This paper presents a mathematical approach to synthesizing a multi-stable behavior by combining multiple bi-stable equilibrium mechanisms in series. Behavior of a bi-stable compliant mechanism, in general, is highly non-linear. Combinations of such non-linearities to capture the behavior of multi-stable (more than two stable positions) mechanisms can be very challenging. We present a simplified mathematical scheme to capture the essential parameters of bi-stability such as force-thresholds that cause the jump to next stable position etc. to derive multi-stable behavior. This mathematical simplification enables us to characterize bi-stable mechanisms using piecewise lower-order polynomials and synthesize multi-stable mechanisms through combination of bi-stable behaviors in series. We present two case studies of combinations of two and three bi-stable behaviors to generate mechanisms with four and five stable positions respectively. A design example of a quadri-stable equilibrium rotational compliant mechanism consisting two bi-stable sub-mechanisms is presented to demonstrate the effectiveness of the approach.
This work presents a framework of tolerance analysis of microparts in microassembly. Tolerance analysis at the micro scale has not been investigated so far even though tolerance analysis at the macro scale has extensively been investigated to improve an assembly yield. It is important to know the positional uncertainties and statistical distribution of parts before and after untethering to improve assembly yield. Positional misalignments of microparts are extracted from raw CCD images and the statistical distribution of parts variances are computed using clustering and transformation of Gaussian distribution. The distributions are not pure Gaussian in nature as might be expected. There are several location peaks found, usually centered at the fabrication location, and at the hard-stop locators.
ABSTRACT: Effects of various fruit and vegetable juices on rubrene oxidation induced by a chemical source of singlet oxygen in a microemulsion system have been studied. The singlet oxygen quenching activities of fruit and vegetable juices were greatly different with different juices. The apple and pear juices exhibited the highest antioxidative activity among the tested juices in singlet oxygen–induced rubrene oxidation, showing 56.69% and 59.34% inhibition, respectively. The grape, kumquat, red cabbage, and spinach juices also showed relatively strong antioxidative activity against singlet oxygen–induced rubrene oxidation. Lemon juice showed the least activity, resulting in 0.63% inhibition of rubrene oxidation. The singlet oxygen quenching activities of 1 mL of apple and pear juices were equivalent to 33.97 and 34.64 mg ascorbate, respectively. Singlet oxygen quenching activities of juices had very low correlation with both ABTS radical scavenging activity ( R 2 = 0.11) and total phenolic contents ( R 2 < 0.1). However, a high correlation ( R 2 = 0.66) was found between the ABTS radical scavenging activities and total phenolic contents of juices. The apple and pear juices also significantly inhibited both erythrocyte lysis and protein oxidation induced by fluorescence light illumination in the presence of methylene blue. Electron spin resonance (ESR) spectroscopy data showed that the protective activities of these juices against biological damages induced by photodynamic ways were, to at least some extent, due to their singlet oxygen quenching abilities. This represents first report on the singlet oxygen quenching activities of the apple and pear juices, and their protective activities against photodynamically induced biological damages.
Abstract In this paper, we present a mathematical approach to synthesize multistable compliant mechanisms by combining multiple bistable equilibrium mechanisms. More specifically, we identify and categorize various types of bistabilities by characterizing the essential elements of their complicated deformation pattern. The behavior of a bistable compliant mechanism, in general, is highly nonlinear. Using combinations of such nonlinearities to capture the behavior of multistable (more than two stable positions) mechanisms can be quite challenging. To determine multistable behavior, our simplified mathematical scheme captures the essential parameters of bistability, such as the load-thresholds that cause the jump to the next stable position. This mathematical simplification enables us to characterize bistable mechanisms by using piecewise lower-order polynomials and, in turn, synthesize multistable mechanisms. Three case studies involving combinations of two, three, and four bistable behaviors are presented for the purpose of generating multistable mechanisms with up to 16 stable positions. The methodology enables us to design a compliant mechanism with a desired number of stable positions. A design example of a quadristable equilibrium rotational compliant mechanism consisting of two bistable submechanisms is presented to demonstrate the effectiveness of the approach.
This study investigates the characteristics of the dry electrical discharge machining (EDM) process. Dry wire EDM experiments of thin workpieces were conducted in air, which was used as the dielectric fluid. The relationships among spark cycle (T), spark on-time (T on ), air flow, thickness of workpieces and work material were studied in the cases of wet and dry EDM conditions. The material removal rate (MRR), in general, in dry EDM was much lower than that in wet EDM, and the effects of various EDM parameters on MRR were comparatively investigated in the cases of dry and wet wire EDM processes. The thickness of workpiece and work-material were critical ones to influence on the MRR. Die-sinking dry EDM process was also investigated by developing the miniaturized desktop dry EDM machine tool. The aluminum workpiece was dry-EDMed with the copper tubular electrode under the conditions of no air, air blowing and suction, and the machined results were compared.
