SPATIAL COHERENCE OF SOUND IN THE CONVERGENCE ZONES

Dinghua GUAN,Ruichao ZHU,Renhe ZHANG,Yaoming CHEN 한국소음진동공학회 1994 한국소음진동공학회 국제학술대회논문집 Vol.1994 No.3

To Protect and Utilize Suburban Green Space and To Expend Green Ecological Space at Urban Periphery

Dinghua Liu,Yaojiong Mei Korean Institute of Landscape Architecture 2004 Journal of the Korean institute of landscape archi Vol.2 No.-

Suburban green space is an important component part of urban ecological system, the third largest space between urban center and peripheral countryside. Because of the specific regional location of the suburban green space, it differs from the green space in the center of the city in the respects of construction and planning. Anyhow, it has the features of less investment, quicker efficiency, free and easy management and good ecological effects. The writer of this paper holds that urban ecological construction should be planned rationally and laid out in an overall way under the prerequisite of making full use of and protecting local species so as to further extend the green ecological space at urban periphery, to create dense green surroundings, and to explore a way for ecological construction to develop in a scientific, effective and healthy way.

An approach for machining allowance optimization of complex parts with integrated structure

Zhang, Ying,Zhang, Dinghua,Wu, Baohai Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.4

Currently composite manufacturing process, such as linear friction welding plus NC machining, is the main method for the manufacturing and repairing of complex parts with integrated structure. Due to different datum position and inevitable distortion from different processes, it is important to ensure sufficient machining allowance for complex parts during the NC machining process. In this paper, a workpiece localization approach for machining allowance optimization of complex parts based on CMM inspection is developed. This technique concerns an alignment process to ensure sufficient stock allowance for the single parts as well as the whole integrated parts. The mathematical model of the constrained alignment is firstly established, and then the symmetric block solution strategy is proposed to solve the optimization model. Experiment result shows that the approach is appropriate and feasible to distribute the machining allowance for the single and whole parts for adaptive machining of complex parts.

Structural, photoluminescent, and dielectric properties of Eu3+-doped Ba0.7Sr0.3TiO3 thin films

Ling Liu,Ni Qin,Dinghua Bao 한국물리학회 2015 Current Applied Physics Vol.15 No.6

Eu3+-doped Ba0.7Sr0.3TiO3 thin films were prepared by a chemical solution deposition method and characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence and dielectric measurements. The thin films were well crystallized with a pure perovskite structure. A contraction of the unit cell was observed upon incorporation of Eu3+ ions below 2 mol%, while an expansion occurred as the Eu3+ concentration was further increased above 2 mol%, indicating that Eu3+ ions with different concentrations occupied different lattice sites. Photoluminescence spectra showed two prominent transitions of Eu3+ ions at 594 nm (5D0→7F1) and 618 nm (5D0→7F2) upon excitation at 395 nm (7F0→5L6). There existed two quenching concentrations at 2 mol% and 4 mol% due to different lattice sites of the Eu3+ ions. We also investigated the dielectric properties of the thin films. Our study suggests that Eu3+-doped Ba0.7Sr0.3TiO3 thin films have potential applications in multifunctional optoelectronic devices.

A Model Reconstruction Method of Blade Repair Based on Linear Combination

Baohai Wu,Hai Zheng,Ying Zhang,Ming Luo,Dinghua Zhang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.3

Repair of damaged blade in aero-engine reduces economic losses and has been applied widely in factory areas. However, the actual blade model after service is not consistent with the theoretical model. Thus, the reconstructed blade model is required. Different damage areas, damage forms and operations in the additive process may lead to different deformations of the blades, thus the actual CAD model of the blade is also different, resulting in the challenge when reconstruct the model. In this paper, a new model reconstruction method of blade-repair is proposed based on the linear combination of base curves blending algorithm. Firstly, the blade after additive processing is measured and such data is processed and registered with the theoretical model. Secondly, the area created by measurement data is smoothly blended to the theoretical area utilizing a developed linear combination algorithm, leading to the capability of providing the reconstructed concave and convex surfaces. Finally, the reconstructed concave and convex surfaces are bridged to theoretical leading and trailing edges. Consequently, the intact reconstructed model of the damaged blade is obtained. The blade-repair case study demonstrates the availability of the proposed method and the analysis of machining error indicates that the blending between the reserved area and the theoretical area of the reconstructed model is smooth.

Bipolar resistive switching effect and mechanism of solution-processed orthorhombic Bi2SiO5 thin films

Ruqi Chen,Wei Hu,Lilan Zou,Yifu Ke,Aize Hao,Dinghua Bao 한국물리학회 2019 Current Applied Physics Vol.19 No.9

Orthorhombic Bi2SiO5 thin films with dense surface were synthesized by using a chemical solution deposition method. The crystallized films were first utilized to implement resistive memory cells with Pt/Bi2SiO5/Pt sandwich architecture. It exhibited outstanding switching parameters including concentrated distributions of low and high resistance states, uniform switching voltages, cycling endurance, and long retention. Furthermore, the model of formation and rupture of conductive filaments consisted of oxygen vacancies was used to well explain resistive switching behavior. The results revealed that the solution-processed Bi2SiO5 thin film devices have great potential for forefront application in nonvolatile memory.

