Wyniki wyszukiwania - BazTech

1

Mathematical modeling of fluid flow in brain tumor

Riahi D. N., Roy R.

Journal of Theoretical and Applied Mechanics

|

2014

|

Vol. 52 nr 1

271--279

EN

We consider the problem of fluid flow in a brain tumor. We develop a mathematical model for the one-dimensional fluid flow in a spherical tumor where the spatial variations of the interstitial velocity, interstitial pressure and the drug concentration within the tumor are only with respect to the radial distance from the center of the tumor. The interstitial ve- locity in the radial direction and the interstitial pressure are determined analytically, while the radial variations of two investigated drug concentrations were determined numerically. We calculated these quantities in the tumor, in a corresponding normal tissue and for the concentrations also in the cavity that can exist after the tumor is removed. We determine, in particular, the way the interstitial pressure and velocity vary, which agrees with the expe- riments, as well as the way one drug concentration changes in the presence or absence of a second drug concentration within the tumor. We find that the amount of drug delivery in the tumor can be enhanced in the presence of another drug in the tumor, while the ratio of the amount of one drug in the tumor to its amount in the normal tissue can be reduced in the presence of the second drug in the tumor and the tissue.

2

Two-phase flow in a catheterized artery with atherosclerosis

Ledesma J. M., Riahi D. N., Roy R.

Journal of Theoretical and Applied Mechanics

|

2013

|

Vol. 51 nr 2

409--418

EN

We consider the problem of blood flow in a catheterized artery and in the presence of atherosclerosis, which is chosen based on the available experimental data. The atherosclerosis is a condition where an artery wall thickens as a result of fatty materials such as cholesterol. The use of catheter is of immense importance as a standard tool for diagnosis and treatment in a patience whose artery is affected adversely by the presence of atherosclerosis within the artery. The blood flow in the arterial tube is represented by a two-phase model composing a suspension of erythrocytes (red cells) in plasma. The coupled differential equations for both fluid (plasma) and particles (red cells) are solved theoretically subjected to reasonable modeling and approximations. The important quantities such as plasma speed, velocity of red cells, blood pressure force, impedance (blood flow resistance) and the wall shear stress are computed for different values of the catheter size, axial location of atherosclerosis and the hematocrit due to the red cells-plasma combination of the blood flow system.

PL

W pracy omówiono problem przepływu krwi w tętnicy po zabiegu koronarografii w obecności zmian miażdżycowych, opierając się na osiągalnych danych z badań klinicznych. Miażdżycą nazywamy stan, w którym ściana tętnicy pogrubia się do wewnątrz wskutek odkładania się tłuszczy, głownie cholesterolu. W standardowej metodzie leczenia miażdżycy stosuje się zabieg koronarografii polegający na wprowadzeniu cewnika do upośledzonej tętnicy. W pracy opisano przepływ krwi w przekroju tętnicy za pomocą dwufazowego modelu odzwierciedlającego zawiesinę czerwonych ciałek krwi w osoczu. Sprzężone, różniczkowe równania przepływu płynu (osocza) i ruchu cząstek (czerwonych ciałek) rozwiązano analitycznie w stopniu akceptowalnie przybliżonym. Tak istotne wielkości, jak prędkość przepływu osocza, prędkość czerwonych ciałek, ciśnienie krwi, impedancja (opory przepływu) oraz naprężenia ścinające w ścianie tętnicy obliczono dla rożnych rozmiarów cewnika, osiowego rozkładu złogów miażdżycowych oraz hematokrytu wywołanego dwufazową kombinacją czerwone ciałka-osocze w badanym układzie krwionośnym.

3

Applicability of a few analytical formulations for dynamic characteristics of elevated tanks with battered stagings

Dutta S. C., Roy R., Dutta S.

International Journal of Applied Mechanics and Engineering

|

2004

|

Vol. 9, no 4

803-819

EN

The applicability of available analytical formulations for elevated tanks with vertical stagings is shown to the similar tanks with battered stagings. The formulation includes the dynamic characteristics like lateral and torsional stiffness and natural periods. Both frame and shaft supported stagings for elevated tanks are considered with and without accounting for the effect of soil-structure interaction. The values obtained through analytical formulation are compared to the results of finite element analysis and found to have reasonable performance. Thus the study yields handy formulations to be used for seismic design of elevated tanks with battered stagings.

4

Differential settlement among isolated footings of building frames: the problem, its estimation and possible measures

Roy R., Dutta S. C.

International Journal of Applied Mechanics and Engineering

|

2001

|

Vol. 6, no 1

165-186

EN

The conventional design of building frames is based on the assumption that the settlement of footings has no effect on the load of the corresponding columns. In reality, the differential settlements among various footings result in a redistribution of the column loads, the amount of which depends on the rigidity of the structure and the load-settlement characteristics of the soil. The present paper attempts to study the effect of the same on design force quantities for frame members of building frames with isolated footings. The nonlinear settlement versus stress relationship arising in case of building frames with isolated footings on clayey soils is attempted to be dealt with two alternative iterative approaches. Results of a few simple three-dimensional frames obtained by the simpler approach are compared with the results of the more rigorous approach and found to be satisfactory. Frames resting on sandy soil are also studied by idealising the soil medium below the footing as linear elastic springs. Various representative case studies are presented for frames resting on sandy and clayey soil. These case studies may help in arriving at design provisions to account for such effects. The simpler iterative approach may be exercised with the help of available commercial frame analysis software and may prove useful in improved design of buildings accounting for the effect of soil-structure interaction. Adequacy of providing tie beams, continuous lintels, and diagonal braces in minimising the redistribution of force quantities are also studied and presented in the paper in limited form. The addition of diagonal braces are found to be effective in substantially minimising the change in force quantities due to the soil-structure interaction.