Laboratory Model Studies Research Articles

Preface

The edition contains the proceedings of the All-Russian Open Conference on Cloud Physics and Weather Modification, held at the High-Mountain Geophysical Institute on September 08-10, 2021, and related to the Year of Science and Technology in Russia.The main part of the work is devoted to numerical modeling of cloud processes, including modeling of microphysical and electrical processes in clouds, verification of the results of numerical modeling of cloud processes, modeling of the conditions for the development and evolution of powerful convective clouds. The results of laboratory modeling and field studies of cloud processes, studies of electrical processes in clouds, as well as various aspects of active influence on thunderstorm processes, including the possibilities of their prediction, are presented. Part of the work is devoted to the issue of artificially increasing precipitation and evaluating the effectiveness of work on weather modification. The currently observed climate change has led to a significant number of papers presented at the conference on the environmental and climatological aspects of active influence and dangerous convective weather phenomena.The edition is intended for meteorologists, specialists in the field of physics of clouds and precipitation, weather modification, as well as for students and postgraduates.List of Program Committee and Organizing Committee are availble in this pdf.

First X-ray Spectroscopic Observations of Atmospheric Titanium Species: Size Dependence and the Emission Source.

Titanium dioxide (TiO2) in mineral dust is considered as one of the driving forces of photocatalytic reaction at the aerosol surface in the atmosphere. As a precursor of mineral dust, soil contains ilmenite (FeTiO3) and titanite (CaSiTiO5), which have lower photochemical reactivities than TiO2. However, Ti species other than TiO2 in aerosol particles are not well recognized due to the lack of observation in ambient samples. In this study, Ti species in size-fractionated aerosol samples collected in the Noto Peninsula, Japan, were determined by macroscopic and semi-microscopic X-ray absorption fine structure spectroscopy. Regardless of aerosol particle size, Ti species were primarily composed of rutile, anatase, ilmenite, and titanite. Semi-microscopic Ti speciation showed that Ti-poor spots associated with mineral dust were composed of a mixture of rutile, anatase, ilmenite, and titanite, and Ti-rich spots were primarily composed of TiO2 (rutile or anatase) derived from authigenic minerals or anthropogenic materials. Thus, the Ti species in aerosol particles, especially mineral dust, were not composed solely of TiO2 polymorphs. Therefore, the photochemical reactivities of Ti in aerosol particles may be overestimated when laboratory experiments or model studies employ TiO2 as the representative Ti species.

Influence of micropile parameters on bearing capacity of footings.

Micropiles, on account of their versatility, can serve as both a new foundation and a long-term option for prevailing foundations without disturbing the subgrade underneath. They can improve highway facilities, historically significant structures, or distressed structures. The present laboratory model study is conducted on a square footing installed with micropiles all around it and subjected to vertical concentric loading. A parametric analysis based on the impact of five micropile parameters is also performed. The results obtained from this study reveal that the inclination of micropiles has little effect on ultimate vertical load but can profoundly impact the horizontal load. As the diameter of micropiles is progressively increased from 10 to 20 mm, the bearing capacity improves by around 27%. As the micropile spacing decreases from five times diameter (5d) to three times diameter (3d), the footing system's bearing capacity increases nearly by 22.2%. The bearing capacity ratio shows a reduction beyond the value of L/b = 2. Installing micropiles nearer to the footing edge (ED/b = 0.3) provided approximately 76% improvement with respect to the unreinforced footing. The optimum value of the different parameters is equal to L/b = 2, d = 20 mm, ED/b = 0.3, and S/d = 3. There is a 98% improvement in bearing capacity at the optimum values for 30° inclined micropiles.

