检索结果-内蒙古大学图书馆

Physics of a strongly oscillating axisymmetric air-water interface with a fixed boundary condition

Physical Review Fluids 2022年第4期7卷 044003-044003页

作者： Cong Wang Morteza Gharib Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA

In this work, we experimentally investigate the physics of a strongly oscillating, millimeter-sized, axisymmetric air-water interface with a fixed contact line boundary condition. Many previous studies focused on the regime of small oscillation amplitude, e.g., R=d/D≪1, where d is the oscillation amplitude and D is the characteristic size of the air-water interface. The current investigation instead focuses on a less-studied oscillation regime with large R that is up to 0.33. The dynamic oscillations induce different steady streaming patterns, such as a low-speed streaming vortex or a fast-speed streaming jet. The steady streaming jet, in particular, was not much studied previously and is the major focus of this work. The streaming jet is only generated when the oscillating interface exhibits the higher-order axisymmetric oscillation modes with a large oscillation amplitude, which correspond to the regime with large R and large Weber number (We). The streaming jet has a larger Reynolds number [Re∼O(100)] than the typical streaming motions induced by an oscillating interface [Re∼O(1)]. In addition, the streaming jet has a high ratio of the streaming velocity versus the oscillatory velocity, which suggests a high efficiency in generating steady streaming motion. The dynamic velocity and vorticity field of the streaming jet in both the initiation stage and the quasisteady stage are presented, which demonstrates that the streaming jet onset process is a consequence of vorticity generation, transportation, and accumulation happening at the oscillating interface. As a zero-mass-flux jet, the streaming jet is sustained by entraining fluid mass flux from the circumferential regions through a process similar to the classical Stokes drift. It is further found that a streaming jet can be induced by an oscillating elastic no-slip membrane as well, when the oscillation has large R and We. The extraordinary characters of the streaming jet can be employed in many engineering appli

关键词： Interfacial flows Vortex flows

来源：评论

学校读者我要写书评

暂无评论

Dynamic Strength of Iron at High Pressures and Strain Rates

引用

Physical Review Letters 2022年第1期128卷 015705-015705页

作者： Vatsa Gandhi Suraj Ravindran Guruswami Ravichandran Division of Engineering and Applied Science California Institute of Technology Pasadena California 91125 USA

Accurate modeling of meteorite impacts, and deformation of planetary cores require characterization of the flow strength and in-elasticity of iron in its different phases. In this Letter, we investigate the flow strength of both the ambient α phase and high-pressure ε phase of iron at strain rates of 1×105 s−1 and pressures up to 42 GPa using high-pressure–pressure shear plate impact experiments. We report the strength of the ε iron to be significantly higher than α phase but consequently one order smaller than the previously reported dynamic strength at high pressures. The complete stress-strain response of the ε phase is reported for the first time.

关键词： Compressive strength Equations of state Phase transitions Plasticity Shear deformation Shock waves High strain-rate tests Impact test

来源：评论

学校读者我要写书评

暂无评论

Measurement of Entangled States Before, During, and After a Proposed Entangled Two-Photon Molecular Excitation

Measurement of Entangled States Before, During, and After a ...

引用

Quantum 2.0, QUANTUM 2022

作者： Hickam, Bryce He, Manni Szoke, Szilard Cushing, Scott Division of Chemistry and Chemical Engineering California Institute of Technology 1200 E. California Blvd PasadenaCA91125 United States Division of Engineering and Applied Science California Institute of Technology 1200 E. California Blvd PasadenaCA91125 United States

Entangled photons are predicted to linearize and enhance the probability of multiphoton processes. We construct an interferometer to measure the quantum state before, during, and after an entangled excitation and dist... 详细信息

ISBN: (纸本)9781957171111

关键词： Multiphoton processes

来源：评论

学校读者我要写书评

暂无评论

Fermionic tensor network contraction for arbitrary geometries

arXiv

引用

arXiv 2024年

作者： Gao, Yang Zhai, Huanchen Gray, Johnnie Peng, Ruojing Park, Gunhee Liu, Wen-Yuan Kjønstad, Eirik F. Chan, Garnet Kin-Lic Division of Engineering and Applied Science California Institute of Technology PasadenaCA91125 United States Division of Chemistry and Chemical Engineering California Institute of Technology PasadenaCA91125 United States

We describe our implementation of fermionic tensor network contraction on arbitrary lattices within both a globally ordered and locally ordered formalism. We provide a pedagogical description of these two conventions as implemented for the quimb library. Using hyperoptimized approximate contraction strategies, we present benchmark fermionic projected entangled pair states simulations of finite Hubbard models defined on the three-dimensional diamond lattice and random regular graphs. Copyright © 2024, The Authors. All rights reserved.

