Small Footprint Research Articles

Industrial application of a low-cost structural health monitoring system in large-scale airframe tests

A small, novel, integrated SHM system has been deployed during full-scale testing of a wing fatigue test for several weeks and a fuselage pressurisation test for several months. Complementary NDE measurement techniques were combined, with inputs from visible and infrared optical sensors, as well as resistance strain gauges. Sensor units were deployed at regions of interest and integrated board computers permitted near real-time data processing. The outputs were full-field measurement datasets from digital image correlation and thermoelastic stress analysis systems. Changes in these datasets in the regions of interest were successfully quantified using orthogonal decomposition and were indicative of changes in the condition of the structure. The results from these case studies demonstrate that this system can be successfully deployed in spatially restricted areas within airframe structures to monitor crack growth. The low cost and small footprint of the system presents the opportunity for installation of arrays of similar sensors for both test and in-service data collection. Near real-time data processing would allow timely reporting to service engineers, informing maintenance or operational decisions.

Optimal arrangement of heliostat field based on simulated annealing algorithm

In this study, a simulated annealing algorithm is proposed as an optimisation method for the mirror arrangement of heliostat mirrors in a tower solar thermal power plant. Firstly, the optimal number and position of heliostats in the whole mirror field in radial staggered layout (EB unobstructed layout) were solved using simulated annealing method. Then further optimisation, i.e. changing the mirror width, mirror height and mounting height of the heliostats and solving for the optimal number and position of heliostats using simulated annealing again, resulted in an increase in the number of heliostats in the optimised mirror field by 77.92% but a decrease in the total area by 18.77%, and an increase in the average annual thermal power output per unit area of the mirrors by 4.76%. Therefore, this result shows that the heliostat field optimised using the simulated annealing algorithm has a higher efficiency and a smaller footprint.

Efficient Parametric Frequency Conversions in Chalcogenide‐Loaded Etchless Thin‐Film Lithium Niobate Waveguides

AbstractParametric frequency conversion based on second‐order nonlinearity (χ(2)) is critical in many applications. The implementation of second‐order nonlinearity on integrated photonic platforms, in particular on the lithium niobate‐on‐insulator platform, has attracted considerable interest due to its low power consumption and small footprint. However, high‐efficiency on‐chip parametric frequency conversion remains challenging due to fabrication complexity. Here, efficient parametric frequency conversions via modal phase matching (MPM) in etchless thin‐film lithium niobate (TFLN)‐chalcogenide glass (ChG) hybrid waveguides fabricated by a simplified process free from domain engineering and etching of TFLN are proposed and demonstrated. An overall conversion efficiency of 25.55% W−1 for second‐harmonic generation is experimentally achieved in a 1‐cm‐long waveguide, significantly over the reach of the etchless counterparts and in the same order of magnitude as those of the etched cases based on MPM. Broadband frequency conversion with a 3‐dB bandwidth of 57 nm is achieved based on cascaded second‐harmonic generation and difference‐frequency generation via MPM in a nanophotonic waveguide using a continuous‐wave pump. This device shows great promise for efficient on‐chip parametric frequency conversion, enabling a wide range of photonic applications, and paving the way for further integration with various advanced ChG photonic devices toward on‐chip multifunctional microsystems.

M3ICRO: Machine learning-enabled compact photonic tensor core based on programmable multi-operand multimode interference