Carbon Dioxide Contamination of Aqueous Morpholine Solutions and Effects on Secondary Coolant Chemistry Under CANDU Conditions

Exposure to air can cause amine solutions in CANada Deuterium Uranium (CANDU) reactor secondary coolant circuit feed tanks to absorb carbon dioxide (CO2). Likewise, carbon dioxide can be absorbed directly into the amine-containing secondary coolant by air ingress during shutdown, lay-up, and startup. Sampling operations, including transferring the sample to the laboratory and subsequent analyses, can also provide opportunities for CO2 contamination. This paper reports the results of laboratory and chemical modeling studies to examine the effects of CO2 contamination on aqueous morpholine solutions. The chemistry of CO2 uptake by feed tanks containing up to 50 wt% (11.5 mol·kg−1) morpholine at 25°C was modeled using the OLI Studio 9.5.2 chemical equilibrium model, and the speciation was confirmed by 13C nuclear magnetic resonance spectroscopy (NMR) measurements. The effects of CO2 contamination on the pH of the secondary coolant containing 60 ppm (0.006 wt%, 7.00 × 10−4 mol·kg−1) morpholine and the resulting effects on the solubility of magnetite and nickel oxide from 25°C and 250°C at steam saturation were modeled as a function of CO2 loading using the Electrical Power Research Institute chemical modeling software MULTEQ v.8. The chemical modeling calculations show that concentrated alkaline morpholine solutions at room temperature and pressure would be expected to have a strong tendency to absorb CO2 and have additional uptake abilities due to the formation of morpholine carbamates. For dilute morpholine solutions at room temperature and pressure, the solutions are still sufficiently alkaline to absorb enough CO2 to cause a measurable change in the pH of the secondary coolant. This effect was shown to be negligible under reactor operating conditions. The absorption of CO2 would potentially have the most effect on either unprotected feed tanks or during lay-up conditions in the steam generators, as it could depress the pH of the lay-up solution and adversely affect the rate of corrosion in the internal components of the steam generators (e.g., carbon steel materials). The 13C NMR measurements on samples of 50 wt% aqueous morpholine solutions from feed tanks at the Ontario Power Generation’s Pickering Nuclear Generating Station found that CO2 was below the 0.02 wt% detection limit, and suggest that the procedures used to avoid CO2 contamination in feed tanks are effective. The 13C NMR was shown to be an effective tool for monitoring CO2 uptake by morpholine solution in the feed tanks under conditions in which they may have undergone abnormal exposure to air.

Exploring dependence of COVID-19 on environmental factors and spread prediction in India

COVID-19 has taken the world by storm, with the majority of nations still being challenged by the novel coronavirus. The present work attempts to evaluate the spread of COVID-19 in India using the Susceptible-Exposed-Infectious-Removed (SEIR) model to establish the impact of socio-behavioural aspects, especially social distancing. The impact of environmental factors like temperature and relative humidity (RH) using statistical methods, including Response Surface Methodology (RSM) and Pearson’s correlation, is also studied on numbers of COVID-19 cases per day. Here we report the resultant changes of lockdowns-unlocks initiated by the Government of India for COVID-19, as against the scenario of total lockdown. The phased unlocks and crowded gatherings result in an increase in the number of cases and stretch the mitigation timeline of COVID-19 spread, delaying the flattening of the curve. The SEIR model predictions have been fairly validated against the actual cases. The daily spread of COVID-19 cases is also fairly correlated with temperature in Indian cities, as supported by well-established causation of the role of higher temperatures in disrupting the lipid layer of coronavirus, but is greatly undermined by the key factor of social distancing and gets confounded with other multiple unknown co-varying environmental factors. However, the analysis couldn’t clearly establish the role of RH in affecting daily COVID-19 cases. Hence, it becomes essential to include environmental parameters into epidemiological models like SEIR and to systematically plan controlled laboratory experiments and modeling studies to draw conclusive inferences, assisting policymakers and stakeholders in formulating comprehensive action plans to alleviate the COVID-19 spread.

