基于光纤形状改变实现的液位传感器实验

利用光纤自身形状的变化制作的传感器是一种新型液位传感器.本文介绍了光纤液位传感器的实验原理、光纤尖的制作方法,并利用光纤液位传感器实验系统测量了光纤尖在空气、甘油、酒精和水中不同位置的反射光功率.     

准确测量液位的反射式螺旋塑料光纤传感器

为消除工质成分和折射率（RI）对液位测量准确性的影响,利用低包层RI侧发光塑料光纤、反射镜、光纤固定杆和空气密封装置构建了反射式液位光纤传感器。首先,从理论及实验角度研究了光纤包层折射率对不同工质及不同折射率的同种工质液位测量的影响。然后,为了提高传感器灵敏度,研究了光纤螺旋直径和螺距对传感器灵敏度的影响。最后,研究了液位变化速率和工质温度对传感器响应特性的影响。研究结果表明,当工质RI大于光纤包层RI、液位变化速率为10～100 cm/min、工质温度变化范围为10～70℃时,传感器的输出与液位间具有线性关系。此外,测量结果不受工质成分、RI及工质液位变化速率的影响,传感器灵敏度可达0.0101 cm^-1,最大相对误差小于6.85%。     

基于啁啾布喇格光栅的液位传感器

设计了一种基于啁啾光纤布喇格光栅的新型液位传感器,该传感器主要由矩形悬臂梁构成的传感机构和光纤光谱仪组成。导出了啁啾光纤布喇格光栅的反射谱带宽与液位的关系;通过光谱仪检测啁啾光纤布拉格光栅反射谱的带宽,就可以得到被测液位的高度。并对设计的传感器系统进行了实验验证,实验结果表明,该啁啾光纤布拉格光栅反射谱带宽对温度变化不敏感,且在测量范围内,反射谱带宽与被测液位间有很好的线性关系。     

光纤布喇格光栅沉降传感器

根据光纤布喇格光栅的光学传感原理,提出了一种基于悬臂梁及金属弹性膜片的光纤布喇格光栅沉降传感器结构,对其传感特性进行了实验研究.实验通过产生水的液位差来模拟地基沉降,分析结果显示,光纤布喇格光栅中心反射波长漂移对液位差呈现良好的线性关系,线性度高于0.999,灵敏度可达-2.11 pm/mm.通过改变悬臂梁厚度和有效长度,可以对传感器测量范围和灵敏度进行调整,以满足各种应用场合.综合实验结果,该传感器在桥梁、铁路地基等沉降监测方面具有重要意义.     

基于在线型光纤迈克耳孙干涉仪的液位传感器

为了简化光纤液位传感器的设计与制作工艺,提出了一种基于纤芯失配模间干涉的在线型光纤迈克耳孙干涉仪,由单模光纤熔接一段细径光纤构成。单模-细径光纤熔点处充当耦合器,激发出光纤高阶包层模,纤芯基模与高阶包层模被细径光纤端面反射后传输至单模光纤产生模间干涉并输出。传感器干涉条纹清晰、对比度高,对环境液位改变敏感。对细径光纤长度为12mm的传感器进行了不同溶液液位和温度响应特性的实验研究,实验结果表明在0~9mm的液位变化范围内,干涉谷波长与液位呈线性关系,水液位灵敏度为-0.116nm/mm,质量分数为4.7%的NaCl溶液液位灵敏度为-0.129nm/mm;在20~80℃的水温变化范围内,干涉谷的温度灵敏度为0.038nm/℃。传感器结构简单、制作简便,而且成本低廉,在石油化工等领域具有较好的应用前景。     

光纤法布里-珀罗(Fabry-Perot)腔液位传感器

提出了一种用于测量液体容器液位高度的新型光纤F-P(Fabry-Perot)腔传感器,它灵敏度高,实现了全光传感和传输,特别适用于一些有害、易燃、易爆液体容器液位的测定.详细分析了该类传感器的传感原理,并给出了传感头参量设计方法.实验结果表明,光纤F-P腔传感器测量液位方法简单,并且可达到相当高的精度.文中分析了实验中的误差,探讨了传感器的稳定性及改进方法,是光纤法布里-珀罗腔传感器实用化的有效尝试.     

