Cost-sensitive Applications Research Articles

Effect of Heat Treatments on Microstructure and Mechanical Properties of Fe-Mn-Ni-Al-Gd Shape Memory Alloy

There are significant scientific and industrial efforts to develop and optimize Iron-based shape memory alloys (SMA) such as FeMnNiAl for cost-sensitive applications. This alloy system shows shape memory and superelastic properties across a large temperature range. However, many studies have pointed out the need for rather complex thermo-mechanical treatments for the optimization of the SMA properties. In addition, works considering the effects of alloying on the development of microstructures that are more conducive to pseudo-elasticity in this system remain limited. Hence, systematic studies aiming at the investigation of the microstructural evolution of the FeMnNiAl(Gd) system are of great interest. In this study, solution heat treatment is done to tune the microstructure for optimum mechanical properties. The effect of phase distribution on mechanical properties is investigated at different heat treatments. Whereas cyclic heat treatment induced abnormal grain growth (AGG) in all samples, so large grains were obtained. The phase variation and elemental composition are analyzed by X-ray diffraction and Energy Dispersive Spectroscopy, respectively. The microstructure and phase distribution are observed using Scanning Electron Microscope and then related to the microhardness results. The microstructure has a good correlation with mechanical properties where the fine distribution of phases results in a higher hardness number.

Three-dimensional hybrid fusion networks for current-based bearing fault diagnosis

Abstract Intelligent fault diagnosis (IFD) techniques commonly use vibration-based measurements to perform health monitoring of critical rotating components in industrial systems. However, these vibration-based approaches may be limited in cost-sensitive applications, because the installation of vibration sensors is inconvenient and vibration sensors are expensive. Considering the difficulties of IFD using only current-related information from the motor current signal (MCS), this paper proposes a three-dimensional hybrid-fusion neural network (3D-HFN) that can automatically perform both data- and feature-level fusion of multi-phase current signals for MCS-based IFD of the rolling bearing. The 3D-HFN consists of the multivariate variational mode decomposition (MVMD) and an improved three-dimensional convolution neural network (3D-CNN). Firstly, MVMD is proposed to process multi-phase current signals, which adaptively acquire several intrinsic mode functions with mode-alignment properties. Subsequently, signal-to-image conversion and 3D stacking methods are used to construct 3D-like data in the current-phase dimension, which can fully preserve the interaction relationship between different phases using data-level fusion. Finally, an improved 3D-CNN with multiscale feature fusion and the smooth maximum unit is proposed to learn the 3D-like data and identify different health conditions for the rolling bearing. An open-source dataset with composite bearing faults is used to validate the merits of the proposed method. Experimental results show that the proposed approach has achieved more reliable diagnosis performance than other hand-crafted or 2D/3D-CNN-based algorithms in MCS-based IFD of the rolling bearing.

Development of a Low-Cost Lightweight Advanced K-Band Horn Antenna With Charge-Programmed Deposition 3-D Printing

We present the first development of a lightweight, monolithic, circularly polarized (CP) K-band horn antenna developed using a novel charge-programmed deposition (CPD) manufacturing process. The horn has a polymer body with metalized interior surface. The CPD process creates complex geometries with programmed charged surfaces via three-dimensional (3D) printing and allows the deposition of metallics anywhere within the 3D layout. Intricate internal structures of the horn, such as the meandered waveguide transition and the septum polarizer, were successfully constructed. Measured patterns of the horn demonstrated great agreement with simulations, with an axial ratio below 2.5 dB in the range of 17.5 - 20.5 GHz. The total weight of the horn is only 11 g, marking a significant weight reduction of around 80% compared to traditionally fabricated horns of similar size and operating frequency. The low-cost and lightweight horn antennas enabled by this process can significantly benefit mass- and cost-sensitive applications such as small satellite and CubeSat missions.

