Academic literature on the topic 'Open-ended coaxial cable'

An open-ended coaxial cable is used to measure the dielectric properties of lossy liquid. The method which is based on the measurement of the reflection coefficient of the open-ended cable makes it easy to operate and postprocess. To meet the accuracy requirements, the dimensions of the coaxial cable need to be taken into consideration; therefore, it is necessary to select an appropriate coaxial cable for the measurement. This paper investigates the influence of cable dimensions on dielectric measurement accuracy. With careful choice of the coaxial cable, the relative error of calculated results can be less than 0.1%.

We have developed a transmission-based, open-ended coaxial dielectric probe that can be used in clinical situations and overcomes many of the limitations related to the typical reflection-based dielectric probes. The approach utilizes the low profile, open-ended coaxial cables enabling clinicians to still probe relatively compact spaces. The sensing depth can be extended to as large as 1.5 to 2 cm compared with the more typical range of 0.3 mm for conventional probes and is dramatically less affected by measurement technique variability including poor sample contact and cable bending. As a precursor to an actual clinical implementation, we study the technique in a range of homogeneous liquids with substantially varying dielectric properties. The initial results demonstrate good agreement between the transmission-based probe and commercial, reflection-based probes and pave the way for more substantial clinical implementation.

This paper describes a detailed study on the application of an open ended coaxial probe technique to determine the permittivity of NixZn1-xFe2O4 in the frequency range between 1 GHz and 10 GHz. The x compositions of the spinel ferrite were 0.1, 0.3, 0.5, 0.7, and 0.9. The NixZn1-xFe2O4 samples were prepared by 10-hour sintering at 900°C with 4°C/min increment from room temperature. Particles showed phase purity and crystallinity in powder X-ray diffraction (XRD) analysis. Surface morphology measurement of scanning electron microscopy (SEM) was conducted on the plane surfaces of the molded samples which gave information about grain morphology, boundaries, and porosity. The tabulated grain size for all samples was in the range of 62 nm–175 nm. The complex permittivity of Ni-Zn ferrite samples was determined using the Agilent Dielectric Probe Kit 85070B. The probe assumed the samples were nonmagnetic homogeneous materials. The permittivity values also provide insights into the effect of the fractional composition of x on the bulk permittivity values NixZn1-xFe2O4. Vector Network Analyzer 8720B (VNA) was connected via coaxial cable to the Agilent Dielectric Probe Kit 85070B.

This study aimed to investigate the kinetics of an aerobic bioremediation process of diesel oil removal by indigenous microorganisms, and to define the optimal operative conditions by means of response surface methodology. This was carried out by setting up a series of microcosms (200 g of soil), polluted with the same diesel oil concentration (70 g·kg−1 of soil), but with different water contents (u%) and carbon to nitrogen (C/N) ratios. The process was monitored by: (1) residual diesel oil concentration, to measure the removal efficiency, and (2) fluorescein production, to check the microbial activity. These two parameters were the objective variables used for the analysis of variance (ANOVA) and response surface methodology (RSM). The results allowed the interactions between u% and C/N to be defined and the optimal range to be adopted for each. The process kinetics was modeled with first- and second-order reaction rates; slightly better results were achieved for the second-order model in terms of parameter variability. Biological processes like degradation may have effects on dielectric properties of soil; an open-ended coaxial cable was used to measure the dielectric permittivity of microcosm matrices at the start and after 130 days of bioremediation. The evolution of the real and the imaginary components of dielectric permittivity provided results that supported the evidence of a biodegradation process in progress.

AbstractThis study aimed to monitor the aerobic bioremediation of diesel oil-contaminated soil by measuring: a) the CO2 production; 2) the fluorescein production; 3) the residual diesel oil concentration. Moreover, the complex dielectric permittivity was monitored through an open-ended coaxial cable. Several microcosms were prepared, changing the water content (u% = 8–15% by weight), the carbon to nitrogen ratio (C/N = 20–450), and the soil amount (200 and 800 g of dry soil). The cumulative CO2 and fluorescein production showed similar trends, but different values since these two parameters reflect different features of the biological process occurring within each microcosm. The diesel oil removal efficiency depended on the microcosm characteristics. After 84 days, in the microcosms with 200 g of dry soil, the highest removal efficiency was achieved with a water content of 8% by weight and C/N = 120, while in the microcosms with 800 g of dry soil the best result was achieved with the water content equal to 12% by weight and C/N = 100. In the tested soil, the bioremediation process is efficient if the water content is in the range 8–12% by weight, and C/N is in the range 100–180; under these operative conditions, the diesel oil removal efficiency was about 65–70% after 84 days. The dielectric permittivity was monitored in microcosms with 200 g of dry soil. The open-ended coaxial cable detected significant variations of both the real and the imaginary component of the dielectric permittivity during the bioremediation process, due to the physical and chemical changes that occurred within the microcosms.

