Sub-nanosecond silicon-on-insulator optical micro-ring switch with low crosstalk

We demonstrate a sub-nanosecond electro-optical switch with low crosstalk in a silicon-on-insulator (SOI) dual-coupled micro-ring embedded with p-i-n diodes. A crosstalk of -23 dB is obtained in the 20-mu m-radius micro-ring with the well-designing asymmetric dual-coupling structure. By optimizations of the doping profiles and the fabrication processes, the sub-nanosecond switch-on/off time of < 400 ps is finally realized under an electrical pre-emphasized driving signal. This compact and fast-response micro-ring switch, which can be fabricated by complementary metal oxide semiconductor (CMOS) compatible technologies, have enormous potential in optical interconnects of multicore networks-on-chip.

Dispersion-compensating photonic crystal fibers with special characteristics

Based on the modified dual core structure, three kinds of special photonic crystal fibers are presented, which are extremely large negative dispersion, super-broad bond, and large area made field dispersion-compensating photonic crystal fibers (DCPCF). For extremely large negative dispersion DCPCF, the peak of negative dispersion reaches -5.9 x 10(4) ps/(mn km). Super-broad bond DCPCF has broadband large negative dispersion and the dispersion value varies linearly from -380 ps/(nm km) to -420 ps/(nm km) in the C band. The designed large area made field DCPCF has a peak dispersion of -1203 ps/(nm km) with the inner core mode area of 47 mu m(2) and outer core mode area of 835 mu m(2). Furthermore, for the large area mode field DCPCF, the experimental result is also obtained. (C) 2008 Wiley Periodicals, Inc.

A composite polymer film with both superhydrophobicity and superoleophilicity

A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual-scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an 'intelligent' wettability property can be utilized to separate oil and water systems efficiently.

Inclusive teaching practice in the Jewish day school: general studies teachers' experiences /

Little research has been done on inclusive education in the context of the Jewish day school general studies classroom. This qualitative case study research examines the inclusive teaching experiences of 2 general studies teachers in their respective grade 4 classrooms in 2 traditionally structured dual curriculum Jewish day schools. Data analysis of qualitative open-ended interviews, classroom observations, postobservation discxissions, and school and formal curriculum documents yielded understandings about the participants' inclusive practice and the challenges of the traditional Jewish day school structure. Eight themes that emerged related to understandings and questions about time limitations, an emphasis on efficiency, the day school structure, inclusion models, the need for increased teacher collaboration, and tension between curriculum-as-plan and curriculum-as-lived. Discussion of the findings suggests the need for further research in inclusion and integrated curriculimi in order to better understand possible restructuring of the traditional Jewish day school fi-om the time efficiency constrained dual curriculiun structure to a more flexible structure conducive of a meaningful and dynamic lived curriculum.

Influência do tratamento térmico sobre a tenacidade de um aço com AISI SAE 1045 com médio teor de carbono, avaliada por ensaios de impacto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização mecânica e microestrutural de um aço de baixo carbono

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

RF-sputter fabrication of magnetic garnet thin films and simulation modeling for 1-D magnetic photonic crystal waveguide devices

