15,518 research outputs found
Control and Filtering for Discrete Linear Repetitive Processes with H infty and ell 2--ell infty Performance
No full textRepetitive processes are characterized by a series of sweeps, termed passes, through a set of dynamics defined over a finite duration known as the pass length. On each pass an output, termed the pass profile, is produced which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. This can lead to oscillations which increase in amplitude in the pass to pass direction and cannot be controlled by standard control laws. Here we give new results on the design of physically based control laws for the sub-class of so-called discrete linear repetitive processes which arise in applications areas such as iterative learning control. The main contribution is to show how control law design can be undertaken within the framework of a general robust filtering problem with guaranteed levels of performance. In particular, we develop algorithms for the design of an H? and dynamic output feedback controller and filter which guarantees that the resulting controlled (filtering error) process, respectively, is stable along the pass and has prescribed disturbance attenuation performance as measured by and – norms
Acoustic radiation due to scattering of T-S wave by the mean-flow distortion induced by steady local suction
No full textSubstantial sound waves can be generated by boundary-layer instability modes when the latter are scattered by a rapid mean-flow distortion. This is a rather generic mechanism and operates when an oncoming T-S wave is scattered by a steady local suction slot. This paper focuses on this problem by extending a recently developed Local Scattering Theory (Wu & Dong, J. Fluid Mech. submitted), where a so-called transmission coefficient, defined as the ratio of the T-S wave amplitude downstream of the scatter to that upstream, is introduced to characterize the effect of a local scatter on boundary-layer instability and transition. As in the earlier work, the mathematical formulation is based on triple-deck formulism, but in order to accommodate the acoustic far field, which was not considered in the paper mentioned, the unsteady terms in the upper deck, which play a leading-order role in radiation, are retained, and the influence of the radiated sound on the near-wall perturbation is included. The upper deck equation for the pressure is the Helmholtz equation rather than the Laplace equation. This leads to a modified pressure-displacement relation, which is coupled with the linearized boundary-layer equations in the lower deck. Discretization of the whole system formulates a generalized eigenvalue problem, which is solved numerically. It is found that suction suppresses oncoming T-S waves, and this effect increases with the suction velocity and the slot width. The directivity is ndependent of the flow parameters only when the Mach number is low. The intensity of the radiated sound in general increases with the frequency, the suction velocity and the width of the suction slot. Interestingly, for O(1) suction velocities, the radiated sound is very weak, indicating that the gain of stabilizing effect does not cause aeroacoustic penalty
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Tim Wu & “The Curse of Bigness”
No full textHost Nicholas Lemann sits down with Tim Wu, author of The Curse of Bigness, to discuss the politics of Louis Brandeis and Theodore Roosevelt as antitrust has reemerged this year as a major issue in the run-up to the 2020 U.S. Presidential Election.
Measurement of dwell times of spin polarized rubidium atoms on octadecyltrichlorosilane- and paraffin-coated surfaces
No full textWe report the measurement of dwell times of spin polarized Rb atoms on octadecyltrichlorosilane OTS- and paraffin-coated surfaces. We find that at a cell temperature of 72 °C the dwell times for OTS- and paraffin-coated surfaces are 0.9+-0.1 microsecond and 1.8 +-0.2 microsecond , respectively. Since the relaxation probability on paraffin is almost one order of magnitude smaller than that on OTS, the longer dwell time for paraffin indicates that the average strength of the interactions experienced by Rb atoms while they are inside paraffin is much weaker than while they are inside OTS.Peer reviewe
[[alternative]]A Study on History of Shin-Wu Elementary School at Tao-Yuan（1905-2003）
No full text[[abstract]]To explore the school cultural development in Shin-Wu Elementary school in the last hundred years and the significance of school history research in educational history, this study examines documents and files in the school history room of Shin-Wu Elementary school and has oral history interviews as well. The main findings of this study are as follows.
1. In late Meiji, most of the teachers were Japanese or Taiwanese from the nearby common schools, however, the turnover was high. At that time, only affluent students attended schools while later, more students were from poor families. Yet, the drop-out rate was relatively high.
2. As for the age, most students went to school in their teens, for they had to share responsibilities in home chores.
3. In Taisyo period, there were more and more teachers who had been Shin-Wu graduates and students were from different sources.
4. Owing to the air raid during the war, schools got closed very often and the content of education was mainly about laboring.
5. Post-war education, compared with that before, varied little in educational contents and forms because of the position-retaining teachers and staff.
6. For the last hundred years, nearly one-third of Shin-Wu teachers were their graduates and principals and teachers of branch schools came form Shin-Wu Elementary School, too. Therefore, Shin-Wu Elementary School had played an influential role in the elementary education and the local people cultivation in Shin-Wu area.
