Double Umbrella Research Articles

Effect of surface energy on the contamination characteristics of porcelain double umbrella insulators

To explore the influence of surface energy on the contamination characteristics of insulators, COMSOL Multiphysics software was used to simulate the contamination characteristics of XWP 2-160 insulators under wind tunnel conditions, and the rationality of the modified expression of the dynamic deposition model of the contaminated particles was verified. The change of contamination characteristics before and after changing the surface energy of insulators under natural conditions was simulated and analyzed. The results show that under the original surface energy (72 mJ/m 2) and low surface energy (6.7 mJ/m 2) with the increase in particle size, the contamination amount of an insulator surface area decreases first and then increases. When the wind speed is 2 m/s, the change in the particle size has the most pronounced effect on the amount of contamination. The amounts of contamination for the low surface energy are 64–75%, 60–95%, 55–91% and 54–78% lower than those for the original surface energy for particle sizes of 10, 15, 20 and 25 μm, respectively. For the same wind speed, when the size of contamination particles increases, the difference between the ratio of DC and AC contamination accumulation is gradually increasing because of the influence of the electric field force. From the perspective of the insulator preparation process, the development of low surface energy insulators can improve their anti-fouling performance.

Assessment of collapse mechanism of a High Speed Railway Tunnel (T341 Tunnel, Turkey)

Excavation and implementation of tunnel support system of T341 tunnel of Ankara-Sivas High Speed Train Project were completed recently. Throughout the tunnel excavation, serious stability problems occurred both in the entrance portal section and tunnel. The purposes of this study are to explain the failure mechanism and to propose a suitable support system for the section between Km: 341 + 040 - 341 + 114. Tunnel works were interrupted after the collapse, which occurred in a section of approximately 74 m between Km: 341 + 040 - 341 + 114. As a result of the collapse in the tunnel, local settlements emerged on the surface and it was observed that the effects of the collapse on the surface, as well. To surpass the collapsed section, extra reinforcements were performed by grouting taking place both at the surface and inside the tunnel. Afterwards, tunnel excavation was completed in relatively short stages by applying double umbrella system and rigid support system. Consequently, the causes of the failure, excavation and support system design and results of the numerical analyses are discussed.

Magnetic ordering of Ho and its role in the magnetization reversal and coercivity double peaks in the Ho3Fe5O12 garnet

Rare-earth based garnet system, Ho3Fe5O12 shows magnetization compensation phenomenon at Tcomp = 138 K and a magnetic transition at 50 K. In the present work, we reveal the physics of these low temperature magnetic transitions by carrying out detailed dc magnetization, ac susceptibility, neutron depolarization, and neutron diffraction studies. Interestingly, our dc magnetization study under low (≲ 50 Oe) magnetic fields has shown a previously unknown sign reversal of magnetization (below the Tcomp) that persists down to 5 K, the lowest measured temperature. Magnetic measurements under moderate fields between 50 Oe and 1 kOe reveal two compensation temperatures (in the range of 105 – 150 K depending upon the applied field value) leading to double magnetization reversals. Interestingly, for magnetic fields ≥ 1 kOe, these two compensation temperatures merge to a single Tcomp (=138 K). A modified Stoner-Wohlfarth model has been used to explain the asymmetrical nature of double peak around the Tcomp in the temperature dependent coercivity data. The ac susceptibility study supports the existence of both the transitions with an evidence of deep minimum at the Tcomp (138 K) and a broad peak at 50 K. Mesoscopic neutron depolarization study has revealed a zero domain-magnetization state at the Tcomp. Temperature dependent neutron diffraction study has revealed that Ho carries an induced moment above the Tcomp due to polarizing effect under the internal magnetic field of the two magnetically ordered Fe sublattices at 567 K, whereas a single umbrella type ordering of Ho sublattice moments appears below the Tcomp, resulting in the distortion of magnetic unit cell from cubic to rhombohedral symmetry. However, below 50 K, Ho3+ sites are divided into two inequivalent magnetic sublattices, having different moments and canting angles, and it leads to double umbrella type magnetic structure. Neutron diffraction study has revealed an asymmetric variation of the tetrahedral, octahedral, and dodecahedral sublattice moments resulting in a magnetization reversal at ~ 138 K which is very well supported by the mean field theory calculations. In the present study, we have resolved the ambiguity of magnetic ordering of the rare-earth (Ho3+) sublattice and its role in multiple magnetic transitions. The utility of such compensated ferrimagnetic materials in spin polarizers/analyzers and fast switching memory devices has been emphasized.

