Message and Its Origin Authentication Protocol for Data Aggregation in Sensor Networks †

Abstract. In distributed sensor networks, the researches for authentication in sensor network have been focused on broadcast authentication. In this paper, we propose a message and its origin authentication protocol for data aggregation in sensor networks, based on one way hash chain and Merkle tree authentication with pre-deployment knowledge. Proposed protocol provides not only for downstream messages but also for upstream messages among neighbors, and it solves the secret value update issue with multiple Merkle trees and unbalanced energy consumption among sensor nodes with graceful handover of aggregator. In treating compromised node problem, our protocol provides an equivalent security level of pair-wise key sharing scheme, while much less memory requirements compared to pair-wise key sharing scheme

A New Relative Receiver Autonomous Integrity Monitoring Algorithm for Multiple Failures

authors' final manuscriptIn near future, GNSS GPS modernization, renewed GLONASS and a new Galileo signal will be available. And the accuracy of position solution will be better by courtesy of improved quality of ranging signal. As an expected accuracy is better, the threshold for failure will be reduced. As a result, the prior probability of failures could be larger than what is used now. Due to the increased prior probability of failures, probability of simultaneous multiple failures cannot be neglected any more. Furthermore there will be many more ranging sources makes it necessary to consider the possibility of simultaneous multiple failures. This paper develops and analyzes a new Relative Receiver Autonomous Integrity Monitoring (RRAIM) algorithm which can treat no only a single failure but also simultaneous multiple failures. A proposed algorithm uses measurement residuals and satellite observation matrices of several consecutive epochs for Failure Detection and Exclusion (FDE). It detects failures by monitoring the error vector itself instead of monitoring the projection of the error vector. The simulation results show that the algorithm is able to detect any instance of multiple failures which are not detected by the conventional RAIM algorithm.OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000003405/18SEQ:18PERF_CD:SNU2012-01EVAL_ITEM_CD:104USER_ID:0000003405ADJUST_YN:NEMP_ID:A000360DEPT_CD:446CITE_RATE:0FILENAME:Manuscript_HoYun.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]:

Unlocking performance potential of two-dimensional SnS2 transistors with solution-processed high-k Y:HfO2 film and semimetal bismuth contact

Two-dimensional (2D) tin disulfide (SnS2) is emerging as a viable channel material for high-performance field-effect transistors (FET) with high intrinsic mobility. To implement a high-performance two-dimensional SnS2 FET, high field-effect mobility (μFE), steep subthreshold swing (SS), high on-current value (Ion), and high on/off ratio (Ion/Ioff) must be realized. To improve these parameters, we first fabricated a high-k (∼30.5) yttrium-doped hafnium dioxide (Y:HfO2) film through a solution process to suppress Coulomb electron scattering, and to enhance the semiconductor-dielectric interface with an efficient metal–oxygen framework and a very smooth (root mean square = 0.29 nm) surface. Second, we induced Fermi level depinning by introducing a semimetal bismuth (Bi) contact with a low density of states (DOS) at the Fermi level to suppress the metal-induced gap state (MIGS). Through these two strategies, the SnS2 FET obtained high μFE (60.5 cm2V-1s−1), the SS theoretical limit of 60 mV/dec, negligible Schottky barrier height, high normalized on-current (IonL/W) of 90.6 μA, and high Ion/Ioff of 3 × 107, demonstrating that SnS2 can be re-evaluated as a potentially effective 2D channel material. © 2023 Elsevier B.V.FALS

Attitude determination method using single-antenna GPS, Gyro and Magnetometer

In this paper, we propose the attitude estimation algorithm integrating SAGPS (Single Antenna GPS), Gyroscope and Magnetometer. Pseudo-attitude from SAGPS has low output rate and time delay property. And it differs from actual attitude according to flight condition of airplane because it is based on velocity measurements of GPS. We adopted gyroscope and magnetometer to improve attitude accuracy and output rate of the pseudo-attitude. For validation of the algorithm, simulation is performed and flight data of small UAV is post-processed and compared with commercial AHRS.OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000003405/4SEQ:4PERF_CD:SNU2012-01EVAL_ITEM_CD:104USER_ID:0000003405ADJUST_YN:NEMP_ID:A000360DEPT_CD:446CITE_RATE:0FILENAME:APISAT2012_Paper_HeekwonNo.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]:

Implementation and Outdoor Test Results for GPS and Pseudolite System

OAIID:oai:osos.snu.ac.kr:snu2012-01/104/0000003405/9SEQ:9PERF_CD:SNU2012-01EVAL_ITEM_CD:104USER_ID:0000003405ADJUST_YN:NEMP_ID:A000360DEPT_CD:446CITE_RATE:0FILENAME:Implementation and Outdoor Test Results for GPS and Pseudolite System.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]:

