Load Height Research Articles

Parametric Study of High-Efficiency and Low-Emission Gas Burners

The objective of this study is to investigate the influence of three significant parameters, namely, swirl flow, loading height, and semi-confined combustion flame, on thermal efficiency andCOemissions of a swirl flow gas burner. We focus particularly on the effects of swirl angle and inclination angle on the performance of the swirl flow burner. The results showed that the swirl flow burner yields higher thermal efficiency and emits lowerCOconcentration than those of the conventional radial flow burner. A greater swirl angle results in higher thermal efficiency andCOemission. With increasing loading height, the thermal efficiency increases but theCOemission decreases. For a lower loading height (2 or 3 cm), the highest efficiency occurs at the inclination angle 15°. On the other hand, at a higher loading height, 4 cm, thermal efficiency increases with the inclination angle. Moreover, the addition of a shield can achieve a great increase in thermal efficiency, about 4-5%, and a decrease inCOemissions for the same burner (swirl flow or radial flow).

Effect of organic and inorganic fertilizers on root yield and nutrient uptake pattern inAsparagus racemosusWilld. in a semi-arid tropical climate

A field experiment was conducted to study the effect of organic (vermicompost) and inorganic fertilizers (NPK) on growth, root yield and nutrient uptake pattern in satavari in semi-arid tropical climate. Results revealed that combined application of vermicompost (5 t ha−1) + inorganic fertilizers NPK (50:25:25 kg ha−1) significantly increased the height of the plant, root yield and nutrient uptake and soil microbial load as compared to control. The root yield increased by 68.19% with which clearly indicated that 50% inorganic fertilizer can be supplemented with organic fertilizer without any yield loss of satavari. Similarly nitrogen (N) and potassium (K) contents of the plant except phosphorus (P) have also increased.

Effect of Load Height on Buckling Resistance of Steel Beams

This paper presents a detailed investigation of effect of load height on buckling resistance of steel beams. Shapes that are intended to be used primarily as a beam are generally proportioned so that moment of inertia about the principal axis is considerably larger than that about minor axis. Hence monosymmetric sections are preferable. The lateral stability of beam subjected to transverse loading is very complicated in monosymmetric sections. The distance of transverse load from shear centre axis may significantly affect the buckling resistance of a simply supported beam. When transverse concentrated load W acts at (Yq-Yo) below the shear centre and moves with the beam it acts as an additional torque W(Yq-Yo) about shear centre which opposes twist and increases resistance to buckling. Conversely, when load above shear centre, additional torque increases the twist rotation and reduces buckling resistance of beam. To verify the effect of load height on buckling resistance, a simply supported beam subjected to concentrated and uniformly distributed load is considered. The effect of load height on buckling resistance has been plotted.

Numerical simulation on windowed tubes subjected to oblique impact loading and a new method for the design of obliquely loaded tubes

Tubular structures under oblique loading may collapse in axial or bending mode when the load angle is smaller or larger than certain critical value, and the bending mode has much lower energy absorption. In the present study, windowed square tubes subject to oblique impact were numerically studied, with variables being load angle, width and height of window and impact velocity. Next, a new design method was proposed which can effectively increase the tube’s critical load angle without compromising its energy absorbing capacity. The method therefore has great potential in industrial applications where large load angles are expected.

Buckling and lateral buckling interaction in thin-walled beam-column elements with mono-symmetric cross sections

Effects of axial forces on beam lateral buckling strength are investigated here in the case of elements with mono-symmetric cross sections. A unique compact closed-form is established for the interaction of lateral buckling moment with axial forces. This new equation is derived from a non-linear stability model. It includes first order bending distribution, load height level and effect of mono-symmetry terms (Wagner’s coefficient and shear point position). Compared to the so-called three-factors (C1–C3) formula commonly employed in beam lateral buckling stability, another factor C4 is added in presence of axial loads. Pre-buckling deflection effects are considered in the study and the case of doubly-symmetric cross sections is easily recovered. The proposed solutions are validated and compared to finite element simulations where 3D beam elements including warping are used. The agreement of the proposed solutions with bifurcations observed on the non-linear equilibrium paths is good. Dimensionless interaction curves are dressed for the beam lateral buckling strength and the applied axial load, where the flexural-torsional buckling axial force is a taken as reference.

