652 research outputs found
Stochastic Ergodicity Breaking: a Random Walk Approach
The continuous time random walk (CTRW) model exhibits a non-ergodic phase
when the average waiting time diverges. Using an analytical approach for the
non-biased and the uniformly biased CTRWs, and numerical simulations for the
CTRW in a potential field, we obtain the non-ergodic properties of the random
walk which show strong deviations from Boltzmann--Gibbs theory. We derive the
distribution function of occupation times in a bounded region of space which,
in the ergodic phase recovers the Boltzmann--Gibbs theory, while in the
non-ergodic phase yields a generalized non-ergodic statistical law.Comment: 5 pages, 3 figure
Non-ergodic Intensity Correlation Functions for Blinking Nano Crystals
We investigate the non-ergodic properties of blinking nano-crystals using a
stochastic approach. We calculate the distribution functions of the time
averaged intensity correlation function and show that these distributions are
not delta peaked on the ensemble average correlation function values; instead
they are W or U shaped. Beyond blinking nano-crystals our results describe
non-ergodicity in systems stochastically modeled using the Levy walk framework
for anomalous diffusion, for example certain types of chaotic dynamics,
currents in ion-channel, and single spin dynamics to name a few.Comment: 5 pages, 3 figure
Minimal Diagnosis and Diagnosability of Discrete-Event Systems Modeled by Automata
In the last several decades, the model-based diagnosis of discrete-event systems (DESs) has increasingly become an active research topic in both control engineering and artificial intelligence. However, in contrast with the widely applied minimal diagnosis of static systems, in most approaches to the diagnosis of DESs, all possible candidate diagnoses are computed, including nonminimal candidates, which may cause intractable complexity when the number of nonminimal diagnoses is very large. According to the principle of parsimony and the principle of joint-probability distribution, generally, the minimal diagnosis of DESs is preferable to a nonminimal diagnosis. To generate more likely diagnoses, the notion of the minimal diagnosis of DESs is presented, which is supported by a minimal diagnoser for the generation of minimal diagnoses. Moreover, to either strongly or weakly decide whether a minimal set of faulty events has definitely occurred or not, two notions of minimal diagnosability are proposed. Necessary and sufficient conditions for determining the minimal diagnosability of DESs are proven. The relationships between the two types of minimal diagnosability and the classical diagnosability are analysed in depth
Twin‐engined diagnosis of discrete‐event systems
Diagnosis of discrete-event systems (DESs) is computationally complex. This is why a variety of knowledge compilation techniques have been proposed, the most notable of them rely on a diagnoser. However, the construction of a diagnoser requires the generation of the whole system space, thereby making the approach impractical even for DESs of moderate size. To avoid total knowledge compilation while preserving efficiency, a twin-engined diagnosis technique is proposed in this paper, which is inspired by the two operational modes of the human mind. If the symptom of the DES is part of the knowledge or experience of the diagnosis engine, then Engine 1 allows for efficient diagnosis. If, instead, the symptom is unknown, then Engine 2 comes into play, which is far less efficient than Engine 1. Still, the experience acquired by Engine 2 is then integrated into the symptom dictionary of the DES. This way, if the same diagnosis problem arises anew, then it will be solved by Engine 1 in linear time. The symptom dic- tionary can also be extended by specialized knowledge coming from scenarios, which are the most critical/probable behavioral patterns of the DES, which need to be diagnosed quickly
On Kaluza's sign criterion for reciprocal power series
T. Kaluza has given a criterion for the signs of the power series of a
function that is the reciprocal of another power series. In this note the
sharpness of this condition is explored and various examples in terms of the
Gaussian hypergeometric series are given. A criterion for the monotonicity of
the quotient of two power series due to M. Biernacki and J. Krzy\.z is applied.Comment: 13 page
Sign-time distribution for a random walker with a drifting boundary
We present a derivation of the exact sign-time distribution for a random
walker in the presence of a boundary moving with constant velocity.Comment: 5 page
Treatment options for localised renal cell carcinoma of the transplanted kidney
Currently, there is no consensus among the transplant community about the treatment of renal cell carcinoma (RCC) of the transplanted kidney. Until recently, graftectomy was universally considered the golden standard, regardless of the characteristics of the neoplasm. Due to the encouraging results observed in native kidneys, conservative options such as nephron-sparing surgery (NSS) (enucleation and partial nephrectomy) and ablative therapy (radiofrequency ablation, cryoablation, microwave ablation, high-intensity focused ultrasound, and irreversible electroporation) have been progressively used in carefully selected recipients with early-stage allograft RCC. Available reports show excellent patient survival, optimal oncological outcome, and preserved renal function with acceptable complication rates. Nevertheless, the rarity and the heterogeneity of the disease, the number of options available, and the lack of long-term follow-up data do not allow to adequately define treatment-specific advantages and limitations. The role of active surveillance and immunosuppression management remain also debated. In order to offer a better insight into this difficult topic and to help clinicians choose the best therapy for their patients, we performed and extensive review of the literature. We focused on epidemiology, clinical presentation, diagnostic work up, staging strategies, tumour characteristics, treatment modalities, and follow-up protocols. Our research confirms that both NSS and focal ablation represent a valuable alternative to graftectomy for kidney transplant recipients with American Joint Committee on Cancer stage T1aN0M0 RCC. Data on T1bN0M0 lesions are scarce but suggest extra caution. Properly designed multi-centre prospective clinical trials are warranted
A Stimulated Raman Loss spectrometer for metrological studies of quadrupole lines of hydrogen isotopologues
We discuss layout and performance of a high-resolution Stimulated Raman Loss
spectrometer that has been newly developed for accurate studies of spectral
lineshapes and line center frequencies of hydrogen isotopologues and in general
of Raman active transitions. Thanks to the frequency comb calibration of the
detuning between pump and Stokes lasers and to an active alignment of the two
beams, the frequency accuracy is well below 100 kHz. Over the vertical axis the
spectrometer benefits from shot-noise limited detection, signal enhancement via
multipass cell, active flattening of the spectral baseline and measurement
times of few seconds over spectral spans larger than 10 GHz. Under these
conditions an efficient averaging of Raman spectra is possible over long
measurement times with minimal distortion of spectral lineshapes. By changing
the pump laser, transitions can be covered in a very broad frequency span, from
50 to 5000 , including both vibrational and rotational bands.
The spectrometer has been developed for studies of fundamental and collisional
physics of hydrogen isotopologues and has been recently applied to the
metrology of the Q(1) 1-0 line of
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