Smart Bioimpedance Spectroscopy Device for Body Composition Estimation

The purpose of this work is to describe a first approach to a smart bioimpedance spectroscopy device for its application to the estimation of body composition. The proposed device is capable of carrying out bioimpedance measurements in multiple configurable frequencies, processing the data to obtain the modulus and the bioimpedance phase in each of the frequencies, and transmitting the processed information wirelessly. Another novelty of this work is a new algorithm for the identification of Cole model parameters, which is the basis of body composition estimation through bioimpedance spectroscopy analysis. Against other proposals, the main advantages of the proposed method are its robustness against parasitic effects by employing an extended version of Cole model with phase delay and three dispersions, its simplicity and low computational load. The results obtained in a validation study with respiratory patients show the accuracy and feasibility of the proposed technology for bioimpedance measurements. The precision and validity of the algorithm was also proven in a validation study with peritoneal dialysis patients. The proposed method was the most accurate compared with other existing algorithms. Moreover, in those cases affected by parasitic effects the proposed algorithm provided better approximations to the bioimpedance values than a reference device.Ministerio de Economía y Competitividad (Instituto de Salud Carlos III) PI15/00306Junta de Andalucía PIN-0394-2017Unión Europea "FRAIL

Microwave Characteristics of Particulate Magnetic Composites

Spherical magnetic particles have recently become of interest for applications in microwave communications devices as they exhibit magnetic absorption modes at frequencies much larger than conventional materials. These higher order modes allow composites comprising spherical magnetic particles in dielectric matrices to have relative permeabilities above unity at frequencies surpassing conventional magnetic materials. The higher order magnetic modes seen in spherical iron powders are a result of the vortex domain structure of magnetic spheres and exist also in magnetic spherical shells. Composite materials containing these magnetic spheres have use in miniaturisation of communications devices and allow access to frequency bands previously unattainable for communications as the increase in permeability at high frequencies will not only increase the refractive index of the material, but also decrease the impedance of the material, improving impedance matching to air. This thesis presents work for the investigation of higher order modes in spherical iron powders, particularly carbonyl iron powders, with the intent to demonstrate how properties such as particle size distribution affects the higher order resonances exhibited. A stripline technique for broadband characterisation of dielectric and magnetic composites is presented in the thesis, which demonstrates an ability to extract the relative permittivity and permeability of composites across an unprecedented broadband frequency range of 0.2 - 50 GHz. Although the relative permittivity and permeability of composites was able to be extracted for most cases, the refractive index of materials was shown to be significantly more resistant to uncertainty across broad frequencies. This technique employed a simple method for sample manufacture by wet-casting composites for characterisation, giving a fast and reliable method for characterising small amounts of material across a frequency range that surpasses most readily available methods. The technique was used for characterisation of several carbonyl iron powder grades. The carbonyl iron grades were imaged by scanning electron microscopy (SEM) analysis to give particle size distributions that were able to be compared between grades to allow an investigation into how the particle size distribution for carbonyl iron powders affects their microwave characteristics. Particle size distribution was confirmed to be a strong factor when considering the strength and position in frequency of these higher order resonances, so a technique was developed for filtration of powders into subgrades with different particle size distributions and average particle sizes. The results of this investigation displayed that the emergence of higher order magnetic absorption modes in carbonyl iron is heavily dependent on the average size and distribution of sizes for the powder used. The filtration technique developed is able to be used for filtration of spherical particles in the single micron size regime and uses only the flow of air through a set of stainless steel tubing and glass bottles. This experimental method is not only cheap, but is simple to assemble and achieves filtration of powders smaller than most mechanical sieves are capable of filtering. Finally, an investigation into the behaviour of these higher order modes under externally applied magnetic bias fields was performed. Samples were subject to a DC magnetic field during characterisation and the complex refractive index of composites was extracted as a field dependent value across the frequency range 0.2 - 30 GHz. The results showed that the primary absorption mode of these composites, at low GHz frequencies, was strongly affected by the application of a DC bias field, changing in both intensity and position in frequency. The higher order modes showed a less strong dependence on DC bias field strength until saturation fields were reached, and the modes were suppressed. The higher order modes not being supported at high DC bias fields is indicative of the vortex domain structure being necessary for higher order spherical modes to exist in magnetic powders.Engineering and Physical Sciences Research Council (EPSRC

