More Like this

1. An STL-Based Formulation of Resilience in Cyber-Physical Systems

   https://doi.org/10.1007/978-3-031-15839-1_7  

   Chen, Hongkai; Lin, Shan; Smolka, Scott A.; Paoletti, Nicola (August 2022, Formal Modeling and Analysis of Timed Systems)

   Bogomolov, Sergiy; Parker, David (Ed.)

   Resiliency is the ability to quickly recover from a violation and avoid future violations for as long as possible. Such a property is of fundamental importance for Cyber-Physical Systems (CPS), and yet, to date, there is no widely agreed-upon formal treatment of CPS resiliency. We present an STL-based framework for reasoning about resiliency in CPS in which resiliency has a syntactic characterization in the form of an STL-based Resiliency Specification (SRS). Given an arbitrary STL formula φ, time bounds α and β, the SRS of φ, Rα,β (φ), is the STL formula ¬φU[0,α]G[0,β)φ, specifying that recovery from a violation of φ occur within time α (recoverability), and subsequently that φ be maintained for duration β (durability). These R-expressions, which are atoms in our SRS logic, can be combined using STL operators, allowing one to express composite resiliency specifications, e.g., multiple SRSs must hold simultaneously, or the system must eventually be resilient. We define a quantitative semantics for SRSs in the form of a Resilience Satisfaction Value (ReSV) function r and prove its soundness and completeness w.r.t. STL’s Boolean semantics. The r-value for Rα,β (φ) atoms is a singleton set containing a pair quantifying recoverability and durability. The r-value for a composite SRS formula results in a set of non-dominated recoverability-durability pairs, given that the ReSVs of subformulas might not be directly comparable (e.g., one subformula has superior durability but worse recoverability than another). To the best of our knowledge, this is the first multi-dimensional quantitative semantics for an STL-based logic. Two case studies demonstrate the practical utility of our approach. https://doi.org/10.1007/978-3-031-15839-1_7 

   more » « less
2. Raman scattering applied to human breath analysis

   https://doi.org/10.1016/j.trac.2024.117791  

   Arachchige, Charuka Muktha; Muller, Andreas (August 2024, TrAC Trends in Analytical Chemistry)

   The chemical composition of exhaled human breath can be strongly correlated to medical conditions such as lung cancer or gastrointestinal diseases. To establish these correlations and, most importantly, to use them in diagnostics, chemical gas detection needs to be performed at trace concentrations, typically at parts-per-million (ppm) levels or below, for many compounds simultaneously. Traditional methods such as gas chromatography, a workhorse in scientific laboratories, is ill-suited for the fast, inexpensive point-of-care diagnostics that would be needed to build statistically-meaningful ensembles over large populations. With the increasing availability and decreasing cost of high power diode lasers and of uncooled CMOS cameras, spontaneous Raman spectroscopy (SRS), a vibrational molecular fingerprinting tool, is emerging as an economic alternative. Although gas SRS scattering cross sections are only on the order of 10$$^{-31}$$ cm$^2$/sr, considerable progress in the development of enhancement techniques has been made over the past decade. The purpose of this work is to review SRS enhancement approaches in the context of established human breath tests, and to provide a comparison with alternatives. Already, numerous trace gases such as H$$_2$$, CH$$_4$$, $$^{13}$$CO$$_2$$, and volatile organic compounds like acetone can be rapidly quantified in breath at concentrations below 1 ppm with SRS. With improvements in resolution and design of enhancement systems, SRS-based sensors could be scalably deployed in, e.g., pharmacies, and non-invasively screen for dozens of analytes at the parts-per-billion level. 

   more » « less
3. Background-free imaging of chemical bonds by a simple and robust frequency-modulated stimulated Raman scattering microscopy

   https://doi.org/10.1364/OE.391016  

   Xiong, Hanqing; Qian, Naixin; Zhao, Zhilun; Shi, Lingyan; Miao, Yupeng; Min, Wei (May 2020, Optics Express)