Protecting Riverbank’s Environment Towards Scour with Combined Reinforcement of Gabion and Tetrapod: a Laboratory Model Study

The purpose of combined reinforcement installation is to direct the water flow and to reduce the scour process in order to protect the riverbank. The study was conducted by employing a laboratory model using a trapezoidal flume/channel with dimensions of 0.8 m width and 0.5 m height. The length of river bend model was 5 m. Observation was made with a constant flow rate of 7.07 liters/second. Tetrapod and gabion were installed at the angle of 45° and a distance of 51 cm. The running duration of installation variation was 180 minutes each. The results of the test showed that the river model with tetrapod-gabion-tetrapod reinforcement experienced an average scour of 4.16 cm for the beginning, 1.08 cm for the middle and 3.3 cm for the end. The gabion-tetrapod-gabion reinforcement can be considered as more effective reinforcement combination to reduce scour with an average scour of 4.03 cm in the beginning of the channel, 2.64 cm in the middle of the channel and 1.97 in the end of the channel.

Laboratory Model Studies on the Drying Efficiency of Transformer Cellulose Insulation Using Synthetic Ester

This paper presents the results of laboratory tests of cellulose insulation drying with the use of synthetic ester. The effectiveness of the drying process was investigated depending on the initial moisture of cellulose samples (2%, 3%, and 4%), ester temperature (55, 70, and 85 °C), initial moisture of the ester (70, 140, and 220 ppm), drying time (48, 96, and 168 h), and the weight ratio of cellulosic materials to ester (0.067 and 0.033). A large influence of temperature and time of drying on the efficiency of the drying process was found. This is important information due to the application of the results in the transformers drying procedure. The heating and drying ester unit should provide the highest possible temperature. For the assumed experiment conditions the initial moisture of the ester had little effect on the drying efficiency. An ester with a moisture content below 140 ppm can still be considered as meeting the requirements for drying cellulose with significant moisture. The weight ratio of cellulose products to ester has no major effect on drying efficiency during cellulose drying by circulating dry ester.

Experimental and Numerical Analysis of a Dam-Break Flow through Different Contraction Geometries of the Channel

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography.

Application of Coir Geotextiles in Rural Roads of India

Worldwide, there is continuous search for finding new materials for use in civil/geotechnical Engineering practice. This paper presents the emergence of one such material known as coir geotextiles. Efforts have been made to present the significant technological developments that have taken place in the evolution of coir geotextiles, particularly for application in low-volume roads. This paper summarizes the various studies conducted to evaluate the potential of coir geotextiles through extensive laboratory model studies and field trials.

Behaviour of model footing on bamboo mat-reinforced sand beds

Soil reinforcement is one of the most common and cost-effective methods among ground-improvement techniques. Recently, sustainable and natural materials for soil reinforcement have attracted the attention of soil engineers. Bamboo is considered to be one of the most effective materials for soil reinforcement due to it’s excellent mechanical and engineering properties. This paper discusses the results of laboratory model studies conducted on sand beds reinforced with traditionally woven bamboo mats. An improvement in the bearing capacity of about 2.5 times was seen when the reinforcement was placed at the optimum depth. The effective spacing of the reinforcement between two layers of bamboo mats was found to be equal to the optimum depth value, i.e., 0.3B. An improvement in the bearing capacity of about seven times was observed when four layers of reinforcement were placed at a spacing of 0.3B. The results obtained from the present study reveal the excellent capacity of bamboo mat for soil reinforcement.

Effect of Hammer Impact on Wave Propagation Characteristics of Soil

Wave transmission through soil due to dynamic load causes many problems to civil engineers craving safe construction. In this article, a laboratory model study is conducted to investigate the vibration propagation characteristics of soil due to the falling masses at different depths. Different types of impact, soils, and relative densities are used to study the characteristics of vibration transmission and energy dissipation. It was found that the increase in relative density and decrease in the depth causes an increase in the Peak Particle Acceleration and wave velocity of soil. An attempt is also made to determine the dynamic properties of soil using wave velocity ratios. A simple laboratory arrangement discussed here can be used to predict the wave propagation in soil reasonably and can determine its elastic constants. From the studies, it was revealed that the wave travel in soil and the peak particle acceleration depends on many factors like density, particle gradation, impact energy, etc.

