Discriminative Region Suppression for Weakly-Supervised Semantic Segmentation

Weakly-supervised semantic segmentation (WSSS) using image-level labels has recently attracted much attention for reducing annotation costs. Existing WSSS methods utilize localization maps from the classification network to generate pseudo segmentation labels. However, since localization maps obtained from the classifier focus only on sparse discriminative object regions, it is difficult to generate high-quality segmentation labels. To address this issue, we introduce discriminative region suppression (DRS) module that is a simple yet effective method to expand object activation regions. DRS suppresses the attention on discriminative regions and spreads it to adjacent non-discriminative regions, generating dense localization maps. DRS requires few or no additional parameters and can be plugged into any network. Furthermore, we introduce an additional learning strategy to give a self-enhancement of localization maps, named localization map refinement learning. Benefiting from this refinement learning, localization maps are refined and enhanced by recovering some missing parts or removing noise itself. Due to its simplicity and effectiveness, our approach achieves mIoU 71.4% on the PASCAL VOC 2012 segmentation benchmark using only image-level labels. Extensive experiments demonstrate the effectiveness of our approach. The code is available at https://github.com/qjadud1994/DRS.Comment: AAAI 2021, Accepte

Bosonization of Non-Fermi Liquids

Understanding non-Fermi liquids in dimensions higher than one remains one of the most formidable challenges in modern condensed matter physics. These systems, characterized by an abundance of gapless degrees of freedom and the absence of well-defined quasiparticles, defy conventional analytical frameworks. Inspired by recent work on the bosonization of Fermi surfaces [Delacretaz, Du, Mehta, and Son, Physical Review Research, 4, 033131 (2022)], we present a procedure for bosonizing non-Fermi liquids, which provides a holistic approach capable of addressing their intricate physics. Our method involves parameterizing the generalized fermionic distribution function through a bosonic field that describes frequency-dependent local variations of the chemical potential in momentum space. We propose an effective action that produces the collisionless quantum Boltzmann equation as its equation of motion and can straightforwardly be used for any dimension and Fermi surface of interest. Even at the quadratic order, this action reproduces highly non-trivial results obtainable only through involved analysis with alternative means. By offering a comprehensive description of the physics of non-Fermi liquids, our work stands as an important building block in advancing the comprehension of strange metals and associated phenomena.Comment: 10+8 pages, 1 figur

Complex fixed points of the non-Hermitian Kondo model in a Luttinger liquid

Non-Hermitian physics in open quantum many-body systems provides novel opportunities for discovery of exotic quantum phenomena unexpected in Hermitian systems. A previous study of the non-Hermitian Kondo problem in ultra-cold atoms reports reversion of renormalization group flows which violates the $g$-theorem and produces an unusual quantum phase transition. In this work, we study the effect of electron-electron interactions by considering the non-Hermitian Kondo problem in a Luttinger liquid. By performing a perturbative renormalization group analysis to two-loop order, we find that the interplay between non-Hermitian Kondo couplings and electron-electron interactions can produce a pair of complex fixed points. Complex fixed points have often been discussed in an attempt to understand extremely long correlation length of Hermitian systems with weakly first-order transitions. Here, we show that complex fixed points arise naturally and can be physically realized in open quantum systems. We discuss consequences of the complex fixed points and future directions.Comment: 7+4 pages, 3 figures, 1 tabl

Microscopic theory of multi-stage Fermi surface reconstruction in heavy fermion systems with quartet multipolar local moments

Recent experiments on $\text{Ce}_{3}\text{Pd}_{20}\text{(Si,Ge)}_{6}$ show novel quantum critical behaviors associated with two consecutive quantum phase transitions upon varying the external magnetic field. Interestingly, the derivative of the Hall conductivity shows a discontinuous jump at each phase transition, which was attributed to sequential Fermi surface reconstructions. Motivated by this discovery and previous theory work, we consider a microscopic model of itinerant electrons coupled to the local moments described by a quartet of ground states in a crystal-electric-field (CEF). Such a quartet arises due to two degenerate Kramers doublets of $\text{Ce}^{3+}$ ions in a cubic CEF and supports a large number of dipolar, quadrupolar, and octupolar moments. Specifically, we investigate emergent quantum phase transitions and criticality in a local effective model, the so-called Bose-Fermi Kondo model. This model describes the competition between the Kondo effect with the itinerant electrons and RKKY interaction for all of the 15 symmetry-allowed multipolar moments. Using renormalization group analyses, we demonstrate that a multitude of quantum phase transitions can occur depending on which multipolar moments participate in the Fermi surface formation and which other multipolar moments are decoupled via Kondo destruction. We provide a concrete example of two consecutive quantum phase transitions that involve the quadrupolar and dipolar/octupolar moments at two different stages. Our work provides an illuminating insight as to the importance of local symmetries in understanding multipolar Kondo lattice systems and an outlook for future directions.Comment: 12+12 pages, 5+10 figures, 9+2 tables; the first two authors contributed equally to this wor

