Leakage Fraction Research Articles

Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance

The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over ∼75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale CMB polarization to constrain the tensor-to-scalar ratio and the optical depth to last scattering. This paper presents the optical characterization of the 90 GHz telescope. Observations of the Moon establish the pointing while dedicated observations of Jupiter are used for beam calibration. The standard deviations of the pointing error in azimuth, elevation, and boresight angle are 1.′3, 2.′1, and 2.′0, respectively, over the first 3 yr of observations. This corresponds to a pointing uncertainty ∼7% of the beam’s full width at half-maximum (FWHM). The effective azimuthally symmetrized instrument 1D beam estimated at 90 GHz has an FWHM of 0.°620 ± 0.°003 and a solid angle of 138.7 ± 0.6(stats.) ± 1.1(sys.) μsr integrated to a radius of 4°. The corresponding beam window function drops to bℓ2=0.93,0.71,0.14 at ℓ = 30, 100, 300, respectively. Far-sidelobes are studied using detector-centered intensity maps of the Moon and measured to be at a level of 10−3 or below relative to the peak. The polarization angle of Tau A estimated from preliminary survey maps is 149°.6 ± 0°.2(stats.) in equatorial coordinates. The instrumental temperature-to-polarization (T → P) leakage fraction, inferred from per-detector demodulated Jupiter scan data, has a monopole component at the level of 1.7 × 10−3, a dipole component with an amplitude of 4.3 × 10−3, with no evidence of quadrupolar leakage.

BCH modelling studies on biocementation process in mitigating leaks from a CO2 sequestrated aquifer

BCH modelling studies on biocementation process in mitigating leaks from a CO2 sequestrated aquifer

Leakage Flow Impact on Shrouded Stator Cavity Flow Topology and Associated High-Speed Axial Compressor Stage Performance

AbstractThis paper presents the investigation of realistic cavity leakage flow for the von Karman Institute for Fluid Dynamics H25 axial compressor stage, equipped with a shroud cavity of average Reynolds number Rer = 2.2 * 106 and average aspect ratio G = 0.06. On top of overall performance measurements, time averaged data from unprecedented experimental dataset are used to characterize the stator hub shroud cavity flow field and its interaction with the power stream. The sensitivity of the stage performance and stability as well as the cavity flow topology is evaluated against injection conditions, compressor throttling, and compressor speed. Parametric steady RANS simulations of the stage under injection are used to support the findings and state on the relevance of such approach in the preliminary design phase of axial compressor components. As an example, a stage efficiency reduction of 0.97% for a leakage fraction of 0.56% at design point is retrieved. This performance drop is attributed to the effect of cavity flow on: the blockage ratio, the boundary layer skewness, and total temperature increase at stator row inlet. It is also presented that there is a mutual interaction between the cavity geometry and the cavity flow field organization. The injection homogenizes the cavity flow field and the associated pressure gradient. The various operating conditions presented also demonstrate that the cavity flow studied is, on average (i.e., time), sensitive to changes in compressor rotation speed and changes in stage loading.

Predicting tungsten erosion and leakage properties for the new V-shaped small angle slot divertor in DIII-D

Impurity transport modeling of the new tungsten (W)-coated, V-shaped small angle slot (SAS) divertor in the DIII-D tokamak was conducted using the SOLPS-ITER plasma edge code package and the DIVIMP impurity tracking code. The inboard baffle of the current SAS divertor will be shifted closer to the outboard baffle, creating a V-corner at the slot vertex. In addition, the outboard baffle will be coated with 10–15 μm of W for experiments studying high-Z sourcing and leakage in a closed divertor. Modeling of the ‘SAS-VW’ divertor predicts that these changes to the inner baffle will reduce W gross erosion by 40× relative to the existing SAS divertor when the outer strike point (OSP) is at the V-corner and the ion B × ∇B drift is towards the divertor, driven primarily by significant cooling near the slot vertex. Most W erosion in SAS-VW is expected to occur near the slot entrance, which may pose a higher risk to core contamination than W eroded deeper in the slot. Adding a new sheath-based prompt redeposition model outlined in Guterl et al (2021 Nucl. Mater. Energy 27 100948) increases the sensitivity of redeposition estimates to near-target plasma conditions and may provide more accurate predictions of net erosion. Moving the OSP outboard from the slot vertex ∼4 cm onto the W-coated region yields a 40× increase in the gross erosion rate and a 50% decrease in the core leakage fraction. Thus slight variations in strike point location may counteract the potential benefits of the tightly-baffled V slot on minimizing erosion. This impurity transport modeling provides useful guidance for future experiments on the SAS-VW divertor focused on high-Z erosion/redeposition, scrape-off layer transport, and core leakage.

