DV-Hop localization algorithm has greater localization error which estimates distance from an unknown node to the different anchor nodes by using estimated average size of a hop to achieve the ...location of the unknown node. So an improved DV-Hop localization algorithm based on correctional average size of a hop, HDCDV-Hop algorithm, is proposed. The improved algorithm corrects the estimated distance between the unknown node and different anchor nodes based on fractional hop count information and relatively accurate coordinates of the anchor nodes information, and it uses the improved Differential Evolution algorithm to get the estimate location of unknown nodes so as to further reduce the localization error. Simulation results show that our proposed algorithm have lower localization error and higher localization accuracy compared with the original DV-Hop algorithm and other classical improved algorithms.
Radio frequency identification（RFID） technology has been extensively used in various practical applications, such as inventory management and logistics control, with its outstanding features（e.g. ...non-line-ofsight reading and fast identification）. And in a large RFID system, unknown tag identification uses total execution time as the performance criterion. However, the performance of existing protocols in terms of execution time is not ideal. To get better time efficiency, a novel unknown tag identification protocol（NUTIP） is proposed. The novelty of NUTIP is demonstrated mainly in two aspects： i） NUTIP deactivates some known tags and identifies or labels some unknown tags during its first phase to prevent these tags from interfering unknown tag identification. ii） We optimize the parameter settings to minimize the total execution time. Simulation experiments show that the proposed protocol is far superior to other relevant protocols and suitable for both sparse unknown tags environment and dense unknown tags environment.
The present study investigates the impact of complex material flow-induced interfacial reaction layers on the fatigue performance of friction stir-welded (FSW) S45C steel and 6061-T6 aluminum alloy. ...The material flow analysis reveals that the intermixing between aluminum and steel forms intermetallic compounds (IMCs) mainly limited to the upper side of the stir zone (SZ). The IMC layers in various regions of the aluminum/steel interface within the SZ are visualized by scanning electron microscopy, and their possible chemical compositions are identified using energy-dispersive spectroscopy analysis. The chemical composition, morphology, and thickness of IMC layers exhibit significant heterogeneity owing to the asymmetric material flow of aluminum and steel between the top and bottom sides of the SZ. The non-uniform IMC layers considerably influence surface microhardness values and the fatigue behavior of the FSW joint. Moreover, the significance of IMC thickness on the morphology of the fatigue failure mechanism is examined using detailed microstructural analysis in proximity to fatigue fracture locations of the FSW joint. SEM images suggest that fatigue cracks inside the FSW joint initiate more frequently in thick IMC lamella than in the comparatively thinner Al-rich reaction layers.
Received signal strength indicator (RSSI) of WiFi access point (AP) is a primary sensor data used for indoor fingerprint localization. User sends its online RSSI to server to estimate its position by ...matching with RSSI fingerprints database which built in the offline phase. An important goal of indoor fingerprint localization is to increase the accuracy while reduce the storage cost. Meanwhile, APs perform different effects on target estimation and mapping metric in RSSI fingerprint localization. In this paper, a novel localization model based on the nonuniform quantization RSSI entropy (NQRELoc) is proposed to address these problems. First, to select the APs that contribute more to the localization, the nonuniform quantization RSSI entropy (NQRE) is introduced to quantify AP's discernibility and select APs whose signals show sufficient differentiation to construct an offline fingerprints database. Then, the entropy-weighted euclidean distance (EWED) is used as a metric to measure the similarity of online RSSI vectors and offline RPs fingerprints. Finally, NQRELoc locates the target by the improved entropy-weighted K nearest neighbor (IEWKNN) algorithm, which takes the APs effect into target estimation. To validate the proposed algorithm, a large scale of experiments and simulations are implemented. The results demonstrate that NQRELoc can not only reduce the storage overhead but also improve the positioning accuracy compared to the other existing techniques.
A novel welding method, induction pressure welding (IPW) process was used to join steel and aluminum alloy. The effects of input power, air gap and heating time on welding point width, intermetallic ...compound (IMC) thickness and tensile strength were investigated during the IPW process using response surface method. The results indicate that the heating time has the most marked effect on micro-structure and mechanical performance in all single factors. The air gap and heating time have the greatest interaction effect on tensile strength and welding point width while the input power and heating time have the greatest interaction influence on IMC thickness. The most desirable process parameters with input power 30kW, air gap 4.4mm, and heating time 10s are expected to be able to minimize IMC thickness and maximize tensile strength. The comparison between the predicted and experimental results for tensile strength and IMC thickness indicates that the mathematical model built by response surface method is reliability.
