Performance comparison of the exact run-length distribution between the run sum X and EWMA X charts

The run sum (RS) X and exponentially weighted moving average (EWMA) X charts are very effective in detecting small and moderate process mean shifts. The design of the RS X and EWMA X charts based on the average run length (ARL) alone, can be misleading and confusing. This is due to the fact that the run-length distribution of a control chart is highly right-skewed when the process is in-control or slightly out-of-control; while that for the out-ofcontrol cases, the run-length distribution is almost symmetric. On the other hand, the percentiles of the run-length distribution provide the probability of getting a signal by a certain number of samples. This will benefit practitioners as the percentiles of the run-length distribution give comprehensive information regarding the behaviour of a control chart. Accordingly, this paper provides a thorough study of the run-length properties (ARL, standard deviation of the run length and percentiles of the run-length distribution) for the RS X and EWMA X charts. Comparative studies show that the EWMA X chart outperforms the RS X charts for detecting small mean shifts when all the control charts are optimized with respect to a small shift size. However, the RS X charts surpass the EWMA X chart for all sizes of mean shifts when all the control charts are optimized with respect to a large shift size

IMPROVING THROUGHPUT AND COMPLETION DATE ESTIMATION IN HIGH PRECISION COMPONENT MANUFACTURER USING SIMULATION APPROACH

Simulation has become an indispensable tool which enables engineers, designers, planner and managers, to study, analyze and evaluate complex situations that would not be otherwise possible. In this paper, a job shop simulation model with stochastic variables and constraints in a high precision component manufacturer is presented. Data was collected from the manufacturer of high-mix and low volume products, each product with different processing specifications. A discrete event simulation model was developed using the Witness Simulation software. The model is then verified and validated with the data from the company. Simulation experiments were conducted to identify bottlenecks in the manufacturing system and to test several scenarios of operators’ overtime. The experiments also have the ability to estimate the completion date for customer orders. Results show that simulation model gives better estimates of the completion dates of the customer orders compared to the production planner of the company

Novelty Search in Competitive Coevolution

One of the main motivations for the use of competitive coevolution systems is their ability to capitalise on arms races between competing species to evolve increasingly sophisticated solutions. Such arms races can, however, be hard to sustain, and it has been shown that the competing species often converge prematurely to certain classes of behaviours. In this paper, we investigate if and how novelty search, an evolutionary technique driven by behavioural novelty, can overcome convergence in coevolution. We propose three methods for applying novelty search to coevolutionary systems with two species: (i) score both populations according to behavioural novelty; (ii) score one population according to novelty, and the other according to fitness; and (iii) score both populations with a combination of novelty and fitness. We evaluate the methods in a predator-prey pursuit task. Our results show that novelty-based approaches can evolve a significantly more diverse set of solutions, when compared to traditional fitness-based coevolution.Comment: To appear in 13th International Conference on Parallel Problem Solving from Nature (PPSN 2014

Identification of material properties of orthotropic composite plate using hybrid non-destructive evaluation approach

Identification of material properties is one of the key issues in composite materials research. The mechanical properties of composite materials depend on diverse factors such as configuration of the laminates, constituent materials used and production method adopted. Conventional testing approach tends to be time-consuming, expensive and destructive. As an alternative, a rapid, inexpensive, hybrid and non-destructive evaluation approach which utilises experimental modal analysis and finite element analysis is proposed. Experimental modal data which consist of natural frequencies and mode shapes of an orthotropic composite plate are utilised for correlation purpose with its finite element model. This finite element model of the composite plate is continuously updated and achieves less than 5% in difference of natural frequencies and over 70% in modal assurance criterion. Material properties such as Young's moduli, inplane shear modulus and Poisson ratio of the composite plate are then successfully determined using the well-correlated FE model

Energy Harvesting Based on a Novel Piezoelectric 0.7PbZn0.3Ti0.7O3-0.3Na2TiO3 Nanogenerator

