bluuebunny/crossref_metadata_2025 huggingface dataset:
The association between childhood sexual and physical abuse with incident adult severe obesity across 13 years of the National Longitudinal Study of Adolescent Health
Authors: Richardson A. S. , Dietz W. H. , Gordon‐Larsen P.
Published: October 2013

What is already known about this subject

Severe obesity prevalence in adults has close to doubled from the 1990s to 2010 and is expected to double again by 2030.

Over 3 million reports of child maltreatment were received by child protective services in 2008.

While clinic and population‐based studies have found high rates of adult psychological distress among severely obese individuals, little is known about how the experience of abuse during childhood relates to the risk of severe obesity later in life.

What this study adds

Using data from a nationally representative, longitudinal study, we found that incidence rates and 13‐year risk of developing severe obesity in adulthood varied by abuse type.

We found significantly higher risk of incident severe obesity in non‐minority females and males who experienced the combined occurrence of sexual and physical abuse during childhood, relative to individuals with no history of abuse.

In addition to other social and emotional risks, exposure to sexual and physical abuse during childhood may increase risk of severe obesity later in life.

Background

Severe obesity has increased, yet childhood antecedents of adult severe obesity are not well understood.

Objective

Estimate adult‐onset severe obesity risk in individuals with history of childhood physical and/or sexual abuse compared with those who did not report abuse.

Methods

Longitudinal analysis of participants from the US National Longitudinal Study of Adolescent Health (n = 10 774) wave II (1996; aged 12–22 years) followed through wave IV (2008–2009; aged 24–34 years). New cases of adult‐onset severe obesity (body mass index [BMI] ≥ 40 kg/m2 using measured height and weight) in individuals followed over 13 years who were not severely obese during adolescence (BMI <120% of 95th percentile Centers for Disease Control and Prevention National Center for Health Statistics growth curves).

Results

The combined occurrence of self‐reported sexual and physical abuse during childhood was associated with an increased risk of incident severe obesity in adulthood in non‐minority females (hazard ratio [HR; 95% Confidence Interval] = 2.5; 1.3, 4.8) and males (HR = 3.6; 1.5, 8.5) compared with individuals with no history of abuse.

Conclusion

In addition to other social and emotional risks, exposure to sexual and physical abuse during childhood may increase risk of severe obesity later in life. Consideration of the confluence of childhood abuse might be considered as part of preventive and therapeutic approaches to address severe obesity.
Optimization of Gas Adsorption Porosimetry for Geopolymer Analysis
Authors: Glad Brayden E. , Kriven Waltraud M.
Published: October 2013

Gas adsorption porosity measurement of geopolymers (GPs) is required for quantitative understanding of such mesoporous structures, but the complex nature of the GP system makes analysis difficult. Previous results in the literature are often ambiguous or contradictory. A systematic investigation of metakaolin GP gas adsorption results was conducted to optimize the use of this measurement technique and verify that results match known theory about GP structure. It was found that GP undergoes structural change upon degassing at 100°C or higher. If and only if this change is prevented by degassing at a lower temperature could it be shown that specific surface area and total gas adsorption increases with both increasing curing temperature and decreased Si:Al ratio. This observation is consistent with previous suggestions of increased zeolitic character under these conditions, where previous gas adsorption investigations had not observed this expected relationship. Hydrogen physisorption is proposed as a substitute technique for micropore isotherms in GPs due to the difficulty of removing trace gasses from GPs and the measurement effect of such gasses at high vacuum. A hydrogen physisorption isotherm qualitatively resembled an equivalent nitrogen micropore isotherm.
Enhancement of Interparticle Exchange Coupling in CoFe2O4/CoFe2 Composite Nanoceramics Via Spark Plasma Sintering Technology
Authors: Zhang Yue , Xiong Rui , Yang Zhi , Yu Wei , Zhu Benpeng , Chen Shi , Yang Xiaofei
Published: October 2013

Powders and nanoceramics composed of composites of CoFe2O4, CoFe2, and a small amount of FeO were prepared by heating CoFe2O4 powder in reducing atmosphere and by sintering the product of reducing reaction at 350°C via spark plasma sintering technology. In the powders, increase in the molar ratios of CoFe2:CoFe2O4 and a great change in magnetic parameters were observed with the change in heating temperature from 300°C to 400°C, and the dominance of dipole interaction over exchange coupling in the interparticle interactions was confirmed by the steps in magnetic hysteresis loops and the negative Henkel plots. However, in the nanoceramics, significant enhancement in exchange coupling was found when the sintering temperature was raised to 500°C and 650°C, which was confirmed by both the positivity of Henkel plot and the single‐phase style of the magnetic hysteresis loop.
Onychomatricoma has channel‐like structures on in vivo reflectance confocal microscopy
Authors: Sanchez MI , Hu S , Miteva M , Tosti A
Published: October 2013

Background

Onychomatricoma is a benign fibroepithelial nail matrix tumor that infiltrates the nail plate leading to multiple tunneled cavities lined with matrix epithelium and filled with serum. Diagnostic features of onychomatricoma on reflectance confocal microscopy (RCM) have not been previously described.

Objective

We sought to demonstrate the feasibility of using RCM to diagnose onychomatricoma.

