| 1. |
- Minelli, Caterina, et al.
(författare)
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Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles
- 2022
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 14, s. 4690-4704
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Tidskriftsartikel (refereegranskat)abstract
- We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles.
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| 2. |
- Laksmono, Hartawan, et al.
(författare)
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Anomalous Behavior of the Homogeneous Ice Nucleation Rate in No-Man's Land
- 2015
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 6:14, s. 2826-2832
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Tidskriftsartikel (refereegranskat)abstract
- We present an analysis of ice nucleation kinetics from near-ambient pressure water as temperature decreases below the homogeneous limit T-H by cooling micrometer-sized droplets (microdroplets) evaporatively at 10(3)-10(4) K/s and probing the structure ultrafast using femtosecond pulses from the Linac Coherent Light Source (LCLS) free-electron X-ray laser. Below 232 K, we observed a slower nucleation rate increase with decreasing temperature than anticipated from previous measurements, which we suggest is due to the rapid decrease in water's diffusivity. This is consistent with earlier findings that microdroplets do not crystallize at <227 K, but vitrify at cooling rates of 10(6)-10(7) K/s. We also hypothesize that the slower increase in the nucleation rate is connected with the proposed fragile-to-strong transition anomaly in water.
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| 3. |
- Ernens, Dennis, et al.
(författare)
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On the Sealability of Metal-to-Metal Seals With Application to Premium Casing and Tubing Connections
- 2019
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Ingår i: SPE Drilling & Completion. - : Society of Petroleum Engineers. - 1064-6671 .- 1930-0204. ; 34:4, s. 382-396
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Tidskriftsartikel (refereegranskat)abstract
- Metal-to-metal seals are used in connections of casing and tubing in oil and gas wells. This paper describes the mechanisms of sealing metal-to-metal seals as investigated using an experimental setup and a stochastic numerical sealing model. Experiments were conducted for a variety of thread compounds and applied pin/box surface coatings. The results were used to validate a stochastic numerical sealing model for sealability. The model couples a contact-mechanics model with a flow model and takes into account the influence of all the surface-topography features by introducing the concept of seal permeability. Once validated, the model was used together with the experimental results to better understand the sealing mechanisms of metal-to-metal seals.The sealing configuration is a face seal with an 80-mm roundoff radius on one face pressing against a flat on the other face. The face-seal specimens were manufactured from P110 tubing to ensure material properties that are representative for casing or tubing. The test setup used is designed for investigating only the metal-to-metal seal of the connection. The setup can perform rotary sliding under constant load to simulate surface changes during makeup and subsequently perform a leakage test. The sealing limit is determined by applying 700-bar fluid pressure and then gradually reducing the normal force until leakage is observed. The data are subsequently used to validate the previously published stochastic numerical sealing model.The results indicate a strong dependence on the type of thread compound used for the onset of leakage. The thread compound affects the amount of wear and thus changes the surface topography of the interacting surfaces. It is shown that the stochastic numerical sealing model is capable of predicting the onset of leakage within the experimental accuracy. The model shows further that certain surface topographical features improve the sealing performance. In particular, a surface manufactured by turning on a lathe that is in contact with, for instance, a smooth shot-blasted surface topography leads to highly localized contact areas, which in turn yield the best sealing performance.
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| 4. |
- Ernens, Dennis, et al.
(författare)
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On the Sealability of Metal-to-Metal Seals with Application to Premium Casing Connections
- 2019
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Ingår i: SPE/IADC International Drilling Conference and Exhibition. - 9781613996423
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Metal-to-metal seals are used in connections of casing in oil and gas wells. This paper describes the mechanisms of sealing of metal-to-metal seals as investigated using an experimental set-up and a sealability model. Experiments were conducted for a variety of thread compounds and applied pin/box surface coatings. The results were used to validate a numerical model for sealability. The stochastic model couples a contact mechanics model with a flow model and takes the influence of all the surface topography features into account. Once validated, the model was used together with the experimental results to explain the sealing mechanisms of metal-to-metal seals. The sealing configuration is a face seal with an R=80 mm round-off radius pressing against a flat. The face seal specimens were manufactured from P110 tubing. The used test set-up is designed for investigating only the metal-to-metal seal of the connection. The set-up can carry out rotary sliding under constant load to simulate surface evolution during make-up and subsequently perform a leakage test. The sealing limit is determined by applying 700 bar fluid pressure and then gradually reducing the normal force until leakage is observed. The data is subsequently used to validate a previously published model. The results indicate a strong dependence of the type of thread compound used on the onset of leakage. The thread compound affects the amount of wear and thus changes the surface topography of the interacting surfaces. It is shown that the sealability model is capable to predict the onset of leakage within the experimental accuracy. The model shows further that certain surface topographical features improve the sealing performance. Namely, a turned against a flat surface topography leads to highly localized contact areas, which in turn yields the best sealing performance. The combination of experimental data with the validated model leads to much deeper insights for the sealing mechanisms than what could be obtained using either on their own.
