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The sand cat swarm optimization algorithm (SCSO) is a metaheuristic algorithm proposed by Amir Seyyedabbasi et al. SCSO algorithm mimics the predatory behavior of sand cats, which gives the algorithm a strong optimized performance. However, as the number of iterations of the algorithm increases, the moving efficiency of the sand cat decreases, resulting in the decline of search ability. The convergence speed of the algorithm gradually decreases, and it is easy to fall into local optimum, and it is difficult to find a better solution. In order to improve the search and movement efficiency of the sand cat, and enhance the global optimization ability and convergence performance of the algorithm, an improved sand cat Swarm Optimization (ISCSO) algorithm was proposed. In ISCSO algorithm, we propose a low-frequency noise search strategy and a spiral contraction walking strategy according to the habit of sand cat, and add random opposition-based learning and restart strategy. The frequency factor was used to control the search direction of the sand cat, and the spiral contraction hunting was carried out, which effectively improved the randomness of the population, expanded the search range of the algorithm, enhanced the moving efficiency of the sand cat, and accelerated the convergence speed of the algorithm. We use 23 standard benchmark functions and IEEE CEC2014 benchmark functions to compare ISCSO with 10 algorithms, and prove the effectiveness of the improved strategy. Finally, ISCSO was evaluated using five constrained engineering design problems. In the results of these problems, using ISCSO has 3.08%, 0.23%, 0.37%, 22.34%, 1.38% improvement compared with the original algorithm respectively, which proves the effectiveness of the improved strategy in practical application problems. The source code website for ISCSO is https://github.com/Ruiruiz30/ISCSO-s-code. [ABSTRACT FROM AUTHOR]

Noise reduction in various industrial and building systems such as ventilation ducts, vehicles, wind tunnels, and test facilities for jet engines, automobiles, and factories has always interested engineers, especially the problematic noise reduction at low frequencies. This problem is even more important with passive silencers, which require absorbent materials and more space. Passive silencers include reactive and dissipative silencers. Among reactive silencers, Helmholtz resonators, expansion chambers, flute-like, drum-like, and plate silencers have proven effective at low frequencies. Combining some of these silencers with a dissipative silencer, called a hybrid silencer, can achieve excellent performance at a wide range of low to high frequencies. In these silencers, the reactive part reduces noise at low frequencies, and the dissipative part reduces noise at medium and high frequencies. The aim of this work, which focuses more on experimental studies, is to introduce the mentioned silencers, investigate the presented methods to improve the performance of these silencers at low frequencies, and offer the practical advantages and disadvantages of these methods. [ABSTRACT FROM AUTHOR]

Abstract Low-frequency noise (LFN) characteristics of semiconductor devices pose a significant importance for understanding their working principle, particularly concerning material imperfections. Accordingly, substantial research endeavors have focused on characterizing the LFN of devices. However, the LFN characteristics of the ambipolar transistors have been rarely demonstrated. Herein, we investigate the effects of ambipolar carrier transport and CYTOP-induced p-type doping on low-frequency noise characteristics of MoTe2 transistors. The source of the 1/f noise differs between the n-type (electron transport) and p-type (hole transport) modes. Notably, the influence of contact resistance is more pronounced in the n-type mode. CYTOP doping suppresses the n-type mode by introducing hole doping effects. Furthermore, CYTOP doping mitigates the impact of contact resistance on excess noise.

Industrial noise sources are among the environmental noise sources that are ranked second among the causes of ill health in Europe by the World Health Organization. The aim of this paper is to summarize and review of published information focusing on noise annoyance from industrial activities and mining. A search for articles was performed using the bibliographic databases platforms. The epidemiological evidence shows that environmental noise may be associated with cardiovascular and metabolic diseases, impaired cognitive development in children, mental health, post-irritability, and sleep disturbances. As a result of efforts to minimize the effects of industrial noise on human health, the New South Wales Environment Protection Authority published A Guide to the Noise Policy for Industry in 2017, which sets out recommended noise levels, methods, and procedures for noise management based on the latest scientific evidence. Social networks can be used to assess the population’s noise annoyance and to verify the effectiveness of the measures. The industrial noise sources are typically defined by low-frequency noise. Low-frequency noise has very low attenuation and is only slightly affected by obstacles, therefore it can be a major cause of night noise annoyance. An association was confirmed between exposure to low-frequency noise and sleep disturbance, psychological problems, cognitive impairment, increased social conflicts, anxiety, emotional instability, nervousness, and reduced mental performance – concentration, and visual perception. In view of the long tradition of mining and industry, the assessment of noise from these activities from the perspective of its impacts on human health is an inherent part of legislative processes. Med Pr Work Health Saf. 2024;75(5):425–431