7. Shin-Wu Elementary School had always followed the national educational policy, seldom did they have local standpoints, which meant, they had to strengthen their autonomy and capacity when faced with new challenges especially after the lifting of Martial Law.
8. Through elaborative school cultural analysis, relationship among education, politics, economy and society, in particular, individual area development will be more carefully investigated.
Fighting Inequalities: Impact of Urban-Rural Health Insurance Integration in Rural China
No full textIntegrating social health insurance, which helps unify the administration, policies, and funds of various health insurance programs, is expected to combat health inequalities. This paper provides the first micro-level evidence from China on the impact of health insurance integration on health care. We exploit the China Health and Retirement Longitudinal Study (CHARLS) dataset and combine it with original city-level data on social health insurance policy. We employ difference-in-difference models with matching to estimate the effects of integrating the Urban Resident Basic Medical Insurance (URBMI) and the New Rural Cooperative Medical Insurance (NRCMI) on individuals’ health care utilization (including inpatient and outpatient care) and health outcomes. We find that the health insurance integration has significantly increased inpatient and outpatient care utilization. Moreover, we provide evidence of a possible mechanism that drives this relationship: the inpatient reimbursement rate significantly increased after the integration. We further find that after the integration, people traveled longer distances to seek inpatient and outpatient care, and their health, as measured by self-assessed health status, has improved. Nonetheless, these results are found in the rural sample only, and we observe no significant impact of the health insurance integration on total hospital charges or patients’ out-of-pocket payments.Peer reviewe
Hypoplastic constitutive models for frozen soil
No full textDie Modellierung von Permafrost-Böden liefert wichtige Beiträge für die Bodenmechanik und die Bauwerke in Permafrostregionen. In dieser Arbeit werden drei Stoffmodelle im Rahmen der Hypoplastizitätstheorie für gefrorene Böden präsentiert. Das erste Modell, „Extended Hypoplastic Constitutive Model“ genannt, wurde, basierend auf dem Modell von Wu (1992), durch Erweiterung um einen temperaturabhängigen Kohäsionstensor sowie eine verformungsabhängige Skalarfunktion entwickelt. Die Güte dieses Stoffmodells wurde durch die Simulation von dreiaxialen Kompressionsversuchen bei unterschiedlichen Temperaturen und Seitendrücken demonstriert. Dieses Modell ist unabhängig von Geschwindigkeit und kann das viskose Verhalten der Permafrost-Böden nicht beschreiben. Aus diesem Grunde wurde ein zweites Modell entwickelt. Es wird als „Visco-Hypoplastic Constitutive Model“ bezeichnet. Dieses viskose Modell wurde durch die Aufteilung der Spannung und ihre Rate in einen statischen und einen dynamischen Teil dargestellt. Für die statische Spannungsrate wird ein einfaches Stoffgesetz zugrundegelegt, während für die dynamische Spannung ein Stoffgesetz mit höheren Gradienten der Dehnungsrate verwendet wird. Die Gültigkeit dieses viskosen Modells wurde durch Simulation von Kompressionsversuchen mit unterschiedlichen Belastungsgeschwindigkeiten, sowie Simulation von mehreren Kriechversuchen gezeigt. Das dritte Modell, als „Hypoplastic Creep Model“ bezeichnet, wurde speziell für die Simulation der rheologischen Eigenschaften von Permafrost-Böden entwickelt. Anhand von Druck-Kriechversuchen konnte gezeigt werden, dass dieses Modell ebenso zur Beschreibung des Kriechverhaltens von Permafrost-Böden, wie z.B. der Zeit bis zum Kriechversagen und der minimalen Kriechrate im sekundären Kriechen, geeignet ist. Außerdem kann auch die Spannungsrelaxation von Permafrost-Böden in diesem Modell bestimmt werden.Constitutive modeling for frozen soil is an important topic for the mechanics of frozen soils and for construction activities in permafrost regions. This study, with the help of hypoplasticity theory, presents three constitutive models for frozen soils. The first model, called extended hypoplastic constitutive model, is obtained by introducing a temperature-dependent cohesion tensor and a deformation-related scalar function into the pioneer model developed by Wu (1992). Then by simulating some triaxial compression tests at different temperatures and confining pressures, the extended model is shown to have a good ability in describing the strength behavior and volumetric change of frozen soil. However, this model is rate-independent and thus cannot account for the loading rate effect and rheological properties of frozen soil. In view of this, the second model, named as visco-hypoplastic constitutive model, is then developed. This viscous model is obtained by dividing the stress rate into a statical and a dynamical part, which are represented by the extended model and a high order model with respect to strain, respectively. Then the versatility of this viscous model is verified by simulating some compression tests at different loading rates and creep tests at different stress levels. The third model, termed hypoplastic creep model, is developed especially for the rheological properties of frozen soil. By simulating some compression creep tests, this creep model is also shown to be capable of describing the creep behaviors of frozen soil, e.g. the time to creep failure and the minimum creep rate in the secondary creep stage. Besides, the relaxation of creep strength of frozen soil can also be described by this creep model.submitted by Guofang XuZsfassung in dt. SpracheWien, Univ. für Bodenkultur, Diss., 201
