Rise Height Research Articles

Study on Ecological Threshold of Groundwater in Typical Salinization Area of Qian’an County

A suitable groundwater level is an important condition to maintain the stability of the vegetation community, especially in arid and semi-arid areas. The surface of Qian’an County in Western Jilin Province is often accompanied by salinization due to the influence of natural and human factors. In order to maintain the healthy development of ecological vegetation and reduce the risk of soil salinization, the concept of an ecological threshold of groundwater level is proposed, and two methods are used to determine the reasonable ecological threshold of groundwater. (1) Based on field investigation and indoor experiment, the data layer of soil texture, land use type and groundwater mineralization degree in the research area was established by using remote sensing technology and GIS technology. According to the thickness of vegetation root layer and the height of capillary rise of different soil and water types, the influence of groundwater salinity is considered, and the sum of the two is taken as the ecological threshold of groundwater in the study area. The reasonable threshold value of suitable growth of various vegetation crops is 3.76~5.66 m. (2) According to the relationship between the normalized vegetation index (NDVI) and the groundwater buried depth and phreatic salt, the groundwater buried depth and the mineralization degree under the best vegetation cover are analyzed as follows: the buried depth of groundwater is between 4.8 m and 6.1 m, and the salinity of groundwater is between 0.37 and 1.25 g/L, which are reasonable groundwater properties in the study area of the ecological threshold. This result not only enriches and broadens the content of groundwater research, but also helps to predict the prospect of water resource development.

Duration of immobilisation after Achilles tendon rupture repair by open surgery: a retrospective cohort study

BackgroundThe best treatment for acute Achilles tendon ruptures remains controversial. No cohort studies have compared different immobilisation durations after open surgery. This retrospective cohort study aimed to determine the optimal duration of immobilisation after this surgery.MethodsA total of 266 patients with acute Achilles tendon rupture were divided into 4 groups (A, B, C, and D) according to immobilisation duration of 0, 2, 4, and 6 weeks, respectively. All patients underwent the same suture technique with a similar rehabilitation protocol and were examined clinically at 2, 4, 6, 8, 10, 12, 14, 16, 24, and 48 weeks, with a final follow-up at a mean of 22.3 months postoperatively. The primary outcome was the time of return to light sports activity (LSA). Secondary outcomes included range of motion (ROM) and single-legged heel rise height (SHRH). Data on operation time, complications, visual analogue pain scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score, and Achilles tendon Total Rupture score (ATRS) were also collected. Demographic baseline data were analysed using one-way analysis of variance; outcome parameters were analysed using Kruskal-Wallis H test, and complications were analysed using Fisher’s exact test. Statistical significance was considered at P ≤ 0.05.ResultsVAS scores decreased significantly, reaching 0 in all groups after 12 weeks. The AOFAS and ATRS scores were significantly different between the groups from weeks 2 to 12 (P<0.001) and weeks 2 to 16 (P<0.001), respectively. All the mean scores showed better results in group B than in the other groups. In terms of recovery time of ROM, SHRH, and LSA, groups A and B were significantly faster than groups C and D (P<0.001). There were 13 (13/266, 4.9%) complications: 5 superficial infections, 3 deep venous thrombosis, and 5 trauma-related re-ruptures. On the last follow-up, all complications had recovered. There were no significant differences in complications between the groups.ConclusionsImmobilisation for 2 weeks after this open surgery is the best choice for early rehabilitation and weight-bearing while minimising pain and other complications.

The next step in optimising the stair horizontal-vertical illusion: Does a perception-action link exist in older adults?

