43 research outputs found
Approaches for Enhancing Composting Process of Farmyard Manure in Dhankuta District, Nepal
No full text東京農業大学博士（農業工学
Evaluation of Growth, Yield and Bioactive Compounds of Ethiopian Kale (Brassica carinata A. Braun) Microgreens under Different LED Light Spectra and Substrates
No full textMicrogreens are innovative vegetable products whose production and consumption are gaining popularity globally thanks to their recognized nutraceutical properties. To date, the effects of lighting conditions and growing substrate on the performances of Brassica carinata microgreens (indigenous to Africa) remain underexplored. The present study aimed at providing insights into the influence of different lighting treatments provided by LEDs, namely monochromatic blue (B), red (R), cool white (W) and a combination of three color diodes (B + R + W), and substrates (cocopeat, sand and cocopeat–sand mix (v/v) (1:1)) on the growth, yield and bioactive compounds of B. carinata microgreens. Seeds were germinated in dark chambers and cultivated in growth chambers equipped with LED lighting systems for 14 days under a fixed light intensity of 160 ± 2.5 μmol m−2 s−1 and photoperiod of 12 h d−1. The best performances were associated with the spectrum that combined B + R + W LEDs and with substrate resulting from the cocopeat–sand mix, including the highest yield (19.19 g plant−1), plant height (9.94 cm), leaf area (68.11 mm2) and canopy cover (55.9%). Enhanced carotenoid and flavonoid contents were obtained with B + R + W LEDs, while the B LED increased the total amount of chlorophyll (11,880 mg kg−1). For plants grown under B + R + W LEDs in cocopeat, high nitrate levels were observed. Our results demonstrate that substrate and light environment interact to influence the growth, yield and concentration of bioactive compounds of B. carinata microgreens
Hydrological drought forecasting in Africa at different spatial and temporal scales
No full textWater ManagementCivil Engineering and Geoscience
Analysis of the Hydro-Climatic Regime of the Snow Covered and Glacierised Upper Indus Basin Under Current and Future Climates
No full textIn the high elevation Hindukush Karakoram Himalaya (HKH) mountain region, the complex weather system and sparse measurements make the elevation-distributed precipitation among the most significant unknowns and limit the realistic and comprehensive assessment of precipitation. In addition, due to local orographic effects, precipitation can vary highly over short horizontal distances. Accurate quantification of precipitation, however, is critical for understanding hydro-climatic dynamics. Moreover, snow and glacier dynamics, and their contribution to river flow in the HKH region, are also mostly unknown, leading to serious concerns about current and future water availability. The recent acceleration in climate change (CC) heightens concerns about future water availability from high elevation mountain regions. The HKH region heavily depends on its upstream frozen water resources, and an accelerated melt may severely affect future water availability. In line with rapid population growth in the Indo-Gangetic plain, there will be increased water, food and energy demands in the future. Therefore, increasing knowledge of the hydro-climatic regime and glacier and snowmelt contributions to the river flow under current and future climate change scenarios is essential. The Indus basin, with a downstream population of around 250 million, is among three highly populated river basins originating from the HKH mountains, followed by Ganges and Brahmaputra. This PhD research was designed to quantitatively and comprehensively assess precipitation and its distribution for the Gilgit and Hunza sub-basins of the Upper Indus Basin (UIB). In addition, the hydrological regime and snow and glacier dynamics were investigated, and the future hydro-climatic regime and water availability from the highly glaciated Hunza basin were analysed. For the present-day investigations, the elevation-distributed precipitation was derived from better performing global precipitation datasets which include the high resolution (0.1°x0.1°) and newly developed ERA5-Land, and a coarser resolution (0.55°x0.55°) JRA-55. These estimates were forced to a data parsimonious precipitation-runoff model, Distance Distribution Dynamics (DDD), with its energy balance and temperature index approaches for snow/glacier melt simulation. The model was calibrated from 1997–2005 and validated from 2006–2010. For future scenarios, the ERA5-Land corrected precipitation against the observed flow was employed to bias correct the precipitation from two global circulation models (GCM) using the newly released Coupled Model Intercomparison Project Phase 6 (CMIP6) climate projections. The DDD model was set up again using these bias corrected GCM projections for baseline (1991–2010), mid-century (2041–2060) and end-century (2081–2100) projections under Shared Socioeconomics Pathways (SSP) SSP1, SSP2 and SSP5 emission scenarios.Water Resource
Battery energy storage system control algorithm design
No full textMicrogrid is based on smaller decentralised low voltage system with the use of modern power technology puts different types of Distributed Energy sources solar power, wind power, and energy storage devices together, improving the electrical supply reliability, reducing the feeder loss and ensures the stability of the voltage. The current trend of incorporating energy storage devices in the microgrid is aimed to mitigate the power imbalance and improve the electrical supply reliability. The thesis uses Kalbarri, Western Australia as a case study site with an aim to investigate the appropriate battery technology and formulate control algorithm for the microgrid.
