Size Selector Research Articles

Accelerating matrix-centric graph processing on GPUs through bit-level optimizations

Even though it is well known that binary values are common in graph applications (e.g., adjacency matrix), how to leverage the phenomenon for efficiency has not yet been adequately explored. This paper presents a systematic study on how to unlock the potential of the bit-level optimizations of graph computations that involve binary values. It proposes a two-level representation named Bit-Block Compressed Sparse Row (B2SR) and presents a series of optimizations to the graph operations on B2SR by the intrinsics of modern GPUs. It additionally introduces Deep Reinforcement Learning (DRL) as an efficient way to best configure the bit-level optimizations on the fly. The DQN-based adaptive tile size selector with dedicated model training can reach 68% prediction accuracy. Evaluations on the NVIDIA Pascal and Volta GPUs show that the optimizations bring up to 40▪ and 6555▪ for essential GraphBLAS kernels SpMV and SpGEMM, respectively, accelerating GraphBLAS-based BFS by up to 433▪, SSSP, PR, and CC 35▪, and TC 52▪.

A 6.78 MHz, 95.0% Peak Efficiency Monolithic Two-Dimensional Calibrated Active Rectifier for Wirelessly Powered Implantable Biomedical Devices.

In this paper, a fully integrated active rectifier with triple feedback loops is proposed to enhance power conversion efficiency (PCE) over a wide loading range by calibrating both the gate transition timing and power switch size. The on- and off-transitions of the power switches are calibrated using a hybrid delay-based gate control circuit (HDGCC) with hybrid feedback loops. Conventional active rectifiers that only focused on calibrating the gate transition timing of a NMOS power switch with a fixed power switch size exhibit a low PCE when the loading condition deviates from the predetermined range. Thus, an automatic size selector based on a third feedback loop is proposed, which changes the power switch size based on the loading condition and ensures a stable operation of the hybrid loops by maintaining the voltage drop across the NMOS switches. An active rectifier was fabricated using the standard 0.18 μm CMOS process. The effectiveness and robustness of the two-dimensional calibration were verified through measurements under an AC input voltage ranging from 2.5 to 5.0 V and an output power ranging from 1.25 to 125 mW. The peak voltage conversion ratio and peak PCE were 97.6% and 95.0%, respectively, at RL = 500 Ω.

A field study on the possible attachment of DPM and respirable dust in mining environments

Typcial monitoring procedures for diesel particulate matter (DPM) in mines include the collection of filter samples using particle size selectors. The size selectors are meant to separate the DPM, which is generally considered to occur in the submicron range (i.e., < 0.8 μm), from larger dust particles that could present analytical interferences. However, previous studies have demonstrated that this approach can sometimes result in undersampling, therefore, excluding significant fractions of the DPM mass. The excluded fraction may represent oversized DPM particles, but another possibility is that submicron DPM attaches to supramicron dust particles such that it is effectively oversized. To gain insights into this possibility, a field study was conducted in an underground stone mine. Submicron, respirable, and total airborne particulate filter samples were collected in three locations to determine elemental carbon (EC) and total carbon (TC), which are commonly used as analytical surrogates for DPM. Concurrent with the collection of the filter samples, a low-flow sampler with an electrostatic precipitator was also used to collect airborne particulates onto 400-mesh copper grids for analysis by transmission electron microscope (TEM). Results indicated that, while typical submicron sampling did account for the majority of DPM mass in the study mine, DPM-dust attachment can indeed occur. The effect of exposure to such attached particulates has not been widely investigated.

A field study on the possible attachment of DPM and respirable dust in mining environments.

