Yoonsuk Choi

Multichannel Data Compression using Wavelet Subbands Arranging Technique

To reduce the amount of data and preserve necessary signal quality for multichannel data transmission in many applications such as meteorology, or telemedicine, a new technique called WSAT is presented. The proposed technique is designed to deal with the large amount of multichannel data for transmission, and real-time analysis. The proposed approach has exact control on the bit rate in order to achieve the required quality. For different applications, the proposed method is tested. For telemedicine, the method is employed on selected records from the MIT-BIH arrhythmia database. For meteorology, climate data from Nevada climate change database is utilized. From the obtained results, it is concluded that the proposed technique is an appropriate approach to simultaneously compress multichannel data with significant low compressed data rate at low error. As an example, APRD values for multichannel ECG compression is mostly less than 5% which is recommended by the American Heart Association for routine visual readings of compressed and reconstructed ECG signals.

Remotely detecting weapons of mass destruction

Weapons of mass destruction (WMD) detection systems are typically based on sensing fissile materials (capable of sustaining nuclear fission chain reactions) using gamma rays or neutrons.1–4 Current WMD detection methods, however, have limited distances over which they are effective. Moreover, variable environmental conditions (e.g., humidity and temperature) can affect the detection range and limit it further. In addition, radiation related to gamma rays can be easily shielded by high density and atomic number materials such as lead, thus making these detection systems redundant.5, 6 Alternative methods for remote detection of concealed WMD use hyperspectral imaging (HSI) and wideband (WB) data, which reveal information about the surface and the content of the objects, respectively.7, 8 Radiation in the visible-near-IR and in the short-, mid-, and long-wavelength IR ranges are all used in this HSI data. The analysis of WB data focuses on the difference in the rate at which electromagnetic waves penetrate different materials. High-frequency waves are absorbed more easily than low-frequency waves, which facilitates object recognition. The stages of our proposed WMD detection method, using HSI and WB data, are illustrated in Figure 1. We first process HSI data to estimate the presence of WMD and subsequently confirm the possible detection using WB data.8 We have also performed simulations of the detection process to better understand the procedure of WMD detection based on HSI imaging and WB technology, and the impacts of environmental conditions on WMD detection. In our simulations, the target objects are modeled as having different layers with variable thicknesses and compositions. The different materials can be detected by altering the center frequency and power of the WB signal. In an example simulation scenario, a WMD encased in steel is inside a wooden box in the back of a truck and the target is 1km from the detection system. We performed the simulations under the same environmental Figure 1. Schematic of the proposed weapons of mass destruction (WMD) remote sensing detection method, using hyperspectral imaging (HSI) and wideband (WB) data processing.

Wavelet-based compression of multichannel climate data

To simultaneously compress multichannel climate data, the Wavelet Subbands Arranging Technique (WSAT) is studied. The proposed technique is based on the wavelet transform, and has been designed to improve the transmission of voluminous climate data. The WSAT method significantly reduces the number of transmitted or stored bits in a bit stream, and preserves required quality. In the proposed technique, the arranged wavelet subbands of input channels provide more efficient compression for multichannel climate data due to building appropriate parent-offspring relations among wavelet coefficients. To test and evaluate the proposed technique, data from the Nevada climate change database is utilized. Based on results, the proposed technique can be an appropriate choice for the compression of multichannel climate data with significantly high compression ratio at low error.

New sensors could evaluate astronauts' vital signs in flight

During NASA space missions, the physical condition of astronauts must be monitored in real time, either onboard or from Earth, and the collected data must be analyzed and interpreted. In-flight sensors for astronaut healthcare monitoring must be near-real time, minimally invasive, highly sensitive, and easily repairable or replaceable. The system must also enjoy gravity-independent functionality, compact size, low power consumption, minimal human interaction, and efficient temperature control. In our work, we have proposed the design of an automated system for onboard use to monitor the crew’s physiological signals. Ultra-wideband (UWB) wireless biodetectors can be placed either on or underneath the astronauts’ suits, eliminating the need for sensor-to-skin contact to collect data about respiration and heart rate. This is more comfortable for the astronauts because they do not have to wear a specific garment or connect to another recording device for a long time to have their vital signs monitored. Measuring respiration, heart rate, and metabolic rates that would include such feedback as pH and oxygen levels in the blood, the system would transfer the data to an onboard ‘smart’ integrated circuit for analysis and further action. A smart circuit can automatically perform and control monitoring using a cognitive system that acts like a healthcare expert. If it detects an abnormality, the system will run a diagnostic procedure and suggest preliminary medical treatments to be administered by a fellow crew member. Reconfigurability—in voltage, bandwidth, and precision—in the front-end circuits is necessary to provide a broad range of physiological signals, which vary by different orders of magnitude in frequency and amplitude. Our adaptive system is designed to run firmware updates, system software attestation, Figure 1. (a) Ultra-wideband (UWB) detectors transmitting and receiving waves to and from the heart via a series of single UWB pulses. (b) A single UWB pulse. mV: Millivolts. ns: Nanoseconds.

