Miracle-dz/UniFAR-FTUs huggingface dataset:
Disassembling a 3D mechanism for efficient packing

This paper introduces a disassemble‐and‐pack algorithm to disassemble a mechanical 3D model in groups that can be efficiently packed within a box, with the objective of reassembling them easily after delivery. Its key feature is that, mostly, the mechanism can be disassembled at the joint and each part can be an adjusted motion structure based on its joint type. Our system consists of two steps: disassembling the mechanical object into a group set and packing them within a box efficiently. The first step consists in the creation of a hierarchy of possible group set of parts that can be tightly packed within their minimum bounding boxes. Use the breadth‐first search algorithm to traverse the hierarchy of possible group set in order to disconnect the joints and get the group set. In the second step, according to the reverse order of volume, each group in the set is inserted into the specified box. The fact that mechanism disassembly and shape packing are both an NP‐complete problem justifies finding approximated solutions according to efficacy and efficiency. Experimental results show that our approach can really efficiently pack a range of mechanisms from a simple model to complex objects.
Variance-Gamma approximation via Stein's method

Variance-Gamma distributions are widely used in financial modelling and contain as special cases the normal, Gamma and Laplace distributions. In this paper we extend Stein’s method to this class of distributions. In particular, we obtain a Stein equation and smoothness estimates for its solution. This Stein equation has the attractive property of reducing to the known normal and Gamma Stein equations for certain parameter values. We apply these results and local couplings to bound the distance between sums of the form P m;n;r i;j;k=1XikYjk, where the Xik and Yjk are independent and identically distributed random variables with zero mean, by their limiting VarianceGamma distribution. Through the use of novel symmetry arguments, we obtain a bound on the distance that is of order m 1 +n 1 for smooth test functions. We end
Crystallisation Instability in Glassforming Mixtures

Understanding the mechanisms by which crystal nuclei form is crucial for many phenomena such as gaining control over crystallisation in glassforming materials or accurately modelling rheological behaviour of magma ﬂows. The microscopic nature of such nuclei, however, makes their understanding extremely hard in experiments, while computer simulations have hitherto been hampered by short timescales and small system sizes. Here we use highly-eﬃcient GPU simulation techniques to address these challenges. The larger systems we access reveal a general nucleation mechanism in mixtures. In particular, we ﬁnd that the supercooled liquid of a prized atomistic model glassformer (Kob-Andersen model) is inherently unstable to crystallisation, i.e. that nucleation is unavoidable on the structural relaxation timescale, for system sizes of 10 , 000 particles and larger. This is due to compositional ﬂuctuations leading to regions comprised of one species that are larger than the critical nucleus of that species, which rapidly crystallise. We argue that this mechanism provides a minimum rate of nucleation in mixtures in general, and show that the same mechanism pertains to the metallic glassformer copper-zirconium (CuZr).
Robust Control of Grid-Tied Parallel Inverters Using Nonlinear Backstepping Approach

In modern electrical systems, solar energy extracted is integrated into electrical grid using power converters. In most cases, several inverters are connected across the same dc link so that the circulating currents between the inverter are made zero and the input power is shared among the available inverters. Because of the nonlinear nature of grid-tied photovoltaic (PV) system and the inherent modeling uncertainties, conventional control schemes cannot provide satisfactory performances under all operating conditions. Nonlinear control techniques for grid-tied inverter have been explored in this paper. However, the design of nonlinear controllers for the control of grid-tied parallel inverters has been rarely reported. Therefore, the purpose of this paper is to design a nonlinear controller for the control of grid-tied parallel inverter system. A novel control strategy is devised that utilizes backstepping inspired integral sliding mode control to maintain a constant dc link voltage and control power flow to the grid. An algorithm is developed, which determines the number of inverters connected across the dc link. The control strategy employs Lyapunov approach to ensure stability in an event of disturbance and guarantees robustness. With the proposed control scheme, better and superior performance is observed in transient response, total harmonic distortion minimization and integrating power into the grid at unity power factor. Furthermore, with the control strategy, the available power from the PV array is successfully distributed among multiple inverters operating in parallel.
Practical distributed MIMO for WiFi and LTE

