Figure Of Merit For Performance Research Articles

Processing and properties of Al–Si microcapsules with a biomimetic-corrugated structure and corundum-mullite composite shell

The encapsulation of metal-based phase change materials using ceramics can realize safe and effective storage of high-temperature thermal energy. However, the use of a low toughness ceramic shell around the microcapsules cannot ensure the provision of a high latent heat and thermal cyclic stability. Here, we provide a new and effective design strategy for preparing biomimetic Al–Si microcapsules that are based on a sea-shell corrugated structure and a nano-scale corundum-mullite composite shell. The latent heat of the microcapsules was over 400 J/g, much greater than other metal-based microcapsules reported to date. The unique biomimetic-corrugated structure microcapsules obtained by a heat treatment at 1000 °C exhibited excellent thermal stability, achieving near zero heat loss after 5000 thermal cycles, whose latent heat of absorption and release reached up to 448.3 J/g and 451.8 J/g respectively. Furthermore, the microcapsules possessed a giant heat storage density of 945.8 J/g within 300–700 °C, and the performance figure of merit was 6384.2 × 106 J2·K–1·s–1·m–4, approximately 15 times higher than that of commercial solar salt. This new approach provides a pathway the practical application of Al–Si alloys as thermal storage materials for renewable energy applications.

Standard-Cell-Based Comparators for Ultra-Low Voltage Applications: Analysis and Comparisons

This work is focused on the performance of three different standard-cell-based comparator topologies, considering ultra-low-voltage (ULV) operation. The main application scenarios in which standard-cell-based comparators can be exploited are considered, and a set of figures of merit (FoM) to allow an in-depth comparison among the different topologies is introduced. Then, a set of simulation testbenches are defined in order to simulate and compare the considered topologies implemented in both a 130 nm technology and a 28 nm FDSOI CMOS process. Propagation delay, power consumption and power–delay product are evaluated for different values of the input common mode voltage, as a function of input differential amplitude, and in different supply voltage and temperature conditions. Monte Carlo simulations to evaluate the input offset voltage under mismatch variations are also provided. Simulation results show that the performances of the different comparator topologies are strongly dependent on the input common mode voltage, and that the best values for all the performance figures of merit are achieved by the comparator based on three-input NAND gates, with the only limitation being its non-rail-to-rail input common mode range (ICMR). The performances of the considered comparator topologies have also been simulated for different values of the supply voltage, ranging from 0.3 V to 1.2 V, showing that, even if standard-cell-based comparators can be operated at higher supply voltages by scaling their performances accordingly, the best values of the FoMs are achieved for VDD = 0.3 V.

Comparative Performance Evaluation for 1.2–10kV Conventional and Superjunction GaN Current Aperture Vertical Electron Transistors

The performance potentials and limits for GaN current aperture vertical electron transistors with conventional, doped, and natural polarization superjunction (PSJ) drift layers at 1.2–10 kV breakdown voltage (BV) ratings are quantitatively compared. The static and dynamic performance parameters for each device are simulated and extracted. The specific on‐resistance RON,sp and specific total charge QT,sp (defined as the sum of specific gate charge QG,sp and specific drain–source charge QDS,sp) are extracted from Medici technology computer‐aided design simulations representing both the static and dynamic performance respectively. Moreover, a developed figure‐of‐merit (FoM) (RON,sp · QT,sp) is used to quantitively compare the performance of these field‐effect transistors in the range of BV ratings. Compared to the doped superjunction (DSJ) and conventional CAVETs, natural PSJ CAVET exhibits 1%–60% and 70%–99% reduction in RON,sp, while it is 100 to 1000× reduction in QT,sp, at BV between 1.2 and 10 kV respectively. Simultaneously, 22%–80% and 80%–99% reduction in performance FoM respectively are found.

