bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical modeling and computational fluid dynamics simulation of cabinet type solar dryer: Optimal temperature control
Authors: Chaudhari Vishal D. , Kulkarni Govind N. , Sewatkar Chandrashekhar M.
Published: January 2021

The mathematical model for determination of auxiliary energy required to maintain set air temperature in the drying chamber is proposed for cabinet type solar dryer. The model is developed considering the heat exchanges across the dryer control volume with solar radiation intensity and set temperature as input. The sole purpose is to minimize the auxiliaries. The computational fluid dynamics (CFD) technique is used to simulate the air flow inside the drying chamber for different operating conditions. The simulations results for the temperature are very close to the results from mathematical model. The dryer configuration discussed in illustrative example found to have minimum auxiliary consumption at 45°C with total auxiliary expense of 97.3 kWh per day. When applied to full calendar year, the optimum temperature is found to be function of ambient temperature and solar radiation intensity. The results obtained from mathematical model are found to be in well agreement with simulation results. The simulation results provide a region with 1.2 m to 1.6 m on X‐ordinate, 0.8 m to 1.0 m on Y‐ordinate and 0.7 m to 1.2 m and 3.7 m to 4.3 m on Z‐ordinate where average temperature can be sensed. It helps in modulating the auxiliary input/s in integration with solar heat.
Effects of androgenic properties of progestin combined with ethinyl estradiol on vascular endothelial reactivity, plasma lipids and free radical production in women with endometriosis
Authors: Sakurada Takahiro , Matsushita Hiroshi , Noguchi Yasuyuki , Shinohara Koichi , Watanabe Kazushi , Wakatsuki Akihiko
Published: January 2021

Aim

Endothelial reactivity is inhibited and oxidative stress is enhanced in women with endometriosis. Testosterone may adversely affect lipids and endothelium. We investigated the effects of androgenic properties of progestins combined with ethinyl estradiol (EE) on endothelial function, lipids and free radical production in such women.

Methods

Women with endometriosis were treated with 20 μg EE + 3 mg drospirenone (DRSP) or 35 μg EE + 1 mg norethisterone (NET) for 3 months. Plasma concentrations of sex hormone‐binding globulin (SHBG), lipids, copper (Cu), derivatives of reactive oxygen metabolites (d‐ROMs), biological antioxidant potential (BAP), nitrite/nitrate, endothelin‐1 and asymmetrical dimethylarginine (ADMA) were measured before and after treatment. Flow‐mediated vasodilation (FMD) of the brachial artery was measured by ultrasonography.

Results

DRSP group, but not NET group, significantly increased FMD and concentrations of nitrite/nitrate and small dense LDL cholesterol, while decreased endothelin‐1 concentrations. In both groups, ADMA and LDL cholesterol concentrations were significantly decreased, but triglyceride, SHBG, d‐ROMs, Cu and ceruloplasmin concentrations increased, and BAP concentrations did not change. DRSP group significantly increased HDL cholesterol concentrations, whereas NET group decreased its concentrations. Changes in triglyceride correlated positively either with changes in SHBG (r = 0.57, P < 0.001) or with small dense LDL cholesterol (r = 0.45, P = 0.005). Changes in Cu correlated positively with changes in d‐ROMs (r = 0.87, P < 0.001).

Conclusion

Androgenic properties of progestin may counteract EE's favorable effects on endothelial function and HDL cholesterol, while eliminating its adverse effects on increased triglyceride‐induced small dense LDL cholesterol in women with endometriosis.
Threonine incorporation in tissues of growing broiler chickens using L‐[15N] threonine
Authors: Suzuki Rafael Massami , Reis Matheus de Paula , Denadai Juliana Célia , Pacheco Letícia Graziele , Nascimento Carolina Cardoso Nagib , Sakomura Nilva Kazue
Published: January 2021

Most amino acid requirement trials appear for whole‐body responses, but there is little information concerning amino acid incorporation in individual tissues, which may vary according to the age. L‐[15N] threonine was used to evaluate its incorporation rate and distribution among broiler tissues in different ages. Seventy‐two male broiler chickens were distributed into three different phases: starter (4 to 9 days old), grower (18 to 23 days old) and finisher phase (32 to 37 days old). L‐[15N] threonine was added on balanced diets, and birds were fed for five days in each phase. Enriched samples of breast muscle, feathers, liver, jejunum and plasma were collected at 0, 6, 12, 24, 48, 72, 96 and 120 hr after fed birds with the tracer in each phase. In the tissues were analysed dry matter, nitrogen and stable nitrogen. The 15N isotope abundance according to the time was fitted into exponential or linear equations using a same intercept. The ratio of the steepness or slope coefficients was determined to compare the L‐[15N] threonine incorporation according to the age. In addition, L‐[15N] threonine mass balances were performed to assess the L‐[15N] threonine distribution among the evaluated tissues. Except for feathers, the L‐[15N] threonine incorporation rate decreased with ageing. Taking into account the L‐[15N] threonine distribution in the tissues, only in the jejunum was not observed an increase as the broiler grew. The L‐[15N] incorporation varied in each tissue and according to the age of the broiler chickens. These outcomes could be useful to comprehend changes in amino acid requirements tissue‐specific according to age.
Metagenomic sequencing provides new insights into the subgingival bacteriome and aetiopathology of periodontitis
Authors: Ng Ethan , Tay John R. H. , Balan P. , Ong Marianne M. A. , Bostanci Nagihan , Belibasakis Georgios N. , Seneviratne Chaminda J.
Published: January 2021

