Fabrication and characterization of microencapsulated PA with SiO<Subscript>2</Subscript> shell through sol–gel synthesis via sodium silicate precursor

In the present study, the microencapsulated phase change material with palmitic acid as core and inorganic SiO₂ shell was successfully fabricated by a sol–gel method in alkaline medium via sodium silicate precursor. The chemical compositions, crystalloid phase, microstructure and morphology of PA@SiO₂ microcapsule were studied by Fourier transform infrared spectroscopy, X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. Differential scanning calorimetry and thermogravimetric analysis were used to determine the thermal properties and thermal stability of microcapsules, respectively. According to the XRD and FT-IR results, all the characteristic peaks of PA and SiO₂ were observed and there is no chemical reaction between them. Scanning electron microscopy images indicated that the microcapsule synthesized in pH 11 had a perfect spherical shape with smooth surfaces compared with other samples, and transmission electron microscopy images confirm that the PA have been well encapsulated by SiO₂. Differential scanning calorimetry analysis showed that the microcapsules indicated similar phase change behaviors as those of pristine PA, which melt at 67.2?°C with a latent heat of 111.2 J/g and freezing at 56.5?°C with a latent heat of 103.2 J/g. TGA analysis indicated that the thermal stability of the PA was also improved due to the protection of SiO₂ shell toward the encapsulated PA.     

Moisture and heat transfer in hybrid weft knitted fabric with artificial intelligence

One of the most important properties of clothes is their ability to help the body's thermal system to keep the body temperature in its natural range, even if the environmental conditions or physical activities are outside the body's ideal range. Perspiring is one of the most important effects of physical activities in warm weather for shedding the body's excessive heat. Therefore, the basic requirement of a fabric worn next to the skin is to transfer this moisture to the atmosphere to reach comfort through the avoidance of a feeling of wetness and clamminess and also through the generation of a situation for the best surface evaporation of moisture. The main goal of this study was to achieve a kind of fabric that guarantees comfort for the body by good heat and moisture transport. To achieve this goal, a group of double‐surface fabrics containing hydrophilic and hydrophobe fibers were knitted, and their simultaneous heat and moisture transport was evaluated with the help of a perspiration‐simulation machine; the results were analyzed as transfer process plots. Also, the transmission of heat and moisture was evaluated for all of the samples by differential modeling as an artificial neural network. Effective parameters on heat and moisture transfer were taken into consideration with modeling and statistical methods. The results were analyzed to find a suitable fabric with optimum comfort. The final results showed that a fabric made of micropolyester filaments and cotton yarns on the bottom and top surfaces, respectively, had the best heat and moisture transfer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Computational modelling of unsaturated flow of liquid in heap leaching—using the results of column tests to calibrate the model

Unsaturated flow of liquid in a bed of uniform and spherical ore particles is studied numerically and experimentally. An unsteady and two-dimensional model is developed based on the mass conservation equations of liquid phase in the bed and in the particles. The model equations are solved using a fully implicit finite difference method giving the distribution of the degree of saturation in the particles and in the bed and the vertical velocity of flow in the bed, as well as, the effect of periodic infiltration on the above distributions. To calibrate the computational model, several column tests are performed using periodic infiltration of water on 40 cm high columns composed of ore having particles smaller than 25 mm. The numerical analysis shows that (a) the results obtained from numerical modelling under the same operating conditions as used for column tests, are in good agreement with those from experimental procedure, (b) the degree of saturation of the bed and the time required to reach steady state conditions depend on the inflow of water and intrinsic permeability of the bed and (c) the velocity fluctuations and the fluctuations of the degree of saturation in the bed depend on the inflow of water, period of infiltration, height and intrinsic permeability of the bed.     

Apical hypertrophic cardiomyopathy of the Japanese type coexistent with a coronary muscle bridge. A case report and review

We describe the case of a 21-year-old Italian male who presented with giant negative T-waves and left ventricular hypertrophy on the electrocardiogram suggestive of apical hypertrophic cardiomyopathy. Clinically, he suffered from new onset of exertional angina, dyspnea and palpitations during soccer playing or heavy exercise beginning one week before admission. Echocardiography and cardiac catheterization conformed the rare combination of a nonobstructive apical hypertrophic cardiomyopathy of the "Japanese" type coexistent with an extensive muscular bridge involving almost the entire anterior interventricular branch of the left coronary artery. Although the patient complained of exertional angina pectoris, absence of objective evidence of myocardial ischemia by means of treadmill stress test, exercise thallium scan, dobutamine stress echocardiography as well as atrial pacing stress emphasized the benign nature of this complex anomaly.     

Shear behavior of soft-matrix composites reinforced with polyethylene loop-formed fibers

A soft material is defined as a substance that its mechanical properties depend on ambient conditions, e.g. external stresses, temperature, etc. Since composite structures with soft-material matrix do not have adequate pullout resistance with flat-type reinforcements such as fibers, there are a large number of cases where reinforcements with passive resistance are used in conjunction with ordinary fibers. Randomly distributed loop-formed fiber (RDLFF) is a novel idea to reinforce these types of composite materials. Therefore, the main aim of this paper is to use polyethylene RDLFF elements in soft-matrix composites. First, shear behavior of polyethylene RDLFF-reinforced composite was modeled with the use of force-equilibrium method, and then it was compared with that of flat-polyethylene fiber. In the next step, a set of laboratory direct shear tests was conducted on different samples including the neat treatment, polyethylene RDLFF and polyethylene fiber-reinforced composites. Thus, it was shown that through the shearing, a loop-formed fiber has two reinforcing effects including the “fiber effect” and the “loop effect”. The “loop effect” is the main advantage of using RDLFF to ordinary fibers at the same orientation and it is also the major difference in using the two kinds of fibers. The proposed model also indicated that the number of looped-form fibers, fiber diameter, coefficient of friction between fiber and matrix, loop dimension, tensile modulus of fiber, shearing zone and vertical compressive stress determine the shear resistance of RDLFF-reinforced composite. Therefore, the proposed model adequately predicts the shear behavior of soft-matrix composites reinforced with fibers and/or loop-formed fibers.     

