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Near-zero stiffness accelerometer with buckling of tunable electrothermal microbeams

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Microsystems & Nanoengineering 2024年第2期10卷 67-81页

作者： Hussein Hussein Chen Wang Rui Amendoeira Esteves Michael kraft Hossein Fariborzi Department of Mechanical Engineering MSFEAAmerican University of BeirutBeirut11072020Lebanon King Abdullah University of science and Technology Thuwal23955-6900Saudi Arabia EsAT-MNs University of Leuven3001LeuvenBelgium

Pre-shaped microbeams,curved or inclined,are widely used in MEMs for their interesting stiffness *** mechanisms allow a wide range of positive and negative stiffness tuning in their direction of motion.A mechanism of pre-shaped beams with opposite curvature,connected in a parallel configuration,can be electrothermally tuned to reach a near-zero or negative stiffness behavior at the as-fabricated *** simple structure helps incorporate the tunable spring mechanism in different designs for accelerometers,even with different transduction *** sensitivity of the accelerometer can be considerably increased or tuned for different applications by electrothermally changing the stiffness of the spring *** inclined beams are implemented in a capacitive micromachined *** measurements on fabricated prototypes showed more than 55 times gain in sensitivity compared to their initial *** experiments showed promising results in enhancing the resolution of acceleration sensing and the potential to reach unprecedent performance in micromachined accelerometers.

关键词： properties. mechanism. stiffness

Explaining the influence of dopant concentration and excitation power density on the luminescence and brightness of β-NaYF4:Yb^3+,Er^3+ nanoparticles:Measurements and simulations

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Nano Research 2019年第8期12卷 1871-1879页

作者： Martin Kaiser Christian Wurth Marco kraft Tero soukka Ute Resch-Genger Division Biophotonics Federal Institute for Materials Research and Testing (BAM)Richard-Willstaetter-Str. 11D-12489 BerlinGermany Department of Biotechnology University of TurkuKiinamyllynkatu 10TurkuFI-20520Finland

We assessed the influence of Yb^3+ and Er34 dopant concentration on the relative spectral distribution, quantum yield (Фuc), and decay kinetics of the upconversion luminescence (UCL) and particle brightness (BUC) for similarly sized (33 nm) oleate-capped p-NaYF4:Yb3t,Er^3+ upconversion (UC) nanoparticles (UCNPs) in toluene at broadly varied excitation power densities (F). This included an Yb^3+ series where the Yb^3+ concentration was varied between 11%—21% for a constant Er^3+ concentration of 3%, and an Er^3+ series, where the Er^3+ concentration was varied between 1%-4% for a constant Yb^3+ concentration of 14%. The results were fitted with a coupled rate equation model utilizing the UCL data and decay kinetics of the green and red Er34 emission and the Yb34 luminescence at 980 nm. An increasing Yb34 concentration favors a pronounced triphotonic population of 4F9/2 at high P by an enhanced back energy transfer (BET) from the 4G11/2 level. simultaneously, the Yb^3+-controlled UCNPs absorption cross section overcompensates for the reduction in Фuc with increasing Yb^3+ concentration at high P, resulting in an increase in sue. Additionally, our results show that an increase in Yb34 and a decrease in Er^3+ concentration enhance the color tuning range by P. These findings will pave the road to a deeper understanding of the energy transfer processes and their contribution to efficient UCL, as well as still debated trends in green-to-red intensity ratios of UCNPs at different P.

