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Railway communication is undergoing a transitional period worldwide, and 5G for railway (5G-R), which has been adopted by the Railway International Union (UIC) in China and in many other countries, which is a common concern all over the world. The 2100 MHz frequency band, which ranks among the top three mainstream frequency bands for public 5G network deployment globally, has recently been issued by MIIT for a 5G-R trial in China, and the frequency is fairly close to 5G-R frequency band of 1900 MHz in Europe. Propagation study for railway communication, especially for mainline, which is the most common and widely used scenario, is of great importance, because it is closely related to passengers' lives and properties. In this article, based on the 5G-R dedicated network testing environment constructed along the test line of loop railway of National Railway Track Test Center of China, the 2100 MHz 5G-R propagation measurement campaign is conducted, with an in-service SS-RSRP signal-based passive 2100 MHz large-scale channel testing system, as well as a SDR-based 2100 MHz 5G-R channel sounding system, based on which the large-scale as well as small-scale channel characteristics are derived and extensively analyzed. With data derived from the passive testing system, the classical FI, CI as well as TR 38.901 large-scale channel models are properly fitted and compared by calculating RMSE as well as MAE values. Moreover, based on the SDR-based channel sounding system, conclusions on the relationship between the parameters of multi-path component numbers, RMS time spread, received power and distance between the transmitter and the receiver are drawn. The 5G-R system studied in this letter is symmetric FDD communication system, apart from the 2 aspects of channel modeling characteristics, which are large-scale and small-scale complementing each other, the research methodology adopted of the letter also has two aspects, passive measurement, as well as active measurement, and both methods have their own advantages and different focuses, which can also complements each other. Relevant research results of this letter will be helpful for facilitating the R&D, deployment, as well as network optimization of a future mobile communication system under railway mainline scenario. [ABSTRACT FROM AUTHOR]

This study aimed to overcome the difficulty of conducting the horizontal-well cavity leaching test in the field and to investigate the long-term stability of the horizontal-well salt-cavity natural gas storage. The simulation test design is combined with the similarity theory to study the cavity expansion characteristics and the influence law of cavity leaching parameters. Through the design of a rubber hose connection, an integrated closed test system for multi-stage horizontal-well cavity leaching and brine drainage was built. The test system also realises the repeatable backward movement of the injection well during the test. A similarity simulation of the test design was carried out, and the test platform was constructed to carry out multi-stage horizontal-well leaching tests with a nitrogen cushion. In the horizontal-well leaching tests with a nitrogen cushion, the influence laws of the well spacing, flow rate and liquid level position on cavity expansion were investigated. Based on the morphological characteristics of the horizontal-well cavity, a numerical model of the horizontal-well salt cavity was developed, which reflects the real cavity morphology leached in the test. The long-term stability of the horizontal-well salt-cavity natural gas storage under different internal pressures was investigated through numerical simulation. [ABSTRACT FROM AUTHOR]

China implemented the China VI emission standard in 2020. The China VI emission standard has added requirements for the RDE (real-world driving emission) test. To evaluate vehicle CO2 emission for different vehicles, 10 conventional gasoline vehicles were tested under the RDE procedure using the PEMS (portable emission testing system) method. All vehicles tested meet the sixth emission regulation with a displacement of 1.4 L~2.0 L. Among the vehicles tested, the highest CO2 emission factor was 281 g/km and the lowest was 189 g/km, while the acceleration of RDE gets a wider distribution, varying from −2.5 m/s2 to 2.5 m/s2. The instantaneous mass emission rate could reach around 16 g/s. The amounts of total CO2 emission in the positive region and the negative region make up 82~89% and 11~18% of the overall CO2 emission during the entire RDE driving period, respectively. The same vehicle has a wide range of CO2 emission factors at different VSP (vehicle specific power) intervals. Different RDE test conditions can lead to large differences in CO2 emissions. [ABSTRACT FROM AUTHOR]

