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The satellite gravimetry technology effectively recovers the global Earth’s gravity field. Since 2000s, HL-SST satellite CHAMP, LL-SST satellite GRACE, Gravity Gradient Measurement (GGM) satellite GOCE have been launched successfully, producing some Earth’s gravity models solely from satellites data. However, the space and time resolution of the Earth’s gravity fields do not adequately satisfy scientific objectives. The main reason is that the gravimetry satellites are not enough and observation data insufficient. The paper outlines the current and future status of Chinese gravity satellite missions. The Chinese gravimetry satellite system, named Chinese Gravimetry augment and Mass change exploring mission (ChiGaM), successfully launched in Dec. 2021 after four years of production and over a year of calibration and valiation. The accelerometer, K-band ranging system and the three stellar sensors, among others, were precisely calibrated and trimmed. The satellite mass center was determined and coordinated with the proof center of accelerometer with an accuracy 100μm. The inter-satellite ranging system and BDS/GPS receiver operate together seamlessly. The range and range rate noise is less than 3μm/Hz1/2 and 1μm/s/Hz1/2, respectively, in band of 0.025~0.1Hz. The electrostatic suspension accelerometer is working well. Its high-sensitive axis noise level is 3×10-10 m/s2/Hz1/2 near the frequency 0.1Hz, and 1×10-9 m/s2/Hz1/2 for the less-sensitive axis. Meanwhile the BDS/GPS receiver is used to achieve data for precise orbit determination, yielding an orbit result with accuracy better than 2cm. When compared with KBR observations, the RMS of the bias is less than 1mm. Besides above mission, next gravimetric satellite is being developed now. TQ-2 mission is designed as a totally experimental satellite for gravitational wave detection at low Earth orbit, which can detect the Earth’s gravity field simultaneously. The Bender-type mission is considered the most promising configuration for TQ-2 and consists of two polar satellites and two inclined satellites. Due to the extra observations at the east-west direction derived from the inclined satellite pair, significant improvements has been made in detecting temporal signals with higher accuracy and spatial-temporal resolution. To achieve the scientific goal, the ACC MBW can shift from 0.001~0.1Hz to 0.004~0.1Hz for ACC, and the LRI MBW can shift from 0.01~1Hz to 0.1~1Hz. For future research, a gravimetric potential survey using cold-atomic-clock based on the general relativity theory, cold atom gradiometer should be pursued. Gravimetric technologies should be mined and researched, and the gravimetry satellite constellation should be developed, so as to improve the time resolution and space resolution for meeting the requirements of geophysics, geodesy, earthquake, water resources environment, oceanography, etc.

A Q345 steel butt-welded joint was manufactured using laser–arc hybrid welding (LAHW) technology, and its microstructure, microhardness, and residual stress (RS) distribution were measured. Using ABAQUS software, a sequentially coupled thermo-metallurgical-mechanical finite element method was employed to model the welding RS distribution in the LAHW joint made of Q345 steel. The effects of solid-state phase transformation (SSPT) and transverse restraint on the welding RS distribution were explored. The results show that a large number of martensite phase transformations occurred in the fusion zone and heat-affected zone of the LAHW joint. Furthermore, the SSPT had a significant effect on the magnitude and distribution of RS in the LAHW joint made of Q345 steel, which must be taken into account in numerical simulations. Transverse restraints markedly increased the transverse RS on the upper surface, with a comparatively minor impact on the longitudinal RS distribution. After the transverse restraint was released, both the longitudinal and transverse RS distributions in the LAHW joint reverted to a level akin to that of the welded joint under free conditions. [ABSTRACT FROM AUTHOR]

The engine casing components operate in high-temperature and high-pressure environments. Process holes are drilled when defects occur. Welding is employed in the repair of process holes as a process for permanently joining materials. The traditional welding method relies on padding, which results in poor back formation of process holes. Additionally, the shape of the process holes imposes high requirements on the size of the droplet transition. The conventional approach of adjusting a welding current makes it difficult to achieve stable droplet transition and precise formation of small holes. It poses a challenge for the robotic welding process. To deal with this problem, the influence of the high-frequency vibration GTAW process on the directional transition of molten droplets is studied. The molten droplet directional transition process is developed. The impact of vibration energy on the molten pool is reduced. Welding repair experiments for process holes are successfully conducted. When the frequency is 3 Hz, the transition of droplets changes from a continuous one-droplet transition to a discontinuous liquid bridge transition. The residual height and mechanical properties of the repaired area are tested. The experimental results indicated that the residual height after dual-side repair is ≤0.7 mm. The X-ray and fluorescent penetration tests have a 100% first-pass qualification rate. The repaired area demonstrates a hardness of 480 HV and a room-temperature tensile strength of 1069 MPa. The repair process requirements for the casing are met. [ABSTRACT FROM AUTHOR]

Byline: Lian. Liu, Jiayu. Sun, Yunlong. Pan, Xian. Jiang Sir, A 6-year-old female was brought with port-wine stain, Mongolian spot, nevus anemicus, and atrophy of the right upper and lower [...]

Objective: Hyaluronic acid (HA) intra‐articular injection after arthroscopic knee surgery has been widely applied but its efficacy and safety remain controversial. The aim of this systematic review is to analyze the efficacy and safety of HA intra‐articular injection after arthroscopic knee surgery, and to compare the efficacy of HA with different molecular weights. Methods: We conducted a systematic literature search in PubMed, Embase, Google scholar and the Cochrane library from inception to 16 September 2022 for English‐written articles, in order to identify randomized controlled trials that evaluated the clinical efficacy and/or safety of HA intra‐articular injection after arthroscopic knee surgery. Then we meta‐analyzed the outcomes of patients given intra‐articular HA injections postoperatively and control patients. We also evaluated the influence of HA with different molecular weights. In every calculation, sensitive analysis was performed. The visual analogue scale (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and adverse events were selected as the primary outcome measurements, while Lysholm, International Knee Documentation Committee (IKDC) and Tegner score were selected as the secondary outcome measurements. Publication bias of every outcome was evaluated using egger test. Results: Fifteen studies involving 951 knees were included and 12 of them were used to performed the meta‐analysis. The results showed no significant difference between the HA group and control group according to VAS, whether assessed at less (P = 0.90) or more than 6 months (P = 0.55). Besides, there were no statistical differences between the HA group and control group according to subgroup analysis (Ps = 0.77, 0.91 and 0.81 in anterior cruciate ligament reconstruction, meniscectomy and overall groups, respectively). Compared to control group, the overall effect of WOMAC score showed no significant differences (P = 0.25), nor did in two subgroups (P = 0.37 and P = 0.22). Outcomes measured by Lysholm (P = 0.13), IKDC (P = 0.86) and Tegner (P = 0.42) scores showed no significant differences, either. The analysis of the risk of adverse events indicated no increase in HA groups (P = 0.06). We found no significant differences between high‐ and low‐molecular‐weight HA at 6 (P = 0.96) or 12 months (P = 0.93) postoperatively. Two studies failed to pass the sensitive analysis and the reasons were discussed detailly and acceptable publication bias was observed. Conclusions: Although HA injection after arthroscopic knee surgery is safe, the available evidence does not support its efficacy in pain relief and functional recovery. Therefore, the application of HA injection after arthroscopic knee surgery is not recommended. [ABSTRACT FROM AUTHOR]