P型 α-多孔 SiC. 的光致發光光潽硏究

이기환,김영유,두영뢰,우배매 公州大學校 基礎科學硏究所 1998 自然科學硏究 Vol.7 No.-

The photoluminescence (PL) spectra from p-type a-porous silicon carbides prepared under UV photo-assisted process and under dark-current condition are investigated in detail. Emission bands with peak energies of 2.35, 2.50, 2.70, and 3.43 are resolved. The PL stability in tune and the PL difference arising from different tuning excitation energies are studied. It is found that the PL spectra of the a-porous silicon carbide depend strongly on the preparation conditions for electrochemical etching. The PL spectrum of the sample prepared under photo-assisted process has an enhancement on the lower-energy side of the emission; on the contray, another one under dark-current condition has an enhancement at the higher energy side, and the former stability is better than the latter one, and the latter PL intensity decreases with the increase of the time in the air. The reasons about these differences are discussed.

Frequent Items Mining Algorithm Over High Speed Network Flows Based on Double Hash Method

Lei Bai,Chao Chen 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.5

In the high-speed backbone network, with the increasing speed of network link, the number of network flows increase rapidly. Meanwhile, with restrictions on hardware computing and storage resources, so, how to identify and measure large flows timely and accurately in massive data become a hot issue in high speed network flow measurement area. In this paper, we propose a new algorithm based on double hash algorithm to realize large flow frequent items identification, according to the defect of MF algorithm which produces false positive easily and frequent updates to bring the huge pressure to the system. The complexity and false positive rate of the algorithm was analyzed. The effect of large flow frequent items statistical accuracy and discard rate for parameter configuration was analyzed through simulation. The theoretical analysis and the simulation result indicate that compare to MF algorithm, our algorithm can identify large flow frequent items more accurately, and satisfies the need of actual measurement.

A Study on the Modeling of Flyback Converter for LED Power Based on State-space Averaging

Lei Bai,배진용 한국동력기계공학회 2023 동력시스템공학회지 Vol.27 No.3

Switch mode power supply is a high-frequency electrical energy conversion apparatus that is widely used in many home appliances, industrial products, and military applications. In this study, a Flyback converter with LED as the load is modeled. To verify the system stability, a pulse-width modulated switching control circuit is evolved into a small-signal model with linear characteristics based on state-space averaging. Through MATLAB simulation results, it is shown that the current-control mode is superior to the voltage-control mode. A DC 46 V LED power output closed-loop feedback control switching power supply is fabricated, and the experimental and simulation results verify the superiority of the design. From this study, the current control mode is suitable for the use in flyback LED switching power supplies because the current mode method shows more stable characteristics with GM = 11.975 dB and PM = 46.073°.

Differences in the mandibular premolar positions in Angle Class I subjects with different vertical facial types

Jun Duan,Feng Deng,Wan-Shan Li,Xue-Lei Li,Lei-Lei Zheng,Gui-Yuan Li,Yan-Jie Bai 대한치과교정학회 2015 대한치과교정학회지 Vol.45 No.4

Objective: To compare the positions of the mandibular premolars in Angle Class I subjects according to vertical facial type. The results will provide a theoretical basis for predicting effective tooth movement in orthodontic treatment. Methods: Cephalometric parameters were determined using cone-beam computed tomography in 120 Angle Class I subjects. Subjects were categorized as short, normal, and long face types according to the Frankfort mandibular angle. Parameters indicating the position of the mandibular right premolars and the mandible were also measured. Results: The angle between the mandibular first premolar axis and buccal cortex, the distance between the root apex and buccal cortex, angle of vestibularization, arc of vestibularization, and root apex maximum movable distance were significantly greater in the short face type than in the long and norm face types. The angle between the mandibular second premolar axis and buccal cortex, the distance from root apex to buccal cortex, and the arc of vestibularization were significantly greater in the short face type than in the normal face type. Conclusions: There are significant differences in the mandibular premolar positions in Class I subjects according to vertical facial type.

