41 research outputs found
Hållbar omvandling av kaffesump till högkvalitativ biografit
No full textSustainable management of waste resources is a key challenge in energy engineering. Spent coffee grounds (SCG) are abundant organic waste (over eight million tons generated annually, around the world) that often end up in landfills, leading to environmental concerns and lost resource potential. This thesis examines the conversion of SCG into a high-value, graphitic carbon material of biological origin (“bio-graphite”) via a novel, multi-step thermochemical process. The process begins with drying the SCG material and subjecting it to low-temperature pyrolysis at 550 °C to obtain a carbon-rich char, followed by combined ball-milling the char with iron powder and a subsequent graphitisation heat treatment at 1300 °C. Dispersed iron particles catalyse the rearrangement of the amorphous char into well-ordered graphite layers at temperatures several hundred degrees below those typically required for graphitisation. A subsequent mild acid leach, followed by thorough water rinsing, strips out the residual metal and delivers a high-purity bio-graphite powder. Comprehensive material characterisation by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, and gas chromatography-mass spectrometry (GC–MS) was carried out. The produced bio-graphite exhibits a high degree of crystallinity (graphitisation rate ~95.6%) and a favourable carbon conversion yield (~74%), demonstrating that SCG can be upgraded into a sustainable graphite material of promising quality and yield. The results demonstrate that upgrading waste-stream biomass material can provide essential carbon resource for next-generation sustainable energy applications.Hållbar hantering av avfallsresurser är en nyckelutmaning inom det energitekniska kunskapsområdet. Uttjänt kaffesump (spent coffee grounds, SCG) utgör ett rikligt organiskt avfall – mer än åtta miljoner ton genereras årligen världen över – som ofta deponeras, vilket medför miljöproblem och förlorad resurspotential. Detta examensarbete undersöker omvandlingen av SCG till ett högvärdigt grafitiskt kolmaterial av biologiskt ursprung (”biografit”) genom en ny flerstegs termokemisk process. Metoden omfattar torkning och lågtemperaturpyrolys av SCG vid 550 °C för att erhålla kolrika rester (char), följt av bearbetning i kulkvarn där kolpartiklarna mals samman med järnpulver och därefter skickas till grafitisering vid 1300 °C. Det utsprida järnpulvret katalyserar den fysiska omvandlingen av de amorfa kolatomerna till väldefinierade grafitstrukturer (grafitskikt) vid temperaturer flera hundra grader lägre än de som normalt krävs för grafitisering. En efterföljande mild syralakning, följd av noggrann vattensköljning, avlägsnar kvarvarande metall och levererar ett högrent biografitpulver. Omfattande materialkarakterisering har genomförts med hjälp av termogravimetrisk analys (TGA), svepelektronmikroskopi (SEM), Ramanspektroskopi, röntgendiffraktion (XRD), Brunauer–Emmett–Teller (BET)-ytanalysering och gaskromatografi–masspektrometri (GC–MS). Den framställda biografiten uppvisar hög kristallinitet (grafitiseringsgrad ≈ 95,6 %) och ett gynnsamt kolutbyte (≈ 74 %), vilket visar att SCG kan uppgraderas till ett hållbart grafitmaterial med lovande kvalitet och processeffektivitet. Resultaten härmed demonstrerar att uppgradering av bioavfall kan tillhandahålla essentiella kolmaterialflöden för nästa generations hållbara energitillämpningar
Hållbar omvandling av kaffesump till högkvalitativ biografit
No full textSustainable management of waste resources is a key challenge in energy engineering. Spent coffee grounds (SCG) are abundant organic waste (over eight million tons generated annually, around the world) that often end up in landfills, leading to environmental concerns and lost resource potential. This thesis examines the conversion of SCG into a high-value, graphitic carbon material of biological origin (“bio-graphite”) via a novel, multi-step thermochemical process. The process begins with drying the SCG material and subjecting it to low-temperature pyrolysis at 550 °C to obtain a carbon-rich char, followed by combined ball-milling the char with iron powder and a subsequent graphitisation heat treatment at 1300 °C. Dispersed iron particles catalyse the rearrangement of the amorphous char into well-ordered graphite layers at temperatures several hundred degrees below those typically required for graphitisation. A subsequent mild acid leach, followed by thorough water rinsing, strips out the residual metal and delivers a high-purity bio-graphite powder. Comprehensive material characterisation by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, and gas chromatography-mass spectrometry (GC–MS) was carried out. The produced bio-graphite exhibits a high degree of crystallinity (graphitisation rate ~95.6%) and a favourable carbon conversion yield (~74%), demonstrating that SCG can be upgraded into a sustainable graphite material of promising quality and yield. The results demonstrate that upgrading waste-stream biomass material can provide essential carbon resource for next-generation sustainable energy applications.Hållbar hantering av avfallsresurser är en nyckelutmaning inom det energitekniska kunskapsområdet. Uttjänt kaffesump (spent coffee grounds, SCG) utgör ett rikligt organiskt avfall – mer än åtta miljoner ton genereras årligen världen över – som ofta deponeras, vilket medför miljöproblem och förlorad resurspotential. Detta examensarbete undersöker omvandlingen av SCG till ett högvärdigt grafitiskt kolmaterial av biologiskt ursprung (”biografit”) genom en ny flerstegs