Search

This brief presents the concept of one-shot refresh (OSR) for dynamic memories. The uniqueness of OSR that differs from the conventional row-by-row refresh operations, is that OSR is able to refresh all rows in the entire array by just one single refresh without the need to read out the stored data in each row. By doing so, significant energy savings could be achieved, and the time window accessible for regular read and write operations is widened with less disruption by the refresh traffic. We show that a few devices could be used to update existing designs to gain the OSR capability. These devices all exhibit hysteretic I-V characteristics and support the OSR data-independent refresh without the need to read out data first. The enabler is the proposed circuit technique for refresh and standby. As a proof of concept, we showcase an OSR-enabled embedded dynamic random-access memory (eDRAM) using the nano-electromechanical (NEM) relay, a type of CMOS-compatible device. Comparative evaluations show the merits of OSR more thoroughly.

Photoacoustic imaging (PAI), an emerging imaging technique, exploits the merits of both optical and ultrasound imaging, equipped with optical contrast and deep penetration. Typical linear PAI relies on a nanosecond laser pulse to induce photoacoustic signals. To construct a multi-wavelength PAI system, a multi-wavelength nano-second laser source is required, which greatly increases the cost of the PAI system. However, according to the nonlinear photoacoustic effect, the amplitude of the photoacoustic signals will vary with different base temperatures of the tissue. Therefore, using continuous-wave lasers with different wavelengths to induce different temperature variations at the same point of the tissue, and then using a single-wavelength pulsed laser to induce photoacoustic signals has been an alternative method to achieve multi-wavelength PAI. In this paper, based on the nonlinear photoacoustic effect, we developed a continuous-wave multi-wavelength laser source to cut down the cost of the conventional multi-wavelength PAI system. The principle will be introduced firstly, followed by qualitative and quantitative experiments.

Photoacoustic imaging (PAI) is a fast-developing non-invasive imaging technique, which provides optical contrast in deep scattering tissue with high spatial resolution. Conventional photoacoustic (PA) imaging has been widely studied based on linear PA effect, which is induced by single short laser pulse. Recently, nonlinear photoacoustic effect has been proposed by using two consecutive laser pulses with two laser sources. In this paper, we report a dual-contrast nonlinear photoacoustic (dNPA) sensing and imaging technique by single high-repetition-rate laser induced nonlinear PA effect. Using the high-repetition-rate pulsed laser, two different kinds of imaging contrasts can be extracted: optical and thermal contrasts. Unlike conventional PA imaging that exhibits optical absorption only, we could extract thermal contrast that is reflected by the rising slope/trend of temperature and consequent PA signals. In this paper, the high-repetition-rate nonlinear PA effect and dual-contrast mechanism were proposed in theory with detailed mathematical modeling. The dual-contrast PA sensing and imaging were demonstrated by experimental results with both in vitro phantom and ex vivo porcine tissues. The results indicate both optical absorption and thermal accumulation properties of different samples, which could enhance the image contrast significantly.

Photoacoustic tomography (PAT) combining both optical absorption and ultrasound detection, is a unique and emerging technology in the field of medical imaging developed in recent years. PAT is based on the generation and detection of high-frequency pulsed PA signals. Therefore, a multi-channel data acquisition (DAQ) system with high sampling rate is crucial to simultaneously receive the multiway PA signals for real-time imaging. However, the cost of a high-speed multi-channel DAQ is quite high. In this brief, a multiway PA signal delay-line module for PAT was proposed, which merges four channels of PA signals in one channel that significantly reduces DAQ’s channel number needed for PAT system. Specifically, an analog circuit design is proposed to accurately delay four-channel PA signals and sum them into one channel before digitization, which records both timing and amplitude of the raw PA signals. Additionally, we reconstruct the four PA waveforms from the recorded signal for image reconstruction by delay-and-sum (DAS) algorithm. To verify the feasibility of the delay-line module in the PAT system, we conducted both simulations and experiments with promising results.

