检索结果-内蒙古大学图书馆

Active doping controls the mode of failure in dense colloidal gels

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Zhou, Tingtao Brady, John F. Division of Chemistry and Chemical Engineering California Institute of Technology United States Division of Engineering and Applied Science California Institute of Technology United States

Mechanical properties of disordered materials are governed by their underlying free energy landscape. In contrast to external fields, embedding a small fraction of active particles within a disordered material generates non-equilibrium internal fields, which can help to circumvent kinetic barriers and modulate the free energy landscape. In this work, we investigate through computer simulations how the activity of active particles alters the mechanical response of deeply annealed polydisperse colloidal gels. We show that the’swim force’ generated by the embedded active particles is responsible for determining the mode of mechanical failure, i.e., brittle vs. ductile. We find, and theoretically justify, that at a critical swim force the mechanical properties of the gel decrease abruptly, signaling a change in the mode of mechanical failure. The weakening of the elastic modulus above the critical swim force results from the change in gel porosity and distribution of attractive forces among gel particles, while below the critical swim force, the ductility enhancement is caused by an increase of gel structural disorder. Above the critical swim force, the gel develops a pronounced heterogeneous structure characterized by multiple pore spaces, and the mechanical response is controlled by dynamical heterogeneities. We contrast these results with those of a simulated monodisperse gel that exhibits a non-monotonic trend of ductility modulation with increasing swim force, revealing a complex interplay between the gel energy landscape and embedded activity. © 2024, CC BY.

关键词： Ductility

Using solar-viewing FTS observations to inform spectroscopic parameters

学校读者我要写书评

暂无评论

Using solar-viewing FTS observations to inform spectroscopic...

2023 Fourier Transform Spectroscopy, FTS 2023 in Optica Sensing Congress - Part of Optical Sensors and Sensing Congress 2023

作者： Laughner, Joshua L. Toon, Geoffrey C. Roehl, Coleen M. Wunch, Debra Wennberg, Paul Jet Propulsion Laboratory California Institute of Technology PasadenaCA United States Division of Geological and Planetary Sciences California Institute of Technology PasadenaCA United States Department of Physics University of Toronto Toronto Canada Division of Engineering and Applied Science California Institute of Technology PasadenaCA United States

Accurate information on molecular absorption line parameters is crucial to accurately interpret remotely sensed observations of atmospheric composition. We show how ground-based, solar-viewing FTS data can identify an... 详细信息

ISBN: (纸本)9781957171241

关键词： Atmospheric composition

High-field charge transport and noise in p-Si from first principles

学校读者我要写书评

暂无评论

Physical Review B 2023年第3期107卷 035201-035201页

作者： David S. Catherall Austin J. Minnich Division of Engineering and Applied Science California Institute of Technology Pasadena 91125 CA United States

The parameter-free computation of charge transport properties of semiconductors is now routine owing to advances in the ab initio description of the electron-phonon interaction. Many studies focus on the low-field regime in which the carrier temperature equals the lattice temperature and the current power spectral density (PSD) is proportional to the mobility. The calculation of high-field transport and noise properties offers a stricter test of the theory as these relations no longer hold, yet few such calculations have been reported. Here, we compute the high-field mobility and PSD of hot holes in silicon from first principles at temperatures of 77 and 300 K and electric fields up to 20 kV cm−1 along various crystallographic axes. We find that the calculations quantitatively reproduce experimental trends including the anisotropy and electric-field dependence of hole mobility and PSD. The experimentally observed rapid variation of energy relaxation time with electric field at cryogenic temperatures is also correctly predicted. However, as in low-field studies, absolute quantitative agreement is, in general, lacking, a discrepancy that has been attributed to inaccuracies in the calculated valence-band structure. Our paper highlights the use of high-field transport and noise properties as a rigorous test of the theory of electron-phonon interactions in semiconductors.