Photonic computing shows promise for transformative advancements in machine learning (ML) acceleration, offering ultrafast speed, massive parallelism, and high energy efficiency. However, current photonic tensor core (PTC) designs based on standard optical components hinder scalability and compute density due to their large spatial footprint. To address this, we propose an ultracompact PTC using customized programmable multi-operand multimode interference (MOMMI) devices, named M3ICRO. The programmable MOMMI leverages the intrinsic light propagation principle, providing a single-device programmable matrix unit beyond the conventional computing paradigm of one multiply-accumulate operation per device. To overcome the optimization difficulty of customized devices that often requires time-consuming simulation, we apply ML for optics to predict the device behavior and enable differentiable optimization flow. We thoroughly investigate the reconfigurability and matrix expressivity of our customized PTC and introduce a novel block unfolding method to fully exploit the computing capabilities of a complex-valued PTC for near-universal real-valued linear transformations. Extensive evaluations demonstrate that M3ICRO achieves a 3.5–8.9× smaller footprint, 1.6–4.4× higher speed, 9.9–38.5× higher compute density, 3.7–12× higher system throughput, and superior noise robustness compared to state-of-the-art coherent PTC designs. It also outperforms electronic digital A100 graphics processing unit by 34.8–403× higher throughput while maintaining close-to-digital task accuracy across various ML benchmarks.

A Scalable Dendritic Si‐Clad NiSn Anode via One‐Step Electrodeposition with Ultrahigh Areal Capacity for Micro Lithium‐Ion Battery

High energy density, long cyclability, and enhanced stability in a small footprint achieved through microfabrication are crucial for micro lithium‐ion batteries. Herein, a 3D Si‐clad NiSn anode characterized by a dendritic NiSn network and silicon nanoparticles is proposed. The dendritic network facilitates fast ion/electron transfer and provides expansion space for the silicon, while the uniformly distributed silicon enhances capacity and stability. The anode, scalable to the hundred‐micron scale, is fabricated via one‐step electrodeposition incorporating the dynamic template technique. This technique generates interconnected pores extending from the inner to the outer surface of the anode, facilitating electrolyte penetration and ion transport. As a result, the anodes in the Swagelok cells exhibit an ultrahigh areal capacity of up to 28.2 mAh cm−2 and an enhanced stability of 91% capacity retention after 300 cycles. The dendritic Si‐clad NiSn anode, based on microfabrication, presents an excellent opportunity to advance micro energy systems.

Influence of the inner diameter of the bottom plate on the cleaning performance of double-layer filter cartridges

Dust collectors are used in various industries to separate pollutants from the air. Filter cartridge dust collectors are favored for their stability and small footprint. However, conventional cleaning techniques make it difficult to solve the problem of incomplete cleaning of filter cartridges, which require frequent replacement. Inner cone double-layer filter cartridges are utilized to improve the incomplete cleaning of filter cartridges. The size of the inner diameter (ID) of the bottom plate is one of the main factors affecting the cleaning performance of the double-layer filter cartridge. Double-layer filter cartridges' inside flow field is investigated by numerical simulation in this work. Selection of evaluation indexes such as peak static pressure and comprehensive pressure to assess cleaning performance and analyze the effect of ID on cleaning performance. It was shown that increasing ID could optimize the upper section of the filter cartridges' static pressure distribution. Both larger (ID = 160 mm) and smaller (ID = 40 mm) filter cartridges ID possessed better bottom static pressure accumulation capacity. As the inner diameter of the bottom plate decreases, the cleaning performance increases and then decreases, and the best results were obtained at an ID of 140 mm, with a PC of 1175 Pa. Notably, IDs exceeding 160 mm have a significant negative impact on the cleaning performance of the filter cartridges.

Characterization of broadband Purcell filters with compact footprint for fast multiplexed superconducting qubit readout

Engineering the admittance of external environments connected to superconducting qubits is essential, as increasing the measurement speed introduces spontaneous emission loss to superconducting qubits, known as Purcell loss. Here, we report a broadband Purcell filter within a small footprint, which effectively suppresses Purcell loss without losing the fast measurement speed. We characterize the filter's frequency response at 4.3 K and also estimate Purcell loss suppression by finite-element-method simulations of superconducting planar circuit layouts with the proposed filter design. The filter is fabricated with 200 nm-thick niobium films and shows the measured bandwidth over 790 MHz within 0.29 mm2 of compact size owing to densely packed spiral resonators. The estimated lifetime enhancement indicates the effective protection of the qubit from Purcell loss. The presented filter design is expected to be easily integrated on existing superconducting quantum circuits for fast and multiplexed readout without occupying large footprint.

