bluuebunny/crossref_metadata_2025 huggingface dataset:
The history of public health in the modern Middle East: The environmental–medical turn
Authors: Rose Christopher S.
Published: April 2021

The field of Middle Eastern history began as an attempt to understand how Europeans came to dominate the region. As a result, when medicine and the environment were discussed, they were used to highlight European technological and scientific advances in these fields, and describe the processes through which Islamic medical and scientific concepts were replaced. The first wave of scholarship on the history of medicine in the region focused primarily on 19th‐century Egypt, where the state sponsored the development of a public health system to protect military readiness and combat epidemic diseases such as cholera and plague. This article highlights recent scholarship in the history of health, medicine, and the environment during the 19th and early 20th centuries, and illustrates how this lens (the “environmental‐medical turn”) provides new perspectives on the social and political history of the Middle East. I argue that the environmental‐medical turn provides a new avenue for locating illiterate members of society—the peasant and middle classes—in the archive; by exploring moments of crisis leading to protest and rebellion, and examining data revealing hardship and suffering, Middle Eastern historians can explore the complex roots of social and political events, and historians of medicine and the environment can include the region in transnational and comparative studies.
Searching for a new normal—Hospital‐employed researchers' experiences during the COVID‐19 pandemic
Authors: Berthelsen Connie , Beck Malene , Hølge‐Hazelton Bibi
Published: April 2021

Background

This study focuses on hospital‐employed researchers, a relatively new staff group. Their job descriptions vary, which may lead to lack of clarity or preparedness regarding their roles and core tasks during a crisis such as COVID‐19.

Aim

The aim of this study was to explore hospital‐employed healthcare researchers' experiences of work during the COVID‐19 pandemic.

Design

A qualitative design based on Graneheim and Lundman's latent content analysis of two focus groups with researchers in clinical practice was chosen to explore researchers' experiences of work during the COVID‐19 pandemic.

Methods

Fifteen hospital researchers participated in two focus groups, divided into predoctoral and postdoctoral researchers. Focus groups were conducted in May 2020 during the COVID‐19 pandemic, using the voice over IP service, Skype®, due to risk of contagion.

Findings

‘Searching for a new normal during the COVID‐19 pandemic’ was the main theme during the latent content interpretation, with subthemes of (i) balancing calm and insecurity, (ii) negotiating core tasks and (iii) considering the future.

Conclusion

The 15 researchers tried to balance calm and insecurity within work and family, on standby for the hospital's contingency plan, and in their research tasks. This led them to negotiate their core tasks and to reflect on the changes and consequences for their positions as researchers in clinical practice in the future.
Children’s experiences of living with maternal breast cancer: A qualitative study
Authors: Chin Jui‐Chih , Lin Miao‐Hui
Published: April 2021

Aims

To investigate the experiences of Taiwanese school‐aged children coping with maternal breast cancer.

Design

A qualitative interview study.

Methods

A cohort of 10 boys and 12 girls aged 6 to 13 years (mean age, 9.86 years) whose mothers were diagnosed with breast cancer in the last 2 years were recruited from patient networks in Taiwan. Data were collected from February to June 2019 via semi‐structured individual interviews. Their responses were subjected to content analysis.

Results

Content analysis yielded six themes: (1) reluctance to share feelings with others; (2) recognizing changes in the tone of family life; (3) casting the cause of breast cancer onto oneself; (4) engaging in active coping; (5) maturing and gaining life lessons; and (6) family communication matters.

Conclusion

The findings shed light on how family processes and cultural beliefs shape children's experiences. School‐aged children came to terms with the significance of maternal breast cancer from a broad context of family experiences over time, and thus gained insights into their self‐expectations and future aspirations.

Impact

Healthcare professionals can help school‐aged children develop a rational view of breast cancer pathogenesis. In addition, we suggest nursing interventions to support a family‐oriented approach to coping. Such interventions should address changes in family processes to improve coping abilities of children and the entire family.
The experience of family caregivers of patients receiving home nasogastric tube feeding in China: A descriptive qualitative study
Authors: Xue Min , Zhai Xiaoyuan , Liu Sihan , Xu Nana , Han Jing , Zhou Min
Published: April 2021

Background

The value of caregivers with respect to ensuring safety during home nasogastric tube (NGT) feeding is increasingly acknowledged. However, little attention has been given to the experience of caregivers.

Methods

A qualitative descriptive design using semi‐structured interviews via purposive sampling at a comprehensive hospital in China was employed. Family caregivers of patients with home NGT feeding were recruited. Interviews were recorded, transcribed verbatim and analysed qualitatively using inductive content analysis.

Results

Thirteen family caregivers of patients with home NGT feeding were interviewed. Four main themes were generated: negative experience (uncertainty and ambivalence, transition gaps between hospitals and home care services), new role: adapting to the lifestyle (participating in decision‐making, being responsible for everything, adjusting own life to NGT feeding), perceived benefit of caregiving (personal growth, development of positive attitudes and achievements) and expectations (expectations from continuity health system services, expectations from social support).

