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This thesis is focused on design and commissioning of appliance for operating and status display in the aquarium. The first part of the thesis deals with the possibilities of solving particular problems of the system and defines the requirements which the system has to fulfil. The next section of the thesis describes design of hardware part of the system and its software.

This thesis is consisting of three parts. In first part was conducted market research and then start preparation concept of project Graphic indicator units using in industrial environment. Creating a basis for continued in making electronic schemes and board. Then the board was made in external specialization company. Then all components were installed. After testing all of function the device was ready for implementation firmware. Firmware was consist of few parts – communication with RS232 protocol, RS485, web interface and last parts is communication with touch display.

Les références de temps et de fréquence sont largement distribuées sur réseaux informatique et de communications, pour une large gamme d'applications scientifiques et industrielles. Poussé par une demande pour de meilleures performances, un certain nombre de nouvelles méthodes de transfert de temps et de fréquence sur des réseaux à fibres optiques ont été développées ces dernières années. Dans cette thèse, notre objectif est de développer une approche de transfert de temps et de fréquence multi-utilisateurs, compatible avec les réseaux de télécommunications et compétitive avec la distribution de temps par GNSS. Nous nous intéressons donc aux méthodes pour les réseaux à commutation par paquets, comme le NTP (Network Time Protocol) et le PTP (Precision Timing Protocol). Nous nous concentrons également sur les liaisons “unidirectionnelles”, où les signaux aller et retour entre les nœuds de réseau se propagent sur des fibres distinctes, non au sein d’une même fibre (liaisons “bidirectionnelles”). En particulier, nous utilisons une méthode appelée White Rabbit PTP (WR). Développée au CERN, basée sur PTP, utilisant l’Ethernet synchrone et d'autres techniques pour atteindre des performances élevées, WR réalise une stabilité du temps sous-nanoseconde pour la synchronisation d'instruments sur des réseaux à l'échelle de 10 km. Nous sommes particulièrement intéressés par l'extension de cette méthode pour la distribution de références au niveau régional ou national, sur des liaisons allant jusqu'à 1000 km.Nous étudions d’abord les performances de l'équipement réseau White Rabbit, en particulier le commutateur White Rabbit. Nous y apportons diverses améliorations : sur le verrouillage du commutateur grand maître à la référence externe, améliorant ainsi sa stabilité à court terme de plus d'un ordre de grandeur ; sur la bande passante de verrouillage du commutateur esclave ; et en augmentant le débit des messages PTP entre les commutateurs maître et esclave.Nous étudions ensuite les liaisons WR moyennes et longues distances. Nous construisons un lien unidirectionnel de 100 km en utilisant des bobines de fibres dans le laboratoire. Nous découvrons que la performance à court terme est limitée par la dispersion chromatique de la fibre, tandis que la performance à long terme est dégradée par le bruit thermique. Pour limiter l'effet de la dispersion chromatique sur les liaisons longue distance, nous proposons l'utilisation d'une approche en cascade. Nous réalisons un lien en cascade de 500 km, à nouveau avec des bobines de fibres. Nous utilisons le multiplexage en longueur d'onde dense pour construire ce lien par des passages multiples à travers des bobines plus courtes. Nous obtenons une stabilité de transfert de fréquence de 2 × 10-12 à une seconde de temps d'intégration et de 5 × 10-15 en un jour, limitée par le bruit thermique à long terme. Nous obtenons une stabilité temporelle de 5 ps à une seconde de temps d'intégration, diminuant jusqu'à un minimum de 1,2 ps à 20 secondes et restant inférieure à une nanoseconde pour des durées plus longues. Ces performances sont similaires à court terme, et deux ordres de grandeur meilleures à long terme, qu’un récepteur GPS de bonne qualité. Nous nous attendons à ce que les fluctuations thermiques et donc l'effet du bruit thermique des fibres soient réduits d'un facteur d'environ cinq pour les installations sur le terrain.Enfin, nous faisons des études préliminaires sur l'étalonnage en temps