Ordered dynamic channel assignment scheme with reassignment inhighway microcells

An ordered dynamic channel assignment with reassignment (ODCAR) scheme is proposed, and its performance is studied in a highway microcellular radio environment. Channels are assigned in an ordered basis in conjunction with a minimax algorithm under cochannel interference constraints, to provide high capacity and to alleviate worst case channel congestion in each microcell. Simulation results show significant performance improvements in terms of channel utilization and probability of call failure, at the expense of an increase in complexity and call switching requirements     

Strength degradation of sandstone and granodiorite under uniaxial cyclic loading

Change in mechanical properties of rocks under static loading has been widely studied and documented. However, the response of rocks to cyclic loads is still a much-debated topic. Fatigue is the phenomenon when rocks under cyclic loading fail at much lower strength as compared to those subjected to the monotonic loading conditions. A few selected cored granodiorite and sandstone specimens have been subjected to uniaxial cyclic compression tests to obtain the unconfined fatigue strength and life. This study seeks to examine the effects of cyclic loading conditions, loading amplitude and applied stress level on the fatigue life of sandstone, as a soft rock, and granodiorite, as a hard rock, under uniaxial compression test. One aim of this study is to determine which of the loading conditions has a stronger effect on rock fatigue response. The fatigue response of hard rocks and soft rocks is also compared. It is shown that the loading amplitude is the most important factor affecting the cyclic response of the tested rocks. The more the loading amplitude, the shorter the fatigue life, and the greater the strength degradation. The granodiorite specimens showed more strength degradation compared to the sandstone specimens when subjected to cyclic loading. It is shown that failure modes of specimens under cyclic loadings are different from those under static loadings. More local cracks were observed under cyclic loadings especially for granodiorite rock specimens.     

Dynamic channel assignment with queuing in highway microcells

The effect of queuing on an ordered dynamic channel assignment with reassignment (QODCAR) scheme in a highway microcellular environment are studied. Results show that queuing improves channel use by approximately 9-43%, and significantly lowers the probability of call failure.<>     

Therapeutic Targeting of the Leukaemia Microenvironment

In recent decades, the conduct of uniform prospective clinical trials has led to improved remission rates and survival for patients with acute myeloid leukaemia and acute lymphoblastic leukaemia. However, high-risk patients continue to have inferior outcomes, where chemoresistance and relapse are common due to the survival mechanisms utilised by leukaemic cells. One such mechanism is through hijacking of the bone marrow microenvironment, where healthy haematopoietic machinery is transformed or remodelled into a hiding ground or “sanctuary” where leukaemic cells can escape chemotherapy-induced cytotoxicity. The bone marrow microenvironment, which consists of endosteal and vascular niches, can support leukaemogenesis through intercellular “crosstalk” with niche cells, including mesenchymal stem cells, endothelial cells, osteoblasts, and osteoclasts. Here, we summarise the regulatory mechanisms associated with leukaemia–bone marrow niche interaction and provide a comprehensive review of the key therapeutics that target CXCL12/CXCR4, Notch, Wnt/b-catenin, and hypoxia-related signalling pathways within the leukaemic niches and agents involved in remodelling of niche bone and vasculature. From a therapeutic perspective, targeting these cellular interactions is an exciting novel strategy for enhancing treatment efficacy, and further clinical application has significant potential to improve the outcome of patients with leukaemia.     

A predictive load-sharing scheme in a microcellular radioenvironment

In a metropolitan microcellular environment, the cell coverage zone can be highly irregular. Thus highly overlapping areas can result due to an attempt to achieve ubiquitous coverage. The authors propose a predictive load sharing (PLS) scheme to alleviate localised congestion by using the knowledge of users potentially entering and leaving a cell. They study the system in a linear bidirectional highway environment. Results show that load carried is increased and the handoff failure rate is lowered compared to the fixed channel assignment (FCA) scheme. A lower handoff failure rate is a desirable feature since the forced termination of an existing call can be very annoying to a user     

Priority handoff analysis

Handoff will become an increasingly important issue in mobile phone communications, especially in microcellular systems with the increase of handoff traffic between cells. Many approaches have been proposed for handoff analysis. In a previous analysis, it was assumed that the probability density function (pdf) of the speeds of cell-crossing terminals is the same as the pdf of the speeds of all terminals. In contrast to this assumption, we argue that both pdf's are unequal. The pdf of the speeds of cell-crossing terminals is given by a biased sampling formula. This boundary condition is used in our study and improves the accuracy of performance measures in handoff analysis. In previous work, a priority handoff system which has dedicated channels for handoff calls and uses a blocked call cleared (BCC) policy has been analyzed. In this paper, we use a different approach in performance analysis. The proposed approach has low computational complexity and high accuracy.The author was a visiting scholar at WINLAB while this work was completed.     

High UV/solar rejection ratios in GaN/AlGaN/GaN p-i-n photodiodes

The solar-blind detection capability of heterostructure diodes employing an i-Al_0.33Ga_0.67N layer sandwiched between two doped GaN layers is investigated via simulations using MEDICI. It is shown that the introduction of quantum features, such as InGaN quantum wells and delta-doped regions of p-Al_0.33Ge_0.67N, can successfully suppress the current due to photogeneration in the low-bandgap GaN regions, leading to UV/solar rejection ratios of over three orders of magnitude