Improved air-booster vacuum preloading method for newly dredged fills: Laboratory model study

Newly dredged fills feature a high moisture content and a high floating mud content. Based on the conventional vacuum preloading (CVP) method, this article presents a new method of air-booster vacuum preloading (AVP) to reinforce newly dredged fills for different air-booster periods (45, 60 and 90 min). Compared with other methods, this new method features no sand cushion and adopts a self-developed air-booster pipe and a water–air separation device. A series of laboratory model tests were performed to explore the effect of the improved AVP method for the enhancement of newly dredged fills. A comparison of variables monitored during reinforcement (vacuum pressure, surface settlement, water discharge and pore-water pressure) and after reinforcement (water content, vane shear strength, SEM and MIP) indicates that the reinforcement effect of the AVP method is superior to that of the CVP method; the former can effectively alleviate the problem of prefabricated vertical drain (PVD) clogging, greatly reducing engineering costs and significantly shortening construction periods.

Study on the Performance of Lime Column Technique for Treatment of a Na-Bentonite Clay

Lime column technique is one of the common methods which are used in order to treat swelling soils. The improvement mechanism of lime columns is based on reactions between lime and clay as a result of ion migration from the column. In this study, the performance of lime column technique on treatment of a Na-bentonite clay was investigated. For the purpose of the study, a laboratory model study was conducted. In the model, the column diameter was chosen 50 mm and a curing time of 60 days was considered. At the end of the curing time, free swelling tests were performed on the specimens extracted from different distances to the column in order to determine the changes on swelling behaviour of the bentonite. According to test results, a treatment distance of 50 mm was achieved and an improvement of 46.36% was obtained within the distance of treatment. The results of this study show that the most appropriate soils for lime column technique are the soils which have high permeability and contain a considerable amount of tree-layered clay minerals (such as Na-smectite).

Reproducing Field Measurements Using Scaled-Down Hydraulic Model Studies in a Laboratory

Little efforts have been made to the value of laboratory model study in closing the gap between results from idealized laboratory experiments and those from field data. Thus, at first, three bridge sites were selected and equipped with fathometers to find the bed elevation change in the vicinity of bridge pier over time. After and during the flooding, the stream flow variables and their bathymetry were measured using current viable technologies at the field. Then, to develop and suggest a laboratory modeling techniques, full three-dimensional physical models including measured river bathymetry and bridge geometry were designed and fabricated in a laboratory based on the scale ratio except for the sediment size, and the laboratory results were compared with the field measurements. Size of uniform sediment was carefully selected and used in the laboratory to explore the scale effect caused by sediment size scaling. The comparisons between laboratory results and field measurements show that the physical models successfully reproduced the flow characteristics and the scour depth around bridge foundations. With respect to the location of the maximum scour depth, they are not consistent with the results as in the previous research. Instead of occurring at the nose of each pier, the maximum scour depths are located further downstream of each pier column in several experimental runs because of the combination of complex pier bent geometry and river bathymetry, and the resulting unique flow motions around the pier bent.

An experimental investigation on effect of drawdown rate and drawdown ratios on stability of cohesionless river bank and evaluation of factor of safety by total strength reduction method

ABSTRACTThis paper presents an experimental investigation on the stability of a model river bank composed of homogeneous cohesionless soil under rapid drawdown condition. The effects of major influencing parameters controlling Factor of Safety (FoS) of a river bank under depletion of water level have been considered in the present study. A series of laboratory model studies have been carried out to investigate the cases of drawdown rate and drawdown ratios rendering the bank to maximum damage. Moreover, the effect of water level drawdown on the response variables namely pore water pressure, deformation of the bank profile, and shear strength of bank material have been observed and analysed. Stability analysis of the experimental model banks under drawdown conditions was carried out by evaluating FoS using the principle of reduced shear strength methodology. The in-situ total shear strength after each drawdown was measured using a laboratory vane shear apparatus. The minimum shear strength among these values has been identified. Now the FoS against each drawdown ratio has been computed from the ratio of total shear strength obtained after drawdown for that particular drawdown ratio to the minimum shear strength as obtained. This experimental programme examined the optimum combination of drawdown rate and drawdown ratio causing mass failure of the bank. It was revealed from the variation of pore pressure after drawdown that changes of pressures at points close to the toe of the bank slope is strongly controlled by the stress-state induced by drawdown. From the failure observations it was found that the drawdown rate is the dominating cause of maximum deformation of the bank than that of drawdown ratio. The findings of the present research work may help in predicting the actual failure scenario and stability condition of prototype river under similar boundary conditions.

