Number Of Ribs Research Articles

Multi-objective optimization of disc brake structure based on heat transfer performance

As an important basis for its structural optimization design, the heat transfer performance has a key influence on the reliability of automobile brake. Based on the finite element method, the transient heat transfer of automobile disc brake is analyzed under the condition of dynamic convection heat transfer coefficient. According to the simulation results, the CCD (Central Composite Design) sampling scheme is used to transform the optimization variable and target variable into multiple design points in the decision space. The optimization variable includes the total thickness, the height of the ventilation slot, the angle between the sides of the ribs, the number of ribs while the target variable includes the mass and temperature peak. According to the multiple quadratic regression model, the response surface function is constructed, and the approximate model of optimization analysis is obtained. The error analysis shows that the response surface function is equipped with good fitting accuracy. In order to facilitate the extremum search, the optimization of the quality is transformed into the constraint condition, and the multi-objective optimization problem of the brake disc is transformed into the single objective optimization problem. Through the sequential quadratic programming method, the Pareto optimal solution set of the optimal mathematical model is found. The results show that the temperature peak value is reduced by 7.8 % under the condition where the quality of the ventilation plate is basically unchanged. By weighting the Pareto optimal solution sets of different quality intervals, a good result evaluation of ventilation panel optimization is achieved.

A Polymorphing Wing Capable of Span Extension and Variable Pitch

This paper presents the development of a novel polymorphing wing capable of Active Span morphing And Passive Pitching (ASAPP) for small UAVs. The span of an ASAPP wing can be actively extended by up to 25% to enhance aerodynamic efficiency, whilst its pitch near the wingtip can be passively adjusted to alleviate gust loads. To integrate these two morphing mechanisms into one single wing design, each side of the wing is split into two segments (e.g., inboard and outboard segments). The inboard segment is used for span extension whilst the outboard segment is used for passive pitch. The inboard segment consists of a main spar that can translate in the spanwise direction. Flexible skin is used to cover the inboard segment and maintain its aerodynamic shape. The skin transfers the aerodynamic loads to the main spar through a number of ribs that can slide on the main spar through linear plain bearings. A linear actuator located within the fuselage is used for span morphing. The inboard and outboard segments are connected by an overlapping spar surrounded by a torsional spring. The overlapping spar is located ahead of the aerodynamic center of the outboard segment to facilitate passive pitch. The aero-structural design, analysis, and sizing of the ASAPP wing are detailed here. The study shows that the ASAPP wing can be superior to the baseline wing (without morphing) in terms of aerodynamic efficiency, especially when the deformation of the flexible skin is minimal. Moreover, the passive pitching near the wingtip can reduce the root loads significantly, minimizing the weight penalty usually associated with morphing.

Molecular and morphological evidence revalidates Acrobrycontarijae (Characiformes, Characidae) and shows hidden diversity.

We conducted a revision of the Neotropical genus Acrobrycon. A previous study synonymized the species, A.ipanquianus, distributed from the western portion of the Amazon River to the north-western region of the La Plata River Basin, and A.tarijae, with type locality in the Lipeo River in Bolivia. We revisited this result by collecting new morphometric, meristic, and genetic data (COI mitochondrial gene) for 24 individuals distributed along La Plata River Basin in Argentina, and discussed our results in the context of multiple biogeographic processes of isolation in that basin. Our results revealed a more complex history of diversification and geographic distribution across Acrobrycon species than previously suspected, probably associated with multiple biogeographic processes of isolation in La Plata River Basin. We present new evidence that led us to reconsider the validity of A.tarijae, which is distinguishable from A.ipanquianus by the number of vertebrae (37–39 vs. 41–42) and pleural ribs (12–13 vs. 14). These results were also supported by our molecular analyses that revealed a genetic divergence >4% between A.ipanquianus and A.tarijae. We also identified two main genetic clusters within A.tarijae: the first cluster consisted of specimens from the Bermejo, Pilcomayo, Itiyuro and Juramento river basins (northern Argentina); and the second cluster included specimens from the southernmost basins, such as the Salí River in Tucumán, Cuarto River in the province of Cordoba and the Quinto River in the province of San Luis. Our results suggest that the genetic structure observed in A.tarijae is the result of the type of drainage (endorheic vs. exorheic) and geographical distance.

