Experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering boundary effect

The boundary condition is a crucial factor affecting the permeability variation due to suffusion.An experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted,where the hydraulic head difference(DH)varies,and the boundary includes non-loss and soil-loss conditions.Soil samples are filled into seven soil storerooms connected in turn.After evaluation,the variation in content of fine sand(ΔR_(f))and the hydraulic conductivity of soils in each storeroom(C_(i))are analyzed.In the non-loss test,the soil sample filling area is divided into runoff,transited,and accumulated areas according to the negative or positive ΔR_(f) values.ΔR_(f) increases from negative to positive along the seepage path,and Ci decreases from runoff area to transited area and then rebounds in accumulated area.In the soil-loss test,all soil sample filling areas belong to the runoff area,where the gentle-loss,strengthened-loss,and alleviated-loss parts are further divided.ΔR_(f) decreases from the gentle-loss part to the strengthened-loss part and then rebounds in the alleviated-loss part,and C_(i) increases and then decreases along the seepage path.The relationship between ΔR_(f) and Ci is different with the boundary condition.Ci exponentially decreases with ΔR_(f) in the non-loss test and increases with ΔR_(f) generally in the soil-loss test.

Auto-parametric resonance of a continuous-beam-bridge model under two-point periodic excitation:an experimental investigation and stability analysis

The auto-parametric resonance of a continuous-beam bridge model subjected to a two-point periodic excitation is experimentally and numerically investigated in this study.An auto-parametric resonance experiment of the test model is conducted to observe and measure the auto-parametric resonance of a continuous beam under a two-point excitation on columns.The parametric vibration equation is established for the test model using the finite-element method.The auto-parametric resonance stability of the structure is analyzed by using Newmark's method and the energy-growth exponent method.The effects of the phase difference of the two-point excitation on the stability boundaries of auto-parametric resonance are studied for the test model.Compared with the experiment,the numerical instability predictions of auto-parametric resonance are consistent with the test phenomena,and the numerical stability boundaries of auto-parametric resonance agree with the experimental ones.For a continuous beam bridge,when the ratio of multipoint excitation frequency(applied to the columns)to natural frequency of the continuous girder is approximately equal to 2,the continuous beam may undergo a strong auto-parametric resonance.Combined with the present experiment and analysis,a hypothesis of Volgograd Bridge's serpentine vibration is discussed.

Experimental Investigation on the Strength and Ductility Performance of Steel-Timber-Steel Joints with Screw and Steel-Tube Fasteners

This article presents experimental results of steel-timber-steel(STS)joints loaded parallel to grain.Eight groups of specimens were designed,and tensile tests were performed.The fastener types and fastener numbers were considered to evaluate the tensile strengths and ductility performances of the STS joints.The screws with 6 mm diameter and the innovative steel-tubes with 18 mm diameter were adopted as connecting fasteners.The experimental results were discussed in terms of yielding and ultimate strengths,slip stiffness,and ductility factors.The ductility classification and failure mechanisms of each group of specimens were analyzed.It was demonstrated that the STS joint with large diameter steel-tubes showed acceptable ductility,which was close to the ductility of the STS joint with small diameter screws,thanks to the hollow structure of the steel-tube.The theoretical strengths of various failure modes for the joints with small diameter screws or large diameter steel-tubes were calculated and compared with the experimental results.The ductile performance of the STS joint was discussed by comparing the theoretical strengths of various failure modes.The effective number of the STS joint with multifasteners was also analyzed by considering the failure mechanisms in aspects of tensile strength and slip stiffness.

Dynamic parameters of multi-cabin protective structure subjected to low-impact load e Numerical and experimental investigations

The dynamic response of a multi-cabin protective structure subjected to impact load directly affects the protective performance of materials;thus,studying the dynamic response and communication law of wave effect of the load plays an important role in the prediction of protective performance.In this study,the protection experiments of box-structure under air-and/or water-medium are conducted,the dynamic response of the structure subjected to low-impact load is analyzed,and the corresponding numerical simulations are analyzed using the theory of finite element method(FEM).Combined with experimental and FEM simulations,the shock strain distribution,acceleration attenuation,and signal energy in defensive materials are determined.Based on the results,the metal structure exhibits good absorption characteristics for shock vibration.Using the experimental data,we also show that the attenuation of shock wave in water medium should be significantly better than that in air medium,and the protective structure should be designed for a combination of water and air mediums.Meanwhile,the numerical simulation can provide a quantitative analysis process for dynamic analysis of defensive materials.

