University of California, Santa Barbara
  • Santa Barbara, CA, United States
Recent publications
In the traditional processing methods of azimuth multi-channel spaceborne synthetic aperture radar (SAR), the azimuth spectrum reconstruction and subsequent azimuth focusing are always via full-aperture processing. However, if the multi-channel full-aperture echo data are stored on the satellite, and then the full-aperture algorithms are used for the on-board imaging processing, the huge amount of echo data will require more on-board storage resources and computing resources, and the imaging processing time will become longer. To solve above problems, a novel on-board imaging processing algorithm via the idea that the data acquisition and the on-board imaging processing of the sub-aperture data are carried out simultaneously is proposed in this paper. In the algorithm, the azimuth spectrum ambiguity is eliminated by the sub-aperture azimuth spectrum reconstruction. Then, the range cell migration correction (RCMC) and the range compression for the unambiguous sub-aperture signals are accomplished by the chirp scaling algorithm (CSA). After that, the low-resolution subaperture images are got via the sub-aperture focusing. By coherently combining all sub-aperture images, the final result with high-resolution of all echo data can be obtained. At last, the simulation for the point targets is given to verify the effectiveness of the proposed algorithm.
High-resolution pixel-level classification of the roads and rivers in the remote sensing system has extremely important application value and has been a research focus which is received extensive attention from the remote sensing society. In recent years, deep convolutional neural networks (DCNNs) are used in the pixel-level classification of remote sensing image, which has shown extraordinary performance. However, the traditional DCNNs mostly produce discontinuous and incomplete pixel-level classification results when dealing with thin-stripped roads and rivers. To solve the above problem, we put forward a high-resolution strong fusion network (abbreviated as HRSF-Net) which can keep the feature map at high resolution and minimize the texture information loss of the thin-stripped target caused by multiple downsampling operations. In addition, a pixel relationship enhancement and dual-channel attention (PRE-DC) module are proposed to fully explore the strong correlation between the thin-stripped target pixels, and a hetero-resolution fusion (HRF) module is also proposed to better fuse the feature maps with different resolutions. The proposed HRSF-Net is examined on the two public remote sensing datasets. The ablation experimental result verifies the effectiveness of each module of the HRSF-Net. The comparative experimental result shows that the HRSF-Net has achieved mIoU of 79.05% and 64.46% on the two datasets respectively, which both outperform some advanced pixel-level classification methods.
The literature on “benign overfitting” in overparameterized models has been mostly restricted to regression or binary classification; however, modern machine learning operates in the multiclass setting. Motivated by this discrepancy, we study benign overfitting in multiclass linear classification. Specifically, we consider the following training algorithms on separable data: (i) empirical risk minimization (ERM) with cross-entropy loss, which converges to the multiclass support vector machine (SVM) solution; (ii) ERM with least-squares loss, which converges to the min-norm interpolating (MNI) solution; and, (iii) the one-vs-all SVM classifier. First, we provide a simple sufficient deterministic condition under which all three algorithms lead to classifiers that interpolate the training data and have equal accuracy. When the data is generated from Gaussian mixtures or a multinomial logistic model, this condition holds under high enough effective overparameterization. We also show that this sufficient condition is satisfied under “neural collapse”, a phenomenon that is observed in training deep neural networks. Second, we derive novel bounds on the accuracy of the MNI classifier, thereby showing that all three training algorithms lead to benign overfitting under sufficient overparameterization. Ultimately, our analysis shows that good generalization is possible for SVM solutions beyond the realm in which typical margin-based bounds apply.
  • Ning Yang
    Ning Yang
  • Yuebin Wang
    Yuebin Wang
  • Xiangguo Liu
    Xiangguo Liu
  • [...]
  • Jeffrey Ross-Ibarra
    Jeffrey Ross-Ibarra
The origins of maize were the topic of vigorous debate for nearly a century, but neither the current genetic model nor earlier archaeological models account for the totality of available data, and recent work has highlighted the potential contribution of a wild relative, Zea mays ssp. mexicana . Our population genetic analysis reveals that the origin of modern maize can be traced to an admixture between ancient maize and Zea mays ssp. mexicana in the highlands of Mexico some 4000 years after domestication began. We show that variation in admixture is a key component of maize diversity, both at individual loci and for additive genetic variation underlying agronomic traits. Our results clarify the origin of modern maize and raise new questions about the anthropogenic mechanisms underlying dispersal throughout the Americas.
  • James F. Buckwalter
    James F. Buckwalter
  • Alireza Zolfaghari
    Alireza Zolfaghari
  • Drew A. Hall
    Drew A. Hall
  • [...]