Methods

Reflectance confocal microscopy was used to evaluate four patients with onychomatricoma before tumor excision. We evaluated the affected nail and one unaffected nail of each patient with VivaScope 1500 (Lucid Inc., Rochester, NY, USA).

Results

Reflectance confocal microscopy evaluation of onychomatricomas revealed longitudinal dark areas and bright/grey lines, forming channel like structures. The channels were outlined by bright circular lines with grey dot centers. These RCM features correlated with the pathology of the onychomatricomas within the nail plate.

Limitations

Proximal portion of onychomatricoma was not reach by RCM.

Conclusions

Reflectance confocal microscopy can assist in rapid and noninvasive diagnosis of onychomatricoma showing characteristic channel like structures within nail plates.
Pressure ulcer in patients with severe traumatic brain injury: significant factors and association with neurological outcome
Authors: Dhandapani Manju , Dhandapani Sivashanmugam , Agarwal Meena , Mahapatra Ashok K
Published: October 2013

Aims and objectives

To assess the factors associated with development of pressure ulcer in patients with severe traumatic brain injury (TBI) and study its prognostic significance with respect to neurological outcome at three months.

Background

Patients with severe TBI are prone to develop pressure ulcer due to various factors, which have never been studied in detail.

Design

Prospective longitudinal study.

Methods

Eighty‐nine patients of TBI in age group 20–60 years admitted with Glasgow Coma Scale (GCS) 4–8 without serious systemic disorder were enrolled for the study. Patient characteristics, haemoglobin, serum albumin levels at admission and their weekly changes till 21 days were noted along with daily assessment for presence of pressure ulcer. Mortality was assessed at 21 days and neurological outcome at three months through telephonic interview.

Results

Of 89 patients studied, pressure ulcer was observed in 6 (7%) and 14 (16%) at the end of two and three weeks, respectively. Pressure ulcer in univariate analysis was significantly associated with poorer GCS (p = 0·05), delayed enteral feeding (p = 0·005) and fall in haemoglobin at two weeks (p = 0·005). Only the latter two were found significant in multivariate analysis. Age, gender, surgical intervention, tracheostomy, prolonged fever and change in albumin had no significant association with pressure ulcer development. Presence of pressure ulcer was significantly associated with mortality at 21 days (p = 0·006) and unfavourable neurological outcome at three months (p = 0·01).

Conclusions

The significant factors influencing pressure ulcer development in patients with TBI were delayed enteral feeding and fall in haemoglobin. Pressure ulcer had significant association with mortality at 21 days and recovery status at three months.

Relevance to clinical practice

Early nutritional supplementation and monitoring of haemoglobin should be an important part of nursing care interventions for patients at increased risk of developing pressure ulcer.
Optimal Emission Policy under the Risk of Irreversible Pollution
Authors: LE KAMA ALAIN AYONG , POMMERET AUDE , PRIEUR FABIEN
Published: October 2013

We consider an optimal consumption and pollution problem that has two important features. Environmental damages due to economic activities may be irreversible and the level at which the degradation becomes irreversible is unknown. Particular attention is paid to the situation where agents are relatively impatient and/or do not care a lot about the environment and/or Nature regenerates at low rate. We show that the optimal policy of the uncertain problem drives the economy in the long run toward a steady state while, when ignoring irreversibility, the economy follows a balanced growth path accompanied by a perpetual decrease in environmental quality and consumption, both asymptotically converging toward zero. Therefore, accounting for the risk of irreversibility induces more conservative decisions regarding consumption and polluting emissions. In general, however, we cannot rule out situations where the economy will optimally follow an irreversible path and consequently will also be left, in the long run, with an irreversibly degraded environment.
A Note on Discounting an Increasingly Uncertain Future
Authors: CHIU W. HENRY
Published: October 2013

This note clarifies the roles played by the wealth and precautionary effects in determining the socially efficient discount rate for public investment projects and how the rate should vary over time. We first give a general characterization of the effects of stochastic shifts in the consumption growth rate on the magnitude of the socially efficient discount rate. We then show that increasing uncertainty in the consumption growth rate provides a natural and compelling rationale for discounting more distant future consumption at a lower rate.
Revisiting Ross and Sims (1971): toward a molecular phylogeny of the Biddulphiaceae and Eupodiscaceae (Bacillariophyceae)
Authors: Ashworth Matt P. , Nakov Teofil , Theriot Edward C.
Published: October 2013

