bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant community persistence strategy is elevation‐specific
Authors: Rosbakh Sergey , Poschlod Peter
Published: April 2021

Aims

Persistence plays a key role in both plant population and community dynamics as it allows withstanding temporarily habitat conditions unsuitable for growth and reproduction. Plants can exploit three different strategies to persist in situ (building soil seed banks, increasing adult longevity and/or clonal reproduction), the dominance of which in a community might vary along environmental gradients. Yet, their relative role in plant persistence has never been investigated.

Location

The Bavarian Alps, Germany.

Methods

We collected data on seed soil persistence, adult longevity and clonality for 290 species occurring in 18 grasslands located along an elevational gradient of 1,000 metres and examined their contribution to persistence in a community. Linear models were used to estimate the relationship between elevation and these persistence strategies.

Results

We found that dominance of a certain persistence strategy varied depending on environmental variability. Specifically, persistence in lowlands was mainly achieved by persistent and dense soil seed banks along with extended clonal growth (larger spread distances and higher number of offspring). Contrastingly, the main persistence strategy in the alpine communities was increased adult longevity.

Conclusions

The changes in relative contribution of each strategy to community persistence along the elevational gradient are interrelated suggesting a trade‐off among them. We conclude that this trade‐off plays an important role in species co‐existence and community assembly, and might be useful to understand vegetation dynamics under ongoing climate change and improve restoration efforts of upland ecosystems.
Breastfeeding and breastmilk substitute use and feeding motivations among mothers in Bandung City, Indonesia
Authors: Green Mackenzie , Pries Alissa M. , Hadihardjono Dian N. , Izwardy Doddy , Zehner Elizabeth , Moran Victoria Hall
Published: April 2021

Suboptimal breastfeeding is common in Indonesia, with only half of infants 0–5 months of age exclusively breastfed and feeding of breastmilk substitutes (BMS) highly prevalent among infants and toddlers. Various factors influence these feeding practices, including social norms, limited health system support and BMS manufacturer marketing practices. This cross‐sectional survey aimed to identify the prevalence of breastfeeding and BMS feeding among children aged 0–35 months, explore socio‐demographic characteristics and motivating factors associated with these feeding behaviours and identify the prevalence of mothers' exposure to BMS promotions. Indonesian mothers of children <3 years of age (n = 595) were interviewed in Bandung City health facilities using structured questionnaires. Although all children were ever breastfed, half of children across all age groups received BMS in the previous day. Maternal employment outside the home and insufficient breastmilk production were associated with BMS use. The most important motivational factors for feeding BMS were perceived benefits for growth, intelligence and immunity. Despite Indonesian legislation restricting some BMS marketing, 93% of mothers reported observing a BMS promotion outside the health system, with television, social media and newspapers as the most common sources. Half of mothers (43%) reported observing a BMS promotion within the health system, and half (46%) reported receiving recommendations from health workers to use BMS. Such high prevalence of BMS marketing may be influencing caregivers' feeding choices; stronger national legislation and implementation of laws are needed to ensure mothers' ability to make feeding choices free from manufacturer influence.
Online estimation model for passenger flow state in urban rail transit using multi‐source data
Authors: Tao Zhengping , Tang Jinjin , Hou Kaiwen
Published: April 2021

The estimation of present passenger flow state plays a vital role in the urban rail transit (URT) operation process and it is the basis of passenger flow control and train dispatching. Most of the existing researches used the Automatic Fare Collection (AFC) System data as the single data source for estimating present passenger flow state. In consideration of the delay in the data uploading process, the obtained estimation results based on the single AFC data source are not accurate enough, which could lead to the improper handling and decision failure and cause high risk and low efficiency for the operation and management of URT. To address problems mentioned above, this paper adopted the automatic differentiation method as the framework for the fusion of multi‐source heterogeneous data (including uploaded AFC data, the mobile phone signaling data provided by mobile phones, and the historical passenger flow data, etc.). Then, this paper proposed the online estimation model and the error layered optimization algorithm to implement the estimation of present passenger flow state. The calculation results indicate that the proposed model and algorithm can obtain reasonable and reliable URT passenger flow state. Finally, the study developed a present passenger flow state estimation system using the proposed model and algorithm. The system has been deployed in Chengdu Metro that serves about 3 million passengers per day from October 2018 to April 2020, with the overall error within 3% as of now.
Low bee visitation rates explain pollinator shifts to vertebrates in tropical mountains
Authors: Dellinger Agnes S. , Pérez‐Barrales Rocio , Michelangeli Fabián A. , Penneys Darin S. , Fernández‐Fernández Diana M. , Schönenberger Jürg
Published: April 2021

Evolutionary shifts from bee to vertebrate pollination are common in tropical mountains. Reduction in bee pollination efficiency under adverse montane weather conditions was proposed to drive these shifts. Although pollinator shifts are central to the evolution and diversification of angiosperms, we lack experimental evidence of the ecological processes underlying such shifts.