  • Dominique Morche
    Dominique Morche
This Special Section of IEEE JOURNAL OF SOLID-STATE CIRCUITS (JSSC) highlights outstanding papers presented at the 2023 IEEE International Solid-State Circuits Conference (ISSCC), which was held from February 19 to 23, 2023, in San Francisco, USA, under the conference theme “Building on 70 Years of Innovation in Solid-State Circuit Design.” ISSCC is the foremost global forum for the presentation of advances in solid-state circuits and systems-on-a-chip and offers a unique opportunity for engineers working at the cutting edge of integrated circuit (IC) design and application. The conference includes several technical programs ranging from analog to mixed-mode, digital, radio frequency (RF), and power management circuits and systems with applications in various fields. This JSSC Special Section highlights selected papers from ISSCC, specifically on topics related to RF, wireless, analog, power management, and data converter circuits.
The rise of technology has brought with it a heightened awareness of the necessity to shield personal data and maintain exclusive access to specific knowledge. A notable solution that emerged from this consciousness is Zero-Knowledge Proofs (ZKPs) and, more specifically, Schnorrs Protocol. Historically, Zero-Knowledge Proofs have a compelling lineage, tracing their roots back to the fervent discussions among cryptographers aiming to achieve a balance between information sharing and privacy. ZKPs are cryptographic methods that allow one party to prove to another that a statement is true, without revealing any specific information about the statement itself. In the midst of these developments, Schnorrs Protocol emerged as a renowned interactive proof system. It possesses an intuitive structure that has made it pivotal in the enhancement of digital security. The typical flow of Schnorrs Protocol begins with the prover sending a commitment to the verifier. The verifier then sends a random challenge back to the prover, who, in turn, produces a response. Whats captivating is that the verifier can ascertain the validity of the proof without gaining insight into the underlying secret. Interactive Schnorrs Protocol involves real-time back-and-forth communication between the prover and verifier. On the other hand, the non-interactive version eliminates this need by using a cryptographic hash function, thereby streamlining the process.
  • Andy J Turko
    Andy J Turko
  • Britney L Firth
    Britney L Firth
  • Paul M Craig
    Paul M Craig
  • [...]
  • Brittney G Borowiec
    Brittney G Borowiec
Laboratory-based research dominates the fields of comparative physiology and biomechanics. The power of lab work has long been recognized by experimental biologists. For example, in 1932, Georgy Gause published an influential paper in Journal of Experimental Biology describing a series of clever lab experiments that provided the first empirical test of competitive exclusion theory, laying the foundation for a field that remains active today. At the time, Gause wrestled with the dilemma of conducting experiments in the lab or the field, ultimately deciding that progress could be best achieved by taking advantage of the high level of control offered by lab experiments. However, physiological experiments often yield different, and even contradictory, results when conducted in lab versus field settings. This is especially concerning in the Anthropocene, as standard laboratory techniques are increasingly relied upon to predict how wild animals will respond to environmental disturbances to inform decisions in conservation and management. In this Commentary, we discuss several hypothesized mechanisms that could explain disparities between experimental biology in the lab and in the field. We propose strategies for understanding why these differences occur and how we can use these results to improve our understanding of the physiology of wild animals. Nearly a century beyond Gause's work, we still know remarkably little about what makes captive animals different from wild ones. Discovering these mechanisms should be an important goal for experimental biologists in the future.
  • Su Jin Kim
    Su Jin Kim
  • Rifqi O. Affan
    Rifqi O. Affan
  • Hadas Frostig
    Hadas Frostig
  • [...]
  • Andrew S. Alexander
    Andrew S. Alexander
  • Maron Greenleaf
    Maron Greenleaf
  • Jeffrey Hoelle
    Jeffrey Hoelle
  • Magaly Medeiros
    Magaly Medeiros
  • Alberto Tavares
    Alberto Tavares
REDD+ is often characterised as a ‘global’ environmental framework implemented in tropical forests around the world. Yet studying actual cases of REDD+ can reveal complex interactions between scales, including under-recognised innovations at subnational and local scales. To understand these dynamics, this article brings together academics and policymakers to analyse the System of Incentives for Environmental Services (SISA)—a pioneering subnational policy in the Amazonian state of Acre, Brazil that includes a prominent jurisdictional REDD+ programme. While institutions, people, and ideas from outside of Acre contributed to its formulation, SISA is not a standardised local expression of a global policy. Rather, key aspects of it originated in ongoing and historical Acrean forest-use and governance. This analysis shows how innovative, place-based conservation policy can be influential, both within and beyond specific localities, in ways that challenge analyses of REDD+ that are primarily top-down. Our study of SISA also shows how topics of importance in contemporary REDD+ and forest conservation scholarship—efforts to make the living forest valuable, non-carbon social and environmental “co-benefits,” and landscape- and jurisdiction-wide approaches to combating deforestation—are connected to Acrean forest governance and history. Overall, this analysis elucidates the strengths and challenges of subnational forest governance and the complex inter-scalar dynamics in REDD+ and other conservation and climate policies. Portuguese abstract:
  • Roselia Mendez Murillo
    Roselia Mendez Murillo
  • Jennifer A Kam
    Jennifer A Kam
  • Andy J Merolla
    Andy J Merolla
Prior relational maintenance research primarily (a) considers only one family member’s perspective, (b) explores introspective communication, and (c) examines romantic relationships among highly resourced white samples in the United States. This study considered low-income, Latina/o/x/e immigrant families’ maintenance before, during, and after migration-related separation, using standpoint theory, social communication theory, and the long-distance relational maintenance model. We conducted semi-structured interviews with Latina/o/x/e parents and children who lived in separate countries (N = 20 dyads). Findings cast light on temporal (e.g., fathers often provided little to no notice to children of the upcoming separation, complicating the families’ ability to prospectively co-construct relational continuity) and cultural factors (e.g., endorsing traditional gender norms, relying on mothers to explain the separation to children after it had begun) in families’ maintenance processes. This study offers new insight into how families communicatively construct “ongoingness” in their bonds despite emotional, technological, and legal challenges posed by migration-related separation.