Reduction in Lateral Displacement of Cohesionless Soil at Box Tunnel Face Using Nails in Overburden

The construction of shallow box tunnel underpass below rail/road traffic using jack pushing has become a quite common technique these days to create an uninterrupted flow of traffic in metropolitan cities. During the driving of shallow box tunnel underpass, the overburden cohesionless soil experiences large stresses and excessive lateral displacements at the box tunnel face, which sometime causes an accident leading to loss of lives. In order to overcome this problem, a laboratory model study has been conducted. A steel tank of size 450 mm × 300 mm × 300 mm, filled with cohesionless soil was used, in which a square steel box tunnel of size 34 mm × 34 mm (inner) with 1 mm wall thickness was moved through jacks. This tunnel was slowly pushed into the soil mass with the help of jack. Three vertical offsets from top of soil surface as well as three horizontal offsets from center of loading. To restrict the excessive lateral displacement, the overburden soil above the box tunnel was reinforced with 8 mm diameter tor steel nails prior to pushing of box tunnel. The lateral displacement of soil at tunnel face was found reduced from 6.92 mm in case of ‘without nailed’ to 0.23 mm in case of ‘with nailed’ overburden soil. Further, there was also a gain in load carrying capacity of soil in case of reinforced overburden soil. The study shows that if, overburden soil is reinforced with nails prior to the driving of box tunnel, the chances of collapse or lateral displacement at box tunnel face soil can be minimized for construction of shallow underpass.

Improved Synchronous and Alternate Vacuum Preloading Method for Newly Dredged Fills: Laboratory Model Study

Improved Synchronous and Alternate Vacuum Preloading Method for Newly Dredged Fills: Laboratory Model Study

Fluid therapy in trauma resuscitation : A review of changing practices.

Background: Haemorrhage is the leading preventable cause of post trauma death. Acute trauma resuscitation has evolved over the last decade. The ATLS guidance used since 2012 is being updated in 2018.Objectives : To search relevant representative literature over 6 years between 2012 and 2018 to gain an insight into changing concepts, practices and recent advances in acute trauma fluid resuscitation and provide a structured review of the topic.Search methods: A relevant MEDLINE search was undertaken to obtain a list of 1512 articles from which 107 were utilised to prepare this review.Selection criteria:1. Inclusion: Articles from human medicine relevant to fluid resuscitation in trauma published in English between January 2012 and January 2018. 2.Exclusion: Articles restricted to Brain, spinal trauma or cardiovascular trauma, post traumatic arrest patients, animal or human laboratory model studies and articles on septic, postoperative, obstetric patients and single case studies were excluded.Results: This review categorises the topic into various parts to explain the evolving understanding of fluid resuscitation, trauma induced coagulopathy and endotheliopathy of trauma. The strategies for acute fluid management like damage-controlled resuscitation, balanced and haemostatic resuscitation and massive transfusion protocol are explained. A detailed discussion is carried out regarding crystalloid, colloid and blood transfusion. Special consideration is given to specific age groups, combat casualties and prehospital trauma care.Conclusions: Fluid resuscitation in trauma is a complex and rapidly evolving subject. Massive transfusion protocols and principles of damage control are significant for patient outcome. Standard guidance like ATLS is relevant and important for training professionals to deliver systematic, high quality of trauma care. There is scope for local improvisation based on resources and need for more high-quality trials and frequent systematic reviews.Bangladesh Crit Care J March 2018; 6(1): 31-39

Restoration of a eutrophic hard-water lake by applying an optimised dosage of poly-aluminium chloride (PAC)

