Experimental determination of material damping using vibration analyzer

Structural damping is an important dynamic characteristic of engineering materials that helps to damp vibrations by reducing their amplitudes. In this investigation, an experimental method is illustrated to determine the damping characteristics of engineering materials using a dual channel Fast Fourier Transform (FFT) analyzer. A portable Compaq III computer which houses the analyzer, is used to collect the dynamic responses of three metal rods. Time-domain information is analyzed to obtain the logarithmic decrement of their damping. The damping coefficients are then compared to determine the variation of damping from material to material. The variations of damping from one point to another of the same material, due to a fixed point excitation, and the variable damping at a fixed point due to excitation at different points, are also demonstrated

Storage stability of fish oil from Langkawi Island, Malaysia

Fish oils extracted from 6 species of marine fin fish caught from Pulau Tuba area, near Langkawi Island, a famous tourism destination in Malaysia, were evaluated for their oxidative stability during storage at both -27 and 4°C. The five fish species were “kerisi” (threadfin breams,sScomberomorus commersoni), “kerapu” (groupers, Cynoglossus lingua), “kembong” (Indian mackerel, Psettodes crumei), “gelama kling” (drum-croaker-jewfish, Pristipomodes typus), and “tinggiri batang” (Spanish mackerels, Scolidon sorrakowah). Results showed that stability of oils stored at -27°C was better than that of oils stored at 4°C. Iodine value (IV) of oils decreased during storage, while other parameters, namely peroxide value (PV), anisidine value (AnV), acid value (AV) and thiobarbituric acid (TBA) value increased. However, the rate of quality deterioration of oil samples was relatively low, as shown by very little changes in fatty acid profiles of the oil, meaning that both storage temperatures might be used for storage purposes of fish oil

Structured Peer-to-Peer Overlays for NATed Churn Intensive Networks

The wide-spread coverage and ubiquitous presence of mobile networks has propelled the usage and adoption of mobile phones to an unprecedented level around the globe. The computing capabilities of these mobile phones have improved considerably, supporting a vast range of third party applications. Simultaneously, Peer-to-Peer (P2P) overlay networks have experienced a tremendous growth in terms of usage as well as popularity in recent years particularly in fixed wired networks. In particular, Distributed Hash Table (DHT) based Structured P2P overlay networks offer major advantages to users of mobile devices and networks such as scalable, fault tolerant and self-managing infrastructure which does not exhibit single points of failure. Integrating P2P overlays on the mobile network seems a logical progression; considering the popularities of both technologies. However, it imposes several challenges that need to be handled, such as the limited hardware capabilities of mobile phones and churn (i.e. the frequent join and leave of nodes within a network) intensive mobile networks offering limited yet expensive bandwidth availability. This thesis investigates the feasibility of extending P2P to mobile networks so that users can take advantage of both these technologies: P2P and mobile networks. This thesis utilises OverSim, a P2P simulator, to experiment with the performance of various P2P overlays, considering high churn and bandwidth consumption which are the two most crucial constraints of mobile networks. The experiment results show that Kademlia and EpiChord are the two most appropriate P2P overlays that could be implemented in mobile networks. Furthermore, Network Address Translation (NAT) is a major barrier to the adoption of P2P overlays in mobile networks. Integrating NAT traversal approaches with P2P overlays is a crucial step for P2P overlays to operate successfully on mobile networks. This thesis presents a general approach of NAT traversal for ring based overlays without the use of a single dedicated server which is then implemented in OverSim. Several experiments have been performed under NATs to determine the suitability of the chosen P2P overlays under NATed environments. The results show that the performance of these overlays is comparable in terms of successful lookups in both NATed and non-NATed environments; with Kademlia and EpiChord exhibiting the best performance. The presence of NATs and also the level of churn in a network influence the routing techniques used in P2P overlays. Recursive routing is more resilient to IP connectivity restrictions posed by NATs but not very robust in high churn environments, whereas iterative routing is more suitable to high churn networks, but difficult to use in NATed environments. Kademlia supports both these routing schemes whereas EpiChord only supports the iterating routing. This undermines the usefulness of EpiChord in NATed environments. In order to harness the advantages of both routing schemes, this thesis presents an adaptive routing scheme, called Churn Aware Routing Protocol (ChARP), combining recursive and iterative lookups where nodes can switch between recursive and iterative routing depending on their lifetimes. The proposed approach has been implemented in OverSim and several experiments have been carried out. The experiment results indicate an improved performance which in turn validates the applicability and suitability of ChARP in NATed environments

An evaluation of EpiChord in OverSim

EpiChord is a Distributed Hash Table (DHT) algorithm which supports data storage/retrieval in large scale distributed systems. It removes the typicalO(logn)-state-per-node restriction imposed by the majority of other DHT topologies by employing a reactive routing state maintenance strategy that amortizes network maintenance costs into lookup queries. Under ideal condition, EpiChord’s lookup performance can approach O(1) hops – with maintenance costs comparable to traditional multi-hop DHTs. This paper presents an implementation of EpiChord in OverSim, and validates the performance of our model against the performance reported in the original EpiChord paper. We also present some adjustments to the algorithm to remove a discrepancy and then compare our modified results with the original ones. Finally, we present additional results showing the EpiChord algorithm is stable over time and performs well for larger networks

