bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Global Stiffness Matrix Method for 3-D Truss Dynamics
Authors: Fricke J. Robert , Hayner Mark A. 
Published: March 2021

Abstract
This paper deals with the acoustical design goal for a new approach in submarine architecture calling for the use of an internal truss to support the ship’s control and living spaces in the forward section. The acoustical design goal is to minimize truss vibration over a broad band of frequency through the application of passive damping treatments. Damping can be placed in three generic locations: 1) in or along the truss members, 2) in the joints between members, and 3) in dynamic absorbers placed at discrete locations along the truss members. This paper develops the framework for evaluating ways to achieve the stated acoustical goal. We outline the formulation of the Direct Global Stiffness Matrix method (DGSM), which is used to relate externally applied forces and moments at truss joints to joint displacements everywhere on the truss. The model is kinematically constrained by matching welded boundary conditions at the joints, and the joint displacements are computed by a sparse matrix inversion method. From these displacements, wave amplitudes for each of the three wave types, longitudinal, torsional, and flexural, may be computed on any of the beam members. An example of the use of this method illustrates the sensitivity of the global energy decay rate to the truss damping parameters, which are the only free parameters of the model. [Work sponsored by ARPA/ONR]
Equipment Representations for Shock Calculations: Time Domain Dirichlet to Neumann Maps
Authors: Barbone Paul E. 
Published: March 2021

Abstract
Large scale dynamic simulations can often be simplified by appropriately replacing large portions of the domain by a Dirichlet to Neumann, or DtN map (Givoli, 1992). Here we consider the problem of representing a dynamical subsystem, a piece of equipment aboard a naval vessel for example, in terms of an equivalent time domain DtN map. The exact DtN map is computed as a modal summation. The exact map is then approximated in both the low and high modal density regimes. The approximate DtN in the high modal density limit is computed utilizing fuzzy-structures concepts recently developed by Pierce, Sparrow and Russel (1993) and others. The resulting DtN map depends on just two easily determined system parameters: the total mass and the high-frequency stiffness.
The Influence of Discontinuities on Structure Sound Radiation
Authors: Lebedev Andrey V. 
Published: March 2021

Abstract
The problem concerned with the influence of local and distributed discontinuities on sound radiation by complex mechanical systems was considered. To analyze the problem in the case of a small discontinuity there were used simple approximations that permitted to make this analysis in a general form. The appearance of small discontinuities was shown to be a reason of a strong increase of sound radiation. The largest alternation took place in a case of a single local discontinuity.
To analyze problems of sound radiation by structures the mean-value method was suggested. This method was earlier suggested by Skudrzyk (Skudrzyk, 1968; Skudrzyk, 1980) for determining the vibration response of complex mechanical systems. The method permits to simply analyze a relatively wide range of problems, some of them were not solved before.
Using the method (Lebedev, 1993) the influence of impedance type discontinuity on sound radiation by a thin elastic cylindrical shell was studied. The problem of sound radiation by a shell with rigidity slowly varying along its axis was considered as well. The largest alternation of sound radiation level take place when there are turning points, restricting shell vibration in longitudinal direction. Against the previous results (Lebedev, 1993) sources of radiation in this case are distributed.
Product Sound Audit and Quieting Methods
Authors: Cann Richard G. 
Published: March 2021

Abstract
Engineers, responsible for modifying a product’s sound quality, from noise to quiet or from irritating to pleasant, take the first step by auditing the product’s sound. The audit is a listing of the hardware components that emit significant sound and the contribution each makes to the total product sound. The audit process also helps determine how much of the radiated sound, in the form of structure-borne vibration, travels by different paths throughout the product.
To accomplish this, the product may be physically modified so that measurements can be made on each component part. But in the modification process, the actual loading on the component must be maintained by using brakes, motors, and other loading devices. Alternatively or in combination, special acoustical measurement techniques are used to single out particular sound-radiating features. Where it is not possible to make the required direct measurements, the reciprocal measurement procedures may be applied. As the audit process continues, experimental cross-checking is employed to give confidence to estimates. In addition, the upper and lower bounds of results are evaluated.
The audit is not complete until there is reconciliation; when the contributions of all components are combined, the total is found to be equivalent to the original product sound.
Isoparametric Timoshenko Elements for Dynamic Analysis of Structures and Mechanical Systems
Authors: Smaili Ahmad , Bagci Ismail , Sannah Muhammad 
Published: March 2021

