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THE PROTECTIVE EFFECT OF Na^+ CHANNEL BLOCKERS AGAINST CELL DAMAGE CAUSED BY ISCHEMIA 被引量:1
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作者 Zhu Zhongliang, Li Hui, Fan Xiaoli et al(Department of Physiology, Xi’an Medical University)$$$$ 《Journal of Pharmaceutical Analysis》 CAS 1999年第2期156-156,共1页
In order to observe it blockers of sodium channel obsesses the neuroprotective effect on hippocampal CA 1 pyramidal cell under the condition of transient brain ischemia, the present experiment used 24 male Wistar rat... In order to observe it blockers of sodium channel obsesses the neuroprotective effect on hippocampal CA 1 pyramidal cell under the condition of transient brain ischemia, the present experiment used 24 male Wistar rats aged 9 months and divided them into four groups. Lidocaine and/or furosemide were injected introcerebroventicularlly (I.C.V). Stained with H E and accounted the CA 1 pyramidal cell numbers by computer in each group suggested following findings: Although 5 μl of 2% lidocaine was injected I.C.V, the results indicated lidocaine didn't have any blockade to pyramidal cell injuries in hippocampal CA 1 area (P<0 05). In the group medicated with 2 5μl of both 2% lidocaine and 2% furosemide, the results showed that the combined approach had a blockade to injuries of pyramidal cells compared with control group (P<0 01). The present experiment indicates that the combined blockade of lidocaine and furosemide injected I.C.V. to Na + channel can prevent the injuries from hippocampal neurons owing to ischemia. 展开更多
关键词 the protectIVE EFFECT of Na AGAINST CELL DAMAGE CAUSED BY ISCHEMIA channel BLOCKERS
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Lithium-Ion Charged Polymer Channels Flattening Lithium Metal Anode 被引量:2
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作者 Haofan Duan Yu You +11 位作者 Gang Wang Xiangze Ou Jin Wen Qiao Huang Pengbo Lyu Yaru Liang Qingyu Li Jianyu Huang Yun‑Xiao Wang Hua‑Kun Liu Shi Xue Dou Wei‑Hong Lai 《Nano-Micro Letters》 SCIE EI CAS CSCD 2024年第4期379-393,共15页
The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein... The concentration difference in the near-surface region of lithium metal is the main cause of lithium dendrite growth.Resolving this issue will be key to achieving high-performance lithium metal batteries(LMBs).Herein,we construct a lithium nitrate(LiNO_(3))-implanted electroactiveβphase polyvinylidene fluoride-co-hexafluoropropylene(PVDF-HFP)crystalline polymorph layer(PHL).The electronegatively charged polymer chains attain lithium ions on the surface to form lithium-ion charged channels.These channels act as reservoirs to sustainably release Li ions to recompense the ionic flux of electrolytes,decreasing the growth of lithium dendrites.The stretched molecular channels can also accelerate the transport of Li ions.The combined effects enable a high Coulombic efficiency of 97.0%for 250 cycles in lithium(Li)||copper(Cu)cell and a stable symmetric plating/stripping behavior over 2000 h at 3 mA cm^(-2)with ultrahigh Li utilization of 50%.Furthermore,the full cell coupled with PHL-Cu@Li anode and Li Fe PO_(4) cathode exhibits long-term cycle stability with high-capacity retention of 95.9%after 900 cycles.Impressively,the full cell paired with LiNi_(0.87)Co_(0.1)Mn_(0.03)O_(2)maintains a discharge capacity of 170.0 mAh g^(-1)with a capacity retention of 84.3%after 100 cycles even under harsh condition of ultralow N/P ratio of 0.83.This facile strategy will widen the potential application of LiNO_(3)in ester-based electrolyte for practical high-voltage LMBs. 展开更多
