Modal Expansions and Orthogonal Complements in the Theory of Complex Media Waveguide Excitation by External Sources for Isotropic, Anisotropic, and Bianisotropic Media

A unified electrodynamic approach to the guided wave excitation by external sources in the waveguiding structures with bianisotropic media is developed. Effect of electric, magnetic, and magneto- electric losses in such media manifests itself in the special form of eigenmode orthogonality referred to as the quasi-orthogonality relation. It reflects the existence of the cross-power flow and for any pair of modes which are rigidly linked to each other by this relation. The quasi-orthogonality relation remains true in the limiting case of lossless waveguides yielding the customary relations of orthogonality and normalization for propagating (active) modes and also their generalization for nonpropagating (reactive) modes. It is shown that the eigenmode set for a waveguiding structure is complete only outside the region of exciting sources. Inside this region the modal expansions of fields are incomplete and must be supplemented with the orthogonal complementary fields which extend the proper Hilbert space spanned by waveguide eigenfunctions. Among exciting sources there are the external bulk sources (currents, fields, and medium perturbations) and the external surface currents. Besides, the orthogonal complementary fields generate the effective surface currents on boundaries of the bulk exciting sources. The problem of waveguide excitation by external sources is solved by means of determining both the mode amplitudes for the modal field expansions and the orthogonal complementary fields inside the source region. The equations of mode excitation are derived on the basis of three approaches applying the direct use of Maxwell's equations, the electrodynamic analogy with the mathematical method of variation of constants, and the conjugate reciprocity theorem.Comment: LaTeX 2.09, 46 pages with two mathematical appendixe

Excitation Theory for Space-Dispersive Active Media Waveguides

A unified electrodynamic approach to the guided-wave excitation theory is generalized to the waveguiding structures containing a hypothetical space-dispersive medium with drifting charge carriers possessing simultaneously elastic, piezoelectric and magnetic properties. Substantial features of our electrodynamic approach are: (i) the allowance for medium losses and (ii) the separation of potential fields peculiar to the slow quasi-static waves. It is shown that the orthogonal complementary fields appearing inside the external source region are just associated with a contribution of the potential fields inherent in exciting sources. Taking account of medium losses converts the usual orthogonality relation into a novel form called the quasi-orthogonality relation. It is found that the separation of potential fields reveals the fine structure of interaction between the exciting sources and mode eigenfields: in addition to the exciting currents interacting with the curl fields, the exciting charges and the double charge (surface dipole) layers appear to interact with the quasi-static potentials and the displacement currents, respectively.Comment: LaTeX 2.09, 28 pages with mathematical appendi

Nonstationary Superconductivity: Quantum Dissipation and Time-Dependent Ginzburg-Landau Equation

Transport equations of the macroscopic superfluid dynamics are revised on the basis of a combination of the conventional (stationary) Ginzburg-Landau equation and Schrödinger's equation for the macroscopic wave function (often called the order parameter) by using the well-known Madelung-Feynman approach to representation of the quantum-mechanical equations in hydrodynamic form. Such an approach has given (a) three different contributions to the resulting chemical potential for the superfluid component, (b) a general hydrodynamic equation of superfluid motion, (c) the continuity equation for superfluid flow with a relaxation term involving the phenomenological parameters GL and GL, (d) a new version of the time-dependent Ginzburg-Landau equation for the modulus of the order parameter which takes into account dissipation effects and reflects the charge conservation property for the superfluid component. The conventional Ginzburg-Landau equation also follows from our continuity equation as a particular case of stationarity. All the results obtained are mutually consistent within the scope of the chosen phenomenological description and, being model-neutral, applicable to both the low-c and high-c superconductors

Substrate Effect on the Optical Reflectance and Transmittance of Thin-Film Structures

A rigorous and consistent approach is demonstrated to develop a model of the 4M structure (the four-media structure of a film on a substrate of finite thickness). The general equations obtained for the reflectance and transmittance spectra of the 4M structure are simplified by employing a procedure of the so-called device averaging to reduce them to a succinct form convenient for processing of experimental spectra for the structures with a thick substrate. The newly derived equations are applied to two special cases: (i) an arbitrary film on highly absorbing substrates and (ii) a slightly absorbing film on transparent substrates. The reflectance and transmittance spectra represented in the simplified (with the device averaging) form have a practical application for determining the film thickness and optical constants from experimental spectra by using the known techniques