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| 5. |
- Marattukalam, Jithin J., et al.
(författare)
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Development of process parameters for selective laser melting of a Zr-based bulk metallic glass
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- Parameters for selective laser melting of Zr59.3Cu28.8Al10.4Nb1.5 (trade name AMZ4), allowing crack-free bulk metallic glass with low porosity, have been developed. The phase formation was found to be strongly influenced by the heating power of the laser. X-ray amorphous samples were obtained with laser power at and below 75 W. The as-processed bulk metallic glass was found to devitrify by a two-stage crystallization process within which the presence of oxygen was concluded to play an essential role. At laser powers above 75 W, the observed crystallites were found to be a cubic phase (Cu2Zr4O). The hardness and Young’s modulus in the as-processed samples was found to increase marginally with increased fraction of the crystalline phase.
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| 6. |
- Perakis, Fivos, et al.
(författare)
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Coherent X-rays reveal the influence of cage effects on ultrafast water dynamics
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of liquid water feature a variety of time scales, ranging from extremely fast ballistic-like thermal motion, to slower molecular diffusion and hydrogen-bond rearrangements. Here, we utilize coherent X-ray pulses to investigate the sub-100 fs equilibrium dynamics of water from ambient conditions down to supercooled temperatures. This novel approach utilizes the inherent capability of X-ray speckle visibility spectroscopy to measure equilibrium intermolecular dynamics with lengthscale selectivity, by measuring oxygen motion in momentum space. The observed decay of the speckle contrast at the first diffraction peak, which reflects tetrahedral coordination, is attributed to motion on a molecular scale within the first 120 fs. Through comparison with molecular dynamics simulations, we conclude that the slowing down upon cooling from 328 K down to 253 K is not due to simple thermal ballistic-like motion, but that cage effects play an important role even on timescales over 25 fs due to hydrogen-bonding.
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| 7. |
- Rabih, A. A. S., et al.
(författare)
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MetalMUMPs resonator for acetone vapor sensing
- 2017
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Ingår i: Proceedings of the 2017 IEEE regional symposium on micro and nanoelectronics (RSM). - : IEEE. - 9781509040292 ; , s. 5-9
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Konferensbidrag (refereegranskat)abstract
- Acetone vapor monitoring is essential in workplace for human health and safety, where exposure to acetone concentration more than 176 parts per million (ppm) can cause damage to eyes, liver, kidneys and central nervous system. In addition, acetone in exhaled breath is known to be good biomarker for non-invasive screening of diabetes. The most common used acetone vapor sensors are based on metal oxide semiconductor sensors, which work at higher temperatures, and hence consume more power. This paper reports MetalMUMPs device for acetone vapor sensing for environmental monitoring. The device is based on electrothermal actuation and capacitive sensing using differential capacitance measurement technique. MS3110 universal capacitive readout circuit was used to readout the small change of the static capacitance when the device is actuated using 0.71 Vrms with a driving frequency range of 0.5 kHz-8 kHz. The output signal of the circuit is given as a voltage and it can be directly related to the capacitance change. The output voltage change was found to increase linearly with increasing the acetone vapor concentration from 100 ppm to 500 ppm with a concentration sensitivity of 0.65 mV/ppm.
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| 8. |
- Öberg, Henrik, et al.
