فهرست مطالب علی لشگری

Periodontal surgeries complications and related factors are one of the most important things that surgeons in each clinic should be aware of to prevent them. Therefore, the aim of this study was to determine and compare the frequency, severity and trend of complications after periodontal flap surgeries with and without ostectomy and related factors in the periodontics department of Tehran University of Medical Sciences.

patients in the periodontics department of Tehran University of Medical Sciences, who underwent periodontal flap surgery or gingivectomy, were included in this prospective study. The pain, swelling, and bruising levels were asked on the same day, one and three days later. At the follow-up session on the seventh day, the pain, swelling and bruising levels were asked again, the tenderness and swelling levels were recorded by the surgeon, and flap dehiscence and pus presence were assessed. The difference between the complications’ levels on different days and also the difference in their trends between different surgeries was measured by GEE test, alongside testing the association of background and surgery characteristics with the complications’ levels by Mann-Whitney and correlation tests.

The pain and swelling means on days 0 and 1 respectively were significantly higher than other days. The trend of means for complications were not different between the two groups of flap surgery with and without ostectomy. Tenderness, swelling, flap dehiscence and pus were present in 31%, 31%, 1% and 0% of patients after one week, respectively.

Complications after periodontal flap surgeries were uncommon, except for mild pain and swelling.

In this study, the effect of pulse like and non-pulsed near field records on the displacement and axial force of the nail in the soil nail wall has been investigated. Pulse liked records are created under physical factors such as the effect of Forward directivity, Fling Step, the effect Hanging wall, etc., A pulse has a large amplitude with medium to long period, which contains most of the energy due to fault rupture. It has been used to investigate the effects of near-field records by the finite element method and by using the HSS behavioral model due to considering the effect of small strains and hysteresis damping. In this research, Song and Rodrigues seismic bank in 2015 including 62 pulsed and non-pulsed near field records has been used. The obtained results showed that the soil nailed walls have good performance against seismic loads. pulsed records have a direct effect on the axial force and displacement of the nailed wall, also the axial force of the nails and displacements in the pulsed records have a good correlation with the PGV (peak ground velocity) parameter, the axial force of the nails in the non-pulsed records with the parameter It had Ia (Arias intensity) and non-pulse displacement with seismic parameter PGV.

Oil pollution in the pipelines transporting petroleum products is an inevitable consequence of population growth and industrialization of communities. In addition to negative environmental effects such as groundwater and soil contamination, it causes changes in the geotechnical properties of local soil. Changes in soil engineering properties can lead to soil rupture and poor performance of transmission lines. Therefore, this study intended to assess the effects of the oil pipeline in the north of Iran on the environment using environmental geotechnic parameters during operation. By analyzing the Iranian matrix, it was found that there were 5 negative effects and consequences in the row and column. The consequences in the column were related to the diversion of the river, creating dams, and spinning, while in the row, these were related to landslides and soil contamination. The results of laboratory studies to investigate the effect of soil contamination on geotechnical parameters showed that the uniaxial strength of samples is decreased by 22%. In addition, the analysis of soil rupture by PLAXIS software showed that by changing the angle of the reinforcements from 20 to 23 degrees, the slope reliability of the soil decreases to less than the minimum reliability in the regulations. Finally, it was suggested that in order to reduce the negative effects and consequences of the projects, the pipelines should not be crossed through forested and sloping areas as much as possible.

The Iranian plateau is one of the seismic active zones of shallow crustal earthquakes in the world so that annually thousands earthquake occurs in the Iranian plateau. Meanwhile, due to the effect of topographic and geological characteristics of its relief, the Iranian plateau is subjected to diffuse phenomena of landslide, especially in Alborz and Zagros mountains, which are exacerbated by the high seismic activity. The earthquake-induced landslides have reportedly caused major human fatalities and economic losses in Iran. The prediction of sliding displacement can decrease landslide hazards to the civil engineering strcutures. The semi-empirical models have recently received more attention from the geotechnical earthquake engineering practitioners because of their applicability, simplicity, and reasonable performance in large displacements. The rigid block-rotation approach was developed based on the increase of critical acceleration caused by the downward movement of sliding soil mass. This paper represents a semi-empirical model for the earthquake-induced displacement of Iran's slopes using the rigid block-rotation approach. A collection of 3954 strong motion records was used to generate the model based on the results of slidinganalyses. The semi-empirical model is presented based on more than 138,000 rigid block-rotation analyses using several input parameters. The model predicts sliding displacement in terms of yield coefficient (ky), slip length of sliding mass (L), and Arias Intensity (Ia). It is shown that slip length of sliding mass has an important role in the prediction of seismic permanent displacement, which is generally ignored in the semi-empirical models. The proposed model can be simply used to estimate the seismic displacement of slopes and earthquake-landslide hazards in seismic prone regions of the Iranian plateau.

