Evaluating POS tagging under sub-optimal conditions : or: does meticulousness pay?

In this paper, we investigate the role of sub-optimality in training data for part-of-speech tagging. In particular, we examine to what extent the size of the training corpus and certain types of errors in it affect the performance of the tagger. We distinguish four types of errors: If a word is assigned a wrong tag, this tag can belong to the ambiguity class of the word (i.e. to the set of possible tags for that word) or not; furthermore, the major syntactic category (e.g. "N" or "V") can be correctly assigned (e.g. if a finite verb is classified as an infinitive) or not (e.g. if a verb is classified as a noun). We empirically explore the decrease of performance that each of these error types causes for different sizes of the training set. Our results show that those types of errors that are easier to eliminate have a particularly negative effect on the performance. Thus, it is worthwhile concentrating on the elimination of these types of errors, especially if the training corpus is large

Microfluidic detection and analysis by integration of thermocapillary actuation with a thin-film optical waveguide

We demonstrate a nonintrusive optical method for microfluidic detection and analysis based on evanescent wave sensing. The device consists of a planar thin-film waveguide integrated with a microfluidic chip for directed surface flow. Microliter droplets are electronically transported and positioned over the waveguide surface by thermocapillary actuation. The attenuated intensity of propagating modes is used to detect droplet location, to monitor dye concentration in aqueous solutions, and to measure reaction rates with increasing surface temperature for a chromogenic biochemical assay. This study illustrates a few of the capabilities possible by direct integration of optical sensing with surface-directed fluidic devices

Generation of high-resolution surface temperature distributions

We have performed numerical calculations to study the generation of arbitrary temperature profiles with high spatial resolution on the surface of a solid. The characteristics of steady-state distributions and time-dependent heating and cooling cycles are examined, as well as their dependence on material properties and device geometry. Ideally, low-power consumption and fast response times are desirable. The simulations show that the achievable spatial resolution is on the order of the substrate thickness and that the response time t+ depends on the width of the individual heating elements. Moreover, the rise time t+ can be significantly shortened by deposition of a thermal insulation layer, which also reduces the power consumption and increases lateral resolution

Direct printing of polymer microstructures on flat and spherical surfaces using a letterpress technique

We have developed a letterpress technique capable of printing polymer films with micrometer scale feature sizes onto flat or spherically shaped nonporous substrates. This printing technique deposits polymer only in desired regions thereby eliminating subsequent developing and subtraction steps. Flat or curved printing plates, which are fabricated from either rigid or deformable materials, are used to transfer thin molten polymer films onto flat target substrates. By deforming the printing plates into a spherical shape, it is also possible to print patterned films onto the concave side of a spherically deformed target substrate. These printed films serve as good resists for both wet chemical etching and reactive ion etching. Interferometric measurements of the polymer film thickness are used to probe physical mechanisms affecting printing instabilities, pattern fidelity, and edge resolution. Our experimental study indicates that this letterpress technique may prove suitable for high-throughput device fabrication involving large-area microelectronics

Photoresist-free printing of amorphous silicon thin-film transistors

Conventional fabrication of amorphous silicon thin-film transistors (a-Si TFTs) requires patterning numerous photoresist layers, a subtractive process that is time consuming and expensive. This letter describes transistor fabrication by a photoresist-free approach in which polymer etch masks are letterpress printed from flexible polyimide stamps. Pattern registration is achieved through optical alignment since the printed masks are thin and optically transparent. This modified fabrication scheme produces transistor performance equivalent to conventionally fabricated a-Si TFTs. The ability to directly print etch masks onto nonhomogeneous substrates brings one step closer the realization of flexible, large-area, macroelectronic fabrication

Physical mechanisms governing pattern fidelity in microscale offset printing

We have studied the offset printing of liquid polymers curable by exposure to ultraviolet light onto flat and unpatterned silicon and glass substrates. The interplay of capillary, viscous, and adhesion forces dominates the dynamics of ink transfer at small feature sizes and low capillary number. For smooth and nonporous substrates, pattern fidelity can be compromised because the ink contact lines are free to migrate across the substrate during plate separation. Using a combination of experiments and equilibrium simulations, we have identified the physical mechanisms controlling ink transfer and pattern fidelity. In considering the resolution limit of this technique, it appears that the dynamics of ink flow and redistribution during transfer do not explicitly depend on the absolute feature size, but only on the aspect ratio of film thickness to feature size. Direct printing holds promise as a high-throughput fabrication method for large area electronics

De Internationale Bauausstellung in Berlijn (1957)