Here, we combine phylogenetic and distributional data for 138 species of the Neotropical plant tribe Merianieae (Melastomataceae) with pollinator observations of 11 and field pollination experiments of six species to test whether the mountain environment may indeed drive such shifts.

We demonstrate that shifts from bee to vertebrate pollination coincided with occurrence at high elevations. We show that vertebrates were highly efficient pollinators even under the harsh environmental conditions of tropical mountains, whereas bee pollination efficiency was lowered significantly through reductions in flower visitation rates. Furthermore, we show that pollinator shifts in Merianieae coincided with the final phases of the Andean uplift and were contingent on adaptive floral trait changes to alternative rewards and mechanisms facilitating pollen dispersal.

Our results provide evidence that abiotic environmental conditions (i.e. mountain climate) may indeed reduce the efficiency of a plant clade’s ancestral pollinator group and correlate with shifts to more efficient new pollinators.
Unveiling spatial metabolome of Paeonia suffruticosa and Paeonia lactiflora roots using MALDI MS imaging
Authors: Li Bin , Ge Junyue , Liu Wei , Hu Dejun , Li Ping
Published: April 2021

Paeonia suffruticosa (PS) and Paeonia lactiflora (PL) belong to the only genus in the family Paeoniaceae. Comparative analysis of the spatial metabolomes of PS and PL has rarely been performed.

In this work, combined with multiple matrixes and dual‐polarity detection, high mass resolution matrix‐assisted laser desorption/ionization MS imaging (MALDI MSI) and MALDI tandem MSI were performed on the root sections of the two Paeonia species.

The spatial distributions of many metabolites including monoterpene and paeonol glycosides, tannins, flavonoids, saccharides and lipids were systematically characterized. The ambiguous tissue distribution of the two isomers paeoniflorin and albiflorin were distinguished by tandem MSI using lithium salt doped 2,5‐dihydroxybenzoate matrix. In addition, the major intermediates involved in the biosynthetic pathway of gallotannins were successfully localized and visualized in the root sections.

High‐mass resolution MALDI full‐scan MSI provides comprehensive and accurate spatial distribution of metabolites. The analytical power of the technique was further tested in the tandem MSI of two isomers. The ion images of individual metabolites provide chemical and microscopic characteristics beyond morphological identification, and the detailed spatiochemical information could not only improve our understanding of the biosynthetic pathway of hydrolyzable tannins, but also ensure the safety and effectiveness of their medicinal use.
Real Estate Boom and Firm Productivity: Evidence from China
Authors: Jia Junxue , Gu Jia , Ma Guangrong
Published: April 2021

Studies on the relationship between housing prices and firm behaviours have focused on the relationship between housing prices and firm financing and investment decisions. However, housing prices may affect other firm decisions. This study investigates the impact of housing prices on manufacturing firm productivity in China. To identify the causal effect, we use a national land regulation policy and city‐level developable land area as exogenous sources of variation in housing prices. Using an instrumental variable approach to regression analysis and firm‐level data, we find that a 10% increase in housing prices leads to a 2.1% reduction in manufacturing firms' total factor productivity (TFP). An important transmission channel is the inflow of bank credit to the real estate market caused by rising housing prices, thus crowding out loans to manufacturing firms. Due to China's distinctive dual‐track land market, rising housing prices do not translate into an increase in the price of industrial land; therefore, collateral values for manufacturing firms do not increase. We further find that the negative effect of housing prices on TFP is more pronounced for firms with greater external financial dependence or greater financial constraints.
A LATE MESOLITHIC FORAGER DISPERSAL CAUSED PRE‐AGRICULTURAL DEMOGRAPHIC TRANSITION IN NORWAY
Authors: Nielsen Svein Vatsvåg
Published: April 2021

Population growth has always played a key role in human mobility, even before the age of farming and husbandry. This paper explores population dynamics among early Holocene (∼9500–1700 cal BCE) hunter‐fisher‐gatherers in Southern Norway, focusing in particular on the Mesolithic‐Neolithic transition (4000/3900 cal BCE). Radiocarbon dates are calibrated and turned into summed probability distributions (SPDs). A heuristic linear method is used to calculate annual growth rates from the SPDs. Observed fluctuations in the SPDs are tested for significance by applying a Monte Carlo‐based simulation method. The paper finds evidence of a steady growth rate from the Boreal period until a sudden population trough at ∼4330–4300 cal BCE. The trough coincides with indications from the archaeological record of a dispersal of hunter‐fisher‐gatherers from Southern Scandinavia to Norway. The dispersal was likely an effect of lowered habitat suitability and social stress caused by population pressure among Southern Scandinavian hunter‐fisher‐gatherers. In Southern Norway, the proxy data show that the trough enabled a subsequent ‘boom’ in population and the emergence of regional technological innovations that define the Mesolithic‐Neolithic transition.
Bacillus velezensis tolerance to the induced oxidative stress in root colonization contributed by the two‐component regulatory system sensor ResE
Authors: Zhang Huihui , Liu Yunpeng , Wu Gengwei , Dong Xiaoyan , Xiong Qin , Chen Lin , Xu Zhihui , Feng Haichao , Zhang Ruifu
Published: April 2021

