Accurate Formulation Research Articles

A highly accurate spectral dynamic stiffness method for efficient broadband modal and dynamic response analysis of membranes assemblies with arbitrary boundary conditions

A highly accurate and efficient spectral dynamic stiffness (SDS) formulation is presented for the broadband dynamic analysis of damped membranes and their assemblies with arbitrary boundary conditions (BCs). First, the general solution satisfying exactly the governing differential equations is derived, and any general BCs are represented by the modified Fourier series (MFS). Second, the modified Fourier coefficients of the force BCs are associated with those of the displacement BCs by eliminating the coefficients in the general solution, where the SDS matrix is formulated. The SDS elements can be assembled through line nodes to model complex geometries and arbitrary BCs can be described. Finally, highly reliable and efficient eigenvalue and dynamic response solution techniques are employed. The performance of the proposed method is illustrated by convergence and efficiency studies. Modal analysis and damped dynamic response analysis are performed for either individual membranes or complex membrane assemblies subjected to general BCs. This method is demonstrated to be more versatile than the classical dynamic stiffness method, and yields highly accurate results with reasonable computational efficiency by comparison with the FEM. Due to these excellent features, this method can serve as a powerful alternative tool for the fluid–structure interaction and broadband vibro-acoustic problems.

Fluctuation of fracturing curves indicates in-situ brittleness and reservoir fracturing characteristics in unconventional energy exploitation

Reservoir brittleness is a key index to evaluate the fracability and to predict the fracturing characteristics in unconventional energy exploitation. Traditional brittleness indices could only be derived from laboratory experiments, which are far from the field conditions and may lead to deviations. In this paper, a fracturing-curve based in-situ brittleness evaluation method is proposed and the in-situ brittleness of Woodford Shale is derived under field stress and temperature conditions. Based on the analysis of real-time micro-seismic data, it is confirmed that the real-time fracturing characteristics can be known by observing the fluctuations in the fracturing curves. Results showed that the in-situ brittleness is much lower than that derived in laboratory experiments. About 78% of micro-seismic events happen at the extreme value and the fastest fluctuation of the fracturing curve. These provide guidance for accurate formulation and real-time optimization of exploitation scheme.

An Investigation of the MIMO Space Time Block Code Based Selective Decode and Forward Relaying Network over n-u Fading Channel Conditions

In this paper, we examine the end-to-end average pairwise error probability (PEP) and output probability (OP) performance of the maximum ratio combining (MRC) based selective decode and forward (S-DF) system over an η–µ scattering environment considering additive white Gaussian noise (AWGN). The probability distribution function (PDF) and cumulative distribution function (CDF) expressions have been derived for the received signal-to-noise (SNR) ratio and the moment generating function (MGF) technique is used to derive the novel closed-form (CF) average PEP and OP expressions. The analytical results have been further simplified and are presented in terms of the Lauricella function for coherent complex modulation schemes. The asymptotic PEP expressions are also derived in terms of the Lauricella function, and a convex optimization (CO) framework has been developed for obtaining optimal power allocation (OPA) factors. Through simulations, it is also proven that, depending on the number of multi-path clusters and the modulation scheme used, the optimized power allocation system was essentially independent of the power relation scattered waves from the source node (SN) to the destination node (DN). The graphs show that asymptotic and accurate formulations are closely matched for moderate and high SNR regimes. PEP performance significantly improves with an increase in the value of η for a fixed value of µ. The analytical and simulation curves are in close agreement for medium-to-high SNR values.

Personality Disorders in Childhood: Validity of the Coolidge Personality and Neuropsychological Inventory for Children (CPNI)

Background: A growing body of evidence has shown that maladaptive traits and emerging patterns of personality can be traced to an early stage of development and may be assessed in childhood. The goal of present study was to provide preliminary data on the validity of the Coolidge Personality and Neuropsychological Inventory for Children (CPNI), an instrument designed to assess personality pathologies and other clinical conditions in childhood. Method: A sample of 146 clinicians completed the CPNI, as well as the Child Behavior Checklist (CBCL) to evaluate the behavioral problems and social competencies, regarding a child (aged 6–11 years) who had been in their care between 2 and 12 months. The clinicians also filled out a clinical questionnaire to provide information on the children, their families, and psychotherapies. Results: There were significant and clinically consistent associations between the CPNI and CBCL. They confirmed the good concurrent (convergent and discriminant) validity of the CPNI. Conclusions: The findings seem to support the validity of the CPNI as diagnostic instrument, taking children’s PDs and behavioral problems into account. Despite some limitations, the CPNI represents a helpful measure to evaluate the children’s personality configurations according to the DSM model. It may be employed along with other tools based on other diagnostic frameworks within the context of a multi-method and multi-informant assessment to provide an accurate and comprehensive formulation of children’s overall functioning.

