Since the emergence of the process-oriented approach to second language writing instruction two main questions have been what and how error feedback should be given to the students. The question of whether teachers should provide feedback on grammar in the writing assignments of English as a foreign language students, and if so how, has been a matter of considerable debate in the field of secon...

The self-amplified, spontaneous emission free-electron laser (SASE FEL) gain process is a collective instability which induces microbunching in the electron beam. Microbunching approaching unity at the fundamental FEL wavelength (845 nm), and its second harmonic, have been measured at the VISA FEL, at or near saturation. These measurements, which use the beam's coherent transition radiation (CT...

We propose a simple method to significantly enhance the temporal coherence and spectral brightness of a self-amplified spontaneous emission (SASE) free-electron laser (FEL). In this purified SASE (pSASE) FEL, a few undulator sections (called slippage-boosted section) resonant at a subharmonic of the FEL radiation are used in the middle stage of the exponential growth regime to amplify the radia...

Humans monitor their behavior to optimize performance, which presumably relies on stable representations of correct responses. During second language (L2) learning, however, stable representations have yet to be formed while knowledge of the first language (L1) can interfere with learning, which in some cases results in persistent errors. In order to examine how correct L2 representations are s...

Differential settlement of the foundation of the LCLS Undulator Hall will cause quadrupoles to move and the electron beam trajectory to distort. The resulting phase errors will decrease the FEL power and require time consuming beam-based alignment sessions to correct. By supporting quadrupoles on girders, with three quadrupoles to a girder, the foundationmotion induced phase error between the b...

Numerical simulation codes are basic tools for designing Free Electron Lasers (FEL). They are used to study the impact of di!erent parameters, e.g. wiggler errors and external focusing, which allow FEL users to optimize the performance. For faster execution some simulation codes assume radial symmetry or decompose the radiation "eld into a few azimuthal modes, although then this treatment does ...

This paper introduces a development of a normalized axial velocity distribution function and a susceptibility term for an electron beam m a planar wiggler FEL. The model includes the independent contributions of the energy spread and the angular spread, the ennttance and the betatron motion, to the axial velocity distribution function. In the case of an emittance dominated spread, the resulting...

control of robotic systems is an interesting subject due to their wide spectrum applications in medicine, aerospace and other industries. this paper proposes a novel continuous control mechanism for tracking problem of a 5-dof upper-limb exoskeleton robot. the proposed method is a combination of a recently developed robust integral of the sign of the error (rise) feedback and neural network (nn...

Robots execute a wide array of rhythmic behaviors like walking, running, dribbling, etc. Rhythmic movement primitives are parametric models that can be used to represent these behaviors. Previously, these models have been learned either by means of demonstrations or by means of reward signals. While executing a rhythmic behavior, a stabilizing controller is needed in most robots to prevent fail...