Circuit Modification Research Articles

Enhancement of material removal rate in EDM process using silicon carbide based strenx 900 steel

Material removal rate (MRR) plays an important role in metal industries. Its mainly depends on hardness, strength and toughness of the material. Light hardness materials are easily machined by conventional machining processes. High hardness materials are easily machined by unconventional machining processes. Electrical discharge machining (EDM) process is one of the effective methods to machine very hard materials. To achieve high material removal rate in very hard material is difficult and it takes more time. The silicon carbide-based strenx 900 steel is used as work material for this experimental investigation. The material removal rate has enhanced by modification of electrical circuit, powder mixed dielectric fluid and install oxygen arrangement. These additional facilities are used to improve the machinability characteristics and tool life of the EDM process.

A high-efficiency Doherty Power Amplifier for wireless base stations

ABSTRACT This paper presents a new high-efficiency two-way Doherty Power Amplifier (DPA) with a modified output matching structure for Wideband Code Division Multiple Access (W-CDMA) low-to-medium power base station applications. A blended design is proposed using the symmetrical topology of equal rated power amplifying devices with unequal output impedances for the carrier and peaking amplifier to achieve enhanced efficiency and desired linearity in 1900 MHz band. The proposed output circuit modifications encompass the usage of parasitic capacitor compensation technique for the carrier amplifier, optimum offset line along with the Doherty combiner to achieve high efficiency over 6 to 10 dB extended range of back-off operation. The measured results of the DPA demonstrate a Power Added Efficiency (PAE) of more than 49.9% at +34 dBm W-CDMA signal power, which is between 8 and 8.5 dB back-off from the peak power level of 42.2 dBm. The DPA has a large signal power gain of 13 dB at 1960 MHz. Further, the PAE is 39.5% and linearised Adjacent Channel Power Ratio (ACPR) is −46.2 dBc, both at 10 dB back-off from peak power. In these back-off power levels, this implementation provides significant efficiency improvement using symmetrical devices and with excellent linearity.

Etching sharp tips from thin metallic wires for tuning-fork-based scanning probe microscopy

Sharp tips are critical for obtaining high resolution images in scanning probe microscopy (SPM), particularly in samples with large variations in topography. For tuning-fork-based SPM, such tips are commonly obtained by electrochemical etching of metallic wires (e.g., tungsten). Electrochemical etching of metallic wires is the preferred means of preparing tips for scanning tunneling microscopy (STM), and techniques for obtaining sharp tips have been investigated extensively. However, the requirements for STM and tuning-fork-based SPM are different. In particular, the wires used in STM are typically 250−500μm in diameter, while the wires used for tuning-fork-based SPM are usually an order of magnitude narrower in order to minimize loading of the tuning fork: 25−50μm and sometimes down to a few micrometers in diameter. Consequently, many of the recipes developed for etching thicker metallic wires for STM tips do not give optimal results for smaller diameter wires. The authors describe here a modification of the etching circuit of Ibe et al. that significantly improves the reproducibility and reliability of the etching process for thin wires, and discuss the parameters that affect the aspect ratio of produced tips.

Minimum phase bipolar converter for DC microgrid applications

This study proposes a minimum phase bipolar converter for dc microgrid applications, which is derived from the combination of C'uk and Sepic converters with some modifications in both of them in order to get a minimum phase system. In the proposed bipolar converter (PBC), the equivalent series resistance of transfer capacitors of both C'uk and Sepic converters is increased by adding resistances and introducing magnetic coupling between the filter inductors of the Sepic converter with a series RC network. These circuit modifications eliminate right half plane zero from the PBC and thereby make it a minimum phase, unlike the conventional C'uk-Sepic bipolar converter. Due to the minimum phase behaviour, the proposed converter can deliver high load current, achieves high bandwidth and facilitates simpler controller design in contrast to the conventional C'uk-Sepic bipolar converter. Detailed steady state and dynamic modelling of the PBC has been carried out in order to show its advantages. A 500 W laboratory prototype has been developed and implemented using field programmable gate array-based system to verify the operation of the proposed converter.

