EPR/Homotaurine: A possible dosimetry system for high doses

An EPR investigation of radiation induced radicals in Homotaurine revealed that there are two types of radicals produced after exposure to gamma radiation (⁶⁰Co). EPR spectra were recorded and analyzed; also the microwave power saturation curves for both radicals were studied. The effect of change in modulation amplitude on peak-to-peak signal height and line width was investigated; this is in addition to the evaluation of energy dependence parameters compared to soft tissue and alanine dosimeters. Response of Homotaurine to different radiation doses (0.5 kGy-50 kGy) was studied and found to follow a linear relationship. Radiation induced radicals in Homotaurine persisted and showed a noticeable stability over 30 days following irradiation. It was found that Homotaurine possesses good dosimetric properties using EPR spectroscopy in high doses and is characterized by its simple spectrum.     

A method based on random-fuzzy variables for online estimation of the measurement uncertainty of DSP-based instruments

The evaluation of the uncertainty of the result of a measurement performed by a DSP-based instrument is usually a complex and difficult task. The sources of uncertainty are the instrument input stage and the analog-to-digital converter (ADC), so that each input sample to the instrument can be considered a measurement result with its associated uncertainty. The uncertainty on the final measurement result is obtained as the combination of the uncertainty values of each sample, according to the measurement algorithm implemented on the digital signal processing (DSP) system. This paper proposes an innovative approach, based on the representation of the measurement result and its associated uncertainty in terms of random-fuzzy variables, that, after having suitably characterized the metrological performance of the input stage and analog-to-digital converter, provides an online estimation of the measurement uncertainty. The method has been validated experimentally, and the results of the experimental work are reported.     

Maximum-Likelihood Data Fusion of Phase-Difference and Threshold-Detection Techniques for Wind-Speed Measurement

Analyses of threshold-detection and phase-difference techniques for wind-speed measurement using ultrasonic transducers are presented. The influence of uncertainties that are associated with additive noise and attenuation of the ultrasonic signal on the wind-speed measurement uncertainty is analyzed. A data-fusion procedure based on the maximum-likelihood estimation (MLE) algorithm is developed for the determination of wind speed, with data gathered through threshold-detection and phase-difference techniques. The data-fusion procedure provides a lower measurement uncertainty than those obtained with the above techniques when taken separately. Practical design issues are considered, and an application example is shown to illustrate the proposed procedure.      

Calculated Uncertainty of Temperature Due to the Size-of-Source Effect in Commercial Radiation Thermometers

The article evaluates the uncertainty in the temperature indicated by a radiation thermometer with a direct readout in temperature, due to the uncertainty in measuring the size-of-source effect (SSE) by the so-called “direct method.” Radiation thermometers of this type are the ones most frequently used in practice. The uncertainty of the SSE characteristic is usually not a useful quantity to report to users of commercial radiation thermometers. Instead, they would prefer to know the uncertainty in the measured temperature that results from the uncertainty of the SSE characteristic, and this will be the result of our analysis. The user of a direct reading radiation thermometer will be able to take into account the uncertainty of temperature due to the SSE, if a target with known dimensions is measured. The uncertainty in temperature due to the SSE of analyses based on Planck’s law and its approximation, Wien’s law is compared.     

Gamma-irradiated EPR response of nano-structure hydroxyapatite synthesised via hydrolysis method

In this paper, the gamma-irradiated EPR responses of hydroxyapatite (HAP) samples were investigated from a dosimetric point of view. For this purpose, nano-structure hydroxyapatite was synthesised via a hydrolysis method. A portion of the produced powder was annealed at 600 °C for 4 h. All the samples were irradiated under the (60)Co gamma-ray source at different absorbed doses from 0.1 to 45 kGy. EPR signal intensities of HAP samples were measured at room temperature in air. Subsequently, the EPR signal intensities were constructed as a function of radiation dose and were compared with the results of bone powder samples. The results show that the EPR responses of non-annealed HAP samples are higher than others for several times.     

