Variable sweep geometry primary structure actuation

Critical behavior at the isotropic to nematic, nematic to smectic-A and smectic-A to smectic-C phase transitions in a pyrimidine liquid crystal compound

This study explores the presence of time lag in crystalline to smectic A (K–SmA) phase transition of 4-decyl-4-biphenylcarbonitrile (10CB) liquid crystal. A non-isothermal heating and cooling study were performed for 10CB liquid crystal using calorimetric technique where heating scan was performed from 250 to 350 K, and cooling scan was performed from 350 to 250 K. A clear difference in K–SmA phase transition was observed between heating and cooling scans. An attracting inclination effect in K–SmA transition was observed on cooling which is completely absent on heating. The inclination of the K–SmA transition peak increases and shows an existence of time lag during cooling, whereas other family member shows no effect i.e., 8CB. K–SmA peak shows a lower enthalpy with higher activation when compared with 8CB. The presence of time lag and increase in activation can be explained in terms of the density and nature of the material.

Dielectric relaxation behavior of a ferroelectric liquid crystal (Felix-15/100) showing SmC*–SmA phase transition have been reported. Thickness dependent dielectric constant measured by varying the cell thickness (∼6, 11, 18, 36, 59 and 79 µm) showed increase of dielectric constant and the ferroelectric transition (Curie temperature TC) with increase of cell thickness. The observed non-linear variation of TC as a function of thickness is better described by an empirical formula of the form Tx=TC-γd-β (where β and γ are sample dependent parameters). Since d is related to the domain width, different values of β and γ are related to the domain width and hence with the dipolar ordering. Different values of the sample dependent parameters β and γ may, therefore, be considered as a measure of molecular ordering (depending on molecular interaction) which causes the change of TC with thickness. It is thus concluded that the values of β and γ should be related to the dipolar interaction in the ferroelectric system under consideration.

The phenomenon of moving the new capital city in Indonesia creates a new geostrategic perspective. Where in the process must be prepared carefully, especially in the aspect of defense and security systems. This study aims to provide an analysis concept of stealth Unmanned Aerial Vehicle (UAV) to support the air defense system in Indonesia's new capital city area. The research method used is a qualitative approach by conducting a literature study. The results of the study reveal that the air defense system for Indonesia's new capital city is in accordance with the concept of a smart defense, the need for a platform/ air vehicle that can be used to carry out intelligence, surveillance, reconnaissance and even be able to carry out attacks in maintaining security in the Indonesian new capital city area by minimizing enemy detection. . And one platform is to use UAV with stealth which can provide advantages in terms of flexibility, reach, minimized operational risk, and the ability to perform operations that are not detected by enemy defense radar sensors.

Towards Gun- and Aircraft - launched MAVs: Embedded Flight Control System

The ability to accurately predict both static and dynamic stability characteristics of air vehicles using computational fluid dynamics (CFD) methods could revolutionize the air vehicle design process, especially for military air vehicles. A validated CFD capability would significantly reduce the number of ground tests required to verify vehicle concepts and, in general, could eliminate costly vehicle ‘repair’ campaigns required to fix performance anomalies that were not adequately predicted prior to full-scale vehicle development. This paper outlines the extended integrated experimental and numerical approach to assess the of stability and control prediction method capabilities as well as the design and estimation the control device effectiveness for highly swept low observable UCAV configurations. The aim of the AVT-201 Task Group is to provide an assessment of the CFD capabilities using model scale experiments and transferring this knowledge to real scale applications

A Green’s-function method is used to study spin-wave excitations and phase transition in a three-dimensional uniformly frustrated Heisenberg spin system of simple cubic structure. The frustration is made to vary by changing the antiferromagnetic bond strength. We take into account different sublattices that result in gaps at the Brillouin zone boundaries in the spin-wave spectrum. The sublattice order parameters as a function of temperature and the critical temperature are calculated self-consistently. Comparison with Monte Carlo simulations performed by us is shown and discussed.

