Horizontal Resistances Research Articles

A facile fabrication of an integrated electromagnetic interference shielding material with low electrical resistance based on silver particles/thermoplastic polyurethane composite@copper foil

As microelectronic technology advances, electronic devices have become faster and smaller. The electromagnetic radiation has negative effects on electronic device operation, how to eliminate the electromagnetic radiation has attracted much attention. Copper foil is the most commonly used and effective material for reducing electromagnetic radiation. In practical applications, it is necessary to use adhesive to fix it onto the surface of electronic devices. In this work, an integrated electromagnetic shielding material (AgPs/TPU@Cu hybrid film) was designed and prepared by a facile way, in which the mixture of silver particles (AgPs) and thermoplastic polyurethane (TPU) was cured to form a AgPs/TPU composite film on the surface of copper foil (Cu) by a one-pot heating press processing. The horizontal and vertical electrical resistances of AgPs/TPU composite film decreased to 0.2 Ω and 0.47 Ω at the AgPs loading of 38 wt%, respectively, and the corresponding thermal conductivity reached 0.81 W m−1 K−1. Moreover, the AgPs/TPU@Cu hybrid film at the AgPs loading of 38 wt% exhibited the maximum electromagnetic interference shielding effectiveness (EMI SE) value of 105 dB. This work provides valuable information about EMI shielding technologies for practical electronic applications.

Effects of shear strength variability on the peak and residual horizontal resistance of on-bottom subsea pipelines in clay

Subsea production pipelines in deep water oil and gas fields are susceptible to a phenomenon called lateral buckling which is a major pipeline design concern. Accurate estimation of lateral buckle formation and the additional stresses generated are of particular importance for High-Temperature High-Pressure (HTHP) pipelines resting on soft clay and is the subject of pipe-soil interaction studies (PSI). Variability in pipe embedment and soil resistances constitute the largest uncertainty in PSI analyses. Best practice methods for PSI studies constitute multi-step strategies that involve finding solutions to nonlinear and implicit equations. In the present study, the impact of soil strength variability on embedment and subsequently peak (Hpeak/V) and residual (Hres/V) lateral friction factors are evaluated. An R code, PSI-Lateral, is developed and verified against published case studies. It is used to calculate the pipeline embedment and horizontal resistances mobilized in a parametric study on three pipe diameters (0.6, 0.8 m and 1.0 m) with three different wall thicknesses. For each pipe diameter-weight combination, embedment and lateral friction factors (peak and residual) are calculated for a series of mean shear strengths ranging from 2 kPa to 8 kPa and COV ranging from 5% to 37.5%. The high estimate and low estimate shear strengths, suHE and suLE, correspond to values that are +/- two standard deviations from the mean. Hence, the range of strengths encompassed between these two extremes represents approximately 95% of the shear strength distribution. The results of the parametric runs conducted are presented in the form of graphical charts where high and low embedment and lateral friction factors can be read-off for any selected pair of mean shear strength and COV. Similar trends are observed in the charts for all pipelines evaluated. It is found that the range of normalized embedment, z/D, increases with increasing COV and decreases with increasing mean shear strength for all pipelines tested. A similar trend is observed for the residual horizontal resistance. The expected range of peak horizontal resistance Hpeak/V shows the same trend but only for soils with mean strengths less than 4 kPa. For soils with higher mean strengths, the range of Hpeak/V is found to be mostly insensitive to variations in COV and further increases in the mean strength.

Electrical conductivity of anisotropic PMMA composite filaments with aligned carbon fibers - predicting the influence of measurement direction.

In order to study the electrical conductivity of anisotropic PMMA/carbon fiber (CF) composites, cylindrical PMMA/CF filaments were extruded through a capillary rheometer, resulting in an induced CF orientation along the extrusion direction. The aspect ratios of the CFs in the filaments were accurately regulated using a two-step melt mixing process. By measuring the vertical and horizontal resistances of filaments where the outermost layer was successively peeled off, the anisotropic conductivities could be calculated. This was done using a novel analytical model where each cylindrical composite filament was defined as a structure consisting of three concentric cylinders with potentially different conductivities and CF orientations. The electrical conductivity increased with the degree of fiber orientation along the voltage direction and the effects of anisotropy and measurement direction were incorporated into the (isotropic) McLachlan equation. The required distance for electrical contact between the CFs was calculated to be 16 nm. Finite element (FEM) simulations were successfully utilized to confirm the data.

