bluuebunny/crossref_metadata_2025 huggingface dataset:
Global Security and Neurophilosophy
Authors: Al-Rodhan Nayef , Puscas Ioana-Maria
Published: March 2021

This chapter evaluates the fundamental starting point in political theory: human nature. In doing so, it goes beyond conventional wisdom in International Relations. To understand conflict and to chart a way forward, we must re-examine our understanding of human nature. The two dominant theories of International Relations, Realism and Idealism/Internationalism, derived their intellectual origins from such contrasting and dichotomous views of human nature. One, exemplified by Thomas Hobbes, was pessimistic both about human nature and States. The other, exemplified by Immanuel Kant and to some extent Jean-Jacques Rousseau, believed in an innate perfectibility of humans, of States and the international society, which would evolve towards peace. Today, a growing body of evidence from neuroscience permits the re-examination of long-held claims about human nature and what it is that truly drives and motivates human behaviour. Neurophilosophy, the interdisciplinary field connecting findings from neuroscience and philosophy, is relevant for global security and for understanding what can propel good governance, peace, and security.
Terrorism and the Security Council
Authors: Duffy Helen , van den Herik Larissa
Published: March 2021

This chapter details the United Nations Security Council’s (UNSC) intense regulatory approach to counter-terrorism and its consequences, including the direct and indirect repercussions for affected individuals, and the broader global security landscape. The main argument is that the expansion of the UNSC’s role has gradually opened up a space of indeterminacy and unaccountability. Two dimensions are explored here: (i) the creation of a quasi-permanent counter-terrorism sanctions regime under Chapter VII and (ii) the Council’s ever-expanding ‘legislative’ activities, amongst others in relation to ‘foreign terrorist fighters’ and incitement or provocation. The chapter exposes underlying tendencies and ulterior effects of the UNSC’s approach, including the expansive reach of undefined or ill-defined phenomena, a reflex of over-criminalization, and the increasing involvement of the private sector, including financial institutions, in the counter-terrorism sphere. The impact on human rights, participatory democracy, the shrinking space for civil society, humanitarian assistance and peacebuilders, accountability, and rule of law is profound. Ultimately, the chapter tells a story of uncertain threats and unaccountable actors in counter-terrorism practice and the adverse effects on security in the long run.
Aggression
Authors: Kreß Claus
Published: March 2021

This chapter discusses the concept of aggression. Article 39, the opening clause of the United Nations Charter’s collective security system, contains the term ‘act of aggression’, the existence of which in a given case falls to be determined by the United Nations (UN) Security Council. Recalling Article 39, the UN General Assembly, in 1974, adopted a resolution on the Definition of Aggression (Resolution 3314 (XXIX)). As the term ‘act of aggression’ is used alongside the terms ‘threat to peace’ and ‘breach of the peace’ in Article 39, the UN Security Council is not bound to determine the existence of an act of aggression to activate the Charter's collective security system and authorize the use of force by one or more States in order to maintain or restore international peace and security. In the view of the International Court of Justice and the International Law Commission, the prohibition of aggression forms part of customary international law. Here again, however, the distinct legal significance of the concept compared to ‘use of force’ and ‘armed attack’ is of quite limited reach. Contrariwise, the concept of aggression has been of considerable importance in the realm of international criminal law since the latter’s inception.
Climate Change and Security
Authors: Gupta Joyeeta , Bosch Hilmer
Published: March 2021

This chapter describes the relationship between climate change and security. Successive reports of the Intergovernmental Panel on Climate Change have provided growing evidence of the impacts of climate change. Climate change can affect human well-being in terms of access to water, food, energy, and land, as well as in terms of risks to human health. Thus, climate change is seen as a driver of other socio-ecological problems worldwide. Climate change is also seen as a risk and threat multiplier, as it can exacerbate existing challenges faced by States, including poor governance institutions and poverty. However, climate change policy could potentially be a ‘threat minimizer’ if mitigation and adaptation measures are integrated into the development paradigm. Against this background, the chapter addresses the following issue: What is the nature of the security debate raised by the climate change issue and how is this being addressed within scholarly, policy, and legal fora? It looks at the different ways in which security has been defined in the literature and its diverse implications for law and policy.
We Who Are Not as Others
Authors: Tzanakopoulos Antonios
Published: March 2021

