Добірка наукової літератури з теми "Powerful underwater spark discharges"

Underwater sensor networks have wide application prospects, but the large-scale sensing node deployment is severely hindered by problems like energy constraints, long delays, local disconnections, and heavy energy consumption. These problems can be solved effectively by optimizing sensing node deployment with a genetic algorithm. However, the genetic algorithm (GA) needs many iterations in solving the best location of underwater sensor deployment, which results in long running time delays and limited practical application when dealing with large-scale data. The classical parallel framework Hadoop can improve the GA running efficiency to some extent while the state-of-the-art parallel framework Spark can release much more parallel potential of GA by realizing parallel crossover, mutation, and other operations on each computing node. Giving full allowance for the working environment of the underwater sensor network and the characteristics of sensors, this paper proposes a Spark-based parallel GA to calculate the extremum of the Shubert multi-peak function, through which the optimal deployment of the underwater sensor network can be obtained. Experimental results show that while faced with a large-scale underwater sensor network, compared with single node and Hadoop framework, the Spark-based implementation not only significantly reduces the running time but also effectively avoids the problem of premature convergence because of its powerful randomness.

In this research, the peculiarities of micro- and nanoparticles generation are considered. Two techniques of micro- and nanoparticles' formation using electric arc and underwater discharge plasma sources are proposed. Molybdenum oxide crystals were deposited on side surface of the bottom electrode (anode) of the free-burning discharge between metallic molybdenum electrodes. Friable layer of MoO₃, which consists of variously oriented transparent prisms and platelets (up to few hundreds of $mu;m in size), was formed by vapor deposition around the electrode. In the second technique, plasma of the underwater electric spark discharges between metal granules was used to obtain stable colloidal solutions with nanoparticles of 20-100 nm sizes.

In the Black Sea near Yalta in 1927 there were massive methane outbursts, accompanied by flames over the water. The fire was associated with methane emissions that entered through tectonic faults. The faults were caused by seismic movements. The article analyses the depth structure of the focal zones and the nature of the seismic process and assesses the nature of the manifestations of the fires. The main factor is thought to be methane, which rises from the earth’s crust during earthquakes. The electric spark discharges generated by friction and collision of the earth’s crust ignited methane gas. The massive gas emissions of millions of cubic meters that can be called gas plumes have been fixed. The spatial and temporal direction of the fire phenomena has been established. The main fire outbreaks over the water extended in two directions. The first, the Sevastopol­Evpatoria zone, stretches submeridionally to the coast and follows the Mykolayiv fault system. The second one is the Yalta­ Alushta zone with north-eastern extension. It is associated with tectonic faults within the Circum­Black Sea region, fault zone. This fault zone is active even at present, as indicated by seismicity, the structure of the consolidated crust and sedimentary strata, bottom topography forms, etc. Analysis of geological and geophysical materials, and seismicity of the northern Black Sea region, indicate that the fire events during the Yalta earthquakes in 1927 were caused by massive methane ejections as a result of a powerful mantle gas-fluid flow into the dissolved zones of the crystalline basement along the tectonic faults of different scales within the Odessa­Sinop and Circum Black Sea fault zones. Earthquakes triggered the activation of tectonic faults in benthic sedimentary horizons for the migration of focused deep-seated gas-fluid streams.

