bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of screening for geriatric conditions and advance care planning at the Medicare Annual Wellness Visit
Authors: Nothelle Stephanie K. , McGuire Maura , Boyd Cynthia M. , Colburn Jessica L.
Published: November 2021

Background

The Medicare Annual Wellness Visit (AWV) requires screening for geriatrics conditions and can include advance care planning (ACP). We examined (1) the prevalence of positive screens for falls, cognitive impairment, and activities of daily living (ADL) impairment, (2) referrals/orders generated potentially in response, and (3) the increase in ACP among those with two AWVs.

Methods

In this retrospective analysis, we used electronic medical record data from a Mid‐Atlantic group ambulatory practice. We included adults age > 65 who had ≥1 AWV (n = 16,176) in years 2014–2017. Analyses on high‐risk prescribing were limited to those (n = 13,537) with ≥3 months of follow up and ACP to those (n = 9097) with two AWVs. We used responses from the AWV health risk questionnaire to identify screening status for falls, cognitive and ADL impairment and whether an older adult had an ACP. For each screen we identified orders/referrals placed potentially in response (e.g., physical therapy for falls). High‐risk medications were based on the 2019 Beers Criteria.

Results

Positive screening rates were 38% for falls, 23% for cognition, and 32% for ADL impairment. The adjusted odds of having an order placed potentially in response to the screening were 1.8 (95% CI 1.6–2.0) for falls, 1.4 (1.3–1.7) for cognition, 2.8 (2.4–3.3) for ADL impairment. The adjusted odds of a high‐risk prescription in the 3 months after a positive screen were 2.1 (95% CI 1.8–2.5) for falls and 1.9 (95% CI 1.6–2.4) for cognition. Of those with two AWVs, 48% had an ACP at the first AWV. Among the remaining 52% with no ACP at the first AWV, the predicted probability of having an ACP at the second AWV was 0.22 (95% CI 0.18–0.25).

Conclusion

Our results may indicate positive effects of screening for geriatric conditions at the AWV, and highlight opportunities to improve geriatrics care related to prescribing and ACP.
ɑO‐Conotoxin GeXIVA isomers modulate N‐type calcium (CaV2.2) channels and inwardly‐rectifying potassium (GIRK) channels via GABAB receptor activation
Authors: Yousuf Arsalan , Wu Xiaosa , Bony Anuja R. , Sadeghi Mahsa , Huang Yen‐Hua , Craik David J. , Adams David J.
Published: November 2021

αO‐Conotoxin GeXIVA is a 28 amino acid peptide derived from the venom of the marine snail Conus generalis. The presence of four cysteine residues in the structure of GeXIVA allows it to have three different disulfide isomers, that is, the globular, ribbon or bead isomer. All three isomers are active at α9α10 nicotinic acetylcholine receptors, with the bead isomer, GeXIVA[1,2], being the most potent and exhibiting analgesic activity in animal models of neuropathic pain. The original report of GeXIVA activity failed to observe any effect of the isomers on high voltage‐activated (HVA) calcium channel currents in rat dorsal root ganglion (DRG) neurons. In this study, we report, for the first time, the activity of globular GeXIVA[1,3] at G protein‐coupled GABAB receptors (GABABR) inhibiting HVA N‐type calcium (Cav2.2) channels and reducing membrane excitability in mouse DRG neurons. The inhibition of HVA Ba2+ currents and neuroexcitability by GeXIVA[1,3] was partially reversed by the selective GABABR antagonist CGP 55845. In transfected HEK293T cells co‐expressing human GABABR1 and R2 subunits and Cav2.2 channels, both GeXIVA[1,3] and GeXIVA[1,4] inhibited depolarization‐activated Ba2+ currents mediated by Cav2.2 channels, whereas GeXIVA[1,2] had no effect. The effects of three cyclized GeXIVA[1,4] ribbon isomers were also tested, with cGeXIVA GAG being the most potent at human GABABR‐coupled Cav2.2 channels. Interestingly, globular GeXIVA[1,3] also reversibly potentiated inwardly‐rectifying K+ currents mediated by human GIRK1/2 channels co‐expressed with GABABR in HEK293T cells. This study highlights GABABR as a potentially important receptor target for the activity of αO‐conotoxin GeXIVA to mediate analgesia.

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EU‐China trade and intra‐EU trade: Substitute or complementary?
Authors: Chen Huiyao , Luo Changyuan , Renard Mary‐Françoise , Sun Shiyi
Published: November 2021

This paper examines how EU‐China trade affected intra‐EU trade. The estimation shows that when a country's share of trade with China increased, its share of trade with EU partners declined. This suggests that stronger trade links with China resulted in weaker trade links among EU countries. Furthermore, the “disintegration” effect of the export to China was stronger than that of import from China, meaning that the influence of China as an export destination was greater than that of China as a source of import. An extended analysis shows that the disintegration effect was most strongly felt in trade links among EU core countries, less strongly felt in trade links between EU core and periphery countries, and least strongly felt in trade links among EU periphery countries. In comparison, we find that EU import from the United States and India significantly weakened and strengthened intra‐EU trade, respectively. Estimation results using product level data demonstrate that the effects depend on the types of products we are concerned with. Whether using gross value or value added, the conclusions remain valid.
Population‐based approaches for monitoring the nurturing care environment for early childhood development: A scoping review
Authors: Pedroso Jéssica , dos Anjos Coelho Kubo Stefanie Eugênia , Silva Priscila Olin , Ferreira de Castro Gabriel , Pimentel Juliana Lopes , Pérez‐Escamilla Rafael , Gubert Muriel Bauermann , Buccini Gabriela
Published: November 2021

