Secondary flow control using endwall jet fence in a high-speed compressor cascade

Huaping Liu,Shuai Jiang,Yongchuan Yu,Dongfei Zhang,Huanlong Chen 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

This paper proposes a secondary flow control concept using Endwall jet fence (EJF). A parametric investigation concerning the variations of the jet location along the axial and pitch-wise direction as well as the skew angle is conducted numerically to validate the potential of EJF in a high-speed compressor cascade with an inlet Mach number of 0.67. And then the interaction mechanisms between the EJF and the endwall secondary flow are discussed in detail. The results show that the EJF could reduce the corner separation and losses significantly by inputting transverse momentum component, inducing a concentrated jet vortex to block the pitch-wise migration of the passage vortex as well as enhancing the energy exchange between the endwall boundary layer and the mainstream. The jet location and the skew angle are important for the influence of EJF on the cascade performance. In this work, a maximum total pressure loss reduction of 11.6 % is obtained by the EJF located at 30 % of the axial chord and 10 % of the pitch with a skew angle of β = 40°, whereas the jetto-inflow mass flow ratio is only about 0.4 %, validating the high efficiency of this flow control concept. For the off-design points, the EJF also shows appreciable potential on the endwall secondary flow control and loss reduction.

Computationally Efficient Lattice Reduction Aided Detection for MIMO-OFDM Systems under Correlated Fading Channels

Wei Liu,최권휴,Huaping Liu 한국전자통신연구원 2012 ETRI Journal Vol.34 No.4

We analyze the relationship between channel coherence bandwidth and two complexity-reduced lattice reduction aided detection (LRAD) algorithms for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems in correlated fading channels. In both the adaptive LR algorithm and the fixed interval LR algorithm, we exploit the inherent feature of unimodular transformation matrix P that remains the same for the adjacent highly correlated subcarriers. Complexity simulations demonstrate that the adaptive LR algorithm could eliminate up to approximately 90 percent of the multiplications and 95 percent of the divisions of the brute-force LR algorithm with large coherence bandwidth. The results also show that the adaptive algorithm with both optimum and globally suboptimum initial interval settings could significantly reduce the LR complexity, compared with the brute-force LR and fixed interval LR algorithms, while maintaining the system performance.

Reliability and Validity of the Behavioral Regulation in Exercise Questionnaire-2 for Nursing Home Residents in China

Lei Liu,Mingqiang Xiang,Hong Guo,Zhe Sun,Tao Wu,Huaping Liu 한국간호과학회 2020 Asian Nursing Research Vol.14 No.1

Purpose This study aimed to examine the reliability and validity of the Chinese-translated Behavioral Regulation in Exercise Questionnaire-2 (BREQ-2) for nursing home residents. Methods A convenience sample of 204 nursing home residents were used for measuring the instrument performances. Demographics form and BREQ-2 developed by Markland were applied. Results The translated BREQ-2 model was a good fit for the results of confirmatory factor analysis, χ2 was 276.75, comparative fit index was .94, standardized root mean square residual was .05, and root mean square error of approximation was .07. Results in the BREQ-2 indicated good consistency, Cronbach's α coefficient of BREQ-2 was .78, and each of the five subscales were ranged from .78 to .83. The test–retest was valued .84, and the five subscales ranged from .75 to .89, which supporting the stability of instrument. Conclusion This study provided psychometric evidence for the application of BREQ-2 among nursing home residents in China.

Performance optimization of diesel engine fueled with diesel–jatropha curcas biodiesel blend using response surface methodology

Huaping Xu,Bifeng Yin,Shengji Liu,Hekun Jia 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

The present work is aimed at unfolding the effect of fuel supply parameters such as Fuel injection pressure (FIP), Start of injection timing (SOI), Pilot-main injection intervals (PMII) on performance and emission characteristics of 20 % blend of Jatropha curcas biodiesel (J20) under light load operation of a diesel engine. The experiments were designed using design of experiments based on the fractional factorial design of Response surface methodology (RSM). Multiple regression models developed using RSM for measured responses like nitrogen oxides (NO X ), SOOT, hydrocarbon (HC), Brake specific fuel consumption (BSFC) and Brake thermal efficiency (BTE), were found to be statistically significant by Analysis of variance (ANOVA). Interactive effects among FIP, SOI and PMII were analyzed using response surface graphs that were fitted using developed RSM models. Optimization was performed using the desirability approach of the RSM for lesser emissions and BSFC simultaneously with superior BTE. A FIP of 134.11 MPa, SOI of 6.4 BTDC, and PMII of 5.8 CA were found to be optimal values for J20 in the test engine of 21 kW at 1800 rpm. The results of this study show that at optimal input parameters, the values of the NO X , SOOT, HC, BSFC and BTE with a high desirability of 96.7 % are 603.44 ppm, 0.037 FSN, 12.73 ppm, 233.26 g/kW h and 37.31 %, respectively.

