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Wedge-shaped HfO_(2) buffer layer-induced field-free spin-orbit torque switching of HfO_(2)/Pt/co.structure

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Chinese Physics B 2024年第4期33卷 662-667页

作者：陈建辉梁梦凡宋衍袁俊杰张梦旸骆泳铭王宁宁 School of Electronics and Information Engineering Hangzhou Dianzi UniversityHangzhou 310018China co.estro lnvestment co. LtdShanghai 200126China

Field-free spin-orbit torque(SOT)switching of perpendicular magnetization is essential for future spintronic devices.This study demonstrates the field-free switching of perpendicular magnetization in an HfO_(2)/Pt/co.TaO_(x) structure,which is facilitated by a wedge-shaped HfO_(2)buffer layer.The field-free switching ratio varies with HfO_(2)thickness,reaching optimal performance at 25 nm.This phenomenon is attributed to the lateral anisotropy gradient of the co.layer,which is induced by the wedge-shaped HfO_(2)buffer layer.The thickness gradient of HfO_(2)along the wedge creates a co.responding lateral anisotropy gradient in the co.layer,co.relating with the switching ratio.These findings indicate that field-free SOT switching can be achieved through designing buffer layer,offering a novel approach to innovating spin-orbit device.

关键词： spin-orbit torque field-free switching HfO_(2) buffer layer

In Situ Analysis of Tobacco.Leaves Based on Microwave Plasma Torch Desorption Ionization Mass Spectrometry

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Journal of Analysis and Testing 2024年第1期8卷 9-15页

作者： He Tang Yonggang Zhang Zhiguang Reng Junchen Zhu Yue Xie Xiaobin Zhang Hongru Feng Kailong Yuan Yuanjiang Pan Department of Chemistry Zhejiang UniversityHangzhou 310027China Zhejiang China Tobacco.Industrial co. Ltd.Hangzhou310008China

Tobacco.is an important eco.omic crop worldwide.Tobacco.leaves co.tain a large number of natural products.Therefore,the analysis of tobacco.co.position is crucial for the co.trol of tobacco.safety and quality assessment.Microwave plasma torch desorption ionization mass spectrometry(MPT-MS) is an emerging ambient mass spectrometry(AMS) technique that can be used for rapid real-time analysis of s amples without pretreatment.Our work focuses on the chemical co.position analysis of tobacco.using MPT-MS,and 14 co.pounds were detected in green flue-cured tobacco.leaves,while 30 co.pounds were detected in cured flue-cured tobacco.leaves,which co.firms that curing can enhance the flavor of cigarettes.Furthermore,we successfully in situ identified characteristic fragment ions of α/β-CBD(α/β-cembranoids),an important aroma co.pound in tobacco.by MPT-MS.The results demonstrate the capability of MPT-MS for in situ analysis of tobacco.co.ponents and its potential for evaluating tobacco.quality.

关键词： Microwave plasma torch Ambient mass spectrometry Tobacco α/β-Cembranoids

A Security Trade-Off Scheme of Anomaly Detection System in IoT to Defend against Data-Tampering Attacks

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co.puters, Materials & co.tinua 2024年第3期78卷 4049-4069页

作者： Bing Liu Zhe Zhang Shengrong Hu Song Sun Dapeng Liu Zhenyu Qiu Zhejiang Institute of industry and Information Technology Hangzhou310000China Digital Eco.omy Development Center of Zhejiang Hangzhou310000China co.lege of co.puter and Information Science Chongqing Normal UniversityChongqing401331China Bank of Suzhou Suzhou215000China hangzhou Hikvision Digital Technology co. Ltd.Hangzhou310051China

Internet of Things(IoT)is vulnerable to data-tampering(DT)attacks.Due to resource limitations,many anomaly detection systems(ADSs)for IoT have high false positive rates when detecting DT attacks.This leads to the misreporting of normal data,which will impact the normal operation of IoT.To mitigate the impact caused by the high false positive rate of ADS,this paper proposes an ADS management scheme for clustered IoT.First,we model the data transmission and anomaly detection in clustered IoT.Then,the operation strategy of the clustered IoT is formulated as the running probabilities of all ADSs deployed on every IoT device.In the presence of a high false positive rate in ADSs,to deal with the trade-off between the security and availability of data,we develop a linear programming model referred to as a security trade-off(ST)model.Next,we develop an analysis framework for the ST model,and solve the ST model on an IoT simulation platform.Last,we reveal the effect of some factors on the maximum co.bined detection rate through theoretical analysis.Simulations show that the ADS management scheme can mitigate the data unavailability loss caused by the high false positive rates in ADS.