关键词 Polymer ionic channel Li metal batteries Artificial protective layer Uniform Li deposition Electrochemical performances
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Fast and Accurate Detection of Masked Faces Using CNNs and LBPs
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作者 Sarah M.Alhammad Doaa Sami Khafaga +3 位作者 Aya Y.Hamed Osama El-Koumy Ehab R.Mohamed Khalid M.Hosny 《Computer Systems Science & Engineering》 SCIE EI 2023年第12期2939-2952,共14页
Face mask detection has several applications,including real-time surveillance,biometrics,etc.Identifying face masks is also helpful for crowd control and ensuring people wear them publicly.With monitoring personnel,it... Face mask detection has several applications,including real-time surveillance,biometrics,etc.Identifying face masks is also helpful for crowd control and ensuring people wear them publicly.With monitoring personnel,it is impossible to ensure that people wear face masks;automated systems are a much superior option for face mask detection and monitoring.This paper introduces a simple and efficient approach for masked face detection.The architecture of the proposed approach is very straightforward;it combines deep learning and local binary patterns to extract features and classify themasmasked or unmasked.The proposed systemrequires hardware withminimal power consumption compared to state-of-the-art deep learning algorithms.Our proposed system maintains two steps.At first,this work extracted the local features of an image by using a local binary pattern descriptor,and then we used deep learning to extract global features.The proposed approach has achieved excellent accuracy and high performance.The performance of the proposed method was tested on three benchmark datasets:the realworld masked faces dataset(RMFD),the simulated masked faces dataset(SMFD),and labeled faces in the wild(LFW).Performancemetrics for the proposed technique weremeasured in terms of accuracy,precision,recall,and F1-score.Results indicated the efficiency of the proposed technique,providing accuracies of 99.86%,99.98%,and 100%for RMFD,SMFD,and LFW,respectively.Moreover,the proposed method outperformed state-of-the-art deep learning methods in the recent bibliography for the same problem under study and on the same evaluation datasets. 展开更多
关键词 Convolutional neural networks face mask detection local binary patterns deep learning computer vision social protection Keras OPENCV TensorFlow Viola-Jones
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Validating the CorrectWearing of Protection Mask by Taking a Selfie:Design of a Mobile Application“CheckYourMask”to Limit the Spread of COVID-19 被引量:2
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作者 Karim Hammoudi Adnane Cabani +1 位作者 Halim Benhabiles Mahmoud Melkemi 《Computer Modeling in Engineering & Sciences》 SCIE EI 2020年第9期1049-1059,共11页
In a context of a virus that is transmissive by sputtering,wearing masks appear necessary to protect the wearer and to limit the propagation of the disease.Currently,we are facing the 2019-2020 coronavirus pandemic.Co... In a context of a virus that is transmissive by sputtering,wearing masks appear necessary to protect the wearer and to limit the propagation of the disease.Currently,we are facing the 2019-2020 coronavirus pandemic.Coronavirus disease 2019(COVID-19)is an infectious disease with first symptoms similar to the flu.The symptom of COVID-19 was reported first in China and very quickly spreads to the rest