Seismic behavior of FRP-concrete-steel double skin tubular columns with a rib-stiffened Q690 steel tube and high-strength concrete

Fiber-reinforced polymer (FRP)-concrete-steel double skin tubular columns (DSTCs) are a form of novel hybrid columns with a particular merit of lightweight due to the existence of the void core. Utilization of high-strength materials (e.g., high-strength steel (HSS) and high-strength concrete (HSC)) tubes in DSTCs amplifies the advantage of DSTCs by earning a further decrease in the dead weight. In this study, behavior of DSTCs with HSC and a rib-stiffened HSS tube (referred to as R-DSTCs in this paper) under seismic loadings was experimentally investigated. The influences of the quantity of stiffeners, the FRP tube thickness and the axial load ratio on the seismic behavior of R-DSTCs were investigated. The test results demonstrate that DSTCs with HSC and HSS tubes exhibit a good seismic behavior, and an increase in the number of ribs leads to an increase in the lateral loading capacity, a small increase in the stiffness, a significant increase in the resistance to stiffness degradation and an increase in the energy dissipation of the R-DSTCs. Additionally, the axial load ratio and the GFRP tube thickness has a small effect on seismic performance of DSTCs.

Flexural capacity of steel-UHTCC (ultra-high toughness cementitious composite) bridge deck considering different shear connection degrees

Due to the excellent cracking prevention behavior of ultra-high toughness cementitious composite (UHTCC), the stud number and reinforcement ratio of composite bridge decks could be reduced, and hence the fatigue properties could be improved. In this study, a theoretical model was proposed to predict ultimate flexural capacity of steel-UHTCC composite bridge decks with different shear connection degrees. To evaluate the accuracy of the theoretical model, 10 examples were designed for finite element (FE) validation and parametric study, and the results indicated that the theoretical model can predict the ultimate flexural capacity of steel-UHTCC composite bridge decks with satisfactory accuracy. Then, quantitative analysis was conducted to reveal the effect of key design parameters on the ultimate flexural capacity. The design parameters involved in the parametric study included: (1) normalized stud number; (2) shear span length; (3) thickness of UHTCC slab; (4) reinforcement ratio; and (5) the number of longitudinal plate ribs. The reasonable range of the normalized stud number in a shear span can be determined between 0.5 and 1 in practical design and increasing of longitudinal reinforcement ratio has limited effect on ultimate flexural capacity of steel-UHTCC composite bridge decks.

In-hospital outcomes of intercostal nerve cryoablation and surgical stabilization of rib fractures.

Severe pain and pulmonary complications commonly follow rib fractures, both of which may be improved by surgical stabilization of rib fractures (SSRFs). However, significant postoperative pain still persists which may negatively impact in-hospital outcomes. Combining intercostal nerve cryoablation (INCA) with SSRF may improve those outcomes by further decreasing postoperative pain, opioid consumption, and pulmonary complications. The hypothesis is that INCA plus SSRF reduces opioids consumption compared with SSRF alone. The retrospective analysis included trauma patients 18 years or older who underwent SSRF, with or without INCA, in a Level I trauma center between 2015 and 2021. Patients received INCA at the surgeons' discretion based on familiarity with the procedure and absence of contraindications. Patients without INCA were the historical control group. Reported data include demographics, mechanism and severity of injury, number of ribs stabilized, cryoablated nerves, intubation rates and duration of mechanical ventilation. The primary outcome was total morphine milligrams equivalent consumption. Secondary outcomes were intensive care unit length of stay, hospital length of stay, incidence of pneumonia, and tracheostomy rates, and discharge disposition. Long-term outcomes were examined up to 6 months for adverse events. Sixty-eight patients were included, with 44 receiving INCA. There were no differences in rates of pneumonia ( p = 0.106) or duration of mechanical ventilation ( p = 0.687), and hospital length of stay was similar between groups ( p = 0.059). However, the INCA group demonstrated lower total morphine milligrams equivalent ( p = 0.002), shorter intensive care unit length of stay ( p = 0.021), higher likelihood of home discharge ( p = 0.044), and lower rate of intubation ( p = 0.002) and tracheostomy ( p = 0.032). Combining INCA with SSRF may further improve in-hospital outcomes for patients with traumatic rib fractures. Therapeutic/Care Management; Level III.

