Tip Diameter Research Articles

Assessing Electrode Characteristics in Continuous Resistance Spot Welding of BH 340 Steel Based on Dynamic Resistance

The aim of this investigation is to offer a data-based scheme for predicting electrode wear in resistance spot welding. One of the major factors affecting the mechanical properties of spot welds and the variation in weld quality is electrode wear and alloying. In this study, Rogowski coils and twisted pairs attached to the top and bottom electrodes were used to obtain the welding current and the voltage between the electrodes in the welding process, thereby calculating the dynamic resistance value during the welding process. The electrode tip diameter was obtained from the pressure exerted by the upper and lower electrodes on the carbon paper when the current was cut off and was regarded as an indicator of electrode wear. By continuously welding 0.5 mm thick BH 340 steel plates until the electrode failed, the dynamic resistance signal was recorded in real time. Simultaneously, the electrode diameter after every several welds was also recorded. On this basis, the correlation between electrode tip diameter and dynamic resistance is studied. In order to quantitatively study the mapping relationship between dynamic resistance and electrode wear, 10 characteristic values were extracted from the dynamic resistance, and the stepwise regression method was used to obtain the regression formula between the characteristic values and the electrode tip diameter. Using new data to verify the effectiveness of the regression model, the acquired results display that the maximum error between the predicted value of the electrode tip diameter and the measured value obtained by the regression equation with the interactive quadratic term is 0.3 mm, and the corresponding relative error is 7.69%. When welding with a new pair of electrodes, the maximum absolute error was 0.72 mm, and the relative error of the model prediction is within 20% according to the linear regression model with interaction terms. This indicates that this regression model is barely satisfactory for monitoring electrode condition.

Effect of four different mono and multi-wave light-curing units on the Knoop hardness of veneer resin composites

ObjectivesTo evaluate the effect of mono and multi-wave light-curing units (LCUs) on the Knoop hardness of resin-based composites (RBC) that use different photoinitiators. MethodsCentral incisor-shaped specimens 12 mm long, 9 mm wide, and 1.5 mm thick were made from 2 RBCs that use different photoinitiators: Tetric N-Ceram (Ivoclar Vivadent) - and Vittra APS (FGM), both A2E shade. They were light-cured with 4 different LCUs: two claimed to be multi-wave - VALO Grand (Ultradent) and Emitter Now Duo (Schuster); and two were monowave - Radii Xpert (SDI) and Elipar DeepCure-L (3 M Oral Care) using 2 different light exposure protocols: one 40 s exposure centered over the specimen; and two 20 s light exposures that delivered light from two positions to better cover the entire tooth. 16 groups with 10 specimens in each group were made. The Knoop hardness (KH, kg/mm2) was measured at the top and bottom of the specimen in the center and at the cervical, incisal, mesial, and distal peripheral regions. The active tip diameters (mm) and spectral radiant powers (mW/nm) of the LCUs were measured with and without the interposition of the RBC, as well as the radiant exposure beam profiles (J/cm²) delivered to the top of the RBCs. The data was analyzed using Three-way ANOVA and Tukey's tests (α = 0.05). ResultsThe VALO Grand (1029 mW) emitted twice the power of the Radii Xpert (500 mW). The KH values of VI and TN resin composite specimens were significantly affected by the LCU used (p < .001), the measurement location (p < .001), and the surface of the specimen (p < .001). LCUs with wider tip diameters produced greater Knoop hardness values at the peripheries of the 12 mm of long, 9 mm wide specimens. In general, the VALO Grand produced the highest KH values, followed by Elipar DeepCure-L, then by Radii Xpert. The Emitter Now Duo LCU produced the lowest values. Exposing the veneers from two locations reduced the differences between the LCUs and the effect of the measurement location. Only the VALO Grand could fully cover the composite veneer with light when the two locations were used. SignificanceThe light tip must cover the entire restoration to photocure the RBC beneath the light tip.

