Constant Factor Research Articles

Dielectric Properties and Microwave Absorbing Properties of Silicon Carbide Nanoparticles and Silicon Carbide Nanowhiskers

Silicon carbide (SiC) is well known for their outstanding microwave absorbing properties. SiC nanomaterials (SiCNMs) are expected to have better microwave absorption performance due to their high specific surface area. To date, no study was reported to compare the dielectric properties and microwave absorbing properties of different type of SiCNMs. Therefore, the objective of this paper is to compare the dielectric properties and microwave absorption properties of different types of SiCNMs. In this paper, SiC nanoparticles (SiCNPs) and SiC nanowhiskers (SiCNWs) were characterised using SEM and XRD. In addition, their dielectric properties and microwave absorbing properties were measured using network analyser and transmission line theory. It was found that SiCNWs achieved higher dielectric constant and loss factor which are and εr’ =17.94 and εr″ = 2.64 compared to SiCNPs that only achieved εr’ = 2.83 and εr″ = 0.71. For microwave absorbing properties, SiCNWs and SiCNPs attained minimum reflection loss of -10.41 dB and -6.83 dB at 5.68 GHz and 17.68 GHz, respectively. The minimum reflection loss of SiCNPs and SiCNWs obtained in this study is much lower than the nanometer-SiC reported previously. These results suggested that SiCNWs can be an ideal candidate of microwave susceptors for various microwave applications.

Degree-Constrained Minimum Spanning Hierarchies in Graphs

The minimum spanning tree problem in graphs under budget-type degree constraints (DCMST) is a well-known NP-hard problem. Spanning trees do not always exist, and the optimum can not be approximated within a constant factor. Recently, solutions have been proposed to solve degree-constrained spanning problems in the case of limited momentary capacities of the nodes. For a given node, the constraint represents a limited degree of the node for each visit. Finding the solution with minimum cost is NP-hard and the related algorithms are not trivial. This paper focuses on this new spanning problem with heterogeneous capacity-like degree bounds. The minimum cost solution corresponds to a graph-related structure, i.e., a hierarchy. We study the conditions of its existence, and we propose its exact computation, a heuristic algorithm, and its approximation.

Dielectric Heating Protocol of Three Low Moisture Flours as Affected by Moisture, Temperature and Mass at 2.45 and 5.8 GHz

ABSTRACT Present studies investigate the dielectric properties (dielectric constant and dielectric loss factor) of three low moisture flours (barley, chickpea and wheat) in the moisture content range 2%–10% (w. b.) and temperatures 10°C–60°C at 2.45 and 5.8 GHz. Measurements were taken using cavity perturbation method in conjunctions with Vector Network Analyzer. Results show that dielectric constant and loss factor increased with temperature as well as moisture content both at 2.45 and 5.8 GHz but decreased with increase in frequency. Change in mass of all flours during heating does not affect dielectric properties at both frequencies. A second order regression equation is generated to predict dielectric properties at both frequencies for entire temperature and moisture. Penetration depths of all flours decreased with increase in moisture content and temperature at 2.45 and 5.8 GHz. These studies provide valuable insights to heating protocol of flours in view of recent flours-related disease outbreaks.

Computing Orientations from the Endomorphism Ring of Supersingular Curves and Applications

