Hypothesis: Dispersion polymerization has proven to be a useful technique for preparing uniform polymer particles in the micrometer size range. The polymer synthesized with this method can be utilized in various applications. The knowledge of the effect of process parameters on the droplets size and droplets size distribution is very important. As a result, this study was designed to investigate the effect of processing parameters on the droplets size and droplets size distribution of polystyrene (PS) microspheres synthesized by dispersion polymerization. Method: Dispersion polymerization was performed in a sealed glass tube at 65° C for 24 h. The effect of solvent type, stabilizer and co-stabilizer concentration on the droplets size and droplets size distribution of polystyrene microspheres was investigated by scanning electron microscopy (SEM) and Image J software. Also, the effect of a mixture of solvents and co-stabilizer concentration on the molecular weight and molecular weight distribution (PDI) of polystyrene was studied by gel permeation chromatography (GPC). Finding: The morphology results revealed that the aliphatic length of polar solvents affects the droplet size and droplet size distribution. At first, increase in the aliphatic length of polar solvent enhanced droplet size and droplet size distribution of polystyrene microspheres. Further increase in aliphatic length of polar solvent led to decrease in the droplet size and droplet size distribution. Addition of water to ethanol led to reduced droplets size compared to pure ethanol and enhancement in molecular weight and PDI. In addition to this, the presence of co-stabilizer did not change the droplet size and its distribution however, it increased molecular weight and PDI of polystyrene microspheres.

This paper suggests a method for designing PSS to damp multi-machine power system oscillations. The method is based on robust control theory. First, the conventional method for designing robust controller in LMI framework is illustrated. Then, the suggested method is given, in which, a PID output feedback controller is tuned using the LMI approach. Mostly, the classical methods are used to tune a PSS, but in this paper a robust approach is investigated to guarantee the robustness of the given PSS. The performance of the controller is tested on a sample power system. Simulation results show the effectiveness, robustness, and good performance of the suggested controller.

Literature published TerraZyme stabilization case studies are analyzed rationally for evaluating the performance of TerraZyme as a stabilizer. As a measure of the degree of stabilization, the percentage variation in soil index and engineering properties induced by enzyme treatment for various soil types are investigated. The literature shows inconsistent enzyme stabilization results. The causes of the inconsistency in test results and factors affecting the effectivity of enzyme stabilization are elaborated. The effect of soil characteristics on the efficacy of enzyme stabilization is analyzed. The results of enzyme treatment on soil properties such as Atterberg limits and indices, optimum moisture content, maximum dry density, unconfined compressive strength and California bearing ratio, for various soil groups with different enzyme doses and conditions of curing are also studied. An attempt has been made to quantify the attribute variation of treated soils, establishing, the underlying reasons, for the effectivity of enzyme stabilization and its performance within and among various soil groups. The effect of enzymatic treatment on each soil group is also classified. The research emphasizes the necessity of an elaborate organized study on the enzyme and soil characterization, to have a better knowhow of the effectiveness of enzymatic stabilization.

In this paper the inversion of gravity data using L1–norm stabilizer is considered. The inversion is an important step in the interpretation of data. In gravity data inversion, the goal is to estimate density and geometry of the unknown subsurface model from a set of known observation measured on the surface. Commonly, rectangular prisms are used to model the subsurface under the survey area. The unknown density contrasts within each prism are the parameters which should be estimated. The inversion of gravity data is an example of underdetermined and ill-posed problem, i.e. the solution can be non-unique and unstable. Thus, in order to find an acceptable solution regularization should be imposed. Solution is usually obtained by minimizing a global objective function consisting of two terms, data misfit and the regularization term. Data misfit measures how well an obtained model can reproduce the observed data. Usually, it is assumed noise in gravity data is Gaussian, therefore a L2–norm measure of the error between observed and predicted data is well suited for data misfit. There are several choices for a stabilizer, depends on type of features one wants to see from inverted model. A typical choice is a L2 –norm of a low-order differential operator applied to the model, which also a priori information and depth weighting can be incorporated (Li and Oldenburg, 1996). In this case the objective function is quadratic, then minimization of the function results a linear system to be solved. However, the models recovered in this way are characterized by smooth feature which are not always consistent with the real geological structures. There are situations in which the sources are localized and separated by sharp, distinct interfaces. To deal with this problem, during last decades, researchers have proposed a few types of stabilizer. Last and Kubik (1983) presented a compactness criterion for gravity inversion that seeks to minimize the area (or volume in 3D) of the causative body. Portniaguine and Zhdanov (1999) based on this stabilizer, who named the minimum support (MS), developed the minimum gradient support (MGS) stabilizer. For both constraint, the regularization term can be written as the weighted L2–type norm of the model. Therefore, the problem of the minimization of the objective function can be treated same as conventional Tikhonov functional. The only difference is that a priori variable weighting matrix for model parameters incorporated in the regularization term. Thus the Iteratively Reweighted Least Square (IRLS) algorithm is required to solve the problem. Other possibility for stabilizer is the minimization of the L1-norm of model or gradient of model, the latter indicates total variation regularization. The L1–norm stabilizer allows occurrence of large elements in the inverted model among mostly small values. Therefore, it can be used to obtain sharp boundaries and blocky features. Although the L1–norm stabilizer has favorable properties, in reconstruction of sparse models, its numerical implementation in a minimization problem can be difficult because its derivatives with respect to an element is not defined at zero. To overcome this difficulty, in this paper, the L1–norm stabilizer is approximated by a reweighted L2 –norm term. The algorithm is extended to gravity inverse problem, which needs depth weighting and other priori information to be included in the objective function. For estimating the regularization parameter, which balances between two terms of objective function, the Unbiased Predictive Risk Estimator (UPRE) method is used. The solution of the resulting objective functional is found using Generalized Singular Value Decomposition (GSVD), also provides for efficient determination of the regularization parameter at each iteration. Simulation using synthetic data of a dipping dike demonstrates that the method is capable to reconstruct focused image, boundaries and slop of the reconstructed model are close to those of the original model. The method is applied on gravity data acquired over the Gotvand dam site, in the south-west of Iran. The results show rather good agreement with those obtained from the boreholes.

