Zulkurnain Abdul-Malek

Temperature and Magnetic Field Driven Modifications in the I-V Features of Gold-DNA-Gold Structure

The fabrication of Metal-DNA-Metal (MDM) structure-based high sensitivity sensors from DNA micro-and nanoarray strands is a key issue in their development. The tunable semiconducting response of DNA in the presence of external electromagnetic and thermal fields is a gift for molecular electronics. The impact of temperatures (25–55 °C) and magnetic fields (0–1200 mT) on the current-voltage (I-V) features of Au-DNA-Au (GDG) structures with an optimum gap of 10 μm is reported. The I-V characteristics acquired in the presence and absence of magnetic fields demonstrated the semiconducting diode nature of DNA in GDG structures with high temperature sensitivity. The saturation current in the absence of magnetic field was found to increase sharply with the increase of temperature up to 45 °C and decrease rapidly thereafter. This increase was attributed to the temperature-assisted conversion of double bonds into single bond in DNA structures. Furthermore, the potential barrier height and Richardson constant for all the structures increased steadily with the increase of external magnetic field irrespective of temperature variations. Our observation on magnetic field and temperature sensitivity of I-V response in GDG sandwiches may contribute towards the development of DNA-based magnetic sensors.

A new method to extract the resistive component of the metal oxide surge arrester leakage current

Many studies have been conducted to monitor the degradation of MO arresters. The arresterpsilas leakage current, in particular, the third harmonic component of the resistive leakage current, is known to be directly related to the degree of degradation of the MO arrester. In order to extract the resistive component from the total leakage current, the voltage across the arrester terminals is usually measured as well. Although the measurement of total leakage current in substations or other installations can be easily done by using current shunts or current transformers, the measurement of voltage is relatively difficult if not prohibitive. Apart from the difficult and risky high voltage access for the voltage probe, the voltage measurement in a single phase may suffer from interference from nearby phases resulting in an unclean voltage reference. This paper introduces a new method to extract the resistive current from the total leakage current without the need of the voltage signal. It is referred to as the Modified Shifted Current Method (MSCM). The new modified shifted current method of extracting resistive current component from the metal-oxide surge arrester leakage total current is shown to work well based on the simulated as well as experimental results. The new technique compares very well with the conventional compensation technique, especially for resistive dominated leakage current waveforms. The new technique promises a simplified metal-oxide surge arrester monitoring of resistive leakage current since no additional high voltage transducer, as in commercially available devices, is needed. The consequential benefits are reduced cost and safer working procedure for the maintenance staff.

An Improved Circuit-Based Model of a Grounding Electrode by Considering the Current Rate of Rise and Soil Ionization Factors

The behavior of a grounding system can be predicted by using either the electrical equivalent circuit models or electromagnetic computation. Despite its advantages over the latter, the equivalent circuit model fails to accurately predict the behavior under transient conditions due to the absence of two key factors, namely: 1) the current rate-of-rise and 2) soil ionization. This paper proposes a method to enhance the performance of the equivalent circuit model by taking into consideration of both mentioned factors. It is discovered that by using the proposed method, the estimated values of R and L of the equivalent circuit model are improved. The computed inductance dynamically changes with the change in the lightning current parameters, thus improving its accuracy for all current rate-of-rise conditions. The soil ionization effect is implemented as recommended by CIGRE, and this further improves the accuracy of the model. As a result, the voltage response of the model becomes more accurate and comparable to the electromagnetic computation results. Another important feature of the proposed model is that it can be directly applied or connected to power system equipment. Thus, an accurate grounding system effect on the transient performance of key power equipment, such as surge arresters, can be obtained.

A NEW ROTATING SPARK GAP DESIGN

Standard spark gaps have lower time limits of gap recovery when testing with high repetition rate impulses and in high-current high-voltage multiple impulse testing. More important, they are not suitable for the generation of opposite-polarity successive impulses using conventional capacitive-type generation techniques. In this article, an improved design incorporating two rotating spark gaps is described. The new spark gap was used to test ZnO surge arresters with two successive impulses of currents up to 5 kA and voltages up to 50 kV. Time intervals as low as 10 ms were achieved between the two impulses. Both similar and opposite polarity tests were carried out successfully.

Statistical analysis of lightning electric field measured under Malaysian condition

Lightning is an electrical discharge during thunderstorms that can be either within clouds (Inter-Cloud), or between clouds and ground (Cloud-Ground). The Lightning characteristics and their statistical information are the foundation for the design of lightning protection system as well as for the calculation of lightning radiated fields. Nowadays, there are various techniques to detect lightning signals and to determine various parameters produced by a lightning flash. Each technique provides its own claimed performances. In this paper, the characteristics of captured broadband electric fields generated by cloud-to-ground lightning discharges in South of Malaysia are analyzed. A total of 130 cloud-to-ground lightning flashes from 3 separate thunderstorm events (each event lasts for about 4–5 hours) were examined. Statistical analyses of the following signal parameters were presented: preliminary breakdown pulse train time duration, time interval between preliminary breakdowns and return stroke, multiplicity of stroke, and percentages of single stroke only. The BIL model is also introduced to characterize the lightning signature patterns. Observations on the statistical analyses show that about 79% of lightning signals fit well with the BIL model. The maximum and minimum of preliminary breakdown time duration of the observed lightning signals are 84 ms and 560 us, respectively. The findings of the statistical results show that 7.6% of the flashes were single stroke flashes, and the maximum number of strokes recorded was 14 multiple strokes per flash. A preliminary breakdown signature in more than 95% of the flashes can be identified.

