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Parental report of the association between screen time and social emotional development of children aged 18 and 36 months old in the district of Gombak, Malaysia / Catherine Thamarai Arumugam
No full textThe increasing popularity of screen-based media has raised public health concern
on potential effects of their excessive usage among developing children. The World
Health Organization (WHO) and American Academy of Pediatrics (AAP) call for
limitation of screen time to one hour per day for children aged two to five years old and
children below the age of two are encouraged for screen time avoidance. This study is
aimed to determine the influence of screen-based media on early childhood social
emotional development from an ecological techno-subsystem perspective. Divided into
two phases, the first phase of study involves translation into Malay language and
validation of four instruments used in the second phase of study. The “Ages and Stages
Questionnaires: Social-emotional”, 2nd edition (ASQ:SE-2) 18-Month and 36-Month
intervals are instruments that assess the dependent variable of the study – social emotional
development. Other three instruments assess independent variables of the study, namely
the “Parent Problematic Digital Technology Use” and “Media and Technology Usage and
Attitudes Scale”, both of which measure parental media behaviour and “Technology
Related Parenting Scale” which measures home media environment. Second phase of this
research work is a cross-sectional study that probes into the association of child screen
time and other independent variables with social emotional development. Study duration
of proposal development to report writing was more than two years from August 2018 to
December 2020. Internal consistency and reliability of instruments were tested on 100
and 60 respondents, respectively in the first phase from the district of Gombak, Malaysia.
Construct validity through factor analyses for Parental Media Behaviour and Home Media
Environment (Malay language) scales were tested on 150 subjects. For second phase of
study, cluster sampling technique was used to recruit 600 respondents from five health
clinics in Gombak, Malaysia. Data collection was done via self-administered
questionnaires distributed to Malaysian parents of children aged 18 and 36 months old
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brought to primary care health clinics for their routine medical examination. Screen time
was measured using Global Time Estimate method. Results from phase I of study shows
all instruments display good psychometric properties. Phase II indicates 27.8% children
documented exposure to screen-based media within first year of life. Mean screen time
per day was found to be 141.7 minutes (SD 131.6). Non-adherence to screen time
recommendation was recorded by 82.2% toddlers. The odds of children with excessive
screen time to have poor mastery of social emotional development is 2.5 times higher
than children adhering to screen time recommendations, with association persisting after
adjustment to confounders (adjusted odds ratio 2.50, 95% CI: 1.07 - 5.86). This study
contributes by producing cross-culturally adapted questionnaires on developmental
screening, parental media behaviour, and home media environment which can be utilized
in the local setting. This research work which has identified non-adherence to screen time
recommendations as risk factor to early childhood social emotional development is hoped
to pave the way for foundation of a national screen time policy which advocates for
mindful usage of screen-based media among young children and their families.
Keywords: screen-based media, screen time, early childhood social emotional
developmen
Influence of inhibitor on corrosion behaviour of Al-Mg alloy / Muhamad Nur Irfan Mohd Adly
No full textFrom pure aluminium to a series of aluminium alloy, the evolution of the steel led by a continuous demand for a superior and more efficient steel. Since then, aluminium alloy have been employed in numerous engineering applications such as engine parts, marine applications, and other applications demands the large volumes of aluminium alloys. However, Al-Mg are exposed to continuous attacks from corrosion, thus usage of corrosion inhibitors is necessary to enhance Al-Mg corrosion resistance. The aim of this research is to study the previous literature journal on the effect of inorganic inhibitor on Al-Mg in corrosive media and surface morphology of Al-Mg with or without inorganic inhibitors from.
