bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of physicochemical conditions and nutrient sources on maximizing the growth and lipid productivity of green microalgae
Authors: da Silva Ferreira Veronica , Sant'Anna Celso
Published: December 2016

Biodiesel is a renewable fuel produced mostly from edible and non‐edible vegetables, by transesterification of neutral lipids (triacylglycerols). However, vegetable oil‐based biodiesel production competes with food crops for arable land, increasing food prices and leading to biodiversity loss. The production of biodiesel from oleaginous microorganisms – particularly microalgae – has attracted attention due to the higher lipid productivity of these organisms, when compared with vegetables. Several environmental factors – including light, temperature, pH and the presence of nutrients (particularly nitrogen, phosphorus and iron) – influence directly the ability of microalgae to produce and store triacylglycerols and other lipids, and also modulate microalgal growth. Although some environmental factors affect several species in a similar manner, differential responses between species are frequent, highlighting the importance of identifying optimal cultivation conditions for each species, to balance growth and lipid productivity for biodiesel production. Here, we reviewed the particular influence of the physicochemical and nutritional factors on the growth and lipid productivity of different green oleaginous microalgae species.
Testing and Confidence Intervals for High Dimensional Proportional Hazards Models
Authors: Fang Ethan X. , Ning Yang , Liu Han
Published: December 2016

The paper considers the problem of hypothesis testing and confidence intervals in high dimensional proportional hazards models. Motivated by a geometric projection principle, we propose a unified likelihood ratio inferential framework, including score, Wald and partial likelihood ratio statistics for hypothesis testing. Without assuming model selection consistency, we derive the asymptotic distributions of these test statistics, establish their semiparametric optimality and conduct power analysis under Pitman alternatives. We also develop new procedures to construct pointwise confidence intervals for the baseline hazard function and conditional hazard function. Simulation studies show that all tests proposed perform well in controlling type I errors. Moreover, the partial likelihood ratio test is empirically more powerful than the other tests. The methods proposed are illustrated by an example of a gene expression data set.
Improving With Practice: A Neural Model of Mathematical Development
Authors: Aubin Sean , Voelker Aaron R. , Eliasmith Chris
Published: December 2016

The ability to improve in speed and accuracy as a result of repeating some task is an important hallmark of intelligent biological systems. Although gradual behavioral improvements from practice have been modeled in spiking neural networks, few such models have attempted to explain cognitive development of a task as complex as addition. In this work, we model the progression from a counting‐based strategy for addition to a recall‐based strategy. The model consists of two networks working in parallel: a slower basal ganglia loop and a faster cortical network. The slow network methodically computes the count from one digit given another, corresponding to the addition of two digits, whereas the fast network gradually “memorizes” the output from the slow network. The faster network eventually learns how to add the same digits that initially drove the behavior of the slower network. Performance of this model is demonstrated by simulating a fully spiking neural network that includes basal ganglia, thalamus, and various cortical areas. Consequently, the model incorporates various neuroanatomical data, in terms of brain areas used for calculation and makes psychologically testable predictions related to frequency of rehearsal. Furthermore, the model replicates developmental progression through addition strategies in terms of reaction times and accuracy, and naturally explains observed symptoms of dyscalculia.
Temporal and spatial changes in gene expression, metabolite accumulation and phytohormone content in rice seedlings grown under drought stress conditions
Authors: Todaka Daisuke , Zhao Yu , Yoshida Takuya , Kudo Madoka , Kidokoro Satoshi , Mizoi Junya , Kodaira Ken‐Suke , Takebayashi Yumiko , Kojima Mikiko , Sakakibara Hitoshi , Toyooka Kiminori , Sato Mayuko , Fernie Alisdair R. , Shinozaki Kazuo , Yamaguchi‐Shinozaki Kazuko
Published: December 2016

In order to analyze the molecular mechanisms underlying the responses of plants to different levels of drought stress, we developed a soil matric potential (SMP)‐based irrigation system that precisely controls soil moisture. Using this system, rice seedlings were grown under three different drought levels, denoted Md1, Md2 and Md3, with SMP values set to −9.8, −31.0 and −309.9 kPa, respectively. Although the Md1 treatment did not alter the visible phenotype, the Md2 treatment caused stomatal closure and shoot growth retardation (SGR). The Md3 treatment markedly induced SGR, without inhibition of photosynthesis. More severe drought (Sds) treatment, under which irrigation was terminated, resulted in the wilting of leaves and inhibition of photosynthesis. Metabolome analysis revealed the accumulation of primary sugars under Md3 and Sds and of most amino acids under Sds. The starch content was increased under Md3 and decreased under Sds. Transcriptome data showed that the expression profiles of associated genes supported the observed changes in photosynthesis and metabolites, suggesting that the time lag from SGR to inhibition of photosynthesis might lead to the accumulation of photosynthates under Md3, which can be used as osmolytes under Sds. To gain further insight into the observed SGR, transcriptome and hormonome analyses were performed in specific tissues. The results showed specific decreases in indole‐3‐acetic acid (IAA) and cytokinin levels in Md2‐, Md3‐ and Sds‐treated shoot bases, though the expression levels of hormone metabolism‐related genes were not reflected in IAA and cytokinin contents. These observations suggest that drought stress affects the distribution or degradation of cytokinin and IAA molecules.
DNA‐based probes for flow cytometry analysis of endocytosis and recycling
Authors: Dumont Claire , Czuba Ewa , Chen Moore , Villadangos Jose A. , Johnston Angus P.R. , Mintern Justine D.
Published: December 2016

