Mitigating Cache Pollution Attack in Information Centric Mobile Internet

( Jia Chen ),( Liang Yue ),( Jing Chen ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.11

Information centric mobile network can significantly improve the data retrieving efficiency by caching contents at mobile edge. However, the cache pollution attack can affect the data obtaining process severely by requiring unpopular contents deliberately. To tackle the problem, we design an algorithm of mitigating cache pollution attacks in information centric mobile network. Particularly, the content popularity distribution statistic is proposed to detect abnormal behavior. Then a probabilistic caching strategy based on abnormal behavior is applied to dynamically maintain the steady-state distribution for content visiting probability and achieve the purpose of defense. The experimental results show that the proposed scheme can achieve higher request hit ratio and smaller latency for false locality content pollution attack than the CacheShield approach and the baseline approach where no mitigation approach is applied.

High-performance COF-based composite anion exchange membrane sandwiched by GO layers for alkaline H2/O2 fuel cell application

Jia Chen,Mingming Guan,Kai Li,Shaokun Tang 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.104 No.-

With well-defined structure and high stability, covalent organic framework (COF) inspires the preparationof new ion-conducting materials for anion exchange membrane (AEM) in alkaline fuel cell. In orderto reveal the influence of micro-nano structure within COF ordered channels on the hydroxide diffusion,we construct a multi-dimensional composite membrane by combining two-dimensional lamellar COFwith one-dimensional polymer chains. The quaternary ammonium-modified COF-LZU1 (QAmCOFLZU1)is incorporated into quaternized poly (2,6-dimethyl-1,4-phenylene oxide) (QAPPO) to fabricateQAmCOF-LZU1/PPO composite membranes. The rapidly diffusion of hydroxide ions in the first solventshell formed by the huge amount of quaternary ammonium groups in the ordered COF channels is investigatedby molecular dynamics simulations. Afterwards, sulfonated graphene oxide (GO) is coated onboth surfaces of the membranes via ionic interactions and p-p interactions to obtain GO@QAmCOFLZU1/PPO sandwich membranes, which would avoid excessive swelling of membranes and leakage ofQA groups. Especially, the GO-sandwiched membrane exhibits strikingly high stabilities and excellentH2/O2 fuel cell performance with a peak power density of 242 mW cm 2 at 60 C. This study providesan effective strategy to construct ion-conducting COF-based composite membranes for highperformancealkaline fuel cell.

Chemical constituents from Viburnum fordiae Hance and their anti-inflammatory and antioxidant activities

Jia Chen,Jianhua Shao,Chunchao Zhao,Jie Shen,Ziling Dong,Wenyan Liu,Min Zhao,Judi Fan 대한약학회 2018 Archives of Pharmacal Research Vol.41 No.6

Three new neolignans, fordianoles A-C (1–3),characterized as (7S,8R)-4-hydroxy-3,30,50-trimethoxy-80,90-dinor-8,40-oxyneolignan-7,70,9-triol, (7R,8R)-4-hydroxy-3,30,50-trimethoxy-80,90-dinor-8,40-oxyneolignan-7,70,9-triol, and (7R,8R)-4-hydroxy-3,30,50-trimethoxy-8,40-oxyneolignan-7,9,90-triol-70-one, together with an unusual c-lactone,3-(3,4-dihydroxyphenyl)-4-pentanolide (4), andtwenty-five known compounds (5–29) were isolated fromthe aerial parts of Viburnum fordiae Hance. Their structuresincluding absolute configurations were determined byspectroscopic and chemical methods. Among them, compounds6, 7, 11–15, 17–28 were isolated from the Viburnumgenus for the first time. The anti-inflammatory and antioxidantactivities of all compounds were evaluated in vitro. Compounds 15, 19, 20 and 29 showed significant inhibitoryactivity on NO production in RAW264.7 cells stimulated byLPS with IC50 values ranging from 8.60 to 13.92 lM. Meanwhile, compounds 1–4, 15, 19, 20, 22, 23, 25, 26 and29 exhibited varying antioxidant activities through DPPH,ABTS free radical scavenging and FRAP assays.

