Modeling of helical gear contact with tooth deflection

The majority of gear tribological studies are made on spur gears. However, helical gears are generally used in industry, and their contact behavior deserves more attention to establish a realistic base for detailed friction, wear and life studies. This study focuses on the modeling of helical gear contact with tooth deflection. A calculation model for helical gear contact analysis is introduced. Helical gear surface profiles are constructed from gear tool geometry by simulating the hobbing process. The model uses three-dimensional finite elements for the calculation of tooth deflection including tooth bending, shearing and tooth foundation flexibility. The model combines contact analysis with structural analysis to avoid large meshes. Tooth foundation flexibility was found to have an essential role in contact load sharing between the meshing teeth, whereas contact flexibility plays only a minor role. The capability of different local contact calculation methods was also studied.     

Extensions of MSO and the monadic counting hierarchy

In this paper, we study the expressive power of the extension of first-order logic by the unary second-order majority quantifier Most¹. In 1 it was shown that the extension of FO by second-order majority quantifiers of all arities describes exactly the problems in the counting hierarchy. We consider first certain sublogics of FO(Most¹) over unary vocabularies. We show that over unary vocabularies the logic MSO(R), where MSO is monadic second-order logic and R is the first-order Rescher quantifier, can be characterized by Presburger arithmetic, whereas the logic MSO(Rⁿ)_n∈Z+, where Rⁿ is the nth vectorization of R, corresponds to the Δ₀-fragment of arithmetic. Then we show that FO(Most¹)?MSO(Rⁿ)_n∈Z+ and that, on unary vocabularies, FO(Most¹) collapses to uniform-TC⁰. Using this collapse, we show that first-order logic with the binary second-order majority quantifier is strictly more expressive than FO(Most¹) over the empty vocabulary. On the other hand, over strings, FO(Most¹) is shown to capture the linear fragment of the counting hierarchy. Finally we show that, over non-unary vocabularies, FO(Most¹) can express problems complete via first-order reductions for each level of the counting hierarchy.     

Debarking and drying of downy birch (Betula pubescens) and Scots pine (Pinus sylvestris) fuelwood in conjunction with multi-tree harvesting

Fuelwood moisture content is an important parameter for small and medium-sized heating plants. Optimal storage location and good fuelwood storage maintenance promotes drying efficiency and ensures good fuelwood quality. The effective drying period is limited to spring and summer. It is known that partial debarking of wood will enhance drying and improve fuelwood quality.The aim of the study was to test strip debarking as a mean to speed up the drying rate and to lower moisture and bark contents. The prerequisite was that debarking had to be integrated into the processing phase of a single grip harvester. The changes made in the harvester head had to be simple, easily installed and inexpensive.The mechanical objective was solved by drilling holes into the delimbing knives and placing bolts through the knives. In this manner the bolt head would strip bark off the stems when fed through the delimbing knives. The qualitative goal was to see if debarking improved drying rate and if harvesting season and species played a role.The data was collected on non-frozen and frozen pine wood in spring 2005 and in winter 2006, and on non-frozen birch in spring 2007. The debarking results of the non-frozen pine were 3-6% of the total surface area for the normal harvester head and 7-9% for the modified harvester head. The results for frozen pine were correspondingly 1% and 2-2.5%. The debarking results of non-frozen birch were 5-6% and 5-8%. Both studies of pine show that the bolts in delimbing knives doubled the amount of bark removed. There was no significant difference in birch.The delimbed Scots pine fuelwood storages reached 30% moisture content on fresh weight basis during the first drying season at landing. This result was obtained independently of the rate of debarking or the harvesting season. Seasoning over the second summer lowered the moisture content of pine fuelwood by another 5% units to 25%. Birch reached 20% during the first season.     

A 119 GHz planar Schottky diode mixer for a space application

A planar single-ended GaAs Schottky diode mixer has been designed, built, and tested at 119 GHz. The mixer front end includes also a waveguide filter for image rejection, and a temperature compensated ring filter. Measurements at room temperature showed a conversion loss of 7 dB and a noise temperature of 900 K (SSB). At 100 K the measured noise temperature of the mixer was 500 K (SSB).     

