Drop-in Replacement Research Articles

Theoretical Characterizations on the Eco-Friendly Gas Tetrafluoropropyne for Electrical Insulation to Replace Sulfur Hexafluoride.

Gases for electric insulation are essential for various types of high-voltage power equipment. Sulfur hexafluoride (SF6) has been a dielectric medium commonly used in electrical grids for decades but it is the most potent industrial greenhouse gas. The continuous increase of SF6 emissions in the atmosphere exerts a significant impact on global warming. The identification of suitable drop-in replacements for all SF6-filled apparatuses has been elusive experimentally and theoretically. We claim that tetrafluoropropyne, C3F4, is a breakthrough in chemical alternatives to SF6. The performance of C3F4 was assessed systematically in a 6-dimensional manner, including dielectric strength, liquefaction temperature, global warming potential, thermal stability, toxicity, and arc interruption. On the basis of the extensive ab initio calculations, it has been demonstrated rigorously that C3F4 is an environmentally sustainable solution that may fulfill the complex combination of performance, stability, safety, and environmental properties, namely, the dielectric strength is about 50% higher than that of SF6, the boiling point is -50 °C, the GWP for 100 year time horizons is only 3, the decomposition temperature is above 600 °C, the toxicity is as low as HFOs, and the interruption capability is two-thirds of SF6. Two protocols are suggested for the practical use of C3F4. First, equivalence to 0.5 MPa SF6 could be obtained by filling 0.33 MPa C3F4 pure gas and lead minimum operating temperature down to -21 °C. Second, by taking advantage of synergism effect, the 40% C3F4/60% CO2 mixture is a viable alternative to SF6 with the operating temperature -30 °C without causing any environmental and safety concerns. The present theoretical work sheds new light on the challenging topic of the development of alternative dielectric gases and may stimulate experimental tests on the electrical applications of C3F4 in the future.

Thermodynamic analysis of a linear compressor vapour compression system

Linear compressors are advantageous in terms of miniaturization, high efficiency, and continuous operation without a crank mechanism. The drop-in replacement for R134a in domestic refrigerators is R1234yf. This study aims to investigate the linear compressor thermodynamic performance in vapour compression system with R1234yf by modelling and measuring key parameters such as pressure-volume (P-V) diagram, refrigerant distribution, mass flow rate, volumetric efficiency, cooling capacity, and coefficient of performance (COP). Results show that at 40 °C condenser temperature and 2 pressure ratio, the linear compressor vapour compression system achieved a maximum 299.1 W cooling capacity, which gives 4.12 COP. The thermodynamic analysis calculations are in good agreement to the results of experimental measurements, verifying the accuracy of the model.

Sustainable Syntheses of Paracetamol and Ibuprofen from Biorenewable β-pinene.

Scalable processes have been developed to convert β-pinene into 4-isopropenylcyclohexanone which is then used as a feedstock for the divergent synthesis of sustainable versions of the common painkillers, paracetamol and ibuprofen. Both synthetic routes use Pd(0) catalysed reactions to aromatise the cyclohexenyl rings of key intermediates to produce the benzenoid ring systems of both drugs. The potential of using bioderived 4-hydroxyacetophenone as a drop-in feedstock replacement to produce sustainable aromatic products is also discussed within a terpene biorefinery context.

Building Tunable Degradation into High-Performance Poly(acrylate) Pressure-Sensitive Adhesives.

Pressure-sensitive adhesives (PSAs) based on poly(acrylate) chemistry are common in a wide variety of applications, but the absence of backbone degradability causes issues with recycling and sustainability. Here, we report a strategy to create degradable poly(acrylate) PSAs using simple, scalable, and functional 1,2-dithiolanes as drop-in replacements for traditional acrylate comonomers. Our key building block is α-lipoic acid, a natural, biocompatible, and commercially available antioxidant found in various consumer supplements. α-Lipoic acid and its derivative ethyl lipoate efficiently copolymerize with n-butyl acrylate under conventional free-radical conditions leading to high-molecular-weight copolymers (Mn > 100 kg mol-1) containing a tunable concentration of degradable disulfide bonds along the backbone. The thermal and viscoelastic properties of these materials are practically indistinguishable from nondegradable poly(acrylate) analogues, but a significant reduction in molecular weight is realized upon exposure to reducing agents such as tris (2-carboxyethyl) phosphine (e.g., Mn = 198 kg mol-1 → 2.6 kg mol-1). By virtue of the thiol chain ends produced after disulfide cleavage, degraded oligomers can be further cycled between high and low molecular weights through oxidative repolymerization and reductive degradation. Transforming otherwise persistent poly(acrylates) into recyclable materials using simple and versatile chemistry could play a pivotal role in improving the sustainability of contemporary adhesives.

