Robust stability of second-order systems

A feedback linearization technique is used in conjunction with passivity concepts to design robust controllers for space robots. It is assumed that bounded modeling uncertainties exist in the inertia matrix and the vector representing the coriolis, centripetal, and friction forces. Under these assumptions, the controller guarantees asymptotic tracking of the joint variables. A Lagrangian approach is used to develop a dynamic model for space robots. Closed-loop simulation results are illustrated for a simple case of a single link planar manipulator with freely floating base

Theory and computation of optimal low- and medium-thrust transfers

This report presents the formulation of the optimal low- and medium-thrust orbit transfer control problem and methods for numerical solution of the problem. The problem formulation is for final mass maximization and allows for second-harmonic oblateness, atmospheric drag, and three-dimensional, non-coplanar, non-aligned elliptic terminal orbits. We setup some examples to demonstrate the ability of two indirect methods to solve the resulting TPBVP's. The methods demonstrated are the multiple-point shooting method as formulated in H. J. Oberle's subroutine BOUNDSCO, and the minimizing boundary-condition method (MBCM). We find that although both methods can converge solutions, there are trade-offs to using either method. BOUNDSCO has very poor convergence for guesses that do not exhibit the correct switching structure. MBCM, however, converges for a wider range of guesses. However, BOUNDSCO's multi-point structure allows more freedom in quesses by increasing the node points as opposed to only quessing the initial state in MBCM. Finally, we note an additional drawback for BOUNDSCO: the routine does not supply information to the users routines for switching function polarity but only the location of a preset number of switching points

On the structure of the Si(103) surface

Although (103) is a stable nominal orientation for both silicon and germanium, experimental observations revealed that in the case of silicon this surface remains disordered on an atomic scale even after careful annealing. We report here a set of low-energy reconstruction models corresponding to $1\times 2$, $2\times 2$, and $1\times 4$ periodicities, and propose that the observed disorder stems from the presence of several coexisting reconstructions with different morphologies and nearly equal surface energies. These models also suggest that the model structures previously reported in the literature for the (103) orientation have very high surface energies and are thus unlikely to be experimentally observed.Comment: 4 pages, 3 figures, submitted for publicatio

High Dynamic Range RF Front End with Noise Cancellation and Linearization for WiMAX Receivers

This research deals with verification of the high dynamic range for a heterodyne radio frequency (RF) front end. A 2.6 GHz RF front end is designed and implemented in a hybrid microwave integrated circuit (HMIC) for worldwide interoperability for microwave access (WiMAX) receivers. The heterodyne RF front end consists of a low-noise amplifier (LNA) with noise cancellation, an RF bandpass filter (BPF), a downconverter with linearization, and an intermediate frequency (IF) BPF. A noise canceling technique used in the low-noise amplifier eliminates a thermal noise and then reduces the noise figure (NF) of the RF front end by 0.9 dB. Use of a downconverter with diode linearizer also compensates for gain compression, which increases the input-referred third-order intercept point (IIP3) of the RF front end by 4.3 dB. The proposed method substantially increases the spurious-free dynamic range (DRf) of the RF front end by 3.5 dB

Model reconstructions for the Si(337) orientation

Although unstable, the Si(337) orientation has been known to appear in diverse experimental situations such as the nanoscale faceting of Si(112), or in the case of miscutting a Si(113) surface. Various models for Si(337) have been proposed over time, which motivates a comprehensive study of the structure of this orientation. Such a study is undertaken in this article, where we report the results of a genetic algorithm optimization of the Si(337)-$(2\times 1)$ surface. The algorithm is coupled with a highly optimized empirical potential for silicon, which is used as an efficient way to build a set of possible Si(337) models; these structures are subsequently relaxed at the level of ab initio density functional methods. Using this procedure, we retrieve most of the (337) reconstructions proposed in previous works, as well as a number of novel ones.Comment: 5 figures (low res.); to appear in J. Appl. Phy

