Contract Length Research Articles

Roughing Nitrogen-Doped Carbon Nanosheets for Loading of Monatomic Fe and Electroreduction of CO2 to CO.

The catalyst is the pivotal component in CO2 electroreduction systems for converting CO2 into valuable products. Carbon-based single-atom materials (CSAMs) have emerged as promising catalyst candidates due to their low cost and high atomic utilization efficiency. The rational design of the morphology and microstructure of such materials is desirable but poses a challenge. Here, we employed different Mg(OH)2 templates to guide the fabrication of two kinds of amorphous nitrogen-doped carbon nanosheet-supported Fe single atoms (FeSNC) with rough and flat surface structures. In comparison to flat FeSNC with saturated FeN4 sites, the rough FeSNC (R-FeSNC) exhibited unsaturated FeN4-x sites and contracted Fe-N bond length. The featured structure endowed R-FeSNC with superior capacity of catalyzing CO2 reduction reaction, achieving an exceptional CO selectivity with Faradaic efficiency of 93% at a potential of -0.66 V vs. RHE. This study offers valuable insights into the design of CSAMs and provides a perspective for gaining a deeper understanding of their activity origins.

Understanding the Impacts on Automobile Leasing Firm Loss in China: An Analysis of Vehicle Residual Value Risk and Lease Price Patterns

ABSTRACTThe paper addresses vehicle depreciation and pricing issues in the automobile leasing industry in China. Under the current industry climate, operating lease firms face large residual value risk, and therefore, how to price contracts that minimises such risk is an important question. By analysing market data of used vehicles, an exponential decay function was developed to model the price dynamics across different brands and model series. Specifically, we estimate the depreciation rate directly from the data. In addition, by considering all revenue and cost components and converting them into present value terms, appropriate deposit and rents combintions were sought under different profit expectations. Length of contracts, age of vehicles and purchase cost factors were also considered to detect any further patterns in rents. The research outcomes will provide guidance on lease pricing given the current development of the industry, thereby improving firms’ profitability position as well as helping maintain their competitiveness and growth.

Transcriptome-Guided Characterization of the Environmental Toxicity of Metformin: Disruption of Energy Homeostasis and Inhibition of Embryonic Development of Zebrafish at Environmentally Relevant Concentrations.

Metformin has been widely detected in aquatic ecosystems, yet the knowledge of its impact on aquatic organisms, particularly at environmentally relevant concentrations, remains limited. In the present study, we characterized the developmental toxicity of metformin in zebrafish, utilizing a transcriptome-guided toxicological assessment framework. Transcriptomic analysis conducted at metformin concentrations within the μg/L range revealed significant disruptions in biological processes associated with nucleotide, hydrocarbon, and amino acid metabolism, suggesting a significant disturbance in energy homeostasis. This observation was corroborated by energy-targeted metabolomic analysis, wherein a considerable number of metabolites involved in purine metabolism, pyrimidine metabolism, and the citrate cycle displayed significant alterations. Notably, most intermediates in the citrate cycle such as acetyl-CoA exhibited remarkable decreases. Additionally, our study identified significant impediments in zebrafish embryonic development, including decreased yolk extension progress, spontaneous contraction and body length, and increased yolk sac area and yolk/while body lipid content ratio, at metformin concentrations as low as 0.12 μg/L. Furthermore, the disruption of energy homeostasis by metformin was observed to persist into adulthood even after a prolonged recovery period. The present findings highlighted the disruptive effects of metformin on energy homeostasis and embryonic development in teleost at environmentally relevant concentrations, thereby prompting a reevaluation of its environmental risk to nontarget aquatic organisms.