Phase transformation and mechanical properties of heat-treated nickel-titanium rotary endodontic instruments at room and body temperatures

BackgroundThe aim of this study was to evaluate the phase composition, phase transformation temperatures, bending property, and cyclic fatigue resistance of different heat-treated nickel-titanium (NiTi) rotary instruments with the same tip diameter and taper at room (RT; 25 ± 1 °C) and body (BT; 37 ± 1 °C) temperatures.MethodsFive heat-treated NiTi rotary instruments, HyFlex EDM (EDM), HyFlex CM (CM), Vortex Blue (VB), RE file CT (RE) and JIZAI, and a non-heat-treated NiTi rotary instrument (Mtwo) with a size 40, 0.04 taper were investigated. Temperature-dependent phase transformation was examined with differential scanning calorimetry (DSC). The bending loads of the instruments at RT and BT were evaluated using a cantilever-bending test. Cyclic fatigue resistance at RT and BT was measured using a dynamic test, during which the instruments were rotated in combination with a 2-mm back-and-forth motion in an artificial curved canal, and the number of cycles to failure (NCF) was determined. The results were analyzed using two-way repeated measures analysis of variance, a simple main effect test, and the Bonferroni test (α = 0.05).ResultsDSC results indicated that EDM and Mtwo were primarily composed of martensite/R-phase and austenite, respectively, while the other heat-treated instruments were composed of a mix of martensite/R-phase and austenite at the tested temperatures. Regardless of the temperature setting, the bending loads of heat-treated instruments were significantly lower than those of Mtwo (p < 0.05). EDM showed the lowest bending loads and highest NCF at both temperatures (p < 0.05). CM, VB, and JIZAI showed significantly higher bending loads at BT than at RT (p < 0.05). The NCF of all the heat-treated instruments, except VB, was lower at BT than at RT (p < 0.05). At BT, the NCF of CM, VB, RE, and JIZAI were not significantly higher than that of Mtwo (p > 0.05).ConclusionsHeat-treated NiTi instruments exhibited lower bending loads and higher NCF values than Mtwo. However, this tendency was less pronounced at BT than at RT, especially in the NCF values of instruments with a mixture of martensite/R-phase and austenite phases at the tested temperatures.

Can we use X-ray CT to generate 3D penetration resistance data?

Noninvasive imaging of soils with X-ray CT has proven to be a useful method to assess soil structure from a pore space perspective. In contrast, methods like cone penetration tests reflect soil structure from the perspective of the soil matrix as assessed by its mechanical strength. Because both the gray value (GV) obtained with X-ray CT and the penetration resistance (PR) obtained with a cone penetration test depend on soil density there should be a relationship between the two. To the best of our knowledge, no studies attempted so far to investigate the nature of the PR ∼ GV relationship and to understand how well PR and GV are correlated. We aimed at bridging that gap and carried out a combined analysis of local GV and PR with undisturbed soil cores sampled in two soil textures, i.e., loam and sand. To carry out the GV measurements, we developed a new approach which considers an adaptive volume of the zone of influence of the penetrometer tip as a function of soil density. For sand and when looking at samples individually, the correlation between PR and GV was best when the soil microscale heterogeneity was high, i.e., when dense and loose zones of soil were present on the course of the penetrometer tip. For loam, the correlation between PR and GV was not dependent on soil heterogeneity. When looking at the whole dataset, the agreement between PR and GV was better in loam than in sand, with a distance correlation metric of 0.66 for loam and 0.34 for sand, respectively. For loam, the relationship PR ∼ GV had a trend which was similar to that of a hyperbola, i.e., with escalating PR values in a narrow GV range. For sand, no particular model could be recognized. In order to provide a proof-of-concept on how to generate 3D PR maps, the co-located measurements of GV and PR were used to establish an empirical relationship and X-ray CT was used to extrapolate it in 3D. This was carried out with the loam dataset by fitting a hyperbolic function to the PR ∼ GV data pairs. This model was then used to convert GVs into PR values, at a spatial resolution equal to that of the shaft diameter of the penetrometer tip we have used. Notwithstanding the fact that the suggested approach is dependent on numerous experimental conditions and edaphic factors, we advocate for the use of 3D PR maps. These maps could be used in root-soil interactions research, for which the study and breeding of cultivars that could show plastic response in their root systems under mechanical stress is becoming more and more important. This is particularly relevant in the context of mechanized modern agriculture.