Enhanced cognitive demodulation with artificial intelligence

The low-cost ‘THz Torch’ wireless link technology is still in its infancy. Until very recently, inherent limitations with available hardware has resulted in a modest operational figure of merit performance (Range times Bit Rate). However, a breakthrough was reported here by the authors, with the introduction of ‘Cognitive Demodulation’. This bypassed the thermal time constant constraints normally associated with both the thermal emitter and sensor; allowing step-change increases in both Range and Bit Rate with direct electronic modulation. This paper concentrates on advancements to the bit error rate (BER) performance. Here, separate techniques are introduced to the demodulation software that, when combined, result in enhanced Cognitive Demodulation. A factor of more than 100 improvement in BER was demonstrated within the laboratory and approximately a 60-fold improvement in a non-laboratory environment; both at the maximum Range and Bit Rate of 2 m and 125 bps, respectively, demonstrated recently. Moreover, demodulation speed is increased by almost a factor of 10,000; allowing for real-time demodulation while easing future computational hardware requirements. In addition to these software advancements, the paper demonstrates important improvements in hardware that has brought the technology out of the laboratory, with field trials being performed within an office corridor.

An Improved Optimum-Damping Current-Mode Buck Converter With Fast-Transient Response and Small-Transient Voltage Using New Current Sensing Circuits

This article presents an improved optimum damping current-mode buck converter with fast-transient response and small-transient voltage using new current sensing circuits. The improved optimum-damping circuit, consisting of the dynamic slope generator and the proposed rail-to-rail current sensor, can stabilize the converter during the output current change and can accelerate the transient response to achieve better figure of merit performance. The dynamic slope generator can compensate the slope to prevent subharmonic oscillation issue and lower undershoot/overshoot without an extra slope compensator. The proposed rail-to-rail current sensor increases the input voltage range, accurately captures the inductor current information, and accelerates the transient response as the load current changes, because it eliminates spikes without the need for a sample-and-hold circuit in a conventional current-sensing circuit. The contributions of the proposed converter are listed in the following: 1) we have proposed a new current-sensing circuit without voltage divider, which can be operated rail-to-rail and improve the dynamic response; 2) the new current-sensing circuit consisted of no switches and therefore, without switching noises; 3) the new current-sensing circuit without voltage divider has a smaller chip area and a smaller path delay; 4) the proposed current-sensing circuit needs no sample-and-hold circuits to reduce current spikes; 5) the transient response and transient voltage of the proposed converter are better than others' works; and 6) we have designed and implemented a new optimum-damping current-mode buck converter with better performances compared with previous publications.

Promises of Main Group Metal–Based Nanostructured Materials for Electrochemical CO2 Reduction to Formate

AbstractSelective CO2 reduction to formic acid or formate is the most technologically and economically viable approach to realize electrochemical CO2 valorization. Main group metal–based (Sn, Bi, In, Pb, and Sb) nanostructured materials hold great promise, but are still confronted with several challenges. Here, the current status, challenges, and future opportunities of main group metal–based nanostructured materials for electrochemical CO2 reduction to formate are reviewed. Firstly, the fundamentals of electrochemical CO2 reduction are presented, including the technoeconomic viability of different products, possible reaction pathways, standard experimental procedure, and performance figures of merit. This is then followed by detailed discussions about different types of main group metal–based electrocatalyst materials, with an emphasis on underlying material design principles for promoting the reaction activity, selectivity, and stability. Subsequently, recent efforts on flow cells and membrane electrode assembly cells are reviewed so as to promote the current density as well as mechanistic studies using in situ characterization techniques. To conclude a short perspective is offered about the future opportunities and directions of this exciting field.