The internalization of proteins plays a key role in cell development, cell signaling and immunity. We have previously developed a specific hybridization internalization probe (SHIP) to quantitate the internalization of proteins and particles into cells. Herein, we extend the utility of SHIP to examine both the endocytosis and recycling of surface receptors using flow cytometry. SHIP was used to monitor endocytosis of membrane‐bound transferrin receptor (TFR) and its soluble ligand transferrin (TF). SHIP enabled measurements of the proportion of surface molecules internalized, the internalization kinetics and the proportion and rate of internalized molecules that recycle to the cell surface with time. Using this method, we have demonstrated the internalization and recycling of holo‐TF and an antibody against the TFR behave differently. This assay therefore highlights the implications of receptor internalization and recycling, where the internalization of the receptor‐antibody complex behaves differently to the receptor‐ligand complex. In addition, we observe distinct internalization patterns for these molecules expressed by different subpopulations of primary cells. SHIP provides a convenient and high throughput technique for analysis of trafficking parameters for both cell surface receptors and their ligands.
Pathogen inactivation by riboflavin and ultraviolet light illumination accelerates the red blood cell storage lesion and promotes eryptosis
Authors: Qadri Syed M. , Chen Deborah , Schubert Peter , Perruzza Darian L. , Bhakta Varsha , Devine Dana V. , Sheffield William P.
Published: December 2016

BACKGROUND

Pathogen reduction treatment using riboflavin and ultraviolet light illumination (Mirasol) effectively reduces the risk of transfusion‐transmitted infections. This treatment is currently licensed for only platelets and plasma products, while its application to whole blood (WB) to generate pathogen‐inactivated red blood cells (RBCs) is under development. RBC storage lesion, constituting numerous morphologic and biochemical changes, influences RBC quality and limits shelf life. Stored RBCs further show enhanced susceptibility to RBC programmed cell death (eryptosis) characterized by increased cytosolic Ca2+‐provoked membrane phosphatidylserine (PS) externalization.

STUDY DESIGN AND METHODS

Using a “pool‐and‐split” approach, we examined multiple variables of RBC storage lesion and eryptosis in RBC units, derived from Mirasol‐treated or untreated WB, after 4 to 42 days of storage, under blood bank conditions.

RESULTS

In comparison to untreated RBC units, Mirasol treatment significantly altered membrane microvesiculation, supernatant hemoglobin, osmotic fragility, and intracellular adenosine triphosphate levels but did not influence membrane CD47 expression and 2,3‐diphosphoglycerate levels. Mirasol‐treated RBCs showed significantly higher PS exposure after 42, but not after not more than 21, days of storage, which was accompanied by enhanced cytosolic Ca2+ activity, ceramide abundance, and oxidative stress, but not p38 kinase activation. Mirasol treatment significantly augmented PS exposure, Ca2+ entry, and protein kinase C activation after energy depletion, a pathophysiologic cell stressor. Mirasol‐treated RBCs were, however, more resistant to cell shrinkage.

CONCLUSIONS

Prolonged storage of Mirasol‐treated RBCs significantly increases the proportion of eryptotic RBCs, while even short‐term storage enhances the susceptibility of RBCs to stress‐induced eryptosis, which could reduce posttransfusion RBC recovery in patients.
Severe cardiac iron toxicity in two adults with sickle cell disease
Authors: Oduor Hellen , Minniti Caterina P. , Brofferio Alessandra , Gharib Ahmed M. , Abd‐Elmoniem Khaled Z. , Hsieh Matthew M. , Tisdale John F. , Fitzhugh Courtney D.
Published: December 2016

BACKGROUND

Use of chronic blood transfusions as a treatment modality in patients with blood disorders places them at risk for iron overload. Since patients with β‐thalassemia major (TM) are transfusion‐dependent, most studies on iron overload and chelation have been conducted in this population. While available data suggest that compared to TM, patients with sickle cell disease (SCD) have a lower risk of extrahepatic iron overload, significant iron overload can develop. Further, previous studies have demonstrated a direct relationship between iron overload and morbidity and mortality rates in SCD. However, reports describing the outcome for patients with SCD and cardiac iron overload are rare.