In vitro comparison of simulated intrapelvic pressure in an artificial kidney model during retrograde intrarenal surgery among various single-use ureteroscopes.

This study compares intrapelvic pressure (IPP) during retrograde intrarenal surgery with various single-use flexible ureteroscopes (f-URS) in an artificial kidney model. We created an artificial kidney model with a pressure sensor using a bladder evacuation device. The model was completely closed and the only backflow was on the side of the ureteroscope inside the ureteral access sheath (UAS). We tested five single-use f-URSs (LithoVue, Wiscope, PU3022A, PU3033A, and AXIS) with six different types of UAS (9.5/11.5-14/16 Fr). Using the automatic irrigation system, 30 s of irrigation was performed at various pressures (40-180 mmHg) and steady-state IPP was recorded. IPP was compared between the five single-use f-URSs. IPP cutoff value was determined at 30 mmHg. The diameter of the endoscope tip and the curved and shaft parts were also measured and recorded. The diameters of all parts were significantly different between single-use f-URSs. The maximum IPP tended to be higher in ureteroscopes with larger diameters of the proximal parts (curved part/shaft part). In LithoVue and Uscope PU3022A f-URSs, the maximum IPP did not exceed 30 mmHg when UAS ≥12/14 Fr was used. In AXIS and Wiscope f-URSs, it did not exceed the cutoff value when the UAS ≥11/13 Fr was used. In Uscope PU3033A f-URS, it did not exceed 30 mmHg when the UAS ≥10/12 Fr was used. Maximum IPP tended to be higher in f-URSs with larger diameters of the proximal part and the appropriate size of the UAS differed between various single-use f-URSs.

The Effect of 10% Sodium Ascorbate and Er: YAG Laser on the Microtensile Bond Strength of Composite Resin to Bleached Enamel

Background: There are various methods proposed to prevent the reduction of substrate micro tensile bond strength to bleached enamel. Therefore, this study aims to evaluate and compare the effectiveness of two common methods, namely 10% sodium ascorbate and Er:YAG laser irradiation, in increasing the microtensile bond strength of composite resins to bleached enamel. Methods: In this in vitro study, 72 maxillary premolar teeth were divided into four equal groups: bleached control group, unbleached control group, treated with 10% sodium ascorbate, and Er:YAG laser-treated group (60 mJ, frequency = 10 Hz, and power of 0.6 W with a 400-µm diameter tip). The samples were cut by a CNC cutting machine for a microtensile bond strength test. Results: The Er:YAG laser group showed the highest mean bond strength (27.3 MPa), while the bleached control group had the lowest (15.06 Mpa). There was a significant difference between the bleached and unbleached control groups (P&lt;0.001). Samples prepared with 10% sodium ascorbate and the Er:YAG group had higher tensile bond strength than the bleached control group (P&lt;0.0001). Tensile bond strengths were not significantly different between the 10% sodium ascorbate and the Er:YAG laser preparation groups (P=0.361). Conclusion: The findings of this study indicate that the microtensile bond strength of composite resins to bleached enamel can be increased by 10% sodium ascorbate and Er:YAG laser irradiation.