Weibo Disaster Rumor Recognition Method Based on Adversarial Training and Stacked Structure

Lei Diao,Zhan Tang,Xuchao Guo,Zhao Bai,Shuhan Lu,Lin Li 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.10

To solve the problems existing in the process of Weibo disaster rumor recognition, such as lack of corpus, poor text standardization, difficult to learn semantic information, and simple semantic features of disaster rumor text, this paper takes Sina Weibo as the data source, constructs a dataset for Weibo disaster rumor recognition, and proposes a deep learning model BERT_AT_Stacked LSTM for Weibo disaster rumor recognition. First, add adversarial disturbance to the embedding vector of each word to generate adversarial samples to enhance the features of rumor text, and carry out adversarial training to solve the problem that the text features of disaster rumors are relatively single. Second, the BERT part obtains the word-level semantic information of each Weibo text and generates a hidden vector containing sentence-level feature information. Finally, the hidden complex semantic information of poorly-regulated Weibo texts is learned using a Stacked Long Short-Term Memory (Stacked LSTM) structure. The experimental results show that, compared with other comparative models, the model in this paper has more advantages in recognizing disaster rumors on Weibo, with an F1_Socre of 97.48%, and has been tested on an open general domain dataset, with an F1_Score of 94.59%, indicating that the model has better generalization.

Experimental research on local buckling of BS700 high-strength steel thin-walled box-section members under axial compression

Lei Gao,Fei Shao,Linyue Bai,Xingkun Xie,Xiaohui He 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

In this study, the ultimate bearing capacity and local buckling failure mode of members were investigated, and the results were compared to the predicted values of the existing steel structures design code. The results indicated that the failure mode of the specimen was local buckling. Finite element model is verified using experimental results. FE model is capable of predicting the behaviour of specimens and it is used for further numerical analyses. Experimental results are compared with recommendations of the steel structures design code of GB50017-2017, ANSI/AISC 360-16 and Eurocode 3. It is observed that the 83.3 % of the test bearing capacity are slightly higher than the predictions of existing codes with a variance of 5 %. It is concluded that the provisions of existing codes can meet the design requirements. However, the number of tests is limited and further related experimental and FE numerical studies are required.

Auto-Covariance Analysis for Depth Map Coding

( Lei Liu ),( Yao Zhao ),( Chunyu Lin ),( Huihui Bai ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.9

Efficient depth map coding is very crucial to the multi-view plus depth (MVD) format of 3-D video representation, as the quality of the synthesized virtual views highly depends on the accuracy of the depth map. Depth map contains smooth area within an object but distinct boundary, and these boundary areas affect the visual quality of synthesized views significantly. In this paper, we characterize the depth map by an auto-covariance analysis to show the locally anisotropic features of depth map. According to the characterization analysis, we propose an efficient depth map coding scheme, in which the directional discrete cosine transforms (DDCT) is adopted to substitute the conventional 2-D DCT to preserve the boundary information and thereby increase the quality of synthesized view. Experimental results show that the proposed scheme achieves better performance than that of conventional DCT with respect to the bitrate savings and rendering quality.

Soluble Epoxide Hydrolase Inhibitory and Anti-inflammatory Components from the Leaves of <i>Eucommia ulmoides</i> Oliver (Duzhong)

Bai, Meng-Meng,Shi, Wei,Tian, Jun-Mian,Lei, Ming,Kim, Jang Hoon,Sun, Ya Nan,Kim, Young Ho,Gao, Jin-Ming American Chemical Society 2015 Journal of agricultural and food chemistry Vol.63 No.8