Breaking All the Rules: Information Technology Procurement in the Government of Canada

AbstractThe Government of Canada has recently faced intense parliamentary and public scrutiny of the role played by private contractors in its information technology (IT) projects, most notably in the case of the ArriveCAN application. With these ongoing investigations as its backdrop, this article analyzes patterns in federal government IT procurement between 2017 and 2022, drawing on a comprehensive analysis of the federal contracting open dataset. We reveal that the federal government betrays accepted best practice in modern government IT procurement on several key dimensions, including on contract values and lengths; on the diversity of suppliers; on the source of IT expertise; and in the management of intellectual property. We argue that the Canadian approach to IT procurement is an historically overlooked but crucial driver of its failing digital reform efforts. We conclude by turning to IT procurement policy reforms gaining traction outside Canada that may help the Government of Canada improve how it buys and deploys IT going forward—a task we argue is essential if the government wants to avoid future IT contracting scandals and deliver on its long‐standing promise of digital era modernization.

Efficacy and safety of peroral endoscopic myotomy for pediatric achalasia: A nationwide study.

Achalasia, a rare esophageal motility disorder characterized by the inability of the lower esophageal sphincter to relax and loss of esophageal peristalsis, significantly impacts pediatric patient quality of life through symptoms like dysphagia, chest pain, and weight loss. This nationwide retrospective cohort study evaluates the efficacy and safety of peroral endoscopic myotomy (POEM) for pediatric achalasia in Mongolia, contributing to the limited global data on this minimally invasive treatment in children. Conducted between February 2020 and March 2022 at 2 tertiary centers, the study included symptomatic achalasia patients, treatment-naive or those with unsatisfactory outcomes from previous esophageal dilations. The POEM procedure was assessed for its impact on esophageal structure and function, symptom severity via the Eckardt score, and procedure-related safety, with outcomes measured at baseline, 3 days, and 12 months post-procedure. The study demonstrated notable post-procedure improvements across all measured outcomes: abnormal contraction length and esophageal width significantly reduced, underscoring the procedure's effectiveness. More precisely, the integrated relaxation pressure showed a significant improvement from a mean of 26.8 mm Hg (standard deviation [SD], 5.4 mm Hg) pre-procedure to 10.8 mm Hg (SD, 1.1 mm Hg) 12 months (P < .001). Similarly, Eckardt scores, which assess symptom severity, improved significantly from a pre-procedure mean of 7.0 (SD, 1.0) to a substantially lower score post-procedure (P < .001), reflecting enhanced patient quality of life and symptom alleviation. This study underscores POEM's role as an effective, minimally invasive option for pediatric achalasia management within the Mongolian population, offering significant symptomatic relief and improved esophageal function.

Cost Optimization in Cloud Computing: Capacity Reservation for Intermittent Random Demand Surges

The adoption of cloud computing has been accelerating over the last decade, while enterprise cloud users (“firms”) are struggling to manage their growing cloud expenditures in the face of intermittent digital demand surges caused by planned or random events. To deal with such challenges, a firm can employ reserved instances with the standard contract length (e.g., one year) to meet the stationary base demand, which we refer to as the base contracts, complemented by additional reserved instances with either standard or shorter contract lengths, which we refer to as the supplementary contracts, to cope with the demand surges. We first analyze a model whereby the surge and inter-surge durations are deterministic, demand magnitude is random, and cancellation of the reservations is allowed. We develop a capacity management plan for the firm including not only the optimal capacity levels, which follow a newsvendor-type solution, but also the optimal policy for managing the purchase, renewal, cancellation, or expiration of the supplementary contracts, which can be characterized as a two-threshold policy. Due to the complexity of the structure of the optimal policy, we also construct an effective heuristic policy by excluding the renewal option from the action space, which can be applied to a more general setting where the surge and inter-surge durations are random. We examine two model extensions: (1) when trades of reserved instances are allowed in a secondary marketplace; (2) when the firm does not have exact information about the distributions of the surge magnitude and duration while it can adjust the capacity levels as data unveils. Our analysis shows that the optimal policy for managing the supplementary contracts depends on the relative magnitude of the surge and inter-surge durations in relationship to the cancellation fee. Moreover, our numerical results show that cloud platforms that offer a secondary marketplace are more attractive to firms from a cost standpoint than those that allow cancellation only. The latter, without the secondary marketplace, however, can achieve parity with the former by offering a deeper discount rate for the reserved instances, thereby bypassing the cost of administering the secondary marketplace.

