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Olanzapine (OLZ) is an antipsychotic drug with low aqueous solubility. Cyclodextrin (CD) complexation is a potential approach employed to improve the solubility of poorly water-soluble drugs belonging to BCS classes II and IV. The solubility of olanzapine was improved using βCD, HPβCD and methyl βCD which was reported in earlier works. In the current study, a combination of βCD and HPβCD in 1:1 molar ratio was used in the preparation of complexes along with βCD and HPβCD. Methods such as slugging, hydration and granulation which are slight modifications of conventional methods like physical mixing and slugging were used. AL type curves were obtained in phase solubility studies specifying a linear increase in the solubility of drug with increase in concentration of cyclodextrin. The values of slopes calculated for AL type plots are less than one which suggests that OLZ:CD complexes are formed in 1:1 molar ratio. The stability constants obtained were 188.98 M -1, 140.63 M -1 and 157.48 M -1 with βCD, HPβCD and βCD+HPβCD and these values indicate that stable OLZ : CD complexes are formed. The drug : cyclodextrin binary complexes demonstrated a 2.27 to 3.67 - fold increment in aqueous solubility when compared to pure drug. The percentage of drug released in 60 minutes was 46 (pure drug), 65 - 89 (OLZ-βCD complexes), 59 - 80 (OLZ-HPβCD complexes) and 61 - 84 (OLZ-βCD+HPβCD complexes). Results of DSC, XRD and SEM indicated partial inclusion complexation. The complexes prepared by hydration method showed higher solubility when compared to other methods. In hydration method, the complexes were prepared using water which does not cause any harm to individual and environment. [ABSTRACT FROM AUTHOR]

Petrolatum, also known as petroleum jelly, is a widely used topical agent, with a variety of uses in dermatology. Despite its popularity, many myths surround this ubiquitous dermatologic staple. This review details the history of petrolatum and how it is manufactured as well as how its biologic properties make it a great moisturizer. Additionally, data on its potential for flammability, allergenicity, and comedogenicity are detailed, dispelling misconceptions about petrolatum use around oxygen and as a cause of acne. The uses and benefits of petrolatum in dermatology are wide-ranging—a patch test instrument, a vehicle for medicated ointments, and a wound care essential. Given its ubiquitous presence, it is important for dermatologists to understand the history, safety profile, and myths surrounding this humble skincare staple. [ABSTRACT FROM AUTHOR]

The growing popularity of unconventional wells has led to increased interest in assessing and predicting their production performance. These wells, with their extended-reach structures, are able to generate and access larger reservoir volumes. Therefore, understanding the impact of a well’s lateral trajectory on its transient production performance is crucial. This study investigates the effect of lateral-trajectory undulation amplitude on flow behavior based on the experimental results obtained at the University of North Dakota using an undulated two-phase (UTP) flow loop. The experiments involved injecting an air-and-water mixture through a section with variable undulation amplitude followed by a vertical section. The results revealed that the increasing undulation amplitude resulted in lower translational velocity, frequency, and length, with consistent slug acceleration along the system profile. Additionally, the frequency of slugs decreased as they traveled through the vertical section. The measured data indicated that higher undulation amplitudes led to increased horizontal pressure losses and variability, suggesting larger instabilities. The numerical simulations predicted lower translational velocity and frequency, longer slug length, and similar vertical pressure losses when compared to the experimental results.

The growing popularity of unconventional wells has led to increased interest in assessing and predicting their production performance. These wells, with their extended-reach structures, are able to generate and access larger reservoir volumes. Therefore, understanding the impact of a well's lateral trajectory on its transient production performance is crucial. This study investigates the effect of lateral-trajectory undulation amplitude on flow behavior based on the experimental results obtained at the University of North Dakota using an undulated two-phase (UTP) flow loop. The experiments involved injecting an air-and-water mixture through a section with variable undulation amplitude followed by a vertical section. The results revealed that the increasing undulation amplitude resulted in lower translational velocity, frequency, and length, with consistent slug acceleration along the system profile. Additionally, the frequency of slugs decreased as they traveled through the vertical section. The measured data indicated that higher undulation amplitudes led to increased horizontal pressure losses and variability, suggesting larger instabilities. The numerical simulations predicted lower translational velocity and frequency, longer slug length, and similar vertical pressure losses when compared to the experimental results. [ABSTRACT FROM AUTHOR]

