bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Video Prompting to Teach Mathematical Problem Solving of Real-World Video-Simulation Problems
Authors: Saunders Alicia F. , Spooner Fred , Ley Davis Luann
Published: December 2017

Mathematical problem solving is necessary in many facets of everyday life, yet little research exists on how to teach students with more severe disabilities higher order mathematics like problem solving. Using a multiple probe across participants design, three middle school students with moderate intellectual disability (ID) were taught to solve video-simulation real-world mathematical problems by finger counting using video prompting (VP) in conjunction with systematic instruction (e.g., least intrusive prompting) with error correction and feedback. The simulated videos covered a variety of thematic units (i.e., pet store, grocery store, household chores, sporting goods store, outside chores, and thrift store) students may encounter in their everyday lives. The results of this study demonstrated a functional relation between VP and participants’ mathematical problem-solving skills. Findings from this study provide several implications for practice and research for using video-based interventions to teach mathematical problem solving to students with moderate ID.
Youth Civic Engagement: Do Youth Councils Reduce or Reinforce Social Inequality?
Authors: Augsberger Astraea , Collins Mary Elizabeth , Gecker Whitney , Dougher Meaghan
Published: December 2017

Youth engagement in municipal government has the potential to benefit both youth and the community. Yet, some forms of youth civic engagement may be related to social class and race resulting in benefits to select youth and communities, thus perpetuating a longer term trajectory of privilege or marginalization. Informed by theories of social capital and civic engagement, the present study examined how youth councils may reduce or reinforce social inequality among young people at the city level. Data collection included interviews with youth council members, interviews with adult allies, observations of youth council meetings, and a review of council documents. Thematic analysis identified four overarching themes related to social inequality: member representation, social networks, community engagement, and youth engagement in governmental decision making. Although the council was committed to diversity and authentic youth engagement, findings identified areas in need of further attention. One important area is recruiting diverse youth, including those who attend non-traditional school settings. Another key area is providing youth with ongoing training and support focused on effective strategies for community engagement. Finally, more emphasis should be placed on engaging socially disadvantaged youth in municipal government and assisting them in enhancing their social networks.
The Relationship of Paranasal Sinus Opacification to Hospital-Acquired Pneumonia in the Neurologic Intensive Care Unit Patient
Authors: Huyett Phillip , Rowan Nicholas R. , Ferguson Berrylin J. , Lee Stella , Wang Eric W.
Published: December 2017

Background:

The association between intensive care unit (ICU) sinusitis and the development of lower airway infections remains unclear. The objective of this study was to determine the correlation between the development of radiographic sinus opacification and pneumonia in the neurologic ICU setting.

Methods:

A retrospective review of head computed tomography or magnetic resonance imaging of 612 patients admitted to the neurocritical care unit at a tertiary care center from April 2013 through April 2014 was performed. Paranasal sinus opacification was measured using Lund-Mackay scores (LMS). A diagnosis of pneumonia was determined by the ICU team from radiographic, laboratory, and pulmonary data. Exclusion criteria included a history of endonasal surgery, sinonasal malignancy, facial fractures, ICU admission less than 3 days, or inadequate imaging.

Results:

Worsening sinus opacification occurred in 42.6% of patients and pneumonia in 18.5% of patients during ICU admission. Of the patients who developed pneumonia, 71.7% also developed worsening sinus opacification ( P < .001). In 80.2% of cases, the sinus opacification developed prior to the diagnosis of pneumonia. The mean highest LMS for patients who developed pneumonia was 4.24 compared to 1.99 in patients who did not develop pneumonia ( P < .001). Sinus air–fluid levels or complete sinus opacification occurred in a larger proportion of patients who developed pneumonia (46.9% vs 19.4%, P < .001). Mortality rates for patients with no pneumonia or sinusitis, pneumonia only, sinusitis only, and sinusitis with pneumonia were 7.6%, 15.6%, 18.3%, and 25.9%, respectively ( P < .001).

Conclusions:

This study finds a strong relationship between worsening sinus opacification in the neurologic ICU patient to the development of hospital-acquired pneumonia and increased mortality.
Outcomes of Tracheostomy With Concomitant and Delayed Percutaneous Endoscopic Gastrostomy in the Neuroscience Critical Care Unit
Authors: Nobleza Christa O’Hana S. , Pandian Vinciya , Jasti Ravirasmi , Wu David H. , Mirski Marek A. , Geocadin Romergryko G.
Published: December 2017

Background:

In patients with severe neurologic conditions, percutaneous endoscopic gastrostomy (PEG) is typically performed either alone or with a tracheostomy. The characteristics and outcomes of patients receiving PEG concomitantly with a tracheostomy (CTPEG) and those receiving delayed PEG (DPEG) after a tracheostomy were compared.

