Study of Neutron Cross Talk Rejection Based on Testing Experiment and Simulation

Experimental data analysis and simulation calculations were performed in order to evaluate the cross-talk rejection performance of a typical neutron detection array. For very closely packed scintillation bars, the CT rejection may rely on the position relation between the two signals. The criteria ｜△x｜≤ 15 cm and ｜△y｜≤12 cm are currently proposed for a rejection rate higher than 90%. For signals coming from distanced bars, the energy conservation relationship can be applied to reject the CT events with a similar performance. In both cases the results of simulation agree very well with the experimental data, assuring their applicability to other detection systems and physics problems.

Numerical and Experimental Evaluation of New Coldform Inverted “U” Section in Single or Multiple FamilyDwellings’ Flooring Systems

This article will introduce a new version of the metal deck for building residential flooring with a newly designed cold form U section. This flooring will allow residential structures to be built more quickly while also reducing the necessary thickness of the floor. The level of strength and deflection of this floor will be determined via analysis of a floor bed comprised of cold-formed inverted U sections (IUS) covered by sheathing that is subjected to different loading scenarios. The necessary computational quantities associated with the experiment have been compared to established laboratory values by performing all related and applicable tests. Then, these quantities are compared to different existing flooring techniques to determine the efficacy of this technique. The results show that this flooring technique can be effective and cost-efficient in residential applications.

Analytical and Experimental Studies on Hydrodynamic Performance of Semi-Immersed Jarlan-Type Perforated Breakwaters

The present study proposes a new semi-immersed Jarlan-type perforated breakwater including a perforated front wall, a solid rear wall, and a horizontal perforated plate connecting the lower tips of the two walls. An analytical solution is developed to estimate the hydrodynamic performance of the new breakwater. The analytical solution is confirmed by solutions for special cases, an independently developed multi-domain boundary element method solution and experimental data. Numerical examples based on the analytical solution indicate that compared with previous semi-immersed breakwaters, the new breakwater may have better wave-absorbing performance and smaller wave forces. Some useful results are presented for practical designs of semi-immersed Jarlan-type perforated breakwaters.

Experimental Verification and Research for the Distortion in the Integrated Frequency Responses of the High-Pressure Sealed Cabin and Magnetic Field Sensor

Although magnetotelluric sounding method applied to the land is advanced, there are many difficulties when it is applied to marine environment, one of which is how to lay magnetic field sensors down to the seafloor to complete measurements. To protect the magnetic field sensors from intense erosion and high pressure, suitable high-pressure sealed cabins must be designed to load them. For the consideration of magnetic measurement and marine operation, the sealed pressure cabin should be nonmagnetic and transportable. Among all optional materials, LC4 super.hard aluminum alloy has the highest performance of price/quality ratio to make the sealed pressure cabin. However, it does not mean that the high-pressure sealed cabin made using LC4 will be perfect in performance. In fact, because of its weak magnetism, the pressure cabin made using LC4 has distorting effect on frequency responses of the magnetic field sensors sealed in it. This distorting effect does not affect the use of the magnetic field sensor, but if we want to eliminate its effect, we should study it by experimental measurements. In our experiment tests, frequency sweep magnetic field as excitation signal was used, and then responses of the magnetic field sensor before and after being loaded into the high-pressure sealed cabin were measured. Finally, normalized abnormal curves for the frequency responses were obtained, through which we could show how the high-pressure sealed cabin produces effects on the responses of the magnetic field sensor. Experimental results suggest that the response distortion induced by the sealed pressure cabin appears on mid- and high-frequency areas. Using experimental results as standardization data, the frequency responses collected from seafloor magnetotelluric measurements can be corrected to restore real information about the seafloor field source.