Inspiratory leakage flow fraction for surgical masks with varying gaps and filter materials

Leakage flows due to a poor fit can greatly reduce the mask protection efficiency. However, accurate quantification of leakages is lacking due to the absence of standardized tests and difficulties in quantifying mask gaps. The objective of this study is to quantify the leakage flows around surgical masks with gaps of varying areas and locations. An integrated ambient–mask–face–airway model was developed with a pleated surgical mask covering an adult's face, nose, and chin. To study the gap effects, the mask edge along the facile interface was divided into different domains, which could be prescribed either as the mask media or air. A low Reynolds number k-ω turbulence model with porous media was used to simulate inspiratory flows. Experimentally measured resistances of two surgical masks were implemented in porous media zones. Results show that even a small gap of 1-cm2 area could cause a 17% leakage. A gap area of 4.3 cm2 at the nose bridge, the most frequent misfit when wearing a surgical mask, led to a leakage of 60%. For a given mask, the increase rate of leakage slowed down with the increasing gap area. For a given gap, the leakage fraction is 30–40% lower for a mask with a resistance of 48.5 Pa than a mask of 146.0 Pa. Even though the flow dynamics were very different among gaps at different locations, the leakage intensity appeared relatively insensitive to the gap location. Therefore, correlations for the leakage as a function of the gap area were developed for the two masks.

Flow dynamics in the sinus and downstream of third and fourth generation balloon expandable transcatheter aortic valves

ObjectiveThe early success of transcatheter aortic valve (TAV) replacement (TAVR) has fueled further innovations in the field leading to the emergence multiple iterations of TAV designs. Whether these newer designs are associated with similar hemodynamic outcomes remains unknown. Recently, the SAPIEN 3 Ultra valve received FDA approval for use in patients with published clinical outcomes. The aim of this study is (1) to evaluate and compare the flow dynamics downstream of the SAPIEN 3 Ultra and a SAPIEN 3 (2) and to evaluate and compare the resulting sinus hemodynamics and washout characteristics for a complete hemodynamic characterization. MethodsThe hemodynamic assessment was performed in a pulse duplicating system and particle image velocimetry was used to assess the flow dynamics. Pressure gradient (ΔP), effective orifice area (EOA), leakage fraction (LF), velocity in the flow downstream and the sinus, viscous shear stress (VSS) downstream and adjacent to the leaflet in the sinus, and sinus washout were calculated. ResultsEOA for the SAPIEN 3 Ultra was 1.81 ± 0.05 cm2 and 1.86 ± 0.05 cm2 with the SAPIEN 3, ΔP with the SAPIEN 3 Ultra was 10.56 ± 0.62 mmHg and 14.73 ± 0.79 mmHg with the SAPIEN 3, and LF with the SAPIEN 3 Ultra was 10.4 ± 0.5% and 9.7 ± 0.4% with the SAPIEN 3 (p<0.05). The instantaneous VSS for both valves ≤15 Pa, which is not sufficient to induce hemolysis, but may lead to platelet activation. RSS — an indicator of blood damage — exceeded 100 Pa at peak systole with both TAVs. The sinus velocity at peak systole was 0.24 ± 0.08 m/s with the SAPIEN 3 Ultra and 0.22 ± 0.10 m/s with the SAPIEN 3. VSS range reached 3.9 Pa with the SAPIEN 3 Ultra and 4.0 Pa with the SAPIEN 3. Complete sinus washout was achieved in ∼1.5 and ∼2.4 cardiac cycles for the SAPIEN 3 Ultra and SAPIEN 3, respectively. ConclusionCompared to its predecessor, the hemodynamic performance and sinus hemodynamics of SAPIEN 3 Ultra are comparable.

