Process metallurgical evaluation and application of very fine bubbling technology

The potential of VFB(v ery f ine b ubbling)‐technology in steelmaking, developed for the production of super clean steels, was investigated. Recent R&D work has proven that with very fine argon bubbling through a developed special porous plug (SPP) at low flow rates, the total oxygen content of low carbon steel grades can be lowered to a level of 6 ppm under industrial vacuum conditions [1; 2] and to a level of 10 ppm under argon protective atmosphere [2]. The perspective of industrial application of the VFB technology to a 56‐t ladle furnace of Helliniki Halyvourgia S.A., Greece, in order to improve steel cleanliness, requires additional R&D efforts. It is important to define the limits of VFB technology in respect of alloys dissolution, mixing time and homogenisation of steel and slag/metal reactions. In this work, a gas driven bubble aqueous reactor model simulating the bottom gas stirred ladle by means of gas injection through a SPP and a conventional porous plug was studied. Various operating conditions as well as different positions for the porous plug with and without a top oil layer were simulated. Tests concerning mixing time, solid‐liquid mass transfer and critical gas flow rate, liquid/liquid mass transfer, using the SPP and a conventional porous plug have been performed. The evaluation of experimental results delivered important information for the design and operation of steel ladles, applying VFB‐technology. Experimental results with SPP bubbles’ agitated steel (1600 °C) in laboratory and technical scale experiments in IF and VIF are presented and discussed.     

General-purpose inverse kinematics transformations for robotic manipulators

Real-time robot control requires efficient inverse kinematics transformations to compute the temporal evolution of the joint coordinates from the motion of the end-effector. The development of a coherent, general-purpose framework, incorporating position, velocity and acceleration transformations, is the theme of this paper. In this framework, the computational requirements of a new inverse kinematic algorithm are delineated. The algorithm is applicable to serial (open-chain) manipulators with arbitrary axes of motion. Comparative evaluations of the computational cost of the algorithm demonstrate its efficacy and feasibility for real-time applications.     

Structure-radical scavenging activity relationship of alkannin/shikonin derivatives

Alkannins and shikonins (A/S) are naturally occurring isohexenylnaphthazarins (IHNs) of great interest in the field of life sciences due to their broad spectrum of biological properties and are used as food colourants in some countries. In the present study for the first time assessment of the radical scavenging activity of A/S and selected derivatives was carried out using the Crocin Bleaching Assay (CBA) and a modified DPPH assay. Exploration of structure-radical scavenging activity relationship (SAR) was approached with a wide range of A/S derivatives. To accomplish this task, a computational approach was also employed for the two enantiomers and other structurally related compounds. The findings indicated that the side chain –OH group at C-1′ has a positive effect to the radical scavenging properties of alkannin/shikonin by assisting hydrogen atom donation from this carbon atom. Thus, alkannin and shikonin were more potent than deoxyshikonin. Esterification of that hydroxyl group was critical for the activity of the respective compounds (acetyl-, isovaleryl- and β,β-dimethylacryl-shikonin). All of the examined IHN derivatives were found experimentally less potent scavengers than naphthazarin.     

Slow sampling on-line harmonics/interharmonics estimation technique for smart meters

This paper presents a modified gradient search (MGS) technique to estimate harmonics/interharmonics of power system voltages and currents. The proposed technique, which is applied to spectral estimation, consumes very low processing power and needs a few samples per cycle for real-time implementation in smart meters. The computational burden of the proposed technique is lower than the discrete Fourier transform (DFT) and fast Fourier transform (FFT) and can be implemented recursively on digital signal processors (DSPs). In addition, the effects of slow sampling on the accuracy and estimation latency have been investigated. Performance of the proposed method is evaluated by simulations in MATLAB-Simulink and confirmed by experimental results.     

Stability and maturity of thickened wastewater sludge treated in pilot-scale sludge treatment wetlands

Thickened wastewater activated sludge was treated in 13 pilot-scale sludge treatment wetlands of various configurations that operated continuously for three years in North Greece. Sludge was loaded for approximately 2.5 years, and the beds were left to rest for the remaining period. Three different sludge loading rates were used that represented three different population equivalents. Residual sludge stability and maturity were monitored for the last year. Sludge was regularly sampled and microbial respiration activity indices were measured via a static respiration assay. The phytotoxicity of sludge was quantified via a seed germination bioassay. Measurements of total solids, organic matter, total coliforms, pH and electrical conductivity were also made. According to microbial respiration activity measurements, the sludge end-product was classified as stable. The germination index of the final product exceeded 100% in most wetland units, while final pH values were approximately 6.5. The presence of plants positively affected the stability and maturity of the residual sludge end-product. Passive aeration did not significantly affect the quality of the residual sludge, while the addition of chromium at high concentrations hindered the sludge decomposition process. Conclusively, sludge treatment wetlands can be successfully used, not only to dewater, but also to stabilize and mature wastewater sludge after approximately a four-month resting phase.     