An experimental investigation on the effect of grain size on oil-well sand production

Sand production in oil wells is closely related to the mechanical behavior and petrographical properties of sandstones reservoir. Grain size is one of the main parameters controlling the phenomenon, which is studied in this paper. Large-scale hollow cylindrical synthetic samples with the same rock strength but different grain sizes were tested by an experimental setup in the laboratory. Different external stresses and fluid flow rates were applied to the samples and produced sand was measured continuously. Results show two different trends between sanding stress level and grain size. For the samples with finer grain size （D50〈0.3 mm）, the required confining stress for different sanding levels decreased with an increase in the grain size and for the samples with the coarser grains （D50〉0.3 mm） the required confining stress for different sanding levels dramatically increased with an increase in the grain size. Those two different trends were discussed and explained. The first one was production of individual grains and the second was bigger chunks in the slab form. In samples with large grains, plastic zones around hole were changed to a completely loose zone including interlocked individual grains or cluster of grains. In these samples after breakage of these interlocked zones sand was produced in the form of individual grains and clusters. Contrary to this, for samples with smaller grain size, shear bands were formed around the plastified hole and sand was produced in the form of big chunks or slabs.

Experimental Study of Mooring Type Effect on the Hydrodynamic Characteristics of VLFS

Mooring system is a significant part of very large offshore floating structures(VLFS).In this paper,a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response,mooring force,incident coefficient,reflection coefficient and energy dissipation coefficient.Eight mooring cables are symmetrically arranged on both sides of the model.The floating body model satisfies the similarity of stiffness and gravity,while the cable satisfies the similarity of elasticity and gravity.The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response.Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model.The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs.The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types.These results may provide a reference to facilitate the mooring design of VLFS.

Experimental Study on Wave Attenuation Performance of A New Type of Floating Breakwater with Twin Pontoons and Multi Porous Vertical Plates

A floating breakwater(FB)has extensive potential applications in the fields of coastal,offshore,and ocean engineering owing to its advantages such as eco-friendliness,low cost,easy and rapid construction,and quick dismantling and reinstallation.An FB composed of twin pontoons and multi-porous vertical plates is proposed to improve the wave attenuation performance.The wave attenuation performance is investigated for different FB structures and vertical plate types under different incident wave heights and periods using 2D wave physical model tests in a wave flume.The results demonstrate that the proposed FB has a better performance than that of the conventional single pontoon-type FB.It reduces the wave transmission due to its enhanced wave reflection and energy loss.The wave transmission coefficient of the proposed FB decreases with an increase in the number of layers and relative draft depth of the vertical plates.However,a further decrease in the wave transmission coefficient is not observed when the number of porous vertical plates is increased from 4 to 5 layers.An equation has been derived to predict the wave transmission of the proposed FB based on the experimental results.

Experimental Tests on a Pre-Heated Combustion Chamber for Ultra Micro Gas Turbine Device: Air/Fuel Ratio Evaluation

Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.

Wave Force on the Crown Wall of Rubble Mound Breakwaters at Intermediate Depths

Rubble mound breakwaters with a crown wall are a common coastal engineering structure.The wave force on crown walls is an important parameter for the practice engineering design.Particularly,the wave force on crown walls under intermediate depths has been studied through physical model tests and numerical simulations.In this study,a three-dimensional numerical wave flume was developed to investigate monochromatic wave interactions in a rubble mound breakwater with a crown wall.Armor blocks were modeled in detail.The Navier-Stokes equations for two-phase incompressible flows,combined with shear stress transport k-ωturbulence model and volume of fluid method for tracking the free surface,were solved.A set of laboratory experiments were performed to validate the adopted model.Subsequently,a series of numerical simulations were implemented to examine the impacts of different hydrodynamic parameters(including wave height,incident wave period,and water depth)and the berm width on the wave force of the crown wall.Finally,a comparison of the experimental results and Martin method shows that the latter method is not suitable for this experimental scope.New empirical formulas are proposed to predict the wave force on crown walls under intermediate depth.The results can provide a basis for the design of crown wall of rubble mound breakwaters at intermediate depths.

