About

Hua Lee is a Distinguished Professor in the Department of Electrical and Computer Engineering at UC Santa Barbara. His research interests include High-Resolution Imaging Techniques, Microwave, Acoustic, and Ultrasound Imaging Systems, Medical Imaging Devices, and Distributed Sensing and Imaging Networks. He is associated with the Imaging Systems Laboratory and is based in Harold Frank Hall, Room 4155. For contact, he can be reached by phone at +1 805-893-4480 or via email at hualee@ece.ucsb.edu.

Research topics

• Computer Science
• Physics
• Telecommunications
• Algorithm
• Engineering
• Mathematics
• Electronic engineering
• Acoustics
• Condensed matter physics
• Speech recognition
• Statistics
• Quantum mechanics

Selected publications

• Cascade AOA estimation technology based on combined array antenna with computational complexity analysis

  ICT Express · 2021

  • Computer Science
  • Algorithm
  • Computer Science

  Since most studies for estimating an angle-of-arrival (AOA) based on the antenna array have considered the antenna array with a single configuration, they are not proper to simultaneously estimate AOAs of multiple signals with various frequencies. In this paper, we introduce a cascade AOA estimation technique consisting of CAPON and Beamspace Multiple Signal Classification (MUSIC), based on a Combined Array Antenna (CAA) with Uniform Rectangular Frame Array (URFA) and Uniform Circular Array (UCA), for enhancing the above problem. In addition, we provide the computational complexity analysis for showing the low computational complexity of this technique comparing to the conventional technique.

  PublisherDOI

• The Informational Role of Earnings Smoothing in Diversification

  Review of Economics and Finance · 2021-01-01

  articleOpen access1st authorCorresponding

  This paper examines whether managers smooth earnings to affect information asymmetry upon diversification. Using a sample of firms listed in Taiwan Stock Exchange, the results show that earnings smoothing increases the positive association between industrial diversification and bid-ask spread but reduces the negative association between global diversification and bid-ask spread. Our results are robust with respect to alternative research methodology (3SLS), alternative proxy for information asymmetry (analyst following), refined measure of earnings smoothing (i.e., discretionary earnings smoothing) after controlling for leverage, negative earnings, and return on equity. Collectively, the evidence suggests that discretionary earnings smoothing conveys managers' favorable information for firms with global diversification, but garbles managers' unfavorable information for firms with industrial diversification.

  PublisherOA PDFDOI

• Cascade AOA Estimation Based on Combined Array Antenna with URFA and UCA

  2021 · 1 citations

  • Computer Science
  • Computer Science
  • Acoustics

  Since most studies for estimating an angle-of-arrival (AOA) based on the antenna array have considered the antenna array with a single configuration, they are not proper to simultaneously estimate AOAs of multiple signals with various frequencies. In order to enhance this problem, in this paper, we propose a cascade AOA estimation technique based on a Combined Array Antenna (CAA) with Uniform Rectangular Frame Array (URFA) and Uniform Circular Array (UCA). It consists of Capon for roughly finding AOA groups including multiple signal AOAs, followed by Beamspace Multiple Signal Classification (MUSIC) for detailedly estimating signal AOAs in the calculated AOA groups. The proposed algorithm does not only have low computational complexity compared to the conventional AOA estimation technique like MUSIC, but also it has both characteristics of URFA and UCA.

  PublisherDOI

• Gapless spin liquid in a square-kagome lattice antiferromagnet

  Nature Communications · 2020 · 74 citations

  • Condensed matter physics
  • Physics
  • Quantum mechanics

  Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (μSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.

  PublisherOA PDFDOI

• Rigidity of selling, general, and administrative costs and managerial incentives to meet earnings thresholds: Evidence from conglomerates

  Review of Economics and Finance · 2019-01-01 · 5 citations

  articleSenior author

  Does the conventional wisdom of decreasing marginal cost in economics hold in the real world? Surprisingly, previous accounting literature has found opposite evidence and documented cost stickiness. This paper examines the effect of managerial incentives to avoid loss and earnings decrease on rigidity of selling, general, and administrative (SG&A) costs for conglomerates and parent companies, and the resultant implication for parent company¡¯s cost management decisions. The results show that the estimates of cost rigidity are negatively significant in the absence of managerial incentives to meet earnings thresholds for both parent company and conglomerate. In the presence of such managerial incentives for both parties, the estimates are significantly positive and indicate disappearance of cost rigidity. The results hold after controlling for asset intensity, employee intensity, ROA, and GDP growth. Additionally, parent company cuts its cost more aggressively to avoid either party¡¯s loss, but cuts conglomerate¡¯s cost more aggressively to avoid either party¡¯s decrease in earnings. This suggests that parent company is more concerned about its performance in cost management than for the conglomerate¡¯s. Overall, the evidence suggests that the decreasing marginal cost concept is conditional on managerial incentives to meet earnings thresholds and that parent company makes selective SG&A cost reduction decisions to meet earnings thresholds.

