Symmetric Signal Research Articles

Symmetry in Signals: A New Insight

Symmetry is a fundamental property of many natural systems, which is observable through signals. In most out-of-equilibrium complex dynamic systems, the observed signals are asymmetric. However, for certain operating modes, some systems have demonstrated a resurgence of symmetry in their signals. Research has naturally focused on examining time invariance to quantify this symmetry. Measures based on the statistical and harmonic properties of signals have been proposed, but most of them focused on harmonic distortion without explicitly measuring symmetry. This paper introduces a new mathematical framework based on group theory for analyzing signal symmetry beyond time invariance. It presents new indicators to evaluate different types of symmetry in non-stochastic symmetric signals. Both periodic and non-periodic symmetric signals are analyzed to formalize the problem. The study raises critical questions about the completeness of symmetry in signals and proposes a new classification for periodic and non-periodic signals that goes beyond the traditional classification based on Fourier coefficients. Furthermore, new measures such as “symmetrometry” and “distorsymmetry” are introduced to quantify symmetry. These measures outperform traditional indicators like Total Harmonic Distortion (THD) and provide a more accurate measurement of symmetry in complex signals from applications where duty cycle plays a major role.

Model Predictive Current Control for Six-Phase PMSM with Steady-State Performance Improvement

The application of finite control set model predictive control (FCS-MPC) in six-phase permanent magnet synchronous motors (PMSMs) often faces a trade-off between computational burden and accurate voltage vector selection, as well as challenges related to harmonic components and torque generation. This paper introduces an improved model predictive current control (MPCC) method to address these problems. Firstly, 12 virtual voltage vectors are synthesized to improve torque output performance while suppressing harmonic currents. Then, to generate symmetrical switching signals and reduce switching loss, the largest basic vector used to synthesize the virtual vector is replaced by two medium vectors. Secondly, to solve the problem of the increased computational burden caused by the increase in discrete virtual vectors, a two-step vector selection method is proposed. In this method, each part is divided into several parts according to N, and the traditional cost function is also replaced by two-step functions. Different control performances can be achieved according to different values of N. Experimental results show that the proposed control scheme not only achieves stable current quality but also significantly improves steady-state performance throughout the entire speed range.

Achieving smooth motion in displacement amplification piezoelectric stick-slip actuator.

Traditional piezoelectric stick-slip actuators often suffer from significant backward motion phenomena, which greatly impact their output performance. To overcome this issue, a novel displacement amplification piezoelectric stick-slip actuator was meticulously designed. It integrates an L-shaped displacement amplification mechanism with a parallelogram-compliant mechanism. By dynamically adjusting the compressive force between the stator and the mover, this actuator effectively increases the single-step displacement, resulting in smooth and stable motion output. The design process involved thorough structural feasibility validation and core dimension optimization, utilizing Castigliano's second theorem and finite element simulation analysis. These efforts successfully yielded a substantial increase in the single-step output displacement. Experimental results demonstrate the actuator's capability to achieve smooth and stable motion output, even under challenging conditions, such as symmetric excitation signals and horizontal loading. Under specific operating parameters-preloading force of 3 N, input voltage of 100VP-P, and driving frequency of 625Hz sinusoidal excitation signal, the actuator achieves an impressive maximum driving speed of 25.22 mm/s, with a substantial maximum load capacity of 2.1 N. Compared to previous studies, the designed actuator exhibits superior adaptability to various excitation signals, offering significant potential for enhancing the performance and expanding the applications of piezoelectric stick-slip actuators.

Study of high-order non-equal probability QAM for visible light communication systems.

