The Effects of Infrared Roasting on HCN Content,Chemical Composition and Storage Stability of Flaxseed and Flaxseed Oil

Flaxseeds were roasted at 1150 W/m² radiation intensity with short and medium wave infrared (IR) emitters for specific durations, which provided good visual and sensory quality. The effects of IR roasting on color properties, hydrogen cyanide (HCN) content, tocopherols and fatty acid composition of the flaxseed and flaxseed oil were investigated. Further, flaxseeds were stored for 6 months and free fatty acid content and peroxide values were followed at 1-month intervals to understand the effect of IR treatment on hydrolytic and oxidative stability. HCN content of the flaxseeds was reduced up to 59% with IR roasting. Tocopherol content of the IR roasted flaxseed oil was higher than that of the control. No notable variation was observed in fatty acid composition with regard to IR treatment. Free fatty acid content of IR roasted flaxseeds did not increase during storage, while peroxide value of the seeds significantly increased up to 95 mEq O₂/kg oil.     

Numerical Investigation of Flow and Heat Transfer Characteristics of Two Tandem Circular Cylinders of Different Diameters

Unsteady laminar flow and heat transfer characteristics from a downstream cylinder of two tandem circular cylinders of different in diameters are numerically investigated. The working fluid is air, and the downstream cylinder is isothermal while the upstream cylinder is kept adiabatic. Two-dimensional numerical simulations are carried out for Reynolds numbers of 100 and 200. The ratio of the upstream to downstream cylinder diameters (diameter ratio) and the ratio of the gap distance to the downstream cylinder diameter (gap ratio) are considered in the range of 0.3 to 2 and 0.5 to 4, respectively. Numerical solutions are obtained using the FLUENT® software. The flow parameters such as the rms lift/drag coefficients and Strouhal numbers are computed and analyzed for the diameter ratio and gap ratio intervals investigated. The iso-vorticity lines and isotherms are also generated to understand, identify and analyze the flow and heat transport characteristics. Four basic flow structures are observed and classified as (i) over-shoot, (ii) symmetric-reattachment, (iii) front-side reattachment and (iv) co-shedding flow. The critical spacing, which marks the minimum gap spacing for the vortex formation to begin, depends on the diameter ratio and Reynolds number, and it decreases with increasing Reynolds number. The convective heat transfer phenomenon is observed to be strongly influenced by diameter ratio, gap ratio and Reynolds number. The mean and the local Nusselt number along the perimeter of isothermal cylinder are computed and discussed in connection with the flow characteristics.     

Ambient Vibration Data Analysis for Structural Identification and Global Condition Assessment

System identification is an area which deals with developing mathematical models to characterize the input-output behavior of an unknown system by means of experimental data. Structural health monitoring (SHM) provides the tools and technologies to collect and analyze input and output data to track the structural behavior. One of the most commonly used SHM technologies is dynamic testing. Ambient vibration testing is a practical dynamic testing method especially for large civil structures where input excitation cannot be directly measured. This paper presents a conceptual and reliable methodology for system identification and structural condition assessment using ambient vibration data where input data are not available. The system identification methodology presented in this study is based on the use of complex mode indicator functions (CMIFs) coupled with the random decrement (RD) method to identify the modal parameters from the output only data sets. CMIF is employed for parameter identification from the unscaled multiple-input multiple-output data sets generated using the RD method. For condition assessment, unscaled flexibility and the deflection profiles obtained from the dynamic tests are presented as a conceptual indicator. Laboratory tests on a steel grid and field tests on a long-span bridge were conducted and the dynamic properties identified from these tests are presented. For demonstrating condition assessment, deflected shapes obtained from unscaled flexibility are compared for undamaged and damaged laboratory grid structures. It is shown that structural changes on the steel grid structure are identified by using the unscaled deflected shapes.     

An alternative strategy for corn drying (Zea mays) resulted in both energy savings and reduction of fumonisins B1 and B2 contamination

The objectives of this study were to investigate the effect of harvest date on fumonisins contamination and to offer an alternative drying procedure with low energy costs. Corn kernel samples above 13% moisture content were dried with hot air (HA), the technique more usually utilised by farmers and compared with infrared and infrared–hot air (IR–HA) combination techniques. The effect of harvest date on fumonisin contamination was found to be significant while drying had no influence. Due to the fact that the corn remains in the field longer than necessary for economic reasons, energy expenses of the drying techniques were calculated in terms of specific energy consumption for unit of evaporated water. It was found that the energy expenses to reduce the moisture level from 15 to 13% with HA drying were higher than the expenses to reduce the moisture level from 29 to 13% with IR–HA drying combination.     