关键词： Carrier dynamics Electrical conductivity Electron relaxation Electron-phonon coupling Fluctuations & noise Transport phenomena Elemental semiconductors Boltzmann theory

Charge transport in BAs and the role of two-phonon scattering

学校读者我要写书评

暂无评论

Physical Review B 2023年第16期108卷 165202-165202页

作者： Iretomiwa Esho Austin J. Minnich Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA

The semiconductor BAs has drawn significant interest due to experimental reports of simultaneous high thermal conductivity and ambipolar charge mobility. The ab initio prediction of high electron and hole mobility assumed the dominance of charge carrier scattering by one phonon. Recently, higher-order electron-phonon scattering processes in polar and nonpolar semiconductors have been reported to have a non-negligible impact on charge transport properties, suggesting they may play a role in BAs as well. Here, we report an ab initio study of two-phonon electron and hole scattering processes in BAs. We find that inclusion of these higher-order processes reduces the computed room-temperature electron and hole mobility in BAs by around 40% from the one-phonon value, resulting in an underestimate of experimental values by a similar percentage. We suggest an experimental approach to test these predictions using luminescence spectroscopy that is applicable to the defective samples which are presently available.

关键词： Carrier dynamics Electron-phonon coupling First-principles calculations

Wave or Physics-Appropriate Multidimensional Upwinding Approach for Compressible Multiphase Flows

学校读者我要写书评

暂无评论

arXiv 2025年

作者： Chamarthi, Amareshwara Sainadh Division of Engineering and Applied Science California Institute of Technology PasadenaCA United States

This paper introduces multidimensional algorithms for simulating multiphase flows, leveraging the wave structure of the Euler equations in characteristic space and the physical properties of variables in physical space. The algorithm applies different reconstruction schemes to acoustic, vorticity, and entropy waves in characteristic space to enhance accuracy and minimize numerical artifacts. In characteristic space, upwind schemes are used for acoustic waves, central schemes for vorticity and entropy waves, and Tangent of Hyperbola for INterface Capturing (THINC) reconstruction for material interfaces and contact discontinuities (a subset of entropy waves). This approach prevents spurious vortices in periodic shear layers, accurately captures vortical structures in gas-gas and gas-liquid interactions, and improves the accuracy of shock-entropy wave interactions. In physical space, phasic densities are computed using THINC in regions of contact discontinuities and material interfaces, while tangential velocities are calculated with central schemes to improve vortical structures. An adaptive reconstruction technique is also introduced to mitigate oscillations near shocks, which arise from primitive variable reconstruction, by combining primitive and characteristic variable reconstructions with the liquid phase being identified using the stiffened gas parameter. The proposed multidimensional upwinding approach outperforms traditional schemes, demonstrating superior accuracy in capturing physical phenomena, reducing numerical artifacts, and better matching experimental results across complex test cases. © 2025, CC BY-NC-ND.

关键词： Euler equations

Microneedle sensors for dermal interstitial fluid analysis

学校读者我要写书评

暂无评论

Med-X 2024年第1期2卷 238-260页

作者： Gwangmook Kim Hyunah Ahn Joshua Chaj Ulloa Wei Gao Andrew and Peggy Cherng Department of Medical Engineering Division of Engineering and Applied ScienceCalifornia Institute of TechnologyPasadenaCAUSA

The rapid advancement in personalized healthcare has driven the development of wearable biomedical devices for real-time biomarker monitoring and *** invasive blood-based diagnostics are painful and limited to sporadic health *** address these limitations,microneedle-based sensing platforms have emerged,utilizing interstitial fluid(ISF)as an alternative biofluid for continuous health monitoring in a minimally invasive and painless *** review aims to provide a comprehensive overview of microneedle sensor technology,covering microneedle design,fabrication methods,and sensing ***,it explores the integration of monitoring electronics for continuous on-body *** applications of microneedle sensing platforms for both monitoring and therapeutic purposes are introduced,highlighting their potential to revolutionize personalized ***,the review discusses the remaining challenges and future prospects of microneedle technology.

关键词： Microneedles Biosensors Interstitial fluid Wearable

Metal-based nanowires in electrical biosensing

学校读者我要写书评

暂无评论

Rare Metals 2024年第12期43卷 6233-6254页

作者： Shen-Jie Zhong Kang-Yu Chen Shao-Lei Wang Farid Manshaii Nan Jing Kai-Dong Wang Shi-Chang Liu Yun-Lei Zhou Hangzhou Institute of Technology Xidian UniversityHangzhou311231China Department of Bioengineering Henry Samueli School of Engineering and Applied ScienceUniversity of California Los AngelesLos AngelesCA90095USA Division of Cardiology Department of MedicineDavid Geffen School of MedicineUniversity of California Los AngelesLos AngelesCA90095USA Hong-Hui Hospital Xi’an Jiaotong University College of MedicineXi’an710054China

