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مرکز اطلاعات علمی SID1
اسکوپوس
دانشگاه غیر انتفاعی مهر اروند
ریسرچگیت
strs
Author(s): 

NAVALI A.M. | ROUHANI A.R.

Issue Info: 
  • Year: 

    2006
  • Volume: 

    28
  • Issue: 

    4
  • Pages: 

    119-122
Measures: 
  • Citations: 

    0
  • Views: 

    925
  • Downloads: 

    237
Abstract: 

Background and Objectives: In patients suffering of hand trauma, zone II injuries of flexor tendons could cause significant disability if not properly managed. In the treatment of such injuries prevention of adhesion and the resulting stiffness is of main concern. Surgical treatment should achieve a primary tendon repair of sufficient tensile strength to allow application of a postoperative rehabilitation program. The aim of this study was to analyze prospectively the results of such repair using the MODIFIED Strickland technique.Methods and Materials: In a period of 3 years, 50 patients with 70 flexor tendon lacerations were enrolled in this study. After repair using MODIFIED Strickland technique, the rehabilitation program using dorsal splinting and rubber band technique was started. The mean age of the patients was 28 years (ranging from 4 to 55 years). Eight patients did not followed-up and 42 patients with sixty flexor tendon repairs were followed for a mean period of eight months (ranging from 6 to 12 months).Results: Results of This study showed that according to Strickland's criteria in 47 tendon repairs (78.3%) the result was excellent with total active motion of 153 degrees. In 6 cases (10%) the result was good, in 3 cases (5%) it was fair and in four cases (6.7%) the result was poor.Conclusion: Despite improvements in repair site strength and in the understanding of repair - site biology, adhesions still frequently form between the tendon and surrounding fibro - osseous sheath. The result of this study showed that the MODIFIED Strickland's technique if used properly with attention to details of an atraumatic and delicate surgical repair and postoperative rehabilitation can produce good or excellent results in more than 85% of cases.

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Author(s): 

ARDALAN A.A. | KARIMI R.

Issue Info: 
  • Year: 

    2005
  • Volume: 

    38
  • Issue: 

    6 (88)
  • Pages: 

    853-859
Measures: 
  • Citations: 

    0
  • Views: 

    1011
  • Downloads: 

    228
Keywords: 
Abstract: 

The possibility of modeling GRAVITY field of the Earth along the leveling lines using the GRAVITY observations at the leveling benchmarks has been studied. As the case study, GRAVITY observations along the first order-leveling network of Iran has been considered. The mathematical models that have been developed for this purpose are polynomials of degree 4 and degree 8. The efficiency of the aforementioned models has been compared with the ellipsoidal harmonic expansion to degree and order 20, 180, 360 and the Somigliana-Pizzeti GRAVITY field. The test computations have proven that a polynomial model of degree 4 can be considered as the best choice for the GRAVITY field modeling along the leveling lines. Based on the case study of GRAVITY field modeling along the leveling lines of Iran, the polynomial model of degree 4 can provide 20 mGal accuracy which is quite enough to provide the accuracy level of the GRAVITY data needed for the precise leveling based on the current demands. Therefore, by applying such a model the need for the GRAVITY observations along the leveling lines will be reduced and as such great reduction in the expense of the precise leveling observations will be achieved.

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Author(s): 

PEREZ A.

Issue Info: 
  • Year: 

    2013
  • Volume: 

    16
  • Issue: 

    -
  • Pages: 

    3-3
Measures: 
  • Citations: 

    447
  • Views: 

    18175
  • Downloads: 

    26465
Keywords: 
Abstract: 

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گارگاه ها آموزشی
Author(s): 

GOLI M.