Magnetic study of the low temperature anomalies in the magnetodielectric terbium iron garnet

The anomalous magnetic properties at low temperatures of terbium iron garnet (TbIG) are analyzed and summarized using neutron powder diffraction (NPD) experiments together with high field magnetization, magnetostriction and specific heat measurements performed on single crystals. Reliable information at both microscopic and macroscopic levels is provided about the significant change of the double umbrella structure observed in the NPD results near 54 K. The positions of the observed maxima at 55–65 K in the paraprocess magnetic susceptibility along the three mean directions and paraprocess of the forced magnetostriction along the easy axis of magnetization 〈111〉 agree with the manifestations of the “low-temperature point” TB predicted by Belov at 58 K. However, the pronounced maximum at 57 K in the excess of specific heat in zero magnetic fields reveals that the Schottky effect causes anomaly at temperature close the TB point. The results are discussed and compared with previous magnetic, magneto-optical and magnetodielectric reports.

Computer Methods for Geometrical and Colorful Transition between Facial Prosthesis and Surrounding Tissues

This paper is to describe the method of fitting the facial prosthesis for the surrounding tissues not only in geometry but also in color. The method can be depicted as following: On the one hand, the iteration algorithm based on double umbrella operation can minimize the sum of the main curvature between the junction of the facial prosthesis and its surrounding tissue area, ensuring a smooth transition in geometry at the margin area of the facial prosthesis. On the other hand, with the areal 3D scanner, the point cloud with special structure can be acquired which can conform the texture map almost has no distortion. The method of solving the Poisson equation for the color field that best fits the color gradients was used, which can produce a seamlessly textured surface quickly. The phenomenon of the light and texture seam were greatly reduced. Some clinical applications showed that the resulted facial prosthesis can fit the patient’s appearance well.

Group theory analysis of the rhombohedral magnetic structures in rare earth iron garnets revisited

The representation analysis of Bertaut is used to enumerate all possible magnetic structures in rare earth iron garnets (RE3Fe5O12) for the RE and Fe ions on the 6e, 6e' and 12f, 2b, 6d Wyckoff positions respectively in the highest rhombohedral subgroup R3̄c of the cubic space group Ia3̄d. The basis vectors of the one-dimensional irreducible representation A2g lead to noncollinear magnetic structures of the RE moments which produce a better description than those based on the models of Wolf et al. Some results of the "double umbrella" structure found in our recent neutron powder diffraction studies of terbium iron garnet are reported.

Evaluation of directional drilling implication of double layered pipe umbrella system for the coal mine roof support with composite material and beam element methods using FLAC 3D

This study demonstrates possible scenarios of double-layered umbrella pipe system installed over a longwall take down room in a western coal mine, where holes are drilled and cased from an adjacent entry in advance of undermining. Finite difference analysis in FLAC 3D with strain hardening gob model is used because this method is a complex and rigorous way for solving boundary value problems, such stress and strain in a continuum and at an excavation boundary due to undermining. Support system was simulated with two different methods: composite material method and beam element method. We realized that the composite material method is very conservative compared to beam element method. Thus, in the rest of the simulation, we used the beam element method to investigate the effect of different angles of umbrella pipes on the roof support. To validate the modeling results, we compare the numeral modeling results with empirical formula widely used in subsidence calculation. Also, this computer simulation compared displacement of roof between in the presence and absence of this pipe umbrella support system. In this paper, we demonstrated that a relative stiffness increase ∼185% for a reinforced zone can decrease the displacement ∼ 12.5 cm (∼ 5 in.) in the longwall recovery room roof based on results from the equivalent stiffness method. This reduction is a substantial amount, which could be really beneficial to mine operators during mining processes.

Anomalous magnetic reordering in magnetodielectric terbium iron garnet at low temperatures

