Aims The use of intrauterine devices (IUDs) has been one of the most effective, the safest and cost-effective methods for preventing pregnancy, for a long time. However, some complications have been reported for IUDs. The complications may be reduced by using a specific Technique for placement of IUD. The objective of this study was to introduce the rotating withdrawal Technique for the first time, which was investigated to reduce the complications of IUD insertion. Materials & Methods This historical cohort study was conducted on 1199 females who referred to Sarem Medical Center for IUD insertion from 1984 to 1995. After primary examinations, IUD was inserted by rotating withdrawal Technique. The subjects were followed up for 2 years. Findings Displacement was observed just in 20 cases (1. 67%). All of them were seen in the first month after placement. For these cases, IUD insertion was done again. After the second replacement, displacement was observed in 4 cases (0. 035%) after one month. Therefore, it was recommended to them to use another preventive method. There was no pregnancy or displacement in the other cases during 2 years. Conclusion The rotating withdrawal Technique can minimize the pregnancy rate when IUD is used. In addition to the type and quality of IUD, insertion method of IUD can increase its effectiveness.

In this paper, a new method for extending and relaxing the noise-coupling (NC) Technique is proposed to enhance the noise-shaping order without adding the number of integrators. The noise-shaping order of the introduced ∑∆ modulator whit applying a second-order noise-coupling Technique is enhanced and its performance with optimizing the noise transfer function (NTF) zeros is improved. Also, by removing the analog adder at feedforward path and transferring it to a new feedback branch before the last integrator and adding second-order NC path can be decreased the input voltage swing to the quantizer. Thus, by improving the modulator resolution, power consumption can be reduced. Mathematical analyses and behavioural simulation results confirm the effectiveness of the new NC method. To examine its performance, a 2nd-order single loop ΣΔ modulator was designed. The new noise-coupling method is used to achieve the three-order noise shaping to increase the resolution with low complexity and low-power. The results show an outstanding improvement in signal-to-noise and distortion ratio (SNDR) compared to the conventional structure.

Thermal energy storage is among the highly efficient approaches to overcome the energy crisis. Using phase change material (PCM) is one of the most effective Techniques in thermal energy storage applications. Several types of PCM with distinct characteristics and different ranges of melting and solidification temperature have found their way in various industries. However, commercialized PCMs generally suffer from low thermal conductivity which limits their application. In this study, the effect of adding different weight percentages of various nanoparticles, such as CuO, TiO2, Al2O3 and graphene to paraffin, as a standard PCM, on the improvement of the thermal properties of PCM was investigated. Thermophysical properties and morphology of the nanocomposites, such as phase change temperature and latent heat of melting were characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscope (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR). SEM images display the proper distribution of nanoparticles in phase change material. FTIR results verified the formation of nanocomposites. A comparison between the investigated PCM nanocomposites showed that the nanocomposites containing 2 wt. % TiO2 with the enthalpy of 179. 88 J/g, and 1 wt. % graphene nanocomposite with the enthalpy of 120. 38 J/g had the highest and lowest energy storage capacity compared to paraffin, respectively. The results indicated that Nano-enhanced phase change materials (NEPCMs) could be particularly useful in applications in which temperature control is crucial. The new types of nanocomposites used in this study showed remarkable thermal performance, and they are capable of being used in thermal management applications. © 2020 Journal of Energy Management and Technology.

One of the dangers of storing materials in storage tanks is the leakage of materials due to corrosion to the surrounding environment, which in addition to cause damage due to the loss of valuable material and environmental pollution, can lead to accidents. PCM method is one which is used for inspecting pipelines by electromagnetic method. Electromagnetic fields easily pass-through soil, water, asphalt, etc. Therefore, without drilling and through the ground, pipelines are inspected and monitored. By measuring the amount of induced alternating current in its strong magnetic sensors, it is able to detect the current amount in pipelines, the position of sacrificial anodes, the quality of coating, and the location of its defects. In this method, alternating current is used to inspect pipelines. By increasing the frequency of alternating current, the inductive effect of this method increases on foreign structures and adjacent metal structures. In this case, by using different frequencies as well as very low frequencies, they eliminate the impact of adjacent foreign structures on the inspection results.