Cross Arm Research Articles

Pentachlorophenol causes redox imbalance, inhibition of brush border membrane and metabolic enzymes, DNA damage and histological alterations in rat kidney

Pentachlorophenol (PCP) is a synthetic organochlorine compound that is widely used in biocide and pesticide industries, and in preservation of wood, fence posts, cross arms and power line poles. Humans are usually exposed to PCP through air, contaminated water and food. PCP enters the body and adversely affects liver, gastrointestinal tract, kidney and lungs. PCP is a highly toxic class 2B or probable human carcinogen that produces large amount of reactive oxygen species (ROS) within cells. This work aimed to determine PCP-induced oxidative damage in rat kidney. Adult rats were given PCP (25, 50, 100, 150 mg/kg body weight), in corn oil, once a day for 5 days while control rats were given similar amount of corn oil by oral gavage. PCP increased hydrogen peroxide level and oxidation of thiols, proteins and lipids. The antioxidant status of kidney cells was compromised in PCP treated rats while enzymes of brush border membrane (BBM) and carbohydrate metabolism were inhibited. Plasma level of creatinine and urea was also increased. Administration of PCP increased DNA fragmentation, cross-linking of DNA to proteins and DNA strand scission in kidney. Histological studies supported biochemical findings and showed significant damage in the kidneys of PCP-treated rats. These changes could be due to redox imbalance or direct chemical modification by PCP or its metabolites. These results signify that PCP-induced oxidative stress causes nephrotoxicity, dysfunction of BBM enzymes and DNA damage.

Influence of bone joints on the axial compression stability of GFRP hollow cross arms

Axial compression tests are carried out for GFRP hollow cross-arms with different slenderness ratios. With increase in the slenderness ratio of a member, its buckling bearing capacity decreases significantly compared with its axial compression failure bearing capacity. To address this issue, according to the principle of bionics, in this study, a glass fiber-reinforced polymer (GFRP) hollow cross arm model with bone joints is proposed and examined for axial compression buckling; this is followed by simulation experiments. After the bone joints are set, improved buckling bearing capacity of the components is obtained, and there are obvious economic benefits. The buckling bearing capacity and displacement of the specimens increase with increase in the height and number of bone joints. With increase in the slenderness ratio of the specimen, the buckling bearing capacity of the bone joints increases slightly. Finite element simulations are carried out to establish the formula for calculating the bearing capacity of the GFRP hollow cross arms with bone joints. The calculated results are in good agreement with the experimental results, thus providing insights for engineering design.

All Right. Good Night. (Excerpt)

All Right. Good Night. (Excerpt)

Interview with Eirini Giorgou

Dr Eirini Giorgou is a Legal Adviser in the International Committee of the Red Cross (ICRC) Arms and Conduct of Hostilities Unit, where she works, among other issues, on explosive weapons in populated areas and on nuclear weapons. She has several years’ experience in multilateral disarmament and arms control diplomacy and negotiations outside the ICRC. She is a licensed lawyer and holds a PhD in international law from the University of Geneva.

Properties of Basalt Fiber Core Rods and Their Application in Composite Cross Arms of a Power Distribution Network.

As basalt fiber has better mechanical properties and stability than glass fiber, cross arms made of continuous basalt-fiber-reinforced epoxy matrix composites are capable of meeting the mechanical requirements in the event of typhoons and broken lines in coastal areas, mountainous areas and other special areas. In this paper, continuous basalt-fiber-reinforced epoxy matrix composites were used to fabricate the core rods and composite cross arms. The results verified that basalt fiber composite cross arms can meet the strict requirements of transmission lines in terms of quality and reliability. In addition to high electrical insulation performance, the flexural modulus and the flexural strength of basalt fiber core rods are 1.8 and 1.06 times those of glass fiber core rods, respectively. Basalt fiber core rods were found to be much better load-bearing components compared to glass fiber core rods. However, the leakage current and the result of scanning electron microscopy (SEM) analysis reveal that the interface bonding strength between basalt fibers and the matrix resin is weak. A 3D reconstruction of micro-CT indicates that the volume of pores inside basalt fiber core rods accounts for 0.0048% of the total volume, which is greater than the 0.0042% of glass fiber rods. Therefore, improving the interface bond between basalt fibers and the resin can further improve the properties of basalt fiber core rods.