Based on the key module-lifting arm system, based on the principle of similarity and the hydrodynamic experimental method of a multi-dimension vibration test platform, an experimental platform for dismantling equipment is designed and built. Subsequently, the motion control model of the six-degrees-of-freedom platform is established. The three-ring control model of a servo electric cylinder is established, and the active heave compensation control of a servo electric cylinder is realized by combining position control theory. Based on the co-simulation of ADAMS and Simulink, the co-simulation system of the integrated dismantling equipment experimental platform is designed and built, and the simulation system is tested and verified. Finally, simulation and experimental verification are carried out based on the experimental platform and co-simulation system. The results show that the heave compensation rate reaches 58.3% in third-class sea conditions, 61.2% in fourth-class sea conditions, and 62.4% in fifth-class sea conditions. The integrated dismantling scheme of super large offshore oilfield facilities is feasible but, in order to ensure the safety and reliability of the operation, a heave compensation system needs to be added. The error between the simulation results and the experimental results is about 15%. Based on the analysis of external interference factors in the experiment, the error results are within a reasonable range, which proves that the experimental platform, the co-simulation system of the experimental platform, and the heave compensation strategy are accurate and effective. This study, for the first time in China, provides an effective experimental platform and co-simulation platform for the design and optimization of the integrated dismantling equipment of super large offshore oilfield facilities and lays a good research foundation for the construction and engineering demonstration of subsequent equipment. [ABSTRACT FROM AUTHOR]

For data-driven dynamic stability assessment (DSA) in modern power grids, DSA models generally have to be learned from scratch when faced with new grids, resulting in high offline computational costs. To tackle this undesirable yet often overlooked problem, this work develops a light-weight framework for DSA-oriented stability knowledge transfer from off-the-shelf test systems to practical power grids. A scale-free system feature learner is proposed to characterize system-wide features of various systems in a unified manner. Given a real-world power grid for DSA, selective stability knowledge transfer is intelligently carried out by comparing system similarities between it and the available test systems. Afterward, DSA model fine-tuning is performed to make the transferred knowledge adapt well to practical DSA contexts. Numerical test results on a realistic system, i.e., the provincial GD Power Grid in China, verify the effectiveness of the proposed framework. [ABSTRACT FROM AUTHOR]

• Using spring sets and built-in water bag to simulate aquifer; embedding guide lift hose and branch conduit as prefabricated water-conducting channel; Using "cutting-support-blocking" integrated device to simulate key equipment of ARFMP. • The floor failure characteristics of ARFMP are obtained and its effectiveness in preventing water inrush is verified. • An engineering treatment scheme combining ARFMP and floor regional control is proposed, and reliability of the model test results is verified after field application. The coal mining in North China is seriously threatened by floor water inrush from the Ordovician limestone, so it is particularly important to explore failure characteristics. Automatic roadway formation mining without pillars (ARFMP) provides an effective method for reducing floor failure. To explore failure characteristics above confined water, a two-dimensional model test system is built up. Such a system can be applied to compare the difference of floor failure between ARFMP above confined water and traditional retained coal pillar mining, and to intuitively analyze the lifting law of confined water under dynamic disturbance. The core features of this system include the customized spring sets and water bag adopted as materials to simulate the floor aquifer, the guide lift hose and branch conduit used as the lifting channel of confined water, and the flow rate and cumulative volume monitored in real time. The customized "cutting-support-blocking" integrated device is the key equipment to simulate ARFMP. Then, the model test is conducted on a typical engineering case. By comparing stress, displacement, and water inrush characteristics of floor in different areas, failure characteristics of the roof-cutting side, the middle of working face, the collapse column area, and the coal pillar side were obtained, and it was clarified that ARFMP can effectively prevent floor water inrush. According to the results of model test, a comprehensive treatment scheme combining ARFMP with the floor regional control is proposed to ensure the safe mining of working face. [ABSTRACT FROM AUTHOR]

• A novel hybrid model and data-driven voltage stability online assessment approach is proposed. • The parameters in the model-driven method are modified based on the response data. • To improve accuracy, impedance difference is included in the data-driven input data. • The proposed method combines the clear mechanism of the model-driven and high accuracy of the data-driven. With the continuously increasing integration of renewable energy sources into power grids, the dynamic response of a power system is becoming more complex. For example, the interaction between the dynamic loads and low-voltage ride-through of renewable energy generators makes the voltage response more rapid and unpredictable. Ensuring the accuracy and speed of traditional voltage stability assessment methods is difficult. This study developed a novel hybrid model and data-driven voltage stability assessment approach. First, the equivalent parameters of a power system were calculated based on the measured data, and the parameters were constantly modified based on the response data. To further improve the accuracy of the approach, a data-driven method was introduced to correct the assessment results using a Thevenin equivalent-based assessment. The difference between the Thevenin and system impedances, which better reflects the system stability, was included in the data-driven input data. Finally, by combining the clear physical mechanism of the model-driven method and high accuracy of the data-driven method, the final the assessment process was a serial combination of the model- and data-driven methods. The effectiveness of the method was verified using an IEEE New England 10-generator 39-bus test system and a 100-bus actual system in China. The results showed that the method developed was more accurate and had higher robustness under data loss and noise conditions than other methods. [ABSTRACT FROM AUTHOR]