Tripping on stairs results from insufficient foot to step edge clearance and can often lead to a fall in older adults. A stair horizontal-vertical illusion is suggested to increase the perceived riser height of a step and increase foot clearance when stepping up. However, this perception-action link has not been empirically determined in older adults. Previous findings suggesting a perception-action effect have also been limited to a single step or a three-step staircase. On larger staircases, somatosensory learning of step heights may be greater which could override the illusory effect on the top step. Furthermore, the striped nature of the existing stair horizontal-vertical illusion is associated with visual stress and may not be aesthetically suitable for use on public stairs. These issues need resolving before potential future implementation on public stairs. Experiment 1. A series of four computer-based perception tests were conducted in older (N=14: 70±6years) and young adults (N=42: 24±3years) to test the influence of different illusion designs on stair riser height estimation. Participants compared images of stairs, with horizontal-vertical illusions or arbitrary designs on the bottom step, to a plain stair with different bottom step riser heights and selected the stair they perceived to have the tallest bottom riser. Horizontal-vertical illusions included a previously developed design and versions with modified spatial frequencies and mark space ratios. Perceived riser height differences were assessed between designs and between age groups. Experiment 2. To assess the perception-action link, sixteen older (70±7years) and fifteen young (24±3years) adults ascended a seven-step staircase with and without horizontal-vertical illusions tested in experiment 1 placed onto steps one and seven. Foot clearances were measured over each step. To determine whether changes in perception were linked to changes in foot clearance, perceived riser heights for each horizontal-vertical illusion were assessed using the perception test from experiment 1 before and after stair ascent. Additional measures to characterise stair safety included vertical foot clearance, margins of stability, foot overhang, stair speed, and gaze duration, which were assessed over all seven steps. Experiment 1. All horizontal-vertical illusion designs led to significant increases in the perceived riser height in both young and older adults (12-19% increase) with no differences between age groups. Experiment 2. On step 7, each horizontal-vertical illusion led to an increase in vertical foot clearance for young (up to 0.8cm) and older adults (up to 2.1cm). On step 1 significant increases in vertical foot clearance were found for a single horizontal-vertical illusion when compared to plain (1.19cm increase). The horizontal-vertical illusions caused significant increases in the perceived riser height (young; 13% increase, older; 11% increase) with no differences between illusion design, group or before and after stair ascent. No further differences were found for the remaining variables and steps. Results indicate a perception-action link between perceived riser height and vertical foot clearance in response to modified versions of the horizontal-vertical illusion in both young and older adults. This was shown with no detriment to additional stair safety measures. Further evaluating these illusions on private/public stairs, especially those with inconsistently taller steps, may be beneficial to help improve stair safety for older adults.

A model for the fate of carbon dioxide from a simulated carbon storage seep

Offshore geological carbon storage (GCS) is a rapidly developing technology essential for meeting international climate goals. While the likelihood of leakage from a properly planned geological sequestration site is low, assurance that CO2 stays contained will require robust monitoring programs. While seismic imaging methods are used to monitor the geological reservoir, the ideal method for monitoring the water column above the reservoir depends on the fate and transport of CO2. Whether CO2 is likely to be present as a rising seep of bubbles or dissolved in the water column near the seafloor will determine the appropriate monitoring technology and lead to a better understanding of the environmental impact of a potential leak. In this study, high definition video of a laboratory release of a carbon dioxide bubble seep recorded the size distribution of bubbles as a function of flow rate and orifice diameter. The transport of CO2 from different bubble size distributions was then modeled using the Texas A&M Oil Spill Calculator modeling suite. Model results show that the most important factor determining the rise height and transport of CO2 from the simulated leak was the maximum initial bubble size. For a maximum bubble radius of 5 mm, 95% of CO2 in the simulated seep reached a height of 17.1 m above the seafloor. When the maximum bubble radius was limited to 3 mm, 95% of CO2 dissolved by 7.8 m above the seafloor. The modeled results were verified during a controlled release of CO2 in Oslo Fjord.

Analysis of the level of technical development of mobile lifts with working platforms

Problem. Currently, there are about 150 manufacturers of mobile lifts with working platforms (MLWP), which constantly design and introduce into production new machines with expanded capabilities. Therefore, there is a need to determine the level of technical development of MLWP, which is not possible without the analysis of statistical data of their nomenclature depending on the classification features and operational parameters. Goal. The purpose of the work is to analyze the impact of classification features and operational parameters of MLWP on the level of their technical development. Methodology. The analytical methods of studying the statistical data were used. The methods of mathematical modulation were used to develop the general trend of the jib MLWP technical level. Results. As a result of the analysis the general trend of the technical level of the jib MLWP by the height of rise of the working platform depending on the weight of the machine, the general trend of the technical level of the jib MLWP by the magnitude of the working platform horizontal reach, and the general trend of the technical level of the jib MLWP by the height of rise of the working platform depending on the working platform horizontal reach were obtained. Originality. The telescopic and articulated lifts are usually considered as separate groups, although they have much in common, because at least one section of the jib of modern articulated lifts consists of retractable (telescopic) sections, so during the statistical analysis of the MLWP technical level, these machines were considered as a single group of jib machines. Practical value. With the help of the obtained statistical dependences of the jib MLWP technical level on the technological parameters of the machine, it is possible to assess the technical development of both an individual machine and a group of MLWP with the determination of trends for further development.