Issue Info: 
  • Year: 

    2014
  • Volume: 

    40
  • Issue: 

    2
  • Pages: 

    97-111
Measures: 
  • Citations: 

    0
  • Views: 

    1500
  • Downloads: 

    442
Abstract: 

Generally, GRAVITY anomaly is the difference between the observed acceleration of Earth's GRAVITY and a normal value. Topography (all masses above geoid) plays a main role in definition of the GRAVITY anomaly. Based on modeling of the effect of topography, there are different models of GRAVITY anomaly such as free-air and Bouguer anomaly. The main goal of the Bouguer anomaly is removing of gravitational effect of all masses above the geoid (topography and atmosphere). This anomaly is widely used in exploration geophysics. In geodetic applications, in the absence of topography, Bouguer GRAVITY anomaly is smooth and thus more suitable for interpolation and even stable downward continuation.In the other hand, GRAVITY anomaly is the difference between real GRAVITY at a point and normal GRAVITY in corresponding point where the real and normal potentials in both points are the same. In geodesy, the GRAVITY disturbance is defined as the difference between the real GRAVITY observed at a point and normal GRAVITY at the same point. In many geophysics literatures, GRAVITY anomaly is replaced by GRAVITY disturbance together a corrective term called geophysical indirect effect. This correction is computed by application of the free-air (and usually the Bouguer) correction over the geoid–ellipsoid separation. This correction must be computed by application of only free air correction to separation of the real equipotential surface and its equivalence in normal GRAVITY field at GRAVITY observation. The free-air (FA) correction is used to up/downward continuation of normal GRAVITY anomaly. In practice, only linear approximation, 0.3086 mGal/m, is used while a second-order FA correction is more realistic than the linear approximation. Note that the FA correction is not a reduction formula for downward continuation of GRAVITY anomaly.One of the most ambiguities in definition of Bouguer effect GRAVITY anomaly arises from formulating the effect of topography. The gravitational of topography can be split into Bouguer term, which is the dominant term, plus minor effect, terrain roughness. In the evaluation of a topographical effect, planar or spherical models of topography can be used. Many studies have shown that planar and spherical model of topography give very different results for Bouguer anomalies. Also, it was shown that the planar topography model (in form of infinite Bouguer plate) yields to a mathematically and physically meaningless quantity. To compute the terrain correction in geophysics, the gravitational effect of only masses up to about distance 167 km (Hayford zone) is considered. In principle the domain of computation of the topographical effect is the whole of the Earth. Despite the fact that the gravitational effect decreases with distance, the effect of beyond Hayford zone is large and should be considered.The removal of the topographical masses disturbs the isostasic equilibrium of the crust. As a result, the equipotential surface can be moved up to several hundred meters. The indirect topographic effect is defined as the effect on GRAVITY due to removing the topographical masses. The indirect effect of topography (ITE) in Bouguer GRAVITY anomaly was first introduced by Vanicek, et al (2004). Their computations show that the numerical values of ITE can be reached up to 150 mGal in mountainous area. While, in most studies, ITE does not take into account and only direct topographical effect is considered.In analogy with topographical effect, in the computation of Bouguer GRAVITY anomaly, the direct and indirect effects of atmospheric masses should be considered. Usually the GRAVITY effect of the atmosphere is evaluated by IAG formula. This formula considers only the direct topographical effect as the correction to GRAVITY anomaly. The indirect atmospherical effect is not discussed in this context. In this study, the method proposed by Sjoberg (2000) is recommended and applied.In order to investigate differences between classic and new Bouguer GRAVITY anomalies, numerical calculations were performed in a mountainous area bounded by , where there are 2385 land GRAVITY observation. The classic planar Bouguer anomalies were computed from where g and are observed and normal GRAVITY, H is the orthometric height of point and is the terrain correction computed up to Hayford zone. The new spherical Bouguer anomalies were computed from where FA is second-order free-air correction, DTE is the direct topographical effect (spherical shell + terrain roughness), ITE is the indirect topographical effect, DAE is the direct atmospherical effect and, IAE is the indirect Atmospherical effect. The results indicate that there are large differences (over 100 mGal) between classical and new Bouguer anomalies. The new Bouguer anomalies are less correlated with terrain heights. Therefore the planar model cannot completely remove the gravitational effect of topography.