Flexible Pressure and Temperature Microsensors for Textile-Integrated Wearables

Environmental factors, such as pressure and temperature, are known to contribute to the formation of ulcers that seriously affect bedridden individuals. Researchers have proposed several technologies to achieve the long-term monitoring of those parameters, usually relying on sensing mats, which poses difficulties in correlating the measurements with specific parts of the body. In this work, we aim to develop microsensors to be integrated into patient clothing. They should be highly flexible, thin with a small footprint, and can be achieved by taking advantage of the microfabrication on polyimide (PI) thin-film substrates (total device thicknesses below 30 µm). Both resistive and capacitance transduction mechanisms were explored, targeting operation ranges of 1 to 40 kPa and 24 to 42 °C. The sensors were integrated into textiles using silicone elastomers and electrical connections based on conductive silver yarn. The experimental characterization showed a nominal capacitance of 21 pF, a sensitivity of −8.44 fF/kPa for the pressure sensors, and a 0.0021 Ω/Ω°C sensitivity of the temperature sensor (with resistance of 29 kΩ at 22 °C). The proposed approach can potentially be implemented not only in wearable devices but also in many other applications for health monitoring or human–machine interfaces.

Switchable Diffraction Pattern Based on Cascaded Metasurfaces

AbstractMetasurfaces have great advantages in the field of laser detection because of their ability to generate large amounts of point sources or various diffraction patterns. Here,cascaded metasurfaces (CM) for generating switchable spatial light distributions is utilized, which can be used for optical scanning and identifications. The light distribution is composed of several distinct diffraction patterns, and the scanning of the diffraction space is realized by multiple pixel‐scale alignment strategies between two pieces of CM. Through combining Dammann optimization and the gradient descent method, various diffraction patterns under different matching situations can be guaranteed by phase superposition. Various diffraction conditions with highly identifiable intensity distribution are guaranteed by using the optimization method. Such optical scanning devices based on CM have small footprints, high integration, flexible composition, and stable diffractive combination features. By manipulating CM to generate changeable spatial diffraction phenomenon may provide flexible modulation properties to optical scanning, measurement, and other applications.

Brewing alcohol 101: An undergraduate experiment utilizing benchtop NMR for quantification and process monitoring.

In recent years there has been a renewed interest in benchtop NMR. Given their lower cost of ownership, smaller footprint, and ease of use, they are especially suited as an educational tool. Here, a new experiment targeted at upper-year undergraduates and first-year graduate students follows the conversion of D-glucose into ethanol at low-field. First, high and low-field data on D-glucose are compared and students learn both the Hz and ppm scales and how J-coupling is field-independent. The students then acquire their own quantitative NMR datasets and perform the quantification using an Electronic Reference To Access In Vivo Concentration (ERETIC) technique. To our knowledge ERETIC is not currently taught at the undergraduate level, but has an advantage in that internal standards are not required; ideal for following processes or with future use in flow-based benchtop monitoring. Using this quantitative data, students can relate a simple chemical process (fermentation) back to more complex topics such as reaction kinetics, bridging the gaps between analytical and physical chemistry. When asked to reflect on the experiment, students had an overwhelmingly positive experience, citing agreement with learning objectives, ease of understanding the protocol, and enjoyment. Each of the respondents recommended this experiment as a learning tool for others. This experiment has been outlined for other instructors to utilize in their own courses across institutions, with the hope that a continued expansion of low-field NMR will increase accessibility and learning opportunities at the undergraduate level.

Ultraflexible Monolithic Three-Dimensional Static Random Access Memory.

