Johnson Model Research Articles

The strain rate sensitive flow stresses and constitutive equations of a selective-laser-melt and an annealed-rolled 316L stainless steel: A comparative study

The strain rate dependent compressive flow stresses of a Selective-Laser-Melt 316L (SLM-316L) alloy and a commercial (annealed-extruded) 316L (C-316L) alloy were determined, for comparison, between 1x10-4 and ∼2500 s-1 and between 1x10-4 and ∼2800 s-1, respectively. The Johnson and Cook flow stress material model parameters of both alloys were also determined. The microstructural examinations of the deformed cross-sections of tested specimens (interrupted tests) showed a twinning-induced-plasticity in SLM-316L alloy and a martensitic transformation-induced-plasticity in C-316L alloy. Twin and martensite formations were detected microscopically higher in the dynamically tested specimens until about 0.22 strain, while the twin and martensite formations decreased at increasing strains due to adiabatic heating. The rate sensitivity of SLM-316L was determined slightly higher than that of C-316L within the quasi-static strain rate range (1x10-4 and 1x10-2 s-1), while the rate sensitivities of both alloys were similar in the quasi-static-high strain rate range (1x10-4 and ∼2500-2800 s-1) at low strains. A more rapid decrease in the rate sensitivity of C-316L at increasing strains was found in the quasi-static-high strain rate range. The similar activation volumes of both alloys, corresponding to the dislocation intersections, indicated a similar thermally activated deformation process involvement in both alloys.

Intergenerational transmission of personality disorder severity and the role of psychosocial risk factors.

Familial influences on the development of many psychopathologies are well recognised, yet the psychosocial risk factors that could help explain apparently intergenerational continuities of personality disorder (PD) are less well understood. To establish whether there is an association between the severity of PD in men and their offspring in a community cohort, and whether factors recognised as having the potential to increase risk of psychopathology mediate this. Participants in the Cambridge Study in Delinquent Development (n=452dyads) were assessed using the Tyrer and Johnson model of PD severity. Severe PD was defined as antisocial PD plus at least one other PD from a different cluster. Original participants were assessed by interview and their offspring by screening questionnaire. Chi-square tests and mediation models were used to investigate the intergenerational continuity of PD severity and its relationship with psychosocial risk factors. An association between severe PD in fathers and severe PD in their offspring was confirmed, regardless of whether the offspring were male or female. Whilst preliminary tests suggested that employment problems, poor parental supervision and family disruption we associated with severe PD in daughters, mediation analysis suggested that these variables had very little effect once severity of father's disorder was in the model. Psychosocial risk factors appear to play a limited role in the intergenerational transmission of PD severity, although future studies should take account of interaction data, for example, quality and quantity of paternal interaction given a child's temperamental traits.

Physical parameters influence on the transmitted signal through a rigid porous medium in the low-frequency range of ultrasound

The acoustic characterization of porous materials with rigid structure plays an important role in the prediction of the acoustic behavior of these media. In order to obtain an accurate prediction of its response as a function of frequency, several parametric models have been proposed. However, semi-phenomenological models are the most used to describe the acoustic behavior of porous materials with rigid or flexible structures according to a certain number of macroscopic physical properties related to the internal structure of the material and essential for their valuation. Among these models, the one proposed by Johnson et al. to describes the complex density of an acoustic porous material with an immobile skeleton having arbitrary pore shapes. The objective of this work is to study the effect of these parameters involved in Johnson's model as well as other new parameters, recently introduced by Sadouki [ Phys. Fluids 33, (2021)), on the transmitted signal in the low-frequency regime of ultrasound.

Effect of physical and mechanical parameters on the reflected signal from the first interface of human cancellous bone—application of Biot's theory

In this work, a simulated study on the effects of physical and mechanical parameters describing human cancellous bone on reflected ultrasound waves is proposed. The visco-inertial exchanges between the structure and the saturating fluid are described by the Biot theory modified by the Johnson model. A simplified expression of the reflection coefficient at the first interface is obtained in the frequency domain. This expression depends on three physical parameters which are porosity, tortuosity, and viscous characteristic length as well as the mechanical parameters; Young's modulus and Poisson's ratio. The reflected signal is calculated in the frequency domain by the product of the spectrum of the incident signal with the reflection coefficient. In the time domain, the reflected wave is obtained by taking the inverse Fourier transform of the reflected frequency signal. The effect of each parameter on the reflected signal is studied. The results obtained are discussed and compared with those given in the literature.