High Figure of Merit Lossy Mode Resonance Sensor with Graphene

Lossy mode resonance (LMR) is the resonance of the lossy mode with a specific type of guided mode. LMR can be generated both for TE and TM polarizations; hence, it can overcome the problem of the polarization and make up for deficiencies in the surface plasmon resonance (SPR). However, conventional LMR sensors get much lower figure of merit (FOM) by comparison with SPR sensors. Based on the deficiency of LMR sensor in FOM performance, a new type of graphene thin layer LMR sensor is proposed in this paper to greatly improve FOM performance and enhance the detection sensitivity of the target in practical applications. In particular, the maximum value of FOM as high as 410 RIU−1 has been reached in TM mode for the LMR sensor which is nearly 10 times that of SPR sensor. It is believed that the proposed LMR sensor will be widely used in biological detection, chemical inspection, and environmental monitoring.

Characterization of Ge Quantum Dot Optical Waveguides for High Speed Optical Modulators

Quantum Dot (QD) Optical Modulators can provide high speed modulation in low cost indirect bandgap materials. Si based optical modulators can be realized with the inclusion of self-assembled Ge QDs to provide low cost, high speed CMOS compatible optical devices. In this paper, we present the optical characterization of a novel Ge-QD Si-SiO2 based waveguide for use in as an optical modulator. Optical performance figures of merit are investigated including insertion loss (IL) measurements, and Wavelength dependent loss (WDL). We present a multimode waveguide fabricated with conventional CMOS processing. The waveguide provides 4.43dB/cm loss and individual discrete absorption regimes corresponding to the unique minibands produced by superlattice properties of the self-assembled Ge QDs in the IR regime. Absorption properties of the Ge QDs are demonstrated and verified against the QD superlattice bandgap model. Analysis and simulation is presented to qualitatively compare the QD bandgap energies with the reported optical properties. The QD functionalized structure demonstrates the fundamental optical principles of a QD waveguide, setting the foundation for a active modulation testing of this QD based optical modulator.

Reconsidering figures of merit for performance and stability of perovskite photovoltaics

We propose a new approach for assessing the lifetimes of perovskite photovoltaics based on daily energy output which accounts for reversible diurnal changes.

A V-band VCO with on-chip body bias voltage control technique using 40-nm CMOS process

This paper presents a V-band voltage-controlled oscillator (VCO) implemented in 40-nm CMOS Process. The on-chip body bias voltage control technique is adopted to improve phase noise and stability of the output signal and to design an LC tank and output buffer circuitry that compensates for the process, voltage, and temperature variations. The design was fabricated in RF Mixed-signal CMOS process with die size 0.078 mm2. Based on the silicon results, the proposed VCO achieve a phase noise of −86 dBc/Hz at 1 MHz offset. The VCO draws 17.8 mA current from a 1.2 V supply. Compared with the traditional structure VCO of the same batch, the measured figure of merit (FOM) is optimized from −165.4 to −169 dB. The novel VCO demonstrates better FOM performance compared to the traditional VCO structure. Moreover, the measured output signal power offset of novel VCO is reduced by 1.8 dBm, which will contribute to the improvement in the yield of chip manufacturing.

Low-Dose CT for Craniosynostosis: Preserving Diagnostic Benefit with Substantial Radiation Dose Reduction.

Given the positive impact of early intervention for craniosynostosis, CT is often performed for evaluation but radiation dosage remains a concern. We evaluated the potential for substantial radiation dose reduction in pediatric patients with suspected craniosynostosis. CT projection data from pediatric patients undergoing head CT for suspected craniosynostosis were archived. Simulated lower-dose CT images corresponding to 25%, 10%, and 2% of the applied dose were created using a validated method. Three neuroradiologists independently interpreted images in a blinded, randomized fashion. All sutures were evaluated by using 3D volume-rendered images alone, and subsequently with 2D and 3D images together. Reference standards were defined by reader agreement by using routine dose and 2D and 3D images. Performance figures of merit were calculated based on reader response and confidence. Of 33 pediatric patients, 21 had craniosynostosis (39 positive sutures and 225 negative sutures). The mean volume CT dose index was 15.5 ± 2.3 mGy (range, 9.69-19.38 mGy) for the routine dose examination. Average figures of merit for multireader analysis ranged from 0.92 (95% CI, 0.90-0.95) at routine pediatric dose to 0.86 (95% CI, 0.79-0.94) at 2% dose using 3D images alone. Similarly, pooled reader figures of merit ranged from 0.91 (95% CI, 0.89-0.95) at routine pediatric dose to 0.85 (95% CI, 0.76-0.95) at 2% dose using 2D and 3D images together. At 25% and 10% dose, 95% CI of the difference in figures of merit from routine dose included 0, suggesting similar or noninferior performance. For pediatric head CT for evaluation of craniosynostosis, dose reductions of 75%-90% were possible without compromising observer performance.