Ternary content addressable memory (TCAM) has been a critical component in caches, routers, etc., in which density, speed, power efficiency, and reliability are the major design targets. There have been the conventional low-write-power but bulky SRAM-based TCAM design, and also denser but less reliable or higher-write-power TCAM designs using nonvolatile memory (NVM) devices. Meanwhile, some TCAM designs using dynamic memories have been also proposed. Although dynamic design TCAM is denser than CMOS SRAM TCAM and more reliable than NVM TCAM, the conventional row-by-row refresh operations land up with a bottleneck of interference with normal TCAM activities. Therefore, this paper proposes a custom low-power dynamic TCAM using nanoelectromechanical (NEM) relay devices utilizing one-shot refresh to solve the memory refresh problem. By harnessing the unique NEM relay characteristics with a proposed novel cell structure, the proposed TCAM occupies a small footprint of only 3 transistors (with two NEM relays integrated on the top through the back-end-of-line process), which significantly outperforms the density of 16-transistor SRAM-based TCAM. In addition, evaluations show that the proposed TCAM improves the write energy efficiency by 2.31x, 131x, and 13.5x over SRAM, RRAM, and FeFET TCAMs, respectively; The search energy-delay-product is improved by 12.7x, 1.30x, and 2.83x over SRAM, RRAM, and FeFET TCAMs, respectively., To be published in 24th Design, Automation and Test in Europe Conference (DATE) in 2021

Ant Forest, a mobile app by the monolithic Alibaba Group, is greening individuals' daily activities and transforming human capacity to reverse global environmental degradation. Over 500 million e-trees being cultivated every day in China using Ant Forest. Over 122 million trees planted over more than 112,000 ha of degraded land areas. This is a showcase of how innovation via internet technology combined with digital finance is contributing to solving environmental issues, also the potential to match an individual's daily footprint to their digital footprint and converting this to an ecological footprint.

Ant Forest, a mobile app developed by the monolithic Alibaba Group, is greening individuals' daily activities and transforming human capacity to reverse global environmental degradation. Over 500 million e-trees are being cultivated every day in China using Ant Forest, and over 122 million real trees have been planted over more than 112 000 ha of degraded land. Ant Forest showcases how internet technology innovation combined with digital financing and philanthropy is contributing to solving environmental issues while attracting and retaining customer loyalty. This powerful business model has the potential to spread to all manner of environmental outcomes.

Precise classification to distinguish malignancy of tumors is of great significance to accomplish high specificity diagnosis and avert unnecessary biopsy. Photoacoustic tomography (PAT) is a burgeoning new imaging modality, which combines optical contrast and ultrasound penetrating in a deep medium. However, it has not been fully exploited on the capability of PAT to discriminate tumors malignancy. In this paper, a multistatic classification approach in photoacoustic is proposed, which could discriminate malignant/benign tumors based on a feature in clinical diagnosis that tumors show different shape irregularity. The multistatic photoacoustic waves extract two different features to differentiate the two types of tumor models with high accuracy in three different scenarios using Support Vector Machines. In addition, two conventional PAT image reconstructing algorithm are also performed to reconstruct images as a comparative study, which unfortunately cannot differentiate their malignancy precisely because of limited detector bandwidth and strong acoustic distortion. We performed the feasibility study in this paper with both simulation and experimental results, which shows that the proposed multistatic photoacoustic classification to distinguish between malignant and benign tumors models works well, and could be easily applied for state-of-art array-based PAT system to ameliorate the diagnostic accuracy.

Photoacoustic imaging has been intensively studied in recent years and many of the achievements have already been applied in clinical diagnosis and therapy, e.g., using spectroscopic photoacoustic imaging to extract functional and molecular information. However, spectroscopic photoacoustic imaging requires expensive and bulky tunable laser source, which severely hinders its further development toward a portable device. In this paper, we propose a novel imaging method, named optical spectroscopic ultrasound displacement (OSUD) imaging, which enables optical spectroscopic imaging in deep scattering tissue using multiple low-cost continuous-wave laser sources and ultrasound imaging equipment. The principle of the OSUD imaging method will be introduced, followed by preliminary experimental results. The OSUD imaging may exploit the deep penetration merit of ultrasound and provide another pathway to provide spectroscopic optical absorption contrast in deep scattering tissue beyond commonly used photoacoustic imaging, which will be further validated in the future work. Accepted version

Magnetoacosutic tomography is a kind of hybrid imaging modality providing electrical conductivity contrast with magnetic field illumination. In this paper, we propose to use low-power low-frequency magnetic field to induce magnetoacoustic signals. By dedicatedly improving the design of the driver circuit, the coil can operate at much lower power (30W) to induce magnetoacoustic signals. To the best of our knowledge, our developed magnetoacoustic sensing system utilizes the lowest power source compared with literatures, which pave the way towards low-cost and portable magnetoacoustic tomography system development.

