Applied Mechanics and Materials Vol. 771

Abstract: Terahertz Signal generated from chiral metamaterial due to the second order non-linear process has been observed. Chiral metamaterial used in this research have a periodic square pattern with different depth on a silver film and was fabricated by Focused Ion Beam System. Terahertz emission spectroscopy has been conducted using two amplified 100 fs laser pulses with a central wavelength of 800 nm. The emission will emerge due to an optical rectification process as a result of an intense femtosecond laser pulses radiation on a chiral metamaterial sample. The measurement result clearly shows that the terahertz signal is emitted at 2 THz frequency and sufficiently fit with a square of laser power, which is consistent with an expected optical rectification process.

Abstract: Optical system is important and optimized for highly spatial resolution in certain wavelength bandwidth. We tested three small refractor telescopes with different aperture (two telescopes with 80 mm in diameter and one with 66 mm diameter) and focal-length (544 mm, 400 mm, and 389 mm, respectively) in order to know the resolution from visual to near infra red regions. The images of sinusoidal bar test chart were recorded from CCD detector. The reference filter of Sloan Digital Sky Survey (SDSS) is also attached in front of detector. The filters have the range of G (401-550 nm), R (555-695 nm), I (690-820 nm), Z (>820 nm), Z_s (826-920 nm), and Y (950-1058 nm). The last filter is referred to the limit of quantum efficiency of the detector. The maximum frequency for each pixel from each Modulation Transfer Function (MTF) was performed. We found that smaller diameter telescope is better resolution in the visual wavelength than the wider diameter and longer focal-length. In the near infra red region, the opposite results were obtained. The coating lens quality may affect the wavelength dependences. This study has advantages of selecting low cost and high resolution optical system for different applications, e.g. very young crescent moon observation, etc.

Abstract: A sensitive gas detection system using a distributed feedback CW Quantum Cascade Laser (QCL) centered at 4610 nm as a radiation source has been developed. QCL was used in combination with an off-axis integrated cavity output spectroscopy (ICOS) for Carbon Monoxide (CO) gas detection in a low gas pressure. a 15 cm long high-finesse cavity with an effective optical path length of 400 m has been used as a sample gas cell. We demonstrated detection limit of 1 ppbv with less than 2 second averaging time. The best detection limit is obtained at 0.4 ppbv for a 128 s acquisition time. All measurement results has shown that the QCL based ICOS detector system proved to be suitable for monitoring CO gas in a low gas pressure condition with sub-ppb sensitivity.

Abstract: An airflow control system is one of important parts in the scanning mobility particle sizers system (SMPS) used in the field of aerosol and air filtration. In this paper, the air flow control system that consists of an air filter, a blower, an air flow sensor, a controller, and a computer are reported. A flow rate adjustment was performed by varying the rotation speed of the blower using a pulse width modulation (PWM) technique. The air flow sensor capable of measuring flow rate up to 20 liters / min was used to measure the air flow rate. In order to keep at a certain value of the flow rate, a proportional-integral-derivative (PID) control action was employed in which PID controller were manually tune. The results showed that the desired value of flow rate was quickly achieved with little overshoot was observed in the system output.

Abstract: This paper reports the influence of light exposure (photodynamic) and magnetic field application on viability activation of anaerobic photosynthetic bacteria (rhodobacter sphaeroides). For photosynthetic process, the rhodobacter sphaeroides have bacteriochlorophyll and carotenoid as major and accessory pigments, respectively. A customized equipment was developed for investigating the effect of light and magnetic field applications on the growth of the bacterial colonies. It was consisted of three main parts, namely a sample holder, an array of light emitting diode (LED) as light source and Helmholtz coils as magnetic field source. The systems of this equipment were controlled by a microntroller of AVR ATMega-8535. Prior to the application in vitro, all LEDs were calibrated, both their intensity and wavelength. After the treatments, all bacteria substances were grown in photosynthetic media (PMS) for 48 hours followed by calculating the number bacterial colonies growth using a total plate count (TPC) method and Quebec colony counter. It was found that the growths of bacterial colonies were influenced by both light intensity and wavelength of LED array. At the same intensities, the wavelength of 430 nm showed highest effect on the growth of bacterial colonies. In addition, upon application of the optimum light combined with magnetic field, the highest growth of bacterial colonies was achieved more than 110% when the optimized light source of energy dose was 204 J/cm² and magnetic field was 1.8 mT.

