Oxycephaly Research Articles

Numerical simulation of turbulent airflow around a tall telecommunication tower model

In this study, wind flow around a telecommunication tower (Milad Tower) model was numerically simulated. Several computational fluid dynamics (CFD) simulations were performed using the Reynolds Averaged Navier–Stokes (RANS) and the Delayed Detached Eddy Simulation (DDES) models. Two cases resembling the tower head with different inlet turbulence intensity profiles were considered, and computational results for wind flow and pressure distributions on various sections around the tower head and structure were presented and compared with the available wind tunnel data. Good agreement of the simulated pressure coefficient distributions around the head section in the windward and leeward sides of the tower with the wind tunnel data was observed. The regions with positive and negative pressures on the tower surface were identified based on the pressure coefficient distributions. In addition, the airflow characteristics around a model of the entire Milad Tower were studied. The simulation results for the airflow and the drag and lift coefficients acting on the tower for the high and low-intensity winds were evaluated and discussed. It was demonstrated that the DDES model was preferred for the simulation of mean pressure coefficients over the tower; however, the RNG k–ε model results, which were obtained at lower computational costs, were also satisfactory. In addition, the DDES showed better performance in simulating the maximum and minimum pressure coefficients on different tower levels and predicting the mean aerodynamics drag and lift coefficients. The results of the DDES model illustrated the higher power spectral density of velocity fluctuations on the leeward side of the tower compared with the windward side.

Research on the gap value and optimization of 500 kV large span tower head

Research on the gap value and optimization of 500 kV large span tower head

Surgical Technique of Fronto-orbital Advancement And Strip Craniectomy for Correction of Oxycephaly With Towering of Bregma, a Case Report

Background: Craniosynostosis is a congenital problem of brain development that causes disfigurement of the head and face. Multiple synostoses is an abnormal development of head where fusion ofmany or all cranial sutures ’! oxycephaly (tower skull with undeveloped sinuses and shallow orbits). The most accepted surgical correction involves frontoorbital advancement and forehead remodeling. Aim of the Study: In this study, we described our experience and technique in surgical correction of multiple synostoses (Oxycephaly) in BSMMU,department of neurosurgery. Bang. J Neurosurgery 2022; 11(2): 134-137

Investigation on the Critical Wind Speed of Instability Failure of UHV Transmission Tower-line Coupling System under Typhoon

Wind is one of the most destructive external loads of transmission lines, and typhoon-caused severe damage or even destruction of electric power facilities occurred frequently. In order to research the critical wind speed of instability failure of UHV transmission tower-line coupling system under typhoon, the UHV transmission line in Zhejiang is chosen as the research subject and a finite element model of the UHV tower-line coupling system is established. By using the improved generalized force calculation method, the dynamic response of the transmission tower is converted to the static response. Then the LRC method is used to calculate the equivalent static wind load of the tower and obtains the wind response of the UHV transmission tower-line coupling system. The results show that under the typhoon wind field, the component at the junction of the tower head and the body first reaches the supercritical state. Specifically, when the wind speed at 10-meters height reaches 31m/s, the profile component of the tower head will be damaged. With the increase of wind speed, the damaged area of the tower head also expends. When the wind speed at 10-meters height reaches 37m/s, the main load-bearing component of the tower head-body junction will lose its stability, which will directly threaten the safety of the transmission tower.

Investigation on aerodynamic characteristics for steel tubular cross-arms of transmission tower under skew wind

A study of the aerodynamic characteristics of steel tubular butterfly-shaped cross-arms in a transmission tower head under skew wind is presented. A wind tunnel test was conducted under skew wind by using a scaling model, and a numerical simulation was performed with a high-precision three-dimensional tower head model. The drag coefficient, skew wind load factor, and wind load distribution factor of the cross-arms obtained from the experiment and numerical simulation were identified and compared with those acquired from different codes. It is concluded that the indirect force measurement method was found to underestimate aerodynamic forces acting on windward cross-arms. For single cross-arm, the horizontal cross-arm showed stronger shielding effect than the inclined cross-arm. A fitting formula for the skew wind load factor of the cross-arm is proposed, and values obtained from it matched experimental and simulation data well. A comparison between calculated and measured wind load distribution factors showed that although longitudinal load distribution factors calculated with the Chinese standard (2018) were consistent with measured data, calculated transverse load distribution factors did not match measurements well. It is suggested that the effect of the transverse lift wind force should be considered in the calculation of wind load distribution factors.

