Notch Position Research Articles

Recognition of dicrotic notch in arterial blood pressure pulses using signal processing techniques

The Physiological condition of cardiovascular system is analyzed by arterial blood pressure pulse wave. The arterial pulse wave displays the genetic traits of the heart, average records of a heartbeat and variation in pressure as the heart spouts blood. This pulse monitoringis a standard process used to assess the cardiovascular system’s medical history. A waveform ofthe Arterial blood pressure usually involves a systolic level, diastolic occurrence, and dicrotic spike and dicrotic notch. The cardiac cavity contracting and relaxing leads to systolic and diastolic blood pressure respectively. The dicrotic notch which is a drop on the down slope shows systole termination and depicts the aorta closure of successive backward stream. The position of the dicrotic notch throughout the cardiac activity differs as per the duration of aortic closure. Dicrotic notch plays an essential part in sclerosis, occlusion, stenosis, arterial spasm and erythromelalgia diagnostic test. Hence Discrete Wavelet transform is utilized in this proposed work to examine and assess the dicrotic notch in arterial pulse wave form. Arterial pulse data are processed using a data acquisition system consisting of multiple channels sensor signal processing and a computer to collect the necessary data for future examination. The uniform peer group of 22 patients has been evaluated utilizing two distinct Haar and Daubuchies4 (db4) wavelet transformations. The peripheral wave in the patients seems to have a sharp rise and a notch on dropping slope, has been identified. The data collected are contrasted between the two techniques, and the Haar wavelet is observed to reasonably represent the best outcome.

Sense current dependent coercivity and magnetization relaxation in Gd-Fe-Co Hall bar

The understanding of the characteristics of a magnetic layer in a different environment is crucial for any spintronics application. Before practical applications, thorough scrutiny of such devices is compulsory. Here we study such a potential Hall device of MgO-capped Hf/GdFeCo bilayer (FeCo-rich) for magnetization relaxation around nucleation fields at different voltage probe line widths and dc sensing currents. The device is characterized by anomalous Hall measurements in transverse and longitudinal Hall geometries for two different probe widths A (5 µm) and B (1 µm). The coercivities of the Hall loops (ρxy-H and Rxx-H) drop with increasing the sense current for both the probes. For probe B, the sharp and large drop in coercivity (ρxy-H loops) at comparatively lower sensing currents is observed, which is attributed to the negligible current shunting and presence of pinning site at B caused by the patterning process. The average domain wall velocities at various sensing currents for probe B are found to be smaller than probe A, from the transverse and longitudinal Hall geometry magnetization relaxation measurements, which agrees with pinning sites and Joule heating effect at probe B. The notch position in the pattern and the longitudinal Hall resistance curve peak shape suggest the domain wall propagation direction from probe B to probe A in the current channel. This study highlights the domain wall propagation at different nucleation fields, sensing currents, and the Hall probe aspect ratios.

Effect of the double grading on the internal electric field and on the carrier collection in CIGS solar cells

In this article, we look, from the carrier perspective, at the effect of the double grading in a CIGS absorber, in order to understand its benefit compared to a single grading. We focus on the double grading effects on the conduction band edge, generation rate and carrier collection. We first show that, when the minimum bandgap position (notch position) is outside of the absorber depletion region, a local maximum of the conduction band edge appears at the back of the depletion region, creating a hump, which hinders the collection of electrons. Interpreting the effect of the grading as an effective electric field, we show that the hump is caused by the competition between the absorber internal electric field and the grading created effective electric field. From this, we deduce that the notch should be positioned in the depletion region. As expected, the generation rate increases significantly at the notch position. However, studying carrier collection and the recombination rate, we show that, even if in the ideal case we should observe a total collection of carriers generated in the depletion region, the recombination rate in the SCR increases significantly when the notch is in it. We propose that this is caused by the increased carrier generation close to recombination centres. The ideal notch position is, therefore, a compromise between being close enough to the front to have a maximal carrier collection and avoiding the creation of a hump, while minimizing the carrier recombination.