Methods:

Retrospective cohort study in a 24-bed neuroscience critical care unit (NCCU) at a tertiary care hospital. Consecutive patients admitted to the NCCU from April 2007 to July 2013 who underwent percutaneous tracheostomy and gastrostomy by the percutaneous tracheostomy team were included and grouped according to the timing of PEG placement: CTPEG versus DPEG.

Results:

Of the 290 patients, 234 (81%) received CTPEG. Demographic and clinical characteristics were similar among the 2 groups except for a lower median (interquartile range [IQR]) body mass index (BMI; 27 [22.67-31.60] versus 30.8 [24.55-40.06], P = .017) and lower rate of acute respiratory distress syndrome (3.85% vs 10.71%, P = .048) in the CTPEG cohort. Furthermore, 59% of CTPEG cohort were neurology patients while 63% of DPEG were neurosurgery patients, P = .004. Primary outcomes showed shorter mean NCCU length of stay (LOS; 25 [12] vs 33 [17] days, P < .001) and median hospital LOS (32 [25-43] vs 37 [31-56] days, P = .002) for the CTPEG cohort. Secondary outcomes showed higher predischarge prealbumin levels (15.6 [7.75] vs 11.58 [5.41], P = .021) and lower median overall hospital cost (US$123 860.20 [US$99 024-US$168 713.40] vs US$159 633.50 [US$121 312-US$240 213.10], P = .0003) in the CTPEG group. Anatomic contraindications were the most common reason for DPEG (30%).

Conclusions:

Among institutions with a tracheostomy team, the practice of tracheostomy with concomitant PEG placement may be considered as feasible as delayed PEG in carefully selected neurocritically ill patients with possible advantages of overall shorter NCCU and hospital LOS, higher predischarge prealbumin, and lower hospital costs. These findings may aid in decisions regarding the timing of PEG placement in the NCCU. Further prospective studies are warranted.
Hard Time
Authors: Casey Rachel C.
Published: December 2017

As the number of women incarcerated in the United States continues to rise and their complex needs become more apparent, social workers must fortify their historical commitment to criminal justice reform. However, crafting more effective and compassionate responses to the needs of justice-involved women may very well require a more nuanced understanding of the holistic impact of incarceration on women’s well-being than the current literature offers. Utilizing the framework of feminist standpoint epistemology, the researcher engaged in qualitative content analysis to examine published personal accounts from 43 women to better understand their experiences in prisons and jails in the United States. Two overarching themes emerged from the analysis. First, the personal accounts illustrated that women experience prisons and jails as environments of denial insofar as these carceral environments deny women’s basic needs, their sense of humanity, and their personal power. The second overarching theme pertains to the holistic impact of the carceral environment upon women’s lives, meaning it has expansive effects on women’s biopsychosocial–spiritual functioning. Social workers should dedicate efforts to dramatically reducing the number of women behind bars and engaging in holistic intervention approaches that might counteract the negative effects of incarceration across domains of well-being.
Reshaping the Study of Recidivism: Exploring Variations in the Timing of Recidivism Following Release From Prison
Authors: Denver Megan
Published: December 2017

While hazard analyses allow researchers to identify distributional changes over time, this powerful benefit is often underutilized. This article incorporates the shape parameter—in addition to level—into lognormal hazard models to examine recidivism patterns for individuals returning home from prison. Using a sample of adults released in 1994 from 15 state prison facilities, the results indicate that factors influencing the shape are both individual-level (race, age, prior arrest history) and jurisdiction-driven (prison admission type and state). While targeting the highest “risk” individuals is a well-established best practice, the present study suggests that reentry planners may benefit from focusing on groups undergoing change in the postrelease period in addition to those experiencing the highest hazard levels on average. Future research would benefit from incorporating the shape parameter into recidivism studies and including additional factors in shape analyses, such as social indicators, to further contextualize the reentry–recidivism relationship.
Is Getting Tough With Low-Risk Kids a Good Idea? The Effect of Failure to Appear Detention Stays on Juvenile Recidivism
Authors: Ogle Meghan R. , Turanovic Jillian J.
Published: December 2017

Although the juvenile justice system has adopted many alternatives to detention, the practice of detaining youth for failing to appear in court remains common. Despite its widespread use, it is unclear whether this form of detainment is harmful to juvenile offenders—especially to those who pose no credible threat to public safety. Accordingly, using data from the Florida Department of Juvenile Justice (FDJJ) and propensity score matching, we assess whether failure to appear (FTA) detention increases recidivism for low-risk youth. The results indicate that FTA detention increases official recidivism, technical recidivism, and re-detainment, and suggest that alternate policies be considered for low-risk juvenile offenders.
Is Burglary a Violent Crime? An Empirical Investigation of the Armed Career Criminal Act’s Classification of Burglary as a Violent Felony
Authors: Kopp Phillip M.
Published: December 2017