Photoacoustic imaging (PAI) combines the deep penetration of ultrasound imaging and the high absorption contrast of optical imaging, which has attracted increasing research interest in recent years. The PAI based on multi-wavelength laser source is conducive to detecting different components in the blood such as oxygen saturation. The generation of PA signals could rely on the relative low-cost pulsed laser diode. However, the multi-wavelength PAI system requires multiple pulsed laser diodes, which will multiply the cost of the imaging system. On the other hand, the amplitude of the PA signals will change when inducing the Gruneisen relaxation effect due to the heat accumulation. In this paper, we proposed a continuous multi-wavelength photoacoustic imaging (CMPAI) system based on the combination of a single-wavelength pulsed laser diode and a multi-wavelength continuous laser diode module. The continuous wave (CW) laser is adapted for heating the sample. The PA signals are induced by a single-wavelength pulsed laser. By controlling the laser irradiation sequence (pulse-CW-pulse), the images before and after heating will be attained. By proper differentiating operations, the images with different-wavelengths’ light absorption could be revealed. Furthermore, using this proposed system to detect the concentration of ink that is mixed by different portion of green and red ink would be demonstrated in the following.

Making embedded memory symmetric provides the capability of memory access in both rows and columns, which brings new opportunities of significant energy and time savings if only a portion of data in the words need to be accessed. This work investigates the use of ferroelectric field-effect transistors (FeFETs), an emerging nonvolatile, low-power, deeply-scalable, CMOS-compatible transistor technology, and proposes a new 3transistor/cell symmetric nonvolatile memory (SymNVM). With $\sim 1.67\mathrm{x}$ higher density as compared with the prior FeFET design, significant benefits of energy and latency improvement have been achieved, as evaluated and discussed in depth in this paper.

Magnetically mediated thermoacoustic imaging (MMTAI) exploits the low frequency band, under 20 MHz, of radio frequency magnetic field to perform thermoacoustic imaging, which has deeper penetration than microwave and light induced thermoacoustic imaging. It provides the conductivity contrast of matter at ultrasonic resolution. In this paper, we will introduce the principle and the state of the art research progress of MMTAI.

Photoacoustic imaging has attracted increasing research interest in recent years due to its unique merit of combining light and sound. Enabling deep tissue imaging with high ultrasound spatial resolution and optical absorption contrast, photoacoustic imaging has been applied in various application scenarios including anatomical, functional and molecular imaging. However, the bulky and expensive laser source is one of the key bottlenecks that need to address for further compact system development. Photoacoustic imaging system based on low-cost laser diode (LD) is one of the promising solutions. In this paper, we report a custom-made fingertip laser diode system enabling both pulsed and continuous modulation modes with shortest pulse-width of 40 ns, largest driving current of 13 A, and highest modulation frequency of 3 MHz, which are suitable for both time and frequency domain photoacoustic imaging. To the best of our knowledge, this may be the most compact laser source reported for photoacoustic imaging. Owing to its super-compact size, the proposed LD system could pave the pathway to low-cost photoacoustic sensing and imaging device, even wearable photoacoustic biomedical sensors.

Faraday rotation spectroscopy (FRS) employs the Faraday effect to detect Zeeman splitting in the presence of a magnetic field. In this article, we present system design and implementation of radical sensing in a photolysis reactor using FRS. High sensitivity (100 ppb) and time resolved in situ HO2 detection is enabled with a digitally balanced acquisition scheme. Specific advantages of employing FRS for sensing in such dynamic environments are examined and rigorously compared to the more established conventional laser absorption spectroscopy (LAS). Experimental results show that FRS enables HO2 detection when LAS is deficient, and FRS compares favorably in terms of precision when LAS is applicable. The immunity of FRS to spectral interferences such as absorption of hydrocarbons and other diamagnetic species absorption and optical fringing are highlighted in comparison to LAS.

Photoacoustic imaging has been intensively studied in recent years, and many of the achievements have already been applied in important biomedical and clinical applications, e.g. spectroscopic photoacoustic imaging to extract functional and molecular information. However, spectroscopic photoacoustic imaging requires expensive and bulky tunable laser source, which severely hinder its further development towards portable device. In this paper, we propose a novel imaging method, named optical spectroscopic ultrasound displacement (OSUD) imaging, which enables optical spectroscopic imaging in deep scattering tissue using multiple low-cost continuous-wave laser sources and ultrasound imaging equipment. The principle of the OSUD imaging method will be introduced, and followed by preliminary experimental results. The OSUD imaging may provide another pathway to provide spectroscopic optical absorption contrast in deep scattering tissue beyond commonly used photoacoustic imaging.