A Transmission Tower Tilt State Assessment Approach Based on Dense Point Cloud from UAV-Based LiDAR

Transmission towers are easily affected by various meteorological and geological disasters. In this paper, a transmission tower tilt state assessment approach—based on high precision and dense point cloud from UAV LiDAR—was proposed. First, the transmission tower point cloud was rapidly located and extracted from the 3D point cloud obtained by UAV-LiDAR line patrol. A robust histogram local extremum extraction method with additional constraints was proposed to achieve adaptive segmentation of the tower head and tower body point cloud. Second, an accurate and efficient extraction and simplification strategy of the contour of the feature plane point cloud was proposed. The central axis of the tower was constrained by the contour of the feature plane through the four-prism structure to calculate the tilt angle of the tower and evaluate the state of the tower. Finally, the point cloud of tower head from UAV-based LiDAR was accurately matched with the designed tower head model from database, and a tower head state evaluation model based on matching offset parameters was proposed to evaluate tower head tilt state. The experimental results of simulation and measured data showed that the calculation accuracy of the tilt parameters of transmission tower body was better than 0.5 degrees, that the proposed method can effectively evaluate the risk of tower head with complex structure, and improve the rapid and mass intelligent perception level of the risk state of the transmission line tower, which has a wide prospects for application.

Characteristics of Partial Discharge on 10 kV Covered Conductor Around Tower Head

The widely use of covered conductor increases the reliability of distribution network. However, a new problem of partial discharge caused by covered conductor at the position of tower head is generated at the same time. This kind of partial discharge will damage the insulation layer or accelerate the deterioration of insulation, which may cause the single-phase grounding fault and affect the power supply reliability. At present, there is few systematic studies on the characteristics of this partial discharge. This paper mainly analyzes the electric field distribution near the covered conductor around tower head, builds the partial discharge experiment platform, and obtains the pulse current characteristics of partial discharge under different working conditions. The results show that the maximum electric field intensity is located at the interface between covered conductor, binding wire and air. The main causes of partial discharge are the wet and dirty of the surface of porcelain insulator and conductor insulation. The minor cause is the breakage of covered conductor insulation. Under different conditions, the initial partial discharge pulse current wave front time is 8ns ~ 45ns, the tail time is 30ns ~ 150ns. The discharge time interval can be as low as 30μs. In addition, it is found that there are two types of partial discharge through spectral analysis. One occurs when the covered conductor insulation is damaged under binding wire; the other is the covered conductor insulation is intact.

Propagation Characteristics of Partial Discharge Pulse Current on 10kV Covered Conductor

With the application of covered conductor in distribution overhead lines, the grounding and short circuit faults caused by foreign objects have been eliminated. But new partial discharge problem has appeared on the surface of the covered conductors around tower head. It may cause the single-phase grounding fault and affect the power supply reliability. To increase the reliability, status monitoring must be used to prevent the faults from beginning. Currently, the partial discharge on overhead lines is usually measured by coils. It utilizes pulse currents to check whether there is a partial discharge. However, it cannot be used in status monitoring as the propagation characteristics is not clear. This paper carried out a simulation study on the propagation characteristics. By constructing a simulation model of overhead lines with covered conductor by the distribution parameters, the initial pulse current amplitude and front time transformation rule in different transmission distance is obtained. Considering different conditions such as pulse current frequency domain (10~50MHz), covered conductor height (4.5~8.0m), covered conductors’ phase spacing (0.6~1.0m), and conductor cross-sectional area (50~185mm2), simulation results show that the amplitude attenuation rate is between 1.5% and 6.3% per 100m, and the front time growth rate is between 1.5% and 5.7% per 100m. The height of covered conductor has the greatest influence on the pulse current waveform transformation, and the main frequency of the pulse current takes the second place, while the difference between the phase spacing and the cross-sectional area has less than 1% influence on transformation.