[ES] Conocer las propiedades electromagnéticas de los tejidos biológicos con la mayor exactitud posible tiene una gran importancia en el diseño de un elevado número de aplicaciones biomédicas. El diseño de dispositivos médicos inalámbricos, antenas superficiales e intracorporales, evaluación de tasas de absorción electromagnética, técnicas de tratamiento y detección de cáncer como la hipertermia e imágenes médicas son ejemplos de aplicaciones que requieren esta información para su desarrollo. Debido a que el cáncer provoca modificaciones estructurales en las células que a su vez generan cambios en las propiedades electromagnéticas, es posible desarrollar aplicaciones de detección de cáncer que se basen en este hecho. Un objetivo potencial es el cáncer de colon (CRC), debido a que los tejidos de colon sospechosos son accesibles de forma más o menos sencilla durante procedimientos endoscópicos. Este tipo de cáncer es uno de los más extendidos, siendo responsable de aproximadamente el 10% de casos y muertes totales. Existe un gran número de factores de riesgo que pueden explicar la aparición de la enfermedad, aunque esencialmente la probabilidad se incrementa significativamente con el aumento de la edad de la población. Los programas de cribado sobre la población son críticos: si el cáncer se detecta en etapas tempranas, la probabilidad de sobrevivir se incrementa en gran medida, y además se reducen los costes asociados. Uno de los objetivos principales de esta tesis es proponer aplicaciones que ayuden en la detección de CRC durante la colonoscopia haciendo uso de las diferencias en las propiedades electromagnéticas. Aparte de mejoras en el diagnóstico, complementar la colonoscopia puede conllevar otros beneficios colaterales como una reducción en la carga de anatomía patológica. Para demostrar la viabilidad y el potencial desarrollo futuro de estas aplicaciones, en esta tesis se miden y se trata de encontrar diferencias entre las propiedades electromagnéticas de tejidos sanos, cancerosos y patológicos de colon humano. Las medidas han sido llevadas a cabo mediante la técnica del coaxial terminado en abierto. Con el propósito de incrementar la precisión del método, se ha evaluado el principio de funcionamiento y se ha mejorado el proceso de calibración. Dos fuentes de tejido de colon han sido analizadas en esta tesis: tejidos procedentes de colonoscopias (biopsias) y tejidos obtenidos a partir de procedimientos quirúrgicos. Aparte de tejido sano, se estudian las siguientes patologías: Adenocarcinomas (CRC), adenomas sin displasia, adenomas con bajo grado de displasia, adenomas con alto grado de displasia, hiperplasias y hamartomas. Debido a la alta variabilidad entre distintos sujetos, las propiedades electromagnéticas de los tejidos sospechosos de un paciente en concreto deben ser siempre comparadas con las propiedades de sus tejidos sanos, no evaluadas de forma independiente. El segundo gran objetivo de esta tesis es el desarrollo de una nueva base de datos de las propiedades electromagnéticas de tejidos biológicos medidas in vivo. Ahora mismo, las colecciones disponibles están limitadas en número de tejidos o frecuencias caracterizadas, obligando a los investigadores a escoger bases de datos más completas pero realizadas ex vivo. No obstante, usar este tipo de colecciones tienen fuentes de incertidumbre adicionales dado que las medidas están condicionadas por la deshidratación de los tejidos y la perdida de flujo sanguíneo. El desarrollo de esta nueva base de datos puede facilitar el diseño de aplicaciones que requieran conocer las propiedades electromagnéticas con alto grado de precisión.
[CAT] Conéixer les propietats electromagnètiques dels teixits biològics amb la major exactitud possible té una gran importància en el disseny d'un gran nombre d'aplicacions biomèdiques. El disseny de dispositius metges sense fil, antenes superficials i intracorporales, l'avaluació de taxes d'absorció electromagnètica, tècniques de tractament i detecció de càncer com ara la hipertèrmia i imatges mediques són exemples d'aplicacions que requerixen esta informació. Com el càncer provoca modificacions estructurals en les cèl·lules que generen canvis en les propietats electromagnètiques, es possible desenrotllar aplicacions de detecció de càncer que es basen en este fet. Un objectiu potencial és el càncer de colon (CRC), pel fet que els teixits de colon sospitosos són accessibles de forma més o menys senzilla durant procediments endoscòpics. Este tipus de càncer és un dels més estesos, sent responsable d'aproximadament el 10% de casos i morts totals. N'hi ha un gran nombre de factors de risc que poden explicar l'aparició de la malaltia, encara que en resum la probabilitat s'incrementa significativament amb l'augment de l'edat de la població. Els programes de cribratge sobre la població són crítics. Si el càncer es detecta en etapes primerenques, la probabilitat de sobreviure s'incrementa en gran manera, i a més es reduïxen els costos associats. Un dels objectius principals d'esta tesi és proposar aplicacions que ajuden en la detecció de CRC durant la colonoscòpia fent ús de les diferències en les propietats electromagnètiques. A banda de millores en el diagnòstic, complementar la colonoscòpia pot comportar altres beneficis col·laterals com una reducció en la càrrega d'anatomia patològica. Per a demostrar la