Comparison of changes in the nasal cavity, pharyngeal airway, and maxillary sinus volumes after expansion and maxillary protraction with two protocols: Rapid palatal expansion versus alternate rapid maxillary expansion and constriction

Weitao Liu,Shaonan Zhou,Edwin Yen,Bingshuang Zou 대한치과교정학회 2023 대한치과교정학회지 Vol.53 No.3

Objective: To evaluate and compare a series of volume changes in the nasal cavity (NC), nasopharynx, oropharynx, and maxillary sinuses (MS) in growing Class III patients after either rapid palatal expansion (RPE) or alternate rapid maxillary expansion and constriction (Alt-RAMEC) followed by facemask (FM) therapy, by using cone-beam computed tomography (CBCT). Methods: Forty growing Class III patients were retrospectively selected and divided into two matched groups: RPE/FM (14 females, 6 males; mean age, 9.66 ± 1.23 years) and Alt-RAMEC/FM groups (14 females, 6 males; mean age, 10.28 ± 1.45 years). The anteroposterior and vertical displacements of Point A, the volumes of the NC, nasopharyngeal, oropharyngeal, and MS were measured at different time points: pretreatment (T1), postexpansion (T2), and postprotraction (T3). Results: Both groups demonstrated significant maxilla advancement (by 1.3 mm) during expansion, with a statistically significant intergroup difference during protraction (RPE/FM, 1.1 mm; Alt-RAMEC/FM, 2.4 mm; p < 0.05) and throughout the treatment (RPE/FM, 2.4 mm; Alt-RAMEC/FM, 3.7 mm; p < 0.05). NC and nasopharyngeal airway volumes increased significantly in both groups after expansion, protraction, and treatment. The oropharyngeal and MS volumes increased in both groups after protraction and post-treatment. However, no volumetric differences were observed between the two groups. Conclusions: There was no significant difference in airway volume changes, including NC, nasopharyngeal, oropharyngeal airway, and MS, between RPE/FM and Alt-RAMEC/FM groups at different time points. Although there was significantly more forward movement after protraction in the Alt-RAMEC/FM group, the difference was deemed too small to be clinically relevant.

Stress Evolution Law and Failure Characteristics of Mining Floor Rock Mass above Confined Water

Shiliang Liu,Weitao Liu,Jianjun Shen 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.7

The discussion of stress evolution law and failure characteristics of rock mass in mining floor above confined water is the key to control the floor water inrush in deep mining. Based on analyzing the strike support pressure of working face, the mechanical model of coal floor above the confined water was established. Then, vertical, horizontal and shear stress distribution maps and the failure range morphological map of mining floor were calculated based on data processing software Origin. Then, with the similar simulation test bed for water inrush from coal seam floor, the fluid solid coupling simulation material was selected, and the stress evolution law and failure characteristics of coal seam mining floor were improved. The results showed that the vertical stress contour is a “semi-elliptical” shape distribution and the greater the floor depth, the smaller the affected degree, but the influenced range increased. The higher shear stress zone occurred in the vicinity of working face coal wall. The failure range morphological map of mining floor was approximately a spoon shape and maximum failure depth was 14.0 m based on the mechanical theory. The maximum failure depth of the floor was 13.4 m based on the similar simulation experiment. So, the experimental results are in agreement with the theoretical results. The results in this paper can provide theory basis for safety mining above confined water.

An Improvement of the Response Surface Method Based on Reference Points for Structural Reliability Analysis

Weitao Zhao,Weihua Liu,Qijiao Yang 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.7

The Response Surface Method (RSM) is a powerful technique to evaluate the structural reliability. However, for a Limit State Function (LSF) with highly non-linear, the accuracy of the approximation of the failure probability does not depend very much upon the design point. It is necessary for RSMs to consider the design point and the non-linear trend of actual LSF around the design point, because both of them influence the failure probability. Thus, in order to improve the fitting precision of the Response Surface Function (RSF) to the actual LSF over a larger region containing the design point, the reference points of experimental points are constructed in this paper. Experimental points used to obtain parameters of a RSF are selected according to the information of reference points. Four examples are discussed in detail. The numerical results indicate that the accuracy and the efficiency of the proposed method are both desirable for both numerical and implicit LSFs, and the proposed method is superior to the classical RSM in terms of efficiency and accuracy.

A Novel Hybrid Suspension Electromagnet for Middle-low Speed Maglev Train

Han Weitao,Sun Jinji,Liu Xiankai,Guo Haixia,Wang Jinsha 한국자기학회 2017 Journal of Magnetics Vol.22 No.3

This paper proposes a novel hybrid suspension electromagnet for application in the middle-low speed maglev train. Its configuration and working principle are introduced. Mathematical models of the suspension force and guidance force are established accurately by equivalent magnetic circuit method (EMCM), from which the relationships of suspension force-control current-suspension gap and guidance force-guidance displacement are derived. Finite element method (FEM) is also applied to analyze the performances and characteristics of the novel hybrid suspension electromagnet. The analysis results are in good agreement with those calculated by EMCM, which is helpful in designing and optimizing the suspension system. The comparisons are made between the performances of the novel and the traditional electromagnets. The contrast results indicate that the proposed hybrid suspension electromagnet possesses better performances compared to the traditional structure, especially the little control current and the low suspension power loss.

