A comparison between EGR and lean-burn strategies employed in a natural gas SI engine using a two-zone combustion model

Exhaust gas recirculation (EGR) strategy has been recently employed in natural gas SI engines as an alternative to lean burn technique in order to satisfy the increasingly stringent emission standards. However, the effect of EGR on some of engine performance parameters compared to lean burn is not yet quite certain. In the current study, the effect of both EGR and lean burn on natural gas SI engine performance was compared at similar operating conditions. This was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. The combustion model was validated using experimental data and a good agreement between the results was found. It was demonstrated that adding EGR to the stoichiometric inlet charge at constant inlet pressure of 130 kPa decreased power more rapidly than excess air; however, the power loss was recovered by increasing the inlet pressure from 130 kPa at zero dilution to 150 kPa at 20% EGR dilution. The engine fuel consumption increased by 10% when 20% EGR dilution was added at inlet pressure of 150 kPa compared to using 20% air dilution at 130 kPa. However, it was found that EGR dilution strategy is capable of producing extremely lower NO emission than lean burn technique. NO emission was reduced by about 70% when the inlet charge was diluted at a rate of 20% using EGR instead of excess air.     

Slender Steel Columns Strengthened Using High-Modulus CFRP Plates for Buckling Control

This paper presents the results of an experimental investigation into the behavior of slender steel columns strengthened using high-modulus (313?GPa), carbon fiber-reinforced polymer (CFRP) plates. Eighteen slender hollow structural section square column specimens, 44×44×3.2?mm, were concentrically loaded to failure. The effectiveness of CFRP was evaluated for different slenderness ratios (kL/r), namely, 46, 70, and 93. The maximum increases in ultimate load ranged from 6 to 71% and axial stiffness ranged from 10 to 17%, respectively, depending on kL/r. As kL/r reduced, the effectiveness of CFRP plates also reduced, and failure mode changed from CFRP plate crushing after occurrence of overall buckling, to debonding prior to, or just at, buckling. A simplified analytical model is proposed to predict the ultimate axial load of FRP-strengthened slender steel columns, based on the ANSI/AISC 360-05 provisions, which were modified to account for the transformed section properties and a failure criteria of FRP derived from the experimental results. It was shown that for a given FRP reinforcement ratio, there is a critical kL/r at the low end, below which FRP may not enhance the strength of the column.     

Damage Detection of FRP-Strengthened Concrete Structures Using Capacitance Measurements

In this study, a new concept for detecting air voids, water intrusion, and glue infiltration damages in fiber-reinforced polymers (FRPs)-strengthened concrete structures was developed. The concept, based on detecting the local dielectric permittivity variations, was employed to design coplanar capacitance sensors (CCSs) to detect such defects. An analytical model was used to introduce the sensor operation theory and analyze the influence of different sensor parameters on the output signals and to optimize sensor design. Two dimensional finite element (FE) simulations were performed to assess the validity of the analytical results and to evaluate other sensor design-related parameters. To experimentally verify the FE model, dielectric properties of various materials involved in FRP-strengthened concrete systems were measured. In addition, two concrete specimens strengthened with FRP laminates and containing preinduced defects were constructed and inspected in a laboratory setting. Good agreement was found between experimental capacitance measurements and those predicated by the FE simulations. The proposed CCS design, coupled with commercially available portable capacitance meters, would facilitate field implementation of the proposed technique for rapid inspection of FRP-strengthened concrete structures without the need for sophisticated data analyses usually required by other more expensive and time consuming methods.     

Inhibitory properties of camel whey protein hydrolysates toward liver cancer cells,dipeptidyl peptidase-IV,and inflammation

This report describes an investigation of camel whey protein hydrolysates (CWPH) produced by gastric and pancreatic enzymes for their in vitro antidiabetic, anticancer, and anti-inflammatory properties. Degree of hydrolysis (DH) ranged from 8.54 to 47.53%, with hydrolysates generated using chymotrypsin for 6 h displaying the highest DH. Reverse phase-HPLC analysis showed that α-lactalbumin underwent complete degradation, with no intact α-lactalbumin detected in CWPH. The CWPH displayed enhanced antidiabetic activity compared with intact whey proteins; with pepsin- and chymotrypsin-generated CWPH displaying greater inhibition of dipeptidyl peptidase IV (DPP-IV), α-glucosidase, and α-amylase compared with trypsin-generated CWPH. The highest antiproliferative effect was observed for CWPH generated by chymotrypsin for 3 h, with only 4.5 to 6.5% viable liver cancer cells (HepG2) remaining when tested at concentrations from 400 to 1,000 µg/mL. The highest anti-inflammatory activity was manifested by CWPH generated by pepsin at 6-h hydrolysis. We report enhanced antiproliferative, antidiabetic, and anti-inflammatory activities upon hydrolysis of camel whey proteins, indicating their potential utilization as bioactive and functional ingredients.     

Reinforcement of Polypropylene Composites Based on Recycled Wool or Cotton Powders

This article addresses the preparation and characterization of polymer composites of polypropylene (PP) containing recycled wool or cotton micro-powder. The PP composites were produced in a lab-scale twin-screw extruder. The recycled wool or cotton powder was obtained from wool and cotton waste fibers (from textile industry) by freeze milling technique. The amount of powder (wool or cotton) was varied from 1% to 10 %. Cotton and wool powders were homogenously distributed in the polymer matrix, as observed from scanning electron microscopic (SEM) images. Thermal, physical, and mechanical properties of the obtained composites were investigated by differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), tensile strength, dyeability as well as the moisture uptake behavior is also explored. The overall results clarify that wool or cotton powders could be used as effective reinforcing materials for the production of PP composites with enhanced properties.     