STUDY DESIGN AND METHODS

We performed a retrospective analysis and identified two SCD patients with cardiac iron overload. We provide detailed descriptions of both cases and their outcomes.

RESULTS

Serum ferritin levels ranged between 17,000 and 19,000 μg/L. Both had liver iron concentrations in excess of 35 mg of iron per gram of dried tissue as well as evidence of cardiac iron deposition on magnetic resonance imaging. One patient died of an arrhythmia and had evidence of severe multiorgan iron overload via autopsy. On the other hand, after appropriate therapy, a second patient had improvement in cardiac function.

CONCLUSION

Improper treatment of iron overload in SCD can lead to a fatal outcome. Alternatively, iron overload may potentially be prevented or reversed with judicious use of blood transfusions and early use of chelation therapy, respectively.
Excretions/secretions from medicinal larvae (Lucilia sericata) inhibit complement activation by two mechanisms
Authors: Tamura Tetsuro , Cazander Gwendolyn , Rooijakkers Suzan H. M. , Trouw Leendert A. , Nibbering Peter H.
Published: December 2016

Larvae of the blowfly Lucilia sericata facilitate wound healing by removing dead tissue and biofilms from non‐healing and necrotic wounds. Another beneficial action of larvae and their excretions/secretions (ES) is down‐regulation of excessive inflammation. As prolonged complement activation is key to excessive inflammation, the aim of this study was to elucidate the mechanisms underlying the anti‐complement activities of ES. Results revealed that heat sensitive serine proteases in ES degrade multiple complement proteins in all steps of the three complement activation pathways. Importantly, C3a and C5a—major activators of inflammation—were also degraded by ES and pretreatment of these factors with ES completely blocked their ability to induce activation of human neutrophils. Pre‐exposure of the neutrophils to ES did not affect their responsiveness to C3a/C5a and fMLP, indicating that the receptors for these activators on neutrophils were not affected by ES. Surprisingly, heat and serine protease inhibitor pretreatment did not affect the ability of ES to inhibit C5b‐9 complex formation despite degrading complement proteins, indicating a second complement‐inhibiting molecule in ES. Heated ES was as effective as intact ES in inhibiting C3 deposition upon activation of the alternative pathway, but was significantly less effective in wells with a classical or lectin pathway‐specific coating. Unfortunately, the molecules affecting the complement system could not be identified due to an insufficient database for L. sericata. Together, larval ES inhibit complement activation by two different mechanisms and down‐regulate the C3a/C5a‐mediated neutrophil activation. This attenuates the inflammatory process, which may facilitate wound healing.
Biofilm detection by wound blotting can predict slough development in pressure ulcers: A prospective observational study
Authors: Nakagami Gojiro , Schultz Gregory , Gibson Daniel J , Phillips Priscilla , Kitamura Aya , Minematsu Takeo , Miyagaki Tomomitsu , Hayashi Akitatsu , Sasaki Sanae , Sugama Junko , Sanada Hiromi
Published: December 2016

Bacteria have been found to form multicellular aggregates which have collectively been termed “biofilms.” It is hypothesized that biofilm formation is a means to protect bacterial cells including protection form the immune response of humans. This protective mechanism is believed to explain persistent chronic wound infections. At times, the biofilms are abundant enough to see, and remove by simple wiping. However, recent evidence has shown that the removal of these visible portions are not sufficient, and that biofilms can continue to form even with daily wiping. In this work, we tested an approach to detect the biofilms which are present after clinically wiping or sharp wound debridement. Our method is based on a variation of impression cytology in which a nitrocellulose membrane was used to collect surface biofilm components, which were then differentially stained. In this prospective study, members of an interdisciplinary pressure ulcer team at a university hospital tested our method's ability to predict the generation of wound slough in the week that followed each blotting. A total of 70 blots collected from 23 pressure ulcers produced 27 wounds negative for staining and 43 positive. In the negative blots 55.6% were found to have decreased wound slough, while 81.4% with positive staining had either increase or unchanged wound slough generation. These results lead to an odds ratio of positive blotting cases of 9.37 (95% confidence intervals: 2.47–35.5, p = 0.001) for slough formation; suggesting that the changes in wound slough formation can be predicted clinically using a non‐invasive wound blotting method.
Ownership Structure and Firm Performance: An Empirical Analysis of Chinese Companies
Authors: Zhang Hui , Kyaw Khine
Published: December 2016

This study examines the relationship between ownership structure and firm performance in Chinese companies. We hand collected ownership data on 1178 non-financial companies with a total of 5815 firm-years from annual reports. Through fixed-effect panel model, this study has the following findings. First, there is a positive relationship between firm performance and institutional ownership in Chinese companies. Second, the proportion of tradable shares negatively affects firm performance. Third, ownership concentration and state ownership appear to not affect firm performance.
Empirical Evidence on the Impact of City Taxes
Authors: Swenson Charles
Published: December 2016

