961 research outputs found
Modelling cross-border transport: Three cases in Ăresund
Transport models, and transport/land-use interaction models, are important decision support tools for large-scale infrastructure investments, for example in the road network. A bothersome feature of these tools are their distant forecasting horizon of 10--30 years ahead, and the uncertainty following from this. Although widely used, these models have rarely been put to test after this period have passed. The predictive power of a transport model is dependent on its ability to reproduce reality, which is assessed by validation. Apart from modelling the specific transport demand, which is based partly on socio-economic (demand) factors and partly on the supply of transport facilities (infrastructure), a number of scenarios of the future socio-economic development must be set up, called the scenario assumptions. In this paper we will present three different transport models: FREDRIK/ SSV, COMVIN and SAMPERS/ SkĂ„ne, out of which the first two have been used to model the transport across the Ăresund Strait. The model structure, forecast results and scenario assumptions are considered in order to identify the key sources of uncertainties, and to prepare for the estimation of the true model error versus the error caused by incorrect scenario assumptions. Key words: infrastructure planning, transport models, validation, Ăresund, before-and-after data.
A propensity score matching method for the link between accessibility and productivity
The connection between accessibility (or "highways" or "infrastructure") and productivity on a regional scale has been a matter of debate since Aschauer (1989). In this paper we use a panel data approach on the micro level, and a fine zonal subdivision in order to capture the effects on individual firms, both in terms of productivity and agglomeration. We study a cost function with a translog specification which we apply on a large unbalanced data set of firms in the Swedish part of the Ăresund region: Scania. We use matching estimators for non-parametric tests of spatial dependence (agglomeration) and the accessibility dependence of productivity, thus avoiding sample selection bias. Key words: panel data, cost function, translog, Ăresund region, accessibility, matching estimator
Translation of an Interdisciplinary PBL Strategy to the Formation of Interdisciplinary Competences:A Report
An approach to produce a stack of photo definable polyimide based flat UTCPs
Getting output of multiple chips within the volume of a single chip is the driving force behind development of this novel 3D integration technology which has a broad range of industrial and medical electronic applications. This can be achieved by laminating multiple layers of spin-on polyimide based ultrathin chip packages (UTCPs) with fine pitch through hole interconnects
Predicting a clinically important outcome in patients with low back pain following McKenzie therapy or spinal manipulation:a stratified analysis in a randomized controlled trial
Investigation of pressing and ejection performance of friction-reducing powder-compaction tool coatings
Pressing in dies followed by sintering is the most commonly used process for shaping metal powders into components. The mechanical properties (e.g. tensile and fatigue strength) of the final sintered component depend on the green-compact properties resulting from the compaction process. Apart from the powder material used, process-specific factors, such as geometry complexity, compaction pressure and lubrication strategy, have a major impact on the properties of the green compact. The lubrication strategy is also decisive for the economic efficiency of the process as it influences the service life of the tools. Friction-reducing powder-compaction tool coatings (e.g. diamond-like-carbon-based/DLC) provide the potential to positively influence the lubrication conditions during compaction and ejection, thus simultaneously improving product quality and service life. In this study, experimental investigations on the performance of friction-reducing coatings in the die pressing of steel powder (Fe + 0.6 wt% C) with and without admixed lubricant (AncorLube, GKN Hoeganaes) are presented. The results are evaluated by force-displacement measurements, which allows for a more profound analysis of compaction and ejection behaviour. It is shown that the application of the coatings reduces the ejection loads significantly when no admixed lubricant is used, and moderately when lubricant is admixed. However, without lubricant, wear still occurs after a few pressing cycles, so it cannot be completely avoided
Investigation on the microstructure of ecap-processed iron-aluminium alloys
The present work deals with adjusting a fine-grained microstructure in iron-rich iron-aluminium alloys using the ECAP-process (Equal Channel Angular Pressing). Due to the limited formability of Fe-Al alloys with increased aluminium content, high forming temperatures and low forming speeds are required. Therefore, tool temperatures above 1100âŠC are permanently needed to prevent cooling of the work pieces, which makes the design of the ECAP-process challenging. For the investigation, the Fe-Al work pieces were heated to the respective hot forming temperature in a chamber furnace and then formed in the ECAP tool at a constant punch speed of 5 mm/s. Besides the chemical composition (Fe9Al, Fe28Al and Fe38Al (at.%âAl)), the influences of a subsequent heat treatment and the holding time on the microstructure development were investigated. For this purpose, the average grain size of the microstructure was measured using the AGI (Average Grain Intercept) method and correlated with the aforementioned parameters. The results show that no significant grain refinement could be achieved with the parameters used, which is largely due to the high forming temperature significantly promoting grain growth. The holding times in the examined area do not have any influence on the grain refinement. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
ACUPA: Exploring the Campus Policy Process (Working Paper)
Purpose: The purpose of this study is to make an exploratory inquiry into the state of policy development processes in institutions of higher education, and to review the history and mission of the Association of College and University Policy Administrators (ACUPA). Methodology: Members of ACUPA were surveyed concerning their opinions of the status of policy development, and where the policy process was located in local governance structures. A survey was conducted of ACUPA membership in March and April 2005. Results: 24 institutions responded to the survey, half of them identifying themselves as Doctoral or Research Universities (Carnegie Classification, 2000). 75% of respondents rated their policy development processes as âaverageâ, âabove averageâ, or âvery goodâ. 60% report to a President or Vice President. Conclusions: The results were inconclusive. There appeared to be a tendency for those who portrayed their policy process as âcentralizedâ or âbothâ to rate their process more favorably than those who described their setting as âdecentralizedâ or âdisorganized.â Nearly 65% (9 of 14) of those who chose âcentralizedâ or âbothâ rated their process either âvery goodâ or âabove average.â Even though this small survey sample had inconclusive results, it is a significant contribution to the literature in the field, which is scarce. Recommendations: This brief survey raised additional questions which need further research. Persons who are interested in joining the network of policy administrators and developers of ACUPA should view the web site at http://www.acupa.org/ for more information
Transfer of ausforming parameters to scaled forging tools
Forging tools are exposed to cyclically changing thermo-mechanical stress conditions leading to its failure. Damage phenomena on the tool engraving cannot be entirely avoided by hardening the surface, as this leads to a more brittle behaviour and thus to lower ductility of the material, which can intensify the occurring damage effects. The forming of steel below the recrystallisation temperature in the metastable austenite area, known as ausforming, offers the possibility to increase strength and hardness without affecting ductile properties, due to simultaneous grain refinement. In this study, ausforming was used to produce forging dies with increased wear resistance from tool steel X37CrMoV5-1 (AISI H11) by achieving higher hardness in the surface area while maintaining a ductile base material. Suitable forming and tempering parameters were derived from previous studies in which ausformed cups from tool steel X37CrMoV5-1 (AISI H11) with a downscaled geometry have been investigated in mechanical pulsation tests. To achieve comparable properties, a process route with adapted surface-cooling conditions, a global true plastic strain of Ï = 0.25 and a tempering temperature of 300 °C were applied. Further, the ausformed dies were compared with conventionally forged dies. The metallographic analysis and hardness measurements show that an increased hardness in the surface area can also be obtained for the actual formed dies. In order to see the influence of the thermomechanical alternating load on the die engraving under forging conditions, the performance of the ausformed tool will be investigated in service-life-time tests and compared to warm-formed and machined reference tools
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