An efficient time-variant reliability-based design optimization method based on probabilistic feasible region

Zihao Wu,Zhenzhong Chen,Ge Chen,Xiaoke Li,Chen Jiang,Xuehui Gan,Haobo Qiu,Liang Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

Time-variant reliability-based design optimization (T-RBDO) issues are probabilistic design problems that assess the dependability of the design across time. The engineering situation is most closely resembled by it. The approaches to resolving T-RBDO problems, nevertheless, are convoluted and time-consuming. In this paper, an effective strategy for solving RBDO issues are extended to resolving TRBDO problems in order to increase efficiency. To solve T-RBDO challenges, the time-variant probabilistic feasible region (T-PFR) approach, which is based on the PFR method for resolving RBDO issues, was presented. The idea of the equivalent inverse most probable point (EIMPP) is put out in this methodology. Based on the EIMPP, the probabilistic feasible region is likewise developed for time-variant constraints. The effective tactic of the proposed method is to identify the non-active time-variant constraints using the probabilistic feasible region and to forego conducting time reliability analysis on them. Three mathematics and two engineering issues demonstrate that the suggested solution is viable and effective.

A novel probabilistic feasible region method for reliability-based design optimization with varying standard deviation

Zihao Wu,Zhenzhong Chen,Ge Chen,Xiaoke Li,Chen Jiang,Xuehui Gan,Haobo Qiu,Liang Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

An effective method for reliability-based design optimization (RBDO) problems taking uncertainties into account is the probabilistic feasible region (PFR) approach. The PFR approach is built around the fixed nature of the standard deviation in general RBDO problems. Therefore, the accuracy of the PFR approach will be affected when dealing with RBDO problems with varying standard deviation. To improve the accuracy of PFR method in solving the RBDO problems with varying standard deviation, a novel probabilistic feasible region strategy considering varying standard deviations (PFR-vstd) approach is suggested in this paper. In place of the initial probabilistic feasible region in standard normal space, a new probabilistic feasible region is established in original design space in this novel approach. The results of four applications demonstrate the high accuracy and sufficient efficiency of PFR-vstd method. The findings demonstrate that PFR-vstd method is capable of accurately resolving RBDO problems with varying standard deviation.

Role of the Mean Nocturnal Baseline Impedance in Identifying Evidence Against Pathologic Reflux in Patients With Refractory Gastroesophageal Reflux Disease Symptoms as Classified by the Lyon Consensus

( Yanhong Wu ),( Zihao Guo ),( Chuan Zhang ),( Yutao Zhan ) 대한소화기기능성질환·운동학회 2022 Journal of Neurogastroenterology and Motility (JNM Vol.28 No.1

Background/Aims Mean nocturnal baseline impedance (MNBI) is a new reflux metric for mucosal integrity. It remains unclear whether MNBI can help identify evidence against pathological reflux by the Lyon Consensus in patients with refractory gastroesophageal reflux disease (GERD) symptoms. Methods Three hundred and forty-nine patients with refractory GERD symptoms enrolled in this study were subjected to high-resolution manometry, 24-hour multichannel intraluminal impedance-pH (MII-pH) monitoring, and endoscopy. Conventional indexes (ie, reflux events and acid exposure time) and the novel index (MNBI) of MII-pH monitoring were extracted and analyzed. The value of MNBI in diagnosing patients with evidence against pathologic reflux was evaluated by receiver-operating-characteristic analysis. Results There were 102 (29.2%) patients with evidence against pathologic reflux, 149 (42.7%) with inconclusive or borderline evidence and 98 (28.1%) with conclusive evidence for pathologic reflux. The MNBI was significantly higher while the proportion of pathological MNBI was significantly lower in subjects with evidence against pathologic reflux than in patients with inconclusive or borderline evidence and in patients with conclusive evidence for pathologic reflux (2444.3 [1977.9-2997.4] vs 1992.8 [1615.5-2253.6] and vs 1772.3 [758.6-2161.3], both P < 0.001; 42.2% vs 79.7% and vs 80.0%, both P < 0.05). When identifying evidence against pathologic reflux in patients with refractory GERD symptoms, the MNBI yielded an area under the curve of 0.749 (P < 0.001) at a cutoff value of 1941.8 Ω. Conclusions The MNBI has a good diagnostic value for evidence against pathological reflux in patients with refractory GERD symptoms. For its simplicity and reproducibility, we believe that MNBI should be referred to in reports of impedance-pH tracings by physicians. (J Neurogastroenterol Motil 2022;28:121-130)