This work introduces several algorithms related to the computation of orientations in endomorphism rings of supersingular elliptic curves. This problem is at the heart of several results regarding the security of oriented-curves in isogeny-based cryptography. Under the Deuring correspondence, it can be expressed purely in terms of quaternion and boils down to representing integers by ternary quadratic forms. Our main contribution is to show that there exist efficient algorithms to solve this problem for quadratic orders of discriminant n up to O ( p 4 / 3 ) . Our approach improves upon previous results by increasing this bound from O ( p ) to O ( p 4 / 3 ) and removing some heuristics. We introduce several variants of our new algorithm and provide a careful analysis of their asymptotic running time (without heuristic when it is possible). The best proven asymptotic complexity of one of our variants is O ( n 3 / 4 / p ) in average. The best heuristic variant has a complexity of O ( p 1 / 3 ) for big enough n . We then introduce several results regarding the computation of ideals between oriented orders. The first application of this is a simplification of the known reduction from vectorization to computing the endomorphism ring, removing the assumption on the factorization of the discriminant. As a second application, we relate the problem of computing fixed-degree isogenies between supersingular curves to the problem of computing orientations in endomorphism rings, and we show that for a large range of degree d , our new algorithms improve on the state-of-the-art, and in important special cases, the range of degree d for which there exist a polynomial-time algorithm is increased. In the most special case we consider, when both curves are oriented by a small degree endomorphism, we show heuristically that our techniques allow the computation of isogenies of any degree, assuming they exist.

Quantum Procedures for Nested Search Problems

In this paper we study search problems that arise very often in cryptanalysis: nested search problems, where each search layer has known degrees of freedom and/or constraints. A generic quantum solution for such problems consists of nesting Grover's quantum search algorithm or amplitude amplification (QAA) by Brassard et al., obtaining up to a square-root speedup on classical algorithms. However, the analysis of nested Grover or QAA is complex and introduces technicalities that in previous works are handled in a case-by-case manner. Moreover, straightforward nesting of l layers multiplies the complexity by a constant factor (pi/2)^l. In this paper, we aim to remedy both these issues and introduce a generic framework and tools to transform a classical nested search into a quantum procedure. It improves the state-of-the-art in three ways: 1) our framework results in quantum procedures that are significantly simpler to describe and analyze; 2) it reduces the overhead factor from (pi/2)^l to sqrt(l); 3) it is simpler to apply and optimize, without needing manual quantum analysis. We give generic complexity formulas and show that for concrete instances, numerical optimizations enable further improvements, reducing even more the gap to an exact quadratic speedup. We demonstrate our framework by giving a tighter analysis of quantum attacks on reduced-round AES.

Memory adds no cost to lattice sieving for computers in 3 or more spatial dimensions

The security of lattice-based crytography (LWE, NTRU, and FHE) depends on the hardness of the shortest-vector problem (SVP). Sieving algorithms give the lowest asymptotic runtime to solve SVP, but depend on exponential memory. Memory access costs much more in reality than in the RAM model, so we consider a computational model where processors, memory, and meters of wire are in constant proportions to each other. While this adds substantial costs to route data during lattice sieving, we modify existing algorithms to amortize these costs and find that, asymptotically, a classical computer can achieve the previous RAM model cost of 2 0.2925 d + o ( d ) to sieve a d -dimensional lattice for a computer existing in 3 or more spatial dimensions, and can reach 2 0.3113 d + o ( d ) in 2 spatial dimensions, where “spatial dimensions” are the dimensions of the physical geometry in which the computer exists. Since this result implies an increased cost in 2 spatial dimensions, we make several assumptions about the constant terms of memory access and lattice attacks so that we can give bit security estimates for Kyber and Dilithium. These estimates support but do not increase the security categories claimed in the Kyber and Dilithium specifications, at least with respect to known attacks.

Efficient Maliciously Secure Oblivious Exponentiations

Oblivious Pseudorandom Functions (OPRFs) allow a client to evaluate a pseudorandom function (PRF) on her secret input based on a key that is held by a server. In the process, the client only learns the PRF output but not the key, while the server neither learns the input nor the output of the client. The arguably most popular OPRF is due to Naor, Pinkas and Reingold (Eurocrypt 2009). It is based on an Oblivious Exponentiation by the server, with passive security under the Decisional Diffie-Hellman assumption. In this work, we strengthen the security guarantees of the NPR OPRF by protecting it against active attacks of the server. We have implemented our solution and report on the performance. Our main result is a new batch OPRF protocol which is secure against maliciously corrupted servers, but is essentially as efficient as the semi-honest solution. More precisely, the computation (and communication) overhead is a multiplicative factor o ( 1 ) as the batch size increases. The obvious solution using zero-knowledge proofs would have a constant factor overhead at best, which can be too expensive for certain deployments. Our protocol relies on a novel version of the DDH problem, which we call the Oblivious Exponentiation Problem (OEP), and we give evidence for its hardness in the Generic Group model. We also present a variant of our maliciously secure protocol that does not rely on the OEP but nevertheless only has overhead o ( 1 ) over the known semi-honest protocol. Moreover, we show that our techniques can also be used to efficiently protect threshold blind BLS signing and threshold ElGamal decryption against malicious attackers.