Feldberger Haussee (NE Germany) was polluted for almost a century. During the late 1970s, the nutrient input reached a maximum of approximately 1.9/11.5 g TP/TN m−2 yr−1. As a result, the lake became a hypertrophic ecosystem and had largely lost its recreational value. In 1980, the sewage discharge was stopped, decreasing the external loading by approximately 90%. Because of vast amounts of phosphorus stored in the sediment, the lake remained highly eutrophic until 1985 with a TP concentration of ca. 1 mg L−1. To accelerate recovery, biomanipulation was applied from 1985 to 2002 but was successful to only a minor extent. Eventually, due to sediment sequestration and discharge to downstream lakes the TP spring maximum (2006–2010) dropped to 0.112–0.078 mg L−1. However, given the trend, it was obvious that it would take another 10–15 years for the concentration to approach the desired mesotrophic level. Thus, it was suggested to inactivate the surplus phosphorus by treating the lake with poly-aluminium chloride (PAC) as precipitant. To ensure good water quality, the objective was to decrease concentrations below 0.035 mg TP L−1, while optimising the amount of PAC applied (as much as needed, but as little as possible). As a prerequisite, the status of the lake was carefully studied; external phosphorus loading and the amount of mobile phosphorus stored in the sediment being of specific interest. Laboratory experiments, modelling studies and field observations eventually resulted in an estimated dosage of 27 g Al m−2 (molar Al/P 12). Following the treatment in April 2011, prime water quality parameters showed two opposing trends: (1) TP concentration immediately dropped below the restoration target (≤0.025/0.035 mg L−1), primary production and phytoplankton biomass declined substantially. (2) However, water clarity did not improve for another four years. The likely reason for the delay was the structure of the phytoplankton community. It was dominated by cyanobacteria with the potential to trigger intensive calcite precipitation and thus impair transparency. In spring 2015, the cyanobacteria suddenly disappeared and transparency increased significantly. We speculate that these changes of the planktonic community shifted the ratio of assimilation and respiration in favour of the latter. This allowed an increase of free CO2* (dissolved CO2 & dissociated carbonic acid) altering the carbonate buffering system and thus halting the formation of calcite crystals. Also, the phytoplankton, now represented by small readily ingestible taxa, promoted a flourishing Daphnia population inflicting heavy grazing losses, resulting in clear water stages (2015 June, 4.20 m; 2016, August 3.70 m; 2017 August, 4.5 m). We conclude that the drastic decrease of phosphorus availability in concert with structural and functional changes of the plankton community eventually improved the water quality of Haussee significantly. The lake is now in a mesotrophic status; well in accordance with the aim of the restoration project.

Prediction of Quantitative Response of Under-Reamed Anchor Piles in Soft Clay Using Laboratory Model Study

Abstract The foundation of many civil engineering structures is required to be designed as an anchor foundation subjected to upward load action. The shallow as well as deep anchor in soft clay is an important but complex soil-foundation system that must be analyzed theoretically. As direct determination of the quantitative response by the field test is a very difficult and expensive exercise, the physical modelling technique is considered as an easy alternative for prediction of (i) ultimate pulling capacity and (ii) pull-rise curve. This paper highlighted the potential use of two parameters viz. (i) factor of geometrical relationship (K) and (ii) cohesion factor (N), obtained by conducting laboratory tests on two models of different scale factors for the intended purpose. The K and N parameters were constant for both the prototype foundation and small size model tested in laboratory. The under-reamed concrete pile in soft clay was considered as a soil-foundation system and shallow as well as deep under-reamed anchor piles were investigated in this study. Besides, straight shafted concrete piles were also considered in both categories of shallow and deep anchors. It was found that the physical modelling technique using two characteristic system parameters and by incorporating the model scale factor effect enables the prediction of the earlier stated quantitative response of prototype under-reamed anchor pile foundation in soft clay with a reasonable degree of accuracy. A methodology involving curve fitting procedure was also developed to predict the “pull-rise” curve for a prototype soil-foundation system under consideration.