Numerical simulation and laser-based imaging of mixture formation, ignition, and soot formation in a diesel spray

Laser-based imaging of fuel vapor distribution, ignition, and soot formation in diesel sprays was carried out in a high-pressure, high-temperature spray chamber under conditions that correspond to temperature and pressure in a diesel engine. Rayleigh scattering and laser-induced incandescence are used to image fuel density and soot volume fraction. The experimental results provide data for comparison with numerical simulations. An interactive cross-sectionally averaged spray model based on Eulerian transport equations was used for the simulation of the spray, and the turbulence-chemistry interaction was modeled with the representative interactive flamelet (RIF) concept. The flamelet calculation is coupled to the Kiva3V computational fluid dynamics (CFD) code using the scalar dissipation rate and pressure as an input to the RIF-code. The flamelet code computes the instationary flamelet profiles for every time step. These profiles were integrated over mixture fraction space using a prescribed β-PDF to obtain mean values, which are passed back to the CFD-code. Thereby, the temperature and the relevant species in each CFD-cell were obtained. The fuel distribution, the average ignition delay as well as the location of ignition are well predicted by the simulation. Furthermore, simulations show that the experimentally observed injection-to-injection variations in ignition delay are due to temperature inhomogeneities. Experimental and simulated spatial soot and fuel vapor density distributions are compared during and after second stage ignition.     

A dynamic model to determine vibrations in involute helical gears

A method to determine the dynamic load between two rotating elastic helical gears is presented. The stiffness of the gear teeth is calculated using the finite element method and includes the contribution from the elliptic distributed tooth load. To make sure that the new incoming contacts which are the main excitation source are properly simulated, the necessary deformation of the gears is determined by using the true geometry and positions of the gears for every time step of the dynamic calculation. This allows the contact to be positioned outside the plane of action. A numerical example is presented with figures that show the behaviour of the dynamic transmission error as well as the variation of the contact pressure due to the dynamic load for different rotational speeds.     

Comparison of the efficiency of different GLC multi-residue methods on crops containing pesticide residues

Summary The efficiency of the extraction methods with acetone and with ethyl acetate are compared with regard to the multi-pesticide residue determination in fruits and vegetables. The ethyl acetate-method gave higher recoveries for polar pesticides and seems somewhat easier, quicker and cheaper in handling but some co-extractives in the GC-extract are observed. In general, both methods gave acceptable and equivalent recoveries for the pesticides tested.     

Photoelectron Spectroscopy of Nickel, Palladium, and Platinum Oxide Anions

The 364-nm negative ion photoelectron spectra of XO and OXO molecules (X=Ni, Pd, and Pt) are reported. The spectra yield the electron affinities (EAs): EA(NiO)=1.455±0.005 eV; EA(PdO)=1.672±0.005 eV; EA(PtO)=2.172±0.005 eV; EA(ONiO)=3.043±0.005 eV; EA(OPdO)=3.086±0.005 eV; EA(OPtO)=2.677±0.005 eV. In addition, for the diatomics, transitions from the anion X?²Π_3/2 and X?′²Π_1/2 states into neutral X?³Σ⁻, ³Π, and for NiO and PdO, ¹Π, are assigned. Several states have been reassigned from those in the existing literature. Anion ²Π_3/2-²Π_1/2 spin-orbit splittings are measured, as are neutral ³Π₂-³Π₁ spin-orbit splittings: the XO ³Π ₂-³Π₁ splittings increase from 405±30 cm⁻¹ (NiO) to 805±30 cm⁻¹ (PdO) to 3580±40 cm⁻¹ (PtO). A bond length shortening of 0.03±0.01 Å is measured upon electron detachment from NiO⁻, resulting in an anion bond length of 1.66±0.01 Å. The bond length does not change upon electron detachment from PdO⁻ using 3.4-eV photons. The Pt-O bond length decreases by 0.035±0.010 Å in the ³Π₁←²Π_3/2 transition. The spectrum of OPtO displays a significantly more extended vibrational progression than those of ONiO or OPdO, and the O-Pt bond length is found to decrease by 0.07±0.01 Å upon electron detachment. The spectra support the view that the Ni-O bond is largely ionic, the Pd-O bond is somewhat less so, and the Pt-O bond displays a substantial covalent character.     