Analysis of the Reformulated Source to Drain Tunneling Probability for Improving the Accuracy of a Multisubband Ensemble Monte Carlo Simulator.

As an attempt to improve the description of the tunneling current that arises in ultrascaled nanoelectronic devices when charge carriers succeed in traversing the potential barrier between source and drain, an alternative and more accurate non-local formulation of the tunneling probability was suggested. This improvement of the probability computation might result of particular interest in the context of Monte Carlo simulations where the utilization of the conventional Wentzel-Kramers-Brillouin (WKB) approximation tends to overestimate the number of particles experiencing this type of direct tunneling. However, in light of the reformulated expression for the tunneling probability, it becomes of paramount importance to assess the type of potentials for which it behaves adequately. We demonstrate that, for ensuring boundedness, the top of the potential barrier cannot feature a plateau, but rather has to behave quadratically as one approaches its maximum. Moreover, we show that monotonicity of the reformulated tunneling probability is not guaranteed by boundedness and requires an additional constraint regarding the derivative of the prefactor that modifies the traditional WKB tunneling probability.

Energy systems and laying hens an evaluation of energy systems for the formulation of practical diets for laying hens

Robust energy systems ( ES ) are required to execute accurate feed formulation. Based on the premise that the more accurate an ES is, the better it will predict performance, a predictive model was developed to evaluate the veracity of five ES proposed for formulating layer diets. Data were derived from a meta-analysis of three experiments conducted on individually housed brown laying hens flocks. Congruency was demonstrated using a single model to predict feed intake (r = 0.802), justifying their combination into a single, consolidated flock. A matrix of energy values was determined for each ES, and dietary energy content was recalculated for all diets. Hen production parameters were predicted using each ES, and all predictions were similar. The correlation for energy utilisation efficiency for egg output between all ES was high (r > 0.96), suggesting that no one ES offered any advantage. Adjusting dietary energy values according to the lipid, protein or fiber content did not improve predictions. A least-cost feed formulation exercise, using the different ES, showed that the ingredient content of the diets varied considerably, depending on the ES used and the relative cost of ingredients. Differences in feed costs were negligible. The ideal ES system to use for formulation purposes depends on the relative cost of ingredients. In conclusion, the AME n system accurately predicts laying hen production parameters and allows for cost-effective feed formulation of layer diets. There was no advantage in predicting performance or the formulated feed cost for any ES evaluated.

The classifier of surgical operations and manipulations in system of medical services financing in the Kyrgyz Republic

The health care reforms in the Kyrgyz Republic are directed to develop hospital financing system. In 2003 the system of clinical-cost groups was introduced. The surgical clinical-cost groups are organized on the basis of existing classifier "The Surgical Operations and Manipulations", which is not revised since its approval in 1997, that resulted in distortion of statistical information. Hence, need in development and implementation of modern reference book is obvious. The purpose of the study is to comparatively analyze international classifiers of surgical operations and manipulations, to evaluate their accordance to clinical practice in the Kyrgyz Republic and to develop new national classifier to be applied in the Kyrgyz Republic. The actually applied national classifier of Surgical Operations and Manipulations includes 2181 types of surgical interventions, 250 (12%) out of which have no accurate formulation (for example "The other types of brain surgeries"). In addition, 453 (21%) surgical operations are not applied. The detailed analysis of such international classifiers as the International Classification of Diseases-10 Procedure Coding System (ICD-10-PCS), the Australian Classification of Health Interventions (ACHI), the NOMESCO Classification of Surgical Procedures (NCSP), Nomenclature of Health Services, the Russian Nomenclature of Health Services (RNHS) was implemented. The systematization of analyzed data permitted to determine the Russian classifier "Nomenclature of medical services" as the most optimal for implementation in the Kyrgyz Republic. The obtained and analyzed data made it possible for the Ministry of Health of the Kyrgyz Republic to proceed activities related to development of new classifier of surgical interventions on the basis of the Nomenclature of Medical Services of the Russian Federation.

