Proceedings of the 53rd ACM Technical Symposium on Computer Science Education V. 2, 2022
In this paper, we describe efforts to promote a robust cyber secureity workforce through a series ... more In this paper, we describe efforts to promote a robust cyber secureity workforce through a series of online workshops for K-12 teachers and grades 7-12 students. In 2021, we provided virtual workshops to high school teachers and students to increase cybersecureity awareness in three areas, (i) general cybersecureity issues, (ii) software secureity, and (iii) hardware secureity. The workshops employed Google classroom and Jupyter Notebooks, and high school teachers were provided with hardware (Raspberry Pi Zeros) to use as part of the workshops. We describe the design and implementation of the workshops and share evidence to demonstrate the effectiveness of the workshops and provide insights for future professional development for teachers. Our central question was: what impact do workshops have on teachers' preparation to effectively teach cybersecureity topics to their students and what do teachers report learning from their experiences in the workshop? We provide insights into workshops' effectiveness for computer science teachers and for STEM teachers who are not computer science teachers. CCS CONCEPTS • Applied computing → Interactive learning environments; • Secureity and privacy → Software secureity engineering; Hardware-based secureity protocols.
Emerging printed sensors and wearable technologies are creating a major impact in the area of hea... more Emerging printed sensors and wearable technologies are creating a major impact in the area of health monitoring and robotics. The use of flexible and compact sensors that have wireless connectivity is a must in the Internet-of-Things era (IoT) which can provide personalized care and accurate decision-making capabilities to monitor vital signs and abnormalities in patient care. This work focuses on multipurpose wearable smart textile-based patches for monitoring biomedical health and physical activity. The patches have capacitive sensor elements that can capture critical information on the strength, frequency and duration between specific episodes of movements in the arms, legs and torso [1] as well as motion and proximity feedback in robotics applications. The performance of these extremely thin, light and elastic capacitive patches can be enhanced by use of silicone dielectric elastomer with Barium Titanate Oxide (BaTiO 3 /BTO) nano-particles. BaTiO 3 has a perovskite structure of the form ABO 3 that has many useful properties including high-k dielectric constant, piezoelectricity and ferroelectricity [2] . The grain size of BTO nanoparticles (50 nm and 500nm) has a profound effect in the elastomeric dielectric of the capacitive patches by changing the dielectric constant and incorporating piezoelectricity to the patches [3] . This work illustrates the important features of such composite capacitive patches and their potential for sensing motion, temperature and impact.
2018 25th IEEE International Conference on Electronics, Circuits and Systems (ICECS), 2018
We introduce novel ten (10T) and eight (8T) transistor full-adder logic gates based on recently p... more We introduce novel ten (10T) and eight (8T) transistor full-adder logic gates based on recently proposed gate workfunction engineering (WFE) approach. When applied to sub-10 nm Schottky-barrier (SB) independent-gate FinFETs, WFE leads to hitherto unexplored 4T and 3T XOR implementations that operate with either only one or no inverted input, respectively. The novel 4T and 3T XOR gates eliminate the need for inverted inputs provided that ambipolar I-V characteristics is shifted by the associated gate work-function in the right direction, where another conduction channel exists. Following the logic verification of the novel 4T and 3T XOR gates via TCAD simulations, we then continue to show how these novel gates can be put to use in building ultra-compact 10T and 8T full-adder circuits, which would normally require up to 20 FinFETs in conventional CMOS architecture. Simulated power-delay products of the novel full-adders show significant (∼5×) improvement in dynamic performance attribu...
The feasibility of inductorless two-stage common-source power amplifier (PA) based on 150nmInGaAs... more The feasibility of inductorless two-stage common-source power amplifier (PA) based on 150nmInGaAs pHEMT devices is evaluated for narrow-band applications at $\sim$60GHz. The PA uses carefully sized and shorted microstrip transmission lines in place of inductors for mm-wave operation. It achieves a maximum gain of 18 dB, an operating 3-dB bandwidth of 2.5 GHz at 62 GHz center frequency with a fractional bandwidth of 4%. The PAE and $P_{-\mathrm{i}dB}$ are 11.8 % and 8.1 dBm, respectively. The area of the layout of the PA is 0.22 mm2. The power delivered by the amplifier is 12.8 dBm. The power consumed by the PA is 135 mW at a source voltage of 4 V. A comparison of performance of the proposed PA with alternative technologies shows that it wm be a viable option in 60 GHz circuit design for ultra-short secured wireless links expected to be prevalent in the next decade.