超声液位检测频率选择的理论计算和实验研究

非介入式超声液位检测中,中间层介质对反射回波强度有着显著的影响,为得到较强的检测回波信号,发射频率的选择是非常必要的。本文采用传输矩阵方法,对非介入式超声液位检测中声波在多层介质中的传播进行了研究,给出了反射回波声强与入射声波频率之间的关系,从理论上计算得到了最佳入射声波频率。实验结果与理论计算一致,由此为非介入式超声液位检测的频率选择提供了一有效的技术途径。     

超声空化现象影响因素的实验研究

超声空化在许多不同的学科和工业生产中有着广泛的应用。超声空化的应用与声场的分布及空化的机理密切相关,精准地反映空化场和空化机理是超声空化技术实际应用的关键。该文通过分析采集的声信号和金属箔膜空蚀法对空化区域随液位发生变化的现象进行研究,并利用Matlab对金属箔膜空蚀程度量化。实验发现,超声波会在液面与实验箱体底部形成驻波场。在某一液体温度下,随着液位高度的变化,超声空化现象的出现具有周期性。并且,在同一液位下,当超声功率改变时,空化区域强度分布情况随之改变。小功率时各空化区域空化强度分布均匀,当功率增大到一定时,会出现空化屏蔽现象。该研究为超声清洗设备的改良提供了借鉴,对进一步认识和利用超声空化效应具有重要意义。     

光纤布喇格光栅沉降传感器

根据光纤布喇格光栅的光学传感原理,提出了一种基于悬臂梁及金属弹性膜片的光纤布喇格光栅沉降传感器结构,对其传感特性进行了实验研究.实验通过产生水的液位差来模拟地基沉降,分析结果显示,光纤布喇格光栅中心反射波长漂移对液位差呈现良好的线性关系,线性度高于0.999,灵敏度可达一2.11 pm/mm.通过改变悬臂梁厚度和有效长...     

基于非本征Fabry-Perot腔光纤液位传感器研究

介绍了适用于液位测量的强度型非本征法布里-珀罗（F-P）腔光纤液位传感器的结构设计及其性能.实验观察到F-P腔具有良好的多周期输出特性和局部的线性特性,选用局部的1/4周期输出线性段作为线性工作区间可对液位进行高准确度、连续性测量.恰当选择敏感组件的尺寸可设计不同量程的传感器.实验结果表明,传感器测量3.5 m水位时,精确度为±2 mm,最小分辨率为1 mm.     

Acoustic load dependency of electroacoustic efficiency in the electrostrictive ultrasonic transducer and acoustical matching

The acoustic load dependency of the electroacoustic efficiency in the electrostrictive transducer is derived theoretically and measured experimentally. The results show that there is an optimum acoustic load resistance which maximizes the electroacoustic efficiency. It is considered reasonable to cite the optimum condition as ‘acoustical matching’ of the transducer to the acoustic load.     

Mechanical measurement of the parameters in a pseudo-stationary ultrasonic field in liquids

After recalling the formulae relating the energy density of a progressive wave with the sonic field parameters, the problem of deducing these parameters in a pseudo-stationary field is discussed. This field is produced in a ‘fixed force interferometer’ by two torsion balances; it is shown how to deduce from the radiation pressure, measured simultaneously at transducer and at reflector, the local pressure and velocity amplitudes, discussing the errors involved in treating pseudo-stationary fields as purely stationary.     

