Sectional Area Ratio Research Articles

Numerical simulations and parametric study of SDCM and DCM piles under full scale axial and lateral loads

The new kind of reinforced Deep Cement Mixing (DCM) pile namely, Stiffened Deep Cement Mixing (SDCM) pile is introduced to mitigate the problems due to the low flexural resistance, quality control problem and unexpected failure of DCM pile. The SDCM pile consists of DCM pile reinforced with concrete core pile. Previously, the full scale pile load test and the full scale embankment loading test were successfully conducted in the field. To continue the study on the behavior of SDCM and DCM piles, the 3D finite element simulations using PLAXIS 3D Foundation Software were conducted in this study. The simulations of full scale pile load test consisted of two categories of testing which are the axial compression and the lateral loading. For DCM C-1 and C-2 piles, the clay–cement cohesion, C DCM , and clay–cement modulus, E DCM , were obtained from simulations as 300 kPa and 200 kPa as well as 60,000 kPa and 40,000 kPa, respectively. For the SDCM piles, the simulation results show that increasing length ratio, L core/L DCM , increased the bearing capacity whereas the sectional area ratio, A core/A DCM , has only small effects on the bearing capacity for the axial compression loading. The verified parameters such as the clay–cement cohesion, C DCM , and clay–cement modulus, E DCM , from simulations of axial compression tests were 200 kPa and 30,000 kPa, respectively. On the other hand, increasing the sectional area ratio, A core/A DCM , significantly influenced the ultimate lateral resistance while the length ratio, L core/L DCM , is not significant in the ultimate lateral load capacity when the length of concrete core pile is longer than 3.5 m. In addition, the tensile strength of DCM, T DCM , and concrete core pile, T core , are very important to the lateral pile resistance. The back-calculation results from simulations of tensile strength were 5000 kPa and 50 kPa for the T core and T DCM , respectively.

Parameterization Design and Virtual Assembly of a Jet Pump

The jet pump is widely applied to industry fields. The nozzle, throat tube, and diffusion tube of the jet pump is variable to meet different working conditions. Parameterization design of a jet pump can be used to design the throat tube and diffusion tube via a given nozzle diameter and sectional area ratio. The virtual assembly of the jet pump, which consists of upper body, pump core, under body, and pump shell, is used to verify the fitting allowance of parts. The result provides an anticipated inspection for manufacture and improves the design efficiency.

Fundamental Performance of Disk-shaped Magnetohydrodynamics Accelerator

This paper investigates the acceleration performance of a disk-shaped magnetohydrodynamics (MHD) accelerator. Quasi-1-dimensional (Q1D) numerical simulation employing the MacCormack scheme was developed. For the longer channel length of 0.9 m, thermal loss was estimated at over 60% and effective acceleration could not be achieved owing to large heat loss and large friction loss. For shorter channel lengths, thermal loss can be reduced below 20% owing to the smaller heat and the friction losses. However, with too short a channel length, accelerator performance was decreased by the MHD compression due to excessive Faraday current density. The effect of ratio of cross sectional area on performance was also studied. For a larger area ratio, the gas can be accelerated smoothly throughout the MHD channel. However, for the excessive expansion case of a sevenfold channel, gas velocity near the exit decreased due to transition to a “generator mode”. For the best acceleration performance, the design channel length should be as short as possible preventing compression at the channel inlet. The area ratio should be large enough to prevent the compression but not too large, to prevent transition to a “generator mode”.

Finite Element Analysis on the Temperature Field within Steel Tube Reinforced Columns

The temperature field analysis method of steel tubes reinforced columns under fire by finite element analysis software ABAQUS is proposed in this paper. The theoretical method is validated by tests, and the calculated results agree well with those of tests. On the basis of that, the influencing laws of section perimeter; steel reinforcement ratio and sectional core area ratio on temperature field are discussed. It has been found that the effects of section size and sectional core area ratio on temperature field are significant, but steel ratio has very little effect on temperature both of steel tube and of sectional center. These achievements make it possible to study further theoretical study on the fire resistance of steel tube reinforced concrete columns.

