Design of an Active Cooling System for Thermally Activated Soft Actuators.

A new type of actuator made from twisting a silver-plated nylon thread presents new possibilities for the way wearable mechatronic rehabilitation devices are designed. The twisted coiled actuator (TCA) has been previously shown to provide a power density up to 100 times that of biological muscles, while also encompassing biomimetic characteristics. However, since TCAs require heat to contract, the main drawbacks preventing this type of actuator are its inherent low efficiency and slow reaction times. To combat both of these issues, a simple tube enclosure was designed to provide active cooling using forced air. The two main parameters affecting the efficiency and bandwidth are the cooling air pressure and tube diameter. This study presents a two-way repeated measures test to compare these parameters on the cooling and heating rates of the TCA system, as well as the thermal capacitance with three pressure levels (10, 15, and 20 psi) and three tube diameters (4, 4.5, and 5 mm). The results show that an increase in pressure significantly improves the rate of cooling, while a decrease in tube diameter has negative effects on the efficiency and cooling rate of the system. The mean values of the cooling time $(\tau_{\text {cool}})$ were 2.972, 2.210, and 2.682 seconds for 4, 4.5, and 5 mm diameters, respectively. These results indicate that a decrease in diameter improves the cooling rate up to the point at which the walls of the tube become so close to the TCA strand, that they prevent rapid heat transfer while cooling.

Stiffness control of a nylon twisted coiled actuator for use in mechatronic rehabilitation devices.

Mechatronic rehabilitation devices, especially wearables, have been researched extensively and proven to be promising additions to physical therapy, but most designs utilize traditional actuators providing unnatural, robot-like movements. Therefore, many researchers have focused on the development of actuators that mimic biological properties to provide patients with improved results, safety, and comfort. Recently, a twisted-coiled actuator (TCA) made from nylon thread has been found to possess many of these important properties when heated, such as variable stiffness, flexibility, and high power density. So far, TCAs have been characterized in controlled environments to define their fundamental properties under simple loading configurations. However, for an actuator like this to be implemented in a biomimetic design such as an exoskeleton, it needs to be characterized and controlled as a biological muscle. One major control law that natural muscles exhibit is stiffness control, allowing humans to passively avoid injury from external forces, or move the limbs in a controlled or high impact motion. This type of control is created by the antagonistic muscle arrangement. In this paper, an antagonistic apparatus was developed to model the TCAs from a biological standpoint, the stiffness was characterized with respect to the TCA temperature, and a fully functional stiffness and position controller was implemented with an incorporated TCA thermal model. The stiffness was found to have a linear relationship to the TCA temperatures (R2=0.95). The controller performed with a stiffness accuracy of 98.95% and a position accuracy of 92.7%. A final trial with varying continuous position input and varying stepped stiffness input exhibited position control with R2=0.9638.

The development and validation of The Inquiry Science Observation Coding Sheet.

Evaluation reports increasingly document the degree of program implementation, particularly the extent to which programs adhere to prescribed steps and procedures. Many reports are cursory, however, and few, if any, fully portray the long and winding path taken when developing evaluation instruments, particularly observation instruments. In this article, we describe the development of an observational method for evaluating the degree to which K-12 inquiry science programs are implemented, including the many steps and decisions that occurred during the development, and present evidence for the reliability and validity of the data that we collected with the instrument. The article introduces a method for measuring the adherence of inquiry science implementation and gives evaluators a full picture of what they might expect when developing observation instruments for assessing the degree of program implementation.

Involving program stakeholders in reviews of evaluators' recommendations for program revisions.

Why is the use of stakeholder expertise a sound rationale for involving program staff and beneficiaries in reviewing evaluators' recommendations for program revisions? What procedures might evaluators use for involving these stakeholders in this task? What can we conclude about the likely success of these procedures? This article seeks to address these questions. In the context of educational program evaluation, some of the theoretical and practical issues about the participation of stakeholders in reviewing recommendations are discussed. The participation of program stakeholders for the purpose of tapping their expertise is explained; a recent evaluation, in which program stakeholders reviewed evaluators' recommendations for program revisions, is described; and the implications of the article for stakeholder-based evaluation and practical participatory evaluation are presented.

State-level evaluations of school programs funded under the Drug-Free Schools and Communities Act.

Although the Drug-Free Schools and Communities Act of 1986 and the 1989 Amendments to the Act require states to evaluate their drug-education programs, no guidelines for conducting these evaluations have been produced, and little has been reported on how the states are conducting such evaluations. In this article, the results of a telephone survey on current state-level efforts to evaluate school programs funded under the Act are reported. Some states report studies of the implementation of the program and some report drug- and alcohol-use surveys. Together, these two types of evaluation efforts form the foundation of an approach for conducting evaluations under the Act. Reasons are presented why experimental and quasi-experimental designs might be inappropriate and impractical for the evaluations, and an evaluation approach linking program implementation findings and drug- and alcohol-use survey results is suggested.