Energy efficient cosine similarity measures according to a convex cost function

We propose a new family of vector similarity measures. Each measure is associated with a convex cost function. Given two vectors, we determine the surface normals of the convex function at the vectors. The angle between the two surface normals is the similarity measure. Convex cost function can be the negative entropy function, total variation (TV) function and filtered variation function constructed from wavelets. The convex cost functions need not to be differentiable everywhere. In general, we need to compute the gradient of the cost function to compute the surface normals. If the gradient does not exist at a given vector, it is possible to use the sub-gradients and the normal producing the smallest angle between the two vectors is used to compute the similarity measure. The proposed measures are compared experimentally to other nonlinear similarity measures and the ordinary cosine similarity measure. The TV-based vector product is more energy efficient than the ordinary inner product because it does not require any multiplications.     

Measurement of directional thermal properties of biomaterials

This paper presents an experimental technique to measure the directional thermal conductivity and thermal diffusivity of materials. A heated thermistor heats the sample and a sensing thermistor placed about 2.5 mm away measures the temperature rise due the heating pulse at the heated thermistor. An empirical relation between the power delivered by the first thermistor and the temperature rise recorded by the sensing thermistor is used to measure the thermal conductivity of the material along the line joining the thermistors. Diffusivity of the material is determined from the delay between the power pulse in the heated thermistor and the temperature pulse at the sensing thermistor. Signal processing was done to eliminate errors in the measurement due to change of base line temperature. Uncertainty of the measurement technique was found to be 5% when tested in media of known thermal properties. The thermal conductivity and thermal diffusivity of swine left ventricle in normal and ablated conditions were measured using this technique. The thermal conductivity of the tissue dropped significantly from 0.61 to 0.50 W.m(-1).K(-1) after ablation while the diffusivity dropped from 2.1 x 10(-7) to 1.7 x 10(-7)m2.s(-1).     

Impulse Noise Detector Performance Measure Based on Intensity Volume

An accurate detector performance evaluation method provides a fair comparison platform and can also support in parameter optimization for existing Impulse noise detectors in the applications of medical imaging. The Impulse noise detector performance measure (INDPM) package is widely applied as tools for quantitative comparison among detectors, which contains recall measure, accuracy measure, precision measure, specificity measure and F-measure. However, these five measures suffer from limited accuracy in correctly evaluating the performance of a detector and are not in well agreement with human subjective evaluation. To solve this problem, five new measures are proposed by introducing a new concept of intensity volume to form a new Impulse noise detector performance package (IV-INDPM). Using a standard image dataset, we conduct experimental and comparative tests with 32 different original images and 5 different existing detectors. Results demonstrate the superior performance of each new measure within IV-INDPM in reaching a much closer agreement with human subjective evaluation, compared to existing measures in INDPM. Even though five new measures are efficient in evaluating detectors’ performance from different perspectives, a new benchmark algorithm (IND-BA) is proposed as a robust and overall metric for ease of general-purpose use by making the most of these five new measures. Comparison results demonstrate its efficiency and accuracy.     

Measures of information for continuous observations

Certain measures of information between a state process and an observation process and between a state process and an estimate of the state process are considered. The observations are assumed to have sample paths which are almost surely continuous. The calculus of martingales and probability measure transformations are used to determine representations of the observation process and the state estimate on different probability spaces obtained by a change in the sub-o-algebra and/or the probability measure. The Radon-Nikodym derivatives required to calculate the information theoretic quantities are obtained from these representations.     

激光闪射法测量双层材料导热系数的实验探索

通过设计不同厚度绝缘层的铝基板试样,使用激光闪射法测量其绝缘层及金属层的综合导热系数,并使用稳态热流法理论计算平均导热系数与之进行对比,指出两种测试方法存在的差异。分析了激光闪射法不适合用于测量双层材料综合导热系数的原因。最后引入平均导热系数与综合导热系数之间的计算关系式,说明激光闪射法测量双层材料导热系数的应用。     

Reliability-importance and dual failure-mode components

There are several measures of the importance of a component within a system in determining system reliability; these measures include structural importance, marginal reliability-importance. Some reliability-importance, and link importance. These measures are reviewed and then related to each other. Extensions are proposed to each importance measure to cover reliability models in which the components have two failure-modes rather than the conventional one failure-mode; these extensions have properties similar to those in the one failure-mode model     

Calculating the High-Frequency Electrical Conductivity of a Thin Metallic Layer for an Ellipsoidal Fermi Surface

The conductivity of a thin metallic layer in an ac electric field is calculated with respect to different specular reflection coefficients of the layer surfaces for an ellipsoidal Fermi surface. The ratio between the free path of electron conduction and layer thickness is not limited. The dependences of the absolute value and the argument of dimensionless conductivity on the dimensionless layer’s thickness, dimensionless external electric field frequency, and specular reflection coefficient of one of the layer surfaces at different ellipticity parameters of the Fermi surface are analyzed.     