유기 발광 소자에 대한 임피던스 분광 분석 방법에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2019. 2. 홍용택.In this dissertation, the method of analyzing the characteristics of organic light-emitting diodes using impedance spectroscopy was studied. Generally, the organic light-emitting device has a structure in which organic materials necessary for light emission are thinly laminated between a TCO (Transparent Conductive Oxide) and a metal electrode. Due to chemical vulnerability of organic materials as well as the complexity with their hetero-junction, it is necessary to investigate the characteristics of fabricated an organic light-emitting diodes in a non-destructive manner rather than destructive manner. Classically, a method of measuring a current-voltage curve using a current-voltage meter and measuring a luminescence using luminance meter is used to evaluate the characteristics of the OLEDs. However, in order to investigate details at intrinsic interface state or carrier dynamics of OLEDs, it is require measuring the impedance response under operating condition. Impedance spectroscopy (IS) covers all impedance responses in the frequency range from milli hertz to megahertz, while focusing primarily on capacitance in solid-state electronics. This makes it possible to construct a high-resolution equivalent circuit and analyze each measured impedance. Each impedance is measured by applying ac small signal after determining the dc operating voltage. The dc operating voltage and ac small signal should be strategically chosen to describe the behavior of the device. In Chapter 1, an overview of the Impedance Spectroscopy Analysis is introduced and the background of the impedance measurement method is explained. Then the motivation for applying this impedance analysis method to OLEDs is explained and the methods of analyzing the characteristics of OLEDs through impedance spectroscopy are discussed. Chapter 2 reviews previously reported papers about impedance analysis methods of OLEDs and explains the limitations of these papers. In particular, the contributions of the diffusion capacitance that they underestimate are very important to prevent errors when characterizing of OLEDs. To explained diffusion capacitance the Laux & Hess model is applied. This model can explain the impedance response to the residual current and even demonstrate the negative capacitance phenomenon. The analytical results using the Laux & Hess model[1] were verified to describe the characteristics of the OLEDs during operation and an approximate and fitting process for the analytical method of this model is proposed. In Chapter 3, ITO/a-NPD[N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine]/Alq3[Tris-(8-hydroxyquinolinato)aluminum]/LiF/Al type OLEDs were fabricated and investigated using the improved impedance analysis method proposed in Chapter 2. First, according to the structural (thickness) change, the physical analysis was performed quantitatively by changing the impedance response. The measured impedance at high frequencies represents the interface and buck characteristics in the OLEDs, and the impedance at low frequencies explains the dynamics of carriers in the OLEDs. In addition, the impedance changes due to OLEDs degradation are analyzed. Using the proposed Impedance Spectroscopy Analysis method in this paper, the origin of degradation can be accurately and effectively separated from the state change of the interface and the buck. The results strengthen the existing interpretation of the interface trap effect of HTL/EML and showed that it can be traced with the rate of change of the extracted impedance value. Chapter 4 briefly introduces the program tool for analyzing the OLEDs used in this paper, and attached an appendix for derived the formula. And I will discuss the possibility of applying this Impedance Spectroscopy Analysis to mass products industry in the future.