Perforation Pattern Research Articles

Development and Validation of a Prognostic Nomogram for Postoperative Recurrence-Free Survival of Ameloblastoma.

PurposeAmeloblastoma is a benign odontogenic neoplasm with a high local recurrence rate if the operation is not thorough. However, a useful clinical tool for the quantitative assessment of the prognosis and risk of postoperative recurrence of ameloblastoma has not yet been constructed. This study aims to develop a prognostic nomogram model for ameloblastoma of the jaw to assist surgeons in surgical decision-making.Patients and MethodsPatients who underwent initial surgery for ameloblastoma in our department from October 2004 to March 2020 were enrolled and randomly divided into training and validation sets. Univariate and multivariate Cox proportional hazards regression analyses were performed to identify the independent prognostic factors, from which a nomogram for predicting 3-, 5- and 10-year recurrence-free survival (RFS) of ameloblastoma was constructed using the training set and internally validated using the validation set. The model performance was assessed by Harrell's concordance index (C-index) and calibration curves.ResultsA total of 302 eligible patients with ameloblastoma were enrolled, 54 of whom were confirmed to relapse during the follow-up period of 6 to 191 months. Four independent predictors, including cortical bone perforation, root(s) resorption, WHO classification, and treatment pattern, were identified and included in the construction of a nomogram for recurrence-free survival (RFS), which showed promising calibration performance and discrimination in the training set (C-index 0.790, 95% confidence interval [CI] 0.735–0.845) and the validation set (C-index 0.734, 95% CI 0.599–0.869).ConclusionA favorable nomogram was developed that accurately predicted the RFS of patients with ameloblastoma based on individual characteristics. Risk stratification using the nomogram could optimize tailored therapy and follow-up.

Impact of frame perforations on passive cooling of photovoltaic modules: CFD analysis of various patterns

Geometry of the frames used in a photovoltaic (PV) module affects the fluid flow and heat transfer around the system. As a method of passive cooling, various perforation patterns are introduced into the aluminum frame of a PV module, and the resulting flow field, temperature distribution, and power output are investigated in the present study. Three-dimensional computational fluid dynamics (CFD) simulations are performed in the cases of forced (wind velocity of 4 m/s) and natural convection (zero wind velocity). After comparing two types of conventional frames with a frameless module, different perforation patterns are utilized and the resulting flow field and heat transfer distributions are carefully investigated for the equivalent heat flux value of 600 W/m2. Results show that perforations are effective in case of natural convection, in which a 3.8 K temperature drop is observed in the best case. However, the average PV temperature is almost the same in forced convection. Finally, two selected designs are studied in different typical weather conditions. As a result, the frame with 10 mm circular perforations on all sides achieves a 0.62% improvement in power generation in the temperate climate and zero wind velocity compared to the panel with a conventional frame.

Form Finding Architectural Shading Device: Reinterpretation of Batik Pattern through Parametric Approach

The use of technology is a big opportunity to explore architectural design. This research examines the possibility of form-finding process by using computational design approach to generate shading devices that can represent local identity and provide efficient energy use of the building. Some examples of geometric Batik patterns found on the local screen used in one of the Indonesian traditional houses will be transformed into perforated shading devices. The process consists of three stages: understanding the symmetry group of each pattern with crystallographic chart analysis, generating a digital mesh of the objects by using photogrammetry method, and reinterpreting the object mesh to the perforated panel using parametric approach. The result shows that Banji pattern on p4gm symmetry group, while Kawung pattern on p4mm, Parang pattern on p1, and Nitik pattern on c2mm. On the photogrammetric stage, the digital three-dimensional meshes are successfully formed by using 13-19 overlapping photographs of the objects. From the last stage, perforated batik pattern panels are generated and it is possible to set the perforation percentage to reach desired WWR value. This experiment indicates that the use of computational design is possible to develop the local ornaments into a controllable perforated shading device.

