| 42471. |
- Kataeva, Irina, 1980
(författare)
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Superconductor Digital Signal Processor
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Superconductor digital technology based on Rapid Single Flux Quantum logic (RSFQ) offers more than 50 times gain in speed and more than 100 reduction in power consumption over mainstream CMOS devices. However, the necessity of cooling down to 4 K and modest degree of integration density currently available mean that employing RSFQ is reasonable only for the tasks that are impossible or ineffective to implement in CMOS technology. One of the promising applications of the RSFQ technology is Digital Signal Processing (DSP) for telecommunications. Interference cancellation is a bottleneck for all existing systems in terms of the performance gain that is theoretically possible and technically realizable using conventional technology. The crucial factor is computational complexity required to handle multiple access interference. The general approach is to compute the interference using available data about propagation channels and then either remove it from received signal or use to predistort the transmitted signal. Computation of the interference matrix can easily fall into 100 Gops range, furthermore, the most e±cient algorithms are based on successive iterations. This requires not only high overall performance of the DSP but also high actual clock rate.This thesis reports a proposed architecture of an RSFQ Successive Interference Canceller and a design of an RSFQ Digital Signal Processor based on hybrid RSFQ-CMOS memory suitable for a general matrix on matrix multiplication algorithm. The processor consists of an RSFQ Multiply-Accumulate Unit, memory caches and a synchronization block, partitioned into multiple chips, and a large CMOS memory.The complexity of the RSFQ DSP is 10x10 multiplication, rounding to 14 bits, 18 bits accumulator length and 3.7 Kb memory cache. In order to implement the RSFQ DSP, we have developed approach to simulate and describe the RSFQ circuits using VHDL. The maximum simulated clock frequency is equal to 24 GHz for Hypres 4.5 kA/cm2 process and optimum communication bandwidth with CMOS memory is 2 Gbps.Components of the processor such as 4x4 two's complement and 5x5 parallel multipliers, 4x5, 20x5 and 4x15 parallel shift registers, a 5-bit serial adder have been designed and experimentally tested. The simplified version of the RSFQ DSP consisting of a 4x4 MAC with rounding to 5 bits and 17x6 memory caches has been designed for Hypres 4.5 kA/cm2 process and fabricated.
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| 42472. |
- Katayama, Tohru, et al.
(författare)
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Trends in Systems and Signals
- 2005
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Ingår i: Proc. 16th IFAC World Congress, Selected Plenaries, Milestones and Surveys. ; , s. 111-121
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Konferensbidrag (refereegranskat)
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| 42473. |
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| 42474. |
- Kateb, Movaffaq, 1985, et al.
(författare)
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Epitaxial growth and characterization of (001) [NiFe/M]20 (M = Cu, CuPt and Pt) superlattices
- 2023
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Ingår i: Surfaces and Interfaces. - : Elsevier BV. - 2468-0230. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- We present optimization of [(15 Å) Ni80Fe20/(5 Å) M]20 single crystal multilayers on (001) MgO substrates, with M being Cu, Cu50Pt50 and Pt. These superlattices were characterized by high resolution X-ray reflectivity (XRR) and diffraction (XRD) as well as polar mapping of important crystal planes. It is shown that cube on cube epitaxial relationship can be obtained when depositing at substrate temperature of 100 °C regardless of the lattice mismatch (5% and 14% for Cu and Pt, respectively). At lower substrate temperatures poly-crystalline multilayers were obtained while at higher substrate temperatures {111} planes appear at ∼10° off normal to the film plane. It is also shown that as the epitaxial strain increases, the easy magnetization axis rotates towards the direction that previously was assumed to be harder, i.e. from [110] to [100], and eventually further increase in the strain makes the magnetic hysteresis loops isotropic in the film plane. Higher epitaxial strain is also accompanied with increased coercivity values. Thus, the effect of epitaxial strain on the magnetocrystalline anisotropy is much larger than what was observed previously in similar, but polycrystalline samples with uniaxial anisotropy (Kateb et al. 2021).
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| 42475. |
- Kateb, Movaffaq, 1985, et al.
