高温聚合物电解质膜燃料电池膜电极中磷酸分布及调控策略研究进展

高温聚合物电解质膜燃料电池(HT-PEMFC)由于其较高的运行温度(140–200℃)而具有较快的电极反应动力学和良好的抗CO等杂质气体毒化能力以及简化水热管理等优势,是PEMFC的重要发展方向之一。HT-PEMFC的核心部件为基于磷酸掺杂聚合物电解质膜(HT-PEM)组装的膜电极(MEA)。在高温膜电极(HT-MEA)中,一方面聚合物电解质膜和催化层中的离子传导极大地依赖于磷酸的含量;而另一方面磷酸分子填充在高分子链周围会引起聚合物膜力学性能的下降,迁移进催化层中的磷酸容易导致阴阳极催化层的“酸淹”以及在铂催化剂表面吸附而降低催化剂活性。因此,研究磷酸在高温聚合物电解质膜电极中的分布状态和迁移过程,对构建高性能和高稳定性的HT-PEMFC至关重要。基于此,本文对近年来HT-MEA中磷酸的分布、动态迁移过程的研究现状进行了梳理分析,对HT-MEA(包括高温聚合物电解质膜和催化层)中磷酸分布和迁移的调节与优化策略研究进展进行了较全面的综述,并对其未来发展趋势进行了评述和展望。

A Direct Liquid Fuel Cell with High Power Density Using Reduced Phosphotungstic Acid as Redox Fuel

Direct liquid fuel cells(DLFCs)are proposed to address the problems of high cost and complex storage and transportation of hydrogen in traditional hydrogen-oxygen proton exchange membrane fuel cells.However,present fuels of organic small molecules used in DLFCs are restricted to problems of sluggish electrochemical kinetics and easily poisoning of precious metal catalysts.Herein,we demonstrate reduced phosphotungstic acid as a liquid fuel for DLFCs based on its advantages of high chemical and electrochemical stability,high electrochemical activity on common carbon material electrodes,and low permeability through proton exchange membranes.The application of phosphotungstic acid fuel effectively solves the problems of high cost of anode catalysts and serious fuel permeation loss in traditional DLFCs.A phosphotungstic acid fuel cell achieves a peak power density of466 mW cm^(-2)at a cell voltage of 0.42 V and good stability at current densities in the range from 20 to 200 mA cm^(-2).

Distributed Cooperative Secondary Voltage Control in an Unbalanced Microgrid

The negative-sequence reactive power-conductance(Q^(−)-G) droop control strategy is a conventional method to compensate for the output unbalanced voltages in an islanded MG.Nevertheless, the conflict between unbalanced voltage compensation and negative-sequence reactive power sharing, caused bythe impedance mismatching of distribution lines and distributedgenerators, has not been solved only by Q^(−)-G droop control.In this paper, a distributed cooperative secondary unbalancedvoltage control strategy is proposed to decrease the outputvoltage unbalance factor (VUF) of each droop-controlled DG,as well as to further enhance the negative-sequence reactivepower sharing effectiveness among DGs by properly shiftingup and down the Q^(−)-G droop characteristics of each DG.An algorithm for adaptive VUF weight coefficient is proposedto better suppress VUF under severe imbalance conditions.Furthermore, a negative-sequence small-signal model of an MGunder an unbalanced condition, considering the communicationdelay time of the proposed SUVC, is established to analyze thesystem’s stability and transient performance under the influenceof some critical parameters. Finally, the effectiveness of theproposed strategy is validated by the simulation results froma real-time emulator of StarSim HIL.

SRS-Net: Training object detectors from scratch for remote sensing images without pretraining

Most of the current object detection algorithms use pretrained models that are trained on ImageNet and then fine-tuned in the network,which can achieve good performance in terms of general object detectors.However,in the field of remote sensing image object detection,as pretrained models are significantly different from remote sensing data,it is meaningful to explore a train-fromscratch technique for remote sensing images.This paper proposes an object detection framework trained from scratch,SRS-Net,and describes the design of a densely connected backbone network to provide integrated hidden layer supervision for the convolution module.Then,two necessary improvement principles are proposed:studying the role of normalization in the network structure,and improving data augmentation methods for remote sensing images.To evaluate the proposed framework,we performed many ablation experiments on the DIOR,DOTA,and AS datasets.The results show that whether using the improved backbone network,the normalization method or training data enhancement strategy,the performance of the object detection network trained from scratch increased.These principles compensate for the lack of pretrained models.Furthermore,we found that SRS-Net could achieve similar to or slightly better performance than baseline methods,and surpassed most advanced general detectors.

