196,154 research outputs found
A fastalgorithm for the uniquedecipherability of multivalued encodings
No full textMultivalued encodings constitute an interesting generalization of ordinary encodings in that they allow each source symbol to be encoded by more than one codeword. In this paper the problem of testing the property of uniquedecipherability of multivalued encodings is considered. We provide an efficient algorithm whose time complexity is O(|C|Δ), where |C| is the number of codewords and Δ is the sum of their lengths. It is remarkable that the running time equals that of the fastestalgorithms for testing the much simpler property of uniquedecipherability of ordinary encodings
Decoders with Initial State Invariance for Multivalued Encodings
No full textMultivaluedencodings constitute an interesting generalization of ordinary encodings in that they allow each source symbol to be encoded by more than one codeword. In this paper we characterize the class of multivaluedencodings that admit invariant decoders and provide an algorithm for constructing such decoders. Invariant decoders have the useful property that their behavior does not depend on the state in which they are, thus exhibiting optimal tolerance to accidental state transitions and/or errors in the input sequence
Efficient q-ary Immutable Codes
No full textA fixed length code is called immutable if no codeword can be transformed into another codeword by using only a restricted set of symbol changes. Immutablecodes are used to prevent undetectable updates of information stored over write-once memories [14]. In this paper we consider immutablecodes on the alphabet Q={0,..., q−1}. We prove that a maximum size immutablecode of block length n can be obtained by taking the set of all vectors in Q^n of weight ⌈n(q−1)⧸2⌉. Furthermore, we propose an encoding rule to map information sequences of length k into codewords of an immutablecode of length k+p. The number k of information digits and the number p of parity digits must satisfy the inequality k≤2(q^p−1)⧸(q−1)−p. The proposed encoding algorithm has computational complexity O(k)
Process analysis of a novel humidification-dehumidification-adsorption (HDHA) desalination method
No full textThe desalination through humidification-dehumidification (HDH) presents still a high energy-footprint but
shows many unique attributes that pushed a recent revival of R&D for decentralized production of water. In this
paper, a novel process scheme consisting of a multiple extraction humidification-dehumidification with vapour
adsorption (HDHA) and brine recirculation is analysed. It works with bottom brine temperatures below the
coldest heat source and direct recirculation. With respect to the common classification, the process can be
considered a closed-air closed-water (CACW) HDH. The study of the degrees of freedom and the mathematical
model for the sensitivity analysis are presented. Process simulation showed how to increase the performances
above the GOR of 10 with multiple extractions. The basic design of a HDHA producing> 30 m3 day−1 of
distilled water, with higher performance (GOR of 7 and a RR of 50%) than the current state-of-the-art, is discussed.
Furthermore, the paper reports the process scheme and the mathematical model of the adsorption unit
integrated with the HDH, the breakthrough curves and the mass of sorbent needed to carry the novel process.
The considerations here presented highlight the key benefits of the new process and bode well for its technological
development
"Hydrodynamic Cavitation Of P-Nitrophenol: A Theoretical And Experimental Insight"
No full textThis paper presents a theoretical and experimental study of cavitation as an advanced oxidation process. The degradation rate of p-nitrophenol (PNP) was experimentally investigated and used as an estimator of the sonochemical effect in hydrodynamic cavitation. The PNP initial concentration was varied in the range 0.1-1 g L-1 and the pressure in the range 0.2-0.7 MPa, with a corresponding flow rate of 3.5 to 6.9 L min-1. In terms of removal rate and energy efficiency, an optimal inlet pressure value was found close to 0.4 MPa and cavitation number of 0.25. The calculated first-order kinetic constant values show the existence of an optimal configuration: k = 1.13·10-2 min-1 at 0.45 MPa with a value for the electrical energy per order EEO = 66.7 kWh m-3. Moreover, the kinetic data was purged from the influence of the experimental apparatus configuration, allowing for the evaluation of an intrinsic kinetic constant. The physical-chemical behavior of hydrodynamic cavitation is discussed on the basis of single bubble dynamics. The numerical simulations, at different inlet pressures, provided a good explanation of the values observed. Furthermore, a simple energy balance on cavitating bubbles, taking into account for the actual production of cavitating events, gave a further confirmation of the experimental trends
A continuous Markovian model for neuronal activity
No full textA diffusion model for the description of neurons' membrane potential fluctuations is proposed. Though retaining the well known feature consisting of the spontaneous exponential decay of the membrane potential to its resting value, the model discussed differs substantially from the ones in the current literature. Moreover, the Fokker-Planck equation now describing the membrane potential fluctuations is singular. The neuron's firing times probability density function is calculated in closed form as in a first passage time problem, and its expectation value and variance are evaluated. A detailed study of the mode of the firing times probability density function as related to the noise's intensity is performed. Some other auxiliary results are also obtained
A diffusion model for population growth in random environment
No full textThe growth of a population in a randomly varying environment is modeled by replacing the Malthusian growth rate with a delta-correlated normal process. The population size is then shown to be a random process, lognormally distributed, obeying a diffusion equation of the Fokker-Planck type. The first passage time p.d.f. through any arbitrarily assigned value and the probability of absorption are derived. The asymptotic behavior of the population size is investigated
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