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PurposeThe purpose of this study is to compare and analyze the anti-aging durability of asphalt and asphalt mixture under the conditions of inherent and improved performance. The research contents include: the mechanical properties (dynamic stability, bending strain, freeze-thaw splitting tensile strength ratio (TSR)) of different modified asphalt mixtures were tested by using the best modified asphalt.Design/methodology/approachThe anti-aging durability of different modified asphalt was analyzed by using the results of macro tests such as penetration and softening point as evaluation indexes. Meanwhile, the change of the asphalt colloid instability index (Ic) in the aging process was used as the evaluation index to verify the results of the macroscopic test, and the best modified asphalt was obtained. On this basis, the composition of different modified asphalt mixtures was designed by using the best modified asphalt. Meanwhile, water stability was used as evaluation indexes to study the anti-aging durability of different modified asphalt mixtures.FindingsThe results show that styrene-butadiene-styrene (SBS) modified asphalt has better aging resistance. Due to the special storage time, the performance of rubber asphalt is also the best. Meanwhile, in terms of modified asphalt mixture, its high temperature performance and durability of anti-aging is as follows: 4% SBS /16% rubber modified asphalt mixture (IV) > 4% SBS modified asphalt mixture (II) > asphalt mixture (90#) (I) > 16% rubber modified asphalt mixture (III). The low temperature performance and durability of anti-aging is as follows: Ⅱ > IV > Ⅰ > Ⅲ. The water stability performance and durability of anti-aging is as follows: IV > Ⅲ > Ⅱ > Ⅰ.Originality/valueThe research results have important theoretical and guiding significance for exploring the change of intrinsic properties and improved properties of asphalt and asphalt mixture in the aging process and revealing the anti-aging mechanism of different modified asphalt mixtures.

The existing research on modified asphalt is primarily focused on how to improve the high- and low-temperature performances (high-temperature rutting and low-temperature cracking) of asphalt, but the improvement of the anti-ageing performance of asphalt is also important. The research objects of the present study were equivalent-penetration (high-temperature performance) and equivalent-ductility (low-temperature performance) asphalt specimens, and the anti-ageing performances of different specimens were compared from both the macro- and micro-perspectives. From the macro-perspective, taking the penetration, ductility, viscosity and softening point of asphalt as the experimental indexes, the anti-ageing performances of different asphalt specimens were compared and analysed based on the changes in different indicators at different ageing times. From the micro-perspective, the macro-test results of asphalt specimens with different durabilities were verified by an asphalt component test and the analysis of environmental scanning electron microscopy images. The research results have certain theoretical value for scientifically understanding the technical characteristics of different modifiers, the research and development of modifiers and the formation mechanism of modified asphalt.

Reasonable establishment of maintenance prediction mechanism plays an important role in service performance and long-term performance of asphalt pavement. The presented study proposed a comprehensi...

Growing global energy needs and demand over imminent reductions of harmful greenhouse gas emissions, call for development of highly efficient, clean and reliable power generation from both renewable and fossil resources. A hybrid solid oxide fuel cell gas turbine (SOFC-GT) system is a promising candidate for fulfilling such need of a low emission, highly efficient power generation. This system can be applied to stationary, transportation, aviation, and maritime power generation applications. This study focuses on understanding operational characteristics of the pressurized SOFC as a key component for the successful design and construction of a highly efficient SOFC-GT hybrid system. Pressurization of an SOFC can cause improvement on electrode kinetics, stack lifetime and round-trip efficiency by cell integration with downstream components such as gas turbines and catalytic reactors (for electrolysis) [1-4]. However, literature data from experimental studies on the electrochemical behavior of the SOFC as a function of operating pressure is relatively scarce. This is presumably due to the complexity involved in the construction and operation of pressurized system. To address such research challenge, a pressurized SOFC test rig as shown in Fig. 1 has been constructed and commissioned at Tennessee Technological University (TTU) to allow tubular SOFCs to be characterized under a maximum operating pressure of 60 psia (~4 bar) and maximum operating temperature of 825oC. A detailed system set-up shown in Fig. 2. The power generation capacity for the test rig can be scaled up to 2.4 kW. For this study, performance of single anode supported SOFC tubes with H2 and CH4 fuels were examined by varying pressure from 1 bara to 4 bara and temperature from 675oC to 775oC, with fuel utilization held constant at 50% and an oxygen-to-carbon ratio (O/C) of 0.6 for the methane operation. The testing cells were gratuitously supplied by Special Power Sources (SPS) LLC, USA, with cathode/electrolyte outside-layers supported on the anode inner-layer as a 14”-long tube. Silver ink and wires are used for cell current collection from active surface area of ⁓100 cm2 . The connection fixture can be seen in Fig. 1. V-I curves of tubular SOFCs in Fig. 3 measured from step-wise electronic load profile indicate total performance gain of 13% as H2 pressure increases from 1 bara to 4 bara, with highest peak power density obtained at 0.61 Wcm-2. As comparison Fig.4 and 5 demonstrate pressurization suppressed gas diffusion limit for tubular SOFC at higher current density in CH4 fuel, leading to 44 % increase of peak power density to 0.51 Wcm-2 at 4 bara. Electrochemical impedance spectroscopy (EIS) studies were performed using a Solartron 1260/PAR 263 electrochemical testing system in 4-point connection measurement to understand effects of pressurization on the SOFC performance. SOFC impedance spectra as Nyquist and Bode plots in Fig.6 (b) and (d) indicate the tubular SOFC performance is mainly limited by anode mass transports, which are greatly improved by pressurization. From non-linear, least-square cell impedance fitting and previous findings on impedance of similar larger cells, an equivalent-circuit model (ECM) in Fig. 6(a) has been identified to best represent impedance responses from the most rate-limiting processes of tubular SOFCs. The Warburg component (Ws) in the ECM with resonance frequency around 10Hz typically corresponds to gas diffusion in porous electrode of tubular SOFC [3-5], while paralleled R-CPE component at References can be seen in the figure document. Figure 1