Electrochemical corrosion testing was performed on Al-Mg alloy with various type corrosive media and inorganic inhibitor. The corrosion mechanism with or without inhibited on Al-Mg was observed by potentiodynamic polarization study. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to investigate the surface microstructure morphology. The result from the reviewed journal shows that the Al-Mg was seriously corroded under acidic corrosive media due to the aggressive ion. Addition of inorganic inhibitors such as chromates, molybdates, phosphates and nitrates proved to reduce the rate of corrosion of the Al-Mg alloy. The result from the literature also confirmed that higher concentration will give a better corrosion protection. Inorganic inhibitor molecules suppress corrosion by adsorbing to the alloy surface, forming an exterior protective coating that prevents corrosion. The result was confirmed and reviewed by the electrochemical measurements, scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS)
Effect of blending plastic pyrolytic oil and waste cooking biodiesel on engine performance, emissions and lubricity of a small diesel engine fuel with palm oil biodiesel (B30) / Muhamad Sharul Nizam Awang
No full textMalaysia is expected to adopt B30 (30% palm oil biodiesel (POB) content in diesel)
by 2025. However, because 30% POB degrades diesel engine performance and increases
exhaust emission, it is not advised for use in diesel engines. Plastic waste and waste
cooking oil are preferable alternatives to be converted into fuel and blended with POB
and diesel to generate B30 blends due to their cost-effectiveness and abundant availability
in Malaysia, provided that these wastes are appropriately handled. The objectives of this
study were to study the diesel engine performance and emission characteristics of
quaternary fuels, comprising waste plastic pyrolytic oil (WPPO), waste cooking oil
biodiesel (WCOB), POB and diesel as well as to analyse their lubricity properties. Gas
chromatography-mass spectrometry (GC-MS) was used to examine their compositions.
Mechanical stirring was used to prepare four quaternary fuels with varying compositions.
B30a (30% POB and 70% diesel) mixture was prepared as a reference fuel. To enhance
fuel characteristics, engine performance, and emission parameters, 5%, 10%, and 15% of
each WPPO and WCOB were blended with POB-diesel blend. The POB of the quaternary
fuel mixture was kept constant at 10%. The findings were compared to Malaysian
commercial diesel (B10) and B30a fuel. All quaternary fuel blends' brake power (BP) and
brake thermal efficiency (BTE) were enhanced by up to 2.78 % and 9.81 %, respectively,
when compared to B30a fuel. All quaternary fuels exhibited a reduction in brake-specific
fuel consumption (BSFC) when compared to B30a. B40 quaternary fuel showed the
maximum reduction in carbon monoxide (CO) and carbon dioxide (CO2) emissions by
19.66 and 4.16%, respectively when compared with B30a. When compared to B30a, the
B20 quaternary mix demonstrated a maximum reduction of 41.86 % in hydrocarbon (HC)
emissions. The average coefficient of friction (COF) of the quaternary fuel mixtures B40,
B30b, and B20 were lowered by 7.63, 6.89, and 3.17%, respectively, when compared to
B10. As a conclusion, quaternary blends have a high potential to be used in diesel engine
Numerical closed-form solutions of skin flap surgeries using 3D face models / Nur Nadirah Khairu Najhan
No full textA computational-based surgical simulation that typically relies on the Finite Element method has added value to surgical planning. A plethora of FE modeling in local flap surgery has been developed to better understand the biomechanics of local flaps. However, to the best of our knowledge, none considered using a three-dimensional head template as a base model as well as associating ethnic and gender demographics. Therefore, the present work aims to address these gaps, including exploring the stress profiles of three common flap designs on their respective anatomic locations. It is expected that incorporating three-dimensional patient-like models into the simulations would provide better post-operative visualization of facial reconstruction instead of two-dimensional planar approaches as well as serves as training aids and pre-operative patient information. The intended study began with creating a set of facial deformities using a Caucasian-like head template. The deformities were formed by cut-extruding a set of local flap designs: advancement, rotation, and rhomboid flaps at three different facial locations: forehead, cheek, and temple, respectively. These local flaps were embedded in the outermost face layer (epidermis). Concurrently, a single layer of skin thicknesses and third-order Yeoh hyper-elastic skin properties were adopted from the work of existing literature and implemented into the face models to accommodate the realization of human skin behaviors. The post-operative simulations demonstrated standard local flap closures along with the commonplaces of peak tensions in which were found consistent with the available literature. Additionally, Burow’s triangles were superimposed on the advancement