Efficient root colonization of plant growth‐promoting rhizobacteria is critical for their plant‐beneficial functions. However, the strategy to overcome plant immunity during root colonization is not well understood. In particular, how Bacillus strains cope with plant‐derived reactive oxygen species (ROS), which function as the first barrier of plant defence, is not clear. In the present study, we found that the homolog of flg22 in Bacillus velezensis SQR9 (flg22SQR9) has 78.95% identity to the typical flg22 (flg22P.s.) and induces a significant oxidative burst in cucumber and Arabidopsis. In contrast to pathogenic or beneficial Pseudomonas, live B. velezensis SQR9 also induced an oxidative burst in cucumber. We further found that B. velezensis SQR9 tolerated higher H2O2 levels than Pst DC3000, the pathogen that harbours the typical flg22, and that it possesses the ability to suppress the flg22‐induced oxidative burst, indicating that B. velezensis SQR9 may exploit a more efficient ROS tolerance system than DC3000. Further experimentation with mutagenesis of bacteria and Arabidopsis showed that the two‐component regulatory system, ResDE, in B. velezensis SQR9 is involved in tolerance to plant‐derived oxidative stress, thus contributing to root colonization. This study supports a further investigation of the interaction between beneficial rhizobacteria and plant immunity.
Constrained Assortment Optimization Problem under the Multilevel Nested Logit Model
Authors: Wang Yanqiao , Shen Zuo‐Jun Max
Published: April 2021

We study the choice‐based constrained assortment optimization problem under the multilevel nested logit model with a no‐purchase option in every choice stage. For this problem, each candidate product is associated with a fixed profit. The goal is to identify the optimal assortment satisfying a cardinality constraint to maximize the expected profit per customer. There is a cardinality limitation imposed on nodes in the second lowest level. A polynomial‐time algorithm with computational complexity O( nmax{ m,  k}) is provided to locate the optimal assortment for the m‐level nested logit model with n products, where k is the maximum number of products within any node in level m − 1.
Assessing the Outbreak Risk of Epidemics Using Fuzzy Evidential Reasoning
Authors: Shi Xianliang , Li Jiangning , Huang Anqiang , Song Shaohua , Yang Zaili
Published: April 2021

Epidemic diseases (EDs) present a significant but challenging risk endangering public health, evidenced by the outbreak of COVID‐19. Compared to other risks affecting public health such as flooding, EDs attract little attention in terms of risk assessment in the current literature. It does not well respond to the high practical demand for advanced techniques capable of tackling ED risks. To bridge this gap, an adapted fuzzy evidence reasoning method is proposed to realize the quantitative analysis of ED outbreak risk assessment (EDRA) with high uncertainty in risk data. The novelty of this article lies in (1) taking the lead to establish the outbreak risk evaluation system of epidemics covering the whole epidemic developing process, (2) combining quantitative and qualitative analysis in the fields of epidemic risk evaluation, (3) collecting substantial first‐hand data by reviewing transaction data and interviewing the frontier experts and policymakers from Chinese Centers for Disease Control and Chinese National Medical Products Administration. This work provides useful insights for the regulatory bodies to (1) understand the risk levels of different EDs in a quantitative manner and (2) the sensitivity of different EDs to the identified risk factors for their effective control. For instance, in the case study, we use real data to disclose that influenza has the highest breakout risk level in Beijing. The proposed method also provides a potential tool for evaluating the outbreak risk of COVID‐19.
Interactions between SARS coronavirus 2 papain‐like protease and immune system: A potential drug target for the treatment of COVID‐19
Authors: Mahmoudvand Shahab , Shokri Somayeh
Published: April 2021

Coronaviruses (CoVs) are a large family of respiratory viruses which can cause mild to moderate upper respiratory tract infections. Recently, new coronavirus named as Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has been identified which is a major threat to public health. Innate immune responses play a vital role in a host's defence against viruses. Interestingly, CoVs have evolved elaborate strategies to evade the complex system of sensors and signalling molecules to suppress host immunity. SARS‐CoV‐2 papain‐like protease (PLpro), as an important coronavirus enzyme, regulates viral spread and innate immune responses. SCoV‐2 PLpro is multifunctional enzyme with deubiquitinating (DUB) and deISGylating activity. The PLpro can interact with key regulators in signalling pathways such as STING, NF‐κB, cytokine production, MAPK and TGF‐β and hijack those to block the immune responses. Therefore, the PLpro can be as an important target for the treatment of COVID‐19. Until now, several drugs or compounds have been identified that can inhibit PLpro activity. Here we discuss about the dysregulation effects of PLpro on immune system and drugs that have potential inhibitors for SCoV‐2 PLpro.
Social innovation in times of flood and eviction crisis: The making and unmaking of homes in the Ciliwung riverbank, Jakarta
Authors: Widyaningsih Anastasia , Van den Broeck Pieter
Published: April 2021

