Modeling of SACK-based Fast Retransmission and Recovery

Zhiming Wang,Xiaoping Zeng,Xiaofan Jia,Xue Liu,Li Chen 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.6

Selective acknowledgment (SACK)-based retransmission and recovery mechanism has been implemented in most of current transmission control protocol (TCP) stacks. A new SACK-based loss recovery algorithm is defined in RFC6675 under standard track. Existing models in literatures on modeling TCP SACK, which usually use SACK-based retransmission and recovery mechanism, is no longer accurate for two reasons: 1) they ignore transmission of new packets before retransmission of the last loss; 2) they are based on the strategy that pipe is decreased by 2 upon receipt of a partial ACK, where pipe is the estimated number of outstanding packets. This paper develops a new method to derive the expected number of new packets transmitted between retransmission of the first loss and the last, proposes a model that estimates the expected number of packets transmitted during fast retransmission and recovery phase (FRR) and the corresponding expected duration based on RFC6675. The numerical results show that the proposed model can accurately estimate the expected number of packets transmitted during FRR and the corresponding expected duration based on RFC6675.

Characteristics of calcium carbonate fouling on heat transfer surfaces under the action of electric fields

Zhiming Xu,Hongliang Chang,Bingbing Wang,Jingtao Wang,Qi Zhao 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

The present study examined the effect of electric fields in calcium carbonate (CaCO 3 ) scale formation on a heat transfer surface. The effects of electric fields ranging from 0 V to 4000 V on the fouling properties of CaCO 3 were investigated. Results showed that the optimal electric voltage was approximately 500 V, at which the asymptotic value of fouling resistance and the deposited weight were minimal and corresponded to 52.8 % and 61.3 % reductions, respectively, compared with the results recorded at 0 V. At higher voltages of 3000 V or 4000 V, the asymptotic value of fouling resistance and the weight of fouling deposits increased relative to those obtained at 0 V. The scanning electron microscope images of the fouling deposits obtained at 0 V showed mainly aragonites with sharp and needle-like crystal structures. The structure of CaCO 3 fouling changed from aragonites to spherical vaterites as the applied voltage was increased.

Maximum magnetic entropy change modulated toward room temperature in perovskite manganites La0.7−xNdx(Ca,Sr)0.3MnO3

Zhiming Wang,Qingyu Xu,Kaixin Chen 한국물리학회 2012 Current Applied Physics Vol.12 No.4

With Nd3þ doping and Ca2+, Sr2+ modulating in the solegel technique, a series of polycrystalline perovskite samples La0.7-xNdx(Ca,Sr)0.3MnO3 (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25) was prepared, their maximum magnetic entropy changes were tuned to room temperature (ΔSH=-1.47 J/kg K at 298 K for La0.45Nd0.25(Ca,Sr)0.3MnO3), an enhancement of the maximum magnetic entropy change (ΔSH=-1.89 J/kg K at 315 K) and its refrigerant capacity (about 45.3 J/kg) had also been obtained under 9 kOe magnetic field variation for La0.55Nd0.15(Ca,Sr)0.3MnO3 contrast to La0.7(Ca,Sr)0.3MnO3.

Fouling characteristics of MgO particles under subcooled flow boiling

Siyuan Wang,Zhiming Xu,Jingtao Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

In order to investigate the particulate fouling characteristics, experiments of water based magnesia particulate suspensions were carried out in an annular test section under subcooled flow boiling. The sizes of magnesia particles were 40 nm and 10 μm, respectively. The influence of particle concentration, heat flux, mass flow rate and inlet temperature on fouling resistance were investigated, and the Chilton-Colburn analogy was applied to analyze the fouling process. The results show that the asymptotic value of fouling resistance increases with the increase of particle concentration. The asymptotic value of fouling resistance tends to fall when mass flow rate increases. As inlet temperature increases, there will be an obvious drop in the asymptotic value of fouling resistance. Regarding to heat flux, opposite variation trend was found between nano and micro-magnesia particles when changing the heat flux. Moreover, there is an obvious difference in asymptotical value of fouling resistance between nano-particles and micro-particles.

Improved Channel Estimation Algorithms based on a Proposed Signal Model for PUCCH Format 3 in LTE-A

Xiaoping Zeng,Ya Wen,Zhiming Wang,Yuemei Jin 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.1

SORTD (Space Orthogonal-Resource Transmit Diversity) has already become a better way of transmit diversity for PUCCH format 3 in LTE-A [1]. SORTD technology lies in the characteristic that each antenna port transmits signal by using different cyclic shift [2] to make orthogonal each other. Using the SORTD’s feature of incoherence in different antennas, this paper proposes a special form of signal model. Based on this proposed model, we propose a low complexity channel estimator based on LS and cubic spline interpolation, and then we put a LS and DCT algorithm to improve the interpolation performance. Finally, for more accurate estimator we drive the third approach based on MMSE and DCT. A series of theoretical researches and simulation results show that all of them are suitable for the proposed signal model even in the environment of high-speed movement; especially the algorithms with DCT have a better performance.