关键词： upconversion quantum yield color tuning nanoparticles dopant concentration rate equation model

MEMs gyroscope control system using a band-pass continuous-time sigma-delta modulator

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science China(Information sciences) 2013年第10期56卷 180-189页

作者： DING HaiTao YANG ZhenChuan WANG ZhanFei kraft Michael YAN GuiZhen National Key Laboratory of science and Technology on Micro/Nano Fabrication Institute of MicroelectronicsPeking University school of Electronics and Computer science University of Southampton

This paper presents a MEMs gyroscope control system of using a high-order band-pass continuoustime sigma-delta *** with a low-pass discrete-time sigma-delta modulator based solution,the band-pass modulator can considerably decrease the sampling frequency;moreover,the continuous-time architecture has an obvious advantage on PCB prototyping and shorter lead time of the implementation in *** level simulations using MATLAB/simulink show the proposed sixth order sigma-delta modulator can achieve a high sNR of 100 dB for an angular rate input with an amplitude of 200/s and a frequency of32 Hz.A PCB circuit implementation is simulated using Orcad/Pspice to analyze the stability,and implemented in *** of the power spectral density of the output bitstream reveals a noise floor of90 dBV/Hz1/*** prototype is tested on a rate table with an angular rate input,verifying that the principle of the approach of using an electro-mechanical band-pass sigma-delta modulator control system for a MEMs gyroscope.

关键词： band-pass continuous-time control system MEMs gyroscope sigma-delta modulator

Optimal Placement of Phasor Measurement Unit in smart Grids Considering Multiple Constraints

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Journal of Modern Power systems and Clean Energy 2023年第2期11卷 479-488页

作者： Tengpeng Chen He Ren Yuhao sun Markus.kraft Gehan A.J.Amaratunga Department of Instrumental and Electrical Engineering Xiamen UniversityXiamenChina shenzhen Research Institute of Xiamen University ShenzhenChina CTC Intelligence(shenzhen)Technology Co. Ltd.ShenzhenChina Department of Chemical Engineering and Biotechnology University of CambridgeCambridgeUK Cambridge Centre for Advanced Research and Education in singapore CREATE TowerSingapore school of Chemical and Biomedical Engineering Nanyang Technological UniversitySingapore Department of Engineering University of CambridgeUK

The distribution of measurement noise is usually assumed to be Gaussian in the optimal phasor measurement unit(PMU)placement(OPP)***,this is not always accurate in *** paper proposes a new OPP method for smart grids in which the effects of conventional measurements,limited channels of PMUs,zero-injection buses(ZIBs),single PMU loss contingency,state estimation error(sEE),and the maximum sEE variance(MsEEV)are *** sEE and MsEEV are both obtained using a robust t-distribution maximum likelihood estimator(MLE)because t-distribution is more flexible for modeling both Gaussian and non-Gaussian *** A-and G-optimal experimental criteria are utilized to form the sEE and MsEEV *** allows the optimization problem to be converted into a linear objective function subject to linear matrix inequality observability *** performance of the proposed OPP method is verified by the simulations of the IEEE 14-bus,30-bus,and 118-bus systems as well as the 211-bus practical distribution system in China.

关键词： Phasor measurement unit(PMU) smart grids optimal placement state estimation(sE).

Particle-size-dependent upconversion luminescence of NaYF4:Yb,Er nanoparticles in organic solvents and water at different excitation power densities

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Nano Research 2018年第12期11卷 6360-6374页

作者： Marco kraft Christian Würth Verena Muhr Thomas Hirsch Ute Resch-Genger Federal Institute for Matefiab Research and Testing (BAM) Division1.2BiophotonicsRichard-Willstaetter-Str.1112489BerlinGermany Institute of Analytical Chemistry Chemo-and BiosensorsUniversity of Regensburg93040RegensburgGermany

A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12-43 nm is presented utilizing steady-state and time-resolved f... 详细信息

A systematic study of the luminescence properties of monodisperse β-NaYFsub>4sub>: 20% Ybsup>3+sup>, 2% Ersup>3+sup> upconversion nanoparticles (UCNPs) with sizes ranging from 12-43 nm is presented utilizing steady-state and time-resolved fluorometry. special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by high-energy O-H and C-H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated population pathways of the sup>4sup>Fsub>9/2sub> energy level of Ersup>3+sup> were examined. Our results highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Ersup>3+sup> emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. Because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the sup>4sup>Fsub>9/2sub> energy level of Ersup>3+sup>, which correlate with the size-, environment-, and P-dependent quenching states of the higher Ersup>3+sup> energy levels.