Advanced Pressure Compensation in High Accuracy NDIR Sensors for Environmental Studies

Measurements of atmospheric gas concentrations using of NDIR gas sensors requires compensation of ambient pressure variations to achieve reliable result. The extensively used general correction method is based on collecting data for varying pressures for a single reference concentration. This one-dimensional compensation approach is valid for measurements carried out in gas concentrations close to reference concentration but will introduce significant errors for concentrations further away from the calibration point. For applications, requiring high accuracy, collecting, and storing calibration data at several reference concentrations can reduce the error. However, this method will cause higher demands on memory capacity and computational power, which is problematic for cost sensitive applications. We present here an advanced, but practical, algorithm for compensation of environmental pressure variations for relatively low-cost/high resolution NDIR systems. The algorithm consists of a two-dimensional compensation procedure, which widens the valid pressure and concentrations range but with a minimal need to store calibration data, compared to the general one-dimensional compensation method based on a single reference concentration. The implementation of the presented two-dimensional algorithm was verified at two independent concentrations. The results show a reduction in the compensation error from 5.1% and 7.3%, for the one-dimensional method, to -0.02% and 0.83% for the two-dimensional algorithm. In addition, the presented two-dimensional algorithm only requires calibration in four reference gases and the storing of four sets of polynomial coefficients used for calculations.

Digital Control and Demodulation Algorithm for Compact Open-Loop Fiber-Optic Gyroscope.

With the advantages of small size, low cost, and moderate accuracy, an open-loop fiber-optic gyroscope (FOG) has a wide range of applications around control and automation. For the most cost-sensitive applications, a simple and stable digital algorithm with a reduced control-circuit volume and cost is highly desirable to realize high-precision control of a FOG. In this work, a new algorithm for an open-loop FOG is proposed based on the discrete multi-point demodulation in the sinusoidal modulation period. Utilizing this algorithm, stable control and angular velocity calculation of a gyro are realized with effectively suppressed gyro error. The use of this algorithm greatly reduces the requirements for processing power and simplifies the gyro circuit. Based on this algorithm, a digital FOG with a volume of only 25 × 20 × 40 mm3 achieves a bias instability of less than 0.15°/h, an angle random walk (ARW) of less than 0.015°/√h, a start-up time of less than 1 s, and a 3 dB bandwidth beyond 160 Hz. This low-cost, compact, and high-performance gyro is sufficient to satisfy the requirements of applications in the navigation and control fields such as unmanned driving.

Carbon fibers derived from liquefied and fractionated poplar lignins: The effect of molecular weight.

Lignin recovered from poplar, a key woody biomass resource proposed for lignocellulosic refineries, was investigated for conversion into carbon fibers. Aqueous solutions of ethanol at selected temperatures and compositions, where the requisite solvent and liquefied-lignin phases form, were used to purify and fractionate hybrid poplar (HP) lignin using the Aqueous Lignin Purification with Hot Agents (ALPHA) process. Sugars (<0.1%) and ash (0.01± 0.01%) content of the highest molecular weight fraction (Mw= 52kDa) approached the limits of detection. This 52kDa fraction could be dry spun with excellent stability and was subsequently converted into carbon fibers having strength (1.1± 0.2 GPa) and modulus (78± 8 GPa) essentially double those previously achieved with neat poplar and other hardwood lignins. Of equal importance, stabilization times were decreased by a factor of five. Such stabilization and strength/modulus improvements are essential for reducing the overall manufacturing cost of carbon fibers being proposed for cost-sensitive applications.

Experimental Demonstration of Constant-Envelope OFDM to Reduce Intermodulation Impairments and Increase Robustness Against Fiber Nonlinearities

Direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems have been proposed as a well-suited solution for cost-sensitive applications, but also for metro/regional optical links. In this article, we experimentally demonstrate tolerance enhancements of constant-envelope OFDM (CE-OFDM) signals towards Mach–Zehnder modulator (MZM) intermodulation impairments and fiber nonlinear Kerr effects. The additional tolerance is achieved by the reduced peak-to-average power ratio (PAPR) of CE-OFDM signals, unlike conventional OFDM signals that inherently possess high PAPR values and therefore, are prone to distortions induced by the above-mentioned impairments. The experiments show that the transmission of CE-OFDM signals with PAPR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$=3$</tex-math></inline-formula> dB over 1000 km of dispersion-uncompensated standard single-mode fiber (SSMF) is successfully accomplished. The proper choice of the MZM bias point, as well as the electrical phase modulation index, provides link length enlargements at the same bit error rate. An enlargement around 320 km of SSMF was achieved with an optical launch power of 10 dBm and with a guard-band of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx 16\%$</tex-math></inline-formula> of the signal bandwidth when compared to conventional DDO-OFDM systems.

Design and Analysis of a Doubly Salient Wound Field Starter Generator for Cost-Effective Automobile Application

Doubly salient wound field machines exhibit the advantages of robust structure and controllable flux, and hence have been utilized as generators in applications of automobiles and renewable energy. However, the inherent unbalanced phase back-electromotive force (EMF) waveform caused by the asymmetric flux path brings difficulties for precise control and smooth operation. To solve the problem caused by unbalanced back-EMF waveform in conventional doubly salient machines, this paper presents a novel doubly salient wound field machine with balanced and symmetrical back-EMF waveform as starter generator in automobile application. The robust structure and the controllable flux are inherited, while the magnetless feature makes it promising for cost-sensitive applications. The proposed machine can be operated as an assistant motor for torque boosting at start-up stage, as well as a power recycling generator for battery charging at steady state. It is revealed that the proposed wound field machine exhibits similar cost, comparable torque density, improved torque ripple, and higher efficiency than the switched reluctance machine. Finally, the proposed prototype is fabricated, and dynamic experiment is conducted to validate the feasibility for automobile starter generator application.

Metal Assisted Chemical Etch of Polycrystalline Silicon

Abstract Metal-assisted chemical etching (MacEtch) of silicon shows reliable vertical anisotropic wet etching only in single-crystal silicon, which limits its applications to a small number of devices. This work extends the capabilities of MacEtch to polysilicon which has potential to enable high-volume and cost-sensitive applications such as optical metasurfaces, anodes for high capacity and flexible batteries, electrostatic supercapacitors, sensors, nanofluidic deterministic lateral displacement devices, etc. This work presents a MacEtch of polysilicon that produces nanostructure arrays with sub-50 nm resolution and anisotropic profile. The three demonstrated structures are pillars of 5:1 aspect ratio and 50 nm spacing for comparison to single crystal silicon MacEtch literature, pillars of 30 nm spacing, and a diamond pillar array with sharp corners to establish resolution limits of polysilicon MacEtch.

Deep-learning-enabled high-performance full-field direct detection with dispersion diversity.

Data center interconnects require cost-effective photonic integrated optical transceivers to meet the ever-increasing capacity demands. Compared with a coherent transmission system, a complex-valued double-sideband (CV-DSB) direct detection (DD) system can minimize the cost of the photonic circuit, since it replaces two stable narrow-linewidth lasers with only a low-cost un-cooled laser in the transmitter while maintaining a similar spectral efficiency. In the carrier-assisted DD system, the carrier power accounts for a large proportion of the total optical signal power. Reducing the carrier to signal power ratio (CSPR) can improve the information-bearing signal power and thus the achievable system performance. To date, the minimum required CSPR is ∼7 dB for all the reported CV-DSB DD systems having electrical bandwidths of approximately half of baud rates. In this paper, we propose a deep-learning-enabled DD (DLEDD) scheme to recover the full optical field of the transmitted signal at a low CSPR of 2 dB in experiment. Our proposal is based on a dispersion-diversity receiver with an electrical bandwidth of ∼61.0% baud rate and a high tolerance to laser wavelength drift. A deep convolutional neural network enables accurate signal recovery in the presence of a strong signal-signal beat interference. Compared with the conventional method, the proposed DLEDD scheme can reduce the optimum CSPR by ∼8 dB, leading to a significant signal-to-noise ratio improvement of ∼5.8 dB according to simulation results. We experimentally demonstrate the optical field reconstruction for a 28-GBaud 16-ary quadrature amplitude modulation signal after 80-km single-mode fiber transmission based on the proposed DLEDD scheme with a 2-dB optimum CSPR. The results show that the proposed DLEDD scheme could offer a high-performance solution for cost-sensitive applications such as data center interconnects, metro networks, and mobile fronthaul systems.