Deutsch-Jozsa algorithm as a test of quantum computation

A redundancy in the existing Deutsch-Jozsa quantum algorithm is removed and a refined algorithm, which reduces the size of the register and simplifies the function evaluation, is proposed. The refined version allows a simpler analysis of the use of entanglement between the qubits in the algorithm and provides criteria for deciding when the Deutsch-Jozsa algorithm constitutes a meaningful test of quantum computation.Comment: 10 pages, 2 figures, RevTex, Approved for publication in Phys Rev

Prediction of the number of cloud droplets in the ECHAM GCM

In this paper a prognostic equation for the number of cloud droplets (CDNC) is introduced into the ECHAM general circulation model. The initial CDNC is based on the mechanistic model of Chuang and Penner [1995], providing a more realistical prediction of CDNC than the empirical method previously used. Cloud droplet nucleation is parameterized as a function of total aerosol number concentration, updraft velocity, and a shape parameter, which takes the aerosol composition and size distribution into account. The total number of aerosol particles is obtained as the sum of marine sulfate aerosols produced from dimethyl sulfide, hydrophylic organic and black carbon, submicron dust, and sea-salt aerosols. Anthropogenic sulfate aerosols only add mass to the preexisting aerosols but do not form new particles. The simulated annual mean liquid water path, column CDNC, and effective radius agree well with observations, as does the frequency distributions of column CDNC for clouds over oceans and the variations of cloud optical depth with effective radius

讀藍氏箸中國之家庭與社會 = On Olga Lang : Chinese family and society

藍氏(Olga Lang)係曾在北平協和醫院社會服務部工作之—俄國女子，此書於一九三五年至三七年受社會硏究所(哥侖比亞大學)及太平洋學會委託而硏究之結果，但遲至一九四六年始由耶魯大學出版部印行。全書分爲兩編：舊時中國之家庭及現代中國之家庭。 第一編首將中國舊時社會狀況作—簡要之叙述,然後列舉舊家庭生活之各方面：家庭之功能與結構；家庭中各種關係：愛情，婚姻，離婚；女子在舊日中國家庭及社會中地位；殿以‘家庭與社會’一章，作者指出孝道過度發展之種種弊病。 第二編所佔篇幅數倍於前，似爲作者所硏究之主要部分。作者首將中國鄕村與城市之新經濟與社會環境說明，再述舊式家庭之受人攻擊。然後暢論現代中國之愛情與婚姻及其與舊日之對照。再在舉出家庭之類型與人數後，將家庭中各方面關係分爲數章詳述：家庭分子之合作，親戚關係，家庭勢力，人情主義，夫妻關係，老年人地位，兒童，靑年及友誼。最後一章係‘總結’

Kawaii In Taiwan Politics

By investigating the case of A-Bian Doll (扁娃, see Figure 1), this paper explores how Kawaii (可愛い, the Japanese word for "cute") has pervaded in Taiwan, and has since been appropriated by Taiwanese politicians as one of the significant methods for advancing democratisation, and constructing collective imagination and national identities. Particularly, this paper explores how Kawaii is represented and reproduced in Taiwan politics. I will first discuss how Kawaii is produced and consumed in Taiwanese people's everyday life in relation to the process of democratisation and the formation of consumer society. I will then move to the discussion of the A-Bian Doll and its accessories, which is arguably the most significant example of how Kawaii is made tangible in Taiwanese politics. I will examine how Kawaii is appropriated as a familiar element from Taiwanese culture by former President Chen's staffers, and is then injected into ingredients drawn from Taiwanese baseball culture and the features of Chen to produce the A-Bian Doll and its accessories. By making and advertising the A-Bian Doll and its accessories, Chen's staffers create a new culture, and then feed this back into social circulation, mobilise supporters and gain votes

Statistical analysis of the 70 meter antenna surface distortions

Statistical analysis of surface distortions of the 70 meter NASA/JPL antenna, located at Goldstone, was performed. The purpose of this analysis is to verify whether deviations due to gravity loading can be treated as quasi-random variables with normal distribution. Histograms of the RF pathlength error distribution for several antenna elevation positions were generated. The results indicate that the deviations from the ideal antenna surface are not normally distributed. The observed density distribution for all antenna elevation angles is taller and narrower than the normal density, which results in large positive values of kurtosis and a significant amount of skewness. The skewness of the distribution changes from positive to negative as the antenna elevation changes from zenith to horizon