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Machine-learned wearable sensors for real-time hand-motion recognition: toward practical applications

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National Science Review 2024年第2期11卷 231-263页

作者： Kyung Rok Pyun Kangkyu Kwon Myung Jin Yoo Kyun Kyu Kim Dohyeon Gong Woon-Hong Yeo Seungyong Han Seung Hwan Ko department of mechanical engineering Seoul National University IEN center for Human-Centric Interfaces and engineering Institute for Electronics and NanotechnologyGeorgia Institute of Technology School of Electrical and Computer engineering Georgia Institute of Technology department of Chemical engineering Stanford University department of mechanical engineering Ajou University George W.Woodruff School of mechanical engineering Georgia Institute of Technology Institute of Advanced Machinery and Design(SNU-IAMD) Seoul National University

Soft electromechanical sensors have led to a new paradigm of electronic devices for novel motion-based wearable applications in our daily lives. However, the vast amount of random and unidentified signals generated by complex body motions has hindered the precise recognition and practical application of this technology. Recent advancements in artificial-intelligence technology have enabled significant strides in extracting features from massive and intricate data sets, thereby presenting a breakthrough in utilizing wearable sensors for practical applications. Beyond traditional machine-learning techniques for classifying simple gestures, advanced machine-learning algorithms have been developed to handle more complex and nuanced motion-based tasks with restricted training data sets. Machine-learning techniques have improved the ability to perceive, and thus machine-learned wearable soft sensors have enabled accurate and rapid human-gesture recognition, providing real-time feedback to users. This forms a crucial component of future wearable electronics, contributing to a robust human–machine interface. In this review, we provide a comprehensive summary covering materials, structures and machine-learning algorithms for hand-gesture recognition and possible practical applications through machine-learned wearable electromechanical sensors.

关键词： wearable sensor soft electronics artificial intelligence machine learning human–machine interfaces gesture recognition

Synergistic effect of adsorption and photocatalytic degradation of oilfield-produced water by electrospun photocatalytic fibers of Polystyrene/Nanorod-Graphitic carbon nitride

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Journal of Environmental Sciences 2024年第7期141卷 287-303页

作者： Parisa Azmoon Mehrdad Farhadian Alireza Pendashteh Amir H.Navarchian department of Chemical engineering Faculty of EngineeringUniversity of IsfahanIsfahanIran department of Chemical engineering Faculty of EngineeringUniversity of GuilanRashtIran department of Water and Environmental engineering Caspian Sea Basin Research CenterUniversity of GuilanRashtIran

Graphitic carbon nitride with nanorod structure(Nr-GCN)was synthesized using melamine as a precursor without any other reagents by hydrothermal pretreatment method.XRD,FTIR,SEM,N_(2)adsorption-desorption from BET,UV-Vis DRS spectroscopy,and photoluminescence were used to characterize the prepared samples.Also,the photoelectrochemical behavior of nanoparticles was studied by photocurrent transient response and cyclic voltammetry analysis.Polystyrene(PS)fibrous mat was fabricated by electrospinning technique and used as a support for the stabilization of the nanoparticles.The performance of the synthesized nanoparticles and photocatalytic fibers(PS/Nr-GCN)was evaluated in oilfield-produced water treatment under visible light irradiation.During this process,oil contaminants were adsorbed by hydrophobic polystyrene fibers and simultaneously degraded by Nr-GCN.The removal efficiency of chemical oxygen demand(COD)has been obtained 96.6%and 98.4%by Nr-GCN and PS/Nr-GCN,respectively,at the optimum conditions of pH4,photocatalyst dosage 0.5 g/L,COD initial concentration 550 mg/L,and illumination time 150 min.The gas chromatography-mass spectroscopy analysis results showed 99.3%removal of total petroleum hydrocarbons using photocatalytic fibers of PS/Nr-GCN.The results demonstrated that the GCN has outstanding features like controllable morphology,visible-light-driven,and showing high potential in oily wastewater remediation.Moreover,the synergistic effect of adsorption and photocatalytic degradation is an effective technique in oilfield-produced water treatment.

