Approximate Calculation Research Articles

Predicted bismuth–tellurium under high pressures

ABSTRACT The high-pressure structures of the Bi–Te system were theoretically predicted by this work, which also clarified some ambiguous structures. Using variable-composition evolutionary algorithms, the crystal structures of the Bi–Te system at high pressures were searched, and one new stable structure BiTe-P-1 was proposed. BiTe-P-1 was discovered to be the experiment's undetected structure by comparing with the experimental XRD. Thereafter, the pressure-composition diagram of the Bi–Te system was calculated using the first-principles method. In contrast to previous reports, Bi2Te3 only had two high-pressure structures, R-3m and C2/m, and it would decompose into BiTe and Te at 13.4 GPa. The calculation of quasi-harmonic approximation shown that the BCC alloy phase of Bi2Te3 only could exist stably under high temperature and high pressure. For BiTe, The phase transition route was P-3m1 → P-1 → Pm-3m, and the transition pressure was 7.5 and 11.2 GPa, respectively.

Non-invasive evidence of mercury soaps in painted miniatures on ivory

This work focuses on a non-invasive study of two selected painted miniature portraits on ivory to describe the degradation processes resulting from the interaction between mercury-based and lead-based pigments with oils. In the studied miniatures, containing both lead white and cinnabar, the formation of metal soaps has been clearly detected. However, until now they have been identified exclusively as lead soaps. In this study, the formation of mercury soaps has been evidenced in painted artworks for the first time, together with the well-known lead soaps. The fully non-invasive analytical approach involved the use of large-area X-ray fluorescence scanning, X-ray powder diffraction and Fourier transform infrared spectroscopy accompanied by Raman spectroscopy. It enabled complex description of the miniatures, leading to both the identification and the deduction of approximate composition of mercury soaps. In addition, approximate calculations of the amount of pigments consumed by saponification unveiled the complex processes taking place in the oil-based paint containing both cinnabar and lead white, which were further studied within long-term model experiments monitored by both Fourier transform infrared spectroscopy and X-ray powder diffraction.

Design of Low-Power ECG Sampling and Compression Circuit

Compressed Sensing (CS) has been applied to electrocardiogram monitoring in wireless sensor networks, but existing sampling and compression circuits consume too much hardware. This paper proposes a low-power and small-area sampling and compression circuit with an Analog-to-Digital Converter (ADC) and a CS module. The ADC adopts split capacitors to reduce hardware consumption and uses a calibration technique to decrease offset voltage. The CS module uses an approximate addition calculation for compression and stores the compressed data in pulsed latches. The proposed addition completes the accurate calculation of the high part and the approximate calculation of the low part. In a 55 nm CMOS process, the ADC has an area of 0.011 mm2 and a power consumption of 0.214 μW at 10 kHz. Compared with traditional design, the area and power consumption of the proposed CS module are reduced by 19.5% and 31.7%, respectively. The sampling and compression circuit area is 0.325 mm2, and the power consumption is 2.951 μW at 1.2 V and 100 kHz. The compressed data are reconstructed with a percentage root mean square difference of less than 2%. The results indicate that the proposed circuit has performance advantages of hardware consumption and reconstruction quality.

Attention-Oriented Deep Multi-Task Hash Learning

Hashing has wide applications in image retrieval at large scales due to being an efficient approach to approximate nearest neighbor calculation. It can squeeze complex high-dimensional arrays via binarization while maintaining the semantic properties of the original samples. Currently, most existing hashing methods always predetermine the stable length of hash code before training the model. It is inevitable for these methods to increase the computing time, as the code length converts, caused by the task requirements changing. A single hash code fails to reflect the semantic relevance. Toward solving these issues, we put forward an attention-oriented deep multi-task hash learning (ADMTH) method, in which multiple hash codes of varying length can be simultaneously learned. Compared with the existing methods, ADMTH is one of the first attempts to apply multi-task learning theory to the deep hashing framework to generate and explore multi-length hash codes. Meanwhile, it embeds the attention mechanism in the backbone network to further extract discriminative information. We utilize two common available large-scale datasets, proving its effectiveness. The proposed method substantially improves retrieval efficiency and assures the image characterizing quality.

