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Human safety is the most important factor to determine any grounding system, therefore low‐frequency grounding resistance (LFGR) of wind power generation systems should be very low. Lightning protection is another factor for the grounding system design. Grounding conductors (GCs) are used to reduce the LFGR. A long GC however, does not reduce peak voltages for lightning currents with steep‐front waveshapes. Thus, the GC length is an important factor for an effective grounding system. This paper proposes a method for determining the effective length of GC based on traveling wave theory in time domain. Based on this calculation, it describes a grounding system design for wind power generation systems that considers both, the LFGR and the lightning protection. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The presence of bamboo fiber has been distributed to improve the structural integrity of construction. It has been used to resist impact loads and reduce crack widths in composite materials. This can be utilized for reinforcement in construction, particularly in mortar elements. Bamboo fiber has been used to resist impact loads and reduce crack widths in composite materials. This can be utilized for reinforcement in construction, particularly in mortar elements. By combining good treatment with alkaline NaOH, the quality of the fiber used as a mortar mix will increase and the capacity to absorb impact energy will be greater. In this study there were 2 stages, the first stage was to look at the effect of the effective length of bamboo fiber and alkaline molarity. The effect of treatment using alkaline is to reduce the lignin and hemicellulose substances which reduce the bond in the mortar mixture. The optimal value for the Pull-out test, which involved manipulating the molarity of NaOH as a treatment and the effective length of bamboo fiber, was determined to be 2.5 cm of embedded fiber or a total length of 5 cm when 4 molar NaOH was utilized. All fiber bamboo-composite bars had a cross section of average at 1Ã--1 mm. And the second stage tested Charpy for impact load resistance in mortar with the optimum effective fiber length while varying the alkaline molarity. The objective of the Charpy impact test was to determine the optimal quantity of bamboo fiber to be incorporated into mortar when subjected to impact loads. standard Charpy impact test specimen is 55Ã--10Ã--10 mm in dimension. Experimental data show that the effective length and treatment of bamboo fiber affected the bond strength with mortar. A proportional relationship was observed between the addition of fiber to the mortar and an increase in compressive strength. The research findings indicate that the lowest modulus of toughness is 0.329 MPa, or equivalent compressive strength at 15.583 MPa, while employing 3.25 % bamboo fiber in mortar with a fiber length of 5 cm and a 12 % alkaline treatment. [ABSTRACT FROM AUTHOR]

Two types of grounding systems are recommended for use in the international standard IEC 62305-3, Part 3: Physical damage to structures and life hazard. One of these is a radial-based grounding system (type-A), which is used in soil resistivities of up to 3000 Ω m and is considered in this paper. It is a well-known fact that during lightning strikes, only a part of the grounding wire contributes to dissipating the lightning current into the surrounding soil. This effective part of the grounding system depends on several features, such as soil resistivity, burial depth, and rise time of the dissipated lightning current. The effect of all of these features on the effective length of the type-A grounding system is explored in this paper. A suitable supervised machine learning regression model is developed, which will enable readers to accurately approximate the effective length of the type-A grounding system for realistic values of input features. The trained model in the paper yielded an R 2 value of 0.99998 on the test set. In addition, two simple mathematical formulas are also provided, which produce similar but less accurate results ( R 2 values of 0.989883 and 0.998557, respectively). [ABSTRACT FROM AUTHOR]

Under planar conditions, separation of a thin rigid inclusion in an orthotropic body subjected to cyclic stress load parallel to its extension line has been investigated. Separation is preceded by the development of localized prefracture process zones (weakened contact), such as plastic zones, damage accumulation zones, partial debonding zone, etc. Analytical formulas for the effective length of the inclusion depending on the orthotropy parameters, load amplitude, number of cycles, strength and elastic characteristics of the matrix have been obtained. The effective length of the inclusion has been calculated for specific composite's characteristics and the applied load. [ABSTRACT FROM AUTHOR]

This study examined essential factors in the use of hollow fiber membranes that affect CO2 removal efficiency. In the simulation, a finite element model for a membrane with ten fibers was used. Each fiber is 175 mm long with inner radius of 0.75 mm and outer radius of 1.5 mm. Liquid and gas flow rates were set at 100–800 mL min−1, and adsorbent concentration was adjusted in the range of 200–1500 mol m−3 for monoethanolamine, piperazine (PZ), and ethylenediamine absorbents. Increasing the liquid flow rate, gas flow rate, and absorbent concentration leads to an increase, decrease, and increase in efficiency, respectively. Thus, using PZ as absorbent with a concentration of 1080 mol m−3 liquid and gas flow rates of 400 and 180 mL min−1, respectively, showed a CO2 removal efficiency of > 95 % for a membrane effective length of 0.3 m. [ABSTRACT FROM AUTHOR]

