A Localization Algorithm based on RSSI for Wireless Sensor Network

Dong Dong,Sungrae Cho,Rong Ping Duan 한국통신학회 2008 한국통신학회 학술대회논문집 Vol.2008 No.7

Measurement and correlation of phase equilibria in aqueous two-phase systems containing ionic liquid ([EOMiM]Br) and potassium citrate/ammonium citrate/potassium tartrate at different temperatures

Dongdong Wang,Yang Lu,Zhuo Sun,Wei Liang,Dongshu Sun,Changli Qi,ChengZhuo Sheng,Xiaopeng Yu 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.2

An aqueous two-phase system (ATPS) containing an ionic liquid (1-(2-methoxyethyl)-3-methylimidazolium bromide) and three organic salts (K3C6H5O7, (NH4)3C6H5O7, and K2C4H4O6) at different temperatures was designed. Binodal data were correlated using two empirical equations, and tie-line data were fit with the utilization of Bancroft and Othmer-Tobias equations. In the systems investigated, three conclusions were drawn from the study of the phase-forming ability of salt through effective excluded volume, Gibbs free energy of ions, and the phase diagram. First, if the same cations of salt were present, the ability of salt to form phases increased with increasing valence of the anion. Second, the larger the effective excluded volume, the stronger the aforementioned ability of salt in forming phases. Third, salt had more ability to form phases if cations (or anions) contained in the salt possessed higher negative Gibbs free energy when the cation (anion) of the salt was the same. The effect of temperature on ATPSs was also investigated. It was found that it was easier to form ATPSs at lower temperature, and the tie-line slope showed growing absolute values as the temperature was decreased.

A Novel Two-Stage Training Method for Unbiased Scene Graph Generation via Distribution Alignment

Dongdong Jia,Meili Zhou,Wei Wei,Dong Wang,Zongwen Bai 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.12

Scene graphs serve as semantic abstractions of images and play a crucial role in enhancing visual comprehension and reasoning. However, the performance of Scene Graph Generation is often compromised when working with biased data in real-world situations. While many existing systems focus on a single stage of learning for both feature extraction and classification, some employ Class-Balancing strategies, such as Re-weighting, Data Resampling, and Transfer Learning from head to tail. In this paper, we propose a novel approach that decouples the feature extraction and classification phases of the scene graph generation process. For feature extraction, we leverage a transformer-based architecture and design an adaptive calibration function specifically for predicate classification. This function enables us to dynamically adjust the classification scores for each predicate category. Additionally, we introduce a Distribution Alignment technique that effectively balances the class distribution after the feature extraction phase reaches a stable state, thereby facilitating the retraining of the classification head. Importantly, our Distribution Alignment strategy is model-independent and does not require additional supervision, making it applicable to a wide range of SGG models. Using the scene graph diagnostic toolkit on Visual Genome and several popular models, we achieved significant improvements over the previous state-of-the-art methods with our model. Compared to the TDE model, our model improved mR@100 by 70.5% for PredCls, by 84.0% for SGCls, and by 97.6% for SGDet tasks.

Application of Archimedean Copulas to the Analysis of Drought Decadal Variation in China

Dongdong Zuo,Guolin Feng,Zengping Zhang,Wei Hou 한국기상학회 2018 Asia-Pacific Journal of Atmospheric Sciences Vol.54 No.2

The joint probability and return period were calculated to analyze the drought characteristics and decadal variation. According to the fit analysis, the Gumbel-Hougaard copula provided the best fit to the observed data. Based on four drought duration classifications and four severity classifications, the drought events were divided into 16 drought types according to the different combinations of duration and severity classifications, and the probability and return period were analyzed for different drought types. The results showed that the occurring probability of six common drought types (0 < D ≤ 1 and 0.5 < S ≤ 1, 1 < D ≤ 3 and 0.5 < S ≤ 1, 1 < D ≤ 3 and 1 < S ≤ 1.5, 1 < D ≤ 3 and 1.5 < S ≤ 2, 1 < D ≤ 3 and 2 < S, and 3 < D ≤ 6 and 2 < S) accounted for 76% of the total probability of all types.

