Advanced Materials Research Vol. 979

Abstract: Solvolytic sol-gel synthesis was applied for the low temperature production of photoelectrode for dye-sensitized solar cell (DSSC). In this study, commercial TiO₂ standard (Degussa P25) was used as the main component in the preparation of photoelectrode film. Addition of TiO₂ gel prepared from a solvolytic sol-gel method reduced cracking in the dry film while still maintains porosity. Further modification by simply adding hydrofluoric acid (HF) and ammonia (NH₃) increase porosity and improve interconnection between fluorine doped tin oxide (FTO) layer on the substrate and the coated TiO₂ layer even under low temperature baking condition (<150°C). The modified TiO₂ electrode showed significantly better electrical and electrochemical properties. Furthermore, the DSSC cell with modified TiO₂ film also showed higher cell efficiency when compared with the controlled cell that used only Degussa P25.

Abstract: In this research is presented electricity production of sanitary ware, which can be covered kinetic energy of water to electric current from water delivery system. A small electric generator will be set on the water delivery system of sanitariums. It consists with a turbine electric generator and a big tank which build in on tank of a sanitarium. Turbine generator is generated small electric currents by a lot of water inside pipe. If this system were set in a large building for example such as department store, etc. the electric currents would be on generating in order to cumulative energy. In which Bangkok has a population about ten millions of people which sanitariums are used about a hundred millions of time per day. The experimental results of this model can be calculated electric currents to compare with systems which were set on large building.

Abstract: Thermal asperity (TA) resulting from the collision between the slider and the asperity on a magnetic medium during read process can deteriorate the performance of hard disk drives (HDDs). Without TA detection and correction algorithms, the system performance can be unacceptable, depending on how severe the TA is. This paper presents an improved TA suppression method for coded partial response (PR) channels, which consists of two channels running in parallel. Specifically, one channel is matched to the target H(D), while the other is matched to the target H(D)G(D), where G(D) = 1 – D² is a bandpass filter and D is a delay operator. The soft-output Viterbi algorithm (SOVA) detector in the H(D) channel yields the high-quality soft information in absence of the TA, while that in the G(D)H(D) channel produces the high-quality soft information in presence of the TA. Then, the overall soft information chosen from these two detectors, depending on if a TA is detected or not, is sent to the decoder according to the turbo equalization principle. Experimental results show that the proposed method performs better than the conventional and the previously proposed ones, when operating at high signal-to-noise ratio (SNR) region where a practical HDD works.

Abstract: Hard disk drives (HDDs) employ the magneto-resistive (MR) head to sense the change in magnetic flux via the transitions of magnetization pattern, resulting in a readback signal. Thus, head instability plays an important role on the reliability of HDDs because it can deteriorate the system performance considerably. Baseline popping (BLP) is one of the crucial problems caused by the head instability, whose effect can distort the readback signal to the extent of causing a sector read failure. This paper proposes three BLP detection and correction algorithms for a perpendicular magnetic recording (PMR) system. Specifically, to suppress the BLP effect experienced in the readback signal, the first algorithm is based on an averaging filter and a threshold detector; the second one relies on the estimated BLP signal obtained from a linear curve fitting technique; and finally the third one uses two sequence detectors running in parallel. Experimental results indicate that the third algorithm performs better than the other schemes because it can detect and correct the BLP better than the others, especially when the peak BLP amplitude is large.

Abstract: Bit-patterned media recording (BPMR) is one of the promising technologies for realizing an areal density up to 4 Tb/in²; however, it poses new challenges to read channel design, including the two-dimensional (2D) interference, media noise, and track mis-registration. Furthermore, the BPMR system encounters the insertion, deletion and substitution errors, which are primarily caused by mis-synchronization between the write clock and the island positions. In this paper, we propose a novel detection method that exploits the trellis structure to detect the occurrence of insertion/deletion bits. Specifically, the specific marker bits are inserted periodically inside an input data sequence before recording onto a magnetic medium. Hence, the branch metric calculation is monitored during the marker bits to determine if there is any insertion/deletion error in the system. Numerical results indicate that the proposed method can performs better than the conventional one in terms of the percentage of detection and the percentage of missed detection and false-alarm, especially at low signal-to-noise ratio scenario.