Performance analysis of structured peer-to-peer overlays for mobile networks

Distributed Hash Table (DHT) based Peer-to-Peer (P2P) overlays have been widely researched and deployed in many applications such as file sharing, IP telephony, content distribution and media streaming applications. However, their deployment has largely been restricted to fixed, wired networks. This is due to the fact that supporting P2P overlays on wireless networks such as the public mobile data network is more challenging due to constraints in terms of data transmissions on cellular networks, limited battery power of the handsets and increased levels of node churn. However, the proliferation of smartphones makes the use of P2P applications on mobile handsets very desirable.  In this paper, we have analysed and evaluated the performance and efficiency of five popular DHT based structured P2P overlays (Chord, Pastry, Kademlia, Broose and EpiChord) under conditions as commonly experienced in public mobile data networks. Our results show that the conditions in mobile networks, including a high churn rate and the relatively low bandwidth availability is best matched by Kademlia and EpiChord. These overlays exhibit a high lookup success ratio and low hop count while consuming a moderate amount of bandwidth. These characteristics make these two overlays suitable candidates for use in mobile networks

Fatty acid, mineral and heavy metal contents of different Malaysia fish species

Fish are popularly recognized as an excellent source of lipids that are composed of a wide range of important fatty acids. Fish also contain good quality protein and are an adequate source of many vitamins (e.g. fat soluble A, D, E and the water soluble B-complex), in addition to important minerals such as calcium and phosphorous. We recently investigated the fatty acid (FA) profiles, mineral and heavy metal contents of 13 different species of commonly consumed, wild marine fin-fish found off Langkawi Island, a popular Malaysian tourist destination. The fish species were “jenahak” (Lutjanus agentimaculatus), “kebasi” (Anadontostoma chacunda), “duri” (Arius umatranus), “tenggiri batang” (Scomberomorus commersonii), “kembong” (Rastrelliger kanagurta), “kintan” (Psettodes crumei), “kerisi” (Pristipomoides typus), “kerapu” (Epinephelus sexfasciatus), “gelama keling” (Sciaena dussumieri),“malong” (Congresax talabon), “laban” (Cynoglossus lingua), “yu 9” (Scolidon sorrakowah) and “bagi” (Aacnthurs nigrosis). The overall findings reveal that all fish showed a considerable amount of unsaturated fatty acids particularly those with 4, 5 and 6 double bonds. Two physiologically important n-3 polyunsaturated fatty acids (PUFAs), i.e. eicosapentaenoic acid (EPA) and docasahaexaenoic acid (DHA), made up more than 50% of the total PUFAs. It can be concluded that fin fish found in Langkawi Island coastal areas are beneficial for human health as they have considerable amounts of PUFAs, especially AA and DHA fatty acids. In the case of heavy metal analysis, the result reveals the safety of the consumption of fish from the human health point of vie

Social Anchor: Privacy-Friendly Attribute Aggregation From Social Networks

In the last decade or so, we have experienced a tremendous proliferation and popularity of different Social Networks (SNs), resulting more and more user attributes being stored in such SNs. These attributes represent a valuable asset and many innovative online services are offered in exchange of such attributes. This particular phenomenon has allured these social networks to act as Identity Providers (IdPs). However, the current setting unnecessarily imposes a restriction: a user can only release attributes from one single IdP in a single session, thereby, limiting the user to aggregate attributes from multiple IdPs within the same session. In addition, our analysis suggests that the manner by which attributes are released from these SNs is extremely privacy-invasive and a user has very limited control to exercise her privacy during this process. In this article, we present Social Anchor, a system for attribute aggregation from social networks in a privacy-friendly fashion. Our proposed Social Anchor system effectively addresses both of these serious issues. Apart from the proposal, we have implemented Social Anchor following a set of security and privacy requirements. We have also examined the associated trust issues using a formal trust analysis model. Besides, we have presented a formal analysis of its protocols using a state-of-the-art formal analysis tool called AVISPA to ensure the security of Social Anchor. Finally, we have provided a performance analysis of Social Anchor

Evaluation of Oral Health Status Among Pregnant Women Using Oral Hygiene Index- Simplified (OHI-S) Score

Background: Oral health of women is often neglected during pregnancy. We need to address this issue in a developing country’s perspective, as oral healthcare is not an integral part of antenatal protocols. Objective: To evaluate the oral health status of pregnant women using the Oral Hygiene Index-Simplified (OHI-S) Score as well as explore oral hygiene practice by them and conduct a mini-assessment of their knowledge of oral health. Methods: This cross-sectional, descriptive study was conducted using data by using a semi-structured questionnaire among 170 pregnant women attending an antenatal center in Dhaka city, Bangladesh, from March to August 2018. A pre-tested semi-structured questionnaire containing OHI-S index was used for data collection. Dental mirror and probe were used for oral hygiene assessment. Results: The mean age of the participants was 24.22±5.07 years. 140(82.4%) were found to use toothbrushes as a tooth-cleaning aid and 146(85.9%) used toothpaste as a tooth cleaning material. Among them, 132(94.3%) were found to brush at least once a day. The predominant health problems identified by clinical examination among those pregnant women were gum bleeding, mild to severe periodontitis, halitosis (bad breath), and loose teeth. The majority did not know the safe period of dental treatment and the consequences of having poor oral health during pregnancy. The overall oral hygiene status of the maximum pregnant women was ‘Fair’ (50.6%) (OHI-S score 0-1.2), while 39.4% had ‘Poor’ oral hygiene status (OHI-S score 1.3-3.0) and only 10% had ‘Good’ oral hygiene status (OHI-S score 3.1-6.9). Conclusion: Pregnant women in Bangladesh suffer from various oral health issues during pregnancy; however, they exhibit that they do not address this issue due to a lack of awareness and other factors. Hence, it is crucial to plan and implement effective oral health programs for pregnant women all over the countr