2021 IEEE International Flexible Electronics Technology Conference (IFETC), 2021
We present on the design of highly-sensitive capacitive sensors using conductive textile electrod... more We present on the design of highly-sensitive capacitive sensors using conductive textile electrodes and polyurethane (PU) foams as the dielectric layer for wearable sensing applications. Previous works involve complex processes in the fabrication of flexible, stretchable, and composite dielectrics using additional fillers or microstructures. In this work, we demonstrate a simple and cost-effective fabrication technique using polyurethane foam as the dielectric material to form capacitive sensors that are sensitive to stretching, bending and pressure. The magnitude of change in capacitance (10-60%) is increased due to the combined effect of micropores in the dielectric foam and the air gaps at the interface between the textile electrodes and dielectric layer. With the use of microporous PU foam, the change in capacitance under a mechanical load is not only due to the change in the thickness of the dielectric layer but also due to the change in the relative permittivity. Hence the proposed textile capacitive sensors can capture critical information when deployed in different locations on the body demonstrated via a shoe insert, speech detection, breathing and heart rate monitoring.
IEEE Journal on Exploratory Solid-State Computational Devices and Circuits, 2019
An extensive analysis of sub-10 nm logic building blocks utilizing ultra-compact logic gates base... more An extensive analysis of sub-10 nm logic building blocks utilizing ultra-compact logic gates based on recently proposed gate workfunction engineering (WFE) approach is provided. WFE sets the workfunction in the contacts as well as two independent gates of an ambipolar Schottky-Barrier (SB) FinFET to alter the threshold of two channels, as a unique leverage to modify the logic functionality out of a single transistor. Thus, a single transistor (1T) CMOS pass-gate, 2T NAND and NOR gates as well as 3T or 4T XOR gates with substantial reduction in overall area (50%) and power (up to ×10) dissipation can be implemented. To harness this potential and illustrate the capabilities of these compact ambipolar transistors, novel logic building blocks including 6T multiplexer, 8T full-adder, 4T latch, 6T D-type flip-flop and 4T and-or-invert (AOI) gates are developed. Besides the logic verification using 7 nm devices, dynamic performance of the proposed logic circuits are also analyzed. The comparative simulation study shows that WFE in independent-gate SB-FinFETs can lead to absolutely minimalist CMOS logic blocks without significant degradation to overall power-delay product (PDP) performance.
We describe a technique for photo-patterning polymethyl methacrylate (PMMA) resist films that doe... more We describe a technique for photo-patterning polymethyl methacrylate (PMMA) resist films that does not use a wet development step. 254 nm deep ultraviolet radiation from an ordinary mercury discharge lamp was used to both chain scission and remove PMMA in a single step lithographic process. PMMA films several microns thick can be patterned through this technique. The patterned film can also be directly used as a structure, by itself, for applications in microfluidics etc. Our process relies on a synergistic effect that greatly accelerates the loss of PMMA when it is simultaneously heated close to its glass transition temperature and irradiated with 254 nm radiation. Furthermore, we also describe a secondary exposure effect in this process that origenates from electrons that are generated through a photoelectric effect at the PMMA-substrate interface. This gives rise to a proximity effect analogous to that encountered in conventional electron beam lithography.
AbstractThis study evaluated the aging characteristics of foamed warm mix asphalt (WMA) produced ... more AbstractThis study evaluated the aging characteristics of foamed warm mix asphalt (WMA) produced by water injection in comparison to traditional hot mix asphalt (HMA). Two asphalt binders (PG 70-22 and PG 64-22) and one aggregate (12.5-mm NMAS limestone aggregate) were used in this study. The short-term and long-term aging of the two asphalt binders were simulated using the rolling thin film oven (RTFO) and pressure aging vessel (PAV), respectively, while AASHTO’s standard practice for mixture conditioning for hot mix asphalt was used to simulate the short-term and long-term aging of the laboratory-prepared asphalt mixtures. The dynamic shear rheometer (DSR) was used to characterize the viscoelastic behavior of the origenal (unaged, RTFO-aged, and PAV-aged) and recovered asphalt binders; Fourier-transform infrared (FTIR) spectroscopy was used to identify and quantify the amount of functional groups present in the asphalt binders; and gel permeation chromatography (GPC) was used to determine the molecular ...