Fiber optic sensors based on circular and elliptical polymer optical fiber for measuring refractive index of liquids

Measurement of refractive index (RI) is required in laboratory and industry for many applications, especially that of liquids. Though there have been commercial products for precision RI measurement, miniaturized and low-cost solutions are still desired and thus have attracted a great number of researchers’ attention. Among various competitive technologies, fiber optic sensors based on macro-bending loss (e.g. U-shaped fibers) exhibit advantages including facile fabrication and low cost. In order to make this kind of sensors more reliable for real applications, this study proposes to bend a section of pristine polymer optical fibers around circular or elliptical solid slices to form the sensor tip for sensing RI of liquids. Such configuration can precisely and firmly fix the geometry of the bent fiber, while most bent fibers in U-shaped sensors previously reported are free-standing and their shapes are prone to change in long-term usage. Impacts of bending shape and radius on sensors’ sensitivity to RI are investigated. Among all fabricated sensors, the highest sensitivity is −66.58 dB/RIU in the RI range of 1.33–1.46, which is yielded by the sensor consisted of POF in elliptical shape in diameters of 5 and 3 mm. It is lower than those of U-shaped silica fibers bent in smaller diameters or those of cladding-processed U-shaped sensors. However, the proposed sensor has advantages in precise geometry control and facile fabrication, making it competitive to other RI sensing techniques for those cost-sensitive applications. Besides, the geometry of the fiber can be optimized to further enhance sensors’ sensitivity in future.

A 125 μm × 245 μm Mainly Digital UHF EPC Gen2 Compatible RFID Tag in 55 nm CMOS Process

This paper presents a compact and largely digital UHF EPC Gen2-compatible RFID implemented using digital IP blocks that are easily portable. This is the first demonstration of a digital Gen2-compatible RFID tag chip with an area of 125 μm and -2 dBm sensitivity operating in the 860-960MHz band. It is enabled by a) largely standard cell-based digital implementation using dual-phase RF-only logic approach, b) near-threshold voltage operation, and c) elimination of area intensive, complex, and less scalable rectifiers, storage capacitors, and power management units used in conventional RFID tags. In this demonstration, all but six cells were directly used from the standard cell library provided by the foundry. This makes it suitable for cost-sensitive applications, and as embedded RFIDs for tagging counterfeit Integrated Circuits (ICs).

Induction Machine On-Line Parameter Identification for Resource-Constrained Microcontrollers Based on Steady-State Voltage Model

This paper presents a new, computationally modest on-line identification method for the simultaneous estimation of the rotor resistance and magnetizing inductance of an induction machine suitable for electric drives that use an indirect field-oriented control strategy (IFOC), and their control hardware is equipped with a resource-constrained microcontroller. Such drives can be found both in the manufacturing industry and railway traction vehicles in the thousands, having either older control hardware that cannot cope with computationally excessive identification methods or being in cost-sensitive applications, thus being equipped with a low-cost microcontroller. IFOC is a very common control strategy for such drives due to its good dynamic properties and comparatively simple implementation. However, it is sensitive to inaccuracies of rotor resistance and magnetizing inductance. These two parameters change during the operation of the drive, being influenced by the temperature, frequency, and saturation of the magnetic circuit. Improper values of parameters in the controller can degrade the performance of IFOC, resulting in slower acceleration or unnecessary oversaturation of the machine. Respecting these changes can therefore bring significant benefits such as the good dynamic properties of the drive, which can shorten operations in the manufacturing industry or travel times of vehicles. A number of on-line identification methods for monitoring the parameter changes have been published so far, but the majority of them are demanding on microcontroller time or its memory. The proposed method, on the contrary, is comparatively simple and thus easy for implementation with low requirements to the microcontroller. Therefore, it is suitable for both upgrades of existing drives or new low-cost applications. Derivation of the method from the mathematical model and the final algorithm for the microcontroller are presented. The performance of the proposed method is validated with experimental results obtained with a 3.5 kW induction machine drive with an industrial microcontroller during a warming test and under various loads and frequencies.

