A zeolite family with expanding structural complexity and embedded isoreticular structures

Guo, Peng,Shin, Jiho,Greenaway, Alex G.,Min, Jung Gi,Su, Jie,Choi, Hyun June,Liu, Leifeng,Cox, Paul A.,Hong, Suk Bong,Wright, Paul A.,Zou, Xiaodong Nature Publishing Group, a division of Macmillan P 2015 Nature Vol.524 No.7563

The prediction and synthesis of new crystal structures enable the targeted preparation of materials with desired properties. Among porous solids, this has been achieved for metal–organic frameworks, but not for the more widely applicable zeolites, where new materials are usually discovered using exploratory synthesis. Although millions of hypothetical zeolite structures have been proposed, not enough is known about their synthesis mechanism to allow any given structure to be prepared. Here we present an approach that combines structure solution with structure prediction, and inspires the targeted synthesis of new super-complex zeolites. We used electron diffraction to identify a family of related structures and to discover the structural ‘coding’ within them. This allowed us to determine the complex, and previously unknown, structure of zeolite ZSM-25 (ref. 8), which has the largest unit-cell volume of all known zeolites (91,554 cubic ångströms) and demonstrates selective CO<SUB>2</SUB> adsorption. By extending our method, we were able to predict other members of a family of increasingly complex, but structurally related, zeolites and to synthesize two more-complex zeolites in the family, PST-20 and PST-25, with much larger cell volumes (166,988 and 275,178 cubic ångströms, respectively) and similar selective adsorption properties. Members of this family have the same symmetry, but an expanding unit cell, and are related by hitherto unrecognized structural principles; we call these family members embedded isoreticular zeolite structures.

Compact Band-notched UWB Antenna Design Based On Transmission Line Model

Xiaoming Zhu,Xiaodong Yang,Peng Chen 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.1

In order to avoid the interference from existing narrowband communication systems, this paper proposes a compact band-notched UWB (ultra wideband) antenna with size of 12mm×22mm ×1.6mm. Transmission line model is applied to analyzing wide impedance matching characteristic of the modified base antenna, which has a gradual stepped impedance feeder structure. The proposed antenna realizes dual band-notched function by combining two biased T-shaped parasitic elements on the rear side with a window aperture on the radiation patch. The simulation current distributions of the antenna reflect resonant suppression validity of the two methods. In addition, the measured radiation characteristics demonstrate the proposed antenna prevents signal interference from WLAN (5.15-5.825GHz) and WiMAX (3.4-3.69GHz) effectively, and the measured patterns show the antenna omnidirectional radiation in working frequencies.

Robust model predictive current control for six-phase PMSMS with virtual voltage vectors

Yao, Ming,Peng, Jingyao,Sun, Xiaodong The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.11

In this paper, a compensation prediction model current control based on the extended state observer is proposed for the static errors and oscillations of output current caused by parameter disturbance deviations. First, the parameter change part is regarded as the total disturbance, and a mathematical model of the motor is established. Then, virtual voltage vectors are introduced to eliminate the effect of leakage inductance mismatch and to further suppress current harmonics. Furthermore, the state observer is designed to estimate disturbances and currents. The estimated values from the state observer are used as the feedforward part to cancel disturbances in the system. Then, the stability of the proposed algorithm is verified by a pole configuration analysis. Finally, the effectiveness of the proposed method is confirmed by a six-phase permanent magnet synchronous hub motor experiment.

Online Hot Topic Detection Based on Segmented Timeline and Aging Theory

Ruiguo Yu,Xiaodong Xie,Yongxing Li,Mankun Zhao,Xuyuan Dong,Muwen He,Peng Chang,Zan Wang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.2

With a great deal of digitized textual information now available on the internet, it is almost impossible for people to assimilate all the information timely. Therefore, the technologies of topic detection and tracking are used for constructing news topics from news stories in order to bring convenience to people. However, traditional topic detection methods are not always so effective in detecting emerging hot news topics in a short period of time, and most topic detection methods use single-pass clustering algorithm which is with low accuracy and very sensitive to the input sequence of news documents. In order to improve clustering accuracy, we utilize a temporal distance factor to segment timeline into equal parts and propose a novel two-times single-pass clustering algorithm to deal with news stories in each part of timeline separately. Moreover, the aging theory is combined with our approach to build life-span model of topics from which we can obtain variation trend of hotness value of topics. The results of experiments show that our approach is effective and the life circle model of topics established by our method can conform to reality well.

Fault-tolerant Model Predictive Current Control of Six-Phase Permanent Magnet Synchronous Motors with Pulse Width Modulation

Yao Ming,Peng Jingyao,Sun Xiaodong,Sun Yueping 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

A model predictive current control strategy with pulse width modulation is proposed for a single-phase open circuit fault. This method decomposes the change matrix based on the normal vector space to ensure that the decoupling matrix remains unchanged so that there is no need to reconfigure the controller topology. By analysing the fault phase voltage difference under normal and fault conditions, 24 synthetic virtual voltage vectors are used to compensate the voltage vector during a single-phase fault and eliminate the current coupling problem. In addition, a standard pulse width modulation switching sequence is implemented to achieve the purpose of unifying the switching frequency, which makes the method easy to implement. Finally, the effectiveness of the proposed method is verified by experiments.