Nonlinear Buckling Analysis and Optimization Design of the Y‐Type Composite Insulator String

Under the action of extreme wind load, the overhead transmission line will lead to the fracture of the traditional V‐type insulator string, which greatly affects the safety of the power system. Compared with the V‐type insulator string, the Y‐type insulator string has better stability under the wind load. Therefore, the overhead lines in the mountainous areas of Anhui Province are taken as the research object, considering the combined effect of wind load and conductor dead weight, and through theoretical derivation, the calculation formula of insulator string wind deflection angle is obtained. Using numerical simulation software, the nonlinear mechanical analysis of Y‐type insulator strings is conducted, and under the action of different wind speeds, the windage yaw angle and unloading angle of the Y‐type insulator string are obtained. Compared with the calculation results of the V‐type insulator string, the stability of the Y‐type insulator string in the structure is better than that of the V‐type insulator string, and the Y‐type insulator string can make full use of the distance between layers and the gap margin of the tower head, reduce the length of the cross arm, and reduce the weight of the tower, which has obvious advantages. Combined with the results of theoretical analysis and numerical simulation, the optimal design method of the Y‐type insulator string is given. Under the condition of ensuring the safety and stability of insulators, the distance of the cross arm is shortened as much as possible and the weight of the transmission line tower is reduced. The research results will provide a theoretical reference for engineering design and improvement.

Study on Type Selection and Head Layout of Zhangzhou Long Crossing Tower

By comparing the schemes of combined angle steel and steel tube tower, the tower type of Zhangzhou long crossing tower was optimized, and through different tower head layout, the tower head types of long crossing tower and anchor tower were compared from the technical and economic aspects, in order to provide a certain practical significance for the design and application of long crossing tower.

Синдром Апера (Apert): літературна довідка та власний клінічний випадок

Acrocephalosyndactyly (ACS) is a group of multiple malformations, the main clinical manifestations of which are acrocephaly and syndactyly. The most common forms are Apert (type I), Pfeiffer (type V), Setra–Hotzen (type II) syndromes. Apert syndrome is the most explored and common form of all types of ACS and Apert syndrome is estimated to occur in 1 in: 100 000 newborns. The syndrome is inherited in an autosomal dominant manner. If the gene is carried by one of the parents, the risk of having a child with Apert syndrome is 50%. The syndrome genome (FGFR2) is located on the long arm of chromosome 10 at locus 10q26. Apert syndrome occurs due to mutations at this locus, but the children karyotype is not changed. The pathognomonic clinical signs of Apert syndrome are craniofacial dysostosis and symmetrical syndactyly of the hands and feet. Acrocephaly («tower skull») — is a consequence of early synostosis of some sutures of the skull. Orbital hypertelorism and exophthalmos are referred to typical facial changes. Among other abnormalities there are heart and vascular defects (25%), cleft palate, malformations of the gastrointestinal tract and kidneys. The diagnosis is made on the basis of clinical symptoms. No treatment has been developed. Life expectancy is short. Purpose — to present a clinical case of a newborn with Apert syndrome. Clinical case. Apert syndrome was suspected prenatally, confirmed after birth. The newborn girl had the characteristic signs of the above-described pathology: «tower head», hypertelorism, saddle bridge of the nose, closed large fontanelle, phalanges of the first finger were wide, the proximal phalanx was triangular, complete cutaneous syndactyly of the II–IV fingers was observed symmetrical on both upper extremities; on the lower extremities — thickening of the proximal phalanges of the big toes, complete cutaneous syndactyly of the II–IV toes. Conclusions. The article describes a clinical case of a child with Apert syndrome. Prenatal diagnosis takes one of the leading places in confirming genetic abnormalities, determining the prognosis for life. Genetic counseling for parents is necessary and important at all stages of pregnancy planning. The research was carried out in accordance with the principles of the Helsinki Declaration. The study protocol was approved by the Local Ethics Committee of these Institutes. The informed consent of the patient was obtained for conducting the studies. No conflict of interest was declared by the authors. Key words: Apert syndrome, children, prenatal diagnosis.

