孔隙分布不均匀性对渗透率影响的MRTLBM法研究

孔隙率与渗透率是多孔介质非常重要的属性参数,采用MRT LBM研究孔隙率损失与渗透率损失相关性以及同孔隙率异构孔隙对渗透率特性的影响。结果表明：当存在使孔隙率均匀变小的沉积、沉降或结焦等因素时,渗透率损失率是孔隙率损失率的2倍左右;同孔隙率异构多孔体中,渗透率有巨大差异;同孔隙率异构多孔体中最大孔喉最小孔喉比越大渗透率越小;同孔隙率多孔体中迂曲度越大渗透率越小。     

Learning anatomy enhances spatial ability

Spatial ability is an important factor in learning anatomy. Students with high scores on a mental rotation test (MRT) systematically score higher on anatomy examinations. This study aims to investigate if learning anatomy also oppositely improves the MRT‐score. Five hundred first year students of medicine (n = 242, intervention) and educational sciences (n = 258, control) participated in a pretest and posttest MRT, 1 month apart. During this month, the intervention group studied anatomy and the control group studied research methods for the social sciences. In the pretest, the intervention group scored 14.40 (SD: ± 3.37) and the control group 13.17 (SD: ± 3.36) on a scale of 20, which is a significant difference (t‐test, t = 4.07, df = 498, P < 0.001). Both groups show an improvement on the posttest compared to the pretest (paired samples t‐test, t = 12.21/14.71, df = 257/241, P < 0.001). The improvement in the intervention group is significantly higher (ANCOVA, F = 16.59, df = 1;497, P < 0.001). It is concluded that (1) medical students studying anatomy show greater improvement between two consecutive MRTs than educational science students; (2) medical students have a higher spatial ability than educational sciences students; and (3) if a MRT is repeated there seems to be a test effect. It is concluded that spatial ability may be trained by studying anatomy. The overarching message for anatomy teachers is that a good spatial ability is beneficial for learning anatomy and learning anatomy may be beneficial for students' spatial ability. This reciprocal advantage implies that challenging students on spatial aspects of anatomical knowledge could have a twofold effect on their learning. Anat Sci Educ 6: 257–262. © 2013 American Association of Anatomists.     

Average SNR of maximum ratio transmission with selection combining

Two kinds of selection combining schemes including generalized selection combining （GSC） and generalized order selection combining （GOSC） are investigated. In the GSC scheme, L strongest diversity branches from a total of R diversity branches are selected and coherently combined by maximal ratio combining. GOSC means that the Lth strongest diversity branch from R diversity branches is selected for reception. Closed-form expressions for the average signal-to-noise ratios of maximum ratio transmission with GSC and GOSC are derived in Rayleigh fading channels.