СТАБІЛІЗАЦІЯ ДИНАМІЧНИХ ПАРАМЕТРІВ ГРАДІЄНТНОГО ПРОЦЕСУ АДАПТАЦІЇ РАДІОТЕХНІЧНИХ СИСТЕМ З АНТЕННОЮ РЕШІТКОЮ В УМОВАХ АКТИВНИХ ШУМОВИХ ЗАВАД

The article proposes an algorithm for parametric adaptation of radiotechnikal systems (RTS) with an adaptive antenna array (AAR) with stable dynamic parameters (DP) operating under conditions of active noise interference (ANI). When applying gradient methods, not only the convergence of successive approximations is essential, but also their speed, which can vary significantly depending on the existing signal-interference situation. The problem of choosing the convergence step of gradient methods is non-trivial due to the lack of a priori information about the target function which is minimized (maximized). A fixed adaptation step does not guarantee stable convergence and stability of the adaptation process. It is proposed to replace the constant constant of the adaptation step with a variable whose elements depend on the contrast of the spectral distribution of the correlation matrix of observation, and to increase the speed of convergence of these processes, to apply the second-order gradient method. As a result of the synthesis, a generalized analytical form of the quasi-Newton algorithm for an arbitrary step of adaptation for adaptive RTS with an antenna array was obtained. Quasi-Newtonian algorithms for stabilizing the dynamic parameters of the adaptation process of the adaptive interference compensator (AIC) and AAR have been synthesized, which are the best among the algorithms of approximate calculations. The use of these algorithms is advisable in the case of limited computing resources. The conducted study of the efficiency of the quasi-Newtonian algorithm of parametric adaptation for AIC and AAR according to the signal/(interference+noise) ratio criterion, which is achieved at the RTS output, maintains its stability in any of the considered situations, regardless of the influence of arbitrary intensity ANI. Keywords: adaptation, adaptive antenna array, adaptive interference compensator, interference, signal/(interference+noise), quasi-Newton, gradient method.

Evaluation of seismic residual capacity ratio for reinforced concrete structures

Use of indices that quantify the seismic residual capacity of buildings damaged in earthquakes is one way to draw judgements on the building's safety and possibility of future use. In Japanese damage assessment guidelines, several approximate calculation methods exist to evaluate the residual capacity of buildings based on visually observed damage and simplifying assumptions on the nature of the building's response mechanism and member capacities. While these methods provide a useful residual capacity ratio that enables a ‘relative’ comparison between buildings, the exact relationship to a physically meaningful residual capacity is unclear. The aim of this study is to benchmark the ‘approximations’ of residual capacity. To do so, a shake-table test was conducted on a ¼ scale 4-storey RC structure and a residual capacity evaluation was undertaken based on observed damage states. With the help of a numerical model, a benchmark residual capacity at each of the damage states is determined and compared to the approximate residual capacity calculation results via guidelines. It was found that approximate methods are generally accurate prior to yield but can become overly conservative post-yield. Simplifying assumptions of equal member deformation capacity used in the residual capacity ratio calculation was found to be suitable given constraints of rapid field evaluations.

Approximate calculation of natural frequencies of oscillations of the diamond-shaped plates of the discrete-continuous inter-resonance vibrating table

Conventional single- and two-mass vibrating machines do not have a sufficient level of energy efficiency. There are vibration machines based on inter-resonance oscillating systems, which make possible the significant reduction in the use of electricity. To implement highly effective inter-resonance operation modes of vibrating machines, the oscillating masses of such a system must precisely calculate values of inertial-rigid parameters, as well as their frequency of oscillations. Since the synthesis of continuous sections into classical discrete models of multi-mass mechanical oscillating systems has recently become widespread, the most optimal option is to use a continuous member as a reactive mass of a vibrating machine. The continuous member combines inertial and stiffness parameters and makes it extremely easy to perform the reactive mass. In particular, rectangular plates are used as continuous members. The rectangular shape of the plate is not the only option for making a continuous member. This paper proposes the construction of a discrete-continuous inter-resonance vibration machine with electromagnets, where a diamond-shaped plate is used as a continuous member. The authors carried out the computation of the first natural frequency of the diamond-shaped plate using the Rayleigh-Ritz method with the equation of the hyperboloid. The determined eigenfrequency was confirmed in the Ansys software.

