Recoverability Condition Research Articles

Extracting error thresholds through the framework of approximate quantum error correction condition

The robustness of quantum memory against physical noises is measured by two methods: the exact and approximate quantum error correction (QEC) conditions for error recoverability and the decoder-dependent error threshold which assesses if the logical error rate diminishes with system size. Here we unravel their relations and propose a unified framework to extract an intrinsic error threshold from the approximate QEC condition, which could upper bound other decoder-dependent error thresholds. Our proof establishes that relative entropy, effectively measuring deviations from exact QEC conditions, serves as the order parameter delineating the transition from asymptotic recoverability to unrecoverability. Consequently, we establish a unified framework for determining the error threshold across both exact and approximate QEC codes, addressing errors originating from noise channels as well as those from code space imperfections. This result sharpens our comprehension of error thresholds across diverse QEC codes and error models. Published by the American Physical Society 2024

Pattern of Patients in Intensive Care Unit in a Tertiary Care Hospital in Lumbini Province Nepal

BACKGROUND Intensive care is a crucial component of hospital care, reserved for patients with potentially recoverable conditions who can benefit from invasive treatment. However, in developing countries like Nepal, resources and availability of intensive care become hurdles in delivering healthcare. This study presents the pattern of admission and outcome of patients' management in a general intensive care unit (ICU) of this tertiary care center in Lumbini Province, Nepal. 
 METHODS A cross sectional study conducted in the Department of Internal Medicine, Bheri Hospital between July 2021 to June 2022. A total of 792 patient’s details were obtained from the record section. Demographic data, diagnosis, duration of stay in ICU, managing units, and outcome were collected and analyzed with Statistical Package for the Social Sciences 20.
 RESULTS A total of 729 patients were admitted in the study period; 57.82% were male and 42.18% were female. Majority 60% of admissions were from Department of Medicine followed by Cardiology 24% and Surgery 10%. Pneumonia and Chronic Obstructive Pulmonary Disease 18.30% followed by Myocardial Infraction 14.52%, Acute abdomen 10.22% and sepsis 9.84% were the most common morbidity. Mean duration of ICU stay was 3.5. days. Discharge rate was 69.82% and the mortality rate was 17.80 %. 
 CONCLUSION The most common patients admitted in the ICU of Bheri hospital were mostly Medical cases. Surgical and obstetric cases were lesser in number. The outcomes were comparable with other multidisciplinary ICU of similar settings.

Spectrum situation generation from sparse spatial sampling: model and algorithm

With the increasingly complex electromagnetic spectrum environment and the growing demand for the available spectrum, it is urgent to mine the spectrum situation information of wide geographical areas from limited sensing nodes to maintain the order and security of the electromagnetic spectrum and improve the overall utilization efficiency of spectrum resources. Starting from the multidimensional representations of spectrum situations in time, frequency, and space, this paper discusses and summarizes the model and generation mechanisms of electromagnetic spectrum situations based on sparse spatial sampling. The spectrum situation representation method based on a multivariate function is proposed, and the spectrum situation model, in accordance with the propagation characteristics of different transmitters, is established. This paper analyzes the identifiability and recoverability conditions of the spectrum situation model under sparse spatial sampling, which theoretically guides the reliable generation of the spectrum situation. Finally, the performance characteristics of different spectrum situation generation algorithms are compared and analyzed by simulations.

Cost Evaluation of Approximate Controllability and Fault Recoverability for Switched Infinite-Dimensional Linear Systems

This article finds the minimum cost that is needed to achieve the approximate controllability of switched infinite-dimensional linear systems (IDLSs) by a newly defined Gramian operator. Such a new cost evaluation method helps to establish a fault recoverability condition, which reveals the ability of faulty switched IDLSs to maintain the approximate controllability under given energetic constraints. An example of the swarming system is taken to illustrate the theoretical results.

Largest recoverable component based fault recoverability of UAV swarm with removal of faulty individuals

This paper focuses on UAV swarm with some faulty individuals that usually cause abnormal interactive information or communication link failure, and can propagate over the swarm network. A two-layer and multipartite structure of the swarm and a cascading failure model are established, based on which a fault recoverability condition is established based on a newly proposed concept namely “largest recoverable component”. The new condition reveals the capability of the swarm to maintain connectivity and consistency between followers and leaders after removing these faulty individuals. Simulation results show the efficiency of the proposed methods.

A new sufficient condition for sparse vector recovery via ℓ1 − ℓ2 local minimization

In this paper, we provide a necessary condition and a sufficient condition such that any [Formula: see text]-sparse vector [Formula: see text] can be recovered from [Formula: see text] via [Formula: see text] local minimization. Moreover, we further verify that the sufficient condition is naturally valid when the restricted isometry constant of the measurement matrix [Formula: see text] satisfies [Formula: see text]. Compared with the existing [Formula: see text] local recoverability condition [Formula: see text], this result shows that [Formula: see text] local recoverability contains more measurement matrices.