This study considers displacement occurring around the Jakarta flood mitigation projects between 2015–17 and explores the emergence of social innovation by affected kampung communities along the Ciliwung River. A framework combining theories on domicide and social innovation is developed to scrutinize two main case studies, Bukit Duri and Kampung Tongkol, revealing their connection to the city's urban development trajectory as well as the continuous struggle over adequate housing for low‐income groups. The study questions official plans, policies and responses towards flood‐induced displacement and resettlement planning. It also brings social innovation into the debate to unpack how displacement became a key moment for transformative change. The paper argues that, although urban eviction is related to globalization, outcomes are not foreclosed. Predominant urban mechanisms are contested, shaped, and transformed by local communities.
The effect of speed on Achilles tendon forces and patellofemoral joint stresses in high‐performing endurance runners
Authors: Starbuck Chelsea , Bramah Christopher , Herrington Lee , Jones Richard
Published: April 2021

Achilles tendinopathy and patellofemoral pain are common running injuries associated with increased Achilles tendon (AT) forces and patellofemoral joint (PFJ) stresses. This study examined AT forces and PFJ stresses at different running speeds in high‐performing endurance runners. Twenty runners ran overground at four running speeds (3.3, 3.9, 4.8, and 5.6 m/s). AT forces and PFJ stresses were estimated from kinematic and kinetic data. Repeated measures ANOVA with partial eta squared effect sizes was conducted to assess differences between running speeds. Increased peak AT forces (19.5%;p < 0.001) and loading rates (57.3%;p < 0.001) from 3.3 m/s to 5.6 m/s were observed. Cumulative AT loading was greater in the faster speeds compared to the slower speeds. Faster running speeds resulted in increased peak plantar flexor moments, increased peak plantar flexion angles, and a more flexed knee and an anterior center of pressure position at touchdown. Peak PFJ stress was lower in the slowest speed (3.3 m/s) compared to the faster running speeds (3.9–5.6 m/s;p = 0.005). PFJ stress loading rate significantly increased (43.6%;p < 0.001). Greater AT loading observed could be associated with strategies such as increased plantar flexor moments and altered lower body position at touchdown which are commonly employed to generate greater ground contact forces. Greater AT and PFJ loading rates were likely due to shorter ground contact times and therefore less time available to reach the peak. Running at faster speeds could increase the risk of developing Achilles tendinopathy and patellofemoral pain or limit recovery from these injuries without sufficient recovery.
The Problem with “Confederate” Monuments on our Heritage Landscape
Authors: Lees William
Published: April 2021

Objective

This article seeks to reframe so‐called Confederate monuments as monuments to the revisionist “Lost Cause.” I define these monuments as a problem for historic preservation that has long been based on a preference for in‐place protection of things “historic.”

Methods

I compare Confederate monuments’ original intent with arguments that these are Civil War, soldier, or veteran memorials. I also explore monuments’ value as sculpture and their de facto status as nationally significant and worthy of preservation.

Results

Confederate monuments are monuments to the Lost Cause, a narrative supporting the resurgence of white supremacy. We must reconsider the in‐place preservation of these monuments as a de facto choice of historic preservation.

Conclusion

The structural problem of Confederate monuments for our national historic preservation program calls for its broader evaluation for inclusivity and racial justice. We must find other ways to tell the history of the Confederacy than through physical propaganda pieces of the failed national insurrection of the 1860s.
Non‐Price Competitiveness Factors—A simple measure and implications for the five largest euro area countries
Authors: Xifré Ramon
Published: April 2021

This paper obtains a versatile measure of non‐price competitiveness factors (NPCF) based on a simple international trade model. Trade frictions are reinterpreted as the NPCF conditions (inferior product quality, suboptimal geographical and industry specialisation of exports and any other limitations of the production and exporting channels) that inhibit trade. The set‐up is applied to the five largest euro area economies for the period 2000–2018. Over this period, NPCF have improved significantly in the Netherlands and Spain, mildly in Italy and Germany and mildly worsened in France. In all countries, the improvement in NPCF has been more intense and sustained in the first half of the period and more unstable in the second half. The set‐up is also applied at the product level, considering four types of products depending on the stage of processing, rendering results which are similar across product types and aligned with those for the whole economy. The results suggest that the conventional North–South divide in the euro area might not be entirely applicable regarding NPCF.
A randomized controlled trial of three‐dimensional versus two‐dimensional imaging system on duration of surgery and mental workload for laparoscopic gastropexies in dogs
Authors: Balsa Ingrid M. , Giuffrida Michelle A. , Mayhew Philipp D.
Published: April 2021

Objective

To evaluate the effect of three‐dimensional (3D) laparoscopy compared to two‐dimensional (2D) laparoscopy when evaluating duration of surgery for canine intracorporeally sutured gastropexy.

Study Design

Randomized controlled clinical trial.