Abstract—The adhesive properties of the filament–matrix interface were studied in experiments on pulling filaments from a polymer matrix manufactured using additive technologies. The limiting shear stresses at the interface between the carbon filament and the polymer matrix are determined, as is the influence of the length of the filament "embedding" on the pulling force. For this purpose, specimens with different lengths of filament "embedding" were made. To estimate the displacement fields, the digital image correlation (DIC) method was used. Pictures of the fields of displacements and strains on the surface of the specimen were obtained, from which one can judge the processes occurring at the filament–matrix interface. The characteristic fields of strain when pulling a single filament from the matrix solid are shown. The length of the thread at which the load bearing capacity of the composite is realized more efficiently and the load is close to the limit for the filament itself was determined experimentally. Based on experimental data, the minimum effective length of filament "embedding" in the manufacturing of composite structural elements using additive methods was calculated. [ABSTRACT FROM AUTHOR]

The z-scan is a straightforward method of determining the phase shift generated on a laser beam as it passes through a nonlinear medium. It specifies the sign and amplitude of the phase change, Δ Φ 0 which is proportional to the change in the index of refraction, Δ n . Furthermore, z-scan determines the change in transmission induced by nonlinear absorption, which is proportional to the change in the absorption coefficient. The phase shift increases as the sample thickness increases and all the phase shifts pass through the same points for all values of sample thicknesses. In the closed aperture nonlinear refraction, the signal measured would shows a peak and valley as the sample is moved and the location of peak and valley depends on the sign of the nonlinear phase shift, Δ Φ 0 . [ABSTRACT FROM AUTHOR]

Two types of grounding systems are recommended for use in the international standard IEC 62305-3, Part 3: Physical damage to structures and life hazard. One of these is a radial-based grounding system (type-A), which is used in soil resistivities of up to 3000 Ωm and is considered in this paper. It is a well-known fact that during lightning strikes, only a part of the grounding wire contributes to dissipating the lightning current into the surrounding soil. This effective part of the grounding system depends on several features, such as soil resistivity, burial depth, and rise time of the dissipated lightning current. The effect of all of these features on the effective length of the type-A grounding system is explored in this paper. A suitable supervised machine learning regression model is developed, which will enable readers to accurately approximate the effective length of the type-A grounding system for realistic values of input features. The trained model in the paper yielded an R2 value of 0.99998 on the test set. In addition, two simple mathematical formulas are also provided, which produce similar but less accurate results (R2 values of 0.989883 and 0.998557, respectively).

Acid fracturing as an important stimulation technique, provides strong technical support for the exploration breakthrough and efficient development of carbonate oil and gas reservoirs. Accurately predicting the effective length of acid-fracturing fractures is of great significance for guiding the acid-fracturing design and improving the stimulation effect of acid fracturing. This article fully considers the essential requirement that the long-term conductivity of acid-fracturing fractures is not zero within the effective length segment. Based on the principle of the same acid concentration and acid dissolution amount, the long-term conductivity testing experiment of acid-fracturing fractures under different residual acid concentrations was designed and carried out with the consideration of the common ion effect. The critical acid concentration with long-term conductivity of 0 was obtained. This method overcomes the shortcomings of the existing methods that result in the overestimation of the effective length of acid-fracturing fractures due to inaccurate values of residual acid concentration or short-term conductivity as the determining criterion. The experimental results show that the higher the acid concentration, the deeper the acid etching groove, and the higher the initial conductivity of acid-fracturing fractures. The long-term conductivity decline rate of different acid concentrations is above 80%, which means that using short-term conductivity as an evaluation indicator alone will overestimate the effective length of acid-fracturing fracture and the yield-increasing effect of acid-fracturing treatment. In the case presented in this paper, the critical acid concentration for acid-fracturing fracture with long-term conductivity of 0 is 4%, and the effective length of acid-fracturing fractures is 120 m. [ABSTRACT FROM AUTHOR]

There has been a study of resonant gas oscillations in a closed tube with different vertex angle of the cone-shaped end. Amplitude-frequency responses of the tubes have been obtained. It has been discovered that a decrease in the vertex angle of the cone-shaped end leads to a shift in the resonant frequency decreasingly, i.e., to dispersion. There has been found a range of vertex angles of the cone-shaped end, when the gas pressure oscillation amplitude increases in all sections of the tube comparing to oscillations in a uniform tube of the equivalent length. [ABSTRACT FROM AUTHOR]

The algorithm for the numerical solution of the quasistatic thermoelasticity problem in the domains of simple spatial forms is briefly described. The initial validation and verification of the developed numerical technique was performed. Some results of the solution of the quasistatic thermoelasticity problem in the simplest structural elements of aircraft. [ABSTRACT FROM AUTHOR]

