Three-phase inverter with a variable control algorithm

The paper presents the construction of a three-phase frequency converter with the possibility of choosing the type of PWM modulation and a smooth change of the frequency of the modulated signal. In a practical way, various inverter control algorithms were implemented in the same hardware system using the STM ARM Cortex M3 processor. The use of THIPWM modulation allowed to reduce the harmonic content in the output signal and effectively use the possibilities of the power source. The system can choose one of two scalar control algorithms, with the option of compensation for the influence of the stator resistance on the motor shaft torque in the initial range of the linear control characteristic at a constant voltage to frequency ratio. The research confirmed that the most advantageous type of PWM in this system is unipolar double-edge modulation. The use of the THIPWM method resulted in a gain in the amplitude of the fundamental harmonic of the output voltage for the three-phase inverter operation mode compared to the SPWM method. The appropriate precision of the frequency control step was also obtained, and the test results confirmed the functionality of the converter.

Changes in the concentrations of selected toxic and essential elements in ewe milk from area with a potentially undisturbed environment

The aim of this study was to evaluate the effect of lactation on the concentration of selected essential and toxic elements in sheep milk from an area of Slovakia with a potentially undisturbed environment and to find out the actual contamination of the selected area, in the aspect of its environmental character. The research was conducted with 400 sheep (Tsigai breed), and the milk samples were taken during the lactation periods (early, middle and late lactation stage). Sheep were reared on the extensive pastures, reared indoors afterward, fed with pasture ad libitum. Milk samples were collected after morning and afternoon milking. The samples of milk were analysed toxic and essential elements (Ca, Se, Mg, Zn, Fe, Cu, As, Cd, Hg, Ni, Pb) by the method of atomic absorption spectroscopy (AAS). The macro elements concentration in milk changes following the stages of lactation (p<0.05). There was found that Ca milk concentration increased gradually in the following stages of lactation while Mg, Se, and Fe only in the last stage of lactation. The Zn concentration in milk was the highest during summer (p<0.05). Simultaneously the contents of essential elements (Cu) and toxic elements (As, Cd, Hg, Ni, Pb) in milk were very low, below the limit of quantification. In conclusion, ewe's milk from potentially analysed areas of Slovakia is safe and poses no risk to consumer health, and is suitable for use directly or in dairy processing.

Research of the internal environment of the military camp buildings

One of the key tasks of this research work is to assess the carbon dioxide (CO₂) pollution in the resting areas of military camps under the current deployment conditions and to assess its impact on soldiers. In the process, the environmental impacts that affect the CO₂ concentration were researched in different rooms in different ways. In addition to the rest areas of a military camp, enumerating the major camp facilities that affect the “welfare” feeling of soldiers on foreign mission, we arrived at the kitchen complex and the work environment of the kitchen staff. One of the key parts of the camp kitchen complex is the food storage, where the raw materials needed for the supply are stored. Storage is very important in a crisis situation, when you have to be prepared to stay away from the homeland, to prevent any supply or procurement problems. A particularly important task in providing food raw materials is the so-called "Fresh" storage. The aim of the paper is to examine the changes in the CO₂ concentration of the camp storage room, which is of key importance in food supply, in the vegetable (fruit) storage places. By modeling at a measurement site set up in the laboratory of the host institution, we measure the CO₂ composition of the indoor air in the warehouse by placing various vegetables and fruits. The change of CO₂ concentration is examined separately for certain types of vegetables and fruits stored in closed storage rooms, taking into account the degree of effective storage capacity and determine the required fresh air value to ensure proper storage conditions. Finally, a mathematical model to simulate changes in storage conditions will be created, which offer help to plan of the military camp.

Effect of temperature and relative humidity on the milk production of dairy cows

The aim of this study was to evaluate the influence of environmental housing conditions on the milk yield of dairy cows. Measurements were taken in the summer period from June to September 2020 and in the winter period during January 2021 on a large-capacity farm of Holstein Friesian cattle. Cows were housed in free stall barn with the lying boxes and selected during the second or third lactations, in the summer period from the 51st day to the 135th day and in the winter period from the 64th day to the 120th day of lactation. The average temperature in the housing was 23 °C in summer, and 7.05 °C in winter. The average THI (thermal humidity index) value in summer was 70.43, but during the day the THI values sometimes reached 75. The dairy cows were therefore exposed to heat stress during summer. Increasing THI and temperature values negatively affected the milk yield, as there was a negative correlation between both THI and milk yield (r = -0.641; p <0.01) and temperature and milk yield (r = -0.637; p <0.01). Milk production in winter was at 58.77 kg per day and in summer at 49.55 kg per day. In the summer, the milk had a significantly lower content of fat (p <0.05), proteins (p <0.001), lactose (p <0.001), minerals (p <0.001) and conversely, a higher number of somatic cells (p <0.01). These results show that worse environmental conditions during the summer negatively affected the level of milk yield and the composition of the cows’ milk.