Analysis of the Impact of Johnson's Behavioral Model on Anxiety of Mothers of Children with Cancer

Background : Nowadays, cancer is one of the most critical health problems. The present study aimed to investigate the impact of the Johnson Behavioral Model on the anxiety of mothers of children with cancer. Methods : This empirical study was done on 66 mothers of children with cancer in the centers covered by children with cancer in 2020. The samples were selected using simple random sampling. Data were collected using the Spielberger demographic and anxiety inventory. After data collection, data analysis was done in SPSS18 using descriptive statistics and independent t-test, paired t-test, chi-square test, fisher, and covariance test. The significant level was set at 0.05. Results : The anxiety level was equal to 112.39±18.22 and 111±20.07 before intervention and equal to 81.21±6012 and 108.42±18.37 after the intervention in the intervention and control group, respectively. The independent t-test showed no significant difference between the two groups before the intervention (Pvalue=0.769). However, the difference was significant after the intervention (Pvalue<0.01). The paired t-test showed a significant difference between the two groups before and after the intervention in the intervention (Pvalue=0.001) and control (Pvalue<0.001) groups. Conclusions : The results obtained from this study showed that the Johnson theory plays a key role in reducing the anxiety of mothers of children with cancer. Keywords : Johnson Behavioral Model, Anxiety, Mothers of children, Cancer

The Preparation of High-Volume Fraction SiC/Al Composites with High Thermal Conductivity by Vacuum Pressure Infiltration

The high-volume fraction SiC/Al composite is the new type of electronic packaging material, which plays an important role in the field of high-power integrated circuits. In this study, SiC/Al composites with high-volume fraction of SiC particles were prepared by vacuum pressure infiltration. The influence of SiC particle size and NH4HCO3 on the pores in the preform was explored, aiming to accurately adjust the volume fraction of SiC to meet the thermal performance requirements in different fields. In addition, the preform was infiltrated with different Al alloys, and the relationship between the porosity and thermal conductivity of SiC/Al was studied. For the SiC preform, the volume fraction of SiC can be adjusted regularly when 12 μm and 100 μm SiC particles are mixed in different proportions, and the volume fraction reaches the maximum when the proportion of coarse particles is about 77%. NH4HCO3 is conducive to the connectivity of pores in the preform, and about 40 vol.% of NH4HCO3 can effectively increase the porosity of the preform. Thermal conductivity is sensitive to the porosity of composites, especially in the range of 2.5–4.5%. A simple application of the Hasselman–Johnson model and a new thermal conductivity model, λd, established in this article, offer a good agreement with the experimental results.

Computational fluid dynamic simulations of regular bubble patterns in pulsed fluidized beds using a two‐fluid model

AbstractThis simulation study explores the two‐fluid model's (TFM) capability to reproduce the alternating bubble patterns in a sinusoidal pulsed fluidized bed (PFB). Simulations were performed with frictional limits ranging between 0.58–0.62 with the inlet gas frequency being varied in the range of 3–6 Hz. The preliminary investigations showed that the Johnson and Jackson frictional model with a frictional limit of 0.61 yields a regular bubble pattern. The inference of this regular bubble pattern was based on the discrete Fourier analysis of the temporal pressure signals obtained at different spatial locations inside the PFB. Although the one‐dimensional temporal pressure signals characterized a regular bubble pattern behaviour, the staggered bubbles visually observed were highly unstable. Moreover, in‐depth insights into the PFB's regime classification showed that the predicted regular bubble patterns are susceptible to uncertainties due to the inherent mathematical limitations of the frictional closures of the TFM. Besides, the combinations of the frictional models/ limits in the TFM simulations could not predict the high stability and intermediate stability regimes of PFB. The present investigations helped identify the limitations of frictional closure models of TFM in predicting the regular bubble patterns and the regime classification for the PFB. It also expresses the need to develop better strategies to model the frictional closure of TFM to accurately account for the ever‐evolving dense and dilute particle regions of a PFB.