分布式电导率在线测试分析系统

介绍了一种应用于半导体清洗技术的分布式电导率在线测试分析系统,该系统基于CAN总线传输网络,真正实现了一个全数字化的,双向的、多结点的通信链接,系统是具有测量、控制、执行和过程诊断的综合控制网络,并可方便地扩展底层检测设备.还提出了一种值得探讨的测量电导率的新方法,该方法利用单片机C8051F040内部的比较器和捕捉计数器实现,大大简化了硬件电路设计,能实现自动换档,温度自动补偿,电导率超限报警等功能.     

Electrical impedance tomography: induced-current imaging achievedwith a multiple coil system

An experimental study of induced-current electrical impedance tomography verifies that image quality is enhanced by employing six rather than three induction coils by increasing the number of independent measurements. However, with an increasing number of coils, the inverse problem becomes more sensitive to measurement noise. Using 16 electrodes to measure surface voltages, it is possible to collect 6×15=90 independent measurements. For comparison purposes, images of two-dimensional conductivity perturbations are reconstructed by using the data for three and six coils with the truncated pseudoinverse algorithm. By searching for the optimal truncation index that minimizes the noise error plus the resolution error, the signal-to-noise ratio of the data acquisition system was established as 58 db. Images obtained with this six-coil system reveal the sizes and locations of the conductivity perturbations. This system also provides images within the central region of the object space, a capability not achieved in previous experimental studies using only three circular coils. Nevertheless, the three-coil system can identify the conductivity perturbations near the periphery. However, it displays shifts in the locations and spread in the sizes of perturbations near the center of the object     

Three-dimensional EIT imaging of breast tissues: system design and clinical testing

Results of development and testing of the new medical imaging system are described. The system uses a planar array consisting of 256 electrodes and enables obtaining images of the three-dimensional conductivity distribution in regions below the skin's surface up to several centimeters deep. The developed measuring system and image reconstruction algorithm can be used for breast tissue imaging and diagnostics, in particular for malignant tumor detection. Examples of tomographic images obtained in vivo during clinical tests are presented. The mammary gland, being an organ-target, alters at the background with such physiological events as menstrual cycle, pregnancy, lactation, and postmenopause. The objectives of this paper include estimation of the possibilities of electrical impedance mammography for investigation of mammary glands' state among women with different hormonal status. We found that electrical impedance mammograms from different groups had clear visual distinctions and statistically significant differences in mammary glands' conductivity. Our data on conductivity distribution in the mammary gland during different physiological periods will allow us to use it as normal values in the future, to continue this research on mammary glands with different pathology.     

Measurement of material properties with a tunable resonant cavity

A tunable resonant cavity is used to measure the complex permittivity of dielectrics and the surface conductivity of metals with high precision. The analytical approximations, traditionally used in the cavity perturbation techniques, have been replaced with a rigorous numerical solution of the electromagnetic field distribution inside the rotationally symmetric cavity filled with inhomogeneous dielectrics. The measured values of the unloaded Q factor are compared with the numerically computed values over the tuning range. The least-squares data fitting procedure yields simultaneously the values of the loss tangent and the surface conductivity, and their standard deviations.<>     

Impedance imaging of lung ventilation: do we need to account forchest expansion?

Electrical Impedance Tomography (EIT) uses surface electrical measurements to image changes in the conductivity distribution within a medium. When used to measure lung ventilation, however, measurements depend both on conductivity changes in the thorax and on rib cage movement. Given that currently available reconstruction techniques assume that only conductivity changes are present, certain errors are introduced. A finite element model (FEM) is used to calculate the effect of chest expansion on the reconstructed conductivity images. Results indicate that thorax expansion accounts for up to 20% of the reconstructed image amplitude and introduces an artifact in the center of the image tending to “move” the reconstructed lungs closer together. Although this contribution varies depending on anatomical factors, it is relatively independent of inspiration depth. For certain applications in which one is only interested in changes in the level of physiological activity, the effect of the expansion can be neglected because it varies linearly with impedance changes. It is concluded that chest expansion can contribute significantly to the conductivity images of lung ventilation and should be taken into account in the interpretation of these images     

3D Helmholtz coil system setup for thermal conductivity measurements of magnetic nanofluids

This study aims to design a mechatronic system that involves a 3D Helmholtz coil system implemented with the 3ω method to measure the thermal conductivity of magnetic nanofluids under uniform and rotating magnetic fields. For this purpose, a 3D Helmholtz coil system was designed and manufactured to generate a uniform and rotating magnetic field up to 400 G. First, the uniformity and rotation abilities of the magnetic field generated by the system were investigated numerically and experimentally. The investigations pointed out that the 3D Helmholtz coil system can generate a uniform magnetic field in 1D, 2D, and 3D with a maximum non-uniformity factor of 0.0016. After that, the thermal conductivity of Fe₃O₄ – water magnetic nanofluid samples with 1, 2, 3, 4, and 4.8 vol.% were measured under 1D, 2D, and 3D uniform magnetic field application. The magnetic field was applied at different direction angles between X, Y, and Z axes in the Cartesian coordinate system. The results pointed out that the thermal conductivity of the samples increases as the magnetic field and particle concentration increase. The maximum thermal conductivity enhancement was observed as ∼9.1% and the minimum thermal conductivity was observed as ∼1.9% when the magnetic field is applied in parallel and perpendicular directions, respectively. The measurement results also pointed out that under the external uniform magnetic field application at 2D and 3D, thermal conductivity enhancement is less affected by the particle concentration increment.     