Comportamento capilar em siltes sedimentares usando modelo reduzido e altas cargas de sucção

Estudos de ascensão capilar em solos de granulometria fina são necessários para melhor compreensão de suas propriedades hidráulicas e não saturadas. Dois siltes sedimentares amarelo (A) e cinza (B) foram submetidos a ascensão capilar com cargas de sucção de 2 m usando tubos. Adicionalmente, o solo amarelo também foi submetido a ascensão capilar em modelo reduzido usando uma caixa de acrílico. Para os ensaios em tubos, os resultados evidenciaram que a água capilar foi capaz de saturar a coluna de ambos os solos até os 70 cm de altura, onde foi encontrado o ponto de entrada do ar. A água tardou 41 dias em alcançar os 200 cm de altura no solo A e 65 dias no solo B, enquanto, aproximadamente 1,6 kg de água entraram em ambos solos devido à carga de sucção. O coeficiente de permeabilidade medido (kc) durante o ensaio capilar passou de 0,0001 cm/s (solo A) e de 0,00008 cm/s (solo B) na altura de entrada de ar até 0,00002 cm/s aos 2 m de altura. A sucção matricial registrou valores maiores a 500 kPa na fase não saturada dos solos. Enquanto ao modelo reduzido para o solo amarelo, compactado em 3 densidades diferentes, os resultados demostraram que a velocidade de ascensão da água pelos capilares do solo aumentou quando o solo foi compactado com um peso específico seco maior. À medida que o tempo transcorreu, o kc diminuiu em todas as densidades desde 0,0005 cm/s até 0,0003 cm/s. A sucção matricial no solo registrou valores de 600-800 kPa para graus de saturação entre 90%-100%. Foi verificado, para os ensaios em tubo e na caixa, que a curva de altura de ascensão pelo tempo está influenciada principalmente pela porosidade de moldagem, coeficiente de permeabilidade em estado saturado e altura de entrada do ar.

Study on Vegetative Propagation of Elionurus latiflorus (Nees Ex Steud.) Hack

Aims: Elionurus latiflorus (Nees ex Steud.) Hack. commonly known as Brazilian lemongrass is a medicinal plant native to Brazil. Present experiment was conducted to study the effect of number of tillers/vegetative unit of transplants on biomass production in a period of 480 days.&#x0D; Study design: The experiment was conducted by using completely randomized design with three treatments i.e. plants transplanted with one tiller (T1), plants transplanted with 2 tillers (T2) and plants transplanted with 3 tillers (T3). These treatments were replicated eight times where transplantations were done in polybags which containing mixture of soil, dung and carbonized rice in 3:1:1 ratio. These polybags were kept for 160 days in greenhouse and pruning was done in every plant by maintaining 5 cm of the plant biomass for its regrowth.&#x0D; Duration of Study: This experiment was carried out over 16 months.&#x0D; Methodology: Every plant seedling was submitted to a cut maintaining approximately 5 cm of the plant biomass for its regrowth. After each pruning, survival percentage, increment in the number of tillers propagated, rise of plants height, fresh as well as dry mass weight were evaluated.&#x0D; Results: Lower initial number of main stems influenced survival only in the early growth phase after transplantation with a loose of 73% of the population transplanted with an unique main stem. Survival kept a constant value without plant mortalities in the successive 320 days evaluated after the first pruning. The number of tillers propagated weren’t affected significantly by the number of initial main stems in a single period. In the other hand, in the comprehensive period of the experiment there was a change with mean variation from 9.68 to 36.75. Height decreased the mean from 102.82 cm to 26.66 cm. Fresh and Dry Plant Mass increased from 5.19 g/plant to 11.47 g/plant and from 2.17 g/plant to 4.93 g/plant respectively, P˂0.05.&#x0D; Conclusion: This study even if elementary represents a required approach for the domestication of the species avoiding the waste of time and plant material for successive propagation works. It represents a suggestion for further research work in greenhouses with this specie for a validation of these results.