CASE STUDY: THE APPROACH OF MILITARY UNIT COMMAND WITH THE QUALITY MODEL OF THE EUROPEAN FOUNDATION FOR QUALITY MANAGEMENT IN THE CONTEXT OF STRATEGIC PLANNING

Nowadays, many organizations try to ensure the best result with the minimum necessary sources by following the practices of the propulsion of self-valuation throughout the European Foundation for Quality Management (EFQM) approach, within the frame of a Strategic Planning. The self-valuation criterions of the EFQM, can also be implemented in military units. The case of the EFQM self-valuation criterions’ implementation in a military Unit is examined in this study. It is tried a critical analysis of the case, by examining the following practice of its Commander within the context that his activities are emerged. Then, a particular proposal which concerns the implementation of the planning that follows the Johnson and Scholes (1993) model, is presented. The various manifestations and meanings of the self-valuation criterions and the useful tool of the Strategic Planning are revealed. Moreover, the characteristics of the leader-Commander are presented, so that the unit can meet the standards of the desired final state. The demand of active Commanders with vision, who can inspire the personnel by the proper guidance and the ability to convince them to follow the procedures, is the conclusion that comes out of the proposal. By carrying out a continuous self-valuation, within the frame of the EFQM criterions, and then, following the necessary actions, the improvement can be achieved. The personnel and the potential of its progress, the stuff maintenance, the facilities’ improvement, the exploration of the environment, in order recourses can be found, are the crucial factors so that actions can be taken over, which will targer to the exploitation of the unit’s potentials, the reduction of the threats and the weaknesses’ change into potentials. Commanding and leading skills are necessary with the simultaneous participation of all bodies in the various procedures. Yet, unpredictable situations, limitations and moral dilemmas may appear, making thus difficult Strategic Planning’s implementation.

On a simple, stable and efficient bond model for inter-particle adhesion

In this work, we explore the underlying structure of most common bond models used in particle dynamics and discrete element methods, to derive simple equilibrium conditions and stability requirements that must be fulfilled for a model to stand effective and reliable. We then propose a simple model taking into account such considerations, with which we are able to capture inter-particle bonding very straightforwardly once a given bonding criterion is met. The model can be particularized to work with different contact models, such as Hertzian contact, as well as with different adhesion models, such as the classical Johnson, Kendal and Roberts (JKR) model. The derived requirements yield guidelines that may help the selection of proper parameter values (such as, but not only, the stiffness of the bond) for most common bond models, thereby guiding (or even avoiding) burdensome problem-dependent calibration. Numerical examples are provided for illustration.

Individual growth profiling improves growth modelling in the geoduck clam Panopea generosa

Abstract Contemporary modelling of growth based on shell-length to terminal age (SLTA) in long-lived clams is subject to inaccuracies as a consequence of low representation of early age classes in population samplings. To increase early age representation and improve growth modelling, we implemented an approach that used individual growth profile (IGP) data recorded in shells of the Pacific geoduck (Panopea generosa). We compared IGP against SLTA and a combination of both IGP + SLTA data through a multi-model approach for the southernmost known P. generosa population. The most parsimonious model for both IGP and IGP + SLTA data sets was the Schnute model, with L∞ = 127.9 and 122.5 mm, respectively, with the asymptotic phase attained at ∼15 years. For SLTA data alone, the most parsimonious was the Johnson model, with L∞ = 161.6 mm reaching the asymptotic phase at &amp;gt;25 years. In terms of performance, the IGP and IGP + SLTA data sets informed individual growth models with stronger relationships (r2 &amp;gt; 0.9) and higher modelling efficiency (ME &amp;gt; 0.9) than those fitted to SLTA alone (r2 = 0.51; ME = 0.51). The results demonstrate that IGP yields reliable information from relatively few organisms, improves the biological knowledge of the population, and increases the accuracy of parameter estimates for better fishery management.

