Ikasleen hizkuntza erroreak eta hutsegiteak : zuzentzeko proposamena

[Es]El presente trabajo se basa en las consultas que los profesores y profesoras de distintas asignaturas nos hacen al profesorado de lengua. Muchas veces los profesores debemos corregir no sólo el contenido de los trabajos de nuestros alumnos, sino también la lengua. La discusión no es nueva: ¿somos todos los profesores también profesores de lengua? Es un desafío del que difícilmente podemos escapar, ya que la lengua además de ser una materia de estudio también es el vehículo en el que se imparten los contenidos de todas las asignaturas. Con el presente trabajo pretendemos ayudar a los profesores que no imparten lengua como asignatura a corregir los trabajos de sus alumnos. Esta propuesta consta de tres ejes de actuación marcados por un orden de prioridad: prevenir, autocorregir y ayudar.

Lattice quantum codes and exotic topological phases of matter

This thesis addresses whether it is possible to build a robust memory device for quantum information. Many schemes for fault-tolerant quantum information processing have been developed so far, one of which, called topological quantum computation, makes use of degrees of freedom that are inherently insensitive to local errors. However, this scheme is not so reliable against thermal errors. Other fault-tolerant schemes achieve better reliability through active error correction, but incur a substantial overhead cost. Thus, it is of practical importance and theoretical interest to design and assess fault-tolerant schemes that work well at finite temperature without active error correction.

In this thesis, a three-dimensional gapped lattice spin model is found which demonstrates for the first time that a reliable quantum memory at finite temperature is possible, at least to some extent. When quantum information is encoded into a highly entangled ground state of this model and subjected to thermal errors, the errors remain easily correctable for a long time without any active intervention, because a macroscopic energy barrier keeps the errors well localized. As a result, stored quantum information can be retrieved faithfully for a memory time which grows exponentially with the square of the inverse temperature. In contrast, for previously known types of topological quantum storage in three or fewer spatial dimensions the memory time scales exponentially with the inverse temperature, rather than its square.

This spin model exhibits a previously unexpected topological quantum order, in which ground states are locally indistinguishable, pointlike excitations are immobile, and the immobility is not affected by small perturbations of the Hamiltonian. The degeneracy of the ground state, though also insensitive to perturbations, is a complicated number-theoretic function of the system size, and the system bifurcates into multiple noninteracting copies of itself under real-space renormalization group transformations. The degeneracy, the excitations, and the renormalization group flow can be analyzed using a framework that exploits the spin model's symmetry and some associated free resolutions of modules over polynomial algebras.

Rewriting Schemes for Flash Memory

Flash memory is a leading storage media with excellent features such as random access and high storage density. However, it also faces significant reliability and endurance challenges. In flash memory, the charge level in the cells can be easily increased, but removing charge requires an expensive erasure operation. In this thesis we study rewriting schemes that enable the data stored in a set of cells to be rewritten by only increasing the charge level in the cells. We consider two types of modulation scheme; a convectional modulation based on the absolute levels of the cells, and a recently-proposed scheme based on the relative cell levels, called rank modulation. The contributions of this thesis to the study of rewriting schemes for rank modulation include the following: we

•propose a new method of rewriting in rank modulation, beyond the previously proposed method of “push-to-the-top”;

•study the limits of rewriting with the newly proposed method, and derive a tight upper bound of 1 bit per cell;

•extend the rank-modulation scheme to support rankings with repetitions, in order to improve the storage density;

•derive a tight upper bound of 2 bits per cell for rewriting in rank modulation with repetitions;

•construct an efficient rewriting scheme that asymptotically approaches the upper bound of 2 bit per cell.

The next part of this thesis studies rewriting schemes for a conventional absolute-levels modulation. The considered model is called “write-once memory” (WOM). We focus on WOM schemes that achieve the capacity of the model. In recent years several capacity-achieving WOM schemes were proposed, based on polar codes and randomness extractors. The contributions of this thesis to the study of WOM scheme include the following: we

•propose a new capacity-achievingWOM scheme based on sparse-graph codes, and show its attractive properties for practical implementation;

•improve the design of polarWOMschemes to remove the reliance on shared randomness and include an error-correction capability.

