Evaluation of Three Harvest Control Rules for Bigeye Tuna(Thunnus obesus) Fisheries in the Indian Ocean

The stock of Bigeye tuna(Thunnus obesus) in the Indian Ocean supports an important international fishery and is considered to be fully exploited. The responsible management agency, the Indian Ocean Tuna Commission(IOTC), does not have an explicit management decision-making framework in place to prevent over-fishing. In this study, we evaluated three harvest control rules, i) constant fishing mortality(CF), from 0.2 to 0.6, ii) constant catch(CC), from 60000 to 140000 t, and iii) constant escapement(CE), from 0.3 to 0.7. The population dynamics simulated by the operating model was based on the most recent stock assessment using Stock Synthesis version Ⅲ(SS3). Three simulation scenarios(low, medium and high productivity) were designed to cover possible uncertainty in the stock assessment and biological parameters. Performances of three harvest control rules were compared on the basis of three management objectives(over 3, 10 and 25 years): i) the probability of maintaining spawning stock biomass above a level that can sustain maximum sustainable yield(MSY) on average, ii) the probability of achieving average catches between 0.8 MSY and 1.0 MSY, and iii) inter-annual variability in catches. The constant escapement strategy(CE=0.5), constant fishing mortality strategy(F=0.4) and constant catch(CC=80000) were the most rational among the respective management scenarios. It is concluded that the short-term annual catch is suggested at 80000 t, and the potential total allowable catch for a stable yield could be set at 120000 t once the stock had recovered successfully. All the strategies considered in this study to achieve a ‘tolerable' balance between resource conservation and utilization have been based around the management objectives of the IOTC.

The Optimized Disign of the Fuzzy Controller(Ⅰ)——The predigested disquisition of rules of fuzzy control

To improve the ability and precisions of the fuzzy control,this thesis points out the adjusted fuzzy control method,realizes the precision of the fuzzy quantity, and reduces the number of the fuzzy control rules,so that it can predigest the process of disigns and realize the methods without influencing the idiocratic control,which are on the base of the domain flexing.

RULED SURFACE MACHINING BY 4-AXES SIMULTANEOUS CONTROL WIRE-EDM

On the tasis of study in the mathematical model of 3-dimensional ruled surface (RS),this paper introduces a new concept of distance paramcter (DP) and also puts forward that themethod of modeling a RS depends on not only two boundary curves but also DP. According toabove theory, the formulas to calculate corresponding point coordinates to any kind of top and bot-tom profile of a workpiece and formulas to calcuate the maximum inclination angle of ruling linehave been obtained. Then a different top and bottom RS mathining method including profile withline-are combination as well as parametric curves has been achieved by 4-axes simultancous con-trol programming proposed.

A Novel Computerized Water Level Control System of PWR Steam Generator of Nuclear Power Plant

This paper presents a novel method to solve old problem of water level control system of pressurized water reactor (PWR) steam generator (SG) of nuclear power plant (NPP) .The level control system of SG plays an important role which effects the reliablity,safty,cost of SG and its mathematical models have been solved.A model of the conventional controller is presented and the existing problems are discussed. A novel rule based realtime control technique is designed with a computerized water level control (CWLC) system for SG of PWR NPP.The performance of this is evaluated for full power reactor operating conditions by applying different transient conditions of SG′s data of Qinshan Nuclear Power Plant (QNPP).

The Optimized Design of The Fuzzy Controller(Ⅱ)——the disquisition of optimized triangle subjection function

The subjection function of the fuzzy quantity is bell like,which is on the base of the theory;but during the course of the control,each fuzzy grade should be predigested into a triangle of W=4.

Integral Performance Criteria Based Analysis of Load Frequency Control in Bilateral Based Market

Performance index based analysis is made to examine and highlight the effective application of Particle Swarm Optimization (PSO) to optimize the Proportional Integral gains for Load Frequency Control (LFC) in a restructured power system that operates under Bilateral based policy scheme. Various Integral Performance Criteria measures are taken as fitness function in PSO and are compared using overshoot, settling time and frequency and tie-line power deviation following a step load perturbation (SLP). The motivation for using different fitness technique in PSO is to show the behavior of the controller for a wide range of system parameters and load changes. Error based analysis with parametric uncertainties and load changes are tested on a two-area restructured power system. The results of the proposed PSO based controller show the better performance compared to the classical Ziegler-Nichols (Z-N) tuned PI and Fuzzy Rule based PI controller.

Evaluating effectiveness of biological reference points for bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) fisheries in the Indian Ocean

Biological reference point(BRP)is one of the essential components in the management strategy evaluation that is used to determine the status of fishery stock and set management regulations.However,as BRPs can be derived from different models and many different BRPs are available,the effectiveness and consistency of different BRPs should be evaluated before being applied to fisheries management.In this study,we used a computation-intensive approach to identify optimal BRPs.We systematically evaluated 1500 combinations of alternative BRPs in managing the bigeye tuna(Thunnus obesus)and yellowfin tuna(Thunnus albacares)fisheries in the Indian Ocean.The effectiveness and consistency of these BRPs were evaluated using four performance measures related to fisheries landing performance and biomass conservation.Monte Carlo simulation was used to evaluate various uncertainties.The results suggest that the proposed computation-intensive approach can be effective in identifying optimal BRPs with respect to a set of defined performance measures.We found that the current maximum sustainable yield(MSY)-based BRP combinations are effective target BRPs to manage the bigeye and yellowfin tuna fisheries with the“linear”harvest control rule(HCR).However,using the“knife-edge”HCR,better BRPs could be found for both the bigeye and yellowfin tuna fisheries management with improved fisheries and conservation performance.The framework developed in this study can be used to identify suitable BRPs based on a set of defined performance measures for other fisheries.