Ratio Of Bed Research Articles

Experimental investigation of axially loaded group of piles with and without building frame: a parametric study

In the design of structures, stability and safety play a crucial role in serviceability. The response of the soil which influences the motion of the structure and vice versa is termed soil–structure interaction (SSI). Interaction effect is ignored to simplify the mathematical model for the analysis of problems involving soil interaction. In reality, the actual behaviour of the substructure is altered significantly if one considers the interaction among the foundations and the soil medium. In this study, a large-scale test setup (1.4 m × 0.8 m × 1.0 m) has been developed and model pile has been designed to find out the influence of SSI. Experimental tests were conducted on single pile, pile group (2 × 2), and pile-group-supported building frame subjected to an axial load. Parametric studies were conducted by varying pile spacing (3D, 4D, and 5D), aspect ratio (15, 25 and 40), and relative density of sand bed (35% and 70%). Pile cap rotation, pile head deflection, and bending moment values were measured for various configurations. The results showed that experimental findings are more useful for the evaluation of soil–structure interaction, and there is a necessity to consider the interaction effects in the calculation of design forces.

Visual Experimental Study on Gradation Optimization of Two-Stage Gravel Packing Operation in Unconventional Reservoirs

During the development of unconventional reservoirs with high sand production rate and fine silt content such as heavy oil and hydrate reservoirs, silt sand blockage problem is a serious issue. A two-stage gravel-packing sand control technique is applied to solve the silt sand blockage now. However, traditional experiments on this technique could not obtain the dynamic distribution law of intrusive sand in the gravel pack. In this study, a new visualization experiment based on hydrodynamic similarity criterion for studying particle blockage in gravel packs was conducted. Real-time monitoring of sand particle migration in the gravel pack could be achieved. Also, the stable penetration depth and the distributing disciplinarian of invaded particles could be determined. The results show that when the gravel-to-sand median size ratio of gravel bed I is less than five, the sand bridge can be formed at the front end of the gravel pack. This could prevent sand from further intruding. As the grain size of gravel bed II is increased, the flow velocity is reduced. Thus, the sand invading into gravel bed II tends to settle at the interface. A large amount of sand intrusion can happen to gravel pack II when the pore filling front breaks through the gravel bed I.

Impact of repeated loading on mechanical response of a reinforced sand

Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes, which may lead to a thicker pavement design for addressing the required strength. Geosynthetics have been proven to be effective for mitigating the adverse mechanical behaviors of weak soils as integrated constituents of base and sub-base layers in road construction. This study investigated the behaviors of unreinforced and reinforced sand with nonwoven geotextile using repeated CBR loading test (followed by unloading and reloading). The depth and number of geotextile reinforcement layers, as well as the compaction ratio of the soil above and below the reinforcement layer(s) and the compaction ratio of the sand bed, were set as variables in this context. Geotextile layers were placed at upper thickness ratios of 0.3, 0.6 and 0.9 and the lower thickness ratio of 0.3. The compaction ratios of the upper layer and the sand bed varied between 85% and 97% to simulate a dense layer on a medium dense sand bed for all unreinforced and reinforced testing scenarios. Repeated CBR loading tests were conducted to the target loads of 100 kgf, 150 kgf, 200 kgf and 400 kgf, respectively (1 kgf = 9.8 N). The results indicated that placing one layer of reinforcement with an upper thickness ratio of 0.3 and compacting the soil above the reinforcement to compaction ratio of 97% significantly reduced the penetration of the CBR piston for all target repeated load levels. However, using two layers of reinforcement sandwiched between two dense soil layers with a compaction ratio of 97% with upper and lower thickness ratios of 0.3 resulted in the lowest penetration.