Research on External Insulation Characteristics of Composite Cross-Arm of 10 kV Distribution Network Based on Multi-Factor Aging.

With the application of the composite cross-arm in power systems, comprehensive anti-aging performance is a key factor to determine whether it can operate safely. In order to study the influence of the operating environment on the external insulation characteristics of composite cross-arms of distribution networks, various aging conditions such as voltage, rain, temperature, humidity, salt fog and ultraviolet light were simulated in a climate chamber based on the real operation conditions of the 10-kV composite cross-arm. A multi-factor aging test of composite cross-arms with two kinds of cross-section shapes (T-shaped and square) was carried out for 5000 h. The change trends of leakage current and flashover voltage of the composite cross-arms before and after aging were analyzed. Finally, the aging mechanism of the silicone rubber sheaths was analyzed to further explain the reasons for the change of external insulation performance of composite cross-arms. The results show that the leakage current rising rate of T-shaped and square composite cross-arms after aging increases significantly, and the minimum flashover voltage decreases to 58.3 kV and 49.502 kV, respectively. The results of FTIR, SEM and hydrophobic angle tests show that, after aging, the performance of the silicone rubber outer sheath material decreases in varying degrees. In general, UV aging has the greatest influence on the external insulation characteristics of composite cross arms. Generally speaking, after 5000 h of multi factor aging, although the external insulation characteristics of the 10-kV composite cross-arm decreases to a certain extent, there is still enough margin to meet the normal operation.

Flexural Creep Behaviour of Pultruded GFRP Composites Cross-Arm: A Comparative Study on the Effects of Stacking Sequence.

Pultruded glass fibre reinforced polymer (pGFRP) composites provide outstanding properties for composite polymer cross arms in power transmission line applications. This study has investigated the effects of various stacking sequences of fibres directions of pGFRP on flexural strength and creep behaviour. The use of static four-point bending flexural tests revealed that Stacking Sequence 2 (±45/0/90/0/90/0) had a significant flexural strength of 399.9 MPa while Stacking Sequence 1 (±45/90/0/±45) had a flexural strength of 242.5 MPa. Furthermore, the four-point bending creep experiments were performed at three distinct stress levels, notably 12%, 24%, and 37% of the ultimate flexural strength, to characterise the creep behaviour of distinct stacking sequences. Moreover, Findley’s power law equation for bending creep behaviour has revealed that the time-dependent reduction factor of Stacking Sequence 1 and Stacking Sequence 2 estimates a drop in flexural modulus of 23% and 10% respectively.

A Novel Energy Absorption-Based Protection Scheme for Surge Transients in Large-Scale Wind Farm System

Onshore wind farms are usually connected to the power grid by 35 kV transmission lines. Due to the high altitude of the wind turbines and their associated long transmission corridors, lightning activities are more frequent for onshore wind farms compared to the power plant in plain areas. In addition, the insulation levels of 10–35 kV distribution lines are generally low. All these facts make proper lightning strike protection a technical challenge for onshore wind farms. Taking a typical onshore wind farm as the testing object, the structure of the 35 kV distribution line connected to this wind farm is modeled by EMTP software in this paper. The leakage current and absorbed energy of the arrester at the head tower when lightning currents of different amplitudes inject into the overhead line are studied. By calculating the energy accumulated in the arrester within 100 µs, the causes of the lightning trip and damage to the arrester of the distribution line, i.e., the energy accumulation mechanism, are clarified. Eventually, the lightning protection updating scheme for this distribution line is proposed: a combination of refitting the porcelain cross arm at the head and end of the tower and filling the grounding body of the tower with a drag-reduction agent, which shows that the lightning resistance level of the distribution can be improved by 50 times in maximum.