Hypoplastic constitutive models for frozen soil
No full textDie Modellierung von Permafrost-Böden liefert wichtige Beiträge für die Bodenmechanik und die Bauwerke in Permafrostregionen. In dieser Arbeit werden drei Stoffmodelle im Rahmen der Hypoplastizitätstheorie für gefrorene Böden präsentiert. Das erste Modell, „Extended Hypoplastic Constitutive Model“ genannt, wurde, basierend auf dem Modell von Wu (1992), durch Erweiterung um einen temperaturabhängigen Kohäsionstensor sowie eine verformungsabhängige Skalarfunktion entwickelt. Die Güte dieses Stoffmodells wurde durch die Simulation von dreiaxialen Kompressionsversuchen bei unterschiedlichen Temperaturen und Seitendrücken demonstriert. Dieses Modell ist unabhängig von Geschwindigkeit und kann das viskose Verhalten der Permafrost-Böden nicht beschreiben. Aus diesem Grunde wurde ein zweites Modell entwickelt. Es wird als „Visco-Hypoplastic Constitutive Model“ bezeichnet. Dieses viskose Modell wurde durch die Aufteilung der Spannung und ihre Rate in einen statischen und einen dynamischen Teil dargestellt. Für die statische Spannungsrate wird ein einfaches Stoffgesetz zugrundegelegt, während für die dynamische Spannung ein Stoffgesetz mit höheren Gradienten der Dehnungsrate verwendet wird. Die Gültigkeit dieses viskosen Modells wurde durch Simulation von Kompressionsversuchen mit unterschiedlichen Belastungsgeschwindigkeiten, sowie Simulation von mehreren Kriechversuchen gezeigt. Das dritte Modell, als „Hypoplastic Creep Model“ bezeichnet, wurde speziell für die Simulation der rheologischen Eigenschaften von Permafrost-Böden entwickelt. Anhand von Druck-Kriechversuchen konnte gezeigt werden, dass dieses Modell ebenso zur Beschreibung des Kriechverhaltens von Permafrost-Böden, wie z.B. der Zeit bis zum Kriechversagen und der minimalen Kriechrate im sekundären Kriechen, geeignet ist. Außerdem kann auch die Spannungsrelaxation von Permafrost-Böden in diesem Modell bestimmt werden.Constitutive modeling for frozen soil is an important topic for the mechanics of frozen soils and for construction activities in permafrost regions. This study, with the help of hypoplasticity theory, presents three constitutive models for frozen soils. The first model, called extended hypoplastic constitutive model, is obtained by introducing a temperature-dependent cohesion tensor and a deformation-related scalar function into the pioneer model developed by Wu (1992). Then by simulating some triaxial compression tests at different temperatures and confining pressures, the extended model is shown to have a good ability in describing the strength behavior and volumetric change of frozen soil. However, this model is rate-independent and thus cannot account for the loading rate effect and rheological properties of frozen soil. In view of this, the second model, named as visco-hypoplastic constitutive model, is then developed. This viscous model is obtained by dividing the stress rate into a statical and a dynamical part, which are represented by the extended model and a high order model with respect to strain, respectively. Then the versatility of this viscous model is verified by simulating some compression tests at different loading rates and creep tests at different stress levels. The third model, termed hypoplastic creep model, is developed especially for the rheological properties of frozen soil. By simulating some compression creep tests, this creep model is also shown to be capable of describing the creep behaviors of frozen soil, e.g. the time to creep failure and the minimum creep rate in the secondary creep stage. Besides, the relaxation of creep strength of frozen soil can also be described by this creep model.submitted by Guofang XuZsfassung in dt. SpracheWien, Univ. für Bodenkultur, Diss., 201
Conversazione con Wu Ming 1 sul New Italian Epic e la critica letteraria italiana
No full textIn this conversation, Wu Ming 1 of the collective author Wu Ming, offers a detailed explanation of its aesthetics and literary philosophy. While the starting point is the recent publication of the memorandum about "The New Italian Epic," Wu Ming 1 takes advantage of the questions to survey their ethical stance as intellectuals very much involved in the public sphere
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