Amplitude Transformation Research Articles

Unusual phenomenon of optimizing the Griewank function with the increase of dimension

The Griewank function is a typical multimodal benchmark function, composed of a quadratic convex function and an oscillatory nonconvex function. The comparative importance of Griewank’s two major parts alters in different dimensions. Different from most test functions, an unusual phenomenon appears when optimizing the Griewank function. The Griewank function first becomes more difficult and then becomes easier to optimize with the increase of dimension. In this study, from the methodology perspective, this phenomenon is explained by structural, mathematical, and quantum analyses. Furthermore, frequency transformation and amplitude transformation are implemented on the Griewank function to make a generalization. The multi-scale quantum harmonic oscillator algorithm (MQHOA) with quantum tunnel effect is used to verify its characteristics. Experimental results indicate that the Griewank function’s two-scale structure is the main reason for this phenomenon. The quantum tunneling mechanism mentioned in this paper is an effective method which can be generalized to analyze the generation and variation of solutions for numerous swarm optimization algorithms.

Influence of ECG Lead Reduction Techniques for Extracellular Potassium and Calcium Concentration Estimation

Abstract Chronic kidney disease (CKD) affects 13% of the worldwide population and end stage patients often receive haemodialysis treatment to control the electrolyte concentrations. The cardiovascular death rate increases by 10% - 30% in dialysis patients than in general population. To analyse possible links between electrolyte concentration variation and cardiovascular diseases, a continuous non-invasive monitoring tool enabling the estimation of potassium and calcium concentration from features of the ECG is desired. Although the ECG was shown capable of being used for this purpose, the method still needs improvement. In this study, we examine the influence of lead reduction techniques on the estimation results of serum calcium and potassium concentrations.We used simulated 12 lead ECG signals obtained using an adapted Himeno et al. model. Aiming at a precise estimation of the electrolyte concentrations, we compared the estimation based on standard ECG leads with the estimation using linearly transformed fusion signals. The transformed signals were extracted from two lead reduction techniques: principle component analysis (PCA) and maximum amplitude transformation (Max- Amp). Five features describing the electrolyte changes were calculated from the signals. To reconstruct the ionic concentrations, we applied a first and a third order polynomial regression connecting the calculated features and concentration values. Furthermore, we added 30 dB white Gaussian noise to the ECGs to imitate clinically measured signals. For the noisefree case, the smallest estimation error was achieved with a specific single lead from the standard 12 lead ECG. For example, for a first order polynomial regression, the error was 0.0003±0.0767 mmol/l (mean±standard deviation) for potassium and -0.0036±0.1710 mmol/l for calcium (Wilson lead V1). For the noisy case, the PCA signal showed the best estimation performance with an error of -0.003±0.2005 mmol/l for potassium and -0.0002±0.2040 mmol/l for calcium (both first order fit). Our results show that PCA as ECG lead reduction technique is more robust against noise than MaxAmp and standard ECG leads for ionic concentration reconstruction.

Experimentally obtained and computer-simulated X-ray asymmetric eight-beam pinhole topographs for a silicon crystal.

In this study, experimentally obtained eight-beam pinhole topographs for a silicon crystal using synchrotron X-rays were compared with computer-simulated images, and were found to be in good agreement. The experiment was performed with an asymmetric all-Laue geometry. However, the X-rays exited from both the bottom and side surfaces of the crystal. The simulations were performed using two different approaches: one was the integration of the n-beam Takagi-Taupin equation, and the second was the fast Fourier transformation of the X-ray amplitudes obtained by solving the eigenvalue problem of the n-beam Ewald-Laue theory as reported by Kohn & Khikhlukha [Acta Cryst. (2016), A72, 349-356] and Kohn [Acta Cryst. (2017), A73, 30-38].