The IBTIS score, a new predictive score for arthroscopic biceps tenotomy

Objectives:Shoulder pain related to long head of biceps tendinopathy is common. Surgical treatment by arthroscopic tenotomy has proven to be effective. The objective was to evaluate the preoperative clinical and radiological prognostic factors of arthroscopic tenotomy of the long head of biceps, and to establish a predictive score of good response to treatment.Methods:We conducted a retrospective single-center study including 64 patients who underwent surgery between January 2018 and March 2020 by arthroscopic LHB tenotomy, whether or not associated with tenodesis. We identified 2 groups of patients based on a clinical evaluation 3 months postoperatively, which included subjective assessment by the Single Shoulder Value (SSV), Constant, C-Test, and pain scores: a good responder group and a poor responder group. Prognostic factors for good response were then identified in the 2 groups based on questioning, clinical examination and preoperative imaging. Based on these factors, a predictive score for a good response was established.Results:All evaluation criteria showed postoperative improvement: Mean SSV (72.2 vs 50.7; p 65 years (p = 0.01), cuff tear on preoperative imaging (p = 0.01), the Cross Arm Test (p = 0.02), night-time pain (p = 0.08), Yergason’s test (p = 0.16), the Speed Test (p = 0.22). Manual labor appeared to be a factor in an unfavorable outcome (p = 0.07). These factors were incorporated into the 10-point IBTIS score. A score above 5 was associated with a favorable outcome in more than 80% of the patients (p <0.001).Conclusion:The IBTIS (Isolated Biceps Tenotomy Index Score) is a preoperative clinical and radiological score with 7 items for surgical treatment by arthroscopic tenotomy of the long head of biceps. Further studies are required to validate the prognostic accuracy.

Filament-wound glass-fibre reinforced polymer composites: Potential applications for cross arm structure in transmission towers

Filament-wound glass-fibre reinforced polymer composites: Potential applications for cross arm structure in transmission towers

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.

Lightning protection performance of quadruple-circuit 500 kV transmission lines on the same tower with composite cross arm

In recent years, composite materials cross-arm (CMCA) towers have been gradually used in 10 kV, 35 kV or other transmission lines with lower voltage level in China. However, it is rarely used in higher voltage level transmission lines, especially in multi circuit lines on the same tower. Because of its higher height, we should pay more attention to the lightning protection performance of high voltage level multi circuit lines on the same tower. In this work, the simulation and calculation analysis of Lightning stroke model of quadruple-circuit 500 kV transmission line is done to compare CMCA tower with steel tower. The research shows that the tolerance lightning level of CMCA tower is superior to conventional steel tower, The lightning withstand level of single circuit flashover is 45% higher than that of steel tower and the minimum shielding failure lightning withstand level is 47% higher than that of steel tower. The data can provide the theoretical basis for the construction and optimization design of high voltage CMCA tower.

The IBTIS score; a new prognostic score for arthroscopic biceps tenotomies

IntroductionShoulder pain associated with tendinopathy of the long head of biceps (LHB) is common. Surgical treatment with arthroscopic tenotomy of the LHB has been shown to be effective. However, it's efficacy is inconsistent. The objective of this study was to assess the pre-operative clinical and radiological prognostic factors of arthroscopic tenotomy of the long head of biceps, and to establish a predictive score for good responses to treatment; the IBTIS score (Isolated Biceps Tenotomy Index Score). HypothesisPrognostic factors representing a good response to treatment of LHB tendinopathy by arthroscopic tenotomy exist. Materials and methodsWe conducted a retrospective monocentric study including 64 patients who underwent surgery of the LHB by arthroscopic tenotomy (with or without tenodesis) between January 2018 and March 2020. We identified 2 patient groups (good responder group and poor responder group) from a 3-month post-operative clinical assessment, which included a subjective assessment comprising Single Shoulder Value (SSV), Constant score, C-Test, and pain level. Prognostic factors of a good response were then sought from the 2 groups using interviews, clinical examinations and pre-operative imaging. Based on these findings, a predictive score for a good response was established. ResultsAll evaluation criteria demonstrated post-operative improvement: mean SSV (72.2 vs 50.7; p<0.001), relative constant (78.2 vs 64.3; p<0.001), pain level (3.2 vs 7; p<0.001) and C-Test (94.1 vs 85.6; p=0.07). 34 patients (58.6%) were considered good responders, while 24 patients (41.38%) were considered poor responders. There was a trend towards a favourable result for: age>65 years (p=0.01), rotator cuff rupture on preoperative imaging (p=0.01), Cross Arm Test (p=0.02), nocturnal pain (p=0.08), Yergason's test (p=0.16) and Speed's Test (p=0.22). Manual labour appeared to be an unfavourable factor (p=0.07). These factors were incorporated into the 10-point IBTIS score. A score greater than 5 was associated with a favourable result in more than 80% of patients (p<0.001). DiscussionOur score consists of 7 items. We identified 7 pre-operative prognostic factors for a good result after LHB tenotomy. Over 65 years of age was found to be statistically significant in univariate analysis, as was visualization of rotator cuff rupture on pre-operative imaging. The Cross Arm Test was included given its high statistical significance. The Speed's Test and Yergason's Test are ubiquitous in the literature. Nocturnal pain was found in more than 80% of patients. Undertaking manual labour represented an unfavourable prognostic factor after arthroscopic surgery of the LHB. ConclusionThe IBTIS score (Isolated Biceps Tenotomy Index Score) is a pre-operative clinico-radiological score for the surgical treatment of arthroscopic tenotomy of the long head of biceps. Further studies are required to validate its prognostic accuracy. Level of evidenceIII; case-control.