关键词： Graphitic carbon nitride(GCN) Nanorod structure Polystyrene fibrous mat Photocatalytic fibers Oilfield-produced water(OPW)

Investigation of electrostatically tunable adhesion and instability of flying head slider

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Friction 2024年第3期12卷 462-473页

作者： Fan ZHANG Yu WANG Yueqiang HU Mingquan ZHANG Baotong LI School of mechanical engineering Xi’an Jiaotong UniversityXi’an 710049China National engineering research center for High Efficiency Grinding College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

The interfacial adhesion between microstructures is inevitable in a micro-electro-mechanical system(e.g.,hard disk drive(HDD)),which may lead to complicated microtribodynamics problems.This research has investigated the effect of surface potential on the interfacial adhesion and microtribodynamics of the head–disk interface(HDI)in an HDD.A dynamic continuum surface force model,where the electrowetting is considered,is proposed to evaluate the interfacial interaction,and then employed into a two-degree-of-freedom(2DOF)model to theoretically analyze the potential influence mechanism on the microtribodynamics.The results confirm that the elimination of potential can effectively repress the adhesion retention,which is further proved by the measured slider response with a laser Doppler vibrometer(LDV).Moreover,the effect of the potential on the adhesion-induced instability is also analyzed through the phase portrait.It tells that the critical stable flying height can be lowered with the elimination of potential.

关键词： electric field(EF) retention instability adhesion

Experimental Study on Heat Storage Properties Comparison of Paraffin/Metal Foams Phase Change Material Composites

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Journal of Thermal Science 2024年第2期33卷 469-478页

作者： Waqar AHMED Abid HUSSAIN Hanzla SHAHID Imran ALI Hafiz Muhammad ALI department of mechanical engineering University of Engineering and TechnologyTaxila47080Pakistan department of mechanical engineering Institute of Space TechnologyIslamabadPakistan department of mechanical Mechatronics and Manufacturing EngineeringUniversity of Engineering and Technology LahoreFaisalabad CampusPunjabPakistan mechanical engineering department King Fahd University of Petroleum and MineralsDhahran31261Saudi Arabia Interdisciplinary research center for Renewable Energy and Power Systems(IRC-REPS) King Fahd University of Petroleum and MineralsDhahran31261Saudi Arabia

Heat storage properties of phase change materials(PCMs) are essential characteristics that perform a key role in thermal heat energy storage systems.The thermal properties of PCMs can be improved by developing metal foam/PCM composites.The addition of metal foam in PCMs has a significant effect on the thermal characteristics of PCMs.In this paper,the heat storage properties of two different metal foam/PCM composites were experimentally examined.The behavior of paraffin in metal foam(copper and iron-nickel)/paraffin composites concerning pure paraffin at a constant heat flux of 1000 W/m^(2) in three directions simultaneously(x,y,and z) was studied.Paraffin was infiltrated into copper and iron-nickel foams to develop composite materials which resulted in enhancing the thermal conductivity of the paraffin.A comparative analysis is made on the heat storage properties of paraffin in copper and iron-nickel foams/paraffin composites.Inner temperature distribution during the phase transition process is experimentally evaluated.This comparison indicates that temperature uniformity in copper foam/paraffin composite is better than in iron-nickel foam/paraffin composite and pure paraffin at the same heat flux.Experimental results show that at heat flux of 1000 W/m^(2),the heat storage time for copper foam/paraffin composite is 20.63% of that of iron-nickel foam/paraffin composite.

关键词： heat storage capacity paraffin/metal foam composite temperature uniformity heat storage rate phase transition process

Synthesis and Thermal Characterization of Solar Salt-Based Phase Change Composites with Graphene Nanoplatelets

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Journal of Thermal Science 2024年第2期33卷 491-500页

作者： Pethurajan VIGNESHWARAN Saboor SHAIK Sivan SURESH Müslüm ARICI Asif AFZAL department of Thermal and Energy engineering School of Mechanical Engineering(SMEC)Vellore Institute of TechnologyVelloreTamil NaduIndia Nanotechnology research Laboratory Department of Mechanical EngineeringNational Institute of TechnologyTiruchirappalliTamil NaduIndia mechanical engineering department Engineering FacultyKocaeli UniversityUmuttepe CampusKocaeli41001Turkey department of mechanical engineering P.A.College of Engineering(affiliated to Visvesvaraya Technological UniversityBelagavi)Mangaluru574153India