“Open‐ended” molecular techniques such as 16S rRNA sequencing have revealed that the oral bacteriome of subgingival plaque is more diverse than originally thought. 16S rRNA analysis has demonstrated that constituents of the overall bacterial community are qualitatively similar in health and disease, differing mainly in their relative proportions with respect to each other. Species in low abundance can also act as critical species, leading to the concept of global community dysbiosis which relates to shifts in community structure, rather than shifts in membership. Correlation analysis suggests that coordinated interactions in the community are essential for incipient dysbiosis and disease pathogenesis. The subgingival bacteriome also provides biomarkers that are useful for disease detection and management. Combined with clinical and biological parameters, these may assist clinicians in developing and implementing effective treatment strategies to restore microbial homeostasis and monitor disease. Identification of higher risk groups or poor responders to treatment using unique subgingival bacteriome signatures may also lead to early intervention.
Expansion of dysfunctional CD56‐CD16+ NK cells in chronic hepatitis B patients
Authors: Wijaya Ratna S. , Read Scott A. , Schibeci Stephen , Han Shuanglin , Azardaryany Mahmoud K. , van der Poorten David , Lin Rita , Yuen Lawrence , Lam Vincent , Douglas Mark W. , George Jacob , Ahlenstiel Golo
Published: January 2021

Background & Aims

Natural killer (NK) cells are primary innate effector cells that play an important role in the control of human viral infections. During chronic viral infection, NK cells undergo significant changes in phenotype, function and subset distribution, including the appearance of CD56‐CD16+ (CD56‐) NK cells, previously identified in chronic human immunodeficiency virus (HIV) and hepatitis C virus infection. However, the presence of CD56‐ NK cells in the pathogenesis of chronic hepatitis B (CHB) remains unknown.

Methods

Phenotype and function of CD56‐ NK cells from patients with CHB (n = 28) were assessed using flow cytometry and in vitro stimulation with HBV antigen.

Results

CHB patients had a higher frequency of CD56‐ NK cells compared to healthy controls in peripheral blood (6.2% vs 1.4%, P < .0001). Compared to CD56+ NK cells, CD56‐ NK cells had increased expression of inhibitory receptors, and reduced expression of activating receptors, as measured by MFI and qPCR. CD56‐ NK cells were less responsive to target cell and cytokine stimulation compared to their CD56+ counterparts. In addition, CD56‐ NK cells demonstrated defective dendritic cells (DCs) interactions resulting in reduced DCs maturation, lower expression of NK CD69 and impaired capacity of NK cells to eliminate immature DCs in co‐culture studies. Finally, frequency of CD56‐ NK cells was positively correlated with serum HBV DNA levels.

Conclusion

Chronic HBV infection induces the expansion of highly dysfunctional of CD56‐ NK cells that likely contribute to inefficient innate and adaptive antiviral immune response in chronic HBV infection.
Study on the pathophysiological mechanism responsible for lower urinary tract symptoms associated with prostate cancer using an animal model
Authors: Hsu Lin‐Nei , Tsai Yuh‐Shyan , Tsai Hsin‐Tzu , Su Wen‐Pin , Tong Yat‐Ching
Published: January 2021

Objectives

To investigate the pathophysiological mechanism leading to lower urinary tract symptoms in prostate cancer (PCa) by using an animal model.

Methods

An orthotopic PCa model in mice was established by injection of human DU145 cells into the prostate gland lateral lobe of NOD.CB17‐Prkdcscid/NcrCrlBltw (NOD‐SCID) mice. Cancer growth was quantified by a luciferase‐based in vivo imaging system (IVIS) serially every 7 days. Comparisons were made for urodynamic parameters, bladder histology, and biological markers until the sixth week. Bladder wall structural changes were assessed by the bladder wall thickness and degree of fibrosis. Biomarker expressions in bladder tissue including muscarinic acetylcholine receptor 2 (M2), transient receptor potential cation channel subfamily V member 4 (TRPV4), BCL2‐associated X protein (Bax), and caspase3 were evaluated by immunohistochemical staining and immunofluorescence confocal laser scanning microscopy.

Results

DU145 cell growth in the prostate was successfully monitored by a luciferase‐based IVIS. after orthotopic injection. Using our injection technique, no anatomical obstruction of the bladder outlet and urethra was noted up to 6 weeks after injection. The presence of PCa induced changes in urinary bladder histology, biomarkers, and urodynamic parameters. Cystometry showed features of detrusor overactivity with increased voiding frequency and high‐amplitude voiding contractions from the fourth week onward. Histological analyses 4 weeks after DU145 injection demonstrated detrusor thickening and bladder wall fibrosis. Immunohistochemistry showed increased expressions of bladder M2, TRPV4, Bax, and caspase3 in the PCa mice as early as in the first or second week.

