bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating Burning Mouth Syndrome as a Comorbidity of Atypical Odontalgia: The Impact on Pain Experiences
Authors: Tu Trang T. H. , Miura Anna , Shinohara Yukiko , Mikuzuki Lou , Kawasaki Kaoru , Sugawara Shiori , Suga Takayuki , Watanabe Takeshi , Watanabe Motoko , Umezaki Yojiro , Yoshikawa Tatsuya , Motomura Haruhiko , Takenoshita Miho , Toyofuku Akira
Published: October 2017

Objective

This study aimed (1) to investigate the differences in clinical characteristics of patients between 2 groups, those who have atypical odontalgia (AO) only and those who have AO with burning mouth syndrome (BMS), and (2) to assess the influence of psychiatric comorbidity factors on patients' experiences.

Method

Medical records and psychiatric referral forms of patients visiting the Psychosomatic Dentistry Clinic of Tokyo Medical and Dental University between 2013 and 2016 were reviewed. The final sample included 2 groups of 355 patients: those who have AO only (n = 272) and those who have AO with BMS (AO‐BMS; n = 83). Clinicodemographic variables (gender, age, comorbid psychiatric disorders, and history of headache or sleep disturbances) and pain variables (duration of illness, pain intensity, and severity of accompanying depression) were collected. Initial pain assessment was done using the Short‐Form McGill Pain Questionnaire, and depressive state was determined using the Zung Self‐Rating Depression Scale.

Results

The average age, female ratio, and sleep disturbance prevalence in the AO‐only group were significantly lower than those in AO‐BMS group. AO‐BMS patients rated overall pain score and present pain intensity significantly higher than did the AO‐only patients (P = 0.033 and P = 0.034, respectively), emphasizing sharp (P = 0.049), hot‐burning (P = 0.000), and splitting (P = 0.003) characteristics of pain. Patients having comorbid psychiatric disorders had a higher proportion of sleep disturbance in both groups and a higher proportion of depressive state in the AO‐only group.

Conclusions

AO‐BMS patients have different epidemiological characteristics, sleep quality, and pain experiences compared to AO‐only patients. The presence of psychiatric comorbidities in both groups may exacerbate sleep quality. We suggest that BMS as a comorbid oral disorder in AO patients contributes to a more intensively painful experience.
A systematic review of team formulation in clinical psychology practice: Definition, implementation, and outcomes
Authors: Geach Nicole , Moghaddam Nima G. , De Boos Danielle
Published: October 2017

Purpose

Team formulation is promoted by professional practice guidelines for clinical psychologists. However, it is unclear whether team formulation is understood/implemented in consistent ways – or whether there is outcome evidence to support the promotion of this practice. This systematic review aimed to (1) synthesize how team formulation practice is defined and implemented by practitioner psychologists and (2) analyse the range of team formulation outcomes in the peer‐reviewed literature.

Methods

Seven electronic bibliographic databases were searched in June 2016. Eleven articles met inclusion criteria and were quality assessed. Extracted data were synthesized using content analysis.

Results

Descriptions of team formulation revealed three main forms of instantiation: (1) a structured, consultation approach; (2) semi‐structured, reflective practice meetings; and (3) unstructured/informal sharing of ideas through routine interactions. Outcome evidence linked team formulation to a range of outcomes for staff teams and service users, including some negative outcomes. Quality appraisal identified significant issues with evaluation methods; such that, overall, outcomes were not well‐supported.

Conclusions

There is weak evidence to support the claimed beneficial outcomes of team formulation in practice. There is a need for greater specification and standardization of ‘team formulation’ practices, to enable a clearer understanding of any relationships with outcomes and implications for best‐practice implementations.

Practitioner points

Under the umbrella term of ‘team formulation’, three types of practice are reported: (1) highly structured consultation; (2) reflective practice meetings; and (3) informal sharing of ideas.

Outcomes linked to team formulation, including some negative outcomes, were not well evidenced.

Research using robust study designs is required to investigate the process and outcomes of team formulation practice.
Peanuts that keep aflatoxin at bay: a threshold that matters
Authors: Sharma Kiran K. , Pothana Arunima , Prasad Kalyani , Shah Dilip , Kaur Jagdeep , Bhatnagar Deepak , Chen Zhi‐Yuan , Raruang Yenjit , Cary Jeffrey W. , Rajasekaran Kanniah , Sudini Hari Kishan , Bhatnagar‐Mathur Pooja
Published: October 2017

Aflatoxin contamination in peanuts poses major challenges for vulnerable populations of sub‐Saharan Africa and South Asia. Developing peanut varieties to combat preharvest Aspergillus flavus infection and resulting aflatoxin contamination has thus far remained a major challenge, confounded by highly complex peanut–Aspergilli pathosystem. Our study reports achieving a high level of resistance in peanut by overexpressing (OE) antifungal plant defensins MsDef1 and MtDef4.2, and through host‐induced gene silencing (HIGS) of aflM and aflP genes from the aflatoxin biosynthetic pathway. While the former improves genetic resistance to A. flavus infection, the latter inhibits aflatoxin production in the event of infection providing durable resistance against different Aspergillus flavus morphotypes and negligible aflatoxin content in several peanut events/lines well. A strong positive correlation was observed between aflatoxin accumulation and decline in transcription of the aflatoxin biosynthetic pathway genes in both OE‐Def and HIGS lines. Transcriptomic signatures in the resistant lines revealed key mechanisms such as regulation of aflatoxin synthesis, its packaging and export control, besides the role of reactive oxygen species‐scavenging enzymes that render enhanced protection in the OE and HIGS lines. This is the first study to demonstrate highly effective biotechnological strategies for successfully generating peanuts that are near‐immune to aflatoxin contamination, offering a panacea for serious food safety, health and trade issues in the semi‐arid regions.
Self‐Control as a Normative Capacity
Authors: Kalis Annemarie
Published: October 2017