Recently, piezoelectric materials have achieved remarkable attention for charging wireless sensor nodes. Among piezoelectric materials, non-ferroelectric materials are more cost effective because they can be prepared without a polarization process. In this study, a non-ferroelectric nanogenerator was manufactured from 0.7PbZn0.3Ti0.7O3-0.3Na2TiO3 (PZnT-NT). It was demonstrated that the increment of conductivity via adding the Na2TiO3 plays an essential role in increasing the permittivity of the non-ferroelectric nanogenerator and hence improved the generated power density. The dielectric measurements of this material demonstrated high conductivity that quenched the polarization phase. The performance of the device was studied experimentally over a cantilever test rig; the vibrating cantilever (0.4 ms-2) was excited by a motor operated at 30 Hz. The generated power successfully illuminated a light emitting diode (LED). The PZnT-NT nanogenerator produced a volume power density of 0.10 μw/mm3 and a surface power density of 10 μw/cm2. The performance of the proposed device with a size of (20 × 15 × 1 mm3) was higher in terms of power output than that of the commercial microfiber composite (MFC) (80 × 57 × 0.335 mm3) and piezoelectric bimorph device (70 × 50 × 0.7 mm3). Compared to other existing ferroelectric and non-ferroelectric nanogenerators, the proposed device demonstrated great performance in harvesting the energy at low acceleration and in a low frequency environment

Prognostic utility of ADAMTS13 activity for the atypical hemolytic uremic syndrome (aHUS) and comparison of complement serology between aHUS and thrombotic thrombocytopenic purpura

Background Atypical hemolytic uremic syndrome (aHUS) involves dysregulation of the complement system, but whether this also occurs in thrombotic thrombocytopenic purpura (TTP) remains unclear. Although these conditions are difficult to differentiate clinically, TTP can be distinguished by low (<10%) ADAMTS13 activity. The aim was to identify the differences in complement activation products between TTP and aHUS and investigate ADAMTS13 activity as a prognostic factor in aHUS. Methods We analyzed patients with thrombotic microangiopathy diagnosed as TTP (N=48) or aHUS (N=50), selected from a Korean registry (N=551). Complement activation products in the plasma samples collected from the patients prior to treatment and in 40 healthy controls were measured by ELISA. Results The levels of generalized (C3a), alternate (factor Bb), and terminal (C5a and C5b-9) markers were significantly higher (all P<0.01) in the patients than in the healthy controls. Only the factor Bb levels significantly differed (P=0.008) between the two disease groups. In aHUS patients, high normal ADAMTS13 activity (≥77%) was associated with improved treatment response (OR, 6.769; 95% CI, 1.605–28.542; P=0.005), remission (OR, 6.000; 95% CI, 1.693–21.262; P=0.004), exacerbation (OR, 0.242; 95% CI, 0.064–0.916; P=0.031), and disease-associated mortality rates (OR, 0.155; 95% CI, 0.029–0.813; P=0.017). Conclusion These data suggest that complement biomarkers, except factor Bb, are similarly activated in TTP and aHUS patients, and ADAMTS13 activity can predict the treatment response and outcome in aHUS patients

Termoreverzibilni mukoadhezivni in situ hidrogel za oftalmičku primjenu: dizajniranje i optimizacija koristeći kombinaciju polimera

The purpose of the study was to develop an optimized thermoreversible in situ gelling ophthalmic drug delivery system based on Pluronic F 127, containing moxifloxacin hydrochloride as a model drug. A 32 full factorial design was employed with two polymers Pluronic F 68 and Gelrite as independent variables used in combination with Pluronic F 127. Gelation temperature, gel strength, bioadhesion force, viscosity and in vitro drug release after 1 and 10 h were selected as dependent variables. Pluronic F 68 loading with Pluronic F 127 was found to have a significant effect on gelation temperature of the formulation and to be of importance for gel formation at temperatures 3336 ºC. Gelrite loading showed a positive effect on bioadhesion force and gel strength and was also found helpful in controling the release rate of the drug. The quadratic mathematical model developed is applicable to predicting formulations with desired gelation temperature, gel strength, bioadhesion force and drug release properties.Cilj rada bio je razvoj i optimizacija termoreverzibilnog sustava za isporuku lijekova koji gelira in situ. Sustav je napravljen na bazi Pluronic F 127, a sadrži moksifloksacin hidroklorid kao modelni lijek. U radu je primjenjeno 32 potpuno faktorijsko dizajniranje s dva polimera, Pluronic F 68 i Gelrite kao nezavisnim varijablama koji su kombinirani s Pluronic F 127. Kao zavisne varijable odabrane su temperatura geliranja, čvrstoća gela, jačina bioadhezije, viskoznost i in vitro oslobađanje lijeka nakon 1 i 10 h. Pronađeno je da Pluronic F 68 u kombinaciji s Pluronic F 127 ima značajan učinak na temperaturu geliranja u rasponu od 33 do 36 C. S druge strane, Gelrite ima povoljan učinak na jačinu bioadhezije, čvrstoću gela i oslobađanje lijeka. Razvijen je kvadratni matematički model pomoću kojeg se može predvidjeti temperatura geliranja, čvrstoća gela, jačina bioadhezije i oslobađanje ljekovite tvari