The durability of asphalt mixture is one of the main indicators of the mechanical performance of asphalt pavement. Three kinds of composite modified asphalts (4%SBS/3%SBR, 4%SBS/15% rubber powder a...

The anti-aging performance/durability of an asphalt mixture is an important technical performance indicator of asphalt pavement. Although hybrid-modified asphalt mixtures have better high- and low-...

In this work, an unexpected failure phenomenon in 3D NAND flash memory was fist studied. It was found that the raw bit errors of flash memory might suddenly increase during P/E cycling and result in endurance failure. And an effective flash controller-embedded predictor was constructed by FPGA to prevent the unexpected failure in flash memory. Simulation results show that the predictor is able to prevent unexpected failure effectively and improve flash memory lifetime by 1.7 × -7.9x.

In Solid State Drives, flash management techniques such as wear-leveling and refresh usually assume NAND flash memories have the same endurance value. However, the actual endurance values differ from blocks to blocks. This reliability difference is introduced by process-variation during flash fabrication. In recent years, for improving flash management techniques, various works have been done on the reliability variation of 2D flash memory. As 2D NAND transmitted to 3D NAND flash, the vertical structure and multi-layer stacking changed the effect of previously known reliability problems. In this paper, we are first to characterize the process-variation effects on 3D TLC flash reliability. The characterization includes two parts: endurance variation and error feature variation. Second, we propose an adaptive error prediction scheme to mitigate the process-variation effects. This scheme uses the machine-learning model to realize the error prediction operation. We also discuss the implications of this scheme on main flash management techniques.

Wear-out has been a critical reliability problem in NAND flash memory. As executing repeated program and erase operations on the NAND flash chips, the number of errors increases and ultimately exceeds the ECC capability. In previous work, error characteristics of flash wear-out are observed by endurance tests on a single type of NAND flash memory. We wonder if the experimental results cover the entire error characteristics of NAND flash memory. In this paper, we tested more than 20 types of NAND flash chips with different vendors and structures and presented an overlook of test results. Through the test results, we found an unexpected error-explosion phenomenon that errors of flash blocks first increase over several cycles and then reach a high value without warning. We analyzed the features of the error-explosion and explored its influence on operation time. And we propose an error-explosion prediction scheme to find the blocks that will occur an error-explosion in the next 1000 P/E cycles. The block identifying operation is realized by the machine-learning model. The performance of six machine-learning methods is compared. The results demonstrate that the Decision Trees and Bagged Classification Trees have the best accuracy.

In this paper, a low-power voltage-control oscillator (VCO) with switch current source and pseudo current-mode logic (CML) frequency divider is proposed. 1-bit switch current source is utilized to increase the oscillator start-up margin and output swing under low supply condition. Capacitor desensitization technology and cross-coupled bias varactor are utilized to resist process fluctuation and increase tuning range. A pseudo differential CML Divider is introduced for frequency division and 4 quadrature signal generation. The proposed VCO achieves 21.8% tuning range from 4.5 GHz to 5.6 GHz, while performs phase noise -116~-122 dBc/Hz@1MHz. In 110nm CMOS process, only 2.12mA current is consumed across PVT fluctuation.