Selecting indicators to monitor nurturing care (NC) environments that support decision‐making and guide the implementation of integrated early childhood development (ECD) programmes has become a priority globally. Several population‐based approaches have been attempted to create a set of indicators or a composite index methodology to measure the NC environment using existing secondary data. However, they have not been systematized. Our scoping review aimed to analyse the population‐based approaches for monitoring the domains of the NC (e.g. good health, adequate nutrition, responsive caregiving, security and safety, and opportunities for early learning). ECD experts, peer‐reviewed, and grey literature were systematically searched with no year or language restrictions. Data extraction used a standard predefined protocol. Thirty‐two population‐based approaches were identified. Most approaches were composed of a set of indicators (53.1%, n = 17) versus composite indexes (46.9%, n = 15) and had the country as their unit of analysis (68.8%, n = 22). Twenty‐seven approaches were applied in middle‐income countries (84.4%) and thirteen in low‐income countries (40.6%). Four approaches were guided by the NC framework (12.5%), and 56.3% (n = 18) did not include any indicator representing responsive caregiving. NC indicators (n = 867) were sorted into 100 groups of indicators. Twenty of the 32 approaches had some kind of methodological validation (62.5%). We identified six methodological challenges to build a population‐based approach. Standardized methods for selecting and validating indicators, and coordinated efforts to share findings/data with stakeholders should be prioritized. Given the great variability in methods and indicators used to measure NC environments, valid approaches should be flexible to work well across different contexts.
Effect of LSD1 on osteogenic differentiation of human periodontal ligament stem cells in periodontitis
Authors: Shao Qing , Liu ShiWei , Zou Chen , Ai Yilong
Published: November 2021

Objective

Periodontitis is a chronic inflammation of periodontal tissues. This study is expected to assess the effect of LSD1 on the osteogenic differentiation of hPDLSCs in periodontitis.

Methods

hPDLSCs were separated, cultivated, and identified, and then treated by LPS to induce inflammatory microenvironment and subjected to osteogenic differentiation. Subsequently, LSD1 expression was determined, and then silenced to assess its effect on hPDLSCs. Next, the binding relation between LSD1 and miR‐590‐3p was analyzed. miR‐590‐3p expression was detected and then overexpressed to evaluate its role in hPDLSCs in periodontitis. Afterward, the relation between LSD1 and OSX was analyzed. H3K4me2 level and OSX transcription were measured, and the role of H3K4me2 was determined. Additionally, the role of OSX in hPDLSCs was verified.

Results

LSD1 was poorly expressed after osteogenic differentiation of hPDLSCs while it was rescued upon LPS induction. The osteogenic differentiation of hPDLSC in periodontitis was strengthened upon LSD1 downregulation. Besides, miR‐590‐3p targeted LSD1 transcription, and LSD1 inhibited OSX transcription via H3K4me2 demethylation. miR‐590‐3p overexpression improved osteogenic differentiation of hPDLSCs in periodontitis. But this improvement was annulled by OSX inhibition.

Conclusion

miR‐590‐3p targeted LSD1 transcription and upregulated H3K4me2 methylation to promote OSX transcription, thereby encouraging osteogenic differentiation of hPDLSCs in periodontitis.
Optimal Scale‐Up of HIV Treatment Programs in Resource‐Limited Settings Under Supply Uncertainty
Authors: Deo Sarang , Mehta Sameer , Corbett Charles J.
Published: November 2021

This study is motivated by the challenges faced by clinics in sub‐Saharan Africa in allocating scarce and unreliable supply of antiretroviral drugs (ARVs) among a large pool of eligible patients. Existing discussion of ARV allocation is focused on qualitative rules for prioritizing certain socioeconomic and demographic patient segments over others at the national level. However, such prioritization rules are of limited utility in providing quantitative guidance on scaling up of treatment programs at individual clinics. In this study, we take the perspective of a clinic administrator whose objective is to maximize the quality‐adjusted survival of the entire patient population in its service area by allocating scarce and unreliable supply of drugs among two activities: initiating treatment for untreated patients and continuing treatment for previously treated patients. The key trade‐off underlying this allocation decision is between the marginal health benefit obtained by initiating an untreated patient on treatment and that obtained by avoiding treatment interruption of a treated patient. This trade‐off has not been explicitly studied in the clinical literature, which focuses either on the incremental value obtained from initiating treatment (over no treatment) or on the value of providing continuous treatment (over interrupted treatment) but not on the difference of the two. We cast the clinic's problem as a stochastic dynamic program and provide a partial characterization of the optimal policy, which consists of dynamic prioritization of patient segments and is characterized by state‐dependent thresholds. We use this structure of the optimal policy to design a simpler Two‐Period heuristic and show that it substantially outperforms the Safety‐Stock heuristic, which is commonly used in practice. In our numerical experiments based on realistic parameter values, the performance of the Two‐Period heuristic is within 4% of the optimal policy whereas that of the Safety‐Stock heuristic can be as much as 20% lower than that of the optimal policy. Our model can serve as a basis for developing a decision support tool for clinics to design their ARV treatment program scale‐up plans.
Habitat selection in a southern Lake Sturgeon population: implications of temporal, spatial, and ontogenetic variation for restoration
Authors: Moore Michael J. , Paukert Craig P. , Owens Seth P. , Moore Travis L.
Published: November 2021