Abstract
This paper presents 4-, 5-, 6- and 7-node isoparametric Timoshenko beam elements for modeling constant and varying cross-section thick and thin beams with various boundary conditions. Numerical integration is employed to determine the mass and stiffness matrices to facilitate modeling of varying cross-section beams. The accuracy of each proposed element is illustrated by determining the natural frequencies of: Thick and thin beams with constant and varying cross-section; linearly tapered cantilever circular tube with small wall thickness; chimney structure; and of a four-bar mechanism. In all examples, the results obtained using the proposed elements are compared, whenever available, with exact solution and with solutions determined when other elements available in the literature are used. The proposed elements did not cause shear locking when tested on thin beams of aspect ratio 500.
Concise Equations for Rotor Dynamics Analysis
Authors: Chen W. J. 
Published: March 2021

Abstract
Concise equations for rotor dynamics analysis are presented. Two coordinate ordering methods are introduced in the element equations of motion. One is in the real domain and the other is in the complex domain. The two proposed ordering algorithms lead to more compact element matrices. A station numbering technique is also proposed for the system equations during the assembly process. This numbering technique can minimize the matrix bandwidth, the memory storage and can increase the computational efficiency.
Cracked Shaft Detection Using the Unbalance Excitation Technique
Authors: Kavarana Farokh H. , Kirk R. Gordon 
Published: March 2021

Abstract
The ever-growing interest of the modern rotordynamicist in the early detection of rotor cracks in turbomachinery has been the direct result of multiple catastrophic experiences that industry has faced in recent times due to cracked rotors. The complete failure of the rotor due to crack propagation is easily recognized as one of the most serious modes of plant failure. Even though the past decade has witnessed some laudable attempts that have been moderately successful in detecting cracked rotors, this aspect has not received the attention it warrants.
A complete test rig has been designed and constructed for experimental research on the response characteristics of cracked rotors, the results of which will permit increased confidence in detecting the presence of rotor cracks in turbomachinery. The rig is capable of testing cracked shafts under the effect of lateral and coupled lateral/torsional vibrations. Conventional vibration signature analysis has been employed for the purpose of crack detection. This paper presents the details of the rig capabilities and results from the unbalance excitation technique applied for crack detection. The response of a cracked shaft differs markedly from that of an uncracked shaft when subjected to a known unbalance. This paper shows that unbalance excitation is a promising tool for cracked shaft detection.
Nonlinear Analysis of Cracked Rotors With Multiple Supports
Authors: Kiciński Jan , Ostachowicz Wiesław M. 
Published: March 2021

Abstract
A nonlinear dynamical model of a rotor-support system is presented in this paper. The model includes a treatment of typical perpendicular cracks as encountered in rotor systems. In addition to this a new method for the description of elasto-damping properties of oil films is proposed. The rotor system is also discussed in the context of multiple supports involving the principles of kinetostatic bending.
Certain numerical examples are presented within the paper, namely a study of the trajectory of arbitrarily chosen system nodes, and also of a spectral analysis of vibration for cases where the cracks are arbitrarily spatially located.
It is considered that the proposals within this paper are of particular relevance to software implementations for diagnostics simulations. The nonlinear description of the model considered also allows for the creation of a catalogue of diagnostic relational phenomena which can be used to describe the inter-relationships between defects which appear during running of a rotor system and their causal symptoms.
Two-Time Scale Control of Flexible Structures
Authors: Chen Luping , Xi Yugeng , Zhang Zhongjun 
Published: March 2021