One-Pot Synthesis of Nanodendritic PtIr Alloy with High Electrochemical Activity for Ethylene Glycol Oxidation

Xuedong Gao,Lulu Liu,Qiyu Wang,Kun Qi,Zhao Jin,WEITAO ZHENG,XIAOQIANG CUI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.2

Nanodendritic Pt-based bimetallic alloys are one promising catalyst with three-dimensional (3D) networks structure composed of integrating branches for electrochemical catalytic reaction. We successfully synthesized dendrites Pt6Ir4 alloy with small size of 20 nm in oleylamine. The dendritic Pt6Ir4 alloy are characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical tests suggest that the as-prepared dendritic Pt6Ir4 alloy exhibits greatly enhanced ethylene glycol oxidation reaction (EGOR) activity than commercial Pt/C with high EGOR mass activity, anti-poisoning and stability.

71% Common‑mode voltage suppression modulation strategy for indirect matrix converters

Shanhu Li,Zijing Lu,Sunpeng Cao,Xu Liu,Zhaoyang Jin,Weitao Deng 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.2

Common-mode voltage (CMV) with a high amplitude and frequency is generated when an indirect matrix converter (IMC) is operating, which damages the motor winding insulation and accelerates motor aging. Existing IMC modulation methods can only suppress the CMV by 42.3%. However, this paper proposes a modulation strategy with a 71% reduction in the peak CMV. The proposed method selects active vectors based on the characteristics of the CMV amplitude under each of the active vectors. The rectifier stage selects two active vectors within each modulation sector. According to the sector where the input reference current vector is located, the inverter stage chooses active-voltage vectors whose corresponding peak CMV is 1/3 the minimum peak line voltage for modulation. Moreover, the CMV spikes caused by the dead zone effect are eliminated by reasonably arranging the switching sequence of the voltage vectors in the inverter stage. The proposed approach considerably lowers the peak CMV and has a good suppression effect on the amplitude of high-frequency CMV. Finally, experimental results illustrate the CMV reduction efficiency of the modulation strategy.

Earth Pressure and Internal Forces of Tunnel Lining in Jet Grouting Reinforced Mud Stratum

Haibo Jiang,Shunhua Zhou,Honggui Di,Weitao Ye,Zhi Liu,Yu Zhao 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.10

In this study, field measurements of the earth pressures and the main reinforcement strains were carried out at three shield tunnel linings in mud stratum reinforced by vertical jet-grouted piles during tunnel construction and post-construction. The measured strains were used to back-calculate the linings' internal forces. The measured earth pressures and the back-calculated internal forces were compared to corresponding design values. The results indicate that the earth pressure and the internal forces increased rapidly, before exhibiting a fluctuating decrease and finally a long-term slow change, after lining assembly. The vertical jet-grouted piles were beneficial to mobilise the soil arching effect and led to the real earth pressure on the lining significantly smaller than the full overburden pressure, even with a relatively shallow buried depth. The vertical jet-grouted piles intensified the influence of backfill grouting on the earth pressure and caused the lining segments near the backfill grouting holes to continuously bear more radial pressure in the long-term. The resultant internal forces during lining assembly were large, and the Conventional Model failed to consider this element of the internal forces. The findings can provide a reference for the design and the construction of similar projects.

Exploiting Anti-T-shaped Graphene Architecture to Form Low Tortuosity, Sieve-like Interfaces for High-Performance Anodes for Li-Based Cells

Wang, Dong,Zhang, Wei,Drewett, Nicholas E.,Liu, Xiaofei,Yoo, Seung Jo,Lee, Sang-Gil,Kim, Jin-Gyu,Deng, Ting,Zhang, Xiaoyu,Shi, Xiaoyuan,Zheng, Weitao American Chemical Society 2018 ACS central science Vol.4 No.1

<▼1><P/><P>Graphitic carbon anodes have long been used in Li ion batteries due to their combination of attractive properties, such as low cost, high gravimetric energy density, and good rate capability. However, one significant challenge is controlling, and optimizing, the nature and formation of the solid electrolyte interphase (SEI). Here it is demonstrated that carbon coating via chemical vapor deposition (CVD) facilitates high electrochemical performance of carbon anodes. We examine and characterize the substrate/vertical graphene interface (multilayer graphene nanowalls coated onto carbon paper via plasma enhanced CVD), revealing that these low-tortuosity and high-selection graphene nanowalls act as fast Li ion transport channels. Moreover, we determine that the hitherto neglected parallel layer acts as a protective surface at the interface, enhancing the anode performance. In summary, these findings not only clarify the synergistic role of the parallel functional interface when combined with vertical graphene nanowalls but also have facilitated the development of design principles for future high rate, high performance batteries.</P></▼1><▼2><P>We explored an anti-T-shaped graphene surface-coating concept which offers a low-tortuosity, sieve-like interface that may be exploited for optimized Li-based anodes.</P></▼2>