System Simulation Modeling for Near-field Millimeter Wave Synthetic Aperture Imaging Radiometer

Jianfei Chen,Yuehua Li,Jianqiao Wang,Yuanjiang Li 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.6

Due to the fact that theoretical analysis and instrument construction for antenna array of synthetic aperture imaging radiometer (SAIR) are both complicated, and designers usually hope to predict the imaging effect and analysis the influence of relevant parameters of SAIR before the system design. The imaging simulation is a very useful method in the system design of SAIR. This paper is devoted to establishing an accurate imaging model for simulating the process of near-field millimeter wave SAIR. In this model, the target radiation signals and received signals of receivers are represented by the accurate signals in the time domain, which improves the efficiency of this simulation model significantly. The visibility function is collected by the cross-correlation between I/Q signals of the antenna pairs just as the imaging process of the practical SAIR. Some characteristics (such as the coherence between targets, the resolution and no-aliasing FOV of SAIR and so on) are verified by the corresponding 1D and 2D simulation experiments, and the effectiveness of this imaging model is also tested by these simulation experiments. The simulation experiment results show that this model is an efficient, accurate imaging simulation model, and can be employed in the system design of near-field millimeter wave SAIR.

Prevalence of Decreased Myocardial Blood Flow in Symptomatic Patients with Patent Coronary Stents: Insights from Low-Dose Dynamic CT Myocardial Perfusion Imaging

Yuehua Li,Mingyuan Yuan,Mengmeng Yu,Zhigang Lu,Chengxing Shen,Yining Wang,Bin Lu,Jiayin Zhang 대한영상의학회 2019 Korean Journal of Radiology Vol.20 No.4

Objective: To study the prevalence and clinical characteristics of decreased myocardial blood flow (MBF) quantified by dynamic computed tomography (CT) myocardial perfusion imaging (MPI) in symptomatic patients without in-stent restenosis. Materials and Methods: Thirty-seven (mean age, 71.3 ± 10 years; age range, 48–88 years; 31 males, 6 females) consecutive symptomatic patients with patent coronary stents and without obstructive de novo lesions were prospectively enrolled to undergo dynamic CT-MPI using a third-generation dual-source CT scanner. The shuttle-mode acquisition technique was used to image the complete left ventricle. A bolus of contrast media (50 mL; iopromide, 370 mg iodine/mL) was injected into the antecubital vein at a rate of 6 mL/s, followed by a 40-mL saline flush. The mean MBF value and other quantitative parameters were measured for each segment of both stented-vessel territories and reference territories. The MBFratio was defined as the ratio of the mean MBF value of the whole stent-vessel territory to that of the whole reference territory. An MBFratio of 0.85 was used as the cut-off value to distinguish hypoperfused from non-hypoperfused segments. Results: A total of 629 segments of 37 patients were ultimately included for analysis. The mean effective dose of dynamic CT-MPI was 3.1 ± 1.2 mSv (range, 1.7–6.3 mSv). The mean MBF of stent-vessel territories was decreased in 19 lesions and 81 segments. Compared to stent-vessel territories without hypoperfusion, the mean MBF and myocardial blood volume were markedly lower in hypoperfused stent-vessel territories (77.5 ± 16.6 mL/100 mL/min vs. 140.4 ± 24.1 mL/100 mL/min [p < 0.001] and 6.4 ± 3.7 mL/100 mL vs. 11.5 ± 4 mL/100 mL [p < 0.001, respectively]). Myocardial hypoperfusion in stentvessel territories was present in 48.6% (18/37) of patients. None of clinical parameters differed statistically significantly between hypoperfusion and non-hypoperfusion subgroups. Conclusion: Decreased MBF is commonly present in patients who are symptomatic after percutaneous coronary intervention, despite patent stents and can be detected by dynamic CT-MPI using a low radiation dose.

An Algorithm of De-noising of Millimeter Wave Radar Signal based on Stochastic Resonance

Han Lingyun,Li Yuehua 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.6

Millimeter wave radar echo signals often contain noise and clutter because of rain and fog’s influence on the performance of which, and its performance drop greatly. In recent years, bi-stable stochastic resonance and multi-scale wavelet decomposition theory received great attentions in the field of signal de-noising. This paper proposed a novel mechanism of stochastic resonance which is induced by multi-scale noise for weak signal detection in millimeter wave radar signal. Firstly by multi-scale wavelet decomposition, input signal which is in heavy background noise was decomposed to several signals with different frequencies. After that they were induced by contraction factors of each noise scale, and then were as the input signal of bi-stable system. Simulations of different parameters show that under suitable contraction factors, SNR of output signal can be improved greatly.

Modified Constraint Scores for Semi-Supervised Feature Selection

Jianqiao Wang,Yuehua Li,Kun Chen 보안공학연구지원센터 2014 International Journal of Signal Processing, Image Vol.7 No.5

Semi-supervised constraint scores, which utilize both pairwise constraints and the local property of the unlabeled data to select features, achieve comparable performance to the supervised feature selection methods. The local property is characterized without considering the pairwise constraints and these two conditions are introduced independently. However, the pairwise constraints and the local property may contain conflicting information. In this paper, we utilize the conflicting information to improve the local property. Instead of characterizing the local property by all neighbors, samples which do not appear in the cannot-link constraints can be used. A performance indicator, called neighborhood-cannot-link (NC) coefficient, is proposed to measure the improvement of the local property. We use the improved local property and the pairwise constraints to perform semi-supervised constraint scores algorithm. Experiments on several real world data sets demonstrate the effectiveness of the methods.