The ocellate and pseudocellate diatoms in the Eupodiscaceae and Biddulphiaceae (respectively) are common inhabitants of the marine littoral (and plankton zone) with a rich fossil history making them important components of marine stratigraphic studies and good candidates for molecular dating work. These diatoms are important for un‐derstanding the phylogeny of the diatoms as a whole, as molecular phylogenies have blurred the traditional distinction between the pennate and multipolar non‐pennate diatoms. However, the convoluted taxonomic history of these groups has the potential to disrupt both stratigraphic and molecular dating studies. Although efforts have been made to examine frustule morphology of several ocellate and pseudocellate diatoms and develop a morphological scheme to define genera, very little work has been done to determine how these groups are interrelated. In this study, we use nuclear and chloroplast molecular markers to construct a phylogeny of a diverse sampling of Eupodiscaceae and Biddulphiaceae taxa. The ocellus‐bearing taxa (Eupodiscaceae) are monophyletic, and thus the ocellus may be a useful character in delimiting the Eupodiscaceae, the Biddulphiaceae are polyphyletic and scattered across a number of lineages of multipolar non‐pennate diatoms. Hypothesis testing aimed at assessing the likeliness of several morphology based hypotheses against the molecular data highlights uncertainty in both types of data. We present evidence that there are monophyletic genera within both the Biddulphiaceae and Eupodiscaceae, and recommend the taxa within the Odontella mobilensis/sinensis/regia clade be transferred to a new genus: Trieres Ashworth & Theriot.
Immigration, Growth, and Unemployment: Panel VAR Evidence from OECD Countries
Authors: Boubtane Ekrame , Coulibaly Dramane , Rault Christophe
Published: October 2013

This paper examines empirically the interaction between immigration and host country economic conditions. We employ panel vector autoregression (VAR) techniques for a large annual data set on 22 OECD countries over the period 1987–2009. The VAR approach addresses the endogeneity problem by allowing for endogenous interactions between the variables in the system. Our results provide evidence of migration contribution to host economic prosperity (positive impact on GDP per capita and negative impact on aggregate unemployment, native‐ and foreign‐born unemployment rates). We also find that migration is influenced by host economic conditions (migration responds positively to host GDP per capita and negatively to host total unemployment rate).
Chloral hydrate sedation for magnetic resonance imaging in newborn infants
Authors: Finnemore Anna , Toulmin Hilary , Merchant Naz , Arichi Tom , Tusor Nora , Cox David , Ederies Ash , Nongena Phumza , Ko Christopher , Dias Ryan , Edwards Anthony D. , Groves Alan M.
Published: October 2013

Background

The aim of this study was to look for clinically significant adverse effects of chloral hydrate used in a large cohort of infants sedated for magnetic resonance imaging.

Method

Case notes of infants who underwent magnetic resonance imaging (MRI) scanning from 2008 to 2010 were reviewed, with patient demographics, sedation dose, comorbidities, time to discharge, and side effects of sedation noted.

Results

Four hundred and eleven infants (median [range] postmenstrual age per weight at scan 42 [31+4–60] weeks per 3500 g [1060–9900 g]) were sedated with chloral hydrate (median [range] dose 50 [20–80] mg·kg−1). In three cases (0.7%), desaturations occurred which prompted termination of the scan. One infant (0.2%) was admitted for additional observation following sedation but had no prolonged effects. In 17 (3.1%) cases, infants had desaturations which were self‐limiting or responded to additional inspired oxygen such that scanning was allowed to continue.

Conclusion

When adhering to strict protocols, MRI scanning in newborn infants in this cohort was performed using chloral hydrate sedation with a relatively low risk of significant adverse effects.
Wnt inhibitory factor (WIF)‐1 promotes melanogenesis in normal human melanocytes
Authors: Park Tae Jun , Kim Misun , Kim Hyeran , Park Sun Yi , Park Kyoung‐Chan , Ortonne Jean‐Paul , Kang Hee Young
Published: October 2013

Wnt signaling plays a role in the differentiation as well as the development of melanocytes. Using a microarray analysis, hyperpigmentary skin of melasma expressed high levels of Wnt inhibitory factor‐1 (WIF‐1) compared with perilesional normal skin. In this study, the expression and functional roles of WIF‐1 on melanocytes were investigated. WIF‐1 was expressed both in the melanocytes of normal human skin and in cultured melanocytes. The upregulation of WIF‐1 on cultured normal human melanocytes significantly induced expressions of MITF and tyrosinase, which were associated with increased melanin content and tyrosinase activity. Consistent with the stimulatory effect of WIF‐1, WIF‐1 siRNA reduced melanogenesis in the cells. Moreover, WIF‐1 increases pigmentation in melanocytes co‐cultured with WIF‐1‐overexpressed fibroblasts and of organ‐cultured human skin. These findings suggest that melanocytes express WIF‐1 constitutively in vivo and in vitro and that WIF‐1 promotes melanogenesis in normal human melanocytes.
Synthesis, Characterization, Photophysics and Photochemistry of Pyrylogen Electron Transfer Sensitizers
Authors: Clennan Edward L. , Liao Chen
Published: October 2013

A series of new dicationic sensitizers that are hybrids of pyrylium salts and viologens has been synthesized. The electrochemical and photophysical properties of these “pyrylogen” sensitizers are reported in sufficient detail to allow rationale design of new photoinduced electron transfer reactions. The range of their reduction potentials (+0.37–+0.05 V vs SCE) coupled with their range of singlet (48–63 kcal mol−1) and triplet (48–57 kcal mol−1) energies demonstrate that they are potent oxidizing agents in both their singlet and triplet excited states, thermodynamically capable of oxidizing substrates with oxidation potentials as high as 3.1 eV. The pyrylogens are synthesized in three steps from readily available starting materials in modest overall 11.4–22.3% yields. These sensitizers have the added advantages that: (1) their radical cations do not react on the CV timescale with oxygen bypassing the need to run reactions under nitrogen or argon and (2) have long wavelength absorptions between 413 and 523 nm well out of the range where competitive absorbance by most substrates would cause a problem. These new sensitizers do react with water requiring special precautions to operate in a dry reaction environment.
Genetic diversity of Botrytis in New Zealand vineyards and the significance of its seasonal and regional variation
Authors: Johnston P. R. , Hoksbergen K. , Park D. , Beever R. E.
Published: October 2013

