Active Protection Method Research Articles

Coal‐wall spalling prevention mechanism using advance‐grooving pressure relief in the large‐mining‐height working face of a shallow coal seam

AbstractIn mining, the roof structure of a working face with a large mining height in a shallow‐buried coal seam is prone to cutting instability in front of the support, which causes support crushing and coal‐wall spalling. This study analyzes 2201 working faces with large mining heights in the Haiwan No. 3 Mine by investigating the mechanical response law of coal walls under the transient excitation of roof structure instability. A mechanical model of coal walls under dynamic and static load coupling is established, revealing the formation mechanism of coal wall spalling and its main influencing factors. Prevention and control technologies of advanced grooving and pressure relief are proposed, and grooving parameters are determined. The results show that: During the mining process of large mining height working face in shallow buried coal seam, the step change of static response of coal wall is induced by the transient instability of roof structure, and the high abutment pressure is formed on the coal wall. At the same time, the strain energy and gravitational potential energy of roof cutting instability are released to form a dynamic load. Under the action of dynamic and static load, the plastic failure dissipation power of the coal wall is greater than the critical power, and the coal wall spalling occurs. The main influencing factors are mining load, mining height, and internal friction angle of the coal wall. The method of advanced grooving pressure relief can change the roof structure and coal force mechanism, by cutting off the connection between the coal wall and immediate roof, reducing the height of the coal wall force, effectively controlling the position of the roof cut off break line, reducing the static load effect of the roof on the coal, and transferring the position of the dynamic load response to the depth of the coal wall. When the grooving height‐depth ratio k is 0.75, the peak value of the abutment pressure moves 5.57 m to the front of the working face, and the pressure relief effect is the best. The above research results provide an effective active protection method for controlling coal wall spalling in fully mechanised working face with large mining height.

An active protection method based on superimposed phase currents for active distribution systems

To enhance the fault current amplitude of active distribution systems during the weak fault period and decrease the influence of the measurement equipment noise, this paper proposes an active protection method based on superimposed phase currents for active distribution systems. This method is shown as follows. First, the reference value of the filter inductor current of each distributed generator (DG) is set as different values when the fault intensity of the active distribution system changes. Second, the superimposed phase current in each relay is obtained by subtracting each sample of phase current from its corresponding sample of phase current in the previous cycle. Third, the fundamental phase angle of the superimposed phase current is extracted. This is because the fundamental current component of the superimposed current cannot be affected by the active control strategy, which is proved in this paper in detail. Meanwhile, the feature direction is built by fundamental phase angles at both ends of the line to detect faulty zone. Finally, the proposed protection method has been validated in a modified IEEE 13-bus test system, and the test results prove the effectiveness of the proposed active protection method that can enhance the faulty feature to detect faults.

PADVG: A Simple Baseline of Active Protection for Audio-Driven Video Generation

Over the past few years, deep generative models have significantly evolved, enabling the synthesis of realistic content and also bringing security concerns of illegal misuse. Therefore, active protection for generative models has been proposed recently, aiming to generate samples with hidden messages for future identification while preserving the original generating performance. However, existing active protection methods are specifically designed for generative adversarial networks (GANs), restricted to handling unconditional image generation. We observe that they get limited identification performance and visual quality when handling audio-driven video generation conditioned on target audio and source input to drive video generation with consistent context, e.g., identity and movement, between frame sequences. To address this issue, we introduce a simple yet effective active P rotection framework for A udio- D riven V ideo G eneration, named PADVG. To be specific, we present a novel frame-shared embedding module in which messages to hide are first transformed into frame-shared message coefficients. Then, these coefficients are assembled with the intermediate feature maps of video generators at multiple feature levels to generate the embedded video frames. Besides, PADVG further considers two visual consistent losses: (i) intra-frame loss is utilized to keep the visual consistency with different hidden messages; (ii) inter-frame loss is used to preserve the visual consistency across different video frames. Moreover, we also propose an auxiliary denoising training strategy through perturbing the assembled features by learnable pixel-level noise to improve identification performance, while enhancing robustness against real-world disturbances. Extensive experiments demonstrate that our proposed PADVG for audio-driven video generation can effectively identify the generated videos and achieve high visual quality.

