Field Test Results Research Articles

Numerical simulation of the spatial and temporal distributions of the downwash airflow and spray field of a co-axial eight-rotor plant protection UAV in hover

The downwash airflow of a multi-rotor unmanned aerial vehicle (UAV) in hover can improve the penetration rate of droplets in the canopy of fruit trees, but the uncertain distribution of the downwash airflow can also lead to the generation of uneven distribution of droplets. With a co-axial eight-rotor plant protection UAV as the research object, the computational fluid dynamics (CFD) method is adopted in this study to establish the coupled flow field model of the downwash airflow and the two-phase flow model of airflow-droplets in hover. The spatial and temporal distribution law of the downwash airflow is analyzed, and the impact of the motion law of the droplets in the spray field is investigated. The results show that the downwash airflow shifts from an unsteady state to a steady state over time. Various wind vortices such as wake vortex, ground diffusion airflow, and vortex ring are generated during the evolution process, with a “negative velocity channel” of downwash airflow velocity identified in the central region under the rotors. The farther the airflow is from the rotor, the larger the area field of wake vortex airflow. Consequently, there is a gradual coupling of the left and right adjacent wake vortices from mutual independence, with the “spiral effect” of the downwash wind field offset by the mutual coupling of the upper and lower rotors of the UAV. When the installation position of the nozzle falls within the below-rotor region, the distribution of droplet deposition becomes more penetrative than the central axis installation position of the nozzle. It indicates that the below-rotor installation position of the nozzle can prevent droplets from entering into the coupling region of the trailing vortex, which reduces droplet drift. According to the field test, the measurement and simulation results of the downwash air velocity are consistent, with the minimum and maximum relative error reaching 4% and 29%.

New approaches to modeling the critical refreezing length of a Philberth melt probe for ice sheet exploration

In recent years, interest in using Philberth melt probes in the exploration of subglacial lakes or extraterrestrial ice-covered planets has significantly increased. Consequently, several Philberth melt probes have been developed or are currently being developed. The critical refreezing length is a key parameter in determining the distribution of the lateral heater of the Philberth melt probe. In this study, two new approaches for calculating the critical refreezing length were proposed. Approach I was established based on the refreezing of a virtual borehole, whereas approach II was developed in the COMSOL Multiphysics 5.6a software by modeling the phase change of water and ice in the non-heated section of the Philberth melt probe. The two novel approaches were validated with the field test results of RECoverable Autonomous Sonde (RECAS) in Antarctica. The difference between the two approaches and the existing calculation methods was less than 32% and approach I presented a smaller critical refreezing length. The thermal head efficiency and ice temperature had significant influence on the critical refreezing length. Usually, the critical refreezing length increased with an increase in the thermal-head diameter, penetration rate, and ice temperature, whereas it decreased with an increase in the thermal head efficiency.

Robotic Path Planning for Rice Seeding in Hilly Terraced Fields

To realize the autonomous operation of a terraced rice sowing robot, a set of sowing robot operation path planning algorithms with universal significance for small, irregular terraced plots is proposed. According to the characteristics of terraces and the agronomic requirements of sowing seeding, the operation path mainly includes parallel operation and boundaries surrounding the operation path. The boundary pre-collision detection method is expounded, and the cyclic detection method judges the U-turn area. The Bézier curve fitting algorithm was used to smooth the boundary wrapping path. To verify the feasibility of the algorithm, four typical irregular small fields located in 666.7-hectare terraces of Sama in Hong He Prefecture, Yunnan Province, were randomly selected, and a field map was obtained through Google Earth. An existing seeding robot was used as a model, and the simulation and comparison tests were carried out with the mainstream EHNS algorithm and boundary polyline algorithm under the ROS-kinetic platform in the Cen Village Scientific Research Base of South China Agricultural University. The actual boundaries of the four fields with the same simulation test were used as the map to verify the field experiment. The simulation test results show that the area coverage of the sowing operation is greater than 93.53% and the replay rate is less than 3.46%, and the field test results show that the area coverage of the sowing operation is greater than 94.33% and the replay rate is less than 3.03%. The simulation test is in good agreement with the field test results, indicating that the algorithm has good adaptability, which meets the requirements of a sowing robot for sowing operation path planning and can provide a certain reference for the path planning of irregular field operation robots in hilly and mountainous areas.