Underwater compressed gas energy storage (UW-CGES) holds significant promise as a nascent and viable energy storage solution for a diverse range of coastal and offshore facilities. However, liquid accumulation in underwater gas pipelines poses a significant challenge, as it can lead to pipeline blockages and energy transmission interruptions and adversely impact pipeline operation. In this paper, experimental and Oil and Gas Assays (OLGA) simulation studies have been conducted on the formation process of slug flow in pipelines. Firstly, experiments are conducted to capture high-speed camera images of slug flow under various liquid accumulation volumes and inclination angles. Subsequently, an OLGA model is developed to verify the experimentally observed flow regime, pressure, and slugging speed. Therefore, the flow regime verification results exhibit substantial consistency, and pressure variations display uniform trends, with an average slugging velocity error of 6.42%. The results indicate that the formation of slug flow involves three distinct stages: slug flow growth, ejection, and backflow. By analyzing slug flow, it can gain insights into the relationship between pressure and slug flow formation, exposing the sensitivity of this phenomenon to pressure fluctuations. These results further enhance recognition of the operational status of UW-CGES pipelines and provide support for safe operation. [ABSTRACT FROM AUTHOR]

A periodic pigging operation performed to clean off sediment and provide operators with detailed health information for a pipeline is mandatorily required. The research on pigging-induced issues for the steel catenary riser (SCR), one of the key parts in offshore hydrocarbon recovery pipelines between the floating production system and the seabed, has been scarce until now. As a result, there is an urgent need for theories to guide the pigging operation to ensure safe pigging is achieved in deepwater risers. In this paper, a study aiming to determine the effects of the pigging impact load and the pigging-induced slugging load on the dynamic response of the riser is reported. A SCR pigging model was established and proposed based on the finite element analysis (FEA) method. The stress distribution and displacement of the SCR were investigated under the pigging conditions, with the consideration of the effects of waves, currents, and floating platform movements. It was found that the pigging load has large effects on the stress and displacement of the touchdown zone (TDZ), especially the touchdown point (TDP). The displacement of the TDZ in the Y (vertical) direction is more significant than that in the X (horizontal) direction under pigging conditions, and the maximum displacement of the TDZ in the Y direction is proportional to the weight of the pig, as well as the length of the pigging-induced slugging. [ABSTRACT FROM AUTHOR]

• Systematic investigation of liquid flooding upon compressor start-up. • Characteristic flooding curve shown for 12 combinations of heat exchangers and refrigerants. • Correlation proposed capturing influence of heat exchanger size and refrigerant properties. Refrigeration cycles with fixed speed compressors cycle on and off to modulate their time averaged cooling capacity. While the cycles are turned off, refrigerant can migrate from the condenser into the colder evaporator. The next start-up process can then pull liquid refrigerant out of the evaporator and into the compressor causing liquid flooding. This phenomenon results in a loss of latent heat for cooling, can undercool the lubricant, and may cause damage to the compression mechanism. The geometric and thermophysical conditions that lead to liquid flooding are poorly understood. Experimental data collected for four refrigerants and three heat exchangers was analyzed for flooding conditions. A correlation was fitted to the experimental data, predicting the experimentally determined charge threshold for flooding with an average deviation of 6.6% and a maximum deviation of 16.7%. Repeating the tests with other heat exchanger types and smaller or larger compressors is suggested as important future work. [ABSTRACT FROM AUTHOR]

Underwater compressed gas energy storage (UW-CGES) holds significant promise as a nascent and viable energy storage solution for a diverse range of coastal and offshore facilities. However, liquid accumulation in underwater gas pipelines poses a significant challenge, as it can lead to pipeline blockages and energy transmission interruptions and adversely impact pipeline operation. In this paper, experimental and Oil and Gas Assays (OLGA) simulation studies have been conducted on the formation process of slug flow in pipelines. Firstly, experiments are conducted to capture high-speed camera images of slug flow under various liquid accumulation volumes and inclination angles. Subsequently, an OLGA model is developed to verify the experimentally observed flow regime, pressure, and slugging speed. Therefore, the flow regime verification results exhibit substantial consistency, and pressure variations display uniform trends, with an average slugging velocity error of 6.42%. The results indicate that the formation of slug flow involves three distinct stages: slug flow growth, ejection, and backflow. By analyzing slug flow, it can gain insights into the relationship between pressure and slug flow formation, exposing the sensitivity of this phenomenon to pressure fluctuations. These results further enhance recognition of the operational status of UW-CGES pipelines and provide support for safe operation.