Traditionally considered a non-violent property offense, burglary is nonetheless classified as a violent crime under the federal Armed Career Criminal Act (ACCA). The ACCA, a three-strikes law that provides a mandatory minimum sentence of 15 years, is triggered when an offender, who has been previously convicted for a crime classified under the ACCA as either a “violent felony” or “serious drug offense,” is convicted at the federal level for any felony committed while in possession of a firearm. The present study investigated the ACCA’s classification of burglary as violent through analysis of National Crime Victimization Survey data for the period of 2009 to 2014. Results showed that burglary is overwhelmingly a non-violent offense. The national incidence of actual violence or threats of violence during a burglary was 7.9%. At most, 2.7% of burglaries involved actual acts of violence. Legislative reform of the ACCA classification to match the empirical description of burglary is discussed.
The Role of Private Legal Representation and the Implicit Effect of Defendants’ Demographic Characteristics in Setting Bail and Obtaining Pretrial Release
Authors: Hissong Rod V. , Wheeler Gerald
Published: December 2017

Misdemeanor bail schedules use the seriousness of the alleged crime and the defendant’s criminal history. Court officials contend the schedules ensure that only legal factors are considered for bail. Using longitudinal data from randomly selected misdemeanor cases filed during the first quarter of 2012 in Harris County, Texas we use ordinary least squares (OLS) to test the influence of demographic characteristics of defendants and their ability to retain private representation on the process of setting the monetary amount for bail. We find evidence of implicit bias and a distinct advantage of private representation. Using logit analysis, we estimate how demographic factors and monetary bail influence the probability of pretrial release, and present point estimates of making bail by demographic type. Demographics matter but retaining private counsel increases the probability of bail by sevenfold. Policy recommendations include expanding the use of public defenders and allowing them access to clients much earlier in the process.
Better Practices in the Development and Validation of Recidivism Risk Assessments: The Minnesota Sex Offender Screening Tool–4
Authors: Duwe Grant
Published: December 2017

This study examines the development and validation of the Minnesota Sex Offender Screening Tool–4 (MnSOST-4) on a dataset consisting of 5,745 sex offenders released from Minnesota prisons between 2003 and 2012. Bootstrap resampling was used to select predictors, and k-fold and split-sample methods were used to internally validate the MnSOST-4. Using sex offense reconviction within 4 years of release from prison as the failure criterion, the data showed that 130 (2.3%) offenders in the overall sample were recidivists. Multiple classification methods and performance metrics were used to develop the MnSOST-4 and evaluate its predictive performance on the test set. The results from the regularized logistic regression algorithm showed that the MnSOST-4 performed well in predicting sexual recidivism in the test set, achieving an area under the curve (AUC) of 0.835. Additional analyses on the test set revealed that the MnSOST-4 outperformed the Minnesota Sex Offender Screening Tool–3 (MnSOST-3), Minnesota Sex Offender Screening Tool–Revised (MnSOST-R), and Static-99 in predicting sexual reoffending.
Multilayered hybrid roving as a manufacturing concept of continuous fiber–reinforced thermoplastic materials
Authors: Jung Gihune , Mitschang Peter
Published: December 2017

A new manufacturing concept named multilayered hybrid (MLH) roving was invented in the form of a fiber roving separated evenly into several sublayers by thermoplastic films, which is manufactured by the sequential processes of spreading, fixing, and folding. This concept is aimed to combine the variety in processing of commingled roving and the variety in material configuration of organic sheet. For the review on impregnation basics, the Kozeny–Carman equation was examined on the packed bed of fibers, not of particles, to check out the controllable parameter. Also, the newly derived spreading equation was prepared to prevent the current problem of center splitting during fiber spreading processes. The impregnation quality was practically verified by the bending test on the unbalanced (2/1) woven fabric made of polypropylene (PP) and glass fiber (GF) MLH roving, PP/GF45 vol.% (70 wt%), which had been impregnated by the continuous compression molding machine considering the conditions of mass production. The representative flexural properties were statistically determined with the characteristic behavior of stress–strain curve. The coefficient-of-variation values were in the moderate range of around 5%, except for the strength and strain in minor direction that can be explained by the waving of fibers due to the lack of applied tension during and before impregnation.
Preparation and properties of polyamide 6 nanocomposites covalently linked with amide functional graphene oxide
Authors: O’Neill Aidan , Bishop David , Dalton Brendan , Archer Edward , McIlhagger Alistair , Dixon Dorian
Published: December 2017

