Modulation Index Research Articles

Orthogonal Chirp Division Multiplexing With Index Modulation

Orthogonal Chirp Division Multiplexing With Index Modulation

Experimental and numerical investigation on detection of BVID in CFRP composite plates using vibro-acoustic modulation

ABSTRACT Carbon fibre reinforced plastic (CFRP) composite has gained popularity due to the advantages such as its high strength-to-weight ratio and high corrosion resistance, but susceptibility to barely visible impact damage limits their use in engineering. This study experimentally and numerically investigates the detection of BVID in CFRP composite plates using Vibro-acoustic modulation (VAM) technique. An experimental system of VAM was constructed for measuring sidebands induced by the nonlinear effects of BVID. An integrated finite element (FE) model is developed to further explore the nonlinear interaction between the BVID, low-frequency pump, and high-frequency probe waves. To address this issue of the mesh size and computational time step mismatch caused by the large difference in frequency between the pump and probe waves, a regionally refined mesh was employed at the BVID region. Furthermore, the effects of BVID’s size and depth on the modulation were discussed. Through the Hilbert-Huang Transform (HHT), the amplitude modulation (AM) and frequency modulation (FM) indexes were extracted from the VAM responses to quantitatively characterise the impact damages. The results demonstrate that the MIA index increases steadily with the exciting voltage and damage degree, making it a suitable indicator to accurately assess the impact damage in CFRP composites.

Determination of phase components of impedance in the environments over hydrocarbon accumulation

Abstract The article presents a novel method for hydrocarbon accumulation exploration based on determining the phase components of impedance in environments over hydrocarbons. Experimental studies were conducted at the Rechitsa hydrocarbon field and Osipovichi underground gas storage. The phase characteristics of surface impedance of hydrocarbon accumulation were measured using amplitude-frequency-modulated signals. The results show that determining two components of surface impedance in this mode significantly improves the accuracy of hydrocarbon boundary determination. The developed method can be implemented at frequencies of 0.1-2 GHz, using modulation frequencies of 10-100 MHz, amplitude modulation coefficients of 0.1-1.0, and frequency modulation indices of 20-95. The findings of this research can be applied in electrical exploration for prospecting hydrocarbon accumulation.

Performance Analysis of RIS-Aided Index Modulation With Greedy Detection Over Rician Fading Channels

Performance Analysis of RIS-Aided Index Modulation With Greedy Detection Over Rician Fading Channels

Peak-to-Average Power Ratio Reduction Scheme in DCO-OFDM with a Combined Index Modulation and Convex Optimization

Peak-to-Average Power Ratio Reduction Scheme in DCO-OFDM with a Combined Index Modulation and Convex Optimization

Protograph LDPC Code and Shaped Index Modulation Design for Multi-Mode OAM Systems

Protograph LDPC Code and Shaped Index Modulation Design for Multi-Mode OAM Systems

Index Modulation for Fluid Antenna-Assisted MIMO Communications: System Design and Performance Analysis

Index Modulation for Fluid Antenna-Assisted MIMO Communications: System Design and Performance Analysis

Enhanced connectivity through double RIS uplink MIMO and advanced modulation

Reconfigurable Intelligent Surfaces (RISs) have garnered significant attention in the development of Internet of Things (IoT) networks and vehicular communication systems, offering improved spectral efficiency with reduced power consumption and complexity overhead. However, employing a single RIS (S-RIS) may limit certain application scenarios and prove insufficient for ensuring reliable communication between transmitters and receivers. Consequently, the use of multiple RISs is recommended to further enhance coverage, capacity, and spectral efficiency. In this paper, we introduce the concept of Index Modulation (IM) into the double RIS (D-RIS) uplink Multiple-Input Multiple-Output (MIMO) communications, utilizing the antenna indices at the base station (BS). IM is realized through a combination of Space-Shift Keying (SSK) and Spatial Modulation (SM) techniques. We present an analytical model for the Double RIS based on SSK/SM methods and obtain a closed-form expression for the theoretical bit error probability (BEP), employing a greedy detector. To validate our theoretical BEP derivations for d-RIS-SSK/SM, we compare them with simulated BEP results. Our simulation data reveals an excellent match between the derived BEP and the simulated BEP, especially at lower Signal-to-Noise Ratios (SNRs), specifically -34 dB for SSK and -24 dB for SM. Furthermore, we evaluate the performance of the proposed d-RIS-aided IM methods by contrasting them with conventional d-RIS and single RIS-aided IM systems. Our simulation results demonstrate that the d-RIS-assisted IM outperforms the conventional d-RIS and single RIS-aided IM, achieving lower BEP at lower SNRs. d-RIS aided IM saves 15 dB in SNR compared to d-RIS without IM. Moreover, it saves 9 dB and 7 dB in SNR compared to single RIS-SSK and single RIS-SM, respectively when N = 64 and saves 3.5 dB and 1 dB in SNR with N = 128.

