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1. chinaXiv:202109.00020 [pdf]

工作记忆训练诱发的神经可塑性——基于系列fMRI实验的脑区分布递减时空模型

党彩萍; 付彤; 刘昌; 伏云发; 李恩泽; 陈幸明; Jian ZHANG; 陈盛强; 张宾
Subjects: Psychology >> Cognitive Psychology

工作记忆训练(Working Memory Training, WMT)诱发神经可塑性,但其具体机制尚不明晰。为探讨WMT诱发正常人群大脑功能变化的时空特性,以“扩展的智力顶额整合理论”和“神经效率假说”为假设依据,采用逐层递进方法,对近20年来正常人群WMT的37篇fMRI文献进行梳理。首先,用叙述性综述、频数分析和卡方检验法比较脑区激活模式和功能连接在WMT前后发生的改变,发现大脑的5个联合区、7个宏观区和3个子区参与WMT。尤其,额上回、顶下小叶和扣带回这3个子区各自的减弱激活多于其增强激活,且这种差异分别具有统计学意义。其次,采用激活似然估计法对其中26篇进行元分析,发现WMT前后激活水平的差异具有统计学意义的子区有3个,即额中回(BA6和8)、额上回(BA6)和前扣带回(BA24和32)。再次,综合定性和定量分析结果,提出WMT脑区分布递减时空模型,并据此产生五个结果和讨论。然后,采用非参数检验进一步分析WMT效应可能的调节因素,发现WMT的任务类型和时间分别对脑区激活的影响具有统计学意义。接着,针对正常人群WMT诱发神经可塑性的时空特性,得出四个结论:第一,WMT可改变正常人群相应脑区的神经活动,表现为或减弱、或增强,但减弱更加突出,且更新和较短时间的WMT倾向于诱发较多减弱;第二,这些神经活动变化主要发生在额顶叶联合区,但也包括分别以颞叶、枕叶、扣带回及纹状体为主的联合区,在一定范围内体现了整脑功能联合;第三,额中回、额上回和前扣带回这3个子区的神经活动改变重点体现了WMT神经可塑性的空间特点,而额上回、顶下小叶和扣带回这3个子区重点体现了其时间特性;第四,“扩展的智力顶额整合理论”和“神经效率假说”分别支持了WMT脑区分布的空间和时间特性。最后,指出未来研究可能需要辨析额上回、顶下小叶和扣带回这三个子区体现的WMT效应、WMT导致脑区激活减弱或增强的综合性影响因素。

submitted time 2021-09-10 Hits2758Downloads481 Comment 0

2. chinaXiv:201803.01548 [pdf]

Optimized thermoelectric properties of AgSbTe2 through adjustment of fabrication parameters

Jian Zhang; Xiaoying Qin; Di Li; Chunjun Song; Yongfei Liu; Hongxing Xin; Tianhua Zou; Yuanyue Li
Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology

AgSbTe2 bulk sample is obtained by hot-pressing under different fabrication parameters, and their thermoelectric properties are investigated in the temperature range of 300-550K. The highest ZT=0.86 is achieved at 475K for the sample hot-pressed at 423K and 500MPa due to the lower thermal conductivity and higher power factor. The results indicate that the optimized thermoelectric properties can be obtained for AgSbTe2 compound at the sintering temperature of 423K under the pressure of 500MPa.

submitted time 2018-03-30 Hits2955Downloads1449 Comment 0

3. chinaXiv:201803.01550 [pdf]

Enhanced thermoelectric performance of CuGaTe2 by Gd-doping and Te incorporation

Jian Zhang; Xiaoying Qin; Di Li; Chunjun Song; Xiaoguang Zhu; Yongfei Liu; Hongxing Xin; Li Chen; Tianhua Zou
Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology

Gd-doped compounds CuGa1-xGdxTe2 (0?x?0.02) incorporated with tellurium nanoparticles are synthesized by fusion method. Their thermoelectric properties are investigated in the temperature range of 300-800K. The results indicate that the synergistic effect of Gd-doping and Te incorporation remarkably enhances the thermoelectric performance of CuGaTe2. Specially, the thermal conductivity ? of the specimen CuGa0.98Gd0.02Te2/0.7vol.%Te reduces to 0.45 Wm-1K-1 at 684K, which is ~74% smaller than that of pure CuGaTe2 (?=1.76 W?m-1?K-1 at 684K) due to the incorporation of nanostructure Te. The thermoelectric figure of merit value (ZT) reaches 0.75 at 737K for the specimen CuGa0.99Gd0.01Te2/0.7vol.%Te, which is ~115% larger than that of pure CuGaTe2.

submitted time 2018-03-30 Hits2682Downloads1332 Comment 0

4. chinaXiv:201803.01551 [pdf]

Enhanced thermoelectric performance of CuGaTe2 based composites incorporated with graphite nanosheets

Jian Zhang; Xiaoying Qin; Di Li; Yongfei Liu; Yuanyue Li; Chunjun Song; Hongxing Xin; Xiaoguang Zhu
Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology

CuGaTe2 based composites incorporated with graphite nanosheets(GNs) CuGaTe2/x G (G=GNs, 0?x?3.04 vol.%) were prepared, and the thermoelectric properties of the composites were studied from 300 to 875 K. The results show that the incorporation of GNs into the CuGaTe2 matrix can enhance the Seebeck coefficient and power factor over the whole temperature range investigated due to energy filtering effects, and the reduction of thermal conductivity below 750K owing to interface scattering. Although the resistivity increases, energy filtering significantly raises the Seebeck component, and the overall effect on power factor is positive. The sample with 2.28 vol.% GNs had the largest ZT value, reaching 0.93 at 873K, which is a ~21% improvement on pure CuGaTe2.

submitted time 2018-03-30 Hits2314Downloads1125 Comment 0

5. chinaXiv:201608.00191 [pdf]

Cosmographic analysis from distance indicator and dynamical redshift drift

Ming-Jian Zhang; Hong Li; Jun-Qing Xia
Subjects: Physics >> Nuclear Physics

Cosmography is a model-independent de 1. To ensure data in the convergence radius, y=z/(1+z) redshift was defined. However, discussions about the usefulness of y-redshift and the leading cause of the issue are commonly absent. In the present paper, we study the cosmography in both z and y redshift using the supernova and mock redshift drift data. By introducing the bias-variance tradeoff, we reveal that the large bias square between cosmography and Union2.1 supernova data is the "chief culprit" of convergence issue. Moreover, expansion up to higher order and introduction of the y-redshift both are not effective to reconcile this contradiction. Minimizing risk, it suggests that Taylor expansion up to the second term is a better choice for available supernova data. Forecast from future supernova data and redshift drift shows that redshift drift can give much tighter constraints on the cosmography. We also investigate the effect of convergence issue on the deceleration parameter and dark energy. It inspires us that dynamical observations including redshift drift can give more detailed information on cosmic evolution

submitted time 2016-08-30 Hits1366Downloads727 Comment 0

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