Design and performance analysis of a novel swimming robot with waterbomb origami wheel

Junfeng Hu,Ning Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

This paper proposes a novel swimming robot with waterbomb origami wheel. The wheel of the swimming robot is a waterbomb origami that acts like a paddle blade. The origami wheel provides a new propulsion way for the swimming vehicle. The propulsion principle is to use the water flow to push the origami structure like the blade to propel it move forward. The analytical model describing the mechanical behavior of the origami wheel was built to illustrate the superior swimming characteristics of the robot. The model uncovers propulsive force variation with respect to origami structure parameters. The prototypes of the swimming robot are manufactured to analyze the influence of the structural parameters on their performances such as swimming speed, steering, and propulsive force. The analysis results showed that the proposed swimming robot has advantages such as high propulsion force and fast response. Meanwhile, it provides a guideline for the structural design of the origami wheel that enables it to be suitable to swim in the water. In a word, the origami wheel provides a light and efficient propulsion for swimming vehicles. The origami wheel provides a novel and simple propulsion way for swimming vehicles, and the structure promotes the development of a new class of swimming vehicles.

Efficient LDPC-Based, Threaded Layered Space-Time-Frequency System with Iterative Receiver

Junfeng Hu,Hailin Zhang,Yuan Yang 한국전자통신연구원 2008 ETRI Journal Vol.30 No.6

We present a low-density parity-check (LDPC)-based, threaded layered space-time-frequency system with emphasis on the iterative receiver design. First, the unbiased minimum mean-squared-error iterative-tree-search (U-MMSE-ITS) detector, which is known to be one of the most efficient multi-input multi-output (MIMO) detectors available, is improved by augmentation of the partial-length paths and by the addition of one-bit complement sequences. Compared with the U-MMSE-ITS detector, the improved detector provides better detection performance with lower complexity. Furthermore, the improved detector is robust to arbitrary MIMO channels and to any antenna configurations. Second, based on the structure of the iterative receiver, we present a low-complexity belief-propagation (BP) decoding algorithm for LDPC-codes. This BP decoder not only has low computing complexity but also converges very fast (5 iterations is sufficient). With the efficient receiver employing the improved detector and the low-complexity BP decoder, the proposed system is a promising solution to high-data-rate transmission over selective-fading channels.

Dynamics of Compliant Mechanisms Using Transfer Matrix Method

Junfeng Hu,Tao Wen,Jiankang He 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.11

In this paper, a new closed-form dynamic model describing vibration characteristics of compliant mechanisms is proposed by using transfer matrix method. The advantage of the method is that it can simply and accurately describe the dynamic performance without the need for overall dynamic equation of the system, which is different from previous the dynamic modeling methods of compliant mechanisms. The vibration mechanical model of compliant mechanisms is established at first and the transfer matrices of the compliant mechanisms with serial and parallel configuration are derived. The transfer matrices of planar elliptic flexure hinges and vibration rigid bodies are deduced in detail according to the basic idea of the free vibration characteristics of elements. Finally, the dynamic performances of compliant mechanisms, such as the natural frequency, vibration model, and frequency response, are analyzed utilizing the established model. A comparison of the method with the finite element method for three typical compliant mechanisms discovers a maximum error of the natural frequency is less than 4.65%, which verifies the feasibility of the presented approach.

Combined effect of initial biomass density and nitrogen concentration on growth and astaxanthin production of Haematococcus pluvialis (Chlorophyta) in outdoor cultivation

Junfeng Wang,Milton R. Sommerfeld,Congming Lu,Qiang Hu 한국조류학회I 2013 ALGAE Vol.28 No.2

Nitrogen availability and cell density each affects growth and cellular astaxanthin content of Haematococcus pluvialis, but possible combined effects of these two factors on the content and productivity of astaxanthin, especially under outdoor culture conditions, is less understood. In this study, the effects of the initial biomass densities IBDs of 0.1, 0.5, 0.8, 1.5, 2.7, 3.5, and 5.0 g L-1 DW and initial nitrogen concentrations of 0, 4.4, 8.8, and 17.6 mM nitrate on growth and cellular astaxanthin content of H. pluvialis Flotow K-0084 were investigated in outdoor glass column photobioreactors in a batch culture mode. A low IBD of 0.1 g L-1 DW led to photo-bleaching of the culture within 1-2 days. When the IBD was 0.5 g L-1 and above, the rate at which the increase in biomass density and the astaxanthin content on a per cell basis was higher at lower IBD. When the IBD was optimal (i.e., 0.8 g L-1), the maximum astaxanthin content of 3.8% of DW was obtained in the absence of nitrogen, whereas the maximum astaxanthin productivity of 16.0 mg L-1 d-1 was obtained in the same IBD culture containing 4.4 mM nitrogen. The strategies for achieving maximum Haematococcus biomass productivity and for maximum cellular astaxanthin content are discussed.

