Optimal control of a distributed parameter system with applications to beam vibrations using piezoelectric actuators

This paper addresses the issue of the active vibration control of the transverse modes in a flexible elastic systems. The control is implemented by discrete sets of piezoelectric actuators that apply the optimal forces. The performance index is a time-dependent quadratic functional of state variables and their time derivatives, and control forces which are determined by minimizing the objective functional subject to a penalty term on the control functions. A combination of Galerkin and variational approaches are employed to determine the control forces in the time domain explicitly in terms of coupled amplitudes and velocities. The effectiveness of the proposed method is demonstrated by applying it to a physical problem controlled by piezoelectric patch actuators.     

Books Received

Abstract

This paper analyses the organizational, financial and technological incentives that service organizations used to motivate farmers to finance agricultural research and extension in Benin. Understanding the foundations and implications of these motivation systems is important for improving farmer financial participation in agricultural research and extension.

We studied three cases of farmer financial participation in the field of agricultural research and extension in Benin. We conducted semi-structured interviews with leaders of service organizations and farmers’ associations, local authorities and individual farmers. Our interviews focused on service delivery systems, mechanisms of farmers’ financial contribution, the functioning of farmers’ associations, and the appropriateness of services provided. We performed thematic and comparative analyses at the interfaces between (1) service providers and partner–farmer associations, (2) service providers and delivered services, and (3) farmers/farmers’ associations and services.

Incentives for farmer financial participation are the increasing participation strategy, the fulfillment of farmers’ needs and the local leadership valorization. The selection and combination of their variants determine the motivating capacity and orientation of service organizations. Conversely to the increasing participation strategy, an effective fulfillment of farmers’ needs and local leadership valorization can lead to sustainable motivation. As the fulfillment of farmers’ needs determines importantly the effectiveness and sustainability of farmers’ motivation, the strategies of farmer financial participation are likely to fail if there are no successful agricultural technological incentives.

In the current context of privatization of agricultural services in developing countries, this analytical framework is of interest for policy makers and development workers for identifying conditions of farmer financial participation and designing effective motivation strategies.     

Fifth Graders’ Learning About Simple Machines Through Engineering Design-Based Instruction Using LEGO™ Materials

This study is part of a 5-year National Science Foundation-funded project, Transforming Elementary Science Learning Through LEGO? Engineering Design. In this study, we report on the successes and challenges of implementing an engineering design-based and LEGO?-oriented unit in an urban classroom setting and we focus on the impact of the unit on students’ content understanding of simple machines. The LEGO? engineering-based simple machines module, which was developed for fifth graders by our research team, was implemented in an urban school in a large city in the Northeastern region of the USA. Thirty-three fifth grade students participated in the study, and they showed significant growth in content understanding. We measured students’ content knowledge by using identical paper tests and semistructured interviews before and after instruction. Our paired t test analysis results showed that students significantly improved their test and interview scores (t?=??3.62, p?<?0.001 for multiple-choice items and t?=??9.06, p?<?0.000 for the open-ended items in the test and t?=??12.11, p?<?0.000 for the items in interviews). We also identified several alternative conceptions that are held by students on simple machines.     

Popular pedagogy and the changing political landscape: a case study of a women's housing movement in South Africa

This paper sets out to explore the relationship between popular education and the changing South African political landscape through case study research of the Victoria Mxenge Housing Development Association. The research took place over an extended period of time from 1992–2003 and discusses how popular education was advocated by the South African Homeless People's Federation and its parent NGO (People's Dialogue); how it was implemented, how an increasing disjuncture between teaching and learning occurred, and how pedagogy was shaped by both political and personal factors. The paper discusses the interactions between social movements and NGOs and the limitations of social movements and popular education. It argues for a more nuanced conceptual understanding of learning in social movements within development contexts.     

Body Composition Relative to Motor Aptitude for Preadolescent Boys

Abstract

The data for 40 variables were obtained from 81 Purdue University faculty sons between 10 and 12 years of age inclusive. Among the 40 variables, 680 correlation coefficients were obtained. Factor analysis was used to identify the factors which could explain the items measuring body composition and motor aptitude. As a result, eight factors were isolated and given names. The factors underlying the 40 variables seemed to permit the following names: growth and maturity factor, “body fitness” factor, body balance on object factor, coordination of the lower extremities factor, general kinesthetic sense factor, general static balance factor, directionality factor, and laterality factor. Observing the factor loadings in Factor I, it may be concluded that the measurement of lean body weight by liquid scintillation counting technique is significant in the assessment of growth and maturity in preadolescent boys. Furthermore, in the assessment of “body fitness” pertaining to preadolescent boys, it is revealed that the percent lean body weight is the most important item as indicated by the value of factor loading presented in Factor II.     