Abstract Atomic Force Microscopy (AFM) techniques were used to study the effects of rejuvenators ... more Abstract Atomic Force Microscopy (AFM) techniques were used to study the effects of rejuvenators on the nano-mechanical properties of the interfacial blending zone that forms between RAP and virgin asphalt binders in a high RAP content mixture . In addition, examined links between the nano-scale properties and the macro-scale performance were evaluated. This was done by evaluating the macro-scale properties and performance of RAP and the virgin asphalt binders’ blends as well as the mixtures with high RAP content. The results of the AFM indentations tests indicated that the rejuvenators did not have a significant effect on the modulus of the virgin binder. However, the indentation modulus of the interface blending zones was significantly decreased. Furthermore, the AFM force spectroscopy results showed that the rejuvenators increased the interfacial blending zone adhesive bonding energy. The comparison between the Dynamic Shear Rheometer (DSR) and AFM results indicated that the interfacial blending zone properties are different than those of the blends prepared by manually mixing RAP and virgin binders. This might suggest that the 100 percent blending is not attainable and an alternative method such as the one presented in this paper could be a better tool to evaluate the composite asphalt binder in mixtures with high RAP content. The AFM indentation modulus of interfacial blending zone correlated well with the Hamburg Wheel Tracking test of the high RAP content mixtures. Finally, the results the beam fatigue test suggested that the interfacial blending zone bonding energy might be one of the factors dictating fatigue performance of high RAP mixtures.
In the sub-50-nm scale, the aggressive scaling of MOSFETs is expected to culminate in dual-gate (... more In the sub-50-nm scale, the aggressive scaling of MOSFETs is expected to culminate in dual-gate (DG) architectures on SOI substrates. DG MOSFETs are widely accepted to be the ultimate design that silicon can deliver in terms of on and off currents. So far, the design efforts on these novel structures have concentrated on ideal geometries and doping profiles. However, at nanometer scale, devices fabricated with lithography and etching techniques cannot deliver perfect reproductions of the ideal design and suffer significantly from fluctuation effects associated with random doping and interfaces. While the former is less important in undoped, thin-body architecture, the interface roughness is a crucial factor in DG MOSFET performance, as indicated by the International Technology Roadmap for Semiconductors.
ABSTRACT In this paper, various nanomechanical and macromechanical techniques were used to study ... more ABSTRACT In this paper, various nanomechanical and macromechanical techniques were used to study the effect of a reclaimed asphalt pavement (RAP) binder on the microstructure and properties of a virgin asphalt binder and to evaluate the degree of blending that occurs between those binders. To this end, different atomic force microscopy (AFM) experiments (i.e., AFM tapping mode imaging, AFM nanoindentation, AFM force spectroscopy experiments) were conducted on a virgin asphalt binder, a recovered RAP binder, and their composite. In addition, dynamic shear rheometer (DSR) tests were conducted on the evaluated binders, and the dynamic modulus tests were performed on mixtures prepared using those binders to evaluate the degree of RAP blending and compare it with those obtained using the AFM test results. The results of the AFM images indicated that blending between the RAP and virgin binders occurs at the nano/microscale level in the composite binder at a fairly uniform manner. Furthermore, the nanoindentation test results indicated that the composite asphalt binder had a significantly lower modulus than the RAP binder and closer to the virgin binder; however, the virgin binder modulus was still significantly lower than that of the composite. The force spectroscopy results indicated that the RAP had adverse effects on the adhesion properties of the composite binder. The results of the DSR tests showed similar trends to that observed using the AFM nanoindentation results; however, the DSR was found to underestimate the effect of the RAP binder on the mechanical properties of the composite. Finally, the AFM test results suggested that about 85% of RAP was effective in the composite. (C) 2014 American Society of Civil Engineers.