A matheuristic for a multi-period three-echelon network design problem with temporary capacity acquisition

This study addresses a three-echelon network design problem that determines the location and size of new warehouses, the removal of company-owned warehouses, the inventory levels of multiple products at the warehouses, and the assignment of suppliers as well as customers to warehouses over a multi-period planning horizon. A distinctive feature of our problem is that new warehouses operate with modular capacities that can be expanded or reduced over several periods, the latter not necessarily having to be consecutive. Moreover, in every period, the demand of a customer for a given product has to be satisfied by a single warehouse. The problem arises in the context of warehousing-as-a-service, a business scheme that offers flexible conditions for temporary capacity leasing. The associated fixed warehouse lease cost reflects economies of scale in the capacity size and the length of the lease contract. We develop a mixed-integer linear programming formulation and propose a matheuristic to solve this problem, which exploits the structure of the optimal solution of the linear relaxation to successively assign customers to open warehouses and fix other binary variables related to warehouse operation. Additional variable fixing rules are also developed, based on a scheme for managing inventories at warehouses and using the product quantities provided by suppliers. Numerical experiments with randomly generated large-sized instances reveal that the proposed matheuristic outperforms a general-purpose solver in 74% of the instances by identifying higher quality solutions in a substantially shorter computing time.

Ingesting yeast extract causes excitation of neurogenic and myogenic colonic motor patterns in the rat.

Fermented foods play a significant role in the human diet for their natural, highly nutritious and healthy attributes. Our aim was to study the effect of yeast extract, a fermented substance extracted from natural yeast, on colonic motility to better understand its potential therapeutic role. A yeast extract was given to rats by gavage for 3 days, and myogenic and neurogenic components of colonic motility were studied using spatiotemporal maps made from video recordings of the whole colon exvivo. A control group received saline gavages. The yeast extract caused excitation of the musculature by increasing the propagation length and duration of long-distance contractions, the major propulsive activity of the rat colon. The yeast extract also evoked rhythmic propulsive motor complexes (RPMCs) which were antegrade in the proximal and mid-colon and retrograde in the distal colon. RPMC activity was evoked by distention-induced neural activity, but it was myogenic in nature since we showed it to be generated by bethanechol in the presence of tetrodotoxin. In conclusion, ingestion of yeast extract stimulates rat colon motility by exciting neurogenic and myogenic control mechanisms.

Collagen fibers within skeletal muscle extracellular matrix dynamically change their alignment in a stretch-dependent fashion

