Cell loss dynamics and output process in a finite-buffer discrete-time queue with correlated arrivals

This paper analyzes the performance of an ATM switching node considering cell arrival correlation. An ATM switching node is modeled as a discrete-time finite-buffer queue. Cell arrivals are assumed to follow a semi-Markovian process, where the number of cell arrivals in a lot depends on the states of the underlying (M-state) Markov chain in the current and previous slots. This paper presents analyses for various characteristics of the cell loss, as well as the distribution function of the cell output process from an ATM switching node. Obtained results include the cell loss probability, the consecutive loss probability, the distribution of loss period lengths, the joint distribution of successive cell interdeparture times, and the distribution of busy and idle periods. Through the numerical results, it is shown that both the correlation and the variation of cell arrivals significantly affect the cell loss and the output process characteristics

Performance Evaluation of a Packetized Voice System Simulation Study

Introduction of the packet switching technique into digitized voice communication may afford great advantages in efficient use of the channel, compared to both circuit-switched and DSI systems. Detailed characteristics, however, have not been obtained because of difficulty in the exact analysis. Hence, simulation models are developed in this paper for the packetized voice transmission system, and various characteristics such as transmission delays and loss probability of voice packets are obtained. We further evaluate three types of voice packet reassembly strategy at t he receiving terminal, and obtain the optimal packet length, which keeps each of overall packet transmission delay and packet loss probability less than a certain permissible values. Comparison among three strategies is also stated

Performance Evaluation of an Integrated Access Scheme in a Satellite Communication Channel

A method for realizing a circuit and packet integrated access scheme in a satellite communication channel is considered. Two kinds of terminals are assumed, namely, bursty terminals for handling bursty traffic and heavily loaded terminals for long-holdingtime message traffic. In this method, the channel frame is divided into two subframes: one is for bursty terminals, and the other is for heavily loaded terminals. The subframe for heavily loaded terminals is further divided into two subchannels, a reservation subchannel (consisting of small slots) and a message subchannel. The bursty terminals transmit their packets in their dedicated subframes on the slotted ALOHA protocol. The heavily loaded terminal having a message transmits, first of all, a reservation packet in a randomly selected small slot of the reservation subchannel to reserve slots in the coming message subchannels. One slot in the same position of each of the succeeding message subchannels is reserved for the terminal until the end-of-use flag, transmitted from the terminal, is received by the satellite. Mean transmission delays for both kinds of traffic in this method are analytically obtained. We show that there exists an optimal frame length which minimizes mean transmission delay for one kind of traffic while keeping mean transmission delay for the other kind under some permissible value

A Study of Fermi Surfaces of the α-Phase Cu-Ge and Cu-Si Alloys by Positron Annihilation(Physics)

Angular correlation measurements on the fcc solid solutions of Cu-Ge and Cu-Si alloys have been carried out on single crystals with four crystallographic orientations by a crossed-slit geometry. The results on both the alloys are nearly the same. The -neck radius and the -radius of the Fermi surfaces increase almost linearly with increasing electron concentration in accord with previous results on Cu-Al and Cu-Zn alloys. The Fermi surface does not touch the square faces of the Brillouin zone at the solubility limit. The results agree fairly well with a calculation based on the sinking-conduction band model

The Fermi Surfaces of Cu-Pd Alloys Studied by Positron Annihilation(Physics)

The Fermi surfaces of Cu-Pd alloys below 63% Pd are studied by means of the angular correlation of positron annihilation with crossed-and long-slit geometries. The (001)- and (110)-radii decrease with increasing palladium content up to 30% in agreement with a calculation based on the rigid band model. The (111) neck radius also decreases with increasing composition, and it is suggested that the Fermi surface detaches from the hexagonal face of the Brillouin zone around 20% Pd, but remains to bulge in this direction at higher compositions. No detectable change is found in the correlation curves of the ordered and disordered states at 15 and 19% Pd. The origin of stabilization of the long period ordered structure near Cu_3Pd is discussed in the light of the present results

Analysis of Dual Use of a Trunk Group with Reservation

This paper considers the traffic aspects of a multitrunk communication system under a dual use of trunks for both direct and store-and-forward (S/F) traffic, in which one trunk is held in reserve for direct traffic. A method of computation, some results for trunk efficiencies and blocking probabilities of direct traffic and also of S/F traffic are presented. Numerical results are obtained for the various cases. The numerical results show that the trunk efficiency of the system can be twice as high as that of the system with no S/F traffic. This is possible without any significant impairment of the grade of service to direct traffic due to mixing S/F traffic. Moreover, in the system, the grade of service of S/F traffic is not significantly impaired due to the trunk held in reserve for direct traffic

