A Reliable and Cost-Efficient Auto-Scaling System for Web Applications Using Heterogeneous Spot Instances

Cloud providers sell their idle capacity on markets through an auction-like mechanism to increase their return on investment. The instances sold in this way are called spot instances. In spite that spot instances are usually 90% cheaper than on-demand instances, they can be terminated by provider when their bidding prices are lower than market prices. Thus, they are largely used to provision fault-tolerant applications only. In this paper, we explore how to utilize spot instances to provision web applications, which are usually considered availability-critical. The idea is to take advantage of differences in price among various types of spot instances to reach both high availability and significant cost saving. We first propose a fault-tolerant model for web applications provisioned by spot instances. Based on that, we devise novel auto-scaling polices for hourly billed cloud markets. We implemented the proposed model and policies both on a simulation testbed for repeatable validation and Amazon EC2. The experiments on the simulation testbed and the real platform against the benchmarks show that the proposed approach can greatly reduce resource cost and still achieve satisfactory Quality of Service (QoS) in terms of response time and availability

Near-infrared Study of the Carina Nebula

We have carried out near-infrared (NIR) imaging observations of the Carina Nebula for an area of ~400 sq. arcmin. including the star clusters Trumpler 14 (Tr 14) and Trumpler 16 (Tr 16). With 10 sigma limiting magnitudes of J ~ 18.5, H ~ 17.5 and K_s ~ 16.5, we identified 544 Class II and 11 Class I young star candidates. We find some 40 previously unknown very red sources with H-K_s > 2, most of which remain undetected at the J band. The red NIR sources are found to be concentrated to the south-east of Tr 16, along the `V' shaped dust lane, where the next generation of stars seems to be forming. In addition, we find indications of ongoing star formation near the three MSX point sources, G287.51-0.49, G287.47-0.54, and G287.63-0.72. A handful of red NIR sources are seen to populate around each of these MSX sources. Apart from this, we identified two hard Chandra X-ray sources near G287.47-0.54, one of which does not have an NIR counterpart and may be associated with a Class I/Class 0 object. The majority of the Class II candidates, on the other hand, are seen to be distributed in the directions of the clusters, demarcating different evolutionary stages in this massive star-forming region. A comparison of the color-magnitude diagrams of the clusters with pre-main sequence model tracks shows that the stellar population of these clusters is very young (< 3 Myr). The K_s band luminosity function (KLF) of Tr 14 shows structure at the faint end, including a sharp peak due to the onset of deuterium burning, implying an age of 1-2 Myr for the cluster. The KLF of Tr 16, in contrast, is found to rise smoothly until it turns over. The slopes of the mass functions derived for the clusters are found to be in agreement with the canonical value of the field star initial mass function derived by Salpeter.Comment: Accepted for publication in ApJ; 45 pages, 18 figures, and 3 tables. The manuscript with higher resolution figures can be downloaded from http://cepheus.astro.ncu.edu.tw/~kaushar/download/ms.pd

An Extragalactic HI Cloud with No Optical Counterpart?

We report the discovery, from the HI Parkes All-Sky Survey (HIPASS), of an isolated cloud of neutral hydrogen which we believe to be extragalactic. The HI mass of the cloud (HIPASS J1712-64) is very low, 1.7 x 10^7 Msun, using an estimated distance of ~3.2 Mpc. Most significantly, we have found no optical companion to this object to very faint limits (mu(B)~ 27 mag arcsec^-2). HIPASS J1712-64 appears to be a binary system similar to, but much less massive than, HI 1225+01 (the Virgo HI Cloud) and has a size of at least 15 kpc. The mean velocity dispersion, measured with the Australia Telescope Compact Array (ATCA), is only 4 km/s for the main component and because of the weak or non-existent star-formation, possibly reflects the thermal linewidth (T<2000 K) rather than bulk motion or turbulence. The peak column density for HIPASS J1712-64, from the combined Parkes and ATCA data, is only 3.5 x 10^19 cm^-2, which is estimated to be a factor of two below the critical threshold for star formation. Apart from its significantly higher velocity, the properties of HIPASS J1712-64 are similar to the recently recognised class of Compact High Velocity Clouds. We therefore consider the evidence for a Local Group or Galactic origin, although a more plausible alternative is that HIPASS J1712-64 was ejected from the interacting Magellanic Cloud/Galaxy system at perigalacticon ~ 2 x 10^8 yr ago.Comment: 23 pages, 7 figures, AJ accepte

The Endogenous Market Structures Approach. A Non-technical Survey with Applications to the Crisis and Future Scenarios for the New Economy

The EMSs approach to macroeconomics introduces strategic interactions and endogenous entry decisions in the analysis of aggregate phenomena as business cycle, international trade and growth. This survey provides a non-technical discussion of the applications of the EMSs approach to positive and normative issues, and relates these with recent debates on the current recession, future scenarios for glabalization, policymaking and the New Economy.