Rethinking DRAM's Page Mode With STT-MRAM

STT-MRAM is a promising candidate for drop-in replacement for DRAM-based main memory because of its higher energy efficiency and similar latency to DRAM. However, simply replacing DRAM with STT-MRAM without optimizations severely limits STT-MRAM from exploiting its full potential. STT-MRAM employs costly sense amplifiers that demand an order of magnitude more area and power than DRAM. To manage the high cost, STT-MRAM shares one sense amplifier across multiple bit-lines, exploiting the non-destructive nature of its read operation. This sense amplifier sharing reduces the size of row buffers; as a result, it incurs higher activation energy and lower performance. Other issues arise if STT-MRAM is required to be compatible with DRAM interfaces and policies. To address these challenges in a cost-effective manner, we propose SMART that, unlike DRAM and conventional STT-MRAM, waits to do bit-line sensing until after receiving a column access command instead of a row activation command. This results in several benefits: larger pages, fewer sense amplifiers, lower activation power, higher bank-level parallelism, shorter latency, fewer address pins, and more efficient repairing of defective columns than conventional STT-MRAM. Our evaluation shows that SMART consumes lower energy while providing higher performance than conventional STT-MRAM and DRAM. Additionally, SMART consumes less area compared to conventional STT-MRAM.

Drop-In Replacement of R134a in a Household Refrigerator with Low-GWP Refrigerants R513A, R516A, and R1234ze(E)

This study proposes the experimental evaluation of alternative refrigerants with low global warming potentials (GWPs) such as R1234ze(E), R513A, and the mixture R516A as a drop-in replacement for R134a in a domestic refrigerator with a volumetric capacity of 513 L. Initially, the optimal charge for each refrigerant was defined based on the minimum energy consumption of the refrigerator, then the thermal and energy performance of the refrigerator was evaluated. Finally, a total equivalent warming impact analysis (TEWI) was performed. The main results indicated that the optimal charge of the alternative refrigerants was below that corresponding to R134a (105 g), of which R516A (86 g) presented the greatest charge reduction. Regarding the average temperature of the refrigerator compartments, very adequate thermal conditions were observed; thus, the alternative refrigerants showed very similar conditions to R134a. For the coefficient of performance (COP) and considering R134a as a reference, it was observed that R513A presented the greatest reduction of around 28%, while R1234ze(E) showed an increase of 13% in relation to R134a. Finally, the TEWI analysis showed R1234ze(E) as the refrigerant with the least impact.

Manufacturing a Ceramic Turbine Rotor for a Compact Jet Engine

Abstract Compact military-grade jet engines offer many potential applications, including use in remotely piloted vehicles, but can be expensive to use for research and development purposes. A study aimed at increasing the power and thrust output of an inexpensive commercial compact engine found a material limitation issue in the turbomachinery. To gain the additional power, hotter turbine inlet temperatures were required. This temperature increase exceeded the limit of current uncooled metal turbine rotors but could be achieved through turbine rotors made from ceramics, such as silicon nitride, which would allow an increase in the thrust and power output by a factor of 1.44. Current ceramic turbine manufacturing methods are costly and time-consuming for rapid prototyping, but recent breakthroughs in ceramic additive manufacturing have allowed for cheaper methods and faster production which are beneficial for use in research and development when designs are being rapidly changed and tested. This research demonstrated, through finite element analysis, that a silicon nitride turbine rotor could meet the increased turbine inlet temperature conditions to provide the desired thrust and power increase. Furthermore, as a proof of concept, an additively manufactured drop-in replacement alumina turbine rotor was produced for the JetCat P400 small-scale engine in a manner that was cost-effective, timely, and potentially scalable for production. This compact engine was used to demonstrate that a cost-effective ceramic turbine could be manufactured. At the time of publication, the desired ceramic material, silicon nitride, was not available for additive manufacturing.

High Performance Transparent Silver Grid Electrodes for Organic Photovoltaics Fabricated by Selective Metal Condensation.

We report silver grid electrodes on glass and flexible plastic substrates with performance that exceeds that of commercial indium-tin oxide (ITO) coated glass and show their suitability as a drop-in replacement for ITO glass in solution processed organic photovoltaics (OPVs). When supported on flexible plastic substrates these electrodes are stable towards repeated bending through a small radius of curvature over tens of thousands of cycles. The grid electrodes are fabricated by the unconventional approach of condensation coefficient modulation using a perfluorinated polymer shown to be far superior to the other compounds used for this purpose to date. The very narrow line-width and small grid pitch that can be achieved also opens the door to the possibility of using grid electrodes in OPVs without a conducting PEDOT:PSS layer to span the gaps between grid-lines. This article is protected by copyright. All rights reserved.

