Search

Aims: Suboptimal device programming is frequent in non‐responders to cardiac resynchronization therapy (CRT). However, the role of device optimization and the most appropriate technique are still unknown. The aim of our study was to analyse the effect of different CRT optimization techniques within a network meta‐analysis. Methods: A systematic search was conducted on MEDLINE, Embase and CENTRAL for studies comparing outcomes with empirical device settings or optimization using echocardiography, static algorithms or dynamic algorithms. Studies investigating the effect of optimization in non‐responders were also analysed. Results: A total of 17 studies with 4346 patients were included in the quantitative analysis. Of the treatments and outcomes examined, a significant difference was found only between dynamic algorithms and echocardiography, with the former leading to a higher echocardiographic response rate [odds ratio (OR): 2.02, 95% confidence interval (CI) 1.21–3.35], lower heart failure hospitalization rate (OR: 0.75, 95% CI 0.57–0.99) and greater improvement in 6‐minute walk test [mean difference (MD): 45.52 m, 95% credible interval (CrI) 3.91–82.44 m]. We found no significant difference between empirical settings, static algorithms and dynamic algorithms. Seven studies with 228 patients reported response rates after optimization in non‐responders. Altogether, 34.3%–66.7% of initial non‐responders showed improvement after optimization, depending on response criteria. Conclusions: At the time of CRT implantation, dynamic algorithms may serve as a resource‐friendly alternative to echocardiographic optimization, with similar or better mid‐term outcomes. However, their superiority over empirical device settings needs to be investigated in further trials. For non‐responders, CRT optimization should be considered, as the majority of patients experience improvement. [ABSTRACT FROM AUTHOR]

The Schockley–Quisser (SQ) limit of 28.64% is distant from the Sb2S3 solar cells' record power conversion efficiency (PCE), which is 8.00%. Such poor efficiency is mostly owing to substantial interface-induced recombination losses caused by defects at the interfaces and misaligned energy levels. The endeavor of this study is to investigate an efficient Sb2S3 solar cell structure via accurate analytical modeling. The proposed model considers different recombination mechanisms such as non-radiative recombination, Sb2S3/CdS interface recombination, Auger, SRH, tunneling-enhanced recombination, and their combined impact on solar cell performance. This model is verified against experimental work (Glass/ITO/CdS/Sb2S3/Au) where a good coincidence is achieved. Several parameters effects such as thickness, doping, electronic affinity, and bandgap are scrutinized. The effect of both bulk traps located in CdS and Sb2S3 on the electrical outputs of the solar cell is analyzed thoroughly. Besides, a deep insight into the effect of interfacial traps on solar cell figures of merits is gained through shedding light into their relation with carriers' minority lifetime, diffusion length, and surface recombination velocity. Our research findings illuminate that the primary contributors to Sb2S3 degradation are interfacial traps and series resistance. Furthermore, achieving optimal band alignment by fine-tuning the electron affinity of CdS to create a Spike-like conformation is crucial for enhancing the immunity of the device versus the interfacial traps. In our study, the optimized solar cell configuration (Glass/ITO/CdS/Sb2S3/Au) demonstrates remarkable performance, including a high short-circuit current (JSC) of 47.9 mA/cm2, an open-circuit voltage (VOC) of 1.16 V, a fill factor (FF) of 54%, and a notable improvement in conversion efficiency by approximately 30% compared to conventional solar cells. Beyond its superior performance, the optimized Sb2S3 solar cell also exhibits enhanced reliability in mitigating interfacial traps at the CdS/Sb2S3 junction. This improved reliability can be attributed to our precise control of band alignment and the fine-tuning of influencing parameters. [ABSTRACT FROM AUTHOR]

Charge balance is one of the most important factors for realizing high performance organic light emitting devices (OLEDs). In this work, we provide a novel strategy to improve the charge balance in OLEDs by optimizing the hole injection layer (HIL) as well as the electron transporting layer (ETL) and thereby controlling the charge carrier supplies in the device. First, we develop a p‐dopant material (PD02), with a lowest unoccupied molecular orbit (LUMO) of −4.63 eV, much shallower than that of the commercial material (PD01) of which the LUMO is −5.04 eV. Nevertheless, this enables us to modulate the supply of holes to the emissive layer through tuning doping concentration. We demonstrate that device performances are significantly improved by employing such a scheme. With a 23% molar doping of PD02, a bottom emission red OLED achieves an external quantum efficiency (EQE) of over 30%, an operating voltage of 3.4 V and a LT95 ~15,000 h at 10 mA/cm2, with a Digital Cinema Initiative P3 (DCI‐P3) chromaticity of CIE (X, Y) = (0.68, 0.32). Moreover, the efficiency roll‐off is suppressed up till ~3500 cd/m2, a desirable feature in display applications. The lateral conductivity of by using such HIL is also found to be much lower than that of PD01, resulting in reduced crosstalk among RGB pixels. Next, a new electron transporting material (ETM‐02) with a deep LUMO of −2.86 eV is also introduced to further optimize the charge balance. Although devices with ETM‐02 shows lower voltage and higher EQE, lifetime is compromised. In order to improve lifetime, additional fine tuning of the charge balance is essential. Finally, a second p‐dopant PD03 with a LUMO of −4.91 eV is added to the HIL to further extend the modulation flexibility in the hole injection. A double‐layer HIL consisting of 8 nm of HTM:16% PD02 and 2 nm of HTM:3% PD03, where the former is in contact with anode, is adopted in the device structure. The bottom emission deep red device achieve EQE over 30%, an operating voltage of 3.2 V and an improved LT95 ~13,000 h at 10 mA/cm2 with a BT.2020 range chromaticity of CIE (X, Y) = (0.701, 0.299). In the double HIL configuration, the introduction of PD03 provides one more parameter for tuning and therefore improves the overall device performances. [ABSTRACT FROM AUTHOR]