关键词： Network security Internet of Things data-tampering attack anomaly detection

Flow Boiling Heat Transfer Characteristics and Delayed Dry-Out Ability of Non-Azeotropic Mixtures R245fa/R134a in Microchannels

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Journal of Thermal Science 2024年第3期33卷 1174-1188页

作者： LU Yongjie LING Yongjun ZHUANG Yuan LI Chenyang OUYANG Hongsheng HAN Xiaohong Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province Institute of Refrigeration and CryogenicsZhejiang UniversityHangzhou310007China Zhejiang Zhongguang Electrical co. Ltd.Lishui323000China State Key Lab for Fluorine Greenhouse Gases Replacement and co.trol Treatment Zhejiang Research Institute of Chemical IndustryHangzhou310014China

Microchannel flow boiling heat transfer has the advantages of strong heat dissipation capacity,good temperature uniformity,and co.pact structure.It is an excellent way to thermally manage electronic devices,but when the heat flux exceeds CHF(Critical Heat Flux),the heat transfer performance deteriorates as the working fluid dries out.Non-azeotropic mixtures have the potential to effectively delay or avoid dry-out during the boiling process due to their temperature slide characteristics which causes the mass transfer resistance.To understand the influence of non-azeotropic mixtures on microchannel flow boiling,using the phase-change microchannel heat sink as the research object,the experiments on the flow boiling heat transfer performance of R245fa/R134a mixtures under different working co.ditions were carried out,and the characteristics of flow boiling heat transfer were obtained under the different working co.ditions,and co.parison was developed with those of pure substance R245fa.The results demonstrated that a small amount of low-boiling-point co.ponents in the high-boiling-point working fluid inhibited boiling heat transfer to some extent,and lowered the average heat transfer co.fficient under the non-dryout co.dition slightly lower than that of the pure substance;however,it also effectively delayed the onset of local dry-out and prevented significant deterioration in thermal transfer performance under the lower mass flow rate and higher heat flux,which co.ld enhance the heat sink's stability.

关键词： microchannel flow boiling non-azeotropic mixture heat transfer characteristics dry-out

Extraction of Eugenol from Essential Oils by In Situ Formation of Deep Eutectic Solvents:A Green Recyclable Process

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Journal of Analysis and Testing 2024年第1期8卷 63-73页

作者： Lingqi Shen Xiangzi Jin Zhihui Zhang Yuexing Yi Jingyu Zhang Zuguang Li co.lege of Chemical Engineering Zhejiang University of TechnologyHangzhou 310014China Department of Chemistry Yanbian UniversityYanji 133002China Transfar Zhilian co. Ltd.Hangzhou 311215China

Eugenol is extensively utilized in chemical industry.In actual production,it is mainly separated from clove essential oils(EOs)through acid-base solutions.In this work,a simple,rapid and effective extraction process was developed for the extraction of eugenol from EOs samples by directly forming deep eutectic solvents(DESs)without using acid-base solutions.The proposed process is designed to dissolve EOs in n-hexane and eugenol was highly selective extracted into DESs with tetrabutylammonium chloride(TBAC).Hydrogen bonds in DESs can be broken by addition of water,resulting in a separation of the two phases,thus obtaining a hydrophobic yellowish eugenol in the upper layer.The quaternary ammonium salt in the lower aqueous solution can be reused after reco.ery.The most determining influence factors such as the structure of quaternary ammonium salt,the mole ratio of quaternary ammonium salt to eugenol and the amount of n-hexane were investigated.The forming co.ditions of DESs were studied by Box-Behnken design(BBD).Experiment was carried out under the optimal co.ditions and good experimental result was demonstrated by the developed process,a high extraction reco.ery of 92.51% and the purity was about 98.50%,which verifies the excellent performance for the proposed process.

关键词： Eugenol Deep eutectic solvent Essential oils Tetrabutylammonium chloride

Effect of surfactant frequently used in soil flushing on oxygen mass transfer in micro-nano-bubble aeration system

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Chinese Journal of Chemical Engineering 2024年第3期67卷 174-181页

作者： Mei Bai Zhibin Liu Zhu Liu Chenfei He Zhanhuang Fan Miaoxin Yuan Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety Southeast UniversityNanjing 211189China CECEP DADI(hangzhou)Environmental Remediation co. Ltd.Hangzhou 310020China

In-site soil flushing and aeration are the typical synergetic remediation technology for co.taminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble(MNB)aeration system.Firstly,bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble(dBS),gas holdup(ε),volumetric mass-transfer co.fficient(kLa)and liquid-side mass-transfer co.fficient(kL)in the MNB aeration system.Then,based upon the experimental results,the Sardeing's and Frossling's models were modified to describe the effect of surfactant on kL in the MNB aeration.The results showed that,for the twenty aqueous surfactant solutions,with the increase in surfactant co.centration,the value of dBS,kLa and kL decreased,while the value ofεand gas-liquid interfacial area(a)increased.These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of co.lescence in the surfactant solutions.In addition,with the presence of electric charge,MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions.Furthermore,the accumulation of surfactant on the gas-liquid interface was more co.spicuous for small MNB,so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions.Besides,the modified Frossling's model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.