The problem of labor protection and monitoring of emergencies in the conditions of the spread of graphite dust

The article deals with the issues of labor protection and monitoring of emergencies in workshops for the production of carbon electrodes. A numerical study of the problem of the spread of coal dust in the production room is carried out. The possible height of dust rise and the distance of movement of the most probable particle size are estimated. The data obtained indicate that in order to prevent coal dust from sticking to clothing and spreading it around the room, it is necessary to provide for labor protection measures. Based on the results obtained, recommendations can be formulated to improve safe working conditions in production associated with the formation of graphite dust: first of all, attention should be directed to the removal of a loose dust layer.

On the Nonlinear Dynamics of Rapidly Moving Splashes

The splashes that form on the surface of water bodies under the effect of strong winds have a considerable effect on evaporation, as well as on the exchange by heat and momentum and the transport of matter, e.g., salt aerosol, which affects clouds and precipitation. An important factor in this case is the height of splash rise and the time it spends in the air. In the case of rapidly moving splashes, these characteristics are difficult to evaluate because of the nonlinear law of resistance at high speed. An efficient calculation method is proposed, providing approximate explicit dependences of the parameters mentioned above on the initial speed and the size of splashes.

Mechanical approach to surface tension and capillary phenomena

Many textbooks dealing with surface tension favor the thermodynamic approach (minimization of some thermodynamic potential such as free energy) over the mechanical approach (balance of forces) to describe capillary phenomena, stating that the latter is flawed and misleading. Yet, a mechanical approach is more intuitive for students than free energy minimization, and does not require any knowledge of thermodynamics. In this paper, we show that capillary phenomena can be correctly described using the mechanical approach, as long as the system on which the forces act is properly defined. After reviewing the microscopic origin of a tangential tensile force at the interface, we derive the Young–Dupré equation, emphasizing that this relation should be interpreted as an interface condition at the contact line, rather than a force balance equation. This correct interpretation avoids misidentification of capillary forces acting on a given system. Moreover, we show that a reliable method to correctly identify the acting forces is to define a control volume that does not embed any contact line on its surface. Finally, as an illustration of this method, we apply the mechanical approach in a variety of ways on a classic example: the derivation of the equilibrium height of capillary rise (Jurin's law).

Rivulets of finite height

In this study two situations in which capillary rivulets rise only to a finite height are examined. The first case is for a vertical corner with an opening angle and contact angle satisfying the Concus–Finn criterion [1], thus resulting normally in an infinite capillary rivulet rise. However, the substrate is vertically dipped into the liquid pool (forced wetting), thus resulting in a finite rivulet rise height, which depends on the dip velocity. In the second situation the fluid and substrate are chosen such that the Concus–Finn criterion is not satisfied; hence, yielding also a finite capillary rise height. For both cases experiments have been performed. Theoretical expressions have been derived for both cases. Surface Evolver simulations were performed to complement the results of the latter model for contact angles exceeding the Concus–Finn criterion.

Study on hazard characteristics and safety distance of small-scale boilover fire

Boilover is one of the most destructive tank fire scenarios, occurring in the specific conditions of explosive evaporation of the water sublayer, which causes a sudden rise in flame height accompanied by the splashing of burning fuel. In order to estimate the thermal hazards of the boilover fire, a series of experiments were conducted where the influence of pool diameters, initial fuel layer thickness and fuel types on the boilover characteristics were investigated. The results show that the boilover fire can be divided into four stages including the initial stage, steady stage, boilover stage and decay stage. The boilover onset time which is defined based on the flame enlargement, show a slight downward trend with the pool diameter but increased with the initial fuel layer thickness. The boilover intensity defined based on the mass loss rate increased with the fuel layer thickness but decreased with the pool diameter. Analysis of these phenomena was conducted based on the thermal mechanism of the boilover occurrence. The boilover splash coverage ratio is approximately exponentially distributed with distance. A model for predicting the safe distance based on boilover splash is derived by introducing the boilover intensity and critical thickness at which boilover occurs. The present results provide a guidance for boilover fire prevention during fuel storage and transportation.