An SLA-driven framework for dynamic multimedia content delivery federations

Recently, the Internet has become a popular platform for the delivery of multimedia content. However, its best effort delivery approach is ill-suited to guarantee the stringent Quality of Service (QoS) requirements of many existing multimedia services, which results in a significant reduction of the Quality of Experience. This paper presents a solution to these problems, in the form of a framework for dynamically setting up federations between the stakeholders involved in the content delivery chain. More specifically, the framework provides an automated mechanism to set up end-to-end delivery paths from the content provider to the access Internet Service Providers (ISPs), which act as its direct customers and represent a group of end-users. Driven by Service Level Agreements (SLAs), QoS contracts are automatically negotiated between the content provider, the access ISPs, and the intermediary network domains along the delivery paths. These contracts capture the delivered QoS and resource reservation costs, which are subsequently used in the price negotiations between content provider and access ISPs. Additionally, it supports the inclusion of cloud providers within the federations, supporting on-the-fly allocation of computational and storage resources. This allows the automatic deployment and configuration of proxy caches along the delivery paths, which potentially reduce delivery costs and increase delivered quality

Infrared Dark Clouds in the Small Magellanic Cloud?

We have applied the unsharp-masking technique to the 24 $\mu$m image of the Small Magellanic Cloud (SMC), obtained with the Spitzer Space Telescope, to search for high-extinction regions. This technique has been used to locate very dense and cold interstellar clouds in the Galaxy, particularly infrared dark clouds (IRDCs). Fifty five candidate regions of high-extinction, namely high-contrast regions (HCRs), have been identified from the generated decremental contrast image of the SMC. Most HCRs are located in the southern bar region and mainly distributed in the outskirts of CO clouds, but most likely contain a significant amount of H2. HCRs have a peak-contrast at 24 $\mu$m of 2 - 2.5 % and a size of 8 - 14 pc. This corresponds to the size of typical and large Galactic IRDCs, but Galactic IRDCs are 2 - 3 times darker at 24 $\mu$m than our HCRs. To constrain the physical properties of the HCRs, we have performed NH3, N2H+, HNC, HCO+, and HCN observations toward one of the HCRs, HCR LIRS36-EAST, using the Australia Telescope Compact Array and the Mopra single-dish radio telescope. We did not detect any molecular line emission, however, our upper limits to the column densities of molecular species suggest that HCRs are most likely moderately dense with n ~ 10^{3} cm-3. This volume density is in agreement with predictions for the cool atomic phase in low metallicity environments. We suggest that HCRs may be tracing clouds at the transition from atomic to molecule-dominated medium, and could be a powerful way to study early stages of gas condensation in low metallicity galaxies. Alternatively, if made up of dense molecular clumps < 0.5 pc in size, HCRs could be counterparts of Galactic IRDCs, and/or regions with highly unusual abundance of very small dust grains.Comment: accepted for publication in the Astronomical Journa

Limits on chemical complexity in diffuse clouds: search for CH3OH and HC5N absorption

Context: An unexpectedly complex polyatomic chemistry exists in diffuse clouds, allowing detection of species such as C2H, C3H2, H2CO and NH3 which have relative abundances that are strikingly similar to those inferred toward the dark cloud TMC-1 Aims: We probe the limits of complexity of diffuse cloud polyatomic chemistry. Methods: We used the IRAM Plateau de Bure Interferometer to search for galactic absorption from low-lying J=2-1 rotational transitions of A- and E-CH3OH near 96.740 GHz and used the VLA to search for the J=8-7 transition of HC5N at 21.3 GHz. Results: Neither CH3OH nor HC5N were detected at column densities well below those of all polyatomics known in diffuse clouds and somewhat below the levels expected from comparison with TMC-1. The HCN/HC5N ratio is at least 3-10 times higher in diffuse gas than toward TMC-1. Conclusions: It is possible to go to the well once (or more) too ofte

Business Integration as a Service

This paper presents Business Integration as a Service (BIaS) which enables connections between services operating in the Cloud. BIaS integrates different services and business activities to achieve a streamline process. We illustrate this integration using two services; Return on Investment (ROI) Measurement as a Service (RMaaS) and Risk Analysis as a Service (RAaaS) in two case studies at the University of Southampton and Vodafone/Apple. The University of Southampton case study demonstrates the cost-savings and the risk analysis achieved, so two services can work as a single service. The Vodafone/Apple case study illustrates statistical analysis and 3D Visualisation of expected revenue and associated risk. These two cases confirm the benefits of BIaS adoption, including cost reduction and improvements in efficiency and risk analysis. Implementation of BIaS in other organisations is also discussed. Important data arising from the integration of RMaaS and RAaaS are useful for management of University of Southampton and potential and current investors for Vodafone/Apple