Hybrid polymer matrix composite (UHMWPE-HPMC) as solid particle erosion resistant coating for sharp pipe elbows using numerical simulation and experimental analysis

A hybrid polymer matrix composite coating, resistant to solid particle erosion inside sharp elbows, consisting interlocking chains of molecules with the ability to deflect the surface impact stress and to uniformly distribute stresses along the hard-ceramic reinforcement mixture surface was developed. Formulated mixture of ceramic reinforcement particles mixtures (alumina, tungsten carbide, and silicon carbide) with polymer coupling agents; to increase adhesion to the metal surface, led to 600–700 HVN in ternary and 500–550 HVN in binary mixtures. This behavior coincides with high shear strength of 70–76 MPa, Young's and shear modulus of 8.86 and 13.4 GPa in ternary 15%Al₂O₃-5%WC-10%SiC, respectively. The low erosion weight loss of 0.1% and small coefficient of friction near 0.18 indicates the significant wear resistance of the ternary sample. The electron microscopic micrographs determined the dense smooth coating surfaces with adhesive interfaces with the substrate.     

Mathematical Modeling the Drying of Poplar Wood Particles in a Closed-Loop Triple Pass Rotary Dryer

Closed-loop drying systems are an attractive alternative to conventional drying systems because they provide a wide range of potential advantages. Consequently, type of drying process is attracting increased interest. Rotary drying of wood particles can be assumed as an incorporated process involving fluid–solid interactions and simultaneous heat and mass transfer within and between the particles. Understanding these mechanisms during rotary drying processes may result in determination of the optimum drying parameters and improved dryer design. In this study, due to the complexity and nonlinearity of the momentum, heat, and mass transfer equations, a computerized mathematical model of a closed-loop triple-pass concurrent rotary dryer was developed to simulate the drying behavior of poplar wood particles within the dryer drums. Wood particle moisture content and temperature, drying air temperature, and drying air humidity ratio along the drums lengths can be simulated using this model. The model presented in this work has been shown to successfully predict the steady-state behavior of a concurrent rotary dryer and can be used to analyze the effects of various drying process parameters on the performance of the closed-loop triple-pass rotary dryer to determine the optimum drying parameters. The model was also used to simulate the performance of industrial closed-loop rotary dryers under various operating conditions.     

Minimization of exceptional elements and voids in the cell formation problem using a multi-objective genetic algorithm

Cell formation problem is the main issue in designing cellular manufacturing systems. The most important objective in the cell formation problem is to minimize the number of exceptional elements which helps to reduce the number of intercellular movements. Another important but rarely used objective function is to minimize the number of voids inside of the machine cells. This objective function is considered in order to increase the utilization of the machines. We present a bi-objective mathematical model to simultaneously minimize the number of exceptional elements and the number of voids in the part machine incidence matrix. An ε-constraint method is then applied to solve the model and to generate the efficient solutions. Because of the NP-hardness of the model, the optimal algorithms can not be used in large-scale problems and therefore, we have also developed a bi-objective genetic algorithm. Some numerical examples are considered to illustrate the performance of the model and the effectiveness of the solution algorithms. The results demonstrate that in comparison with the ε-constraint method, the proposed genetic algorithm can obtain efficient solution in a reasonable run time.     

New,Non‐quinone Fluorogeldanamycin Derivatives Strongly Inhibit Hsp90

Streptomyces hygroscopicus is a natural producer of geldanamycin. Mutasynthetic supplementation of an AHBA‐blocked mutant with all possible monofluoro 3‐aminobenzoic acids provided new fluorogeldanamycins. These showed strong antiproliferative activity and inhibitory effects on human heat shock protein Hsp90. Binding to Hsp90 in the low nanomolar range was determined from molecular modelling, AFM analysis and by calorimetric studies.     

Experimental investigation of tornado-like vortex dynamics with swirl ratio: The mean and turbulent flow fields

An experimental simulation of tornado-like vortices is conducted in a small tornado vortex simulator in order to study the effect of swirl ratio on flow characteristics. Particle Image Velocimetry (PIV) method is employed to quantitatively determine the tornado-vortex velocity field for swirl ratios ranging from 0.08 to 1. The radial and tangential components of velocity as well as the core radius of the tornado increase with increase in swirl ratio. The location of the maximum radial and tangential velocities is adjacent to the ground where the tornado vortex interacts with the surface. The values of normal and shear turbulent stresses indicate the existence of a laminar core for small swirl. As expected the shear stresses increase with swirl ratio as the vortex becomes turbulent. The highest turbulent production corresponds to the critical case of vortex touchdown.     