Weight-Reduced Stabilizer Codes with Lower Overhead

Stabilizer codes are the most widely studied class of quantum error-correcting codes and form the basis of most proposals for a fault-tolerant quantum computer. A stabilizer code is defined by a set of parity-check operators, which are measured in order to infer information about errors that may have occurred. In typical settings, measuring these operators is itself a noisy process and the noise strength scales with the number of qubits involved in a given parity check, or its weight. Hastings has proposed a method for reducing the weights of the parity checks of a stabilizer code, though it has previously only been studied in the asymptotic regime. Here, we instead focus on the regime of small to medium-size codes suitable for quantum computing hardware. We both provide a fully explicit description of Hastings’s method and propose a substantially simplified weight-reduction method that is applicable to the class of quantum product codes. Our simplified method allows us to reduce the check weights of hypergraph- and lifted-product codes to at most six, while preserving the number of logical qubits and at least retaining (in fact, often increasing) the code distance. The price we pay is an increase in the number of physical qubits by a constant factor but we find that our method is much more efficient than Hastings’s method in this regard. We benchmark the performance of our codes on a simulated photonic quantum computing architecture based on Gottesman-Kitaev-Preskill qubits and passive linear optics, finding that our weight-reduction method substantially improves code performance. Published by the American Physical Society 2024

Experimental and numerical analysis of the vibrational behaviour of metallic structures filled with damping materials

This work focuses on characterizing and modeling the vibrational behavior of hollow metallic structures filled with damping material. Vibration tests are first carried on a hollow structure, then two filling materials are considered: a cast viscoelastic material and a granular material composed of epoxy and polyurethane beads. Modal parameters (natural frequencies, modal damping and mode shapes) are extracted from the Frequency Response Functions with experimental modal analysis tools. Damping ratios greater than 5~\% are measured. Given the difference in the nature of the filling materials, dissipation mechanisms are different. The effectiveness of a damping material depends on the type of structural modes (bending, torsion or wall mode) to be damped, and dissipation in filling materials cannot be modelled by a constant loss factor or viscous damping. Consequently, a finite element modeling of the structure filled with viscoelastic material is proposed. Numerical modal parameters of the structure are correlated with experimental measurements. By extension, a bead mix material law, based on a fractional Zener model, is proposed, whose parameters are obtained by inverse identification.

Tight conic approximation of testing regions for quantum statistical models and measurements

Quantum statistical models (i.e., families of normalized density matrices) and quantum measurements (i.e., positive operator-valued measures) can be regarded as linear maps: the former, mapping the space of effects to the space of probability distributions; the latter, mapping the space of states to the space of probability distributions. The images of such linear maps are called the testing regions of the corresponding model or measurement. Testing regions are notoriously impractical to treat analytically in the quantum case. Our first result is to provide an implicit outer approximation of the testing region of any given quantum statistical model or measurement in any finite dimension: namely, a region in probability space that contains the desired image, but is defined implicitly, using a formula that depends only on the given model or measurement. The outer approximation that we construct is minimal among all such outer approximations, and close, in the sense that it becomes the maximal inner approximation up to a constant scaling factor. Finally, we apply our approximation to provide sufficient conditions, that can be tested in a semi-device-independent way, for the ability to transform one quantum statistical model or measurement into another.