This chapter assesses sanctions as a (global) security governance tool. Law is an obvious tool for ‘security governance’, and ‘sanctions’ are an inextricable element of law. The chapter begins by discussing the meaning of sanctions and (global) security. It then traces the historical trajectory in the use of collective and unilateral sanctions in the service of security. It argues that global security is nothing but national security projected onto the international plane. When a hegemonic concept of security—that is to say, of the existential threats ‘we’ need to protect against—is imposed and accepted, and for as long as it is accepted, collective sanctions rule supreme and can be particularly effective. When there is fragmentation and antagonism as to what the threats are, when there is no hegemonic national security accepted as synonymous to international security, there is a return to unilateral sanctions and a concomitant sidelining of collective security mechanisms.
Supplemental Intraoperative Oxygen and Long-term Mortality: Subanalysis of a Multiple Crossover Cluster Trial
Authors: Jiang Qiliang , Kurz Andrea , Zhang Xiaobao , Liu Liu , Yang Dongsheng , Sessler Daniel I.
Published: March 2021

Background

Whether supplemental oxygen worsens long-term mortality remains unclear, with contradictory trial results. The authors therefore tested the hypothesis that supplemental oxygen (80% vs. 30%) increases the hazard for long-term mortality.

Methods

The authors conducted a post hoc analysis of a large multiple crossover cluster trial in which more than 5,000 colorectal surgeries on 4,088 adults were allocated to receive either 30% or 80% inspired oxygen during general anesthesia. The authors assessed the effect of 80% versus 30% target-inspired oxygen on long-term mortality and calculated Kaplan–Meier survival estimates. Analysis was restricted to patients with a home address in Ohio because the authors could obtain reliable vital status information from the Ohio Department of Health (Columbus, Ohio) for them.

Results

A total of 3,471 qualifying colorectal surgeries performed in 2,801 patients were analyzed, including 1,753 (51%) surgeries in 1,577 patients given 80% oxygen and 1,718 surgeries in 1,551 patients given 30% oxygen. The observed incidence of death after a median of 3 yr was 13% (234 of 1,753) in the 80% oxygen group and 14% (245 of 1,718) in the 30% oxygen group. The estimated hazard ratio for mortality was 0.94 (95% CI, 0.78 to 1.13; P = 0.493).

Conclusions

In this post hoc analysis of a large, controlled trial, supplemental oxygen did not increase postoperative mortality.

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New
Comparison of Trauma Severity Scores (ISS, NISS, RTS, BIG Score, and TRISS) in Multiple Trauma Patients
Authors: Höke Mehmet Hilmi , Usul Eren , Özkan Seda
Published: March 2021

Background:

Trauma severity scoring systems are routinely used to monitor trauma patient outcomes. Yet, the most accurate scoring system remains an elusive target.

Objective:

We aim to compare trauma severity scales (ISS, NISS, RTS, TRISS, and BIG) in multitrauma patients and investigate BIG as one of the new trauma severity scoring systems.

Methods:

The demographic data of the patients, vital signs, injury mechanisms, body regions exposed to trauma, final diagnosis, the injury severity scales—Injury Severity Score (ISS), New Injury Severity Score (NISS), Revised Trauma Score (RTS), base deficit, international normalized ratio, and Glasgow Coma Scale (BIG), and Trauma and Injury Severity Score (TRISS)—the length of stay in hospital, and the progress of the patients were examined.

Results:

A total of 426 cases were included in the study. The best performing score in determining mortality was TRISS (area under the curve [AUC]: 0.93, sensitivity 97.1% and specificity 76.7%). This was followed by the NISS, BIG, ISS, and RTS, respectively. For the prediction of intensive care unit admission, the NISS was the most successful with an AUC value of 0.81. There was a significant relationship in terms of the length of stay in all trauma scores (p < .05).

Conclusions:

The most successful score in predicting mortality in trauma patients was the TRISS, whereas the NISS was the most successful in predicting intensive care unit admission. The newly developed BIG score can be used as a strong scoring method for predicting prognosis in trauma patients.
Biomechanical analysis of the closed reduction internal fixation with cannulated screw of femoral neck fractures
Authors: Wang Jian-Guang , Wu Jun-Xian , Li Yu-Min , Xu You-Yin
Published: March 2021

The influencing factors in closed reduction internal fixation with cannulated screw of femoral neck fractures have not been well investigated. This study evaluated these factors in patients with femoral neck fractures.