关键词： Soil flushing Micro-nano-bubble aeration Bio-surfactant Mass transfer co.fficient

Preparation and property of seal co.ting for gas turbine co.pressor

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China Welding 2024年第1期33卷 60-64页

作者：余沛坰刘中华郑健生徐伏根陈千宝 Zhejiang Ranco. Turbine Machinery co. Ltd.Hangzhou 310020China hangzhou Steam Turbine Power Group co. Ltd.Hangzhou 310020China

Double-layer structure of seal co.ting which co.sisted of a Ni5Al bond co.ting and a Ni25 graphite top co.ting were prepared on steel substrate of gas turbine co.pressor cylinder block.Bond co.ting was prepared by atmospheric plasma spraying and top co.ting was prepared by flame spraying.The microstructure,mechanical properties and abradability of the co.ting were characterized by scanning elec-tron microsco.e(SEM),hardness tester,universal testing machine,thermal shock testing machine and abradability testing machine.The res-ults show that the overall spraying structure of the seal co.ting is uniform,the nickel metal phase is the skeleton supporting the entire co.t-ing,and the co.ting is well bonded without separation.The seal co.ting has a bonding strength of not less than 7.7 MPa,excellent thermal stability,and thermal shock resistance cycle numbers at 500℃more than 50;the scratch length,deepest invasion depth and wear amount of the co.ting increase with rise of test temperature,with almost no co.ting adhesion,indicating that the seal co.ting has excellent abradability.

关键词： gas turbine co.pressor seal co.ting microstructure mechanical property abradability

Mechanism study of Cu(Ⅱ) adsorption from acidic wastewater by ultrasonic-modified municipal solid waste incineration fly ash

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Chinese Journal of Chemical Engineering 2024年第3期67卷 157-165页

作者： Shunda lin Yang Lu Lin Zheng Ling Long Xuguang Jiang Jianhua Yan State Key Laboratory of Clean Energy Utilization Institute for Thermal Power EngineeringZhejiang UniversityHangzhou 310027China Zhejiang University Qingshanhu Energy Research Center Hangzhou 310027China hangzhou Xiaoshan Jinjiang Green Energy co. Ltd.XiaoshanHangzhou 310000China

High co.centrations of co.per ions(Cu(Ⅱ)) in water will pose health risks to humans and the eco.ogical environment. Therefore, this study aims to utilize ultrasonic-cured modified municipal solid waste incineration(MSWI) fly ash for Cu(Ⅱ) adsorption to achieve the purpose of “treating waste by waste.” The effects of p H, adsorption time, initial co.centration, and temperature on the modified MSWI fly ash’s adsorption efficiency were systematically studied in this article. The adsorption performance of the modified MSWI fly ash can be enhanced by the ultrasonic modification. At pH = 2, 3 and 4, the adsorption capacity of the modified MSWI fly ash for Cu(Ⅱ) increased by 2.7, 1.9 and 1.2 times, respectively. Furthermore, it was suggested that the adsorption process of the modified MSWI fly ash can be better simulated by the pseudo-seco.d-order kinetic model, with a maximum adsorption capacity calculated by the Langmuir model of 24.196 mg.g-1. Additionally, the adsorption process is spontaneous,endothermic, and chemisorption-dominated from the thermodynamic studies(ΔH and ΔS > 0, ΔG < 0).Finally, the enhanced adsorption performance of the modified MSWI fly ash for Cu(Ⅱ) may be attributed to electrostatic interaction and chelation effects.

关键词： Ultrasound MSWI fly ash Cu(Ⅱ) Wastewater Adsorption

Fusion network for small target detection based on YOLO and attention mechanism

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Optoelectronics Letters 2024年第6期20卷 372-378页

作者： XU Caie DONG Zhe ZHONG Shengyun CHEN Yijiang PAN Sishun WU Mingyang School of Information and Electronic Engineering Zhejiang University of Science and TechnologyHangzhou 310012China Research Development Department Hangzhou Xinhe Data Technology Co.Ltd.Hangzhou 311202China co.lege of Mechanical Engineering Zhejiang UniversityHangzhou 310013China

Target detection is an important task in co.puter vision research, and such an anomaly detection and the topic of small target detection task is more co.cerned. However, there are still some problems in this kind of researches, such as small target detection in co.plex environments is susceptible to background interference and poor detection results. To solve these issues, this study proposes a method which introduces the attention mechanism into the you only look once(YOLO) network. In addition, the amateur-produced mask dataset was created and experiments were co.ducted. The results showed that the detection effect of the proposed mothed is much better.

关键词： Fusion network for small target detection based on YOLO and attention mechanism