Bi-level optimization for a dynamic multiobjective problem

In this article, a bi-level optimization problem covering upper (design) and lower (operation) levels is defined and a solution procedure for bi-level optimization problems is presented. This is devised as a dynamic multiobjective optimization problem, i.e. the values of the control and state variables change over a predefined time horizon and several competing criteria are optimized simultaneously. Moreover, the interaction between the upper and lower levels is analysed. The benefits of bi-level dynamic multiobjective optimization are illustrated in detail by examining an industrial case in which the design of a paper mill (upper level) and the mill operation (lower level) are optimized at the same time. However, the problem definition and the solution procedure are not limited to any specific application but can be exploited in many different industrial areas.     

Atomic layer deposition process with TiF4 as a precursor for depositing metal fluoride thin films

A novel atomic layer deposition process for the preparation of fluoride thin films in a temperature range of 225 degrees C-400 degrees C is introduced. The crystallinity, morphology, composition, thicknesses, refractive indices, and transmittance of the films are analyzed. Low impurity levels are obtained at 350 degrees C-400 degrees C with good stoichiometry. Refractive indices of 1.34-1.42 for MgF(2), 1.43 for CaF(2), and 1.57-1.61 for LaF(3) films are obtained.     

Identification of late-stage glycosylation steps in the biosynthetic pathway of the anthracycline nogalamycin

Nogalamycin is an anthracycline antibiotic that has been shown to exhibit significant cytotoxicity. Its biological activity requires two deoxysugar moieties: nogalose and nogalamine, which are attached at C7 and C1, respectively, of the aromatic polyketide aglycone. Curiously, the aminosugar nogalamine is also connected through a C-C bond between C2 and C5'. Despite extensive molecular genetic characterization of early biosynthetic steps, nogalamycin glycosylation has not been investigated in detail. Here we show that expression of the majority of the gene cluster in Streptomyces albus led to accumulation of three new anthracyclines, which unexpectedly included nogalamycin derivatives in which nogalamine was replaced either by rhodosamine with the C-C bond intact (nogalamycin R) or by 2-deoxyfucose without the C-C bond (nogalamycin F). In addition, a monoglycosylated intermediate-3',4'-demethoxynogalose-1-hydroxynogalamycinone-was isolated. Importantly, when the remaining biosynthetic genes were introduced into the heterologous host by using a two-plasmid system, nogalamycin could be isolated from the cultures, thus indicating that the whole gene cluster had been identified. We further show that one of the three glycosyltransferases (GTs) residing in the cluster-snogZ-appears to be redundant, whereas gene inactivation experiments revealed that snogE and snogD act as nogalose and nogalamine transferases, respectively. The substrate specificity of the nogalamine transferase SnogD was demonstrated in vitro: the enzyme was able to remove 2deoxyfucose from nogalamycin F. All of the new compounds were found to inhibit human topoisomerase I in activity measurements, whereas only nogalamycin R showed minor activity against topoisomerase II.     

System- and circuit-level optimization of PLL designs for DVB-T/H receivers

This article proposes a framework for the optimization of voltage-controlled oscillator (VCO) designs in frequency synthesizers for digital video broadcasting ?C terrestrial/handheld (DVB-T/H) receivers. Linear time-invariant phase-domain model of a charge-pump phase-locked loop (PLL) is devised and includes both flicker (1/f) and thermal noise contributions from the loop oscillators. By modeling the entire receiver, it is shown that there are combinations of flicker and thermal noise contributions that result in a constant sum of inter-carrier interference (ICI) and adjacent channel interference, and constant symbol error rate as well. Consequently, optimization of the VCO phase noise spectrum is defined while maintaining the standard-specified symbol-error rate. Link-level performance evaluation is carried out to validate the stipulated trade-off. The effect of ICI mitigation schemes is discussed. Circuit-level VCO design approaches utilizing the derived trade-off are finally presented. The proposed optimization procedure is generic and is also applicable to other systems based on Orthogonal Frequency-Division Multiplexing.     

Controlling the crystallinity and roughness of atomic layer deposited titanium dioxide films

The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS). In this work, TiO2 films made by atomic layer deposition (ALD) with the TiCl4-H2O process were characterized for their growth, roughness and crystallinity as function of deposition temperature (110-300 degrees C), film thickness (up to approximately 100 nm) and substrate (thermal SiO2, RCA-cleaned Si, Al2O3). TiO2 films got rougher with increasing film thickness and to some extent with increasing deposition temperature. The substrate drastically influenced the crystallization behaviour of the film: for films of about 20 nm thickness, on thermal SiO2 and RCA-cleaned Si, anatase TiO2 crystal diameter was about 40 nm, while on Al2O3 surface the diameter was about a micrometer. The roughness could be controlled from 0.2 nm up to several nanometers, which makes the TiO2 films candidates for adhesion engineering in MEMS.     