Chemically engineered polyamide 6 (PA6)/graphene oxide (GO) nanocomposites were produced via the functionalization of GO with an amide (CONH2) functional group, in order to produce amide-GO with improved interfacial bonding and dispersion in the host polymer matrix. In situ polymerization of ε-caprolactam was carried out in the presence of amide-GO to create PA6/amide-GO nanocomposites. The nanomaterial (pre- and post-polymerization) and the composites were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and tensile testing. The single-layer nature of GO was attested by TEM. FTIR, XPS, XRD and thermal analysis techniques confirmed the successful amide modification of GO. The expected attachment of PA6 to the surface of GO is demonstrated, along with the reduction of GO during polymerization. Some reduction of GO during the chemical functionalization process was also observed. The thermal stability of the nanocomposites was confirmed, while promotion of α-phase crystallite formation and a molecular weight change of attached PA6 are observed. A linear improvement in stiffness and yield strength was observed as functionalized GO content increased from 0.1 wt% to 0.75 wt%. A levelling off of mechanical properties ensued once the GO content reached 1 wt%, and a decrease was seen at 2 wt%.
Hostile Media or Hostile Source? Bias Perception of Shared News
Authors: Yun Gi Woong , Park Sung-Yeon , Lee Sooyoung , Flynn Mark A.
Published: December 2017

An experiment was conducted with college students to examine the effects of source and user comments on the perceptions of a shared news story embedded in a blog post. When the shared news was credited to a news organization source incongruent with the participants’ political orientation, it was perceived to be biased against the participants’ issue position. When credited to a congruent source, the same news was perceived to be biased in favor of the participants’ position. In addition, the shared news from an incongruent source was perceived to have greater influence on others’ issue position than the same news from a congruent source, although perceived reach of the shared news was not different between the two conditions. A subsequent regression analysis identified source and perceived influence, but not perceived reach, as predictors of news bias perception. On the other hand, the second factor, user comments either agreeable or disagreeable to the participants’ issue position, did not influence how the shared news was perceived. In the discussion, theoretical implications of these findings are elaborated, and suggestions are made to refine the methods of shared news research.
Interest Group Activity in the Context of Common Core Implementation
Authors: Supovitz Jonathan , McGuinn Patrick
Published: December 2017

This article analyzes the messages and strategies of a sample of education interest groups, and assesses their interpretations of the political context to understand how the Common Core State Standards (CCSS) lost both political and public support during the crucial period of 2013-2014. Based on interviews with representatives of 19 interest groups who were actively involved in communicating about the standards, it focuses on the arguments, communication strategies, and targeted audiences of professional advocacy groups, policy membership organizations, and testing organizations. Our findings identify six themes that contributed to the climate of increased partisanship and politicization, and helped shape perceptions about the Common Core, both within the education sector and among the broader public. We argue that these policy factors, strategic factors, and contextual factors played an important role in shaping the environment within which the CCSS were being understood and implemented.
Value-Added Models for Teacher Evaluation and Accountability: Commonsense Assumptions
Authors: Amrein-Beardsley Audrey , Holloway Jessica
Published: December 2017

Despite the concerns regarding value-added models (VAMs), advocates hold strong to VAMs’ theoretical strengths and potentials, while adopting a set of agreed-upon albeit “heroic” set of assumptions, without research in support. These assumptions transcend promotional, policy, media, and research-based pieces, but they have never been made explicit as analyzed as a set or whole. The purpose of this study was to make unambiguous the assumptions that have been made within the VAM narrative that have often been accepted without challenge, and situate these assumptions within the research. Sources for analyses included 470 pieces, published within traditional and nontraditional outlets, from which we derived 27 prevailing assumptions.
Gendered Dimensions and Capabilities: Opportunities, Dilemmas and Challenges
Authors: Hobson Barbara
Published: December 2017

Looking through the lens of gender, this article engages with the opportunities, dilemmas and challenges posed by Sen’s framework to sociological research. Sen’s capability approach offers sociological research a dynamic framework through its concept of agency and its multidimensional approach. It also poses dilemmas, revealed in the tensions within agency and choice and the challenges in operationalizing Sen’s framework: adapting it to sociological models and applying it to empirically grounded research. Through conversion factors and processes, a central component in the capabilities approach, I reveal the potential of Sen’s approach for developing more dynamic frameworks in sociological research, with respect to (1) changes in gendered norms (how new norms are seeded); (2) how entitlements are converted into a sense of entitlement to make claims; and (3) how the capabilities approach can lead toward a more dynamic institutional analysis of welfare states. My contribution to Sen’s framework involves elaborating two mechanisms in the conversion of capabilities to agency freedoms and achievements: the sense of entitlement to make claims and the perceived scope of alternatives in exercising rights.
Power ≠ Power: Against the Mix-Up of Nietzsche and Spinoza
Authors: Rehmann Jan
Published: December 2017