termokemisk process. Metoden omfattar torkning och lågtemperaturpyrolys av SCG vid 550 °C för att erhålla kolrika rester (char), följt av bearbetning i kulkvarn där kolpartiklarna mals samman med järnpulver och därefter skickas till grafitisering vid 1300 °C. Det utsprida järnpulvret katalyserar den fysiska omvandlingen av de amorfa kolatomerna till väldefinierade grafitstrukturer (grafitskikt) vid temperaturer flera hundra grader lägre än de som normalt krävs för grafitisering. En efterföljande mild syralakning, följd av noggrann vattensköljning, avlägsnar kvarvarande metall och levererar ett högrent biografitpulver. Omfattande materialkarakterisering har genomförts med hjälp av termogravimetrisk analys (TGA), svepelektronmikroskopi (SEM), Ramanspektroskopi, röntgendiffraktion (XRD), Brunauer–Emmett–Teller (BET)-ytanalysering och gaskromatografi–masspektrometri (GC–MS). Den framställda biografiten uppvisar hög kristallinitet (grafitiseringsgrad ≈ 95,6 %) och ett gynnsamt kolutbyte (≈ 74 %), vilket visar att SCG kan uppgraderas till ett hållbart grafitmaterial med lovande kvalitet och processeffektivitet. Resultaten härmed demonstrerar att uppgradering av bioavfall kan tillhandahålla essentiella kolmaterialflöden för nästa generations hållbara energitillämpningar
Step-like contrast structure of singularly perturbed optimal control problem
No full textIn this paper, the existence of step-like contrast structure for a class of singularly perturbed optimal control problem is shown by the contrast structure theory. By means of direct scheme of boundary function method, we construct the uniformly valid asymptotic solution for the singularly perturbed optimal control problem. Finally, an example is presented to show the result
Internal Layer Solution of Singularly Perturbed Optimal Control Problem with Integral Boundary Condition
No full textA dual-band bandpass filter with substrate integrated waveguide-to-folded defected ground structure split ring resonator unit
No full textA Simplified Thermal Model and Online Temperature Estimation Method of Permanent Magnet Synchronous Motors
No full textMonitoring critical temperatures in permanent magnet synchronous motors is crucial for improving working reliability. Aiming at resolving the difficulty in online temperature estimation, an accurate and simple five-node lumped parameter thermal network (LPTN) is proposed and the mathematical model of the LPTN is built. Both radial and axial heat transfer paths inside the motor are considered to model the complete thermal circuit. In addition, an innovative parameter identification method based on multiple linear regression is applied to identify the parameters of the LPTN model. The parameters in the state equation are identified instead of the data of the motor, which are strongly dependent on the material and geometrical parameters. Finally, an open-loop estimation scheme based on the state equation and Kalman filter algorithm is adopted to predict the motor temperature online. The model performances are validated by extensive experiments under varying speed and torque conditions in terms of the accuracy and robustness. The results indicate that the temperature estimation error is within the range of ±5 °C in most cases and the proposed model can quickly follow the load variation. Besides, the online temperature estimation scheme and parameter identification method are easy and convenient to implement in an embedded system, which is feasible in automobile applications
Author Correction: SNPs and blood inflammatory marker featured machine learning for predicting the efficacy of fluorouracil-based chemotherapy in colorectal cancer
No full text
Co-Designed Architectures for Modular Superconducting Quantum Computers
No full textNoisy, Intermediate Scale Quantum (NISQ) computers have reached the point
where they can show the potential for quantum advantage over classical
computing. Unfortunately, NISQ machines introduce sufficient noise that even
for moderate size quantum circuits the results can be unreliable. We propose a
co-designed superconducting quantum computer using a Superconducting Nonlinear
Asymmetric Inductive eLement (SNAIL) modulator. The SNAIL modulator is designed
by considering both the ideal fundamental qubit gate operation while maximizing
the qubit coupling capabilities. First, the SNAIL natively implements
gates realized through proportionally scaled pulse
lengths. This naturally includes , which provides an
advantage over as a basis gate. Second, the SNAIL enables
high-degree couplings that allow rich and highly parallel qubit connection
topologies without suffering from frequency crowding. Building on our
previously demonstrated SNAIL-based quantum state router we propose a quantum
4-ary tree and a hypercube inspired corral built from interconnected quantum
modules. We compare their advantage in data movement based on necessary
\texttt{SWAP} gates to the traditional lattice and heavy-hex lattice used in
latest commercial quantum computers. We demonstrate the co-design advantage of
our SNAIL-based machine with basis gates and rich
topologies against /heavy-hex and /lattice for
16-20 qubit and extrapolated designs circa 80 qubit architectures. We compare
total circuit time and total gate count to understand fidelity for systems
dominated by decoherence and control imperfections, respectively. Finally, we
provide a gate duration sensitivity study on further decreasing the SNAIL pulse
length to realize qubit systems to reduce
decoherence times.Comment: This paper has been accepted to appear in the IEEE Symposium on High
Performance Computer Architecture (HPCA), 202
