Dental residents’ perception of learning environment: Experience of a Nigerian training institution

Background: Learning environment has been described as crucial in determining the success of medical and dental education. Continuous evaluation of this environment will help in maximizing the learning opportunities of the training program.Objective: To assess the resident doctors’ perception of their learning environment at a teaching hospital in Nigeria.Method: The DREEM questionnaire was administered to participants undergoing residency training in the faculty of Dental Surgery at the University College Hospital, Ibadan.Result: Thirty-nine resident doctors participated in the study (23 Males, 16 Females), mean age (+SD) was 35.7 (±4.22) ranging from 28 years to 46years. Mean global score (+SD) was 105.3 (±26.8), 52.7%, out of a maximum of 200. The mean global score according to gender was significantly higher among males than females. The overall perception of the training environment by residents is more positive than negative and the male gender appears to have a more positive perception than the female gender. However, this perception is borderline as the environment was perceived as having many problems and residents’ perception of their learning environment is mostly negative. Attention of the institution and trainers should be drawn to possibilities of combating the problem areas for better outcome of residency training in our environment. &nbsp

Exergy, Performance And Environmental Impact Analysis Of Compression Refrigeration Systems

Major concern in refrigeration hinges largely on energy conservation, environmental safety and efficient cooling system. The concept of quality of useful energy which invariably leads to energy conservation is naturally related to exergy. This study therefore experimentally conducts exergy, performance and environmental impact analysis of compression refrigeration systems using R134a, R410a and R407c, refrigerants. The experiment was performed using a modified exiting R134a refrigerating system. The refrigerator was built with Scroll compressor, 48m3 evaporator space, 1m throttle length and 0.2mm array of rods in the condensing unit coupled with thermocouple K attached at the various components and a digital 10^-3 accuracy weighing scale for charging refrigerant in the required grams. The results show that for 100 grams charge of the refrigerants, the exergetic efficiency, coefficient of performance (COP) and the degree of environmentally friendliness of each of the refrigerants are of order R410a > R407c,> R134a and for 80 grams charge of the refrigerants, the order of performance is R410a > R134a> R407c. While for 60 grams charge of the refrigerants, the exergetic efficiency, coefficient of performance and the degree of environmentally friendliness of each of the refrigerants are of order R407c> R410a > R134a, that of 40 grams charge of the refrigerants is of order R134a> R407c> R410a. The study therefore established that irrespective of the grams charge values of the investigated refrigerants used, R410a is the best, closely followed by R134a and lastly R407c

Quality Improvement of Foundry Operation in Nigeria Using Six Sigma Technique

In this paper Six Sigma DMAIC analysis was applied in an aluminium mill in order to identify sources and causes of waste with the intention of providing veritable solutions. The foundry section was the segment under scrutiny. Re-work or defects in this firm was found to be on the average of about 37.05% of total production for the twenty-three months under study (January 2009- December 2010). Defect reduction was therefore chosen as the Critical-to-Quality (CTQ) factor. The sigma level of 1.87 in the firm indicated the existence of opportunities for improvement. Analysis was carried out using SPSS, SPC for Excel to perform regression analysis, process capability analysis, generate descriptive statistics, histograms and run charts. The results of these analyses identified three major defects and some of their behaviours. Based on the analysis, solutions were proffered in the Improve and Control phases of this project. Implementation of the proffered solutions resulted in noticeable improvement and led to the firm operating with near- perfect processes thus proving the applicability of Six Sigma

Dataset of experimental and adaptive neuro-fuzzy inference system (ANFIS) model prediction of R600a/MWCNT nanolubricant in a vapour compression system

This research paper assessed the performance of R600a with the base lubricant and Multi-walled Carbon Nanotube (MWCNT) nanolubricant at steady state. It describes the instruments required for measurement of the data parameter and its uncertainties, steps involved in preparing and replacing the MWCNT nanolubricant concentration with base lubricant in vapour compression refrigeration. The system’s temperature data was collected at the components inlets and outlets. Pressure data was also registered at the compressor outlet and inlet. The data was captured at 27 °C ambient temperature at an interval of 30 min for 300 min. The experiment includes the experimental data collection, Adaptive Neuro-Fuzzy Inference System (ANFIS) training and testing dataset. The use of ANFIS model is explained in predicting the efficiency of MWCNT nanolubricant in a vapour compression refrigerator system. The ANFIS model also provides statistical output measures such as Root Mean Square Error (RMSE) and Mean Absolute Deviation (MAD), Mean Absolute Percentage Error (MAPE), and determination coefficient (R2). The data is useful and important for replacing MWCNT nanolubricant with base lubricant in a vapour compression refrigeration system for researchers in the specialisation of energy-efficient materials in refrigeration. The data present can be reused for vapour compression refrigeration systems simulation and modelling

