496 research outputs found
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
Enhanced Thermoelectric Properties in Bulk Nanowire Heterostructure-Based Nanocomposites through Minority Carrier Blocking
To design superior thermoelectric materials the minority carrier blocking effect in which the unwanted bipolar transport is prevented by the interfacial energy barriers in the heterogeneous nanostructures has been theoretically proposed recently. The theory predicts an enhanced power factor and a reduced bipolar thermal conductivity for materials with a relatively low doping level, which could lead to an improvement in the thermoelectric figure of merit (ZT). Here we show the first experimental demonstration of the minority carrier blocking in lead telluride–silver telluride (PbTe–Ag_2Te) nanowire heterostructure-based nanocomposites. The nanocomposites are made by sintering PbTe–Ag_2Te nanowire heterostructures produced in a highly scalable solution-phase synthesis. Compared with Ag_2Te nanowire-based nanocomposite produced in similar method, the PbTe–Ag_2Te nanocomposite containing ∼5 atomic % PbTe exhibits enhanced Seebeck coefficient, reduced thermal conductivity, and ∼40% improved ZT, which can be well explained by the theoretical modeling based on the Boltzmann transport equations when energy barriers for both electrons and holes at the heterostructure interfaces are considered in the calculations. For this p-type PbTe–Ag_2Te nanocomposite, the barriers for electrons, that is, minority carriers, are primarily responsible for the ZT enhancement. By extending this approach to other nanostructured systems, it represents a key step toward low-cost solution-processable nanomaterials without heavy doping level for high-performance thermoelectric energy harvesting
Composition Modulation of Ag_2Te Nanowires for Tunable Electrical and Thermal Properties
In this article, we demonstrated that composition modulation of Ag_2Te nanowires can be achieved during the self-templated transformation of Te nanowires into Ag_2Te nanowires during solution phase synthesis, which provides a mean to tune the carrier density of the Ag_2Te nanowires. Both nearly stoichiometric and Ag-rich nanowires have been synthesized, which give rise to p-type and n-type Ag_2Te nanocomposites after hot press, respectively. The electrical and thermal properties of the two kinds of samples have been measured. Theoretical modeling based on the near-equilibrium Boltzmann transport equations has been used to understand the experimental results. We found that ZT of the heavily doped n-type sample reaches 0.55 at 400 K, which is the highest ZT value reported for Ag_2Te at the same temperature mainly due to the reduced thermal conductivity by the nanostructures. Theoretical analysis on the carrier transport shows that the power factor is also very well optimized in the doped Ag_2Te sample considering the reduced carrier mobility by the nanostructures
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Acute ischaemic stroke in Listeria monocytogenes meningoencephalitis.
Listeria monocytogenes is the third most frequent cause of bacterial meningitis and has a predilection for elderly patients and the immunosuppressed. A small number of patients with Listeria monocytogenes meningoencephalitis have previously been reported to experience stroke-like symptoms that were attributed to microabscess formation and the mass effect of collections of infection in the brain. These infections led to temporary neurological deficits that resolved with antimicrobial treatment, rather than to true strokes with permanent neurological deficits. This report discusses the case of an 80- year-old male, who was immunosuppressed with mesalazine for the treatment of Crohn's disease, and who went on to develop Listeria monocytogenes meningoencephalitis. 1 week into his admission, for antibiotic therapy, the patient began to experience new onset right upper limb weakness, nystagmus and past pointing. These symptoms were initially thought to be a complication of the infection. However, subsequent diffusion-weighted MRI revealed that the patient had more likely suffered an acute ischaemic event and a contrast-enhanced MRI performed later could not detect any abscess or large infective focus in a region that could explain the symptoms. This case report highlights the fact that ischaemic and infective pathologists may coexist in immunosuppressed Listeria patients and that clinical signs and symptoms should guide the use of appropriate imaging modalities such as MRI to clarify differentials so that ischaemia is not mistaken for the more common stroke mimic caused by infection in these patients
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