Improvements in the understanding of the physiology of the central airways require an appropriate representation of the non-uniform ventilation at its terminal branches. This paper proposes a new technique for estimating the non-uniform ventilation at the terminal branches by modelling the volume change of their distal peripheral airways, based on vascular segmentation. The vascular tree is used for sectioning the dynamic CT-based 3D volume of the lung at 11 time points over the breathing cycle of a research animal. Based on the mechanical coupling between the vascular tree and the remaining lung tissues, the volume change of each individual lung segment over the breathing cycle was used to estimate the non-uniform ventilation of its associated terminal branch. The 3D lung sectioning technique was validated on an airway cast model of the same animal pruned to represent the truncated dynamic CT based airway geometry. The results showed that the 3D lung sectioning technique was able to estimate the volume of the missing peripheral airways within a tolerance of 2%. In addition, the time-varying non-uniform ventilation distribution predicted by the proposed sectioning technique was validated against CT measurements of lobar ventilation and showed good agreement. This significant modelling advance can be used to estimate subject-specific non-uniform boundary conditions to obtain subjectspecific numerical models of the central airway flow.

Advances in volumetric medical imaging techniques allowed the subject-specific modeling of the bronchial flow through the first few generations of the central airways using computational fluid dynamics (CFD). However, a reliable CFD prediction of the bronchial flow requires modeling of the inhomogeneous deformation of the central airways during breathing. This paper addresses this issue by introducing two models of the central airways motion. The first model utilizes a node-to-node mapping between the discretized geometries of the central airways generated from a number of successive computed tomography (CT) images acquired dynamically (without breath hold) over the breathing cycle of two Sprague-Dawley rats. The second model uses a node-to-node mapping between only two discretized airway geometries generated from the CT images acquired at end-exhale and at end-inhale along with the ventilator measurement of the lung volume change. The advantage of this second model is that it uses just one pair of CT images, which more readily complies with the radiation dosage restrictions for humans. Three-dimensional computer aided design geometries of the central airways generated from the dynamic-CT images were used as benchmarks to validate the output from the two models at sampled time-points over the breathing cycle. The central airway geometries deformed by the first model showed good agreement to the benchmark geometries within a tolerance of 4%. The central airway geometry deformed by the second model better approximated the benchmark geometries than previous approaches that used a linear or harmonic motion model.

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The most recent technique to study the behavior of tunnel ventilation is computational fluid dynamics (CFD). This approach is capable of modeling the multi-dimensional, obstructed and non-obstructed tunnels of arbitrary geometry. This paper addressed the methodology improvement for the design of ventilated road tunnels using CFD technique. A comprehensive CFD simulation has been carried out to examine the velocity, pressure and temperature distributions in the main scenario of tunnel ventilation in case of normal and halted traffic. The predicted results are used to enhance the design and evaluate the ventilation system capability to fulfill the required thermal environment inside the tunnel. The base design of tunnel ventilation system was modified to avoid the unsafe regions in the tunnel where the effects of carbon monoxide (CO) are hazard. NOMENCLATURE CFD Computational Fluid Dynamics CO Carbon monoxide k The turbulence energy LES Large Eddy Simulation MTFVTP Memorial Tunnel Fire Ventilation Test Program MVS Mechanical ventilation systems NO x Oxides of Nitrogen NRC National Research Council RANS Reynolds-averaged Navier-Stokes SES Subway Environmental Simulation SO 2 Sulfur dioxide ε The rate of viscous dissipation of turbulence energy ω The turbulence dissipation rate * Syrian Armed Forces ** Egyptian Armed Forces

In the commertial utilization of sheets produced by cold rolling, it is desirable that the gauge of the material be as uniform as possible and the shape defects are minimum.Flatness of cold rolled products is important when they are used in some fields such as rocket engine casings and other aerospace: hardware. • A steady state multivariable control scheme is presented in the paper aiming at controlling the minimum and maximum thicknesses of the rolled sheets against any disturbance. Required models are derived in general form and the model gain coeffic4. ients are obtained for the cold rolling line of the Egyptian ' ' Iron and Steel Company. The paper presents the different ways of applying the propos-: ed control scheme including simple manual method suitable for the developed. countries.