  Publisher

• DESIGN OF PROBING WAVEFORMS IN SOFTWARE-DEFINED SENSING AND IMAGING SYSTEMS

  UA Campus Repository (The University of Arizona) · 2019-10-01

  articleOpen access1st authorCorresponding

  The probing waveforms play a crucial role in the performance of software-defined sensing-imaging systems. The characteristics of the probing waveforms govern both the computation complexity and accuracy of the estimation. This paper describes the concepts of the design and utilization of the probing waveforms for sensing and imaging applications.

  Publisher

• Changes in the position of Chinese courts on the approval and enforcement of foreign judgments

  The Legal Studies Institute of Chosun University · 2019-08-31

  article1st authorCorresponding

  이론적으로 법원의 판례는 한 나라의 사법주권을 나타내는 것으로 그 영토 내에서만 효력을 가진다. 하지만 국제거래와 분쟁이 심심치 않게 발생하는 현재, 각국의 법률제 도나 사법 이념이 다르더라도 국제예양 또는 호혜에 근거하여 외국 법원의 판결에 대해 전반적으로 존중하는 태도를 가지는 추세다. 그러나 서로 다른 국가의 판결 효력은그 속지(&#23646;地)성 때문에 당연히 본국에서 승인과 집행을 받을 수 있는 것은 아니다. 각 국가마다 그 요건을 달리하고 있는데 중국은 기본적으로 국제조약에 가입되어 있거나 호혜관계가 존재할 것을 요구한다. 중국은 2019년전까지 한국판결을 승인 및 집행한 적도 없었고 호혜관계를 신중하게 인정하여 외국판결의 승인 비율이 상당히 낮은 편이었다. 그러나 이러한 국면이 일대일로 정책의 일환으로 사법서비스를 개선할 것을 발표하고 나서는 선후로 호혜원칙에 근거하여 처음으로 싱가포르 법원의 판결을 승인 하였고, 미국법원의 판결, 올해는 한국법원의 판결을 호혜원칙에 따라 승인한 바 있다. 일대일로 의견 발표 후, 처음으로 호혜원칙을 적용하여 싱가포르 법원의 판결을 승인및 집행한 사건은 최고법원에 의해 <일대일로 지도판례> 중 13호 전형적인 사례로 선정되기도 하였다. 싱가포르도 한국과 마찬가지로 중국과 민&#8228;상사 사법공조협약은 체결했으나 승인 및 집행에 관한 규정은 두고 있지 않다. 싱가포르가 일대일로 제창에 참여한 국가라는 점도 흥미롭고 시기적으로 일대일로 의견과 난닝성명이 발표된 후의 판례라는 점에도 주목할 필요가 있다.In theory, each judgement demonstrates the jurisdictional sovereignty of a country, taking effect only within the country’s territory. Yet, with international trade and dispute ever-increasing, there is a global trend where many countries start to acknowledge foreign judgements based on the reciprocity principle and international comity, even though their legal systems and ideologies are different from one another. Nevertheless, recognition and enforcement may not work in all foreign legal cases due to the principle of territorial privilege for jurisdiction. Every country has its own criteria for recognising and enforcing a foreign judgement. In the case of the People’s Republic of China, a state party concerned should be a member of the relevant international treaty or have a reciprocity relation with China. Until 2019, not a single Korea’s judgement was recognised and enforced in China. In addition, not only Korea’s judgements but also those of other foreign countries were rarely recognised. This is because China strictly builds its reciprocity relation with other countries. However, now there are new developments in China’s legal system. As part of the Belt and Road initiative, the Chinese government announced its willingness to improve the current legal services and after the declaration, it recognised the Singapore Court’s judgement for the first time, based on the reciprocity principle. Subsequently, it recognised the judgements of the United State and Korea, respectively one after another. The recognition and enforcement of Singapore’s judgement is seen as a historic event, which has been set as the 13th typical case in the judicial reports called “Guiding cases regarding the Belt and Road Initiative,” by the China’s Supreme People s Court. Like the Republic of Korea, Singapore signed with China the convention on mutual assistance in foreign civil and commercial affairs but has not stipulated rules for the recognition and enforcement of foreign judgements yet. It is noteworthy that Singapore is engaging in the Belt and Road Initiative and that the decision took place after the announcement of Several Opinions of the Supreme People s Court on Providing Judicial Services and Safeguards for the Construction of the “Belt and Road” by People s Courts, and the Nanning Statement of the 2nd China-ASEAN Justice Forum.