Huge advancements in the understanding of photovoltaic (PV) physics have been made, but still, PV has not overtaken conventional energy sources due to PV materials cost, toxicity, and stability concerns. In the pursuit of discovering a new solar energy harvester which satisfies criteria such as low cost, earth-abundance, non-toxicity, high efficiency and long-term stability, extensive research has been conducted on the potential of copper iron oxide (CuFeO2), also known as delafossite oxide. CuFeO2 possesses optimal bandgap (1.5 eV), with a high absorption coefficient and carrier mobility, suitable for potentially cost-effective solar cells. Theoretical modelling based on the optical and electrical characteristics of the CuFeO2 system is performed here on delafossite CuFeO2 to examine its photovoltaic performance. We explored various buffer counterparts for CuFeO2 absorber, and a stack of p–n+–n++is simulated for device optimization. ZnO showed zero conduction band offset with CuFeO2 and a corresponding efficiency of 28% for CuFeO2/ZnO/ITO (p–n+–n++) device. The optimal range of crucial design parameters, such as doping profile, absorber thickness, surface recombination velocity, back contact work function, resistances, and bulk defects, that allow CuFeO2 solar cells to reach power conversion efficiencies above 25% are quantified. The spectrum loss (thermalization and non-absorption loss) stands at 59.6%, extrinsic recombination loss at 12.3%, and the performance ceiling of CuFeO2 at 28.1%. Theoretical analysis shows that the maximum achievable efficiency of 28% is close to the Shockley–Queisser (S–Q) limit and comparable to contemporary inorganic solar cells. The findings presented in this study are anticipated to stimulate experimentalists to fabricate stable, high-efficiency CuFeO2-based thin film solar cells. [ABSTRACT FROM AUTHOR]

A large efficiency improvement, ≈4.5 times, in a solar cell based on earth‐abundant low‐cost SnS absorber with configuration glass/Mo/SnS/CdS/i‐ZnO/AZO/Al is reported in sharp contrast to prior experimental reports in the literature. Efficiency enhancement is attributed to tailored design at the absorber/buffer interface implemented via two‐step design modification vis‐à‐vis experimental benchmark. Design tailoring using simulation comprises substitution of sulfur composition in SnS by Se followed by replacing CdS buffer layer with wide bandgap, nontoxic Zn (O, S). The effect of sulfur composition variation by Se (i.e., SnS1−xSex) indicates an optimal Se mole fraction (x = 0.4) exhibiting maximum efficiency. In addition, optimization of the thickness, carrier density, and bulk defect density of the SnS1−xSex absorber result in an improved design. Replacing CdS buffer layer by ZnO1−ySy in SnS absorber‐based solar cell results in substantial improvement in device parameters; open circuit voltage (VOC) of ≈86% and current density (JSC) of ≈78% due to optimal band alignment at the SnS1−xSex/ZnO1−ySy heterojunction. It occurs when the sulfur mole fraction is 60% in the absorber layer and 70% in the buffer layer causing efficiency to rise to ≈17.87%. An optimal design comprising all the parameters including metal back contact work function, series and shunt resistance deliver an efficiency of ≈19.2%. [ABSTRACT FROM AUTHOR]

Background: We aimed to evaluate if optimization by maximizing QRS duration (QRSd) reduction is feasible in an all-comer cardiac resynchronization therapy (CRT) population, and if reduced, QRSd is associated with a better clinical outcome. Methods: Patients with LBBB receiving CRT implants during the period 2015–2020 were retrospectively evaluated. Implants from 2015–2017 were designated as controls. Starting from 2018, an active 12-lead electrogram-based optimization of QRSd reduction was implemented (intervention group). QRSd reduction was evaluated in a structured way at various device AV and VV settings, aiming to maximize the reduction. The primary endpoint was a composite of heart failure hospitalization or death from any cause. Results: A total of 254 patients were followed for up to 6 years (median 2.9 [1.8–4.1]), during which 82 patients (32%) reached the primary endpoint; 53 deaths (21%) and 58 (23%) heart failure hospitalizations. Median QRS duration pre-implant was 162 ms [150–174] and post-implant 146ms [132–160]. Mean reduction in QRS duration was progressively larger for each year during the intervention period, ranging from − 9.5ms in the control group to − 24 in the year 2020 (p = 0.005). QRS reduction > 14 ms (median value) was associated with a lower risk of death or heart failure hospitalization (adjusted HR 0.54 [0.29–0.98] (p = 0.04). Conclusions: Implementing a general strategy of CRT device optimization by aiming for shorter QRS duration is feasible in a structured clinical setting and results in larger reductions in QRS duration post-implant. In patients with a larger QRS reduction, compared to those with a smaller QRS reduction, there is an association with a better clinical outcome. [ABSTRACT FROM AUTHOR]

The existing von Neumann architecture for artificial intelligence (AI) computations suffers from excessive power consumption and memory bottlenecks. As an alternative, compute-in-memory (CIM) technology has been emerging. Among various CIM device candidates, split-gate NOR flash offers advantages such as a high density and low on-state current, enabling low-power operation, and benefiting from a high level of technological maturity. To achieve high energy efficiency and high accuracy in CIM inference chips, it is necessary to optimize device design by targeting low power consumption at the device level and surpassing baseline accuracy at the system level. In split-gate NOR flash, significant factors that can cause CIM inference accuracy drop are the device conductance variation, caused by floating gate charge variation, and a low on-off current ratio. Conductance variation generally has a trade-off relationship with the on-current, which greatly affects CIM dynamic power consumption. In this paper, we propose strategies for designing optimal devices by adjusting oxide thickness and other structural parameters. As a result of setting Tox,FG to 13.4 nm, TIPO to 4.6 nm and setting other parameters to optimal points, the design achieves erase on-current below 2 μA, program on-current below 10 pA, and off-current below 1 pA, while maintaining an inference accuracy of over 92%. [ABSTRACT FROM AUTHOR]

