Critical Point Analysis Research Articles

Analysis and Realization of Critical Points on Hardware Design of FPGA

FPGA is one kind of important devices that can realize many functions. As the development of communication technology and computer science, more and more technologies are invented and more and more hardware design technologies are sifted out. Therefore, the hardware design based on ASIC can be not fit on the new theories realization. As a new device, FPGA has many advantages including strength function, shorter design circle, less money, more flexible and more intelligent design tools. More and More hardware designs of FPGA are pay more attentions. Therefore, it is significant to make analysis on hardware design of FPGA. The hardware design for FPGA will be related to the FPGA device. In the market Altera and Xilinx FPGAs are used frequently by engineers. Therefore, in this dissertation will be make analysis and realization the critical points in hardware design based on Xilinx FPGA. In this dissertation, the critical point of Hardware Design of FPGA will be described. It will include power source, impedance matching and clock circuit design. There are many hardware design tools used for hardware design including Altium Designer, Protel, Cadence and others. Compared with other design tools, Cadence will have more advantages. Therefore, in this dissertation, Cadence will be used as the design tool for hardware design analysis and realization. With the help of Cadence, one hardware design and signal transmission simulation will be made analysis. With the development of the micro-electronics technology and computer science, the hardware design about FPGA will be taken more and more attentions.

Implementación del análisis de riesgo en la industria alimentaria mediante la metodología AMEF: enfoque práctico y conceptual

El análisis de riesgo mediante el Análisis Modal de Efectos y Fallas (AMEF) se aplicó y se incorporó en conjunto con el Análisis de Peligros y Puntos Críticos de Control (HACCP) para establecer la evaluación de riesgos en una maquiladora de pavo deshuesado. En este trabajo se calculó y se predijo, por medio de la significancia del riesgo, la importancia de establecer medidas preventivas en las etapas de proceso más vulnerables. El cálculo de la significancia se realizó obteniendo el Índice de Criticidad (IC). Los puntos críticos de control se establecieron con la metodología del árbol de decisiones, que se enfocó en aquellas etapas que mostraron tener los valores más altos relativos al IC. Las principales causas posibles que generan una desviación de los puntos críticos de control fueron enlistadas y analizadas a través de un análisis causa-raíz, con el uso del diagrama de Ishikawa. La integración del análisis de riesgo dentro de un plan HACCP demostró proveer amplias ventajas que facilitan el control de los procesos de manufactura y el aseguramiento de la salud pública a los consumidores finales, al generar alimentos inocuos y de alta calidad, al tiempo que mejora el desempeño operacional del ciclo productivo. Se identificaron las etapas de almacenamiento y descongelación como los principales segmentos con tendencia a mostrar altos valores de IC. Las acciones correctivas sugeridas bajaron notablemente los valores del IC por debajo del límite aceptable. Los resultados del presente estudio muestran claramente la importancia de la incorporación de un buen sistema de control sistemático para la gestión de riesgos en la industria avícola.

Challenges in Performance of Food Safety Management Systems: A Case of Fish Processing Companies in Tanzania

This study provides insight for food safety (FS) performance in light of the current performance of core FS management system (FSMS) activities and context riskiness of these systems to identify the opportunities for improvement of the FSMS. A FSMS diagnostic instrument was applied to assess the performance levels of FSMS activities regarding context riskiness and FS performance in 14 fish processing companies in Tanzania. Two clusters (cluster I and II) with average FSMS (level 2) operating under moderate-risk context (score 2) were identified. Overall, cluster I had better (score 3) FS performance than cluster II (score 2 to 3). However, a majority of the fish companies need further improvement of their FSMS and reduction of context riskiness to assure good FS performance. The FSMS activity levels could be improved through hygienic design of equipment and facilities, strict raw material control, proper follow-up of critical control point analysis, developing specific sanitation procedures and company-specific sampling design and measuring plans, independent validation of preventive measures, and establishing comprehensive documentation and record-keeping systems. The risk level of the context could be reduced through automation of production processes (such as filleting, packaging, and sanitation) to restrict people's interference, recruitment of permanent high-skilled technological staff, and setting requirements on product use (storage and distribution conditions) on customers. However, such intervention measures for improvement could be taken in phases, starting with less expensive ones (such as sanitation procedures) that can be implemented in the short term to more expensive interventions (setting up assurance activities) to be adopted in the long term. These measures are essential for fish processing companies to move toward FSMS that are more effective.