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Author(s): 

MOSTAFA ZADEH ALI

Issue Info: 
  • Year: 

    2005
  • Volume: 

    5
  • Issue: 

    3
  • Pages: 

    53-58
Measures: 
  • Citations: 

    0
  • Views: 

    74799
  • Downloads: 

    30797
Abstract: 

We elaborate on some recent results on a solution of the Hilbert-space problem in minisuperspace quantum cosmology and discuss the consequences of making the (geometry of the) Hilbert space of ordinary no relativistic quantum systems time-dependent. The latter reveals a remarkable similarity between Quantum Mechanics and General Relativity.

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Author(s): 

VATANKHAH SAEED

Issue Info: 
  • Year: 

    2016
  • Volume: 

    42
  • Issue: 

    2
  • Pages: 

    337-348
Measures: 
  • Citations: 

    0
  • Views: 

    993
  • Downloads: 

    273
Abstract: 

In this paper the inversion of GRAVITY data using L1–norm stabilizer is considered. The inversion is an important step in the interpretation of data. In GRAVITY data inversion, the goal is to estimate density and geometry of the unknown subsurface model from a set of known observation measured on the surface. Commonly, rectangular prisms are used to model the subsurface under the survey area. The unknown density contrasts within each prism are the parameters which should be estimated. The inversion of GRAVITY data is an example of underdetermined and ill-posed problem, i.e. the solution can be non-unique and unstable. Thus, in order to find an acceptable solution regularization should be imposed. Solution is usually obtained by minimizing a global objective function consisting of two terms, data misfit and the regularization term. Data misfit measures how well an obtained model can reproduce the observed data. Usually, it is assumed noise in GRAVITY data is Gaussian, therefore a L2–norm measure of the error between observed and predicted data is well suited for data misfit. There are several choices for a stabilizer, depends on type of features one wants to see from inverted model. A typical choice is a L2 –norm of a low-order differential operator applied to the model, which also a priori information and depth weighting can be incorporated (Li and Oldenburg, 1996). In this case the objective function is quadratic, then minimization of the function results a linear system to be solved. However, the models recovered in this way are characterized by smooth feature which are not always consistent with the real geological structures. There are situations in which the sources are localized and separated by sharp, distinct interfaces. To deal with this problem, during last decades, researchers have proposed a few types of stabilizer. Last and Kubik (1983) presented a compactness criterion for GRAVITY inversion that seeks to minimize the area (or volume in 3D) of the causative body. Portniaguine and Zhdanov (1999) based on this stabilizer, who named the minimum support (MS), developed the minimum gradient support (MGS) stabilizer. For both constraint, the regularization term can be written as the weighted L2–type norm of the model. Therefore, the problem of the minimization of the objective function can be treated same as conventional Tikhonov functional. The only difference is that a priori variable weighting matrix for model parameters incorporated in the regularization term. Thus the Iteratively Reweighted Least Square (IRLS) algorithm is required to solve the problem. Other possibility for stabilizer is the minimization of the L1-norm of model or gradient of model, the latter indicates total variation regularization. The L1–norm stabilizer allows occurrence of large elements in the inverted model among mostly small values. Therefore, it can be used to obtain sharp boundaries and blocky features. Although the L1–norm stabilizer has favorable properties, in reconstruction of sparse models, its numerical implementation in a minimization problem can be difficult because its derivatives with respect to an element is not defined at zero. To overcome this difficulty, in this paper, the L1–norm stabilizer is approximated by a reweighted L2 –norm term. The algorithm is extended to GRAVITY inverse problem, which needs depth weighting and other priori information to be included in the objective function. For estimating the regularization parameter, which balances between two terms of objective function, the Unbiased Predictive Risk Estimator (UPRE) method is used. The solution of the resulting objective functional is found using Generalized Singular Value Decomposition (GSVD), also provides for efficient determination of the regularization parameter at each iteration. Simulation using synthetic data of a dipping dike demonstrates that the method is capable to reconstruct focused image, boundaries and slop of the reconstructed model are close to those of the original model. The method is applied on GRAVITY data acquired over the Gotvand dam site, in the south-west of Iran. The results show rather good agreement with those obtained from the boreholes.

