Constraints Perceived by Students in School Vegetable Gardening

The study was conducted in Thiruvananthapuram district of Kerala to identify the constraints experienced by students in the course of engaging in school vegetable gardening programme. Ten schools were selected for data enumeration. A total of 130 respondents with 100 students comprising ten students each and 30 teachers comprising three each, from each school were selected for meeting the objectives of the study. The reaction to each constraint was obtained on a four-point continuum namely most important, important, less important and least important with the score 4, 3, 2 and 1 respectively. Mean rank cumulative index for each constraint was worked out and the constraints were ranked and catalogued. The major constraints as perceived by students in school vegetable garden projects were, high input cost followed by lack of student’s participation, lack of teacher’s involvement, non-availability of implements, high labour cost, poor storage facilities and lack of knowledge about gardening

SEMANTIC WEB BASED INTEGRATION BETWEEN BIM COST AND GEOMETRIC DOMAINS

In the architecture, engineering, construction, and facilities management (AEC/FM) industry methodologies are needed to ensure the interoperability of data and effective management of information from different sources. Integration of the cost domain and cost estimation within the Building Information Model (BIM) in the AEC/FM sector is still an unresolved problem and one of the most critical tasks due to the lack of a standardised cost domain, especially in the tendering phase. To ensure interoperability between cost data and geometric data, this research aims to address this gap by analyzing methods of converting cost data into Linked Building Data, thereby defining a cost domain in the Semantic Web, by collecting them into a graph database. This allows for structuring a cost domain, translating an IFC based structure previously developed by the research group, visualizing it using a graph system, and connecting it to the BIM geometric domain. Furthermore, it is possible to extend the cost ontology previously identified in the IFC model and facilitate the queries and analysis of cost data currently fragmented and based on unstructured data. The results show how Semantic Web technology can be used to improve data interoperability, develop a cost ontology, and join both cost data and BIM models

Power conversion for a novel AC/DC aircraft electrical distribution system

This paper proposes a novel and compact AC/DC electrical distribution system for new generation aircraft. In these new aircraft power systems, all loads are fed by two dc bus systems: at 28V and at +/-270V. The electrical distribution system, whose design and implementation are described in this paper, has only one primary AC source (360-900Hz at 230V) with all the required dc voltage levels being derived from this source. This solution enables elimination of the complex mechanical coupling apparatus currently used, for fixed frequency AC systems, to maintain the generator speed at constant level while the engines operate at variable speed. Under the proposed solution, all conversion stages needed to generate the various output voltage levels are implemented using power converters assembled in one unit. Each converter has a current control loop in order to regulate the output current even during output line short circuits and also to limit the inrush current to the circuit at turn-on. To prove the concept a 5 kW prototype was designed and tested, and demonstrated to meet all the specifications within relevant standards regarding input and output power quality

Repetitive control for high-performance resonant pulsed power supply in radio frequency applications

This paper presents a novel three phase series resonant parallel loaded (SRPL) resonant converter topology for radio frequency (RF) applications. The proposed converter is capable to produce as output voltage a series of “long pulses”, each one lasting 1ms in time. Three individual single phase resonant stages are able to operate independently in conjunction with three separate single phase output rectification stages. Due to this important feature, the converter has a strong ability of rejecting the influence of unbalance in the resonant tanks. A PI + Repetitive Control (RC) strategy has been used for the output pulsed voltage regulation, resulting in a fast rise time, reduced overshoot, and constant amplitude. The soft-switching of semiconductor devices is ensured at full power by a combined frequency and phase shift modulation (CFPS), even in the presence of large tank unbalances

Radial force control of Multi-Sector Permanent Magnet machines considering radial rotor displacement

A mathematical model enabling to predict the electromagnetic x-y forces and torque for a given input current in a Multi-Sector Permanent Magnet Synchronous (MSPMS) machine is presented. The rotor static eccentricity is also accounted and the analytical calculations are validated by means Finite Element Analysis (FEA). Furthermore, a novel force and torque control is proposed based on input current minimization and is applied to suppress the Unbalanced Magnetic Pull (UMP) caused by the rotor eccentricity. The effective operation of the force suppression technique is verified by means of FEA

Position control study of a bearingless multi-sector permanent magnet machine

Bearingless motors combine in the same structure the characteristics of conventional motors and magnetic bearings. Traditional bearingless machines rely on two independent sets of winding for suspension force and torque production, respectively. The proposed Multi-Sector Permanent Magnet (MSPM) motor exploits the spatial distribution of the multi-three-phase windings within the stator circumference in order to produce a controllable suspension force. Therefore, force and torque generation are embedded in the same winding setting. In this paper the force and torque generation principles are investigated and a mathematical model is presented considering the rotor displacement. A two Degree of freedom (DOF) position controller is designed taking into consideration the rotor overall dynamic system and a controller gains selection strategy is suggested. A simulation study of the bearingless system in different operating conditions is presented and the suspension force and torque produced are validated through Finite Element Analysis (FEA)

Radial force control of multi-sector permanent magnet machines for vibration suppression

Radial force control in electrical machines has been widely investigated for a variety of bearingless machines, as well as for the conventional structures featuring mechanical bearings. This paper takes advantage of the spatial distribution of the winding sets within the stator structure in a multisector permanent-magnet (MSPM) machine toward achieving a controllable radial force. An alternative force control technique for MSPM machines is presented. The mathematical model of the machine and the theoretical investigation of the force production principle are provided. A novel force control methodology based on the minimization of the copper losses is described and adopted to calculate the d–q axis current references. The predicted performances of the considered machine are benchmarked against finite-element analysis. The experimental validation of the proposed control strategy is presented, focusing on the suppression of selected vibration frequencies for different rotational speeds

Delivering COBie data - Focus on curtain walls and building envelopes

COBie is a standard data framework whose main purpose is to transmit useful, reliable and us-able information collected throughout the whole building process and to be consumed in order to properly maintain the facility. Focusing on Facility Management information exchanges and considering the UK BIM policies and requirements, this paper shows the results obtained applying COBie to complex products such as curtain walls. Two Information Delivery Manuals (IDMs) were also developed, in order to provide a com-monly known and standardized framework, which can regulate the COBie-based information exchanges. Fu-ture developments of this study could concern the application of the developed IDMs to different case studies in order to overtake that specificity characterizing each single project and verify the validity of the proposal

Radial force control of multi-sector permanent magnet machines

The paper presents an alternative radial force control technique for a Multi-Sector Permanent Magnet machine (MSPM). Radial force control has been widely investigated for a variety of bearingless machines and can be also applied to conventional PMSM aiming the reduction of the mechanical stress on the bearings as well as reduce the overall vibration. Traditional bearingless motors rely on two independent sets of windings dedicated to torque and suspension respectively. The work presented in this paper takes advantage of the spatial distribution of the winding sets within the stator structure towards achieving a controllable net radial force. In this paper the α-β axis model for the MSPM and the theoretical investigation of the force production principle is presented. A novel force control methodology based on the Single Value Decomposition (SVD) technique is described. The predicted performances of the MSPM have been validated using Finite Element simulations and benchmarked against state of the art control techniques