Modelling disaggregated lumber demand and supply by constrained estimation techniques

1990 ◽  
Vol 20 (6) ◽  
pp. 781-789
Author(s):  
William McKillop ◽  
Gao Liu
Keyword(s):  
Quadratic Programming ◽  
A Priori ◽  
Douglas Fir ◽  
Demand Elasticity ◽  
Statistical Efficiency ◽  
Constrained Estimation ◽  
Programming Technique ◽  
Demand And Supply ◽  
Estimation Techniques ◽  
Lack Of Information

Constrained estimation techniques were used to estimate a 12-equation demand and supply system for Douglas-fir and hemlock–fir (true fir) lumber by clear and common grades. Such techniques combine sample information with nonsample information and produce estimates with smaller variances than those based only on sample data. Conventional econometric estimation was compared with a quadratic programming technique with regression coefficients constrained to their a priori correct signs. A goal programming technique that minimized the sum of the absolute deviations was rejected because of its substantially different results and lack of information on the statistical properties of its estimates. The quadratic programming technique had the advantages of statistical efficiency, objectivity, and speed. The conventional estimation technique excluded fewer variables from the system and thus was less susceptible to omission of variables bias. Elasticity estimates for most key variables were similar. Quadratic programming versus conventional estimates of demand elasticity were, respectively, −0.95 and −0.88 for Douglas-fir clears, −2.83 and −2.91 for Douglas-fir commons, and −2.13 and −2.27 for all Douglas-fir; whereas supply elasticities for hemlock–fir commons were 1.35 and 1.37, and for all hemlock–fir, −1.76 and −1.42.

Improving Predictive Power of Conjoint Analysis by Constrained Parameter Estimation

1983 ◽  
Vol 20 (4) ◽  
pp. 433-438 ◽  
Author(s):  
V. Srinivasan ◽  
Arun K. Jain ◽  
Naresh K. Malhotra
Keyword(s):  
Parameter Estimation ◽  
Conjoint Analysis ◽  
Predictive Validity ◽  
Predictive Power ◽  
A Priori ◽  
A Priori Knowledge ◽  
Constrained Estimation ◽  
First Choice ◽  
Full Profile ◽  
Different Levels

The prediction of first choice preferences by the full-profile method of conjoint analysis can be improved significantly by imposing constraints on parameters based on a priori knowledge of the ordering of part worths for different levels of an attribute. Constrained estimation however, has little effect on the predictive validity of the tradeoff method because the preference judgments within rows (or columns) of tradeoff tables have largely the same role as the constraints.

scholarly journals Interventions Aiming to Promote Active Commuting in Children and Adolescents: An Evaluation From a Sex/Gender Perspective

2020 ◽  
Vol 2 ◽  
Author(s):  
Isabel Marzi ◽  
Sandra Emmerling ◽  
Yolanda Demetriou ◽  
Jens Bucksch ◽  
Carolin Schulze ◽  
...  
Keyword(s):  
Children And Adolescents ◽  
A Priori ◽  
Active Commuting ◽  
Future Health ◽  
Intervention Effects ◽  
Eligibility Criteria ◽  
Single Sex ◽  
Lack Of Information ◽  
Intervention Content ◽  
Gender Specific

Active commuting (AC) provides numerous health benefits and is one way to improve physical activity in children and adolescents. Boys are more likely to use active transport modes than girls. Girls and boys benefit differently from interventions that promote AC. The aim of this systematic review is to evaluate the effects of interventions on girls and boys and to appraise the extent to which previous studies have taken sex/gender into account. Eleven electronic databases were searched to identify all relevant randomized and non-randomized controlled trials based on a priori defined eligibility criteria. Two independent reviewers screened the literature for eligibility and assessed risk of bias. Semiquantitative analyses were conducted to evaluate the effects of intervention effects by taking sex/gender aspects into account. To evaluate sex/gender considerations in interventional studies, a recently developed sex/gender checklist was applied. Twelve studies were included that examined intervention effects on AC in girls and boys. Three intervention studies showed significant effects in increasing AC, with one study favoring girls, one favoring boys, and another focusing on a single sex/gender (only girls). According to the checklist, the overall sex/gender rating highlighted a lack of information in sex/gender consideration. Studies with and without significant effects indicated no differences in the sex/gender checklist. The results indicate that sex/gender is not considered adequately in primary interventional research on AC. To evaluate the effectiveness of intervention in boys and girls, detailed analyses of sex/gender are required, and better reporting about sex/gender-specific intervention content is necessary. In future health research to promote AC, sex/gender should be systematically taken into account.

Simulation of Market Price Formation as a Game Between Stochastic Automata

1976 ◽  
Vol 98 (1) ◽  
pp. 91-100 ◽  
Author(s):  
Y. M. El-Fattah ◽  
R. Henriksen
Keyword(s):  
Conditional Probability ◽  
A Priori ◽  
Market Price ◽  
Competitive Market ◽  
Price Formation ◽  
Market Conditions ◽  
Reinforcement Scheme ◽  
Stochastic Automata ◽  
Lack Of Information ◽  
Simulation Results

A seller in a free competitive market attempts to optimize his profit by manipulating the price of his commodity. A seller does not know a priori the market conditions such as the conditional probability of the buyers demand, the criteria or even the number of his seller opponents. Subject to this lack of information, the process of market price formation can be simulated as a game between stochastic automata. As time unfolds each seller-automaton learns the market conditions and changes accordingly its price probabilities in view of maximizing its profit. A simple reinforcement scheme is introduced for the design of such automata. The simulation results demonstrate the expediency of the automata behavior.

