Mixture Design and Response Surface Analysis of Densification of Silicon Carbide Ceramics with (SiO2–Dy2O3–Al2O3) Additives

Statistical mixture designs are used to systematically study the densification properties of silicon carbide (SiC) ceramics sintered with SiO₂, Dy₂O₃, and Al₂O₃. Mixture models for percentage theoretical density and SiC weight loss as a function of the SiO₂, Dy₂O₃, and Al₂O₃ oxide proportions have been determined and validated by analysis of variance. The results indicate a region confined by about 0–20 mol% silica, 50–65 mol% dysprosia, and 40–65 mol% alumina, with all samples containing 10% by volume of additives, and simultaneously maximization of density values and minimization of weight loss during SiC-based ceramic sintering.     

Carbon print studies for the energy conservation regulations of the UK and China

The recently published building energy conservation regulation of China (GB50189-2005, 2005 [1]) was compared with the latest UK building energy conservation regulation (Part L) (Building Regulation Approved Document L2A, 2006 [2]). The UK regulation appeared stricter in its requirements and standards than the Chinese regulation. In two case studies, the design of a sample building is altered to fulfil the minimum requirements of the two regulations. The energy consumption and Carbon print of the virtual building under the two set of regulations are estimated by computer based models in the two case studies based on a building in the Cold regions. The building under the UK regulation showed higher energy efficiency and less Carbon emissions per year. The high level estimate in the case studies discovered a potential energy savings of 29% by strengthening the design requirements in the Chinese regulation to the UK level. The improvement on energy efficiency of buildings can be achieved in strengthening the proactive design aspects on building envelope, efficient HVAC, lighting and lighting control system. The software used was SBEM which is the default tool in the UK Part L regulation.     

Impact of climate variability on tropospheric ozone

A simulation with the climate-chemistry model (CCM) E39/C is presented, which covers both the troposphere and stratosphere dynamics and chemistry during the period 1960 to 1999. Although the CCM, by its nature, is not exactly representing observed day-by-day meteorology, there is an overall model's tendency to correctly reproduce the variability pattern due to an inclusion of realistic external forcings, like observed sea surface temperatures (e.g. El Ni?o), major volcanic eruption, solar cycle, concentrations of greenhouse gases, and Quasi-Biennial Oscillation. Additionally, climate-chemistry interactions are included, like the impact of ozone, methane, and other species on radiation and dynamics, and the impact of dynamics on emissions (lightning). However, a number of important feedbacks are not yet included (e.g. feedbacks related to biogenic emissions and emissions due to biomass burning). The results show a good representation of the evolution of the stratospheric ozone layer, including the ozone hole, which plays an important role for the simulation of natural variability of tropospheric ozone. Anthropogenic NO(x) emissions are included with a step-wise linear trend for each sector, but no interannual variability is included. The application of a number of diagnostics (e.g. marked ozone tracers) allows the separation of the impact of various processes/emissions on tropospheric ozone and shows that the simulated Northern Hemisphere tropospheric ozone budget is not only dominated by nitrogen oxide emissions and other ozone pre-cursors, but also by changes of the stratospheric ozone budget and its flux into the troposphere, which tends to reduce the simulated positive trend in tropospheric ozone due to emissions from industry and traffic during the late 80s and early 90s. For tropical regions the variability in ozone is dominated by variability in lightning (related to ENSO) and stratosphere-troposphere exchange (related to Northern Hemisphere Stratospheric dynamics and solar activity). Since tropospheric background chemistry is regarded only, the results are quantitatively limited with respect to derived trends. However, the main results are regarded to be robust. Although the horizontal resolution is rather coarse in comparison to regional models, such kind of simulations provide useful and necessary information on the impact of large-scale processes and inter-annual/decadal variations on regional air quality.     

