Time-Delay Estimation in the Multi-Path Channel based on Maximum Likelihood Criterion

( Shengdong Xie ),( Aiqun Hu ),( Yi Huang ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.4

To locate an object accurately in the wireless sensor networks, the distance measure based on time-delay plays an important role. In this paper, we propose a maximum likelihood (ML) time-delay estimation algorithm in multi-path wireless propagation channel. We get the joint probability density function after sampling the frequency domain response of the multi-path channel, which could be obtained by the vector network analyzer. Based on the ML criterion, the time-delay values of different paths are estimated. Considering the ML function is non-linear with respect to the multi-path time-delays, we first obtain the coarse values of different paths using the subspace fitting algorithm, then take them as an initial point, and finally get the ML time-delay estimation values with the pattern searching optimization method. The simulation results show that although the ML estimation variance could not reach the Cramer-Rao lower bounds (CRLB), its performance is superior to that of subspace fitting algorithm, and could be seen as a fine algorithm.

Localization Algorithm based on Positive Semi-definite Programming in Wireless Sensor Networks

Shengdong Xie,Jin Wang,Aiqun Hu,Yunli Gu,Jiang Xu,Mingsheng Zhang 보안공학연구지원센터(IJSIP) 2013 International Journal of Signal Processing, Image Vol.6 No.1

Partial Oxidation of Methane over Ni/SiO2

노현석,Wen-ShengDong,1Ki-WonJun,Zhong-WenLiu,Sang-EonPark,Young-SamOh 대한화학회 2002 Bulletin of the Korean Chemical Society Vol.23 No.5

Study on Intrusion Detection Policy for Wireless Sensor Networks

Jiang Xu,Jin Wang,Shengdong Xie,Wenliang Chen,Jeong-Uk Kim 보안공학연구지원센터 2013 International Journal of Security and Its Applicat Vol.7 No.1

Conventional vs Pylorus-preserving Pancreaticoduodenectomy with Pancreaticogastrostomy

( Jiongze Fang ),( Caide Lu ),( Shengdong Wu ),( Jing Huang ),( Jie Zhou ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1

Aims: Between conventional pancreaticoduodenectomy (CPD) and pylorus-preserving pancreaticoduodenectomy (PPPD), there is still controversy about the superiority of adopting one method over the other in combination with pancreaticogastrostomy (PG).There are few reports about cases of PPPD with PG. Methods: We studied cases of pancreaticoduodenectomy (PD) with PG for pancreatic head and periampullary carcinoma in our medical center, retrospectively. The data were gathered from 152 patients who underwent CPD/PPPD with PG from January 2010 to April 2015. Cases under study were divided into two groups: CPD group (group A, 101 cases) and PPPD group (group B, 51cases). The data included preoperative, intraoperative and postoperative conditions of both groups. The outcomes of perioperative data were investigated. Results: No significant statistical difference of the preoperative data was detected between two groups. Despite less blood loss (P=0.011), the overall postoperative complications of group B was significantly higher than that of group A (56.7% vs 34.7%, P=0.009). The single complication, majorly the postoperative pancreatic fistula (POPF) rate, of group B was significantly higher than that of group A (29.4% vs 11.9%, P=0.008). Conclusions: Although PPPD with PG may reduce intraoperative blood loss, it can significantly increase postoperative complications, especially POPF. Therefore, PPPD with PG is not recommended for treatment of pancreatic head and periampullary lesions.

Stratigraphic classification of the Quaternary North Hebei Plain using geophysical methods

Peng Dai,Kongyou Wu,Shengdong Wang,Sicong Zheng,Tianshe Cheng,Xiaohong Deng 한국지질과학협의회 2024 Geosciences Journal Vol.28 No.2