Conclusions

PCa can induce bladder microenvironment changes involving neural receptors and biological mediators leading to histological and functional alterations even in the absence of overt anatomical obstruction.
Convergence in Sovereign Debt Defaults: Quantifying the Roles of Institutions
Authors: Bhattacharya Mita , Inekwe John
Published: January 2021

In this study, using an ex ante measure, we examine the convergence patterns in sovereign defaults among 101 developing countries for the period from 1990 to 2015. We employ the club convergence algorithm to determine convergence paths across countries and examine the role of institutions in shaping the observed convergence patterns. The merging of clubs reveals three distinct convergent sub‐clubs. Countries in each of these sub‐clubs tend to exhibit a similar pattern of long‐run convergence in cases of sovereign debt default. Countries with better institutions are less likely to belong to a club with greater risks of sovereign defaults by 7% points. Unlike trade openness, levels of external debt, inflation and current account balance increase the probability of default in these economies.
Long‐Term Efficacy of Screw Fixation vs Hemiarthroplasty for Undisplaced Femoral Neck Fracture in Patients over 65 Years of Age: A Systematic Review and Meta‐Analysis
Authors: Xu Wen‐nan , Xue Qing‐yun
Published: January 2021

Objective

To compare the long‐term efficacy of screw fixation and hemiarthroplasty in elderly patients with undisplaced femoral neck fractures.

Methods

We searched Cochrane Library, EMBASE, and MEDLINE from inception to 10 June 2020 to identify studies about undisplaced femoral neck fracture in elderly patients over 65 years of age. The included studies were assessed by two researchers according to the Cochrane risk‐of‐bias criteria and Newcastle–Ottawa Scale. Meta‐analysis was performed with Revman 5.3 software. The odds ratios (OR) and mean differences (MD) were used to compare dichotomous and continuous variables.

Results

A total of 750 patients were included in this meta‐analysis. In elderly patients, undisplaced femoral neck fracture treated with hemiarthroplasty had a lower implant‐related complication rate (OR, 4.05 [95% CI, 2.38 to 6.89]; P < 0.00001; I2 = 0), lower reoperation rate (OR, 4.88 [95% CI, 2.84 to 8.38]; P < 0.00001; I2 = 0), and superior Harris score (WMD, −5.05 [95% CI, −7.30 to −2.80]; P < 0.0001; I2 = 0) in the early postoperative period. Although screw fixation was associated with shorter operative time (WMD, −36.22 [95% CI, −50.72 to −21.73]; P < 0.00001; I2 = 98%) and less blood loss (WMD, −165.84 [95% CI, −209.29 to −122.38]; P < 0.00001; I2 = 96%), there was no significant difference in long‐term mortality (OR, 0.65 [95% CI, 0.28 to 1.48]; P < 0.31; I2 = 75%) between these two treatments.

Conclusion

In elderly patients with undisplaced femoral neck fractures, hemiarthroplasty provided a lower implant‐related complication rate, lower reoperation rate, superior hip function without increased long‐term mortality. Hemiarthroplasty should be recommended as a better alternative in such patients compared with multiple cannulated screws.
Per Pedicel‐Ligament Flavum Tunnel Outside‐In Foraminoplasty for T10–T12 Discectomy under a Percutaneous Endoscope
Authors: Lin Wei , Liu Wei , Ma Wen‐ting , Xue Yuan
Published: January 2021

Objective

To describe the effectiveness of T10–T12 discectomy and per pedicel‐ligament flavum tunnel outside‐in foraminoplasty protocols under percutaneous endoscope.

Methods

This retrospective study from September 2017 to June 2019 comprised 10 patients (mean age was 64.7 years, with 7 men and 3 women) with symptomatic thoracic disc herniation. Patients who had 12 months of follow‐up and no cervical and lumbar spine surgery or trauma during the follow up period were included in the study. Patients underwent surgery at different levels: 3 patients for T10–T11 and 7 patients for T11–T12. Percutaneous endoscopic thoracic discectomy was performed following under‐vision foraminoplasty, which was based on lower pedicel‐ligament flavum tunnel detection. Patients who presented with symptomatic soft disc herniation of the thoracic spine and did not respond to conservative treatments were included. Patients with calcified disc herniation or concomitant ossification of the posterior longitudinal ligament were excluded. The surgery involves four steps: (i) facet joint reaching procedures; (ii) sliding the working sleeve caudally to attach the pedicel, rotating the scope to detect the lower border of the superior articular process, the pedicel, and the lower pedicel‐ligamentum flavum tunnel (PEFT) under vision, respectively; (iii) milling the superior articular process under vision; and (iv) finding and removing the disc protrusion after the posterior longitudinal ligament is resected. Patient outcomes were evaluated using vision analog scale scores, Oswestry disability index scores, and Japanese Orthopaedic Association scores. The VAS scores, Oswestry disability index scores, and Japanese Orthopaedic Association scores before and after the operation were compared by t‐test for statistical analysis. MRI, CT, and plain X‐rays were performed in of all the patients before and after surgery.

Results

The patient was usually able to stand and walk approximately 2 h after the surgery. During the 12‐month follow‐up, all patients showed a significant improvement in pain. Postoperative thoracic MRI examination of all patients showed full decompression of the spinal cord and no residual pressure. Postoperative back pain and nerve root pain were significantly alleviated in all patients, and spinal cord function was significantly restored. The mean visual analog scale scores of patients postoperation were significantly better than those of patients preoperation (6.10 ± 1.37 vs 1.80 ± 0.79, P < 0.05). The mean ODI scores of patients postoperation were better than those of patients preoperation (13% ± 2.36% vs 55% ± 9.20%, P < 0.05). The mean JOA scores increased from 3.2 ± 0.75 to 9.3 ± 0.64. The JOA improvement rate was 79.6% ± 5.1%. There was 1 patient who had transient intercostal neuralgia.

