| 41. |
- Jansson, Ronnie, et al.
(författare)
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Functionalized silk assembled from a recombinant spider silk fusion protein (Z-4RepCT) produced in the methylotrophic yeast Pichia pastoris
- 2016
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Ingår i: Biotechnology Journal. - : Wiley-VCH Verlagsgesellschaft. - 1860-6768 .- 1860-7314. ; 11:5, s. 687-699
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Tidskriftsartikel (refereegranskat)abstract
- Functional biological materials are a growing research area with potential applicability in medicine and biotechnology. Using genetic engineering, the possibility to introduce additional functions into spider silk-based materials has been realized. Recently, a recombinant spider silk fusion protein, Z-4RepCT, was produced intracellularly in Escherichia coli and could after purification self-assemble into silk-like fibers with ability to bind antibodies via the IgG-binding Z domain. In this study, the use of the methylotrophic yeast Pichia pastoris for production of Z-4RepCT has been investigated. Temperature, pH and production time were influencing the amount of soluble Z-4RepCT retrieved from the extracellular fraction. Purification of secreted Z-4RepCT resulted in a mixture of full-length and degraded silk proteins that failed to self-assemble into fibers. A position in the C-terminal domain of 4RepCT was identified as being subjected to proteolytic cleavage by proteases in the Pichia culture supernatant. Moreover, the C-terminal domain was subjected to glycosylation during production in P. pastoris. These observed alterations of the CT domain are suggested to contribute to the failure in fiber assembly. As alternative approach, Z-4RepCT retrieved from the intracellular fraction, which was less degraded, was used and shown to retain ability to assemble into silk-like fibers after enzymatic deglycosylation.
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| 42. |
- Mühlig, Kerstin, et al.
(författare)
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Nanometre-sized droplets from a gas dynamic virtual nozzle
- 2019
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Ingår i: Journal of Applied Crystallography. - : INT UNION CRYSTALLOGRAPHY. - 1600-5767 .- 0021-8898. ; 52, s. 800-808
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on improved techniques to create and characterize nanometre-sized droplets from dilute aqueous solutions by using a gas dynamic virtual nozzle (GDVN). It describes a method to measure the size distribution of uncharged droplets, using an environmental scanning electron microscope, and provides theoretical models for the droplet sizes created. The results show that droplet sizes can be tuned by adjusting the gas and liquid flow rates in the GDVN, and at the lowest liquid flow rates, the size of the water droplets peaks at about 120 nm. This droplet size is similar to droplet sizes produced by electrospray ionization but requires neither electrolytes nor charging of the solution. The results presented here identify a new operational regime for GDVNs and show that predictable droplet sizes, comparable to those obtained by electrospray ionization, can be produced by purely mechanical means in GDVNs.
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| 43. |
- Nygren, Kristian
(författare)
-
Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today’s electronic society relies on the functionality of electrical contacts. To achieve good contact properties, surface coatings are normally applied. Such coatings should ideally fulfill a combination of different properties, like high electrical conductivity, high corrosion resistance, high wear resistance and low cost. A common coating strategy is to use noble metals since these do not form insulating surface oxides. However, such coatings are expensive, have poor wear resistance and they are often applied by electroplating, which poses environmental and human health hazards.In this thesis, nanocomposite carbide-based coatings were studied and the aim was to evaluate if they could exhibit properties that were suitable for electrical contacts. Coatings in the Cr-C, Cr-C-Ag and Nb-C systems were deposited by magnetron sputtering using research-based equipment as well as industrial-based equipment designed for high-volume production. To achieve the aim, the microstructure and composition of the coatings were characterized, whereas mechanical, tribological, electrical, electrochemical and optical properties were evaluated. A method to optically measure the amount of carbon was developed.In the Cr-C system, a variety of deposition conditions were explored and amorphous carbide/amorphous carbon (a-C) nanocomposite coatings could be obtained at substrate temperatures up to 500 °C. The amount of a-C was highly dependent on the total carbon content. By co-sputtering with Ag, coatings comprising an amorphous carbide/carbon matrix, with embedded Ag nanoclusters, were obtained. Large numbers of Ag nanoparticles were also found on the surfaces. In the Nb-C system, nanocrystalline carbide/a-C coatings could be deposited. It was found that the nanocomposite coatings formed very thin passive films, consisting of both oxide and a-C.The Cr-C coatings exhibited low hardness and low-friction properties. In electrochemical experiments, the Cr-C coatings exhibited high oxidation resistance. For the Cr-C-Ag coatings, the Ag nanoparticles oxidized at much lower potentials than bulk Ag. Overall, electrical contact resistances for optimized samples were close to noble metal references at low contact load. Thus, the studied coatings were found to have properties that make them suitable for electrical contact applications.
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| 44. |
- Ollas, Patrik, et al.
