Adaptive programming

An adaptive program is one that changes its behavior base on the current state of its environment. This notion of adaptivity is formalized, and a logic for reasoning about adaptive programs is presented. The logic includes several composition operators that can be used to define an adaptive program in terms of given constituent programs; programs resulting from these compositions retain the adaptive properties of their constituent programs. The authors begin by discussing adaptive sequential programs, then extend the discussion to adaptive distributed programs. The relationship between adaptivity and self-stabilization is discussed. A case study for constructing an adaptive distributed program where a token is circulated in a ring of processes is presented     

Deadlock Detection for a Class of Communicating Finite State Machines

LetMandNbe two communicating finite state machines which exchange one type of message. We develope a polynomial algorithm to detect whether or notMandNcan reach a deadlock. The time complexity of the algorithm isO(m^{3}n^{3}and its space isO(mn)wheremandnare the numbers of states inMandN, respectively. The algorithm can also be used to verify that two communicating machines which exchange many types of messages are deadlock-free.     

A periodic state exchange protocol and its verification

We present an elegant protocol for reliably transmitting data messages from a sender to a receiver over a highspeed network that may reorder, lose, or corrupt messages. The protocol is based on a new principle that calls for the periodic exchange of state information between the sender and receiver. Our formal definition of the protocol is abstract and does not include explicit timing information such as the rate of sending state information. The abstract definition makes our formal verification of the protocol simple and based solely on well-established concepts: invariants, well-foundedness, and action fairness. We use the formal definition of the protocol and its proof of correctness to deduce the required timing information. In particular, we show that the rate of sending state information is at most (m-1)/2T where m is a measure of the memory size in the sender, and T is an upper bound on the required time for one message to be sent, propagated, and received between the sender and receiver     

Corrosion fatigue behaviour of brass in aqueous solutions

The corrosion fatigue behaviour of α-brass was investigated in NaCl, NaNO₂, (NH₄)₂SO₄ and (NH₄)₂SO₄ + CuSO₄ solutions by applying the reverse bending technique at 60 cycles/min. With the exception of NaCl, all electrolytes reduced the fatigue life compared with that in air or water. Anodic polarization caused further reduction in the fatigue life in all solutions. In NaCl the failure was mainly due to electrochemical dissolution of the brass, while in ammoniacal solution both thinning and corrosion fatigue occurred. In NaNO₂ solution corrosion was inhibited but severe corrosion fatigue occurred. The fracture mode changed from transgranular in air to mixed mode, with different percentages of the intergranular type depending on the electrolyte.     

Design,synthesis, <Superscript>99<Emphasis Type="Italic">m</Emphasis></Superscript>Tc labeling,and biological evaluation of a novel pyrrolizine derivative as potential anti-inflammatory agent

The design and synthesis of ethyl 4-(6-amino-7-cyano-2,3-dihydro-1H-pyrrolizine-5-carboxamido)-benzoate (KH16) were discussed, and its structure was determined. The anti-inflammatory activity of a new compound was evaluated using in vitro cyclooxygenase (COX) inhibitory assay. KH16 exhibits higher selectivity to COX-2 than to COX-1 with the selectivity index of 3.46. KH16 was labeled with ^99mTc with the maximum radiochemical yield of ^99mTc-KH16 of 90.5 ± 1.5%. Biodistribution of ^99mTc-KH16 in normal, infected, and inflamed mice was studied. The uptake in inflamed muscle was higher than that in normal muscle throughout the examined time interval. This work is a step ahead in the direction of using pyrrolizine derivatives for site-specific delivery to the inflamed tissue.     

The corrosion behaviour in organic acid solutions—II. A steel electrode

The corrosion behaviour of steel in stagnant de-aerated citric and oxalic acid solutions (10^?5–10^?1M) in the pH range 2–6 was studied. It was found that the corrosion behaviour of steel in both acids was generally the same but it depended on the acid concentration and the pH value.In 10^?4–10^?1M, the corrosion rate (W) increased with the increase of acid concentration and decreased with the increase of pH value as follows:

$\text{log}\text{W = a+b}\text{log}\text{C, where b=0.485 and}\text{d}\text{log}\text{W}\text{d}\text{pH}\text{=?0.15?0.25.}$

At high concentration (10^?1 and 10^?2) and in the pH range 2–5, the steady state potential varied by 64 and 58 mV for a unit change of pH in oxalic and citric, respectively. The corrosion process was found to be cathodically controlled.In dilute solutions (10^?5–10^?3M) in the pH range of 2–5 and in all acid concentrations at pH 6, the steady state corrosion potential shifted in the negative direction with increase of acid concentration accompanied by an increase in the corrosion rate, indicating that the corrosion process became anodically controlled.     

Nash equilibria in stabilizing systems

The objective of this paper is three-fold. First, we specify what it means for a fixed point of a stabilizing distributed system to be a Nash equilibrium. Second, we present methods that can be used to verify whether or not a given fixed point of a given stabilizing distributed system is a Nash equilibrium. Third, we argue that in a stabilizing distributed system, whose fixed points are all Nash equilibria, no process has an incentive to perturb its local state, after the system reaches one fixed point, in order to force the system to reach another fixed point where the perturbing process achieves a better gain. If the fixed points of a stabilizing distributed system are all Nash equilibria, then we refer to the system as perturbation-proof. Otherwise, we refer to the system as perturbation-prone. We identify four natural classes of perturbation-(proof/prone) systems. We present system examples for three of these classes of systems, and show that the fourth class is empty.     

Study on the wire electrochemical groove turning process

In this study a copper wire is proposed as a tool electrode in electrochemical groove turning process (WECGT). The working parameters, namely, radial feed rate, wire diameter, and rotational speed are investigated to study the performance criteria via MRR, groove width, and roundness error. An experimental study is presented through performing series of designed experiments. Key features of a WECGT setup that was designed and developed incorporating several unique features are also highlighted. The experimental results are statistically analyzed and mathematically modeled through response surface methodology (RSM). The mathematical model adequacies are checked using analysis of variance (ANOVA). Furthermore, optimal combination of working parameters has been evaluated to maximize MRR and minimize roundness error. The results reveal that using wire as an electrode in electrochemical turning instead of using a profiled tool proved its powerfulness to produce circular grooves. The results also demonstrate that the groove width has greatly increased by increasing the wire diameter, while it is decreased by increasing both the radial feed rate and rotational speed. Lower roundness errors are obtained by increasing both radial feed rate and wire diameter. The optimum combination of parameters setting is: radial feed rate of 0.08 mm min⁻1, wire diameter of 2.3 mm, and rotational speed of 578 rpm.     

Galvanic cells encountered in the corrosion of steel reinforcement — II. Differential salt concentration cells

Two differential salt concentration cells have been studied at pH 6·5, 10, 12 and 12·5. The rest potentials of uncoupled steel immersed in chloride solutions of pH 6·5 and 10 were more negative than those obtained in pH 12 and 12·5. This is ascribed to the occurrence of general attack in the former and pitting in the latter solutions. The results of coupling showed that steel electrodes immersed in the half cells of the lower Cl^? ion concentration were completely protected from corrosion. The galvanic currents obtained from the differential salt concentration cells at pH 6·5 or 10 were considerably higher than those obtained at pH 12 or 12·5. In the anodes of the former cells general corrosion occurred while in those of the latter cells pitting corrosion occurred. The increase of the salt concentration range caused an increase in the galvanic current and in the cell e.m.f., negativation of the mixed potential and depolarization of the anodic and cathodic processes. The controlling factors of corrosion in the cells, at different pH values, were mainly determined by the kinetics of the anodic and to a lesser extent by the cathodic process.