GnRH pulse generator frequency is modulated by kisspeptin and GABA-glutamate interactions in the posterodorsal medial amygdala in female mice

Kisspeptin neurons in the arcuate nucleus of the hypothalamus generate GnRH pulses, and act as critical initiators of functional gonadotrophin secretion, and reproductive competency. However, kisspeptin in other brain regions, most notably the posterodorsal subnucleus of the medial amygdala (MePD), plays a significant modulatory role over the hypothalamic kisspeptin population; our recent studies using optogenetics have shown that low frequency light stimulation of MePD kisspeptin results in increased LH pulse frequency. Nonetheless, the neurochemical pathways that underpin this regulatory function remain unknown. To study this, we have utilised an optofluid technology, precisely combining optogenetic stimulation with pharmacological receptor antagonism, to investigate the neurotransmission involved in this circuitry. We have shown that functional neurotransmission of both GABAA and glutamate is a requirement for effective modulation of the GnRH pulse generator by amygdala kisspeptin neurons.

Forced mode locking in a semiconductor laser

A brief description of the theory of mode locking of a semiconductor laser when the modulating generator frequency is close to the intermode frequency is given. It is shown that during mode locking there is phase locking, due to which the dispersion of summed intensity in the interpulse interval tends to zero.

ESTIMATION OF THE MASS OF CARGO DUMP TRUCK

The article discusses an on-board weighing system for the load of a mining dump truck, which simplifies measurements and, unlike existing systems, does not require the integration of sensors into the structure and electrical circuits of the truck and represents a compact, autonomous device that can be located at any convenient place in the cab. In order to create such a device, it is proposed to use the magnitude of the magnetic field strength generated by DC traction motors as a signal carrying information about the mass of the transported cargo. To measure the magnetic field strength, a flux gate is used, which converts the magnitude of the magnetic field strength into the magnitude of the current. An original circuit for powering the fluxgate excitation winding using a modulated signal generator based on logic elements is proposed. The used power supply scheme allows to exclude the influence of the fluxgate excitation winding on the generator frequency, as well as to increase the fluxgate sensitivity, which makes it possible to install the sensor in any convenient place in the dump truck cabin, and not in the immediate vicinity of the traction motors.

EVOLUTION OF ENERGY CONVERTERS FOR WIND TURBINES

A wind generator system requires a power conversion circuit called a power converter that is capable of regulating the generator frequency and line voltage. Several types of converter topologies have been developed over the past decades; each of them has its own advantages and disadvantages. Currently, there are mainly two converter topologies used in industrial wind turbines. Most of the proposed converters require line filters and transformers to improve the power quality and raise the voltage level accordingly. These heavy and bulky components add significantly to tower construction, turbine installation and maintenance costs. Recent advances in power semiconductors and magnetic materials have led to the development of new converter designs that could be a possible solution to reduce the size, weight and cost of power converters. This article provides an in-depth study of energy converter technology, ongoing research and development.

Analysis of the Influence of Renewable Generator Frequency Endurance Capability on Low-Frequency Load Shedding: A Hunan Case Study

With the rapid development of renewable generators such as distributed photovoltaic and profound changes of the power structure, this paper analyzes the frequency characteristics of the power system with high penetration of renewable generations in the process of low-frequency load shedding and discusses the influence of the distributed renewable generator frequency endurance capabilities on the implementation effect of low-frequency load shedding in detail. Finally, the influences of the distributed renewable generator frequency endurance capability and the capacities of the distributed renewable generator on frequency response characteristics of an actual Hunan power grid are simulated. The simulation results show that more distributed photovoltaic capacity without frequency endurance capability leads to deeper frequency drops after the disturbance and requires more basic rounds of load shedding. When the penetration rate of distributed photovoltaic is too high, it may cause load shedding, resulting in power grid load losses and, at the same time, leading to an overshoot phenomenon in the process of frequency recovery. Therefore, the influence of distributed photovoltaic on the control of low-frequency load shedding should be considered when designing low-frequency load shedding schemes for the power grid with high penetration of distributed photovoltaic.

Method for estimating the frequency-time parameters of signals in the system of simultaneously and independently functioning generators.