Objective The noise generated by air-conditioning system is a primary source of static noise in trams, with most of the interior noise originating from the air-conditioning supply fan. Aimed at reducing the noise in air-conditioning duct, research focusing on the duct structure is carried out to design a low-frequency, broadband noise elimination and reduction structure. Method Noise reduction optimization is performed on the noise transmission path of the air-conditioning return air duct in trams. Referring to the original air return structure, a composite noise reduction device is designed, which is based on a perforated plate combined with porous sound-absorbing materials, to mitigate the fan noise transmitted through the return air duct. A statistical energy model that includes the return air duct and the fan noise source is established. Combined with the theoretical calculation of sound absorption structure, the noise reduction characteristics of diversion and noise elimination air duct are calculated and analyzed. Result & Conclusion The adoption of a flow division and noise elimination duct effectively decreases the noise transmitted by the fan. By building a test platform for air-conditioning duct, the feasibility of using the noise reduction duct to eliminate tram air-conditioning system noise is validated.

The low-frequency noise (LFN) in downscaled silicon transistors has become prominently large, and it occurs as a limiting factor for diverse applications. Considerable interest is paid to the “slow” (as compared to the operating frequency of the devices) noise. Therefore, we address the trends for LFN from an extensive analysis of data from many publications over a very long period. The impact of LFN on high-frequency device performance, the penalties associated with using composite materials, and unsolved issues are also discussed. [ABSTRACT FROM AUTHOR]

Low-frequency noise (LFN) characteristics of semiconductor devices pose a significant importance for understanding their working principle, particularly concerning material imperfections. Accordingly, substantial research endeavors have focused on characterizing the LFN of devices. However, the LFN characteristics of the ambipolar transistors have been rarely demonstrated. Herein, we investigate the effects of ambipolar carrier transport and CYTOP-induced p-type doping on low-frequency noise characteristics of MoTe2 transistors. The source of the 1/f noise differs between the n-type (electron transport) and p-type (hole transport) modes. Notably, the influence of contact resistance is more pronounced in the n-type mode. CYTOP doping suppresses the n-type mode by introducing hole doping effects. Furthermore, CYTOP doping mitigates the impact of contact resistance on excess noise. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) with different GaN channel layers grown on AlN buffer layer are fabricated and investigated in order to optimize the device performances and to study the noise properties. To investigate the strain effect of the GaN channel layer grown on the AlN buffer layer, the positive shift of Raman peak is observed as the GaN channel becomes thinner. The threshold voltages (Vth) of the fabricated devices shift to positive direction according to the decreased GaN channel layer due to the decreased 2‐dimensional electron gas (2DEG) and deteriorated crystal quality of GaN channel layer. All devices demonstrated 1/f noise properties and the dominance of the carrier number fluctuations (CNF) noise mechanism. The largest trap density (Nt) value in the narrowest GaN channel device is because of the degraded crystal quality and the enhanced strain effect of the GaN channel layer. However, the lowest noise levels at the drain current (Id) > 10−6 A for the device with the GaN channel thickness of 30 nm grown on AlN buffer layer are observed to be due to the fully depleted GaN channel layer although its poor crystal quality. [ABSTRACT FROM AUTHOR]

[Objective] The noise generated by air-conditioning system is a primary source of static noise in trams, with most of the interior noise originating from the air-conditioning supply fan. Aimed at reducing the noise in air-conditioning duct, research focusing on the duct structure is carried out to design a low-frequency, broadband noise elimination and reduction structure. [Method] Noise reduction optimization is performed on the noise transmission path of the air-conditioning return air duct in trams. Referring to the original air return structure, a composite noise reduction device is designed, which is based on a perforated plate combined with porous sound-absorbing materials, to mitigate the fan noise transmitted through the return air duct. A statistical energy model that includes the return air duct and the fan noise source is established. Combined with the theoretical calculation of sound absorption structure, the noise reduction characteristics of diversion and noise elimination air duct are calculated and analyzed. [Result & Conclusion] The adoption of a flow division and noise elimination duct effectively decreases the noise transmitted by the fan. By building a test platform for air-conditioning duct, the feasibility of using the noise reduction duct to eliminate tram air-conditioning system noise is validated. [ABSTRACT FROM AUTHOR]

Wood pellets are increasingly promoted as a renewable and sustainable energy source, driving the global wood pellet market to a projected value of $16 billion by 2026. However, the rapid expansion of this industry disproportionately affects predominantly Black and low-income communities in the rural South, where approximately 100 pellet manufacturing plants are currently located in the United States. From August 2023 to March 2024, we conducted a noise exposure assessment in Gloster, Mississippi, a community affected by pellet production, and compared it to Mendenhall, a nearby community without industrial activity. In collaboration with a local organization, we measured noise metrics and found significantly higher A-weighted, C-weighted, and Z-weighted sound levels in Gloster, along with elevated decibels at multiple center frequencies. These findings suggest that wood pellet manufacturing can severely alter the soundscape of rural communities, raising environmental justice concerns. Our findings underscore the importance of investigating the cumulative health impacts of noise and other environmental burdens on these vulnerable communities to better inform policy.

