Simultaneously Suppressing Low-Frequency and Relaxation Oscillation Intensity Noise in a DBR Single-Frequency Phosphate Fiber Laser

Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20dB from 0.2 to 5kHz and over lOdB from 5 to lOkHz. The relaxation oscillation peak is suppressed by 22dB. In addition, a long term （24h） laser instability of less than 0.05% is achieved.

Behavioral and Physiological Responses of Sea Slug (Onchidium reevesii) to Low-Frequency Noise

A large amount of marine noise pollution from coastal industrial construction and the water transportation industry affects the growth and development of marine life,which is a big issue threatening marine organisms.However,most studies have focused on vertebrates,such as marine mammals and fishes,and little is known about the effects of noise on invertebrates.Therefore,the impacts of low-frequency noise(100,300,and 500 Hz)on behavioral and physiological responsesof the sea slug(Onchidium reevesii)were investigated.Under laboratory conditions,sea slugs were stimulated with low-frequency noise at 100,300,and 500 Hz for 1 h.Then,hemolymph enzyme activities(glucose,albumin,triglycerides,superoxide dismutase,catalase,and malondialdehyde)were measured,and mRNA expression of the hsp70 gene was detected in hemolymph and the nervous system by quantitative realtime polymerase chain reaction(qRT-PCR)analysis,while expression of the hsp70 protein was analyzed by immunohistochemistry.The results demonstrated that sea slugs were away from the stimulus source under the influence of low-frequency noise compared to the control group.Enzyme activities,as well as hsp70 gene mRNA and protein expression levels,were significantly higher in the noiseexposed groups than those in the control group.Overall,these changes indicate that low-frequency noise caused oxidative stress in sea slugs in vivo,and the oxidative damage gradually increased when the noise frequency was increased from 100 to 500 Hz.

Low-Frequency Noise in Gate Tunable Topological Insulator Nanowire Field Emission Transistor near the Dirac Point

Low-frequency flicker noise is usually associated with material defects or imperfection of fabrication procedure. Up to now, there is only very limited knowledge about flicker noise of the topological insulator, whose topologically protected conducting surface is theoretically immune to back scattering. To suppress the bulk conductivity we synthesize antimony doped Bi2Se3 nanowires and conduct transport measurements at cryogenic temperatures. The low-frequency current noise measurement shows that the noise amplitude at the high-drain current regime can be described by Hooge＇s empirical relationship, while the noise level is significantly lower than that predicted by Hooge＇s model near the Dirac point. Furthermore, different frequency responses of noise power spectrum density for specific drain currents at the low drain current regime indicate the complex origin of noise sources of topological insulator.

Influence of Total Ionizing Dose Irradiation on Low-Frequency Noise Responses in Partially Depleted SOI nMOSFETs

Total ionizing dose effect induced low frequency degradations in 130nm partially depleted silicon-on-insulator （SOI） technology are studied by ^60Co γ -ray irradiation. The experimental results show that the flicker noise at the front gate is not affected by the radiation since the radiation induced trapped charge in the thin gate oxide can be ignored. However, both the Lorenz spectrum noise, which is related to the linear kink effect （LKE） at the front gate, and the flicker noise at the back gate are sensitive to radiation. The radiation induced trapped charge in shallow trench isolation and the buried oxide can deplete the nearby body region and can activate the traps which reside in the depletion region. These traps act as a GR center and accelerate the consumption of the accumulated holes in the floating body. It results in the attenuation of the LKE and the increase of the Lorenz spectrum noise. Simultaneously, the radiation induced trapped charge in the buried oxide can directly lead to an enhanced flicker noise at the back gate. The trapped charge density in the buried oxide is extracted to increase from 2.21×10^18 eV^-1 cm^-3 to 3.59×10^18？eV^-1 cm^-3 after irradiation.

Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator

Low-frequency noise（LFN） in all operation regions of amorphous indium zinc oxide（a-IZO） thin film transistors（TFTs） with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric,and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al2 O3 gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge＇s parameter is about 1.18×10^-3.Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the △N-△μ model, and the total trap density near the IZO/oxide interface is about 1.23×10^18 cm^-3eV^-1.