Successful species reintroduction requires restoration of receiving habitats to support growth, survival, and reproduction that reverse the initial causes of decline. Little is known about whether present habitat conditions can support all life stages of reintroduced southern Lake Sturgeon populations that were possibly extirpated by the mid‐1900s due to overharvest and habitat degradation. Therefore, we conducted a telemetry study to assess annual adult and subadult and overwinter age‐0 Lake Sturgeon habitat selection and suitability in two Missouri River U.S. tributaries near the southern edge of the species range. Spring habitat selection models were unable to define spawning habitat criteria, but criteria from other studies suggest that substrate and depths for spawning are suitable in both rivers. In the summer and winter, adult and subadult Lake Sturgeon exhibited strong selection for pools greater than 8 m deep, which comprised less than 5% of our study streams. Habitat selection in the fall and winter by age‐0 Lake Sturgeon differed from adults with age‐0s selecting shallower habitats both rivers and swifter current velocities in the Gasconade River. General habitat patterns persisted for both life stages in each river regardless of habitat availability, suggesting specialized habitat requirements in southern Lake Sturgeon that differ from previously studied populations further north. These results may be used to direct sampling for validation of reproduction and restoration of not only spawning habitats, but age‐0 and summer and winter refugia that may be potential restoration bottlenecks for southern Lake Sturgeon populations.
An account of the exporter wage gap: Wage structure and composition effects across the wage distribution
Authors: Groizard José L. , Oliver Xisco , Sard María
Published: November 2021

Globalisation is a prominent driver of wage inequality in advanced economies, and wage differentials paid by the exporter vis‐à‐vis domestically oriented firms play an unmistakable role. In this paper, we measure and decompose the exporter wage gap into several explanatory components by estimating counterfactual distributions for the Spanish economy between 2006 and 2014. To measure the exporter wage gap, an extended Mincer‐type wage equation is estimated along different points of the wage distribution using Unconditional Quantile Regression. Then, we apply the technique of Fortin, Lemieux and Firpo to decompose the exporter wage gap. We find that workers earn higher wages if they work in an exporting firm and that these differences are not constant across the wage distribution: they are greater for middle and middle‐high wages and narrower at the extremes of the distribution. Moreover, the exporter wage gap increased during and after the Great Recession. Characteristics, especially those related to firm and job heterogeneity, play an important role in explaining the gap, mainly in the upper part of the wage distribution. Though in the lower part, wage structure also plays an important role. With some variation across periods, there is a consistent pattern in which occupation, sector and firm size lead to an exporter wage premium resulting in a more unequal wage distribution. These factors are partially compensated by other factors, such as the collective bargaining system.
Factors Associated With the Resilience of Nurses During the COVID‐19 Pandemic
Authors: Alameddine Mohamad , Clinton Michael , Bou‐Karroum Karen , Richa Nathalie , Doumit Myrna A. A.
Published: November 2021

Background

The delivery of health care during the COVID‐19 outbreak imposed significant challenges on the global nursing workforce and placed them at a higher risk of occupational burnout and turnover. In Lebanon, the pandemic hit when nurses were already struggling with an economic collapse caused by government failures. Resilience may play a protective factor against adversity and enable effective adaption to the burden of the pandemic.

Aims

To determine the level of resilience in the nursing workforce and its relationship to burnout, intention to quit, and perceived COVID‐19 risk.

Methods

A cross‐sectional study was employed among all registered nurses affiliated with the Order of Nurses in Lebanon and working in patient care positions in hospitals. The online survey questionnaire incorporated the Connor–Davidson Resilience Scale and the Copenhagen Burnout Inventory. Quartile scores were used to differentiate levels of resilience and burnout. Multiple logistic regression identified variables significantly associated with resilience.

Results

Five‐hundred and eleven nurses responded to the questionnaire. Nurses had a moderate level of resilience (M  = 72 ± 13.5). In multivariate analyses, being male (OR = 3.67; 95% CI [1.46, 9.22]; p = .006) and having a master’s degree (OR = 4.082; 95% CI [1.49, 11.20]; p = .006) were independently associated with higher resilience. Resilience levels decreased with higher personal burnout (OR = 0.12; 95% CI [0.03, 0.435]; p = .001), work‐related burnout (OR = 0.14; 95% CI [0.04, 0.46]; p = .001), and client‐related burnout rates (OR = 0.09; 95% CI [0.03, 0.34]; p < .001). Nurses reporting the intention to quit their job had lower resilience scores (OR = 0.20; 95% CI [0.04, 0.88]; p = .033).