Total and extractable element concentrations in bed sand material from a medium-sized (32 MW) municipal district heating plant incinerating peat, stumps, sawdust and recycled wood

In Finland, the new limit values of total heavy metal, polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH), as well as the extractable heavy metal, dissolved organic carbon (DOC), fluoride, sulphate, and chloride concentrations for bed sand material used as an earth construction agent came into force in June 2009. The total heavy metal (i.e. Cd, Cu, Pb, Cr, Zn, As, V, Ba and Mo) concentrations in the studied bed sand material were clearly lower than the current Finnish limit values for the maximum allowable heavy metal concentrations for materials used as an earth construction agent. However, the extractable concentration of Ba (24.6 mg kg⁻¹; d.w.) in the bed sand material exceeded the limit value for covered structures (20 mg kg⁻¹; d.w.). However, in Finland, the competent environmental authority may relax the maximum limit values up to 30% in certain circumstances. Therefore, if, the environmental authority relaxes the maximum limit value for the extractable concentration of Ba by up to 30% to the value of 26 mg kg⁻¹ (d.w.) for covered structures, the extractable concentration of Ba (24.6 mg kg⁻¹; d.w.) in the bed sand material is below this relaxation.     

Failure mechanism of thin Al2O3 coatings grown by atomic layer deposition for corrosion protection of carbon steel

Combined analysis by electrochemical impedance spectroscopy (EIS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and field emission scanning electron microscopy (FESEM) of the corrosion protection provided to carbon steel by thin (50 nm) Al₂O₃ coatings grown by atomic layer deposition (ALD) and its failure mechanism is reported. In spite of excellent sealing properties, the results show an average dissolution rate of the alumina coating of ∼7 nm h⁻¹ in neutral 0.2 M NaCl and increasing porosity of the remaining layers with increasing immersion time. Alumina dissolution is triggered by the penetration of the solution via cracks/pinholes through the coating to the substrate surface where oxygen reduction takes place, raising the pH. At defective substrate surface sites of high aspect ratio and concentrated residual mechanical stress (along scratches) presumably exposing a higher steel surface fraction, localized dissolution of the coating is promoted by a more facile access of the solution to the substrate surface enhancing oxygen reduction. De-adhesion of the coating is also promoted in these sites by the ingress of the anodic dissolution trenching the steel surface. Localized corrosion of the alloy (i.e. pitting) is triggered prior to complete dissolution of the alumina film on the elsewhere still coated surface matrix.     

Effects of Compression and Filler Particle Coating on the Electrical Conductivity of Thermoplastic Elastomer Composites

Elastomeric polymers can be filled with metallic micro- or nanoparticles to obtain electrical conductivity, in which the conductivity is largely determined by the intrinsic conductivity of and contact resistance between the particles. Electrons will flow through the material effectively when the percolation threshold for near-neighbor contacts is exceeded and sufficiently close contacts between the filler particles are realized for electron tunneling to occur. Silver-coated glass microparticles of two types (fibers and spheres) were used as fillers in a thermoplastic elastomer composite based on styrene–ethylene–butylene–styrene copolymer, and the direct-current (DC) resistance and radiofrequency impedance were significantly reduced by coating the filler particles with octadecylmercaptan. Not only was the resistance reduced but also the atypical positive piezoresistivity effect observed in these elastomers was strongly reduced, such that resistivity values below 0.01 Ω cm were obtained for compression ratios up to 20%. In the DC measurements, an additional decrease of resistivity was obtained by inclusion of π-extended aromatic compounds, such as diphenylhexatriene. Some qualitative theories are presented to illuminate the possible mechanisms of action of these surface coatings on the piezoresistivity.     

Hardware Cost Measurement of Lightweight Security Protocols

The feasibility of security solution for RFID tags relies heavily on its hardware cost and performance. In the literature the term lightweight solution is used liberally and causes problems when selecting a solution for e.g. RFID environment. Evaluating the actually feasibility of the solution requires electrical engineering skills that many security developers and decision makers may lack. In this paper we describe simple guidelines for approximating the feasibility of the security solution in terms of gates and clock cycles. These guidelines make it easier to evaluate the cryptographic solutions feasibility for targeted hardware and provide a basis for categorisation of lightweight security solutions.     

Displacement control of a mobile crane using a digital hydraulic power management system

The Digital Hydraulic Power Management System (DHPMS) is an innovation that is claimed to significantly improve the energy efficiency of hydraulic systems. It is based on digital pump-motor technology but has multiple independent outlets; hence, the transformer function can be realized as well. A new idea is to connect the outlets of the DHPMS directly into the cylinder chambers without any throttling valves in order to minimize hydraulic losses and to enable energy recovery. This article introduces the first experimental results of using this direct connection approach. Firstly, the system under study is presented and then a method for the displacement control is proposed. Open-loop position tracking responses with different loadings are presented, as is an analysis of the accuracy of steady-state velocity tracking. In addition, energy losses in the system are studied. The results show that the technique is valid. Moreover, the open-loop positioning error is under one percent in the measured trajectories, even though the DHPMS used has only six pistons. However, more pistons will be needed to improve the control of low velocities and to reduce the pressure ripple. On/off valve technology is a challenge, and compact, fast and leak-free valves with high flow capacity are required.