因视物模糊就诊的1例糖尿病患者的全科-专科分级管理

报道1例因视物模糊就诊的糖尿病患者的全科-专科分级管理过程。患者由社区全科医生首诊为重度非增殖期糖尿病视网膜病变,并在社区对患者进行综合评估,及时转诊,专科医生针对并发症进行规范治疗。

Mechanistic investigation on Hg^(0) capture over MnO_(x) adsorbents:effects of the synthesis methods

This study demonstrated the impacts of the synthesis methods on the textural structures,chemical properties,and Hg^(0)capture capability of the MnO_(x)system.Compared with the samples synthesized using the precipitation(PR)and hydrothermal(HT)methods,the adsorbent prepared via the sol-gel(SG)technique gave the best performance.At 150℃,ca.90%Hg^(0)removal efficiency was reached after 7.5 h for MnO_(x)prepared by the SG method,ca.40%higher than that of the other two methods.The specific surface area of the adsorbent synthesized via the SG technique(23 m^(2)/g)was almost double that of the adsorbent prepared by the HT method(12 m^(2)/g)and three times that of the one prepared by the PR method(7 m^(2)/g).The presence of plentiful acid sites from the SG method facilitated the physisorption of Hg^(0),making more Hg^(0)available to be oxidized to HgO by the redox sites and thus giving the adsorbent prepared by the SG method the highest Hg^(0)removal efficiency.The strong oxidative ability accelerated the oxidation of the physically adsorbed Hg^(0)to HgO,which explained the higher Hg^(0)removal efficiency of the sample prepared using the HT method than that of the one synthesized by the PR technique.During the whole Hg^(0)removal cycles,chemisorption dominated,with the initial adsorption stage and the external mass-transfer process playing important roles.

Learning power Gaussian modeling loss for dense rotated object detection in remote sensing images

Object detection in Remote Sensing(RS)has achieved tremendous advances in recent years,but it remains challenging for rotated object detection due to cluttered backgrounds,dense object arrangements and the wide range of size variations among objects.To tackle this problem,Dense Context Feature Pyramid Network(DCFPN)and a powerα-Gaussian loss are designed for rotated object detection in this paper.The proposed DCFPN can extract multi-scale information densely and accurately by leveraging a dense multi-path dilation layer to cover all sizes of objects in remote sensing scenarios.For more accurate detection while avoiding bottlenecks such as boundary discontinuity in rotated bounding box regression,a-Gaussian loss,a unified power generalization of existing Gaussian modeling losses is proposed.Furthermore,the properties ofα-Gaussian loss are analyzed comprehensively for a wider range of applications.Experimental results on four datasets(UCAS-AOD,HRSC2016,DIOR-R,and DOTA)show the effectiveness of the proposed method using different detectors,and are superior to the existing methods in both feature extraction and bounding box regression。

Impacts of corridor design:An investigation on occupant perception of corridor forms in elderly facilities

The study addresses the issue of monotonous and lengthy corridors with a single spatial form commonly found in Chinese elderly facilities.We aim to assess the influence of the built spatial environment on the emotions of the elderly quantitatively.To do this,Virtual Reality(VR)technology was employed to construct a digital twin model featuring three corridor forms:straight,arc,and folded,respectively.Forty participants experienced walking in each corridor form for 144 s,while electroencephalogram(EEG)data and subjective questionnaires were collected to explore the psychological and physiological effects caused by different corridors.The results of the questionnaire indicate that arc corridor yielded the highest satisfaction,followed by straight corridor,and the satisfaction for folded corridor is the lowest.EEG results show that folded corridor has 26.0%higher average power than arc corridor and 6.6%higher than straight corridor.The participants consume less energy and are more satisfied in arc corridor,compared to straight and folded corridors.The results establish a correlation between spatial form and occupant perception,suggesting that moderate spatial variations contribute to a better experience of the elderly.Moreover,this study provides quantitative cross-referencing information to optimize the design methods of public space in elderly facilities.