The composite performance of modified asphalt is divided into inherent performance and improved performance. The inherent performance of asphalt refers to the original performance of the virgin asphalt. The performance obtained by modifying the virgin asphalt by different methods is referred to the improved performance of the asphalt. In most studies of modified asphalt, researchers pay more attention to how to improve the performance of virgin asphalt at high and low temperatures (i.e., rutting at high temperatures and cracking at low temperatures); however, little attention has been paid to the anti-aging durability of the improved performance. In this project, the macro and micro mechanisms of modified asphalt were compared and analyzed through a series of comparative experiments on the inherent and improved performance of modified asphalt to explore the anti-aging durability of the modified asphalt based on the inherent performance and improved performance at high and low temperatures.

Compared with a modified asphalt mixture (MAM), a composite-modified asphalt mixture (CMAM) demonstrates improved performance at high and low temperatures. However, the durability of CMAM requires further study. Asphalt mixture durability can be divided into aging durability, plastic deformation durability, and fatigue durability. Therefore, based on inherent and improved performance, this paper considers three kinds of CMAM (4% SBS/3% SBR, 4% SBS/15% rubber, and 4% SBR/15% rubber) as research objects to analyze and compare durability and explore the change rule of mechanical properties in different CMAMs. This paper outlines CMAM design, mechanical property tests, and comparative durability analysis. Results indicate the durability of different CMAMs exhibit unique characteristics. Findings provide theoretical and practical value for research on asphalt mixture durability.

The new type of double-layer continuous paving can effectively improve the interlayer adhesion of asphalt mixture and the comprehensive performance of asphalt pavement. However, in the actual process of double-layer continuous paving, the interlayer adhesion of asphalt mixture is affected by many factors (compaction function, construction temperature, process, etc). Therefore, the finite element software (ABAQUS) was used to carry on the three-dimensional modeling of the asphalt pavement, and cohesive zone model (CZM) was used to define the interlayer adhesion of the asphalt mixture to analyze the factors affecting the interlayer adhesion of continuous paving. This paper mainly discusses the influence of different underlayer compaction degree, underlayer compaction temperature, asphalt layer thickness and load action on interlayer bonding and mechanical response. Finally, the grey correlation theory was used to rate the different influencing factors. The results show that when the lower layer is compacted for 50 times, the interlayer adhesion of asphalt pavement is the best, and the ability to resist the displacement crack is the strongest. Increasing the thickness of the upper layer and the compaction temperature of the lower layer of the asphalt pavement can improve the interlayer adhesion and reduce the displacement cracks. At the same time, it is found that the number of precompaction times of lower layer and horizontal braking force are the main factors that affect the interlayer adhesion. The research results have certain theoretical and practical value for the construction technology of double-layer continuous paving of asphalt pavement.

Asphalt mixtures will inevitably be affected by rainwater and the effect the of dry-wet cycle during the process of use. To explore the decay of the stability of asphalt mixtures under different dry-wet cycle conditions, a dry-wet cycle laboratory test was carried out based on standard Marshall specimens. The asphalt mixture specimens were subjected to dry-wet cycle treatment for specified cycle durations and numbers of cycles at three temperatures, and Marshall stability tests were then carried out. In this way, the decay of the stability of the asphalt mixture under different dry-wet cycle conditions was evaluated. The results show that the number of dry-wet cycles exhibited good linear relationships with the stability and the stability decay rate, respectively. As the temperature of the dry-wet cycle increased, the stability of the asphalt mixture was found to decrease; the higher the temperature, the greater the stability decay rate. A power function relationship was found between the dry-wet cycle duration and the stability decay rate of the asphalt mixture, and exhibited a decreasing trend. Under the premise of a fixed total dry-wet cycle duration, the dry-wet cycle conditions of a short duration and many cycles were found to have the greatest influence on the stability decay rate of the asphalt mixture. Moreover, a BP neural network prediction model was established by MATLAB software. By comparing the predicted and true values, the established BP neural network prediction model was found to well predict the stability of the asphalt mixture under different dry-wet cycle conditions.

