37,113 research outputs found
A solar water heater for remote communities
The RADG has been developing a solar water heater suitable for use in remote areas. The original inspiration for this project was to provide hot water for remote Aboriginal communities. It was felt that a regular and plentiful supply of hot water would encourage showering and laundering and hence improve personal hygiene.
Electric, fuel burning and solar water heaters are currently used in some communities. Solar water heaters are attractive for remote areas because they stand alone i.e. they require no external fuel source. Wood has traditionally been used as a fuel by Aboriginal people, but in permanent communities the demand on this resource may have a large impact on the environment. Solar water heaters can help to reduce this demand
Instant restore after a media failure
Media failures usually leave database systems unavailable for several hours
until recovery is complete, especially in applications with large devices and
high transaction volume. Previous work introduced a technique called
single-pass restore, which increases restore bandwidth and thus substantially
decreases time to repair. Instant restore goes further as it permits read/write
access to any data on a device undergoing restore--even data not yet
restored--by restoring individual data segments on demand. Thus, the restore
process is guided primarily by the needs of applications, and the observed mean
time to repair is effectively reduced from several hours to a few seconds.
This paper presents an implementation and evaluation of instant restore. The
technique is incrementally implemented on a system starting with the
traditional ARIES design for logging and recovery. Experiments show that the
transaction latency perceived after a media failure can be cut down to less
than a second and that the overhead imposed by the technique on normal
processing is minimal. The net effect is that a few "nines" of availability are
added to the system using simple and low-overhead software techniques
Energy Gap from Tunneling and Metallic Sharvin Contacts onto MgB2: Evidence for a Weakened Surface Layer
Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reveal
a sharp superconducting energy gap that is confirmed by subsequent metallic
Sharvin contacts made on the same sample. The peak in the tunneling conductance
and the Sharvin contact conductance follow the BCS form, but the gap values of
4.3 meV are less than the weak-coupling BCS value of 5.9 meV for the bulk Tc of
39 K. The low value of Delta compared to the BCS value for the bulk Tc is
possibly due to chemical reactions at the surface.Comment: 3 pages, 3 figure
Probing the Phase Diagram of Bi2Sr2CaCu2O8+d with Tunneling Spectroscopy
Tunneling measurements are performed on Ca-rich single crystals of
Bi2Sr2CaCu2O8+d (Bi2212), with various oxygen doping levels, using a novel
point contact method. At 4.2 K, SIN and SIS tunnel junctions are obtained with
well-defined quasiparticle peaks, robust dip and hump features and in some
cases Josephson currents. The doping dependence of tunneling conductances of
Ca-rich Bi2212 are analyzed and compared to stoichiometric Bi2212. A similar
profile of energy gap vs. doping concentration is found although the Ca-rich
samples have a slighly smaller optimum Tc and therefore smaller gap values for
any doping level. The evolution of tunneling conductance peak height to
background ratios with hole concentration are compared. For a given doping
level, the Ca-rich spectra showed more broadened features compared to the
stoichiometric counterparts, most likely due to increased disorder from the
excess Ca. Comparison of the dip and hump features has provided some potential
insights into their origins.Comment: 4 pages, 4 figures; presented at the Applied Superconductivity
Conference (August 4-9, 2002) in Houston, TX; to be published in IEEE Trans.
Appl. Supercon
Recommended from our members
Sugar intake among German adolescents: trends from 1990-2016 based on biomarker excretion in 24-h urine samples
Trend analyses based on dietary records suggest decreases in the intakes of total (TS), added (AS) and free sugar (FS) since 2005 among children and adolescents in Germany. In terms of age trends, TS intake decreased with increasing age. However, self-reported sugar intake in epidemiological studies is criticized, as it may be prone to bias due to selective underreporting. Furthermore, adolescents are more susceptible to underreporting than children. We thus analyzed time and age trends in urinary fructose excretion (FE), sucrose excretion (SE) and the sum of both (FE+SE) as biomarkers for sugar intake among 8.5-16.5-year-old adolescents. Urinary sugar excretion was measured by UPLC-MS/MS in 997 24-h urine samples collected from 239 boys and 253 girls participating in the DONALD study cohort between 1990 and 2016. Time and age trends of log-transformed FE, SE and FE+SE were analyzed using polynomial mixed-effects regression models. Between 1990 and 2016 FE as well as FE+SE decreased (linear time trend: p=0.0272 and p<0.0001, respectively). A minor increase in excretion during adolescence was confined to FE (linear age trend: p=0.0017). The present 24-h excretion measurements support a previously reported dietary-record based decline in sugar intake since 2005. However, the previous seen dietary record-based decrease in TS from childhood to late adolescence was not confirmed by our biomarker analysis, suggesting a constant sugar intake for the period of adolescence
- …