The effects of anchored piles on the horizontal and uplift resistances in offshore structures

To increase the horizontal and uplift resistances of piles in offshore structures, pile reinforcements such as anchored piles, batter piles, and micro piles have been generally applied. In this study, the emphasis was on quantifying the reinforcement effect of an anchored pile on the horizontal and uplift resistances of a submerged breakwater. A framework for determining the seabed soil spring constants (p-y curve and t-z curve) is proposed from an analytical method and numerical analysis. Based on the results, a new hyperbolic load transfer curve is proposed to design anchored piles by considering the reinforcement effect, which considers the reinforcement coefficients of horizontal and uplift loads obtained from the load transfer curves. The proposed load transfer curves are compared against the results from the full modeling analysis and show good agreement. Through comparisons with case studies, it is found that the effects of the shear force, bending moment, and displacement are more significant for anchored piles than for unreinforced piles. Thus, the proposed curves appropriately represent the reinforcement effect of anchored piles in offshore structures.

Analysis and Verification on Mechanics Mechanism for Flat Digging of Grab

The research on digging resistances is the key to designing the grab, improving the grab’s structure and realizing the automatic flat digging of grab dredger. This article focuses on the mechanical analysis and experimental research of grab’s flat digging combining with theoretical calculation and experiments in dredging process. The theoretical digging resistances in both horizontal and vertical directions have been investigated in mathematical model. With the help of flat digging experiments, the forces on hoist rope and closing rope have been recorded. Then, work out the horizontal and vertical digging resistances based on moment balance. Since a good agreement is achieved between the theoretical calculations with the corresponding independent experimental results, the research has been verified and provides technical support for flat digging in dredging process.

Force-velocity profiling of sprinting athletes: single-run vs. multiple-run methods.

This study explored the agreement between a single-run and a multiple-run method for force-velocity (Fv) profiling of sprinting athletes; we evaluated both absolute values and changes over time caused by sprint training. Seventeen female handball players (23 ± 3years, 177 ± 7cm, 73 ± 6kg) performed 30m un-resisted and resisted sprints (50, 80 and 110N resistance) before and after an 8-week sprint training intervention. Two approaches were used to calculate theoretical maximal velocity (v0), horizontal force (F0), power (Pmax), and the force-velocity slope (SFv): (1) the single-run method, based on inverse dynamics applied to the centre-of-mass movement, was calculated from anthropometric and sprint split time data; and (2) the multiple-run method, where peak velocity from un-resisted and resisted sprints were plotted against the horizontal resistances. Trivial differences in v0 (0.7%) were observed between the two calculation methods. Corresponding differences for F0, Pmax and SFv were 16.4, 15.6 and 17.6%, respectively (most likely; very large effect size). F0 showed poor agreement between the methods (r = 0.26 and 0.16 before and after the intervention). No substantial correlation between the changes (from pre- to post-training tests) in SFV calculated with the single-run and the multiple-run methods were observed (r = 0.03) [corrected]. This study revealed poor agreement between the Fv relationships of the investigated calculation methods. In practice, both methods may have a purpose, but the single-run and the multiple-run methods appear to measure somewhat different sprint properties and cannot be used interchangeably.

Horizontal dynamic response of a large-diameter pipe pile considering the second-order effect of axial force

The second-order effect of axial force on horizontal vibrating characteristics of a large-diameter pipe pile is theoretically investigated. Governing equations of the pile-soil system are established based on elastodynamics. Three-dimensional wave equations of soil are decoupled through differential transformation and variable separation. Consequently, expressions of soil displacements and horizontal resistances can be obtained. An analytical solution of the pile is derived based on continuity conditions between the pile and soil, subsequently from which expressions of the complex impedances are deduced. Analyses are carried out to examine the second-order effect of axial force on the horizontal vibrating behavior of the pipe pile. Some conclusions can be summarized as follows: stiffness and damping factors are decreased with the application of axial force on the pile head; distributions of the pile horizontal displacement and rotation angle are regenerated due to the second-order effect of the applied axial force; and redistributions of the bending moment and shearing force occur due to the second-order effect of the applied axial force.