점토지반에 근입된 송전철탑 연결형 말뚝기초의 저항력증가계수

Pile foundation for transmission tower constructed in weak ground can cause the damage of the tower due to the different settlement between the foundations. In Japan and USA, connected-pile foundations whose 4 foundations are connected each other by beams were used for transmission tower (TEPCO 1988, IEEE 2001). Resistance increasing factors for connected-pile foundation signify increasing amount of resistance due to the effect of connected-pile material. In this study, we performed model lateral load tests of connected-pile foundations for transmission tower and found the resistance increasing factors for connected-pile foundation. The tests were performed in silty clay, and the resistance increasing factors were founded in various conditions that lateral load directions and height, the stiffness of beams in the connected-pile foundations were changed. The resistance increasing factors from our research were presented as a function of normal lateral loading height and normal stiffness of the connected-pile material. The resistances which were estimated from the resistance increasing factors were similar to measured values.

UWB Waveguide Bandpass Filter With A Narrow Notched Band

A compact ultra-wideband (UWB) bandpass filter (BPF) with a narrow notched band based on ridged waveguide is presented. Capacitive loading stub structure is introduced to reject the undesired wireless local-area network (WLAN) radio signals. By simply adjusting the height of the capacitive loading post, the centre frequencies of the notched band can be changed from 5.16 to 6.2GHz, while the bandpass is nearly not affected. The UWB BPF has been simulated, fabricated and measured, with good agreement between the simulated and measured results. The measured insertion loss of the UWB BPF is less than 0.7 dB throughout the pass band of 3.05 to 10.9GHz, the variation of group delay less than 0.20 ns in this band except for the notched band. The notched band of the BPF centred at 5.2GHz has 10dB fractional bandwidth of about 3.7%.

“Dynamic Fusion” in Degenerative Lumbar Spine Disorders

Introduction Dynamic stabilization in lumbar degenerative disorders has become very popular in the last few years. The basic concept of pedicle-screw-based systems is to reduce stiffness of the implants to allow load sharing between instrumentation system and functional spine (movement) unit to prevent adjacent segment syndrome. Basic biomechanical requirements for this philosophy are as follows: (a) a predicable load distribution to the intervertebral disk, (b) the limitation (control) of range of motion, and (c) to maintain and/or to restore the sagittal (sacral) balance. Disk degeneration results in loss of disk height and increase of axial compression loading in the posterior spine elements, probably accompanied with accelerated facet degeneration (arthrosis). Challenged by G. Perrinás reports in the late 1990s we started in 2002 with dynamic (semirigid) transpedicular stabilization systems in degenerative lumbar spine disorders using Isolock device, later using Isobar and AladynR device also. Materials and Methods This paper presents an inhomogene case presentation of 26 patients with different perception of degenerative lumbar disorders. Patients underwent a so called “Dynamic Fusion” between 2003 and 2007 using PLIF or TLIF added by posterior transpedicular dynamic (semirigid) stabilization. The case presentation presents preoperative, postoperative radiographs, and maximally follow-up radiographs to show a perfect bony healing in anterior elements. Definition of Dynamic Fusion Semirigid pedicle screw systems allow an increased anterior column load-sharing leading to favor osteogenesis with enhanced interbody fusion. This physical phenomenon is related to Wolffás Law. Lavaste and Perrin validated in 1993 in a finite element model of the lumbar spine that semirigid posterior instrumentation increases compared to rigid instrumentation of the load transmission through the anterior column. This observation and the publication by Goel et al confirmed that dynamic stabilization systems enable more load through the anterior column and the interbody graft compared to rigid systems without compromising stability, led to changing philosophy. We started to combine PLIF/TLIF with posterior transpedicular semirigid stabilization over the instrumented segment. Results No loosening signs of the PLIF/TLIF implants have been followed-up in this patient cohort. The evaluated pain relief is depended on many factors but all patients had a pain level degree in the VAS (25%). Conclusion The PLIF/TLIF in degenerative lumbar spine disorders showed in combination with posterior semirigid stabilization good clinical and radiographical results. No implant loosening has been followed up. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Perrin G: Treatment of lumbar spondylolisthesis and related unstable spinal lesions: the usefulness of PLIF with cages and dynamic interpedicular posterior fixation for circumferential arthrodesis and prevention of adjacent level degeneration. presented at the 3rd World Spine Meeting, Rio de Janeiro, 2005 Goel VK, Lim Th, Gwon J, et al. Effects of rigidity of an internal fixation device. A comprehensive biomechanical investigation. Spine 1991;16:155–161

A geometrically exact approach to lateral-torsional buckling of thin-walled beams with deformable cross-section

In this paper, a new geometrically exact beam formulation is presented, aiming at calculating buckling (bifurcation) loads of Euler–Bernoulli/Vlasov thin-walled beams with deformable cross-section. The resulting finite element is particularly efficient for problems involving coupling between lateral-torsional buckling and cross-section distortion/local-plate buckling. The kinematic description of the beam is geometrically exact and employs rotation tensors associated with both cross-section rotation and the relative rotations of the cross-section walls in the cross-section plane. Moreover, arbitrary deformation modes, complying with Kirchhoff’s assumption, are also included, which makes it possible to capture local/distortional/global buckling phenomena. Load height effects associated with cross-section rotation/deformation are also included. The examples presented throughout the paper show that the proposed beam finite element leads to accurate solutions with a relatively small number of degrees-of-freedom (deformation modes and finite elements).

