@article { author = {Wainwright, M.S.}, title = {Phase-Transformation of Gamma-Allumina to Alpha-Alumina as an Industrial Catalyst Support}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {1-12}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The phase transformation of aluminum hydrates yields various forms of alumina (d, q, K) and eventually alpha-alumina. The decrease in the specific surface area of alumina upon heat treatment is due to changes in crystalline structure and hence a decrease in the porosity of the material, Although the conversion of gamma-alumina to alpha-structure takes place with a lowering in surface area and pores, the use of such a material as a catalyst support yields high selectivity where the acidity is lowered and the surface area is maintained to some extent sufficiently low in catalyst preparation. The yield of alpha-alumina formation on the surface of starting material (gamma alumina) was investigated by the application of the final product in catalytic dehydration of methanol to dimethyl ether via kinetics measurements. The study of phase-transition kinetics and the influence of the effective factors leads to the possibility of selecting the desired process conditions for production of high selectivity alumina support. The activity, mechanical strength and stability of the catalyst supports are desired for application in certain chemical processes. While the low specific surface area alumina is produced, the porosity may be maintained high under firing conditions the favorable characteristics for appropriate industrial catalyst supports. The improvement of activity and selectivity of such supports is the main point of consideration.}, keywords = {}, url = {https://www.ije.ir/article_71035.html}, eprint = {https://www.ije.ir/article_71035_af7332f551015105f27178d373257d5a.pdf} } @article { author = {Moshfeghian, M.}, title = {Prediction of Thermodynamic Properties of Refrigerants in the Superheated Ragion}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {13-22}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This paper demonstrates the capabilities of the PFGC-MES equation of state (EOS) for calculating the thermodynamic properties in the superheated region for pure refrigerants. In addition the ability of this EOS is also tested for predicting the VLE behavior of binary mixtures. For pure compounds several properties in the superheated region are predicted. The calculated results and the experimental data are presented as pressure-enthalpy diagrams and also summarized in tables for five selected refrigerants. For mixtures the predicted results for different properties are also compared with the experimental data.}, keywords = {}, url = {https://www.ije.ir/article_71036.html}, eprint = {https://www.ije.ir/article_71036_1fe161fca7bd35a1dd3fc4a42e398fde.pdf} } @article { author = {Anvari, M.}, title = {A Database Model for Medical Consultation}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {23-30}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The database model presented in this paper is suitable for application in which queries may require non-crisp references to certain attributes. The data item (attribute) values may be crisp or fuzzy. For instance, such adjectives as 'high' or 'normal' may be attribute values for the attribute blood pressure. A disease or a condition can be described by a number of symptoms which may be crisp alphanumeric values or fuzzy terms such as 'high' or 'normal'. A query into this database can retrieve diseases which have 'similar' symptoms. The similarity or 'indistinguishabiIity' is a measure defined by the database user on the relations that describe a family of diseases. database system in conjunction with a rule base can provide the framework for a medical consultation system.}, keywords = {}, url = {https://www.ije.ir/article_71037.html}, eprint = {https://www.ije.ir/article_71037_5ae55708139e51e046f3926d44c785cb.pdf} } @article { author = {Katebi, S.D.}, title = {A Robust Control Design Technique for Discrete-Time Systems}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {31-36}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {A robust state feedback design subject to placement of the closed loop eigenvalues in a prescribed region of unit circle is presented. Quantitative measures of robustness and disturbance rejection are investigated. A stochastic optimization algorithm is used to effect trade-off between the free design parameters and to accomplish all the design criteria. A numerical example is given to illustrate the usefulness of the developed approach.}, keywords = {}, url = {https://www.ije.ir/article_71038.html}, eprint = {https://www.ije.ir/article_71038_bc65d6bec6f0c56719cc55c6dd66c882.pdf} } @article { author = {Hope, G.S. and Malik, O. P.}, title = {A Microprocessor-Based Hybrid Duplex Fault-Tolerant System}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {37-44}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Reliability is one of the fundamental considerations in the design of industrial control equipment. The microprocessor-based Hybrid Duplex fault-tolerant System (HDS) proposed in this paper has high reliability to meet this demand although its hardware structure is simple. The hardware configuration of HDS and the fault tolerance of this system are described. The switching control strategies in HDS are studied in detail. The disputes between two modules are avoided. The reliability estimation methods are also given.