Flexible static random access memory (SRAM) plays an important role in flexible electronics and systems. However, achieving SRAM with a small footprint, high flexibility, and high thermal stability has always been a big challenge. In this work, an ultraflexible six-transistor SRAM with high integration density is realized based on a monolithic three-dimensional (M3D) design. In this design, vertical stacked n-type indium gallium zinc oxide thin film transistors and p-type carbon nanotube transistors share common gate and drain electrodes, respectively, saving interlayer vias used in traditional M3D designs. This compact architecture reduces the footprint of the SRAM cell from a six-transistor to a four-transistor area, saving 33% of the area, and significantly enables the SRAM to have the highest flexibility among the reported ones, withstanding a harsh deforming process (6000 cycles of bending at a radius of 500 μm) without performance degradation. Moreover, this design facilitates the thermal stability of the SRAM under high temperature (333 K). It also exhibits great static and dynamic performance, with the highest normalized hold noise margin of 73.6%, a maximum gain of 151.2, and a minimum static power consumption of 3.15 μW in hold operation among the reported flexible SRAMs. This demonstration provides possibilities for SRAMs to be used in advanced wearable system applications.

Palm-Sized Wireless Transient Elastography System with Real-Time B-Mode Ultrasound Imaging Guidance: Toward Point-of-Care Liver Fibrosis Assessment.

Transient elastography (TE), recommended by the WHO, is an established method for characterizing liver fibrosis via liver stiffness measurement (LSM). However, technical barriers remain towards point-of-care application, as conventional TE requires wired connections, possesses a bulky size, and lacks adequate imaging guidance for precise liver localization. In this work, we report the design, phantom validation, and clinical evaluation of a palm-sized TE system that enables simultaneous B-mode imaging and LSM. The performance of this system was validated experimentally using tissue-equivalent reference phantoms (1.45-75 kPa). Comparative studies against other liver elastography techniques, including conventional TE and two-dimensional shear wave elastography (2D-SWE), were performed to evaluate its reliability and validity in adults with various chronic liver diseases. Intra- and inter-operator reliability of LSM were established by an elastography expert and a novice. A good agreement was observed between the Young's modulus reported by the phantom manufacturer and this system (bias: 1.1-8.6%). Among 121 patients, liver stiffness measured by this system and conventional TE were highly correlated (r = 0.975) and strongly agreed with each other (mean difference: -0.77 kPa). Inter-correlation of this system with conventional TE and 2D-SWE was observed. Excellent-to-good operator reliability was demonstrated in 60 patients (ICCs: 0.824-0.913). We demonstrated the feasibility of employing a fully integrated phased array probe for reliable and valid LSM, guided by real-time B-mode imaging of liver anatomy. This system represents the first technical advancement toward point-of-care liver fibrosis assessment. Its small footprint, along with B-mode guidance capability, improves examination efficiency and scales up screening for liver fibrosis.

Modeling Circle Runway to Increase Runway Capacity

Runway is a runway for airplanes to land (landing) or to fly (takeoff). Runway is a major component in an airport, it is necessary to plan a good runway. The runway at Juanda Airport uses a conventional system where the runway is rectangular. In this final project the author plans a runway with a circular runway model. The circular runway is a radical new runway design with a circular shape. With a circular runway, airport operators can operate the runway regardless of the wind direction and for all types of aircraft. Airports with circular runways have a smaller footprint than airports with conventional runways. With the existence of a circular runway, it is expected to increase runway capacity compared to conventional runway capacity. Circular runways can also allow airports to continue operating without interference from crosswinds. From the calculation results, it is found that the runway has a circumference of 9864 m. The ARFL length obtained for a circular runway with a Boeing 747-400 aircraft as a reference is 3795 m. The width of the circular runway is determined to be 140 m wide. The slope of the runway starts at an angle of 0° and then increases gradually to 20°. While the force felt by the aircraft when landing on a circular runway is 0.43 g. Juanda's conventional runway capacity is 32 operations per hour. Where the circular runway capacity is 64 operations per hour, this capacity may increase depending on the type of aircraft served.

