Analysis and Design of a Bidirectional Cycloconverter-Type High Frequency Link Inverter with Natural Commutated Phase Angle Control

Zainal Salam,Nge Chee Lim,Shahrin Md. Ayob 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.5

In this paper a cycloconverter-type high frequency transformer link inverter with a reduced switch count is analyzed and designed. The proposed topology consists of an H-bridge inverter at the transformer’s primary side and a cycloconverter with three bidirectional switches at the secondary. All of the switches of the cycloconverter operate in non-resonant zero voltage and zero current switching modes. To overcome a high voltage surge problem resulting from the transformer leakage inductance, phase angle control based on natural commutation is employed. The effectiveness of the proposed inverter is verified by constructing s 750W prototype. Experimentally, the inverter is able to supply a near sinusoidal output voltage with a total harmonic distortion of less than 1%. For comparison, a PSpice simulation of the inverter is also carried out. It was found that the experimental results are in very close agreement with the simulation.

Carbon precursor analysis for catalytic growth of carbon nanotube in flame synthesis based on semi-empirical approach

Zainal Muhammad Thalhah,Mohd Yasin Mohd Fairus,Wan Ali Wan Fahmin Faiz,Tamrin Khairul Fikri,Ani Mohd Hanafi 한국탄소학회 2020 Carbon Letters Vol.30 No.5

Although fame synthesis promises economic beneft and rapid synthesis of carbon nanotube (CNT), the lack of control and understanding of the efects of fame parameters (e.g., temperature and precursor composition) impose some challenges in modelling and identifying CNT growth region for obtaining better throughput. The present study presents an investigation on the types of carbon precursor that afect CNT growth region on nickel catalyst particles in an ethylene inverse difusion fame. An established CNT growth rate model that describes physical growth of CNT is utilised to predict CNT length and growth region using empirical inputs of fame temperature and species composition from the literature. Two variations of the model are employed to determine the dominant precursor for CNT growth which are the constant adsorption activation energy (CAAE) model and the varying adsorption activation energy (VAAE) model. The carbon precursors investigated include ethylene, acetylene, and carbon monoxide as base precursors and all possible combinations of the base precursors. In the CAAE model, the activation energy for adsorption of carbon precursor species on catalyst surface Ea,1 is held constant whereas in the VAAE model, Ea,1 is varied based on the investigated precursor. The sensitivity of the growth rate model is demonstrated by comparing the shifting of predicted growth regions between the CAAE model and the VAAE model where the CAAE model serves as a control case. Midpoint-based and threshold-based techniques are employed within each model to quantify the predicted CNT growth region. Growth region prediction based on the midpoint-VAAE approach demonstrates the importance of acetylene and carbon monoxide to some extent towards CNT growth. Ultimately, the threshold-VAAE model shows that the dominant precursor for CNT growth is the mixture of acetylene and carbon monoxide. A simplifed reaction mechanism is proposed to describe the surface chemistry for precursor reactions with nickel catalyst where decomposition of the ethylene fuel source into acetylene and carbon monoxide is accounted for by chemisorption.

Prevalence of Depression in Breast Cancer Survivors: a Systematic Review of Observational Studies

Zainal, Nor Zuraida,Nik-Jaafar, Nik Ruzyanei,Baharudin, Azlin,Sabki, Zuraida Ahmad,Ng, Chong Guan Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.4

