527 research outputs found
Non-Intrusive Measurement in Packet Networks and its Applications
PhDNetwork measurementis becoming increasingly important as a meanst o assesst he performanceo f
packet networks. Network performance can involve different aspects such as availability, link
failure detection etc, but in this thesis, we will focus on Quality of Service (QoS). Among the
metrics used to define QoS, we are particularly interested in end-to-end delay performance.
Recently, the adoption of Service Level Agreements (SLA) between network operators and their
customersh as becomea major driving force behind QoS measurementm: easurementi s necessaryt o
produce evidence of fulfilment of the requirements specified in the SLA.
Many attempts to do QoS based packet level measurement have been based on Active Measurement,
in which the properties of the end-to-end path are tested by adding testing packets generated from
the sending end. The main drawback of active probing is its intrusive nature which causes extraburden
on the network, and has been shown to distort the measured condition of the network. The
other category of network measurement is known as Passive Measurement. In contrast to Active
Measurement, there are no testing packets injected into the network, therefore no intrusion is caused.
The proposed applications using Passive Measurement are currently quite limited. But Passive
Measurement may offer the potential for an entirely different perspective compared with Active
Measurements
In this thesis, the objective is to develop a measurement methodology for the end-to-end delay
performance based on Passive Measurement. We assume that the nodes in a network domain are
accessible.F or example, a network domain operatedb y a single network operator. The novel idea is
to estimate the local per-hop delay distribution based on a hybrid approach (model and
measurement-based)W. ith this approach,t he storagem easurementd ata requirement can be greatly
alleviated and the overhead put in each local node can be minimized, so maintaining the fast
switching operation in a local switcher or router.
Per-hop delay distributions have been widely used to infer QoS at a single local node. However, the
end-to-end delay distribution is more appropriate when quantifying delays across an end-to-end path.
Our approach is to capture every local node's delay distribution, and then the end-to-end delay
distribution can be obtained by convolving the estimated delay distributions. In this thesis, our
algorithm is examined by comparing the proximity of the actual end-to-end delay distribution with
the estimated one obtained by our measurement method under various conditions. e. g. in the
presence of Markovian or Power-law traffic. Furthermore, the comparison between Active
Measurement and our scheme is also studied.
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Network operators may find our scheme useful when measuring the end-to-end delay performance.
As stated earlier, our scheme has no intrusive effect. Furthermore, the measurement result in the
local node can be re-usable to deduce other paths' end-to-end delay behaviour as long as this local
node is included in the path. Thus our scheme is more scalable compared with active probing
A new and efficient intelligent collaboration scheme for fashion design
Technology-mediated collaboration process has been extensively studied for over a decade. Most applications with collaboration concepts reported in the literature focus on enhancing efficiency and effectiveness of the decision-making processes in objective and well-structured workflows. However, relatively few previous studies have investigated the applications of collaboration schemes to problems with subjective and unstructured nature. In this paper, we explore a new intelligent collaboration scheme for fashion design which, by nature, relies heavily on human judgment and creativity. Techniques such as multicriteria decision making, fuzzy logic, and artificial neural network (ANN) models are employed. Industrial data sets are used for the analysis. Our experimental results suggest that the proposed scheme exhibits significant improvement over the traditional method in terms of the time–cost effectiveness, and a company interview with design professionals has confirmed its effectiveness and significance
Factor Structure of Multicultural Teaching Competency Scale for School-teachers in Hong Kong
This study investigates the perceptions of teaching competency in multicultural classrooms held by 421 teachers at 16 schools in Hong Kong. The aims of the study are (a) to use confirmatory factor analysis to validate a culturally appropriate version of the Multicultural Teaching Competency Scale (MTCS), (b) to assess three types of multicultural-teaching competency, and (c) to provide recommendations for teacher-education institutes and policy makers on developing effective training in multicultural education. The results indicate that a tripartite model assessing skills, knowledge, and relationships, the core features of multicultural-teaching competency as assessed by the MTCS from a Hong Kong sample. The teachers all identified multicultural-teaching relationships as the most important component of multicultural-teaching competency. Future researchers should examine the concurrent validity of the MTCS and the cultural contexts of multicultural-teaching relationships. Recommendations are also made for incorporating the Confucian beliefs of fairness, justice, and equity into multicultural classroom
R-process nucleosynthesis during explosion of low-mass neutron stars in close binaries
