52 research outputs found
Application of the nonsmooth dynamics approach to model and analyze the contact-impact events in cam-follower systems
No full textThe dynamic modeling and analysis of planar rigid multibody systems that experience contact-impact events is presented and discussed throughout this work. The methodology is based on the nonsmooth dynamics approach, in which the interaction of the colliding bodies is modeled with multiple frictional unilateral constraints. Rigid multibody systems are stated as an equality of measures, which are formulated at the velocity-impulse level. The equations of motion are complemented with constitutive laws for the forces and impulses in the normal and tangential directions. In this work, the unilateral constraints are described by a set-valued force law of the type of Signorini’s condition, while the frictional contacts are characterized by a set-valued force law of the type of Coulomb’s law for dry friction. The resulting contact-impact problem is formulated and solved as an augmented Lagrangian approach, which is embedded in the Moreau time-stepping method. The effectiveness of the methodologies presented in this work is demonstrated throughout the dynamic simulation of a cam-follower system of an industrial cutting file machine.This work is supported by the Portuguese Foundation for the Science and Technology under the research project BIOJOINTS (PTDC/EME-PME/099764/2008). The first author expresses his gratitude to the Portuguese Foundation for the Science and Technology for the postdoctoral scholarship (SFRH/BPD/40067/2007). This research was conducted during a post-doctoral stay of the first author with Professor Christoph Glocker at the Center of Mechanics, ETH Zurich
The effect of student aid on the duration of study
No full textIn this paper I evaluate the effect of student aid on the success of academic studies. I focus on two dimensions, the duration of study and the probability of actually graduating with a degree. While there is an extensive literature on the impact of student aid on its intended outcome, the uptake of tertiary education, the impact on the outcome and on study incentives has been mainly ignored. But introducing student aid changes the students' budget constraint. The increase in the budget-set might lead to shorter time-to-degree if paid work is substituted by study time. I analyze the effect of financial student aid granted by the German Federal Education and Training Assistance Act (BAfoeG). To determine its impact, I estimate a discrete-time duration model allowing for competing risks to account for different exit states (graduation and dropout) using individual level panel data from the German Socio-Economic Panel (SOEP) for the years 1984-2007. My findings suggest that the duration of study is responsive to the type of financial support a student receives. There are three main results. First, student aid recipients finish faster than comparable students who are supported by the same amount of parental/private transfers only. Second, although higher financial aid does on average not affect the duration of study, this effect is (third) dominated by the increased probability of actually finishing university successfully
Eine mikroökonometrische Analyse für Deutschland
No full textThis thesis analyzes the determinants of university enrollment and successful
completion of university studies. The main questions analyzed are: What are
the enrollment effects of different tuition fee schemes? How does taxation of
future earnings affect enrollment? What is the impact of student aid on the
success of studies? To answer the first two questions, I develop a structural
university enrollment model, explicitly accounting for expectations about
future earnings and the associated risk. A high-school graduate enters
university studies if expected lifetime utility from this choice is greater
than from other alternatives. Ex-ante expectation and variance of after-tax
income for German high-school graduates are estimated, accounting for non-
random selection into education and employment. The results indicate that
higher expected returns to an academic education increase, and higher
uncertainty decreases the probability of university enrollment. Based on these
results I conduct simulations to evaluate-ex ante-different funding and
financing policies. First, the impact of recently introduced tuition and
funding schemes on enrollment is evaluated. I then extend the analysis to
three different financing schemes: a pure mortgage loan, income-contingent
loans and graduate taxes, also varying the levels of fees. Second I evaluate
the effect on the expected distribution of earnings in each of the scenarios.