Mathematical modelling of haemorrhagic transformation after ischaemic stroke

With an increasingly elderly population globally, the impacts of cerebrovascular diseases, such as stroke and dementia, become increasingly significant. Haemorrhagic transformation (HT) is one of the most common complications of ischaemic stroke that is caused by dysfunction of endothelial cells in the blood–brain barrier (BBB) and that can be exacerbated by thrombolytic therapy. Recent studies also suggest that HT can lead to an increase in intracranial pressure (ICP) and result in capillary compression. The aim of this study is to develop a mathematical model that can be used to simulate the consequence of HT over a range of vasculature length scales. We use a 2D vasculature model to investigate the severity of HT with different vascular geometry. The resulting model shows that the haematoma radius is approximately constant across different length scales (100-1000μm) and in good agreement with the available experimental data. In addition, this study identified that the effects of capillary compression do appear to have a significant impact on the leakage fraction of blood and hence act to restrain the development of a haematoma.

CFD‐DEM analysis of the spouted fluidized bed with non‐spherical particles

AbstractHydrodynamics of spouted fluidized beds of spherical and elongated sphero‐cylindrical particles with an aspect ratio (AR) of 4 were studied by the CFD‐DEM technique. The multi‐sphere method was adopted to present the sphero‐cylindrical particles. Simulations were validated with the experimental data for both particle types. Bubble equivalent diameter, bubble shape factor, and leakage fraction were obtained in the simulations. Time‐averaged particle velocity and porosity profiles, solids circulation rate, particle exchange distribution at the spout‐annulus interface, were investigated in the beds filled with spherical and sphero‐cylindrical particles at gas mass flow rates of 0.005, 0.007, and 0.009 kg/s. The equivalent bubble diameter was found to be lower for spherical particles compared to sphero‐cylindrical particles. The leakage fraction of the bubble was lower for sphero‐cylindrical particles. Solid circulation rate and spout diameter were larger for the bed of spherical particles. A higher probability of particles transition into the spout was observed for spherical particles. Investigating the orientation showed that sphero‐cylindrical particles tend to orient almost vertically against the gas flow in the spout region, which lowers the exerted drag force, whereas the particles align nearly horizontally in the annulus region. The results revealed that the CFD‐DEM approach is a promising method for investigating the fluid and both spherical and non‐spherical particle behaviours in spouted fluidized beds.

Biochar Mediated-Alleviation of Chromium Stress and Growth Improvement of Different Maize Cultivars in Tannery Polluted Soils.

Soil pollution with heavy metal is a serious problem across the globe and is on the rise due to the current intensification of chemical industry. The leather industry is one of them, discharging chromium (Cr) in huge quantities during the process of leather tanning and polluting the nearby land and water resources, resulting in deterioration of plant growth. In this study, the effects of biochar application at the rate of 3% were studied on four maize cultivars, namely NK-8441, P-1543, NK-8711, and FH-985, grown in two different tannery polluted Kasur (K) and Sialkot (S) soils. Maize plants were harvested at vegetative growth and results showed that Cr toxicity adversely not only affected their growth, physiology, and biochemistry, but also accumulated in their tissues. However, the level of Cr toxicity, accumulation, and its influence on maize cultivars varied greatly in both soils. In this pot experiment, biochar application played a crucial role in lessening the Cr toxicity level, resulting in significant increase in plant height, biomass (fresh and dry), leaf area, chlorophyll pigments, photosynthesis, and relative water content (RWC) over treatment set as a control. However, applied biochar significantly decreased the electrolyte leakage (EL), antioxidant enzymes, lipid peroxidation, proline content, soluble sugars, and available fraction of Cr in soil as well as Cr (VI and III) concentration in root and shoot tissues of maize plant. In addition to this, maize cultivar differences were also found in relation to their tolerance to Cr toxicity and cultivar P-1543 performed better over other cultivars in both soils. In conclusion, biochar application in tannery polluted soils could be an efficient ecofriendly approach to reduce the Cr toxicity and to promote plant health and growth.