Abstract: High-density bit-patterned media recording (BPMR) can be obtained by reducing the spacing between data bitislands in both the along-and across-track directions, thus leading to severe intersymbol interference (ISI) and intertrack interference (ITI) because of small bit and track pitches, respectively. Here, we propose to use the graph-based detector, instead of the trellis-based detector, in iterative decoding to combat the ISI and the ITI for a multi-head multi-track BPMR system. Specifically, the readback signal is sent to the graph-based detector before iteratively exchanging the soft information with a decoder. Experimental results indicate that at low to moderate complexity, the proposed scheme outperforms the existing schemes, especially at high recording density.

Abstract: In this paper, a feedforward bulk-driven class AB fully-differential second-generation current conveyer (FDCCII) is presented. Bulk-driven differential pair is employed for the input stage allowing the FDCCII to operate with rail-to-rail operation. Feedfoward technique is also incorporated into input stage to increase the DC gain and minimize the common mode gain. The circuit performance is verified using HSPICE in 0.18 μm CMOS technology. The simulation results show rail-to-rail input and output swings. The DC voltage transfer characteristic between ports Y and X and DC current transfer characteristic between ports X and Z shows good linearity. The bandwidths show 25.7 MHz (V_X/V_Y), 30 MHz (I_Z/I_X), respectively. The power dissipation is 267.5 μW.

Abstract: In this work, hydroxyapatite (HA) powder derived from pig bone was prepared by thermal processes. The effect of heat treatment temperatures on crystallinity and microstructure of the HA powder were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The powders are uniaxially compact and then sintering at 900°C-1050°C in air. The microstructural characterization of the porous was carried out by SEM. Filtration studies using the sintered porous HA ceramic were performed for sanitary wastewater. The analysis of raw water sample and filtered water were performed. The results showed that the water permeated through the porous HA ceramics could be cleaner water to meet of environmental standard.

Abstract: This paper presents a new coding algorithm of irregular low-density parity-check (LDPC) codes. This algorithm consists of two parts of block codes; parity bits was encoded using the magic square based algorithm (MSBA) which suitable for the short block (less than 500 bits) and the data bits, the rest part of all block codes, was encoded using the random number table. This proposed coding algorithm is called ‘Combined Coding Algorithm LDPC codes (CCA-LDPC codes)’ which can be used in bit-patterned media recording (BPMR) channels. The performance of the constructed codes was numerically simulated in BPMR channels model. The obtained performance of the proposed codes was compared with the comparable existing codes. The simulation results show that, at a block length of 4110 bit and code rate of 0.9, the proposed CCA-LDPC codes yields better performance than the existing ones, especially at high signal-to-noise ratio scenario.

Abstract: An optical method to determine a speed of sound (or ultrasound) in water was described in this work. The measuring system composes of ultrasonic transducer, glass water bath, He-Ne laser source, lens, and screen. An ultrasound fog generator used for producing an ultrasound with a frequency f of 1.74 MHz was immersed in DI water. It was fixed at one side of water bath. When the sound wave travels in water along the length of water bath, a standing wave is obtained from the interference of the incidence wave and the wave reflected from the opposite side of water bath. The node and antinode of the standing wave act as an opaque and transparent medium. As a He-Ne laser beam with a wavelength of 632.8 nm travelled to a convex lens with a focal length of 5 cm and diverged through the sound field, an enlarged standing wave pattern was shown on a white screen. The wavelength of sound wave λ was obtained using geometry (similar triangle). Therefore, the speed of ultrasound in water was calculated by v = fλ. In this work, the water temperature was varied in a range of 15 - 39 °C. The results showed that the speed of sound increased with increasing the water temperature. The percentage error was below 2.8. This proposed method can be used for demonstrating physics principles such as waves and optics for high school students and undergraduates.