Off-Center High Velocity Impact on Cylindrical Pipes and Shells

Damage to cylindrical shells, such as pipes and structural elements, that results from collision with supersonically moving particles is studied. Unlike existing work, we examine the effects of off-center impact, where the impactor hits at an angle to the cylinder diameter at the point of contact. A numerical assessment of damage and perforation patterns is calculated. New types of damage patterns, including cases of breakup and ricocheting impactors are shown and discussed.

Seismic behavior of thin cold-formed steel plate shear walls with different perforation patterns

Thin perforated Steel Plate Shear Walls (SPSWs) are among the most common types of seismic energy dissipation systems to protect the main boundary components of SPSWs from fatal fractures in the high-risk zones. In this paper, the cyclic behavior of the different circular hole patterns under cyclic loading is reported. Based on the experimental results, it can be concluded that a change in the perforation pattern of the circular holes leads to a change in the locations of the fracture tendency over the web plate, especially at the plate-frame interactions. Accordingly, the cyclic responses of the tested specimens were simulated by finite element method using the ABAQUS package. Likewise, perforated shear panels with a new perforation pattern obtained by implementing Topology Optimization (TO) were proposed. It was found that the ultimate shear strength of the specimen with the proposed TO perforation pattern was higher than that of the other specimens. In addition, theoretical equations using the Plate-Frame Interaction (PFI) method were used to predict the shear strength and initial stiffness of the considered specimens. The theoretical results showed that the proposed reduced coefficients relationships cannot accurately predict the shear strength and initial stiffness of the considered perforated shear panels. Therefore, the reduced coefficients should be adopted in the theoretical equations based on the obtained experimental and numerical results. Finally, with the results of this study, the shear strength and initial stiffness of these types of perforated shear panels can be predicted by PFI method.

The Biomechanical Properties of Meshed versus Perforated Acellular Dermal Matrices (ADMs).

Background:Acellular dermal matrices (ADMs) are used for soft tissue augmentation across surgical specialties. Since allograft incorporation depends on direct opposition between the ADM and a vascular bed, seroma formation can be detrimental to incorporation. Since most ADM products are available in many meshed and perforated forms, there is a lack of consistency between manufacture designs. We set out to determine the fluid egress properties and increase in surface area resulting from common cut patterns.Methods:Three ADM cut patterns were studied: 1 meshed and 2 perforated. We calculated the surface area of these modified ADM samples. Fluid was passed through each ADM, and time required for fluid passage was recorded. An ANOVA (P < 0.05) was used to determine if there was a significant difference in egress properties across the 3 patterns.Results:Meshing in a 1:1 pattern resulted in a 97.50% increase in surface area compared with the uncut product. In comparison, only a 0.30% increase resulted from Perforation Pattern #1 and a 0.59% increase resulted from Perforation Pattern #2. There was a significant difference in egress properties across the three cut patterns (P = 0.000). The average egress time of Mesh Pattern #1 was 1.974 seconds. The average egress time of Perforation Pattern #2 was 6.504 seconds, and of Perforation Pattern #1 was 10.369 seconds.Conclusions:Quantitative comparison revealed that meshing ADM significantly improves fluid egress and increases the surface area. Therefore, the use of meshed ADM tissue could improve the incorporation of ADM with the recipient, with improved patient outcomes.

Computational Study of Mass Reduction of a Conceptual Microsatellite Structural Subassembly Utilizing Metal Perforations

A subassembly from the structural subsystem for a conceptual microsatellite designed for earth resources missions underwent normal modes analyses, after implementing an alternative approach to mass reduction, other than implementing advanced space qualified materials. This approach involved developing and implementing a set of geometric patterns that imposed upon certain components of the structural subassembly as perforation patterns, hence achieving mass reduction through straightforward material removal. This approach was proposed to introduce a relatively low-cost and easily implemented mass reduction methodology, which can be utilized by entities with little or no infrastructure and experience in advanced materials, though aspiring to develop their own satellite developing capabilities. The subassembly was the primary load path through which the launch loads pass, the so-called central box, consisting of four Aluminum 6061 identical planar plates, fastened together by titanium fasteners. The subassembly's fundamental natural frequency and attendant mode shape, for all cases, were computed utilizing the finite element method. The current work's approach to mass reduction resulted in an approximate 20% percent reduction in mass from the unperforated case, depending upon the exact thickness value employed for the subassembly plates, hence indicating that the perforation approach is valid.