Conclusions

The present study highlights the vulnerability and perceived benefits embedded in the role of a family caregiver. Improving communication and standardising practices between home and hospitals should be considered.
Sanctioned licensing board violations for marriage and family therapists spanning a 10‐year period
Authors: Rollins Pamela , Grames Heath
Published: April 2021

Although disciplinary data on violations committed by licensed mental health professionals are important information for training programs, supervisors, and regulators, little disciplinary information is available on licensed marriage and family therapists (MFTs). This study collected data publicly available from state regulatory board websites and open records requests from 35 states for a total of 1241 separate cases, 889 of which were from CA. The findings indicated that the five most common violations for MFTs in 34 states (not including CA) were nonsexual dual relationships, failure to meet CE hour requirements, sexual dual relationships, unlicensed practice, and misrepresentation on licensing applications or renewals. For CA, the most common violations included criminal charges‐misdemeanor, DUI/inappropriate substance use, unprofessional conduct, misrepresentation on licensure paperwork, and failure to meet CE hour requirements. MFTs licensed between 2 and 5 years committed the majority of violations. Implications for training programs, supervisors, and regulators are discussed.
Hyaluronic acid (HA) stimulates the in vitro expression of CD44 proteins but not HAS1 proteins in normal human epidermal keratinocytes (NHEKs) and is HA molecular weight dependent
Authors: Gruber James V. , Holtz Robert , Riemer Jed
Published: April 2021

Background

In the skin, hyaluronic acid is broken down to smaller fragments by hyaluronidase enzymes, particularly when skin is wounded. The impact of various molecular weight fragments of HA on normal human epidermal keratinocytes (NHEK) with regard to expression of important cellular proteins has not been deeply explored.

Aims

Examination of three molecular weight (Mw) fractions of hyaluronic acid: 1) average Mw of the high fraction: 1.5–2 MDa, 2) average Mw of the medium fraction: 200–500 kDa, and 3) average Mw of the low fraction: 5–10 kDa and a unique 1:1:1 composite complex of the three HA fragments (Triluronic® Acid) was done to examine the influence of the HA on two critical skin cell protein targets: hyaluronan synthase‐1 (HAS‐1) and the HA binding protein cluster of differentiation 44 (CD44).

Methods

NHEKs were treated in vitro with a 1.0% stock solution of each HA Mw fraction at 1.0, 0.5, and 0.1% concentrations of the 1.0% solution and the polysaccharide composite at the same concentrations for 48 Hrs. The cells were than analyzed by ELISA protein assays for HAS‐1 and CD44 protein content.

Results

Examination of HAS‐1 protein expression indicates that none of the HA test materials influenced the expression of HAS‐1 at any concentration. Examination of the CD44 protein expression indicated that the low Mw fraction and the commercial complex of the three Mw fractions upregulated CD44 protein expression in NHEKs, but the medium Mw and high Mw HA fractions did not.

Conclusions

In this work, it was demonstrated that HA can influence the expression of CD44 protein, a critical HA transmembrane HA binding protein, and the influence appears to be molecular weight dependent.
Decreased serum human leukocyte antigen‐G levels are associated with gestational diabetes mellitus
Authors: Oztekin Ozer , Cabus Umit , Enli Yasar
Published: April 2021

Aim

This study was designed to determine serum human leukocyte antigen‐G (HLA‐G) levels and establish whether serum HLA‐G level is related with gestational diabetes mellitus (GDM).

Methods

Twenty‐five GDM patients aged between 24 and 34 years and 24 healthy pregnant women aged between 22 and 33 years were included in this study. Health status of subjects was determined by medical history, physical, and obstetric examinations. Absence of family history for Type 2 diabetes mellitus, absence of diagnosis or clinical evidence of any major disease, and absence of medication use altering glucose metabolism constituted the inclusion criteria. GDM cases who are at their 24–28 weeks of pregnancy and who have not been using any oral hypoglycemic agents were included in GDM group. Control group consisted of healthy pregnant women at their 24–28 weeks of pregnancy.

Results

Women with GDM had significantly lower levels of serum HLA‐G than controls. HLA‐G levels were negatively correlated with all parameters of glucose metabolism including insulin (r = − 0.14; p = 0.338), fasting blood glucose (r = − 0.220; p = 0.129), 1‐h oral glucose tolerance test (OGTT) blood glucose (r = − 0.18; p = 0.271), 2‐h OGTT blood glucose (r = − 0.314; p = 0.172), homeostasis model assessment (r = − 0.226; p = 0.119), HbA1C (r = −0.342; p = 0.108), and WBC (r = −0.149; p = 0.307). There was a negative correlation between HLA‐G and BMI (r = −0.341; p = 0.016).

Conclusion

Decreased circulating HLA‐G level is found to be associated with insulin resistance and GDM, in this study.
Does oropharyngeal administration of colostrum reduce morbidity and mortality in very preterm infants? A randomised parallel‐group controlled trial
Authors: Aggarwal Rahul , Plakkal Nishad , Bhat Vishnu
Published: April 2021

Aim

To evaluate whether a strategy of oropharyngeal administration of colostrum reduces morbidity and mortality in very preterm infants.