Animals

Thirty client‐owned dogs.

Methods

Dogs were randomized into 2D or 3D groups and underwent a three‐port laparoscopic intracorporeally sutured incisional gastropexy with barbed suture. Procedures were performed by a single board‐certified surgeon. Duration of surgery was recorded and workload was assessed immediately after surgery using the NASA Task Load Index (TLX).

Results

Median duration of surgery was 3 min shorter for 3D versus 2D (95%CI −10 to 13; p = .51). Surgical component durations, total and component TLX scores, and intraoperative complications also did not differ between groups. In a subgroup analysis excluding the first eight cases due to presumption of a learning curve with suturing technique, total TLX score (p = .004) and all component scores were lower for 3D as compared to 2D laparoscopy, although duration of surgery did not differ (p = .20).

Conclusion

The use of 3D laparoscopy was not associated with shorter duration of surgery when compared to 2D laparoscopy.

Clinical Significance

3D laparoscopy requires further investigation in veterinary medicine to determine its utility in decreasing surgical duration, surgical complications or surgeon mental or physical workload.
Phylogenomic resolution of the monotypic and enigmatic Amarsipus, the Bagless Glassfish (Teleostei, Amarsipidae)
Authors: Harrington Richard C. , Friedman Matt , Miya Masaki , Near Thomas J. , Campbell Matthew A.
Published: April 2021

Amarsipus carlsbergi is a rare mesopelagic fish distributed in the Indian and Pacific Oceans and is the only species classified in the family Amarsipidae. Since its description in 1969, phylogenetic hypotheses have varied regarding its relationship with other percomorph lineages, but most have indicated a close relationship with the traditional suborder Stromateoidei. Molecular phylogenies place families previously classified in Stromateoidei within a diverse clade—Pelagiaria—that includes fishes such as tunas, cutlassfishes and pomfrets. A recent analysis of a small number of loci resolved a clade containing Amarsipus and the stromateoid lineage Tetragonurus. A subsequent high‐throughput sequence phylogeny based on ultraconserved elements (UCEs) of Pelagiaria lacked Amarsipus, but revealed both strong support for stromateoid paraphyly and high levels of gene tree incongruence. We gathered UCE sequence data for 610 UCE loci from Amarsipus and integrate these with samples from all remaining pelagiarian families. This provides a taxonomically comprehensive phylogenomic framework to test the evolutionary relationships of Amarsipus, and evaluate the support for stromateoid monophyly. As in previous studies, our analyses find high levels of gene tree topological discordance with regard to some deeper pelagiarian inter‐relationships. However, we resolve Amarsipus as the sister lineage of a clade containing Tetragonurus and a family not considered a stromateoid lineage, Chiasmodontidae. This relationship is supported by both high gene tree concordance and node support. Our analyses also provide strong support for the paraphyly of Stromateoidei, casting uncertainty on previous hypotheses of the evolution of morphological traits across members of Pelagiaria.
Geodiversity as part of Heritage Rivers: The Example of São Francisco, River of National Unity - Along the Stretch its River Source to the Casca d’Anta Waterfall
Authors: Oliveira Carmélia Kerolly Ramos de , Amorim Castro Paulo De Tarso , Ruchkys Úrsula De Azevedo , Pereira Diamantino Manuel Insua , De Sordi Michael Vinicius
Published: April 2021

Rivers are key parts of geodiversity and have special proximity with society. Hence, river heritage is characterized by uncommon rivers with singular aspects of geodiversity, historical and cultural values, ecological and landscape elements of high scenic quality. In such context, the present study aimed to identify the set of elements or places of interest which could be used to recognize river heritage based on geodiversity values along a 17 km stretch between São Francisco river headwaters and the Casca d’Anta waterfall within Canastra Range National Park (Minas Gerais State - Brazil). Here, seven elements of river heritage were recognized: i) landscape set ofthe Canastra Range; ii) São Francisco historic headwater; iii) Curral de Pedras; Casca d’Anta waterfall; v) Nesting area of the Mergus octosetaceus; vi) diamond mining; vii) the Canastra cheese. The identified elements of river heritage highlight the scientific, ecological, cultural, historic and touristic/economic importance of the analyzed. stretch Moreover, such elements illustrate need for improvement of the existing legislations and more effective instruments of river management and river conservation.
Tribological Properties of a New Alloy Laser Cladded on Hypereutectoid Rails
Authors: Fasihi Panahsadat , Abrahams Ralph , Mutton Peter , Yan Wenyi
Published: April 2021