  • Caroline A Famiglietti
    Caroline A Famiglietti
  • Matthew Worden
    Matthew Worden
  • Leander D L Anderegg
    Leander D L Anderegg
  • Alexandra G Konings
    Alexandra G Konings
The South Atlantic Convergence Zone (SACZ) profoundly modulates precipitation from central to southeastern Brazil in the present‐day climate. However, the understanding of its long‐term behavior responding to various climate forcings remains limited. Here, we use an isotope‐enabled atmospheric general circulation model (ECHAM4.6) to examine the precipitation response of the SACZ during the mid‐Holocene about six thousand years ago. The model simulates a northward intensification of the SACZ in the mid‐Holocene, resulting in a dipole anomaly pattern relative to today's climate. The mid‐Holocene precipitation increased along the northern margin of the SACZ due to the strengthening of easterly winds across the tropical Atlantic, while an eastward deflection of the South American low‐level jet reduced moisture transport to southern Brazil, resulting in reduced precipitation along the southern margins of the SACZ. The north–south dipole response in precipitation is consistent with the mid‐Holocene hydroclimate change observed in proxy records from the region.
Individuals often employ simple rules that can emergently synchronize behaviour. Some collective behaviours are intuitively beneficial, but others like mate signalling in leks occur across taxa despite theoretical individual costs. Whether disparate instances of synchronous signalling are similarly organized is unknown, largely due to challenges observing many individuals simultaneously. Recording field collectives and ex situ playback experiments, we describe principles of synchronous bioluminescent signals produced by marine ostracods (Crustacea; Luxorina) that seem behaviorally convergent with terrestrial fireflies, and with whom they last shared a common ancestor over 500 Mya. Like synchronous fireflies, groups of signalling males use visual cues (intensity and duration of light) to decide when to signal. Individual ostracods also modulate their signal based on the distance to nearest neighbours. During peak darkness, luminescent ‘waves’ of synchronous displays emerge and ripple across the sea floor approximately every 60 s, but such periodicity decays within and between nights after the full moon. Our data reveal these bioluminescent aggregations are sensitive to both ecological and social light sources. Because the function of collective signals is difficult to dissect, evolutionary convergence, like in the synchronous visual displays of diverse arthropods, provides natural replicates to understand the generalities that produce emergent group behaviour.
In this paper, I examine the Literary Chinese reflexive zì , which exhibits a crosslinguistically uncommon pattern: it performs both anaphoric and emphatic uses in adverbial position. I show that it has several uses: signalling coreference between the subject and the object, the object’s possessor or the topic or focus of a complement clause, emphasising that the subject’s identity, and indicating that the event affected the subject itself or had no external cause. I argue against categorically dividing these uses into anaphoric and emphatic uses. I propose four properties to unify the various uses: the referent of zì is centrally relevant to the event denoted by the predicate, coreferential with the subject, unexpected in its role in the event, and often contrasts with an alternative referent that may play same role. I compare my account to properties of reflexives in other languages, and argue that zì only partially supports Levinson’s (Levinson, Stephen C. 1991. Pragmatic reduction of the binding conditions revisited. Journal of Linguistics 27(1). 107–161) theory of the development of anaphoric reflexives from emphatics.
We identify emergent hydrodynamics governing charge transport in Brownian random time evolution with various symmetries, constraints, and ranges of interactions. This is accomplished via a mapping between the averaged dynamics and the low-energy spectrum of a Lindblad operator, which acts as an effective Hamiltonian in a doubled Hilbert space. By explicitly constructing dispersive excited states of this effective Hamiltonian using a single-mode approximation, we provide a comprehensive understanding of diffusive, subdiffusive, and superdiffusive relaxation in many-body systems with conserved multipole moments and variable interaction ranges. Our approach further allows us to identify exotic Krylov-space-resolved diffusive relaxation despite the presence of dipole conservation, which we verify numerically. Therefore, we provide a general and versatile framework to qualitatively understand the dynamics of conserved operators under random unitary time evolution.
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11,257 members
Kai Ewert
  • Materials Research Laboratory
Samuel P Burke
  • Department of Physics
Alan Fridlund
  • Department of Psychological and Brain Sciences
Bruce Edward Kendall
  • Bren School of Environmental Science and Management
Gerald Jacobs
  • Department of Psychological and Brain Sciences
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