Recently, two apparent truisms about self‐control have been questioned in both the philosophical and the psychological literature: the idea that exercising self‐control involves an agent doing something, and the idea that self‐control is a good thing. Both assumptions have come under threat because self‐control is increasingly understood as a mental mechanism, and mechanisms cannot possibly be good or active in the required sense. However, I will argue that it is not evident that self‐control should be understood as a mechanism, suggesting that we might also argue the other way around: if we have independent reason to hold onto the idea that self‐control is inherently good and active, the conclusion might be that self‐control cannot be a mechanism. I will show that Aristotle's original analysis of self‐control actually offers grounds for both assumptions: he took there to be conceptual connections between self‐control and goodness/activity. By examining these connections, I argue that an Aristotelian approach could offer promising leads for a contemporary non‐mechanistic understanding of self‐control as a normative capacity.
Help not needed? Optimal host country regulation of expatriate NGO workers
Authors: Glazer Amihai , Jansen Hagen Rune , Rattsø Jørn
Published: October 2017

Motivated by interventions in poor countries to increase the use of local labor in foreign nongovernmental organizations (NGOs), we address the behavior of these organizations under host government regulation. We extend existing NGO models by distinguishing between local workers and expatriates. The model covers both NGO monopoly and competition in the market for donations. Assuming that NGOs maximize output, we show that regulations in the form of a quota on the number of expatriates or a work permit fee for foreigners reduces NGO output, but increases employment of locals. The optimal quota is more likely to bind in the market structure generating the highest total fundraising surplus. An optimal work permit fee is equivalent to an optimal quota in both the monopoly and duopoly cases. For both instruments, the optimal tightness of regulation is decreasing in the weight the government attaches to the public good relative to domestic incomes and in the importance of NGO output to the supply of the public good. Aggregate NGO output and the level of the public good produced could be higher with a monopoly NGO.
Achilles and patellar tendinopathy display opposite changes in elastic properties: A shear wave elastography study
Authors: Coombes B. K. , Tucker K. , Vicenzino B. , Vuvan V. , Mellor R. , Heales L. , Nordez A. , Hug F.
Published: October 2017

To compare tendon elastic and structural properties of healthy individuals with those with Achilles or patellar tendinopathy. Sixty‐seven participants (22 Achilles tendinopathy, 17 patellar tendinopathy, and 28 healthy controls) were recruited between March 2015 and March 2016. Shear wave velocity (SWV), an index of tissue elastic modulus, and tendon thickness were measured bilaterally at mid‐tendon and insertional regions of Achilles and patellar tendons by an examiner blinded to group. Analysis of covariance, adjusted for age, body mass index, and sex was used to compare differences in tendon thickness and SWV between the two tendinopathy groups (relative to controls) and regions. Tendon thickness was included as a covariate for analysis of SWV. Compared to controls, participants with Achilles tendinopathy had lower SWV at the distal insertion (Mean difference MD; 95% CI: −1.56; −2.49 to −0.62 m/s; P < .001) and greater thickness at the mid‐tendon (MD 0.19; 0.05‐0.33 cm; P = .007). Compared to controls, participants with patellar tendinopathy had higher SWV at both regions (MD 1.25; 0.40‐2.10 m/s; P = .005) and greater thickness proximally (MD 0.17; 0.06‐0.29 cm; P = .003). Compared to controls, participants with Achilles and patellar tendinopathy displayed lower Achilles tendon elastic modulus and higher patellar tendon elastic modulus, respectively. More research is needed to explore whether maturation, aging, or chronic load underlie these findings and whether current management programs for Achilles and patellar tendinopathy need to be tailored to the tendon.
The effects of topical aqueous sirolimus on tear production in normal dogs and dogs with refractory dry eye
Authors: Spatola Ronald , Nadelstein Brad , Berdoulay Andrew , English Robert V.
Published: October 2017

Purpose

To evaluate the effect of twice daily aqueous 0.02% sirolimus drops on tear production in normal dogs and dogs with refractory keratoconjunctivitis sicca (KCS).

Methods

Two groups of dogs were studied. Ten normal dogs with no signs of ocular disease were administered topical 0.02% sirolimus ophthalmic solution in right eye, and a vehicle control in the left eye twice daily for 4 weeks. Complete ophthalmic examinations, including Schirmer tear test were performed weekly. Eighteen dogs with refractoryKCSwere randomly assigned to receive 0.02% sirolumus ophthalmic solution or 0.02% tacrolimus ophthalmic solution twice daily. Complete ophthalmic examinations were was performed at 2 and 6 weeks following treatment.