To overcome the previous limitations imposed by standard laser cladding alloys, a novel iron-based laser cladding alloy, SS415, is developed and investigated. The wear and rolling contact fatigue resistance properties of the novel SS415 laser cladded on a premium railway hypereutectoid rail are experimentally investigated using a custom-made roller-on-disc test machine. The obtained results are compared with our previously published results of non-clad rail and the standard iron-based cladding alloys, namely, 410L and SS420, specimens under the same conditions. The accumulated wear rate and the pileup area were quantified with the aid of an optical profilometer. The obtained results were correlated to in-depth wear surface characterization using optical microscopic images. The experimental results showed that the novel SS415 exhibits favorable hardness variation, more ductile behavior, promising work hardenability, and a 95% reduction in the wear rate, in comparison to the non-cladded samples. Moreover, the SS415 cladding resulted in less surface damage and the lowest degree of third-body abrasive wear modes, after the completion of the rolling contact cycles. Based on this investigation, the novel SS415 is a promising iron-based laser cladding alloy that offers the best wear and fatigue performance compared to both 410L and SS420 cladded samples. Additionally, this novel alloy offers significantly improved mechanical and tribological properties compared to the two standard alloys.
Friction Mechanism and Characteristics of Reticle Based on Contact Theory
Authors: Wu Jianwei , Wang Hui , Chen Tianfeng , Ma Yarui , Cui Jiwen , Tan Jiubin
Published: April 2021

With the development of integrated circuits, the structure of chips becomes more and more complex, and the processing cost increases accordingly. To improve the productivity of lithography, the acceleration of the reticle stage should be increased to reduce the positioning time. However, the increase of acceleration will cause the relative slip between the reticle and the vacuum chuck, which seriously affects the accuracy and the product yield of lithography. To suppress the slippage, the friction mechanism and the characteristics between the reticle and the chuck are studied in this article. First, based on the Kogut–Etsion contact model and the Majumdar–Bhushan (MB) fractal contact model, the maximum static friction coefficient model between nano-scale surfaces was established. Then, the surface morphology parameters of reticle and chuck adsorption surface were obtained by atomic force microscopy (AFM) scanning. Finally, the maximum static friction force experiments show that the MB model is more suitable for the study of friction mechanism between reticle and vacuum chuck, and the model is more instructive for the suppression of reticle slip.
Effect of Fin Orientation on Melting Process in Horizontal Double Pipe Thermal Energy Storage Systems
Authors: Boulaktout Nesrine , Mezaache El Hacene , Teggar Mohamed , Arıcı Müslüm , Ismail Kamal A. R. , Yıldız Çağatay
Published: April 2021

Immersion of fins in latent heat thermal energy storage (LHTES) systems has been used as an influential approach to remedy the poor thermal conductivity of phase-change materials (PCMs). This paper numerically investigates heat transfer and phase-change improvement by means of longitudinal fins in a double pipe thermal energy storage unit. The main aim of this study is to investigate the effect of fin orientation on the performance of the thermal storage unit. Six configurations of different fin numbers (2, 4, and 8 fins) and orientations (π/2, π/4, and π/8) are tested. For simulations, a two-dimensional mathematical model incorporating the enthalpy-porosity method and finite volume techniques are established and solved by ansys-fluent. The numerical predictions are successfully validated by comparison with experimental and numerical data from the literature. Heat transfer characteristics and melting process are analyzed through streamlines, isotherms, mean temperature, heat flux (HF), and heat transfer coefficient (HTC) as well as transient melting front position and liquid fractions. Results show that orientation of fins has a significant impact on the charging time for two cases (2 and 4 fins) whereas no significant reduction in charging time was obtained for the case of 8 fins. In case of utilizing 2 fins, a fin orientation of 0 deg (vertical fins) shortens the charging time by up to 2.5 folds compared with the horizontal fins (90 deg). These results could help designing efficient latent thermal energy storage units.
Analysis of Aqueous Lithium Bromide Absorption Refrigeration Systems
Authors: You Dongchuan , Metghalchi Hameed
Published: April 2021

Aqueous lithium bromide absorption refrigeration systems have been studied in recent years and their advantages such as environmental safety and utilization of low-grade energy have been proved. Research on improving their performance has been increasing lately. In this paper, single effect and parallel flow double-effect aqueous lithium bromide absorption refrigeration systems have been studied. Mass, energy, entropy, and exergy balances have been used to model the absorption refrigeration systems. Parametric studies have been done to investigate the effects of cooling load, evaporator exit temperature, condenser exit temperature, generator vapor exit temperature, absorber exit temperature, and solution energy exchanger effectiveness on the performance of the system. The analyses show the coefficient of performance, and exergetic efficiency of double-effect absorption refrigeration is higher than those of single-effect refrigeration. The effect of other parameters on the performance of both single- and double-effect systems has been described in detail in this article.
Direct Kinematic Analysis of the Spatial Parallel Mechanism With 3-R(P)S Structure Based on the Point Pair Relationship
Authors: Zhu Ganmin , Wei Shimin , Zhang Ying , Liao Qizheng
Published: April 2021