Model-Based Conceptual Design Optimization Methods: Disaggregated Weather System Follow-On

The future of space-based defense weather systems is uncertain due to the cancellation of the National Polar-Orbiting Operational Environmental Satellite System and Defense Weather Satellite System programs. The U.S. Department of Defense Weather Satellite Follow-On program has been identified as the follow-on program and a potential pathfinder for the concept of disaggregation. The concept of disaggregation has the potential to reduce costs and increase system resiliency. However, current research literature does not address a systematic method for performing conceptual trades between large multifunction and small functionally cohesive spacecraft. A multifunction/multiorbit disaggregated space-system optimization methodology is proposed and applied to the weather system follow-on conceptual architecture problem. Real-coded mixed-integer optimization techniques are implemented to identify, assess, and compare alternative space-based weather system conceptual architectures. The resulting cost and performance figures of merit are analyzed to assess disaggregated space-based weather constellation cost effectiveness. The potential estimated life-cycle cost savings of approximately 3 billion U.S. dollars are modeled for a disaggregated weather system follow-on program versus a Defense Weather Satellite System analogous architecture. The resulting analysis is intended to demonstrate the applicability of the disaggregated integral system concept optimization methodology to assess multifunction, multiorbit disaggregation problems.

An Exploration on the Suitability of Airborne Carbonyl Compounds Analysis in relation to Differences in Instrumentation (GC-MS versus HPLC-UV) and Standard Phases (Gas versus Liquid)

The relative performance figure of merits was investigated for the two most common analytical methods employed for carbonyl compounds (CC), for example, between high performance liquid chromatography (HPLC)-UV detector (with 2,4-dinitrophenylhydrazine (DNPH) derivatization) and thermal desorption (TD)-gas chromatography (GC)-mass spectrometry (MS) (without derivatization). To this end, the suitability of each method is assessed by computing the relative recovery (RR) between the gas- and liquid-phase standards containing a suite of CC such as formaldehyde (FA), acetaldehyde (AA), propionaldehyde (PA), butyraldehyde (BA), isovaleraldehyde (IA), and valeraldehyde (VA) along with benzene (B) as a recovery reference for the GC method. The results confirm that a TD-GC-MS is advantageous to attain the maximum recovery for the heavier CCs (i.e., with molecular weights (MW) above BA−MW ≥ 74). On the other hand, the HPLC-UV is favorable for the lighter CCs (like FA and AA) with the least bias. Such compound-specific responses for each platform are validated by relative ordering of CCs as a function of response factor (RF), method detection limit (MDL), and recovery pattern. It is thus desirable to understand the advantages and limitations of each method to attain the CC data with the least experimental bias.

Methodology for vetting heavily doped semiconductors for intermediate band photovoltaics: A case study in sulfur-hyperdoped silicon

We present a methodology for estimating the efficiency potential for candidate impurity-band photovoltaic materials from empirical measurements. This methodology employs both Fourier transform infrared spectroscopy and low-temperature photoconductivity to calculate a “performance figure of merit” and to determine both the position and bandwidth of the impurity band. We evaluate a candidate impurity-band material, silicon hyperdoped with sulfur; we find that the figure of merit is more than one order of magnitude too low for photovoltaic devices that exceed the thermodynamic efficiency limit for single band gap materials.