Assessment of the physical and mechanical properties of the soils in the different agroecological zones of Benin

The physical properties of soils are important for proper monitoring of soil functions. In order to evaluate soil resistance to agricultural equipment, a study was carried out on the four main soil types (ferralitic, ferruginous, hydromorphic and vertisol) in the eight agroecological zones of Benin. The objective of this work was to determine the physical and mechanical parameters of the soils. A sampling of soil types by agroecological zone was carried out in 36 localities in Benin to record vertical and horizontal soil strengths using a compactometer and a penetrometer. These data were complemented by measurements of texture, density and water content of the soil samples. Ananalysis of variance, polynomial regressions and Pearson correlation were performed between the parameters studied. It is noted that majority of soils assessed were sandy loam. The high sand content in most soils would be due to the depth considered (20 cm). The bulk densities range from 1.21 to 1.73gcm-3 and water contents from 4.9 to 35.11%. Vertical resistances range from 3.89 to 16.36 kg cm-2 and horizontal resistances from 1.03 to 4.44 kg cm-2. Strong soil resistances (vertical and horizontal) are recorded in the northern part of Benin where large proportions of the gravelswere observed in the samples taken. A positive correlation was observed between vertical resistance and horizontal soil resistance. It can be concluded that soil resistance in Benin vary from one agro-ecological zone to another, but the linking of soil properties is less significant between zones.Keywords: Soil compaction, soil resistance, penetrometer, agroecological zones, Benin

Повышение точности моделирования трансформаторов напряжения

Transformers designed for operation at network frequencies (50 or 60 Hz) unavoidably transform also the voltages of higher harmonic components with frequencies up to 2 kHz. In modelling a voltage transformer (VT), a standard T-equivalent circuit with constant parameters at all frequencies is commonly used. This circuit contains a horizontal branch and a vertical branch. The horizontal branch parameters were taken equal for the primary and secondary windings. For an ideal VT, the horizontal branch resistances and inductances are equal to zero, and the vertical branch resistance and inductance are equal to infinity. The article analyzes the transformation ratio equal to the ratio of the effective voltage across the VT secondary winding to the effective voltage across its primary winding. The transformation ratio of an ideal VT is equal to the ratio of the numbers of turns in its secondary and primary windings. The transformation ratio error depends on the extent to which the VT parameters differ from the ideal values mentioned before. The necessary VT transformation accuracy depends on its application. Experimental investigations were carried out on a multipurpose Type OSM-1.0 UZ voltage transformer. Its parameters were determined in the frequency band from 50 Hz to 2 kHz according to the three voltmeter method using a 34401A voltmeter. To improve the modeling adequacy, the same parameters were determined by a Type E7-22 RLC meter at the frequencies equal to 120 and 1000 Hz. For both methods, the uncertainty of the VT parameter measurements and the actual discrepancy between the measured values obtained by both these methods were within 2%. To obtain generalized results, a normalized transformation ratio was introduced, the value of which for the ideal VT is equal to unity. The measured VT parameters were used to study the VT errors, as well as the errors of their assessments by means of three models: (i) the conventional one (involving four constant values of the parameters measured at the 50 Hz frequency), (ii) the reference one (involving the VT parameter values measured at all analyzed frequencies), and (iii) the new one (involving nine parameters measured at DC and at the 50 and 2000 Hz frequencies). The transformation ratio was calculated for all these models using the MicroCap and Wofram Mathematics computer programs in the no-load operation mode, during operation with the nominal active load of 50 Ω, and during operation with the nominal active load connected in parallel with a 10 µF capacitor. The frequency errors of the first and third models were determined with respect to the reference model and the 50 Hz frequency. It has been demonstrated from the simulation results that the proposed model yields the accuracy a factor of 1.5 to 3.6 better than the standard one.