and rotation flaps to assist the mobility of the flaps towards the defect. The study was then further in applying the original method to Asian-like head templates with a focus on gender-related differences. Rotation and rhomboid flaps demonstrated maximal tension at the apex of the flap for both genders as well as advancement flap in the female face model. However, advancement flap closure in the male face model presented otherwise. Yet, the deformation patterns and the maximal tension of the discussed flaps were consistent with the conventional. Moreover, male face models generated higher stress compared to the female face models with a 70.34% mean difference. Overall, these operations were executed manually and the designed surgery models met the objectives successfully while acknowledging the study limitations. Future work will involve the adoption of multiple layering, pre-stress effects, and specific material properties according to a particular demographic
Process and impact evaluations preschool oral healthcare programme (POHP) in Selangor / Muhammad Farid Nurdin
No full textPreschools provide an efficient setting to promote the oral health of young children as
children attend preschools on daily basis, the structures and system at preschools are
established, and vital facilities for conducive oral health environment such as clean water
supply and sanitation are already in place. Because of these promising potentials, the
Ministry of Health (MOH), Malaysia has introduced the Preschool Oral Healthcare
Programme (POHP) in 1984. This programme aims to improve the oral health status of
children aged 5 to 6 years who attend preschools. To date, there has been no evaluation
conducted on the POHP in terms of its process implementation and potential impacts on
the oral health parameters of preschool children. Such evaluations are important because
the findings will inform policymakers on the extent to which the POHP has contributed
towards preschool children’s oral health. The findings could also be used to address any
shortcomings of the POHP in order to achieve the National Oral Health Plan (NOHP)
targets for preschool children. Objectives: The study consisted of process and impact
evaluations of the POHP. For the process evaluation, the specific objectives were: i) to
explore the effectiveness, feasibility, and suggestions for improvement of the POHP in
Selangor state from the perspectives of dental therapists (DT), ii) to explore the
effectiveness, feasibility, and suggestions for improvement of the oral health-related
activities (OHRA) and oral health-related facilities (OHRF) at preschools in Selangor as
recommended in the Guidelines on Oral Health Care for Preschool Children (2003) using
the perspectives of preschool teachers. For the impact evaluation, the specific objectives
were: iii) to compare between preschools with POHP and preschools without POHP in
terms of oral health and related behaviours of preschool children, oral health literacy
(OHL) of preschool teachers, OHRA at preschool, and OHRF at preschool, and iv) to
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evaluate factors associated with preschool children’s oral health and related behaviours,
and OHRA and OHRF at preschools. Methods: The study consisted of 2 phases; Phase
1 and Phase 2. Phase 1 was a qualitative study involving 2 sample populations; DT from
9 districts in Selangor state using focus group discussion (FGD) as method of data
collection, and preschool teachers from 4 districts in Selangor state using in-depth
interview (IDI) as method of data collection. Both FGDs and IDIs were conducted using
an interview schedule developed by the researcher and a dental public health specialist
(DPHS). The qualitative data were transcribed verbatim and analysed using the
framework method analysis. Phase 2 was a cross-sectional study involving preschool
children and preschool teachers as sample populations from preschools with POHP and
preschools without POHP. Sample size for preschool children was 1082 (teachers were
recruited using convenience sampling). Multistage cluster sampling method
proportionate to size was employed to collect preschool children sample. Preschool
children were randomly selected from 2 districts in Selangor, which were Petaling (urban)
and Sepang (rural) districts. Study tools included a parent self-administered questionnaire
(proxy) which assessed socio-demographic characteristics of parents and child, parent’s
oral health knowledge (OHK), parent’s oral health behaviours (OHB), global self-rating
items of oral health, and child OHB at home. Teacher self-administered questionnaire
assessed socio-demographic characteristics, OHL using the Malay version of Dental
Health Literacy Assessment Instrument (DHLAI), OHRA, and OHRF at preschools. Data
were assessed using the SPSS version 23 software. Results: 114 DTs were involved in
13 FGDs. In terms of POHP effectiveness, DTs felt the POHP was effective to improve
OHK of the children and teachers, promote oral health monitoring by teachers, promote
healthy diet at school, inculcate toothbrushing habit in children, control caries, well