(författare)
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Stability of Pt-Modified Cu(111) in the Presence of Oxygen and Its Implication on the Overall Electronic Structure
- 2013
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:32, s. 16371-16380
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and stability of Cu(111)-hosted Pt overlayers with and without the presence of atomic oxygen have been studied by means of core-level spectroscopy and density functional theory (DFT). Because of lattice mismatch, Pt(111) overlayers grown on Cu(111) are compressively strained, and hard X-ray photoelectron spectroscopy together with Pt L-3-edge X-ray absorption spectroscopy (XAS) reveals a pronounced downshift of the Pt d-band owing to the increased overlap of the d-orbitals, an effect also reproduced theoretically. Exposure to oxygen severely alters the surface composition; the O-Cu binding energy largely exceeds that of O-Pt, and DFT calculations predict surface segregation of Cu atoms. Comparing the adsorbate electronic structure for O on unstrained Pt(111) with that of O on Pt-modified Cu(111) using O K-edge XAS and X-ray emission spectroscopy salient differences are observed and calculations show that Cu-segregation to the topmost layer is required to reproduce the measured spectra. It is proposed that O is binding in a hollow site constituted by at least two Cu atoms and that up to 75% of the Pt atoms migrate below the surface.
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| 9. |
- Adjrad, M., et al.
(författare)
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Interference monitoring for GNSS bands in indoor and urban environments
- 2007
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Ingår i: Proceedings of the 20th International Technical Meeting of the Satellite Division of the Institute of Navigation. - : Institute of Navigation, The. ; , s. 1211-1220
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Konferensbidrag (refereegranskat)abstract
- A collaborative research project between the University of Leeds and Luleå University of Technology, Sweden, has taken place aiming to characterize the man-made noise in urban and indoor environments in the Galileo allocated frequency bands: E5 (1191.795 ± 25.575 MHz), E6 (1278.75 ± 20 MHz), and L1 (1575.42 ± 16 MHz), obviously, also covering the GPS L1 and L5 bands. This project has been co-funded by the European GNSS Supervisory Authority (EGSA), with funding from the 6th Framework Program of the European Community for research and technological development. The project includes the development of two receiver systems: the first instrument is based on the use of a spectrum analyzer (SA-based instrument), a wideband GNSS antenna, and a front-end capable of capturing each Galileo band separately using appropriate filtering and switches. The second instrument addresses the issues of cost and portability, providing interference detection and alarm triggering without the need for complex instrument. This is accomplished using low cost components in a small form factor where the instrument is based on a core GNSS front-end. This instrument will only cover the L1/E1 band. The interference measurement is obtained by combining the information from the automatic gain control (AGC) voltage that controls the AGC amplifier gain and the spectrum analysis of the analogue-to-digital converter (ADC) output raw data. The AGC information will be very important for detecting the presence of wideband interference signals where this will be difficult using spectrum analysis (in contrast to the case to narrowband interference signals). Control and data logging from both instruments are performed using a laptop computer where the spectrum analyzer traces and the FE-based instrument data are recorded for offline analysis via a suite of MATLAB® scripts. This paper describes the spectrum survey conducted at various indoor and urban locations, operationally significant to GNSS, in the North of the UK. The survey sites were selected to obtain geographically diverse measurement results and provide a general representation of the spectral environment. In addition, the temporal variation of man-made noise (MMN) is considered, this latter being correlated with the human activity at the measurement site, by performing the measurements day and night, weekdays and weekends.
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| 10. |
- Do, J., et al.
(författare)
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L and S bands spectrum survey in the San Francisco Bay area
- 2004
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Ingår i: PLANS 2004. - Piscataway, NJ : IEEE Communications Society. - 0780384164 ; , s. 566-572
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Konferensbidrag (refereegranskat)abstract
- The Global Positioning System (GPS) is a radio frequency (RF) communication system that consists of transmitters on the satellites and receivers on the ground. Because of substantial path loss, the received signal power from satellites is extremely weak and even below the thermal noise floor and as such is very sensitive to changes in the underlying noise floor. The goal of this work is to investigate the radio spectrum environment in the GPS band along with two additional bands, the Unified-S band and 2.4 GHz Industrial Scientific and Medical (ISM) band. The spectrum survey was conducted at various locations in the San Francisco Bay area including various urban, rural areas and airports and harbors which are operational significant to GPS. The measurement data collected in this study will provide a more accurate representation of the current status and the characteristics of the spectrum environment. Geographical variation within the sites will reveal correlation between the spectrum environment and the level of urbanization and also a comparative study on the frequency bands under different level of regulations can be used to investigate the effectiveness of the current spectrum policy
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