Machining strategy development and parameter selection in 5-axis milling based on process simulations

Fused deposition modeling (FDM) is one of the most popular additive manufacturing technologies for fabricating prototypes with complex geometry and different materials. However, current commercial FDM machines have the limitations in process reliability and product quality. In order to overcome these limitations and increase the levels of machine intelligence and automation, machine conditions need to be monitored more closely as in closed-loop control systems. In this study, a new method for in situ monitoring of FDM machine conditions is proposed, where acoustic emission (AE) technique is applied. The proposed method allows for the identification of both normal and abnormal states of the machine conditions. The time-domain features of AE hits are used as the indicators. Support vector machines with the radial basis function kernel are applied for state identification. Experimental results show that this new method can potentially serve as a non-intrusive diagnostic and prognostic tool for FDM machine maintenance and process control.     

Evaluation of the Particle Bonding for Aluminum Sample Produced by Spark Plasma Sintering

Journal of Materials Engineering and Performance - Spark plasma sintering (SPS) is a powder metallurgy process that sinters powder materials within a short time by simultaneous application...     

Enhanced Catalytic,Antibacterial and Anti-cancer Activities of Erythromycin Capped Gold Nanoparticles

Journal of Inorganic and Organometallic Polymers and Materials - In this study, the nanosized spherical erythromycin capped gold nanoparticles (eryth-Au(0)NPs) were fabricated for the first time....     

Creep behavior analysis of additively manufactured fiber-reinforced components

This research study reports the creep behavior analysis of the new composite materials manufactured by 3D printing technology. Nylon was used as a polymer matrix, and carbon fiber, Kevlar, and fiberglass were used as reinforcing agents. Since the properties of 3D-printed components are usually insufficient for robust engineering applications, adding reinforcing fibers improves the performance of these components for several engineering applications. Fiber-reinforced additive manufacturing (FRAM) is an almost 4-year-old technology. Additionally, there is not sufficient research on the behavior of FRAM components specifically at high temperatures. Therefore, the investigation of the high-temperature behavioral analysis of FRAM components was focused on in this study. Creep properties of the composite specimens reinforced by different fibers were measured by the dynamic mechanical thermal analysis system. The statistical analyses were conducted to analyze the experimental data using mathematical models. The microstructural analysis was performed to further investigate parts’ morphology, 3D printing quality, and fracture mechanisms. The results indicated that the creep compliance of reinforced composite specimens was significantly improved in comparison with pure nylon. Overall, this paper presents quantitative creep analysis results demonstrating the capabilities of FRAM components to be used for several engineering applications.     

Effects of reactive and nonreactive POSS types on the mechanical,thermal, and morphological properties of plasticized poly(lactic acid)

The aim of this study is to investigate the effects of the reactive and nonreactive polyhedral oligomeric silsesquioxane (POSSs) types and their composition on the mechanical, thermal, and morphological properties of poly(ethylene glycol) plasticized poly(lactic acid) (PLA) composites prepared with melt compounding. The results showed that the incorporation of POSS decreased the melt viscosity of the compounds regardless of POSS type. The lowest viscosity was obtained with epoxy‐POSS, which is the only one that is liquid at processing temperature in comparison to the others. It was revealed from the mechanical tests that the toughness‐related properties such as impact strength and elongation at break improved by the addition of POSS without remarkable deterioration in stiffness. The chemical structure of the POSS influenced the level of dispersion and hence the mechanical performance of the composites. Octaisobutyl‐POSS, being the nonreactive and nonpolar one, had the best dispersion among the other reactive and polar POSS types. The glass transition temperature of the matrix decreased in the presence of POSS types. In addition, the POSS particles also had an impact on the crystallization of PLA. The thermal stability of the composites improved in the presence of POSS particles with respect to the POSS content and the POSS type. POLYM. ENG. SCI., 54:264–275, 2014. © 2013 Society of Plastics Engineers     

Determination of Myricetin in Medicinal Plants by High-Performance Liquid Chromatography

The concentrations of myricetin in medicinal plants such as Rosa canina L. (rosa hip), Terebinthina chica L. (terebinth), Urtica dioica L. (nettle), and Portuca oleracea L. (purslane) were determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS). The aglycones of myricetin were extracted using methanol–ascorbic acid– hydrochloric acid, methanol–hydrochloric acid, and methanol, separated within 5 min, and individually quantitated in the positive ionization mode using optimized conditions for HPLC-MS. Methanol–ascorbic acid–hydrochloric acid was the optimum extraction solvent. The myricetin concentration in the plants were between 3 and 58 mg kg^?1, with a limit of quantification equal to 0.1 mg L^?1.     