The thesis starts by examining the Australian electrical market including the: socio‐economic, political, and regulatory environment and presents the rationale of having an Energy Storage System in rural Australia. The thesis investigates the various available BESS battery technology options and suggests the most appropriate options for the BESS comprised Kalbarri microgrid model. The MATLAB/Simulink BESS control algorithm design model is presented with an aim to test voltage and frequency regulation under different load condition, including the process of seamless transition from the grid‐connected operation to a grid‐disconnected operation of the microgrid.
The research presents a theoretical control model based on the Power Control theory and existing academic literature on the topic. The thesis examines the control algorithm design to regulate the frequency and voltage using the BESS system to connect to the main three phase AC grid. The overall site model includes a power conversion of two DC sources: BESS and PV system. The BESS control algorithm model comprises of a Power Conversion system that use three‐phase full bridge Insulated Gate Bipolar Transistors (IGBTs) with LCL filter and a Power Control System based on Phased Lock Loop to synchronise with the grid frequency. The Power Control system uses a three‐phase sinusoidal abc frame conversion to a DC reference signal dq0 frame to incorporate PI controller with an aim that the intermittence of the renewable energy generation Wind and PV system can be maintained to a balanced state in the grid within a short frame of time. The BESS control algorithm model uses a Current Controlled Voltage Source Converter for its simple controller design, better performance during grid fault and the overall cost saving of the system. The thesis simulation utilized CCVSC for its tight regulation of the line current, mainly VSC protection against overcurrent and a high accuracy instantaneous current control.
However, the author acknowledges the simulation result indicate an anomaly with voltage control while using CCVSC in the control algorithm model in power source transition test condition. Hence, as a part of future improvement with a focus on the overcurrent, the author concludes possible testing with the VCVSC based control algorithm model for rapid and continuous response for smooth dynamic control and automated P and Q power control in both steady‐state and dynamic system conditions.
Finally, the impact on the microgrid is presented with an in‐depth analysis of the results, including the achievements, innovations, challenges and the suggestion for future improvement in the discussion section of the report
Expected changes in future temperature extremes and their elevation dependency over the Yellow River source region
No full textUsing the Statistical DownScaling Model (SDSM) and the outputs from two global climate models, we investigate possible changes in mean and extreme temperature indices and their elevation dependency over the Yellow River source region for the two future periods 2046–2065 and 2081–2100 under the IPCC SRES A2, A1B and B1 emission scenarios. Changes in interannual variability of mean and extreme temperature indices are also analyzed. The validation results show that SDSM performs better in reproducing the maximum temperature-related indices than the minimum temperature-related indices. The projections show that by the middle and end of the 21st century all parts of the study region may experience increases in both mean and extreme temperature in all seasons, along with an increase in the frequency of hot days and warm nights and with a decrease in frost days. By the end of the 21st century, interannual variability increases in all seasons for the frequency of hot days and warm nights and in spring for frost days while it decreases for frost days in summer. Autumn demonstrates pronounced elevation-dependent changes in which around six out of eight indices show significant increasing changes with elevation.Water ManagementCivil Engineering and Geoscience
An analysis of snow cover changes in the Himalayan region using MODIS snow products and in-situ temperature data
No full textAmidst growing concerns over the melting of the Himalayas’ snow and glaciers, we strive to answer some of the questions related to snow cover changes in the Himalayan region covering Nepal and its vicinity using Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products from 2000 to 2008 as well as in-situ temperature data from two high altitude stations and net radiation and wind speed data from one station. The analysis consists of trend analysis based on the Spearman’s rank correlation on monthly, seasonal and annual snow cover changes over five different elevation zones above 3,000 m. There are decreasing trends in January and in winter for three of the five elevation zones (all below 6,000 m), increasing trends in March for two elevation zones above 5,000 m and increasing trends in autumn for four of the five elevation zones (all above 4,000 m). Some of these observed trends, if continue, may result in changes in the spring and autumn season river flows in the region. Dominantly negative correlations are observed between the monthly snow cover and the in-situ temperature, net radiation and wind speed from the Pyramid station at 5,035 m (near Mount Everest). Similar correlations are also observed between the snow cover and the in-situ temperature from the Langtang station at 3,920 m elevation. These correlations explain some of the observed trends and substantiate the reliability of the MODIS snow cover products.Water ManagementCivil Engineering and Geoscience