Research on Active Protection Method for Microgrids Based on Harmonic Injection

Research on Active Protection Method for Microgrids Based on Harmonic Injection

Alleviating competition increases raptor breeding success: A case study of Jackdaws and Lesser Kestrels

Anthropogenic changes in the natural environment have led to the need to find alternative resources to ensure the persistence of biodiversity. In birds, nest sites can be a limiting resource in stenotopic populations. A method of active protection is the building of nest boxes. However, attractive nest sites attract target species and their competitors. From the species conservation point of view, our target species was the Lesser Kestrel (Falco naumanni), whose populations have recovered owing to the establishment of nest box colonies across Europe. However, they have been out-competed by Jackdaws (Corvus monedula) in recent years. Because corvids are intelligent and aggressive, we had to artificially control the competition from Jackdaws to allow Lesser Kestrels to nest. We aimed to discourage Jackdaws from taking over the studied colony and to ensure the continued breeding of Lesser Kestrels by manipulating access to the nest boxes. Data were collected during three breeding seasons in a Lesser Kestrel nest box colony using two manipulations in which we prevented Jackdaw occupation by closing some of the nest boxes and then gradually opening them. We found a significantly lower probability of Lesser Kestrels nesting and lower breeding performance in the control year than in the years in which access to the boxes was manipulated. The field experiment shows the high efficiency of manipulating the accessibility of nest boxes by closing and opening them at the right time in the context of their occupation by the target species and thus influencing their breeding performance.

Mitigating grapevine winter damage in cold climate areas

Growing grapes in cool climate areas is the same front type challenging due to the high risk of winter injury. Passive and active methods can be used to reduce or prevent cold damage and protect the vineyards. Passive protection methods are generally cultural practices and performed before cold damage events, such as cultivar and rootstock selection. The proper scion-rootstock combination would ideally help the vines acclimate earlier in the fall, allowing them to withstand colder weather in the fall and winter and de-acclimate later in the spring to minimise the late spring frost damage. The introduction of new North American hybrid cultivars accompanied with other cultural practices has increased the hope for developing viticulture in areas with lower cold hardiness zones. Furthermore, active protection methods are usually performed at the time of cold damage events to protect the vineyard by preventing or reducing the loss of thermal energy from vine tissues. The objective of this manuscript is to review the viticulture challenges in cold climates and mitigate the risks with Ontario, Canada as an example of a cold climate area.

Risk evaluation of internal short circuit for lithium‐ion battery based on an active protection method

Risk evaluation of internal short circuit for lithium‐ion battery based on an active protection method

Protection and Strengthening of Corroded Prestressing Tendons

As of late, structural deterioration of RC structures affected by corrosion is widely reported. A new evolution in maintenance of RC structures is by cathodic protection by the use of carbon fiber reinforced polymers (CFRP). Using steel bar as a cathode and wrapping of CFRP as anode, which prevents removal of concrete cover and blocks further corrosion of steel. This article presents the utilization of CFRP for the protection of the strand. Series of laboratory trials using cathodic protection systems were performed on pre-stressed concrete structures in order to set up reliable cathodic protection systems. To initiate initial corrosion in the specimens, pre-stressing tendon used as the cathode and CFRP used as the anode while the in the active protection, the impressed charge was passed through the strand. Then, CFRP sheets were bonded by using conductive adhesive to the block samples. Extensively corrosive environment was imposed on the samples for the particular period of time and it was observed that the active protection method is very effectual in slowing down the corrosion of the strand.

How environmental stressors affect reproductive potential in a saltmarsh plant species Plantago maritima.