Spectral image fusion using band reduction and contourlets

Spectral images have relatively low spatial resolution, compared to high-resolution single band panchromatic (PAN) images. Therefore, fusing a spectral image with a PAN image has been widely studied to produce a high-resolution spectral image. However, raw spectral images are too large to process and contain redundant information that is not utilized in the fusion process. In this study, we propose a novel fusion method that employs a spectral band reduction and contourlets. The band reduction begins with the best two band combination, and this two-band combination is subsequently augmented to three, four, and more until the desired number of bands is selected. The adopted band selection algorithm using the endmember extraction concept employs a sequential forward search strategy. Next, the image fusion is performed with two different spectral images based on the frequency components that are newly obtained by contourlet transform (CT). One spectral image that is used as a dataset is multispectral (MS) image and the other is hyperspectral (HS) image. Each original spectral image is pre-processed by spectrally integrating over the entire spectral range to obtain a PAN source image that is used in the fusion process. This way, we can eliminate the step of image co-registration since the obtained PAN image is already perfectly aligned to the spectral image. Next, we fuse the band-reduced spectral images with the PAN images using contourlet-based fusion framework. The resultant fusion image provides enhanced spatial resolution while preserving the spectral information. In order to analyze the band reduction performance, the original spectral images are fused with the same PAN images to serve as a reference image, which is then compared to the band-reduced spectral image fusion results using six different quality metrics.

Wavelet-based identification of objects from a distance

In remote sensing, accurate identification of concealed far objects is difficult. Here, to detect concealed objects from a distance, the wideband technology is utilized. As the wideband data includes a broad range of frequencies, it can reveal information about both the surface of the object and its content. To better detect the object and to improve the accuracy of target identification, the collected wideband data is processed in the wavelet domain. Information about the target is spread over different wavelet subbands, and it is possible to better discriminate the target from background for which their frequency content is placed in the same frequency range. Simulation is done at different frequency ranges and different powers to identify targets. In conclusion, wavelet-based processing of collected wideband data helps to appropriately estimate the presence of a target in the scene, and improves the process of target identification.

Fusion and quality analysis for remote sensing images using contourlet transform

Recent developments in remote sensing technologies have provided various images with high spatial and spectral resolutions. However, multispectral images have low spatial resolution and panchromatic images have low spectral resolution. Therefore, image fusion techniques are necessary to improve the spatial resolution of spectral images by injecting spatial details of high-resolution panchromatic images. The objective of image fusion is to provide useful information by improving the spatial resolution and the spectral information of the original images. The fusion results can be utilized in various applications, such as military, medical imaging, and remote sensing. This paper addresses two issues in image fusion: i) image fusion method and ii) quality analysis of fusion results. First, a new contourlet-based image fusion method is presented, which is an improvement over the wavelet-based fusion. This fusion method is then applied to a case study to demonstrate its fusion performance. Fusion framework and scheme used in the study are discussed in detail. Second, quality analysis for the fusion results is discussed. We employed various quality metrics in order to analyze the fusion results both spatially and spectrally. Our results indicate that the proposed contourlet-based fusion method performs better than the conventional wavelet-based fusion methods.

High efficient reconfigurable PUF through spin hall-induced coupled-oscillators

In recent decades, hardware security has played a more and more important role. Among various types of hardware, the Physical Unclonable Function (PUF) has been considered as security primitives to generating keys in order to keep systems safe, authentic, informative, and identified. Recently, leveraging the physics of emerging devices to implement on PUF has long been envisioned. However, current emerging devices based PUF are unreliable due to environmental variations. In this paper, we propose High Efficient Reconfigurable PUF using Spin Hall-Induced Coupled-Oscillators, which embraces and exploits spin oscillation of spintronic devices instead of diminishing or circumventing them. Compared with conventional emerging devices based on PUF, our proposed PUF can generate more delay pairs, can be more reliable to environmental variations, faster, and low power. Comprehensive results demonstrate that the proposed PUF can sufficiently support our conclusion.

A simulation study of target detection using hyperspectral data analysis

Target detection is difficult when the target is concealed or placed under ground or water. To detect and identify concealed objects from a distance, the analysis of the HyperSpectral Imaging (HSI) and Wideband (WB) data is studied. While the HSI analysis may render surface information about objects, the WB data can reveal information about inner layers of the object and its content. Two of the challenging issues with object identification using HSI are (i) computational complexity of the analysis and (ii) signature mismatch. Here, the robust matched filter is emphasized for HSI processing. In addition, the wideband technology is utilized to provide more information about concealed target, and to support spectral processing for object uncovering more effectively. During simulation, electromagnetic waves and propagation areas are modeled. In fact, an object is modeled as different layers with different thicknesses. The existence of a target is estimated by the detection of spectral signatures relating to materials used in the target. In other words, the simultaneous presence of spectral signatures corresponding to the main materials of the target in the hyperspectral data helps detecting the target. The reflected higher frequency signals provide information about exterior layers of both an object and the background; in addition, the reflected lower frequency signals provide information about interior layers of the object. To identify different objects, the simulation is performed using HSI, and WB technology at different frequencies (MHz- GHz) and powers. Based on simulation, the proposed method can be a promising approach to detect targets.

Modern flash technologies: a flash translation layer perspective

Since the introduction of the first flash memory in 1984, flash memory has been a very important member of the non-volatile semiconductor memory family due to its advantages, such as high density, low-cost, shock resistance, fast access time, low-power consumption and reliability. Despite the advantages, flash memory is still facing many technical limitations that need to be further studied. Various solutions have been developed to improve the performance of flash memory by overcoming the technical limitations; however, flash translation layer has a great impact on the overall performance improvement due to its cost-efficiency and usefulness. In this paper, three main aspects of flash memory are discussed from a perspective of flash translation layer. First, we discuss and classify flash translation layer based on the mapping method. Second, we discuss the current technical limitations that flash memory is facing and how these can be overcome by adopting flash translation layer. Third, we investigate the latest flash translation layer schemes that have been recently studied and proposed, and analyse their advantages and drawbacks.