Results

Tear production in the sirolimus‐treated eyes of normal dogs was greater when compared to vehicle controls with a mean difference over all time points of 3.46 mm (95%CI1.17, 5.75;P= 0.006). After 4 weeks of treatment, the mean difference was 5 mm (95%CI1.95, 8.05;P= 0.002). In dogs with refractory dry eye, 37.5% of eyes treated with sirolimus exhibited increased tear production >4 mm/min after 6 weeks of treatment, compared to 20% of eyes receiving tacrolimus (P= 0.433). One normal dog experienced topical irritation to both sirolimus and vehicle‐treatment. Side effects were not reported in any treated eyes with chronicKCS.

Conclusion

Topical 0.02% sirolimus might be an alternative treatment for canine patients with keratoconjunctivits sicca. The drug appears safe when applied topically in an aqueous suspension for up to 6 weeks. While initial results are promising, further studies are warranted.
Extracellular Cl− regulates electrical slow waves and setting of smooth muscle membrane potential by interstitial cells of Cajal in mouse jejunum
Authors: Saravanaperumal Siva Arumugam , Gibbons Simon J. , Malysz John , Sha Lei , Linden David R. , Szurszewski Joseph H. , Farrugia Gianrico
Published: October 2017

New Findings

What is the central question of this study?

The aim was to investigate the roles of extracellular chloride in electrical slow waves and resting membrane potential of mouse jejunal smooth muscle by replacing chloride with the impermeant anions gluconate and isethionate.

What is the main finding and its importance?

The main finding was that in smooth muscle cells, the resting Cl− conductance is low, whereas transmembrane Cl− movement in interstitial cells of Cajal (ICCs) is a major contributor to the shape of electrical slow waves. Furthermore, the data confirm that ICCs set the smooth muscle membrane potential and that altering Cl− homeostasis in ICCs can alter the smooth muscle membrane potential.

Intracellular Cl− homeostasis is regulated by anion‐permeable channels and transporters and contributes to excitability of many cell types, including smooth muscle and interstitial cells of Cajal (ICCs). Our aims were to investigate the effects on electrical activity in mouse jejunal muscle strips of replacing extracellular Cl− (Cl−o) with the impermeant anions gluconate and isethionate. On reducing Cl−o, effects were observed on electrical slow waves, with small effects on smooth muscle membrane voltage (Em). Restoration of Cl− hyperpolarized smooth muscle Em proportional to the change in Cl−o concentration. Replacement of 90% of Cl−o with gluconate reversibly abolished slow waves in five of nine preparations. Slow waves were maintained in isethionate. Gluconate and isethionate substitution had similar concentration‐dependent effects on peak amplitude, frequency, width at half peak amplitude, rise time and decay time of residual slow waves. Gluconate reduced free ionized Ca2+ in Krebs solutions to 0.13 mm. In Krebs solutions containing normal Cl− and 0.13 mm free Ca2+, slow wave frequency was lower, width at half peak amplitude was smaller, and decay time was faster. The transient hyperpolarization following restoration of Cl−o was not observed in W/Wv mice, which lack pacemaker ICCs in the small intestine. We conclude that in smooth muscle cells, the resting Cl− conductance is low, whereas transmembrane Cl− movement in ICCs plays a major role in generation or propagation of slow waves. Furthermore, these data support a role for ICCs in setting smooth muscle Em and that altering Cl− homeostasis in ICCs can alter smooth muscle Em.
Wireless Implantable Sensor for Noninvasive, Longitudinal Quantification of Axial Strain Across Rodent Long Bone Defects
Authors: Klosterhoff Brett S. , Ghee Ong Keat , Krishnan Laxminarayanan , Hetzendorfer Kevin M. , Chang Young-Hui , Allen Mark G. , Guldberg Robert E. , Willett Nick J.
Published: October 2017

Bone development, maintenance, and regeneration are remarkably sensitive to mechanical cues. Consequently, mechanical stimulation has long been sought as a putative target to promote endogenous healing after fracture. Given the transient nature of bone repair, tissue-level mechanical cues evolve rapidly over time after injury and are challenging to measure noninvasively. The objective of this work was to develop and characterize an implantable strain sensor for noninvasive monitoring of axial strain across a rodent femoral defect during functional activity. Herein, we present the design, characterization, and in vivo demonstration of the device’s capabilities for quantitatively interrogating physiological dynamic strains during bone regeneration. Ex vivo experimental characterization of the device showed that it possessed promising sensitivity, signal resolution, and electromechanical stability for in vivo applications. The digital telemetry minimized power consumption, enabling extended intermittent data collection. Devices were implanted in a rat 6 mm femoral segmental defect model, and after three days, data were acquired wirelessly during ambulation and synchronized to corresponding radiographic videos, validating the ability of the sensor to noninvasively measure strain in real-time. Together, these data indicate the sensor is a promising technology to quantify tissue mechanics in a specimen specific manner, facilitating more detailed investigations into the role of the mechanical environment in dynamic bone healing and remodeling processes.
Mathematical Model of the Grinding Force With Account for Blunting of Abrasive Grains of the Grinding Wheel
Authors: Ardashev Dmitrii V. , Dyakonov Aleksandr A.
Published: October 2017

