Synthesis of Minimal Error Control Software

Software implementations of controllers for physical systems are at the core of many embedded systems. The design of controllers uses the theory of dynamical systems to construct a mathematical control law that ensures that the controlled system has certain properties, such as asymptotic convergence to an equilibrium point, while optimizing some performance criteria. However, owing to quantization errors arising from the use of fixed-point arithmetic, the implementation of this control law can only guarantee practical stability: under the actions of the implementation, the trajectories of the controlled system converge to a bounded set around the equilibrium point, and the size of the bounded set is proportional to the error in the implementation. The problem of verifying whether a controller implementation achieves practical stability for a given bounded set has been studied before. In this paper, we change the emphasis from verification to automatic synthesis. Using synthesis, the need for formal verification can be considerably reduced thereby reducing the design time as well as design cost of embedded control software. We give a methodology and a tool to synthesize embedded control software that is Pareto optimal w.r.t. both performance criteria and practical stability regions. Our technique is a combination of static analysis to estimate quantization errors for specific controller implementations and stochastic local search over the space of possible controllers using particle swarm optimization. The effectiveness of our technique is illustrated using examples of various standard control systems: in most examples, we achieve controllers with close LQR-LQG performance but with implementation errors, hence regions of practical stability, several times as small.Comment: 18 pages, 2 figure

Destinations of Male Outmigration and their Drivers in Indian Sundarbans

Economic liberalisation has created opportunities for semi-skilled labours within and outside India. This study investigates the male out-migration from the Sundarbans region of India with special reference to the choice of their destinations. Following a mixed-method approach, we collected data through a questionnaire survey, in-depth interviews, focus group discussions, key-informant interviews, and Participatory Rural Appraisal. Analyses revealed that migrants tended to travel to diverse inland and even to overseas destinations on a fixed condition, facilitated by pre-existing support networks. The decision on choosing a destination is regulated by several micro-level determinants such as migration chronology, education, and acquired skill, life cycle stage of the migrants, the expected amount of remittance, the reason for migration, and nature of the job at the destination. The destinations abroad are often preceded by migration to inland destinations leading to higher acquired skill and savings. Joint families, having the ability to support international travel and access to support networks, were more prone to reach international destinations

Recursive Male Out-migration and the Consequences at Source: A Systematic Review with Special Reference to the Left-behind Women

Male out-migration from rural to urban areas has amplified worldwide in the face of economic globalisation. Migration literature for long has engaged with the life of migrants at the destination and their support for the left-behind families in the form of remittances. Explicit scholastic undertaking for the left-behind women and their life experiences has started to receive attention only recently. We take stock of the existing literature to examine this social process and debate it within a women empowerment-disempowerment framework. Following a systematic review of the ‘migration left-behind nexus’ literature, we find a clear trend of transformation in the gender role of women everywhere, especially in the form of ‘feminisation of agriculture’. This process is largely moderated by the nature and amount of remittances received at source. The resultant well-being and empowerment of women is shaped by the socio-cultural context within which migration takes place. Both positive and/or negative outcomes for left-behind women are recorded in the literature, although its choice as a conscious decision and its subsequent permanence in a society is debatable. We expect a deeper engagement of future research that takes up the migration-led women empowerment issue within the context of the general social transformation process

On the Generation of Precise Fixed-Point Expressions

Several problems in the implementations of control systems, signal-processing systems, and scientific computing systems reduce to compiling a polynomial expression over the reals into an imperative program using fixed-point arithmetic. Fixed-point arithmetic only approximates real values, and its operators do not have the fundamental properties of real arithmetic, such as associativity. Consequently, a naive compilation process can yield a program that significantly deviates from the real polynomial, whereas a different order of evaluation can result in a program that is close to the real value on all inputs in its domain. We present a compilation scheme for real-valued arithmetic expressions to fixed-point arithmetic programs. Given a real-valued polynomial expression t, we find an expression t' that is equivalent to t over the reals, but whose implementation as a series of fixed-point operations minimizes the error between the fixed-point value and the value of t over the space of all inputs. We show that the corresponding decision problem, checking whether there is an implementation t' of t whose error is less than a given constant, is NP-hard. We then propose a solution technique based on genetic programming. Our technique evaluates the fitness of each candidate program using a static analysis based on affine arithmetic. We show that our tool can significantly reduce the error in the fixed-point implementation on a set of linear control system benchmarks. For example, our tool found implementations whose errors are only one half of the errors in the original fixed-point expressions