of the world.The COVID-19 contagiousness is known to be high by comparison with the flu.In this paper,we propose a design of a mobile application for permitting everyone having a smartphone and being able to take a picture to verify that his/her protection mask is correctly positioned on his/her face.Such application can be particularly useful for people using face protection mask for the first time and notably for children and old people.The designed method exploits Haar-like feature descriptors to detect key features of the face and a decision-making algorithm is applied.Experimental results show the potential of this method in the validation of the correct mask wearing.To the best of our knowledge,our work is the only one that currently proposes a mobile application design“CheckYourMask”for validating the correct wearing of protection mask. 展开更多
关键词 face protection masks public health support health education COVID-19 CORONAVIRUS E-HEALTH m-health mobile health public health system epidemic prevention and control
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Urban Market-Gardening in Parakou (Republic of Benin): Spatial Dynamics, Food Security, Protection of the Environment and Creation of Employments 被引量:1
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作者 Abdoul-Ramane Abdoulaye Aboudou Yacoubou Mama Aboudou Ramanou 《Journal of Geoscience and Environment Protection》 2015年第5期93-103,共11页
Nowadays, African cities are subjected to upsets which result from the extraordinary growth of urban populations. The growth of the population of cities has induced some changes in the structure of the activity of tho... Nowadays, African cities are subjected to upsets which result from the extraordinary growth of urban populations. The growth of the population of cities has induced some changes in the structure of the activity of those cities. Agriculture which was formerly confined to the countryside henceforth develops in the urban area and occupies a preponderant place as a strategy of survival, of insertion and of food supplying of the city-dwellers. It has become an activity integrated to the urban tissue through systems of occupying and exploitation of land in the urban area. Population growth (4.81%) between 2002 and 2013 is a critical poverty rate (65%) of the population of Parakou city, entailing a misery perceptible in all its social and economic dimensions. The market-gardening activity has integrated itself to the urban tissue. The objective of this study is to understand how urban agriculture through market-gardening can be a solution for rural farmers who have moved to Parakou city. In this study, documentary research, interviews and field observation are used for data collection. The main results to be signaled among others are: evolution and status of the market-gardening areas in Parakou, the reduction of food insecurity with the permanent availability in quantity and in quality of market-gardening products accessible to the population: the protection of the environment through the drainage of the urban area and the preservation of the diversity of vegetables;the increase of the income of the households of the farmers and the creation of employments. 展开更多
关键词 URBAN Agriculture Food Security Market-Gardening channel Land Dynamics protectION of the Environment Employment Parakou
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Enhancing Identity Protection in Metaverse-Based Psychological Counseling System
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作者 Jun Lee Hanna Lee +1 位作者 Seong Chan Lee Hyun Kwon 《Computers, Materials & Continua》 SCIE EI 2024年第1期617-632,共16页