Numerical investigation and optimization of a heat sink having hemispherical pin fins

A numerical study was conducted aiming to examine the hydrothermal performance of a heat sink having hemispherical pin fins (HSPFs) under fully turbulent flow conditions and to find the optimum HSPFs configuration. In the first stage, a heat sink having staggered arranged cylindrical pin fins (CPFs) was selected as the reference case, and the numerical procedure followed in the present study was validated. In the second stage, the hydrothermal performance of solid-HSPs was numerically investigated and compared with the performance of the reference case. The highest the hydrothermal performance factor (HTPF) was found as 1.87 for the fin diameter (d) to channel height (H) ratio (d/H = 0.833), and Reynolds number (Re = 21,367). This configuration was selected as the base case, and in the last stage, its hydrothermal performance was augmented through the perforation technique. The effects of six different perforation patterns having a various number of holes on the hydrothermal performance were investigated in detail. The highest HTPF was obtained as 1.98 which is around %5.6 times higher than the base case, for the pattern with the most holes. In addition, with the proposed HSPFs configuration, the volume of the heat sink was reduced up to 76% compared to the reference case.

Aetiological Pattern of Gastrointestinal Perforations: A Prospective Observational Study

Introduction: Peritonitis secondary to gastrointestinal perforation is one of the commonest surgical emergencies encountered all over the world. This study was done to highlight the spectrum of perforation peritonitis encountered in surgery unit of Dhaka Medical College Hospital.&#x0D; Method: It was observational prospective of 100 cases of perforation peritonitis treated in our hospital. All cases of perforative peritonitis whether spontaneous, infective or neoplastic pathology were included in this study.&#x0D; Results: The maximum numbers of patients were in age group between 31 to 40 years (39 %) with mean age 35 years. Male female ratio was 9:1. The most common aetiology of perforation peritonitis was peptic ulcer disease (73%) followed by enteric fever (12%), appendicitis (10%), tuberculosis (3%) and malignancy (2%). The most common sites of perforation were in descending order of frequency - first part of the duodenum (65%), terminal ileum (12%), appendix (10%), gastric antrum (9%), jejunum (3%) and rectum (1%). Abdominal pain (100%) and vomiting (81%) were the most common symptoms while tachycardia (96%), muscle guard and rigidity (100%) were the common signs. Approximately 15-20% presented late with features of shock. Mortality rate was 2% and was significantly high in patients coming hospital late.&#x0D; Conclusion: Gastrointestinal perforations are one of the most common surgical emergencies. Duodenal perforations are most common. Ileal perforations secondary to enteric fever have highest morbidity. Early recognition and timely appropriate intervention is very important in reducing morbidity and mortality.&#x0D; J Dhaka Medical College, Vol. 29, No.2, October, 2020, Page 106-109

Issues with Belt Guidance and Device Controls in the Automated Conveyor and Drive Belt Perforation Process

The perforation process for multi-layer composite polymer belts presents numerous challenges due to the varied mechanical characteristics and geometrical parameters of the entire range of belts used in the industry. Many problems can be minimized or eliminated with correct development of construction features of the machines for high precision mechanical belt perforation. Regardless of the construction solutions employed in the devices, a major factor influencing the quality of the final product as well as machine reliability is the method of controlling their operation as well as the correct guidance of the belt throughout the entire flow of material in the manufacturing process. The present work provides an analysis of the assemblies ensuring correct belt guidance and presents the causes and effects of incorrect development of these systems. Furthermore, it touches upon the aspects involving the control solutions for such equipment involving the definition of actuators and controllers, the selection of sensors and methods of measuring linear displacement of the belt and perforating head position together with the control algorithms for carrying out different patterns of perforation.

