Green Materials Comparation of Sawdust and Coconut Fibre Acoustical Waffle Panel

Abstract. The natural wealth of Indonesia produces a wide range of natural resources. This research will discuss sawdust and coconut fibre for example from natural resources which can be processed into building materials. The use of the absorber as a facade is needed, especially for buildings located in noisy urban areas. Various research has studied the absorber made from sawdust and coconut fibre, but only a few studies that study the absorber material that has the texture of waffle on its surface. The research method used is the method comparisons of the value of the absorption coefficient, density and Sound Transmission Loss (STL) impedance tube with 1/3 octave filter. The result is that the waffle the panel from the sawdust has a higher density than waffle the panel from coconut fibre. The value of the coconut fibre panel STL ranged 46,134 – 51,312 dB. This value is lower than the STL material from sawdust that has a value between 47,301 – 62,688 STL. Absorption coefficient, coconut fibre panels between 0,432 – 0,511, while the value of the coefficient of absorption sawdust panel range 0,469 – 0,529. (max 200 words)

Ultrafast pump-probe dynamics in ZnSe-based semiconductor quantum-wells

Pump-probe experiments are used as a controllable way to investigate the properties of photoexcited semiconductors, in particular, the absorption saturation. We present an experiment-theory comparison for ZnSe quantum wells, investigating the energy renormalization and bleaching of the excitonic resonances. Experiments were performed with spin-selective excitation and above-bandgap pumping. The model, based on the semiconductor Bloch equations in the screened Hartree-Fock approximation, takes various scattering processes into account phenomenologically. Comparing numerical results with available experimental data, we explain the experimental results and find that the electron spin-flip occurs on a time scale of 30 ps.Comment: 10 pages, 9 figures. Key words: nonlinear and ultrafast optics, modeling of femtosecond pump-probe experiments, electron spin-flip tim

Blind estimation of reverberation time in classrooms and hospital wards

This paper investigates blind Reverberation Time (RT) estimation in occupied classrooms and hospital wards. Measurements are usually made while these spaces are unoccupied for logistical reasons. However, occupancy can have a significant impact on the rate of reverberant decay. Recent work has developed a Maximum Likelihood Estimation (MLE) method which utilises only passively recorded speech and music signals, this enables measurements to be made while the room is in use. In this paper the MLE method is applied to recordings made in classrooms during lessons. Classroom occupancy levels differ for each lesson, therefore a model is developed using blind estimates to predict the RT for any occupancy level to within ±0.07s for the mid-frequency octave bands. The model is also able to predict the effective room and per person absorption area. Ambient sound recordings were also carried out in a number of rooms in two hospitals for a week. Hospital measurements are more challenging as the occurrence of free reverberant decay is rarer than in schools and the acoustic conditions may be non-stationary. However, by gaining recordings over a period of a week, estimates can be gained within ±0.07 s. These estimates are representative of the times when the room contains the highest acoustic absorption. In other words when curtains are drawn, there are many visitors or perhaps a window may be open

Time-gated transillumination of biological tissues and tissuelike phantoms

The applicability and limits of time-resolved transillumination to determine the internal details of biological tissues are investigated by phantom experiments. By means of line scans across a sharp edge, the spatial resolution (Ax) and its dependence on the time-gate width (At) can be determined. Additionally, measurements of completely absorbing bead pairs embedded in a turbid medium demonstrate the physical resolution in a more realistic case. The benefit of time resolution is especially high for a turbid medium with a comparatively small reduced scattering coefficient of approximately pL,' = 0.12 mm-1. Investigations with partially absorbing beads and filled plastic tubes demonstrate the high sensitivity of time-resolving techniques with respect to spatial variations in scattering or absorption coefficients that are due to the embedded disturber. In particular, it is shown that time gating is sensitive to variations in scattering coefficients. Key words: Time-resolved transillumination, turbid media, light scattering, streak camera

Extractive Multi Document Summarization using Dynamical Measurements of Complex Networks

Due to the large amount of textual information available on Internet, it is of paramount relevance to use techniques that find relevant and concise content. A typical task devoted to the identification of informative sentences in documents is the so called extractive document summarization task. In this paper, we use complex network concepts to devise an extractive Multi Document Summarization (MDS) method, which extracts the most central sentences from several textual sources. In the proposed model, texts are represented as networks, where nodes represent sentences and the edges are established based on the number of shared words. Differently from previous works, the identification of relevant terms is guided by the characterization of nodes via dynamical measurements of complex networks, including symmetry, accessibility and absorption time. The evaluation of the proposed system revealed that excellent results were obtained with particular dynamical measurements, including those based on the exploration of networks via random walks.Comment: Accepted for publication in BRACIS 2017 (Brazilian Conference on Intelligent Systems

Vigor, Dedication and Absorption: Work engagement among secondary school English teachers in Indonesia

Abstract This paper investigates the work engagement among a sample of 152 secondary school English teachers in Yogyakarta, Indonesia, sampled from a competency-based integrated training course. Data were collected using the short form of the Utrecht Work Engagement Scale (UWES 9; Schaufeli et al, 2002). Reliability in the Indonesian context was high (alpha=.91 overall; alphas=.76, .83, .79 respectively, for component vigor, dedication, and absorption subscales). Results suggest that teachers’ work engagement is generally high (overall M=5.04 on the 7-point scale; Ms=4.99, 5.44, 4.71 respectively, for component vigor, dedication, and absorption subscales). Findings are interesting in the context of low student English achievement in this region and implications are suggested in relation to teachers’ continuing professional development and enhancement of student achievement. Key words: work engagement, teachers’ work engagemen

Absorption suppression in photonic crystals

We study electromagnetic properties of periodic composite structures, such as photonic crystals, involving lossy components. We show that in many cases a properly designed periodic structure can dramatically suppress the losses associated with the absorptive component, while preserving or even enhancing its useful functionality. As an example, we consider magnetic photonic crystals, in which the lossy magnetic component provides nonreciprocal Faraday rotation. We show that the electromagnetic losses in the composite structure can be reduced by up to two orders of magnitude, compared to those of the uniform magnetic sample made of the same lossy magnetic material. Importantly, the dramatic absorption reduction is not a resonance effect and occurs over a broad frequency range covering a significant portion of photonic frequency band