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A multibody system including a drilling riser system, tensioners and a floating platform is key equipment for offshore oil and gas drilling. Most of the previous studies only focus on the drilling riser system rather than the multibody system. Mechanical characteristics of the deepwater drilling riser system cannot be analyzed accurately in a simplified model. Therefore, a three-dimensional multibody analysis program is developed. The static and dynamic characteristics of the deepwater drilling riser system under different platform motions are analyzed based on the developed program. The results show that the static displacement of the riser system with tensioners is smaller than that without tensioners, which means the tensioners can suppress the deformation of the riser system. Under surge and sway motions of the platform, the dynamic displacement of the riser system with tensioners is also smaller than that without tensioners due to the tensioner suppression effect. Besides, the heave motion induces a uniform axial vibration of the riser system, while roll and pitch motions excite the riser system to vibrate laterally. Compared with the stress amplitude due to surge and sway motions, the stress amplitude of the riser system due to heave, roll and pitch motions is relatively small but cannot be neglected.

The Wulian complex is located on the northern margin of the Sulu orogenic belt, and was formed by collision between the North China Craton (NCC) to the north and South China Craton (SCC) to the south. It consists of the metasedimentary Wulian Group, gneissic granite and meta-diorite. The U–Pb analyses for the detrital zircons from the Wulian Group exhibit one predominant age population of 2600–2400 Ma with a peak at c. 2.5 Ga and several secondary age populations of > 3000, 3000–2800, 2800–2600, 2200–2000, 1900–1800, 1500–1300 and 1250–950 Ma; some metamorphic zircons have metamorphic ages of c. 2.7, 2.55–2.45, 2.1–2.0 and 1.95–1.80 Ga, which are consistent with magmatic-metamorphic events in the SCC. Additionally, the Wulian Group was intruded by the gneissic granite and meta-diorite at c. 0.76 Ga, attributed to Neoproterozoic syn-rifting bimodal magmatic activity in the SCC and derived from partial melting of Archaean continental crust and depleted mantle, respectively. The Wulian Group therefore has tectonic affinity to the SCC and was mainly sourced from the SCC. The detrital zircons have positive and negative ϵHf(t) values, indicating that their source rocks were derived from reworking of both ancient and juvenile crustal rocks. The major early Precambrian crustal growth took place during c. 3.4–2.5 Ga with a dominant peak at 2.96 Ga and several secondary peaks at 3.27, 2.74 and 2.52 Ga. The two oldest zircons with ages of 3307 and 3347 Ma record the recycling of ancient continental crust (> 3.35 Ga) and crustal growth prior to c. 3.95 Ga in the SCC.

Ground target position estimation of near space vehicle is the key technology in military and civilian field. In this paper, we propose an effective method using the cubature Kalman filter (CKF) based on direction of arrival (DOA) and its rate of change. Comparisons with the location method only using DOA and the classic EKF algorithm are conducted respectively. Simulation results indicate that the proposed method has faster convergence speed and better location precision.

Spectrum assignment and power assignment are both key technology to use spectrum resource for cognitive radio networks effectively. In this paper, an effective joint resources assignment method is proposed. The objective is to maximize the system throughput and to guarantee the quality of service for the users simultaneously. The method is based on harmony search algorithm and graph coloring theory. It gives a more proper representation of the interference between the users in our system model. Thus, the users can reuse the spectrum more effectively. Simulations show that the proposed method can achieve higher system throughput in the new model than that in the traditional graph model.

Spectrum sensing is critical for cognitive radio networks as it allows a secondary user to find spectrum holes for opportunistic reuse. In this paper, an improved maximum-minimum eigenvalue detection method is proposed for a cognitive user equipped with a single receiving antenna. The proposed method utilizes the temporal smoothing technique to form a virtual multiple antennas structure. At the same time, the jackknifing resampling strategy is employed to improve the detection performance. Simulation results are presented to verify the effectiveness of the proposed method.

Spectrum sensing is a key technology to reliably detect spectrum holes in multi-dimensions for cognitive radio networks. In this paper, a joint spatial-temporal spectrum sensing scheme is proposed. First of all, the secondary users (SUs) located inside the primary exclusive region (PER) perform temporal sensing. When the primary user (PU) is present, the SUs located outside the PER perform spatial spectrum sensing. The proposed method can improve the spectrum utilization by exploiting both temporal and spatial spectrum holes. The achievable throughput for the secondary network of joint spatial-temporal sensing is higher than that of pure temporal sensing. Simulation results demonstrate the effectiveness of the proposed approach.

Spectrum sensing is a fundamental problem for cognitive radio system as it allows secondary user (SU) to find spectrum holes for opportunistic reuse. This paper presents a new spectrum sensing method based on the data stacking technique (temporal smoothing technique) and power method. The “maximum eigenvector” is used to detect the spectrum holes. Compared with the previous works, the proposed approach can provide better performance, such as higher detection probability in the lower signal-to-noise-ratio (SNR) scenario, etc.

In order to get better trade-off between detection performance and calculating complexity, an improved detection algorithm was presented here. QRD-M algorithm is performed for several layers firstly, and successive interference cancellation detection algorithm was used to detect the bottom several layers parallel, and the candidate sequence with smaller PAM was selected out as the answer. Simulation results show the validity of proposed algorithm.

In multiple-input multiple-output wireless communication system, the order of symbol detection in Chase framework is critical because of error propagation. In order to improve chase detector’s performance, sorted chase detection algortihm to reduce error propagation is proposed here. By setting parameters at different values, trade-off between performance and complexity can be obtained properly. Simulation experiment results show the validity of proposed algorithm.

Very recently, the LHCb Collaboration at the Large Hadron Collider at CERN observed new resonance X(4630). The X(4630) is decoded as a charmoniumlike molecule with hidden-strange quantum number well in the one-boson-exchange mechanism. Especially, the study of its hidden-charmed decays explicitly shows the dominant role of J/ψϕ among all allowed hidden-charmed decays of the X(4630), which enforces the conclusion of X(4630) as a charmoniumlike molecule. The discovery of the X(4630) is a crucial step of constructing charmoniumlike molecule zoo.