新型疫苗佐剂的研究进展

近年来,核酸疫苗、基因工程疫苗、合成肽疫苗等新型疫苗的研究取得快速的发展,但这些疫苗与传统的灭活或活体疫苗相比,往往存在免疫原性差等问题,因此需要佐剂来增强其作用。佐剂已被证明是疫苗中的关键成分,佐剂种类众多,尚无统一的分类方法,目前应用最多的佐剂是铝佐剂和弗氏佐剂,但随着新型疫苗的开发,新型佐剂的开发必不可少。根据目前佐剂的研究现状,主要从免疫调节分子类佐剂、抗原递送类佐剂、复合佐剂3个方面进行分析阐述,以期对佐剂的研制提供参考。

主动性人格与建言行为的关系——一个被中介的调节效应模型

基于特质激活理论,本研究引入了上下级关系和内部人身份感知两个情境因素,系统探讨主动性人格特质如何被激活并表达为员工的建言行为。通过两阶段的追踪调查,对227份配对数据分析发现:主动性人格对建言行为产生正向影响;上下级关系和内部人身份感知在主动性人格与建言行为的关系中起到调节作用。此外,上下级关系通过内部人身份感知对主动性人格与建言行为关系产生影响,表现为一种被中介的调节效应。

Construction of porous covalent organic polymer as photocatalysts for RhB degradation under visible light

In the present work,a novel porous,and chemically stable amine-based covalent organic polymer(POP-1) was designed and synthesized under solvothermal conditions.The porosity,crystallinity,chemical stability,electrochemical properties,and diffuse reflectance of POP-1 were investigated via N_2 sorption experiment,power X-ray diffraction,thermogravimetric analysis,cyclic voltammetry,and ultraviolet visible near infrared spectrometry,respectively.POP-1 exhibits good chemical stability in both acidic and alkaline aqueous solutions,as well as in organic solvents.Undoped POP-1 can be directly used as a photocatalyst for rhodamine B irradiation degradation under light-emitting diode and natural light.The E_a of POP-1 for RhB degradation is 82.37 kJ/mol.Furthermore,POP-1 can be reused as a catalyst in RhB degradation without degraded catalytic activity.

Elucidating the electro-catalytic oxidation of hydrazine over carbon nanotube-based transition metal single atom catalysts

Elucidating the reaction mechanism of hydrazine oxidation reaction(HzOR)over carbon-based catalysts is highly propitious for the rational design of novel electrocatalysts for HzOR.In present work,isolated first-row transition metal atoms have been coordinated with N atoms on the graphite layers of carbon nanotubes via a M-N_(4)-C configuration(MSA/CNT,M=Fe,Co and Ni).The HzOR over the three single atom catalysts follows a predominant 4-electron reaction pathway to emit N_(2) and a negligible 1-electron pathway to emit trace of NH3,while their electrocatalytic activity for HzOR is dominated by the absorption energy of N2H4 on them.Furthermore,FeSA/CNT reverses the passivation effect on Fe/C and shows superior performance than CoSA/CNT and NiSA/CNT with a recorded high mass activity for HzOR due to the higher electronic charge of Fe over Co and Ni in the M-N_(4)-C configuration and the lowest absorption energy of N_(2)H_(4) on FeSA/CNT among the three MSA/CNT catalysts.

Optimizing flow field in an SCR system of a 600 MW power plant:effects of static mixer alignment style

The fluid flow in a selective catalytic reduction(SCR)system of a 600 MW power station is optimized using the numerical simulation method in this work.Given that guide plates and straightening gratings are properly installed,the relative standard deviation(C_(v))of velocity related to the inlet of an ammonia injection grid(AIG)and catalysts satisfy the engineering demand of<15%,suggesting that a relatively uniform velocity field is obtained.The in-line arrangement of static mixers strengthens the disturbance of fluid,promoting the mixing of reductant NH_(3)with flue gas.The NH_(3)mole fraction C_(v)value correlated to the inlet of catalysts drops to ca.3.5%,which is lower than that in the cases when the mixers are aligned in a staggered style.These results indicate that a solid foundation is achieved for the effective abatement of NO_(x)in practical applications.