EXPERIMENTAL INVESTIGATION ON R134A AIRBORNE VAPOR-COMPRESSION REFRIGERATION SYSTEM

The airborne high power electrical equipments have been widely used in modern aircrafts , which consequently causes the dramatic increase of heating load up to dozens of kilowatts.Accordingly , vapor-compression refrigeration system ( VCRS ) with lower engine bleed air and larger refrigeration capacity has been paid much attention in recent years.Therefore , based on the analysis of the characteristics of VCRS , an experiment system of VCRS using R134ais set up to simulate operation performances.The influences of different parameters including evaporation pressure , condensing pressure , refrigerant mass flow rate and compressor rotation speed are also investigated.The impacts of different parameters on the system performance are various.This work can help to establish the specific control law under different work conditions.

Experimental Investigation into Shaping Particle-reinforced Material by WEDM-H

Al 2O 3 particle-reinforced material (6061 alloy ), which is one of new composites and characterized by high strength and small spe cific gravity, good wear resistance and corrosion resistance, has been widel y used in industry. But it is difficult to machine. Because of electric conducti vity, it can be shaped and processed by electro-machining means. However, this kind of material is mixed with the electrically conductive substances and the di electrically conductive substances, its machining process shows substantially di fferent from the machining of ordinary metal materials. This paper, based on a c ontrast experiment, investigates the machining mechanism and technique by WEDM t o shape the material and gives the optimum selection for the electric paramete rs in operation. The technologic index of shaping the new material by WEDM includes the cutting r ate and the surface roughness. There are a lot of factors that affect the techno logic index of WEDM, in which the electric parameters such as the machining volt age and current as well as the pulse duration, interval and frequency, play an i mportant part. In this experiment, the study focus mainly on the effect of the e lectric parameters on machining process and an orthogonal design is employed to select the proper electric parameters. By experiment, we find how the voltage and current affect machining process and study the removal mechanism by WEDM-HS to machine Al 2O 3 particle-reinforce d material. Besides the machining current and voltage, there are still other fac tors that can affect machining process and state. In order to find out which is the most important factor and to optimize the electric parameters, the orthogona l design has been adopted to perform the experiment. By the analysis to the rela tive differences among different factor levels, the rank of significance for fou r factors is in turn the pulse duration, the voltage, the machining current and the pulse interval. At last we can draw a conclusion that 6061 alloy can be shaped by WEDM-HS, and give the suitable electric parameters to obtain good surface roughness and high machining efficiency.

Experimental investigation on coal pore-fracture variation and fractal characteristics synergistically affected by solvents for improving clean gas extraction

Chemical solvents instead of pure water being as hydraulic fracturing fluid could effectively increase permeability and improve clean methane extraction efficiency.However,pore-fracture variation features of lean coal synergistically affected by solvents have not been fully understood.Ultrasonic testing,nuclear magnetic resonance analysis,liquid phase mass spectrometry was adopted to comprehensively analyze pore-fracture change characteristics of lean coal treated by combined solvent(NMP and CS_(2)).Meanwhile,quantitative characterization of above changing properties was conducted using geometric fractal theory.Relationship model between permeability,fractal dimension and porosity were established.Results indicate that the end face fractures of coal are well developed after CS2and combined solvent treatments,of which,end face box-counting fractal dimensions range from 1.1227 to 1.4767.Maximum decreases in ultrasonic longitudinal wave velocity of coal affected by NMP,CS_(2)and combined solvent are 2.700%,20.521%,22.454%,respectively.Solvent treatments could lead to increasing amount of both mesopores and macropores.Decrease ratio of fractal dimension Dsis 0.259%–2.159%,while permeability increases ratio of NMR ranges from 0.1904 to 6.4486.Meanwhile,combined solvent could dissolve coal polar and non-polar small molecules and expand flow space.Results could provide reference for solvent selection and parameter optimization of permeability-enhancement technology.