The reception of Nietzsche’s philosophy is still predominated by a widespread “hermeneutics of innocence” (Losurdo) that dissimulates Nietzsche’s elitist perspectives. This article challenges a core element of this hermeneutics, the conflation of Spinoza and Nietzsche. The assumption of a continuity of their power concepts overlooks that the late Nietzsche took a sharp anti-Spinozian turn and introduced his “will to power” against Spinoza’s “conatus.” Whereas Spinoza’s potentia agendi designates a collective and cooperative capacity to act, which can be reconceptualized with the help of Gramsci’s theory of hegemony, Nietzsche’s “will to power” naturalizes the principle of domination. An ethics inspired by Nietzsche can never get rid of its inherent “pathos of distance,” which manifests itself even in its most “leftist” forms as a celebration of social distinctions against ordinary people. Recourse to Spinoza can help redefine life affirmation in a democratic-socialist way and thus provides an ethics for a hegemony from below.
Patient Satisfaction of Pharmacist-Provided Care via Clinical Video Teleconferencing
Authors: Hatton Jessica , Chandra Rachel , Lucius David , Ciuchta Elizabeth
Published: December 2017

Purpose:

Patient satisfaction with the use of telehealth in disease state management provided by pharmacists has not been fully studied. We hypothesized that patient satisfaction with pharmacist-provided consultations via clinical video teleconferencing (CVT) would not differ from face-to-face delivery.

Methods:

Patients were recruited from 2 primary care provider sites from September 2015 to May 2016. Patients completed a survey to evaluate their satisfaction and quality of provider–patient communication with the method in which consultation with a pharmacist was provided. The survey was a 10-item, patient self-reported questionnaire. The primary outcome evaluated patients’ scores on assessment of the provider’s use of patient-centered communication. The secondary outcome evaluated patients’ scores on assessment of the provider’s clinical competence and skills and interpersonal skills.

Results:

There were a total of 57 surveys collected. For both the primary outcome and secondary outcome, over 80% of collected responses for each question in both clinics were scored a 5 that indicates patients were very satisfied with the provider’s use of patient-centered communication and clinical competence and skills. For both the primary and secondary outcomes, there were no statistically significant differences in patients’ scores that assessed provider’s use of patient-centered communication nor the provider’s clinical competence and skill.

Conclusion:

The results of this study indicate patients are satisfied with pharmacists’ use of patient-centered communication and clinical competence and skills via both CVT and face-to-face consultations supporting our research hypothesis that patient satisfaction with care provided via CVT did not differ from face-to-face provided care.
Occupational Prestige and Gender-Occupational Segregation
Authors: García-Mainar Inmaculada , Montuenga Víctor M , García-Martín Guillermo
Published: December 2017

The purpose of this article is to determine whether there is a relationship between the proportion of women working in an occupation and the prestige assigned to that occupation. Based on a representative sample of Spanish employees from the Spanish Quality of Working Life Survey, pooled-sample data (2007–2010) are used to show that occupations with larger shares of women present lower prestige, controlling for a set of objective individual and work-related variables, and self-assessed indicators of working conditions. However, the results obtained do not support the devaluation theory since an inverted-U relationship between female share and occupational prestige is observed. This conclusion holds even after passing a battery of robustness checks.
The impact of Wisconsin’s Act 10 on municipal management in smaller municipalities: Views from local elected officials
Authors: Ford Michael R , Ihrke Douglas M
Published: December 2017

This article examines elected officials’ opinions on Wisconsin’s controversial 2011 collective bargaining reform. Survey results from elected officials serving on city councils and village boards with less than 10,000 residents demonstrate that Act 10 is still viewed through a partisan lens, making its overall impact on municipal governance unsettled. We also find that officials who first came to office prior to Act 10 generally think the law has had a positive fiscal impact. Overall, the authors conclude that Act 10 cannot yet be viewed as a successful governance reform because it is still viewed by local policymakers through a narrow fiscal and partisan lens.
Thermal and mechanical properties of cyanate ester resin modified with acid-treated multiwalled carbon nanotubes
Authors: Li Hongfeng , Gu Jiyou , Liu Changwei , Wang Dezhi , Qu Chunyan
Published: December 2017

Multiwalled carbon nanotubes (MWCNTs) that were treated with mixed acids were used to reinforce the cyanate ester resin. Meanwhile, the relationship among structure, morphology, and property of the modified resin was investigated. The treated MWCNTs were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, and X-ray photoelectron spectroscopy (XPS). The XPS results showed that the oxygen content in the treated MWCNTs was higher than that of untreated MWCNTs and the FTIR results indicated the presence of oxygen-containing functional groups on the treated MWCNTs. The microstructure of the resin was characterized by scanning electron microscopy and transmission electron microscopy. The results showed that the dispersion properties of the treated MWCNTs in the resin matrix were improved and compared with the untreated analogue. Addition of MWCNTs to the resin had little effect on the thermodynamic properties of the resin system. Upon addition of 0.8 wt% of MWCNTs to the resin, the glass transition temperature of the cured resin changed from 298°C to 285°C, maintaining a relatively high value. For the resins containing 0.6 wt% of treated MWCNTs, the plane strain critical stress intensity factor and plane strain critical strain energy release rate in the system were determined to be 1.39 Pa·m0.5 and 364 J m−2, respectively, and the fracture toughness is increased by 45.7 and 76.0%, respectively. Furthermore, the modified resin system exhibits excellent toughness and thermal properties. Therefore, the modified resin may be suitable for future applications involving high performance composites and adhesives.
Research on DC dielectric properties of polyaniline nanofibers/LDPE composites
Authors: Li Changming , Duan Sixu , Zhang Chengcheng , Zhang Jian , Han Baozhong
Published: December 2017

