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Modeling of heavy vehicle braking related to accident reconstruction for a range of vehicle and road characteristics / Mahdieh Zamzamzadeh
No full textIn today's heavy-vehicle accidents, one of the major contributors is emergency braking, particularly for vehicles without an anti-lock braking system (ABS), which is dominant in developing countries like Malaysia. As the heavy vehicle driver applies emergency braking, there is a high chance of wheel lock-up, at which point the vehicle will skid along the road, creating braking marks from the tires. These braking marks are often used in crash reconstructions. Braking marks are mainly used by investigators to examine the vehicle's pre-impact velocity. There are many models and formulations based on kinetic energy that show the effect of some
parameters. Still, there has been less discussion about vehicle dynamics' and loading condition's effects on slip ratio and wheel lock-up. This study used a multi-body dynamics method to examine the braking process in emergency braking for a better understanding of the characteristics of heavy vehicle braking, the performance of heavy vehicles during emergency braking, wheel lockup, and skidding as evaluated by the critical pedal force that triggers wheel lock-up, PFcrit. The findings generated from this study indicated that a minimum pedal force exists regardless of the factors involved. This inadvertently creates the PFcrit, which causes wheel lock-up and skidding. With that in mind, this study also highlighted the importance of PFcrit. Two phases were involved. The first phase examined PFcrit. Here, the wheel lock-up data for various pedal forces of the heavy vehicle's loading condition, its speeds, and the road surface conditions were generated through a multi-body dynamic model. Then the parameters that have a significant effect on the heavy vehicle's wheel lock-up were validated through statistical analysis. The results showed that the vehicle's dynamic characteristics could change during emergency braking situations, particularly for overloaded vehicles. This change can affect the heavy vehicle's wheel lock-up and the ability to stop safely. These parameters are fundamental, and so should be considered when determining braking marks distances. The most important finding to be noted from this study is the difference detected in the skidding distance when the vehicle's gross vehicle weight (GVW) is changed. The second phase of this study concentrated on the skidding distance and whether there is a contributory relation between skidding and vehicle dynamics. An alternative model was developed and then subjected to various vehicle characteristics and road conditions for this purpose. The primary consideration for developing the new regression model was to look at how vehicle dynamics and road conditions may impact the wheel lock-up and skidding distance. A nonlinear model to estimate the skidding distance. This model was derived as a case study by considering the nonlinear effect of the vehicle loading condition, tire forces, and longitudinal tire slip. According to the data presented here, this model provides information on how heavy vehicle GVW affects vehicle performance during emergency braking
Under frequency load shedding scheme for islanded distribution system based on mixed integer linear programming / Sohail Sarwar
No full textIn recent years, significant climate changes have pivoted the distribution system towards utilization of renewable energy, particularly through distributed generators (DGs). Although DGs offer many benefits, its integration affects the stability of the system, which could lead to blackout, when the grid is disconnected. The system frequency will drop drastically if DG’s generation capacity is less than the total load demand in the network. In order to sustain the system stability, Under Frequency Load Shedding (UFLS) is a commonly used technique to minimize the difference in load demand and power generation. However, existing load shedding techniques are lack in accurate estimation of power imbalance. Conventional load shedding sheds random loads sequentially until the system’s frequency is recovered. Random and sequential selection of loads without priority results in excessive load shedding, which in turn causes frequency overshoot. Thus, a technique yielding an optimal solution for load shedding incorporating load priority is needed. In this regard, this work proposes an efficient load shedding technique for islanded distribution system. This technique utilizes voltage stability index to rank the unstable loads for load shedding. In the proposed technique, polynomial regression is used to establish a function of power imbalance in the form of frequency decay. Mixed Integer Linear Programming (MILP) optimization produces optimal load shedding strategy based on the priority of the loads (i.e., non-critical, semi-critical, and critical) and the load ranking from voltage stability index. The effectiveness of the proposed technique is tested on three test systems, i.e., 28 bus system, which is a part of the Malaysian distribution network, the IEEE 69 bus system, and the IEEE 137 bus system, using PSCAD/EMTDC. Results obtained prove the effectiveness of the proposed technique in stabilizing the system’s frequency without overshoot by disconnecting unstable non-critical loads on priority. Furthermore, results show that the proposed technique is superior compared to other adaptive techniques on the basis it increases sustainability by reducing the load shed amount and avoiding overshoot in system frequency. Also, its performance is not affected by increasing the number of loads for a large-scale system
