Task Scheduling for Context Minimization in Dynamically Reconfigurable Platforms

Dynamically reconfigurable hardware provides useful means to reduce the time-to-prototype and even the time-to-market in product designs. It also offers a good alternative in reconfiguring hardware logics to optimize the system performance. This paper targets an essential issue in reconfigurable computing, i.e., the minimization of configuration contexts. We explore different constraints on the CONTEXT MINIMIZATION problem. When the resulting subproblems are polynomial-time solvable, optimal algorithms are presented. We also present a greedy algorithm for the CONTEXT MINIMIZATION problem, that is proved NP\mathcal{NP}-complete. The capability of the proposed algorithm is evaluated by a series of experiments.     

Numerical predictions of design and operating parameters of reformer on the fuel conversion and CO production for the steam reforming of methanol

SIMPLE-C algorithm and Arrhenius form of reaction model were employed to simulate the three-dimensional laminar flow field and the chemical reaction in a cylindrical methanol reformer under steam reforming. The effects of geometrical and thermo-fluid parameters on the CO and CO₂ productions as well as the heat and mass transfer in a cylindrical methanol reformer with a constant-volume catalyst bed will be observed in the present study. Low CO concentration in hydrogen-rich gas denotes a low load of CO removal in purifying processes. The results indicate that the smaller diameter-to-length ratio of chamber with a thicker catalyst bed enhances the methanol conversion and reduces the overall CO concentration in the cylindrical methanol reformer. This is because that a lower temperature distribution restrains the reverse water–gas-shift reaction to reduce the production of CO with a thicker catalyst bed.     

Nano-structured Cu2O solar cells fabricated on sparse ZnO nanorods

Nano-structured Cu₂O/ZnO nanorod (NR) heterojunction solar cells fabricated on indium tin oxide (ITO)-coated glass are studied. Substrate film and NR density have a strong influence on the preferred growth of the Cu₂O film. The X-ray diffractometer (XRD) analysis results show that highly (2 0 0)-preferred Cu₂O film was formed when plating on plain ITO substrate. However, a highly (1 1 1)-preferred Cu₂O film was obtained when plating on sparse ZnO NRs. SEM, TEM and XRD studies on sparse NR samples indicate that the Cu₂O nano-crystallites mostly initiate its nucleation on the peripheral surfaces of the ZnO NRs, and are also highly (1 1 1)-oriented. Solar cells with ZnO NRs yielded much higher efficiency than those without. In addition, ZnO NRs plated on a ZnO-coated ITO glass significantly improve the shunt resistance and open-circuit voltage (V_oc) of the devices, with consistently much higher efficiency obtained than when ZnO NRs are directly plated on ITO film. However, longer NRs do not improve the efficiency due to low short-circuit current (J_sc) and slightly higher series resistance. The best conversion efficiency of 0.56% was obtained from a Cu₂O/ZnO NRs heterojunction solar cell fabricated on a 80 nm ZnO-coated ITO glass with V_oc=0.514 V, J_sc=2.64 mA/cm² and 41.5% fill factor.     

Crystalline Gaq3 Nanostructures: Preparation, Thermal Property and Spectroscopy Characterization

Crystalline Gaq₃ 1-D nanostructures and nanospheres could be fabricated by thermal evaporation under cold trap. The influences of the key process parameters on formation of the nanostructures were also investigated. It has been demonstrated that the morphology and dimension of the nanostructures were mainly controlled by working temperature and working pressure. One-dimensional nanostructures were fabricated at a lower working temperature, whereas nanospheres were formed at a higher working temperature. Larger nanospheres could be obtained when a higher working pressure was applied. The XRD, FTIR, and NMR analyses evidenced that the nanostructures mainly consisted of δ-phase Gaq₃. Their DSC trace revealed two small exothermic peaks in addition to the melting endotherm. The one in lower temperature region was ascribed to a transition from δ to β phase, while another in higher temperature region could be identified as a transition from β to δ phase. All the crystalline nanostructures show similar PL spectra due to absence of quantum confinement effect. They also exhibited a spectral blue shift because of a looser interligand spacing and reduced orbital overlap in their δ-phase molecular structures.     

Environmentally assisted cracking of two-phase Fe-Mn-Al alloys in NaCl solution

Three two-phase Fe-Mn-Al alloys with nominal compositions, Fe-24Mn-9Al, Fe-27Mn-9Al-3Cr,. and Fe-27Mn-9Al-6Cr, were prepared in the solution-treated and cold-rolled conditions. The fractions of ferrite in the solution-treated condition were controlled at 46 to 60 pct, mainly by adjusting the carbon content and the relative amounts of Mn and Al. The ferrite fractions were reduced to 30 to 37 pct after 75 pct deformation by cold-rolling. Specimens were tensile tested at open circuit in aerated 3.5 pct NaCl solution at slow strain rates ranging from 4 × 10^-7 to 4 × 10^-5 s^-1 at room temperature. All of the alloys were quite susceptible to environmentally assisted cracking (EAC). The deformed specimens showed less susceptibility, presumably because the plasticity was already too limited. The EAC appeared to occur at or after the onset of plastic deformation. In this alloy system, the ferritic phase was less resistant to EAC than the austenitic phase, in contrast to the Fe-Cr-Ni stainless steels. The crack propagated preferentially through the ferrite grains or along the ferrite/austenite grain boundaries. The addition of up to 6 pct Cr did not improve the EAC resistance. Formerly Graduate Student, Department of Materials Science and Engineering, National Tsing Hua University     

Genetic algorithm-based decision support for the restoration budget allocation of historical buildings

Historical building preservation is becoming increasingly important world-wide due to the emphasis on cultural heritage and its potential benefits. Restoration management and cost allocation for these valuable buildings have been constant concerns. This study discusses problems concerning restoration budget allocation for historical buildings of the Tainan local government. A new contracting method based on genetic algorithm (GA) is presented to support decision makers in determining the optimal budget allocation and relevant contracting methods. Compared with traditional contracting methods, the result of a pilot test shows that the new method provides more effective and economical decision suggestions. Lessons learned in Tainan city could be useful for many other cities that are facing similar problems.     

Effect of quenching temperature on the morphology and separation properties of polypropylene microporous tubular membranes via thermally induced phase separation

Polypropylene microporous tubular membranes were prepared by using camphene as solvent and through thermally induced phase separation at various quenching temperatures. Characterization of the resulting membrane included scanning electron microscopy, differential scanning calorimetry, and wide angle X-ray scattering. Microscopic observation showed that the membrane was composed of spherical clusters and had a leafy structure. The crystallinity increased with the quenching temperature. The crystalline structure was of smectic form. Permeation performance was also determined, including pure water permeability and retention of dextran. The results showed that at lower quenching temperatures, the structure of membrane was denser. Therefore, the permeability was lower and the retention was higher.     

One-dimensional organic and organometallic nanostructured materials

One-dimensional (1D) organic and organometallic nanomaterials are of considerable interests for both fundamental research and potential applications. They are likely to play critical roles in improving the efficiency of various electronic, photonic, biosensing devices, etc. In this context, the authors present a comprehensive review of current research on 1D organic and organometallic nanostructures. The synthetic strategies for achieving the 1D growth are elucidated by four categories: (1) template-based synthesis, (2) vapor-solid method, (3) solution-based self-assembly, and (4) dictation by the anisotropic nature. The unique thermal, optical, electronic, field emission properties and biocidal activity of 1D organic and organometallic nanostructures are consequently highlighted. Some promising applications in (integrated) molecular electronic, optoelectronic and photonic devices are also discussed.