Simulation of scale dependency on tensile mechanical properties of single crystal copper nano-rod

The tension process of single crystal Cu nano–rods with different cross section shapes were simulated by molecular dynamics at atomic scale. Based on centrosymmetry parameter method and combined with the nucleation theory, the effect of cross–section shape, cross–sectional area and slenderness ratio on the tensile mechanical properties of the nano–rods were analyzed, and the scale dependency of tensile mechanical properties of the single crystal Cu nano–rods has been revealed. The results show that after first yield, the nano–rods produce plastic deformation under the dislocation nucleation–extended and sliding–lattice atom cross–slip mechanism of the alternating cycle. The geometry of cross-section has negligible effects on the tensile initial plasticity of the nano–rods, while it shows apparent effects on the tensile mechanical properties. With the increase of cross–sectional area, two types of nano–rods have the phenomenon of early yield point, yield strength decreases and young’modulus increases. Compared with that of the square cross–sectional nano–rod, the variable rate of yield stess of the circular cross-sectional nano–rod is smaller while the variable rate of young’s modulus is lager. As the cross–sectional area increases to 500 nm2, the young’s modulus of the two types of nano–rods become stable, and is close to the theoretical value of 84 GPa. Moreover, the slenderness ratio of the nano–rods has a slight effect on the tensile mechanical properties when the simulation size increased.

Mixing parameters for an airlift bioreactor considering constant cross sectional area of riser to downcomer: Effect of sparging gas location

The effect of mode of sparging gas on the mixing parameters of an internal loop airlift bioreactor was investigated. Two bioreactors of identical volume of 14×103 cm3 and the optimum riser to downcomer cross sectional area ratio of 0.6 were studied. In one bioreactor a gas sparger was located in the draft tube and in the annulus in another. Liquid mixing characteristics, i.e., mixing time and circulation time, were employed to describe the performance of the bioreactors. The tracer injection method was used to determine the mixing parameters. A mathematical modeling based on the tanks-in-series model was employed to characterize the hydrodynamics behavior of the bioreactors. Matlab 7.1 software was used to solve the model equations in the Laplace domain and determine the model parameter, the number of stages. A comparison between the simulation results and experimental data showed that the applied model can accurately describe the behavior of the bioreactors. The results showed that when the gas sparger was located in the draft tube, the liquid mixing time, circulation time, and the number of stage were less than while the gas sparger was located in annulus. This is due to more wall effects, more energy losses and pressure drop in the case of gas injection in the annulus.

Minimum and Complete Fluidization Velocity for Sand-Palm Shell Mixtures, Part I: Fluidization Behavior and Characteristic Velocities

Problem statement: Palm shell on its original state cannot be fluidized solely. However, mixing palm shell with a second fluidizable material can facilitate proper fluidization. Approach: The minimum and complete fluidization velocity (Umf and Ucf) for sand/palm shell binary mixtures had been studied in a partitioned reactor known as Compartmented Fluidized Bed Gasifier (CFBG). The pilot scale reactor ID is 66 cm with 60:40 cross sectional area ratio for combustor and gasifier respectively. The bed materials constitute of sand and palm shell up to 15 weight percent (wt%). The particle size and density ratio for palm shell and sand are about 5÷53 and 0.55 respectively. Results: Despite of the unique reactor feature, the mixture bed pressure drop profiles were closely resemble to those observed in the laboratory scale cylindrical column. It was found that partial fluidization occurred for the smallest sand size with any palm shell size and weight percent in the gasifier. Poor fluidization was also found with the same sand in the combustor but limited to the largest palm shell and higher weight percent. The Umf and Ucf values increase with the increase of palm shell size and weight percent in both compartments and are in tandem with the increase of effective particle diameter. However, although increase in the sand size also increased the effective particle diameter, the characteristic velocities show both increasing and decreasing trends. These findings proved that the characteristic velocities of the sand-palm shell binary mixtures not only depend on the effective bed properties, but also influenced by the mixing/segregating condition. In addition, bed geometry is an equally important factor for the present system. Conclusion/Recommendation: Despite of the large difference in particle size and density, palm shell in sand can be fluidized well, making it a suitable biomass feedstock for gasification in CFBG pilot plant.

Variations in the dorso‐ventral organization of leaf structure and Kranz anatomy coordinate the control of photosynthesis and associated signalling at the whole leaf level in monocotyledonous species

Photosynthesis and associated signalling are influenced by the dorso-ventral properties of leaves. The degree of adaxial/abaxial symmetry in stomatal numbers, photosynthetic regulation with respect to light orientation and the total section areas of the bundle sheath (BS) cells and the surrounding mesophyll (M) cells on the adaxial and abaxial sides of the vascular bundles were compared in two C(4)[Zea mays (maize) and Paspalum dilatatum] and one C(3)[Triticum turgidum (Durum wheat)] monocotyledonous species. The C(3) leaves had a higher degree of dorso-ventral symmetry than the C(4) leaves. Photosynthetic regulation was the same on each side of the wheat leaves, as were stomatal numbers and the section area of the BS relative to that of the M cells (BS/M section area ratio). In contrast, photosynthetic regulation in maize and P. dilatatum leaves showed a marked surface-specific response to light orientation. Compared to the adaxial sides of the C(4) monocotyledonous leaves, the abaxial surfaces had more stomata and the BS/M section area ratio was significantly higher. Differences in dorso-ventral structure, particularly in Kranz anatomy, serve not only to maximize photosynthetic capacity with respect light orientation in C(4) monocotyledonous leaves but also allow adaxial and abaxial-specific signalling from the respective M cells.