The paper deals with five topics: i) the single three-dimensional irreductible representation (Г 4 g =T 1 g ) of the paramagnetic space group Ia 3 ¯ d No. 230 is chosen according to the representation analysis of Bertaut for the interpretation of the neutron powder diffraction experiments performed on terbium iron garnet (Tb 3 Fe 5 O 12 ); ii) the use of the method of the “symmetry lowering device” of Bertaut in order to select the appropriate rhombohedral subgroup of Ia 3 ¯ d which allows to deal with the case where the cubic description provides an incomplete answer to the changes observed below 160 K in the ferrimagnetic structure around the [1 1 1] axis from the Néel model toward the “double umbrella” observed at 13 K; iii) the magnetic modes belonging to the one-dimensional irreductible representation A 2 g of the highest rhombohedral subgroup R 3 ¯ c No. 167 are able to describe the occurrence of its anisotropic character which steeply increases below 160 K due to the concomitant anisotropic effects; iv) the broad anomaly observed near 54 K in the temperature dependences of the components of both sublattices of the Tb 3+ ions in the Wyckoff positions (6e) and (6e′) is explained partially on the basis of the concept of Belov of the strong paraprocess which has been termed “exchange-enhanced paramagnetism” at the so-called “low-temperature point” ( T B ); v) the results are related to the magnetodielectric effect in low magnetic field and to the significant coupling between exchange magnons and ligand-field excitations reported recently in this compound. • We examine the changes of the “double umbrella” in TbIG using neutron diffraction. • Symmetry arguments of Bertaut clarify suitable rhombohedral space group at 13 K. • Its opening leads to an increasing of anisotropy of the Tb components below 160 K. • The “low-temperature point” of Belov explains partly its intricate behavior near 54 K. • A relationship with the magnetodielectric effects revealed in this garnet is discussed.

Perventricular device closure of a large residual perimembranous interventricular septal defect after previous surgical correction

A 21 years albanian patient was referred with important residual left to right shunt. He was undergone 7 years before conventional surgical correction of a perimembranous ventricular septal defect (VSD). The patient underwent sternotomy and perventricular device closure of the residual employing a 16 mm multifenestrated atrial septal defect occlude, which was positioned through the anterior wall of the right ventricle. across the defect. The previous autologous pericardial patch was compressed into the double umbrella device. We may conclude that perventricular device closure can employed successfully in patients with residual perimembranous VSD after previous surgical repair as an alternative to the conventional surgery with excellent hemodynamic and postoperative outcome. Such a technique should be part of the surgical armamentarum.

Hemólisis aguda post implante de Paraguas de Rashklind en Ductus Arterioso Persistente. Tratamiento Quirúrgico.

We report a case of an acute mechanical haemolisis in a woman of 50 years old that ocurred after a percutaneous closure of a patent ductus arteriosus by a Rashkind double umbrella prosthesis.Surgical removal of the device using Cardiopulmonary bypass and ligation of the duct were required before haemolisis was abolished.

Symmetry analysis of the magnetic structures in TbIG and Tb:YIG at low temperature

Magnetic structures in TbIG and in terbium-yttrium ferrite garnet Tb0.37Y2.63IG are revisited using Bertaut' representation analysis for the highest crystallographic subgroups of the space group Ia 3̄ d with the wave vector k = 0. Powder neutron diffraction experiments performed only on TbIG are combined with single crystal magnetization measurements. Three field-induced phase transitions are observed at 4.2 K in high magnetic fields up to 150 kOe along the <001> direction while <111> remain the easy axis of magnetization. New parameters of the previous Tb3+ double umbrella magnetic structure are found at 5 K in a modified model of the rhombohedral subgroup R3̄c . From magnetizations on Tb0.37Y2.63IG single crystal, non collinear magnetic structure is evidenced at 4.2 K along the easy axis <001>. The parameters of a 'square pyramid' umbrella are predicted using both the basis vectors of the tetragonal subgroup I41/acd and a model based on the effective spin Hamiltonian with anisotropic exchange G̃ and magnetic g̃ tensors with the requirement gyGy < gzGz ≪ gxGx. Anisotropy of magnetization is observed by comparison with the hard axis <111> below Ta = 80 K where the earlier spin reorientation phase transitions <001>↔<uuw>↔<111> occur between T1 = 40 K and T2 = 140 K. The basis vectors of the monoclinic subgroup C2/c are tentatively proposed for the low symmetry angular phases <uuw>. All results are compared to previous works.

Lung Compliance and Airways Resistance in Healthy Neonates

Traditionally, closure of ventricular septal defects (VSDs) has been a surgical procedure, however in 1988 Lock et al. [1] ushered in the era of percutaneous ventricular septal defect closure when they reported on the results of transcatheter VSD closure using the Rashkind double umbrella device in six patients with congenital and acquired VSDs. These investigators also reported on the technique of using an arteriovenous wire loop as part of the closure that is still in use today. Since their initial report, multiple devices other than the Rashkind device have been used to close VSDs including devices that are specifically designed for this purpose. Percutaneous VSD closure has therefore become an acceptable alternative to surgical closure of muscular, traumatic, postoperative residual and post-infarct VSDs. Transcatheter device closure remains controversial for perimembranous VSDs however secondary to the risk of heart block. The purpose of this paper is to report on the current status of percutaneous closure of VSDs.