Burnup Performance of CANDLE Burning Reactor Using Sodium Coolant

The CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy production) reactor concept was proposed to overcome the disadvantages of current reactor technologies. In this study, a Monte Carlo–based procedure is developed for quantitative comparison of burnup performance and neutronic characteristics between lead bismuth eutectic (LBE)–cooled and sodium-cooled CANDLE reactors to demonstrate the possibility of using sodium coolant in a small CANDLE burning reactor. In this procedure, a neutron transport equation is solved using the MVP code with the JENDL-4.0 library, and the burnup calculation is solved using the MVP-BURN code with the detailed burnup chain. To simulate the fuel-shuffling process, an auxiliary code was developed using Python. The results show that for the same fuel pin design and core volume, changing the coolant from LBE to sodium reduced the keff by 2.3% and the average discharge burnup by 15.6%, due to the softer neutron spectrum and larger neutron leakage fraction. It would be necessary to increase the fuel volume and core radius approximately 38% and 17%, respectively, for criticality in a sodium-cooled CANDLE core.

Determination of radon leakage from sample container for gamma spectrometry measurement of 226Ra

Gamma spectrometry is widely used for radionuclide activity measurement of environmental sample including 226Ra in soil because it is versatile, easy to implement, non-destructive, and relatively cheap compared to other methods. By gamma spectrometry, 226Ra can be determined directly using its energy peak of 186.2 keV or indirectly by its decay products which are in secular equilibrium with 226Ra, i.e. 214Bi and 214Pb. However, both methods have challenges where for direct measurement, interfering from 235U energy peak of 185.7 keV can add significant contribution to the 186.2 keV of 226Ra gamma peak while for indirect measurement using energy peaks of 214Bi and 214Pb, decay products of 222Rn gas, longer time (at least 21 days) for their equilibrium ingrowth is needed and radon tightness of sample container must be ensured. In some measurements, the equilibrium could not be reached due to radon leakage from sample container. Therefore, in this paper, the radon leakage fraction from three different sealing methods of Marinelli beaker used in soil activity measurement were studied using HPGe detector and radon accumulation chamber with RAD7. The three sealing methods were only lid without sealing (MB1), sealed with paraffin film (MB2), sealed with silicone glue and vacuumed plastic bag (MB3) and their leakage fractions were 53%, 30%, and negligible leakage, respectively. Significant radon leakage from MB1 and MB2 have caused underestimation of 226Ra activity concentration measured by indirect gamma spectrometry. The study result recommends using MB3 sealing method for gamma spectrometry measurement because it is simple and cheap and has negligible leakage, moreover, its vacuumed plastic bag facilitates visual inspection to possible radon leakage.

Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: 40 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance

Abstract The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over 75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale (1° ≲ θ 90°) CMB polarization to constrain the tensor-to-scalar ratio at the r ∼ 0.01 level and the optical depth to last scattering to the sample variance limit. This paper presents the optical characterization of the 40 GHz telescope during its first observation era, from 2016 September to 2018 February. High signal-to-noise observations of the Moon establish the pointing and beam calibration. The telescope boresight pointing variation is &lt;0.°023 (&lt;1.6% of the beam’s full width at half maximum (FWHM)). We estimate beam parameters per detector and in aggregate, as in the CMB survey maps. The aggregate beam has an FWHM of 1.°579 ± 0.°001 and a solid angle of 838 ± 6 μsr, consistent with physical optics simulations. The corresponding beam window function has a sub-percent error per multipole at ℓ &lt; 200. An extended 90° beam map reveals no significant far sidelobes. The observed Moon polarization shows that the instrument polarization angles are consistent with the optical model and that the temperature-to-polarization leakage fraction is &lt;10−4 (95% C.L.). We find that the Moon-based results are consistent with measurements of M42, RCW 38, and Tau A from CLASS’s CMB survey data. In particular, Tau A measurements establish degree-level precision for instrument polarization angles.