accepted by children, promote oral health lessons in class, and provide toothbrushing
facility at preschool. In terms of facilitators to implement POHP, the factors were good
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dental workforce teamwork, monitoring and support from dental administration,
provision of financial aid, availability of transportation, sufficient time to implement
programme, cooperation form school administration, cooperation from preschool
teachers and preschool children, availability of dental materials, and training in dealing
with preschool children. In terms of barriers to implement the POHP, the factors were
lack of manpower, lack of support from dental administration, uncooperative preschool
administration, availability of sugary food and drinks at school, lack of transportation and
driver, lack of time, uncooperative teachers, uncooperative children, lack of space for
OHRA, lack of dental materials, and uncooperative parents. For suggestions to improve
the POHP, the DTs suggested to improve oral health education (OHE) materials and
facilities, provide financial support, provide further training, involve parents in the
programme, monitor OHRA and OHRF at preschool, include oral health in teacher’s
training, increase number of DTs and assistants, introduce a dedicated team for preschool,
provide additional dental equipment, collaborate with dental industry, use social media in
OHE, and pay honorarium for dental visits to non-governmental preschools. With regards
to IDI, 15 teachers were interviewed. In terms of effectiveness, the OHRA and OHRF
were effective to instil positive attitudes among children and teachers, improve OHK of
children and teachers, instil toothbrushing habit in children, and control caries. In terms
of facilitators for OHRA and OHRF at preschools, the factors were good cooperation
from school administration, provision of financial aid, availability of oral health-related
materials, cooperation from parents, oral health seminar for teachers, helpful teacher’s
assistant, good relationship with dental personnel, cooperation from preschool children,
and good time management. In terms of barriers to implement OHRA and OHRF, the
factors were lack of financial support, lack of oral health learning materials, lack of space,
uncooperative children, environmental factors, extensive teaching duties, uncooperative
parents, accessibility to sugary food and drinks at school, and insufficient number of
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assistants. For suggestions to improve OHRA and OHRF at preschools, the teachers
suggested to provide them with oral hygiene kit and OHE materials, improve oral hygiene
kit storage and tooth brushing area, increase parental involvement, increase frequency of
oral health seminar for teachers, reinstate dental treatment at school, provide financial aid
for oral health, and conduct OHE exhibition at preschool. For impact evaluation of POHP,
the response rate was 69.8% for preschool children and 76.5% for preschool teachers. A
significantly higher proportion of children from the preschools with POHP used fluoride
toothpaste at home than children from the preschools without POHP (p = 0.021).In terms
of teacher’s OHL, a significantly higher proportion of teachers who worked at the
preschool with POHP had a higher mean score of knowledge domain of the DHLAI than
teachers who worked at the preschools without POHP (p = 0.033) and more teachers who
worked at the preschools with POHP had good level of knowledge domain of DLAI than
teachers who worked at the preschools without POHP (p <0.001) . In terms of OHRA
and OHRF at preschools, a significantly higher proportion of teachers who worked at
preschool with POHP taught oral health syllabus at preschool (p = 0.009), displayed oral
health-related posters/pamphlets at preschool (p = 0.029), performed oral health-related
role play at preschool (p <0.001), performed toothbrushing activity (p <0.001),
performed toothbrushing activity everyday/alternate days (p = 0.042), brushed teeth using
toothpaste (p = 0.001), used fluoridated toothpaste (p <0.001), examined children’s teeth
(p = 0.046), examined children’s teeth ≥1x/6 months (p = 0.043), provided toothbrush
storage at preschool (p <0.001), provided toothbrushing facilities at preschool (p <0.001),
and provided a mirror for children to use after toothbrushing (p <0.001) than teachers
who worked at preschools without POHP. In terms of significant factors associated with
children having “more good” OHB at home when other factors were controlled were
children living in urban location (p = 0.025), parents with good OHK (p = 0.001), parents
who brushed ≥2/day (p <0.001), parents who visited dentist <6 months (p = 0.015),
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parents with no oral health problem in the past 3 months (p = 0.001), parents who had
low perceived oral health impact on daily life (p = 0.006), and female children (p =
0.022). A significantly higher proportion of teachers who worked at the preschools with
POHP implemented “more good” OHRA and OHRF at preschools than teachers who
worked at the preschools without POHP when other factors were controlled (p <0.001).