New modifications of a Bennet doubler circuit-based electrostatic vibrational energy harvester

In this work, theoretical and experimental studies of the conditioning circuit based on the Bennet doubler with a power source in a variable capacitor branch having one, two and three variable capacitors are carried out for electrostatic vibrational energy harvesters (e-VEHs). Analytical expressions for evaluation of the e-VEH conditioning circuit main parameters are derived. All three modifications of the conditioning circuit have two operation modes: autostabilization and the mode of unlimited capacitors charge and voltage growth. The change between the operation modes for one-, two- and three-capacitor circuits with switches takes place when the maximal-to-minimal capacitance ratio η is equal to 2, 1.618 and 1.414, respectively. For e-VEHs with switches in the autostabilization regime, a three-capacitor circuit will be the most efficient when the capacitance modulation depth η is less than 1.414, a two-capacitor circuit will be the most efficient when 1.414 <η < 1.618, and, for 1.618 <η < 2, the most efficient will be a one-capacitor circuit. In the steady-state autostabilization mode, the saturation voltage will be greater than the primary voltage source V0 if the capacitance modulation depth η is greater than 1.5, 1.366 and 1.302 for the circuit with one, two and three variable capacitors, respectively. The use of diodes instead of switches in the circuits results in the decrease of saturation voltage and leads to the increase of the critical values of ηcr when the change between the operation modes occurs. As the diode inverse currents increase, the effect of the saturation voltage reduction in the autostabilization mode becomes stronger and can even lead to the circuit nonoperabilities. The employment of the Bennet doubler based conditioning circuit modifications considered here enables solving its two main problems: operation only for the capacitance modulation depth more than 2 and the uncontrolled capacitors charge and voltage growth. It should be noted that the observed two conditioning circuit operation regimes will be also inherent for electret vibrational microgenerators and for microgenerators based on using electrodes with materials having different work functions. In addition, the considered two- and three-capacitor circuits make it possible to use e-VEHs at lower values of an external mechanical force or with greater stiffness of spring suspensions minimizing the pull-in effect probability.

Curing of Hot-Carrier Induced Damage by Gate-Induced Drain Leakage Current in Gate-All-Around FETs

Gate oxide aging in a gate-all-around (GAA) FET fabricated on a bulk substrate was successfully cured by gate-induced drain leakage (GIDL) current. High level of GIDL current flows during the off-state cures the gate oxide aging by hot-carrier injection (HCI). The recovery behaviors were analyzed by tracing changes in the device parameters. Especially, it was found that the curing was not associated with the electric field or created holes under the bias conditions for GIDL, but was associated with the elevated temperature. The GIDL recovery requires neither extra apparatus for Joule heating nor circuit modification. This work can be useful for various FETs which have high off-state current.

Aorto-pulmonary bypass shunt for intraoperative right ventricular support during LVAD implantation.

We describe a simple modification of the cardiopulmonary bypass (CPB) circuit that allows selective intraoperative circulatory support of the right ventricle during left ventricular assist device (LVAD) implantation. The addition of a side branch to the arterial line and an intermediate line connector allows selective venting and perfusion through a cannula inserted in the main pulmonary artery. This modification of the CPB circuit allows for selective evaluation of right ventricular function, titration of inotropic support, and early identification of patients that require right ventricular assist device (RVAD) support.

Network Degeneracy and the Dynamics of Task Switching in the Feeding Circuit inAplysia

The characteristics of a network are determined by parameters that describe the intrinsic properties of the component neurons and their synapses. Degeneracy occurs when more than one set of parameters produces the same (or very similar) output. It is not clear whether network degeneracy impacts network function or is simply a reflection of the fact that, although it is important for a network to be able to generate a particular output, it is not important how this is achieved. We address this issue in the feeding network of the mollusc Aplysia In this system, there are two stimulation paradigms that generate egestive motor programs: repetition priming and positive biasing. We demonstrate that circuit parameters differ in the 2 cases (e.g., egestive repetition priming requires activity in an interneuron, B20, which is not essential for positive biasing). We show that degeneracy has consequences for task switching. If egestive repetition priming is immediately followed by stimulation of an ingestive input to the feeding central pattern generator, the first few cycles of activity are egestive (not ingestive). In this situation, there is a task switch cost. This "cost" is in part due to the potentiating effect of egestive repetition priming on B20. In contrast, there is no switch cost after positive biasing. Stimulation of the ingestive central pattern generator input immediately triggers ingestive activity. Our results indicate that the mechanisms used to pattern activity can impact network function in that they can determine how readily a network can switch from one configuration to another.SIGNIFICANCE STATEMENT A particular pattern of neural activity can be generated by more than one set of circuit parameters. How or whether this impacts network function is unclear. We address this issue in the feeding network of Aplysia and demonstrate that degeneracy in network function can have consequences for task switching. Namely, we show that, when egestive activity is generated via one set of circuit modifications, an immediate switch to ingestive activity is not possible. In contrast, rapid transitions to ingestive activity are possible if egestive activity is generated via a different set of circuit modifications.