Correlation Analysis of CBR and Sand Cone Values at the Sub Base of Simpang Tambue-Lhok Dagang Road at STA 1+050 to STA 6+450

The rapid increase in traffic volume will lead to a lower level of road service, so that the traffic flow on the road becomes less smooth. To overcome this situation, efforts are needed, including repairing the pavement layer, one of which is the subbase layer. To determine the bearing capacity and degree of density of the subbase course, CBR field and Sand Cone tests are carried out. The purpose of this study was to analyze the relationship between the CBR value and the Sand Cone, the data were from the results of field and laboratory tests carried out by the executor, the CBR test results obtained were between 60.27% and 72.87% while the Sand Cone was between 59.88% and 62. .71% but after an average CBR and Sand Cone values become 62.48% and 60.44%. From the results of the Product Moment correlation test, a correlation value of -0.225 was obtained. This shows a negative relationship between CBR and Sand Cone values. Furthermore, from the results of the correlation coefficient significance test, it was obtained that t count = -0.730, this t count value is smaller than t table= 2.228 with degrees of freedom 12 -2 = 10 and an error rate of 5% for the 2-party test, so it can be concluded that Ho is accepted and H1 is rejected. This means that there is no significant correlation between CBR and Sand Cone values.

Development of Learning Using Flipped Classroom Models in Basic Web Programming Subjects at SMK Al Hafidz Leuwiliang

The purpose of this study is the development of basic learning of web programming class XI RPL based on Microsoft teams using the flipped classroom model at SMK Al Hafidz Leuwiliang and to find out its feasibility and effectiveness. The research method used is Research and Development (RD). The learning development model used is the ASSURE learning system design model which is integrated with the PEDATI learning model at the Model Design stage. The subjects of this study were students of class XI RPL. The results of this study based on the results of the feasibility test include (1) the results of testing learning materials obtained a percentage of 78% and are categorized as good; (2) the test results of learning media were 79% and were in the good category; and (3) learning design test results of 83% and categorized as good. One to One test results obtained a percentage of 88% and were classified in the good category, small group test results were categorized as good (85%) and field test results were also in the good category (87%). To determine the effectiveness of learning, it is carried out through testing the N-Gain value from the results of the pre-test and posttest. The result obtained was 0.75 (75%). Based on these values, and the paired test results are T count Ttable or 13.72 2.06866 so that through flipped classroom learning can improve the learning outcomes of basic subjects of web programming, because there is a noticeable difference between learning outcomes in pretest and posttest data.

Design and Test of a Crawler-Type Tiger-Nut Combine Harvester

Traditional harvesters of tiger nuts (Cyperus esculentus) face problems including low harvesting efficiency, high loss rate, high impurity rate, and high labor intensity. To solve these problems and improve the harvesting efficiency and quality of tiger nuts, a crawler-type tiger-nut combine harvester that integrates digging, soil removal, picking, screening, and collection was designed. The machinery comprises crawler devices and working devices. The key devices were designed through theoretical analysis. Therein, the digging and hoisting devices consist of digger blades, combined soil-breaking blades, and vibrating hoisting chains. The tuber picking and screening device is composed of the tuber picking drum, double-deck heterodromous vibrating screens, impurity removal blowers, and soil-crushing guide rollers. The crawler devices include the track assemblies and the hydraulic driving systems. SolidWorks was used to establish the virtual prototype model. Combined with simulation using the discrete element software, the law of motion of tiger-nut tubers in the digging, elevation, and screening processes was studied, which verified the feasibility of the design. Finally, a prototype was manufactured and fabricated to conduct field harvesting tests on tiger nuts. Field test results indicate that the harvesting efficiency, harvest rate, and impurity rate of the tiger-nut harvester are separately 0.216 ha/h, 98.14%, and 3.24%, which meet the harvesting requirements for tiger-nut growers.