A Simple Online Tuning Flux Weighting Factor in Finite Control Set – Predictive Torque Control for Induction Motor Drive

The Finite Control Set-Predictive Torque Control (FSC-PTC) is a practical and intuitive method to control an Induction Motor (IM). However, the challenge of this technique is the difficulty of tuning the weighting factor so that it performs optimally at all speeds. Hence, this paper proposes a new method for improving the optimization technique by automatically tuning the weighting factor using a flux controller. The flux controller is represented as a DC gain and designed to be proportional to the absolute value of the predicted stator flux error. This method eliminates the need for complex computation to select the suitable weighting factor while also efficiently regulating flux and torque. The proposed method is experimentally validated on a DS1104 controller board and compared to a constant flux weighting factor method that was tested under speed conditions. The results demonstrate that the new method can further decrease the torque ripple compared to the constant weighting factor while maintaining the flux ripple and harmonic distortion limits.

Phase transition suppression, thermal and electrical properties of (YNb)0.2Zr0.6P2O7

ZrP2O7 is a promising material with excellent thermal and electrical properties. However, when temperature approaches to 563 K, it undergoes a structural phase transition, which will cause large thermal stresses. When Zr is substituted by Y and Nb, a new material of (YNb)0.2Zr0.6P2O7, was successfully prepared and the phase transition of material was effectively inhibited. This new material adopts a cubic structure similar to ZrP2O7, and exhibits medium thermal expansion (α = 7.1×10-6 K-1) in the measured range of 200-1073 K. The values of thermal conductivity from RT to 973 K are between 0.4474 W·m-1·K-1 and 0.8526 W·m-1·K-1, which can be comparable to the values of traditional thermal insulation materials. The dielectric constant and dielectric loss factor at the frequencies above 1 MHz are stable and low. The electrical conductivity of the material indicates that it is electronically insulating at RT-573 K.

Korvais in Karnatak Music - Improvisation through Training

Korvai is a Tamil word meaning joining or beading. When rhythmic syllables are joined or beaded together in a logical development and culminate in a structural format of definable Purvanga and Uttaranga then they can be termed as Korvai. Korvais form an essential part of every Karnatak concert. They are being extensively used by Vocalists, Instrumentalists and various types of percussion artistes also. Since, Korvai is an integral and important aspect of a concert, there is a necessity to analyze the process of making them and also quantify them for easier approaches to its various types. There are two parts in a Korvai, that are generally being used to identify them distinctively. They are Purvanga (the first part or the introductory part) and Uttaranga (the ending part or the subsequent part). The purvanga and uttaranga are constant factors irrespective of the rhythmic structure or Tala structure. Same Purvanga can be used with different Uttarangas for same tala or extended to other talas as well. Such being the case, the purvangas and uttarangas are clearly quantifiable in terms of numbers and rhythmic phrases or combination of phrases. When a number is being used, there can be logical build up and hence this article explores such logical build-up using numbers in a structured way converted as cognizable rhythmic varieties. Talas are cyclical in nature having specified fixed number of beats per cycle. For a tala which is having 9 beats per cycle, the total number for 3 or 4 cycles can be calculated by simple multiplication. For example, for 4 cycles the total would be 36 beats. Whenever calculations are made mostly they are done on either as number of beats or on pulses. Both methods can be employed for quick results. In the above case, there were 36 beats which can give us 144 pulses (36 X 4).The purvanga can be anything like 108 and the uttaranga can be 36. The general ratio of purvanga and uttaranga could be 60:40 or 70:30 for. Longer Purvangas of 90:10 or shorter purvangas of 20:80 are generally not preferred. This article also covers various examples where different combinations are improvised. Different types of korvais can also be made using such improvisations.

