Generic Transformation Research Articles

Impedance Modeling of Modular Multilevel Converter in D-Q and Modified Sequence Domains

Modular multilevel converters (MMCs) are characterized by the multiharmonic coupling interactions among internal dynamics. In this work, multiple <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> references and multiharmonic frames, which are developed through dynamic phasor and harmonic state space, are used to derive the generalized impedance models of MMC in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> and modified sequence domain, respectively. Although some previous studies have been devoted to revealing the equivalence of different impedance models, this article attempts to elaborate the relation of different multifrequency modeling approaches and provide a more comprehensive review of MMC impedance models. A rigorous comparison of modeling procedure, impedance response, and stability analysis result between different MMC models is conducted. It is demonstrated that the MMC impedance models in the two domains can be related by a generic linear transformation matrix. Furthermore, the stability analysis results given by the generalized Nyquist criterion are identical in these two domains. Application recommendations for different impedance models are given as well. The developed impedance models and their effectiveness for stability and resonance analysis are validated by a 501-level aggregated model in MATLAB/SIMULINK.

Rotating black holes in valid vector-tensor theories after GW170817

Vector-tensor theories beyond General Relativity have widely been studied in the context of ultraviolet completion of gravity, endowing a mass to the graviton and explaining dark energy phenomena. We here construct rotating black hole solutions in vector-tensor theories valid after the binary neutron star merger event GW170817 that placed very stringent bound on the propagation speed of gravitational waves away from the speed of light. Such valid vector-tensor theories are constructed by performing a generic conformal transformation to Einstein-Maxwell theory, and the new rotating black hole solutions are constructed by applying the same conformal transformation to the Kerr-Newman solution. These theories fall outside of beyond generalized Proca theories but are within an extended class of vector-tensor theories that satisfy a degenerate condition to eliminate instability modes and are thus healthy. We find that such conformal Kerr-Newman solutions preserve the location of the singularities, event horizons and ergoregion boundary from Kerr-Newman, as well as the multipole moments and the Petrov type. On the other hand, the Hamilton-Jacobi equation is no longer separable, suggesting that the Carter-like constant does not exist in this solution. The standard Newman-Janis algorithm also does not work to construct the new solutions. We also compute the epicyclic frequencies, the location of the innermost stable circular orbits, and the Schwarzschild precession and apply the latter to the recent GRAVITY measurement to place bounds on the deviations away from Kerr-Newman for Sgr A$^*$.

Practical CCA-Secure Functional Encryptions for Deterministic Functions

Functional encryption (FE) can implement fine-grained control to encrypted plaintext via permitting users to compute only some specified functions on the encrypted plaintext using private keys with respect to those functions. Recently, many FEs were put forward; nonetheless, most of them cannot resist chosen-ciphertext attacks (CCAs), especially for those in the secret-key settings. This changed with the work, i.e., a generic transformation of public-key functional encryption (PK-FE) from chosen-plaintext (CPA) to chosen-ciphertext (CCA), where the underlying schemes are required to have some special properties such as restricted delegation or verifiability features. However, examples for such underlying schemes with these features have not been found so far. Later, a CCA-secure functional encryption from projective hash functions was proposed, but their scheme only applies to inner product functions. To construct such a scheme, some nontrivial techniques will be needed. Our key contribution in this work is to propose CCA-secure functional encryptions in the PKE and SK environment, respectively. In the existing generic transformation from (adaptively) simulation-based CPA- (SIM-CPA-) secure ones for deterministic functions to (adaptively) simulation-based CCA- (SIM-CCA-) secure ones for randomized functions, whether the schemes were directly applied to CCA settings for deterministic functions is not implied. We give an affirmative answer and derive a SIM-CCA-secure scheme for deterministic functions by making some modifications on it. Again, based on this derived scheme, we also propose an (adaptively) indistinguishable CCA- (IND-CCA-) secure SK-FE for deterministic functions. The final results show that our scheme can be instantiated under both nonstandard assumptions (e.g., hard problems on multilinear maps and indistinguishability obfuscation (IO)) and under standard assumptions (e.g., DDH, RSA, LWE, and LPN).

