Fabrication of Hollow Polymer Microchannels Using the MIMIC Technique with Subsequent Heat Treatment

Weiren Li,Wenqiang Xing,Fengzhou Zhao,Lichun Zhang,Yupeng Huang,Jinxiu Li,Linwei Zhu,Zheng Xu,Dengying Zhang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.8

The hollow polymer microchannels with different shapes and dimensions have been fabricated by the MIMIC method and the heating process for the first time. The smallest cross-sectional dimensions of hollow polymer microchannels were about 2.6 μm in the vertical direction and 3.5 μm in the horizontal direction. The length of hollow polymer microchannels increased parabolically with the heating temperature in the range of 30–135 °C. And the influence of the PDMS mold crosssectional areas on the length of the microchannels was invetigated. Furthermore, the forming mechanism of hollow polymer microchannels was disscussed in detail. This technique provides a cheap, simple and controllable way for the preparation of microchannels.

Room Temperature Electroluminescence from n-ZnO:Ga/i-ZnO/p-GaN:Mg Heterojunction Device Grown by PLD

Lichun Zhang,Qingshan Li,Feifei Wang,Chong Qu,Fengzhou Zhao 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.3

The n-ZnO:Ga/p-GaN:Mg and n-ZnO:Ga/i-ZnO/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated by the pulsed laser deposition (PLD) technique. The blue electroluminescence (EL) of the n-ZnO:Ga/ p-GaN:Mg heterojunction LEDs is emitted mainly from the p-GaN layer instead of the n-ZnO:Ga layer, for the reason that the electron injection from n-ZnO:Ga prevailed over the hole injection from p-GaN:Mg due to the higher carrier concentration and carrier mobility in n-ZnO:Ga. On the other hand, the n-ZnO:Ga/i-ZnO/p- GaN:Mg heterojunction LEDs exhibited dominant ultraviolet-blue emission. The reason for this difference is attributed to the inserted undoped i-ZnO layer between n-ZnO:Ga and p-GaN:Mg, in which the holes from p- GaN:Mg and the electrons from n-ZnO:Ga are recombined.

Optoelectronic Characteristics of UV Photodetector Based on GaN/ZnO Nanorods p-i-n Heterostructures

Qingshan Li,Lichun Zhang,Fengzhou Zhao,Caifeng Wang,Feifei Wang,Ruizhi Huang 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4

We demonstrate an efficient ultraviolet (UV) photodetector operating at room temperature based on n-ZnO nanorods/i-ZnO/p-GaN heterojunctions. We employ x-ray diffraction and field-emission scanning electron microscopy to confirm the high quality of the ZnO nanorods using an undoped ZnO film as the interlayer. Then, we investigate the photoelectric properties of the fabricated photodetector with UV light illumination under a different reverse bias. Based on the current-voltage curve, the photocurrent to dark current ratio is approximately 73.3 at −4 V. At zerobias voltage, the peak responsivity was 138.9 mA/W at 362 nm under front-illumination conditions. Time-varying measurements indicate the reproducibility and stability of the heterojunction photodetector.

Mixing matrix estimation method for dual‐channel time‐frequency overlapped signals based on interval probability

Zhipeng Liu,Lichun Li,Ziru Zheng 한국전자통신연구원 2019 ETRI Journal Vol.41 No.5

For dual‐channel time‐frequency (TF) overlapped signals with low sparsity in underdetermined blind source separation (UBSS), this paper proposes an effective method based on interval probability to estimate and expand the types of mixing matrices. First, the detection of TF single‐source points (TF‐SSP) is used to improve the TF sparsity of each source. For more distinguishability, as the ratios of the coefficients from different columns of the mixing matrix are close, a local peak‐detection mechanism based on interval probability (LPIP) is proposed. LPIP utilizes uniform subintervals to optimize and classify the TF coefficient ratios of the detected TF‐SSP effectively in the case of a high level of TF overlap among sources and reduces the TF interference points and redundant signal features greatly to enhance the estimation accuracy. The simulation results show that under both noiseless and noisy cases, the proposed method performs better than the selected mainstream traditional methods, has good robustness, and has low algorithm complexity.