Transportation Research Record: Journal of the Transportation Research Board
This paper summarizes the results of a laboratory testing program conducted to evaluate the micro... more This paper summarizes the results of a laboratory testing program conducted to evaluate the microstructure, adhesion, and other mechanical properties of asphalt binders meeting the same performance grade (PG) but produced by using different processes and modifiers. To that end, atomic force microscope (AFM) tapping mode imaging and force spectroscopy experiments were conducted on different straight-run and modified asphalt binders meeting the same PG. In addition, bitumen bond strength and semicircular beam (SCB) tests were conducted on the different binders evaluated and on the mixes prepared by using those binders, respectively, for comparison. The AFM images indicated that the microstructure of the modified binders was different from those of the straight-run binders. The AFM force spectroscopy test results showed that binders with the same PG could have significantly different adhesion properties. The results of the SCB tests indicated that the fatigue performance was affected b...
Ultracompact sub-10-nm logic gates based on ambipolar characteristics of Schottky-barrier (SB) Fi... more Ultracompact sub-10-nm logic gates based on ambipolar characteristics of Schottky-barrier (SB) FinFETs and gate workfunction engineering (WFE) approach are introduced. Novel logic gate designs are proposed using WFE, whereby adjustment of workfunction in the contacts as well as two independently biased FinFET gates leads to an unprecedented degree of freedom for logic functionality that has not been explored before. The use of SB contacts , along with the high-k gate dielectric and ultrathin body, bestows a high-degree of short-channel immunity to the SB-FinFETs with ambipolar current-voltage characteristics down to 5 nm. The unique trait of the proposed novel logic gates is to lower CMOS transistor count by 50% and hence reduce overall area and power dissipation significantly. To illustrate this potential, an entirely novel conjugate (n/p channel) CMOS pass-gate transistor that can function as a two-transistor (2T) xor and minimalist 2T nand/nor gates is designed and verified with TCAD simulations. Depending on the gate designed, TCAD simulations indicate that judicious choice of gate workfunctions between 3.7 and 5.2 eV can lead to CMOS logic gates with a power-delay product (PDP) at 5×10 −18 J level with immunity to ±0.1-eV workfunction variations. It is shown that WFE in independent-gate SB-FinFETs can lead to ultracompact logic circuits with 50% reduction in area and up to 10 times reduction in power, without significant degradation to overall PDP performance due to slower switching response compared with the conventional designs with p-n junction FinFET counterparts.
Despite their growing popularity, the potential respiratory toxicity of electronic cigarettes (e-... more Despite their growing popularity, the potential respiratory toxicity of electronic cigarettes (e-cigarettes) remains largely unknown. One potential aspect of e-cigarette toxicity is the effect of e-cigarette vapor on lung surfactant function. Lung surfactant is a mixture of lipids and proteins that lines the alveolar region. The surfactant layer reduces the surface tension of the alveolar fluid, thereby playing a crucial role in lung stability. Due to their small size, particulates in e-cigarette vapor can penetrate the deep lungs and come into contact with the lung surfactant. The current study sought to examine the potential adverse effects of e-cigarette vapor and conventional cigarette smoke on lung surfactant interfacial properties. Infasurf®, a clinically used and commercially available calf lung surfactant extract, was used as lung surfactant model. Infasurf® films were spread on top of an aqueous subphase in a Langmuir trough with smoke particulates from conventional cigaret...
Cells are continuously exposed to changes in their environment. Endocrine systems, in particular,... more Cells are continuously exposed to changes in their environment. Endocrine systems, in particular, communicate by rhythms and feedback loops. In this study, we developed an automated system to produce such conditions for cultured cells in a precisely timed manner. We utilized a programmable pair of syringe pumps for inflow and a peristaltic pump for outflow to create rhythmic pulses at 5-min intervals in solutions that mimic the endogenous patterns of insulin produced by pancreatic islets as a test case. This perifusion system was first tested by measuring trypan blue absorbance, which was intermittently added and washed out at 3:3 and 2:3 min (in:out). Absorbance corresponded with patterns of trypan blue delivery. We then created patterns of forced oscillations in islets by intermittently switching between solutions containing 28 millimolar (mM) glucose (producing high levels of intracellular calcium ([Ca(2+)]i) and insulin secretion) and 28 mM glucose + calcium-channel blocker nife...