Fifty-seven patients (36 males and 21 females) diagnosed with femoral neck fracture with the average age of 52.44 ± 15.04 years who underwent closed reduction internal fixation with cannulated screw were included in this study. Data were collected through case report reviews, phone call follow-ups, and outpatient follow-ups to evaluate pre- and postoperative radiograph images. Statistical analysis was performed using Garden classification, binary and multinomial logistic regression analysis by including factors such as patient's age, gender, fracture type, time to fixation, reduction quality, functional recovery period, removal of cannulated screw, and preoperative traction. Logistic regression analysis revealed that age and reduction quality was statistically significant (P < .05) to clinical outcome and other factors were not statistically significant.

The main factors affecting clinical outcomes were functional recovery and reduction quality. The biomechanical effects of fixation provide a good foundation for fracture healing. Patient's conditions should be carefully evaluated before selecting reduction procedures to reach an optimal surgical outcome.
Study of quorum-sensing LasR and RhlR genes and their dependent virulence factors in Pseudomonas aeruginosa isolates from infected burn wounds
Authors: Elnegery Aya Ahmad , Mowafy Wafaa Kamel , Zahra Tarek Ahmed , Abou El-Khier Noha Tharwat
Published: March 2021

Background.
Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen responsible for burn-wound infection. High incidence, infection severity and increasing resistance characterize

P. aeruginosa

-induced burn infection.

Purpose. To estimate quorum-sensing (QS)-dependent virulence factors of

P. aeruginosa

isolates from burn wounds and correlate it to the presence of QS genes.

Methods. A cross-sectional descriptive study included 50

P

.

aeruginosa

isolates from burn patients in Mansoura University Plastic and Burn Hospital, Egypt. Antibiotic sensitivity tests were done. All isolates were tested for their ability to produce biofilm using a micro-titration assay method. Protease, pyocyanin and rhamnolipid virulence factors were determined using skimmed milk agar, King’s A medium and CTAB agar test, respectively. The identity of QS lasR and rhlR genes was confirmed using PCR.

Results. In total, 86 % of isolates had proteolytic activity. Production of pyocyanin pigment was manifested in 66 % of isolates. Altogether, 76 % of isolates were rhamnolipid producers. Biofilm formation was detected in 96 % of isolates. QS lasR and rhlR genes were harboured by nearly all isolates except three isolates were negative for both lasR and rhlR genes and two isolates were positive for lasR gene and negative for rhlR gene. Forty-nine isolates were considered as extremely QS-proficient strains as they produced QS-dependent virulence factors. In contrast, one isolate was a QS deficient strain.

Conclusions. QS affects

P. aeruginosa

virulence-factor production and biofilm in burn wounds. Isolates containing lasR and rhlR seem to be a crucial regulator of virulence factors and biofilm formation in

P. aeruginosa

whereas the lasR gene positively regulates biofilm formation, proteolytic activity, pyocyanin production and rhamnolipid biosurfactant synthesis. The QS regulatory RhlR gene affects protease and rhamnolipid production positively.
Changing geographies of fashion during COVID‐19: The Australian case
Authors: Brydges Taylor , Heinze Lisa , Retamal Monique
Published: March 2021

COVID‐19 has impacted a range of industries, of which the fashion industry is no exception. Here, we examine the effects of COVID‐19 on the geographies of that industry in Australia. We use a path‐dependency framework to understand the evolution of the Australian fashion industry and to evaluate the impact of COVID‐19 as an external shock to this evolution. The Australian fashion industry has been hit particularly hard by the pandemic. Drawing upon a qualitative methodology and associated set of methods consisting of 24 semi‐structured interviews with key industry actors, we explore three key themes. First, we examine the impact of COVID‐19 on firm dynamics, investigating how fashion brands have navigated a period of significant uncertainty through a combination of highly nimble internal business practices and industry collaborations. Second, in light of unstable globalised supply chains, we consider the important role of local garment production in supporting industrial resilience. Third, we explore how changing consumption behaviours are altering the retail geographies of the Australian fashion industry in both physical and virtual spaces. Based on our analysis of preliminary results, we reflect on the suitability of an evolutionary approach in this context and outline a number of themes of future research.
Suicide prevention: The role of families and carers
Authors: Edwards Todd M. , Patterson Jo Ellen , Griffith James L.
Published: March 2021

