InGaAs/AlGaAs QWIP Heterostructures for Large-Format Focal Plane Arrays Photosensitive in the Spectral Range 3–5 μm

Photoelectric properties of different stressed InGaAs/AlGaAs heterostructures with quantum wells grown by the method of molecular beam epitaxy on GaAs substrates for mid-wavelength infrared largeformat photodetector arrays operating in the spectral range 3–5 μm have been investigated. It has been shown that the change in the composition of barrier layers leads to a significant shift of the photosensitivity spectra of such heterostructures.     

Erlang loss queueing system with batch arrivals operating in a random environment

We consider the BMAP/PH/N/0$\text{<italic>BMAP</italic>}/\text{<italic>PH</italic>}/N/0$ queueing system operating in a finite state space Markovian random environment. Disciplines of partial admission, complete rejection and complete admission are analyzed. The stationary distribution of the system states is calculated. The loss probability and other main performance measures of the system are derived. The Laplace–Stieltjes transform of the sojourn time distribution of accepted customers is obtained. Illustrative numerical examples are presented. They show effect of an admission strategy, a correlation in an arrival process, a variation of a service process. Poor quality of the loss probability approximation by means of more simple models utilization is illustrated.     

An Optimal Multithreshold Control for the Input Flow of the GI/PH/1 Queueing System with a BMAP Flow of Negative Customers

A GI/PH/1 queueing system with an additional flow of negative customers is studied. The system has many operation modes differing in the distribution of inter-arrival lengths. Mode control depends on the queue length at arrival instants defined by a multithreshold strategy. The stationary state probability distribution of the system for fixed thresholds is studied. Numerical examples are given to illustrate the determination of the optimal threshold set in a fixed search domain.     

Information security in distributed computing systems. A review

The solution of large-dimension information-computing tasks with the use of globally distributed computing environments requires that special attention be paid to the problem of information security. This is urgent for both an information-computer system itself and its constituent subsystems and its users.     

M|M|N queueing system with controlled service mode and disaster

An M|M|N queueing system with identical servers and controlled mode, which is characterized by the parameter, “exponential distribution of service time,” is considered. The mode varies in accordance with a multithreshold strategy. The system is subjected to the action of catastrophic failures that induce the departure of all the customers from the system. An algorithm is developed for calculating the stationary state probability of the system and the performance characteristics with fixed control strategy. An optimal strategy is found numerically in a limited region of values of the threshold. Numerical examples are presented.     

A queueing system with batch arrival of customers in sessions

This paper describes and analyzes a single-server queueing model with a finite buffer and session arrivals. Generation of the sessions is described by the Markov Arrival Process (MAP). Arrival of the groups of the requests within any admitted session is described by the Terminating Batch Markov Arrival Process (TBMAP). Service time of the request has Phase (PH) type distribution. The number of the sessions that can be simultaneously admitted to the system is under control.     

A two-phase queuing system with access control and correlated arrival processes

A two-phase queuing system with access control is studied whose first phase consists of an infinite number of servers, while the second one consists of a finite number of servers. To the first phase, a Markovian input flow of queries arrives. On completion of the first-phase service, the customer either leaves the system or is passed to the second phase. In addition, a Markovian input flow of queries that do not require any first-phase service arrives to the second phase. An algorithm for finding a steady-state distribution of the system’s state probabilities is given, and some problems of the system’s paramaters optimization are considered.     

High-power low-threshold laser diodes (λ=0.94μm) based on MBE-grown In0.1Ga0.9As/AlGaAs/GaAs heterostructures

The parameters of high-power laser diodes operating at λ=0.94 μm, based on MBE-grown In_0.1Ga_0.9As/AlGaAs/GaAs quantum-dimensional heterostructures, are reported. The laser diodes manufactured using an optimized MBE technology and specially selected dopant profiles are characterized by a lowthreshold current density, a high optical output power, a high differential quantum efficiency, and a long working life (above 10000 h).