(författare)
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Nanoscale Elasto-Capillarity in the Graphene-Water System under Tension: Revisiting the Assumption of a Constant Wetting Angle
- 2023
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Ingår i: Langmuir. - 1520-5827 .- 0743-7463. ; 39, s. 12610-12617
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Tidskriftsartikel (refereegranskat)abstract
- Wetting highly compliant surfaces can cause them to deform. Atomically thin materials, such as graphene, can have exceptionally small bending rigidities, leading to elasto-capillary lengths of a few nanometers. Using large-scale molecular dynamics (MD), we have studied the wetting and deformation of graphene due to nanometer-sized water droplets, focusing on the wetting angle near the vesicle transition. Recent continuum theories for wetting of flexible membranes reproduce our MD results qualitatively well. However, we find that when the curvature is large at the triple-phase contact line, the wetting angle increases with decreasing tension. This is in contrast to existing macroscopic theories but can be amended by allowing for a variable wetting angle.
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| 42476. |
- Kathiresan, S., et al.
(författare)
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Polymorphisms associated with cholesterol and risk of cardiovascular events
- 2008
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Ingår i: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 358:12, s. 1240-1249
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Tidskriftsartikel (refereegranskat)abstract
- Background: Common single-nucleotide polymorphisms (SNPs) that are associated with blood low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol modestly affect lipid levels. We tested the hypothesis that a combination of such SNPs contributes to the risk of cardiovascular disease. Methods: We studied SNPs at nine loci in 5414 subjects from the cardiovascular cohort of the Malmo Diet and Cancer Study. We first validated the association between SNPs and either LDL or HDL cholesterol and subsequently created a genotype score on the basis of the number of unfavorable alleles. We used Cox proportional-hazards models to determine the time to the first cardiovascular event in relation to the genotype score. Results: All nine SNPs showed replication of an association with levels of either LDL or HDL cholesterol. With increasing genotype scores, the level of LDL cholesterol increased from 152 mg to 171 mg per deciliter (3.9 to 4.4 mmol per liter), whereas HDL cholesterol decreased from 60 mg to 51 mg per deciliter (1.6 to 1.3 mmol per liter). During follow-up (median, 10.6 years), 238 subjects had a first cardiovascular event. The genotype score was associated with incident cardiovascular disease in models adjusted for covariates including baseline lipid levels (P<0.001). The use of the genotype score did not improve the clinical risk prediction, as assessed by the C statistic. However, there was a significant improvement in risk classification with the use of models that included the genotype score, as compared with those that did not include the genotype score. Conclusions: A genotype score of nine validated SNPs that are associated with modulation in levels of LDL or HDL cholesterol was an independent risk factor for incident cardiovascular disease. The score did not improve risk discrimination but did modestly improve clinical risk reclassification for individual subjects beyond standard clinical factors.
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| 42477. |
- Kati, Maliheh Sadeghi, et al.
(författare)
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Robust Static Output Feedback With Dynamic Disturbance Feed-Forward for Lateral Control of Long-Combination Vehicles at High Speeds
- 2023
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Ingår i: Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME. - : ASME International. - 0022-0434 .- 1528-9028. ; 145:3
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Tidskriftsartikel (refereegranskat)abstract
- A control strategy is proposed to improve the high-speed lateral performance of an A double (tractor-semitrailer-dolly-semitrailer) combination vehicle using active steering of the dolly axles. The strategy is realized as an H1-type static output feedback (SOFB) based on a previous work, combined with dynamic disturbance feed-forward (DDFF). In order to synthesize DDFF in a way to facilitate performance improvement in practical problems, the disturbance is accurately characterized with the use of a dynamic weighting filter. As a contribution to the existing literature, novel linear matrix inequality (LMI) conditions are derived for this case, which facilitate the synthesis of a robust DDFF controller when the plant depends on uncertain time-varying parameters. An alternative DDFF synthesis method is also provided based on an adaptation of a previous work. The proposed overall controller has a simple structure and is easy to implement from a practical point of view since it requires only the driver steering angle (for feed-forward) and just one articulation angle measurement (for feedback). Obtained using a high-fidelity vehicle model, the simulation results for an example synthesis confirm a significant reduction in the rearward amplifications of the yaw rate and the lateral acceleration as well as the high-speed transient off-tracking during sudden lane change maneuvers.