Conclusion: The DTs and preschool teachers perceived that the POHP, OHRA and
OHRF at the preschools could help to control caries and suggested that parents should be
involved in the programme. However, lack of financial support is a barrier for the DT to
implement POHP and the teachers to implement OHRA and OHRF at the preschools.
Nevertheless, the POHP in Selangor has positive impact in providing conducive oral
health environment at the preschools. Further improvement of POHP to include parents
should be considered as parents’ factors were significant factors for children’s OHB apart
from location and child’s gender.
Keywords: School-based oral health programme, preschool oral healthcare programme,
children’s OHB, OHL, conducive oral health environment
Trade analysis among ASEAN, Japan, Korea and China / Chew Shiau Ping
No full textThis study explores the central problem of whether the regional economic co-operation – ASEAN plus Three (APT) - can produce beneficial trade creation or harmful trade diversion effects on ASEAN’s export industries with the objectives: (1) to examine the trade relationship among APT; (2) to explain the factors affecting changes in the pattern of trade among them; (3) to explore the qualitative issues of whether the presence of high technology exports signifies technological capability in the context of ASEAN; and (4) to explore the implications of ASEAN’s role in these supply chains, and how dependent are they on China in terms of inputs or outputs. It found that the rise of China as ASEAN’s most important trading partner, displacing mainly Japan, while South Korea is not a big trading partner, is especially significant. Then, the indices such as revealed comparative advantage, trade complementarity and intra-industry trade, all point to trade creation as a consequence of APT. However, ASEAN lacks domestic technological capability related to domestic constrains and needs to develop capability domestically. Furthermore, there is evidence of China’s growing importance in the many supply chains ending there. The implications for ASEAN countries lagging increasingly behind China are ominous. Overall, the results of this study point to the need for ASEAN member states as a whole to upgrade their technological capability through training programs or emulate Singapore’s Technical and Vocational Education and Training (TVET) system
Pyrolysis of palm oil solid waste using helical screw fluidized bed reactor / Khan Muhammad Qureshi
Get PDFBiomass pyrolysis processes for bio-oil production were commonly done using batch, semi-continuous or continuous process. However, past studies have shown many concerning issues in regard to the use of batch process such as high residence time, product inconsistencies across batches, high labor cost and difficulty in industrial scale up. Therefore, a quantitative study was performed using slow and fast pyrolysis mode over novel Helical Screw Fluidized Bed Reactor (HSFBR) stainless-steel (CS309) with an internal diameter of 228 mm and total length of 1,524 mm using palm shell (PS) for bio-oil production. The stainless-steel (CS309) helical screw has a total length of 1,550 mm including 6 flights a pitch distance of 95.25 mm and an external diameter of 203.2 mm. Accordingly, this research aims to investigate the performance of novel HSFBR with some desired outcomes: high particle dynamics, heat transfer rate, feed rate, effect of temperature, pyrolysis time and vapor residence time with high liquid and low biochar yield with improved properties. The torque was optimized to 50 rpm with slow heating rate of 10°C/min to achieve 500°C without involving any inert gas. The maximum quantity of organic phase with lower oxygen content and biochar products were obtained with 51.6 wt.% and 26.6 wt.%, respectively. The further experiments were performed with low, medium and high heating rates from 75 to 275°C/min at 50 rpm torque to achieve the reaction temperature of 500°C without involving any inert gas. Present study showed the major improvement in formation of organic yield was basically linked with increasing heating rate. The maximum bio-oil yield of 72.84 wt.% with HHV of about 44.41 MJ/kg was achieved at heating rate of 275°C/min, which is compatible with the diesel fuel HHV (45 MJ/kg). The parametric results also showed that the temperature and the feed rate had significant effects on pyrolytic products. When pyrolysis temperature was increased from 400 to 650oC the yields of bio-oil and biochar were decreased while iv gas yield was increased. In addition, on increasing feed rate from 3 to 25 g/min the bio-oil and gas yield were increased, while biochar yield was decreased. The effect of particle size, pyrolysis time and vapor residence time showed the optimum bio-oil yield obtained at 2 mm particle size, 30 min pyrolysis time and 0.25s vapor residence time with (72.11 wt.