Dataset of experimental and adaptive neuro-fuzzy inference system (ANFIS) model prediction of R600a/MWCNT nanolubricant in a vapour compression system

This research paper assessed the performance of R600a with the base lubricant and Multi-walled Carbon Nanotube (MWCNT) nanolubricant at steady state. It describes the instruments required for measurement of the data parameter and its uncertainties, steps involved in preparing and replacing the MWCNT nanolubricant concentration with base lubricant in vapour compression refrigeration. The system’s temperature data was collected at the components inlets and outlets. Pressure data was also registered at the compressor outlet and inlet. The data was captured at 27 °C ambient temperature at an interval of 30 min for 300 min. The experiment includes the experimental data collection, Adaptive Neuro-Fuzzy Inference System (ANFIS) training and testing dataset. The use of ANFIS model is explained in predicting the efficiency of MWCNT nanolubricant in a vapour compression refrigerator system. The ANFIS model also provides statistical output measures such as Root Mean Square Error (RMSE) and Mean Absolute Deviation (MAD), Mean Absolute Percentage Error (MAPE), and determination coefficient (R2). The data is useful and important for replacing MWCNT nanolubricant with base lubricant in a vapour compression refrigeration system for researchers in the specialisation of energy-efficient materials in refrigeration. The data present can be reused for vapour compression refrigeration systems simulation and modelling

EXPERIMENTAL STUDY OF LPG AND R134a REFRIGERANTS IN VAPOR COMPRESSION REFRIGERATION

Natural refrigerants, such as hydrocarbons, have been renewed in recent years as a result of the environmental problems associated with chlorofluorocarbon (CFC) and hydro-chlorofluorocarbon (HCFC) refrigerants. Due to the depletion of the ozone layer and global warming effects, synthetic refrigerants are being gradually phased out in accordance with the international protocols that aim to protect the environment. A refrigerator designed to work with R134a was used for this experiment, liquefied petroleum gas (LPG) which consists of 60% propane (R290) and 40% butane (R600) was compared with R134a refrigerant in a vapor compression refrigerator with a total volume of 62 L. The experiments were carried out using different charges of 40, 60, 80, and 100 g for R134a and LPG refrigerants, the charges were measured with a digital charging scale. The K-type thermocouples were used to measure the temperatures at the inlet and outlet of the four major components (evaporator, compressor, condenser, and expansion device) of the refrigeration system. The system was instrumented with two pressure gauges at the inlet and outlet of the compressor for measuring the suction and discharge pressures. The results obtained were used to determine the thermodynamic properties of the refrigerants using Refprop, version 9. The results obtained showed that the design temperature and pull-down time set by the International Standard Organisation (ISO) for a refrigerator were achieved with LPG earlier than with R134a. The coefficient of performance (COP) of the system increases by 9.5% and the power consumption is reduced by 12%, when compared with R134a. Therefore, LPG can successfully substitute R134a in domestic refrigerator

Thermodynamic Performance Analysis and Optimization of Domestic Refrigerator with Varying Refrigerant Charge and Capillary Tube Lengths

In this paper, thermodynamic performance analysis and optimization of a domestic refrigerator were experimentally carried out by simultaneously varying the refrigerant charge (wr) and the capillary tube length (L). Continuous running and cycling tests were performed on a domestic refrigerator under tropical conditions using three refrigerants (R12, LPG and R600A) with different capillary tube lengths and various charges. The results show that the design temperature and pull-down time set by ISO for small refrigerator are achieved earlier using refrigerant charge 60g of LPG with 1.5m capillary tube length. The highest COP (4.8) was obtained using 60g charge of LPG with L = 1.5m. The average COP obtained using LPG was 1.14% and 15.09 % higher than that of R600a and R12 respectively. Based on the results of this study, R600a offered lowest power consumption. The compressor consumed 20 % less power compared to LPG and 32% less power than R12 in the system. In conclusion, the system performed best with LPG in terms of COP and cooling capacity. In term of power consumption R600a performed best.This shows that both LPG and R600A can be used as replacement for R12 in domestic refrigerator