   Being able to image chemical bonds with high sensitivity and speed, stimulated Raman scattering (SRS) microscopy has made a major impact in biomedical optics. However, it is well known that the standard SRS microscopy suffers from various backgrounds, limiting the achievable contrast, quantification and sensitivity. While many frequency-modulation (FM) SRS schemes have been demonstrated to retrieve the sharp vibrational contrast, they often require customized laser systems and/or complicated laser pulse shaping or introduce additional noise, thereby hindering wide adoption. Herein we report a simple but robust strategy for FM-SRS microscopy based on a popular commercial laser system and regular optics. Harnessing self-phase modulation induced self-balanced spectral splitting of picosecond Stokes beam propagating in standard single-mode silica fibers, a high-performance FM-SRS system is constructed without introducing any additional signal noise. Our strategy enables adaptive spectral resolution for background-free SRS imaging of Raman modes with different linewidths. The generality of our method is demonstrated on a variety of Raman modes with effective suppressing of backgrounds including non-resonant cross phase modulation and electronic background from two-photon absorption or pump-probe process. As such, our method is promising to be adopted by the SRS microscopy community for background-free chemical imaging. 

   more » « less
4. Closing the Wearable Gap—Part V: Development of a Pressure-Sensitive Sock Utilizing Soft Sensors

   https://doi.org/10.3390/s20010208  

   Luczak, Tony; Burch V, Reuben F.; Smith, Brian K.; Carruth, Daniel W.; Lamberth, John; Chander, Harish; Knight, Adam; Ball, J.E.; Prabhu, R.K. (January 2020, Sensors)

   The purpose of this study was to evaluate the use of compressible soft robotic sensors (C-SRS) in determining plantar pressure to infer vertical and shear forces in wearable technology: A ground reaction pressure sock (GRPS). To assess pressure relationships between C-SRS, pressure cells on a BodiTrakTM Vector Plate, and KistlerTM Force Plates, thirteen volunteers performed three repetitions of three different movements: squats, shifting center-of-pressure right to left foot, and shifting toes to heels with C-SRS in both anterior–posterior (A/P) and medial–lateral (M/L) sensor orientations. Pearson correlation coefficient of C-SRS to BodiTrakTM Vector Plate resulted in an average R-value greater than 0.70 in 618/780 (79%) of sensor to cell comparisons. An average R-value greater than 0.90 was seen in C-SRS comparison to KistlerTM Force Plates during shifting right to left. An autoregressive integrated moving average (ARIMA) was conducted to identify and estimate future C-SRS data. No significant differences were seen in sensor orientation. Sensors in the A/P orientation reported a mean R2 value of 0.952 and 0.945 in the M/L sensor orientation, reducing the effectiveness to infer shear forces. Given the high R values, the use of C-SRSs to infer normal pressures appears to make the development of the GRPS feasible. 

   more » « less
5. Management of Implicit Requirements Data in Large SRS Documents: Taxonomy and Techniques

   https://doi.org/10.1145/3552490.3552494  

   Dave, Dev; Celestino, Angelica; Varde, Aparna S.; Anu, Vaibhav (July 2022, ACM SIGMOD Record)

   Implicit Requirements (IMR) identification is part of the Requirements Engineering (RE) phase in Software Engineering during which data is gathered to create SRS (Software Requirements Specifications) documents. As opposed to explicit requirements clearly stated, IMRs constitute subtle data and need to be inferred. Research has shown that IMRs are crucial to the success of software development. Many software systems can encounter failures due to lack of IMR data management. SRS documents are large, often hundreds of pages, due to which manually identifying IMRs by human software engineers is not feasible. Moreover, such data is evergrowing due to the expansion of software systems. It is thus important to address the crucial issue of IMR data management. This article presents a survey on IMRs in SRS documents with the definition and overview of IMR data, detailed taxonomy of IMRs with explanation and examples, practices in managing IMR data, and tools for IMR identification. In addition to reviewing classical and state-of-the-art approaches, we highlight trends and challenges and point out open issues for future research. This survey article is interesting based on data quality, hidden information retrieval, veracity and salience, and knowledge discovery from large textual documents with complex heterogeneous data. 

   more » « less