The effect of the flux creep on the dissipation phenomena in tapes based on YBCO leading to the essentially non-linear voltage-current characteristic of a superconductor is discussed. The obtained ...results are compared to the calculations made in the framework of the existing thermal stabilization theory based on the model assuming a jump transition from a superconducting state to a normal one. It is shown that the latter model incorrectly describes the dissipation modes, first of all, in a temperature range up to the critical temperature of the superconductor. It is proved that the type of nonlinearity of voltage-current characteristics has a significant effect on the dissipative phenomena in tapes in this temperature region. As a result, the allowable currents stably flowing in superconducting tapes may be higher than a priory defined critical current determined for continuously rising voltage-current characteristic. Correspondingly, the critical current of high-Tc superconducting tapes, which is determined using continuously increasing voltage-current characteristic, has no physical meaning. Therefore, fundamentals of the thermal stabilization theory must consider the real temperature dependence of the dissipated energy in high-Tc superconducting tapes, which depends on the nonlinearity of their voltage-current characteristic.
The problems of ensuring the unity of non-invasive blood pressure measurements are considered. It is shown that the artery and surrounding tissues of the body serve as a means of comparing the values ...of blood pressure and air pressure in the cuff, and that the metrological traceability of measurement results to pressure standards only partially determines the reliability of these results. The potential possibilities of the surface pulse wave method in comparison with the Korotkov tone method are estimated.
Currently, there is a steady trend in increasing the volume of electrical equipment used in shipboard needs. At the same time, the primary electric power system of ships has long been based on an ...alternating current system. However, due to the changing and increasing requirements for the quality of the generated electric energy, the marine industry is developing more and more promising directions for the development of electrical systems. Thus, the most efficient and environmentally friendly shipboard power distribution system is the direct current (DC) system, which was adopted for a single power plant installation in combination with an alternating current network. This article discusses the current topic of electric propulsion on ships. The circuit design of a rowing electric installation with a distributed DC bus of a port icebreaker is considered. The expressions used to calculate the static load and build an electromagnetic model of a permanent magnet synchronous motor are given. Computer models for calculating the load in static and dynamic modes are shown.
The relevance of numerical modeling of flood zones, characteristics of flow velocity field and marks of the river water levels is caused by the necessities of engineering practical work in ...development of mineral deposits, which are often situated in extremely difficult hydrographic conditions. In such conditions, the standard methods for calculating the mentioned characteristics do not allow us to achieve the desired result or do not take into account the whole variety of processes occurring in open flows, which are able to significantly affect the safe and trouble-free operation of the designed constructions. The aim of the work is to show how the objects affect the change in the shape of the estimated flood zone, the flow velocity field, and water levels in conditions of constraining impact on the living cross-section of the flow during the passage of water rate of rare exceedance probability (1 % occurrence) on the example of the Kondoma river site and both existing and planned hydraulic constructions (flood control dams) and construction sites located in its floodplain. Methods. Numerical modeling of flow characteristics (estimated flood zone, distribution of speeds and directions of flow, estimated water levels) on the site of the Kondoma river was conducted using the HEC-RAS (Hydrologic Engineering Center – River Analysis System) modeling system ver. 5.0.5. The model comprised three different scenarios. Scenario 1, the floodplain is relatively unbroken and there are no flood control dams and overburden dump; Scenario 2, there is a current flood control dam and overburden dump in the floodplain; Scenario 3, there are all the current objects mentioned in Scenario 2 and a designed flood control dam in the floodplain. The studied characteristics of the Kondoma river on the site under investigation were compared within all three implemented scenarios. Results. A simulation model for the passage of flood (1 % of the exceedance probability) according to three scenarios was developed for the site of the Kondoma river, with Scenario 1 taken as the control. The model was calibrated, and the roughness coefficients of the floodplain and channel were chosen as adequate to actual conditions. Numerical flow characteristics were obtained (the shape of the estimated flood zone, the distribution of speeds and directions of flow, and water levels and depths) according to the three mentioned scenarios and the conclusions were drawn concerning the extent of influence of the current structures in the left floodplain of the Kondoma river on the shape of free surface, and also the influence under condition of a new flood control dam appearing in the left floodplain was forecasted.
