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The accumulation-mode metal-oxide-semiconductor (MOS) capacitor is commonly employed to implement MOS varactors in frequency-tuning circuits for radio frequency (RF) and analog applications. A subcircuit model for the accumulation-mode MOS (AMOS) capacitor based on the Berkeley Short-channel IGFET Model (BSIM) for the MOS field effect transistor (MOSFET) is presented. The proposed model accurately fits the capacitance-voltage (C-V) characteristics of an AMOS capacitor fabricated in a submicron CMOS process over the full range of operating gate voltages. The model also accounts for the impact of the distributed series resistance on the transient response of the AMOS capacitor. Notably, the gate capacitance and the associated series resistance are modeled as a distributed resistor-capacitor (RC) network to derive a subcircuit-based model with the bias-dependent resistance of the accumulation layer modeled as a voltage-controlled resistor (VCR). The proposed model is evaluated based on SPICE simulation of the intrinsic transient response of the AMOS capacitor using a basic circuit, representing the distributed RC network associated with the MOS device structure. Fine tuning of the effective series resistance in the subcircuit model can be achieved by fitting the measured data characterizing the charge–discharge behavior of the AMOS capacitor to the simulated data characterizing the intrinsic transient response generated by SPICE.

Lung cancer is the most common and lethal cancer in many parts of the world. The establishment of lung cancer screening by low-dose computerized tomography (CT) scan has led to finding lung cancers in early stages as very small nodules. However, finding those nodules, particularly when located deep in the lung parenchyma, could be impossible during lung surgeries without preoperative or intraoperative localization. This study introduces a simple and safe method having the potential to localize in-depth pulmonary nodules intraoperatively. In this regard, a bioimpedance probe with four spherical electrodes was designed and built. By an in vitro study, the bioimpedance data of 286 lung tissue samples obtained from 38 patients in a frequency range of 50 kHz–5 MHz were collected and analyzed with Nyquist curves and boxplot charts. Finally, a smart system was designed based on the bioimpedance phase and magnitude to differentiate healthy lung tissue from the tumoral lung tissue. Our proposed system consists of two parts: the feature reduction with principal component analysis (PCA) and the classification with support vector machine (SVM), linear discriminant analysis (LDA), and K-nearest neighbors (KNN). Classifier analysis showed that the accuracy of all classifiers was more than 95% for 15 principal components; the SVM classifiers had the highest accuracy above 98%. This research sheds light on the feasibility of designing a real-time, safe, and smart system to localize the invisible/impalpable pulmonary nodules by the bioimpedance spectrum of the lung tissue.

Tissue electrical conductivity measurements are very important for diagnostic purposes. In this paper, an electrical bio-impedance sensor with a biopsy forceps shape was introduced for measuring electrical conductivity of the tissue inside the body. For this purpose, based on the Laplace’s equation and the forced boundary conditions in the mouth of the forceps, the relation between electrical conductivity of the tissue and measured electrical potential was analytically obtained. The obtained analytical formula was verified by modeling the electrical bio-impedance forceps and biological tissue in COMSOL software. A prototype of the designed bio-impedance forceps was fabricated and experimentally validated. The validation process was performed by measuring electrical conductivity of the Phosphate -Buffered Saline (PBS) solution with different concentrations. Finally, by measuring electrical impedance spectrum of pulmonary tissues in three different samples at a frequency band of 50 kHz to 5 MHz, it was found that this sensor could be potentially beneficial to discriminate tumoral tissues from healthy ones in biopsy process.

In this paper, a bioimpedance sensor used to measure the impedance behavior of the biological cells cultured on a scaffold of collagen thin films. The collagen thin films with different concentrations were created on a 1-hexadecanethiol modified surface of the interdigitated electrodes(IDEs). The mesenchymal stem cells(MSCs) and human umbilical vein endothelial cells(HUVECs) were cultured on the collagen thin films. The interaction and the proliferation rate of these cells were investigated by the microscopic, and bioimpedance approaches. Results showed that the MSCs, and HUVECs excellently attached to the collagen thin films. Impedance measurements of the cells cultured on the collagen thin film were performed by a Hioki IM3570 impedance analyzer at the frequency band of 10 kHz to 1MHz at 10 mV. Bioimpedance measurements showed that the proliferation rate of both MSCs, and HUVECs increased by decreasing the collagen thin films concentration. After 48 h, the differential impedances (ΔΖ ) of the MSCs cultured on the collagen thin layers with concentrations of 250μg/mL,500μg/mL , and 1000μg/mL measured 3.09Ω≤Δ≤48.03Ω, 2.62Ω≤Δ≤45.79Ω, and 1.9Ω≤Δ≤25.22Ω, respectively. Also, ΔΖ of the HUVECs obtained 27.3Ω≤Δ≤39.2Ω, 8.25Ω≤Δ≤18.43Ω, and 0.96Ω≤Δ≤9.6Ω for the corresponding frequency band and collagen thin films concentrations.