Linking Evidence to Action

Nursing stakeholders must introduce programs to regularly assess and enhance the resilience of nurses especially at time of crisis. Such programs would protect nurses from the perils of burnout and enhance their retention during times when they are most needed. Protecting nurses from burnout is an ethical imperative as well as an operational requirement.
The Sulawesi Thrush (Cataponera turdoides; Aves: Passeriformes) belongs to the genus Turdus
Authors: Reeve Andrew Hart , Blom Mozes P. K. , Zahl Marki Petter , Batista Romina , Olsson Urban , Edmark Veronica Nyström , Irestedt Martin , Jønsson Knud Andreas
Published: November 2021

The Asian and Australo‐Papuan faunas meet and intermix across the islands of Wallacea. Untangling the origins and relationships of the species inhabiting these archipelagos is an ongoing project that has lasted for well over a century. In recent years, molecular phylogenetic studies have made considerable progress in clarifying the affinities of enigmatic Wallacean taxa, but taxonomic riddles remain, even in groups as well studied as birds. Such is the case with Sulawesi Thrush Cataponera turdoides, a scarce and elusive montane songbird whose taxonomic placement has remained controversial since its description. To determine the evolutionary relationships of this monotypic genus, we obtained a museum specimen and employed whole‐genome resequencing to generate a multi‐locus dataset. Phylogenetic analyses were performed using UCEs, and individual mitochondrial and nuclear genes. We show that Cataponera is a true thrush of the large and geographically widespread genus Turdus. It belongs to a clade predominantly composed of migratory Palearctic species, but has no close relatives within that group. Sulawesi Thrush is one of only two members of the genus Turdus known to have crossed Wallace's Line to form resident populations.
Graphics Processing Unit-Based Element-by-Element Strategies for Accelerating Topology Optimization of Three-Dimensional Continuum Structures Using Unstructured All-Hexahedral Mesh
Authors: Ratnakar Shashi Kant , Sanfui Subhajit , Sharma Deepak
Published: November 2021

Topology optimization has been successful in generating optimal topologies of various structures arising in real-world applications. Since these applications can have complex and large domains, topology optimization suffers from a high computational cost because of the use of unstructured meshes for discretization of these domains and their finite element analysis (FEA). This article addresses this challenge by developing three graphics processing unit (GPU)-based element-by-element strategies targeting unstructured all-hexahedral mesh for the matrix-free precondition conjugate gradient (PCG) finite element solver. These strategies mainly perform sparse matrix multiplication (SpMV) arising with the FEA solver by allocating more compute threads of GPU per element. Moreover, the strategies are developed to use shared memory of GPU for efficient memory transactions. The proposed strategies are tested with solid isotropic material with penalization (SIMP) method on four examples of 3D structural topology optimization. Results demonstrate that the proposed strategies achieve speedup up to 8.2 × over the standard GPU-based SpMV strategies from the literature.
A Disk-Type Magneto-Rheologic Fluid Damper for Rotor System Vibration Control
Authors: Zhu Changsheng , Robb David A. , Ewins David J.
Published: November 2021

Using the particular characteristic of a magneto-rheological (MR) fluid, i.e., a rapid, reversible and dramatic change in its rheological properties produced by an external magnetic field, a simple disk-type MR fluid damper based on shear operation mode is presented in this paper. The magnetic field of the disk-type MR fluid damper is analyzed by the finite element method in order to show if the design is reasonable. The effect of excitation current in the coil on the magnetic flux density in the axial gaps filled with the MR fluid is studied both theoretically and experimentally. Finally, the effectiveness of the disk-type MR fluid damper for attenuating the vibration of rotor systems and of a simple open-loop on-off control based on the feedback of rotational speed on controlling vibration of rotor systems are experimentally studied in a two-disk flexible rotor system. It is shown that the dynamic characteristics of the MR fluid damper can be easily controlled by a magnetic field produced by a simple electrical magnetic coil with a low voltage (less than 50 V) and that the MR fluid damper is very effective for attenuating and controlling the vibration of a rotor system. It is possible to give the optimum supporting damping for every vibration mode in the rotor system by controlling the MR damper, provided that the MR fluid damper is not located at the main nodes of rotor system modes.
Precision Shaping of Deployable Thin Film Mirrors
Authors: Martin Jeffrey W. , Redmond James M. , Henson Tammy D. , Main John A. , Nelson George C.
Published: November 2021

Large aperture thin-film mirrors have peaked the interest of the optics community over the past few years. The promise of seeing further with more clarity than the Hubble Space Telescope makes large apertures the golden carrot of optics. This research into precision shape control of thin-film mirrors has emphasized the development of electron gun systems for application of control charges to piezoelectric structures to control their shape. Maximum and minimum possible shape corrections of a thin film structure, which is intended to be analogous to an optical mirror, are investigated, as are the characteristics of noncontact electron gun shape control in a closed loop control system.
Development of Commercially Viable Compliant Mechanisms Using the Pseudo-Rigid-Body Model: Case Studies of Parallel Mechanisms
Authors: Mattson Christopher A. , Howell Larry L. , Magleby Spencer P.
Published: November 2021

