Development of a TEM holder for electronic conductance measurement of suspended graphene nanoribbons

Xiaobin ZHANG,Shinya IWASHITA,Marek SCHMIDT,Manoharan MURUGANATHAN,Hiroshi MIZUTA,Yoshifumi OSHIMA 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Rotordynamic characteristics of a novel pocket damper seal with self-regulated injection

Wanfu Zhang,Pengbo Qin,Xiaobin Zhang,Kai Ma,Lu Yin,Chun Li 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8

The conventional fully partitioned pocket damper seal (FPDS) was improved by introducing several nozzles on the first seal tooth, which generates a reverse injection fluid suppressing the cavity flow in the circumferential direction. Computational fluid dynamics (CFD) models of the conventional FPDS and current novel FPDS were established. An infinitesimal theory was employed to identify the rotordynamic coefficient of the FPDS. The influence of nozzle types (negative, straight, positive), inlet/outlet areas, deflection angles (θ) on the rotordynamic performance was comprehensively analyzed. It was found that reducing the circumferential flow in the first seal cavity is crucial for increasing the stability of the FPDS. A negative nozzle angle can restrict the circumferential flow effectively and significantly improve the effective damping and system stability. The crossover frequency for the novel FPDS with θ = -10° is ~62 Hz, which is much lower than that for the conventional FPDS (~85 Hz). The increasing inlet/outlet area ratio of the nozzle can also enhance the seal stability. Increasing the negative nozzle angle (θ = none, -10°, -15°, -20°) can effectively increase the effective damping and reduce the crossover frequency from ~85 Hz to ~38 Hz. However, the novel FPDS with three kinds of nozzles shows a slight increase (< 2.5 %) in the leakage flow rate compared with the conventional FPDS.

A brain somatic RHEB doublet mutation causes focal cortical dysplasia type II

Shanshan Zhao,Zhenghui Li,Muxian Zhang,Lingliang Zhang,Honghua Zheng,Jinhuan Ning,Yanyan Wang,Feng-Peng Wang,Xiaobin Zhang,Hexia Gan,Yuanqing Wang,Xian Zhang,Hong Luo,Guojun Bu,Huaxi Xu,Yi Yao,Yun-wu 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

Focal cortical dysplasia type II (FCDII) is a cerebral cortex malformation characterized by local cortical structure disorganization, neuronal dysmorphology, and refractory epilepsy. Brain somatic mutations in several genes involved in the PI3K/AKT/mTOR pathway are associated with FCDII, but they are only found in a proportion of patients with FCDII. The genetic causes underlying the development FCDII in other patients remain unclear. Here, we carried out whole exome sequencing and targeted sequencing in paired brain–blood DNA from patients with FCDII and identified a brain somatic doublet mutation c.(A104T, C105A) in the Ras homolog, mTORC1 binding (RHEB) gene, which led to the RHEB p.Y35L mutation in one patient with FCDII. This RHEB mutation carrier had a dramatic increase of ribosomal protein S6 phosphorylation, indicating mTOR activation in the region of the brain lesion. The RHEB p.Y35L mutant protein had increased GTPλS-binding activity compared with wild-type RHEB. Overexpression of the RHEB p. Y35L variant in cultured cells also resulted in elevated S6 phosphorylation compared to wild-type RHEB. Importantly, in utero electroporation of the RHEB p.Y35L variant in mice induced S6 phosphorylation, cytomegalic neurons, dysregulated neuron migration, abnormal electroencephalogram, and seizures, all of which are found in patients with FCDII. Rapamycin treatment rescued abnormal electroencephalograms and alleviated seizures in these mice. These results demonstrate that brain somatic mutations in RHEB are also responsible for the pathogenesis of FCDII, indicating that aberrant activation of mTOR signaling is a primary driver and potential drug target for FCDII.