A digital twin (DT) method is proposed to estimate the dynamic and structural behaviors of a Steel Lazy Wave Riser (SLWR) under environmental conditions. This method uses a 1D finite element (FE) riser model that can include various loads and boundary conditions measured from sensors. We selected a spread-moored Floating Production Storage and Offloading (FPSO) vessel to validate the proposed method, which hosts multiple Production and Injection SLWRs. Using the time-domain dynamics simulation program, we built a reference model considering the fully coupled FPSO with mooring lines and risers in various wind/wave/current conditions. The synthetic sensor data, which represents the motions and internal fluid density changes, were generated from the simulation of the reference model. Then, two riser DT models, the Top Oscillation Model (TOM) and the Two-Point Oscillation Model (TPOM), were built, considering only a single riser made of the 1D FE model. TOM employed vessel motions as boundary conditions while internal fluid density and ocean current could be inputted as external loads. TPOM incorporated an additional motion sensor attached to the riser. The motion data obtained from the reference model were first inputted into the respective riser DT models. Next, we further evaluated their performance with and without the estimated ocean currents and slugs of internal fluid. The time histories, spectra, and statistical data of displacements and stresses along the riser were systematically compared and analyzed for various test cases and environments. While the hull-motion sensor alone can provide practically acceptable results using the developed methodology, additional consideration of current load and internal fluid's density variation improves the overall riser monitoring performance. The present method can significantly reduce the number of sensors compared to traditional riser monitoring methods. [ABSTRACT FROM AUTHOR]

Slugging as a flow assurance challenge is an upsetting condition to the oil and gas industry due to the instabilities it poses on the system. The negative repercussions associated with slug flow stems from the inlet through to the topside facilities where processing is done. Active control has been established as one of the best techniques to eradicate slug and its accompanying challenges, however the controller robustness and some setbacks make improvement a necessity. Again, the robustness of the controller has been in question.Due to the potential of active control, several other researchers have delved into it. Many outcomes from pilot scale experiments (usually 2–4 inch valves), that shows promising and improved benefits fail to replicate when emulated on real offshore facilities (over 8 inch valve diameters). This is because of the difference in the valve stroke time (time taken for a valve to move from fully open to fully close or vice versa). Comparatively, larger diameter valves are designed to have larger stroke time than smaller diameter.In this paper, an advancement and extension of an active slug control strategy that uses measurement signals from the topside of the riser, will be used to deal with systems with time-delay as a result of large valve stroke time. The Smith predictor model was specially modified not just to deal with time-delay but also to deal with variable time-delay in both stable and unstable systems. Thus, a design of a modified smith predictor where the modification mitigates the direct estimation of the time delay itself. This is supposedly due to the internal structure of the proposed modification which, accounts for plant-model mismatch and makes small changes to the control input based on a reference controller.

Casual carpooling is an informal form of commuter ridesharing operating in Washington, D.C.; Houston, Texas; and San Francisco, California. In contrast to new forms of shared-use mobility, casual carpooling has been in existence for over 30 years and uses no information communication technology, and is entirely run informally by its users. Researchers have been fascinated by this phenomenon and have conducted studies in the past, but there remains a lack of up-to-date quantitative data. This study examines the motivations and behaviors of casual carpoolers in the San Francisco Bay Area to understand user characteristics and motivations. In Winter 2014, the authors observed and counted participants and vehicles at four casual carpooling locations, interviewed participants riding in carpooling vehicles (N=16), and conducted intercept surveys (N=503) at ten East Bay pickup locations. The results indicate that the motivations for casual carpooling participation include convenience, time savings, and monetary savings, while environmental and community-based motivations ranked low. Casual carpooling is an efficient transportation option for these commuters, while environmental sustainability benefits are a positive byproduct. Seventy-five percent of casual carpool users were previously public transit riders, and over 10% formerly drove alone. Logit modeling found that casual carpool role (i.e., always a rider or sometimes a driver), age, and employment status were key drivers in modal choice. Further research on a larger scale is needed to identify the elements needed for system replication in different areas.