My findings suggest that the introduction/the increase of student fees reduces
university enrollment. This effect can be attenuated by incorporating a
financing scheme where repayment conditions account for future income
uncertainty, i.e. income-contingent loans. Since future earnings are a major
determinant in the university enrollment decision and taxation changes
expectations about the net-return to education, I evaluate the effect of
different taxation schemes on university enrollment. I analyze the effects of
the Tax Reduction Act of 2000, as well as two hypothetical revenue neutral
flat-rate tax scenarios. Here I find that tax schemes with a lower tax rate at
the relevant income segment increase university enrollment. The income effect
thus dominates the insurance effect (in form of a reduced variance in net
income) in all scenarios. The last question focuses on the success of study
measured in two dimensions: the duration of study and the probability of
actually graduating with a degree. Again I consider variation in financing,
here changes in student aid. I estimate a discrete-time duration model
allowing for competing risks to account for different exit states (graduation
and dropout). There are three main results: 1) student aid recipients finish
faster than comparable students who are supported by the same amount of
parental/private transfers only. 2) although higher financial aid does on
average not affect the duration of study, this effect is (3) dominated by an
increased probability of actually finishing university successfully.Diese Dissertation beschäftigt sich mit den Faktoren, die die
Studierwahrscheinlichkeit und den Erfolg des Studiums beeinflussen. Im
Speziellen untersuche ich folgende Fragen: Wie wirken sich Studiengebühren,
insbesondere verschiedene Finanzierungsformen von Studiengebühren, auf die
Einschreiberate aus? Wie wirkt sich die Besteuerung des zukünftigen Einkommens
auf die Aufnahme eines Studiums aus? Welchen Einfluss hat die Studienförderung
in Form von BAFöG auf den erfolgreichen Abschluss des Studiums? Um diese
Fragen zu beantworten, entwickle ich ein strukturelles Modell, welches
Erwartungen über zukünftiges Nettoeinkommen und dessen Unsicherheit explizit
modelliert. Ein Abiturient entscheidet sich für ein Studium, wenn der Nutzen
aus dieser Alternative, den Nutzen aus jeder anderen Alternative übersteigt.
Hierfür werden ex ante Lebenseinkommensprofile und deren Varianzen, unter
Berücksichtigung von Selektion, berechnet. Die Ergebnisse zeigen, dass ein
höheres erwartetes Einkommen die Immatrikulationswahrscheinlichkeit erhöht,
und größere Einkommensunsicherheit diese senkt. Auf Basis des strukturellen
Modells werden verschiedene ex ante Politik-Simulationen durchgeführt.
Zunächst untersuche ich den Effekt von Studiengebühren sowie deren
Finanzierungsmöglichkeiten auf die Studierwahrscheinlichkeit. Im folgenden
dann auch deren Einfluss auf die erwartete zukünftige Einkommensungleichheit.
Meine Ergebnisse zeigen, dass die Einführung, bzw. eine Erhöhung von
Studiengebühren einen negativen Einfluss auf die Studierwahrscheinlichkeit
hat. Jedoch kann dieser Effekt durch ein Finanzierungssystem, welches die
Rückzahlungsbedingung an die Höhe des zukünftigen Einkommens bindet,
abgemildert werden. Da Einkommensbesteuerung die Erwartungen über zukünftige
Nettoeinkommen beeinflusst, untersuche ich den Effekt von verschiedenen
Steuersystemen (Steuerreform von 2000, sowie zwei hypothetische
einkommensneutrale Einheitssteuerszenarien) auf die Studierwahrscheinlichkeit.
Ein geringerer Steuersatz, und somit ein höheres Nettoeinkommen dominiert, den
Versicherungseffekt (in Form von einer geringeren Einkommensvarianz). Die
letzte Frage analysiert die Faktoren eines schnellen und erfolgreichen
Studienabschlusses. Insbesondere konzentriere ich mich auf den Einfluss von
finanzieller Unterstützung (BAföG) auf den erfolgreichen Abschluss eines
Studiums, gemessen in Form der Studiendauer und der Wahrscheinlichkeit das
Studium mit einem Abschluss zu beenden. Ich schätze ein diskretes
Verweildauermodell, welches explizit konkurrierende Risiken (erfolgreicher
Abschluss und Studienabbruch) berücksichtigt. Die drei zentralen Ergebnisse
sind: 1. BAföG-Empfänger beenden ihr Studium schneller, als Studenten die mit
dem gleichen Betrag von ihren Eltern/privat unterstützt werden. 2. ein höherer
BAföG Betrag führt nicht zu einem schnelleren Studienabschluss, jedoch wird
(3.) dieser Effekt durch eine erhöhte Wahrscheinlichkeit, das Studium
erfolgreich zu beenden, dominiert
The effect of student aid on the duration of study
No full textIn this paper I evaluate the effect of student aid on the success of academic studies. I focus on two dimensions, the duration of study and the probability of actually graduating with a degree. To determine the impact of financial student aid, I estimate a discrete-time duration model allowing for competing risks to account for different exit states (graduation and dropout) using individual level panel data from the German Socio-Economic Panel (SOEP) for the years 1984-2007. My findings suggest that the duration of study is responsive to the type of financial support a student receives. There are three main results. First, student aid recipients finish faster than comparable students who are supported by the same amount of parental/private transfers only. Second, although higher financial aid does on average not affect the duration of study, this effect is (third) dominated by the increased probability of actually finishing university successfully.Academic outcomes Student aid Duration of study BAfoeG German Socio-Economic Panel