Methods

A total of 260 neonates with gestational age 26–31 weeks at birth were randomised between August 2017 and August 2018 to receive 0.2 mL of human milk or placebo respectively via the oropharyngeal route, beginning within 24 h after birth, and continued every 3 h until oral feeds were initiated. The primary outcome was a composite of death, late‐onset sepsis (LOS) or necrotising enterocolitis (NEC) in the neonatal period.

Results

A total of 260 infants (mean gestational age 29.5 weeks, and mean birthweight 1201.7 g) were included in the primary analysis. The composite primary outcome occurred in 43 (33.6%) infants in the colostrum group and 38 infants (29.7%) in the placebo group, and the difference was not statistically significant (P = 0.50). Secondary outcomes including the incidence of death, NEC, LOS, probable sepsis, intraventricular haemorrhage, ventilator‐associated pneumonia, retinopathy of prematurity, bronchopulmonary dysplasia, time to full feeds, time to regain birthweight, duration of hospital stay and survival to 6 months without major neurosensory impairment were also comparable between the two groups.

Conclusion

A strategy of oropharyngeal administration of colostrum in very preterm and extremely preterm neonates did not decrease the composite primary outcome of death, LOS or NEC. This finding is consistent with most published literature in the area.
Luteoviruses affected energy reserves and fatty acid composition of their aphid vectors
Authors: Ghodoum Parizipour Mohamad Hamed , Tahmasebi Aminallah , Shahriari Amir Ghaffar , Khashman Moslem , Hemmati Farshad
Published: April 2021

Luteoviruses are plant‐infecting RNA viruses that are transmitted by aphids in a persistent circulative mode. Luteoviruses have been shown to positively influence their aphid vectors fitness. To find out the physiological responses of aphid vectors to luteoviruses, fatty acid (FA) composition and energy components (EC) of aphid vectors including pea aphid (Acyrthosiphon pisum Harris), black bean aphid (Aphis fabae Scopoli) and bird cherry‐oat aphid (Rhopalosiphum padi L.) were evaluated in response to Pea enation mosaic virus 1 (PEMV1), Bean leafroll virus (BLRV) and Barley yellow dwarf virus‐PAV (BYDV‐PAV), respectively. Our results showed that the number and the proportion of FA of total lipid are altered in aphid vectors in response to the luteoviruses. Compared to non‐viruliferous (NV) aphids, BLRV and PEMV1 elevated the amount of myristic acid (1.13 and 1.03‐fold increase) in A. fabae and A. pisum, respectively. V R. padi individuals exhibited a 1.11‐fold increase in palmitic acid content compared to the NV individuals. In contrast, other V aphids showed a reduced proportion of FA in response to the viruses. These changes in FA profile enhanced the ratio of saturated to unsaturated FA in V aphids (4.09‐fold increase). BLRV decreased protein and lipid contents in its aphid vector, A. fabae, while carbohydrate content was found to increase in V R. padi and A. pisum. Thus, our results demonstrate that luteoviruses change the content of some FA and EC in their aphid vectors highlighting a specific interaction among virus species, plant host and aphid vector.
Functional convergence of growth responses to shade and warmth in Arabidopsis
Authors: Romero‐Montepaone Sofía , Sellaro Romina , Esteban Hernando Carlos , Costigliolo‐Rojas Cecilia , Bianchimano Luciana , Ploschuk Edmundo L. , Yanovsky Marcelo J. , Casal Jorge J.
Published: April 2021

Shade and warmth promote the growth of the stem, but the degree of mechanistic convergence and functional association between these responses is not clear.

We analysed the quantitative impact of mutations and natural genetic variation on the hypocotyl growth responses of Arabidopsis thaliana to shade and warmth, the relationship between the abundance of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and growth stimulation by shade or warmth, the effects of both cues on the transcriptome and the consequences of warm temperature on carbon balance.

Growth responses to shade and warmth showed strong genetic linkage and similar dependence on PIF4 levels. Temperature increased growth and phototropism even within a range where damage by extreme high temperatures is unlikely to occur in nature. Both cues enhanced the expression of growth‐related genes and reduced the expression of photosynthetic genes. However, only warmth enhanced the expression of genes involved in responses to heat. Warm temperatures substantially increased the amount of light required to compensate for the daily carbon dioxide balance.

We propose that the main ecological function of hypocotyl growth responses to warmth is to increase the access of shaded photosynthetic organs to light, which implies functional convergence with shade avoidance.
Repetitive seasonal drought causes substantial species‐specific shifts in fine‐root longevity and spatio‐temporal production patterns in mature temperate forest trees
Authors: Zwetsloot Marie J. , Bauerle Taryn L.
Published: April 2021

Temperate forest ecosystems are exposed to a higher frequency, duration and severity of drought. To promote forest longevity in a changing climate, we require a better understanding of the long‐term impacts of repetitive drought events on fine‐root dynamics in mature forests.

Using minirhizotron methods, we investigated the effect of seasonal drought on fine‐root dynamics in single‐species and mixed‐species arrangements of Fagus sylvatica (European beech) and Picea abies (Norway spruce) by means of a 4‐yr‐long throughfall‐exclusion experiment.