When a thermocouple is used to measure gas temperature, the measured temperature is the thermocouple bead temperature, which is not equal to the gas temperature. The bead temperature results from its energy balance. Through the wire convection and conduction, the temperature of the bead is related to the gas temperature within a certain geometric range around it, and this range is quantified by the effective length. Under the sinusoidal incoming gas temperature condition, the analytical expression for the effective length is deduced, and its accuracy is validated by the one-dimensional numerical solution. The differences between the analytical and numerical effective lengths are less than 10.5% for the test cases. Similar to that under the uniform incoming gas temperature condition, the effective length under the sinusoidal gas temperature condition increases with the thermal conductivity and the diameter of the wire and decreases with the heat transfer coefficient of the wire. The influence of the amplitude, wavelength and phase of the gas temperature on the effective length are very weak, meaning that the theoretical expression under the uniform gas temperature can calculate the effective length under the non-uniform gas temperature with good accuracy. [ABSTRACT FROM AUTHOR]

Owing to its crooked trajectory and small full width at half-maximum, photonic hook (PH) has attracted wide attention since its inception and experimental confirmation. However, the present generation and regulation of PH are mostly dependent on the breaking of the symmetry of the system composed of the incident light and the regular structure particles, which inevitably limits the research of PH. In this work, the PH of the irregular particles is demonstrated with the help of a structure-constrained function (SCF). By varying the coefficients of the function, characteristic parameters of the PH, such as the bending angle, the effective length and the bending direction, can be effectively modulated. Meanwhile, high-quality PHs with a bending angle of up to 46° and an effective length of up to 11.90λ, as well as PHs with three bends, can be obtained using this method. The formation mechanism of the PH is revealed by simulating the distribution of the field intensity with the finite element method and analyzing with ray optics. This is the first time that we introduce a function into the investigation of PH, paving a new way for a more interesting exploration of PH. [ABSTRACT FROM AUTHOR]

The combination of a labyrinth weir with an orifice is a proper solution for floating material to pass over the weir and transfer sediment through the orifice. Additionally, creating a slot in the overflow wing leads to higher discharge. This study examined four discharges (5, 10, 15, and 20 liters per second) with channel width and height of 30 and 40 cm in trapezoidal-orifice, square-orifice, and triangular-orifice labyrinth weirs in the laboratory and using Flow3D with RNG k-epsilon (k-ε) turbulence model, the results were compared with one another. Comparing the discharge flow over weirs and measuring the discharge coefficient among the mentioned models showed that the triangular-orifice labyrinth weir had the highest discharge rate. Moreover, the increased Ht/P ratio (Ht represents total hydraulic head; P denotes weir height) for all models resulted in the increased discharge coefficient. Due to the efficiency of this type of weirs, the highest discharge coefficient was obtained at low Ht/P ratios. At lower ratios, since there was free flow, the coefficient of weir discharge increased, and as the ratio increased, the weir was partially submerged. Furthermore, for the weir design, the best Ht/P ratio was between 0.13 to 0.41, and the maximum discharge coefficient (Cd = 1.2) was within this range.

This paper is focussed on the investigation of the strengthened column by steel-fibre-reinforced (SFR) and carbon fibre-reinforced polymer (CFRP) on a part or a whole of the length of the column under axial force, and to obtain the effective length, which is responsible for the increasing of the ability of the column to resist buckling. Seven samples were designed as slender reinforced columns with dimensions of 2000 mm length and cross-sections of 120 mm x 60 mm. It was shown that the strengthening of the middle half of the column length by SFR gave an ultimate load similar to the strengthening of the whole column with same material. Also, it was found that the column strengthened by SFR increased its ultimate load by 42.6 %, 42.1 % and 33.3 % for strengthened lengths of dimensions L, L/2 and L/3, respectively, compared to the non-strengthened column. The increase in ultimate load that could be borne by the column strengthened by CFRP were 53.0 % and 33.8 % for strengthened lengths of L and L/2, respectively, only. Interaction diagram had been depended as a theoretical analysis for slender concrete columns. The interaction diagram for the column strengthened by CFRP is greater than for the column strengthened by SFR, which in turn is greater than the non-strengthened column.

Nonlinear gas oscillations in a homogeneous closed tube and in a tube with a cone tip near the resonating excitation frequency were studied. A good agreement is obtained between the gas amplitude-frequency characteristics and pressure epure of the analytical theory and numerical experiment. [ABSTRACT FROM AUTHOR]

A low complexity scheme is developed to design the sparse linear phase FIR filters based on the improved iteratively re-weighted orthogonal matching pursuit(OMP) algorithm. The scheme employs the Frobenius norm to simplify searching for the desired sparse FIR filter at each iteration. Furthermore, a log function is introduced to enhance the weight updating process at each iteration. The simulation results demonstrate that our scheme can effectively generate the sparse linear phase FIR filters which satisfy the various given design specifications. [ABSTRACT FROM AUTHOR]

