Water Inrush Characteristics with Roadway Excavation Approaching to Fault

Water inrush disaster is an important factor in restricting safe production of the coal mine. Taking the roadway in seam in Danhou Coal Mine, as the engineering background, according to the spatial relationship of the roadway, the impermeable layer, the fault and the loading conditions, the fault activation mechanical model under the roadway excavation disturbance was built, and the fault activation conditions, roadway water inrush criterion and water inrush three modes were put forward. A three-dimensional numerical calculation models were built by using FLAC3D. Through fluid-solid coupling calculation, the surrounding rock damage and failure, the water inrush channel formation, and the evolution process of water inrush of the roadway excavation approaching the fault were analyzed. Moreover, the displacement field, the stress field and the surrounding rock plastic failure characteristics of the roadway were revealed. Furthermore, under the conditions of different water pressure, impermeable rock thickness, fault displacement, and fault dip angles, the roadway water inrush modes and their evolution characteristics were comparatively analyzed

Multi-objective Optimization of Construction Project Based on Improved Ant Colony Algorithm

It is the key and difficult problem for the current project management to consider the multi-objective optimization of the four elements, such as quality, duration, cost and safety. To improve the accuracy and efficiency of project management during the engineering construction, considering the advantages and disadvantages of the traditional quality-cost-time model, the four elements were regarded as a system, and a multi-objective optimization model was established. The improved ant colony algorithm was used to carry out multi-objectives of construction projects to overcome the premature defect of the traditional method. The optimal plan of the project was found and the overall efficiency of the construction project management was improved. Results show the optimized ant colony algorithm can avoid the low efficiency of the optimal solution search and the shortcoming of the initial pheromone. The engineering practice proves that the enhanced algorithm has solved the problem of the multi-objective optimization of quality, duration, cost and safety. The obtained conclusions are of significant reference value to direct the similar engineering practice

Impact of submodule faults on the performance of modular multilevel converters

Modular multilevel converter (MMC) is well suited for high-power and medium-voltage applications. However, its performance is adversely affected by asymmetry that might be introduced by the failure of a limited number of submodules (SMs) or even by severe deviations in the values of SM capacitors and arm inductors, particularly when the number of SMs per arm is relatively low. Although a safe-failed operation is easily achieved through the incorporation of redundant SMs, the SMs' faults make MMC arms present unequal impedances, which leads to undesirable internal dynamics because of unequal power distribution between the arms. The severity of these undesirable dynamics varies with the implementation of auxiliary controllers that regulate the MMC internal dynamics. This paper studied the impact of SMs failure on the MMC internal dynamics performance, considering two implementations of internal dynamics control, including a direct control method for suppressing the fundamental component that may arise in the dc-link current. Performances of the presented and widely-appreciated conventional methods for regulating MMC internal dynamics were assessed under normal and SM fault conditions, using detailed time-domain simulations and considering both active and reactive power applications. The effectiveness of control methods is also verified by the experiment. Related trade-offs of the control methods are presented, whereas it is found that the adverse impact of SMs failure on MMC ac and dc side performances could be minimized with appropriate control countermeasures

Evolution Characteristics of Pressure-Arch and Elastic Energy during Shallow Horizontal Coal Mining

To ensure safety mining during shallow horizontal coal mining based on the monitoring data of the roof weighting of a typical mining engineering in China, the load distribution characteristics of the roof in the mining field were analysed, and the mechanical model of the pressure-arch in the surrounding rock was established. Then the evolution characteristics of the pressure-arch and elastic energy were revealed during shallow coal mining by theoretical and numerical analyses. Results show that the continuous pressure-arch can form when the horizontal stress exceeds the vertical stress, and the elastic energy of the roof is released by the mining unloading effect. The caved zone of the overlying strata is formed below the inner boundary of the pressure-arch. The elastic energy is accumulated in the pressure-arch and the energy becomes the highest at the front arch foot. The sliding of the caved zone along the shear zone in the mining field can induce the strong roof weighting. The concentrated stress and the released energy during each mining stage increase with the working face advancing, and the height of the shear zone also increases. This study can provide a theoretical reference for similar mining engineering

Analysis of Vibration Attenuation and Energy Consumption of Blasting Demolition Chimney: A Case Study

Demolishing a tall chimney by directional blasting can save time and cost. However, the blasting vibration and the touchdown vibration of the parts of the chimney falling to the ground will cause noise disturbance to the local residents. To reduce the vibration effect of blasting demolition of the chimney, taking the 180 m high chimney in Jiaozuo, China, as the engineering background, the loose accumulation body with a right-angled trapezoid section 3-6 m thick was piled with three kinds of graded gravel particles as the buffer layer. According to the site restrictions, the chimney was demolished by directional blasting in two stages. The vibration propagation and attenuation rules of the blasting demolition of the chimney were analyzed and touchdown vibrations of two parts of the chimney were monitored also. Results show that the low frequency vibrations generated by the blasting and chimney touchdown have a greater impact on the surrounding environment. The vibration velocity and energy attenuation represent a form of power function. With the increase of the number of chimney touchdowns, the energy absorption rate of the loose accumulation body becomes lower. The obtained conclusions in this study can provide a reference for the similar blasting demolition practice

Big Data Transforms Discovery-Utilization Therapeutics Continuum.