Quantum analog-digital conversion

Many quantum algorithms, such as Harrow-Hassidim-Lloyd (HHL) algorithm, depend on oracles that efficiently encode classical data into a quantum state. The encoding of the data can be categorized into two types; analog-encoding where the data are stored as amplitudes of a state, and digital-encoding where they are stored as qubit-strings. The former has been utilized to process classical data in an exponentially large space of a quantum system, where as the latter is required to perform arithmetics on a quantum computer. Quantum algorithms like HHL achieve quantum speedups with a sophisticated use of these two encodings. In this work, we present algorithms that converts these two encodings to one another. While quantum digital-to-analog conversions have implicitly been used in existing quantum algorithms, we reformulate it and give a generalized protocol that works probabilistically. On the other hand, we propose an deterministic algorithm that performs a quantum analog-to-digital conversion. These algorithms can be utilized to realize high-level quantum algorithms such as a nonlinear transformation of amplitude of a quantum state. As an example, we construct a "quantum amplitude perceptron", a quantum version of neural network, and hence has a possible application in the area of quantum machine learning.

Auto clustering of the variety of pulse signals based on their symbolic description

In a number of applied studies of geophysics, medicine, cosmophysics, atomic physics and other fields of knowledge, useful information is often hidden in the character of the behavior of a stream of frequency modulated pulses, which are represented by a large variety of forms, significantly different from each other up to several orders value of magnitude amplitude and durations. Noise is often present in the signal. Under these conditions, the problem arises of identifying both individual pulses and groups of pulses to assess the connection between their dynamic characteristics and the state of system. To solve the problem by a method is proposed that includes signal cleaning from interference, the operation of extracting and converting pulses into a code representing a sequence of invariant amplitude and time transformations of similar pulses combined by a single graphic pattern called “symbol”. All symbols extracted from the signal make up the alphabet. A procedure for narrowing the dimension of the alphabet is shown, which allows you to automatically divide it into clusters according to the degree of coincidence of the code. The results of the practical application of the developed method for the selection of base classes of the geoacoustic emission (GAS) signals related to the objective data of the state of the signal-generating medium are presented. The study used data from the archives of observations IKIR FEB RAS.

Planar Broadband Huygens’ Metasurfaces for Wave Manipulations

Electrically thin and effectively 2-D material composites, metasurfaces, have been widely exploited for the manipulation of electromagnetic waves. For many applications, it is desired to transform incident waves of a specific frequency range keeping the metasurface invisible at other frequencies. Such a frequency-selective response can be achieved based on subwavelength Huygens’ inclusions. However, their fabrication requires sophisticated processes due to the 3-D geometry. Here, we propose a planar Huygens’ meta-atom with the goal to open a way to realize broadband invisible metasurfaces with topologies suitable for the conventional printed circuit board fabrication technology. We synthesize and analyze, both numerically and experimentally, three different metasurfaces capable of polarization and amplitude transformations of incident waves.

Melt flow and grain refining in ultrasonic vibration assisted laser welding process of AZ31B magnesium alloy

During the laser welding process of magnesium (Mg) alloy, it is easy to produce welding defects, which deteriorates the mechanical properties of welded joint. Since ultrasonic vibration can decrease weld defects considerably, the ultrasonic-assisted welding technology has become a hotspot in the current research field of welding and joining. In this study, the ultrasonic vibration assisted laser welding technology used for the joining of AZ31B Mg was carried out. Setting amplitude transformer and welding specimen in contact makes ultrasonic travel to the weld pool as well as promote melt flow and bubble escape by the cavitation, acoustic streaming and thermal effects. Owing to these effects, the weld porosity decreases significantly to less than 1%. Besides, in the crystallization process of the weld pool, ultrasonic vibration increases the number of nucleation particles and refine grain, which improve the mechanical properties of welded joint. As a result, the average grain area in weld center area decreases from 359.9 μm2 to 213.7 μm2. Also, compared with laser welding, the tension strength σb, and elongation Agt increase from 235.1 MPa to 274.1 MPa and 6.6% to 7.5%, respectively.

Double-curved disc ultrasonic-assisted lapping of precision-machined crowned rollers

To improve the convexity uniformity, processing efficiency, and surface quality of precision-machined crowned rollers, this paper proposes a double-curved disc ultrasonic-assisted lapping (DUAL) method. Firstly, a DUAL machine is designed according to the technical requirements of crowned roller lapping, and the working principle is presented. Then, the ultrasonic-coupled processing mechanism for crowned roller surfaces is analyzed, and the abrasive particle motion and material removal regularities under cavitation are acquired. Subsequently, an ultrasonic amplitude transformer for DUAL is developed, and the DUAL experimental platform for precision-machined crowned rollers is established. Finally, comparative processing experiments using non-ultrasonic lapping and through-feed super-finishing are performed. The experimental results indicate that the proposed DUAL method can improve processing efficiency and surface roughness, and also the batch uniformity of the convex metric.