We examined whether the presence or absence of different environmental stressors influenced the reproductive potential of a saltmarsh species—Plantago maritima. We focused on total seed output, seed quality, and biomass of progeny. So far, there are no studies trying to answer the question of how different saltmarsh management affects the quality of seed in saltmarsh species. For the purposes of the study, plots subjected to light mowing, light or heavy grazing, trampling, or rooting were designated in three nature reserves in Poland. On each plot, the abundance of infructescences per sq. meter was calculated. Mature infructescences were collected, and their length and number of fruit capsules were measured. The seeds obtained from fruit capsules were weighted and sown in controlled conditions. The germination rate and the final germination percentage were calculated. A representative number of sprouts were grown. After a period of 2 months, the individuals of P. maritima were harvested and their total dry mass was measured. It was found that heavy grazing had the greatest effect on all of the studied characteristics. The presence of this factor resulted in shorter infructescences with a smaller number of fruit capsules. However, this phenomenon was compensated by the higher abundance of infructescences per sq. meter. At the same time, seeds produced by grazed individuals were significantly lighter. Interestingly, intensive trampling by people affected P. maritima individuals in a similar way to heavy grazing, while mowing and rooting had less impact on the considered characteristics. Although a positive correlation between seed mass and germination success was found, the altogether lower seed mass had a negligible effect on germination parameters. Also, the differences in seed parameters did not affect dry mass of obtained progeny grown in laboratory conditions. Synthesis and applications: Different environmental stressors, such as grazing and mowing, have an effect on reproductive potential of a saltmarsh species P. maritima. In the case of habitats created anthropogenically, such as brackish saltmarshes, the role of management is crucial for their conservation. Therefore, searching for the best active protection methods is important. In light of the results obtained, extensive or rotational grazing appears to be the best form of saltmarsh management.

Frost Monitoring Cyber–Physical System: A Survey on Prediction and Active Protection Methods

Frost damage in broadacre cropping and horticulture (including viticulture) results in substantial economic losses to producers and may also disrupt associated product value chains. Frost risk windows are changing in timing, frequency, and duration. Faced with the increasing cost of mitigation infrastructure and competition for resources (e.g., water and energy), multiperil insurance, and the need for supply chain certainty, producers are under pressure to innovate in order to manage and mitigate risk. Frost protection systems are cyber-physical systems (CPSs) consisting of sensors (event detection), intelligence (prediction), and actuators (active protection methods). The Internet-of-Things communication protocols joining the CPS components are also evaluated. In this context, this article introduces and reviews existing methods of frost management. This article focuses on active protection methods because of their potential for real-time deployment during frost events. For integrated frost prediction and active protection systems, prediction method, sensor types, and integration architecture are assessed, research gaps are identified and future research directions proposed.

Design of a Magnet and Gradient Coils for a Tabletop Liquid-Helium-Free, Persistent-Mode 1.5-T MgB$_2$ Osteoporosis MRI

We have finalized the design of a full-scale tabletop 1.5-T/90-mm MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> finger MRI magnet system for osteoporosis screening based on our preliminary test results of small coils and superconducting joints. The magnet will operate in persistent mode at 10 K with an additional 5 K temperature margin. The magnet design which includes six main coils and an iron shield satisfies the required specification of a field intensity of 1.5 T, homogeneity of ≤5 ppm over a 20-mm diameter of spherical volume, and a fringe field of ≤5 gauss at 0.5 m in radius from the magnet center. An active protection method using external heaters will be applied to prevent a local hot spot in the MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> windings from being overheated when quench occurs. Active shield transverse and axial gradient coils for this tabletop osteoporosis MRI, having primary and shield coil pairs, are designed to minimize stray fields that can induce eddy currents on nearby metal surface and thus imaging artifacts. This paper covers design and analysis of: 1) the main coils and iron shield; 2) coil former; 3) quench protection; and 4) active shield gradient coils. We also discuss design changes of the cryostat and equipment plan for the overall system. The magnet system will be completed and then, equipped with other MRI hardware components including an in-house-made gradient coil assembly and RF coils for demonstration of 1.5-T finger MRI in 2020.

