Analytical and Numerical Solutions of Boundary Value Problems for the Regularized 13 Moment Equations

Abstract. Classical hydrodynamics-the laws of Navier-Stokes and Fourier-fails in the description of processes in rarefied gases. For not too large Knudsen numbers, extended macroscopic models offer an alternative to the solution of the Boltzmann equations. Anlytical and numerical solutions show that the regularized 13 moment equations can capture all important linear and non-linear rarefaction effects with good accuracy

A hybrid of Delphi, AHP and TOPSIS Methods for project portfolio management

Due to the importance and complexity of the portfolio management issue, over 100 different techniques have already been presented. In general, the final result of these tools is to create a prioritized list of the projects that must be selected for allocating resources. The use of financial strategies may be misleading in some cases, and it is necessary to combine these methods with other methods such as strategic approaches in order to guarantee a balanced portfolio toward the organizational strategies. On the other, categorizing projects into different baskets allows the organizations to select, evaluate and prioritize the projects in a subset using a set of similar criteria and techniques. In this article, by choosing agriculture sector as a case study, an attempt has been made to study the evaluation, ranking and management of projects with investment classifying strategy of the projects using Delphi, TOPSIS and AHP methods. The results reveal that in similar cases we can use the presented model by determining the type of activity and investment and localization of the indexes

Experimental and numerical investigation of a method for strengthening cold-formed steel profiles in bending

Perforated cold-formed steel (CFS) beams subjected to different bending scenarios should be able to deal with different buckling modes. There is almost no simple way to address this significant concern. This paper investigates the bending capacity and flexural behavior of a novel-designed system using bolt and nut reinforcing system through both experimental and numerical approaches. For the experiential program, a total of eighteen specimens of three types were manufactured: a non-reinforced section, and two sections reinforced along the upright length at 200 mm and 300 mm pitches. Then, monotonic loading was applied to both the minor and major axes of the specimens. The finite element models were also generated and proved the accuracy of the test results. Using the proposed reinforcing system the flexural capacity of the upright sections was improved around either the major axis or minor axis. The 200 mm reinforcement type provided the best performance of the three types. The proposed reinforcing pattern enhanced flexural behavior and constrained irregular buckling and deformation. Thus, the proposed reinforcements can be a very useful and cost-effective method for strengthening all open CFS sections under flexural loading, considering the trade-off between flexural performance and the cost of using the method

Investigation of a method for strengthening perforated cold-formed steel profiles under compression loads

Cold-formed steel (CFS) storage rack structures are extensively used in various industries to store products in safe and secure warehouses before distribution to the market. Thin-walled open profiles that are typically used in storage rack structures are prone to loss of stability due to different buckling modes such as local, distortional, torsional and flexural, or any interaction between these modes. In this paper, an efficient way of increasing ultimate capacity of upright frames under compression load is proposed using bolts and spacers which are added externally to the section with certain pitches along the height. Hereinto, experimental tests on 81 upright frames with different thicknesses and different heights were conducted, and the effect of employing reinforcement strategies was examined through the failure mode and ultimate load results. Non-linear finite element analyses were also performed to investigate the effect of different reinforcement spacing on the upright performance. The results showed that the reinforcement method could restrain upright flange and consequently increase the distortional strength of the upright profiles. This method can also be effective for any other light gauged steel open section with perforation. It was also observed that the reinforcement approach is much more useful for short length upright frames compared to the taller frames

Hemato-immunological, serum metabolite and enzymatic stress response alterations in exposed rainbow trout (Oncorhynchus mykiss) to nanosilver

The aim of present study was to investigate the effects of sub-lethal concentrations of silver nanoparticles (AgNP) on hematological parameters, differential tests of white blood cells, serum metabolite parameters, serum enzymes activity and serum ions in rainbow trout, Oncorhynchus mykiss. Healthy rainbow trout, were exposed to sub-lethal concentrations (0, 1.5 and 2.5 ppm) of nanosilver for 14 days. RBC, WBC and Hct levels were significantly (P<0.05) increased in exposed groups. Within the white blood cells, only neutrophils showed a significant increase at 7 and 14 days post exposure (P<0.05). Serum triglyceride, total serum protein, albumin and globulin levels were decreased (P<0.05) in exposed fish, however, cholesterol levels increased in the 2.5 ppm group at 7 days after exposure (P<0.05). Cortisol and glucose increased significantly at 7 and 14 days of exposure in both concentrations of AgNPs (P<0.05). Decreases in serum ions level were observed, although reduction in chloride ions occurred earlier and more severe than other measured parameters (P<0.05). Elevation in serum ALP, LDH, ALT and AST enzymes were observed during the experiment (P<0.05), although SOD and CAT activity were significantly decreased in exposed groups (P<0.05). The results revealed that AgNP can affect the hematological, serum metabolite and enzymatic parameters of O. mykiss, as well as AgNP exposure induce a general oxidative stress response in O. mykiss

