A Q-gram Filter for Local Alignment in Large Genomic Database

Decai Sun,Xiaoxia Wang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.1

Fast and exact searching for sequences similar to a query sequence in genomic databases remains a challenging task in molecular biology. In this paper, the problem of finding all e-matches in a large genomic database is considered, i.e. all local alignments over a given length w and an error rate of at most e. A new database searching algorithm called QFLA is designed to solve this problem. The proposed algorithm is a full-sensitivity algorithm which is a refined q-gram filter and implemented on a q-gram index. First, new features are extracted from match-regions by logically partitioning both query sequence and genomic database. Second, a large part of irrelevant subsequences are eliminated quickly by these new features during the searching process. Last, the unfiltered regions are verified by the well-known smith-waterman algorithm. The experimental results demonstrate that our algorithm saves time by improving filtration efficiency in a short filtration time.

Insight Into the Crystallinity of Chinese Ancient Silk by Synchrotron Radiation-Based and Conventional X-ray Diffraction Methods

Decai Gong,Xiaoning Zhang,Yuxuan Gong 한국문화재보존과학회 2020 보존과학회지 Vol.36 No.1

This study investigates the crystallinity distribution of ancient silk. Owing to the inherent multi-hierarchical structure of silk protein and the complicated structural changes that occur due to various burial environments, it is challenging but worthwhile to study ancient silk ageing behavior, which is based on the fact that ageing begins with a single fiber and then spreads to a whole fabric. Crystallinity was one of the most effective indicators found to reveal the ageing status of silk. Therefore, a synchrotron radiation-based X-ray diffraction(SR-XRD) method was employed to study the crystallinity distribution of single fibers of ancient silk unearthed from seven archaeological sites in China from historical periods including the warring states, Han dynasty, Song dynasty, and Ming dynasty. In comparison, the conventional X-ray diffraction method, which uses large amounts of samples, was also performed to determine the integral crystallinity of ancient silk. Thermal stability experiments by thermogravimetry(TG) as well as morphology observations by scanning electron microscopy(SEM) and optical microscopy(OM) all confirmed the deterioration of ancient silk. Moreover, the ageing mechanism of ancient silk was proposed with the assistance of an artificial ageing study. The results confirmed the effectiveness of SR-XRD as an ageing indicator, revealing the crystallinity distribution. This research could provide motivation to determine the deterioration status of ancient silk, and would also aid in explaining the fragility of ancient silk due to ageing.

Numerical Analysis and Experiment Study of Magnetic Fluid Boundary in Seals

Yibiao Chen,Decai Li,Yanjuan Zhang,Anmin Xi 한국자기학회 2018 Journal of Magnetics Vol.23 No.2

Magnetic fluid seals are widely used technical applications of magnetic fluid. This paper presents a numerical simulation model to obtain the boundary of magnetic fluid in seals. The magnetic field in the seal is solved by finite element method, and the boundary is calculated by using Navier-Stokes equations in magnetic fluid. In order to observe the surface and obtain the seal capacity, the plane magnetic fluid seal experiment is carried out. The relationship between the seal capacity and the magnetic fluid volume is presented. The seal capacity which is obtained by the theoretical analysis has well congruence with the result of the experiment. The displacement of boundary with the pressure difference is quantitatively depicted.

Investigation on the Influence of Temperature on Starting Torque of Magnetic Fluid Seal

Jiawei Chen,Decai Li,Du Hao 한국자기학회 2018 Journal of Magnetics Vol.23 No.3

The widest application of magnetic fluid is in magnetic fluid seals. The starting torque varying with temperature of magnetic fluid seal has limited its application in special seal field such as military industry. This paper firstly measure the starting torque of magnetic fluid seals under different temperature conditions from −55 oC to 70 ℃ after holding for 2.5 hours in a closed environment with uniform temperature. And the law of starting torque with temperature change is studied experimentally. The results show that the starting torque of the magnetic fluid seal changes unobvious at 25 ℃ or higher temperature. The starting toque of magnetic fluid seal increases with the decrease of temperature, and the causes of which are analyzed. The results of this study provide experimental and theoretical reference for reducing the staring torque of magnetic fluid seal in low temperature environment.

Research on the Axial Magnetic Levitation Force Acting on the Ring Magnet Suspended in Magnetic Fluid : Considering a Radial Eccentricity

Jun Yu,Decai Li,Nannan Di,Ningning Guo 한국자기학회 2019 Journal of Magnetics Vol.24 No.2

The self-suspension of magnet in magnetic fluid has been widely used in micromechanical systems, sensors, and dampers. The magnetic field associated with the ring magnet is obtained by numerical calculation and simulation through which the axial magnetic levitation force is calculated, and the numerical calculation, simulation, and experimental results agree with each other. The influence of the radial eccentricity of the ring magnet on the axial magnetic levitation force is studied, the ring magnet will experience a maximum axial magnetic levitation force without radial eccentricity. With the increase of radial eccentricity and the decrease of the distance between the bottom of the ring magnet and container, the axial magnetic levitation force will continue to decrease. But it is worth noting that the magnitude of the change caused by radial eccentricity is negligible compared to that of the axial magnetic levitation force.

