Optimal Controls for a Single Species Fishery and the Economic Value of Research

1976 ◽  
Vol 33 (4) ◽  
pp. 793-809 ◽  
Author(s):  
C. C. Huang ◽  
Ilan B. Vertinsky ◽  
Norman J. Wilimovsky
Keyword(s):  
Optimal Allocation ◽  
Probability Distributions ◽  
Economic Value ◽  
Mesh Size ◽  
Single Species ◽  
Complete Information ◽  
Optimal Controls ◽  
Optimal Policies ◽  
Solution Methods ◽  
Parameter Values

Mathematical proofs and analyses of solution methods are presented for determining optimal policies for the management of a single species fishery under equilibrium conditions. Previous intuitive arguments for solution of optimal policies controlling mesh size and fishing rate given complete information are explicitly proven. The analysis is extended to the case where some of the parameters describing the dynamics of the population are known only imprecisely to the manager. Using probability distributions for those unknown parameter values the problem is cast as a stochastic program where expected sustained net revenues from the fishery are maximized. The associated problem of optimal allocation of research resources under uncertainty conditions is considered by evaluating the direct value of such information to management activities.Examples and algorithms are presented for the class of problems discussed.

scholarly journals Optimal Allocation of Surface Water Resources at the Provincial Level in the Uzbekistan Region of the Amudarya River Basin

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1446
Author(s):  
Min Wang ◽  
Xi Chen ◽  
Ayetiguli Sidike ◽  
Liangzhong Cao ◽  
Philippe DeMaeyer ◽  
...  
Keyword(s):  
River Basin ◽  
Water Allocation ◽  
Water Distribution ◽  
Optimal Allocation ◽  
Probability Distributions ◽  
Economic Benefits ◽  
Aral Sea ◽  
Incoming Flow ◽  
Provincial Level ◽  
Water Users

Water users in the Amudarya River Basin in Uzbekistan are suffering severe water use competition and uneven water allocation, which seriously threatens ecosystems, as shown, for example, in the well-known Aral Sea catastrophe. This study explores the optimized water allocation schemes in the study area at the provincial level under different incoming flow levels, based on the current water distribution quotas among riparian nations, which are usually ignored in related research. The optimization model of the inexact two-stage stochastic programming method is used, which is characterized by probability distributions and interval values. Results show that (1) water allocation is redistributed among five different sectors. Livestock, industrial, and municipality have the highest water allocation priority, and water competition mainly exists in the other two sectors of irrigation and ecology; (2) water allocation is redistributed among six different provinces, and allocated water only in Bukhara and Khorezm can satisfy the upper bound of water demand; (3) the ecological sector can receive a guaranteed water allocation of 8.237–12.354 km3; (4) under high incoming flow level, compared with the actual water distribution, the total allocated water of four sectors (except for ecology) is reduced by 3.706 km3 and total economic benefits are increased by USD 3.885B.

scholarly journals A Note on Ordering Probability Distributions by Skewness

Symmetry ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 286
Author(s):  
V. García ◽  
M. Martel-Escobar ◽  
F. Vázquez-Polo
Keyword(s):  
Data Analysis ◽  
Probability Distributions ◽  
Continuous Distributions ◽  
Parameter Values

This paper describes a complementary tool for fitting probabilistic distributions in data analysis. First, we examine the well known bivariate index of skewness and the aggregate skewness function, and then introduce orderings of the skewness of probability distributions. Using an example, we highlight the advantages of this approach and then present results for these orderings in common uniparametric families of continuous distributions, showing that the orderings are well suited to the intuitive conception of skewness and, moreover, that the skewness can be controlled via the parameter values.

scholarly journals Probability distributions of COVID-19 tweet posted trends use a nonhomogeneous Poisson process

2020 ◽  
Vol 1 (4) ◽  
pp. 229-238
Author(s):  
Devi Munandar ◽  
Sudradjat Supian ◽  
Subiyanto Subiyanto
Keyword(s):  
Social Media ◽  
Poisson Process ◽  
Exponential Distribution ◽  
Probability Distributions ◽  
Nonhomogeneous Poisson Process ◽  
Time Interval ◽  
Initial State ◽  
Time Intervals ◽  
Time Parameters ◽  
Parameter Values