Defense of beach by active coast-protecting structures

The results of physical modeling of recreational beach protection by active protection methods are presented. The experiments were carried out in the wave pool on models of intermittent breakwaters with T-shaped and V-shaped traverses and dike dam systems. The use of active shore protection methods makes it possible to preserve natural and artificial beaches with the formation of a stable coastline. The geometrical parameters and hydrodynamic characteristics of the shore protection structures are established and recommendations for their operation are developed. Based on the research results, the dike dam system has been put into practice to protect the coastal strip of the “Urzuf” recreation complex on the shore of the Sea of Azov.

Investigation of the impressed current cathodic protection method for the cable parallel wires in the rainwater electrolyte based on acoustic emission method

The corrosion durability of bridge cables in operation is prominent. This study proposes an active protection method to apply impressed current cathodic protection (ICCP) to bridge cable parallel wires. The weight loss method, scanning electron microscopy, electrochemical test, and acoustic emission (AE) signal characteristic analysis were used to study the test method for electrochemical corrosion protection of cable parallel wires using rainwater conduction. Results show that cable wires are corroded on the surface and inside, whereas the cable wires with ICCP show different changes. The cable wires are effectively protected in the environment where a sodium chloride solution is used to simulate rainfall. In the AE test of the cable wires after corrosion using a signal generator, the main frequency of the AE signal gradually increases with the increase in corrosion degree. The high corrosion degree of the cable wires induces dispersion. The characteristics of AE signal can reflect the corrosion degree of the cable wires, and ICCP can decrease the corrosion rate of the cable wires.

Tunnel fire active protection: improving ventilation system

The main aim of this work is to evaluate how the use of an active protection method, consisting in an improved forced longitudinal ventilation system, can determine a positive impact on heat extraction and people evacuation time in a tunnel fire scenario, by considering a case study which simulations are based on a real gallery.

The method of active protection of information from the laser acoustic intelligence systems

In this paper, we analyzed the optoelectronic technical channel of information leakage and Laser Spy System, analyze the threats which they make and offer solutions to existing information security issues. The Laser Spy System is considered by many to be the Holy Grail of high tech spy devices because it can give the user the ability to listen in on conversations that take place in a distant building without having to install a bug or transmitter at the location. The Laser Spy System was said to be invented in the Soviet Union by Leon Theremin in the late 1940s. Using a non-laser based infrared light source, Theremin's system could detect sound from a nearby window by picking up the faint vibrations on the glass surface. The KGB later used this device to spy on the British, French and US embassies in Moscow. The Laser Spy System goes by several names such as the Laser Microphone, Laser Listener, Laser Bug, Window Bounce Listener and a few similar names. The Laser Spy certainly works well under ideal conditions, but it has many strengths and weaknesses that will be discussed in this paper. General component in the Laser Spy system is the laser, which will target a distant reflective object and send the beam back to your receiver for decoding. When the laser reflects from the target window, the slight vibrations from conversations or noise that vibrate the windows cause a very slight change in position of the returning laser beam. These changes in the laser fluctuations are taken by a phototransistor and then converted into sound. The most common methods and means of protection are presented, these methods can be both active and passive, but they all have a number of shortcomings, such as high cost, the creation of acoustic noise, insufficient protection, etc. We are proposed the method of laser noise as an alternative to the existing one, and the concept of its implementation is given. This method is based on the creation of counter laser radiation. This radiation consists of a plurality of laser beams that have parameters that are similar to the parameters of the rays of the attacker. Experiments have shown that the interception of the reflected laser beam is complicated if anti-radiation is applied.