Evaluation and optimization of VPSA processes with nanostructured zeolite NaX for post-combustion CO2 capture

We present a comprehensive experimental and simulation study on a low-cost and efficient CO2 capture technique using nanostructured zeolite NaX in a vacuum pressure swing adsorption (VPSA) process. The nanostructured zeolite NaX adsorbent has a high CO2 adsorption capacity, a relatively high adsorption and desorption rate, and a large CO2 selectivity over N2. Therefore, it is suitable for post combustion CO2 capture from dry flue gas. A series of nanostructured zeolite NaX pellets are prepared with different ratios of binder material and at different sintering temperatures. The results from mechanical properties, adsorption isotherms, kinetics and breakthrough experiments demonstrate that nanostructured zeolite material prepared with a low ratio of binder that sintered at 500 °C has the best separation performance for a CO2/N2 mixture. In addition, the results indicate that the nanostructured zeolite NaX samples lead to a better separation performance compared with the commercial microsized zeolite NaX. Process optimization studies employing the above adsorbents were performed to minimize the energy consumption of the process for a specified product purity and recovery rate. The decision variables include the feed pressure, blowdown pressure, evacuation pressure, feed flow rate, and length to diameter ratio of the adsorption bed. The effect of cycle time was investigated independently due to the need for synchronization of the multi-bed configuration. The optimization results indicate that the energy consumption of the process with nanostructured zeolite is about 30% lower while achieving a higher CO2 purity and productivity compared with a process employing a commercial microsized zeolite.

Hydrodynamics of bubbling fluidized bed for adsorption of CO2 with KOH/K2CO3

AbstractThe aim of this study is to assess the performance of carbon dioxide (CO2) capture in a bubbling fluidized bed using a proper adsorbent. A mixture of potassium hydroxide (KOH) and potassium carbonate (K2CO3) adsorbents was used as bed materials, which provide proper kinetic and fluidization behaviours. The adsorbents consisted of two different mean particle sizes: size 1 is composed of K2CO3 with mean particle size of 335 μm and KOH with mean particle size of 197 μm; whereas, size 2 contained the K2CO3 with mean particle size of 605 μm and KOH with mean particle size of 197 μm. The weight fraction of KOH in both sizes was 0.3 g/g (30 mass%). The pressure fluctuations of the bed were measured and characterized in a time domain. The effects of several hydrodynamic parameters (i.e., superficial gas velocity, aspect ratio of bed, and particle size distribution of the adsorbent mixture) on CO2 adsorption were investigated. The results showed that the larger bubbles caused an improvement in solid mixing in the bed and consequently enhanced the CO2 capture capacity. Fluidization of the adsorbents mixture with narrower distribution (size 1) led to the formation of larger bubbles and an improvement of mixing in the bed. Therefore, size 1 adsorbent exhibited a higher CO2 capture capacity compared to a wider distribution of (size 2) adsorbent. Furthermore, the bubble size is increased with an increase in the aspect ratio of the bed leading to a better mixing in the bed.

Damping Ratio of Foundation Bed with Multi-layered Rubber-Soil Mixtures

In this paper, a series of plate load tests on a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) under incremental cyclic loading was performed. To evaluate the settlement response and damping ratio of foundation bed, incremental cyclic loading in five steps with amplitudes of 140, 280, 420, 560 and 700 kPa were applied to the loading plate. The results show that both the total and residual settlements of the loading plate decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. There is also an appreciable improvement in the value of the damping capacity with increase in the number of RSM layers as the damping ratio increases by 4-5% beyond the value of 12-15% obtained on untreated sand. On the basis of the study, the concept of using multiple RSM layers not only is a very attractive material to achieve less settlement and vibration attenuation for machine foundation and railway track beds, but also, the environmental impacts of waste tires are attenuated by using as composite materials in geotechnical applications.

An experimental investigation on effective parameters of batch impregnation systems: a case study on Pt\u2013Sn/Al2O3 catalyst

The adsorption of hexachloroplatinic acid on Sn-impregnated γ-alumina support in the presence of the competitive chloride ion, as a step in preparation of multi-metallic Pt-based catalyst (such as Pt–Sn/Al2O3), was studied. The transient adsorption data were obtained by studying the impregnation of Sn/Al2O3 with H2PtCl6 in an external recycle packed-bed impregnation system. The effect of important parameters such as pH of the impregnating solution, circulation flow rate, and height/diameter ratio of support bed on competitive adsorption was studied. It was observed that upon increasing pH and decreasing circulation rate, the rate of Pt adsorption as well as axial non-uniformity along the bed was increased. On the other hand, a time lag was observed in bulk adsorbate concentration in certain runs which was attributed to deviation from well-mixed contacting pattern being necessary for a uniform catalyst product. This could be minimized by increasing the recycling flow rates and using appropriate amounts of competitive ion concentration.