New insights into the relationships between performance and physicochemical properties of FeO_(x)-NbO_(x)mixed oxide catalysts for the NH_(3)-SCR reactions

In this study,we prepared Fe_(2)O_(3)-Nb_(2)O_(5)binary mixed oxide catalysts using co-precipitation(CP),sol-gel(SG),and solid process(SR)methods and tested their performance.All the catalysts exhibited over 75%NO_(x)removal efficiency between 250℃and 400℃.Compared with the samples prepared by the SR method,catalyst synthesized using CP and SG methods possessed a larger specific surface area,which could compensate for the lower surface area-normalized reaction rate originat-ing from the insufficient reactive surface oxygen species,hence exhibiting a relatively high low-temperature apparent deNO_(x)activity.However,at a high-temperature region,limited amount of reactive surface oxygen species,together with abundant strong acid sites,facilitated the proceeding of NH_(3)reduction of NO_(x),which well explained the higher apparent activity of the catalyst prepared by SG method than the other two samples.It seemed that specific surface area had an important role to play in the low-temperature apparent performance of the catalysts,while chemical properties mainly decided the activity at an elevated temperature.

Investigation on the Hg^(0) adsorption performance of Na_(2)S- and S^(0)-modified ZSM-5 adsorbent

In this study,a series of Na_(2)S-and S^(0)-decorated ZSM-5 adsorbents were prepared and their Hg^(0) adsorption performance was evaluated.Given that S^(0) and Na_(2)S were co-doped with the mass ratio of S^(0) to ZSM-5 fixed to 2:1,Hg^(0) removal efficiency quadruples compared with raw ZSM-5 and reached ca.100%at 300°C.Combined with the characterization results,it could be concluded that chemical properties,instead of physical structures,played an important role in Hg^(0) removal.Among the various gas components,O_(2),NO,and SO_(2) made negligible impacts on Hg^(0) capture over 2:1-S/ZSM-5 adsorbent surface.After recycling four times,Hg^(0) removal efficiency of 2:1-S/ZSM-5 adsorbent remained higher than 80%,which was indica-tive of a certain recyclability.Finally,XPS results illustrated that S^(0) and S^(2−)on 2:1-S/ZSM-5 surface functioned as the active sites for the transformation of Hg^(0) to HgS,which facilitated the chemisorption process and consequently led to an improved Hg^(0) capture performance.

Detecting incentivized review groups with co-review graph

Online reviews play a crucial role in the ecosystem of nowadays business(especially e-commerce platforms),and have become the primary source of consumer opinions.To manipulate consumers’opinions,some sellers of e-commerce platforms outsource opinion spamming with incentives(e.g.,free products)in exchange for incen-tivized reviews.As incentives,by nature,are likely to drive more biased reviews or even fake reviews.Despite e-commerce platforms such as Amazon have taken initiatives to squash the incentivized review practice,sellers turn to various social networking platforms(e.g.,Facebook)to outsource the incentivized reviews.The aggre-gation of sellers who request incentivized reviews and reviewers who seek incentives forms incentivized review groups.In this paper,we focus on the incentivized review groups in e-commerce platforms.We perform the data collections from various social networking platforms,including Facebook,WeChat,and Douban.A measurement study of incentivized review groups is conducted with regards to group members,group activities,and products.To identify the incentivized review groups,we propose a new detection approach based on co-review graphs.Specifically,we employ the community detection method to find the suspicious communities from co-review graphs.We also build a“gold standard”dataset from the data we collected,which contains the information of reviewers who belong to incentivized review groups.We utilize the“gold standard”dataset to evaluate the effectiveness of our detection approach.

Empirical study on journal literature guarantee of academic library: A case study of Wuhan University

The rising acceptance of e-only policy and open access initiative transforms the collection composition in academic libraries. Accordingly, the roles of electronic, print and open access journals as part of a library’s journal holdings have become different from the past, which needs to be brought to the forefront. Samples of this research are drawn from the articles whose first author is from Wuhan University. They should be issued in 2013 and indexed by SCIE, SSCI or A&HCI. The authors introduced an improved citation checking method to the study by matching the journal cited references of the sample with the journals from print, electronic collections and the world’s major open access databases that are available at the Wuhan University Library in accordance with the publishing year instead of the volume number. Thus, the availability and unavailability of the source journals in open access, electronic, and print journal resources can be examined and compared in a comprehensive manner. By comparing the effectiveness of these three formats of resources as the reference source of published articles, this article attempts to analyze their features and tendencies under the current open access environment as well as discusses how the development of open access journals has impacted the collection building of university libraries in China, so as to provide enlightenment and reference for academic libraries to optimize their resource provision and meet the patrons’ current needs.