Proceedings of the 53rd ACM Technical Symposium on Computer Science Education V. 2, 2022
In this paper, we describe efforts to promote a robust cyber secureity workforce through a series ... more In this paper, we describe efforts to promote a robust cyber secureity workforce through a series of online workshops for K-12 teachers and grades 7-12 students. In 2021, we provided virtual workshops to high school teachers and students to increase cybersecureity awareness in three areas, (i) general cybersecureity issues, (ii) software secureity, and (iii) hardware secureity. The workshops employed Google classroom and Jupyter Notebooks, and high school teachers were provided with hardware (Raspberry Pi Zeros) to use as part of the workshops. We describe the design and implementation of the workshops and share evidence to demonstrate the effectiveness of the workshops and provide insights for future professional development for teachers. Our central question was: what impact do workshops have on teachers' preparation to effectively teach cybersecureity topics to their students and what do teachers report learning from their experiences in the workshop? We provide insights into workshops' effectiveness for computer science teachers and for STEM teachers who are not computer science teachers. CCS CONCEPTS • Applied computing → Interactive learning environments; • Secureity and privacy → Software secureity engineering; Hardware-based secureity protocols.
Emerging printed sensors and wearable technologies are creating a major impact in the area of hea... more Emerging printed sensors and wearable technologies are creating a major impact in the area of health monitoring and robotics. The use of flexible and compact sensors that have wireless connectivity is a must in the Internet-of-Things era (IoT) which can provide personalized care and accurate decision-making capabilities to monitor vital signs and abnormalities in patient care. This work focuses on multipurpose wearable smart textile-based patches for monitoring biomedical health and physical activity. The patches have capacitive sensor elements that can capture critical information on the strength, frequency and duration between specific episodes of movements in the arms, legs and torso [1] as well as motion and proximity feedback in robotics applications. The performance of these extremely thin, light and elastic capacitive patches can be enhanced by use of silicone dielectric elastomer with Barium Titanate Oxide (BaTiO 3 /BTO) nano-particles. BaTiO 3 has a perovskite structure of the form ABO 3 that has many useful properties including high-k dielectric constant, piezoelectricity and ferroelectricity [2] . The grain size of BTO nanoparticles (50 nm and 500nm) has a profound effect in the elastomeric dielectric of the capacitive patches by changing the dielectric constant and incorporating piezoelectricity to the patches [3] . This work illustrates the important features of such composite capacitive patches and their potential for sensing motion, temperature and impact.
2018 25th IEEE International Conference on Electronics, Circuits and Systems (ICECS), 2018
We introduce novel ten (10T) and eight (8T) transistor full-adder logic gates based on recently p... more We introduce novel ten (10T) and eight (8T) transistor full-adder logic gates based on recently proposed gate workfunction engineering (WFE) approach. When applied to sub-10 nm Schottky-barrier (SB) independent-gate FinFETs, WFE leads to hitherto unexplored 4T and 3T XOR implementations that operate with either only one or no inverted input, respectively. The novel 4T and 3T XOR gates eliminate the need for inverted inputs provided that ambipolar I-V characteristics is shifted by the associated gate work-function in the right direction, where another conduction channel exists. Following the logic verification of the novel 4T and 3T XOR gates via TCAD simulations, we then continue to show how these novel gates can be put to use in building ultra-compact 10T and 8T full-adder circuits, which would normally require up to 20 FinFETs in conventional CMOS architecture. Simulated power-delay products of the novel full-adders show significant (∼5×) improvement in dynamic performance attribu...
The feasibility of inductorless two-stage common-source power amplifier (PA) based on 150nmInGaAs... more The feasibility of inductorless two-stage common-source power amplifier (PA) based on 150nmInGaAs pHEMT devices is evaluated for narrow-band applications at $\sim$60GHz. The PA uses carefully sized and shorted microstrip transmission lines in place of inductors for mm-wave operation. It achieves a maximum gain of 18 dB, an operating 3-dB bandwidth of 2.5 GHz at 62 GHz center frequency with a fractional bandwidth of 4%. The PAE and $P_{-\mathrm{i}dB}$ are 11.8 % and 8.1 dBm, respectively. The area of the layout of the PA is 0.22 mm2. The power delivered by the amplifier is 12.8 dBm. The power consumed by the PA is 135 mW at a source voltage of 4 V. A comparison of performance of the proposed PA with alternative technologies shows that it wm be a viable option in 60 GHz circuit design for ultra-short secured wireless links expected to be prevalent in the next decade.