This paper demonstrates a novel geometric modeling and computational method of the family of spatial parallel mechanisms (PMs) with 3-R(P)S structure for direct kinematic analysis based on the point pair relationship. The point pair relationship, which is derived from the framework of conformal geometric algebra (CGA), consists of the relationship between the point and the point pair and two point pairs. The first research is on the distance relationship between the point and the point pair. Second, the derivation of the distance relationship between two point pairs is based on the aforementioned result, which shows the mathematical homogeneity. Third, two formulations for a point of the point pairs that satisfy the distance relationship between two point pairs are reduced. Fourth, the point pair relationship is applied to solve the direct kinematic analysis of the spatial parallel mechanism with 3-R(P)S structure. Finally, four numerical examples are provided to verify the validity of the proposed algorithm. Overall, the proposed method can be generalized for the direct kinematics of a series of spatial parallel mechanisms with 3-R(P)S structure.
Application of AI in Optimization of Machining Conditions
Authors: Chen Tongjian , Wang Weiping , Wang Xiaofang
Published: April 2021

In these days researchers have been attempting to build up a versatile optimization method which is adaptable for all the purposes but no ideal one has been appeared. The paper proposes a new consideration for practising the optimization of machining conditions in various machining processes on workshop scenes. The optimizing strategy is through an expert system of selection to determine a most effective algorithm from the current sophiticated optimizing algorithms collected in the knowledge base as subroutines, then to run the algorithem program and obtain the optimized results by means of the interactive function of expert system. The method not only has the versatile property to be used in various sorts of machining easily but also keeps the completeness of each sophiticated optimizing method developed for a special machining process without compromise.
Product Design Analysis Using the Assembly Design Evaluation Metric
Authors: Lee David E. , Melkanoff Michel A.
Published: April 2021

Analysis of a product’s assembly properties is needed during the initial design stage in order to identify potential assembly problems. These problems affect product performance in the later stages of a product’s life cycle. An analysis methodology has been developed that supports product design analysis for assembly during the initial design stage. The methodology, referred to as the Assembly Design Evaluation Metric (ADEM), utilizes the incomplete nature of initial design data and a generic model of assembly operations in the analysis of a product design. ADEM generates ratings for each component of a product design and each process that would be needed to assemble the components together. From the individual component and process ratings, ADEM computes overall ratings for the product design itself. These overall product ratings can then be used to compare the differing iterations of a product design. Because ADEM provides an explicit model of assembly operations, different levels of data and process abstraction can be maintained and analyzed. This enables ADEM to evaluate product designs earlier in the design stage than existing design analysis methods such as DFA (design for assembly) techniques.
Developing Function Structures of Engineering Systems Using C and X-Toolkit Intrinsics
Authors: Hundal M. S. , Langholtz Louis D.
Published: April 2021

An interactive graphical program is described, which uses an object oriented approach for developing conceptual designs. The program is written in the C programming language and designed on a UNIX operating system. It starts with the specifications list, develops function structures and searches for solutions, for systems with mechanical, electrical/electronic, fluid and other components. It can be used for developing new and improving existing devices, systems and processes. Applications include any designs which can be described in terms of interconnected functional blocks with definable input and output parameters. By running the system, the variety of functional blocks can be tested to determine the optimal solution based on the given specifications. Designers will benefit from the pictorial representation; data-based functional and connective representation; and the generation and evaluation of concept variants. The use of the program is illustrated by an industrial design example.
Analogical Problem Solving in Mechanical Design: The Knowledge Base Model
Authors: Bardasz Theodore , Zeid Ibrahim
Published: April 2021

Mechanical design activities can be categorized as two classes: creating new designs for new problems and modifying old designs to fit new problems. A vast majority of mechanical design activities can be associated with the latter class. In most cases, it is more effective to modify the design process that created the mechanical artifact than it is to modify the mechanical artifact itself. A scheme for design automation that uses Analogical Problem Solving (APS) as its intelligent agent offers an effective method to solve both classes of mechanical design. It is particularly suited to the latter class of design activities. It would rely heavily on a design knowledge base for storing design cases generated while solving design problems, and retrieving design cases that are applicable in a new design problem context. In this paper, a cognitive model of memory for storing design plans is presented. The memory model is four layers deep: product design plans, assembly design plans, mechanical component design plans, and recurring engineering problems. The storage and retrieval mechanism is based on some of the more popular work found in Case Based Reasoning. To alleviate the user(s) from operating in a restricted vocabulary set, a semantic network is integrated into the memory model for use as an elaboration and cross-reference mechanism. Mechanical design plans for products, assemblies, mechanical components and recurring engineering problems can be stored and retrieved from the memory model using information found in the description of the design problem. Sample examples are presented to demonstrate the potential of the memory model.
Interference/Collision Detection Using Geometric Halfspaces
Authors: Letter John G. , Ling Zhi-Kui
Published: April 2021

Analyzing engineering problems with solid modelling has significantly increased in popularity in recent years. One of the areas of analyses is interference and collision detection between solid objects. Interference is defined as a condition in which two objects share a portion of space at the same instance of time. Collision is defined as a condition in which the surfaces of two objects are in contact. This paper presents a method of determining interferences and collisions between objects defined by geometric halfspaces. Specifically, it is implemented in a process of determining collision free paths of a three degree of freedom manipulator installed in a recirculating nuclear steam generator. Possible interference / collision between the components of the manipulator and generator are examined.

