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A discussion of fatigue properties of notched specimens subjected to prestressing treatment machined from FGH4097

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Chinese Journal of Aeronautics 2024年第4期37卷 508-523页

作者： Rongxi SHI Dasheng WeI le HAN Shun YANG School of energy and Power engineering Beihang UniversityBeijing 100191China Jiangxi Research Institute Beihang UniversityNanchang 330096China Research Institute of Aero-engine Beihang UniversityBeijing 100191China

experimental and numerical investigations were performed to reveal the effect of prestress on the fatigue properties of FGH4097 so as to quantitatively evaluate the overspeed benefit of the disc of aeroengine. A corresponding experiment was performed to examine the effect of prestress on the fatigue life of FGH97. A complete model describing the fatigue properties of the prestressed notch specimen was proposed. After the modification of mean stress, stress gradient and prestressing treatment, the model is finally verified by fatigue test of presstressed notch specimens machined from FGH4097 with satisfactory accuracy and good engineering applicability. The new model highlights that for the variable fatigue loads, the introduction of appropriate prestress is expected to benefit to the notch specimens and certainly to the disc of aeroengine regards of their fatigue properties. Both the calculation method of fatigue life parameters and the prestress correction model are proved to have good prediction accuracy.

关键词： Turbine blisk Overspeed test Prestress Fatigue life prediction FGH4097

Heat Transfer and Flow Structure of a Turbine Blade's Air-cooled leading edge Considering Different Hole Shapes and Additional Flow Angles

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Journal of Thermal Science 2024年第4期33卷 1421-1442页

作者： QIN Runxuan ZHOU Xun WANG Songtao CAI le School of energy Science and engineering Harbin Institute of TechnologyHarbin150001China

A numerical study is conducted to elucidate the impact of hole shapes and additional flow angles on the flow structure of the coolant and temperature field in the leading edge area of the gas turbine *** typical hole shapes are considered for the Ge-e3 *** impact of the additional flow angle(e)within each hole shape on the temperature field is *** results indicate that for the leading edge area and suction surface,the fan-shaped hole case performs best in decreasing temperatures,with a decrease of about 43 *** is mainly due to the fact that the fan-shaped hole has the maximum expansion in hole spanwise *** the pressure surface,the console hole case performs best in decreasing temperatures,with a maximum reduction of about 47.2 *** influence of e on the surface temperature at leading edge area varied between the different hole *** the cylinder hole and console hole,the e=-20°case has the lowest area-averaged *** both the fan-shaped hole and the 7-7-7 shaped hole are expansion holes,the pattern of variation of the leading edge area temperature with increasing e is similar for the fan-shaped hole case and 7-7-7 shaped hole *** e=20°case shows the lowest spanwise-averaged temperature near the hole outlet,and the e=-20°case shows the lowest spanwise-averaged temperature further downstream.

关键词： film cooling Ge-e3 turbine rotor blade conjugate heat transfer leading edge

Your personal choices in transportation and food are important for lowering carbon emissions

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Frontiers of environmental Science & engineering 2024年第6期18卷 27-32页

作者： Bruce Logan Fang Zhang Wulin Yang le Shi Institute of energy and the environment The Pennsylvania State UniversityUniversity ParkPA 16802USA School of environment Tsinghua UniversityBeijing 100084China College of environmental Sciences and engineering Peking UniversityBeijing 100871China College of environmental and Resource Sciences Zhejiang UniversityHangzhou 310058China

There is a global need to reduce greenhouse gas emissions to limit the extent of climate change.A better understanding of how our own activities and lifestyle influence our energy use and carbon emissions can help us enable changes in activities that can lead to reductions in carbon *** we discuss an approach based on examining carbon emissions from the perspective of the unit C,where 1 C is the CO_(2)from food a person would on average eat every *** approach shows that total CO_(2)emissions in China,normalized by the population,is 22.5 C while carbon emissions for a person in the US is 43.9 C.A better appreciation of our own energy use can be obtained by calculating carbon emissions from our own activities in units of C,for example for driving a car gasoline or electric vehicle a certain number of kilometers,using electricity for our homes,and eating different *** this information,we can see how our carbon emissions compare to national averages in different countries and make decisions that could lower our personal CO_(2)emissions.

