A DEM for visualising damage evolution and predicting failure of composite lamina under uniaxial and biaxial loads

Fibre-reinforced composites have many outstanding advantages that attract commercial industries to use them such as, automotive industry, aerospace industry, marine industry, wind turbines, and sports goods. Fibre-reinforced composites characterised as a high strength/stiffness to weight ratio comparing with natural metals resulting in very lightweight structures which in turn reduce fuel consumed by aircraft, for instance. They also provide an excellent resistance to, corrosion, fatigue stress, impact force and chemical attack. The main concern in use of these materials is the complexity of damages that are taken place in different scale lengths starting from micro-scale level. With the development of computer power, however, the door is opened to enhance concepts such as a multi-scale analysis that can bridge microscale to macro-scale. The new tools provide excellent substitutes of the costly and time-consuming experimental tests. In this thesis, Discrete Element Method (DEM) is developed for micromechanical modelling of fibre-reinforced composites. In Chapter 2, a new method is proposed for generating random fibre distribution. Unlike prior methods that have proposed, this method can be used to generate a high fibre volume fraction with any inter-fibres distance. The new method is then applied throughout the thesis. In Chapter 3, a Representative Volume Element (RVE) containing fibres distributed randomly subjected to uniaxial transverse tension is studied. The DEM is showed to a genuine tool to investigate damage propagation in fibre-reinforced composites. Chapter 4 is dedicated to determining the elastic properties of the fibrereinforced composite using DEM. The results are then compared with selected analytical methods, namely Voigt and Mori-Tanaka methods, other numerical method such as Finite Element Method (FEM), and experimental results. The methodology developed in previous chapters are then adopted in Chapter 5 to study the failure of fibre-reinforced composite under uniaxial compression, transverse shear and biaxial transverse loads. Results are compared with experiments and analytical method such as Hashin and Puck models

Financial markets: very noisy information processing

We report new results about the impact of noise on information processing with application to financial markets. These results quantify the tradeoff between the amount of data and the noise level in the data. They also provide estimates for the performance of a learning system in terms of the noise level. We use these results to derive a method for detecting the change in market volatility from period to period. We successfully apply these results to the four major foreign exchange (FX) markets. The results hold for linear as well as nonlinear learning models and algorithms and for different noise models

The maximum drawdown of the Brownian motion

The MDD is defined as the maximum loss incurred from peak to bottom during a specified period of time. It is often preferred over some of the other risk measures because of the tight relationship between large drawdowns and fund redemptions. Also, a large drawdown can even indicate the start of a deterioration of an otherwise successful trading system, for example due to a market regime switch. Overall, the MDD is a very important risk measure. To be able to use it more insightfully, its analytical properties have to be understood. As a step towards this direction, we have presented in this article some analytic results that we have developed. We hope more and more results will come out from the research community analyzing this important measure

Identification of Causes and Effects of Poor Communication in Construction Industry: A Theoretical Review

Construction industry is characterized in nature as complex, fragmented, dynamic and involves many parties therefore effective communication is essential to overcome these challenges. Many researchers found that the industry faces major challenge to ensure effective and successful communication throughout the lifecycle of the project which therefore resulted to project failure. Poor communication in construction industry had been addressed in previous research studies; however, this paper presents and examines the identification of causes and effects which lead to poor communication. Further investigations on previous literature were conducted to extract the causes and effects which contributed to poor communication in construction industry. Similarity technique was applied to avoid duplications in the identified causes and effect of poor communication. Using the frequency technique, from the 33 causes of poor communication it was found that the most dominant cause is lack of effective communication. Whereas, out of 21 effects from poor communication, it was found that highly repeated effect is time overrun. These findings will serve a good platform for further investigation on the relevancy of causes and effects to the local construction practitioners

Introduction to the special issue on neural networks in financial engineering

There are several phases that an emerging field goes through before it reaches maturity, and computational finance is no exception. There is usually a trigger for the birth of the field. In our case, new techniques such as neural networks, significant progress in computing technology, and the need for results that rely on more realistic assumptions inspired new researchers to revisit the traditional problems of finance, problems that have often been tackled by introducing simplifying assumptions in the past. The result has been a wealth of new approaches to these time-honored problems, with significant improvements in many cases

Simulation and Development of Instrumental Setup to Be Used for Cement Grouting of Sand Soil

Most of Arab countries areas are occupied with deserts that is covered with sandy soil. Thus, it is necessary to make use of this huge volume of sand to be as construction materials. It is proven that, sand is initially uneven and unstable. It requires pre-modifications of its primer properties in order to be used as construction materials. One of the common techniques is injecting the sand with binders. Many grouting techniques has been implanted to modify or rehabilitate the structure of soil but for sandy soil the methods has not yet been introduced Therefore, this study aimed at developing simulation and instrumental setup to be used for cement grouting. The simulation has been custom made and utilized to form grouted samples for further investigation. The method of injecting sand is by applying pressure to produce force flow in order to be injected into the sand. After the formation of injected sand samples, an experimental investigation was carried out to determine the basic properties. Shear strength of the sand was recorded before and after grouting. It was found that, the shear strength has increased after injecting the sand with cement and the setup has produced accurate grouted samples with even distribution of the cement mix. The results of the various investigations conclusively proved that grouting can be used as an effective way to improve the strength characteristics significantly and can also contribute to the stabilization of sand

