Diffraction in a Fourier-transform spectrometer

The distortions of the line shape and the shifts of the line positions caused by diffraction in a Fourier-transform spectrometer are described. A simple rule of thumb to calculate the amount of the line-shape distortion is presented. Two methods for the determination of the shifts of the line positions are presented and compared. We also present an approximation for the dependence of the line-position shifts on the solid angle of the source and on the radius of the diffracting hole. Finally we present a method to study the shifts of the line positions experimentally, and some measured results are compared with theoretical ones.     

An Enhanced Facet Determination Scheme in 3D

An enhanced scheme for the determination of equilibrium crystal shapes is introduced. The emphasis of the present study is put on the proper detection of the facets appearing on the crystal surface. The original formulation presented in [1] employs the principle of the virtual work, and the enhanced scheme additionally makes use of a penalty formulation approach. The derivation of the penalty terms is discussed in detail. Finally, the corresponding discrete method is applied to a certain problematic example case presented in [1] resulting now in the correct crystal shape.     

Design and evaluation of mood pictures in social music discovery service

This paper describes the iterative design process and evaluation of mood pictures in a social music discovery service. The service enables users to consume and collaboratively create playlists based on the pictures. In total, 45 Finnish users took part in the qualitative evaluations. This paper presents the results regarding the preset mood picture design and introduces user-generated mood picture playlists. Based on the results, a set of design implications for mood pictures is introduced. In addition, the consistency of user responses from a quantitative picture–music association test shows the applicability of mood picture–music associations to a music discovery service.     

Distributed power allocation over indoor multi-pico stations

A low-complexity distributed power allocation algorithm is proposed to reduce the interference and improve the transmitting rate of edge users. Different scenarios are considered and user experience of indoor communication is promoted. The simulation results prove the effectiveness of our algorithm. The proposed power control scheme ensures that more users can achieve their required rate and the fairness of different users is improved. Besides, more than 50% energy can be saved without loss in outage ability, and energy efficiency is also promoted. In addition, the proposed algorithm can be extended to scenarios that the required rates of pico stations can be changed periodically.     

Optimal power allocation for homogeneous and heterogeneous CA-MIMO systems

Carrier aggregation (CA) technique has been adopted by 3GPP LTE-Advanced due to its ability of enhancing the spectrum efficiency and peak data rates through aggregating multiple component carriers (CCs). Two main factors make power control optimization very essential for CA-MIMO radio link: the different channel characteristics in multiple CCs, and multiple power constraint conditions (per-CC, per-antenna and pertransmitter power constraints) in the actual CA system deployment. This paper firstly derives the degenerate conditions of optimal power allocation for a single-transmitter CA-MIMO system. Stemming from the derived degenerate conditions, we propose a modified hybrid gradient optimal power allocation(MHGOPA) algorithm to maximize the system performance. Simulation results verify the validity of the proposed resource allocation approach by comparing with baseline average power allocation algorithm. Finally, we extend the MHGOPA algorithm into a heterogeneous CA network with multiple transmitters working simultaneously.     

Spatial and temporal constraints in variational correspondence methods

This paper proposes a new method for optical-flow and stereo estimation based on the inclusion of both spatial and temporal constraints in a variational framework. These constraints bound the solution based on a priori information, or in other words, based on what is known of a possible solution or how it is expected to change temporally. This knowledge can be something that (a) is known since the geometrical properties of the scene are known or (b) is deduced by a higher-level algorithm capable of inferring this information. In the latter case, the constraint terms enable the exchange of information between high- and low-level vision systems: the high-level system makes a hypothesis of a possible scene setup which is then tested by the low-level one, recurrently. Since high-level vision systems incorporate knowledge of the world that surrounds us, this kind of hypothesis testing loop between the high- and low-level vision systems should converge to a more coherent solution.     

Optimizing Thermal Shock Resistance of Layered Refractories

Severe thermal shocks may cause critical thermal stresses and failure in refractories or ceramic materials. To increase the thermal shock resistance, layered material structures are suggested. In order to optimize properties of these alternative structures, thermo‐mechanical simulations are required. In this study, a finite difference method (FDM) is used for solving the partial differential equation of heat conduction with spatially varying parameters. The optimization of the strip's thermal shock resistance is exemplarily done on a 10 layered strip subjected to constant temperature jump on the top surface. Each layer can be set with different porous Al₂O₃ and MgO ceramics, whose material properties are theoretically determined. In this study, an improved optimization method is developed that consists of a combination and sequence of Monte Carlo simulations and evolution strategies to overcome certain disadvantages of both techniques.     

Passivation of nanostructured silicon optical devices by thermal carbonization

Nanostructured silicon interference filters have been thermally carbonized by acetylene decomposition at different temperatures in order to passivate their high internal surface area. Stability has been studied by periodically measuring the optical spectrum of treated and untreated porous silicon filters stored in oxidizing environments. Experimental results show that thermal carbonization stabilizes the structures against oxidation, since treated samples show no significant shift of their optical spectra after storage in either ambient air or ethanol for up to two months. Moreover, the thermal carbonization process has no significant effect on the optical performance of the filters. Results show that thermal carbonization by acetylene decomposition provides an effective way to produce chemically stable porous silicon optical devices for biological and chemical sensing.     

A Frequency Tuning Method for a Planar Inverted-F Antenna

A novel method is presented for electrically tuning the frequency of a planar inverted-F antenna (PIFA). A tuning circuit, comprising an RF switch and discrete passive components, has been completely integrated into the antenna element, which is thus free of dc wires. The proposed tuning method has been demonstrated with a dual-band PIFA capable of operating in four frequency bands. The antenna covers the GSM850, GSM900, GSM1800, PCS1900 and UMTS frequency ranges with over 40% total efficiency. The impact of the tuning circuit on the antenna's efficiency and radiation pattern have been experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex PIFA structures as well as other types of antennas to give enhanced electrical performance.     

A microwatt switched-capacitor voltage doubler-based voltage regulator for ultra-low power energy harvesting systems

This paper presents an SC voltage doubler-based voltage regulator for ultra-low power energy harvesting applications. It produces a stable 1.2-V power supply, using inputs from 0.63 to 1.8 V. External compensation and an on-chip output capacitor ensure good performance even with zero load current and any load capacitance. The regulator tolerates arbitrary input ramp-ups, and is immune to blackout and brownout. A stability analysis for the regulator control loop is presented. The regulator ASIC is implemented in a 180 nm CMOS process. The measured regulator peak power and current efficiency are 63 and 49 %, respectively. The performance has been characterized with load currents from zero to \(100\,\upmu\)A.