Single and multi degree of freedom analysis of steel beams under blast loading

This paper presents detailed analysis of the results of field tests on 13 full scale wide flange steel beams subjected to blast loads generated by the detonation of up to 250 kg of ANFO explosive. The experimental results are analyzed using an equivalent Single-Degree-of-Freedom (SDOF) model of a beam, which includes material nonlinearity and strain rate effects. To account for strain rate effect on beam stiffness and strength, its full moment-curvature response is determined by dividing its cross-section into a number of layers and a strain rate-dependent stress-strain relationship, based on the Cowper–Symonds strain rate model, is used to capture the nonlinear stress distribution over the section. To determine the effects of higher modes of vibration and the variation of beam mechanical properties along its length on its dynamic response, the test beams are also analyzed using a Multi-Degree-of-Freedom (MDOF) model involving beam finite elements. Each element has two nodes and three degrees of freedom and is again divided into a number of layers to capture the strain rate effect and nonlinear stress distribution over its depth. The predicted displacements and strains by the two models are compared with the corresponding experimental data and the results show that for the given beams, the time-dependant deformations, internal forces, and moments can be adequately predicted by either model because the first mode of vibration is found to dominate their response; however, the use of a constant strain rate through the so-called Dynamic Increase Factor (DIF) can lead to highly conservative estimate of the actual strength of such members.     

Construction Risks: Single versus Portfolio Insurance

Risks and uncertainties are naturally inherent in the construction industry and negatively affect contracting parties and executed projects. This paper explores the possibility of insuring against construction risks, which are beyond the control of contractors and not covered by surety policies, through single and portfolio insurance strategies. Accordingly, the writers programmed Iman and Conover’s bootstrapping method for inducing correlations using Microsoft Excel and consequently, developed a technique for pricing insurance premiums as an exotic option using Monte Carlo simulation. The aforementioned methodology was applied on a data set of five defined risks that were collected from small, medium, and large scale projects in California. Pursuant to this study, the calculated premiums for insuring against the defined risks are in line with the premiums available in market for other insurance policies. Moreover, the estimated premium for the proposed portfolio insurance product is more advantageous to contractors in both risk coverage and cost because it is well below the estimated premiums for single insurance products covering individual risks. It is foreseen that this research could open horizons for new construction related insurance products, which would significantly contribute to the efficiency of the risk management process in the construction industry.     

周期结构和均匀结构隔振器滤波特性的对比研究

采用谱有限元和传递矩阵法推导了波在均匀结构和周期结构隔振器中的传播模型,对比了均匀结构（铝）和周期结构（铝/橡胶）隔振器的滤波特性,讨论了几何尺寸和材料特性对周期结构隔振器滤波特性的影响。研究结果表明：改变周期结构单元的几何尺寸和材料特性,能将带隙频率范围扩大并延伸至低频。通过实验证实了理论模型预测的正确性。     

Structure-Activity Relationships for 5′′ Modifications of 4,5-Aminoglycoside Antibiotics

Modification at the 5’’-position of 4,5-disubstituted aminoglycoside antibiotics (AGAs) to circumvent inactivation by aminoglycoside modifying enzymes (AMEs) is well known. Such modifications, however, unpredictably impact activity and affect target selectivity thereby hindering drug development. A survey of 5’’-modifications of the 4,5-AGAs and the related 5-O-furanosyl apramycin derivatives is presented. In the neomycin and the apralog series, all modifications were well-tolerated, but other 4,5-AGAs require a hydrogen bonding group at the 5’’-position for maintenance of antibacterial activity. The 5’’-amino modification resulted in parent-like activity, but reduced selectivity against the human cytosolic decoding A site rendering this modification unfavorable in paromomycin, propylamycin, and ribostamycin. Installation of a 5’’-formamido group and, to a lesser degree, a 5’’-ureido group resulted in parent-like activity without loss of selectivity. These lessons will aid the design of next-generation AGAs capable of circumventing AME action while maintaining high antibacterial activity and target selectivity.     

Smart and Multifunctional Fiber-Reinforced Composites of 2D Heterostructure-Based Textiles

Smart and multifunctional fiber reinforced polymer (FRP) composites with energy storage, sensing, and heating capabilities have gained significant interest for automotive, civil, and aerospace applications. However, achieving smart and multifunctional capabilities in an FRP composite while maintaining desired mechanical properties remains challenging. Here, a novel approach for layer-by-layer (LBL) deposition of 2D material (graphene and molybdenum disulfide, MoS₂)-based heterostructure onto glass fiber fabric using a highly scalable manufacturing technique at a remarkable speed of ≈150 m min⁻¹ is reported. This process enables the creation of smart textiles with integrated energy storage, sensing, and heating functionalities. This methodology combines gel-based electrolyte with a vacuum resin infusion technique, resulting in an efficient and stable smart FRP composite with an areal capacitance of up to ≈182 µF cm⁻² at 10 mV s⁻¹. The composite exhibits exceptional cyclic stability, maintaining ≈90% capacitance after 1000 cycles. Moreover, the smart composite demonstrates joule heating, reaching from ≈24 to ≈27 °C within 120 s at 25 V. Additionally, the smart composite displays strain sensitivity by altering electrical resistance with longitudinal strain, enabling structural health monitoring. These findings highlight the potential of smart composites for multifunctional applications and provide an important step toward realizing their actual real-world applications.