TU‐E‐134‐01: Radiography & Fluoroscopy: An Update On Imaging Detector Technologies

Part 1. Developments in Imaging Receptors and Applications in Projection X‐Ray Imaging Speaker: John Yorkston, Carestream Health In the last decade there has been an explosion in the number of digital projection x‐ray acquisition systems available in the marketplace. There has been an accompanying explosion in the terminology describing the different x‐ray detector technologies used in the different commercial systems. Various companies use similar nomenclature to describe systems that incorporate markedly different detector technologies, while others use different terminology to describe essentially the same technology. This lecture will review the most common digital projection x‐ray detector technologies, such as photo‐stimulable phosphors, “flat‐panel” and CCD/CMOS detectors, with a focus on identifying the differentiating aspects of their design and capabilities. Particular attention will be paid to the similarities and differences in the detector's fundamental imaging components with a view to explaining the range of imaging capabilities of the different approaches. The lecture will also discuss the emergence of “advanced application” enabled systems, such as dual energy, tomosynthesis and “photon counting” capabilities, and review the characteristics of the detector technologies that determine their functionality. The lecture will conclude with a short review of some of the exciting new detector and imaging system developments that will begin to be introduced into the clinical environment in the coming years. Part 2: State of the Art and New Trends in Computed‐Tomography Detector Technology, and Enabled Applications Speaker: Ami Altman, Philips Healthcare Over the last two decades CT detection evolved to support three major CT imaging trends: increasing number of slices and axial coverage, increasing rotation and acquisition speed, and patient dose reduction. Advanced solid state detectors, segmented to isolated detection pixels, read simultaneously in parallel by miniaturized electronics, have been the main technology enablers for these trends. In recent years, some niche CT types, categorized as Cone‐Beam CT, especially in association with online verification of radiation therapy, have been using Flat‐Panel detectors practiced in digital & interventional X‐Ray radiography and fluoroscopy. Finally, very new trends related to spectral CT lead to the pursuit of spectral‐detector solutions, with some published results. For this purpose, Direct‐Conversion photon‐counting detectors have been investigated intensively, in recent years. The goal of this talk is to review current and state of the art CT detectors, along with their performance figure of merit, and the clinical applications enabled by them. In addition, the new trends of spectral radiation detectors, especially those based on photon‐counting direct‐converting material are reported. The major components current CT detector arrays are described along with their unique features enabling them to meet the requirements of a fast‐rotating Multi‐Slice CT, and its applications. This include the scintillator arrays converting X‐Ray to visible light, the photodiode arrays that converts visible light to electric current, the electronic readout for signal digitization, and the anti‐scatter grid. The various approaches to implement a large area detector array for CT scanners are described, along with the main required calibrations and corrections needed for these detectors. Few specific types of spectral detectors for CT are discussed, with emphasis on photon‐counting. The main issues associated with these detectors are reviewed, especially the capability to tolerate CT high flux. Various solutions proposed by different groups are discussed along with their advantages and drawbacks. Clinical applications and procedures, enabled by the various CT detectors types are reviewed and discussed with specific examples. Major differences between the imaging features: MTF, DQE, and CNR, of the various CT detectors types are presented. CT scanners continue to be the leading imaging modality in use, for its evolving and new capabilities, scanning speed, and availability. The enabling of its continuously emerging new clinical applications is, to a large extent, due to the evolutions and revolutions in its detection system over the last two decades.Learning Objectives:1. Identify and understand the differentiating features of different digital projection x‐ray detector technologies2. Understand the impact of detector design on system imaging performance3. Appreciate the detector capabilities that enable advanced applications4. Develop an awareness of future detector/system capabilities5. Understanding the clinical advantages and opportunities associated with current and future CT detection systems6. Understanding some of the limitations of the various CT detectors types and how to take them in account in decision making in applying CT scanners for different clinical procedures and needs.Conflict of Interest: John Yorkston is an employee of Carestream Health Ami Altman is an employee of Philips Healthcare Carestream Health Inc, Philips Healthcare