Characterization of non-membrane-damaging cytotoxin of non-toxigenic Vibrio cholerae O1 and its relevance to disease

The non-membrane-damaging cytotoxin which causes dramatic cell rounding of cultured HeLa cells was purified to homogeneity from a clinical strain (WO5) of non-toxigenic Vibrio cholerae O1 Inaba belonging to the El Tor biotype. The purified protein has a denatured molecular weight of 35 kDa and a native molecular weight of approximately 37 kDa indicating the monomeric nature of the protein. The 15 N-terminal amino acid sequence of non-membrane-damaging cytotoxin showed complete homology to the hemagglutinin protease previously purified and characterized from V. cholerae O1. Purified non-membrane-damaging cytotoxin from V. cholerae O1 was immunologically and biochemically identical to that previously purified from V. cholerae O26. Non-membrane-damaging cytotoxin was found to be enterotoxic in rabbit ileal loop assay inducing accumulation of non-hemorrhagic fluid at 100 μg and elicited a concentration dependent increase in short circuit current and tissue conductance of rabbit ileal mucosa mounted on Ussing chambers. A significant serum immunoglobulin G response against non-membrane-damaging cytotoxin was elicited by patients infected with V. cholerae O139 but not with V. cholerae O1. These properties make non-membrane-damaging cytotoxin a potential virulence factor of V. cholerae which should be taken into consideration while making live, attenuated recombinant vaccine strains against cholera

Studies on a Novel Serine Protease of a ΔhapAΔprtV Vibrio cholerae O1 Strain and Its Role in Hemorrhagic Response in the Rabbit Ileal Loop Model

BACKGROUND: Two well-characterized proteases secreted by Vibrio cholerae O1 strains are hemagglutinin protease (HAP) and V. cholerae protease (PrtV). The hapA and prtV knock out mutant, V. cholerae O1 strain CHA6.8ΔprtV, still retains residual protease activity. We initiated this study to characterize the protease present in CHA6.8ΔprtV strain and study its role in pathogenesis in rabbit ileal loop model (RIL). METHODOLOGY/PRINCIPAL FINDINGS: We partially purified the residual protease secreted by strain CHA6.8ΔprtV from culture supernatant by anion-exchange chromatography. The major protein band in native PAGE was identified by MS peptide mapping and sequence analysis showed homology with a 59-kDa trypsin-like serine protease encoded by VC1649. The protease activity was partially inhibited by 25 mM PMSF and 10 mM EDTA and completely inhibited by EDTA and PMSF together. RIL assay with culture supernatants of strains C6709 (FA ratio 1.1+/-0.3 n = 3), CHA6.8 (FA ratio 1.08+/-0.2 n = 3), CHA6.8ΔprtV (FA ratio 1.02+/-0.2 n = 3) and partially purified serine protease from CHA6.8ΔprtV (FA ratio 1.2+/-0.3 n = 3) induced fluid accumulation and histopathological studies on rabbit ileum showed destruction of the villus structure with hemorrhage in all layers of the mucosa. RIL assay with culture supernatant of CHA6.8ΔprtVΔVC1649 strain (FA ratio 0.11+/-0.005 n = 3) and with protease incubated with PMSF and EDTA (FA ratio 0.3+/-0.05 n = 3) induced a significantly reduced FA ratio with almost complete normal villus structure. CONCLUSION: Our results show the presence of a novel 59-kDa serine protease in a ΔhapAΔprtV V. cholerae O1 strain and its role in hemorrhagic response in RIL model