One dimensional magnetic photonic crystals (1D-MPC) are promising structures for integrated optical isolator applications. Rare earth substituted garnet thin films with proper Faraday rotation are required to fabricate planar 1D-MPCs. In this thesis, flat-top response 1D-MPC was proposed and spectral responses and Faraday rotation were modeled. Bismuth substituted iron garnet films were fabricated by RF magnetron sputtering and structures, compositions, birefringence and magnetooptical properties were studied. Double layer structures for single mode propagation were also fabricated by sputtering for the first time. Multilayer stacks with multiple defects (phase shift) composed of Ce-YIG and GGG quarter-wave plates were simulated by the transfer matrix method. The transmission and Faraday rotation characteristics were theoretically studied. It is found that flat-top response, with 100% transmission and near 45o rotation is achievable by adjusting the inter-defect spacing, for film structures as thin as 30 to 35 μm. This is better than 3-fold reduction in length compared to the best Ce-YIG films for comparable rotations, thus allows a considerable reduction in size in manufactured optical isolators. Transmission bands as wide as 7nm were predicted, which is considerable improvement over 2 defects structure. Effect of repetition number and ratio factor on transmission and Faraday rotation ripple factors for the case of 3 and 4 defects structure has been discussed. Diffraction across the structure corresponds to a longer optical path length. Thus the use of guided optics is required to minimize the insertion losses in integrated devices. This part is discussed in chapter 2 in this thesis. Bismuth substituted iron garnet thin films were prepared by RF magnetron sputtering. We investigated or measured the deposition parameters optimization, crystallinity, surface morphologies, composition, magnetic and magnetooptical properties. A very high crystalline quality garnet film with smooth surface has been heteroepitaxially grown on (111) GGG substrate for films less than 1μm. Dual layer structures with two distinct XRD peaks (within a single sputtered film) start to develop when films exceed this thickness. The development of dual layer structure was explained by compositional gradient across film thickness, rather than strain gradient proposed by other authors. Lower DC self bias or higher substrate temperature is found to help to delay the appearance of the 2nd layer. The deposited films show in-plane magnetization, which is advantageous for waveguide devices application. Propagation losses of fabricated waveguides can be decreased by annealing in an oxygen atmosphere from 25dB/cm to 10dB/cm. The Faraday rotation at λ=1.55μm were also measured for the waveguides. FR is small (10° for a 3mm long waveguide), due to the presence of linear birefringence. This part is covered in chapter 4. We also investigated the elimination of linear birefringence by thickness tuning method for our sputtered films. We examined the compressively and tensilely strained films and analyze the photoelastic response of the sputter deposited garnet films. It has been found that the net birefringence can be eliminated under planar compressive strain conditions by sputtering. Bi-layer GGG on garnet thin film yields a reduced birefringence. Temperature control during the sputter deposition of GGG cover layer is critical and strongly influences the magnetization and birefringence level in the waveguide. High temperature deposition lowers the magnetization and increases the linear birefringence in the garnet films. Double layer single mode structures fabricated by sputtering were also studied. The double layer, which shows an in-plane magnetization, has an increased RMS roughness upon upper layer deposition. The single mode characteristic was confirmed by prism coupler measurement. This part is discussed in chapter 5.

A novel carbonic anhydrase from the giant clam Tridacna gigas contains two carbonic anhydrase domains

This report describes the presence of a unique dual domain carbonic anhydrase (CA) in the giant clam, Tridacna gigas. CA plays an important role in the movement of inorganic carbon (C-i) from the surrounding seawater to the symbiotic algae that are found within the clam's tissue. One of these isoforms is a glycoprotein which is significantly larger (70 kDa) than any previously reported from animals (generally between 28 and 52 kDa). This alpha-family CA contains two complete carbonic anhydrase domains within the one protein, accounting for its large size; dual domain CAs have previously only been reported from two algal species. The protein contains a leader sequence, an N-terminal CA domain and a C-terminal CA domain. The two CA domains have relatively little identity at the amino acid level (29%). The genomic sequence spans in excess of 17 kb and contains at least 12 introns and 13 exons. A number of these introns are in positions that are only found in the membrane attached/secreted CAs. This fact, along with phylogenetic analysis, suggests that this protein represents the second example of a membrane attached invertebrate CA and it contains a dual domain structure unique amongst all animal CAs characterized to date.

A gyenge hazai innovációs teljesítmény intézményi magyarázatához. Vitaírás a nemzetközi innovációs versenyben való részvétel akadályairól (Towards an institutional explanation of the country's weak innovation performance)