Multi-objective optimization of heat sink with multi-cross-ribbed-fins for a motor controller

A novel multi-cross-ribbed-fin layout was proposed to supersede the original smooth fin to fulfill the lightweight requirement of the air-cooled heat sink for the electrical vehicle motor controller. The thermal design with multi-cross-ribbed-fins was optimized using the multi-objective optimization method to minimize the chip’s temperature rise and the weight of the heat sink simultaneously. The design variables are the number of multi-cross-ribbed-fins ranging from 12 to 24, the number of cross ribs on either side varying from 1 to 4, and cross rib height in the region of 1.00–2.50mm. The standard k-ε turbulence model was validated compared to the experimental data for the original heat sink with smooth fins. The Pareto front solution set was obtained by performing the mixed-level orthogonal design procedure with the numerical simulations, constructing the surrogated-based model with backpropagation neural net training, and implementing the genetic algorithm. The numerical results showed that the recommended optimal designs have the multi-cross-ribbed-fin number of 17–19, the number of cross ribs of 2–3, and a cross rib height of 2.13–2.50mm. The maximum decreases in the temperature rise and weight are 7.63% and 9.45%, respectively. For verifying the superiority of current optimal designs, one of the optimal designs of the heat sink, which yields comparative temperature rise of the chip but reduced weight, was selected to be experimentally tested and compared with the data for the original heat sink.

Design and optimization of bio-inspired thin-walled structures for energy absorption applications

Thin-walled structures are widely used in the automobile, aerospace, and other engineering disciplines for impact energy absorption purposes for their lightweight and high energy absorption capacities. In this study, the energy absorption characteristics of various designs of the bionic structures inspired from bamboo are investigated so that the optimum design with the highest energy absorption can be achieved. For high-velocity impact applications (100 m/s), a rate-dependent material model is employed in all analyzes. Different design-cases with various connecting ribs are studied, and the optimum number of connecting ribs is obtained for each design-case. For the best performing designs, design parameters are optimized using Non-Sorting Genetic Algorithm 2 (NSGA2) to enhance the energy absorption properties further, yielding a 17% increase in the energy absorption capacity. Finally, for a more popular number of ribs, i.e. 4 and 6, design parameters are optimized using NSGA2 for practical applications. It is shown that it is crucial to employ a rate-dependent material model in the impact modeling as the results are highly reliant on the dynamic behavior of the material.

Finite-element modelling, analysis and design of anisogrid composite lattice spoke of an umbrella-type deployable reflector of space antenna

Practical design procedure of a new configuration of anisogrid composite lattice spoke of an umbrella-type deployable reflector of space antenna is presented in the paper. The spoke has a form of long lattice shell with the cross-section made in the form of rounded rectangle. The loads applied to the spoke are generated by the radio-reflective stretched mesh of the deployed reflector. Mass of the spoke is taken as an objective function in the formulated design problem, with constraints imposed on the characteristics of deformability, strength, and stability of the structure. The solution of the problem is based on the results of parametric analyses performed using the finite-element method. The set of design parameters of lattice structure includes the angle orientation of helical ribs, number of helical ribs of one orientation, widths of the helical and hoop ribs, and height of the ribs. A specialised algorithm is developed and applied to the generation of finite-element model for the anisogrid lattice spoke with rectangular cross-section. Using this model, the effects of variations of the parameters of lattice structure on the maximum deflection, maximum stresses in the ribs, and buckling load factor are analysed. Based on the results of these analyses the optimum set of the parameters of lattice structure is identified. At the first stage, feasible values of the structural parameters satisfying the set of constraints are calculated. Then, the optimum combination delivering the minimum value of the spoke mass is determined.

Effect of Pumice Stone and Sugar Molasses on the Behavior of Reinforced Concrete One-Way Ribbed Slabs