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strs
Author(s): 

ARDALAN A.A. | ARAB SAHEBI R.

Issue Info: 
  • Year: 

    2006
  • Volume: 

    39
  • Issue: 

    5 (93)
  • Pages: 

    633-644
Measures: 
  • Citations: 

    1
  • Views: 

    1584
  • Downloads: 

    557
Keywords: 
Abstract: 

Detailed GRAVITY field modeling requires ground, sea, airborne and satellite GRAVITY observations. Sea GRAVITY observations have been always suffering from the low accuracy and noises.  On the other hand satellite altimetry provides accurately sea level variations. In this paper possibility of GRAVITY field modeling at sea areas, especially at islands, using satellite altimetry is studied. A method for this purpose is devised which algorithmically can be explained as follows: (1) Obtain Mean Sea Level (MSL) from satellite altimetry. (2) Obtain Sea Surface Topography (SST) from oceanographic sea current and studies. (3) Compute the geoid by removing SST from MSL. (4) Apply inverse ellipsoidal Bruns formula and compute the GRAVITY potential at the reference ellipsoid. (5) Remove gravitational effect of ellipsoidal harmonic expansion to degree and order 360 and the centrifugal acceleration. (6) Remove terrain effect using Newton integral over the terrain masses at the radius of 55 km around the computational points. (7) Upward continue the harmonic gravitational potential derived in step 6 using ellipsoidal Abel-Poisson integral. (8) Restore the effects removed in steps 5 - 6 at the computational point. This procedure is applied for GRAVITY field modeling at Geshm Island and its surrounding area. The details of the method and results of the case study are presented in this paper.

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    3
  • Issue: 

    1
  • Pages: 

    79-84
Measures: 
  • Citations: 

    0
  • Views: 

    208
  • Downloads: 

    127
Abstract: 

Patients Information: Laparoscopic Vaginoplasty with MODIFIED Vecchietti Technique is a new method in the treatment of vaginal agenesis. In this method, a combination of dilatation and graftless surgery is used. This technique was first developed in 1992 for the first time in the world, and it was used in Sarem Hospital in 2009 for the first time in Iran. After primary examinations and the definitive diagnosis of Mayer-Rokitansky and Kuster-Hauser syndrome, 9 patients with vaginal agenesis were operated by Laparoscopic Vaginoplasty, using MODIFIED Mecchietti Technique between 2009 and 2014; their surgical outcomes and their subsequent consequences including sexual satisfaction were followed up and studied. Only 2 out of 9 patients had complaints about their vaginal length because of lack of regular intercourse. The average time for surgery was 2 hours and 8 minutes and the mean vaginal length was 6. 5 cm. According to the last patients’ follow up, the minimum increased vaginal length was 3 cm and maximum vaginal length was 10 cm. Also, the average hospitalization time was 7. 3 days. Conclusion: All in all, compared with other vaginoplasty methods, the mentioned technique has fewer side effects and it is more effective. Because of lack of transplantation, there was no side effect of transplantation.

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Author(s): 

POLDER M.

Issue Info: 
  • Year: 

    2002
  • Volume: 

    40
  • Issue: 

    -
  • Pages: 

    12-22
Measures: 
  • Citations: 

    436
  • Views: 

    20374
  • Downloads: 

    24441
Keywords: 
Abstract: 

Yearly Impact:

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Author(s): 

M. KABIR HASSAN

Issue Info: 
  • Year: 

    2001
  • Volume: 

    12
  • Issue: 

    -
  • Pages: 

    0-0
Measures: 
  • Citations: 

    455
  • Views: 

    20512
  • Downloads: 

    28126
Keywords: 
Abstract: 

Yearly Impact:

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