In this Letter, we propose and experimentally demonstrate a high-order non-equal probability quadrature amplitude modulation (NEP-QAM) scheme for visible light communication (VLC) systems, where NEP-72QAM is considered as an example. Nonlinear coding is introduced to generate the NEP-18QAM signal in the first quadrant, which is then jointly mapped with the other two bits to obtain the four-quadrant symmetric NEP-72QAM signal. Moreover, a bit-to-symbol labeling scheme is proposed to achieve thorough Gray mapping. The experimental results show that the NEP-72QAM scheme achieves better performance than the traditional 64QAM scheme regardless of whether the light-emitting diode (LED) operates in the linear or nonlinear range. Compared with the probabilistically shaped 72QAM scheme, the available range of the driving peak-to-peak voltage of the NEP-72QAM scheme is only reduced by 20 mV when 0.92 is used as the normalized generalized mutual information threshold, but the complexity is much lower.

Cheap talk with two-sided private information

This paper studies how the transmission of information from a biased expert to a decision maker is affected when the latter has access to an unbiased symmetric private signal. The extra information has two distinct effects on the expert's incentives to communicate. First, there is an information effect that allows the decision maker to choose a better action on expectation. This reduces the implicit cost of transmitting coarse messages and hence hampers communication. Second, there is a risk effect that arises because the extra information introduces uncertainty to the expert. For risk averse experts, this effect increases the cost of sending coarse messages and hence favours communication. I show that the information effect dominates the risk effect, and for any symmetric signal structure there are always sufficiently biased experts for which communication is no longer possible in equilibrium. Moreover, for any bias of the expert, no communication is possible if the signal structure is sufficiently precise. For the uniform signal structure I show that communication decreases with the precision of the signal. Finally, I provide non degenerate examples for which the decision maker's private information cannot make up for the loss of communication implying that the welfare of both agents decreases.

Effect of sleep-disordered breathing on stable electroencephalographic characteristics during night sleep in patients with arterial hypertension

Introduction. Obstructive sleep apnea (OSA) is the most common sleep-disordered breathing condition. A significant number of OSA patients often present with cardiovascular comorbidities, particularly arterial hypertension. OSA is associated with changes in bioelectrical activity of the brain, such as slowing of electroencephalographic activity in the cortex and reduced interhemispheric synchronization. These changes can become pathophysiological markers of sleep-disordered breathing.Aim. To investigate the effect of sleep-disordered breathing on a range of quantitative electroencephalogram (EEG) characteristics during nighttime sleep in patients with arterial hypertension and clinically significant OSA.Materials and methods. The material for this retrospective study consisted of 84 polysomnographic records of patients predominantly diagnosed with arterial hypertension. Patients were divided into three groups based on the apneahypopnea index (AHI). Polysomnographic records were used to assess the synchronization measure of brain electrical activity between occipital EEG leads. The synchronization measure was evaluated using a method based on wavelet bicoherence calculation.Results. Statistically significant differences were observed in the low-frequency ranges Δf1-Δf4: 0.2-1.0 Hz, 0.8-1.6 Hz, 1.0-2.0 Hz, 1.0-4.0 Hz. In these frequencies, the interhemispheric synchronization measure significantly decreased with increasing severity of apnea.Conclusion. To determine the severity of obstructive sleep apnea, a parameter based on the synchronization measure evaluated from symmetrical occipital EEG signals in the frequency ranges 0.2-1.0 Hz, 0.8-1.6 Hz, 1.0-2.0 Hz, and 1.0-4.0 Hz can be considered. This may serve as the basis for developing and implementing new diagnostic tools for assessing the severity of sleep-disordered breathing in practice.

General relativistic effects and the near-infrared variability of Sgr A*

A systematic study, based on the third-moment structure function, of Sgr A*’s variability finds an exponential rise time, τ1,obs = 14.8−1.5+0.4 minutes, and decay time, τ2,obs = 13.1−1.4+1.3 minutes. This symmetry of the flux-density variability is consistent with earlier work, and we interpret it as being caused by the dominance of Doppler boosting, as opposed to gravitational lensing, in Sgr A*’s light curve. A relativistic, semi-physical model of Sgr A* confirms an inclination angle of i ≲ 45°. The model also shows that the emission of the intrinsic radiative process can have some asymmetry even though the observed emission does not. The third-moment structure function, which is a measure of the skewness of the light-curve increments, may be a useful summary statistic in other contexts of astronomy because it senses only temporal asymmetry; that is, it averages to zero for any temporally symmetric signal.