Dielectric function spectra and inter-band optical transitions in TlGaS2

TlGaS2 with a quasi-two-dimensional structure has been accessed by spectroscopic ellipsometry over the 1.5–6.0eV spectral range. A uniaxial approach applicable to monoclinic TlGaS2 at room temperature has been employed for ellipsometric data treatment. Principal components of the dielectric function tensor have then been retrieved. Inter-band optical transitions associated with the obtained dielectric function have been determined by using standard critical point analysis. The transitions have been assigned within the electronic band structure obtained for TlGaS2 from calculations based on density functional theory.

Hydrogen Bond Cooperativity in Water Hexamers: Atomic Energy Perspective of Local Stabilities

Atomic energies are used to describe local stability in eight low-lying water hexamers: prism, cage, boat 1, boat 2, bag, chair, book 1, and book 2. The energies are evaluated using the quantum theory of atoms in molecules (QTAIM) at MP2/aug-cc-pVTZ geometries. It is found that the simple, stabilizing cooperativity observed in linear hydrogen-bonded water systems is diminished as clusters move from nearly planar to three-dimensional structures. The prism, cage, and bag clusters can have local water stabilities differing up to 5 kcal mol(-1) as a result of mixed cooperative and anticooperative interactions. At the atomic level, in many cases a water may have a largely stabilized oxygen atom but the net water stability will be diminished due to strong destabilization of the water's hydrogen atoms. Analysis of bond critical point (BCP) electron densities shows that the reduced cooperativity results in a decrease in hydrogen bond strength and an increase in covalent bond strength, most evident in the prism. The chair, with the greatest cooperativity, has the largest average electron density at the BCP per hydrogen bond, whereas the cage has the largest total value for BCP density at all hydrogen bonds. The cage also has the second largest value (after the prism) for covalent bond critical point densities and an oxygen-oxygen BCP which may factor into the experimentally observed stability of the structure.

Odd linking and bifurcation in gaps: the weakly indefinite case

In this paper, we consider nonlinear Schrödinger equations of the following type:−Δu(x)+ V(x)u(x) − q(x)|u(x)|σu(x) = λu(x), x ∈ ℝN, u ∈ H1(ℝN)\{0},where N ≥ 2 and σ > 0. We concentrate on situations where the potential function V appearing in the linear part of the equation is of Coulomb type; by this we mean potentials where the spectrum of the linear operator −Δ + V consists of an increasing sequence of eigenvalues λ1, λ2,… followed by an interval belonging to the essential spectrum.We study, for λ kept fixed inside a spectral gap or below λ1, the existence of multiple solution pairs, as well as the bifurcation behaviour of these solutions when λ approaches a point of the spectrum from the left-hand side. Our method proceeds by an analysis of critical points of the corresponding energy functional. To this end, we derive a new variational characterization of critical levelsc0 (λ) ≤ c1(λ) ≤ c2(λ) ≤ ⋯ corresponding to an infinite set of critical points.We derive such a multiplicity result even if some of the critical values cn(λ) coincide; this seems to be a major advantage of our approach. Moreover, the characterization of these values cn(λ) is suitable for an analysis of the bifurcation behaviour of the corresponding generalized solutions.The approach presented here is generic; for instance, it can be applied when V and q are periodic functions. Such generalizations are briefly described in this paper and will be the object of a forthcoming article.