Typcial monitoring procedures for diesel particulate matter (DPM) in mines include the collection of filter samples using particle size selectors. The size selectors are meant to separate the DPM, which is generally considered to occur in the submicron range (i.e., < 0.8 μm), from larger dust particles that could present analytical interferences. However, previous studies have demonstrated that this approach can sometimes result in undersampling, therefore, excluding significant fractions of the DPM mass. The excluded fraction may represent oversized DPM particles, but another possibility is that submicron DPM attaches to supramicron dust particles such that it is effectively oversized. To gain insights into this possibility, a field study was conducted in an underground stone mine. Submicron, respirable, and total airborne particulate filter samples were collected in three locations to determine elemental carbon (EC) and total carbon (TC), which are commonly used as analytical surrogates for DPM. Concurrent with the collection of the filter samples, a low-flow sampler with an electrostatic precipitator was also used to collect airborne particulates onto 400-mesh copper grids for analysis by transmission electron microscope (TEM). Results indicated that, while typical submicron sampling did account for the majority of DPM mass in the study mine, DPM-dust attachment can indeed occur. The effect of exposure to such attached particulates has not been widely investigated.

Combining the Particle Size Selector and a condensation particle counter to determine the number size distribution of airborne nanoparticles

This study fits in the general framework of developing methods for the measurement of the number size distribution of airborne submicrometer particles suited for field measurements. An approach based on the combination of a Particle Size Selector (PSS) and a portable Condensation Particle Counter (CPC) is proposed in this work. The methodology relies on the successive measurement of the number concentration under 6 operational configurations (n = 0, 1, 2, 6, 12 and 18 diffusion screens). A first part of this work consisted of determining particle penetration through different sets of diffusion grids, both experimentally and theoretically. On that basis, a specific data processing was developed, assuming that aerosol size distribution follows a monomodal lognormal law. In the second part of this study, the combined PSS-CPC approach was applied to a series of test aerosols produced in the laboratory, covering a range of modal diameters from 9 to 270 nm. Compared to reference SMPS data, the output number size distributions calculated from the PSS-CPC approach were found to be within ± 11% in terms of modal diameter, which is considered satisfactory.

Development of a Portable Aerosol Collector and Spectrometer (PACS).

This article presents the development of a Portable Aerosol Collector and Spectrometer (PACS), an instrument designed to measure particle number, surface area, and mass concentrations continuously and time-weighted mass concentration by composition from 10 nm to 10 μm. The PACS consists of a six-stage particle size selector, a valve system, a water condensation particle counter to detect number concentrations, and a photometer to detect mass concentrations. The stages of the selector include three impactor and two diffusion stages, which resolve particles by size and collect particles for later chemical analysis. Particle penetration by size was measured through each stage to determine actual collection performance and account for particle losses. The data inversion algorithm uses an adaptive grid-search process with a constrained linear least-square solver to fit a tri-modal (ultrafine, fine, and coarse), log-normal distribution to the input data (number and mass concentration exiting each stage). The measured 50% cutoff diameter of each stage was similar to the design. The pressure drop of each stage was sufficiently low to permit its operation with portable air pumps. Sensitivity studies were conducted to explore the influence of unknown particle density (range from 500 to 3,000 kg/m3) and shape factor (range from 1.0 to 3.0) on algorithm output. Assuming standard density spheres, the aerosol size distributions fit well with a normalized mean bias of -4.9% to 3.5%, normalized mean error of 3.3% to 27.6%, and values of 0.90 to 1.00. The fitted number and mass concentration biases were within ±10% regardless of uncertainties in density and shape. However, fitted surface area concentrations were more likely to be underestimated/overestimated due to the variation in particle density and shape. The PACS represents a novel way to simultaneously assess airborne aerosol composition and concentration by number, surface area, and mass over a wide size range.

Impact of aging on the performance of impactor and sharp-cut cyclone size selectors for DPM sampling

Impact of aging on the performance of impactor and sharp-cut cyclone size selectors for DPM sampling

Integrated Virtual Impactor Enabled PM2.5Sensor

As more and more proofs show that fine particles (diameter of $2.5~\mu \text{m}$ and below) pose more risk on human health than coarse particles, an increasing need for monitoring fine particles has emerged. A miniaturized sensor designed for measuring fine particle concentration is presented in this paper. The proposed sensor possesses a compact size of only 15 mm $\times10$ mm $\times1$ mm. A virtual impactor has been integrated as a particle size selector and the design is optimized by simulation-assisted analysis. The sensor is realized by silicon microfabrication and wafer-level packaging. Testing results show that a high measurement accuracy of $2.55~\mu \text{g}/\text{m}^{3}$ has been achieved.