Collagen fiber architecture within the skeletal muscle extracellular matrix (ECM) contributes to muscle passive mechanical properties. There is evidence that collagen fibers change their alignment during muscle lengthening (stretching). Thus, the goal of this study was to characterize the dynamic changes of collagen fiber alignment in the muscle ECM during muscle stretching, and to assess the relationship between dynamic collagen re-alignment and muscle passive mechanics. We hypothesized that collagen fibers increase their alignment as the muscle is stretched, and that increased collagen alignment in stretched muscle is correlated to higher elastic stiffness. Extensor digitorum longus (EDL), soleus, and diaphragm muscles were collected from wildtype (WT) and D2.mdx (MDX) mice of 48-52 weeks of age. Muscles underwent a series of twitches to determine the optimum length (Lo) for isometric contraction, and then were decellularized to isolate the muscle ECM. Decellularized muscles (DCMs) were then mechanically tested using a series of stress-relaxation tests at 5% increments from 85% to 115% length relative to Lo. Elastic stiffness was measured as the slope of the tangent line on the stress-strain curve following stress-relaxation. Following mechanical testing, DCMs were imaged using second harmonic generation microscopy to visualize collagen alignment across the range of lengths used in mechanical testing. Collagen alignment was reported as an alignment index on a scale of 0 (perfect unalignment) to 1 (perfect alignment). We found that MDX diaphragm DCMs were less stiff than WT (WT: 910.2±586.7, MDX: 238±168.7, p=0.0041), but there were no significant differences in stiffness between WT and MDX EDL and soleus DCMs. We also observed a significant effect of stretch on collagen alignment in all DCMs tested (Diaphragm: p=0.0071, EDL: p=0.0004, soleus: p&lt;0.0001). Interestingly, the collagen fibers of the epimysium, the outermost layer of the muscle ECM, were more aligned in WT diaphragm DCMs than in MDX (WT 85%: 0.672±.14, MDX 85%: 0.344±0.16, p=0.0027; WT 115%: 0.783±0.04, MDX 115%: 0.480±0.19, p=0.0036). Finally, we found a significant positive correlation between the alignment and elastic stiffness at 110% Lo across all DCMs (p=0.0038, R2=0.1713). These data indicate that collagen fibers dynamically re-align as muscle is stretched. Additionally, increased collagen fiber alignment is associated with higher passive stiffness in the decellularized muscle ECM. Overall, we find that dynamic architectural changes in the muscle ECM contribute to passive mechanical behavior during a muscle stretch. This work was supported by a grant from the NIH NIAMS (R01-AR079545). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

NaV1.1 and NaV1.6 Play Unique and Essential Roles in Muscle Spindle Afferent Function in Adult Mice

Voltage gated sodium channels (NaVs) are crucial for the generation and propagation of action potentials. There are 9 different isoforms found in mammals (NaV1.1-1.9), and NaV1.1, NaV1.6, and NaV1.7 are found in the muscle proprioceptors that sense muscle stretch, the muscle spindle afferents. This sensory information is critical for motor reflexes and the sense of body and limb position in space. We previously found that mice lacking one or both copies of NaV1.1 in peripheral sensory neurons displayed motor deficits, including intention tremors. Muscle spindle afferents in these mice also had unstable static stretch sensitivity but normal dynamic sensitivity, suggesting a specific deficit in the maintenance of proprioceptor excitability when the Piezo2 channel was likely to be closed (Espino, et al., 2022). We hypothesized that NaV1.6 would also be necessary for normal motor behavior and muscle spindle afferent function. We generated sensory neuron specific deletions of NaV1.6 by crossing NaV1.6fl/fl mice with mice expressing PirtCre (NaV1.6cko) and observed severe motor deficits on the open field and rotarod test only in NaV1.6cko (n=15) and not NaV1.6Het (n=12) mice compared to NaV1.6fl/fl controls (n=8). In contrast to mice lacking NaV1.1, we did not observe intention tremors. We used an ex vivo muscle nerve preparation consisting of the extensor digitorum longus muscle and peroneal branch of the sciatic nerve. The muscle was maintained at the length of maximal twitch contraction (Lo) and given a battery of 9 ramp-and-hold stretches (2.5, 5, and 7.5% Lo repeated 3 times each) and 16 sinusoidal vibrations (5-100 μm amplitude; 10-100 Hz frequency). Preliminary results include recordings from 18 adult mice of both sexes (NaV1.6fl/fl n=8; NaV1.6cko n=10). We were only able to find stretch sensitive responses in 3 of 10 NaV1.6cko mice, and those were severely impaired with firing rates less than 5 Hz. In contrast, we found robust slowly adapting responses to stretch in all 8 NaV1.6fl/fl mice. Only 1 of 10 NaV1.6cko mice had any firing in response to vibration, in contrast to the normal dynamic sensitivity observed in NaV1.6fl/fl and NaV1.1cko afferents. This suggests that NaV1.6 plays a critical role in initiating muscle spindle afferent transmission, whereas NaV1.1 is essential for maintaining proprioceptor excitability during static stretch. Future studies will determine whether loss of NaV1.7, which does not result in motor deficits, alters muscle spindle afferent function. This work was supported by NIH Grant 5SC3GM127195 (KAW) a RISE Fellowship 5R25GM71381 (SO), NIH 5T32GM099608-10 and 1T32GM1144303-01A1 (CE). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Foreign market entry with circular business models: a customer-centric approach