하중고 효과를 고려한 비탄성 횡-비틀림 좌굴강도 연구

본 논문에서는 비탄성 영역 내 비지지 길이가 존재하는 I형보의 하중고 효과를 고려한 비탄성 횡-비틀림 좌굴강도에 대한 연구를 수행하였다. 하중조건으로는 집중하중과 등분포하중을 적용시켰으며, 비선형 횡-비틀림 좌굴 해석을 위해 잔류응력 및 초기변형을 고려하였다. Pi와 Trahair(1995)가 고려한 단순직선분포를 잔류응력으로 가정하였으며, 국내 I형강 표준 치수 허용치(현대제철, 2006)에 근거하여 부재 길이의 0.1%를 초기 최대 횡변위로 적용하여 초기제작오차로 고려하였다. 새롭게 제안된 모멘트구배계수식은 유한요소해석결과와 매우 유사한 값을 나타내고 있으며, 제안식은 하중고 효과를 고려한 비선형 횡-비틀림 좌굴강도 산정뿐만 아니라 휨부재 극한강도 산정에도 크게 기여할 것이다. This paper investigates inelastic lateral-torsional buckling strengths of I-beams with load height effects. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. The distribution of the residual stress in the cross-section is same as shown in Pi and Trahair(1995). The initial imperfection of the beam is set by a central displacement equal to 0.1% of the unbraced length of the beam. New moment gradient factors for load height effect of inelastic beams are very similar to the results from finite element analyses. The proposed equations will greatly contribute to calculate the inelastic lateral torsional buckling strengths with load height effect.

A polynomial equation to predict low back compression force: accounting for the effects of load height on instability

The purpose of this study was to develop a regression equation that, incorporating the potential energy of the load in the hands, was capable of improved predictions of spinal compression forces. A stepwise polynomial equation was developed from EMG profiles of 15 muscles, and its spinal joint loading predictions at L4/L5 were compared to current methods of calculating spinal compression. Absolute muscle activation was shown to increase with increased loading height, indicating that the central nervous system responds to changes in spinal stability. The inclusion of potential energy into the calculation of spinal disc compression at L4/L5 improved estimates of the compressive forces acting on the spine. This is the first model to incorporate potential energy into a predictive model for lumbar spine compression without the use of electromyography. It was concluded that potential energy plays a vital role in dictating the recruitment patterns of the trunk.

Elastic lateral buckling of cantilever Litesteel Beams under transverse loading

The LiteSteel Beam (LSB) is a new hollow flange channel section developed by OneSteel Australian Tube Mills using its patented dual electric resistance welding and automated continuous roll-forming technologies. The LSB has a unique geometry consisting of torsionally rigid rectangular hollow flanges and a relatively slender web. Its flexural strength for intermediate spans is governed by lateral distortional buckling characterised by simultaneous lateral deflection, twist and web distortion. Recent research on LSBs has mainly focussed on their lateral distortional buckling behaviour under uniform moment conditions. However, in practice, LSB flexural members are subjected to non-uniform moment distributions and load height effects as they are often under transverse loads applied above or below their shear centre. These loading conditions are known to have significant effects on the lateral buckling strength of beams. Many steel design codes have adopted equivalent uniform moment distribution and load height factors based on data for conventional hot-rolled, doubly symmetric I-beams subject to lateral torsional buckling. The non-uniform moment distribution and load height effects of transverse loading on cantilever LSBs, and the suitability of the current design modification factors to include such effects are not known. This paper presents a numerical study based on finite element analyses of the elastic lateral buckling strength of cantilever LSBs subject to transverse loading, and the results. The applicability of the design modification factors from various steel design codes was reviewed, and suitable recommendations are presented for cantilever LSBs subject to transverse loading.

