957 research outputs found
An experimental study of semiactive modal neuro-control scheme using MR damper for building structure
No full textIn this study, a semiactive modal neuro-control scheme which combines the modal neuro-control algorithm with a semiactive MR damper is proposed, and its effectiveness is experimentally verified through a series of shaking table tests. A modal neuro-control scheme uses modal coordinates as inputs of neuro-controller. Hence, it is more convenient to design the controller compared with conventional neuro-control schemes. A Kalman filter is introduced to estimate modal states from measurements. Moreover, the clipped algorithm is adopted to provide an appropriate command voltage to an MR damper. For shaking table tests, a scaled three-story shear building model is considered. Two types of semiactive modal neuro-controllers are trained with a reproduced El Centro earthquake for their own purposes. The performance of the proposed semiactive modal neuro-control scheme is compared with that of the passive-optimal case. In the experiments, the proposed semiactive modal neuro-controllers show better performance than the passive-optimal case, especially in adaptability over various excitations and reducing inter-story drifts as well as accelerations. Moreover, the proposed scheme can be designed for specific purpose which fulfills the designer's requirement (e. g., focusing on reducing inter-story drifts). Therefore, the proposed semiactive modal neuro-controller can be effectively used in reducing seismic responses of large engineering structures
RUNNING PATTERN GENERATION OF HUMANOID BIPED WITH A FIXED POINT AND ITS REALIZATION
No full textThis paper discusses the generation of a running pattern for a humanoid biped and verifies the validity of the proposed method of running pattern generation via experiments. Two running patterns are generated independently in the sagittal plane and in the frontal plane and the two patterns are then combined. When a running pattern is created with resolved momentum control in the sagittal plane, the angular momentum of the robot about the Center of Mass (COM) is set to zero, as the angular momentum causes the robot to rotate. However, this also induces unnatural motion of the upper body of the robot. To solve this problem, the biped was set as a virtual under-actuated robot with a free joint at its support ankle, and a fixed point for a virtual under-actuated system was determined. Following this, a periodic running pattern in the sagittal plane was formulated using the fixed point. The fixed point is easily determined in a numerical approach. In this way, a running pattern in the frontal plane was also generated. In an experiment, a humanoid biped known as KHR-2 ran forward using the proposed running pattern generation method. Its maximum velocity was 2.88 km/h
Comparison of the effective oxide thickness determined by ellipsometry with the result by medium energy ion scattering spectroscopy and high-resolution transmission electron microscopy
No full textEllipsometric results may be inaccurate for the measured thickness of ultrathin oxide films on silicon because of the apparent refractive index changes with thickness. We have assessed this problem by comparing results on oxide thickness measured by ellipsometry with results of measurements by two independent techniques, such as medium energy ion scattering spectroscopy and high-resolution transmission electron microscopy, which should not be subject to error. The results show that appropriate ellipsometric models can provide thickness information consistent with two independent techniques, which improves the reliability of ellipsometric analysis in the nm range. (C) 2001 American Vacuum Society
Localization of VEGFR-2 and PLD2 in endothelial caveolae is involved in VEGF-induced phosphorylation of MEK and ERK
No full textTo clarify the role of caveolae in VEGF/VEGF receptor-2 (VEGFR-2)-mediated signaling cascades, primary cultured human umbilical vein endothelial cells (HUVECs) were fractionated to isolate caveolae-enriched cell membranes. Interestingly, VEGFR-2, phospholipase D-2 (PLD2), and Ras were enriched in caveolae-enriched fractions. Moreover, VEGF increased PLD activity in a time- and dose-dependent manner in HUVECs, whereas a ligand specific for VEGFR-1 placental growth factor did not change PLD activity. A PLD inhibitor, 1-butanol, almost completely suppressed VEGF-induced ERK phosphorylation and cellular proliferation, whereas the negative control for 1-butanol, 3-butanol, did not produce significant changes. Addition of phosphatidic acid