Papers by Keyword: Spectrum

Abstract: The paper represents the results of the effective lighting introduction based on LED technology on the basis of a green house. It is shown that in order to reduce electricity costs, as well as increase yields, it is necessary to replace traditional sodium lamps with LED lighting lamps. Based on the results obtained, mathematical calculations confirm the above statement.

Abstract: This paper aimed to compare obtained results and collected theory for 100 Hz frequency vibration of hydropower generator stator core and transformer core. Electromagnetic vibration with 100 Hz frequency occurred both at slow-speed salient poles synchronous generator stator core and oil-filled power transformers tank, but the nature of hydropower and transformer 100 Hz vibration was different. The vibration analysis procedure and acceptable limits for hydropower generator stator core were already covered in the standards, while the health grade system for vibration measurements of power transformer has not beet yet developed. This study discussed the experimental results aiming to extend the knowledge about reasoning for non-existing statistical health grade system, based on power transformers vibrations, measured on tank. The experimental results of hydropower generator stator and power transformer spectrum were reported. Two salient pole hydropower generator stators and four transformers with different construction (including shell-type) and different cooling system (including air forced cooling system) were chosen to present vibration spectrum results. It was demonstrated that increasing clamping pressure of the core does not always reduce 100 Hz harmonic component neither for hydrogenerator stator, nor for transformer. Bad clamping pressure and defects in core, in contrary, will not result into increase of 100 Hz component for some units. Results showed that air forced cooling equipment (fans) would not add higher harmonics to vibration spectrum of the power transformer tank. It was shown that the shell-type construction of transformer core would not necessarily result in high vibration values on tank.

Abstract: In the paper the basis for the use of the LED light sources in the space greenhouses is described. It is shown that the change in the spectral composition and the intensity of the radiation will reduce the electricity consumption of the irradiation facilities. The unicellular alga "Chlorella" and the greenhouse lettuce "Afitsion" were chosen as prototype models. On the basis of the experiments conducted, the basic principles of the irradiator’s energy efficiency that can be applied in the space greenhouses were defined.

Abstract: The article reports the results of the experiment studied the effect of radiation spectral content (considering its equal intensity in terms of photosynthetically active radiation) on the growth and development of Boets greenhouse tomato breed. We have shown that the effective development of model subjects requires the adaptation of radiation spectral content depending on the growth period and type of a plant, unlike the illumination level. The obtained results demonstrate the necessity of creating an adaptive irradiation unit.

Abstract: Machine tool vibrations cause uncomfortable noise, may damage the edges of cutting tools or certain parts of machine tools, but most importantly, they always have negative effect on the quality of the machined surface of workpieces. These vibrations are especially intricate in case of milling processes where complex tool geometries are used, like helical, serrated, non-uniform pitch angles, and so on. During the milling process, the arising vibrations include free, forced, self-excited, and even parametrically forced vibrations together with their different combinations. Regarding surface quality, the most harmful is the self-excited one called chatter, which is related to the regenerative effect of the cutting process. Its relation to machined surface quality is demonstrated in an industrial case study. The modelling and the corresponding cutting stability are presented in case of a helical tool applied for milling with large axial immersions. The extremely rich spectrum of the measured vibration signals are analyzed by means of model-based predictions, and the results are compared with the spectral properties of the corresponding machined surfaces. The conclusions open the way for new kinds of chatter identification.

Abstract: It is an inevitable phenomenon that flash is generated in the process of hypervelocity impact. The research on impact flash is of important significance for assessing the collision between space debris and spacecraft, identifying the material properties on the surface of planet, evaluating the damage of weapon system. A measurement system was built in order to acquire flash spectrum ranging in wavelength from 200 to 1100nm. The relationship between flash intensity and impact velocity was studied. The spectrum consists of line spectrum and continuous spectrum. Line spectrum mainly concentrates in the range of 200-500nm. The spectral lines of the elements were identified. The strong flash happens within 2.2ms after beginning to impact. In addition, the electron temperature of plasma produced in hypervelocity impact is calculated by spectral method, and compared with the temperature measured by Langmuir three probes.

Abstract: The phenomenon of rubber consumption in Malaysia has been increased parallel with the world demand. Hence, it is necessary for the cultivators to gain some knowledge for differentiating various rubber tree clone breed which may give them high latex yield after 5 years or more of planting. This paper discusses the identification of several rubber tree clones breed based on the best percentage of the reflectance wavelength obtained from the respected latex. In this work, there were three selected rubber tree clones which are RRIM 2025, PB 355 and PB 350 suggested by Rubber Research Institute of Malaysia (RRIM) will undergo a preliminary analysis on the significant information of spectrum properties acquired from the latex. A hundred of latex samples have been collected from each clone and extracted the optical measurements of the primary color spectrum (Red, Green and Blue) using spectrometer. The next step is to analyze the acquired information based on its reflectance wavelength with respect to clones and at the end it will be evaluated statistically. As a result, there were two out of three clones could be discriminated between each other with refer to the green wavelength (573nm).

Abstract: In this paper we consider the oscillation and spectrum of a class of high order two-term differential operators. Using the oscillation and non-oscillation criteria of related equation obtained here, we describe some spectral information of differential operators. In particular, the conditions which guarantee that any self-adjoint extension of differential operators has spectrum discrete and bounded below are given.

Abstract: The actual tailings dam as an object, analyzes on tailings dam of the different slope ratio, which under earthquake dynamic response characteristics and stability. The results show that, with the increase of the tailings dam slope than the maximum relative displacement becomes larger, the absolute acceleration amplification factor decreases. In the same slope ratio, the tailings dam displacement and maximum acceleration dam piled high with increased accumulation becomes larger. Sand soil absorption of seismic waves of high frequency, low frequency component.

Abstract: An understanding of normal tissue response is necessary for the optimization of radiation treatment in cancer therapy. Cancer cells exhibit altered local dielectric properties compared to normal cells because of the difference in shape, size and orientation. These properties are measurable as a difference in electrical conductance using electrical impedance spectroscopy. Multiple frequency bioimpedance analysis is used to measure change in electrical properties of the irradiated tissues as a function of frequency and time. From the experimental results, it is clear that the electrical properties demonstrated good detection performance. The electrical parameters of the tissues could be used to distinguish the tissue's status. Changes in electrical properties at different frequencies show, that there are differences between conductivity of non-irradiated and irradiated tissues.