Distributed MIMO has long been known theoretically to bring large throughput gains to wireless networks. Recent years have seen significant interest and progress in developing practical distributed MIMO systems. Multiple systems have developed coordination protocols to synchronize multiple nodes and enable them to transmit simultaneously without interference. However, there are still several challenges that need to be addressed in order to have a practical distributed MIMO system for WiFi and LTE. In this thesis, we address the practical limitations in distributed MIMO systems. We present algorithms that enable practical distributed MIMO in the context of WiFi and LTE. Furthermore, we demonstrate these algorithms through Hardware/Software architectures which are implemented on an FPGA platform and run in real-time. We present two different systems in this thesis. For WiFi, we present MegaMIMO 2.0, the first real-time 802.11 distributed MIMO system. MegaMIMO 2.0 builds on top of state of the art work in distributed MIMO, and adds support for dynamic environments and mobile clients while meeting the tight timing requirements of the 802.11 WiFi standard. We also introduce Chorus the first scalable distributed MIMO system for LTE. Chorus works with the different modes of LTE and is resilient to changes in network configuration. Both MegaMIMO 2.0 and Chorus require no change to the user devices, and are fully compatible with the 802.11 standard for WiFi and the 3GPP standard for LTE. Thesis Supervisor: Dina Katabi Title: Professor
Lattices in $\mathrm{PU}(n,1)$ that are not profinitely rigid

Using conjugation of Shimura varieties, we produce nonisomorphic, cocompact, torsion-free lattices in $\mathrm{PU}(n,1)$ with isomorphic profinite completions for all $n \ge 2$. This disproves a conjecture of D. Kazhdan and gives the first examples nonisomorphic lattices in a semisimple Lie group of real rank one with isomorphic profinite completions, answering two questions of A. Reid.
Investigação de novas abordagens em sistemas imunes artificiais para otimização

O custo computacional do processo de otimizacao de dispositivos eletromagneticos esta diretamente relacionado ao numero de avaliacoes da funcao objetivo. Isso tem motivado o estudo de novos metodos que sejam capazes de determinar resultados eficientes com o menor numero de avaliacoes possiveis. Esta dissertacao propoe dois algoritmos imunes para otimizacao mono e multi-objetivo. A versao mono-objetivo, nomeada Distributed Clonal Selection Algorithm - DCSA, implementa um operador principal chamado hipermutacao somatica distribuida, enquanto a versao multi-objetivo, nomeadaMulti-Objective Clonal Selection Algorithm - MCSA, alem do operador anterior, implementa tamb´em um operador de edicao de receptores. A hipermutacao somatica, composta por diferentes funcoes densidade de probabilidade, normal, uniforme e caotica, efetua uma busca local balanceada ao redor das solucoes de maior afinidade, alem de favorecer a melhor distribuicao das solucoes ao longo da extensao da fronteira Pareto-otima no MCSA. Ja a edicao de receptores, implementada com base na evolucao diferencial, efetua implicitamente uma pesquisa dinâmica sobre a regiao factivel, garantindo ummelhor refinamento local das solucoes otimas, e favorecendo o aumento da velocidade de convergencia do metodo. Os parâmetros dos algoritmos de otimizacao sao submetidos a analises de sensibilidade, o que permite determinar faixas aceitaveis aos mesmos. Alem disso, os operadores imunes sugeridos sao avaliados quanto ao ganho que cada um proporciona ao desempenho dos metodos. Os algoritmos imunes propostos sao validados por meio da solucao de problemas analiticos com diferentes caracteristicas de otimizacao, tais como, alta suavidade, multimodalidade, multiplas variaveis e restricoes, apresentando solucoes eficientes quando comparados a outros metodos evolucionarios conhecidos. Finalmente sao realizados testes com problemas eletromagneticos de alto custo computacional associado, resultando mais uma vez solucoes de boa qualidade, e tambem um menor esforco de maquina, em relacao ao numero de avalicoes realizadas, quando comparados a outros algoritmos da literatura.
On the Performance Analysis of One Tap Equalizers in Oversampled OFDM Systems

