Terahertz quantum plasmonics at nanoscales and angstrom scales

Through the manipulation of metallic structures, light-matter interaction can enter into the realm of quantum mechanics. For example, intense terahertz pulses illuminating a metallic nanotip can promote terahertz field-driven electron tunneling to generate enormous electron emission currents in a subpicosecond time scale. By decreasing the dimension of the metallic structures down to the nanoscale and angstrom scale, one can obtain a strong field enhancement of the incoming terahertz field to achieve atomic field strength of the order of V/nm, driving electrons in the metal into tunneling regime by overcoming the potential barrier. Therefore, designing and optimizing the metal structure for high field enhancement are an essential step for studying the quantum phenomena with terahertz light. In this review, we present several types of metallic structures that can enhance the coupling of incoming terahertz pulses with the metals, leading to a strong modification of the potential barriers by the terahertz electric fields. Extreme nonlinear responses are expected, providing opportunities for the terahertz light for the strong light-matter interaction. Starting from a brief review about the terahertz field enhancement on the metallic structures, a few examples including metallic tips, dipole antenna, and metal nanogaps are introduced for boosting the quantum phenomena. The emerging techniques to control the electron tunneling driven by the terahertz pulse have a direct impact on the ultrafast science and on the realization of next-generation quantum devices

Reliance, Immersion, and Enjoyment: An Exploratory Socio-Psychological Analysis on Internet Involvement

The purpose of this paper is to explore the relationships between various socio-psychological variables and the level of involvement in the Internet. Two hundred thirty-four college students completed a self-administered questionnaire that contains the measures of Internet involvement, Internet usage, face-to-face interaction anxiety, computer ownership, and socio-demographic variables. A factor analysis identified three dimensions of Internet involvement: Reliance, Immersion, and Enjoyment. The results of stepwise regressions showed that face-to-face interaction anxiety is a significant indicator of both the Reliance and Immersion dimensions of Internet involvement. Age was another positive indicator of the Immersion dimension, whereas computer ownership contributed significantly to the prediction of the Reliance dimension of Internet involvement. The Enjoyment dimension was not significantly affected by any of the independent variables

Blow-up behavior of solutions for some ordinary and partial differential equations

There are two parts in this project. Part 1 the Riccati initial-value problem is looked at. Part 2 considers blow-up property solutions for the degenerate semilinear parabolic initial-boundary value problem

A cost benefit analysis of Radio Frequency Identification (RFID) implementation at the Naval Postgraduate School's Dudley Knox Library

MBA Professional ReportThe purpose of this MBA project is to evaluate the potential of implementing Radio Frequency Identification (RFID) technology at the Naval Postgraduate School's Dudley Knox Library (DKL). DKL is an academic library supporting a graduate student population only. This study has both quantitative and qualitative analyses. A Cost Benefit Analysis (CBA) was conducted using data gathered from research which included personal interviews, site visits, and a survey questionnaire. Time and motion studies of selected library processes were conducted at DKL and a major public library. Vendors were invited to submit proposals for RFID systems to get the latest equipment available and associated cost estimates. The qualitative analysis addressed the advantages and disadvantages of an RFID system as well as privacy and other ancillary issues surrounding its implementation. This study did not attempt to quantify potential savings from collection management, an intangible benefit that could be addressed in future studies. Finally, the study presented several options to aid NPS decision makers on whether or not to implement an RFID system at DKL.http://archive.org/details/acostbenefitnaly1094510100US Navy (USN) authorApproved for public release; distribution is unlimited

Associations of multicultural status with depressive mood and suicidality among Korean adolescents: the roles of parental country of birth and socioeconomic position