The latest advances in perovskite solar cells (PSCs) are reported with efficiencies over 25%. PSCs are one of the best developing research-level photovoltaic technologies. To the best of our knowledge, for the first time, we optimize all parameters containing thicknesses, conduction and valence band offset of ETLs (electron transport layers) and hole transport layer, defect densities and doping concentration densities for Cs0.05(FA0.77 MA0.23)0.95Pb(I0.77Br0.23)3. As an absorber layer with numerous stacked ETLs including SnO2/C60, ZnO/C60, TiO2/C60, CdZnS/C60 and CdSe/C60 are used. To find the efficiency, the SCAPS (Solar Cell Capacitance Simulator)-1D program is performed to realize which of stacked ETLs is more appropriate for both cost-effectiveness and high efficiency. After all, the efficiency for stacked SnO2/C60 at 31.16%, stacked ZnO/C60 at 31.22%, stacked TiO2/C60 at 30.55%, stacked CdZnS/C60 at 30.46% and stacked CdSe/C60 at 31.24% are reached. [ABSTRACT FROM AUTHOR]

We demonstrate improved charge balance in organic light emitting devices (OLEDs) by optimizing the hole injection layer (HIL) to control the hole density through the device. Two novel p‐dopants (PDs), PD02 with a shallow lowest unoccupied molecular orbital (LUMO) at ‐4.63 eV (reported in our previous work) and PD03 with a relatively deep LUMO of ‐4.91 eV were used. A two‐layer HIL consisting of HTM:PD02 and HTM:PD03 introduces new design flexibility to improve charge balance in the light emission layer. Using 16% by mass of PD02 and 3% by mass of PD03, we achieve, (1) a bottom emission deep red device with an external quantum efficiency (EQE) of over 30% at a CIE of (0.701, 0.299), an operating voltage of 3.2 V and LT95~13, 000 h at 10 mA/cm2. In particular, the efficiency roll‐off of this device is greatly reduced, which is highly desirable in the display industry. (2) a top emission deep red device with a current efficiency (CE) of 75 cd/A at a CIE of (0.707, 0.293), an operating voltage of 3.6 V and LT95 over 15, 000 h at 10 mA/cm2. An additional benefit from this novel dual p‐doped HIL approach is its much lower lateral conductivity compared to the standard single HIL device structure, resulting in reduced lateral crosstalk between RGB pixels. [ABSTRACT FROM AUTHOR]

In this paper, we use numerical simulations to investigate ultrathin Cu (In1−xGax) Se2 solar cells. In the first part, we focus on the cell configuration in which the PV parameters fit and match the fabricated cell characteristics. Our goal is to investigate the impact of different loss mechanisms, such as interface trap density (Dit) and absorber trap density (Nt), in different cell pitch sizes on cell performances. Dit defines the number of carrier traps at CIGS/Al2O3 interfaces to recombine with photogenerated carriers. Nt defines the number of carrier traps in the absorber layer. Recombination through traps has been found to be the primary loss process in the investigated cell. Additional numerical simulations reveal appreciable gains in cell performance for various cell pitch sizes, absorber doping densities, Ga content, and graded bandgap under AM1.5 illumination. Research during the recent decade has clarified that the most promising strategy to achieve maximum efficiency consists of the so-called tandem configuration. Therefore, we here propose a u-CIGS/PERT silicon device employing, as a top cell, a u-CIGS cell optimized to take into account the above procedure. The results of these simulations provide insights into the optimization of ultrathin-film CIGS solar cells. [ABSTRACT FROM AUTHOR]

Cardiac resynchronization therapy (CRT) has developed into a very effective technology for patients with decreased systolic function and has substantially improved patients' clinical course. However, non-responsiveness to CRT, described as lack of reverse cardiac chamber remodeling, leading to lack to improve symptoms, heart failure hospitalizations or mortality, is common, rather unpredictable, and not fully understood. This article aims to discuss key factors that are impacting CRT response, from patient selection to LV lead position, to structured follow-up in CRT clinics. Secondly, common causes and interventions for CRT non-responsiveness are discussed. Next, insight is given into technologies representing new and feasible interventions as well as pacing strategies in this group of patients that remain challenging to treat. Finally, an outlook is given into future scientific development. Despite the progress that has been made, CRT non-response remains a significant and complex problem. Patient management in interdisciplinary teams including heart failure, imaging, and cardiac arrhythmia experts appears critical as complexity is increasing and CRT non-response often is a multifactorial problem. This will allow optimization of medical therapy, and the use of new integrated sensor technologies and telemedicine to ultimately optimize outcomes for all patients in need of CRT. [ABSTRACT FROM AUTHOR]

We report gallium nitride (GaN) vertical trench junction barrier Schottky (TJBS) diodes and systematically analyzed the effects of the key design parameters on the reverse and forward characteristics of the devices. By taking advantage of the shielding effects from both the trenches and pn junctions in the TJBS structure, the high electric field at the Schottky contact region can be effectively suppressed. We found that the doping concentration, thickness, and spacing of p-GaN, as well as the depth and angle of the trench sidewalls are closely associated with the electric field distribution and the reverse characteristics of the TJBS diodes. With an optimal set of design parameters, the local electric field crowding at either the corner of the trench or the edge of the p-GaN can also be alleviated, resulting in a boosted breakdown voltage of up to 1250 V in the TJBS diodes. In addition, an analytical model was developed to explore the physical mechanism behind the forward conduction behaviors. We believe that the results can provide a systematical design strategy for the development of low-loss, high-voltage, and high-power GaN power diodes towards an efficient power system. [ABSTRACT FROM AUTHOR]