Optimization of bubble sheet shading using an infrared technology based pen

Almost everyone feels nervous or at least experiences some levels of anxiety in exams or quizzes. Nowadays people find all exams turns to multiple choice questions as it is more useful to ensure students’ understanding. Shading the bubble sheet is a big problem for most students because it takes long time, accordingly this will affect the anxiety's level of students. In addition, Optical Mark Recognition (OMR) systems appear to make exams’ marking faster and easier, leading to save the professors effort. This paper discusses a solution for the problem of feeling anxious and the wasted time in answering and marking exams by designing a unique pen. Additionally, it regards the need of making use of exam time by changing the used pen tip diameter. This gives the ability of shading in one pen press. Also, an alarm electronic circuit is added to avoid any mistakes in shading. Besides, an erasing mechanism is performed to make it easier if the student decides to change his answer. Consequently, bubble sheet exams will be easy for both students and professors. As a result, the proposed pen is time efficient as it gives approximately 70 % efficiency over the ordinary pen.

Design of percutaneous transluminal coronary angioplasty balloon catheters

BackgroundEight commercially available percutaneous transluminal coronary angioplasty (PTCA), including semi-compliant and non-compliant balloons, have been assessed in detail on their tip, balloon, shaft, RX-Port, and hypotube design. Important performance characteristics such as tip deformation, balloon elongation, and deflation rate have been quantified.MethodsFive catheters of each model were evaluated during various tests. The robustness of the tips was evaluated through compression, measuring any occurrence of damage. The longitudinal growth of the balloons was recorded during inflation up to Rated Burst Pressure (RBP). The forces required to move the catheter forward and retract it into the guide catheter were measured in a simulated use test setup. The deflation behavior was studied by measuring extracted contrast media over time. Furthermore, balloon compliance and catheter dimensions were investigated.ResultsThe outer dimensions of the catheter were found to be smallest at the hypotube (0.59–0.69 mm) and highest at the balloon, respectively, the crossing profile (0.9–1.2 mm). The tip diameter increased after compression by 1.7–22%. Cross-sections of the folded balloons revealed a tri- and two-fold, respectively. The measured balloon elongation ranged from 0.6 to 2.0 mm. After the inflation of the balloon, an increase in friction between the guide wire and the catheter was observed on four catheters. A maximum increase of 0.12 N to 1.07 N was found. Cross-sections of the RX-Port revealed a semicircular-shaped inflation lumen and a circular guide wire lumen. The measured deflation rate ranged from 0.004 to 0.013 µL/s, resulting in an estimated balloon deflation time of 10.2–28.1 s.ConclusionThis study provides valuable insights into the design characteristics of RX PTCA balloon catheters, which can contribute to facilitating the development of improved catheter designs and enhancing clinical outcomes. Distinctions between SC and NC catheters, such as balloon performance and dimensions, are evident. It is important to note that no single catheter excels in all aspects, as each possesses unique strengths. Therefore, it is essential to consider individual intervention requirements when selecting a catheter.The research also identifies specific catheter weaknesses, such as reduced wall thickness, fringes at the tip, and reduced performance characteristics.

HSAFM-MIREBA – Methodology for Inferring REsolution in biological applications

Due to a lack of requirement for any direct labelling of the target molecule, high speed atomic force microscopy (HS-AFM) is a potentially powerful procedure for the assessment of biological processes involving macromolecules. When the sample is static the AFM device can be purposefully setup to recover high-resolution information about the feature in question. However, when the feature to be studied moves an appreciable amount during the course of the measurement, the obtained image will be blurred. Encountering such blurred observations prompts the experimenter to sacrifice higher resolution images for higher scanning speeds by tuning available experimental parameters (such as the scanned image area, the image pixel size, the resonance frequency of the cantilever and/or the diameter of the AFM tip). The present work describes a software tool, HSAFM-MIREBA (High Speed Atomic Force Microscopy - Methodology for Inferring REsolution in Biological Applications) that allows for pre-experimental optimization of such parameters through iterative rounds of simulation of both the dynamic surface process and the HS-AFM measurement (based on the particular set of governing parameters). A representative set of five dynamic biological processes that describe a range of diffusive and directed motions (which can themselves be tuned by altering characteristic governing parameter sets) are provided.

