A review on measurement science needs for real-time control of additive manufacturing metal powder bed fusion processes

Additive manufacturing technologies are increasingly used in the development of new products. However, variations in part quality in terms of material properties, dimensional tolerances, surface roughness and defects limit its broader acceptance. Process control today based on heuristics and experimental data yields limited improvement in part quality. In an effort to identify the needed measurement science for real-time closed-loop control of additive manufacturing (AM) processes, this paper presents a literature review on the current AM control schemes, process measurements and modelling and simulation methods as it applies to the powder bed fusion process, though results from other processes are reviewed where applicable. We present our research findings to identify the correlations between process parameters, process signatures and product quality. We also present research recommendations on the key control issues to serve as a technical basis for standards development in this area. Complimentary details to this paper with summary tables, range of values, preliminary correlations and correlation figures can be accessed from a National Institute of Standards and Technology Report (http://nvlpubs.nist.gov/nistpubs/ir/2015/NIST.IR.8036.pdf). This paper is developed based on the report.     

Structural,linear and nonlinear optical,electrical and NBO reports on 4-aminopyridine-1-ium 4-aminobenzoate single crystal for SHG,optoelectronics and violet laser emission applications

Good quality NLO single crystal 4-aminopyridine-1-ium 4-aminobenzoate (4AP4AB) were grown by slow evaporation method. The Single crystal XRD analysis shows that the 4AP4AB compound belongs to the monoclinic system with non-centrosymmetric group C. Further, the molecular structure and vibrational assignments of the grown crystal were analysed by NMR and Fourier transform infrared (FT-IR) analysis. NBO analysis analysed inter and intramolecular interactions. Optical and thermal stabilities have been characterized by UV–Visible and DSC analysis. Linear optical parameters of the 4AP4AB crystal were quantified and listed by UV–visible study. Vicker's microhardness test at room temperature shows that the hardness number increases with increasing the load. The laser damage threshold (LDT) energy has been measured using an Nd:YAG laser. The impedance analysis recorded the dielectric response of the grown 4AP4AB crystal. The appearance of semicircle in Cole–Cole plot represents the dielectric relaxation and resistivity of the 4AP4AB crystal. Solid-state parameters of 4AP4AB were quantified and listed for the theoretical approaches.

     

On the existence of weak solutions of nonlinear degenerate parabolic system with variable exponents

The main goal of the present paper is establishing the existence and uniqueness of weak solutions for the nonlinear degenerate reaction–diffusion system with variable exponents. A model also is proposed to characterize the invasion of cancer cells towards healthy cells with acidification environment. Moreover, the main results of this paper are obtained using regularization problem, the Faedo–Galerkin approximation method, some apriori estimates, compactness results and the Gronwall Lemma.     

Low-Temperature Fine-Grained Alumina–Aluminum Titanate Composites Produced from a Titania-Coated Alumina Precursor

A method for the preparation of alumina–aluminum titanate (AT) composites, which can be sintered to high density with a fine-grained microstructure at <1450°C, is reported. The composite precursor is alumina particles coated by sol–gel-derived titania, which reacts during sintering to form AT in situ at temperature as low as 1300°C. The composite can be sintered at 1350°C to 98% density with 1.5–2.0 μm grain size. Other composites containing 5–50 wt% AT are also investigated.     

Vibrational Energy Transport in Hybrid Ordered/Disordered Nanocomposites: Hybridization and Avoided Crossings of Localized and Delocalized Modes

Vibrational energy transport in disordered media is of fundamental importance to several fields spanning from sustainable energy to biomedicine to thermal management. This work investigates hybrid ordered/disordered nanocomposites that consist of crystalline membranes decorated by regularly patterned disordered regions formed by ion beam irradiation. The presence of the disordered regions results in reduced thermal conductivity, rendering these systems of interest for use as nanostructured thermoelectrics and thermal device components, yet their vibrational properties are not well understood. Here, the mechanism of vibrational transport and the reason underlying the observed reduction is established in detail. The hybrid systems are found to exhibit glass‐crystal duality in vibrational transport. Lattice dynamics reveals substantial hybridization between the localized and delocalized modes, which induces avoided crossings and harmonic broadening in the dispersion. Allen/Feldman theory shows that the hybridization and avoided crossings are the dominant drivers of the reduction. Anharmonic scattering is also enhanced in the patterned nanocomposites, further contributing to the reduction. The systems exhibit features reminiscent of both nanophononic materials and locally resonant nanophononic metamaterials, but operate in a manner distinct to both. These findings indicate that such “patterned disorder” can be a promising strategy to tailor vibrational transport through hybrid nanostructures.     

Development of an Instrument to Measure Perspectives of Engineering Education Among College Students

The number of engineering students has been declining for decades and attracting qualified students has become an urgent task for engineering schools in The United States. Perspectives students hold towards engineering play an important role in their college major selection. An effective standardized instrument measuring general perspectives about engineering among college students is designed in this project and survey development, instrument administration, and factor analysis are presented. The statistical analysis reveals that college students in general agree that engineering is beneficial to the society; however, they tend to believe that it takes too much effort to gain an engineering degree and that engineering is a demanding career. Further, they are neutral about the personal benefits of pursuing a degree in engineering, and finally, they do not feel that studying engineering or making engineering as their profession is particularly interesting. These findings provide a good explanation to the declining enrollment and increasing dropout rates in engineering schools in the United States.     