In this study, a new idea is suggested for designing an appropriate bio-impedance probe in the form of a biopsy forceps to measure the electrical properties of the tissues inside the body. First, by analytically solving the Laplace equation for wedge-shaped tissue in the mouth of the probe, the relationship between electric potential (results from excitation current) in a different point on the tissue and the electrical properties of the tissue is obtained. Then, to evaluate the designed bio-impedance probe using the finite element method and the experimental data obtained for different tissues by Gabriel et al., modelling and simulation at different frequencies from 50 Hz to 5 MHz were done. Finally, to evaluate the performance of the designed probe in comparison to other methods, measurements were carried out using three methods for the same tissue. Nyquist curves were drawn and electrical properties extracted for all the three methods. It was found that the designed probe results are close to the actual values with an error of

The accumulation of cerebrospinal fluid (CSF) in brain ventricles and subarachnoid space is known as hydrocephalus. Hydrocephalus is a result of disturbances in the secretion or absorption process of CSF. A hydrocephalus shunt is an effective method for the treatment of hydrocephalus. In this paper, at first, the procedures of secretion, circulation, and absorption of CSF are studied and subsequently, the mathematical relations governing the pressures in different interacting compartments of the brain are considered. A mechanical-electrical model is suggested based on the brain physiology and blood circulation. In the proposed model, hydrocephalus is modeled with an incremental resistance (Ro) and hydrocephalus shunt, which is a low resistance path to drain the accumulated CSF in the brain ventricles, is modeled with a resistance in series with a diode. At the end, the simulation results are shown. The simulation results can be used to predict the shunt efficiency in reducing CSF pressure and before a real shunt implementation surgery is carried out in a patient’s body.

Purpose: Identifying and localizing the invisible and nonpalpable pulmonary nodules are among the main challenges surgeons face during open and thoracoscopic surgeries. This in vitro study ...

Intraoperative localization of small and in-depth pulmonary nodules particularly during video-assisted thoracoscopic surgery (VATS), is one of the main challenges for Thoracic surgeons. Failure to determine the location of nodules may lead to a large incision in the normal lung tissue or the conversion of the minimally invasive surgery to an open thoracotomy. The aim of this study is to evaluate the use of electrical bio-impedance measurement to precisely determine the position of in-depth pulmonary nodules and tumors, which are not visible during thoracoscopic surgeries or even are not palpable during open thoracic surgeries. With this regard, a suitable bio-impedance sensor similar to a biopsy forceps has been designed in order to measure the lung tissue bio-impedance. Using the available data on the electrical properties recorded from lung tissue during inhalation and exhalation, combined with the tumor modeling in COMSOL software, the effect of different parameters including the size and depth of tumor and the relative difference of electrical properties between healthy and tumoral tissue has been assessed. Furthermore, the geometric characteristics of the proposed sensor are considered. The results generally verify that larger size of nodules results in an easier distinguishing process. Additionally, it is worthy to note that applying a larger geometrically sensor is essential to detect the small and in-depth nodules.

Identifying and localizing of deep pulmonary nodules are among the main challenges that thoracic surgeons face during operations, particularly in thoracoscopic procedures. To facilitate this, we have tried to introduce a non-invasive and safe method by measuring the lung electrical bio-impedance spectrum with a four-electrode array sensor. To study the feasibility of this method, since any change in the depth or diameter of the nodule in the lung tissue is not practical, we used the finite element modeling of the lung tissue and pulmonary nodule to allow changes in the depth and diameter of the nodule, as well as the distance in between the injection electrodes. Accordingly, a bio-impedance sensor was designed and fabricated. By measuring the electrical impedance spectrum of pulmonary tissues in four different specimens with a frequency band of 50 kHz to 5 MHz, 4 pulmonary nodules at four different depths were identified. The obtained bio-impedance spectrum from the lung surface showed that the magnitude and phase of electrical bio-impedance of the tumoral tissue at each frequency is smaller than that of the healthy tissue. In addition, the frequency characteristic varies in the Nyquist curves for tumoral and healthy lung tissues.

Lens is the most general element in optic systems. In branch of ophthalmology and optic engineering measurement the power of lens is very significant. There are different methods and instruments to measure the power of lens, such as using standard lens box, using spherometer and using manual and automatic lensometer. The automatic lensometer is a way to avoid from human error. In this article we have designed an automatic lensometer based on image processing techniques.

In the design of mobile electronics, power is one of the most difficult restrictions to overcome; and current trends indicate this will continue to be an issue in the future. Consumer electronic equipments are becoming small, portable devices that provide users with a wide range of functionality, from communication to music playing. The battery technology and the power consumption of the device limit the size, weight and autonomous lifetime. One promising alternative to batteries is to use parasitic energy dissipated in the movement of the wearer of device to power it. In this paper we designed a system included a rotary arm extending down from the sole, which ultimately drove the small electrical generator through a stepped-up gearbox. A one- way clutch mechanism was used to transmit torque to the gearbox. This allowed for additional spin following the initial impact of a step, also preventing lockup due to rotary inertia in the gears. The entire generator system was designed to fit in the heel of a standard running shoe, with the rotary arm compressing once during each heel strike.

—Angiography is a widely used procedure for vessel observation in both clinical routine and medical research. Often for the subsequent analysis of the vasculature it is needed to measure the angiogram area covered by vessels and/or the vessel length. For this purpose we need vessel enhancement and segmentation. In this paper, we evaluate the performance of a fuzzy inference system and morphology filters for blood vessel segmentation in a noise angiograms image.