Atherectomy with a Novel Device Offering Wider Options

Catheter-based atherectomy has been discussed for some years, although the conclusions have been controversial. Recent study data did show the feasibility of multifunctional atherectomy devices for complex lesion morphologies, with moderate material use. This is then thus an alternative to bypass surgery, although a direct comparison is lacking.The results of the ByCross approval study were compared to technical and clinical data from various atherectomy systems in terms of range of indication, limitations as defined by the manufacturer, the success and complication rate and the instructions for use. As in many recent studies, a residual stenosis ≤50% after atherectomy and ≤30% in the completion imaging was defined as the primary endpoint and proof of technical success.Lesions recruited for the ByCross study were more complex than in other studies, with respect to the lesion length (124.7mm vs. 34mm in the EASE study and 67.2mm in the VISION study) and the degree of stenosis (99.4% vs. 88.5% in the EASE and 78,7% in the VISION study). Calcification was also more severe - as defined by the PACSS (Peripheral Artery Calcification Severity Score). ByCross allowed recanalisation of lesions without wire passage prior to atherectomy (26.82%), which is a must for all other systems. The variable tip diameter of the ByCross can achieve a lumen gain of 4.7mm without tip or wire exchange or run time limits. The 0% rate of embolic events, which is unique for atherectomy device approval studies, can be explained by the working principle and the high aspiration rate. No vessel injuries occurred, and the 6-month follow-up results showed 0% revascularisation rate.New generation atherectomy systems offer safe and effective enlargement of the endovascular portfolio. The ByCross device is an atherectomy, thrombectomy and crossing device free from investment and has a wider range of indications for the iliac and the femorodistal segments, which supports ByCross atherectomy as an alternative for bypass surgery.

EVALUATION OF FABRICATED SOLID MICRONEEDLES AS SMART APPROACH FOR TRANSDERMAL DRUG DELIVERY SYSTEM OF ASTAXANTHIN

Objective: The lack of drugs to effectively cross the stratum corneum (SC), has recently been a significant barrier to transdermal administration. In order to increase the effectiveness of transdermal distribution, this issue has been solved through the development of micron-scale needles. The objective is to develop, formulate and evaluate biocompatible polymeric solid microneedles with a TDDS-loaded Astaxanthin patch involving the poke and patch method. Methods: The solid microneedle arrays were fabricated using an SLA printer with high-resolution potential and was examined using scanning electron microscopy (25 microns at the z-axis and 140 microns at the x-axis, respectively). Fabricated Astaxanthin transdermal film was evaluated by many characterization parameters. The developed microneedle was examined for skin insertion and a drug permeation study was carried out across the porcine skin. Results: Solid MN arrays of 1.85 µm tip-to-tip distance, 600 µm height, 300 µm width, and 30 µm tip diameter, were created using biocompatible Class I Dental SG resin. Microneedle crossed stratum corneum layer and penetrated porcine skin with 381.356 mm in depth, with no structural change. Transdermal patches loaded with astaxanthin drug was developed and using various polymer concentration consistent, good, and transparent films were created of thickness between 0.85±0.07 mm to 0.87±0.01 mm range, with average weights ranging from 168.02±1.05 to 172.22±1.25 10/cm2), Folding Endurance with 10-12 folds was reported for formulated transdermal films; also tensile strength was 0.414±0.002 kg/mm2 and drug content was 94.41±0.42% of the best formulation reported. According to studies on drug permeation, Astaxanthin transdermal patches did not significantly permeate porcine skin without being pierced by microneedles the medication exhibited good penetration characteristics. Conclusion: Upon evaluation, formulated transdermal film was reported to be best for solid microneedle-TDDS of astaxanthin for improved patient compliance, bioavailability, and biomedical applications.