In this article, polyaniline (PANI) nanofibers were prepared and added to low-density polyethylene (LDPE) to produce PANI nanofibers/LDPE composites. LDPE and the composites were tested for direct current (DC) conductivity, breakdown strength, and space charge characteristics. The results suggested that DC breakdown strength of PANI nanofibers/LDPE composites significantly declined once PANI was added, and the decline was more evident with the increase of PANI nanofibers. Meanwhile, the addition of PANI nanofibers contributed to a decrease in the conductivity of LDPE. As the content of PANI nanofibers increased, the conductivity of the composites declined first and then raised. DC conductivity properties of LDPE could be improved by adding an appropriate amount of PANI nanofibers. Compared with LDPE, the space charge distribution was changed in LDPE due to the addition of PANI nanofibers. With the increase of content of PANI nanofibers, the amount of space charges close to the electrodes decreased gradually.
Energy consumption modeling and prediction of the milling process: A multistage perspective
Authors: Zhang Chaoyong , Zhou Zhiheng , Tian Guangdong , Xie Yang , Lin Wenwen , Huang Zhengtao
Published: December 2017

In order to provide an accurate estimation of energy consumption, this work proposes a novel energy consumption modeling and prediction approach for a milling process from a multistage perspective. Based on its work stages, each stage’s energy consumption model is established by sliding filter, multiple linear regression, and improved gene expression programming (variable neighborhood search–based gene expression programming) methods and then the total energy consumption is predicted through their combination. A case study is given to illustrate the proposed model and its effectiveness. Compared with the full quadratic model, which can fully consider the interaction between cutting factors, the proposed method can achieve the higher accuracy to predict the energy consumption of the milling process.
Precision design of hydrostatic thrust bearing in rotary table and spindle
Authors: Zha Jun , Chen Yaolong , Zhang Penghai
Published: December 2017

According to the increasing needs of rotary table and spindle to satisfy high-precision machining requirements, the accuracy of rotary table and spindle becomes an important issue due to the error averaging effect of hydrostatic thrust bearing. The objective of this study is to research a methodology to guide the precision design of hydrostatic thrust bearing in rotary table and spindle. A run-out error model based on error averaging effect is established using the Reynolds equation, pressure boundary conditions, flux continuity equations of pad and dynamic equations of shaft. The axial run-out error and angular error are calculated considering perpendicularity error and flatness error of the components. The simulation results show that the two perpendicularity errors between axis line and thrust bearing bushing surface have same direction, and the axial run-out error could reach to the maximum values. Also, the flatness error of thrust bearing bushing surface has a big influence on axial run-out error. Following the outcomes, the precision design of hydrostatic thrust bearing was conducted. The axial run-out errors of rotary table and spindle with hydrostatic thrust bearing were experimentally studied, and the results have good coherence to the simulation data. The run-out error model is demonstrated to be an effective approach to guide the precision design of hydrostatic thrust bearing in other rotary tables and spindles.
Resonant frequencies of perforated plates with rectangular slots
Authors: Barry Oumar R , Tanbour Emadeddin Y
Published: December 2017

Most previous work on perforated plates employed elasticity theory to determine equivalent material properties that make the deflection of the solid plate identical to that of the perforated plate. However, it will be inaccurate to utilize the proposed elastic properties to predict the natural frequencies of a perforated plate. In this paper, the free vibrations of perforated plates with rectangular slots and rectangular slot-patterns are examined using theoretical and finite-element methods. The natural frequencies are obtained for various cases of perforations. An explicit expression is obtained for the equivalent elastic properties using the regression analysis method. These effective material properties are used in a solid-plate model to predict the natural frequencies of the corresponding perforated plate. To validate the theoretical analysis, the effective resonant frequencies are compared with the exact natural frequencies of the perforated plates. Parametric studies are conducted to examine the effect of both parallel and perpendicular ligament efficiencies on the resonant frequencies.
Mechanical analysis of spherical roller bearings due to surface waviness
Authors: Xing Yu , Xu Hua , Liu Xuejing , Xi Hui , Wang Shibin
Published: December 2017