In this work, we provide a novel strategy to improve the charge balance in organic light emitting devices (OLEDs) by optimizing the hole injection layer (HIL) and thereby controlling the overall hole supply in the device. The lowest unoccupied molecular orbit (LUMO) of the p‐dopant proposed in this work, PD02, is ‐4.63 eV, much shallower than that of the commercial material (PD01). Nevertheless, this enables use of the doping concentration to modulate the supply of holes to the emissive layer to control the charge balance. We demonstrate that device performances are significantly improved by employing such a scheme. With 23% molar doping of PD02, a bottom emission red OLED achieves external quantum efficiency (EQE) over 30%, operating voltage of 3.4 V and LT95 ~ 15,000 h at 10 mA/cm2. Moreover, the efficiency roll‐off is also suppressed up till ~ 3,500 cd/m2, a desirable feature in display applications. A study of exciton distribution within the emissive layer suggests that improved charge balance is indeed achieved in the optimized structure. An additional benefit from the modified HIL is its lower lateral conductivity relative to the standard formula, which reduces crosstalk between RGB pixels. [ABSTRACT FROM AUTHOR]

The piezoelectric nature of collagen has been known for decades, yet its manifestation across, and interactions between, hierarchies remains elusive. Here, piezoelectricity at the tropocollagen‐, microfibril‐, and fibril‐level hierarchies is examined experimentally, using collagen assembled from solution onto muscovite mica substrates. An amplification of the d15 response of 35–50% is observed between the tropocollagen and fibril levels, with no difference observed between the microfibril and fibril levels. Comparison of experimental results with simulation indicates the potential to optimize collagen piezoresponse via tropocollagen packing to exceed the piezoelectric properties of native collagen fibrils. By improving electromechanical performance through adjustments to winding angle and packing, it may therefore be possible to utilize collagen in low‐cost, biodegradable, and biocompatible sensing or harvesting devices. [ABSTRACT FROM AUTHOR]

A feedback field-effect transistor (FBFET) is a novel device that uses a positive feedback mechanism. FBFET has a high on-/off ratio and is expected to realize ideal switching characteristics through steep changes from off-state to on-state. In this paper, we propose and optimize FBFET devices with asymmetric source/drain doping concentrations. Additionally, we discuss the changes in electrical characteristics across various channel length and channel thickness conditions and compare them with those of FBFET with a symmetric source/drain. This shows that FBFET with an asymmetric source/drain has a higher on-/off ratio than FBFET with a symmetric source/drain. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shenyang Agricultural University is the property of Journal of Shenyang Agricultural University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbon nanotube (CNT) field-effect transistors (FETs) have recently reached high-frequency (HF) performance similar to that of silicon RF-CMOS at the same gate length despite a tube density and current per tube that are far from the physical limits and suboptimal device architecture. This work reports on an investigation of the optimal device design for practical HF applications in terms of cut-off frequencies, power gain, and linearity. Different fundamental designs in the gate contact arrangement are considered based on a 3D device simulation of both CNTs and contacts. First, unit cells with a single CNT and minimal contact sizes are compared. The resulting simulation data are then extended toward a structure with two gate fingers and realistic contact sizes. Corresponding parasitic capacitances, as well as series and contact resistances, have been included for obtaining realistic characteristics and figures of merit that can be used for comparison with corresponding silicon RF MOSFETs. Finally, a sensitivity analysis of the device architecture with the highest performance is performed in order to find the optimal device design space. [ABSTRACT FROM AUTHOR]

Existing obstacle avoidance systems do not consider the situation of hollowed-out obstacles. Therefore, in this paper, we design an assistive cane with visual odometry based on these requirements of the blind to aid them in attaining safe indoor navigation. The proposed device is portable, compact and adaptable. The assistive cane with visual odometry can be used not only to directly detect obstacles, but also to draw the attention of people around, providing multiple protection for the blind. In order to optimize the device parameters, we select the height of the camera and the speed of the voice broadcast as factors to design a complete factorial design, aiming to explore the parameter level that can make the passing time shortest and the success rate of obstacle avoidance highest. We invited two visually impaired people and two blindfolded students with normal vision as the experimental subjects. Each subject was required to conduct the experiments under nine combinations of device parameters. The subjects tried to avoid obstacles according to the voice prompts. The passing time and the success rate of obstacle avoidance were recorded. The experimental results show that the broadcast speed causes the significant effect to the success rate and both the two factors affect the passing time. In addition, we discuss the results of different subjects’ response surfaces and perceptual patterns and get the conclusion that different visual perceptual patterns, namely route representation and two different survey representations, have a certain impact on the setting of the optimal parameter level and the optimal passing time. The congenitally blind subject with route representation has the shortest optimal passing time in an unfamiliar environment, and the camera height should be set at the center of the hollowed-out obstacle, while the results are somewhat different for the acquired visual impairment subjects and the blindfolded normal vision subjects with survey representation. The camera height should be set between the center and the upper position of the obstacle. In summary, the camera height should be set at the center of the hollowed-out barrier and the broadcast speed should be set at the highest level. At the same time, the device parameters should be adjusted appropriately according to the visual perception pattern of users. Further researches are needed to analyze the perceptual patterns in depth. [ABSTRACT FROM AUTHOR]