A comparative study of quantum yield and electrical energy per order (E(Eo)) for advanced oxidative decolourisation of reactive azo dyes by UV light

This paper evaluates the quantum yield and electrical energy per order (E(Eo)) efficiency of Reactive Orange 4 (RO4) and Reactive Yellow 14 (RY14) azo dyes by three advanced oxidation processes (AOPs). Both dyes were completely decolourised by all these processes. The relative decolourisation efficiencies of these processes were in the following order: Fe(2+)/H(2)O(2)/UV>UV/TiO(2)>UV/H(2)O(2). The low efficiency of UV/H(2)O(2) process is mainly due to low UV absorption by hydrogen peroxide at the 365nm. The figure of merit E(Eo) values showed that UV/H(2)O(2) process consumes more electrical energy than the other two processes. The electrical energy consumption is in the following order: UV/H(2)O(2)>UV/TiO(2)>Fe(2+)/H(2)O(2)/UV. At low initial dye concentration higher quantum yield was observed in UV/TiO(2) process, whereas in photo-Fenton process higher quantum yield was observed at high initial dye concentration. The structure of dye molecule also influences the quantum yield and E(Eo) value.     

Metabolic Analysis of the Development of the Plant-Parasitic Cyst Nematodes Heterodera schachtii and Heterodera trifolii by Capillary Electrophoresis Time-of-Flight Mass Spectrometry

The cyst nematodes Heterodera schachtii and Heterodera trifolii, whose major hosts are sugar beet and clover, respectively, damage a broad range of plants, resulting in significant economic losses. Nematodes synthesize metabolites for organismal development and social communication. We performed metabolic profiling of H. schachtii and H. trifolii in the egg, juvenile 2 (J2), and female stages. In all, 392 peaks were analyzed by capillary electrophoresis time-of-flight mass spectrometry, which revealed a lot of similarities among metabolomes. Aromatic amino acid metabolism, carbohydrate metabolism, choline metabolism, methionine salvage pathway, glutamate metabolism, urea cycle, glycolysis, gluconeogenesis, coenzyme metabolism, purine metabolism, pyrimidine metabolism, and tricarboxylic acid (TCA) cycle for energy conversion (β-oxidation and branched-chain amino acid metabolism) energy storage were involved in all stages studied. The egg and female stages synthesized higher levels of metabolites compared to the J2 stage. The key metabolites detected were glycerol, guanosine, hydroxyproline, citric acid, phosphorylcholine, and the essential amino acids Phe, Leu, Ser, and Val. Metabolites, such as hydroxyproline, acetylcholine, serotonin, glutathione, and glutathione disulfide, which are associated with growth and reproduction, mobility, and neurotransmission, predominated in the J2 stage. Other metabolites, such as SAM, 3PSer, 3-ureidopropionic acid, CTP, UDP, UTP, 3-hydroxy-3-methylglutaric acid, 2-amino-2-(hydroxymethyl-1,3-propanediol, 2-hydroxy-4-methylvaleric acid, Gly Asp, glucuronic acid-3 + galacturonic acid-3 Ser-Glu, citrulline, and γ-Glu-Asn, were highly detected in the egg stage. Meanwhile, nicotinamide, 3-PG, F6P, Cys, ADP-Ribose, Ru5P, S7P, IMP, DAP, diethanolamine, p-Hydroxybenzoic acid, and γ-Glu-Arg_divalent were unique to the J2 stage. Formiminoglutamic acid, nicotinaminde riboside + XC0089, putrescine, thiamine 2,3-dihydroxybenzoic acid, 3-methyladenine, caffeic acid, ferulic acid, m-hydrobenzoic acid, o- and p-coumaric acid, and shikimic acid were specific to the female stage. Overall, highly similar identities and quantities of metabolites between the corresponding stages of the two species of nematode were observed. Our results will be a valuable resource for further studies of physiological changes related to the development of nematodes and nematode–plant interactions.     

Synthesis and spectral,thermal, and photocrosslinking studies of poly(benzylidene phosphoramide ester)s

A new class of poly(benzylidene phosphoramide ester)s containing a photoreactive benzylidene chromophore in the main chain were synthesized from bis(4-hydroxy-3-methoxy benzylidene) acetone with various substituted N-aryl phosphoramidic dichlorides by an interfacial polycondensation technique. The synthesized polymers were characterized by inherent viscosity, IR, and ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. The molecular weights of these polymers were determined by gel permeation chromatography. These polymers were studied for their thermal stability and photochemical properties. Thermal properties were evaluated by thermogravimetric analysis and differential scanning calorimetry. It was found that halogen-containing polymers show a higher thermal stability than that of nonhalogenated polymers. The photocrosslinking property of these polymers was studied by ultraviolet spectroscopy. The photoreactive benzylidene chromophore in the main chain dimerizes via 2π + 2π cycloaddition reaction to form a cyclobutane derivative and leads to crosslinking. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2151–2157, 1997