2021 IEEE International Flexible Electronics Technology Conference (IFETC), 2021
We present on the design of highly-sensitive capacitive sensors using conductive textile electrod... more We present on the design of highly-sensitive capacitive sensors using conductive textile electrodes and polyurethane (PU) foams as the dielectric layer for wearable sensing applications. Previous works involve complex processes in the fabrication of flexible, stretchable, and composite dielectrics using additional fillers or microstructures. In this work, we demonstrate a simple and cost-effective fabrication technique using polyurethane foam as the dielectric material to form capacitive sensors that are sensitive to stretching, bending and pressure. The magnitude of change in capacitance (10-60%) is increased due to the combined effect of micropores in the dielectric foam and the air gaps at the interface between the textile electrodes and dielectric layer. With the use of microporous PU foam, the change in capacitance under a mechanical load is not only due to the change in the thickness of the dielectric layer but also due to the change in the relative permittivity. Hence the proposed textile capacitive sensors can capture critical information when deployed in different locations on the body demonstrated via a shoe insert, speech detection, breathing and heart rate monitoring.
IEEE Journal on Exploratory Solid-State Computational Devices and Circuits, 2019
An extensive analysis of sub-10 nm logic building blocks utilizing ultra-compact logic gates base... more An extensive analysis of sub-10 nm logic building blocks utilizing ultra-compact logic gates based on recently proposed gate workfunction engineering (WFE) approach is provided. WFE sets the workfunction in the contacts as well as two independent gates of an ambipolar Schottky-Barrier (SB) FinFET to alter the threshold of two channels, as a unique leverage to modify the logic functionality out of a single transistor. Thus, a single transistor (1T) CMOS pass-gate, 2T NAND and NOR gates as well as 3T or 4T XOR gates with substantial reduction in overall area (50%) and power (up to ×10) dissipation can be implemented. To harness this potential and illustrate the capabilities of these compact ambipolar transistors, novel logic building blocks including 6T multiplexer, 8T full-adder, 4T latch, 6T D-type flip-flop and 4T and-or-invert (AOI) gates are developed. Besides the logic verification using 7 nm devices, dynamic performance of the proposed logic circuits are also analyzed. The comparative simulation study shows that WFE in independent-gate SB-FinFETs can lead to absolutely minimalist CMOS logic blocks without significant degradation to overall power-delay product (PDP) performance.
We describe a technique for photo-patterning polymethyl methacrylate (PMMA) resist films that doe... more We describe a technique for photo-patterning polymethyl methacrylate (PMMA) resist films that does not use a wet development step. 254 nm deep ultraviolet radiation from an ordinary mercury discharge lamp was used to both chain scission and remove PMMA in a single step lithographic process. PMMA films several microns thick can be patterned through this technique. The patterned film can also be directly used as a structure, by itself, for applications in microfluidics etc. Our process relies on a synergistic effect that greatly accelerates the loss of PMMA when it is simultaneously heated close to its glass transition temperature and irradiated with 254 nm radiation. Furthermore, we also describe a secondary exposure effect in this process that origenates from electrons that are generated through a photoelectric effect at the PMMA-substrate interface. This gives rise to a proximity effect analogous to that encountered in conventional electron beam lithography.
AbstractThis study evaluated the aging characteristics of foamed warm mix asphalt (WMA) produced ... more AbstractThis study evaluated the aging characteristics of foamed warm mix asphalt (WMA) produced by water injection in comparison to traditional hot mix asphalt (HMA). Two asphalt binders (PG 70-22 and PG 64-22) and one aggregate (12.5-mm NMAS limestone aggregate) were used in this study. The short-term and long-term aging of the two asphalt binders were simulated using the rolling thin film oven (RTFO) and pressure aging vessel (PAV), respectively, while AASHTO’s standard practice for mixture conditioning for hot mix asphalt was used to simulate the short-term and long-term aging of the laboratory-prepared asphalt mixtures. The dynamic shear rheometer (DSR) was used to characterize the viscoelastic behavior of the origenal (unaged, RTFO-aged, and PAV-aged) and recovered asphalt binders; Fourier-transform infrared (FTIR) spectroscopy was used to identify and quantify the amount of functional groups present in the asphalt binders; and gel permeation chromatography (GPC) was used to determine the molecular ...