Numerical investigation of the late-time tails of the solutions of the Fackerell–Ipser equation

The late-time behaviour of the solutions of the Fackerell–Ipser equation (which is a wave equation for the spin-zero component of the electromagnetic field strength tensor) on the closure of the domain of outer communication of sub-extremal Kerr spacetime is studied numerically. Within the Kerr family, the case of Schwarzschild background is also considered. Horizon-penetrating compactified hyperboloidal coordinates are used, which allow the behaviour of the solutions to be observed at the event horizon and at future null infinity as well. For the initial data, pure multipole configurations that have compact support and are either stationary or non-stationary are taken. It is found that with such initial data the solutions of the Fackerell–Ipser equation converge at late times either to a known static solution (up to a constant factor) or to zero. As the limit is approached, the solutions exhibit a quasinormal ringdown and finally a power-law decay. The exponents characterizing the power-law decay of the spherical harmonic components of the field variable are extracted from the numerical data for various values of the parameters of the initial data, and based on the results a proposal for a Price’s law relevant to the Fackerell–Ipser equation is made. Certain conserved energy and angular momentum currents are used to verify the numerical implementation of the underlying mathematical model. In the construction of these currents a discrete symmetry of the Fackerell–Ipser equation, which is the product of an equatorial reflection and a complex conjugation, is also taken into account.

Assessing wind turbine blade durability longevity utilizing national renewable energy laboratory tools

With the escalating significance of renewable energy, there exists a pressing demand for precise software and tools capable of designing and forecasting wind turbine blade service life. OpenFAST, TurbSim, and MLife are pivotal open-source wind turbine simulation tools that integrate aerodynamics, structural dynamics, wind simulation, and control systems. They enable accurate prediction of wind turbine performance. This study aims to leverage these software resources to model turbulent wind conditions using predefined basic parameters and then calculate fatigue and longevity of the wind turbine blade to determine service life. Particularly, MLife was employed for rose loading, enhancing the fidelity of the loading cycle simulation. Collaboration between the National Renewable Energy Laboratory and the research team played a crucial role in establishing a foundational baseline and implementing realistic input parameters for evaluating the ultimate load, determining damage equivalent loads (DEL), and projecting service life. In all simulations, a constant factor of safety (FOS) of 1.5 was consistently applied. Additionally, Finite Element Analysis (FEA) was employed to validate our numerical experiments, ensuring the accuracy of the obtained results by correlating simulation outcomes with real-world scenarios, further strengthening the credibility of the study.

Rare earth samarium substituted barium-calcium hexaferrites: Insight into structure, dielectric and magnetic aspects

This study presents the synthesis of samarium-substituted Ba-Ca hexaferrites (Ba0.5Ca0.5Fe12-xSmxO19) utilizing the sol–gel method. X-ray diffraction (XRD) analysis is performed to evaluate the structure of fabricated materials. The lattice shows an expansion up to a doping concentration of x = 0.12, and minor contraction at x = 0.16. Both X-ray density and bulk density exhibit an upward trend with increasing doping levels, while porosity reduces and dislocation density shows an increase. Scanning electron microscopy (SEM) confirms the homogeneity and uniformity of the doped samples. The dielectric properties displays the interaction of the materials with an external electric field, revealing that the dielectric constant (ε′), dielectric loss (ε″), and dissipation factor progressively increases with samarium concentration. Magnetic characterizations demonstrate a significant enhancement in saturation magnetization and coercivity, attaining peak values of 33.19 emu/g and 1.805 kOe, respectively. Moreover, the anisotropy field (Ha) and anisotropy constant (K) shows an increase with higher doping concentrations confirming the prepared material as an alternative for electric and magnetic industry applications.

Low N2O emissions induced by root-derived residues compared to aboveground residues of red clover or grass mixed into soil

