The Prevalence and Risk Factors of GERD Among Indonesian Medical Doctors

Background: Based on our knowledge, the study of gastrointestinal reflux disease (GERD) among certain profession has never been conducted. The aim of this study is to determine the prevalence and risk factors of GERD among Indonesian doctors. Methods: A consecutive study involving 515 doctors was conducted in October 2015. The GerdQ score was used to the diagnosis of GERD and determined its impact on daily life. All possible risk factors were also analysed. Results: A total of 515 subjects completed the questionnaire. The mean age of them was 41.37 ± 11.92 years old. Fifty-five percent of them were male and 60.6% general practitioners. The prevalence of GERD was 27.4% of which 21.0% was had GERD with low impact on daily life, and 6.4% was GERD with high impact on daily life. The statistically significant risk factors of GERD was found in age >50 y.o (p = 0.002; OR = 2.054), BMI >30 kg/m2 (p = 0.016; OR = 2.53), and smokers (p = 0.031; OR = 1.982). Sex and education level were not found significant statistically as the risk factors of GERD. Conclusions: The prevalence of GERD among Indonesian physician was 27.4%. We found that age over 50 y.o, obesity and smoking habit were the risk factors of GERD in Indonesian doctors.&nbsp

Detecting the signature of motion stage non-linearity for focus variation microscopy using measurement noise and surface topography repeatability

Measurement noise is one of the ISO-proposed metrological characteristics of areal surface texture instruments [1, 2, 3, 4]. Measurement noise includes all of the unwanted contributions to the output signals when the instrument is used in its normal operating condition [5, 6]. This paper focuses on detecting the non-linearity signature of the vertical stage of a focus variation microscope using the measurement noise and surface topography repeatability. The paper presents a procedure and material measure to determine the measurement noise and surface topography repeatability. The procedure is carried out at different height levels (5 %, 40 %, 55 % and 85 %) of the total vertical scanning range of the instrument, with equal contrast and brightness parameters. An optical flat with nano-scale surface texture is used as the material measure [7, 8]. One objective lens, with magnification of 100×, is used to measure the flat surface. Subtraction and averaging methods are used to evaluate the measurement noise. The surface topography repeatability is evaluated by calculating the standard deviation of the root mean square (Sq) surface texture parameter from several measurements taken successively under the same measurement conditions [9, 10]. The repeatability at each height level is calculated with five and ten repetitions. The results contain the signature of the non-linear motion of the vertical stage, which can be observed from the results of both the noise and the repeatability measurements. An increasing trend for both the noise and the repeatability is apparent. Using the subtraction method, the noise value is (1.1 ± 0.18) nm (see figure 1). For the surface topography repeatability, the obtained value is (0.06 ± 0.02) nm (see figure 3). The differences of measurement noise from different height levels are statistically significant. The non-linear behaviour of the vertical stage is attributed to the way in which the drive mechanism is guided and how the vertical axis is mounted on its guiding rails. In addition, the results of the motion stage non-linearity signature are compared with the results from the manufacturer (Alicona) and show good agreement (see figure 2 and 4)

Performance improvement for optimization of the non-linear geometric fitting problem in manufacturing metrology

Product quality is a main concern today in manufacturing; it drives competition between companies. To ensure high quality, a dimensional inspection to verify the geometric properties of a product must be carried out. High-speed non-contact scanners help with this task, by both speeding up acquisition speed and increasing accuracy through a more complete description of the surface. The algorithms for the management of the measurement data play a critical role in ensuring both the measurement accuracy and speed of the device. One of the most fundamental parts of the algorithm is the procedure for fitting the substitute geometry to a cloud of points. This article addresses this challenge. Three relevant geometries are selected as case studies: a non-linear least-squares fitting of a circle, sphere and cylinder. These geometries are chosen in consideration of their common use in practice; for example the sphere is often adopted as a reference artifact for performance verification of a coordinate measuring machine (CMM) and a cylinder is the most relevant geometry for a pin-hole relation as an assembly feature to construct a complete functioning product. In this article, an improvement of the initial point guess for the Levenberg–Marquardt (LM) algorithm by employing a chaos optimization (CO) method is proposed. This causes a performance improvement in the optimization of a non-linear function fitting the three geometries. The results show that, with this combination, a higher quality of fitting results a smaller norm of the residuals can be obtained while preserving the computational cost. Fitting an 'incomplete-point-cloud', which is a situation where the point cloud does not cover a complete feature e.g. from half of the total part surface, is also investigated. Finally, a case study of fitting a hemisphere is presented

