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Articles 1 - 12 of 12
Full-Text Articles in Engineering
Raising Dielectric Permittivity Mitigates Dopant-Induced Disorder In Conjugated Polymers, Meenakshi Upadhyaya, Michael Lu-Díaz, Subhayan Samanta, Muhammad Abdullah, Keith Dusoe, Kevin R. Kittilstved, Dhandapani Venkataraman, Zlatan Akšamija
Raising Dielectric Permittivity Mitigates Dopant-Induced Disorder In Conjugated Polymers, Meenakshi Upadhyaya, Michael Lu-Díaz, Subhayan Samanta, Muhammad Abdullah, Keith Dusoe, Kevin R. Kittilstved, Dhandapani Venkataraman, Zlatan Akšamija
Electrical and Computer Engineering Faculty Publication Series
Conjugated polymers need to be doped to increase charge carrier density and reach the electrical conductivity necessary for electronic and energy applications. While doping increases carrier density, Coulomb interactions between the dopant molecules and the localized carriers are poorly screened, causing broadening and a heavy tail in the electronic density-of-states (DOS). The authors examine the effects of dopant-induced disorder on two complimentary charge transport properties of semiconducting polymers, the Seebeck coefficient and electrical conductivity, and demonstrate a way to mitigate them. Their simulations, based on a modified Gaussian disorder model with Miller-Abrahams hopping rates, show that dopant-induced broadening of the …
Experimental Study Of Microwave Attenuation In A Compartment Fire, Sang Gi Hong, Hakjune Lee, Hoesung Yang, Junho Jin, Hyesun Lee, Kangbok Lee
Experimental Study Of Microwave Attenuation In A Compartment Fire, Sang Gi Hong, Hakjune Lee, Hoesung Yang, Junho Jin, Hyesun Lee, Kangbok Lee
Electrical and Computer Engineering Faculty Publication Series
In this letter, we show the experimental results of microwave attenuation characteristics for representative communication frequencies (UHF, public safety long-term evolution [PSLTE], LoRa, Wi-Fi, and LTE) in a compartment fire. We used kerosene, lumber, and urethane foam as fuels, which can be easily found in homes, and measured the signal intensity with three antenna heights to investigate the effect of the flame and smoke. In the compartment environment, the ionized particles were the dominant attenuation factor of the signals. Furthermore, measurements revealed that the attenuation depends on frequencies and fuel types. In particular, large attenuation was observed at particular frequencies …
Cloud And Edge Computation Offloading For Latency Limited Services, Ivana Kovacevic, Erkki Harjula, Savo Glisic, Beatriz Lorenzo, Mika Ylianttila
Cloud And Edge Computation Offloading For Latency Limited Services, Ivana Kovacevic, Erkki Harjula, Savo Glisic, Beatriz Lorenzo, Mika Ylianttila
Electrical and Computer Engineering Faculty Publication Series
Multi-access Edge Computing (MEC) is recognised as a solution in future networks to offload computation and data storage from mobile and IoT devices to the servers at the edge of mobile networks. It reduces the network traffic and service latency compared to passing all data to cloud data centers while offering greater processing power than handling tasks locally at terminals. Since MEC servers are scattered throughout the radio access network, their computation capacities are modest in comparison to large cloud data centers. Therefore, offloading decision between MEC and cloud server should minimize the usage of the resources while maximizing the …
Quantifying As Path Inflation By Routing Policies, Qixin Gao, Feng Wang, Lixin Gao
Quantifying As Path Inflation By Routing Policies, Qixin Gao, Feng Wang, Lixin Gao
Electrical and Computer Engineering Faculty Publication Series
A route in the Internet may take a longer AS path than the shortest AS path due to routing policies. In this paper, we systematically analyze AS paths and quantify the extent to which routing policies inflate AS paths. The results show that AS path inflation in the Internet is more prevalent than expected. We first present the extent of AS path inflation observed from the RouteView and RIPE routing tables. We then employ three common routing policies to show the extent of AS path inflation. We find that No-Valley routing policy causes the least AS path inflation among the …