The excessive mineral contents in water circulation systems could cause severe fouling in heat transfer equipment. The present study investigated the effect of underwater pulsed spark discharges on the mitigation of mineral fouling in a concentric counterflow heat exchanger. Artificial hard water with calcium carbonate hardness of 250 mg/L was used with velocity ranging from 0.1 m/s to 0.5 m/s and zero blowdown. Fouling resistances decreased by 50–72% for the plasma treated cases compared with the values for no-treatment cases, indicating that the pulsed spark discharge could significantly mitigate the mineral fouling on the heat exchanger surface.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.09.13 – техніка сильних електричних та магнітних полів. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017. Дисертація присвячена вдосконаленню електророзрядного обладнання, що використовується для обробки речовин сильно струмовим підводним іскровим розрядом. Проведено аналіз здобутих властивостей матеріалів та рідин в залежності від електричних параметрів розрядного кола, розмірів міжелектродного проміжку, конструкцій електрогідравлічних реакторів і тиску у реакторі. Запропоновані технологічні рекомендації щодо вдосконалення обладнання та процесів електрофізичного впливу на матеріали і рідкі середовища. В дисертації вдосконалено математичну модель щодо дослідження ранньої стадії розвитку іскрового каналу потужного іскрового розряду в парі води та у парогазовій оболонці. Вперше виявлено можливість швидкої (5–20 с) зміни окислювально-відновного потенціалу рідин в бік від'ємних значень з помірним підвищенням водневого показника. Проведено діагностику зміни фізико-хімічних властивостей води. Визначено склад та розміри частинок, що утворюються під час електричної ерозії електродів, запропоновано хімічну схему їх впливу на властивості води. Виявлено можливість подрібнення матеріалів, що моделюють відпрацьоване ядерне паливо, з метою вдосконалення методів його переробки. Оптимізовано параметри розрядного кола та реактора для подрібнення гумовотехнічних виробів у середовищі рідкого азоту. Доведено можливість обробки та зменшення розмірів зерен металів, що переплавляються в вакуумно-дугових пічках під впливом механіко-акустичних імпульсів, які утворюються високовольтними потужними підводними іскровими розрядами.
Thesis for the scientific degree of the candidate of engineering sciences by specialty 05.09.13 – Technology of Strong Electric and Magnetic Fields. – National Science Center "Kharkiv Institute of Physics and Technology", Ministry of education and science of Ukraine National Technical University "Kharkiv Politechnic University" Kharkiv, 2017. This thesis is devoted to the improvement of the electric discharge equipment that is used for the substance treatment by heavy-current underwater spark discharges. The properties of materials and liquids were analyzed as a function of the electric parameters of discharge circuit, in particular, the charging voltage, the capacitance and the spark gap size. The structures of electrohydraulic reactors that are used for the treatment of general mechanical rubber goods and materials that simulate in the first approximation the spent solid nuclear fuel were developed and modernized to improve the methods of fuel recycling. The liquid degassing intensification method was suggested to initiate underwater spark discharges in the electrohydraulic reactor under the evacuation. The electrode system was created to provide the ordered motion of a pulsating steam and gas cavity in the water space at a reduced pressure in the reactor. A structure of the electric discharge generator of elastic vibrations that allows us to have an influence on the metal melts in vacuum-arc furnaces has been developed. It has been proved that mechanical acoustic vibrations generated by spark discharges in the liquid have a positive effect on the distribution of admixtures in treated metals and a decrease in the size of crystal grains. Technological recommendations on the improvement of the processes of electrophysical impact on the materials and liquid media were given. A mathematical model used for the investigation of the progress of current conducting channel that short-closes the spark gap at an early stage of its development, in particular a process of the expansion of current conducting channel and steam-gas cavity was improved. An opportunity for a fast (5–20 s) change in the redox potential of the liquid to the side of negative values with a moderate increase in the pH value was revealed for the first time. It has been shown that a change in the redox potential depends on the input of total energy into the treated volume. We established that a change in the redox potential is related to the processes that occur inside the steam-gas cavity, in particular chemical transformations that occur in its volume and the formation of electric erosion products of the electrodes that result in the chemical changes in the composition of treated medium. The size and dimensions of the particles that are formed during the electric erosion of electrodes have been defined. The chemical diagram of their influence on water properties has been suggested. A degree of the change in the redox potential is related to a number of formed polydisperse particles. Nanosize particles (37 % of the total volume of particles) with an increased physical and chemical activity were revealed.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.09.13 – техніка сильних електричних та магнітних полів. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017. Дисертація присвячена вдосконаленню електророзрядного обладнання, що використовується для обробки речовин сильно струмовим підводним іскровим розрядом. Проведено аналіз здобутих властивостей матеріалів та рідин в залежності від електричних параметрів розрядного кола, розмірів міжелектродного проміжку, конструкцій електрогідравлічних реакторів і тиску у реакторі. Запропоновані технологічні рекомендації щодо вдосконалення обладнання та процесів електрофізичного впливу на матеріали і рідкі середовища. В дисертації вдосконалено математичну модель щодо дослідження ранньої стадії розвитку іскрового каналу потужного іскрового розряду в парі води та у парогазовій оболонці. Вперше виявлено можливість швидкої (5–20 с) зміни окислювально-відновного потенціалу рідин в бік від'ємних значень з помірним підвищенням водневого показника. Проведено діагностику зміни фізико-хімічних властивостей води. Визначено склад та розміри частинок, що утворюються під час електричної ерозії електродів, запропоновано хімічну схему їх впливу на властивості води. Виявлено можливість подрібнення матеріалів, що моделюють відпрацьоване ядерне паливо, з метою вдосконалення методів його переробки. Оптимізовано параметри розрядного кола та реактора для подрібнення гумовотехнічних виробів у середовищі рідкого азоту. Доведено можливість обробки та зменшення розмірів зерен металів, що переплавляються в вакуумно-дугових пічках під впливом механіко-акустичних імпульсів, які утворюються високовольтними потужними підводними іскровими розрядами.
Thesis for the scientific degree of the candidate of engineering sciences by specialty 05.09.13 – Technology of Strong Electric and Magnetic Fields. – National Science Center "Kharkiv Institute of Physics and Technology", Ministry of education and science of Ukraine National Technical University "Kharkiv Politechnic University" Kharkiv, 2017. This thesis is devoted to the improvement of the electric discharge equipment that is used for the substance treatment by heavy-current underwater spark discharges. The properties of materials and liquids were analyzed as a function of the electric parameters of discharge circuit, in particular, the charging voltage, the capacitance and the spark gap size. The structures of electrohydraulic reactors that are used for the treatment of general mechanical rubber goods and materials that simulate in the first approximation the spent solid nuclear fuel were developed and modernized to improve the methods of fuel recycling. The liquid degassing intensification method was suggested to initiate underwater spark discharges in the electrohydraulic reactor under the evacuation. The electrode system was created to provide the ordered motion of a pulsating steam and gas cavity in the water space at a reduced pressure in the reactor. A structure of the electric discharge generator of elastic vibrations that allows us to have an influence on the metal melts in vacuum-arc furnaces has been developed. It has been proved that mechanical acoustic vibrations generated by spark discharges in the liquid have a positive effect on the distribution of admixtures in treated metals and a decrease in the size of crystal grains. Technological recommendations on the improvement of the processes of electrophysical impact on the materials and liquid media were given. A mathematical model used for the investigation of the progress of current conducting channel that short-closes the spark gap at an early stage of its development, in particular a process of the expansion of current conducting channel and steam-gas cavity was improved. An opportunity for a fast (5–20 s) change in the redox potential of the liquid to the side of negative values with a moderate increase in the pH value was revealed for the first time. It has been shown that a change in the redox potential depends on the input of total energy into the treated volume. We established that a change in the redox potential is related to the processes that occur inside the steam-gas cavity, in particular chemical transformations that occur in its volume and the formation of electric erosion products of the electrodes that result in the chemical changes in the composition of treated medium. The size and dimensions of the particles that are formed during the electric erosion of electrodes have been defined. The chemical diagram of their influence on water properties has been suggested. A degree of the change in the redox potential is related to a number of formed polydisperse particles. Nanosize particles (37 % of the total volume of particles) with an increased physical and chemical activity were revealed.