Developments in recent electronics result in electronic components that produce heat, namely, Central Processing Units (CPUs). One solution to this problem is using a heat pipe. In this study, a cascade straight heat pipe (CSHP) is analyzed as a CPU cooling system with three effective lengths: 20 cm, 23 cm, and 26 cm. The first workload provided was Idle; the processor only ran the operating system without a software load, so that the processor utilization was only 1-10%. The second was full load, where the processor utilization was 95-100%. The CSHP-based CPU-cooling system with an effective length of 20 cm was able to reach processor temperatures of up to 43.32oC (idle) and 63.62oC (full load). For the effective length of 23 cm, processor temperatures of 46.99oC idle) and 64.81oC full load was attained. Lastly, while using the effective length of 26 cm, processor temperatures of 50.67oC idle and 65.21oC full load were reached. CPU cooling systems using CSHP are thermally resistant when in idle conditions; respectively, the temperatures for the effective lengths of 20 cm, 23 cm, and 26 cm are 0.168oC/W, 0.197oC/W, and 0.223oC/W. In contrast, for the same effective lengths, the thermal resistance at full load was 0.262oC/W, 0.236oC/W, and 0.224oC/W, respectively. Overall, the cascade heat pipe shows better cooling performance than a stock cooler.

Many failures of wind turbine blades and electrical equipment due to powerful lightning strikes have occurred. The lightning-induced wind turbine failures that have occurred in recent years can be classified into two main categories. The first is a mechanical component failure. The second is a failure or malfunction of electric or electronic equipment inside or around the wind turbine due to an increase in the potential of the wind turbine grounding system or the electromagnetic induction caused by the lightning strike. In the latter case, the equipment often fails owing to the increase in the potential of the grounding system, the method of suppressing the potential rise by laying a grounding wire vertically or horizontally to the wind turbine foundation is adopted. We propose an empirical expression for the effective length of counterpoises connected to a large grounding electrode such as a wind turbine foundation, and verify the expression using finite-difference time-domain (FDTD) method. [ABSTRACT FROM AUTHOR]

When a thermocouple is used to measure gas temperature, the measured temperature is the thermocouple bead temperature, which is not equal to the gas temperature. The bead temperature results from its energy balance. Through the wire convection and conduction, the temperature of the bead is related to the gas temperature within a certain geometric range around it, and this range is quantified by the effective length. Under the sinusoidal incoming gas temperature condition, the analytical expression for the effective length is deduced, and its accuracy is validated by the one-dimensional numerical solution. The differences between the analytical and numerical effective lengths are less than 10.5% for the test cases. Similar to that under the uniform incoming gas temperature condition, the effective length under the sinusoidal gas temperature condition increases with the thermal conductivity and the diameter of the wire and decreases with the heat transfer coefficient of the wire. The influence of the amplitude, wavelength and phase of the gas temperature on the effective length are very weak, meaning that the theoretical expression under the uniform gas temperature can calculate the effective length under the non-uniform gas temperature with good accuracy.

The combination of a labyrinth weir with an orifice is a proper solution for floating material to pass over the weir and transfer sediment through the orifice. Additionally, creating a slot in the overflow wing leads to higher discharge. This study examined four discharges (5, 10, 15, and 20 liters per second) with channel width and height of 30 and 40 cm in trapezoidal-orifice, square-orifice, and triangular-orifice labyrinth weirs in the laboratory and using Flow3D with RNG k-epsilon (k-ε) turbulence model, the results were compared with one another. Comparing the discharge flow over weirs and measuring the discharge coefficient among the mentioned models showed that the triangular-orifice labyrinth weir had the highest discharge rate. Moreover, the increased Ht/P ratio (Ht represents total hydraulic head; P denotes weir height) for all models resulted in the increased discharge coefficient. Due to the efficiency of this type of weirs, the highest discharge coefficient was obtained at low Ht/P ratios. At lower ratios, since there was free flow, the coefficient of weir discharge increased, and as the ratio increased, the weir was partially submerged. Furthermore, for the weir design, the best Ht/P ratio was between 0.13 to 0.41, and the maximum discharge coefficient (Cd = 1.2) was within this range. [ABSTRACT FROM AUTHOR]

Labyrinth weirs are the economic structures to increase the weir output efficiency in limited widths, which can be seen in the plane f trapezoidal and triangular forms. These weirs with a hydraulic load and fixed width pass the more discharge in comparison to other type of weirs. In this study, labyrinth weirs trapezoidal in plane form were investigated. The experiments were performed on 27 laboratory models with 9 different discharge rates and a total of 243 tests. The results showed that, in all of the composite trapezoidal labyrinth weirs, the ratio of discharge coefficient to Ht/p (Ht: Total hydraulic load and p: weir length) weir length was increased at first; after reaching the maximum rate, it started to decrease. According to the suggested general relation, the utmost impact on discharge coefficient resulted from the cycle number and Ht/p relation. Creating new labyrinth on the wing of the weir led to the increase of the effective length; as a result of it, the discharge rate increased in a specific amount of Ht/p. Also, the discharge through a trapezoidal labyrinth weir with the semicircular planform was better than the square; the square, in turn, was better than the simple trapezoidal weirs.