fiabilitat i el potencial desenrotllament d'aquestes aplicacions, en aquesta tesi es mesuren i es tracta de trobar diferències entre les propietats electromagnètiques de teixits sans, cancerosos i patològics de colon humà. Les mesures han sigut realitzades mitjançant la tècnica del coaxial acabat en obert. Amb el propòsit d'incrementar la precisió del mètode, s'ha avaluat el seu principi de funcionament i s'ha millorat el procés de calibratge. Dos fonts de teixit de colon s'han analitzat en aquesta tesi: teixits procedents de colonoscòpies (biòpsies) i teixits obtinguts a partir de procediments quirúrgics. Apart de teixit sà, s'estudien els següents teixits: Adenocarcinomes (CRC), adenomes sense displàsia, adenomes amb baix grau de displàsia, adenomes amb alt grau de displàsia, hiperplàsies y hamartomes. Degut a l'alta variabilitat entre diferents subjectes, les propietats electromagnètiques dels teixits sospitosos d'un pacient en particular han de ser comparades amb les propietats dels seus teixits sans, no avaluats independentment. El segon gran objectiu d'esta tesi és el desenrotllament d'una nova base de dades de les propietats electromagnètiques de teixits biològics mesurades in vivo. Ara mateix, les col·leccions disponibles estan limitades en nombre de teixits o freqüències caracteritzades, obligant els investigadors a triar bases de dades més completes però realitzades ex vivo. No obstant això, este tipus de col·leccions te fonts d'incertesa addicionals atés que les mesures estan condicionades per la deshidratació dels teixits i la pèrdua de flux sanguini. El desenrotllament d'esta nova base de dades pot facilitar el disseny d'aplicacions que requerisquen conéixer les propietats electromagnètiques amb alt grau de precisió.
[EN] Nowadays, a careful knowledge of the electromagnetic properties of biological tissues is required for developing a great number of applications. The development of wireless medical devices, the design of in-body and on-body antennas, specific absorption rate evaluations, cancer treatment techniques such as hyperthermia and detection techniques like medical imaging are some examples of applications that rely on these data. Since cancer causes modifications on the biological structure of cells that can lead in turn to changes in the electromagnetic properties of the tissues, it is possible to develop novel detection applications taking advantage of it. One potential target is colorectal cancer (CRC), as suspicious tissues can be accessed quite easily through colonoscopy procedures. This kind of cancer is one of the most spread kinds, being responsible of about 1 out of 10 new cancer cases and deaths. There are several risk factors currently related to the apprising of this cancer, although in essence the higher the age of the population, the higher the incidence of CRC. Screening programs are key for detecting and diagnosing cancer: if found at early stages, the probability of survival increases greatly, and the cost of the treatment can be reduced as well. One of the major objectives of this dissertation is proposing applications for detecting CRC that aid in the colonoscopy procedures by making use of the differences in electromagnetic properties. Aside from enhancement in the diagnosis of CRC, improving the colonoscopy procedure can lead to collateral benefits like a lowering of the burden of anatomical pathology unit. With the aim at demonstrating the feasibility and the potential future development of these applications, in the framework of this thesis the dielectric properties of healthy, cancerous and pathological human colon tissues are measured and compared in order to find electromagnetic differences. Measurements are carried out by means of an open-ended coaxial system. Its principle of operation has been revisited with the aim at maximizing the accuracy of the method, and the calibration procedure has been optimized serving the same purpose. Two main sources of colon tissue have been analyzed: samples from colonoscopy biopsies and samples from surgery resections. Besides healthy tissue, the following colon tissues have been characterized: Adenocarcinomas (CRC), adenomas without dysplasia, adenomas with low-grade dysplasia, adenomas with high-grade dysplasia, hyperplastic polyps and hamartomatous polyps. Given the variability that can appear among subjects, the electromagnetic properties of suspicious tissues from a particular patient have to be always compared with those of his healthy ones, not evaluated independently. The second major objective of this thesis involves the development of a new database of electromagnetic properties of biological tissues obtained at in vivo conditions. Nowadays, the available collections are limited either in the number of tissues or the measured frequencies, and hence researchers have to make use of more complete databases but that were performed ex vivo. The drawback of using these collections is that results can be compromised by factors such as lack of blood perfusion and tissue dehydration. Developing this new database can facilitate the design of applications that needs of a careful knowledge of these properties.
Fornés Leal, A. (2019). Dielectric Characterization of Biological Tissues for Medical Applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/132188
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