High-precision X-ray diffraction data, experimental and theoretical study of 2H-MoS2

The crystal structure of MoS2 was for the first time refined based on precise three-dimensional X-ray diffraction data collected from the synthesized single crystal. The results of the refinement using the Hansen—Coppens multipole model based on X-ray diffraction data and quantum chemical calculations for the molybdenum disulfide monolayer and single crystal were analyzed in terms of Bader’s quantum theory of Atoms in Molecules (QTAIM). An analysis of the bond critical points (bcp) for S...S attests to a weak van der Waals interaction having the energy of ∼1.25 kcal mol−1 per S...S contact and the binding energy of the layers of ∼7.5 kcal mol−1.

Nanoscale assembly of silicon-like [Al(As1−xNx)]ySi5−2yalloys: Fundamental theoretical and experimental studies of structural and optical properties

Ab initio theoretical simulations of Al(As${}_{1\ensuremath{-}x}$N${}_{x}$)Si${}_{3}$ alloys, a new class of optoelectronic materials, confirm that these compounds are likely to be disordered via a mechanism that preserves the integrity of the constituent III-V-Si${}_{3}$ tetrahedra but randomizes their orientation in the average diamond lattice of the compound. This type of disorder is consistent with experimental structural data and with the proposed growth mechanism for such alloys, according to which ``III:V(SiH${}_{3}$)${}_{3}$'' intermediate complexes are formed in the gas phase from reactions between group-III atomic beams and V(SiH${}_{3}$)${}_{3}$ molecules, delivering the entire III-V-Si${}_{3}$ tetrahedra to the growing film. Experimental optical studies of these Al(As${}_{1\ensuremath{-}x}$N${}_{x}$)Si${}_{3}$ alloys as well as more general [Al(As${}_{1\ensuremath{-}x}$N${}_{x}$)]${}_{y}$Si${}_{5\ensuremath{-}2y}$ compounds grown on Si substrates were carried out using spectroscopic ellipsometry. The resulting dielectric functions are found to be similar to broadened versions of their counterparts in pure Si. This broadening may have important practical applications, particularly in photovoltaics, because it dramatically enhances the optical absorption of Si in the visible range of the electromagnetic spectrum. A critical point analysis reveals the existence of direct optical transitions at energies as low as 2.5 eV, well below the lowest direct absorption edge of Si at 3.3 eV. Such transitions are predicted theoretically for perfectly ordered III-V-Si${}_{3}$ compounds, and the experimental results suggest that they are robust against tetrahedra orientational disorder.

Structural, electronic, and linear optical properties of organic photovoltaic PBTTT-C14 crystal

Poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (PBTTT-C14) is an important electro-optical polymer, whose three-dimensional crystal structure is somewhat ambiguous and the fundamental electronic and linear optical properties are not well known. We carried out first-principles calculations to model the crystal structure and to study the effect of side-chains on the physical structure and electronic properties. Our calculations suggest that the patterns of side-chain has little direct effect on the valence band maximum and conduction band minimum but they do have impact on the bandgap through changing the π-π stacking distance. By examining the band structure and wave functions, we conclude that the fundamental bandgap of the PBTTT-C14 crystal is determined by the conduction band energy at the Q point. The calculations indicate that the bandgap of PBTTT-C14 crystal may be tunable by introducing different side-chains. The significant peak in the imaginary part of the dielectric function arises from transitions along the polymer backbone axis, as determined by the critical-point analysis and the large optical transition matrix elements in the direction of the backbone.