Harnessing the unique attributes of metal-based nanowires(MNWs),such as their adaptability,high aspect ratio and conductivity,this review elucidates their burgeoning role as a distinct class of nanomaterials poised to revolutionize sensor *** provide an in-depth examination of MNW assembly methods,highlighting procedural details,foundational principles and performance *** ele ctrochemical biosensors and field-effect transistor(FET)biosensors by MNWs offers advantages such as enhanced sensitivity,improved signal-to-noise ratios and increased surface area for efficient biomolecule *** contribute to precise and reliable biosensing platforms,optimizing the performance of these devices for various applications,such as diagnostics and environmental *** biosensors are noted for their speed,costeffectiveness,ease of use and compatibility with compact instrumentation,offering potential for precise biomarker ***,FET biosensors demonstrate the potential for early-stage biomarker identification and pharmaceutical applications with nanoscale materials like MNWs,thereby enhancing their detection ***,we explore the prospects of integrating machine learning and digital health with MNWs in electrical biosensing,charting an innovative path for future advancements in this *** advancement is facilitated by their electronic properties,compact design and compatibility with existing *** expect this review to highlight future trends and challenges in the use of MNWs for biosensors.

关键词： Metal-based nanowires Electrical biosensing Field-effect transistor Electro-chemical biosensors Machine learning

Consistent Interface Capturing Adaptive Reconstruction Approach for Viscous Compressible Multicomponent Flows

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Chamarthi, Amareshwara Sainadh Division of Engineering and Applied Science California Institute of Technology PasadenaCA United States

The paper proposes a physically consistent numerical discretization approach for simulating viscous compressible multicomponent flows. It has two main contributions. First, a contact discontinuity (and material interface) detector is developed. In those regions of contact discontinuities, the THINC (Tangent of Hyperbola for INterface Capturing) approach is used for reconstructing appropriate variables (phasic densities). For other flow regions, the variables are reconstructed using the Monotonicity-preserving (MP) scheme (or Weighted essentially non-oscillatory scheme (WENO)). For reconstruction in the characteristic space, the THINC approach is used only for the contact (or entropy) wave and volume fractions and for the reconstruction of primitive variables, the THINC approach is used for phasic densities and volume fractions only, offering an effective solution for reducing dissipation errors near contact discontinuities. The second contribution is the development of an algorithm that uses a central reconstruction scheme for the tangential velocities, as they are continuous across material interfaces in viscous flows. In this regard, the Ducros sensor (a shock detector that cannot detect material interfaces) is employed to compute the tangential velocities using a central scheme across material interfaces. Using the central scheme does not produce any oscillations at the material interface. The proposed approach is thoroughly validated with several benchmark test cases for compressible multicomponent flows, highlighting its advantages. The numerical results of the benchmark tests show that the proposed method captured the material interface sharply compared to existing methods. © 2024, CC BY-NC-ND.

关键词： Viscous flow

Valleytronics and negative differential resistance in cubic boron nitride: a first-principles study

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Hatanpää, Benjamin Minnich, Austin J. Division of Engineering and Applied Science California Institute of Technology PasadenaCA United States

Cubic boron nitride (c-BN) is an ultrawide-bandgap semiconductor of significant interest for high-frequency and high-power electronics applications owing to its high saturation drift velocity and high electric breakdown field. Beyond transistors, devices exploiting the valley degree of freedom or negative differential resistance are of keen interest. While diamond has been found to have potential for these applications, c-BN has not been considered owing to a lack of knowledge of the relevant charge transport properties. Here, we report a study of the high-field transport and noise properties of c-BN using first-principles calculations. We find that c-BN exhibits an abrupt region of negative differential resistance (NDR) below 140 K, despite the lack of multivalley band structure typically associated with NDR. This feature is found to arise from a strong energy dependence of the scattering rates associated with optical phonon emission. The high optical phonon energy also leads to an intervalley scattering time rivaling that of diamond. The negative differential resistance and long intervalley scattering time indicate the potential of c-BN for transferred-electron and valleytronic devices, respectively. Copyright © 2024, The Authors. All rights reserved.

关键词： Cubic boron nitride