Families and carers can play an important role in helping prevent suicide. Unfortunately, silence and secrecy within the family environment have sometimes prevented family members from intervening to potentially change the course of suicide intent. This article describes a family‐oriented assessment process that can facilitate family‐involvement in care. Suicide risk assessment requires a skilled interview with the individual patient to determine accurately suicidal intent. However, family members provide a vital source of collateral information for assessing risk and the relational support needed to diminish risk. Strength‐based strategies for intervening with patients and family members to help prevent suicide are described.
A possible case of recipient anti‐neutrophil and anti‐human leukocyte antigen antibody‐mediated fatal reverse transfusion‐related acute lung injury
Authors: Jug Rachel , Anani Waseem , Callum Jeannie
Published: March 2021

Background

Transfusion‐related acute lung injury (TRALI) is a transfusion complication often mediated by recipient exposure to plasma from donors with human leukocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies. Recipient anti‐donor HLA or HNA antibodies have rarely been implicated.

Study Design and Methods

Herein, we describe a case of fatal TRALI mediated by recipient anti‐HLA and anti‐HNA antibodies. Cognate antibody–antigen match was confirmed with serologic and molecular assays.

Results

A 69‐year‐old G5P5 female with no prior transfusion history and metastatic cholangiocarcinoma with thromboembolic complications presented with heart failure and dyspnea. She was transfused 15 ml of a unit of Fya‐negative red blood cells and subsequently developed acute onset dyspnea, hypoxemia, hypotension, and fever. Clinical investigations revealed bilateral infiltrates on chest X‐ray and cognate recipient HLA and HNA antibodies to donor antigens. The patient died of acute respiratory failure within 24 h of transfusion. In total, the patient had Fya, HLA Class I, HNA, and human platelet antigen (HPA) alloantibodies. The 63‐year‐old female donor had detectable HLA class II antibodies (recipient class II genotype unavailable).

Conclusion

The pathophysiology of TRALI has traditionally been ascribed to underlying conditions that put the recipient at risk in combination with donor biological response modifiers. This case illustrates alternative pathogenic mediators including alloantibodies to donor HLA and HNA. Additional studies to determine the contribution and frequency of recipient alloantibodies in TRALI may inform future mitigation strategies to further reduce the incidence of TRALI, particularly in female transfusion recipients.
Design for Manufacturability
Authors: Azam Mohammed A. , Holmes William P.
Published: March 2021

Research has been carried out at Coventry University Centre for Integrated Design on the concept design process and it is funded by the Coventry University Research Fund.

An experiment, simulating product design in industry, was conducted by concept designers which were, in turn, acted by student industrial designers and student engineering designers.

In general the product design process is a sequential process. The first part of the process is the conceptual phase. This is followed by the engineering design phases which include all the manufacturing information. In this case the downstream engineering design focuses on designs for manufacture and process selection. Information on the requirements of conceptual designers in these areas was collected from these experiments. The information is ultimately to be incorporated into rules in a knowledge base which can be readily accessed by the industrial designer during concept development via a CAD system.
Optimal Design of Coupled Structures Subjected to Random Excitation
Authors: Sampath Arun M. , Nataraj C. , Ashrafiuon H.
Published: March 2021

This paper presents optimization of the response of coupled structures subjected to random excitation. The dynamic system involves discrete and continuous models of coupled structures. The structures are assumed to be subjected to white noise excitation of known power spectral density. The mean square response of the structure is taken as the objective function. The physical properties such as length, thickness, stiffness and damping are taken as the design variables. The discrete system is assumed to be subjected to two kinds of excitation; band-limited white noise excitation and ideal white noise excitation. Coupling stiffness and damping characteristics are used as design variables. For the case of continuous coupled beam model, band-limited white noise excitation is considered and the root mean square response of the structure is minimized for a range of excitation frequency. Geometric properties of the structure are used as design variables.
Optimal Tolerance Band and Manufacturing Target for Monotonic Loss Functions With Functional Limits
Authors: Söderberg Rikard
Published: March 2021

Individual tolerances in a tolerance chain are often constrained by the tolerance of a critical dimension. This tolerance is often based on functional considerations with some economical constraints. For the customer, this may not be the optimal solution. This paper presents a method for tolerance allocation, based on trade-off analysis between manufacturing cost and quality loss. By considering both the economical loss due to poor quality and the manufacturing cost, it is possible to determine the combination of manufacturing target and tolerance band that minimizes the worst case total cost for the customer. This paper concentrates on critical dimensions, where the quality aspect studied can be described by a monotonic loss function with a functional limit.