This work presents a theoretical model to research the vibration due to surface waviness of spherical roller bearings (SRBs), taking account of the self-aligning feature and the external axial load. The surface waviness is described by cosinoidal functions. The self-aligning features, including the variation law of the self-aligning contact angle and the interaction with the external loads, are introduced into the non-Hertzian contact model. The nonlinear equations are solved by Runge–Kutta method and the proposed model is validated by comparing with the results of the published references. The results show more characteristic frequencies will be excited under the self-aligning operating condition, whereby the improved equations proposed in this paper are recommended to instead of the previous ones to predict characteristic frequencies of the waviness vibration in an SRB. In addition, these characteristic vibrations caused by waviness are obviously influenced by the magnitude and the direction of the self-aligning contact angle. A proper pretightening load should be chosen according to the self-aligning feature or else it will lead to hidden dangers. The radial clearance and the waviness amplitude can both highlight the effect of waviness. And the vibration caused by a larger radial clearance may be fiercer than the vibration due to waviness.
Nonstationary analysis of nonlinear rotating shafts passing through critical speed excited by a nonideal energy source
Authors: Mahmoudi A , Hosseini SAA , Zamanian M
Published: December 2017

In this paper, the effect of nonlinearity on vibration of a rotating shaft passing through critical speed excited by nonideal energy source is investigated. Here, the interaction between a nonlinear gyroscopic continuous system (i.e. rotating shaft) and the energy source is considered. In the shaft model, the rotary inertia and gyroscopic effects are included, but shear deformation is neglected. The nonlinearity is due to large deflection of the shaft. Firstly, nonlinear equations of motion governing the flexural–flexural–extensional vibrations of the rotating shaft with nonconstant spin are derived by the Hamilton principle. Then, the equations are simplified using stretching assumption. To analyze the nonstationary vibration of the nonideal system, multiple-scale method is directly applied to the equations expressed in complex coordinates. Three analytical expressions that describe variation of amplitude, phase, and angular acceleration during passage through critical speed are derived. It is shown that Sommerfeld effect in specific range of driving torque occurs. Finally, effect of damping and nonlinearity on occurrence of Sommerfeld effect is investigated. It is shown that the linear model predicts the range of Sommerfeld effect occurrence inaccurately and, therefore, nonlinear analysis is necessary in the present problem.
A new vehicle path-following strategy of the steering driver model using general predictive control method
Authors: Cao Yang , Cao Jianyong , Yu Fan , Luo Zhe
Published: December 2017

In order to build an accurate and effective model, simulation of driver behavior is absolutely essential for the development of advanced driver assistance systems and the current assessment of vehicle handling stability. The purpose of the proposed active steering control is to assist the driver to follow the desired path, especially in situations of the vehicle under strong external disturbance, distracted driver, or other unforeseen circumstances that can cause deviations. Based on the preview optimal simple artificial neural network driver model, an active steering system using general predictive control method is established. In order to improve the path-following capability of vehicles under disturbances, a general predictive controller, with the deviation between the vehicles’ actual and desired lateral positons as inputs and with the corrective steering wheel angle as outputs, is developed to follow the desired path. Meanwhile, adapting recursion least square method with the forgetting factor to estimate the parameters of the controlled auto-regressive and integrated moving average model of the vehicle is designed. The proposed vehicle path-following control system is evaluated in some typical conditions (e.g. under strong crosswind condition in standard double-lane-change, etc.). Simulation results and analysis have verified that this new vehicle path-following strategy, given by general predictive controller, is capable of capturing driver’s steering behavior and the amended driver steering angle can improve the dynamic performance of vehicle under some external disturbances.
A computationally efficient universal platform for thermal numerical modeling of laser-based additive manufacturing
Authors: Stathatos Emmanuel , Vosniakos George-Christopher
Published: December 2017

A macroscopic thermal finite element analysis modeling platform for laser-based additive manufacturing is presented and validated. Its key characteristics include highly automated creation of simulation scenarios and increased computational efficiency. An investigation is carried out proving thermal shells a viable alternative to traditional solid elements, for building smaller and faster models. Full parameterization allows for rapid creation of specific modeling instances/scenarios. The use of shell elements, combined with model reduction techniques and advanced solver technology, result in very significantly reduced simulation times, compared to conventional modeling methods. Validation of the presented platform is carried out by comparison to results from other numerical models as well as experiments identified in the literature. Very good agreement for a wide range of materials and process parameters attest to its accuracy and universal application. This platform is the necessary basis for an Integrated Multiscale Modeling framework for systematically studying thermal patterns thereby ultimately increasing the scope of simulation to complete layers and whole parts.
Three-parameter transmission gear-shifting schedule for improved fuel economy
Authors: Miao Chengsheng , Liu Haiou , Zhu Guoming G
Published: December 2017