The paper offers a simulation model of the grinding force with account for the current condition of the grinding wheel's working surface—the value of the abrasive grain blunting area. The model of blunting area takes into account various wear mechanisms for abrasive grains: the mechanical wear is realized on the provisions of the kinetic theory of the strength of a solid subjected to cyclic loads, and the physicochemical wear is based on the intensity of interaction between the abrasive and the treated material at grinding temperatures. The offered model of the grinding force takes into account the unsteady stochastic nature of the interaction between abrasive grains of the grinding wheel and the working surface and the intensity of workpiece material deformation resistance. The model is multifactorial and complex and can be realized by supercomputer modeling. The numerical implementation of the model was performed with application of supercomputer devices engaging parallel calculations. The performed experiments on measurement of the grinding force during circular grinding have shown a 10% convergence with the calculated values. The developed grinding force model can be used as a forecast model to determine the operational functionality of grinding wheel when used in varying technological conditions.
Performance of Diamond and Silicon Carbide Wheels on Grinding of Bioceramic Material Under Minimum Quantity Lubrication Condition
Authors: Suya Prem Anand P. , Arunachalam N. , Vijayaraghavan L.
Published: October 2017

Advanced ceramic materials like sintered and presintered zirconia are frequently used in biomedical applications, where minimum quantity lubrication (MQL) assisted grinding is required to achieve a good surface finish instead of conventional flood coolant. However, insufficient cooling and wheel clogging are the major problems that exist in the MQL grinding process, which depends upon the type of work piece material and the grinding wheel being used. The present study is to determine the performance of the grinding wheels on presintered zirconia under MQL conditions in terms of grinding forces, specific energy, surface integrity, and wheel wear. Experiments are conducted with two different types of grinding wheels as silicon carbide (SiC) and diamond grinding wheels under the same condition. The results indicated that the diamond wheel provided a better surface finish and reduced tangential force under MQL condition, compared to the conventional SIC wheel. This was due to the reduction of wheel loading in the diamond grinding wheel. The specific energy of diamond grinding wheel was reduced with higher material removal rate compared to the conventional SiC wheel. The ground surfaces generated by the diamond grinding wheel showed fine grinding marks with better surface finish. The percentage of G-ratio calculated for the diamond wheel was higher than the SiC wheel by 77%. This was due to the sliding of the grains and less wheel loading in the diamond wheel. The cost difference between the corresponding wheels was discussed to improve the productivity of the grinding process.
Steady-State Hydrodynamic Power Attenuation by Finned-Buoys
Authors: Spicer Bak A. , McCormick Michael E.
Published: October 2017

Results of experimental and computational fluid dynamics (CFD) studies conducted to compare the flow-energy-attenuating performances of two different buoy configurations are presented. A finned-body was experimentally studied in two orientations—one with a splitter and one in a 22.5 deg yaw orientation (with no splitter). The finned-buoy is designed for both wave and current attenuation; however, only the current application is discussed here. Scaled models were subjected to wind tunnel testing and CFD analyses. For this study, the steady-state drag coefficient (CD) is considered to be the performance measure. The CFD model is used to match the physical testing by utilizing the k–ω turbulence model. Reynolds numbers (based on the tip-to-tip fin diameter) approaching the drag crisis are used to evaluate the bodies of interest, both of which have an aspect ratio (draft-to-diameter) of 1.85. The finned-bodies do encounter a drag crisis (as commonly seen with a cylinder), since the fins cause the buoys to act as a bluff body. The flow structures around the bodies are examined and compared to those predicted by established theories. For the finned-body, the 22.5 deg yaw orientation is found to have a consistently higher drag than the splitter orientation. The drag enhancement is explained by two phenomena. The first is a low-pressure area located in pockets adjacent to the upstream fins. The second is the absence of the drag-crisis, due to fixed separation points at the fin tips for all Reynolds numbers.
Short Helical Combustor: Flow Control in a Combustion System With Angular Air Supply
Authors: Ariatabar Behdad , Koch Rainer , Bauer Hans-Jörg
Published: October 2017

The concept of the novel short helical combustor (SHC) was investigated in our previous work (Ariatabar et al., 2016, “Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor With Angular Air Supply,” ASME J. Eng. Gas Turbines Power, 138(3), p. 031503 and Ariatabar et al., 2017, “Short Helical Combustor: Dynamic Flow Analysis in a Combustion System With Angular Air Supply,” ASME J. Eng. Gas Turbines Power, 139(4), p. 041505). Based on the insight gained from these previous investigations, we propose a generic design improvement to address the tremendous loss of initial angular momentum as well as inhomogeneous flow and temperature field at the outlet of the SHC. In the present paper, the main features of this design are introduced. It is shown that a three-dimensional shaping of the sidewalls, the dome, and the liners can effectively counteract the suboptimal interaction of the swirl flames with these surrounding walls. As a result, the flow at the outlet of the combustor features a high angular momentum and exhibits a uniform flow angle and temperature field. The insight gained from these generic investigations, and the resulting design optimization provides a useful framework for further industrial optimization of the SHC.
Development of a Simulation Model of Transient Operation of Micro-Combined Heat and Power Systems in a Microgrid
Authors: Ippolito Francesco , Venturini Mauro
Published: October 2017