Secure unlinkability schemes for privacy preserving data publishing in weighted social networks / Chong Kah Meng
No full textPreserving privacy of users has been one of the important research issues in social networks. Social networks contain sensitive personal information that are often released for business and research purposes. The privacy of a user can be breached if the data are not released in an anonymized form. In this thesis, we address edge weight disclosure, link disclosure and identity disclosure problems in publishing weighted network data. To counter these privacy risks while preserving high utility of the published data, we define two key privacy properties, namely edge weight unlinkability and node unlinkability. We design two novel anonymization schemes namely MinSwap an
State, market and society: The development of Ikat textile value chains among the Iban of Sarawak, Malaysia / Wong Pui Yi
No full textStudies about the developmental state have focused on the role of the state in guiding a rapidly industrialising economy, by creating a nexus between the state and business, primarily large enterprises. There is no study within the literature on the role of state-society relations in nurturing community-based rural enterprises. This thesis examines the commercial development of handwoven ikat textiles, a niche cottage industry promoted by the state to preserve cultural heritage and to alleviate poverty. This study expands the developmentalist framework, which focuses on public policy outcomes and economic performance as contingent on the configurations of state agencies, national goals and political power, by incorporating value chain concepts to better analyse market and social logics that drive economic development. The overall aim of this study is to shed light on how the developmentalist and value chains frameworks enhance the understanding of the Malaysian (and Sarawakian) developmentalist state in the context of a rural cottage industry. The three key objectives are: To examine the nature of the federal and Sarawak governments; to analyse the roles played by market and societal actors and how they interacted with state actors; and to assess the challenges faced in the commercial development of ikat textiles in Sarawak. Qualitative data was collected through semi-structured, in-depth interviews with 119 informants comprising state actors and non-state actors involved in value chains, selected in a non-random manner. The Malaysian development model has been both developmental and clientelist; the needs of political survival and power asymmetries shape developmental outcomes even at this small scale of production in Sarawak. The development of ikat weaving in Sarawak is underlined by the “embedded interdependence” of key state, market and societal actors. In the more developed value chains, power is concentrated in the hands of the key actors, namely the patrons who were either part of the state, or who had formed institutionalised alliances with the state. The power asymmetry in the value chains determined the form of governance and upgrading outcomes. The embedded interdependence of the key actors enabled them to elicit the cooperation of the weavers to engage in value chain upgrading, while the captive form of value chain governance allowed the patrons to dictate the weaving process and products to meet market demands. However, the clientelist and exclusive nature of patron-weaver ties have also constrained the viability of the cottage industry. State institutions and CSOs have key roles to play in facilitating collective action models that can better empower communities. As enterprise development policies in Malaysia have been simultaneously interventionist and market-oriented in nature, even in a rural-based industry, state intervention has essentially focused on private sector development and the grooming of “lead firms” or patrons. While market-oriented, patron-led development has contributed to the growth of this industry, there is increasing disparities in income and opportunities among weaving communities, with many being left out. This thesis reveals the interdependent nature of state, market and society, and the importance of collaboration, consultation, and systemic reforms to ensure equitable and lasting development
Integrating finance dictionary in lexicon-based approach with machine learning algorithm to analyse the impact of OPEC news sentiment on financial market / Wu Ling
No full textSince last few decades, machine learning algorithm which trains computers to learn from experience, is one of the most rapidly developing techniques which settles in the intersection research field of statistics and computer science. This research aims to build a properly trained machine learning classifier to study the impact of Organization of Petroleum Exporting Countries (OPEC) news sentiment on stock prices of six Malaysian public listed companies (energy sector) in the main board of Bursa Malaysia. The data used in this research are collected during the period 2012-2017. To carry out the research, firstly, lexicon-based approach is used to analyze the sentiment of sentences in the financial news articles. A sentiment dictionary from a finance domain is applied to improve the accuracy in labelling the financial news sentences. The labelled sentences are then used to train the supervised machine learning classifiers. The classifiers classify the OPEC news sentences into three different categories – negative (labeled with sentiment score -1), neutral (labeled with sentiment score 0), and positive (labeled with sentiment score 1). The performance of the supervised machine learning classifier is found to achieve 70% accuracy. The OPEC news article’s sentiment score is calculated using relative