Role and distribution of different Ba-containing phases in supported Pt–Ba NSR catalysts

Pt–Ba/MeO (where MeO = Al₂O₃, CeO₂, SiO₂ and ZrO₂) NO _x storage-reduction catalysts with Ba-loading varying from 0 wt.% to 28 wt.% were investigated concerning stability of Ba phases and NO _x storage-reduction efficiency. For Pt–Ba/Al₂O₃ three different Ba-containing phases with different thermal stability are distinguished based on their interaction with the support. The relative concentration of these phases varies with the Ba-loading and NO _x storage tests indicated that the BaCO₃ phase decomposing between 400 °C and 800 °C (LT-BaCO₃) is the most efficient Ba containing phase for NO _x storage. Similar investigations of Pt–Ba catalysts supported on CeO₂, SiO₂ and ZrO₂ showed that the relative amount of LT-BaCO₃ phase depends also on the support material. NO _x storage measurements confirmed a correlation between the concentration of LT-BaCO₃ and NO _x storage efficiency. Basicity and textural properties of the support are identified as crucial parameters for efficient NO _x storage catalysts.     

Generalized model of vibro-isolation systems with seated human body for single-axis transmission of vibration

A generalized model of vibration isolation systems with a human body in a seated position is developed. The system dynamics is modeled for a single-axis transmission of vibration, that is, longitudinal x, lateral y and vertical z, to limit whole-body vibration exposure. The developed model can be successfully employed to describe the propagation of vibration waves from the source to a vibrating object. The proposed mathematical model can be widely used to protect a human body against vibration.     

Selective reduction of NO by NH3 over manganese–cerium mixed oxides: Relation between adsorption, redox and catalytic behavior

Manganese–cerium mixed oxide catalysts with different molar ratio Mn/(Mn + Ce) (0, 0.25, 0.50, 0.75, 1) were prepared by citric acid method and investigated concerning their adsorption behavior, redox properties and behavior in the selective catalytic reduction of NO_x by NH₃. The studies based on pulse thermal analysis combined with mass spectroscopy and FT-IR spectroscopy uncovered a clear correlation between the dependence of these properties and the mixed oxide composition. Highest activity to nitrogen formation was found for catalysts with a molar ratio Mn/(Mn + Ce) of 0.25, whereas the activity was much lower for the pure constituent oxides. Measurements of adsorption uptake of reactants, NO_x (NO, NO₂) and NH₃, and reducibility showed similar dependence on the mixed oxide composition indicating a clear correlation of these properties with catalytic activity. The adsorption studies indicated that NO_x and NH₃ are adsorbed on separate sites. Consecutive adsorption measurements of the reactants showed similar uptakes as separate measurements indicating that there was no interference between adsorbed reactants. Mechanistic investigations by changing the sequence of admittance of reactants (NO_x, NH₃) indicated that at 100–150 °C nitrogen formation follows an Eley–Rideal type mechanism, where adsorbed ammonia reacts with NO_x in the gas phase, whereas adsorbed NO_x showed no significant reactivity under conditions used.     

Formation and stability of barium aluminate and cerate in NOx storage-reduction catalysts

The formation and stability of BaAl₂O₄ and BaCeO₃ in Pt-Ba/Al₂O₃ and Pt-Ba/CeO₂ based NO_x storage-reduction (NSR) catalysts has been investigated using kinetic measurements, X-ray diffraction, thermal analysis and X-ray absorption spectroscopy. In as-prepared state, the Ba-component in the NSR catalysts was made up of amorphous BaO and BaCO₃. The formation of BaAl₂O₄ started above 850 °C, whereas the formation of BaCeO₃ was already observed at 800 °C and was faster than that of BaAl₂O₄. The stability of BaAl₂O₄ and BaCeO₃ in various liquid and gaseous atmospheres was different. BaAl₂O₄ was rapidly hydrated at room temperature in the presence of water and transformed to Ba(NO₃)₂ and γ-alumina in the presence of HNO₃, whereas BaCeO₃ was decomposed to much lower extent under these conditions. Interestingly, BaCeO₃ was transformed to Ba(NO₃)₂/CeO₂ in the presence of NO₂/H₂O at 300–500 °C. Also, the presence of CO₂ led to decomposition of barium cerate, which has important consequences for the catalyst ageing under NO_x-storage conditions and can be exploited for regeneration of thermally aged NSR-catalysts.     

Measurement of secondary colony formation after 5 weeks in long-term cultures in patients with myelodysplastic syndrome