Cutting edge orthogonal contact-zone analysis using detailed tool shape representation

A new method for numerically controlled (NC)-simulation-based numerical analysis of the tool-workpiece contact area in cutting processes is presented. To gain enhanced knowledge about tool-workpiece interaction, determination of chip thickness, contact length, and resulting cross-section area of the undeformed chip is of major interest. Compared to common simulation approaches, where rotationally symmetrically constructed tool shape is used, the new method uses a detailed three-dimensional tool shape model for an extended and more accurate contact zone analysis. As a corresponding representation of the workpiece and its time-dependent change of shape, a multidexel model is used. To perform contact zone analysis, each cutting element and a multidexel model are intersected in discrete time steps corresponding to the tool rotation. Subsequently, the intersection point of each dexel is mapped on the local coordinate system of the cutting geometry. The parametric cutting geometry allows a direct computation of local cutting depth and contact length for each involved point. Based on the local values of contact length and cross section area of the undeformed chip, the characteristic values for the entire contact zone are calculated and used to predict mechanical loads caused by the cutting process. To demonstrate the application of the novel approach, a prediction of forces in slot milling and drilling of 1.1191 steel (C45EN) is presented.     

Chemometric Analysis of <Superscript>1</Superscript>H NMR Fingerprints of <Emphasis Type="Italic">Coffea arabica</Emphasis> Green Bean Extracts Cultivated under Different Planting Densities

High planting density has been used to increase coffee production but there are few studies related to the variations it provokes in metabolite compositions. The use of ¹H NMR data associated with chemometric techniques allows the determination of metabolic fingerprints and verification of metabolic changes when coffee is subjected to high planting densities. The aim of this work is to investigate ¹H NMR spectral data of green bean extracts of Coffea arabica cv. IAPAR 59 grown in a square pattern at two planting densities, 6000 and 10,000 plants ha^?1. Thirty extracts were obtained using a simplex centroid design with four solvents (ethanol, acetone, dichloromethane, and hexane). The lyophilized extracts were dissolved in DMSO-d₆ to obtain the ¹H NMR spectra. The spectral data were analyzed with principal component (PCA) and cluster analyses (CA). Significant differences between ethanolic and non-ethanolic extracts were found by PCA. Only the ethanolic mean spectrum showed characteristic chemical shifts of sugars and trigonelline. Acetone extracts were separated by cluster analysis.     

Thermal deformations of cutting tools: measurement and numerical simulation

Challenges for machining include greater and greater material removal rates coupled with an increase in the use of difficult to machine materials, as well as environmental-friendly dry or minimum quantity lubrication machining, small manufacturing batches and frequently changed manufacturing orders. These trends are accompanied by high temperatures in the machining process and large, variable heat flows causing thermo-elastic displacements of the tool, the workpiece and the clamping devices. Although the displacements are small, in the range of a few micrometers, they have assumed more and more importance because of growing requirements for manufacturing accuracy. Thermo-elastic displacements of the tool due to heat flow during machining are investigated and analysed in this paper. Temperatures and displacements are measured on a test bed equipped with measuring instruments. The identification of the thermal boundary and contact conditions is supported by finite element models. Knowledge of the heat flows resulting from the machining process is a prerequisite for control of and compensation for displacements. Since these heat flows either cannot be measured or can only be measured with enormous effort, heat flows are determined by means of numerical simulation of the machining process itself. This strategy has been previously used as a systematic approach for turning in orthogonal cutting conditions. However, further investigations are needed for oblique turning conditions, milling and drilling operations.     

Analysis of Over- and Underdetermined Nonlinear Differential-Algebraic Systems with Application to Nonlinear Control Problems

 We study over- and underdetermined systems of nonlinear differential-algebraic equations. Such equations arise in many applications in circuit and multibody system simulation, in particular when automatic model generation is used, or in the analysis and solution of control problems in the behavior framework.?We give a general (local) existence and uniqueness theory and apply the results to analyze when nonlinear implicit control problems can be made regular by state or output feedback.?The theoretical analysis also leads immediately to numerical methods for the simulation as well as the construction of regularizing feedbacks. Date received: February 21, 2000. Date revised: November 14, 2000.     

Photolithographic patterning of polymer-encapsulated optical oxygen sensors

In this paper we show a novel fabrication process capable of yielding arbitrarily-shaped optical oxygen sensor patterns at micron resolution. The wafer-level process uses a thin-film sacrificial metal layer as intermediate mask, protecting the sensor material and enabling the use of conventional semiconductor patterning techniques. Feature sizes down to 3 μm are demonstrated and only limited by the lithographic process. Gaseous oxygen detection using the patterned sensors shows Stern–Volmer behaviour with a measured intensity ratio I₁₀₀/I₀ of 10.8, the highest reported for a lab-on-a-chip compatible glass substrate. The process has the potential to enable the integration of multiple sensor patches underneath single cells for laterally registered oxygen sensing in cell-culture applications.