Implantable electrophoretic drug delivery devices have shown promise for applications ranging from treating pathologies such as epilepsy and cancer to regulating plant physiology. Upon applying a voltage, the devices electrophoretically transport charged drug molecules across an ion‐conducting membrane out to the local implanted area. This solvent‐flow‐free "dry" delivery enables controlled drug release with minimal pressure increase at the outlet. However, a major challenge these devices face is limiting drug leakage in their idle state. Here, a method of reducing passive drug leakage through the choice of the drug co‐ion is presented. By switching acetylcholine's associated co‐ion from chloride to carboxylate co‐ions as well as sulfopropyl acrylate‐based polyanions, steady‐state drug leakage rate is reduced up to sevenfold with minimal effect on the active drug delivery rate. Numerical simulations further illustrate the potential of this method and offer guidance for new material systems to suppress passive drug leakage in electrophoretic drug delivery devices. [ABSTRACT FROM AUTHOR]

This paper presents a framework for automated optimization of double-heater convective PCR (DH-cPCR) devices by developing a computational fluid dynamics (CFD) simulation database and artificial neural network (ANN) model. The optimization parameter space that includes the capillary tube geometries and the heater sizes of DH-cPCR is established, and a database consisting of nearly 10,000 CFD simulations is constructed. The database is then used to train a two-stage ANN models that select practically relevant data for modeling and predict PCR device performance. The trained ANN model is then combined with the gradient-based and the heuristics optimization approaches to search for optimal device configuration that possesses the shortest DNA doubling time. The entire design process including model meshing and configuration, parallel CFD computation, database organization, and ANN training and utilization is fully automated. Case studies confirm that the proposed framework can successfully find the optimal device configuration with an error of less than 0.3 s, and hence, representing a cost-effective and rapid solution of DH-cPCR device design. [ABSTRACT FROM AUTHOR]

Remote areas in Northwest China are blind regions without large-scale power grid coverage. To satisfy the residential electricity demand, it is essential to utilize small-scale distributed wind power systems and increase wind energy utilization. The seagull airfoil wind energy conversion device is adopted to improve the aerodynamic performance and increase the use of wind energy. Based on the wind tunnel experiment and numerical simulation, the bending shape of the seagull airfoil is optimized. Further, the cascade structure is constructed using the central bending seagull airfoil to explore the flow mechanisms. The front and rear cascades are the main and secondary regions, accounting for 84% and 16% of the force generated, respectively. The deformation of the blade is significantly larger at the trailing edge than at the leading edge, thereby exhibiting unique deformation characteristics of seagull airfoils. When the impeller is rotated, the average force of each seagull airfoil was 15.1% more than that of the flat airfoil, thereby enabling the absorption of more wind energy and device optimization. Owing to the stress and deformation distribution, the seagull airfoil blade can adapt to different aerodynamic loads by changing the cambers and angles of attack to ensure smooth operation of the device. [ABSTRACT FROM AUTHOR]

A 7.1-μm-pitch lock-in pixel (LIP) CMOS image sensor (CIS) that is capable of simultaneously phasing with two different near-infrared-band (NIR-band) light pulses is developed for remote physiological measurement, particularly a heart rate variability (HRV) signal monitor. The proposed dual NIR-band lock-in operation is realized by a four-tap-wise charge modulation with adjacent two-tap LIPs by means of a column-interdigital pixel driving scheme combining with in-LIP lateral electric field modulators (LEFMs). For attaining the weak HRV signal, the implemented CIS achieves a subelectron temporal noise of 0.67 e−rms at 64 times correlated multiple sampling (CMS) and a high charge modulation contrast (MC) up to 96% at maximum. These remarkable properties primarily result from the in-LIP dark current and LEFM controlling optimizations proposed in device domain. The experimental results show that the developed CIS exhibits not only a 98.5% accuracy in HRV signal capture with −39.1-dB signal-to-background ratio (SBR) against a fluctuant brightness ambient light but also a moderate artificial motion robustness benefited from the proposed dual NIR-band lock-in technique. [ABSTRACT FROM AUTHOR]

In this article, we have systematically investigated the impact of different structural parameters on the breakdown voltage for GaN-based trench MIS barrier-controlled Schottky (TMBS) rectifier. Compared with the planar Schottky rectifier, the TMBS rectifier has field plates on the mesa sidewalls so that the drift region can be depleted in a 2-D manner, which helps to decrease the electric field at the metal/mesa interface. However, the adoption of mesas can make the electric potential lines at the mesa corner dense and has large curvatures. Therefore, the premature breakdown can occur when the electric field therein reaches the critical condition. We find that the electric field profiles can be affected by insulation layer thickness, mesa width, trench depth, and different types of insulation layers. Then, we increase the breakdown voltage by homogenizing the electric field distribution in the mesa region, e.g., the electric field at mesa corners can be decreased by adopting properly thick sidewall insulator and small trench depth. Meanwhile, TMBS rectifier using sidewall insulating material with a large dielectric constant more favors a large breakdown voltage. [ABSTRACT FROM AUTHOR]

Interfacial engineering provides an important tool for optimizing the performances of optoelectronic devices. We show that poly[(2,7-(9,9′-dioctyl)fluorene)-alt-(2,7-(9,9′-bis(5″-trimethylammonium bromide)pentyl)fluorene)])], an alcohol-soluble π-conjugated polymer based on polyfluorene backbone and ammonium groups on the alkyl side chains, is capable of modifying the interface between the organic layer and the metal cathode in both organic solar cells and light-emitting diodes based on commercial materials and conventional architectures, improving their performances. The introduction of the cathode interlayer enhances the efficiency of a red-emitting phosphorescent OLED by 15% and decreases its turn-on voltage. The same polymer improves the power conversion efficiency of a PTB7/PC71BM solar cell by 55% and shows a beneficial effect in terms of device stability. [ABSTRACT FROM AUTHOR]