Species‐ and population‐specific differences in fungicide resistance and aggressiveness within Botrytis makes basic data on genetic diversity important for understanding disease caused by this fungus. Genetic diversity of Botrytis was surveyed between 2008 and 2012 from grapes from five New Zealand wine‐growing regions. A total of 1226 isolates were gathered from symptomless flower buds at the start of the growing season and 1331 isolates from diseased fruit at harvest. Two species were found, B. cinerea and B. pseudocinerea. Botrytis pseudocinerea was common in both Auckland vineyards sampled, and infrequent elsewhere. However, even in Auckland, it was rarely isolated from diseased fruit. The presence of the Boty and Flipper transposons was assessed. Isolates with all four transposon states (Boty only, Flipper only, both Boty and Flipper, no transposons) were found for both species. Both vineyards in the Auckland region had high numbers of Flipper‐only isolates at flowering; both vineyards from the Waipara region had high numbers of Boty‐only isolates at flowering. Most isolates from diseased fruit at harvest contained both transposons. These observations suggest that B. pseudocinerea, and isolates with one or both of the transposons missing, may be less aggressive than B. cinerea, or than isolates with both transposons present. Two clades were resolved within B. pseudocinerea, only one of which has been reported from European vineyards. Phylogenetic diversity within B. cinerea in New Zealand was similar to that known from Europe, including isolates that appear to match Botrytis ‘Group S’. The taxonomic implications of this genetic diversity are discussed.
Immunogenicity and Protective Efficacy Conferred by a Novel Recombinant Mycobacterium bovis Bacillus Calmette‐Guérin Strain Expressing Interleukin‐12p70 of Human Cytokine and Ag85A of Mycobacterium tuberculosis Fusion Protein
Authors: Deng Y. H. , He H. Y. , Zhang F. J.
Published: October 2013

Mycobacterium bovis bacillus Calmette‐Guérin (BCG) immunization provides protection against tuberculosis (TB) in infants, but the antituberculosis protective immunity wanes gradually after initial immunization and lasts less than 15 years. Therefore, more efficacious vaccines are urgently needed. In this study, we constructed a new tuberculosis vaccine of recombinant BCG strain (rBCG‐IA), which could express IL‐12p70 of human cytokine and Ag85A of M. tuberculosis fusion protein, and investigated its immunogenicity in BALB/c mice by measuring antibody titres, proliferation rate of splenocytes, ratios of CD4+ T and CD8+ T cells stimulated by specific antigens and levels of IFN‐γ production in antigen‐stimulated splenocyte cultures. Meanwhile, we evaluated its protective efficacy against M. tuberculosis H37Rv infection through detecting lung histopathology, organ bacterial loads and lung acid‐fast stain. Immunogenicity experiments illustrated that from 2nd to 8th week after immunization, the rBCG‐IA vaccine was able to induce the highest level of antibody titres, proliferation rate of splenocytes and IFN‐γ production among groups and gained improved ratio of CD4+ T and CD8+ T cells from 6th to 8th week after vaccination. And from 2nd to 8th week after M. tuberculosis H37Rv infection, the score of pathology and bacterial loads in the rBCG‐IA group were obviously lower than that in rBCG‐I group, rBCG‐A group or control group (PBST group), but similar to that in BCG group. This study suggested that rBCG‐IA was able to elicit stronger humoral and cellular immune responses, but could only confer similar protective efficacy compared with its parental BCG vaccine.
The effects of individualistic‐collectivistic value orientations on non‐fatal suicidal behavior and attitudes in Turkish adolescents and young adults
Authors: Eskin Mehmet
Published: October 2013

This study aimed at investigating the effects of individualistic‐collectivistic value orientations on non‐fatal suicidal behavior and attitudes in Turkish adolescents and young adults. A questionnaire containing measures of individualism, collectivism (INDCOL), non‐fatal suicidal behaviors and suicidal attitudes was used to collect the data. The results showed that both suicidal ideation and attempts were significantly more frequent in participants classified as individualist than those who were classified as collectivist on the basis of INDCOL scale scores. Participants with individualistic tendencies displayed more permissive attitudes toward suicide than those with collectivistic tendencies but collectivists believed to a greater extent than the individualists that people should communicate suicidal problems to others. Participants with collectivistic tendencies showed more accepting and helping reactions to an imagined suicidal friend than those with individualistic tendencies. Suicidal ideation and attempts were more common among adolescents than young adults. The findings suggest that individualistic and collectivistic value orientations and developmental status specific stressors play a role in the distribution of nonfatal suicidal behavior and the nature of suicidal attitudes.
Male‐sterile maize plants produced by targeted mutagenesis of the cytochrome P450‐like gene (MS26) using a re‐designed I–CreI homing endonuclease
Authors: Djukanovic Vesna , Smith Jeff , Lowe Keith , Yang Meizhu , Gao Huirong , Jones Spencer , Nicholson Michael G. , West Ande , Lape Janel , Bidney Dennis , Carl Falco Saverio , Jantz Derek , Alexander Lyznik Leszek
Published: October 2013

