Energy Release Rate due to Friction at Bimaterial Interface in Dams

The interface between concrete dam and rock foundation is one of the most important regions governing the strength and stability of gravity dams. Many researchers have attempted to extend the fracture mechanics approach to study this rock concrete interface assuming stress free crack surfaces. In a real-life situation, because of the combined compression and shear loading, the crack faces come in contact resulting in a sizeable contact zone near the crack tip. Thus, frictional contact of the crack surfaces cannot be neglected. The frictional contact alters the stress singularity to become either weaker or stronger than the inverse square root singularity observed in homogeneous crack problems. Consequently, the strain-energy release rate as conventionally defined, either vanishes or becomes unbounded and thus cannot be used as a fracture parameter. In this work, an attempt is made to include the effect of friction associated with the sliding of crack surfaces and compute the energy dissipated during crack propagation. It is shown that the total energy release rate decreases with crack length when friction is accounted for between the rock-concrete interface in gravity dams.     

Disturbed State Model for Porous Saturated Materials

The widely used Terzaghi theory for deformation or consolidation in porous materials is based on the effective stress, a rather fictitious quantity, carried by the soil skeleton through the particle contact area, which is assumed to be negligible. This note presents a new generalized model based on the disturbed state concept, in which the average or weighted stress carried by the soil skeleton and fluid is defined on the basis of the change in contact area during deformation, that can be proportional to quantities such as the void ratio. A simple problem is solved in which the predictions from the proposed model and Terzaghi theory are compared. The proposed model has potential application as a general procedure for deformation in porous materials.     

Arsenic Removal from Groundwater by Iron Impregnated Sand

A granular media known as iron impregnated sand (IIS), developed in the laboratory by impregnating iron on a quartz sand surface by a simple and easy process has proved more effective than iron oxide coated sand (IOCS). Kinetic and isothermal studies showed that the uptake potential of IIS media was much more than IOCS media. The sequence of anions studied competing with respect to As(III) on IIS media was SO42?>HCO31?>Cl?. The presence of Ca2+ ions significantly improved the removal efficiency. During column studies the breakthrough loadings of IOCS (qb = 0.042 and 0.068) and IIS (qb = 0.097 and 0.217) for water and simulated water, respectively, show that qb for IOCS is lower than for IIS under similar experimental conditions. A filter effluent of 68 L of simulated water passed through 250 g IIS contained less than 0.05 mg As/L.     

A study of CaO (Fe2O3)1−x (Al2O3)x system

The members of the ferrite series CF_1?1A_x and with O ? × ? 0.8 have been studied by x-ray diffraction and Mössbauer spectroscopic techniques. The observed Mössbauer parameters are explained in the light of the following model, which is supported by the x-ray data. For non-zero x, the two phases CF and CA co-exist such that Al and Fe are distributed in these, respectively. With increase in x, the CF phase decreases and the CA phase increases.     

The electrical resistance of a graph captures its commute and cover times

View ann-vertex,m-edge undirected graph as an electrical network with unit resistors as edges. We extend known relations between random walks and electrical networks by showing that resistance in this network is intimately connected with thelengths of random walks on the graph. For example, thecommute time between two verticess andt (the expected length of a random walk froms tot and back) is precisely characterized by the effective resistanceR _st betweens andt: commute time=2mR _st . As a corollary, thecover time (the expected length of a random walk visiting all vertices) is characterized by the maximum resistanceR in the graph to within a factor of logn:mR<-cover time<-O(mRlogn). For many graphs, the bounds on cover time obtained in this manner are better than those obtained from previous techniques such as the eigenvalues of the adjacency matrix. In particular, we improve known bounds on cover times for high-degree graphs and expanders, and give new proofs of known results for multi-dimensional meshes. Moreover, resistance seems to provide an intuitively appealing and tractable approach to these problems.     