Modified Duo Tir as an Alternative Training Media to Improve Shooting Accuracy in Petanque

Le Duo TirObut is a training medium to improve the accuracy of shooting petanque. The price of these tools is relatively expensive and to get them must be imported. This study aims to: (1) produce a tool, namely Duo Tir which is modified with the materials used are relatively cheap and easy to obtain, this tool as an alternative training medium to improve shooting accuracy, and (2) determine the effectiveness of using a modified Duo Tir for increase the accuracy of shooting petanque. This study uses research and development methods by Borg and Gall. Data collection in this study implemented 6 data collection activities using 4 main instruments, namely observation, questionnaires, interviews, and shooting accuracy tests. The results of this study are: (1) the modified Duo Tir instrument to improve the accuracy of shooting petanque both from the content and construct aspects is valid and reliable, (2) the validator's assessment of the modified Duo Tir product, the results of preliminary field testing and main field testing with the percentage of eligibility 75% is feasible, and (3) the results of the effectiveness test show that training using a modified Duo Tir has a greater effect than conventional training on the results of increasing the accuracy of shooting for petanque athletes in NTB. Based on this explanation, it is concluded that the modified Duo Tir is feasible and effective to use to increase the accuracy of shooting petanque

Finite Element Model for Vibration Serviceability Evaluation of a Suspended Floor with and without Tuned Mass Dampers

This study aims to provide an accurate finite element (FE) modeling method for structural vibration serviceability evaluation of the suspended floor under human-induced excitation. The fundamental dynamic characteristics and human-induced vibration responses of a typical suspended floor were first measured via a series of field tests. Subsequently, the overall and local equivalent FE models of the suspended floor were respectively established, and their applicability was then verified by comparing the predicted dynamic characteristics and responses of the suspended floor with the corresponding field test results. Finally, passive tuned mass dampers (TMDs) were designed for vibration control of the suspended floor using the local equivalent FE model, and the applicability of the local FE model in assessing the vibration serviceability of the suspended floor with TMDs was further confirmed via pedestrian-induced vibration tests. Results demonstrate that the simplified local equivalent FE model proposed in this study can well replace the complicated overall FE model to evaluate the vibration serviceability of the suspended floor with and without TMDs.

Geometric Quality Assessment of Prefabricated Steel Box Girder Components Using 3D Laser Scanning and Building Information Model

Prefabricated steel box girders (SBGs) are widely adopted in bridge engineering due to their light weight and low lifecycle cost. To smoothly assemble SBG components on a construction site, it is necessary to inspect their geometric quality and ensure that all the as-is SBG components have the correct dimensions. However, the traditional inspection method is time-consuming and error-prone. This study developed a non-contact geometric quality assessment technique based on 3D laser scanning to accurately assess the locations and dimensions of SBG components. First, a robust normal-based region-growing algorithm was developed to divide the SBG components into segments with different labels. The scanned data related to the T ribs were then extracted through the proposed subtraction algorithm after the identification of the steel cabin. Lastly, the required items for geometric quality inspection were calculated based on the extracted as-is SBG components. The feasibility of the proposed geometric quality assessment method was validated through a real SBG project. Field test results showed that the developed inspection technique could assess the geometric quality of prefabricated SBG components in a more accurate and efficient manner compared to traditional measurement approaches.

Calibration of the PM4Sand model for hard-rock mine tailings based on laboratory and field testing results

A comprehensive campaign of laboratory and field tests has been conducted to characterize the behaviour of tailings from a hard-rock mine. Cyclic triaxial, direct simple shear, and triaxial simple shear tests have shown that the contractive tailings are susceptible to liquefaction and that their behaviour is similar to loose sand despite their higher fines’ content. To model the behaviour of tailings’ impoundments in dynamic simulations, the PM4Sand constitutive model is calibrated based on the dataset presented here. Some of the model parameters are defined based on consolidation and compression tests, while the critical state line (CSL) is defined based on the results of monotonic triaxial and direct simple shear tests. The CSL is lower for tailings than for most natural sands, which is consistent with previous studies. The calibrated model can reproduce reasonably well the monotonic behaviour and provides an excellent fit of the cyclic strength curves measured in the lab at different confining pressures and density index. The results presented in this paper indicate that the PM4Sand model can be used to simulate the cyclic behaviour of low-plasticity, hard-rock tailings. The proposed procedure also provides general guidelines regarding model calibration for other types of tailings.