Assessing the Influence of Precipitation on the Modulation of the Water Quality Index in a Forested Catchment: The Case of a Tropical Montane Forest in Brazil

Assessing the Influence of Precipitation on the Modulation of the Water Quality Index in a Forested Catchment: The Case of a Tropical Montane Forest in Brazil

A new subcarrier‐index modulation schemes for downlink NOMA systems

SummaryIn this paper, we propose two downlink multiple access architectures for networks where human‐type communication users (HTCUs) and machine‐type communication devices (MTCDs) coexist. The proposed schemes combine non‐orthogonal multiple access (NOMA), orthogonal frequency division multiplexing (OFDM), and index modulation (OFDM‐IM) concepts. In the first scheme, the base station (BS) transmits bits of HTCUs using modulated symbols and bits of MTCDs by the subcarrier activation pattern (SAP). This approach called IM‐NOMA with null subcarriers (IM‐NOMA‐NS) ensures that inactive subcarriers are always null, which improves the system bit error rate (BER) performance. To improve the spectral efficiency (SE), we propose a second approach, termed IM‐NOMA with dual‐mode modulation (IM‐NOMA‐DM), in which the HTCUs' bits are transmitted using two‐dimensional modulation and the MTCDs' bits are transmitted using one‐dimensional modulation and the SAP. For each proposed system, a near‐optimal low‐complexity detector, based on the energy‐detection (ED) and the log‐likelihood ratio (LLR) criterion, is provided to mitigate the detection burden of the optimal maximum‐likelihood (ML) detector. The BER performances and SE of the proposed schemes are investigated. The average BERs of IM‐NOMA‐NS and IM‐NOMA‐DM are derived in closed‐form expressions corroborated by the simulation results. We have proved numerically that the proposed schemes achieve a good trade‐off between BER performance, SE, and the number of supported users, making them more suitable for Internet of Things (IoT) applications.

On the performance of OFDM-IM systems in the presence of CFO effects

This study presents a comprehensive analysis of the performance degradation effects of carrier frequency offset (CFO) on orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems operating over frequency-selective multipath fading channels. CFO is an impairing factor that degrades the signal-to-noise ratio (SNR) through signal attenuation and inter-carrier interference (ICI). We derive a closed-form expression to quantify the SNR degradation under CFO for OFDM-IM systems. Additionally, we formulate a very tight upper bound for the bit error rate (BER), accounting for index modulation errors, CFO distortion, and multipath fading.The presented analytical formulations capture the unique characteristics of OFDM-IM systems and facilitate precise performance evaluation. The findings yield valuable insights into mitigating CFO-induced BER degradation through appropriate system parameter selection and CFO compensation techniques. Moreover, this investigation makes significant contributions towards designing reliable OFDM-IM communication links resilient to the combined effects of index modulation, frequency offsets, and dispersive channel conditions.

Suppression of crystallization process in Atomic Layer Deposited hafnium oxide films

Research on the deposition process of atomic layer deposition (ALD) of hafnium oxide thin films is important because it enhances the performance of nonvolatile memory devices and optical coatings and contributes significantly to advancements within the semiconductor industry. In this study, the alternating deposition of tetrakis(dimethylamido) hafnium and cyclopentadienyl tris(dimethylamino) hafnium precursors was studied. Moreover, this method allows for modulation of the refractive index, surface morphology, preferred orientation and phases of the material. Theoretical calculations revealed that the two precursors selectively adsorb on different crystal planes during the ALD process, elucidating the mechanism behind their preferred orientations. This study reports a method for regulating the phase development of thin films. The crystallization of the hafnium oxide thin films was suppressed by controlling the conditions of deposition.

Diffractionless transmission of optical beams through a four-level atomic system affected by a plasmonic nanostructure

A nondiffracting propagation of an optical beam through a four-level double-V-type quantum system near a plasmonic nanostructure is investigated. We study the linear absorption and dispersion properties of the quantum system as it interacts with two laser fields. We discuss the effect of the control beam with a Laguerre-Gaussian (LG) profile on the focusing of the probe beam in the presence of a plasmonic nanostructure. An appropriately selected control beam excites one transition of the atomic system and generates a spatially varying refraction index modulation for a weak probe beam that couples to the other transition. We demonstrate that placing a plasmonic nanostructure at a nanometer distance from the atomic system and using a control field with the spatial structure leads to the diffraction-less propagation of the probe beam through the atomic system. Also, it is shown that the optical properties and probe beam focusing can be controlled by adjusting the distance of the plasmonic nanostructure from the atomic system. The proposed all-optical waveguide with high contrast and transmission can be used to implement applications such as image transfer through the medium and image processing.