Communicating Correlated Sources Over MAC and Interference Channels II: Joint Source-Channel Coding

We present the second part of our work on communicating correlated sources over multiple access (MAC) and interference channels (IC). Specifically, we undertake a Shannon-theoretic study of the above scenarios and focus on characterizing sufficient conditions for lossless recoverability of the sources at the decoder(s). We enhance the fixed block-length (B-L) coding technique by incorporating the technique of inducing source correlation onto channel inputs, originally discovered by Cover, El Gamal and Salehi. In contrast to the first part, performance analysis of a joint source-channel decoder poses new challenges. We enhance the earlier developed suite of coding and analytical tools to overcome these challenges and derive (simplified) single-letter characterizations for a new set of sufficient conditions for both scenarios. For both the MAC and IC problems, the derived sufficient conditions are (i) subsumed in the current known tightest, and (ii) strictly weaker for identified examples. Lastly, we propose simple `plug-in' approaches that can further weaken the derived sufficient conditions. Our findings enable us to subsume Dueck's findings (1981) and go even further for the example considered therein.

Discourse-related V1 declaratives in Dutch

Abstract This paper discusses two types of discourse-related V1 declaratives in Dutch. The first type involves a missing argument. In the position before the finite verb a referential 3rd person pronoun is deleted. The deletion of the pronoun is constrained by the recoverability condition, which requires that its referential features can be reconstructed from context. I will argue that only the deletion of a d(emonstrative)-pronoun is “topic drop”. Deleted topic d-pronouns are subject to the same syntactic conditions as overt topic d-pronouns. Like the overt d-pronoun, the deleted d-pronoun refers to the focus constituent of the preceding sentence. A deleted p(ersonal)-pronoun, by contrast, does not have a uniquely determined antecedent. The second type of V1 declarative is found in so-called “narrative inversion” in which all arguments are present, and no empty element needs to be postulated. Various types of narrative inversion and the kind of discourse relation they imply are discussed.

Eerstezinsdeeldeletie in het Nederlands

Abstract First-constituent-deletion in Dutch. What topic drop is and what it is not This paper discusses the phenomenon of pronoun deletion in Dutch. In the position before the finite verb a 3rd person pronoun may be deleted. The deletion of the pronoun is constrained by the recoverability condition, which requires that its referential features can be reconstructed from the context. It will be argued that only the deletion of a d(emonstrative)-pronoun is ‘topic drop’, which is typical for spoken Dutch. Deleted topic d-pronouns are subject to the same syntactic conditions as overt topic d-pronouns (Van ). Like the overt topic d-pronoun, the deleted d-pronoun refers to the focus constituent of the preceding sentence. A deleted p(ersonal)-pronoun, by contrast, does not have a uniquely determined antecedent and therefore it cannot be analyzed as discourse topic drop. In written texts, it solely maintains the preceding subject referent. I will further discuss the deletion of 1st person pronouns and the deletion of d-pronouns in imperatives.

Exponential small-gain theorem and fault tolerant safe control of interconnected nonlinear systems

This paper considers a class of interconnected nonlinear systems where each subsystem, in the absence of coupling, is individually exponentially stable. The cyclic-small-gain theorem is significantly extended in such a way that the interconnected system is proved to be globally exponentially stable, an exponential converging upper bound of state norm is obtained which fully reveals the relations between the gains, the decay rate and the upper bound of the states. The new result is further applied to fault tolerant safe control problem of interconnected nonlinear systems. A fault recoverability condition with respect to safety is established, under which both individual and cooperative fault tolerant safe control strategies are provided under the decentralized control structure. This guarantees that the states are always within a given safe domain in the presence of faults.

Beyond MaxElide: An Investigation of Ā-Movement from Elided Phrases

Using Takahashi and Fox 2005 as an exemplar, this article argues that analyses of English ellipsis that make recourse to a MaxElide constraint (first introduced in Merchant 2008 ) are untenable, and that one must look beyond MaxElide to explain the distribution of acceptability in the “rebinding” elliptical constructions that MaxElide was originally invoked to explain. A novel analysis is outlined that attributes the unacceptability observed in the rebinding dataset to an inability to satisfy a more restrictive, reflexive version of Takahashi and Fox’s parallelism condition on ellipsis recoverability. More broadly, the success of this analysis supports the notion that clausal and nonclausal ellipsis are governed by distinct recoverability conditions. This article therefore provides support for a nonunitary approach to the semantic licensing of ellipsis.

Fault-tolerant control for a class of linear interconnected hyperbolic systems by boundary feedback

This paper considers a fault-tolerant control problem for a class of interconnected linear hyperbolic partial differential equation systems. Both subsystem faults and coupling faults are considered. Firstly, the well-posedness of the faulty system is analyzed by using semigroup theory. Secondly, for the fault-free case, a stabilizing boundary feedback control based on small-gain theorem is proposed. Consequently, in the presence of faults, fault recoverability conditions are established that maintain the stability of the faulty systems. The fault-tolerant control strategies are also provided. A heat exchanger example is taken to illustrate the effectiveness and practicality of the proposed methods.