Political Turmoil: Early Modern British Literature in Transition, 1623–1660. Edited by Stephen B. Dobranski. Cambridge: Cambridge University Press, 2019. Pp. xvi+365.

<i>Political Turmoil: Early Modern British Literature in Transition, 1623–1660</i>. Edited by Stephen B. Dobranski. Cambridge: Cambridge University Press, 2019. Pp. xvi+365.

Complete set of translation invariant measurements with Lipschitz bounds

In image and audio signal classification, a major problem is to build stable representations that are invariant under rigid motions and, more generally, to small diffeomorphisms. Translation invariant representations of signals in C n are of particular importance. The existence of such representations is intimately related to classical invariant theory, inverse problems in compressed sensing and deep learning. Despite an impressive body of literature on the subject, most representations available are either not stable due to the presence of high frequencies or non discriminative. In the present paper, we construct low dimensional representations of signals in C n that are invariant under finite unitary group actions, as a special case we establish the existence of low-dimensional and complete Z m -invariant representations for any m ∈ N . Our construction yields a stable, discriminative transform with semi-explicit Lipschitz bounds on the dimension; this is particularly relevant for applications. Using some tools from Algebraic Geometry, we define a high dimensional homogeneous function that is injective. We then exploit the projective character of this embedding and see that the target space can be reduced significantly by using a generic linear transformation. Finally, we introduce the notion of non-parallel map, which is enjoyed by our function and employ this to construct a Lipschitz modification of it.

Stability analysis and nonlinear current‐limiting control design for DC micro‐grids with CPLs

In this study, a DC micro-grid consisting of multiple paralleled energy resources interfaced by both bidirectional AC/DC and DC/DC boost converters and loaded by a constant power load (CPL) is investigated. By considering the generic dq transformation of the AC/DC converters' dynamics and the accurate nonlinear model of the DC/DC converters, two novel control schemes are presented for each converter-interfaced unit to guarantee load voltage regulation, power sharing and closed-loop system stability. This novel framework incorporates the widely adopted droop control and using input-to-state stability theory, it is proven that each converter guarantees a desired current limitation without the need for cascaded control and saturation blocks. Sufficient conditions to ensure closed-loop system stability are analytically obtained and tested for different operation scenarios. The system stability is further analysed from a graphical perspective, providing valuable insights of the CPL's influence onto the system performance and stability. The proposed control performance and the theoretical analysis are first validated by simulating a three-phase AC/DC converter in parallel with a bidirectional DC/DC boost converter feeding a CPL in comparison with the cascaded PI control technique. Finally, experimental results are also provided to demonstrate the effectiveness of the proposed control approach on a real testbed.

On metric transformations with a U(1) gauge field

We study metric transformations including not just the field strength tensor of a $U(1)$ gauge field, but also its dual tensor. We first consider an arbitrary symmetric matrix built up with these two tensors in the metric transformation. It turns out the form of transformation reduces to a quite simple form on imposing the parity evenness of the transformed metric and by utilising the Cayley-Hamilton theorem as well as other useful identities. Interestingly, the same form for the transformation was recently argued in the process of seeking for a generic metric transformation but without the inclusion of the dual tensor.

A Framework for Temporal Verification Support in Domain-Specific Modelling

In Domain-Specific Modelling (DSM) the general goal is to provide Domain-Specific Modelling Languages (DSMLs) for domain users to model systems using concepts and notations they are familiar with, in their problem domain. Verifying whether a model satisfies a set of requirements is considered to be an important challenge in DSM, but is nevertheless mostly neglected. We present a solution in the form of ProMoBox , a framework that integrates the definition and verification of temporal properties in discrete-time behavioural DSMLs, whose semantics can be described as a schedule of graph rewrite rules. Thanks to the expressiveness of graph rewriting, this covers a very large class of problems. With ProMoBox , the domain user models not only the system with a DSML, but also its properties, input model, run-time state and output trace. A DSML is thus comprised of five sublanguages, which share domain-specific syntax, and are generated from a single metamodel. Generic transformations to and from a verification backbone ensure that both the language engineer and the domain user are shielded from underlying notations and techniques. We explicitly model the ProMoBox framework's process in the paper. Furthermore, we evaluate ProMoBox to assert that it supports the specification and verification of properties in a highly flexible and automated way.