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| 42478. |
- Katins, Christopher, et al.
(författare)
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Assessing User Apprehensions About Mixed Reality Artifacts and Applications: The Mixed Reality Concerns (MRC) Questionnaire
- 2024
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Ingår i: Conference on Human Factors in Computing Systems - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Current research in Mixed Reality (MR) presents a wide range of novel use cases for blending virtual elements with the real world. This yet-to-be-ubiquitous technology challenges how users currently work and interact with digital content. While offering many potential advantages, MR technologies introduce new security, safety, and privacy challenges. Thus, it is relevant to understand users' apprehensions towards MR technologies, ranging from security concerns to social acceptance. To address this challenge, we present the Mixed Reality Concerns (MRC) Questionnaire, designed to assess users' concerns towards MR artifacts and applications systematically. The development followed a structured process considering previous work, expert interviews, iterative refinements, and confirmatory tests to analytically validate the questionnaire. The MRC Questionnaire offers a new method of assessing users' critical opinions to compare and assess novel MR artifacts and applications regarding security, privacy, social implications, and trust.
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| 42479. |
- Katke, C., et al.
(författare)
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Colony-like Protocell Superstructures
- 2023
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Ingår i: Acs Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 17:4, s. 3368-3382
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Tidskriftsartikel (refereegranskat)abstract
- We report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments. We show that the model colonies encapsulate DNA and accommodate nonenzymatic, strand displacement DNA reactions. The membrane envelope is able to disassemble and expose individual daughter protocells, which can migrate and attach via nano tethers to distant surface locations, while maintaining their encapsulated contents. Some colonies feature "exocompartments", which spontaneously extend out of the enveloping bilayer, internalize DNA, and merge again with the superstructure. A continuum elastohydrodynamic theory that we developed suggests that a plausible driving force behind subcompartment formation is attractive van der Waals (vdW) interactions between the membrane and surface. The balance between membrane bending and vdW interactions yields a critical length scale of 236 nm, above which the membrane invaginations can form subcompartments. The findings support our hypotheses that in extension of the "lipid world hypothesis", protocells may have existed in the form of colonies, potentially benefiting from the increased mechanical stability provided by a superstructure.
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| 42480. |
- Kato, H., et al.
(författare)
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Z/E-photoisomerizations of olefins with 4nπ- or (4n + 2)π-electron substituents: Zigzag variations in olefin properties along the T1 state energy surfaces
- 2005
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 70:23, s. 9495-9504
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Tidskriftsartikel (refereegranskat)abstract
- A quantum chemical study has been performed to assess changes in aromaticity along the T1 state Z/E-isomerization pathways of annulenyl-substituted olefins. It is argued that the point on the T1 energy surface with highest substituent aromaticity corresponds to the minimum. According to Baird (J. Am. Chem. Soc. 1972, 94, 4941), aromaticity and antiaromaticity are interchanged when going from S0 to T1. Thus, olefins with S0 aromatic substituents (set A olefins) will be partially antiaromatic in T1 and vice versa for olefins with S 0 antiaromatic substituents (set B olefins). Twist of the C=C bond to a structure with a perpendicular orientation of the 2p(C) Orbitals ( 3p*) in T1 should lead to regaining substituent aromaticity in set A and loss of aromaticity in set B olefins. This hypothesis is verified through quantum chemical calculations of T1 energies, geometries (bond lengths and harmonic oscillator measure of aromaticity), spin densities, and nucleus independent chemical shifts whose differences along the T1 PES display zigzag dependencies on the number of π-electrons in the annulenyl substituent of the olefin. Aromaticity changes are reflected in the profiles of the T1 potential energy surfaces (T1 PESs) for Z/E-isomerizations because olefins in set A have minima at 3p* whereas those in set B have maxima at such structures. The proper combination (fusion) of the substituents of set A and B olefins could allow for design of novel optical switch compounds that isomerize adiabatically with high isomerization quantum yields.
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