The influence of social media in disseminating information, especially during the COVID-19 pandemic, can be observed with time interval, so that the probability of number of tweets discussed by netizens on social media can be observed. The nonhomogeneous Poisson process (NHPP) is a Poisson process dependent on time parameters and the exponential distribution having unequal parameter values and, independently of each other. The probability of no occurrence an event in the initial state is one and the probability of an event in initial state is zero. Using of non-homogeneous Poisson in this paper aims to predict and count the number of tweet posts with the keyword coronavirus, COVID-19 with set time intervals every day. Posting of tweets from one time each day to the next do not affect each other and the number of tweets is not the same. The dataset used in this study is crawling of COVID-19 tweets three times a day with duration of 20 minutes each crawled for 13 days or 39 time intervals. The result of this study obtained predictions and calculated for the probability of the number of tweets for the tendency of netizens to post on the situation of the COVID-19 pandemic.

Intervention Time in Target-Oriented Chaos Control

2021 ◽  
Vol 31 (09) ◽  
pp. 2150134
Author(s):  
Juan Segura
Keyword(s):  
Discrete Time ◽  
Chaos Control ◽  
Control Method ◽  
Single Species ◽  
Positive Equilibrium ◽  
Population Stability ◽  
Determine Parameter ◽  
And Control ◽  
Parameter Values ◽  
Proportional Feedback

The timing of interventions plays a central role in managing and exploiting biological populations. However, few studies in the literature have addressed its effect on population stability. The Seno equation is a discrete-time equation that describes the dynamics of single-species populations harvested according to the proportional feedback method at any moment between two consecutive censuses. Here we study a discrete-time equation that generalizes the Seno equation by considering the management and exploitation of populations through the target-oriented chaos control method. We investigate the combined effect of timing, targeting, and control on population stability, focusing on global stability. We prove that high enough control values create a positive equilibrium that attracts all positive solutions. We also prove that it is possible to determine parameter values to stabilize the controlled populations at any preset population size. Finally, we investigate the parameter combinations for which the management and exploitation are optimized in different scenarios.

AMERICAN OPTIONS AND INCOMPLETE INFORMATION

2019 ◽  
Vol 22 (06) ◽  
pp. 1950035 ◽  
Author(s):  
ERIK EKSTRÖM ◽  
MARTIN VANNESTÅL
Keyword(s):  
Incomplete Information ◽  
American Options ◽  
Lower Boundary ◽  
Complete Information ◽  
Call Option ◽  
Standard Case ◽  
Underlying Process ◽  
Parameter Values ◽  
American Put

We study the optimal exercise of American options under incomplete information about the drift of the underlying process, and we show that quite unexpected phenomena may occur. In fact, certain parameter values give rise to stopping regions very different from the standard case of complete information. For example, we show that for the American put (call) option it is sometimes optimal to exercise the option when the underlying process reaches an upper (lower) boundary.

scholarly journals Calibrating a global three-dimensional biogeochemical ocean model (MOPS-1.0)

2017 ◽  
Vol 10 (1) ◽  
pp. 127-154 ◽  
Author(s):  
Iris Kriest ◽  
Volkmar Sauerland ◽  
Samar Khatiwala ◽  
Anand Srivastav ◽  
Andreas Oschlies
Keyword(s):  
Large Scale ◽  
Environmental Changes ◽  
Single Species ◽  
Ocean Model ◽  
Biogeochemical Model ◽  
Parameter Estimates ◽  
Spatial And Temporal Scales ◽  
Ocean Models ◽  
Biogeochemical Tracers ◽  
Parameter Values

Abstract. Global biogeochemical ocean models contain a variety of different biogeochemical components and often much simplified representations of complex dynamical interactions, which are described by many ( ≈ 10 to  ≈ 100) parameters. The values of many of these parameters are empirically difficult to constrain, due to the fact that in the models they represent processes for a range of different groups of organisms at the same time, while even for single species parameter values are often difficult to determine in situ. Therefore, these models are subject to a high level of parametric uncertainty. This may be of consequence for their skill with respect to accurately describing the relevant features of the present ocean, as well as their sensitivity to possible environmental changes. We here present a framework for the calibration of global biogeochemical ocean models on short and long timescales. The framework combines an offline approach for transport of biogeochemical tracers with an estimation of distribution algorithm (Covariance Matrix Adaption Evolution Strategy, CMA-ES). We explore the performance and capability of this framework by five different optimizations of six biogeochemical parameters of a global biogeochemical model, simulated over 3000 years. First, a twin experiment explores the feasibility of this approach. Four optimizations against a climatology of observations of annual mean dissolved nutrients and oxygen determine the extent to which different setups of the optimization influence model fit and parameter estimates. Because the misfit function applied focuses on the large-scale distribution of inorganic biogeochemical tracers, parameters that act on large spatial and temporal scales are determined earliest, and with the least spread. Parameters more closely tied to surface biology, which act on shorter timescales, are more difficult to determine. In particular, the search for optimum zooplankton parameters can benefit from a sound knowledge of maximum and minimum parameter values, leading to a more efficient optimization. It is encouraging that, although the misfit function does not contain any direct information about biogeochemical turnover, the optimized models nevertheless provide a better fit to observed global biogeochemical fluxes.