Live load effects in hammer-head piers of continuous highway bridges and design equations based on numerical simulations verified by field tests

In this study, design equations are proposed to calculate the internal forces in hammer-head bridge pier components under the effect of live loads. For this purpose, first, the finite element model (FEM) of an existing bridge is built and the modeling approach is verified against field test results. Next, a four-span benchmark bridge representative of the bridges in the US is selected. FEM of the benchmark bridge is built, and sensitivity analyses are performed on the bridge model to identify the bridge parameters affecting the magnitude and distribution of the girder live load support reactions and hence the internal forces in the hammer-head pier components. The sensitivity analyses revealed that the number of girders, girder spacing, girder type, slab thickness and the overhang distance significantly affect the magnitude and distribution of the girder live load support reactions and hence the forces in hammer-head pier components. Then, parametric analyses of bridges are performed based on the sensitivity analyses results where each parameter is assigned a wide range of values. Subsequently, minimum least squares regression analyses of more than 50,000 data are performed to obtain equations to estimate the maximum cap beam moment and shear force, the maximum column moment and accompanying axial load as well as the maximum column axial load and accompanying moment. The hammer-head pier forces calculated using the design equations are shown to be in reasonably good agreement with FEM analyses results.

STUDI KETAHANAN ELEMEN STRUKTUR KOLOM GEDUNG PERKANTORAN DENGAN USIA LAYAN 40 TAHUN

The service life of the structure and the addition of additional dead loads on the floor slabs have caused a decrease in the capacity of the slab and beam structural elements. The study on the column section was carried out to analyze the capacity under these conditions. Inspection and field testing are carried out to obtain the suitability of the column reinforcement installed on the as built drawings and the quality of the concrete surface with a hammer test. Field test results show that 80% of the columns have low concrete quality below 21 MPa. The column structure experienced a decrease in the bearing capacity of the structural elements based on the results of the analysis where the axial and flexural forces were outside the cross-sectional capacity in the interaction diagram.

Some neurotoxic effects of lead nanoparticles on NMDA glutamate receptor gene expression and behavioral responses in Wistar rats

Introduction. Industrial pollution of the workplace air and the environment with lead oxide nanoparticles (PbO NPs) poses the risk of neurodegenerative diseases in workers of lead and copper smelters and the population living around these enterprises. Various studies showed the involvement of N-methyl-D-aspartate (NMDA) receptor expression in the mechanisms of lead toxicity. Materials and methods. During two months, outbred female rats were exposed to lead nanoparticles (PbO NPs) at a concentration of 0.2 mg/m3 in a “nose-only” inhalation exposure system. The behavioral responses of the rats were assessed using the open field and the elevated plus maze tests. Quantitative expression of the NMDA receptor genes (GRIN1, GRIN2A, GRIN2B) in the rat hippocampus was assessed using a real-time PCR. Statistical data analysis was carried out using the Mann-Whitney U test. Results. The neurotoxic effect of PbO NPs manifested itself in the suppression of GRIN2A gene expression in the hippocampus of experimental rats. The expression of the GRIN1 gene also showed a tendency to decrease in rats under effect of PbO NPs, while the expression of the GRIN2B gene did not change. The results of the open field test did not reveal any differences between the experimental and control groups of rats. The elevated plus maze test revealed a significant decrease in the number of entries into the open arms of the maze in rats from the experimental group. Limitations. This work was performed on female Wistar rats and does not take into account possible inter-gender differences. Conclusion. The results of the experiment demonstrated the neurotoxic effect of PbO NPs including the reduced expression level of the GRIN2A gene of the NMDA receptor and a decrease in the proportion of time spent in the open arms in the elevated plus maze test.