Modeling and Analysis of Low Frequency Noise in Ion-Field-Effect Transistors Sensors

Ions Sensitive Field Effect Transistors (ISFETs) are becoming the platform sensors for important chemical and biomedical applications. However, the accuracy of ISFET output measurement is greatly affected by the presences of low-frequency noise, drift and slow response of the device. This requires more safety in measured results and the tools of analysis. In this paper, we present fundamental limits on the sensitivity of ISFETs micro-sensors, arising from intrinsic and extrinsic noise sources. We developed an algorithm in MATLAB in order to model the frequency analysis of the 1/f noise in ISFET sensor using Hooge theory. We have shown that the 1/f noise of the ISFETs sensors is due to both the electrochemical system (pH solution) and the MOS component (canal size, insulator thickness). The temperature effect on the ISFET noise and the signal conditioning are also performed.

New Applications of the Noise Spectroscopy for Hydrogen Sensors

Peculiarities of the low-frequency noise spectroscopy of hydrogen gas sensors made on MgFeO4 n-type porous semiconductor covered by the palladium catalytic nanosize particles are investigated. Behavior of the low-frequency noise spectral density and its exponent value from sensitive layer thickness in the frequency range 2 - 300 Hz are analyzed. Sensitivity of the sensor calculated by the noise method is several tenth times higher as compared with the resistive method. It is shown that besides of the well-known applications, noise spectroscopy can be also used for definition of the unknown thickness of gas sensitive layer, for definition of the sensitive layer subsurface role in the formation of the low-frequency noises and for definition of the intensity of trapping-detrapping processes of the gas molecules.

Association of Road Traffic Noise with Obesity and the Role of Meat Intake:A Prospective Study from UK Biobank

Emerging evidence has indicated the linkage of traffic noise with cardiovascular diseases,However,there’s a lack of extensive studies exploring the linkage of traffic noise with cardiometabolic risk factors such as obesity.Additionally,the role of diet in the associations remains unknown.The aim is to prospectively examine the linkage of road traffic noise with obesity,especially by focusing on evaluating the impact of meat.Participants recruited in the UK Biobank with at least one repeated measurement of obesity indicators including body mass index(BMI),waist circumference(WC),waist-to-hip ratio(WhR),and waist-to-height ratio(WhtR)were included.The Common Noise Assessment Methods of the simplified version were used to estimate road traffic noise exposure.Participants were categorized into“less meat intake”and“more meat intake”based on the median of meat intake,assessed by the frequency of unprocessed red meat and processed meat consumption.Modified Poisson regression models were employed to evaluate the linkage of road traffic noise with obesity.Additionally,the modification effects of meat intake on this relationship were evaluated.The incidence risk ratios(IRRs)and 95%confidence interval(CI)of overall obesity,WC-based central obesity,WhR-based central obesity,and WhtR-based central obesity were 1.11(1.02,1.21),1.09(1.03,1.14),1.06(1.02,1.10),and 1.08(1.02,1.13),respectively,for every 10 dB(A)increase for noise.Compared with individuals with lower meat intake,those with higher meat intake exhibited a stronger linkage of road traffic noise with central obesity.The prospective study demonstrates a linkage of road traffic noise with obesity,emphasizing the significance of diet on traffic noise-related obesity risk.

Low-frequency blood oxygen level-dependent fluctuations in the brain white matter： more than just noise

The spontaneous activity of the blood oxygen level-dependent(BOLD)signal has been demonstrated as a promising way for understanding how the brain intrinsically organized.However,most of these studies focused solely on the spontaneous activity in gray matter(GM)and not on white matter(WM).This is

Propeller cavitation viscous simulation and low-frequency noise prediction with non-uniform inflow