Circular business models have been developed in recent years, driven by concerns over environmental sustainability. The circular business models are initially tested domestically, but businesses may aspire to expand internationally with it. However, entering foreign markets with circular business models, which include novel products and innovative services, may be challenging. Moreover, generalized foreign market entry criteria for circular business models are lacking. This in-depth case study utilized a mixed-method approach to shed light on the tactical adaptations businesses need to make in their circular business model when entering foreign markets while also ensuring economic competitiveness. The case includes foreign market entry with a circular “service" business model; therefore, we emphasized the customer side of the business model canvas related to customer relationships. In our conclusion, we identify five tactical adaptations, namely implementing a co-creation tool for customization, offering tangible customized benefits, increasing investment in social media marketing, utilizing start-up incubators/accelerators/co-working spaces as a marketing channel and offering adjustable contract lengths. Foreign markets with circular business models and involving the value network partners of the business are also expected to expand the positive externalities of circular economy internationally.

Teachers’ motivation and engagement to harness generative AI for teaching and learning: The role of contextual, occupational, and background factors

Since their release in late 2022, generative AI (genAI) tools have led to widespread use, including among teachers. The aim of our study is to examine several factors that may be implicated in teachers' motivation and engagement to harness genAI in teaching and learning. We examined contextual (i.e., autonomy-supportive leadership, autonomy-thwarting leadership), occupational experience (i.e., professional growth striving, change-related stress), and background factors (i.e., gender, age, teaching experience, contract length, class size, school level) as predictors of motivation (i.e., genAI valuing) and, in turn, engagement (i.e., integration in teaching-related work and student learning activities). Among 339 Australian teachers, our findings revealed that perceived autonomy-supportive leadership, professional growth striving, and change-related stress were linked with greater genAI valuing. In turn, genAI valuing was associated with greater genAI integration in both teaching-related work and student learning activities. Perceived autonomy-thwarting leadership was directly linked with greater genAI integration in student learning activities, and professional growth striving was directly associated with greater genAI integration in teaching-related work. Teachers’ gender and school level were also linked with the motivation and engagement factors, and there were several indirect associations as well. Our results pinpoint areas of focus for future research, policy, and practice to support genAI and its application in schools.

Consumer Preferences for Wood-Pellet-Based Green Pricing Programs in the Eastern United States

Co-firing wood pellets with coal is an attractive alternative energy generation method with economic, social, and environmental benefits for the US energy generation sector. One way to sustainably use wood pellets for co-firing is to create consumer-supported green pricing programs (GPPs). Our study surveyed residents of five states (Alabama, New Jersey, New York, Pennsylvania, and Virginia) to investigate preferences for the attributes of a hypothetical GPP. The study applied the Best Worst Choice method, which employs the Best Worst Scaling (BWS) and binary choice (BC) task. The BWS analysis showed that residents of all five states most value the flexibility of contracts, the location of energy generation, and the reduction of carbon emissions as attributes of GPPs. The BC analysis, however, showed that residents are willing to pay a premium for length of contract, followed by reduction of carbon emissions and variability of payments. This study shows that the adoption of optimal GPP attributes can create real customer value. The success of GPPs will depend on increasing enrollment and public support; hence, the next step will be to increase awareness levels and green consciousness through sensitization in the form of public education exercises and media campaigns. Such measures will serve to inform and educate residents on the benefits of GPPs and lessen the gap between intrinsic value and willingness to pay for select attributes.

Auto-ejection of liquid from a nozzle.