Abstract
In this paper, a direct iteration method is presented for two-time scale decomposition of flexible structures. This direct eigenspace approach has less computation burden than the eigenvector approach. It is also a canonical transformation to keep the equation symmetry and has also explicit inverse so that the input and output matrices of decoupled model with the same sensor and actor as the original system can be easily obtained.
A Pointwise Approach for Synthesizing Semi-Active Vehicle Suspensions
Authors: Chang Pei-Ming , Jayasuriya Suhada 
Published: March 2021

Abstract
Presented in this paper is a pointwise optimization approach for synthesizing semi-active vehicle suspensions. In particular, the control algorithm is obtained by optimizing a performance index pointwise in time. The resulting control law has a state feedback structure suitable for real time implementation and is a hybrid control scheme combining a simple one-step ahead minimization and an optimal-aiming strategy specifically chosen for increased ride comfort while satisfying constraints on road traction and rattle space. Simulations with a quarter car model confirm the efficacy of the proposed approach.
Optimum Structure/Control Design Using Multiobjective Optimization Techniques
Authors: Sunar M. , Rao S. S. 
Published: March 2021

Abstract
A novel multiobjective optimization formulation is presented for the combined structural and control design of flexible structures using several multiobjective optimization techniques. The quadratic performance index, control energy and structural weight are integrated into one single objective function for minimization and various stability and performance constraints along with the constraints on the closed-loop eigenvalues are imposed on the structure. Weighting method, goal programming technique and modified game theory are used as multiobjective optimization techniques to collapse the three objective functions into one single objective function. A substructural control technique is employed for the structural control design in order to reduce the computational cost of the optimization procedure. The proposed multiobjective control optimization scheme produces optimum structure/control design and because of its numerical efficiency, it can be applied to large flexible structures.
Parameter Estimation of Flexible One-Link Manipulator Using B-Spline Approximations
Authors: Kojima Fumio 
Published: March 2021

Abstract
A finite approximation strategy is considered for parameter estimation of flexible one-link manipulator using B-spline approximations. A variational formulation of an Euler-Bernoulli system model is presented for a one-link flexible robot arm with a tip mass at its free end. Approximation schemes employing cubic B-splines are developed for the computational model. The experimental apparatus is constructed from a single cantilevered beam attached to the DC servo motor. The joint angle are measured by built-in optical encoder in the motor and the vibration at the free end can be measured by accelerometer attached to the flexible arm. Parameter estimation problems are solved with experimental data and summaries of numerical studies are reported.
Incorporation of Joint Flexibility With Link Flexibility: Dynamic Modeling and Analysis
Authors: Li Degao , Zu Jean W. , Goldenberg Andrew A. 
Published: March 2021

Abstract
Flexible robots with both link flexibility and joint flexibility have received increasing attention recently. In modeling the flexible robots with the assumed mode method, the model accuracy is highly dependent on the mode shapes of the link deflection. For flexible-link, flexible-joint robots, conventionally used clamped-free or pinned-free modes may cause large errors. To address this problem, this paper presents a systematic approach to dynamic modeling and mode analysis of a single-link flexible robot, which has a flexible joint and a hub at the base end and a payload at the free end. Accurate modes of the system are obtained. The following important conclusions are obtained: (1) Even a small joint flexibility can significantly affect the system frequencies; (2) The fundamental frequency is sensitive to the change in the payload and is not sensitive to the change in the hub inertia.
Upconversion Nanoparticles Decorated with Polysialic Acid for Solid Tumors Visualization In Vivo
Authors: Demina P. A. , Sholina N. V. , Akasov R. A. , Khochenkov D. A. , Nechaev A. V. , Balalaeva I. V. , Khaydukov E. V. , Generalova A. N. , Deev S. M. 
Published: March 2021

Abstract
Upconversion nanoparticles (UCNPs) are a promising nanoplatform for bioreagent formation for in vivo imaging, which emit UV and blue light under the action of near-infrared radiation, providing deep tissue penetration and maintaining a high signal-to-noise ratio. In the case of solid tumor visualization, the UCNP surface functionalization is required to ensure a long circulation time, biocompatibility, and non-toxicity. The effective UCNP accumulation in the solid tumors is determined by the disturbed architecture of the vascular network and lymphatic drainage. This work demonstrates an approach to the UCNP biofunctionalization with endogenous polysialic acid for in vivo bioreagent formation. Bioreagents possess a low level of nonspecific protein adsorption and macrophage uptake, which allow the prolongation of the circulation time in the bloodstream up to 3 h. This leads to an intense photoluminescent signal in the tumor.
The Map of Need: identifying and predicting the spatial distribution of financial hardship in Scotland’s veteran community
Authors: Kiernan Matthew D , Rodrigues M , Mann E , Stretesky P , Defeyter M A 
Published: March 2021