Miért van a magyar gazdaság hasonlóan kritikus helyzetben, mint a rendszerváltást megelőző időkben? Miért nem sikerül az eladósodást megállítani, a gazdaságot konszolidálni, és fenntartható növekedési pályára állítani? Ennek közvetlen okát a szerzők a fejlődés féloldalasságában és a duális gazdasági szerkezetben látják. A piacgazdasági intézmények bevezetése ugyanis nem járt együtt az egész gazdaságot (vagy legalábbis annak nagy részét) átfogó, a tudásvezérelt információgazdaság felé mutató, gyors fejlődéssel. Számos indikátor azt jelzi, hogy az ország lemaradt a nemzetközi innovációs versenyben. Az innovációk elégtelensége azonban nem véletlen, nem exogén adottság, hanem a formális piaci intézmények mögött meghúzódó valós intézményi berendezkedéssel, a gazdaságban ténylegesen észlelhető magatartásmintákkal magyarázható. A piacgazdasági intézmények és jogi keretek, amelyek elvileg lehetőséget adnak az erőforrásokhoz való szabad és nyílt hozzáférésre, csak részben töltődtek meg tartalommal. Az országban még mindig meglehetősen korlátozott a sikeres belépés lehetősége a piaci és a politikai arénába, azaz a magyar társadalom - a north-i terminológiával élve - "korlátozott hozzáférésre alapozott társadalomként" írható le. Az a tény, hogy a piaci szereplők esélyei az államhoz és intézményeihez fűződő kapcsolatoktól függően nagyban különböznek egymástól, és a gazdasági szereplők rendszerszerűen használják e kapcsolatokat járadékszerzésre, lefojtja az innovációt, és újra és újra megakasztja a fejlődést. / === / Why is Hungary's economy still in a critical state similar to the one before the change of system? Why is the indebtedness not being halted, the economy consolidated or vital structural reforms performed? The authors see the direct cause in lopsided development and a dual economic structure. The introduction of market economic institutions was not followed by rapid, overall development towards a knowledge-led, information economy. Several indicators show how Hungary has fallen behind in competition for international innovation. The inadequacy is not a fortuitous, exogenous attribute, but explicable in terms of a real institutional setup underlying the formal market institutions, and of actual behaviour patterns found in the economy. Only in part has substance been gained by the institutions and legal frames of a market economy that theoretically would provide free and open access to resources. The scope for successful entry into the market or political arena remains very narrow, so that in Douglass North's terms, Hungary's is still "a society based on restricted access." Innovation is stifled and development repeatedly impeded by the fact that market players' chances differ widely depending on their connections with the state and its institutions and such connections are used regularly in rent-seeking.

Norms of inner derivations for multiplier algebras of C ∗ -algebras and group C ∗ -algebras, II

Peer reviewed

Norms of inner derivations for multiplier algebras of C ∗ -algebras and group C ∗ -algebras, II

Peer reviewed

Dual yolk-shell structure of carbon and silica-coated silicon for high-performance lithium-ion batteries

Silicon batteries have attracted much attention in recent years due to their high theoretical capacity, although a rapid capacity fade is normally observed, attributed mainly to volume expansion during lithiation. Here, we report for the first time successful synthesis of Si/void/SiO2/void/C nanostructures. The synthesis strategy only involves selective etching of SiO2 in Si/SiO2/C structures with hydrofluoric acid solution. Compared with reported results, such novel structures include a hard SiO2-coated layer, a conductive carbon-coated layer, and two internal void spaces. In the structures, the carbon can enhance conductivity, the SiO2 layer has mechanically strong qualities, and the two internal void spaces can confine and accommodate volume expansion of silicon during lithiation. Therefore, these specially designed dual yolk-shell structures exhibit a stable and high capacity of 956 mA h g−1 after 430 cycles with capacity retention of 83%, while the capacity of Si/C core-shell structures rapidly decreases in the first ten cycles under the same experimental conditions. The novel dual yolk-shell structures developed for Si can also be extended to other battery materials that undergo large volume changes.

A novel dual-wavelength DFB fiber laser based on symmetrical FBG structure

A novel grating structure is proposed and demonstrated to obtain stable dual-wavelength (DW) distributed-feedback (DFB) fiber lasers at room temperature. The proposed grating is based on a symmetrical structure, where one half is periodically sampled by "0"-to-"pi" period and the other half is done by "pi"-to-"0" period. This structure can create two separated resonance cavities and hence achieve the stable DW lasing operation. By fabricating the proposed grating on a piece of Er: Yb-codoped fiber, we experimentally obtain a stable DW-DFB fiber laser with wavelength spacing of similar to 440 pm at room temperature.

Dual-mode compact structure comprising of side-fed bifilar and quadrifilar helix antenna

A side-fed bifilar helix antenna can be integrated with a quadrifilar helix antenna in a piggy back configuration in order to achieve a dual-mode radiating structure. The overall length of the structure is 0.44 lambda at the resonant frequency (1.54 GHz) of the space mode antenna and 0.39 lambda at the resonant frequency (1.34 GHz) of the terrestrial mode antenna. The computed results are validated by experimental data.