Data quality problems in discrete event simulation of manufacturing operations

High-quality input data are a necessity for successful discrete event simulation (DES) applications, and there are available methodologies for data collection in DES projects. However, in contrast to standalone projects, using DES as a daily manufacturing engineering tool requires high-quality production data to be constantly available. In fact, there has been a major shift in the application of DES in manufacturing from production system design to daily operations, accompanied by a stream of research on automation of input data management and interoperability between data sources and simulation models. Unfortunately, this research stream rests on the assumption that the collected data are already of high quality,and there is a lack of in-depth understanding of simulation data quality problems from a practitioners’ perspective.Therefore, a multiple-case study within the automotive industry was used to provide empirical descriptions of simulation data quality problems, data production processes, and relations between these processes and simulation data quality problems. These empirical descriptions are necessary to extend the present knowledge on data quality in DES in a practical real-world manufacturing context, which is a prerequisite for developing practical solutions for solving data quality problems such as limited accessibility, lack of data on minor stoppages, and data sources not being designed for simulation. Further, the empirical and theoretical knowledge gained throughout the study was used to propose a set of practical guidelines that can support manufacturing companies in improving data quality in DES

Not the End of the World? Post-Classical Decline and Recovery in Rural Anatolia

Between the foundation of Constantinople as capital of the eastern half of the Roman Empire in 330 CE and its sack by the Fourth Crusade in 1204 CE, the Byzantine Empire underwent a full cycle from political-economic stability, through rural insecurity and agrarian decline, and back to renewed prosperity. These stages plausibly correspond to the phases of over-extension (K), subsequent release (Ω) and recovery (α) of the Adaptive Cycle in Socio-Ecological Systems. Here we track and partly quantify the consequences of those changes in different regions of Anatolia, firstly for rural settlement (via regional archaeological surveys) and secondly for land cover (via pollen analysis). We also examine the impact of climate changes on the agrarian system. While individual histories vary, the archaeological record shows a major demographic decline between ca .650 and ca. 900 CE in central and southwestern Anatolia, which was then a frontier zone between Byzantine and Arab armies. In these regions, and also in northwest Anatolia, century-scale trends in pollen indicate a substantial decline in the production of cereal and tree crops, and a smaller decline in pastoral activity. During the subsequent recovery (α) phase after 900 CE there was strong regional differentiation, with central Anatolia moving to a new economic system based on agro-pastoralism, while lowland areas of northern and western Anatolia returned to the cultivation of commercial crops such as olive trees. The extent of recovery in the agrarian economy was broadly predictable by the magnitude of its preceding decline, but the trajectories of recovery varied between different regions

USE OF HIGH SURFACE NANOFIBROUS MATERIALS IN MEDICINE

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The intelligent memory allocator selector

Memory fragmentation is a serious obstacle preventing efficient memory usage. Garbage collectors may solve the problem; however, they cause serious performance impact, memory and energy consumption. Therefore, various memory allocators have been developed. Software developers must test memory allocators, and find an efficient one for their programs. Instead of this cumbersome method, we propose a novel approach for dynamically deciding the best memory allocator for every application. The proposed solution tests each process with various memory allocators. After the testing, it selects an efficient memory allocator according to condition of operating system (OS). If OS runs out of memory, then it selects the most memory efficient allocator for new processes. If most of the CPU power was occupied, then it selects the fastest allocator. Otherwise, the balanced allocator is selected. According to test results, the proposed solution offers up to 58% less fragmented memory, and 90% faster memory operations. In average of 107 processes, it offers 7.16±2.53% less fragmented memory, and 1.79±7.32% faster memory operations. The test results also prove the proposed approach is unbeatable by any memory allocator. In conclusion, the proposed method is a dynamic and efficient solution to the memory fragmentation problem. © 2015 Elsevier Ltd. All rights reserved

Surgical treatment of subcondylar fractures of the mandible

Subcondylar fractures of the mandible may be treated either with conservative management or surgical approach. Although the conservative treatment is the widely preferred method, unfavorable results such as malocclusion, limitation of jaw movement and open-bite deformity may occur. For many years, we have routinely tried surgical treatment to overcome these problems. In this paper, the indications for surgical or conservative treatment in subcondylar mandibular fractures have been examined on the basis of patients treated in our clinic. The conclusion is that surgical treatment is superior to other modalities of treatment. © 1989 Springer-Verlag

Interferometric optical fiber sensor for optoacoustic endomicroscopy.