Discrete element modeling of strongly deformed particles in dense shear flows

The discrete element method (DEM) proposed by Cundall and Strack [1] is a widely used numerical approach to study the fundamentals of particulate matter at the particle scale. In our present study, the flow behavior of dense configurations of soft particles was studied by means of a new formulation of the multi-contact force closure for the DEM. The first step was to verify the response of the new force closure, and calibrate its parameters based on a comparison of the results for simple uniaxial compression with results from a reference simulation. This reference simulation used a highly accurate nonlocal formulation of contact mechanics in the quasi-static limit [2], which accounts for the interplay of deformations due to multiple contact forces acting on a single particle. The newly developed and calibrated model results show significant improvement over those derived via the existing multi-contact model. Also, the dependence of the stress in the sheared granular matter on the Poisson's ratio was unveiled when using the newly derived advanced multi-contact force closure. Therefore, an extensive campaign of simple shear flow simulations was performed (at a fixed volume of the simulation box) to probe the effect of particle volume fraction and the speed of shearing. These simulations show that the stress at particle volume fractions larger than a critical value depends not only on the friction coefficient and particle stiffness, but also on the Poisson's ratio of the material. Finally, we report a response surface for the pressure in a sheared particle bed as a function of all key influence parameters. This response surface is beneficial for calibrating DEM model parameters in extremely dense flow configurations.

Nonlinear transient analysis of porous P-FGM and S-FGM sandwich plates and shell panels under blast loading and thermal environment

The present work is an attempt to develop a simple and accurate finite element formulation based on C0 continuity of transverse displacement for obtaining and comparing nonlinear transient response of porous functionally graded material (FGM) sandwich plates and shell panels. The volume fraction for the layers made of FGM is computed according to the power-law (P-FGM) or sigmoid (S-FGM) model. The FGM sandwich panel is subjected to blast loading and thermal environment considering the heat conduction in thickness direction and the material properties are assumed to be temperature-dependent. An eight-noded isoparametric element along with first-order shear deformation theory is used to develop a finite element model. The strain–displacement relation is obtained using Sander’s approximation incorporating von Karman type nonlinear strains. Two configurations, first having the top and the bottom layers made of pure ceramic and pure metal and the core of same composed of FGM, second having the top and the bottom layers made of FGM and the core composed of pure metal are considered for the present investigation. The FGM layers for the two configurations are porous and two types of porosity, viz., evenly spaced and unevenly spaced are considered for the analysis. The results obtained from the present finite element formulation are first validated with several benchmark examples available in the literature. Parametric studies are carried out to investigate the effect of volume fraction index, porosity model, temperature gradient, core to facesheet thickness ratio and blast load on nonlinear transient analysis of porous P-FGM and S-FGM sandwich plate and shell panels. It is observed that by selecting optimum parameters, the amplitude of the nonlinear transient response due to different blast loading is controlled.

Spectral quadrature for the first principles study of crystal defects: Application to magnesium

We present an accurate and efficient finite-difference formulation and parallel implementation of Kohn-Sham Density (Operator) Functional Theory (DFT) for non periodic systems embedded in a bulk environment. Specifically, employing non-local pseudopotentials, local reformulation of electrostatics, and truncation of the spatial Kohn-Sham Hamiltonian, and the Linear Scaling Spectral Quadrature method to solve for the pointwise electronic fields in real-space and the non-local component of the atomic force, we develop a parallel finite difference framework suitable for distributed memory computing architectures to simulate non-periodic systems embedded in a bulk environment. Choosing examples from magnesium-aluminum alloys, we first demonstrate the convergence of energies and forces with respect to spectral quadrature polynomial order, and the width of the spatially truncated Hamiltonian. Next, we demonstrate the parallel scaling of our framework, and show that the computation time and memory scale linearly with respect to the number of atoms. Next, we use the developed framework to simulate isolated point defects and their interactions in magnesium-aluminum alloys. Our findings conclude that the binding energies of divacancies, Al solute-vacancy and two Al solute atoms are anisotropic and are dependent on cell size. Furthermore, the binding is favorable in all three cases.