Analysis of phase change material integration in retail display cabinets for energy management

Nowadays, retail stores are highly interested in the application of strategies such as demand response (DR) in refrigerated display cabinets (turning off the cold machine during a certain time) to increase their flexibility in energy management and to facilitate the integration of renewable energy sources. One of the main concerns related to DR deployment is the product and air temperature increase inside the cabinets when the refrigeration machine is turned off. Thermal energy storage TES by phase change materials (PCM) has been demonstrated to be a solution to replace for a limited time the refrigeration unit and maintain the product at low temperature. However, the presence of PCM heat exchanger altered the air curtain performance as well as the thermal behaviour of the display cabinet. Successful integration of PCM needs implementing new cabinet design and operating conditions. Moreover, if this technology is applied for many display cabinets, management strategies need to be considered so that the PCM can be charged and discharged in suitable conditions. If renewable energy sources are available, energy management scenarios combining electrical sources (grid and renewable) and thermal energy storage (PCM) can be planned. The main objectives of the present work are, first, to identify improvement options and optimized parameter ranges that can request the PCM integration in the display cabinet; and second, to test different energy management scenarios at the scale of a supermarket. The study shows that by improving the perforation pattern of the rear duct channel and increasing the fan power, a more homogeneous product temperature distribution and better thermal behaviour of the cabinet are obtained. The effects of the operating conditions (ambient and setpoint temperatures) on thermal behavior, energy consumption and PCM charging/discharging time are analyzed by experimental investigations. A simulation tool was developed to evaluate the global efficiency of a supermarket equipped with PCM display cabinets. For different energy management scenarios, it evaluates the potential of this technology to support DR applications, reduce the electricity contract power of the retail and facilitate the utilization of renewable energy sources, photovoltaic (PV) solar panels in particular. PCM integration allows a reduction of maximal power demand by 8% in the scenario without PV panels and by 13% in the scenario with PV panels.

Surgical anatomy of the submental artery perforator flap and assessment for application in postoperative reconstruction following oral cancer surgery: a prospective clinical study

The submental artery perforator flap (SMAPF) has an elongated pedicle, allowing good cosmetic outcomes to be achieved following oral reconstruction surgery. The improper dissection of perforators often leads to a vascular flap crisis. To avoid this, some surgeons choose to carry amounts of connective tissue around the pedicle. However the inclusion of connective tissue on the pedicle raises concerns about oncological safety. A surgical anatomical study of the submental vessel patterns and subdivisions of the cervical level I lymph nodes was conducted on 33 patients with primary oral cancer who underwent reconstruction with a SMAPF after tumour resection. The variations in vessels and cervical level I lymph nodes observed during SMAPF harvesting were recorded and analyzed. Two patterns of submental artery perforators and three patterns of submental veins were identified. The different characteristics of the lymph node distribution were elucidated for five subdivisions. All SMAPFs survived (n=33, 100%); however, two SMAPFs exhibited partial losses. The 3-year survival rate of patients was 84.5±6.4%, and there were no suspected flap-related recurrences. With detailed anatomical information on the vascular system and lymph node subdivision, SMAPFs are a reliable choice for postoperative reconstruction following oral cancer surgery, meeting the standards for oncological safety.

Acoustic behaviour of 3D printed bio-degradable micro-perforated panels with varying perforation cross-sections

Influence of perforations having arbitrarily varying cross-sections on the acoustic behaviour of 3D printed bio-degradable panels made of Poly Lactic Acid (PLA) is presented. Circular perforations having six different types of cross-sectional variations namely convergent-divergent (CD), divergent-convergent (DC), convergent (C), divergent (D) with two different perforation diameters are realized using Fused Filament Fabrication (FFF) based 3D printing. Sound absorption and transmission loss characteristics of these perforated panels are estimated through impedance tube technique. Results revealed that sound absorption of perforated panels with varying cross-section is better than uniform cross-sectional perforation for the given frequency range. Among, the different cross-sectional variations explored, comparable and lower transmission losses are exhibited by DC and D perforation pattern with respect to constant diameter 1 mm panel. The sound transmission results of all other five specimens were significantly higher than constant diameter 8 mm panel and observed to be increasing with frequency. Geometrical perforation variations are noted to be a very crucial factor in designing soundproof panels as presented in this work. The experimental results are compared with the numerical results and found to be in good agreement. Such numerical analysis paves the guidelines for designing optimum perforation geometries prior to the on-field testing of the functional prototypes.