Optical fiber sensors can offer robust and miniaturized detection of wideband ultrasound, yielding high sensitivity and immunity to electromagnetic interference. However, the lack of cost-effective manufacturing methods prevents the disseminated use of these sensors in biomedical applications. In this study, we developed and optimized a simple method to create optical cavities with high-quality mirrors for acoustic sensing based on micro-manipulation of UV-curable optical adhesives and electroless chemical silver deposition. This approach enables the manufacturing of ultrasound sensors based on Fabry-Pérot Interferometers (FPI) on optical fiber tips with minimal production costs. Characterization and high-resolution optoacoustic imaging experiments show that the manufacturing process yielded a fiber sensor with a small NEP (11 mPa/ Hz ) over a broad detection bandwidth (25 MHz), generally outperforming conventional piezoelectric based transducers. We discuss how the new manufacturing process leads to a high-performance acoustic detector that, due to low cost, can be used as a disposable sensor

A submicrometre silicon-on-insulator resonator for ultrasound detection.

The widely available silicon-on-insulator technology is used to develop a miniaturized ultrasound detector, which is 200 times smaller than the wavelengths of sound that it can detect.Ultrasound detectors use high-frequency sound waves to image objects and measure distances, but the resolution of these readings is limited by the physical dimensions of the detecting element. Point-like broadband ultrasound detection can greatly increase the resolution of ultrasonography and optoacoustic (photoacoustic) imaging(1,2), but current ultrasound detectors, such as those used for medical imaging, cannot be miniaturized sufficiently. Piezoelectric transducers lose sensitivity quadratically with size reduction(3), and optical microring resonators(4)and Fabry-Perot etalons(5)cannot adequately confine light to dimensions smaller than about 50 micrometres. Micromachining methods have been used to generate arrays of capacitive(6)and piezoelectric(7)transducers, but with bandwidths of only a few megahertz and dimensions exceeding 70 micrometres. Here we use the widely available silicon-on-insulator technology to develop a miniaturized ultrasound detector, with a sensing area of only 220 nanometres by 500 nanometres. The silicon-on-insulator-based optical resonator design provides per-area sensitivity that is 1,000 times higher than that of microring resonators and 100,000,000 times better than that of piezoelectric detectors. Our design also enables an ultrawide detection bandwidth, reaching 230 megahertz at -6 decibels. In addition to making the detectors suitable for manufacture in very dense arrays, we show that the submicrometre sensing area enables super-resolution detection and imaging performance. We demonstrate imaging of features 50 times smaller than the wavelength of ultrasound detected. Our detector enables ultra-miniaturization of ultrasound readings, enabling ultrasound imaging at a resolution comparable to that achieved with optical microscopy, and potentially enabling the development of very dense ultrasound arrays on a silicon chip

Gamma Knife 3-D dose distribution near the area of tissue inhomogeneities by normoxic gel dosimetry

The accuracy of the Leksell GammaPlan (R), the dose planning system of the Gamma Knife Model-B, was evaluated near tissue inhomogeneities, using the gel dosimetry method. The lack of electronic equilibrium around the small-diameter gamma beams can cause dose calculation errors in the neighborhood of an air-tissue interface. An experiment was designed to investigate the effects of inhomogeneity near the paranosal sinuses cavities. The homogeneous phantom was a spherical glass balloon of 16 cm diameter, filled with MAGIC gel; i.e., the normoxic polymer gel. Two hollow PVC balls of 2 cm radius, filled with N-2 gas, represented the air cavities inside the inhomogeneous phantom. For dose calibration purposes, 100 ml gel-containing vials were irradiated at predefined doses, and then scanned in a MR unit. Linearity was observed between the delivered dose and the reciprocal of the T2 relaxation time constant of the gel. Dose distributions are the results of a single shot of irradiation, obtained by collimating all 201 cobalt sources to a known target in the phantom. Both phantoms were if-radiated at the same dose level at the same coordinates. Stereotactic frames and fiducial markers were attached to the phantoms prior to MR scanning. The dose distribution predicted by the Gamma Knife planning system was compared with that of the gel dosimetry. As expected, for the homogeneous phantom the isodose diameters measured by the gel dosimetry and the GammaPlan (R) differed by 5% at most. However, with the inhomogeneous phantom, the dose maps in the axial, coronal and sagittal planes were spatially different. The diameters of the 50% isodose curves differed 43% in the X axis and 32% in the Y axis for the Z = 90 mm axial plane; by 44% in the X axis and 24% in the Z axis for the Y = 90 mm coronal plane; and by 32% in the Z axis and 42% in the Y axis for the X = 92 mm, sagittal plane. The lack of ability of the GammaPlan (R) to predict the rapid dose fall off, due to the air cavities behind or near the lesion led to an overestimation of the dose that was actually delivered. Clinically, this can result in underdosing of lesions near tissue inhomogeneities in patients under treatment. (c) 2007 American Association of Physicists in Medicine