Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid
crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby
allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role
of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied
for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane,
and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed
us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form).
The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants
as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic
surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the
oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed
very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The
results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient
for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures
advantageous. 相似文献
Parents of six children are facing a trial on charges of aggravated manslaughter in the care a 5 1/2 month old infant who
died suddenly and neglect of their four older children for causing them to be malnourished by feeding them all an exclusively
raw foods vegan diet. Both parents declined plea bargains and plan to defend themselves in court. 相似文献
This paper presents a three node curved three dimensional beam element for linear static analysis where the element displacement approximation in the axial () and transverse directions ( and ) can be of arbitrary polynomial orders p, p and p. This is accomplished by, first constructing one dimensional hierarchical approximation functions and the corresponding nodal variable operators in , and directions using Lagrange interpolating polynomials and then taking the products (also called tensor product) of these hierarchical one dimensional approximation functions and the corresponding nodal variable operators. The resulting approximation functions and the corresponding nodal variables for the three dimensional beam element were hierarchical. The formulation guarantees C0 continuity. The element properties are established using the principle of virtual work. In formulating the properties of the element all six components of the stress and strain tensor are ratained. The geometry of the beam element is defined by the coordinates of the nodes located at the axis of the beam and node point vectors representing the nodal cross-sections. The results obtained from the present formulation are compared with analytical solutions (when available) and the h-models using isoparametric three dimensional solid elements. The formulation is equally effective for very slender as well as deep beams since no assumptions are made regarding such conditions during the formulation. 相似文献
International Journal of Control, Automation and Systems - In this paper, we consider the fuzzy moving sliding surface anti-sway control problem for container cranes. We first introduce the dynamic... 相似文献
Given a collection of parameterized multi-robot controllers associated with individual behaviors designed for particular
tasks, this paper considers the problem of how to sequence and instantiate the behaviors for the purpose of completing a
more complex, overarching mission. In addition, uncertainties about the environment or even the mission specifications
may require the robots to learn, in a cooperative manner, how best to sequence the behaviors. In this paper, we approach this
problem by using reinforcement learning to approximate the solution to the computationally intractable sequencing problem,
combined with an online gradient descent approach to selecting the individual behavior parameters, while the transitions
among behaviors are triggered automatically when the behaviors have reached a desired performance level relative to a task
performance cost. To illustrate the effectiveness of the proposed method, it is implemented on a team of differential-drive
robots for solving two different missions, namely, convoy protection and object manipulation. 相似文献
The satellite-based regression model provides the data model that identifies water quality for inland and coastal waters. However, the satellite regression usually depends on the selection of observation, satellite data, and model type. A resampling simulation technique, such as sequential simulation using geographically weighted regression (GWR simulation), can be applied in generating multiple realizations for water quality estimation to reduce the sampling effect and consider spatial heterogeneity. Traditional models often result in considerable underestimation in extreme observations. The GWR simulation provides the best goodness of fit and spatial varying relationship between observed water quality and remote sensing considering parameter outlier and noise removal for parameter stability. This simulation model can increase the sampling diversity from various observations and reduce the neighboring effects of observations using outlier and noise removal. The model that handles spatial uncertainty and heterogeneity is a novel tool for inferring the characteristics of water quality from a series of sample subsets.
Microsystem Technologies - This paper reports a design and fabrication process of a micro cam system (MCS) with a flat-faced translating follower. The cam rim with cover diameter of 2.4 mm... 相似文献
This paper presents a three-electrode capacitive fluidic sensor for detecting an air bubble inside a fluidic channel such as blood vessels, oil or medical liquid channels. The capacitor is designed and fabricated based on a printed circuit board (PCB). The electrodes are fabricated by using copper via structure through top to bottom surface of the PCB. A plastic pipe is layout through the capacitive sensor and perpendicular to the PCB surface. Capacitance of sensor changes when an air bubble inside fluidic flow cross the sensor. The capacitance change can be monitored by using a differential capacitive amplifier, a lock-in amplifier, filter and an NI acquisition card. Signal is processed and calculated on a computer. Air bubble inside the liquid flow are detected by monitor the unbalance signal between the three electrode potential voltages. Output voltage depends on the volume of the air bubble due to dielectric change between capacitor’s electrodes. Output voltage is up to 53 mV when an 2.28 mm3 air bubble crosses the sensing channel. Air bubble velocity can be estimated based on the output pulse signal. This proposed fluidic sensor can be used for void fraction detection in medical devices and systems; fluidic characterization; and water–gas, oil–water and oil–water–gas multiphase flows in petroleum technology. That structure also can apply to the micro-size for detecting in microfluidic to monitor and control changes in microfluidic channels. 相似文献