Capacity Magnification by Imposing Composite Action of Precast Concrete Flanged Girders

This paper presents an experimental study in order to verify the efficiency of different connecting techniques in improving the horizontal shear resistance of composite concrete flanged beams. The studied composite beams consisted of precast concrete webs interconnected with precast concrete flanges. Different connecting techniques had been considered; namely, plain/reinforced Ultra- High-Performance Strain-Hardening Cementitious Composites (UHP-SHCC) shear pockets, UHP-SHCC shear buckets in the flange accommodated extended steel dowels from the web, unbonded internal steel fasteners and intermediate shear intrusions. Eight composite flanged beams incorporating different connecting techniques along with three reference beams; monolithic, successively cast flanged beam and unconnected web/flange beams were prepared and tested up to failure under two cycles of non-reversal repeated loading. Furthermore, the push-off test method was employed in order to determine the horizontal shear resistance of the used connecting techniques. Each technique came up with advantages and disadvantages. Therefore, it is a matter of compromise to decide the most appropriate technique according to the necessary criteria (ultimate capacity or ductility). Finally, the horizontal shear resistances were calculated based on the experimental findings and compared with the stipulated resistances in the ECP 203-2007 and the ACI 318-14 design codes. It was found that the design codes’ values showed conservative results.

A new theoretical model of aircraft arresting system based on polymeric foam material

The engineering material arresting system (EMAS) has been widely employed in airports around the world for purpose of stopping the overrun airplanes from damage. However, the foamed concrete, which is used as the EMAS core at present, has drawn increasing criticism from the public opinion for environmental issue and aging problem. In this paper, a new arresting system made of polyurethane foam with high energy absorption capacity was proposed to overcome the above problems. An analytical model based on the Avalle empirical model, which takes into account the coupling effect between the aircraft wheel and the foam material, was presented to estimate the horizontal resistances exerted on the aircraft wheel, including the crushing drag, the tearing drag, the adhesive drag and the friction drag. In addition, the stopping distance required to arrest the overrun aircraft was predicted. Furthermore, the accuracy of the theoretical results was validated through comparison with the results of FAA full-scale arresting tests. Besides, the influences of the arrestor height, material strength, aircraft weight and the radius of aircraft wheel on the arresting performance of polyurethane foam material were performed, indicating that a reasonable parametric selection is extremely crucial to obtain the optimal design for the aircraft arresting system.

土質による降伏条件の違いが群杭の杭周水平地盤抵抗に与える影響

The behavior of pile foundation during earthquake is affected by soil-pile-building interaction and its nonlinearity. When we calculate the pile stress, the nonlinearity of soil material should be considered. For failure criterions which can express nonlinearity of soil, Mohr-Coulomb failure criterion and Drucker-Prager failure criterion are used. However, the influences on soil resistance around piles caused by the difference of these failure criterions are not clear yet. On the other hand, horizontal soil resistances in pile groups are affected by the interaction between piles, which is called the effect of pile groups. In our past researches, we have analyzed about soil resistances around each pile in pile groups in sandy soil, but we have not discussed the case of cohesive soil. The failure criterion of cohesive soil is different from sandy soil. This difference may affect the behavior of pile groups. Therefore, it is necessary to discuss soil resistance of a pile group in cohesive soil. This paper discusses the influences on soil resistance of a pile group caused by different failure criterions. Nonlinear static analyses on the 25-pile groups were performed using 3-dimensional finite element method. The piles are steel pipe piles with a length of 11m and a diameter of 600mm. The pile group is arranged in a 5x5 pattern. Each pile is located with center-to-center spacing of 1.5m. Soil parameters of internal frictional angle and cohesion are mainly discussed. Both springs at the pile head and around pile shaft are calculated. When calculating the spring at the pile head, the piles are modeled by the elastic shell elements and forced displacement is given to the pile head. When calculating the soil spring around the pile shaft, the piles are modeled as the excavated ground and uniform forced displacement is given to the whole of the piles. The major conclusions of this paper can be summarized as follows: 1) Under the Mohr-Coulomb failure criterion, the strength of sand differs between triaxial compression and triaxial tensile. The difference determines the subgrade reaction of piles. Near ground surface, the subgrade reaction is determined by the strength under triaxial compression, while in deeper parts of the ground, the subgrade reaction is determined by the strength under triaxial tensile. 2) In the case of sandy soil, subgrade reaction concentrates on front piles in a pile group. While in the case of cohesive soil, the concentration on front piles is softened by side piles. 3) Concentration ratio of the subgrade reaction is discussed. In sandy soil, concentration ratio on front piles goes higher with the growth of displacement, while the concentration ratio of side piles gets lower. But in cohesive soil, concentration ratio of front piles and side piles hardly change with displacement. 4) Both in sandy soil and cohesive soil, the subgrade reaction concentration ratios on front piles and side piles get lower near ground surface. While in deeper parts of the ground, they are almost constant values.