A synergistic extraction mixture containing chlorinated cobalt dicarbollide (CCD), carbamoylmethyl phosphine oxide (CMPO), and polyethylene glycol (PEG) has been investigated for the simultaneous ...recovery of cesium, strontium, lanthanides, and actinides from highly acidic media. The extraction properties of this mixture depend on the concentration ratio of the components. For recovery of all major radionuclides, the optimal ratio of CCD:PEG: CMPO = 5:1:1 should be used. The use of diphenyl-N,N-dibutylcarbamoylmethyl phosphine oxide and PEG-400 provides the most efficient recovery of cesium, strontium, lanthanides, and actinides. The possibility of using polyfluorinated ethers, esters, ketones, and sulfones as diluents was examined. Phenyltrifluoromethyl sulfone was the most suitable diluent tested. The use of this diluent allows good extraction properties, chemical and radiation stability, excellent explosion/fire-safety properties, and favorable hydrodynamic characteristics. The extraction of radionuclides from HNO
3
media by mixtures of CCD:PEG:CMPO in phenyltrifluoromethyl sulfone and the subsequent stripping behavior were evaluated.
Актуальность моделирования зон максимального разлива рек (зон затопления) при проведении инженерных изысканий для проектирования и строительства объектов хозяйственной деятельности, разработки ...проектов рекультивации нарушенных земель в зонах непосредственного влияния водных объектов связана с тем, что в современных условиях, при постоянно растущих требованиях к безопасности и бесперебойности работы проектируемых сооружений, существующие методики оценки опасности затопления не всегда дают удовлетворительный результат, чтобы в полной мере оценить наличие или отсутствие риска для проектируемого сооружения. Цель работы: анализ отечественного и зарубежного опыта моделирования зон затопления при максимальных уровнях воды рек для практического решения задач инженерного проектирования, оценка достоинств и недостатков основных подходов в практике изысканий, демонстрация возможностей одного из способов моделирования при решении конкретной инженерной задачи. Методы. При подготовке исходных данных для создания цифровой модели рельефа применялся метод анализа пространственных данных при помощи геоинформационных систем, для расчета максимальной зоны затопления – метод численного моделирования зоны затопления р. Иня и расположенной по левому берегу отработанной карьерной выемки в рамках производства работ по подготовке проекта рекультивации нарушенных земель. Численное моделирование выполнялось при помощи моделирующей системы HEC-RAS версии 5.0.5. Результаты. Произведен обзор существующей мировой и отечественной практики численного моделирования зон затопления рек при решении задач в области инженерного проектирования, приведена собственная модель расчетной зоны затопления на примере участка рекультивации «Моховское поле», показан пример оценки влияния на рекультивируемый объект при реализации наиболее негативного сценария (вероятное затопление карьерной выемки в период прохождения максимального расхода воды 1 % обеспеченности), описаны достоинства и недостатки применения разных подходов на практике.
The extraction properties of diamide derivatives of dipicolinamide (2,6-pyridinedicarboxylamide or DPA, (R′R″NCO)
2
C
5
NH
3
) in mixtures containing chlorinated cobalt dicarbollide in the acid form ...(HCCD), with and without a substituted polyethylene glycol (PEG), have been investigated. Distribution ratios of Cs, Sr, U, Eu and Am have been measured for various concentrations of diamide, PEG, aqueous phase nitric acid, with various HCCD:diamide ratios, and using different organic diluents. In the absence of HCCD, the diamides show little affinity for the extraction of Am or Eu from nitric acid solutions (distributions typically <1). Addition of HCCD with the diamide extractants indicates a pronounced synergistic effect with regard to actinide and lanthanide extraction; the observed Am and Eu distribution ratios typically increase by several orders of magnitude. Cesium is also appreciably extracted by the HCCD in the presence of the various diamides. Addition of PEG (to simultaneously extract Sr) with HCCD and diamide has minimal impacts on the Eu and Am distribution ratios. The initial data indicate that alkyl substituted DPA derivatives weakly affect the extraction properties with regard to actinides and lanthanides, while aryl substituents decrease extraction ability of the mixture. The results of this preliminary work indicate that numerous HCCD-PEG-DPA systems are promising and effective for the simultaneous extraction Cs, Sr, Am, and Eu from acidic solutions.
Study of the doubly charmed tetraquark Tcc Abdelmotteleb, A. S. W; Ajaltouni, Z; Andreianov, A ...
Nature communications,
12/2022, Letnik:
13, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and ...mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar Tcc+ tetraquark with a quark content of ccu¯d¯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector Tcc+ state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the Tcc+ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.The existence and properties of tetraquark states with two heavy quarks and two light antiquarks have been widely debated. Here, the authors use a unitarized model to study the properties of an exotic narrow state compatible with a doubly charmed tetraquark.
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