The I–CreI homing endonuclease from Chlamydomonas reinhardti has been used as a molecular tool for creating DNA double‐strand breaks and enhancing DNA recombination reactions in maize cells. The DNA‐binding properties of this protein were re‐designed to recognize a 22 bp target sequence in the 5th exon of MS26, a maize fertility gene. Three versions of a single‐chain endonuclease, called Ems26, Ems26+ and Ems26++, cleaved their intended DNA site within the context of a reporter assay in a mammalian cell line. When the Ems26++ version was delivered to maize Black Mexican Sweet cells by Agrobacterium‐mediated transformation, the cleavage resulted in mutations at a co‐delivered extra‐chromosomal ms26‐site in up to 8.9% of the recovered clones. Delivery of the same version of Ems26 to immature embryos resulted in mutations at the predicted genomic ms26‐site in 5.8% of transgenic T0 plants. This targeted mutagenesis procedure yielded small deletions and insertions at the Ems26 target site consistent with products of double‐strand break repair generated by non‐homologous end joining. One of 21 mutagenized T0 plants carried two mutated alleles of the MS26 gene. As expected, the bi‐allelic mutant T0 plant and the T1 progeny homozygous for the ms26 mutant alleles were male‐sterile. This paper described the second maize chromosomal locus (liguless‐1 being the first one) mutagenized by a re‐designed I–CreI–based endonuclease, demonstrating the general utility of these molecules for targeted mutagenesis in plants.
The Adhesion Failure Mode in Stainless Steel Trim Spring-Operated Pressure Relief Valves
Authors: Bukowski Julia V. , Gross Robert E. , Goble William M.
Published: October 2013

This paper addresses dangerous failures of stainless steel (SS) trim spring-operated pressure relief valves (SOPRV) due to a particular failure mode (SS-to-SS adhesion), which is not currently being included in SOPRV failure rates. As a result, current methods for estimating or predicting failure rates for SS trim SOPRV significantly underestimate these failure rates and, consequently, overestimate the safety provided by the SOPRV as measured by its average probability of failure on demand (PFDavg) or its corresponding safety integrity level (SIL). The paper also illustrates the critical importance of root cause analysis (RCA) of dangerous SOPRV failures in understanding the impacts of various failure modes. Over 1300 proof test results for both new and used SS trim SOPRV from the Savannah River Site (SRS) were identified. RCA was used on the failed valves to classify those failed due to SS-to-SS adhesions. Statistical analysis of the data convincingly demonstrates adhesions, previously assumed to be only an in-storage failure phenomenon, are also an in-service failure mode, which needs to be included in SOPRV failure rates. The paper discusses the factors which potentially influence the adhesion failure mode, and suggests a possible approach to including this mode in failure rate predictions. An example illustrates how current failure rate models overestimate SS trim SOPRV safety by 1 or 2 orders of magnitude.
Rational Determination of Lower-Bound Fracture Toughness Curves Using Master Curve Approach
Authors: Miura Naoki , Soneda Naoki , Sawai Shu , Sakai Shinsuke
Published: October 2013

The Master Curve gives the relation between the median of fracture toughness of ferritic steels and the temperature in the ductile–brittle transition temperature region. The procedure used to determine the Master Curve is provided in the current American Society for Testing and Materials (ASTM) E1921 standard. By considering the substitution of the alternative lower-bound curves based on the Master Curve approach for the KIc curves based on reference data sets in the present codes such as ASME Code Cases N-629 and N-631, the statistical characteristic should be well incorporated in the determination of the lower-bound curves. Appendix X4 in the ASTM standard describes the procedure used to derive the lower-bound curves; however, it appears to be addressed without sufficient consideration of the statistical reliability. In this study, we propose a rational determination method of lower-bound fracture toughness curves using the Master Curve approach. The method considers the effect of sample size in the determination of the tolerance-bound curve. The adequacy of the proposed method was verified by comparing the tolerance-bound curve with the fracture toughness database for national reactor pressure vessel (RPV) steels including plate and forging obtained from 4 T to 0.4 T C(T) specimens and 0.4 T SE(B) specimens. The method allows the application of the Master Curve using fewer specimens, which can coexist with the present surveillance program.
Theoretical and Experimental Analysis of a One-Stage Water Hydraulic Relief Valve With a One-Way Damper
Authors: Luo Xiaohui , He Xiaofeng , Cao Shuping , Ba Xin
Published: October 2013