The last part of the thesis studies the local rank-modulation (LRM) scheme, in which a sliding window going over a sequence of real-valued variables induces a sequence of permutations. The LRM scheme is used to simulate a single conventional multi-level flash cell. The simulated cell is realized by a Gray code traversing all the relative-value states where, physically, the transition between two adjacent states in the Gray code is achieved by using a single “push-to-the-top” operation. The main results of the last part of the thesis are two constructions of Gray codes with asymptotically-optimal rate.

Solutions for New Terrestrial Broadcasting Systems Offering Simultaneously Stationary and Mobile Services

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基于RS编码及网格编码调制的光PPM通信纠错技术

分析了RS（Reed-Solomon）纠错码和网格编码调制（Trellis Coded Modulation，TCM）技术在光脉冲位置调制通信中的应用．在此基础上，提出了以RS码作为外码，以网格编码调制技术作为内码，用于光脉冲位置调制通信的新编码方案，能以几乎不减少通信速率的优势，提高传统RS码系统在时变带限光信道中的通信性能．模拟研究了在不同空间光信道条件下，传统RS码的符号正确传输率和误码率，并对网格编码调制的编码增益、RS码与网格编码调制级联时的编码增益进行了仿真研究，证实了本方案的有效性．

光栅位移测量系统的误差自修正方法研究

文中介绍的误差自修正方法是通过光栅位移测量系统中单片机对光栅传感器的多个零位信号进行计数,并根据测量值和系统设定值得到的误差函数自动进行误差修正。实验结果表明,该方法对光栅位移测量系统的误差既可自动进行有效的修正,又可提高系统的测量精度。

Comparisons between gigabit NRZ, CAP and optical OFDM systems over FEC enhanced POF links using LEDs

Simulations have been performed to compare the link power budget and power dissipation of carrierless amplitude and phase modulation-64 (CAP-64) and 64-quadrature amplitude modulation-orthogonal frequency division multiplexing (64-QAM-OFDM) systems over feedforward error correction (FEC) enhanced plastic optical fibre (POF) links using light emitting diodes (LEDs). It is shown that CAP-64 outperforms 64-QAM-OFDM and supports record high 2.1Gb/s over 50m POF transmission. The CAP-64 and 64-QAM-OFDM links consume similar powers which are 2 (2.5) times of that of NRZ for the single POF link (twin POF links) case. © 2012 IEEE.

FEC-free 50 m 1.5 Gb/s plastic optical fibre link using CAP modulation for home networks

LED-based carrierless amplitude and phase modulation is investigated for a multi-gigabit plastic optical fibre link. An FPGA-based 1.5 Gbit/s error free transmission over 50 m standard SI-POF using CAP64 is achieved, providing 2.9 dB power margin without forward error correction. © 2012 OSA.

Mode division multiplexing exploring hollow-core photonic bandgap fibers

We review our recent exploratory investigations on mode division multiplexing using hollow-core photonic bandgap fibers (HC-PBGFs). Compared with traditional multimode fibers, HC-PBGFs have several attractive features such as ultra-low nonlinearities, low-loss transmission window around 2 μm etc. After having discussed the potential and challenges of using HC-PBGFs as transmission fibers for mode multiplexing applications, we will report a number of recent proof-of-concept results obtained in our group using direct detection receivers. The first one is the transmission of two 10.7 Gbit/s non-return to zero (NRZ) data signals over a 30 m 7-cell HC-PBGF using the offset mode launching method. In another experiment, a short piece of 19-cell HC-PBGF was used to transmit two 20 Gbit/s NRZ channels using a spatial light modulator for precise mode excitation. Bit-error-ratio (BER) performances below the forward-error-correction (FEC) threshold limit (3.3×10-3) are confirmed for both data channels when they propagate simultaneously. © 2013 IEEE.