Fine‐root production of both species decreased under drought. However, this reduction was not evident for P. abies when grown intermixed with F. sylvatica. Throughfall‐exclusion prolonged the lifespan of P. abies roots but did not change the lifespan of F. sylvatica roots, except in 2016. Fagus sylvatica responded to drought by reducing fine‐root production at specific depths and during roof closure.

This is the first study to examine long‐term trends in mature forest fine‐root dynamics under repetitive drought events. Species‐specific fine‐root responses to drought have implications for the rate and depth of root‐derived organic matter supply to soil. From a root dynamics perspective, intermixing tree species is not beneficial to all species but dampens drought impacts on the belowground productivity of P. abies.
Tomographic assessment of infrazygomatic crest bone depth for extra‐alveolar miniscrew insertion in subjects with different vertical and sagittal skeletal patterns
Authors: Tavares Alana , Montanha‐Andrade Kátia , Cury Patricia Ramos , Crusoé‐Rebello Ieda , Neves Frederico Sampaio
Published: April 2021

Objective

To evaluate bone availability at the infrazygomatic crest for extra‐alveolar bone miniscrew insertion in subjects with different vertical and sagittal skeletal patterns.

Setting and sample population

Measurements of the infrazygomatic crest were performed on multislice computed tomography scans from 58 adults with different skeletal patterns.

Materials and methods

Infrazygomatic crest bone depth was measured at 4, 5 and 6 mm from the cementoenamel junction (CEJ) of the maxillary first molar at three different angles (60°, 70° and 80°) in the first molar occlusal plane. The sagittal and vertical skeletal patterns were determined. Analysis of variance followed by Tukey's post hoc test was used (P ≤ .05).

Results

Bone depth was greater near the CEJ (8.7 ± 3.1 mm) and lower in the apical area (5.8 ± 2.7 mm). In Class II subjects, considering 6 mm from the CEJ, there was a significantly lower depth at the 80° angle (5.4 ± 2.5 mm) than at 60° (8.6 ± 3.5 mm; P = .007). In mesofacial subjects, considering 5 and 6 mm from the CEJ, bone depth was lower at 80° (5.7 ± 3.2 mm and 5.3 ± 2.5 mm) than at 60° considering 4 mm from the CEJ (P ≤ .019).

Conclusion

Bone availability was lower at the apical level, especially in Class II and mesofacial subjects. Therefore, when the planned insertion site is located in the apical direction, it is recommended to choose shorter miniscrews (2.0 x 12mm) and a smaller insertion angle (60°) and/or to plan a miniscrew bone insertion deep enough to allow bicortical fixation.
Identifying conversion efficiency as a key mechanism underlying food webs adaptive evolution: a step forward, or backward?
Authors: Fritsch Coralie , Billiard Sylvain , Champagnat Nicolas
Published: April 2021

Body size or mass is one of the main factors underlying food webs structure. A large number of evolutionary models have shown that indeed, the adaptive evolution of body size (or mass) can give rise to hierarchically organised trophic levels with complex between and within trophic interactions. However, these models generally make strong arbitrary assumptions on how traits evolve, casting doubts on their robustness. In particular, biomass conversion efficiency is always considered independent of the predator and prey size, which contradicts with the literature. In this paper, we propose a general model encompassing most previous models which allows to show that relaxing arbitrary assumptions gives rise to unrealistic food webs. We then show that considering biomass conversion efficiency dependent on species size is certainly key for food webs adaptive evolution because realistic food webs can evolve, making obsolete the need of arbitrary constraints on traits' evolution. We finally conclude that, on the one hand, ecologists should pay attention to how biomass flows into food webs in models. On the other hand, we question more generally the robustness of evolutionary models for the study of food webs.
A replication of “Representative bureaucracy and the willingness to coproduce”
Authors: Sievert Martin
Published: April 2021

Research on symbolic representation suggests that citizen–state interactions might benefit from public organizations' representativeness. Recent experiments on symbolic gender representation provide contradictory findings regarding the influence on citizens' co‐production intentions. This study conducts a wide replication based on new data to reexamine the positive impact of symbolic gender representation identified by Riccucci et al. (2016, Public Administration Review, 76(1), pp. 121–130). The applied survey experiment closely resembles the original design aspects. The experiment is set in criminal justice policy, a policy field featuring co‐production of core public services such as prisoner rehabilitation. The results do not confirm a positive effect of symbolic gender representation on willingness to co‐produce. Instead, several arguments point to citizens' perceptions of uncertainty related to the co‐production context and procedures as a boundary condition for the effects of symbolic gender representation.
China's Pathway to Domestic Emergency Management: Unpacking the Characteristics in System Evolution
Authors: Liu Zezhao , Zhu Zhengwei
Published: April 2021

China's emergency management (EM) system has undergone a series of reforms and organizational changes since the SARS epidemic in 2003. However, institutional segmentation, unbalanced power for the Emergency Management Office, pervasive internal corruption, and state monopoly control are threats to the administration's goal of resilient and modern EM systems. The new round of 2018 reforms was intended to promote integration through the establishment of the Ministry of Emergency Management and related institutional restructuring involving power redistribution. The reforms are nevertheless likely to face some potential problems like the operation of a super‐ministry, interorganizational integration, state‐society relations, and supervision. Through field interviews, the article investigates and uncovers issues in China's EM system and the perception from government sectors at different levels. The article suggests that cooperative governance in coping with state‐society relations and decentralization of power could be of great significance for future EM reform in China.