Effect of Ion Concentration on the Electro-Optic Response in Polymer-Stabilized Cholesteric Liquid Crystals

We have previously reported that the application of a DC field can adjust the position and/or bandwidth of the selective reflection notch in polymer-stabilized cholesteric liquid crystals (PSCLCs). The proposed mechanism of these electro-optic (EO) response is ion-facilitated electromechanical deformation of the polymer stabilizing network. Accordingly, the concentration of ions trapped within the polymer network should considerably influence the EO response of PSCLC. Our prior studies have indicated that photoinitiators can increase ion density in PSCLC by an order of magnitude. Here, we isolate the contribution of ionic impurities associated with liquid crystal monomers (LCMs) by utilizing initiator-less polymerization. PSCLCs prepared with LCM with low ion concentration show bandwidth broadening of the reflection band whereas PSCLCs prepared with LCM with high ion concentration exhibit a red shifting tuning of the reflection band. The extent of the tuning or bandwidth broadening of the CLC reflection band depends on the concentration of LCMs and the chirality of the LCM.

Addressing Fracture Properties of Individual Constituents Within a Cu-WTi-SiOx-Si Multilayer

With modern materials applications continually decreasing in size, e.g., microelectronics, sensors, actuators, and medical implants, quantifying materials parameters becomes increasingly challenging. Specifically, addressing individual constituents of a system, such as interfaces or buried layers in a multilayer structure, emerges as a topic of great importance. We demonstrate herein a technique to assess fracture parameters of different interfaces of a Cu-WTi-SiOx-Si model system based on in situ microcantilever testing in a scanning electron microscope. Positioning the initial notch position with respect to the interface of interest enabled selection of different crack paths, while an additional overlaid sinusoidal signal permitted continuous measurement of stiffness changes and thereby experimental measurement of the actual crack extension. We thus achieved continuous J–Δa curve measurements for the interface between Cu and WTi, the bulk WTi, and the interface between WTi and SiOx. The localized nature of this novel approach makes it generally applicable to testing specific interfaces.

Ultrawideband Frequency-Selective Absorber Designed With an Adjustable and Highly Selective Notch

In this article, the working mechanism of a wideband absorber designed with an adjustable and highly selective notch band is studied, in which the narrow notch band is independently controlled by the lower lossless layer of the absorber, whereas the upper lossy layer loaded with lumped resistors realizes absorption. We present two instances with geometrically controlled and electrically controlled notch bands, respectively. Without decreasing absorption performance, the notch position can be flexibly adjusted throughout the entire frequency band by simply modifying the dimension of the lossless frequency-selective surface (FSS) or changing the capacitance of the varactor, i.e., using geometric control or electrical control. The narrow notch band allows two wide absorption bands to be retained on both sides; therefore, good stealth performance is still guaranteed. Equivalent circuit models (ECMs) are proposed to further explain the principle. The frequency-domain simulation, ECM, time-domain simulation, and experimental results are in good agreement and validate the adjustability and high selectivity of the notched absorbers. At the end of this article, an FSA-backed monopole antenna is simulated and measured, which clearly illustrates that these FSAs can serve as the ground plane for antennas and realize out-of-band RCS reduction.

Frequency-Coded Chipless RFID Tags: Notch Model, Detection, Angular Orientation, and Coverage Measurements.

This paper focuses on the frequency coded chipless Radio Frequency Identification (RFID) wherein the tag’s information bits are physically encoded by the resonators’ notch position which has an effect on the frequency spectrum of the backscattered or retransmitted signal of the tag. In this regard, the notch analytical model is developed to consider the notch position and quality factor. Besides, the radar cross section (RCS) mathematical representation of the tag is introduced to consider the incident wave’s polarization and orientation angles. Hence, the influences of the incident wave’s orientation and polarization mismatches on the detection performance are quantified. After that, the tag measurement errors and limitations are comprehensively explained. Therefore, approaches to measureing RCS- and retransmission-based tags are introduced. Furthermore, the maximum reading range is theoretically calculated and practically verified considering the Federal Communications Commission (FCC) Ultra Wideband (UWB) regulations. In all simulations and experiments conducted, a mono-static configuration is considered, in which one antenna is utilized for transmission and reception.

Interfacial fracture toughness measurement in both steady state and transient regimes using four-point bending test

The paper describes some extensions of four-point bending tests for determining the interfacial fracture toughness $$\Gamma $$, in both steady-state and transient regimes, as a function of the fracture mode mixity. Two sets of multimaterial systems were studied: (i) Aluminum alloy (ASTM 2017)/epoxy/PMMA polymer and, (ii) Aluminum alloy (ASTM 2017)/stainless steel (ASTM 301) obtained by bonding and thermal spray coating techniques respectively. The interfacial fracture toughness was investigated by means of analytical and Finite Element Analysis using ABAQUS software. The numerical trend solution of both interfacial fracture toughnesses as function of crack length, and friction coefficient has been obtained and compared to an analytical one. We will propose a method on (i) how both reversed notch position in multimaterial systems and crack delamination beyond the inner loading points (transient regime) are explored to extend the measurement of interfacial fracture toughness, (ii) how the numerical analysis is used to determine the interfacial fracture toughness through an experimental compliance measurement in transient regime, and (iii) we attempt to reveal why the interfacial toughness has strong phase angle dependence.