The multi-terminal hybrid LCC/MMC HVDC has been applied to overcome the simultaneous commutation failure problem caused by the multi-infeed LCC-HVDCs in the East China. The high-speed and selectivity line protection method is required for the multi-terminal hybrid HVDC system. In this paper, the reflection and refraction of the fault traveling waves at different kinds of line terminals are characterized by transfer functions. Then the fault voltage as well as its first peak time at different line terminals when different internal and external faults occur are derived respectively. The conclusion proves that the first peak time of line-mode fault component voltage (FPTV) for internal faults is smaller than that for external faults, which is independent of fault impedance and fault type as well. Therefore, a FPTV-based non-unit ultra-high-speed dc line protection method is proposed. The algorithm is implemented in the developed protection prototype and validated in the Kun-Liu-Long three-terminal hybrid HVDC RTDS test system. The test results show that the proposed method can fast and correctly identify line faults in the multi-terminal hybrid HVDC system, even with 500 Ω fault impedance. Comparing with the traveling wave protection method of ABB, the proposed method improves the sensitivity when high-impedance faults occur. [ABSTRACT FROM AUTHOR]

Robust look-ahead dispatch (RLAD) is essential to manage uncertainties in power systems. As its key step, the worst-case scenario identification (WCSI) problem is cast to a max-min program. This computationally intensive procedure has to be performed repeatedly, impairing the computational efficiency of RLAD. To address this issue, an efficient RLAD scheme incorporating critical region preparation in gap time is proposed. The computation burden is mostly transferred from the online decision stage to the gap time via a customized technique based on multi-parametric programming. The accuracy of computing the critical regions is validated by the test in a six-bus system, and the proposed method is shown to cut down 21% of total iterations and save computational time dramatically by the test in a practical-scale system in Northeastern China. [ABSTRACT FROM AUTHOR]

Variable seeding by sowing decision can improve the utilization rate of resources. In order to achieve more accurate position control and sowing rate control, precision sowing decision control system was developed, and the integral separation Proportional Integral Derivative (PID) control algorithm of metering disc speed and grid based dead reckoning method were proposed. In order to test the performance of the system, the experiment of the influence of integral switching on step response and the experiment of seeding response based on simulated sowing decision were carried out. The results showed that average lag distance based on dead reckoning was 72.2 cm less than that of non-dead reckoning; system response distance of integral separation PID control algorithm was 43.1 cm shorter than that of ordinary PID control algorithm. The field experiment showed that the error of the monitoring sowing rate relative to the actual sowing rate was 3.5%, the average transition distance within the speed range of 3-9 km/h was 139.5 cm, and the standard deviation was 12.8 cm. The developed seeding control system improves the accuracy of seeding based on sowing decision, and provides a technical reference for low-cost sowing decision based control system in China. [ABSTRACT FROM AUTHOR]

This article proposes a novel optimal sizing method for the energy station in the multienergy system (MES) integrated with data center. First, an overall framework of the energy station, data center, and multienergy loads is constructed to describe the interconnection of energy system and information system. Then, the dynamic voltage frequency scaling (DVFS) technique, the thermal inertia, and the deep coupling relationships of the electricity load, waste heat, cooling load, and workload in the data center are respectively modeled. On this basis, the optimal sizing model of the energy station is established, in which the data center can participate in the integrated demand response by the DVFS technique and thermal inertia. The capacity of energy station and the scheduling schemes of energy devices and servers are optimized simultaneously to coordinate the energy flow and information flow. Based on the quasi-steady-state assumption of thermal balance, the model is simplified to a mixed-integer quadratic program problem, and it is solved by Gurobi. Case studies based on a real-world test system in China illustrate that the integration of data center can be utilized to reduce the total cost of energy station planning in MES. [ABSTRACT FROM AUTHOR]