The pursuit of sub‐1‐nm field‐effect transistor (FET) channels within 3D semiconducting crystals faces challenges due to diminished gate electrostatics and increased charge carrier scattering. 2D semiconductors, exemplified by transition metal dichalcogenides, provide a promising alternative. However, the non‐idealities, such as excess low‐frequency noise (LFN) in 2D FETs, present substantial hurdles to their realization and commercialization. In this study, ideal LFN characteristics in monolayer MoS2 FETs are attained by engineering the metal‐2D semiconductor contact and the subgap density of states (DOS). By probing non‐ideal contact resistance effects using CuS and Au electrodes, it is uncovered that excess contact noise in the high drain current (ID) region can be substantially reduced by forming a van der Waals junction with CuS electrodes. Furthermore, thermal annealing effectively mitigates sulfur vacancy‐induced subgap density of states (DOS), diminishing excess noise in the low ID region. Through meticulous optimization of metal‐2D semiconductor contacts and subgap DOS, alignment of 1/f noise with the pure carrier number fluctuation model is achieved, ultimately achieving the sought‐after ideal LFN behavior in monolayer MoS2 FETs. This study underscores the necessity of refining excess noise, heralding improved performance and reliability of 2D electronic devices. [ABSTRACT FROM AUTHOR]

Interface issues with organic semiconductors on metal oxide challenge realizing a high‐performance anti‐ambipolar transistor (AAT) with stable operation. The motivation behind this research delves into the intricate landscape of AATs, elucidating their envisioned applications and constituent materials. Central to the authors, discourse is the pivotal role that fluoropolymers assume, acting as a bridge uniting n‐type metal oxide semiconductors (n‐oxide) with p‐type organic semiconductors (p‐organic), thereby unveiling a hitherto concealed facet of transistor advancement. Adopting a spatially separating layer (SSL) between p‐ and n‐type semiconductors of AAT is unconventional, but this p‐organic/SSL/n‐oxide junction (pSn) AAT exhibits stable operation also 215 days after fabrication and minimal hysteresis, which is 13.67 times smaller than a conventional p‐organic/n‐oxide junction (pn) AAT. The effect of SSL is closely studied through comparisons of the performance of single‐type transistors, trap density, and carrier behavior, which define the order of 1/f at low‐frequency noise analysis. In addition, the contribution of SSL is confirmed via the channel formation mechanism of AAT investigated through a two‐dimensional (2D) finite‐element simulation. The operation stability of pSn AAT is evaluated through combined stress tests, long‐term stability tests, and transient response tests. This research proposes SSL as a new design parameter to improve the AAT. [ABSTRACT FROM AUTHOR]

We have previously shown that one-dimensional edge contact to two-dimensional heterostructure field effect transistors with a graphene channel, and hexagonal boron nitride, as both the substrate material and top encapsulated layer, show ultrahigh carrier mobility and ultralow carrier noise (low frequency noise, LFN). Although the noise mechanism of the transistor devices in the ON state was modeled based on microscopic scattering mechanisms caused by charge carriers and phonons, the model was based on normalized noise spectral density following Hooge's noise model in the ON-state. In this article, we show that the normalized noise current densities within the charge residual region of two similarly fabricated edge-contacted and encapsulated graphene heterostructure field effect transistors show different trends with overdrive voltage that resemble previously reported results in the literature. Here we explain the poorly understood and conflicting LFN trends in the charge residual region (low charge carrier regime) by correlating the spatial charge inhomogeneity near the Dirac point in heterostructure devices to electron–hole puddles. By systematically studying the temperature-dependent transport, LFN and by modeling the channel characteristics in such devices within the charge residual region, we show that the carriers inside electron–hole puddles get pinned at lower temperatures and unpinned at higher temperatures, as consistently shown in their normalized flat-band spectral variation as a function of overdrive voltage. More generally, near the charge neutrality region of single-layer graphene devices, the LFN is described by a correlated carrier number and mobility fluctuations of the charge carriers. Understanding the carrier physics in encapsulated high-performance and edge-contacted heterostructure two-dimensional devices will aid us in not only engineering low-noise graphene-based FETs for future digital and analog electronics but also understanding the noise associated with Dirac-type materials. [ABSTRACT FROM AUTHOR]

This paper describes a new method for automatic preparation of a noisy seismic record for further analysis using expert information systems. The method is based on seismogram fingerprints, which, due to their concise but informative pattern, allow the development of a reliable algorithm for finding important noise characteristics. The search for the optimal cutoff frequency for a high-pass filter is especially important under conditions of partial overlap of the signal and noise spectra, when the latter have high intensity. It is precisely this difficult case that this study aims to address. The article analyzes the methodology developed here in application to several hundred records of regional earthquakes and explosions. The analysis showed that reliable results can be achieved in more than 90% of the cases. In addition, the defects and limitations of the method are mentioned, which are logical consequences of its advantages. The Appendix to this article contains a detailed description of the algorithm underlying the method. [ABSTRACT FROM AUTHOR]