Design and performance analysis of a novel compressed air–liquid CO2 energy storage

The application of aboveground artificial tank frees the compressed air energy storage (CAES) from geographical limitations, while one significant issue is how to reduce the price of storage tanks and achieves high efficiency concurrently. The compressed CO2 energy storage (CCES) with flexible gas holder may be an effective and economic proposal, but it can only be used in sparsely populated areas due mainly to the huge size of flexible gas holder. Therefore, this study reports a new aboveground energy storage system with a small footprint, high efficiency and low investment cost. This system is an integration of CAES and CCES by arranging the CCES flexible gas holder into the CAES air chamber. With this configuration, the isobaric CAES is ensured and the size of flexible gas holder is significantly lessened. The integrated system is systematically evaluated in the view of a technical and economic standpoint. It is found that the system efficiency is 67.47 % (charge and discharge pressures being 5.5 MPa), which is increased by 12 % of the CAES efficiency (charge pressure being 10 MPa and discharge pressure being 3.5 MPa). One of the deficiencies of the proposed system may be the larger gas storage volume, which is 1.27 times of that in the CAES system. The system levelized cost of storage is 0.1491 $/kWh, representing a 14.05 percent reduction compared to that of the CAES system. More importantly, the system gas storage pressure is only 5.5 MPa, carrying about half of that in the CAES system. The reliability and safety of the energy storage plant is extensively intensified.

Compact module for complementary-channel THz pulse slicing

We present a modular quasi-optical pulse slicer designed for use at terahertz (THz) frequencies. Given a quasi-cw input, the two outputs of a module are (1) a pulse with programmable duration and (2) its complement. The quasi-optical design incorporates a laser-driven silicon switch at Brewster's angle to the incoming THz beam, which limits undesired reflections before the switch is activated such that THz power is only transmitted when the switch is “on.” An “off” switch ensures that no power is leaked after the pulse and that the switching profile is sharp. The slicer's small footprint (0.048×0.072×0.162 m3) and small insertion loss (1.2 dB at 320 GHz) as well as high switching efficiency (∼70%) allows modules to be stacked to create multiple pulses. The output channel that is not used for experiments can be used for concurrent analysis of beam parameters. Stacking modular assemblies will enable more complex sequences of kW-level pulses than are currently achievable for applications including free-electron-laser or gyrotron-powered pulsed electron spin resonance at high magnetic fields.

Genetic Algorithm Based 3D IC Partitioning Approach for TSV Minimization and Efficient Layer Assignment

The rise of three-dimensional (3D) IC layouts necessitates the development of unique partitioning methods that will be suitable for the 3D component designs. Net lists partitioning is a key aspect of the physical design of a 3D IC. Reducing wire lengths between gates is possible with 3D-ICs since they have a small footprint as well as vertical connectivity among dies. As a result, they consume less power and have shorter connection delays. This paper presents an efficient genetic algorithm (GA) based layer partitioning technique for 3D ICs that focuses on proper layer assignment to reduce area deviation and minimization of Through Silicon Vias (TSVs) to reduce IC footprint. The method starts with random initial solutions and refines the solutions with efficient crossover and mutation operator till the optimized solution is achieved. Our methodology produces high-quality solutions on well-known benchmarks. The experimental findings are compared with state-of-the-art methodologies and the suggested strategy is found to be very effective in the case of decreasing the TSV count and space need of the 3-dimensional IC design. In addition, the performance of our strategy is also compared with two recent publications that use GA and Particle Swarm Optimization (PSO) and it is found that the proposed method achieves 20.18% and 38.66% average reduction in terms of TSV count respectively. Thus, the suggested technique is beneficial for multilayered 3D IC partitioning, as it can reduce TSV count while also satisfying balancing criteria and latency.

Space-qualifying silicon photonic modulators and circuits.

Reducing the form factor while retaining the radiation hardness and performance matrix is the goal of avionics. While a compromise between a transistor's size and its radiation hardness has reached consensus in microelectronics, the size-performance balance for their optical counterparts has not been quested but eventually will limit the spaceborne photonic instruments' capacity to weight ratio. Here, we performed space experiments of photonic integrated circuits (PICs), revealing the critical roles of energetic charged particles. The year-long cosmic radiation exposure does not change carrier mobility but reduces free carrier lifetime, resulting in unchanged electro-optic modulation efficiency and well-expanded optoelectronic bandwidth. The diversity and statistics of the tested PIC modulator indicate the minimal requirement of shielding for PIC transmitters with small footprint modulators and complexed routing waveguides toward lightweight space terminals for terabits communications and intersatellite ranging.

