Practical Schemes for Tunable Secure Network Coding

( Guangjun Liu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.3

Network coding is promising to maximize network throughput and improve the resilience to random network failures in various networking systems. In this paper, the problem of providing efficient confidentiality for practical network coding system against a global eavesdropper (with full eavesdropping capabilities to the network) is considered. By exploiting a novel combination between the construction technique of systematic Maximum Distance Separable (MDS) erasure coding and traditional cryptographic approach, two efficient schemes are proposed that can achieve the maximum possible rate and minimum encryption overhead respectively on top of any communication network or underlying linear network code. Every generation is first subjected to an encoding by a particular matrix generated by two (or three) Vandermonde matrices, and then parts of coded vectors (or secret symbols) are encrypted before transmitting. The proposed schemes are characterized by tunable and measurable degrees of security and also shown to be of low overhead in computation and bandwidth.

Homomorphic Subspace MAC Scheme for Secure Network Coding

Guangjun Liu,Xiao Wang 한국전자통신연구원 2013 ETRI Journal Vol.35 No.1

Existing symmetric cryptography-based solutions against pollution attacks for network coding systems suffer various drawbacks, such as highly complicated key distribution and vulnerable security against collusion. This letter presents a novel homomorphic subspace message authentication code (MAC) scheme that can thwart pollution attacks in an efficient way. The basic idea is to exploit the combination of the symmetric cryptography and linear subspace properties of network coding. The proposed scheme can tolerate the compromise of up to r–1 intermediate nodes when r source keys are used. Compared to previous MAC solutions, less secret keys are needed for the source and only one secret key is distributed to each intermediate node.

State estimation of a heavy-duty hexapod robot with passive compliant ankles based on the leg kinematics and IMU data fusion

Yufei Liu,Haibo Gao,Liang Ding,Guangjun Liu,Zongquan Deng,Nan Li 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8

To control autonomous walking of a legged robot, it is essential to obtain the instantaneous velocity and posture of the robot. This paper presents a full body state estimation algorithm for a hexapod robot to estimate the velocity and posture of the trunk body without geometric knowledge of the environment. The velocity and posture estimates of the hexapod robot with passive compliant ankles are further processed by a data fusion method that is proposed based on the extended Kalman filter (EKF) technique, utilizing the leg kinematics model of the robot and the readouts from an on–board inertial measurement unit (IMU). The absolute footholds of the hexapod robot are estimated together with the velocity and posture of the trunk body, with consideration of intermittent ground contacts. Experiments have been conducted on both flat and uneven terrains, and the results have confirmed the effectiveness of the proposed approach.

Study on wear mechanism of coated carbide tool in turning of pearlitic gray cast iron with Al additives

Siyu Liang,Guangjun Liu,Gaoyang Wu,Tao Chen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

In the process of Al-added pearlitic gray cast iron material cutting, the tool surface will form an adhesive layer due to extrusion and friction, which will have a complex impact on the machining quality and tool life. Therefore, it is necessary to study its formation process and tool wear mechanism in detail. This paper investigates the evolution laws of tool wear and workpiece surface roughness in different cutting parameters, which is based on orthogonal tests. Using the data of the orthogonal tests, an optimization model is carried out to find optimum cutting parameters which can keep a good balance among cutting efficiency, machined surface roughness and tool life. Then, the SEM and energy spectrometer are used to analyze the formation of adhesive layers and the distribution of elements. Compared with the comprehensive test, the orthogonal test can reduce the number of experiments and improve the efficiency on the premise of ensuring accuracy and can be easily applied to practical production. And the results of SEM micrograph and elements distribution map show that the stability of the mass ratio of aluminium to titanium on the tool surface can directly reflect the stability of the adhesive layer, thus affecting the tool life and the machined surface quality.

Effect on measurements of anemometers due to a passing high-speed train

Jie Zhang,Guangjun Gao,Sha Huang,Tanghong Liu 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equationsand k-ε double equations turbulent model were used to investigate the effect on the measurements ofanemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat themoving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriagegaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the presentnumerical method was validated to be used for further study. In addition, the difference of slipstreambetween three-car and eight-car grouping models was analyzed, and a series of numerical simulations werecarried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and thedirections of the induced slipstream on the measurements of the anemometers. The results show that theinfluence factors of the train-induced slipstream are the passing head car and tail car. Using the three-cargrouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstreamvelocity tend to reduce as the height of the anemometer increases. With the train speed increasing, therelationship between Vtrain and Vinduced slipstream can be expressed with linear increment. In the absence ofnatural wind conditions, from the head car arriving to the tail car leaving, the induced wind directionchanges about 330°, while under the crosswind condition the wind direction fluctuates around -90°. With thecrosswind speed increasing, the peaks of VX, |VXY -Vwind| of the head car and that of VX of the tail car tend toenlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effecton the measurements of anemometers due to the train-induced slipstream.