Optimising the refrigeration cycle with a two-stage centrifugal compressor and a flash intercooler

The optimisation of a refrigeration process with a two-stage centrifugal compressor and flash intercooler is presented in this paper. The two-stage centrifugal compressor stages are on the same shaft and the electric motor is cooled with the refrigerant. The performance of the centrifugal compressor is evaluated based on semi-empirical specific-speed curves and the effect of the Reynolds number, surface roughness and tip clearance have also been taken into account. The thermodynamic and transport properties of the working fluids are modelled with a real-gas model. The condensing and evaporation temperatures, the temperature after the flash intercooler, and cooling power have been chosen as fixed values in the process. The aim is to gain a maximum coefficient of performance (COP). The method of optimisation, the operation of the compressor and flash intercooler, and the method for estimating the electric motor cooling are also discussed in the article.     

Ships as a sensor network to observe ice field properties

This paper introduces a concept and a prototype system of using ships and coastal stations as a sensor network to obtain additional information about the ice field. The system collects marine radar images and ship performance observations, forms mosaics of images from multiples radars, calculates ice drift from subsequent radar images, analyzes trafficability in different sea areas using performance observations, and delivers processed images, trafficability estimation, and ice drift information to end-users. The prototype was developed and tested during the winters of 2008 and 2009 in the Baltic Sea. In this paper, we describe the prototype and discuss the usability of a ship sensor network. The concept appears to be feasible, and such a system would provide additional information about prevailing ice conditions.     

Direct photolithographic deforming of organomodified siloxane films for micro-optics fabrication

Direct photolithographic deforming of hybrid glass films is used to fabricate optical structures. The structure is fabricated in polyethylene-oxide-acrylate modified hybrid glass films with (1) binary and gray-scale photomasks using a mercury UV-lamp exposure and (2) maskless UV-laser patterning. Fabrication of isolated lenslets, lens arrays, and gratings is presented, including the associated exposure patterns. The hybrid glass material yields light-induced deformation peak-to-valley (p.v.) heights up to 12.8 microm with mercury UV-lamp exposure and p.v. deformation heights up to 6.8 microm with 365-nm UV-laser exposure. The fabricated lenslets' surface data are presented as Zernike-polynomial fit coefficients. Material synthesis and processing-related aspects are examined to understand and control the material's deformation under exposure. The hybrid glass material exhibits a maximum spectral extinction coefficient of 1.6 x 10(-3) microm(-1) at wavelengths ranging from 450 to 2,200 nm and has a refractive index of 1.52 at 632.8 nm. The fabricated structures exhibit rms surface roughness between 1 and 5 nm.     

Dependence between $$\varvec{\upeta }$$-factor and crack location relative to a fusion boundary between hard and soft materials in a SE(B) specimen

The current solutions in ASTM E1820 and E1921 for the calculation of the J-integral are not necessary directly applicable for strength mismatched welds. The problem is connected to the \(\eta \)-factor relating the experimentally measured work to the J-integral. Previous, investigations on \(\eta \)-factors for welds have focused mainly on cracks at the center of the weld. However, characterisation of the \(\eta \)-factor at other locations is also important since the crack can form anywhere in the weld. In this study, the \(\eta \)-factors for SE(B) specimens were investigated, with focus on the effect of the crack location relative to the fusion boundary between a hard base metal and a soft weld metal of a dissimilar metal weld. The results show a dependence between the \(\eta ^{\textit{CMOD}}\)-factor, the distance of the crack to the fusion boundary, the size of the remaining ligament, and the size of the plastic deformation zone. This dependence cannot be generalised based on this study alone, but the results give insight for developing an analytical \(\eta ^{\textit{CMOD}}\)-equation for strength mismatched specimens.     

Groups are not always the same

The idea of supporting group meetings at the same time and at the same place by computer raises the problem of how salient features of group behaviors are understood in meetings. In this paper we take a critical look at several beliefs about group behaviors in research dealing with electronic meeting systems (EMS). The paper argues based on an empirical study that the concept of a small, cohesive business team, so widely held, in all EMS research is not necessarily a valid starting point in thinking of meeting support. In particular, the paper critically evaluates a number of beliefs of user aspects, group features such as composition, structure and protocols, and task characteristics such as nature, importance and meeting goals. In consequence, if these prominent features can vary markedly all meeting support cannot be designed in ways envisaged in current research. In conclusion we outline some research questions—both of empirical and constructive nature—that need to be addressed if the EMS research wants to address issues in computer support in groups that are not similar with business teams.An earlier version of this paper was presented at 25th HICSS conference, 10–12.1.1993.This research was in part funded by the Academy of Finland.The opinions presented in this work are not official statements of any of the participating organizations.This research was in part funded by the Finnish Technology Development Center