This article continues and supplements the article with the same title published in Russian Journal of Nondestructive Testing, no. 1, 2022, which provides six ways to assess the quality and reliability of semiconductor products (SCPs) using low-frequency (LF) noise parameters. This paper presents a generalization of the results previously obtained by the authors and describes four more methods for diagnosing and evaluating the reliability of SCPs by varying the parameters of low- frequency noise under additional external influences such as electrostatic discharge and (or) thermal annealing. It is shown that additional impacts make it possible to increase the reliability of the assessment of the SCP reliability. [ABSTRACT FROM AUTHOR]

Reinforcement learning (RL), exhibiting outstanding performance in various fields, requires large amounts of data for high performance. While exploration techniques address this requirement, conventional exploration methods have limitations: complexity of hardware implementation and significant hardware burden. Herein, in‐memory RL systems leveraging intrinsic 1/f noise of synaptic ferroelectric field‐effect‐transistors (FeFETs) for efficient exploration are proposed. The electrical characteristics of fabricated FeFETs with low‐power operation capability verify their suitability for neuromorphic systems. The proposed system achieves comparable performance to the conventional exploration method without additional circuits. The intrinsic 1/f noise of the FeFETs facilitates efficient exploration and offers significant advantages: efficiency in hardware implementation and simplicity in adjusting the 1/f noise level for optimal performance. This approach effectively addresses the challenges of conventional exploration methods. The operation mechanism of the exploration method utilizing the 1/f noise is systematically analyzed. The proposed in‐memory RL system demonstrates robustness and reliability to the device‐to‐device variation and the initial conductance distribution. This work provides further insights into the exploration methods of RL, paving the way for advanced in‐memory RL systems. [ABSTRACT FROM AUTHOR]

Introduction and purpose: Noise is one of the most harmful physical factors in workplaces in both developed and developing countries. Still, low-frequency noise has not received enough attention, and the current regulations on its control are inadequate. To address this issue, the present study was conducted to examine the physiological response and cognitive functions of individuals before and after exposure to low-frequency noise. Methods: This study was conducted in the solar year 1401 and involved 40 students from Mazandaran University of Medical Sciences. Low-frequency noise with a level of 65 dB A was played for one hour. The patients' heart rates, blood pressure, and core temperatures were collected before and after exposure to low-frequency noise. Moreover, the continuous performance test was used to examine their cognitive performance. The data was analyzed using the Friedman and Voilcoxon tests in SPSS 25 software. Results: Low-frequency noise adversely impacted individual cognitive performance, increasing response error, omission error, and reaction time. However, according to the Wilcoxon test, only the increase in reaction time was statistically significant (P0.05). Conclusion: Exposure to low-frequency noise generates greater discomfort than background noise with the same intensity level and has adverse effects on the individual's performance. Thus, the adverse effects of low-frequency noise are particularly significant in workstations that require mental processing of information and specific attention, such as control rooms and offices.

Rapid transit or mass rapid transit (MRT) is a high-capacity public transport designed to carry a large number of passengers, especially during the peak hours. They are becoming very popular in major cities and some deem the presence of the rapid transit system in a city as a symbol of modern development and essential feature of urban life. As the rapid transit system expands, the traveling time on a rapid transit train may increase due to longer journey and cabin noise has become an environmental concern for the passengers. In the present study, we would attempt to do a more detailed study of the effect of viaduct height, in particular viaducts of different heights on the cabin noise of various rapid transit systems. The present study examined and benchmarked the cabin noise in terms of both dB(A) and dB(C) for four different rapid transit systems, namely part of the East-West line including the Tuas-West extension on elevated tracks with very high viaduct of the Singapore MRT System; part of Paris Line 2 from Anvers to Belleville station including a stretch of elevated track on viaduct; part of the Piccadilly line of London from Heathrow Airport to Green Park station with a stretch on surface ground; and finally part of Chongqing Line 3 from Gongmao to Lianglukou station across the Yangtze river. It was found that the cabin noise would be dominated by low-frequency content and would be better reflected if the measurements were presented in dB(C), especially for trains running on elevated tracks of greater height.

With the continuous warming of the global climate, expanding the use of renewable energy has become one of the main social responsibilities. However, as the number of installed wind turbines and their physical dimensions continue to increase, the issue of generated noise has become increasingly significant in influencing the acceptance and endorsement of wind power projects by neighboring communities. In this paper, we investigated the noise generated by two wind turbine units with rated powers of 1.5 MW and 4.5 MW and analyzed the variations in low-frequency noise during their operation and shutdown periods. This research shows that the power of a single unit has a significant impact on the low-frequency noise emitted into the environment. Compared with 1.5 MW wind turbines, 4.5 MW wind turbines generate more low-frequency noise when operating at the same wind speed. Further analysis of the narrowband frequency spectra and one-third octave spectra of the measured noise indicates that the low-frequency noise from the 4.5 MW wind turbine increases significantly in the range of approximately 80 Hz to 300 Hz, with more pronounced variations below 250 Hz corresponding to changes in wind speed. However, the overall variations in low-frequency noise with wind speed are not as notable as those observed for the 1.5 MW wind turbine. Due to the relatively weak attenuation of low-frequency noise in the atmosphere, the higher low-frequency content of large wind turbines may cause more distress to residents near wind farms. The result of this study emphasizes that in the planning and design of wind power projects, in addition to considering the efficiency of single-unit power generation and the contribution of renewable energy, it is also necessary to pay full attention to noise emission issues to ensure that the project is widely supported and accepted in the community. [ABSTRACT FROM AUTHOR]

