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- ItemReducing energy consumption of air-conditioners in warm-humid climates through desiccant cooling: a CFD study(KNUST, 2019-03) BAAH, BismarkThe ambient temperature and relative humidity in hot-humid climates, particularly in most countries in sub-Saharan Africa, can get as high as 41 °C and 84%, respectively. For indoor thermal comfort for people, temperature of 20–25 °C and relative humidity of 50–55% should be maintained. Air-conditioners that operate with vapour compression cycle are used to maintain such conditions. In conventional Vapour Compression Systems (VCS), inlet air is cooled below its dew point for dehumidification and then reheated again to obtain air flow with desired temperature and humidity. This process of dehumidification and reheating is inefficient and leads to high consumption of energy. In Desiccant Cooling Systems, dehumidification of air is done by utilizing desiccant material to get desirable humidity and then the dry air is cooled by evaporation method or cooling coils down to suitable temperature. The process of using desiccant to control the air humidity before the air-conditioning process makes the system more energy efficient. In this work, a CFD study has been conducted to ascertain how desiccant can be used to reduce the relative humidity of air prior to the air-conditioning process. The CFD simulations were conducted using TRNSYS software with input data from the Typical Metrological Year (TMY) data for Kumasi. The results show that the desiccant system is able to reduce the cooling load of a selected inefficient VCS in an office in Kumasi by as much as 65%. In addition, analysis in this study has shown that there is potential electricity savings of 2406 kWh/year with the desiccant cooling system over the conventional VCS.
- ItemAssessing the impact of septic tanks on groundwater quality of Selected communities around knust campus(KNUST, 2019-10) TAKAL, JeremiWater is an indispensable resource to mankind and life in general. Over the world, issues of water scarcity and quality are becoming pronounced with increasing global population, industrialization and urbanization. As a result, groundwater has become an important source of water supply throughout the world. The pressure on land and its resources in the study communities as they serve as residence for students, lecturers and the business community has impacted on groundwater quality. Small pieces of land acquired for building virtually does not give room for considering the siting of septic tanks and underground water. The quality of groundwater from eight boreholes/wells from Ayeduase, Boadi and Kotei in the Oforikrom Sub-Metro of the Ashanti Region were analyzed between February and July 2017. Water samples were collected from the eight boreholes/wells within the three communities and analyzed for temperature, pH, and some selected anions NO3- , SO2 -4 and Cl and bacteriological parameters such as total coliform and faecal coliform. The GPS locations of other 54 boreholes and the closest septic tank were taken and the kriging interpolation was applied to extrapolate values of the measured parameters at these locations. The results from the analysis showed that pH of the water was slightly acidic (4.8 to 5.9). With the chemical parameters measured, all of them were within the WHO guidelines for drinking water, ranging from 11.7587 to 53.4723 mg/L, 0.00048 mg/l to 19.4753mg/l, and 4.22 to 40.32 mg/l for chlorides, sulfates and nitrates respectively. Both the total coliform and the faecal coliform levels were low, 0.07 CFU/100ml iv – 7.94 CFU/100ml for the total coliform count and 2.59 CFU/ml – 19.89 CFU/ml for the faecal coliform count. The research also measured the effect of septic tank-borehole/well distance on the variables measured. A regression analysis revealed that there was zero to weak correlation in all the parameters measured, with the “r” values as -0.02, -0.05, -0.04, 0.06, -0.09, 0.11 and -0.42 for total coliform, sulfate, pH, faecal coliform, nitrates and chlorides respectively.
- ItemAn approach to selectively block mobile Phone communication within a mobile phone restricted area(KNUST, 2019-07) AGYARE, MichaelThe use of mobile phone jammers to discourage mobile phone usage in mobile phone restricted areas has some limitations. One major limitation is that, once the jammer is activated no mobile phone can be able to function within the restricted area. For that reason, in the case of emergencies, no mobile phone can either make or receive phone calls or perform emergency calls (police, fire and ambulance services). Works done in literature can detect and block phone calls in a certain way but depends on the mobile switching centre in order to block communication in the restricted area. Therefore, in this thesis, a selective mobile phone communication blocking system is proposed which does not depend on the mobile switching centre in order to perform blocking of communication. The proposed system seeks to allow privilege users access to communication and block non-privilege users with respect to a specific user location. Some mobile phone user locations were considered in this thesis (Hospitals, Banks and Schools). A user from a particular user location cannot enjoy the same privileges at a different location provided that user is privileged. The selective blocking nature of the system was simulated using Fuzzy Inference System (FIS) toolbox (mamdani). The inference method is based on a set of IF-THEN rules and membership functions of the input variable and output variables of the system. Users for the different locations were converted into input triangular membership functions. The output is the decision (“allow” and “not allow”) for each of the inputs. S-shape and Z-shape membership functions were used as the output decision variables. The set of IF-THEN rules were used to link the input variables to the output variables. The fuzzy inference system was able to perform selective blocking of communication services for privileged and non-privileged users. The results in this work shows that when the proposed system is implemented mobile phone communication service can be prioritised to suit privilege users in specific mobile phone restricted areas.