Impact force identification with pseudo-inverse method on a lightweight structure for under-determined, even-determined and over-determined cases

Force identification using inverse technique is important especially when direct measurement through force transducer is not possible. Considering the effects of impact excitation force on the integrity of a lightweight structure, impact force identification has become the subject of several studies. A methodology utilising Operating Deflection Shape (ODS) analysis, Frequency Response Function (FRF) measurement and pseudo-inverse method to evaluate the dynamic force is presented. A rectangular plate with four ground supports was used as a test rig to simulate the motions of a simple vehicle body. By using the measured responses at remote points that are away from impact locations and measured FRFs of the test rig, unknown force locations and their time histories can be recovered by the proposed method. The performance of this approach in various cases such as under-determined, even-determined and over-determined cases was experimentally demonstrated. Good and bad combinations of response locations were selected based on the condition number of FRF matrix. This force identification method was examined under different response combinations and various numbers of response locations. It shows that in the over-determined case, good combination of response locations (i.e. low average of condition number of FRF matrix) and high number of response locations give the best accuracy of force identification result compared to under-determined and even-determined cases

Coevolutionary systems and PageRank

Coevolutionary systems have been used successfully in various problem domains involving situations of strategic decision-making. Central to these systems is a mechanism whereby finite populations of agents compete for reproduction and adapt in response to their interaction outcomes. In competitive settings, agents choose which solutions to implement and outcomes from their behavioral interactions express preferences between the solutions. Recently, we have introduced a framework that provides both qualitative and quantitative characterizations of competitive coevolutionary systems. Its two main features are: (1) A directed graph (digraph) representation that fully captures the underlying structure arising from pairwise preferences over solutions. (2) Coevolutionary processes are modeled as random walks on the digraph. However, one needs to obtain prior, qualitative knowledge of the underlying structures of these coevolutionary digraphs to perform quantitative characterizations on coevolutionary systems and interpret the results. Here, we study a deep connection between coevolutionary systems and PageRank to address this issue. We develop a principled approach to measure and rank the performance (importance) of solutions (vertices) in a given coevolutionary digraph. In PageRank formalism, B transfers part of its authority to A if A dominates B (there is an arc from B to A in the digraph). In this manner, PageRank authority indicates the importance of a vertex. PageRank authorities with suitable normalization have a natural interpretation of long-term visitation probabilities over the digraph by the coevolutionary random walk. We derive closed-form expressions to calculate PageRank authorities for any coevolutionary digraph. We can precisely quantify changes to the authorities due to modifications in restart probability for any coevolutionary system. Our empirical studies demonstrate how PageRank authorities characterize coevolutionary digraphs with different underlying structures

Tapping into the glial reservoir: cells committed to remaining uncommitted

The development and maturation of the oligodendrocyte requires a series of highly orchestrated events that coordinate the proliferation and differentiation of the oligodendrocyte precursor cell (OPC) as well as the spatiotemporal regulation of myelination. In recent years, widespread interest has been devoted to the therapeutic potential of adult OPCs scattered throughout the central nervous system (CNS). In this review, we highlight molecular mechanisms controlling OPC differentiation during development and the implication of these mechanisms on adult OPCs for remyelination. Cell-autonomous regulators of differentiation and the heterogeneous microenvironment of the developing and the adult CNS may provide coordinated inhibitory cues that ultimately maintain a reservoir of uncommitted glia