Understanding Watching Patterns of Live TV Programs on Mobile Devices: A Content Centric Perspective

( Yuheng Li ),( Qianchuan Zhao ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.9

With the rapid development of smart devices and mobile Internet, the video application plays an increasingly important role on mobile devices. Understanding user behavior patterns is critical for optimized operation of mobile live streaming systems. On the other hand, volume based billing models on cloud services make it easier for video service providers to scale their services as well as to reduce the waste from oversized service capacities. In this paper, the watching behaviors of a commercial mobile live streaming system are studied in a content-centric manner. Our analysis captures the intrinsic correlation existing between popularity and watching intensity of programs due to the synchronized watching behaviors with program schedule. The watching pattern is further used to estimate traffic volume generated by the program, which is useful on data volume capacity reservation and billing strategy selection in cloud services. The traffic range of programs is estimated based on a naive popularity prediction. In cross validation, the traffic ranges of around 94% of programs are successfully estimated. In high popularity programs (>20000 viewers), the overestimated traffic is less than 15% of real happened traffic when using upper bound to estimate program traffic.

Layer-by-Layer Assembly of Graphene on Polyimide Films via Thermal Imidization and Synchronous Reduction of Graphene Oxide

Yuheng Li,최면천,정극민,정재훈,이혁기,김규현,하창식 한국고분자학회 2017 Macromolecular Research Vol.25 No.6

To investigate the effects of holding time after deposition of polyethylenimine (PEI) solution and molecular weight of PEI on the surface morphology of multilayer films prepared by layer-by-layer (LbL) method, polyamic acid (PAA)/PEI/ graphene oxide (GO) films were prepared using different holding times and different molecular weights of PEI. To convert PAA into polyimide (PI), the films were thermally imidized after film deposition. In this process, GO was also converted into partially reduced GO (rGO). The effects of holding time and molecular weight of PEI on the surface morphology and the sheet resistance of PI/PEI/rGO films were investigated. Also, to investigate the effect of rGO on the barrier properties of PI based multilayer films, (PI/PEI/rGO/PEI)6 films were prepared by LbL method. Longer holding time (10 min) and smaller molecular weight (25,000) of PEI lead to relatively flat surfaces, but shorter holding time (5 min) and larger molecular weight (75,000) result in wrinkled and overlapped surfaces. The sheet resistance of PI/ PEI25K/rGO films prepared with holding time 10 and 5 min is 502.1 kΩ/sq and out of range (> 2000 kΩ/sq), respectively. The sheet resistance of PI/PEI75K/rGO films prepared with holding time 10 min is out of range (> 2000 kΩ/sq). Gas transmission rate (GTR) and permeability coefficient of (PI/PEI25K/rGO/PEI25K)6 are lower than those of (PI/PEI75K/rGO/PEI75K)6, respectively.

Dual-Band Antenna with OAM Mode Radiated by Ground Plane

Li Yuheng,Yang Guang,Li Weiwen,Liu Qing Huo 한국전자파학회 2023 Journal of Electromagnetic Engineering and Science Vol.23 No.3

Antennas that radiate orbital angular momentum (OAM) modes are usually large and have complex structures. In this paper, in combination with characteristic mode analysis, the ground plane is used as the OAM wave radiator. To excite degenerate modes of the ground plane with phase quadrature by using a single-fed structure, two bent metal strips with grounded ends are introduced around the rectangular ground plane, and a corner of one of the bent strips is set as the feeding point. For ground radiators, a first-order OAM mode is generated at the high-frequency end by synthesizing the degenerate modes. In case of the bent side strip, an inverted-F antenna that operates in the low-frequency mode is formed. This compact antenna has dual-band characteristics and facilitates simple feeding, which makes it suitable for mobile terminal applications.