Anticoagulation in Neonatal ECMO: An Enigma Despite a Lot of Effort!

Extracorporeal membrane oxygenation (ECMO) is a valuable modality used to support neonates, children, and adults with cardiorespiratory failure refractory to conventional therapy. It requires use of anticoagulation to prevent clotting in the extracorporeal circuit. Balancing bleeding from excessive anticoagulation with thrombotic risk remains a difficult aspect of ECMO care. Despite many advances in ECMO technology, better understanding of the coagulation cascade and new monitoring schemes to adjust anticoagulation, bleeding and thrombosis remain the most frequent complications in ECMO and are associated with morbidity and mortality. In neonates, ECMO is also complicated by the immature hemostatic system, laboratory testing norms which are not specific for neonates, lack of uniformity in management, and paucity of high-quality evidence to determine best practices. Traditional anticoagulation focuses on the use of unfractionated heparin. Direct thrombin inhibitors are also used but have not been well-studied in the neonatal ECMO population. Anticoagulation monitoring is complex and currently available assays do not take into account thrombin generation or platelet contribution to clot formation. Global assays may add valuable information to guide therapy. This review provides an overview of hemostatic alterations, anticoagulation, monitoring and management, novel anticoagulant use, and circuit modifications for neonatal ECMO. Future considerations are also presented.

Predicting and interpreting uncertainty propagation in separation circuits using functional unit evaluation

The estimation and analysis of uncertainty propagation in separation circuits is an important, but challenging, aspect of a comprehensive circuit design strategy. Owing to the sophisticated and complex modeling requirements, many of the current separation circuit design tools rely on deterministic models, despite the ubiquity of uncertainty in the model input parameters. Additionally, many of the uncertainty assessment protocols, which rely on mathematical solutions, provide few insights on how particular circuit modifications will influence uncertainty propagation. As a supplement to these methods, the current paper describes a method of assessing and evaluating separation circuit uncertainty by integrating the fundamentals of linear circuit analysis, the law of propagation of error, and the separation functional unit evaluation technique. This analysis shows how the addition or modification of units within circuits, based on separation functional unit definitions, can be used to predict how uncertainty propagation will change, even with limited a priori data. The capabilities of this innovative approach are illustrated and critically evaluated through a systematic separation experimental study using the roll-type corona electrostatic concentrator for separating titanium from silica within a heavy mineral sand feed.

Experimental demonstration of a digital quantum simulation of a general PT -symmetric system

$\mathcal{PT}$-symmetric systems are one of the most interesting research fields in modern quantum physics, where various theoretical and experimental progress has been made. In our work, we experimentally demonstrate how to realize a general $\mathcal{PT}$-symmetric two-level operation in a quantum computation frame with a universal circuit model. It is based on enlarging the system with ancillary qubits and encoding the subsystem with the non-Hermitian Hamiltonian with postselection. Furthermore, we use the general formula to demonstrate one particular interesting issue, entanglement restoration induced by local $\mathcal{PT}$-symmetric operation in our four-qubit liquid nuclear magnetic resonance platform, and a theoretical explanation for the physical characteristics has been proposed. We also extend the protocol to the realization of an arbitrary two-level Hamiltonian evolution without a Hermitian restriction by an appropriate modification of the original quantum circuit. Our work lays the foundation for quantum simulation of the general $\mathcal{PT}$-symmetric problem in realistic quantum simulators, and the scheme can be extended to other quantum computation platforms.

Multivariate pattern analysis of the neural correlates of smoking cue attentional bias

The automatic capture of attention by drug cues, or attentional bias, is associated with craving and predicts future drug use. Despite its clinical significance, the neural bases of attentional bias to drug cues is not well understood. To address this gap, we undertook a neuroimaging investigation of the neural correlates of attentional bias towards smoking cues. Twenty-nine adults, including 14 active smokers and 15 non-smokers, completed a spatial cuing task during fMRI. A multivariate pattern analysis (MVPA) decoded the neural responses to the brief presentation of smoking versus neutral images. These data were correlated with behavioral measures of attentional bias, which included analyses targeting the neural correlates of response facilitation and cue-related task interference. We detected a set of brain-behavioral correlates that were similar across both smokers and non-smokers, indicating a role for stimuli salience in the absence of nicotine conditioning in smoking cue attentional bias. However, multiple smoking-related modifications to the neural correlates of attentional bias and its components were also identified. For example, regions demonstrating smoking-related differences in the neural correlates of attentional bias included the rostral anterior cingulate cortex and inferior frontal gyrus. Response facilitation effects of smoking were observed in the right orbitofrontal gyrus and bilateral middle temporal gyrus. Smoking-cue related task interference was related to smoking-related effects in the frontal eye fields. Our findings suggest that multiple cognitive, affective, and visual object recognition processes contribute to attentional bias towards smoking cues, and suggest multiple circuit modifications that may contribute to perpetuation of addiction.