Owing to its crooked trajectory and small full width at half-maximum, photonic hook (PH) has attracted wide attention since its inception and experimental confirmation. However, the present generation and regulation of PH are mostly dependent on the breaking of the symmetry of the system composed of the incident light and the regular structure particles, which inevitably limits the research of PH. In this work, the PH of the irregular particles is demonstrated with the help of a structure-constrained function (SCF). By varying the coefficients of the function, characteristic parameters of the PH, such as the bending angle, the effective length and the bending direction, can be effectively modulated. Meanwhile, high-quality PHs with a bending angle of up to 46∘ and an effective length of up to 11.90λ, as well as PHs with three bends, can be obtained using this method. The formation mechanism of the PH is revealed by simulating the distribution of the field intensity with the finite element method and analyzing with ray optics. This is the first time that we introduce a function into the investigation of PH, paving a new way for a more interesting exploration of PH.

In this paper, an efficient modeling approach called improved MTL is used to predict effective length of counterpoise wires considering both ionization and dispersion of soils. This paper consists of two parts. At first part, validity of the model for computing effective length of counterpoise wires considering only soil ionization is investigated. The simulation results show that the improved MTL-based effective length of counterpoise wire are in good agreement with the existing formulae. Application of this modeling approach to include ionization and dispersion effects simultaneously (both-affected soil) is carried out in the second part. The simulation results show that in both-affected soils, the effective length with respect to only-ionized soils, is decreased especially in highly resistive soils under slow-fronted currents. This makes inclusion of both effects financially important in designing counterpoise wires.

In the paper, the concept of non-local line method is presented and used for determining the effective length for notched elements. Experimental tests and calculations were performed for 40 HM-T (42CrMo4+QT) steel made specimens of two types, i.e. smooth specimens, and notched specimens with notch radius equal to 0.2 mm, 0.5 mm, 0.8 mm, and 1 mm. The performed FEM calculations took into account the multi-linear hardening model and cyclic material properties. The concept of the presented non-local line method bases on finding the position of critical plane and determining the effective length, meant as the fracture process zone. During numerical stress gradient simulations, also the weight function was implemented. It was observed that the effective length increases as the load increases.

Developments in recent electronics result in electronic components that produce heat, namely, Central Processing Units (CPUs). One solution to this problem is using a heat pipe. In this study, a cascade straight heat pipe (CSHP) is analyzed as a CPU cooling system with three effective lengths: 20 cm, 23 cm, and 26 cm. The first workload provided was Idle; the processor only ran the operating system without a software load, so that the processor utilization was only 1-10%. The second was full load, where the processor utilization was 95-100%. The CSHP-based CPU-cooling system with an effective length of 20 cm was able to reach processor temperatures of up to 43.32°C (idle) and 63.62°C (full load). For the effective length of 23 cm, processor temperatures of 46.99°C idle) and 64.81°C full load was attained. Lastly, while using the effective length of 26 cm, processor temperatures of 50.67oC idle and 65.21°C full load were reached. CPU cooling systems using CSHP are thermally resistant when in idle conditions; respectively, the temperatures for the effective lengths of 20 cm, 23 cm, and 26 cm are 0.168°C/W, 0.197°C/W, and 0.223°C/W. In contrast, for the same effective lengths, the thermal resistance at full load was 0.262°C/W, 0.236°C/W, and 0.224°C/W, respectively. Overall, the cascade heat pipe shows better cooling performance than a stock cooler. [ABSTRACT FROM AUTHOR]

This study presents an investigation into effective length of passing lanes on rural two-lane highways using field and simulation data. Field data from two study sites in Oregon were used to calibrate and validate the traffic simulation program used in this study. The calibrated simulation model was then used in evaluating the effective length of passing lane under different traffic levels and percent no-passing zones. Study results showed that the effective length of a passing lane is a function of traffic level as well as the percent no-passing zones for any segment of two-lane highway. Further, results confirmed that the operational benefits of passing lanes generally last for a significant distance downstream of the passing lane, with this distance varying in the range between 3 and 20 miles depending on traffic level and percent no-passing zones. Expectedly, higher traffic levels and higher percentage of no-passing zones were found to result in shorter effective lengths. [ABSTRACT FROM AUTHOR]

An essential requirement to improve the lightning performance of transmission line is the achievement of low impulse impedance of grounding system, which diminishes the occurrence of the external overvoltages. In this study, for the first time, a multi‐cross structure used as transmission line tower‐footing grounding system is investigated by means of hybrid continuous circuit‐trapezoidal integration method (HCCTIM). It is discovered that the angle of minimum impulse impedance or the optimal structure of multi‐cross grounding system is mainly dependent on the branch length compared to the effective length of a single horizontal conductor. Furthermore, in the current work, the trapezoidal integration method is used to solve the continuous circuit equations which elements are extracted from electromagnetic integral method, called HCCTIM. Coupling elements and soil ionisation are considered in this model. This method is an accurate, simple, and less time‐consuming computational method. The comparison of the results with measurements, other recent simulations and CDEGS software, satisfactorily validate the proposed method. [ABSTRACT FROM AUTHOR]

