1,447 research outputs found
Study On Recovery And Utilization Of Valuable Components From Glycerol Residue
The Malaysian palm-based oleochemicals industry is growing rapidly and producing an
increasing array of products like fatty acid methyl esters, fatty alcohols and glycerine. In
the production of these oleochemicals, by-products are produced in which many of
them are potentially useful. One of the by-products is glycerol residue which is
generated by a glycerol refining plant (the glycerine source is from methanolysis of
palm kernel oil). Glycerol residue is a waste under Schedule Waste SI8I of the
Environmental Regulations in Malaysia. Currently, this waste is disposed off in landfills
with the cost of about RM700.00/tonne. This research was therefore undertaken to
characterize the glycerol residue, and to recover and utilize its valuable components. It
was found that thirteen batches of glycerol residue, GRI to GR13, showed variation in
the contents of glycerol, ash, moisture and matter organic non-glycerol (MONG). Salt
(63.7%), glycerol (19.7%) and MONG (12.9%, mainly as soap) were the three mai
Channel Access Management in Data Intensive Sensor Networks
There are considerable challenges for channel access in Data Intensive Sensor Networks - DISN, supporting Data Intensive Applications like Structural Health Monitoring. As the data load increases, considerable degradation of the key performance parameters of such sensor networks is observed. Successful packet delivery ratio drops due to frequent collisions and retransmissions. The data glut results in increased latency and energy consumption overall. With the considerable limitations on sensor node resources like battery power, this implies that excessive transmissions in response to sensor queries can lead to premature network death. After a certain load threshold the performance characteristics of traditional WSNs become unacceptable. Research work indicates that successful packet delivery ratio in 802.15.4 networks can drop from 95% to 55% as the offered network load increases from 1 packet/sec to 10 packets/sec. This result in conjunction with the fact that it is common for sensors in an SHM system to generate 6-8 packets/sec of vibration data makes it important to design appropriate channel access schemes for such data intensive applications.In this work, we address the problem of significant performance degradation in a special-purpose DISN. Our specific focus is on the medium access control layer since it gives a fine-grained control on managing channel access and reducing energy waste. The goal of this dissertation is to design and evaluate a suite of channel access schemes that ensure graceful performance degradation in special-purpose DISNs as the network traffic load increases.First, we present a case study that investigates two distinct MAC proposals based on random access and scheduling access. The results of the case study provide the motivation to develop hybrid access schemes. Next, we introduce novel hybrid channel access protocols for DISNs ranging from a simple randomized transmission scheme that is robust under channel and topology dynamics to one that utilizes limited topological information about neighboring sensors to minimize collisions and energy waste. The protocols combine randomized transmission with heuristic scheduling to alleviate network performance degradation due to excessive collisions and retransmissions. We then propose a grid-based access scheduling protocol for a mobile DISN that is scalable and decentralized. The grid-based protocol efficiently handles sensor mobility with acceptable data loss and limited overhead. Finally, we extend the randomized transmission protocol from the hybrid approaches to develop an adaptable probability-based data transmission method. This work combines probabilistic transmission with heuristics, i.e., Latin Squares and a grid network, to tune transmission probabilities of sensors, thus meeting specific performance objectives in DISNs. We perform analytical evaluations and run simulation-based examinations to test all of the proposed protocols
Search for serendipitous TNO occultation in X-rays
To study the population properties of small, remote objects beyond Neptune's
orbit in the outer solar system, of kilometer size or smaller, serendipitous
occultation search is so far the only way. For hectometer-sized Trans-Neptunian
Objects (TNOs), optical shadows actually disappear because of diffraction.
Observations at shorter wave lengths are needed. Here we report the effort of
TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June
2007 to October 2011. No definite TNO occultation events were found in the 334
ks data. We investigate the detection efficiency dependence on the TNO size to
better define the sensible size range of our approach and suggest upper limits
to the TNO size distribution in the size range from 30 m to 300 m. A list of
X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA
Smart Pacing for Effective Online Ad Campaign Optimization
In targeted online advertising, advertisers look for maximizing campaign
performance under delivery constraint within budget schedule. Most of the
advertisers typically prefer to impose the delivery constraint to spend budget
smoothly over the time in order to reach a wider range of audiences and have a
sustainable impact. Since lots of impressions are traded through public
auctions for online advertising today, the liquidity makes price elasticity and
bid landscape between demand and supply change quite dynamically. Therefore, it
is challenging to perform smooth pacing control and maximize campaign
performance simultaneously. In this paper, we propose a smart pacing approach
in which the delivery pace of each campaign is learned from both offline and
online data to achieve smooth delivery and optimal performance goals. The
implementation of the proposed approach in a real DSP system is also presented.
Experimental evaluations on both real online ad campaigns and offline
simulations show that our approach can effectively improve campaign performance
and achieve delivery goals.Comment: KDD'15, August 10-13, 2015, Sydney, NSW, Australi
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