Dome Type Research Articles

Design aspects of a fixed focus type Scheffler concentrator and its receiver for its utilization in thermal processing units

Fixed focus type Scheffler concentrators introduced by Wolfgang Scheffler are popularly used for different low to medium industrial process heat applications. These Scheffler concentrators are available in the standard sizes of 8 m2 and 16 m2. The present paper provides a detailed stepwise procedure for the design of a standing type 16 m2 Scheffler concentrator and its fixed focus receiver, intended to be utilized in a solar thermal processing unit for essential oil distillation at our institute. The dome type receivers of boiler steel grade material, SS-304, are selected for the present application. The diameter of the receiver is estimated based on the analysis of the image formed at the receiver of the Scheffler concentrator. The crossbar equations, seasonal parabola calculations and aperture area calculations for the Scheffler concentrator have also been presented in the paper. The geometrical concentration ratio for the Scheffler reflector dish and receiver system are also evaluated for any given day of the year. The design procedure presented in the paper can be used for designing any suitable size Scheffler concentrator and its receiver as per the energy requirement of the application.

Features of the structure and formation of oil deposits in the sediments of the Bashkirian stage of small oil fields on the western slope of the South Tatar arch

Oil-bearing carbonate complexes of the Bashkirian stage of low-amplitude brachianticlinal structures on the western slope of the South Tatar arch are considered. It has been established that the prospects for oil production are associated with the upper parts of the sections, where layers of algal-foraminiferal limestones - packstone occur, overlain by dense clayed mudstone-wackestone limestones. Oil deposits of the dome type, hydrodynamically isolated, are under the pressure of regional or bottom waters. Cap rocks, reservoir rock, water-oil contacts are clearly distinguished in the structure of deposits. The formation of the main elements of oil fields occurred at the stage of sedimentation due to eustatic fluctuations in the level of the epicontinental sea basin. At the stage of transgression, the formation of future reservoir rocks took place, at the stages of regression - cap rocks. The reservoir rocks acquired high capacitive-filtration properties during the period of migration of water-oil fluids. At this time, the dissolution of micritic calcite cement took place, the removal of the dissolved substance outside the reservoir bed, the filling of the void space with oil, and the displacement of residual water to the wings of uplifts. The next stage of transformation of reservoir rocks is associated with the processes of natural waterflooding of oil deposits. The penetration of regional pressure water into the oil reservoir contributed to the formation of local zones of water-oil contacts. Due to the oxidation of hydrocarbons inside the oil deposits in the OWC zone, bituminous and water-bearing subzones were formed. In the first one, intensive leaching of calcite occurred with the simultaneous formation of patchy-banded segregations of calcitized rocks, healing of cavern cavities with diagenetic dolomite and anhydrite. In the second subzone, the process of dissolution of bituminous films on the walls of caverns was going on, accompanied by secondary cementation of pre-existing cavities with diagenetic calcite and chalcedony, which determined the light color of reservoir rocks.

Morphological variety of capillary ends invading the epiphyseal plate in rat femora using scanning electron microscopy with osmium maceration

ObjectivesThe function of capillary ends at the epiphyseal plate has been actively investigated. However, their morphology is still poorly understood. This study was designed to examine the capillary ends invading the epiphyseal plate three-dimensionally by scanning electron microscopy and discuss the relationship between their morphology and function. MethodsDistal halves of the femora of eight-week-old male Wistar rats were used. The specimens were divided into two groups for transmission and scanning electron microscopy. For transmission electron microscopy, sagittal ultrathin sections were routinely prepared after the demineralization of the specimens, and the chondro-osseous junction was examined at the epiphyseal plate. For scanning electron microscopy, the specimens were sagittally freeze-cracked, osmium-macerated, and routinely processed. ResultsEndothelial cells of capillary ends had fine fenestrations, and hence they were distinguishable from perivascular cells (also known as septoclasts). Based on the outline and the presence or absence of pores, the capillary ends were divided into four types: closed dome, closed spire, porous dome, and porous spire. The two dome types generally occupied more than half of a lacuna, whereas the two spire types generally occupied only a small part of a lacuna. The porous types engulfed cellular remnants, indicative of degraded chondrocytes, via their pores. Some of the spire types penetrated the transverse septum. ConclusionsThe morphological variety of capillary ends reflected their functional variety. Observations suggest that the capillary ends change their morphology dynamically in response to various functions, including the removal of degraded chondrocytes and perforation of transverse septa.

