IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY TRANSACTION B- ENGINEERING
Year:1997 | Volume:21 | Issue:1|Papers Count:6

Equilibrium equations on Zero Extension Lines (ZEL, lines with zero linear strain) are important ii soil engineering because a suitable displacement field (network of ZEL) is often more: practical for geomechanics problems. The stress characteristic equilibrium equations for soil, having an angle of friction phi and cohesion c are available on the stress characteristics field. However, because the ZEL field is distinct, the stress characteristic equations do not apply on ZEL. In this paper, equations of equilibrium are derived on zero extension lines. In addition, the application of equilibrium equations on ZEL to the static bearing capacity of clay, seismic bearing capacity of clay soils and dynamic lateral pressure on retaining walls is presented.

For the purpose of determining the effects of strain rate on the complete load-displacement curves of specimens containing a single joint when subjected to gradually increasing compressive loading, a series of tests was conducted at constant strain rates of 2.08 x 10(-6)/s (slow rate), 4.17 x 10(-5)/s (medium rate) and 8.33 x 10(-4)/s (fast rate). Triaxial tests were carried out under satisfactory end-specimen conditions on two types of sandstone from various locations by a 5 MN servo-controlled stiff testing machine up to 30 MPa confining pressure. For intact specimens in zero confining pressure (uniaxial test) a higher strain rate resulted in a higher modulus of elasticity (steeper positive slope before strength failure) and in a higher failure stress of the specimens. Increased confining pressure reduced the strain rate effects. Strain rates had no similar effect on the jointed specimens of different rocks under uniaxial condition. Change of strain rate from slow to fast resulted in a higher stress value at the initiation of sliding for both rock types under different confining pressures. The behavior varied in different rocks when sliding continued. Strain rate had a significant effect on the modes of failure for both the intact and jointed specimens.

The paper focuses attention on the influence life cycle stages exerts on travel behavior. It presents the family Life cycle concept and its usefulness in the trip generation phase of the urban transportation planning process. The concept refers to the household structure reflected in life cycle stages expressed as the major break points through which a household passes as it evolves. A life cycle classification scheme is formulated using available data from the city of Shiraz in Iran to better explain travel behavior. Different stages in the household life cycle (or family structure) consistent with significant changes of activity time allocation and travel behavior are identified. Disaggregate behavioral trip generation models which incorporate a wide spectrum of independent variables such as household socioeconomic characteristics, family structure and life cycle stage, and land use attributes of residence location were pursued. Based on the assumption of the stage in the life cycle, it is found that there is a significant effect on the estimated number of trips made for different purposes. Stepwise regression analysis is used to test the adequacy of the life cycle based model. Results demonstrate the usefulness of the family life cycle variables in replicating travel behavior through the disaggregate trip generation models.

This paper describes an experimental technique for measuring the local convective heat transfer coefficient in complex flows. The technique employs a copper-coated plastic sheet, known as a printed circuit board (PCB), to generate a nearly uniform wall heat flux. The sheet is mounted on an insulated substrate of the desired shape and heating is achieved by passing an electrical current through the copper coating. The main advantage of this technique is that it does not require thermocouples to be mounted for surface temperature measurements, and it is quite simple and cheap to construct. Three applications of this technique are described: Heat transfer from a blunt plate with flow separation and reattachment, heat transfer from a blunt plate with unheated semi-circular and elliptical leading edges and heat transfer from a blunt plate at various angles of attack. Refinements necessary for improved accuracy are also identified.

Using a fullwave analysis, the integral equation for unknown electric field distribution on the slot apertures of GCPW is derived. Then it is numerically solved in the space domain using the method of moments. Using derived electric field distribution and ideal transmission line theory, the discontinuity parameters of short-end and open-end GCPW are computed and compared with CPW. In addition, a comparison between the CPW and GCPW effective dielectric constant is presented.

The design and analysis of multivariable fuzzy logic feedback control systems are presented in this paper. A general design procedure is discussed and a multi-dimensional rule base in the form of the Fuzzy Relational Matrix (FRM) developed. The decision-making components of the Fuzzy Logic Controller(FLC) are not explicitly based on the conventional Fuzzy Associative Memory (FAM). The compositional rule of inference is employed to transform the set of fuzzy rules into the corresponding I;RM"s. A fuzzy connective OR (Maximum) is operated on the set of derived FRM"s to obtain a final fuzzy matrix which essentially constitutes the rule base of the FLC. This matrix establishes the relationship between a given controller input with every controller output. Hence, instead of using a forward changing technique for firing the applicable rule, an unknown output is evaluated by the composition of the related input with the FRM. Different MIMO control system configurations are investigated and direct interaction control as well as the cross-coupled fuzzy controllers implemented. Results of extensive simulation studies of two linked tanks are presented to illustrate the usefulness of the proposed approach.