Minimizing the Age of Information in Wireless Networks with Stochastic Arrivals

We consider a wireless network with a base station serving multiple traffic streams to different destinations. Packets from each stream arrive to the base station according to a stochastic process and are enqueued in a separate (per stream) queue. The queueing discipline controls which packet within each queue is available for transmission. The base station decides, at every time t, which stream to serve to the corresponding destination. The goal of scheduling decisions is to keep the information at the destinations fresh. Information freshness is captured by the Age of Information (AoI) metric. In this paper, we derive a lower bound on the AoI performance achievable by any given network operating under any queueing discipline. Then, we consider three common queueing disciplines and develop both an Optimal Stationary Randomized policy and a Max-Weight policy under each discipline. Our approach allows us to evaluate the combined impact of the stochastic arrivals, queueing discipline and scheduling policy on AoI. We evaluate the AoI performance both analytically and using simulations. Numerical results show that the performance of the Max-Weight policy is close to the analytical lower bound

Model Predictive Control for Signal Temporal Logic Specification

We present a mathematical programming-based method for model predictive control of cyber-physical systems subject to signal temporal logic (STL) specifications. We describe the use of STL to specify a wide range of properties of these systems, including safety, response and bounded liveness. For synthesis, we encode STL specifications as mixed integer-linear constraints on the system variables in the optimization problem at each step of a receding horizon control framework. We prove correctness of our algorithms, and present experimental results for controller synthesis for building energy and climate control

Deciding Quantifier-Free Presburger Formulas Using Parameterized Solution Bounds

Given a formula in quantifier-free Presburger arithmetic, if it has a satisfying solution, there is one whose size, measured in bits, is polynomially bounded in the size of the formula. In this paper, we consider a special class of quantifier-free Presburger formulas in which most linear constraints are difference (separation) constraints, and the non-difference constraints are sparse. This class has been observed to commonly occur in software verification. We derive a new solution bound in terms of parameters characterizing the sparseness of linear constraints and the number of non-difference constraints, in addition to traditional measures of formula size. In particular, we show that the number of bits needed per integer variable is linear in the number of non-difference constraints and logarithmic in the number and size of non-zero coefficients in them, but is otherwise independent of the total number of linear constraints in the formula. The derived bound can be used in a decision procedure based on instantiating integer variables over a finite domain and translating the input quantifier-free Presburger formula to an equi-satisfiable Boolean formula, which is then checked using a Boolean satisfiability solver. In addition to our main theoretical result, we discuss several optimizations for deriving tighter bounds in practice. Empirical evidence indicates that our decision procedure can greatly outperform other decision procedures.Comment: 26 page

The antecedents and consequences of value co-creation behaviors in a hotel setting: a two-country study

This study examines the antecedents and consequences of value co-creation behavior in a hospitality context. An online questionnaire with samples of hotel patrons in the United States and Australia was used to obtain data and partial least square modeling was used in the analysis. The results suggest patron fairness perception enhances trust and identification with a hotel, which encourage engagement in the value co-creation behavior. Furthermore, this behavior enhances patron well-being and respect for the hotel. The study contributes to the literature by suggesting a value co-creation behavior model in the hospitality context and empirically examining the antecedents and consequences of this behavior. The results have important implications for managers designing service encounters that can encourage hotel patrons to engage in the value co-creation behavior

Yak Rearing on High Altitude Pastures of Northeastern Himalaya of India: Their Utilization Strategies and Rejuvenation

Yak rearing on alpine pastures is the main occupation of the highland pastoral nomads (Brokpa and Dokpas) of north-east (NE) India. These pastoral nomads living in the remote mountains solely rely on high altitude pastures for their nutritional and livelihood security because of virtual existence of agricultural activities in this area. They rear yaks under transhumance and utilize various pastures while migrating from low land winter pastures to high altitude alpine pastures during summer. Therefore, the temperate and alpine pastures are the major feed resources for the yaks. The indiscriminate use of pastures and impending climate change results in their degradation that may affect the productivity of the animals reared on them. In this study, an attempt was made to evaluate the status of pastures used for yak rearing in NE India and an initiative has been taken to test the adaptability of palatable high yielding temperate grasses for pasture development and rejuvenation