Exposure to intense low-frequency sounds, for example inside tanks and armoured vehicles, can lead to noise-induced hearing loss (NIHL) with a variable audiometric pattern, including low- and mid-frequency hearing loss. It is not known how well existing methods for diagnosing NIHL apply in such cases. Here, the audiograms of 68 military personnel (mostly veterans) who had been exposed to intense low-frequency noise (together with other types of noise) and who had low-frequency hearing loss (defined as a pure-tone average loss at 0.25, 0.5 and 1 kHz ≥20 dB) were used to assess the sensitivity of three diagnostic methods: the method of Coles, Lutman and Buffin, denoted CLB, which depends on the identification of a notch or bulge in the audiogram near 4 kHz, and two methods specifically intended for diagnosing NIHL sustained during military service, the rM-NIHL method, which depends on the identification of a notch or bulge in the audiogram near 4 kHz and/or a hearing loss at high frequencies greater than expected from age alone, and the MLP(18) method based on a multi-layer perceptron. The proportion of individuals receiving a positive diagnosis for either or both ears, which provides an approximate measure of sensitivity, was 0.40 for the CLB method, 0.79 for the rM-NIHL method and 1.0 for the MLP(18) method. It is concluded that the MLP(18) method is suitable for diagnosing NIHL sustained during military service whether or not the exposure includes intense low-frequency sounds. [ABSTRACT FROM AUTHOR]

In this paper, an analytical drain current model of double gate MoS2 FET Transistor for low‐frequency noise (LFN) power spectral density is developed, and compared its response with the device simulation of the proposed device structure. The developed low‐frequency noise power spectral density (PSD) model is analyzed with respect to different Trap densities, Oxide thicknesses, and high K‐dielectric materials using the TCAD Device simulation tool. Low‐frequency noise is one of the most important noises in any device since it degrades the device's performance. So, in this paper, we used a unique charge‐control model for analyzing the low‐frequency noise by considering the mobility degradation, trapping, and de‐trapping effects caused by trap densities and device lattice structure. Usually, all the previous studies on drain currents with low frequency are based on fluctuations caused by mobility and carrier variations. In our paper, we even considered the charge density fluctuation to analyze the drain current equation. Using a Charge Control Model, we can compute the parameters like gate capacitance (Cgs, Cgd), channel length modulation, and body effect. While other LFN models like the DC model, small signal model, and hybrid model will focus mainly on the static characteristics of the device such as its DC current–voltage (I‐V) relationship, terminal resistances, and input/output conductance of the devices. All the analytical model results were calibrated with the device simulation and it is observed that both are matches each other. Further, it is observed that with an increase in Trap density, the low‐frequency noise increases and low‐frequency noise is dominant at lower frequencies only (1–10 Hz), and after this frequency range the thermal noise will be the dominant noise factor. [ABSTRACT FROM AUTHOR]

Low-frequency noise has a long wavelength, decays very slowly, and is extremely penetrating. Traditional marine acoustic insulation materials have difficulty achieving effective control of this low-frequency noise. In this paper, a series-parallel arrangement structure of a low-frequency metamaterial is designed, which mainly comprises convoluted channels and Helmholtz cavities in series and a sandwich arrangement of multiple cells (as opposed to the traditional parallel arrangement). We use a numerical method to establish an acoustic-solid coupling model for the metamaterial, consider the influence of thermal and viscous losses on its sound absorption performance, and investigate the sound absorption characteristics and mechanisms of the single-cell and multicell structures. The metamaterial designed in this paper shows an average absorption coefficient of 0.97 in the range of 130–145 Hz. An experimental model was prepared by 3D printing, and the intended sound absorption effect was experimentally verified. [ABSTRACT FROM AUTHOR]

Reinforcement learning (RL), exhibiting outstanding performance in various fields, requires large amounts of data for high performance. While exploration techniques address this requirement, conventional exploration methods have limitations: complexity of hardware implementation and significant hardware burden. Herein, in‐memory RL systems leveraging intrinsic 1/f noise of synaptic ferroelectric field‐effect‐transistors (FeFETs) for efficient exploration are proposed. The electrical characteristics of fabricated FeFETs with low‐power operation capability verify their suitability for neuromorphic systems. The proposed system achieves comparable performance to the conventional exploration method without additional circuits. The intrinsic 1/f noise of the FeFETs facilitates efficient exploration and offers significant advantages: efficiency in hardware implementation and simplicity in adjusting the 1/f noise level for optimal performance. This approach effectively addresses the challenges of conventional exploration methods. The operation mechanism of the exploration method utilizing the 1/f noise is systematically analyzed. The proposed in‐memory RL system demonstrates robustness and reliability to the device‐to‐device variation and the initial conductance distribution. This work provides further insights into the exploration methods of RL, paving the way for advanced in‐memory RL systems.