关键词： Tensors

来源：评论

学校读者我要写书评

暂无评论

Tensor Network Computations That Capture Strict Variationality, Volume Law Behavior, and the Efficient Representation of Neural Network States

arXiv

引用

arXiv 2024年

作者： Liu, Wen-Yuan Du, Si-Jing Peng, Ruojing Gray, Johnnie Chan, Garnet Kin-Lic Division of Chemistry and Chemical Engineering California Institute of Technology PasadenaCA91125 United States Division of Engineering and Applied Science California Institute of Technology PasadenaCA91125 United States

We introduce a change of perspective on tensor network states that is defined by the computational graph of the contraction of an amplitude. The resulting class of states, which we refer to as tensor network functions, inherit the conceptual advantages of tensor network states while removing computational restrictions arising from the need to converge approximate contractions. We use tensor network functions to compute strict variational estimates of the energy on loopy graphs, analyze their expressive power for ground-states, show that we can capture aspects of volume law time evolution, and provide a mapping of general feed-forward neural nets onto efficient tensor network functions. Our work expands the realm of computable tensor networks to ones where accurate contraction methods are not available, and opens up new avenues to use tensor networks. Copyright © 2024, The Authors. All rights reserved.

关键词： Tensors

来源：评论

学校读者我要写书评

暂无评论

Unsupervised RGB-to-Thermal Domain Adaptation via Multi-Domain Attention Network

Unsupervised RGB-to-Thermal Domain Adaptation via Multi-Doma...

引用

IEEE International Conference on Robotics and Automation (ICRA)

作者： Lu Gan Connor Lee Soon-Jo Chung Division of Engineering and Applied Science California Institute of Technology Pasadena CA USA

This work presents a new method for unsupervised thermal image classification and semantic segmentation by transferring knowledge from the RGB domain using a multi-domain attention network. Our method does not require any thermal annotations or co-registered RGB-thermal pairs, enabling robots to perform visual tasks at night and in adverse weather conditions without incurring additional costs of data labeling and registration. Current unsupervised domain adaptation methods look to align global images or features across domains. However, when the domain shift is significantly larger for cross-modal data, not all features can be transferred. We solve this problem by using a shared backbone network that promotes generalization, and domain-specific attention that reduces negative transfer by attending to domain-invariant and easily-transferable features. Our approach outperforms the state-of-the-art RGB-to-thermal adaptation method in classification benchmarks, and is successfully applied to thermal river scene segmentation using only synthetic RGB images. Our code is made publicly available at https://***/ganlumomo/thermal-uda-attention.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Atomic layer etching of niobium nitride using sequential exposures of O2 and H2/SF6 plasmas

arXiv

引用

arXiv 2025年

作者： Hossain, Azmain A. Murphy, Sela Catherall, David Ardizzi, Anthony J. Minnich, Austin J. Division of Engineering and Applied Science California Institute of Technology CA91125 United States Department of Material Science and Engineering University of California BerkeleyCA94720 United States

Niobium nitride (NbN) is a metallic superconductor that is widely used for superconducting electronics due to its high transition temperature (Tc) and kinetic inductance. Processing-induced damage negatively affects the performance of these devices by mechanisms such as microwave surface loss. Atomic layer etching (ALE), with its ability to etch with Angstrom-scale control and low damage, has the potential to address these issues, but no ALE process is known for NbN. Here, we report such a process consisting of sequential exposures of O2 plasma and H2/SF6 plasma. Exposure to O2 plasma rather than O2 gas yields a greater fraction of Nb in the +5 oxidation state, which is then volatilized by NbF5 formation with exposure to an H2/SF6 plasma. The SF6:H2 flow rate ratio is chosen to produce selective etching of Nb2O5 over NbN, enabling self-limiting etching within a cycle. An etch rate of 1.77 Å/cycle was measured at 125 ◦C using ex situ ellipsometry. The Tc of the ALE-etched film is higher than that of an RIE-etched film of a similar thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of NbN in single-photon detectors and superconducting microresonators. Copyright © 2025, The Authors. All rights reserved.