Integrated energy performance optimization of a passively designed high-rise residential building in different climatic zones of China

This paper mainly focuses on investigating the influence of weather conditions on the sensitivity analysis and optimization of a typical passively designed high-rise residential building. A holistic passive design approach combining a variance-based factor prioritizing and surrogate model based multi-objective optimization was previously proposed to explore the green building solution in the hot and humid climate of Hong Kong. The design approach is further extended for application into a broader spectrum of climates across the mainland of China, including the severe cold zone, cold zone, hot summer cold winter zone, temperate zone as well as hot summer warm winter zone. The relative weight analysis is first compared with the Fourier Amplitude Transformation Analysis (FAST) in prioritizing the weighting of design inputs for different climatic zones. The relative weight analysis is then proved a feasible alternative sensitivity analysis method when its corresponding multiple linear regression (MLR) model can achieve good prediction performance. Furthermore, a tuning program in R is developed to improve the prediction performance of surrogate models with the Support Vector Machine (SVM) algorithm under above climatic zones. The model fitting performance with SVM is proved to be greatly improved by modifying the Sigma and C parameters. Finally, optimum design options under the five climatic zones are discussed in relation to the outdoor thermal, ventilation and solar radiation conditions. This research explored the applicability of the proposed passive design optimization approach in diverse climates, and can therefore prompt decision-makers’ endorsement as a national green building design tool in the early planning stage.

Geometry and Radiometry Invariant Matched Manifold Detection

Consider a set of deformable objects undergoing geometric and radiometric transformations. As a result of the action of these transformations, the set of different realizations of each object is generally a manifold in the space of observations. Assuming the geometric deformations an object undergoes, belong to some finite dimensional family, it has been shown that the universal manifold embedding (UME) provides a set of nonlinear operators that universally maps each of the different manifolds, where each manifold is generated by the set all of possible appearances of a single object, into a distinct linear subspace of an Euclidean space. In this paper, we generalize this framework to the case where the observed object undergoes both an affine geometric transformation, and a monotonic radiometric transformation, and present a novel framework for the detection and recognition of the deformable objects. Applying to each of the observations an operator that makes it invariant to monotonic amplitude transformations, but is geometry-covariant with the affine transformation, the set of all possible observations on that object is mapped by the UME into a single linear subspace-invariant with respect to both the geometric and radiometric transformations. The embedding of the space of observations is independent of the specific observed object; hence it is universal. The invariant representation of the object is the basis of a matched manifold detection and tracking framework of objects that undergo complex geometric and radiometric deformations: the observed surface is tessellated into a set of tiles such that the deformation of each one is well approximated by an affine geometric transformation and a monotonic transformation of the measured intensities. Since each tile is mapped by the radiometry invariant UME to a distinct linear subspace, the detection and tracking problems are solved by evaluating distances between linear subspaces. Classification in this context becomes a problem of determining which labeled subspace in a Grassmannian is closest to a subspace in the same Grassmannian, where the latter has been generated by radiometry invariant UME from an unlabeled observation.

Analysis and Experimental Study of Vibration System Characteristics of Ultrasonic Compound Electrical Machining

The effect of applying ultrasonic vibration in the ultrasonic compound electrical machining is analyzed. According to the resonance system during machining and on the basis of vibration theory, the shape and dimension parameters of the ultrasonic amplitude transformer and the tool head are calculated and analyzed. The amplitude transformer and the tool head used in this experiment have been designed to meet the requirements of this investigation. Under different conditions, ultrasonic vibration parameters are measured online using the high-speed high-precision micro-displacement laser sensor. The obtained results show high accuracy and efficiency of the investigation. The relationship parameters between the ultrasound amplitude and the ultrasonic excitation voltage are obtained from the mathematical calculations. The results provide the basic conditions for online optimization of the ultrasonic compound electrical machining parameters. Meanwhile, the working stability of the ultrasonic vibration system and the technical advantages of the ultrasonic compound electrical machining method are verified using the analysis results. In order to do this, the processing parameters have been reasonably selected, while the ultrasound machining and ultrasonic compound electric machining have been tested on ceramics, carbide, and other hard yet brittle materials.

