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- Blomqvist, Lars, 1962-
(författare)
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Laminated Veneer Products : Shape Stability and Effect of Enhanced Formability on Bond-Line Strength
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns two aspects of the manufacture of laminated veneer products (LVPs). The first aspect is related to the possible improvement of the shape stability of LVPs, and the second has its starting point in the modification of the veneer for enhanced formability as well as the question of whether and how these modifications affect the bond-line strength.LVPs are veneers bonded with adhesive into predetermined shapes, mostly for the production of furniture and interior fittings. Since any deviation from the intended shape is a problem for both manufacturer and customer, various studies have sought to evaluate the influence of different materials and process parameters on shape stability. Parameters studied have included wood species (beech and birch), an adhesive system based on urea formaldehyde, the adhesive distribution on the veneer, climate, moisture content and fibre orientations of the veneers, as well as the orientation of the individual veneers in a multiply.Manufacturers of LVPs must consider some basic facts about wood in orders adequately to provide shape-stable LVPs to customers. Wood emits and absorbs moisture in relation to the surrounding climate, and this can lead to shrinkage and swelling. Such moisture induced movements differ in the wood’s different directions, and the magnitude is specific for the species. A thorough understanding of this is the basis for achieving shape-stable LVPs.Symmetry is defined in this thesis such that the veneer properties are balanced in the laminate. This means that opposite veneers on either side of the centre veneer have similar characteristic. An LVP will become distorted if the veneers are asymmetrically oriented before the press. Deviation from the desired shape can be small immediately after the pressing, but it may increase significantly with moisture content (MC) variations. Asymmetry may result when veneers with different fibre orientations are included in the laminate or when the veneers are placed asymmetrically. It may also occur if veneers with different MCs are bonded together asymmetrically. One aggravating factor is that the lathe checks that are introduced when the veneers are peeled or sliced from the log affect the shape stability. In 3-ply crosswise-oriented plywood, the veneer surfaces on which the lathe checks occur should be oriented in the same way for high shape stability.Based on existing knowledge, the production of shape-stable LVPs requires that the veneers are conditioned to a uniform MC and sorted with regard to fibre orientation and the side with lathe checks before bonding. End-user climates should govern the MC of the veneers and the moisture added with the adhesive during the process. Straight-grain veneers and symmetry should always be the goal.Moulding can cause stretching, i.e. strain, of the veneers depending on the curvature of the mould. To prevent the veneers from rupture, there are various ways to strengthen the veneers particularly in the transverse direction in which the veneer is weakest. However, tests have shown that these pre-treatments of veneers for enhanced formability can prevent the adhesive from penetrating the wood surface. It is therefore important to confirm that the pre-treatment does not affect the bond-line strength.
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- Blomqvist, Niklas, 1987-
(författare)
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Essays on Labor Economics : The Role of Government in Labor Supply Choices
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- "Right to Work Full-time" Policies and Involuntary Part-time EmploymentThis paper investigates the effect of right to full-time policies implemented to decrease involuntary part-time work for public care workers employed by Swedish municipalities. Taking advantage of a staggered decision process, these policies are evaluated using a difference-in-differences approach. Results show that involuntary part-time employment is real and significant, with 10% of part-time employed workers choosing full-time when given the opportunity. The effect mainly comes from a decrease in contracts of <75% of full-time and an increase in contracts of 80% of full-time and above. Further results from the full-time policies show that being more flexible in the choice of hours worked is popular among workers, indicated by an increase in tenure and reduced turnover in municipalities that offer more flexibility in the choice of hours worked.Hours Constraints and Tax Elasticity Estimates - Evidence from Swedish Public Care WorkersThere is a concern that tax elasticity estimates may be downward biased in the presence of optimization frictions for workers. So far, there is limited evidence on the nature of these optimization frictions. This paper provides new insight into one part of the optimization frictions black box, namely hours constraints. Using unique and newly collected data, I exploit a staggered implementation of a policy that gave some public care workers the opportunity to choose their preferred hours of work. Taking advantage of this policy, I estimate differences in tax elasticities between constrained and unconstrained public care workers by comparing bunching at a large tax kink in the Swedish tax system. The empirical evidence points to the conclusion that hours constraints do not affect tax elasticity estimates.Restricting Residence Permits - Short-Run Evidence from a Swedish ReformIn June 2016, the Swedish parliament decided to restrict the granting of permanent residence permits for asylum seekers in Sweden. The new status quo for a refugee is a temporary rather than a permanent residence permit. In a first evaluation of this reform we use a Regression discontinuity analysis in which we follow refugees, aged 25-65, over their first years after arrival. Our main results show that a temporary residence permit increases the probability of working and enrolling in regular education.Mom and Dad Got Jobs: Natural Resources, Economic Activity, and Infant HealthThe impact of local economic shocks, such as the discovery and exploitation of natural resources, on labor markets and health is not well understood. Both positive and negative effects have been documented in the literature. In this paper, we show that the phase before active resource extraction begins directly affects the local economy. This implies that previous estimates – typically based on designs exploiting differences before and after the active phase of extraction begins - may have understated the actual effect of natural resource extraction on outcomes of interest. Using rich data from Sweden combined with differences in the timing and location of mineral exploitation permits, we find a positive impact on female and male employment and earnings and a negative effect on housing prices. Children’s health outcomes are also negatively affected, an effect likely driven by the increase in local economic activity rather than extraction-related externalities.
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- Blomqvist, Peter, et al.
(författare)
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Lakes. Origin, ontogeny and natural functions
- 1999
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Ingår i: Sustainable Water Management in the Baltic Sea Basin Vol. 1: Water in Nature. ; , s. 93-108
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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- Blomqvist, Peter
(författare)
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Structural and Magnetic Properties of Fe/Co (001) and Fe/V (001) Superlattices
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The structural and magnetic properties of Fe/Co (001) and Fe/V (001) superlattices have been investigated. The thin film structures were deposited on MgO (001) substrates using a four source ultra-high-vacuum based sputtering equipment.Reflection high energy electron diffraction showed that the body-centered cubic phase of Co could be stabilized up to a thickness of about eight atomic monolayers. X-ray diffraction measurements confirmed that the Fe/Co superlattices were single-crystalline with a pure body-centered cubic structure. The crystalline quality and the interface profile were found to be strongly dependent on the growth temperature. Furthermore, the Fe/Co superlattices were also found to exhibit novel magnetic properties. The first order magnetic anisotropy constant for the body-centered cubic Co phase was determined to be negative with a magnitude of 110 kJ/m3. Magnetization and Mössbauer measurements showed that the Fe and Co magnetic moments in the superlattices were enhanced. Spin polarized neutron reflectometry proved that all the magnetic moments were collinear.The interlayer exchange coupling and the giant magnetoresistance effect in Fe/V superlattices were also studied. The strength of the coupling was found to be dependent on the thickness of the Fe and the V layers. This was also true for the giant magnetoresistance effect. Mössbauer measurements showed that the V-on-Fe interfaces (V deposited on Fe) were more abrupt and less diffuse than the Fe-on-V interfaces. Finally, the lattice parameters of a series of different Fe/V superlattices were determined by x-ray diffraction. The experimental lattice expansion was found to be in good agreement with a simple theoretical model.
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