Effect of Cell Thickness on the Electro-optic Response of Polymer Stabilized Cholesteric Liquid Crystals with Negative Dielectric Anisotropy.

It has previously been shown that for polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy, the position and bandwidth of the selective reflection notch can be controlled by a direct-current (DC) electric field. The field-induced deformation of the polymer network that stabilizes the devices is mediated by ionic charges trapped in or near the polymer. A unique and reversible electro-optic response is reported here for relatively thin films (≤5 μm). Increasing the DC field strength redshifts the reflection notch to longer wavelength until the reflection disappears at high DC fields. The extent of the tuning range is dependent on the cell thickness. The transition from the reflective to the clear state is due to the electrically controlled, chirped pitch across the small cell gap and not to the field-induced reorientation of the liquid crystal molecules themselves. The transition is reversible. By adjusting the DC field strength, various reflection wavelengths can be addressed from either a different reflective (colored) state at 0 V or a transparent state at a high DC field. Relatively fast responses (~50 ms rise times and ~200 ms fall times) are observed for these thin PSCLCs.

PROCESSING OF GRADE A LOW CARBON STEEL BY EQUAL CHANNEL ANGULAR PRESSING

Grade A steel was processed using equal channel angular pressing (ECAP). 1 pass ECAP did not cause considerable decrease in the grain size of the steel. It brought about two different microstructures on flow and transverse planes of the ECAP billet, instead. Microstructure consists of elongated ferrite and perlite grains aligned in a direction having mainly 45° angle with the extrusion direction on the flow plane while nearly equiaxed grains were formed on the transverse plane. These differences between the microstructures of two different planes of the ECAP sample is attributed to the share planes that operative during ECAP. ECAP increased hardness and strength values of the steel significantly due to the increase in the dislocation density during the process. However, it decreased elongation to failure considerably. It was found that impact energy of the ECAP-processed sample is dependent on the notch position of the Charpy impact test sample

Three- Dimensional Simulation of Crack Propagation using Finite Element Method

The 3D finite element software ANSYS Workbench software has been employed for simulation of engineering geometries which are containing a pre-cracks and holes. The new feature in this software is using the smart crack growth procedure and the mesh smoothing technique which provides an adaptive and smooth mesh around the crack path as well as the higher stresses area. Under the assumption of LEFM, the stress intensity factors was used as a crack growth criterion which provided as indicators of failure compared to the fracture toughness or threshold stress intensity factors (SIFs) in both static and dynamic loading respectively. The stress intensity factors were calculated for every crack growth step and the fatigue life time was predicted according to the number of cycles. The effect of the nominal notch position of the crack was illustrated. Simulations performed with Ansys show an identical crack path on structures that is in line with that of the experimental and numerical results performed by other researchers.

Regulating crack propagation in laminated metal matrix composites through architectural control

To regulate the bending behavior of laminated metal matrix composites, the effects of stacking sequence and notch position were studied by using both numerical simulation and experimental testing. Laminated composites consisting of TiB/Ti6Al4V composite layer and Ti6Al4V ductile layer were fabricated. The results of numerical simulation on specimen with alloy layer as the outermost layer indicate a better bending ductility compared with the other stacking sequence, and this conjecture was also confirmed by the experimental result where a double increase in bending strain was observed. This was attributed to the tunneling crack blunting by adjacent alloy layers. As for the notch position, crack was preferentially to generate in the composite layer first whether the pre-notch existed in alloy layer or in composite layer. If pre-notched on the alloy layer, tunneling crack in the composite layer would extend earlier than the fracture of the notched outermost layer. For specimen with pre-notch in the composite layer, the adjacent alloy layer and the inner composite layer would fracture at the same time after the crack initiation of the notched composite layer. The fracture behavior of laminated composites can be manipulated by conveniently tailoring stacking sequences and notch position.