Design and experimental testing of a control system for a morphing wing model actuated with miniature BLDC motors

The paper deals with the design and experimental validation of the actuation mechanism control system for a morphing wing model.The experimental morphable wing model manufactured in this project is a full-size scale wing tip for a real aircraft equipped with an aileron.The morphing actuation of the model is based on a mechanism with four similar in house designed and manufactured actuators,positioned inside the wing on two parallel lines.Each of the four actuators used a BrushLess Direct Current(BLDC)electric motor integrated with a mechanical part performing the conversion of the angular displacements into linear displacements.The following have been chosen as successive steps in the design of the actuator control system:(A)Mathematical and software modelling of the actuator;(B)Design of the control system architecture and tuning using Internal Model Control(IMC)methodology;(C)Numerical simulation of the controlled actuator and its testing on bench and wind tunnel.The morphing wing experimental model is tested both at the laboratory level,with no airflow,to evaluate the components integration and the whole system functioning,but also in the wind tunnel,in the presence of airflow,to evaluate its behavior and the aerodynamic gain.

Reflection and Transmission of Regular Waves from/Through Single and Double Perforated Thin Walls

In this paper, reflection and transmission coefficients of regular waves from/through perforated thin walls are investigated. Small scale laboratory tests have been performed in a wave flume firstly with single perforated thin Plexiglas plates of various porosities. The plate is placed perpendicular to the flume with the height from the flume bottom to the position above water surface. With this thin wall in the flume wave overtopping is prohibited and incident waves are able to transmit. The porosities of the walls are achieved by perforating the plates with circular holes. Model settings with double perforated walls parallel to each other forming so called chamber system, have been also examined. Several parameters have been used for correlating the laboratory tests’ results. Experimental data are also compared with results from the numerical model by applying the multi-domain boundary element method （MDBEM） with linear wave theory. Wave energy dissipation due to the perforations of the thin wall has been represented by a simple yet effective porosity parameter in the model. The numerical model with the MDBEM has been further validated against the previously published data.

FE modeling of concrete beams and columns reinforced with FRP composites

Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure.In the present work,numerical analysis of square and circle short columns,and reinforced concrete(RC)beams reinforced with fiber reinforced polymer composites are carried out.This work is divided into two parts.In the first part,numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer(GFRP)and Basalt Fiber Reinforced Polymer(BFRP)bars and spiral,and Carbon Fiber Reinforced Polymer(CFRP)wraps is conducted.The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio.In addition,the results of the numerical analysis showed good correlation with the experimental ones.An interaction diagram for BFRP RC columns is also developed with considering various eccentricities.The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column.For the cases considered in this study,column with two middle closely spaced CFRP wraps demonstrated the best performance.In the second part of this research,flexural behavior of RC beams reinforced with BFRP,GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests.The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams.It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.

Optimization of Baffled Rectangular and Prismatic Storage Tank Against the Sloshing Phenomenon

The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental damages. In the present study, a series of experimental tests are performed to investigate the sloshing phenomenon in a baffled rectangular storage tank. In addition, the sloshing phenomenon is also modeled by using Open Foam. Based on the experimental and numerical studies, optimization of the geometric parameters of the tank is performed based on some criteria such as tank area, entropy generation, and the horizontal force exerted on the tank area due to the sloshing phenomenon.The optimization is also carried out based on the entropy generation minimization analysis. It is noted that the optimum baffle height is in the range of h_b/h_w=0.5-0.75 in the present study(where h_b and h_w are the baffle height and water depth, respectively). Based on the results, the optimal design of the tank is achieved with R_A= 0.9-1.0(where R_A=L/W, L and W are the length and width of the tank, respectively). The results also show that the increase of h_b can lead to a decrease of the maximum pressure and horizontal force exerted on the tank. It is also noted that the horizontal force exerted on the tank firstly continues to increase as the sway motion amplitude increases.However, as the normalized motion amplitude parameter, a/L(The parameter a is the motion amplitude), exceeds0.067, the effect of motion amplitude on the force is not obvious. The same optimization is also performed in the multiple-variable-baffled tank and prismatic storage tank.