scholarly journals The Productivity and Quality of Alfalfa (Medicago sativa L.) in Romanian Forest Steppe

2015 ◽  
Vol 43 (1) ◽  
pp. 179-185 ◽  
Author(s):  
Mihai STAVARACHE ◽  
Costel SAMUIL ◽  
Constantin I. POPOVICI ◽  
Doina TARCĂU ◽  
Vasile VÂNTU
Keyword(s):  
Crude Protein ◽  
Growth Stage ◽  
Economic Value ◽  
Food Supplement ◽  
Neutral Detergent Fiber ◽  
Major Influence ◽  
Forest Steppe ◽  
Total Biomass ◽  
Parameter Values

Alternative use of alfalfa, for various purposes, including the production of biofuels or food supplement for human alimentation, is a study topic still in its early stages of research. Studying and understanding the biology of alfalfa and the factors with a major influence on it are very important activities. The productivity and quality of alfalfa are two indicators that help determine, in addition to economic value, the way in which alfalfa can be used. Evolution of alfalfa yield and quality depends on many factors, such as the growth stage of alfalfa plants at harvesting. It was observed over three years of vegetation the influence of alfalfa plant growth stage at harvest on plant height, leaves/stems ratio, production of leaves, stems and whole plant (DM - dry matter) per hectare and on quality indicators (CP - crude protein, NDF - neutral detergent fiber and ADF - acid detergent fiber). The results showed that, with the advancement of phenological phases, from early bud stage to complete flowering, the total biomass output raised from 2.79 Mg·ha-1 to 4.60 Mg·ha-1, the neutral detergent fiber raised from 48.4-50.6% to 62.0-67.7%, while crude protein content decreased from 21.2-24.0% to 13.3-16.5%. The parameter values were correlated with alfalfa growth stage during the harvesting (significant at the 0.05 and 0.01 probability levels).

Robust stock and bond allocation with end-of-horizon effects

2019 ◽  
Vol 53 (1) ◽  
pp. 1-28
Author(s):  
Michael Dziecichowicz ◽  
Aurélie C. Thiele
Keyword(s):  
Stock Returns ◽  
Portfolio Management ◽  
Time Horizon ◽  
Optimal Allocation ◽  
Probability Distributions ◽  
Poor Performance ◽  
Dynamic Allocation ◽  
Fund Management ◽  
Worst Case ◽  
Precise Knowledge

We propose an approach to portfolio management over a finite time horizon that (i) does not require the precise knowledge of the underlying probability distributions, instead relying on range forecasts for the stock returns, and (ii) allows the fund manager to capture the degree of the investor’s risk aversion through a single, intuitive parameter called the budget of uncertainty. This budget represents the worst-case number of time periods with poor performance that the investor is willing to plan for. An application of this setting is target-date funds for pension fund management. We describe an efficient procedure to compute the dynamic allocation between (riskless) bonds and (riskier) stocks at each time period, and we illustrate the risk-to-time-horizon tradeoff on optimal allocation tables, which can easily be provided to fund participants to help them select their strategy. The proposed approach refines rules implemented by practitioners and provides an intuitive framework to incorporate risk in applications with end of horizon effects. In contrast with existing literature providing robust fund management approaches to mathematically sophisticated finance professionals, our goal is to provide a simple framework for less quantitative fund participants who seek to understand how stock return uncertainty and planned retirement date affect the optimal stock-vs-bond allocation in their portfolio. We extend our procedure to the case when the investor’s wealth is penalized for falling short of performance benchmarks across the time horizon. We also discuss the case where the manager can invest in multiple stocks. Numerical results are provided.