Background: Depression is common in breast cancer patients. The aim of this paper was to make a systematic review of its prevalence and associated factors oin breast cancer survivors. Materials and Methods: An extensive systematic electronic review (PUBMED, CINAHL, PsyINFO and Ovid) and handsearch were carried out to retrieve published articles up to November 2012, using Depression OR Dysthymia AND (Cancer OR Tumor OR Neoplasms as the keywords. Information about the design of the studies, measuring scale, characteristics of the participants, prevalence of depression and its associated factors from the included studies were extracted and summarized. Results: We identified 32 eligible studies that recruited 10,826 breast cancer survivors. Most were cross-sectional or prospective designed. The most frequent instrument used to screen depression was the Center for Epidemiological Studies for Depression (CES-D, n=11 studies) followed by the Beck Depression Inventory (BDI, n=6 studies) and the Hospital Anxiety and Depression Scale (HADS, n=6 studies). CES-D returned about similar prevalence of depression (median=22%, range=13-56%) with BDI (median=22%, range=17-48%) but higher than HADS (median=10%, range=1-22%). Depression was associated with several socio-demographic variables, cancer-related factors, treatment-related factors, subject psychological factors, lifestyle factors, social support and quality of life. Conclusions: Breast cancer survivors are at risk for depression so that detection of associated factors is important in clinical practice.

Effect of rice husk ash and silica fume in ternary system on the properties of blended cement paste and concrete

Zainal Arifin Ahmad,Bun Kim Ngun,Hasmaliza Mohamad,Etsuo Sakai 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3

The effects of rice husk ash (RHA) and fume silica (SF) in both binary and ternary systems on the properties of cement pastes and the compressive strength of concretes were studied. The amount of cement replacement in both systems was 15%. The free calcium hydroxide (Ca(OH)2) content was analyzed using XRD and TG/DTA for the hardened cement pastes. The results showed that the amount of Ca(OH)2 decreased significantly the curing ages for all blended cement pastes. At 28 days, the amount of Ca(OH)2 in OPC is 17.31%, 8.18% in RHA and 6.43% in SF replacements, respectively. The ternary system similarly indicates a significant reduction of Ca(OH)2 content. The compressive strength of concretes was improved significantly by blending the aforementioned materials in both systems. In the ternary system, the concretes containing 7.5%SF and 7.5% RHA gave remarkable improvement in the compressive strength. For example after 90 days curing, the strength is 57.8 MPa whilst only 47.5 MPa for OPC. Therefore, the application of proper ratios of RHA and SF in a ternary system is able to increase the properties of the concrete.

Reliability and Validity of the Malay Version of the Breast-Impact of Treatment Scale (MVBITS) in Breast Cancer Women undergoing Chemotherapy

Zainal, Nor Zuraida,Shuib, Norley,Bustam, Anita Zarina,Sabki, Zuraida Ahmad,Guan, Ng Chong Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.1

Background: Body image dissatisfaction among breast cancer survivors has been associated with psychological stress resultant from breast cancer and resultant surgery. This study aimed to examine the psychometric properties of the Malay Version of the Breast-Impact of Treatment Scale (MVBITS) and to investigate the associations of retained factors with the Hospital Anxiety and Depression Scale (HADS) and the Rosenberg Self-Esteem Scale (RSES). Materials and Methods: The MVBITS was 'forward-backward' translated from English to Malay and then administered to 70 female breast cancer patients who came to the Oncology Clinic of University Malaya Medical Centre, Kuala Lumpur, Malaysia to undergo chemotherapy. Principal component analysis (PCA) with varimax rotation was performed to explore the factor structure of the MVBITS. Associations of retained factors were estimated with reference to Spearman correlation coefficients. Results: The internal consistency reliability of MVBITS was good (Cronbach's alpha 0.945) and showed temporal stability over a 3-week period. Principal component analysis suggested two factors termed as 'Intrusion' and 'Avoidance' domains. These factors explained 70.3% of the variance. Factor 1 comprised the effects of breast cancer treatment on the emotion and thought, while Factor 2 informed attempts to limit exposure of the body to self or others. The Factor 1 of MVBITS was positively correlated with total, depression and anxiety sub-scores of HADS. Factor 2 was positively correlated with total and anxiety sub-scores of HADS. MVBITS was also positively correlated with the RSES scores. Conclusions: The results showed that the Malay Version of Breast-Impact of Treatment Scale possesses satisfactory psychometric properties suggesting that this instrument is appropriate for assessment of body change stress among female breast cancer patients in Malaysia.