Underwater spark discharge is one of the most common methods to generate intense acoustic impulses in water for different purposes in practical applications. As compared with chemical explosion, the underwater spark discharges provide a number of advantages: they do not generate toxic compounds or species, no high explosives involved and they provide high degree of controllability. These features have led to a large number of studies of underwater spark discharge mechanisms and their potential practical utilisation. This work is aimed at experimental investigation of the breakdown characteristics of underwater spark discharges with three different initiation mechanisms: free discharge, air-bubble-stimulated discharge and wire-guided discharge. Study on the electrical and acoustic parameters of the discharge process has conducted. A capacitive voltage impulse system was developed to energise three different electrode topologies. Acoustic and electrical parameters of underwater spark discharges were obtained from experimental results, such as acoustic magnitude, period of cavity oscillation, breakdown voltage, plasma resistance and energy delivered into the plasma channel. Phenomenological scaling relations were established for these parameters, which allowed for better understanding and prediction of the acoustic performance of underwater spark discharges. An analytical model, which describes the cavity oscillation, has been developed and comparison of the modelling and experimental results was conducted for all three types of discharges. This model allowed for accurate description of the time-dependent behaviour of different parameters during the underwater spark discharge process. The obtained results are important for optimising the circuit parameters for generation of tailored acoustic impulses for different practical applications.