Genetic associations of residual feed intake with serum insulin-like growth factor-I and leptin concentrations, meat quality, and carcass cross sectional fat area ratios in Duroc pigs

Genetic relationships of measures of residual feed intake and daily feed intake with serum IGF-I concentrations at 8 wk of age and at 105 kg of BW, serum leptin concentration at 105 kg of BW, meat quality, and different fat accumulation traits on 834 Duroc pigs in 7 generations were estimated. Two measures of residual feed intake were estimated from the differences between actual and predicted feed intake: phenotypic residual feed intake (RFI(phe)) and nutritional residual feed intake (RFI(nut)). Meat quality traits included drip loss, cooking loss, pork color score, pork lightness (L*), and pH, whereas fat accumulation traits were subcutaneous fat, intermuscular fat, and total fat percent at 5-6th thoracic vertebra; subcutaneous fat, intermuscular fat, abdominal fat, and total fat percent at one-half body length and at last thoracic vertebra, and seam fat score. The IGF-I concentrations at 8 wk of age and 105 kg of BW had weak genetic correlations with measures of residual feed intake and daily feed intake (absolute values ranging from 0.14 to 0.24). The genetic correlations between measures of residual feed intake and serum leptin concentration were strong and positive (r(g) with RFI(phe) and RFI(nut) were 0.74 and 0.80, respectively). Residual feed intake was moderately but negatively correlated with cooking loss (r(g) with RFI(phe) and RFI(nut) were -0.42 and -0.49, respectively), whereas daily feed intake was moderately and positively correlated with drip loss and pH (0.33 and 0.36, respectively). Daily feed intake was also moderately correlated with subcutaneous fat accumulations at the 5-6th thoracic vertebra (0.31) and one-half body length (0.31) regions and was strongly correlated with accumulations at the last thoracic vertebra region (0.57). The genetic correlations between daily feed intake and intermuscular fat accumulations at all of the carcass sites were strong (0.60, 0.76, and 0.56 for intermuscular fat at 5-6th thoracic vertebra, one-half body length, and last thoracic vertebra, respectively). Residual feed intake was strongly and positively correlated with all of the fat accumulation traits (ranging from 0.53 to 0.88). The results indicate that reducing residual feed intake (increased efficiency) would lead to increased cooking loss and darkness, and decreased serum leptin concentration, fat accumulations at the different sites, and seam fat at the 6th rib interface of pork carcasses.

철근콘크리트 교각의 소요연성도에 따른 심부구속철근량 산정식 수정

Structural Team, Seoyeong Engineering Co., Ltd., Seoul 135-240, KoreaABSTRACT An equation for calculating confining reinforcement amount of RC bridge columns, specified in the current bridge designcodes, has been made to provide additional load-carrying strength for concentrically loaded columns. The additional load-carrying strengthwill be equal to or slightly greater than the resistant strength of a column against axial load, which is lost because the cover concrete spallsoff. The equation considers concrete compressive strength, yield strength of transverse reinforcement, and the section area ratio as majorvariables. Among those variables, the section area ratio between the gross section and the core section, varying by cover thickness, is avariable which considers the strength in the compression-controlled region. Therefore, the cross section ratio does not have a large effectin the aspect of ductile behavior of the tension-controlled region, which is governed by bending moment rather than axial force. However,the equation of the design codes for calculating confining reinforcement amount does not directly consider ductile behavior, which is animportant factor for the seismic behavior of bridge columns. Consequently, if the size of section is relatively small or if the section arearatio becomes excessively large due to the cover thickness increased for durability, too large an amount of confining reinforcement willbe required possibly deteriorating the constructability and economy. Against this backdrop, in this study, comparison and analysis were per-formed to understand how the cover thickness influences the equation for calculating the amount of confining reinforcement. An equationfor calculating the amount of confining reinforcement was also modified for reasonable seismic design and the safety. In addition, appro-priateness of the modified equation was examined based on the results of various test results performed at home and abroad.Keywords : bridge columns, confining reinforcement, section area ratio, cover thickness, safety

Investigation of gas properties, design, and operational parameters on hydrodynamic characteristics, mass transfer, and biomass production from natural gas in an external airlift loop bioreactor

