Applied Mechanics and Materials Vol. 771

Abstract: A method for enhancing VLF˗EM data based on Multivariate Empirical Mode Decomposition (EMD) was presented. The noise assisted multivariate empirical mode decomposition (NA-MEMD) approach to simultaneously decompose bivariate data.The NA-MEMD is applied to enhance bivariate VLF˗EM data. The method was also tested on a synthetic and two fields VLF-EM data sets. The results indicate that the filtered VLF˗EM data based on the NA-MEMD results better data and easier to interpret or further analyzed. In addition, the 2D resistivity profile result estimated from the inversion of filtered VLF˗EM data is appropriate to geological condition.

Abstract: Diffuse optical tomography is promising technology for non destructive evaluation on product quality control. In order to improve the forward sensitivity, structured refine mesh method was applied on continuous wave domain diffuse optical tomography imaging. This study was conducted on numerical and phantom object. These objects were illuminated by the near infrared source from object’s boundary. To obtain the boundary parameter data, a set of near infrared detector were placed on the periphery of the object. To validate our proposed forward analysis method, boundary parameter data of simulation are shown in comparison with that of experiment. In this study, we vary the position and the value of optical coefficient of defect on the object then we analyze the forward problem sensitivity. The result of this study indicated that continuous wave domain-diffuse optical tomography is promising for product quality control.

Abstract: Rayleigh wave dispersion is intensively used to determine near surface of shear wave velocity (Vs). The method has been known as non-invasive techniques which is costly effective and efficient to characterize subsurface. Acquisition of the Rayleigh wave can be approached in two ways, i.e. passive and active. Passive seismic is accurate to estimate dispersion curve in low frequency, although it is not accurate for high frequency. While active seismic is vice versa of passive seismic. The high frequency of Rayleigh wave dispersion reflects to near surface and vice versa. Therefore, we used the combination of both passive and active seismic method to overcome the limitations of each method. The Vs which is resulted by inversion of the combining data gives accurate model if compared to log and standard penetration test (N-SPT) data. Further, the approach has been used to characterize LUSI (Lumpur Sidoarjo) embankments. The result shows that embankment material (0-12 m) has higher Vs than that lower embankment material.

Abstract: Spray cooling is a method to lower the solid surface temperature by splashing droplets. The evaporation of droplet will take the heat from solid surface. One of the factors that contributes to the evaporation rate and droplet spreads on the surface is the wettability of fluid on surface. Contact angle is a parameter in categorizing the wettability of fluid at a solid surface. Many methods have been developed to measure the contact angle on solid surface. This paper will explain how to measure the contact angle by analyzing the image taken when droplet fluid attached to a surface. The method use MATLAB codes as tools for processing image and compute the result. There are four steps in processing an image of droplet on a surface: convert image to binary image, detect the boundary of the surface, determine the correlation of x-y pixel, and take the tangent of a line at the outer point of contact between fluid and surface. Validation is taken by comparing the result with “standard image” with various resolutions. This method also explains droplet dynamics when impacting a hot surface.

Abstract: Advances in science and technology have encompassed ever larger and ever smaller scales of time, distance, mass, electrical and electronic devices, temperature, pressure. However, scientific and science awareness have not developed in step in the general population. Many people still regard science and technology as wizardy and magic, incomprehensible and unattainable for the common person. This could be called a cultural time bomb, as the widening divide between scientist’s and technologist’s views with the common lay person’s views will cause a divide between their culture as well. And when the people's legal representatives become differently cultured compared with scientists and technologists, this will cause legal decisions getting disconnected with the common good, due to the incomprehension about science and the scientific way in the representative's way of thinking. This increasing disconnect will not help improving the common good: the nuclear power plant issue is a clear example. A not-so-recent issue of 'shall we signal our presence to extraterrestrial intelligence, or would that attract evil beings towards us' is also a timely example. Fundamental metrology, with its concern and endeavour to improve and develop appropriate definitions of units and its standards, can decrease uncertainties and increase precision and levels of confidence in its measurements. This can and should play a significant role to improve critical thinking and reflection through improving scientific and science awareness of the general public, to be more able to comprehend some basics in science and technology, and so to recognize relevant ethical issues, realize the sometimes difficult choices between competing technologies, which need critical reflection to be able to discern proper and just choices. This report describes initiation and development of a classroom effort in this direction during these past 15 years, usually receiving appreciation from students, both at the undergraduate and postgraduate level, with an oft-expressed comment, "This should be introduced at secondary level, to become earlier aware of the role and importance of units and standards, and the human aspects of its origins and history". It is proposed that leaders in fundamental metrology of the various units, standards, processes, and history, should enhance efforts and publications to improve scientific and science awareness of the general public, by introducing metrological issues in a popular and interesting way to secondary and university level students.