We investigate the explosion of low-mass neutron stars through Newtonian
hydrodynamic simulations. We couple the hydrodynamics to a nuclear reaction
network consisting of isotopes to study the impact of nuclear
reactions, mainly neutron capture, -decays, and spontaneous fission of
nuclei, on the development of hydrodynamic instability of a neutron star. We
show that after mass removal from the surfaces, low-mass neutron stars undergo
delayed explosion, and an electron anti-neutrino burst with a peak luminosity
of erg s is emitted, while the ejecta is heated to
K. A robust r-process nucleosynthesis is realized in the ejecta.
Lanthanides and heavy elements near the second and third r-process peaks are
synthesized as end products of nucleosynthesis, suggesting that the explosions
of low-mass neutron stars could be a potentially important source of solar
chemical elements.Comment: 12 pages, 13 figure
Accretion-induced Collapse of Dark Matter-admixed Rotating White Dwarfs: Dynamics and Gravitational-wave Signals
We present two-dimensional hydrodynamic simulations of the accretion-induced
collapse (AIC) of rotating white dwarfs admixed with an extended component of
dark matter (DM) comprising of sub-GeV degenerate fermionic DM particles. We
find that the DM component would follow the collapse of the normal matter (NM)
component to become a bound DM core. Thus, we demonstrate how a DM-admixed
neutron star could form through DM-admixed AIC (DMAIC) for the first time, with
the dynamics of DM taken into account. The gravitational-wave (GW) signature
from the DMAIC shows distinctive features. In the diffusive DM limit, the DM
admixture indirectly suppresses the post-bounce spectral peak of the NM GWs. In
the compact DM limit, the collapse dynamics of the DM in a Milky Way event
generate GWs that are strong enough to be detectable by Advanced LIGO as
continuous low-frequency ( Hz) signals after the NM core bounce. Our
study not only is the first-ever computation of GW from a collapsing DM object
but also provides the key features to identify DM in AIC events through future
GW detections.Comment: 14 pages, 13 figure
Comparing the effects of visibility of different neighborhood greenery settings on the preference ratings and noise annoyance responses to road traffic noises
The impact of visual environment on human noise perceptions has always been under scrutiny. Two consecutive sets of laboratory experiments were performed for studying the effect of visual perceptions of different percentages of sea, greenery, and/or road views on noise-induced annoyance responses as well as preference ratings. Both experiments were carried out in a room purposely constructed inside an anechoic chamber to mimic the living room setting of a dwelling in Hong Kong. Video clips were projected consecutively onto the exterior window panel of the living room to simulate neighborhood views containing different percentages of sea, greenery and road. 82 and 58 participants were successfully administered in two experiments. Each participant was presented with 11 video clips and requested to respond to a series of questions regarding perceived noise annoyance and view preferences after presentation of individual clips. The responses collected from each experiment were employed to formulate ordered logit models to predict the probability of evoking a high annoyance response. Findings indicated that participants tended to prefer the presence of sea rather than that of either mountain or trees in views containing a trafficking road. Views containing sea would produce an attenuating effect on noise annoyance while views containing road would produce an aggravating effect. However, the size of the effects did not vary between 0% and 30% sea, or between 30% and 60% road contained in a view. Views containing dense greenery at a close distance would aggravate noise annoyance irrespective of form. However, when the percentage of greenery increased from 30% to 60%, the noise annoyance attenuating effect increased in the case of wooded mountain but decreased in the case of the more transparent tree clumps
Loss of Yeast Peroxiredoxin Tsa1p Induces Genome Instability through Activation of the DNA Damage Checkpoint and Elevation of dNTP Levels
Peroxiredoxins are a family of antioxidant enzymes critically involved in cellular defense and signaling. Particularly, yeast peroxiredoxin Tsa1p is thought to play a role in the maintenance of genome integrity, but the underlying mechanism is not understood. In this study, we took a genetic approach to investigate the cause of genome instability in tsa1Δ cells. Strong genetic interactions of TSA1 with DNA damage checkpoint components DUN1, SML1, and CRT1 were found when mutant cells were analyzed for either sensitivity to DNA damage or rate of spontaneous base substitutions. An elevation in intracellular dNTP production was observed in tsa1Δ cells. This was associated with constitutive activation of the DNA damage checkpoint as indicated by phosphorylation of Rad9/Rad53p, reduced steady-state amount of Sml1p, and induction of RNR and HUG1 genes. In addition, defects in the DNA damage checkpoint did not modulate intracellular level of reactive oxygen species, but suppressed the mutator phenotype of tsa1Δ cells. On the contrary, overexpression of RNR1 exacerbated this phenotype by increasing dNTP levels. Taken together, our findings uncover a new role of TSA1 in preventing the overproduction of dNTPs, which is a root cause of genome instability
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