4-코일 자기 공진 무선 전력 전송 시스템의 해석법 연구

4-코일 자기 공진 무선 전력 전송 시스템의 해석법 중 critical point analysis(CA)와 impedance matching analysis(IA)를 분석하고, 두 결과를 비교하였다. 4-코일 시스템은 가까운 거리에서는 주파수 분리 현상이 나타나고, 먼 거리에서는 효율이 급격히 감소하는 특징을 나타낸다. 따라서 고정된 주파수에서 사용할 경우, 목표하는 거리와 효율에 따라 최적화가 필요하다. CA는 전체 거리에서 효율이 최대가 되는 critical point를 이용하여 최적화하는 방법이고, IA는 목표 지점에서 임피던스 정합을 이뤄 최대 효율을 만족시키는 방법이다. 기존의 해석은 두 가지 방법을 비교하고 시스템 특성을 이해하는데 부족한 점이 있었기 때문에, 본 논문에서 두 방법의 이론을 좀 더 자세히 분석하고 비교하였다. 두 방법의 비교 결과를 통해 IA가 더 우수함을 보였다. 또한, 한쪽만 정합할 경우 발생되는 트레이드-오프에 대해서도 설명하였다. 스파이럴 공진 코일을 이용한 실험에서는 이론 결과와 동일한 결과를 얻을 수 있었다. The critical point analysis(CA) and impedance matching analysis(IA) are performed and compared for a 4-coil magnetic resonance wireless power transfer system. Because the operating frequency splits at short distance while the efficiency drops drastically at long distance in this system, the optimization technique is needed for either a specific distance or efficiency at the fixed frequency. CA uses the critical point where shows maximum efficiency in the entire range and IA uses the impedance matching technique to achieve maximum efficiency at the specific distance. Comparison result shows that IA is more efficient than CA. Also, it shows one side matching has a tradeoff relationship comparing to both side matching. By using four spiral resonant coils, the analysis was experimentally verified. The measured data agreed well with the calculated data.

Quantum criticality of reconstructing Fermi surfaces in antiferromagnetic metals

We present a functional renormalization group analysis of a quantum critical point in two-dimensional metals involving Fermi surface reconstruction due to the onset of spin-density wave order. Its critical theory is controlled by a fixed point in which the order parameter and fermionic quasiparticles are strongly coupled and acquire spectral functions with a common dynamic critical exponent. We obtain results for critical exponents and for the variation in the quasiparticle spectral weight around the Fermi surface. Our analysis is implemented on a two-band variant of the spin-fermion model which will allow comparison with sign-problem-free quantum Monte Carlo simulations.

Benchmark calculations of metal carbonyl cations: relativistic vs. electron correlation effects

In this paper we present benchmark results for isoelectronic metal carbonyl complexes of the groups 11 and 12 of the periodic table. The focus is on the geometry, vibrational frequencies, bond dissociation energy and chemical bonding. The description of these complexes requires a good balance between electron correlation and relativistic effects. Our results demonstrate that the combination of the effective core potential and the MP2 method gives quantitative results for the first- and the second-row transition metal complexes and only qualitative agreement for the third-row complexes. In order to obtain quantitative results for the whole series the use of four-component or X2C methods is mandatory. The fourth-row transition metal carbonyl complexes from groups 11 and 12 have been studied for the first time. The metal-carbon bond strength pattern along the group is shown to be highly dependent on the correct description of the relativistic effects. Finally, the relativistic effects on the bonding are studied by means of electron density difference maps, the analysis of the bond critical points of the electron density and the mechanism for σ-donation and π-backdonation. Our analysis indicates that the fourth-row complexes exhibit a strong covalent character induced by relativistic effects.

A Study on the Occurrence of Non-O157 Shiga Toxin Producing Escherichia coli Isolates in Retail Chicken Meats Marketed in North-East India

North-eastern region of India is inhabited by different ethnic tribes devoted to livestock farming and agriculture. In recent years, tourism has had a significant development with increase in tourist destinations and holiday resorts resulting in increasing demand for supply of meat in the local market. Chicken meat is one of the predominantly consumed animal originated food item with constant increase in demand, usually met by the local retail markets. To assess the microbiological quality and safety of the retail chicken meat sold across the markets of North-East India, a study was undertaken to survey the prevalence of shiga toxin-producing Escherichia coli (STEC). Although there was no E. coli O157 recovered from the retail samples, 22 (11.5 %) of the isolates obtained from different samples were STEC positive and 11 (50 %) of the STEC isolates carried the eae factor but none of them harbored the EHEC-hlyA gene. None of the STEC isolates showed stx2 gene amplification. The counts of E. coli per g in the STEC positive samples exceeded or were close to the limit recommended by the Meat Standard Committee (Australian Standards 2002) and Microbial Food Safety–Indian Regulations. The higher counts observed were attributed to high temperature, poor hygienic practices and fecal contamination of the dressed meat. The present study suggests that retail meat is potential vehicle for transmitting food-borne diseases in the region and there is an urgent need for increased implementation of hazard analysis of critical control point and consumer food safety education programme.