The world is currently heading towards sustainability by reducing the amount of concrete, thus reducing the total unit weight. Moreover, design construction requires materials with a higher strength-to-weight ratio. Ribbed slabs and lightweight concrete (LWC) are considered two leading sustainability facilities. This research developed an experimental study to evaluate the effects of concrete type, steel reinforcement ratio, the geometry of ribs, voiding ratio, and slab type on the structural behavior of one-way ribbed slabs. Eight of the one-way slabs were constructed using pumice stone and by-product material sugar molasses (SM), and one slab was constructed using gravel and SM. These slabs were tested under a static two-point load and simply supported until failure. The results showed that using SM with pumice stone instead of gravel led to high strength-lightweight concrete (HSLWC), with a cylinder compressive strength of 42.2 MPa and a density of 1943 kg/m3, which meets the requirements of HSLWC codes. Using HSLWC instead of high-strength normal-weight concrete (HSNWC) decreased the thermal conductivity by 43.55% and the unit weight by 19.31%. Moreover, the ultimate strength of the HSLWC one-way ribbed slab decreased by 17.70%. Overcoming this strength reduction necessitated increasing the steel reinforcement ratio of the ribs from 0.28 to 0.44% in the HSLWC ribbed slab. Changing the number of ribs at the same amount of HSLWC showed a minor effect on the strength capacity of slabs but showed an economic benefit. However, increasing the rib width to reduce the voiding ratio from 44 to 40% resulted in a greater improvement in structural efficiency (SE) of one-way ribbed slab than reducing it from 44 to 33%. Consequently, the optimum rib width was 120 mm. Moreover, using a ribbed slab instead of a solid slab of HSLWC at the same amount of concrete increased the ultimate strength by 130.37%, decreased deflection by 3.99%, and improved SE by 126.46%. Furthermore, experimental results of ultimate load were compared with the ACI 318-19 code design equation. Doi: 10.28991/CEJ-2022-08-02-011 Full Text: PDF

Parametric study on the flutter sensitivity of a wide-chord hollow fan blade

In recent years, the hollow fan blades have been widely used to meet the demand for light weight and good performance of the aero-engine. However, the relationship between the hollow structure and the aeroelastic stability has not been studied yet in the open literature. In this paper, it has been investigated for an H-shaped hollow fan blade. Before studying the flutter behavior, the methods of parametric modeling and auto-generation of Finite Element Model (FEM) are presented. The influence of the feature parameters on the vibration frequency and mode shape (as the input of flutter calculation) of the first three modes are analyzed by the Orthogonal Experimental Design (OED) method. The results show that the parameters have a more remarkable impact on the first torsional mode and thus it is concerned in the flutter sensitivity analysis. Compared with the solid blade, the minimum aerodynamic damping of the hollow blade decreases, indicating that the hollow structure makes the aeroelastic stability worse. For the parameters describing the hollow section, the rib number N has the greatest influence on the minimum aerodynamic damping, followed by the wall thickness W5. For the parameters in the height of hollow segment, the aerodynamic damping increases with the increase of parameters M1 and M2. This means that reducing the height of the hollow segment is helpful to improve the aeroelastic stability. Compared with the impact of parameters in hollow section, the variation of aerodynamic damping caused by the height of the hollow segment is small.

Effect of Ribs as Passive Control on Base Pressure at Sonic Mach Numbers

Passive control is a method used to control the base pressure of the convergent-divergent nozzle for high speed vehicles. The passive control contributes significant reduction of base pressure which mainly depending on many factors such as number of ribs, flow Mach number and rib’s size. The flow behaviour inside the nozzle at the respected factors still unknown. Therefore, this study aims to assess the effect of ribs in a suddenly expanded flow to control the base pressure at sonic Mach numbers. The study is performed using ANSYS Fluent. The flow expands in a duct with 18 mm diameter and 108 mm length. The ribs have aspect ratios of 3:1 to 3:3 which were fixed to the duct circumferentially. The position of the rib varies from 1D (duct diameter) to 4D and having different aspect ratios. The level of expansion varies from 1.5 to 5 while the rib is fixed at a 3:3 aspect ratio. The variation of pressure and velocity contours of the flow inside the nozzle are presented. The simulation analysis indicates that the flow expansion with the presence of ribs considerably improves the base pressure. It is concluded that at the flow with sonic Mach number, the rib with a 3:3 aspect ratio located at 4D has shown the highest improvement in base pressure.