Experimental Characterization of Rutting Performance of HMA Designed with Aggregate Gradations According to Superpave and Marshall Methods

The permanent deformation (rutting) of pavement is a major distress in flexible pavement. It is related to vehicles properties and/or pavement materials and conditions. This article presents an extensive experimental investigation in order to compare between the aggregate gradation according to Superpave and Marshall methods of asphalt concrete mix design on pavement rutting and to examine the sensitivity of rutting resistance to aggregate gradation. A wheel truck machine has been used for measurement of pavement rutting (permanent deformation). The tests were carried out at two controlled different air temperature 55℃ and 25℃. The results obtained showed that the adopting of aggregate gradation procedure of Superpave method of pavement mix design for Marshall method of asphalt concrete mix design can reduce the pavement rutting by about 50%. This achievement may be related to missing of three sieves in aggregate gradation procedure of Marshall method which controls rounded and finer aggregate particles. These sieves provide more continuity for aggregate gradation to ensure filling unnecessary gaps and produce more contact points between the aggregates in Hot Mix Asphalt (HMA). The outputs of the research support modifying Marshall method of asphalt concrete mix design by adopting aggregate gradation proposed in Superpave method. The results of study also showed that the coarser aggregate provided more resistance to pavement rutting.

Experimental investigations on structural improvement of morphing mechanism for nose cone of aerospace vehicle adopting a bionic redundant constraint strategy

Aerospace vehicles have recently received great attention for their completely reusable in aviation and aerospace.To achieve the optimal aerodynamic performance of the aerospace vehicle,the nose cone needs to change its aerodynamic shape under different flight conditions.However,the structural design of a morphing nose cone that is capable of changing aerodynamic shape adaptively and withstanding prescribed aerodynamic loads remains an ongoing challenge.To overcome this issue and to further advance our previous work,the motion performance of a morphing nose cone inspired by the deformation mechanism of the honeybee abdomen was tested to evaluate the deformation ability and bearing capacity.The dynamic prediction analysis of the morphing nose cone with a clearance joint and flexible links was then investigated to elucidate the crucial issues in the deformation movement.To improve the motion performance,a performance improvement scheme based on redundant constraints drawn from the muscle distribution of the honeybee abdomen was proposed.Finally,the structural stiffness,dynamic analysis,and experimental testing of the improved morphing nose cone were conducted.The experimental results indicate that the extension and contraction ratios and bending angles of the improved morphing nose cone under loads of 0,10,and 25 kg loads improve by 1.51%and 2.329°,2.78%and-1.902°,and 5.06%and 1.111°,respectively,verifying the rationality and effectiveness of the performance improvement scheme.This work provides a new reference for the design of the morphing structure for aerospace vehicles.

Experimental investigation of photovoltaic systems for performance improvement using water cooling

This research aims to analyse the comparative performance of two identical photovoltaic(PV)panels with load variations and integrating an automated water-cooling process under the climatic conditions of the United Arab Emirates.The work also presents the steps of system design,implementation and performance evaluation of the proposed PV system,and all electrical,control and mechanical components along with how they were integrated within a 100-W PV system.MATLAB/Simulink?was used only to simulate the behaviours of the PV panel under wide ranges of incident sunlight and ambient temperature.The tests were performed for a day-long operation during a clear summer day.The experimental results demonstrate an improvement in the PV system performance compared with the uncooled system by~1.6%in terms of total harvested energy using the proposed water-cooling process with a frequency of 2 minutes of cooling operation every 30 minutes during day hours.