Situational constraint effects on performance, affective reactions, and turnover: A field replication and extension.

Administered a demographic questionnaire, ability and personality tests, and measures of job performance, satisfaction, turnover, and situational constraints to 731 20–65 yr old store managers, 555 22–62 yr old supervisors, and 164 25–60 yr old district managers from the same company. Results replicate previous laboratory findings and show that higher situational constraints were associated with lower employee performance. The performance ratings given to managers facing the most severe situational constraints were significantly poorer than those received by managers dealing with lower levels of constraints. The presence of situational constraints is associated with employees expressing greater dissatisfaction and frustration. The group facing the highest level of situational constraints had the highest level of turnover. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring the recovery of fatigue damage in bituminous mixtures: the role of rest periods

Recovery capability of bituminous materials plays a significant role in the development of new technologies for extending the service life of asphalt pavements. This capability originates from various phenomena such as thixotropy, cooling, relaxation of hardening, or healing. However, their real effect on mechanical response is not clear. This article aims to investigate how rest periods (RPs) available between traffic loads can contribute to the damage recovery of bituminous materials. For this purpose, different types and durations of RPs were applied during the laboratory evaluation of fatigue resistance of these materials using the University of Granada Fatigue Asphalt Cracking Test method. The results indicate that the addition of RPs to the loading regime could lead to an extension in the fatigue life of bituminous materials. Additionally, an increase in the RP duration showed a positive impact on the resistance of the materials against cyclic loading. Nonetheless, these benefits are not only related to the recovery of lost properties during RPs, but also a growth in the amount of plastic deformations as a result of the applying RPs could delay the appearance of damages (i.e. cracking). Consequently, the bituminous material can tolerate a higher number of load cycles during fatigue test.     

Metal‐Based Nanomaterials in Biomedical Applications: Antimicrobial Activity and Cytotoxicity Aspects

Microbial colonization on material surfaces is ubiquitous. Biofilms derived from surface‐colonized microbes pose serious problems to the society from both an economical perspective and a health concern. Incorporation of antimicrobial nanocompounds within or on the surface of materials, or by coatings, to prevent microbial adhesion or kill the microorganisms after their attachment to biofilms, represents an important strategy in an increasingly challenging field. Over the last decade, many studies have been devoted to preparing meta‐based nanomaterials that possess antibacterial, antiviral, and antifungal activities to combat pathogen‐related diseases. Herein, an overview on the state‐of‐the‐art antimicrobial nanosized metal‐based compounds is provided, including metal and metal oxide nanoparticles as well as transition metal nanosheets. The antimicrobial mechanism of these nanostructures and their biomedical applications such as catheters, implants, medical delivery systems, tissue engineering, and dentistry are discussed. Their properties as well as potential caveats such as cytotoxicity, diminishing efficacy, and induction of antimicrobial resistance of materials incorporating these nanostructures are reviewed to provide a backdrop for future research.     

Advances in Antimicrobial Microneedle Patches for Combating Infections

Skin infections caused by bacteria, viruses and fungi are difficult to treat by conventional topical administration because of poor drug penetration across the stratum corneum. This results in low bioavailability of drugs to the infection site, as well as the lack of prolonged release. Emerging antimicrobial transdermal and ocular microneedle patches have become promising medical devices for the delivery of various antibacterial, antifungal, and antiviral therapeutics. In the present review, skin anatomy and its barriers along with skin infection are discussed. Potential strategies for designing antimicrobial microneedles and their targeted therapy are outlined. Finally, biosensing microneedle patches associated with personalized drug therapy and selective toxicity toward specific microbial species are discussed.     

Effect of surface modification of fibers on the medium density fiberboard properties

Surface modification of mixed hardwoods fibers by sodium hydroxide (NaOH) was conducted to investigate the effect of chemical treatment on the fiber properties along with physico-mechanical characteristics of the medium density fiberboard (MDF). The results indicated that the NaOH treatments can dissolve a portion of hemicelluloses and almost all amount of extractives from the fibers, but it was not strong enough to remove the lignin thoroughly. The FTIR results illustrated that chemical changes can occur during the various NaOH treatments of the fibers. X-ray diffraction analysis revealed that the crystallinity of the studied fibers increased after the alkaline treatment. Investigation of mechanical properties of the MDF showed that modulus of rupture and internal bond strength of the treated samples were decreased compared to the control ones. In addition, water absorption and thickness swelling of treated boards were higher than that of untreated samples. This study indicated that the physico-mechanical properties of the boards were negatively affected by the NaOH treatment.