Traditionally the transmission gear-shifting schedule is based upon the throttle position and the vehicle (or engine) speed. This paper proposes to add a third parameter, called the terrain coefficient, to form a three-parameter gear-shifting schedule for improving the fuel economy of a vehicle. The terrain coefficient is a compound parameter consisting of the road grade and the rolling resistance coefficient. It can be estimated in real time by the proposed multi-step recursive least-squares method. The dynamic programming and the moving least-squares method are adopted to optimize the gear sequences and to generate the three-parameter gear-shifting schedule. The proposed gear-shifting schedule is evaluated against the traditional two-parameter gear-shifting schedule via Simulink simulations and on-road experiments using a heavy-duty vehicle. The simulation results for the Urban Dynamometer Driving Schedule and the US06 Supplemental Federal Test Procedure driving cycles show that the fuel economies of the proposed gear-shifting schedule are improved by 3.3% and 2.7% respectively over that of the traditional two-parameter schedule. The experimental results indicate that the three-parameter gear-shifting schedule improves the fuel economy by 3.5% over the traditional schedule with a satisfactory acceleration performance.
Robust tracking controller design for active dolly steering
Authors: Varga Balázs , Kulcsár Balázs , Laine Leo , Islam Manjurul , Németh Balázs
Published: December 2017

In this paper, different actuation level steering control methods for an A-double vehicle combination (tractor–semitrailer–dolly–semitrailer) are proposed. The aim of the paper is to show the viability of advanced actuation control strategies for a practical vehicular application. Three different types of robust controller are proposed: a robust proportional–integral–derivative controller, an output feedback linear ℋ∞ controller and an induced ℒ2-norm minimizing linear parameter-varying controller. All controllers are augmented with anti-windup compensators to respect the steering-angle limit and the steering-rate limit. Each model-based controller robustly rejects external disturbances and tracks a reference steering angle generated by the motion control system. Frequency-domain analysis and time-domain analysis prove that the ℋ∞ controller and the linear parameter-varying controller outperform the proportional–integral–derivative controller in terms of reference tracking and disturbance rejection. Comparative simulation scenarios are provided on the basis of the high-fidelity vehicle simulator developed by Volvo Group Trucks Technology.
Simulation on mechanism of contamination mitigation through Higee and hydrocyclone techniques in fluid power system
Authors: Hui Ji , Song-Lin Nie , Xiao-Rong Bai
Published: December 2017

In this study, an innovative Higee hydraulic oil purification device capable of removing the solid particle contaminants and water moisture simultaneously is developed for dealing with the contamination control problem of fluid power systems. The purification device is considered as a combination of two units (hydrocyclone separator and rotating packed bed) according to different separation functions. The mathematical models about the migration regularity and dynamic behavior of different phases have been established, in which discrete phase model model is employed to simulate the solid particles – hydraulic oil separation, and Eulerian model is selected as the multiphase simulation model to simulate the hydraulic oil – water moisture separation. Simulation results demonstrate that the hydrocyclone separator can remove solid particles of 5 to 15 µm, while the rotating packed bed can mitigate water moisture. The results indicate that the developed Higee hydraulic oil purification device can provide an effective and efficient manner for controlling the contamination level of fluid power systems.
Numerical simulation of cavitating flow in a centrifugal pump as turbine
Authors: Li Wenguang , Zhang Yuliang
Published: December 2017

In this study, the cavitating flow and cavitation performance are studied by employing the computational fluid dynamics method in the turbine mode of a centrifugal pump at part-load, best efficiency, and over-load points. The flow models are validated in the pump mode under noncavitation condition. The relationships between the performance variables and net positive suction head available are obtained, and the corresponding net positive suction heads required are extracted. The flow patterns, location, and shape of the cavity are illustrated; the pressure coefficient profiles on the blade surfaces are clarified and compared with those in the pump mode under both noncavitation and critical cavitation conditions. The cavitation performance and flow pattern as well as cavity shape in the turbine mode are distinguishably different from the pump mode. It is found out that the cavitation behavior in the turbine mode exhibits three notable features: a lower and less flow rate-dependent net positive suction head required, a flow rate-dependent suppressed rotational flow in the draft tube, as well as a rotational and extendable cavitating rope originated from the impeller cone. The results and methods can be important and useful for the design and selection of a centrifugal pump as turbine.
Comparison of stationary and rotary matrix heat exchangers using teaching-learning-based optimization algorithm
Authors: Hajabdollahi Hassan
Published: December 2017

In this paper, two kinds of compact heat exchanger including plate fin heat exchanger and rotary regenerator, respectively the stationary and rotary matrix heat exchanger, are compared. For this purpose, both heat exchangers are optimized by considering three simultaneous objective functions including effectiveness, heat exchanger volume, and total pressure drop using multi-objective teaching learning based optimization algorithm. Six different design parameters are considered for the both plate fin heat exchanger and rotary regenerator. Optimization is performed for the same and different hot and cold side mass flow rates. The optimum results reveal 13.26% growth in the effectiveness, 475.17% increase in the volume, and 95.45% reduction in the pressure drop in RR as compared with plate fin heat exchanger and for the final optimum point. As a result, rotary regenerator is more suitable in the case of high effectiveness and low pressure drop while plate fin heat exchanger is more suitable in the case of space limitation (lower heat exchanger volume).