Application of TRIZ Theory in the Design of Cross Arm Rotating Clamping Mechanism

In order to solve the problem of the stainless steel pipe falling off during the debugging process of the cross arm rotating clamping mechanism, the TRIZ theory is applied to the innovative design of the mechanism. Firstly, the problem description, causal analysis and function analysis are carried out, then the invention principle and separation principle of conflict resolution theory and the standard solution of substance-field analysis model are used to solve the design problem. After feasibility evaluation, the optimization schemes such as changing the clamping direction and increasing the shape of the clamping rubber bulge are obtained. The optimized cross arm rotating clamping mechanism is applied to the stainless steel tube automatic packaging production line, which solves the problem of the stainless steel tube falling off, and provides a reference for the design of similar clamping mechanism.

Interventions for tophi in gout.

Interventions for tophi in gout.

Numerical Modelling Of Glass Fibre Reinforced Polymer (Gfrp) Tube Subjected To Torsion

Glass Fibre Reinforced Polymer (GFRP) tubes have been used widely as cross arm of electric transmission towers to replaced old wooden cross arms. Cross arm is a part of transmission tower which is required to support conductors or electrical cables. Due to nature of assembly of these GFRP tubes, it will induce torsional force to the individual GFRP tubes of cross arm. The importance of torsional effect to the cross arm has encouraged researcher to study on torsional strength of the single tube itself in order to support a complete set cross arm. In this paper, the performance of glass fiber-reinforced polymer (GFRP) tubes under statically torsional loads was studied numerically. The specimens’ ultimate twisting angle and strain were studied through tests for validation of the numerical model. Explicit solver of ANSYS was chosen and simulation results matched experiment results well with 4 % different. There are six model were simulated and analyzed in this research. It is concluded that model 4 shown the highest ultimate strains as well as twisting angle while model 3 has the lowest ultimate strains and twisting angle. The presence of fiber orientation of 90o in model 4 has contributed to the torsional capacity of the tubes.

Path planning and forming of wire multi-arc additive collaborative manufacture for marine propeller bracket

The propeller bracket is an essential structural component of the large ship, with large structural size, high precision and performance. Multi-arc collaborative additive manufacturing is an effective method for forming high precision and performance large-scale propeller bracket. This paper studies the high-precision and performance multi-arc collaborative additive manufacturing propeller bracket forming strategy and path planning method. In the multi-arc cooperative additive manufacturing of the bracket, the two arcs in the front are used to form the contour of the depositing layer, while the rear three arcs are used to fill the contour. Finally, the five arcs collaborated additive manufacturing bracket is formed. Based on the structural characteristics of the bracket, it is divided into four regions: the hub, support arm, cross arm and intersecting area. The hub is a rotating body of equal thickness and cross-section. The relative positions of the five arcs are fixed, and the path is calculated by adjusting the attitude angle of the device in real-time during the printing process. The intersecting area, support arm and cross arm are all curved bodies with variable thickness and cross-section. The contour torches are used to form the two sides of the contour separately, and then the filling torch is used to variable amplitude swing filling the contour. The five arcs collaborative additive manufacture propeller bracket with a length of 3.5 m is formed by the above forming strategy and path planning method. The forming accuracy of the bracket is ±0.6 mm. The microstructure is composed of pearlite and massive ferrite. The tensile strength is 774 MPa, and the yield strength is 642 MPa. The mechanical properties are higher than the castings one with the same composition, and the forming efficiency reaches 1800 cm3/h.