Photoacoustic (PA) tomography is a new imaging techniques widely used in biomedical applications. It has an open challenge that the signal-to-noise (SNR) is poor in the situation of low laser power or deep penetration. Data averaging is conventional way to solve the problem, but it is time-consuming. In this paper, we introduce our de-noising methods to increase photoacoustic signal SNR and imaging contrast. It also ensures the imaging speed and has a potential to develop low-cost PA imaging system with low-power laser.

Accurate diagnosis of malignancy tumor in early stage is great significance to achieve high curability, which could improve survival rate in this stage. Precise classification to differentiate malignancy of tumors is favourable to reduce cost in treatment when there is no obvious features in radiology diagnose in early phase. Photoacoustic tomography (PAT) is a burgeoning new imaging modality, which combines optical contrast and ultrasound penetrating in deep medium. However, it has not been fully exploited on the capability of PAT to discriminate tumor’s malignancy. In this paper, a multistatic classification approach in PAT is proposed, which could discriminate malignant/benign tumors based on its morphological feature in clinical diagnosis that tumors usually show different shape irregularity compared with healthy tissue. The multistatic photoacoustic waves were used to extract two different features to differentiate the two types of tumors with high accuracy (

Photoacoustic tomography (PAT) is a non-invasive imaging technique which provided high lateral resolution and axial resolution. Conventional linear photoacoustic (PA) imaging has been widely applied to state-of-art PA system, which excited by short pulse laser. Recently, nonlinear photoacoustic effect has been excavated and utilized, which indicates the different character with linear PA by dual-pulse laser. In this paper, we report a dual-contrast photoacoustic sensing by quasi-CW nonlinear PA effect. Using the high-repetition pulsed laser, and two different contrast imaging were extracted. Unless conventional contrast that using short laser pulse by detected tissue light absorption, we extracted another contrast that indicated the rising of temperature. The quasi-CW nonlinear PA effect could be illustrated by a simple mathematical derivation. The dual-contrast PA imaging have been demonstrated by experiment in vitro and ex vivo imaging. The results indicate different heat absorbency of different materials, which could be utilized to distinguish materials and intensify imaging contrast. Compared with conventional PA imaging, the proposed method has more scope of works and potential applications.

In the recent times, optical technology is progressing by leaps and bounds largely due to the contribution of computer science. However, such optical system configuration is often difficult even for students from computer science as well as students from other disciplines to understand. The sophisticated nature of optics poses to many students as a challenge as the majority of them may experience difficulty in setting up the optical systems and struggle to comprehend them to a greater depth. In this paper, a novel optical engineering kit developed and maintained by OPSS is proposed. We hope that students may benefit from the hands-on experience by experimenting with the Optics Kit and gain insights from the various interesting applications of optics.

Multi-wavelength photoacoustic (PA) imaging has been studied extensively to explore the spectroscopic absorption contrast of biological tissues. To generate strong PA signals, a high-power wavelength-tunable pulsed laser source has to be employed, which is bulky and quite expensive. In this paper, we propose a hybrid multi-wavelength PA imaging (hPAI) method based on combination of single-wavelength pulsed and multi-wavelength continuous-wave (CW) laser sources. By carefully controlling laser illumination sequence (pulse-CW-pulse), and extracting the PA signals' difference before and after heating of CW lasers, the optical absorption property of multi-wavelength CW lasers could be obtained. Compared with conventional PA imaging, the proposed hPAI shows much lower system cost due to the usage of single-wavelength pulsed laser and cheap CW lasers. Theoretical analysis and analytical model are presented in this paper, followed by proof-of-concept experimental results.

Photoacoustic tomography (PAT), a promising medical imaging method that combines optical and ultrasound techniques, has been developing for decades mostly in preclinical application. A recent trend is to utilize the economical laser source to develop a low-cost sensing and imaging system, which aims at an affordable solution in clinical application. These low-cost laser sources have different modulation modes such as pulsed modulation, continuous modulation and coded modulation to generate different profiles of PA signals in photoacoustic (PA) imaging. In this paper, we review the recent development of the photoacoustic sensing and imaging based on the economical laser sources such as laser diode (LD) and light-emitting diode (LED) in different kinds of modulation types, and discuss several representative methods to improve the performance of such imaging systems based on low-cost laser sources. Finally, some perspectives regarding the future development of portable PAT systems are discussed, followed by the conclusion.