Study on blast-induced ground vibration velocity limits for slope rock masses

Seismic waves induced by blasting can cause damage to slope rock masses and thus lower the stability of the slope. The vibration standards of many countries do not specify the allowable blasting vibration velocity for slope rock masses. “Blasting Safety Regulations” (GB 6722-2014) in China recommends the allowable blasting vibration velocity of slope rock masses. However, the strength of rock mass and geometric characteristics of slope are not considered in the criterion. Therefore, based on the wave equation of Rayleigh wave, the mathematical relationship between the additional dynamic stress of the rock mass near the slope surface and the peak particle velocity (PPV) on the ground is analyzed. Under the control conditions that no tensile and shear damage occur in the slope, a calculation method of allowable blasting vibration based on a simple slope model is proposed, in which the strength of rock mass and the angle of the slope are considered. The theoretical basis of the proposed method is verified by numerical experiments. Based on the field test results of the slope of Xiaowan Hydropower Station, the proposed method was verified further. The damage control target of the rock mass determined by the proposed method was in good agreement with the actual damage detection result.

Field Study and Evaluation of KrCl* Far UV-C Device Capability for Inactivation of Phi6 Bacteriophage.

"Far UV-C" is an effective disinfection method that can be deployed in occupied areas. Commercially available Krypton Chloride (KrCl*) excimer lamps filtered to emit at 222 nm are effective in disinfecting pathogens and safe for human exposure up to an allowable threshold exposure, which is much longer than for conventional UV lamps emitting at 254 nm. Laboratory and controlled field testing of a filtered KrCl* excimer lamp for disinfection of a virus suspended in a thin film aqueous solution in an occupied office setting was conducted. Complete inactivation of almost 6 log (99.9999%) of Phi6 bacteriophage virus was achieved in ~20 min of exposure time in a field setting, equivalent to a dose of about 10 mJ cm-2 . The Phi6 inactivation rate constant for the field test results were not statistically different from laboratory values (P > 0.05, paired t-test). When positioned at 1 m distance from possible human exposure, this device can be used safely for almost 4.5 h of continuous direct exposure without any acute or long-term adverse health effects. This study illustrates the applicability and deployment of Far UV-C for pathogen reduction and can help in decision making for implementation of Far UV-C for disinfection in human-occupied environments.

Monopile installation in clay and subsequent response to millions of lateral load cycles

The installation-induced changes in the state of clayey soils caused by pile driving processes are investigated numerically. Hydro-mechanically coupled Coupled-Eulerian–Lagrangian analyses are carried out for this purpose. After installation, the piles are subjected to one million lateral loading cycles using a novel high-cycle accumulation (HCA) model for clay implemented in an in-house code, modelling loading conditions to which piles are subjected in the offshore environment. Consistent with the results of field tests, it is found that higher values of initial overconsolidation ratio result in a greater increase in radial effective stress during the installation process. Compared to simulations neglecting the installation process, jacked piles show less accumulation of deformations when subjected to lateral cyclic loading, especially for a larger number of load cycles and for initially overconsolidated soil. It is concluded that the assumption of wished-in-place conditions is conservative in terms of pile rotation in most cases, while the stiffness of the soil–pile system at small rotations is comparable for jacked and wished-in-place piles.

Impact and explosion resistance of NPR anchor cable: Field test and numerical simulation

With the reduction of shallow resources, the degree of damage and the frequency of dynamic hazards, such as deep rock bursts and impact ground pressure, are increasing dramatically. However, the existing support materials are incapable of meeting the safety requirements of the refuges and roadways under a strong impact force. To effectively solve these problems, a novel negative Poisson's ratio (NPR) anchor cable with excellent properties, such as impact resistance and the ability to withstand large deformation, is proposed. In the present study, a series of field tests and numerical simulations are conducted to investigate the mechanical and support characteristics of NPR anchor cables under blast impact. Laboratory mechanical tests show that NPR anchor cables can maintain constant resistance and produce large deformation under the action of multiple drop hammer impacts. According to the results of field tests, the roadway supported by conventional anchor cables was unable to endure the blast impact, while the roadway supported by NPR anchor cables was able to withstand the severe impact equivalent to a Class 3 mine earthquake. The dynamic response of the NPR anchor cable that supports the roadway under explosion is investigated using the innovative coupled modeling approach that combines the finite element method and the discrete element method, and the support effect of the NPR anchor cable is verified. The study shows that the NPR anchor cable has a superior impact and blast resistance performance, and a broad application prospect in the support of chambers and roadways that are at high risk of rock bursts and impact ground pressure.