Multi-energy industrial parks, composed of the district energy supply system and terminal industrial loads, are dominant energy consumers with over 50% occupation of total energy consumption. Considering the energy conversion in the district energy supply system and adjustment of production subtasks in terminal industrial loads, the industrial parks could provide considerable flexibility for utility multi-energy systems to deal with contingencies. However, industrial parks may have multiple uncertainties originating from the production subtasks' variability, distributed renewable energy's fluctuation, and random failures of equipment. These uncertainties could make the flexibility assessment of industrial parks unreliable, which may further exacerbate utility system risks. To address the problem, this paper innovatively proposes the concept of probabilistic integrated flexible regions and corresponding characterization approaches, which can effectively describe the credible multi-energy adjustment ability of industrial parks. First, the energy-material flows in the industrial park are modeled considering multiple uncertainties while subject to constraints such as operating limits of equipment, energy and material balancing, and production targets. Then, the modeling and calculation methods of probabilistic integrated flexible regions are given. These regions are labeled with certain probability requirements and visualized in the input multi-energy space. Using a real-world test system that produces air conditioning equipment in China, the results show that the proposed model can effectively reflect the probability characteristics of the integrated flexibility under multiple uncertainties. For this test system, the area of a highly credible integrated flexibility, represented by the probabilistic integrated flexible region with 99% probability, is about half of that obtained by the deterministic model. That is, half of the integrated flexibility evaluated by the deterministic method in the test system may not be practically utilized considering the impacts of uncertainties. Therefore, the proposed method could provide a credible and comprehensive evaluation of the multi-energy industrial park's flexibility considering multiple uncertainties. • Exploiting the multi-energy(integrated) flexibility of industrial parks • Describing the probability characteristics of the integrated flexibility • Uncertainties in industrial parks shrink their integrated flexibility • Facilitating the interaction between demand and utility side in energy systems [ABSTRACT FROM AUTHOR]

Water–sand inrush is one of the most serious disasters for mining in China. The evaluation of the occurrence and development of a high-concentration water and sand mixed fluid is an important issue for mining in China. In this study, contraposing to the 3 phases of water–sand inrush, three kinds of experiments are designed for the investigation of initiation, development, and occurrence of the disaster. A new sand–water transport testing system is setup to perform the tests. The results show that there are two key points in the disaster: (1) sand particle incipient motion and (2) porous skeleton structural instability. The incipient motion of sand grains is accompanied with the phenomena of volumetric dilatation and granular fluidization. The critical velocity of the incipient motion of the water–sand mixed fluid is significantly affected by the particle size and external stress. The interaction between water and sand grains is the key factor affecting the motion characteristics of water–sand mixture. When the hydraulic conditions exceed the threshold, the water and sand grains are mutually promoted, and the aquifer skeleton becomes unstable. Furthermore, during the water–sand inrush, the curves of volumetric flow rates of sand and water, respectively, for different samples manifest as two distinct waveforms. [ABSTRACT FROM AUTHOR]

With the depth increasing and the improvement of mining mechanization of the coal mine, heat hazard is becoming more and more serious, the ice cooling system is gradually promoted and applied in China for recent years, but the cooling capacity and energy efficiency ratio (EER) test and analysis for such system is seldom reported. The cooling capacity and EER of the refrigerating equipment of an ice cooling system of a coal mine are tested and analyzed in Shandong Province in this paper. The test result indicates that the refrigerating capacity and EER are lower and both the pre-cooling units and the ice making system have a large variable range. It points out that it should not evaluate the ice cooling system by the test data only in this mine but expect more test data and analysis of the ice cooling system in other coal mines to get a more scientific conclusion. And the test, analysis and comparison for different kinds of cooling system are also expected to explore suitable cooling system while a full consideration of the geological conditions and other factors of the mine are taken into consideration. [ABSTRACT FROM AUTHOR]

Currently, the increasing wind power penetration, with consequent randomness and variability, presents great challenges to power system planning and operation. Probabilistic power flow (PPF) has been developed to calculate the power flow under uncertain circumstances. However, the current wind power models are subject to specific probability distributions, limiting their accuracies in wider applications. Additionally, the cumulant method (CM)-based PPF, if nonlinear relationship is considered in, would face an impractically high computational complexity. To address these problems in modeling and cumulant calculation, this article proposes a novel generalized density/distribution fitting method (GDFM) combining with the Copula function to establish a joint probability model for wind power generation. A special impulse- mixed probability density (IMPD) integration method is also introduced to derive the input cumulants from the model. Finally, a fast cumulant method (FCM) is proposed to reduce the computational burden of output cumulant calculation while retaining a high accuracy in a nonlinear context. Case study on the IEEE-118 test system validates the effectiveness of the proposed methods, and a real application to a provincial power grid in China provides some useful power flow risk information for decision making. The whole FCM-based PPF scheme can be helpful for future power flow examination in power system planning and operation. [ABSTRACT FROM AUTHOR]