proportional difference evaluating method: S = (P-N) / (P+N), whereby, P and N are the number of positive and negative sentences in the article, respectively. The sentiment score of each article ranges from -1 to 1. Using event study method, this sentiment score is used to compare with the historical stock prices of the six selected public listed energy sector companies. Results of the analysis show that OPEC news sentiment shows impact on the stock prices of these six companies. However, the impact did not occur on the news release date. During the event window period (i.e., five days before and after a news released), there is a negative correlation between OPEC news sentiment and the six companies’ average cumulative abnormal return. Cumulative abnormal return is the average of daily abnormal return during the event window, which can be used to show the overall fluctuation of the stock prices. The findings of this research show that applying financial sentiment dictionary to train the supervised machine learning algorithm can enhance the performance of machine learning classifier. Results of statistical analysis in this research also provides a clear picture to the stock investors on the movement of the six Malaysian energy sector companies’ stock prices during the event window period. This can help them to make better decisions in their trading in order to obtain profitable stock returns
Mental workload assessment among healthcare workers during pandemic COVID-19 at Hospital Tunku Azizah / Mohd 'Aizat Mohd Basari
No full textWorkload is the amount of work an individual has to do. There is a distinction between
the actual amount of work and the individual's perception of the workload. In addition,
with current pandemic situation, definitely causes an increased workload among
healthcare workers. Somehow, front-liners are doing their best in battling COVID-19 to
protect publics from any adverse effects by this aggressive identified Coronavirus. The
purpose of this study is to determine level of mental workload and its relationship on
mental health status and job satisfaction among healthcare workers. Scope of this study
involving medical laboratory workers in Pathology Department Hospital Tunku Azizah.
Here, 85 workers from this department has been recruited as study subjects. This is a
cross-sectional quantitative descriptive study using questionnaire. Research tools used for
this questionnaire are CarMen-Q, DASS-21 and Job Satisfaction Survey (JSS).
Questionnaire conducted via Google Form an analysed by SPSS-21 software. Mental
workload are the independent variable of this study while the dependent variables are
mental health status (depression, anxiety and stress) and job satisfaction. Data were
analyses using descriptive statistics (percent, mean and standard deviation) and inference
statistics (correlation). The findings of this study show Pathology Department workers
are burdened with high mental workload with at least M=54.23, SD= 12.193. In this
context, mental workload dimensional was found to have a significant correlation on
mental health status and job satisfaction level among health workers. To conclude, this
study has proven that healthcare workers are experiencing high mental working and have
significant effects on their mental health status and their job satisfaction. Sets of strategies
managing high level mental workload in Pathology Department need to be implemente
Financial development and unemployment in Malaysia / Hii Puong Hung
No full textIn the past decades, the topic financial development and economic growth has
been popularly discussed by scholars. From the past literature, financial development
is an important component in promoting economic growth. However, there has been
less study about the relationship of financial development and unemployment rate.
Therefore, this study aims to investigate the relationship between the financial
development and unemployment rate in the case of Malaysia from year 1981 until
2018. This study analyses the relationship by using two model equations to test
separately the effect of each financial development indicators (Domestic Credit to
Private Sector and Stock Market Capitalization) on the unemployment rate.
Autoregressive Distributed Lag (ARDL) method and Cumulative Sum (CUSUM)
control chart have been used to test the long run and short run relationships of
financial development variable and unemployment rate in Malaysia. As the results,
this study finds that there is a significant long-term relationship of financial
development and unemployment rate for both models. However, results also revealed
that the short run relationship among the financial development and unemployment
rate is not significant. This shows that the financial development indicators need to
take time (long term) in exerting its effect on the economic variables (unemployment
rate) in the case of Malaysia. Therefore, policymakers are suggested to plan their
regulations in a long-term way by taking into the consideration of implementing lag
The effect and feasibility of the SIMS programme to improve preschool children's oral hygiene level and related behaviours: A cluster randomised control trial / Nurul Hayati Anwar
No full textBackground: The preschool oral healthcare programme (POHP) was introduced by the
Ministry of Health in 1984 to provide oral healthcare to 5-6-year-old children in Malaysia.
Due to some limitations, a new programme called the ‘Senyuman Indah Milik Semua’
Programme (SIMSP) was introduced with the aim to improvise the POHP. In the SIMSP,
a triad of dental therapists (DTs), teachers, and parents was set up to promote children’s
oral hygiene level, oral health behaviours (OHBs), and parents’ oral health literacy
(OHL). The POHP only involved DTs.