Brain MRI findings in paediatric genetic disorders associated with white matter abnormalities.

To describe the specific brain magnetic resonance imaging (MRI) patterns of the paediatric genetic disorders associated with white matter abnormalities in Northern Finland. In this retrospective population-based longitudinal study, brain MRI scans accumulated from 1990 to 2019 at Oulu University Hospital, Finland, were assessed. Inclusion criteria were defined as leukodystrophies or genetic diseases with significant white matter abnormalities that did not meet the criteria for leukodystrophy, at least one brain MRI, and age under 18 years at diagnosis. A total of 83 patients (48 males, 35 females) were found with 52 different diseases. The median age at the time of the brain MRI was 22 months (interquartile range [IQR] = 46 months). In 72 (87%) of the children, brain MRIs revealed abnormal findings, including cerebral white matter abnormalities (n = 49, 59%), brainstem signal abnormalities (n = 28, 34%), thinning of the corpus callosum (n = 30, 36%), delayed myelination (n = 11, 13%), and permanent hypomyelination (n = 9, 11%). Symmetrical and bilateral white matter signal patterns of the brain MRI should raise suspicion of genetic disorders when the clinical symptoms are compatible. This study illustrates brain imaging patterns of childhood-onset genetic disorders in a population in Northern Finland and improves the diagnostic accuracy of rare genetic disorders.

An algorithm of the sequence of artificial symmetric signals for comparing and creating a new convolution method

The objective of this article is to create an algorithm of the sequence of artificial signals that can be used to compare and create methods for processing one- and two-dimensional signals. It will then be implemented to compare feature extraction methods that rely on discrete wavelet transforms. The discrete wavelet transform is superior to other signal processing techniques in several ways. Developing a feature set is a crucial step in using the discrete wavelet transform. Mean value and standard deviation are suggested as feature extraction techniques in this study. The mean value is the only option selected for the first feature extraction method; the mean value and standard deviation are selected for the second feature extraction method. To build any number of artificial signal sequences from a single, several conditions are taken into account, for example, their symmetry, they are supposed to be located at the same distance from each other, that is, with an equal step. Symmetrical signal sequences constructed in this way differ from common wellknown signal sequences, such as Fourier series, in that they converge to a given signal in equal steps.

Clinical features and ALDH5A1 gene findings in 13 Chinese cases with succinic semialdehyde dehydrogenase deficiency

Background and aimsTo investigate the clinical features, ALDH5A1 gene variations, treatment, and prognosis of patients with succinic semialdehyde dehydrogenase (SSADH) deficiency.Materials and methodsThis retrospective study evaluated the findings in 13 Chinese patients with SSADH deficiency admitted to the Pediatric Department of Peking University First Hospital from September 2013 to September 2023.ResultsThirteen patients (seven male and six female patients; two sibling sisters) had the symptoms aged from 1 month to 1 year. Their urine 4-hydroxybutyrate acid levels were elevated and were accompanied by mildly increased serum lactate levels. Brain magnetic resonance imaging (MRI) showed symmetric abnormal signals in both sides of the globus pallidus and other areas. All 13 patients had psychomotor retardation, with seven showing epileptic seizures. Among the 18 variants of the ALDH5A1 gene identified in these 13 patients, six were previously reported, while 12 were novel variants. Among the 12 novel variants, three (c.85_116del, c.206_222dup, c.762C > G) were pathogenic variants; five (c.427delA, c.515G > A, c.637C > T, c.755G > T, c.1274T > C) were likely pathogenic; and the remaining four (c.454G > C, c.479C > T, c.1480G > A, c.1501G > C) were variants of uncertain significance. The patients received drugs such as L-carnitine, vigabatrin, and taurine, along with symptomatic treatment. Their urine 4-hydroxybutyric acid levels showed variable degrees of reduction.ConclusionsA cohort of 13 cases with early-onset SSADH deficiency was analyzed. Onset of symptoms occurred from 1 month to 1 year of age. Twelve novel variants of the ALDH5A1 gene were identified.