Hypoxia-hindered methylation of PTGIS in endometrial stromal cells accelerates endometriosis progression by inducing CD16− NK-cell differentiation

Haiyan Peng,Lichun Weng,Shating Lei,Shuhui Hou,Shaoliang Yang,Mingqing Li,Dong Zhao 생화학분자생물학회 2022 Experimental and molecular medicine Vol.54 No.-

Prostacyclin (PGI2) plays key roles in shaping the immune microenvironment and modulating vasodilation, whereas its contribution to endometriosis (EMs) remains largely unclear. Our study suggested that prostacyclin synthase (PTGIS)-dependent PGI2 signaling was significantly activated in EMs, which was involved in the hypoxic microenvironment of ectopic lesions and deficient methylation status of the PTGIS promoter. Notably, in vitro assays, hypoxia promoted PTGIS expression through DNA methyltransferase 1 (DNMT1)-mediated DNA methylation deficiency in endometrial stromal cells (ESCs); PTGIS overexpression enhanced the adhesive ability of ESCs and led to elevated PGI2 production, and PGI2 triggered CD16− (encoded by FCGR3, Fc fragment of IgG receptor IIIa) natural killer (NK)-cell differentiation through PGI2 receptor (IP, PTGIR) in an ESC/NK-cell coculture system. Our rodent model experiment suggested that treatment with the PGI2 analog iloprost and adoptive transfer of fcgr3 knockout (fcgr3−/−) NK cells aggravated EMs progression and that genetic ablation of ptgis (ptgis−/−) in ectopic lesions and treatment with the PTGIR antagonist RO1138452 partially rescued this outcome. Thus, our findings identified the contribution of PGI2 to EMs progression via enhancement of the adhesive ability of ESCs and inhibition of the activity of NK cells. We hypothesized that PGI2 is a target for EMs intervention and provide a rationale for studying pharmacological PTGIR inhibition and PTGIS genetic depletion therapies as therapeutic strategies for EMs.

Modeling Knot Properties for Mongolian Pine in Northeast China

Jia, Weiwei,Li, Fengri,Jiang, Lichun Korean Society of Forest Science 2008 한국산림과학회지 Vol.97 No.5

This study was performed in 14 unthinned Mongolian pine (Pinus sylvestris L. var. mongolica Litvin) plantations in northeast China. Data were collected on 70 sample trees of different canopy position with diameter at breast height (DBH) ranging from 6.9 cm to 34.5 cm. Diameter and length of knots per whorl below the living crown were studied by different vertical levels divided by relative knot height (RHK) in this paper. Models taking DBH and height to the crown base (HCB) as independent variables were developed to predict knot diameter (KD) in a sample whorl. According to the vertical distribution tendency and range of sound knot length (KLsound), KLsound was modeled as multiple linear function of DBH, KD and relative knot height (RHK). The loose knot length (KLloose) was described as a function of DBH, KD and height above the ground for knots (HK) in a mixed log-linear model. Results from this study can provide abundant knot information so as to describe the knot size and vertical distribution tendency of Mongolian pine plantation.

Fluorescent Microarrays of <i>in Situ</i> Crystallized Perovskite Nanocomposites Fabricated for Patterned Applications by Using Inkjet Printing

Liu, Yang,Li, Fushan,Qiu, Lichun,Yang, Kaiyu,Li, Qianqian,Zheng, Xin,Hu, Hailong,Guo, Tailiang,Wu, Chaoxing,Kim, Tae Whan American Chemical Society 2019 ACS NANO Vol.13 No.2

<P>Perovskite materials have exhibited promising potential for universal applications including backlighting, color conversion, and anticounterfeiting labels fabricated using solution processes. However, owing to the tendency of those materials to have uncontrollable morphologies and to form large crystals, they cannot be utilized in discontinuous microminiaturization, which is crucial for practical optoelectronic applications. In this research, combining the effects of adding polyvinylpyrrolidone (PVP), precisely controlling the inkjet printing technique, and using a postprocessing procedure, we were able to fabricate <I>in situ</I> crystallized perovskite-PVP nanocomposite microarrays with perfect morphologies. The viscosity of the perovskite precursor increased with the addition of PVP, eliminating the outward capillary flow that induces the coffee-ring effect. In addition, because of the presence of metallic bonds with the C═O groups in PVP and the spatial confinement of such a polymer, we were able to fabricate regulated CsPbBr<SUB>3</SUB> nanocrystals capped with PVP and with a uniform size distribution. The as-printed patterns showed excellent homogeneity on a macroscale and high reproducibility on a microscale; furthermore, those patterns were invisible in the ambient environment, compatible with flexible substrates, and cost-efficient to produce, indicating that this technique holds promising potential for applications such as anticounterfeiting labels.</P> [FIG OMISSION]</BR>