New Paradigms in Defining Optimum Cost Conditions in Thermoelectric Energy Recovery Designs

Cost is just as important as power density or efficiency for the adoption of waste heat recovery (WHR) thermoelectric generators (TEG). Prior work [1] has shown that the system design that minimizes cost (e.g., the G [$/W] value) can be close to the designs that maximize power, but these design regimes are not necessarily aligned with high system conversion efficiency or power density. Recent work [2–5] further explores the impact of heat exchanger conditions on the optimum TEG fill factors and cost scaling of a waste heat recovery thermoelectric generator with a detailed treatment of the hot side exhaust heat exchanger. The cost scaling analysis considers the overall TEG system costs, including TE material costs, manufacturing costs, and specifically heat exchanger costs; and the performance analysis accounts for heat lost to the environment and updated relationships between the optimum hot-side and cold-side conductances that maximize power output. The optimum fill factor, Fopt, to minimize TEG energy recovery system costs is strongly dependent on the heat leakage fraction, σ, the mass flow rate of the exhaust, the hot-side heat exchanger effectiveness, heat exchanger UAu, and interfacial heat flux [1]. A more rigorous analysis and conclusion for the optimum fill factor was recently introduced and characterized at the 14th European Conference on Thermoelectrics [5] in 2016. A new, more comprehensive relationship for Fopt has created an updated, more rigorous relationship for the optimum cost, Gopt, relationship for thermoelectric energy recovery systems. These new [Gopt, Fopt] relationships are explored and characterized to show the inherent design complexities. The heat exchanger costs can often dominate the TEG cost equation and it is critical to fully understand the tradeoff between heat exchanger performance, TEG manufacturing and material costs, optimum TEG fill factors, and TE performance to establish potentially optimum design points within the cost-performance design space. This work explores and characterizes new design tradeoffs and new cost minimization relationships within this cost-performance design space for a typical thermoelectric energy recovery system application where the interplay between optimum TEG fill factors, TE device design parameters, and heat exchanger design parameters can impact system footprint, volume, and mass in weight-sensitive applications. This work shows how heat exchanger UAu, interfacial heat flux, and Fopt govern cost minimization and create and control cost regimes within the overall cost-performance design domain. This shift of emphasis acknowledging the interdependence of optimum TE fill factors, heat exchanger performance, and interfacial heat flux has significant implications on thermoelectric WHR system designs, their performance, and their operation.

Effects of gas leakage on the separation performance of a cyclone. Part 1: Experimental investigation

This paper, first of a two-paper series, analyzes the experimental results to clarify the effects of gas leakage on the separation performance of a cyclone. Experiments were carried out in a cold model of a cyclone. Varied parameters were inlet gas velocity, inlet solid concentration, and gas leakage velocity. In the experimental range, the pressure drops over a cyclone showed small variation with the increase in gas leakage velocity. When the gas leakage fraction exceeded 4%, experiments showed that the separation performance deteriorated significantly. Gas leakage re-entrained separated fine particles in the standpipe into the cyclone, indicated by a significant decrease of the separation efficiency for fine particles.

Heat Exchanger Performance Impacts on Optimum Cost Conditions in Thermoelectric Energy Recovery Designs