Error analysis in 532 nm nanosecond laser cutting of solar glass

Laser cutting path is potentially important to glass nanosecond laser cutting accuracy and precision. Influence of cutting path error on surface quality was investigated in 532 nm nanosecond laser cutting of solar glass. 9 groups of experiments with different angles (5°, 10°, 15°, 20°, 25°, 30°, 35°,40°,45°, respectively) show that error distribution ranged between -0.12° and 0.07° with a random feature, and had no relationship with the cutting angle. Roughness at extreme corner positions is between 3.55 and 5.71 μm and randomly distributed. A negative effect on the kerf width can be observed using helix laser path. There is no obvious fillet on the inner glass of the intersection cutting curve, while a Φ 642.15 μm fillet can be observed under the example parameters on the outer glass of the curve. The diversity of fillets is caused by differences in the inner and outer sides of two helixes transition region. Textures with Δh under 30 μm are easier to appear when using low helix overlap rate under the condition with same width. Inclined texture will appear because of combination of transverse and longitudinal texture when each rise in height over a threshold.

Thermal convection of nano-liquid in an electronic cabinet with finned heat sink and heat generating element

Development of electronic devices depends on cooling techniques. An efficiency of cooling methods can be improved using more effective heat-transfer fluids and extended heat-exchange surfaces. Free convection of alumina nanoliquid in a chamber with a copper finned thermal sink and a thermally-producing unit is simulated in the present research. Basic equations written by means of non-dimensional non-primitive characteristics have been solved using the finite difference method. Influences of the Rayleigh number, fins height and nanoparticles concentration on energy transport and flow structures within the chamber have been scrutinized. It has been ascertained that a rise of the fins height and particles concentration intensifies the heat removal from the heated source.

Mathematical and numerical investigation of Ledinegg flow excursion and dynamic instability of natural circulation loop at supercritical condition

In this present work mathematical and numerical analysis are carryout to determine the existence of Ledinegg and dynamic instability phenomena in a rectangular shape of natural circulation loop at supercritical condition using supercritical water as a working fluid. A mathematical model has been developed based on the thermal hydraulic (TH) conversion equations of mass, energy and momentum with and without considering the heating structure. Then this dimensional mathematical model has been validated with the SPORT and SUCLIN benchmark model. A rectangular shape with constant diameter of supercritical water natural circulation (RSCWNCL) is investigated and various simulations are performed to find a threshold stability boundary (TSB) at supercritical conditions. Numerical simulations have been carried out to determine the effect of inlet pressure, hydraulic loop diameter and loop riser height on the Ledinegg instability.

Research of a conical pneumatic grain separator with a device for forced light fraction removal

The article studies a modernized conical air grain separator. It describes modern agricultural production and post-harvest grain processing in the north of Omsk region. The need for using new farm developments for cleaning grain is substantiated. The design of a modernized conical air grain separator is described. The modernization concerns the accelerated efficient removal of light impurities. Some modes of the system of forced removal of light fraction are effective when cleaning grain from light impurities using a conical air separator. The loss of high-grade grain may increase. To test the consistency of the hypothesis, two series of experiments were carried out. During the first series, the field of air flow velocities was investigated. It resembles a downward convex figure associated with the loss of air friction against the walls. During the second series, experiments on cleaning grain from impurities with the participation of a system for removing light impurities were conducted. A classic experiment with a conical air separator and a working system for removing light impurities was carried out and its results were processed. It was found that the height of the probe rise above the edge of the conical air separator, equal to 20 mm, gives the highest result when removing light impurities. The processes were interpreted and the results obtained were analyzed. A comparison of the quantitative and qualitative characteristics of the modernized separator with those of the classical one was carried out. It was found that the system of forced removal of light impurities is efficient: with fixed separation completeness, the performance of the separator increases 1.6 times.

Design of the Reconnaissance UAV based on TGAM

The application of UAV in military reconnaissance field is mostly fixed-wing aircraft, such as global hawk and predator. But they have no fixed wing aircraft bulky, need a runway to land, the reconnaissance mission is confined to the reconnaissance range larger operations, is now considering the individual special operations to the demand of the UAV reconnaissance, is adopted to helicopter down small four rotor design, convenient carrying, used to fill a vacancy low-altitude reconnaissance a small scale. In addition, considering the clarity and planning of the purpose of the reconnaissance mission, the UAV can carry out the reconnaissance mission of aerial photography and return according to the predetermined route completely, and no excessive human intervention is needed in this process. Therefore, the small quadrotor is mainly designed for autonomous flight system. But fully autonomous flight can not be very good to adapt to the complex environment, for the sake of it, and the principle of liberation operators hands as far as possible, decided to adopt a simple electrical control of auxiliary control flight, to complete after being spotted by enemy UAV height of rise and fall, immediately return to action, such as to ensure the practicability of the reconnaissance drones.