An example of a radial journal bearing is used to describe the method.
Geometric Design of Smooth Composite Ruled Surface Strips Using Dual Spherical Geometry
Authors: Ge Q. J. , Kang Donglai
Published: March 2021

This paper deals with geometric construction of smooth composite ruled surface strips. Oriented lines that constitute the rulings of the ruled surfaces are represented by unit vectors with three components over the ring of dual numbers. The problem of designing a smooth ruled surface is studied as that of designing a one-real-parametric curve on the unit dual sphere. Geometric conditions for piecing two ruled surfaces smoothly are developed using differential geometry of curves on the dual sphere. A coordinate-frame invariant method for line segmentation is also presented. Finally, a geometric algorithm is presented for constructing composite Bézier ruled surface strips with second-order geometric continuity. The resulting surface strips are coordinate-frame invariant and their rulings are more uniformly parameterized than those obtained with other methods.
Survey of Active Truss Modules
Authors: Williams Robert L.
Published: March 2021

This paper presents a survey of active truss modules (ATMs) which can be used to construct modular, long-reach, lightweight truss-based manipulators (TBMs). Theoretical classification is presented for candidate ATM geometries. A survey of the literature is presented to subjectively compare practical modules which have been proposed. Kinematically-equivalent serial analogies are given for each of the in-parallel-actuated ATMs; use of these analogies can simplify TBM control. The intent of this paper is to present ATM alternatives and discuss subjective criteria for design selection, rather than to choose one best module.
Mini Baja Off-Road Vehicle Design and Optimization Using Finite Element Analysis
Authors: Gjessing Anthony M. , Noorani Rafiqul I.
Published: March 2021

This paper describes the design, analysis and optimization of a Mini Baja off-road vehicle which will be used to compete with other schools of the nation. The project is undertaken by a group of mechanical engineering students of Loyola Marymount University. The finite element software package used for the optimization is COSMOS/M from SAC in Santa Monaco, CA. Suggestions on how to best use the software to support design decisions is also given. The optimization is made based on material and weight of the vehicle.
Energy Approach for Multiaxial Fatigue Life Prediction Using Finite Element Analysis
Authors: Jadaan Osama M. , Boys Gregory
Published: March 2021

A new approach, based on virtual strain energy, has recently been proposed and proven successful in collapsing all data for various loading conditions for a given material and environment into a single curve. Two energy parameters associated with two different physical modes of failure were used to predict the lifetime. The first parameter is a Mode I energy parameter associated with the critical plane where principal stress and strain take place, while the second parameter is a mode II energy parameter associated with the critical planes where maximum shear stresses and strains occur. The objective of this research is to incorporate this theory into a Finite Element Method (FEM) code in order to predict the lifetime of structural components subjected to complex loading. During the post processing stage of the program, the calculated stresses and strains will be used to evaluate the normal (Mode I) and shear (mode II) energy parameters, which subsequently can be used to predict the lifetime for the given structural component. Biaxial fatigue data obtained from the literature for SAE 1045 steel were used in this study to demonstrate the ability of incorporating this energy approach into FEM codes to predict the fatigue life of structural components. This ability is demonstrated by comparing the energy parameters calculated using FEM to those calculated using the experimental data.
Failure Analysis of Composite Materials and Multi Material Interfaces
Authors: Yosibash Zohar , Szabó Barna A.
Published: March 2021

Composite materials and multi-material interface problem usually have one or more singular points. In the neighborhood of these points the solution of two-dimensional linear elastostatic problems is characterized by a series of eigenpairs and their coefficients, called the generalized stress intensity factors (GSIFs). Accurate and reliable computation of the eigenpairs and the GSIFs is important because failure theories directly or indirectly involve these quantities.

New efficient and accurate methods for numerical computation of the eigenpairs and the GSIFs, based on the p-version of the finite element method, are presented and demonstrated.