The Mn2+‐Doped Chiral 2D Perovskite with Strong Orange Fluorescent and Enhanced Circularly Polarized Luminescence

AbstractRecently, the potential circularly polarized luminescence (CPL) property of chiral 2D organic–inorganic hybrid perovskites has garnered attention due to their strong stability. However, the photoluminescence (PL) intensity of chiral 2D perovskite is generally low, which undoubtedly limits its development. Therefore, improving the PL and CPL intensity of chiral 2D perovskite has become an important focal point. To overcome this problem, a series of Mn2+‐doped R/S‐(MPEA)2PbBr4 thin films is successfully synthesized. The Mn2+‐doped films can produce strong orange emission under UV excitation with the highest photoluminescence quantum yield (PLQY) of 37.37%, a high value among reported chiral 2D perovskites. Moreover, all Mn: (R/S‐MPEA)2PbBr4 films show symmetric CPL signals. The flexible regulation of CPL is meaningful for applications, which is generally lacking in current studies. Here, it is found that the strength of CPL can be effectively regulated by doping guanidine (Gua), and the maximum glum value of 1.4 × 10−2 and PLQY of 51.31% is achieved, which are the highest among reported chiral 2D perovskites. This work provides a new idea for the development of CPL‐active materials and lays the foundation for spin devices based on chiral hybrid 2D perovskite.

Affinity Coefficient for Clustering Autoregressive Moving Average Models

In various fields, such as economics, finance, bioinformatics, geology, and medicine, namely, in the cases of electroencephalogram, electrocardiogram, and biotechnology, cluster analysis of time series is necessary. The first step in cluster applications is to establish a similarity/dissimilarity coefficient between time series. This article introduces an extension of the affinity coefficient for the autoregressive expansions of the invertible autoregressive moving average models to measure their similarity between them. An application of the affinity coefficient between time series was developed and implemented in R. Cluster analysis is performed with the corresponding distance for the estimated simulated autoregressive moving average of order one. The primary findings indicate that processes with similar forecast functions are grouped (in the same cluster) as expected concerning the affinity coefficient. It was also possible to conclude that this affinity coefficient is very sensitive to the behavior changes of the forecast functions: processes with small different forecast functions appear to be well separated in different clusters. Moreover, if the two processes have at least an infinite number of π- weights with a symmetric signal, the affinity value is also symmetric.

Unveiling the Role of the Globus Pallidus in Schizophrenia: A Case Report and Neuroimaging Study

Schizophrenia is a complex psychiatric disorder characterized by anomalies in thought, perception, and behavior. Despite advancements in pharmaceutical treatments, managing the disorder remains challenging. Recent research has focused on understanding its biological basis, with particular attention to subcortical structures like the basal ganglia and thalamus, including the globus pallidus. Anomalies in the globus pallidus have been associated with various neurological and psychiatric conditions, showcasing its importance in schizophrenia. However, studies specifically examining abnormalities within the globus pallidus in schizophrenia are limited. In this case report we present the case of a 22-year-old male, Mr. A, diagnosed with schizophrenia. Mr. A exhibited auditory hallucinations, paranoid delusions, and disorganized behavior. Neurological examinations and laboratory tests ruled out underlying medical causes, prompting further investigation with neuroimaging studies. Magnetic resonance imaging revealed bilateral and symmetrical signal anomalies in the posterior part of the globus pallidus, consistent with previous research implicating the basal ganglia in schizophrenia.

Serial analog QAM modems based on complex band-pass filters with LF Bessel prototypes

The article is devoted to the development and implementation of algorithms for quadrature amplitude modulation and demodulation based on analog complex band pass filters with low-frequency Bessel prototypes. The use of complex Bessel filters makes it possible to obtain orthogonal carrier signals close in shape to symmetric signals with practically non-overlapping spectra. Overview of the development and implementation of a serial QAM modem based on analog complex band-pass Bessel filters. The procedure for obtaining the expression for the impulse response of analog complex band-pass Bessel filters is considered. With the help of circuit simulation, the frequency response and impulse response of such a filter are determined. The choice of the center frequency is carried out by setting two coefficients. A block diagram of a serial data transmission system with quadrature amplitude modulation (QAM) based on analog complex band-pass Bessel filters is proposed. The results of its circuit simulation in the Micro-Cap environment are presented.