Multi-objective optimization of cross-section integrity rate and sawing power consumption in sawing Caragana korshinskii Kom. branches

Caragana korshinskii Kom. (CKK) is one of the main trees for wind and sand control in northwest China. According to its biological characteristics, flat stubble is the main measure and the critical stage of nurturing management. However, the quality of the CKK sawing surface not only affects the sprouting rate of the following year but also reflects the mechanical properties of flat stubble. To reduce the sawing power consumption of the CKK stubble device and improve the quality of sawing cross-section, this paper conducted branch sawing tests on a self-designed sawing experiment rig. Using the central composite design test method, the operating parameters of the sawing experiment rig were studied experimentally, with sawing speed (va), moving speed (v’f), and inclination angle of the circular blade (α) as the influencing factors, sawing power consumption (Y1) and cross-section integrity rate (Y2) as the objective functions, to establish a multiple mathematical regression model between them. The test results show that the influence of each factor on the sawing power consumption in the order of significance is the va, v’f, and α, and the influence of each factor on the cross-section integrity rate in the order of significance is the v’f, va, and α. The optimal combination of working parameters is va of 42 m/s, v’f of 0.3 m/s, and α of 10°, which corresponds to Y1 and Y2 of 279.73 W and 82.6% respectively. Based on the optimal combination of working parameters, the prototype was processed and field tests were conducted. The field test results showed that the stubble breaking rate and missed cutting rate of the CKK harvester are 5.5% and 4.7% respectively, and the CKK branches sprouted well in the following year after flattening the stubble, which all met the requirements of the CKK harvesting operation.

Identification of Pacejka model parameters of a light commercial vehicle tire for dynamic research

This article is devoted to the research of the interaction of the wheel of a GAZ light commercial vehicle with a hard supporting surface. The relevance of this problem is due to the need to adequately reproduce the force reactions acting on the tire in the contact patch, when modelling the vehicle dynamics. High similarity of the real process and its modelling are guaranteed if there is a significant empirical data set for a particular tire model, which can be ensured only by the results of field tests. Specialists from Nizhniy Novgorod State Technical University have developed a schematic diagram of a road measuring unit, a test methodology and built testing unit as well as conducted full-scale tests. The experiment was conducted in the auto racing track at an ambient air temperature of 20 °C on a dry road asphalt surface with a high friction coefficient (0.4 - 0.8). The resulting array of experimental data was processed and presented in numerical trigonometric polynomials form (PAC 2002). The table comparing theoretical and experimental values presented in the results of this article confirms the high level of convergence. The maximum discrepancy in absolute value does not exceed 5%.

Testing reinforced soil cushions on the soaked subsidence base

Neogene friable deposits of the Quaternary age, widespread in Mongolia, belong to loess-like subsidence soils, mainly of type I in terms of subsidence, and are of kyrogenic-sublimation origin. As a result of the sublimation process of permafrost ice (the most recent Altai-Tunguska ice age, which covered most of the Euro-Asian region 15-18 thousand years ago) and seasonal deep frozen soils, occurring for many years in deep frozen subsidence soils, the structure is decompacted, as a result of the latter, porosity n=(50÷65)%, porosity coefficient e = (0.70÷0.84), density of dry soil ρd=(1.35÷1.60) ton/m3 or undercompacted, moisture content of sandy loam W=(0.04÷0.06) and loam W=(0.05÷0.08), as a result of repeated freezing and thawing, cracking and grinding of the solid part of the soil occurs, based on this, the content of silty parts is 50-60%. In recent years, experimental and theoretical studies have been actively carried out in many countries of the world to improve traditional soil cushion solutions using geosynthetic materials for horizontal and vertical reinforcement. Currently, in the soil conditions of Mongolia, research work has not been carried out to introduce the method of reinforced soil cushions due to the lack of an appropriate design standard and other regulatory documents. This article discusses the results of stamp field tests to determine the deformation characteristics of highly compacted soil cushions made of crushed stone-sand mixtures and local sandy loam soils with horizontal geosynthetic reinforcements from geogrid and geotextile, modeled in 6 different combinations on pre-soaked subsidence bases.