NUMERICAL AND EXPERIMENTAL APPROACH FOR THE OPTIMAL DESIGN OF A DUAL PLATE UNDER BALLISTIC IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1538-1543
Author(s):  
JEONGHOON YOO ◽  
DONG-TEAK CHUNG ◽  
MYUNG SOO PARK
Keyword(s):  
Numerical Simulation ◽  
Optimization Technique ◽  
Mesh Size ◽  
Experimental Tests ◽  
Ballistic Impact ◽  
Plastic Energy ◽  
Dual Plate ◽  
Element Erosion ◽  
Parameter Values ◽  
The Impact

To predict the behavior of a dual plate composed of 5052-aluminum and 1002-cold rolled steel under ballistic impact, numerical and experimental approaches are attempted. For the accurate numerical simulation of the impact phenomena, the appropriate selection of the key parameter values based on numerical or experimental tests are critical. This study is focused on not only the optimization technique using the numerical simulation but also numerical and experimental procedures to obtain the required parameter values in the simulation. The Johnson-Cook model is used to simulate the mechanical behaviors, and the simplified experimental and the numerical approaches are performed to obtain the material properties of the model. The element erosion scheme for the robust simulation of the ballistic impact problem is applied by adjusting the element erosion criteria of each material based on numerical and experimental results. The adequate mesh size and the aspect ratio are chosen based on parametric studies. Plastic energy is suggested as a response representing the strength of the plate for the optimization under dynamic loading. Optimized thickness of the dual plate is obtained to resist the ballistic impact without penetration as well as to minimize the total weight.

Research on the Effects of Roughness on the Tactile Properties of Rice Straw Particleboard Surface

2020 ◽  
Vol 12 (6) ◽  
pp. 795-801 ◽  
Author(s):  
Xian-Qing Xiong ◽  
Ying-Ying Yuan ◽  
Yi-Ting Niu ◽  
Liang-Ting Zhang
Keyword(s):  
Surface Roughness ◽  
Rice Straw ◽  
Interior Design ◽  
Roughness Parameter ◽  
Chemical Properties ◽  
Mesh Size ◽  
Design Guidelines ◽  
Before And After ◽  
The Difference ◽  
Parameter Values

To explore the effects of roughness on the tactile properties of rice straw particleboard (RSP), the surface roughness and psychological tactile and visual experiments were conducted for RSP substrates with 0.76 g/cm3 and 0.55 g/cm3 densities after sanding with sandpaper (mesh 180#, 360#, and 600#). The effects of different sandpaper types, sanding time, and density of RSP on the surface roughness were analyzed. The experimental results are as follows. The sanding treatment had significant influence on the surface roughness characterization parameters Ra and Rpv of the RSP specimens. Surface roughness differences between the 180# and 360# mesh-prepared samples were obvious. The tactile and visual psychological values of the 360# and 600# mesh-sanded specimens were higher, and the psychological quantities of untreated and 180# mesh-sanded specimens were lower. After comparing the samples with sanding treatment of sandpaper 0∼180#, the change in surface roughness of RSP with a density of 0.76 g/cm3 was smaller than that of the specimen with a density of 0.55 g/cm3. The psychological quantity difference of RSP specimens with a density of 0.55 g/cm3 was evident. When the sanding time was 1 min., the values of the roughness characterization parameters Ra and Rpv increased slightly. After 3 min. sanding, the Ra and Rpv values stabilized. When the sanding time was 5 min, the roughness was essentially unchanged. With the change in sanding time, the measured values of the tactile psychological quantity varied greatly and the measured values of the visual psychology were very close. For the RSP substrates with higher density, the surface roughness was less after sanding with a smoother surface and better tactile properties. There were significant differences between the surface roughness of the RSPs before and after sanding. After manual sanding over the same time span, the surface roughness evaluation parameter values decreased with an increase of mesh size of the sandpaper, and the tactile properties were improved. The longer the sanding time, the smaller the difference in the surface roughness parameter values, and the smaller the difference between the tactile psychological quantity and the visual psychological quantity. To expand the research scope of RSP products, this study investigates not only the physical and chemical properties but also the subjective feelings when using the RSP products. This will provide analytical methods and design guidelines for the consideration of environmental factors in furniture and interior design.

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