<P><I>Eucommia ulmoides</I> leaves have been used as a functional food and drink in China. The purpose of this study was to identify the bioactive constituents with soluble epoxide hydrolase (sEH) inhibitory activity and anti-inflammatory properties. Twenty-seven known compounds (<B>1</B>–<B>27</B>) were isolated from the leaves of <I>E. ulmoides</I> Oliver, and their structures were identified by NMR and ESIMS analysis; three of these, 2,5-dimethoxy-3-glucopyranosyl cinnamic alcohol (<B>11</B>), foliasalacioside E<SUB>2</SUB> (<B>26</B>), and icariside F<SUB>2</SUB> (<B>27</B>), were obtained from this plant for the first time. Compounds <B>1</B>–<B>7</B> exhibited soluble epoxide hydrolase (sEH) inhibitory activity at 100 μM; among them, quercetin (<B>1</B>) and kaempferol (<B>5</B>) displayed potential activities with IC<SUB>50</SUB> values of 22.5 ± 0.9 and 31.3 ± 2.6 μM, respectively, with noncompetitive inhibition mode. Nuclear factor kappa B (NF-κB) inhibitory activity of the isolated compounds was evaluated by the NF-κB liciferase assay in HepG2 cells. Compounds <B>1</B>, <B>9</B>, <B>20</B>, and <B>27</B> displayed potent NF-κB inhibitory effects, with IC<SUB>50</SUB> values of 15.14 ± 2.29, 15.23 ± 2.34, 16.88 ± 2.17, and 16.25 ± 2.19 μM, respectively, whereas other compounds showed weak inhibition of NF-κB transcriptional activity ranging from 17.54 to 92.6 μM. A structure–activity relationship of flavonoids <B>1</B>–<B>9</B> was also discussed. The results obtained in this work might contribute to the understanding of pharmacological activities of <I>E. ulmoides</I> leaves and further investigation on its potential application values for food and drug.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2015/jafcau.2015.63.issue-8/acs.jafc.5b00055/production/images/medium/jf-2015-00055j_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jf5b00055'>ACS Electronic Supporting Info</A></P>

Wing weight estimation considering constraints of structural strength and stiffness in aircraft conceptual design

Bai, Chen,Mingqiang, Luo,Zhong, Shen,Zhe, Wu,Yiming, Man,Lei, Fang The Korean Society for Aeronautical and Space Scie 2014 International Journal of Aeronautical and Space Sc Vol.15 No.4

According to the requirement of wing weight estimation and frequent adjustments during aircraft conceptual design, a wing weight estimation method considering the constraints of structural strength and stiffness is proposed to help designers make wing weight estimations rapidly and accurately. This method implements weight predictions on the basis of structure weight optimization with stiffness constraints and strength constraints, which include achievement of wing shape parametric modeling, rapid structure layout, finite element (FE) model automated generation, load calculation, structure analysis, weight optimization, and weight computed based on modeling. A software tool is developed with this wing weight estimation method. This software can realize the whole process of wing weight estimation with the method and the workload of wing weight estimation is reduced because much of the work can be completed by the software. Finally, an example is given to illustrate that this weight estimation method is effective.

Sustained ocular delivery of desmopressin acetate via thermoreversible in situ gel formulation: preparation and in vitro/in vivo evaluation

Lei Fang,Zhang Huimin,Luo Rui,Fei Qingsong,Bai Luyu,He Ning 한국약제학회 2022 Journal of Pharmaceutical Investigation Vol.52 No.5

Purpose The present study was designed to formulate a thermoreversible in situ gel system for sustained ocular delivery of desmopressin acetate (DDAVP) for the treatment of polyuria. Methods The cold method was employed for the preparation of in situ gel formulations using different levels of poloxamer 407 (F-127) and carboxymethyl chitosan (CMCTS). The optimal formulation was selected based on gelation temperature, rheological behavior, and in vitro drug release, and further evaluated by thermal, ocular irritation, residence time, in vivo pharmacokinetics, and pharmacodynamic analyses. Results The optimal formulation, composed of F-127 (20%) and CMCTS (1.5%), showed appropriate fluidity at room temperature (25 °C) and transitioned to semisolid gels at physiological temperature (34 °C). The optimal gels showed pseudoplastic fluid properties and favorable thixotropy characteristics in rheological tests. Differential scanning calorimetry analysis revealed even dispersal of DDAVP in the matrix of gels. Results from in vivo studies demonstrated that the newly prepared gel successfully prolonged the residence time of DDAVP, improved ocular bioavailability, and exerted the same antidiuretic effect as ophthalmic drops. Conclusion The developed thermoreversible ophthalmic in situ gel of DDAVP presents a promising formulation for the treatment of polyuria.