Trends in temperature and rainfall extremes in the Yellow River source region, China
No full textSpatial and temporal changes in daily temperature and rainfall indices are analyzed for the source region of Yellow River. Three periods are examined: 1960–1990, 1960–2000 and 1960–2006. Significant warming trends have been observed for the whole study region over all the three periods, particularly over the period 1960–2006. This warming is mainly attributed to a significant increase in the minimum temperature, and characterized by pronounced changes in the low temperature events composing a significant increase in the magnitude and a significant decrease in the frequency. In contrast to the temperature indices, no significant changes have been observed in the rainfall indices at the majority of stations. However, the rainfall shows noticeable increasing trends during winter and spring from a basin-wide point of view. Conversely, the frequency and contribution of moderately heavy rainfall events to total rainfall show a significant decreasing trend in summer. To conclude, this study shows that over the past 40–45 years the source region of the Yellow River has become warmer and experienced some seasonally varying changes in rainfall, which also supports an emerging global picture of warming and the prevailing positive trends in winter rainfall extremes over the mid-latitudinal land areas of the Northern Hemisphere.Water ManagementCivil Engineering and Geoscience
Coping with the uncertainties in the climate change adaptation of river dikes using risk-aversion economic optimization
No full textTo guarantee a safe flood defence in a changing environment, the adaptation to climate change needs to be considered in the design of river dikes. However, the large uncertainty in the projections of future climate leads to varied estimations of future flood probability. How to cope with the uncertainties in future flood probability under climate change is an inevitable question in the adaptation. In this paper, the uncertainty introduced by climate projections was integrated into the ‘expected predictive flood probability’, and the risk-aversion attitude was introduced in the adaptation of river dikes. In detail, the uncertain effect of climate change on flood probability was represented by the uncertainty in the parameters of the probabilistic model. This parameter uncertainty was estimated based on the outputs from the GCMs participated in IPCC AR4. The parameter uncertainty estimated from different GCMs under selected scenarios was integrated into the expected predictive probability of flooding, which was used in the risk-aversion economic optimization. Different optimal results were obtained based on varied values of the risk-aversion index. The case of Bengbu Dike in China was studied as an example using the proposed approach. The results show that the uncertain effect of climate change causes an increase of optimal dike height but a decrease of the optimal safety level. The proposed approach enables decision makers to cope with the uncertain effects of climate change by adjusting their risk-aversion attitude.Hydraulic EngineeringCivil Engineering and Geoscience
Climate trends and impacts on crop production in the Koshi River basin of Nepal
No full textUnderstanding crop responses to climate is essential to cope with anticipated changes in temperature and precipitation. We investigated the climate–crop yield relationship and the impact of historical climate on yields of rice, maize and wheat in the Koshi basin of Nepal. The results show significant impact of growing season temperature and precipitation on crop production in the region. Rice, maize and wheat cultivated at altitudes below 1,100, 1,350 and 1,700 m amsl (above mean sea level), respectively, suffer from stress due to higher temperatures particularly during flowering and yield formation stages. Responses of crop yields to a unitary increment in growing season mean temperature vary from -6 to 16 %, -4 to 11 % and -12 to 3 % for rice, maize and wheat, respectively, depending on the location and elevation in the basin. In most parts of the basin, we observe warming trends in growing season mean temperatures of rice, maize and wheat over the last few decades with clear evidence of negative impacts on yields. However, at some high-elevation areas, positive impacts of warming are also observed on rice and maize yields. If the observed trends in temperature continue in future, the impact is likely to be mostly negative on crop production in the basin. However, crop production may gain from the warming at relatively higher altitudes provided other conditions, e.g., water availability, soil fertility, are favorable.Water ManagementCivil Engineering and Geoscience
