Reliability modelling and analysis of a two unit continuous casting plant

The aim of this paper is to present a reliability modeling and analysis of a two-unit system of a continuous casting (CC) plant. Real maintenance data of a steel production plant have been used for the purpose. Three types of failures were noted: repairable, replaceable and reconditioning/reinstallation. The two-unit system is operating in parallel, on full-reduced installed capacity. Upon the unit failure, an inspection is carried out to decide the type of maintenance task to be performed. Optimized reliability indices of the plant such as mean time to system failure, availability, expected busy periods of the repairman for various maintenance tasks, expected number of visits by the repairman, expected number of repairs, replacements and reconditioning/reinstallation are obtained. Semi-Markov processes and regenerative point techniques are used for the analysis. Profit incurred to the CC plant is also evaluated and related graphs are plotted to demonstrate the results.     

A simple design method for the cosine-modulated filter banks using weighted constrained least square technique

This paper presents a simple and efficient design method for cosine-modulated filter banks with prescribed stopband attenuation, passband ripple, and channel overlap. The method casts the design problem as a linear minimization of filter coefficients such that their value at ω=π/2M is 0.707, which results in a simpler, more direct design procedure. The weighted constrained least squares technique is exploited for designing the prototype filter for cosine modulation (CM) filter banks. Several design examples are included to show the increased efficiency and flexibility of the proposed method over the exiting methods. An application of the proposed method is considered in the area of sub-band coding of the ECG and speech signals.     

A validated search assessment tool: assessing practice-based learning and improvement in a residency program

Objective:

The objective of this study was to validate an assessment instrument for MEDLINE search strategies at an academic medical center.

Method:

Two approaches were used to investigate if the search assessment tool could capture performance differences in search strategy construction. First, data from an evaluation of MEDLINE searches from a pediatric resident''s longitudinal assessment were investigated. Second, a cross-section of search strategies from residents in one incoming class was compared with strategies of residents graduating a year later. MEDLINE search strategies formulated by faculty who had been identified as having search expertise were used as a gold standard comparison. Participants were presented with a clinical scenario and asked to identify the search question and conduct a MEDLINE search. Two librarians rated the blinded search strategies.

Results:

Search strategy scores were significantly higher for residents who received training than the comparison group with no training. There was no significant difference in search strategy scores between senior residents who received training and faculty experts.

Conclusion:

The results provide evidence for the validity of the instrument to evaluate MEDLINE search strategies. This assessment tool can measure improvements in information-seeking skills and provide data to fulfill Accreditation Council for Graduate Medical Education competencies.

Highlights

• The University of Michigan MEDLINE Search Assessment tool can be used to assess search skills in residency education.
• Five elements were identified as critical elements in the development of an effective MEDLINE search strategy: inclusion of all search concepts, appropriate use of Medical Subject Headings, appropriate use of search limits, successful combination of all concepts, and search efficiency.

Implications

• This validated assessment tool can serve as an effective means to measure improvements in residents'' information-seeking skills and provide data to fulfill Accreditation Council for Graduate Medical Education competencies.

     

Pheromone synthesis in a biomicroreactor coated with anti-adsorption polyelectrolyte multilayer

To prepare a biosynthetic module in an infochemical communication project, we designed a silicon/glass microreactor with anti-adsorption polyelectrolyte multilayer coating and immobilized alcohol acetyl transferase (atf), one of the key biosynthetic enzymes of the pheromone of Spodoptera littoralis, on agarose beads inside. The system reproduces the last step of the biosynthesis in which the precursor diene alcohol (Z,E)-9,11-tetradecadienol is transformed into the major component (Z,E)-9,11-tetradecadienyl acetate. The scope of this study was to analyze and implement a multilayer, anti-adsorption coating based on layer-by-layer deposition of polyethylenimine/dextransulfate sodium salt (PEI/DSS). The multilayers were composed of two PEI with molecular weights 750 and 1.2 kDa at pH 9.2 or 6.0. Growth, morphology, and stability of the layers were analyzed by ellipsometry and atomic force microscopy (AFM). The anti-adsorption functionality of the multilayer inside the microreactor was validated. The activity of His(6)-(atf) was measured by gas chromatography coupled to mass spectrometer (GC-MS).     

