In the described research an investigation was performed into how thermal comfort in residential buildings could be improved by means of the smart control and optimization of weather-controlled air-to-water heat pumps, taking into account the new-generation heat pumps which can be adapted to different environmental conditions. A novel approach to the off-line optimization of weather-dependent heating curves is proposed. Outdoor temperature controlled heating is extended into the field of linearly parametrized generalized heating curves, considering additional influencing factors such as solar radiation, temperature gradients, and other near-future effects. Off-line optimization is performed in order to maximize indoor thermal comfort for each different parametrization case. The study is based on a TRNSYS simulation of a residential building which included a heat pump model, and a predicted mean vote (PMV) thermal comfort model. A simulation framework for the global optimization of generalized heating curves is developed. The importance of this study is demonstrated through the results of the study which confirmed that a considerable improvement in thermal comfort in residential buildings can be achieved by including (in addition to the outdoor temperature) other factors which can affect the operation of the heat pump, solar radiation being the factor with the strongest effect.
COBISS.SI-ID: 16069915
An annular laser beam based powder cladding head, which enables an axial powder feeding and variation of the laser beam intensity distribution (LBID) on the workpiece surface is presented. The influence of typical LBIDs, including Ring, Tophat(-), Tophat(+), and Gaussian-like, on a cladding process has been characterized based on the process and melt pool visualization, powder catchment efficiency, clad layer geometry, and porosity. The results showed that the most stable process without plasma formation but with low dilution and porosity of the clad layer can be achieved within the range from a Ring to a Tophat(-) LBID. Additionally, axial powder feeding results in a high powder catchment efficiency above 80%. The importance of the study is reflected in the results that LBID is an important influencing parameter of the laser cladding process, and that innovative axial powder feeding enables significantly higher powder catchment efficiency than conventional lateral feeding. These results enable new possibilities for optimizing the process of laser powder cladding aiming at achieving higher cladding rates with the desired clad layer properties and high powder catchment efficiency without the presence of plasma.
COBISS.SI-ID: 16026395
Semi-supervised vibration-based classification and condition monitoring of the reciprocating compressors installed in refrigeration appliances is proposed in this paper. The method addresses the problem of industrial condition monitoring where prior class definitions are often not available or difficult to obtain from local experts. The proposed method combines feature extraction, principal component analysis, and statistical analysis for the extraction of initial class representatives, and compares the capability of various classification methods, including discriminant analysis (DA), neural networks (NN), support vector machines (SVM), and extreme learning machines (ELM). The use of the method is demonstrated on a case study which was based on industrially acquired vibration measurements of reciprocating compressors during the production of refrigeration appliances. The paper presents a comparative qualitative analysis of the applied classifiers, confirming the good performance of several nonlinear classifiers. If the model parameters are properly selected, then very good classification performance can be obtained from NN trained by Bayesian regularization, SVM and ELM classifiers. The method can be effectively applied for the industrial condition monitoring of compressors. The importance of the achievement is reflected in the introduction of state-of-the-art non-linear methods of machine learning to the field of classification and diagnostics of industrial production of household appliances. The effects of the achievement will be reflected in the improved quality of product classification and detection.
COBISS.SI-ID: 15296539
In the paper a novel system for drop-on-demand (DoD) generation from a metal wire is presented, whose main component is a newly developed laser droplet generation head, consisting of annular laser beam shaping optics and a wire feeding system. In the pendant droplet formation phase of the DoD generation, a laser pulse is used to melt the wire-end, which is fed into the focus of an annular laser beam. The formed pendant droplet is then detached by means of a detachment pulse, which induces Rayleigh - Plateau instability of the molten column of wire above the neck of the pendant droplet. The main process parameters, including the laser pulse and wire feeding parameters as well as the additional parameters which influence particular phases of the DoD generation process, have been identified. The empirical correlations between the influencing process parameters and the droplet characteristics, including droplet diameter and temperature, were determined, based on the analysis of high speed IR records of the process, images being acquired by an optical microscope and temperature data being acquired by pyrometers. As an example, DoD generation from a commercially pure 99.6 Ni wire (Nickel 200) of 0.6 mm diameter is considered. It is shown that droplets with diameters ranging from 0.85 to 1.25 mm can be generated, with a resolution of 50 m and a standard deviation of 15 m. The temperature of the detached droplet remains above the melting point of the Ni wire, and increases with the droplet diameter within the range from 1650 °C to 1750 °C. Some examples of Ni droplets deposited on a Ti sheet surface are presented, with the aim of demonstrating the capability of the proposed system, and motivating further applications in which drops on demand having a high temperature and a precisely defined diameter need to be generated, while limiting the thermal loading of the surroundings. In the developed system a novel concept of annular laser beam is applied, which assures process symmetry and stability. The presented results are important for further development of novel droplet based technologies including micro joining of temperature resistant joints in electronic and electrical industry and 3D metal printing technology. In addition to this, the annular laser beam concept can be adapted for laser direct deposition of metal wire or powder.
