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21.
Kien Tiek Wong Boris Brigljević Jeong Hyeon Lee So Yeon Yoon Seok Byum Jang Choe Earn Choong Inwook Nah Hyeongjun Kim Hyun-Seog Roh Sang Kyu Kwak Hankwon Lim Min Jang 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(1):2204336
This study focuses on the applicability of single-atom Mo-doped graphitic carbon nitride (GCN) nanosheets which are specifically engineered with high surface area (exfoliated GCN), NH2 rich edges, and maximum utilization of isolated atomic Mo for propylene carbonate (PC) production through CO2 cycloaddition of propylene oxide (PO). Various operational parameters are optimized, for example, temperature (130 °C), pressure (20 bar), catalyst (Mo2GCN), and catalyst mass (0.1 g). Under optimal conditions, 2% Mo-doped GCN (Mo2GCN) has the highest catalytic performance, especially the turnover frequency (TOF) obtained, 36.4 h−1 is higher than most reported studies. DFT simulations prove the catalytic performance of Mo2GCN significantly decreases the activation energy barrier for PO ring-opening from 50–60 to 4.903 kcal mol−1. Coexistence of Lewis acid/base group improves the CO2 cycloaddition performance by the formation of coordination bond between electron-deficient Mo atom with O atom of PO, while NH2 surface group disrupts the stability of CO2 bond by donating electrons into its low-level empty orbital. Steady-state process simulation of the industrial-scale consumes 4.4 ton h−1 of CO2 with PC production of 10.2 ton h−1. Techno-economic assessment profit from Mo2GCN is estimated to be 60.39 million USD year−1 at a catalyst loss rate of 0.01 wt% h−1. 相似文献
22.
Damping characteristics of a musical bell plays an important role in characterizing the musical sound. The total damping consists
of acoustical damping and internal damping. Acoustical damping depends upon resonating frequencies and vibration patterns
while internal damping is a material property. The acoustical damping of a vibrating structure is formulated via boundary
element method and finite element method using eigenmode decomposition. The design sensitivity of acoustical damping is derived
using an adjoint variable method of the eigenvalue problem. Design optimization of a musical bell is then performed in terms
of acoustical parameters. The goal of the optimization problem is to design a harmonically tuned bell with given acoustical
damping values. The proposed automated design process integrates finite element analysis, boundary element analysis, design
sensitivity analysis, mode-tracking algorithm and optimization module, seamlessly. It is demonstrated by numerical examples
to show practical applications. 相似文献
23.
Musun Kwak Jungwoo Park Jongho Jeon Kyoungri Kim Yoonseon Yi Donsik Choi Youngseok Choi Kyongdeuk Jeong 《Journal of the Society for Information Display》2011,19(9):576-582
Abstract— To understand the mechanism of the disclination defect of the liquid‐crystal (LC) phase, this study was conducted to directly analyze the polymer‐network (PN) structure of polymer‐stabilized blue phase (PSBP), which is minutely formed on all LC layers. The PN was examined after first removing the glass decap and then the LC. Important to note is that the removal of the glass decap did not affect or damage the PN structure. The PN was determined to be a stable structure without any change to the thickness of the layer. When removing the LC, both hexane and acetone solutions were used. Moreover, there was no structural deformation to the PN when using the hexane solution. The results of the study show that the actual size of the polymer chain is in fact 50–60 nm, five times larger than previous theories which estimated the size to be only 10 nm. In addition, this study confirmed that the pores between the PN are 100–200 nm. The PN structure was shown to be susceptible to change based on different heating temperatures. In summation, now that defect lines of a LC display (LCD) could be directly measured, further progress and development in the theoretical interpretations of the Kerr effect on PSBP can be realized. 相似文献
24.
Musun Kwak Hanrok Chung Hyukmin Kwon Daekyung Han Yoonsun Yi Jongho Jeon Sangmun Lee Chulgu Lee Sooyeol Cha 《Journal of the Society for Information Display》2010,18(12):1072-1077
Abstract— The surface‐friction characteristics of the post‐bake temperature were compared to that of the rubbing condition on VA‐mode alignment films (AFs) using frictional force microscopy (FFM). The surface roughness and the surface frictional force increased when the temperature was elevated. However, the frictional asymmetry could not be detected by the frictional loop due to the instability of the side‐chain molecular arrangement. For the inter‐influences of the total friction and surface roughness, the density of the side chain was changed and it was intentionally rubbed for evaluation. The results showed that the total friction was higher when the rubbing was stronger and side‐chain density lower, and the surface roughness also increased in the same manner. This can be explained by the potential interaction due to the curved structure of the side‐chain surface that establishes the probe that is scanned and the top surface layer. In order to confirm the influence of the pre‐tilt angle on the tilt of the side chain, a test cell was produced under the same conditions and evaluated. The results showed that the pre‐tilt‐angle decreased according to the difference in density of the side chain and strength of rubbing after injecting liquid‐crystal (LC). 相似文献
25.