Recently, environmental impact assessment (EIA) was considered as a green path to sustainable development. The major part of development is construction industry. EIA can also identify the environmental impacts which have been caused through construction activities. EIA can suggest the appropriate adoptions to prevent environmental degradation. Recently, the construction of cement factories as a productive industry has been developed in Iran while through the general EIA reports the influence of its geotechnical parameters in environment is not investigated. The purpose of the present study is to fill the gap using geotechnical investigation. In this paper, environmental and geotechnical impacts of Abyek cement factory as one of the prevalent cement factories in Iran were evaluated using Iranian matrix and aerial photos. Afterward the results of two methods were compared. The results show that dissimilarity of topography has the most negative effect on environmental and geotechnical conditions. Additionally, it is the reason of significant environmental and geotechnical hazards in the region.

To evaluate the visual and anatomical outcomes of pars plana vitrectomy (PPV) in patients with dropped intraocular lens (IOL) following complicated phacoemulsification (PE) and to determine the prognostic factors.

The present retrospective study was conducted on the patients, who were referred after complicated PE and underwent PPV. Patients’ demographic characteristics, the interval between complicated PE and PPV, pre- and post-PPV visual acuity (VA), the final intraocular lens (IOL) status, and complications were recorded.

Twenty-three patients (23 eyes) with a mean age of 67.7 years and mean follow-up of 28.3 months were evaluated. Mean interval between cataract surgery and PPV was 14.1 days. Pre-PPV mean best corrected visual acuity (BCVA) was 1.03±0.24 LogMAR, which was improved to 0.45±0.17 logMAR at final visit (P<0.001). Pre-PPV VA of 20/200 or better was significantly associated with good final VA of 20/50 or better (P=0.001). Complicated course after PPV was significantly associated with poor visual outcome (P<0.001). However, timing of PPV (the interval between complicated PE and PPV) and final IOL status were not significantly associated with visual outcome.

PPV for dropped IOL was associated with VA improvement. Better pre-PPV VA is associated with good visual outcome, while complicated course after PPV is associated with poor visual outcome.

In recent decades, the non-connected piled raft system has been used to cope with substructure vulnerability in piles junction point. This system decreases settlement of foundation. Also, this system is able to decrease stress concentration in pile cap and improve the mechanism of loading transfer to the soil whose proper performance of non-connected pile raft is dependent on the performance of its components. In this paper, the effect of large and small pile rafts is evaluated on lateral displacement by abaqus 3d software which is based on finite-element method. In this study, the effects of variation of gravel layer strength and thickness are assessed on foundation settlement. The results show that increasing non-connected piles diameter increases the proportion of pile group loading capacity. Addition, increasing raft thickness has more influence on the reduction of partial settlement.
The results of this paper show that using non-connected pile raft system increases loading capacity of system up to 17% until 18%. Also, increasing gravel layer strength leads to decreasing non-connected pile raft settlement up to 1.6 times, whose optimal strength parameters, such as friction angle and young's modulus, suggest 36 degree and 120 mpa, respectively.