Oversampling is commonly encountered in orthogonal frequency division multiplexing (OFDM) systems to ease various performance characteristics. In this paper, we investigate the performance and complexity of one tap zero-forcing (ZF) and minimum mean-square error (MMSE) equalizers in oversampled OFDM systems. Theoretical analysis and simulation results show that oversampling not only reduces the noise at equalizer output but also helps mitigate ill effects of spectral nulls. One tap equalizers therefore yield improved symbol-error-rate (SER) performance with the increase in oversampling rate, but at the expense of increased system bandwidth and modest complexity requirements.
Some Results about the Contractions and the Pendant Pairs of a Submodular System

Submodularity is an important property of set functions with deep theoretical results and various applications. Submodular systems appear in many applicable area, for example machine learning, economics, computer vision, social science, game theory and combinatorial optimization. Nowadays submodular functions optimization has been attracted by many researchers. Pendant pairs of a symmetric submodular system play essential role in finding a minimizer of this system. In this paper, we investigate some relations between pendant pairs of a submodular system and pendant pairs of its contractions. For a symmetric submodular system $left(V,fright)$ we construct a suitable sequence of $left|Vright|-1$ pendant pairs of its contractions. By using this sequence, we present some properties of the system and its contractions. Finally, we prove some results about the minimizers of a posimodular function.
Control-Display Affordances in Simulation Based Education

Mixed reality opens new ways of connecting users to virtual content. With simulation-based education and training (SBET), mixed reality offers an enriched environment to experience digital learning. In turn, learners can develop their mental models to process and connect 2D/3D information in real-world settings. This paper reports on the use of the Microsoft HoloLens to create a mixed reality SBET environment. The challenges of this investigation are harmonising augmented real-world content, including the use of real-time, low-latency tracking of tangible objects and the interaction of these with the augmented content. The research emphasis is on technology-mediated affordances. For example, what affordance does the HoloLens provide the leaner in terms of interactive manipulation or navigation in the virtual environment? We examine this through control-display (CD) gain in conjunction with cyber-physical systems (CPS) approaches. This work builds on previously attained knowledge from the creation of an AR application for vocational education and training (VET) of stonemasonry.
Advanced Acquisition Methods for Anisotropic X-ray Dark-field Imaging

X-ray Dark-field is a relatively new contrast mechanism that combines the high resolution of X-ray scattering to the large field-of-view of X-ray imaging. It exhibits the property of orientation-selectivity, which forms the basis of a new sub-category of imaging methods, namely, Anisotropic X-ray Dark-field (AXDF) imaging. AXDF imaging utilizes the orientation selectivity of the dark-field signal to reveal information about sub-pixel sized structures without the need of directly resolving them. In addition, AXDF tomography aims at the reconstruction of the three dimensional scattering information inside every three dimensional volume element. AXDF imaging is a suitable candidate for non-destructive testing, a field with an ever increasing demand for higher resolution and larger field-of-view. Currently available high resolution imaging methods, such as X-ray micro Computed Tomography, are unable to meet these demands due to the trade-off between the spatial resolution and the measurable sample size. AXDF imaging, with at least two orders of magnitude difference between the size of the structures probed versus the size of the investigated sample, is a promising tool for this industry. However, AXDF imaging methods require bulky hardware and long acquisition time that severely hinder their translation to industrial applications. Development of optimized and industrially compatible AXDF acquisition protocols is the main goal of this thesis. With the above goal in mind, we present a method for fast two dimensional AXDF imaging of continuously moving samples. Further, we investigate AXDF tomographic methods where the directional dependence of the dark-field signal renders standard tomographic acquisition unusable. We present two approaches to design tomographic acquisition schemes for optimal sampling of the real and reciprocal space, simultaneously. We validate the proposed methods with numerical and experimental analysis. In both cases, the proposed methods reduce the hardware and time complexity of two and three dimensional AXDF imaging methods and, hence, are a significant step forward for using these methods outside the laboratory.
Hunting down the ohmic contact of organic field-effect transistor