Abstract: Abstract. This paper presents the measurement results of three building wall materials which are commonly used for residential housings in Indonesia, namely clay brick, batako (concrete brick), and precast concrete. In-situ measurement of the steady state thermal flow (heat flux) at building walls (envelopes) is conducted in order to determine the thermal resistance of building wall according to ASTM C1155. The results show that all three building materials having a thermal resistance values are far below the energy conservation provisions of ASHRAE 90.1 and especially when compared to the provision of high performance green building ASHRAE 189.1 It is found that precast concrete has higher thermal resistance (or has lower thermal conductivity) than that of other two materials, hence a better compliance to the ASHRAE standards.

Abstract: In manufacturing system, 3D Coordinate Measuring Machines (CMM) are widely used for inspection services where the product should be subjected to the verification of design specifications. It is usually necessary to know the accuracy of 3D CMM equipment during the verification process of the product quality in mass production. To insure and increase the accuracy of 3D CMM the international series standards ISO 10360 are used. This paper presents the importance of the establishment of traceability to international standards as a key role for the reliability of 3D CMM measurement results.

Abstract: Accurate information of microscopic topography is very important for efficacy assessment of a surface texture of skin health. Due to the limitations of the direct visual assessment of skin microscopic topography, an optical dermastocopy is very common to be used as skin imaging device to magnify skin topography based on a white light reflection. The limitation of this method is its poor spatial resolution to quantify skin topography. In this work, microscopic skin imaging based on phase shifting method is configured using a DLP pico-projector with LED illumination and a handheld digital microscope. As illuminator for the digital microscope, the DLP projector is programmed to generate patterned light on skin surface. Image processing is required in providing accurate information of surface topography. The first step, a wrapped phase shifting must be extracted from acquired intensity images. The second step is obtaining unwrapped phase image, which is a critical process because it must be recovered from wrapped phase shifting that containednoise. Finally, phase offset due to multiples of 2π during phase unwrapping must be removed. Early experiments on simple object are carried out to test the level of distortion of fringe in several variations of contrast and also to test the performance of the system on several frequency variations. The test results indicate the depth proportion obtained from absolute phase image has the same trend as the proportion of direct measurement. Implementation on the skin surface profile performed on three test areas: the back of the hand and knuckle creases. Based on quantitative and qualitative analysis,our proposed scheme of skin imaging based on phase shifting is promising for surface profile measurement and imaging of the skin.

Abstract: Determination of Heart Rate Variability (HRV) derived from the Pulse Rate Variability (PRV) of the SpO₂ signals measurement can be used to monitor cardiac activity. One disadvantage of the use of SpO₂ probe is due to existence unavoidable movement artifacts. These artifacts tend to reduce the accuracy of PRV determination. In order to quantify the influence of moving artifacts on the measured SpO₂ signals, the Short-time Fourier Transform (STFT) method is used and this has not been done in previous studies. This method is regarded to be suitable since the artifacts only occurs momentarily, i.e. as the finger moves. Three modes of finger movements were simulated, in addition to the still finger as a control, i.e. in direction of up-down, left-right, and rotating one. Contributing spectra from each of these movements will be recognized, and suitable filtering schemes are then being applied to suppress the influence of these moving artifacts. Parallelly measurements using three-leads ECG were also done to determine the HRV for each of the finger movements condition. Results show that by implementing filtering scheme to each mode of finger movements may reduce the error rate in HRV determination from SpO₂ measurements, i.e. from 6 - 25 % (without filtering) to be only 0 - 1.56 %. Meanwhile measurements both HRV and PRV under still finger show only 0-3.33 % difference for each of data groups.

Abstract: The aim of this study is to discriminate herbal medicines (here after referred to as herbals) by an electronic nose (e-nose) based on an array of eight commercially gas sensors and multivariate statistical analyses. Seven kinds of herbal essential oils purchased from local market in Yogyakarta Indonesia, including zingiber officinale (ZO), kaempferia galanga (KG), curcuma longa (CL), curcuma zedoaria (CZ), languas galanga (LG), pogostemon cablin (PO), and curcuma xanthorrizha roxb (CX) were measured by using this e-nose consecutively. Due to the use of dynamic headspace in this e-nose, data for one cycle (sampling and purging) were recorded every five second for 10 cycles. Each kind of herbals was analyzed for five replications and relative amplitude of the responses was extracted as a feature. The statistical analyses of principal component analysis (PCA) and cluster analysis (CA) were used for discriminating samples. The PCA score plot shows that these 35 essential oil samples were separated into 7 groups based on similarity of patterns. The first two components, PC₁ and PC₂, capture 96.2% of data variance. Meanwhile, by using 80% similarity, the CA clusters 7 herbals into 3 classes. In this case, the first class consists of ZO and CZ and the second class consists of KG, CL, LG and CX, while the PO sample is clustered in the third class. These classes need to be validated using a standard analytical instrument such as GC/MS. The technique shows some advantages including easy in operation because of without any sample preparation, rapid detection, and good repeatability.