An external airlift loop bioreactor (EALB) was used for production of biomass from natural gas. The effect of riser to downcomer cross sectional area ratio ( A r / A d ), volume of gas–liquid separator, superficial gas velocity ( U sgr ), and physical properties of gases and their mixtures [ υ g ( μ/ ρ) and D g ] were investigated on mixing time, gas hold-up, and volumetric gas liquid mass transfer coefficients ( k La ). It was found that A r / A d has remarkable effects on gas hold-up and k La due to its influence on mixing time. Kinematic viscosity ( υ g ) showed its significant role on mixing time, gas hold-up and k La when different gases used (mixing time changes directly whereas gas hold-up and k La change indirectly). Moreover, it was found that diffusion coefficient of gas in water ( D g ) has remarkable effect on k La . The volumetric mass transfer coefficients for methane and its mixtures with oxygen (three different mixtures) were determined at different geometrical and operational factors. In average, the rate of oxygen utilization is approximately 1.8 times higher than that of methane. A gas mixture of 25 vol% methane and 75 vol% oxygen was the best gas mixture for biomass production in the EALB. The correlations developed for predicting the mixing time, gas hold-up, and k La in terms of U sgr , A r / A d , volume of gas–liquid separator, and gas phase properties have been found to be encouraging.

Non-steady Flow Method for Measuring the Micro Flow at Constant Micropressure

In order to measure the micro flow in micro channel precisely and easily, a new measuring method based on the idea of utilizing non-steady flow state to be equivalent to steady flow state used in traditional measurement is proposed. The applicable condition of pressure head for the new measuring method is derived. Based on Lagrange integral principle in fluid dynamics, a mathematic model in form of non-linear differential equation is built and analyzed numerically by using MATLAB software, so the theoretical error of the proposed method is obtained. The numerical results reveal that the difference between measurement result under the non-steady flow state and that under the steady flow state reduces with the decreasing of the ratio of the areas of the micro channel and the tube in upper stream when the pressure loss in the tube is omitted. Then, an apparatus for measuring the micro flow is established according to the proposed method. The measured results from the apparatus agree well with the theoretical calculation results. Both results show that the measuring error is lower than 2.27% when the applicable condition of pressure head is satisfied and the ratio of cross sectional areas of the micro channel and the tube in upper stream is smaller than 3.422%.

Theoretical explanation of the ‘local resonance’ in stepped acoustic horn based on Four-End Network method

By using Four-End Network method, the ‘local resonance’ frequency equation of stepped horn can be deduced from the resonance frequency equation of conical composite horn, and the formula to calculate the stress in stepped horn is obtained. According to the results of finite element analysis (FEA) on stepped horn, the ‘local resonance’ phenomenon is caused by the abrupt change of section area, and, correspondingly, high stress concentration. It is shown that section area ratio is closely related to the ‘local resonance’ frequency.

1A1-A04 遠隔油圧駆動ハンドの受圧面積差による力増幅(ロボットハンドの機構と把持戦略)

Generally, human hands are more dexterous and powerful than robot hands. It is very difficult that robot hands obtain these characteristics simultaneously. The hydraulic remote drive system may have the possibility to satisfy this requirement. A plunger pump was connected to a cylinder mounted in a finger. The cylinder output force is exaggerated by the cross section area ratio of the cylinder and the plunger. The diameter of the cylinder was limited to 10 mm. The experimental data shows that the plunger diameter is limited to 2 mm by the buckling characteristic. The maximum force exaggerating ratio was to 25.

Root tapering between branching points should be included in fractal root system analysis

The proportionality factor ( p) is a parameter used for fractal root system modelling. It describes tapering along root axes and is calculated by the ratio of total cross sectional area (CSA) before and after branching. The exact point where the area of the parent branch is measured is often not defined. By measurement of the CSA adjacent to a branching point tapering without branching is not included in factor p. In this study p was measured on six tropical tree species ( Clethra revoluta, Graffenrieda emarginata, Vismia tomentosa, Weinmannia loxensis, Clusia sp. and Styrax foveolaria). The measurement was conducted in three different ways, quantifying (i) tapering of roots by branching ( p branch), (ii) tapering without branching ( p within), and (iii) total root tapering ( p total). For five species p total was significantly higher than p branch ( p < 0.05). For three species p within contributed significantly more to p total than p branch. There was only a weak correlation between p and root segment diameter. The slope of the regression line was often higher for p within than for p branch. The results suggest that the exclusive use of p branch in fractal branching models leads to an underestimation of total root system tapering and to an overestimation of total root system biomass and root length in fractal branching models. Furthermore in some species self-similarity decreases when tapering without branching is included in the proportionality factor p. This may imply that models should allow p to change with increasing diameter.