Phased array radar system design based on single-send and multiple-receive for LSS-UAV target

In order to improve the precision of radar target positioning, the phased array frequency modulated continuous wave (FMCW) radar system based on single-send and multiple-receive is proposed for low altitude, slow speed, small Unmanned Aerial Vehicle (LSS-UAV) target. The much lower-cost passive electronically scanned array (PESA) radar technology has been employed for the azimuth electronically scanning. In addition, wide beam scanning beam of elevation direction is used to further expand the range of space coverage. Phase-comparison method is adopted to high-precision angle measurement of elevation direction in interferometer angle measurement system with dual distributed receivers. As a result, the novel radar system possesses the abilities of Doppler velocity measurement and linear FMCW distance measurement, as well as the high precision angle measurement at the same time. It can provide long distance, wide range, all-weather/time detection accurate target location information for optical system and electronic interception system to detect LSS-UAV targets for some more cost-sensitive applications in the homeland security market.

Hard X-ray and [formula omitted]-ray spectroscopy at high temperatures using a COTS SiC photodiode

A commercial-off-the-shelf (COTS) silicon carbide (4H-SiC) UV photodiode was electrically characterized and investigated as a low-cost spectroscopic photon counting detector of X-rays and γ-rays. The detector was coupled to a custom-built low-noise charge-sensitive preamplifier, and illuminated by 55Fe and 109Cd radioisotope X-ray sources and an 241Am radioisotope γ-ray source, thus providing photon energies from 5.9 keV to 59.5 keV. The detector and preamplifier were operated uncooled at temperatures between 20 °C and 100 °C. The energy resolution (full width at half maximum, FWHM) of the spectrometer was found to be 1.66 keV ± 0.15 keV at 5.9 keV and 22.16 keV, and 1.83 keV ± 0.15 keV at 59.5 keV when operated at 20 °C. At a temperature of 100 °C, the FWHM were 2.69 ± 0.25 keV, 2.65 keV± 0.25 keV, and 3.30 keV ± 0.30 keV, at the same energies. Shaping time noise analysis found dielectric noise to be the dominant noise source, except when long amplifier shaping times were used at high temperatures when white parallel noise dominated. Noise associated with incomplete charge collection was found to be negligible at energies up to 22.16 keV and at temperatures ≤60 °C; but incomplete charge collection noise could not be discounted when the spectrometer was operated at higher temperature (80 °C) and at higher energy (59.5 keV). Although the detector was thin (and thus inefficient at high photon energies) the low cost and commercial availability of the SiC device make it an attractive prospect for use in cost-sensitive applications such as university-led CubeSat missions.

Low-Cost, Large-Scale Production of the Anti-viral Lectin Griffithsin.

Griffithsin, a broad-spectrum antiviral lectin, has potential to prevent and treat numerous viruses including HIV, HCV, HSV, SARS-CoV, and SARS-CoV-2. For these indications, the annual demand for Griffithsin could reach billions of doses and affordability is paramount. We report the lab-scale validation of a bioprocess that supports production volumes of >20 tons per year at a cost of goods sold below $3,500/kg. Recombinant expression in engineered E. coli enables Griffithsin titers ∼2.5 g/L. A single rapid precipitation step provides > 90% yield with 2-, 3-, and 4-log reductions in host cell proteins, endotoxin, and nucleic acids, respectively. Two polishing chromatography steps remove residual contaminants leading to pure, active Griffithsin. Compared to a conventional one this process shows lower costs and improved economies of scale. These results support the potential of biologics in very large-scale, cost-sensitive applications such as antivirals, and highlight the importance of bioprocess innovations in enabling these applications.

