Growth and suitability of some tree species selected for planting in adverse environments in Eritrea and Ethiopia

The thesis addresses some important silvicultural issues raised in Eritrea and Ethiopia and the objective was to evaluate various tree species in terms of growth in adverse environments. Three field and two greenhouse studies were performed using the main species Eucalyptus globulus, Cordia africana, Casuarina cunninghamiana, and Acacia tortilis, A. nilotica and Leucaena leucocephala. Growth of E. globulus tree was influenced by altitude and stand density when assessed in a planted stand in Ethiopia. Decreasing altitude increased growth only up to the middle of the valley hillside. Increasing density increased growth. Soil depth had no impact on growth of E. globulus and this shows that the species is suitable for planting on shallow soils. Data from a C. africana spacing trial in Eritrea were analysed to improve the management of C. africana plantations established on degraded dry lands by evaluating the response of the species to various initial spacings. Planting C. africana trees at wider spacing can be advantageous in terms of growth, but not stem quality. Different provenances of C. cunninghamiana were tested in two field trials in Eritrea to identify the provenance matching marginal lands of the Eritrean highlands. For firewood and small pole production, the use of the fast growing provenances ‘Coonabarabran’ (CN), ‘Flag stone’ (FS), and ‘Rollingstone’ (RS) is recommended. However, the use and wide spread of the three provenances must be taken with caution due to the risks involved in the use of exotic tree species. Two greenhouse experiments investigated the suitability of A. tortilis for manure production and rehabilitating salt affected marginal lands. The species has a greater potential to produce mulch rich in nitrogen and phosphorus compared to L. leucocephala. Nevertheless, further research under field conditions would be needed to confirm the results and the sustainability of such a practice. A. tortilis and A. nilotica seem to be sensitive to salinity. However, because the two acacias have a wide distribution covering a large salinity gradient, there could be other provenances or ecotypes of both species that are more tolerant to salinity. Therefore, screening tests involving various genotypes of both species could be promising to find suitable trees for afforestation on salt affected soils in arid and semiarid Africa

Measuring and Ranking Value Drivers

Analysis of the strength of value drivers is crucial to understand their influence in the process of free cash flow generation. The paper addresses the issue of value driver measurement and ranking. The research reveals that, value drivers have similar pattern across industries. Furthermore, it is found that the effect of operating cost and interest expenses, on free cash flow, is much more important than sales (revenue)

Evaluating the Capacity of Standard Investment Appraisal Methods

The survey findings indicate the existence of gap between theory and practice of capital budgeting. Standard appraisal methods have shown a wider project value discrepancy, which is beyond and above the contingency limit. In addition, the research has found the growing trend in the use of value management models. The presence of correlation between the frequency of monitoring and project value discrepancy, and the absence of uniformity in the use of evaluation methods throughout the life span of a project are among the results of the study

Openwifi : a free and open-source IEEE802.11 SDR implementation on SoC

Open source Software Defined Radio (SDR) project, such as srsLTE and Open Air Interface (OAI), has been widely used for 4G/5G research. However the SDR implementation of the IEEE802.11 (Wi-Fi) is still difficult. The Wi-Fi Short InterFrame Space (SIFS) requires acknowledgement (ACK) packet being sent out in 10μs/16μs(2.4 GHz/5GHz) after receiving a packet successfully, thus the Personal Computer (PC) based SDR architecture hardly can be used due to the latency (≥100μs) between PC and Radio Frequency (RF) front-end. Researchers have to do simulation, hack a commercial chip or buy an expensive reference design to test their ideas. To change this situation, we have developed an open-source full-stack IEEE802.11a/g/n SDR implementation — openwifi. It is based on Xilinx Zynq Systemon-Chip (SoC) that includes Field Programmable Gate Array (FPGA) and ARM processor. With the low latency connection between FPGA and RF front-end, the most critical SIFS timing is achieved by implementing Physical layer (PHY) and low level Media Access Control (low MAC) in FPGA. The corresponding driver is implemented in the embedded Linux running on the ARM processor. The driver instantiates Application Programming Interfaces (APIs) defined by Linux mac80211 subsystem, which is widely used for most SoftMAC Wi-Fi chips. Researchers could study and modify openwifi easily thanks to the modular design. Compared to PC based SDR, the SoC is also a better choice for portable and embedded scenario

Screening interacting factors in a wireless network testbed using locating arrays

Wireless systems exhibit a wide range of configurable parameters (factors), each with a number of values (levels), that may influence performance. Exhaustively analyzing all factor interactions is typically not feasible in experimental systems due to the large design space. We propose a method for determining which factors play a significant role in wireless network performance with multiple performance metrics (response variables). Such screening can be used to reduce the set of factors in subsequent experimental testing, whether for modelling or optimization. Our method accounts for pairwise interactions between the factors when deciding significance, because interactions play a significant role in real-world systems. We utilize locating arrays to design the experiment because they guarantee that each pairwise interaction impacts a distinct set of tests. We formulate the analysis as a problem in compressive sensing that we solve using a variation of orthogonal matching pursuit, together with statistical methods to determine which factors are significant. We evaluate the method using data collected from the w-iLab.t Zwijnaarde wireless network testbed and construct a new experiment based on the first analysis to validate the results. We find that the analysis exhibits robustness to noise and to missing data

A Monte Carlo Comparison between the Free Cash Flow and Discounted Cash Flow Approaches

One of the debates in the capital budgeting model selection is between the free cash flow and DCF methods. In this paper an attempt is made to compare SVA against NPV model based on Monte Carlo simulations. Accordingly, NPV is found less sensitive to value driver variations and has got higher forecast errors as compared to SVA model

Adding Shareholder Value through Project Performance Measurement, Monitoring & Control

We present the various views and methods of measuring and controlling project performance, and factors affecting a project. The review indicates that there is a shift in the type and understanding of factors of project success or failure. However, the presence of various measurement methods, in addition to diverse interest groups, makes performance decision-making more complex and subjective. A holistic and uniform measurement approach is suggested for both project appraisal and subsequent follow-ups