본 논문은 임피던스 분광법을 이용한 유기 발광 다이오드의 특성 분석 방법에 대한 연구이다. 일반적으로 유기 발광 소자는 TCO (Transparent Conductive Oxide)와 금속 전극 사이에 발광에 필요한 유기 물질이 얇게 적층 된 구조를 갖는다. 유기 물질의 화학적 취약성과 헤테로 접합의 복잡성으로 인해 파괴적인 방식 보다는 비파괴 방식으로 제조된 유기 발광 다이오드의 특성을 조사해야 한다. 고전적으로, 전류-전압계를 사용하여 전류-전압 곡선을 측정하고 휘도 계를 사용하여 발광을 측정하는 방법이 OLEDs의 특성을 평가하는데 사용된다. 그러나 OLEDs의 인터페이스 상태 또는 캐리어 동역학에 대한 세부 사항을 조사하기 위해서는 작동 조건 하에서의 임피던스 응답을 측정해야 한다 일반적인 고체 물리에서의 임피던스 분석 방법은 커패시턴스에 주로 초점을 맞추고 있는 반면에, 임피던스 분광법 (IS)은 miliherz 에서 megaherz의 주파수 범위에서 모든 임피던스 응답을 다루는 것이 특징이다. 이를 통해 분해능이 높은 등가 회로를 구성하고 각각 측정 된 임피던스를 면밀히 분석 할 수 있다. 각 임피던스는 작동 직류 전압을 결정한 후 교류 소신호를 인가하여 측정되는데, 이 작동 직류 전압과 교류 소신호는 소자의 동작을 적절히 설명하기 위해 전략적으로 선택되어야 한다. 제 1 장에서는 임피던스 분광 분석의 개요를 소개하고 임피던스 측정 방법의 배경을 설명한다. 그리고 임피던스 분석 방법을 OLEDs에 적용하려는 동기에 대해서 설명하고 임피던스 분광학을 통해 OLEDs의 특성을 분석하는 다양한 방법들이 논의된다. 제 2 장은 OLEDs의 임피던스 분석 방법에 대해 이전에 보고된 논문을 검토하고 이들 논문의 한계를 설명한다. 특히, 이전에 과소평가된 확산 캐패시턴스의 기여는 OLEDs의 특성을 결정할 때 오류를 방지하는 데 매우 중요하다는 것을 보여줄 것이다. 이러한 확산 용량을 설명하기 위해 Laux & Hess 모델이 적용되었다. 이 모델은 잔류 전류에 대한 임피던스 응답을 매우 잘 설명 할 수 있고 심지어 음의 커패시턴스 현상도 잘 설명해 준다. Laux & Hess 모델을 사용한 분석 결과는 작동 중의 OLEDs의 특성을 잘 묘사 하고 있음을 보였고 이 모델의 분석 방법을 위한 근사 프로세스를 제안하였다. 제 3 장에서는 ITO/a-NPD[N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine]/Alq3[Tris-(8-hydroxyquinolinato)aluminum]/LiF/Al 형 OLED를 제작하여 제 2 장에서 제안된 개선된 임피던스 분석법을 사용하여 조사하였다. 먼저, 구조적(두께) 변화에 따른 임피던스 응답의 변화를 측정하여 물리적, 정량적 해석이 수행되었다. 높은 주파수에서 측정된 임피던스는 OLEDs의 인터페이스 및 버크 특성을 나타내며 저주파수에서의 임피던스는 OLEDs의 캐리어의 동적 이동을 설명한다. 또한 OLEDs의 열화로 인한 임피던스 변화를 분석하였다. 본 논문에서 제안 된 Impedance Spectroscopy Analysis 방법을 사용하면, 열화의 원인으로서 계면과 버크의 상태 변화가 정확하고 효과적으로 분리 될 수 있다. 결과는 HTL/EML의 인터페이스 트랩 효과에 대한 기존 해석을 강화하는 것으로 나왔고 추출된 임피던스 값의 변화율을 추적 할 수 있음을 보여 주었다. 4 장 에서는 이 논문에서 사용된 OLEDs를 분석하기 위한 프로그램 도구를 간략하게 소개하고 수식에 대한 부록을 첨부 했다. 그리고 향후 이 임피던스 분광학 분석을 산업에 적용 시킬 가능성에 대해 논의하고 요약하도록 하겠다.Abstract i Contents v List of Figures viii List of Tables xiii Chapter 1 Introduction 1 1.1 Motivation 1 1.1.1 History of Organic Light Emitting Diodes 6 1.1.2 OLEDs Hetero Structures 8 1.1.3 OLEDs life time 11 1.2 Materials 15 1.2.1 Alq3 16 1.2.2 HAT-CN 17 1.2.3 α-NPB 18 1.2.4 DCM 19 1.3 Equipment & Instrument 20 1.3.1 Thermal Evaporator 20 1.3.2 Impedance Measurement Equipment for OLEDs 23 Chapter 2 Analytic Theory of OLED Impedance Spectroscopy 26 2.1 Problems of Previous Reported Impedance Spectroscopy to extract parameter on OLEDs 28 2.2 Complex Capacitance Concepts for IS 31 2.2.1 ARC 31 2.2.2 ZARC 34 2.2.3 Negative Capacitance 38 2.2.4 Equivalent circuit strategy for OLEDs 43 2.3 Theory 45 2.3.1 Impedance Spectroscopy 45 2.3.2 Small-Signal Model 49 2.3.3 Complex Plane Diagram 51 2.3.4 Equivalent Circuit Modeling 54 2.3.5 Superposition of various Impedance Component 58 2.3.6 Debye relaxation plot( -plot) 60 2.4 How to extract reasonable parameter from impedance spectroscopy 64 Chapter 3 Experiments 71 3.1 Thickness modification OLEDs 72 3.1.1 Analysis of the Interface of the OLEDs 76 3.1.2 Analysis of the Carrier Distribution of OLEDs 78 3.2 Thickness ratio modification 80 3.2.1 Relation between efficiency and M-plot 82 3.3 DCM doping ration Modification 84 3.3.1 Correlation between Current-Voltage-Efficiency and Impedance Response 84 Chapter 4 Discussion 90 4.1 Consideration of Effects of Interface Properties 90 4.2 Consideration of Effects of Bulk properties 92 4.3 Negative Capacitance relation with efficiency analysis 93 4.4 Mobility Measurement Using Impedance analysis 96 Chapter 5 Conclusion 101 Appendix 109 Bibliography 116 Publications 122 초 록 127Docto