Irrigation development and environmental degradation in developing countries — a dynamic model of investment decisions and policy options

In the wake of increased environmental and sustainability concerns associated with agricultural development, developing countries are faced with the dilemma of choice between the short-run technological gains and the long-run environmental conservation. A dynamic investment decision model is developed to optimize the use of scarce public investment funds in the magagement of irrigation water supply, depth to water table and soil salinity. Four major classes of investments with different impacts on the hydrological balance within the Indus basin are considered: (a) expansion of the surface irrigation network, (b) public drainage projects, (c) tax and subsidy policies designed to influence the rate of private groundwater exploitation and (d) investment in improving the efficiency of the existing canal system by reducing conveyance losses. The crop area lost due to water logging and salt accumulation is treated as a damage cost of increasing the application of surface irrigation water. The resulting optimality conditions from the model are used to assess the development and operation of public drainage projects. The model results are compared for areas underlain by fresh and saline groundwater. The model is also used to analyze recent policy debate which has focused on the use of incentives such as subsidized credit, energy subsidies, and electrical grid expansion to accomplish the transfer of tubewell operation from the public to the private sector. Optimal switching conditions for such transfers are derived. The results show that a private farmer's optimal decision will diverge more from the societal optimal decision as more externalities from surface irrigation are accounted for.     

Nasal sill augmentation in adult incomplete cleft lip nose deformity using superiorly based turn over orbicularis oris muscle flap: an anatomic approach

Adult incomplete cleft lip nose deformity is not uncommon in India. Poverty, ignorance, and parental neglect account for its late presentation. Besides the classical features of cleft lip nose deformity, the constant findings observed in this patient population have been a widened and depressed nasal sill. This is attributable to the sparse, hypoplastic, and abnormally orientated orbicularis oris muscle in the region of the sill. Failure to restore the nasal sill symmetry by suitably augmenting the sill frequently leads to unsatisfactory and asymmetric results. However, in the literature, satisfactory restoration of the nasal sill has not been given the importance it deserves while performing cleft lip rhinoplasty. We present a method of augmenting the depressed nasal sill in cases of adult incomplete nose deformity using a superiorly based orbicularis oris muscle flap, which is harvested from the soft tissues between the apex of the cleft and the nostril sill. Following de-epithelialization of the overlying skin, the exposed muscle is raised as a superiorly based flap after dissecting it from the underlying mucosa. It is folded, turned over, and tucked into the nasal sill base and anchored to the anterior nasal spine to give the desired augmentation. Satisfactory results have been obtained in 18 cases of nasal deformity associated with incomplete cleft lip. In our opinion, this technique offers a simple and effective method of augmenting the depressed sill by utilizing locally available tissues and without the need for procuring autologous tissue from distant sites.     

The Role of Fuzzy and Genetic Algorithms in Part Family Formation and Sequence Optimisation for Flexible Manufacturing Systems

Group technology (GT) is one of the key issues in the successful implementation of flexible manufacturing systems (FMSs). The success of GT implementation is in the effective formation of part families (PFs) and similarity coefficients measures. Over the past three decades, many similarity coefficients have been proposed, but a better similarity coefficient measure is required. The decision-making process in a manufacturing system often involves uncertainties and ambiguities. Under such circumstances, fuzzy methodologies have proved to be an effective tool for taking fuzziness into consideration. The first part of this paper deals with the fuzzy part-family formation. This was achieved in the following ways: 1. A new similarity coefficient measure has been developed and this coefficient measure is used to form a part-family. 2. A mathematical model that uses this similarity coefficient for solving the part-family formation problems optimally in an FMS is developed. The fuzzy approach has the special advantage of producing more accurate results than conventional clustering and other methods. It not only reveals the specific part family that a part belongs to, but also provides the degree of membership of a part associated with each part family. This will give a balanced work load for the machine. In the second part of this paper, the introduction of the concept of genetic algorithms is proposed to eliminate more job sequences and, finally, the optimum sequence is obtained through the minimum penalty cost. Software is developed and implemented to obtain an optimum sequence and, finally, a numerical example is given as an illustration.