Lagrangian particle modelling of spherical nanoparticle dispersion and deposition in confined flows

Particle diffusional losses in confined flows such as pipes are important for identification of erosion or accretion build-up. Its applications are varied and prominent in industrial and biomedical applications where essentially, tubular geometries transport fluid-particle flows. Computational modelling of dilute suspensions of ultrafine and nano-scale particles dispersing in a fluid often use the Lagrangian particle tracking approach. The Euler Implicit scheme in FLUENT v16 was evaluated for tracking such particles through a standard pipe geometry. It was found that the particles’ Brownian dispersion was dependent on the computational mesh, and the integration time step for a given particle size. For the pipe geometry well established analytical solutions for particle deposition efficiency are available to directly compare the simulated results. For irregular geometries (such as human respiratory anatomy) there are no analytical solutions and experimental deposition data is scarce and an alternative method is required to verify the simulation setup. In this case the computational models were set with zero velocity and the nanoparticles released from rest. The particle motion was then initiated purely by Brownian motion. The root mean square displacement was used to compare the time step size selector (either by the Length Scale Factor, LS, or the Step Length Factor SLF approach in FLUENT; and a fixed time step using an in-house code ‘PARTICLE’). This provides a modelling verification framework to determine the most appropriate time step selection that reproduces the particle Brownian dispersion behaviour correctly.

Real-time diesel particulate monitor for underground mines.

The standard method for determining diesel particulate matter (DPM) exposures in underground metal/ nonmetal mines provides the average exposure concentration for an entire working shift, and several weeks might pass before results are obtained. The main problem with this approach is that it only indicates that an overexposure has occurred rather than providing the ability to prevent an overexposure or detect its cause. Conversely, real-time measurement would provide miners with timely information to allow engineering controls to be deployed immediately and to identify the major factors contributing to any overexposures. Toward this purpose, the National Institute for Occupational Safety and Health (NIOSH) developed a laser extinction method to measure real-time elemental carbon (EC) concentrations (EC is a DPM surrogate). To employ this method, NIOSH developed a person-wearable instrument that was commercialized in 2011. This paper evaluates this commercial instrument, including the calibration curve, limit of detection, accuracy, and potential interferences. The instrument was found to meet the NIOSH accuracy criteria and to be capable of measuring DPM concentrations at levels observed in underground mines. In addition, it was found that a submicron size selector was necessary to avoid interference from mine dust and that cigarette smoke can be an interference when sampling in enclosed cabs.

An efficient graphics processing unit‐based parallel algorithm for pricing multi‐asset American options

SUMMARYWe develop highly efficient parallel PDE‐based pricing methods on graphics processing units (GPUs) for multi‐asset American options. Our pricing approach is built upon a combination of a discrete penalty approach for the linear complementarity problem arising because of the free boundary and a GPU‐based parallel alternating direction implicit approximate factorization technique with finite differences on uniform grids for the solution of the linear algebraic system arising from each penalty iteration. A timestep size selector implemented efficiently on GPUs is used to further increase the efficiency of the methods. We demonstrate the efficiency and accuracy of the parallel numerical methods by pricing American options written on three assets. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Adaptive and high-order methods for valuing American options

Space–time adaptive and high-order methods for valuing American options using a partial differential equation (PDE) approach are developed in this paper. The linear complementarity problem that arises due to the free boundary is handled using a penalty method. Both finite difference and finite element methods are considered for the space discretization of the PDE, while classical finite differences, such as Crank–Nicolson, are used for the time discretization. The high-order discretization in space is based on an optimal finite element collocation method, the main computational requirements of which are the solution of one tridiagonal linear system at each timestep, while the resulting errors at the grid points and midpoints of the space partition are fourth order. To control the space error we use adaptive grid-point distribution based on an error equidistribution principle. A timestep size selector is used to further increase the efficiency of the methods. Numerical examples show that our methods converge fast and provide highly accurate options prices, Greeks and early exercise boundaries.