des liaisons WR. Le principal défi est de mesurer l'asymétrie de longueur optique entre les deux fibres utilisées pour le transfert des signaux aller et retour. Nous démontrons une technique d'échange de fibres, en utilisant une liaison suburbaine White Rabbit sur fibre noire. Nous décrivons et testons ensuite une nouvelle méthode variationnelle pour l'étalonnage, impliquant une méthode de mesure différentielle basée sur l'exploitation de deux liaisons WR à différentes longueurs d'onde sur la même liaison. / Time and frequency references are widely distributed over communications and computer networks, for a variety of scientific and industrial applications. Driven by a demand for improved performance, a number of new methods for time and frequency transfer over optical fiber-based networks have been developed in recent years. In this thesis our objective is to develop a scalable network time and frequency transfer approach, providing multi-user dissemination, compatible with large telecommunication networks and competitive with GNSS-based time distribution. Therefore we are concerned with methods for use in packet-based networks, like the Network Time Protocol (NTP) and Precision Timing Protocol (PTP). We also concentrate on “unidirectional” links, where the forward and backward signals between network nodes propagate over separate fibers, not within the same fiber (“bidirectional” links).In particular we use a method called White Rabbit PTP (WR). This is a novel technology developed at CERN, based on PTP while using Synchronous Ethernet and other techniques to achieve high performance. It demonstrates sub-nanosecond time stability and synchronization of arrays of instruments over 10 km scale networks. We are particularly interested in extending this method for large scale distribution of references at regional or national level, over links of up to 1000 km.We first study extensively the default performances and limitations of White Rabbit network equipment, in particular the White Rabbit switch. We make various improvements to its operation: on the locking of the grandmaster switch to the external reference, thus improving its short-term stability by more than an order of magnitude; optimizing the locking bandwidth of the slave switch; and increasing the PTP messaging rate between master and slave switches.We then study medium and long-distance WR links. We construct a 100 km, unidirectional link using fiber spools in the laboratory. We discover that the short-term performance is limited by chromatic dispersion in the fiber, while the long-term performance is degraded by the influence of temperature variations on the fiber. To limit the effect of chromatic dispersion for long-haul links, we propose the use of a cascaded approach. We realise a national scale, cascaded, 500 km link, again utilizing fiber spools. We use Dense Wavelength Division Multiplexing methods to construct this link by mutliple passages through shorter spools. We achieve a frequency transfer stability of 2 × 10−12 at one second of integration time and 5 × 10−15 at one day, limited by thermal noise in the long term. We achieve a time stability of 5 ps at one second of integration time, decreasing to a minimum of 1.2 ps at 20 seconds and remaining below one nanosecond for longer averaging times. These performances are similar in the short term, and two orders of magnitude better in the long term, than good quality GPS receivers. We expect thermal fluctuations and therefore the effect of fiber thermal noise to be suppressed by a factor of approximately five for installations in the field.Finally we make preliminary investigations of time calibration of WR links. The main challenge here is to measure the optical length asymmetry between the two fibers used for signal transfer in the forward and backward directions. We demonstrate a fiber swapping technique, using a mid range, suburban White Rabbit link over dark fiber. We then describe and test a new variational method for calibration, involving a differential measurement method based on operating two WR links at different wavelengths over the same optical fiber link.In conclusion, we demonstrate high performance, long haul White Rabbit links for time and frequency dissemination to multiple users. With the level of frequency transfer performance achieved, White Rabbit PTP provides a competitive and scalable technique for comparing industrial atomic clocks at regional and national scales.