Aiming at predicting ship propeller＇s cavitation low-frequency noise spectrum, a hy- brid method combining the cavitation multi-phase flow unsteady simulation with the pulsating spherical bubble radiated noise theory was proposed. Then, both of the NSRDC4383 5-bladed propeller and a 7-bladed highly-skewed propeller＇s cavitation low-frequency noise spectrum sub- jected to the full appended SUBOFF submarine＇s nominal wake were investigated. The effects of thrust loading and cavity extension on the discrete line spectrum frequency and its spectrum source level were analyzed. The improved Sauer cavitation model and modified shear stress transport turbulence models were adopted to simulate the propeller sheet cavitation along with integrated verification. The cavity volume acceleration related to the characteristic length rep- resenting the unsteady sheet cavitation extension, which was more reasonable than the spherical cavity hypothesis, was used to the cavitation low-frequency noise spectrum prediction. Results show that the 7-bladed propeller truly appreciates the advantages of smaller loads, latter cav- itation inception and lower cavitating tonal noise comparing to that of the 5 blades. Under the same cavitation index based on ship speed, the interaction of wake inflow and blades will induce significantly low frequency line spectrums and strengthen their source level. Given the submarine wake, cavitation index and rotating speed condition, the thrust, torque and cavity area of blades will decrease with the decreasing load, but the fluctuated acceleration amplitude of cavity volume and the tonal noise spectrum level increases, and the discrete line spectrum components shift mainly to the even times of the BPF harmonics from the odd. If the cavita- tion extension lightens, the BPF harmonics line spectrums will be depressed, and the spectrum level at 1 kHz reduces 2.54 dB. The numerical method above constructs a numerical system to measure the cavitating hydrodynamics and noise performances of ship propellers, which can be productive for the numerical design of wake adapted low noise submarine propeller.

Current oscillations and low-frequency noises in GaAs MESFET channels with sidegating bias

Low-frequency noises (LFN) and noise-like oscillations (NLO) in GaAs metal semiconductor field effect transistor (MESFET) channel current were investigated under sidegating bias conditions.It was found that the fluctuations of the channel current were directly dependent upon the sidegating bias.As the sidegating bias decreased,the amplitudes of the oscillations would increase correspondingly.Furthermore,the LFN and NLO would attenuate sharply when the sidegating bias increased to more than a certain voltage.Two mechanisms are presented to demonstrate that the effective substrate resistivity or the channel-substrate junction modulated by sidegating bias and deep level traps would take responsibilities for the LFN and NLO.

Low-frequency noise characteristics in the MOSFETs processed in 65 nm technology

Low-frequency noise behavior in the MOSFETs processed in 65 run technology is investigated in this paper.Low-frequency noise for NMOS transistors agrees with McWhorter＇s theory（carrier number fluctuation）,low-frequency noise in the sub-threshold regime agrees with McWhorter＇s theory for PMOS transistors while it agree with Hooge＇s theory（carrier mobility fluctuation） in the channel strong inversion regime.According to carrier number fluctuation model,the extracted trap densities near the interface between channel and gate oxide for NMOS and PMOS transistor are 3.94×10^（17） and 3.56×10^（18） cm^（-3）/eV respectively.According to carrier mobility fluctuation model,the extracted average Hooge＇s parameters are 2.42×10^（-5） and 4×10^（-4）.By consideration of BSIM compact model,it is shown that two noise parameters（NOIA and NOIB） can model the intrinsic channel noise.The extracted NOIA and NOIB are constants for PMOS and their values are equal to 3.94×10^（17） cm^（-3）/eV and 9.31×10^（-4） V^（-1）.But for NMOS,NOIA is also a constant while NOIB is inversely proportional to the effective gate voltage.The extracted NOIA and NOIB for NMOS are equal to 3.56×10^（18） cm^（-3）/eV and 1.53×10^（-2） V^（-1）.Good agreement between simulation and experimental results is achieved.

进气道滚流比对发动机压升率及噪声的影响

以某双喷射6缸发动机为研究对象,设计高滚流比和低滚流比2种进气道,通过三维计算流体动力学软件AVL Fire对缸内流场进行仿真,分析发动机燃烧特性,并进行台架燃烧测试和噪声测试。仿真结果表明:在转速为2800 r/min、平均有效压力为1.3 MPa工况下,相比高滚流进气道方案,低滚流气道方案的缸内第一、二个峰值滚流比分别降低了43.3%、34.9%,最大缸内平均压力降低544 kPa,最大压力升高率降低16.84%。台架试验结果表明:2种进气道的燃烧持续期相差不大,相比高滚流进气道方案,低滚流方案以曲轴转角表示的燃烧重心推迟了2.02°,燃油消耗率增大0.67%,压力升高率(压升率)降低了19.87%,发动机在频率为700~1300 Hz时的噪声约降低6.0 dB,噪声改善效果明显。

