Energy Efficiency Trade-Off Between Duty-Cycling and Wake-Up Radio Techniques in IoT Networks

Wireless Personal Communications - For robust monitoring, control and proper energy management of renewable energy sources (RES), wireless sensing networks (WSNs) are proved to be a vital solution....     

The Numerical Comparison of Heat Transfer in a Coated and Fixed Bed of an Adsorption Chiller

Ecological adsorption technology is becoming a focus of attention by industry due to the utilization of low grade thermal energy sources for cooling production. It can be a promising part of sustainable development concept of the global economy. Therefore, research aiming at improving their performance i.e. Coefficient of Performance (COP) by optimizing the construction of sorption beds with a built in heat exchanger system is crucial. The heat transfer characteristics between the bed of porous media (sorbent) and surface of the heat exchanger system determine the heating power of an adsorption chiller. The HP increase can be obtained by heat transfer intensification due to the increase in the thermal conductivity of the sorbent layer in the vicinity of the heat exchanger’s surface. The novel modification of the sorbent layer structure is proposed in the paper in order to improve the heat transfer processes in the heat exchanger boundary layer. The analysis of desorption process conditions in the parametric model of a coated and fixed adsorption bed design is presented in the paper. The computational fluid dynamics (CFD) with conjugate heat transfer analysis is used to determine the crucial input parameters (temperature distribution in the sorbent bed) for further analytical calculations. The commercial code Ansys Fluent was used to perform numerical simulations. The developed computational model consisted of three subdomains representing heating water, heat exchanger material (copper) and sorbent (silica gel). The comparison of a novel coated design and a conventional fixed bed is discussed in the paper. The numerical analysis is based on experimental thermal conductivity measurements of the sorbent layer in different configurations, which were performed using Laser Flash Method.     

The efficiency of thin-film optical-waveguide modulators using electrooptic films or substrates

This paper describes a new method for characterizing thin-film modulators which utilize TErightleftarrowsTM wave conversion. The conversion is described in terms of a coupled wave model. The coupling constantkdescribes the strength of the coupling between the TE and TM waves. It is expressed in the formk = k_{pw}Cwhere kpwis the coupling constant of plane waves traveling through the relevant bulk medium. The coefficientCcontains the parameters which characterize the guide. The model allows the comparison of structures utilizing electrooptic films and electrooptic substrates. Our results show that in general for single mode films (those approximately a half-wavelength thick), modulators of either type are about equally effective. It is tacitly assumed that kpwis identical for each structure. For films which can support several modes (films a few wavelengths thick), the coefficient for devices utilizing electrooptic substrates approach zero. In contrastCapproaches unity for similar thick-film devices which use electrooptic films.     

A ray-optical analysis of thin-film polarization converters

A compact formula is given for the Goos-Haenchen shifts occurring for total internal reflection of light from anisotropic media. This is used in a coupled-wave analysis of polarization conversion in thin-film waveguides deposited on optically birefringent substrates. A numerical example illustrates the considerable influence of the Goos-Haenchen shifts on the conversion length.     

Giant adrenal cyst

A genetic marker, the tumor gene Tu, which causes the formation of abnormal melanophores, the T-melanophores, in the skin of Xiphophorine fish has been transferred by donor DNA from a Tu genotype to recipient embryos lacking Tu. Abnormal melanophores which are identical to the T-melanophores of the donor genotype occurred only in recipients treated with Tu-DNA and not in those treated with Tu-free control DNA.     

Diffusion length determination in thin film CdS/CuInSe2 solar cells by the EBIC method

Minority carrier diffusion lengths in thin film p-CuInSe₂ and n-CdS were determined from the decay of the short-circuit current generated by the electron beam of a scanning electron microscope (SEM) for different accelerating voltages. The bulk diffusion lengths were determined taking into account the surface recombination velocity at the scanned surface: they were 0.6 μm in CuInSe₂ and 1.17 μm in CdS.     

Optical saturation measurements of fluorophores in solution with pulsed femtosecond excitation and two-dimensional CCD camera detection

We present a new method for the measurement of saturation of the optical transition of fluorescent molecules in solution, which is based on detection with a CCD camera of a two-dimensional projection of the three-dimensional, spatially nonuniform fluorescence intensity distribution as generated in a bulk solution of the fluorophore by excitation with focused femtosecond optical pulses. Essential to the method is (a) a combination of information from a measurement in saturation and one not in saturation and (b) for the measurement in saturation, the simultaneous observation of both saturated and nonsaturated regions of the fluorescence intensity distribution. The experimental setup is straightforward and good agreement is found between the theory and the experimental data.