The Influence of Shaft Eccentricity on the Magnetic Fluid Sealing Performance

Shicong Li,Decai Li,Shuangxi Li 한국자기학회 2023 Journal of Magnetics Vol.28 No.2

This manuscript delves into the impact of shaft eccentricity and diameter on the pressure resistance and magnetic force of a magnetic fluid seal (MFS), through both magnetic circuit analysis method (MCAM) and finite element method (FEM). The study proposes a systematic approach to enhance the performance of eccentric MFS based on MCAM. The results show a near-linear decrease in the pressure resistance of the MFS with increasing eccentricity, with a maximum decline of 65 %. However, the MFS model with a 100 mm shaft diameter renders more precise results in predicting the sealing performance for larger shaft diameters since the pressure resistance decrease remains below 5 % as shaft diameter is increased. The optimal range of pole tooth structure parameters has also been determined. Remarkably, the proposed method affords a precise analysis of the performance of large-diameter eccentric MFS, which is not feasible using two-dimensional axisymmetric magnetic field models.

Influence of Particle Size Distribution of Magnetic Fluid on the Resistance Torque of Magnetic Fluid Seal

Siyu Chen,Decai Li 한국자기학회 2017 Journal of Magnetics Vol.22 No.4

Magnetic fluid seal is widely used in military and aerospace industry owing to its zero leakage property, long life and reliability. The resistance torque is often required to be small and stay within allowable scope with the standing time expanding and the working environment changing. In this paper, we discussed the influence of the particle size distribution of magnetic fluid on the resistance torque of magnetic fluid seal. Samples of magnetic fluid of different particle size distribution were processed by applying a magnetic field gradient. Afterwards, the rheological property of different samples was analyzed using rheometer. Besides, the resistance torque of magnetic fluid seal on different occasions was measured. We explained these results from the point of formation and destruction of magnetic aggregations based on the theory of magnetoviscous effect, thus provided feasible ways to improve the performance of magnetic fluid seal.

Analysis on Seal Capacity of Magnetic Fluid Seal Using Ring Magnet

Jiawei Liu,Decai Li 한국자기학회 2022 Journal of Magnetics Vol.27 No.1

Magnetic fluid seal is one of the most mature applications of magnetic fluid. When the shaft has a large radial runout, the classical pole piece is easily damaged. Due to its small size, the commonly used pole piece structure harbors problems like poor seal performance under a large gap and poor processability. By exploring the distribution law of the magnetic field on the magnet’s surface, we provided theoretical support for the magnetic fluid seal using axially-magnetized ring magnets. New structures for the magnetic fluid seal using axially-magnetized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets were proposed. Then, comparisons were made between the classical magnetic fluid seal and the magnetic fluid seal using ring magnets. The results revealed that the magnetic fluid seal using axially-magnetized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets exhibited a certain seal capacity, which could replace the classical magnetic fluid seal structure.

Design and Analysis of a Plane Vibration-based Electromagnetic Generator Using a Magnetic Spring and Ferrofluid

Siqi Wang,Decai Li 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.5

This paper describes the design and characterization of a plane vibration-based electromagnetic generator that is capable of converting low-frequency vibration energy into electrical energy. A magnetic spring is formed by a magnetic attractive force between fixed and movable permanent magnets. The ferrofluid is employed on the bottom of the movable permanent magnet to suspend it and reduce the mechanical damping as a fluid lubricant. When the electromagnetic generator with a ferrofluid of 0.3 g was operated under a resonance condition, the output power reached 0.27 mW, and the power density of the electromagnetic generator was 5.68 μW/cm2. The electromagnetic generator was also used to harvest energy from human motion. The measured average load powers of the electromagnetic generator from human waist motion were 0.835 mW and 1.3 mW during walking and jogging, respectively.

Experiment Study and Machine Learning Prediction of Damping Performance of Ferrofluid Dynamic Vibration Absorber

Xiao Liu,Decai Li 한국자기학회 2022 Journal of Magnetics Vol.27 No.1

In this research, we study four influence factors of the damping performance of ferrofluid dynamic vibration absorber, as well as predict and optimize the damping performance by machine learning method. The vibration absorber in our research is based on the second order buoyancy principle, which consists of a non-magnetic container, a small amount of ferrofluid and a permanent magnet. The effects of the initial amplitude, the cone angle of the cover, the thickness of the gasket and the mass of the ferrofluid on the damping performance are investigated by experiments. Based on the experiment data, we use BP neural network to establish a prediction model between the four influence factors and the damping performance. The prediction error of damping efficiency predicted by BP neural network is mainly within ± 0.4%. Meanwhile, the determination coefficient R² of test data is 0.96242. The both indicate that BP neural network has a good performance in predicting the damping efficiency. Furthermore, we use the search algorithm to find the optimized values of each influence factor through the prediction model and the high damping efficiency is confirmed by experiments. Our work introduces machine learning into the field of vibration absorber designing, which provides an innovative method for the rapid design of high efficiency vibration absorber.