- ItemAnalysis and detection of traffic from dos attack tools using Data mining(KNUST, 2019-10) KOTEY, Seth DjanieThere has been a significant increase in the use of the internet over the past 20 years. As of June 2019, it was estimated that the number of internet users worldwide was over 4.4 billion, corresponding to about 57% of the world’s population. The increase in the use and dependability of the internet has left in its trail a wide variety of vulnerabilities to defend against. One of the key security concepts that helps to guide cybersecurity policies is availability. In a computer network, a denial of service prevents users from having access to resources or services over the network. Denial of service (DoS) attacks are attacks purposely to disrupt availability of a network infrastructure. In past years, a DoS attack required a lot of skill and knowledge in networking for an attack to be launched. However, in recent years, DoS attack tools have been developed by various individuals and groups of people and are readily available on the internet for free or for a little amount of money. Such tools can be used by even the least skilled or knowledgeable attacker. This research therefore sought to develop a defence mechanism against these easy-to-use tools. Attack traffic was captured from some DoS tools and compared with benign traffic. Based on the differences between the attack traffic and benign traffic captured, a signature-based detection algorithm based on support vector machine (SVM) classifier was proposed. The algorithm was tested using the Snort IDS tool and the results were compared with some existing DoS defence schemes. Tests results from the algorithm showed the proposed defence mechanism had a high detection accuracy, low false positive rate and fast detection time.
- ItemAssessment of landuse induced land surface temperature changes in the Greater Accra Region, Ghana(KNUST, 2019-10) AGBOZO, MathiasThis study explored the application of geospatial technology in understanding change pattern of Land use/Land cover (LULC) and associated Land Surface Temperature (LST) variability in the Greater Accra region between 1986 and 2018. Landsat satellite imagery between the months of December and February (dry season) were used for LULC analysis and LST Estimation. MODIS LST data for 1986, 2002 and 2018 were also utilized for the validation of satellite derived LST. The aim of this research was to investigate how LULC changes affects LST. The results of analysis show that LULC in Greater Accra region has changed significantly over the 32-year period. Four major LULC types identified were; vegetation, built-up, bare land and waterbody. Bare land cover type indicated decrease from 1986 to 2018 of 60.22%. Water bodies experienced varying trend of 7.84% decrease representing 9.11 Km2 . Vegetation cover indicated 16.20% increase in 2002 and 28.02% decrease in 2018. This amounted to a total of 11.82% decrease in vegetation cover. On the contrary, built-up increased by 654.03% (724.3 Km2 ) between 1986 and 2018. LST was observed to have increased by 3.05 over the 32-year period of this study across the Greater Accra region. with the highest LST of 36.95 and the lowest of 20.19 , both recorded in 2002. The trend however indicated a significant increase between 1986 and 2002 but a decrease in LST from 2002 to 2018. The increasing trend in LST over time was found to be consistent with the observed urban expansion of the study area. High temperatures are also more apparent along the coastal belt of the region stretching northwards as development spread in the same direction. Total change in LST for the entire period of the study show increases of 3.53 , 3.04 , 2.78 and 2.65 for bare land, vegetation, built-up and waterbody land use/land cover types respectively. LULC association with LST shows that bare land experienced the highest negative change of 60.22% and this corresponded to the highest increase in LST of 3.53 over the same period. Correlation analysis and Coefficient of variation indicated largely that, MODIS LST data validated derived LST from Landsat satellite imagery. Trend of both LST values follow identical pattern with few instances where derived LST is greater than MODIS LST. Both NDBAI and NDBI exhibited a positive correlation with LST. NDVI demonstrated a negative linear correlation while NDWI indicated the strongest negative linear correlation with LST. Land use/Land cover change can be linked to rising Land Surface Temperature Changes in the Greater Accra region of Ghana. The research stresses the need to ensure effective land use planning by relevant regulatory bodies to control urban development and address anthropogenic causes of surface temperature changes.