PEMBERDAYAAN MASYARAKAT MELALUI PELATIHAN PENGOLAHAN LIMBAH TERNAK MENJADI ENERGI TERBARUKAN (BIOGAS) DI DESA LA’BO’

La'bo 'Village is one of the villages in North Toraja Regency. It is located about 8 km from the city of Rantepao. The people live as farmers. In addition, generally every household raises livestock in a pen at the back of the house. Manure from each livestock pen is disposed of freely, causing an unhealthy odor around the house. To solve the pollution problem, a training was conducted for the La'bo 'community to build a biogas installation as a tool to properly process livestock manure and provide added value to the community. To build a biogas installation, training is carried out using the on-job training method. The community is invited to work directly to build the installation together so that they can receive the knowledge and skills from this waste treatment technology. The training to build a biogas installation was carried out in collaboration with the Marante Tampang Allo Farmer Group and the Biang Farmer Group. From this training, the community has gained knowledge and skills to build and manage livestock waste into biogas. The result of this collaboration with farmer groups has succeeded in building 2 units of biogas installations with a capacity of 4 m3 of the fixed dome type. With the construction of the biogas installation, the air pollution around the house becomes healthier and the demand for LPG for each household has been replaced by biogas produced from the biogas installation

A Numerical Investigation of the Structural Performance of Double-layered Grid Domes Using Software Packages

In the 21th-century, large exhibitions halls covered by domes were constructed. Development of domes promoted by using metal structures, which has opened a new era for civil engineers in connection with the decision of maintenance problems of high strength and weight reduction of structures. Grid domes are a preferred structural form of roofs coverage. The paper aims to study the structural performance of double-layered grid domes using SAP2000 (v.14) and ETABS18. Four different types of double-layered grid domes considered in this work were the Schwedler dome (Type 1), three-way grid dome (Type 2), grid dome with different layers (Type 3), and grid dome with hexagonal patterns (Type 4). The configurations of grid domes were generated by Formian program software. The static linear analysis and design of mentioned grid domes were done and different load cases and their combinations were applied according to ASCE 7-10. It was observed that a double-layered grid dome with different layers (Type 3) was the most efficient in structural performance because the density of members per joint gave a very good distribution of axial forces distribution of the whole dome and then minimized the axial force in members and vertical deflections. The present study indicates that further detailed studies of the subject may lead to a more precise understanding of the performance of grid domes subjected to different load cases and this may bring about increased structural safety and serviceability and the economy in cost constructions.

Parametric study of the factors affecting the structural performance of braced domes subjected to gravity loads

Nowadays, single-layer braced domes are widely used by architects and engineers. The strength, economy, and fast installation were the main reasons for spreading this system around the world. The architectural design constraints of a dome impose structural challenges for the design engineer, especially when the span is large, with a small aspect-ratio or heavy design loads. Therefore, the structural engineer looks for different methods to strengthen the single-layer braced dome. This paper studied three different methods for improving the structural performance of the single-layer braced dome, including the grid-density, the member geometry (size), and the bracing systems with double-layer. A total of 96 finite element models were analyzed and designed using SAP2000 commercial software. Four main types of braced domes were studied, including Schwedler, Ribbed, Geodesic, and Kiewit-6. Two different types of joint connections were modeled (i.e., rigidly-connected and pin-connected). In addition, all models were pin-supported at the bottom ring and subjected to static gravity load only.The results indicated that the joint rigidity had a significant impact on the linear buckling load and a minor effect on the maximum displacement and internal forces. Furthermore, it was found that the increase in grid-density, enlarging member size, or using bracing systems significantly improved the structural performance, but at the expense of increasing the of a single-layer brace dome 's weight.