Some Comments on the Stevens Linear and Quadratic Programming Versions of von Thünen's Theory of Agricultural Land Usage

1979 ◽  
Vol 11 (8) ◽  
pp. 943-962 ◽  
Author(s):  
W D Macmillan
Keyword(s):  
Linear Programming ◽  
Quadratic Programming ◽  
General Equilibrium ◽  
Agricultural Land ◽  
Programming Model ◽  
Linear Programming Model ◽  
Demand Elasticity ◽  
Partial Equilibrium ◽  
Land Usage ◽  
Working Definition

This paper examines the Stevens linear and quadratic programming formulations of von Thünen's analysis of agricultural land usage (Stevens, 1968). The first section contains a description of the Walras—Wald version of general economic equilibrium, plus a working definition of the expressions: general equilibrium sketch, paticularised general equilibrium sketch, and partial equilibrium sketch. [The author's distinction between a sketch and a model is explained in Macmillan (1978).] In section 2, von Thünen's assumptions, Stevens's (first) revised version of those assumptions, and Stevens's linear programming model are described. In section 3, the relationship between the Stevens linear programming model and the Walras—Wald model is examined. The fourth section contains a description of Stevens's approach to the relaxation of von Thünen's assumption of infinite demand elasticity, and a comparison of that approach with the so-called partial equilibrium approach to the same problem. It is claimed that this comparison is of some general, methodological interest. Section 5 contains the paper's conclusions.

scholarly journals Design of circular flexible plates under of corrosion wear

2021 ◽  
Vol 263 ◽  
pp. 03007
Author(s):  
Vladimir Mavzovin ◽  
Igor Ovchinnikov
Keyword(s):  
Fatigue Life ◽  
Optimal Design ◽  
Service Life ◽  
Quadratic Programming ◽  
Sequential Quadratic Programming ◽  
Minimax Problem ◽  
Corrosive Wear ◽  
Optimal Thickness ◽  
Programming Technique ◽  
Metal Structures

The problems of optimal design of metal structures are usually formulated as the problem of finding such values of the selected parameters of structures that provide the smallest (or largest) value of the selected optimality criterion in the area of admissible design solutions. In most works on the optimization of metal structures, parametric problems are considered, limited by the preliminary assignment of a constructive form with the possibility of changing its parameters. To solve these problems, both deterministic and probabilistic optimization models can be used. A deterministic problem of optimal design of flexible round metal plates exposed to the combined action of a load and an aggressive environment causing corrosive wear of one of the plate surfaces is considered. A feature of the statement is that it takes into account the effect of the stressed state of the plates on the kinetics of their corrosive wear. Due to the insufficient efficiency of random search methods, the sequential quadratic programming technique is used. Two formulations of the optimal design problem are formulated, which are reduced to the minimax problem. 8 optimization projects were considered, their comparative analysis was carried out. It is shown that the realization of the found optimal thickness profiles leads either to a significant decrease in the stress level at the end of the plate’s service life, or to a significant increase in the service life. Calculation results show that maximum fatigue life designs are equal at end-of-life, and the maximum increase in fatigue life for hard- pinned inserts along the contour is 59%. As a result of the study, it was found that the problems of optimal design of flexible round plates under conditions of corrosive wear (the rate of which depends on the level of stresses in the plates), presented in the form of a minimax problem, can be effectively solved using the sequential quadratic programming technique, and the study of time evolution is intense -strain state can be carried out using a combination of the mesh method and the Adams method. Realization of the found optimal thickness profiles leads either to a significant decrease in the stress level at the end of the plate’s service life, or to a significant increase in the service life.

scholarly journals Causality and Randomness as Objects of Perception in the Structure of Criminalistic Thinking

2019 ◽  
Vol 13 (2) ◽  
pp. 252-261
Author(s):  
Dmitry Bakhteev
Keyword(s):  
Cognitive Distortions ◽  
Negative Impact ◽  
Random Search ◽  
A Priori ◽  
Synthesis Mechanism ◽  
Cause And Effect ◽  
Flexible System ◽  
Problem Situations ◽  
Lack Of Information ◽  
Subject Of Cognition

The author analyzes criminalistic mindset from two standpoints — as a set of guidelines and as a flexible system of tools for studying the crime incident — and notes that the process of investigating and solving crimes is represented in the cognition of the person studying it as a dynamic system developing from cause to effect. Thus, there is a transition from the a priori (fragmented) probability of evidential information to the a posteriori, reliable probability. The author stresses the importance of the analysis and synthesis mechanism of the investigator’s thinking, which allow them to avoid investigation mistakes or other distortions of information perception. Each consequence has a corresponding concrete cause, although one cause could lead to multiple consequences. Thus, the causality of a crime and the appearance of its traces are perceived in detail, i.e., the investigator studies the mechanism of how the crime was committed through the trace picture of crime consequences and chooses the most probable of all possible causes. The author points out the importance of verifying the obtained information because material information is subject to destructive physical and chemical processes, while the ideal information — to cognitive distortions of perception, memory and reproduction. However, even when the trace information is distorted, the cause-and-effect relations remain intact. The author stresses the significance of the version process in the establishment of the cause-and-effect relations. He also discusses the random factors present in the process of crime investigation and solution, which, on the one hand, have a negative impact on this process and, on the other, make it possible to resolve problem situations characterized by a lack of information. Randomness is most evident in the investigative situations of problematic or risky nature. It is noted that randomness acts as a strictly subjective feature dependent on the specifics of the criminalistic mindset of the subject of cognition, not on the features of the objective reality; the characteristics of randomness could differ at different levels of examining a problem. The author analyzes the structure of the consequences of random search as a decision-making method in the conditions of insufficient information: it is possible to continue random search, to update the version or to transform the investigative situation from the simple into the complex or vice versa.

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