This paper introduces a device performance optimization approach for the FinFET through optimization of the gate length. As a result of reducing the gate length, the leakage current (Ioff) increases, and consequently, the stress along the channel enhances which leads to an increase in the drive current (Isat) of the PMOS. In order to sustain Ioff, work function is adjusted to offset the effect of the increased stress. Changing the gate length of the transistor yields different drive currents when the leakage current is fixed by adjusting the work function. For a given device, an optimal gate length is found to provide the highest drive current. As an example, for a standard performance device with Ioff = 1 nA/um, the best performance Isat = 856 uA/um is at L = 34 nm for 14 nm FinFET and Isat = 1130 uA/um at L = 21 nm for 7 nm FinFET. A 7 nm FinFET will exhibit performance boost of 32% comparing with 14 nm FinFET. However, applying the same method to a 5 nm FinFET, the performance boosting is out of expectance comparing to the 7 nm FinFET, which is due to the severe short-channel-effect and the exhausted channel stress in the FinFET. [ABSTRACT FROM AUTHOR]

A comprehensive study of the breakdown voltage optimization of trench MOS barrier Schottky (TMBS) rectifiers is performed by means of drift-diffusion simulations. First, the principles of operation are explained in terms of the charge-sharing effect between the Schottky and trench MOS components of the unit cell, and correlated with the profiles of the electric field along the drift region ESch and the MOS capacitor ETMOS. Then, the systematic variation of relevant design parameters is used to determine breakdown voltage and leakage current trends, which are analyzed in terms of the electric field. Our results show that ESch is the dominating component in structures with thick oxides, shallow trenches, or high-doping concentrations, whereas ETMOS is the limiting factor for devices with thin oxides, deep trenches, or low doping. Finally, optimum BV is found when the peak value of ESch and ETMOS is approximately the same, and this condition can be reached in a wide range of trench depths for devices with long drift regions and high doping, but in a very narrow window for thin epi-layers or low-doping concentration. [ABSTRACT FROM AUTHOR]

This paper presents a fundamental investigation on optimizing the power takeoff (PTO) for maximizing wave energy conversion of the wave-activated bodies (WABs) wave energy converters. In this research, two relative heave motions are taken for capture power, and a linear PTO is considered in the primary analysis. For such a linear dynamic system, the frequency-domain analysis can be carried out, and an analytical formula can be derived for the optimized frequency-dependent PTO damping coefficient, which can be used to determine an optimized PTO damping for maximizing wave energy conversion in regular waves. However, when an optimized PTO is required for maximizing energy conversion from ocean waves, the PTO damping optimization may be very different and much less certain, because it may be based on one of many characteristic periods of the given sea state and the dependency may change from different sea states. For this reason, the optimized PTO damping coefficient for a given sea state must be studied carefully. Another important aspect of the research is to examine whether an optimized nonlinear PTO can take more energy out from waves than that of an optimized linear PTO. For this purpose, the maximized capture powers by the optimized linear and nonlinear PTOs are compared using the time-domain analysis. It has been shown from the examples that the maximized capture power by a nonlinear PTO system may exceed that by the linear PTO, but only marginally (less than 1%). Hence, it can be generally concluded that the maximized power using a linear PTO system can be a very good indicator for the device in extracting the maximal energy from waves regardless of the linear or nonlinear PTO in actual use. This conclusion may help simplify the analysis of the wave energy converters in terms of the energy production as well as the device optimization for improving energy conversion capacity. [ABSTRACT FROM PUBLISHER]

Polymer solar cells (PSCs) were fabricated by combining a diketopyrrolopyrrole-based terpolymer (PTBT-HTID-DPP) as the electron donor, and [6,6]-phenyl C butyric acid methyl ester (PCBM) as the electron acceptor, and the power conversion efficiency (PCE) of 4.31% has been achieved under AM 1.5 G (100 mW cm) illumination condition via optimizing the polymer/PCBM ratio, the variety of solvent and the spin-coating speed. The impact of the spin-coating speed on the photovoltaic performance of the PSCs has been investigated by revealing the effects of the spin-coating speed on the morphology and the absorption spectra of the polymer/PCBM blend films. When the thickness of the blend films are adjusted by spin-coating a fixed concentration with different spin-coating speeds, the blend film prepared at a lower spin-coating speed shows a stronger absorption per unit thickness, and the correspond device shows higher IPCE value in the longer-wavelength region. Under the conditions of similar thickness, the blend film prepared at a lower spin-coating speed forms a more uniform microphase separation and smaller domain size which leads to a higher absorption intensity per unit thickness of the blend film in long wavenumber band, a larger short-circuit current density ( J ) and a higher power conversion efficiency (PCE) of the PSC device. Noteworthily, it was found that spin-coating speed is not only a way to control the thickness of active layer but also an influencing factor on morphology and photovoltaic performance for the diketopyrrolopyrrole-based terpolymer. [ABSTRACT FROM AUTHOR]

The low band gap polymer based on benzodithiophene (BDT)-thieno[3,4-b]thiophene (TT) backbone, PBDT-TS1, was synthesized following our previous work and the bulk heterojunction (BHJ) material comprising PBDT-TS1/PC71BM was optimized and characterized. By processing the active layer with different additives i.e. 1,8-diiodooctane (DIO), 1-chloronaphthalene (CN) and 1, 8-octanedithiol (ODT) and optimizing the ratio of each additive in the host solvent, a high PCE of 9.98% was obtained under the condition of utilizing 3% DIO as processing additive in CB. The effect of varied additives on photovoltaic performance was illustrated with atomic force microscopy (AFM) and transmission electron microscope (TEM) measurements that explained changes in photovoltaic parameters. These results provide valuable information of solvent additive choice in device optimization of PBDTTT polymers, and the systematic device optimization could be applied in other efficient photovoltaic polymers. Apparently, this work presents a great advance in single junction PSCs, especially in PSCs with conventional architecture. [ABSTRACT FROM AUTHOR]