  PublisherDOI

• Towards non-invasive electrocardiographic imaging using regularized neural networks

  Medical Imaging 2018: Physics of Medical Imaging · 2018-03-09 · 2 citations

  article

  We present a new data-driven technique for non-invasive electronic imaging of cardiovascular tissues using routinely-measured body-surface electrocardiogram (ECG) signals. While traditional ECG imaging and 3D reconstruction algorithms typically rely on a combination of linear Fourier theory, geometric and parametric modeling, and invasive measurements via catheters, we show in this work that it is possible to learn the complicated inverse map, from body-surface potentials to epicardial or endocardial potentials, by exploiting the powerful approximation properties of neural networks. The key contribution here is a formulation of the inverse problem that allows historical data to be leveraged as ground-truth for training the inverse operator. We provide some initial experiments, and outline a path for extending this technique for real-time diagnostic applications.

  PublisherDOI

• Nonlinear electrocardiographic imaging using polynomial approximation networks

  APL Bioengineering · 2018-10-16 · 8 citations

  articleOpen access

  Electrocardiography is a valuable tool to aid in medical understanding and treatment of heart-related ailments, specifically atrial fibrillation (AF) and other irregular cardiac behavior. Although signs of AF will manifest in conventional electrocardiogram (ECG) recordings, interpretation and localization of AF sources require significant clinical expertise. In this vein, electrocardiographic imaging has emerged as an important medical imaging modality that provides reconstructions of the heart's electrical activity from non-invasive multi-lead body-surface ECG and anatomical x-ray computed tomography images. In this paper, we present a nonlinear inversion model for computing this mapping to improve upon the reconstruction performance of current methods. While contemporary techniques typically determine an inverse solution by discretizing and inverting an underdetermined linear system of partial differential equations governing the relationship between voltage potentials of the heart and torso, the presented technique re-casts this problem as a task in function approximation and provides a direct parameterization of the inverse operator using a polynomial neural network. That is, the outlined nonlinear inversion technique is a generalization of contemporary reconstruction techniques which allows geometrical and material parameterizations of the forward-model to be optimized using real experimental data collected from patients suffering from AF, as to better represent the inverse operator with respect to reconstruction metrics applicable to electrophysiology. The accuracy of our model is evaluated against a dataset of real-patient recordings to demonstrate its validity, and mathematical analysis is provided to support the polynomial expansion used in our inversion model.

  PublisherDOI

• Detection and tracking of human targets in indoor and urban environments using through-the-wall radar sensors

  Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2017-05-01 · 1 citations

  articleSenior author

  Radar based detection of human targets behind walls or in dense urban environments is an important technical challenge with many practical applications in security, defense, and disaster recovery. Radar reflections from a human can be orders of magnitude weaker than those from objects encountered in urban settings such as walls, cars, or possibly rubble after a disaster. Furthermore, these objects can act as secondary reflectors and produce multipath returns from a person. To mitigate these issues, processing of radar return data needs to be optimized for recognizing human motion features such as walking, running, or breathing. This paper presents a theoretical analysis on the modulation effects human motion has on the radar waveform and how high levels of multipath can distort these motion effects. From this analysis, an algorithm is designed and optimized for tracking human motion in heavily clutter environments. The tracking results will be used as the fundamental detection/classification tool to discriminate human targets from others by identifying human motion traits such as predictable walking patterns and periodicity in breathing rates. The theoretical formulations will be tested against simulation and measured data collected using a low power, portable see-through-the-wall radar system that could be practically deployed in real-world scenarios. Lastly, the performance of the algorithm is evaluated in a series of experiments where both a single person and multiple people are moving in an indoor, cluttered environment.

  PublisherDOI

Frequent coauthors

• G. Wade

  Queensland University of Technology

  32 shared

• Martin O. Culjat

  31 shared

• Warren S. Grundfest

  Samueli Institute

  21 shared

• Rahul Singh

  Jawaharlal Nehru Medical College

  21 shared

• E. R. Brown

  Cincinnati Children's Hospital Medical Center

  21 shared

• Jing-Ming Guo

  National Taiwan University of Science and Technology

  13 shared

• Vincent R. Radzicki

  12 shared

• Michael P. André

  University of California, San Diego

  11 shared