Structure functions and general final state properties in the linked dipole chain model

We have in an earlier paper, [1], presented a generalization, the Linked Dipole Chain Model LDC, of the model developed by Ciafaloni-Catani-Fiorani-Marchesini, [2], to decribe the structure functions and the states in Deep Inelastic Scattering events. In this paper we would like to present an investigation of a set of general features of the LDC Model, viz the behaviour of the structure functions (we will show how the result interpolates in a precise way in between the well-known DGLAP and BFKL approaches), the average bremsstrahlung emission in the states and finally a partitioning of the structure functions into three different channels: the “ordinary” parton-probe events, where all bremsstrahlung emissions are below the probeQ ², the boson-gluon fusion events where the last splitting of the parton chains contain transverse momentum aboveQ ², and the resolved Rutherford scattering events between the probe and the hadron (where the largest transverse momentum occur somewhere along the emission lines away from the ends).     

A method to determine dynamic loads on spur gear teeth and on bearings

A method is described which can be used to calculate dynamic gear tooth force and bearing forces. The model includes elastic bearings. The gear mesh stiffness and the path of contact are determined using the deformations of the gears and the bearings. This gives contact outside the plane-of-action and a time-varying working pressure angle. In a numerical example it is found that the only important vibration mode for the gear contact is the one where the gear tooth deformation is dominant. The bearing force variation, however, will be much more affected by the other vibration modes. The influence of the friction force is also studied. The friction has no dynamic influence on the gear contact force or on the bearing force in the gear mesh line-of-action direction. On the other hand, the changing of sliding directions in the pitch point is a source for critical oscillations of the bearings in the gear tooth frictional direction. These bearing force oscillations in the frictional direction appear unaffected by the dynamic response along the gear mesh line-of-action direction.     

The use of uncertainty estimates of test results in comparisons with acceptance limits

When a test is performed in order to qualify a material or a product for a certain use, the result is generally compared with an acceptance limit. The test result has an uncertainty which should be estimated and stated (e.g. in accordance with GUM). Very often this is not the case. Further, discussions often arise on the issue of how the uncertainty shall be considered in relationship to the acceptance limit. The intention of this note is to describe, in simple terms, the statistical background and to give some recommendations. In short, there are two clean-cut, extreme situations. The first case is when the uncertainty of the testing procedure is the dominating factor. Here it is found that the estimates of single laboratories cannot, generally, be used for comparisons with acceptance limits. One should have standardised, well-verified estimates based on comprehensive investigations of the method. It can also be concluded that comparisons between test results and acceptance limits have to be made with regard to the actual circumstances, as, e.g. how the acceptance limit is related to the risk. In the second case, the variation in the property of the material or product dominates and the uncertainty of the testing procedure is negligible. When the results are non-quantitative (go – no go), statistical methods can be used to estimate the risk taken with a certain sampling and acceptance strategy that a certain proportion of the batch to be delivered does not qualify. This should be considered more often in standardisation of product test methods. When the results are quantitative, a statistical analysis should be performed and the uncertainty should be compared with the acceptance limit as before, from the actual circumstances. When effects of testing uncertainty and product variation are comparable a sound treatment requires extensive experimental work. No short cuts can be made without loss of confidence! Received: 17 August 2001 Accepted: 21 March 2002     

An α/β-HSQC-α/β Experiment for Spin-State Selective Editing of IS Cross Peaks

A generalized version of the TROSY experiment allows the spin-state selective editing of the four multiplet components of¹⁵N–¹H cross peaks of amide groups in proteins into four different subspectra, with no penalty in sensitivity. An improvement by in sensitivity results, if only two of the four multiplet components are selected. Use of the experiment for the measurement of¹J_HNcoupling constants is discussed. A water flip-back version of the experiment is demonstrated with a 45 kDa fragment of¹⁵N/²H labeledStaphylococcus aureusgyrase B.