P2P 캐싱을 기반으로 한 효율적인 브로드캐스트 스트리밍 기법

이치훈,계이기,정인범,최창열,최황규 강원대학교 정보통신연구소 2006 정보통신논문지 Vol.10 No.-

Video-on-Demand is undoubtedly a promising technology for many important applications. Several periodic broadcast techniques have been proposed for the cost-effective implementation of such systems. However, there is a server delay for all of them. To address the shortcoming, we present a new scheme improving the staggered broadcasting by jointly using prefix caching scheme of VOD system in P2P environments. In thins paper, each client plays a role in the first segment staggered broadcasting server to serve the prefix stream to other clients that request the same video stream. The buffer can be empty after the client has served the following client. As a result, we are able to achieve no service latency time and the low buffer space.

Experiment and molecular simulation for liquid phase adsorption of triethylenetetramine on activated carbon: equilibrium, kinetics, thermodynamics and molecular behavior

Qi Zhang,Xiang C. Ma,Chang He,Qing L. Chen,Bing J. Zhang 한국탄소학회 2023 Carbon Letters Vol.33 No.7

Modification of the surface of raw activated carbon using chemical solvents can significantly improve the adsorption performance of activated carbon. Triethylenetetramine is one of the most important chemical solvents used to modify raw activated carbon for formaldehyde removal indoor. We conducted the liquid impregnation experiments at different initial concentrations, temperatures, adsorbent dosage and time ranges to fully investigate the adsorption of triethylenetetramine on the surface of raw activated carbon for modification. We found that the Langmuir isotherm model and pseudo-first-order kinetic model fit quite well with the experimental data and the R2 are 0.9883 and 0.9954, respectively. The theoretical maximum adsorption capacity is 166.67 mg/g. The change in Gibbs free energy (ΔG0), enthalpy change (ΔH0) and entropy change (ΔS0) were also calculated to study the direction and driving force of the liquid adsorption process. In order to understand the adsorption process at the molecular level, a new activated carbon model based on the actual physical and chemical properties of activated carbon was carefully established in the Materials Studio to simulate the liquid-phase adsorption. The pore structure, elemental composition, functional group content, density, pore volume, and porosity of the activated carbon model converge close to the actual activated carbon and the adsorption isotherms obtained from the simulation agree well with the experimental results. The results show that the adsorption of triethylenetetramine on activated carbon is a spontaneous, endothermic and monolayer physical adsorption process.

Teaching international students from Confucian Heritage Culture countries: perspectives from three U.S. host campuses

Qi Sun,Haijun Kang,Bo Chang,David Lausch 서울대학교 교육연구소 2019 Asia Pacific Education Review Vol.20 No.4

U.S. host campuses face instructional challenges from increasing numbers of international students from Confucian Heritage Culture (CHC) countries. Yet, the presence of CHC students offers learning opportunities for U.S. faculty in the context of internationalizing their higher education campuses. This study surveyed faculty at three U.S. host universities. It explored faculty understandings of Confucian culture, their perceptions of CHC countries’ international student learning, strategies used by faculty when teaching CHC students, and value faculty recognized when learning from CHC students. Results showed that a majority of faculty recognized the core values of Confucian culture. Yet, they were not fully aware of the cultural impact on CHC students’ learning, and the strategies they employed were mainly from the American perspectives. They did not integrate CHC students’ cultural heritages in their teaching practices and only partially accommodated CHC learners in teaching. This study calls for consciousness to transform faculty mindsets understanding the importance of students’ cultural differences in order to bring about a dramatic change in their teaching practices. Doing so may enhance the success of CHC students fomenting further internationalization at their host universities.

Modeling, analysis, and experiments of a pause-and-leap jumping robot during takeoff, flight, and landing buffering

Qi Yang,Jing Zhao,Ziqiang Zhang,Bin Chang,Xingkun Liu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

Jumping robots can overcome obstacles strongly and are suitable for complex terrain environments. However, the takeoff parameters of most jumping robots, especially pause-and-leap jumping robots, cannot be changed accurately. Moreover, the stability of the flight and landing of these robots needs to be improved. On the basis of observations of the jumping process of a locust, leg mechanisms, including one-degree-of-freedom jumping leg and series buffering leg, are designed. Then, dynamic models for takeoff, flight, and landing buffering are established and combined with Lagrange/Newton-Euler dynamic modeling methods and conservation of momentum moment. For the former, the effects of structural parameters, including position of the driving spring, absolute position of the center of mass, and stiffness coefficient of the driving spring, on takeoff velocity and acceleration can be obtained. The takeoff parameters can also be changed accurately. For the flight phase, the relationship between the relative position of the center of mass and the stability of flight is revealed. For the latter, the effects of two buffering modes on the supporting forces and energy storage capacity are analyzed. On the basis of the parameters determined by the abovementioned modeling method, a prototype is developed, and an experiment is conducted to verify the rationality of the modeling method. Experimental results show that the prototype can acquire accurate takeoff parameters and achieve stable flight and landing buffering. This study provides a useful reference for the design and control of jumping robots.