Background and Objectives: Mulching is one of the most common ways to soil stabilization, prevent wind erosion and control dusts. Some types of mulches is not economically practical choices, thus use of inexpensive and safe industrial wastes in the mulch compositions have both economically and environmentally important (waste recycling). Therefore, a key objective of this research is to use two types of industrial waste for preparation of mulch. Since Proctor method has been considered to test and compare the strength of mulches, so another purpose of this research is simplification of Proctor method to estimate the strength of soil stabilizer mulches under the influence of wind erosion.Materials and Methods: Based on the results of previous studies and pre-treatments, some mulches were tested. These mulches were non-living composed of different percentages of stone powder, converter sludge, clay soil and sandy soil. Instron device was used to measure the compressive strength of the mulch. Considering applying of the Proctor method for working with Instron device, simplification of the procedure was also performed. These two methods were called as “Proctor” and “simplified Proctor” methods, whose results were compared as the criterion for utilizing the simplified method. The treatments included five types of mulch in three replications, where their compressive strength was measured by the two methods of “Proctor” and “simplified Proctor” and were compared by the random factorial designs.Results: Reducing the clay percentage from 80 to 50 and increasing the percentage of sand from 20 to 50 in the treatments containing clay and sand in both methods resulted in compressive strength reduction of mulches. Increasing the percentage of the stone powder from 5 to 25 and simultaneous reduction of clay percentage from 85 to 65 together with constant percentage of converter sludge led to decreased compressive strength through the simplified Proctor method. The differences between the results of the two Proctor and simplified Proctor methods were not significant, but the simplified Proctor method had specific order in the results.Conclusion: Compressive strength reduction with reduced clay percentage and increased stone powder percentage was shown in the comparison of the treatments containing clay and stone powder through the simplified Proctor method. However, the results of the Proctor method lacked a logical order. The comparison of the treatments containing clay and sand indicated that in both methods, as the clay decreases and the sand increases, compressive strength reduced. Compressive strength test results using Instron device was compared in both simplified Proctor and Proctor methods, therefore it was shown that these two methods did not have a significant statistic difference, although orderly changes of the simplified Proctor method results was found. Considering the simplicity and time reduction in the simplified Proctor method, this method is recommended for mulch comparisons in wind erosion.

Background: Sensitization to common mold allergens is one of the major causes of allergic rhinitis and asthma. Therefore, there is a critical need for standard sensitivity tests including skin prick tests to improve the stability of fungi extracts in traditional allergenic formulations. To address this concern, the present study aimed to develop a formulation to preserve allergenic activity of mold extracts. Methods: 48 stabilizer formulations were designed and monitored for allergenic activity during a 40-days incubation period at 37 ˚ C using an ELISA. Specifically, the IgE reactivity of allergenic A. alternata extracts were examined. After establishing the most effective stabilizer formulation, we evaluated whether it could protect the allergenic activity of Alt a1, A. fumigatus, and C. herbarum using an IgE inhibition ELISA after 40 days at 37 ˚ C. Results: We demonstrated that the most effective stabilizer formulation was a glycerol-based extract containing Arg and Glu. This formulation had an equal ratio of sucrose, sorbitol and protein and was able to preserve more than 95% of allergenic A. alternata extract activity during a 40-days incubation period at 37 ˚ C. Conclusions: The present study reveals a novel formulation that is an efficient stabilizer of allergenic mold extract activity and has practical applications in mold skin prick tests, ELISAs, immunotherapies, and RAST.

In this paper, the H¥ robust control technique is presented to design a power system stabilizer. First, the H¥ standard problem is expressed and then, the modeling and stability analysis of power systems are studied. Finally, a H¥ power system stabilizer is designed and the simulation results are discussed.