Non-face-to-face psychological counseling systems rely on network technologies to anonymize information regard-ing client identity.However,these systems often face challenges concerning voice data leaks and the subopt... Non-face-to-face psychological counseling systems rely on network technologies to anonymize information regard-ing client identity.However,these systems often face challenges concerning voice data leaks and the suboptimal communication of the client’s non-verbal expressions,such as facial cues,to the counselor.This study proposes a metaverse-based psychological counseling system designed to enhance client identity protection while ensuring efficient information delivery to counselors during non-face-to-face counseling.The proposed systemincorporates a voicemodulation function that instantlymodifies/masks the client’s voice to safeguard their identity.Additionally,it employs real-time client facial expression recognition using an ensemble of decision trees to mirror the client’s non-verbal expressions through their avatar in the metaverse environment.The system is adaptable for use on personal computers and smartphones,offering users the flexibility to access metaverse-based psychological counseling across diverse environments.The performance evaluation of the proposed system confirmed that the voice modulation and real-time facial expression replication consistently achieve an average speed of 48.32 frames per second or higher,even when tested on the least powerful smartphone configurations.Moreover,a total of 550 actual psychological counseling sessions were conducted,and the average satisfaction rating reached 4.46 on a 5-point scale.This indicates that clients experienced improved identity protection compared to conventional non-face-to-face metaverse counseling approaches.Additionally,the counselor successfully addressed the challenge of conveying non-verbal cues from clients who typically struggled with non-face-to-face psychological counseling.The proposed systemholds significant potential for applications in interactive discussions and educational activities in the metaverse. 展开更多
关键词 Metaverse counseling system face tracking identity protection
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Research progress of TRP channel's protective effect on myocardial ischemia-reperfusion injury
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作者 XIE Feng DUAN Guang-jing +7 位作者 QU Xin-liang ZHAO Bo JIANG Ya-ni YAN Ruo-nan ZHANG Jia-hao OU Li GAO Feng LI Min 《Journal of Hainan Medical University》 2022年第19期69-73,共5页
Transient receptor potential(TRP)channels are a type of cation channel located on the cell membrane.TRP channels are divided into 7 subfamilies(TRPC,TRPA,TRPM,TRPV,TRPN,TRPP and TRPML)and widely expressed in myocardia... Transient receptor potential(TRP)channels are a type of cation channel located on the cell membrane.TRP channels are divided into 7 subfamilies(TRPC,TRPA,TRPM,TRPV,TRPN,TRPP and TRPML)and widely expressed in myocardial tissue.In recent years,with the application of gene knockout and transgenic model animals,it has been found that members of the TRP channel subfamilies TRPM,TRPC and TRPV are closely related to myocardial ischemia-reperfusion injury.The activation or inhibition of TRP channels participates in the regulation of myocardial ischemia-reperfusion injury,reduces the infarct area of the myocardium,and exerts a protective effect.Therefore,this paper first summarizes the structural characteristics of TRPM,TRPC,and TRPV and their distribution in the cardiovascular system,and then summarizes the mechanisms of TRPM,TRPC,and TRPV that regulate myocardial ischemia and reperfusion,which will provide a certain theoretical basis for treatment of myocardial ischemia-reperfusion injury. 展开更多