Characterizing Community Forests in the United States

Abstract Research on community forests (CFs), primarily governed and managed by local forest users in the United States, is limited, despite their growth in numbers over the past decade. We conducted a survey to inventory CFs in the United States and better understand their ownership and governance structures, management objectives, benefits, and financing. The ninety-eight CFs in our inventory are on private, public, and tribal lands. They had various ways of soliciting input from, or sharing decision-making authority with, local groups, organizations, and citizens. Recreation and environmental services were the most important management goals, but timber production occurred on more than two-thirds of CFs, contributing to income on many CFs, along with a diversity of other income sources to fund operations. We discuss the difficulties in creating a comprehensive CF inventory and typology given the diversity of models that exist, reflecting local social and environmental conditions and the bottom-up nature of community forestry in the United States. Study Implications: Despite their small footprint in the United States, community forests are a rapidly developing model of forest ownership, governance, and management that helps protect forestlands and open space and demonstrates how market and nonmarket forest goods and services can be produced for broad and enduring community benefits. This study inventories and characterizes community forests in the United States to increase understanding of this model, its prevalence, and its potential. It provides a baseline of information that serves as a foundation for further exploration and research on the impacts and contributions of community forests.

Multi-Ported GC-eDRAM Bitcell with Dynamic Port Configuration and Refresh Mechanism

Embedded memories occupy an increasingly dominant part of the area and power budgets of modern systems-on-chips (SoCs). Multi-ported embedded memories, commonly used by media SoCs and graphical processing units, occupy even more area and consume higher power due to larger memory bitcells. Gain-cell eDRAM is a high-density alternative for multi-ported operation with a small silicon footprint. However, conventional gain-cell memories have limited data availability, as they require periodic refresh operations to maintain their data. In this paper, we propose a novel multi-ported gain-cell design, which provides up-to N read ports and M independent write ports (NRMW). In addition, the proposed design features a configurable mode of operation, supporting a hidden refresh mechanism for improved memory availability, as well as a novel opportunistic refresh port approach. An 8kbit memory macro was implemented using a four-transistor bitcell with four ports (2R2W) in a 28 nm FD-SOI technology, offering up-to a 3× reduction in bitcell area compared to other dual-ported SRAM memory options, while also providing 100% memory availability, as opposed to conventional dynamic memories, which are hindered by limited availability.

Nanocavity tuning and formation controlled by the phase change of sub-micron-square GST patterns on Si photonic crystals.

It has been well established that photonic crystal nanocavities with wavelength sized mode volume enable various integrable photonic devices with extremely small consumption energy and small footprint. In this study, we explore the possibility of non-volatile functionalities employing photonic crystal nanocavities and phase change material, Ge2Sb2Te5 (GST). Recently, non-volatile photonic devices based on GST have attracted significant interest and are expected to enable energy-efficient photonic processing, especially for optical computing. However, the device size and the area of GST in previous studies have been rather large. Here, we propose and fabricate Si photonic crystal nanocavities on which submicron-square GST patterns are selectively loaded. Because of the strong light confinement, extremely small area of GST is sufficient to manipulate the cavity mode. We have succeeded to fabricate 30-nm-thick and several-100nm-square GST blocks patterned at the center of photonic crystal cavity with a high alignment accuracy. We confirmed that the resonant wavelength and Q-factor of cavity modes are controlled by the phase change of GST. Moreover, cavity formation controlled by submicron-sized GST is also demonstrated by GST-loaded photonic-crystal line-defect waveguides. Our approach in which we place sub-micron-sized GST inside a photonic crystal nanocavity is promising for realizing extremely energy-efficient non-volatile integrable photonic devices, such as switches, modulators, memories, and reconfigurable novel devices.