Robust scheduling practices in the U.S. airline industry: Costs, returns, and inefficiencies

Airlines use robust scheduling to mitigate the impact of unforeseeable disruptions on profits. We examine how effectively three common practices—flexibility to swap aircraft, flexibility to reassign gates, and scheduled aircraft downtime—accomplish this goal. We first estimate a multiple-input, multiple-outcome production frontier, which defines the attainable set of outcomes from given inputs. We then recover unobserved input costs and calculate how expenditure on inputs affects outcomes and revenues. We find that the per-dollar return from expenditure on gates, or more effective management of existing gate capacity, is three times larger than the per-dollar returns from other inputs. Next, we use the estimated trade-offs faced by carriers along the frontier to measure the value to carriers of reducing delays. Finally, we calculate the improvement in carriers’ outcomes and profits if their operational inefficiencies are eliminated. On average, we estimate that operational inefficiencies cost carriers about $1.7 billion in revenue annually

Exchange in silicon-based quantum computer architecture

The silicon-based quantum computer proposal has been one of the intensely pursued ideas during the past three years. Here we calculate the donor electron exchange in silicon and germanium, and demonstrate an atomic-scale challenge for quantum computing in Si (and Ge), as the six (four) conduction band minima in Si (Ge) lead to inter-valley electronic interferences, generating strong oscillations in the exchange splitting of two-donor two-electron states. Donor positioning with atomic scale precision within the unit cell thus becomes a decisive factor in determining the strength of the exchange coupling--a fundamental ingredient for two-qubit operations in a silicon-based quantum computer.Comment: 5 pages, 2 figure

Double Hole Cyclotron-Resonance in Zero-Gap HgTe-CdTe Superlattices

Magnetic-field-dependent band structures for HgTe-CdTe superlattices with zero band gap have been calculated by the transfer-matrix method. We find that there is an unusual mixing of cyclotron resonance and interband transitions. The analysis predicts that the hole cyclotron resonance should display two peaks corresponding to transitions in different regions of the Brillouin zone. Agreement with recent data showing a double peak in the Faraday geometry is quite good

Man on a mission for waste to wealth transformation

Shri. Ramdas Tukaram Kokare, presently working as Chief Officer in Municipal Corporation, Karjat which has a total population of 30,000 and generates Class III Municipal Solid Waste (MSW) in the tune of 12 metric tonnes per day. Earlier during 2010 to 2015 he had served as Chief Officer at Municipal Corporation Dapoli, Maharashtra and during 2015-2017 he at Vengurla also in Maharashtra. In 2010, Shri Ramdas came up with the idea of waste management at the source level and decided to segregate plastic waste into recyclable and non-recyclable categories. Plastic carry bags of less than 50 micron thickness were in the non-recyclable category, while bottles, packaging material of food items and wrappers were to be recycled for further usage. Local self-help groups were roped in to produce paper bags and some awareness campaigns were organized

Experimental evidence of strong phonon scattering in isotopical disordered systems: The case of LiH_xD_{1-x} crystals

The observation of the local - mode vibration, the two - mode behavior of the LO phonons at large isotope concentration, as well as large line broadening in LIH - D mixed crystals directly evidence strong additional phonon scattering due to the isotope - induced disorder.Comment: 9 pages, 4 figure

Incidence of glaucomatous visual field loss after two decades of follow-up: the Rotterdam Study

To determine the incidence of glaucomatous visual field loss (GVFL) two decades after the start of the Rotterdam Study, and to compare known risk factors for open-angle glaucoma (OAG) between different clinical manifestations of OAG. Of 6806 participants aged 55 years and older from the population-based Rotterdam Study, 3939 underwent visual field testing at baseline and at least one follow-up round. The ophthalmic examinations included optic disc assessment and measurements of intraocular pressure (IOP), refractive error, diastolic blood pressure (DBP), and height and weight. The incidence rate of GVFL was calculated. Associations with the risk factors age, gender, baseline IOP, family history, myopia, DBP, and body-mass index [BMI] were assessed using Cox regression, with different clinical manifestations of OAG as outcome measure (glaucomatous optic neuropathy (GON), GVFL, GVFL and GON, GVFL without GON, and GON without GVFL). Median follow-up was 11.1 (IQR 6.8–17.2; range 5.0–20.3) years. The incidence rate of GVFL was 2.9 (95% confidence interval 2.4–3.4) per 1000 person years (140 cas

Infrared Nonlinear Optics

Contains report on one research project.U.S. Air Force - Office of Scientific Research (Contract F49620-80-C-0008

Evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu1−x_{1-x}Gdx_{x}O

Raman scattering studies as functions of temperature, magnetic field, and Gd-substitution are used to investigate the evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu$_{1-x}$Gd$_{x}$O. These studies reveal a greater richness of phase behavior than have been previously observed using transport measurements: a spin-fluctuation-dominated paramagnetic (PM) phase regime for T $>$ T$^{*}$ $>$ T$_{C}$, a two-phase regime for T $<$ T$^{*}$ in which magnetic polarons develop and coexist with a remnant of the PM phase, and an inhomogeneous ferromagnetic phase regime for T $<$ T$_{C}$

Gems: Objects of aesthetic beauty and scientific curiosity

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