Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801Proposals for a Failure Criterion Applicable to Discontinuous Rocks12513271104ENA. FahimifarCivil & Environmental Engineering, Amirkabir University of Technology0000-0002-9397-6269Journal Article19700101The existing failure criteria to evaluate discontinuous rocks are predominatly based on the relations between principal stresses at failure. None of the criteria has a direct reference to the magnitude of deformation as a major parameter in rock Several reasons are identified indicating that the selection of peak stress as a major parameter, which is obtained through the evaluation of a failure criterion, is not reliable. On the other hand, the experimental investigations indicate that the state of strain is equally important to the state of stress. The proposed failure criterion is to describe the behavior of a jointed rock mass under various loading conditions taking the major principal strain into consideration.Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801Safety Verification of Real Time Systems Serving Periodic Devices13314271105ENM. NaghibzadehComputer Engineering, Ferdowsi University of MashhadJournal Article19700101In real-time systems response to a request from a controlled object must be correct and timely. Any late response to a request from such a device might lead to a catastrophy. The possibility of a task overrun, i.e., missing the deadline for completing a requested task, must be checked and removed during the design of such systems. Safe design of real-time systems running periodic tasks under the rate monotonic preemptive (RM) scheduling strategy is considered in this paper. A safety verification procedure that is an improvement over previously developed procedures is presented.Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801Theoretical Studies of Electrical Characteristics of the Nitrogen Laser14315471106ENA. Ashrafi, Sharif University of TechnologyH. GolnabiWater & Energy, Sharif University of TechnologyJournal Article19700101A theoretical analysis of the circuits for a nitrogen laser driven by the Blumlein or capacitor charge transfer transmission line is given in detail. The electrical characteristics of the charge line for a special case of resonant charging are discussed and the effects of various parameters on voltage and current are investigated. By using MICRO-CAP software the transient behavior of the current and voltage in both the charge and discharge processes are studied and an optimum situation for a better laser performance is reported. The theoretical results obtained here could provide insights into the design and construction of high power gas lasers.Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801A Unified Approach for Design of Lp Polynomial Algorithms15516071107ENZ. Zhang, Beijing Machinery and Electricity Institute Co Ltd (BMEI)Journal Article19700101By summarizing Khachiyan's algorithm and Karmarkar's algorithm forlinear program (LP) a unified methodology for the design of polynomial-time algorithms for LP is presented in this paper. A key concept is the so-called extended binary search (EBS) algorithm introduced by the author. It is used as a unified model to analyze the complexities of the existing modem LP algorithms and possibly, help designing new algorithms with polynomial-time iterations for problems in other areas.Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801Steep. Short-Crested Waves and Related Phenomena16117271108ENA. R. KolainiNational Center for Physical Acoustics, University of MississippiJournal Article19700101Steep, short-crested waves, as well as a large variety of three-dimensional propagating wave patterns have been created in laboratory, utilizing a plunging half-cone. Monochromatic waves, over a range of frequencies and amplitudes through breaking and including soliton wave groups near resonance, have been observed and studied in a small wave flume. This monochromatic wavemaker creates complex wave patterns which depend upon the wavemaker shape, its frequency, and the tank width. The theory is presented along with computer simulation and experimental data to describe these three-dimensional waves. The effect of viscosity at the wall is taken into account to explain the attenuation of wave energy down-tank. In the neighborhood of the first cut-off frequency, strong nonlinear-effects were observed. Symmetric-standing sloshing waves generated at the wavemaker spontaneously form a moving hump (soliton), which propagates very slowly down-tank. The hump then builds up again in time at the wavemaker and the process is repeated. In the case of two-mode propagation, waves produced are diamond-shaped patterns and propagate in such a way that the amplitude of individual wave crests oscillate with distance down-tank. As a result, intermittent breaking can be caused to occur at specific locations away from the wavemaker. The inception of breaking was found to occur over a range of wave steepness, from a minimum (consistent with other experiments, and decreasing with short-crestedness) to a maximum (close to the Stokes limiting steepness). Breaking was observed to occur, providing: (i) the wave steepness exceeds a threshold (minimum) value; and, simultaneously, (ii) the propagating wave crest reaches a maximum and begins to decline. These observations suggest a new criteria for the inception of breaking.Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801Tv and or Fm Transmitting Antennas Desien Using Computer Graphic System (RESEARCH NOTES)17318071109ENA. Radji, I. R. 1. B. FacultyJournal Article19700101The purpose of this paper is three fold. First, the major theoretical pattern relationships of TV and/or FM transmitting antennas are dealt with. Secend, the computer calculation method and designing of such patterns using the given relationships. And third, a method in which a computer graphic system can be used to design such antennas for a specific pattern is introduced and its results are presented.Materials and Energy Research CenterInternational Journal of Engineering1025-24957319940801Moditication Factor for Sizing Equation of Electrical Machines-Single and Three Phase Induction Motors(RESEARCH NOTE)18118471110ENS. HonarparvarElecterical Engineering, University of TabrizJawad. FaizElectrical and Computer Engineering, University of TehranJournal Article19700101Comparison between the results from the design procedure based upon the value of D2L (volume of iron) and IEC standard used by manufacturers indicates that the basic design equation of electrical machines must be modified by a proper modification factor. This modification factor is evaluated for single- and three-phase induction motors and its variation with motor rating and poles number is obtained and compared.