Related Articles

Ash, John. 2010. “New Nuclear Energy, Risk, and Justice: Regulatory Strategies for an era of Limited Trust.” Politics & Policy 38 (2): 255‐284. https://doi.org/10.1111/j.1747‐1346.2010.00237.x

Brogan, Michael James. 2017. “Evaluating Risk and Natural gas Pipeline Safety.” Politics & Policy 45 (4): 657‐680. https://doi.org/10.1111/polp.12211

Neill, Katharine A., and John C. Morris. 2012. “A Tangled web of Principals and Agents: Examining the Deepwater Horizon oil Spill through a Principal–Agent Lens.” Politics & Policy 40 (4): 629‐656. http://onlinelibrary.wiley.com/doi/10.1111/j.1747‐1346.2012.00371.x/full
Bull sperm selection by attachment to hyaluronic acid semi‐interpenetrated hydrogels
Authors: Liaudat Ana Cecilia , Blois Damian , Capella Virginia , Morilla Gricelda , Rivero Rebeca , Barbero César , Rodríguez Nancy , Rivarola Claudia , Bosch Pablo
Published: April 2021

We report the development of a hydrogel‐based approach to select bull spermatozoa, a crucial step for successful assisted reproductive techniques (ARTs). Hyaluronic acid (HA) semi‐interpenetrated N‐isopropylacrylamide (PNIPAM) co‐20% N‐Tris (hydroxymethyl) methyl acrylamide (HMA) hydrogels were synthetized on glass surfaces and cultured in presence of frozen‐thawed bull spermatozoa. A fraction of motile bull spermatozoa population strongly attached to hydrogels and was partially released by treatment with hyaluronidase. Fifty‐nine (59 ± 7.24) per cent of sperm cells attached to PNIPAM‐HMA‐HA hydrogels and 31.16 ± 4.81% of them were released upon treatment with medium containing hyaluronidase. This attached‐released sperm fraction has acceptable characteristics of progressive motility (50.0 ± 5.0%), vigour (4), high viability (58.7 ± 11.7%) and low percentage of acrosome reacted spermatozoa (23.36 ± 4.1%). Our findings indicate that PNIPAM‐HMA‐HA hydrogels are non‐toxic and allow the selection of high‐quality sperm cells for ART.
Prevention of strain‐induced impairments of patellar tendon micromorphology in adolescent athletes
Authors: Mersmann Falk , Domroes Theresa , Pentidis Nikolaos , Tsai Meng‐Shiuan , Bohm Sebastian , Schroll Arno , Arampatzis Adamantios
Published: April 2021

High‐level patellar tendon strain may cause impairments of the tendon's micromorphological integrity in growing athletes and increase the risk for tendinopathy. This study investigated if an evidence‐based tendon exercise intervention prevents high‐level patellar tendon strain, impairments of micromorphology and pain in adolescent basketball players (male, 13–15 years). At three time points over a season (M1‐3), tendon mechanical properties were measured using ultrasound and dynamometry, proximal tendon micromorphology with a spatial frequency analysis and pain and disability using VISA‐P scores. The control group (CON, n = 19) followed the usual strength training plan, including sprint and change‐of‐direction drills. In the intervention group (INT, n = 14), three sessions per week with functional exercises were integrated into the training, providing repetitive high‐magnitude tendon loading for at least 3 s per repetition. The frequency of high‐level strain (ie, ≥9%) continuously decreased in INT, while tending to increase in CON since tendon force increased in both (p < 0.001), yet tendon stiffness only in INT (p = 0.004). In CON, tendon strain was inversely associated with tendon peak spatial frequency at all time points (p < 0.05), indicating impairments of tendon micromorphological integrity with higher strain, but not at M2 and M3 in INT. Descriptively, the fraction of asymptomatic athletes at baseline was similar in both groups (~70%) and increased to 100% in M3 in INT, while remaining unchanged in CON. We suggest that functional high‐load tendon exercises could reduce the prevalence of high‐level patellar tendon strain and associated impairments of its micromorphology in adolescent athletes, providing new opportunities for tendinopathy prevention.
PARA UNA CRÍTICA DE LA VIOLENCIA DEL DERECHO CIVIL
Authors: Rico Sandoval Ronald Zuleyman
Published: April 2021

La violencia se encuentra presente en el derecho desde su emergencia, estoes, desde que el animal humano se convierte en animal social. Dicha violenciapermanece en todas las facetas del derecho, incluida el área civil, comoviolencia conservadora a la cual se le puede oponer una violencia pura conpotencialidad de articular una nueva subjetividad social. Sin embargo, paraentender la violencia del derecho debe rastrearse hasta el núcleo mismo dela subjetividad humana como base de la sociedad, y para ello una miradaal psicoanálisis se presenta como una propuesta transdisciplinaria para elestudio de la ciencia jurídica.
Research on the Flow Resistance Coefficient of a Multihole, Secondary Pressure-Reducing Sleeve Valve
Authors: Xu Dong-tao , Ge Chang-rong , Meng Xiang-rui
Published: April 2021