The increase of liquid saturation badly affects the fluidization dynamics, even resulting in the failure of fluidization. Nevertheless, few researches focus on characterizing the flow pattern transition of wet particles. In this work, we discuss the effects of the liquid saturation, gas velocity and the particle size on the global fluidization dynamics of Geldart D particles by analyzing the pressure fluctuations in the fluidized bed. The results show that the bubble dynamics is intensified with the increasing liquid saturation and decreasing particle size. When the superficial gas velocity increases, the fluidization regimes change from expanding regime, to multi-bubbling regime and slugging. During the normal fluidization and slugging, the liquid bridge forces prevent the growth of large bubbles and promote the probability of bubble break-up. Thus, the average bubble size decreases and the number of bubbles increases, which lead to the intense bubble behavior. With the decreasing particle size, the effect of liquid bridge forces is enhanced, contributing to the intensified bubble dynamics, including fast rising, frequent coalescence and eruption of a large number of bubbles. Compared to dry particles, wet particles are easily to cause defluidization when the gas velocity is small. The PSD patterns have the sharp narrow peaks at frequency lower than 0.8 Hz. When the liquid saturation is increased to 30%, a gas channel forms in the bed, which resists the normal works of the fluidized bed. Basically, reducing the liquid saturation is a reasonable way to avoid defluidization. [Display omitted] • Pressure fluctuation analysis is used to study the fluidization of wet particles. • Bed changes from normal fluidization to slugging regime with increasing liquid saturation • The decreasing particle size intensifies the bubble behavior. • Reducing liquid saturation can repress the whole-bed slugging and defluidization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pressure fluctuation analysis was used to study the fluidization of cohesive particles. • Polymer coating was applied to introduce thermal-induced cohesive force. • Bed changes from multiple-bubbling to single-bubbling regime with increasing cohesion. • Bubble-promoted operations benefit the whole-bed slugging under strong cohesion. • Reducing static bed height can repress the whole-bed slugging. Abstract The increase of inter-particle cohesive force greatly changes the fluidization dynamics, finally leading to the partial or complete failure of fluidization. However, few studies concern such transition process. This paper investigates the fluidization dynamics of Geldart B particles with a wide-range of cohesive force by analyzing the in-bed pressure fluctuation signals. Combining the bubble information reported in Part I, the local and global fluidization dynamics under different cohesive forces were discussed. The results show that bulk bubble dynamics is weaken with the presence of inter-particle cohesive force. As the force increases, fluidization changes from multi-bubbling regime to single-bubble regime and the factor governing the pressure fluctuation changes from bubble formation to bubble eruption. When the cohesive force is strong, slugging appears near the bed surface, then gradually extends toward the bottom bed by capturing freely fluidizing particles, and finally develops into the whole-bed slugging. At this time, regular fluidization turns into an alternative process between whole-bed slugging and regular status, corresponding to two distinct peaks in power spectral density of pressure signals at 0.1 Hz and 1 Hz respectively. The size of gas slug decreases with the elevation of measurement height. Basically, any operations that promote bubble growth will also facilitate the appearance of whole-bed slugging under strong cohesive force. Reducing the static bed height is a preferable approach to weaken, or even avoid the defluidization of whole-bed slugging, without changing other operational parameters. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fluidization using 'rough' 3D-printed walls is studied for the first time. • 3D-printing does not negatively influence wall effects in micro-fluidized beds. • Macro-fluidization behaviour is observed for bed diameter ratios of D h /D p > 75. • A new quantitative method for identifying the onset of slugging is proposed. • 3D-printing has the potential to unlock more complex fluidized bed designs. Abstract Additive manufacturing could be used to facilitate the rapid fabrication and testing of small-scale fluidized beds for use in screening applications, such as adsorbent screening for carbon capture. In this work, experiments were performed in order to map the different flow regimes produced in small-scale (D h = 3–15 mm) gas-solid fluidized beds that were fabricated using additive manufacturing using the stereolithography approach. Here, the effects of bed hydraulic diameter (D h), static particle height (H s), and particle type/size (D p and ρ p) were considered. Pressure drop data and high speed camera images were used to develop simple flow regime maps for these printed beds showing the operating windows for packed bed, bubbling, slugging and turbulence applicable to a wide range of bed size to particle diameter ratios (D h /D p = 20–200) and gas velocities (U g = 1–400 mm/s) in both '2D' and '3D' bed aspect ratios. Fast Fourier transforms of the pressure drop signals were also used to study the evolution of bubbling/slugging behaviour as the gas velocity was increased by creating 2D colour maps of the frequency spectra. These allowed a new quantitative method to be proposed for the identification of slugging – the point where the dominant frequency in the power spectrum becomes constant as the gas velocity increases. It is concluded in this study that the rougher surfaces generated by additive manufacturing do not influence the fluidization characteristics nor modify the wall effects of small-scale beds. Macro-scale fluidization could also be achieved at smaller D h /D p ratios in these 3D printed beds compared to more conventional Plexiglas beds (D h /D p = 75 compared to D h /D p = 300). [ABSTRACT FROM AUTHOR]