The North Hebei Plain is a typical example of a deep-covered area, with a thickness of more than 200 m Quaternary loose sediments. Previous studies have tried various stratigraphic classification methods but lack an effective combination of geophysical methods. Based on the analysis of rock strata and dating tests, combined with geophysical well-logging data, shallow seismic reflection, and paleomagnetic dating, the Quaternary strata of the deep-covered area in the Hebei Plain was divided into the Lower Pleistocene series, the Middle Pleistocene series, the Upper Pleistocene series, and the Holocene series. By observing the cores of the Quaternary borehole QHJ02, this paper focused on dividing its loose sediments into eight lithological sections, according to the lithology, sediment colour, sedimentary assemblage, and sedimentary environment. The geomagnetic polarity belt is divided according to the paleomagnetic inclination of the paleomagnetic sample in borehole QHJ02. The results of the paleomagnetic test show that the interval of 0–101.3 m is Brunhes normal polarity chron, the interval from 101.3 to 219.5 m is Matuyama reversed polarity chron, and the interval from 219.5 to 350 m is Gauss normal polarity chron. The amplitude of the geophysical logging curve shows a good correspondence with the lithology of the QHJ02 borehole. The lithology changes can be identified through the abrupt abnormal positions of logging curves such as gamma ray, resistivity, and magnetization to analyze the sedimentary environment combination and determine the formation boundary. According to the combination of paleomagnetic, shallow seismic reflection, and geophysical well logging methods, we can determine the bottom boundaries of the Quaternary and middle Pleistocene are 219.5 m and 101.3 m, respectively. According to the combination of geophysical well-logging, lithostratigraphic assessment, dating experiment of Accelerator Mass Spectrometry 14C (AMS 14C), and Optically Stimulated Luminescence (OSL), we can determine the bottom of the upper Pleistocene and the lower limit of Holocene to be at 45.4 m and 21.4 m, respectively. Based on a comprehensive analysis of rock stratigraphic characteristics and well-logging curves, this study investigated the paleoenvironmental characteristics of borehole QHJ02 at different ages. The Upper Neogene was characterized by branch channels and river floodplains, with localized occurrences of alluvial fans, avulsion fans, and inter-channel lowlands. During the Early Pleistocene, branch channels and inter-channel lowlands dominated, with localized river floodplains. The Middle Pleistocene witnessed alternating branch channels and river floodplains as the main paleoenvironments. In the Late Pleistocene, branch channels and inter-channel lowlands were prevalent. The Holocene saw a combination of natural levees and river floodplain environments. These findings enhance our understanding of the geological evolution and paleoenvironmental changes in the North Hebei Plain.

Optimal design for torsional vibration suppression of non-smooth NES

Yanbo Cao,Hongliang Yao,Jinxin Dou,Shengdong Han 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11

Nonlinear energy sinks (NESs) have received increasing attention for their ability to passively inhibit a large amount of vibration energy over a wide range of frequencies. However, although many studies have focused on dynamics of NES, few have addressed the optimal design method of NES, especially for the non-smooth NES (NSNES). Therefore, the parameter optimization method for an NSNES which can be applied to supress torsional vibration of rotor system was developed. First, the design variables were reduced by using piecewise linear torsional stiffness to equivalently fit cubic torsional stiffness; then, taking the torsional vibration of single-disk rotor system as an example, the genetic algorithm (GA) was used to solve the optimization problem of the NSNES in torsional vibration suppression of rotor system. Finally, the optimized NSNES was verified by numerical simulation and experiment to suppress the torsional vibration of a rotor system. The results show that the optimally designed NSNES can effectively suppress torsional vibration of a rotor system. In transient vibration suppression, the optimal percentage of accumulated energy dissipation of NSNES can reach 95.3 %. For steady-state vibration suppression, the peak vibration suppression of NSNES can reach 82.2 % in the simulation and 81.9 % in the test.

Transcriptome and proteome analysis of pregnancy and postpartum anoestrus ovaries in yak

Zhou Chen,Jine Wang,Junyuan Ma,Shuyuan Li,Shengdong Huo,Yanmei Yang,Yingpai Zhaxi,Yongqing Zhao,Derong Zhang 대한수의학회 2022 Journal of Veterinary Science Vol.23 No.1

Background: Domestic yaks are the most important livestock species on the Qinghai-Tibetan Plateau. Adult female yaks normally breed in the warm season (July to September) and enter anestrous in the cold season (November to April). Nevertheless, it is unclear how ovarian activity is regulated at the molecular level. Objectives: The peculiarities of yak reproduction were assessed to explore the molecular mechanism of postpartum anestrus ovaries in yaks after pregnancy and parturition. Methods: Sixty female yaks with calves were observed under natural grazing in Haiyan County, Qinghai Province. Three yak ovaries in pregnancy and postpartum anestrus were collected. RNA sequencing and quantitative proteomics were employed to analyze the pregnancy and postpartum ovaries after hypothermia to identify the genes and proteins related to the postpartum ovarian cycle. Results: The results revealed 841 differentially expressed genes during the postpartum hypoestrus cycle; 347 were up-regulated and 494 genes were down-regulated. Fifty-seven differential proteins were screened: 38 were up-regulated and 19 were down-regulated. The differential genes and proteins were related to the yak reproduction process, rhythm process, progesterone-mediated oocyte maturation, PI3K/AKT signaling pathway, and MAPK signaling pathway categories. Conclusions: Transcriptome and proteomic sequencing approaches were used to investigate postpartum anestrus and pregnancy ovaries in yaks. The results confirmed that BHLHE40, SF1IX1, FBPX1, HSPCA, LHCGR, BMP15, and ET-1R could affect postpartum hypoestrus and control the state of estrus.