关键词： Carbon dioxide Climate change Daily energy Greenhouse gas

Formadinium Cation Doping Stabilized Ultra-deep-blue lead Halide Perovskite Nanocrystal Light-emitting Diodes

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Chemical Research in Chinese Universities 2024年第3期40卷 556-560页

作者： Pui Kei KO Jonathan e.HALPeRT Department of Chemistry The Hong Kong University of Science and TechnologyKowloonHong Kong 999077P.R.China

The halide migration effect in mixed-halide lead-based perovskite is a serious problem hindering the development of its display *** this study,we have successfully addressed this issue by reporting formadinium(FA)doped mixed-halide perovskite nanocrystals(NCs)with ultra-deep-blue emission of 450 nm,narrow bandwidth of 16 nm,and a high photoluminescence quantum yield(PLQY)of 66%.The perovskite nanocrystal light-emitting diodes(NC-leDs)using this nanocrystal as an active layer achieved a maximum external quantum efficiency(eQe)of 0.32%,30-fold improved compared to that of pristine and stable electroluminescence(eL)spectra at 450 nm under a 4.9–8.0 V *** findings demonstrate the potential of our approach in developing stable and efficient deep blue perovskite NC-leDs.

关键词： Halide perovskite Light-emitting diode Deep-blue

Chirality enables thermal magnon transistors

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 161-166页

作者： Tao Yu Chengyuan Cai Gerrit e.W.Bauer School of Physics Huazhong University of Science and TechnologyWuhan 430074China .WPI-AIMR and Institute for Materials Research and SCIS Tohoku UniversitySendai 980-8577Japan Kavli Institute for Theoretical Sciences University of Chinese Academy of SciencesBeijing 100190China

We report a theory of thermal spin pumping into proximity magnets under a transverse-bias-driven heat flow of magnons in magnetic films when the dipolar coupling to the magnetic gate is tuned to be “chiral”. While there is no rectification of the magnon current in the film, we predict that chirality diverts a large percentage(50% for perfect chirality) of it into the gate. This transverse thermal spin pumping effect can be controlled by rotating the film magnetization and may help manage the heat flow in future magnonic circuits.

关键词： magnon chirality quantum transport transistor

Re-entry rocket basic flow characteristics and thermal environment of different retro-propulsion modes

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Chinese Journal of Aeronautics 2024年第7期37卷 190-203页

作者： Yifei SU Peijie SUN Yangwen CUI Guigao le School of Mechanical engineering Nanjing University of Science and TechnologyNanjing 210094China Shanghai Institute of Aerospace System engineering Shanghai 200000China Southwest Institute of Technology and engineering Chongqing 400039China

During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere,the basic flow state becomes increasingly complex due to the coupling effect between the retropropulsion plumes and the freestream.A numerical method using the hybrid Reynolds-Averaged Navier-Stokes and Large eddy Simulation(ReS)method and discrete coordinate method is developed to accurately estimate the thermal *** addition,finite rate chemical kinetics is used to calculate the afterburning *** numerical results agree well with wind tunnel data,which confirms the validity and accuracy of the numerical *** are conducted for the heavy carrier rocket re-entry from 53.1 km to 39.5 km altitude with 180°angle of attack by using three different Supersonic Retro-Propulsion(SRP)*** numerical results reveal that these three SRP flow fields are all Short Penetration Models(SPM).As the re-entry altitudes decrease,both the plume-plume interaction and the plume-freestream interaction become *** highest temperatures in the plume shear layers of the three SRP modes increase by 8.36%,7.33%and 6.92%respectively after considering afterburning reactions,and all occur at a reentry altitude of 39.5 *** the rocket re-enters the atmosphere,the maximum heat flux on the rocket base plate of three SRP modes stabilizes at 290,170 and 200 kW/m^(2) respectively,but the maximum heat flux on the side wall increases *** the altitude declines to 39.5 km,the extreme heat flux of the three modes increase by 84.16%,49.45%and 62.97%respectively compared to that at 53.1 km.

关键词： Re-entry rocket Multi-nozzle Supersonic retro propulsion Thermal environment Afterburning effect

Human dental pulp stem/stromal cells in clinical practice

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World Journal of Stem Cells 2024年第2期16卷 54-57页

作者： Mohammed e Grawish Department of Oral Biology Faculty of DentistryMansoura UniversityMansoura 35561Egypt Department of Oral Biology Faculty of Oral and Dental MedicineDelta University for Science and TechnologyMansoura 11152Egypt