The Design of the Patellar Component Does Not Affect the Patient-Reported Outcome Measures in Primary Posterior-Stabilized Total Knee Arthroplasty: A Randomized Prospective Study

This randomized comparative study was conducted to investigate the outcomes of patellar resurfacing with a medialized dome or an anatomical type in patients receiving primary unilateral posterior-stabilized TKA. Between March 2019 and January 2021, 98 knees were randomly assigned to receive patellar resurfacing by a medialized dome type (group D, 49 knees) or an anatomic type (group A, 49 knees). The primary outcome was the Knee Injury and Osteoarthritis Outcome Score. The secondary outcomes were the Western Ontario and McMaster Universities Osteoarthritis Index, Feller’s patella score, the Kujala anterior knee pain score, knee joint range of motion (ROM), and postoperative complications, including periprosthetic patellar fracture, patellar tilt angle, and lateral patellar shift. Patient-reported outcomes were not significantly different between the two groups. The ROM of the knee joint was significantly better in group A at six months after surgery (p = 0.021). No complications such as patellar fractures were observed. The anatomic type of patellar component showed a significant improvement of the patellar tilt angle after surgery compared with the medialized dome type of component. However, there were no significant differences in patient-reported clinical outcomes between the two groups during the follow-up period of 12 months.

Thermal and Structural Analysis of Different Piston Geometries of Compression Ignition Engine

Improvement in performance of the diesel engines is carried out by focusing on several parameters. One among these is piston which undergoes higher thermal loads and thermal stresses during its entire working cycle and duration. Therefore, it is necessary to analyse the stresses that the piston can be able to withstand and give its contribution to maximize the engine performance. In this study, four different piston shapes were considered namely, flat, dome, cup and bowl type pistons. 3D models were developed for these pistons and simulations was carried out in the ANSYS at steady state conditions using finite element method (FEM). Based on the investigations, it was observed that the maximum temperature distributed was nearly same in all the types of pistons as 1133K which appeared near the combustion area. The thermal stress and total deformation values of the piston was found to be lesser for the flat and dome types of pistons. Based on the data obtained for thermal stress, temperature distribution, heat flux and total deformation, it can be suggested that flat or dome type pistons can be considered for use in the IC engine to maximize the performance of diesel engine.

Effect of hydraulic retention time on some properties of liquid organic manure produced in locally originated anaerobic digester

The study was conducted at the field of poultry at the Agricultural Advisory Office , College of Agriculture , University of Basra in (Karmat Ali), where the anaerobic digester of the fixed dome type bioreactor model was designed and installed on site to be exploited, Fresh poultry droppings as raw material for producing liquid organic manure through anaerobic fermentation and taking into account the qualitative characteristics of the maturation of the fermented materials inside the anaerobic digester during periods of Hydraulic Retention Time 0, 2, 4, 6, 8 weeks The averages were compared using the averaged least significant difference (RLSD) at the 5% level.. And the results showed that the periods of Hydraulic Retention at 8 weeks is the period best which the fermented material is decomposed in anaerobic digestion. An organic manure with positive qualitative characteristics in terms of pH 7.02, electrical conductivity EC 17.43 dS m-1 organic carbon 318.27 g kg-1 total (nitrogen, phosphorous, potassium) recorded 38.03, 13.70 and 25.25 g kg-1 Straight, the ratio of organic carbon to total nitrogen was 8.37, the total solids was 6.80% and The chemical oxygen requirement (COD) 2150 mg L-1. Paper cited by a master's thesis of the first author

Real-time Structural Stability of Domes through Limit Analysis: Application to St. Peter’s Dome

ABSTRACT A digital tool is presented and made available for the rapid structural assessment of historic masonry domes. It is especially suited for masonry domes that present long meridian cracks; ergo partitioned slices governed by a pushing failure mode. The proposed procedure considers a Heyman’s no-tension mechanical model that has been implemented within a user-friendly visual programming environment. The numerical approach includes parametric modelling of the failure mechanism that allows exploring the domain of solutions using the kinematic theorem of limit analysis. A heuristic search method is subsequently adopted to refine the geometry of the collapse mechanism and to compute the value of the horizontal trust. Validation of the results has been achieved considering St. Peter’s dome. As reported in the literature, the behaviour of this dome shifted from a rigid shell-type — stiffened by hoop stresses — towards a pushing type of dome partitioned by long meridian cracks. Unlike time-consuming and advanced methods of analysis, the present procedure allows the users to perform a structural assessment of a historic masonry dome in a few seconds and offers the possibility of including: (i) the dome’s drum in the analysis, if applicable; and (ii) rings as strengthening measure, whose number, position (dome or drum) and material (capacity) are user-defined. The goal is to make the tool easily and freely available at the disposal of students, researchers, and structural engineers.

The Frequency Characteristic of Silicone Domes in Receiver in the Canal Hearing Aids.