When fluid flows through a regulating valve, static pressure changes due to the change of fluid area. If the static pressure is lower than saturated vapor pressure, cavitations erosion, and flash vaporization will occur. Cavitations and flash vaporization are the main causes of the vibration and noise of the valve. A multihole sleeve valve with a secondary pressure-reducing function is presented in this paper, two pressure-reducing components are assembled to the valve. The high-pressure difference in the valve can be broken down into several small pressure differences. But the pressure-reducing components have a significant influence on the flow resistance coefficient of the valve. So, the common flow resistance coefficient is no longer suitable for designing the multihole, secondary pressure-reducing sleeve valve. In this paper, the relationship of the flow rate, the flow area, and flow resistance coefficient of the valve is established. The flow area and the flow rate of the valve at the different openings are obtained using simulation software. They are substituted into the relationship equation, in this way, the flow resistance coefficients of the valve can be obtained. In order to verify the reliability of the simulation, a parallel flow test equipment for the valve is established, and the flow rate at different opening are detected. The test result shows that the valve designed by simulation conforms to the specified flow characteristics. By the revision of the flow resistance coefficient, the throttling holes of the valve can be designed conveniently and accurately. The designed valve has good flow regulating ability and can solve the problem of cavitations erosion and flash vaporization.
Vortex Dynamics and Instability Mechanisms in a Radially Lobed Nozzle
Authors: Sekaran Aarthi , Amini Noushin
Published: April 2021

The application of radially lobed nozzles has seen renewed challenges in the recent past with their roles in combustion chambers and passive flow control. The free jet flow from such nozzles has been studied for different flow conditions and compared to jets from round nozzles, verifying their improved mixing abilities. The precise mixing mechanisms of these nozzles are, however, not entirely understood and yet to be analyzed for typical jet parameters and excitation modes. This study carries out three-dimensional large eddy simulations (LESs) of the flow from a tubular radially lobed nozzle to identify instability mechanisms and vortex dynamics that lead to enhanced mixing. The flow is studied at two Reynolds numbers of around 6000 and 75,000, based on the effective jet diameter. The low Reynolds number jet is compared to that from a round nozzle and experimental data to demonstrate changes in mixing mechanisms. The present simulations confirmed the presence of Kelvin–Helmholtz (K–H)-like modes and their evolution. The analysis also confirms the evolution of three distinct types of structures—the large-scale streamwise modes at the lobe crests, corresponding K–H structures at the troughs, and an additional set of structures generated from the lobe walls. The higher Reynolds number simulations indicate changes in the mechanics with a subdued role of the lobe walls.
A Taxonomy of Mechanical Design
Authors: Ullman D. G.
Published: April 2021

Over the last few years there has been a flurry of activity in the study of the mechanical design process. This has been fostered by a perceived lack of efficiency and resulting quality in U.S. product designs compared with those of the Japanese and the Europeans. Research activity is broad and has varied over areas as diverse as: the development of computer codes using AI techniques to solve specific problems requiring expertise in a narrow domain; the commercialization of general, parametric design tools; and the modeling of the human cognitive design process. As results have been published, it has become obvious that the term “design” means different things to different researchers. The field is mature enough to allow techniques and results to be classified, compared and contrasted. However, this is difficult because there is no agreed upon description of the types of design and design studies. In other words, there is a need for a taxonomy to characterize the mechanical design process and the research on it.
Partitioning and Guided Search: A Generalized Approach to Problem Solving in Preliminary Design
Authors: Srinivasan S. , Allen R. H.
Published: April 2021

We report on using problem partitioning and constraint-guided search as a generalized approach to problem-solving in preliminary design. Specifically, a generic design template has been created as a tool to structure information to facilitate problem-solving in three different domains. The approach has been tested through the implementation of knowledge-based systems for the preliminary design of mechanical springs, composite sublaminates and expert systems. Information in each implementation has been partitioned as hierarchical levels of abstraction related through constraints. Function identifies the top level design goals to reduce the search involved for feasible solutions. Goal-directed search, driven by the design application and top-down refinement, reduces the number of possible alternatives. The commonalities extant in the domains have been represented as design goals at three levels of abstraction in the design template. Similar frame-based knowledge representations with inheritance hierarchies and mixed reasoning have been developed for the KEE™-based implementations in each domain. Distinctions among the domains have been modelled as low level slots in the frame hierarchy.