Thermal energy storage(TES) systems use solar energy despite its irregular availability and day-night temperature difference.Current work reports the thermal characterizations of solar salt-based phase change composites in the presence of graphene nanoplatelets(GNP).Solar salt(60:40 of NaNO_(3):KNO_(3)) possessing phase transition temperature and melting enthalpy of 221.01℃ and 134.58 kJ/kg is proposed as a phase change material(PCM) for high-temperature solar-based energy storage applications.Thermal conductivity must be improved to make them suitable for widespread applications and to close the gap between the system needs where they are employed.GNP is added at weight concentrations of 0.1%,0.3%,and 0.5% with solar salt using the ball milling method to boost its thermal conductivity.Morphological studies indicated the formation of a uniform surface of GNP on solar salt.FTIR spectrum peaks identified the physical interaction between salt and GNP.Thermal characterization of the composites,such as thermal conductivity,DSC and TGA was carried out for the samples earlier and later 300 thermal cycles.0.5% of GNP has improved the thermal conductivity of salt by 129.67% and after thermal cycling,the enhancement reduced to 125.21% indicating that thermal cycling has a minor impact on thermal conductivity.Phase change temperature decreased by around 2.32% in the presence of0.5% GNP and the latent heat reduced by 4.34% after thermal cycling.TGA thermograms depicted the composites initiated the weight loss at around 550℃ after which it was rapid.After thermal cycling,the weight loss initiated at ~40℃ lower compared to pure salt,which was found to be a minor change.Thermal characterization of solar salt and GNP-based solar salt composites revealed that the composites can be used for enhanced heat transfer in high-temperature solar-based heat transfer and energy storage applications.

关键词： thermal energy storage high temperature solar salt graphene nanoplatelets thermal characterization

research on the flow stability and noise reduction characteristics of quasi-periodic elastic support skin

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Defence Technology（防务技术） 2024年第3期33卷 222-236页

作者： Lu Chen Shao-gang Liu Dan Zhao Li-qiang Dong Kai Li Shuai Tang Jin Cui Hong Guo department of mechanical and Electrical engineering Harbin Engineering UniversityHarbin150001China

To enhance flow stability and reduce hydrodynamic noise caused by fluctuating pressure,a quasiperiodic elastic support skin composed of flexible walls and elastic support elements is proposed for fluid noise reduction.The arrangement of the elastic support element is determined by the equivalent periodic distance and quasi-periodic coefficient.In this paper,a dynamic model of skin in a fluid environment is established.The influence of equivalent periodic distance and quasi-periodic coefficient on flow stability is investigated.The results suggest that arranging the elastic support elements in accordance with the quasi-periodic law can effectively enhance flow stability.Meanwhile,the hydrodynamic noise calculation results demonstrate that the skin exhibits excellent noise reduction performance,with reductions of 10 dB in the streamwise direction,11 dB in the spanwise direction,and 10 dB in the normal direction.The results also demonstrate that the stability analysis method can serve as a diagnostic tool for flow fields and guide the design of noise reduction structures.

关键词： Flow stability Quasi-period Flexible wall Elastic support element Hydrodynamic noise

Supposition of graphene stacks to estimate the contact resistance and conductivity of nanocomposites

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Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 663-676页

作者： Y.ZARE M.T.MUNIR G.J.WENG K.Y.RHEE Biomaterials and Tissue engineering research Group Department of Interdisciplinary TechnologiesBreast Cancer Research CenterMotamed Cancer InstituteTehran ***Iran College of engineering and Technology American University of the Middle EastEgaila 54200Kuwait department of mechanical and Aerospace engineering Rutgers UniversityNew BrunswickNJ 08903U.S.A. department of mechanical engineering(BK21 Four) College of EngineeringKyung Hee UniversityYongin 446701Republic of Korea

In this study,the effects of stacked nanosheets and the surrounding interphase zone on the resistance of the contact region between nanosheets and the tunneling conductivity of samples are evaluated with developed equations superior to those previously reported.The contact resistance and nanocomposite conductivity are modeled by several influencing factors,including stack properties,interphase depth,tunneling size,and contact diameter.The developed model's accuracy is verified through numerous experimental measurements.To further validate the models and establish correlations between parameters,the effects of all the variables on contact resistance and nanocomposite conductivity are analyzed.Notably,the contact resistance is primarily dependent on the polymer tunnel resistivity,contact area,and tunneling size.The dimensions of the graphene nanosheets significantly influence the conductivity,which ranges from 0 S/m to90 S/m.An increased number of nanosheets in stacks and a larger gap between them enhance the nanocomposite's conductivity.Furthermore,the thicker interphase and smaller tunneling size can lead to higher sample conductivity due to their optimistic effects on the percolation threshold and network efficacy.