Precise, portable and wide band alternating current source for extremely low current values

Alternating current (AC) sources which provide currents in micro ampere ranges have become essential for testing of electronic components, simulation of sensors, eddy current analysis, small signal analysis of transistors, electro-cutaneous stimulation in therapeutics, current injection in medical imaging techniques etc. This manuscript proposes a precise voltage mode AC source for extremely low current values. A simple AC source with load in the feedback is optimised experimentally by compensating the capacitive effects (approx. 4.7 pF) by employing a novel combination of general impedance converter (gic) or Negative Capacitance Converter (NCC) circuits along with basic circuit. The design is proposed with precise value of 160 $$\upmu A$$ for applications including physiological measurements. It is seen that GIC circuit modification offers better consistency and performance in load analysis compared to NCC. Load analysis (10–2000 $$\Omega$$), frequency analysis (100 Hz to 1 MHz), stability analysis and reliability testing confirm the optimised and precise operation of the proposed current source. With very high degree of matching in theoretical and practical results, calculation of output impedance is also done and the value is fair enough. The hardware incorporates direct digital synthesis chip driven by a microcontroller for generation of sine wave, thereby reducing the need of bulky power supplies and function generators. This precise alternating current source is suitable for wide band portable applications.

Theoretical Investigation into the Ripple Source of External Gear Pumps

External gear pumps are among the most popular fluid power positive displacement pumps, however they often suffer of excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power system, a better understanding of the ripple source of gear pumps is desirable. This paper presents a novel approach for the analysis of the ripple source of gear pumps based on decomposition into a kinematic component and a pressurization component. The pump ripple can be regarded as the superposition of the displacement solution and the pressurization solution. The displacement solution is driven by the kinematic flow, and it can be derived from the kinematic flow theory; instead, the pressurization solution can be approximated by overlapping the pressurization flow for a single displacement chamber. Furthermore, in this way the changes of these two components with modification of the delivery circuit are determined in both analytical and numerical ways. The result of this analysis provides a good interpretation of the pulsation simulated by a detailed lumped-parameter simulation model, thus showing its validity. The result also indicates that the response of two ripple sources to the change of the loading in the downstream hydraulic circuit is very different. These findings reveal the limitation of the traditional experimental method for determining the pump ripple, that new experimental methods which are more physics-based can be potentially formulated based on this work.

Internal Current Return Path for Ground Leakage Current Mitigation in Current Source Inverters

This paper analyzes in detail the effect of a simple solution for ground leakage current mitigation applicable to transformerless three-phase current source inverter (CSI). The circuit modification solution is assessed for both traditional CSI topology and for CSI with an additional seventh switch, in literature named CSI7 (or H7), in particular with the splitting of the dc input inductance. In the present work, the solution is applied to grid-connected converters for string photovoltaic applications: scope of the circuit modification is to provide an internal return path from the wye connected capacitors of the output CL filter. This additional return path is able to significantly reduce the ground leakage current without adversely affecting THD. The performance of the proposed solution is assessed by the numerical simulations in case of a string of photovoltaic (PV) modules and the different behavior of CSI and CSI7 topologies is thoroughly investigated. Furthermore, the definition of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</sub> ZC is assessed by applying it to the common mode equivalent circuits for CSI7 with additional return path and their validation by means of a two-step simulation. The simulation results and experimental validation shows good agreement and confirm that the proposed solution is able to strongly reduce the ground leakage current.

Memristor-based quinary half adder

This paper theorizes the possibilities of generalizing a memristor based ternary adder circuit, to a memristor based multi-valued logic adder. The proposition tries to achieve the theoretical advantages of processing different numbering systems, increasing the density, and decreasing the processing time, by utilizing the memristor properties and dynamics. This is done using a memristor cell based circuit structure. The memristor is quantized to more levels in order to accommodate more values of logic being processed. Quinary numbering system is used to demonstrate the generalization, then a process of generalization is shown. Circuit modifications can be made to process different numbering systems.