Experiments and Lattice-Boltzmann Simulation of Flow in a Vertically Aligned Gearbox

Abstract This paper presents a study of the oil flow in a vertically arranged FZG gearbox. The splash and churning losses are experimentally evaluated using measurements of the resistance torque. Using high-speed imaging, the instantaneous oil splashing inside the gearbox is also presented and compared to computational fluid dynamics (CFD) results from the lattice-Boltzmann method with the volume of fluid model, instead of the traditional finite volume method. Four different configurations, including a spur gear based on the standard FZG geometry and a disc pair wheel-pinion with the same tip diameters of the standard geometries, are used. The experiments cover a range from 500 to 3000 rpm and three oil levels are studied. For the CFD simulations, the same oil levels and rotational speeds are used. The experimental results indicate torque differences depending on the oil level and the configuration. The splashing pattern is also different from the standard horizontal FZG case, which is typically studied in the literature. On the other hand, the CFD simulations and flow visualization experiments are in relative agreement with one another. The similarities and differences in the torque values for the different configurations and the splashing pattern for both experiments and CFD simulations are analyzed and discussed.

Normal vector centering method for probe correction in cylindrical worm tooth profile measurement

Abstract The measurement results of cylindrical worms vary greatly under different probe tip diameters on the Gear Measuring Centre (GMC). Considering toroidal enveloping cylindrical worm (ZC1 worm) as an instance, after analysing the worm grinding coordinate system, the probe correction method based on normal vector centreing (NVC) is established. The theoretical coordinate values of the points on the normal equidistant line which is rotated into the axial section are used as the probe tip centre trajectory. Experiments were carried out with probe tip diameters of 1.0 mm, 1.5 mm and 2.0 mm for the worm tooth profile measurement on a GMC. Compared with the traditional method, the variation between the profile deviations results using the proposed method become smaller and the variation of ‘profile deviation, total’ is reduced from 8.3 μm to 0.5 μm, the profile slope deviation variation is reduced from 8.6 μm to 0.5 μm. The proposed method in ZC1 worm tooth profile measurement can effectively reduce the variation between the measurement results under different GMC probe tip diameters, and also the methodology can be applied to other kinds of cylindrical worms. The method has significance for other curved profiles measurement on coordinate measurements.

Implementation of New Design Concepts to an Axial Compressor and a Case Study with CFD

The present study elaborates on new concepts in designing an axial-flow compressor. With the help of an innovative in-house design code, a rotor design is obtained. Computational fluid dynamics (CFD) was used to explore the level of achievement in the performance of the device with the new attributes. In that, the features including local angle of attack, chord length, camber, and thickness were radially adjusted to fulfill flow rate and pressure head requirements at a specific rotational speed, hub, and tip diameters. At the core of this methodology lies the effective use of a lookup table that interrelates airfoil shapes to their corresponding lift coefficients. The most important outcome was the machine attaining the endurance to stall. Furthermore, the rotor geometry is optimized so that the maximum efficiency coincides with the design point of the device, where a low-pitch air motion with a uniform pressure was observed downstream of the rotor, inducing improved aerodynamic conditions. This leads to the minimization of the tangential stresses, and the level of turbulence remained consistently below 15%, signifying a controlled and efficient flow environment. This research expands the understanding of compressor dynamics and offers a practical design methodology, promising increased operational stability and performance across diverse applications.

Target Design in SEM-Based Nano-CT and Its Influence on X-ray Imaging.

Nano-computed tomography (nano-CT) based on scanning electron microscopy (SEM) is utilized for multimodal material characterization in one instrument. Since SEM-based CT uses geometrical magnification, X-ray targets can be adapted without any further changes to the system. This allows for designing targets with varying geometry and chemical composition to influence the X-ray focal spot, intensity and energy distribution with the aim to enhance the image quality. In this paper, three different target geometries with a varying volume are presented: bulk, foil and needle target. Based on the analyzed electron beam properties and X-ray beam path, the influence of the different target designs on X-ray imaging is investigated. With the obtained information, three targets for different applications are recommended. A platinum (Pt) bulk target tilted by 25° as an optimal combination of high photon flux and spatial resolution is used for fast CT scans and the investigation of high-absorbing or large sample volumes. To image low-absorbing materials, e.g., polymers or organic materials, a target material with a characteristic line energy right above the detector energy threshold is recommended. In the case of the observed system, we used a 30° tilted chromium (Cr) target, leading to a higher image contrast. To reach a maximum spatial resolution of about 100 nm, we recommend a tungsten (W) needle target with a tip diameter of about 100 nm.