Evaluation of Equivalent Bending Stiffness by Simplified Theoretical Solution for an FRP–aluminum Deck–truss Structure

Dongdong Zhang,Feng Li,Fei Shao,Chengfei Fan 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1

A hybrid Fiber-Reinforced Polymer (FRP)–aluminum spatial deck–truss structure that incorporates an innovative structural form and advanced extrusion-type FRP profiles has the advantages of a lightweight, high-bearing capacity, and faster installation. In this study, a design-oriented investigation was conducted with a simplified theoretical solution to conveniently evaluate the equivalent bending stiffness of the above-mentioned unique structure. The simplified theoretical solution was derived using the equivalent continuum beam method based on the homogenization concept and shearing equivalence principle. The theoretical prediction enabled a direct format and simple calculation process convenient for engineers in terms of the calculation and design. The theoretical solution was experimentally and numerically calibrated to ensure that the formulae have the satisfactory accuracy. The accuracy of the predicted bending stiffness exceeded 90%. The derivation procedures and formulae further indicated that the FRP web diagonals played a key role in resisting the global bending stiffness of the unique structure, and thus, the shear deformation should be considered in the structural design in terms of stiffness-driven. When compared with the conventional calculation method for obtaining the bending stiffness of steel solid-web beams and planar trusses, the proposed method was more accurate and applicable for the unique hybrid structures.

EMI based multi-bolt looseness detection using series/parallel multi-sensing technique

Dongdong Chen,Linsheng Huo,Gangbing Song 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.4

In this paper, a novel but practical approach named series/parallel multi-sensing technique was proposed to evaluate the bolt looseness in a bolt group. The smart washers (SWs), which were fabricated by embedding a Lead Zirconate Titanate (PZT) transducer into two flat metal rings, were installed to the bolts group. By series connection of SWs, the impedance signals of different bolts can be obtained through only one sweep. Therefore, once the loosening occurred, the shift of different peak frequencies can be used to locate which bolt has loosened. The proposed multi input single output (MISO) damage detection scheme is very suitable for the structural health monitoring (SHM) of joint with a large number of bolts connection. Another notable contribution of this paper is the proposal of 3-dB bandwidth root mean square deviation (3 dB-RMSD) which can quantitatively evaluate the severity of bolt looseness. Compared with the traditional naked-eye observation method, the equivalent circuit based 3-dB bandwidth can accurately define the calculation range of RMSD. An experiment with three bolted connection specimens that installed the SWs was carried out to validate our proposed approach. Experimental result shows that the proposed 3 dB-RMSD based multi-sensing technique can not only identify the loosened bolt but also monitor the severity of bolt looseness.

The Response Mechanism of Geomorphological Evolution and Hydrological Process in Loess Platform

( Dongdong Yan ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Due to the large area of agricultural irrigation in the Loess Plateau, the groundwater table in the plateau has been greatly increased and a large number of landslides have been induced. In the Heifangtai area of Gansu Province, dozens of loess landslides caused by irrigation, This paper studies the response law of landslide hazard and groundwater in Heifangtai area through field investigation and numerical simulation. The landslide in Heifangtai area has obvious geomorphological evolution characteristics. On this basis, the numerical model of black platform hydrogeology is established. The simulation results show that the occurrence of loess flowslide will affect the boundary conditions of the groundwater system, and increase the drainage of the Heifangtai Groundwater system through the expanding seepage face. At the same time, because the irrigated area becomes smaller, the total recharge of the groundwater system is reduced. For a fixed recharge amount, the groundwater phreatic level first peaked with the continuation of the landslide, and then decreased to a level close to the 2004 level, and the cumulative volume of the landslide reached 4 600×104 m3. Considering that the groundwater level in 2004 is still high enough to cause flowslides, the area of the Heifangtai will be reduced by less than 7.8 km2. If effective measures are not taken, the landslide will continue to occur and the risk of landslide disasters in the study area will continue for a long time.