%), (72.40 wt.%) and (73.86 wt.%), respectively at 500oC. In addition, 10 mm particle size also showed an acceptable bio-oil yield of 71.23 wt.% which saved the costs of biomass grinding and size reduction time. The optimum value of HHV for fuel properties of bio-oil (organic phase) at 0.25 mm particle size, 30 min pyrolysis time and 0.25 vapor residence time were found 42.80, 43.02 and 43.14, respectively. The qualitative and quantitative evaluation of pyrolytic products (organic phase and by-product biochar) strongly suggests their significance in liquid and solid fuel applications. These findings of novel HSFBR reactor technology ranked well for biomass material and have provided a good understanding when it was used in pyrolysis modes slow medium and high heating rate
Development of novel phase change material (PCM)-based nanocomposites using emerging nanomaterials for energy storage applications / Navid Aslfattahi
Get PDFEnergy storage is a global critical issue and important area of research as most of the renewable sources of energy are intermittent. In this thesis, novel nanomaterials including recently emerged two-dimensional nanomaterial MXene (Ti3C2), hybrid graphene-silver (Gr-Si), hexagonal boron nitride (hBN), magnesium oxide (MgO) and alumina (Al2O3) nanoparticles are used as additives into various types of organic/inorganic phase change materials (PCMs) for formulation of promising PCM-based nanocomposites to improve their thermo-physical properties. This research work focuses on synthesis, preparation, characterization, thermal storage properties and thermal stability characteristic of new class of nanocomposites induced with advanced/emerging nanomaterials. Novel two_dimensional MXene (Ti3C2) nanomaterial is synthesized experimentally in laboratory using wet-chemical etching method through in-situ preparation of hydrofluoric acid incorporating two types of fluoride salts. Conducted structural analysis including XRD and Raman spectroscopy analysis confirmed the purity of the as-synthesized two_dimensional Ti3C2 nanomaterial. Thermal energy storage properties of the developed novel organic/inorganic PCM-based nanocomposites have been measured at elevated temperatures using differential scanning calorimetry analysis. It is evident experimentally that the PW70/MXene nanocomposite with loading concentration of 0.3 wt.% shows the improvement of thermal energy storage property by ~43%. The experimentally achieved specific heat capacity (cp) results for hybrid PCM/Graphene-Silver nanocomposites with loading concentration of 0.3 wt.% shows promising improvement of thermal energy storage property by ~40%. The measured average cp value of the synthesized binary PCM-based hBN nanocomposite with the highest loading concentration of 1.5 wt.% represented promising enhancement of ~180%. Enthalpy of the binary nitrate based PCM/MgO nanocomposites decreased by 12.4% which proves more exothermic reaction in melting point. The experimental methods for synthesized eutectic ternary nitrate based PCM/Alumina nanocomposite showed that the enthalpy increased by 16.5% by the introduction of 1 wt.% of Al2O3 nanoparticles. Conducted experiments for palmitic acid PCM/MXene nanocomposites revealed enhancement in enthalpy by 10.3%. It was also found that 25.8% increase in volumetric specific heat capacity of the developed nanocomposite (palmitic acid PCM/MXene) makes it suitable for TES applications. Assessment of the thermal degradation for all of the synthesized PCM-based nanocomposites is conducted by using thermo-gravimetric analysis method. The focal degradation temperature of PW70/MXene nanocomposite with loading concentration of 0.3 wt.% is found to be 384 °C with ~6% improvement. Thermal durability measurements for hybrid PCM/Graphene-Silver nanocomposites revealed that the weight loss occurs within the temperature range from 263 to 424 °C. Developed binary nitrate PCM-based hBN nanocomposite with loading concentration of 1.5 wt.% represented ~16% enhancement in thermal stability. The experimentally acquired results revealed the increment of decomposition temperature from 734.29 to 750.73 °C for the binary nitrate based PCM/MgO nanocomposite. It is found that ternary nitrate-based PCM/Alumina nanocomposite with loading concentration of 1 wt.% reached the focal degradation temperature of 694 °C. Thermal degradation temperature of the developed palmitic acid PCM/MXene nanocomposite enhances from 270 ⁰C to 305 ⁰C by introduction of 0.3 wt.% of Ti3C2 nanomaterial. The experimentally achieved improvements in thermo-physical properties reveals the beneficial aspects of the developed organic/inorganic PCM-based nanocomposites in thermal energy storage applications