伝統木造の束の回転めり込みメカニズムと定式化

The important structural elements of traditional timber structures in Japan are rotational resistances of column-beam joints. The restoring forces characteristics of their structures depend on the rotational resistances of the joints. Therefore, the elasto-plastic restoring force characteristics of embedment of joints is the most significant in order to evaluate the seismic performances of the traditional timber structures. The authors have already applied Pasternak Model (abbreviated to PM) to the embedment and established the formulation of embedment mechanisms of partial compression of wood, which is the most appropriate embedment mechanical model for embedment problems. Furthermore, they developed the Elasto-plastic Pasternak Model (abbreviated to EPM) for the elasto-plastic embedment mechanism considering the strain hardening behavior. However, there are many types of joints and their resisting mechanisms are different. Thus, the mechanisms of different types of joints should be made clear. The authors have already established the formulation of crosspiece joint applying the EPM of the mechanism and confirmed the formulation based on the static loading tests. In this paper, the authors focus on the strut which has not been considered as a structural element so far, and propose the formulation of embedment mechanism of the strut, as a model of rotational embedment under the constraint conditions. Then, they carried out loading tests of the struts, and obtained their restoring forces characteristics. The loading test of two types of struts were carried out; one is Y-series (six specimens) which support the floor beams standing on the base stone. The other is T-series (three specimens) which stand between two beams, called, “Taihei tuka”. The dimentions of the strut are: depth:120mm, breadth:120mm, height:280mm. Beams depth:180mm(Y-1～3) and 90mm(Y-4～6), and 150mm (T-1～3). All species of specimens are Japanese cedar (Sugi). The test results showed that the maximum horizontal resistances of Y-1～3 were 8～11kN, the maximum normal loads were 36～50kN. The maximum horizontal resistances of Y-4～6 were 6～7kN, the maximum normal loads were 18～28kN. T-1～3 were the maximum horizontal resistances of 12kN, the maximum normal loads were 48～53kN and had the large deformability up to 200mm. The resisting mechanism of strut joints due to horizontal loads is “Diagonal Effect” which push up the beam, rotating and embedding into the beam in accordance with the rotation of the strut. The mechanism is due to geometrical fact that the diagonal line of the strut is longer than the height of the strut. Another mechanism is the distance between beams decreases due to inclination of column. The same mechanism is found in short beams between inclined columns and panel walls within the frames. The authors considered the mechanism of struts is rotational embedment of strut into beams under the constraint conditions and proposed Elasto-plastic Pasternak Model formulation established by the author, in order to analyse them appropriately. Then the formulation is discussed and verified by the simulation based on the Elasto-plastic Pasternak Model formulation. As a result, the deformability is very large and the strut should be considered as a structural element for exact seismic estimation of traditional timber structures.

Evaluation of buttress wall shapes to limit movements induced by deep excavation

Three-dimension finite element analyses of deep excavations with buttress walls were performed to evaluate the effect of buttress wall shapes on limiting movements induced by deep excavation. Results showed that a combination of the rectangular and the capital L-letter shapes (RL-shape) yielded the greatest performance in reducing wall deflections and ground surface settlements. The main deformation-control mechanism mainly came from the horizontal and vertical frictional resistances of buttress walls against adjacent soils which were pushed by wall deflections and the soil heave at the excavation bottom, respectively. Besides, the RL-shape buttress walls were successfully verified through a well-documented case history.