There are several types of silicone domes in receiver in the canal hearing aids (RICs), which have different occlusion levels. However, the frequency characteristics of each type of silicone dome are unclear. This study aimed to determine the frequency characteristics of three types of silicone domes (open domes, double-type power domes, and tulip domes) in RICs. This is an interventional study. In total, 11 participants with a normal sense of hearing were prospectively enrolled. Participants were fitted with hearing aids, which were adjusted to similar settings, and only the silicone domes were changed. The acoustic gain of hearing aids was adjusted to 20 dB in the range of 250 Hz to 4 kHz using the 2-cc coupler. We measured the real-ear aided gain (REAG) for each type of silicone dome. In each frequency, we statistically compared the REAG of each type of dome. Acoustic gain using the Open Fit coupler of each type of dome was also measured. The REAG was obtained with no leakage with open domes only at 2 kHz, and with tulip domes and double-type power domes in the range of 1 to 2 kHz. Double-type power domes obtained significantly higher REAG than tulip domes at 250 and 500 Hz. Under the Open Fit coupler, all types obtained higher acoustic gain than the REAG. This study provides the analysis of the frequency characteristics of silicone domes in RICs. The highest degree of occlusion was observed in double-type power domes, followed by tulip domes, and the lowest was observed in open domes.

Control equation of feasible pre-stresses and feasibility of new types of rotating surface cable domes

The study proposes the control equation of feasible pre-stresses and the corresponding solving algorithm, and verifies three new types of rotating surface cable domes. First, the study takes that the structural displacements are zero as the control equation of feasible pre-stresses, and proposes a novel solving algorithm based on that target values of structural displacements are zero. Second, the study develops three new types of cable domes with different rotating surfaces, which have different Gaussian curvature. And then their feasibility in nature are verified through determining their feasible pre-stresses using the solving algorithm. Last, their ultimate bearing capacity under full and half-span vertical loads are investigated. The results indicate that the solving algorithm can determine the feasible pre-stresses efficiently and accurately, and three new cable domes proposed in the study are feasible in nature, and they have sufficient stiffness to bear external loads. The appearance of the three new rotating surface cable domes extends the cable domes from the traditional positive Gaussian curvature to the zero Gaussian and negative Gaussian curvature.

Design of a Community-Based Anaerobic Digester for Sustainable Solid Waste Management in Ile-Oluji Ondo State Nigeria

Aim: A Community-Based Anaerobic Digester was designed in this study for sustainable solid waste management in Ile-Oluji, Ondo state Nigeria.
 Methodology: Waste samples were collected from selected households for a period of one month and the components and percentage composition were determined. Afterwards, the physico-chemical characteristics of the substrate was investigated and the result used to design a community-based anaerobic digester.
 Results: The quantity, components and characteristics of waste generated was determined. The rate of waste generation was found to be 0.2kg/capita/day while the organic fraction of the total waste generated was found to be 55.7%. Physico-chemical characterization of the substrate was also investigated. The pH was found to be 6.36 ± 0.18, while the alkalinity 692.81 ± 78.62. The moisture content was found to be in the range of 71.20 ± 4.63%. Total solid was in the range 38.91 ± 5.25 while volatile solid was found to be 26.44 ± 2.83. carbon oxygen demand was found to be 834.33 ± 12.61, total phosphorus was in the range 4.20 ± 0.33. The Carbon on a dry weight basis was found to be in the range 60.41 ± 2.38, while nitrogen was found to be 4.79 ± 1.03. The C/N ration was found to be 21.61. The biogas yield ranged from 0 – 320 cm3 and 0 – 380cm3 per litre of substrate for biodegradable-only samples and biodegradable-cow dung samples respectively, for a forty days period of retention. The cylindrical dome type biogas digester was chosen for this study because of its simplicity in design and maintenance coupled with lower set up cost. The optimum volume of hydraulic chamber and gas storage chamber were designed to be the same as 850m3. Volume of fermentation chamber and sludge layer were calculated to be 2014m3 and 246m3 respectively, while the height and diameter of the fermentation chamber were 7m and 17m respectively.
 Conclusion: Anaerobic digestion of the biodegradable fraction of solid waste is a viable alternative that government and non-government organizations can key into for the improvement of public health especially in developing countries. The standardization of digester design parameters may pose challenges because of varying climatic conditions and complex socio-economic factors across different geographical contexts. Solutions may have to be adapted and localized to achieve a sustainable world.