Optimal Design and Dynamic Simulation of Mountain Bike with Rear Suspension

This paper investigates the dynamic design methodology of mountain bikes with rear suspension. Firstly, a multi-rigid body dynamic model of rider and mountain bike coupled system is constructed. The rider model includes 19 skeletons, 18 joints and 118 main muscles. Secondly, to validate the feasibility of the model, an experiment test is designed to reflect the real cycling status. Finally, aiming at enhancing the performance of the rider vibration comfort, the scale parameters of rear suspension are optimized with computer simulation and uniform design. The mathematical model in the vibration performance and the design variables is constructed with regression analysis. The result shows that when the length of side link is 90 mm, the length of connected rod is 336.115 1 mm and the included angle between absorber and side link is 60°, the mountain bike has better vibration comfort. This study and relevant conclusions are of practical importance to the design of the mountain bike＇s rear suspension system.

Impact and Friction Sensitivity of Energetic Materials：Methodical Evaluation of Technological Safety Features

Key methods developed and used in the USSR and in the Russian Federation to determine the impact and friction sensitivity of energetic materials and explosives have been discussed.Experimental methodologies and instruments that underlie the assessment of their production and handling safety have been described.Studies of a large number of compounds have revealed relationships between their sensitivity parameters and structure of individual compounds and compositions.The range of change of physical and chemical characteristics for the compounds we examined covers the entire region of their existence.Theoretical methodology and equations have been formulated to estimate the impact and friction sensitivity parameters of energetic materials and to evaluate the technological safety in use.The developed methodology is characterized by high-accuracy calculations and prediction of sensitivity parameters.

Numerical and experimental study on dynamics of the planar mechanical system considering two revolute clearance joints

Due to assembly,wear and manufacturing errors and clearance in the joints are inevitable.When the clearance is introduced into a mechanical system,the impact force in the clearance joint will cause undesirable vibration of the system.In this paper,the dynamic responses of the mechanical system with two revolute clearance joints are studied using computational and experimental methodology.The clearance joint is considered as force constraint.The normal contact force and tangential friction force between the journal and bearing in a clearance joint are modeled using a nonlinear contact force model considering energy loss and a modified Coulomb friction model considering a dynamic friction coefficient,respectively.A planar slider-crank mechanism with two revolute clearance joints is used to implement the study.The dynamic responses obtained from numerical simulation are compared with the experimental test.Numerical simulations and experimental tests for different clearance sizes and crank speeds are presented and discussed,respectively.The simulation results agree quite well with those of the experiment for different cases,which proves the accuracy and efficiency of the computational method for dynamics analysis of the mechanical system with two revolute clearance joints in this study.The investigation indicates that the clearances in revolute joints significantly affect the dynamic characteristics of mechanical systems,which must be considered in the precision analysis,design,and control of multibody systems,especially for high-speed machinery.

Safe antifungal lipopeptides derived from Bacillus marinus B-9987 against grey mold caused by Botrytis cinerea

