Subjects: Nuclear Science and Technology >> Engineering of Nuclear Power submitted time 2024-02-01
Abstract： Betavoltaic nuclear batteries offer a promising alternative energy source that harnesses the power of beta particles emitted by radioisotopes. To satisfy the power demands of microelectromechanical systems (MEMS), 3D structures have been proposed as a potential solution. Accordingly, this paper introduces a novel 3D 63Ni-SiC-based P+PNN+ structure with a multi-groove design, avoiding the need for PN junctions on the inner surface, and thus reducing leakage current and power losses. Monte Carlo simulations were performed considering the fully coupled physical model to extend the electron–hole pair generation rate to a 3D structure, enabling the efficient design and development of betavoltaic batteries with complex 3D structures. As a result, the proposed model produces the significantly higher maximum output power density of 19.74 µW/cm2 and corresponding short-circuit current, open-circuit voltage, and conversion efficiency of 8.57 µA/cm2, 2.45 V, and 4.58%, respectively, compared with conventional planar batteries. From analysis of the carrier transport and collection characteristics using the COMSOL Multiphysics code, we provide deep insights regarding power increase, and elucidate the discrepancies between the ideal and simulated performances of betavoltaic batteries. Our work offers a promising approach for the design and optimization of high-output betavoltaic nuclear batteries with a unique 3D design, and serves as a valuable reference for future device fabrication.
Subjects: Linguistics and Applied Linguistics >> Linguistics and Applied Linguistics submitted time 2023-11-01
Abstract： In a typical SL task, participants are first exposed to a nonsensical artificial language for 5~10 mins and then asked to finish a 2 alternative forced choice task (2AFC). Transitional probabilities (TPs), the core concept in SL, represent the predictably between syllables. In a given artificial language, syllables within a target word occur together more frequently, resulting in higher TPs than those of the syllables that span across word boundaries. The latter is referred to as partwords and consist of lower TPs. After the exposure phase, participants enter the test phase and are presented with a partword and target word in each trial of the 2AFC task. If the accuracy across participants is higher than chance level, it is assumed that learning has occurred. However, studies have also shown that factors other than TPs, such as word token frequency, word length variations (or the lack thereof) also impact SL performance in such tasks. To date, these factors as well as their interactive effects remain under studied.
In the experiment one, we aimed to investigate whether TPs affect SL learning performance when controlling for target words’ and partwords’ token frequencies. In doing so, we created the artificial language by randomizing the order of two trisyllabic words and two disyllabic words. During the 2AFC task, three types of items (target word, partword, and nonword) were paired together, with two items in equal length in each trial. There were 24 trials in the test. 40 native Mandarin monolinguals participated in the experiment; they first listened to the artificial language for 5mins and then finished the 2AFC task. In the experiment two, an artificial language was generated with 10 syllables and presented in exposure phase, to examine whether experiment one’s learning effect came from the TP or participants’ prior language bias.
Results in experiment one showed that the accuracy of all trials was significantly higher than chance (0.5) at the group level, suggesting that participants were able to segment the artificial language of mixed word lengths. Participants were also marginally better at choosing target words over partwords, and partwords over nonwords. To investigate the independent effect of TP in SL, we subset the data by word length and found that participants’ accuracy choosing trisyllabic target words over partwords was marginally lower than their choosing disyllabic target words over partword, which suggests that disyllabic words confer advantage in SL for this group of participants. In addition, participants’ accuracy in choosing trisyllabic partwords over nonwords was significantly higher than that of disyllabic target partwords over nonwords. In the experiment two, there were no significant learning effect in any levels when the statistical information was absent.
A series of results across two behavior experiments highlight the unique contribution from TPs alone, since accuracy was assessed by controlling for word token frequency and word length. Thus, the present study suggests that TP exerts effect on verbal SL performance independent of word token frequency. Further studies should take into account more types of statistical rule such as mutual information and backward TP.
Peer Review Status:
Awaiting Review
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-09-08
Abstract： Purposes Through the analysis of capital anomie intervention in the chaos of international academic journal publishing, this paper provides research reference for the standardized management and ethical governance of academic journal publishing in China under the Open access model. Methods Combining with Cabells' predatory journal report and IAP predatory journal case data, from the perspective of capital misconduct intervention, the paper reveals the reasons and ethical issues of the current chaos in the international academic journal publishing field. Findings International academic journals that have been intervened by capital misconduct exhibit publishing chaos such as false peer reviews, cloning of well-known journals, teasing academic research, precise targeted harvesting, and kidnapping submissions for compensation. From the perspective of capital misconduct intervention, there are ethical issues such as intensified ethical misconduct, differentiation of academic norms, targeted resource plundering, and distortion of academic values. Conclusion Clarifying the essence of the problem focuses on source governance, comprehensively improving the cognitive ability of researchers to identify academic misconduct in the field of academic publishing, creating correct academic values, and actively resisting the temptation of misconduct and profit with scientific integrity.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： Targeted poverty alleviation involved by universities is an important part of the poverty alleviation strategy in China, which reflects the responsibility of universities to serve the national strategy. This study has reviewed the specific practices, experiences and some achievements of poverty alleviation works conducted by University of Science and Technology of China (USTC) in Liuzhi Special District, Guizhou Province, China. According to actual situation of Liuzhi, USTC gives full play to the advantages of education and research, and carries out a series of poverty alleviation assistances by supporting party building, education, industrial development and sales of agricultural products. Over the past five years, USTC summed up its experience continuously and conducted a number of distinctive projects, which help Liuzhi achieve the goal of poverty alleviation and lay a solid foundation for rural revitalization.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The Ni- based superalloys are widely used as microstructural components of modern turbine engines due to its good high temperature strength, good fatigue and creep property and excellent hot-corrosion resistance. In order to increase their high temperature strength, more and more refractory elements, such as W and Mo, are added into these alloys while Cr content gradually decreases. During long-term aging, these alloys generally experience various microstructural changes, including coarsening of g' phase coarsening, formation of a continuous grain boundary (GB) carbide network, precipitation topologically close-packed (TCP) phase, and degeneration of MC carbide. However, there is limited available data about the effect of (W+Mo)/Cr ratios on the microstructural evolution of Ni- based superalloys. In this work, the cast Ni- based superalloys with different (W+Mo)/Cr ratios (mass ratios) are fabricated by vacuum induction furnace. After standard heat treated (1110 ℃, 4.5 h, air cooling+ 750 ℃, 10.5 h, air cooling), they are thermally exposed at 850 ℃ for different times. The stress-rupture tests are operated under the condition of 800 ℃, 294 MPa. Effects of (W+Mo)/Cr ratios on the microstructure evolutions and mechanical properties are investigated by the combination of OM, SEM, TEM and stress-rupture tests. The experiment results show that the (W+Mo)/Cr ratio has no obvious influence on the standard heat treated microstructure, which is mainly composed of g matrix, g' phase, MC carbide and secondary carbides distributing at grain boundaries. During long-term thermal exposure, the microstructure evolutions occur by g' phase coarsening, TCP phases formation, MC degeneration and grain boundary coarsening. The g' phase coarsening behavior is not affected obviously by the (W+Mo)/Cr ratio. However, the amount of TCP phases decreases significantly with decreasing of (W+Mo)/Cr ratio and the type of TCP phases transforms from m phase to coexist of m and s phases when (W+Mo)/Cr ratio decreases from 0.55 to 0.37. There are no TCP phases observed in the sample with (W+Mo)/Cr ratio of 0.22. The thermal stability of MC carbide is reduced obviously and the grain boundaries coarsen more severely by the decrease of (W+Mo)/Cr ratio. The degradation of stress-rupture property is attributed to the coarsening of g'phase and grain boundaries and the formation of TCP phases. Combined with the effect of (W+Mo)/Cr ratio on the solid solution strengthening, microstructure evolution and stress-rupture property, it can be concluded that the optimumstress-rupture property can be obtained when the (W+Mo)/Cr ratio is about 0.37.
Subjects: Materials Science >> Materials Science (General) submitted time 2022-06-20
Li, Xiangyan
Li, Xiaolin
Zhang, Yange
Xu, Yichun
Wu, Xuebang
Xie, Zhuoming
Wang, Xianping
Pan, Bicai
Liu, Changsong
Fang, Qianfeng
Chen, Junling
Luo, Guangnan
Wang, Zhiguang
Abstract：
The behavior of nano-voids composed of vacancies (Vs) at grain boundaries (GBs) is fundamental to the design of the radiation tolerance of poly-crystalline metals (PCs) via GB engineering. In this study, based on differential evolution, a framework for determining the stable structure of GB nano-voids is developed. Combining the framework with multiscale simulations, we elucidate the vacancy-accumulation and GB void
formation mechanism under irradiation. A GB-structure dependent picture is revealed. At special coincidence-site-lattice (CSL) GBs of Ʃ5(310) and Ʃ5(210) with a medium V-GB binding energy, the V could be reemitted from the GB and also has driving force to be clustered at the GB, developing particularly stable V-clusters from a linear configuration to a platelet and finally to three-dimensional void that has large strain fields in iron with small bulk modulus and a bulk-void alike structure in the GB with large bulk modulus. A group of vacancies reconstruct their positions during the growth. The ripening is also mediated by the mobility of small V-clusters in addition to free Vs. General high-angle and low-angle GBs trap Vs efficiently, where V-clusters only align one-dimensionally or hardly nucleate. Based on the bonding among the vacancies and their neighboring atoms of a nano-void, we propose a high-accuracy predictive linear energetic model applied to the nano-void both at the iron/molybdenum/tungsten GBs and in the grain interior. The model captures the anisotropic feature of a nano-void and reproduces the oscillated vacancy energy level near a nano-void, showing distinct advantages over conventional continuum model and Wulff construction based energy model. Finally, the collective behavior of multiple GBs plays a role in the GB void formation. The present work offers fundamental mechanistic insights to GB nano-void formation and growth and sets a key step towards GB-void prevention in PCs by reducing the fraction of special CSL-GBs.
Peer Review Status:Awaiting Review
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2022-06-06 Cooperative journals: 《计算机应用研究》
Abstract： Cluster assignment is a compiler optimization that plays an important role in performance of programs. However, the existing algorithms only work on straight-line program area, and is difficult to be optimal. Aiming at these problems, this paper proposed a unified cluster assignment and instruction scheduling method based on integer linear programming. This method used zero-one decision variables to represent cluster assignment, local instruction scheduling and global scheduling of inter-cluster transfer instructions, and formulated dependency and processor resources competition between instructions into linear constraints, eventually got an integer linear programming model whose objective is to minimize the estimated execution time of the function. Experimental results show that the cluster assignment and scheduling scheme from solving the model significantly outperforms the existing algorithms on accelerating programs, and the time required to solve the model is acceptable.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2022-05-18 Cooperative journals: 《计算机应用研究》
Abstract： Reinforcement learning method has many advantages in solving the robot manipulation problems. However, the traditional reinforcement learning algorithm faces the difficulty of sparse reward, and the policy is difficult to be directly applied to the reality. In order to improve the success rate of policy migration from simulation to reality, this paper proposes a goal-based domain randomization method: The method uses the goal-based reinforcement learning algorithm to train the model, which can effectively deal with the sparse reward of robot manipulation tasks, and the policy can run well in the simulation environment. At the same time, the method uses the goal-conditioned domain randomization algorithm, which has a good performance on improving the universality of policy and overcoming the reality gap between simulation and reality. The policy in simulation is easy to migrate to reality and execute successfully. The results show that the reinforcement learning algorithm using the goal-based domain randomization method helps to improve the success rate of policy migration from simulation to reality.
Subjects: Electronics and Communication Technology >> Electron Technology submitted time 2018-06-25
Abstract： "
Peer Review Status:Awaiting Review
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. submitted time 2017-09-20
Abstract：维生素K2（VK2）是一类脂溶性甲萘醌类化合物，根据其侧链中异戊烯基单元个数的不同，可用Menaquinone-n (MK-n, n=1~14) 表示。研究表明，VK2具有促凝血、预防及治疗骨质疏松症、帕金森症及心血管疾病等生理功能。利用微生物发酵生产的VK2具有全反式侧链、生物相容性高等优势，作为食品和药品更易于被消费者接受。但是，其下游分离纯化过程中存在产物浓度低、成分复杂、纯化工艺繁琐、产品得率低等诸多问题，目前还鲜有高纯度VK2制备工艺的报道。 黄杆菌可以合成MK-5和MK-6等VK2同系物，本研究针对其发酵产物的特点，开发了一整套相应的分离纯化工艺。首先通过膜浓缩和离心的方法快速获得黄杆菌菌体，菌体经干燥后，采用甲醇进行固-液萃取，固-液比为4:1（ml/g），萃取时间为20分钟，连续萃取3次，获得的VK2甲醇萃取液的萃取得率可达99.1%以上。然后，通过大孔树脂吸附层析,以甲醇/二氯甲烷=1/1（V/V）为洗脱液，可获得纯度约为15%的VK2粗品；再经过分子筛层析，在高径比为255:15，二氯甲烷为流动相时，可获得纯度约为57%的VK2低纯度产品；之后，经过反相硅胶柱层析，分别以甲醇/二氯甲烷=9:1,6:1,3:1（V/V）依次进行梯度洗脱，即可分离并纯化各VK2的同系物，其HPLC纯度均达90%以上。最后采用冷却结晶的方法制得一系列淡黄色晶体。通过质谱、红外光谱及核磁共振氢谱检测，均符合相应的VK2光谱特征，确定其为MK-5和MK-6晶体。经HPLC检测，MK-5和MK-6晶体纯度分别达到98.0%和99.3%。经多次重复实验后，表明全套工艺稳定，产物回收率可以达到88%以上。各填料经过15次重复利用后，其对VK2的纯度及回收率无明显的影响。 本研究所建立的从黄杆菌发酵液中提取和纯化VK2的方法具有工艺简单、处理能力大、产品纯度及得率高等优点，其为实现VK2的生物制备及其产业化奠定了优化的基础。在整个的提取、纯化及结晶的过程中，只有两种有机溶剂被使用，这更有利于有机溶剂的回收利用和VK2的规模化生产。
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