Impact and close-in blast response of auxetic honeycomb-cored sandwich panels: Experimental tests and numerical simulations

Qi, Chang,Remennikov, Alex,Pei, Lian-Zheng,Yang, Shu,Yu, Zhi-Hang,Ngo, Tuan D. Elsevier 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.180 No.-

<P><B>Abstract</B></P> <P>Protecting building, critical infrastructure and military vehicles from Improvised Explosive Devices (IEDs) has become a critical task. This study aims to examine the performance of a new protective system utilizing auxetic honeycomb-cored sandwich panels for mitigation of shock loads from close-in and contact detonations of high explosives. Both field blast tests and drop weight tests were performed using the proposed sandwiches asa shield for concrete panels in combination with conventional steel protective plates. The combined shield was found to be effective in protecting reinforced concrete structures against severe impact and close-in blast loadings. The honeycomb core with re-entrant hexagonal cells shows evident auxetic characteristics which contribute substantially to outstanding force mitigation and blast-resistance performances of such sandwich panels. Numerical simulations showed good agreement with the experimental results. The proposed auxetic panels were found to perform better than conventional honeycomb panels of the same size, areal density and material. Both were found to boost the energy absorption of the monolithic steel plate by a factor of 2.5 by changing its deformation pattern under close-in blast loading. In addition, a combination of the steel plate and an auxetic sandwich panel has aerial specific energy absorption (<I>ASEA</I>) higher than either of them, showing great potential for the development of lightweight blast protection of civil, mining, military, nuclear infrastructure and vehicles.</P>

Measurement of the whole abrasive surface topography of a grinding wheel

Chang-cai Cui,Qi-feng Yang,Yi-qi Yu 한국생산제조학회 2016 한국생산제조시스템학회 학술발표대회 논문집 Vol.2016 No.10

The Optimization of Control Parameters: Finite-time and Fixed-time Synchronization of Inertial Memristive Neural Networks with Proportional Delays and Switching Jumps Mismatch

Qi Chang,Yongqing Yang,Li Li,Fei Wang 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.7

This thesis’s object is inertial memristive neural networks (IMNNs) with proportional delays and switching jumps mismatch. Different from the traditional bounded delay, the proportional delay will be infinite as t → ∞. The finite-time synchronization (FN-TS) and fixed-time synchronization (FX-TS) can be realized with the devised controllers for the drive-response systems (D-RSs). Along with the Lyapunov function and some inequalities, the synchronization criteria of D-RSs are given. This paper presents an optimization model with minimum control energy and dynamic error as objective functions, aiming to obtain more accurate and optimized controller parameters. An intelligent algorithm: particle swarm optimization with stochastic inertia weight (SIWPSO) algorithm is introduced to solve the optimization model. Meanwhile, an integrated algorithm for selecting optimal control parameters is presented as well. In this method, the optimal control parameters and the setting time of synchronization can be obtained directly. At last, some simulations are presented to verify the theorems and the optimization model.

Petrogenesis of the Cenozoic volcanic rocks in Baekdu volcano in northeastern Asia and the expected depth of the magma chamber based on geochemistry, mineral chemistry, and Sr-Nd-Pb isotope chemistry

Chang Whan Oh,Seung Hwan Lee,Youn Soo Lee,Seung-Gu Lee,Jia-Qi Liu 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10