Clinical and Immunological Factors Associated with Postpartum Hepatic Flares in Immune-Tolerant Pregnant Women with Hepatitis B Virus Infection Treated with Telbivudine

( Junfeng Lu ),( Xiaoxiao Wang ),( Yunxia Zhu ),( Lina Ma ),( Sujun Zheng ),( Zhongjie Hu ),( Xinyue Chen ) 대한간학회 2021 Gut and Liver Vol.15 No.6

Background/Aims: To investigate postpartum hepatic flares and associated factors in highly viremic pregnant patients in the immune tolerance phase who adopted telbivudine (LdT) treatment in the last trimester to reduce vertical transmission of hepatitis B virus. Methods: Hepatitis B e antigen (HBeAg)-positive, highly viremic pregnant women were recruited for this prospective study. Treatment with LdT was started from 28 weeks of gestation. Virological and biochemical markers were examined before LdT treatment, antepartum and postpartum. Serial blood samples at the same time were collected to detect cytokines and cortisol (COR). Results: Fifty-six of 153 patients (36.6%) had postpartum hepatic flares, defined as a 2-fold increase in alanine aminotransferase 6 weeks after delivery. Age and the antepartum alanine aminotransferase and postpartum HBeAg levels were independent influencing factors of postpartum hepatic flares. Cytokines showed no regularity during or after pregnancy. Compared with the patients with no postpartum flares, the patients with flares had lower baseline interferon γ and COR levels (p=0.022 and p=0.028) and higher postpartum interferon γ levels (p=0.026). Conclusions: A high proportion of highly viremic and immune-tolerant pregnant patients treated with LdT in the last trimester had postpartum hepatic flares, which implied that these patients entered the immune clearance phase after delivery. Thus, this may create an appropriate opportunity for re-antiviral therapy. (Gut Liver 2021;15:887-894)

Double-Input DC-DC Converter for Applications with Wide-Input-Voltage-Ranges

Hu, Renjun,Zeng, Jun,Liu, Junfeng,Yang, Jinming The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

The output power of most facilities for renewable energy generation is unstable due to external environmental conditions. In distributed power systems with two or more sources, a stable output can be achieved with the complementary power supply among the different input sources. In this paper, a double-input DC-DC converter with a wide-input-voltage-range is proposed for renewable energy generation. This converter has the following advantages: the circuit is simple, and the input voltage range is wide and the fault tolerance is excellent. The operation modes and the steady-state analysis are examined. Finally, experimental results are illustrated to verify the correctness of the analysis and the feasibility of the proposed converter.

Double-Input DC-DC Converter for Applications with Wide-Input-Voltage-Ranges

Renjun Hu,Jun Zeng,Junfeng Liu,Jinming Yang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

The output power of most facilities for renewable energy generation is unstable due to external environmental conditions. In distributed power systems with two or more sources, a stable output can be achieved with the complementary power supply among the different input sources. In this paper, a double-input DC-DC converter with a wide-input-voltage-range is proposed for renewable energy generation. This converter has the following advantages: the circuit is simple, and the input voltage range is wide and the fault tolerance is excellent. The operation modes and the steady-state analysis are examined. Finally, experimental results are illustrated to verify the correctness of the analysis and the feasibility of the proposed converter.

Combined effect of initial biomass density and nitrogen concentration on growth and astaxanthin production of Haematococcus pluvialis (Chlorophyta) in outdoor cultivation

Wang, Junfeng,Sommerfeld, Milton R.,Lu, Congming,Hu, Qiang The Korean Society of Phycology 2013 ALGAE Vol.28 No.2

Nitrogen availability and cell density each affects growth and cellular astaxanthin content of Haematococcus pluvialis, but possible combined effects of these two factors on the content and productivity of astaxanthin, especially under outdoor culture conditions, is less understood. In this study, the effects of the initial biomass densities IBDs of 0.1, 0.5, 0.8, 1.5, 2.7, 3.5, and 5.0 g $L^{-1}$ DW and initial nitrogen concentrations of 0, 4.4, 8.8, and 17.6 mM nitrate on growth and cellular astaxanthin content of H. pluvialis Flotow K-0084 were investigated in outdoor glass column photobioreactors in a batch culture mode. A low IBD of 0.1 g $L^{-1}$ DW led to photo-bleaching of the culture within 1-2 days. When the IBD was 0.5 g $L^{-1}$ and above, the rate at which the increase in biomass density and the astaxanthin content on a per cell basis was higher at lower IBD. When the IBD was optimal (i.e., 0.8 g $L^{-1}$), the maximum astaxanthin content of 3.8% of DW was obtained in the absence of nitrogen, whereas the maximum astaxanthin productivity of 16.0 mg $L^{-1}\;d^{-1}$ was obtained in the same IBD culture containing 4.4 mM nitrogen. The strategies for achieving maximum Haematococcus biomass productivity and for maximum cellular astaxanthin content are discussed.

Polaron-bipolaron Transition and Spin Polarized Current in an Organic Device

Yubin Zhang,Junfeng Ren,Guichao Hu,Shijie Xie 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Electronic Structure and Optical Properties of a Mn-Doped InSe/WSe2 van der Walls Heterostructure: First Principles Calculations

Liang Rundong,Zhao Xiuwen,Hu Guichao,Yue Weiwei,Yuan Xiaobo,Ren Junfeng 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.7

InSe-based van der Walls heterostructures (vdWHs) have attracted research interests recently because of their particular properties. In this work, the electronic structure and the optical properties of Mn-doped InSe/WSe2 vdWHs are investigated by using first-principles calculations. Mn doping in InSe/WSe2 vdWHs induces an increase in the system's band gap. The optical properties of the vdWHs are also studied, and the absorption intensity of Mn-doped InSe/WSe2 is found to be enhanced in the near-infrared and ultraviolet regions. In addition, built-in electric fields are generated in InSe/WSe2 and Mn-doped InSe/WSe2, which can inhibit recombination of photogenerated electron-hole pairs. This work predicates the feasibility of enhancing the optical properties in InSe/WSe2 vdWHs by introducing dopants, which extends the applications of InSe materials in the field of optoelectronics.