Analytical model for the design of volumetric solar flow receivers

The development of efficient solar thermal receivers has received significant interest for solar to electrical power conversion and heating applications. Volumetric flow receivers, where the incoming solar radiation is absorbed in the volume of a heat transfer fluid (HTF), promise reduced heat loss at the surface compared to surface absorbers. In order to efficiently store the thermal energy in the volume, nanoparticles can be suspended in the HTF to absorb the incoming radiation. In such systems, compact models are needed to design and optimize the performance. This paper presents an analytical model that investigates the effect of heat loss, particle loading, solar concentration and channel height on receiver efficiency. The analytical model was formulated by modeling the absorption of solar radiation by the suspended nanoparticles as a volumetric heat release inside the flowing HTF. The energy equation was solved with the surface heat losses modeled using a combined radiative and convective heat loss coefficient. The analytical solution provides a convenient tool for predicting the effect of different parameters, in terms of dimensionless numbers ( Pe, Nu E , G ¯ , and θ amb ), on two-dimensional temperature profiles and system performance. By combining the receiver efficiency with a power generation efficiency, idealized by the Carnot efficiency, an optimum receiver length where the total efficiency is maximized is determined. However, in practice, the maximum efficiency depends on the maximum allowable temperature of the working HTF. As a case study, predictions were made for Therminol® VP-1 with suspended graphite nanoparticles in a 1 cm deep channel with a solar concentration of 10. The model predicts an optimum total system efficiency of 0.35 for a dimensionless receiver length of 0.86. Finally, the analytical model was used to estimate the optimum efficiency and the corresponding optimum receiver length for different design configurations with varying Nu E and G ¯ . The results from this paper will help guide experimental design of volumetric flow receivers for solar thermal based power systems.

Application of the strain energy to estimate the rock load in squeezing ground condition of Eamzade Hashem tunnel in Iran

Estimation of rock load is a very important issue because the selection of a support system is highly related to this parameter. Several methods are used to estimate this parameter such as experimental, empirical, and numerical methods. This study propose a new empirical method to estimate the rock load in squeezing ground condition using actual collapses data of Emamzade Hashem tunnel of Iran based on the ration of the post-failure residual strain energy to the pre-failure stored strain energy. Prediction of squeezing ground condition in this study is performed based on Jethwa, Singh, and Hoek criterions. Results show that some sections in shale and sandstone of the Shemshak formation are prone to squeezing. Finally, the relation between the rock load and the ratio of the post-failure residual strain energy to the pre-failure stored strain energy, Ψ, in squeezing ground condition is estimated. Based on the statistical analysis, the maximum correlation between both parameters is achieved when Alejano’s equations are used to estimate the drop modulus. As the rock mass behavior changes from elastic–plastic to elastic–brittle, the drop modulus changes from 0 to infinite. The reason is that by increasing the quality of rock mass and reducing the minimum principal stresses, the ratio of post-failure residual strain energy to pre-failure stored strain energy and rock load height (Hp) reduce. So, regression analysis is used to investigate the relation between the rock load height and the ratio of post-failure residual strain energy to pre-failure stored strain energy, and finally, a formulation is presented to determine rock load height based on power function.

Moment modification factor of I-girder with trapezoidal-web-corrugations considering concentrated load height effects

Moment modification factors of the I-girder with trapezoidal web corrugations subjected to concentrated load, applied at different heights on the cross section and various end restraint conditions, are investigated. The moment modification factors are obtained by finite element buckling analyses. The new FEM program is developed by using beam elements and new general formulas of cross-section properties as well as a new warping constant of the I-girder with trapezoidal web corrugations. The theoretical results of moment modification factors are compared with commercial finite element software (ABAQUS) using shell elements. A series of finite element analyses with different corrugation profiles and lengths is performed. Through comparative numerical studies, the theoretical results are successfully verified. The moment modification factors from the SSRC Guide are compared with present FEM results. The new values of the variable C b , the moment modification factor, in the SSRC Guide are proposed as the variable C b,c to improve the accuracy of lateral–torsional buckling strength.

A Quasistatic Antenna Design Approach for Minimum-Q Antennas

The quasistatic antenna-design algorithm uses electrostatic methods to calculate the antenna's shape. The asymptotic conical dipole is a classic quasistatic design. A charged disk is added to the asymptotic conical dipole to model a thick top-loaded monopole. The antenna's shape is an equipotential surface. The disk height and radius control the width and height of the top load. The minimum Q for this design is lower than the ideal thin-disk-loaded monopole. A Computer Simulation Technology model confirmed the predicted Q value of twice Chu's limit. Measurements on a 16-wire, 0.5 m physical antenna agreed with the NEC 4 model. The tradeoff in Q and radiation resistance is illustrated with detailed examples. Several designs have a lower Q than the ideal thin-disk-loaded monopole. This design approach gives a very good design with only two degrees of freedom. The computational time for the algorithm is a small fraction of one NEC 4 modeling run. The algorithm can be extended to design antennas with a cylindrical, elliptical, or conical form factor.