Using microneedle array electrodes for non-invasive electrophysiological signal acquisition and sensory feedback evoking.

Introduction: Bidirectional transmission of information is needed to realize a closed-loop human-machine interaction (HMI), where electrophysiological signals are recorded for man-machine control and electrical stimulations are used for machine-man feedback. As a neural interface (NI) connecting man and machine, electrodes play an important role in HMI and their characteristics are critical for information transmission. Methods: In this work, we fabricated a kind of microneedle array electrodes (MAEs) by using a magnetization-induced self-assembly method, where microneedles with a length of 500-600μm and a tip diameter of ∼20μm were constructed on flexible substrates. Part of the needle length could penetrate through the subjects' stratum corneum and reach the epidermis, but not touch the dermis, establishing a safe and direct communication pathway between external electrical circuit and internal peripheral nervous system. Results: The MAEs showed significantly lower and more stable electrode-skin interface impedance than the metal-based flat array electrodes (FAEs) in various testing scenarios, demonstrating their promising impedance characteristics. With the stable microneedle structure, MAEs exhibited an average SNR of EMG that is more than 30% higher than FAEs, and a motion-intention classification accuracy that is 10% higher than FAEs. The successful sensation evoking demonstrated the feasibility of the MAE-based electrical stimulation for sensory feedback, where a variety of natural and intuitive feelings were generated in the subjects and thereafter objectively verified through EEG analysis. Discussion: This work confirms the application potential of MAEs working as an effective NI, in both electrophysiological recording and electrical stimulation, which may provide a technique support for the development of HMI.

Distribution of Oxygen Tension on Microvessels and in Tissue of Rat Brain Cortex at Severe Arterial Hypocapnia

Arterial hypocapnia (AH), induced by voluntary or forced hyperventilation of the lungs, is accompanied by a decrease in cerebral blood flow (due to an increase in the arteriole tone) and an increase in the affinity of hemoglobin for oxygen. As a result, an insufficient oxygen supply to cortical tissue take place and zones with a critically low oxygen tension (pO2) are formed in brain tissue. The distribution of pO2 to cerebral cortex during AH has not been studied enough. The aim of the work was to evaluate the effectiveness of oxygen supply to brain tissue at the level of arterial and venous microvessels at AH. To do this, the following tasks were set: 1) to study the distribution of the pO2 on the arterial and venous microvessels of the rat cerebral cortex; 2) to analyze tissue pO2 profiles near the walls of these microvessels. On anesthetized Wistar rats under conditions of forced hyperventilation (PaCO2 = 17.1 ± 0.7 mm Hg), the distribution of oxygen tension on the wall of pial and radial arterioles with a lumen diameter of 7–70 μm and on the wall of pial and ascending venules with a lumen diameter of 7–300 µm was studied. In tissue, near the wall of cortical arterioles and venules with a lumen diameter of 10–20 μm, tissue pO2 profiles were measured. Measurements of pO2 during spontaneous breathing of the animal with air served as a control. All pO2 measurements were made using platinum polarographic microelectrodes with a tip diameter of 3–5 μm. Visualization of the electrode tip and microvessels was carried out using a LUMAM-K1 microscope with epiobjectives of the contact type. This work presents for the first-time direct measurements of pO2 on the walls of arterioles and venules of the rat cerebral cortex and in tissues at different distances from the walls of these microvessels at AH. It has been shown that AH results in significant decrease in the oxygen supply to cerebral cortex, that is manifested by a significant drop of the pO2’s on venous microvessels and in tissue in the immediate vicinity of the studied microvessels. It has been shown, that the role of arterioles as a direct source of oxygen to brain tissue, is significantly reduced during arterial hypocapnia. Forced hyperventilation results in significant deterioration of oxygen supply to cerebral cortex, despite elevated pO2 values in the systemic arterial blood and in blood of systemic cerebral veins (sagittal sinus).

