Untenable nonstationarity: An assessment of the fitness for purpose of trend tests in hydrology

The detection and attribution of long-term patterns in hydrological time series have been important research topics for decades. A significant portion of the literature regards such patterns as ‘deterministic components’ or ‘trends’ even though the complexity of hydrological systems does not allow easy deterministic explanations and attributions. Consequently, trend estimation techniques have been developed to make and justify statements about tendencies in the historical data, which are often used to predict future events. Testing trend hypothesis on observed time series is widespread in the hydro-meteorological literature mainly due to the interest in detecting consequences of human activities on the hydrological cycle. This analysis usually relies on the application of some null hypothesis significance tests (NHSTs) for slowly-varying and/or abrupt changes, such as Mann-Kendall, Pettitt, or similar, to summary statistics of hydrological time series (e.g., annual averages, maxima, minima, etc.). However, the reliability of this application has seldom been explored in detail. This paper discusses misuse, misinterpretation, and logical flaws of NHST for trends in the analysis of hydrological data from three different points of view: historic-logical, semantic-epistemological, and practical. Based on a review of NHST rationale, and basic statistical definitions of stationarity, nonstationarity, and ergodicity, we show that even if the empirical estimation of trends in hydrological time series is always feasible from a numerical point of view, it is uninformative and does not allow the inference of nonstationarity without assuming a priori additional information on the underlying stochastic process, according to deductive reasoning. This prevents the use of trend NHST outcomes to support nonstationary frequency analysis and modeling. We also show that the correlation structures characterizing hydrological time series might easily be underestimated, further compromising the attempt to draw conclusions about trends spanning the period of records. Moreover, even though adjusting procedures accounting for correlation have been developed, some of them are insufficient or are applied only to some tests, while some others are theoretically flawed but still widely applied. In particular, using 250 unimpacted stream flow time series across the conterminous United States (CONUS), we show that the test results can dramatically change if the sequences of annual values are reproduced starting from daily stream flow records, whose larger sizes enable a more reliable assessment of the correlation structures

Financial Applications of Human Perception of Fractal Time Series

The purpose of this thesis is to explore the interaction between people’s financial behaviour and the market’s fractal characteristics. In particular, I have been interested in the Hurst exponent, a measure of a series’ fractal dimension and autocorrelation. In Chapter 2 I show that people exhibit a high level of sensitivity to the Hurst exponent of visually presented graphs representing price series. I explain this sensitivity using two types of cues: the illuminance of the graphs, and the characteristic of the price change series. I further show that people can learn how to identify the Hurst exponents of fractal graphs when feedback about the correct values of the Hurst exponent is given. In Chapter 3 I investigate the relationship between risk perception and Hurst exponent. I show that people assess risk of investment in an asset according to the Hurst exponent of its price graph if it is presented along with its price change series. Analysis reveals that buy/sell decisions also depend on the Hurst exponent of the graphs. In Chapter 4 I study forecasts from financial graphs. I show that to produce forecasts, people imitate perceived noise and signals of data series. People’s forecasts depend on certain personality traits and dispositions. Similar results were obtained for experts. In Chapter 5 I explore the way people integrate visually presented price series with news. I find that people’s financial decisions are influenced by news more than the average trend of the graphs. In the case of positive trend, there is a correlation between financial forecasts and decisions. Finally, in Chapter 6 I show that the way people perceive fractal time series is correlated with the Hurst exponent of the graphs. I use the findings of the thesis to describe a possible mechanism which preserves the fractal nature of price series