An upper bound on the time required to implement unitary operations

We derive an upper bound for the time needed to implement a generic unitary transformation in a d dimensional quantum system using d control fields. We show that given the ability to control the diagonal elements of the Hamiltonian, which allows for implementing any unitary transformation under the premise of controllability, the time T needed is upper bounded by where is the smallest coupling constant present in the system. We study the tightness of the bound by numerically investigating randomly generated systems, with specific focus on a system consisting of d energy levels that interact in a tight-binding like manner.

Sustainability assessment of novel transformer technologies in distribution grid applications

Abstract As more renewable energy sources are integrated in the distribution grid, congestions might arise due to voltage band violations or overloaded grid components. Novel transformer technologies have the potential to extend the otherwise limited grid capacity without necessitating extensive grid enforcements. A comparative sustainability analysis is provided covering generic transformer technologies such as state-of-the-art line-frequency transformers, transformers equipped with on-load tap changers, entirely power electronic based solid-state transformers, and hybrid transformers. An accurate and realistic system environment is modeled based on real grid topologies combined with yearly measurement data. The life-cycle assessment shows that the conventional line-frequency transformer is most eco-friendly. However, if the transformer’s ability to extend the grid’s capacity for integrating renewable energy sources is considered, a negative environmental impact can be compensated. We recommend hybrid transformers as future replacements of conventional line-frequency transformers in situations where grid congestions arise in the course of implementing the goals of the Swiss Energy Strategy 2050. Hybrid transformers are capable of enhancing the grid capacities on both, medium- and low-voltage level, while being highly eco-friendly at the same time.

Key regeneration-free ciphertext-policy attribute-based encryption and its application

Attribute-based encryption (ABE) provides a promising solution for enabling scalable access control over encrypted data stored in the untrusted servers (e.g., cloud) due to its ability to perform data encryption and decryption defined over descriptive attributes. In order to bind different components which correspond to different attributes in a user’s attribute-based decryption key together, key randomization technique has been applied in most existing ABE schemes. This randomization method, however, also empowers a user the capability of regenerating a newly randomized decryption key over a subset of the attributes associated with the original decryption key. Because key randomization breaks the linkage between this newly generated key and the original key, a malicious user could leak the new decryption key to others without taking any responsibility for the key abuse. To solve this problem, we think of key regeneration-free ABE to disallow a user from randomizing his/her decryption key in any manner, i.e., a user can only delegate his/her decryption key in exactly the same form without any modification so that any abused or pirated key can be traced back to its original owner. Motivated by strongly unforgeable signature, we first define a security notion called strong key unforgeability, and show that ABE schemes equipped with the strong key unforgeability are immune to key regeneration. We then provide a generic transformation to convert ciphertext-policy ABE (CP-ABE) schemes of certain type to key regeneration-free CP-ABE schemes, and show how the transformation works by presenting two concrete constructions.

Towards Efficient Information-Theoretic Function Secret Sharing

A $(t,r)$ -function secret sharing ( $(t,r)$ -FSS) scheme allows a dealer to secret-share a function $f$ among $r$ parties as $r$ secret keys $k_{1},\ldots,k_{r}$ such that for any input $x$ the parties can compute $r$ output shares that allow the reconstruction of $f(x)$ but any $\leq t$ of the parties cannot learn any information about $f$ . FSS schemes for point functions have been constructed under the name of distributed point functions (DPFs). The existing DPFs are computationally secure and based on the existence of PRGs or OWFs. As a result, the protocols where DPFs work as building blocks are computationally secure as well. In this paper, we study information-theoretically secure $(t,r)$ -FSS (called $(t,r)$ -itFSS) and propose a generic transformation from information-theoretic private information retrieval (PIR) schemes to itFSS schemes for point functions. We measure the efficiency of itFSS with its communication complexity, which can be defined as the total length of the secret keys and the output shares, maximized over the choices of $f$ and $x$ . By instantiating the generic transformation, we obtain $(t,r)$ -itFSS schemes for a variety of choices of $(t,r)$ , which have sublinear (in the functions’ domain size) communication complexity. How to make sure that the parties’ shares of $f(x)$ do not reveal more information than what needed to compute $f(x)$ is an interesting problem. An itFSS with this property is called function-private. In this paper, we also define a parameter called the mutual rate of itFSS in order to measure the amount of information that will be leaked by the parties’ output shares. We calculate the mutual rates for several specific itFSS schemes. We also define computational function privacy and propose a 2-party itFSS scheme with computational function privacy.

