of computing technologies in all domains (i.e., handheld devices, autonomous vehicles, medical devices, and massive supercomputers), testability, reliability and security of electronic systems are crucial issues to guarantee safeness of human life. Emerging technologies coupled with new computing paradigms (e.g., approximate computing, neuromorphic computing, in-memory computing) are together exacerbating these problems posing significant challenges to researchers and designers. To address this increased complexity in the hardware testing/reliability/security domain, it is imperative to employ design and analysis methods working at all levels of abstraction, starting from the system level down to the gate level. In this context, the selected papers span from the important field of the yield analysis and modeling, which is becoming fundamental for the manufacturing of modern technologies to the error detection, correction and recovery when the new devices are operative on field. At the same time, papers do not forget that the fault tolerance can be achieved by a cross-layer approach to the dependability that includes the analysis of the effect of faults and the techniques and methodologies to deploy more resilient devices by means of hardening of the design. Eventually, the dependability of the systems is nowadays deeply linked with the security aspects, including the impact on the design trade-offs and the test and validation. The IEEE VLSI Test Symposium (VTS) invited the highest-ranked papers to be included in this special issue of IEEE Transactions on Emerging Technologies in Computing (TETC) in 2020. All aspects of design, manufacturing, test, monitoring and securing of systems affected by defects and malicious attacks are covered by the accepted paper. It is our great pleasure to publish this special issue containing 12 high-quality papers covering all aspects of the emerging trends on testing and reliability: - FTxAC: Leveraging the Approximate Computing Paradigm in the Design of Fault-Tolerant Embedded Systems to Reduce Overheads by Aponte-Moreno, Alexander; Restrepo-Calle, Felipe; Pedraza, Cesar, the design of Fault-Tolerant systems is exploited by means of approximate computing techniques to reduce the implicit overhead of the common redundancy. - A Statistical Gate Sizing Method for Timing Yield and Lifetime Reliability Optimization of Integrated Circuits by Ghavami, Behnam; Ibrahimi, Milad; Raji, Mohsen, the reliability of CMOS devices is improved tackling the joint effect of process variation and transistor aging. - 3D Ring Oscillator based Test Structures to Detect a Trojan Die in a 3D Die Stack in the Presence of Process Variations by Alhelaly, Soha; Dworak, Jennifer; Nepal, Kundan; Manikas, Theodore; Gui, Ping; Crouch, Alfred, the issue of Trojan insertion into 3D integrated circuits has been explored from the use of in-stack circuitry and various testing procedures point of view, showing their detection capability. - Defect Analysis and Parallel Testing for 3D Hybrid CMOS-Memristor Memory by Liu, Peng; You, Zhiqiang; Wu, Jigang; Elimu, Michael; Wang, Weizheng; Cai, Shuo; Han, Yinhe, a new parallel March-like test is proposed to test CMOS Molecular architectures. - Attacks toward Wireless Network-on-Chip and Countermeasures by Biswas, Arnab Kumar; Chatterjee, Navonil; Mondal, Hemanta; Gogniat, Guy; DIGUET, Jean-Philippe, Wireless Network-on-Chip security vulnerabilities are described and their countermeasures proposed. - A Novel TDMA-Based Fault Tolerance Technique for the TSVs in 3D-ICs Using Honeycomb Topology (by Ni, Tianming; Yang, Zhao; Chang, Hao; Zhang, Xiaoqiang; Lu, Lin; Yan, Aibin; Huang, Zhengfeng; Wen, Xiaoqing) proposes a chain-type time division multiplexing access (TDMA)-based fault tolerance technique showing huge area overheads reduction. - Design and analysis of secure emerging crypto-hardware using HyperFET devices by Delgado-Lozano, Ignacio María; Tena-Sánchez, Erica; Núñez, Juan; Acosta, Antonio J., Power Analysis attacks against FinFET device have been tackled by incorporating HyperFET devices to deliver an x25 factor security level improvement. - Detection, Location, and Concealment of Defective Pixels in Image Sensors by TAKAM TCHENDJOU, Ghislain; SIMEU, Emmanuel, image sensors are empowered with online diagnosis and self-healing methods to improve their dependability. - Defect and Fault Modeling Framework for STT-MRAM Testing by Wu, Lizhou; Rao, Siddharth; Taouil, Mottaqiallah; Cardoso Medeiros, Guilherme; Fieback, Moritz; Marinissen, Erik Jan; Kar, Gouri Sankar; Hamdioui, Said, a framework to derive accurate STT-MRAM fault models is described, together with its employment to model resistive defects in interconnect and pinhole defects in MTJ devices, allowing test solutions for detecting those defects. - Online Safety Checking for Delay Locked Loops via Embedded Phase Error Monitor by Huang, Shi-Yu; Chu, Wei, the Automotive Safety Integrity Level (ASIL) is targeted by proposing a phase error monitoring scheme for Delay-Locked Loops (DLLs). - Protecting Memories against Soft Errors: The Case for Customizable Error Correction Codes by Li, Jiaqiang; Reviriego, Pedro; Xiao, Li; Wu, Haotian, the memory protection is supported by a tool able to automate the error correction code design. - Autonomous Scan Patterns for Laser Voltage Imaging by Tyszer, Jerzy; Cheng, Wu-Tung; Milewski, Sylwester; Mrugalski, Grzegorz; Rajski, Janusz; Trawka, Maciej, authors demonstrate how to reuse on-chip EDT compression environment to generate and apply Laser Voltage Imaging-aware scan patterns for advanced contactless test procedures. We sincerely hope that you enjoy reading this special issue, and would like to thank all authors and reviewers for their tremendous efforts and contributions in producing these high-quality articles. We also take this opportunity to thank the IEEE Transactions on Emerging Topics in Computing (TETC) Editor-in-Chief (EIC) Prof. Cecilia Metra, past Associate Editor Ramesh Karri, the editorial board, and the entire editorial staff for their guidance, encouragement, and assistance in delivering this special issue

