Reducing polarization-dependent loss of silicon-on-insulator fiber to chip grating couplers

For many telecommunication applications, low polarization-dependent loss (PDL) operation is mandatory. On the silicon-on-insulator photonic wire platform, this can be achieved using polarization diversity configurations. However, as we show here, when using two-dimensional grating couplers for near vertical fiber input and output, the low PDL bandwidth is limited. We propose and demonstrate the use of a phase shifter in one of the arms of the polarization diversity circuit to effectively reduce PDL (0.15-dB PDL is shown) and increase the low PDL bandwidth

Prikaz slobodnog prostora za dvonožne hodajuće robote

Motion planning for biped walking robots is a highly demanding task because of the complex kinematics of such machines and the many degrees of freedom involved. One approach to dealing with this problem is to determine a feasible path in a reduced configuration space of the robot and then to perform the motion planning by searching for an appropriate sequence of steps which allows the locomotion along this path. In this work, a novel method for creating a free space representation for biped walking robots is presented. The method rests upon the approximation of the robot by a set of 3D hulls whose shapes allow efficient determination of feasible paths in a 3D configuration space, involving stepping over obstacles and changing the walking level. The robot’s environment is partitioned into two regions. In the first region, 2D motion planning can be performed, while the complexity of 3D motion planning in the second region can be significantly reduced by considering only a restricted set of paths sufficient for solving a wide range of locomotion tasks.Planiranje kretanja dvonožnih hodajućih robota predstavlja iznimno zahtjevan zadatak zbog složenosti kinematike takvih strojeva i velikog broja stupnjeva slobode gibanja. Jedan pristup tom problemu je da se prvo pronađe izvediva staza u reduciranom konfiguracijskom prostoru robota te da se zatim traži odgovarajući niz koraka koji omogućuje kretanje tom stazom. U ovom radu predstavljena je nova metoda stvaranja prikaza slobodnog prostora za dvonožne hodajuće robote. Metoda se temelji na aproksimaciji robota skupom jednostavnih trodimenzionalnih geometrijskih tijela čiji oblici omogućuju učinkovito određivanje izvedivih staza u 3D konfiguracijskom prostoru, koje mogu uključivati prekoračivanje prepreka te prelazak između hodnih površina različitih visina. Okolina robota dijeli se na dva područja. U prvom području može se primijeniti 2D planiranje koraka, dok se složenost 3D planiranja koraka u drugom području može značajno smanjiti tako što se pri planiranju uzima u obzir samo jedan reducirani skup staza, koji je pak dostatan za rješavanje velikog broja praktičnih zadataka

Can Zipf's law be adapted to normalize microarrays?

BACKGROUND: Normalization is the process of removing non-biological sources of variation between array experiments. Recent investigations of data in gene expression databases for varying organisms and tissues have shown that the majority of expressed genes exhibit a power-law distribution with an exponent close to -1 (i.e. obey Zipf's law). Based on the observation that our single channel and two channel microarray data sets also followed a power-law distribution, we were motivated to develop a normalization method based on this law, and examine how it compares with existing published techniques. A computationally simple and intuitively appealing technique based on this observation is presented. RESULTS: Using pairwise comparisons using MA plots (log ratio vs. log intensity), we compared this novel method to previously published normalization techniques, namely global normalization to the mean, the quantile method, and a variation on the loess normalization method designed specifically for boutique microarrays. Results indicated that, for single channel microarrays, the quantile method was superior with regard to eliminating intensity-dependent effects (banana curves), but Zipf's law normalization does minimize this effect by rotating the data distribution such that the maximal number of data points lie on the zero of the log ratio axis. For two channel boutique microarrays, the Zipf's law normalizations performed as well as, or better than existing techniques. CONCLUSION: Zipf's law normalization is a useful tool where the Quantile method cannot be applied, as is the case with microarrays containing functionally specific gene sets (boutique arrays)

Comparatively Assessing different Shapes of Lithium-ion Battery Cells

Different shapes of lithium-ion batteries (LIB) are competing as energy storages for the automobile application. The shapes can be divided into cylindrical and prismatic, whereas the prismatic shape can be further divided in regard to the housing stability in Hard-Case and Pouch. Within this paper, the differences in manufacturing costs and efforts as well as the shape related advantages and disadvantages for an automobile application are discussed. Additionally, the process steps for manufacturing the prismatic hard-case and the pouch cell are analyzed in terms of their individual value contribution to the manufacturing costs. Within the analysis, manufacturing errors can be allocated to specific process steps and economically quantified.BMWi, 01MX12046G, Verbundprojekt: ProTrak - Produktionstechnik für die Herstellung von Lithium-Zellen; Teilvorhaben: Technologieportfoliomanagement und Wertschöpfungsanalys

Open ocean carbon monoxide photo-production

Sunlight-initiated photolysis of chromophoric dissolved organic matter (CDOM) is the dominant source of carbon monoxide (CO) in the open-ocean. A modelling study was conducted to constrain this source. Spectral solar irradiance was obtained from two models (GCSOLAR and SMARTS2). Water-column CDOM and total light absorption were modelled using spectra collected along a Meridional transect of the Atlantic ocean using a 200-cm pathlength liquid waveguide UV-visible spectrophotometer. Apparent quantum yields for the production of CO (AQYCO) from CDOM were obtained from a parameterisation describing the relationship between CDOM light absorption coefficient and AQYCO and the CDOM spectra collected. The sensitivity of predicted rates to variations in model parameters (solar irradiance, cloud cover, surface-water reflectance, CDOM and whole water light absorbance, and AQYCO was assessed. The model\u27s best estimate of open-ocean CO photoproduction was 47 +/- 7 Tg CO-C yr-1, with lower and upper limits of 38 and 84 Tg CO-C yr-1, as indicated by sensitivity analysis considering variations in AQYs, CDOM absorbance, and spectral irradiance. These results represent significant constraint of open-ocean CO photoproduction at the lower limit of previous estimates. Based on these results, and their extrapolation to total photochemical organic carbon mineralisation, we recommend a downsizing of the role of photochemistry in the open-ocean carbon cycle. (c) 2006 Elsevier Ltd. All rights reserved

Vođenje hodajućeg robota u strukturiranom prostoru zasnovano na računalnome vidu

Locomotion of a biped robot in a scenario with obstacles requires a high degree of coordination between perception and walking. This article presents key ideas of a vision-based strategy for guidance of walking robots in structured scenarios. Computer vision techniques are employed for reactive adaptation of step sequences allowing a robot to step over or upon or walk around obstacles. Highly accurate feedback information is achieved by a combination of line-based scene analysis and real-time feature tracking. The proposed vision-based approach was evaluated by experiments with a real humanoid robot.Lokomocija dvonožnog robota u prostoru s preprekama zahtijeva visoki stupanj koordinacije između percepcije i hodanja. U članku se opisuju ključne postavke strategije vođenja hodajućih robota zasnovane na računalnome vidu. Tehnike računalnoga vida primijenjene za reaktivnu adaptaciju slijeda koraka omogućuju robotu zaobilaženje prepreka, ali i njihovo prekoračivanje te penjanje na njih. Visoka točnost povratne informacije postignuta je kombinacijom analize linijskih segmenata u sceni i praćenjem značajki scene u stvarnome vremenu. Predloženi je sustav vođenja hodajućih robota eksperimentalno provjeren na stvarnome čovjekolikome robotu