negated the 1-butanol-induced suppression. Pharmacological analyses using several inhibitors indicated that PKC-delta regulates the VEGF-induced activation of PLD/ERK. Thus PLD2 could be involved in MEK/ERK signaling cascades that are induced by the VEGF/VEGFR-2/PKC-delta pathway in endothelial cells. Pretreatment with the cholesterol depletion agent methyl-beta-cyclodextrin (MbetaCD) almost completely disassembled caveolar structures, whereas the addition of cholesterol to MbetaCD-treated cells restored caveolar structures. Pretreatment with MbetaCD largely abolished phosphorylation of MEK/ERK by VEGF, whereas the addition of cholesterol restored VEGF-induced MEK/ERK phosphorylations. These results indicate that intact caveolae are required for the VEGF/VEGFR-2-mediated MEK/ERK signaling cascade
Die Zukunft der EU-Finanzierung: Beiträge contra Steuern
No full textKritiker der derzeitigen Finanzierung der Europäischen Union (EU) verweisen auf die Intransparenz des bestehenden Eigenmittelsystems. Zur Lösung dieses Problems wird eine eigene EU-Steuer vorgeschlagen. Sie soll dazu beitragen, die Finanzautonomie der Europäischen Union zu stärken und die Verteilungsauseinandersetzungen zwischen den Mitgliedstaaten bei den Verhandlungen über die mehrjährige Finanzielle Vorausschau der EU zu entschärfen. Die vorliegende Analyse untersucht die Eignung verschiedener Steuerarten zur Finanzierung des EU-Haushalts und diskutiert das Für und Wider der beiden maßgeblichen Finanzierungsalternativen: Beiträge und Steuern. Im Ergebnis wird vor allem aus politökonomischen Gründen eine Steuerfinanzierung abgelehnt, weil sie die Budgetrestriktion für die EU lockern würde. Solange der EU-Etat im Wesentlichen aus Beiträgen finanziert wird, die aus den nationalen Haushalten zu bestreiten sind, besteht ein Anreiz für die Mitgliedstaaten, für eine Begrenzung der EU-Ausgaben zu sorgen. Konkret lautet der Vorschlag, die EU vorrangig über Beiträge zu finanzieren, deren Höhe sich am einzelstaatlichen Bruttonationaleinkommen bemisst.Critics of the present system for financing the European Union (EU) point to the lack of transparency in the way the EU currently raises funds and propose the introduction of an EU tax to solve this problem. Their aim is to help strengthen the financial autonomy of the European Union while at the same time defusing the arguments between the member states over the distribution of funds when the EU's multiannual Financial Perspective is being negotiated. The present analysis examines the suitability of different sorts of tax for financing the EU budget and discusses the arguments for and against the two main financing alternatives: contributions and taxes. The author concludes by rejecting tax financing, primarily for politico-economic reasons, as it would lead to a relaxation of the EU's budget restrictions. As long as the EU budget is largely financed by contributions paid for out of national budgets there remains an incentive for the member states to ensure that EU expenditures are limited. The author makes the concrete suggestion that the EU be funded primarily by means of contributions based on the gross national income of the individual member states
Freiheit und Eigenverantwortung: Empirische Befunde und ordnungspolitische Grundlagen der Sozialen Marktwirtschaft
No full textDer Beitrag nimmt die Debatte um die Reformen des Sozialstaates zum Anlass, die Grundwerte von Freiheit und Eigenverantwortung in einen ordnungspolitischen Zusammenhang zu stellen und ihre Akzeptanz empirisch zu prüfen. Der Staat hat zwar diese Grundwerte zu schützen und zu verteidigen, ist aber in eine ordnungspolitische Falle geraten, indem er den Menschen immer mehr die Freiheit zur Selbstsorge abgenommen hat. Die empirischen Daten zeigen, dass die Gewährung von Freiheit und Eigenverantwortung für Wachstum und Wohlstand unverzichtbar ist. Die Bevölkerung ist zwar dem liberalen Modell zugeneigt, doch starke Gewöhnungseffekte zeitigen oftmals ein Festhalten an kollektiven Sicherungen. Im internationalen Vergleich gehört Deutschland zu den westeuropäischen Ländern, deren Menschen liberale Werte mit am deutlichsten befürworten.Prompted by the current debate over social reforms, the author looks at the role of freedom and individual responsibility in the way German society is structured and investigates the empirical evidence for the population's attitude to these fundamental values. Although theoretically responsible for protecting and defending these basic principles, the State has in fact fallen into a trap whereby the country's political structures increasingly deprive people of their freedom to fend for themselves. The empirical data show that guarantees of freedom and individual responsibility are essential for growth and prosperity. Although the population as a whole takes a favourable view of the liberal model of society, they have also grown accustomed to collective social security arrangements and tend to cling to them tenaciously. Among western European nations, Germany is one of the countries whose populations most clearly endorse liberal values
