Fast servo signal acquisition in tape drives using servo and data channels

In a tape drive, the head assembly hosting servo readers and data writers/readers must initially be moved to a target position, so that information can be written to or read from the desired tracks. In tape systems with flangeless rollers, as recently introduced in IBM’s tape drives for improved performance and extended drive and tape lifetime, the initial positioning of the servo readers over the servo bands, from which the position-error signal for steady-state track-following operation is obtained, has to be fast. This requirement is dictated by the nonnegligible lateral tape motion experienced in tape paths with flangeless rollers. In this paper, a method is proposed to utilize both the servo readers and the data readers in a drive to detect the presence of a valid servo signal. If the servo readers are not positioned over a servo band, the distance between servo readers and servo band can thereby be continuously estimated by identifying the data reader detecting the presence of a servo signal. This information is then provided to a control element that controls the joint operation of a coarse stepper motor and a voice-coil motor based fine actuator with large stroke in a feedback or feed-forward configuration to achieve fast servo reader positioning. In the feedback-based approach, all data channels are continuously monitored to detect the presence of a valid servo signal and a pseudo position-error signal is generated and fed back to the control unit to drive the actuator towards the target position. In the feed-forward approach, a trajectory for the actuator is determined as soon as the servo band is in the capture range of the fine actuator and a control signal is generated so that the servo reader rapidly lands over the servo band with optimum control effort.     

High-mobility organic thin-film transistors based on a small-molecule semiconductor deposited in vacuum and by solution shearing

The small-molecule organic semiconductor 2,9-di-decyl-dinaphtho-[2,3-b:2′,3′-f]-thieno-[3,2-b]-thiophene (C₁₀-DNTT) was used to fabricate bottom-gate, top-contact thin-film transistors (TFTs) in which the semiconductor layer was prepared either by vacuum deposition or by solution shearing. The maximum effective charge-carrier mobility of TFTs with vacuum-deposited C₁₀-DNTT is 8.5 cm²/V s for a nominal semiconductor thickness of 10 nm and a substrate temperature during the semiconductor deposition of 80 °C. Scanning electron microscopy analysis reveals the growth of small, isolated islands that begin to coalesce into a flat conducting layer when the nominal thickness exceeds 4 nm. The morphology of the vacuum-deposited semiconductor layers is dominated by tall lamellae that are formed during the deposition, except at very high substrate temperatures. Atomic force microscopy and X-ray diffraction measurements indicate that the C₁₀-DNTT molecules stand approximately upright with respect to the substrate surface, both in the flat conducting layer near the surface and within the lamellae. Using the transmission line method on TFTs with channel lengths ranging from 10 to 100 μm, a relatively small contact resistance of 0.33 kΩ cm was determined. TFTs with the C₁₀-DNTT layer prepared by solution shearing exhibit a pronounced anisotropy of the electrical performance: TFTs with the channel oriented parallel to the shearing direction have an average carrier mobility of (2.8 ± 0.3) cm²/V s, while TFTs with the channel oriented perpendicular to the shearing direction have a somewhat smaller average mobility of (1.3 ± 0.1) cm²/V s.     

Nature of the Interfaces Between Stoichiometric and Under‐Stoichiometric MoO3 and 4,4′‐N,N′‐dicarbazole‐biphenyl: A Combined Theoretical and Experimental Study

A combination of density functional theory and experimental measurements via ultraviolet and X‐ray photoelectron spectroscopies is used to explore the nature of the interface between the stoichiometric molybdenum trioxide (MoO₃) or its under‐stoichiometric counterpart with oxygen vacancies, and an organic hole‐transport layer represented by 4,4′‐N,N′‐dicarbazole‐biphenyl (CBP). Upon adsorption of CBP, special attention is paid to i) the appearance of gap states and the reduction of the molybdenum oxide surface, and ii) the evolution of the work function. Very good agreement is found between theory and experiment. The near alignment of the CBP highest occupied molecular orbital with the Fermi level and the conduction band edge of molybdenum oxide points to facile hole collection or injection.     

Graphene Paper Doped with Chemically Compatible Prussian Blue Nanoparticles as Nanohybrid Electrocatalyst

Along with reduced graphene oxide (RGO), water soluble Prussian blue nanoparticles (PBNPs, around 6 nm) are synthesized and broadly characterized. These two types of highly stable, low‐cost and chemically compatible nanomaterials are exploited as building ingredients to prepare electrically enhanced and functionally endorsed nanohybrid electrocatalysts, which are further transformed into free‐standing graphene papers. PBNPs doped graphene papers show highly efficient electrocatalysis towards reduction of hydrogen peroxide and can be used alone as flexible chemical sensors for potential applications in detection of hydrogen peroxide or/and other organic peroxides. The as‐prepared PBNPs–RGO papers are further capable of biocompatible accommodation of enzymes for development of free‐standing enzyme based biosensors. In this regard, glucose oxidase is used as an example for electrocatalytic oxidation and detection of glucose. The present work demonstrates a facile and highly reproducible way to construct free‐standing and flexible graphene paper doped with electroactive catalyst. Thanks to high stability, low‐cost and efficient electrocatalytic characteristics, this kind of nanohybrid material has potential to be produced on a large scale, and offers a broad range of possible applications, particularly in the fabrication of flexible sensing devices and as a platform for electrocatalytic energy conversion.     