关键词： graphene polymer composite stacked nanosheet tunneling conductivity contact resistance interphase

Room and cryogenic deformation behavior of AZ61 and AZ61-xCaO(x = 0.5, 1 wt.%) alloy

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Journal of Magnesium and Alloys 2024年第5期12卷 1996-2009页

作者： Umer Masood Chaudry Hafiz Muhammad Rehan Tariq Nooruddin Ansari Soo Yeol Lee Tea-Sung Jun department of mechanical engineering Incheon National University research Institute for engineering and Technology Incheon National University department of Materials Science&engineering Chungnam National University

This study investigates the influence of CaO(0.5, 1(wt.%)) alloying on the microstructural evolution, texture development and deformation behavior of AZ61 magnesium alloy. The uniaxial tension tests at room(RT) and cryogenic(CT,-150 ℃) temperature were performed to investigate the twinability and dislocation behavior and its consequent effect on flow stress, ductility and strain hardening rate. The results showed that the AZ61-1CaO exhibited superior strength/ductility synergy at RT with a yield strength(YS) of 223 MPa and a ductility of 23% as compared to AZ61(178 MPa, 18.5%) and AZ61-0.5CaO(198 MPa, 21%). Similar trend was witnessed for all the samples during CT deformation, where increase in the YS and decrease in ductility were observed. The Mtex tools based in-grain misorientation axis(IGMA) analysis of RT deformed samples revealed the higher activities of prismaticslip in AZ61-CaO, which led to superior ductility.Moreover, subsequent EBSD analysis of CT deformed samples showed the increased fraction of fine {10-12} tension twins and nucleation of multiple {10-12} twin variants caused by higher local stress concentration at the grain boundaries, which imposed the strengthening by twin-twin interaction. Lastly, the detailed investigations on strengthening contributors showed that the dislocation strengthening has the highest contribution towards strength in all samples.

关键词： Magnesium Twinning Twinning variant EBSD Cryogenic deformation

Type Synthesis of Self-Alignment Parallel Ankle Rehabilitation Robot with Suitable Passive Degrees of Freedom

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Chinese Journal of mechanical engineering 2024年第1期37卷 160-175页

作者： Ya Liu Wenjuan Lu Dabao Fan Weijian Tan Bo Hu Daxing Zeng School of mechanical engineering Yanshan UniversityQinhuangdao 066004China School of mechanical engineering Dongguan University of TechnologyDongguan 523808China Dongguan engineering Technology research center for Parallel Robot Dongguan 523808China The DGUT Innovation center of Robotics and Intelligent Equipment Dongguan 523808China

The current parallel ankle rehabilitation robot(ARR)suffers from the problem of difficult real-time alignment of the human-robot joint center of rotation,which may lead to secondary injuries to the patient.This study investigates type synthesis of a parallel self-alignment ankle rehabilitation robot(PSAARR)based on the kinematic characteristics of ankle joint rotation center drift from the perspective of introducing"suitable passive degrees of freedom(DOF)"with a suitable number and form.First,the self-alignment principle of parallel ARR was proposed by deriving conditions for transforming a human-robot closed chain(HRCC)formed by an ARR and human body into a kinematic suitable constrained system and introducing conditions of"decoupled"and"less limb".Second,the relationship between the self-alignment principle and actuation wrenches(twists)of PSAARR was analyzed with the velocity Jacobian matrix as a"bridge".Subsequently,the type synthesis conditions of PSAARR were proposed.Third,a PSAARR synthesis method was proposed based on the screw theory and type of PSAARR synthesis conducted.Finally,an HRCC kinematic model was established to verify the self-alignment capability of the PSAARR.In this study,93 types of PSAARR limb structures were synthesized and the self-alignment capability of a human-robot joint axis was verified through kinematic analysis,which provides a theoretical basis for the design of such an ARR.

关键词： Ankle rehabilitation robot Self-alignment Parallel mechanism Type synthesis Screw theory