scholarly journals On the Performance of an Aerosol Electrometer with Enhanced Detection Limit

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3889 ◽  
Author(s):  
Yixin Yang ◽  
Tongzhu Yu ◽  
Jiaoshi Zhang ◽  
Jian Wang ◽  
Wenyu Wang ◽  
...  
Keyword(s):  
Detection Limit ◽  
Detection Efficiency ◽  
Particle Diameter ◽  
Electrical Current ◽  
Statistical Correlation ◽  
Measurement Noise ◽  
Mean Square ◽  
Particle Detection ◽  
Faraday Cup ◽  
Feedback Resistor

An aerosol electrometer with enhanced detection limit was developed for measuring the collected particles electrical current ranging from −50 pA to 50 pA with no range switching necessary. The detection limit was enhanced by suppressing the electric current measurement noise and improving the detection efficiency. A theoretical model for the aerosol electrometer has been established to investigate the noise effect factors and verified experimentally. The model showed that the noise was a function of ambient temperature, and it was affected by the characteristics of feedback resistor and operational amplifier simultaneously. The Faraday cup structure of the aerosol electrometer was optimized by adopting a newly designed cup-shaped metal filter which increased the surface area of the cup; thus the particle interception efficiency was improved. The aerosol electrometer performance-linearity, noise and the particle detection efficiency, were evaluated experimentally. When compared with TSI-3068B, a 99.4% ( R 2 ) statistical correlation was achieved. The results also showed that the root mean square noise and the peak-to-peak noise were 0.31 fA and 1.55 fA, respectively. The particle detection efficiency was greater than 99.3% when measuring particle diameter larger than 7.0 nm.

scholarly journals Event-Triggered Bipartite Consensus of Single-Integrator Multi-Agent Systems with Measurement Noise

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Cui-Qin Ma ◽  
Yun-Bo Zhao ◽  
Wei-Guo Sun
Keyword(s):  
Sufficient Conditions ◽  
Measurement Noise ◽  
Mean Square ◽  
Multi Agent Systems ◽  
Negative Effects ◽  
Consensus Protocol ◽  
Agent Systems ◽  
Multi Agent ◽  
Bipartite Consensus ◽  
Event Triggered

Event-triggered bipartite consensus of single-integrator multi-agent systems is investigated in the presence of measurement noise. A time-varying gain function is proposed in the event-triggered bipartite consensus protocol to reduce the negative effects of the noise corrupted information processed by the agents. Using the state transition matrix, Ito^ formula, and the algebraic graph theory, necessary and sufficient conditions are given for the proposed protocol to yield mean square bipartite consensus. We find that the weakest communication requirement to ensure the mean square bipartite consensus under event-triggered protocol is that the signed digraph is structurally balanced and contains a spanning tree. Numerical examples validated the theoretical findings where the system shows no Zeno behavior.

scholarly journals Detection limit of a VCO based detection chain dedicated to particles recognition and tracking

2018 ◽  
Vol 170 ◽  
pp. 09002
Author(s):  
K. Coulié ◽  
W. Rahajandraibe ◽  
H. Aziza ◽  
G. Micolau ◽  
R. Vauché
Keyword(s):  
Detection Limit ◽  
Alpha Particle ◽  
Current Response ◽  
Particle Detection ◽  
Detection Cell ◽  
Tcad Simulation

A particle detection chain based on CMOS-SOI VCO circuit is presented. The solution is used for the recognition and the tracking of a given particle at circuit level. TCAD simulation of the detector has been performed on a 3×3 matrix of diodes based detector for particles recognition and tracking. The current response of the detector has been used for a case study in order to determine the ability of the chain to recognize an alpha particle crossing a 3×3 detection cell. The detection limit of the proposed solution is investigated and discussed in this paper.

scholarly journals Determination of Alpha Particle Detection Efficiency of an Imaging Plate (IP) Detector