Fully biodegradable septal defect occluder—A double umbrella design

Current percutaneous devices for septal defect treatment are made of nondegradable metallic and synthetic fabric materials. These devices are not ideal due to risks of future complications from device erosions and potential obstructed access for future transseptal procedures. The biodegradable double umbrella device was made of fully biodegradable polymers, featured with two discs connected with a stretchable stem. The devices were inserted across the PFO model created on Yorkshire swines through a short sheath by open thoracotomy. Fluoroscopic imaging and echocardiography obtained during the 1-month follow-up study period showed that the devices were in stable position with no shunt. The in-vitro degradation study and post-mortem explantation confirmed that the devices have good integrity and mechanical strength during the 1-month trial. Furthermore, the devices appeared to be well endothelialized after 1 month. These results showed clearly that it is feasible to replace the current nondegradable devices with the new generation biodegradable PFO occluders. This work studied and proved the feasibility of interventional closure of patent foramen ovale (PFO) with a fully biodegradable device, that we call the "double umbrella" (DU) for its symbolic design. © 2010 Wiley-Liss, Inc.

Muscular ventricular septal defect closure with Gianturco coil at Soetomo hospital (a case report)

Ventricular septal defect (VSD) is the mostcommon congenital heart disease (CHD)in children.1'2 It occurs in 1.5 to 3.5 of1,000 live births and constitutes 20% ofcongenital cardiac defects.1 The VSD may be small,medium or large and is classified based on its locationin the interventricular septum. There are four types ofVSD, i.e., perimembranous (80% ofVSDs), musculartype (5% to 20%) inlet or AV canal type (8%), andfinally, subpulmonary (5% to 7%).1-4 When multiplemuscular defects are seen, it is often referred to as"Swiss-cheese" type of VSD. 1•2The management strategies, which consist ofmedical, surgical and intervention techniques, depend toa large degree on the size of the VSD.1-4 Approximately40% of VSDs spontaneously and completely closed,with closure rates approaching 80-90% by age 2 years.2Indication ofVSD closure are symptoms of heart failure,left heart chambers overload and history of endocarditis.The surgical approach is considered gold standard butit is associated with morbidity and mortality, high cost,patient discomfort, sternostomy and skin scar.3 Since1988, percutaneous techniques have been conductedin order to reduce those drawbacks of surgery. Morerecently, percutaneous techniques and devices havebeen developed specifically for closure of muscularVSD (m VSD) and perimembranous VSD (pm VSD)using either the Rashkind double umbrella, the BardClamshell, the Button device, theAmplatzer septal, duct118 • Paediatr lrulones, Vol. 50, No. 2, March 2010or muscular VSD occluder, or the Gianturco coils.3AGianturco coils have been widely used to closeunwanted vascular communications and small- tomoderate- sized patent ductus arteriosus, withexcellent closure rates. In 1999, Latiff et al successfullyused this coil to close multiple muscular VSDs in a10-month old boy. Thus, percutaneuos closure ofVSDs using Gianturco coils is a feasible, reasonablealternative to surgery.5'6 We report a case of fouryear-old girl with muscular VSD who underwentcardiac catheterization and transcatheter closure withGianturo coil in Dr. Soetomo Hospital, Surabaya.

Optimising device imaging in atrial septal closure by three-dimensional transoesophageal echocardiography

Percutaneous closure of atrial septal defect and patent foramen ovale has become a routine interventional procedure.1 Two main types of device are currently used: the double umbrella and the double...

Shallow Tunnelling in Soft Ground – Influence of the Chosen Support System on the System Behaviour

AbstractThe Brenner corridor is part of the new North‐South European rail link for high‐speed trains and combined transport services connecting Munich in Germany and Verona in Italy. As the Lower Inn Valley in Austria is narrow and densely populated with towns lined up along the Inn river, the characteristics of the alignment of the new route is that 83 % of the 41 km long Unterinntal route will run underground. The new route includes the tunnel Vomp‐Terfens which is about 8 km long and is constructed through different types of ground – competent rock and soft ground (quaternary sediments such as ground moraine and gravel). The applied support measures varied from 150 mm steelfibre reinforced shotcrete in the hard rock sections (dolomite) to 300 mm reinforced shotcrete lining with advance support consisting of double layered pipe roof umbrella in the sections with low overburden and layers of potentially unstable gravel.Two advance support systems were used in similar ground conditions – forepoling with spiles and a pipe roof umbrella support. This paper deals with conclusions drawn from the monitoring results in the tunnel, on the surface and from the evaluation of a horizontal inclinometer which was installed in one of the pipe roofs. The main objective pursued by the authors is the comparison of the mode of loading and its effect on the overall system behaviour, not an evaluation of the “advantages” or “disadvantages” of the two different types of advance support systems. In the authors' opinion there are always “two plus” possibilities to solve a tunnelling task – the chosen solution depends on a variety of factors such as the given geotechnical boundary conditions, the adopted safety level and economic considerations.