A novel and cost-effective double-capsule nanocomposite coating based on carbon hollow spheres with self-healing performance for corrosion protection

The ability of a cost-effective self-healing nanocomposite system to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this research, a self-healing epoxy coating was fabricated by incorporation of carbon hollow spheres (CHSs) doped separately with epoxy and polyamine as film forming agents. Graphene-based CHSs were synthesized via silica templating method in presence of sucrose as a carbon precursor. After encapsulation of epoxy and polyamine agents in CHSs denoted as Ep-DCSs and Am-DCSs, respectively, 10 wt. % and 5 wt. % of Ep-DCSs and Am-DCSs were introduced in an epoxy matrix. The final nanocomposite coating was applied on the surface of mild steel substrates. A blank epoxy coating was also used as a control sample. The synthesized CHSs were characterized before and after the silica core removal using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The CHSs loaded with the film forming agents were evaluated using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the protective and self-healing properties of the coatings were studied using electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and salt spray testing. The obtained results showed that the fabricated nanocomposite epoxy coating can heal appropriately the scratches applied on the surface of the coating barricading the accessibility of corrosive species to the metal substrate (Figure 1). Please click Additional Files below to see the full abstract

Comparison of outcome following dacryocystorhinostomy with or without silicon stent appliance; a randomized clinical trial

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Limited knowledge of chronic kidney disease and its main risk factors among Iranian community: an appeal for promoting national public health education programs

Background: The aim of this survey was to explore the baseline knowledge of the Iranian community about Chronic Kidney Disease (CKD) definition and its two main risk factors, i.e. diabetes and hypertension. This study also introduced a model of public education program with the purpose of reducing the incidence of CKD in high-risk groups and thereby decreasing the economic burden of CKD in Iran. Methods: This cross-sectional study was conducted on world kidney day 2013 in Isfahan, Iran. Self-administered anonymous questionnaires evaluating the knowledge of CKD and its risk factors were distributed among subjects who participated in a kidney disease awareness campaign. Chi-square test and logistic regression analysis were used to examine the differences in the level of knowledge across different socio-demographic groups. Results: The questionnaires were completed by 748 respondents. The majority of these respondents believed that “pain in the flanks” and “difficulty in urination” was the early symptoms of CKD. Roughly, 10.4% knew that CKD could be asymptomatic in the initial stages. Only 12.7% knew diabetes and 14.4% knew hypertension was a CKD risk factor. The respondents who had a CKD risk factor (i.e. diabetes and/or hypertension) were significantly more likely than respondents without CKD risk factor to select “unmanaged diabetes” [Odds Ratio (OR)= 2.2, Confidence Interval (CI) ( 95%) : 1.4–3.6] and “unmanaged hypertension” [OR= 1.9, CI( 95%) : 1.2–3.0] as “very likely to result in CKD”. No more than 34.6% of all respondents with diabetes and/or hypertension reported that their physician has ever spoken with them about their increased risk for developing CKD. Conclusion: The knowledge of Iranian population about CKD and its risk factors is low. Future public health education programs should put efforts in educating Iranian community about the asymptomatic nature of CKD in its initial stages and highlighting the importance of regular renal care counseling. The high-risk individuals should receive tailored education and be encouraged to adopt lifestyle modifications to prevent or slow the progression of CK

General Thermal Texturization Process of MoS_2 for Efficient Electrocatalytic Hydrogen Evolution Reaction

Molybdenum disulfide (MoS_2) has been widely examined as a catalyst containing no precious metals for the hydrogen evolution reaction (HER); however, these examinations have utilized synthesized MoS_2 because the pristine MoS_2 mineral is known to be a poor catalyst. The fundamental challenge with pristine MoS_2 is the inert HER activity of the predominant (0001) basal surface plane. In order to achieve high HER performance with pristine MoS_2, it is essential to activate the basal plane. Here, we report a general thermal process in which the basal plane is texturized to increase the density of HER-active edge sites. This texturization is achieved through a simple thermal annealing procedure in a hydrogen environment, removing sulfur from the MoS_2 surface to form edge sites. As a result, the process generates high HER catalytic performance in pristine MoS_2 across various morphologies such as the bulk mineral, films composed of micron-scale flakes, and even films of a commercially available spray of nanoflake MoS_2. The lowest overpotential (η) observed for these samples was η = 170 mV to obtain 10 mA/cm_2 of HER current density