In-frame and inter-frame information based infrared moving small target detection under complex cloud backgrounds

Infrared moving small target detection under complex cloud backgrounds is one of the key techniques of infrared search and track (IRST) systems. This paper proposes a novel method based on in-frame inter-frame information to detect infrared moving small targets accurately. For a single frame, in the spatial domain, a directional max-median filter is developed to make a pre-processing and a background suppression filtering template is utilized on the denoised image to highlight target. Then, targets in cloud regions and non-cloud regions are extracted by different thresholds according to a cloud discrimination method so that a spatial domain map (SDM) is acquired. In the frequency domain, we design an α-DoB band-pass filter to conduct coarse saliency detection and make an amplitude transformation with smoothing processing which is the so-called elaborate saliency detection. Furthermore, a frequency domain map (FDM) is acquired by an adaptive binary segmentation method. Lastly, candidate targets in single frame are extracted by a discrimination based on intensity and spatial distance criteria. For consecutive frames, a false alarm suppression is conducted on account of differences of motion features between moving target and false alarms to improve detection accuracy again. Large numbers of experiments demonstrate that the proposed method has satisfying detection effectiveness and robustness for infrared moving small target detection under complex cloud backgrounds.

Experimental study on horizontal ultrasonic electrical discharge machining

Electrical discharge machining (EDM) is usually used to machine conductive difficult-to-machine materials by pulse discharge, which can achieve high processing quality, but the machining efficiency is low. Ultrasonic vibration of the electrode changes the discharge gap and enhances the chip removal ability, which is deemed as an excellent method to increase the EDM efficiency. In this paper, firstly, a new ultrasonic vibration unit is designed with the assistance of finite element method (FEM) simulation for the resonance oscillation of the workpiece on the end of the amplitude transformer in horizontal direction. Secondly, the machining parameters, including the gap voltage, pulse interval, pulse width and peak current in the traditional EDM process, are optimized by experiments, and the optimized condition is applied to the horizontal ultrasonic electrical discharge machining (HU-EDM) process. In comparison with the traditional EDM, HU-EDM increases the material removal rate (MRR) by nearly 3 times, and improves the processing accuracy by 20%. Through this research, it is confirmed that both advantages of machining accuracy and machining efficiency are achieved in HU-EDM.

Bragg Fibers with Soliton-like Grating Profiles

Nonlinear dynamical system corresponding to the optical holography in a nonlocal nonlinear medium with dissipation contains stable localized spatio-temporal states, namely the grid dissipative solitons. These solitons display a non-uniform profile of the grating amplitude, which has the form of the dark soliton in the reflection geometry. The transformation of the grating amplitude gives rise many new atypical effects for the beams diffracted on such grating, and they are very suitable for the fiber Brass gratings. The damped nonlinear Schrodinger equation is derived that describes the properties of the grid dissipative soliton.

Design of the Acoustic Signal Receiving Unit of Acoustic Telemetry While Drilling

Signal receiving unit is one of the core units of the acoustic telemetry system. A new type of acoustic signal receiving unit is designed to solve problems of the existing devices. The unit is a short joint in whole. It not only can receive all the acoustic signals transmitted along the drill string, without losing any signal, but will not bring additional vibration and interference. In addition, the structure of the amplitude transformer is designed, which can amplify the signal amplitude and improve the receiving efficiency. The design of the wireless communication module makes the whole device can be used in normal drilling process when the drill string is rotating. So, it does not interfere with the normal drilling operation.

HYPERSONIC WIND TUNNEL FREE-FLIGHT TEST WITH BIPLANAR OPTICAL SYSTEM ON THE NON-SPINNING BLUNT CONE

To investigate the dynamic stability of the non-spinning blunt cone, wind-tunnel free-flight tests with biplanar optical system, were conducted at Mach 6 in the hypersonic wind tunnel. The tests show that coning motion appears for all the models,and in the range of viewing area the amplitude of angle of sideslip is larger than that of angle of attack, though only angle of attack is preset. For all the models, the amplitude of both angles of attack and sideslip is no more than 10 degree, while damping moment shows obvious nonlinearity and static moment exhibits approximate linearity. One of the models shows the tendency of limit planar motion or limit coning motion with small amplitude of angle of attack, others all tend to limit coning motion. End cover has little effect on the angular motion of the models, while the protuberance symmetrically placed on the model tail can affect the transformation of amplitude of angular motion, and the fluctuation of angular motion amplitude is obviously smaller for models with strake.

