Personal Exposure in Displacement Ventilated Rooms

Personal exposure in a displacement ventilated room is examined. The stratified flow and the considerable concentration gradients necessitate an improvement of the widely used fully mixing compartmental approach. The exposure of a seated and a standing person in proportion to the stratification height is examined by means of full-scale measurements. A breathing thermal manikin is used to simulate a person. It is found that the flow in the boundary layer around a person is able to a great extent to entrain and transport air from below the breathing zone. In the case of non-passive, heated contaminant sources, this entrainment improves the indoor air quality. Measurements of exposure due to a passive contaminant source show a significant dependence on the flow field as well as on the contaminant source location. Poor system performance is found in the case of a passive contaminant released in the lower part of the room close to the occupant. A personal exposure model for displacement ventilated rooms is proposed. The model takes the influence of gradients and the human thermal boundary layer into account. Two new quantities describing the interaction between a person and the ventilation are defined.     

Identification of intra-individual variation in intracranial arterial flow by MRI and the effect on computed hemodynamic descriptors

Magnetic Resonance Materials in Physics, Biology and Medicine - To determine the intra-individual flow variation in serially acquired studies, and the influence of this variation on subsequent...     

tweezercalib 2.0: Faster version of MatLab package for precise calibration of optical tweezers

We present a vectorized version of the MatLab (MathWorks Inc.) package tweezercalib for calibration of optical tweezers with precision. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum, as described in vs. 1 of the package [I.M. Toli?-Nørrelykke, K. Berg-Sørensen, H. Flyvbjerg, Matlab program for precision calibration of optical tweezers, Comput. Phys. Comm. 159 (2004) 225-240]. The graphical user interface allows the user to include or leave out each of these factors. Several “health tests” are applied to the experimental data during calibration, and test results are displayed graphically. Thus, the user can easily see whether the data comply with the theory used for their interpretation. Final calibration results are given with statistical errors and covariance matrix.

New version program summary

Title of program: tweezercalibCatalogue identifier: ADTV_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV_v2_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandReference in CPC to previous version: I.M. Toli?-Nørrelykke, K. Berg-Sørensen, H. Flyvbjerg, Comput. Phys. Comm. 159 (2004) 225Catalogue identifier of previous version: ADTVDoes the new version supersede the original program: YesComputer for which the program is designed and others on which it has been tested: General computer running MatLab (Mathworks Inc.)Operating systems under with the program has been tested: Windows2000, Windows-XP, LinuxProgramming language used: MatLab (Mathworks Inc.), standard licenseMemory required to execute with typical data: Of order four times the size of the data fileHigh speed storage required: noneNo. of lines in distributed program, including test data, etc.: 135 989No. of bytes in distributed program, including test data, etc.: 1 527 611Distribution format: tar. gzNature of physical problem: Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system.Method of solution: Elimination of cross-talk between quadrant photo-diode's output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects: Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for “virtual filtering” caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting. Statistical support for fit is given, with several plots facilitating inspection of consistency and quality of data and fit.Summary of revisions: A faster fitting routine, adapted from [J. Nocedal, Y.x. Yuan, Combining trust region and line search techniques, Technical Report OTC 98/04, Optimization Technology Center, 1998; W.H. Press, B.P. Flannery, S.A. Teukolsky, W.T. Vetterling, Numerical Recipes. The Art of Scientific Computing, Cambridge University Press, Cambridge, 1986], is applied. It uses fewer function evaluations, and the remaining function evaluations have been vectorized. Calls to routines in Toolboxes not included with a standard MatLab license have been replaced by calls to routines that are included in the present package. Fitting parameters are rescaled to ensure that they are all of roughly the same size (of order 1) while being fitted. Generally, the program package has been updated to comply with MatLab, vs. 7.0, and optimized for speed.Restrictions on the complexity of the problem: Data should be positions of bead doing Brownian motion while held by optical tweezers. For high precision in final results, data should be time series measured over a long time, with sufficiently high experimental sampling rate: The sampling rate should be well above the characteristic frequency of the trap, the so-called corner frequency. Thus, the sampling frequency should typically be larger than 10 kHz. The Fast Fourier Transform used works optimally when the time series contain n² data points, and long measurement time is obtained with n>12-15. Finally, the optics should be set to ensure a harmonic trapping potential in the range of positions visited by the bead. The fitting procedure checks for harmonic potential.Typical running time: SecondsUnusual features of the program: NoneReferences: The theoretical underpinnings for the procedure are found in [K. Berg-Sørensen, H. Flyvbjerg, Power spectrum analysis for optical tweezers, Rev. Sci. Ins. 75 (2004) 594-612].     