Epidemiology and resistance features of Acinetobacter baumannii isolates from the ward environment and patients in the burn ICU of a Chinese hospital

Yali Gong,Xiaodong Shen,Guangtao Huang,Cheng Zhang,Xiaoqiang Luo,Supeng Yin,Jing Wang,Fuquan Hu,Yizhi Peng,Ming Li 한국미생물학회 2016 The journal of microbiology Vol.54 No.8

Acinetobacter baumannii is an important opportunistic pathogen that causes severe nosocomial infections, especially in intensive care units (ICUs). Over the past decades, an everincreasing number of hospital outbreaks caused by A. baumannii have been reported worldwide. However, little attention has been directed toward the relationship between A. baumannii isolates from the ward environment and patients in the burn ICU. In this study, 88 A. baumannii isolates (26 from the ward environment and 62 from patients) were collected from the burn ICU of the Southwest Hospital in Chongqing, China, from July through December 2013. Antimicrobial susceptibility testing results showed that drug resistance was more severe in isolates from patients than from the ward environment, with all of the patient isolates being fully resistant to 10 out of 19 antimicrobials tested. Isolations from both the ward environment and patients possessed the β-lactamase genes blaOXA-51, blaOXA-23, blaAmpC, blaVIM, and blaPER. Using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST), these isolates could be clustered into 4 major PFGE types and 4 main sequence types (ST368, ST369, ST195, and ST191) among which, ST368 was the dominant genotype. Epidemiologic and molecular typing data also revealed that a small-scale outbreak of A. baumannii infection was underway in the burn ICU of our hospital during the sampling period. These results suggest that dissemination of β-lactamase genes in the burn ICU might be closely associated with the high-level resistance of A. baumannii, and the ICU environment places these patients at a high risk for nosocomial infection. Cross-contamination should be an important concern in clinical activities to reduce hospital acquired infections caused by A. baumannii.

AlN with Strong Blue Emission Synthesized Through a Solventless Route

Wei Wang,Peng Zhang,Xiaobai Wang,Xiang Lei,Xiaodong Chen,Hong Ding,Hua Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.2

Aluminum nitride (AlN) with strong blue emission at 450 nm has been synthesized from hexahydrate aluminum chloride and urea above 850℃ via a solventless route. Several aluminum and nitrogen sources are selected and well investigated to determine the effect of AlN synthesis. Moreover, the structure, component, morphology, photoluminescence properties and possible synthesis mechanism are also discussed carefully.

Achieving Maximal NJRL Method for Jamming UAVs Network

Zhang Yu,Peng Xiaodong,Liu Feng 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.2

Different from others, we focus on designing jamming methods for disrupting UAVs network efficiently. The jamming problem is formulated. Then we introduce two new methods (AMN-U2C and AMN-U2U) for jamming UAVs network. Both of them adopt the idea intending to achieve maximal number of jammed receiving links. AMN-U2C method searches locations for jammer by moving jammers along the path from the point of a UAV to the center point of others. AMN-U2U method searches by shifting jammers from the point of a UAV to another UAV. Finally we simulate the jamming attack on UAVs network using AMN-U2C, AMN-U2U, TP, GA and Random methods. The result shows AMN-U2U does best at most cases.

New Strategy for Eliminating Zero-sequence Circulating Current between Parallel Operating Three-level NPC Voltage Source Inverters

Kai Li,Zhenhua Dong,Xiaodong Wang,Chao Peng,Fujin Deng,Josep M. Guerrero,Juan Vasquez 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

Improvement of Microstructure, Mechanical Property and Corrosion Resistance of Mg–9Li–3Al–1Ca Alloy Through Centrifugal Casting

Zhenduo Ma,Qiang Peng,Guobing Wei,Yan Yang,Tiancai Xu,Weidong Xie,Gang Liu,Xiaodong Peng 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11

The microstructure, mechanical property and corrosion behavior of gravity casting and centrifugal casting Mg–9Li–3Al–1Ca alloy were investigated. The results indicate that the Mg–9Li–3Al–1Ca alloy is mainly composed of α-Mg phases, β-Liphases and Al2Caphases. After centrifugal casting, the blocky and elongated α-Mg phases of the gravity casting alloy canbe refined and spheroidized. Meanwhile, the amount of α-Mg and AlLi phases increases, however, the number of Al2Caphases decreases. Besides, a strong texture of β-Li phase on the (200) plane can be formed. The microstructure refinementand the decrease of Al2Caphases lead to the improvement of comprehensive property. The property of centrifugal alloyshas gradient along radius direction because the strength of centrifugal force varies with the centrifugal radius. The centrifugalcasting Mg–9Li–3Al–1Ca alloy at outside exhibits excellent comprehensive properties. The ultimate tensile strengthand elongation of centrifugal casting alloy achieve the value of 198.3 MPa and 6.0%, corresponding to 83.6% and 300.0%increments compared with gravity casting ones, respectively. The corrosion current also decreases to 89.4 μA/cm2, whichattributes to the weakening of galvanic corrosion attributing to the decrease of number of Al2Caphases and the transformationof corrosion pattern caused by grain refinement.