An important issue is whether cities can influence their own economic growths through municipal-level tax policy. There is little evidence on this to date, nor is there a clear a priori answer to this question. This study first documents municipal business tax rates across the United States, and finds they are a relatively significant cost to business. Next, using very a unique and precise government data set, the study examines the economic impacts of two previous tax cuts in Los Angeles and finds that these cuts generally resulted in growth in both the number of jobs and establishments.
The Struggle with Anxiety and Depression among the Elderly: Predicting Elderly Behavior in Crisis and Conflict Situations – The Case of Operation Protective Edge
Authors: Bitzur Avi
Published: December 2016

Existing theories cast the elderly as individuals likely to crumble under pressure, suggesting that crisis situations may exacerbate underlying conditions, such as depression.The conflict between Israel and the Palestinians breeds numerous stress situations, which are bound to affect the lives of the elderly population on both sides. This inspired the author to examine whether the elderly population in Israel does, in fact, behave according to existing theories.A prominent example of a crisis situation was the 2014 conflict, which triggered a crisis in Israeli communities that found themselves under the threat of direct rocket fire. The situation lent itself to the assumption that there would be a spike in depression and anxiety among the area's residents, especially the elderly, which would translate into "mass migration" to safer areas.This study sought to substantiate or refute the "helplessness" of elderly people in crisis situations. It was based on a qualitative analysis of questionnaires answered by Holocaust survivors, former Soviet Union immigrants, and long-time residents of the Gaza vicinity communities, shortly after the conflict.The study found little to no evidence of depression or anxiety among elderly Israelis, proving their resilience in the reviewed crisis.While the rationale varied among participants, a clear sentiment came through, spelling devotion among the border communities' residents, defiance among immigrants from the former USSR, and a combination of both among Holocaust survivors.The study indicated the elderly tend to be mentally tougher than younger generations, proving their resilience by weathering multiple threats. To conclude: Senior citizens can be used to bolster the home front's resilience; depression and anxiety experienced by the elderly in crisis situations can be alleviated by providing them with information about the nature of the threat; and it is best to form permanent resilience centers in threatened areas.
Prevalence of Teachers’ Professional Malpractices in Tanzanian Public Secondary Schools: What Ought to Be Done?
Authors: Mfaume Hamisi , Bilinga Margareth
Published: December 2016

This study explored stakeholders’ views on preventive measures towards increasing teachers’ malpractices in schools in Tanzania. Specifically, the study sought to identify prevalent forms of teachers' malpractices; explore factors for their occurrence; and explore views on how to forestall the problem. It draws on qualitative and quantitative data generated from 75 respondents including the Teachers’ Service Department (TSD) officers, education officers, school inspectors, teachers, and students. The data were generated from questionnaires, interviews, Focused Group Discussion, documentary search and non-participant observation. Data analysis involved both qualitative and quantitative approaches. While Qualitative data were subjected to thematic analysis, Quantitative data were converted into frequencies and percentages and then presented in tabular forms. The findings unveiled that absenteeism, abusive and violent behaviours, sexual abuse to mention a few were prevalent forms of teachers’ malpractices in schools. Their occurrence were attributed to teachers’ low salaries and remunerations, poor living and working conditions, influence of science and technology, lack of professional knowledge and poor management as well as infrequent visits and inspections of schools. In order to remedy the problem respondents proposed that teachers’ needs and plights to be addressed timely, funds allocated to the TSD should be raised and involvement of stakeholders in all decision making related to the teaching profession. It was also suggested for the TSD to be empowered to oversee teachers’ discipline both in public and private owned schools. In the light of the findings, the study concludes that teachers’ malpractice is still a problem of great concern in rural and urban schools in Tanzania. Therefore, rigorous collaborative effort by the government and the wider community is needed in order to promote desirable professional behaviour in schools.
Low-Order Modeling of Nonlinear High-Frequency Transversal Thermoacoustic Oscillations in Gas Turbine Combustors
Authors: Hummel Tobias , Hammer Klaus , Romero Pedro , Schuermans Bruno , Sattelmayer Thomas
Published: December 2016

