Retained Austenite Control for the Soft Machining of High-Hardness Tool Steels

Most high-hardness tool steels comprising forming dies require expensive finish machining operations to compensate for the dimensional distortion and surface oxidation caused by the die heat treatment. Precipitation-hardening (PH) tool steels allow for soft finish machining followed by an aging treatment without major deformation or oxidation in the die, but exhibit poor wear performance owing to the lack of carbides in their structure. This drawback can be overcome by combining laser cladding technology, austenite retention, and cryogenic treatments. Hence, an alternative die manufacturing route based on laser cladding was explored. The forming surface of a modified chemistry tool steel die was subjected to cladding. The martensite finish (M-f) temperature of the steel was tuned to enhance austenite retention at room temperature. The cladded surface was then machined in a reduced-hardness condition resulting from retained austenite formation. Subsequent deep cryogenic treatment of the die favoured the retained-austenite-to-martensite transformation, thereby increasing the die hardness without major distortion or oxidation. This process combined the advantages of high-carbide-bearing tool steels and PH steels, allowing for a die with hardness exceeding 58 HRC to be finish machined at <52 HRC. Controlling the occurrence of retained austenite represents an effective strategy for achieving new manufacturing scenarios.The authors gratefully acknowledge the funding provided by the Department of Research and Universities of the Basque Government under Grant No. IT947-16 and the University of the Basque Country UPV/EHU under Program No. UFI 11/29

Experimental Air Impingement Crossflow Comparison and Theoretical Application to Photovoltaic Efficiency Improvement

The photovoltaic cell temperature is a key factor in solar energy harvesting. Solar radiation raises temperature on the cell, lowering its peak efficiency. Air jet impingement is a high heat transfer rate system and has been previously used to cool the back surface of photovoltaic modules and cells. In this work, an experimental comparison of the cooling performance of two different air jet impingement crossflow schemes was performed. Crossflow is defined as the air mass interacting with a certain jet modifying its movement. This leads to a change in its heat exchange capabilities and is related with the inlet-outlet arrangement of the fluid. In this work, zero and minimum crossflow schemes were compared. The main contribution of this work considered the consumption of the flow supplying devices to determine the most suitable system. The best configuration increased the net power output of the cell by 6.60%. These results show that air impingement cooling can play a role in increasing photovoltaic profitability. In terms of uniformity, on small impingement plates with a low number of nozzles, the advantages expected from the zero crossflow configuration did not stand out.This work was funded by the Regional Development Agency of the Basque Country (SPRI) [grant number KK-2018/00109]

Comparison of Different Finite Element Models for the Transient Dynamic Analysis of Laminated Glass for Structural Applications

Commercial laminated glass is usually composed of two glass layers and an interlayer of PVB. The viscoelastic behaviour of the PVB layer has to be taken into account when dealing with dynamic loads. This paper shows different Finite Element (FE) models developed to characterize laminated glass. Results are contrasted with data from different reference test cases. First, a quasi-static test is reproduced with a 2d model through a transient analysis. In addition, flexural modes of vibration in a free-free test configuration have been analysed using 2d as well as 3d FE models. Apart from using transient analysis in order to simulate the dynamic behaviour of laminated glass, an iterative procedure has been employed which permits to identify the correct value of the shear modulus of the PVB layer for each mode in an eigenvalue analysis

Design of a Microscale Refrigeration System for Optimizing the Usable Space in Compact Refrigerators

This research aims to enter the miniature refrigeration machine sector with the objective of designing a small scale unit while maintaining a competitive coefficient of performance (COP), comparing with a Peltier plates system. To this end, a research of the current technology was carried out in order to obtain indicative values on the scales that were being worked on and their application. After the previous research, a refrigeration cycle was designed in EES (engineering equation solver). From this design, different conclusions were obtained: (1) The correct sizing of the compressor revolutions together with its displacement is crucial for the equipment to be able to provide the desired cooling capacity. (2) In order to obtain the desired cooling capacity in the microscale refrigeration system, the heat exchangers must have fins. (3) Of the analysed refrigerants, R600a is the best choice, as it shows favourable characteristics (high COP and low compression ratio) when working in this type of cycle.This work was supported by the Basque Government in the Elkartek call through the SOLRUC project “Knowledge acquisition for the design of new ultra-compact cooling solutions”, project reference: KK-2020/00115

The Different Microbial Etiology of Prosthetic Joint Infections According to Route of Acquisition and Time After Prosthesis Implantation, Including the Role of Multidrug-Resistant Organisms