Discrete element method investigation of the milling characteristic in a rice mill

Abstract. A milling chamber consisting of a rice sieve and a rotating roller plays critical roles in modulating the milling performance of rice grains. However, the mechanism of how the geometries of the rice sieve and rotating roller affect the particle collisions and the interaction time remains not fully understood. Our experimental results show that the milling degree and rate of broken rice of the octagonal rice sieve are largest among the hexagonal sieve, octagonal sieve, and circular sieve. Through the discrete element method, we illustrate that the peak milling degree at the octagonal sieve is attributed to the competition between the decreasing force and increasing milling time with the increase in edges. In addition, the geometries of the convex ribs of the rotating roller are investigated to optimize the structure of the milling chamber. In the left-hand spiral or right-hand spiral of the convex ribs, the rice particles are accumulated in the inlet or outlet regions, respectively, which leads to an uneven milling degree in the axial direction. The uniformity of a milling process can be promoted by increasing the number of convex ribs, which will reduce the milling degree on the other hand.

Influencing Factors of Interfacial Behavior between Geogrid and Coal Gangue

Coal gangue is a type of solid waste that is generated in the process of coal mining and washing. This concept can be effectively used in reinforced engineering fillings. The influences of shear rates and geogrid transverse ribs were studied using a large indoor direct shear test. The test results showed that the relationship between shear stress and shear displacement of geogrid‐coal gangue is nonlinear, and the shear process is accompanied by the crushing of coal gangue particles. The addition of geogrid significantly improved the shear stress and interfacial quasi‐cohesion of geogrid‐coal gangue, whereas the interfacial quasi‐friction angle remained almost unaffected. When normal stress was greater than 25 kPa, the shear stress gradually increased as the shear rate was increased from 1 to 5 mm/s. With an increasing shear rate, the interfacial quasi‐friction angle increased, whereas the interfacial quasi‐cohesion decreased. The interfacial shear stress, interfacial adhesion, and interfacial friction angle decreased with the number of geogrid ribs; the contribution of the middle transverse rib to the interfacial shear strength was smaller than that of the transverse rib at the far end in the shearing direction.

Effect of Upstream Cylinder on the Wake Structure and Evolution of Flow over a Finned Circular Cylinder

This paper reports the results of Computational Fluid Dynamics (CFD) simulations to investigate the effect of an upstream cylinder on the wake structure and evolution of flow over a finned circular cylinder evenly attached with rectangular ribs around its circumference and identifying the near-wall vortex structure are formed. Also examined the effect of the number of ribs (n=3, 5) in a low Reynolds number range of 60–180. The main concern in the aerospace domain is the vortex induced vibrations. It is necessary to find ways to reduce the fluid forces and stabilise the flow wake either actively or passively. Therefore, be it in the field of aerodynamics and in offshore wind turbines. The near-wall vortices and their evolution are sensitive to Re as well as n. The evolution of flow around the cylinder with 3 ribs (n = 3) QS are formed in the corners over which the boundary layers stride. The subordinate vortices disappear at Re=60, possibly attributed to the relatively great viscous force at such lower Re. The evolutions of flow over the finned cylinder with 5 ribs at three representative Re cases are compared. The number of Sub created in accompany with a main vortex grows with the increase in Re. and then generates the main vortices behind the associated ribs

Automatic method for determining the number of lumbar and thoracic vertebrae in rabbits using Computer Tomography images

There are several studies dealing with the phenotypic variance of the vertebral number in the spinal column of rabbits. According to the literature the number of thoracic and lumbar vertebrae varies between 11-13 and 6-8, respectively. The length of the m. longissimus dorsi (MLD) - a valuable meat part of rabbits - is determined by the length of the vertebral column therefore the number of vertebrae may have economic importance in breeding. The aim of this study was to create an automatic counter using computed tomography (CT) images. In the first step, a skeleton binary mask was created using the radiodensity range between 120 and 3071 HU, then the lumbar and thoracic regions were processed by two different methods. The lumbar part was evaluated based on the frequency of the bone voxels along the axial plane. The number of thoracic vertebrae was determined from the number of ribs. The left and right ribs were processed separately. The developed method was tested on CT examination of 40 Hycole rabbits compared to manual evaluation. The results of the automatic algorithm had few errors: in one case in the lumbar region (2.5%) and in 3 cases in the thoracic region (5%). The automated evaluation process takes a few seconds per individual and then the program visualizes the results on a graph. The incorrectly evaluated rabbits are recognizable on graphs and they can be easily corrected with a minimal time investment.

Physician-Led Thoracic Trauma Management in a Specialist Emergency Care Centre.