Non-Fermi liquid behavior and quantum criticality in cubic heavy fermion systems with non-Kramers multipolar local moments

Notable non-Fermi liquid and quantum critical behaviors are observed in rare-earth metallic systems with non-Kramers local moments supporting a number of different multipolar moments. A prominent example is $\text{Pr(Ti,V)}_{2}\text{Al}_{20}$, where the non-Kramers doublet of the $\text{Pr}^{3+}$ ion allows quadrupolar and octupolar moments, but lacks a dipolar moment. Previous theoretical studies show that a single impurity Kondo problem with such an unusual local moment leads to novel non-Fermi liquid states. In this work, we investigate possible quantum critical behaviors arising from the competition between non-Fermi liquid states and multipolar-ordered phases induced by the RKKY interaction. We consider a local version of the corresponding Kondo lattice model, namely the Bose-Fermi Kondo model. Here, the multipolar local moments are coupled to fermionic and bosonic bath degrees of freedom representing the multipolar Kondo effect and RKKY interactions. Using a perturbative renormalization group (RG) study up to two loop order, we find critical points between non-Fermi liquid Kondo fixed points and a quadrupolar ordered fixed point. The critical points describe quantum critical behaviors at the corresponding phase transitions and can be distinguished by higher order corrections in the octupolar susceptibility that can be measured by ultrasound experiments. Our results imply the existence of a rich expansion of the phases and quantum critical behaviors in multipolar heavy fermion systems.Comment: 7+7 pages, 3+10 figures, 1+1 tables; changed title, added more references, modified introduction, and corrected typos; the first two authors contributed equally to this wor

Digital Forensic Methodology for Detection of Abnormal Flight of Drones

When a drone accident has occurred, it is difficult to decide whether it is due to a crime, malfunction, mistake, or external force. Although the cause of the accident is elucidated through analysis of artifacts or flight data, there are many limitations. In this study, we present a method for detecting an abnormal flight using the motor current values and controller direction values of a drone. The experimental result revealed that, in the case of a normal flight, the current values of four motors were similar in hovering state and the current value of rear motors were increased when the drone was flying forwards. In the case of an abnormal flight, when the drone moved rightwards due to external force in hovering state, the current values of the two motors on the right side were increased greatly. After a period of time following the movement to the right side, the current values of all the motors converged to 0. In the future, motor current values and controller direction values may be used to determine whether an abnormal flight in a drone accident has occurred because of external force by wind, birds, persons, or the like

Facile electrodeposition of high-density CuCo2O4 nanosheets as a high-performance Li-ion battery anode material

High-density CuCo2O4 nanosheets are grown on Ni foam using electrodeposition followed by air annealing for a Li-ion battery anode. The anode exhibits a high discharge capacity of 1244 mAh/g at 0.1 A/g (82% coulombic efficiency) and excellent high-rate performance with 95% capacity retention (1100 mAh/g after 200 cycles at 1 A/g). The outstanding battery performance of the CuCo2O4 anode is attributed to its binder-free direct contact to the current collector and high-density nanosheet morphology. The present experimental findings demonstrate that the electrodeposited binder-free CuCo2O4 material may serve as a safe, low-cost, long-cycle life anode for Li-ion batteries

Nanoflake NiMoO4 based smart supercapacitor for intelligent power balance monitoring.

A supercapacitor is well recognized as one of emerging energy sources for powering electronic devices in our daily life. Although various kind of supercapacitors have been designed and demonstrated, their market aspect could become advanced if the utilisation of other physicochemical properties (e.g. optical) is incorporated in the electrode. Herein, we present an electrochromic supercapacitor (smart supercapacitor) based on a nanoflake NiMoO4 thin film which is fabricated using a facile and well-controlled successive ionic layer adsorption and reaction (SILAR) technique. The polycrystalline nanoflake NiMoO4 electrode exhibits a large electrochemically active surface area of ~ 96.3 cm2. Its nanoporous architecture provides an easy pathway for the intercalation and de-intercalation of ions. The nanoflake NiMoO4 electrode is dark-brown in the charged state and becomes transparent in the discharged state with a high optical modulation of 57%. The electrode shows a high specific capacity of 1853 Fg–1 at a current rate of 1 Ag–1 with a good coloration efficiency of 31.44 cm2/C. Dynamic visual information is obtained when the electrode is charged at different potentials, reflecting the level of energy storage in the device. The device retains 65% capacity after 2500 charge-discharge cycles compared with its initial capacity. The excellent performance of the nanoflake NiMoO4 based smart supercapacitor is associated with the synergetic effect of nanoporous morphology with a large electrochemically active surface area and desired chemical composition for redox reaction