Influence of welded joint microstructures on fatigue behaviour of specimens with a notch in the heat affected zone

In this paper, the results of determining the Paris law coefficients, C and m, are presented, based on the experimental data obtained by three-point bending testing of 8 welded joint specimens. The specimens were taken from a welded plate, with P460NL1 used as the parent material and VAC 65 used as filler material. The specimens had a 1.4 mm notch in the heat affected zone, either in the root or the weld face side. After the fatigue crack growth tests performed using the Fractomat 7609/213 (RUMUL), the obtained crack growth rate vs. number of cycles (da/dN vs. N) diagrams were used to calculate the coefficients. The values of these coefficients were then compared to each other, in order to determine the cause of noticeable differences, which were assumed to be a result of different microstructures in different specimens, caused by the increased temperature measured in the specimens near the end of the welded joint. Since the specimens used in the experiment had differences in terms of notch position and temperature, they were divided into four groups. Analysis of the results involved the comparison of obtained a-N curves with the images of microstructures, as seen on the broken specimens, in order to determine whether the changes in the curve's slope correspond to the changes in microstructures along the specimens' cross-sections. The experimental results confirmed this assumption, and it was determined that the crack growth rate was the highest in the weld metal, whereas the lowest rates (highest resistance to fatigue crack growth) were observed in the parent material, with the heat affected zone being between these two value ranges.

Surface driven reflection tuning in chiral nematic liquid crystals

Cholesteric liquid crystals (CLCs) are stimuli driven, photonic bandgap materials that can be used for several optical applications, among which color tuning devices and tunable mirrors. Although many methods for controlling the reflection spectra have been proposed, few of them are able to control the position of the reflection notch and its bandwidth altogether. Here we propose a surface driven method to control the reflection notch center position and width based on an active surface. We theoretically formulated the equations involved and solved them to obtain the dynamical configuration of the liquid crystal and the resulting reflection spectra. Both notch position and potential broadening can be obtained using this method. We also identified the range of parameters which results in one of these regimes or a combination of both. Our results can be helpful for designing surface driven optical devices with CLC materials.

Fatigue crack growth behavior of a selective laser melted AlSi10Mg

Selective Laser Melting is an additive manufacturing technology capable of producing relatively dense parts from metallic and alloy powders using a high-power laser beam. The present study examines the high cycle fatigue crack growth behavior in the linear region of da/dN vs. ΔK diagrams of the AlSi10Mg alloy produced by SLM. Specimen building orientation and notch position have been combined to obtain 4 different crack growth orientations. Further, specimens were tested in both as-built (AB) and T6 heat treated (T6) conditions. The Fatigue Crack Growth (FCG) curves revealed the beneficial influence of the heat treatment on the FCG response, as compared to the as-built case. On the other hand, the fatigue crack growth behavior of the latter is found to be strongly dependent on material orientation. Fractographic analysis have been further performed to understand the mechanisms involved. Additionally, residual stress measurements were also performed to comprehend its contribution on the FCG curves.

Experimental determining of fracture behaviour of P460NL1 steel welded joint specimens

This paper is focused on the experimental measuring of impact energy as a part of the doctoral dissertation involving the fatigue behaviour of welded joints, made of fine grain normalised micro-alloyed low carbon high strength steel P460NL1 [1,2], typically used for pressure vessels working at subzero temperatures. VAC 65 [3] was used as filler material, and two plates were welded using the MAG welding procedure (with 82% Ar + 18% CO2 shielding gas).The specimens were taken from two opposite ends of the welded plate, taking into account the measured values of groove edge temperature in these locations, wherein the temperatures in Location 2 (near the end of the weld) were higher than those in Location 1 (near the weld’s beginning). Based on their specific position, in terms of temperature and notch position (weld root or face), the specimens were divided into four groups of three. This testing was performed using a SCHENCK-TREBEL instrumented Charpy pendulum. The total impact energy was determined, along with its components, crack initiation and crack propagation energy.The obtained results have confirmed that the test specimens were of high toughness, with total impact energy ranging from 165-200 J, at room temperature. The crack propagation energy was the dominant component, being several times greater than the crack initiation energy, as was expected.

Photoplethysmographic characterization of vascular tone mediated changes in arterial pressure: an observational study.