Conclusion

Following pedicel‐ligament flavum tunnel outside‐in foraminoplasty protocols, T10–T12 discectomy is relatively safe when conducted under percutaneous endoscope.
Physiological responses to fire that drive tree mortality
Authors: Hood Sharon M.
Published: January 2021

This article comments on: Short‐ and long‐term effects of fire on stem hydraulics in Pinus ponderosa saplings
MicroRNA profile in immune response of alveolar and cystic echinococcosis patients
Authors: Eroglu Fadime , Dokur Mehmet , Ulu Yüksel
Published: January 2021

It is known that miRNAs are effective in immune response in the diagnosis and treatment of many infectious diseases. However, the miRNAs profile is unknown in Alveolar and Cystic Echinococcosis which can be fatal if left untreated. The miRNAs profile that activates the T and B cells forming the immune system in Alveolar and Cystic Echinococcosis patients was investigated in this study. A total of 50 liver tissue samples were obtained from Alveolar and Cystic Echinococcosis patients in Kilis State Hospital Pathology Laboratory in southeast of Turkey. The circulating cell‐free miRNAs were evaluated by a quantitative real‐time polymerase chain reaction, statistically calculated within ΔΔCt values and fold changes were evaluated by Welch T test, in which P < .05 was considered to be significant. Twenty‐five microRNAs, including let‐7a‐5p, let‐7c, let‐7e‐5p, miR‐15b‐5p, miR16, miR‐17‐5p, miR‐23a‐5p, miR‐24‐3p, miR‐25‐3p, miR‐26a‐3p, miR‐26b‐3p, miR‐29b‐3p, miR‐29c‐3p, miR‐30a‐5p, miR‐30b‐5p, miR‐30c‐5p, miR‐30d‐5p, miR‐30e‐5p, miR‐98‐5p, miR‐101‐3p, miR‐106b‐5p, miR‐125b‐5p, miR‐142‐5p, miR‐222‐3p and miR‐223‐3p, were found as down‐regulated in Alveolar and Cystic Echinococcosis patients than control groups. Twelve miRNAs, including miR‐15a‐5p, miR‐21‐5p, miR‐27a‐3p, miR‐29a‐3p, miR‐146a‐5p, miR‐181a‐5p, miR‐181b‐5p, miR‐181d, miR‐181c‐5p, miR‐195‐5p, miR‐214‐3p and miR‐365‐3p, were found as up‐regulated in Alveolar and Cystic Echinococcosis patients than healthy person. It has been shown that T‐ and B‐cell activities are related in the progressive of both Alveolar and Cystic Echinococcosis in this study. The miRNA panel activated by T and B cells may be important for exploring the mechanisms underlying early development in Alveolar and Cystic Echinococcosis providing novel information that may be used to discover new therapeutics for these diseases.
Analyticity of rotational traveling gravity two‐layer waves
Authors: Chu Jifeng , Wang Ling‐Jun
Published: January 2021

The aim of this paper is to prove real analytic properties of all streamlines of two‐dimensional steady rotational gravity water waves in two‐layer flows. Provided that there are no stagnation points in the flow, we show that each streamline, including the free surface and the interface, is a real analytic curve if the height function is in , which corresponds to an arbitrarily bounded and measurable vorticity function. Our results generalize those for the situation of single layer flow, and improve the results in the work by Chu, Escher, and Wang [Analyticity of rotational travelling waves in two‐layer flows, submitted], where the analyticity is obtained for rotational two‐layer water waves when the height function is in corresponding to a Hölder continuous vorticity function.
What Guns Mean: Who Sees Guns as Important, Essential, and Empowering (and Why)?
Authors: Warner Tara D. , Ratcliff Shawn
Published: January 2021

There is a fairly well‐established demographic profile of gun owners in the United States, yet much less is known about the meaning and importance individuals attach to guns, their right to own them, or the varying facets of gun owner identity. Unknown is if and/or how the attitudes, fears, concerns, and anxieties that influence gun ownership also shape the significance of guns in individuals’ lives. To that end, we examine three assessments of gun meaning: the importance of the right to own guns for one’s sense of freedom; the importance of being a gun owner to one’s personal identity; and the extent to which owners find guns emotionally and morally empowering (e.g., guns making one feel confident, important, in control). Using data from an original Mechanical Turk survey (n = 876), we show that diffuse political, social, and cultural anxieties shape gun meaning more so than do instrumental fears around crime and victimization.
Constitutive equation determination and dynamic numerical modelling of the compression deformation of concrete
Authors: Seven Semih Berk , Çankaya M. Alper , Uysal Çetin , Tasdemirci Alper , Saatçi Selçuk , Güden Mustafa
Published: January 2021