Floquet valley Hall edge solitons

We introduce traveling Floquet valley Hall edge solitons in a genuinely continuous system consisting of a waveguide array with a dynamically varying domain wall between two honeycomb structures exhibiting broken inversion symmetry. Inversion symmetry in our system is broken due to periodic and out-of-phase longitudinal modulation of the refractive index applied to the constituent sublattices of the honeycomb structure. By combining two honeycomb arrays with different initial phases of refractive index modulation we create a dynamically changing domain wall that supports localized linear Floquet edge states despite the fact that on average two sublattices in each honeycomb structure forming the domain wall have the same refractive index. In the presence of focusing nonlinearity, bright or dark Floquet edge solitons may bifurcate from such linear Floquet edge states. We numerically identified family of these solitons and compared them with the results obtained from the analytical approach, which involved averaging over one longitudinal period in the evolution coordinate. These solitons exhibit localization in both spatial directions – along the interface due to nonlinear self-action and across the interface as the edge states – that allows them to travel along the domain wall over long distances without noticeable shape variations.

A Novel High-Gain Switched-Capacitor Multilevel Inverter with Reduced Components for Grid Integration

This paper introduces a novel Multi-Level Inverter (MLI) design which utilizes a single input and leverages capacitor voltages source to generate a four-fold increase in output voltage as the main problem that stays with the inverters is their low boost ability and efficiency while maintaining power quality at the same time. One capacitor is charged to match the input voltage magnitude, while the other two capacitors store twice this magnitude. Through a series-parallel combination with switching operations, all capacitors are effectively charged and discharged within each cycle, ensuring natural voltage balance. A comprehensive comparative analysis is conducted to highlight the advantages of this innovative approach, particularly in terms of component reduction and mitigation of voltage stress. Detailed assessment of power losses within the proposed circuit is undertaken, simulation studies are first carried out while extensive experimentation verifies its operational efficiency under diverse conditions such as varying modulation indices, loads, and supply-side fluctuations with an impressive maximum efficiency of 96.9 % at a 200 W power rating, our research contributes to advancing compact power converters, addressing crucial challenges in modern power electronics applications, and paving the way for enhanced performance and reliability in such systems.

Active Full‐Color Generation Based on a Liquid Crystal‐Integrated Plasmonic Metasurface

Structural colors based on metasurfaces outperform traditional pigments and dyes in terms of nonfading, high spatial resolution, and high stability, usually incorporating active materials for tunability. Liquid crystals (LCs) are suitable for tunable structural color design due to their large birefringence and fast modulation by external stimuli. However, most LC‐integrated structural colors focus on tailoring the polarization angle of incident light to generate two colors and their mixing. Herein, a scheme of full‐color generation based on a plasmonic metasurface integrated with LCs utilizing the combination of the polarization angle rotation effect of the twisted‐nematic LCs and the refractive index modulation through the realignment of the LCs near the metasurface is demonstrated. Based on the proposed structural color method, full‐color generation of a record color gamut of 60.7% standard Red Green Blue region, equivalent to 43% National Television Standards Committee area, in the LC‐integrated metasurface, has been numerically realized by tuning the bias voltage of the LCs in reflection. The achieved color gamut is nearly 4 times wider than the previously reported result. The proposed active full‐color generation metasurface shows great potential in applications for low‐power reflective color display, anticounterfeiting, and optical encoding.

Evolution of microstructure and spectral characteristics of silver nanoparticles in photo-thermo-refractive glass

Photo-thermo-refractive (PTR) glass is widely used in volume holographic devices. After photo-thermo treatment, silver nanoparticles (Ag-NPs) and sodium fluoride (NaF) crystals can precipitate in the glass matrix to realize refractive index modulation (RIM). The Ag-NPs are the foundation for subsequent precipitation of NaF crystals and significantly affect the absorption and luminescence characteristics of PTR glass. Within the nucleation temperature range of 440 °C-480 °C, the Ag-NPs formed by photo-thermo-induced nucleation are within 5 nm. Increasing nucleation heat treatment time causes an increase in the average size of Ag-NPs and the thickness of AgBr shell. Increasing the UV exposure dose significantly increases the concentration of Ag-NPs. The long nucleation time and high UV exposure doses can both increase the content of luminescent silver molecular cluster [Agm]n+, while high nucleation temperatures over 500 °C cause fluorescence quenching of PTR glass due to the formation of large Ag-NPs over 10 nm and NaF crystals. The formation of Ag-NPs effectively reduces the crystallization temperature of PTR glass. The refractive index of PTR glass can be effectively controlled by adjusting the parameters of photo-thermo-induced nucleation. Under the condition of crystallization at 550 °C for 30 min, a maximum RIM value of 1500 ppm can be achieved.