Printed Organic Transistor‐Based Enzyme Sensor for Continuous Glucose Monitoring in Wearable Healthcare Applications

AbstractA printed extended‐gate‐type organic transistor‐based enzyme sensor for the continuous monitoring of D‐glucose has been developed through a simple modification of the electrical circuit. The sensor is composed of a glucose oxidase (GOx)/Prussian blue (PB)‐modified extended‐gate electrode and an Ag/AgCl reference electrode, which are connected to the gate and source electrodes of an organic transistor, respectively. The GOx/PB‐modified extended‐gate electrode and Ag/AgCl reference electrode were short‐circuited by an external resistor to spontaneously induce redox cycling of PB. Continuous monitoring of the source‐drain current of the organic transistor for various concentrations of D‐glucose was successfully demonstrated in this system. This is the first report of the transistor‐based enzyme sensor exhibiting reversible response to the analytes in physiologically buffered solution without the addition of any chemical reagents. This new type of printed organic transistor‐based enzyme sensor will greatly contribute to the development of wearable biosensors for non‐invasive monitoring of biomarkers in externally secreted bodily fluids such as tears, saliva, and sweat.

Cortical Neuromodulation of Remote Regions after Experimental Traumatic Brain Injury Normalizes Forelimb Function but is Temporally Dependent.

Traumatic brain injury (TBI) results in well-known, significant alterations in structural and functional connectivity. Although this is especially likely to occur in areas of pathology, deficits in function to and from remotely connected brain areas, or diaschisis, also occur as a consequence to local deficits. As a result, consideration of the network wiring of the brain may be required to design the most efficacious rehabilitation therapy to target specific functional networks to improve outcome. In this work, we model remote connections after controlled cortical impact injury (CCI) in the rat through the effect of callosal deafferentation to the opposite, contralesional cortex. We show rescue of significantly reaching deficits in injury-affected forelimb function if temporary, neuromodulatory silencing of contralesional cortex function is conducted at 1 week post-injury using the γ-aminobutyric acid (GABA) agonist muscimol, compared with vehicle. This indicates that subacute, injury-induced remote circuit modifications are likely to prevent normal ipsilesional control over limb function. However, by conducting temporary contralesional cortex silencing in the same injured rats at 4 weeks post-injury, injury-affected limb function either remains unaffected and deficient or is worsened, indicating that circuit modifications are more permanently controlled or at least influenced by the contralesional cortex at extended post-injury times. We provide functional magnetic resonance imaging (MRI) evidence of the neuromodulatory effect of muscimol on forelimb-evoked function in the cortex. We discuss these findings in light of known changes in cortical connectivity and excitability that occur in this injury model, and postulate a mechanism to explain these findings.

Low power, high speed and noise immune wide-OR footless domino circuit using keeper controlled method

In this paper, a new circuit is proposed for enhancing the performance of the wide fan-in OR footless domino circuits in terms of noise immunity and speed. The proposed circuit is the modification of standard footless domino circuit by an adding keeper controlling network between the gate of the keeper transistor and the dynamic node. The keeper controlling network consists of a PMOS transistor, a diode and delay elements to control the keeper transistor. At the beginnings of evaluation phase for either low or high inputs, the keeper controlling network turns OFF the keeper transistor, which increases the circuit speed. In the same condition (when clock is high), if all the inputs of the pull down network are low then the noise immunity of the circuit gets increased. The proposed circuit and the other previously existing circuits are demonstrated through simulations using 90-nm CMOS technology for 4, 8, 16 and 32 inputs OR gate. The simulation results for 32 inputs OR gate show that the proposed circuit reduces the power consumption, delay, and power delay product by 31.42, 0.69, and 31.91%, and the noise immunity is increased by 0.23% as compared to the HS-domino circuit.

An Improved Inductive Loop Detector Design for Efficient Traffic Signal Operations and Leaner Space Requirements

Inductive loop detectors (ILDs) are one of the most widely deployed traffic sensors. At present, for lane-by-lane detection, ILDs require separate connecting cables for each loop (each lane) and separate data acquisition systems or detector channels to process them. This becomes problematic with limited conduit and cabinet space. In most cases, transportation agencies use ILDs connected in series to avoid these constraints, in which case the lane-by-lane information is lost. However, research has shown that lane-by-lane detection can lead to safer and more efficient operations at signalized intersections. In order to ease the application of lane-by-lane detection, the current study proposes a solution that uses electronic circuit modification to convert the existing serially connected loops to carry out lane-by-lane detection. This system achieved 100% accuracy of lane-by-lane detection in test runs. The paper also proposes an improved loop design, for future installations, that can be used for vehicle classification and wrong way detection. The study implemented machine-learning algorithms for vehicle classification and direction determination with an accuracy of 99.6% and 78.57%, respectively, using single loop configuration.