Assessment of the performance and effects of metro-induced ground-borne vibration for mitigation measures of resilient tracks

A methodology that judges the performance and estimates the effects of metro-induced ground-borne vibration is presented for the mitigation measures of resilient tracks. Two criteria are proposed for the purpose of judgment and estimation, respectively. One is the force ratio obtained by comparing the forces transmitted to the track bed of the resilient track with those of a reference track. As the force ratio of the track bed does not vary with the excitation and environment conditions, it can be used for judging the performance of the ground-borne vibration, i.e. the inherent ability to mitigate vibration, of the resilient track. Another criterion is the overall frequency-weighted root-mean-square acceleration at the receivers. This criterion is used for the estimation of the real effects of the ground-borne vibration of a resilient track in practical conditions. Calculation results demonstrate that the practical effects of ground-borne vibration of the mitigation measures studied vary with the excitation and environment factors and tend to be more effective when the unevenness excitation is rougher or the monitoring points are closer to the source of vibration. The proposed criteria, the corresponding models developed, and the methodology presented exhibit both high efficiency in computation and great convenience for assessing the mitigation measures of resilient tracks.

Integrated two‐stage adsorption for selective removal of CO2 and SO2 by amine‐functionalized SBA‐15

AbstractA novel process for integrated two‐stage selective removal of CO2 and SO2 from a simulated flue gas by an adsorption method was developed. Triethylolamine (TEA)‐loaded SBA‐15 was selected as the SO2 adsorbent, and tetraethylenepentamine (TEPA)‐loaded SBA‐15 was the CO2 adsorbent. Scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, N2 adsorption/desorption, X‐ray photoelectron spectroscopy, and X‐ray diffraction techniques were used to characterize the properties of the adsorbents. The effects of the height–diameter ratio (H/D) of the adsorbent bed and operation temperature were tested for the removal of SO2. The results indicated that the pore volume and surface area of SBA‐15‐TEA‐50 and SBA‐15‐TEPA‐50 dropped with the increase of amine loading. SO2 breakthrough adsorption capacity of SBA‐15‐TEA‐50 was 146.3 mg of SO2/(g of adsorbent). The integrated two‐stage removal experiment of SO2 and CO2 over SBA‐15‐TEA and SBA‐15‐TEPA showed that CO2 and SO2 in gas mixture can be removed in two stages, respectively. Regeneration experiment showed that both the SO2 and CO2 breakthrough capacity almost kept a constant in the multiple cycles, and the regeneration of integrated two‐stage system was stable. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Removal and recovery of o-xylene by silica gel using vacuum swing adsorption

The removal and recovery of o-xylene (a typical volatile organic compounds, VOCs) by silica gel has been systematically investigated by vacuum swing adsorption (VSA) process. Laboratory scale measurements show that the adsorption of o-xylene on silica gels could be significantly enhanced by increasing the height to diameter ratio (H/D) of adsorption bed, the inlet flowrate and o-xylene initial concentration. However, reducing the H/D and desorption pressure or increasing the amount of purging gas are observed to be favorable for the desorption of o-xylene from the silica gels. The optimized operational conditions are determined at 5:1 for H/D, 5kPa (absolute) of desorption pressure and 0.45L/min of purge gas flowrate. According to further kinetic fitting and analysis, it is found that the adsorption of o-xylene on this silica gel is film-diffusion control, which could be enhanced by increasing gas flowrate or initial o-xylene concentration. In addition, reducing the particle size of the silica gel is also found to increase the saturation of adsorbed o-xylene in silica gels. A scaled-up integrated VSA setup was applied to confirm the above results, leading to a complete o-xylene removal from the gas (100% removed) with 87% of o-xylene recovered directly as liquid. Based on a rough economic calculation, the VSA shows greater merits than those of traditional thermal treatment and absorption methods, due to its recovered VOCs as products. Additional tests by other aromatic VOCs further approved the feasibility of the VSA using silica gels. These findings indicate that the VSA with air cooling at ambient temperature would be a promising and ‘green’ technology for treating high boiling VOCs.