Brainstem Chipmunk Sign: A Diagnostic Imaging Clue across All Subtypes of Alexander Disease.

While classic brain MR imaging features of Alexander disease have been well-documented, lesional patterns can overlap with other leukodystrophies, especially in the early stages of the disease or in milder phenotypes. We aimed to assess the utility of a new neuroimaging sign to help increase the diagnostic specificity of Alexander disease. A peculiar bilateral symmetric hyperintense signal on T2-weighted images affecting the medulla oblongata was identified in an index patient with type I Alexander disease. Subsequently, 5 observers performed a systematic MR imaging review for this pattern by examining 55 subjects with Alexander disease and 74 subjects with other leukodystrophies. Interobserver agreement was assessed by the κ index. Sensitivity, specificity, and receiver operating characteristic curves were determined. The identified pattern was present in 87% of subjects with Alexander disease and 14% of those without Alexander disease leukodystrophy (P < .001), 3 with vanishing white matter, 4 with adult polyglucosan body disease, and 3 others. It was found equally in both type I and type II Alexander disease (28/32, 88% versus 18/21, 86%; P = .851) and in subjects with unusual disease features (2/2). Sensitivity (87.3%; 95% CI, 76.0%-93.7%), specificity (86.5%; 95% CI, 76.9%-92.5%), and interobserver agreement (κ index = 0.82) were high. The identified pattern in the medulla oblongata, called the chipmunk sign due to its resemblance to the face of this rodent, is extremely common in subjects with Alexander disease and represents a diagnostic tool that can aid in early diagnosis, especially in subjects with otherwise atypical MR imaging findings and/or clinical features.

Sensitivity-enhanced two-dimensional bending sensor based on single-mode fiber measurement

A sensitivity-enhanced two-dimensional bending sensor using four-core fiber (FCF) transition to realized single-channel demodulation of seven-core fiber Bragg grating (FBG) is proposed. A section of FCF was added between the single-mode fiber (SMF) and the seven-core fiber (SCF), and the thermal diffusion technology (TDT) was used so that the signal of the SMF could be transmitted to the three side cores of the SCF through the FCF. Then, a 45° reflective circular cone (45° RCC) is fabricated at the end of the SCF, enabling the coupling of the symmetrical side core signals of the SCF. By inscribing the FBGs with different reflection wavelengths on the side cores of the SCF, the signals of each side core can be distinguished during single-channel demodulation. Monitoring the reflection wavelength shifts of the FBGs on the SCF can realize two-dimensional bending measurements. Furthermore, through the differential operation of the symmetrical side cores, the bending sensitivity can be enhanced while eliminating temperature crosstalk. The proposed sensor with high integration, high sensitivity, and reduced crosstalk, is expected to be applied in the field of structural inspection or interventional medical treatment.

Ultra-high-field 7-Tesla magnetic resonance imaging in fragile X tremor/ataxia syndrome (FXTAS).

Fragile X tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder characterized by premutation expansion of fragile X mental retardation 1 (FMR1) gene. It is a common single-gene cause of tremor, ataxia, and cognitive decline in adults. FXTAS affects the central, peripheral and autonomic nervous systems, leading to a range of neurological symptoms from dementia to dysautonomia. A characteristic imaging feature of FXTAS is symmetric T2 hyperintensity in the deep white matter of the cerebellar hemispheres and middle cerebral peduncle. However, recent studies have reported additional findings on diffusion weighted images (DWI), such as a symmetric high-intensity band-like signal at the cerebral corticomedullary junction. These findings, along with the characteristic cerebellar signal alterations, overlap with imaging findings seen in adult-onset neuronal intranuclear inclusion disease (NIID). Importantly, recent pathology studies have shown that both FXTAS and NIID can manifest intranuclear inclusion bodies, posing a diagnostic challenge and potential for misdiagnosis. We describe a 58-year-old man with FXTAS who received an erroneous diagnosis based on imaging and histopathology results. We emphasize the potential pitfalls in distinguishing NIID from FXTAS and stress the importance of genetic analysis in all cases with suspected NIID and FXTAS for confirmation. Additionally, we present the 7T MRI brain findings of FXTAS.