关键词 Transient receptor channel Myocardial ischemia reperfusion INJURY protective effects
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Research on 3D Modeling and Visualization of Coal Pillars for Surface Protection
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作者 LIU Ya-jing MAO Shan-jun +1 位作者 YAO Ji-ming JIANG Yun-feng 《Journal of China University of Mining and Technology》 EI 2006年第3期254-257,共4页
In order to safely exploit coal resource, protection coal pillars must be prepared in coal mines. Some correlative parameters of protection coal pillar are calculated by Drop face and Drop line methods. Models of prot... In order to safely exploit coal resource, protection coal pillars must be prepared in coal mines. Some correlative parameters of protection coal pillar are calculated by Drop face and Drop line methods. Models of protecting surface objects and coal pillars are established by TIN modeling and object-oriented technique. By using ACCESS2000as the database and the VC++ and OpenGL as the language, the calculation of protective coal pillars is realized and the 3D-visulizaiton system for protected objects on ground surface and for coal pillars is developed. The system can obtain the data of characteristic points on the surface interactively from the digitized mine topography map, constructing 3D model automatically. It can also obtain the interrelated parameters of the coal seam and drill hole data from existing geolog!cal surveying database to calculate the location, surface area and the total coal columns. The whole process can be computed quickly and accurately. And the 3D visualization system was applied in a mine, showing that the system solve the problem of complex calculation, not only realized the automatic 3D mapping and visualization of coal pillars for buildings protection, but also greatly improves the working efficiency. 展开更多
关键词 protection coal pillar drop face drop line 3D visualization object-oriented modeling
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Suitable retention and recovery technology of floor coal at ends of fully mechanized face with great mining heights 被引量:3
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作者 Zhang Nenghu Wu Qi +1 位作者 YuanYong Bai Qingsheng 《Mining Science and Technology》 EI CAS 2011年第2期281-285,共5页
Gateways at faces of great mining heights are mostly driven along the roof of coal seams.For gateway height restrictions,a 1-3 m floor coal is retained,leaving a triangular floor coal at the face ends,causing a loss o... Gateways at faces of great mining heights are mostly driven along the roof of coal seams.For gateway height restrictions,a 1-3 m floor coal is retained,leaving a triangular floor coal at the face ends,causing a loss of coal.In order to improve coal recovery rates and to ensure efficiency of equipment at coal mining faces,we investigated suitable retention methods and recovery technology of floor coal at face ends.The upper floor coal can directly be recovered by a shearer with floor dinting.The lower floor coal is recovered by shearer with floor dinting after advanced floor dinting and retaining a step for protecting coal sides in a haulage gateway.Field practice shows that this method can improve the coal recovery rates at fully mechanized working faces with great mining heights. 展开更多