The hydrology of subglacial overdeepenings: A new supercooling threshold formula

AbstractOverdeepenings are a hallmark glacial landform of broad geomorphologlogical and glaciological interest. Their formation mechanism has not yet been fully uncovered, but subglacial drainage is likely a key factor. One prominent hypothesis states that the depth of an overdeepening stabilizes at the supercooling threshold. This threshold is reached when the adverse bed slope terminating an overdeepening is sufficiently large to shut down the efficient, channelized drainage system. Classic theory puts this threshold at a ratio of bed to surface slope of −1.6. Here I extend that theory by taking into account that downstream water pressure can be below overburden pressure. The new formula agrees well with results from one‐ and two‐dimensional subglacial drainage models. Applying it to observations of 147 overdeepenings from alpine glaciers and ice sheets shows that the depth of overdeepenings rarely exceeds the new supercooling threshold. Thus, this work supports the stabilizing hypothesis.

Scaling analysis and numerical studies on water vapour adsorption in a columnar porous silica gel bed

This article presents a theoretical analysis of heat and mass transfer in a silica gel+water adsorption process using scaling principles. A two-dimensional columnar packed adsorber domain is chosen for the study, with side and bottom walls cooled and vapour inlet from the top. The adsorption process is initiated from the cold walls with a temperature jump of 15K, whereas the water vapour supply is maintained at a constant inlet pressure of 1kPa. The first part of the study is dedicated to deriving relevant scales for the adsorption process by an order of magnitude analysis of energy, continuity and momentum equations. In the latter part, the derived scales are compared with the outcome of numerical studies performed for various domain widths and aspect ratio of bed. A good correlation between scaling and simulation results is observed, thereby validating the scaling approach.

Thermal treatment of soil co-contaminated with lube oil and heavy metals in a low-temperature two-stage fluidized bed incinerator

This study presents the application of a low-temperature two-stage fluidized bed incinerator to remediate contaminants in the soil. The system was designed to control emissions of both gaseous pollutants and heavy metals during combustion. Soil co-contaminated with lube oil and heavy metals such as cadmium, chromium, copper, and lead was examined. Experiments were conducted by estimating various parameters such as operating temperature in the first-stage reactor (500–700 °C), ratio of sand bed height/diameter in the second-stage reactor (H/D: 3, 4, 6), and gas velocity (0.21–0.29 m/s). Heavy metal and gaseous pollutant emissions were also investigated during contaminated soil co-firing with polyethylene. The experimental results indicated that the destruction and removal efficiency of lube oil in treated soil products ranged from 98.27 to 99.93%. On the other hand, leaching tests of bottom ashes illustrated that heavy metals such as chromium, copper, and lead in leachates were complied with the regulations. For gaseous emissions, carbon monoxide concentrations decreased apparently with increasing ratio of sand bed height/diameter in the second-stage reactor. The increase of gas velocity had significant potential to generate the lowest carbon monoxide and particulate matter emissions. Nevertheless, during co-firing with polyethylene, emissions of organic pollutants such as benzene, toluene, ethylbenzene, and xylene and polycyclic aromatic hydrocarbons decrease by using the low-temperature two-stage fluidized bed incineration system.