COBISS.SI-ID: 14120731
The subject of this study is the vertical mass-spring-like oscillation of a pendant droplet and its resonant detachment, which was experimentally observed in the process of laser droplet generation from a metal wire. The process was characterized by various time series, which were generated from a sequence of infrared intensity images of the process. Following a visual inspection of pendant droplet images and an analysis of a wavelet based time-frequency map of the droplet's vertical displacement time series, the pendant droplet's oscillation is described by a time-variable mass-spring system. Based on the characteristics of the time-frequency map, the resonant nature of the pendant droplet detachment was demonstrated. Additionally, an algebraic expression was formulated, which can be used to predict the detached droplet's diameter as a function of the laser pulse frequency. The presented results are important for application of the laser droplet generation process in the fields of droplet joining and 3D structuring technologies. The theoretical description of the process dynamics by a time-variable mass-spring system enables selection of process parameters values in advance for generation of metal droplets with a selected diameter.
COBISS.SI-ID: 14623515
The paper presents recurrence plot based stability analysis of the horizontal band sawing process of structural steel profiles. The analysis is performed in the parameter space defined by the cutting speed, the distance between the blade supports, and the feed rate. The corresponding stability diagrams have been constructed using the recurrence plot characteristic, the determinism of the sound pressure emitted by the process, which quantifies the process predictability. The topology of the experimentally obtained stability diagrams revealed non-linear non-monotonic dynamic behaviour, which made two different chatter avoidance strategies possible by cutting speed variation. Presented results are important from the point of view of assuring the stability of band sawing process which is reflected in chatter phenomena and related low quality of the cut surface or tool brakeage. The results are basis for development of a system for an automatic detection of chatter onset by which a higher productivity and quality of the band sawing could be achieved.
COBISS.SI-ID: 13966107
In this paper the performance of static and adaptive models for short-term natural gas load forecasting has been investigated. The study is based on two sets of data, i.e. natural gas consumption data for an individual model house, and natural gas consumption data for a local distribution company. Various forecasting models including linear models, neural network models, and support vector regression models, were constructed for the one day ahead forecasting of natural gas demand. The models were examined in their static versions, and in adaptive versions. A cross-validation approach was applied in order to estimate the generalization performance of the examined forecasting models. Compared to the static model performance, the results confirmed the significantly improved forecasting performance of adaptive models in the case of the local distribution company, whereas, as was expected, the forecasts made in the case of the individual house were not improved by the adaptive models, due to the stationary regime of the latter's heating. The results also revealed that nonlinear models do not outperform linear models in terms of generalization performance. In summary, if the relevant inputs are properly selected, adaptive linear models are recommended for applications in daily natural gas consumption forecasting. The importance of this study is demonstrated through the recommendations for the construction of the most appropriate model structures for forecasting future daily natural gas consumption, which is needed for on-line optimization of modern energy systems.
COBISS.SI-ID: 13478939
Organising and optimising production in small and medium enterprises with batch production and many different products can be very difficult due to high complexity of possible solutions. The paper presents a method of fine layout planning that rearranges production resources and minimises work and material flow transfer between production cells. The method is based on self-organising map clustering which organises the production cells into groups sharing similar product properties. The proposed method improves the internal layout of each cell with respect to a material flow diagram and a from-to matrix, and fine workspace positioning also considers various restrictions on placement, specifications and types of transportation. The method is particularly suitable for improving the existing layouts. The importance of the achievement has been demonstrated through the practical implementation of a self-organizing neural network for clustering. The method was applied in the Slovenian company KGL d.o.o. where promising results were achieved, namely a reduction by more than 40% in the total transport length with respect to the current production layout was observed.
COBISS.SI-ID: 13421083
Electronic computer circuits consisting of a large number of connected logic gates of the same type, such as NOR, can be easily fabricated and can implement any logic function. In contrast, designed genetic circuits must employ orthogonal information mediators owing to free diffusion within the cell. Combinatorial diversity and orthogonality can be provided by designable DNA- binding domains. Here, we employed the transcription activator–like repressors to optimize the construction of orthogonal functionally complete NOR gates to construct logic circuits. We used transient transfection to implement all 16 two-input logic functions from combinations of the same type of NOR gates within mammalian cells. Additionally, we present a genetic logic circuit where one input is used to select between an AND and OR function to process the data input using the same circuit. This demonstrates the potential of designable modular transcription factors for the construction of complex biological information processing devices. Cell response management is becoming increasingly important for therapeutic use. The cellular response can be manipulated by controlling the transcription of genes with transcription factors. Unlike natural transcription factors, whose number is limited, it is possible to prepare artificial repressors using combinations of DNA-binding domains. In this way, we can implement logic gates NOT and NOR. Using a combination of NOR gates, however, any logic function can be implemented, since the OR operator is a functionally complete system.
COBISS.SI-ID: 5408026
This paper considers the dynamics of traffic on a ring road-based transportation network around a major city, via traffic flow time series analysis and characterization. In particular, three traffic flow time series are examined. Two of the time series are acquired from measurement stations located on highways, while one is from a station on the ring road around Ljubljana city. For the analysis and characterization of time series the novel test called 01 test for chaos is applied. Based on the outputs of the test it is concluded that the observed traffic dynamics is inherently chaotic. Additionally, a more detailed characterization of traffic dynamics is carried out on Lyapunov spectrum basis, which reveals that traffic dynamics on the highway is quantitatively quite different from the traffic dynamics on the ring road. The importance of the method has been demonstrated through the practical implementation.
COBISS.SI-ID: 13074715