We report properties of contact resistances observed on pentacene organic field-effect transistors (OFET) with four different source/drain electrodes, namely, copper (Cu), gold (Au), silver (Ag), and germanium (Ge). The metals were selected to provide a wide range of energy barriers for charge injection, from blocking contact to smooth injection. All OFETs exhibited strong voltage dependence of the contact resistance, even for devices with smooth injection, which is in strong disagreement with the definition of ohmic contacts. A comparison with current crowding, resistive network, Fowler–Nordheim tunneling, and electric field enhanced thermionic injection (Schottky emission) pointed to importance of local electric fields and/or electrostatic field charges.
Improving the Robustness of Adaptive Steganographic Algorithms Based on Transport Channel Matching

Moving steganography and steganalysis from the laboratory into the real world, the robustness of steganography needs to be further considered. In this paper, we propose a robust steganographic algorithm to resist the JPEG compression of transport channel based on transport channel matching. Transport channel matching can adjust images to meet the requirements of transport channel so that the impact of JPEG compression from the channel can be reduced. To improve the robustness of steganography, the embedded message bits will be encoded by the error correction code. Then, the adaptive steganographic algorithms will be used to embed messages. To enhance the coding rate, the error correction capability ${t}$ of the error correction code is dynamically adjusted according to the images. Experimental results on the local simulation of JPEG compression and social network site demonstrate that the proposed steganographic algorithm has a good performance with respect to both robustness and security.
Symmetric Walks on Paths and Cycles

Summary We study a symmetric simple random walk on a finite section of the integer lattice (with various end conditions) and on the vertices of a polygon whose nodes are labeled as . We study the probability distributions (specifically the expectation and the variance) of the time until first return to the starting position, the number of nodes visited during this time, the time until all nodes are visited, the last node to be visited, the time to return to the starting position after visiting all nodes and the number of nodes visited in the interim. These questions are answered using elementary methods readily understood by college mathematics students—methods such as symmetry, recursive relations and mathematical induction.
Industrial process deep feature representation by regularization strategy autoencoders for process monitoring

Autoencoders and stacked autoencoders (SAEs) are efficient for detecting abnormal situations in process monitoring because of their powerful deep feature representation capability. However, SAEs are easy to overfit during training, thereby affecting this representation. Furthermore, several nodes of the same layer in the SAE carry duplicate information, and thus the features are strongly correlated. To solve these problems, a novel regularization strategy, in which the inner product is introduced, is proposed for the SAE to reduce overfitting more effectively. The modified SAE is called an inner product-based stacked autoencoder (IPSAE). SAEs aim to reduce the Euclidean distance between the output and input matrices through iterative calculation, whereas the IPSAE adds the inner products between the outputs of the neurons to the objective function to regularize the features and reduce feature redundancy. Hence, after determining the structure of the SAE, it is trained to lower the reconstruction error and inner product between the outputs of the neurons to improve the deep feature representation of the industrial process. The proposed model is applied to a numerical system and a Tennessee Eastman dataset, and demonstrates the best performance when compared with several state-of-the-art models.
Toward Absolute Phase Change Recovery With InSAR: Correcting for Earth Tides and Phase Unwrapping Ambiguities