}, keywords = {}, url = {https://www.ije.ir/article_71039.html}, eprint = {https://www.ije.ir/article_71039_314c86bb7ebd6c88b408fdeba7cd7f4c.pdf} } @article { author = {Malik, O. P.}, title = {Application to Adaptive Control to Synchronous Machine Excitation}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {45-52}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Self-tuning adaptive control technique has the advantage of being able to track the system operating conditions so that satisfactory control action can always be produced. Self-tuning algorithms can be implemented easily. Because the power systems are usually time varying non-linear systems and their parameters vary, adaptive controllers are very suitable for power systems. Characteristics of a few adaptive control algorithms are discussed from the point of view of their application to generator excitation control. Basic principles and application of self-tuning controllers to an electric generating unit are given.}, keywords = {}, url = {https://www.ije.ir/article_71040.html}, eprint = {https://www.ije.ir/article_71040_d603324227ff7009b1eca257a33daa94.pdf} } @article { author = {Van Bronswijk, W. and Barton, A. P. and Saatchi, A.}, title = {Electrochemical Noise Analysis of Anaerobic (Bacterial) Corrosion of Steel}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {53-64}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Corrosion of structural steel in an SRB containing environment for as long as 9 months, is studied using the Electrochemical Noise Analysis technique. The results show that the activity of the system, which was very low initially, started to increase after 6 months exposure to the environment. The power spectral density curves of the Electrochemical Potential Noise of the system, using the maximum entropy method (MEM), indicate the existence of a characteristic pattern in the spectra. The effect of the yeast extract in the culture media, added periodically to support the growth of the bacteria was shown to suppress the signals, which is related to the corrosion inhibition effect of the yeast extract. After feeding, it usually took 3 weeks before the corrosion activities, as manifested by the values of electrochemical potential noise of the system, reached the values prior to the addition of the culture media to the system. These preliminary results indicate that analysis of electrochemical noise may offer promise in detection and monitoring of bacterial corrosion.}, keywords = {}, url = {https://www.ije.ir/article_71041.html}, eprint = {https://www.ije.ir/article_71041_b87245892c877bb42fe69f87ebd0768f.pdf} } @article { author = {Sadrnezhaad, S.K.}, title = {Effect or Inoculation on Microstructure and Properties of Low C-Mn and Low Alloy Steels}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {65-71}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Effect of the addition of various inoculants on the morphology and mechanical properties of low C-Mn and low alloy steel samples is studied by thermal and mechanical processing of the samples after solidification. According to the results obtained from metallographic studies with the electron microscope and microanalysis with x-rays, the distribution of inoculating agents in the steel matrix is seen in the form of very fine precipitates dispersed in the austenite-ferrite microstructure. These precipitates retard low-temperature recrystallization of austenite, increase the specific boundary area of retained grains and enhance concentration of more favored nucleation sites when austenite to ferrite transformation occurs at the final cooling stage from normalization temperature and thus cause a recognizable refinement in the steel microstructure. Both the strength and hardness of the samples are considerably enhanced by increasing the content of the inoculating agents, while the decrease in the elongation of the samples is limited to an acceptable range.}, keywords = {}, url = {https://www.ije.ir/article_71042.html}, eprint = {https://www.ije.ir/article_71042_7eb5272245a007323caa97ae53138df1.pdf} } @article { author = {Lucas, C.}, title = {Further Observations on Blocking Zeros in Linear Muitivariabie systems (RESEARCH NOTE).}, journal = {International Journal of Engineering}, volume = {4}, number = {1}, pages = {72-75}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {While attempting to clarify the confusion concerning the conceptualization of "blocking zeros" in state space in the recent literature, some new observations are made on the relationship between pole-zero cancellation and transmission blocking. An important distinction between uncontrollable and unobservable eigenvalue s is pointed out; and it is argued that the description of a Blocking Zero, at the functional-behavioral level, is not sufficient.}, keywords = {}, url = {https://www.ije.ir/article_71043.html}, eprint = {} }