Assessment of Myocardial Bridge by Cardiac CT: Intracoronary Transluminal Attenuation Gradient Derived from Diastolic Phase Predicts Systolic Compression

Mengmeng Yu,Yang Zhang,Yuehua Li,Minghua Li,Wenbin Li,Jiayin Zhang 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.4

Objective: To study the predictive value of transluminal attenuation gradient (TAG) derived from diastolic phase of coronary computed tomography angiography (CCTA) for identifying systolic compression of myocardial bridge (MB). Materials and Methods: Consecutive patients diagnosed with MB based on CCTA findings and without obstructive coronary artery disease were retrospectively enrolled. In total, 143 patients with 144 MBs were included in the study. Patients were classified into three groups: without systolic compression, with systolic compression < 50%, and with systolic compression ≥ 50%. TAG was defined as the linear regression coefficient between intraluminal attenuation in Hounsfield units (HU) and length from the vessel ostium. Other indices such as the length and depth of the MB were also recorded. Results: TAG was the lowest in MB patients with systolic compression ≥ 50% (-19.9 ± 8.7 HU/10 mm). Receiver operating characteristic curve analysis was performed to determine the optimal cutoff values for identifying systolic compression ≥ 50%. The result indicated an optimal cutoff value of TAG as -18.8 HU/10 mm (area under curve = 0.778, p < 0.001), which yielded higher sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy (54.1, 80.5, 72.8, and 75.0%, respectively). In addition, the TAG of MB with diastolic compression was significantly lower than the TAG of MB without diastolic compression (-21.4 ± 4.8 HU/10 mm vs. -12.7 ± 8 HU/10 mm, p < 0.001). Conclusion: TAG was a better predictor of MB with systolic compression ≥ 50%, compared to the length or depth of the MB. The TAG of MB with persistent diastolic compression was significantly lower than the TAG without diastolic compression.

Structure Analysis of 16S rDNA Sequences from Strains ofAcidithiobacillus ferrooxidans

Xuan Li,Xueduan Liu,Yuehua Hu,Hong Peng,Yu Yang,Guanzhou Qiu,Jufang Huang 한국생화학분자생물학회 2006 BMB Reports Vol.39 No.2

Heterologous Expression and Purification of Zea mays Transglutaminase in Pichia pastoris

Hongbo Li,Yanhua Cui,Lanwei Zhang,Huaxi Yi,Xue Han,Yuehua Jiao,Ming Du,Rongbo Fan,Shuang Zhang 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.5

Transglutaminases (TGases) are a family ofenzymes that catalyze the cross-linking of proteins and arewidely used in the food industry to improve the texture ofdairy, meat, and bread products. Zea mays transglutaminase(TGZ) is a new type of TGase with a wide potential. TGZwas expressed in the yeast Pichia pastoris under an alcoholoxidase promoter. Maximal expression of recombinantTGZ was achieved by inducing recombinant GS115(pPIC9K-tgz) in BMMY medium using 1.5% methanol for96 h. Secreted TGZ was initially separated using Superdex200 resin and further purified on cation exchange resin. The activity of TGZ following purification was 0.32 U/mgof protein. The polymerization effect of TGZ on caseincatalyzed by recombinant TGZ was slightly lower than theeffect of microbial transglutaminase (MTG). TGZ is a newpotential additive for the food industry.

Analysis of Differential-expressed Proteins of Acidithiobacillus ferrooxidansGrown under Phosphate Starvation

Guiyuen Li,Yuehua Hu,Hui Zhong,Shengmu Xiao,Jiarshe Liu,Jin Xu 한국생화학분자생물학회 2005 BMB Reports Vol.38 No.5

The Development and Application of Hierarchical Experimenting Platform for Embedded System Course

Kaisheng Zhang,Yuehua Li,Yao Gong 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.11

There are many disadvantages existing in the current experimenting platforms for embedded system course. Therefore, this paper has devised a hierarchical experimenting platform based on the CDIO education mode to improve both the teaching and learning experience. The experimenting platform devised in this paper is composed of a motherboard and several microprocessor plug-in boards. The motherboard can meet with various experimenting requirements by changing different plug-in boards. The demonstration source code is plug-in board independent, so the source code can be shared by different plug-in boards. The teaching practical shows that, this hierarchical experimenting platform can significantly improve the teaching and learning experience.

Calcification Remodeling Index Characterized by Cardiac CT as a Novel Parameter to Predict the Use of Rotational Atherectomy for Coronary Intervention of Lesions with Moderate to Severe Calcification

Mengmeng Yu,Yuehua Li,Wenbin Li,Zhigang Lu,Meng Wei,Jiayin Zhang 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.5

Objective: To assess the feasibility of calcification characterization by coronary computed tomography angiography (CCTA) to predict the use of rotational atherectomy (RA) for coronary intervention of lesions with moderate to severe calcification. Materials and Methods: Patients with calcified lesions treated by percutaneous coronary intervention (PCI) who underwent both CCTA and invasive coronary angiography were retrospectively included in this study. Calcification remodeling index was calculated as the ratio of the smallest vessel cross-sectional area of the lesion to the proximal reference luminal area. Other parameters such as calcium volume, regional Agatston score, calcification length, and involved calcium arc quadrant were also recorded. Results: A total of 223 patients with 241 calcified lesions were finally included. Lesions with RA tended to have larger calcium volume, higher regional Agatston score, more involved calcium arc quadrants, and significantly smaller calcification remodeling index than lesions without RA. Receiver operating characteristic curve analysis revealed that the best cutoff value of calcification remodeling index was 0.84 (area under curve = 0.847, p < 0.001). Calcification remodeling index ≤ 0.84 was the strongest independent predictor (odds ratio: 251.47, p < 0.001) for using RA. Conclusion: Calcification remodeling index was significantly correlated with the incidence of using RA to aid PCI. Calcification remodeling index ≤ 0.84 was the strongest independent predictor for using RA prior to stent implantation.