415 research outputs found
Python scripts to test gravity with the dynamics of wide binary stars
No full textA wide binary sample within 200 pc, a virtual Newtonian sample, and several python scripts are provided to supplement Chae, K.-H. 2023, to be published in the Astrophysical Journal (arXiv:2305.04613).
'gaia_dr3_MSMS_d200pc.csv' is the sample of wide binaries extracted from Gaia DR3 (El-Badry, Rix, & Heintz 2021). It includes all information needed for statistical analyses.
A virtual Newtonian sample 'Newton_dr3_MSMS_d200pc_1.csv' was generated with 'make_Newton_sample_gaia.py'. The user can generate his/her own Newtonian sample.
A mass-magnitude (and inverse) relation is needed as an input. Three options are provided.
'accel_plane_ortho_wb.py' can be used to produce figures from one Monte Carlo set. The user is encouraged to start with this code to have a feel for what is going on.
'run_wb.py', based on the python class 'accel_ortho_wb.py', calculates an ensemble of Monte Carlo sets of accelerations. It uses 'multiprocessing' and requires a significant number of cores. The author has been using 128 cores/threads.
The user is strongly encouraged to read carefully Chae, K.-H. 2023, to be published in the Astrophysical Journal (arXiv:2305.04613) before using these codes.
Questions can be directed to [email protected] or [email protected].
Last updated 2023-06-21.Chae, K.-H. 2023, to be published in the Astrophysical Journal (arXiv:2305.04613
Python scripts to test gravity with the dynamics of wide binary stars
No full textA wide binary sample within 200 pc, a virtual Newtonian sample, and several python scripts are provided to supplement Chae, K.-H. 2023, to be published in the Astrophysical Journal (arXiv:2305.04613).
'gaia_dr3_MSMS_d200pc.csv' is the sample of wide binaries extracted from Gaia DR3 (El-Badry, Rix, & Heintz 2021). It includes all information needed for statistical analyses.
A virtual Newtonian sample 'Newton_dr3_MSMS_d200pc_1.csv' was generated with 'make_Newton_sample_gaia.py'. The user can generate his/her own Newtonian sample.
A mass-magnitude (and inverse) relation is needed as an input. Three options are provided.
'accel_plane_ortho_wb.py' can be used to produce figures from one Monte Carlo set. The user is encouraged to start with this code to have a feel for what is going on.
'run_wb.py', based on the python class 'accel_ortho_wb.py', calculates an ensemble of Monte Carlo sets of accelerations. It uses 'multiprocessing' and requires a significant number of cores. The author has been using 128 cores/threads.
The user is strongly encouraged to read carefully Chae, K.-H. 2023, to be published in the Astrophysical Journal (arXiv:2305.04613) before using these codes.
Questions can be directed to [email protected] or [email protected].
Last updated 2023-06-21.Chae, K.-H. 2023, to be published in the Astrophysical Journal (arXiv:2305.04613
Real-time hybrid simulation for a base-isolated building with the transmissibility-based semi-active controller
No full text© The Author(s) 2022.The transmissibility-based semi-active (TSA) controller was developed in the existing study by the authors, which can effectively enhance the performance of base-isolated buildings under both strong long- and short-period earthquake ground motions. Since the performance of the TSA controller was only evaluated with numerical simulation in the existing study, this paper further validates its performance experimentally by conducting real-time hybrid simulation (RTHS). A three-story base isolated building was designed based on a simplified design procedure, where the base isolation system of the building consisted of three different devices, that is, a magneto-rheological (MR) damper, rubber bearing, and linear bearings. The base isolation system was experimentally tested with the MR damper controlled by the TSA controller, and the building superstructure was analytically modeled. It was shown that the TSA controller makes the system damping high under long-period ground motions and low under short-period ground motions, which performed uniquely as intended. As a result, the isolator displacement was effectively reduced under long-period ground motions, while the story drift and acceleration responses were also reduced under short-period ground motions, all of which are difficult to achieve at the same time using passive damping only.N
A Closer Look at the Personality-Turnover Relationship: Criterion Expansion, Dark Traits, and Time
No full textRecent advances in the personality and turnover literatures suggest the importance of expanding current turnover criteria, incorporating dark personality traits, and examining the role of time in these relationships. The present study investigates these issues by considering both the speed and the reasons for leaving, examining a wider range of personality variables as predictors by including both “bright” and “dark” traits, and exploring the potential moderating effect of time in such predictions. Data were collected from a sample of 617 employees working in an electronics manufacturing firm in the United States. Using a Bayesian survival analysis framework, we found that dark traits were just as useful in predicting turnover outcomes as traditional personality traits and best predicted the specific turnover reasons, “deviant behavior” and “no call no show.” Investigating the role of time showed that job satisfaction and intellectual curiosity (i.e., Openness) grew in predictive strength over the course of organizational tenure but that the time-dependent effects of other predictors were negligible. © 2016, The Author(s) 2016.11Nssciscopu