ТЕСТУВАННЯ БЕЗПЕКИ ПРИСТРОЇВ ІНТРЕНЕТУ РЕЧЕЙ НА БАЗІ МІКРОКОНТРОЛЕРА ESP32

In the paper analysis of current trends in IoT technologies enabled us to identify a segment for which information security assurance may encounter a lack of its level. These are IoT devices based on ESP32 microcontroller, that designed and implemented at home by non-professionals. The physical model of a handmade IoT system that includes device for measuring temperature based on ESP32 (small-sized ESP32-based development board ESP32 devKit V2 produced by Espressif and digital temperature sensor DS18B20), WiFi home network (based on router TL-WR841N) and web interface (based on node-red-dashboard) was proposed and implemented upon laboratory scale. The initial conditions of the experiment included the following: the use of the UDP protocol, authentication and data encryption based on WPA2-PSK specification, attacker skill level sufficient for use Aircrack-ng tools, Airmon-ng, Airodump-ng, Aireplay-ng, Besside-ng, Wireshark. The result of the experiment based on this model to attempt to gain unauthorized access to the transmitted data was successful. Attack scenario was formulated and consist of four stages: 1 – gaining unauthorized access to a network (network card transfers to monitor mode (Airmon-ng), view available access points (Airodump-ng), handshake interception, guessing the password (Besside-ng); 2 – network traffic interception and analysis (Wireshark); 3 – creating fake ESP32 client using the captured data (Arduino) and connect it to the network; 4 – disconnecting original ESP32 from a server (Aircrack-ng). It is shown that the attacker, who has the basic knowledge and skills in working with common wireless network hacking tools and a basic knowledge of ESP32 and ESP32 programming skills can access the system and send fake information to the web interface. To reduce the probability of the proposed scenario it is recommended to use TCP protocol, which is in contrast to UDP ensures data integrity and sender notification of transmission results.В статті на основі аналізу сучасних тенденцій в області IoT технологій визначено сегмент, для якого забезпечення інформаційної безпеки може зіткнутися з недостатністю її рівня. Це пристрої IoT на основі мікроконтролера ESP32, які розроблені і впроваджені в домашніх умовах непрофесіоналами. Запропонована і реалізована на лабораторному масштабі фізична модель непрофесіональної саморобної системи IoT, яка включає в себе пристрій для вимірювання температури на базі ESP32 (малогабаритний ESP32 на основі набору ESP32 DevKit V2 виробництва Espressif та цифровий датчик температури DS18B20), домашню мережу WiFi (на базі маршрутизатора TL-WR841N) і веб-інтерфейс (на базі модуля node-red-dashboard). Початкові умови експерименту включали в себе наступне: використання протоколу UDP, аутентифікація і шифрування передачі даних на основі специфікації WPA2-PSK, рівень кваліфікації зловмисника достатній для використання інструментів Aircrack-ng, Airmon-ng, Airodump-ng, Aireplay-ng, Besside-ng, Wireshark. В результаті експерименту на основі цієї моделі був успішно реалізований сценарій отримання несанкціонованого доступу до переданих даних. Сценарій атаки складається з чотирьох етапів: 1 – отримання несанкціонованого доступу до мережі (зміна режиму мережевої карти на режим моніторингу (Airmon-ng), перегляд доступних точок доступу (Airodump-ng), перехоплення рукостискання, вгадування пароля (Besside-ng); 2 – перехоплення і аналізу мережевого трафіку (Wireshark); 3 – створення підробленого клієнта ESP32 використовуючи отримані раніше дані (Arduino) і підключення його до мережі; 4 –від’єднання оригінального пристрою на базі ESP32 від сервера (Aircrack-ng). Показано, що зловмисник, який має базові знання та навички в роботі із розповсюдженими засобами злому бездротових мереж і базові знання та навички програмування ESP32 може отримати доступ до системи і відправити підроблену інформацію на веб-інтерфейс. Для того, щоб зменшити ймовірність пропонованого сценарію рекомендується використовувати протокол TCP, який на відміну від UDP забезпечує цілісність даних і повідомлення відправника про результати передачі

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