Photoinduced phase transitions have become a very important field of study with the advent of diverse time-resolved experimental techniques whose time resolution matches the electron, lattice, and spin relaxation dynamics associated with elementary excitations in quantum materials. Most techniques currently available rely on stroboscopic data-averaging over multiple transition outcomes. However, each time a transition takes place, fluctuations close to the time of the transition ensure that the phase transition outcome is different, with the emergence of different topological defect textures. In this paper, we briefly review the non-perturbative processes in selected charge-ordered quantum systems and the methods for their observation with different time-resolved techniques and scanning tunneling microscopy, which avoids the problem of averaging. The topological defect dynamics are seen to play an essential role in stabilizing emergent states in non-equilibrium transitions, appearing on different timescales as well as determining the emergent properties of the system. The phenomena are fundamentally important for understanding the fabric of matter in the Universe, as well as for possible applications in non-volatile memory devices.

The ability to accurately predict both static and dynamic stability characteristics of air vehicles using computational fluid dynamics methods could revolutionize the air vehicle design process, especially for military air vehicles. A validated computational fluid dynamics capability would significantly reduce the number of ground tests required to verify vehicle concepts and, in general, could eliminate costly vehicle “repair” campaigns required to fix performance anomalies that are not adequately predicted before full-scale vehicle development. This paper outlines the extended integrated experimental and numerical approach to assess the stability and control prediction method capabilities, as well as the design and estimation of the control device effectiveness, for highly swept low observable unmanned combat aerial vehicle configurations. The aim of the AVT-201 Task Group is to provide an assessment of the computational fluid dynamics capabilities using model-scale experiments and transfer this knowledge to real-scale applications.

It is possible that micro air vehicle (MAV) designs of the future will exploit flapping flight to perform missions that require extreme agility, such as rapid flight beneath a forest canopy or within the confines of a building. Many of nature's most agile fliers generate flapping motions through resonant excitation of an aeroelastically tailored structure: muscle tissue is used to excite a vibratory mode of their flexible wing structure that creates propulsion and lift. A number of micro air vehicle concepts have been proposed that would operate in a similar fashion. An ongoing research activity is described in which mechanization and control concepts with application to resonant flapping MAVs are being explored. Structural approaches, mechanical design, sensing, and wingbeat control concepts inspired by hummingbirds, bats, and insects are examined. Experimental results from a testbed capable of generating vibratory wingbeat patterns that approximately match those exhibited by hummingbirds in hover, cruise, and reverse flight are presented

For the last 40 years high - capacity Unmanned Air Vehicles have been use mostly for military services such as tracking, surveillance, engagement with active weapon or in the simplest term for data acquisition purpose. Unmanned Air Vehicles are also demanded commercially because of their advantages in comparison to manned vehicles such as their low manufacturing and operating cost, configuration flexibility depending on customer request, not risking pilot in the difficult missions. Nevertheless, they have still open issues such as integration to the manned flight air space, reliability and airworthiness. Although Civil Unmanned Air Vehicles comprise 3% of the UAV market, it is estimated that they will reach 10% level within the next 5 years. UAV systems with their useful equipment (camera, hyper spectral imager, air data sensors and with similar equipment) have been in use more and more for civil applications: Tracking and monitoring in the event of agriculture / forest / marine pollution / waste / emergency and disaster situations; Mapping for land registry and cadastre; Wildlife and ecologic monitoring; Traffic Monitoring and; Geology and mine researches. They can bring minimal risk and cost advantage to many civil applications, in which it was risky and costly to use manned air vehicles before. When the cost of Unmanned Air Vehicles designed and produced for military service is taken into account, civil market demands lower cost and original products which are suitable for civil applications. Most of civil applications which are mentioned above require UAVs that are able to take off and land on limited runway, and moreover move quickly in the operation region for mobile applications but hover for immobile measurement and tracking when necessary. This points to a hybrid unmanned vehicle concept optimally, namely the Vertical Take Off and Landing (VTOL) UAVs. At the same time, this system requires an efficient cost solution for applicability / convertibility for different civil applications. It means an Air Vehicle having easily portability of payload depending on application concept and programmability of operation (hover and cruise flight time) specific to the application. The main topic of this project is designing, producing and testing the TURAC VTOL UAV that have the following features : Vertical takeoff and landing, and hovering like helicopter ; High cruise speed and fixed-wing ; Multi-functional and designed for civil purpose ; The project involves two different variants ; The TURAC A variant is a fully electrical platform which includes 2 tilt electric motors in the front, and a fixed electric motor and ducted fan in the rear ; The TURAC B variant uses fuel cells.

