Dynamic Scaling, Data-collapse and Self-Similarity in Mediation-Driven Attachment Networks

Recently, we have shown that if the $i$th node of the Barab\'{a}si-Albert (BA) network is characterized by the generalized degree $q_i(t)=k_i(t)t_i^\beta/m$, where $k_i(t)\sim t^\beta$ and $m$ are its degree at current time $t$ and at birth time $t_i$, then the corresponding distribution function $F(q,t)$ exhibits dynamic scaling. Applying the same idea to our recently proposed mediation-driven attachment (MDA) network, we find that it too exhibits dynamic scaling but, unlike the BA model, the exponent $\beta$ of the MDA model assumes a spectrum of value $1/2\leq \beta \leq 1$. Moreover, we find that the scaling curves for small $m$ are significantly different from those of the larger $m$ and the same is true for the BA networks albeit in a lesser extent. We use the idea of the distribution of inverse harmonic mean (IHM) of the neighbours of each node and show that the number of data points that follow the power-law degree distribution increases as the skewness of the IHM distribution decreases. Finally, we show that both MDA and BA models become almost identical for large $m$.Comment: 8 pages, 8 captioned figure

Charged Scalar Pair Production in Strong-Field Photon-Photon Interaction

Following the pioneering work of H. Reiss [1], we provide a covariant calculation of the charged scalar particle pair production. The calculation is facilitated by the use of two-dimensional Bessel functions and light-font coordinates.Comment: 8 page

Market Efficiency, Time-Varying Volatility and Equity Returns in Bangladesh Stock Market

This paper empirically examines the issue of market efficiency and time- varying risk return relationship for Bangladesh, an emerging equity market in South Asia. The study utilizes a unique data set of daily stock prices and returns compiled by the authors which was not utilized in any previous study. The Dhaka Stock Exchange (DSE) equity returns show positive skewness, excess kurtosis and deviation from normality. The returns display significant serial correlation, implying stock market inefficiency. The results also show a significant relationship between conditional volatility and the stock returns, but the risk- return parameter is negative and statistically significant. While this result is not consistent with the portfolio theory, it is possible theoretically in emerging markets as investors may not demand higher risk premia if they are better able to bear risk at times of particular volatility (Glosten, Jagannathan and Runkle, 1993). While circuit breaker overall did not have any impact on stock volatility, the imposition of the lock-in period has contributed to the price discovery mechanism by reverting an overall negative risk-return time-varying relationship into a positive one. As a policy to improve the capital market efficiency, the timely disclosure and dissemination of information to the shareholders and investors on the performance of listed companies should be emphasized.

Construction dispute mitigation through multi-agent based simulation and risk management modeling

The construction industry is regarded not only as a backbone of the nation’s economy but also as an integral indicator of its efficiency and effectiveness. However, as a result of the risks and complexities that are naturally inherent with construction projects as well as the diverging interests of the parties involved, claims and disputes could be considered an unavoidable consequence of the construction processes. In fact, over the years, the frequency and severity of claims and disputes have significantly increased to the extent that the estimated total annual cost of construction conflicts and disputes in the U.S. is $5 billion. That said, the main goal of this dissertation was to develop an integrated and coherent methodology for mitigation of construction disputes through both, multi agent based simulation concepts and risk management modeling principles. In this regard, the associated work carried out under this research has: (1) developed an innovative method for using logical induction decision support in construction claims and disputes; (2) created a multi agent system for construction dispute resolution (MAS-COR) that will simulate legal discourse in construction disputes; (3) developed a new method for addressing the issue of risks in the construction industry using portfolio insurance; and (4) created an innovative way for mitigating negative effects of contractor’s construction claims and disputes using a risk retention approach. It is conjectured that the attainment of the aforementioned objectives, as detailed under this dissertation, would mitigate the negative effects of claims and disputes in the construction industry and thus, have a positive impact on the contracting parties, their projects, the construction industry as a whole, and consequently, the nation’s economy

Market Efficiency, Time-Varying Volatility and Equity Returns in Bangladesh Stock Market

This paper empirically examines the issue of market efficiency and time-varying risk return relationship for Bangladesh, an emerging equity market in South Asia. The study utilizes a unique data set of daily stock prices and returns compiled by the authors which was not utilized in any previous study. The Dhaka Stock Exchange (DSE) equity returns show positive skewness, excess kurtosis and deviation from normality. The returns display significant serial correlation, implying stock market inefficiency. The results also show a significant relationship between conditional volatility and the stock returns, but the risk-return parameter is negative and statistically significant. While this result is not consistent with the portfolio theory, it is possible theoretically in emerging markets as investors may not demand higher risk premia if they are better able to bear risk at times of particular volatility (Glosten, Jagannathan and Runkle, 1993). While circuit breaker overall did not have any impact on stock volatility, the imposition of the lock-in period has contributed to the price discovery mechanism by reverting an overall negative riskreturn time-varying relationship into a positive one. As a policy to improve the capital market efficiency, the timely disclosure and dissemination of information to the shareholders and investors on the performance of listed companies should be emphasized.

Assessment of the knowledge of dentists about halitosis at two dental teaching hospitals in Khartoum city

The present study is a descriptive cross-sectional study that was conducted to assess the level of knowledge about halitosis among dental surgeons in Khartoum city.One hundred and six dental surgeons were randomly selected from two dental teaching hospitals: Khartoum Dental Teaching Hospital and Ribat Teaching Hospital in Khartoum city. A fully structured, close ended questionnaire was used. Data collected was assembled and analyzed using the SPSS statistical software. Most of the respondents were general practitioners. The knowledge about the causes and diagnosis of halitosis was generally poor (81%). The awareness about the treatment wasgenerally moderate (37%) and good (38%). No association was found between gender and the level of knowledge about halitosis (p\u3e0.05).A significant association was noted between the level of qualification or the years of clinical experience and the knowledge about the causes and diagnosis of halitosis (p\u3c0.05). The study revealed that dentists lack adequate knowledge regarding causes and diagnosis of halitosis especially for those with lesser years of clinical experience. An increase in knowledge levels could be achieved by emphasizing on this subject during professional training