According to the function and operating characteristics of water hydraulic relief valves in a high-pressure water pipe system, a novel one-stage relief valve with a one-way damper was designed and analyzed in this study. The one-way damper consists of a damping chamber and a check valve. Moreover, a damping orifice is bored along the axis of the check-valve spool. When the main spool moves to open the valve port, the check valve is fully open, and the damping orifice generates no damping force on the main spool; otherwise, the check valve is completely closed, and the damping orifice produces a damping force on the main spool. Furthermore, based on a mathematical model describing the dynamic characteristics of the relief valve, the effect of the one-way damper on the dynamic characteristics of the relief valve was simulated and analyzed, and certain optimal parameters of the one-way damper were obtained (e.g., the diameter and length of the damping orifice and the initial volume of the damping chamber). Lastly, the experimental results obtained from a prototype of the relief valve, which was manufactured to the optimal dimensions, demonstrated that the pressure overshoot was 7.5%, the response time was 1.43 × 10−2 s, and the transition time was 3.9 × 10−2 s. Thus, the one-way damper could significantly improve the dynamic characteristics of the relief valve.
Seepage Induced Soil Failure and its Mitigation During Suction Caisson Installation in Silt
Authors: Wang Lizhong , Yu Luqing , Guo Zhen , Wang Zhenyu
Published: October 2013

Suction caisson is an advantaged foundation option for offshore wind turbines in sandy and clayey soils. In this work, a series of model tests were conducted to investigate the installation behavior of a suction caisson in silty soils. The test results showed that the total soil resistance to the caisson increased steadily with penetration depth in the beginning of the suction-assisted penetration (SP) process, but rose slowly or remained constant after reaching a certain depth with excessive soil heave. This failure mechanism, which was quite different from that identified in sandy or clayey soils, was caused by the seepage induced silt soil failure in the caisson, such as erosion, liquefaction or piping, with reducing internal side friction and tip resistance. To suppress this type of failure, a special filtration method was introduced to help caisson penetration. The test results showed that such filtration technique had the advantage of reducing the height of soil heave and prevent seepage induced soil failure in the silt, but also suppress the under pressure effects on reducing the soil resistance. Numerical simulations were also performed to aid in understanding the observed test results and mitigation mechanisms.
Effect of Inlet Tangential Port Area on the Performance of Small – Scale Simplex Atomizer
Authors: Muthu Selvan G. , Muralidhara H. S. , Vyas Vinod Kumar , Dinesh Kanth T. P. , Kumaran S. , Magesh R.
Published: October 2013

An experimental investigation was conducted to study the effects of increased area of inlet tangential ports on the performance of small scale simplex atomizer. The spray characteristics of three different simplex atomizer representing increasing area of inlet tangential ports are examined using water as a working fluid. Measurements of coefficient of discharge, spray cone angle, Sauter mean diameter and droplet size distribution were carried out over wide range of injection pressure. Coriolis mass flow meter was used to measure coefficient of discharge. Spray cone angle was measured by image processing technique. Sauter mean diameter and droplet size distributions were measured by Malvern droplet sizing instrument. It was observed that with increase in area of inlet tangential ports the size of air core produced along the center line reduced, which increases the coefficient of discharge. Spray cone angle decreases with increase in area of inlet tangential ports. It was found that increase in area of inlet tangential ports reduces swirl strength inside swirl chamber, which results in increasing Sauter mean diameter. Better droplet size distribution was observed for lower area of inlet tangential port configuration. The obtained experimental results were compared with experimental correlations available in literatures. Deviations in the obtained experimental results and experimental correlations was observed. This is due to difference in the size of atomizer used and difference in experimental techniques used between the present work and other investigations.
Comparison of Fluid-Structure Coupling Methods for Blade Forced Response Prediction
Authors: Payer Florent , Ferrand Pascal , Dugeai Alain , Thouverez Fabrice
Published: October 2013

A time-marching coupled method has been applied to a high pressure compressor forced response case. The purpose of the study is to compare the contribution of the coupled scheme against the state of the art decoupled methodology. Although the time-marching scheme allows for a stronger coupling between the motion and aerodynamic field, results have shown good agreement with the decoupled method. The additional computing cost arising from the long transient state and the small difference in amplitude prediction with the decoupled scheme reduce the interest for the coupled one. A new transient state method is proposed to combine both coupled and decoupled schemes features. Here, the forcing and damping functions are extracted during the mechanical transient state of the coupled simulation and forced response is calculated as in the decoupled method. Results have shown good agreements with the experiment and all the methods are compared in terms of underlying assumptions and performances.
Phenomenon of Flow Pumping Through Counterbore Cavities
Authors: Srinivasan Karthik , Sendilkumaran S.
Published: October 2013

CFD analysis of flow through high pressure packaging seal passage of a typical land based gas turbine was performed which contained a rotating bolted joint region. Analysis reveals that the annular space between the nut and the counterbore surface acts as a fluid pump, sucking and pumping out fluid with significant temperature rise as high as 40 F. Factorial DoEs were carried out to filter out vital few parameters among geometric, flow and operational parameters that impacts counterbore flow. A detailed space filling DoE with more than 100 CFD models were developed and studied to estimate the influence of parameters impacting counterbore mass flow. A mathematical model (transfer function) developed using PEZ was created to calculate counterbore mass flow as a function of vital few geometric and flow variables. Finally, 2D Axi symmetric thermal analysis with counterbore mass flow modelling better matched the field temperature compared to that of one without counterbore model.
Numerical Analysis of Flow in S-Duct Diffusers With and Without Flow Control
Authors: Sullerey R. K. , Bhat S. P.
Published: October 2013

The intakes of Unmanned Ariel Vehicles (UAV) and Unmanned Combat Ariel Vehicles (UCAV) have complex serpentine geometries that include curvature, area increase and offsets. This is from the requirements of stealth features in such inlets. There is also a design requirement to keep the intake length short. Tight geometrical curvatures coupled with flow diffusion are known to generate secondary flows and many a time lead to flow separation. So flow at the exit may be quite distorted and total pressure losses may be high. Therefore some kind of flow control is required to ensure that the design goals of pressure recovery and flow quality are maintained.