COMPARISON OF THE EFFECT OF PTEROCARPUS MARSUPIUM WITH PIOGLITAZONE IN DEXAMETHASONE-INDUCED INSULIN RESISTANCE

ABSTRACTObjective: This study was undertaken to evaluate the preventive effect of heartwood of P. marsupium in dexamethasone-induced hyperinsulinemiaand hyperglycemia and compare it with that of pioglitazone.Methods: Male albino wistar rats were divided into five groups (n=6). Plain control group received gum acacia (2%) orally from d 1 to d 12. Dexacontrol group received gum acacia (2%) orally for d 1 to d 12 and Dexa (8 mg/kg) intraperitoneal (i.p.) from d 7 to d 12, during the study period.Two test groups received ethanolic extract of Pterocarpus marsupium heartwood (PME) (1 and 2 g/kg/) per oral (PO), and standard control groupreceived pioglitazone (60 mg/kg/PO) from d 1 to d 12. During the 12-d study period, the two test groups and standard control group received Dexa(8 mg/kg/i.p.) from d 7 to d 12. On last day of the study, the blood samples were collected by retro-orbital sinus punctureand used for estimation ofserum insulin and glucose levels. Homeostatic Model Assessment (HOMA) method was employed to calculate the degree of insulin resistance(IR).Results were analyzed by using one-way analysis of variance followed by Scheffe's multiple comparison test (p<0.05).Results: Treatment with ethanolic extract of P. marsupium and pioglitazone significantly (p<0.05) reduced the elevated insulin and glucose levels aswell as HOMA-IR and HOMA-IS values in dexa treated animals.Conclusion: Ethanolic extract of P. marsupium heartwood effectively countered dexamethasone-induced hyperinsulinemia and hyperglycemia.Insulin-sensitizing activity of P. marsupium heartwood was found to be more effective than pioglitazone.Keywords: Pterocarpus marsupium, Insulin resistance, Hyperinsulinemia, Hyperglycemia

Context-Aided Variable Elimination for Requirement Engineering

Deriving system-level specifications from component specifications usually involves the elimination of variables that are not part of the interface of the top-level system. This paper presents algorithms for eliminating variables from formulas by computing refinements or relaxations of these formulas in a context. We discuss a connection between this problem and optimization and give efficient algorithms to compute refinements and relaxations of linear inequality constraints

Property Preserving Symmetric Encryption Revisited

At EUROCRYPT~2012 Pandey and Rouselakis introduced the notion of property preserving symmetric encryption which enables checking for a property on plaintexts by running a public test on the corresponding ciphertexts. Their primary contributions are: (i) a separation between `find-then-guess\u27 and `left-or-right\u27 security notions; (ii) a concrete construction for left-or-right secure orthogonality testing in composite order bilinear groups. This work undertakes a comprehensive (crypt)analysis of property preserving symmetric encryption on both these fronts. We observe that the quadratic residue based property used in their separation result is a special case of testing equality of one-bit messages, suggest a very simple and efficient deterministic encryption scheme for testing equality and show that the two security notions, find-then-guess and left-or-right, are tightly equivalent in this setting. On the other hand, the separation result easily generalizes for the equality property. So contextualized, we posit that the question of separation between security notions is property specific and subtler than what the authors envisaged; mandating further critical investigation. Next, we show that given a find-then-guess secure orthogonality preserving encryption of vectors of length 2n, there exists left-or-right secure orthogonality preserving encryption of vectors of length n, giving further evidence that find-then-guess is indeed a meaningful notion of security for property preserving encryption. Finally, we cryptanalyze the scheme for testing orthogonality. A simple distinguishing attack establishes that it is not even the weakest selective find-then-guess secure. Our main attack extracts out the subgroup elements used to mask the message vector and indicates greater vulnerabilities in the construction beyond indistinguishability. Overall, our work underlines the importance of cryptanalysis in provable security