Pedestrian Attribute Recognition: A Survey

Recognizing pedestrian attributes is an important task in computer vision community due to it plays an important role in video surveillance. Many algorithms has been proposed to handle this task. The goal of this paper is to review existing works using traditional methods or based on deep learning networks. Firstly, we introduce the background of pedestrian attributes recognition (PAR, for short), including the fundamental concepts of pedestrian attributes and corresponding challenges. Secondly, we introduce existing benchmarks, including popular datasets and evaluation criterion. Thirdly, we analyse the concept of multi-task learning and multi-label learning, and also explain the relations between these two learning algorithms and pedestrian attribute recognition. We also review some popular network architectures which have widely applied in the deep learning community. Fourthly, we analyse popular solutions for this task, such as attributes group, part-based, \emph{etc}. Fifthly, we shown some applications which takes pedestrian attributes into consideration and achieve better performance. Finally, we summarized this paper and give several possible research directions for pedestrian attributes recognition. The project page of this paper can be found from the following website: \url{https://sites.google.com/view/ahu-pedestrianattributes/}.Comment: Check our project page for High Resolution version of this survey: https://sites.google.com/view/ahu-pedestrianattributes

Achievements and Challenges in Improving Air Quality in China: Analysis of the Long-Term Trends from 2014 to 2022

Due to the implementation of air pollution control measures in China, air quality has significantly improved, although there are still additional issues to be addressed. This study used the long-term trends of air pollutants to discuss the achievements and challenges in further improving air quality in China. The Kolmogorov-Zurbenko (KZ) filter and multiple-linear regression (MLR) were used to quantify the meteorology-related and emission-related trends of air pollutants from 2014 to 2022 in China. The KZ filter analysis showed that PM2.5 decreased by 7.36 ± 2.92% yr􀀀 1, while daily maximum 8-h ozone (MDA8 O3) showed an increasing trend with 3.71 ± 2.89% yr􀀀 1 in China. The decrease in PM2.5 and increase in MDA8 O3 were primarily attributed to changes in emission, with the relative contribution of 85.8% and 86.0%, respectively. Meteorology variations, including increased ambient temperature, boundary layer height, and reduced relative humidity, also contributed to the reduction of PM2.5 and the enhancement of MDA8 O3. The emission-related trends of PM2.5 and MDA8 O3 exhibited continuous decrease and increase, respectively, from 2014 to 2022, while the variation rates slowed during 2018–2020 compared to that during 2014–2017, highlighting the challenges in further improving air quality, particularly in simultaneously reducing PM2.5 and O3. This study recommends reducing NH3 emissions from the agriculture sector in rural areas and transport emissions in urban areas to further decrease PM2.5 levels. Addressing O3 pollution requires the reduction of O3 precursor gases based on site-specific atmospheric chemistry considerations

A novel thermo-mechanical anti-icing/de-icing system using bi-stable laminate composite structures with superhydrophobic surface

A novel anti-icing/de-icing system composed of bi-stable laminate composite structures with superhydrophobic surface and soft electrothermal patch is investigated in this paper. In this system, the superhydrophobic surface has superior performance in anti-icing and de-icing by reducing the adhesion of the ice-skin interface; meanwhile, a thermo-mechanical way to remove ice is conducted by deforming the bi-stable structures using heating actuation method. The superhydrophobic layer is fabricated by decreasing the free energy of copper oxide on the copper surface. The water contact angle of the superhydrophobic surface is tested by an optical contact angle measuring device, which reaches above 155° and the sliding angle is less than 10°. In addition, the microstructure of superhydrophobic layer is characterized by using a scanning electron microscope (SEM) to illustrate the superhydrophobic mechanism. Moreover, outstanding self-cleaning properties and UV-durability are obtained on the prepared surface. Experimental results indicate that the system has good performances in both anti-icing and de-icing processes when working at the subzero temperature. Meanwhile, there is no liquid water left on the surface after the snap-through process of bi-stable structures. Besides, the factors that affect the anti-icing and de-icing performance of system are discussed, including the superhydrophobic property, morphing characteristic of bi-stable laminate composite structures and actuating method. Finally, the finite element method is used to simulate the factors that affect the deformation of bi-stable structures independently, including the single layer thickness, stacking sequence of the laminate and the embedment of the electrothermal alloy

Allelic shift in cis-elements of the transcription factor RAP2.12 underlies adaptation associated with humidity in Arabidopsis thaliana

Populations of widespread species are usually geographically distributed through contrasting stresses, but underlying genetic mechanisms controlling this adaptation remain largely unknown. Here, we show that in Arabidopsis thaliana, allelic changes in the cis-regulatory elements, WT box and W box, in the promoter of a key transcription factor associated with oxygen sensing, RELATED TO AP 2.12 (RAP2.12), are responsible for differentially regulating tolerance to drought and flooding. These two cis-elements are regulated by different transcription factors that downstream of RAP2.12 results in differential accumulation of hypoxia-responsive transcripts. The evolution from one cis-element haplotype to the other is associated with the colonization of humid environments from arid habitats. This gene thus promotes both drought and flooding adaptation via an adaptive mechanism that diversifies its regulation through noncoding alleles

