HEAD: HEtero-Assists Distillation for Heterogeneous Object Detectors

Conventional knowledge distillation (KD) methods for object detection mainly concentrate on homogeneous teacher-student detectors. However, the design of a lightweight detector for deployment is often significantly different from a high-capacity detector. Thus, we investigate KD among heterogeneous teacher-student pairs for a wide application. We observe that the core difficulty for heterogeneous KD (hetero-KD) is the significant semantic gap between the backbone features of heterogeneous detectors due to the different optimization manners. Conventional homogeneous KD (homo-KD) methods suffer from such a gap and are hard to directly obtain satisfactory performance for hetero-KD. In this paper, we propose the HEtero-Assists Distillation (HEAD) framework, leveraging heterogeneous detection heads as assistants to guide the optimization of the student detector to reduce this gap. In HEAD, the assistant is an additional detection head with the architecture homogeneous to the teacher head attached to the student backbone. Thus, a hetero-KD is transformed into a homo-KD, allowing efficient knowledge transfer from the teacher to the student. Moreover, we extend HEAD into a Teacher-Free HEAD (TF-HEAD) framework when a well-trained teacher detector is unavailable. Our method has achieved significant improvement compared to current detection KD methods. For example, on the MS-COCO dataset, TF-HEAD helps R18 RetinaNet achieve 33.9 mAP (+2.2), while HEAD further pushes the limit to 36.2 mAP (+4.5).Comment: ECCV 2022, Code: https://github.com/LutingWang/HEA

Controlling mass and energy diffusion with metamaterials

Diffusion driven by temperature or concentration gradients is a fundamental mechanism of energy and mass transport, which inherently differs from wave propagation in both physical foundations and application prospects. Compared with conventional schemes, metamaterials provide an unprecedented potential for governing diffusion processes, based on emerging theories like the transformation and the scattering cancellation theory, which enormously expanded the original concepts and suggest innovative metamaterial-based devices. We hereby use the term ``diffusionics'' to generalize these remarkable achievements in various energy (e.g., heat) and mass (e.g., particles and plasmas) diffusion systems. For clarity, we categorize the numerous studies appeared during the last decade by diffusion field (i.e., heat, particles, and plasmas) and discuss them from three different perspectives: the theoretical perspective, to detail how the transformation principle is applied to each diffusion field; the application perspective, to introduce various intriguing metamaterial-based devices, such as cloaks and radiative coolers; and the physics perspective, to connect with concepts of recent concern, such as non-Hermitian topology, nonreciprocal transport, and spatiotemporal modulation. We also discuss the possibility of controlling diffusion processes beyond metamaterials. Finally, we point out several future directions for diffusion metamaterial research, including the integration with artificial intelligence and topology concepts.Comment: This review article has been accepted for publication in Rev. Mod. Phy

A synergistic ozone-climate control to address emerging ozone pollution challenges

Tropospheric ozone threatens human health and crop yields, exacerbates global warming, and fundamentally changes atmospheric chemistry. Evidence has pointed toward widespread ozone increases in the troposphere, and particularly surface ozone is chemically complex and difficult to abate. Despite past successes in some regions, a solution to new challenges of ozone pollution in a warming climate remains unexplored. In this perspective, by compiling surface measurements at ∼4,300 sites worldwide between 2014 and 2019, we show the emerging global challenge of ozone pollution, featuring the unintentional rise in ozone due to the uncoordinated emissions reduction and increasing climate penalty. On the basis of shared emission sources, interactive chemical mechanisms, and synergistic health effects between ozone pollution and climate warming, we propose a synergistic ozone-climate control strategy incorporating joint control of ozone and fine particulate matter. This new solution presents an opportunity to alleviate tropospheric ozone pollution in the forthcoming low-carbon transition.This study was supported by the Research Grants Council of Hong Kong Special Administrative Region via General Research Funds (HKBU 15219621 and PolyU 15212421) and a Theme-based Research Scheme (T24-504/17-N). The authors acknowledge the support of the Australia–China Centre on Air Quality Science and Management. R.S. acknowledges support from ANID/FONDAP/1522A0001. D.S. thanks the program of Coordination for the Improvement of Higher Education Personnel (CAPES) (436466/2018-0). X.X. acknowledges funding from the Natural Science Foundation of China (41330422) and the Chinese Academy of Meteorological Sciences (2020KJ003). K.L. is supported by the Natural Science Foundation of China (42205114), Jiangsu Carbon Peak and Neutrality Science and Technology Innovation fund (BK20220031), and the Startup Foundation for Introducing Talent of NUIST. We sincerely appreciate all the organizations and programs introduced in the section “experimental procedures” for freely providing ozone data. We thank Dr. Owen Cooper (University of Colorado, Boulder, and NOAA) for insightful guidance and discussion. No organization or program will be responsible for the results generated from their data.Peer reviewe

