Study on the Micro-vibration Suppression of a MnCu Spring Isolation Platform with Low Stiffness and High Damping

Xianbo Yin,Yang Xu,Xiaowei Sheng,Song Wan,Yixin Wang 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

Reaction wheels are the primary micro-vibration sources for microsatellites. To reduce the adverse effects of micro-vibrations, a six-degree-of-freedom (6-DOF) vibration isolation scheme with low stiffness and high damping is proposed. Through six-component force measurements, the harmonic characteristics of the micro-vibrations generated by a reaction wheel are determined. Based on an assumption of small deformation linear elasticity, a dynamic model of a convergent isolation platform is established. With high damping characteristics, helical springs made of MnCu (manganese copper) alloy are selected as the isolation element of the platform. After a modal analysis and stiffness design, the key structural parameters of the isolator are determined. According to the coupling of degrees of freedom, the transmissibility of the isolator is simulated and compared to titanium and aluminum alloys. Combined with on-ground and on-board tests, the effectiveness of the isolation platform is verified. The research shows that the 6-DOF isolation platform based on the MnCu spring realizes multidirectional low-frequency and low-magnitude micro-vibration suppression. The minimum initial isolation frequency of the designed isolator is 16.8 Hz, and the best suppression effect reaches 17.5 dB. The proposed isolator’s application successfully controls high-order harmonics and sensitive load response behaviors.

Construction Project Risk Management in Singapore: Resources,Effectiveness, Impact, and Understanding

Xianbo Zhao,황본강,Weisheng Phng 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.1

While previous studies have focused on the need for Project Risk Management (PRM), highlighting its potential benefits,resources invested in PRM have been rarely identified. This study aims to investigate the resource allocation, effectiveness, impact and understanding of construction PRM in Singapore. To achieve the objectives, a questionnaire survey was conducted with professionals and 43 complete questionnaires were returned. The results revealed that higher proportion of costs was invested in PRM than time and labor resources, and that more resources invested would not necessarily lead to a higher level of PRM effectiveness and greater assurance with the achievement of project objectives. Also, the results showed the low-level understanding of PRM in the survey firms and suggested that the overall impact of PRM on project outcomes differed according to levels of understanding. Despite the low-level understanding, all the nine PRM principles and guidelines were significantly agreed. Hence,this study provides a clear picture of PRM in the Singapore construction industry. The findings of this study can help practitioners to better implement PRM and assure the achievement of project outcomes.

Efficient Certificateless Authenticated Asymmetric Group Key Agreement Protocol

( Guiyi Wei ),( Xianbo Yang ),( Jun Shao ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

Group key agreement (GKA) is a cryptographic primitive allowing two or more users to negotiate a shared session key over public networks. Wu et al. recently introduced the concept of asymmetric GKA that allows a group of users to negotiate a common public key, while each user only needs to hold his/her respective private key. However, Wu et al.`s protocol can not resist active attacks, such as fabrication. To solve this problem, Zhang et al. proposed an authenticated asymmetric GKA protocol, where each user is authenticated during the negotiation process, so it can resist active attacks. Whereas, Zhang et al.`s protocol needs a partially trusted certificate authority to issue certificates, which brings a heavy certificate management burden. To eliminate such cost, Zhang et al. constructed another protocol in identity-based setting. Unfortunately, it suffers from the so-called key escrow problem. In this paper, we propose the certificateless authenticated asymmetric group key agreement protocol which does not have certificate management burden and key escrow problem. Besides, our protocol achieves known-key security, unknown key-share security, key-compromise impersonation security, and key control security. Our simulation based on the pairing-based cryptography (PBC) library shows that this protocol is efficient and practical.

Culture-Positive Spontaneous Ascitic Infection in Patients with Acute Decompensated Cirrhosis: Multidrug-Resistant Pathogens and Antibiotic Strategies

Jing Liu,Yanhang Gao,Xianbo Wang,Zhiping Qian,Jinjun Chen,Yan Huang,Zhongji Meng,Xiaobo Lu,Guohong Deng,Feng Liu,Zhiguo Zhang,Hai Li,Xin Zheng 연세대학교의과대학 2020 Yonsei medical journal Vol.61 No.2

Purpose: This study investigated multidrug-resistant (MDR) pathogens and antibiotic strategies of culture-positive spontaneousascitic infection (SAI) in patients with acute decompensated cirrhosis. Materials and Methods: We retrospectively analyzed 432 acute decompensated cirrhotic patients with culture-positive SAI from11 teaching hospitals in China (January 2012 to May 2018). A Cox proportional hazards model analysis was conducted to identifyindependent predictors of 28-day mortality. Results: A total of 455 strains were isolated from 432 ascitic culture samples. Gram-negative bacteria (GNB), gram-positive bacteria(GPB), and fungi caused 52.3, 45.5, and 2.2% of all SAI episodes, respectively. Episodes were classified as nosocomial (41.2%), healthcare-related (34.7%), and community-acquired (24.1%). Escherichia coli (13.4%) and Klebsiella pneumoniae (2.4%) were extendedspectrumβ-lactamase producing isolates. The prevalence of methicillin-resistant Staphylococcus aureus was 1.1%. Ceftazidime,cefepime, aztreonam, and amikacin were recommended as first-line antibiotics agents for non-MDR GNB infections; piperacillin/tazobactam and carbapenems for MDR GNB in community-acquired and healthcare-related or nosocomial infections, respectively;and vancomycin or linezolid for GPB infections, regardless of drug-resistance status. Multivariate analysis revealed days ofhospital stay before SAI, upper gastrointestinal bleeding, white blood cell count, alanine aminotransferase, serum creatinine concentration,total bilirubin, and international normalized ratio as key independent predictors of 28-day mortality. Conclusion: MDR pathogens and antibiotic strategies were identified in patients with acute decompensated cirrhosis with culture-positive SAI, which may help optimize therapy and improve clinical outcomes.