Utilization of specific primers in legume allergens based polymorphism screening

Different types of allergies became a part of life of many people around the world. The research activities connecting to allergens are actually not oriented only for protein and immunological interactions, but to the genomic and transcriptomic background of them, too. Analysis and description of genomic variability of allergens in plant food resources will help to manage the allergen based strategies in the future. Here, the bioinformatic approach was used to develop and validate the specific primers for genomic screening of polymorphism of profilins (Profilin Based Amplicon Polymorphism; PBAP) and vicilins (Vicilin Based Amplicon Polymorphism; VBAP) among the legumes. The alignment of existing public databases data for these allergens in the group of legumes was performed. Subsequently, specific primers were designed and their ability to generate polymorphic amplicons were tested for three legumes – bean, lentil and chickpeas. In all cases, amplicons were generated and polymorphism was detected in all three species for profilin as well as for vicilin.

The effect of post-harvest storage on the weight of Golden Delicious apples

Apples, like other fruits, are exposed to stress during their growth and development in the field, also during harvest and the postharvest environment (processing, storage, and transportation). The refrigeration system allows for bulk handling of food products from harvest to market, ensuring that food products are maintained in their freshness and integrity for an extended period through careful management of storage temperature and humidity. This study investigated the effects of storage on the weight loss of apples (Golden Delicious fruits harvested at maturity), under refrigerated conditions at a temperature of 5±0.5°C and relative humidity of 82% and under ambient storage at a temperature of 25 ±0.5 °C and relative humidity of 60 %, over 3 months. The findings revealed that the two groups of apples experienced weight reduction at different levels. Apples placed at cold storage presented a loss of weight between 3.31g and 4.49g; however, apples stored at ambient temperature showed a significant loss of weight between 21.9g and 31.76g.

BBAP amplification profiles of apple varieties

Several types of allergies are currently known and are characterized by an exaggerated response of the immune system to substances from various sources called allergens. One of them is a food allergy, which is becoming more common in the population. For this reason, it is necessary to describe the issue from several aspects including genomic variability of plant allergens. The objective of this study was to analyse intraspecific variability of Bet v 1 of 10 different varieties of apple species (Malus domestica Borkh.). BBAP technique for genomic determination of the presence of Bet v 1 homologs at the DNA level was performed. Degenerate primers that anneal a variable and conserved part of PR-10 protein homologues genes were used in the analyse. Amplicons were generated and formed relatively monomorphic profiles, indicating the stability of the given isoforms of Bet v 1 within the selected apple varieties. To evaluate the potential allergenicity of selected varieties further studies on another molecular level such as a comparison of gene expression of the PR-10 family members and their protein expression levels are needed.

APEKS - a method of making decisions

The APEKS method was developed in the 1970s. It has a wide range of applications for making a decision. The article describes the APEKS method, which is a multi-criteria method and consists of 10 steps. The application of this method was presented in the example of car selection. The problem of choosing a passenger car was analyzed taking into account 6 evaluation criteria: fuel consumption, power, price, annual operating costs, aesthetic values, and utility values. Following the APEKS method, the analysis was completed with the selection of the best variant, using the forced decision method, consisting of an individual comparison of all criteria with one another. The APEKS variant is used for this, which has all the best features of the variants to choose from. This indicates that APEKS is an idealized and fictional variant.

Synchronization of Transmission Systems with ANS-DM Codecs

Adaptive Delta Modulation with Non-uniform Sampling (ANS-DM) is one of the waveform coding techniques, where a sampling instant and a quantization step size are adapted to the signal. The ANS-DM modulator produces an output binary stream, that carries information about the signal and includes necessary data of coder parameters (sampling instant and quantization step). In the demodulator, these values are recovered for proper signal reconstruction. The paper reports the problem of synchronizing clocks (transmitting and receiving) in the (ANS-DM) delta codecs systems. The original synchronization method, valuable in systems dedicated to the transmission of the bits with variable time duration was projected and experimentally verified. Performed measurements and observations have shown the elimination of the synchronization loss phenomenon.

Mobile image processing system based on the Raspberry Pi 4 platform

The article presents an image processing system based on the Raspberry Pi (RPi) platform. At the beginning of the article, the basic assumptions and purpose of the system are discussed. The following section presents the structure and operation of the system. The window application managing the system and allowing to perform contextual and spectral transformations on images as well as the measurement of parameters such as image processing time and mean square error (MSE) was discussed. The transformations performed were based both on ready formulas contained in the OpenCV library and the author's implementations, including the function implementing the Fast Fourier Transform algorithm radix-2. Examples of transformations were presented along with their usefulness. In the end, the development potential of the created system is presented and its application in specific solutions is proposed.