STR-896: POTENTIAL PITFALLS IN THE PRACTICAL APPLICATION OF THE RANDOM DECREMENT TECHNIQUE

The Random Decrement Technique (RDT) has been widely used to extract as-built structural dynamic properties of civil engineering structures under ambient excitation, such as natural frequency, damping ratio, and their nonlinearity. This paper aims to clarify firstly that the RDT itself is not a damping evaluation technique (DET), but rather a data conditioning technique, akin to a filter. It results in what is called a “random decrement signature” (RDS) that is considered to represent the free decay response of the system, mode, or DOF being investigated. This paper also aims to show that a number of parameters influence the outcome of the RDT and the chosen DET. This was done by generating different sets of synthetic data, for which the actual damping and frequency values are known, which in turn are analyzed using RDT and appropriate DETs, and the results are then presented and discussed. Three important findings are: that damping may typically be overestimated especially the higher the noise is, any type of data filtering greatly affects the results, and some amplitude dependency may appear even if there was none. A discussion on how these potential pitfalls in the practical application of the RDT is then offered

A Preliminary Exploration of the Placental Position Influence on Uterine Electromyography Using Fractional Modelling

The uterine electromyogram, also called electrohysterogram (EHG), is the electrical signal generated by uterine contractile activity. The EHG has been considered an expanding technique for pregnancy monitoring and preterm risk evaluation. Data were collected on the abdominal surface. It has been speculated the effect of the placenta location on the characteristics of the EHG. In this work, a preliminary exploration method is proposed using the average spectra of Alvarez waves contractions of subjects with anterior and non-anterior placental position as a basis for the triple-dispersion Cole model that provides a best fit for these two cases. This leads to the uterine impedance estimation for these two study cases. Non-linear least square fitting (NLSF) was applied for this modelling process, which produces electric circuit fractional models' representations. A triple-dispersion Cole-impedance model was used to obtain the uterine impedance curve in a frequency band between 0.1 and 1 Hz. A proposal for the interpretation relating the model parameters and the placental influence on the myometrial contractile action is provided. This is the first report regarding in silico estimation of the uterine impedance for cases involving anterior or non-anterior placental positions.info:eu-repo/semantics/publishedVersio