The dynamic compression deformation of an in‐house cast concrete (average aggregate size of 2–2.5 mm) was modelled using the finite element (FE), element‐free Galerkin (EFG) and smooth particle Galerkin (SPG) methods to determine their capabilities of capturing the dynamic deformation. The numerical results were validated with those of the experimental split Hopkinson pressure bar tests. Both EFG and FE methods overestimated the failure stress and strain values, while the SPG method underestimated the peak stress. SPG showed similar load capacity profile with the experiment. At initial stages of the loading, all methods present similar behaviour. Nonetheless, as the loading continues, the SPG method predicts closer agreement of deformation profile and force histories. The increase in strength at high strain rate was due to both the rate sensitivity and lateral inertia caused by the confinement effect. The inertia effect of the material especially is effective at lower strain values and the strain rate sensitivity of the concrete becomes significant at higher strain values.
Egyptian broomrape sucrose metabolism in response to different host plants
Authors: Farrokhi Zahra , Alizadeh Hassan , Alizadeh Houshang
Published: January 2021

Broomrapes are important parasitic weeds in many vegetable crops in dry and warm regions of the world. The study of weed parasite physiology will increase knowledge of broomrape‐host interactions that may be applied to the development of improved parasitic plant control programmes. In this study, developmental patterns of activities of essential enzymes (sucrose synthase [SUS], mannose 6‐phosphate reductase [M6PR], cell wall invertase [CWI] and soluble acid invertase [SAI]) involved in Egyptian broomrape osmoregulation were investigated using three hosts (celery, tomato and cucumber). The earliest broomrape emergence occurred on cucumber; however, the total biomass of the parasite did not differ between cucumber and tomato. The reducing sugars content, gene expression and enzyme activity in the parasite significantly varied with the parasite organs and the hosts. Maximum SAI activity was observed in the apical part (AP) of the flowering shoot of parasite growing on cucumber. However, the peak of genes expression occurred in the same organ across the three hosts, for example SAI1 was expressed maximally in tubercle bearing the flowering shoot (Tub‐FS). The largest amount of reducing sugars was observed in the AP of the parasite grown on tomato. High M6PR activity in the parasite and its matching with M6PR transcriptional levels in three hosts are deemed promising for broomrape management through the deployment of the proteinaceous inhibitors or gene silencing constructs in host plants. Overall, the results indicated that differences in sugar metabolism of Egyptian broomrape grown on different hosts can potentially be exploited for effective management of this difficult‐to‐control parasite.
The hard problem: Mechanotransduction perpetuates the myofibroblast phenotype in scleroderma fibrosis
Authors: Leask Andrew
Published: January 2021

The effector cells ultimately responsible for fibrosis are myofibroblasts. In the fibrotic autoimmune connective tissue disease scleroderma, myofibroblasts are autonomously activated, and retain their phenotype upon culturing. Since the 1990s, researchers have exploited this fact to use scleroderma fibroblasts as a model system to uncover the fundamental mechanisms underlying myofibroblast persistence in fibrotic conditions. These studies have suggested that an autocrine transforming growth factor (TGF)beta signaling loop is insufficient to explain the persistent myofibroblast phenotype but instead support the hypothesis that fibrotic myofibroblasts possess an intrinsically activated pro‐adhesive signaling pathway, and that this contributes to the perpetuation of pathological fibrosis. This review focuses on these observations.
Containment and Arrest of Blade Shedding in Gas Turbine Engines Using Novel Dual-Ring Design
Authors: Roy P. A. , Meguid S. A.
Published: January 2021

In this paper, we examine the energy absorption and containment capabilities of a newly proposed dual-ring design accounting for interactions between a released blade and fully bladed fan disk using three-dimensional finite element analysis. The components of this dual-ring design are strategically selected to ensure high energy absorption and high impact resistance, thus leading to reduced damage of the disk and increased safety. Three containment ring designs are examined: (i) conventional single-ring design composed of one of titanium, aluminum, or Kevlar; (ii) a newly proposed aluminum-Kevlar dual-ring arrangement; and (iii) dual-ring arrangement with an interfacial gap between them to arrest and contain the released blade and ensure free passage of the trailing blades. The results of our numerical simulations indicate that although the single-ring design resists penetration and contains the released blade within the confines of the disk, it does not remove the released blade from the path of the trailing blades leading to severe damage to the fan disk. On the contrary, our new dual-ring design, which contains an interfacial gap, has potential to successfully arrest the released blade within the confines of the ring and out of the path of the trailing blades. This design can significantly reduce the impact damage to the fan disk and reduce kinetic energy of the released blade to near zero in less than half a rotation of the fan disk.
Investigation of Fuel and Load Flexibility in a Siemens Gas Turbine-600/700/800 Burner Under Atmospheric Pressure Conditions Using High-Speed Hydroxyl-PLIF and Hydroxyl Radical Chemiluminescence Imaging
Authors: Subash Arman Ahamed , Kim Haisol , Möller Sven-Inge , Richter Mattias , Brackmann Christian , Aldén Marcus , Lantz Andreas , Lindholm Annika , Larfeldt Jenny , Lörstad Daniel
Published: January 2021