Restricted second order information for the solution of optimal control problems using control vector parameterization

A new scheme using a Truncated Newton algorithm with and exact Hessian-search direction vector product is presented for the solution of optimal control problems. The derivation of formulae for second order parametric sensitivity analysis of differential-algebraic equations is presented, following earlier published work [V.S. Vassiliadis, E. Balsa-Canto, J.R. Banga, Second order sensitivities of general dynamic systems with application to optimal control problems. Chem. Eng. Sci. 54 (17) (1999) 3851–3860]. An original result in this work is the derivation of Hessian matrix-vector product forms which are shown to have the same computational complexity as the evaluation of first order sensitivities. This result for optimal control Hessian-vector products using control vector parameterization is shown to be a very effective way to solve optimal control problems. It is also noted that this work introduces the use of suitable Truncated Newton solvers which can exploit the exact vector products in using conjugate gradient iterations to converge the Newton equations. Such a solver is the TN algorithm of Nash [(S.G. Nash-Newton type minimization via the Lanczos method. SIAM J. Num. Anal. 21, (1984) 770–778)]. Because no full Hessian update is necessary it is demonstrated that the resulting optimal control solver performs very well for a very large number of degrees of freedom, limited only by the necessity for many right-hand-side calculations in the first and second order sensitivity equations (the Hessian vector product). It is also demonstrated by several case studies that the scheme is capable of starting far from the solution and yet arrive there in almost invariant performance.     

Modification of functional properties of egg-white proteins

Egg-white proteins are extensively utilised as food ingredients due to their unique functional properties. Several attempts have been made in order to improve the functional properties of egg-white proteins and to identify the optimal formulations for unique food products. Experimental data proves that controlled denaturation of egg-white proteins can have a beneficial impact on various functional applications in the food industry such as emulsifying ability, heat stability, and gelation. This review describes the effect of heat-induced denaturation on protein structure and functionality. Studies on the impact of Maillard reaction, which aim to elucidate the structure-function relationship of egg-white proteins, are presented. A novel approach which could be the basis for the development of new methods aiming to improve the functional properties of egg-white proteins is also discussed.     

Bacterial species associated with sound and Botrytis-infected grapes from a Greek vineyard

Grape bacterial microbiota plays central roles in the quality of grapes and wine, yet its diversity remains poorly described. In the present study, bacterial species associated with sound and Botrytis-infected grapes of two cultivars originating from the same vineyard were assessed. Isolates were identified by PCR-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and sequence analysis of partial 16S rRNA gene. Comparable counts were recorded between Botrytis-infected and sound grape samples. In all cases, the majority of isolates belonged to different species of Enterobacteriaceae. The dominant species in the vineyard was Klebsiella oxytoca that was found in different combinations with Citrobacter freundii, Enterobacter spp., Erwinia sp., Pantoea dispersa, Tatumella ptyseos or other species. In fermenting musts, those populations declined while other species evolved, like Lactobacillus plantarum and Enterobacter ludwigii. Populations in botrytised samples persisted longer during spontaneous fermentations. Present study suggests that bacterial diversity on grapes may be wider than previously described.     

Sternal instability in a hemodialysis patient with secondary hyperparathyroidism

A 77‐year‐old man, 11 years under chronic hemodialysis treatment for chronic renal failure of unknown origin, presented with anterior chest pain, dyspnea with paradoxical breathing, and sternal instability after a simple fall from a standing height. Patient underwent three‐vessel coronary artery bypass grafting 31 months ago. Computed tomography with three‐dimensional volume rendering showed sternal nonunion with a great gap between the two halves of the sternum and at least one fracture in the left half of the sternum. A successful surgical repair followed. Patient suffered from severe secondary hyperparathyroidism for many years. Despite treatment with sevelamer, paricalcitol and cinacalcet, intact parathyroid hormone was 1682 pg/mL. During the last 5 years, serum intact parathyroid hormone remained steadily above 1000 pg/mL. Patient refused parathyroidectomy in the past. We assume that long‐lasting severe hyperparathyroidism contributed to this rare and life‐threatening complication of median sternotomy in our patient, due to the detrimental effect of hyperparathyroidism on bone metabolism and its association with increased incidence of bone fractures and defect in bone fracture healing.