关键词 Great mining heights Floor coal at face ends Floor coal recovery Floor dinting Step for protecting coal side
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Joint resource allocation for MIMO-OFDM video transmission systems with unequal error protection 被引量:3
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作者 张成文 刘鑫 谭学治 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2012年第2期119-124,共6页
To improve the performance of MIMO-OFDM video transmission systems on the limitation of wireless bandwidth and transmitting power,we propose an adaptive joint resource allocation algorithm with unequal error protectio... To improve the performance of MIMO-OFDM video transmission systems on the limitation of wireless bandwidth and transmitting power,we propose an adaptive joint resource allocation algorithm with unequal error protection(UEP) based on joint source-channel coding(JSCC) according to H.264 video compression standard and RCPT channel coding.According to different thresholds of the average SNR of subchannels,the algorithm dynamically allocates the source coding parameters of original video data and the channel coding parameters of RCPT,which realizes UEP for the compressed video data of different importance.Through the bit and power allocation based on MQAM modulation and the subspace allocation based on beamforming technology for different subcarriers,an adaptive joint resource allocation making full use of space-frequency domain resources have been realized.The simulation results indicate that the algorithm improves the adaptability of video transmission systems in different wireless environments and the quality of video retrieval. 展开更多
关键词 video transmission MIMO-ofDM unequal error protection joint source-channel coding
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Template Protection Based on Chaotic Map for Face Recognition
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作者 Jinjin Dong Xiao Meng +2 位作者 Meng Chen Zhifang Wang Linlin Tang 《国际计算机前沿大会会议论文集》 2017年第1期58-59,共2页
With the widespread deployment of biometric recognition,personal data security and privacy are attracted more and more attentions.A crucial privacy issue is how to ensure the security of user template.This paper propo... With the widespread deployment of biometric recognition,personal data security and privacy are attracted more and more attentions.A crucial privacy issue is how to ensure the security of user template.This paper proposes a novel template protection algorithm for face recognition based on chaotic map.Each face template is corresponding to different chaotic sequence produced by system master key and user identification number.The order of chaotic sequence controls the substitution index of face template.Experiment results on facial FERET database show that our algorithm can significantly improve the recognition performance and ensure the security of face template. 展开更多
关键词 TEMPLATE protection face recognition LOGISTIC MAP SUBSTITUTION index
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Polarization and Breakdown Analysis of AlGaN Channel HEMTs with AlN Buffer
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作者 Godwin Raj Mohan Kumar Chandan Kumar Sarkar 《World Journal of Condensed Matter Physics》 2015年第3期232-243,共12页