Individual growth analysis of the Pacific yellowlegs shrimp Penaeus californiensis via multi-criteria approach

Length-frequency data of juveniles and sub-adults of Penaeus californiensis were analyzed, collected from January 2002 to January 2003 in the Agiabampo lagoon system and adjacent marine coastal zone. Six models were parameterized with four criteria, in addition to a mixed criterion (fat-tail and depensatory), to estimate the parameters that best fit the growth curve. The model that best fit was the Johnson model with the mixed criterion in females and males: k = 6.02 (5.93-6.12); L∞ = 188.8 (186.3-191.8); t0 = 0.0221 (0.0207-0.0234); and: k = 8.98 (8.85-9.12); L∞ =153.3 (151.7-155.0); t0 = 0.0386 (0.0378-0.0394), respectively. The conclusion is that: 1) the mixture approach found in this study as best leads to the application of a very high-performance objective function to analyze individual length-at-age variability, 2) shows that the best model to describe the growth trajectory of P. californiensis in marine and estuarine environments is a sigmoid curve with an inflection point near to cero age (Johnson model).

Improved core model of the indentation for the experimental determination of mechanical properties of elastic-plastic materials and its application

The improvement of Johnson's model (Johnson (1970), (1985)) takes into account the additional pressure and shear stresses jump at the boundary with the hydrostatic core where it is formed from the material of the elastic-plastic zone. This causes additional volumetric deformations and additional pressure in the core that increases the magnitude of the constant in the Tabor ratio. The effects of the proposed improvement of the Johnson model: additional volumetric deformations and pressure in the core, changes in the Tabor constant and related values of yield strength as well as characteristic size of the elastic-plastic region, were determined on a wide class of materials with different elastic-plastic properties. An analysis of the concept of characteristic (representative) strain is given for these materials.

New Knowledge for the Profession: Case for Using Nursing Theory

First, the authors of this column reiterate the need for using nursing theory as a foundation for nursing research and practice. A study underpinned by Johnson's behavioral model is presented as an excellent example of the use of nursing theory to guide research in the care of people with heart failure.

A Critical Review and Assessment of Different Thermoviscoplastic Material Models for Simultaneous Hot/Cold Forging Analysis

The simultaneous hot/cold forging is an innovative production process, taking advantage of the high accuracy for cold forming and low forces for hot forming. However, the choice of a suitable material model for such a large temperature range is a difficult issue and insufficiently regarded. Hence, the aim of this contribution is a critical review and assessment of the prediction capability and accuracy of three already existing thermo-viscoplasticity models. Therefore, the simulation results of the Bammann, Chiesa and Johnson (BCJ) model, the Evolving Microstructural M odel of I nelasticity (EMMI) and a recently proposed user defined constitutive model by Bröcker and Matzenmiller, based on an enhanced concept of rheological elements, are compared to test data considering a large range from room temperature up to approximately 1400 K (1127 ∘C). All three material models may represent the thermo-viscoplastic characteristics of metals, whereby each investigated material model comprises different approaches for the temperature dependency of the initial yield stress, nonlinear isotropic hardening, and strain rate sensitivity. All material parameters are identified with the test data of the low alloy steel 50CrV4/51CrV4, the case hardening steel 16MnCr5, the low carbon steel C15 and the aluminium alloy AlMgSi1 by using the commercial optimisation software LS-OPT. The prediction capability and accuracy of each model is evaluated on the basis of the mean squared error by means of a comparsion of real and predicted stress-strain curves for the four different metals. Finally, an industrial oriented hot/cold forging process for the production of a gear shaft made of the low alloy steel 51CrV4 is simulated with LS-DYNA using the three material models and, subsequently, their performance is discussed. As achievement of this model assessment, suitable as well as inappropriate temperature dependent approaches are identified for this large temperature range providing new insights into suitable material models for the analysis of a simultaneous hot/cold forging process.