Significant previous research has been carried out by one of the authors on flow control in S-Duct and serpentine duct geometries with various options of passive and active controls (1, 2, 3 and 4). In one of the latest of such studies (5), very encouraging results have been obtained in improving performance of S-duct diffusers using a zero net mass flow (ZNMF) active control. The present paper is a CFD study on modeling the flow in such a duct with and without flow control. As large amount of experimental data is available for both passive and active control on this geometry, it can be used to validate CFD predictions. The experimental results are available for improvement in pressure recovery and reduction of flow distortion using both passive and active flow controls including a combination of suction and blowing (vortex generator jets) for low-subsonic flow regime. Once the CFD model is proven to make good predictions for the present geometry, the same could be applied to more complex and realistic intake geometries.

The numerical (CFD) study carried out is a turbulent flow analysis in S-duct geometry to estimate pressure recovery and flow distortion with and without use of flow control techniques. The flow is modeled inside a rectangular section S-shaped duct with a Reynolds number of 1.479×105 based on the intake duct height. The diffusing duct has an area ratio of 1.25. The location of vortex generators and suction are based on the benchmarked experimental data (5) and is remodeled for CFD computations. The analysis is carried out for the low-subsonic (incompressible) flow and the CFD results are compared with the experimental results. The results obtained for bare duct and zero net mass flow (ZNMF) agree very well with the experimental data. As such, in future, work can be carried out at high subsonic, more complicated geometries and at various vortex generator jet angles to optimize the pressure recovery for high Mach number flows.
Numerical Investigation of High Pressure Hydrogen Released in Air
Authors: Umesh U. , De Ashoke , Das Malay K.
Published: October 2013

The constantly growing energy needs of the world accompanied by the emphasis on environmental pollution control have driven us to look at the possibility of hydrogen as a potential source of energy for the future. However, there are serious self-ignition hazards associated with its use, which are not yet fully understood phenomena. The issue of spontaneous ignition of highly pressurized hydrogen release is an important safety concern and it is necessary to understand its mechanism in order to adopt adequate safety measures.

This paper describes a numerical investigation of the flow physics of a high-pressure hydrogen gas released through a tube into the atmosphere. The formation of a strong shock wave ahead of the high-pressure hydrogen jet causes an increase in temperature of the ambient atmospheric air, thereby leading to the possibility of ignition of the hydrogen-air mixture formed at the contact surface. The analysis of the physical mechanism of shock propagation and associated temperature profiles of the flow field are presented. Parametric studies based on the numerical results of temperature profiles obtained for the various initial conditions of release pressure and tube length have been carried out to study their effects on this high-pressure hydrogen gas behaviour and how they would favour occurrence of spontaneous ignition.
The Fluid-Thermal-Structure Coupled Analysis and Optimization of Turbine Mortise/Disc
Authors: Shen Xiuli , Dong Shaojing , Qi Xiaodong
Published: October 2013

In the design of modern engine, high thrust-weight ratio becomes an important indicator. In these engines, the turbine disc bears complicated loads caused by high rotating speed and high temperature difference. Reducing its thermal stress by fine-tuning the shape and temperature field without changing the revolving speed so as to achieve weight loss has become the new focus. Based on the structure of the turbine disc, this paper discussed multi-disciplinary optimization method. Firstly, we studied the fluid-thermal coupled numerical method of the turbine disc. The temperature field on solid domain of the turbine disc is obtained without changing the air-entraining. And then, we accomplished the data transmission of temperature between fluid-thermal coupled calculation and strength calculation by interpolation process accurately. The strength calculation is carried out with the temperature as the boundary condition of the solid domain. Secondly, based on the feature-based parametric model of the mortise/disc structure, the fluid and strength calculation software are integrated to the optimization platform. It is through batch and convergence programs to achieve the automated operation of multi-disciplinary calculation. Take the lightest weight as the objective function and the weight-sensitive parameters as design variables. The fluid-thermal-structure coupled optimization of mortise/disc is achieved by using the classic multi-disciplinary feasible optimization strategy. To take full advantage of the optimization space to find the optimal solution of design problems, we have taken hybrid algorithms of MIGA and NLPQL. Finally, on the basis of the above calculations and optimization, a satisfactory result is obtained with the total weight of the mortise/disc decreased by about 5%. The plastic analysis of the optimized mortise/disc is carried out at last and met the strength requirements. Through this paper, a complete multi-disciplinary method containing fluid-thermal-structure of the mortise/disc is formed. The method takes full account of the influence of the fluid flow and heat transfer. It also shortens the design cycle and promotes design efficiency.
Simulations of 3D Separation in the Diffuser
Authors: Shende Amitkumar , Verma Manoj , Vashist T. K. , Mathew Joseph
Published: October 2013