2006 ◽  
Vol 41 (4) ◽  
pp. 272-278
Author(s):  
Naureen Mahbub RAHMAN ◽  
Takao IIDA ◽  
Hiromi YAMAZAWA ◽  
Jun MORIIZUMI
Keyword(s):  
Alpha Particle ◽  
Detection Efficiency ◽  
Imaging Plate ◽  
Particle Detection

scholarly journals Nanopore sequencing detects structural variants in cancer

2015 ◽  
Author(s):  
Alexis L. Norris ◽  
Rachael E. Workman ◽  
Yunfan Fan ◽  
James R. Eshleman ◽  
Winston Timp
Keyword(s):  
Detection Efficiency ◽  
Electrical Current ◽  
Read Length ◽  
Therapeutic Monitoring ◽  
Base Substitution ◽  
Nanopore Sequencing ◽  
Structural Variants ◽  
Large Deletions ◽  
Long Reads ◽  
Generation Sequencing

Despite advances in sequencing, structural variants (SVs) remain difficult to reliably detect due to the short read length (<300bp) of 2nd generation sequencing. Not only do the reads (or paired-end reads) need to straddle a breakpoint, but repetitive elements often lead to ambiguities in the alignment of short reads. We propose to use the long-reads (up to 20kb) possible with 3rd generation sequencing, specifically nanopore sequencing on the MinION. Nanopore sequencing relies on a similar concept to a Coulter counter, reading the DNA sequence from the change in electrical current resulting from a DNA strand being forced through a nanometer-sized pore embedded in a membrane. Though nanopore sequencing currently has a relatively high mismatch rate that precludes base substitution and small frameshift mutation detection, its accuracy is sufficient for SV detection because of its long reads. In fact, long reads in some cases may improve SV detection efficiency. We have tested nanopore sequencing to detect a series of well-characterized SVs, including large deletions, inversions, and translocations that inactivate the CDKN2A/p16 and SMAD4/DPC4 tumor suppressor genes in pancreatic cancer. Using PCR amplicon mixes, we have demonstrated that nanopore sequencing can detect large deletions, translocations and inversions at dilutions as low as 1:100, with as few as 500 reads per sample. Given the speed, small footprint, and low capital cost, nanopore sequencing could become the ideal tool for the low-level detection of cancer-associated SVs needed for molecular relapse, early detection, or therapeutic monitoring.

scholarly journals Magnetic interference mapping of four types of unmanned aircraft systems intended for aeromagnetic surveying

2020 ◽  
Author(s):  
Loughlin E. Tuck ◽  
Claire Samson ◽  
Jeremy Laliberté ◽  
Michael Cunningham
Keyword(s):  
High Sensitivity ◽  
Electrical Current ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Mean Square ◽  
Magnetic Intensity ◽  
Motor Current ◽  
Aircraft Systems ◽  
Speed Controller ◽  
Preparation Step

Abstract. Magnetic interference source identification is a critical preparation step for magnetometer-mounted unmanned aircraft systems (UAS) used for high-sensitivity geomagnetic surveying. A magnetic field scanner was built for mapping the interference that is produced by a UAS. It was used to compare four types of electric-powered UAS capable of carrying an alkali-vapour magnetometer: (1) a single-motor fixed-wing, (2) a single-rotor helicopter, (3) a quad-rotor helicopter, and (4) a hexa-rotor helicopter. The scanner’s error was estimated by calculating the root-mean-square deviation of the background total magnetic intensity over the mapping duration; averaged values ranged between 3.1–7.4 nT. Each mapping was performed above the UAS with the motor(s) engaged and with the UAS facing in two orthogonal directions; peak interference intensities ranged between 21.4–574.2 nT. For each system, the interference is a combination of both ferromagnetic and electrical current sources. Major sources of interference were identified such as servo(s) and the cables carrying direct current between the motor battery and the electronic speed controller. Magnetic intensity profiles were measured at various motor current draws for each UAS and a change in intensity was observed for currents as low as 1 A.

scholarly journals Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies

2011 ◽  
Vol 4 (4) ◽  
pp. 4165-4208
Author(s):  
F. Gaie-Levrel ◽  
S. Perrier ◽  
E. Perraudin ◽  
C. Stoll ◽  
N. Grand ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Detection Limit ◽  
Mass Spectrometer ◽  
Single Particle ◽  
Detection Efficiency ◽  
Linear Time ◽  
Scattered Light ◽  
Optical Detection ◽  
Organic Aerosol ◽  
Polystyrene Latex

Abstract. A single particle instrument has been developed for real-time analysis of organic aerosols. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE is ranging from 0.1 to 90 % for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. Scattered light is detected by two photomultipliers and the detected signals are used to trigger a UV excimer laser (λ = 248 nm) used for laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 attograms. DOP particles were also used to test the overall functioning of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first scientific application of the instrument. Single particle mass spectra are obtained with a global hit rate of 10 %. They are found to be very different from one particle to another, reflecting chemical differences of the analyzed particles, and most of the detected mass peaks are attributed to oxidized products of indene.