光纤作为量子信道的性能

本文研究光纤作为量子信道在密波分复用时模式间非线性干扰造成的信道噪声的性质 ,和光纤量子信道在该噪声下的经典容量 .用位移算符方法计算量子噪声的累加 ,同时建立了有衰减和噪声时的信道的量子模型 .本文论证如果干扰是各其他模式独立而均等的贡献的叠加 ,信道噪声是热辐射噪声类型的 ,并求出了在给定参数的情况下的经典容量     

Multiparameter optimization of inverse filtering algorithms

This paper investigates inverse filtering of transient signals. The problem is ill-conditioned, which means that a small uncertainty in the measurement causes large deviations in the reconstructed signal. This amplified noise has to be suppressed at the price of bias in the estimation. The most difficult task is to find the optimal degree of noise reduction. Deconvolution algorithms are usually controlled by one or a few parameters. Several algorithms can be found in the literature to find the best setting of inverse filtering methods; however, usually methods with only one free parameter are handled. In this paper, an algorithm is proposed to optimize several parameters, on the basis of a spectral model. Multiparameter inverse filtering methods have the advantage that they can be better adapted to the measurement system, and to the noise and signal to be measured. The superiority of the proposed optimization method is demonstrated both on simulated and on experimental data     

原子钟钟差预测不确定度的建模与分析

钟差预测是原子钟时标产生和原子钟驾驭的关键环节。原子钟作为精准的信号源,其信号由确定信号部分和固有噪声即随机部分组成。氢钟和铯钟主要包含两种噪声,即调频白噪声和调频随机游走噪声,这两种噪声是产生预测不确定度的主要因素。根据原子钟数学模型补充推导出原子钟时差数据预测不确定度的数学表达式,并得出了钟组的最小预测不确定度,分析了钟组的台数对预测不确定度的影响。最后通过数据仿真验证了理论的正确性。     

Diagnostic entropy: a quantitative measure of the effects of signal incompleteness on system diagnosis

A set of measures quantifying the effects of signal incompleteness upon system diagnosis are defined and investigated. The most important is diagnostic entropy, a new quantitative measure of the effects of signal incompleteness upon system uncertainty. Diagnostic entropy is defined as the average uncertainty of a system when the system is indicated to be in an undesired state. This measure appears to be more useful for quantifying the difficulty of system diagnosis than conventional system entropy or conditional system entropy measures due to its relevance to the difficulty of human diagnosis of the system when it is in an undesired state. The magnitude of the diagnostic entropy is shown to be usually larger than that of the conditional entropy for typical highly reliable systems. This means that the uncertainty of the system is larger than usual when a reliable system is in an undersired state. We also suspect, but have not identified, the existence of a relationship between the diagnostic entropy of a system and the average physiological stress of human operators in diagnosing the system.     

An Alternative Calculation of the Size-of-Source Effect Uncertainty for Non-uniform Sources

For a correct determination of the size-of-source effect (SSE), it is necessary to use a large (e.g., 50-mm diameter) radiation source of uniform spectral radiance. The non-uniformity of the source can be an important component of the uncertainty because it is difficult to obtain sources with good uniformity over the whole aperture. In the indirect method to measure the SSE, the component due to the source non-uniformity comes from the measurement of S(L,∞), usually measured outside the spot that blocks radiation from the radiation thermometer target. By expressing the SSE as an experimental sum of successive contributions of radiating rings at the source aperture, the uncertainty due to the non-uniformity can be reduced. In this article, the calculus of the SSE and its uncertainty for the usual equation is compared with the calculus based on an experimental equation that considers the SSE as a sum of the contributions from radiating rings.     

On uncertainties and errors

The accuracy of radiation protection dosimetry measurementsis important because such measurements are used to determineeffective doses received by radiation workers. When reportingany measured quantity, it is important to follow the recommendationsof the Guide to the Expression of Uncertainty in Measurement(GUM)⁽¹⁾. The GUM states that the report of a measurement mustbe accompanied by a quantitative evaluation of its quality sothat the reliability of the result can be judged. The quantitativemeasure is usually provided in the form of an estimation ofthe measurement uncertainty. This requirement is well knownto the national metrology     

The zero signal and glow curves of bare LiF:Mg,Ti detectors in a hot gas TLD system

The uncertainty in very low doses measured with TLDs is partly caused by the uncertainty in the zero signal of the detector. A mathematical model for the thermodynamics of TLD heating and the zero signal in a hot gas reader with constant gas temperature is presented. The major component of the heating is described as diffusion limited conductive heating, the major component of the zero signal is black body radiation from the hot TLD. The parameters in the model were determined from the glow curves recorded at five different gas temperatures. The model explains the shape and statistics of a zero signal glow curve and can be used in the quality control of non-irradiated TLDs before calibration irradiation and readout.     