ANATOMICAL STUDY OF THE PERFORATORS OF THE FRONT OF THE THIGH AND ITS CLINICAL APPLICATIONS

Throughout the years, the lower limb in general and thigh specifically remained the largest and preferred donor site in the human body for flap harvest. Reconstructive surgery could be traced back to the sixteenth century and surgeons have competed through history to attain reliable and versatile tissue transfer. However, the dilemma of good flap survival with minimal thickness persisted to provoke anatomists and surgeons to search for methods to secure the vitality of thin flaps. This was made possible with the emergence of the concept of “Perforator flaps” between the 1980s and 1990s. It is for these reasons that sound knowledge of the vascular anatomy of the human integument provides the framework for successful flap elevation. Therefore, it is pivotal for the reconstructive surgeon to have a proper understanding of the vascular anatomy of the skin. This study considered the vasculature of the whole anterior thigh area including the different patterns of perforators as regards their origin and distribution from the parent vessel. It also considered to compare between different regions in the whole area.

Preoperative computed tomography assessment for a deep inferior epigastric perforator (DIEP) flap: a new easy technique from the Bologna experience.

Deep inferior epigastric perforator (DIEP) flap reconstruction is the gold standard reconstructive technique for women undergoing breast cancer surgery. A preoperative computed tomography angiography (CTA)-dedicated protocol and 3D reconstructions are mandatory for correct surgical planning. To evaluate the diagnostic performance of a new preoperative CTA protocol and a new reconstruction method in the assessment of DIEP technique. A total of 263 women (median age 49 years, age range 26-73 years) underwent preoperative CTA examination before DIEP flap breast reconstruction. A CTA-dedicated protocol followed by 3D-reconstructions were performed. Identification, branching pattern, and caliber at origin were assessed for each perforator. Intraoperative findings were the standard of reference. The sensitivity, positive predictive value, and diagnostic accuracy of the preoperative CTA protocol were calculated. In 255/263 (97%) patients, the dominant perforators assessed by CTA resulted adequate for surgical reconstruction. In 260/263 (99%) cases, the imaging localization of the dominant perforators corresponded with those seen intraoperatively (mean errors ≤1 cm). The preoperative CTA imaging sensitivity, positive predictive value, and diagnostic accuracy in determining the localization of perforators were 99% (95% CI 98-100), 100% and 99% (95% CI 98-100), respectively. No statistically significant differences were found between the CTA findings and the surgical findings for the assessment of branching pattern and caliber of the dominant perforators (P < 0.001). The present protocol has demonstrated high accuracy in the CTA imaging assessment of the perforators before DIEP flap reconstruction with high reproducibility between CT and surgical findings.

The Biomechanical Properties of Meshed Versus Perforated Acellular Dermal Matrices: Analysis of Surface Area and Fluid Egress

