Feeds

Inventor flames Reg, HP in memristor brouhaha

Empties flammenwerfer tank over hapless hack, boffins

Internet Security Threat Report 2014

Not so says HP, not so at all

Williams agrees Chua broadened his definition but this had nothing to do with saving HP's face, nothing at all.

This issue was made much clearer in a second paper8 published with his then student Sung Mo Kang ... a critical generalization of the simple memristor concept of the first paper.

Chua and Kang introduced the fact that a 'memristive device' has a state variable (or variables), indicated by w, that describes the physical properties of the device at any time. A memristive system is characterized by two equations, the 'quasi-static' conduction equation that relates the voltage across the device to the current through it at any particular time, v = R(w,i) i, and the dynamical equation, which explicitly asserts that the state variable w is a time varying function f of itself and possibly the current through the device, dw/dt = f(w,i).

Neither the flux φ nor the charge q appears in either of these two equations, but it is relatively 'easy to show' that if both R and f are independent of the current i, the two equations reduce to the original definition of a memristor.

Williams then notes that Chua and Kang introduce a key new idea:

Furthermore, the quasi-static conduction equation places a requirement on the current-voltage characteristic of the device – if a memristive system is driven with some type of cyclic excitation, such as a sinusoidal current, the plot of the voltage vs. the current will be a Lissajous curve for which the voltage is always equal to zero when the current is zero, and vice versa.

Chua called this curve a 'pinched hysteresis loop', and it has an important physical interpretation – neither a memristor nor a memristive system stores either charge or energy (like a capacitor, for example), but they do 'remember' their history because of their changing resistance.

This generalised memristor idea was independent of any physical mechanism at the time. In Williams' view: "The key result was that any electronic circuit element that displayed a pinched hysteresis loop in its current-voltage characteristic could be described mathematically by the two memristive system equations."

This led on the generalised memristor idea:

As more researchers began to cite the original works, it became clear to most that the distinctions between 'memristors' and 'memristive systems' were unimportant, so Chua has recommended that the nomenclature be simplified by referring to both as memristors.

What is a memristor?

William's document provides a memristor definition:

According to the general mathematical model, a memristor is any passive electronic circuit element that displays a pinched hysteresis loop in its i-v characteristic, independent of what the physical mechanism is that causes the hysteresis.

The 2-terminal passive electronic circuit restriction has gone away.

Williams says: "Examples of memristors include bipolar and unipolar resistive switches, often called RRAM or ReRAM; 'atomic switches'; spin-torque transfer RAM devices, phase-change memory devices, and several other systems based on a wide variety of materials and mechanisms9."

Mouttet is quite wrong. There is no HP propaganda campaign to take credit for the memristor. HP Is not trying to impose an HP brand on the memristor idea: "We have chosen to use the term memristor to describe the devices in our papers, not because we are trying to impose an 'HP brand' (especially since the term was invented by Leon Chua), but because we feel the general term connotes a broader range of applications."

Also the memristor was a distinct discovery:

It is a rigorous mathematical model that can be used to predict the behavior of a wide variety of physical devices. There have been many developments of different types of memristors, now called by many different names, based on different materials and physical mechanisms, but they are all described by the same general mathematical formalism developed by Chua.

To get deeper into these matters read Williams' short history of memristor development, and make your own mind up whether HP has discovered the Fourth Element or not.

Compliments of the season to you all. ®


Notes 1. Blaise Mouttet assisted in the formation of the patent class for nanotechnology used by the US Patent and Trademark Office. He maintains a blog devoted to reviewing newly issued U.S. patents in nanotechnology and is an inventor in 11 US patents related to memristive electronics applied to signal processing and adaptive control. He has given presentations related to memristive devices at the 1st Memristor and Memristive Systems Symposium held at UC Berkeley in 2008 and at the IEEE International Symposium on Circuits and Systems (ISCAS) held in Paris, France in 2010.

2. Strukov et al., The missing memristor found, Nature 453, 80-83 (2008)

3. S Thakoor et al, Solid-state thin-film memsistor for electronic neural networks, Journal of Applied Physics, v67, n.6, 1990.

4. L. O. Chua, Memristor – the missing circuit element, IEEE Trans. Circuit Theory 18, 507-519 (1971)

5. Read Mouttet's Memsistors, Memristors, and Memresistors paper to get into the detail here.

6. L. Chua, Resistance switching memories are memristors, Appl. Phys. A 102, 765-783 (2011)]

7. Memristive Systems and Devices, published in the Proceedings of the IEEE, vol 64, No 2, 1976.

8. L. O. Chua & S. M. Kang, Memristive devices and systems, Proc. IEEE 64, 209-223 (1976).

9. L. Chua, Resistance switching memories are memristors, Appl. Phys. A 102, 765-783 (2011)

Intelligent flash storage arrays

More from The Register

next story
NSA SOURCE CODE LEAK: Information slurp tools to appear online
Now you can run your own intelligence agency
Azure TITSUP caused by INFINITE LOOP
Fat fingered geo-block kept Aussies in the dark
Yahoo! blames! MONSTER! email! OUTAGE! on! CUT! CABLE! bungle!
Weekend woe for BT as telco struggles to restore service
Cloud unicorns are extinct so DiData cloud mess was YOUR fault
Applications need to be built to handle TITSUP incidents
Stop the IoT revolution! We need to figure out packet sizes first
Researchers test 802.15.4 and find we know nuh-think! about large scale sensor network ops
Turnbull should spare us all airline-magazine-grade cloud hype
Box-hugger is not a dirty word, Minister. Box-huggers make the cloud WORK
SanDisk vows: We'll have a 16TB SSD WHOPPER by 2016
Flash WORM has a serious use for archived photos and videos
Astro-boffins start opening universe simulation data
Got a supercomputer? Want to simulate a universe? Here you go
Microsoft adds video offering to Office 365. Oh NOES, you'll need Adobe Flash
Lovely presentations... but not on your Flash-hating mobe
prev story

Whitepapers

10 ways wire data helps conquer IT complexity
IT teams can automatically detect problems across the IT environment, spot data theft, select unique pieces of transaction payloads to send to a data source, and more.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
How to determine if cloud backup is right for your servers
Two key factors, technical feasibility and TCO economics, that backup and IT operations managers should consider when assessing cloud backup.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Mitigating web security risk with SSL certificates
Web-based systems are essential tools for running business processes and delivering services to customers.