We demonstrate the use of laser induced incandescence (LII) of submicron tungsten carbide (WC) particles as a method for particle image velocimetry (PIV). The technique allows a single laser to be used for separate measurements of velocity of two phases in a droplet-laden flow. Submicron tungsten carbide (WC) particles are intentionally seeded into a two-phase flow, and heated by a light sheet generated by a double-pulsed PIV laser operating at sufficiently high pulse energy. The small size and large absorption cross-section allows particles to be heated up to several thousand degrees Kelvin to emit strong incandescence signals, whilst the laser-induced temperature increase in liquid droplets/large particles is negligible. The incandescence signal from WC and Mie scattering from droplets/large particles are separately captured by deploying different filters to a PIV camera. The consecutive images of the laser-induced incandescence (LII) are used to determine the velocity field of the gas-phase flow, and those of Mie scatter are used to extract the velocity of droplets/large particles. The proposed technique is demonstrated in an air jet first and compared with the result given by a normal PIV test, which shows that submicron WC particles can accurately follow the gas flow, and that the LII images can be used to perform cross-correlations. We then apply this technique on an ethanol droplet/air jet (non-reacting), demonstrating the resulting slip velocity between two phases. The proposed technique combining PIV and LII with a single laser requires little additional equipment, and is applicable to a much higher droplet/particle density than previously feasible. Finally the possibility of applying this technique to a flame is demonstrated and discussed.

Photoacoustic imaging has attracted increasing research interest in recent years, due to its unique merit of combining light and sound. Enabling deep tissue imaging with high ultrasound spatial resolution and optical absorption contrast, photoacoustic imaging has been applied in various application scenarios including anatomical, functional and molecular imaging. However, the bulky and expensive laser source is one of the key bottlenecks that needs to be addressed for further compact system development. A photoacoustic imaging system based on a low-cost laser diode (LD) is one of the promising solutions. In this paper, we report a custom-made fingertip laser diode system enabling both pulsed and continuous modulation modes with shortest pulse-width of 40 ns, largest driving current of 13 A, and highest modulation frequency of 3 MHz, which is suitable for both time and frequency domain photoacoustic imaging. To the best of our knowledge, this may be the most compact laser source reported for photoacoustic imaging enabling both two modulation modes. Owing to its super-compact size, the proposed LD system could pave the pathway to a low-cost photoacoustic sensing and imaging device, even wearable photoacoustic biomedical sensors.

Multi-wavelength photoacoustic (PA) imaging has been studied extensively to explore the spectroscopic absorption contrast of biological tissues. To generate strong PA signals, a high-power wavelength tunable pulsed laser source has to be employed, which is bulky and quite expensive. In this Letter, we propose a hybrid multi-wavelength PA imaging (hPAI) method based on the combination of a single-wavelength pulsed laser source and multi-wavelength continuous-wave (CW) laser sources. By carefully controlling the laser illumination sequence (pulse-CW-pulse) and extracting the PA signal difference before and after the heating of CW lasers, the optical absorption property of multi-wavelength light illumination could be obtained. Compared with conventional PA imaging, the proposed hPAI shows a much lower system cost due to the usage of single-wavelength pulsed lasers and multiple inexpensive CW lasers. As the preliminary results show in this Letter, hPAI imaging has the potential to provide another pathway for high spectroscopic optical absorption contrast in PA imaging.

Application-specific extensions to the computational capabilities of a processor provide an efficient mechanism to meet the growing performance and power demands of embedded applications. Hardware, in the form of new function units (or coprocessors), and the corresponding instructions are added to a baseline processor to meet the critical computational demands of a target application. In this paper, the design of a system to automate the instruction set customization process is presented. A dataflow graph design space exploration engine efficiently identifies computation subgraphs to create custom hardware and a compiler subgraph matching framework seamlessly exploits this hardware. We demonstrate the effectiveness of this system across a range of application domains and study the applicability of the custom hardware across an entire application domain. Generalization techniques are presented which enable the application-specific hardware to be more effectively used across a domain.