Effect of biomimetic non-smooth unit morphology on thermal fatigue behavior of H13 hot-work tool steel

The thermal fatigue behavior of hot-work tool steel processed by a biomimetic coupled laser remelting process gets a remarkable improvement compared to untreated sample. The ‘dowel pin effect’, the ‘dam effect’ and the ‘fence effect’ of non-smooth units are the main reason of the conspicuous improvement of the thermal fatigue behavior. In order to get a further enhancement of the ‘dowel pin effect’, the ‘dam effect’ and the ‘fence effect’, this study investigated the effect of different unit morphologies (including ‘prolate’, ‘U’ and ‘V’ morphology) and the same unit morphology in different sizes on the thermal fatigue behavior of H13 hot-work tool steel. The results showed that the ‘U’ morphology unit had the optimum thermal fatigue behavior, then the ‘V’ morphology which was better than the ‘prolate’ morphology unit; when the unit morphology was identical, the thermal fatigue behavior of the sample with large unit sizes was better than that of the small sizes.     

The use of fast field cycling to evaluate the time domain relaxation of starches from tropical fruit seeds

ABSTRACT

A proton NMR relaxation study of the molecular dynamics in flour samples of ‘Eugenia uniflora’ (‘Pitanga’), ’Citrus reticulate’ (‘Tangerine’), ‘Prunus persica’ (‘Peach’), ‘Vitis vinifera’ (‘Grape’), and ‘Cucumis melo’ (‘Honeydew melon’) seeds is presented. The spin–lattice relaxation time was obtained over a broad frequency range from 100?kHz to 100?MHz using both conventional and fast field-cycling NMR techniques. This relaxometry study made possible a comparison between the molecular dynamics behaviour of starch from different fruit seeds and from potatoes. I was possible to conclude that the spin–lattice dispersion presents slightly differences for all samples, in particular at low frequencies. All relaxation dispersions could be well interpreted in terms of power-law relaxation models and domains with different power-law relaxation exponents. For the Peach seeds flour the relaxation dispersion at low frequencies was very similar to that observed for potato’s starch incorporated with 5% organoclay Viscogel B8 nanoparticles.     

Wideband focused film transducer for optoacoustic tomography

The response of a focused film transducer to wideband acoustic signals is studied both theoretically and experimentally. The transducer has the form of a narrow PVDF strip placed on a concave cylindrical surface. A software package is developed for calculating the impulse transient response functions depending on the position of the point source of spherical waves. The experiments are performed using laser thermooptical sources of acoustic spherical wave pulses excited by a pulsed diode-pumped Nd: YAG laser. The theoretical and measured temporal profiles of signals recorded by the transducer are shown to be in good agreement for the source positioned near the transducer’s focus. For this region, a transducer sensitivity map is investigated. For the case of the source positioned at the focus of the transducer, the absolute value of the transducer sensitivity is 8 µV/Pa.     

水毒性的光生物法检测与评价

本文提出一种新的光生物法对水的毒性进行检测,文中介绍了测试原理、测试装置及实测数据。根据实测数据,提出水的毒性分为“无毒”、“微毒”、“中等毒性”及“剧毒”四级以实现半定量评价。     

‘Majorana Mass’ Fermions as Untrue Majorana Particles,Rather Endowed with Pseudoscalar-Type Charges than Genuinely Neutral

The idea of a ‘Majorana mass’ to make a chiral neutrino really neutral is here reconsidered. It is pointed out that such an approach, unlike Majorana’s (non-chiral) old one, does not strictly lead, in general, to a true self-conjugate particle. This can be seen on directly using the basic definition (or fundamental representation) of charge conjugation C in Quantum Field Theory, as an operation just acting on annihilation and creation operators and just expressing particle–antiparticle interchange. It is found, indeed, that the ‘active’ and ‘sterile’ whole fields which can be obtained from mixing the chiral components of two mutually charge-conjugate Dirac fields are themselves ‘charge conjugate’ to each other (rather than individually self-conjugate). These fields, taken as mass eigenfields (as in the ‘Majorana mass’ case), are shown to describe particles carrying pseudoscalar-type charges and being neutral relative to scalar-type charges only. For them, ‘CP symmetry’ would be nothing but pure mirror symmetry, and C violation (already implied in their respective ‘active’ and ‘sterile’ behaviors) should then involve time-reversal violation as well. The new (no longer strictly chargeless) ‘Majorana mass’ neutrino model still proves, however, neither to affect the usual expectation for a neutrinoless double β-decay, nor to prevent ‘active’ and ‘sterile’ neutrino varieties from generally taking different mass values. One has, on the other hand, that any fermion being just a genuine (i.e. really self-conjugate) Majorana particle cannot truly exist in two distinct—‘active’ and ‘sterile’—versions, and it can further bear only a unified mass kind which may at once be said to be either a ‘Majorana-like’ or a ‘Dirac-like’ mass kind.     