Transport and shear in a microfluidic membrane bilayer device for cell culture

Microfluidic devices have been established as useful platforms for cell culture for a broad range of applications, but challenges associated with controlling gradients of oxygen and other soluble factors and hemodynamic shear forces in small, confined channels have emerged. For instance, simple microfluidic constructs comprising a single cell culture compartment in a dynamic flow condition must handle tradeoffs between sustaining oxygen delivery and limiting hemodynamic shear forces imparted to the cells. These tradeoffs present significant difficulties in the culture of mesenchymal stem cells (MSCs), where shear is known to regulate signaling, proliferation, and expression. Several approaches designed to shield cells in microfluidic devices from excessive shear while maintaining sufficient oxygen concentrations and transport have been reported. Here we present the relationship between oxygen transport and shear in a "membrane bilayer" microfluidic device, in which soluble factors are delivered to a cell population by means of flow through a proximate channel separated from the culture channel by a membrane. We present an analytical model that describes the characteristics of this device and its ability to independently modulate oxygen delivery and hemodynamic shear imparted to the cultured cells. This bilayer configuration provides a more uniform oxygen concentration profile that is possible in a single-channel system, and it enables independent tuning of oxygen transport and shear parameters to meet requirements for MSCs and other cells known to be sensitive to hemodynamic shear stresses.     

Perfusion systems that minimize vascular volume fraction in engineered tissues

This study determines the optimal vascular designs for perfusing engineered tissues. Here, "optimal" describes a geometry that minimizes vascular volume fraction (the fractional volume of a tissue that is occupied by vessels) while maintaining oxygen concentration above a set threshold throughout the tissue. Computational modeling showed that optimal geometries depended on parameters that affected vascular fluid transport and oxygen consumption. Approximate analytical expressions predicted optima that agreed well with the results of modeling. Our results suggest one basis for comparing the effectiveness of designs for microvascular tissue engineering.     

Complex three-dimensional high aspect ratio microfluidic network manufactured in combined PerMX dry-resist and SU-8 technology

In this paper we present a new fabrication method that combines for the first time popular SU-8 technology and PerMX dry-photoresist lamination for the manufacturing of high aspect ratio three-dimensional multi-level microfluidic networks. The potential of this approach, which further benefits from wafer-level manufacturing and accurate alignment of fluidic levels, is demonstrated by a highly integrated three-level microfluidic chip. The hereby achieved network complexity, including 24 fluidic vias and 16 crossing points of three individual microchannels on less than 13 mm(2) chip area, is unique for SU-8 based fluidic networks. We further report on excellent process compatibility between SU-8 and PerMX dry-photoresist which results in high interlayer adhesion strength. The tight pressure sealing of a fluidic channel (0.5 MPa for 1 h) is demonstrated for 150 μm narrow SU-8/PerMX bonding interfaces.     

Adept through adaptation: Third culture individuals’ interpersonal sensitivity

This study evaluated the interpersonal sensitivity of third culture individuals, defined as people who lived in a country other than that of their nationality during their developmental years, by comparing them to mono-cultured individuals. While the notion that third culture individuals develop enhanced perceptual skills as a result of intercultural adaptation is widely accepted in popular and professional literature, this assertion has not been empirically tested. Previous research on intercultural communication competence and adaptation has almost exclusively focused on intercultural exposure among adults. This study collected data from 142 individuals using web-based surveys. The instruments measured two aspects of participants’ interpersonal sensitivity: social and emotional sensitivity. Results showed that third culture individuals have significantly higher social sensitivity than mono-cultured individuals, while mono-cultured individuals reported higher emotional sensitivity. Additionally, no significant correlation was found between greater intercultural experience and increased interpersonal sensitivity.     

A review of the acculturation experiences of international students

Universities in Western countries host a substantial number of international students. These students bring a range of benefits to the host country and in return the students gain higher education. However, the choice to study overseas in Western countries may present many challenges for the international student including the experience of acculturative stress and difficulties with adjustment to the environment of the host country. The present paper provides a review of current acculturation models as applied to international students. Given that these models have typically been empirically tested on migrant and refugee populations only, the review aims to determine the extent to which these models characterise the acculturation experience of international students. Literature pertaining to salient variables from acculturation models was explored including acculturative stressors encountered frequently by international students (e.g., language barriers, educational difficulties, loneliness, discrimination, and practical problems associated with changing environments). Further discussed was the subsequent impact of social support and coping strategies on acculturative stress experienced by international students, and the psychological and sociocultural adaptation of this student group. This review found that the international student literature provides support for some aspects of the acculturation models discussed; however, further investigation of these models is needed to determine their accuracy in describing the acculturation of international students. Additionally, prominent acculturation models portray the host society as an important factor influencing international students’ acculturation, which suggests the need for future intervention.