IntroductionDuring military service, many household costs for both married and single service personnel are subsidised, and transition can leave veterans unprepared for the financial demands of civilian life. Armed Forces organisations such as Sailor, Soldier, Air Force Association (SSAFA) play a central role in understanding the financial challenges that UK veterans face and provide an insight into the financial hardship experienced by veterans. The aim of this study was to use SSAFA beneficiary data as a proxy to identify the nature of financial benefit, the spatial distribution of financial hardship in the Scottish SSAFA beneficiary community and explore factors that might predict where those recipients are located.MethodsUsing an anonymised data set of Scottish SSAFA financial beneficiaries between 2014 and 2019, this study used a geographical methodology to identify the geospatial distribution of SSAFA benefit recipients and exploratory regression analysis to explore factors to explain where SSAFA beneficiaries are located.ResultsOver half of benefit applicants (n=10 735) were concentrated in only 50 postcode districts, showing evidence of a clustered pattern, and modelling demonstrates association with area-level deprivation. The findings highlight strong association between older injured veterans and need for SSAFA beneficiary assistance.ConclusionThe findings demonstrate that beneficiaries were statistically clustered into areas of high deprivation, experiencing similar challenges to that of the wider population in these areas. Military service injury or disability was strongly associated with areas of high SSAFA benefit use and in those areas high unemployment was also a significant factor to consider.
Relationship between heavy metal exposure and type 2 diabetes: a large-scale retrospective cohort study using occupational health examinations
Authors: Ji Jun Ho , Jin Mi Hyeon , Kang Jung-Hun , Lee Soon Il , Lee Suee , Kim Sung-Hyun , Oh Sung Yong 
Published: March 2021

ObjectivesTo investigate the associations between heavy metal exposure and serum ferritin levels, physical measurements and type 2 diabetes mellitus (DM).DesignA retrospective cohort study.SettingChangwon, the location of this study, is a Korean representative industrial city. Data were obtained from medical check-ups between 2002 and 2018.ParticipantsA total of 34 814 male subjects were included. Of them, 1035 subjects with lead exposure, 200 subjects with cadmium exposure and the 33 579 remaining were assigned to cohort A, cohort B and the control cohort, respectively. Data including personal history of alcohol and smoking, age, height, weight, the follow-up duration, haemoglobin A1c (HbA1c), fasting blood sugar (FBS), ferritin levels, and lead and cadmium levels within 1 year after exposure were collected.Primary outcome measureIn subjects without diabetes, changes in FBS and HbA1c were analysed through repeated tests at intervals of 1 year or longer after the occupational exposure to heavy metals.ResultsIn Cohort A, DM was diagnosed in 33 subjects. There was a significant difference in lead concentrations between the subjects diagnosed with DM and those without DM during the follow-up period (3.94±2.92 mg/dL vs 2.81±2.03 mg/dL, p=0.002). Simple exposure to heavy metals (lead and cadmium) was not associated with DM in Cox regression models (lead exposure (HR) 1.01, 95% CI: 0.58 to 1.77, p 0.971; cadmium exposure HR 1.48, 95% CI: 0.61 to 3.55, p=0.385). Annual changes in FBS according to lead concentration at the beginning of exposure showed a positive correlation (r=0.072, p=0.032).ConclusionOur findings demonstrated that simple occupational exposure to heavy metals lead and cadmium was not associated with the incidence of DM. However, lead concentrations at the beginning of the exposure might be an indicator of DM and glucose elevations.
Measurement and prognosis of frail patients undergoing transcatheter aortic valve implantation: a systematic review and meta-analysis
Authors: Li Zhe , Dawson Emily , Moodie Jessica , Martin Janet , Bagur Rodrigo , Cheng Davy , Kiaii Bob , Hashi Adam , Bi Ran , Yeschin Michelle , John-Baptiste Ava 
Published: March 2021