Visualization of combustion performance and emission characteristics of a four-cylinder diesel engine at various inlet oxygen concentrations at part loads

Huaping Xu,Shengji Liu,Bifeng Yin,Hekun Jia,Shenghao Yu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.6

Although exhaust gas recirculation (EGR) is a common way to suppress the nitrogen oxide (NO X ) emissions, it also brings some negative impact on soot emissions and the thermal efficiency in internal combustion engines. We investigated the effects of ambient oxygen concentrations on engine performance, combustion characteristics, and emissions using a four-cylinder diesel engine equipped with an endoscopic visualization system. To estimate the flame temperature and soot distribution, we analyzed these images using a postprocessing program. Experimental results showed that the luminosity of flames in the images was degraded comparatively for the reduced oxygen concentration. Flame temperature distribution also showed similar behavior. As the oxygen concentration decreased, area of soot distribution significantly reduced at IMEP = 0.13 MPa, and only a slight decrease at IMEP = 0.3 MPa. But locally high soot concentration regions increased.

Quasi-Synchronous CDMA Using Properly Scrambled Walsh Codes as User-Spreading Sequences

Kwonhue Choi,Huaping Liu IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.7

<P>An orthogonal spreading code family based on scrambled Walsh-Hadamard (WH) sequences is proposed for quasi-synchronous (QS) code-division multiple-access (CDMA) systems. With 1 chip offset, either the top or the bottom half rows of the WH matrix remain orthogonal if they are scrambled using the proposed scrambling patterns. With quadriphase scrambling applied on a quarter row of the WH matrix, the zero-correlation zone (ZCZ) is extended to 3 chips. The proposed spreading codes satisfy the theoretical limit of code size for a given code length and ZCZ. Compared with existing spreading codes for QS-CDMA, the proposed spreading codes have several advantages: 1) A special procedure for code family construction is not needed; it only requires a simple modification to the scrambling sequence of the conventional CDMA, which employs WH sequences as user signatures. 2) Flexible code family size; the size can easily be extended for multicell applications without having to consider existing codes used. Moreover, if synchronization is guaranteed to be within 1 chip, the code size can be doubled by allocating another quarter member of the WH sequence set. 3) The benefits of long code scrambling from the conventional cellular CDMA systems are inherited, such as robustness against interception and multiaccess interference randomization.</P>

Polyphase Scrambled Walsh Codes for Zero-Correlation Zone Extension in QS-CDMA

Kwonhue Choi,Huaping Liu IEEE 2012 IEEE Communications Letters Vol.16 No.4

<P>Polyphase complex scrambling patterns are designed to extend the zero-correlation zone (ZCZ) of a family of user spreading sequences, called properly scrambled Walsh-Hadamard (PSW) codes, recently proposed for quasi-synchronous (QS) code-division multiple-access systems. The merits of the binary (ZCZ equals 2) and quadri-phase (ZCZ equals 4) PSW codes over the existing QS spreading codes are still retained in the proposed polyphase PSW codes. Scrambling patterns for the case of ZCZ of 8 are derived first. Then, the scrambling pattern design rules are generalized for greater ZCZs and a structured procedure to generate polyphase PSW codes for any ZCZ is developed. Finally, the cross-correlation properties of the proposed spreading codes are evaluated.</P>

Robustness of RED in Mitigating LDoS Attack

( Jing Zhang ),( Huaping Hu ),( Bo Liu ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.5

The Random Early Detection algorithm is widely used in the queue management mechanism of the router. We find that the parameters of the RED algorithm have a significant influence on the defense performance of the random early detection algorithm and discuss the robust of the algorithm in mitigating Low-rate Denial-of-Service attack in details. Simulation results show that the defense performance can be effectively improved by adjusting the parameters of Q_min and Q _max. Some suggestions are given for mitigating the LDoS attack at the end of this paper.

Power Allocation for Distributed Transmit Diversity with Feedback Loop Delay

Kwonhue Choi,Huaping Liu IEEE 2011 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.59 No.1

<P>We study two power allocation (PA) schemes for distributed transmit diversity systems. We first derive the performance of the instantaneous channel gain feedback-based PA (ICG-PA) scheme in the presence of channel variation during feedback delay. We then study channel gain variance feedback-based PA (CGV-PA) to mitigate the performance degradation of ICG-PA caused by feedback delay. Finally, we derive design rules for optimum CGV-PA from a compact and accurate performance expression derived.</P>

The Novel Infrared Target Localization Algorithm for Free Floating Space Robot

Xiong Luo,Xiaolu Jie,Huaping Liu,Fuchun Sun 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10

With regards to the complicated characteristic of outer space, the infrared target recognition system has been investigated for free floating space robot. A novel algorithm is proposed based on visual location method for free floating space robot. Firstly, we set an omnidirectional camera with fixed lens on the ceiling. Here, the free floating robot is moving on the platform. Especially, in order to reduce image noise, we fix an infrared filter in the lens. Then, we place a number of infrared-emitting diodes on the free floating space robot and the targets. Finally, we can get the accurate positions and angle information of the robot and the target according to the location of the infrared light. The experimental results prove that this approach presented in this paper is an effective method for target detection and static target capture for free floating space robot.