This paper presents the development of a simulation tool for modeling the transient behavior of micro-CHP (combined heat and power) systems, equipped with both thermal and electric storage units and connected with both electric and district heating grid (DHG). The prime mover (PM) considered in this paper is an internal combustion reciprocating engine (ICE), which is currently the only well-established micro-CHP technology. Different users, characterized by different demands of electric and thermal energy, both in terms of absolute value and electric-to-thermal energy ratio, are analyzed in this paper. Both summer and winter hourly trends of electric and thermal energy demand are simulated by using literature data. The results present a comprehensive energy analysis of all scenarios on a daily basis, in terms of both user demand met and energy share among system components. The transient response of the PM and the thermal energy storage (TES) is also analyzed for the two scenarios with the lowest and highest daily energy demand, together with the trend over time of the state of charge of both thermal and electric energy storage (EES).
A Comprehensive Approach for Detection, Classification, and Integrated Diagnostics of Gas Turbine Sensors
Authors: Fabio Ceschini Giuseppe , Gatta Nicolò , Venturini Mauro , Hubauer Thomas , Murarasu Alin
Published: October 2017

Anomaly detection in sensor time series is a crucial aspect for raw data cleaning in gas turbine (GT) industry. In addition to efficiency, a successful methodology for industrial applications should be also characterized by ease of implementation and operation. To this purpose, a comprehensive and straightforward approach for detection, classification, and integrated diagnostics of gas turbine sensors (named DCIDS) is proposed in this paper. The tool consists of two main algorithms, i.e., the anomaly detection algorithm (ADA) and the anomaly classification algorithm (ACA). The ADA identifies anomalies according to three different levels of filtering based on gross physics threshold application, intersensor statistical analysis (sensor voting), and single-sensor statistical analysis. Anomalies in the time series are identified by the ADA, together with their characteristics, which are analyzed by the ACA to perform their classification. Fault classes discriminate among anomalies according to their time correlation, magnitude, and number of sensors in which an anomaly is contemporarily identified. Results of anomaly identification and classification can subsequently be used for sensor diagnostic purposes. The performance of the tool is assessed in this paper by analyzing two temperature time series with redundant sensors taken on a Siemens GT in operation. The results show that the DCIDS is able to identify and classify different types of anomalies. In particular, in the first dataset, two severely incoherent sensors are identified and their anomalies are correctly classified. In the second dataset, the DCIDS tool proves to be capable of identifying and classifying clustered spikes of different magnitudes.
Exploiting Microstructural Instabilities in Solids and Structures: From Metamaterials to Structural Transitions
Authors: Kochmann Dennis M. , Bertoldi Katia
Published: October 2017

Instabilities in solids and structures are ubiquitous across all length and time scales, and engineering design principles have commonly aimed at preventing instability. However, over the past two decades, engineering mechanics has undergone a paradigm shift, away from avoiding instability and toward taking advantage thereof. At the core of all instabilities—both at the microstructural scale in materials and at the macroscopic, structural level—lies a nonconvex potential energy landscape which is responsible, e.g., for phase transitions and domain switching, localization, pattern formation, or structural buckling and snapping. Deliberately driving a system close to, into, and beyond the unstable regime has been exploited to create new materials systems with superior, interesting, or extreme physical properties. Here, we review the state-of-the-art in utilizing mechanical instabilities in solids and structures at the microstructural level in order to control macroscopic (meta)material performance. After a brief theoretical review, we discuss examples of utilizing material instabilities (from phase transitions and ferroelectric switching to extreme composites) as well as examples of exploiting structural instabilities in acoustic and mechanical metamaterials.
Vortex Dynamics in the Wake of Three Generic Types of Freestream Turbines
Authors: Boudreau Matthieu , Dumas Guy
Published: October 2017

An analysis of the vortex dynamics in the wake of three different freestream turbine concepts is conducted to gain a better understanding of the main processes affecting the energy recovery in their wakes. The turbine technologies considered are the axial-flow turbine (AFT), the crossflow turbine (CFT), also known as the H-Darrieus turbine, and the oscillating-foil turbine (OFT). The analysis is performed on single turbines facing a uniform oncoming flow and operating near their optimal efficiency conditions at a Reynolds number of 107. Three-dimensional (3D) delayed detached-eddy simulations (DDES) are carried out using a commercial finite volume Navier–Stokes solver. It is found that the wake dynamics of the AFT is significantly affected by the triggering of an instability, while that of the CFT and the OFT are mainly governed by the mean flow field stemming from the tip vortices' induction.
Inducer and Centrifugal Pump Contributions to the Rotordynamic Fluid Forces Acting on a Space Turbopump
Authors: Pace Giovanni , Valentini Dario , Pasini Angelo , Torre Lucio , Hadavandi Ruzbeh , d'Agostino Luca
Published: October 2017

The fluid-induced rotordynamic forces acting on a whirling space turbopump composed by an inducer and a radial impeller have been compared to the same forces measured on each single component of the turbomachine (i.e., on the inducer and on the radial impeller). The experimental campaign has been carried out in cold water at design and off-design conditions (80%, 100%, and 120% of the design flow rate) both in noncavitating (NC) and cavitating regimes. The paper illustrates the different trends of the rotordynamic forces on the axial and radial pumps and highlights their contributions on the overall turbomachine. At positive whirl ratios, the behavior of the inducer is dominant while, at negative ones, both the pumps show the same trends in such a way that the overall behavior is roughly the sum of each single component.
Optimization of Trailing-Edge Serrations to Reduce Open-Rotor Tonal Interaction Noise
Authors: Jaron Robert , Moreau Antoine , Guérin Sébastien , Schnell Rainer
Published: October 2017