关键词： Superconducting transition temperature

来源：评论

学校读者我要写书评

暂无评论

Hot electron diffusion, microwave noise, and piezoresistivity in Si from first principles

arXiv

引用

arXiv 2023年

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

Ab-initio calculations of charge transport properties in materials without adjustable parameters have provided microscopic insights into electron-phonon interactions which govern charge transport properties. Other transport properties such as the diffusion coefficient provide additional microscopic information and are readily accessible experimentally, but few ab-initio calculations of these properties have been performed. Here, we report first-principles calculations of the hot electron diffusion coefficient in Si and its dependence on electric field over temperatures from 77-300 K. While qualitative agreement in trends such as anisotropy at high electric fields is obtained, the quantitative agreement that is routinely achieved for low-field mobility is lacking. We examine whether the discrepancy can be attributed to an inaccurate description of f-type intervalley scattering by computing the microwave-frequency noise spectrum and piezoresistivity. These calculations indicate that any error in the strength of f-type scattering is insufficient to explain the diffusion coefficient discrepancies. Our findings suggest that the measured diffusion coefficient is influenced by factors such as space charge effects which are not included in ab-initio calculations, impacting the interpretation of this property in terms of charge transport processes. Copyright © 2023, The Authors. All rights reserved.

关键词： Diffusion

来源：评论

学校读者我要写书评

暂无评论

Transport and noise of hot electrons in GaAs using a semi-analytical model of two-phonon polar optical phonon scattering

arXiv

引用

arXiv 2023年

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

Recent ab-initio studies of electron transport in GaAs have reported that electron-phonon (e-ph) interactions beyond the lowest order play a fundamental role in charge transport and noise phenomena. Inclusion of the next-leading-order process in which an electron scatters with two phonons was found to yield good agreement for the high-field drift velocity, but the characteristic non-monotonic trend of the power spectral density of current fluctuations (PSD) with electric field was not predicted. The high computational cost of the ab-initio approach necessitated various approximations to the two-phonon scattering term, which were suggested as possible origins of the discrepancy. Here, we report a semi-analytical transport model of two-phonon electron scattering via the Fröhlich mechanism, allowing a number of the approximations in the ab-initio treatment to be lifted while retaining the accuracy to within a few percent. We compare the calculated and experimental transport and noise properties as well as scattering rates measured by photoluminescence experiments. We find quantitative agreement within 15% for the drift velocity and 25% for the Γ valley scattering rates, and agreement with the Γ − L intervalley scattering rates within a factor of two. Considering these results and prior studies of current noise in GaAs, we conclude that the most probable origin of the non-monotonic PSD trend versus electric field is the formation of space charge domains rather than intervalley scattering as has been assumed. Copyright © 2023, The Authors. All rights reserved.

关键词： Gallium arsenide

来源：评论

学校读者我要写书评

暂无评论

Investigation of drain noise in InP pHEMTs using cryogenic on-wafer characterization

Investigation of drain noise in InP pHEMTs using cryogenic o...

引用

Microwave, MTT-S International Symposium

作者： Bekari Gabritchidze Kieran Cleary Anthony Readhead Austin J. Minnich Cahill Radio Astronomy Lab California Institute of Technology USA Division of Engineering and Applied Science California Institute of Technology USA

We present on-wafer measurements of microwave noise temperature and S-parameters of InP pseudomorphic high electron mobility transistors (pHEMTs) over various drain-source voltages (V DS ) and physical temperatures (T ph ). From these data, we extract the small signal model (SSM) and drain noise temperature T d at each V DS and T ph . We find that T d follows a non-linear trend with both V DS and T ph . The observed trends are consistent with a recent drain noise model [1], [2], where T d originates from the sum of a thermal noise, attributed to physical temperature of electrons (T el ) in the channel; and real-space transfer (RST) noise, attributed to thermionic emission of electrons from the channel to the barrier. Using this model, we find that at the bias that minimizes the noise temperature, RST accounts for ∼ 50% of T d at 300 K and ∼ 30 % at 40 K. Possible improvements in noise performance in pHEMTs if RST were suppressed are discussed.

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：