Flexible endoscopic micro-optical coherence tomography for three-dimensional imaging of the arterial microstructure

Abstract Micro-optical coherence tomography (µOCT) is a novel imaging approach enabling visualization of the microstructures of biological tissues at a cellular or sub-cellular level. However, it has been challenging to develop a miniaturized flexible endoscopic µOCT probe allowing helical luminal scanning. In this study, we built a flexible endoscopic µOCT probe with an outer diameter of 1.2 mm, which acquires three-dimensional images of the arterial microstructures via helical scanning with an axial and lateral resolutions of 1.83 µm and 3.38 µm in air, respectively. Furthermore, the depth of focus of the µOCT imaging probe was extended two-fold using a binary phase spatial filter. We demonstrated that the present endoscopic µOCT could image cellular level features of a rabbit artery with high-risk atheroma and a bioresorbable scaffold-implanted swine coronary artery. This highly-translatable endoscopic µOCT will be a useful tool for investigating coronary artery disease and stent biology

Quasiparticle interference and impurity resonances on WTe2

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Using scanning tunneling microscopy/spectroscopy (STM/STS), we examine quasiparticle scattering and interference properties at the surface of WTe2. WTe2, layered transition metal dichalcogenide, is predicted to be a type-II Weyl semimetal. The Weyl fermion states in WTe(2)emerge as topologically protected touching points of electron and hole pockets, and Fermi arcs connecting them can be visible in the spectral function on the surface. To probe the properties of surface states, we have conducted low-temperature STM/STS (at 2.7 K) on the surfaces of WTe(2)single crystals. We visualize the surface states of WTe(2)with atomic scale resolution. Clear surface states emerging from the bulk electron pocket have been identified and their connection with the bulk electronic states shows good agreement with calculations. We show the interesting double resonance peaks in the local density of states appearing at localized impurities. The low-energy resonant peak occurs near the Weyl point above the Fermi energy and it may be mixed with the surface state of Weyl points, which makes it difficult to observe the topological nature of the Weyl semimetal WTe211sciescopu

Highly Effective Multiple-Patterned Plasmonic Nanostructures for Flexible Organic Photodetectors

Introducing plasmonic structures is a viable way to enhance the performance of optoelectronic devices by improving surface plasmon couplings. In this study, we combined block-copolymer lithography and nano-imprinting lithography to fabricate metal electrodes with highly effective multiple-patterned plasmonic nanostructures. The metal electrodes were then used as back reflectors in organic photodiodes (OPDs). The multiple-patterned electrodes exhibited increased light absorption compared to conventional flat electrodes, increasing the light responsivity of OPDs from 0.82 AW-1 to 5.91 AW-1 under 532-nm-wavelength light illumination at an intensity of 20 µW cm-2. Theoretical study and near-field scanning optical microscopy revealed strong surface plasmon coupling of these nanostructured electrodes. Moreover, the multiple-patterned OPDs fabricated on a plastic substrate showed highly stable device performance. Furthermore, flexible 8??8 photosensor arrays were successfully fabricated and used for detecting incident photonic signals with high resolution. These results demonstrate that the developed multiple patterns provide a versatile and effective route for developing high-performance organic optoelectronic devices

SNR enhanced high-speed two-photon microscopy using a pulse picker and time gating detection

Abstract Two-photon microscopy (TPM) is an attractive biomedical imaging method due to its large penetration depth and optical sectioning capability. In particular, label-free autofluorescence imaging offers various advantages for imaging biological samples. However, relatively low intensity of autofluorescence leads to low signal-to-noise ratio (SNR), causing practical challenges for imaging biological samples. In this study, we present TPM using a pulse picker to utilize low pulse repetition rate of femtosecond pulsed laser to increase the pulse peak power of the excitation source leading to higher emission of two-photon fluorescence with the same average illumination power. Stronger autofluorescence emission allowed us to obtain higher SNR images of arterial and liver tissues. In addition, by applying the time gating detection method to the pulse signals obtained by TPM, we were able to significantly reduce the background noise of two-photon images. As a result, our TPM system using the pulsed light source with a 19 times lower repetition rate allowed us to obtain the same SNR image more than 19 times faster with the same average power. Although high pulse energy can increase the photobleaching, we also observed that high-speed imaging with low total illumination energy can mitigate the photobleaching effect to a level similar to that of conventional illumination with a high repetition rate. We anticipate that this simple approach will provide guidance for SNR enhancement with high-speed imaging in TPM as well as other nonlinear microscopy