Background and Aim: The accuracy of linear measurements in CBCT images is one of the critical parameters in treatment planning. Slice Thickness and exposure parameters seem to affect the accuracy of linear measurements. In this study, we investigated the impact of the above factors on the accuracy of linear measurements in CBCT. Materials and Methods: For the in vitro experiment, three dry human maxilla and mandibles were selected and the roots of their teeth were used as markers at the points of the anterior, premolars, and molars on both sides and placed in the desired locations. A digital caliper was used to measure its height and width prior to placement as the Gold Standard. For each location, the images were examined in slice Thickness with dimensions of 0. 5, 1, 2 and 3 mm and a kVp = 84 and a kVp = 90 and the results were then compared with Gold standard. The data were analyzed using the ANOVA test. Results: The results of this study showed that the effect of slice Thickness, kvp, location and type of jaw were not significant for measuring the length of the marker (p>0. 05) but about measuring the width of marker, in maxillary anterior and molar area and in mandibular premolar and molar area slice Thickness was significant (p <0. 05) and the effect of kVp was not significant (p >0. 05). Similarly, the effects of slice Thickness and kVp were also significant in the maxillary premolar area (p <0. 05), whereas in the anterior mandibular area, the effect was not significant (p >0. 05). Conclusion: The accuracy of CBCT in measurement is very high although, for CBCT measurements to be as accurate as possible, it is desirable to use thinner slice Thicknesses and higher voltages.

Local scour around bridge pier is one of the most important destruction factors of bridges. Many researchers have investigated scour around bridge pier; however, there is still not available single solution for this issue due to complexity of the problem and multiplicity of the effective factors. Different methods have been proposed to prevent or reduce scouring around bridge piers such as Riprap, collar, slot, submerge sheet and so on. According to researches, installing a collar around the base to delay the onset of scour in some cases significantly reduced the depth of scour around the base. In this study, by using the rectangular collar around the cylindrical pier, the effect of the collar Thickness on scour Reduction around bridge pier was investigated. The results of the experiments showed with installation of the collar not only velocity of scour is reduced but the depth of scour hole around the pier especially in downstream of the pier is also decreased. Also, with increasing collar Thickness, the performance of the collar is reduced. Based on the results, the collar Thickness was equal to 5 percent of the pier diameter and less than that had negligible Reduction in the performance of the collar. However, the performance of the collar decreased when the collar Thickness was more than 5 percent. Therefore, the appropriate Thickness of the collar is proposed 5 percent of the pier diameter.

Purpose: To compare the anatomical and functional results of deep vitrectomy with and without ILM peeling for full Thickness macular hole.Materials & Methods: 37 eyes of 37 patients with full Thickness macular hole (FTMH), confirmed by clinical examination and optical coherence tomography (OCT), enrolled in this clinical trial. Based on the stage of FTMH (stage 2, 3, 4) as described by Gass and the techniques of surgery (with or without ILM peeling) the patients were randomized into two different groups. All patients underwent preoperative Act and at least one OCT image was obtained during the postoperative follow up.After obtaining informed consent, deep vitrectomy and 20% SF6 injection was performed. The patients were unaware of their allocation status. Patients data & surgical outcome were collected and statistically analyzed. Anatomical success was defined as hole closure at postoperative OCT and functional success was referred to any improvement in visual acuity. Macular hole index (MHI) was defined as a ratio of the greatest height to the base diameter of the hole on cross-sectional OCT images.Results: 37 eyes of 37 patients (15 men & 22 women) were enrolled. The mean age of the patients was 56.4±21.94 years and FTMH were traumatic in 13 cases (35%) and Idiopathic in 24 (65%) cases. Twenty cases underwent deep vitrectomy with ILM peeling (ILM group) and the remaining cases underwent vitrectomy without ILM peeling (no ILM group).The mean preoperative 10gMAR visual acuity was 1.38±1 in the ILM group and 1.22±0.13 in the no ILM group, these improved to 0.95±1 and 0.77±0.31 postoperatively in the ILM and no ILM group, respectively (P=0.871). The overall anatomical success rate was 64%. The hole was closed in 70% of ILM peeling and 47% in the no ILM group (Chi-square test, P=0.15). In anatomically successful cases the mean of postoperative VA was significantly improved (P=0.001).In traumatic subgroup, ILM peeling seems did not affect the anatomical (P=0.2) and visual Success rates (P=0.5). There was no significant differences in hole closure rates between the traumatic and idiopathic FTMH (P=0.968). Visual acuity significantly improved after operation In MHI ³ 0.5 group compared with the MHk 0.5 group. The stage of the hole did not affect the anatomical success rate (P=0.52) or visual acuity improvement (P=0.741). Macular hole index ³ 0.5 had a prognostic value for postoperative visual acuity improvement. The hole duration was not related to anatomical success rate but there is an inverse relation between duration of the symptoms and improvement in VA.Conclusion: Deep vitrectomy and SF6 injection was a safe & effective surgical technique for full Thickness macular hole and peeling of the ILM seems did not affect the anatomical or functional success rates. The hole duration, stage and origin of the hole (traumatic or idiopathic) does not related to the anatomical success or visual acuity improvement. MHI  ³ 0.5 seems to be a prognostic factor for postoperative visual improvement but not for closure rate.