An Efficient GPU-Based Parallel Algorithm for Pricing Multi-Asset American Options

We develop highly-efficient parallel Partial Differential Equation (PDE) based pricing methods on Graphics Processing Units (GPUs) for multi-asset American options. Our pricing approach is built upon a combination of a discrete penalty approach for the linear complementarity problem arising due to the free boundary and a GPU-based parallel Alternating Direction Implicit Approximate Factorization technique with finite differences on uniform grids for the solution of the linear algebraic system arising from each penalty iteration. A timestep size selector implemented efficiently on GPUs is used to further increase the efficiency of the methods. We demonstrate the efficiency and accuracy of the parallel numerical methods by pricing American options written on three assets.

Bioaerosol sampling by a personal rotating cup sampler CIP 10-M

High concentrations of bioaerosols containing bacterial, fungal and biotoxinic matter are encountered in many workplaces, e.g. solid waste treatment plants, waste water treatment plants and sewage networks. A personal bioaerosol sampler, the CIP 10-M (M-microbiologic), has been developed to measure worker exposure to airborne biological agents. This sampler is battery operated; it is light and easy to wear and offers full work shift autonomy. It can sample much higher concentrations than biological impactors and limits the mechanical stress on the microorganisms. Biological particles are collected in 2 ml of liquid medium inside a rotating cup fitted with radial vanes to maintain an air flow rate of 10 l min(-1) at a rotational speed of approximately 7,000 rpm. The rotating cup is made of sterilisable material. The sampled particles follow a helicoidal trajectory as they are pushed to the surface of the liquid by centrifugal force, which creates a thin vertical liquid layer. Sterile water or another collecting liquid can be used. Three particle size selectors allow health-related aerosol fractions to be sampled according to international conventions. The sampled microbiological particles can be easily recovered for counting, incubation or further biochemical analysis, e.g., for airborne endotoxins. Its physical sampling efficiency was laboratory tested and field trials were carried out in industrial waste management conditions. The results indicate satisfactory collection efficiency, whilst experimental application has demonstrated the usefulness of the CIP 10-M personal sampler for individual bioaerosol exposure monitoring.

Development of a new cluster size selector

A new cluster size selector is being developed to realize low-damage nano-processing applied gas cluster ion beam (GCIB) technology. The selector consists of several pairs of deflection electrodes and high-frequency deflection biases are applied. Depending on the velocity of a cluster ion, a desired size of cluster can pass through the selector. It can select any target cluster sizes without changing the structure. The length of this device is about 200mm and it is much smaller than that of traditional mass spectrometers, because of its simple structure. Preliminary experiments showed a good mass resolution and high transmittance for a cluster size selector with this device.

Spatial Mapping of Droplet Velocity and Size for Direct and Indirect Nebulization in Plasma Spectrometry

Two novel laser-based imaging techniques centered on particle image velocimetry and optical patternation are used to map and contrast the size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. The flow field of droplets is illuminated by two pulses from a thin laser sheet with a known time difference. The scattering of the laser light from droplets is captured by a charge-coupled device (CCD), providing two instantaneous images of the particles. Pointwise cross-correlation of the corresponding images yields a two-dimensional velocity map of the aerosol velocity field. For droplet size distribution studies, the solution is doped with a fluorescent dye and both laser-induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. The ratio of the LIF/Mie images provides relative droplet size information, which is then scaled by a point calibration method via a phase Doppler particle analyzer. Two major findings are realized for three nebulization systems: (1) a direct injection high-efficiency nebulizer (DIHEN); (2) a large-bore DIHEN; and (3) a PFA microflow nebulizer with a PFA Scott-type spray chamber. First, the central region of the aerosol cone from the direct injection nebulizers and the nebulizer-spray chamber arrangement consists of fast (>13 and >8 m/s, respectively) and fine (<10 and <5 microm, respectively) droplets as compared to slow (<4 m/s) and large (>25 microm) droplets in the fringes. Second, the spray chamber acts as a momentum separator, rather than a droplet size selector, as it removes droplets having larger sizes or velocities. The concepts and results presented in this research may be used to develop smart-tunable nebulizers, for example, by using the measured momentum as a feedback control for adjusting the nebulizer, i.e., its operating conditions, its critical dimensions, or both.