Objectives: The primary objective of the study was to assess the effect of SIMSP versus
POHP on oral hygiene level of 5-6-year-old children in the Kampar District, Perak over
6 months. The secondary objectives were: (i) to assess the impact of SIMSP versus POHP
over 6 months in terms of children’s OHBs and parents’ OHL; (ii) to assess the
implementation fidelity of SIMSP’s protocol; and (iii) to explore the process
implementation of SIMSP from the perspectives of the dental team.
Methods: This study was a pragmatic, cluster-randomised, parallel-group, matched pair,
examiner-blind, controlled trial with a 1:1 allocation ratio where preschools in Kampar
district were the clusters. Using computer generated numbers, 14 government preschools
were allocated to intervention (SIMSP) and another 14 to control (POHP) groups with
allocation concealed at cluster level (317 sample per group). Children and parents who
fulfilled the inclusion criteria were enrolled by DTs. The study tools included a
questionnaire to assess demographics and children’s OHBs, the International Caries
Detection and Assessment System (ICDAS), the Oral Cleanliness index, and the Malay
version of Dental Health Literacy Assessment Instrument (Malay-DHLAI). Data were
collected before intervention, and again after 6 months. Implementation fidelity data was
self-reported by DTs and teachers. Focus group discussions (FGD) were conducted
among DTs and health assistants (HA) in the SIMSP. Quantitative data were analysed
iv
using SPSS software. Qualitative data were transcribed verbatim and thematically
analysed using Nvivo software.
Results: At 6-month, 83.4% of children in the SIMSP and 76.4% in POHP completed
oral examinations, while response rates for questionnaire was 91.5% and 81.1%,
respectively. Mean plaque score decrement was higher in SIMSP than POHP (ES =
+0.64). Significantly more SIMSP children took carbonated drinks <1-3x/week (p =
0.033). Parents in the SIMSP had a significantly higher mean knowledge score (mean =
0.54, SD = 2.75, p = 0.024) and higher OHL scores (ES = +0.97) than parents in POHP.
The implementation fidelity data showed majority of parents (83.1%) attended the parent�DT meetings, majority of teachers delivered the in-class oral health lessons including
worksheets (96.8%) and supervised daily toothbrushing (93.7%), and all DTs delivered
the oral health infographics to parents (100%). FGD participants perceived that SIMSP
was an appropriate programme, effective to improve parents’ OHL, and received good
support from the administrators. The main barrier was to get full parental involvement in
the SIMSP. Recommendations for improvement included a dental officer in the SIMSP,
gain feedback from other stakeholders, and collaborate with private sectors on the SIMSP.
Conclusion: The SIMSP was shown to be effective in reducing children’s dental plaque
scores, carbonated soft drinks intake, and improving parental OHL than the POHP over
6 months. The SIMSP’s implementation fidelity was high, and the programme was
perceived as acceptable by the dental team with rooms for improvement.
Keywords: dental plaque, oral hygiene, preschool, child, Malaysia, behaviour, health
literac
Abundance and distribution of microplastics and persistent organic pollutants in selected rivers of Peninsular Malaysia / Norkhairiyah Anuar
No full textNearly 70 to 80 percent of microplastics are believed to be transported to the sea through rivers. Yet, less attention has been given to the accumulation of microplastics in the freshwater environment. They are emerging anthropogenic contaminants on account of their potential to adsorb and/or release POPs from and/or to the surrounding environment, and become the vector transferring these pollutants from water to the food web. This study is aimed to explore the abundance and distribution of microplastics and POPs in six rivers of Peninsular Malaysia, which comprised of three rivers from the West Coast (Sepetang River, Serkam River, and Ayer Masin River) and three rivers from the East Coast (Sedili Besar River, Cherating River, and Semerak River). The objectives of this research are to identify the anthropogenic activities that may contribute to the generation of microplastics and POPs, to investigate the abundance and distribution of microplastics, to determine the concentrations of POPs, and, to analyze the relationship between the microplastics abundance, POPs concentration and anthropogenic activities along these rivers. Eight sites were established along each river to ensure maximum coverage of the rivers studied, while anthropogenic activities were investigated through observation of 5 km radius along each river. River sediment samples were collected using shovel, while plankton nets were utilized to capture microplastics in river water. Density separation was conducted to extract microplastics in the sediment, using concentrated NaCl solution followed by wet sieving