This paper analyzes transversal thermoacoustic oscillations in an experimental gas turbine combustor utilizing dynamical system theory. Limit-cycle acoustic motions related to the first linearly unstable transversal mode of a given 3D combustor configuration are modeled and reconstructed by means of a low-order dynamical system simulation. The source of nonlinearity is solely allocated to flame dynamics, saturating the growth of acoustic amplitudes, while the oscillation amplitudes are assumed to always remain within the linearity limit. First, a reduced order model (ROM) which reproduces the combustor's modal distribution and damping of acoustic oscillations is derived. The ROM is a low-order state-space system, which results from a projection of the linearized Euler equations (LEE) into their truncated eigenspace. Second, flame dynamics are modeled as a function of acoustic perturbations by means of a nonlinear transfer function. This function has a linear and a nonlinear contribution. The linear part is modeled analytically from first principles, while the nonlinear part is mathematically cast into a cubic saturation functional form. Additionally, the impact of stochastic forcing due to broadband combustion noise is included by additive white noise sources. Then, the acoustic and the flame system is interconnected, where thermoacoustic noncompactness due to the transversal modes' high frequency (HF) is accounted for by a distributed source term framework. The resulting nonlinear thermoacoustic system is solved in frequency and time domain. Linear growth rates predict linear stability, while envelope plots and probability density diagrams of the resulting pressure traces characterize the thermoacoustic performance of the combustor from a dynamical systems theory perspective. Comparisons against experimental data are conducted, which allow the rating of the flame modes in terms of their capability to reproduce the observed combustor dynamics. Ultimately, insight into the physics of high-frequency, transversal thermoacoustic systems is created.
Lab Testing and Finite Element Method Simulation of Hole Deflector Performance for Radial Jet Drilling
Authors: Wang Bin , Li Gensheng , Huang Zhongwei , Ma Tianqi , Zheng Dongbo , Li Kui
Published: December 2016

Radial jet drilling (RJD) is an efficient approach for improving the productivity of wells in low permeability, marginal and coal-bed methane (CBM) reservoirs at a very low cost. It uses high-pressure water jet to drill lateral holes from a vertical wellbore. The length of the lateral holes is greatly influenced by the frictional resistance in the hole deflector. However, the hole deflector frictional resistance and structure design have not been well studied. This work fills that gap. Frictional resistances were measured in a full-scale experiment and calculated by numerical simulation. The structure of the hole deflector was parameterized and a geometric model was developed to design the hole deflector track. An empirical model was then established to predict the frictional resistance as a function of the hole deflector structure parameters and an optimization method for designing the hole deflector was proposed. Finally, four types of hole deflectors were optimized using this method. The results show good agreement between the numerical simulation and the experimental data. The model error is within 11.6%. The bend radius R and exit angle β are the key factors affecting the performance of the hole deflector. The validation test was conducted for a case hole deflector (5½ in. casing). The measured frictional resistance was decreased from 31.44 N to 23.16 N by 26.34%. The results from this research could serve as a reference for the design of hole deflectors for radial jet drilling.
On Heat Transfer Issues for Wind Energy Systems
Authors: Sunden Bengt , Wu Zan
Published: December 2016

Control of heat transfer is important in wind power systems. In cold climate, the problems of icing and de-icing of the turbine blades need to be handled by efficient heat transfer technologies. Heat-generating components like electric generator, gear box, and frequency converters usually need cooling under operation by various cooling solutions such as air cooling, liquid cooling, and evaporative cooling. This paper reviews heat transfer problems in wind energy systems and presents some existing solutions to manage the thermal issues, and also discusses the challenges and new ideas on finding improved methods to control the heat transfer or cooling. Advanced liquid and evaporative cooling methods are suggested. Also, the need for improved ice sensors is discussed particularly for the ice accretion on the turbine blades.
A Three-Dimensional Load Sharing Model of Planetary Gear Sets Having Manufacturing Errors
Authors: Leque N. , Kahraman A.
Published: December 2016

Planet-to-planet load sharing is a major design and manufacturing tolerancing issue in planetary gear sets. Planetary gear sets are advantageous over their countershaft alternatives in many aspects, provided that each planet branch carries a reasonable, preferably equal, share of the torque transmitted. In practice, the load shared among the planets is typically not equal due to the presence of various manufacturing errors. This study aims at enhancing the models for planet load sharing through a three-dimensional (3D) formulation of N planet helical planetary gear sets. Apart from previous models, the proposed model employs a gear mesh load distribution model to capture load and time dependency of the gear meshes iteratively. It includes all the three types of manufacturing errors, namely, constant errors such as carrier pinhole position errors and pinhole diameter errors, constant but assembly dependent errors such as nominal planet tooth thickness errors, planet bore diameter errors, and rotation, and assembly dependent errors such as gear eccentricities and run-outs. At the end, the model is used to show combined influence of these errors on planet load sharing to aid designers on how to account for manufacturing tolerances in the design of the gears of a planetary gear set.
A Goal-Oriented, Sequential, Inverse Design Method for the Horizontal Integration of a Multistage Hot Rod Rolling System
Authors: Nellippallil Anand Balu , Song Kevin N. , Goh Chung-Hyun , Zagade Pramod , Gautham B. P. , Allen Janet K. , Mistree Farrokh
Published: December 2016

