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151.
This study reports the electrohydrodimerization of pyruvic acid to 2,3-dimethyltartaric acid in sulphuric acid medium (0.5 M H2SO4) on a lead cathode. The main products detected were lactic acid and 2,3-dimethyltartaric acid. The selectivity towards the formation of 2,3-dimethyltartaric acid was studied vs. pyruvic acid concentration in sulphuric acid solution, at −1.1 V vs. MSE. The best selectivity of 2,3-dimethyltartaric acid reached 69% for an initial concentration of 1.7 M pyruvic acid. The yield of pyruvic acid was 84%. 相似文献
152.
The processing–property relationship of a model cryogenically mechanically alloyed polymer–polymer system [polycarbonate (PC) and poly(aryl ether ether ketone) (PEEK)] was investigated. PC and PEEK powders were cryogenically mechanically alloyed for 10 h, and the resulting two‐phase powder particles were processed into testable coupons with a miniature ram‐injection molder. The bulk mechanical properties of the coupons made from the mechanically alloyed powders and nonmechanically alloyed powders were investigated as a function of mechanical alloying and injection‐molding parameters. The injection‐molded coupons were mechanically tested in the three‐point‐bending mode. The results demonstrated that no measurable improvement was achieved in the energy to break, strain at failure, or failure strength in the coupons made from the mechanically alloyed materials in comparison with those of the coupons made from the nonmechanically alloyed powders. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1196–1202, 2003 相似文献
153.
Thomas J. Brumm C. R. Hurburgh Jr. 《Journal of the American Oil Chemists' Society》1990,67(11):747-749
Drought stress created shriveled and wrinkled (S/W) soybeans in the 1988 soybean crop. Seven lots of 1988 soybeans were examined
to validate the Federal Grain Inspection Service (FGIS) definition of S/W. Lots were subdivided into sized fractions with
both slotted and round-hole screens. Shriveled and wrinkled soybeans were found in all size fractions, whether those fractions
were determined by a slotted or a round-hole screen. None of the size fractions adequately isolated or characterized S/W soybeans.
The FGIS definition of shriveled and wrinkled does not sonsider larger wrinkled soybeans, but only shriveled soybeans passing
through a 10/64″ by 3/4″ slotted screen. The most accurate determination of S/W soybeans can be made by examining the entire
soybean sample, not a sized fraction. 相似文献
154.
Protein topology can be described at different levels. At themost fundamental level, it is a sequence of secondary structureelements (a `primary topology string'). Searching predictedprimary topology strings against a library of strings from knownprotein structures is the basis of some protein fold recognitionmethods. Here a method known as TOPSCAN is presented for rapidcomparison of protein structures. Rather than a simple two-letteralphabet (encoding strand and helix), more complex alphabetsare used encoding direction, proximity, accessibility and lengthof secondary elements and loops in addition to secondary structure.Comparisons are made between the structural information contentof primary topology strings and encodings which contain additionalinformation (`secondary topology strings'). The algorithm isextremely fast, with a scan of a large domain against a libraryof more than 2000 secondary structure strings completing in 相似文献
155.
This paper presents a method for assessing the normalized age factors, which allow accelerated alkali-aggregate reaction (AAR) tests performed at various temperatures (20, 40 and 60 °C) to be related to the conditions encountered in situ in concrete structures. The evaluation of normalized age factors is based on the comparison of many experimental results taken from the literature concerning laboratory tests and in situ measurements. The use of these factors permits us to evaluate, from the results of an accelerated test performed at 60 °C, the protection time against AAR that could be expected for in situ concretes containing mineral admixtures (silica fume and fly ashes). The results show that, in addition to the inhibitory action of mineral admixtures leading to a strong decrease in the final AAR-swelling, the protection against abnormal expansion caused by AAR increases significantly when mineral admixtures are used. Abnormal expansion is expected at 2-4 years for plain concrete compared to 7-50 years for concrete with mineral admixtures. 相似文献
156.
Florian Seidel Clemens Hage Martin Kleinsteuber 《Machine Vision and Applications》2014,25(5):1227-1240
An increasing number of methods for background subtraction use Robust PCA to identify sparse foreground objects. While many algorithms use the \(\ell _1\) -norm as a convex relaxation of the ideal sparsifying function, we approach the problem with a smoothed \(\ell _p\) -quasi-norm and present pROST, a method for robust online subspace tracking. The algorithm is based on alternating minimization on manifolds. Implemented on a graphics processing unit, it achieves realtime performance at a resolution of \(160 \times 120\) . Experimental results on a state-of-the-art benchmark for background subtraction on real-world video data indicate that the method succeeds at a broad variety of background subtraction scenarios, and it outperforms competing approaches when video quality is deteriorated by camera jitter. 相似文献
157.