Highly hydroxide-conductive anion exchange membrane with PIL@MOF-assisted ion nanochannels

Jia Chen,Mingming Guan,Kai Li,Shaokun Tang 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.94 No.-

A highly hydroxide-conducting anion exchange membrane with well-organized multi ion channels werefabricated via incorporating poly ionic liquids modified MIL101 (PIL@MIL101) into imidazolated poly(2,6-dimethyl-1,4-phenylene oxide) (ImPPO). 1-Vinyl-3-ethylimidzolium bromine wasfirst immobilizedin MIL101 cages via supercriticalfluid impregnation method. Afterwards, the rigid-assisted ionnanochannels were constructed by in-situ polymerization of ionic liquids within the long-range orderedpores of MIL101. Meanwhile, PPO was functionalized by 1-ethyl-2-methyimidzolium to prepare combshapedImPPO with enhanced microphase separation structure. Then the PIL@MIL101 was combinedwith ImPPO to fabricate hybrid anion exchange membrane with well-organized multiple ion channels. The OH conductivity of the hybrid membrane significantly reached 138 mS/cm at 80 C (176% higherthan that of pristine membrane). Furthermore, the stability and mechanical properties of the hybridmembranes were remarkably enhanced. The excellent performances render the hybrid membrane a goodcandidate for the application in anion exchange membrane fuel cells.

Shear rheology of circular particle suspensions in a Bingham fluid using numerical simulations

Jia Chen,황욱렬 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.3

In this study, we performed direct simulations of particle suspensions in a simple shear flow with a viscoplastic model (Bingham fluid) using a finite-element/fictitious-domain method, as a model system for cuttings transport with a drilling mud in the oil and gas exploration. Bulk rheology and particle interaction were investigated via several example problems including single-particle, two-interacting particle, and many-particle problems for various solid fractions in both Bingham and Newtonian fluids. We report that, at low shear rate, huge reductions occur in both the relative bulk viscosity and angular velocity of particle suspension in a Bingham fluid compared to that in a Newtonian fluid. This indicates that, although particle incorporation increases bulk viscosity in a Bingham fluid, the amount of increase appears much smaller than that with the Newtonian medium, and particle motions were restricted to some extend at a low shear rate with a yield stress fluid. Moreover, the suppression in viscosity increase with particles disappears at a high shear rate, just like Newtonian particle suspension. This phenomenon has been interpreted by the suppressed particle angular rotation in a Bingham fluid. In addition, flow fields with low shear regions, where the viscosity of a Bingham fluid is high and the fluid mobility decreased significantly, on the left and right sides of a particle also confirm this interpretation. The two-interacting particle problem reveals delayed particle interaction with increased time period in particle trajectories (drafting, kissing, tumbling and separation) in a Bingham fluid. Similar behaviors with the suppression in viscosity increase can be also observed in the many-particle problem.

A Comparative Study of Flame Kernel Development Using Conventional Spark Igniter and Non-Thermal Plasma Under Gasoline Engine Relevant Conditions

Jiachen Zhai,Seong-Young Lee 한국연소학회 2022 KOSCOSYMPOSIUM논문집 Vol.2022 No.11

In a constant volume combustion chamber (CVCC), experiments of spark ignition and non-thermal plasma ignition are compared under gasoline engine relevant conditions: initial ambient pressure ranges (6.5, 8.3, 11.3 bar), a range of equivalence ratios (0.7 – 1.0), EGR percentages (10% - 25%)m and cross flow speeds (0 – 30 m/s). The results showed that non-thermal plasma successfully ignites under very lean (equivalence ratio below 0.8), high-diluted mixture (25% EGR), and high-speed cross flow of 30 m/s where conventional spark can never reach within the range of current study.