To determine whether a classification based on the contour of the photoplethysmography signal (PPGc) can detect changes in systolic arterial blood pressure (SAP) and vascular tone. Episodes of normotension (SAP 90-140mmHg), hypertension (SAP > 140mmHg) and hypotension (SAP < 90mmHg) were analyzed in 15 cardiac surgery patients. SAP and two surrogates of the vascular tone, systemic vascular resistance (SVR) and vascular compliance (Cvasc = stroke volume/pulse pressure) were compared with PPGc. Changes in PPG amplitude (foot-to-peak distance) and dicrotic notch position were used to define 6 classes taking class III as a normal vascular tone with a notch placed between 20 and 50% of the PPG amplitude. Class I-to-II represented vasoconstriction with notch placed > 50% in a small PPG, while class IV-to-VI described vasodilation with a notch placed < 20% in a tall PPG wave. 190 datasets were analyzed including 61 episodes of hypertension [SAP = 159 (151-170) mmHg (median 1st-3rd quartiles)], 84 of normotension, SAP = 124 (113-131) mmHg and 45 of hypotension SAP = 85(80-87) mmHg. SAP were well correlated with SVR (r = 0.78, p < 0.0001) and Cvasc (r = 0.84, p < 0.0001). The PPG-based classification correlated well with SAP (r = - 0.90, p < 0.0001), SVR (r = - 0.72, p < 0.0001) and Cvasc (r = 0.82, p < 0.0001). The PPGc misclassified 7 out of the 190 episodes, presenting good accuracy (98.4% and 97.8%), sensitivity (100% and 94.9%) and specificity (97.9% and 99.2%) for detecting episodes of hypotension and hypertension, respectively. Changes in arterial pressure and vascular tone were closely related to the proposed classification based on PPG waveform.Clinical Trial Registration NTC02854852.

Characterization of dual band and double polarized notched metallic ring FSS and their equivalent parallel metallic strip structures

ABSTRACTIn this work three rejecting band filters for multi band and dual polarization applications are proposed. The first proposed structure is an open quasi square FSS with a centered notch. The variation of the notch position to the left leads to the tenability of frequencies in both directions of polarization. The addition of a second notch has resulted in a third frequency in the y direction maintaining two resonant frequencies in the x direction. The structures are simulated by the Wave concept Iterative Method and the Comsol Multiphysics software 4.3b. In the second part of this paper a new approach is proposed to obtain an equivalent FSS structures based on non-coupled parallel metallic strips. The new equivalent FSS structures allow the frequency adjustment by the variation of the corresponding strip lengths. The results obtained by the WCIP method and measurements are compared and a good agreement is obtained.

Arterial Pulse Waveform Characteristics Difference between the Three Trimesters of Healthy Pregnant Women.

During pregnancy, the pregnant mother undergoes significant physiological changes in order to accommodate the developing fetus. In recent years, arterial pulse wave has been widely used to reflect these physiological changes. The aim of this study was to investigate the changes of radial pulse and photoplethysmography (PPG) pulse waveform characteristic with gestational age in normal pregnant women. 40 pregnant women volunteers were recruited from February 2016 to September 2016 from the Haidian Maternal & Child Health Hospital in Beijing. Both radial pulses and PPG pulses were recorded simultaneously using a PowerLab data collection system at a sampling rate of 1000Hz for offline analysis. Their pulses were measured from each pregnant woman at three trimesters (first trimester between week 11-13; second trimester between week 20-22 and the third trimester between week 3739). Three waveform characteristics (total pulse area; pulse area1: the area before the notch position; pulse area2: the area after the notch position) were derived. The results showed that the total pulse area and pulse area2 from both radial and PPG pulses decreased significantly between two paired consecutive trimesters (all P<0.01, except the comparisons between the second and third trimesters for PPG pulses). In summary, this study has quantified the pulse waveform characteristic differences in terms of pulse areas between the three trimesters, providing useful scientific evidence to better understand the cardiovascular physiological changes during normal pregnancy.

Meshfree modeling of the dynamic mixed-mode fracture in FRC through an eigensoftening approach

This work is concerned with the numeric study of dynamic mixed-mode fracture in fiber reinforced concrete (FRC). A recently developed eigensoftening algorithm to deal with the fracture of quasi-brittle materials is employed in a meshfree framework. Three point bending tests on notched beams reinforced with steel fibers carried out through a drop weight device at two loading velocities are modelled. Since the notch was placed with an offset from the middle section, mixed-mode crack formation was facilitated. Assuming a linear softening stress-equivalent crack opening relation, the numerical methodology is first validated against experimental results on plain concrete. Subsequently, it is applied to study the dynamic fracture of fiber reinforced concrete with a newly-proposed bilinear relation. The studies reveal that the total fracture energy dissipation plays an important role on the peak reaction load, whereas the transitional point between the two branches has a significant influence on the crack patterns. Parametric studies on the notch position are also carried out. The results show that the notch position has a significant influence on the crack patterns.