Enhanced resistive switching performance of spinel MnCo2O4 resistive random access memory devices: Effects of annealing temperatures and annealing atmospheres

Du Ling,Li Jiacheng,Zhang Yu,Qin Ni,Bao Dinghua 한국물리학회 2023 Current Applied Physics Vol.48 No.-

The spinel MnCo2O4 (MCO) thin films were fabricated on Pt/Ti/SiO2/Si substrates for resistive memories via sol-gel spin-coating deposition method under different annealing temperatures and annealing atmospheres. The 650oC-annealing Pt/MCO/Pt device shows better bipolar resistance switching parameters than the devices annealed at 600 ◦C and 700 ◦C. The nitrogen-annealing Pt/MCO/Pt device exhibits optimum resistance switching parameters due to increasing of the oxygen-vacancies proportion, formation of confined and stable conductive filaments, and suppressing of the randomness of oxygen vacancies. The carrier transportation mechanisms of the devices with numerous oxygen-vacancies content in low resistance state (LRS) and high resistance state (HRS) are dominated by Ohmic conduction and Schottky emission, respectively. For the devices with fewer oxygen-vacancies content, the conduction mechanisms at LRS and HRS can be described by nearest-neighboring hopping conduction and space-charge-limited current model, respectively. This work indicates that the spinel MCO films have good potential application in resistive random access memory.

Elimination of endurance degradation by oxygen annealing in bilayer ZnO/CeO2-x thin films for nonvolatile resistive memory

Muhammad Ismail,Shazia Jabeen,Tahira Akber,Ijaz Talib,Fayyaz Hussain,Anwar Manzoor Rana,Muhammad Hussain,Khalid Mahmood,Ejaz Ahmed,Dinghua Bao 한국물리학회 2018 Current Applied Physics Vol.18 No.8

Effect of oxygen annealing on bipolar resistive switching (BRS) properties of TiN/ZnO/CeO2-x/Pt devices was investigated. Bilayer ZnO/CeO2-x thin films were fabricated by rf-magnetron sputtering. It was observed that the improvement in cycle-to-cycle endurance degradation and uniformity of the bilayer ZnO/CeO2-x thin film is optimum at 400 °C annealing temperature due to decrease in oxygen vacancies during annealing, as confirmed by x-ray photoelectron spectroscopy. The BRS could be caused by the formation of interfacial TiON layer, which is most likely to be accountable for creating an adequate quantity of oxygen vacancies necessary for the formation and rupture of conductive filaments. Smaller Gibbs free energy of the formation of interfacial TiON (−611 kJmol−1) layer as compared to bilayer film ZnO (−650 kJmol−1) and CeO2 (−1024 kJmol−1) results in an easier re-oxidation of the filaments through the oxygen exchange with TiN top electrode. The analysis of current– voltage characteristics shows that the charge transport mechanism is Schottky emission. Moreover, the temperature dependence of high resistance state (HRS) and low resistance state (LRS) revealed the physical origin of the RS mechanism, which entails the oxygen vacancies for the formation and rupture of conducting paths.

Coexistence of resistive switching and magnetism modulation in sol-gel derived nanocrystalline spinel Co3O4 thin films

Chuangye Yao,Wei Hu,Muhammad Ismail,Santhosh Kumar Thatikonda,Aize Hao,Shuai He,Ni Qin,Wenhua Huang,Dinghua Bao 한국물리학회 2019 Current Applied Physics Vol.19 No.11

We report the coexistence of resistive switching and magnetism modulation in the Pt/Co3O4/Pt devices, where the effects of thermal annealing and film thickness on the resistive and magnetization switching were investigated. The sol-gel derived nanocrystalline Co3O4 thin films obtained crack-free surface and crystallized cubic spinel structure. The 110 nm Co3O4 film based device annealed at 600 °C exhibited optimum resistive switching parameters. From I–V curves fitting and temperature dependent resistance, the conduction mechanism in the high-voltage region of high resistance state was dominated by Schottky emission. Magnetization-magnetic field loops demonstrated the ferromagnetic behaviors of the Co3O4 thin films. Multilevel saturation magnetization of the Co3O4 thin films can be easily realized by tuning the resistance states. Physical resistive switching mechanism can be attributed to the rejuvenation and annihilation of conductive filament consisting of oxygen vacancies. Results suggest that Pt/Co3O4/Pt device shows promising applications in the multifunctional electromagnetic integrated devices.

Ti-doping induced antiferroelectric to ferroelectric phase transition and electrical properties in Sm-PbZrO3 thin films

Thatikonda Santhosh Kumar,Huang Wenhua,Du Xingru,Yao Chuangye,Ke Yifu,Wu Jiang,Qin Ni,Bao Dinghua 한국물리학회 2021 Current Applied Physics Vol.24 No.-

The antiferroelectric (Pb0.985Sm0.01) (Zr1-xTix)O3 (Ti-PSZO) thin films were synthesized on Pt(111)/Ti/SiO2/Si substrates using a chemical solution deposition method. The films were crystallized in the perovskite phase with a preferential orientation along (111) direction. With Ti doping in PSZO, a gradual transformation from antiferroelectric to ferroelectric phase transition was noticed at room temperature owing to the Ti doping induced lattice distortion. The phase transition has been confirmed through the P - E hysteresis loops, X-ray diffraction (peak shifting), capacitance-voltage measurements, and Raman scattering analysis. The thin film with Ti = 0.15 doping displayed a ferroelectric behavior with high dielectric constant and large dielectric tunability of about 62%. Also, Ti doping altered the Curie temperature (Tc) and enhanced the order of dielectric diffuseness. It is believed that Ti-doping in PSZO is an effective way to induce an antiferroelectric - ferroelectric phase transition and to tailor the electrical characteristics of PSZO thin films.