We have demonstrated the first carrier density model for AlGaN channel with AlN buffer using spontaneous and piezoelectric polarization comparison with experimental and theoretical results. From the results we proved ... We have demonstrated the first carrier density model for AlGaN channel with AlN buffer using spontaneous and piezoelectric polarization comparison with experimental and theoretical results. From the results we proved that the formation of 2DEG in undoped structure relied both on spontaneous and piezoelectric polarization. The electron distribution of Al concentration (0 < x < 0.5) was measured for both AlGaN channel and barrier. Barrier thickness assumed between 20 and 25 nm for validating the experimental results. The carrier concentration was observed at the specific interface of the N- and Ga-face by assuming x1, x2 = 0. The model results are verified with previously reported experimental data. 展开更多
关键词 ALGAN channel Sheet CARRIER Concentration Model N- and Ga-face POLARIZATION High BREAKDOWN Total Induced Net Interface POLARIZATION
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隧道施工作业人员佩戴颗粒物防护口罩适合性及影响因素分析
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作者 张意 刘晓旭 +4 位作者 乌瀚宝栎尔 陈霞 缪庆 赵子贺 张雪艳 《环境卫生学杂志》 2024年第6期468-474,共7页
目的分析隧道施工作业人员佩戴颗粒物防护口罩适合性与工人头面部尺寸之间的关系,探索相关影响因素。方法选择某隧道施工作业现场工人200人为研究对象,调查个人基本信息,测量身高、体重,使用TSI Pro+8038、8048进行折叠式和杯式口罩适... 目的分析隧道施工作业人员佩戴颗粒物防护口罩适合性与工人头面部尺寸之间的关系,探索相关影响因素。方法选择某隧道施工作业现场工人200人为研究对象,调查个人基本信息,测量身高、体重,使用TSI Pro+8038、8048进行折叠式和杯式口罩适合性检验,手持三维扫描仪进行头面部尺寸测量。结果适合性检验单因素分析,研究对象佩戴口罩形状和所属民族对通过率的影响差异有统计学意义(P<0.05)。通过组与未通过组头面部尺寸测量显示,折叠式口罩9501V+额最小宽,9502V+两耳屏间宽,杯式口罩8576两耳屏点间颌下弧长、两下颌角宽、鼻宽和BMI,8577头冠状弧、耳屏鼻根长、两耳屏点间颏下弧长、颈围、形态面长和BMI差异有统计学意义(P<0.05)。适合性检验多因素分析,形态面长、鼻宽和BMI值与适合性检验通过的概率呈正相关,口宽值呈负相关。相较于折叠式口罩,杯式口罩通过的概率更大。头面部尺寸分栏总体覆盖率为85.0%,折叠式和杯式口罩的#5、#7、#8、#10通过人数较多。结论对于本次现场研究的施工作业人员,杯式口罩较折叠式口罩更为适用;形态面长、鼻宽和BMI的值越大,口宽的值越小,适合性检验的通过概率越高,结合我国头面部尺寸分栏标准,形态面长可作为快速选择口罩的主要判断依据,鼻宽、口宽以及BMI可作为适合性检验的主要参考依据;为提高呼吸防护效果,建议通过适合性检验为工作人员筛选合适的口罩类型。 展开更多
关键词 颗粒物防护口罩 适合性检验 头面部尺寸 颜面分栏
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基于稠密连接的通道混合式PCANet的低分辨率有遮挡人脸识别
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作者 秦娥 何佳瑶 +2 位作者 刘银伟 朱娅妮 李小薪 《高技术通讯》 CAS 北大核心 2024年第6期602-615,共14页
针对低分辨率有遮挡人脸识别问题提出了基于稠密连接的通道混合式主成分分析网络(DCH-PCANet)。现有的PCANet模型的卷积层只使用了通道无关式卷积(CIC)。通道无关式卷积由于未考虑特征图在通道方向上的相关性,可以更好地凸显单个特征图... 针对低分辨率有遮挡人脸识别问题提出了基于稠密连接的通道混合式主成分分析网络(DCH-PCANet)。现有的PCANet模型的卷积层只使用了通道无关式卷积(CIC)。通道无关式卷积由于未考虑特征图在通道方向上的相关性,可以更好地凸显单个特征图的局部纹理特征,对于补偿因低分辨率、遮挡等因素导致的特征损失具有重要意义,但也会强化遮挡区域的特征,从而放大坏特征的影响范围;而通道相关式卷积(CDC)由于充分考虑了各特征图在通道方向上的相关性,可以较好地抑制坏特征的作用,形成较为稀疏的特征图。在PCANet中添加了基于通道相关式卷积的特征图提取分支,形成了通道混合式PCANet;并且引入了稠密连接,以充分利用低阶特征提升有遮挡图像识别的鲁棒性。针对如下4种数据集进行了实验:受控环境、真实遮挡和模拟低分辨率的人脸数据集(AR人脸数据集),非受控环境、真实遮挡和模拟低分辨率的人脸数据集(MFR2和PKUMasked-Face),非受控环境、真实遮挡和真实低分辨率的人脸数据集(自建数据集)。实验结果表明,与现有方法相比,所提出的基于稠密连接的通道混合式PCANet具更好的遮挡鲁棒性和低分辨率鲁棒性,可以作为前沿方法的有效补充,提升其识别性能。 展开更多
关键词 有遮挡人脸识别 主成分分析网络(PCANet) 通道相关式卷积(CDC) 稠密连接
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三通道多姿态面部正面化方法
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作者 高峰 张元 +2 位作者 谢剑斌 闫玮 郭锐 《计算机工程与设计》 北大核心 2024年第5期1490-1498,共9页
针对现有面部正面化网络在复杂环境下难以保留面部显著性特征的问题,提出一种三通道(局部、半全局和全局)面部正面化方法。在TP-GAN算法的原有框架基础上设计半全局网络,融合全局网络和局部网络之间的依赖关系,使生成的正面化图像的分... 针对现有面部正面化网络在复杂环境下难以保留面部显著性特征的问题,提出一种三通道(局部、半全局和全局)面部正面化方法。在TP-GAN算法的原有框架基础上设计半全局网络,融合全局网络和局部网络之间的依赖关系,使生成的正面化图像的分布与真实面部图像更接近;在半全局网络中设计多时空深度注意力模块,促进网络学习到更多面部显著性特征;将所提方法应用于CAS-PEAL-R1数据集和自建数据集,采用Rank-1指标进行评估。实验结果表明,所提方法在所有角度下的Rank-1平均准确率为99.40%,验证添加了多时空深度注意力模块的半全局网络可以有效保留面部显著特征,提高面部匹配准确率。 展开更多
关键词 多姿态面部 面部正面化 生成对抗网络 三通道网络 半全局网络 注意力模块 显著特征
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矩形通道内超临界压力CO_(2)流动换热数值研究
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作者 李妮 浦航 +3 位作者 周林 曲航辰 张义宁 东明 《推进技术》 EI CAS CSCD 北大核心 2024年第8期145-155,共11页