如何应对网上短时学习需求高峰——学习成本节约策略研究

对多数开放大学来说,事实上,在许多大学中,总是会出现这样的情况,所有学生要在同一段时间内集中完成一些网上学习活动。这些活动通常造成学生在一定时间内蜂拥上网。由于学生较好的上网时间选择有限,网上学习拥挤高峰情况就会变得很糟。在通常情况下,只有那些最早上网的学生才能获得最佳在线学习机会。在马来西亚开放大学,当学生确认开设科目和占用网络槽口选择会面时间表的时候,往往就会出现网上使用高峰。大多数学生都会尽早赶去上网以确保能在时间安排表中获得网上会面的机会。那些可以利用的信息技术资源与功能,诸如互联网带宽和服务器等无法应付这些短时网络需求高峰。除非这些需求高峰得到满足,否则网络服务的速度将会迅速变慢,最终导致网络使用者排长队等候网络服务。假如可以提供超额的网络容量,要是可能的话,以确保这些短时需求高峰得到满足,那就不可能有成本效应。因为在大多数时间里,这些网络资源都没有得到充分利用。本论文着重探讨一些具有成本效应的方法以应对和满足短时网络高峰的需求。     

Bearing capacity of thin-walled shallow foundations: an experimental and artificial intelligence-based study

Thin-walled spread foundations are used in coastal projects where the soil strength is relatively low. Developing a predictive model of bearing capacity for this kind of foundation is of interest due to the fact that the famous bearing capacity equations are proposed for conventional footings. Many studies underlined the applicability of artificial neural networks (ANNs) in predicting the bearing capacity of foundations. However, the majority of these models are built using conventional ANNs, which suffer from slow rate of learning as well as getting trapped in local minima. Moreover, they are mainly developed for conventional footings. The prime objective of this study is to propose an improved ANN-based predictive model of bearing capacity for thin-walled shallow foundations. In this regard, a relatively large dataset comprising 145 recorded cases of related footing load tests was compiled from the literature. The dataset includes bearing capacity (Q_u), friction angle, unit weight of sand, footing width, and thin-wall length to footing width ratio (L_w/B). Apart from Q_u, other parameters were set as model inputs. To enhance the diversity of the data, four more related laboratory footing load tests were conducted on the Johor Bahru sand, and results were added to the dataset. Experimental findings suggest an almost 0.5 times increase in the bearing capacity in loose and dense sands when L_w/B is increased from 0.5 to 1.12. Overall, findings show the feasibility of the ANN-based predictive model improved with particle swarm optimization (PSO). The correlation coefficient was 0.98 for testing data, suggesting that the model serves as a reliable tool in predicting the bearing capacity.     

Assessment of farmer-oriented agricultural extension intervention in Iran

Purpose: The main purpose of this study was to determine the characteristics of farmer-oriented policies as regards the Iranian agricultural extension system. Methodology: To fulfill this objective, a Delphi technique was utilized. The study used a series of three steps, engaging a panel of experts on farmer-oriented policies of agricultural extension system. Finding: The characteristics of farmer-oriented policies in agricultural extension system were classified into six categories including: need-based programs, proper interaction among stakeholders, decentralization and higher stakeholders’ participation, enabling stakeholders with emphasis on smallholder farmers, market-oriented programs and integrated policies. The findings indicated that ‘enabling farmers to solve their technical problems’ and ‘engaging farmers in planning, executing and evaluating of the programs’ had the highest percentage of agreement. Theoretical implication: From a theoretical point of view, the finding of this research has introduced six categories as characteristics of a farmer-oriented policy that could have practical implications for agricultural extension system in Iran. Also, this paper proposes a framework for future studies in the field of farmer-oriented policies in agricultural extension system. Practical implications: Recognizing the characteristics of farmer-oriented intervention of agricultural extension shows that targeted extension approaches are needed to pay attention to these characteristics in various stages of planning, delivering and evaluation of extension programs. Originality/value: This paper provides a comprehensive list of characteristics of farmer-oriented policies of agricultural extension that can be helpful for agricultural policy-makers in devising programs of extension services.     

Standard Deviation for Small Samples

Neater representations for variance are given for small sample sizes, especially for 3 and 4. With these representations, variance can be calculated without a calculator if sample sizes are small and observations are integers, and an upper bound for the standard deviation is immediate. Accessible proofs of lower and upper bounds are presented for a broad spectrum of readers.