A Preliminary Exploration of the Placental Position Influence on Uterine Electromyography Using Fractional Modelling

Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.The uterine electromyogram, also called electrohysterogram (EHG), is the electrical signal generated by uterine contractile activity. The EHG has been considered an expanding technique for pregnancy monitoring and preterm risk evaluation. Data were collected on the abdominal surface. It has been speculated the effect of the placenta location on the characteristics of the EHG. In this work, a preliminary exploration method is proposed using the average spectra of Alvarez waves contractions of subjects with anterior and non-anterior placental position as a basis for the triple-dispersion Cole model that provides a best fit for these two cases. This leads to the uterine impedance estimation for these two study cases. Non-linear least square fitting (NLSF) was applied for this modelling process, which produces electric circuit fractional models’ representations. A triple-dispersion Cole-impedance model was used to obtain the uterine impedance curve in a frequency band between 0.1 and 1 Hz. A proposal for the interpretation relating the model parameters and the placental influence on the myometrial contractile action is provided. This is the first report regarding in silico estimation of the uterine impedance for cases involving anterior or non-anterior placental positions.publishersversionpublishe

A comparative overview of modal testing and system identification for control of structures

A comparative overview is presented of the disciplines of modal testing used in structural engineering and system identification used in control theory. A list of representative references from both areas is given, and the basic methods are described briefly. Recent progress on the interaction of modal testing and control disciplines is discussed. It is concluded that combined efforts of researchers in both disciplines are required for unification of modal testing and system identification methods for control of flexible structures

Impedimetric analysis of biological cell monolayers before and after exposure to nanosecond pulsed electric fields

Models and methods for the interpretation of impedance spectra for normal and cancer cells before and after electrical stimulation, focusing on nanosecond pulsed electric fields (nsPEFs), were investigated to describe salient features and their development that were observed in dedicated in situ experimental studies. For the first time a non-invasive, real-time and label-free method was established to explore temporal changes and their underlying physical processes of adherent cells for characteristics of cell-cell connections and the extracellular matrix.Modelle und Methoden zur Interpretation von Impedanzspektren für normale und Krebszellen vor und nach elektrischer Stimulation, mit dem Fokus auf Nanosekunden-gepulste elektrische Feldern, wurden untersucht, um herausragende Merkmale und deren Entwicklung zu beschreiben, die in speziellen In-situ-Experimenten beobachtet wurden. Zum ersten Mal wurde eine nicht-invasive, zeitnahe und markierungsfreie Methode entwickelt, um zeitliche Veränderungen und diesen zugrunde liegenden physikalischen Prozessen hinsichtlich der Eigenschaften von Zell-Zell-Verbindungen und der extrazellulären Matrix zu untersuchen

Panel Damping Loss Factor Estimation Using The Random Decrement Technique

The use of the Random Decrement Technique (RDT) for estimating panel damping loss factors ranging from 1% to 10% is examined in a systematic way, with a focus on establishing the various parameters one must specify to use the technique to the best advantage. Throughout, loss factors are estimated in full or 1/3rd octave frequency bands with standard 1/3rd octave center frequencies. The full octave filters, which are more computationally efficient than the 1/3rd octave filters, are chosen in the experimental analysis of the damped plates with varied loss factor levels. Two computational models are examined: a single degree of freedom oscillator and a computational model of a uniform rectangular panel. The panel computational model is a finite element model of a rectangular plate mechanically exited at a single point. These models are used to establish a systematic process for evaluating: the appropriate narrow band filter selection; trigger conditions; record length required as a function of frequency and damping level; the averaging scheme; and, the curve-fitting scheme for assigning loss factors in narrow frequency bands. Loss factor estimates for three damped plates are computed using the "optimized" Random Decrement estimation algorithm and compared with estimates from the Impulse Response Decay Method. For the highly damped plates, RDT out-performed IRDM because the loss factors from IRDM are underestimated. For lightly damped plates, RDT and IRDM are consistent in most frequency bands