Thermal model of supercapacitors operating in constant power applications: New mathematical expressions for precise calculation of temperature change

Supercapacitors (SCs) are key enablers that can bridge the gap between batteries and conventional capacitors. Certainly, their different merits in high power density, rapid rates of charging/discharging, long life cycles, their ability to handle high levels of charge and discharge currents, and the small values of their internal parameters have drawn attention in modern power systems and energy applications. Unfortunately, although SCs have simple equivalent circuits, the analyses, testing, and mathematical description of these circuits have not been completely resolved. This paper deals with the presentation of new accurate mathematical formulations that allow the calculation of the temperature change of SCs engaged in constant power-based applications precisely in charging and discharging. To achieve this goal, firstly, a comparison is made between well-known mathematical expressions in literature to describe all electrical variables (current, internal voltage, external voltage, power loss, etc.). Secondly, since the discharge process can be accurately represented by a transcendent equation with two solutions, a fast iterative method for solving this equation is proposed and tested. Thirdly, a new mathematical expression is derived for the temperature change of SCs during both the charge and discharge processes without assuming or neglecting SC parameters. Further, a comparison of the proposed expressions with literature-known solutions, as well as numerical results, is presented and discussed. Fourthly, the results of SC temperature change during both charging and discharging are also compared with changing parameters and operating conditions. The findings and analyses confirm that the derived mathematical formulations, proposed in this work, are precise and very close to the numerical results that can facilitate the integrity of the investigation and control of SCs contributing to the work in constant power-based applications.

Frequency spectra based approach to analytical formulation and minimization of voltage THD in staircase modulated multilevel inverters

Staircase Modulation (SCM) is a popular switching strategy for multilevel inverters (MLI), which is often a preferable alternative to Pulse Width Modulation (PWM) due to its reduced switching losses, especially for MLIs with a relatively high number of voltage levels (N). In some applications, such as motor drives, or when output filters are applicable, SCM may also suit MLIs with moderate N values. While MLIs with Equal DC Sources (EDCS) are more common, MLIs with Unequal DC Sources (UDCS), such as asymmetric Cascaded H-Bridge (CHB) MLIs are known to further reduce the waveforms’ Total Harmonic Distortion (THD). The main objective of SCM is to adjust the waveform’s fundamental component, while employing some harmonic mitigation strategy, such as THD minimization. Such an optimization approach relies on an accurate THD formulation, which eliminates underestimation errors associated with numerical THD approximations. This paper reveals novel generic analytical formulations of both Phase-voltage THD (PTHD) for single-phase MLIs and Line-voltage THD (LTHD) for three-phase MLIs. The revealed exact formulation approach is derived from Fourier series representation of THD, resulting in simple closed-form PTHD and LTHD expressions, applicable to any MLI topology, with either EDCS or UDCS configurations, and arbitrary value of N (odd and even). Given an arbitrary N value, the proposed formulations can be used to generate symbolic N-level PTHD or LTHD expressions, which are symbolic functions of the Phase Switching Angles (PSA) and (optionally) the DC source Ratios (DCR). The revealed THD formulations are verified and compared against recently introduced time-domain-based THD formulations. It is shown that when both time and frequency-based formulations are employed in THD minimizations to form a novel Hybrid Temporal-Spectral (HTS) Optimal Minimization of THD (OMTHD) approach, even better results can be achieved. The novel OMTHD is deeply explored and verified by both digital simulations and Controller + Hardware in Loop (C-HIL) based real-time experiments using 7- and 8-level three-phase MLI configurations. A downloadable supplemental file containing Maple and MATLAB functions of the proposed THD expressions, as well as pre-calculated sets of optimum variables for different values of N is provided for readers' convenience.

Dynamical analysis of sliding connections with mesh independent roughness by a total Lagrangian FEM

Sliding connections are present in several applications on the mechanics, civil and aerospace industries. A framework consisting on an accurate and stable formulation to describe the dynamics of flexible systems with sliding connections is developed. The total Lagrangian positional approach of the Finite Element Method is employed using 2D solid and frame elements to discretize bodies and connections. This allows a wide range of applications, particularly the local modelling of joints. The proposed formulation includes roughness along sliding paths independent from the finite element geometry discretization. Following variational principles, Lagrange multipliers are used to impose sliding constraints on the equations of motion. A direct time integration is performed by the generalized-α method and its stability in the present finite deformation context is evaluated. The resulting nonlinear equations are solved by the Newton-Raphson method. Examples are presented where the proposed framework is evaluated regarding its dynamical behavior and to solve practical scenarios for which sliding modelling is a necessity.