A major source of contra-rotating open rotor (CROR) tonal noise is caused by the interaction of the front-rotor (FR) wakes with the aft-rotor blades. Inspired by chevron nozzles, which increase the mixing process in jet shear layers, serrations are implemented at the FR trailing-edge in order to increase the wake mixing and thus reduce the tones. The depth and width of the serrations are optimized with a multi-objective, metamodel-assisted evolutionary algorithm. For each member, a steady-state Reynolds-averaged Navier–Stokes (RANS) simulation is performed, which is coupled with an analytical noise prediction method in order to evaluate the noise reduction due to the serrations. The results confirm that tonal interaction noise can be reduced by means of trailing-edge serrations. It is found that the major noise reduction mechanism for wake interaction is attributed to increased destructive interferences occurring in spanwise direction. The tonal noise generated through the interaction of the rear rotor (RR) potential field with the FR trailing edge is also slightly reduced because of the circumferential and axial shift of the serrated trailing edge. Furthermore, the present study demonstrates the feasibility of performing an acoustic optimization with a hybrid approach that predicts the noise analytically and extracts the aerodynamic input data from a steady-state RANS flow solution.
Diamond Wheel Dressing: A Comprehensive Review
Authors: Ding Wenfeng , Li Haonan , Zhang Liangchi , Xu Jiuhua , Fu Yucan , Su Honghua
Published: October 2017

This paper provides a comprehensive review on the dressing techniques of diamond grinding wheels. The common techniques with different tools were discussed in detail, which included the bonded SiC and diamond abrasive tools, loose abrasives, soft-elastic abrasive belts, and profiled diamond wheels. Meanwhile, laser dressing, electrical discharge dressing (EDD), and electrolytic in-process dressing (ELID) were also addressed. Some critical problems in the above dressing techniques were then analyzed and summarized for further investigation.
Experimental Verification of Dynamic Behavior of a Capsule-Type Modular Machine Tool for Multifunctional Processes
Authors: Lee Sungcheul , Park Jong-Kweon
Published: October 2017

A capsule-type modular machine tool was developed, which was capable of multifunctional processes with a single setup. This mechanism was designed according to the concept of a reconfigurable machine tool (RMT), which can transform from a machining center to a lathe, and is capable of multiple functional processes, such as laser, milling, and grinding processes. After addressing the kinematics of the machine, a static structural analysis was performed and some ribs were added to enhance the stiffness. A frequency response function (FRF) simulation was conducted on the modified machine and natural frequencies were determined to avoid resonance in processing. Then, an FRF test was performed to find the actual natural frequencies, to confirm the simulation results. After investigating the natural frequencies, high-speed machining was performed to make 300 μm sized patterns.
Mixed H1 and H2 Forced Convection in a Rectangular Duct
Authors: Wang C. Y.
Published: October 2017

The constant flux forced convection in a rectangular duct with two highly conductive (H1) walls and two poorly conductive (H2) walls is studied for the first time. This mixed problem is solved analytically using a modified single series method. The Nusselt number is determined for various duct aspect ratios. Depending on the aspect ratio, hot spots and cold spots may occur either on the H1 walls or on the H2 walls.
Direct Simulation of Interstitial Heat Transfer Coefficient Between Paraffin and High Porosity Open-Cell Metal Foam
Authors: Yao Yuanpeng , Wu Huiying , Liu Zhenyu
Published: October 2017

The interstitial heat transfer coefficient (IHTC) is a key parameter in the two-energy equation model usually employed to investigate the thermal performance of high porosity open-cell metal foam/paraffin composite phase change material. Due to the existence of weak convection of liquid paraffin through metal foam during phase change process, the IHTC should be carefully determined for a low Reynolds number range (Re = 0–1), which however has been rarely addressed in the literature. In this paper, a direct simulation at foam pore scale is carried out to determine the IHTC between paraffin and metal foam at Re = 0–1. For this purpose, the cell structures reflecting realistic metal foams are first constructed based on the three-dimensional (3D) Weaire–Phelan foam cell to serve as the representative elementary volume (REV) of metal foam for direct simulation. Then, by solving the Navier–Stokes equations and energy equation for the REV, the influences of Reynolds number (Re), Prandtl number (Pr), foam porosity (ε), and pore density (PPI) on the dimensionless IHTC, i.e., the Nusselt number Nuv, are investigated. According to the numerical results, a correlation of Nuv at Re = 0–1 is proposed for metal foam/paraffin composite material, which covers both diffusion-dominated interstitial heat transfer region (Re ≤ 0.1) and convection-dominated interstitial heat transfer region (0.1 < Re ≤ 1). Finally, the applicability of this correlation in the two-energy equation model for solid–liquid phase change of paraffin in metal foam is validated by comparing the model predicted melting front with that of experimental observations made in this study. It is found that the IHTC correlation proposed in this study can be used in the two-energy equation model for well predicting the phase change process of paraffin in metal foam.
Elastic and Plastic Microscopic Undulation on the Surface of Polycrystalline Pure Titanium Under Tension
Authors: Tada Naoya , Uemori Takeshi , Nakata Toshiya
Published: October 2017