하드 디스크 드라이브 회전수 변화가 드라이브 내 나노 오염 입자 발생에 미치는 영향

In high-density hard disk doves, the slider should be made to fly close to the magnetic recording disk to generate better signal resolution and at an increasingly high velocity to achieve better data rate. The slider disk interaction in CSS (contact-start-stop) mode is an Important source of particle generation. Contamination particles In the hard disk drive can cause serious problems including slider crash and thermal asperities We Investigated the number and the Sizes of particles generated in the hard disk drive, operating at increasing disk rotational speeds, in the CSS mode CNC (condensation nucleus counter) and PSS (particle Size selector) were used for this investigation In addition, we examined the particle components by using SEM (scanning electron microscopes), AES (auger electron spectroscopy), and TOF-SIMS (time of flight-secondary Ions mass spectrometry) The increasing disk rotational speed difectly affected the particle generation by slider disk interaction The number of particles that were generated increased With the disk rotational speed. The particle generation rate Increased rapidly at motor speeds above 8000 rpm Tins Increase may be due to the Increased slider disk Interaction. Particle Sizes ranged from 14 to 200 nm. The particles generated by slider disk Interaction came from the lubricant on the disk, coating layer of the disk, and also slider surface.<br/>

Effect of disk rotational speed on contamination particles generated in a hard disk drive

In high-density hard disk drives, the slider should be made to fly close to the magnetic recording disk to generate better signal resolution and at an increasingly high velocity to achieve better data rate. The slider disk interaction in CSS (contact-start-stop) mode is an important source of particle generation. Contamination particles in the hard disk drive can cause serious problems including slider crash and thermal asperities. We investigated the number and the sizes of particles generated in the hard disk drive, operating at increasing disk rotational speeds, in the CSS mode. Condensation nucleus counter (CNC) and PSS (particle size selector) were used for this investigation. In addition, we examined the particle components by using SEM (scanning electron microscopes), AES (auger electron spectroscopy) and TOF-SIMS (time of flight-secondary ions mass spectrometry). The increasing disk rotational speed directly affected the particle generation by slider disk interaction. The number of particles that were generated increased with the disk rotational speed. The particle generation rate increased rapidly at motor speeds above 8000 rpm. This increase may be due to the increased slider disk interaction. Particle sizes ranged from 14 to 200 nm. The particles generated by slider disk interaction came from the lubricant on the disk, coating layer of the disk, and also slider surface.

Filtration in industrial hygiene.

Filters used in industrial hygiene are of two basic types, corresponding with the two basic airborne hazards: particulate and vapor. They are as different in their construction as they are in their purpose, and each gives negligible protection against the other hazard. By use of the correct type, adequate filtration efficiency can usually be achieved. Most particulate filters are made from fibers, and finer fibers result in higher efficiency. Filters can capture particles much smaller than the fiber diameter, as a result of diffusional motion of the airborne particles and, in the case of filters that hold a permanent electric charge, electrostatic attraction. Most vapor filters are made from granules of activated carbon, which have an extremely large effective surface area, where molecules of contaminant are adsorbed. The performance of all filters tends to alter as the filter material becomes loaded. Electrically neutral particulate filters become more efficient but at the expense of increased resistance to airflow. Particulate filters that act by electric forces may become less efficient, and are often less inclined to clog. Vapor filters usually have a high initial efficiency, but the penetration of vapor increases as the filters become saturated with adsorbed vapor, and the performance of these filters is normally expressed in terms of their lifetime rather than their efficiency. It is important that the choice of a filter should be made with close reference to the situation in which it is to be used, and optimum respiratory protection should be sought, rather than maximum filtration efficiency. Special problems of filters are illustrated by some case histories, and finally the use of filters as size selectors for dust samplers is briefly described.

Evaluation of PM2.5 Size Selectors Used in Speciation Samplers

Evaluation of PM2.5 Size Selectors Used in Speciation Samplers