Predicted and Measured Modal Sound Power Levels for a Fan Ingesting Distorted Inflow

Refinements have been made to a method for estimating the modal sound power levels of a ducted fan ingesting distorted inflow. By assuming that each propagating circumferential mode consists only of a single radial mode (the one with the highest cut-off ratio), circumferential mode sound power levels can be computed for a variety of inflow distortion patterns and operating speeds. Predictions from the refined theory have been compared to data from an experiment conducted in the Advanced Noise Control Fan at NASA Glenn Research Center. The inflow to the fan was distorted by inserting cylindrical rods radially into the inlet duct. The rods were placed at an axial location one rotor chord length upstream of the fan and arranged in both regular and irregular circumferential patterns. The fan was operated at 2000, 1800, and 1400 rpm. Acoustic pressure levels were measured in the fan inlet and exhaust ducts using the Rotating Rake fan mode measurement system. Far field sound pressure levels were also measured. It is shown that predicted trends in circumferential mode sound power levels closely match the experimental data for all operating speeds and distortion configurations tested. Insight gained through this work is being used to develop more advanced tools for predicting fan inflow distortion tone noise levels

Josephson Coupling through a Quantum Dot

We derive, via fourth order perturbation theory, an expression for the Josephson current through a gated interacting quantum dot. We analyze our expression for two different models of the superconductor-dot-superconductor (SDS) system. When the matrix elements connecting dot and leads are featureless constants, we compute the Josephson coupling J_c as a function of the gate voltage and Coulomb interaction. In the diffusive dot limit, we compute the probability distribution P(J_c) of Josephson couplings. In both cases, pi junction behavior (J_c < 0) is possible, and is not simply dependent on the parity of the dot occupancy.Comment: 9 pages; 3 encapsulated PostScript figure

Hidden vector dark matter

We show that dark matter could be made of massive gauge bosons whose stability doesn't require to impose by hand any discrete or global symmetry. Stability of gauge bosons can be guaranteed by the custodial symmetry associated to the gauge symmetry and particle content of the model. The particle content we consider to this end is based on a hidden sector made of a vector multiplet associated to a non-abelian gauge group and of a scalar multiplet charged under this gauge group. The hidden sector interacts with the Standard Model particles through the Higgs portal quartic scalar interaction in such a way that the gauge bosons behave as thermal WIMPS. This can lead easily to the observed dark matter relic density in agreement with the other various constraints, and can be tested experimentally in a large fraction of the parameter space. In this model the dark matter direct detection rate and the annihilation cross section can decouple if the Higgs portal interaction is weak.Comment: 13 pages, 7 figures, JHEP published version (2009) + update of section 7 (reference to arXiv:0912.4496

Production Networks in Asia: A Case Study from the Hard Disk Drive Industry

Production networks have been extensively developed in East Asia. Previous studies on production networks used international trade data or input-output tables, but such aggregate data cannot explain how the networks actually operate. With the aim of understanding the features and characteristics of East Asian production networks, this paper examines the procurement system of a HDD assembler operating in Thailand. This micro-level case study found that this particular production network consists mostly of arm's-length suppliers, who are independent and on an equal footing with the assembler. These arm's-length suppliers are mostly located in the assembling country, but some are located in neighboring countries. This proximity is necessary to establish good relationships between customer and suppliers and allows problems to be solved as soon as they occur. The arm's-length suppliers engaged in each country's leading industries, such as the electronics industry in Malaysia and Singapore and the automobile industry in Thailand, have extended their business to supply the HDD industry. These suppliers have formed an industrial cluster in each country within a two- or three-hour drive area. Each cluster that spans different countries is linked by a well-developed logistic network that employs the just-in-time production method that prevails in East Asia. On a regional level, these separate clusters tend to form international production networks that connect to each other across neighboring countries within a distance that provides a quick response time for problem solving. This study also found that American HDD assemblers outsourced indigenous suppliers in Malaysia and Singapore because American suppliers did not follow the assemblers' move to the region. However, since Japanese suppliers did follow the Japanese HDD assemblers to the Philippines and Thailand, indigenous suppliers were not outsourced

Macroeconomic Effects of Credit Deepening in Latin America

This paper augments a relatively standard dynamic general equilibrium model with financial frictions in order to quantify the macroeconomic effects of the credit deepening process observed in many Latin American (LA) countries in the last decade, most notably in Brazil. In the model, a stylized banking sector intermediates credit from patient households to impatient households and firms. The key novelty of the paper, motivated by the Brazilian experience, is to model the credit constraint faced by (impatient) households as a function of future labor income. In the calibrated model, credit deepening generates only modest abovetrend growth in consumption, investment, and GDP. Since Brazil has experienced one of the most intense credit deepening processes in Latin America, it is argued that the quantitative effects for other LA economies are unlikely to be sizeable

The Global Financial Crisis: Decoupling of East Asia – Myth or Reality?

The decoupling of East Asia from its economic interactions - both in trade and finance - with the rest of the world refers to the phenomenon of a weakening of the impact of demand and supply shocks emanating from the advanced countries on the region's economic performance since the early 1990s. Available empirical evidence, including the faster recovery of East Asia from the 2008 global economic crisis, does not appear to lend credence to the decoupling thesis. However, with increases in income throughout the region and the three free trade agreements (FTAs) of the People's Republic of China (PRC), Japan, and Korea with the Association of Southeast Asian Nations (ASEAN) (which have entered into force), East Asia will witness a continuing expansion in intra-regional trade, much of which will consist of horizontal intra-industry trade. At the same time, if East Asia succeeds in instituting an efficient capital control regime and in strengthening the Chiang Mai Initiative Multilateralization (CMIM), it will be able to cope better with the volatility of capital flows to the region. Together these developments will then help speed up economic integration among ASEAN+3 member states to build a region that is more self-contained than it has been