In most current codes of design steel members and frames, specifications for the design of compression columns or of beam-column use the effective length factor; K. the effective length factor is employed to facilitate the design of framed members by transforming an end-restrained compressive member to an equivalent pinned-ended member. The effective length factor is obtained by solving the exact equations numerically which require many routine calculations or by using a pair of alignment charts for the two cases of braced frames and sway frames. The accuracy of these charts depends on the size of chart and the reader’s sharpness of vision. Instead of using complicated equations or charts, simple equations are required to determine the effective length factor directly as a function of the rotational resistant at column ends (GA, GB). better equations have been available in the French design rules for steel structures since 1966, and have been included in the European recommendations of 1978. In this paper, modification to the French design rules equations for effective length factors are presented using multiple regressions for tabulated exact values corresponding to different practical values of the rotational resistance at column ends (GA, GB). The investigated equations are more accurate than current French rules equations that recommended in some steel constructions codes. Comparisons between the results of the present equations and those obtained by current equations with those obtained by exact solutions are given also in this paper. [ABSTRACT FROM AUTHOR]

The acoustic inertia of the canonical configuration of inclined circular aperture(s) in a finite-thickness plate at the low frequency limit is investigated under the inviscid still-air condition. A hybrid approach combining modal expansion and boundary element method is applied to calculate the effective length of the aperture as a quantitative characterisation of its acoustic inertia. These calculations, covering different inclination angles up to 75°, are performed for a single isolated aperture with a selected range of plate thickness and the periodic aperture arrays of aligned and staggered arrangements with a selected range of aperture spacing respectively. The results are validated by the simulations carried out with the commercial software COMSOL. The parametric studies of geometric dimensions included in this work provide representative results for typical acoustic related engineering applications of finite-length inclined apertures. A link for access to the MATLAB programmes implementing the calculations is provided for interested readers. As an example of application, the hybrid method described in this work is used for the acoustic modelling of a representative multi-perforated liner studied in the literature for the problem of thermo-acoustic instability. The results compared well against those obtained from the Computational Fluid Dynamics simulations reported in the literature. • An efficient method to compute acoustic inertia of inclined apertures is developed. • Inviscid acoustic inertia of inclined apertures in still air is studied. • Application of acoustic inertia calculation to a representative case is demonstrated. [ABSTRACT FROM AUTHOR]

In this article, a formulation was developed for designing a stable disk laser resonator and achieving a high power and a beam quality close to the fundamental mode with a short effective length. In this regard, by taking a matrix approach and using Gaussian beam propagation based on the ABCD law for Gaussian beams, the fundamental-mode spot size inside a resonator and its sensitivity to misalignment, as well as dynamic stability in multiple folded resonators, were analyzed in order to achieve a short effective length. In the presented method, the optimal geometrical parameters of the resonator were obtained by applying the length limits, permissible level of sensitivity to misalignment, and range of dynamic stability with the help of MATLAB software coding. Using this design algorithm, a Z-shaped resonator with the arm length of 50 cm and fundamental-mode spot size of 2.4 mm on the active media was designed, while the resonator had a good dynamic stability and low sensitivity to misalignment. Considering these specifications, it was possible to design a compact disk laser with a power of 1 kW, which had a beam quality close to the fundamental mode. To the best of our knowledge, the laser disk resonator described in this paper, which is resistant to misalignment and has a short effective length, has not been previously documented in the literature. The model developed in this research is a general model that can be used in much more complex structures with any numbers of optical elements in other lasers. • Misalignment sensitivity model is developed for multi-element stable resonators. • Different I-, V-, Z- and W- shaped stable resonators are investigated. • Misalignment tolerable, compact disk laser resonator is designed. [ABSTRACT FROM AUTHOR]

This paper discusses the impulse analysis of horizontal ground electrode buried in uniform and two-layer soils, describing applications of a recently developed model based on transmission line approach for the analysis of high frequency and transient behavior of grounding systems. Simulations were carried out to compute the ground electrode’ potential and the impulse impedance. A practical method to estimate the effective length of horizontal ground electrodes is presented. The results have been successfully compared with those computed using formulas reported in the literature and only developed for uniform soils. The proposed method is intended for estimation of the effective length of horizontal electrodes buried in soils having a two-layer stratification, which has not yet been considered so far. Based on this method, parametric analysis carried out has shown that the parameters influencing the effective length are mainly the soil resistivity and the rise time of the injected current for uniform soils or associated with the upper layer depth and the refection factor for two-layer soils. Using a genetic algorithm, mathematical expressions for the effective length of horizontal ground electrodes are proposed in terms of these parameters. [ABSTRACT FROM AUTHOR]