A COMPARATIVE STUDY ON THE RESISTANCES OF BUCKET FOUNDATION IN SAND WITH DIFFERENT INSTALLATION METHODS

Model tests have been performed to investigate the vertical, horizontal and cone tip resistances of bucket foundations embedded in sand with different installation methods; suction force by pump and jacking force by actuator. Micro-cone penetrometer was used to evaluate the variation of the effective stress inside pile after model pile installation. As a result, in vertical pull-out test, the pile installed jacking force method shows 3 times larger resistance than installed suction force method. In horizontal pull-out test, the ultimate horizontal capacity and the slope of load-displacement curve for the model pile installed by suction force were decreased by 22% and 40% respectively compared to the pile installed by jacking force. In cone penetration test, inside cone tip resistance of the pile installed by suction force shows about 40% smaller than that installed by jacking force. It is because the effective stress was reduced due to upward seepage of inner pile in sand by suction force. Therefore, we can see that the effect of installation method on bucket foundation has to be considered to investigate the behavior of it experimentally.

Comparative Analysis of Bearing Capacity of Inclined and Vertical Excavated Foundation

Excavated foundation has widely used in the field of transmission line engineering because of its large capacity to resist uplift and moment force. Elastic-plastic numerical model were established by using the finite element software ABAQUS focusing on the difference of bearing characteristics of inclined and vertical excavated foundation. There is very slight difference of axial uplift resistances between the both foundations because almost the same soil mass are mobilized at the same displacement loading. However, failure modes and horizontal resistances of negative, positive and vertical foundations are very different. The larger soil mass along the shaft of negative foundation is mobilized than positive and vertical foundations. The uplift resistances of vertical and negative foundations are about 5% and 25% higher than positive foundation at horizontal displacement of 50mm respectively.

횡하중이 작용하는 항만구조물에서 짧은말뚝의 극한지지력 및 평가방법

횡하중이 작용하는 짧은말뚝의 지지거동에 영향을 미칠 수 있는 인자들에 대한 분석을 문헌과 사례를 통해 제시하였다. 가상고정점은 <TEX>$1/{\beta}$</TEX>를 일률적으로 적용하는 것보다 지반의 강성에 따라 적용되어야 하고, Chang(1937)법과 P-Y 해석법이 유사한 고정점 위치를 예측하였다. 점성토의 수평지지력은 실내와 현장이 다른 특성을 보였고, 평가방법은 실내시험에서는 모두 과소예측을 하였고, 현장은 과소 또는 과대 예측을 한다. 현장실험에서는 Hansen(1961)법이 비교적 실측에 근접한 예측결과를 제시하였다. 사질토의 수평지지력 평가법은 실내시험에서는 과대예측을 하였고, 현장도 대부분 과대예측한다. 경험적 수평지지력 분포도를 사용한 Zhang(2005)법이 비교적 실측에 근접한 예측 결과를 보였다. 본 연구에서는 점성토 지반에 대하여 극한수평지지력 분포도 및 산정방법을 제안하였다. 제안법은 다른 방법에 비해 실측과 가장 근접한 결과를 추정하였다. In this study the analysis is performed for influencing factors on the behavior of rigid piles (short pile) by research papers and case study. The results indicated that the point of virtual fixity should be calculated considering the relative stiffness of soil and pile, and Chang (1937) and P-Y method estimated the similar fixity. The values of ultimate resistances of a vertical pile to a lateral load are different for laboratory and field tests in cohesive soils and its ultimate values in laboratory tests are underestimated and in field tests are under or overestimated. The estimated resistance by Hansen (1961)'s method is similar to the value of field tests. The horizontal resistances to laterally loaded pile in cohesionless soils are overestimated in laboratory tests and generally overestimated in field tests. The ultimate resistances by Zhang (2005)'s method, used to the empirical distribution of the resistance, are similar to the test results. In the paper the calculating method and distribution of the ultimate resistance in cohesive soils are proposed. The estimated value by the proposed method is closer to the test results than any other method of calculating ultimate resistance of the piles embedded into cohesive soils.

