Browsing by Subject "Approximate model"

Now showing 1 - 4 of 4

Open Access
Analysis of an Adaptive Modulation and Coding scheme with HARQ for TCP traffic
(IEEE, 2015-04) Öztürk, Onur; Akar, Nail
In this paper, we analyze the aggregate TCP throughput performance of a wireless link utilizing Active Queue Management (AQM) and an Adaptive Modulation and Coding (AMC) scheme with Hybrid ARQ (HARQ) based on the probability of failure in the first transmission attempt. We assume packets arriving out-of-order at the wireless receiver due to random retransmissions are resequenced before being released to the network. For this reason, an approximate model for the delay experienced at the resequencing buffer is also presented. In the light of the results obtained from the presented analysis, we propose a threshold for the aforementioned probability of failure making the investigated AMC scheme work at an overall performance close to that of the optimum policy. © 2015 IEEE.
Open Access
Quality control chart design under jidoka
(John Wiley & Sons, Inc., 2009) Berk, E.; Toy, A. Ö.
We consider design of control charts in the presence of machine stoppages that are exogenously imposed (as under jidoka practices). Each stoppage creates an opportunity for inspection/repair at reduced cost. We first model a single machine facing opportunities arriving according to a Poisson process, develop the expressions for its operating characteristics and construct the optimization problem for economic design of a control chart. We, then, consider the multiple machine setting where individual machine stoppages may create inspection/repair opportunities for other machines. We develop exact expressions for the cases when all machines are either opportunity-takers or not. On the basis of an approximation for the all-taker case, we then propose an approximate model for the mixed case. In a numerical study, we examine the opportunity taking behavior of machines in both single and multiple machine settings and the impact of such practices on the design of an X̄ - Q C chart. Our findings indicate that incorporating inspection/repair opportunities into QC chart design may provide considerable cost savings.
Open Access
Test of accuracy of the generalized boundary conditions in the scattering by thin dielectric strips
(IEEE, 2014-05) Nosich, A. I.; Shapoval, O. V.; Sukharevsky, Ilya O.; Altıntaş, Ayhan
The two-dimensional (2D) scattering of the E and H-polarized plane electromagnetic waves by a free-standing thinner than the wavelength dielectric strip is considered numerically. Two methods are compared: singular integral equations (SIE) on the strip median line obtained from the generalized boundary conditions for a thin dielectric layer and Muller boundary integral equations (BIE) for arbitrarily thick strip. The comparison shows the domain of acceptable accuracy of approximate model derived for thin dielectric strips. © 2014 IEEE.
Open Access
Validity of generalized boundary conditions and singular integral equation method in the scattering of light by thin dielectric strips
(IEEE, 2014) Shapoval O. V.; Sukharevsky, Ilya O.; Altıntaş, Ayhan
We consider the two-dimensional (2D) scattering of a plane wave of light by a thin flat dielectric nanostrip. Empirical method of generalized boundary conditions and singular integral equations on the strip median line is compared with Muller boundary integral equations method that does not assume the strip thickness to be small. The conclusions are achieved about the validity of approximate models for thin dielectric strips.