Mouth-Clicks used by Blind Expert Human Echolocators – Signal Description and Model Based Signal Synthesis

Echolocation is the ability to use sound-echoes to infer spatial information about the environment. Some blind people have developed extraordinary proficiency in echolocation using mouth-clicks. The first step of human biosonar is the transmission (mouth click) and subsequent reception of the resultant sound through the ear. Existing head-related transfer function (HRTF) data bases provide descriptions of reception of the resultant sound. For the current report, we collected a large database of click emissions with three blind people expertly trained in echolocation, which allowed us to perform unprecedented analyses. Specifically, the current report provides the first ever description of the spatial distribution (i.e. beam pattern) of human expert echolocation transmissions, as well as spectro-temporal descriptions at a level of detail not available before. Our data show that transmission levels are fairly constant within a 60° cone emanating from the mouth, but levels drop gradually at further angles, more than for speech. In terms of spectro-temporal features, our data show that emissions are consistently very brief (~3ms duration) with peak frequencies 2-4kHz, but with energy also at 10kHz. This differs from previous reports of durations 3-15ms and peak frequencies 2-8kHz, which were based on less detailed measurements. Based on our measurements we propose to model transmissions as sum of monotones modulated by a decaying exponential, with angular attenuation by a modified cardioid. We provide model parameters for each echolocator. These results are a step towards developing computational models of human biosonar. For example, in bats, spatial and spectro-temporal features of emissions have been used to derive and test model based hypotheses about behaviour. The data we present here suggest similar research opportunities within the context of human echolocation. Relatedly, the data are a basis to develop synthetic models of human echolocation that could be virtual (i.e. simulated) or real (i.e. loudspeaker, microphones), and which will help understanding the link between physical principles and human behaviour

Optimization of warpage defect in injection moulding process using ABS material

Plastic injection moulding process produces various defects such as warpage, sink marks, weld lines and shrinkage. The purpose of present paper is to analyze the warpage defect on Acrylonitrile Butadiene Styrene (ABS) for selected part using FEA simulation. The approach was based on Taguchipsilas Method and Analysis of Variance (ANOVA) to optimize the processing parameters namely packing pressure, mould temperature, melt temperature and packing time for effective process. It was found that the optimum parameters for ABS material are packing pressure at 375 MPa, mould temperature at 40degC, melt temperature at 200degC and packing time at 1 s. Melt temperature was found to be the most significant factor followed by packing time and mould temperature. Meanwhile, packing pressure was insignificant factor contributing to the warpage in present study

Contact Pressure Distribution During the Polishing Process of Ceramic Tiles: A Laboratory Investigation

During the polishing process of porcelain tiles the difference in scratching speed between innermost and peripheral abrasives leads to pressure gradients linearly distributed along the radial direction of the abrasive tool. The aim of this paper is to investigate such pressure gradient in laboratory scale. For this purpose polishing tests were performed on ceramic tiles according to the industrial practices using a custom-made CNC tribometer. Gradual wear on both abrasives and machined surface of the floor tile were measured. The experimental results suggested that the pressure gradient tends to cause an inclination of the abraded surfaces, which becomes stable after a given polishing period. In addition to the wear depth of the machined surface, the highest value of gloss and finest surface finish were observed at the lowest point of the worn out surface of the ceramic floor tile corresponding to the point of highest pressure and lowest scratching speed

The development of Zirconia and Copper toughened Alumina ceramic insert

Ceramic cutting tools have been utilized in industry for over a century for its productivity and efficiency in machine tools and cutting tool material. However, due to the brittleness property the application has been limited. In order to manufacture high strength ceramic cutting tools, there is a need for suitable reinforcement to improve its toughness. In this case, copper (Cu) and zirconia (ZrO2) powders were added to investigate the hardness and physical properties of the developed composite insert. A uniaxial pre-forming process of the mix powder was done prior to densification by sintering at 1000 and 1300°C. The effect of the composition of the reinforcement on the hardness, density, shrinkage and microstructure of the inserts was investigated. It was found that an optimum density of 3.26 % and hardness 1385HV was obtained for composite of 10wt % zirconia and 10wt% copper at temperature 1000 °C

Kajian awal variabiliti ionosfera di Parit Raja, Batu Pahat pada bulan september 2004

Kajian ionosfera di Malaysia ini adalah untuk bulan September 2004 dengan menggunakan sistem penderum ionosfera (ionosonde). Matlamat utama dalam kajian ini adalah bagi menentukan parameter yang digunakan untuk mencari perubahan lapisan ionosfera di Malaysia. Pemerhatian dan analisa menggunakan data yang diperolehi melalui pengumpulan dan penyimpanan dari sistem penderum digital. Keputusan yang diperolehi adalah melalui maklumat gelombang normal frekuensi kritikal pada susun lapis lapisan-F, foF2, ketinggian maya yang diberikan oleh frekuensi kritikal f0F2, h'F2 dan juga gelombang normal frekuensi kritikal pada lapisan terendah yang tebal dilapisan- E. Pengumpulan data dalam masa 24 jam, dari 1 September hingga 30 September dilakukan bagi mendapatkan nilai frekuensi median, lower decile dan upper decile. Perubahan nilai frekuensi ini dilihat mengikut masa dan juga keadaan aktiviti matahari pada waktu siang. Frekuensi kritikal yang diperolehi adalah tinggi ketika aktiviti matahari meningkat pada waktu siang iaitu antara 6.8 hingga 12 MHz dan penurunan nilai frekuensi kritikal ini juga akan menurun ketika waktu lewat petang dan malam iaitu 7 MHz. ketinggian maya bagi nilai frekuensi ini adalah antara 200 hingga 480 km. Bagi lapisan-E, nilai frekuensi adalah dari 2.2 hingga 9.1 MHz

Penggunaan teknologi maklumat dalam pengurusan di Sekolah Menengah Bestari

Kajian ini dijalankan bertujuan untuk meninjau penggunaan teknologi maklumat, keberkesanan penggunaan teknologi dan juga mencari langkah-langkah yang sewajarnya untuk memperkasakan penggunaan teknologi maklumat dalam pengurusan di Sekolah Menengah Bestari iaitu Sekolah Menengah Kebangsaan (A) Nairn Lilbanat, Kelantan. Kajian ini adalah berdasarkan kepada lima aspek pengurusan iaitu pengurusan Sumber Pendidikan, Hal Ehwal Pelajar, Sumber Luar, Perpustakaan dan Asrama. Kaedah kajian adalah secara kuantitatif. Instrumen yang digunakan adalah borang soal selidik. Hasil kajian mendapati bahawa peratusan pengurusan berbantukan teknologi maklumat sudah berada di tahap yang kurang memuaskan iaitu 60%. Setiap pengurusan tetap menggunakan perkakasan yang disediakan oleh pihak sekolah dan penggunaan IT amat berkesan dalam pengurusan untuk memudahkan pengendalian keija walaupun masih ada kekurangan peralatan di situ. Bahagian pengurusan perpustakaan juga mengalami kekurangan komputer untuk kegunaan pelajar dan terdapat peralatan yang rosak untuk proses pengajaran dan pembelajaran. Di bahagian akhir kajian ini beberapa cadangan yang difikirkan sesuai telah dikemukakan untuk membaiki kelemahan yang dikesan walaupun sudah berada dalam tahap yang boleh dibanggakan