Cost is just as important as power density or efficiency for the adoption of waste heat recovery thermoelectric generators (TEG). Prior work [1] has shown that the system design that minimizes cost (e.g., the $/W value) can be close to the designs that maximize the system’s efficiency or power density, however, it is important to understand the relationship between those designs to optimize TEG performance-cost compromises. Expanding on recent work [1, 2, 3] the impact of heat exchanger conditions on the optimum TEG fill factors and cost scaling of a waste heat recovery thermoelectric generator with a detailed treatment of the hot side exhaust heat exchanger has been investigated further. The effect of the heat lost to the environment and updated relationships between the hot-side and cold-side conductances [4] that maximize power output are considered. The optimum fill factor to minimize TEG energy recovery system costs is strongly dependent on the heat leakage fraction, σ, the mass flow rate of the exhaust, the hot-side heat exchanger effectiveness, heat exchanger UAh, and heat flux. These relationships are explored and characterized for typical exhaust gas-flow conditions to show the inherent design complexities. The heat exchanger costs often dominate the TEG cost equation and it is critical to fully understand the tradeoff between heat exchanger performance, optimum TEG fill factors, and cost to establish potentially optimum design points within the cost-performance design space. This work will explore the design tradeoffs and relationships within the cost-efficiency-power density design space for a typical thermoelectric energy recovery system application. The interplay between optimum TEG fill factors and heat exchanger design can impact system footprint, volume, and mass in weight-sensitive applications. Less-effective, low-cost heat exchangers may outperform higher cost alternatives from a market adoption perspective. This shift of emphasis acknowledging the interdependence of optimum TEG fill factors and heat exchanger performance has significant implications on thermoelectric waste heat recovery systems designs and their operation. In addition, preferred TEG design regimes exist that accommodate reasonable compromises in TE performance and cost. This effort highlights how the optimum fill factor–heat exchanger performance relations couple to these optimum TEG performance-cost domains based on TEG-system-level analyses and provides a focus for future system research and development efforts.

A comparison of the effectiveness of the streamlined liner of pharyngeal airway in paralyzed and nonparalyzed patients undergoing gynecological surgery: a randomized trial

Study ObjectiveTo compare the effectiveness of streamlined liner of pharyngeal airway (SLIPA) in paralyzed and nonparalyzed, anesthetized patients undergoing gynecological surgery. DesignProspective randomized double-blind clinical trial. SettingIntraoperative. PatientsA total of 80 female patients with American Society of Anesthesiologists class I or II and who were undergoing gynecological surgery. InterventionsThe patients were randomly allocated to either the nonparalyzed group (group NR, n=40) or the paralyzed group (group R, n=40). MeasurementsOropharyngeal leakage pressure was the primary outcome. Insertion time; number of insertion attempts; success rate at first insertion; involuntary movement; peak inspiratory pressure (PIP); leakage fraction; hemodynamic changes; complications, such as blood tinging, regurgitation, and sore throat; and recovery time were also evaluated for secondary outcomes. Main ResultsOropharyngeal leakage pressure, which is primary outcome, was no difference among the groups. Insertion time, number of insertion attempts, success rate at first insertion, involuntary movement, leakage fraction, hemodynamic changes, and complications were not statistically different among the groups. The PIP in group NR was significantly increased compared to that of group R (P=.002). Recovery time was significantly longer in group R than in group NR (P<.001). ConclusionsSLIPA had good performance in both paralyzed and nonparalyzed patients. There was no difference in SLIPA performance or complications irrespective of muscle relaxant use, except decrease in PIP and prolong recovery time in paralyzed patients.

Cost Scaling of a Real-World Exhaust Waste Heat Recovery Thermoelectric Generator: A Deeper Dive

Cost is equally important to power density or efficiency for the adoption of waste heat recovery thermoelectric generators (TEG) in many transportation and industrial energy recovery applications. In many cases, the system design that minimizes cost (e.g., the $/W value) can be very different than the design that maximizes the system’s efficiency or power density, and it is important to understand the relationship between those designs to optimize TEG performance-cost compromises. Expanding on recent cost analysis work and using more detailed system modeling, an enhanced cost scaling analysis of a waste heat recovery TEG with more detailed, coupled treatment of the heat exchangers has been performed. In this analysis, the effect of the heat lost to the environment and updated relationships between the hot-side and cold-side conductances that maximize power output are considered. This coupled thermal and thermoelectric (TE) treatment of the exhaust waste heat recovery TEG yields modified cost scaling and design optimization equations, which are now strongly dependent on the heat leakage fraction, exhaust mass flow rate, and heat exchanger effectiveness. This work shows that heat exchanger costs most often dominate the overall TE system costs, that it is extremely difficult to escape this regime, and in order to achieve TE system costs of $1/W it is necessary to achieve heat exchanger costs of $1/(W/K). Minimum TE system costs per watt generally coincide with maximum power points, but preferred TE design regimes are identified where there is little cost penalty for moving into regions of higher efficiency and slightly lower power outputs. These regimes are closely tied to previously identified low cost design regimes. This work shows that the optimum fill factor Fopt minimizing system costs decreases as heat losses increase, and increases as exhaust mass flow rate and heat exchanger effectiveness increase. These findings have profound implications on the design and operation of various TE waste heat recovery systems. This work highlights the importance of heat exchanger costs on the overall TEG system costs, quantifies the possible TEG performance-cost domain space based on heat exchanger effects, and provides a focus for future system research and development efforts.

