Colourings of lattices and coincidence site lattices

The relationship between the coincidence indices of a lattice $\Gamma_1$ and a sublattice $\Gamma_2$ of $\Gamma_1$ is examined via the colouring of $\Gamma_1$ that is obtained by assigning a unique colour to each coset of $\Gamma_2$. In addition, the idea of colour symmetry, originally defined for symmetries of lattices, is extended to coincidence isometries of lattices. An example involving the Ammann-Beenker tiling is provided to illustrate the results in the quasicrystal setting.Comment: 9 pages, 6 figure

Multiple CSLs for the body centered cubic lattice

Ordinary Coincidence Site Lattices (CSLs) are defined as the intersection of a lattice $\Gamma$ with a rotated copy $R\Gamma$ of itself. They are useful for classifying grain boundaries and have been studied extensively since the mid sixties. Recently the interests turned to so-called multiple CSLs, i.e. intersections of $n$ rotated copies of a given lattice $\Gamma$, in particular in connection with lattice quantizers. Here we consider multiple CSLs for the 3-dimensional body centered cubic lattice. We discuss the spectrum of coincidence indices and their multiplicity, in particular we show that the latter is a multiplicative function and give an explicit expression of it for some special cases.Comment: 4 pages, SSPCM (31 August - 7 September 2005, Myczkowce, Poland

Small Engine Component Technology (SECT)

A study of small gas turbine engines was conducted to identify high payoff technologies for year-2000 engines and to define companion technology plans. The study addressed engines in the 186 to 746 KW (250 to 1000 shp) or equivalent thrust range for rotorcraft, commuter (turboprop), cruise missile (turbojet), and APU applications. The results show that aggressive advancement of high payoff technologies can produce significant benefits, including reduced SFC, weight, and cost for year-2000 engines. Mission studies for these engines show potential fuel burn reductions of 22 to 71 percent. These engine benefits translate into reductions in rotorcraft and commuter aircraft direct operating costs (DOC) of 7 to 11 percent, and in APU-related DOCs of 37 to 47 percent. The study further shows that cruise missile range can be increased by as much as 200 percent (320 percent with slurry fuels) for a year-2000 missile-turbojet system compared to a current rocket-powered system. The high payoff technologies were identified and the benefits quantified. Based on this, technology plans were defined for each of the four engine applications as recommended guidelines for further NASA research and technology efforts to establish technological readiness for the year 2000

Analitičke metode za određivanje teških metala u tekstilnoj industriji

Heavy metals in textile wastewater represent a major environmental problem, and are a potential danger to human health when present on textiles. Furthermore, the presence of some metals influences the production of textiles. Heavy metals are often used as oxidizing agents, as metal complex dyes, dye stripping agents, fastness improvers, and finishers. Thus, they act as hazardous sources throughout entire textile processing. Toxic effects of heavy metals on humans are well documented. Therefore, it is important to monitor heavy metals throughout the entire production. Today, maximum permissible values for metals in textiles are given by different regulations, according to which the heavy metals have to be determined both qualitatively and quantitatively. Several analytical procedures for the determination of heavy metals were tested for their application on textiles. The advantages and disadvantages of TLC, UV-VIS, GF-AAS, ICP-OES, and ICP-MS methods are discussed.Teški metali u otpadnim vodama tekstilne industrije čine ogroman problem za okoliš, a kada se nalaze na tekstilnim materijalima iskazuju potencijalnu opasnost po ljudsko zdravlje. U tekstilnoj industriji teški se metali vrlo često rabe kao oksidansi, bojila te sredstva za poboljšavanje svojstava postojanosti. S obzirom na to da su toksični učinci teških metala na ljudsko zdravlje danas veoma dobro poznati (Tablica 1), vrlo je važno kontrolirati njihovu prisutnost tijekom proizvodnje i prerade tekstilnih materijala. Maksimalno dopuštene količine teških metala koje se nalaze na tekstilnim materijalima, pa se tijekom uporabe mogu ekstrahirati znojenjem i tako štetno utjecati na zdravlje ljudi, regulirane su različitim standardima (Tablica 2). Prema njima, potrebno je određivati i pratiti metale na materijalima, za što je moguće primijeniti nekoliko različitih analitičkih metoda. U ovom radu razmatrani su prednosti i nedostaci metoda TLC, UV-VIS, GF-AAS, ICP-OES i ICP-MS. Prije analize udjela teških metala na tekstilnim materijalima, uzorke je potrebno pripremiti za analizu. Velika važnost uzorkovanja (Slika 1), priprave i čuvanja uzoraka (tablice 3-4) naglašene su u poglavljima 2.1 - 2.3. Metoda tankoslojne kromatografije opisana u poglavlju 2.4. može se jednostavno i brzo primijeniti za učinkovito razdvajanje i dokazivanje različitih teških metala. Nedostatak te metode su visoke granice detekcije. UV-VIS spektroskopija je također jednostavna analitička metoda za određivanje metala koja zahtijeva pažljivu pripravu uzoraka. Karakteristike UV-VIS određivanja odabranih teških metala prikazane su u Tablici 5. Atomska apsorpcijska spektroskopija (FAAS i GF-AAS) jedna je od najviše upotrebljavanih metoda u analizi metala koja ima niske granice detekcije. Osnovni nedostatak te metode je nemogućnost istodobnog određivanja više elemenata u istom uzorku, kao što je to moguće kod induktivno spregnute plazme. Stoga je i priprava uzorka za analizu AAS-om dugotrajnija te iziskuje veće troškove. Zbog toga danas najprikladnije metode za analizu metala postaju upravo ICP-OES i tehnike ICP-MS, koje imaju mnoge prednosti nad ostalim analitičkim metodama: izrazito niske granice detekcije (Tablica 7), vrlo široko linearno područje (čak i do nekoliko stotina mg kg-1) te mogućnost simultanog određivanja velikog broja elemenata u istom uzorku. Nedostatak je visoka cijena instrumenata te visoki troškovi analize. Kao zaključak pregleda analitičkih metoda za određivanje teških metala na tekstilnim materijalima, iznesena je činjenica da se najbolji rezultati postižu kombinacijom različitih metoda odabranih i validiranih za namijenjenu svrhu