The steel manufacturing process is characterized by the requirement of expeditious development of high quality products at low cost through the effective use of available resources. Identifying solutions that meet the conflicting commercially imperative goals of such process chains is hard using traditional search techniques. The complexity in such a problem increases due to the presence of a large number of design variables, constraints and bounds, conflicting goals and the complex sequential relationships of the different stages of manufacturing. A classic example of such a manufacturing problem is the design of a rolling system for manufacturing a steel rod. This is a sequential process in which information flows from first rolling stage/pass to the last rolling pass and the decisions made at first pass influence the decisions that are made at the later passes. In this context, we define horizontal integration as the facilitation of information flow from one stage to another thereby establishing the integration of manufacturing stages to realize the end product. In this paper, we present an inverse design method based on well-established empirical models and response surface models developed through simulation experiments (finite-element based) along with the compromise decision support problem (cDSP) construct to support integrated information flow across different stages of a multistage hot rod rolling system. The method is goal-oriented because the design decisions are first made based on the end requirements identified for the process at the last rolling pass and these decisions are then passed to the preceding rolling passes following the sequential order in an inverse manner to design the entire rolling process chain to achieve the horizontal integration of stages. We illustrate the efficacy of the method by carrying out the design of a multistage rolling system. We formulate the cDSP for the second and fourth pass of a four pass rolling chain. The stages are designed by sequentially passing the design information obtained after exercising the cDSP for the last pass for different scenarios and identifying the best combination of design variables that satisfies the conflicting goals. The cDSP for the second pass helps in integrated information flow from fourth to first pass and in meeting specified goals imposed by the fourth and third passes. The end goals identified for this problem for the fourth pass are minimization of ovality (quality) of rod, maximization of throughput (productivity), and minimization of rolling load (performance and cost). The method can be instantiated for other multistage manufacturing processes such as the steel making process chain having several unit operations.
Self-Foldability of Rigid Origami
Authors: Tachi Tomohiro , Hull Thomas C.
Published: December 2016

When actuating a rigid origami mechanism by applying moments at the crease lines, we often confront the bifurcation problem where it is not possible to predict the way the model will fold when it is in a flat state. In this paper, we develop a mathematical model of self-folding and propose the concept of self-foldability of rigid origami when a set of moments, which we call a driving force, are applied. In particular, we desire to design a driving force such that a given crease pattern can uniquely self-fold to a desired mode without getting caught in a bifurcation. We provide necessary conditions for self-foldability that serve as tools to analyze and design self-foldable crease patterns. Using these tools, we analyze the unique self-foldability of several fundamental patterns and demonstrate the usefulness of the proposed model for mechanical design.
An Extended Family of Rigidly Foldable Origami Tubes
Authors: Chen Yan , Lv Weilin , Li Junlan , You Zhong
Published: December 2016

Rigidly foldable origami tubes with open ends have been reported in the past. Here, using a mechanism construction process, we show that these tubes can be used as building blocks to form new tubes that are rigidly foldable with a single degree-of-freedom (SDOF). A combination process is introduced, together with a possibility of inserting new facets into an existing tube. The approach can be applied to both single and multilayered tubes with a straight or curved profile. Our work provides designers great flexibility in the design of tubular structures that require large shape change. The results can be readily utilized to build new structures for engineering applications ranging from deployable structures, meta-materials to origami robots.
Characterization of Laser Additive Manufacturing-Fabricated Porous Superalloys for Turbine Components
Authors: Ealy Brandon , Calderon Luisana , Wang Wenping , Valentin Ranier , Mingareev Ilya , Richardson Martin , Kapat Jay
Published: December 2016

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Lately, incremental performance gains responsible for increasing the allowable turbine inlet temperature (TIT) have been made mainly through innovations in cooling technology, specifically convective cooling schemes. Laser additive manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Through a nondestructive approach, the presented geometry is analyzed against the departure of the design by utilizing X-ray computed tomography (CT). Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Flow testing is performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficients of internal impingement arrays and engineered-porous structures are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for direct manufacture of microfeatures in current turbine blade production.
Investigation of Bubble Frequency for Slug Flow Regime in a Uniformly Heated Horizontal Microchannel
Authors: Younes Amen , Hassan Ibrahim , Kadem Lyes
Published: December 2016