Prediction of fabric handle value using ordinal regression model

Bed sheet fabric as a kind of home textile has been used since many years ago. Bed sheet is very significant because of being in direct contact with body consecutively for a long period of time. Bed sheet surplus qualitative parameters such as fiber substance, method of printing, finishing, etc., have a significant parameter called handle. In this paper, we proceeded to consider the relationship between fabric handle as a qualitative parameter and physical parameters which influenced the fabric handle using statistical modeling. The statistical model used was ordinal regression model. The modeling was done by SPSS V.19 software. We used 15 bed sheet fabrics. For subjective evaluation of 15 bed sheet fabrics, we selected 55 persons randomly as sample members according to Cochran’s formula. Population was selected from senior BS students and MS students at Isfahan University of Technology (IUT). We asked persons to classify bed sheet fabrics based on their preference of fabric handle from 1 (lowest) to 5 (highest). Physical parameters values were obtained through standard experiments. Finally, we analyzed obtained data through SPSS V.19 using ordinal regression model. Results showed a satisfying match between extracted data from the software and the real data from person’s evaluation.     

An investigation into the reaction behavior of tubular braids due to internal pressure

Braiding has many applications in different industries as an internal pressurized cylinder. In these conditions, a sustainable structure without any wrinkling and unevenness is quite necessary. Using thin wall structures with closed ends and under internal pressures as a braid is addressed in the present study. With the use of a silicon vessel as the core, the braids with different angles and weavings were produced. They were exposed to internal pressure from zero to failure point. All stages of change in the shapes of the samples were recorded by a camera and the pressure–diameter results were extracted in 10 s once. In this research, the authors elaborate on the theory of stress and wrinkling moment created in these braids under internal pressure, and then they develop a new testing method by which they compare the obtained results with the theory. Following that, the relationship between the angle and failure pressure is investigated to determine the best braid angle in braiding used as thin wall structures. In the braid angle of ± 55°, all the forces created in braid due to internal pressure are along with strands direction and the increase in the cylinder diameter of the braid has been completely controlled depending on strands’ elongation. The rate of diameter increase in the angles of less than ± 55° is fast, especially in pressures close to failure pressure. However, in the bigger angles, the elongation or, in other words, the diameter decrease is observed in braiding.     

Aspect ratio effects of an adiabatic rectangular obstacle on natural convection and entropy generation of a nanofluid in an enclosure

In the present study, aspect ratio (AR) effects of a centered adiabatic rectangular obstacle numerically investigated on natural convection and entropy generation in a differentially heated enclosure filled with either water or nanofluid (Cu-water). The governing equations are solved numerically with finite volume method using the SIMPLER algorithm. The study has been done for Rayleigh numbers between 10³ and 10⁶, the aspect ratio of 1/3, 1/2, 1, 2 and 3 and for base fluid as well as nanofluid. It is found that, using the nanofluid leads to increase the flow strength, average Nusselt number and entropy generation and decrease the Bejan number especially at high Rayleigh numbers. At low Rayleigh numbers entropy generation is very low. By increasing Rayleigh number, entropy generation and Bejan number increases. It is observed that the viscose entropy generation is more considerable than the thermal entropy generation and has dominant role in total entropy generation. The maximum entropy generation occurs at AR = 1/3 and 3 and the minimum entropy generation occurs at AR = 1 and 1/2. It is observed that the effect of AR on Nusselt number, entropy generation and Bejan number depends on Rayleigh number.     

Design of flexible plant layouts

In this paper, we present an approach for the design of plant layouts in stochastic environments. We consider systems where the, product mix and product demand are subject to variability and where duplicates of the same department type may exist in the same facility. In contrast to a job shop layout, we allow these duplicates to be placed in non-adjacent locations on the plant floor and for flow allocation between pairs of individual departments to be made as a function of the layout and the product demand realization. We present a scenario-based procedure that iteratively solves for layout and flow allocation. We show that having duplicates of the same departments, which can be strategically located in different areas of the plant floor, can significantly reduce material handling cost while effectively hedging against fluctuations in flow patterns and volumes. We show that the effect of duplication is of the diminishing kind, with most of the cost reduction occurring with relatively few duplicates. We also show that the quality of the obtained layouts can be quite insensitive to inaccuracies in estimating demand scenario probabilities.     

Influence of yarn texture on the mechanical properties of textile composite castings

In this research, mechanical properties of textile composite castings used for immobilizing a damaged limb have been studied. For this purpose, a fabric composite was made using a new knitted fabric and textured yarn for the first time. This composite possesses suitable mechanical properties. Mechanical and physical properties such as tensile, bending, and thickness of materials were studied. Results indicate that the use of textured yarns instead of flat yarns increases the amount of resin retainment in fabrics. Furthermore, it decreases tensile modulus and bending modulus of fabrics. Properties of the castings produced were compared with a valid commercial casting. Sample with textured warp and weft, with linear density of 1,500 den of weft, had the best physical and mechanical properties among produced samples. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers