Abstract The goal of this paper is to illustrate college students' levels of sophistication of their spectroscopic representations (SRs). For example, a photon is drawn as a wavy line, which might be used to enhance their atomic models (AMs). Study 1 was a quantitative study in which 70 students, enrolled in first semester general chemistry, drew or described their own model of the atom. Despite the fact that they had just completed a unit on atomic structure, only 30.6% of these students were classified as having a good understanding of the Bohr AM. Most of these students, 93.8%, incorporated SRs into their models. Conversely, only 41.2% of those who had a moderate AM understanding and only 5% of those with a poor AM understanding used SR in their AMs. Study 2 was a qualitative study in which 10 volunteers, enrolled in the same course but during a different semester, interacted with a multimedia instructional package and with a tutor. Interviews with two students were selected for in‐depth analyses. Each one enhanced their own AM by adding dynamic SR to their original AMs. 相似文献
The advances in deep reinforcement learning (DRL) have shown a great potential in solving physical layer-related communication problems. This paper investigates DRL for the relay selection in buffer-aided (BA) cooperative networks. The capability of DRL in handling highly-dimensional problems with large state and action spaces paves the way for exploring additional degrees-of-freedom by relaxing the restrictive assumptions around which conventional cooperative networks are usually designed. This direction is examined in our work by advising and analyzing advanced DRL-based BA relaying strategies that can cope with a variety of setups in multifaceted cooperative networks. In particular, we advise novel BA relaying strategies for both parallel-relaying and serial-relaying systems. For parallel-relaying systems, we investigate the added value of merging packets at the relays and of activating the inter-relay links. For serial-relaying (multi-hop) systems, we explore the improvements that can be reaped by merging packets and by allowing for the simultaneous activation of sufficiently-spaced hops. Simulation results demonstrate the capability of DRL-based BA relaying in achieving substantial improvements in the network throughput while the adequate design of the reward/punishment in the learning process ensures fast convergence speeds. 相似文献
Cooperative communication technology has realized the enhancement in the wireless communication system’s spectrum utilization rate without resorting to any additional equipment; additionally, it ensures system reliability in transmission, increasingly becoming a research focus within the sphere of wireless sensor networks (WSNs). Since the selection of relay is crucial to cooperative communication technology, this paper proposes two different relay selection schemes subject to deep reinforcement learning (DRL), in response to the issues in WSNs with relay selection in cooperative communications, which can be summarized as the Deep-Q-Network Based Relay Selection Scheme (DQN-RSS), as well as the Proximal Policy Optimization Based Relay Selection Scheme (PPO-RSS); it further compared the commonly used Q-learning relay selection scheme (Q-RSS) with random relay selection scheme. First, the cooperative communication process in WSNs is modeled as a Markov decision process, and DRL algorithm is trained in accordance with the outage probability, as well as mutual information (MI). Under the condition of unknown instantaneous channel state information (CSI), the best relay is adaptively selected from multiple candidate relays. Thereafter, in view of the slow convergence speed of Q-RSS in high-dimensional state space, the DRL algorithm is used to accelerate the convergence. In particular, we employ DRL algorithm to deal with high-dimensional state space while speeding up learning. The experimental results reveal that under the same conditions, the random relay selection scheme always has the worst performance. And compared to Q-RSS, the two relay selection schemes designed in this paper greatly reduce the number of iterations and speed up the convergence speed, thereby reducing the computational complexity and overhead of the source node selecting the best relay strategy. In addition, the two relay selection schemes designed and raised in this paper are featured by lower-level outage probability with lower-level energy consumption and larger system capacity. In particular, PPO-RSS has higher reliability and practicability. 相似文献
Using the eigenmode analysis, we compute the Cooperative Lamb Shift (CLS) as a function of time from the vector photon model for a system of two-level atoms in a slab-geometry for forward and backward emission in two initial states of weak excitation and complete inversion. 相似文献
X‐ray detectors that combine two‐dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time‐gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter‐scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time‐ and location‐tagged events at rates greater than 107 events per cm2. Time‐gating can be used for improved dynamic range. 相似文献
The spinning riffler is often used to obtain small sub‐samples of a powder, but the move to the use of finer powders in industrial situations presents obstacles to the use of the spinning riffler. 相似文献
To control the temporal profile of a relativistic electron beam to meet requirements of various advanced scientific applications like free-electron-laser and plasma wakefield acceleration, a widely-used technique is to manipulate the dispersion terms which turns out to be one-to-many problems. Due to their intrinsic one-to-many property, current popular stochastic optimization approaches on temporal shaping may face the problems of long computing time or sometimes suggesting only one solution. Here we propose a real-time solver for one-to-many problems of temporal shaping, with the aid of a semi-supervised machine learning method, the conditional generative adversarial network (CGAN). We demonstrate that the CGAN solver can learn the one-to-many dynamics and is able to accurately and quickly predict the required dispersion terms for different custom temporal profiles. This machine learning-based solver is expected to have the potential for wide applications to one-to-many problems in other scientific fields. 相似文献
The machining process is primarily used to remove material using cutting tools. Any variation in tool state affects the quality of a finished job and causes disturbances. So, a tool monitoring scheme (TMS) for categorization and supervision of failures has become the utmost priority. To respond, traditional TMS followed by the machine learning (ML) analysis is advocated in this paper. Classification in ML is supervised based learning method wherein the ML algorithm learn from the training data input fed to it and then employ this model to categorize the new datasets for precise prediction of a class and observation. In the current study, investigation on the single point cutting tool is carried out while turning a stainless steel (SS) workpeice on the manual lathe trainer. The vibrations developed during this activity are examined for failure-free and various failure states of a tool. The statistical modeling is then incorporated to trace vital signs from vibration signals. The multiple-binary-rule-based model for categorization is designed using the decision tree. Lastly, various tree-based algorithms are used for the categorization of tool conditions. The Random Forest offered the highest classification accuracy, i.e., 92.6%.
