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Two solar flares X2.2 and X9.3 erupted over the active region 2673 on 6 September 2017, and the second flare is the strongest since 2005. In order to investigate the ionospheric and thermospheric responses to the two solar flares, the global total electron content and the critical frequency of F2 layer obtained from GPS stations and ionosondes are used. The results indicate that the ionosphere in the sunlit hemisphere increased significantly with magnitudes of 0.1 and 0.5 total electron content units for the X2.2 and X9.3 solar flares, respectively. The electron density, thermospheric neutral density, and neutral temperature simulated by the Thermosphere-Ionosphere Electrodynamics Global Circulation Model show that the behavior of ionospheric and thermospheric responses is different. The ionospheric disturbances occurred at the altitude ranges of 150À300 km, and the thermospheric responses occurred at the altitudes of 250À400 km are caused by solar extreme ultraviolet and ultraviolet photons, respectively. Both ionospheric and thermospheric responses are proportional to the height within their corresponding altitude ranges. Observations and simulations reveal that the ionospheric and thermospheric responses are nonlinearly dependent on the solar zenith angle. The disturbances caused by the X2.2 solar flare are symmetric, but the X9.3 solar flare are not. The O/N 2 density ratio simulated by Thermosphere-Ionosphere Electrodynamics Global Circulation Model increases from lev0 to lev5.0 pressure surface with a magnitude of 0.1-1.8, while the ratio decreases in the American sector with a magnitude of À0.6 to À0.3. The longitudinal asymmetry of O/N 2 density ratio is a major contributor to the longitudinal asymmetry of ionospheric and thermospheric responses. (CMD = 83°) was smaller than that caused by the X17.2 flare on 28 October 2003 (CMD = 8°), which was

Spatial visualization skills are essential in many engineering and technology fields. These skills are especially important in hand sketching and computer-aided design (CAD) of engineering graphics, when it is necessary to visualize and represent three-dimensional (3D) objects and assemblies. Educators and researchers have developed various types of tests to assess students' abilities in spatial visualization tasks. Conventional visualization tests usually use axonometric drawings, mostly isometric projections, to represent 3D objects. However, isometric drawings are dimensionally distorted and lack many features present in a realistic view of 3D objects. They are also prone to drawing errors, which, when combined with the inherent distortions of isometric drawing, may lead to misjudgment of students' visualization abilities. In order to accurately assess students' visualization ability, realistic views are necessary in spatial visualization tests. To investigate the effects of 3D views, the author conducted a comparative study of a popular spatial visualization test given to the first-year graphics and CAD classes at a minority community college. The objects in the Purdue Spatial Visualization Test-Visualization by Rotations (PSVT-R) were recreated with 3D solid modeling CAD software to show more realistic views. The results from both the original test in isometric views and the same test with 3D solid model views are statistically analyzed. Also, a more detailed discussion is presented of the advantages of using solid modeling in spatial visualization tests, and the drawbacks of the conventional test using isometric drawings.

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