Gunn器件中畴的静止-渡越-静止模式的实验观察和计算机模拟

本文讨论在GaAs n^+-n-n^+夹层结构的Cunn器件中畴的静止-渡越-静止模式,进行了实验观察和计算机模拟,指出在超过阈值的偏置电压下,当畴的耗尽层进入阳极附近的高掺杂区后,会逐渐停止下来形成准静态畴,这时畴外电场达到最大值.如果这时阴极凹口仍不能形成新畴,则准静态畴将进一步调整成为真正的静止畴,而畴外电场也将由最大值下降到一个与偏压无关的固定值.经过理论分析,得到了静止畴所固有的与外加偏压无关的畴外电场与有源区掺杂浓度的关系式,并和计算机模拟的结果相比较,得到很好的符合.如果偏压的增加使准静态畴所对应的畴外电场最大值已经足够使阴极凹口形成新的畴,则静止畴将转变为渡越畴.如果偏压继续增加,使积累层尾部覆盖了阴极凹口,则畴会再次静止下来,直到偏压增加到畴发生雪崩为止.计算和实验表明,后一个静止区的电压变化范围要比前一个大得多.本文还讨论了两个转变电压和温度的关系及扩散系数对静止畴的影响.

Experimental investigation of ghost imaging of reflective objects with different surface roughness

We present an experimental demonstration of ghost imaging of reflective objects with different surface roughness.The influence of the surface roughness, the transverse size of the test detector, and the reflective angle on the signal-to-noise ratio(SNR) is analyzed by measuring the second-order correlation of the light field based on classical statistical optics. It is shown that the SNR decreases with an increment of the surface roughness and the detector's transverse size or a decrease of the reflective angle. Additionally, the comparative studies between the rough object and the smooth one under the same conditions are also discussed.

Unsteady experimental and numerical investigation of aerodynamic performance in ultra-high-lift LPT

Detailed experimental and numerical investigations were performed for an ultra-high-lift front-loaded low-pressure turbine cascade (Zw=1.58) with periodic wakes.The interaction mechanisms between the incoming wakes and endwall secondary flow were carefully examined.Wakes were produced by moving upstream rods,and flow field downstream of the cascade was measured using a seven-hole probe.Experimental results revealed that incoming wakes influenced not only the boundary layer development of the blade suction surface but also the complex endwall secondary vortex structures.On the suction surface:Incoming wakes clearly suppressed the suction side separation bubble at a low Reynolds number of 25000.Nevertheless,the effects of different wake passing frequencies were not significantly different at Re=100000,and the profile losses under wake passing were even greater than in the absence of wakes.At the end walls:Incoming wakes more strongly suppressed secondary flow at Re=100000 than at Re=25000,because the lowmomentum fluid inside the incoming wakes clearly increased the endwall cross-passage pressure gradient at Re=25000.The experimental results indicated that periodic wakes decreased the passage vortex and counter vortex core strength by 25% and 30%,respectively,at Re=100000.Instantaneous results also demonstrated that endwall secondary vortices decreased significantly near the position of wakes passing.

Experimental Investigation for Co-Combustion Characteristics of Semi-Coke and Bituminous Coal in a 3 MWth Tangential Combustion Facility

An experimental investigation was conducted in a 3 MW pilot-scale tangential combustion facility to explore the co-combustion characteristics of bituminous coal mixed with semi-coke.The thermal gravimetric analyzer(TGA)was used to obtained fuel thermal analysis.The results presented effects of semi-coke blending ratio(BR)on average furnace temperature,ignition temperature,NO emission and combustion efficiency.The excess air coefficient in main combustion sections and outlet were fixed at 0.85 and 1.2 while BR increased from 0%to 50 wt.%.The temperature profiles of combustion decreases along the height of furnace while average furnace temperature fluctuates slightly with an increasing BR.The concentration of NO has an increasing tendency with the increasing of BR.The ignition temperature obtained from TGA measurement agreed well with experiment result.In addition,combustion efficiency was not sensitive to BR and decreased slightly with the increasing BR.

Design theory and experimental investigation of the low frequency and high power rare earth magnetostrictive flextensional transducer (Ⅰ). Theoretical part

The energy relationships among all the elements, by which the magnetostrictive transducers are manufactured, in Finite Element Method (FEM) are analyzed, then the expres- sions of FEM dynamics equations and performances formulas for magnetostrictive transducers are derived. The vibrating modes of the class VII transducer and its shell vibration are calcu- lated theoretically and the results point out that there is a breathing mode and if the transducer works at this mode, the transducer will vibrate with a greater volume speed and source level.

