Adaptive control to actively damp bistabilities in highly interrupted turning processes using a hardware-in-the-loop simulator

Interruptions in turning make the process forces non-smooth and nonlinear. Smooth nonlinear cutting forces result in the process of being stable for small perturbations and unstable for larger ones. Re-entry after interruptions acts as perturbations making the process exhibit bistabilities. Stability for such processes is characterized by Hopf bifurcations resulting in lobes and period-doubling bifurcations resulting in narrow unstable lenses. Interrupted turning remains an important technological problem, and since experimentation to investigate and mitigate instabilities are difficult, this paper instead emulates these phenomena on a controlled hardware-in-the-loop simulator. Emulated cutting on the simulator confirms that bistabilities persist with lobes and lenses. Cutting in bistable regimes should be avoided due to conditional stability. Hence, we demonstrate the use of active damping to stabilize cutting with interruptions/perturbations. To stabilize cutting with small/large perturbations, we successfully implement an adaptive gain tuning scheme that adapts the gain to the level of interruption/perturbation. To facilitate real-time detection of instabilities and their control, we characterize the efficacy of the updating scheme for its dependence on the time required to update the gain and for its dependence on the levels of gain increments. We observe that higher gain increments with shorter updating times result in the process being stabilized quicker. Such results are instructive for active damping of real processes exhibiting conditional instabilities prone to perturbations.

Non-microbiological turbidity of beer: Part 2 – a case study

Non-microbial beer turbidity of lager beers often indicates a technological problem. Therefore, the occurrence of permanent haze in filtered and stabilized beer should not be underestimated. In this study, practical examples from industrial breweries, where several types of non-microbiological haze of colloidal were identified, are presented. These examples of haze were caused by slightly different factors, and as a result, they had a different microscopic image. It is often accompanied by mechanical impurities and sometimes by microorganisms that function as nucleation centers. Moreover, a very interesting example of almost brilliant permanent beer haze caused by the destruction of yeast cells with the following pouring intracellular contents of cells into beer is introduced. This phenomenon, which could be called “precedent”, was caused by a bad physiological condition of yeasts cells and inappropriately chosen yeast separation technology.

Sealing Mechanism Based on Force Chain and Experimental Investigation of Sealing Fractures

Lost circulation often occurs in fractured formations, which was a main technological problem during drilling. Conventional lost circulation material (LCM) was often used to form a plugging zone to prevent fluid loss during drilling. The formed seal was a granular material system composed of LCMs. This paper presented the physical mechanism of the force chain within the plugging zone. The seal performance is related to the properties of LCMs. A device for testing seal performance of LCMs with long fracture was developed. The effects of LCM performance on seal integrity were investigated using a plugging device with long fracture. The results showed that the wide particle size distribution (PSD) of LCMs tended to form a strong force chain network structure within the sealing zone. Increasing the stiffness and roughness of LCMs resulted in higher breaking pressure. The addition of fiber with high length-diameter ratio could improve the shear strength of the sealing zone and form a strong force chain network structure, and it can reduce fluid loss.

“To Believe in an Image (Again)”

In screen studies and photography studies, the name of the acclaimed film theorist and critic André Bazin is frequently invoked by scholars seeking to defend the import of analogue media on ontological grounds by citing photography's privileged connection to the real. This article seeks to unsettle Bazin's reputation as the patron saint of analogue recording by exploring the ontological implications of the concept of sense in Bazin's writings on neorealism. Placing Bazin's writings into dialogue with a selection of critiques that find the digital image to be lacking in historicity, negativity, and presence, and flag its potentially authoritarian impulses, this essay seeks to reframe Bazin's ontological project as a question of cinema's sense (rather than its essence) to mobilize a different set of conclusions that may in fact prove to restore faith in the digital image and its rapport with the real. By maintaining that what is often treated as a purely technological problem also harbors aesthetics implications, this article confronts the manifest skepticism that has pervaded the discourse around the digital since the 1990s, seeking an alternative outlook in Jean-Luc Nancy's work on sense, an ontological concept that evidences the political potentials (or potential politics) of Bazin's predilection for images, which are said to ameliorate our love for reality by transmitting the excessive sense of the world in its ambiguity, creativity, and unpredictability.