Halfspaces are used to construct solid objects for the purpose of determining interferences and collisions between any two objects. Halfspaces are defined as simple point sets that have characteristic functions. The halfspaces presented in this paper are planes, cylinders, and spheres. Definition points, which are a set of discrete points on the surface of the object, approximate the shape of the object. Halfspaces and definition points are the information required for the interference / collision detection analysis. The technique addressed in this paper checks the relative location of the definition points of one object with the geometric halfspaces of another object. The result of each analysis determines if the objects are either interfering with, in contact with, or separated from each other.
HyperGear: An Object Oriented Design Program for Single Stage Gear Box Design
Authors: Gabriele Gary A. , Serrano Agustî Maria I.
Published: April 2021

The need for superior design tools has lead to the development of better and more complex computer aided design programs. Two of the more important new developments in application tools being investigation are Object Oriented Languages, and HyperMedia. Object Oriented Languages allow the development of CAD tools where the parts being designed and the design procedures specified are conceptualized as objects. This allows for the development of design aids that are non-procedural and more readily manipulated by the user trying to accomplish a design task. HyperMedia allows for the easy inclusion of many different types of data, such as design charts and graphs, into the tool that are normally difficult to include in design tools programmed with more conventional programming languages.

This paper explores the development of a computer aided design tool for the design of a single stage gear box using the development HyperCard® environment and the HyperTalk® programming language. The resulting program provides a user friendly interface, the ability to handle several kinds of design information including graphic and textual, and a non-procedural design tool to help the user design simple, one stage gear boxes. Help facilities in the program make it suitable for undergraduate instruction in a machine elements design course.
Computer Aided Analysis of a Printer Mechanism
Authors: Hari Yogeshwar , Meyer Daniel B.
Published: April 2021

This paper analyzes the dynamics of a printer mechanism used for graphics printing. The torque induced in the drive motor is idealized as a step function. The friction induced in the mechanism is idealized as viscous damping. The structure of the printer mechanism is idealized to be rigid during operation of the print head drive. The Lagrangian method is used to derive a mathematical model. It is represented in a control system schematic applying feedback. A computer program written in Basic simulates the system under control, in order to predict the outputs, velocity and position, given the input, torque. The computer aided analysis enables the designer to minimize print placement error due to imprecision.
Octree-Based Automatic Mesh Generation for Non-Manifold Domains
Authors: Saxena M. , Finnigan P. M. , Graichen C. M. , Hathaway A. F. , Parthasarathy V. N.
Published: April 2021

Automatic mesh generation from solid models heretofore has been confined to manifold objects only. While manifold objects are the most commonly encountered domains in many applications, other applications such as those requiring multiple material models and mixed-model representations (combination of 1-D, 2-D and 3-D domains), fall beyond the realm of the existing automatic meshing procedures as they require a non-conventional modeling environment, namely the non-manifold topology (NMT) based environment. This paper focuses on automatic mesh generation issues in the context of two such applications: (i) finite element modeling for multiple material models and (ii) geometric abstractions requiring a mixed-model representation. Specifically, the paper describes a geometry utility system, built around a NMT data structure and geometry-based meshing algorithms that ensure the validity of the mesh for non-manifold domains.
Extra Drag Force on a Circular Cylinder Due to the Presence of Solid Particles in Subsonic Compressible Flow
Authors: Mellsen Stanley B.
Published: April 2021

The effect of particles, such as dust in air on aerodynamic drag of circular cylinders was calculated for compressible flow at critical Mach number and for incompressible flow. The effect of compressibility was found negligible for particles larger than about 10 μm, for which the air can be considered a continuum. Drag coefficient and collection efficiency are provided for a wide range of inertia parameters and Reynolds numbers for both compressible and incompressible flow.
Prediction of Jets and Flames in Co-Flowing Streams
Authors: Ha S. , Lilley David G.
Published: April 2021

The theoretical computation of jets and flames in co-flowing streams is of considerable interest in aerothermochemistry. Axisymmetric flowfields are considered with time-mean velocity, temperature and species concentrations (three components — fuel, oxygen, and products) being predicted via a version of the GENMIX computer code. It is equipped with the standard Prandtl mixing length model of turbulence and an Arrhenius-type reaction rate expression for kinetically-influenced turbulent flame simulation. The code solves the boundary layer equations using a fully-implicit forward-marching solution procedure.

A variety of production runs have been made to show parameter effects, and results are tabulated, graphed and discussed. Complexities include:

1. The jet and surroundings may have different densities.

2. The surroundings may be co-flowing with nonzero axial velocity.

3. Flame ignition is via an outer annular hot zone.

4. Flames with typical hydrocarbon fuels burning in air are considered, and dissociation effects are included in a simple manner.

Results confirm the previous experimental findings about jet development in co-flowing streams, and extend knowledge to more practical and burning situations.