through a set of Tyler Sieves. Identification of microplastics was conducted based on morphological characteristics (i.e. type, size and colour). As for POPs identification, Liquid-liquid Extraction and Soxhlet Extraction were performed, followed by GC-MS/MS analysis. Sepetang River, Cherating River, and Ayer Masin River substantially demonstrated greater number of anthropogenic activities, characterized as the hotspots of anthropogenic activities, followed by Sedili Besar River, Serkam River and Semerak River. Correspondingly, the highest prevalence of microplastics abundance in river sediment was discovered in Sepetang River with an average abundance of 101.39 ± 54.69 particles/kg, while in river water, Ayer Masin River had the greatest number of microplastics with average abundance of 0.0101 ± 0.0052 particles/m3. Majority of the microplastics were films and white in colour, with a dominant size fractions of 1.0 to 5.0 mm in river sediment, and 0.1 to 0.5 mm in river water. 1,2-Benzenedicarboxylic acid, diisooctyl ester (DIOP), which are generally grouped in Phthalate esters (PAEs), was the dominant POPs identified. The highest concentration of POPs in river sediment was observed in Sedili Besar River (677.49 ppm), while the highest concentration in river water was recorded in Cherating River (153.41 ppm). Generally, it can be said that the problem of microplastics and POPs pollution rooted in the prevailing production and consumption pattern of plastic materials, on grounds of great contributions from various anthropogenic activities. Correlation study revealed no relationship between the abundance of microplastics and POPs concentrations in rivers of Peninsular Malaysia. Overall, the results of this study could provide valuable background information for microplastics and POPs pollution in selected rivers of Peninsular Malaysia
Modeling, fabrication and characterization of coated calcium phosphate scaffolds produced by 3D-Printing for tissue engineering application / Maria Touri
No full textA fully interconnected 3-dimensional scaffold with pre-determined dimensions and porosity can be attained by design-dependent rapid prototyping techniques which possess precise control over the internal and external architecture of the scaffolds thus they can overcome the problems associated with the process-dependent classical approaches. Interruption of vascular flow with fracture or surgical osteotomy results in a transient hypoxic gradient within the wound and subsequent tissue necrosis. Tissue engineering scaffolds with oxygen generating elements have shown to be able to increase the level of oxygen and cell survivability. In this study, biphasic calcium phosphate (BCP) scaffolds with the composition of 60% hydroxyapatite and 40% beta-tricalcium phosphate, which have shown a great potential for bone tissue engineering applications, were fabricated by robocasting technique. Then, the three-dimensional-printed scaffolds were coated with different ratios (1, 3 and 5 wt%) of an oxygen producing biomaterial, calcium peroxide (CPO), which encapsulated within a polycaprolactone (PCL) matrix through dip-coating, and used for in situ production of oxygen in the implanted sites. 3D-printed BCP scaffolds with 70% porosity and large pore size (500 μm) showed a compressive strength of ~21 MPa. The oxygen release behaviour was sustained and dependant on the concentration of CPO encapsulated in the PCL coating matrix. It was also demonstrated that the coated scaffolds, having 3% CPO in the coating system, could provide an increase of approximately 50% in the oxygen concentration and a great potential for promoting bone ingrowth with improving osteoblast cells viability, function and proliferation. The finite element modelling was used to calculate the stress fields in scaffolds and the predicted compressive strength of the robocast scaffolds was ~24 MPa which is so close to the experimental result. Antimicrobial evaluations confirmed the inhibitory properties of the scaffolds on the growth of E. coli and S. aureus because of the release of calcium peroxide from the scaffolds. At in vivo part, a model of 15 mm segmental defect was made at the radius of rabbits. In the experimental group, defects were implanted using BCP scaffold coated with CPO. Control animals were implanted with uncoated BCP scaffolds. No implant was provided for the blank group. Bone repair was assessed by X-ray, biomechanical tests and histological observations at 3 and 6 months post-operation. The results showed that bone formation was increased at the interface and inside the inner pores of CPO coated scaffolds than those of uncoated scaffolds; biomechanical properties in the coated group were superior to those of the uncoated group. Our findings suggested CPO coated scaffolds had enhanced repairing ability in segmental bone defect in rabbit radius, and may serve as a potential material for repairing large bone defects