Information technologies for creating spatiotemporal modems multiposition active-passive radar systems

The methods of synthesis of the directional diagram of active transmitting antenna arrays when receiving signals reflected from radar targets are considered. It is shown that when using multifrequency orthogonal coherent signals in the elements and addressable access at their reception it is possible to provide a small level of the side lobes of the spatial uncertainty function in a given sector of observation by selecting the type of intrapulse modulation of partial signals. Orthogonalization of antenna basis of transmitting and receiving antennas allows digital spectral-correlation processing of samples of aggregate signal from each target to solve the technological problem of multidimensional observation space in multiposition systems of coherent radiolocation when detecting, resolving, estimating coordinates and motion parameters of targets. The results of simulation modeling of spatio-temporal radar modems implemented according to the stated principles are given.

Exceptional Points through Variation of Distances between Four Coaxial Dielectric Disks

By variation of a refractive index and aspect ratio of the isolated disk, we achieved exceptional points (EPs) at which the resonant frequencies and resonant modes coalesce. However, in practice, that kind of variation presents a technological problem. We considered the method to avoid the problem by substitution of two disk’s dimers. In each dimer, variation of the distance between disks was equivalent to a variation of the aspect ratio of the dimer. Moreover, the variation of the distance between dimers provides the second parameter that gives rise to a vast number of EPs. We recovered the initial resonant eigenmode by encircling multiple EPs two, three, and four times in the two-dimensional parametric space of distances.

ЗАСОБИ І МЕТОДИКА ONLINE НАВЧАННЯ ФІЗИКИ В ТЕХНІЧНОМУ УНІВЕРСИТЕТІ

In this paper, we discuss technological and methodological problems that occur during synchronous distance learning. The technological problem is associated with the choice of software products for conducting such classes. It is shown that, instead of the well-known Zoom webinar program, it is possible to use simultaneously one of the webinar programs (Google Meet, FreeConferenceCall or others) and the interactive whiteboard, for example, IDroo, LiveBoard, Jamboard, Twiddla, or others. The technical characteristics of these boards in some respects are more advanced than the whiteboard in the Zoom program. Methodological problems relate to the definition of forms and methods of lectures, practical and laboratory classes, as well as the semester exam. Our survey showed that 1) 78% of students perceive the lecture material better if the form of its presentation is similar to the traditional one; 2) 71% of students prefer to see mathematical expressions written using a Power Point presentation, in which a gradual step-by-step derivation of formulas is implemented. In order to control students' work at the beginning of each online lecture we conduct an express test control of the knowledges of the previous one, and at the end we offered to make a copy of their synopsis and save it in Google Classroom. Students’ grades for the test and synopsis were taken in account when setting the total rating score. Laboratory exercises were carried out using the created virtual labs. To create visual representations of the virtual models, we prepared short videos that illustrate the main stages of work. The most difficult was to conduct the exam in a distance form. We used the test form of exam. To avoid the exchange of correct answers to test items each student dot individual tasks. To reduce the possibility of communicating with strangers during the exam, students performed tasks with the video camera and microphone turned on. All of this reduced the likelihood of academic integrity of the students. Key words: physics, synchronous distance learning, lecture webinar, labs, exam.

Microcomputer Control System of Bridge Dehumidification Based on Energy Consumption Optimization and Wireless Communication

At present, with the development of wireless communication and microcomputer control system, the design and construction level of long-span bridges in China are also improving. How to improve the durability of bridge structure has become a major scientific and technological problem in bridge design and construction. This paper studies a microcomputer control system of bridge dehumidification based on energy consumption optimization and wireless communication. It compares three kinds of dehumidification and anticorrosion methods of bridge engineering, namely, freezing dehumidification system, rotary dehumidification system, and hybrid dehumidification system. In the hardware design of microcomputer control system of dehumidification system, ATmega128 bit main control chip and aluminum designer are used to draw the power circuit. Then, the MCU program of the air dehumidifier is written, and the power of the air dehumidifier is controlled by the PWM signal generated by the timer 0 of the MCU. The air dehumidifier is divided into three tap positions corresponding to three duty cycles, and the power of the air dehumidifier is changed according to the input tap position.