We extend the model of Needham, et al. (2008, The development of slugging in two-layer hydraulic flows, IMA J. Appl. Math. 73, 274–322)—a hydraulic model for turbulent, two-layer, gas–liquid flow with gas velocity much greater than liquid velocity, in a horizontal channel—to include the effect of a small, spatially varying inclination. This allows us to consider the effect of non-horizontal topography of the channel on slug formation. The stratified flow of gas–liquid mixtures is important in many industries, in particular, oil and gas, where the formation of slugs is usually undesirable. We show that, in channels of constant inclination, for sufficiently downhill flows there is a unique spatially uniform steady state. However, as the pipe inclination increases, there are two bifurcations: the first leads to the existence of a second steady state, while the second, a saddle-node bifurcation, means that there are no uniform steady-state solutions for sufficiently uphill flow. The steady state with the thicker liquid layer is unstable except for a very small range of flow rates, while the other steady state is unstable for sufficiently downhill flows and for sufficiently high liquid flow rate. We also study roll waves (periodic travelling wave solutions) and determine the form of these solutions numerically. Finally, we study an initial value problem driven by noise at the inlet of channels with, firstly, constant, and secondly, sinusoidally-varying inclinations. We provide numerical evidence for the likely formation of slugs at points where the inclination of the pipe is anywhere equal to the saddle-node bifurcation angle. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • X-ray tomography was used to reconstruct 3D bubbles in a bubbling bed. • The inter-particle cohesive force facilitates the coalescence of bubbles in the bed. • The fluidization fails as the whole bed slugging under large cohesive force. • Bubble rise velocity sharply drops with the appearance of slugging. Abstract Due to the presence of inter-particle cohesive force, cohesive particles reveal totally different fluidization behaviors as compared to the non-cohesive system. This paper studies the fluidization dynamics of Geldart B particles with varying thermal-induced cohesive forces. Multi-source X-ray tomography was applied to reconstruct 3D temporal images of bubbles, based on which, various bubble properties were extracted. The results show that increasing cohesive force will decrease bubble number while increase bubble size, implying that the presence of cohesive force facilitates bubble coalescence. By examining the bubble size distribution, cohesive force is found to have no effect on the number of median bubbles but greatly influence small and large bubbles. When the cohesive force is strong, the bubbles grow to a considerable size similar with bed dimension, giving rise to slugging near bed surface. With the action of inter-particle cohesive force, particle slug gradually grows by capturing other freely fluidizing particles, finally inducing "whole-bed" slugging. The particle slug may rupture in the rising process, and the bed turns back to normal fluidization. In comparison to normal bubbles, the gas slug has much larger size but far smaller frequency. The rise velocity of gas slug is also very low due to the particle-wall friction and gas-solid momentum dissipation. Therefore, the averaged values of bubble properties dramatically changed as bed temperature exceeds 35 °C. When the temperature attains 45 °C, the cohesive force is so strong that the fluidization completely fails in terms of stable whole-bed slugging. [ABSTRACT FROM AUTHOR]

The hydrodynamics of a slugging fluidized bed is investigated numerically by using a two-fluid model suggested by Brandani and Zhang [22]. Numerical simulations are carried out in the platform of a commercial software package, CFX 4.4, by adding user-defined subroutines. The bed expansion ratio, the pressure drop fluctuation and its power spectrum density at the equipment scale and the solids volume fraction distributions at the grid scale are predicted to explore the slugging fluidization characteristics for Geldart group D particles. By comparing with the experimental data in the literature, the numerical model is found to have better predictive ability when the viscous force term is considered in the gas phase momentum equation.