Design of broadband multilayer dichroic coating for a high-efficiency solar energy harvesting system

Jiachen, Wang,Lee, Sang Bae,Lee, Kwanil The Optical Society 2015 Applied Optics Vol.54 No.15

<P>We report on the design and performance of a broadband dichroic coating for a solar energy conversion system. As a spectral beam splitter, the coating facilitates a hybrid system that combines a photovoltaic cell with a thermal collector. When positioned at a 45° angle with respect to incident light, the coating provides high reflectance in the 40-1100??nm and high transmission in the 1200-2000??nm ranges for a photovoltaic cell and a thermal collector, respectively. Numerical simulations show that our design leads to a sharp transition between the reflection and transmission bands, low ripples in both bands, and slight polarization dependence.</P>

Comparative Study of Non-Electrochemical Hysteresis Models for LiFePO₄/Graphite Batteries

Jiachen Ma,Jiale Xie,Kun Bai 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

The estimation of LiFePO₄/graphite battery states suffers from the prominent hysteresis phenomenon between the respective open-circuit voltage curves towards charging and discharging. A lot of hysteresis models have been documented to investigate the hysteresis mechanism. This paper reviews and deeply interprets four non-electrochemical hysteresis models and some improvements. These models can be conveniently incorporated into commonly used equivalent circuit models to reproduce battery behaviors. Through simulation and experimental comparisons of voltage predictions and state-of-charge estimations, the pros and cons of these models are presented.

Experimental Study on Spray Characteristics of The Internal Impinging Nozzle

( Jiachen Zhai ),( Zongjie Hu ),( Wei Xie ),( Huizhi Chen ),( Cong Xue ),( Yufeng Wang ),( Zhijun Wu ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

The internal impinging nozzle with a bluff body set inside can form a periodic oscillating spray, which is a novel approach of atomization. In this paper, the flow distribution characteristics of the spray are studied with low-pressure water as the medium. Meanwhile, the characteristics of spray cone angle, oscillating frequency, spatial distribution of droplet velocity and particle size are also studied with high-speed Schllieren technique and Malwen particle size analyzer. The results demonstrate that with the increase of the injection pressure, the spray cone angle is almost constant, while the spray oscillating frequency increases gradually, which is tantamount to the variation trend of axial velocity and radial velocity of the droplet. When the injection pressure is elevated from 0.16MPa to 0.18MPa, at the same position, the increase of droplet axial velocity distinctly reaches a maximum. Furthermore, with the development of the spray, the particle size decreases accordingly, and the velocity of the well atomized area near the spray symmetrical center axis is also gradually reduced. The farther away from the nozzle outlet, the more pronounced the symmetry of the spatial distribution of the axial velocity and radial velocity becomes. Moreover, when the injection pressure reaches 0.16MPa, at the position 250mm away from the outlet, the particle size achieves a minimum, and the spray obtains a stable distribution, which is rarefied and uniform in the middle area, while generous on both sides. With the injection pressure increasing to 0.18MPa, the flow of the well atomized area near the spray symmetrical center axis reaches its maximum, and that of the area farthest away from the symmetry center is also raised by degrees as the injection pressure increases.

Compact Non-Cascaded All-Fiber Raman Laser Operating at 1174 nm

Jiachen Wang,Sang-Bae Lee,Kwanil Lee 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.1

We investigate a non-cascaded, all-fiber, single-mode Raman fiber laser (RFL) operating at 1174 nm with an optical slope efficiency of 68%. An 1-km commercial single-mode fiber is used as the Raman gain medium. The RFL cavity is formed between a high reflectivity fiber Bragg grating (FBG) and a perpendicularly-cleaved fiber facet. The laser is pumped by using a homemade ytterbium-doped fiber laser (YDFL) and can be frequency doubled to generate yellow light. Under the optimum condition, A 6.9-W 1174-nm laser is obtained at maximum available power (24 W) of a laser diode pump. The optical conversion efficiency and the net slope efficiency of the RFL were respectively, 29% and 38%, with respect to launched diode laser power. We also demonstrate yellow-light generation by frequency doubling of the RFL.