Sequencing inputs to multi-commodity pipelines

This paper examines the problem of sequencing the input of commodities, e.g. petroleum products, to a pipeline so that a surrogate for pumping and maintenance costs is minimized. This problem is complicated by the need to impose a discrete framework which handles the sequencing choices on a continuous flow problem. By focusing on the discrete aspects of the problem, the proposed model allows decomposition of the sequencing problem into subproblems which can be easily priced out in a branch-and-bound algorithm. Computational results on data generated to mimic a large U.S. petroleum pipeline are presented. These results show that the branch-and-bound algorithm only explores a small region of the solution space within a reasonable amount of time, less than 2.5 minutes to optimally sequence deliveries to twenty-four destinations.     

Emission cross sections for the laser lines of I+ by electron-I2-molecule collisions

We have measured the emission cross sections for the fifteen spectral lines of I⁺ by single electron impact on I₂ molecules, which include the laser lines of the positive column He-I⁺ laser. The measured values are of the order of 10^-19 to 10^-20 cm².     

Rigorous reflectance performance analysis of Si3N4 self-suspended subwavelength gratings

In this paper, we make an investigation into the reflectance performance of the Si₃N₄ self-suspended subwavelength grating (SSG) via changing several parameters including the incident wavelength, the grating period, the grating thickness and the grating filling ratio. For TM polarization of incidence, numerical results by the rigorous coupled-wave method reveal that the reflectance spectrum of the Si₃N₄ SSG has a narrow linewidth (less than 1 nm), high peak reflectance (100%), and low side bands (less than 0.5%) simultaneously in the optical telecommunication wavelength region. By using a micro-electromechanical-systems actuator, it is believed that the Si₃N₄ SSG should serve as tunable optical filters in optical telecommunication systems.     

Direct observation of double diffraction patterns

The double diffraction light intensity of two identical gratings placed parallel in the Fresnel region is sensitive to the lateral displacement ΔX, and is also affected by the air gap R between the gratings. In this note, the dependence of the double diffraction light intensity on ΔX and R for each order beam has been obtained directly by observing the intensity pattern on a screen.     

Broadband antireflection gratings fabricated upon silicon substrates

We fabricated a two-dimensional subwavelength structured (SWS) surface upon a crystal silicon substrate. The SWS surface was patterned by electron beam lithography and etched by an SF(6) fast atom beam. The SWS grating had a conical profile, the period was 150 nm, and the groove was approximately 350 nm deep. The reflectivity was examined at 2002500-nm wavelengths. At 400 nm the reflectivity decreased to 0.5% from the 54.7% of the silicon substrate. We also used HeNe laser light to examine the reflectivity as a function of the incident angle.     

Fabrication of ultrathin color filters for three primary colors using guided-mode resonance in silicon subwavelength gratings

We fabricate reflection color filters for three primary colors using silicon two-dimensional triangular-lattice subwavelength gratings on the same quartz substrate. The grating periods are 480, 390, and 300 nm for red, green, and blue filters, respectively. All of the color filters have the same thickness of 100 nm, which enables the simple fabrication of a color filter array. Maximum reflectances of 75 and 46% are obtained at wavelengths of 647.1 and 522.1 nm for the red and green filters, respectively. The blue filter has a double-peaked spectrum with a reflectance of 30% at the peak wavelengths of 450.0 and 502.7 nm. By rigorous coupled-wave analysis, the dimensions of each color filter are designed, and the calculated theoretical reflectance is compared with the measured one.