Quasi-harmonic self-oscillations in discrete time: analysis and synthesis of dynamic systems

For sampling of time in a differential equation of movement of Thomson type oscillator (generator) it is offered to use a combination of the numerical method of finite differences and an asymptotic method of the slowl-changing amplitudes. The difference approximations of temporal derivatives are selected so that, first, to save conservatism and natural frequency of the linear circuit of self-oscillatory system in the discrete time. Secondly, coincidence of the difference shortened equation for the complex amplitude of self-oscillations in the discrete time with Eulers approximation of the shortened equation for amplitude of self-oscillations in analog system prototype is required. It is shown that realization of such approach allows to create discrete mapping of the van der Pol oscillator and a number of mappings of Thomson type oscillators. The adequacy of discrete models to analog prototypes is confirmed with also numerical experiment.

Labyrinth patterns in Magadi (Kenya) cherts: Evidence for early formation from siliceous gels

Sedimentary cherts, with well-preserved microfossils, are known from the Archean to the present, yet their origins remain poorly understood. Lake Magadi, Kenya, has been used as a modern analog system for understanding the origins of nonbiogenic chert. We present evidence for synsedimentary formation of Magadi cherts directly from siliceous gels. Petrographic thin-section analysis and field-emission scanning electron microscopy of cherts from cores drilled in Lake Magadi during the Hominin Sites and Paleolakes Drilling Project in 2014 led to the discovery of two-dimensional branching "labyrinth patterns" in chert, which are a type of fractal "squeeze" pattern formed at air-liquid interfaces. Labyrinth patterns preserved in chert from Lake Magadi cores indicate invasion of air along planes in dewatering gels. These patterns support the precipitation of silica gels in the saline-alkaline Lake Magadi system and syndepositional drying of gels in contact with air as part of chert formation. Recognizing cherts as syndepositional has been critical for our use of them for U-Th dating. Identification of labyrinth patterns in ancient cherts can provide a better understanding of paleoenvironmental and geochemical conditions in the past.

DINAMIKA KELOMPOK DALAM PROSES EMERGENCY DECISION MAKING (EDM): PEMBELAJARAN DARI SIMULASI TANGGAP DARURAT DI PEMBANGKIT LISTRIK TENAGA NUKLIR

Nuclear Power Plant (NPP) is a non-fossil energy source with very high output and most sustain power plant. NPP is also classified as environmentally friendly because, in normal processes, NPP produces zero Carbon Dioxide (CO2) as the primary air pollutant. However, if there is a disaster, the impact is exceptionally terrible. Besides causing fatalities, it can also result in hazardous health problems and takes hundreds of years to recover the surrounding natural environment. Therefore, to avoid disaster, the skills of nuclear power plant operators are critical, especially in overcoming the crisis. Typical challenges in Analog System-based NPP is the synergy among operators whose numbers are higher than in digital systems. This paper reflects learning outcomes from simulation to overcome the crisis in NPP, particularly the immediacy in making the right decisions. The simulation was carried out at the Analog System-Based NPP Simulation Center in Essen, Germany, and followed by a group of students from the Human Factor Engineering Master Program, Hochschule Niederrhein, with diverse national cultural backgrounds. One result is that the unique characteristics of each nation's cultural background can affect its effectiveness in overcoming the crisis. Two different aspects are initiative and assertive behavior among people inside the group.

MULTI-CHANNEL DIGITAL-ANALOG SYSTEM BASED ON CURRENT-CURRENT CONVERTERS

An approach to building a multi-channel digital-analog system is proposed, in which, unlike the known ones, a code-current converter, a controlled current generator, and also a current communication block are used. For a given accuracy, this saves on the analog system equipment. It has been shown that the proposed principle of building a controlled current source in the form of a highly linear push-pull amplifier – current scalar on bipolar transistors with a grounded load – has a high output resistance and wide bandwidth, which allows the use of current switching to implement the multi-channel system mode.

Affordable Analog OxygenMonitor forMaintaining Safe Oxygen Concentration in IndustrialEnvironments

As industrial fields become more intertwined and complex, there is an increasing demand for a suitable & reliable method of monitoring the concentration of Oxygen in the surrounding work environment. It is often required that these Oxygen levels retain consistent values in order to protect the workforce and the material in use. This paper proposes an analog system which uses a combination of operational amplifiers in different configurations. They have been designed to convert the current signals generated by an Electrochemical sensor and compare these signals to a reference voltage set by the user. Features of the system include long battery life, affordability compared to other monitors on the market, analog signal precision and a wide variety of preset configurations and calibration methods to use in confined spaces. Multiple tests were performed using the device to monitor the concentration of Oxygen outdoors. The device’s output is measured in volts using a voltmeter and converted to a concentration of Oxygen detected according to the formulas derived for the system. The results were then compared to the weather and humidity forecast data provided by internet sources and research done on the relationship between humidity and the concentration of Oxygen. This helped in fine tuning the circuit, fix previous issues with the prototype and implement more features. The system proposed was presented to and certified by Oman Chromite Company (SAOG) for use in their opencast and underground mines.

A Modified Functional Observer-Based EID Estimator for Unknown Continuous-Time Singular Systems

This paper presents the design of a linear quadratic analog tracker (LQAT) based on the observer–Kalman-filter identification (OKID) method and the design of a modified functional observer-based equivalent input disturbance (EID) estimator for unknown square–non-square singular analog systems with unknown input and output disturbances. First, an equivalent mathematical model of the singular analog system is presented to simulate the time response of continuous-time linear singular analog systems to arbitrary inputs via the model conversion method. Then, for the unknown singular analog system, it constructs a linear quadratic analog tracker with state feedback and feed-forward gains based on the off-line OKID method. Furthermore, it extends the design methodology of the EID estimator for strictly proper regular systems with unknown matched–mismatched input and output disturbances to proper regular systems. It is important to mention that the newly developed modified functional observer for proper systems is used to estimate the unknown EID of singular analog systems and that the constraints on the dimensions of unknown disturbances can be eliminated by using the newly proposed EID estimation method. The contributions of this paper can be listed as follows: (1) based on both the OKID method and the discrete-to-continuous model conversion, the simulation of the time responses of the continuous-time linear singular models (which are not feasible using existing MATLAB toolboxes) become feasible; (2) for effective control of the unknown singular analog system, an off-line OKID method is proposed to design an LQAT with state feedback and feed-forward gains; and (3) based on the newly developed modified functional observer for the reduced-order proper regular system, the original EID estimator in the literature is newly extended to estimate the EID from the unknown strictly proper singular analog system, without the original dimensional constraints of the disturbances. It is important to mention that the disturbances of interest can be unknown matched–mismatched input and output disturbances.