Abstract: Research on nanofiber materials is actively done around the world today. Various types of nanofibers have been synthesized using an electrospinning technique. The most important component when synthesizing nanofibers using the electrospinning technique is a DC high voltage power supply. Some requirements must be fulfilled by the high voltage power supply, i.e., it must be adjustable and its output voltage reaches tens of kilovolts. This paper discusses the design and development of a high voltage power supply using a diode-split transformer (DST)-type high voltage flyback transformer (HVFBT). The DST HVFBT was chosen because of its simplicity, compactness, inexpensiveness, and easiness of finding it. A pulse-width modulation (PWM) circuit with controlling frequency and duty cycle was fed to the DST HVFBT. The high voltage power supply was characterized by the frequency and duty cycle dependences of its output voltage. Experimental results showed that the frequency and duty cycle affect the output voltage. The output voltage could be set from 1 to 18 kV by changing the duty cycle. Therefore, the nanofibers could be synthesized by employing the developed high voltage power supply.

Abstract: A good mannequin is needed to improve the quality of clinical skill learning. A strain sensors gauge can be applied into gynecologic bimanual examination mannequin. This study compared a new strain gauge sensors mannequin and non-sensor mannequin for gynecologic bimanual examination training in undergraduate medical student. We made a new female torso model implemented with strain gauge sensors in the definitive landmark, then used this new mannequin for gynecologic bimanual examination training in undergraduate medical student, and evaluated using questioner. We observed 4 parameters: mannequin appearance, student’s self confidence to palpate uterus and ovary, and student’s learning motivation. The new model improved student’s confident to palpate ovary (p<0.05) and student’s motivation (p<0.001) compared to non-sensor mannequin. In contrast, the gross appearance of the new mannequin was inferior (p<0.05). However, there was no difference in defining the uterus position during examination (p>0.05) in both mannequins. A new female torso model with strain gauge sensors can be applied for gynecologic examination training.

Abstract: We extend the application of numerical entropy production, as a smoothness indicator, from conservation laws to balance laws. We aim to indicate the smoothness of solutions to the shallow water equations involving varying width, which are a system of balance laws. The numerical entropy production appears to be accurate to detect discontinuities. As a numerical test, a radial dam break is considered. We assume that there is a higher level of water inside a radial dam than water outside the dam wall. If the radial dam is totally broken, then water flows from inside to outside. The flow results in a solution having shock discontinuities. Finding the positions of the discontinuities is our interest. They are the positions where numerical solutions, such as those generated by a finite volume method, decrease their accuracy. Detecting the position of the discontinuity can help in the improvement of the numerical solution in terms of its accuracy. We obtain that the numerical entropy production is simple to implement but give an accurate detection. The discontinuity of the stage (free water surface) is clearly detected by large values of the numerical entropy production as the smoothness indicator.

Abstract: A capacitance sensor has been designed to investigate the correlation between wood capacitance value, Janka hardness rating and density. The sensor was developed based on parallel plates using copper as the electrodes. Capacitance values were measured using CV-circuit, 20 Vp-p, 2.5 MHz. Five wood specimens from forest plantation that is Karet (Hevea brasiliensis), Pulai (Alstonia sp.), Pinus (Pinus mercusii), Sengon (Paraserianthes falcataria), and fast growing teak (Tectona grandis) were tested. Each specimen was measured in tangential and radial directions under 0% moisture content conditions. The designed sensor was capable to distinguish the capacitance values in tangential and radial directions. The measurement results showed that wood capacitance value has a good relation with wood’s hardness and density.

Abstract: This study aims to determine permeable zones (i.e. fault or fracture zones) in the Rajabasa geothermal field using radon isotopes. Radon concentration of soil gas was measured by Scintrex Radon detector RDA 200 consisting of 123 measurement station. The measurement site spacing are between 200 m and 350 m. The Radon concentration was classified based on a statistical approach, i.e. low, high and very high. Very high value of Radon concentration, called Radon anomaly, associated with permeable zones. From the Radon anomaly contour map, a 2D Radon migration from the source to the surface was modelled by means of numerical simulation. Finally, the Radon contour map was overlaid with the surface geological map and the resistivity contour map in the area of study. It suggests that the Radon anomaly correlates with the location of permeable zone in the centre part of the study area i.e. mud pool manifestation at the Kunjir and the Cugung (Bulakan) fumarole. Based on numerical simulation, the width of the fault is 2,800 m; velocity of fluid is 0.08 m/s and the Radon concentration is 860,000 Beq/m³. The resistivity contour map results low resistivity value of 0 Wm – 100 Wm indicating the conductive zone coincide with permeable zones based on Radon measurements. Furthermore, the peak of the profile curve of Radon concentration could be an indication of fault systems in this area.