Analysis and synthesis of compliant mechanisms has recently been the subject of significant study in the research community. This focus has led to a number of design approaches for developing compliant mechanisms. This paper describes the value of using the Pseudo-Rigid-Body Model (PRBM) to design compliant mechanisms for commercial products. Application of the PRBM is illustrated through the development of two parallel mechanisms: a bicycle derailleur and parallel-motion bicycle brakes. The PRBM allows compliant mechanisms to be modeled and analyzed as rigid-body mechanisms and significantly reduces the complexity of analysis. Mechanisms with straightforward properties are used to demonstrate the use of the PRBM to design commercially viable compliant mechanisms for required motion and force-deflection characteristics.
Design and Manufacturing of Complex Adaptive Structures With Piezoceramic Patch Actuators
Authors: Wierach P. , Sachau D. , Schönecker A.
Published: November 2021

The use of thin monolithic piezoceramic patches as actuators and sensors for adaptive structures is well known and has been described in literature. Nevertheless the manufacturing of adaptive structures is still very challenging. During the manufacturing process it is often necessary to apply high mechanical loads on the extreme brittle piezoceramic material. As a result very often cracks in the piezoceramic material make the structure uselessness. This problem becomes serious when large scale structures with many actuators and sensors are considered. To come to more reliable results the use of encapsulated piezoceramic actuators and sensors came into focus. Within the German industrial project “Adaptronik” a new modular concept has been developed to pre-encapsulate different kinds of piezoceramic materials before further processing. During this manufacturing step the piezoceramic material is provided with a mechanical stabilization, an electrical insulation, electrodes and reliable electric contacts. The multifunctional elements are characterized by an increased damage tolerance, good long term properties and an easy handling. Due to the modular concept, the multifunctional elements can be designed to meet a great variety of different requirements. This involves for example driving voltages, size and shape of the elements and the piezoceramic material itself. The manufacturing of curved elements was demonstrated. A technology to bond these elements on spatial curved surfaces and to integrate them into fiber composite structures was developed. Experiments have been carried out to investigate the active and passive properties of the multifunctional elements and their interaction with structural components.
On the Finite Element Modeling of Smart Structures
Authors: Amir-Yazdani Ali , Sekouri El Mostafa , Hu Yan-Ru
Published: November 2021

The present work examines the effectiveness of the experimental, analytical and finite element methods in modeling smart structures. Three modeling approaches are applied to some flexible structures with bonded piezoelectric sensors and actuators. The theoretical approach is limited to simple geometrical structures, the experimental approach is not cost effective for complex geometrical structures, but FEM is very attractive. Overall, the comparisons between the three approaches are fairly good. The good accuracy of FE results are also validated through the two examples selected from the literature (Crawley, 1987; Yousefi-Koma, 1997).
Development of a Templated Grain Growth System for Texturing Piezoelectric Ceramics
Authors: Seabaugh Matthew M. , Cheney Gwendolyn L. , Hasinska Katarzyna , Azad Abdul-Maheed , Swartz Scott L. , Dawson William J.
Published: November 2021

High strain actuation can be obtained by engineering the crystallographic texture of piezoelectric ceramics. Single crystal piezoelectrics have significantly improved strain performance because crystal orientation can be controlled during use — their highly perfect lattice greatly simplifies the crystal orientation. Single crystals have properties significantly better than those of randomly oriented ceramics, but they are expensive and difficult to produce. Highly textured ceramics offer an alternative means of producing easily aligned crystals, as the majority of the crystallites in the ceramic share a common crystallographic orientation. Textured piezoelectric ceramics are expected to provide improved properties compared to untextured ceramics, with lower processing costs than single crystals. NexTech Materials is developing textured piezoelectrics in PMN-PT system via Templated Grain Growth (TGG). In the TGG process, anisotropic template particles are oriented in a fine particle matrix in the green state. During heat treatment, the crystals consume the surrounding matrix, resulting in a textured polycrystal.

A TGG system requires both matrix and template particles. The matrix must provide significant driving force for densification and grain growth. Templates must be large, anisotropic, and crystallographically isostructural with the matrix material. Anisotropic template shape is difficult to achieve in perovskite-based piezoelectrics, which have highly symmetric (cubic) crystal structures at their processing temperature. In addition, the matrix environment often contains highly corrosive lead based liquid phases that make chemical stability difficult to achieve.

Characterization of textured samples involves texture evaluation and phase analysis via XRD, and SEM analysis of template growth and chemical stability as well as piezoelectric performance measurement The development and characterization of the TGG components and their integration will be discussed.
Nonlinear Characteristics of Piezoelectric Polymers
Authors: Vinogradov Aleksandra M.
Published: November 2021