PIETY ON CONTESTATION

This article studied the phenomenon of contestation between orang Sunnah and orang Yasin in Sidodadi, Aceh Tamiang, to gain the recognition of being the most pious Muslim adherent. The research zoomed in on exploring the shape of the contestation and the socio-religious changes that may occur due to the existence of the mentioned contest. The researchers interviewed a dozens of informant, observed their religious practices and the strategy that they launch to propagate their belief and recruit new members. The study showed that the contestation between the two community take place in almost all religious practices. Some of the worth mentions are ritual practices, broadening and enhancing the religiosity of respective community members, or the approach they used in approaching Islam. Apart from that, the contestation between these two groups also triggered the negotiation and reconciliation of Islamic practices of both groups. The reconciliation of religious practice is in accordance with the "culture in between " theory as proposed by Homi K Bhabha in which he believes that truly there are always no clear boundaries between two groups of different credentials. In Sidodadi, the credentials difference of each group to actualize the ideal of Islam in managing the house of God for instance, triggers the struggle of both groups for the control of the mosques and mushollas in one hand, and in other hand it brings out the empathy of each community to revive the religious activities in worship places, though adapted with the credential feature of their respective groups. Keywords: Piety, Orang Sunnah, Orang Yasin, Aceh Tamian

No Free Lunch for Early Stopping

We show that, with a uniform prior on hypothesis functions having the same training error, early stopping at some fixed training error above the training error minimum results in an increase in the expected generalization error. We also show that regularization methods are equivalent to early stopping with certain non-uniform prior on the early stopping solutions

On the Performance of Energy Criterion Method in Wi-Fi Transient Signal Detection

In the development of radiofrequency fingerprinting (RFF), one of the major challenges is to extract subtle and robust features from transmitted signals of wireless devices to be used in accurate identification of possible threats to the wireless network. To overcome this challenge, the use of the transient region of the transmitted signals could be one of the best options. For an efficient transient-based RFF, it is also necessary to accurately and precisely estimate the transient region of the signal. Here, the most important difficulty can be attributed to the detection of the transient starting point. Thus, several methods have been developed to detect transient start in the literature. Among them, the energy criterion method based on the instantaneous amplitude characteristics (EC-a) was shown to be superior in a recent study. The study reported the performance of the EC-a method for a set of Wi-Fi signals captured from a particular Wi-Fi device brand. However, since the transient pattern varies according to the type of wireless device, the device diversity needs to be increased to achieve more reliable results. Therefore, this study is aimed at assessing the efficiency of the EC-a method across a large set of Wi-Fi signals captured from various Wi-Fi devices for the first time. To this end, Wi-Fi signals are first captured from smartphones of five brands, for a wide range of signal-to-noise ratio (SNR) values defined as low (−3 to 5 dB), medium (5 to 15 dB), and high (15 to 30 dB). Then, the performance of the EC-a method and well-known methods was comparatively assessed, and the efficiency of the EC-a method was verified in terms of detection accuracy.publishedVersio

Under the Shadow of Sharia: Christian Muslim Relations From Acehnese Christian Experience

The implementation of sharia in Aceh has have given a complex impacts to several aspects of life of the Christian, economically, culturally, politically and any other aspects of social life. Unlike other Indonesian Christian in different parts of archipelago, the Christian women in Aceh are experiencing the life that regulated by the sharia. Based on the experience in Langsa, some of them (especially teachers, employee, and students) were appealed to wear headscarf (hijab) in their appearance in Islamic public sphere. Those who reside in Aceh Singkil experienced difficulties in establishing church, beyond any difficulties that experienced by Christians in other part of Indonesian region. However, in Southeast Aceh, the Christian live the life of religious harmony among the Muslim majority who implement the Islamic sharia. This article shows that strong encouragement among the Muslim circle to implementing Islamic sharia through political approach could generate difficulties to certain Christians, while to some others it doesn't give any significant negative impact. This article aims to highlight some issues that experienced by Christians who live amid the Muslim majority who implement Islamic sharia. Data were collected during ethnographical studies conducted in the year 2013-2015 in Langsa, Aceh Singkil and Southeast Aceh. Finally, this article proposes significant policy options for managing Muslim-Christian relations in Aceh, Indonesia. Education is crucial for promoting interreligious harmony, religious freedom, and respect for people of different traditions and religion