(författare)
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Evaluating the role of solar photovoltaic and battery storage in supporting electric aviation and vehicle infrastructure at Visby Airport
- 2023
-
Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 352
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Tidskriftsartikel (refereegranskat)abstract
- Following the societal electrification trend, airports face an inevitable transition of increased electric demand,driven by electric vehicles (EVs) and the potential rise of electric aviation (EA). For aviation, short-haul flightsare first in line for fuel exchange to electrified transportation. This work studies the airport of Visby, Sweden and the effect on the electrical power system from EA and EV charging. It uses the measured airport loaddemand from one year’s operation and simulated EA and EV charging profiles. Solar photovoltaic (PV) and electrical battery energy storage systems (BESS) are modelled to analyse the potential techno-economical gains.The BESS charge and discharge control are modelled in four ways, including a novel multi-objective (MO) dispatch to combine self-consumption (SC) enhancement and peak power shaving. Each model scenario iscompared for peak power shaving ability, SC rate and pay-back-period (PBP). The BESS controls are alsoevaluated for annual degradation and associated cost. The results show that the novel MO dispatch performswell for peak shaving and SC, effectively reducing the BESS’s idle periods. The MO dispatch also results in the battery controls’ lowest PBP (6.9 years) using the nominal economic parameters. Furthermore, a sensitivityanalysis for the PBP shows that the peak power tariff significantly influences the PBP for BESS investment.
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| 45. |
- Parwal, Arvind, et al.
(författare)
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Grid impact and power quality assessment of wave energy parks: Different layouts and power penetrations using energy storage
- 2021
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Ingår i: JOURNAL OF ENGINEERING-JOE. - : Institution of Engineering and Technology (IET). - 2051-3305. ; 2021:8, s. 415-428
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Tidskriftsartikel (refereegranskat)abstract
- Power fluctuations induced by wave energy converters (WECs) may reflect negative impact on the power quality of the power grid. Assessing their impact is an important step to ensure the grid compliance level of the energy park. The IEC 61000-4-15 standard classifies the allowable disturbances in the grid. This study analysed and assessed the grid impact in terms of flicker, harmonic distortion and voltage variations. The assessments were performed without energy storage and compared when using the energy storage. A single WEC is emulated as an irregular power output of a real WEC using a combined model of power take-off in the Simulink model. Time series based on data obtained in earlier offshore experiments, conducted at the Lysekil research site in Sweden, is used to emulate a wave energy park (WEP) power in a land-based test rig in real-time power hardware-in-the-loop simulations. A total of three and ten WECs are emulated by introducing a time delay in the time series to investigate the grid impact in each layout. Flicker emissions, voltage variations, individual and total harmonics of the voltage at the connection point in each layout are studied and compared with the limits to be grid compliant for layouts of the WEP. In addition, voltage and current harmonics for the single WEC and individual harmonics in each phase of the voltage are measured and analysed to assess the compliance level of the WEP.
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| 46. |
- Remouit, Flore, 1988-
(författare)
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Automation of underwater operations on wave energy converters using remotely operated vehicles
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last fifteen years, the Division of Electricity at Uppsala University has been developing a wave energy converter (WEC) concept. The concept is based on a point-absorbing buoy with a directly driven linear generator placed on the seabed. Several units are connected to a marine substation, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.A big challenge in the project is to reduce the costs related to the deployment and maintenance of the WECs and substation. Currently, those operations are performed by divers, which is costly and entail considerable risks. A possibility is to replace divers with automated solutions using small robots called remotely operated vehicles (ROVs). This PhD thesis proposes and analyses a method for deployment and maintenance of underwater devices with no use of diving operations.Existing ROVs need additional modules and equipment in order to carry out operations with the required force and precision. Typical missions are inspection, shackles or slings removal, valve closing, and cable connection. The latter demands especially high precision in the positioning: 5 mm in distance and 5◦ in heading angle. In addition, this operation involves forces up to 200 N. This combination power-precision is not reached by existing ROVs. This PhD thesis presents a positioning system for underwater robot to enable autonomous positioning of the vehicle before cable connection.The positioning system is composed of two green lasers and a monocular camera, and is based on image processing. Experimental results from laboratory testing show that the mean absolute error in distance measurement is as low as 6 mm at 0.7 m from the target, whereas the heading is minimized to 2◦. The computational time for the image processing is 13.6 ms per image, meaning the possibility of a 30 Hz measurement system. Used together with a closed-loop path-following unit, this positioning system can support autonomous docking. This PhD thesis presents the model of an autopilot and results from docking simulations, showing the performance of the positioning system used in closed-loop.
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| 47. |
- Sarmast, Sasan, et al.