Experimental investigation on the time-delay signature of chaotic output from a 1550 nm VCSEL subject to FBG feedback

The time-delay signature(TDS) of chaos output in a 1550 nm vertical-cavity surface-emitting laser(VCSEL) subject to fiber Bragg grating(FBG) feedback is investigated experimentally. Autocorrelation function(ACF) and mutual information(MI) are used for quantitatively identifying the TDS of chaos. For various bias currents, the TDS evolution with the feedback strength is different, as the FBG provides wavelength-selective feedback. Furthermore,based on the TDS map of the FBG feedback VCSEL(FBGF-VCSEL) in the parameter space of feedback strength and bias current, the optimal TDS suppression regions, where the dominant polarization mode of FBGF-VCSEL locates at the edge of the main lobe of FBG reflection spectrum, have been determined. Finally, for comparative purpose,the TDS of chaos in mirror feedback VCSEL(MF-VCSEL) also has been presented, and the results show that an FBGF-VCSEL possesses better TDS suppression performance than an MF-VCSEL.

Sand transport in multiphase flow mixtures in a horizontal pipeline:An experimental investigation

An inherent problem with both oil and natural gas production is the deposition of sand particles in pipeline,which could lead to problems such as excessive pressure drops,equipment failure,pipeline erosion,and production decline.The characterization of sand particles transport and sedimentation in different flow systems such as sandemultiphase mixtures is vital to predict the sand transport velocity and entrainment processes in oil and gas transportation pipelines.However,it seems that no model exists able to accurately characterize the sand transport and deposition in multiphase pipeline.In fact,in the last decade several researchers tried to extend the modeling of liquid-solid flow to gas-liquid-solid flow,but no significant results have been obtained,especially in slug flow condition due to the complexity of the phenomenon.In order to develop and validate a mathematical model properly formulated for the calculation of the sand critical deposition velocity in gas-liquid flow,more and more experimental data are necessary.This paper presents a preliminary experimental study of three phase flows(air-water-sand)inside a horizontal pipe and the application of the sand-liquid models present in literature.Significant observations were made during the experimental study from which several conclusions were drawn.Different sand flow regimes were established by physical observation and data analysis:fully dispersed solid flow,moving dunes and stationary bed.The critical deposition velocities were determined at different sand concentrations.It was concluded that sand transport characteristics and the critical deposition velocity are strongly dependent on the gas-liquid flow regime and on sand concentration.

Experimental investigation on active acoustic flutter control

Experimenial studies on active acoustic fiutter control are carried out successfully in wind-tunnel after the theoretical study The experdrients verify the theory presented in the reference[1] and give valuable experimeotal results which predict a prondsing future of applying new techology and new ideas to the area of vibration induced by flow.

Experimental Investigation of Macro-Bending Loss in Large Mode Area Photonic Crystal Fibers

We measured macro-bending losses for two large mode area photonic crystal fibers. Experimental results show that macro-bending loss and loss window are dependent on the parameter d/∧ and number of air-holes ring in the cladding.

Application of PCM-based Thermal Energy Storage System in Buildings: A State of the Art Review on the Mathematical Modeling Approaches and Experimental Investigations

This review paper critically analyzes the most recent literature(64% published after 2015) on the experimentation and mathematical modeling of latent heat thermal energy storage(LHTES) systems in buildings. Commercial software and in-built codes used for mathematical modeling of LHTES systems are consolidated and reviewed to provide details on the selection of appropriate tools. Insights on software’s computing speed, model simplicity, accuracy(by considering the convective term in the melting process), and application of artificial neural networks are reviewed in detail. Moreover, the overall research status of the experiments conducted on the phase change material-based LHTES systems with different experiment configurations is reviewed. The analysis shows that ANSYS Fluent is the most widely used software for specific heat transfer phenomenon in storage tanks, while self-developed models with simplified terms are evaluated as more flexible and easier to apply. For hybrid systems, self-developed MATLAB, mature parts in ESP-r, TRNSYS, and EnergyPlus are compatible. Further, most of the experimental investigations are conducted on the laboratory scale, providing data for model validation. To provide a clear guidance for the future market application, the scope for future works is presented. With this review, it would be easier to develop a unified, simplified, visual, and accurate simulation platform for the PCM-based thermal energy storage in buildings.