Effects of crosslinking agents on the physical properties of polyimide/amino‐functionalized graphene oxide hybrid films

Jeong, Keuk‐,Min,Li, Yuheng,Yoo, Dae‐,Geon,Lee, Nam‐,Kyoung,Lee, Hyeok‐,Gi,Ando, Shinji,Ha, Chang‐,Sik John Wiley Sons, Ltd 2018 Polymer international Vol.67 No.5

<P><B>Abstract</B></P><P>The effects of crosslinking agents (crosslinkers) on polyimide (PI)/graphene oxide (GO) hybrid films were extensively investigated. The surface of GO was modified with amino groups using 4‐aminobenzylamine to improve compatibility with pyromellitic dianhydride/4,4′‐oxydianiline PI, and two kinds of crosslinkers were used: tris(4‐aminophenyl)amine and 1,3,5‐triazine‐2,4,6‐triamine (melamine). The mechanical, thermal and optical properties of the PI hybrid films were investigated. In particular, the transparency and physical properties of the PI hybrid films containing amino‐functionalized GO with homogeneous dispersion were improved. As the content of the crosslinker increased, a crosslinking network was formed between the PI chains, and the stiffness of the hybrid films was increased. The glass transition temperature, heat resistance and mechanical properties were also enhanced. The PI hybrids prepared with a rigid crosslinker exhibited higher optical transparency due to the reduction of the intermolecular charge transfer interactions with increasing interchain spacing between the PI chains. © 2018 Society of Chemical Industry</P>

The Efficacy and Prognostic Factors for Long Pulse Neodymium: Yttrium-Aluminum-Garnet Laser Treatment on Onychomycosis: A Pilot Study

( Sha Lu ),( Jing Zhang ),( Yuheng Liang ),( Xiqing Li ),( Wenying Cai ),( Liyan Xi ) 대한피부과학회 2016 Annals of Dermatology Vol.28 No.3

A High Accuracy Method for the Field Dynamic Balancing of Rigid Spindles in the Ultra-Precision Turning Machine

Xiufeng Liu,Wei Wei,JinChun Yuan,Yuxuan Tao,Yuheng Li,Yu Huang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.11

For the ultra-precision turning machine, the spindle system is a core component and plays a decisive role in precise machining. The unbalancing state in the spindle can degrade the quality of the machining surface. Therefore, the spindle system must be exceptionally well balanced before processing. In this paper, we proposed a high accuracy spindle balance method, which adopts the real-time data in the CNC system and combines with disturbance observer (DOB) to estimate the unbalancing vector without any extra sensors. Moreover, this method takes full advantage of the ultra-precision machine structure, the high precision grating, and the high-performance motor servo system to achieve high accuracy measurement for the spindle unbalancing. According to the experimental results, the proposed method accuracy is up to G0.0073, which is at least three levels greater than the highest official ISO balancing quality grade G0.16. In the cutting experiments, the PV value reduce to 0.207 μm from 0.528 μm with upgrading the spindle balance grade to G0.01024 from G0.16, verifies the accuracy of the spindle dynamic balancing method from the practice side.

Core–shell structure g-MnO2-PANI carbon fiber paper-based flexible electrode material for high-performance supercapacitors

Xuxia Ling,Guoliang Zhang,Zhu Long,Xuefeng Lu,Zhibin He,Jie Li,Yuheng Wang,Dan Zhang 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.99 No.-

Good conductivity is the key to ensuring high electrochemical performance, and the uniformity of theactive material directly affects the electrical conductivity. This paper proposes a novel modified stepwisein situ polymerization method to prepare composite materials, and then uses the K/S value method tocharacterize the uniformity of polyaniline distribution. Specifically, the study presents a papermakingwet-lay technique to prepare a carbonfiber paper substrate (CP) that is light-weight,flexible, andfoldable while also having low internal resistance and high porosity. The g-MnO2 is wrapped with PANI toform a core–shell structure, and a modified stepwise in situ polymerization method is adopted to depositthe core–shell structure uniformly on the CP substrate by physical adsorption. This process yields aflexible electrode material for supercapacitors, called g-MnO2-PANI-CP electrode. Results show thatthe g-MnO2-PANI-CP electrode has a high specific capacitance of 642.5 F g 1 at a current density of 1A g 1, and also has a high energy density of 114.2 Wh kg 1 at a power density of 798.6 W kg 1. In addition,the electrode retains 81.3% of the initial capacitance after 5000 cycles, demonstrating high cyclingperformance.