ENHANCING OXIDATION RESISTANCE OF Ni-BASED ALLOYS FOR HIGH TEMPERATURE APPLICATIONS

The demand for energy significantly increases with increasing of world population and industrial activity in developing countries. Nuclear energy can be considered to make an important contribution to future demands for electricity and thermal energy. In order to continue providing inexpensive and safe energy, the operation temperatures of the next generation nuclear reactors should be remarkably increased. Consequently, the alloys used in the high temperature environment will face oxidation degradation problems. Therefore, it is critical to find ways to improve the oxidation resistance of the alloys to be used for high temperature applications. In this thesis, two potential solutions are proposed to enhance the oxidation resistance of three Ni-based alloys. The effect of crystallographic orientation on the oxidation behavior of Hastelloy 230 was investigated to evaluate if texture would affect the oxidation behavior of Ni-based alloys. The obtained results clearly demonstrate that the oxidation rate highly depends on the grain orientation. The oxidation resistance of grains are found to increase in the order of (100) < (110) < (111). The substrates with different grain sizes and similar textures were prepared to inspect the influence of grain sizes on the oxidation behavior of Hastelloy 230 and Hastelloy N. It is demonstrated that the grain size only has a small influence on the oxidation behavior of the high-Cr Hastelloy 230 while it significantly changes the oxidation behavior of the low-Cr Hastelloy N. The oxidation mechanisms of high and low-Cr alloys with coarse and fine grain sizes are discussed. Increasing of the grain boundary density of the low-Cr alloy is believed to promote the diffusivities of Cr ions which results in the formation of a uniform Cr-rich protective oxide layer. The grain refinement process can be an efficient way to enhance the oxidation resistance of investigated low-Cr alloy. The effect of reactive element coating on oxidation behavior of chromium oxide forming alloy was examined. The parameters of electro-deposition process like the current density, deposition time and temperature were optimized to synthesize ceria coating. The coatings were applied to Hastelloy 230 and 625 to investigate the influence of this reactive element on the oxidation behavior. For both alloys, the coating significantly enhanced the oxidation resistance and adherence of the oxide to the substrate. The segregation of reactive element onto grain boundaries is linked to change of the oxidation mechanism from outward diffusion of cations to inward diffusion of anions. Specifically for Hastelloy 230, the addition of ceria coating changed the chromium oxide morphology from columnar to equaxied structure and that is believed to enhance the spallation resistance. In Hastelloy 625, a porous and cracked oxide layer is observed on the uncoated sample, while a layer that is protective against oxidation is formed on the coated sample. The prepared coating suppressed the formation of iron oxide. The oxidation mechanism is suggested and discussed

Pre-Vocational, Pre-Technical and Pre-Professional Programmes: Basic Tools for Vocational Technical Education and Training

It is noted that various institutions of learning such as primary schools, secondary schools, technical colleges, colleges of education, polytechnics and universities adopt different programmes and methods in training their pupils and students. The chosen programmes by these institutions depend on the ability and interest of the students in various institutions. These programmes are the basic tools for vocational technical education and training in various countries of the world. The training required depends on the level of institution of learning. The training starts from primary school level to higher institutions .The study focuses on the meaning of pre-vocational, pre-technical, pre-profession, technical education and vocational education. It also focuses on the occupational competencies required for training vocational technical education students. The study also contained the measures to improve on the training of vocational technical education students. Keywords: Pre-vocational Education, Pre-technical Education, Pre-professional Education, Vocational Technical Education and Training DOI: 10.7176/JEP/10-26-09 Publication date:September 30th 201

Fractional Order Fuzzy Control of Nuclear Reactor Power with Thermal-Hydraulic Effects in the Presence of Random Network Induced Delay and Sensor Noise having Long Range Dependence

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Nonlinear state space modeling of a nuclear reactor has been done for the purpose of controlling its global power in load following mode. The nonlinear state space model has been linearized at different percentage of reactor powers and a novel fractional order (FO) fuzzy proportional integral derivative (PID) controller is designed using real coded Genetic Algorithm (GA) to control the reactor power level at various operating conditions. The effectiveness of using the fuzzy FOPID controller over conventional fuzzy PID controllers has been shown with numerical simulations. The controllers tuned with the highest power models are shown to work well at other operating conditions as well; over the lowest power model based design and hence are robust with respect to the changes in nuclear reactor operating power levels. This paper also analyzes the degradation of nuclear reactor power signal due to network induced random delays in shared communication network and due to sensor noise while being fed-back to the Reactor Regulating System (RRS). The effect of long range dependence (LRD) which is a practical consideration for the stochastic processes like network induced delay and sensor noise has been tackled by optimum tuning of FO fuzzy PID controllers using GA, while also taking the operating point shift into consideration