Advances of composite cross arms with incorporation of material core structures: Manufacturability, recent progress and views

Abstract The existing cross arms in high transmission towers are made of pultruded glass fibre reinforced polymer composite (PGFRPC). The moisture, temperature change in the atmosphere, and other environmental factors affect the performance of these members and cause a complete failure. It is apparent that any material used in such applications is susceptible to attack from environmental factors. Therefore, a feasible solution for this issue is to enhance the PGFRPC with a composite-filled sandwich structure as an alternative that could sustain longer than the existing cross arms due to its superior performance under bending and compressive loads. This paper presents a case study on experimental and analytical mechanical performance of both PGFRPCs and composite-filled sandwich structure. In this review, the composite-filled sandwich structure is proposed as an alternative to the conventional PGFRPC.

Optical chaotic communication using correlation demodulation between two synchronized chaos lasers

This paper theoretically investigates the scheme of optical chaotic communication based on correlation demodulation between two synchronized semiconductor lasers. In the scheme, a semiconductor laser (SL) system, which is subject to phase conjugation and electro-optical phase modulation feedback, generates optical chaos with high-complexity, simultaneously, the time-delay (TD) signature can be well concealed. We use the digital signal “0” and “1” to control the chaotic signal’s switching between two arms of electro-optical (E-O) switch to indirectly achieve spreading spectrum. Concretely, for the “0” bit, at the cross arm the waveform of the optical chaotic signal is reversed by utilizing the cross gain modulation (XGM) effect of semiconductor optical amplifier (SOA); for the “1” bit, the chaotic signal is exchanged from the cross arm into the through arm. Based on the four-wave mixing (FWM) effect of optical parameter amplifier (OPA), the optical chaotic signal is converted to the same center wavelength as SOA’s output, and then two chaotic sequences are coupled into a channel in turn, as a results, the power of the signal of 5 Gbit/s is uniformly distributed and expanded to about 23.45 GHz bandwidth, thus its power spectrum density (PSD) becomes very low. We numerically demonstrate that this chaotic dynamics between the transmitter and the receiver can be identically synchronized due to coupling. The results indicate that the novel correlation-demodulation-based optical chaotic communication scheme can tolerate a higher noise level, and it can achieve a high-quality communication under lower signal-to-noise ratio (SNR). Compared with the scheme of synchronized error monitor, the correlation demodulation way has better ability for anti-noise interference.

Full-wave black-box transmission line tower model for the assessment of lightning backflashover

In order to calculate the overvoltages across the insulator strings of overhead lines, electromagnetic transient (EMT)-type simulators require a model of the tower and its grounding system. In this paper, an electromagnetic field simulation model based on the solution of the full-wave frequency-domain Maxwell’s equations is established to obtain an EMT-compatible black-box representation of the transmission line tower for time-domain simulations. Details of the system, such as the grounding system consisting of counterpoise electrodes, shield wires, phase conductors, and tower cross arms and slant elements are considered in the simulation model. The frequency dependence of soil electrical parameters is included as well. The input data to the frequency-domain simulation model consists of the topology of the tower structure, grounding system, and the parameters of the surrounding medium. As a case study, the developed simulation model is applied to obtain the black-box representation (macromodel) of a 400kV double circuit tower, where the lightning current injected at the tower top is the input, and the output is the induced voltage across the insulator strings. The critical current leading to the flashover of the insulator strings is calculated according to various existing flashover models and two different first stroke lightning current waveforms. Finally, a probabilistic analysis is performed to obtain the percentage of downward negative first strokes leading to a backflashover.