The paper presents a summary review of the scientific progress in the area of material characterization and constitutive modeling of synthetic piezoelectric polymers. Attention is focused on the nonlinear characteristics of a thin film piezoelectric polymer polyvinylidene fluoride (PVDF), which is the principal commercially available synthetic polymer with strong piezoelectric properties. It is shown that, within certain limits, the creep response of PVDF can be treated using the assumptions of linear viscoelasticity. However, under the conditions of superimposed static and oscillatory loads the polymer tends to exhibit accelerated creep rates even in the range of stresses well below the viscoelastic linearity limit. It follows that the long-term cyclic response of PVDF is essentially nonlinear, since it does not represent a simple superposition of the responses to static and fully reversed cyclic loads applied separately. This phenomenon, defined as vibrocreep, requires more adequate constitutive representation than that provided by linear viscoelasticity.
Modeling and Characterization of Piezoelectric and Magnetostrictive Induced Strain Actuators
Authors: Pomirleanu Radu , Giurgiutiu Victor
Published: November 2021

This paper presents the results of theoretical modeling and experimental characterization of PiezoSystems Jena P-177-00 large stroke piezoelectric actuator and of Etrema AA-140J025-ES1 large stroke/large power magnetostrictive actuator. An improved smart-material actuators measurement method suited for static and low frequency actuation was devised. Analytical and finite element modeling (ANSYS) of the experimental setup to determine stiffness component characteristics was performed. The output displacements of the active material actuators were recorded in quasi-static and dynamic regimes, under varied pre-stress level, voltage and frequency values. The measurements indicated a strong dependence of the actuator stiffness and piezoelectric properties on the electromechanical loading conditions. The study also identified and calculated the parameters of the induced strain actuators electro-mechanical model. These parameters are necessary for performing design optimization to achieve maximum energy transfer and minimum power requirements. Experimentally verified data characterizing piezoelectric and magnetostrictive actuators in the full stroke/full power regime is provided.
Modeling and Testing of an Autonomous Swimming Vehicle Powered via Smart Materials
Authors: Borgen Michael G. , Washington Gregory N. , Kinzel Gary
Published: November 2021

This work details the design of a miniature swimming vehicle that propels itself through oscillations of a flexible fin mounted in the stern. The fin is driven through a mechanism that is actuated by two curved-beam bending piezoelectric actuators. An optimization routine is used to design the mechanism for rigid body guidance. The actuators are modeled statically using the Bernoulli-Euler method. Hamilton’s principle is applied to the actuators and, by employing modal analysis, a dynamic actuator model is developed and compared to experimental data. The physical evolution of the swimming vehicle is discussed, and a prototype for an onboard digital control circuit is evaluated. The latest vehicle design, which incorporates onboard digital control, is presented in terms of its design and experimental performance characteristics. The current swimming vehicle prototype achieves fish-like maneuvering and an approximate velocity of 0.25 m/s.
Thermal Characteristics of a Free Radial Liquid Jet Impinging on a Hot Surface
Authors: Hassaneen Ahmed , Rahman Muhammad M.
Published: November 2021

This paper presents results of CFD computation of the heat transfer process in a radial impinging free liquid jet. The jet is impinging on a flat circular disk and the flow downstream of the impinging area spreads outward and inward on the disk. The solution is made under steady state and laminar flow conditions. The solution is obtained for the axisymmetric radial jet with two free surfaces. Different incidence angle of the jet and different flow Reynolds number (Re) were considered in the analysis. The effect of jet elevation from the disk is discussed in addition to different thickness of the hot plate. Due to lack of experimental data on this typical flow problem, the results were qualitatively compared with the available experimental data of the closest flow condition in the literature. The jet incidence angle and jet elevation were found to have strong effects on the velocity field and the free surface position of the spreading flow on the disk and consequently affected the heat transfer process. The disc thickness is also found to have a strong effect on the local and average Nusselt number. Results are documented by plotting the distribution of local and average Nusselt number versus the geometrical parameters.
Wettability Measurement and Criterion for a Falling Film Absorber
Authors: Kim Jin-Kyeong , Park Chan Woo , Kim Ig Saeng , Jurng Jong Soo , Kang Yong Tae
Published: November 2021

The objectives of this paper are to develop a new method of wettability measurement and to study the effect of surface roughness on the wettability in a LiBr/H2O falling film absorber. Three absorber tubes with micro-scale roughness are tested in a falling film absorber installed in a test rig. Inlet solution temperature (30–50°C), concentration (55–62 weight % of LiBr) and mass flow rate (0.74–2.71 kg/min) are considered as key parameters. A new method is proposed to estimate the wettability of a tube by measuring a minimum mass flow rate to wet the tube completely. Reynolds number is ranged from 30 to 120 by controlling the inlet mass flow rate. The wettability for the structured surfaces was higher than that for the bare tube. The wettability decreased linearly along the vertical location as low as 65% for the bare tube and 75% for the micro-scale scratched tubes. The wettability increased with increasing the solution temperature and the solution mass flow rate. The effect of film Reynolds number on the wettability in the bare tubes was more significant man that in the micro-scale scratched tubes. The experimental results of wettability can be used in the design of absorbers with micro-scale roughness.
Analysis of Inner-Cylinder Rolling Piston Compressors
Authors: Wang Guoliang , Guo Bei , Zhang Wei , Li Liansheng , Shu Pengcheng
Published: November 2021

A new inner cylinder installed in a rolling piston compressor is proposed here. The rotor is hollowed out in to a new cavity. Thus a new working cavity is formed and the utilization rate of the cylinder increases. Compared with the traditional rolling piston compressor, the proposed one has higher effective volume and will be widely applied.
Study of the Discharge Pressure Pulsation Within Twin Screw Compressors
Authors: Xing Ziwen , Peng Xueyuan , Zhang Xiaojun , Cui Tiansheng
Published: November 2021