Genetic Algorithm‑Based Analysis of the Efects of an Additional Damping Controller for a Doubly Fed Induction Generator

Aiguo Tan,Zhihan Tang,Xianbo Sun,Jianwei Zhong,Honghua Liao,Haibing Fang 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.4

In view of the problem that large-scale and high-penetration wind power access may weaken the stability of small interference in the power grid, this study proposes a novel additional damping controllers for the doubly-fed induction generator (DFIG) based on the genetic algorithm. A DFIG model and its control system is built, and the parameters of the controller are tuned using the genetic algorithm to optimize the control efect. Based on Western System Coordinating Council (WSCC) 3-machine 9-node system, multi-scenario simulation results verifes that the additional damping controller proposed in this study performs better to suppress the low-frequency oscillation than the power system stabilizer (PSS) installed on the synchronous generators which are farther to the disturbance point. Meanwhile, the proposed strategy is compared with the reactive power modulation control, which can provide a reference for engineering applications of an added DFIG damping controller.

A Cut‑Out Strategy for Wind Turbines that Ensures Low‑Voltage Ride‑Through Capability

Aiguo Tan,Zhihan Tang,Xianbo Sun,Jianwei Zhong,Honghua Liao,Haibing Fang 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.4

To ensure the dynamic stability of the system and improve low-voltage ride-through (LVRT) capability, this study presents a cut-out strategy for doubly-fed induction generator (DFIG) wind turbines that combines reactive power output with asynchronous load reduction. This strategy reduces the risk of the large-scale disconnection of DFIGs in a wind farm by regulating the reactive power output of DFIGs in the wind farm and removing DFIGs in an asynchronous state based on the reduction ratio. Simulation results demonstrate that the implementation of this strategy can help increase the voltage at the point of common coupling and the LVRT time for a wind farm.

A Study of Radio Voice Signal Based on the Time Delay Estimation

Xinrui Liu,Jinxiang Chen,Xianbo He,Wei Li,Gangyuan Zhang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.9

The wave of voice signal is narrow and unstable. Besides, it has a non-continuity in time domain and an inconsistent decline of the radio channel, especially the short wave channel, which makes estimating the time delay of the radio’s voice signal very difficult. To solve such problems, the authors creatively combine the voice activity detection with the short-segment processing technology. Meanwhile, by using Weighted Least Squares Phase Fitting method to work out the time delay, we conduct a research in the time delay estimation of radio’s voice signal. The laboratory finding finally shows that this method is far better than the typical Generalized Correlation Method for estimation of time delay.

A Form-Finding Method of Beam String Structures - Offload by Steps Method

Jihong Ye,Ruo-qiang Feng,Xianbo Zhao,Bin Liu 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.2

The problem of form-finding of beam string structures was studied, and the method named offload by steps was put forward in accordance with the properties of the mechanical status of the structures. This method was used to find the form of the unstrained state on the basis of the pre-stressed state without the need to assume the unstrained form first. Numerical simulations and experimental research on the form-finding of beam string structures were carried out to verify the offload by steps method and, more importantly, to study the application of the method in engineering practice. The scale of the experimental model was 1/20, and the stretching pattern was the same as that in practical engineering. Comparisons of internal forces and deformations corresponding to unstrained and pre-stressed states of the model were made between experimental and calculation results. The following conclusions were drawn. First, the offload by steps method can be applied to the engineering practice without assuming the form of the unstrained state, and the form of the unstrained state corresponding to that of the pre-stressed state can be obtained directly. Second, the internal forces of the beam string structures in their pre-stressed states can be obtained easily by using the statically-determinate calculation model in the offload by steps method, which can guide design effectively. Third, the method for estimating the cable tension by balancing the deadweight of the beam string truss can be applied to engineering practice.

Developing the Framework of Tacit Knowledge Externalization in International Construction Projects

Qianwen Zhou,Xiaopeng Deng,Bon-Gang Hwang,Xianbo Zhao,Na Zhang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9

Although tacit knowledge management has gained increasing attention in international construction projects, little effort has been devoted to the externalization of tacit knowledge for project managers and members. This research aims to explore various factors that affect the process of tacit knowledge externalization (TKE) in international construction projects and analyze the influencing mechanism and degree of these factors on the externalization effect. Based on the comprehensive literature review and in-depth investigations, a theoretical model and ten hypotheses were established. Then, data collected from 302 respondents were used to test the model and hypotheses. The results indicated that the differences among project members (i.e., culture distance and knowledge distance) reduce members’ willingness to convert tacit knowledge, which negatively impacts the externalization effect. Furthermore, organizational management (i.e., organizational climate and incentive mechanism) plays an active role in increasing members’ externalization willingness. Incentive mechanism and information technology are beneficial to increasing the coding level of knowledge, which positively impacts the externalization effect. Moreover, a strong willingness to convert tacit knowledge helps enhance the coding level of knowledge, thereby improving the effect of TKE. This study advances previous research by developing a framework for TKE in international construction projects, thereby offering recommendations for project managers and members to promote the externalization process.

LETTER TO THE EDITOR : Gene-Gene Interaction between LCE and CLEC16A Increases the Risk of Psoriasis in a Chinese Population

( Jianbo Wang ),( Yantao Ding ),( Xing Fan ),( Xianbo Zuo ),( Wen Wang ),( Hui Cheng ),( Ping Li ),( Liangdan Sun ),( Sen Yang ),( Xuejun Zhang ) 대한피부과학회 2014 Annals of Dermatology Vol.26 No.3