Purdue University

About: Purdue University is a education organization based out in West Lafayette, Indiana, United States. It is known for research contribution in the topics: Population & Context (language use). The organization has 73219 authors who have published 163563 publications receiving 5775236 citations. The organization is also known as: Purdue & Purdue-West Lafayette.

Design guidelines for wireless sensor networks: communication, clustering and aggregation

Abstract: When sensor nodes are organized in clusters, they could use either single hop or multi-hop mode of communication to send their data to their respective cluster heads. We present a systematic cost-based analysis of both the modes, and provide results that could serve as guidelines to decide which mode should be used for given settings. We determine closed form expressions for the required number of cluster heads and the required battery energy of nodes for both the modes. We also propose a hybrid communication mode which is a combination of single hop and multi-hop modes, and which is more cost-effective than either of the two modes. Our problem formulation also allows for the application to be taken into account in the overall design problem through a data aggregation model.

A review of production planning and scheduling models in the semiconductor industry part i: system characteristics, performance evaluation and production planning

Abstract: Although the national importance of the semiconductor industry is widely acknowledged, it is only recently that the production planning and scheduling problems encountered in this environment have begun to be addressed using industrial engineering and operations research.techniques. These problems have several features that make them difficult and challenging: random yields and rework, complex product flows, and rapidly changing products and technologies. Hence their solution will contribute considerably to die theory and practice of production planning and control. In a two-part project we present a review of research in this area to date, discuss the applicability of the various approaches and suggest directions for future research. In this paper, Part I, we describe the characteristics of the semiconductor manufacturing environment and review models related to performance evaluation and production planning. Part II will review research on shop-floor control in this industry to date.

Conditional-Replication, Integration, Excision, and Retrieval Plasmid-Host Systems for Gene Structure-Function Studies of Bacteria

Abstract: We have developed a series of powerful and versatile conditional-replication, integration, and modular (CRIM) plasmids. CRIM plasmids can be replicated at medium or high copy numbers in different hosts for making gene (or mutant) libraries. They can be integrated in single copies into the chromosomes of Escherichia coli and related bacteria to study gene function under normal physiological conditions. They can be excised from the chromosome, e.g., to verify that phenotypes are caused by their presence. Furthermore, they can be retrieved singly or en masse for subsequent molecular analyses. CRIM plasmids are integrated into the chromosome by site-specific recombination at one of five different phage attachment sites. Integrants are selected as antibiotic-resistant transformations. Since CRIM plasmids encode different forms of resistance, several can be used together in the same cell for stable expression of complex metabolic or regulatory pathways from diverse sources. Following integration, integrants are stably maintained in the absence of antibiotic selection. Each CRIM plasmid has a polylinker or one of several promoters for ectopic expression of the inserted DNA. Their modular design allows easy construction of new variants with different combinations of features. We also report a series of easily curable, low-copy-number helper plasmids encoding all the requisite Int proteins alone or with the respective Xis protein. These helper plasmids facilitate integration, excision (“curing”), or retrieval of the CRIM plasmids. Multicopy plasmids have greatly facilitated gene structurefunction studies. However, the use of such plasmids can lead to high-copy-number artifacts, especially in physiological studies. Thus, several methods have been developed for recombining genes on bacterial chromosomes in order to study their functions in single copies. Such methods are frequently used to construct novel Escherichia coli strains that stably express foreign genes for use in both basic research and biotechnology (5, 18, 27). However, the development of strains encoding complex metabolic or regulatory pathways poses special problems that often require manipulating many genes and expressing them individually at different levels or under separate regulatory controls. To address these concerns, we have developed a series of plasmid-host systems for the introduction of multiple genes into the same cell in single copies. Our approach is based on genome targeting systems that utilize plasmids carrying a conditional-replication origin and a phage attachment (attP) site (17). We refer to our plasmids as CRIM (conditionalreplication, integration, and modular) plasmids. CRIM plasmids can be integrated into or retrieved from their bacterial attachment (attB) site by supplying phage integrase (Int) without or with excisionase (Xis) in trans. Advantages of our CRIM plasmid-host systems include the use of alternative attP and attB sites (for phages , HK022, 80, P21, and P22) and different selectable markers (for chloramphenicol, gentamicin, kanamycin, spectinomycin and streptomycin, tetracycline, and trimethoprim resistance) in conjunc

Teacher value beliefs associated with using technology: Addressing professional and student needs

Abstract: Studies have indicated that when teachers believe technology uses are valuable, they are more likely to incorporate those uses into their practices. This hermeneutical phenomenology study investigated the value beliefs that underlie teachers' uses of technology. To measure value beliefs, teachers' uses (and reasons for those uses) of technology for teaching and learning were examined. Data were collected from eight award-winning teachers through an interview, observation, and electronic portfolio. Findings indicated that teachers used technology to address professional (e.g., creating customized classroom materials, improving classroom management by engaging students) and student needs (e.g., enhancing student comprehension, equipping students with technology skills), all of which related to the underlying value belief of promoting student learning. Based on these findings, professional development activities should emphasize the potential impact of specific technology uses on student learning.

Casting Antimicrobial Packaging Films and Measuring Their Physical Properties and Antimicrobial Activity

Abstract: Antimicrobial film was extruded using LDPE resins and potassium sorbate powder; its tensile properties, transparency and antimicrobial activity were measured to examine the adaptability as a packaging material. The tensile properties were not affected significantly by the incorporation of potassium sorbate to 3% (w/w) in the film. However, transparency of the film decreased as the concentration of potassium sorbate increased. The antimicrobial film decreased the growth rate and maximum growth of yeast, and extended the lag period before mold growth was apparent. Therefore, it can prevent or reduce the rate of microbial spoilage in low viscosity liquids and on the contacted surface area of solid food products and thus may prolong the shelf life of food products when it is used as a packaging material.