Large fluctuations of the nonlinearities in isotropic turbulence. Anisotropic filtering analysis

Using a Navier–Stokes isotropic turbulent field numerically simulated in a box with a discretization of 10243 (Biferale et al., 2005), we show that the probability of having a stretching–tilting larger than a few times the local enstrophy is low. By using an anisotropic kind of filter in the Fourier space, where wavenumbers that have at least one component below a threshold or inside a range are removed, we analyze these survival statistics when the large, the small inertial or the small inertial and dissipation scales are filtered out. By considering a flow obtained by randomizing the phases of the Fourier modes, and applying our filtering techniques, we identified clearly the properties attributable to turbulence. It can be observed that, in the unfiltered isotropic Navier–Stokes field, the probability of the ratio (|ω·∇U|/|ω|2) being higher than a given threshold is higher than in the fields where the large scales were filtered out. At the same time, it is lower than in the fields where the small inertial and dissipation range of scales is filtered out. This is basically due to the suppression of compact structures in the ranges that have been filtered in different ways. The partial removal of the background of filaments and sheets does not have a first order effect on these statistics. These results are discussed in the light of a hypothesized relation between vortical filaments, sheets and blobs in physical space and in Fourier space. The study in fact can be viewed as a kind of test for this idea and tries to highlight its limits. We conclude that a qualitative relation in physical space and in Fourier space can be supposed to exist for blobs only. That is for the near isotropic structures which are sufficiently described by a single spatial scale and do not suffer from the disambiguation problem as filaments and sheets do. Information is also given on the filtering effect on statistics concerning the inclination of the strain rate tensor eigenvectors with respect to vorticity. In all filtered ranges, eigenvector 2 reduces its alignment, while eigenvector 3 reduces its misalignment. All filters increase the gap between the most extensional eigenvalue ⟨λ1⟩ and the intermediate one ⟨λ2⟩ and the gap between this last ⟨λ2⟩ and the contractile eigenvalue ⟨λ3⟩. When the large scales are missing, the modulus of the eigenvalue 1 becomes nearly equal to that of the eigenvalue 3, similarly to the modulus of the associated components of the enstrophy production

A Novel Survey Tool to Quantify the Degree and Duration of STEMI Regionalization Across California.

IntroductionCalifornia has been a global leader in regionalization efforts for time-critical medical conditions. A total of 33 local emergency medical service agencies (LEMSAs) exist, providing an organized EMS framework across the state for almost 40 years. We sought to develop a survey tool to quantify the degree and duration of ST-elevation myocardial infarction (STEMI) regionalization over the last decade in California.MethodsThe project started with the development of an 8-question survey tool via a multi-disciplinary expert consensus process. Next, the survey tool was distributed at the annual meeting of administrators and medical directors of California LEMSAs to get responses valid through December, 2014. The first scoring approach was the Total Regionalization Score (TRS) and used answers from all 8 questions. The second approach was called the Core Score, and it focused on only 4 survey questions by assuming that the designation of STEMI Receiving Centers must have occurred at the beginning of any LEMSA's regionalization effort. Scores were ranked and grouped into tertiles.ResultsAll 33 LEMSAs in California participated in this survey. The TRS ranged from 15 to 162. The Core Score range was much narrower, from 2 to 30. In comparing TRS and Core Score rankings, the top-tertiles were quite similar. More rank variation occurred between mid- and low-tertiles.ConclusionThis study evaluated the degree and duration of STEMI network regionalization from 2004 to 2014 in California, and ranked 33 LEMSAs into tertiles based upon their TRS and their Core Score. Successful application of the 8-item survey and ranking strategies across California suggests that this approach can be used to assess regionalization in other states or countries around the world

Approximate computing design exploration through data lifetime metrics

When designing an approximate computing system, the selection of the resources to modify is key. It is important that the error introduced in the system remains reasonable, but the size of the design exploration space can make this extremely difficult. In this paper, we propose to exploit a new metric for this selection: data lifetime. The concept comes from the field of reliability, where it can guide selective hardening: the more often a resource handles "live" data, the more critical it be-comes, the more important it will be to protect it. In this paper, we propose to use this same metric in a new way: identify the less critical resources as approximation targets in order to minimize the impact on the global system behavior and there-fore decrease the impact of approximation while increasing gains on other criteria