نشریه علوم پایه
سال بیست و یکم شماره 1 (1387)

A new method for measurement the small signal gain of an open CW-CO2 laser in different condition is presented and the theoretical concepts are completely described. This method is based on bringing the laser on critical condition by inserting a loss element in laser cavity. Also, by measuring output power, in a same time, the gain saturation intensity for each condition is obtained. The main point of this method is removing requirement to additional laser that has been used for measuring of small signal gain in oscillator amplifier method. With Inter-Cavity loss element method, easer than classic method, results have been obtained which are comparable with other’s.

In this research work small and cheap four electrode cells with negligible polarization effects are designed and fabricated for conductometric determination of small volume samples. The response time of this cell is about 5sec. with sample volume of 2ml. the electrodes are made of stainless steel. The two electrodes at the middle are voltage electrodes and the two at the ends are current electrodes. Since the measurements are performed on voltage electrodes, the results are not affected by polarization which is happening on the other two electrodes.The coating material and its effect on the cell efficiency as well as the influence of applied voltage range and frequency range of alternative current and the distance between the electrodes are studied and optimized. The optimum ratio of voltage electrodes distance to current electrode distance is found to be 0.6.The best frequency and voltage are found to be 100 KHz and 0.5V respectively. The efficiency of fabricated cell is compared with the commercial cell in a wide range of KCl concentration. The good accuracy and precision of the fabricated cell is confirmed by the results of this comparison. This cell can be used in water and soil analysis laboratories as well as in the hospitals.

In this paper, we introduce very briefly the theory of hidden variables. Then we overview in details the Bohmain Quantum mechanics. This theory, in which observer has no effect in the system, is also called the quantum theory without the observer.

In the study of many-particles system of solids that intraction between particles can be intinify, green function method is a systematic method. In this method, green function of Schrodinger equation including periodic potential can be written as Bloch linear green functions of free electron at about unit cell and finally characteristic equation obtained. Potential also can be written in linear function of atomic charge density and spherical effects of neighbour atoms that can be averaged by Lowdin coefficient method [1]. In this paper, ground stat energy bands in symmetrical orientation for Be crystal were calculated and plotted. By using dispersion relation, effective mass around centeral region and boundary zone of first Brillouin zone were calculated. Also in this paper, we presented a direct method for calculation of effective mass independent of electronic spectrum calculation.

Side-chain liquid crystalline polymers have caused interest because of their theoretical aspects and potential uses in electro-optical and information storage devices. Polypyrrole and polyindole are more promising candidates since 1 and 3 substituted derivatives can be appropriately functionalized while preserving a relatively high conductivity and good thermal stability. In this paper we describe the synthesis of a new liquid crystalline monomer based on N-substituted pyrrole with photochoromic and azochromophore properties. Therefore, first we have prepared Disperse Red 1 and then from reaction it with 3-chloro propionic acid in presence of dicyclohexyl carbodiimide (DCC) and dimethyl amino pyridine (DMAP), 2-[N-ethyl-N-[4-(4´-Nitrophenyl azo) phenylamino] ethyl-3-chloro propionate (Red 1-CP) was prepared, In continue, we have synthesized 2-[N-ethyl-N-[4-(4´-Nitrophenyl) azo] phenylamino]ethyl-N-pyrrolyl propionate (Red 1-PP) from reaction Red 1-CP and potassium salt of pyrrole under a nitrogen atmosphere. The products have been characterized by FT-IR, 13C, 1H-FTNMR and UV-visible spectroscopy.

Rudists of the Tarbur Formation in 10 km, in north of Khorramabad have been Studied. The Tarbur Formation mainly consistis of wackstone to packstone and mudstone which has a rich macrofossil fauna of rudist. The important types of rudist in this Formation include Radiolites and Hippurites. Rudist Study reveals an age of Masstrichtian for the Tarbur Formation that has been deposited in a warm and Relatively low energy shallow marine with Low open shelf margine complex.

In this paper a numerical method for finding the solution of Fredholm – Hammerstein integral equations is proposed. At first the properties of the hybrid functions, which consist of block-pulse functions plus walsh functions are presented. The properties of the hybrid functions with the operational matrices of integration together Newton-cotes nodes are then utilized to reduce the solution of integral equation to the solution of algebraic equations. The method is computationally attractive and application are demonstrated through illustrative examples.