Effective Separation Method for Single-Channel Time-Frequency Overlapped Signals Based on Improved Empirical Wavelet Transform

( Zhipeng Liu ),( Lichun Li ),( Huiqi Li ),( Chang Liu ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

To improve the separation performance of time-frequency overlapped radar and communication signals from a single channel, this paper proposes an effective separation method based on an improved empirical wavelet transform (EWT) that introduces a fast boundary detection mechanism. The fast boundary detection mechanism can be regarded as a process of searching, difference optimization, and continuity detection of the important local minima in the Fourier spectrum that enables determination of the sub-band boundary and thus allows multiple signal components to be distinguished. An orthogonal empirical wavelet filter bank that was designed for signal adaptive reconstruction is then used to separate the input time-frequency overlapped signals. The experimental results show that if two source components are completely overlapped within the time domain and the spectrum overlap ratio is less than 60%, the average separation performance is improved by approximately 32.3% when compared with the classic EWT; the proposed method also improves the suitability for multiple frequency shift keying (MFSK) and reduces the algorithm complexity.

Computerized bone age estimation system based on China-05 standard

Yin, Chuangao,Zhang, Miao,Wang, Chang,Lin, Huihui,Li, Gengwu,Zhu, Lichun,Fei, Weimin,Wang, Xiaoyu Techno-Press 2022 Advances in nano research Vol.12 No.2

The purpose of this study is to develop an automatic software system for bone age evaluation and to evaluate its accuracy in testing and feasibility in clinical practice. 20394 left-hand radiographs of healthy children (2-18 years old) were collected from China Skeletal Development Survey data of 1998 and China Skeletal Development Survey data of 2005. Three experienced radiologists and China-05 standard maker jointly evaluate the stages of bone development and the reference bone age was determined by consensus. 1020 from 20394 radiographs were picked randomly as test set and the remaining 19374 radiographs as training set and validation set. Accuracy of the automatic software system for bone age assessment is evaluated in test set and two clinical test sets. Compared with the reference standard, the automatic software system based on RUS-CHN for bone age assessment has a 0.04 years old mean difference, ±0.40 years old in 95% confidence interval by single reading, a 85.6% percentage agreement of ratings, a 93.7% bone age accuracy rate, 0.17 years old of MAD, 0.29 years old of RMS; Compared with the reference standard, the automatic software system based on TW3-C RUS has a 0.04 years old mean difference, a ±0.38 years old in 95% confidence interval by single reading, a 90.9% percentage agreement of ratings, a 93.2% bone age accuracy rate, a 0.16 years of MAD, and a 0.28 years of RMS. Automatic software system, AI-China-05 showed reliably accuracy in bone age estimation and steady determination in different clinical test sets.

3D PtAu nanoframe superstructure as a high-performance carbon-free electrocatalyst

Yoo, Sungjae,Cho, Sanghyun,Kim, Dajeong,Ih, Seongkeun,Lee, Sungwoo,Zhang, Liqiu,Li, Hao,Lee, Jin Yong,Liu, Lichun,Park, Sungho The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.6

<P>In this work, we demonstrate how to synthesize a three-dimensional (3D) ordered PtAu nanoframe superstructure and evaluated its performance as an electrocatalyst. Compared to carbon supported platinum (Pt) nanocrystal electrocatalysts (wherein the aggregation- and carbon corrosion-induced fast degradation is a well-known drawback), the 3D PtAu nanoframe superstructure is free from aggregation and carbon corrosion. The 3D superstructure was self-assembled<I>via</I>drop-casting and evaporation using truncated octahedral PtAu nanoframes (TOh PtAu NFs) as building blocks that were produced by controlled wet-chemical etching of a TOh Au core whose edges and vertexes were selectively deposited with Pt atoms. Density functional theory calculations revealed that the surface alloy state of PtAu gave rise to an enhanced catalytic activity compared to pure Pt. Experimental investigations showed that such 3D superstructure electrocatalysts exhibited excellent mass transfer efficiency, higher catalytic activity and stability towards the methanol oxidation reaction (MOR) compared to a commercial Pt/C catalyst. The demonstrated 3D nanoframe superstructure shows great potential for practical catalytic application due to its high structural stability, high catalytic activity, high surface area and ease of fabrication.</P>