• Fastener stiffness increases with service time in high-speed railway. • Fastener stiffness is sensitive to low temperature and high frequency. • The temperature- and frequency-dependent characteristics of fastener affect rail vibration and decay rate. • PUEP composed of PTMG1000 and NDI has wide temperature range stiffness characteristics. The operation line of China's high-speed railway has exceeded 40,000 km. The performance decay and even failure to some fastener systems could be caused by complex terrain (mountain and plain), variable environment (−50 °C to 50 °C), high speed (300–350 km/h) and high frequency (500–700 Hz). Herein, the W300-1 fastener is taken as the research object to test and conclude the service performance and online track modal recognition. The comprehensive test system is used to obtain the dynamic characteristics of fasteners with the preload under the temperature-dependent (−70 °C to 50 °C) and frequency-dependent (10–1250 Hz) coupling conditions. It is found that the elastic pad stiffness in fastener system is sensitive to the low temperature and high frequency. In order to study the influences of temperature- and frequency-dependent dynamic characteristics of fasteners on track system, the dynamics analysis model of track system is constructed. The rail receptance curve under constant working condition is verified by the online track recognition. Simultaneously, the dynamic characteristics of the rail under constant working condition (4 Hz) and temperature-/frequency-dependent conditions are contrastively analyzed. The results indicate that the frequency-dependent characteristics of elastic pad enable the first-order modal frequency to shift toward a higher frequency, accompanied by the amplitude increase. The temperature-dependent characteristics of elastic pad make the medium- and high-frequency decay rate of rail wider but smaller. Due to the adverse effects of above conclusions, the polymer materials of elastic pad in fastener system are modified and optimized from two perspectives of polyol type and crosslinking agent type. Based on the standard requirements of Q/CR7-2014, it is certain that the dynamic performances of PUEP samples prepared by PTMG1000 and NDI together can meet the requirements of safety and stability of high-speed railway. [ABSTRACT FROM AUTHOR]

• R&D work on HHLT facility for ITER large vacuum components is successful in China. • A satisfying result (lower than 2.69×10−10 Pa*m3/s) in the 1st HHLT on the shield block full-scale prototype. • H 2 O and H 2 outgassing is the major factor impacting the performance of HHLT facility at different temperatures. • The facilities' performance was improved by at least one order of magnitude after adopting outgassing-removal measures. • HHLT results of 50 shield blocks with the improved facilities are better and stable. China Domestic Agency (DA) will provide ITER with 220 shield blocks (SB) which are important, large, and actively water-cooled components in ITER vacuum vessel, their leakage rate shall not exceed 2.69 × 10 − 10 Pa · m 3 / s in hot helium leak tests (HHLT) at 250±20 °C. The HHLT work started with developing a HHLT facility and manufacturing a SB full-scale prototype (FSP). The result showed the FSP could satisfy ITER's requirement at 235 °C. H 2 outgassing from stainless steel surfaces is the main factor that impacts both the background leakage rate and sensitivity of the testing system in hot testing cases. Hydrogen-removal measures were taken to improve the facility performance, and a new facility was built. A better facility performance came out at 250 °C rather than 235 °C, the background leakage rate decreased by one order of magnitude while the system sensitivity increased by two orders of magnitude. The background is at 10−10 Pa.m3/s and 10−9 Pa.m3/s level at room temperature (RT) and 250 °C, respectively, while the system sensitivity is at 10−12 Pa.m3/s and 10−11 Pa.m3/s level at the two temperatures. With the two facilities, series HHLTs have been carried out on 50 SBs covering two types, with all results complying with ITER requirements. [ABSTRACT FROM AUTHOR]

• In this simulation, the isolation valves of helium cooling system are assumed to be closed in the loss of off-site power accident, which is the worst scenario. The feasibility of removal of decay heat by thermal radiation after LOSP is investigated. • The effect of natural circulation in primary loop during accident, the influence of different power and available time of class III power supply (safety class) are analyzed separately, which provides data for the following design process. Helium Cooled Ceramic Breeder Test Blanket System (HCCB TBS) is proposed by China, which will be tested in ITER facility to validate the tritium breeding blanket technology. Test Blanket Module (TBM) is the core component associated with its helium cooling system (HCS) and other ancillary systems. The accident analysis is necessary during the preliminary design process, and the results obtained provide safety feedback to the following design work. Loss of Off-site Power (LOSP) is one of the design basis accidents (DBA), and is simulated using the best estimated code RELAP5 MOD3.4. For the safety simulation, besides the thermal conductive and convective model, the radiation model is adopted as well. The influence of the natural circulation of the HCS primary loop and the necessity of the Class III power supply (safety class) are discussed. The simulation results show that the peak temperature of the structure material exceeds the design temperature (550 °C) for short duration, which has almost no impact on the structure. In the meantime, the duration of the temperature over 550 °C drops sharply while the natural circulation and the Class III Power are considered. The results verify the integrity and the safety of the HCS primary loop during the LOSP accident. [ABSTRACT FROM AUTHOR]