Over Speed Protection of Horizontal Axis Wind Turbine Using Slot in the Turbine Blade

The wind energy is more reliable, clear, and easilyexploitable form of renewable energy source. Wind turbines are being stationed to capture the wind’s power and convert it to electricity. The wind turbines are operated at rated speed to ensure smooth operation. When the wind turbine faces the higher wind speed, wind forceimpacts the tower head causing immediate damage the turbine blade. Wind turbines are equipped with various Aerodynamic braking systems and mechanical braking system to control the over speeding of the wind turbine rotor at extreme wind velocity. In this novelmethodology, it is attended to reduce the rotational speed of the wind turbine aerodynamically by providing the chord wise slot (opening). The slot modifies the pressure distribution over the upper side and lower side of the turbine blade that slows down the rotational speed of the wind turbine within the safe limit. In this present attempt, the over speeding of the wind turbine rotor is effectively controlled without disturbing the power generation. The different parameters of the slot such as the position of the slot, inclination of the slot, and width of the slot are studied and the slot parameters are computationally optimized.

Research on General Design and Application of Double-circuit T-Connection Tower In 110kV

Based on the investigation results and the current general design of state grid, this paper reasonably planned the design conditions of the tower. Taking the general design module as the basic tower type, a kind of double loop T-connection tower in 110kV with high generality was proposed, then carry out tower head planning and structural internal force analysis. Finally, the electric field finite element simulation is carried out to demonstrate the safety and reliability of the T-connection tower of cross arm arrangement. The tower can cover the T-connection conditions of 110kV double-circuit line in most areas of the country, and draw the tower diagram, which can be included in the general design of state grid transmission tower for reference of line designers. The cross arm of tower head is arranged in a crisscross way, which greatly simplifies the the double-loop T-connection scheme. One tower can replace the traditional multi-tower to complete the T-connection of the line, which reduces the cos t and occupation of land, also achieves good economic and environmental benefits.

CFD analysis of horizontal axis wind turbine braking system using chordwise spacing

Wind energy is an environment- friendly and efficient source of renewable energy to meet the growing demand for energy. The wind turbines are designed to operate at rated wind speed. The sudden wind acceleration and wind gusts can overload the tower head causing immediate damage to the mechanical drive train shaft, gearbox, and turbine blade. The various aerodynamic braking systems are presently used to control the rotational speed of the wind turbine at extreme wind velocity. In this proposed approach, it is attempted to control the over speeding of the wind turbine aerodynamically by providing the chord wise spacing (slot) on the blade. The spacing provided on the blade alters the pressure distribution between the pressure side and the suction side of the turbine blade that brings down the rotational speed of the wind turbine within the allowable limit. In this approach, the over speeding of the wind turbine blades is effectively controlled without affecting the power generation. The primary parameter of the spacing i.e. chord wise position of the spacing is computationally analyzed.

Development and Application of SZ-type double-back straight tower with live replacement overhang insulator suspension line card

In recent years, SZ-type tower and other angular-type cross-bearing head plus slings of the cross-stretcher structure of the tower on-line has been widely used. However, there is currently no special card in line with it. Therefore, this paper puts forward the use of aluminum alloy as a material developed that can be stuck in the cross-stretcher head of the 220 kV SZ-type double-back straight tower with live replacement overhang insulator hanging line card. It includes a screw lever, a wire lever with a hook hook in the lower part of the bar, and a screw lever connected to a crossbar card. The cross-stretcher mount has a cavity in the middle and a screw seat on both sides, with each screw lever standing on the screw seat when used. The cross-load mount holder is on the sZ-type double-back straight-line tower cross-mounted plate, which can be used for installation on the SZ-type tower. It provides a screw hanging point when the SZ-type tower is charged to replace the insulator. It has the characteristics of simple structure, reasonable and safe use.

Calculating wind turbine component loads for improved life prediction

Wind turbines life time is commonly predicted based on statistical methods. However, the success of statistics-based maintenance depends on the amount of variation in the system design, usage and load. Life time prediction based on physical models seeks to overcome this drawback by considering the actual design and evaluating the specific usage, load and operating condition of the considered systems. In this paper, a load-based maintenance approach is proposed to predict wind turbines life time. Physical models are used to evaluate load profiles at wind turbine blade root, rotor hub center and tower head. The effects of surface roughness, side winds, yaw misalignment, rotor tilt and blade cone angle, individual blade pitching and wind turbulences are considered and quantified. It is shown that centrifugal, gravity, Euler and Coriolis accelerations dominate the blade root loads. Tilt and cone angle, as well as individual blade pitching, affect the rotor hub and dynamic tower head loads. Further, the actual wind speed distribution is considered which is also proven to be a critical life time prediction parameter. Finally, a set of parameters is proposed that need to be monitored in a specific wind turbine to enable the practical implementation of a predictive maintenance policy.