一种应用于汽车进气系统的新型消音器设计

近年来,随着我国汽车保有量的急剧上升,汽车噪声已经成为城市噪声污染的主要来源之一,直接影响居民的身心健康,汽车噪声污染问题亟待解决。汽车噪声源中,进气噪声因气体流体动力学特性极其复杂,因而没有固定的降噪措施。针对这个难题,设计了一种集空气滤清器和消音器一体的错列复合阻抗式消音器,可以同时实现除尘和降噪两种功能,而且不会在周期性进气脉冲噪声的激励下产生额外的共振噪声。

发动机空气滤芯结构优化对进气性能提升的实验分析

本研究分析了一种新型汽车空气滤清器结构,通过集成宽频消声器与谐振腔设计,提升了进气效率并降低了噪声水平。实验表明,新型滤清器的进气流量提高了15%~20%,同时噪声水平降低了25 dB,尤其在中低频段降噪效果显著。研究还探讨了滤清器优化设计的持续改进方向,包括滤芯材料的进一步提升、消声结构的优化以及壳体轻量化设计。针对不同车型的实际应用,验证了新型滤清器在SUV、商用车等车型中的推广前景。本文为汽车空气滤清器结构的改进设计提供了数据支持与技术参考,有助于推动空气滤清技术的进一步发展。

某重卡进气噪声分析及降噪措施

文章针对某重卡在低负荷工况下的特定转速范围内,车辆驾驶室内出现的“咚咚”打鼓声,首先通过主观评价,初步判断进气系统为噪声传播源;然后通过换装评测,锁定噪声传播路径;最后结合试验测试,从不同维度有针对性地提出降噪措施,最终采用加大进气扁管厚度、调整进气扁管与车身连接处的橡胶软垫刚度和粘贴阻尼片的综合降噪措施,降低了进气噪声,并进行实车验证。文章解决了车内进气气流噪声过大的问题,提升了整车品质,极大地改善了驾乘人员的驾乘体验,对整车噪声、振动与声振粗糙度(NVH)性能优化设计提供参考,对后续整车降噪工作具有实际指导意义。

某PK车型进气系统WHOOSE噪声的优化与改进

进气系统WHOOSE噪声是增压发动机常见的噪声之一,为避免客户抱怨并有效改善用户驾乘体验,针对进气系统展开一系列的研究工作。在涡壳内壁开槽、空滤内部增加高频消音器、中冷进气管增加壁厚、空滤出气管增加导流罩,并通过CAE分析和NVH测试,以验证方案的有效性。试验结果表明,所实施的优化方案能有效地降低进气系统WHOOSE噪声水平,对相关NVH问题的研究有一定的参考价值。

汽车急加速进气噪声的试验测试与分析

汽车的进气噪声能够直接影响车内的噪声水平和声品质。在车内动力感声品质研究过程中,需要借助进气噪声能量增强车内噪声的动力感,在发动机半消声室单纯测试进气噪声的传统方法无法满足汽车声品质研究需要。因此,本文中提出了一种在整车半消声室NVH底盘测功机上同时获得进气噪声和车内噪声的方法,通过现场测试人员的主观感受和测试数据的分析,验证了该方法的有效性,能够获得相对纯净的进气噪声;并对研究车型急加速工况下的进气噪声和车内噪声品质的关联性进行了分析,通过对4个典型的声品质客观参量的对比分析发现进气噪声是车内动力感声品质实现中比较优秀的噪声源,其研究对汽车声品质设计具有重要意义。

改进车辆进排气系统降低整车车外加速噪声

用GT-POWER建立了发动机与消声器的耦合模型,根据计算得到的发动机的进、排气系统噪声的频谱特性,提出消声器的改进设计方案,通过CFD模拟计算有效抑制消声器内部的再生气体噪声;设计进气谐振腔降低进气噪声。综合运用上述进、排气系统改进措施将所研究的轿车车外加速噪声降低到74dB(A)以下,满足了国家第二阶段噪声强制法规的要求。

微型轿车的降噪实验

针对某微型轿车采用汽车加速行驶车外噪声分离实验和声强法识别噪声源。发现进气噪声是造成车外加速噪声偏高的主要原因。在对发动机进气噪声进行频谱分析后 ,找到进气噪声的主要峰值频率 ,设计出一种三腔并联共振式消声器 ,使进气噪声得以有效的控制。通过道路实验与发动机台架实验评价 ,整车车外加速噪声降到 72 .3dB(A) ,降噪量达 7.9dB(A) ,而发动机输出功率没有明显变化。