Fault Tolerant Control of Switched Systems: A Generalized Separation Principle

This paper addresses the fault tolerant control (FTC) issue of switched systems by using a newly proposed concept named “ generalized separation principle ” (GSP), which allows us to design separately the three elements: the individual mode observer, the individual mode controller, and the switching law, and thus greatly facilitates the design in engineering. Sufficient fault recoverability conditions as well as fault diagnosis (FD) and FTC design procedures are provided. Moreover, “ semi-GSP ” and “ constrained GSP ” are further developed. These new concepts help to provide a framework for observer-based FD and FTC of switched systems. It shows that the FTC goal can be achieved even if only some or no mode of the switched system has available individual FD and FTC schemes. The theoretical results are further applied to the highly maneuverable technology vehicle to illustrate their efficiency and applicability.

Fault Estimation and Accommodation of Interconnected Systems: A Separation Principle.

This paper addresses the fault estimation (FE) and accommodation issues of interconnected systems by using two new concepts namely interconnected separation principle and constrained interconnected separation principle that allow for the separate design not only between diagnostic observer and fault tolerant controller for each subsystem, but also between observer/controller of each subsystem and those of other ones. Sufficient fault recoverability conditions are established, under which both distributed and decentralized FE and accommodation schemes are provided. The new results help to provide a framework for observer-based fault diagnosis and fault tolerant control of interconnected systems, and are further applied to the meta aircraft configuration that consists of multiple aircraft joined together to illustrate their efficiency.

ℓ1-minimization method for link flow correction

A computational method, based on ℓ1-minimization, is proposed for the problem of link flow correction, when the available traffic flow data on many links in a road network are inconsistent with respect to the flow conservation law. Without extra information, the problem is generally ill-posed when a large portion of the link sensors are unhealthy. It is possible, however, to correct the corrupted link flows accurately with the proposed method under a recoverability condition if there are only a few bad sensors which are located at certain links. We analytically identify the links that are robust to miscounts and relate them to the geometric structure of the traffic network by introducing the recoverability concept and an algorithm for computing it. The recoverability condition for corrupted links is simply the associated recoverability being greater than 1. In a more realistic setting, besides the unhealthy link sensors, small measurement noises may be present at the other sensors. Under the same recoverability condition, our method guarantees to give an estimated traffic flow fairly close to the ground-truth data and leads to a bound for the correction error. Both synthetic and real-world examples are provided to demonstrate the effectiveness of the proposed method.

Incipient Actuator Fault Handling in Nonlinear Model Predictive Control

This paper presents a reconfigurable nonlinear model predictive control (NMPC) scheme for handling of incipient actuator faults in nonlinear plants. The scheme seeks to ensure recoverability from an incipient actuator fault in plants where the input redundancy is insufficient to stabilize the faulty system at the nominal operating point, thereby requiring transition to a safe control-invariant set. To this end, the proposed scheme takes into account an estimate of the decrease in remaining actuator capacity from the time of detection of an incipient actuator fault, and minimizes the required control input to steer the plant to the safe set. We provide conditions for stability and fault recoverability of the proposed scheme, and demonstrate its applicability on a numerical example with two CSTRs in series.

Separation design of fault estimation and accommodation for switched systems

This paper is concerned with the fault estimation and accommodation problem of switched systems via a new concept named “generalized separation principle”, which is principles of separation of three elements: individual observer, individual control, and switching law. Based on such a concept, sufficient fault recoverability conditions are established, fault estimation and accommodation design procedures are also given.

Recovering Causal Effects from Selection Bias

Controlling for selection and confounding biases are two of the most challenging problems that appear in data analysis in the empirical sciences as well as in artificial intelligence tasks. The combination of previously studied methods for each of these biases in isolation is not directly applicable to certain non-trivial cases in which selection and confounding biases are simultaneously present. In this paper, we tackle these instances non-parametrically and in full generality. We provide graphical and algorithmic conditions for recoverability of interventional distributions for when selection and confounding biases are both present. Our treatment completely characterizes the class of causal effects that are recoverable in Markovian models, and is suffi- cient for Semi-Markovian models.

Fault recoverability and fault tolerant control for a class of interconnected nonlinear systems

This paper considers a class of interconnected nonlinear systems with reconfigurable physical couplings. Under decentralized control laws, a fault recoverability condition is provided which reveals the capability of the interconnected system to tolerate the faults under given couplings. Consequently three fault tolerant control methods are proposed that rely on both control reconfiguration and coupling topology reconfiguration. The couplings’ effect on system performance is analyzed from the overall system point of view. An example for a system with three pendulums is taken to illustrate the theoretical results.

Identification of Switched Linear Systems via Sparse Optimization

This paper addresses identification problem of switched linear(SL) systems from input-output data. The main challenge is the partitions of data points correspond to different subsystems are unavailable. Inspired by compressed sensing theory, we pursue the sparsity of estimation error and propose `0-norm optimization algorithm to identify parameters. Unfortunately, the computational complexity of this approach is intractable. To overcome this difficulty, we replace `0-norm by `1-norm, which retains sparse property. We not only provide recoverable conditions for identifying SL systems via `1-norm minimization program, but also show that `1-norm estimator is robust to bounded noise. Numerical experiments are included to demonstrate the performance of our algorithms.