Dental pulp stem/stromal cells(DPSCs)are fibroblast-like,neural crest-derived,and multipotent cells that can differentiate into several *** are relatively easy to isolate from healthy and inflamed pulps,with little ethical concerns and can be successfully cryopreserved and *** therapeutic effects of DPSCs derived from animal or human sources have been extensively studied through in-vitro and in-vivo animal experiments and the findings indicated that DPSCs are effective not only for dental diseases but also for systemic *** that translational research is a critical step through which the fundamental scientific discoveries could be translated into applicable diagnostics and therapeutics that directly benefit humans,several clinical studies were carried out to generate evidence for the efficacy and safety of autogenous or allogeneic human DPSCs(hDPSCs)as a treatment modality for use in cell-based therapy,regenerative medicine/dentistry and tissue *** clinical medicine,hDPSCs were effective for treating acute ischemic stroke and human exfoliated deciduous teeth-conditioned medium(SHeD-CM)repaired vascular damage of the corpus cavernous,which is the main cause of erectile *** in clinical dentistry,autologous SHeD was able to rege-nerate necrotic dental pulp after implantation into injured teeth,and micrografts enriched with autologous hDPSCs and collagen sponge were considered a treatment option for human intrabony *** contrast,hDPSCs did not add a significant regenerative effect when they were used for the treatment of post-extraction ***-scale clinical studies across diverse populations are still lacking to provide robust evidence on the safety and efficacy of hDPSCs as a new treatment option for various human diseases including dental-related problems.

关键词： Dental pulp stem/stromal cells Human clinical studies Regenerative medicine Regenerative dentistry Cell-based therapy

Novel Framework for an Intrusion Detection System Using Multiple Feature selection Methods Based on Deep learning

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Tsinghua Science and Technology 2024年第4期29卷 948-958页

作者： A.e.M.eljialy Mohammed Yousuf Uddin Sultan Ahmad Department of Information Systems College of Computer Engineering and SciencesPrince Sattam Bin Abdulaziz UniversityAlkharjSaudi Arabia Department of Computer Science College of Computer Engineering and SciencesPrince Sattam Bin Abdulaziz UniversityAlkharjSaudi Arabiaand also with University Center for Research and Development(UCRD)Department of Computer Science and EngineeringChandigarh UniversityPunjabIndia

Intrusion detection systems (IDSs) are deployed to detect anomalies in real time. They classify a network’s incoming traffic as benign or anomalous (attack). An efficient and robust IDS in software-defined networks is an inevitable component of network security. The main challenges of such an IDS are achieving zero or extremely low false positive rates and high detection rates. Internet of Things (IoT) networks run by using devices with minimal resources. This situation makes deploying traditional IDSs in IoT networks unfeasible. Machine learning (ML) techniques are extensively applied to build robust IDSs. Many researchers have utilized different ML methods and techniques to address the above challenges. The development of an efficient IDS starts with a good feature selection process to avoid overfitting the ML model. This work proposes a multiple feature selection process followed by classification. In this study, the Software-defined networking (SDN) dataset is used to train and test the proposed model. This model applies multiple feature selection techniques to select high-scoring features from a set of features. Highly relevant features for anomaly detection are selected on the basis of their scores to generate the candidate dataset. Multiple classification algorithms are applied to the candidate dataset to build models. The proposed model exhibits considerable improvement in the detection of attacks with high accuracy and low false positive rates, even with a few features selected.

关键词： random forest feature selection decision tree software-defined network logistic regression intrusion detection system XGB classifier AdaBoost

evaluation of the seismic behavior of reinforced concrete structures with flat slab-column gravity frame and shear walls through nonlinear analysis methods

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earthquake engineering and engineering Vibration 2024年第3期23卷 713-726页

作者： M.A.Najafgholipour S.Heidarian Radbakhsh e.erfani Department of Civil and environmental engineering Shiraz University of TechnologyShiraz ***Iran Department of Building Civiland Environmental EngineeringConcordia UniversityMontréal H3G 1M8Canada

This paper presents an investigation of the seismic behavior of reinforced concrete(RC)structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design *** this regard,the behavior of six prototype structures(with different heights and plan layouts)is investigated through nonlinear static and time history analyses,implemented in the Opensees *** results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading ***,the global response of the buildings is discussed in terms of some parameters,such as lateral overstrength due to the gravity flat slab-column *** to the nonlinear static analyses,in structures in which the slab-column connections were designed only for gravity loads,the slab-column connections exhibited a punching mode of failure even in the early stages of ***,the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318(2019)was provided in the slabs at joint ***,despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures,a relatively significant overstrength was imposed on the structures by the gravity frames.

关键词： RC flat slab-column frames seismic behavior nonlinear analysis time history analysis