The aim of our study was to characterize the etiology of prosthetic joint infections (PJIs)-including multidrug-resistant organisms (MDRO)-by category of infection. A multicenter study of 2544 patients with PJIs was performed. We analyzed the causative microorganisms according to the Tsukayama's scheme (early postoperative, late chronic, and acute hematogenous infections (EPI, LCI, AHI) and "positive intraoperative cultures" (PIC)). Non-hematogenous PJIs were also evaluated according to time since surgery: 12 months. AHIs were mostly caused by Staphylococcus aureus (39.2%) and streptococci (30.2%). EPIs were characterized by a preponderance of virulent microorganisms (S. aureus, Gram-negative bacilli (GNB), enterococci), MDROs (24%) and polymicrobial infections (27.4%). Conversely, coagulase-negative staphylococci (CoNS) and Cutibacterium species were predominant in LCIs (54.5% and 6.1%, respectively) and PICs (57.1% and 15.1%). The percentage of MDROs isolated in EPIs was more than three times the percentage isolated in LCIs (7.8%) and more than twice the proportion found in AHI (10.9%). There was a significant decreasing linear trend over the four time intervals post-surgery for virulent microorganisms, MDROs, and polymicrobial infections, and a rising trend for CoNS, streptococci and Cutibacterium spp. The observed differences have important implications for the empirical antimicrobial treatment of PJIs.Acknowledgments: This work was supported by the Instituto de Salud Carlos III, Spanish Ministry of Economy and Competitiveness (grant number PI15/1026) (Co-funded by European Regional Development Fund/European Social Fund "Investing in your future"). REIPI (Spanish Network for Research in Infectious Disease) is supported by the Instituto de Salud Carlos III, Spanish Ministry of Economy and Competitiveness, and by the European Development Regional Fund “A way to achieve Europe”

Resumen ejecutivo de tratamiento de las infecciones de prótesis articulares. Guia clínica práctica de la Sociedad Española de Enfermedades Infecciosas y Microbiologia Clínica

[EN] The incidence of prosthetic joint infection (PJI) is expected to increase in the coming years. PJI has serious consequences for patients, and high costs for the health system. The complexity of these infections makes it necessary to organize the vast quantity of information published in the last several years. The indications for the choice of a given surgical strategy and the corresponding antimicrobial therapy are specifically reviewed. The authors selected clinically relevant questions and then reviewed the available literature in order to give recommendations according to a pre-determined level of scientific evidence. The more controversial aspects were debated, and the final composition was agreed at an ad hoc meeting. Before its final publication, the manuscript was made available online in order that all SEIMC members were able to read it and make comments and suggestions.[ES] Se prevé un incremento de la incidencia de infección de las prótesis articulares (IPA) en los próximos años. Las IPA plantean graves consecuencias para los pacientes y un alto coste el sistema sanitario. La complejidad de estas infecciones hace que sea necesario organizar la inmensa cantidad de información publicada en los últimos años. En estas guías se revisan específicamente las indicaciones para la elección de una estrategia quirúrgica dada y el tratamiento antimicrobiano correspondiente. Los autores seleccionaron las preguntas clínicamente relevantes y revisaron la literatura disponible con el fin de proporcionar recomendaciones de acuerdo con un grado de evidencia científica predeterminada. Los aspectos más controvertidos fueron debatidos y la redacción final se acordó en una reunión ad hoc. Antes de su publicación, el manuscrito estuvo abierto a comentarios y sugerencias de los miembros de la Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica.Peer reviewe

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Microstructural Tuning of a Laser-Cladding Layer by Means of a Mix of Commercial Inconel 625 and AISI H13 Powders

The aim of this work is to evaluate the microstructural evolutions developed by mixing a corrosion-resistant and high-performance material with a high-hardness material in a coating obtained by laser-cladding technology. In this paper, five different mixtures of Inconel 625 alloy and AISI H13 steel powders have been deposited on a plate of 42CrMo4 steel using a 2.2 kW diode pumped Nd:YAG laser. The effect of adding tool steel to a Ni-based superalloy has been analyzed by the characterization of each cladded sample using optical microscopy and scanning electron microscopy (SEM). The precipitates observed in the samples have been analyzed by energy dispersive X-ray spectroscopy (EDS X-ray). SEM micrographs and EDS analysis indicate the existence of Laves phase. It has been observed that the presence of these precipitates is stabilized in a certain range of AISI H13 addition

Multi-Objective Particle Swarm Based Optimization of an Air Jet Impingement System

Air jet impingement systems have proven to be a very efficient way of heat transfer in single phase flows, which has allowed them to be applied in several industries. However, the complexity of the physical phenomena that take place in the cooling or heating processes makes the task of designing and sizing a system of this type very difficult. The objective of this work is to develop a methodology for the optimization of the impingement plate for electronic components cooling systems. The component chosen to exemplify this work is an insulated gate bipolar transistor (IGBT) such as those employed in photovoltaic inverters. The proposed methodology is divided into the thermo-hydraulic calculation process and the optimization of the system. This optimization is carried out using a multi-objective particle swarm optimization (PSO) algorithm that seeks the best compromise between two variables: Component temperature and manufacturing time of the impingement plate. The result is a calculation tool that can quickly find the solution that meets the requirements of the designer without the need to evaluate all possible solutions