FEC-free 50 m 1.5 Gb/s plastic optical fibre link using CAP modulation for home networks

LED-based carrierless amplitude and phase modulation is investigated for a multi-gigabit plastic optical fibre link. An FPGA-based 1.5 Gbit/s error free transmission over 50 m standard SI-POF using CAP64 is achieved, providing 2.9 dB power margin without forward error correction. © 2012 Optical Society of America.

Proposed scheme for parallel 10Gb/s VSR system and its Verilog HDL realization

This paper proposes a novel and innovative scheme for 10Gb/s parallel Very Short Reach (VSR) optical communication system. The optimized scheme properly manages the SDH/SONET redundant bytes and adjusts the position of error detecting bytes and error correction bytes. Compared with the OIF-VSR4-01.0 proposal, the scheme has a coding process module. The SDH/SONET frames in transmission direction are disposed as follows: (1) The Framer-Serdes Interface (FSI) gets 16x622.08Mb/s STM-64 frame. (2) The STM-64 frame is byte-wise stripped across 12 channels, all channels are data channels. During this process, the parity bytes and CRC bytes are generated in the similar way as OIF-VSR4-01.0 and stored in the code process module. (3) The code process module will regularly convey the additional parity bytes and CRC bytes to all 12 data channels. (4) After the 8B/10B coding, the 12 channels is transmitted to the parallel VCSEL array. The receive process approximately in reverse order of transmission process. By applying this scheme to 10Gb/s VSR system, the frame size in VSR system is reduced from 15552x12 bytes to 14040x12 bytes, the system redundancy is reduced obviously.

基于语音和笔的手写数学公式纠错方法

用识别技术的用户界面往往由于识别率的限制容易出错，如何为这类界面提供自然高效的纠错方法十分重要．手写数学公式具有二维结构，难以识别和纠错．提出一种用于纠正手写数学公式识别错误的多通道技术．它允许用户使用笔纠正切分错误，用笔和语音纠正符号识别和表达式结构分析错误．该技术的核心是一个多通道融合算法．融合算法以笔选择的符号和语音作为输入，根据语音输入的类型是数学术语或者数学符号分别选择融合方法，最后修正手写公式并输出最有可能的识别结果．实验结果表明，该技术能有效地纠正手写数学公式识别中的错误，它比基于笔的单通道纠错技术更加高效．

基于多通道融合的连续手写识别纠错方法

在基于识别的界面中,用户的满意度不但由识别准确度决定,而且还受识别错误的纠正过程的影响.提出一种基于多通道融合的连续手写笔迹识别错误的纠正方法.该方法允许用户通过口述书写内容纠正手写识别中的字符提取和识别的错误.该纠错方法的核心是一种多通道融合算法.该算法通过利用语音输入约束最优手写识别结果的搜索,可纠正手写字符的切分错和识别错.实验评估结果表明,该融合算法能够有效纠正错误,计算效率高.与另外两种手写识别错误纠正方法相比,该方法具有更高的纠错效率.

基于信道估计的RS纠错编码改进算法的设计与实现

提出了一种基于信道估计的RS纠错编码改进算法,该算法可以自适应地根据外界条件和环境对传输信道的干扰变化实时地调节编码系统的数据冗余量。仿真与完整的分析结果证实了该改进算法有效地改善了RS编码算法的传输效率;并且通过实际应用表明:良好的性能,高容错性适应于该通信系统的多种传输信道,具有很强的实用性。

Motor Control and Learning by the State Space Model

A model is presented that deals with problems of motor control, motor learning, and sensorimotor integration. The equations of motion for a limb are parameterized and used in conjunction with a quantized, multi-dimensional memory organized by state variables. Descriptions of desired trajectories are translated into motor commands which will replicate the specified motions. The initial specification of a movement is free of information regarding the mechanics of the effector system. Learning occurs without the use of error correction when practice data are collected and analyzed.