Research and Performance Optimization of Jump-Takeoff in Autogyros

The main focus of this article is on the jump-takeoff method for autogyros. On the basis of a high-confidence autogyro model, we design a jump-takeoff simulation experiment to study and optimize jump-takeoff performance. Using a simplified version of blade element theory, we conduct secondary development on the YASim dynamics library in FlightGear software and construct a highly accurate auto-rotation rotor model. The implementation of jump-takeoff requires appropriate control parameters for collective angle and pre-rotation speed. We explore the minimum collective angle condition and minimum pre-rotation speed condition to obtain the jump-takeoff envelope, and we investigate the effect of changes in control parameters within the jump envelope on jump-takeoff performance. Furthermore, we optimize the jump-takeoff performance by varying the rotor diameter and blade tip weighting. Through this study of jump-takeoff performance, we are able to determine appropriate control parameters and rotor parameters for jump-takeoff schemes, establish parameter settings for simulations of jump-takeoff tests, and thereby lay the foundation for future experimental investigations of jump-takeoff of actual autogyros.

Ultra-efficient localized induction heating by dual-ferrite synchronous magnetic field focusing

Induction heating is widely used in aviation, communication, and new energy fields due to its advantages of non-contact, high-power, and controllable heating depth. However, it is still challenging to achieve high energy utilization efficiency of traditional induction heating, mainly due to the magnetic dispersion effect. Herein, a dual-ferrite synchronous focused (DFSF) induction heating method is first proposed by simultaneously placing ferrites inside and outside the induction coil. Meanwhile, an electromagnetic-thermal coupling numerical model was also built to predict the magnetic and temperature fields around the DFSF induction heating system. A conventional induction heating head and two DFSF induction heating heads (cone-type DFSF head and pot-type DFSF head) are compared on soldering the high-power devices. The results show a significant enhancement in magnetic flux density (MFD) with the pot-type DFSF head, exhibiting a remarkable 12-fold increase from 0.02 T to 0.24 T compared to the conventional induction head. Additionally, the pot-type DFSF head generates a substantial 22.3-fold surge in energy within the solder joint, escalating from 0.6 J to 13.4 J, surpassing the traditional induction head. Moreover, the influence mechanism of six external ferrite structural parameters on the heating efficiency was analysed to optimize the pot-type DFSF. It is found that the inner diameter of the ferrite tip has the most significant effect, which can induce a remarkable temperature variation of 310 °C. As a result of optimization, the pot-type DFSF demonstrated an impressive surge of 26% in heating efficiency. Finally, the agreement between the numerical and the experimental temperature proves the accuracy of the model, and the solder joint without defect has been achieved through the pot-type DFSF. This work effectively minimizes the magnetic dispersion and increases the energy utilization efficiency for induction heating, providing new approaches for localized soldering of high-performance power electronic devices.

MoRe Electrodes with 10 nm Nanogaps for Electrical Contact to Atomically Precise Graphene Nanoribbons.

Atomically precise graphene nanoribbons (GNRs) are predicted to exhibit exceptional edge-related properties, such as localized edge states, spin polarization, and half-metallicity. However, the absence of low-resistance nanoscale electrical contacts to the GNRs hinders harnessing their properties in field-effect transistors. In this paper, we make electrical contact with nine-atom-wide armchair GNRs using superconducting alloy MoRe as well as Pd (as a reference), which are two of the metals providing low-resistance contacts to carbon nanotubes. We take a step toward contacting a single GNR by fabricating electrodes with needlelike geometry, with about 20 nm tip diameter and 10 nm separation. To preserve the nanoscale geometry of the contacts, we develop a PMMA-assisted technique to transfer the GNRs onto the prepatterned electrodes. Our device characterizations as a function of bias voltage and temperature show thermally activated gate-tunable conductance in GNR-MoRe-based transistors.