关键词： upconversion nanoparticle quenching diameter water cyclohexane

Experimental and analytical investigation on friction resistance force between buried coated pressurized steel pipes and soil

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Frontiers of structural and Civil Engineering 2024年第4期18卷 615-629页

作者： shaurav ALAM Tanvir MANZUR John MATTHEWs Chris BARTLETT Erez ALLOUCHE Brent KEIL John kraft Department of Civil Engineering and Construction Engineering Technology Louisiana Tech UniversityRustonLA 71270USA Department of Civil Engineering Bangladesh University of Engineering and TechnologyDhaka 1000Bangladesh Georgia Tech Research Institute AtlantaGA 30332USA stantec Inc. Edmonton T5J0K4Canada North West Pipe Company VancouverWA 98684USA

This paper presents an analytical approach for estimating frictional resistance to pipe movement at soil and external pipe surface of buried coated pressurized steel pipes relative to the internal thrust *** proposed analytical method was developed based on 36 experiments,which involved three coating types(cement mortar(CM),polyurethane type-I(PT-I),prefabricated plastic tape(PPT))on pipes’surfaces,three different soils(pea-gravel(PG),sand(s),silty-clay(sC)),and four simulated over burden depths above the pipe’s *** showed frictional resistance decreased with increasing over burden depth above the pipe’s *** degree of frictional resistance at the pipe-soil interface was found to be in the order of PG>sC>s for all coating variations and overburden *** coated pipe buried in all three types of soil produced significantly higher frictional resistance as compared to other coating *** on experimental data,the developed analytical introduced a dimensionless factor“Z”,which included effects of types of coatings,soil,and overburden depths for simplified rapid *** showed that the method provided a better prediction of frictional resistance forces,in comparison to previous analytical methods,which were barely close in predicting friction resistance for different coating variations,soil types,and overburden *** resistance force values reported herein could be considered conservative.

关键词： friction resistance force thrust force coated pressurized steel pipe soil type overburden depth

Investigating the impact of dynamic structural changes of Au/rutile catalysts on the catalytic activity of CO oxidation

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Carbon Energy 2024年第4期6卷 222-232页

作者： Xiaochun Hu Qianwenhao Fan Mingwu Tan Yuqing Luo Xianyue Wu Manoel Y.Manuputty Jie Ding Tej s.Choksi Markus.kraft Rong Xu Zhiqiang sun Wen Liu school of Energy science and Engineering Central South UniversityChangshaChina school of Chemistry Chemical Engineering and BiotechnologyNanyang Technological UniversitySingaporeSingapore Cambridge Centre for Advanced Research and Education SingaporeSingapore Institute of sustainability for Chemicals Energy and EnvironmentJurong IslandSingapore College of Chemistry and Chemical Engineering Central South UniversityChangshaChina Department of Chemical Engineering and Biotechnology University of CambridgeCambridgeUK

The surface properties of oxidic supports and their interaction with the supported metals play critical roles in governing the catalytic activities of oxide‐supported metal *** metals are supported on reducible oxides,dynamic surface reconstruction phenomena,including strong metal–support interaction(sMsI)and oxygen vacancy formation,complicate the determination of the structural–functional relationship at the active ***,we performed a systematic investigation of the dynamic behavior of Au nanocatalysts supported on flame‐synthesized TiO_(2),which takes predominantly a rutile phase,using CO oxidation above room temperature as a probe *** analysis conclusively elucidated a negative correlation between the catalytic activity of Au/TiO_(2) and the oxygen vacancy at the Au/TiO_(2) *** the reversible formation and retracting of sMsI overlayers have been ubiquitously observed on Au/TiO_(2) samples,the catalytic consequence of sMsI remains *** functional theory suggests that the electron transfer from TiO_(2) to Au is correlated to the presence of the interfacial oxygen vacancies,retarding the catalytic activation of CO oxidation.