Closure of a persistent ductus arteriosus Botallo without thoracotomy

A persisting ductus arteriosus (PDA) was closed with the Rashkind occlusion system in 15 patients (12 children, aged 1.0 to 10.8 years, and three adults, aged 21, 33 and 56 years). The method consists of the implantation of a double umbrella of polyurethane foam mounted on platinum or steel wire introduced into the PDA via a transport catheter, the ductus being closed by thrombosing and epithelialization of the implant. The mean diameter of the PDA (as measured in the lateral aortogram) was 2.4 (1.4-5.3) mm. There were no complications of the procedure, nor any embolization or other serious complications. The PDA was completely occluded in eight patients, while a residual shunt remained in seven. In the oldest patient, aged 56 years, who had a residual shunt, increasing haemolysis required surgical closure of the ductus with a pericardial patch. These results indicate that, for patients weighing over 5 kg and with a ductus diameter of less than 10 mm, the closure method after Rashkind is a sparing and only slightly invasive procedure.

Interventional closure of postpneumonectomy bronchial pleural fistula with a self-expandable double umbrella–shaped occluder knitted with nitinol shape memory alloy

Interventional closure of postpneumonectomy bronchial pleural fistula with a self-expandable double umbrella–shaped occluder knitted with nitinol shape memory alloy

Surgical device closure a new technique of ASD closure

Conventional approach of atrial septal defect (ASD) closure with cardio pulmonary bypass using mid sternotomy, minimally invasive or endoscopic technique is time tested. We decided to use custom made device with direct minimally invasive approach without cardio pulmonary bypass. Percutaneous transfemoral route using custom made device is a well established procedure performed by interventional cardiologist with occasional trauma and vessels. We performed the procedure in 3 patients of secundum ASD deemed adequate for device closure. We used a mini Right anterior thoracotomy approach using a double umbrella device which was implanted through direct Right Atrial puncture. In two patients we were successful in deploying the device. The proedure lasted 30 minutes with small infra Mammary scar and the post operative period was uneventful. In the third case where our attempt at surgical device closure failed the inferior margin was only one mm. The optimal size device kept slipping into the right atrium when the guide-wire was tugged after final deployment. The placement of an oversize device distorted the mitral valve, may causing regurgitation. We think that this is a simple and safe technique of secundum ASD closure without cardio pulmonary bypass.

Iatrogenic left internal mammary artery–coronary vein anastomosis treated with covered stent deployment via retrograde percutaneous coronary sinus approach

Percutaneous treatment of acquired coronary fistula with covered stent Acquired aorto-coronary fistulae (ACF) is a rare complication of coronary artery bypass graft (CABG) surgery. Surgical repair has been generally recommended, but percutaneous techniques have also been described; coils were used primarily in smaller fistula while double umbrella or vascular occlusion devices were used in larger ones. To the best of our knowledge the use of coronary covered stent has never been reported. A 73-year-old man underwent CABG in November 2004 for unstable angina and left internal mammary artery (LIMA) was anastomosed to left anterior descending (LAD) coronary artery. Three months later he underwent a control angiogram to check for the reappearance of effort angina, which demonstrated an inadvertent LIMA-great cardiac vein (GCV) anastomosis. After discussions, an attempt to close the ACF with implantation of a covered stent was performed. Using a percutaneous right internal jugular vein approach, coronary sinus was selectively cannulated and a 0.014-in. coronary guide wire was advanced selectively to the GCV, then a covered stent was deployed across the anastomotic site, obtaining the immediate occlusion of the ACF. No contrast medium flowed into the distal part of the GCV at the reinjection of the coronary sinus and a selective injection into LIMA showed the absence of flow through LIMA, confirming the occlusion of the anastomotic site. We have demonstrated successful occlusion of an iatrogenic ACF by using percutaneous stenting of GCV with covered stent via coronary sinus approach, which seems to be technically less demanding, safer, and time sparing.