Slug flow is an essential flow pattern observed in microchannels where its transition boundaries in microchannels are characterized by two complex hydrodynamic phenomena, the bubble confinement and the bubble coalescence. Slug flow may be classified in terms of bubble size into two major zones: isolated bubble zone and coalescence bubble zone. In this paper, a semi-analytical model is developed for predicting the main characteristics of isolated bubble zone for flow boiling in a horizontal microchannel. The influences of surface tension, shear, and inertial forces have been taken into account. The model is developed on the basis of drift flux model, and a fully developed slug unit is chosen as a control volume for deriving the equations of motion. The effects of main operating conditions, mass and heat fluxes, on bubble length and bubble frequency have been investigated. The boundaries of slug flow regime have been identified based on the most proper diabatic flow pattern maps available in the literature for the chosen database. The model has been validated using the database available in the literature for flow boiling of R134a and R245fa in 0.509 mm and 3.0 mm inner diameter horizontal mini-tubes, respectively, and over wide range of mass fluxes (300≤G≤1000 kg/m2 s). This study has shown that the mass flux has a significant effect on the slug length and the bubble frequency. The model gave a good agreement with the experimental data of bubble length and bubble frequency with a mean absolute error (MAE) of 18.0% and 27.34%, respectively.
A New Concept of Needle-Free Jet Injector by the Impact Driven Method
Authors: Mukda Prachya , Pianthong Kulachate , Seehanam Wirapan
Published: December 2016

Currently, most of commercial needle-free jet injectors generate the liquid jet by a method called “driving object method” (DOM); however, the reliability and efficiency are still questioned. This paper proposes a new concept of jet generation method, known as “impact driven method” (IDM). A prototype of an IDM jet injector is designed, built, tested, and compared to a commercial device (Cool.click, Tigard, OR). Fundamental characteristics, i.e., the exit jet velocity and impact pressure, are measured. Jet injection processes are visualized both in air and in 20% polyacrylamide by high speed photography. In this study, from the prototype of the IDM jet injector, a maximum jet velocity of 400 m/s and impact peak pressure of 68 MPa can be obtained. It is clear that the IDM jet injector provides a double pulsed liquid jet, which is a major advantage over the commercial jet injector. Because, the first pulse gives a shorter erosion stage, and then, immediately the second pulse follows and provides a better penetration, wider lateral dispersion, and considerably less back splash. Hence, lower pain level and higher delivery efficiency should be achieved. It can be concluded that the IDM concept is highly feasible for implementation in real applications, either for human or animal injection. However, the control and accuracy of IDM still needs to be carefully investigated.
Statistical Modeling of Stratified Two-Phase Flow
Authors: Benz M. , Schulenberg T.
Published: December 2016

A new numerical model for stratified two-phase flows with wavy interface is derived in this study. Assuming an equilibrium condition between turbulent kinetic energy, potential energy, and surface energy, the turbulent length scale in the inner region of a two-layer turbulence approach can be described by a statistical model to account for the influence of the waves. The average wave number, which is an input parameter to this model, is taken from wave spectra. They can be predicted from a Boltzmann statistic of turbulent kinetic energy. The new turbulence model is compared with the two-phase k–ϵ turbulence model. Time-averaged flow properties calculated by the new approach, such as velocity, turbulence, and void profiles, are shown to be in good agreement with experimental data.
A Review of Safety Analysis Philosophies for Nuclear Reactors
Authors: Schneider A. S. , Yair N.
Published: December 2016

Various questions can be examined when discussing safety in general. Among these, some key issues are the attitude toward risk and its acceptance, the ways of identifying, analyzing, and quantifying risks, and societal factors and public opinion toward risks. The identification and quantification of risks are central in the regulatory framework and decision making and will be the focus of this article. Various approaches have been used for safety analysis over the years. This paper will survey some of the central attitudes in the nuclear reactor regulation philosophy and discuss the historical background surrounding them. Among these, we mention the “defense-in-depth” approach, the design basis accident (DBA), and beyond design basis accident (BDBA) analyses and discuss the rather subjective nature of their associated decision making. We maintain that it has long been recognized that the natural approach that comes out of the scientific method of inquiry is the probabilistic one, which in today's tools is conducted through the probabilistic safety analysis (PSA) method. This approach unlike the deterministic one, which produced concepts like DBA and defense-in-depth, enables us to put risks into context and to compare different risks such as those posed by different activities in particular or by other industries in general. It has consequently been gaining wide acceptance in regulatory bodies around the world as an effective tool in the inspection and regulation of nuclear reactors. Yet, it is also recognized that despite significant development over the past few decades, PSA still suffers from some well-known deficiencies. Its main benefit at this point is its contribution to identification and prioritization of design features, maintenance, management, and quality assurance (QA) important to safety. PSA has mostly been used in the nuclear power industry, but in recent years it has also started to be incorporated in research reactor (RR) safety analysis, and we therefore cover the subject of PSA usage for this purpose as well.
A Simple Model for Identifying the Flutter Bite of Fan Blades
Authors: Zhao Fanzhou , Smith Nigel , Vahdati Mehdi
Published: December 2016

