分类： 核科学技术 >> 核科学与技术 提交时间： 2024-03-28
摘要： Due to their excellent safety performance, dispersion fuels are widely used in advanced reactors, such as high-temperature gas-cooled reactors (HTGRs). Compared with deterministic methods, the Monte Carlo method has more advantages in the geometric modeling of stochastic media. The explicit modeling method has high computational accuracy and high computational cost. The chord length sampling (CLS) method can improve computational efficiency by sampling the chord length during neutron transport using the matrix chord length’s probability density function (PDF). This study shows that the excluded-volume effect in realistic stochastic media can introduce significant deviations into the CLS. A chord length correction approach is proposed to obtain the chord length correction factor by developing the Particle code based on equivalent transmission probability. Through numerical analysis against reference solutions from explicit modeling in the RMC code, it was demonstrated that CLS with the proposed correction method provides good accuracy for addressing the excluded-volume effect in realistic infinite stochastic media.
分类： 核科学技术 >> 粒子加速器 提交时间： 2024-03-24
摘要： X波段高梯度加速结构是能有效减小常温直线型加速器体积的核心部件。清华大学加速器实验室成功研制了0.65 m的X波段高梯度行波等阻抗加速结构。经过一系列精密的加工流程和调谐过程，加速结构的微波测试达到了预期的结果，进而在清华大学X波段高功率微波平台上进行高功率测试。测试过程中，整管的平均加速梯度达到了80 MV/m，首腔的平均加速梯度超过110 MV/m，达到了国际的前列水平。该结构的研制还将为清华大学承建的紧凑型准单能伽马源（VIGAS）项目提供重要的技术支撑。
分类： 心理学 >> 社会心理学 提交时间： 2021-01-28
摘要： Previous studies have demonstrated the possibility that when people are in standing than sitting postures, they have a stronger cognitive control propensity, making them inclined to agree more to sacrificing one innocent and saving more people. Furthermore, this postural effect can be moderated by dual processes. In three studies, participants read dilemma scenarios followed by a proposed behavior to sacrifice one innocent and save five or more people. The participants in sitting or standing postures were asked whether the described action was morally acceptable (moral judgment) and whether they would perform the described action (moral action). The results demonstrated that participants were more approving of the behavioral proposal in the moral action perspective than in the moral judgment perspective across the three studies. The hypothesized postural effect was found in a field study (Study 1) and replicated in a pre-registered replication study (Study 2) and further supported in an experimental study (Study 3). Compared with those in sitting postures, participants in standing postures expressed higher approval of the behavioral proposal compared to their sitting counterparts. Furthermore, the postural effect was dismissed when participants made moral decisions with a dual task to increase cognitive load, and it was reversed when they made moral decisions after deliberate consideration of the behavioral proposal (Study 3). The present research supports and extends the dual-process morality theory by demonstrating that body posture can affect moral decision-making; it also offers novel evidence revealing the moderating role of dual process on embodiment effects. It enriches our knowledge that morality is evolutionarily embodied in postures and that the dual process can moderate embodiment effects.
分类： 心理学 >> 社会心理学 分类： 心理学 >> 医学心理学 提交时间： 2021-01-14
摘要： Previous research found that people with higher level of psychopathy trait would endorse more to the harmful but beneficial action in traditional moral dilemmas. Three possibilities for this effect were confounded: People with higher psychopathy trait, 1) care more about the beneficial consequences; 2) care less about the “no harm” norms; 3) just prefer action irrespective of consequences and norms. A multinomial processing tree model named “CNI” was developed and claimed to dissociated these three possibilities. Four studies have applied CNI model to study the psychopathy-moral decision relationship. However, the CNI model presupposes the agent sequentially processes consequences-norms-generalized inaction/action preferences, which makes the estimated parameters biased and untenable. More recently, an alternative algorithm named “CAN” was developed based on the same data structure to overcome the limitations of CNI model. We applied CAN algorithm and reanalyzed the raw data of the four studies on psychopathy-moral decision relationship. The results demonstrated that people with higher psychopathy trait have weaker consequences and norms sensitivities, stronger overall action preferences, stronger inaction/action preferences irrespective of norms and consequences, and weaker moral principles obedience. Furthermore, the mediation and moderation reanalysis explorations demonstrated that instrumental harm and moral identity partly mediate the psychopathy-moral decision relationship and that perceived societal standards rather than personal standards when making moral decisions can alleviate the positive effects of psychopathy on overall action preference and action preference irrespective of norms and consequences. Present reanalysis exploration study clarified and deepened our insights on the relationship between psychopathy and moral decisions. Theoretical and methodological implications were also discussed.
分类： 数学 >> 控制和优化 提交时间： 2020-06-16
摘要： Quantization is a popular technique to reduce communication in distributed optimization. Motivated by the classical work on inexact gradient descent (GD) \cite{bertsekas2000gradient}, we provide a general convergence analysis framework for inexact GD that is tailored for quantization schemes. We also propose a quantization scheme Double Encoding and Error Diminishing (DEED). DEED can achieve small communication complexity in three settings: frequent-communication large-memory, frequent-communication small-memory, and infrequent-communication (e.g. federated learning). More specifically, in the frequent-communication large-memory setting, DEED can be easily combined with Nesterov's method, so that the total number of bits required is $ \tilde{O}( \sqrt{\kappa} \log 1/\epsilon )$, where $\tilde{O}$ hides numerical constant and $\log \kappa $ factors. In the frequent-communication small-memory setting, DEED combined with SGD only requires $\tilde{O}( \kappa \log 1/\epsilon)$ number of bits in the interpolation regime. In the infrequent communication setting, DEED combined with Federated averaging requires a smaller total number of bits than Federated Averaging. All these algorithms converge at the same rate as their non-quantized versions, while using a smaller number of bits.
分类： 心理学 >> 心理测量 分类： 心理学 >> 社会心理学 提交时间： 2020-04-03
摘要： Gawronski et al. (2017) developed a CNI model to measure an agent’s norms sensitivity, consequences sensitivity, and generalized inaction/action preferences when making moral decisions. However, the CNI model presupposed that an agent considers consequences—norms—generalized inaction/action preferences sequentially, which is untenable based on recent evidence. Moreover, the CNI model generates parameters at the group level based on binary categoric data. Hence, the C/N/I parameters cannot be used for correlation analyses or other conventional research designs. To solve these limitations, we developed the CAN algorithm to compute norms and consequences sensitivities and overall action/inaction preferences algebraically in a parallel manner. We re-analyzed the raw data of Gawronski et al.(2017) to test the methodological predictions. Our results demonstrate that: (1) the C parameter is approximately equal between the CNI model and CAN algorithm; (2) the N parameter under the CNI model approximately equals N/(1 – C) under the CAN algorithm; (3) the I parameter and A parameter are reversed around 0.5 – the larger the I parameter, the more the generalized inaction versus action preference and the larger the A parameter, the more overall action versus inaction preference; (4) tests of differences in parameters between groups with the CNI model and CAN algorithm led to almost the same statistical conclusion; (5) Parameters from the CAN algorithm can be used for correlational analyses and multiple comparisons, and this is an advantage over the parameters from the CNI model. The theoretical and methodological implications of our study were also discussed.
分类： 生物学 >> 生物医药 提交时间： 2017-05-10
摘要： Nanog was identified by its ability to sustain the LIF-independent self-renewal of mouse embryonic stem (ES) cells and has recently been shown to play a role in reprogramming adult fibroblasts into pluripotent stem cells. However, little is known about the structural basis of these remarkable activities of Nanog. We have previously identified an unusually strong transactivator named CD2 at its C terminus. Here we demonstrate that CD2 is required for Nanog to mediate ES cell self-renewal. Furthermore, deletion and point mutation analysis revealed that CD2 relies on at least seven aromatic amino acid residues to generate its potent transactivating activity. A mutant Nanog bearing alanine substitutions for these seven residues fails to confer LIF-independent self-renewal in mouse ES cells. Substitution of CD2 by the viral transactivator VP16 gave rise to Nanog-VP16, which is 10 times more active than wild-type Nanog in ES cells. Surprisingly, the expression of Nanog-VP16 in mouse ES cells induces differentiation and is thus unable to sustain LIF-independent self-renewal for mouse ES cells. Taken together, our results demonstrate that the CD2 domain of Nanog is a unique transactivator that utilizes aromatic residues to confer specific activity absolutely required for ES self-renewal.
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