Study on Quench Protection of Coil Wound of Bi/Ag-Sheathed Wire

Sure quench protection of HTS coils is essential for their sustainable operations in their real applications to HTS power devices. The authors investigate conditions to safely protect HTS coils from quench damages by a detect-and-dump-type active method. In the previous work, the safe area in the V qs versus τ plane was identified by experiment using test coils wound of Bi/Ag-sheathed wires, where V qs is the quench detection voltage, and τ is the decay time constant of the coil current in the active protection method. In this work, the safe area is obtained by numerical calculation, making a simulation model of a winding pack of a coil wound of Bi/Ag-sheathed wires. The analytical results well agree with those of the experimental results, and it is shown analytically that condition to safely protect a coils wound of Bi/Ag-sheathed wires from a quench damage can be analytically predicted.

An Intrusion Tolerance Method Based on Energy Attack for Wireless Sensor Network

Wireless sensor network is vulnerable to malicious attacks because of the broadcast nature of wireless signal. In order to overcome the shortcomings of existing methods, this paper presents an intrusion tolerance method against malicious nodes. Different from the traditional intrusion tolerance methods based on encryption, authentication, and multirouting, the proposed method uses active protection to achieve intrusion tolerance. Small power consumption of many normal nodes is exchanged for large power consumption of relatively small number of malicious nodes to decrease the lifetime of malicious nodes. Theoretical analysis and test results show that the proposed methods not only prolong the lifetime of the sensor network but also achieve the effective protection against malicious nodes. The active protection method provides new ideas for the security in WSN.

Attempts at active protection of Inonotus obliquus by inoculating birches with its mycelium

Practical application of active protection methods of &lt;em&gt;Inonotus obliquus&lt;/em&gt; (Fr.) Pilát. was examined. Thirty live birches and 15 birch stem sections were artificially inoculated with the fungal mycelium in the Mińsk Forest District (E Poland). The mycelium of &lt;em&gt;I. obliquus&lt;/em&gt; was not recorded in the felled test trees and birch stem sections upon the completion of the experiment. Artificial introduction of &lt;em&gt;I. obliquus&lt;/em&gt; in the natural environment faces significant problems caused by strong competition from other birch wood-decay fungi. As &lt;em&gt;in vitro&lt;/em&gt; studies show (individual biotic effect determination), the fungi examined, occurring on birch trees in nature, are dominant species in relation to &lt;em&gt;I. obliquus&lt;/em&gt;.

A novel protection method against direct lightning strike based on the principle of electrostatic field counteraction

Strong electromagnetic radiation around the conventional lightning rod system exists when it is struck by lightning, and serious electromagnetic interference on sensitive electronic equipments could be caused. A novel active protection method against direct lightning strike is proposed in this paper. The method, which is based on the principle of electrostatic field counteraction and shielding, is aimed at weakening the background electric field near the protection region to eliminate the condition for direct lightning strike there. The protection system is composed of three parts, including the monitoring equipments for atmospheric electric field, the active protection device, and the control system. Two working flow charts of the protection system are presented, and the feasibility of the protection method has been verified by scale-model experiment in the laboratory.

A CPAT Simulation Analysis on the Effect of Islanding Protection under Clustered PV Application 500 PV Systems

Since the FY2003, the demonstration site Josai-no-mori including over 500 residences with PV system has been under construction at the Ota City, Gunma prefecture in Japan. It is important to clear the safety of islanding protection. However, it is very difficult to verify the islanding phenomena including many PV systems on the actual utility grid, where the people are leading life actually. Therefore, it becomes important to develop a technique employing simulation analysis for the safety evaluation.Purpose of our study is to clear the details of dangerous islanding phenomena and the effects of various protection methods under clustered installation of over 500 PV systems within a partial area of utility grid. To solve these problems, a new analysis method has been developed, that is based on the CRIEPI's Power system Analysis Tools (CPAT) technology implemented by CRIEPI, so called “Y-method".As a noteworthy result, it has been confirmed that the new simulation method has a capability to expand to the large-scale clustered installation model including 500 PV systems on utility grid. The validity of simulation analysis has been verified by comparing with preliminary indoor tests. In addition, it has been clarified that the combination of passive and active protection methods is very effective to avoid the islanding phenomena.