Even in the absence of valves, flow through the discharge port of a screw compressor is oscillatory in nature. This unsteady but periodic flow variation at the discharge port excites the pressure pulsation. In this paper, the one-dimensional unsteady gas flow equations describing the discharge pressure pulsation are established, which allow for the effects of the viscosity friction and heat transfer between the gas and the pipe, and the boundary conditions of discharge pressure pulsation are considered. With Two-Step Lax-Wendroff scheme used, the one-dimensional unsteady gas flow equations are solved. In order to verify the theoretic analysis, the discharge pressure pulsation at variable working conditions is measured. It is shown that the model established in this paper is valid for getting a better understanding of the mechanism governing the behavior of the pressure pulsation in discharge pipe. It is found that the most important factor that affects the discharge pressure pulsation is the pressure difference between the actual discharge pressure and the design discharge pressure.
Development of Solar/Waste Heat Driven Dual-Mode, Multi-Stage, Multi-Bed Regenerative Adsorption System
Authors: Saha B. B. , Koyama S. , Akisawa A. , Kashiwagi T. , Ng K. C. , Chua H. T. , Yoon J. L.
Published: November 2021

Over the past three decades there have been considerable efforts to use adsorption (solid/vapor) for cooling and heat pump applications, but intensified efforts were initiated only since the imposition of international restrictions on the production and use of CFCs (chloroflurocarbons) and HCFCs (hydrochloroflurocarbons). Closed-type, conventional adsorption refrigeration and heat pump systems have an increasing market share in Japan. In this paper, a dual-mode, three-stage non-regenerative, 6-bed regenerative silica gel-water adsorption chiller design is outlined along with the performance evaluation of the innovative chiller. This adsorption chiller utilizes effectively solar or waste heat sources. Two operation modes are possible for the advanced chiller. The first operation mode will be to work as a highly efficient conventional chiller where the driving source temperature is between 60 and 95°C. The second operation mode will be to work as an advanced three-stage adsorption chiller where the available driving source temperature is very low (between 40 and 60°C). With this very low driving source temperature, no other cycle except an advanced adsorption cycle with staged regeneration will be operational. The drawbacks of this operational mode are its poor efficiency in terms of cooling capacity and COP.
Two-Layer Model to Simulate the Effect of Marangoni Enhancement of Absorption
Authors: Arora Ravi , Herold Keith E.
Published: November 2021

Absorption of vapor into a laminar film of liquid is a well-known problem that has received considerable interest in the literature. In many practical systems, the mass transfer process in the liquid phase is a limiting factor because the diffusion of mass is much slower than the diffusion of energy. Enhancement of absorption usually involves some scheme to mix the liquid, causing the effective diffusivities to increase. One such enhancement method is the use of surfactants that drive Marangoni flow in the liquid. This method is used very effectively in absorption chillers based on aqueous lithium bromide. The complexity of the resulting liquid flow is significant and this may explain why there are few studies of this effect found in the literature.

In the present paper, a model is described which treats the liquid film as composed of two-layers: the inner layer is laminar and the outer layer is fully mixed. The relative thickness of the two layers is a parameter that must be known to enable use of the model. The layer thickness was determined from comparisons between the model results and absorption data from a vertical tube absorber. The layer thickness is found to be a function of liquid flow rate and surfactant concentration.
A Distributed Model for the Transient Performance of a Space Heat Pump
Authors: Jiang Haobo , Radermacher Reinhard
Published: November 2021

A prototype heat pump was designed and tested as a means of active thermal management for electronics packages to be used on stratospheric balloon missions. The evaporator worked as a cold plate to absorb heat dissipated by the electronics, while the condenser rejected heat primarily by radiation to the rarified environment.

To predict the transient performance of the heat pump under varying environmental temperature and cooling load conditions, a dynamic model of the heat pump was created with a graphical user interface (GUI). The simulation of the evaporator and condenser are fully transient and the components are segmented, whereas the compressor and expansion device are lumped models and assumed to be at quasi-steady state. A detailed model for the mass and energy conservation in the two heat exchangers is presented. The spatial and temporal variation of temperature and mass flow rate in the heat exchangers are predicted. Several types of transient conditions such as step changes of the space temperature and cooling load, system start-up, shutdown, and cycling, are studied. The space temperature, cooling load, compressor power, mass flow rates of the compressor and expansion device, pressures and refrigerant charges of the condenser and evaporator, and temperature distribution in the heat exchangers are dynamically displayed on the GUI. The simulation results are compared with experimental data for step changes in the cooling load and show good agreement in terms of trends.
Thermodynamic Analysis of Expander Applications in Refrigeration Cycles
Authors: Vaisman Igor B.
Published: November 2021