Properties of a CaCu3−xMn4+xO12 system synthesized via a solid-state reaction

Zainal Arifin Ahmad 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.6

Design and Implementation of a Single Input Fuzzy Logic Controller for Boost Converters

Zainal Salam,Fazel Taeed,Shahrin Md. Ayob 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4

This paper describes the design and hardware implementation of a Single Input Fuzzy Logic Controller (SIFLC) to regulate the output voltage of a boost power converter. The proposed controller is derived from the signed distance method, which reduces a multi-input conventional Fuzzy Logic Controller (CFLC) to a single input FLC. This allows the rule table to be approximated to a one-dimensional piecewise linear control surface. A MATLAB simulation demonstrated that the performance of a boost converter is identical when subjected to the SIFLC or a CFLC. However, the SIFLC requires nearly an order of magnitude less time to execute its algorithm. Therefore the former can replace the latter with no significant degradation in performance. To validate the feasibility of the SIFLC, a 50W boost converter prototype is built. The SIFLC algorithm is implemented using an Altera FPGA. It was found that the SIFLC with asymmetrical membership functions exhibits an excellent response to load and input reference changes.

Bidirectional High-Frequency Link Inverter with Deadbeat Control

Zainal Salam 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.5

This paper presents a Bidirectional High-Frequency Link (BHFL) inverter that utilizes the Deadbeat controller. The main features of this topology are the reduced size of the inverter and fewer power switches. On the secondary side of the transformer, the active rectifier employs only two power switches, thus reducing switching losses. Using this configuration, the inverter is capable of carrying a bidirectional power flow. The inverter is controlled by a Deadbeat controller, which consists of the inner current loop, outer voltage loop and a feedforward controller. Additional disturbance decoupling networks are employed to improve the system’s robustness towards load variations. A 1-kVA prototype inverter has been constructed and the Deadbeat control algorithm is experimentally verified. The experimental results show that the inverter has high efficiency (91%) with low steady state output voltage total harmonics distortion (1.5%).

An On-Line Harmonic Elimination Pulse Width Modulation Scheme for Voltage Source Inverter

Zainal Salam 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.1

This paper proposes a new harmonic elimination PWM (HEPWM) scheme for voltage source inverters (VSI) based on the curve fittings of certain polynomials functions. The resulting equations to calculate the switching angle of the HEPWM require only the addition and multiplication processes; therefore any number of harmonics to be eliminated and the fundamental amplitude of the pole switching waveform (NP1) can be controlled on-line. An extensive angle error analysis is carried out to determine the accuracy of the algorithm in comparison to the exact solution. To verify the workability of the technique, an experimental single phase VSI is constructed. The algorithm is implemented on a VSI using a 16-bit microprocessor. The results obtained from the test rig are compared to the theoretical prediction and the results of the MATLAB simulations.

Chilled Air System and Size Effect in Micro-milling of Nickel-Titanium Shape Memory Alloys

Zailani Zainal Abidin,Paul Tarisai Mativenga,Gary Harrison 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.2

Although Nickel-Titanium Shape Memory Alloys (NiTi SMAs) are used in a variety of applications due to their shape memory and superelasticity properties, their features of high ductility, temperature sensitivity, and strong work hardening render these materials difficult to machine. The viability of a new approach in improving the machinability through temperature control using chilled air system application was investigated. Differential scanning calorimetry was used to characterise material response to thermal loads. Microstructure phase identification was evaluated with X-ray diffraction. Micro-milling tests were performed using chilled air system and benchmarked to dry cutting and the use of minimum quantity lubricant (MQL). To augment lubrication, chilled air was also applied concurrently with MQL. Results indicated that the application of chilled air reduced cutting temperature and minimised burr height, while their simultaneous application with MQL further improved the machinability. Further investigation was conducted to explore the influence of the ploughing mechanism on machining performance and product quality. The results pointed to higher feed per tooth producing better outcomes. This paper puts forward a new hypothesis that the machinability could be improved by inhibiting or locking in phase transformation through temperature control, and optimising chip thickness, one of the principal parameters of size effect.