One of the most important problems of irrigation networks is damage to the concrete's canal, which resulted from uplift forces in many cases. The uplift force is created due to the lack of control of the hydrostatic pressure of groundwater on the side wall and the bottom of the canal. The aim of this study is to investigate the position and dimensions of weep hole in the floor and side walls of the concrete channel and its effect on the of reverse leakage flow, uplift forces and hydraulic gradient in different levels of groundwater. For this purpose, a concrete channel with hypothetical geometry over the permeable foundation was simulated by Seep/W software. The variables of the study included dimensions and different positions of weep hole under three different levels of groundwater. The results showed that in all dimensions of weep hole, increasing groundwater depth increase the linear reverse leakage flow rate into the concrete channel and the exist hydraulic gradient. Also, in all weep holes, increasing the diameter reduces the uplift force. If two weep holes are used, the reverse leakage flow into the canal and the uplift forces are respectively more and less than a weep hole. In other words, the placement of two weep holes at positions N=6 and 7 showed a good performance in terms of uplift forces and inverse leakage flow. If two weep holes were placed in positions N=2 and 3, it had the best performance in terms of the exist hydraulic gradient.

In order to have an economic design to reduce uplift pressure in weighted concrete dams, so many methods have been proposed that the most important include: adding horizontal apron, cutoffs in upstream and downstream of the dam and weep hole installation in downstream or proper place between the two cutoffs. These implementations also reduce the exit gradient. The effects of these parameters are the main subject of this study. This study focuses on Yusef Kand Mahabad diversion dam, by study on the dam and its simulation in Seep/W software, effect of number of weep hole on uplift pressure, proper location of weep holes on stilling basin and also the length of the dam cutoffs. Simulation was studied on uplift pressure and exit hydraulic gradient in key points of diversion dam and the overall stability of the dam. In this study, it was observed that creating primary upstream cutoff with 8 m length decreases uplifting force about 63% and decrease exit gradient 79% than the case without cutoff. Creating a weep hole in the stilling basin decreases uplifting force 8% and decrease exit gradient 74% than the case without weep hole. Results demonstrate that suitable location of weep holes can reduce uplift pressure and so the diversion dam design can be safe and economical.

Seepage flow modeling beneath hydraulic structures on permeable materials is an essential issue that must be considered before construction processes. Because of no detailed studies, followed by inappropriate design some problems such as foundation erosion, seepage and water escape and structure settlement may be occurring. If we couldn’t overcome these problems in designing process, we can utilize a series of auxiliary actions. Some actions for eliminating the piping and reducing the uplift pressure and hydraulic gradient are construction of horizontal apron, cut-off walls and also weep holes. Hence, in this study the effect of the weep hole on uplift pressure and hydraulic gradient has been investigated. For this purpose, the governing equation of flow through porous media has been solved for different setups, by the numerical method of Control Volume. All calculations have been done by the simple and powerful Excel Spreadsheet tools. Results show that, the application of weep hole reduces the uplift pressure and hydraulic gradient. Installation of a weep hole on stilling basin could reduce the cut-off wall depth and this cause a noticeable reduction of project costs. By moving weep hole toward the downstream of stilling basin and getting away from dam toe, its positive impact will be reduced.

In this paper, the effect of surface curvature on calibration coefficients of the Hole-Drilling method has been studied. Firstly, an FE simulation of the drilling process has been modeled for a flat surface. Then, the simulation has been implemented on a cylinder with different diameters and the calibration coefficients have been extracted. In all analyses, the stain-gauge rosette and hole diameter remain constant and mesh removal in the drilling simulation was achieved in eight increments. The comparison of simulation results and standard published calibration coefficients data for a flat surface show an acceptable error equal to 2.8 variation of errors between 0.6 to 6.2.

I was asked to give a brief review of the black hole-string correspondence [1] as a warm-up for a longer SITP-group discussion of a recent paper by Chen, Maldacena, and Witten [2]. Here are my notes in written form.

There are issues in organizations that require new theoretical formulation. Hence, metaphorical theorizing is used in the study of organizations to interpret them and understand their complexities. In this method, the organization is likened to an entity and one of the key features of that entity is generalized to the organization. It should be borne in mind that most organizational theories are based on a positivist paradigm that focuses on knowledge and data in an attempt to discover the nomothetic of social systems. This article is an attempt to build a theory based on interpretive paradigm that puts the organizational black hole theory forward in a metaphorical way. The black hole theory of the organization has been adopted from the cosmic black hole metaphor. In the first step, the key features of the organizational black hole were summarized in accordance with the researcher's interpretation, taking into account the one-on-one correspondence and adopting the cosmic black hole characteristics. In the second step, the definition of the organizational black hole was presented based on key features, and in the third step the overall framework of the theory was formulated. In addition, by analyzing the characteristics of the organizational black hole theory, it was found that this theory falls under the interpretative paradigm. Finally, how one can test the theory in terms of falsifiability or utility is discussed.

Purpose: To report a case of spontaneous closure of macular lamellar hole, and to discuss its probable mechanisms. Case Report: A 70-year-old woman with a diagnosis of SLE and chronic usage of hydroxychloroquine, presented to our clinic for routine retinal examinations. Her best corrected visual acuity was 7. 10 in both eyes, with a senile lens opacity and no sign of retinal HCQ toxicity. On examination and macular OCT of her left eye, a thick epiretinal membrane with the adjacent lamellar hole was detected. As there were no indications for surgical intervention, she was followed without any treatment. On 1-year follow-up examination, the ERM was seen but the hole was closed, and macular OCT of the left eye approved spontaneous closure of the hole. Conclusion: Herein we report a case of spontaneous resolution of the macular lamellar hole, an event not reported in the literature, in addition to presenting a brief review on pathophysiology and treatment of ERM and lamellar holes. Although the resolution of retinal edema or change in ERM can alter tractional features of a macular hole resembling spontaneous whole closure, in our case there was no retinal edema, and the epiretinal membrane showed no change on follow-up examinations.

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.