Introduction: Falls cause 75% of trauma in patients above 65 years of age, and thoracic trauma is the second commonest injury; rib fractures are the most common thoracic injury. These patients have up to 12% mortality, with 31% developing pneumonias. There is wide variation in care. Northumbria Healthcare has a team of respiratory consultants, physiotherapists, specialist nurses and anesthetists for thoracic-trauma management on a respiratory support unit. Methods: With Caldicott approval, basic demographics and clinical outcomes of patients admitted with thoracic trauma between 20 August–21 April were analyzed. A descriptive statistical methodology was applied. Results: A total of 119 patients were identified with a mean age of 71.1 years (range 23–97). Of the 119 patients, 53 were male, 66 females. The main mechanism of injury was falls from standing (65) and falls down stairs/bed or in the bath (18). Length of stay was 7.3 days (range 1–54). In total, 85 patients had more than one co-morbidity, 26 had a full trauma assessment and 75 had pan CTs. The mean number of rib fractures was 3.6 and 31 (26%) patients had a pneumothorax and/or haemothorax. A total of 18 chest drains were inserted (all small bore) and one needle aspiration was performed. No cardiothoracic input was required. Isolated chest trauma was present only in 45 patients. All patients had a pain team review, 22 erector spinae catheters were inserted with 2 paravertebral blocks. Overall, 82 patients did not require oxygen, 1 required CPAP and 1 HFNC. 7 needed intensive care transfer. Furthermore, 20 (17%) developed pneumonias and 16 (14%) deaths occurred within 30 days—all were in those with falls from standing. There was no correlation between number of fractured ribs, length of stay and mortality. Conclusions: High level care for thoracic trauma can be performed by a physician led team. Overall, 42% pneumothoraces/haemothoraces were observed. Further large scale randomised trials are warranted for definitive outcomes.

Preservation of Features of Anatomical Polymorphism of Deschampsia antarctica É. Desv. (Poaceae) During In Vitro Clonal Reproduction

Abstract We studied the anatomical features of the leaf structure of Deschampsia antarctica É. Desv. (Poaceae) obtained from seeds collected from different habitats of the maritime Antarctic. These plants have been maintained in culture in vitro for more than 7 years. The plants include stable chromosome forms comprising diploids (2 n = 26), a diploid plant with B-chromosomes (2 n = 26 + 0–3B), a triploid with rearranged chromosome morphology, and myxoploids with different ratios of diploid and nondiploid cells in the root meristem. The D. antarctica plants that were studied generally had a similar anatomical structure in culture in vitro and in nature. At the same time, plants of different cultivated genotypes also displayed their own leaf structure features. In particular, qualitative features included asymmetric four-ribs and five-rib leaves instead of typical three-rib leaves for some genotypes, some individuals characterized by the presence of unicellular nonglandular pointed trichomes on an adaxial side, differences in vascular bundle sheath, and other features. No clear dependence of the anatomical structural features on the chromosomal status of the studied genotypes was evident. At the same time, differences were evident in traits that included the number of stomata, thickness of the outer cell walls of the epidermis, bundles sheath state, number of leaf ribs, and the persistent presence of trichomes under prolonged in vitro cloning. The findings indicate that D. antarctica plants collected from different locations of the maritime Antarctic for long-term cultivation in vitro under standard cultivation conditions retain the anatomical characteristics of the wild plants. The polymorphism of in vitro-cultivated plants is not related to the polymorphism of their karyotype, but is apparently due to the heterogeneity of the original plants and possibly the epigenetic fixation of a number of anatomical features produced in the natural microhabitats of D. antarctica populations.

The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Neonatal and Infant Spine.

The AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Neonatal and Infant Spine.

그물형 안테나의 고어 개수에 따른 Radio Frequency (RF) 특성 분석

This research discusses the change in radio frequency (RF) characteristics according to the number of Gores on the deployable mesh antennas for potential micro-satellite applications. The deployable type of lightweight mesh antenna can be used for various space missions such as communication/SAR/ SIGINT. In order to implement an ideal curvature of antenna surface, sufficient number of antenna rib structures are required. However, the increase in antenna ribs affects various design factors of the antenna system, especially total system mass, complexity of deployable mechanism and reliability. In this paper, the proper number of ribs for the mesh antenna were derived by comparison of electro-magnetic (EM) simulation results of example of antenna model in accordance with the various number of ribs.