Dropwise condensation in the presence of non-condensable gas

Dropwise condensation, which collects the condensate liquid in the form of droplets, has attracted a growing interest due to much higher heat transfer coefficient. One important and challenging issue in dropwise condensation is the presence of non-condensable gas (NCG) which drastically reduces its heat transfer performance. Concerning the mechanism understanding, this thesis is aiming to investigate dropwise condensation in case of NCG by combing different methods. Firstly, convective dropwise condensation out of moist air is experimentally investigated under controllable conditions. In modeling, some crucial aspects are reasonably captured: the coupled heat and mass transfer during droplet growth by a multi-scale droplet growth model; the inter-droplet interaction defined by a distributed point sink method; the enhancement of the convective mass transfer using the droplet Sherwood number. Furthermore, a multi-component multi-phase thermal pseudopotential-based LB model is developed to advance the directly numerical simulation of dropwise condensation

Dropwise condensation in the presence of non-condensable gas

Dropwise condensation, which collects the condensate liquid in the form of droplets, has attracted a growing interest due to much higher heat transfer coefficient. One important and challenging issue in dropwise condensation is the presence of non-condensable gas (NCG) which drastically reduces its heat transfer performance. Concerning the mechanism understanding, this thesis is aiming to investigate dropwise condensation in case of NCG by combing different methods. Firstly, convective dropwise condensation out of moist air is experimentally investigated under controllable conditions. In modeling, some crucial aspects are reasonably captured: the coupled heat and mass transfer during droplet growth by a multi-scale droplet growth model; the inter-droplet interaction defined by a distributed point sink method; the enhancement of the convective mass transfer using the droplet Sherwood number. Furthermore, a multi-component multi-phase thermal pseudopotential-based LB model is developed to advance the directly numerical simulation of dropwise condensation

Heat Transfer and Flow Characteristics in Rib-/Deflector-Roughened Cooling Channels with Various Configuration Parameters

The present paper deals with a detailed numerical investigation of the turbulent flow inside a stationary rib-/deflector-roughened cooling channel. Various downstream-shaped deflectors including sloping-board deflectors [Cases A1, A2], guide-shaped deflectors [Cases B1, B2], and drop-shaped deflectors [Cases C1, C2] and configuration parameters such as channel aspect ratio (AR=0.5, 1 and 2), and rib-pitch-to-rib-height ratio (P/e=5, 8, and 10) are investigated. The main objective is to design an appropriate deflector to improve the flow characteristics in the wake of the deflectors and guide the flow between two neighboring rib turbulators to enhance the heat transfer performance. A quasi-three-dimensional flow structure, supported by the stream tracer field in some planes, is established to improve and deepen the understanding as well as the analysis of the complex flow field in the rib-/deflector-roughened channels. In addition, the thermal performance corresponding to various rib-pitch-to-rib-height ratios and aspect ratios emphasizes the role of the configuration parameters in the heat transfer and flow resistance performance. The results demonstrate that the deflectors trip the boundary layer and blend the fluid flow, and that the sloping board deflectors contribute to enlarging the turbulence level of the whole cooling channel, more than in the wake region. It is found that Cases A1 and A2 provide the best heat transfer performance, while Case C1 presents the largest thermal enhancement factor Nu/Nu(0)/(f/f(0))(1/3) at high Reynolds number. The wide-aspect-ratio channel with deflectors and large pitch-to-height ratio ribs exhibits much better heat transfer performance

Numerical study of the effect of forced convective flow on dropwise condensation by thermal LBM simulation

The enhancement mechanism of forced convective flow on dropwise condensation over a cold spot is numerically investigated by two-dimensional hybrid thermal lattice Boltzmann (LB) model based on the Shan-Chen pseudopotential LB model. After validating the present LB model, dropwise condensation over a cold spot as the nucleation region is simulated. The well-known power law for the growth of a single condensing droplet is demonstrated. Finally, the simulation of dropwise condensation considering the convection flow or not is carried out in the constant contact radius (CCR) mode. Using the CCR model, the effect of contact angle can be also investigated. The result of streamline field indicates that the forced convectional flow complicates the internal flow of droplet and main flow. The dragging force from main flow changes the size of two symmetric vortices inside the droplet. And the channel flow is also strongly influenced by the suction effect caused by condensation at the three phase contact line. By comparison, the heat transfer enhancement of the superimposed flow is not worth mentioning. The present study illustrates the mechanisms of dropwise condensation under forced convectional flow