Kaori Kobayashi

Plasma Waves and Sounder (PWS) experiment onboard the Planet-B Mars orbiter

For the purpose of observing the Martian ionosphere under the condition of direct interaction with the solar wind by using a RF sounder together with a plasma density probe and high frequency plasma wave detectors, the Plasma Waves and Sounder (PWS) system onboard the Planet-B Mars orbiter has been developed through a proto-model (PM) which are followed by achievement of a flight-model (FM) for the Planet-B mission. The operation of the achieved system has been tested for function and stability in a simulated space environment. The PWS system is equipped with two sets of long deployable dipole antennas with a tip-to-tip length of 52 m. The high power (600 Watts) transmitter of the sounder experiment makes it possible to measure the electron density profiles of the Martian topside ionosphere in an altitude range from 300 to 3000 km in a density range from 102 to 106/cc with a time resolution of 25 µsec corresponding to a range resolution of 3.75 km. Observations of natural plasma waves and planetary radio waves in the frequency range from 20 kHz to 5 MHz are planned in the passive mode operation of the PWS system, identifying all the polarization characteristics together; observations of natural plasma waves caused by the direct interaction of the Martian ionosphere with the solar wind plasma are also a major purpose of the PWS experiment. For these purposes, a wide dynamic range and high sensitivity characteristics of the PWS receiver have been achieved. As the extended function of the PWS plasma sounder instrument, altitude measurement also will be carried out.

Analysis of a nonpreemptive priority queue with exponential timer and server vacations

We consider multi-class priority queues with nonpreemptive services controlled by an exponential timer and multiple vacations. By reducing this model to the priority model with Bernoulli schedule analyzed by Katayama (1997), we obtain the Laplace-Stieltjes transform for the sojourn time in the system for each priority class, assuming (i) constant service times or (ii) general service times with either 1-limited or exhaustive service, and provide recursive equations to evaluate its first two moments.

System delay analysis for a nonpreemptive time-limited service queueing system with two types of vacations and its application

Abstract We consider an M/G/1 queue with time-limited service and two types of vacations, in whichever single server serves customers until the timer expires or the queue becomes empty, whichever occurs first, and then takes type 1 or type 2 vacations. A type 1 vacation is taken at a timer expiration, while a type 2 vacation in the every case of system emptiness. The customer that had its service interrupted due to the timer expiration may be attended by the nonpreemptive discipline. Applying the analysis results to the time-limited service polling system, we derive an approximate probability density function for evaluating the system delay variance, and formulate an optimal assignment problem of the total time of limited service-periods.

Sojourn time analysis of a two-phase queueing system with exhaustive batch-service and its vacation model

We consider an M/G/1-type, two-phase queueing system, in which the two phases in series are attended alternatively and exhaustively by a moving single-server according to a batch-service in the first phase and an individual service in the second phase. We show that the two-phase queueing system reduces to a new type of single-vacation model with non-exhaustive service. Using a double transform for the joint distribution of the queue length in each phase and the remaining service time, we derive Laplace-Stieltjes transforms for the sojourn time in each phase and the total sojourn time in the system. Furthermore, we provide the moment formula of sojourn times and numerical examples of an approximate density function of the total sojourn time.

Sojourn time analysis for a cyclic-service tandem queueing model with general decrementing service

A sojourn time analysis is provided for a cyclic-service tandem queue with general decrementing service which operates as follows: starting once a service of queue 1 in the first stage, a single server continues serving messages in queue 1 until either queue 1 becomes empty, or the number of messages decreases to k less than that found upon the servers last arrival at queue 1, whichever occurs first, where 1 @? k @? ~. After service completion in queue 1, the server switches over to queue 2 in the second stage and serves all messages in queue 2 until it becomes empty. It is assumed that an arrival stream is Poissonian, message service times at each stage are generally distributed and switch-over times are zero. This paper analyzes joint queue-length distributions and message sojourn time distributions.

A pseudoconservation law for a time-limited service polling system with structured batch poisson arrivals

We consider a cyclic-service queueing system (polling system) with time-limited service, in which the length of a service period for each queue is controlled by a timer, i.e., the server serves customers until the timer expires or the queue becomes empty, whichever occurs first, and then proceeds to the next queue. The customer whose service is interrupted due to the timer expiration is attended according to the nonpreemptive service discipline. For the cyclic-service system with structured batch Poisson arrivals (M^x/G/1) and an exponential timer, we derive a pseudoconservation law and an exact mean waiting time formula for the symmetric system.

Performance analysis of an M/G/1 satellite node with urgent jobs of a central processing node

As modeling for the behavior of each satellite node in a hub network with central node, we consider an M/G/1 queue with preemption of urgent jobs, in which the inter-arrival time of urgent jobs or the arrival rate are easily controllable by setting the most suitable parameters in the central node. Messages (i.e. ordinary jobs) are served in the queueing system, however, the service of messages are interrupted by urgent job arrivals. Basic performance measures such as waiting time and system delay (sojourn time) of messages are derived as the well-known decomposition expression for the Laplace-Stieltjes transform (LST) under the preemptive-resume service-restarting rule for interrupted messages. An optimal inter-arrival time of urgent jobs and the relationship between the data size of urgent jobs and the inter-arrival time are also investigated through numerical examples. The moment formulas of the performance measures are usable and effective for dimensioning of the similar hub networks.

Priority queues with semiexhaustive service and class-dependent setup times

This paper considers a new type of priority queues with semiexhaustive service and setup times, which operates as follows. A single server continues serving class-n messages in queue n until the number of messages decreases to one less than that found upon the servers last arrival at queue n, where 1 @? n @? N. In succession, messages of the highest class present in the system, if any, will be served according to this semiexhaustive service. Two types of class-dependent setup times are considered: Setup Time I (the first service after a setup time is given to the first arrival during an idle period) and Setup Time II (the first service after a setup time is given to the highest class message in the system at the end of the setup time). We derive the Laplace-Stieltjes transforms of the message waiting times for each kind of setup times and explicit formulae for the mean waiting times. We also give some numerical results to assess the influence of setup times.