Status and Needs of In-Situ Real-time Process Particle Detection

1989 ◽  
Vol 32 (5) ◽  
pp. 22-27
Author(s):  
R. Bowling ◽  
Graydon Larrabee ◽  
Wayne Fisher
Keyword(s):  
Semiconductor Device ◽  
Dominant Role ◽  
Experimental Studies ◽  
Particle Diameter ◽  
Submicron Particles ◽  
Wafer Surface ◽  
Yield Losses ◽  
Particle Detection ◽  
Processing Equipment ◽  
Detection Techniques

Particle defects play a major role in yield losses in semiconductor device fabrication. It is generally acknowledged that about 50 percent of all yield losses are due to particles. Processing of devices with 0.35 to 0.5 μm minimum feature sizes will exacerbate the effects of particles due to the large relative abundance of submicron particles. The cleanroom is no longer the major particle contributor because current state-of-the-art cleanrooms have less than 10 particles (&lt;0.5 μm) per cubic foot. Particles in processing equipment now play the dominant role in wafer contamination. An analysis of the status and needs of particle detection techniques for semiconductor processing equipment and processes clearly shows that they are inadequate to meet the requirements of the next generation of devices. Detection limits must be improved both in terms of particle diameter and in the number of particles on a wafer. An experimental laser particle counter was fabricated and used to show that such a detector would be extremely useful for in-vacuum realtime particle detection. Experimental studies on wafer surface measurements show that current wafer surface scanning techniques cannot provide the level of detection needed for future devices. Ideas for a new generation of particle detection equipment are presented.

scholarly journals Reduced particle settling speed in turbulence

2016 ◽  
Vol 808 ◽  
pp. 153-167 ◽  
Author(s):  
Walter Fornari ◽  
Francesco Picano ◽  
Gaetano Sardina ◽  
Luca Brandt
Keyword(s):  
Solid Phase ◽  
Density Ratio ◽  
Mean Square Displacement ◽  
Particle Diameter ◽  
Finite Size ◽  
Mean Square ◽  
Rigid Spheres ◽  
The Mean ◽  
Settling Speed ◽  
Quiescent Fluid

We study the settling of finite-size rigid spheres in sustained homogeneous isotropic turbulence (HIT) by direct numerical simulations using an immersed boundary method to account for the dispersed solid phase. We study semi-dilute suspensions at different Galileo numbers, $Ga$. The Galileo number is the ratio between buoyancy and viscous forces, and is here varied via the solid-to-fluid density ratio $\unicode[STIX]{x1D70C}_{p}/\unicode[STIX]{x1D70C}_{f}$. The focus is on particles that are slightly heavier than the fluid. We find that in HIT, the mean settling speed is less than that in quiescent fluid; in particular, it reduces by 6 %–60 % with respect to the terminal velocity of an isolated sphere in quiescent fluid as the ratio between the latter and the turbulent velocity fluctuations $u^{\prime }$ is decreased. Analysing the fluid–particle relative motion, we find that the mean settling speed is progressively reduced while reducing $\unicode[STIX]{x1D70C}_{p}/\unicode[STIX]{x1D70C}_{f}$ due to the increase of the vertical drag induced by the particle cross-flow velocity. Unsteady effects contribute to the mean overall drag by about 6 %–10 %. The probability density functions of particle velocities and accelerations reveal that these are closely related to the features of the turbulent flow. The particle mean-square displacement in the settling direction is found to be similar for all $Ga$ if time is scaled by $(2a)/u^{\prime }$ (where $2a$ is the particle diameter and $u^{\prime }$ is the turbulence velocity root mean square).

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