Photoresponse of GaAs-based double-heterojunction phototransistors (DHPTs), in surface-illuminated orientation, has been analyzed with a modified small-signal model. The effect of incident optical illumination on various intrinsic parameters has been discussed for In0.49Ga0.51P/GaAs N+p+N- DHPT. Since the primary detecting material is GaAs, the device is optimized to detect short wavelength at 850 nm. A novel formulation for optical flux absorption in DHPTs is also provided along with its comparison with single-heterojunction phototransistors. The analysis of DHPTs presented in this paper can be utilized for performance enhancement through device optimization in sensors, photoreceivers in optical networks, and remote sensing applications employing integrated circuits. [ABSTRACT FROM AUTHOR]

Aims: Encouraging data have been reported on the use of cardiogenic impedance (CI) in cardiac resynchronization therapy (CRT) optimization. The purposes of this study were to: evaluate the stability of certain CI vectors 24 h postimplantation, study the correlation between these CI signals and selected echocardiographic parameters, and examine the possibility of non-invasive calibration of the patient-specific impedance-based prediction model. Methods and results: Thirteen patients received a CRT-defibrillator device with monitor capability of the dynamic impedance between several electrodes. At implantation, a patient-specific impedance-based prediction model was created for identification of optimal atrioventricular and interventricular (VV) delays and calibrated on invasive measurements of left ventricular contractility (LV dP/dt). Simultaneously, non-invasive measurements of LV dP/dt and stroke volume (SV) were obtained using a finger plethysmograph. Patients were re-evaluated with echocardiography and new CI measurements the day after implantation. The hemodynamic benefit achieved by optimal VV setting according to the patient-specific impedance-based prediction model at follow-up was not as large as the one obtained at implantation. In a multivariate partial least square regression analysis, a correlation was found between aortic velocity time integral (VTI) and a generic linear combination of CI features ( P < 0,005). No correlation was found between the patient-specific impedance-based prediction models and the non-invasive measurements of LV dP/dt and SV. Conclusion: Cardiogenic impedance signals can be used to optimize CRT settings but seem less feasible as an ambulatory tool since calibration is required. The positive correlation between aortic VTI and CI measurements seems promising, although a larger cohort is required to create an echocardiography-based patient-specific model. [ABSTRACT FROM AUTHOR]

Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several critical issues have still to be solved. In this work, a systematic approach to the design of integrated thermal flow sensors, with specification of resolution, dynamic range, power consumption and pressure insertion loss is proposed. All the critical components of the sensors, namely thermal microstructure, package and read-out interface are examined, showing their impact on the sensor performance and indicating effective optimization strategies. The proposed design procedures are supported by experiments performed using a recently developed test chip, including several different sensing structures and a flexible electronic interface. [ABSTRACT FROM AUTHOR]

Aims Cardiac resynchronization therapy (CRT) has dramatically improved the symptoms and prognosis of patients with heart failure in large randomized clinical trials. Optimization of device settings may maximize benefit on an individual basis, although the best method for this is not yet established. We evaluated the use of cardiogenic impedance measurements (derived from intracardiac impedance signals) in CRT device optimization, using invasive left ventricular (LV) dP/dtmax as the reference. Methods and results Seventeen patients underwent invasive haemodynamic assessment using a pressure wire placed in the LV cavity at the time of CRT device implantation. Intracardiac impedance measurements were made at different atrioventricular (AV) and interventricular (VV) delays and compared with LV dP/dtmax. We assessed the performance of patient-specific and generic impedance-based models in predicting acute haemodynamic response to CRT. In two patients, LV catheterization with the pressure wire was unsuccessful and in two patients LV lead delivery was unsuccessful; therefore, data were acquired for 13 out of 17 patients. Left ventricular dP/dtmax was 919 ± 182 mmHg/s at baseline and this increased acutely (by 24%) to 1121 ± 226 mmHg/s as a result of CRT. The patient-specific impedance-based model correctly predicted the optimal haemodynamic response (to within 5% points) for AV and VV delays in 90 and 92% of patients, respectively. Conclusion Cardiogenic impedance measurements are capable of correctly identifying the maximum achievable LV dP/dtmax as measured by invasive haemodynamic assessment. This study suggests that cardiogenic impedance can potentially be used for CRT optimization and may have a role in ambulatory assessment of haemodynamics. [ABSTRACT FROM PUBLISHER]

We utilize a fully self-consistent quantum mechanical simulator based on CBR method to optimize 10 nm FinFET devices to meet ITRS projections for High Performance (HP) logic technology devices. Fin width, gate oxide thickness, and doping profiles are chosen to reflect realistic values. We find that the device on-current approaching the value projected by ITRS for HP devices can be obtained using unstrained conventional (Si) channel. Our simulation results also show that quantum nature of transport in ultra small devices significantly enhances the intrinsic switching speed of the device. In addition, small signal analysis has been performed. Sensitivity of device performance to the process variation at room temperature has also been investigated. [ABSTRACT FROM AUTHOR]

The 4H-SiC p-channel IGBTs designed to block 15 and 20 kV are optimized for minimum loss (ON-state plus switching power) by adjusting the parameters of the p JFET region, p- drift layer, and p+ buffer layer, using 2-D MEDICI simulations. Switching loss exhibits a strong dependence on buffer layer thickness, doping, and lifetime due to their influence on the current tail. In contrast, drift layer lifetime has little effect on the crossover frequency at which the MOSFET and IGBT have equal loss. [ABSTRACT FROM AUTHOR]

