- 分享到:
Task Direction:
You will have a choice between two Issue topics. Each topic will appear as a brief quotation that states or implies an issue of general interest. Read each topic carefully; then decide on which topic you could write a more effective and well-reasoned response.
You will have 45 minutes to plan and compose a response that presents your perspective on the topic you select. A response on any other topic will receive a zero. You are free to accept, reject, or qualify the claim made in the topic you selected, as long as the ideas you present are clearly relevant to the topic. Support your views with reasons and examples drawn from such areas as your reading, experience, observations, or academic studies.
GRE readers who are college and university faculty will read your response and evaluate its overall quality, based on how well you do the following
consider the complexities and implications of the issue
organize, develop, and express your ideas on the issue
support your ideas with relevant reasons and examples
control the elements of standard written English.
You may want to take a few minutes to think about the issue and to plan a response before you begin writing. Be sure to develop your ideas fully and organize them coherently, but leave time to reread what you have written and make any revisions that you think are necessary.
Section Direction:
Present your perspective on the issue below, using relevant reasons and/or examples to support your views.
Question: "It is often necessary, even desirable, for political leaders to withhold information from the public."
Composites reinforced with ferromagnetic particles by impregnated in elastomers (e.g., natural or silicon rubber, polyurethane), has been widely used in various engineering areas and have been extensively attracted more attentions for the past decade because of their magnetic dependent properties can be controlled rapidly and reversibly by an external magnetic field. In this study, a conceptual model based on the magnetoactive particles filled with soft composites was proposed, and the numerical research of magneto-fluid-solid coupling behaviours for a soft biomimetic robot fish driven magnetically was carried out. Under the action of magnetic field, the magnetic sensitive materials distributed in specific parts of the robot fish body will deform and cause the whole body of the fish swinging, to flap the liquid and generate forward thrust, resulting in pushing the fish forward. The corresponding multifield coupling equations for the mechanism and responses of magnetically propelled fish-like swimmers were developed and simulated numerically using the COMSOL multiphysics software. The effects of the tail length, the modulus of magnetic sensitive materials and spatial arrangement feature on the swimming ability of the fish-like structure were analyzed in detail. The relevant results are expected to provide a theoretical guidance for the potential applications of such biomimetic devices in intelligent far-field driving, drug delivery and other fields.
