Evaluación del stock de la cohorte occidental de invierno-primavera de Ommastrephes bartramii en el océano Pacífico noroeste utilizando el modelo de DeLury jerárquico bayesiano basado en la mortalidad natural diaria durante los años 2005-2015

The purpose of this study was to evaluate the effect of the intensive commercial jigging fishery on the western winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean and to estimate the exploitation status of this stock during the period 2005-2015. We applied a Bayesian hierarchical DeLury depletion model to the Chinese jigging fisheries data to estimate the stock abundance and catchability for each year, and sensitivity analysis on daily natural mortality (M) was conducted. The results indicated that M values had great impacts on the overall estimates of stock size. Initial annual population sizes varied from 66 to 662 million individuals with the M value of 0.003-0.01 per day during the study period. O. bartramii suffered from a certain degree of overexploitation in 2008. The proportional escapement values (M=0.003-0.01) were 8.94% to 19.82% in 2008, with an average of 13.74%, which may have led to a low abundance of O. bartramii and annual catch since 2009. As short-lived ecological opportunists, O. bartramii are extremely sensitive to changes in multi-scale environmental conditions, especially when anomalous environmental conditions occur, and significant between-year variations in the initial abundance resulted in O. bartramii suffering from a certain degree of overexploitation in 2010. Although the proportional escapement met the management target of 40% from 2011 to 2015, the stock size and annual catch still fluctuated at relatively low levels. Improved knowledge of the influences of environmental conditions on abundance of the western winter-spring cohort of neon flying squid can contribute to the sustainable management of this stock.El propósito de este estudio es evaluar el efecto de la pesca comercial con potera automática sobre la cohorte occidental de invierno-primavera de la pota saltadora (Ommastrephes bartramii) en el océano Pacífico noroeste y estimar el estado de explotación de esta población durante los años 2005-2015. Se utilizó un modelo de DeLury jerárquico bayesiano para estudiar la pesca con potera automática de la flota china. Para estimar la abundancia y capturabilidad del stock para cada año se analizó la mortalidad natural diaria (M). Los resultados indicaron que los valores de M tuvieron un gran impacto en las estimaciones generales del tamaño del stock. El tamaño inicial de la población anual varió entre 66 y 662 millones de ejemplares con el valor M de 0.003-0.01 por día durante 2005-2015. O. bartramii mostró un cierto grado de sobreexplotación en 2008. La proporción de la población preservada de la pesca (M=0.003-0.01) fue de 8.94-19.82% en 2008, siendo en promedio de 13.74%, lo que pudo conducir a una reducida abundancia y captura anual de O. bartramii desde 2009. Como especie oportunista de vida breve, O. bartramii es extremadamente sensible a los cambios en las condiciones ambientales, especialmente cuando aparecen condiciones ambientales anómalas. Variaciones interanuales significativas en su abundancia mostraron que O. bartramii sufrió un cierto grado de sobreexplotación durante algunos años, como por ejemplo durante 2010. Aunque la proporción de la población preservada de la pesca cumplió con el objetivo de su gestión pesquera del 40% durante los años 2011-2015, el tamaño del stock y la captura anual oscilaron entre niveles relativamente bajos. La mejora en el conocimiento de cómo las condiciones ambientales influyen en la abundancia de la cohorte occidental de invierno-primavera de la pota saltadora puede contribuir al manejo sostenible de este stock

Perturbation Analysis of Orthogonal Matching Pursuit

Orthogonal Matching Pursuit (OMP) is a canonical greedy pursuit algorithm for sparse approximation. Previous studies of OMP have mainly considered the exact recovery of a sparse signal $\bm x$ through $\bm \Phi$ and $\bm y=\bm \Phi \bm x$, where $\bm \Phi$ is a matrix with more columns than rows. In this paper, based on Restricted Isometry Property (RIP), the performance of OMP is analyzed under general perturbations, which means both $\bm y$ and $\bm \Phi$ are perturbed. Though exact recovery of an almost sparse signal $\bm x$ is no longer feasible, the main contribution reveals that the exact recovery of the locations of $k$ largest magnitude entries of $\bm x$ can be guaranteed under reasonable conditions. The error between $\bm x$ and solution of OMP is also estimated. It is also demonstrated that the sufficient condition is rather tight by constructing an example. When $\bm x$ is strong-decaying, it is proved that the sufficient conditions can be relaxed, and the locations can even be recovered in the order of the entries' magnitude.Comment: 29 page

A Decentralized Trust Management System for Intelligent Transportation Environments

Commercialized 5G technology will provide reliable and efficient connectivity of motor vehicles that could support the dissemination of information under an intelligent transportation system. However, such service still suffers from risks or threats due to malicious content producers. The traditional public key infrastructure (PKI) cannot restrain such untrusted but legitimate publishers. Therefore, a trust-based service management mechanism is required to secure information dissemination. The issue of how to achieve a trust management model becomes a key problem in the situation. This paper proposes a novel prototype of the decentralized trust management system (DTMS) based on blockchain technologies. Compared with the conventional and centralized trust management system, DTMS adopts a decentralized consensus-based trust evaluation model and a blockchain-based trust storage system, which provide a transparent evaluation procedure and irreversible storage of trust credits. Moreover, the proposed trust model improves blockchain efficiency by only allowing trusted nodes participating in the validation and consensus process. Additionally, the designed system creatively applies a trusted execution environment (TEE) to secure the trust evaluation process together with an incentive model that is used to stimulate more participation and penalize malicious behaviours. Finally, to evaluate our new design prototype, both numerical analysis and practical experiments are implemented for performance evaluation