In a general model (AIMD) of transmission control protocol (TCP)used in internet traffic congestion management, the time dependentdata flow vector x(t) > 0 undergoes a biased random walk ontwo distinct scales. The amount of data of each component x i (t)goes up to x i (t)+a with probability 1-ζ i (x) ona unit scale or down to γ x i (t), 0 < γ < 1 withprobability ζ i (x) on a logarithmic scale, where ζ i depends on the joint state of the system x. Weinvestigate the long time behavior, mean field limit, and the oneparticle case. According to c = lim inf|x|→∞ |x|ζ i (x), the process drifts to ∞ in thesubcritical c < c + (n, γ) case and has an invariantprobability measure in the supercritical case c > c + (n, γ).Additionally, a scaling limit is proved when ζ i (x)and a are of order N –1 and t → N t, in the form of acontinuum model with jump rate α(x).

Objectives: This study is designed to present and evaluate radiobiological-based dose–volume histogram (DVH) reduction schemes to calculate normal tissue complication probability (NTCP) and tumour control probability (TCP) for intensity-modulated radiation therapy (IMRT).

Methods: The proposed DVH reduction schemes were derived for 2 Gy per fraction and prescribed dose per fraction for critical organs and tumours, respectively. Sample computed tomography scans were used to generate two IMRT plans to deliver 54 Gy to PTV1 and 24 Gy to PTV2 via sequential IMRT boost (SqIB) and simultaneous integrated IMRT boost (SIB) plans. Differential DVHs were used to calculate effective volumes using published values of related parameters of critical organs and prostate.

Results: NTCP values for bladder were almost zero for both IMRT plans. The plots between k and NTCP for rectum and femurs (k = 0.1–1.0) show higher NTCP for SqIB than that for SIB. The TCP decreases with increasing clonogenic cell density and is higher for SIB than that for SqIB for all clonogenic cell densities. The value of α proposed by Brenner and Hall shows very low radio sensitivity of clonogens of the prostate, which gives very low TCP for conventional doses of 70–80 Gy delivered in 7–8 weeks, even for very low clonogenic cell density in the prostate.

Conclusion: The presented DVH reduction schemes have radiobiological bearing and therefore seem to be effective in calculating fairly accurate NTCP and TCP.

Inter-observer variations in contouring and their impacts on dosimetric and radiobiological parameters in intensity-modulated radiotherapy (IMRT) treatment for localised prostate cancer patients were investigated. Four observers delineated the gross tumour volume (GTV) (prostate and seminal vesicles), bladder and rectum for nine patients. Contouring done by radiologist was considered as gold standard for comparison purposes and for IMRT plan optimisation. Maximum average variations in contoured prostate, bladder and rectum volumes were 3% (SD = 8.4), 2.5% (SD = 4.12) and 13.2% (SD = 6.77), respectively. The average conformity index for standard contouring set (observer A) was 0.85 (SD = 0.028) and statistically significant differences were observed for observers A–B (p = 0.008), A–C (p = 0.006) and A–D (p = 0.011). Average values of normal tissue complication probability for bladder and rectum for observer A were 0.361% (SD = 0.036) and 1.59% (SD = 0.14). Maximum average tumour control probability was 99.94% (SD = 0.035) and statistically significant difference was observed for observers A–B (p = 0.037) and observers A–C (p = 0.01). Inter-observer contouring variations have significant impact on dosimetric and radiobiological outcome in IMRT treatment planning. So accurate contouring of tumour and normal organs is a fundamental prerequisite to make good correlation between calculated and clinical observed results.

The TCP window size process can be modeled as a piecewise-deterministic Markov process that increases linearly and experiences downward jumps at Poisson times. We present a transient analysis of this window size process. Our main result is the Laplace transform of the transient moments. Formulae for the integer and fractional moments are derived, as well as an explicit characterization of the speed of convergence to steady state. Central to our approach are the infinitesimal generator and Dynkin's martingale.

If one operator in a remote operating room can operate 4 ∼ 5 cranes remotely, which are yard cranes for container loading/unloading in a port container terminal, the port loading/unloading efficiency will dramatically be improved through productivity increase, cost reduction, and so on. This study presents a remote crane control system for container loading/unloading yard cranes of port container terminals. First, a wireless web-based video and audio transmission system to transmit the images and the sounds of a craneyard is designed by using 3 web cameras and a microphone. Next, a TCP/IP-based remote crane control system is presented on the basis of the delay performance simulations of TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) for real-time remote control. The simulation results show that TCP is more advantageous for remote crane control on a local network.

The additive-increase multiplicative-decrease (AIMD) schemes designed to control congestion in communication networks are investigated from a probabilistic point of view. Functional limit theorems for a general class of Markov processes that describe these algorithms are obtained. The asymptotic behaviour of the corresponding invariant measures is described in terms of the limiting Markov processes. For some special important cases, including TCP congestion avoidance, an important autoregressive property is proved. As a consequence, the explicit expression of the related invariant probabilities is derived. The transient behaviour of these algorithms is also analysed.