This paper presents the design and cryogenic electrical characterization of a voltage reference and a linear voltage regulator at temperatures between 6 K and 300 K. Both circuits are employed as test vehicles for the experimental performance evaluation of the 22 nm FDSOI MOS technology when used as platform for the development of cryogenic analog systems, whose role is relevant in Quantum Computing (QC) applications. Additionally, we report the impact that MOS transistor cryogenic phenomena have over these circuits and propose to take advantage of some of those phenomena in analog circuit design. In particular, we focus on the cryogenic threshold voltage $(V_{\text {th}})$ saturation, the transconductance $(g_{m})$ increase and the low frequency (LF) excess noise. Our experimental results indicate that the cryogenic $V_{\text {th}}$ saturation and the $g_{m}$ increase can be used as circuit design tools, while the LF excess noise is a performance handicap for cryogenic analog circuits.

This paper summarizes the currently available knowledge on the impact of infrasound and low frequency noise (LFN) on human health and well-being. This narrative review of the literature data was based on the selected, mostly, peer-reviewed research papers, review articles, and meta-analyses that were published in 1973–2022. It has been focused on infrasound perception, annoyance attributed to infrasound and low-frequency noise, as well as their effects on the cardiovascular system and sleep disorders. Particular attention was also paid to the latest research results and specific sources of infrasound and LFN, i.e., wind turbines. Med Pr Work Health Saf. 2023;74(4):317–32.

Low-frequency noise modeling and estimation is a critical issue in the design of analog and digital circuits, especially for short-channel CMOS technologies. The conventional noise models do not fit the experimental results adequately at frequencies close to DC for amplifiers and close to the carrier frequency for oscillators. Furthermore, measuring this noise necessitates the use of specialized and expensive equipment. In this paper, the bound of carrier trapping and releasing are extracted while examining the characteristics of low-frequency noise using the EMD method, and an innovative model based on carrier number fluctuations is proposed. The method introduces a low-cost measurement system for low-frequency noise. The performance accuracy of this measurement system and the proposed model is evaluated and compared with conventional noise modeling methods. The evaluation results demonstrate the success of the proposed measurement setup and model in estimating near-DC noise.

Background: Subjective everyday hindrances associated with low-frequency noise (LFN) can be high; however, there is still a lot unknown about experienced complaints. This study aims to investigate (1) subjective complaints and (2) coping strategies of individuals reporting everyday hindrances from LFN. Methods: Cognition, depressive symptoms, sleeping, fatigue, stress, and coping questionnaires were administered to participants sampled for their LFN complaints (LFN1 = 181), LFN complainants derived from a community sample (LFN2 = 239), and a comparison group without LFN complaints (CG = 410). Results: Individuals reporting LFN perceptions reported complaints in all domains and showed a higher proportion of above average symptom severity compared to the CG. Most complaints were reported by the LFN1 group, the least by the CG. However, on some sleeping, fatigue, and stress-related variables, a similar or even higher symptom severity was observed in the LFN2 group. Further, all groups used a similar combination of multiple coping strategies, although the LFN1 group scored higher on support seeking. Conclusions: There might be differences in the complaint severity between different LFN subgroups and future investigations of primary and secondary complaints are necessary. Also, more research about the use and success of coping strategies for LFN-related hindrances are needed for clear conclusions. [ABSTRACT FROM AUTHOR]

This paper analyzes the beneficial effects on phase detection arising from the motion of an ac-coupled Doppler radar. Indeed, although the presence of an ac coupling stage suppresses the dc offset after the receiver RF output, due to the coupling capacitor, a high-pass behavior is introduced; the presence of a high-pass behavior leads to signal distortion, particularly for low Doppler frequencies, which are typical in many biomedical or industrial applications. Since the target displacement is usually extracted from the phase history, this effect might, in turn, worsen the overall accuracy of the system. Moreover, if the target alternates stationary and moving time intervals, the phase detection step becomes challenging. Indeed, during the stationary time, the output of the RF front-end shows only noise fluctuations that, in turn, result in uncorrelated phases which might be confused with the real target displacement. This negative effect might be avoided by keeping the radar continuously moving, thus exploiting what is usually considered a state that is negative and worthy of attention. In this contribution, this effect is addressed from a different perspective, and ad hoc experimental case studies are shown to demonstrate the effectiveness of the proposed system. This task has been accomplished through theoretical analysis and related experimental activity. [ABSTRACT FROM AUTHOR]