Evaluation of peripheral blood inflammatory biomarkers in sickle cell disease with and without retinopathy.

The aim of this study was to evaluate the clinical significance of blood-cell associated inflammation markers in patients with sickle cell disease (SCD) and sickle cell retinopathy (SCR). Neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), monocyte to lymphocyte ratio (MLR), systemic immune inflammation index (SIII), systemic inflammation response index (SIRI), systemic inflammation modulation index (SIMI) and aggregate systemic inflammation index (AISI) were calculated. This study included 45 healthy controls (Group 1) and 100 SCD (Group 2). Patients in Group 2 were then divided into two groups: without SCR (Group 3) and with SCR (Group 4), and patients with SCR (Group 4) were further divided into two groups: non-proliferative sickle cell retinopathy (NPSCR) (Group 5) and proliferative sickle cell retinopathy (PSCR) (Group 6). The mean values for NLR, PLR, SIII, SIRI, AISI, and SIMI were significantly higher in Group 2 compared to Group 1 (p = 0.011 for NLR, p = 0.004 for SIII, and p < 0.001 for others). Furthermore, AISI and SIMI parameters demonstrated statistically significant discriminatory power to distinguish Group 5 from Group 6 (p = 0.0016 and p = 0.0006, respectively). Given the critical role of inflammatory mechanisms in the pathogenesis of SCD and its related complications, the assessment of blood-cell-associated inflammatory markers may present a pragmatic and advantageous approach to the clinical oversight and therapeutic intervention of SCD.

4 × 4 differential index modulation for optical orthogonal frequency division multiplexing.

In this Letter, we propose and demonstrate a 4 × 4 differential index modulation (DIM) scheme for optical orthogonal frequency division multiplexing (OOFDM) systems. The 4 × 4 DIM scheme avoids complex channel estimation by performing differential index modulation in the time-frequency domain, with the key aspect lying in the design of the time-frequency dispersion matrix that integrates the indices and constellation symbols. Moreover, we design a deep learning-based DIMFormer detector for the high decoding complexity problem of maximum likelihood (ML) detection. Experimental results show that the 4 × 4 DIM in OOFDM systems eliminates the need for complex channel estimation, and the loss of signal-to-noise ratio (SNR) is no more than 1 dB compared to conventional index modulation. The designed DIMFormer detector reduces the computational complexity by 38.98% as well as the time complexity by 99% compared to ML.

Autism spectrum disorder in young patients with congenital central hypoventilation syndrome: role of the autonomic nervous system dysfunction

BackgroundCongenital central hypoventilation syndrome (CCHS) is a rare condition characterized by alveolar hypoventilation and autonomic nervous system (ANS) dysfunction requiring long-term ventilation. CCHS could constitute a risk factor of autism spectrum disorder (ASD) due to birth injury related to respiratory failure, which remains to be determined. ANS dysfunction has also been described in ASD and there are indications for altered contribution of ANS-central nervous system interaction in processing of social information; thus, CCHS could be a risk factor for ASD based on pathophysiological background also. Our study aimed to determine the prevalence of ASD among CCHS patients, identify risk factors, and explore the relationship between the ANS, evaluated by heart rate variability indices, and adaptative functioning.ResultsOur retrospective study, based on the analysis of records of a French national center of patients with CCHS under 20 years of age, determined that the prevalence of ASD (diagnosed by a psychiatrist, following the criteria of DSM-4 or DSM-5) was 6/69 patients, 8.7% (95% confidence interval: 3.3–18.0%). In a case (CCHS with ASD, n = 6) – control (CCHS without ASD, n = 12) study with matching on sex, longer neonatal hospitalization stay and glycemic dysfunction were associated with ASD. Adaptative functioning was assessed using Vineland Adaptative behavioral scales (VABS) and heart rate variability indices (including daytime RMSSD as an index of parasympathetic modulation) were obtained from ECG Holter performed the same day. In 19 young subjects with CCHS who had both ECG Holter and VABS, significant positive correlations were observed between RMSSD and three of four sub-domains of the VABS (communication: R = 0.50, p = 0.028; daily living skills: R = 0.60, p = 0.006; socialization: R = 0.52, p = 0.021).ConclusionOur study suggests a high prevalence of ASD in patients with CCHS. Glycemic dysfunction and longer initial hospitalization stays were associated with ASD development. A defect in parasympathetic modulation was associated with worse adaptative functioning.