The 1957 Berlin Interbau, the international building exhibition, represented an array of superlatives, beginning with its size. When German Federal President Theodor Heuss opened the show on 6 July 1957, the newly built Hansaviertel was presented and thus for the first time an entire new city district as a component of an architectural exhibition. Centrally located in the heart of Berlin, across an area of 25 ha, a total of 1,300 dwellings were established along with community facilities, including two churches, a library, a retail centre and a school (which was built outside the official exhibition zone). In other words, a miniature model city was created within a city centre, an unprecedented step for a German building exhibition. Besides the size of the exhibition area and the model-city character of the demonstration district, the large number of prominent national and international architects who took part was likewise unique. A total of 53 architects from 14 different countries presented their experimental designs, primarily for public sector housing. In addition, there were experiments with a whole range of different residential building types: tower blocks with 16 to 17 storeys, apartment blocks with seven to nine storeys, rows of apartments with three to four storeys and detached and interlinked single-family houses. Eye-catchers were the high-rise buildings with split-level homes by J.B. Bakema and J.H. van den Broek, Walter Gropius’s lightly curved nine-storey apartment block, and Brazilian Oscar Niemeyer’s seven-storey flats, which stood on V-shaped pilotis. Finland’s Alvar Aalto came up with a hybrid tower block and apartment building that was erected close to the flats created by Sweden’s Sten Samuelson and Fritz Jaenecke, as well as Frenchman Pierre Vago’s building. Outside the exhibition zone, other highlights were the Berlin version of Le Corbusier’s Unité d’habitation and Hugh Stubbins’ Kongresshalle, which the Americans gifted to Interbau.1 In addition to the architecture of the buildings, the Hansaviertel’s urban context emphasized the exhibition zone’s character as a model city. Once a densely built residential district with its blocks of houses aligned to the streets, property division no longer played a role in the urban design and concentration of the residential volumes gave rise to large communal green zones. Interbau was a huge success in terms of the number of visitors. Over 1.3 million members of the general public and professionals visited the exhibition, many of them from East Berlin and abroad. However, the favourable reception from the general public and the publicity the Hansaviertel buildings received was in sharp contrast to the largely negative judgement passed on the urban design concept by the architectural world at large. The most frequent criticism voiced was that ‘the exhibition lacked an idea, an underlying concept’.2 The Hansaviertel was accused of being merely a platform for showcasing individual buildings by prominent architects, without a trace of convincing urban design coherence. The Bauwelt trade journal commented in resignation that perhaps the only successful idea was ‘the presentation of the top architects themselves’,3 and that it was ‘an array of missed opportunities, due to the lack of an urban design concept’.4 While preparations were still underway, Sigfried Giedion, CIAM’s Secretary, advised the Berlin Bausenator to prevent ‘an urban design disaster at so prominent a location’.De Internationale Bauausstellung ‘Interbau’ in Berlijn was er een van superlatieven, op de eerste plaats vanwege de omvang. Toen de West- Duitse bondspresident Theodor Heuss op 6 juli 1957 de opening verrichtte, werd met de nieuwbouw van het Hansaviertel voor het eerst een compleet nieuwe stadswijk als onderdeel van een architectuurtentoonstelling gepresenteerd. Op een oppervlakte van 25 ha, centraal gelegen in de binnenstad van Berlijn, werden in combinatie met openbare voorzieningen, zoals twee kerken, een bibliotheek, een winkelcentrum en een school (die buiten de officiële locatie van de tentoonstelling werd gebouwd) in totaal 1.300 wooneenheden gerealiseerd. Zo ontstond er in binnenstedelijk gebied een modelstad in het klein, iets wat in deze vorm nog nooit op een Duitse architectuurtentoonstelling te zien was geweest. Niet alleen de omvang van het tentoonstellingsterrein en het modelmatige karakter van deze demonstratiewijk waren ongekend, er was ook een nooit eerder vertoond aantal prominente architecten uit binnen- en buitenland bij betrokken: in totaal 53 architecten uit 14 landen toonden er hun experimentele ontwerpen, hoofdzakelijk voor sociale woningbouw. Verder werd er geëxperimenteerd met allerlei gebouwtypen: woontorens van 16, 17 lagen, flatgebouwen van zeven tot negen lagen, woonblokken van drie tot vier lagen en vrijstaande of geschakelde gezinshuizen. Blikvangers waren de torens met split-level woningen van J.B. Bakema en J.H. van den Broek; het negen verdiepingen hoge, licht gebogen flatgebouw van Walter Gropius en de zeven verdiepingen hoge, op V-vormige pilotis rustende flat van Oscar Niemeyer. Alvar Aalto kwam met een tussenvorm van woontoren en flat, die in de buurt verrees van het flatgebouw van de Zweden Sten Samuelson en Fritz Jaenecke en die van de Fransman Pierre Vago. Buiten het tentoonstellingsterrein trokken ook de Berlijnse versie van Le Corbusier’s Unité d’habitation en de congreshal van Hugh Stubbins, een geschenk van de Amerikanen aan Interbau, de aandacht.1 Naast de gebouwen, droeg ook de stedenbouwkundige setting van het Hansaviertel sterk bij aan het modelmatige karakter van de tentoonstellingslocatie. De voormalige dichtbebouwde woonwijk met zijn huizenblokken aan straten werd vervangen door een wijk waar parcellering geen rol meer speelde en waar door een concentratie van bouwmassa’s meer ruimte was voor openbaar groen. Interbau bleek een groot succes vanwege het bezoekersaantal: ruim 1,3 miljoen mensen, zowel leken als vakpubliek, kwamen op de expositie af, onder wie ook velen uit Oost-Berlijn en het buitenland. Maar tegenover die positieve ontvangst bij het algemene publiek en de grote aandacht die de gebouwen van het Hansaviertel te beurt vielen, stond het negatieve oordeel van de vakwereld over het stedenbouwkundig concept. Het meest geuite kritiekpunt was dat ‘de idee – de dragende gedachte achter de architectuurtentoonstelling’ ontbrak.2 Het Hansaviertel zou slechts een platform zijn waarop gerenommeerde architecten losse bouwwerken presenteerden, zonder dat er ook maar een overtuigende stedenbouwkundige samenhang in te ontdekken viel. Gelaten constateerde het vaktijdschrift Bauwelt dat de enige geslaagde idee eventueel de ‘presentatie van de toparchitecten zelf was’.3 Het zou ‘een parade van gemiste kansen zijn, door het ontbreken van een stedenbouwkundig concept’.4 De secretaris van CIAM, Sigfried Giedion, gaf de Berlijnse Bausenator nog tijdens de voorbereidingen het advies om een ‘stedenbouwkundige catastrofe op zo’n prominente locatie’ te voorkomen