Testing Quantum Models of Conjunction Fallacy on the World Wide Web

The ‘conjunction fallacy’ has been extensively debated by scholars in cognitive science and, in recent times, the discussion has been enriched by the proposal of modeling the fallacy using the quantum formalism. Two major quantum approaches have been put forward: the first assumes that respondents use a two-step sequential reasoning and that the fallacy results from the presence of ‘question order effects’; the second assumes that respondents evaluate the cognitive situation as a whole and that the fallacy results from the ‘emergence of new meanings’, as an ‘effect of overextension’ in the conceptual conjunction. Thus, the question arises as to determine whether and to what extent conjunction fallacies would result from ‘order effects’ or, instead, from ‘emergence effects’. To help clarify this situation, we propose to use the World Wide Web as an ‘information space’ that can be interrogated both in a sequential and non-sequential way, to test these two quantum approaches. We find that ‘emergence effects’, and not ‘order effects’, should be considered the main cognitive mechanism producing the observed conjunction fallacies.     

On the active periods of nonlinear Shot Noise

We study the temporal ‘on-and-off’ structure of the recently introduced nonlinear Shot Noise model [I. Eliazar, J. Klafter, PNAS 102 (2005) 13779; I. Eliazar, J. Klafter, Nonlinear shot noise: Lévy, Noah, & Joseph, Physica A (2006), to appear], in which: (i) shots of random magnitudes ‘bombard’ a system stochastically in time; (ii) the magnitudes of ‘incoming’ shots decay to zero nonlinearly; and, (iii) the overall effect of the shots on the system is additive. When the shot-inflow and shot-decay satisfy certain conditions, the resulting Shot Noise alternates randomly between ‘active periods’ (in which the noise is ‘on’) and ‘silent periods’ (in which noise is ‘off’).The statistical properties of the ‘active’ and ‘silent’ periods are analyzed, and the resulting ‘on-and-off’ Shot Noise structure is explored. Explicit formulae for means, variances, Laplace transforms, and other statistics are derived in closed-form. Based on this analysis, Shot Noise systems are categorized into three classes: transient, null-recurrent, and recurrent; and, these classes are characterized both analytically and probabilistically. Within the null-recurrent class, systems whose ‘active periods’ are governed by heavy-tailed probability distributions are further characterized.     

Questioning the equivalence principle

The Equivalence Principle (EP) is not one of the ‘universal’ principles of physics (like the action principle). It is a heuristic hypothesis which was introduced by Einstein in 1907, and used by him to construct his theory of general relativity. In modern language, the (Einsteinian) EP consists in assuming that the only long-range field with gravitational-strength couplings to matter is a massless spin-2 field. Modern unification theories, and notably string theory, suggest the existence of new fields (in particular, scalar fields: ‘dilaton’ and ‘moduli’) with gravitational-strength couplings. In most cases the couplings of these new fields ‘violate’ the EP. If the field is long-ranged, these EP violations lead to many observable consequences (variation of ‘constants’, non-universality of free fall, relative drift of atomic clocks, etc.). The best experimental probe of a possible violation of the EP is to compare the free-fall acceleration of different materials.