Agricultural application studies, including field experiments and acute toxicity tests, were conducted for lipopeptides secreted by marine-derived Bacillus marinus B-9987. Benefiting from commercially available scaled-up lipopeptide purification, the sample of impurities（isolated from target lipopeptides）, raw extracted sample（purity： 9.08%）, partially purified sample（purity： 20.86%）, and highly purified sample（purity： 87.51%） were prepared from B. marinus B-9987 fermentation broth, and used in lab-scale antagonism tests, field experiments, swarming motility tests, and acute toxicity tests. Operations and conditions in field experiments were consistent with the Pesticide-Guidelines for the Field Efficacy Trials（GB/T 17980.28-2000）, and acute toxicity tests were executed according to Toxicological Test Methods of Pesticides for Registration（GB 15670-1995）. In agar diffusion tests in vitro and pot tests in vivo, all lipopeptide samples with different purities significantly inhibited Botrytis cinerea; meanwhile the sample of impurities isolated from target lipopeptides were not effective against B. cinerea. Results of lab-scale tests showed that the target lipopeptides were effective substances against B. cinerea. Thus, partially purified and raw extracted samples were used in field experiments instead of the highly purified sample for cost saving. In the field experiments against rose grey mold, biological control efficacy of 500 mg L–1 lipopeptides reached 67.53%, slightly lower than 74.05% reached by the agrochemical pyrimethanil. However, pyrimethanil severely suppressed B. marinus B-9987, whereas the lipopeptides promoted swarming motility and biocontrol efficacy of Bacillus biomass. Lipopeptides at 87.51% purity were tested for systemic acute toxicity and confirmed as low-toxicity substances. In conclusion, low-toxicity lipopeptides were potential alternatives to agrochemicals, and they also performed good promotion when combined with homologous biological control microorganism. There were 2 breakthroughs in this research：（1） marine-derived bacterial lipopeptides inhibited grey mold caused by B. cinerea in field experiments; and（2） purified bacterial lipopeptides（sample purity： 〉87.51%） were determined to be low-toxicity substances by systemic acute toxicity tests, satisfying the strict requirement of pesticide registration in China（required purity： 〉85%）. This study provides support for using extracellularBacillus-derived lipopeptides commercially similar to Bacillus-based biological control agents.

Influence and experiment of cable-net manufacturing errors on surface accuracy of mesh reflector antennas

Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas,and analyze its influence on reflector surface accuracy.Firstly,the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted.Secondly,a non-button connecting method is proposed and analyzed to reduce manufacturing errors.Thirdly,two physical experiment models based on 2.62-meter mesh reflector antenna are made.Finally,numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method.Compared with the traditional method,the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy.Moreover,the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process,and thereby improves the deployment reliability.

Comparison of Hydrodynamic Performances Between Single Pontoon and Double Pontoon Floating Breakwaters Through the SPH Method

A numerical study adopting the 2Dδ-SPH model is performed to compare the hydrodynamic characteristics of a single pontoon floating breakwater and a double pontoon floating breakwater.Numerical simulations are performed using theδ-SPH model and experimental tests are conducted to validate the numerical model.The numerical results of both the free surface elevations and motions of the floating breakwater are in good agreement with the experimental results.Numerical results show that when the pontoon drafts are larger,the double pontoon floating breakwater performs better in wave attenuations compared with the single pontoon floating breakwater,and for all the drafts,the amplitudes of motions including sway,heave and roll of the double pontoon floating breakwater is always smaller.In addition,increasing the spacing between the two pontoons can further reduce the amplitudes of pontoon motions and improve the wave attenuation ability of the double pontoon floating breakwater.

Mechanical Properties of a Eucalyptus-Based Oriented Oblique Strand Lumber for Structural Applications

Wood and wood-based composite materials have gained increasing attention in the sustainable building industry because of their renewability and environmental friendliness.Oriented oblique strand lumber(Eucalyptus Strand Wood,ESWood),which is manufactured from fast-growing small diameter eucalyptus wood(Eucalyptus urophylla×E.grandis),is introduced in this paper.Small clear specimen tests were conducted to determine the mechanical properties of ESWood material while full-scale component tests were performed to observe the structural performance of ESWood beams.A comparison of mechanical properties of ESWood with other wood/bamboo-based materials is then reported.From the results presented herein,it appears that the strength and stiffness properties of ESWood are affected by grain directionality and glued layers.However,it still has preferable mechanical properties as a building material,which is comparable or superior to those of other engineered wood/bamboo-based products(e.g.,Sitka spruce,LVL,OSL,Glulam,and Glubam).Furthermore,results from full-scale component tests show the stable mechanical performance of beams made by ESWood.This study makes a significant contribution to a potential utilization of fast-growing eucalyptus for general use in construction,and the presented mechanical tests results can serve as a fundamental data for more applications of ESWood in practical engineering.