A review of some epidemiological studies on cancer risk from low-dose radiation or other carcinogenic agents

It is extremely difficult to assess cancer risks accurately due to health effects of low-dose radiation exposure or other carcinogens based on epidemiological studies. For the detection of minute increases of the risk at low-level exposure, most of epidemiological studies lack statistical power, and they involve various complicated confounding factors. This paper reports on a literature survey of epidemiological studies published since 2000 on cancer risks associated with low-dose radiation and other carcinogens to gather major epidemiological data. Integrated risk indices were derived from those data by using, where possible, statistical models. Regarding risk assessment of low-dose radiation exposure, it is important to lower the degree of uncertainty arising from risk estimation. Risk assessment of low-dose radiation exposure could be scientific evidence when uncertainty is considered in comparing carcinogenic risks of radiation with those of other carcinogens.     

Alanine and TLD coupled detectors for fast neutron dose measurements in neutron capture therapy (NCT)

A method was investigated to measure gamma and fast neutron doses in phantoms exposed to an epithermal neutron beam designed for neutron capture therapy (NCT). The gamma dose component was measured by TLD-300 [CaF2:Tm] and the fast neutron dose, mainly due to elastic scattering with hydrogen nuclei, was measured by alanine dosemeters [CH3CH(NH2)COOH]. The gamma and fast neutron doses deposited in alanine dosemeters are very near to those released in tissue, because of the alanine tissue equivalence. Couples of TLD-300 and alanine dosemeters were irradiated in phantoms positioned in the epithermal column of the Tapiro reactor (ENEA-Casaccia RC). The dosemeter response depends on the linear energy transfer (LET) of radiation, hence the precision and reliability of the fast neutron dose values obtained with the proposed method have been investigated. Results showed that the combination of alanine and TLD detectors is a promising method to separate gamma dose and fast neutron dose in NCT.     

In vivo EPR dosimetry to quantify exposures to clinically significant doses of ionising radiation

As a result of terrorism, accident or war, populations potentially can be exposed to doses of ionising radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure to individuals so that those with significant risk can have appropriate procedures initiated immediately, while those without a significant probability of acute effects can be reassured and removed from the need for further consideration in the medical/emergency system. It is extremely unlikely that adequate dosemeters will be worn by the potential victims, and it also will be unlikely that prompt and accurate dose reconstruction at the level of individuals will be possible. Therefore, there is a critical need for a method to measure the dose from radiation-induced effects that occur within the individual. In vivo EPR measurements of radiation-induced changes in the enamel of teeth is a method, perhaps the only such method, which can differentiate among doses sufficiently to classify individuals into categories for treatment with sufficient accuracy to facilitate decisions on medical treatment. In its current state, the in vivo EPR dosemeter can provide estimates of absorbed dose of +/- 0.5 Gy in the range from 1 to >10 Gy. The lower limit and the precision are expected to improve, with improvements in the resonator and the algorithm for acquiring and calculating the dose. In its current state of development, the method is already sufficient for decision-making action for individuals with regard to acute effects from exposure to ionising radiation for most applications related to terrorism, accidents or nuclear warfare.     