Refractory Performance of the Axial Tensile Welded Hollow Spherical Joint

Xiaobin Qiu,Bingsheng Huang,Haoyu Song,Zhen Zhang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.6

To study the refractory performance of the axial tensile welded hollow spherical joint, the steady-state test of heating under constant load was carried out on the joint specimens with different load levels. The failure modes, temperature field, displacement-time curves, and refractory performance of the spherical joints exposed to fire are investigated and analyzed. The experimental results indicate that the failure modes of the joints exposed to fire are pull-out failures. The failure location is at the intersection of the steel tube-hollow sphere. The lowest temperature is located at the intersection of the steel tube-hollow sphere. The closer you get to the equator of the hollow sphere, the higher the spherical temperature. The smaller the load level, the higher the refractory temperature and the longer the refractory limit of the joints. The correctness of the numerical model was verified by comparison with the experimental result. Numerical simulations show that with the increase of the load levels, the refractory performance of the joints gradually decreases, and the downward trend gradually slows down. Compared to the refractory temperature code-recommended, the refractory temperature of the tensile joints is very conservative.

Heterogeneity of Microbial Community Structures inside the Up-flow Biological Activated Carbon (BAC) Filters for the Treatment of Drinking Water

Xiaobin Liao,Chao Chen,Chih-Hsiang Chang,Zhao Wang,Xiaojian Zhang,Shuguang Xie 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.4

Filtration using biological activated carbon (BAC) performs well in the removal of biodegradable dissolved organic carbon from water sources. The application of ozonation followed by up-flow BAC filtration has gained increasing attention in the world scale. In this study, a pilotscale up-flow BAC filtration system was constructed for the treatment of polluted lake water. The operational results indicated that this BAC filtration system could effectively remove organic matter. Spatial heterogeneity of the microbial community structure inside the BAC filtration system was identified using bacterial 16S rRNA clone library analysis. A marked decrease of microbial diversity in the BAC filtration system was observed along the flow path. Alphaproteobacteria,Gammaproteobacteria and Acidobacteria were found to be the major bacterial groups in the BAC filters. Moreover, Novosphingobium aromaticivorans-like microorganisms were detected. This work might add some new insights towards microbial communities in regards to BAC filtration for the treatment of drinking water.

Study of Fire Resistance Performance of Stiffened Welded Hollow Spherical Joint Under Axial Tension

Xiaobin Qiu,Tao Chen,Bingsheng Huang,Jingrui Zhu,Zhen Zhang,Haoyu Song 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2

To study the fire resistance performance of stiffened welded hollow spherical joints under axial tension, two specimens with load ratios of 0.4 and 0.6 were subjected. The temperature distribution, failure mode, and fire resistance performance of stiffened welded hollow spherical joints under axial tension were obtained. The test results show that the failure mode of the joint was a pull-out failure. During the heating process, the closer to the spherical equator, the higher the spherical temperature, and the temperature of the sphere at the stiffener is lower than that of the sphere at the non-stiffener. The load ratio has a great influence on the refractory performance of the stiffened welded hollow sphere joint. When the load ratio of the specimen is reduced from 0.60 to 0.40, the fire resistance time of the specimen increases by 4.47 min, and the critical temperature increases by 21.3 °C. According to the European Code, the finite element model for the stiffened welded hollow spherical joints is established. The effect law of various influencing factors on the fire resistance performance of stiffened welded hollow spherical joints is studied. The research results show that reducing the load ratio and increasing the thickness of the sphere can significantly improve the fire resistance performance of the joint. The calculation formula of the critical temperature of steel members in the current standard not suitable for the calculation of the critical temperature of the welded hollow spherical joint. The critical temperature values with different load ratios recommended by the current standard were relatively more conservative. Taking the ambient temperature as the fire resistance temperature, the finite element analysis results were fitted, and the formula for calculating the fire resistance temperature of the stiffened welded hollow spherical joint was proposed.

Structural analysis of high-rise reinforced concrete building structures during construction

Xiaobin Song,Xianglin Gu,Weiping Zhang,Tingshen Zhao,Xianyu Jin 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.4

This paper presents a three-dimensional finite element method based structural analysis model for structural analysis of reinforced concrete high-rise buildings during construction. The model considered the time-dependency of the structural configuration and material properties as well as the effect of the construction rate and shoring stiffness. Uniaxial compression tests of young concrete within 28 days of age were conducted to establish the time-dependent compressive stress-strain relationship of concrete,which was then used as input parameters to the structural analysis model. In-situ tests of a RC high-rise building were conducted, the results of which were used for model verification. Good agreement between the test results and model predictions was achieved. At the end, a parametric study was conducted using the verified model. The results indicated that the floor position and construction rate had significant effect on the shore load, whereas the influence of the shore removal timing and shore stiffness have much smaller. It was also found that the floors are more prone to cracking during construction than is ultimate bending failure.