The Affairs of Guizhou Province

1. A weak economic foundation and a single source of income is the first major characteristic of the fiscal affairs of Guizhou Province. The vast majority of provincial fiscal revenues comes from industrial and commercial tax revenues. In the past thirty-five years, the proportion of industrial and commercial tax revenue contributed to, on average, 79.4 percent of the [annual] local fiscal revenue. In 1984, industrial and commercial tax revenue made up 90 percent of the local fiscal revenue throughout the province, and, moreover, the tax revenue from cured tobacco and cigarettes made up a large portion of the industrial and commercial tax revenues. In 1984, tax revenue from the "two smokes" made up 41.7 percent of the industrial and commercial tax revenue of the entire province. Therefore, the pace of development of the "two smokes" in reality basically determines the rate of growth of the province's budgetary revenue. However, the "two smokes" are commodities whose production is controlled and restricted by the state. As soon as there is a shift in the supply or demand in the marketplace, it would become exceedingly difficult to assure budgetary revenue. Therefore, to allow the fiscal revenues of Guizhou Province to grow and develop in a stable and sustained fashion, we must, while continuing to develop and give play to the advantageous position occupied by the "two smokes," also open up and explore additional sources of wealth, as well as seek new ways to increase revenue.

An ozone “pool” in South China : investigations on atmospheric dynamics and photochemical processes over the Pearl River Estuary

202310 bcchVersion of RecordRGCOthersGuangzhou Science and Technology Project; Research Funding Scheme from Policy Innovation and Co-ordination Office of the Hong Kong Special Administrative Region Government; Hong Kong Polytechnic UniversityPublishe

Causes of a continuous summertime O₃ pollution event in Jinan, a central city in the North China Plain

In the summer of 2017, measurements of ozone (O3) and its precursors were carried out at an urban site in Jinan, a central city in the North China Plain (NCP). A continuous O3 pollution event was captured during 4–11 August, with the maximum hourly O3 mixing ratio reaching 154.1&thinsp;ppbv. Model simulation indicated that local photochemical formation and regional transport contributed 14.0±2.3 and 18.7±4.0&thinsp;ppbv&thinsp;h−1, respectively, to the increase in O3 during 09:00–15:00&thinsp;LT (local time) in this event. For local O3 formation, the calculated OH reactivities of volatile organic compounds (VOCs) and carbon monoxide (CO) were comparable between O3 episodes and non-episodes (p&gt;0.05), so was the OH reactivity of nitrogen oxides (NOx). However, the ratio of OH reactivity of VOCs and CO to that of NOx increased from 2.0±0.4&thinsp;s−1&thinsp;s1 during non-episodes to 3.7±0.7&thinsp;s−1&thinsp;s1 during O3 episodes, which resulted in the change in the O3 formation mechanism from the VOC-limited regime before the O3 pollution event to the transitional regime during the event. Correspondingly, the simulated local O3 production rate during the event (maximum: 21.3&thinsp;ppbv&thinsp;h−1) was markedly higher than that before the event (p&lt;0.05) (maximum: 16.9&thinsp;ppbv&thinsp;h−1). Given that gasoline and diesel exhaust made large contributions to the abundance of O3 precursors and the O3 production rate, constraint on vehicular emissions is the most effective strategy to control O3 pollution in Jinan. The NCP has been confirmed as a source region of tropospheric O3, where the shift in regimes controlling O3 formation like the case presented in this study can be expected across the entire region, due to the substantial reductions of NOx emissions in recent years.</p