The default The Intergovernmental Panel on Climate Change (IPCC) guidelines assume a constant N2O emission factor (EFN2O) for both belowground crop residues (BGR) and aboveground residues (AGR), and that ∼70 % of total N2O emissions following renewal of temporary grasslands come from BGR. However, empirical evidence is lacking, which motivated this study. BGR-free and BGR-rich clay loam collected in grass or red clover leys were incubated alone or mixed with AGR and different doses of nitrate over 107 days. The average EFN2O of BGR was around 18 % of that of AGR, and remained low even when soil nitrate concentration was very high, whereas EFN2O of AGR varied largely and rocketed even with a small increase in soil nitrate. The decomposition of the carbon present in crop residues was critical for N2O emissions. Lower EFN2O of BGR relative to AGR were related to slower C decomposition, which was not predicted by the biochemical characteristics. It is also likely that BGR were less conducive than AGR to develop into hotspots for N2O emission because of the roots’ finer distribution and closer contact with soil particles. Differences in EFN2O among AGR were mostly linked to the availability of N, either derived from residue mineralization or present in the soil. In conclusion, N2O accountings based on present IPCC default methodology likely overestimate the contribution by crops’ BGR.

Microwave cavity antenna for automatic detection of chicken breast muscles affected by wooden breast defect

Over the past years, artificial selection for meat-type (broiler) chickens has resulted in improved production efficiency, but also in an increased incidence of skeletal muscle abnormalities. In particular, wooden breast (WB) abnormality causes abrupt changes in meat quality and enormous economic losses. Thus, the poultry processing industry requires a reliable method to detect the abnormality in production lines in a non-destructive and contactless way. The present research aimed to evaluate the effect of WB on dielectric properties to develop a potential online technique to distinguish unaffected from affected breasts. Sixty-five pectoralis major muscles were picked 3 h post-mortem from the same flock (42-day-old broilers, 2.8 kg average live weight) and classified by visual inspection according to their phenotype as normal (N, not showing not any signs of the WB condition; n = 33) or WB (exhibiting extensive hardened areas and stiffness perceived by manual palpation throughout the entire fillet; n = 32). WB muscles exhibited remarkably higher values of dielectric constant and loss factor in a wide range of the explored frequencies (200 MHz–14 GHz), suggesting higher water mobility and a higher solvate capacity; this makes the electromagnetic technique for classification promising. Based on the above evidence, a rapid microwave electric technique in the range 1.5 GHz–3 GHz was developed for the online detection of WB. Indeed, combining the use of a cavity antenna (vector network analyzer instrumental chain with partial least square – discriminant analysis), this technique correctly classified 100% of the validation test set.

Theory of Classical Electrodynamics with Topologically Quantized Singularities as Electric Charges

AbstractA theory of classical electrodynamics, where the only admissible electric charges are topological singularities in the electromagnetic field, is formulated. Charge quantization is accounted by the Chern theorem, such that Dirac magnetic monopoles are not needed. The theory allows positive and negative charges of equal magnitude, where the sign of the charge corresponds to the chirality of the topological singularity. Given the trajectory of the singularity, one can calculate electric and magnetic fields identical to those produced by Maxwell's equations for a moving point charge, apart from a multiplicative constant factor related to electron charge and vacuum permittivity. The theory is based on the relativistic Weyl equation in frequency‐wavevector space, with eigenstates comprising the position, velocity, and acceleration of the singularity, and eigenvalues defining the retarded position of the charge. From the eigenstates, one calculates the Berry connection and the Berry curvatures, and identifies the curvatures as electric and magnetic fields.

The equivalent conditions for norm of a Hilbert-type integral operator with a combination kernel and its applications

Introducing adaptation parameters σ,σ1, formal parameters λi(i=1,2,3,4),κ,τ, and type parameters μ,ν, the integration operator is defined as T:Lpp(1−μσˆ)−1(R+)→Lppνσˆ−1(R+), Tf(y)=∫R+eλ1xμyν+κe−λ2xμyνeλ3xμyν+τe−λ4xμyνf(x)dx,y∈R+. Using the weight function method, a general Hilbert-type integral inequality is obtained, thereby proving the boundedness of the operator. The constant factor of the general Hilbert-type inequality is the best possible if and only if the adaptation parameters satisfy σ=σ1. From this, the formula for calculating the operator norm is obtained. In terms of application, some results from the references have been consolidated by discussing the combination of formal parameters and type parameters, and many new operator inequalities of different types and forms have been derived.