Examples, representing two different kinds of singular points demonstrate that the method works well and produces results of high accuracy. Importantly, the method is applicable to anisotropic materials, multi-material interfaces, and cases where the singularities are characterized by complex eigenpairs.
Transient Thermal Stresses in a Flat Plate With a Circular Opening
Authors: Lipp Stephen C. , Herrington Paul D. , Russo Edwin P.
Published: March 2021

Solutions for stress distributions in a flat plate with a circular opening which is undergoing radial and temporal changes in temperature are presented. A typical example would be a hot pipe penetrating a wall or a welding process. The problem is formulated as a partial differential equation on an infinite-domain problem with inhomogeneous boundary conditions. As such, the solution of the problem is obtained through integral-transform methods involving integrals difficult to numerically evaluate. The problem may also be formulated as a finite-domain problem with eigenvalue solution. The results in this case depend on the number of eigenvalues calculated which depends on the time value chosen. Three types of thermal boundary conditions are considered: (1) convection on the boundary, (2) insulated boundary, and (3) sudden heating or cooling, that is, thermal shock. Some sample results comparing the integral-transform and eigenvalue methods are presented. The results indicate that temperature values computed by both methods for an aluminum sample with a 1.5 in (0.0381 m) hole at time 10 s are identical to four decimal places. The finite domain outer radius for the eigenvalue solution was taken to be 18 in (0.4572 m). However, there is a discrepancy when comparing radial and tangential stress. This difference is the stress caused by the constant temperature from the finite boundary to infinity when imposed on the finite-domain problem.
Understanding Design Information Handling Behavior Using Time and Information Measure
Authors: Baya Vinod , Leifer Larry
Published: March 2021

Results from six verbal protocol experiments conducted to understand and characterize the information handling behavior of designers during conceptual design are reported in this study. Information handling behavior is categorized in the following categories: informational activity, information descriptor, information subject-class, information level-of-detail and information level-of-abstraction. The amount of information handled in each of the categories is quantitatively measured using design information measure (dim). Insights gained from the results are discussed. These insights will guide the development of computational tools which will improve the conceptual design process.
Apparent Stiffness of a Bolted Flange
Authors: McKee Robert B. , Reddy Harshavardhan
Published: March 2021

A flat steel flange clamped by 14 bolts was modelled by three dimensional finite element analysis to evaluate its stiffness in compression relative to each bolt. The bolt load was applied via an extremely stiff washer to eliminate the effect of bolt head deflection on the results. The dimensionless stiffness varied linearly with bolt aspect ratio d/L. The slope of this relation was equal to that predicted by a simple cylindrical model with outside diameter of 1.56 d. The pressure between flanges along the bolt circle was calculated for two values of bolt spacing.
Geometric Reasoning in the Analysis of Assemblies and Mechanisms
Authors: Ruiz O. E. , Ferreira P. M.
Published: March 2021

Geometric Reasoning ability is central to many applications in CAD / CAM / CAPP environments. An increasing demand exists for Geometric Reasoning systems which evaluate the feasibility of virtual scenes specified by geometric relations. Thus, the Geometric Constraint Satisfaction or Scene Feasibility (GCS/SF) problem consists of a basic scenario containing geometric entities, whose context is used to propose constraining relations among still undefined entities. If the constraint specification is consistent, the answer of the problem is one of finitely or infinitely many solution scenarios satisfying the prescribed constraints. Otherwise, a diagnostic of inconsistency is expected. The three main approaches used for this problem are numerical, procedural or operational and mathematical. Numerical and procedural approaches answer only part of the problem, and are not complete in the sense that a failure to provide an answer does not preclude the existence of one. The mathematical approach previously presented by the authors describes the problem using a set of polynomial equations. The common roots to this set of polynomials characterizes the solution space for such a problem. That work presents the use of Grobner basis techniques for verifying the consistency of the constraints. It also integrates subgroups of the Special Euclidean Group of Displacements SE(3) in the problem formulation to exploit the structure implied by geometric relations. Although theoretically sound, these techniques require large amounts of computing resources. This work proposes Divide-and-Conquer techniques applied to local GCS/SF subproblems to identify strongly constrained clusters of geometric entities. The identification and preprocessing of these clusters generally reduces the effort required in solving the overall problem. Cluster identification can be related to identifying short cycles in the Spatial Constraint graph for the GCS/SF problem. Their preprocessing uses the aforementioned Algebraic Geometry and Group theoretical techniques on the local GCS/SF problems that correspond to these cycles. Besides improving the efficiency of the solution approach, the Divide-and-Conquer techniques capture the physical essence of the problem. This is illustrated by applying the discussed techniques to the analysis of the degrees of freedom of mechanisms.
Vibration Response and Parametric Instability in Beams With Combined Quadratic and Cubic Material Nonlinearities
Authors: Chelidze David , Farhang Kambiz , Selstad Tyler J.
Published: March 2021