A spectral analysis of the domain decomposed Monte Carlo method for linear systems

The domain decomposed behavior of the adjoint Neumann-Ulam Monte Carlo method for solving linear systems is analyzed using the spectral properties of the linear operator. Relationships for the average length of the adjoint random walks, a measure of convergence speed and serial performance, are made with respect to the eigenvalues of the linear operator. In addition, relationships for the effective optical thickness of a domain in the decomposition are presented based on the spectral analysis and diffusion theory. Using the effective optical thickness, the Wigner rational approximation and the mean chord approximation are applied to estimate the leakage fraction of random walks from a domain in the decomposition as a measure of parallel performance and potential communication costs. The one-speed, two-dimensional neutron diffusion equation is used as a model problem in numerical experiments to test the models for symmetric operators with spectral qualities similar to light water reactor problems. In general, the derived approximations show good agreement with random walk lengths and leakage fractions computed by the numerical experiments.

Token-Leakage Tolerant and Vector Obfuscated IPE and Application in Privacy-Preserving Two-Party Point/Polynomial Evaluations

In mobile environments, data stored in nodes are subject to side-channel attacks such as power analysis, emitted signal, detected radiation, etc. In this work, we propose a leakage-resilient inner-product encryption that the decryption will succeed if and only if the decryption attribute vector (generate the token) meets the orthogonal encryption attribute vector (obfuscated encryption policy), that is, the match holds that the inner product of two vectors is zero. Propose scheme supports the security of attribute-hiding and leakage-resilient in the standard model. The adversary cannot only issue any token reveal query on non-match vector, but also can request at most |$\ell $|-bit information on the token-leakage query even if the queried vector matches the challenge vector. We prove the security by the technique of dual system encryption in the orthogonal subgroups, to be strongly leakage-resilient and adaptively attribute-hiding. We also deploy our scheme as a building block to devise a secure two-party point/polynomial evaluation protocol in mobility environments, in which two parties cooperate to evaluate a polynomial in the sense that their sensitive inputs of both point and polynomial are fully preserved. Finally, we assess the performance of leakage resilience including the leakage bound and the leakage fraction (LF). Analysis shows that the leakage bound is approximate |$(n-1)\log {\pi _2}$| and the LF is about |${1}/{2(1+\omega _1+\omega _3)}$|⁠, where |$n$| is the length of vector, |$\pi _2$| is the order of subgroup |$\mathbb {G}_{\pi _2}$| and |$\omega _1,\omega _3$| are the constants. We can obtain optimized LF |$1/2-o(1)$| by varying the sizes of subgroups.

Experimental protection against evolution of states in a subspace via a super-Zeno scheme on an NMR quantum information processor

We experimentally demonstrate the freezing of evolution of quantum states in one- and two-dimensional subspaces of two qubits, on an NMR quantum information processor. State evolution was frozen and leakage of the state from its subspace to an orthogonal subspace was successfully prevented using super-Zeno sequences, comprising of a set of inverting radio frequency (rf) pulses punctuated by pre-selected time intervals. We demonstrate the efficacy of the scheme by preserving different types of states, including separable and maximally entangled states in one- and two-dimensional subspaces of two qubits. The change in the experimental density matrices was tracked by carrying out full state tomography at several time points. We use the fidelity measure for the one-dimensional case and the leakage (fraction) into the orthogonal subspace for the two-dimensional case, as qualitative indicators to estimate the resemblance of the density matrix at a later time to the initially prepared density matrix. For the case of entangled states, we additionally compute an entanglement parameter to indicate the presence of entanglement in the state at different times. We experimentally demonstrate that the super-Zeno scheme is able to successfully confine state evolution to the one- or two-dimensional subspace being protected.