Simulation of Bionic Anti-Drag Subsoiler with Exponential Curve Feature Using Discrete Element Method

Subsoiling, as an important mode of conservation tillage, can break plowpan and increase permeability and water retention ability of soil which increase the crop yield. Subsoiler, as a key component of subsoiling, significantly effects on the tillage resistance. Reduction of working resistance of subsoiler can decrease output power of tractor and then further reduce the cost of subsoiling operation. The existing subsoilers have problem of overlarge subsoiling resistance. The conventional methods to resolve such problem include optimal design of the structural parameters of subsoiler and application of oscillation subsoiling device, but those methods not only make the structure of subsoiler more complex, but also increase the cost of agricultural production. Based on biomimetics principles, the upper surface outline of the claw of the house mouse (mus musculus), which has exponential function curve feature, was applied to the structural design of cutting soil edge of subsoiler shaft. Accordingly, the bionic subsoiler which has exponential function curve feature was designed and manufactured. The comparative experiments were conducted using the two types of subsoilers which have exponential function curve shape and parabola type in tillage depth at 300mm and 350mm with the forward velocitys of 0.5m/s and 1.0m/s in the indoor soil bin. The horizontal tillage resistances of the two types of subsoilers were measured using remote-measuring system of agricultural machinery dynamic parameters under different experimental conditions. The results showed that the horizontal tillage resistances increased with the increase of tillage depth and forward velocity. The horizontal tillage resistances of bionic anti-drag subsoiler (BAS) were obviously less than those of parabola type subsoiler (PTS) under same experimental conditions and the reduction was in the range of 8.5-38.2%. It indicated that the cutting soil edge of shaft with exponential function curve structure has remarkable anti-drag property. The simulations of tillage processes of the two types of subsoilers were conducted using discrete element method (DEM), the stress fields and velocity fields were obtained under different simulation conditions. The results showed that the directions of stress fields and velocity fields of the two types of subsoilers have forward and upward variation trend, but the directionality of contact stress of PTS was nonuniform compared with BAS, and such results lead to an increase in soil disturbance. The intensities of stress field and velocity field of BAS were obviously less than those of PTS under same experimental conditions, The results of simulation were consistent with the results of tillage experiments, indicating that the bionic subsoiler with exponential function curve feature has significant anti-drag property. The exponential function curve can be applied to the structural design of cutting soil edge of subsoiler aiming to reduce tillage resistance.

Deformation analysis of a geocell mattress using a decoupled iterative method

Deformation analysis is a major concern in many geotechnical applications. In this paper, the deformation behavior of a geocell mattress subjected to symmetric loads was studied. The mattress was idealized as an elastic foundation beam. The horizontal beam-soil interfacial shear resistances at the beam top and bottom sides were taken into account by assuming the resistances to be linear with the relative horizontal displacements. A decoupled iterative method was employed to solve the differential displacement equations derived from the force analysis of a beam element and to obtain the solutions for the deformations and internal forces of the geocell reinforcement. The validity of the present solutions was verified by the existing finite element method and power-series solutions.

Genetic Vulnerability of Modern Crop Cultivars: Causes, Mechanism and Remedies

Plant breeding is one way to confront the challenge of bridging the widening gap between the demand and supply of food. Despite the importance, however, plant breeding has its own negative side effects. The replacement of landraces with a few genetically uniform varieties depletes genetic diversity and provides ideal conditions for diseases and insect pests that called genetic vulnerability. The increasingly growing human population and the subsequently rising demands for more food, on the one hand, and the success of such efforts like the “Green Revolution” from adoption of genetically uniform varieties in many parts of the world, on the other, are the main driving force towards this narrow genetic base. It is, therefore, important to understand the phenomena and plan to minimize the risks from genetic vulnerability. Under marginal conditions where resource-poor farmers dominate, the current plant breeding strategies, variety release, registration and certification procedures leading to genetic uniformity should be reconsidered and some level of genetic diversity should deliberately be maintained in variety development programs. Genetic diversity can be introduced at different levels and in different ways which may include intra-varietal, inter-varietal, inter-parental and inter-specific diversities. Breeding for specific adaptation instead of wide adaptation, systematic spatial and temporal gene deployment, use of inter-specific varietal mixtures and integration of horizontal and vertical resistances have been suggested as solutions.