This paper presents analytical, simulation and experimental results from a study of compliant insertion tasks in microassembly. Gripper compliance is desirable to compensate for positional errors and to prevent the breakage of a gripper during assembly tasks. An analytical model is derived to study the motion and force profiles during compliant insertion. Thermal bimorph microgrippers with a compliant tip are designed and fabricated using a silicon DRIE process, and are mounted on a precision motion stage. A series of micropeg manipulation tasks such as pick up, rotation, and insertion are successfully performed. Finally, a comb structure is integrated in the gripper to calculate insertion force by measuring the deflection of a gripper, which is essential for automated microassembly.
A vision system for the automatic assembly of electronic components is developed. The vision system presents information about positions, orientations, and quality of rectangular-shaped electronic components in real time. The orientation is detected by the windowed Hough transform along with a simple edge-detection method, whereas the position of each component is determined by using the projection method with dynamic thresholding. In addition, real-time implementation of the vision system in which multiple central processors are used for parallel processing of the algorithms is described.< >
To investigate variations in the effects of prehospital advanced airway management (AAM) on outcomes of out-of-hospital cardiac arrest (OHCA) patients according to regional emergency medical service (EMS) systems in four Asian cities.We enrolled adult patients with EMS-treated OHCA of presumed cardiac origin between 2012 and 2014 from Osaka (Japan), Seoul (Republic of Korea), Singapore (Singapore), and Taipei (Taiwan). The main exposure variable was prehospital AAM. The primary endpoint was neurological recovery. We compared outcomes between the prehospital AAM and non-AAM groups using multivariable logistic regression with an interaction term between prehospital AAM and the four Asian cities.A total of 16,510 patients were included in the final analyses. The rates of prehospital AAM varied among Osaka, Seoul, Singapore, and Taipei (65.0%, 19.2%, 84.9%, and 34.1%, respectively). The non-AAM group showed better outcomes than the AAM group (adjusted odds ratio [aOR] for neurological recovery 0.30; 95% confidence interval [CI], 0.24-0.38]). In the interaction model for neurological recovery, the aORs for AAM in Osaka and Singapore were 0.12 (95% CI, 0.06-0.26) and 0.21 (95% CI, 0.16-0.28), respectively. In Seoul and Taipei, the association between prehospital AAM and neurological recovery was not significant (aOR 0.58 [95% CI, 0.31-1.10] and 0.79 [95% CI, 0.52-1.20], respectively). The interaction between prehospital AAM and region was significant (P=0.01).The effects of prehospital AAM on outcomes of OHCA patients differed according to regional variability in the EMS systems.
Purpose: Gastric stump cancer is defined as a cancer that develops in the stomach after a resection in cases of non-malignant or malignant gastric disease. The interval between the gastrectomy and the detection of gastric stump cancer must be over 5 years. Since duodenogastric reflux gastritis is a precancerous condition and one of the most important factors inducing gastric stump cancer, we compared the bile-acid content of gastric juice between gastric stump cancer patients and controls. Materials and Methods: To evaluate retrospectively the surgical treatment of patients with gastric stump cancer, we reviewed the cases histories of 1016 stomach cancer patients who had been operated on at the Department of General Surgery, Kosin University Gospel Hospital, between 1995 and 1998. The gastric juice was collected during the operations on the gastric stump cancer patients by using a needle puncture of the fundus of the stomach and during the endoscopic examinations of the control subjects. The samples were analyzed for various bile acids (gas chromatography/mass spectrometry). Results: The 6 gastric stump cancer cases accounted for of all gastric cancer patients; 5 patients were first operated on for a peptic ulcer and the remaining one for an adenocarcinoma of the stomach. All of the cases were men. The reconstruction method after the initial gastrectomy was a Billroth II in all cases. The sites of the gastric stump cancer were the anastomotic sitein 2 patients, the upper body in 2, the fundus in 1 and the cardia in 1. The operative methods were 3 total gastrectomies, 2 subtotal gastrectomies with Roux en Y anastomosis, and 1 partial gastrectomy with lymph node dissection and had a curative intention in all patients. All of the patients were still surviving at the time of this report. The gastric juices of 4 gastric stump patients showed significantly higher contents of cholic acid () compared to the gastric juices of 35 control subjects ()(p). Chenodeoxycholic acid and lithocholic acid were not significantly different. Conclusion: The gastric juice of gastric stump cancer patients contained a significantly higher cholic acid content. At the time of the initial gastrectomy, an operative method that prevents duodenogastric reflux may prevent or minimize the development of gastric stump cancer, and more aggressive surgical treatment may improve survival.
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