Enabling omic technologies adopt a holistic view to produce unprecedented insights into the molecular underpinnings of health and disease, in part, by generating massive high-dimensional biological data. Leveraging these systems-level insights as an engine driving the healthcare evolution is maximized through integration with medical, demographic, and environmental datasets from individuals to populations. Big data analytics has accordingly emerged to add value to the technical aspects of storage, transfer, and analysis required for merging vast arrays of omic-, clinical-, and eco-datasets. In turn, this new field at the interface of biology, medicine, and information science is systematically transforming modern therapeutics across discovery, development, regulation, and utilization

Pressure-Arching Characteristics of Fractured Strata Structure during Shallow Horizontal Coal Mining

It is an important problem for the alternated strong and weak roof weighting to threat the safety of working face during shallow coal mining and the total thickness breaking of the thin bedrock to cause the serious ground subsidence. To reveal the mechanism of the abnormal mining damage, the pressure-arching rule in overlying strata was studied. Based on the monitoring data of the typical shallow coal working face, the mechanical models of the symmetrical stress arch, the squeezed arch and the hinged structure of the fractured strata were established, and the difference of the load bearing capacity between the structures and the influencing factors was analysed by the deduced formula calculation. Then the evolution characteristics of the pressure-arch in the fractured strata were revealed by the numerical simulation analysis. The results show that the global pressure-arch of multilayer strata always exits in the surrounding rock and moves forward with continuous mining. The single pressure-arch and hinged structure are formed in each stratum under the global pressure-arch. The pressure-arch enables the fractured strata to carry load efficiently, and the instability of the pressure-arch can cause strong roof weighting and ground subsidence. These conclusions provide a theoretical reference for the stability control of the overlying strata structure under shallow coal mining

Analysis of Strength Characteristics and Energy Dissipation of Improved-Subgrade Soil of High-Speed Railway above Mined-Out Areas

To reveal the effect of sand content on the mechanical performance and energy dissipation of cement improved subgrade soil, using universal testing machine and SHPB test device, unconfined compressive strength (UCS) and impact compression strength under different impact load (0.2, 0.3, 0.4, and 0.5 MPa) were carried out for the cement improved subgrade soil with different sand content (0%, 5%, 10%, 15%, and 20%). Results show that the dynamic and static stress-strain curves of the cement improved soil have similar variation trend. With the increase of the sand content, the UCS and impact compressive strength of the cement improved soil both increase first, then decrease later, showing the form of a quadratic function. The strength growth rate and the dynamic increase factor (DIF) reach the maximum values when the sand content is 10%, which is 64.7% and 18.6% larger than that of ordinary improved subgrade soil, respectively. In addition, when the sand content increases from 0% to 20%, the specific dissipation energy increases first, and decreases later. Mixing 10% natural sand is the optimal proportion to obtain better energy dissipation capacity of the sand-cement-improved soil

Shrinking the Semantic Gap: Spatial Pooling of Local Moment Invariants for Copy-Move Forgery Detection

Copy-move forgery is a manipulation of copying and pasting specific patches from and to an image, with potentially illegal or unethical uses. Recent advances in the forensic methods for copy-move forgery have shown increasing success in detection accuracy and robustness. However, for images with high self-similarity or strong signal corruption, the existing algorithms often exhibit inefficient processes and unreliable results. This is mainly due to the inherent semantic gap between low-level visual representation and high-level semantic concept. In this paper, we present a very first study of trying to mitigate the semantic gap problem in copy-move forgery detection, with spatial pooling of local moment invariants for midlevel image representation. Our detection method expands the traditional works on two aspects: 1) we introduce the bag-of-visual-words model into this field for the first time, may meaning a new perspective of forensic study; 2) we propose a word-to-phrase feature description and matching pipeline, covering the spatial structure and visual saliency information of digital images. Extensive experimental results show the superior performance of our framework over state-of-the-art algorithms in overcoming the related problems caused by the semantic gap.Comment: 13 pages, 11 figure