On neural networks in identification and control of dynamic systems

This paper presents a discussion of the applicability of neural networks in the identification and control of dynamic systems. Emphasis is placed on the understanding of how the neural networks handle linear systems and how the new approach is related to conventional system identification and control methods. Extensions of the approach to nonlinear systems are then made. The paper explains the fundamental concepts of neural networks in their simplest terms. Among the topics discussed are feed forward and recurrent networks in relation to the standard state-space and observer models, linear and nonlinear auto-regressive models, linear, predictors, one-step ahead control, and model reference adaptive control for linear and nonlinear systems. Numerical examples are presented to illustrate the application of these important concepts

Dynamic analysis of the GEOS satellite

The assumed modes method is used to investigate the stability of the GEOS satellite. The system is discretized by representing the continuous displacement by finite series of space-dependent admissible functions multiplied by time-dependent generalized coordinates. The spatial dependence is eliminated by integration over the elastic domains, so that the testing functional reduces to a testing function. The sign properties of the testing function are then tested and the equilibrium defined as nontrivial. In considering the stability of small motions about nontrivial equilibrium, it is shown that if the analysis performed by ignoring the motion of the mass center indicates stability, then the system remains stable if the motion of the mass center is included

Penerimaan Guru Sekolah Dasar Terhadap Ujian Nasional Dalam Film Serdadu Kumbang

Penelitian ini bertujuan untuk mengetahui penerimaan guru sekolah dasar terhadap Ujian Nasional dalam film Serdadu Kumbang. Film ini merupakan salah satu film tentang pendidikan yang mengangkat masalah Ujian Nasional. Metode yang digunakan dalam penelitian ini adalah analisis penerimaan. Penelitian jenis deskriptif kualitatif ini memberikan gambaran bagaimana informan yang berprofesi sebagai guru menerima pesan mengenai Ujian Nasional yang ada dalam film Serdadu Kumbang.Hasil penelitian ini menggambarkan bahwa pemaknaan yang diberikan informan dipengaruhi oleh latar belakang pemahaman dan pengalaman mereka masing-masing. Informan pertama dan ketiga memiliki penerimaan opposisional, sedangkan informan kedua memiliki penerimaan negosiasi. Penerimaan kedua informan tersebut dilatarbelakangi oleh pengalaman mereka yang sama-sama pernah mengajar di daerah dan kini bertugas di kota. Sedangkan informan ketiga dilatarbelakangi oleh pengalamannya mengajar di daerah dengan lingkungan sosial dan keadaan ekonomi yang terbatas menyebabkan informan minim mengonsumsi media dan tidak berkembang, sehingga kondisi tersebut berpengaruh pada penerimaannya terhadap Ujian Nasional dalam film Serdadu Kumbang

Metastable states of a ferromagnet on random thin graphs

We calculate the mean number of metastable states of an Ising ferromagnet on random thin graphs of fixed connectivity c. We find, as for mean field spin glasses that this mean increases exponentially with the number of sites, and is the same as that calculated for the +/- J spin glass on the same graphs. An annealed calculation of the number <N_{MS}(E)> of metastable states of energy E is carried out. For small c, an analytic result is obtained. The result is compared with the one obtained for spin glasses in order to discuss the role played by loops on thin graphs and hence the effect of real frustration on the distribution of metastable states.Comment: 15 pages, 3 figure

Geohazards in the three Gorges Reservoir Area, China – Lessons learned from decades of research

Abstract The impoundment of the 660-km long reservoir behind the huge Three Gorges Dam, the world's largest hydropower station, increased regional seismicity and reactivated severe geohazards. Before the reservoir filling was initiated in 2003, the region had approximately two earthquakes per year with magnitudes between 3.0 and 4.9; after the full impoundment in 2008, approximately 14 earthquakes per year occurred with magnitudes between 3.0 and 5.4. In addition, hundreds of landslides were reactivated and are now in a state of intermittent creep. Many landslides exhibit step-like annual pattern of displacement in response to quasi-regular variations in seasonal rainfall and reservoir level. Additional problems include rock avalanches, impulse waves and debris flows. The seriousness of these events motivated numerous studies that resulted in 1) Better insight into the behavior and evolution mechanism of geohazards in the Three Gorges Reservoir Area (TGRA); 2) Implementation of monitoring and early-warning systems of geohazards; and 3) Design and construction of preventive countermeasures including lattice anchors, stabilizing piles, rock bolts, drainage canals and tunnels, and huge revetments. This paper reviews the hydro-geologic setting of TGRA geohazards, examines their occurrence and evolution in the past few decades, offers insight learned from extensive research on TGRA geohazards, and suggests topics for future research to address the remaining challenges