Optimal photon-pair single-mode coupling in narrow-band spontaneous parametric downconversion with arbitrary pump profile

A theoretical investigation of the performance of single-mode coupled spontaneous parametric downconversion sources is proposed, which only requires very few assumptions of practical interest: quasi-degenerate collinear generation and narrow bandwidth obtained through spectral filtering. Other assumptions, such as pump-beam spatial and temporal envelopes, target single-mode profile and size, and nonlinear susceptibility distribution, are only taken into account in the final step of the computation, thus making the theory general and flexible. Figures of merit for performance include absolute coupled brightness and conditional coupling efficiency. Their optimization is investigated using functions that only depend on dimensionless parameters, so that the results provide the best experimental configuration for a whole range of design choices (e.g., crystal length, pump power, etc.). A particular application of the theory is validated by an experimental optimization obtained under compatible assumptions. A comparison with other works and proposals for numerically implementing the theory under less stringent assumptions is also provided.

Design of Low-phase Noise, Low-power Ring Oscillator for OC-48 Application

A low-power, low-phase noise, high tuning range, and fully integrated inductorless RC-VCO (voltage-controlled oscillator) for OC-48 application is designed and simulated in standard 0.18 μm CMOS technology. The proposed inductorless RC-VCO has a simulated phase noise of −141 dBc/Hz at 1 MHz offset from the carrier frequency of 2.4 GHz, with a bias current of 605 μA and voltage headroom of 1.8 V. It has 50% tuning range at 2.4 GHz of operating frequency and consumes 1.09 mW of power. This RC-VCO shows a figure of merit performance of −208.2 dBc/Hz at the desired frequency.

CMOS Prescaler(s) With Maximum 208-GHz Dividing Speed and 37-GHz Time-Interleaved Dual-Injection Locking Range

To enable CMOS prescaler(s) for submillimeter-wave radio-frequency synthesis, we present a new dynamic frequency divider topology according to a time-interleaved dual-injection locking scheme. Consequently, the prototype prescalers implemented with 65-nm CMOS technology have demonstrated ultra high operation speeds up to 208 GHz, with ultra wide locking range up to 37 GHz, with 2.5-mW power consumption. The achieved performance figure of merit (FOM) [i.e., (speed X range)/power in GHz2/mW] is roughly an order of magnitude higher than that of the state of the art.

Electrical conductivity and defect equilibria of Pr0.1Ce0.9O2−δ

Praseodymium-cerium oxide (PCO) solid solutions exhibit mixed ionic electronic conductivity (MIEC) behavior in a relatively high and readily accessible oxygen partial pressure (P(O(2))) regime and as such serve as a model system for investigating the correlation between thermodynamic and kinetic properties and performance figures of merit in the areas of high temperature energy conversion, automotive control, and gas sensing applications. In this paper, we present measurements on the non-stoichiometry of Pr(0.1)Ce(0.9)O(2-δ) and develop a defect equilibria model to predict the dependence of the concentration of all the dominant charge carriers on temperature, P(O(2)), and Pr fraction. The predictive model is then employed to describe the measured electrical conductivity and oxygen nonstoichiometry whereby pre-exponentials and enthalpies of defect formation and migration are extracted.

Multiple Gate Field-Effect Transistors for Future CMOS Technologies

This is a review paper on the topic of multiple gate field effect transistors: MuGFETs, or FinFETs, as they are called. First, the motivation behind multiple gate FETs is presented. This is followed by looking at the evolution of FinFET technologies; the main flavors (variants) of multigate FETs; and their advantages/disadvantages. The physics and technology of these devices is briefly discussed. Results are then presented which show the performance figures of merit of FinFETs, and their strengths and weaknesses. Finally, a perspective on the future of the FinFET technology is presented. This paper is a judicious mix of the author’s original work on FinFETs and other contemporary know-how available in the literature on this topic.