Analyser‐based imaging expands the performance of X‐ray imaging by utilizing not only the absorption properties of X‐rays but also the refraction and scatter rejection (extinction) properties. In this study, analyser‐based computed tomography has been implemented on imaging an articular cartilage sample, depicting substructural variations, without overlay, at a pixel resolution of 3.6 µm. 相似文献
With the increasing energy demands for electronic devices and electrical vehicles, anode materials for lithium‐ion batteries with high specific capacity, good cyclic and rate performance become one of the focal areas of research. A class of them is the copper‐based nanomaterials that have thermal and chemical stability, high theoretical specific capacity, low price and environment friendliness. Now this kind of nanomaterials has been recognized as one of the critical materials for lithium‐ion batteries due to the predicted future market growth. Current status of different copper‐based materials which produced already are discussed. In this review, comprehensive summaries and evaluations are given in synthesis strategies, tailored material properties and different electrochemical performance. Recent progress of general copper‐based nanomaterials for lithium‐ion batteries is carefully presented. 相似文献
Fullerene‐structural carbon‐based dots (f‐CDs) are synthesized for the first time by chemically oxidizing fullerene molecules (C60) using concentrated HNO3. The lateral sizes of the f‐CDs distribute in the range of 7–20 nm, and the heights mainly range from 0.4 to 1.3 nm with an average value of 0.7 nm. The presence of massive pentagonal carbon units makes the f‐CDs different from most of graphitic‐CDs in structure and morphology. The f‐CDs exhibit unique luminescent properties such as photoluminescence (PL) and electrochemiluminescence. Based on the investigation of the UV–vis absorption and luminescent properties, a novel and reasonable model is proposed for the PL mechanism of f‐CDs. Furthermore, the obtained f‐CDs show low cytotoxicity and have potential application in cell imaging. 相似文献
Polyaniline (PANI) has been deposited on a carbon template by chemical oxidation of aniline chloride in acidic aqueous medium using sodium persulfate as oxidant. Two kinds of templates were used: array of aligned multiwall carbon nanotubes (CNTs) grown on silicon substrate and ordered mesoporous carbon (OMC) material. Electronic structure of composites was examined using near‐edge X‐ray absorption spectroscopy and X‐ray photoelectron spectroscopy. Analysis of the spectra showed that PANI developed on the CNT surface is mainly protonated while it contains a marked amount of imine (N ) nitrogen when deposited into the porous of OMC. Testing of electrochemical cell indicated enhancement of performance of composite electrodes as compared with unsupported PANI.
The deployment of Small Cells in fourth generation (4G) communication systems is aimed at providing significant capacity improvements and higher availabilities. However, the design of Small Cell systems in indoor environments is especially challenging due to high shadowing attenuation induced by clutter and human blockage. This paper studies node cooperation and multiple relaying and proposes novel analytical formulas for the outage probability of cooperative Small Cells suffering from shadowing. The channel fading gains are modeled as correlated lognormal random variables, in order to reflect the properties of indoor propagation environments. Various cooperative strategies are considered, taking into account the use of one or two relays and different receiver combining techniques. In addition, the relative performance of each cooperative configuration and the benefit of cooperation over non-cooperation are investigated. Finally, interesting and useful insights are produced regarding the impact of the correlated lognormal environment parameters on the configuration of cooperative Small Cells. 相似文献
To clarify the contrasting impurity effects of Mn and Zn dopants on the critical temperature of optimally doped Ba0.5K0.5Fe2As2 superconductors, extended X‐ray absorption fine‐structure spectroscopy was implemented at the Fe and As K‐edge. In Mn‐doped compounds a gradual deviation of the symmetric FeAs4 tetrahedron and weakening of the Fe—As bond was observed. Conversely, in Zn‐doped compounds the perfect FeAs4 tetrahedron is maintained and the Fe—As bond is rigid. The local structural details are consistent with the development of superconductivity in these two systems, suggesting a significant role played by the topology of the FeAs4 tetrahedron and rigidness of the Fe—As bond in Mn/Zn‐doped Ba0.5K0.5Fe2As2 superconductors. 相似文献
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