Newmark sliding block method is commonly used for estimating earthquake-induced permanent displacement of earth slopes and embankments. Since this method is a simplified dynamic analysis procedure with acceptable accuracy, it has been received considerable attention among the geotechnical practitioners. However, it has some shortcomings such as neglecting system response and sliding mass rotation. Hence, researchers have proposed modified procedure to enhance the realistic features of this method. The effect of sliding mass rotation, which sets the block in a gentler condition, was previously considered by continuous increment of yield acceleration. Since the sliding mass is three dimensional in reality, smaller permanent displacement is expected when the width of block is accounted for. In this paper, width of the rotating-sliding mass is taken into account in the coupled and decoupled solution of block sliding equations. The results show that the width of the slip zone is effective on the resulting displacements. With a constant slip length, whatever slip width is reduced, yield acceleration increases and consequently difference between the modified decoupled (or modified coupled) and decoupled (or coupled) increases.

Since proper functioning of the transportation system is essential in times of crisis, correct design and accurate prediction of earthquake-induced permanent displacement of embankments and trenches have been considered by many engineers. Different methods are available for estimating earthquake-induced permanent displacement of embankments and trenches in roads, such as pseudo-static, numerical, analytical and semi-analytical. Due to its simplicity, Newmarkian rigid block analogy has received considerable attention from geotechnical researchers and practitioners. Since the conventional Newmarkian analogy has many limitations, conservative and non-conservative estimations of sliding displacement would be possible. Therefore, researchers have proposed many modifications to this method. One of these limitations is the effect of rotation. In fact, it is anticipated that the downward rotational (stabilizing) movement of the soil mass, can significantly affect the yielding acceleration of the presumed slip surface. In this paper, keeping in mind the effect of rotation, the conventional formulation of the Newmark approach is modified numerically. The results are presented and compared for several conditions including the conventional rigid block, decoupled assumption of sliding and slope response, coupled consideration of sliding and slope response, and decoupled assumption with the effect of sliding block rotation. According to the results of this study, the period ratio (ratio of natural period of slope to the mean period of input motion) and the length of slip surface, can significantly affect the permanent displacement of sliding mass.

Recent advances in evaluation of earthquake-induced permanent displacement of earth systems are addressed herein. Currently, seismic design of geotechnical structures emphasize on the quantification of system performance with the prescribed levels of permanent displacements. Accordingly, evaluation of earthquake-induced permanent displacement in geotechnical structures such as earth embankments and slopes is a topic of consideration for the geotechnical engineers. Different studies are available for estimating earthquake-induced permanent deformation of earth slopes and embankments. In general, these studies can be divided into three categories: analytical and semi-analytical, empirical and semiempirical, and numerical studies. Analytical and semi-analytical studies are simplified dynamic methods based on Newmarkian rigid block analogy. Based on this analogy, the rigid block displaces once the exciting acceleration exceeds the critical (or yield) acceleration. The original Newmarkian analogy assumes the sliding mass as the rigid block directly subjected to the input acceleration. The decoupled analysis is based on a rigid block but dynamic response of the system is calculated to obtain the equivalent acceleration as the input motion for the sliding block analysis. The decoupled analysis does not consider dynamic response of the slipped mass, while this response affects the overall behavior of the system. In a fully coupled analysis, dynamic response of the sliding mass and the permanent displacement are modeled together so that the effect of sliding displacement on the ground motions is taken into account. Through the empirical approaches, researchers developed correlations to predict seismicallyinduced displacement of slopes using databases of field case histories. These studies make clear that traditional rigid block analysis does not yield acceptable results for the seismic performance of large engineered earth structures. Besides, they provided detailed treatments of specific combinations of site and shaking conditions that are and are not adequately modeled by rigid-block analysis. Furthermore, other semi-empirical correlations have been presented based on the results of the analytical and semianalytical approaches. The third category aims to incorporate advanced constitutive models and numerical procedures such as finite difference, finite element, discrete element, and hybrid methods. This category soon began to be applied to slopes, particularly earth dams, and it provided a valuable tool for modeling the static and dynamic deformation of soil systems. However, advanced constitutive models, which are capable for simulation of soil behavior under dynamic loading, commonly require many parameters such as a high density of high-quality data and sophisticated soil-constitutive models. This problem may prevent prevalent usage of the advanced numerical approaches for estimation of earth slope displacement. For this reason, use of simplified method is preferable for evaluation of seismic permanent displacement. In this paper, major studies and recent developments on the methods of seismic slope displacement are explained based on the aforementioned categories. Moreover, advantages and disadvantages of the recent approaches are explained.