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Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio

Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller even in worst case voltage unbalance conditions. In addition the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5kVA prototype are presented in order to validate the proposed modulation technique

Composite antenna feed

A composite antenna feed subsystem concentrated in a small area at the prime focus of the parabola of a satellite parabolic reflector accomodates a plurality of frequency bands. The arrays comprising the subsystem are mounted on the top cover of a communication module. A multimode horn is arranged at the center of the subsystem axis which functions at X- And C-band frequencies, and a cross array consisting of individual elements form the S-band feed, with one arm of the S-band array containing an element mutually shared with the L-band array. Provision is also made for UHF frequencies, and a dipole arrangement for VHF frequencies is arranged around the S-band arms

Dish antenna having switchable beamwidth

A switchable beamwidth antenna includes a concave parabolic main reflecting dish which has a central circular region and a surrounding coaxial annular region. A feed means selectively excites only the central region of the main dish via a truncated subreflector for wide beamwidth or substantially the entire main dish for narrow beamwidth. In one embodiment, the feed means comprises a truncated concave ellipsoid subreflector and separate feed terminations located at two foci of the ellipsoid. One feed termination directly views all of the main dish while the other feed termination, exciting the main dish via the subreflector, excites only the central region because of the subreflector truncation. In the another embodiment, the feed means comprises one feed termination and a convex hyperboloid subreflector via which the feed excites the main dish

Identification of specific demands on Feed in Dutch Organic Aquaculture

The evaluation of specific demands for organic feed focussed on feed demands for four fish species which can be cultured in Recirculation Aquaculture Systems (RAS), tilapia, African Catfish, shrimp and turbot. The evaluation of the various feed formulations indicates that there are several ingredients, which are common for the four species, and will therefore be used for further elaboration on the organic availability. These feed ingredients, are: fishmeal and oil, corn meal, wheat meal, blood meal, vitamin mix, mineral mix, and antioxidants. Besides the evaluation of the feed ingredients an inventory was made on the demands set by three key organic standards and legislation documents; European legislation (in prep), IFOAM and Naturland. A draft consensus standard containing a synthesis of all demands has been described. The implication of the demands, and the possibilities and bottlenecks for organic feed production were evaluated for the selected feed ingredients. It was concluded that organic feed production for RAS can meet the general criteria set for feed, on GMO material and organic composition. However, for the production of organic feed, a bottleneck will be the necessary requirement of synthetic amino acids for health improvement. The lack of these amino acids in organic feed can result in potential disadvantage for animal needs. This raw material restrictions will most likely also result in the lack of possibilities for fine tuning the feed for animal need

From Grain to Feed

Horse beans are used as an example of grain, which have potentials to substitute fish meal in fish feed. After several grinding and fractionation steps it was possible to obtain a protein-rich horse bean fraction with a yield of 19 %. This fraction contained 55.9 % protein. The high protein content together with the amino acid profile makes the fraction very suitable as a substitute to fish meal in fish feed. The protein-rich fraction was used as a successful additive in extruded fish pellets

A new impedance matching method for an ultra-wide band and dual circularly polarised feed

In traditional antenna design, metal components are not placed in the central part of the antenna as they change the characteristics of near field radiation. However, we show that placing a metal ring in the centre of the strip lines, which connect the ends of folded high-frequency dipoles, does not damage the performance of the feed. Instead it significantly improves the voltage standing wave ratio of the feed whilst other performance indicators are not compromised. Thus, our findings show an excellent way of improving the wide band feed. Based on this foundation, a new circularly polarised feed for operation between 0.4 to 2 GHz is introduced for the Chinese Spectral Radioheliograph in this paper. The issue of a feed impedance matching network is investigated. By optimising the impedance matching, the performance of the feed is enhanced with respect to the previous realisations of the Eleven feed. The simulation and experimental results show that the gain of the feed is about 10 dBi, and the VSWR is less than 2:1. In addition, the feed has a low axial ratio, fixed phase centre location, and constant beam width in the range of 0.4 to 2 GHz

Studi Tentang Persepsi, Praktek Dan Sikap Terhadap Sistem HACCP Pada Industri Pakan Dalam Mencapai Kesesuaian Keamanan Pakan

Industry have not yet been implementing the feed safety system including the feed hygiene practices. Therefore,A study of perceptions, practices and attitudes on hazard analysis critical control point (HACCP) in achieving feedsafety compliance of Indonesian stock-feed production has been conducted. This study was carried out usingframe works of study as follows, i.e. Module I, Assessment on existing conditions using methods of survey,observe, interview, plant visit and distribute a questionnaire to medium and large feed industries at 6 provinces,i.e Lampung, Banten, West Java, Center of Java, East Java and South Sulawesi with the number of samples forrespondents about 20 feed industries; They were also asked about the feed hygiene practices in their business,their systems used such as HACCP, and the perceptions and attitudes toward a range of feed hygiene issues;Module II, Identification of potential critical control points; Module III, Evaluation of HACCP programs. Theanalysis was conducted using descriptive analysis method that developed by Hair et al. and to test the differenceusing one-way statistical analysis of variance. The results showed that the HACCP systems were implemented at95% in the large feed industries and 65% in the medium feed industry, respectively (P< 0.005); 30% medium and15% of large feed industry managers stated that their business represented a low-risk to feed safety. Higherlevels of feed hygiene qualifications among the industry managers and higher perceptions among managers ofthe risk of feed safety of the business were also significantly related to use HACCP in sectors (P<0.05). Sixpotential hazards were identified along the process to be controlled as critical control points (CCPs). Total cost forimplementing the system was around 1 billion and 400 millions rupiahs; while the time needed since designing upto fully operating the system with audit results fulfill the prerequisite programs and HACCP requirement was about7 months

Feed quality problems and management strategies

Feed is the single most important input in increasing aquaculture production and profits. Success or failure in augmenting yield with feeding depends, to a large extent, on the quality of the diet. Feed quality, generally perceived as the responsibility of the feed manufacturer, is affected by factors outside of the plant such as handling, storage, and use. Thus, the maintenance of feed quality becomes partly the responsibility of the farmer. Every fish farmer must be familiar with the nature and occurrence of major feed quality problems and able to prevent and control them. This paper is based on a farmer's viewpoint. Valuable insights are provided for the feed manufacturer