Stationary Navier-Stokes equations in an exterior domain, and some integral identities for Euler and Navier-Stokes equations
No full textWe study: 1) the stationary Navier-Stokes equations in a two-dimensional exterior domain, 2) some integral identities for the Euler and the Navier-Stokes equations. For the first topic, we consider the non-homogenous boundary value problem in a two-dimensional exterior domain together with a prescribed condition at infinity and establish existence of a solution to the problem provided that the boundary value on the boundary of the domain is close to a potential flow; this assumption allows some large boundary value. Indeed, we utilize results of Galdi in 2004 on the Oseen equations, a linearization around a constant nonzero vector. Then we apply ideas used in Russo and Starita's work (in 2008) in three dimension, which is to perturb around a potential flow; in conjunction with the compactness of some linear operator related to the Oseen equations, which is a result again of Galdi in 2004.
For the second topic, Dobrokhotov and Shafarevich in 1994 proved some integral identities for the Euler and Navier-Stokes equations. Chae in 2012 proved these integral identities on a hyperplane for a weak solution with some integrability assumptions on the solution. In this thesis, we prove the integral identities on a hyperplane with some different integrability assumptions. It also furnishes a Liouville type theorem as an immediate application, providing a different approach to some of the results of Hamel and Nadirashvili in 2017, 2019, Chae and Constantin in 2015.Ph.D.Includes bibliographical reference
Correlating advanced microscopies reveals atomic-scale mechanisms limiting lithium-ion battery lifetime
No full textThe original version of this Article omitted a reference to previous work in “Chae, B. G. et al. Evolution and expansion of Li concentration gradient during charge–discharge cycling. Nat Commun 12, 3814 (2021)”. This has been added as reference [14] at “Chae et al. combined... [14]”. This has been corrected in the PDF and HTML versions of the Article. © 2021 The Author(s)
Wearable Technology in Fashion
No full textAs smart clothing is being increasingly recognized as a strong contender in future wearables, with its flexible and comfortable interface becoming more accessible to people, fashion also has been successfully orienting itself as the next game-changer in wearable technology through its connection to a wide range of design, lifestyle, and functionality with its scalability. This chapter introduces the currently available wearables in the fashion industry for varied symbolic, aesthetic, cultural, or functional purposes and the projects concerning smart clothing and soft wearable robot for future living with the enhanced comfort of the wearer. The chapter also discusses the future of wearable technology in the fashion industry.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Emerging Material
Three essays on housing economics
No full textThis dissertation includes two chapters that investigate the spatial behavior of housing price and its volatility and one chapter that focuses on a more fundamental housing issue. The first chapter examines the spatial variation of housing price volatility. I develop a flexible spatial volatility model for squared returns using a Box-Cox transformation for simultaneously testing space-varying volatility and its functional form. The maximum likelihood (ML) method is used to estimate this model and Monte Carlo simulations are conducted to investigate the finite sample performance of the ML estimator. Using housing price data from Chicago, I empirically demonstrate substantial evidence of spatial dependence in volatility and explicitly address the validity of a log-linear specification, after which I propose a new practical indicator, called neighborhood elasticity, which determines how volatility in one neighborhood is linked to that in surrounding neighborhoods. The average annual elasticity is found to be 0.4 across different spatial weight matrices, which can be used as a benchmark to compare different housing markets and a tool for policy makers to assist them to avoid volatility transmission and the risk of contagion in the housing market. Finally, to identify whether the neighborhood elasticity remains constant over time, adjusted quasi score (AQS) tests for testing the presence of temporal heterogeneity in spatial parameters in spatial panel data models are considered. The test results reveal that the neighborhood elasticity becomes homogeneous after controlling for both spatial and temporal heterogeneity in the intercepts of the model.
