			Home About us Contact

Single Path (single + path)

Distribution by Scientific Domains

Engineering	40%

Selected Abstracts

Welfare Regimes for Aging Populations: No Single Path for Reform

POPULATION AND DEVELOPMENT REVIEW, Issue 4 2009
Mehmet F. Aysan
We consider recent trends in pension policies in OECD countries in light of demographic aging associated with welfare regime type (Liberal, Social Democratic, Continental, and Southern European). These regime types represent different responsibilities assumed for social security on the part of the market, the state, and the family. While there are significant differences in labor market characteristics, the demographic similarities in aging bring similar pressures for pension reforms across OECD countries. These reforms address fiscal issues in state pensions, typically by increasing the length of the working life, placing more of the pension responsibility on individuals, or converting to defined-contribution approaches. Our study shows that there is no single path for pension reform. While there are some variations, welfare states tend to follow their traditional paths, which differ across welfare regime types. [source]

Experiment and simulation investigations for effects of flow channel patterns on the PEMFC performance

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2008
Yuh-Ming Ferng
Abstract Experiments and simulations are presented in this paper to investigate the effects of flow channel patterns on the performance of proton exchange membrane fuel cell (PEMFC). The experiments are conducted in the Fuel Cell Center of Yuan Ze University and the simulations are performed by way of a three-dimensional full-cell computational fluid dynamics model. The flow channel patterns adopted in this study include the parallel and serpentine flow channels with the single path of uniform depth and four paths of step-wise depth, respectively. Experimental measurements show that the performance (i.e. cell voltage) of PEMFC with the serpentine flow channel is superior to that with the parallel flow channel, which is precisely captured by the present simulation model. For the parallel flow channel, different depth patterns of flow channel have a strong influence on the PEMFC performance. However, this effect is insignificant for the serpentine flow channel. In addition, the calculated results obtained by the present model show satisfactory agreement with the experimental data for the PEMFC performance under different flow channel patterns. These validations reveal that this simulation model can supplement the useful and localized information for the PEMFC with confidence, which cannot be obtained from the experimental data. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Technology Advances and Tanker Spill Prevention

NAVAL ENGINEERS JOURNAL, Issue 4 2001
Cdr. G. Rodgers USCGR (Ret.)
ABSTRACT Goals to alert the bridge watch for imminent grounding or collision with shallow underwater dangers, have long been stymied by lags in active sonar technology. Thus "lower hemisphere" designs for shallow underwater search have been unable to exploit solutions useful topside for the "upper hemisphere" guarded by radar and other technology. While the radar environment normally exhibits single path, direct line-of-sight conditions for prime targets, the shallow water sonar environment is cluttered by a mix of echoes and multipath returns for identical ranges. Thus we first must accommodate to a quirky hydroacoustic environment as a major design subsystem for any shallow water navigational sonar. Secondly, for large carriers found in the world tanker fleet, there is recognition that some simple backfit solution is needed for any electroacoustic interface, the sonar transducer. Commercial carriers have not been designed or built with special hull considerations such as sonar domes and recesses; therefore, this second vital subsystem requires particular design attention for projecting hydro-acoustic energy and receiving return echoes. Several recent patents are on file which apply to this problem. Thirdly, signal processing considerations provide a set of design-critical factors. High speed digital signal processors (DSPs) of recent "parallel" design offer opportunities to search at high speed and to unravel the confusing mix of acoustic energy found in shallow water returns. Past hurdles are endemic for these three critical subsystems: hydroacoustic environment, electroacoustic transducer design, and signal processing, but now these seem most amenable to technology transfer. [source]

Approximation algorithms for constructing wavelength routing networks

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 1 2002
Refael Hassin
Abstract Consider a requirement graph whose vertices represent customers and an edge represents the need to route a unit of flow between its end vertices along a single path. All these flows are to be routed simultaneously. A solution network consists of a (multi)graph on the same set of vertices, such that it is possible to route simultaneously all of the required flows in such a way that no edge is used more than K times. The SYNTHESIS OF WAVELENGTH ROUTING NETWORK (SWRN) problem is to compute a solution network of a minimum number of edges. This problem has significant importance in the world of fiber-optic networks where a link can carry a limited amount of different wavelengths and one is interested in finding a minimum-cost network such that all the requirements can be carried in the network without changing the wavelength of a path at any of its internal vertices. In this paper, we prove that the SWRN problem is NP-hard for any constant K (K , 2). Then, we assume that GR is a clique with n vertices and we find an "almost" optimal solution network for all values of K (K = o(n)) and present a Min{(K + 1)/2, 2 + 2/(K , 1)}-approximation algorithm for the general case and a 2-approximation algorithm for d -regular graphs. © 2002 Wiley Periodicals, Inc. [source]