Voltage Divider Effect For The Improvement Of Variability And Endurance Of Taox Memristor, Kyung Min Kim, J. Joshua Yang, John Paul Strachan, Emmanuelle Merced Grafals, Ning Ge, Noraica Davila Melendez, Zhiyong Li, R. Stanley Williams
Voltage Divider Effect For The Improvement Of Variability And Endurance Of Taox Memristor, Kyung Min Kim, J. Joshua Yang, John Paul Strachan, Emmanuelle Merced Grafals, Ning Ge, Noraica Davila Melendez, Zhiyong Li, R. Stanley Williams
Electrical and Computer Engineering Faculty Publication Series
The impact of a series resistor (RS) on the variability and endurance performance of memristor was studied in the TaOx memristive system. A dynamic voltage divider between the RS and memristor during both the set and the reset switching cycles can suppress the inherent irregularity of the voltage dropped on the memristor, resulting in a greatly reduced switching variability. By selecting the proper resistance value of RS for the set and reset cycles respectively, we observed a dramatically improved endurance of the TaOx memristor. Such a voltage divider effect can thus be critical for the memristor applications that require low …
Evaluation Of A Scalable Information Analytics System For Enhanced Situational Awareness In Mass Casualty Events, Aura Ganz, James M. Schafer, Zhuorui Yang, Jun Yi, Graydon Lord, Gregory Ciottone
Evaluation Of A Scalable Information Analytics System For Enhanced Situational Awareness In Mass Casualty Events, Aura Ganz, James M. Schafer, Zhuorui Yang, Jun Yi, Graydon Lord, Gregory Ciottone
Electrical and Computer Engineering Faculty Publication Series
We investigate the utility of DIORAMA-II system which provides enhanced situational awareness within a disaster scene by using real-time visual analytics tools and a collaboration platform between the incident commander and the emergency responders. Our trials were conducted in different geographical areas (feature-rich and featureless regions) and in different lighting conditions (daytime and nighttime). DIORAMA-II obtained considerable time gain in efficiency compared to conventional paper based systems. DIORAMA-II time gain was reflected in reduction of both average triage time per patient (up to 34.3% average triage time reduction per patient) and average transport time per patient (up to 76.3% average …
Engineering Nonlinearity Into Memristors For Passive Crossbar Applications, Jianhua Yang, M Zhang, Matthew Pickett, Stanley Williams
Engineering Nonlinearity Into Memristors For Passive Crossbar Applications, Jianhua Yang, M Zhang, Matthew Pickett, Stanley Williams
Electrical and Computer Engineering Faculty Publication Series
Although TaOx memristors have demonstrated encouraging write/erase endurance and nanosecond switching speeds, the linear current-voltage (I-V) characteristic in the low resistance state limits their applications in large passive crossbar arrays. We demonstrate here that a TiO2-x/TaOx oxide heterostructure incorporated into a 50 nm× 50 nm memristor displays a very large nonlinearity such that I(V/2) ≈ I(V)/100 for V ≈ 1 volt, which is caused by current-controlled negative differential resistance in the device.
Anatomy Of A Nanoscale Conduction Channel Reveals The Mechanism Of A High-Performance Memristor, Feng Miao, John Strachan, Jianhua Yang, M Zhang, Ilan Goldfarb, Antonio Torrezan, Peter Eschbach, Ronald Kelley, Gilberto Medeiros-Ribeiro, R Stanley Williams
Anatomy Of A Nanoscale Conduction Channel Reveals The Mechanism Of A High-Performance Memristor, Feng Miao, John Strachan, Jianhua Yang, M Zhang, Ilan Goldfarb, Antonio Torrezan, Peter Eschbach, Ronald Kelley, Gilberto Medeiros-Ribeiro, R Stanley Williams
Electrical and Computer Engineering Faculty Publication Series
By employing a precise method for locating and directlyimaging the active switching region in a resistive random access memory (RRAM) device, a nanoscale conducting channel consisting of an amorphous Ta(O) solid solution surrounded by nearly stoichiometric Ta2O5 is observed. Structural and chemical analysis of the channel combined with temperature-dependent transport measurements indicate a unique resistance switching mechanism.