The second chapter explores the implication of spatial volatility in the context of market efficiency in finance literature. More specifically, this study investigates whether the housing market is spatially efficient by examining linear and nonlinear spatial dependence patterns in housing returns. The spatial ARCH-type model and its extension to the quantile model that allows for possible heterogeneous effects of spatial dependence are applied to house price data in the broader Chicago area. Our study reveals a number of interesting new insights into the spatial market efficiency of the housing market. Specifically, we find: i) while housing returns are not correlated over space, squared returns, which represent volatility, exhibit significant spatial dependence, i.e., spatial market inefficiency and, therefore, the neighborhood housing returns contain information for spatial prediction and ii) the degree of inefficiency varies over quantiles; the spatial dependence is conspicuously distinct from the lower quantiles to the higher quantiles with a gradually increasing trend.
The third chapter investigates spillover effects of house supply on nearby house prices across the housing cycle. Over the past five years, housing inventory shortages have been a primary factor in rising house prices. At the same time, demand for housing has risen aggressively as the job market has improved and millennials are aging into homeownership. The combination of limited homes on the market with high buyer demand has pushed house prices above what they were at the peak of the housing boom in early 2006. The underlying reasoning behind this idea - low supply should lead to price increases - is clear and some influential research has strongly suggested the inverse relationship by applying matching models to the housing market. However, there is a surprising lack of empirical work done on this inverse relationship, in particular, at the level of the local housing market. Furthermore, no empirical research has addressed the role of spatial spillovers between different regions in the relationship. Using a spatial panel model for 77 community areas within the Chicago area between 2009 and 2018, the study shows substantial asymmetric spatial effects; for instance, how the nearby house supply can serve as a key determinant on house prices in a boom period. However, these effects may not hold during a market downturn.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-08-01The student, Jiyoung Chae, accepted the attached license on 2021-07-10 at 09:20.The student, Jiyoung Chae, submitted this Dissertation for approval on 2021-07-10 at 09:39.This Dissertation was approved for publication on 2021-07-13 at 16:30.DSpace SAF Submission Ingestion Package generated from Vireo submission #16845 on 2022-01-12 at 13:04:29Made available in DSpace on 2022-01-12T22:55:03Z (GMT). No. of bitstreams: 2
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A 6.3 μW 20 bit Incremental Zoom-ADC with 6 ppm INL and 1 μV Offset
No full textA 20-bit incremental ADC for battery-powered sensor applications is presented. It is based on an energy-efficient zoom ADC architecture, which employs a coarse 6-bit SAR conversion followed by a fine 15-bit ΔΣ conversion. To further improve its energy efficiency, the ADC employs integrators based on cascoded dynamic inverters for extra gain and PVT tolerance. Dynamic error correction techniques such as auto-zeroing, chopping and dynamic element matching are used to achieve both low offset and high linearity. Measurements show that the ADC achieves 20-bit resolution, 6 ppm INL and 1 μV offset in a conversion timeof 40 ms, while drawing only 3.5 μA current from a 1.8 V supply. This corresponds to a state-of-the-art figure-of-merit (FoM) of 182.7 dB. The 0.35 mm² chip was fabricated in a standard 0.16 μm CMOS process.Accepted Author ManuscriptElectronic Instrumentatio
Quantum communication with time-bin entanglement over a wavelength-multiplexed fiber network
No full textIn a quantum network involving multiple communicating parties, an important goal is to establish high-quality pairwise entanglement among the users without introducing multiple entangled-photon sources which would necessarily complicate the overall network setup. Moreover, it is preferable that the pairwise entanglement of photons is in the time-bin degree of freedom as the photonic time-bin qubit is ideally suited for fiber-optic distribution. Here, we report an experimental demonstration of a field-deployable quantum communication network involving multiple users, all of whom share pairwise entanglement in the time-bin degree of freedom of photons. In particular, by utilizing a single spontaneous-parametric down-conversion source which produces a broadband pair of photons and the wavelength-division demultiplexing/multiplexing technology, all the communicating parties within the network are always simultaneously ready for quantum communication. To further demonstrate the practical feasibility of a quantum network with time-bin entanglement over a wavelength-multiplexed fiber network, we demonstrate entangled-photon quantum key distribution with three users, each separated by 60 km of optical fibers.& nbsp;(c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).11Nsciescopu
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