The microstructure and mechanical properties of electrically assisted brazing (EA-brazing) joints of aluminum alloy 6061-t6 (AA6061-t6) and S45C steel are experimentally investigated. During the ...EA-brazing process, an electric current is directly applied to the cylindrical specimen assembly (S45C and AA6061-t6) and fillers of 88% Al and 12% Si (in the middle of the specimen assembly). The temperature of the specimen assembly rises rapidly to the melting point of the filler and remains nearly constant for a period of time using a pulsed electric current. Two types of EA-brazing joints are fabricated, namely Joint-0s (no temperature holding time) and Joint-12s (12 s temperature holding time). The characteristics of the intermetallic compounds (IMCs) formed at the EA-brazing joint interface are analyzed using scanning electron microscopy and energy dispersive spectrometer. Compared to Joint-0s, the Fe-rich IMCs (FeAl) are observed at the interface of Joint-12s due to the 12 s temperature holding time. In addition, the microstructural analysis shows that the thickness of the diffusion layer increases with increasing temperature holding time. The mechanical properties of the EA-brazing joints are evaluated using bending tests. The results of the mechanical test show that the strength of Joint-12s is higher than that of Joint-0s.
A new method for on-orbit calibration of GRID gamma-ray detector Wu, Jiajun; Gao, Tai; Chen, Xiaoyu ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
November 2023, 2023-11-00, Letnik:
1056
Journal Article
Recenzirano
Gamma Ray Integrated Detectors aim to monitor and locate gamma-ray bursts. However, environmental factors can affect the detectors’ output signal, necessitating an on-orbit calibration to ensure ...accuracy. This paper proposes a new method for on-orbit calibration of scintillator detectors, utilizing a combination of a pure Sn sheet and a 241Am exemption source. Since the GAGG scintillator equipped on the GRID-06 detector has a Gd absorption edge (50.2 keV), two calibration energy points of 59.5 keV and 25.3 keV were constructed to calibrate the upper and lower energy bands of the Gd edge respectively, while the 241Am source was shielded with a Sn sheet. Experimental data revealed that the count rate of the 59.5 keV full-energy peak of the 241Am source decreased from 296 cps to 78 cps after being shielded with a 0.15 mm Sn sheet, while the count rate of the 25.3 keV characteristic X-rays produced by the excitation reached 30 cps. Based on these results, the proposed calibration method was analyzed and found to be applicable for observing GRBs, with the lower limit of flow intensity within 0∼100 keV of 95.5% of the gamma bursts being calculated.
Radio frequency identification(RFID) technology has been extensively used in various practical applications, such as inventory management and logistics control, with its outstanding features(e.g. ...non-line-ofsight reading and fast identification). And in a large RFID system, unknown tag identification uses total execution time as the performance criterion. However, the performance of existing protocols in terms of execution time is not ideal. To get better time efficiency, a novel unknown tag identification protocol(NUTIP) is proposed. The novelty of NUTIP is demonstrated mainly in two aspects: i) NUTIP deactivates some known tags and identifies or labels some unknown tags during its first phase to prevent these tags from interfering unknown tag identification. ii) We optimize the parameter settings to minimize the total execution time. Simulation experiments show that the proposed protocol is far superior to other relevant protocols and suitable for both sparse unknown tags environment and dense unknown tags environment.
To investigate the short-term effectiveness of allogeneic bone transplantation for pelvic reconstruction of large skeletal defects after tumor resection.
Between January 2008 and November 2009, 9 ...patients with pelvic tumor were treated, and the clinical data were retrospectively analyzed. There were 1 male and 8 females with an average age of 36.1 years (range, 18-44 years). There were 5 cases of giant cell tumor of bone, 2 cases of chondrosarcoma, 1 case of malignant giant cell tumor of bone, and 1 case of Ewing sarcoma. According to the Enneking system for staging musculoskeletal tumors, the lesion involved ilium (region I) in 4 cases, acetabulum (region II) in 6 cases, pubis and ischium (region III) in 3 cases, and sacrum (region IV) in 1 case. The average disease duration was 6.8 months (range, 1-36 months). After accurate resection of the tumor, allograft ilium with or without acetabulum was used in 6 cases and 2 cases respectively, and allogenous bone plate in 1 case for pelvic reconstruction; total hip