Non-unitary matrix joint diagonalization for complex independent vector analysis

Independent vector analysis (IVA) is a special form of independent component analysis (ICA), which has demonstrated its prominent performance in solving convolutive blind source separation (BSS) problems in the frequency domain. Most IVA algorithms are based on optimizing certain contrast functions, where the main difficulty of these approaches lies in finding a reliable and fast estimation of the unknown distribution of sources. Despite the rich availability of efficient tensorial approaches to the standard ICA problem, these methods have not been explored considerably for IVA. In this article, we propose a matrix joint diagonalization approach to solve the complex IVA problem. The new factorization neither relies on a whitening process, nor does it require an estimate of the joint probability distribution of the dependent signal groups. The latter is in contrast to most IVA approaches up to date. The underlying geometry of the problem is investigated together with a critical point analysis of the resulting cost function. A conjugate gradient algorithm on the appropriate manifold setting is developed.

Hydrogen bonding investigation in 1-ethyl-3-methylimidazolium based ionic liquids from density functional theory and atoms-in-molecules methods

Because of special importance of hydrogen bond in the non-bonded interaction potential between two ionic liquid's parts is decided to investigate hydrogen bonding in these compounds. Two overviews are chosen to explain the hydrogen bonding in five different popular imidazolium based ionic liquids; EMI-TFSI, EMI-ES, EMI-Lactate, EMI-NO3 and EMI-PF6. Based on van der Waals atomic radii viewpoint, three types of hydrogen bond are determined in these ionic liquids that are CH…N, CH…O and CH…F respectively. Based on our results, the maximum number of hydrogen bond exists in EMI-PF6 while the strongest hydrogen bond is related to the EMI-Lactate ionic liquid.Electron density analysis of hydrogen bond critical points indicated that the type and position of hydrogen bond are in agreement with hydrogen bond length values. From this standpoint, the EMI-Lactate has the largest amount of bond critical points, 0.034amu, while the EMI-PF6 has the maximum number of them. These observations are in agreement with van der Waals atomic radii viewpoint.In addition to hydrogen bond strength, the radius of the hydrogen bonding is also important in non-bonded interaction potential. For this purpose, distance dependence of bond critical point (ρBCP), as a measure of the strength of hydrogen bonds, is examined. Detailed analysis showed that ρBCP is an exponential decaying function of distance, as the hydrogen bond disappeared above 2.5Å. It is consistent with van der Waals atomic radii standpoint.Finally polynomial inverse third order equation is obtained for non-bonded interaction potential as a function of intermolecular distance. Based on the outcomes, these potentials are long-range which leads to a dissociation distance above 8Å in these ionic liquids. These finding non-bonded interaction potentials can be used as initial parameters for force filed definition.

A Systems Approach for Management of Pests and Pathogens of Nursery Crops.

Horticultural nurseries are heterogeneous and spatially complex agricultural systems, which present formidable challenges to management of diseases and pests. Moreover, nursery plants shipped interstate and internationally can serve as important vectors for pathogens and pests that threaten both agriculture and forestry. Current regulatory strategies to prevent this movement of pathogens and pests with nursery plants are based on visual inspections of plants just before shipping, a process that is costly and inadequate. Here we propose the application of a systems approach for horticultural nurseries modeled after the Hazard Analysis of Critical Control Points (HACCP) approach widely used in the food processing industry. We evaluated aspects of the systems approach to analyze contamination hazards by Phytophthora species and then implemented management practices targeting specific critical control points. The systems approach for analyzing and correcting unsafe practices offers a potential alternative strategy for preventing plant contamination that could be broadly applied to many pests and pathogens. One of the hallmarks of this approach is its flexibility, including the ability to improve and adapt the approaches as new technologies are developed or improved and to provide the grower with management options.