Simulation of Lightning Flash in Time of Arrival (TOA) Method by Using Three Broadband Antennas

Various methods are used to locate cloud-to-ground lightning flash. The accuracy of the methods depends on the number of sensor stations, station topology, mathematical model adopted for the analyses, and type of measuring equipment. For a single station with the configuration of short baseline in a measuring system, the accuracy analysis is mostly based on the chosen mathematical equations (and all relative assumptions) which can be solved in either linear or nonlinear mode. This paper concentrates on the simulation of a lightning flash based on Time of Arrival (TOA) method by utilizing three broadband antennas. The accuracy of the TOA method is also evaluated in this work. A Mat lab based simulation of the measuring system is implemented to construct a randomly located lightning flash with its corresponding electromagnetic radiation. Then, suitable mathematical models used as measurement systems based on the TOA method to determine the azimuth and elevation angles.

A Comparative Study on the Positive Lightning Return Stroke Electric Fields in Different Meteorological Conditions

Positive cloud-ground lightning is considerably more complex and less studied compared to the negative lightning. This paper aims to measure and characterize the significant parameters of positive return strokes electric field, namely, the zero-to-peak rise time, 10–90% rise time, slow front duration, fast transition rise time (10–90%), zero-crossing time, and opposite polarity overshoot relative to peak. To the best of the authors’ knowledge, this is the first time such detailed characteristics of positive lightning in Malaysia are thoroughly analyzed. A total of 41 positive lightning flashes containing 48 return strokes were analyzed. The average multiplicity is 1.2 strokes per flash. The majority of positive lightning was initiated from the primary positive charge rather than as a byproduct of in-cloud discharges. The cumulative probability distribution of rise time parameters, opposite polarity overshoot relative to peak, and slow front amplitude relative to peak are presented. A comparison between studies in four countries representing tropic, subtropic, and temperate regions was also carried out. Measured parameters in Florida, Sweden, and Japan are generally lower than those in Malaysia. Positive lightning occurrences in tropical regions should be further studied and analyzed to improve our current understanding on positive return strokes.

The Effect of Grounding Electrode Parameters on Soil Ionization and Transient Grounding Resistance Using Electromagnetic Field Approach

The soil ionization phenomenon occurs during the dispersion of lightning current into the earth. This phenomenon causes the grounding electrode resistance to be effectively reduced. The extension of the soil ionization depends on the current amplitude along the electrode and the resultant electric field intensity surrounding the electrode. The electrical and physical parameters of the grounding electrode system are found as factors that affect the electric field intensity. In this study the electromagnetic field approach and the soil breakdown theory are taken into account to investigate the effect of the mentioned factors on soil ionization and grounding resistance. Changing the parameters of the grounding electrode system affect the electric field distribution around the electrode. Based on the conditions the grounding electrode resistance was reduced between 12% to 75% by considering the soil ionization effect.

Investigation of the Electrical Resistivity of 20μm-Gap Gold-DNA-Gold Structure: Exploiting the Current-Voltage Characteristics under a Variable External Magnetic Field

Deoxyribonucleic acid (DNA), as the most important molecule in nature, holds promise as a key element of the molecular electronics as its utilization in the synthesis of electronic devices such as micro and nanosensors has increased remarkably during the recent years. Our work is devoted to an experimental study of the electrical resistivity of a gold-DNA-gold (GDG) structure in the presence of a variable external magnetic field. The DNA strands, extracted by the PCR method, were used to fabricate the GDG structures. The resistivity of the structure was found to rise sharply with the magnitude of the exerted magnetic field due to onset and progression of the cyclotron effects in charge carriers. Such a distinct current-voltage signature can possibly be employed for realization of an accurate magnetic sensor.

Statistical Analysis of Electrical Tree Inception Voltage, Breakdown Voltage and Tree Breakdown Time Data of Unsaturated Polyester Resin

This paper presents a statistical approach to analyze electrical tree inception voltage, electrical tree breakdown voltage and tree breakdown time of unsaturated polyester resin subjected to AC voltage. The aim of this work was to show that Weibull and lognormal distribution may not be the most suitable distributions for analysis of electrical treeing data. In this paper, an investigation of statistical distributions of electrical tree inception voltage, electrical tree breakdown voltage and breakdown time data was performed on 108 leaf-like specimen samples. Revelations from the test results showed that Johnson SB distribution is the best fit for electrical tree inception voltage and tree breakdown time data while electrical tree breakdown voltage data is best suited with Wakeby distribution. The fitting step was performed by means of Anderson-Darling (AD) Goodness-of-fit test (GOF). Based on the fitting results of tree inception voltage, tree breakdown time and tree breakdown voltage data, Johnson SB and Wakeby exhibit the lowest error value respectively compared to Weibull and lognormal.