Performance Assessment of Low Global Warming Potential Alternative Refrigerants

Global warming is the general increase in global temperature brought on by higher-than-normal concentrations of greenhouse gases. These gases trap heat waves as they approach the world and allow them to continue entering the atmosphere over time without being able to leave. This study used low global warming potential alternative refrigerants to reduce greenhouse gas emissions, in line with global efforts to phase out chlorinated fluids in order to preserve the ozone layer as a result of the Montreal Protocol. A software program called Cycle-D-Hx, which has a graphical user interface and a thermodynamic model of the refrigeration system, was used to evaluate how well household refrigerators working with various types of refrigerants performed. The model was validated using data from a household refrigerator charged with R134A. The performance of several low global warming potential alternative refrigerants, including R404A, R449A, R513A, and R452A, was then assessed using the model.
 The hydrofluoroolefin based R452A refrigerant is an alternative to R404A and R507 that is non-ozone depleting and has a low global warming potential. An azeotropic blend, R-513A is a drop-in replacement for R-134a in existing systems. Common hydrofluorocarbons and the new hydrofluoro-olefin molecule R1234yf are combined to form R449a, which is made up of R32 (24%), R125 (25%), R134a (26%), and R1234yf (25%). R513A, an aceotropic blend with no temperature glide, is composed of 44% R134a and 56% R1234yf.
 The simulation's findings demonstrate that R452A has a coefficient of performance 1.578, a zero potential for ozone depletion, a 0.5oC temperature glide for the evaporator and condenser and also a low potential for global warming unit count of 2140. Along with these thermodynamic and environmental qualities, R452A blend can take the place of R134A as a refrigerant because it is non-flammable and noncorrosive and will not corrode the metal parts of the compressor and evaporator of the refrigeration system.

AI-accelerated protein-ligand docking for SARS-CoV-2 is 100-fold faster with no significant change in detection

Protein-ligand docking is a computational method for identifying drug leads. The method is capable of narrowing a vast library of compounds down to a tractable size for downstream simulation or experimental testing and is widely used in drug discovery. While there has been progress in accelerating scoring of compounds with artificial intelligence, few works have bridged these successes back to the virtual screening community in terms of utility and forward-looking development. We demonstrate the power of high-speed ML models by scoring 1 billion molecules in under a day (50 k predictions per GPU seconds). We showcase a workflow for docking utilizing surrogate AI-based models as a pre-filter to a standard docking workflow. Our workflow is ten times faster at screening a library of compounds than the standard technique, with an error rate less than 0.01% of detecting the underlying best scoring 0.1% of compounds. Our analysis of the speedup explains that another order of magnitude speedup must come from model accuracy rather than computing speed. In order to drive another order of magnitude of acceleration, we share a benchmark dataset consisting of 200 million 3D complex structures and 2D structure scores across a consistent set of 13 million “in-stock” molecules over 15 receptors, or binding sites, across the SARS-CoV-2 proteome. We believe this is strong evidence for the community to begin focusing on improving the accuracy of surrogate models to improve the ability to screen massive compound libraries 100 × or even 1000 × faster than current techniques and reduce missing top hits. The technique outlined aims to be a fast drop-in replacement for docking for screening billion-scale molecular libraries.

Critical assessment of R410A alternatives for mini-split air conditioners in the Egyptian market

In this study, the potential implementation of three different low-GWP refrigerants (R32, R452B, and R454B) as replacements for R410A was investigated. The study was performed using a simulation tool developed by the authors called RACHP-Lab, which is a vapor compression system simulation tool developed based on physics-based simulation for typical mini-split air conditioners. The simulation study was carried out and validated using experimental performance data of 10 different air conditioning units available in the Egyptian market. The units included fixed-speed or variable-speed compressors and operated in cooling or heating modes. Drop-in replacement with the new refrigerants was carried out. For R32, the capacity increased between 4.9% and 13% for cooling cases, and 6.3% and 12.4% for heating cases. However, COP did not improve in all cases. For R452B and R454B with direct replacement, the capacity nearly remained the same, with an increase of COP between 1.6% and 8.0%. Soft optimization was also conducted on cooling cases where compressor suction superheat, condenser subcooling, and compressor volumetric speed were optimized to maximize COP while maintaining the original capacity of R410A. R32 showed an improvement of COP over R410A between 4.6% and 15.5%, while for R452B and R454B between 2.2% and 13.2%.