Submerged aquatic vegetation (SAV), such as seagrass, is flexible and reconfigures (bends) in response to waves and current. The blade motion and reconfiguration modify the hydrodynamic drag. The modified drag can be described by an effective blade length, l e , which is defined as the length of a rigid blade that results in the same drag as a flexible blade of length l. In many natural settings SAV is exposed to combinations of waves and current. This study derived and used laboratory measurements to validate new predictions of effective blade length for combined waves and current based on a Cauchy number, which describes the ratio of hydrodynamic drag to the restoring force due to rigidity of blade. Force measurements on and digital images of blades exposed to waves with a 2-s period and with a range of wave velocity (U w) and current speed (U c) were used to estimate the effective blade length. The measurements were also used to validate a numerical simulation of blade motion. Once validated, the simulation was used to expand the investigated parameter space to a wider range of wave conditions, and in particular longer wave periods. For U c < 1 4 U w , the blade motion and hydrodynamic drag were wave-dominated. For U c > 2 U w , the blade motion and hydrodynamic drag were current-dominated. • A new prediction of drag on a flexible blade in combined wave and current is derived and validated with experiments. • The drag on a flexible blade in waves decreases with increasing current magnitude. • The limits of wave-dominated and current-dominated drag are defined. [ABSTRACT FROM AUTHOR]

We investigate the origins of 'de Vries-like' liquid crystalline behaviour by introducing an ethynyl spacer in the core of the tricarbosilane-terminated 5-phenylpyrimidine mesogens QL16-6 and QL17-6. The rationale for this structural change is based on the assumption that an ethynyl spacer would create more free volume in the core sub-layer and therefore decrease the orientational order parameter S2 in the SmA phase. The tricarbosilane-terminated mesogens WL41-5 and WL42-6 with a 5-(phenylethynyl)pyrimidine core in either a normal or inverted orientation were synthesised, and their mesomorphic and 'de Vries-like' properties characterised using polarised optical microscopy, differential scanning calorimetry, birefringence measurements, small–angle (SAXS) and 2D X-ray scattering. Reduction factors R derived from SAXS and optical tilt angle measurements suggest that neither WL41-5 (R = 0.49) nor WL42-6 (R = 0.80) exhibit 'de Vries-like' properties. The S2(T) profiles show an increase in orientational order with decreasing temperature and a sharp discontinuity at the SmA-SmC transition, which is consistent with 'de Vries-like' behaviour. However, the Leff(T) profiles suggest an increase in interdigitation that reduces the positive effect of increasing S2 in compensating for the molecular tilt. [ABSTRACT FROM AUTHOR]

Labyrinth weirs are the economic structures to increase the weir output efficiency in limited widths, which can be seen in the plane f trapezoidal and triangular forms. These weirs with a hydraulic load and fixed width pass the more discharge in comparison to other type of weirs. In this study, labyrinth weirs trapezoidal in plane form were investigated. The experiments were performed on 27 laboratory models with 9 different discharge rates and a total of 243 tests. The results showed that, in all of the composite trapezoidal labyrinth weirs, the ratio of discharge coefficient to Ht p (Ht: Total hydraulic load and p: weir length) weir length was increased at first; after reaching the maximum rate, it started to decrease. According to the suggested general relation, the utmost impact on discharge coefficient resulted from the cycle number and Ht p relation. Creating new labyrinth on the wing of the weir led to the increase of the effective length; as a result of it, the discharge rate increased in a specific amount of Ht p . Also, the discharge through a trapezoidal labyrinth weir with the semicircular planform was better than the square; the square, in turn, was better than the simple trapezoidal weirs. [ABSTRACT FROM AUTHOR]

Earth tubes are earth-to-air heat exchangers that are frequently utilized in energy conscious low-rise buildings, but are scarcely reported for tall buildings. The feasibility of applying earth tube cooling to tall buildings in a hot summer and cold winter climate zone was studied in this paper. Firstly, the designed cooling load of a tall building was obtained from the energy simulation using the baseline and the modified models with applicable energy efficiency measures. Based on the load, the required cooling capacity, the overall section area and the effective length of the earth tube system was deduced from the heat transfer and fluid flow calculation analytically. Then the performance of the earth tube system was crosschecked and verified via the Computational Fluid Dynamics (CFD) simulation. In the CFD simulation, earth tubes with different diameters and lengths, as well as a full-scale earth tube model with surrounding soil above the depth of constant temperature, were investigated. The outlet air temperatures of the full-scale models were computed with the consideration of different axial distances between adjacent tubes. Meanwhile, multiple conceptual design schemes and the tunnel construction method for the earth tube system were proposed from the perspective of performance enhancement, constructability, efficiency and economy. It revealed that earth tube systems are conditionally feasible for some tall buildings if their design guidelines for climate, underground spaces, construction method, friction of tube interior surface, optimization of effective length and axial distance, as well as synergy with other energy efficiency measures are followed. Even the cooling capacity of earth tubes degrade with time due to the accumulated heat underground, but in a hot summer and cold winter climate zone it can still possibly produce cooled air for a tall building with a Floor Area Ratio of less than 7 effectively in summer. [ABSTRACT FROM AUTHOR]