Nanostructured metal oxides have received increasingly more attention due to their high specific surface area that may increase the active region of the material and hence enhance the performance of many electrochemical devices such as gas sensors or solid oxide fuel cells. However, it is still a major issue to keep these nanostructures stable at the high fabrication and operating temperatures of the electrochemical devices (e.g., solid oxide cells), typically over 1000 °C and 700 °C, respectively. In this work, thermally stable Ce0.8Sm0.2O1.9 mesoporous scaffolds were infiltrated with a Sm0.5Sr0.5CoO3-δ catalyst, which were then used as electrodes for solid oxide cells. The electrochemical properties of these nanocomposite electrodes in a symmetrical cell at 500–750 °C were evaluated using electrochemical impedance spectroscopy. When tested at 700 °C for a long period of time, the cells showed no performance degradation but a 50 % reduction in the area specific resistance (ASR = 0.08 Ω·cm2) after more than 200 h of operation, suggesting that the mesoporous composites are promising electrodes for high-temperature electrochemical devices.

NFC chip can capture power from antenna when it is in magnetic field. At the same time, NFC chip may also be powered by battery at IoT application, and it needs to shutdown battery supply to save battery energy, which makes it complex for power switch architecture. This paper presents an architecture and circuit design for NFC chip to switch power between battery and magnetic field inducing energy. An offchip 1 uF capacitor is used to filter the magnetic field power swing in wireless communication time. This circuit also collects the magnetic field inducing energy and output a current as large as 5mA (3.3V) for other IoT chip or charging battery.

The endurance of NAND flash memory continues to decrease with process scaling, leading to a decline in the reliability of the storage system and a rise on risk of data corruption. To enhance the reliability of the storage system, we utilize a neural network model with high accuracy and full application, to predict how far each block of a NAND flash can be cycled before the uncorrectable data errors occur. The input to the model includes program-time, erase-time and raw bit error (RBE) measured by FPGA (Field-Programmable Gate Array) and its output is a specific numerical value of endurance. Based on this prediction model, we propose a FPGA-based scheme for real-time endurance prediction with an accuracy of over 90%.

Mesostructure characteristics of asphalt mixture, as essential factors, affect the mechanical response and mesoscopic damage of bridge deck pavement. This study explored the effect of different mesostructure characteristics on the mechanical properties and damage behavior of asphalt pavement on a curved concrete deck using a mesostructure-based multiscale method. A two-dimensional (2D) random aggregate generation method was adopted to develop mesoscale models with different aggregate volume fractions (30%, 40% and 50%), aggregate size ranges (4.75mm-2.36mm, 9.5mm-2.36mm, 13mm-2.36mm and 16mm-2.36mm) and aggregate shapes (quadrangle, hexagon, octagon and random). A three-dimensional (3D) macroscopic model of the bridge deck pavement including two structural layers was established. A multiscale algorithm was used to establish the relationship between models at different scales. In addition, the angle index (AI) was used as an evaluation index of coarse aggregates in irregular shapes, and the damage density was used to evaluate the damage possibility of mesostructure. The results showed that the damage density of asphalt mixture mesostructure had a linear relationship with AI, and the damage density became bigger as the AI decreased. Besides, increasing the range of aggregate size and the volume fraction of aggregate could reduce the damage density of asphalt mixture mesostructure, and ultimately improve the comprehensive performance of bridge deck pavement. For the damage density of bridge deck pavement, the angle index of aggregate was the most important factor, followed by the volume fraction and size range of aggregate.

Curved concrete bridges are an important infrastructure form, which meet the needs of modern transportation. Due to their relatively sophisticated geometries, asphalt pavements on the bridge decks are typically subjected to more severe loadings. This study investigated multi-scale mechanical responses of asphalt pavement on a curved bridge deck by using a macro-mesoscale coupling algorithm that can rationally considered the mesostructure of asphalt concrete. The influence of driving speeds, curvature radii, and temperatures on the mechanical responses of different scales was analyzed. The results showed that with the increase of the curvature radius and the decrease of the driving speed, both unevenness of tire loads on the asphalt pavement and stress concentrations in the mesostructure of the asphalt pavement were reduced. Under low temperature, asphalt concrete pavement on the deck encountered stress concentration and mesoscopic damage more easily. Increasing temperature can reduce these effects; however, due to the decrease of its asphalt mortar modulus, plastic deformation may occur in the pavement.