A new interaction mechanism of LiNH2 with MgH2: magnesium bond

Quantum chemical calculations were performed for LiNH2-HMgX (X=H, F, Cl, Br, CH3, OH, and NH2) complexes to propose a new interaction mechanism between them. This theoretical survey showed that the complexes are stabilized through the combinative interaction of magnesium and lithium bonds. The binding energies are in the range of 63.2-66.5 kcal mol(-1), i.e., much larger than that of the lithium bond. Upon complexation, both Mg-H and Li-N bonds are lengthened. Substituents increase Mg-H bond elongation and at the same time decrease Li-N bond elongation. These cyclic complexes were characterized with the presence of a ring critical point and natural population analysis charges.

A theoretical investigation on the nature of Cl⋯N and Br⋯N halogen bonds in F[sbnd]Ar[sbnd]X⋯NCY complexes (X = Cl, Br and Y = H, F, Cl, Br, OH, NH2, CH3 and CN)

A theoretical study was performed to examine intermolecular halogen bonds interactions in FArX⋯NCY complexes (X=Cl, Br and Y=H, F, Cl, Br, OH, NH2, CH3 and CN). Examination of the electrostatic potentials of the NCY monomers indicates that the addition of substituents has a large influence upon the most negative electrostatic potential on the surface of the interacting nitrogen and thus modulates these halogen-bonding interactions. The calculated CCSD(T)/aug-cc-pVTZ interaction energies for the complexes span from −0.88 to −3.20kcal/mol. The nature of Cl⋯N and Br⋯N interactions has been identified in terms of the bond critical point analysis within the quantum theory of atoms in molecules (QTAIM). According to energy decomposition analysis, the stabilities of the FArX⋯NCY interactions are predicted to be attributable mainly to electrostatic and polarization effects, while dispersion forces play a smaller role in stabilizing these complexes.

Natural bond critical point analysis: Quantitative relationships between natural bond orbital‐based and QTAIM‐based topological descriptors of chemical bonding

We have developed a "Natural Bond Critical Point" (NBCP) module for the natural bond orbital (NBO) program that allows mutual analysis of NBO-based versus Bader-type quantum theory of atoms in molecules (QTAIM) topological descriptors of chemical bonding interactions. Conventional QTAIM bond path and bond critical point (BCP) descriptors deduced from total electron density ρ(r) can thereby be compared with analogous "natural" (NBCP) descriptors for idealized densities ρ(NAIM)(r) composed solely from NBO-based "natural atoms in molecules" (NAIM) at the terminal nuclei. Standard ρ(r(BCP)) and [nabla](2)ρ(r(BCP)) descriptors can also be decomposed into unique contributions from individual NBOs or other localized, semilocalized, or delocalized orbital components. These results allow one to recognize many relationships between QTAIM and NBO analyses, showing why close correlations are often found between NBO-based versus ρ(r(BCP))-based characterizations of chemical bonding interactions, despite strongly divergent conceptions of "the atom in the molecule."

Vortex merger and topological changes in two-dimensional turbulence

On the basis of the critical point analysis, we study the reconnection process of vorticity contours associated with coherent vortices in two-dimensional turbulence. After checking topological integrity by the Euler index theorem, we make use of the critical points and their connectivity (so-called surface networks) to characterize topological changes of vorticity contours. We quantify vortex merger by computing the number of centers and saddles of the vorticity field systematically. Surface networks are topological graphs consisting of the critical points and edges connecting them. They can tell in particular which vortices are going to merge in near future. Moreover, we show how this method can remarkably distinguish the dynamics of the vorticity field in the Navier-Stokes equations and that of the Charney-Hasegawa-Mima equation. The relationship between the number of the critical points and hyperpalinstrophy is discussed by deriving the so-called generalized Rice theorem in the spirit of S. Goto and J. C. Vassilicos [Phys. Fluids 21, 035104-1 (2009)]. The Okubo-Weiss' conditional sampling is used to compare reconnection in elliptic and hyperbolic regions. A comparison has been made between topological changes of the vorticity and that of a passive scalar. A study in inviscid flows with different resolutions is also given.