Geometrical Analysis of Oval Domes through Architectural and Mathematical Methods. The Case of the Dome of the Camarín of the Virgin of El Puig (Valencia, Spain)

ABSTRACT The study of oval geometry domes encompasses a broad and interesting field of research that can be approached from multiple points of view. This paper shows the multidisciplinary approach developed for the analysis of the geometry of this type of domes from the architectural and mathematical points of view. This research paper focuses on the geometric study of the dome of the Camarín of the Virgin, of the Monastery of El Puig de Santa Maria (Valencia, Spain), an emblematic building of Valencian history and architecture. It begins with a survey by means of a multi-image photogrammetry and other surveying methods obtaining a point cloud that has served as a base for the geometric analysis. The approach to this analysis is through graphic and mathematical gradients, which allows to determine the graphic layouts and equations that best define the shape of the dome as well as drawing up a geometric construction hypothesis, which is consistent with the data. The conclusion obtained is that the dome is generated by an elliptical plan and five-centered oval arches in the vertical sections and the methodological process developed can applied to other cases.

An Exploratory Study on the Impact of Collective Immersion on Learning and Learning Experience

This paper aims to explore the impact of a collective immersion on learners’ engagement and performance. Building on Bandura’s social learning theory and the theory on the sense of presence, we hypothesise that collective immersion has a positive impact on performance as well as cognitive, emotional and behavioural engagement. Ninety-three participants distributed in four conditions took part in the experiment. The four conditions manipulated the collective and individual dimensions of the learning environment as well as the high and low immersion of the learning material. The two conditions that offered a high immersion setting used two types of the novel immersive dome: a large one for collective immersion and a small one for individual use. All participants were presented with the same stimuli, an 8-min-long video of a virtual neighbourhood visit in Paris in the 18th century. The participants’ reactions were measured during and after the task. The learning outcome, as well as the cognitive, emotional and behavioural engagement, were measured. Final results showed that collective immersion learning outcomes are not significantly different, but we find that collective immersion impacts the cognitive, emotional and behavioural engagement of learners.

Visual complications after coil embolization of internal carotid artery aneurysms at the ophthalmic segment.

Coil embolization of aneurysms of the ophthalmic segment of the internal carotid artery (ICA-OphA ANs) has potential risks of visual complications. We analyzed this risk and focused on the relationship of the ophthalmic artery (OphA) origin with the aneurysm neck. From January 2003 to April 2018, 179 unruptured ICA-OphA ANs were treated with endovascular surgery in our institution. Two ruptured and four aneurysms with missing data were excluded. Finally, 173 unruptured aneurysms were included in this study. The aneurysms were classified into three groups according to the location of the OphA origin: Separate, Shared, and Dome type. We retrospectively assessed visual complications based on the relationship between types of aneurysm and postoperative angiographic findings for the OphA. Visual deficits remained permanent in eleven cases (6.4%). In the Dome type, visual complications were significantly more frequent compared to the Separate type. Change in the OphA flow was significantly associated with a higher complication rate of 2.9%, but patients with changed OphA flow had a significant rate of 7.5% (p = 0.020). We found no significant difference in the incidence of visual complications concerning the use of perioperative antithrombotic therapy. The location of OphA origin regarding the aneurysmal neck and postoperative OphA flow were significantly correlated with the visual outcome after coil embolization for ICA-OphA ANs. Post-procedural flow in the OphA was an important factor affecting the rate of ischemic retinal complications. Retinal embolic events occurred with preserved flow in the OphA, albeit at a lower rate.