Stretchable Electrode Based on Laterally Combed Carbon Nanotubes for Wearable Energy Harvesting and Storage Devices

Carbon nanotubes (CNTs) are a promising material for use as a flexible electrode in wearable energy devices due to their electrical conductivity, soft mechanical properties, electrochemical activity, and large surface area. However, their electrical resistance is higher than that of metals, and deformations such as stretching can lead to deterioration of electrical performances. To address these issues, here a novel stretchable electrode based on laterally combed CNT networks is presented. The increased percolation between combed CNTs provides a high electrical conductivity even under mechanical deformations. Additional nickel electroplating and serpentine electrode designs increase conductivity and deformability further. The resulting stretchable electrode exhibits an excellent sheet resistance, which is comparable to conventional metal film electrodes. The resistance change is minimal even when stretched by ≈100%. Such high conductivity and deformability in addition to intrinsic electrochemically active property of CNTs enable high performance stretchable energy harvesting (wireless charging coil and triboelectric generator) and storage (lithium ion battery and supercapacitor) devices. Monolithic integration of these devices forms a wearable energy supply system, successfully demonstrating its potential as a novel soft power supply module for wearable electronics.     

基于DPHP理论的海洋沉积物热导率检测系统的研究

为了高效精确地对海洋沉积物热导率进行探测,对热脉冲双探针测量理论-DPHP(dual-probe heat-pulse measurement theory)理论,以及基于该理论的测量系统的设计和检测技术进行了深入地研究.在此基础上,设计了一种方便灵活的微型热导率原位测量探头,该探头直径仅为2.5 cm,长20 cm.经过在实验室验证,其平均测量速度 40 s,热导率精度可以达到 0.05.测量速度和精度有了较大提高.     

智能电导率仪的设计

智能电导率仪采用交流测量法来测量电导率。正弦激励的产生是通过阻抗测试芯片AD5933来实现的。AD5933输出的正弦激励加在电导池的电极上,AD5933可以计算出溶液阻抗经过傅里叶变换后阻抗的实部R和虚部I(结果保存在AD5933的寄存器中),然后再计算出校准系数A,就可以通过单片机计算出溶液的真实阻抗,进而计算出溶液的电导率。温度补偿电路测量溶液温度,用于修正温度对测量带来的影响。     

Parametric Evaluation of Video Motion Tracking Data Sets

Video tracking is a complex problem because the environment, in which video motion needs to be tracked, is widely varied based on the application and poses several constraints on the design and performance of the tracking system. Current datasets that are used to evaluate and compare video motion tracking algorithms use a cumulative performance measure without thoroughly analyzing the effect of these different constraints imposed by the environment. But it needs to analyze these constraints as parameters. The objective of this paper is to identify these parameters and define quantitative measures for these parameters to compare video datasets for motion tracking.     

The effect of conductivity values on ST segment shift in subendocardial ischaemia

The aim of this study was to investigate the effect of different conductivity values on epicardial surface potential distributions on a slab of cardiac tissue. The study was motivated by the large variation in published bidomain conductivity parameters available in the literature. Simulations presented are based on a previously published bidomain model and solution technique which includes fiber rotation. Three sets of conductivity parameters are considered and an alternative set of nondimensional parameters relating the tissue conductivities to blood conductivity is introduced. These nondimensional parameters are then used to study the relative effect of blood conductivity on the epicardial potential distributions. Each set of conductivity parameters gives rise to a distinct set of epicardial potential distributions, both in terms of morphology and magnitude. Unfortunately, the differences between the potential distributions cannot be explained by simple combinations of the conductivity values or the resulting dimensionless parameters.     

Performance bounds for estimating vector systems

We propose a unified framework for the analysis of estimators of geometrical vector quantities and vector systems through a collection of performance measures. Unlike standard performance indicators, these measures have intuitive geometrical and physical interpretations, are independent of the coordinate reference frame, and are applicable to arbitrary parameterizations of the unknown vector or system of vectors. For each measure, we derive both finite-sample and asymptotic lower bounds that hold for large classes of estimators and serve as benchmarks for the assessment of estimation algorithms. Like the performance measures themselves, these bounds are independent of the reference coordinate frame, and we discuss their use as system design criteria     

Quantitative Formulations of Electrophysiological Sources of Potential Fields in Volume Conductors

The noninvasive measurement of electrical potentials at the surface of the body (e.g., the electrocardiogram) has long been considered an important tool in clinical diagnosis. Electrophysiological modeling and simulation is valuable as an aid in the interpretation of such potential recordings. In all cases, the potential field can be considered to arise from bioelectric sources operating in a volume conductor. This paper concentrates on the appropriate quantitative formulation for these sources. Such sources arise from excitable cells undergoing action potentials (primary sources) or at passive boundaries between regions of different conductivity (secondary sources). These sources are described and discussed for arbitrary cell shapes, circular cylindrical cells, conductive media with piecewise constant conductivity, and for syncytial tissue whose macroscopic properties are anisotropic.