(författare)
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Validation of the actuator line and disc techniques using the New Mexico measurements
- 2016
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics (IOP). - 1742-6588 .- 1742-6596. ; 753:3
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Tidskriftsartikel (refereegranskat)abstract
- Actuator line and disc techniques are employed to analyse the wake obtained in the New Mexico wind turbine experiment. The New Mexico measurement campaign done in 2014 is a follow-up to the MEXICO campaign, which was completed in 2006. Three flow configurations in axial flow condition are simulated and both computed loads and velocity fields around the rotor are compared with detailed PIV measurements. The comparisons show that the computed loadings are generally in agreement with the measurements under the rotor's design condition. Both actuator approaches under-predicted the loading in the inboard part of blade in stall condition as only 2D airfoil data were used in the simulations. The predicted wake velocities generally agree well with the PIV measurements. In the experiment, PIV measurements are also provided close to the hub and nacelle. To study the effect of hub and nacelle, numerical simulations are performed both in the presence and absence of the hub geometry. This study shows that the large hub used in the experiment has only small effects on overall wake behaviour.
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| 48. |
- Xu, Cheng, et al.
(författare)
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Scalable Validation of Industrial Equipment using a Functional DSMS
- 2017
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Ingår i: Journal of Intelligent Information Systems. - : Springer. - 0925-9902 .- 1573-7675. ; 48:3, s. 553-577
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Tidskriftsartikel (refereegranskat)abstract
- A stream validation system called SVALI is developed in order to continuouslyvalidate data streams from industrial equipment. The functional data model of SVALI allows the user to dene meta-data and queries about the equipment in terms of types and functions. The two system functions model-andvalidate and learn-and-validate provide such validation functionality. The experiments show that parallel stream processing enables SVALI to scale very well with respect to response time and system throughput. The paper is based on a real world application for wheel loader slippage detection at Volvo Construction Equipment.
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| 49. |
- Åhlén, Michelle, et al.
(författare)
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Pore size effect of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based metal-organic frameworks for enhanced SF 6 adsorption with high selectivity
- 2022
-
Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 343
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic greenhouse gas emission poses as serious threat to our environment and it is therefore of utmost importance that efficient systems are developed to mitigate these issues. SF6, in particular, has attracted more attention in recent years due to its global warming potential which severely exceeds that of CO2. In this study we present the SF6 sorption properties of four highly porous 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene-based (TBAPy4−) metal-organic frameworks containing either ytterbium(III), thulium(III), cerium(III), or hafnium(IV). These MOFs can be synthesized with high crystallinity in as little as 5 h and were found to have good SF6 uptakes due to their suitable pore size. The SF6 uptake of the Yb-TBAPy MOF reached 2.33 mmol g−1 with high Henry's law SF6-over-N2 selectivity of ∼80 at 1 bar and 293 K. The TBAPy-MOFs were also found to have good chemical stability and good cyclic SF6 sorption stability with fast SF6 uptake. These TBAPy-MOFs possesses many of the properties desired for an efficient SF6 sorbent and may be suitable sorbents for further development, including sorbent processing for industrial applications.
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| 50. |
- Aghda, Soheil Karimi, et al.
(författare)
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Valence electron concentration- and N vacancy-induced elasticity in cubic early transition metal nitrides
- 2023
-
Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 255
-
Tidskriftsartikel (refereegranskat)abstract
- Motivated by frequently reported deviations from stoichiometry in cubic transition metal nitride (TMNx) thin films, the effect of N-vacancy concentration on the elastic properties of cubic TiNx, ZrNx, VNx, NbNx, and MoNx (0.72 & LE; x & LE; 1.00) is systematically studied by density functional theory (DFT) calculations. The predictions are validated experimentally for VNx (0.77 & LE; x & LE; 0.97). The DFT results indicate that the elastic behavior of the TMNx depends on both the N-vacancy concentration and the valence electron concentration (VEC) of the transition metal: While TiNx and ZrNx exhibit vacancy-induced reductions in elastic modulus, VNx and NbNx show an increase. These trends can be rationalized by considering vacancy-induced changes in elastic anisotropy and bonding. While introduction of N-vacancies in TiNx results in a significant reduction of elastic modulus along all directions and a lower average bond strength of Ti-N, the vacancy-induced reduction in [001] direction of VNx is overcompensated by the higher stiffness along [011] and [111] directions, resulting in a higher average bond strength of V-N. To validate the predicted vacancy-induced changes in elasticity experimentally, close-to-singlecrystal VNx (0.77 & LE; x & LE; 0.97) are grown on MgO(001) substrates. As the N-content is reduced, the relaxed lattice parameter a0, as probed by X-ray diffraction, decreases from 4.128 & ANGS; to 4.096 & ANGS;. This reduction in lattice parameter is accompanied by an anomalous 11% increase in elastic modulus, as determined by nanoindentation. As the experimental data agree with the predictions, the elasticity enhancement in VNx upon N-vacancy formation can be understood based on the concomitant changes in elastic anisotropy and bonding.
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