Study of the tools used for early-stage carbon footprint in building design

The purpose of this study is to construct a digital tool and design process for building a carbon footprint calculation to change the current status of Taiwan's carbon footprint calculation in post-use assessment, and to incorporate both carbon emissions and energy consumption in the environmental impact assessment into the initial considerations of the architectural design. Through the connection of carbon emission calculation tools and optimization tools, the advantages and disadvantages of multiple schemes in relation to carbon emissions and energy consumption can be compared simultaneously, thereby assisting designers to achieve faster results when making design decisions. In addition to the building's area, orientation, and height, various schemes could also further facilitate architectural design plans with lower carbon emissions by adjusting factors such as the external shading depth and the window-to-wall ratio by calculating the building dimensions to pursue the maximum percentage of the visual field (maximum window area), thereby reducing carbon emissions. This study is expected to meet the needs of users by simplifying the calculation tools and operation interface required for carbon emission calculations, visualizing the calculation results, and enabling a comparison of multiple design schemes. In addition, it provides recommended projects that can be reviewed in the early decision-making stage of the architectural design process, and provides designers and planners with approximate building carbon emission calculations for projects. Furthermore, to facilitate a calculation process with the best view, the scheme simulation is optimized under the existing design conditions, and the optimal solution (Pareto optimal solution) is obtained following calculation classification and analysis. The simulated data can be listed for design reference, whereby users can make design decisions based on the design conditions.

A Novel Chrysanthemum-Like Fractal Structure Multi-Band Antenna for Mobile Terminals

This paper incorporates the structural characteristics of chrysanthemums in nature and fractal geometry theory into the antenna structure design and a novel-structured fractal multiband fractal microstrip antenna with a chrysanthemum petal structure is proposed. The antenna can cover commercial frequency bands from the second to fourth generation (4G), satellite navigation, wireless local area networks, and Bluetooth. The antenna radiator imitates the structure of chrysanthemum’s petals in nature, and a basic arc shape is iterated many times according to a certain proportional coefficient. After simulation and comparison, the second iteration can achieve the best antenna performance, and the antenna adopted the coplanar waveguide feeding method to broaden the antenna bandwidth. The antenna covers three effective frequency bands of 1.58–2.68 GHz (64.7%), 2.76–4.01 GHz (33.9%), and 4.68–5.35 GHz (13.4%). The antenna dielectric board is made of FR-4 material, the dielectric constant is 4.4, and the actual size is 41 × 29 × 1.6 mm3. The antenna performs fractal iteration at a small size, and the approximate calculation of the frequency band is completed by comparing the ratio of each ring to the current vector diagram. The design of the antenna is to use HFSS for antenna modeling and parameter optimization, and the model under different conditions were compared and analyzed. By comparing the test results of the antenna prototype with the simulation structure in the electromagnetic anechoic chamber, the rationality of the antenna is verified.

Methodology for determining coordinate points using automated software and aircraft

Engineers are currently facing questions about the use of geographic information systems or software to implement projects in a short time. The problem with using geographic information systems in construction is the relevance of the available data. An example is open sources with satellite images. This problem appeared even before satellite-positioning systems emerged. In this connection, the purpose of this article is to find the deviation of source points when performing photogrammetry with marker detection in Agisoft PhotoScan software. This method of determining coordinates using a single point and its correlation on the ground is applicable in the case of rapid calculations, where the volumes of earth masses are large enough and do not require increased accuracy at the stage of approximate calculations. As a result of the comparison of traditional and automated methods of definition of coordinates on the ground has been found an essential distinction, both in total values and in time spent for the definition of points of coordinates. The considerable difference revealed by the results of the comparison of coordinates is presented in the table as a color gradation. The average deviation between known coordinates and coordinates obtained in Agisoft PhotoScan by axes was: X=0.87%, Y=0.45%, Z=0.12%.