This paper presents the work on part-speed fan flutter due to acoustic reflections from the intake, commonly called “flutter bite.” A simple model for the prediction of the flutter bite is presented. In a previous work by the authors, it was shown that the acoustic effects of the intake are very important and need to be considered during the design of a fan blade. It was also shown that the contribution to blade aerodamping due to blade motion (for the isolated rotor in an infinitely long duct) and intake acoustics is independent and can be analyzed separately. The acoustic reflections from the intake change the damping of the blade by modifying the phase and amplitude of the unsteady pressure at the leading edge of the fan. It will be shown in the paper that, for a given intake, the phase and amplitude of the reflected acoustic waves can be evaluated analytically based on established theories independent of the fan design. The proposed model requires only the design intent of the fan blade and the geometry of the intake, which are available in the early design stages of a new engine, and can predict the operating conditions at which fan flutter is likely to occur.
Numerical Study on Aeroelastic Instability for a Low-Speed Fan
Authors: Lee Kuen-Bae , Wilson Mark , Vahdati Mehdi
Published: December 2016

Over recent years, engine designs have moved increasingly toward low specific thrust cycles to deliver significant specific fuel consumption (SFC) improvements. Such fan blades may be more prone to aerodynamic and aeroelastic instabilities than conventional fan blades. The aim of this paper is to analyze the flutter stability of a low-speed/low pressure ratio fan blade. By using a validated computational fluid dynamics (CFD) model (AU3D), three-dimensional unsteady simulations are performed for a modern low-speed fan rig for which extensive measured data are available. The computational domain contains a complete fan assembly with an intake duct and the downstream outlet guide vanes (OGVs), which is a whole low-pressure (LP) domain. Flutter simulations are conducted over a range of speeds to understand flutter characteristics of this blade. Only the first flap (1F) mode is considered in this work. Measured rig data obtained by using the same fan set but with two different lengths of the intake showed a significant difference in the flutter boundary for the two intakes. AU3D computations were performed for both intakes and were used to explain this difference between the two intakes, and showed that intake reflections play an important role in flutter of this blade. This observation indicates that the experiment with the long intake used for the performance test may be misleading for flutter. In the next phase of this work, two possible modifications for increasing the flutter margin of the fan blade were explored: changing the mode shape of the blade and using acoustic liners in the casing. The results show that it is possible to increase the flutter margin of the blade by either decreasing the ratio of the twisting to plunging motion in 1F mode or by introducing deep acoustic liners in the intake. The liners have to be deep enough to attenuate the flutter pressure waves and hence influence the stability. The results indicate the importance of reflection in flutter stability of the fan blade and clearly show that intake duct needs to be included in flutter study of any fan blade.
Modeling and Analysis of the Rope–Sheave Interaction at Traction Interface
Authors: Shi Xi , Pan Yalu , Ma Xiaolong
Published: December 2016

In this paper, a three-dimensional (3D) finite-element (FE) contact model of a 6 + 1 wire rope strand bent over a simplified traction sheave is developed to investigate the traction behavior at the interface. The stress as well as the tension distribution within the 6 + 1 wire rope are discussed first. The FE analysis indicates that ascending preload at rope-ends leads to the incensement of the real contact wrap angle, which is critical in the calculation of traction capability. Meanwhile, the influences of groove angle on the contact pressure distribution and traction capability are demonstrated as well.
Plasma enhanced atomic layer deposition of Al2O3 gate dielectric thin films on AlGaN/GaN substrates: The role of surface predeposition treatments
Authors: Schilirò Emanuela , Fiorenza Patrick , Greco Giuseppe , Roccaforte Fabrizio , Lo Nigro Raffaella
Published: December 2016

Al2O3 thin films were deposited by plasma enhanced atomic layer deposition (PEALD) from trimethylaluminum precursor and oxygen plasma at 250 °C on AlGaN/GaN heterostructures. Before deposition, the sample surfaces were treated with the following solutions: (A) H2O2:H2SO4 (piranha), (B) fluoride acid (HF) + HCl, and (C) piranha + HF for 10 min each. Transmission electron microscopy analysis revealed that, independently from the surface preparation, all the films are adherent and uniform with thicknesses of about 27–28 nm. However, a different structural evolution has been observed under electron beam effect. In particular, while all the as-deposited films were found to be amorphous, the formation of polycrystalline grains was observed on the sample deposited after the A treatment. On the other hand, oriented layers were formed on the samples deposited after B and C treatments. This result is an indication that in the case of HF-based treatments, the PEALD occurred on a very clean AlGaN surface, which can act as seed layer for the formation of epitaxial films when some energy is provided. Atomic force microscopy (AFM) showed smoother Al2O3 films when grown after HF based treatments. Moreover, further AFM investigation of the initial growth stages (3 nm thick Al2O3 layers) demonstrated that the smallest three-dimensional grain nucleation resulted in deposition on C-treated surfaces. Finally, the predeposition treatments of AlGaN/GaN surfaces with the HF cleaning provided Al2O3 films having the most promising dielectric properties.