Partisan US News Media Representations of Syrian Refugees

We investigate how representations of Syrian refugees (2011-2021) differ across US partisan news outlets. We analyze 47,388 articles from the online US media about Syrian refugees to detail differences in reporting between left- and right-leaning media. We use various NLP techniques to understand these differences. Our polarization and question answering results indicated that left-leaning media tended to represent refugees as child victims, welcome in the US, and right-leaning media cast refugees as Islamic terrorists. We noted similar results with our sentiment and offensive speech scores over time, which detail possibly unfavorable representations of refugees in right-leaning media. A strength of our work is how the different techniques we have applied validate each other. Based on our results, we provide several recommendations. Stakeholders may utilize our findings to intervene around refugee representations, and design communications campaigns that improve the way society sees refugees and possibly aid refugee outcomes

Genomic plasticity associated with antimicrobial resistance in Vibrio cholerae.

The Bay of Bengal is known as the epicenter for seeding several devastating cholera outbreaks across the globe. Vibrio cholerae, the etiological agent of cholera, has extraordinary competency to acquire exogenous DNA by horizontal gene transfer (HGT) and adapt them into its genome for structuring metabolic processes, developing drug resistance, and colonizing the human intestine. Antimicrobial resistance (AMR) in V. cholerae has become a global concern. However, little is known about the identity of the resistance traits, source of AMR genes, acquisition process, and stability of the genetic elements linked with resistance genes in V. cholerae Here we present details of AMR profiles of 443 V. cholerae strains isolated from the stool samples of diarrheal patients from two regions of India. We sequenced the whole genome of multidrug-resistant (MDR) and extensively drug-resistant (XDR) V. cholerae to identify AMR genes and genomic elements that harbor the resistance traits. Our genomic findings were further confirmed by proteome analysis. We also engineered the genome of V. cholerae to monitor the importance of the autonomously replicating plasmid and core genome in the resistance profile. Our findings provided insights into the genomes of recent cholera isolates and identified several acquired traits including plasmids, transposons, integrative conjugative elements (ICEs), pathogenicity islands (PIs), prophages, and gene cassettes that confer fitness to the pathogen. The knowledge generated from this study would help in better understanding of V. cholerae evolution and management of cholera disease by providing clinical guidance on preferred treatment regimens.DBT Indi

Symbolic robustness analysis

Abstract—A key feature of control systems is robustness, the property that small perturbations in the system inputs cause only small changes in its outputs. Robustness is key to designing systems that work under uncertain or imprecise environments. While continuous control design algorithms can explicitly incorporate robustness as a design goal, it is not clear if robustness is maintained at the software implementation level of the controller: two “close ” inputs can execute very different code paths which may potentially produce vastly different outputs. We present an algorithm and a tool to characterize the robustness of a control software implementation. Our algorithm is based on symbolic execution and non-linear optimization, and computes the maximum difference in program outputs over all program paths when a program input is perturbed. As a by-product, our algorithm generates a set of test vectors which demonstrate the worst-case deviations in outputs for small deviations in inputs. We have implemented our approach on top of the Splat test generation tool and we describe an evaluation of our implementation on two examples of automotive control code. I

Trigger Memoization in Self-Triggered Control

Self-triggered implementations of controllers have been proposed as an alternative to traditional time-triggered implementations. In a self-triggered implementation, the control task computes the actuator signal as well as a triggering time that specifies the next time instant at which the control task should be run. Self-triggered implementations have the potential to decrease communication costs and CPU requirements over time-triggered ones, e.g., by running the steady-state plant in open loop for long intervals if there is no disturbance. We show that commonly claimed gains for self-triggered implementations are too optimistic. The analysis of most self-triggering algorithms ignore the execution times for computing the trigger times. We show, using implementations of several self-triggering algorithms proposed in the literature on common embedded platforms, that the execution time to compute the trigger time can be non-negligible compared to the trigger times, and may even be higher than the trigger time itself, rendering a naive implementation infeasible. We propose a hybrid implementation scheme for selftriggered control using state quantization and memoization of trigger times in a cache. We perform trigger-time computation tasks with low priority, and fall back on a timetriggered implementation when the trigger time computations are not guaranteed to finish in time (but use the computed results to update the cache). Our implementation achieves communication costs similar to self-triggered implementations and computation costs close to time-triggered implementations, while providing a bound for the region of practical stability