Композиторско-исполнительская практика пианиста как путь к постижению образно-эмоционального ряда музыкального произведения

The article discusses one of the methods for comprehending the content of a musical work through the interaction of the pianist's composing and performing practice. No one can deny that the listener “gets” a work only “from the hands” of the performerpianist, and if the composer is not a pianist, then the audience in the hall will inevitably receive the product of joint creativity. That is why it seems appropriate to talk about the fact of a single composing and performing practice, without special emphasis on the composing or performing component of the creative process. When such an intratextual structure as the figurative-emotional series of a work is brought to the fore, the line between the composer and the performer becomes even more blurred. Of course, one cannot speak of replacing one with another - each has its own field of activity -but it seems to be quite adequate to assert the presence of some creative conglomerate. Of course, in every piece of music there are many components that must be observed by the performer unconditionally: size, key signs, etc. This article will focus specifically on the figurative and emotional content of the work. As you know, each performer expresses the vision of a musical work in his own way. From the side of performing practice, a detailed analysis of the Second Piano Concerto by Ekaterina Prikhodovskaya was carried out. It is interesting that the composition in question was created practically “in a dialogue” between the authors of the article - the composer who wrote the concerto for piano and orchestra, and the pianist for whom this concerto was written and dedicated. The compositions of Anna Okisheva are considered as a composer's activity. On the example of her own works, Anna Okisheva gives an associative analysis, using works of art and literature as an addition to the figurative-emotional range. The uniqueness of this method lies in the fact that the performer, being a composer, already has an idea of the figurative and emotional content. In this example, we clearly see the process of “encryption” and “decryption” of a musical composition. Together and separately, these works demonstrate a fairly extensive representation of the figurative and emotional range. Thanks to the appeal to related arts (in particular, literature and painting), a more accurate and versatile formulation of the fan-shaped model of the creative process occurs (it was specified earlier). So, there is an inseparable, perhaps invisible at first glance, interconnection between composing and performing practice. Comprehension of the figurative-emotional range of a musical work -in fact, its content - is indeed the right way to create an incentive for cooperation between the composer, performer and listener (even taking into account time distances).

Accurate Formulation of the Skin and Proximity Effects in High-Speed Cable System

An efficient transmission line model of high-speed cables is established, to predict its response at a high-frequency region (up to 20 GHz). Especially, an appropriate conformal mapping technique is applied to formulate the per-unit-length parameters of high-speed cables. Moreover, the skin and proximity effects of the conducting wires and the outer shield are derived in the closed form. As a result, the AC resistance/ inductance of all the conducting materials due to the skin and proximity effects are accurately incorporated for both layered and unlayered conductors. Furthermore, the mixed-mode S-parameters are precisely predicted for both balanced and unbalanced transmission line cables in the high-frequency region. In addition, the effects of the nonuniformities and cable geometry deformation on the mode conversions are also investigated. The proposed model is firstly validated with commercial software tools, COMSOL, FEKO, and HFSS; then, we further performed physical measurements to verify our new algorithm.

Research of the particle swarm method in the problem of optimizing the mode of motion of the manipulator along one of the generalized coordinates

The problems of optimizing the modes of movement of mechanical systems, in particular robots and manipulators, is relevant in the context of modern society. Algorithms for optimal movements of components of robots and manipulators allow to realize complex trajectories of movements of their working bodies with predicted energy consumption, positioning accuracy, speed. Finding optimal modes of motion is a complex task that requires accurate formulation of the optimization function, constraint equations and determination of optimal laws that would meet the criteria of the optimization problem. In this article, the classical particle swarm method for finding the optimal mode of motion of the manipulator boom at one of the generalized coordinates was analyzed. The target energy function is the "energy" of the accelerations of the mechanical system, and the search for the optimal law of displacement was carried out using a fourth-order polynomial.
 The theoretical study showed that the method of particle swarm can be used to find the optimal laws of motion, but when working with this method it is necessary to modernize the algorithm for determining its components, including particle velocity and their correction factors.
 In determining the optimal laws of motion of the manipulator by the swarm method, this study uses an approach where it is assumed that time is discrete, and the value of the objective function was determined only at the accepted sampling points of time.