Localization of VEGFR-2 and PLD2 in endothelial caveolae is involved in VEGF-induced phosphorylation of MEK and ERK
No full textTo clarify the role of caveolae in VEGF/VEGF receptor-2 (VEGFR-2)-mediated signaling cascades, primary cultured human umbilical vein endothelial cells (HUVECs) were fractionated to isolate caveolae-enriched cell membranes. Interestingly, VEGFR-2, phospholipase D-2 (PLD2), and Ras were enriched in caveolae-enriched fractions. Moreover, VEGF increased PLD activity in a time- and dose-dependent manner in HUVECs, whereas a ligand specific for VEGFR-1 placental growth factor did not change PLD activity. A PLD inhibitor, 1-butanol, almost completely suppressed VEGF-induced ERK phosphorylation and cellular proliferation, whereas the negative control for 1-butanol, 3-butanol, did not produce significant changes. Addition of phosphatidic acid negated the 1-butanol-induced suppression. Pharmacological analyses using several inhibitors indicated that PKC-delta regulates the VEGF-induced activation of PLD/ERK. Thus PLD2 could be involved in MEK/ERK signaling cascades that are induced by the VEGF/VEGFR-2/PKC-delta pathway in endothelial cells. Pretreatment with the cholesterol depletion agent methyl-beta-cyclodextrin (MbetaCD) almost completely disassembled caveolar structures, whereas the addition of cholesterol to MbetaCD-treated cells restored caveolar structures. Pretreatment with MbetaCD largely abolished phosphorylation of MEK/ERK by VEGF, whereas the addition of cholesterol restored VEGF-induced MEK/ERK phosphorylations. These results indicate that intact caveolae are required for the VEGF/VEGFR-2-mediated MEK/ERK signaling cascade.X1144sciescopu
Ökonomik des Tarifrechts
No full textSeit Jahren wird in Politik und Wissenschaft recht kontrovers über das deutsche Tarifrecht diskutiert. Die vorliegende Analyse stellt einige der wichtigsten rechtlichen Regelungen dar und erörtert deren ökonomische Auswirkungen. Besonderer Reformbedarf wird beim sogenannten Günstigkeitsprinzip gesehen. Der Gesetzgeber sollte den Günstigkeitsvergleich um den Aspekt der Arbeitsplatzsicherheit erweitern und den zahlreichen betrieblichen Bündnissen eine klare Rechtsgrundlage geben. Außerdem ist zu überlegen, ob die Nachwirkung von Tarifverträgen zeitlich befristet und der Wettbewerb zwischen den Gewerkschaften durch Aufgabe des in der Rechtsprechung entwickelten Prinzips der Tarifeinheit gestärkt werden kann. Forderungen nach einer stärkeren Nutzung des Instruments der Allgemeinverbindlichkeit oder einem gesetzlichen Mindestlohn werden mit Hinblick auf die damit verbundenen negativen Arbeitsmarktwirkungen abgelehnt. Auch eine gesetzliche Stärkung der tarifpolitischen Kompetenzen der Betriebsräte erscheint angesichts der umfassenden Mitbestimmungsrechte ökonomisch nicht ratsam.For years German collective bargaining legislation has been the subject of fierce debate in political and academic circles. The present analysis presents some of the most important statutes and discusses their economic effects. The so-called favourability principle, which allows deviation from collective agreements only in the employees' favour, is considered particularly ripe for reform. The author proposes extending the principle to include arguments involving job security, thus giving the numerous agreements already made on this issue at company level a clear legal basis. The question also arises as to whether collective bargaining agreements, which are currently effective until replaced, should not be subject to time limits. In addition, it might be possible to enhance the competition between unions by abandoning the principle developed by the labour courts of making collective agreements exclusive at plant level. Demands for a legal minimum wage or wider use of decrees extending a wage agreement beyond those represented by its signatories are rejected as detrimental to the labour market. Nor, given the comprehensive right to co-determination, does it seem advisable in economic terms to legislate for an expanded role for works councils in the context of collective bargaining
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