Auto-ejection of liquid is an important process in engineering applications, and is also very complicated since it involves interface moving, deforming, and jet breaking up. In this work, a theoretical velocity of meniscus at nozzle exit is first derived, which can be used to analyze the critical condition for auto-ejection of liquid. Then a consistent and conservative axisymmetric lattice Boltzmann (LB) method is proposed to study the auto-ejection process of liquid jet from a nozzle. We test the LB model by conducting some simulations, and find that the numerical results agree well with the theoretical and experimental data. We further consider the effects of contraction ratio, length ratio, contact angle, and nozzle structure on the auto-ejection, and observe some distinct phenomena during the ejection process, including the deformation of meniscus, capillary necking, and droplet pinch off. Finally, the results reported in the present work may play an instructive role on the design of droplet ejectors and the understanding of jetting dynamics in microgravity environment.

Optimization of contraction cone length in an open-circuit wind tunnel

The studies in the literature mostly focus on the curvature of the contraction cone, while research regarding the impact of contraction length on flow characteristics is limited. This study aims to determine the optimal length of the contraction cone, which ensures uniform flow at the outlet section, considering the wall shear factor. Four contraction cones of varying lengths were designed based on the hydraulic radius of the inlet. Numerical analysis was conducted to obtain static pressure and velocity distributions for the designed geometries. It was observed that wind tunnels designed with contraction cone lengths 2, 3, and 3.5 times the inlet hydraulic radius exhibited similar flow patterns. However, a longer contraction curve minimizes flow disturbances and turbulence, thereby enhancing flow uniformity and steadiness, while thicker boundary layers result from increased wall shears due to boundary layer growth. Consequently, it was concluded that a wind tunnel configured with a contraction cone length of 2 times the inlet hydraulic radius (square contraction cone) is the optimal choice, considering the combined effects of wall shear and flow uniformity.

Does It Hurt Financially, Too? Effects of Injury Proneness on Contract Design in Major League Baseball

Abstract: This paper seeks to determine the financial costs of recent injuries and market expectations of players’ future attrition rates by investigating the impacts on free agent contract designs, as represented by the yearly salary and contract length. The empirical findings, derived from data about 698 free agent contracts in Major League Baseball between 2011 and 2018, indicate that injuries exert different impacts on salaries versus contract lengths. For example, free agents who recently injured an elbow or shoulder receive shorter contracts than those not injured in the previous season, but their salaries are not affected. Market expectations of player attrition in the upcoming season reduce both contract lengths and salaries. For players, these results reaffirm the importance of staying healthy and finding ways to signal the low likelihood of future injuries to ensure their remuneration. For managers, the results emphasize the need to track free agents’ health status carefully, especially to avoid a winner’s curse.

Effects of gait retraining using minimalist shoes on the medial gastrocnemius muscle-tendon unit behavior and dynamics during running.

The effects of a 12-week gait retraining program on the adaptation of the medial gastrocnemius (MG) and muscle-tendon unit (MTU) were investigated. 26 runners with a rearfoot strike pattern (RFS) were randomly assigned to one of two groups: gait retraining (GR) or control group (CON). MG ultrasound images, marker positions, and ground reaction forces (GRF) were collected twice during 9 km/h of treadmill running before and after the intervention. Ankle kinetics and the MG and MTU behavior and dynamics were quantified. Runners in the GR performed gradual 12-week gait retraining transitioning to a forefoot strike pattern. After 12-week, (1) ten participants in each group completed the training; eight participants in GR transitioned to non-RFS with reduced foot strike angles; (2) MG fascicle contraction length and velocity significantly decreased after the intervention for both groups, whereas MG forces increased after intervention for both groups; (3) significant increases in MTU stretching length for GR and peak MTU recoiling velocity for both groups were observed after the intervention, respectively; (4) no significant difference was found for all parameters of the series elastic element. Gait retraining might potentially influence the MG to operate at lower fascicle contraction lengths and velocities and produce greater peak forces. The gait retraining had no effect on SEE behavior and dynamics but did impact MTU, suggesting that the training was insufficient to induce mechanical loading changes on SEE behavior and dynamics.