Gamma-ray and neutron dosimetry by EPR and AMS, using tooth enamel from atomic-bomb survivors: a mini review

The electron paramagnetic resonance (EPR, or electron spin resonance) method was used to measure CO??· radicals recorded in tooth enamel by exposure to atomic-bomb gamma rays. The EPR-estimated doses (i.e. ??Co gamma-ray equivalent dose) were generally in good correlation with cytogenetic data of the same survivors, whereas plots of EPR-estimated dose or cytogenetically estimated dose against DS02 doses turned out to scatter more widely. Because those survivors whose EPR doses were higher (or lower) than DS02 doses tended to show also higher (or lower) responses for cytogenetic responses, the apparent variation appears primarily due to problems in individual DS02 doses rather than the measurement errors associated with the EPR or cytogenetic technique. A part of the enamel samples were also used for evaluation of neutron doses by measuring ?1Ca/??Ca ratios using the accelerator mass spectrometry technique. The results for the measured ratios were on average ~85 % of the calculated ratios by DS02 (but within the 95 % confidence bounds of the simulated results), which lends support to DS02-derived neutron doses to the survivors.     

基于小波奇异性理论的水轮机空化检测

空化噪声谱分析中常采用的功率谱分析在研究空化噪声这种具有很强突变性的信号时具有明显的缺陷,文中提出了一种基于小波奇异性理论的水轮机空化检测方法,并提出了小波基选择方案、突变点检测条件和最佳检测阈值。进行了混流式水轮机的模型转轮试验,观测了模型转轮额定工况下的涡带形态和空化发展情况,并采集存储了大量空化噪声数据。对照观测结果分析实际的检测数据,结果表明该方法的有效性,并很好的检测出空化初生和空化形态转变。     

Self-adaptive noise suppression for characterizing the dispersion of chirped fiber Bragg grating

We propose a method to suppress the beat noise generated in fiber low coherence interferometry (LCI) systems for characterizing the chromatic dispersion of chirped fiber Bragg gratings. The beat noise is considered as the dominant noise in the system because of the spectrum mismatch between interference arms due to the broad bandwidth of the light source and the introduction of dispersive components into the measurement arm, and is unfavorable for the signal quality. An experimental system is set up and interferograms of various situations are provided. Experiment results indicate that our method is feasible and effective, as it improves the signal to noise ratio effectively by a factor of more than 3, thereby expanding the measurement range of the LCI system.     

Aperture Jitter of Sampling System in AWGN and Fading Channels

This paper examines aperture jitter of the sampling system and its effect on communication systems in the additive white Gaussian noise (AWGN) and fading channels. Previous studies have claimed that AWGN power is directly proportional to the jitter noise power. We demonstrate that the aperture jitter can influence the input signal of a sampling system but is independent of AWGN. The noise power, due to the aperture jitter in a frequency-nonselective slowly fading channel, is shown to be a function of the input signal, the aperture jitter, and the channel envelope. The frequency-selective slowly fading channel involves another parameter analyzable paths. The effect of the aperture jitter on the bit-error probability (BEP) of a binary-phase-shift-keying digital communication system is also considered. The received signal-to-noise ratio (SNR) is calculated first, and its probability density function is derived. Then, the average BEP is evaluated as a function of SNR. Simulation results indicate that the aperture-jitter noise severely degrades the average BEP by reducing the received SNR. The results of this paper can be used in designing a wideband or radio-frequency-sampling digital communication system     

A simple method for the evaluation of microwave mixer diodes

A simple method is described for the evaluation of the various microwave mixer diodes which can be used in 9-GHz electron paramagnetic resonance (EPR) spectrometers using magnetic field modulation below 1 kHz. The advantage of this method over other methods is that it is optimized for EPR applications and determines the optimum operating conditions for each microwave diode. This method utilizes a microwave bridge with a reference arm with an attenuator to control the microwave bias power level, and a signal arm where the signal is attenuated, phase shifted, and modulated at the typical magnetic field modulation frequencies. The microwave power from the two arms is recombined and demodulated by the microwave diode. The output of the microwave diode is then recorded with various video loads, microwave bias power, and modulation frequencies. Measurements are performed to determine the effect of the preamplifier that followed the microwave diode on the signal-to-noise ratio (SNR). The recorded spectra are used to determine the SNR, the noise floor, and the 1/f corner frequency. Comparison of these factors for the different types of microwave diodes shows that some Schottky-barrier diodes have noise figures at 1 kHz that are as low as those for tunnel diodes