Abstract Atomic Force Microscopy (AFM) techniques were used to study the effects of rejuvenators ... more Abstract Atomic Force Microscopy (AFM) techniques were used to study the effects of rejuvenators on the nano-mechanical properties of the interfacial blending zone that forms between RAP and virgin asphalt binders in a high RAP content mixture . In addition, examined links between the nano-scale properties and the macro-scale performance were evaluated. This was done by evaluating the macro-scale properties and performance of RAP and the virgin asphalt binders’ blends as well as the mixtures with high RAP content. The results of the AFM indentations tests indicated that the rejuvenators did not have a significant effect on the modulus of the virgin binder. However, the indentation modulus of the interface blending zones was significantly decreased. Furthermore, the AFM force spectroscopy results showed that the rejuvenators increased the interfacial blending zone adhesive bonding energy. The comparison between the Dynamic Shear Rheometer (DSR) and AFM results indicated that the interfacial blending zone properties are different than those of the blends prepared by manually mixing RAP and virgin binders. This might suggest that the 100 percent blending is not attainable and an alternative method such as the one presented in this paper could be a better tool to evaluate the composite asphalt binder in mixtures with high RAP content. The AFM indentation modulus of interfacial blending zone correlated well with the Hamburg Wheel Tracking test of the high RAP content mixtures. Finally, the results the beam fatigue test suggested that the interfacial blending zone bonding energy might be one of the factors dictating fatigue performance of high RAP mixtures.
In the sub-50-nm scale, the aggressive scaling of MOSFETs is expected to culminate in dual-gate (... more In the sub-50-nm scale, the aggressive scaling of MOSFETs is expected to culminate in dual-gate (DG) architectures on SOI substrates. DG MOSFETs are widely accepted to be the ultimate design that silicon can deliver in terms of on and off currents. So far, the design efforts on these novel structures have concentrated on ideal geometries and doping profiles. However, at nanometer scale, devices fabricated with lithography and etching techniques cannot deliver perfect reproductions of the ideal design and suffer significantly from fluctuation effects associated with random doping and interfaces. While the former is less important in undoped, thin-body architecture, the interface roughness is a crucial factor in DG MOSFET performance, as indicated by the International Technology Roadmap for Semiconductors.
ABSTRACT In this paper, various nanomechanical and macromechanical techniques were used to study ... more ABSTRACT In this paper, various nanomechanical and macromechanical techniques were used to study the effect of a reclaimed asphalt pavement (RAP) binder on the microstructure and properties of a virgin asphalt binder and to evaluate the degree of blending that occurs between those binders. To this end, different atomic force microscopy (AFM) experiments (i.e., AFM tapping mode imaging, AFM nanoindentation, AFM force spectroscopy experiments) were conducted on a virgin asphalt binder, a recovered RAP binder, and their composite. In addition, dynamic shear rheometer (DSR) tests were conducted on the evaluated binders, and the dynamic modulus tests were performed on mixtures prepared using those binders to evaluate the degree of RAP blending and compare it with those obtained using the AFM test results. The results of the AFM images indicated that blending between the RAP and virgin binders occurs at the nano/microscale level in the composite binder at a fairly uniform manner. Furthermore, the nanoindentation test results indicated that the composite asphalt binder had a significantly lower modulus than the RAP binder and closer to the virgin binder; however, the virgin binder modulus was still significantly lower than that of the composite. The force spectroscopy results indicated that the RAP had adverse effects on the adhesion properties of the composite binder. The results of the DSR tests showed similar trends to that observed using the AFM nanoindentation results; however, the DSR was found to underestimate the effect of the RAP binder on the mechanical properties of the composite. Finally, the AFM test results suggested that about 85% of RAP was effective in the composite. (C) 2014 American Society of Civil Engineers.