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Background The mental health of the offspring of immigrants is a major public health concern. In this study, we examined associations of multicultural status and parental country of birth with adolescent mental health in South Korea, and assessed the effect of socioeconomic position (SEP) on these associations. Methods We used four waves of the Korea Youth Risk Behavior Web-based Survey (KYRBS) between 2011 and 2014, including 294,324 participants (149,219 boys and 145,105 girls aged 13–18 years) as study subjects. KYRBS is a cross-sectional survey conducted annually by the Korea Centers for Disease Control and Prevention. The participants in the KYRBS were drawn as stratified multistage clustered samples from Korean middle schools and high schools. We calculated the age-adjusted 12-month prevalence of depressive mood and suicidal behaviors by parental country of birth, and estimated the effects of SEP indicators on the relationship. Results The age-standardized prevalence of suicidality (suicide ideation, plans, and attempts) was significantly different between multicultural and non-multicultural boys. The impact of multicultural status on mental health varied with parental foreign-born status and maternal country of birth. Compared with non-multicultural counterparts, boys with Japan-born mothers showed lower prevalence ratios (PRs) of suicidal plans (PR = 0.34, 95% CI 0.16–0.70). Girls with Japan-born mothers also showed lower PRs of depressive mood (PR = 0.77, 95% CI 0.63–0.95) and suicidal ideation (PR = 0.59, 95% CI 0.41–0.83), while adolescents with Korean-Chinese mothers showed similar PRs. Boys with foreign-born fathers as well as boys with two foreign-born parents were at a greater risk of suicidality than non-multicultural boys. The magnitude of the relationship between multicultural status and mental health outcomes was generally attenuated after adjusting for SEP indicators. Conclusions In general, adolescents with Japan-born mothers showed lower PRs of depressive mood and suicidality than non-multicultural adolescents, while those with Korean-Chinese mothers showed similar PRs. Boys who had foreign-born fathers generally showed greater PRs of depressive mood and suicidality than non-multicultural boys. To ensure the effective implementation of policies to reduce mental health problems among multicultural adolescents in South Korea, detailed information should be considered regarding the cultural and socioeconomic backgrounds of families, such as parental country of birth and SEP

Peak intensity measurement of relativistic lasers via nonlinear Thomson scattering

The measurement of peak laser intensities exceeding 10^{20} \text{W/cm^2} is in general a very challenging task. We suggest a simple method to accurately measure such high intensities up to about 10^{23} \text{W/cm^2}, by colliding a beam of ultrarelativistic electrons with the laser pulse. The method exploits the high directionality of the radiation emitted by ultrarelativistic electrons via nonlinear Thomson scattering. Initial electron energies well within the reach of laser wake-field accelerators are required, allowing in principle for an all-optical setup. Accuracies of the order of 10% are theoretically envisaged.Comment: 4 pages, 2 figure

Enhanced terahertz conductivity in ultra-thin gold film deposited onto (3-mercaptopropyl) trimethoxysilane (MPTMS)-coated Si substrates

Various material properties change considerably when material is thinned down to nanometer thicknesses. Accordingly, researchers have been trying to obtain homogeneous thin films with nanometer thickness but depositing homogeneous few nanometers thick gold film is challenging as it tends to form islands rather than homogenous film. Recently, studies have revealed that treating the substrate with an organic buffer, (3-mercaptopropyl) trimethoxysilane (MPTMS) enables deposition of ultra-thin gold film having thickness as low as 5 nm. Different aspects of MPTMS treatment for ultrathin gold films like its effect on the structure and optical properties at visible wavelengths have been investigated. However, the effect of the MPTMS treatment on electrical conductivity of ultra-thin gold film at terahertz frequency remains unexplored. Here, we measure the complex conductivity of nanometer-thick gold films deposited onto an MPTMS-coated silicon substrate using terahertz time-domain spectroscopy. Following the MPTMS treatment of the substrate, the conductivity of the films was found to increase compared to those deposited onto uncoated substrate for gold films having the thickness less than 11 nm. We observed 5-fold enhancement in the conductivity for a 7 nm-thick gold film. We also demonstrate the fabrication of nanoslot-antenna arrays in 8.2-nm-thick gold films. The nanoslot-antenna with MPTMS coating has resonance at around 0.5 THz with an electric field enhancement of 44, whereas the nanoslot-antenna without MPTMS coating does not show resonant properties. Our results demonstrate that gold films deposited onto MPTMS-coated silicon substrates are promising advanced materials for fabricating ultra-thin terahertz plasmonic devices

Solar-Combined Thermoelectric Power Generation Simulator

Photovoltaic (PV) devices are gaining popularity in harnessing solar energy as a form of sustainable energy source to generate electricity. However, these devices including tandem PV cells are limited to utilizing only high energy photons from the solar spectrum. This curtails their efficiency restricting them from being employed in mega Watts scale power generation. This study develops a software tool that allows engineers to tap into the wasted wavelengths of the spectrum by adding a thermoelectric (TE) module and a bottoming steam turbine cycle thus spreading the use of the spectrum. The tool allows investigating how power output and thus overall efficiency can be enhanced by combining these systems. In the TE device, solar heat develops a temperature gradient to generate electricity via the Seebeck effect. A steam-driven Rankine cycle through a heat exchanger connects to thermal storage at the bottom side of the TE. This storage allows dispatchability for off-sunlight power demand at a modest cost. The simulation tool built computes expected power output and efficiency at each individual stage of the combined system. The user is at liberty to manipulate material properties such as the band gap of PV materials which is a key parameter to optimize the PV efficiency. Test runs indicate that overall efficiency of power generation has increased up to 50% by the combined system for 1000 suns using optimized band gap and TE module design. This system can be used as a basis for future models in high efficiency distributed energy production