Active monitoring of pipeline tapered thread connection based on time reversal using piezoceramic transducers

Xiaobin Hong,Gangbing Song,Jiaobiao Ruan,Zhimin Zhang,Sidong Wu,Guixiong Liu 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.4

The monitoring of structural integrity of pipeline tapered thread connections is of great significance in terms of safe operation in the industry. In order to detect effectively the loosening degree of tapered thread connection, an active sensing method using piezoceramic transducers was developed based on time reversal technique in this paper. As the piezoeramic transducers can be either as actuators or sensors to generate or detect stress waves, the energy transmission for tapered thread connection was analyzed. Subsequently, the detection principle for tapered thread connection based on time reversal was introduced. Finally, the inherent relationship between the contact area and tightness degree of tapered thread connection for the pipe structural model was investigated. Seven different contact area scenarios were tested. Each scenario was created by loosening connectors ranging from 3 turns to 4.5 turns in the right tapered threads when the contact area in the left tapered threads were 4.5 turns. The experiments were separately conducted with a highly noisy environment and various excitation signal amplitudes. The results show the focused peaks based on time reversal have the monotonously rising trend with the increase of the contact areas of tapered threads within an acceptable monitoring resolution for metal pipes. Compared with the energy method, the proposed time reversal based method to monitor tapered threads loosening demonstrates to be more robust in rejecting noise in Structural Health Monitoring (SHM) applications.

High step-up isolated forward-flyback DC/DC converter based on resonance with pulse frequency modulation

Zhang, Zhiguo,Liao, Mingyu,Jiang, Dongrong,Yang, Xiaobin,Li, Shan The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.2

A high step-up isolated forward-flyback DC-DC converter with pulse frequency modulation (PFM) is presented in this paper. The proposed converter has features of both a forward and a flyback converter and can deliver energy during the turn-on and turn-off intervals in a switching period. In addition, by utilizing resonance it can achieve zero-voltage switching (ZVS) for the primary switches and zero-current switching (ZCS) for the secondary rectifier diodes. All of the power semiconductors operate under soft switching conditions. The structure of the proposed converter is simple and easily implemented. It also provides a high step-up voltage gain. The current stresses of the power devices in PFM are lower than those in pulse width modulation (PWM). Therefore, the converter efficiency in PFM is higher than that in PWM. The operation principle and characteristic of the presented converter are described in detail, and the converter performances for PWM and PFM are compared. A 160 W hardware prototype has been built, and experimental results verify the validity of the theoretical analysis.

Low-noise reconstruction method for coded-aperture gamma camera based on multi-layer perceptron

Rui Zhang,Xiaobin Tang,Pin Gong,Peng Wang,Cheng zhou,Xiaoxiang Zhu,Dajian Liang,Zeyu Wang 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.10

Accurate localization of radioactive materials is crucial in homeland security and radiological emergencies. Coded-aperture gamma camera is an interesting solution for such applications and can be developed into portable real-time imaging devices. However, traditional reconstruction methods cannot effectively deal with signal-independent noise, thereby hindering low-noise real-time imaging. In this study, a novel reconstruction method with excellent noise-suppression capability based on a multi-layer perceptron (MLP) is proposed. A coded-aperture gamma camera based on pixel detector and coded-aperture mask was constructed, and the process of radioactive source imaging was simulated. Results showed that the MLP method performs better in noise suppression than the traditional correlation analysis method. When the Co-57 source with an activity of 1 MBq was at 289 different positions within the field of view which correspond to 289 different pixels in the reconstructed image, the average contrast-to-noise ratio (CNR) obtained by the MLP method was 21.82, whereas that obtained by the correlation analysis method was 5.85. The variance in CNR of the MLP method is larger than that of correlation analysis, which means the MLP method has some instability in certain conditions.