Analitičke metode za određivanje teških metala u tekstilnoj industriji

Heavy metals in textile wastewater represent a major environmental problem, and are a potential danger to human health when present on textiles. Furthermore, the presence of some metals influences the production of textiles. Heavy metals are often used as oxidizing agents, as metal complex dyes, dye stripping agents, fastness improvers, and finishers. Thus, they act as hazardous sources throughout entire textile processing. Toxic effects of heavy metals on humans are well documented. Therefore, it is important to monitor heavy metals throughout the entire production. Today, maximum permissible values for metals in textiles are given by different regulations, according to which the heavy metals have to be determined both qualitatively and quantitatively. Several analytical procedures for the determination of heavy metals were tested for their application on textiles. The advantages and disadvantages of TLC, UV-VIS, GF-AAS, ICP-OES, and ICP-MS methods are discussed.Teški metali u otpadnim vodama tekstilne industrije čine ogroman problem za okoliš, a kada se nalaze na tekstilnim materijalima iskazuju potencijalnu opasnost po ljudsko zdravlje. U tekstilnoj industriji teški se metali vrlo često rabe kao oksidansi, bojila te sredstva za poboljšavanje svojstava postojanosti. S obzirom na to da su toksični učinci teških metala na ljudsko zdravlje danas veoma dobro poznati (Tablica 1), vrlo je važno kontrolirati njihovu prisutnost tijekom proizvodnje i prerade tekstilnih materijala. Maksimalno dopuštene količine teških metala koje se nalaze na tekstilnim materijalima, pa se tijekom uporabe mogu ekstrahirati znojenjem i tako štetno utjecati na zdravlje ljudi, regulirane su različitim standardima (Tablica 2). Prema njima, potrebno je određivati i pratiti metale na materijalima, za što je moguće primijeniti nekoliko različitih analitičkih metoda. U ovom radu razmatrani su prednosti i nedostaci metoda TLC, UV-VIS, GF-AAS, ICP-OES i ICP-MS. Prije analize udjela teških metala na tekstilnim materijalima, uzorke je potrebno pripremiti za analizu. Velika važnost uzorkovanja (Slika 1), priprave i čuvanja uzoraka (tablice 3-4) naglašene su u poglavljima 2.1 - 2.3. Metoda tankoslojne kromatografije opisana u poglavlju 2.4. može se jednostavno i brzo primijeniti za učinkovito razdvajanje i dokazivanje različitih teških metala. Nedostatak te metode su visoke granice detekcije. UV-VIS spektroskopija je također jednostavna analitička metoda za određivanje metala koja zahtijeva pažljivu pripravu uzoraka. Karakteristike UV-VIS određivanja odabranih teških metala prikazane su u Tablici 5. Atomska apsorpcijska spektroskopija (FAAS i GF-AAS) jedna je od najviše upotrebljavanih metoda u analizi metala koja ima niske granice detekcije. Osnovni nedostatak te metode je nemogućnost istodobnog određivanja više elemenata u istom uzorku, kao što je to moguće kod induktivno spregnute plazme. Stoga je i priprava uzorka za analizu AAS-om dugotrajnija te iziskuje veće troškove. Zbog toga danas najprikladnije metode za analizu metala postaju upravo ICP-OES i tehnike ICP-MS, koje imaju mnoge prednosti nad ostalim analitičkim metodama: izrazito niske granice detekcije (Tablica 7), vrlo široko linearno područje (čak i do nekoliko stotina mg kg-1) te mogućnost simultanog određivanja velikog broja elemenata u istom uzorku. Nedostatak je visoka cijena instrumenata te visoki troškovi analize. Kao zaključak pregleda analitičkih metoda za određivanje teških metala na tekstilnim materijalima, iznesena je činjenica da se najbolji rezultati postižu kombinacijom različitih metoda odabranih i validiranih za namijenjenu svrhu