Sexual Motivators and Endorsement of Models Describing Sexual Response of Men Undergoing Androgen Deprivation Therapy for Advanced Prostate Cancer

BackgroundAndrogen deprivation therapy (ADT) administered against metastatic prostate cancer has significant side effects including sexual dysfunction. AimTo assess sexual interest and motivators for sex during ADT and to find out what model of sexuality best describes the sexual experience for men during this treatment. MethodsA questionnaire was mailed to patients who had received ADT for ≥6 months. Patients were asked to choose all relevant entities from a list of sexual motivators and between models of sexuality described by Masters and Johnson (excitement and physical experiences), Kaplan (sexual desire), and Basson (intimacy and closeness to partner). Erectile function was assessed by the Erection Hardness Scale, and sexual satisfaction was measured on a scale from 0 to 10. OutcomesSexual activity, erectile function, sexual satisfaction, and motivators for sexual interest in the study subjects as well as the proportion of participants who endorsed either of the 3 models of sexuality. ResultsA total of 173 men were invited, and 76 returned the questionnaires (44%). The median age was 76 (range 69–80) years, and the median duration of ADT was 30 months. A total of 62 men had been sexually active before ADT, and of these, 2 were still active. Another 29 were interested in sexual activity. 3 men endorsed the Masters and Johnson model, whereas the remaining participants did not endorse any of the models. The motivators for sexual interest were feeling an emotional connection to the partner (n = 16), sexual desire (n = 10), satisfaction of the partner (n = 8), fear that the partner would leave (n = 4), achieving orgasm (n = 3), and a desire to feel masculine (n = 1). No one was interested in sexual activity to reduce stress or to maintain confidence. Only 1 patient had erections sufficient for penetrative intercourse, and the median sexual satisfaction for the entire group was 0 (interquartile range: 0–5). Clinical ImplicationsSexuality and sexual function should be addressed in men undergoing ADT. Strengths & LimitationsThe main strength of our study is that we are the first to explore both motivators for sexual activity and endorsement of sexual models in men undergoing ADT. The study is limited by the relatively low number of participants and the response rate of 44%. ConclusionADT is detrimental to sexual function. However, many patients maintain an interest in sexual activity, which does not fit our established models. Rather, factors such as keeping an emotional connection with a partner play a role.Fode M, Mosholt KS, Nielsen TK, et al. Sexual Motivators and Endorsement of Models Describing Sexual Response of Men Undergoing Androgen Deprivation Therapy for Advanced Prostate Cancer. J Sex Med 2020;17:1538–1543.

Determination of a Complete Conversion Model for Gasification of Lignite Char

The conversion of solid fuels via gasification is a viable method to produce valuable fuels and chemicals or electricity while also offering the option of carbon capture. Fluidized bed gasifiers are most suitable for abundantly available low-rank coal. The design of these gasifiers requires well-developed kinetic models of gasification. Numerous studies deal with single aspects of char gasification, like influence of gas compositions or pre-treatment. Nevertheless, no unified theory for the gasification mechanisms exists that is able to explain the reaction rate over the full range of possible temperatures, gas compositions, carbon conversion, etc. This study aims to demonstrate a rigorous methodology to provide a complete char gasification model for all conditions in a fluidized bed gasifier for one specific fuel. The non-isothermal thermogravimetric method was applied to steam and CO2 gasification from 500 °C to 1100 °C. The inhibiting effect of product gases H2 and CO was taken into account. All measurements were evaluated for their accuracy with the Allan variance. Two reaction models (i.e., Arrhenius and Langmuir–Hinshelwood) and four conversion models (i.e., volumetric model, grain model, random pore model and Johnson model) were fitted to the measurement results and assessed depending on their coefficient of determination. The results for the chosen char show that the Langmuir–Hinshelwood reaction model together with the Johnson conversion model is most suitable to describe the char conversion for both steam and CO2 gasification of the tested lignite. The coefficient of determination is 98% and 95%, respectively.