The frequency distortion of a one-way signal at the output of a non-directional antenna helicopter, which arises during rotation of the helicopter main rotor, is detected. The power loss of a useful signal for the existence of satellites is appreciated. They arise in near each spectral component of a useful signal. In this case, they exist due to the energy of a useful signal. Therefore, the signal/noise ratio at the output of the non-directional antenna of the helicopter becomes lower than at its input. Reducing the power of a useful signal will result in a corresponding deterioration in the quality of the radio communication. [ABSTRACT FROM AUTHOR]

To obtain the in-plane effective length of members of shells with aluminum alloy gusset (AAG) joints, an experimental program including five shell members under axial loading was carried out to investigate their stability. Finite element (FE) models were established in ABAQUS using solid elements to simulate the test specimens, and their effective lengths were derived using the inflection points. The research results reveal that the in-plane effective length of the members is related to their net length due to the semi-rigidity of AAG joints. Non-linear spring element COMBIN39 was adopted to establish a shell model considering the semi-rigidity of AAG joints in ANSYS. Based on the comparison on the first-order buckling load of the shells and the critical load of the members, it is found that the weakening of constraint due to the stiffness degradation of the compressive members can lead to an increase of effective length by up to about 33%, which cannot be ignored. Through the derivation of the constraint stiffness and the solving of the elastic stability equilibrium differential equation, an in-plane effective length factor table was derived considering the semi-rigidity of the joint and the constraint of the ambient members, which can provide foundation for the design of AAG shell members. [ABSTRACT FROM AUTHOR]

Abstract: To the mechanics of the equivalent T‐stub. The ”equivalent T‐stub“ model is a recognized method of assessing the load bearing capacity of bolted end‐plate connections. In DIN EN 1993‐1‐8 this method is specified as standard. The formulas given there for calculating the effective length are based on the evaluation of a large number of test results and supplementary FE calculations. A conclusive mechanical model is still missing. In the following, such a mechanical model will be presented, which allows to easily calculate the total effective length of yield lines for different collapse patterns on the basis of the plastic hinge line theory. [ABSTRACT FROM AUTHOR]

High-temperature superconductors (HTSs) have a much larger thermal margin than low-temperature superconductors, owing to their high critical temperatures. This characteristic allows HTSmagnets to tolerate extremely high heat loads thatmay arise from radiation. Therefore, research on the development of HTS quadrupole magnets is progressing widely. Quadrupole magnets are commonly used for focusing the transported beams of particles in accelerators. In order to focus the beam, the quadrupole magnet uses an iron yoke with a hyperbolic contour. However, the iron yoke induces nonlinear magnetic characteristics because of saturation. Therefore, an air-core HTS quadrupole magnet is proposed to improve the magnetic characteristics. In this paper, we design air-core and iron-core HTS quadrupole magnet models using a harmonic matching method. The field gradient and effective length of both magnets are 12.1 T/m and 550 mm, respectively. In order to verify the performances of the proposed air-core quadrupole magnet, the magnetic field gradient, field uniformity, and effective length are analyzed for operating currents ranging from 50 to 400 A. [ABSTRACT FROM AUTHOR]

Finite element (FE) modelling was performed to extend the results of a recently completed experimental test program to evaluate the static strength of fillet welds in X-connections between circular hollow sections (CHS). Non-linear FE models with weld fracture were validated by comparison of spot strains, load-deformation response, and fracture load with 12 experimental tests. Two hundred and fifty-six FE weld-critical CHS-to-CHS X-connections, with varied branch-to-chord diameter ratio, chord wall slenderness, branch inclination angle, and branch-to-chord thickness ratio, were analysed under quasi-static branch tension. The effect of these parameters on fillet weld strength is illustrated, and the structural reliability (or safety index) of North American specification provisions for weld effective lengths is confirmed. An alternative method for estimating fillet weld strength, with specific weld effective lengths, is proposed. Recommendations for a new design approach that meets the minimum target safety index in North America are made. [ABSTRACT FROM AUTHOR]

This paper presents an analytical research on the in-plane stability of members in single-layer reticulated latticed shells with aluminum alloy gusset (AAG) joints. The influence of two kinds of actual boundary conditions are considered, namely, the stiffness of the AAG joint ( k 1 ) and restraint of adjacent members ( k 2 ). In order to explore the influence of k 1 , an experimental program including 5 member specimens with AAG joints is introduced, and finite element (FE) models are established and verified. Based on the test and FE results, the effective length of the specimens are obtained. Subsequently, theoretical analysis is conducted to investigate the effect of k 2 , with accounting for the stiffness reduction caused by axial compressive force. Finally, the effective length factors of members in reticulated shell with AAG joints are derived and tabulated. Numerical examples are presented to illustrate the necessity of considering the influence of k 1 and k 2 , and verify the good accuracy of the given effective length factors. [ABSTRACT FROM AUTHOR]