Using convective flow splitting for the direct printing of fine copper lines

Liquid ribbons of solutions of copper hexanoate in a volatile solvent were drawn on a glass slide using either fine glass capillaries or an ink jet printer. After solvent evaporation, the solute was observed to segregate into multiple pairs of stripes much narrower than the initial ribbon diameter. These stripes were then converted to pure copper by annealing. Surface profiles indicate that the thickness, width, and number of lines formed are strongly dependent on the solution viscosity and volume per unit length deposited. From flow visualization studies and surface profiling, we have found that evaporative cooling produces Bénard–Marangoni convection patterns which accrete the solute along two key boundaries of the flow, namely the three phase contact line and the outer edge of a stagnant region about the ribbon apex. These findings suggest that optimization of the deposition and evaporation process can be used to "write" fine metallic lines from a wider liquid precursor

Morphology of liquid microstructures on chemically patterned surfaces

We study the equilibrium conformations of liquid microstructures on flat but chemically heterogeneous substrates using energy minimization computations. The surface patterns, which establish regions of different surface energy, induce deformations of the liquid–solid contact line. Depending on the geometry, these deformations either promote or impede capillary breakup and bulge formation. The contact angles of the liquid on the hydrophilic and hydrophobic regions, as well as the pattern geometry and volume of liquid deposited, strongly affect the equilibrium shapes. Moreover, due to the small scale of the liquid features, the presence of chemical or topological surface defects significantly influence the final liquid shapes. Preliminary experiments with arrays of parallel hydrophilic strips produce shapes resembling the simulated forms. These encouraging results provide a basis for the development of high resolution lithography by direct wet printing

Effect of contact angle hysteresis on thermocapillary droplet actuation

Open microfluidic devices based on actuation techniques such as electrowetting, dielectrophoresis, or thermocapillary stresses require controlled motion of small liquid droplets on the surface of glass or silicon substrates. In this article we explore the physical mechanisms affecting thermocapillary migration of droplets generated by surface temperature gradients on the supporting substrate. Using a combination of experiment and modeling, we investigate the behavior of the threshold force required for droplet mobilization and the speed after depinning as a function of the droplet size, the applied thermal gradient and the liquid material parameters. The experimental results are well described by a hydrodynamic model based on earlier work by Ford and Nadim. The model describes the steady motion of a two-dimensional droplet driven by thermocapillary stresses including contact angle hysteresis. The results of this study highlight the critical role of chemical or mechanical hysteresis and the need to reduce this retentive force for minimizing power requirements in microfluidic devices