Study on Mechanical Properties of Steel on Transmission Tower under Icing Load

In order to determine the failure mode of high-voltage transmission tower materials under the condition of ice-coating load in an actual line. The Qidian-Luoping 500kV wine glass type transmission tower is selected as the prototype, and the one tower with two lines model of the whole beam unit is established by using the ANSYS finite element software. The loading mode is static load considering icing load and wind load. The most unfavorable wind direction of the transmission tower is obtained by comparing and analyzing the maximum displacement and the stress of the rod under different directions of wind load in the transmission tower. Then the failure mode of transmission tower is studied by the variable ice thickness of the tower line system. The results show that the direction parallel to the cross arm is the most unfavorable direction in the transmission tower. And under the most unfavorable wind direction, with the increase of ice thickness, it is found that the tower head part is more sensitive to icing load than the tower body part. When the thickness of ice coating reaches 30mm, the weak load-bearing rod will appear locally in the transmission tower and the position of the rod is mainly distributed on the outer upper crank arm, the outer side of the ground bracket and the upper side of cross arm of the transmission tower.

Novel model of stator design to reduce the mass of superconducting generators

High temperature superconductors (HTS), with much higher current density than conventional copper wires, make it feasible to develop very powerful and compact power generators. Thus, they are considered as one promising solution for large (10 + MW) direct-drive offshore wind turbines due to their low tower head mass. However, most HTS generator designs are based on a radial topology, which requires an excessive amount of HTS material and suffers from cooling and reliability issues. Axial flux machines on the other hand offer higher torque/volume ratios than the radial machines, which makes them an attractive option where space and transportation becomes an issue. However, their disadvantage is heavy structural mass. In this paper a novel stator design is introduced for HTS axial flux machines which enables a reduction in their structural mass. The stator is for the first time designed with a 45° angle that deviates the air gap closing forces into the vertical direction reducing the axial forces. The reduced axial forces improve the structural stability and consequently simplify their structural design. The novel methodology was then validated through an existing design of the HTS axial flux machine achieving a ∼10% mass reduction from 126 tonnes down to 115 tonnes. In addition, the air gap flux density increases due to the new claw pole shapes improving its power density from 53.19 to 61.90 W kg−1. It is expected that the HTS axial flux machines designed with the new methodology offer a competitive advantage over other proposed superconducting generator designs in terms of cost, reliability and power density.

Effects of bolt slippage on the wind induced responses of transmission tower line system

The wind induced responses of transmission tower line system are studied by finite element method. Firstly, a slip model considering eccentricity and bolt joint slippage in diagonal bracings, tower legs and tower head is built by ANSYS. The slip model has a more accurate result compared with conventional models. Secondly, the finite element models of tower line systems are established and the wind speed time histories are simulated using MATLAB. Finally, the wind induced responses of different tower line systems are studied. The results of a single tower and the tower line systems are compared to study the effects of tower-line coupling effects and bolt slippage on wind induced responses of transmission tower line systems.

Impact of forested fetch on energy yield and maintenance of wind turbines

In a wind farm whose turbines have either a forested or unforested fetch, measurements of the wind speed, wind direction and turbulence intensity are made with a 3D scanning LiDAR, and measurements of the tower head aeroelastic deflections are simultaneously made with an opto-mechanical measurement system. It is seen that in the forested fetch there is up to 2.5 times larger turbulence intensity than in the unforested fetch. Aeroelastic deflections of the tower during normal operation are up to 2.8 times larger for a turbine in forested fetch compared to a turbine in an unforested fetch. It is observed that the turbine with forested fetch has 17% lower annual energy yield compared to a turbine in an unforested fetch. The deficits in the direction-wise energy yields are shown to be primarily a function of the upstream streamwise extent of the forest. Furthermore, an analysis of the maintenance logs of the turbines shows that there are 2.2 times more fault durations per year and 20% shorter time intervals between unscheduled and scheduled maintenances for a turbine in a forested fetch; thus more frequent scheduled maintenances are recommended for turbines with a forested fetch.