Certain issues of judicial engineering and environmental examinations regarding environmental violations in the extraction of minerals

The main problems of appointing and conducting judicial engineering and
 nvironmentalexaminationsinadministrative proceedings in the event of detection of violations in the extraction of minerals are considered.
 The purpose of the study is to generalize the problems appointing and conducting judicial engineering and environmental examinations (studies) in response to an administrative violation when using subsoil and providing practical guidelines for their solution.
 The subjects which can be participants of public-law disputes and initiators of engaging an expert in order to undertake investigations in administrative proceedings while considering environmental violations are determined. Subject and objectives of judicial engineering and environmental examinations and types of objects provided to forensic experts to perform these studies are defined.
 Conditions for the qualitative conduct of engineering and environmental examinations and solution of the tasks assigned to the expert are revealed, which depends on the accurate formulation of questions to the expert and completeness of the provision of studied objects. An indicative list of questions that can be solved by forensic experts within the framework of these examinations is proposed.
 The possibility and necessity of conducting a full-scale inspection of the scene by an expert are considered.
 A review of the literature indicates an insufficient development of concepts of the subject and object of this type of examination.
 Promising directions of improvement of theoretical knowledge and practical activity both forensic experts and subjects (bodies) considering this type of environmental violations are outlined

A vibration model of a rotor system with the sinusoidal waviness by using the non-Hertzian solution

The nonlinear contact forces and deformations between the balls and raceways can cause very complex vibration behaviours of rotor systems with the waviness in the support bearings. However, almost all previous works that used sinusoidal waviness took the Hertzian solution as the calculation method, which is not an accurate method based on Johnson’s formulation since the changes in the curvature at the sinusoidal contact surfaces. To overcome this issue, a new dynamic model of a rigid rotor system with the waviness in the support bearings is proposed. To provide a more accurate nonlinear contact force formulation for the sinusoidal waviness profile, the model used the Johnson’s extended Hertzian contact model to replace Hertzian contact model. This model can consider the time-varying curvature between the mating sinusoidal surfaces. The lubricating condition in the support bearing is also considered. A comparative study on the effects of Hertzian contact model, simplified Hertzian contact model, and Johnson's extended Hertzian contact model on the nonlinear vibrations of the rotor system is developed. The effects of the waviness amplitude and orders on the vibrations of the rotor system are discussed. The comparative simulations show that the proposed model can provide a more reasonable approach for predicting the vibrations of the rigid rotor system. Moreover, the simulations give that the nonlinear contact forces in the support bearings can greatly affect the system vibrations.

Bridge buffeting by skew winds: A revised theory

An improved bridge buffeting theory is established with an emphasis on skew wind directions, for both turbulence- and motion-dependent forces. It provides simplifications and generalizations of previously established methods. The formulation starts with a preferred 3D approach, which is suitable when aerodynamic coefficients for different yaw and inclination angles are readily available. The 3D approach includes a new convenient choice of coordinate systems and an intuitive derivation of transformation matrices, supporting clear and compact wind load expressions as well as a more accurate formulation of the quasi-steady motion-dependent forces. When the aerodynamic coefficients have only been obtained for wind normal to the bridge girder, an alternative 2D approach is provided. The 2D approach, where only the normal projection of the wind is considered, is further expanded to include mean wind directions that are both yawed and inclined, axial forces in the longitudinal direction (1D) in an optional 2D ​+ ​1D format, and forces due to all in-plane and out-of-plane motions. All expressions are first presented in a compact non-linear format and then linearized through numerous multivariate Taylor series approximations. A general, more straightforward and more accurate framework is thus established for both time- and frequency-domain analyses of the buffeting response.

Preparing for the COVID-19 paediatric mental health crisis: A focus on youth reactions to caretaker death

To promote clinician preparedness for working with children and adolescents who lost or will lose a parent or caretaker to COVID-19, findings from a review of the literature concerning youth reactions to parent and caretaker death and incapacitation were integrated with recent and emergent data concerning the COVID-19 pandemic. Children and adolescents who lose a parent or caretaker are at an increased risk of anxiety and depressive reactions and disorders, externalizing and health-risk behaviours, and substance use disorders. Particular aspects of the COVID-19 pandemic may influence these presentations and the risk of complicated grief. Youth with prior histories of adverse childhood experiences as well as boys and young men may require special considerations in formulation and planning. Tailored paediatric care based on the evidence advances accurate formulations and effective interventions for children and adolescents who suffer such a loss.