Pancytopenia is a frequent manifestation of myelodysplastic syndromes (MDS). In the presence of an empty bone marrow, clinical distinction from aplastic anemia may be difficult. The hypoplastic marrow morphology seen in some cases of MDS raises questions about etiologic and pathophysiologic relationships between aplastic anemia and MDS. The goal of our study was to compare the degree of the hematopoietic failure in these diseases at the level of the most immature progenitor and stem cells that can be measured in vitro. In a systemic, prospective fashion, we have studied bone marrow (n = 45) and peripheral blood (n = 33) of patients with MDS for the number of long-term culture initiating cells (LTC-IC) in comparison to 17 normal controls and patients with new, untreated aplastic anemia (46 marrow; 62 blood samples). Due to the low numbers of cells available for the analysis, formal limiting dilution analysis could not be performed, instead secondary colony-forming cells (CFC) after 5 weeks of LTBMC were measured. As the number of these cells is proportional to the input number of LTC-IC, the number of secondary CFC per 10(6) mononuclear cells (MNC) initiating the LTBMC can be used as a measure of the content of immature stem cells in bone marrow and peripheral blood. The MDS group consisted of 34 RA, three RARS, eight RAEB and two RAEB-T patients with mean absolute neutrophil values of 1992, 1413, 1441, and 380 per mm3, respectively. The diagnosis was established based on bone marrow morphology and results of cytogenetic studies. In comparison to controls (147 +/- 38/10(6) MNC), significantly decreased numbers of bone marrow secondary CFC were found in MDS: in patients with RA and RARS, 21 +/- 7 secondary CFC per 10(6) bone marrow MNC (P < 0.001); patients with RAEB and RAEB-T: 39 +/- 12 CFC per 10(6) marrow MNC (P < 0.001). In all groups tested, the decrease in peripheral blood secondary CFC numbers was consistently less pronounced. In MDS patients with hypocellular bone marrow, secondary CFC were lower but not significantly different in comparison to MDS with hypercellular marrow (18 +/- 6 vs 35 +/- 11; NS; hypoplastic bone marrow also was not associated with significantly lower neutrophil counts). However, in 24% of patients with MDS, bone marrow secondary CFC were within the normal range, while in the aplastic anemia group only one of the patients showed secondary CFC number within normal range. Bone marrow and blood secondary CFC numbers in hypoplastic RA were significantly higher than those in severe aplastic anemia 919 +/- 5 in bone marrow, P < 0.01; 7 +/- 2 in blood, P < 0.05). This trend was even more pronounced in hypoplastic RA with chromosomal abnormalities. However, no significant differences were found between the secondary CFC numbers in hypoplastic RA and moderate aplastic anemia. We concluded that, although the deficiency in the stem cell compartment is less severe in MDS than in aplastic anemia, depletion of early hematopoietic cells is an essential part of the pathophysiology in both diseases.     

Creep–Environment Interactions in Dwell-Fatigue Crack Growth of Nickel Based Superalloys

A multi-scale, mechanistic model is developed to describe and predict the dwell-fatigue crack growth rate in the P/M disk superalloy, ME3, as a function of creep–environment interactions. In this model, the time-dependent cracking mechanisms involve grain boundary sliding and dynamic embrittlement, which are identified by the grain boundary activation energy, as well as, the slip/grain boundary interactions in both air and vacuum. Modeling of the damage events is achieved by adapting a cohesive zone (CZ) approach which considers the deformation behavior of the grain boundary element at the crack tip. The deformation response of this element is controlled by the surrounding continuum in both far field (internal state variable model) and near field (crystal plasticity model) regions and the intrinsic grain boundary viscosity which defines the mobility of the element by scaling up the motion of dislocations into a mesoscopic scale. This intergranular cracking process is characterized by the rate at which the grain boundary sliding reaches a critical displacement. A damage criterion is introduced by considering the grain boundary mobility limit in the tangential direction leading to strain incompatibility and failure. Results of simulated intergranular crack growth rate using the CZ model are generated for temperatures ranging from 923 K to 1073 K (650 °C to 800 °C), in both air and vacuum. These results are compared with those experimentally obtained and analysis of the model sensitivity to loading conditions, particularly temperature and oxygen partial pressure, are presented.     

The State‐of‐the‐Art in Predictive Visual Analytics

Predictive analytics embraces an extensive range of techniques including statistical modeling, machine learning, and data mining and is applied in business intelligence, public health, disaster management and response, and many other fields. To date, visualization has been broadly used to support tasks in the predictive analytics pipeline. Primary uses have been in data cleaning, exploratory analysis, and diagnostics. For example, scatterplots and bar charts are used to illustrate class distributions and responses. More recently, extensive visual analytics systems for feature selection, incremental learning, and various prediction tasks have been proposed to support the growing use of complex models, agent‐specific optimization, and comprehensive model comparison and result exploration. Such work is being driven by advances in interactive machine learning and the desire of end‐users to understand and engage with the modeling process. In this state‐of‐the‐art report, we catalogue recent advances in the visualization community for supporting predictive analytics. First, we define the scope of predictive analytics discussed in this article and describe how visual analytics can support predictive analytics tasks in a predictive visual analytics (PVA) pipeline. We then survey the literature and categorize the research with respect to the proposed PVA pipeline. Systems and techniques are evaluated in terms of their supported interactions, and interactions specific to predictive analytics are discussed. We end this report with a discussion of challenges and opportunities for future research in predictive visual analytics.     

EasySVM: A visual analysis approach for open-box support vector machines

Computational Visual Media - Support vector machines (SVMs) are supervised learning models traditionally employed for classification and regression analysis. In classification analysis, a set of...     

Method of selecting vibro-isolation properties of vibration reduction systems

An effective optimization method is proposed in this paper to determine the basic characteristics of non-linear visco-elastic elements used in passive vibration reduction systems. The developed method is examined by performing experimental investigations on the exemplary vibration reduction system, i.e., the passive seat suspension. The shaping of vibro-isolation properties is analyzed for different spectral classes of excitation signals.