Processors in embedded systems mostly employ cache architectures in order to alleviate the access latency gap between processors and memory systems. Caches in embedded systems usually occupy a major fraction of the implemented chip area. The power dissipation of cache system thus constitutes a significant fraction of the power dissipated by the entire processor in embedded systems. In this paper, we propose the compressed tag architecture to reduce the power dissipation of the tag store in cache systems. We introduce a new tag-matching mechanism by using a locality buffer and a tag compression technique. The main power reduction feature of our proposal is the use of small tag space matching instead of full tag matching, with modest additional hardware costs. The simulation results show that the proposed model provides a power and energy-delay product reduction of up to 27.8% and 26.5%, respectively, while still providing a comparable level of system performance to regular cache systems. 相似文献
26.
Gu-Min Jeong Hyun-Sik Ahn Sang-Il Choi Nojun Kwak Chanwoo Moon 《International Journal of Control, Automation and Systems》2010,8(1):141-148
In this paper, we propose a new pattern recognition method using feature feedback and present its application to face recognition.
Conventional pattern recognition methods extract the features employed for classification using PCA, LDA and so on. On the
other hand, in the proposed method, the extracted features are analyzed in the original space using feature feedback. Using
reverse mapping from the extracted features to the original space, we can identify the important part of the original data
that affects the classification. In this way, we can modify the data to obtain a higher classification rate, make it more
compact or abbreviate the required sensors. To verify the applicability of the proposed method, we apply it to face recognition
using the Yale Face Database. Each face image is divided into two parts, the important part and unimportant part, using feature
feedback, and the classification performed using the feature mask obtained from feature feedback. Also, we combine face recognition
with image compression. The experimental results show that the proposed method works well. 相似文献
27.
Jong Myoung Ko Choonjong Kwak Youngho Cho Chang Ouk Kim 《Expert systems with applications》2011,38(3):1583-1590
The Radio Frequency Identification (RFID) technology is gradually being adopted and deployed for product flow management in the supply chain. In order to track RFID-tagged products efficiently in the RFID-enabled, large-scale supply chain, this paper first presents the design of a product tracking system that can collaborate with the EPC Network, a suite of network services for RFID data management in the supply chain. Next, we explain a product monitoring procedure that is performed by comparing the actual path of a product with its planned path. Finally, we develop an adaptive product search algorithm based on a reinforcement learning technique to efficiently locate a product deviated from its planned path. Experiment results are provided to show the performance of the search algorithm. 相似文献
28.
Choonjong Kwak Jin Sung Choi Chang Ouk Kim Ick-Hyun Kwon 《Expert systems with applications》2009,36(5):9039-9045
In this research, we deal with VMI (Vendor Managed Inventory) problem where one supplier is responsible for managing a retailer’s inventory under unstable customer demand situation. To cope with the nonstationary demand situation, we develop a retrospective action-reward learning model, a kind of reinforcement learning techniques, which is faster in learning than conventional action-reward learning and more suitable to apply to the control domain where rewards for actions vary over time. The learning model enables the inventory control to become situation reactive in the sense that replenishment quantity for the retailer is automatically adjusted at each period by adapting to the change in customer demand. The replenishment quantity is a function of compensation factor that has an effect of increasing or decreasing the replenishment amount. At each replenishment period, a cost-minimizing compensation factor value is chosen in the candidate set. A simulation based experiment gave us encouraging results for the new approach. 相似文献
29.
Incidental Exposure,Selective Exposure,and Political Information Sharing: Integrating Online Exposure Patterns and Expression on Social Media 下载免费PDF全文
Brian E. Weeks Daniel S. Lane Dam Hee Kim Slgi S. Lee Nojin Kwak 《Journal of Computer-Mediated Communication》2017,22(6):363-379
Political information sharing in social media offers citizens opportunities to engage with news and express their political views, but how do different patterns of online political information exposure, including both incidental and selective exposure, affect sharing? Using two‐wave panel survey data collected in the United States, we examine the relationship between incidental and selective exposure and their consequent links to political information sharing, across different levels of strength of political party affiliation. Our results demonstrate that incidental exposure to counter‐attitudinal information drives stronger partisans to more actively seek out like‐minded political content, which subsequently encourages political information sharing on social media. The results highlight the need to consider both types of political information exposure when modeling citizens' political behavior online. 相似文献
30.
Characterisation of a desktop LCD projector 总被引:3,自引:0,他引:3
A typical desktop LCD projector was characterised. Having determined the optimum settings of the brightness and contrast controls, measurements were made with a spectroradiometer to establish the additivity of the primaries, inter-channel dependence, colour gamut, tone scale, contrast, spatial non-uniformity, temporal stability and viewing angle variation. Four mathematical models were compared for their accuracy in predicting the colours generated by the display for arbitrary signal inputs. A new model was developed for the S-shaped electro-optical transfer function of the LCD device, and was extended to predict the anomalous colour tracking of the primaries. 相似文献