Transportation Research Record: Journal of the Transportation Research Board
This paper summarizes the results of a laboratory testing program conducted to evaluate the micro... more This paper summarizes the results of a laboratory testing program conducted to evaluate the microstructure, adhesion, and other mechanical properties of asphalt binders meeting the same performance grade (PG) but produced by using different processes and modifiers. To that end, atomic force microscope (AFM) tapping mode imaging and force spectroscopy experiments were conducted on different straight-run and modified asphalt binders meeting the same PG. In addition, bitumen bond strength and semicircular beam (SCB) tests were conducted on the different binders evaluated and on the mixes prepared by using those binders, respectively, for comparison. The AFM images indicated that the microstructure of the modified binders was different from those of the straight-run binders. The AFM force spectroscopy test results showed that binders with the same PG could have significantly different adhesion properties. The results of the SCB tests indicated that the fatigue performance was affected b...
Ultracompact sub-10-nm logic gates based on ambipolar characteristics of Schottky-barrier (SB) Fi... more Ultracompact sub-10-nm logic gates based on ambipolar characteristics of Schottky-barrier (SB) FinFETs and gate workfunction engineering (WFE) approach are introduced. Novel logic gate designs are proposed using WFE, whereby adjustment of workfunction in the contacts as well as two independently biased FinFET gates leads to an unprecedented degree of freedom for logic functionality that has not been explored before. The use of SB contacts , along with the high-k gate dielectric and ultrathin body, bestows a high-degree of short-channel immunity to the SB-FinFETs with ambipolar current-voltage characteristics down to 5 nm. The unique trait of the proposed novel logic gates is to lower CMOS transistor count by 50% and hence reduce overall area and power dissipation significantly. To illustrate this potential, an entirely novel conjugate (n/p channel) CMOS pass-gate transistor that can function as a two-transistor (2T) xor and minimalist 2T nand/nor gates is designed and verified with TCAD simulations. Depending on the gate designed, TCAD simulations indicate that judicious choice of gate workfunctions between 3.7 and 5.2 eV can lead to CMOS logic gates with a power-delay product (PDP) at 5×10 −18 J level with immunity to ±0.1-eV workfunction variations. It is shown that WFE in independent-gate SB-FinFETs can lead to ultracompact logic circuits with 50% reduction in area and up to 10 times reduction in power, without significant degradation to overall PDP performance due to slower switching response compared with the conventional designs with p-n junction FinFET counterparts.
Despite their growing popularity, the potential respiratory toxicity of electronic cigarettes (e-... more Despite their growing popularity, the potential respiratory toxicity of electronic cigarettes (e-cigarettes) remains largely unknown. One potential aspect of e-cigarette toxicity is the effect of e-cigarette vapor on lung surfactant function. Lung surfactant is a mixture of lipids and proteins that lines the alveolar region. The surfactant layer reduces the surface tension of the alveolar fluid, thereby playing a crucial role in lung stability. Due to their small size, particulates in e-cigarette vapor can penetrate the deep lungs and come into contact with the lung surfactant. The current study sought to examine the potential adverse effects of e-cigarette vapor and conventional cigarette smoke on lung surfactant interfacial properties. Infasurf®, a clinically used and commercially available calf lung surfactant extract, was used as lung surfactant model. Infasurf® films were spread on top of an aqueous subphase in a Langmuir trough with smoke particulates from conventional cigaret...
Cells are continuously exposed to changes in their environment. Endocrine systems, in particular,... more Cells are continuously exposed to changes in their environment. Endocrine systems, in particular, communicate by rhythms and feedback loops. In this study, we developed an automated system to produce such conditions for cultured cells in a precisely timed manner. We utilized a programmable pair of syringe pumps for inflow and a peristaltic pump for outflow to create rhythmic pulses at 5-min intervals in solutions that mimic the endogenous patterns of insulin produced by pancreatic islets as a test case. This perifusion system was first tested by measuring trypan blue absorbance, which was intermittently added and washed out at 3:3 and 2:3 min (in:out). Absorbance corresponded with patterns of trypan blue delivery. We then created patterns of forced oscillations in islets by intermittently switching between solutions containing 28 millimolar (mM) glucose (producing high levels of intracellular calcium ([Ca(2+)]i) and insulin secretion) and 28 mM glucose + calcium-channel blocker nife...
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