Parkinsonism-dystonia-2: Case-series study from Saudi Arabia.

Parkinsonism-dystonia-2 PKDYS2 is an autosomal-recessive disorder, caused by pathogenic biallelic variants in SLC18A2 which encodes the vesicular monoamine transporter (VMAT2) protein. PKDYS2 is a treatable neurotransmitter disease, and the rate of diagnosis of this disorder has increased significantly with the advance of genomic technologies. Our report highlights a novel pathologic variant in one case and a novel finding on MRI Brain, consisting of a normal symmetrical signal intensity in the dorsal brainstem and pons, and it substantiates the significance of genetic testing in the evaluation of children with developmental delays, which influences clinical decisions to enhance patient outcomes.

Hot cross bun in pediatric age multi-system atrophy an unusual presentation

A 10-year-old female was brought to emergency department with complaint fever, cold, and cough for 5 days followed by weakness of upper limb weakness more than Lower limb associated with inability to walk/stand, brought to emergency with altered sensorium. Nervous system: Confused and altered, tone is normal, power: 3/3 in upper limbs 2/2 in lower limbs and reflexes in bilateral knee brisk, bilateral plantar-extensor; On general examination revealed hypomimia, dysarthria and bilateral bradykinesia along with ataxic gait and pyramidal signs. Blood investigation were normal and diagnosis made by neuroimaging s/o: Bilaterally symmetrical abnormal signal in both postero-medial thalami, bilateral insular cortices, pons and bilateral middle cerebellar peduncles. It is extending into pons involving transverse pontocerebellar tracts and median pontine raphe nuclei giving 'Hot cross bun sign' (HCBS). During course of treatment child had autonomic disturbances. Child was treated with supportive medication and methyl-presdnisolone followed by oral steroid. Child had responded to treatment given and child has been discharged with no neurological deficit on oral medications. We concluded autonomic dysfunction in any patient presenting with acute onset of weakness with short duration must evaluate for MSA and institute appropriate treatment.

Attractiveness of Facial Symmetry in the Context of the Dominant Visual Field

One of the key features of an attractive face is symmetry. The presence of symmetry in living organisms reflects their ability to cope with various adverse environmental or genetic factors, thus a symmetrical face signals the hidden qualities of the organism. Despite the evolutionary basis for the attractiveness of facial symmetry, studies that have examined it have yielded diverse results. One reason may lie in the fact that the symmetrical stimulus faces are often composites that are created by using the mirror image of one, which can lead to contradictory outcomes. When evaluating human faces, the dominance of the left visual field (as a reflection of brain lateralisation functions) comes into play, which may modify the attractiveness of the composite depending on whether it was created as a left-sided mirror image (using the left half of the face) or a right-sided mirror image (using the right half of the face). The study aims to evaluate the attractiveness of left-sided and right-sided symmetrical facial composites and how the evaluator's visual field dominance affects the assessed attractiveness. The research was conducted on a sample of 1,921 participants aged from 15 to 77 (M = 23.57; SD = 9.52); 60.7% women using computerised facial composites in quasi-experimental research design. The results show that left-sided facial composites are significantly (p&lt;0.001) more attractive than right-sided, for both female and male faces. Furthermore, it is noted that visual field dominance is not related to the type (left-sided vs. right-sided) of symmetry or the evaluation of its attractiveness – individuals with dominant left visual fields as well as those with dominant right visual fields universally rate the left-sided composite as significantly more attractive than the right-sided composite.