Effect of Copper on the Carrier Lifetime in Black Silicon

Black silicon is produced by laser annealing of a-Si:H films. During annealing, silicon microstructures are formed on the surface. We use time-resolved terahertz spectroscopy to study the photoconductivity dynamics in black silicon. We find that when a copper film is deposited on top of the a-Si:H layer prior to laser annealing, the carrier lifetime of black silicon is significantly reduced.     

Optimum processing of qpsk signals for site diversity

For satellite communications systems which use frequencies above 10 GHz, rain and clouds attenuate signals severely, leading to an increase in bit error rate (BER) in digital links. This may be coped with by using two or more receivers on the ground, spaced far enough apart to avoid simultaneous rain outages. In this paper, a BER-minimizing decision processor is derived for two receivers and QPSK modulation. In particular, it is applied to a linear attenuating transmission channel adding independent white Gaussian noise. It is found that gains of nearly 3 dB compared to a switched system are possible in down-link limited cases.     

An Inductorless 300 MHz Wideband CMOS Power Amplifier

The power amplifier tends to be one of the most demanding parts to fully integrate when building an entire radio on a CMOS chip. In this paper the design of a fully integrated RF power amplifier without inductors is described. As inductors in CMOS technology are associated with various problems, it is interesting to examine what performance can be achieved without them. An amplifier with an operating band from 60 MHz to 300 MHz (–3 dB) is built in 0.8 m CMOS. A 3 V supply is used. The measured midband power gain is 30 dB with 50 resistive source and load impedance. As linearity is important for many modern modulation schemes, the amplifier is designed to be as linear as possible. The measured third order intercept point is 23 dBm and the 1 dB compression point is 10 dBm, both referred to the output. The output is single ended to avoid an off-chip differential to single ended transformer.     

Photocatalytic Valorization of Plastic Waste over Zinc Oxide Encapsulated in a Metal–Organic Framework

The conversion of waste plastic into high-value-added chemicals is regarded as a promising approach for relieving global plastic pollution and contributing to the circular economy. Herein, a partial calcination strategy is developed to fabricate a zinc oxide/UiO66-NH₂ (ZnO/UiO66-NH₂) heterojunction, in which ZnO is encapsulated in porous UiO66-NH₂ for the photocatalytic valorization of plastic. This strategy preserves the framework structure of UiO66-NH₂, thus enabling the formation of ZnO with ultra-small size distributed inside the skeleton. The synergistic effect of the obtained ZnO/UiO66-NH₂ heterojunction facilitates providing an efficient channel for carrier/mass transfer and guarantees structural stability. As a result, ZnO/UiO66-NH₂ exhibits high activity for converting polylactic acid (PLA) and polyvinyl chloride (PVC) into acetic acid, coupled with H₂ production. This work provides a feasible strategy for rationally designing heterojunction photocatalysts, as well as an insight into understanding the process of photocatalytic valorization of plastic.     

Methods and Procedures for Computer Based Handling of Components Reliability Data at FTL (The Swedish Military Electronics Laboratory)

In order to turn reliability prediction into a readily available tool, a system for computerized handling of failure rates was developed at FTL. This system, which is named RPP-1 (Reliability Program One) is presently covering data of electronic and electromechanical components. From a given list of components and data on stresses and working conditions, the failure rates are automatically searched, processed, and pooled in an assessment for an equipment. To make this possible, a number of decisions and judgements had to be taken regarding codes, formulas, models, bank structure, application factors, etc. This paper gives a summary of the FTL solutions for those basic questions. The system?actually a system of subprograms?has been developed at the Swedish Military Electronics Laboratory. The project was headed by the the author of this paper.