关键词： CO oxidation electronic metal-support interactions flame‐synthesis metal-support interactions oxygen vacancy strong metal-support interaction

Dynamic knowledge graph approach for modelling the decarbonisation of power

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Energy and AI

Energy and AI 2024年第3期17卷 48-64页

作者： Wanni Xie Feroz Farazi John Atherton Jiaru Bai sebastian Mosbach Jethro Akroyd Markus.kraft Department of Chemical Engineering and Biotechnology University of CambridgePhilippa Fawcett DriveCambridge CB30ASUK CAREs Cambridge Centre for Advanced Research and Education in Singapore1 Create WayCREATE Tower#05-05Singapore138602Singapore school of Chemical and Biomedical Engineering Nanyang Technological University62 Nanyang DriveSingapore637459Singapore The Alan Turing Institute LondonNW12DBUK

This paper presents a dynamic knowledge graph approach that offers a reusable,interoperable,and extensible framework for modelling power *** ontologies have been developed to support a linked data representation of infrastructure data,socio-demographic data,areal attributes like demand,and models describing power *** knowledge graph links the data with a hierarchical representation of administrative regions,supporting geospatial queries to retrieve information about the population within the vicinity of a power plant,the number of power plants,total generation capacity,and demand within specific *** agents were developed to operate on the knowledge *** agents performed tasks including data uploading,updating,retrieval,processing,model construction and scenario analysis.A derived information framework was used to track the provenance of information calculated by agents involved in each *** knowledge graph was populated with data describing the UK power *** alternative models of the transmission grid with different levels of structural resolution were instantiated,providing the foundation for the power system simulation and optimisation tasks performed by the *** application of the dynamic knowledge graph was demonstrated via a case study that investigates clean energy transition trajectories based on the deployment of small Modular Reactors in the UK.

关键词： Power system modelling Decarboni sation Dynanic knowledge graph Ontology and semantic Web

Bending reliability of screen-printed vias for a flexible energy module

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npj Flexible Electronics 2020年第1期4卷 210-217页

作者： Manu Kujala Terho Kololuoma Jari Keskinen Donald Lupo Matti Mäntysalo Thomas M.kraft Faculty of Computing and Electrical Engineering Tampere University(formerly Tampere University of Technology)Korkeakoulunkatu 3FI-33720TampereFinland Faculty of Information Technology and Communication sciences Tampere UniversityKorkeakoulunkatu 3TampereFI-33720Finland sasken Finland Oy Vissavedentie 1FI-69600KaustinenFinland VTT Technical Research Centre of Finland Ltd. Kaitoväylä1OuluFI-90590Finland

The future of printed electronics involves advancements not only related to full system integration,but also lean process manufacturing.A critical aspect of this progress is developed in this study,which evaluates a highly flexible screen printed through-hole-via using silver microparticle inks,for applications in energy harvesting and storage *** printed vias’fabrication and durability are evaluated by means of a double sided screen-printing method and repetitive(cyclic)bending ***,through 125-µm-thick PET foil,were laser cut(nominally 50,100,150,and 200µm diameters)then filled,and simultaneously connected to adjacent vias by screen *** investigate the use of the printed via in a monolithic energy module,the vias were used for the fabrication of a flexible printed supercapacitor containing aqueous electrolyte and carbon *** results indicate that the lower viscosity silver ink(DuPont 5064H)fills the via less effectively than the higher viscosity ink(Asahi Ls411AW),and as the via size increases(≥150µm diameter)via walls are coated rather than ***,the more viscous ink fills the via thoroughly and exhibited a 100%yield(1010 vias;100µm nominal via diameter)with the two-step direct screen-printing *** 10-mm radius bending test showed no signs of via specific breakdown after 30,000 *** results indicate that this via filling process is likely roll-to-roll compatible to enable multi-layered printed electronic devices.

关键词： silver printing nominal