Performance of 500 Liter Stainless Steel Portable Biogas Anaerobic Digester with Agitator Designed for the Tropical Developing Country

This document it is established that 2 types of biogas anaerobic digester that usually found in developing country. First type is fixed dome type of anaerobic digester and secondly is floating drum biogas anaerobic digester. Both of this type have draw back that the anaerobic process is not completed with agitation process that yield low rate of biogas production. Other serious problem is the release of slurry cannot optimal. Some of the slurry will still remain stay in the anaerobic digester especially scum. To drain and cleaning the fixed dome or floating drum biogas anaerobic digester is mandatory to be done regularly that consume time and cost. The fixed dome types as well as floating drum type are usually not portable which cause no possibility to relocate in the new site. It is the purpose of this work to introduce portable biogas anaerobic digester that suitable for developing country with volume of digester around 500 liter of slurry. The requirement of agitator is facilitated, and the anaerobic digester is possible to be operated in batch system or continuous system. The material that is used for anaerobic digester is stainless steel 304 with tungsten inert gas welding technology that is used for the manufacturing. With this design the anaerobic digester are easy to be maintenance. The batch system can keep producing biogas until 52 day with total production of biogas around 3320 liters. The continuous system was conducted by releasing for about 5 liters slurry from the outlet and after that filled with new slurry with stirring with agitator was conducted for about 10 minutes for 3 times in a day (morning, noon, and evening). The result for continuous system is a linear biogas production with rate biogas production is around 51.7 liter/day (1550 liter/30days).

Difference in patient-reported outcomes of various patellar component designs in total knee arthroplasty: A randomized clinical study.

This study investigated the clinical effects of different patellar components without being affected by the femoral component design in total knee arthritis (TKA) for patients with knee osteoarthritis (OA). In total, 48 patients with OA who met the criteria of the American College of Rheumatology for OA were enrolled and randomly assigned in a 1:1 ratio to two groups according to the usage of patellar component design for TKA (medialized dome type [dome group] or medialized anatomic type [anatomic group]). To evaluate the clinical outcomes for TKA, knee range of motion (ROM), pain intensity of 0-100 mm visual analog scale (pain VAS), and the Japanese Knee Osteoarthritis Measure (JKOM) score were obtained at baseline and year 1. The difference in knee ROM, pain VAS, or total JKOM score at year 1 was not significant between the dome and anatomic groups (p = 0.398, 0.733 and 0.536, respectively). Moreover, similar results were obtained for changes in knee ROM, pain VAS, or total JKOM scores from baseline. In both groups, the pain VAS and total JKOM scores were significantly improved at year 1. Both dome and anatomic groups in TKA are significantly effective for pain and function using the JKOM score. However, their efficacy did not differ, according to the JKOM score. Results of this study are rare information focusing on the patellar component design and provide one of the insights into the TKA clinical management.

Experimental - theoretical study of the stress-strain state of cable-stayed-rod systems of the dome type

The problem of determining forces and displacements in a spatial hinge-rod system with missing links under static loading is considered. Equilibrium equations and geometric relationships are written in matrix form. The calculated equations are not linear. To solve the equations, a technique is proposed that is not associated with assumptions regarding the structure of the system or the nature of the load, based on the fact that the displacements obtained by solving the linear part of the equations can be significantly improved by interpreting the nonlinear terms as a load, under which the system can be considered as linear. To test the theoretical assumptions and preconditions, an experimental study was carried out on a model made at a scale of 1:30 of a natural design. The analysis of the results obtained is presented.

Performance of Persian brick masonry discontinuous double-shell domes against earthquakes

Despite the fact that Iran is an earthquake prone country and most of its historical buildings are made of brick masonry that is weak in tension, a large number of domical buildings have been constructed all over the country since many centuries ago. Most of magnificent domes in Iran have survived severe earthquakes. The discontinuous double-shell dome has been widely used for important buildings such as mosques and churches. This type of dome provides the possibility of constructing high and large spaces in order to show magnificence and also accommodate a large number of people inside. In this paper, the structural performance of Persian brick masonry discontinuous double-shell domes against earthquakes has been studied. Different shapes of upper and lower shells have been studied. The domes have had spans of 12 m, 15 m and 18 m and a decreasing thickness from the base to the apex with an optimum apex to base thickness ratio. Domes have been analysed under earthquake load by the non-linear finite element method. The Willam-Warnke failure criterion has been used for brick masonry materials. In addition to parametric study, two existing discontinuous double-shell domes of the Imam mosque and Bedkhem church, and two existing single-shell domes of the Saint Mary church and Saint Stepanos monastery in Isfahan have been studied. The values of maximum stresses have been obtained for these domes. Obtained results indicate that selected earthquakes do not cause the failure of the studied domes. The induced stresses increase by increasing the span. The performance of domes is dependent on the geometrical shape of the upper and lower shells. The dome with a drop four-centred upper shell and a drop elliptical lower shell has the best structural behaviour.