Revisiting Hartert's 1962 Calculation of the Physical Constants of Thrombelastography.

Thrombelastography (TEG)/thromboelastometry (ROTEM) devices measure viscoelastic clot strength as clot amplitude (A). Transformation of clot amplitude into clot elasticity (E with TEG; CE with ROTEM) is sometimes necessary (eg, when calculating platelet component of the clot). With TEG, clot amplitude is commonly transformed into shear modulus (G; expressed in Pa or dyn/cm2) as follows: G = (5000 × A)/(100 – A). Use of the constant “5000” stems from Hartert's 50-year-old calculation of G for a normal blood clot. We question the value of calculating G as follows: (1) It may be questioned whether TEG/ROTEM analysis enable measurement of elasticity because viscosity may also contribute to clot amplitude. (2) It has been suggested that absolute properties of a blood clot cannot be measured with TEG/ROTEM analysis because the strain amplitude applied by the device is uncontrolled and changes during the course of coagulation. (3) A review of the calculation of G using Hartert's methods and some updated assumptions suggests that the value of 5000 is unreliable. (4) Recalculation of G for the ROTEM device yields a different value from that with Hartert TEG, indicating a degree of inaccuracy with the calculations. (5) Shear modulus is simply a multiple of E/CE and, because of the unreliability of G in absolute terms, it provides no additional value versus E/CE. The TEG and ROTEM are valuable coagulation assessment tools that provide an evaluation of the viscoelastic properties of a clot, not through measuring absolute viscoelastic forces but through continuous reading of the clot amplitude relative to an arbitrary, preset scale.

Research of Electrical Response Communication Parameters on the Pulse Mechanical Impact with the Stress–Strain State of Concrete Under Uniaxial Compression

The article presents the results of research of the electrical response on elastic impact excitation of heavy concrete samples under uniaxial compression. In this paper we recorded and analyzed electrical responses during uniaxial compression of concrete samples with a constant velocity. Studies have shown that in the process of uniaxial compression of concrete samples, the transformation of amplitude–frequency characteristics of the electrical response is observed. The stage of elastic deformation of concrete samples is characterized by a centershift of gravity of the spectrum of the electrical response towards lower frequencies. Dramatic centershift of gravity of the spectrum of the electrical response to the high frequency region characterizes the beginning of fracturing.

In situ disdrometer calibration using multiple DSD moments

In situ calibration is a proposed strategy for continuous as well as initial calibration of an impact disdrometer. In previous work, a collocated tipping bucket had been utilized to provide a rainfall rate based ∼11/3 moment reference to an impact disdrometer’s signal processing system for implementation of adaptive calibration. Using rainfall rate only, transformation of impulse amplitude to a drop volume based on a simple power law was used to define an error surface in the model’s parameter space. By incorporating optical extinction second moment measurements with rainfall rate data, an improved in situ disdrometer calibration algorithm results due to utilization of multiple (two or more) independent moments of the drop size distribution in the error function definition. The resulting improvement in calibration performance can be quantified by detailed examination of the parameter space error surface using simulation as well as real data.

Principal resonance bifurcation of bending–torsion coupling of aero-engine compressor blade with assembled clearance under lateral displacement excitation of rotor shaft

The principal resonance of bending–torsion coupling of a compressor blade with an assembled clearance and a cubic structural nonlinearity, subjected to the lateral displacement excitation of rotor shaft and aerodynamic loads, is analyzed to explore the topology transformation of amplitude–frequency response along with the changes of the physical parameters. The bifurcation equation of the first-order principal resonance response is derived from using the averaging method. The transition set and the bifurcation figures of the response solution are obtained by the singularity theory. The effects of the main physical parameters of the system on the topology transformation of amplitude–frequency response are discussed.