Martin Saska Tomáš Krajník Vojtěch Vonásek Zdeněk Kasl Vojtěch Spurný Libor Přeučil 《Journal of Intelligent and Robotic Systems》2014,73(1-4):603-622
A fault-tolerant method for stabilization and navigation of 3D heterogeneous formations is proposed in this paper. The presented Model Predictive Control (MPC) based approach enables to deploy compact formations of closely cooperating autonomous aerial and ground robots in surveillance scenarios without the necessity of a precise external localization. Instead, the proposed method relies on a top-view visual relative localization provided by the micro aerial vehicles flying above the ground robots and on a simple yet stable visual based navigation using images from an onboard monocular camera. The MPC based schema together with a fault detection and recovery mechanism provide a robust solution applicable in complex environments with static and dynamic obstacles. The core of the proposed leader-follower based formation driving method consists in a representation of the entire 3D formation as a convex hull projected along a desired path that has to be followed by the group. Such an approach provides non-collision solution and respects requirements of the direct visibility between the team members. The uninterrupted visibility is crucial for the employed top-view localization and therefore for the stabilization of the group. The proposed formation driving method and the fault recovery mechanisms are verified by simulations and hardware experiments presented in the paper. 相似文献
158.
Geschäftsmodelle 总被引:1,自引:1,他引:0
Prof. Dr. Daniel Veit Prof. Eric Clemons Prof. Dr. Alexander Benlian Prof. Dr. Peter Buxmann Prof. Dr. Thomas Hess Prof. Dr. Dennis Kundisch Prof. Dr. Jan Marco Leimeister Prof. Dr. Peter Loos Prof. Dr. Martin Spann 《WIRTSCHAFTSINFORMATIK》2014,56(1):55-64
The business model concept, although a relatively new topic for research, has garnered growing attention over the past decade. Whilst it has been robustly defined, the concept has so far attracted very little substantive research. In the context of the wide-spread digitization of businesses and society at large, the logic inherent in a business model has become critical for business success and, hence, a focus for academic inquiry. The business model concept is identified as the missing link between business strategy, processes, and Information Technology (IT). The authors argue that the BISE community offers distinct and unique competencies (e.g., translating business strategies into IT systems, managing business and IT processes, etc.) that can be harnessed for significant research contributions to this field. Within this research gap three distinct streams are delineated, namely, business models in IT industries, IT enabled or digital business models, and IT support for developing and managing business models. For these streams, the current state of the art, suggest critical research questions, and suitable research methodologies are outlined. 相似文献
159.
Abstract. A Bayesian approach to option pricing is presented in which posterior inference about the underlying returns process is conducted implicitly via observed option prices. A range of models allowing for conditional leptokurtosis, skewness and time‐varying volatility in returns are considered, with posterior parameter distributions and model probabilities backed out from the option prices. Models are ranked according to several criteria, including out‐of‐sample predictive and hedging performance. The methodology accommodates heteroscedasticity and autocorrelation in the option pricing errors, as well as regime shifts across contract groups. The method is applied to intraday option price data on the S&P500 stock index for 1995. While the results provide support for models that accommodate leptokurtosis and skewness, no one model dominates when all criteria are considered. 相似文献
160.
LiNi1/3Co1/3Mn1/3O2 cathode materials have been coated with Al2O3 nano-particles using sol-gel processing to improve its electrochemical properties. The X-ray diffraction (XRD) pattern of the as-prepared Al2O3 nano-particles was indexed to the cubic structure of the γ-Al2O3 phase and had an average size of ∼4 nm. The XRD showed that the structure of LiNi1/3Co1/3Mn1/3O2 was not affected by the Al2O3 coating. However, the Al2O3 coatings on LiNi1/3Co1/3Mn1/3O2 improved the cyclic life performance and rate capability without decreasing its initial discharge capacity. These electrochemical properties were also compared with those of LiAlO2-coated LiNi1/3Co1/3Mn1/3O2 cathode material. The electrochemical impedance spectroscopy (EIS) was studied to understand the enhanced electrochemical properties of the Al2O3-coated LiNi1/3Co1/3Mn1/3O2 compared to uncoated LiNi1/3Co1/3Mn1/3O2. 相似文献