Fuel and load flexibility have been increasingly important features of industrial gas turbines in order to meet the demand for increased utilization of renewable fuels and to provide a way to balance the grid fluctuations due to the unsteady supply of wind and solar power. Experimental investigations were performed using a standard third-generation dry low emission (DLE) burner under atmospheric pressure conditions to study the effect of central and pilot fuel addition, load variations, and hydrogen (H2) enrichment in a natural gas (NG) flame. High-speed kHz planar laser-induced fluorescence (PLIF) of OH radicals and imaging of OH chemiluminescence were employed to investigate the flame stabilization, flame turbulence interactions, and flame dynamics. Along with the optical measurements, combustion emissions were also recorded to observe the effect of changing operating conditions on NOX level. The burner is used in Siemens industrial gas turbines SGT-600, SGT-700, and SGT-800 with minor hardware differences and the study thus is a step to characterize fuel and load flexibility for these turbines. Without pilot and central fuel injections in the current burner configuration, the main flame is stabilized creating a central recirculation zone (CRZ). Addition of the pilot fuel strengthens the outer recirculation zone (ORZ) and moves the flame anchoring position slightly downstream, whereas the flame moves upstream without affecting the ORZ when central fuel injection is added. The flame was investigated utilizing H2/NG fuel mixtures where the H2 amount was changed from 0 to 100%. The results show that the characteristics of the flames are clearly affected by the addition of H2 and by the load variations. The flame becomes more compact, the anchoring position moves closer to the burner exit and the OH signal distribution becomes more distinct for H2 addition due to increased reaction rate, diffusivity, and laminar burning velocity. Changing the load from part to base, similar trends were observed in the flame behavior but in this case due to the higher heat release because of increased turbulence intensity.
Thermo-Structural Analysis of Steam Turbine Startup With and Without Integrated Prewarming System Using Hot Air
Authors: Łuczyński Piotr , Pehle Lukas , Wirsum Manfred , Mohr Wolfgang F. D. , Vogt Jan , Helbig Klaus
Published: January 2021

Motivated by the urgent need for flexibility and startup capability improvements of conventional power plants in addition to extending their life cycle, General Electric provides its customers with a product to prewarm steam turbines using hot air. In this paper, the transient thermal and structural analyses of a 19-stage intermediate pressure (IP) steam turbine in various startup operating modes are discussed in detail. The presented research is based on previous investigations and utilizes a hybrid finite element method (HFEM—numerical FEM and analytical) approach to efficiently determine the time-dependent temperature distribution in the components of the steam turbine. The simulation strategy of the HFEM model applies various analytical correlations to describe heat transfer in the turbine channel. These are developed by means of extensive unsteady multistage conjugate heat transfer (CHT) simulations for both startup turbine operation with steam and prewarming operation with hot air. Moreover, the complex numerical setup of the HFEM model also considers the thermal contact resistance (TCR) on the surfaces between vane and casing as well as blades and rotor. Prior to the analysis of other turbine startup operating modes, the typical startup turbine process is calculated and validated against an experimental data as a benchmark for subsequent analysis. In addition to heat transfer correlations, the simulation of a turbine startup from cold state uses an innovative analytic pressure model to allow for a consideration of condensation effects during first phase of startup procedure. Finally, the presented thermal investigation focuses on the comparison of transient temperature fields in the turbine for different startup scenarios after prewarming with hot air and provides the subsequent structural investigation with required boundary conditions. As a result, the values of the highest stress are numerically determined and compared to the values obtained by means of cold startup simulation. The final evaluation clearly displays the technical potential and the benefits of the prewarming concept.
Analysis of Timewise Compressor Fouling Phenomenon on a Multistage Test Compressor: Performance Losses and Particle Adhesion1
Authors: Vulpio Alessandro , Suman Alessio , Casari Nicola , Pinelli Michele , Kurz Rainer , Brun Klaus
Published: January 2021

The analysis of the performance losses of a multistage compressor concerning the air contaminant is not widespread in literature and, the mutual interactions of particle materials, air humidity, and compressor load are not well studied. The airborne micrometric particles that enter the compressor can deposit on the internal surfaces, causing the loss of performance of the machine. In this paper, several experimental tests have been carried out on a multistage compressor unit. A detailed analysis has been carried out considering soil and soot ingestion, as well as the air relative humidity (RH) (ranging from 50% RH to 80% RH) and compressor rotating velocity. Several combinations of particle diameter, material, and operating conditions have been considered. The amount of contaminant at the compressor outlet has been measured and the capture efficiency of the whole machine has been determined. Over the exposure time, the capture efficiency ranges from 0.2 to 0.6 according to the powder type and compressor inlet conditions. The capability of the compressor to collect particles changes over time as a function of the condition, even if several tested cases appear characterized by an almost constant capture efficiency trend. In addition, the performance degradation has been monitored over time and, with the reference of the particle concentration, the present experimental campaign covers about 500 operating hours of an actual installation. After a detailed evaluation of experimental uncertainty, the performance losses due to particle contamination have been assessed. The losses in the compressor performance have been estimated by means of the pressure ratio of the axial stages. The maximum degradation has been estimated equal to 0.53%/h for the compressor pressure ratio. Soot particles appear stickier, especially in the presence of higher humidity and represent the most detrimental operating conditions for the compressor unit.
Physics-Based Gaussian Process Method for Predicting Average Product Lifetime in Design Stage
Authors: Wei Xinpeng , Han Daoru , Du Xiaoping
Published: January 2021