A Compensation Method for Enhancing Aviation Drilling Robot Accuracy Based on Co-Kriging

Dongdong Chen,Peijiang Yuan,Tianmiao Wang,Lei Xue 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.8

The positional error of aviation drilling robot has a great influence on the strength and lives of aircrafts in the aircraft assembly. In order to improve the position accuracy of aviation drilling robot, an error compensation method based on co-kriging is proposed in this paper. The error similarity based on the kinematic of drilling robot is proposed firstly. Then, the positional errors of a set of points in the workspace are measured by using precision laser tracker. The measurement data are used to fit the cross-variogram of positional error. After the cross-variogram is obtained, the predicted positional errors of verification points can be estimated based on co-kriging. The positions after compensation are given to the drilling robot. The proposed method is carried out on an aviation drilling robot for practical compensation to verify the correctness and effectiveness of the error compensation method. The experimental results show that the average absolute positional error is reduced to 0.1150 mm from 0.7168 mm, and that the maximum absolute positional error is reduced to 0.2664 mm from 1.3073 mm. The experimental results also demonstrate that the proposed method can improve the absolute position accuracy of aviation robot and could meet the requirement of aircraft assembly.

Experimental Investigation of Flow Control Technology for Grouting and Blocking of Flowing Water in Karst Conduits

Dongdong Pan,Zehua Bu,Haiyan Li,Zhenhao Xu,Jie Liu 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.8

Aiming at the grouting treatment in karst conduits with large flow and high velocity, we developed a simulation experiment system for conduit-type grouting blocking and investigated the blocking mechanism of flowing water grouting under the condition of flow control. Firstly, we studied the effect of flow control in conduit by controlling the opening of outlet valve and analyzed the variation law of velocity and pressure in conduits under different water heads, conduit diameters and valve opening quantitatively. Secondly, we conducted experiments of flowing water grouting under different flow control conditions, and revealed the influence law of flow control for flowing water grouting. The results show that: 1) with the increase of the intensity of flow control, the pressure in conduit increased gradually, and the velocity of flowing water decreased gradually. 2) When the volume ratio of water and cement was 1.2:1, the volume ratio of cement and sodium silicate was 2:1, the grouting volume was 540 L/h, and the flowing water velocity was 0.15 m/s, flowing water blocking under the condition of flow control achieved the optimal effect. 3) With flow control, the slurry deposition thickness increased more than 50% compared with no flow control; besides, the slurry retention rate increased, and the blocking effect significantly improved. The technology has been successfully applied in the grouting treatment project of China Resources Cement (Pingnan) Limestone Mine. And main water inflow points in the mine were blocked with an total amount of ~210,200 m3/d water reduction. This study provided some theoretical guidance and reference experience for treatment engineering of water inflow in karst area.

Asymmetric coaxial three‑coil wireless power transmission system optimization

Dongdong Zhang,Xuesong Li,Jie Yang,Xiang Li,Thomas Wu 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.9

With the rapid development of wireless power transmission (WPT) technology and the demand for a wide range of applications, the common two-coil system is becoming increasingly mature. However, the monotonous structure of two-coil systems limits their development. By incorporating relay coils, the distance of power transmission, efficiency, and electromagnetic field (EMF) leakage can be effectively improved. In this paper, the three-coil system is analyzed, and the relay coil parameters are optimized by an evolutionary algorithm. After that, based on the coil optimization, the compensation capacitance of the relay coil is analyzed and an analytical formula of the compensation capacitance of the optimized relay coil is obtained. The results show that the parameter-optimized system reduces current by 86.9%, increases efficiency by 10%, and suppresses EMF leakage by 18 dB. Meanwhile, the capacitor optimization further improves the transmission efficiency of the system.