ObjectivesOur objectives were to review the literature to identify frailty instruments in use for transcatheter aortic valve implantation (TAVI) recipients and synthesise prognostic data from these studies, in order to inform clinical management of frail patients undergoing TAVI.MethodsWe systematically reviewed the literature published in 2006 or later. We included studies of patients with aortic stenosis, diagnosed as frail, who underwent a TAVI procedure that reported mortality or clinical outcomes. We categorised the frailty instruments and reported on the prevalence of frailty in each study. We summarised the frequency of clinical outcomes and pooled outcomes from multiple studies. We explored heterogeneity and performed subgroup analysis, where possible. We also used Grading of Recommendations, Assessment, Development and Evaluation (GRADE) to assess the overall certainty of the estimates.ResultsOf 49 included studies, 21 used single-dimension measures to assess frailty, 3 used administrative data-based measures, and 25 used multidimensional measures. Prevalence of frailty ranged from 5.67% to 90.07%. Albumin was the most commonly used single-dimension frailty measure and the Fried or modified Fried phenotype were the most commonly used multidimensional measures. Meta-analyses of studies that used either the Fried or modified Fried phenotype showed a 30-day mortality of 7.86% (95% CI 5.20% to 11.70%) and a 1-year mortality of 26.91% (95% CI 21.50% to 33.11%). The GRADE system suggests very low certainty of the respective estimates.ConclusionsFrailty instruments varied across studies, leading to a wide range of frailty prevalence estimates for TAVI recipients and substantial heterogeneity. The results provide clinicians, patients and healthcare administrators, with potentially useful information on the prognosis of frail patients undergoing TAVI. This review highlights the need for standardisation of frailty measurement to promote consistency.PROSPERO registration numberCRD42018090597.
Cross-sectional study to measure household water insecurity and its health outcomes in urban Mexico
Authors: Jepson Wendy E , Stoler Justin , Baek Juha , Morán Martínez Javier , Uribe Salas Felipe Javier , Carrillo Genny 
Published: March 2021

ObjectiveTo assess the links between structural and household determinants of household water insecurity and test three water insecurity measures against self-reported diarrhoea, dengue fever and perceived stress in the middle-income and low-income urban areas of Torreón, Mexico.DesignCross-sectional household survey conducted in two waves (rainy and dry seasons).Participants500 households selected via multistage cluster sample in selected communities. Socioeconomic status determined the selection of participant neighbourhoods; five were identified in low socioeconomic status neighbourhoods and five in low-medium socioeconomic status neighbourhoods. We examine how the context of urban water provision is related to a new cross-culturally valid Household Water Insecurity Experiences (HWISE) Scale.Primary outcome measuresThe HWISE Scale, self-reported diarrhoea, dengue fever and the Perceived Stress Scale.ResultsWater system intermittency (adjusted OR (AOR) 3.96, 95% CI 2.40 to 6.54, p<0.001), unpredictability (AOR 2.24, 95% CI 1.34 to 3.74, p=0.002) and the dry season (AOR 3.47, 95% CI 2.18 to 5.52, p<0.001) were structural correlates of the HWISE Scale. This study also found that the HWISE Scale was associated with two health outcomes, self-reported diarrhoea (AOR 1.09, 95% CI 1.03 to 1.15, p=0.002) and perceived stress (β=0.28, SE=0.07,t=4.30, p<0.001), but not self-reported dengue fever (AOR 1.02, 95% CI 0.98 to 1.06). A 3-item hygiene subscore and a 3-item water worry subscore were also both positively associated with self-reported diarrhoea and perceived stress.ConclusionShort-form screeners of water insecurity may be useful for assessing certain health risks by lay survey workers in settings with limited healthcare resources, particularly in lieu of more expensive microbiological tests that require specialised training and facilities.