BACKGROUND: Acellular dermal matrices (ADMs) are used for soft tissue augmentation across surgical specialties. The increased use of ADMs has been particularly apparent in the setting of implant-based breast reconstruction, where matrices are used to supplement the thickness of the mastectomy skin flaps and ensure adequate soft tissue coverage of implants. However, long-term review of these devices has indicated that there is a strong correlation between seroma formation and the use of ADM. Since allograft integration and neovascularization is dependent having on direct opposition between the ADM and a vascular bed, the presence of seromas can inhibit the area of the graft which is in contact with the native tissue. As a result, most ADM products are available in a variety of meshed or perforated forms. Because of the lack of consistency between manufacture designs, we set out to determine the fluid egress properties and the increase in surface area resulting from common cut patterns. METHODS: The fluid egress properties were analyzed for three different commonly encountered commercially available ADM cut patterns: 1 meshed design and 2 distinct perforation designs. Mesh Pattern #1 was designed with 1:1 meshed cuts each measuring 1.5 mm in length. Perforation Pattern #1 was designed with 3 mm diameter perforations at a density of 0.128 perforations per cm2. Perforated Pattern #2 was designed with 3 mm diameter perforations at a density of 0.25 perforations per cm2. The surface area of these modified ADM samples was also calculated, accounting for the mesh length or the perforation diameter and frequency. Fluid egress was calculated by passing fluid through each ADM and measuring the amount of time required for complete passage. An analysis of variance was used to determine if there was a significant difference in egress properties across the three patterns. A P value of <0.05 was used to determine statistical significance. RESULTS: Meshing in a 1:1 pattern resulted in a 97.50% increase in surface area compared to the uncut product. In comparison, only a 0.30% increase resulted from Perforation Pattern #1 and a 0.59% increase resulted from Perforation Pattern #2. There was a significant difference in egress properties across the 3 cut patterns (P = 0.000). The average egress time of Mesh Pattern #1 was 1.974 seconds. The average egress time of Perforation Pattern #2 was 6.504 seconds and of Perforation Pattern #1 was 10.369 seconds. Neither donor (P = 0.249) nor graft thickness (P = 0.914) had a significant impact on the results. CONCLUSION: To our knowledge, this study is the first to directly compare clinically applicable properties between different ADM cut patterns. By comparing a variety of common manufacturer designs, ranging from simple punch-shape perforations to a full 1:1 mesh pattern, we were able to demonstrate that meshing ADM tissue significantly improves fluid egress properties and substantially increases the surface area compared to ADM tissue perforated at levels typically available on the market. Therefore, the use of meshed ADM tissue could improve the ability of the product to incorporate with the recipient, resulting in decreased complications and improved patient outcomes.

Optimization of perforated liner parameters in horizontal oil wells

Nowadays, horizontal wells play a vital role in the production from thin heavy oil reservoirs. Designing a suitable completion for this kind of reservoirs is a decisive factor to boost the efficiency of durable production. This study deals with the optimization of perforated liner design for horizontal wells in Sarvak oil reservoir, which is located in the southwest of Iran. Sarvak is a carbonate oil reservoir, but it contains shale and mudstone. To avoid solid production and formation collapse, the screen liner was selected as a cost-effective solution. There were two choices, either perforated liner or slotted liner. The perforated liner was selected by finite element analysis and strength checking, which was proven by laboratory experiments. Sensitivity analysis was performed on various perforated parameters such as phase angle, hole density, hole diameter and hole distribution to determine the pattern of the holes so that enough strength of the liner was maintained while maintaining the maximum hole density. Then, parameters of perforated liner were determined by calculated loss of the flowing path, collapse resistance strength and tensile strength of casing pipes after perforated. As a result, hole density, hole size and perforated pattern were selected 100 HPM, 10 mm and 4-thread-line, respectively, in 4 ½” liner with 13.5 ppf. The ratio of the strength of the optimized perforated liner was less than 8% for collapse and 5% for tensile compared to the same specification casing.

Numerical study and experimental validation of blastworthy structure using aluminum foam sandwich subjected to fragmented 8 kg TNT blast loading