Commercial pure titanium has been widely used in the aerospace, chemical, and biomedical industries because of its light weight, high corrosion resistance, high strength, high heat resistance, and good biocompatibility. Pure titanium takes the form of a hexagonal closed-pack structure with anisotropic elasticity and plasticity, with most of its components being polycrystalline aggregates having different crystal orientations. Small mechanical loading under elastic conditions therefore always induces inhomogeneous microscopic deformation, and the resulting inhomogeneity brings about various defects such as inhomogeneous plastic deformation, microcracking, and necking. It is therefore important to investigate the microscopic inhomogeneous deformation under elastic and plastic conditions. In this study, a plate specimen of commercial pure titanium was subjected to a tensile test on the stage of a digital holographic microscope (DHM), and the microscopic deformation of grains in the specimen under elastic and plastic conditions were observed and measured. During the test, the grains’ height distribution was measured in a fixed area on the specimen’s surface at each tensile loading step, and the correlation between height distributions at different loads was examined. We found from the measurements that each grain shows a different height change even under elastic conditions with a small load. This inhomogeneous height change was enhanced as the load was increased to plastic conditions. A strong correlation between the height changes under elastic and plastic conditions was also found. This result suggests that the microscopic deformation experienced under plastic conditions is predictable from that observed under elastic conditions.
Effect of Fuel Reactivity on Ignitability and Combustion Phasing in a Heavy-Duty Engine Simulation for Mixing-Controlled and Partially Premixed Combustion
Authors: Voice Alexander K. , Kumar Praveen , Zhang Yu
Published: October 2017

Light-end fuels have recently garnered interest as potential fuel for advanced compression ignition (CI) engines. This next generation of engines, which aim to combine the high efficiency of diesel engines with the relative simplicity of gasoline engines, may allow engine manufacturers to continue improving efficiency and reducing emissions without a large increase in engine and aftertreatment system complexity. In this work, a 1D heavy-duty engine model was validated with measured data and then used to generate boundary conditions for the detailed chemical kinetic simulation corresponding to various combustion modes and operating points. Using these boundary conditions, homogeneous simulations were conducted for 242 fuels with research octane number (RON) from 40 to 100 and sensitivity (S) from 0 to 12. Combustion phasing (CA50) was most dependent on RON and less dependent on S under all conditions. Both RON and S had a greater effect on combustion phasing under partially premixed compression ignition (PPCI) conditions (19.3 deg) than under mixing-controlled combustion (MCC) conditions (5.8 deg). The effect of RON and S were also greatest for the lowest reactivity (RON > 90) fuels and under low-load conditions. The results for CA50 reflect the relative ignition delay for the various fuels at the start-of-injection (SOI) temperature. At higher SOI temperatures (>950K), CA50 was found to be less dependent on fuel sensitivity due to the convergence of ignition delay behavior of different fuels in the high-temperature region. Combustion of light-end fuels in CI engines can be an important opportunity for regulators, consumers, and engine-makers alike. However, selection of the right fuel specifications will be critical in development of the combustion strategy. This work, therefore, provides a first look at quantifying the effect of light-end fuel chemistry on advanced CI engine combustion across the entire light-end fuel reactivity space and provides a comparison of the trends for different combustion modes.
Electrocatalytically Active Niobium Sulfide Modified Carbon Cloth for Lithium–Sulfur Batteries
Authors: Arava Leela Mohana Reddy , Gopalakrishnan Deepesh , Lee Andrew
Published: October 2017

We report a simple novel annealing technique for the synthesis of NbS2 nanoflakes. The synthesized NbS2 flakes were characterized well with different spectroscopic and microscopic techniques and confirmed they are in 3R-NbS2 polymorph structure, which is semiconducting in nature. Later, they were successfully deposited onto carbon cloth (CC) and tested for Li–S cell. Lithium–sulfur batteries suffer from polysulfide (PS) shuttling effects which hinder the performance of the cell. High capacity fade, slow redox kinetics, and the low cyclability of cells are just some of the many problems caused by the shuttling effect that hinder the viability of the battery. Herein, we utilized the catalytic nature of NbS2 along with the high conductivity of CC for better PS adsorption, their liquid to solid conversion, fast PS redox kinetics which substantially enhanced the overall Li–S performance.
Nonuniform Jet Array Impingement on a Curved Surface
Authors: Hossain Jahed , Harrington John , Wang Wenping , Kapat Jayanta , Thorpe Steven , Maurer Michael
Published: October 2017

