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21.
Parkinsonian oscillations and their suppression by closed-loop deep brain stimulation based on fuzzy concept 下载免费PDF全文
This paper provides an adaptive closed-loop strategy for suppressing the pathological oscillations of the basal ganglia based on a variable universe fuzzy algorithm. The pathological basal ganglia oscillations in the theta (4-9 Hz) and beta (12-35 Hz) frequency bands have been demonstrated to be associated with the tremor and rigidity/bradykinesia symptoms in Parkinson's disease (PD). Although the clinical application of open-loop deep brain stimulation (DBS) is effective, the stimulation waveform with the fixed parameters cannot be self-adjusted as the disease progresses, and thus the stimulation effects go poor. To deal with this difficult problem, a variable universe fuzzy closed-loop strategy is proposed to modulate different PD states. We establish a cortico-basal ganglia-thalamocortical network model to simulate pathological oscillations and test the control effect. The results suggest that the proposed closed-loop control strategy can accommodate the variation of brain states and symptoms, which may become an alternative method to administrate the symptoms in PD. 相似文献
22.
The transition phase of GaAs from the zincblende (ZB)
structure to the rocksalt (RS) structure is investigated by ab initio plane-wave
pseudopotential density functional theory method, and the thermodynamic
properties of the ZB and RS structures are obtained through the
quasi-harmonic Debye model. It is found that the transition from the ZB
structure to the RS structure occurs at the pressure of about 16.3\,GPa,
this fact is well consistent with the experimental data and other theoretical results. The
dependences of the relative volume V/V0 on the pressure P, the Debye
temperature \Th and specific heat CV on the pressure P, as well as
the specific heat CV on the temperature T are also obtained
successfully. 相似文献
23.
First-principles calculations for electronic and optical properties of the zinc-blende structured BeS compound under pressure 下载免费PDF全文
The electronic and the optical properties of the cubic zinc-blende
(ZB) BeS under high pressure have been investigated by using \it ab
initio plane-wave pseudopotential density functional theory method
in the generalised gradient approximation (GGA) for
exchange-correlation interaction. The electronic band structure and
the pressure dependence of the total and partial densities of state
under pressure are successfully described. Our calculations show
that the ZB BeS has large and indirect band gaps associated with
(Γ → X) transitions in ambient conditions. The
results obtained are consistent with the experimental data
available and other calculations. The optical properties, including
dielectric function, energy-loss function, complex refractive index,
reflection and absorption spectra, are investigated and analysed at
different external pressures. The results suggest that the optical
absorption appears mostly in the ultra-violet region and the curve
of refractive index shift toward high energies (blue shift) with
pressure increasing. 相似文献
24.
First-principles calculations of structure and high pressure phase transition in gallium nitride 下载免费PDF全文
The phase transitions of semiconductor GaN from the Wurtzite (WZ)
structure and the zinc-blende (ZB) structure to the rocksalt (RS)
structure are investigated by using the first-principles plane-wave
pseudopotential density functional method combined with the
ultrasoft pseudopotential scheme in the generalized gradient
approximation (GGA) correction. It is found that the phase
transitions from the WZ structure and the ZB structure to the RS
structure occur at pressures of 46.1 GPa and 45.2 GPa, respectively.
The lattice parameters, bulk moduli and their pressure derivatives of
these structures of GaN are
also calculated. Our results are consistent with available
experimental and other
theoretical results. The dependence of the normalized formula-unit volume
$V/V_{0 }$ on pressure $P$ is also successfully obtained. 相似文献
25.
Intermolecular interaction potentials of methane-argon complex calculated using LDA approaches 下载免费PDF全文
The intermolecular interaction potential for methane-argon complex is calculated by local density approximation (LDA) approaches. The calculated potential has a minimum when the intermolecular distance of methane-argon complex is 6.75 a.u.; the corresponding depth of the potential is 0.0163eV which has good agreement with experimental data. We also have made a nonlinear fitting of our results for the Lennard-Jones (12-6) potential function and obtain that V(R)=143794365.332/R^{12}-3032.093 / R^6 (R in a.u. and V(R) in eV). 相似文献
26.
Polarizabilities of small Sn (n = 2-8) clusters are calculated by using the higher-order finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters are considered to be higher than the value estimated from the “hard sphere” model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with the increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations. 相似文献
27.
高密度氢气的分子间相互作用与状态方程 总被引:3,自引:2,他引:1
本文从高密度氢气的分子间相互作用出发进行分析,在修改范德瓦耳方程的基础上,提出了一种新的适用于高密度氢气的状态方程,并用来系统地计算了氢气在临界区的等温压缩线.在缺乏实验数据的情况下,这些理论计算结果很有用. 相似文献
28.
聚氨酯一聚丙烯酸酯共聚乳液的合成研究 总被引:4,自引:0,他引:4
以甲基丙烯酸β-羟乙酯封端的聚氨酯大分子单体与丙烯酸酯类单体进行乳液共聚,合成了以聚丙烯酸酯(PA)为主链、聚氨酯(PU)为侧链的接枝共聚物(PA-g-PU)乳液,用IR光谱和^1H NMR光谱对该聚氨酯大分子单体及PA-g-PU接枝共聚物进行了表征,并对影响聚氨酯-聚丙烯酸酯共聚合的因素进行了探讨。结果表明:聚氨酯大分子单体的加入对乳液聚合的速率造成较大的影响。该体系的表观活化自由能为99.39KJ/mol,Rp∝[I]^0.87,Rp∝[S]^0.12。 相似文献
29.
30.
First-principles calculations of structural and thermodynamic properties of BeB2 compound 总被引:1,自引:0,他引:1 下载免费PDF全文
The lattice parameter bulk modulus and pressure derivative of BeB2 are calculated by using the Cambridge Serial Total Energy Package (CASTEP) program in the frame of density function theory. The calculated results agree well with the average experimental data and other theoretical results. Through the quasi-harmonic Debye model, the dependences of the normalized lattice parameters a/ao, c/c0 and the normalized primitive cell volume V/Vo on pressure P, the variation of the thermal expansion coefficient ~ with pressure P and temperature T, as well as the dependences of the heat capacity Cv on pressure P and temperature T are obtained systematically. 相似文献