Dynamic generation of power function gradient profiles in a universal microfluidic gradient generator by controlling the inlet flow rates

We report a two-inlet universal microfluidic gradient generator capable of generating gradient profiles of the functional form xp in the same device by controlling only the inlet flow rates. We...

Impact of Measurement Error on the Power Function of Average Control Chart under Non-Normal Population

In the present article, effect of measurement error on the power function of control charts for mean with control limits is considered based on non-normal population. The non-normality is represented by the first four terms of an Edge-worth series. Tabular and visual comparison is also provided for the better comprehension of the significance of measurement error on power function under non-normality.

Challenges of Hydrate Risk Management at Low Water Cuts Using Anti-Agglomerants

BWOLF (DH 180/185) flowlines, in the deepwater Gulf of Mexico, were being treated continuously with LDHI to manage hydrate risk. Application of the Anti-Agglomerant (AA) was being utilized to treat the asset under the initial conditions, including water cuts up to 20%, for potential unplanned shut ins. Due to a well zone change, water cut dropped from 20% to <1%. The assumption was that chemical treatment volumes for hydrate management would decrease based on water volume. However, at these lower water cuts, it was determined that higher by volume of water treatment dosing was required to provide adequate hydrate risk protection. Additionally, dead-oil circulations were periodically being used to address some pressure build up and return the system back to baseline pressures. Rocking cell testing was conducted to determine the optimal chemical treating doses using AA alone, as well as AA + MeOH as options. However, the rocking cell equipment limitation for water cuts is ~10%, below which results have previously not been trusted. Extrapolation for estimated dosages were needed for the lower water cuts observed in the field. Autoclave tests were done at higher water cuts (30 and 50%) to also provide data for curve fitting to confirm whether the increase need for LDHI at lower water cuts was indeed exponential in nature. Field monitoring of flowline pressures was conducted to determine treatment effectiveness. Additionally, field monitoring of water cut over time was also observed and related back to how the chemical treatment behaved in relation. After the well zone change, application of the AA alone was not enough to effectively address the hydrate risk and resulted in gradual build up of hydrate within the system. Periodic MeOH pills were applied to reduce delta pressure, but care was necessary to avoid reaching MeOH limitations within the crude. Additionally, this method did not effectively remove hydrate formation in the flowline. Less frequently, but when necessary, dead oiling was utilized to remove the build up quite effectively. This was not ideal due to down time and deferred production. It's felt that Webber et al. correctly described the significant increase of AA dosing requirements at very low water cuts (<5%) resulting in a power function relationship. This creates further challenges such as cost of chemical treatment due to higher dosing requirements and potential water quality issues topsides when higher doses of AA are used. The data and results within confirm limited examples of where lower water cut can result in significantly increased dosing requirements for AAs and why a power function relationship should be considered when extrapolating treatment recommendations at 5% or below. There is interest in further understanding the AA requirements at low water cuts and the effectiveness of deal oiling on hydrate build up going forward. This data is particularly relevant for new deepwater projects that consider chemical use as one of the primary options for hydrate management.

An empirical resistance equation for the modelling of corona discharge in saline water

We present a study that was undertaken to calculate the resistance of low current corona discharge in saline water. A novel empirical model was obtained, based on several assumptions, which allowed us to determine the corona resistance using the measured current. This resistance could be then exploited to compute the power deposited to the corona as a function of time. The wall motion of a bubble freely oscillating in saline water was calculated using hydrodynamic equations and the calculated power function. A comparison of numerical simulations with experimental results showed that good agreement was achieved.

The Confidence Interval of the Estimator of the Periodic Intensity Function in the Presence of Power Function Trend on the Nonhomogeneous Poisson Process

The nonhomogeneous Poisson process is one of the most widely applied stochastic processes. In this article, we provide a confidence interval of the intensity estimator in the presence of a periodic multiplied by trend power function. This estimator's confidence interval is an application of the formulation of the estimator asymptotic distribution that has been given in previous studies. In addition, constructive proof of the convergent in probability has been provided for all power functions.