Parametric stability in beams with combined quadratic and cubic material nonlinearities is examined. A general mathematical model is developed for parametrically excited beams accounting for their nonlinear material characteristic. Second- and forth-order nonlinear differential equations are found to govern the axial and transverse motions, respectively. Expansions for displacements are assumed in terms of the linear undamped free-oscillation modes. Boundary conditions are applied to the expansions for displacements to determine the mode shapes. Multiplying the equations of motion by the corresponding shape functions, accounting for their orthogonal properties, and integrating over the beam length, a set of coupled nonlinear differential equations in the time-dependent modal coefficients is obtained. Utilizing the method of multiple scales, frequency response as well as response versus excitation amplitude are obtained for two beams of different cross sectional areas. Results are presented for three boundary conditions. It is found that, qualitatively, the response is similar for all the boundary conditions. Quantitative comparison of the cases considered indicate that the highest response amplitude occurs for the cantilever beam with the end mass. The bifurcation points for simply supported beam occur at lower excitation parameter value. It is apparent that more slender columns have larger response amplitude.
Dynamics of a Nonlinear Parametrically-Excited Partial Differential Equation
Authors: Rand Richard H. , Newman William I. , Denardo Bruce C. , Newman Alice L.
Published: March 2021

We investigate a nonlinear Mathieu equation with diffusion and damping, using both perturbation theory and numerical integration. The perturbation results predict that for parameters which lie near the 2 : 1 resonance tongue of instability corresponding to a mode shape cos nx the resonant mode achieves a stable periodic motion, while all the other modes are predicted to decay to zero. By numerically integrating the p.d.e. as well as a 3-mode o.d.e. truncation, the predictions of perturbation theory are shown to represent an oversimplified picture of the dynamics. In particular it is shown that steady states exist which involve many modes. The dependence of steady state behavior on parameter values and initial conditions is investigated numerically.
A Perturbation Method for the Forced Response of a Weakly Bilinear Oscillator
Authors: Bayly Philip V.
Published: March 2021

Closed-form analytical expressions are obtained for the response of a weakly bilinear oscillator to harmonic forcing. Bilinear systems are used to model cracked beams and rotors; the bilinear oscillator considered here is a lightly damped mass-spring assembly. The spring is linear except that its stiffness is slightly higher when the displacement of the mass is negative. The response is obtained for three ranges of forcing frequencies: far from resonances, and near primary and superharmonic resonances. The difference between the two linear stiffness coefficients is used as the small parameter, ϵ, in a modified perturbation analysis. Of all the behavior analyzed, the response near a super-harmonic resonance of order 2 is the most markedly affected by the weak bilinearity. These results provide insight into the observed behavior of cracked structural members and shafts.
Nonlinear Analysis of a Dynamically Balanced Cryorefrigerator
Authors: Minas Constantinos
Published: March 2021

A nonlinear model describing the dynamic, fluid dynamics and thermodynamics of a dynamically balanced Gifford-McMahon (G-M) cryorefrigerator was developed. The cryorefrigerator consists of two horizontally opposed first- and second-stage displacers, a first- and a second-stage thermal regenerator, and a rotary valve that cycles the compressor supply gas pressure. The model accurately describes the motion of the displacers and the refrigeration produced at the two stages of the cold head. The analytical model consists of a set of twelve first order nonlinear differential equations. The numerical solution of the system is presented in the form of pressure histories in each chamber, position and velocity histories of each displacer, and P-V diagrams of the two stages of the cold head. The performance of the cryorefrigerator is calculated under various conditions. It is clearly shown that the device can achieve non-impacting displacer motion with sufficient cooling capacities of the two stages. This non-impacting operation creates a very low vibration device, which is valuable in applications where low vibration is required, such as magnetic resonance imaging (MRI) systems. It was also shown that the cooling capacity of the device can be optimized over the operating frequency.
Direct Global Stiffness Matrix Method for 3-D Truss Dynamics
Authors: Fricke J. Robert , Hayner Mark A.
Published: March 2021

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

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

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

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

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

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

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

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

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

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

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.