Experiments to investigate the effect of varying jet hole diameter and jet spacing on heat transfer and pressure loss from jet array impingement on a curved target surface are reported. The jet plate configurations studied have varying hole diameters and geometric spacing for spatial tuning of the heat transfer behavior. The configuration also includes a straight section downstream of the curved section, where the effect on heat transfer and pressure loss is also investigated. The jet plate holes are sharp-edged. A steady-state measurement technique utilizing temperature-sensitive paint (TSP) was used on the target surface to obtain local heat transfer coefficients. Pressure taps placed on the sidewall and jet plate of the channel were used to evaluate the flow distribution in the impingement channel. For all configurations, spent air is drawn out in a single direction which is tangential to the target plate curvature. First row jet Reynolds numbers ranging from 50,000 to 160,000 are reported. Further tests were performed to evaluate several modifications to the impingement array. These involve blocking several downstream rows of jets, measuring the subsequent shifts in the pressure and heat transfer data, and then applying different turbulator designs in an attempt to recover the loss in the heat transfer while retaining favorable pressure loss. It was found that by using W-shaped turbulators, the downstream surface average Nusselt number increases up to ∼13% as compared with a smooth case using the same amount of coolant. The results suggest that by properly combining impingement and turbulators (in the post impingement section), higher heat transfer, lower flow rate, and lower pressure drop are simultaneously obtained, thus providing an optimal scenario.
Aerodynamic Optimization of the High Pressure Turbine and Interstage Duct in a Two-Stage Air System for a Heavy-Duty Diesel Engine
Authors: Khairuddin Uswah B. , Costall Aaron W.
Published: October 2017

Turbochargers reduce fuel consumption and CO2 emissions from heavy-duty internal combustion engines by enabling downsizing and downspeeding through greater power density. This requires greater pressure ratios and thus air systems with multiple stages and interconnecting ducting, all subject to tight packaging constraints. This paper considers the aerodynamic optimization of the exhaust side of a two-stage air system for a Caterpillar 4.4 l heavy-duty diesel engine, focusing on the high pressure turbine (HPT) wheel and interstage duct (ISD). Using current production designs as a baseline, a genetic algorithm (GA)-based aerodynamic optimization process was carried out separately for the wheel and duct components to evaluate seven key operating points. While efficiency was a clear choice of cost function for turbine wheel optimization, different objectives were explored for ISD optimization to assess their impact. Optimized designs are influenced by the engine operating point, so each design was evaluated at every other engine operating point, to determine which should be carried forward. Prototypes of the best compromise high pressure turbine wheel and ISD designs were manufactured and tested against the baseline to validate computational fluid dynamics (CFD) predictions. The best performing high pressure turbine design was predicted to show an efficiency improvement of 2.15% points, for on-design operation. Meanwhile, the optimized ISD contributed a 0.2% and 0.5% point efficiency increase for the HPT and low pressure turbine (LPT), respectively.
Analytical Modeling of the Vibro-Acoustic Response of a Double-Walled Cylindrical Shell With Microperforation Excited by Turbulent Boundary Layer Pressure Fluctuations
Authors: Zhang Qunlin , Mao Yijun , Qi Datong
Published: October 2017

An analytical model is developed to investigate the vibro-acoustic response of a double-walled cylindrical shell with the inner wall perforated when excited by the external turbulent boundary layer (TBL) pressure fluctuations. The shell motion is governed by the Donnell’s thin shell theory, and the mean particle velocity model is employed to describe the boundary condition between the microperforated shell and fluid media. Numerical results indicate that the transmission loss (TL) for the configuration of microperforating the inner wall could be larger than that for the conventional solid double-walled cylindrical shell with and without the core of porous material over a wide frequency range. Comparison between TL results with excitations from the TBL and the acoustic diffuse field (ADF) shows that with the thought of microperforating the inner shell, to reduce the acoustical excitation will be of more importance than the flow excitation over the ring frequency for a quiet interior space. Parametric studies illustrate that the perforation ratio is the main factor affecting the sound insulation performance through the total reactance.
Pulsation-Amplitude-Dependent Flame Dynamics of High-Frequency Thermoacoustic Oscillations in Lean-Premixed Gas Turbine Combustors
Authors: Berger Frederik M. , Hummel Tobias , Schuermans Bruno , Sattelmayer Thomas
Published: October 2017

This paper presents the experimental investigation of pulsation-amplitude-dependent flame dynamics associated with transverse thermoacoustic oscillations at screech level frequencies in a generic gas turbine combustor. Specifically, the flame behavior at different levels of pulsation amplitudes is assessed and interpreted. Spatial dynamics of the flame are measured by imaging the OH⋆ chemiluminescence (CL) signal synchronously to the dynamic pressure at the combustor's face plate. First, linear thermoacoustic stability states, modal dynamics, and flame-acoustic phase relations are evaluated. It is found that the unstable acoustic modes converge into a predominantly rotating character in the direction of the mean flow swirl. Furthermore, the flame modulation is observed to be in phase with the acoustic pressure at all levels of the oscillation amplitude. Second, distributed flame dynamics are investigated by means of visualizing the mean and oscillating heat release distribution at different pulsation amplitudes. The observed flame dynamics are then compared against numerical evaluations of the respective amplitude-dependent thermoacoustic growth rates, which are computed using analytical models in the fashion of a noncompact flame-describing function. While results show a nonlinear contribution for the individual growth rates, the superposition of flame deformation and displacement balances out to a constant flame driving. This latter observation contradicts the state-of-the-art perception of root-causes for limit-cycle oscillations in thermoacoustic gas turbine systems, for which the heat release saturates with increasing amplitudes. Consequently, the systematic observations and analysis of amplitude-dependent flame modulation shows alternative paths to the explanation of mechanisms that might cause thermoacoustic saturation in high frequency systems.