Throughput and delay analysis of free access tree algorithm with mini-slots

This paper analyzes throughput and delay performance of two kinds of free access tree algorithms with mini-slots, and the other is that ternary feedback information is available. In these algorithms Q number of mini-slots are provided within a slot to offer feedback information on the state of the channel. The maximum throughputs of binary and ternary feedback algorithms are analytically obtained. It is also shown that the highest maximum throughput of 0.56714 is achieved when Q approaches infinity and mini-slot overhead goes to zero. The lower bound of the average transmission delays in these algorithms is analytically derived. The obtained lower bound is also a lower bound of the average delay of the whole class of free access algorithms

Waiting time analysis of MX/G/1 queues with/without vacations under ramdom order of service discipline

We study(batch arrival)MX/G/1 queues without vacations under random order of service(ROS)discipline.By considering the conditional waiting times given the states of the system when an arbitrary message arrives,we derive the Laplace-Stieltjes transforms of the waiting time distributions and explicitly obtain their first two moments.The relationship for the second moments under ROS and first-come first-served disciplones is shown to be precisely the same as that found by Takacs and Fuhrmann for(single arrival)M/G/1 queues

Risk Factors for Low Bone Mineral Density Determined in Patients in a General Practice Setting

Osteoporosis increases the risk of bone fractures. It is diagnosed based on an individual’s bone mineral density (BMD) or a fracture without trauma. BMD is usually measured by the dual energy X-ray absorptiometry (DXA) method. Here we investigated factors for the earliest possible prediction of decreased BMD by examining the relationships between patients’ BMD values and changes in the patients’ physical and laboratory values. We retrospectively reviewed the medical records of 149 patients who visited our department in 2014-2015 for a variety of reasons and underwent an area BMD examination by DXA. We analyzed the relationships between decreasing BMD and the patients’ gender, age, body mass index (BMI), medical background, hemoglobin, electrolytes, and thyroid function. Thirty-nine of the patients were diagnosed with osteoporosis based on their T-scores. An adjusted analysis showed that female gender, aging, and increased serum calcium level were significantly related to decreasing femoral BMD, whereas high BMI was associated with an increase in femoral BMD. Collectively the results indicate that for the early detection of low BMD, it is important for general-practice physicians to consider conducting a BMD checkup when treating female and elderly patients with a low BMI and/or elevated serum calcium level

Binding of proton and iron to lignite humic acid size-fractions in aqueous matrix

金沢大学理工研究域物質化学系The bioavailability of trivalent iron (Fe3+) to plants can be enhanced using fertilizer solutions containing humic acids (HA) as manifested from the increased crop yield at an iron stress conditions. The lignite-derived HA (HAlignite) facilitates higher diffusion of Fe3+ between the soil layers as attributable to more number of reactive sites in the assemblage compared to those from other origins. In the current work, the proton-binding of HAlignite size-fractions (5–10, 10–30, 30–100, and >100 kDa), as segmented based on the molecular weight distribution, and their complexation with Fe3+ have been studied at varying pH ranging from low to high. The protonation or formation of Fe3+-complexes exhibited a comparable pattern despite the differences in the conformational distribution of HAlignite size-fractions. The protonation behavior specified that the behavior of HAlignite size-fractions has similarity with that of a dibasic acid. The results are interpreted using reactive structural units (RSU) concept to show that the carboxyl and phenolic-hydroxyl groups in the HAlignite size-fractions simultaneously available as the Fe3+-binding sites. The stability constants for larger MW fractions of HAlignite (>100 kDa) was the lowest, as attributed to the increased aggregation rate in an aqueous matrix. The trend in conditional stability constants of HAlignite-size fractions and other Fe-chelators point to a better Fe-binding capability of HAlignite (30–100 kDa) size-fraction than the biodegradable alternatives (GLDA, HIDS, EDDS, IDSA, or NTA), while the Fe-interaction was stronger with classical synthetic chelators (EDTA, DTPA, or EDDHA). © 2018 Elsevier B.V.Embargo Period 12 month