Reconstruction of Smooth 3D Color Functions from Keypoints: Application to Lossy Compression and Exemplar-Based Generation of Color LUTs

3D CLUTs (Color Look Up Tables) are popular digital models used in artistic image and video processing, for color grading, simulation of analog films, and more generally for the description and application of generic non-parametric color transformations. The relatively large size of these models leads to high data storage requirements when trying to distribute them on a large scale (e.g. several hundred at a time). In this article, an effective technique based on a multi-scale anisotropic diffusion scheme is proposed, for the lossy compression of generic CLUTs regularly sampled on a 3D grid. Our method exhibits high average compression rate, while ensuring visually indistinguishable differences with the original (uncompressed) CLUTs. In a second step, a variation of our algorithm for exemplar-based generation of CLUTs is developed, in order to create a complete CLUT from a single pair of before/after images that accounts for the color transformation.

Implementation of a Strongly Robust Identity-Based Encryption Scheme over Type-3 Pairings

Identity-based encryption (IBE) is a powerful mechanism for maintaining security. However, systems based on IBE are unpopular when compared with those of the public-key encryption (PKE). In our opinion, one of the reasons is a gap between theory and practice. For example, a generic transformation of weakly/strongly robust IBE from any IBE has been proposed by Abdalla et al., no robust IBE scheme is explicitly given. This means that, theoretically, anyone can construct a weakly/strongly robust IBE scheme by employing this transformation. However, this seems not easily applicable to non-cryptographers. In this paper, we first introduce the Gentry IBE scheme constructed over Type-3 pairings by employing the transformation proposed by Abe et al., and second we explicitly give strongly/weakly robust Gentry IBE schemes by employing the Abdalla et al. transformation. Finally, we show its implementation result and show that we can add strong robustness to the Gentry IBE scheme with a very few additional costs. We employ the mcl library to support a Barreto-Naehrig curve defined over the 462-bit prime. The encryption requires about 5 ms, whereas the decryption requires about 9 ms.

A intertextualidade camoniana em "...Onde Vaz, Luís?" (1983) de Jaime Gralheiro ou Luís Vaz de Camões revisitado no teatro português contemporâneo

O objetivo do artigo é a comparação d’Os Lusíadas (1572) de Luís Vaz de Camões e de ...Onde Vaz, Luís (1983) de Jaime Gralheiro, mostrando os processos do enxerto narrativo de um padrão epopeico no hipertexto dramático, obrado através de “um mosaico de citações”. Trata-se de uma transformação genérica muito produtiva estética e ideologicamente, com traços visíveis de paródia, disfarce, pastiche, transposição narrativa de mais de um texto só e de muitos escritores quinhentistas portugueses (inclusive Fernão Mendes Pinto, António Ferreira, Pedro de Andrade Caminha, Damião de Góis, Gil Vicente) vinculados a uma peça jocosa, tanto trágica como grotesca, concebida segundo a crítica social e de cariz ideológico Brechteano. O artigo apresenta uma mostra de múltiplas relações entre o hipotexto primário e os textos dele derivados, patenteando o fim do texto em causa em muitas obras e literatura portuguesa de vários autores de romances e peças de teatro. O heróico hipotexto vs. os hipertextos são desdobrados em refabulações dramáticas e novelescas pós-modernas (José Saramago inclusive!). Um outro estudo ainda do imaginário ao abrigo da revisitação de literatura portuguesa é possível em relação à história contemporânea e à existência humana, com as fronteiras espácio-temporais e géneros literários apagados na “lotaria intertextual” de Camões e seus avatares quanto aos autores ficcionais e protagonistas. Um diagnóstico do hic et nunc (agora mesmo!) está a ser produzido de um modo metodologicamente consistente segundo os clássicos, de intertextualidade focalizada na dramaturgia e escrita romanesca em Portugal no ocaso do milénio antecedente, com a revolução dos cravos no pano de fundo e o corolário da pós- -democracia acompanhando o processo analítico empreendido.