Melnikov’s method for controlled stochastic oscillations of a rocking block with fractional derivative

The problem of controlling a rocking block with fractional dissipation so as to prevent it from leaving a prescribed set of bounded oscillations has a number of interesting applications in many scientific and technological fields. This work develops an analytical framework to describe the influence of control on the behavior of a fractionally dissipative rocking block subject to random acceleration of the ground. Control equations are developed and control strategies leading to optimal suppression of instability are asymptotically described under the assumptions of weak dissipation along with a small energy noise. Under these assumptions, the behavior of the block is interpreted as weakly perturbed rocking oscillations close to a generic periodic solution, and the Melnikov approximations are considered as the necessary conditions of instability. The stochastic Melnikov criterion derived in this paper allows for an approximate calculation of an upper bound to the overturning probability as well as to the representation of an optimal control strategy. The Melnikov criterion for stochastic rocking oscillations in the presence of convenient control strategies are derived explicitly for the first time, using an extension of the Melnikov theory to a model with fractional derivative.

Mechanical properties of zeolite-templated carbons from approximate density functional theory calculations

Mechanical properties of zeolite-templated carbons from approximate density functional theory calculations

A Multi-Level Distributed Computing Approach to XDraw Viewshed Analysis Using Apache Spark

Viewshed analysis is a terrain visibility computation method based on the digital elevation model (DEM). With the rapid growth of remote sensing and data collection technologies, the volume of large-scale raster DEM data has reached a great size (ZB). However, the data storage and GIS analysis based on such large-scale digital data volume become extra difficult. The usually distributed approaches based on Apache Hadoop and Spark can efficiently handle the viewshed analysis computation of large-scale DEM data, but there are still bottleneck and precision problems. In this article, we present a multi-level distributed XDraw (ML-XDraw) algorithm with Apache Spark to handle the viewshed analysis of large DEM data. The ML-XDraw algorithm mainly consists of 3 parts: (1) designing the XDraw algorithm into a multi-level distributed computing process, (2) introducing a multi-level data decomposition strategy to solve the calculating bottleneck problem of the cluster’s executor, and (3) proposing a boundary approximate calculation strategy to solve the precision loss problem in calculation near the boundary. Experiments show that the ML-XDraw algorithm adequately addresses the above problems and achieves better speed-up and accuracy as the volume of raster DEM data increases drastically.

Quantum-classical dynamics of vibration-induced autoionization in molecules.

We present a novel method for the simulation of the vibration-induced autoionization dynamics in molecular anions in the framework of the quantum-classical surface hopping approach. Classical trajectories starting from quantum initial conditions are propagated on a quantum-mechanical potential energy surface while allowing for autoionization through transitions into discretized continuum states. These transitions are induced by the couplings between the electronic states of the bound anionic system and the electron-detached system composed of the neutral molecule and the free electron. A discretization scheme for the detached system is introduced, and a set of formulas is derived that enable the approximate calculation of couplings between the bound and free-electron states. We demonstrate our method on the example of the anion of vinylidene, a high-energy isomer of acetylene, for which detailed experimental data are available. Our results provide information on the time scale of the autoionization process and give insight into the energetic and angular distribution of the ejected electrons, as well as the associated changes in the molecular geometry. We identify the formation of structures with reduced C-C bond lengths and T-like conformations through bending of the CH2 group with respect to the C-C axis and point out the role of autoionization as a driving process for the isomerization to acetylene.