Radar interferograms provide a map of the phase difference between the reference and repeat acquisitions modulo <inline-formula> <tex-math notation="LaTeX">${2\pi }$ </tex-math></inline-formula>. Under ideal conditions, the phase can be unwrapped to provide an absolute phase connection across the map, although there is always an unknown integer phase ambiguity (i.e., <inline-formula> <tex-math notation="LaTeX">${N2\pi }$ </tex-math></inline-formula>) for the entire map. Here, we demonstrate a practical time series method to solve for these integer ambiguities in order to recover the absolute phase change between the first and last SAR images. An important first step is to correct the phase of each SAR image for the well-known solid earth tide, which typically produces a line of sight offset ±150 mm, as well as, trends along and across each image of ~20 mm. This tide correction significantly reduces the noise in the InSAR time series, especially at the L-band. These tidally corrected interferograms are then unwrapped and used to solve for a set of integer ambiguities that achieves phase closure when summing around loops in the stack. There is an infinite number of ambiguity combinations that achieve loop closure; thus, regularization is required. In contrast to previous studies that use a least-squares approach to find the ambiguities, we adopt an <inline-formula> <tex-math notation="LaTeX">${L}_{1}$ </tex-math></inline-formula>-norm approach to find the minimum number of ambiguity corrections needed to achieve loop closure. We note that the split-spectrum ionospheric correction can introduce <inline-formula> <tex-math notation="LaTeX">${N\pi }$ </tex-math></inline-formula> ambiguities and suggest two approaches for correcting both <inline-formula> <tex-math notation="LaTeX">${N2\pi }$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">${N\pi }$ </tex-math></inline-formula> ambiguities.
SAR ATR in the phase history domain using deep convolutional neural networks

Synthetic aperture radar (SAR) automatic target recognition (ATR) has been an interesting topic of research for decades. Existing methods perform the ATR task after image formation. However, in principle, image formation does not provide any new information regarding the classification task and it may even cause some information loss. Motivated by this, in this paper, we examine two SAR ATR frameworks that work in the phase history domain. In the first framework, we feed the complex-valued phase histories to a deep convolutional neural network (CNN) directly, and in the second one, we perform image formation, phase removal, and phase history generation before feeding the data to the CNN. CNNs are known for their superior performance on image classification tasks. The effectiveness of CNNs is based on dependency patterns in a given input. Thus, the input of CNNs is not limited to images but any input exhibiting such dependencies. Since complex-valued phase histories also have such a structure, they can be the input of a CNN. We perform ATR experiments on the Moving and Stationary Target Acquisition and Recognition (MSTAR) database and compare the results of image-based and phase history-based classification.
The inventory structure of Person in the Chinese dialect of Puxian

One way to classify person systems across languages is by means of the semantic category of person and/or number, where person forms, with distinct referential values, are supposed to be in complementary distribution to each other. However, when we look into some finer details in a language-particular person system, i.e. that of the Puxian dialect in Chinese, there are person forms or expressions that are engaged in supplementary distribution and have meanings beyond what is literally said (Grice 1989). Different from previous approaches, which tended to analyze a person system into separate domains of study, e.g. reflexivity, intensification, logophoricity, empathy, etc., the author proposes that all the person-related meanings (semantics & pragmatics) constitute a “function inventory”, which has a stable structure called “inventory structure”. In the structure, each of the overtly expressed person meanings is assigned to a choice of node, from which multiple outcomes can be developed. The significance of this approach is that it tries to circumvent some pre-established categories and focuses instead on meaningful differences in a system (Sausurre 1983).
A High Linearity +44.5-dBm IP $3~C$ -Band 6-Bit Digital Phase Shifter Using SOI Technology for Phased Array Applications

A 6-bit digital phase shifter in 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> silicon-on-insulator (SOI) process is presented. It operates over a 4–7-GHz frequency band and provides 360° of phase coverage with 5.625° resolution using 64 phase states. The SOI phase shifter has a compact size of <inline-formula> <tex-math notation="LaTeX">$1320\,\,\mu \text{m}\,\,\times 780\,\,\mu \text{m}$ </tex-math></inline-formula>. Compared to a state-of-the-art 0.15-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> pHEMT-based product design, the SOI IC design is five times smaller in size with 2–6 dB higher IP3 and power handling capability. To the best of authors’ knowledge, this is the highest IP3 of phase shifter using commercial SOI technology. These SOI monolithic microwave integrated circuit (MMIC) phase shifter characteristics are attractive for military radar and commercial phased array communication systems where cost, size, weight, and power (C-SWAP) and high linearity are required.