Finite volume simulation and mould optimization of aluminum profile extrusion

In this paper, finite volume method (FVM) is adopted to simulate irregular Al alloy profile extrusion process since the coefficient of extrusion (ratio of billet and profile cross section area) is too large (more than 25), the plastic deformation is quite severe that it is almost impossible to get satisfactory results using traditional lagrangian finite element method to simulate that kind of deformation. Calculations show it is a good way for the description of material flow, and mesh distortion could be avoided effectively. On the other hand, a computer aided optimization (CAO) model based on orthographic experiments, artificial neural network (ANN) and genetic algorithm (GA) is built and utilized to obtain optimal values of multi-parameters of Al alloy profile extruding processes and moulds, as it's a combination optimization problem and traditional arithmetic algorithm can hardly solve that. Experiment shows satisfactory results, such as process and mould parameters, are obtained.

Hydrodynamics and mass transfer characteristics of gas–liquid ejectors

In the present work, experimental investigations have been carried out on ejectors employing air as a motive fluid and water as the entrained fluid. A semi-empirical model has been developed to predict the liquid entrainment rate taking into account: (i) the compressible nature of air, (ii) pressure drop for two-phase flow and (iii) losses due to changes in cross sectional area. The effects of gas velocity, liquid level in the suction chamber, nozzle diameter and throat diameter on the liquid entrainment, entrainment ratio (L/G), pressure drop, gas hold-up, mass transfer coefficient and interfacial area have been investigated. The liquid entrainment rate increases with the increased liquid level in the suction chamber and with the increase in gas velocity. The ratio of throat cross sectional area to the nozzle cross sectional area (area ratio) was found to be a critical parameter. These results have been explained on the basis of pressure profiles of ejector (along the centre line of the ejector). The liquid entrainment rate predicted from the semi-empirical model is in good agreement with the experimental values. The mass transfer coefficient and interfacial area increase with increase in gas velocity. Correlations have been proposed to estimate the fractional gas hold-up, mass transfer coefficient and interfacial area in the ejectors.

218 コールドスプレーにおける銅皮膜特性に及ぼすノズルののど部と出口部の断面積比とガス圧力の影響(コーティング・溶射・薄膜2)

218 コールドスプレーにおける銅皮膜特性に及ぼすノズルののど部と出口部の断面積比とガス圧力の影響(コーティング・溶射・薄膜2)

PERFORMANCE ANALYSIS OF CYLINDRICAL TYPE AIR EJECTOR

Performance tests were conducted for an air ejector entraining two secondary jets whose axes are coaxia l of that of primary stream. A unique ejector housing was constructed to receive both the convergent or convergent-divergent primary nozzle a nd the cylindrical mixing chamber. The air ejector under investigation has nozzle throat -to- cylindrical section area ratio of 0.12. The investi gation is conducted for ejector having cylindrical length-to-diameter ratio , which varies from 2.31 to 23.08. It covers a range of spacing from -1 to 0.5 of cylindrical lengths and of secondary to ambient pressure ratio of 1.0. The recorded axial distributions of the static wall pressure are plotted in non- dimensional forms and the extent of consistency of the profiles is shown. The induced air flow rate ratio is plotted for the measured primary to secondary stagnation pressure ratio range. Results offered a valuable appreciation of the effect of the cylindrical length and nozzle spacing-to- diameter ratios on both wall pressure distribution and jet entrainment capacity. The occurrence of flow choking in both th e convergent or convergent-divergent primary nozzle was ensured.

The influence of grain size on the ductility of micro-scale stainless steel stent struts

Vascular stents are used to restore blood flow in stenotic arteries, and at present the implantation of a stent is the preferred revascularisation method for treating coronary artery disease, as the introduction of drug eluting stents (DESs) has lead to a significant improvement in the clinical outcome of coronary stenting. However the mechanical limits of stents are being tested when they are deployed in severe cases. In this study we aimed to show (by a combination of experimental tests and crystal plasticity finite element models) that the ductility of stainless steel stent struts can be increased by optimising the grain structure within micro-scale stainless steel stent struts. The results of the study show that within the specimen size range 55 to 190 microm ductility was not dependent on the size of the stent strut when the grain size maximised. For values of the ratio of cross sectional area to characteristic grain length less than 1,000, ductility was at a minimum irrespective of specimen size. However, when the ratio of cross sectional area to characteristic grain length becomes greater than 1,000 an improvement in ductility occurs, reaching a plateau when the ratio approaches a value characteristic of bulk material properties. In conclusion the ductility of micro-scale stainless steel stent struts is sensitive to microstructure and can be improved by reducing the grain size.