Modern expander applications in refrigeration are associated with two-phase expanders to replace the irreversible throttling process of liquid refrigerants. This paper relates to vapor expander applications utilizing available waste heat for complete power recovery to drive power-consuming equipment of R134a air conditioning systems and reducing the global warming effect. The vapor compression and expansion refrigeration cycle is introduced and its thermodynamic analysis is provided. The calculated performance characteristics on boiling temperature in the boiler, condensing temperature in the condenser, evaporating temperature in the evaporator, and compressor and expander isentropic efficiencies are presented and compared with the regular refrigeration cycle and the two-phase expander refrigeration cycle.
CO2 Transcritical Cycles for High Temperature Applications
Authors: Hwang Yunho , Huff Hans-Joachim , Preissner Marcus , Radermacher Reinhard
Published: November 2021

A breadboard CO2 prototype heat pump for stationary applications was designed, constructed, and tested. Test results of the CO2 prototype showed about 12% lower cooling capacity but a similar cooling Coefficient of Performance (COP) at 40°C (104°F) ambient temperature as compared to R-22 environmental control units (ECU). However the projected COP of the CO2 prototype at 52°C (125°F) is lower than that of the original R-22 ECU. Therefore it is necessary to investigate methods to improve the efficiency while considering the design issues especially for high temperature operation. As means to improve the performance of the CO2 cycle at higher ambient conditions, four methods were investigated: a suction-line heat exchanger, an expander, an evaporatively cooled gas cooler, and a two-stage split cycle. It is expected that a suction-line heat exchanger can increase the high temperature capacity and COP of a CO2 system by approximately 10% and 20%, respectively. For an expander inlet temperature of 52 °C (125°F), the COP improvement is about 27% with an expander efficiency of 50%. An improvement in COP of 17% to 24% is achieved by using an evaporatively cooled gas cooler while the system cooling capacity improved by 6% to 8% at ambient temperatures of 35°C (95°F) and 45°C (113°F), respectively. The two-stage split cycle with intercooling offers 38% to 63% COP improvement at 30 to 50°C (86 to 122°F) ambient conditions.

If one of these methods are implemented, the performance of the CO2 system can compete with R-22 ECUs. If two or more of above methods are implemented, the benefits may be higher than each one of them. However the benefit cannot be simply superpositioned due to the counteract effects. Therefore, the benefits of the implementation of two or more of above methods remain as a further study.
A Procedure for Filtering the Induced Effects in the Thermoeconomic Diagnosis of an Energy System
Authors: Verda Vittorio , Serra Luis , Valero Antonio
Published: November 2021

The aim of the diagnosis techniques usually applied in energy systems is the detection of signs of possible malfunctions, in particular those malfunctions that can cause failures, if not removed. The thermoeconomic diagnosis is applied to detect and locate possible inefficiencies of the plant components that provoke variations of the plant efficiency.

Thermoeconomic diagnosis procedures are based on the comparison between the real operation conditions and carefully selected reference conditions, usually characterized by the same qualitative and quantitative plant productions. In this way a difference in the overall fuel consumption (fuel impact) is an index of the presence of malfunctions due to the component inefficiencies. The use of the thermoeconomic theories for the location of anomalies presents the problem of the induced malfunctions [1], In fact, when an anomaly takes place in a component, not only its efficiency decreases, but also other components change their behaviour, due to the modified working conditions provoked by the anomaly. The induced malfunctions have two different causes: 1) the malfunctioning component requires a larger amount of fuel to maintain constant its production, so the other components must increase their production too, thus varying their efficiency; 2) as the values of some set-point variables can have been modified, the regulation system must operate to restore its set-point value. Its action modifies the plant working conditions, inducing new malfunctions.

In this paper a procedure for filtering and canceling the induced malfunctions is proposed. Hence, the devices suffering the real inefficiencies can be identified and located. The proposed procedure is based on the knowledge of the system behaviour when the regulation parameters vary. A first fictitious working condition, called free condition [2], is mathematically built, starting from the operation conditions and restoring the regulation parameters corresponding to the reference operating conditions. In this way the free condition does not include the regulation system contribution. A second state is then built for every single component in order to take into account the malfunctions induced by the degradation of the components behavior. The procedure is particularly useful when the number of malfunctions is unknown, as it happens in the usual operation of an actual plant. If the induced malfunctions are filtered, all the component inefficiencies can be identified at the same time.

The proposed procedure is applied to a 33 MW gas turbine plant, also providing 63 MW of thermal power to a district-heating network. A mathematical model of the plant has been used to simulate the behavior degradation of the gas turbine devices, when several components inefficiencies occur.
A Diagnosis Procedure for Energy Conversion Plants: Part II — Application and Results
Authors: Stoppato Anna , Carraretto Cristian , Mirandola Alberto
Published: November 2021

By applying the diagnostic procedures discussed in Part I to some actual plants (a coal fuelled steam power plant, a combined plant running on natural gas and a steam cogenerative plant fed by solid wastes) significant results have been obtained. A software system has expressly been implemented and connected with plant acquisition and control devices.

Operation data have been collected and processed, focusing on the main components failures (i.e. boiler, condenser and steam turbine stages) and on plant conditions after long periods without maintenance (hence highlighting wear and fouling effects on the overall performances). These tests allowed to validate the system modules and obtain useful information about sensitivity and applicability of the methods. The structure of the software and its available strategies to detect and weigh malfunctions are deepened in the paper.