Experimental evaluation for potential drop in refrigerants under high-ambient conditions

Compliance with the Kyoto Protocol and United Nations Sustainable Development Goals requires nations to lower greenhouse gas emissions. Air conditioners, as contributors to direct and indirect emissions of greenhouse gases, can play a major role in limiting global warming to 1.5 °C above pre-industrial levels. Nations classified as Article Five parties, including 147 nations, are required to completely phase out Hydrochlorofluorocarbons including R-22 in 2040. Some of these nations reside in extremely hot climates, and new refrigerants perform poorly under hot weather conditions. While the time is ticking to the phaseout, transitional solutions can be used to move away from R-22 to facilitate the phase-down, especially for units that are still in service.In this paper, a comparative experimental assessment of R453A and R458A as drop-in replacements for R22 is presented. This study aims to evaluate the performance of the two refrigerants to assess their suitability for countries residing in hot climates during the transitional phase-out and phase-down of refrigerants. R22 is used as the baseline refrigerant because it is widely used in developing nations and performs well under high ambient temperatures, reaching as high as 50 °C. Six ambient temperatures (35 °C, 40 °C, 46 °C, 48 °C, 50 °C, and 52 °C) were tested to evaluate the performance of a concealed ducted split air-conditioning unit. The unit rated cooling capacity is 10.39 kW at 48 °C. The measured cooling capacity in comparison to that of R22 was between 87 % and 96 % and 88 % to 96 % for R453A and R458A, respectively, over the tested range of temperatures. The coefficient of performance compared to the baseline showed degradation of 6 %–17 % and 3–10 % for R435A and R458A, respectively. The compression ratio increased by 9 % to 15 % on average for both tested alternative refrigerants over the tested temperature range. It is concluded that R458A performs well as a drop-in alternative refrigerant to R22 and surpasses that of R453A, as it showed slightly less deviation in coefficient of performance.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment

Mpi4py.futures: MPI-Based Asynchronous Task Execution for Python

We present mpi4py.futures, a lightweight, asynchronous task execution framework targeting the Python programming language and using the Message Passing Interface (MPI) for interprocess communication. mpi4py.futures follows the interface of the concurrent.futures package from the Python standard library and can be used as its drop-in replacement, while allowing applications to scale over multiple compute nodes. We discuss the design, implementation, and feature set of mpi4py.futures and compare its performance to other solutions on both shared and distributed memory architectures. On a shared-memory system, we show mpi4py.futures to consistently outperform Python's concurrent.futures with speedup ratios between 1.4X and 3.7X in throughput (tasks per second) and between 1.9X and 2.9X in bandwidth. On a Cray XC40 system, we compare mpi4py.futures to Dask – a well-known Python parallel computing package. Although we note more varied results, we show mpi4py.futures to outperform Dask in most scenarios.

Exploring Pareto-Optimal Hybrid Main Memory Configurations Using Different Emerging Memories

Main memory system design and corresponding technology requirements have become increasingly challenging for data-dominated high-performance applications. To address the leakage and scalability issues of the conventional DRAM-based memory, new memory technologies with ultra-low leakage and potential for high scalability have been explored extensively over the last decade. However, none of them are mature enough to serve as a drop-in replacement for DRAM. In this paper, we propose a hybrid main memory system solution for utilizing new memory technologies with specific features, based on the target application characteristics and system configurations. To this end, we examine two new memories, 1S-1VCMA and IGZO-based DRAM, along with conventional DRAM in the context of hybrid main memory solutions for high-capacity and low-power Pareto-optimizations, respectively. To better evaluate the power and performance, we consider the page-fault modeling in our evaluations. The results of the simulation show that different combinations of memory technologies in the hybrid memory system, different memory capacities, and different storage systems could provide a promising solution in the system regarding the characteristics of running applications and the requirements of the system.

Sustainable Synthesis of Drop-In Chemicals from Biomass via Chemical Catalysis: Scopes, Challenges, and the Way Forward

A handful of small organics, namely, ethylene, propylene, butadiene, benzene, toluene, xylenes, and methanol, produced from petroleum and other fossilized carbon-based resources, can produce practically all petrochemicals and synthetic organic polymers used in the industrialized societies. The molecules mentioned above, often referred to as primary petrochemicals, must be sourced from renewable carbon feedstock to achieve the long-aspired all-around sustainability in chemical manufacturing. Significant efforts have been devoted to developing efficient chemical–catalytic pathways for selectively converting biomolecules and biopolymers into these petroleum-derived chemical platforms. The processes take advantage of prevalent petrorefinery infrastructure, well-documented synthetic value addition pathways of the chemical platforms, and established markets of the derived products. Relative merits and demerits of various catalytic routes in producing the aforementioned primary petrochemicals from renewable biomass have been deliberated. This review elaborates on the synthetic methodologies available for synthesizing the drop-in replacement of primary petrochemical from renewable biomass, focusing on process selectivity, feedstock selection, and catalyst performance. The critical analyses presented in this review will assist in appraising the research accomplishments to date, identifying the bottlenecks, and realigning the future perspectives.