Effects of Surface Machining by a Lathe on Microstructure of Near Surface Layer and Corrosion Behavior of SA182 Grade 304 Stainless Steel in Simulated Primary Water

( Zhiming Zhang ),( Jianqiu Wang ),( En-hou Han ),( Wei Ke ) 한국부식방식학회(구 한국부식학회) 2019 Corrosion Science and Technology Vol.18 No.1

To find proper lathe machining parameters for SA182 Grade 304 stainless steel (SS), six kinds of samples with different machining surface states were prepared using a lathe. Surface morphologies and microstructures of near surface deformed layers on different samples were analysed. Surface morphologies and chemical composition of oxide films formed on different samples in simulated primary water with 100 μg/L O₂ at 310 ℃ were characterized. Results showed that surface roughness was mainly affected by lathe feed. Surface machining caused grain refinement at the top layer. A severely deformed layer with different thicknesses formed on all samples. In addition to high defect density caused by surface deformation, phase transformation, residual stress, and strain also affected the oxidation behaviour of SA182 Grade 304 SS in the test solution. Machining parameters used for # 4 (feed, 0.15 mm/r; back engagement, 2 mm; cutting speed, 114.86 m/min) and # 6 (feed,0.20 mm/r; back engagement, 1 mm; cutting speed, 73.01 m/min) samples were found to be proper for lathe machining of SA182 Grade 304 SS.

Experimental study on the composite fouling characteristics of calcium carbonate and nanometer magnesia

Zhiming Xu,Jingtao Wang,Zhimin Han,Yu Zhao 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

In order to study the composite fouling characteristics of crystallization and particulate, the fouling characteristics of calcium carbonate (CaCO 3 ) and nanometer magnesia in the alternating elliptical axis tube were investigated experimentally. The results show that CaCO 3has obvious effect on the inhibition of the formation of particulate fouling. The asymptotic value of fouling resistance of the nanometer magnesia is the highest and the CaCO 3 is the lowest, and the composite fouling is between them. The fouling rate and the asymptotic value of composite fouling resistance decrease with the increase of the CaCO 3 concentration. The time reaches to the asymptotic value of the three experiments are similar. The variation of nanometer magnesia concentration has greater influence than the CaCO 3 concentration on the asymptotic value of composite fouling. The fouling rate and the asymptotic value of composite fouling resistance increase obviously with the increase of the nanometer magnesia concentration.

The Deviation Characteristics of High-speed Train Running Time in Section and its Effect on Transport Capacity

Zhiming Yuan,Qi Zhang,Tao Wang,Feng Chen 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.10

Starting from the phenomenon that a large number of trains’ actual arrival & departure time deviate from specified time in train working diagram in the database of high speed railway dispatching system, the paper analyzes the defects of current train running time calculation method. Based on data mining theory, a section running time deviation calculation model for high speed railway train is proposed. Then the properties of train section running time deviation are studied in three different cases (non-stop both at the start and the end of section, stop at the end of section, and departure at the start of section) with the data from a Chinese railway bureau dispatching system, and its further influence on carrying capacity is analyzed. The results show that three deviation cases all fit Gauss distribution and the accumulative deviation time can increase the transport capacity for more than 1 million passengers per year.

Shear Behavior of Marlstone Containing Parallel Fissure under Normal Unloading

Zhiming Yin,Xinrong Liu,Zhongping Yang,Yanlei Wang 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.4

Shear tests under normal unloading were carried out to further study the shear mechanical behavior of marlstone containing parallel fissures. The results reveal that the failure on the rock bridge is tensile failure except for the limited extrusion failure at the tip of the prefabricated fissure. The failure on both sides is generally tensile-shear mixed failure, in which the tensile failure is mainly concentrated in the middle of both sides. In general, it can be summarized as a tensile-shear failure mode of STS-T-STS (S means shear failure, T means tension failure). The failure normal stress of the specimens gradually increases and then decreases with the increase of the fissure inclination, increases with an increase in the initial normal/shear stress, and decreases with the increase of the unloading rate. Strong dilation occurred in the shear process of the specimens, which shows obvious arch effect. The variation law of dilatancy deformation and horizontal deformation in the stage of normal stress unloading is just opposite to that of the failure normal stress. The increasing effect of high shear stress on shear deformation is greater than that of dilatancy deformation, while the inhibiting effect of high normal stress on dilatancy deformation is greater than that of the shear deformation.

The Development of IGCT-based Large Capacity Three-Level Dual-PWM Converter

Lan Zhiming,Li Chongjian,Li Yaohua,Zhu Chunyi,Wang Chengsheng 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In media and high voltage large capacity converter systems the Integrated Gate Commutated Thyristor (IGCT) take the place of Gate Turn Off Thyristor (GTO) duo to its outstanding performance. And IGCT-based large capacity three-level converters are widely used in industrial motor-driving field. In this paper the development of a set of IGCT-based large capacity three-level dual-PWM converter is introduced. The converter includes PWM rectifier, DC capacitors, PWM inverter. The topology of the converter is given. The close-loop control strategy and SVPWM algorithm of PWM rectifier is presented in this paper. The control strategy and algorithm of the PWM inverter is also presented. The experiments were performed and the results show that the converter reaches the design requirement and has excellent performance.