Large eddy simulations of an asymmetric diffuser characterized by complex 3-D flow separation for which RANS models provide qualitatively wrong predictions have been performed.. An incompressible, turbulent, fully-developed flow in a rectangular duct (aspect ratio 1:3.33) expands into this diffuser. Two such diffusers were constructed by deflecting a pair of adjacent walls for the experiments in Cherry et al. [1, 2] (2006, 2008) and Buice, C. U. and Eaton, J. K. [3]. Most of our simulations consider Diffuser 1 with wall deflection angles 11.3° and 2.56°. In the experiments, flow begins to separate at the corner formed by the two deflected walls and then spreads so that flow is separated from the wall at the larger deflection angle. In simulations with RANS models, flow separates from the wall with the smaller deflection. It has been possible to obtain solutions with LES where flow separates correctly, off the wall at the larger deflection angle, as in the experiment. The LES finds a qualitatively correct separation, with characteristics in close quantitative agreement (within 5%) with the experimental values for Diffuser 1. The effects of variations in grid aspect ratio, grid refinement, inlet length, number of flow passes, and secondary flow structure upstream of the diffuser on solutions were determined. An LES was carried out for Diffuser 2 (deflection angles of 9° and 4° respectively), applying all lessons learnt in Diffuser 1 studies. It was found that the results for Diffuser 2 are not as quantitatively close to the experimental results as in case of the Diffuser 1, but the discrepancies appear to have a similar origin in some finer aspect of diffuser inflow conditions.
Investigations Into Creep Behavior of Gas Turbine Component Assemblies
Authors: Raghavan Kotur S.
Published: October 2013

Modern day gas turbines are very complex in construction and consist of a very large number of smaller parts and subassemblies. Hence the most vital parts of the entire assembly are the mechanical devices which are deployed to connect and keep them together. In gas turbines two approaches are normally used in the assembly process. They are the threaded fasteners such as bolt and nut and shrunk-fit or interference-fit assemblies. In the high temperature regions of the gas turbines the effect of creep on the integrity of such fastening arrangements needs to be assessed at the design stage.

A problem commonly faced pertains to lack of creep data which would facilitate detailed nonlinear analysis. The available data invariably exhibit scatter. In this paper parametric studies are undertaken. Creep curves are chosen so that both primary and secondary stages are accounted for. The coefficients are chosen to meet the design needs.

The performance of bolted joints and shrunk-fit assemblies get affected over time due to stress relaxation leading to loss of bolt pretension or the effective interference. The bolt preload as well as the interference is to be optimally chosen. Higher the preload or the interference the more effective is the joint. At the same time the stress levels are higher and hence the stresses will relax to a greater extent. For a design stage assessment of the behavior of assemblies there is need for correlation among the various operating parameters such as stress, temperature and time. For individual components one normally uses empirical correlations such as Larson-Miller to predict rupture life and also creep growth. For assemblies in which relaxation is the main design issue, such parameters are usually not available. There is need to carry out detailed nonlinear analysis.

Typical bolted flange and shrink-fit assemblies are chosen for study. Parametric studies are carried out. Using creep properties as described earlier, nonlinear structural responses are studied. The purpose is to correlate the creep properties, in terms of creep strain with respect to time, stress and temperature, with the joint behavior. The key joint behavior indices are the bolt tensile stress in the case of threaded fastening and the compressive force of “effective interference” in the case of shrunk-fit assemblies.

The studies have established the need for rigorous creep analysis of components having interference fits or threaded fasteners. Once the operational requirements are known, the approach presented helps in material selection.
Numerical Simulation of Effects of Tip Geometry on the Performance of an Axial Compressor
Authors: Ma Hongwei , Zhang Jun
Published: October 2013

The purpose of this paper is to investigate numerically the effects of the tip geometry on the performance of an axial compressor rotor. There are three case studies which are compared with the base line tip geometry. 1) baseline (flat tip); 2) Cavity (tip with a cavity); 3) SSQA (suction side squealer tip) and 4) SSQB (modified suction side squealer tip). The case of SSQB is a combination of suction side squealer tip and the cavity tip. From leading edge to 10% chord, the tip has a cavity. From 10% chord to trailing edge, the tip has a suction side squealer. The numerical results of 2) show that the cavity tip leads to lower leakage mass flow and greater loss in tip gap and the rotor passage. The loading near the blade tip is lower than the baseline, thus the tangential force of the blade is lower. It leads to lower pressure rise than the baseline. The performance of the compressor for the tip with cavity is worse than the baseline.

The results of 3) show that the higher curvature of the suction side squealer increases the loading of the blade and the tangential blade force. With the suction side squealer tip, the leakage flow experiences two vena contractor thus the mass of the leakage flow is reduced which is benefit for the performance of the compressor. The loss in the tip gap is lower than baseline. The performance is better than the baseline with greater pressure rise of the rotor, smaller leakage mass flow and lower averaged loss. For the case the SSQB, the leakage mass flow is lower than the SSQA and the loss in the tip gap and the rotor passage is greater than SSQA. The performance of the case of the SSQB is worse than the case of SSQA.