Free radical crosslinking of unsaturated bacterial polyesters obtained from soybean oily acids

Summary Poly(-3-hydroxy alkanoate) containing unsaturated side chains, PHA-soybean, were produced by feeding Pseudomonas oleovorans with soybean oily acids obtained from soybean oil. Unsaturation of PHA-soybean were found to be 10 mol-% of unsaturated side chains. Main saturated part of the biopolymer was Poly(3-hydroxy octanoate) with minor hexanoate and decanoate units. PHA films were crosslinked via free radical mechanism by means of thermally or under UV irradiation in the presence of benzoyl peroxide, benzophenon, and /or ethylene glycol dimethacrylate (EGDM). Crosslinking yield of the PHA films were found to be from 81 to 93 wt.-% from the sol-gel analysis. Swelling properties of the crosslinked PHA films in chloroform and toluene were also studied. Mc values of crosslinked PHAs were also calculated using Flory-Rehner equation. The crosslinked biopolyester obtained by thermally at 60 °C with benzoyl peroxide indicated the highest crosslinking density. Glass transition temperatures (Tg) of crosslinked biopolyester samples were changed from −33 to −45 °C while that of PHA-soybean was −60 °C. Received: 16 June 2000/Revised version: 22 January 2001/Accepted: 20 May 2001     

Ion Chromatographic Determination of Free Cyanide in Different Classes of Bottled Natural Mineral Water Consumed in Turkey

An ion chromatographic method for the quantitative determination of free cyanide in bottled natural mineral waters were measured in terms of selectivity, linearity, the limit of detection, limit of quantification, repeatability, precision, and accuracy. Chromatographic separation of free cyanide ions was accomplished with an anion-exchange column and detected by pulsed amperometric detection with a silver working electrode. The method was found to be selective, linear (r² = 0.999) at a concentration range of 0.5 to 134 μg L^?1, precise, and accurate. Recovery values of free cyanide in all classes of natural mineral water varied from 65.9 ± 1.6 to 95.2 ± 0.7 at different spiking levels (5–70 μg L^?1). Parameters (total dissolved solids, mineral interferences, and added sodium hydroxide) affecting the recovery values were studied in this project. The limit of detection and limit of quantification were found to be 0.295 and 0.983 μg L^?1, respectively. The proposed method was applied to 27 different brands of commercially available bottled natural mineral water products sold in Turkish markets. These natural mineral waters were classified as: (i) very low mineral concentration, (ii) low mineral concentration, (iii) intermediate mineral concentration, and (iv) high mineral concentration based on their total dissolved solids contents according to European Union Directive (Directive 80/777/EEC). Levels of free cyanide residues in the samples ranged from > limit of detection to 6.12 μg L^?1. The highest average concentration of free cyanide residues was found in the class of “high mineral concentration waters.” However, the determined free cyanide values in all of the tested natural mineral water samples were found to be within the limits of European Union legislation.     

低噪声APD偏置电路

１ＡＰＤ的特性雪崩光电检测器 (ＡＰＤ)和ＰＩＮ二极管通常被作为接收器用于光通信中。其中ＡＰＤ适合于高灵敏度和高带宽的光接收电路。但这种器件在工作时需要施加一个反向结压 ,这样 ,当接收到射线时产生的电子空穴对会被外加电场收集并转换为电流 ,其电流强度正比于射线强度。另外 ,工作时施加在器件上的反向偏置电压会引发雪崩效应 ,其雪崩增益可通过改变偏压来进行调节。这就有可能对光纤接收器的增益进行优化。然而 ,要得到满意的雪崩增益 ,就必须给ＡＰＤ提供一个比较高的反向偏压。很多ＡＰＤ需要４０Ｖ～６０Ｖ的偏压 ,有些器件…