Introduction: Usually osseointegration takes between three to six months after implant placement but patients are interested to have early loading. There are no definitive criteria for measuring bone mineral density (BMD), insertion torque (IT) (final torque force) and resonance Frequency analysis (RFA) (primary implant stability) to determine exact loading time based on the relationship between the above-mentioned parameters. The aim of this study was to determine the relationship between IT, RFA and BMD in screw-type implants.Materials and Methods: This clinical trial was conducted on 18 patients who were candidates for ITI implant placement. Written consent was taken and jaw bone density was determined via a digital radiography technique before surgery. After implant placement, RFA and IT were measured. Fifty-five ITI implants of the total 62 implants placed were evaluated; the implants were 12 mm long with a diameter of 4.1 mm. Data was analyzed with Pearson’s test using SPSS.15 software (a=0.05).Results: There was a significant relationship between IT, RFA and BMD. Pearson’s test showed a correlation coefficient of 0.872 to 0.789 between the three parameters, indicating a strong relationship between them. The mean bone density was 1.468±0.042 g/cm2; the mean RFA was 66.01±2.2 ISQ and the mean IT was 34.62±3.33 N/cm2.Conclusion: Based on the results of the present study there is a significant relationship between, IT, RFA and BMD (p value=0.001).

A theoretical model is developed to consider the effect of demulsifier agent on demulsification of water-in-crude oil emulsion. A thermodynamic approach is considered to correlate the critical micelle concentration of a demulsifier to the Collision Frequency function in population balance equation (PBE). Based on the proposed correlation, the Collision Frequency function is modified to account the effect of demulsifier agent on water droplets coalescence. The water separation capability of a selected group of demulsifiers is investigated via the conventional bottle test method to obtain the adjustable parameter of the developed equation so that the absolute relative error of predicted demulsification efficiency and experimental data are considered as objective. Comparison between the model simulated results and the experimental data showed that the proposed model could appropriately reproduce the experimental data at different agent concentrations.

The main purpose of this research is experimental and theoretical study on demulsifying components effect on demulsification rate of water-in-oil emulsions. In other words، some surfactants is considered and their function as a demulsifier in breaking crude oil emulsions has been investigated by bottle test. To develop a theoretical model to take into account the effect of demulsifier agent on demulsification rate of water-in-oil emulsion. Considering similarity between gas adsorption، and agent adsorption on the water-oil interface، a Langmuir isotherm based model is developed to correlate interfacial tension of water and oil phases to demulsifier concentration. Based on the proposed correlation، the Collision Frequency function in population balance equation is modified to account the effect of demulsifier agent on water droplets coalescence. The proposed model consists of some adjustable parameters that need to be fitted with experimental data. Therefore، a group of surface-active compounds are supplied and their demulsification capability is investigated through bottle test method. The experimental demulsification results are compared with population balance simulation results and it is apperared that the developed model could appropriately reproduce experimental data at different agent concentrations.

In this paper, a new method for radar cross section reduction of a monopole antenna is proposed. In this method, a plasma helix like fluorescent bulbs is placed around the antenna element. The selected plasma parameter for this medium acts as an absorber without disturbing the antenna performance. The simulations show that radar cross section of simulated antenna is reduced in a wide Frequency range. In this paper, the plasma parameter is chosen in such a way that reduces RCS at 4GHz. At this Frequency, the radar cross section reduction is about 10dBsm. Due to the Frequency dependent of the plasma medium, the plasma parameter must be changed for better result in the other frequencies. This change can be performed electrically without any change in the antenna structure. In this simulation, a PEC rode with 3cm diameter and 15cm height is chosen for the monopole antenna element. This monopole antenna resonates at 630 MHz. After placing the plasma helix around the antenna element, there is no significant change in the antenna performance.