The urban transit system is vulnerable to various types of hazards and failures, where the failure of a system component may lead to a redistribution of the pressure and result in cascade failures. It is of great significance to develop an efficient approach to model and assess the system vulnerability for achieving a sustainable transit system. This research develops a novel holistic approach to assess the vulnerability of the urban transit system toward sustainable development. The cascading failure mechanism is incorporated in the established complex network to simulate the process in a dependent system, where the failure of one or a few system components can trigger the failure of other components. Several attack strategies (i.e., static and dynamic intentional attack and random attack strategies) are used to test the system vulnerability, and the impacts of the tolerance parameter and passenger transfer rate on the loss of transport capacity are explored. A complex network consisting of 198 nodes and 415 edges is constructed to model the urban transit system with cascade failures. A realistic urban transit system in China is used as a case to testify the applicability and effectiveness of the developed approach. Results indicate that: (1) The interchange stations display high vulnerability in the network and Xianggang Rd station, Hongtu Boulevard station, Taipingyang station, and Zhongnan Rd are the most vulnerable stations, which should be paid more attention in the operation management; (2) The damage of the attacks in the intentional attack strategies are much more significant than that in the random attack, indicating that the proposed approach presents the ability to identify the important nodes; (3) The metric of node betweenness would be more efficient to identify the vulnerable nodes in the intentional attack; (4) The optimal value of the tolerance parameter is the range [0.8, 0.9], while keeping the passenger transfer rate in the range [0.3, 0.4] can effectively reduce the effect of cascade failures with minimum resources. The developed approach can be used as a decision tool to not only assess the vulnerability in the existing transit system but also optimize the planning of the new transit system. • A holistic approach with detailed procedures to assess vulnerability of transit system is presented. • Several attack strategies are used to test the system vulnerability considering cascade failures. • A complex network with 198 nodes and 415 edges is built to model a realistic metro system. • Impacts of tolerance parameter and passenger transfer rate on transport capacity loss are explored. • The developed approach can be used to optimize the planning of the new transit system. [ABSTRACT FROM AUTHOR]

The reasonable design and in-time optimisation of the supporting scheme is very important for ensuring the safe control of the surrounding rock. The key steps are to conduct in-situ real-time tests and quantitative evaluation of the surrounding rock before and after being supported. In order to solve the difficult problem of in-situ testing the surrounding rock, the surrounding rock digital drilling test system (SDT system) of underground engineering is developed, and the in-situ test and bolt-grouting design evaluation method of surrounding rock in underground engineering based on digital drilling is proposed. The systematic test studies including digital drilling test, borehole inspection and coring test are conducted on typical surrounding rock of chamber in the high stress mine of China. The effectiveness of SDT system and the prediction model of rock equivalent strength based on drilling applied to on-site engineering are validated. The zoning of surrounding rock of deep chamber based on equivalent strength is obtained, which are the strength deterioration zone, strength recovery zone and original rock strength zone, respectively. Based on the results of the in-situ digital drilling test of surrounding rock, the bolt-grouting support scheme to reinforce the surrounding rock is designed and evaluated. The average equivalent strength increase rate of the fractured regions of chamber surrounding rock reinforced by bolt-grouting is 61.6%. The bolt-grouting support can effectively enhance the strength of the fractured surrounding rock and reinforce the fractured rock mass. This study provides an effective means for classifying surrounding rock based on their strengths and design optimisation of the support system. [ABSTRACT FROM AUTHOR]

The mission of Chinese Space station is underway in China and the different type of clock systems will be carried and high stability and accuracy of time transfer is demanded. Laser Time Transfer (LTT) will be implemented between ground and Space Station and the LTT payload is being developed by Shanghai Astronomical Observatory (SHAO) with the time comparison single shot precision of 60ps, stability of less than 1ps @ 300s, and 1ps @ 1day. This paper will introduce the progress of LTT payload, including the design of the detector and timer, the optical design, testing results of the system stability and the future developments of this project. [ABSTRACT FROM AUTHOR]