1,526 research outputs found
Material selection for a new type of fire extinguisher
Nowadays safety is a hot topic, damage inflicted to human beings is intolerable. Fire safety is a big concern in industrial areas, but in residential areas a lot less precautions are in place. Therefore a new type of fire extinguisher should be developed that should encourage the installation of fire extinguishers in commercial environments and at home. The design of this fire extinguisher has to answer to a lot of demands. From a legal point of view, the extinguisher has to comply with the PED regulations and the EN 3 standard. Extra demands are, given the purpose, superb performance, great ergonomics and an attractive visual design. One of the steps in the design process is to make a material selection based on needed and desired properties of materials. Also the possible processes for manufacturing are an important parameter
Herding in Queues with Waiting Costs: Rationality and Regret
We study how consumers with waiting cost disutility choose between two congested services of unknown service value. Consumers observe an imperfect private signal indicating which service facility may provide better service value as well as the queue lengths at the service facilities before making their choice. If more consumers choose the same service facility because of their private information, longer queues will form at that facility and indicate higher quality. On the other hand, a long queue also implies more waiting time. We characterize the equilibrium queue-joining behavior of arriving consumers and the extent of their learning from the queue information in the presence of such positive and negative externalities. We find that when the arrival rates are low, utility-maximizing rational consumers herd and join the longer queue, ignoring any contrary private information. We show that even when consumers treat queues as independently evolving, herd behavior persists with consumers joining longer queues above a threshold queue difference. However, if the consumers seek to minimize ex post regret when making their decisions, herd behavior may be dampened
Analisis Penguasaan Objek Matematika (Kajian pada Lulusan SMA di Provinsi Maluku)
Penelitian ini bertujuan mengidentifikasi penguasaan objek langsung dan objek tidak langsung matematika pada lulusan SMA di provinsi Maluku, serta faktor-faktor yang mempengaruhinya. Sampel penelitian ini adalah 466 lulusan SMA yang menjadi mahasiswa baru jurusan Pendidikan MIPA FKIP Universitas Pattimura Ambon. Hasil penelitian ini menunjukkan bahwa penguasaan objek langsung matematika, yang terdiri atas penguasaan konsep, operasi, dan prinsip matematika masuk dalam kategori sangat rendah. Demikian pula penguasaan objek tak langsung matematika yang meliputi kemampuan pemecahan masalah dan kemampuan penalaran masuk dalam kategori sangat rendah. Terdapat tiga faktor penyebab rendahnya penguasan objek matematika, yakni (1) kualifikasi dan kompetensi guru, (2) rendahnya kualitas pembelajaran dan (3) budaya belajar
Realization of 2-dimensional air-bridge silicon photonic crystals by focused ion beam milling and nanopolishing
We report the design and fabrication of small photonic crystal structures which are combined with conventional dielectric ridge waveguides. We describe in details the fabrication of both rough and smooth membranes, which are used as host for photonic crystals. Two Focused Ion Beam milling experiments are highlighted: the first one shows how photonic crystals can be fast and accurate milled into a Si membrane, whereas the second experiment demonstrates how focused ion beam milling can turn a rough surface into a well-patterned nano-smooth surface. The previously ultra rough surface showed no detectable roughness after milling due to the nanopolishing effect of the focused ion beam milling
Dirac-screening stabilized surface-state transport in a topological insulator
We report magnetotransport studies on a gated strained HgTe device. This
material is a threedimensional topological insulator and exclusively shows
surface state transport. Remarkably, the Landau level dispersion and the
accuracy of the Hall quantization remain unchanged over a wide density range
(). This implies that
even at large carrier densities the transport is surface state dominated, where
bulk transport would have been expected to coexist already. Moreover, the
density dependence of the Dirac-type quantum Hall effect allows to identify the
contributions from the individual surfaces. A model can describe
the experiments, but only when assuming a steep band bending across the regions
where the topological surface states are contained. This steep potential
originates from the specific screening properties of Dirac systems and causes
the gate voltage to influence the position of the Dirac points rather than that
of the Fermi level.Comment: 12 pages 4 figure
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Impact of furnace atmosphere and organic contamination of recycled cullet on redox State and fining of glass melts
The onset temperature of fming and the quantity of fming gases is not only determined by the amount of fming agents in sodalime- silica batches, but also by the level of organic contaminants in the cullet or normal batch and the water vapor pressure in the furnace atmosphere. These conditions will also determine the redox State of the glass and residual sulfate or sulfide concentrations in the glass. Organic contaminants will form char during headng of the batch. This char partly reacts with CO₂ Coming from the decomposition of the soda, limestone or dolomite forming carbon monoxide. Stable types of char or cokes or cuUet-rich batches with only small amounts of carbonates will result in some carbon residues after the CO₂ evolution. This carbon partly reduces Sulfates and ferric iron in the fresh melts. This results in sulfide and ferrous iron formation in these glass melts. At increasing temperatures in the melt, the sulfides and Sulfates react together forming sulfur-containing gases between 1000 to 1250°C. The Sulfate retention decreases, finally the glass even may contain sulfur only in the sulfide form under very reduced conditions. In batches without reducing agents, Sulfates in the melt Start to decompose at temperatures exceeding 1400 °C. Small amounts of carbon and water vapor reduce the fining onset temperature. Water vapor from the furnace atmosphere predominantly Infiltrates the batch blanket during melting and foaming. The water will enhance the bubble and seed growth during fining. Water in the melt will influence the redox State of the final glass. Only in batches containing coarse raw materials or cullet, reducing or oxidizing gases from the furnace atmosphere Infiltrate the batch blanket and these gases will respectively reduce and oxidize components like iron oxides, sulfate/sulfide or chromium oxides in the batch blanket interior
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