Seasonally Modulated Tropical Drought Induced by Volcanic Aerosol

Abstract Major volcanic events with a high loading of stratospheric aerosol have long been known to cause cooling, but their impact on precipitation has only recently been emphasized, especially as an analog for potential geoengineering of climate. Here, the authors use a coupled atmosphere–ocean–land–vegetation model in conjunction with observations to study the effects of volcanic aerosol on the tropical and subtropical precipitation. The small internal variability in the model enables a clear identification of the volcanic impact, which is broadly supported by observations, especially for the large Pinatubo event. Area averaged rainfall over land between 40°S and 40°N decreases by about 0.15 mm day−1, 4–5 months after the height of a major volcanic aerosol loading, such as from Pinatubo, with regional changes as large as 0.6 mm day−1 or higher, such as over the Amazon and equatorial Africa. These anomalies migrate seasonally, following the movement of monsoon rainfall. This is because the low heat capacity of the land leads to rapid response of rainfall there, owing to the energy imbalance caused by volcanic aerosol cooling. In contrast, precipitation response over the ocean is much slower and considerably damped because of the much larger heat capacity. In addition, the difference in heat capacities over land and over ocean leads to an anomalous land–sea thermal contrast, which could further contribute to the reduction of rainfall over land. The volcano-induced drought may have significant impact on the ecosystem, agriculture, and the carbon cycle, especially in the monsoon regions.

A Parametric Study of Fuel Lattice Design for HTR-10

In this study, the multiplication factor and neutron spectrum behaviors were investigated against the moderator-to-fuel ratio, the fuel loading height, and the detector location in high-temperature gas-cooled reactor (HTR)-10. The MCNP5 computer code (version 1.51) was employed to perform all the simulation computations. The results revealed that the multiplication factor varies significantly depending on the moderator-to-fuel ratio and the fuel loading height due to the competition among the neutron moderation and absorption abilities of the moderator as well as the neutron production ability of the fuel. Due to its inherent stability, HTR-10 is deliberately designed such that the multiplication factor decreases and the neutron spectrum softens as the moderator-to-fuel ratio increases. The average neutron energy level in the HTR-10 fuel balls is approximately 240 keV and ranges from smallest to largest at the middle, bottom, and top of the reactor core, respectively.

Impact of HAART on growth and hospitalization rates among HIV-infected children

To evaluate HAART-associated changes in growth and hospitalization rates over time in a cohort of HIV-infected children. Children starting HAART were assessed during the first 3 years of therapy. Clinical response was assessed every 24 weeks by z scores of weight-for-age and height-for-age. Linear regression models were used to detect predictors of clinical response. Pertinent information on hospitalizations was obtained retrospectively through review of medical records. A total of 196 children were assessed. Mean weight z score increased from -1.62 (±1.32) at baseline to -1.14 (±1.12) by week 24. Mean height z score increased from -1.88 (±1.45) at baseline to -1.66 (±1.18). Better z scores at baseline were associated with greater increases in weight z scores over time. Lower viral load and higher height z scores at baseline were also associated with improved height catch-up. Eighty-five children (43.3%) were hospitalized. Most hospitalizations were prompted by infectious disease, with only two due to opportunistic infections. HAART was associated with significant increases in weight and height z scores. Younger age, the use of protease inhibitors and advanced clinical disease were associated with better outcomes. The present study demonstrated the effectiveness of HAART in significantly reducing hospitalization, death, and incidence of opportunistic infections among HIV-infected children.

Finite Element Analysis of Bulging Forming for Sheet Metal with Bottom Compression Drawing Method

For the bulging forming of sheet metal industry, two of the major disadvantages are large punch load and short bulging height, generally referring to the traditional process. In this present work, a new processing technique had been introduced for bulging forming based on bottom compression drawing method. The finite element method (FEM) with DEFORM-2D was used to investigate the bulging process. Besides, the mechanism of dimple defect occurred in bulging process was analysed with numerical simulation. The results showed that the dimple defect divided into four stages in the bulging process, where revealed an inverted cone-shape at the bottom part of the centre workpiece. Moreover, the laboratory experiments were carried out to validate the results of numerical simulation, which showed a good agreement with the FEM simulation results.