The effect of horizontal well trajectory on slug flow development was experimentally studied using a 2.0 in. ID flow loop to mimic different well trajectories. Inclination angle in the lateral section was varied ±1° from the horizontal to simulate three well configurations, namely, toe-down, one-undulation with a sump, and one-undulation with a hump. Slug length and frequency along the well were measured using fourteen conductivity probes located along the test section. Experimental results indicated that slug length in the vertical and lateral sections of a well present values up to four and two times, respectively, larger than typical dimensionless slug length reported in the literature. Furthermore, slug flow development along the vertical section is affected by the lateral section deviation angle and length. At the same time, lateral section slug flow development is affected by liquid fall back from the vertical section and lateral section length. Slug characterization along the well is critical to properly design and operate downhole and surface equipment and properly predict pressure gradient and liquid holdup along the well. [ABSTRACT FROM AUTHOR]

• Presents a novel methodology for simultaneously measuring two-phase flow characteristics and pipe motion. • Utilizes a computer vision algorithm for continuous pipe and liquid monitoring across the entire experimental test section. • Deploys a field scale facility designed to mimic configurations encountered in offshore flowlines. • Analyzes and explains the relationship between two-phase flow parameters (such as superficial velocities and slug characteristics) and pipe response (like pipe displacement amplitude and frequency). One of the governing contributors to offshore structures' (e.g., pipelines and deep-water risers) accumulative long-term fatigue damage is the internal flow-induced vibrations caused by slug flow. Due to the complexity of the numerical modeling of the internal flow and fluid–structure interaction, experimental campaigns are often performed to predict the asset response and provide a benchmark for numerical model validation. In this study, an experimental campaign was conducted which included a unique computer vision data acquisition system and a large-scale facility designed to mimic industry field conditions. This study aims to relate flow parameters to structural response and explain the mechanisms that govern the relationship between both domains. The presented results reveal that the gravitational forces of the fluid dominate the transverse deflections of the pipe and, therefore, the slug liquid holdup, film liquid holdup, and slug length showed strong correlations to pipe deflections. However, centrifugal forces were observed to have significant contributions to pipe deflection for high translational velocity slugs. Additionally, it was found that for most of the test conditions, the primary pipe excitation frequency correlates to the slug frequency. It was discovered that no-slip liquid holdup has a positive correlation to both the magnitude and range of pipe deflection and that increases in superficial gas and liquid velocities led to decreases and increases in pipe deflection, respectively. Furthermore, it was observed that the measured frequency responses of the structure tended to increase with increasing gas velocity until the flow pattern in the pipe began to transition to annular flow. [ABSTRACT FROM AUTHOR]

A comprehensive exercise, suitable for an undergraduate engineering audience studying fluid mechanics, is presented, in which participants were tasked with emptying a bottle. That simple request yielded data collected by students and the author for N = 454 commercially available bottles, spanning nearly four orders of magnitude for volume V , and representing the largest experimental dataset available in the literature. Fundamental statistics are used to describe the emptying time, T ¯ e , for any single bottle. Dimensional analysis is used to transform the raw data to yield a predictive trend, and a method of least-squares regression analysis is performed to find an empirical correlation relating dimensionless time T ¯ e g / d and dimensionless volume V / d 3 . We find that volume, V , and neck diameter, d, can be used to estimate the emptying time for any bottle, although the data suggests that the shape of the neck plays a role. Furthermore, two basic analytical models found in the literature compare favorably to our data and empirical correlation when recast using our dimensionless groups. The documented exercise provides students with the opportunity to use basic engineering statistics and to see the utility of dimensional analysis.

Experiments on aeration from a bubble diffuser pipe having five aeration holes are carried out to investigate effects of the azimuthal angle of the holes on flows inside and outside the pipe. The azimuthal angle is varied by rotating the pipe. When the hole angle becomes larger than a certain angle, the liquid height inside the pipe is fixed just below the holes, which results in the prevention of slugging inside the pipe. The effects of hole angle on bubble generation mode and bubble size are small except for the large hole angles, at which generated bubbles are to break up due to an interaction between the bubbles and the pipe wall. Hence uniform aeration is easily realized just by rotating the pipe to some extent. Uniform aeration is also realized with a longer diffuser pipe having ten aeration holes by rotating the pipe. The power in aeration is evaluated from the pressure difference and the total gas inflow. Although the decrease in the hole diameter is also effective to realize the uniform aeration, the increase in the azimuthal angle is superior to the former from the point of view of energy saving. [ABSTRACT FROM AUTHOR]