Baekdu volcano is a Cenozoic composite volcano in northeastern Asia that consists of a basaltic plateau, a basaltic shield, and a trachytic to comenditic stratovolcano. In this study, the petrogenesis and tectonic setting of Baekdu volcano are studied based on the whole-rock geochemistry and Sr-Nd-Pb isotope compositions of the Baekdu volcanic rocks. The K–Ar age and mineral chemistry are also investigated to estimate the evolution of the magma chamber depth beneath Baekdu volcano. The Toudao and Baishan basalts formed ca. 2.5 Ma and 1.1 Ma and erupted from magma chambers located at depths of 11.5 ± 2.2 km and 24.9 ± 3.8 km, respectively. The Xiaobaishan and Middle trachytes and the comendites formed during the Pleistocene from magma chambers located at depths of 2.9±0.2 km, 5.4±0.45 km, and 4.4±0.3 km, respectively. These data suggest that the trachytes and comendites erupted from magma chambers located at depths of approximately 3–5 km. The Baishan basalts have geochemical characteristics comparable with those of ocean island basalt (OIB), whereas the Toudao basalts show enriched mid-ocean ridge basalt (E-MORB) or OIB characteristics. The trends of several components, such as the CaO/Al₂O₃ ratio and the TiO₂ and Sc concentrations, are different between older basalts(>2 Ma, including the Toudao basalts) and younger basalts (<1.5 Ma, including the Baishan basalts), indicating that the magma-forming process changed ca. 2–1.5 Ma. The enrichment in Th/Yb ratios in the Toudao basalts indicates that they experienced crustal contamination. Trachytes and comendites are considered to be products of the fractional crystallization of the Baishan basalt based on the similar geochemical trends of the two rocks. Crustal assimilation (up to 20%) also occurred with fractional crystallization (more than 70%) during the formation of peralkaline silicic volcanic rocks. All volcanic rocks in Baekdu volcano have Sr-Nd-Pb isotope compositions comparable with the enriched mantle (EM1)-like signature. This EM1-like signature may have originated from the contamination of asthenospheric mantle with Paleoproterozoic lithosphere that sank into the asthenospheric mantle due to delamination caused by regional extensional events in northeastern Asia between the Cretaceous and the Cenozoic. The characteristics of trace element compositions indicate a within-plate tectonic setting for Baekdu volcano. These data imply that Baekdu volcano origin may have been related to a plume of EM1-type upper mantle under the North China Craton.

LIGHT-DEPENDENT CHANGES OF CHLOROPHYLL FLUORESCENCE AND XANTHOPHYLL CYCLE PIGMENTS IN MAIZE LEAVES DURING DESICCATION

Xu, Chang-Cheng,Lee, Choon-Hwan,Zou, Qi Korean Society of Photoscience 1998 Journal of Photosciences Vol.5 No.1

Changes of chlorophyll fluorescence and xanthophyll cycle pigment contents in maize leaves were investigated dunng desiccation in darkness or in the light. In darkness, a drastic dehydration of detached maize leaves down to 50% relative water content (RWC) affected photochemical efficiency of photosystem II (Fv/Fm) and pht)tochemical quenching (qP) only slightly. In contrast, desiccation in the light with a moderate intensity led to a pronounced reduction in Fv/Fm with a Fo quenching when RWC was greater than 70%. This reduction in Fv/Fm could be recovered in darkness under hutrod condition. In leaves with RWC below 70%, significant reduction in Fv/Fm was accompanied by an increase of Fo, which could not be reversed within 5 h in darkness under humid condition. The nonphotochemical quenching increased during desiccation in the light with a concomitant rise in zeaxanthin at the expense of violaxanthin. Pretreatment with dithiothreitol (DTT), an inhibitor of zeaxanthin synthesis, inhibited the development of nonphotochemical quenching and prevented the xanthophyll interconversion during desiccation in the light. These results suggest that even light with a moderate intensity becomes excessive under dehydration and zeaxanthin-associated photoprotection of photosynthetic apparatus against photodamage is involved, but the protection is not complete against severe desiccation.

Inhibition by Imatinib of Expression of O-glycan-related Glycosyltransferases and Tumor-associated Carbohydrate Antigens in the K562 Human Leukemia Cell Line

Sun, Qi-Chang,Liu, Mi-Bo,Shen, Hong-Jie,Jiang, Zhi,Xu, Lan,Gao, Li-Ping,Ni, Jian-Long,Wu, Shi-Liang Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.4

Objective: To study changes of tumor associated carbohydrate antigen (TACAs) expression and mRNA levels for tumor associated glycosyltransferases, and assess subcellular localizations of N-acetyl galactosyltransferases (GalNAc-Ts) in the K562 leukemia cell line after imatinib treatment. Methods: RT-PCR was performed to analyze the expression of glycosyltransferases which synthesize O-glycan in tumor-associated carbohydrate antigens (TCTAs). The expression of Tn antigen, T antigen and sialyl T antigen on K562 cell membranes was measured by flow cytometry after treatment with different concentrations of imatinib. Co-localization of GalNAc-Ts and ER (endoplasmic reticulum) was determined by confocal laser scanning microcopy. Results: Transcript expression levels of several glycosyltransferases related to TCTAs were decreased after imatinib ($0-0.3{\mu}M$) treatment. Expression of Tn antigen and T antigen was increased while that of sialyl T antigen was decreased. Co-localization of GalNAc-Ts and ER was reduced by $0.2{\mu}M$ of imatinib. Conclusion: Imatinib inhibited the expression of O-glycan related TACAs and several related glycosyltransferases, while decreasing the co-localization of GalNAc-Ts and ER and normalizing O-glycosylation in the K562 human leukemia cell.