Efficient approximate multipliers with adjustable accuracy

ABSTRACT The number of smart devices grows rapidly, and the main leakage of many of these devices is their limited batteries, in addition to the need for a fast and low-power computing system. Approximate calculations are an excellent method for such systems to achieve higher speed and less area and power consumption at the cost of lower accuracy. Furthermore, in many applications with inherent tolerance for insignificant inaccuracies such as image processing, approximate computing can be used to achieve acceptable performance with higher speed, lower power or area consumption. In this work, approximate multiplier structures are proposed based on working on the partial product trees with the aim of reducing area consumption and increasing accuracy. Comprehensive experimental analysis is performed to evaluate the performance of the proposed multiplier in terms of area, delay, power consumption, and accuracy. The results show that our suggested design improves at most 29% of power consumption, 11% of delay, and 55% of the area rather than an exact multiplier. Moreover, the performance of our multipliers is investigated based on the peak signal noise ratio (PSNR) for processing two images, which lead to 56.65 and 23.6 dB.

Anesthesia, Coming of Age in the World of Modern In Silico Drug Design.

Anesthesia, Coming of Age in the World of Modern In Silico Drug Design.

Uncertainty evaluation of peak energy of giant dipole resonance propagated from uncertainty of parameters of effective interaction

We evaluate uncertainty of giant dipole resonance (GDR) peak energy propagated from the uncertainty of effective interaction parameter. The Monte Carlo calculation of microscopic random phase approximation using randomized parameter sets is performed. Under the condition that correlations between the parameters are considered, the calculated GDR peak energy has an uncertainty of ∼1 MeV irrespective of nuclear mass and is strongly correlated with the parameters, in the present calculations. Our result serves as a guide for a new parametrization of effective interaction.

Mechanical properties of zeolite-templated carbons from approximate density functional theory calculations

Mechanical properties of zeolite-templated carbons from approximate density functional theory calculations

ПРО ТОЧНІ РОЗВ’ЯЗКИ РІВНЯНЬ ОСІ Й КУТА ПОВОРОТУ ПЕРЕРІЗУ ПРУЖНОЇ БАЛКИ

Calculation of elastic structures for strength and stiffness is important for their safe operation. The need for calculations is caused by structural deformations under the influence of external forces or temperature.The objects of our research are the equation of the axis of an elastic beam during its flat bending, as well as the equation of the angle of rotation of the beam section. These equations are differential. A certain complexity of their solution led to the simplification of equations in classical sources of information. Approximate solutions of these equations are considered there.But when using approximate calculation methods, you need to be able to assess their accuracy, that is, the degree of approximation to the exact result.The goal of our research was to obtain exact solutions. The exact solution of the beam equations is important to avoid its critical deformations.The article presents the exact analytical solutions we obtained for the exact equations of the bent axis of the beam and the angle of rotation of the beam section. The advantage of the exact solution was revealed, in particular, in the fact that the largest value of the deflection and angle of rotation of the beam section can be obtained directly from the properties of thefunctions that describe the solution.Another advantage of the exact solution was the possibility of obtaining an approximate solution with a predetermined accuracy. In the mentioned classical sources of information, the assessment of accuracy was derived from the range of the maximum deflection of the axis during practical calculations of structures.We have obtained a method of analytical assessment of the accuracy of the obtained solutions. The ability to assess the accuracy of calculation results is an important aspect of their practical application. This is important, in particular, for check-ing and clarifying the safe range of movements of beam points during its operation.An example of calculating the deflection and angle of rotation of the beam cross-section with a given load on the axis of the beam is shown

Построение траектории малого космического аппарата для облета базового космического аппарата с целью наружного осмотра и оценка энергетических затрат на маневр облета

The paper presents a methodology for constructing a flyby trajectory of a base spacecraft for the purpose of inspecting it using a small spacecraft carried on board and estimating the required characteristic velocity reserves for the flyby maneuver. The use of approximate calculation methods made it possible to obtain the simplest dependences of trajectory parameters with high accuracy. The technique allows not only to estimate the energy costs for orbital maneuvers, but also allows one to calculate the values of control impulses for the real problem of controlling the motion of a small spacecraft relative to the base spacecraft.