High Switching Endurance In TaoX Memristive Devices, Jianhua Yang, M Zhang, John Strachan, Feng Miao, Matthew Pickett, Ronald Kelley
High Switching Endurance In TaoX Memristive Devices, Jianhua Yang, M Zhang, John Strachan, Feng Miao, Matthew Pickett, Ronald Kelley
Electrical and Computer Engineering Faculty Publication Series
We demonstrate over 1×1010 open-loop switching cycles from a simple memristive device stack of Pt/TaO��/Ta. We compare this system to a similar device stack based on titanium oxides to obtain insight into the solid-state thermodynamic and kinetic factors that influence endurance in metal-oxide memristors.
Diffusion Of Adhesion Layer Metals Controls Nanoscale Memristive Switching, Jianhua Yang, John Strachan, Qiangfei Xia, Douglas Ohlberg, Philip Kuekes, Ronald Kelley, William Stickle, Duncan Stewart, Gilberto Medeiros-Ribeiro,, R Stanley Williams
Diffusion Of Adhesion Layer Metals Controls Nanoscale Memristive Switching, Jianhua Yang, John Strachan, Qiangfei Xia, Douglas Ohlberg, Philip Kuekes, Ronald Kelley, William Stickle, Duncan Stewart, Gilberto Medeiros-Ribeiro,, R Stanley Williams
Electrical and Computer Engineering Faculty Publication Series
Thermal diffusion of Ti through Pt electrode forms Ti atom channels of 1 nm diameter along Pt grain boundaries, seeding switching centers and controlling nanoscale memristive switching. The image shows EFTEM maps of Ti overlaid on HRTEM images for a Si/SiO2 100 nm/Ti 5nm/Pt 15 nm sample in-situ annealed in ultrahigh vacuum at 250 °C for 1 hour.
The Mechanism Of Electroforming Of Metal Oxide Memristive Switches, Jianhua Yang, Feng Miao, Matthew Pickett, Douglas Ohlberg, Duncan Stewart, Chun Ning Lau, R Stanley Williams
The Mechanism Of Electroforming Of Metal Oxide Memristive Switches, Jianhua Yang, Feng Miao, Matthew Pickett, Douglas Ohlberg, Duncan Stewart, Chun Ning Lau, R Stanley Williams
Electrical and Computer Engineering Faculty Publication Series
Metal and semiconductor oxides are ubiquitous electronic materials. Normally insulating, oxides can change behavior under high electric fields—through ‘electroforming’ or ‘breakdown’—critically affecting CMOS (complementary metal–oxide–semiconductor) logic,DRAM (dynamic random access memory) and flash memory, and tunnel barrier oxides. An initial irreversible electroforming process has been invariably required for obtaining metal oxide resistance switches, which may open urgently needed new avenues for advanced computer memory and logic circuits including ultra-dense non-volatile random access memory (NVRAM) and adaptive neuromorphic logic circuits. This electrical switching arises from the coupled motion of electrons and ions within the oxide material, as one of the first recognized …
A Family Of Electronically Reconfigurable Nanodevices, Jianhua Yang, Julien Borghetti, David Murphy, Duncan Stewart, R Stanley Williams
A Family Of Electronically Reconfigurable Nanodevices, Jianhua Yang, Julien Borghetti, David Murphy, Duncan Stewart, R Stanley Williams
Electrical and Computer Engineering Faculty Publication Series
AFM image of 17 nanodevices with a zoom-in cartoon schematically shows an individual crosspoint device consisting of two Pt metal electrodes separated by a TiO2 bi-layer memristive material. By applying an electric field across the memristive material, oxygen vacancies can drift up and down, leading to four current-transport end-states. The switching between these end-states results in a family of nanodevices.