Hardware neuromorphic systems are crucial for the energy‐efficient processing of massive amounts of data. Among various candidates, hafnium oxide ferroelectric tunnel junctions (FTJs) are highly promising for artificial synaptic devices. However, FTJs exhibit non‐ideal characteristics that introduce variations in synaptic weights, presenting a considerable challenge in achieving high‐performance neuromorphic systems. The primary objective of this study is to analyze the origin and impact of these variations in neuromorphic systems. The analysis reveals that the major bottleneck in achieving a high‐performance neuromorphic system is the dynamic variation, primarily caused by the intrinsic 1/f noise of the device. As the device area is reduced and the read bias (VRead) is lowered, the intrinsic noise of the FTJs increases, presenting an inherent limitation for implementing area‐ and power‐efficient neuromorphic systems. To overcome this limitation, an adaptive read‐biasing (ARB) scheme is proposed that applies a different VRead to each layer of the neuromorphic system. By exploiting the different noise sensitivities of each layer, the ARB method demonstrates significant power savings of 61.3% and a scaling effect of 91.9% compared with conventional biasing methods. These findings contribute significantly to the development of more accurate, efficient, and scalable neuromorphic systems. [ABSTRACT FROM AUTHOR]

Low-frequency noise, the frequency range from approximately 10 Hz to 200 Hz, has been recognized as a special environmental noise problem. The World Health Organization recognizes the special place of low-frequency noise as an environmental problem. Noise can damage hearing, and it affects the whole body. Low-frequency sound is heard by humans, but infrasound is not audible. Low-frequency sound is most often measured based on a weighting function of the frequency. The A-weighted level underestimates the effects of low-frequency noise. For the detrimental effects of low-frequency sound, it would be appropriate to apply measurements using Z-weighting. The aim of this paper was to propose a comprehensive method of acoustic risk assessment (CMARA) that implements the effects of low-frequency values of noise exposure. The proposed methodology has been applied in practice at four workplaces for seven work activities. A risk assessment using the proposed CMARA method for individual activities shows that the noise exposure time may pose a health risk in the occupational and environmental process due to exposure to low-frequency noise at the limit of audibility. A high risk was assessed for activities WA2 (machining) and WA3 (spot welding). This paper highlights the need to measure low-frequency noise using Z-filter weighting. [ABSTRACT FROM AUTHOR]

low frequency noise and electrical characteristics of the p-InAsSbP/n-InAs single photodiode heterostructures grown onto n+-InAs substrates have been measured in the presence of atmosphere containing ethanol vapor. Correlation between ethanol vapor density and electrical noise spectral density, as well as the heterostructure resistance, has been estimated, and possible reasons for such correlation have been discussed. [ABSTRACT FROM AUTHOR]

Abstract A meteorologically challenging situation that represents a demanding control task (rotational speed, pitch and yaw) for a wind turbine is presented and its implementation in a simulation is described. A high‐fidelity numerical process chain, consisting of the computational fluid dynamics (CFD) solver FLOWer, the multi‐body system (MBS) software SIMPACK and the Ffowcs Williams‐Hawkings code ACCO, is used. With it, the aerodynamic, servoelastic and aeroacoustic (

This paper presents the design and testing of an ultra-low-noise transimpedance amplifier (TIA) for low-frequency noise measurements on low-impedance (below 1 kΩ) devices, such as advanced IR photodetectors. When dealing with low-impedance devices, the main source of background noise in transimpedance amplifiers comes from the equivalent input voltage noise of the operational amplifier, which is used in a shunt–shunt configuration to obtain a transimpedance stage. In our design, we employ a hybrid operational amplifier in which an input front end based on ultra-low-noise discrete JFET devices is used to minimize this noise contribution. When using IF3602 JFETs for the input stage, the equivalent voltage noise of the hybrid operational amplifier can be as low as 4 nV/√Hz, 2 nV/√Hz, and 0.9 nV/√Hz at 1 Hz, 10 Hz, and 1 kHz, respectively. When testing the current noise of an ideal 1 kΩ resistor, these values correspond to a current noise contribution of the same order as or below that of the thermal noise of the resistor. Therefore, in cases in which the current flicker noise is dominant, i.e., much higher than the thermal noise, the noise contribution from the transimpedance amplifier can be neglected in most cases of interest. Test measurements on advanced low-impedance photodetectors are also reported to demonstrate the effectiveness of our proposed approach for directly measuring low-frequency current noise in biased low-impedance electronic devices. [ABSTRACT FROM AUTHOR]