Fabrication and optimization of PES/PVP hollow fiber membranes using Box–Behnken model and CART algorithm

This study focuses on the optimization of polyethersulfone (PES) hollow fiber membranes fabricated with the phase inversion method. A Box–Behnken experimental design was employed with three different PES concentration ratios (11, 14, 17 wt.%), three polyvinylpyrrolidone (PVP) molecular weight ratios (K30/K90 ratios of 6:0, 3:3, 0:6 wt.%), three different bore fluid (BF) composition ratios (water/alcohol ratios of 20:80, 60:40, 100:0), and three different air gap values (24, 37, and 50 cm). The results were analyzed in terms of pure water permeability (PWP) and porosity as optimization parameters using response surface methodology and the classification and regression tree (CART) model. ANOVA results revealed significant effects of PES concentration, PVP molecular weight, and BF composition on the outcomes. After optimization, the maximum PWP and the maximum porosity were obtained as 360.15 L/m² h bar, 60.57%, respectively. The CART model achieved sufficient accuracy in classifying samples.     

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) beads for heavy metal removal

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150-200 microm) was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with n-vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m2/g. Poly(EGDMA-VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA-VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10-750 mg/l) and at different pH values (3.0-7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA-VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO3. These features make poly(EGDMA-VIM) beads potential candidate adsorbent for heavy metal removal.     

Contact resistance characteristics of coated metallic bipolar plates for PEM fuel cells – investigations on the effect of manufacturing

The main purpose of this study is to understand the interfacial contact resistance (ICR) characteristics of coated metallic bipolar plates (BPP) manufactured through stamping and hydroforming. To this goal, 51 μm thick SS316L stainless steel sheet blanks were formed into BPPs using two forming techniques (stamping and hydroforming); then these formed plates were coated with three different PVD coatings (CrN, TiN, ZrN) at three different coating thicknesses (0.1, 0.5 and 1 μm). Contact resistance of the formed and coated BPP samples were measured before and after they were exposed to the proton exchange membrane fuel cells (PEMFC) operating conditions (i.e., corrosive environment). ICR tests indicated that CrN coating increased the contact resistance of the samples, unexpectedly. TiN samples showed the best performance in terms of low ICR; however, their ICR dramatically increased after short-term exposure to corrosion. ZrN coating, as well, improved conductivity of the SS316L BPP samples and demonstrated similar ICR performance before and after exposure to corrosion.     

结构健康监测和可靠性评估

对美国最大跨度桁架桥中的主要桁架构件以及整个结构系统的可靠性进行评估。根据构件和系统的可靠性指标,可以采用随机方法评估大跨桥的安全水平。然而,大多数旧的大跨桥是基于允许应力设计的,其可靠性不可能被保证。本研究的可靠性分析基于对恒荷载、活荷载和风载分布的评估。通过收集大量的输入和响应数据,对大桥进行长期结构健康监测。根据外部荷载影响的模式和大小,长期监测数据清楚揭示了不同结构的性能。案例显示,采用传统的分析方法难以确定由于温度引起的结构响应。为探讨温度对结构的影响以及在可靠性评估中考虑长期监测数据的作用,也对温度引起的响应进行分析。研究显示：温度导致的响应对整个系统的可靠性具有明显的影响。     

Analysis of low power wireless links in smart grid environments

Recently, wireless sensor networks (WSNs) have been used in various smart grid applications, including remote power system monitoring and control, power fraud detection, wireless automatic metering, fault diagnostics, demand response, outage detection, overhead transmission line monitoring, load control, and distribution automation. However, harsh smart grid environment propagation characteristics cause great challenges in the reliability of WSN communications in smart grid applications. To this end, the analysis of wireless link reliability and channel characterizations can help network designers to foresee the performance of the deployed WSN for specific smart grid propagation environments, and guide the network engineers to make design decisions for the channel modulation, encoding schemes, output power, and frequency band. This paper presents a detailed analysis of low power wireless link reliability in different smart grid environments, such as 500 kV outdoor substation environment, indoor main power control room, and underground network transformer vaults. Specifically, the proposed analysis aims to evaluate the impact of different sensor radio parameters, such as modulation, encoding, transmission power, packet size, as well as the channel propagation characteristics of different smart grid propagation environments on the performance of the deployed sensor network in smart grid. Overall, the main objective of this paper is to help network designers quantifying the impact of the smart grid propagation environment and sensor radio characteristics on low power wireless link reliability in harsh smart grid environments.