The Effect of Student Aid on the Duration of Study
No full textIn this paper I evaluate the effect of student aid on the success of academic studies. I focus on two dimensions, the duration of study and the probability of actually graduating with a degree. While there is an extensive literature on the impact of student aid on its intended outcome, the uptake of tertiary education, the impact on the outcome and on study incentives has been mainly ignored. But introducing student aid changes the students' budget constraint. The increase in the budget-set might lead to shorter time-to-degree if paid work is substituted by study time. I analyze the effect of financial student aid granted by the German Federal Education and Training Assistance Act (BAfoeG). To determine its impact, I estimate a discrete-time duration model allowing for competing risks to account for different exit states (graduation and dropout) using individual level panel data from the German Socio-Economic Panel (SOEP) for the years 1984-2007. My findings suggest that the duration of study is responsive to the type of financial support a student receives. There are three main results. First, student aid recipients finish faster than comparable students who are supported by the same amount of parental/private transfers only. Second, although higher financial aid does on average not affect the duration of study, this effect is (third) dominated by the increased probability of actually finishing university successfully.academic outcomes, student aid, duration of study, BAfoeG, German Socio-Economic Panel
Expected future earnings, taxation, and university enrollment: a microeconometric model with uncertainty
No full textTaxation changes the expectations of prospective university students about their future level and uncertainty of after-tax income. To estimate the impact of taxes on university enrollment, we develop and estimate a structural microeconometric model, in which a high-school graduate decides to enter university studies if expected lifetime utility from this choice is greater than that anticipated from starting to work right away. We estimate the ex-ante future paths of the expectation and variance of net income for German high-school graduates, using only information available to those graduates at the time of the enrollment decision, accounting for multiple nonrandom selection and employing a microsimulation model to account for taxation. In addition to income uncertainty, the enrollment model takes into account university dropout and unemployment risks, as well as potential credit constraints. The estimation results are consistent with expectations. First, higher risk-adjusted returns to an academic education increase the probability of university enrollment. Second, high-school graduates are moderately risk averse, as indicated by the Arrow-Pratt coefficient of risk aversion estimated within the model. Thus, higher uncertainty among academics decreases enrollment rates. A simulation based on the estimated structural model indicates that a revenue-neutral, flat-rate tax reform with an unchanged basic tax allowance would increase enrollment rates for men in Germany because of the higher expected net income in the higher income range
Self-employment: a way to end unemployment? Empirical evidence from German pseudo-panel data
No full textThis paper contributes to the policy-relevant question whether self-employment is a way out of (long-term) unemployment. We estimate the relationship between the entry rate into self-employment and previous (long-term) unemployment on the basis of pseudo-panel data for Germany in the period 1996-2002. The estimation method accounts for cohort fixed effects and measurement errors induced by the pseudo panel structure. We find that previous (long-term) unemployment significantly increases entry rates into self-employment for both men and women. These effects are quantitatively important, both in absolute terms and compared to other potential determinants of self-employment transitions, such as age, the level of vocational qualification and certain household characteristics
Returns to Education across Europe
No full textIncentives to invest in higher education are affected by both the direct wage effect of human capital investments and the indirect wage effect resulting from lower unemployment risks and shorter spells in unemployment associated with higher educated. We analyse the returns to education in Austria, Germany, Italy, Sweden and the United Kingdom, countries which differ significantly regarding both their education systems and labour market structure. We estimate augmented Mincerian wage equations accounting for the effects of unemployment on individual wages using EU-SILC data. Across countries we find a high variation of the effect of education on unemployment duration. Overall, the returns to education are estimated to be the highest in the UK, and the lowest for Sweden. A wage decrease due to time spent in unemployment results in a decline in the hourly wages in Austria, Germany and Italy.EU-SILC; returns to education; unemployment
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