Parametric studies in the domains of mechanical springs, composite sublaminates and expert systems indicate that the minimum number of decision levels required to characterize the preliminary design process in these domains is three; fewer levels would be insufficient to fundamentally characterize the designs. Further, it is observed hierarchical structuring of design information facilitates capturing the interactions among design variables at different levels of abstraction. By using the template representation and reasoning in other divisible domains, the effectiveness of our approach can be further investigated.
Geometric Feature Recognition by Object Decomposition
Authors: Karra C. , Phelps T. A.
Published: April 2021

Design engineers have traditionally have had inadequate manufacturing information. One method of getting that information to them is through its inclusion in computer-based design tools such as geometric solid modelling programs. Analysis of geometry requires methods such as feature recognition. A new approach to feature recognition has been developed which recognizes features by taking apart the original solid object into prismatic primitives. This approach already covers a very large portion of what is currently manufactured. The expected applications of this approach include automatic manufacturability analysis, design for assembly, process planning, etc.
A Simple Practical Criterion to Guarantee Second Order Smoothness of Blend Surfaces
Authors: Pegna J. , Wolter F.-E.
Published: April 2021

Computer Aided Geometric Design of surfaces sometimes presents problems that were not envisioned by mathematicians in differential geometry. This paper presents mathematical results that pertain to the design of second order smooth blending surfaces. Second order smoothness normally requires that normal curvatures agree along all tangent directions at all points of the common boundary of two patches, called the linkage curve. The Linkage Curve Theorem proved here shows that, for the blend to be second order smooth when it is already first order smooth, it is sufficient that normal curvatures agree in one direction other than the tangent to a first order continuous linkage curve. This result is significant for it substantiates earlier works in computer aided geometric design. It also offers simple practical means of generating second order blends for it reduces the dimensionality of the problem to that of curve fairing, and is well adapted to a formulation of the blend surface using sweeps. From a theoretical viewpoint, it is remarkable that one can generate second order smooth blends with the assumption that the linkage curve is only first order smooth. This property may be helpful to the designer since linkage curves can be constructed from low order piecewise continuous curves.
The Modeling of Bevel Gears Using the Exact Spherical Involute
Authors: Al-Daccak M. J. , Angeles J.
Published: April 2021

The solid modeling of bevel gears has been recognized as a major design challenge. Various approaches have been proposed to approximate the theoretical involute-generated contact surface of bevel gears. As a means to accurately represent contact surfaces of these gears, the exact spherical involute is introduced here. The solid models of straight and spiral bevel gears are obtained by applying simple sweeping techniques to their tooth profiles which are described by the exact spherical involute. Furthermore, the volumetric properties of the modeled bevel gears are readily computed from their piecewise-linear approximation.
The Evaluation of Moments of Regions With Piecewise-Linearly Approximated Boundaries via Line Integration
Authors: Angeles J. , Al-Daccak M. J.
Published: April 2021

The subject of this paper is the computation of the first three moments of bounded regions imbedded in the three-dimensional Euclidean space. The method adopted here is based upon a repeated application of Gauss’s Divergence Theorem to reduce the computation of the said moments — volume, vector first moment and inertia tensor — to line integration. Explicit, readily implementable formulae are developed to evaluate the said moments for arbitrary solids, given their piecewise-linearly approximated boundary. An example is included that illustrates the applicability of the formulae.
Expert System Built on a Chip
Authors: Lu P. , Siddall J. N. , Verhaeghe J.
Published: April 2021

The paper describes an exploration of the possibility of embedding the rules of an expert system directly onto a commercial programmable logic array microchip. The rules are first converted to Boolean form and reduced to minimal form. An interface was developed for using the chip with an IBM PC clone for processing inputs and outputs. No control system (inference engine) is required; and the execution of an application is equivalent to parallel processing. The inputs are transferred to the input pins of the logic array chip in successive bytes of data, and the conclusions then immediately appear at the output pins. The success of the approach was verified with two small examples.

We have also extended the concept to develop an original algorithm for minimizing the number of required inputs for a specific application.

This approach to designing expert systems should have an important potential for control systems where speed is important, and also in other systems where size and speed are important performance characteristics.
Optimal and Conforming Motion of a Point in a Constrained Plane
Authors: Ahrikencheikh C. , Seireg A. A. , Ravani B.
Published: April 2021

This paper deals with automatic generation of motion of a point under both geometric and non-geometric constraints. Optimal point paths are generated which are not only free of collisions with polygonal obstacles representing geometric constraints but also conform to non-geometric constraints such as speed of the motion, a maximum allowable change in the velocity vector and a minimum clearance from the obstacle boundaries. The concept of passage networks and conforming paths on the network are introduced. These are used to provide a new representation of the free space as well as a motion generation algorithm with a computational time complexity of only O(n3.log(n)), where n designates the total number of obstacle vertices. The algorithm finds the shortest or fastest (curved) path that also conforms with preset constraints on the motion of the point. The point paths generated are proved to be optimal while conforming to the constraints.
Optimality and Constrained Derivatives in Two-Level Design Optimization
Authors: Azarm S. , Li W.-C.
Published: April 2021

The objective of this paper is twofold. First, an optimality test is presented to show that the optimality conditions for a two-level design optimization problem before and after its decomposition are the same. Second, based on identification of active constraints and exploitation of problem structure, a simple approach for calculating the gradient of a “second-level” problem is presented. This gradient is an important piece of information which is needed for solution of two-level design optimization problems. Three examples are given to demonstrate applications of the approach.
The Method of Alternate Formulations Applied to Optimization Problems With Functionally Dependent State Equations
Authors: Hammond C. R. , Johnson G. E.
Published: April 2021

The Method of Alternate Formulations (MAF) is a non-numerical approach to constrained optimal design. MAF requires that the problem statement be transformed into an objective function, a set of equality-constraints (i.e. state equations), and a set of upper and lower bounds on the variables. In this format, the design vector can be partitioned into decision variable and state variable components. This is the same format as used in the solution of such problems by the generalized reduced gradient method.