Rendering the Directional TSDF for Tracking and Multi-Sensor Registration with Point-To-Plane Scale ICP

Dense real-time tracking and mapping from RGB-D images is an important tool for many robotic applications, such as navigation and manipulation. The recently presented Directional Truncated Signed Distance Function (DTSDF) is an augmentation of the regular TSDF that shows potential for more coherent maps and improved tracking performance. In this work, we present methods for rendering depth- and color images from the DTSDF, making it a true drop-in replacement for the regular TSDF in established trackers. We evaluate the algorithm on well-established datasets and observe that our method improves tracking performance and increases re-usability of mapped scenes. Furthermore, we add color integration which notably improves color-correctness at adjacent surfaces. Our novel formulation of combined ICP with frame-to-keyframe photometric error minimization further improves tracking results. Lastly, we introduce Sim(3) point-to-plane ICP for refining pose priors in a multi-sensor scenario with different scale factors.

GNU Data Language 1.0: a free/libre and open-source drop-in replacement for IDL/PV-WAVE

GNU Data Language 1.0: a free/libre and open-source drop-in replacement for IDL/PV-WAVE

Realization of the triple point of carbon dioxide in a transportable cell using long-stem SPRTs

The action of the Minamata Convention requests in the near term to develop alternative fixed points to replace the mercury triple point (Hg TP) from the set of the defining points of the International Temperature Scale (ITS) of 1990. Carbon dioxide (CO2) TP is a candidate that exhibits the advantages of high chemical and physical stability and low health risk, and the disadvantage of relatively high pressure at room temperature. We report our study on the realization of the CO2 TP using long-stem standard platinum resistance thermometers (SPRTs). We present a novel design for a CO2 TP cell with thermometer immersion depth extending from 110 –200 mm with no increase in sample gas pressure. The outer dimension of the new cell is suitable for a drop-in compatible replacement of a normal cell for the Hg TP. We realized 14 plateaus of the CO2 TP using two long-stem SPRTs over a span of 12 months. The mean temperature at the CO2 TP is 216.591 30 (36) K at the melt fraction F = 0.5 and 216.591 36 (37) K at F = 1.0. Within the given uncertainties, the uncertainty arising from the transformation to ITS-90 contributes a major part of 0.29 –0.30 mK. The uncertainty formed by the pressure-head effect and the axial heat leak through the thermometer well of the new cell, the impurities of the sample gas and the inaccuracy of the electronic instruments contribute a smaller part of 0.21 –0.22 mK. The plateaus consistently exhibit small slopes of heights of less than 0.21 mK and time spans from 147 –347 h between F = 0.3 and F = 0.75. The small slopes of the plateaus demonstrate the repeatability of 0.056 and 0.059 mK, respectively, for the melt fraction F = 0.5 and 1.0, and the long-term stability of 0.031 mK.

CLARINET: A quire-enabled RISC-V-based framework for posit arithmetic empiricism

Many applications require high-precision arithmetic. IEEE 754-2019 compliant (floating-point) arithmetic is the de facto standard for performing these computations. Recently, posit-arithmetic has been proposed as a drop-in replacement for floating-point arithmetic. The posit data representation and arithmetic claim several advantages over the floating-point format and arithmetic, including higher dynamic range, better accuracy, and superior performance-area trade-offs. However, very few accessible and holistic frameworks facilitate the validation of these claims of posit-arithmetic, especially with long accumulations (quire).We present a consolidated general-purpose processor-based framework to support posit-arithmetic empiricism. Users can seamlessly experiment using posit and floating-point arithmetic in their applications since the framework is designed for the two number systems to coexist. Melodica is a posit-arithmetic core that implements parametric fused operations on the quire data type. Clarinet is a Melodica-enabled processor based on the RISC-V ISA. To the best of our knowledge, this is the first-ever integration of the quire in a RISC-V core. We report results from application studies on Clarinet and benchmark common linear algebra and computer vision kernels. We synthesize Clarinet on a Xilinx FPGA and present utilization and timing data. Clarinet and Melodica remain actively under development and are available as open-source.