Subthreshold circuit design is promising for future ultralow-energy sensor applications as well as highly parallel high-performance processing. Device scaling has the potential to increase speed in addition to decreasing both energy and cost in subthreshold circuits. However, no study has yet considered whether device scaling to 45 nm and beyond will be beneficial for subthreshold logic. We investigate the implications of device scaling on subthreshold logic and SRAM and find that the slow scaling of gate-oxide thickness leads to a 60% reduction in Ion/Ioff between the 90- and 32-nm device generations. We highlight the effects of this device degradation on noise margins, delay, and energy. We subsequently propose an alternative scaling strategy and demonstrate significant improvements in noise margins, delay, and energy in sub-Vet, circuits. Using both optimized and unoptimized subthreshold device models, we explore the robustness of scaled subthreshold SRAM. We use a simple variability model and find that even small memories become unstable at advanced technology nodes. However, the simple device optimizations suggested in this paper can be used to improve nominal read noise margins by 64% at the 32-nm node. [ABSTRACT FROM AUTHOR]

A wireless pressure sensor is described for use in a high-pressure manufacturing process with three major subsystems: energy conversion by a stack of piezoelectric disks, energy measurement and control by a threshold modulator, and ultrasonic signal transmission by a piezoelectric transmitter. The second system, the threshold modulator, is the focus of this paper. The charge, proportional to pressure, on a capacitive element is measured and controlled through the use of a two-transistor modulator. Standard NPN and PNP transistors are used to passively control the flow of charge between a piezoelectric stack and an ultrasonic transmitter. The basis for the design is discussed, from which a simulation is developed and compared to a bench top prototype. The results of this comparison indicate the appropriateness of the assumptions used to produce an analytical model of the design and the limiting conditions under which the modulator will effectively measure charge. Finally, the prototype device is optimized with respect to sensitivity, gain, and operating range for use in real-time process monitoring and control. [ABSTRACT FROM PUBLISHER]

Digital circuits operated in the subthreshold region (supply voltage less than the transistor threshold voltage) can have orders of magnitude power advantage over standard CMOS circuits for applications requiring ultralow power and medium frequency of operation. Although the implication of technology scaling on subthreshold operation is not obvious (since an obsolete technology node can deliver the same performance as a scaled technology in subthreshold), it has been shown that technology scaling helps to reduce the supply-voltage and, hence, the power consumption at iso-performance. It is possible to implement subthreshold logic circuits using the standard transistors that are designed primarily for ultra high performance super-threshold logic design. However, an Si MOSFET so optimized for performance in the super-threshold regime is not the best device to use in the subthreshold domain. In this paper, we propose device designs apt for subthreshold operation. Results show that the optimized device improves the delay and power delay product (PDP) of an inverter chain by 44% and 51%, respectively, over the normal super-threshold device operated in the subthreshold region. [ABSTRACT FROM AUTHOR]

A simple one-dimensional (1-D) analytical solution method for analyzing and determining the breakdown properties of reduced surface field (RESURF) lateral devices is presented. The solution demonstrates quantitatively and qualitatively the reshaping and reduction of the electric field and its dependence on the device/process key parameters. The solution is based on a simple and physical charge-sharing approach that takes into account the modulation of the lateral depletion layer spreading caused by the vertical depletion extension, and therefore transforms the inherent two-dimensional effects into a simple 1-D equivalent. It also provides a reasonable insight on the breakdown voltage sensitivity of lateral RESURF devices to key device/process parameters that other researchers failed to provide. Using the technique, device designers can set and choose the optimal processing window of the device's critical layers to yield high breakdown voltages. The results obtained using the proposed solution method agree well with the experimental and simulation results. [ABSTRACT FROM AUTHOR]

The low-temperature performance of vertical cavity lasers (VCL's) is of interest for high-speed data transmission from superconducting and cryogenic semiconductor circuits. Our double-fused 1.5 μm lasers employ a strain-compensated InGaAsP-InP multiquantum-well (MQW) active region that is sandwiched between two AlGaAs-GaAs distributed Bragg reflectors. Continuous wave (CW) lasing at ambient temperature as low as 7 K is measured on the same type of top-emitting devices that previously lased at a record-high temperature of 337 K. The optimum temperature is found at 180 K giving minimum threshold current, maximum modulation bandwidth of 5 GHz, and more than 3 GHz/mA1/2 modulation current efficiency. The optimum temperature agrees very well with the theoretical prediction. Further device optimization for cryogenic high-speed applications is discussed in detail [ABSTRACT FROM PUBLISHER]

In this letter, a double-spacer (DS) design is utilized for the formation of shallow source and lightly doped drain to further optimize the impactionization MOS (1-MOS) transistor structure. The breakdown voltage VBD needed for avalanche breakdown is lowered due to the shallow source extension. With the formation of the lightly doped drain extension, the impact of drain bias on breakdown voltage, and hence, the threshold voltage VT is also reduced. The DS 1-MOS is fabricated and characterized. Detailed analysis and physical explanation of the impact of drain/gate bias on the device characteristics are provided. Compared to the conventional 1-MOS transistor, the shallow source extension reduces the breakdown voltage [drain-induced breakdown voltage lowering (DIBVL)] by 0.3—0.6 V, and the lightly doped drain extension reduces the DIBVL up to 0.17 V/V. In addition, excellent subthreshold swing and good device performance are achieved. [ABSTRACT FROM AUTHOR]

This paper evaluates the hot-carrier performance of the n-channel high-voltage (30 V) MOSFET device. This device is widely used in high-voltage linear products. It can withstand 30 V across any two terminals. This large voltage range requires thorough hot-carrier analysis, investigating potential hot-carrier mechanisms not believed to have been previously explored in the literature. It is established that two different hot-carrier generation mechanisms are occurring: one at ISUB(max) and another at IKIRK. These are investigated through combined device parametric, technology computer-aided design (TCAD) simulation, and hot-carrier reliability data. [ABSTRACT FROM PUBLISHER]