A blastworthy structure is defined as a structure that has the ability to deform with a controlled force and preserve sufficient residual space around the occupants to limit bodily injury during a blast impact incident. In this research, a blastworthy aluminum foam sandwich (AFS) structure that consisted of an occupant side plate (OSP), a struck side plate (SSP), and an aluminum foam (Al-foam) core were numerically and experimentally subjected to blast-fragmented loading. The explosion with high-pressure shock waves was produced by steel-covered TNT, creating a synergistic blast and fragment loading. The interaction between the blast-fragment loading and the AFS created a unique perforation pattern due to Monroe's effect. The measured blastworthiness characteristics included structural integrity, acceleration, and reaction force. A numerical modeling strategy to analyze the blastworthiness performance of the AFS structure was developed to capture the dynamic responses and the damage mechanism. Two types of blast loading, namely load blast enhanced (LBE) and smooth particle hydrodynamic (SPH) blast loading, were utilized along with the Cockcroft-Latham damage modeling on the AFS. A blast experimental setup with a fix-clamped method was used to evaluate the blastworthy characteristics of the panel to acquire the central acceleration and reaction force histories. A two-step process of experimental validation was carried out. First, a pre-test system validation with a very low explosive blast using 60 gram of TNT was conducted on the sandwich specimen to ensure the data acquisition system's functionality and to obtain comparable data for system validation. Second, a blast impact test using 8 kg of steel-covered TNT was carried out to validate the numerical modeling results. The results of the numerical analysis showed that the LBE model had good agreement with the test data for the small deformation blast impact loading with 60 gram TNT. For the large deformation blast impact loading with 8 kg TNT, the SPH models provided excellent agreement with the damage mode and dynamic responses, where the acceleration and the reaction force performances were both within 6.1% and 6.4% of the experimental validation, respectively. As for the structural performance of the AFS construction, it was observed that the sandwich panel met the structural integrity requirements. There were no cracks or fractures in the OSP. The SSP and Al-foam absorbed more than 98.3% of the blast impact energy, providing extra protection for the OSP. This research contributes to the dynamic structural-response and damage investigation of AFS subjected to fragmented 8 kg TNT blast loading.

Experimental and numerical study on largely perforated steel shear plates with rectangular tube–shaped links

Steel plate shear wall is one of the most effective dissipation systems which are commonly used in buildings. In order to improve the hysteretic behavior of shear panels, large perforation patterns may be applied, transforming the shear plate into a sort of grid systems, where plastic deformations are concentrated on specific internal link elements. This study investigates the behavior of grid systems loaded in shear where the internal links are created by cutting out internal parts, leaving rectangular tube–shaped link elements. The influence of internal link geometry on the cyclic performance of the systems is investigated experimentally. To this purpose, two specimens that varied in the width of links were fabricated and tested. The results indicate that any increase in the width of links leads to the growth of the ultimate strength, stiffness, and energy absorption capacity. Likewise, the stress distribution and fracture tendency of the tested specimens have been simulated by the finite element software (ABAQUS) and validated according to the experimental results. Based on finite element results, a suitable analytical formulation for the prediction of the shear strength at several shear deformation demands, considering the effect of thickness of the link, has been provided. Moreover, to improve the fracture tendency of the specimens, butterfly-shaped links, which varied in the middle length, were applied. The obtained results, which have been interpreted by considering the equivalent plastic strain value, prove that the shear panel behavior improves significantly when butterfly-shaped links are considered.

The pattern of neonatal gastro-intestinal perforation in upper Egypt

BackgroundNeonatal gastro-intestinal perforation [NGIP] is one of the major problems in pediatric surgical practice. Although the outcomes of neonatal surgery have improved markedly over the past decade the mortality rates of neonates with NGIP are still high. The aim of this study was to present the possible etiological factors, clinical findings, and operative procedures of NIP in our locality.ResultsA total of 34 neonates with NGIP were included in this study. The median age at presentation was (15.8 ± 7.0 SD) days. The median interval between presentation and surgical interference was (2.0 ± 1.1 SD).Necrotizing enterocolitis [NEC] was the commonest cause of neonatal gastro-intestinal perforation. The commonest site of perforation was the colon [11cases]. The overall mortality rate was 11 cases [32.4%]. The main cause of mortality was neonatal NEC [6 cases]. Eight cases [40 %] died out of 20 cases which the interval between the presentation and interference were more than one day.ConclusionsNeonatal gastro-intestinal perforations are still associated with high mortality rate in our institutions, and delayed diagnosis with increased interval between the presentation and surgical intervention are associated with increased mortality. In our locality, although NEC is the commonest cause of NGIP, the iatrogenic cause is relatively higher than reported.