Effect on measurements of anemometers due to a passing high-speed train

Zhang, Jie,Gao, Guangjun,Huang, Sha,Liu, Tanghong Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations and k-${\varepsilon}$ double equations turbulent model were used to investigate the effect on the measurements of anemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat the moving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriage gaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the present numerical method was validated to be used for further study. In addition, the difference of slipstream between three-car and eight-car grouping models was analyzed, and a series of numerical simulations were carried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and the directions of the induced slipstream on the measurements of the anemometers. The results show that the influence factors of the train-induced slipstream are the passing head car and tail car. Using the three-car grouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstream velocity tend to reduce as the height of the anemometer increases. With the train speed increasing, the relationship between $V_{train}$ and $V_{induced\;slipstream}$ can be expressed with linear increment. In the absence of natural wind conditions, from the head car arriving to the tail car leaving, the induced wind direction changes about $330^{\circ}$, while under the crosswind condition the wind direction fluctuates around $-90^{\circ}$. With the crosswind speed increasing, the peaks of $V_X,{\mid}V_{XY}-V_{wind}{\mid}$ of the head car and that of $V_X$ of the tail car tend to enlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effect on the measurements of anemometers due to the train-induced slipstream.

Preventive effect of Lactobacillus plantarum HFY09 on HCl/ethanol-induced gastric injury in mice

Li Fang,Sun Hailan,Ran Guangjun,Liu Xinhong,Yi Ruokun,Tan Fang,Zhao Xin,Liu Huazhi 한국응용생명화학회 2020 Applied Biological Chemistry (Appl Biol Chem) Vol.63 No.5

The aim of this study was to investigate the effect of Lactobacillus plantarum HFY09 on gastric injury induced by HCl/ ethanol in Kunming mice. The results showed that HFY09-H inhibited any increases in gastric juice volume, maintained the normal pH value of gastric acid, and reduced the damage caused to the gastric mucosa and gastric wall, the inhibition rate on the injury area reaches 63.70%. Compared with the negative control group, HFY09 increased the levels of serum somatostatin (SS) and vasoactive intestinal peptide (VIP), and also decreased the levels of substance P (SP), endothelin-1 (ET-1), interleukin-6 (IL-6), interleukin-12 (IL-12), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ). In addition, real time fluorescent quantitative PCR (Q-PCR) also confirmed that high-dose HFY09 ( 109 CFU/kg/ day) upregulated the mRNA expression of copper/zinc superoxide dismutase (Cu/Zn-SOD), manganese superoxide dismutase (Mn-SOD), catalase (CAT), endothelial nitric oxide synthase (eNOS), and neuronal nitric oxide synthase (nNOS), and downregulated the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). At the same time, the results of the HFY09 treatment group were similar to those of the ranitidine treatment group. These results indicate that HFY09 can prevent gastric injury induced by HCl/ethanol in vivo. Therefore, HFY09 may play a potential role in the treatment of gastric diseases.

Investigating the miscibility of poly (butylene adipate-co-terephthalate)/poly (lactic acid) mixtures through multi-scale simulation and experiments

Xuezhi Li,Yuanyuan Qin,Haojie Li,Guangjun Liu,Junyu Fu,Feng Li,Zhanchun Chen 한국고분자학회 2023 Macromolecular Research Vol.31 No.9

The processability and practical applications of poly (butylene adipate-co-terephthalate) (PBAT) /poly (lactic acid) (PLA) blends are limited due to their lower miscibility. To investigate the miscibility of various PBAT/PLA composite ratios and the mechanism of miscibility between them, PBAT/PLA blends with different ratios were prepared using the melt mixing method. A combination of multi-scale simulations and experiments were employed to investigate the miscibility of the composites. Molecular dynamics simulations analyzed PBAT/PLA mixtures that are incompatible and showed the molecular basis of their incompatibility through the radial distribution function (RDF). The degree of miscibility of different ratios of PBAT/PLA composites was described using the Flory–Huggins interaction parameter, indicating that the 50/50 PBAT/PLA blend has the worst miscibility. Mesoscopic dynamics described the mesoscopic morphology of PBAT and PLA blends visually. The results obtained from the simulations were consistent with scanning electron microscope (SEM) and differential scanning calorimeter (DSC) experiments, indicating the simulations' reliability. This work provides a molecular perspective on the mechanism of thermodynamic insolubility of PBAT and PLA, which can inspire future PBAT/PLA hybrid modifications.