Operational Capabilities on the Nanosatellite Attitude Control Actuated by Electropermanent Magnetorquer

Youngho Eun,Zhicheng Xie,Zihao Wang,Xiaofeng Wu 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11

This study presents the early-stage development status of the novel magnetorquer focusing on its operational capabilities to be applied in space applications. The aim is to show that the new magnetorquer can provide enough torque to a nano-scale satellite to perform a reorientation maneuver which is generally considered beyond the capacity due to its physical limitations. As the actuation process of the new magnetorquer differs from the conventional eletromagnet-based torquers, we designed the control input to have strictly three states only to detour the complexity behind the magnetization process which is subject to magnetic hysteresis. As the objective of this work is to prepare for the follow-on hardware experiment for demonstration, a software-based simulation environment is constructed to reflect the actual circumstances based on our previous measurements and new setups. The simulation result illustrates that such a pointing maneuver is achievable by employing the new magnetorquer with a relatively small amount of control effort while keeping the tracking performance within a predefined boundary.

Three-Dimensional Cooperative Guidance Law Against Maneuvering Target with Time-Varying Communication Delays

ZhiKai Wang,ZhuMu Fu,ZiHao Wu,ChenQi Zhu,JiaCheng Li 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.2

This paper presents a novel three-dimensional time-space cooperative guidance law against maneuvering target despite the presence of time-varying communication delays between missiles. The guidance law is divided into two parts. In the first part, a consensus protocol is designed for a multi-agent system consisting of a virtual leader and multiple followers. The objective is to tackle the problem of consensus convergence among the agents with communication delays. Additionally, the relationship between the upper bound of delays and the controller parameters is established. Based on the consensus protocol and a prescribed-time slide mode control method, the guidance law in the line-of-sight (LOS) direction is designed to ensure that the missiles attack the target simultaneously. In the second part, the multi-missile surrounding attack is achieved by designing different desired LOS azimuth and elevation angles for each missile. A guidance law in the normal LOS direction is designed based on the prescribed-time slide mode control method to ensure that the LOS angle converges to the desired values. To estimate the disturbances caused by the unknown and unpredictable acceleration of the maneuvering target in the LOS and normal LOS directions, fixed-time disturbance observers are designed. The stability analysis of the cooperative guidance law is provided in the appendix section. To demonstrate the effectiveness and superiority of the proposed cooperative guidance law, comparative simulations are performed.

Porous Titanium Scaffolds with Aligned Lamellar Pore Channels by Directional Freeze‑Casting from Aqueous TiH2 Slurries

Mengchen Mao,Yufei Tang,Kang Zhao,Zihao Duan,Cong Wu 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2

Porous titanium scaffolds with aligned lamellar pore channels and smooth inner walls were fabricated by directional freezecasting using aqueous TiH2slurries. The formation of dendrites was inhibited by increasing the TiH2content in slurry. Thepore structures and compression strengths of porous titanium scaffolds that were made with different solid contents werecharacterized. The formation mechanism of aligned lamellar pore channels and the reason for the improvement of compressionstrength were analyzed. With increasing TiH2content in slurry, the open porosity reduced from 38.57 to 29.03% whilelamellar spacing decreased. Young’s modulus was decreased with the increasing open porosity. Directional lamellar porechannels were obtained by controlling the TiH2content in slurry, which can reduce the number of branches and preventstress concentrations during compression. Also, the porous titanium scaffolds prepared by this process had a good biocompatibilitywith osteoblasts.