The average lifetime or the mean time to failure (MTTF) of a product is an important metric to measure the product reliability. Current methods of evaluating the MTTF are mainly based on statistics or data. They need lifetime testing on a number of products to get the lifetime samples, which are then used to estimate the MTTF. The lifetime testing, however, is expensive in terms of both time and cost. The efficiency is also low because it cannot be effectively incorporated in the early design stage where many physics-based models are available. We propose to predict the MTTF in the design stage by means of a physics-based Gaussian process (GP) method. Since the physics-based models are usually computationally demanding, we face a problem with both big data (on the model input side) and small data (on the model output side). The proposed adaptive supervised training method with the Gaussian process regression can quickly predict the MTTF with a reduced number of physical model calls. The proposed method can enable continually improved design by changing design variables until reliability measures, including the MTTF, are satisfied. The effectiveness of the method is demonstrated by three examples.
Deposition Pattern Analysis on a Fouled Multistage Test Compressor
Authors: Suman Alessio , Vulpio Alessandro , Casari Nicola , Pinelli Michele , Kurz Rainer , Brun Klaus
Published: January 2021

Compressor fouling is one of the main causes of gas turbine performance degradation. Microsized particles adhere to the blade surfaces increasing the surface roughness and modifying the airfoil shape. In this work, the contamination of the Allison 250 C18 multistage compressor engine with four sorts of micrometric dust has been provided. The tests were performed changing the relative humidity (RH) at the compressor inlet and the unit rotational speed. After each test, a photographic inspection of the internal fouled parts has been realized and the digital pictures have been analyzed employing an image processing package. The deposit's build-up of stator vanes and rotor blades has been postprocessed and the most affected regions of each compressor stage have been highlighted. Besides, a numerical simulation of the machine has been performed. The numerical flow field has been used to highlight the blade regions, which show the most favorable conditions for particle deposition. A theoretical model has been applied to the flow field to simulate the particle deposition. The combination of the deposition model with the results of the numerical simulations gives the chance to better understand the experimentally founded deposition patterns. Those results have been finally compared to the pictures of the patterns. The possibility to detect and measure the deposition patterns on a rotating test rig and the comparison with models and experiments gave the possibility to assess in detail the particle deposition phenomenon on a multistage axial compressor flow path.
Flame Transfer Functions and Dynamics of a Closely Confined Premixed Bluff Body Stabilized Flame With Swirl
Authors: Nygård Håkon T. , Worth Nicholas A.
Published: January 2021

The flame transfer function (FTF) and flame dynamics of a highly swirled, closely confined, premixed flame is studied over a wide range of equivalence ratios and bulk velocities at a fixed perturbation level at the dump plane. The operating conditions are varied to examine the ratio of flame height to velocity in scaling the FTF. The enclosure geometry is kept constant, resulting in strong flame-wall interactions for some operating conditions due to varying flame height. The resulting effect on the FTF due to changes in the “effective flame confinement” can therefore be studied. For sufficiently high equivalence ratio, and the resulting sufficiently small effective confinement, modulations of the FTF are observed due to interference of the perturbations created at the swirler and at the dump plane. The small length scales and high velocities result in modulations centered at high frequencies and spanning a wide range of frequencies compared to previous studies of similar phenomena. A critical point was reached for increasing effective confinement, where the modulations are suppressed. This is linked to a temporal shift in the heat release rate where the flame impinges on the combustion chamber walls. The shift reduced the expected level of interference, demonstrating effective confinement is important for the FTF response. Additionally, a distributed time lag (DTL) model with two time lags is successfully applied to the FTFs, providing a simple method to capture the two dominant time scales in the problem, recreate the FTF, and examine the effect of effective confinement.
Characteristics of Band Gap and Low-Frequency Wave Propagation of Mechanically Tunable Phononic Crystals With Scatterers in Periodic Porous Elastomeric Matrices
Authors: Ning Shaowu , Chu Dongyang , Yang Fengyuan , Jiang Heng , Liu Zhanli , Zhuang Zhuo
Published: January 2021

The characteristics of passive responses and fixed band gaps of phononic crystals (PnCs) limit their possible applications. For overcoming this shortcoming, a class of tunable PnCs comprised multiple scatterers and soft periodic porous elastomeric matrices are designed to manipulate the band structures and directionality of wave propagation through the applied deformation. During deformation, some tunable factors such as the coupling effect of scatterer and hole in the matrix, geometric and material nonlinearities, and the rearrangement of scatterer are activated by deformation to tune the dynamic responses of PnCs. The roles of these tunable factors in the manipulation of dynamic responses of PnCs are investigated in detail. The numerical results indicate that the tunability of the dynamic characteristic of PnCs is the result of the comprehensive function of these tunable factors mentioned earlier. The strong coupling effect between the hole in the matrix and the scatterer contributes to the formation of band gaps. The geometric nonlinearity of matrix and rearrangement of scatterer induced by deformation can simultaneously tune the band gaps and the directionality of wave propagation. However, the matrix’s material nonlinearity only adjusts the band gaps of PnCs and does not affect the directionality of wave propagation in them. The research extends our understanding of the formation mechanism of band gaps of PnCs and provides an excellent opportunity for the design of the optimized tunable PnCs and acoustic metamaterials (AMMs).
Efficient Parametric Optimization for Expensive Single Objective Problems
Authors: Weaver-Rosen Jonathan M. , Malak Richard J.
Published: January 2021