Robust Geotechnical Design – A New Design Perspective

In routine geotechnical engineering practice, the engineer has to work with a small sample of data due to budget constraint. Because of complexity of soil deposits, it is often difficult to determine correctly the statistics of soil parameters that are required for reliability-based design of foundations. Furthermore, the traditional reliability-based design is sensitive to the variation of noise factors such as uncertain soil parameters. To address this dilemma, the authors present a new design methodology, termed robust geotechnical design. This new design methodology aims to make the response of a geotechnical system immune to, or robust against, the variation of noise factors by carefully adjusting the design parameters. This methodology is realized through a multi-objective optimization, in which all the design requirements such as safety, robustness, and cost are explicitly considered. The results of such optimization are often expressed as a Pareto Front, which defines a trade-off relationship between cost and robustness, whereas safety is guaranteed. This enables the engineer to make an informed design decision according to a target cost or robustness. The significance of new design methodology is illustrated with an example of shallow foundation design

Geohazards and human settlements: Lessons learned from multiple relocation events in Badong, China – Engineering geologist's perspective

Abstract Mountainous regions are inherently susceptible to geohazards, such as landslides and debris flows, with the threat of natural disasters compounded by human activities (mainly settlements). Lessons learned from past events that involved the interactions between human activities and geohazards are helpful for future site selections of human settlements in mountainous regions. To this end, the events associated with county seat relocations in Badong, a typical county in the Three Gorges Reservoir region, China, are studied from an engineering geologist's perspective. Over its history, the county seat was relocated multiple times, with the first relocation traced back to the Song dynasty (960–1279 CE) and the last two relocations linked to the Three Gorges Dam project. By studying geohazards and their interactions with human activities in these county-seat relocations, and through the reconstruction of these events, we secure insights into decision-making for these events. As part of the reconstruction of these relocation events, we analyze a giant pre-historic landslide, whose discovery ultimately prompted the third relocation. Using the case history of this landslide, we also discuss and emphasize the importance of proactive monitoring of geohazards for disaster resilience enhancement, recognizing that our knowledge of nature is vastly incomplete

Soil Liquefaction and Ground Settlement in Chi-Chi Taiwan, Earthquake

This paper presents an investigation of soil liquefaction and ground settlement in the 1999 Chi-Chi, Taiwan, earthquake. The quake killed more than 2400 people and caused a great destruction to buildings, bridges, dams, highways and railways. One of the causes for heavy damages to the structures is soil liquefaction and ground settlement during the earthquake. Six sites that were observed to experience liquefaction are investigated through cone penetration testing (CPT), and the liquefaction potential of each site and the settlement of the liquefied soil strata are analyzed

Self-consistent approach for the quantum confined Stark effect in shallow quantum wells

A computationally efficient, self-consistent complex scaling approach to calculating characteristics of excitons in an external electric field in quantum wells is introduced. The method allows one to extract the resonance position as well as the field-induced broadening for the exciton resonance. For the case of strong confinement the trial function is represented in factorized form. The corresponding coupled self-consistent equations, which include the effective complex potentials, are obtained. The method is applied to the shallow quantum well. It is shown that in this case the real part of the effective exciton potential is insensitive to changes of external electric field up to the ionization threshold, while the imaginary part has non-analytical field dependence and small for moderate electric fields. This allows one to express the exciton quasi-energy at some field through the renormalized expression for the zero-field bound state.Comment: 13 pages, RevTeX4, 6 figure