A FRACTAL MODEL FOR CAPILLARY FLOW THROUGH A SINGLE TORTUOUS CAPILLARY WITH ROUGHENED SURFACES IN FIBROUS POROUS MEDIA

In this paper, a fractal model for capillary flow through a single tortuous capillary with roughened surfaces in fibrous porous media is derived. The determined imbibition height and imbibition mass of capillary rise are in satisfying agreement with the existing models reported in the literature. It is found that the imbibition height and imbibition mass of capillary decreases with increasing relative roughness. Besides, it is observed that the equilibrium time in a single tortuous capillary with roughened surfaces decreases with an increase in relative roughness. In addition, it is seen that the imbibition height and imbibition mass of capillary rise increases with imbibition time. With the proposed fractal model, the physical mechanisms of capillary flow through a single tortuous capillary with roughened surfaces in fibrous porous media are better elucidated. One advantage of our fractal analytical model is that it contains no empirical constant, which is usually required in previous models.

Investigation on Stability and Chemiluminescence Characterization for Liftoff Inverse Diffusion Flames

ABSTRACT In this study, the stability and chemiluminescence characteristics of CH4/O2 liftoff inverse diffusion flame were investigated. The OH* and CH* radiation characteristics, liftoff height and transition (including attachment, liftoff and blow-out) of flames under different conditions were discussed. The OH* chemiluminescence is generated at the root of the flame and increases sharply along the propagation direction. With the increase of oxygen gas velocities, the flame became more instability leading to the radial size of OH* decreases and the reaction zone is generally close to the central axis. Compared to the OH* distribution, the CH* generation area is smaller and the radial dimension is less. At the flame root and OH* peak intensity existed position, OH* is generated by H + O + M = OH*+M reaction and CH+O2 = OH*+CO reaction. While, at the top of flame, CO2 facilitates the OH+CO2 = OH*+CO2 reaction. The flame changes from attachment to blow-out with the increase of velocity. Moreover, O2 velocity of liftoff decreases but the blow-out limit increases when methane velocity increases. There is an obvious linear relationship between the O2 liftoff velocity and the methane velocity. After the methane velocity reached a critical value, the liftoff flame could not be formed even when the oxygen raises and the flame blew out directly. As the methane velocity increases, both the flame height and the methane liftoff height rise. The jet flow entrains the surrounding O2 to form a recirculation zone between the flame root and the nozzle tip, which maintains the liftoff stability.

Capillary rise and sorption ability of hemp fibers oxidized by non-selective oxidative agents: hydrogen peroxide and potassium permanganate

ABSTRACT In this paper, the capillary rise and sorption ability of hemp fibers oxidized with hydrogen peroxide and potassium permanganate were studied, with the aim to get more insight into the changes in the structure of hemp fibers caused by oxidation, and to compare the influence of applied oxidative agents on hemp fibers. Capillary rise was presented as a function of a liquid rise height vs times, with determined all three capillary coefficients, while sorption ability was determined as water retention values and moisture sorption. For structural analysis of the samples the ATR-FTIR technique was used. Also, the amount of aldehyde and carboxyl groups and the lignin content in oxidized fibers were determined. The surface fibers morphology was observed by FESEM. In all oxidized hemp fibers an increase in capillarity was obtained for both oxidizing agents (33–75 mm for H2O2, and 40–114 mm for KMnO4), compared to 31 mm for unmodified fibers, but decreased sorption ability. Application of both oxidative agents, were successful for introduction of functional groups into oxidized fibers, for reduction of the amount of non-cellulosic substances, as well as moisture sorption. Simultaneously, the fibers became finer, cleaner, whiter, softer and more suitable for further processing, while, generally, higher influence on changes into oxidized hemp fibers was achieved by oxidation with KMnO4, compared to oxidation with H2O2.