The fact that there are usually several ways to effect the partition of the design vector gives rise to the existence of alternate formulations. Each alternate formulation contains all of the information about the physical system — and the constrained optima are invariant under the transformation from form to form. Yet all other mathematical properties (e.g., convexity, linearity, scaling, etc.) can change.

In this paper, we consider the special case when the state equations are functionally dependent, hence some of the expected constraint intersections do not exist. Several examples are used to demonstrate the concept of functional dependence and to show how functional dependence affects the search for the solution.
Numerical Optimization of Rotor-Bearing Systems
Authors: Sadler J. P. , Rouch K. E. , Rani A. S.
Published: April 2021

Nonlinear programming techniques are combined with a finite element program for dynamic analysis of rotor-bearing systems. The resulting program provides the means for obtaining optimal designs for improved dynamic performance of a rotor through the automated selection of various design parameters of the rotor-bearing system. Both constrained and unconstrained optimizations are considered. Illustrative examples are presented for the case of optimum placement of critical speeds.
A Procedure Using Manufacturing Variance to Design Gears With Minimum Transmission Error
Authors: Sundaresan S. , Ishii K. , Houser D. R.
Published: April 2021

This paper deals with the design of spur gears that have minimum transmission error and are insensitive to manufacturing variance. We address two stages of design: 1) generation of candidate designs (selection of number of teeth, pressure angle, etc.), and 2) tooth profile modification. The first stage involves a search of discrete combinations of design variables, while the second stage utilizes numerical optimization techniques. The key research issue is finding a candidate design and its profile modification that not only has low transmission error, but is insensitive to variations in the design values caused by the manufacturing process. To achieve this goal, the procedure applies Taguchi’s concept of parameter design. In this paper, we consider a design problem with a set specification: fixed center distance, speed ratio, and transmission torque. We seek to find a limited number of candidate designs by applying conventional design generation techniques and some design heuristics. For each candidate design, the procedure determines the optimum profile modification (linear tip relief) by linking the Load Distribution Program (LDP) for gears with an optimization program package (OPTPAK). From the resulting peak optimum, we further seek the statistical optimum using an algorithm developed in this paper. The statistical optimum shows a nominal increase in the transmission error, but is quite insensitive to typical process error associated with gear manufacturing. The developed algorithm readily applies to other gear designs as well as other types of machine elements. In particular, we foresee our procedure to be particularly effective for helical gears. We hope to further our method by developing a means to add statistical heuristics to the discrete design generation stage.
Determination of the Allowable Manipulator Link Shapes; and Task, Installation, and Obstacle Spaces Using the Monte Carlo Method
Authors: Rastegar J. , Tu Q.
Published: April 2021

The Monte Carlo method is used to solve a number of problems in manipulator link shape design, and in task space and obstacle placement. The shape of links of manipulators that are to operate within geometrically specified enclosures are determined. Within the enclosure, one or several obstacles may be present. The end effector operates within the task space, and may be required to reach points in different regions with different orientations. For a specified operating environment (enclosure geometry and obstacles), the spaces within which a given manipulator may be installed in order to perform the required tasks are identified. For a given enclosure, task space, and position of the fixed joint of the manipulator, regions within which obstacles may be placed are mapped. The developed methods are very simple, numeric in nature, and readily implemented on computer. Several examples are presented.
A Constrained Variational Method for Two-Dimensional Shape Optimization
Authors: West R. L. , Sandgren E.
Published: April 2021

A constrained variational method is presented for the formulation and solution of a class of two-dimensional continuous shape optimization problems with equality constraints. Conceptually, the method casts the shape optimization problem as an analogous application of the principle of virtual work. It is postulated that the optimal shape is that equilibrium shape distinguished by the stationary value of the systems “effective” virtual work. The resulting formulation leads to a direct variational statement of the shape optimization problem, yielding the optimality criteria consisting of the Euler-Lagrange equations, constraints and boundary conditions. The Euler-Lagrange equations are linearized about the current shape and transformed into a set of Poisson’s equations. A direct boundary integral formulation is developed for the solution of Poisson’s equation that results in a continuous expression for the shape in terms of the Lagrange multipliers. The numerical solution procedure involves discretizing the shape into boundary and domain elements and using the direct boundary element method and the linearized constraint set to form a set of matrix equations. The solution to the set of matrix equations yields new estimates of the shape and the Lagrange multipliers. Convergence of the method is achieved when successive iterations of the shape and Lagrange multiplier estimates fail to improve by some prescribed limit. The classical problem of finding the curve with minimum perimeter and a prescribed enclosed area is used to illustrate the method.