The issues of assessing the current frequency of each of the total of simultaneously and independently functioning generators within the electronic system are considered. The most common case is considered, in which the deviation of the true values of the nominal parameters of generators from the estimated values of these parameters has an unknown distribution law, and random deviations of frequency from the true nominal value are subject to the normal distribution law with the corresponding variance. The proposed method of obtaining parameters estimates of both independently functioning generators (true nominal frequency values and long-term instability, accidental deviation of frequency caused by short-term instability of the generator) is based on the measurement of the signals phases of each of the generators during several measuring intervals. The first step in obtaining estimates is to line the relationship between deviations of generator parameters from nominal values and the random deviation of the generator frequency by deviation of the measured phase value from the intended nominal value. This allows the formation of a system of linear algebraic equations relative to unknown values of frequency par deviations and relative instability, random deviation of frequency. Minimally necessary number of measuring intervals estimated in the materials of the article. The method proposed in the article is a further generalization of the previously proposed method of statistical frequency stabilization of the system of simultaneously and independently functioning generators, in which, based on finding the extremum of the multidimensional likelihood function, formed under the assumption of a normal distribution law for each of the arguments, the current duration of the measurement time interval, the nominal frequency and the relative instability of each of the generators. The suggested generalization is as follows: formation of an overdetermined system of equations, the unknowns in which are the deviation of the duration of the measurement time interval from the nominal value, the deviation of the values​​of the nominal frequencies of each of the generators from the corresponding assumed values, the deviation of the values ​​of the relative instabilities of each of the generators from the corresponding assumed values; formation of a system of normal equations, based on the results of the solution of which, a joint assessment of the duration of each of the measurement time intervals, frequency deviations and relative instabilities of each of the generators from the corresponding assumed values ​​is carried out; measurements of the signal phases of each of the generators at each time interval of the measurement. The proposed generalization allows us to abandon the following assumptions: exactly known values ​​of the nominal frequency and relative instability of each of the generators; about the known distribution law of the deviation of the values​​of the specified parameters from the assumed values. At the same time, the use of the proposed method leads to the need to measure the phases of the signals of each of the generators not in one, but in several measurement intervals. On the basis of numerical modeling, an increase in the accuracy of estimating the duration of time intervals of measurements and, accordingly, the frequency of generators is analyzed. It is shown that the refinement of the values ​​of the relative frequency instability of each of the generators does not lead to a practically significant increase in the accuracy of estimates of the current values ​​of the generator frequency. A transition to a simplified likelihood function is proposed, in which only the duration of the measurement time interval and the nominal frequency of each of the generators are estimated.

Features of the use of the statistical method of frequency stabilization of generators in distributed information-measuring systems

The article deals with the problems of frequency stabilization of generators in distributed information-measuring systems on the basis of the static frequency stabilization method. The examples of similar systems are given. The necessity to ensure high stability of signal frequency generated by subscribers to improve the efficiency of the stated systems is noted. Two main features of applying the static frequency stabilization method are stated. The first one is determined with a delay in signal input into the device for estimating the frequency-time signal parameters in relation to the signal phase measurement interval. The second feature involves the entry delay of the formed control signal of generator frequency correction. It is shown that the mentioned features lead to divergence of the current variation of generator frequency and the value under correction, obtained considering the delay. The description of information signals enabling to specify a mathematical model of the process of assessment forming of the information signal frequency variation, taking into account the mentioned factors, is offered. It is shown that the possibility of using a statistical method to stabilize the frequency of generators in distributed informationmeasuring systems is determined not only with the values of nominal frequencies and relative instabilities of generators included into the information-measuring system, but also by the autocorrelation function of a random process describing the change of information signal frequency. In case of small time delays between the evaluation of information signal frequency and frequency stabilization, the use of the method to be considered allows to reduce the relative instability of information signal frequency. When time delays are greater than the correlation interval, the use of the statistical method does not lead to the change of relative instability of information signal frequency. Within the correlation interval, the use of the statistical method of frequency stabilization can cause depending on the autocorrelation function values both decrease and increase of the relative information signal frequency instability.