Perceiving Monocular Regions in Binocular Scenes

Our visual systems combine the two, slightly different, retinal images to arrive at a stable and continuous percept of a given scene around us. While a large proportion of any scene is binocular, there are a host of regions that can only be seen by one eye. Rather than being ignored, these monocular regions are integrated with the surrounding binocular regions and their content is consciously accessible to us. However, our perception of the information contained in monocular regions seems to be slightly different from that of information that is seen by both eyes (binocularly). Ono et al (2003)[1], for example, report that monocular regions appear slightly displaced and compressed, as if to 'fit' into the surrounding binocular space. Here we discuss two experiments that investigate our perception of monocular regions further. We used two relative numerosity tasks to study whether monocular regions lead to a percept that is comparable to that of binocular regions, and we explored how the two types of regions are integrated to form a seemingly stable and continuous percept. This record was migrated from the OpenDepot repository service in June, 2017 before shutting down

Post processing of additively manufactured metal parts by using pulse electrochemical machining

In response of the growing demand for higher product requirements concerning quality, durability and efficiency by simultaneously decreasing product life cycles, the product development has to consider suitable production technologies at an early stage of the development process. This implicates also the choice of new manufacturing or technology approaches. Additively manufactured parts can be produced with a high geometrical complexity. To produce such geometrically complex parts from metal, the so called selective laser melting (SLM) technology is often the method of choice. In order to produce SLM-parts, support structures have to be used. They have several functions, such as connecting the component to a building platform, supporting overhanging and tilted areas but they also dissipate the heat of fusion. However, those support structures have to be removed for the use of the component, which often involves numerous time- consuming and difficult to automatize operation steps. A promising alternative can be pulse electrochemical machining (PECM) as there is no contact between tool and workpiece. This allows the adaption of the tool to complex geometries and the improvement of the workpiece surface quality in one machining step. Therefore, a fundamental study of the electrochemical dissolution behavior and machinability aspects of the support structures is performed

Generalized Riemann sums

The primary aim of this chapter is, commemorating the 150th anniversary of Riemann's death, to explain how the idea of {\it Riemann sum} is linked to other branches of mathematics. The materials I treat are more or less classical and elementary, thus available to the "common mathematician in the streets." However one may still see here interesting inter-connection and cohesiveness in mathematics

Coincidences in 4 dimensions

The coincidence site lattices (CSLs) of prominent 4-dimensional lattices are considered. CSLs in 3 dimensions have been used for decades to describe grain boundaries in crystals. Quasicrystals suggest to also look at CSLs in dimensions $d>3$. Here, we discuss the CSLs of the root lattice $A_4$ and the hypercubic lattices, which are of particular interest both from the mathematical and the crystallographic viewpoint. Quaternion algebras are used to derive their coincidence rotations and the CSLs. We make use of the fact that the CSLs can be linked to certain ideals and compute their indices, their multiplicities and encapsulate all this in generating functions in terms of Dirichlet series. In addition, we sketch how these results can be generalised for 4--dimensional $\Z$--modules by discussing the icosian ring.Comment: 6 pages, conference "Quasicrystals - The Silver Jubilee