Offset ratios and temporary contract designs for climate integrity in carbon farming

In this study, we examine how to enhance the climate integrity of carbon credits from carbon farming practices. The key requirements for climate integrity include permanence, additionality, and measurement and verification. Farmers are typically willing to make carbon contracts for a finite time only in voluntary markets or with the government and receive carbon credits to sell as offsets. This contradicts the requirement of the permanence of carbon sequestered in soils. To solve this problem and to facilitate greater participation by farmers in carbon sequestration, we show how temporary contracts can be made to address the issue of permanence by using offset ratios. The notion of the offset ratio refers to the share of one emission unit that one unit of temporary sequestered carbon replaces. Thus, the offset ratio transforms temporary sequestration to permanent emissions reductions. We propose the use of a discounting method to calculate the offset ratio. The ratio varies with the carbon contract length, employed discount rate, and assumptions about the evolution of the soil carbon stock. We apply this approach to cultivating catch crops for carbon sequestration on a north‒south gradient in Finland, Denmark, and France. We show that the offset ratio approach works well for every selected country. Carbon farming contracts are profitable for farmers provided that revenue under the contract exceeds that in the baseline. Profitability is highly dependent on catch crop cost, annual increase in soil carbon, and the discount rate. We apply offset ratios to assess the climate integrity of some existing crediting programs and find that the discounting method yields a lower offset ratio in almost all cases yielding a lower number of credits than launched in these programs.

Addressing endogeneity in marginal revenue product estimates of shirking in Major League Baseball

PurposeWhile much of the literature testing for shirking by professional athletes have used performance metrics, some works have quantified shirking in dollar terms by comparing salary to estimated marginal revenue product (MRP). However, Ordinary Least Squares (OLS) approaches to measuring shirking by comparing salary to MRP have an endogeneity problem, as salary and contract length are determined simultaneously. We test for shirking in Major League Baseball (MLB) using an MRP approach, addressing this potential endogeneity.Design/methodology/approachThis paper uses instrumental variables regression to address potential endogeneity using MLB season-level player and team data from 2010 to 2017.FindingsUsing OLS regression, the impact of an additional year of guaranteed contract on shirking is estimated at approximately $1m in 2010 US dollars, and the impact of having a long-term contract is estimated at $5m, estimates comparable to those in the literature. Using instrumental variables regression, these impacts increase to $1.6m and over $9m in 2010 dollars.Practical implicationsGiven large, causal shirking estimates, profit maximizing sports organizations should take caution when negotiating long-term contracts. These findings also have important implications for other labor market settings where workers feel job security.Originality/valueTo our knowledge, this is the first work testing for shirking in sports using an MRP approach which uses instrumental variables regression to address potential endogeneity.

Dimensional synthesis of an Inspection Robot for SG tube-sheet

To ensure the operational safety of nuclear power plants, we present a Quadruped Inspection Robot that can be used for many types of steam generators. Since the Inspection Robot relies on the Holding Modules to grip the tube-sheet, it can be regarded as a hybrid robot with variable configurations, switching between 4-RRR-RR, 3-RRR-RR, and two types of 2-RRR-RR, and the variable configurations bring a great challenge to dimensional synthesis. In this paper, the kinematic model of the Inspection Robot in multiple configurations is established, and the analytical solution is given. The workspace mapping is analyzed by the solution-space, and the workspace of multiple configurations is decomposed into the workspace of 2-RRR to reduce the analysis complexity, and the workspace calculation is simplified by using the envelope rings. The optimization problem of the manipulator is transformed into the calculation of the shortest contraction length of the swing leg. The switching performance of the Inspection Robot is evaluated by stride-length, turning-angle, and workspace overlap-ratio. The performance indexes are classified and transformed based on the proportions and variation trends of dimensional parameters to reduce the number of optimization objective functions, and Pareto optimal solutions are obtained using an intelligent optimization algorithm.