Polymers typically have a "specific" density that can provide an approximation of the density of a particular material. However, various factors can affect the density, such as crystallinity, loss of softener or solvent absorption. Components of the same sample may also vary in density due to differences in crystallinity, thermal history, porosity, or changes in material composition, such as the addition of a filler or pigment. The variety of properties of most engineering polymers causes differences in their applications. This can cause variety in density of polymers. In fact, many polymers are identified and classified by this important factor. Like all tests, this test also has uncertainties, and in this article, an attempt has been made to describe the important factors that cause errors and uncertainties in this test method.

Finding a representative fluid in a hydrocarbon reservoir is crucial for integrated reservoir management. In this study, a systematic approach for screening and selecting consistent fluid samples in a reservoir was developed. The model integrated Quality control (QC) of well conditioning before sampling, QC of PVT data, thermodynamic modeling and compositional gradient within a reservoir. Well and separator conditioning were examined as essential steps before sampling at equilibrium conditions. Sampling criteria were deduced according to available data, sampling standards, and tolerance of field measurement devices. Then, PVT data of consistent fluid samples were carefully screened for efficient phase behavior studies. This model suggests that thermodynamic modeling and equation of state (EOS) tuning be performed on screened fluids using only consistent experimental data. The proposed model was implemented on PVT samples of a supergiant gas condensate reservoir in the Middle East. Results show that only 10% of collected samples are at equilibrium, good candidates for PVT studies. Also, ±0.1% change in composition of C12+ causes ±300 psia changes in dew-point pressure, revealing no substantial difference between validated samples for the reservoir under study, and one representative fluid suffices throughout the reservoir.

Carburization is a common way to improve the performance of low carbon steel components used in industries. Accurate control of surface carbon content of carburized steels is the most important factor for the obtainment of desirable properties. A variety of methods exists for determination of surface carbon content, however, all of them are expensive and time consuming, and accordingly, all the samples cannot be tested. In this research, the capability of Eddy Current nondestructive method for determination of surface carbon content of steel components was evaluated. The Eddy Current tests were performed in order to determine the relationship between the surface carbon content and the normalized impedance, the input and output voltages. The results showed an appropriate relationship (with R2=0.82) between the surface carbon content and the normalized impedance. Moreover, the effect of test temperature on the mentioned relationship was also investigated. The relationship obtained in this way was suitable for the determination of the surface carbon content of the steel in a more accurate fashion.

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

Introduction: The evaluation of X-ray and light field coincidence in linear accelerators as a Quality control test is often performed subjectively, involving the manual marking of films and their visual inspection following the irradiation. Therefore, the present study aimed to develop an objective method for the performance of this test leading to the increased levels of accuracy, precision, and speed for the measurement of X-ray and light field coincidence. Material and Methods: The new method involved a portable, lightweight, and inexpensive device containing optically-shielded and non-shielded photodiodes to detect the location and dimensions of the light and X-ray fields. The obtained results were analyzed using purpose-written user-friendly software. Results: On the basis of the results, this system could be a reliable method to measure the coincidence of the two fields with the accuracy of 0. 5 mm and average field size standard deviations of Elekta Presice and Siemens Primus are 22. 47 mm2 and 22. 36 mm2, respectively. The result was well within the tolerance recommended by the American Association of Physicists in Medicine task group report number 142. Conclusion: The proposed method allows accurate and precise measurements through a largely automated process. Therefore, the measurement results benefit from the reduced level of subjectivity or human error, compared to the standard film-based technique.

Introduction: Approaching to the end of the fiscal year, the working stress of auditors becomes doubled so that it places a lot of pressure on auditors’ minds regarding their self-control. In fact, this issue provides an opportunity to make the judgment and decision-making of auditors influenced. Method: This study is correlational in terms of its application and data collection. The sample consisted of 98 auditors working in audit firms. Harley’ s self-control ego depletion was measured using Stroop effect test. Also, the Quality of judgment scale, Hurrt professional skepticism and self-confidence scale were administered in this research. Results: The results indicate that self-control ego depletion affects professional skepticism and Quality of judgment of auditors significantly and negatively, but it has no significant impact on their self-confidence. Conclusion: According to the results, audit firms and auditors’ employers are advised to refrain from putting pressure on auditors in a short period of time. Also, it is suggested that some meetings would be held for auditors and teach the peace of mind to them, hence they can reduce their fatigue while working.