Accurate prediction of effective (overall) viscoelastic properties and mesoscopic responses of asphalt concrete is crucial to investigating the mechanical behavior and damage mechanisms of asphalt pavement. The present study evaluated the effect of aggregate shape on mesomechanical prediction of viscoelastic behavior of asphalt concrete. Two two-dimensional (2D) computational mesomechanics methods, i.e., a random aggregate generation (RAG)-based method and a digital image processing (DIP)-based method, and a three-dimensional (3D) analytical two-layer built-in (TLB) mesomechanics method were adopted. In the RAG-based approach, four regular aggregate shapes (circle, hexagon, pentagon and square) and irregular aggregate shapes were considered. The results showed that when asphalt concrete was treated as a composite consisting of coarser aggregates larger than 2.36 mm, asphalt mortar and air voids, the volume fraction of coarse aggregates was a more critical factor than their shapes for the effective dynamic modulus prediction. The 3D TLB method performed better in predicting the macroscopic effective dynamic modulus of asphalt concrete than the 2D methods, whereas the 2D methods generated superior effective phase angle predictions. The RAG-based model with irregular aggregates and the DIP-based model exhibited significantly higher maximum principal stresses on the mesoscale than those from the RAG-based models with regular aggregates under the compressive loading condition, indicating the importance of applying the realistic aggregate shapes in the mesoscopic stress and damage analysis of asphalt concrete.

Cement emulsified asphalt composite binder (CEACB), composed of cement, asphalt, and some additives, is a typical viscoelastic material. Static and dynamic rheological properties of CEACB are affected by various factors. This study aimed at investigating the effect of different factors on static and dynamic rheological properties of CEACB based on rheology theories. Creep tests and frequency sweep tests were conducted by using a Dynamic Shear Rheometer (DSR). The results show that elasticity of CEACB decreased as the temperature increased, and the temperature sensibility at high temperatures was much lower than that at intermedia temperatures. Elasticity of CEACB increased with the increase of curing age in high frequency region, which means low-temperature cracking resistance of CEACB will be degraded with the increase of curing age. Elasticity of CEACB increased with A/C ratio decreased in low frequency region, which means high-temperature resistance of CEACB increased with the decrease of A/C ratio. Mechanical behaviors of CEACB with A/C = 0.6 and A/C = 1 were more like viscoelastic solid material, while mechanical behaviors of CEACB with A/C = 1.4 were more like viscoelastic fluid material. The 2S2P1D model can characterize the viscoelastic mechanical properties of CEACB well.

The use of mesoporous electrodes in solid oxide cells would lead to a significant enhancement of the performance due to their high surface area and large number of active sites for electrochemical reactions. However, their application in real devices is still hindered by the potential instability of the mesostructure and morphology at high temperatures required for device fabrication and under severe conditions for high-current, long-term operation. Here we report our findings on the preparation and characterization of mesoporous electrodes based on ceria infiltrated with catalysts: an anode consisting of a Ce0.8Sm0.2O1.9 (SDC) scaffold infiltrated with Ni and a cathode consisting of an SDC scaffold infiltrated with Sm0.5Sr0.5CoO3−δ (SSC). In particular, a doped-zirconia electrolyte supported cell with a mesoporous Ni–SDC anode and a mesoporous SSC–SDC cathode demonstrates an excellent peak power density of 565 mW cm−2 at 750 °C (using humidified hydrogen as the fuel). More importantly, both mesoporous electrodes display remarkable stability, yielding a combined electrode virtual non-degradation for the last 500 hours of the test at a constant current density of 635 mA cm−2 at 750 °C, demonstrating the potential of these mesoporous materials as robust electrodes for solid oxide fuel cells or other high-temperature electrochemical energy storage and conversion devices.

In order to study the effect of inherent anisotropy on transverse permeability of porous asphalt mixtures, the transverse permeability performance in different directions of eight kinds of graded porous asphalt mixtures was studied by using the self-made transverse permeability test device of rutting specimen. At the same time, the study combined the grey relation theory, and the influence of the key sieve passing rate on the transverse permeability performance of porous asphalt mixtures is investigated based on inherent anisotropy. The results show that with the increase of the air voids content and the nominal maximum particle size, the transverse permeability coefficient of the rutting specimen increases gradually. The fitting degree of inherent anisotropy can be improved by increasing the nominal maximum particle size and air voids content of asphalt mixtures. The coefficient of variation decreases rapidly when the non-rolled surface is used as the permeable surface. The results of grey correlation analysis showed that the most influential sieve passing rate for the coefficient of variation of OGFC-13 are the 4.75 mm and 1.18 mm, and OGFC-16 are the 2.36 mm and 4.75 mm. For the grey correlation degree of the key sieve passing rate to the coefficient of variation, the OGFC-13 is larger than OGFC-16. The void distribution is uneven for the same rutting specimen surface and the uneven degree of the void distribution in the rolled surface is large.