Speed Control of Motor Based on Improved Glowworm Swarm Optimization

To better regulate the speed of brushless DC motors, an improved algorithm based on the original Glowworm Swarm Optimization is proposed. The proposed algorithm solves the problems of poor robustness, slow convergence, and low accuracy exhibited by traditional PID controllers. When selecting the glowworm neighborhood set, an optimization scheme based on the growth and competition behavior of weeds is applied to a single glowworm to prevent falling into a local optimal solution. After the glowworm’s position is updated, the league selection operator is introduced to search for the global optimal solution. Combining the local search ability of the invasive weed optimization with the global search ability of the league selection operator enhances the robustness of the algorithm and also accelerates the convergence speed of the algorithm. The mathematical model of the brushless DC motor is established, the PID parameters are tuned and optimized using improved Glowworm Swarm Optimization algorithm, and the speed of the brushless DC motor is adjusted. In a Simulink environment, a double closed-loop speed control model was established to simulate the speed control of a brushless DC motor, and this simulation was compared with a traditional PID control. The simulation results show that the model based on the improved Glowworm Swarm Optimization algorithm has good robustness and a steady-state response speed for motor speed control.     

A novel vacuum ultra violet lamp for metastable rare gas experiments

We report on a new design of a vacuum ultra violet (VUV) lamp for direct optical excitation of high laying atomic states, e.g., for excitation of metastable rare gas atoms. The lamp can be directly mounted to ultra-high vacuum vessels (p ≤ 10(-10)mbar). It is driven by a 2.45 GHz microwave source. For optimum operation, it requires powers of ~20 W. The VUV light is transmitted through a magnesium fluoride window, which is known to have a decreasing transmittance for VUV photons with time. In our special setup, after a run-time of the VUV lamp of 550 h the detected signal continuously decreased to 25% of its initial value. This corresponds to a lifetime increase of two orders of magnitude compared to previous setups or commercial lamps.     

Historic Building Stones and Flooding: Changes of Physical Properties due to Water Saturation

Natural stone is a common material in historic constructions. Flood events may directly affect surfaces of historic stone buildings. Since ashlars and stone sculptures often carry valuable cultural information, a more detailed knowledge about changes in physical properties due to water saturation is crucial for the assessment of their surface stability in case of flooding. Water saturation of stones leads to loss of mechanical strength and to expansion of volume (hydric dilatation). On the basis of data from literature, a rough scheme of vulnerability is suggested for different kinds of building stones. The majority of igneous and metamorphic rock types with dense crystalline structure are not vulnerable to flooding, whereas some types of pyroclastic rocks (tuffs) as well as clay-bearing sandstones are highly vulnerable. Detailed laboratory investigations on Elbe sandstone demonstrate the influence of petrographic features on material behavior due to water saturation. Results of laboratory tests are in good accordance to on-site observations made after the great summer flood in Dresden, Germany in 2002.     

Nanoscale Thermometry with a Quantum Dot

A two-terminal quantum dot bridging a temperature difference can operate as a thermometer by probing the Fermi-Dirac distributions of the electron gas on both sides of the quantum dot. This thermometry requires that the dot’s energy levels are spaced in energy by many kT and that the intrinsic energetic width of the energy resonances are either much larger or much smaller than kT. We compare these two regimes of operation and discuss the intermediate regime which separates them. Quantum-dot thermometry can assist in mesoscopic thermal experiments where short-distance temperature gradients elude most thermometry techniques.     

Texture,composition and anatomy of spinach leaves in relation to nitrogen fertilization

BACKGROUND: The postharvest quality and shelf life of spinach are greatly influenced by cultural practices. Reduced spinach shelf life is a common quandary in the Salinas Valley, California, where current agronomic practices depend on high nitrogen (N) rates. This study aimed to describe the postharvest fracture properties of spinach leaves in relation to N fertilization, leaf age and spinach cultivar. RESULTS: Force–displacement curves, generated by a puncture test, showed a negative correlation between N fertilization and the toughness, stiffness and strength of spinach leaves (P > 0.05). Younger leaves (leaves 12 and 16) from all N treatments were tougher than older leaves (leaves 6 and 8) (P > 0.05). Leaves from the 50 and 75 ppm total N treatments irrespective of spinach cultivar had higher fracture properties and nutritional quality than leaves from other N treatments (P > 0.05). Total alcohol‐insoluble residues (AIR) and pectins were present at higher concentrations in low‐N grown plants. These plants also had smaller cells and intercellular spaces than high‐N grown leaves (P > 0.05). CONCLUSION: Observed changes in physicochemical and mechanical properties of spinach leaves due to excess nitrogen fertilization were significantly associated with greater postharvest leaf fragility and lower nutritional quality. Copyright © 2012 Society of Chemical Industry     

Exploring Neighborhoods in the Metagenome Universe

The variety of metagenomes in current databases provides a rapidly growing source of information for comparative studies. However, the quantity and quality of supplementary metadata is still lagging behind. It is therefore important to be able to identify related metagenomes by means of the available sequence data alone. We have studied efficient sequence-based methods for large-scale identification of similar metagenomes within a database retrieval context. In a broad comparison of different profiling methods we found that vector-based distance measures are well-suitable for the detection of metagenomic neighbors. Our evaluation on more than 1700 publicly available metagenomes indicates that for a query metagenome from a particular habitat on average nine out of ten nearest neighbors represent the same habitat category independent of the utilized profiling method or distance measure. While for well-defined labels a neighborhood accuracy of 100% can be achieved, in general the neighbor detection is severely affected by a natural overlap of manually annotated categories. In addition, we present results of a novel visualization method that is able to reflect the similarity of metagenomes in a 2D scatter plot. The visualization method shows a similarly high accuracy in the reduced space as compared with the high-dimensional profile space. Our study suggests that for inspection of metagenome neighborhoods the profiling methods and distance measures can be chosen to provide a convenient interpretation of results in terms of the underlying features. Furthermore, supplementary metadata of metagenome samples in the future needs to comply with readily available ontologies for fine-grained and standardized annotation. To make profile-based k-nearest-neighbor search and the 2D-visualization of the metagenome universe available to the research community, we included the proposed methods in our CoMet-Universe server for comparative metagenome analysis.     

A Case Study in Design and Verification of Manufacturing System Control Software with Hierarchical Petri Nets

The application of Petrinets is one of the well-known approaches for developing provably error-free control software for manufacturing systems. To evaluate the practicability of available methods and tools for at least medium-sized systems, a case study has been performed to develop modularised control software of a production cell with hierarchical Petri nets, supporting reuse as well as stepwise validation.     

Electrical properties of hafnium silicate films obtained from a single-source MOCVD precursor

In the present work, the potential of hafnium silicate (Hf_xSi_yO₂) films as an alternative gate dielectric to SiO₂ for future technology generations is demonstrated. Thermally stable Hf_xSi_yO₂ films are deposited from a single-source MOCVD precursor. I–V and C–V measurement data are presented and effects of post-deposition annealing on electrical properties are discussed. A 900 °C O₂-anneal shows best results in terms of leakage current characteristics and is, therefore, intensively investigated.     

Diffusion-weighted MRI in sporadic Creutzfeldt-Jakob disease

Diffusion-weighted MRI (DWI) was used in three patients with autopsy-proven sporadic Creutzfeldt-Jakob disease (CJD) to provide a rapid noninvasive way to make this sometimes confusing diagnosis. DWI prompted the diagnosis of CJD at an early stage and appears to be particularly useful for monitoring the progression of the disease. We suggest that patients with suspected CJD and no abnormalities on T2- and proton density-weighted images may have cortical involvement on DWI.