Ironing is a conventional metal forming process for producing thin walled cans with uniform Thickness components manufactured from deep drawn cups. The most important drawback of the conventional ironing is that the lower Thickness Reduction ratio (TRR) requires annealing process and multi stage ironing. Recently a new ironing process named constrained ironing was presented by the current authors to achieve an extra TRR to solve the conventional ironing problems. This process which is based on the compressive stresses makes it possible to achieve high TRR without interruption for additional processing such as multi-stage ironing and annealing. In this paper FEM simulation was performed to investigate the effective parameters. The simulation results showed the process load increases with increasing the friction coefficient. Also the state of the stresses is fully compressive in constrained ironing process while it is tensile in the conventional ironing method. Thus compressive stress components minimize formability problems and higher Thickness Reduction ratio is achievable in the new ironing method. Moreover experimental results showed that the tensile strength and hardness increased after constrained ironed of the deep drawn cup.

Background: Some organs in the body are sensitive to radiation such as eyes, breast, and gonads. Protection of sensitive organs against radiation is necessary. Recently, many sensitive organ shields have been developed from different materials. Objective: The aim of this study is to evaluate the dose Reduction and image quality from implementation of Silicone Rubber-Lead (SR-Pb) as an alternative gonad shield in digital radiography (DR). Material and Methods: In this experimental study, the SR-Pb gonad shields with various Thicknesses of 2, 4, 6, 8, and 10 mm were synthesized. This study used the Pb percentage of 5 wt%. An anthropomorphic phantom was used in abdomen plain examinations. The results obtained from the use of the SR-Pb was compared with standard gonad shield, i. e. lead apron. To measure the dose Reduction, the Piranha detector was used. The image quality assessment was evaluated with the signalto-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Results: This study showed the dose Reduction was significant for all SR-Pb Thicknesses, and incrementally increased with the increase of the SR-Pb Thickness. The minimum and maximum of dose Reduction were 22. 8% for 2 mm and 66. 9% for 10 mm SR-Pb, respectively. Conclusion: Compared to the reference image without gonad shield, the SNR and CNR do not significantly change. Hence, the SR-Pb is probably to be used as an alternative gonad shield.

Nowadays, light weight and high strength metals are being used in various industries such as automotive and aerospace. Using aluminum-magnesium alloys is an efficient way to reduce the weight of a specific part. These alloys have poor formability in room temperature thus they should be formed at elevated temperature. Warm hydroforming and hot metal gas forming are conventional methods to form aforementioned alloys. It is proven that using hammering pressure is an efficient way in order to optimize hydroforming process that it improves formability and Thickness distribution. In this paper, the effect of hammering pressure on hot free bulging of an Al6063 tube is investigated numerically and the results are compared with the results of constant pressure path. Results show that Reduction of Thickness is greater for peak constant pressure while using hammering pressure, due to gradual Thickness Reduction, could improve formability and Thickness distribution. Results also show that axial feeding, increase the effect of formability caused by hammering pressure.

Inertial Navigation System (INS) is one of the navigation systems widely used in various land-based, aerial, and marine applications. Among all types of INS, Microelectromechanical System (MEMS)-based INS can be widely utilized, owing to their low cost, lightweight, and small size. However, due to the manufacturing technology, MEMS-based INS suffers from deterministic and stochastic errors, which increase positioning errors over time. In this paper, a new effective noise Reduction method is proposed that can provide more accurate outputs of MEMS-based inertial sensors. The intelligent method in this paper is a combined denoising method that combines Wavelet Transform (WT), Permutation Entropy (PE), Support Vector Regression (SVR), and Genetic Algorithm (GA). Firstly, WT is employed to obtain a time-frequency representation of raw data. Secondly, a four-element feature vector is formed. These four features are (1) amplitude of frequency, (2) its ratio to mean of amplitudes of all frequencies, (3) location of frequency in time-frequency representation, and (4) judgment on behaviors of frequency that is obtained by utilizing PE. Thirdly, based on the feature vector, the GA-SVR algorithm predicts amplitudes of all frequencies in the time-frequency representation of the denoised signal. Finally, by employing inverse WT the denoised signal is obtained. In this work, the outputs of the Inertial Measurement Unit (IMU) in ADIS16407 sensor, as a low-cost and MEMS-based INS, have been utilized for data collection. The proposed method has been compared with other noise Reduction methods and the achieved results verify superior improvement than other methods.