Influence of reactive species on the lean blowout limit of an industrial DLE gas turbine burner

In order to achieve ultra-low emissions of both NO_X and CO it is imperative to use a homogeneous premixed combustor. To lower the emissions further, the equivalence ratio can be lowered. By doing so, combustion is moved towards the lean blowout (LBO) limit. To improve the blowout characteristics of a burner, heat and radicals can be supplied to the flame zone. This can be achieved using a pre-chamber combustor. In this study, a central body burner, called the RPL (rich-pilot-lean) section, was used as a pre-chamber combustor to supply heat and radicals to a downscaled industrial burner. The flue gas from the RPL is mixed with the surrounding fresh mixture and form a second flame zone. This zone acts as a stabilizer for the investigated burner. The LBO limit was modeled using two perfectly stirred reactors (PSRs) in series, which allows the chemical influence on the LBO limit to be isolated. The resulting trends for the modeled LBO limit were in agreement with measured data. Increasing the equivalence ratio in the RPL section, thus increasing the energy supplied by the fuel, is a major contributor to combustion stability up to a limit where the temperature decrease is too large support combustion. For lean RPL combustion, the reactive species O, H and OH in combination affect the stability to a greater extent than the temperature alone. At rich equivalence ratios, the conversion of methane to hydrogen and carbon monoxide in the RPL section is a factor influencing the LBO limit. The results are compared with emission probe measurements that were used to investigate the LBO limit for methane and a generic syngas (10% CH₄, 67.5% H₂, and 22.5% CO). The syngas was also investigated after being diluted with nitrogen to a Wobbe index of 15 MJ/m³.     

Temperature‐Dependent Phase Transitions in the Lead‐Free Piezoceramics (1 – x – y)(Bi1/2Na1/2)TiO3–xBaTiO3–y(K0.5Na0.5)NbO3 Observed by in situ Transmission Electron Microscopy and Dielectric Measurements

Lead‐free piezoelectric (1 – x – y)(Bi_1/2Na_1/2)TiO₃–xBaTiO₃–y(K_0.5Na_0.5)NbO₃ (BNT–BT–KNN) ceramics were examined in situ under increasing temperature in the transmission electron microscope. Changing superstructure reflections indicate a transition from rhombohedral to tetragonal to cubic phase with broad coexistence regions. The additional evolution of the microstructure in combination with dielectric measurements leads to a model of two relaxor‐type phase evolutions with temperature.     

Tribological properties of transition metal di-chalcogenide based lubricant coatings

Transition metal di-chalcogenides MX₂ (X= S, Se, Te; and M= W, Mo, Nb, Ta) are one kind of solid lubricant materials that have been widely used in industry. The lubricant properties of such lubricant coatings are dependent not only on microstructure, orientation, morphology, and composition of the coatings, but also on the substrate, the interface between substrate and lubricant coatings, and the specific application environment. In this review, the effects of parameters on tribological properties of such kind of lubricant coatings were summarized. By comparing advantages and disadvantages of those coatings, the special treatments such as doping, structural modulation and post-treatment were suggested, aiming to improve the tribological performance under severe test conditions (e.g. high temperature, oxidizing atmosphere or humid condition).     

Energiespeicherbeton – ein Beton mit integriertem Latentwärmespeichermaterial

Energy storage concrete – a concrete with integrated latent heat storage material. In times of solar architecture and increased utilisation of renew‐able energy, building components with high thermal heat storage capability are becoming increasingly important. One of the areas future research in building physics and building services will focus on is the development of energy storage units. A particularly interesting research area is latent heat storage. This essay describes the development of a concrete with integrated latent heat storage material (phase change material, PCM) as part of a thesis. This innovative concrete offers significantly improved thermal characteristics. For example, it was possible to more than double the heat capacity within a temperature range of 10 Kelvin around the melting point of the PCM. The PCM has a melting point between approx. 22 °C and 35 °C, depending on application. A highly versatile material such concrete offers a wide range of application options. In principle, it is possible to use latent heat storage concrete to supplement heating systems, to extend the scope of passive solar systems, or to protect against overheating in summer.