针对高马赫数发动机热防护和机载设备长航程供电问题,基于超临界二氧化碳布雷顿循环提出了热防护与发电一体化系统。采用数值模拟方法探究了单侧受热矩形通道内超临界压力下CO_(2)的对流传热特性,并且分析了不同热流密度时入口温度、冷... 针对高马赫数发动机热防护和机载设备长航程供电问题,基于超临界二氧化碳布雷顿循环提出了热防护与发电一体化系统。采用数值模拟方法探究了单侧受热矩形通道内超临界压力下CO_(2)的对流传热特性,并且分析了不同热流密度时入口温度、冷却流量和加热长度对冷却性能的影响。研究发现单侧受热矩形通道内SCO_(2)的流动换热存在周向不均匀性,增大冷却剂流量可以有效降低壁面温度。但对周向壁面温差影响较小并且温差随热流密度增大单调上升,由0.5 MW‧m^(-2)的最大温差75 K增加至2.0 MW‧m^(-2)的最大温差297 K。二次流在通道拐角处形成回流,局部扰流使传热增强。当流体温度高于拟临界温度时,定压比热容随入口温度的升高而减小,但是雷诺数的增大弥补了这一缺陷并使得换热能力增强。不同加热长度的冷却性能受传热特性影响,不发生传热恶化时,相同冷却流量条件下加热长度越大冷却后的壁面最高温度越高。但是当发生传热恶化时,不同加热长度冷却后的壁面最高温度分为相同和随加热长度增大两种情况。 展开更多
关键词 热防护 矩形通道 超临界二氧化碳 对流传热 布雷顿循环
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坚硬顶板切顶卸压技术对巷道围岩变形规律影响 被引量:1
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作者 赵常辛 李晓旭 +2 位作者 石蒙 冀瑞锋 张焱 《工矿自动化》 CSCD 北大核心 2024年第1期147-154,共8页
针对特厚煤层坚硬顶板、宽煤柱条件下临空巷道面临的高围岩应力、大变形等问题,以老石旦煤矿16403综放工作面为工程研究背景,从宽煤柱顶板侧向破断结构角度对临空巷道大变形的影响因素进行了理论分析,采用数值模拟方法研究了对16402运... 针对特厚煤层坚硬顶板、宽煤柱条件下临空巷道面临的高围岩应力、大变形等问题,以老石旦煤矿16403综放工作面为工程研究背景,从宽煤柱顶板侧向破断结构角度对临空巷道大变形的影响因素进行了理论分析,采用数值模拟方法研究了对16402运输巷实施不同切顶卸压方案时,临近采空区的16403回风巷侧向顶板采动应力传递规律,并在现场施工水力压裂钻孔进行切顶卸压,实现临空巷道围岩变形控制。研究结果表明:“低位坚硬岩层悬臂梁+高位坚硬岩层砌体梁”破断结构是特厚煤层宽煤柱临空巷道大变形的主要原因,可采用切顶卸压技术破坏宽煤柱顶板侧向破断结构来控制临空巷道围岩大变形;切顶角变化可使关键块B长度发生改变,切顶角越大,则关键块B长度越小,临空侧顶板载荷向煤柱传递的程度越弱,临空巷道围岩承受的采动应力越小,切顶角为100°时临空巷道围岩垂直应力与变形量最小;在16402运输巷以切顶角100°施工水力压裂钻孔后,16403回风巷顶底板变形量较未实施切顶卸压的16402回风巷减小86.5%,两帮变形量减小87.1%,临空巷道围岩稳定性得到极大提高。 展开更多
关键词 综放工作面 留煤柱护巷 临空巷道 围岩变形控制 切顶卸压 水力压裂
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适应性JPEG图像隐私保护方案
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作者 文泓鑫 胡飞 俞能海 《网络与信息安全学报》 2024年第1期91-101,共11页
由于JPEG图像格式是一种高压缩率图像格式,JPEG图像中的隐私保护方案不仅需要保护隐私区域的内容,同时要控制文件的大小。另外,JPEG图像中包含隐私信息的区域,即感兴趣区域(ROI),往往只占整个图像的一部分。仅对ROI进行保护有助于控制... 由于JPEG图像格式是一种高压缩率图像格式,JPEG图像中的隐私保护方案不仅需要保护隐私区域的内容,同时要控制文件的大小。另外,JPEG图像中包含隐私信息的区域,即感兴趣区域(ROI),往往只占整个图像的一部分。仅对ROI进行保护有助于控制文件的大小。基于此,提出了一种适应性JPEG图像隐私保护方案。利用人脸检测等方法从JPEG图像中提取隐私区域,使用基于块的适应性可逆修改算法对隐私区域进行保护,用可逆信息隐藏方法将复原所需的信息嵌入图像。上述隐私保护过程采用了可逆的算法,合法的被授权者可以完全恢复经过所提方案隐私保护后的区域。由于引入了可变的参数,可以选择合适的参数以适应不同的实际需求,并达到最优效果。对多个ROI重叠的复杂情形进行了讨论并提出了解决方案。在峰值信噪比(PSNR,peak signal-to-noise ratio)和文件膨胀率等指标下,通过实验探索了不同参数对方案性能的影响并找到了推荐的参数组合。实验结果表明,在合适的参数下,所提方案在隐私保护、文件膨胀率等方面中的表现优于已有方案。 展开更多
关键词 JPEG图像 隐私保护 可逆信息隐藏 人脸识别
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西部大采高工作面保护煤柱宽度优化研究
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作者 解成成 刘学生 +2 位作者 范德源 杨康 宋虎 《山东科技大学学报(自然科学版)》 CAS 北大核心 2024年第4期12-22,共11页
保护煤柱尺寸一直是三下开采研究的热点问题,特别是在西部大采高软弱覆岩特厚煤层开采条件下,其对地表建筑物安全的影响有待进一步研究。以榆树湾井田20119工作面为例,综合利用数值模拟和概率积分法确定了合理保护煤柱宽度,并进行现场... 保护煤柱尺寸一直是三下开采研究的热点问题,特别是在西部大采高软弱覆岩特厚煤层开采条件下,其对地表建筑物安全的影响有待进一步研究。以榆树湾井田20119工作面为例,综合利用数值模拟和概率积分法确定了合理保护煤柱宽度,并进行现场验证。结果表明:随着煤柱宽度的减小,地表沿X方向的水平移动呈现倒“S”型趋势,沿Y方向的移动呈现倒“U”型趋势,地表的最大下沉量随煤柱宽度的减小而不断减少;结合概率积分法对保护煤柱宽度进行预计,确定优化后的煤柱宽度为180 m;对现场村庄进行实时监测,地表下沉和倾斜值均满足现场施工要求,验证了保护煤柱宽度的合理性。 展开更多
关键词 大采高工作面 数值模拟 概率积分 保护煤柱宽度
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uBlock算法的低延迟一阶门限实现方法
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作者 姚富 陈华 范丽敏 《电子学报》 EI CAS CSCD 北大核心 2024年第4期1250-1259,共10页
目前已有文献给出了uBlock分组密码算法的侧信道防护方案,但是这些方案不仅延迟较高,难以适用于低延迟高吞吐场景,而且在毛刺探测模型下缺乏可证明安全性.针对这一问题,本文给出了在毛刺探测模型下具有可证明安全性的uBlock算法的低延... 目前已有文献给出了uBlock分组密码算法的侧信道防护方案,但是这些方案不仅延迟较高,难以适用于低延迟高吞吐场景,而且在毛刺探测模型下缺乏可证明安全性.针对这一问题,本文给出了在毛刺探测模型下具有可证明安全性的uBlock算法的低延迟门限实现方案.此外,我们引入了Changing of the Guards技术来避免防护方案在执行过程中需要额外随机数.对于防护方案的安全性,我们用自动化评估工具SILVER验证了S盒的毛刺探测安全性,并用泄露评估技术TVLA(Test Vector Leakage Assessment)验证了防护方案的整个电路的安全性.最后,我们用Design Compiler工具对防护方案的性能消耗情况进行了评估.评估结果显示,与序列化实现方式的uBlock防护方案相比,我们的防护方案的延迟能够减少约95%. 展开更多
关键词 密码芯片 uBlock算法 侧信道攻击与防护 掩码技术 门限实现 Changing of the Guards
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