Comparison of chaos optimization functions for performance improvement of fitting of non-linear geometries

Fitting algorithms play an important role in the whole measuring cycle in order to derive a measurement result. They involve associating substitute geometry to a point cloud obtained by an instrument. This situation is more difficult in the case of non-linear geometry fitting since iterative method should be used. This article addresses this problem. Three geometries are selected as relevant case studies: circle, sphere and cylinder. This selection is based on their frequent use in real applications; for example, cylinder is a relevant geometry of an assembly feature such as pin-hole relationship, and spherical geometry is often found as reference geometry in high precision artifacts and mechanisms. In this article, the use of Chaos optimization (CO) to improve the initial solution to feed the iterative Levenberg–Marquardt (LM) algorithm to fit non-linear geometries is considered. A previous paper has shown the performance of this combination in improving the fitting of both complete and incomplete geometries. This article focuses on the comparison of the efficiency of different one-dimensional maps of CO. This study shows that, in general, logistic-map function provides the best solution compared to other types of one-dimensional functions. Finally, case studies on hemispheres and industrial cylinders fitting are presented

Towards early estimation of part accuracy in additive manufacturing

Additive manufacturing (AM) is becoming more diffused. In spite of its advantages: capability to manufacture complex internal feature and material efficiency, AM has inherent drawback from its layer-by-layer nature. "Staircase effect" is observed due to the slicing process of the computer model in which a rough surface from a theoretically smooth surface will be obtained. Hence, there will be a deviation of the produced part from its nominal model. A methodology to predict the deviation of computer model of an additive manufactured part after fabrication process is presented. A case study is proposed using cylindrical features due to its common real case application. Cylinder is a representation of pin-hole geometry. This geometry is an assembly feature which is very important to guarantee the parts can be assembled with their pair. The dimensional and geometric deviation of the cylindrical feature after fabrication is estimated and could be a useful information for the designer

On combining chaos search and levenberg-marquardt algorithm for non-linear substituted geometric fitting problems

Product quality is becoming a main concern in today manufacturing. As such, dimensional metrology is strictly necessary. High accuracy result while reducing speed in measuring a product has to catch up with the improvement of metrology instrument which can capture many points in less time. Fitting algorithm of point clouds plays a critical role for the measurement accuracy and speed. In this study, non-linear least-square fitting of circle, sphere and cylinder without any prior knowledge of their nominal is addressed. These geometries have common use in practice, such as sphere for calibration and hole-shaft features in mechanical assembly application. The improvement of initial point guess for Levenberg-Marquardt (LM) algorithm by employing Chaos Optimization (CO) method is presented. The results show that, with this combination, higher quality of fitting results in term of smaller norm of the residuals can be obtained while preserving the computational cost

Performance verification of a 4-axis focus variation coordinate measuring system

Performance verification of a coordinate measuring system (CMS) is important for instrument acceptance, reverification, comparability as well as measurement traceability to the definition of the meter. State-of-the-art ISO 10360 standard series is the reference text about the procedure of verification for CMS. Specifically, ISO 10360-8 considers optical distance sensor based CMSs. This article proposes procedures and artifacts for performance verification of focus variation-based CMS for a simultaneous 4-axis measuring mode. The proposal is inspired by, but goes beyond, the ISO 10360 standard, proposing an original solution for simultaneous linear and rotational axes verification

Four-axis micro measuring systems performance verification

This article describes the performance verification of 3D optical measuring instruments integrating a rotational axis using an artifact. The goal is the performance verification of four-axis measuring systems for the full 3D acquisition of micro-geometric parts. This type of measurement has many potential applications, such as in micro-tool, micro-mold, or micro-device manufacturing. The artifact is as simple as possible to reduce manufacturing costs, ensure easy calibration, comply with the ISO 10360 standard and consider all volumetric error contributions. The artifact may be useful to both measuring system manufacturers and users to provide a measurement traceability path