The aim of this study was to optimize the process of tablets compression and identification of film-coating critical process parameters (CPPs) affecting critical quality attributes (CQAs) using quality by design (QbD) approach. Design of experiment (DOE) and regression methods were employed to investigate hardness, disintegration time, and thickness of uncoated tablets depending on slugging and tableting compression force (CPPs). Plackett–Burman experimental design was applied to identify critical coating process parameters among selected ones that is: drying and preheating time, atomization air pressure, spray rate, air volume, inlet air temperature, and drum pressure that may influence the hardness and disintegration time of coated tablets. As a result of the research, design space was established to facilitate an in-depth understanding of existing relationship between CPPs and CQAs of intermediate product (uncoated tablets). Screening revealed that spray rate and inlet air temperature are two most important factors that affect the hardness of coated tablets. Simultaneously, none of the tested coating factors have influence on disintegration time. The observation was confirmed by conducting film coating of pilot size batches. [ABSTRACT FROM PUBLISHER]

A systematic experimental study on two-phase air-water was carried out to evaluate effect of well trajectory on liquid removal in horizontal gas wells. Experiments were conducted in a facility with a 2-in. ID and 62.6-ft. long lateral section and a 41-ft. vertical section, which mimics a horizontal well. Four well configurations were considered; namely, toe-down, toe-up, one-undulation with a sump and one-undulation with a hump. Additionally, different flow conditions were used to simulate the well production as the reservoir pressure depletes. The effect of well trajectory on the liquid removal was evaluated measuring the pressure gradient, liquid holdup, film reversal, and flow pattern. Experimental results indicate that under stable conditions, toe-up is the best configuration for the displacement of the produced fluids from the toe to the kick-off point. However, at very low gas flow rates, severe slugging is observed in this configuration. Furthermore, for the toe-down, one-undulation with a sump, and one- undulation with a hump configurations liquid loading is observed in both lateral and vertical sections of the well. Consequently, significant liquid accumulation and an eventual slugging condition are observed in the well. It was observed that the measured critical gas velocity to avoid liquid loading is lower than gas velocity at the minimum pressure gradient, indicating that minimum pressure gradient criterion is not enough to determine whether the well will be under stable or unstable conditions. Finally, toe-down configuration presents the largest liquid accumulation in the lateral section, indicating lower efficiency to remove liquids from the toe to the kick-off point. [ABSTRACT FROM AUTHOR]

Effects of the total gas flow rate on the water level in a diffuser pipe for a membrane bioreactor, the gas flow rate from each aeration hole and the bubble diameter are investigated. The diffuser has evenly positioned five aeration holes on the top and a larger hole on the bottom for introducing the liquid into the pipe. The gas flow rate from each aeration hole is measured by capturing generated bubbles. The water level and gas velocity inside the diffuser are computed by processing video images. The bubble diameter is calculated using the gas flow rate and the bubble generation frequency measured from the video images. The conclusions obtained are as follows: (1) the gas flow rate from the aeration hole depends on the water level inside the diffuser and becomes constant for all the holes as the total gas flow rate increases since the high total gas flow rate make the water level uniform, which results in a constant gas pressure in the diffuser, (2) the onset of slugging in the diffuser is well correlated in terms of the local gas velocity and the Mishima-Ishii's slugging model, (3) the increase in the total gas flow rate decreases the water level, causing suppression of the onset of slugging, (4) the diameter of aeration hole strongly affects the gas flow rate from each aeration hole and water level, and (5) the Davidson-Schuler correlation gives reasonable estimations of the bubble diameter, provided that the influence of slugging is not significant.

This paper illustrates the potential of nonlinear model-based control applied for stabilization of unstable flow in oil wells. A simple empirical model is developed that describes the qualitative behavior of the downhole pressure during severe riser slugging. A nonlinear controller is designed by an integrator backstepping approach, and stabilization for open-loop unstable pressure setpoints is demonstrated. The proposed backstepping controller is shown in simulations to perform better than PI and PD controllers for low pressure setpoints, and is in addition easier to tune. Operation at a low pressure setpoint is desirable since it corresponds to a high production flow rate. The simulation results are presented to illustrate the effectiveness of proposed control scheme.