Determination of a Complete Conversion Model for Gasification of Lignite Char

The conversion of solid fuels via gasification is a viable method to produce valuable fuels and chemicals or electricity while also offering the option of carbon capture. Fluidized bed gasifiers are most suitable for abundantly available low-rank coal. The design of these gasifiers requires well-developed kinetic models of gasification. Numerous studies deal with single aspects of char gasification, like influence of gas compositions or pre-treatment. Nevertheless, no unified theory for the gasification mechanisms exists that is able to explain the reaction rate over the full range of possible temperatures, gas compositions, carbon conversion, etc. This study aims to demonstrate a rigorous methodology to provide a complete char gasification model for all conditions in a fluidized bed gasifier for one specific fuel. The non-isothermal thermogravimetric method was applied to steam and CO2 gasification from 500 °C to 1100 °C. The inhibiting effect of product gases H2 and CO was taken into account. All measurements were evaluated for their accuracy with the Allan variance. Two reaction models (i.e., Arrhenius and Langmuir–Hinshelwood) and four conversion models (i.e., volumetric model, grain model, random pore model and Johnson model) were fitted to the measurement results and assessed depending on their coefficient of determination. The results for the chosen char show that the Langmuir–Hinshelwood reaction model together with the Johnson conversion model is most suitable to describe the char conversion for both steam and CO2 gasification of the tested lignite. The coefficient of determination is 98% and 95%, respectively.

Facets, weak facets, and extreme functions of the Gomory–Johnson infinite group problem

We investigate three competing notions that generalize the notion of a facet of finite-dimensional polyhedra to the infinite-dimensional Gomory–Johnson model. These notions were known to coincide for continuous piecewise linear functions with rational breakpoints. We show that two of the notions, extreme functions and facets, coincide for the case of continuous piecewise linear functions, removing the hypothesis regarding rational breakpoints. We prove an if-and-only-if version of the Gomory–Johnson Facet Theorem. Finally, we separate the three notions using discontinuous examples.

Analysis of copper-tungsten cold spray coating: Kinetics of coating formation and its thermal properties

The tungsten-copper composites are used in industry as electrical contact materials due to high thermal conductivity, high melting temperature of tungsten and low coefficient of thermal expansion. In this work the process of deposition of the composite copper-tungsten cold spray coating was studied. Kinetics of the coating formation process was analyzed using specially developed analytical model based on the probability approach. It was shown the mass percentage of tungsten mass percentage in the coating could not exceed 52%. The modeling results were in good agreement with experimental data. Thermal conductivity of the composite coatings with different tungsten percentage was experimentally measured and compared with the theoretical results calculated using Hasselman – Johnson model. It was found that the thermal conductivity of the copper-tungsten coating depended on the percentage of the tungsten.

The effect of cell wall material strain and strain-rate hardening behaviour on the dynamic crush response of an aluminium multi-layered corrugated core

The effect of the parameters of the Johnson and Cook material model on the direct impact crushing behaviour of a layered 1050 H14 aluminium corrugated structure was investigated numerically in LS-DYNA at quasi-static (0.0048 m s−1) and dynamic (20, 60, 150 and 250 m s−1) velocities. Numerical and experimental direct impact tests were performed by lunching a striker bar onto corrugated samples attached to the end of the incident bar of a Split Hopkinson Pressure Bar set-up. The numerical impact-end stress-time and velocity-time curves were further compared with those of rigid-perfectly-plastic-locking (r-p-p-l) model. Numerical and r-p-p-l model impact-end stress analysis revealed a shock mode at 150 and 250 m s−1, transition mode at 60 m s−1 and quasi-static homogenous mode at 20 m s−1. The increase of velocity from quasi-static to 20 m s−1 increased the numerical distal-end initial peak-stress, while it almost stayed constant between 20 and 250 m s−1 for all material models. The increased distal-end initial peak-stress of strain rate insensitive models from quasi-static to 20 m s−1 confirmed the effect of micro-inertia. The numerical models further indicated a negligible effect of used material models on the impact-end stress of investigated structure. Finally, the contribution of strain rate to the distal-end initial peak-stress of cellular structures made of low strain rate sensitive Al alloys was shown to be relatively low as compared with that of strain hardening and micro-inertia, but it might be substantial for the structures constructed using relatively high strain rate sensitive alloys.