Phase transitions share the universal feature of enhanced fluctuations near the transition point. Here we show that density fluctuations reveal how a Bose-Einstein condensate of dipolar atoms spontaneously breaks its translation symmetry and enters the supersolid state of matter -- a phase that combines superfluidity with crystalline order. We report on the first direct in situ measurement of density fluctuations across the superfluid-supersolid phase transition. This allows us to introduce a general and straightforward way to extract the static structure factor, estimate the spectrum of elementary excitations and image the dominant fluctuation patterns. We observe a strong response in the static structure factor and infer a distinct roton minimum in the dispersion relation. Furthermore, we show that the characteristic fluctuations correspond to elementary excitations such as the roton modes, which have been theoretically predicted to be dominant at the quantum critical point, and that the supersolid state supports both superfluid as well as crystal phonons.

We have studied thermodynamic and some dynamic properties of a one-dimensional-model system whose displacement field Hamiltonian is strongly anharmonic, and is representative of those used to study displacive phase transitions. By studying the classical equations of motion, we find important solutions (domain walls) which cannot be represented effectively by the usual phonon perturbation expansions. The thermodynamic properties of this system can be calculated exactly by functional integral methods. No Hartree or decoupling approximations are made nor is a temperature dependence of the Hamiltonian introduced artificially. At low temperature, the thermodynamic behavior agrees with that found from a phenomenological model in which both phonons and domain walls are included as elementary excitations. We then show that equal-time correlation functions calculated by both functional-integral and phenomenological methods agree, and that the dynamic correlation functions (calculated only phenomenologically) exhibit a spectrum with both phonon peaks and a central peak due to domain-wall motion.

We have studied thermodynamic and some dynamic properties of a one-dimensional-model system whose displacement field Hamiltonian is strongly anharmonic, and is representative of those used to study displacive phase transitions. By studying the classical equations of motion, we find important solutions (domain walls) which cannot be represented effectively by the usual phonon perturbation expansions. The thermodynamic properties of this system can be calculated exactly by functional integral methods. No Hartree or decoupling approximations are made nor is a temperature dependence of the Hamiltonian introduced artificially. At low temperature, the thermodynamic behavior agrees with that found from a phenomenological model in which both phonons and domain walls are included as elementary excitations. We then show that equal-time correlation functions calculated by both functional-integral and phenomenological methods agree, and that the dynamic correlation functions (calculated only phenomenologically) exhibit a spectrum with both phonon peaks and a central peak due to domain-wall motion.

We revisit a time-dependent, oval-shaped billiard to investigate a phase transition from bounded to unbounded energy growth. The introduction of inelastic collisions between the particle and the boundary limit the unbounded energy increase after the crossover iteration observed for the conservative dynamics. The central phenomenology uses a probability distribution that satisfies the system's boundary conditions to solve the diffusion equation. From this, we express the observables and, using a set of scaling hypotheses and a generalized homogeneous function, obtain a relation between the critical exponents, leading to a scaling law validated through numerical simulations and analytical methods. This transition displays properties similar to continuous phase transitions in statistical mechanics, including scale invariance, interrelated critical exponents governed by scaling laws, and an order parameter (susceptibility) approaching zero (infinity) at the transition. Furthermore, the system exhibits a variation in velocity between collisions mediated by control parameters, known as elementary excitations, which facilitate particle diffusion. The system also does not present topological defects that could alter the probability distribution function.