Estimation of Information Measures for Power-Function Distribution in Presence of Outliers and Their Applications

The measure of entropy has an undeniable pivotal role in the field of information theory. This article estimates the Rényi and q-entropies of the power function distribution in the presence of s outliers. The maximum likelihood estimators as well as the Bayesian estimators under uniform and gamma priors are derived. The proposed Bayesian estimators of entropies under symmetric and asymmetric loss functions are obtained. These estimators are computed empirically using Monte Carlo simulation based on Gibbs sampling. Outcomes of the study showed that the precision of the maximum likelihood and Bayesian estimates of both entropies measures improves with sample sizes. The behavior of both entropies estimates increase with number of outliers. Further, Bayesian estimates of the Rényi and q-entropies under squared error loss function are preferable than the other Bayesian estimates under the other loss functions in most of cases. Eventually, real data examples are analyzed to illustrate the theoretical results.

Analysis of Cumulative Damage Characteristics of Long Spiral Belled Pile under Horizontal Cyclic Loading at Sea

In order to study the cumulative damage and failure characteristics of long spiral belled pile under horizontal cyclic loading of offshore wind and waves, a series of indoor experiments on single piles under horizontal cyclic load were carried out. The cycle times as well as load amplitude at the same frequency were considered during the horizontal pseudo-static cyclic tests. On the basis of the distribution of pile deflection, bending moment, and Earth pressure around the pile, the pile-soil interaction was comprehensively discussed. The cumulative energy dissipation characteristics were introduced to describe the damage of test piles. Meanwhile, the effects of load amplitude and cycle times on the cumulative damage of long spiral belled piles were discussed. A power function model for energy dissipation coefficient prediction under multi-stage cyclic load was proposed. The results show that the horizontal peak bearing capacity of long spiral belled pile is increased by 57.2% and 40.4%, respectively, as compared with the straight pile and belled pile under the same conditions. The horizontal displacement mainly occurs at the upper part of the pile. Under the condition of limited cyclic times, the load amplitude has more significant effect on the bearing characteristics of the long spiral belled pile. In contrast to the straight pile and belled pile, the long spiral belled pile has better energy dissipation capacity, and the rank of the energy dissipation capacity of these three piles is long spiral belled pile > belled pile > straight pile. The power function model can well reflect the cumulative damage characteristics of long spiral belled pile under horizontal cyclic loading, and there is a good linear relationship between power function model parameters and load amplitude. The energy dissipation coefficient of long spiral belled pile with diverse cycle times at different mechanical stages of test pile is analysed. Then, the recommended power function model parameters according to different failure stages are proposed. The verification example indicates that the prediction results are close to the measured values with a calculation error of 22%. The prediction model can provide a certain reference for the application of long spiral belled pile in marine structures.

Study on the impact of confining pressure on gas permeability of tight sandstone cores

Taking the tight sandstone core of Shengli Oilfield as the experimental sample, this paper studies the permeability variation of the tight sandstone under different confining pressures. The experimental results show that when the pore pressure is constant, the measured gas permeability of core decreases with the increase of confining pressure. Power function is more reasonable to describe the influence of confining pressure on permeability of tight sandstone between power function and exponential function. Analyze the impact of confining pressure on gas permeability of tight sandstone cores by using permeability change rate coefficient D and coefficient S.

Analysis of Influencing Factors and Mechanism of Strength of Cement-Modified Silty Sand

The unconfined compressive strength of cement-modified silty sand in Jilin Province was investigated in this study. For this purpose, various tests were conducted, including the screening test, compaction test, CBR test, X-ray fluorescence detection, and unconfined compressive strength test. Effects of compaction degree, soil quality, water quality, cement content, and curing age were considered. The results show that CBR value is positively correlated with compactness. Two kinds of different water qualities have little effect on unconfined compressive strength of cement-improved soil; with the increase in cement content, the unconfined compressive strength increases, and the power function equation established by the two is significantly correlated. The logarithmic relationship between cement-soil strength and curing age is approximately linear. Through regression analysis, the comprehensive characterization parameters of cement-soil strength, such as water-cement ratio, cement content, and curing age, are put forward. The unconfined compressive strength of cement-modified silty sand has a good power function relationship with the comprehensive characterization parameters, and the fitting degree between the strength prediction formula and the existing research and test data exceeds 90%, which verifies the effectiveness of the comprehensive characterization parameters.