Thesis (M. Sc. Agriculture (Agricultural Economics)) -- University of Limpopo, 2021 / South Africa is characterised by low production which can be attributed to a lack of diversification and flexibility in agricultural production. There has been an explosive change in consumer-food relationships due to increased knowledge in the food industry. It is no longer just about supplying what you have, but about what you are selling as a producer that can meet the required need of consumers. Producers’ primary objective in the food industry is to provide the product that consumers need. Rabbit meat is recognised in rural areas, however, most rural smallholder farmers do not take initiative in rabbit production. Madiga Village is one such area where rabbit production is not practised. Farmers at Madiga Village are focusing on livestock such as cattle, goat, sheep and pork; and none of them are focusing on rabbit production. This study’s main purpose was to understand consumers perception of and willingness to pay for rabbit meat and analysing this perception and willingness in relation to their socio-economic characteristics. Moreover, since rabbit meat competes with other types of meat, it was imperative for the scope of this study to compare rabbit meat with other types of meat. As such, rabbit meat was compared with chicken, beef, pork and mutton. Information for this study on the perception of and willingness to pay was collected using a structured questionnaire that was administered through face-to-face interviews. The data that was collected was entered into a Microsoft Excel Spreadsheet and SPSS for analysis. This study used a sample size of 120 respondents at Madiga Village that were randomly selected. Analytical techniques used to analyse the data were Descriptive Statistics, Binomial Logit Model, Likert Scale and Chi-square Analysis. Firstly, the socio-economic characteristics of the respondents were identified and described. From the 120 households sampled and interviewd at Madiga Village, the results revealed that 57% of the respondents were males as compared to 43% of females. The majority, constituting 58% of the respondents were unemployed, whereas 28% of the respondents in this study were full-time employed with only 14% being self-employed. The household size of the respondents was found to be on an average of 5 with a minimum of 1 and a maximum of 13 members. From the Likert scale results using ten items, it was found that rabbit meat was perceived to be the easiest to cook and prepare relative to all the meat types it was compared with. Furthermore, it was perceived to be more nutritious, healthy and cheaper. However, it was found that respondents perceived it as being the difficult meat to find. Rabbit meat was also perceived as tasty compared to pork, chicken, beef and sheep (mutton) meats. To understand socio-economic characteristics affecting perception and willingness to pay, the Binomial Logit Model and Chi-square Analysis were used, respectively. The Binomial Logit results indicated that males were more likely to pay for rabbit meat if it was sold on a farm. Moreover, The results indicated that as household size increases by one, respondents would be more likely to pay for rabbit meat. Furthermore, respondents who perceived rabbit meat as better than pork and sheep meats were likely to pay for rabbit meat. Therefore, the null hypotheses were rejected as there are socio-economic characteristics and consumer perceptions that affect their willingness to pay. Rabbit farming is promising at Madiga village and farmers who would like to take an initiative in rabbit farming are encouraged to do so. The potential of this enterprise suits it to be incorporated into the livestock governmental financial budget as a new business initiatives.

It is well known that the overlap between the thick and thin filaments in striated muscle is responsible for the single active length-tension (L-T) curve. With the lack of visible striations, a sarcomeric unit has not been identified in smooth muscle. Though once thought to function like striated muscle via a sliding filament mechanism of contraction, recent studies on length-adaptation (L-adaptation) in airway smooth muscle (ASM), in which increased tension is generated with repeated contraction, have led to the hypothesis of a dynamic L-T curve in smooth muscle. Although more established in ASM, two studies have shown L-adaptation in vascular smooth muscle (VSM). In this project, the L-T curve over a 3-fold length range in rabbit femoral artery was investigated and the presence of more than one active and passive L-T curve was identified. The third of three repeated KCL-induced contractions at a single, shortened length resulted in L-adaptation in which the phasic and tonic phases of contraction demonstrated a 10-15% increase in active tension (Ta) relative to the first contraction. Experiments investigating possible mechanism(s) responsible for this phenomenon demonstrated that neither an increase in [Ca2+]i nor an increase in MLC20 phosphorylation was responsible for the increased tension. However, actin polymerization did appear to play a role in the L-adaptation of both phases of contraction. Thus directions for future research could include further study of actin polymerization in VSM that contributes to L-adaptation and may ultimately result in artery remodeling.