Energy Sector Governance and Cost Reflective Pricing in West Africa

This study was carried out to consider the effectiveness of energy sector governance and electricity pricing in Nigeria – which also has implications for West Africa’s power pool and energy policies in the region. This paper applies the concept of cost reflectivity to analyze the current electricity tariff regime in Nigeria. Multi Year Tariff Order (MYTO) 2015 methodology was applied in the analysis - employing the marginal cost (MC) and marginal revenue concepts (MR). It was noticed that, the cost of providing a unit of electricity (1 kWh) varies by region while the revenue generated from providing the same unit of electricity also varies by region. However, energy sector governance in the main West African electricity market - Nigeria - is very weak. While, a competitive market structure is gradually emerging, debts accrue along the value chain with every unit of power consumed. More so, the underlying assumptions of the methodology have been consistently violated and as such tariffs have not been completely cost-reflective. Some underlying assumptions of the MYTO methodology need to be reviewed for it to sufficiently de-risk energy investments in Nigerian Electricity Supply Industry (NESI) especially against macroeconomic shocks

Institutional Voids and Employment in Nigerian Agriculture

Governance has always been an issue in the economies of the Less Developed Countries (LDCs) of the world, and Nigeria is not an exception. The economy of Nigeria is managed through Ministries, Departments and Agencies (MDAs) delineated along sectoral lines. The agricultural sector is governed by the Federal Ministry of Agriculture and Rural Development that is responsible for formulating government polices to stimulate agricultural finance, production, storage, processing, value chain development and marketing. These polices are, in turn, expected to stimulate new investments, job creation, and employment in the sector. Time series secondary data covering 1981 to 2014 on the rebased Gross Domestic Product (GDP) and sectoral Gross Value Added (GVA) at 2010 constant basic prices, employment, wage rate, inflation rate and interest rate were collected from the National Bureau of Statistics and the Central Bank of Nigeria on the agricultural sector. The variables were collated and summarised into a table of data. The unit root test was carried out to test for stationarity of variables. Sectoral employment elasticities of growth were measured using Vector Error Correction Model (VECM) regression.  Data was analysed using descriptive statistics and VECM at α0.05. Agriculture sectoral elasticity of employment was -0.02, but it was not significant. Key informants in agricultural policy and agricultural value chains were then interviewed to determine why the job absorptive capacity of the agricultural sector was unexpectedly low, and the result, summarized with Khanna’s Five-Context Model, pointed to institutional voids in the sector that must be addressed before the full employment generating potentials of the agricultural sector may be realised. Keywords: Economic growth, Employment elasticity, Gross Value Added, Agricultural Sector, Institutional Voids. DOI: 10.7176/JESD/12-14-12 Publication date:July 31st 202

Salt tolerance QTLs of an endemic rice landrace, \u3ci\u3eHorkuch\u3c/i\u3e at seedling and reproductive stages

Salinity has a significant negative impact on production of rice. To cope with the increased soil salinity due to climate change, we need to develop salt tolerant rice varieties that can maintain their high yield. Rice landraces indigenous to coastal Bangladesh can be a great resource to study the genetic basis of salt adaptation. In this study, we implemented a QTL analysis framework with a reciprocal mapping population developed from a salt tolerant landrace Horkuch and a high yielding rice variety IR29. Our aim was to detect genetic loci that contributes to the salt adaptive responses of the two different developmental stages of rice which are very sensitive to salinity stress. We identified 14 QTLs for 9 traits and found that most are unique to specific developmental stages. In addition, we detected a significant effect of the cytoplasmic genome on the QTL model for some traits such as leaf total potassium and filled grain weight. This underscores the importance of considering cytoplasm-nuclear interaction for breeding programs. Finally, we identified QTLs co-localization for multiple traits that highlights the possible constraint of multiple QTL selection for breeding programs due to different contributions of a donor allele for different traits