Economical evaluation of greenhouse layout design

This paper offers mutual exchange of knowledge and expertise between agriculture and production-economy by economical evaluation of greenhouses. Greenhouses are Hi-Tech horticulture farms, in which advanced technological infrastructure increase production efficiency by providing optimal growing conditions. However, this infrastructure involves high capital investments. There are other cost sources, of which labor is dominant, generally in horticulture and in greenhouses in particular. Efficient use of space and labor are often conflicting goals in greenhouse layout design. In this paper, these conflicts are presented and illustrated, and tools are developed to evaluate layout design by the resultant annual operational profit, thus enable comparison of alternative layouts. To increase accessibility, spreadsheet software is used for the calculations. Further, the spreadsheet is designed to support WHAT-IF analyses. The applicability of the proposed approach is demonstrated via numerical analyses of layout design of an actual greenhouse for pepper growing using the Holland method. Evidently, the layout design can have significant effect on the economical efficiency of the greenhouse—annual profit increases by, at least 12%, and up to 40%! The tradeoff between space utilization and resource utilization; e.g., labor, is common to all greenhouses, whether vegetables, flowers or other plants are grown in them and the tools presented herein can be easily modified to any desired case.     

Robotics projects and learning concepts in science, technology and problem solving

This paper presents a study about learning and the problem solving process identified among junior high school pupils participating in robotics projects in the Lego Mindstorm environment. The research was guided by the following questions: (1) How do pupils come up with inventive solutions to problems in the context of robotics activities? (2) What type of knowledge pupils address in working on robotics projects? and (3) How do pupils regard or exploit informal instruction of concepts in science, technology and problem solving within a project-based program? Data collection was made through observations in the class, interviews with the pupils, observations of the artifacts the pupils had constructed, and analyses of their reflections on each project. The study revealed that the pupils had often come up with inventive solutions to problems they tackled by intuitively using diverse kinds of heuristic searches. However, they encountered difficulties in reflecting on the problem solving process they had used. In robotics projects, the pupils deal primarily with qualitative knowledge, namely, the ability to identify specific phenomena in a system or factors that affect system performance. The study also showed that pupils are likely to benefit from implementing informal instruction on concepts in science, technology and problem solving into a project-based program. This type of instruction should take place in the context of pupils’ work on their projects, and adopt a qualitative approach rather than try to communicate in the class procedural knowledge learned by rote.     

Problem based learning: application to technology education in three countries

An increasing variety of professional educational and training disciplines are now problem based (eg, medicine, nursing, engineering, community health), and they may have a corresponding variety of educational objectives. However, they all have in common the use of problems in the instructional sequence. The problems may be as diverse as a mechanical predicament, an unexplained phenomena, or patient symptoms. Technology education in secondary schools is undergoing a period of significant change in many countries. It is therefore imperative that technology teacher education adopt not only the technologies that have been identified as being important, but also incorporate appropriate methodologies for the instruction of these technologies. PBL offers a number of relevant features to technology education and it is because of these that the project outlined in this paper has been developed.     

Conditions for a CAPM equilibrium with positive prices

This paper examines the conditions required to guarantee positive prices in the CAPM. Positive prices imply an upper bound on the equity premium. This upper bound depends on the degree of diversity of firms’ fundamentals, and it is independent of investors’ preferences. In economies with realistically diverse assets the only positive-price CAPM equilibrium theoretically possible is a degenerate one, with zero equity premium. Furthermore, when specific standard investors’ preferences are assumed, the CAPM equilibrium with positive prices may be altogether impossible. A possible solution to these fundamental problems may be offered by the segmented-market version of the model.     

Partial carryover of advertising

A model that combines advertising carryover with purchase reinforcement is presented. It accommodates the possibility that certain members of the consumer population rely only on their experience with the product, while others are also affected by past advertising. Empirical results with two product categories indicate that for bimonthly data advertising retention does not exist at all.     

Modeling Methods for Discrete Choice Analysis

This paper introduces new forms, sampling and estimation approaches fordiscrete choice models. The new models include behavioral specifications oflatent class choice models, multinomial probit, hybrid logit, andnon-parametric methods. Recent contributions also include new specializedchoice based sample designs that permit greater efficiency in datacollection. Finally, the paper describes recent developments in the use ofsimulation methods for model estimation. These developments are designed toallow the applications of discrete choice models to a wider variety ofdiscrete choice problems.     

Time Series Analysis of Repeated Surveys: The State–space Approach

Cross sectional estimates from repeated surveys form a time series { y_t }. These estimates can be viewed as the sum y _t = Y _t + e _t of two processes, { Y _t }, the population process and { e _t }, the survey error process. Serial correlations in the latter series are usually present, mainly due to sample overlap. Other sources of data such as censuses, administrative records and demographic population counts are also available. The state–space modelling approach to the analysis of repeated surveys allows combining information from different sources, incorporating benchmarking constraints in a natural way. Results from these methods seem to compare favourably with those from X-11-ARIMA in filtering out survey errors.     

Real Longevity Insurance with a Deductible: Introduction to Advanced-Life Delayed Annuities (ALDA)

Abstract

This paper explores the financial properties of a concept product called an advanced-life delayed annuity (ALDA). The ALDA is a variant of a pure deferred annuity contract that is acquired by installments, adjusted for consumer price inflation, and pays off toward the end of the human life cycle. The ALDA concept is aimed at the growing population of North Americans without access to a traditional defined benefit (DB) pension plan and the implicit longevity insurance that a DB plan contains. I show that under quite reasonable pricing assumptions, a consumer can invest or allocate $1 per month, while saving for retirement, and receive between $20 and $40 per month in benefits, assuming the deductible in this insurance policy is set high enough. The ALDA concept might go a long way in mitigating the psychological barrier to voluntary lump-sum annuitization.     

Quantile regression with sample selection: Estimating women's return to education in the U.S.

This study uses quantile regression techniques to analyze changes in the returns to education for women. The data used is the March Current Population Survey for the years 1968, 1973, 1979, 1986 and 1990. The first step in estimating the single (linear) index selection equation uses Ichimura's (1993) semiparametric procedure. To correct for an unknown form of a sample selection bias in the quantile regression, the second step incorporates a nonparametric method, using an idea similar to one developed by Heckman (1980) and Newey (1991) for mean regression, and Buchinsky (1998) for quantile regression.  The results show that: (a) the returns to education increased enormously for the younger cohorts, but very little for the older cohorts; (b) in general the returns are higher at the lower quantiles in the beginning of the sample period and higher at the higher quantiles by the end of the sample period; (c) there is a significant sample selection bias for all age groups at almost all quantiles; (d) toward the end of the sample period there is a significant convergence of the returns at the various quantiles, especially for the younger cohorts and age groups; and (e) the semiparametric estimates of the selection equation are considerably different from those obtained for a parametric probit model.