Parametric optimization solves optimization problems as a function of uncontrollable or unknown parameters. Such an approach allows an engineer to gather more information than traditional optimization procedures during design. Existing methods for parametric optimization of computationally or monetarily expensive functions can be too time-consuming or impractical to solve. Therefore, new methods for the parametric optimization of expensive functions need to be explored. This work proposes a novel algorithm that leverages the advantages of two existing optimization algorithms. This new algorithm is called the efficient parametric optimization (EPO) algorithm. EPO enables adaptive sampling of a high-fidelity design space using an inexpensive low-fidelity response surface model. Such an approach largely reduces the required number of expensive high-fidelity computations. The proposed method is benchmarked using analytic test problems and used to evaluate a case study requiring finite element analysis. Results show that EPO performs as well as or better than the existing alternative, Predictive Parameterized Pareto Genetic Algorithm (P3GA), for these problems given an allowable number of function evaluations.
Investigation of Printing Parameters of Additive Manufacturing Process for Sustainability Using Design of Experiments
Authors: Khalid Marwan , Peng Qingjin
Published: January 2021

Additive manufacturing (AM) offers many advantages to make objects compared to traditional subtractive manufacturing methods. For example, complex geometries can be easily fabricated, and lightweight parts can be formed while maintaining the parts strength for the low carbon footprint, low material consumption and waste. But there are some areas for AM to improve in sustainability, reliability, productivity, robustness, material diversity, and part quality. Life-cycle assessment studies have identified that the AM printing stage has a big impact on the life-cycle sustainability of 3D printed products. AM building parameters can be properly selected to improve the sustainability of AM. This paper explores the fused deposition modeling (FDM) process parameters for sustainability to reduce the process energy and material consumption. Investigated parameters include the printing layer height, number of shells, material infilling percentage, infilling type, and building orientation. Taguchi design of experiments approach and statistical analysis tools are used to find optimal parameter settings to improve the sustainability of the FDM process. Models formulated in this research can be easily extended to other AM processes.
Investigating Trajectory-Based Combustion Control Using a Controlled Trajectory Rapid Compression and Expansion Machine
Authors: Tripathi Abhinav , Sun Zongxuan
Published: January 2021

This study presents a systematic framework for the real-time implementation of a new combustion control strategy—trajectory-based combustion control—for the operation of free piston engines (FPEs). The free piston engine is an alternative architecture of internal combustion (IC) engines, which does not have a mechanical crankshaft and hence allows extreme operational flexibility in terms of piston trajectory. The key idea of trajectory-based combustion control is to modulate the autoignition dynamics by tailoring the pressure and temperature history of the fuel–air mixture inside the combustion chamber, using the piston trajectory as the control input, for the optimal operation of the free piston engine. Here, we present the experimental investigation of trajectory-based combustion control using a novel instrument called controlled trajectory rapid compression and expansion machine (CT-RCEM) that can be used for studying a single combustion cycle of an internal combustion engine with precisely controlled initial and boundary conditions. The effect of the shape of the piston trajectory on the combustion phasing, combustion efficiency, and the indicated thermal efficiency has been found to be significant. The experimental results indicate that the trajectory-based combustion control is an effective strategy for combustion phasing control for FPE operation.
Image-Based Surface Defect Detection Using Deep Learning: A Review
Authors: Bhatt Prahar M. , Malhan Rishi K. , Rajendran Pradeep , Shah Brual C. , Thakar Shantanu , Yoon Yeo Jung , Gupta Satyandra K.
Published: January 2021

Automatically detecting surface defects from images is an essential capability in manufacturing applications. Traditional image processing techniques are useful in solving a specific class of problems. However, these techniques do not handle noise, variations in lighting conditions, and backgrounds with complex textures. In recent times, deep learning has been widely explored for use in automation of defect detection. This survey article presents three different ways of classifying various efforts in literature for surface defect detection using deep learning techniques. These three ways are based on defect detection context, learning techniques, and defect localization and classification method respectively. This article also identifies future research directions based on the trends in the deep learning area.
An Integrated Framework for Optimal Design of Complex Mechanical Products
Authors: Xue Deyi , Imaniyan David
Published: January 2021

The presently achieved research results are not effective for the design of complex mechanical products when various methods and tools in different schemes have to be employed at different design stages. A new integrated framework for the optimal design of complex mechanical products is introduced in this research considering modeling, simulation, and optimization aspects. First, a hybrid scheme is developed for the integrated modeling of complex mechanical products. In this hybrid scheme, descriptions of a generic product are modeled by an and-or tree. Feasible design candidates are created from the and-or tree through tree-based search. Geometric descriptions in a design candidate are associated with a computer-aided design (CAD) system. Second, a hybrid simulation method is developed for the evaluation of different product aspects with different simulation tools which are integrated through the hybrid modeling scheme. Simulations with geometric descriptions are conducted by analysis functions of the CAD system. Simulations with non-geometric descriptions are conducted by the knowledge-based systems. Third, a hybrid optimization method is developed to identify the optimal design of the complex mechanical product. For each design candidate, parameter optimization is conducted to obtain the optimal parameter values. The optimal design solution is identified from all design candidates through configuration optimization. A prototype system has been implemented for conceptual design and detailed design of complex mechanical products.