Solids oscillation circulation is an unstable solids flow behavior exhibited during the start-up process of a circulating fluidized bed (CFB) with sweeping bend return. It results in significant pressure fluctuation and particle loss, further brings about difficulties in establishing a stable solids circulation and blockage of the heat exchanger for recycling gas. However, the oscillation mechanism and hydrodynamic characteristics of the solids oscillation circulation are still far from understanding, since the variation of solids transfer rate, gas flow rate and their complex interactions are still unknown. In this work, the Eulierian-Eulerian method has been employed for the simulation of solids oscillation circulation in a two-dimension (2D) CFB. The results indicate that solids oscillation circulation is triggered by the formation of slugging in the downer, which leads to a decrease of the downer pressure drop and a sharp increase of the riser bypass gas velocity. Besides, intense slugging fluidization is observed in the downer at larger valve opening or higher inlet gas velocity. Moreover, statistical hydrodynamic shows uniform lateral solids volume distributions in the riser and downer. Solids fluctuating energy spectrum is generated to explore the turbulent characteristics, a segment phenomenon is observed in the inertial sub-region. In addition, the deviation of scale index in the inertial region form the Kolmogorov −5/3 scaling law indicates the flow intermittency. According to the wavelet analysis of particle fluctuation velocity, the particle-particle and particle-wall interaction are found to be the main reason for the flow intermittency. [ABSTRACT FROM AUTHOR]

The threat of slugging to production facilities has been known since the 1970s. This undesirable flow phenomenon continues to attract the attention of researchers and operators alike. The most common method for slug mitigation is by choking the valve at the exit of the riser which unfortunately could negatively affect production. The focus, therefore, is to satisfy the need for system stability and to maximize production simultaneously. Active feedback control is a promising way to achieve this. However, due to the complexity of multiphase flow systems, it is a challenge to develop a robust slug control system to achieve the desired performance using existing design tools. In this paper, a new general method for multiphase flow system stability analysis was proposed. Active feedback control was observed to optimize slug attenuation compared with manual choking. The use of soft sensors was believed to be desirable for the practical implementation of the proposed control technique. [ABSTRACT FROM AUTHOR]

Casual carpooling is an informal form of commuter ridesharing operating in Washington, D.C.; Houston, Texas; and San Francisco, California. In contrast to new forms of shared-use mobility, casual carpooling has been in existence for over 30 years and uses no information communication technology, and is entirely run informally by its users. Researchers have been fascinated by this phenomenon and have conducted studies in the past, but there remains a lack of up-to-date quantitative data. This study examines the motivations and behaviors of casual carpoolers in the San Francisco Bay Area to understand user characteristics and motivations. In Winter 2014, the authors observed and counted participants and vehicles at four casual carpooling locations, interviewed participants riding in carpooling vehicles ( N =16), and conducted intercept surveys ( N =503) at 10 East Bay pickup locations. The results indicate that the motivations for casual carpooling participation include convenience, time savings, and monetary savings, while environmental and community-based motivations ranked low. Casual carpooling is an efficient transportation option for these commuters, while environmental sustainability benefits are a positive byproduct. Seventy-five percent of casual carpool users were previously public transit riders, and over 10% formerly drove alone. Logit modeling found that casual carpool role (i.e., always a rider or sometimes a driver), age, and employment status were key drivers in modal choice. Further research on a larger scale is needed to identify the elements needed for system replication in different areas. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the lubrication properties of hexagonal boron nitride (HBN) on a (1:1) binary mixture of Avicel DG and Starch 1500 after using the dry granulation–slugging method and compare it with conventional lubricants, such as magnesium stearate (MGST), glyceryl behenate (COMP) and stearic acid (STAC). MGST is one of the most commonly used lubricants in the pharmaceutical industry. However, it has several adverse effects on tablet properties. In our current study, we employed various methods to eradicate the work hardening phenomenon in dry granulation, and used HBN as a new lubricant to overcome the adverse effects of other lubricants on tablet properties. HBN was found to be as effective as MGST and did not show any significant adverse effects on the crushing strength or work hardening. From the scanning electron microscope (SEM) images, it was concluded that HBN distributed better than MGST. As well as showing better distribution, HBN’s effect on disintegration was the least pronounced. Semi-quantitative weight percent distribution of B and N elements in the tablets was obtained using EDS (energy dispersive spectroscopy). Based on atomic force microscope (AFM) surface roughness images, formulations prepared with 1% HBN showed better plastic character than those prepared with MGST. [ABSTRACT FROM AUTHOR]