A generic all-purpose transformation for multivariate modeling through copulas

Copulas have been used in various applications in biomedical sciences and finance. We suggest copulas as the generic all-purpose transformations which can enable one to apply various standard multivariate procedures more efficiently and with better statistical properties and results. More specifically, we consider the problem of transformation of any continuous data to multivariate normality using copulas as a device for defining the transformation. Such a transformation effectively enables us to model a variety of problems involving non-normal data using the classical multivariate statistical techniques. We evaluate and illustrate various applications including those in regression, multicollinearity, principal component analysis, factor analysis, partial least square modeling and structural equation modeling where analyses using the appropriate copula transformations result in substantial improvement in implementation, interpretation, prediction as well as in the corresponding models. A great many datasets available in the literature are analyzed which amply demonstrate the power of such an approach.

Transformation formaler Systemmodelle in digitale Fabrikmodelle

Digital factory models have established themselves as decision support in factory planning. However, the transformation between models is a complex and error-prone process. This paper presents a concept that enables the transformation between Digital Factory models and formal models. This is based on a derived generic transformation concept and is illustrated through a common interface.

Heavy Hitters and the Structure of Local Privacy

We present a new locally differentially private algorithm for the heavy hitters problem that achieves optimal worst-case error as a function of all standardly considered parameters. Prior work obtained error rates that depend optimally on the number of users, the size of the domain, and the privacy parameter but depend sub-optimally on the failure probability. We strengthen existing lower bounds on the error to incorporate the failure probability and show that our new upper bound is tight with respect to this parameter as well. Our lower bound is based on a new understanding of the structure of locally private protocols. We further develop these ideas to obtain the following general results beyond heavy hitters. • Advanced Grouposition : In the local model, group privacy for k users degrades proportionally to ≈√ k instead of linearly in k as in the central model. Stronger group privacy yields improved max-information guarantees, as well as stronger lower bounds (via “packing arguments”), over the central model. • Building on a transformation of Bassily and Smith (STOC 2015), we give a generic transformation from any non-interactive approximate-private local protocol into a pure-private local protocol. Again in contrast with the central model, this shows that we cannot obtain more accurate algorithms by moving from pure to approximate local privacy.

From disruptively digital to proudly analog: A holistic typology of digital transformation strategies

Recently booming academic interest in digital transformation aims to provide continuous support to managers in dealing with this important issue. However, as with all new fields, the scholarly literature is characterized by increased variability and diversity of topics covered, constructs used, and the relationships between them, resulting in an unclear and blurry understanding of the whole of digital transformation. Our article closes this gap by identifying distinctive digital transformation strategies in terms of two critical dimensions: usage of digital technologies and readiness of a business model for digital operation. The result is a typology of four generic digital transformation strategies that essentially differ in the primary motivation and target of transformation, leadership style, importance of skills like creativity and entrepreneurial spirit among employees, risks and challenges faced in the process, consequences of potential failure, and available tactics for improvement. By providing heuristics and a systematic basis for comparison of different strategies, it is our belief that the proposed framework will be useful to researchers and managers responsible for and interested in digital transformation.

Binary MDS Array Codes With Optimal Repair

Consider a binary maximum distance separable (MDS) array code composed of an $m\times (k+r)$ array of bits with $k$ information columns and $r$ parity columns, such that any $k$ out of $k+r$ columns suffice to reconstruct the $k$ information columns. Our goal is to provide {\em optimal repair access} for binary MDS array codes, meaning that the bandwidth triggered to repair any single failed information or parity column is minimized. In this paper, we propose a generic transformation framework for binary MDS array codes, using EVENODD codes as a motivating example, to support optimal repair access for $k+1\le d \le k+r-1$, where $d$ denotes the number of non-failed columns that are connected for repair; note that when $d<k+r-1$, some of the chosen $d$ columns in repairing a failed column are specific. In addition, we show how our transformation framework applies to an example of binary MDS array codes with asymptotically optimal repair access of any single information column and enables asymptotically or exactly optimal repair access for any column. Furthermore, we present a new transformation for EVENODD codes with two parity columns such that the existing efficient repair property of any information column is preserved and the repair access of parity column is optimal.