Low-frequency noise modeling and estimation is a critical issue in the design of analog and digital circuits, especially for short-channel CMOS technologies. The conventional noise models do not fit the experimental results adequately at frequencies close to DC for amplifiers and close to the carrier frequency for oscillators. Furthermore, measuring this noise necessitates the use of specialized and expensive equipment. In this paper, the bound of carrier trapping and releasing are extracted while examining the characteristics of low-frequency noise using the EMD method, and an innovative model based on carrier number fluctuations is proposed. The method introduces a low-cost measurement system for low=frequency noise. The performance accuracy of this measurement system and the proposed model is evaluated and compared with conventional noise modeling methods. The evaluation results demonstrate the success of the proposed measurement setup and model in estimating near-DC noise. [ABSTRACT FROM AUTHOR]

AlGaN/GaN Fin-shaped field-effect transistors (FinFETs) with nano-sized Fin width ( $\text{W}_{\mathrm {Fin}}$ ) from 20 nm to 230 nm are characterized using low-frequency noise (LFN) measurement. All devices exhibit 1/ $f$ noise shape with Hooge mobility fluctuations (HMF) at subthreshold region and carrier number fluctuations (CNF) at accumulation region. However, the lowest normalized drain current noise spectral densities ( $S_{Id}/I_{d}^{2}$ ) are obtained in the narrow Fin device ( $\text{W}_{\mathrm {Fin}}$ = 20 nm). This is due to significant contribution of bulk channel without the 2-dimensional electron gas density (2DEG) channel and two sidewall metal-oxide-semiconductor (MOS) channels. It is also noticed that the lowest trap density ( $N_{t}$ ) and a large separation in CNF noise model clearly indicate to the volume accumulation effect caused by bulk conduction in narrow device. The Hooge constants ( $\alpha _{\mathrm {H}}$ ) extracted by HMF noise model for the narrow device are one-order higher than those of the wide Fin device, which tells that the narrow device suffers from the strong phonon scattering in the bulk channel. From the product of ( $S_{Id} \times $ frequency ( $f$ )) versus $\text{I}_{\mathrm {d}}$ curves, the volume accumulation phenomenon is also clearly observed in narrow Fin device.

Subject and Purpose. The subject of research is the flicker noise present in informant signals of search-and-rescue radars, specifically its properties and the effect it may have on algorithms for detecting and identifying manifestations of human breath and heartbeat processes during rescue operations. The work has been aimed at creating a suitable description of flicker noise for developing optimal algorithms of digital signal processing for quick detection and identification of informant signals during rescue missions. Method and Methodology. The low-frequency flicker noise has been modeled within the polynomial equations technique, proceeding from an analysis of real data on noise components in the output signals from a coherent search-and-rescue radar. A comparative analysis is done for a variety of approximating functions suggested for representing the low frequency portion of the spectrum observed. Results. For the low-frequency range wherein spectral components of the informative signal owing to respiration and heartbeat of humans are concentrated, an adequate model of the fluctuating interference is the flicker noise model built on the basis of polynomial equations. The problem of optimized model representation of the noise in digital signal processing algorithms has been analyzed for the case of a coherent search-and-rescue radar. A model of the fluctuating process has been suggested, based on a polynomial approximation for the spectral function in the low-frequency range of the signals observed at the radar output. Conclusion. Spectral characteristics of both interference and informant signals have been investigated. A structural diagram has been proposed for a high sensitivity, coherent search-and-rescue radar implementing a signal storage algorithm based on the polynomial model of the fluctuating process. The advantages and disadvantages of the radar are discussed, with examples given of real signal implementations and of noise spectrograms. Methods of effective estimation of Doppler signal phases are presented. The paper suggests an analysis of basic requirements as to parameters and performance characteristics of the rescue radar.

Comparison of optical power, external quantum efficiency in InGaN/GaN UV LEDs at room temperature and liquid nitrogen temperature is carried out. The spectral densities of the current low-frequency noise have been investigated. The mechanisms of carrier transport, the formation of low-frequency noise, and the dependences of the rates of radiative and nonradiative recombination at room and nitrogen temperatures are considered. [ABSTRACT FROM AUTHOR]

The quality of graphene intended for use in biosensors was assessed on manufactured chips using a set of methods including atomic force microscopy (AFM), Raman spectroscopy, and low-frequency noise investigation. It is shown that local areas of residues on the graphene surface, formed as a result of the interaction of graphene with a photoresist at the initial stage of chip development, led to a spread of chip resistance (R) in the range of 1–10 kOhm and to an increase in the root mean square (RMS) roughness up to 10 times, which can significantly worsen the reproducibility of the parameters of graphene chips for biosensor applications. It was observed that the control of the photoresist residues after photolithography (PLG) using AFM and subsequent additional cleaning reduced the spread of R values in chips to 1–1.6 kOhm and obtained an RMS roughness similar to the roughness in the graphene film before PLG. Monitoring of the spectral density of low-frequency voltage fluctuation (SU), which provides integral information about the system of defects and quality of the material, makes it possible to identify chips with low graphene quality and with inhomogeneously distributed areas of compressive stresses by the type of frequency dependence SU(f). [ABSTRACT FROM AUTHOR]