Nitrogen prediction model through new hybrid model using ant colony optimization and Elman neural network / Pavitra Kumar
Get PDFThe prediction of nitrogen not only assists in monitoring the nitrogen concentration in streams but also helps in optimizing the usage of fertilizers in agricultural fields. A precise prediction model guarantees the delivery of better-quality water for human use, as the operations of various water treatment plants depend on the concentration of nitrogen in streams. Considering the stochastic nature and the various hydrological variables upon which nitrogen concentration depends, a predictive model should be efficient enough to account for all the complexities of nature in the prediction of nitrogen concentration. For two decades, artificial neural networks (ANNs) and other models (such as autoregressive integrated moving average (ARIMA) model, hybrid model, etc.), used for predicting different complex hydrological parameters, have proved efficient and accurate up to a certain extent. The current research work presents the methodology of development of artificial neural network models for the prediction of nitrate-nitrogen and ammonia nitrogen in streams. A new training method is proposed which paves the way of selection of models among the number of models having different combinations of internal parameters providing different levels of prediction accuracy. Using the new training approach, four optimum models have been selected for prediction of both the nitrogen compounds at two different measuring stations i.e. LUI and KAJANG, in Langat River basin in Malaysia. These models provided considerable accuracy of prediction. However, for real time prediction the accuracy needed to be enhanced. To enhance the prediction of the developed artificial neural network models, a new hybrid model was developed. Ant colony optimization and Elman neural network was integrated to form a new ACO-ENN hybrid model. ACO performs a decision-making task and ENN performs learning task. ACO selects a best combination of internal parameters and provides it to ENN for an enhanced starting point, leading to a better result. The same four models were developed based on the same historical data using hybrid modelling technique. The prediction results obtained from the hybrid models had higher accuracy than that obtained from standalone artificial neural network models
Effect of heating on bonding characteristics for copper wire bond technology / Gurbinder Singh
No full textIn recent years, copper has increasingly been used to replace gold to create wire interconnections in microelectronics. While the industry is continuously working on this transition from gold to copper wire to reduce costs, the challenge remain in producing robust and reliable joints for semiconductor devices. The use of copper wire is known to pose threats to devices with thin structures. The impact of hard copper free air ball onto bonding surfaces is undesirable as it can damage the bond pad and the die structure. Since copper requires higher bonding force and excessive ultrasonic energy to create a bond, this research investigates the effect of pedestal and free air ball heating on copper wire bonds. Wire bonding was performed on bond pads consisting of NiPdAu metallization under sixteen different pedestal temperatures. This research also investigates the effects free air ball laser heating on bonding strength and microstructural quality. Results have shown, ball shear strength for copper wire varies linearly with the increase of pedestal temperature. The ball shear strength is the lowest at temperature 40°C and is gradually increased to an average of 25g at temperature 200°C. At pedestal temperature 340°C, average ball shear strengths of 35g was achieved. EBSD analysis indicated the cell-structured zone in the laser-assisted sample is wider near the bonding, whereas, in the laser free FAB sample, two intense deformation zones formed. The results of this research will be of advantage to semiconductor plastic packaging. Copper wire bonding quality can be further improved without the need to use excessive bonding temperature, higher bonding force and excessive ultrasonic energy