Coherent Measurements With MIMO Radar Networks of Incoherent FMCW Sensor Nodes

This work introduces a method for coherent multi-in multi-out (MIMO) processing over a network of frequency-modulated continuous wave (FMCW) radar sensor nodes with independent signal synthesis. The coherency between the bistatic channels is established algorithmically based on the frequency and phase-offset estimation from pairs of sensor nodes and subsequent least-squares estimation on the overdetermined equation system. For the chirp-sequence radar, the proposed processing allows range and speed measurements, as offsets are estimated and corrected for each individual ramp. The applicability of the method is demonstrated in a prototypical setup of a radar network with three sensor nodes comprising integrated 122-GHz transceivers. The obtained bistatic phase precisions of <; 0.1 rad approximately match those of the monostatic measurements of the same radar nodes. For a sequence of 30 ramps of 1-ms duration, this translates to ambiguous range precisions <; 10 μm and speed precision <; 1 mm/s. The absence of wired high-frequency links between the nodes makes the approach well suited for shortrange radar networks in cost-sensitive applications.

Pulse Width Insensitive Design and Verification Methods

Many embedded controllers have some critical system states that depend on an asynchronous event. Currently handling them in design depends on the availability of always-on slow clocks. In this paper we present a generic asynchronous design scheme that doesn't require a clock and ensure a reliable functionality without associated deadlock scenarios sensitive to exact arrival times of asynchronous events. This is enabled by a novel pulse width insensitive design method, which also requires unconventional verification methodology that ensures thorough and comprehensive pre-silicon design quality. These have been applied on the latest, ultra-low cost embedded micro-controller design targeted for cost sensitive applications.

GaN HEMTs on Si With Regrown Contacts and Cutoff/Maximum Oscillation Frequencies of 250/204 GHz

This work demonstrates the high-frequency and high-power performance capacity of GaN high electron mobility transistors (HEMTs) on Si substrates. Using a T-gate and ${n}^{++}$ -GaN source/drain contacts, the InAlN/GaN HEMT with a gate length of 55 nm and a source-drain spacing of 175 nm shows a maximum drain current ${I}_{{D,MAX}}$ of 2.8 A/mm and a peak transconductance ${g}_{m}$ of 0.66 S/mm. The same HEMT exhibits a forward-current-gain cutoff frequency ${f}_{T}$ of 250 GHz and a maximum frequency of oscillation ${f}_{{MAX}}$ of 204 GHz. The ${I}_{{D,MAX}}$ , peak ${g}_{m}$ and ${f}_{T} -{f}_{{MAX}}$ product are among the best reported for GaN HEMTs on Si, which are very close to the state-of-the-art depletion-mode GaN HEMTs on SiC without a back barrier. Given the low cost of Si and the high compatibility with CMOS circuits, GaN HEMTs on Si prove to be particularly attractive for cost-sensitive applications.

Compact Mid-Infrared Gas Sensing Enabled by an All-Metamaterial Design.

The miniaturization of mid-infrared optical gas sensors has great potential to make the "fingerprint region" between 2 and 10 μm accessible to a variety of cost-sensitive applications ranging from medical technology to atmospheric sensing. Here we demonstrate a gas sensor concept that achieves a 30-fold reduction in absorption volume compared to conventional gas sensors by using plasmonic metamaterials as on-chip optical filters. Integrating metamaterials into both the emitter and the detector cascades their individual filter functions, yielding a narrowband spectral response tailored to the absorption band of interest, here CO2. Simultaneously, the metamaterials' angle-independence is maintained, enabling an optically efficient, millimeter-scale cavity. With a CO2 sensitivity of 22.4 ± 0.5 ppm·Hz-0.5, the electrically driven prototype already performs at par with much larger commercial devices while consuming 80% less energy per measurement. The all-metamaterial sensing concept offers a path toward more compact and energy-efficient mid-infrared gas sensors without trade-offs in sensitivity or robustness.