Experimental investigation and numerical analysis of the dynamic characteristics of a laminated hybrid composite bed

To maximize the productivity of precise products in manufacturing industries, machine tools should be operated at high speeds. The machine tools should withstand higher cutting speeds, higher acceleration and deceleration and should be cost effective to give high quality products. The aforesaid expectations cannot be fulfilled simultaneously if conventional metal such as cast iron is employed. Hence, there is a need to replace cast iron with alternative materials. In the present work an attempt is made to replace the mini lathe bed made of cast iron with laminated hybrid composites, carbon, and glass/epoxy, to attain superior dynamic properties with less weight. The manufactured composite bed weighs 3.5 times less than that of the existing cast iron bed. Numerical and experimental modal analysis was done for both the cast iron and composite bed. The results show that the experimentally obtained fundamental natural frequency and damping ratio of composite bed are superior, 37% and 3 times, than that of the existing cast iron bed. POLYM. COMPOS., 38:20–26, 2017. © 2015 Society of Plastics Engineers

Adsorption characteristics of propan-2-ol vapours on activated carbon Sorbonorit 4 in electrothermal temperature swing adsorption process

Adsorption characteristics of propan-2-ol on Sorbonorit 4 activated carbon were determined using the breakthrough curve tests in a cyclic electrothermal temperature swing adsorption process. Maximum adsorption capacity, breakthrough time, throughput ratio and length of unused bed were also evaluated. As a result of multiple regeneration, the adsorption capacity of Sorbonorit 4 increased. Electrothermally-induced changes in the internal structure of Sorbonorit 4 and in the chemical composition of its surface were assessed based on adsorption equilibrium measurements by the gravimetric method and X-ray photoelectron spectroscopy (XPS). Three samples of virgin, direct resistively heated and electrothermally regenerated Sorbonorit 4 were used. The structural characteristics of activated carbon show that that fresh and direct resistive heated Sorbonorit 4 has a bimodal structure. Regenerated activated carbon contains one fraction of micropores. XPS analysis revealed that the same hydroxyl, carbonyl and carboxyl groups were found on the surface of all Sorbonorit 4 samples, albeit in different volume ratios. Regenerated Sorbonorit 4 has higher adsorption capacity than pure adsorbent while resistively heated Sorbonorit 4 displays lower adsorption efficiency.

A tool for modelling the breathing of hydride powder in its container while cyclically absorbing and desorbing hydrogen

Hydrogen storage in metal compounds has been actively studied as a way to store energy by G. Sandrock (1999) and M. Latroche (2004) [1,2]. But even if the importance of studying the mechanical behaviour of hydride compounds has been shown early in M. Kawamura et al. (1981) [3] there is still a lack of phenomenological or predictive models for handling this difficulty. In this paper, the use of Discrete Element Modelling (DEM) is investigated as a way to improve our understanding of the mechanical behaviour of hydrides absorbing and desorbing hydrogen, which is also called the hydride breathing phenomenon, and to develop better macroscopic models in the future. Starting from elementary mechanical characterisation of the hydride powder, from matrix compaction dedicated to determine the powder compressibility, to rotating drum, dedicated to determine the flowing ability of the powder, the parameters of the Discrete Element Model are adjusted, and the model is then confronted to the results experimentally obtained on a volume of hydride breathing within an instrumented elementary cell. The method is developed on a TiVCr BCC alloy.The simulations are consistent with experimental results, and have thus been used for a parametric study. This study reveals a strong impact of the slenderness ratio of the hydride powder bed and the particle shape on both powder volume variations and stress variations during the cyclic absorption and desorption of hydrogen.

낙동강 본류 낙단보 설치 전후의 저서성 대형무척추동물 군집변동

Nakdan weir, which is located in the second weir among the 8 weirs of Nakdong River, had been constructed from Nov. 2009 to Nov. 2011. To analyze the effect of Nakdan weir construction on benthic macroinvertebrates, we studied 2 sites around Nakdan weir (upstream and downstream) from 2007 to 2014. The average numbers of species and individuals were decreased after the construction (in 2012~2014, 51 species 895 inds. m-2) than before construction (in 2007~2009, 25 species 84 inds. m-2), especially in upstream site of Nakdan weir. After the construction, especially in 2012, dominance indices (DI) were increased by the decline of some specific taxon population, such as Ephemeroptera and Trichoptera, etc. After construction, individual ratios of GC (Gathering Collectors) and P (Predator) of FFGs (Functional feeding groups) and BU (Burrowers) of HOGs (Habitat orientation groups) were higher than before construction. So the results of this study indicate that the changes by a weir construction, such as the decline of shallow depth area, reduced velocity of water flow and increased ratio of sand bed, etc., can affect the benthic macroinvertebrate communities variously.

Formation of particle jetting in a cylindrical shock tube

A dense, solid particle flow is numerically studied at a mesoscale level for a cylindrical shock tube problem. The shock tube consists of a central high pressure gas driver section and an annular solid powder bed with air in void regions as a driven section with its far end adjacent to ambient air. Simulations are conducted to explore the fundamental phenomena, causing clustering of particles and formation of coherent particle jet structures in such a dense solid flow. The influence of a range of parameters is investigated, including driver pressure, particle morphology, particle distribution and powder bed configuration. The results indicate that the physical mechanism responsible for this phenomenon is twofold: the driver gas jet flow induced by the shock wave as it passes through the initial gaps between the particles in the innermost layer of the powder bed, and the chaining of solid particles by inelastic collision. The particle jet forming time is determined as the time when the motion of the outermost particle layer of the powder bed is first detected. The maximum number of particle jets is bounded by the total number of particles in the innermost layer of the powder bed. The number of particle jets is mainly a function of the number of particles in the innermost layer and the mass ratio of the powder bed to the gas in the driver section, or the ratio of powder bed mass (in dimensionless form) to the pressure ratio between the driver and driven sections.

Production of Bio Oil by Using Larch Sawdust in a Bubbling Fluidized Bed Reactor

Fast pyrolysis experiments of larch sawdust by using a bubbling fluidized bed (0.076 m I.D. × 0.8 m high) have been investigated to determine, particularly, the effect of temperature, U o /Umf ratio, length/diameter ratio of bed (L/D), particle size of the bed material, and O2 concentration on the bio oil yield and compositions. The operation conditions were as follows: temperature, 350–550°C; L/D, 1.0–3.0; U o /Umf ratio, 2.0–6.0; particle size, 60–128 μm; and O2 concentration, 0–15 vol%. As bio oil yield decreased with operation conditions, the gas yield increased and the number of chemical compounds in bio oil decreased. The maximum oil yield of 58 wt% was obtained at: temperature, 400°C; L/D ratio, 2.0; and O2 concentration, 0%.

Removal of beta-pinene and limonene using compost biofilter

Composting is widely used for the treatment of solid organic wastes; however, emissions from composting are becoming a threat to humans due to the release of toxic volatile organic compounds (VOCs). VOCs from composting operations are characterized by high flow rates and, normally, low pollutant concentration. Typical VOCs include a large amount of terpenes (∼65% of total VOCs). This study was to investigate the efficiency of biofiltration in controlling terpene emissions from composting operations using a laboratory-scale unit. The performance of a biofilter was investigated as a function of inlet flow rate, inlet concentration, and bed length/bed diameter (L/D) ratio of bed. At the lowest total inlet flow rate, removal efficiency of limonene and β-pinene was more than 90%. With the decrease in inlet concentration and increase in L/D ratio, the removal efficiency was effectively increased. Removal efficiency of more than 85% for Limonene and 45% for β-Pinene was attained at a loading rate of 55 g/m3-hr. The maximum elimination capacity was found for 109.7 g/m3-hr for limonene and 10.3 g/m3-hr for β-pinene at a critical loading of 150.1 g/m3-hr. Based on this study, the compost bed could function as a biofilter for controlling terpene odors during the composting process. Implications: The purpose of this research project is to investigate the efficiency of biofiltration in controlling limonene and β-pinene emissions from composting operations using a laboratory scale. In addition, the performance of a biofilter as a function of inlet flow rate, inlet concentration, and L/D ratio of bed was evaluated. Establishing a nexus between the operational parameters and efficiency would be useful in design and operation of compost bed as a biofilter for controlling terpene odors during the composting process.