Capability of Tungsten Carbide Micro-mills to Machine Hardened Tool Steel

Alexandre Gilbin,Michaël Fontaine,Gérard Michel,Sébastien Thibaud,Philippe Picard 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

The aim of this study is to optimize micro-mills and their conditions of use to manufacture plastic injection molds in hardened tool steels by micro-milling. The presented results deal with the test of four types of tungsten carbide square end micro-mills in elementary operations with different feed rates and cutting speeds in order to analyze the evolution of cutting forces, cutting stability, tool life,tool wear, surface roughness and burs formation. This experimental approach allows highlighting the influence of cutting conditions,especially feed rate, on burr formation and tool life. This analysis shows a correlation between the micro-mills characteristics (geometry, composition of tungsten carbide) and their wear behavior. Moreover, some dynamic aspects of the micro-milling process are underlined through the influence of cutting speed on cutting stability. This type of experimental study is suitable for the optimization of the tool edge geometry and it reveals the need to develop a predictive model adapted to micro-milling to optimize the dynamic behavior of the tool.

Relationship between positive end-expiratory pressure levels, central venous pressure, systemic inflammation and acute renal failure in critically ill ventilated COVID-19 patients: a monocenter retrospective study in France

Basse Pierre,Morisson Louis,Barthélémy Romain,Julian Nathan,Kindermans Manuel,Collet Magalie,Huot Benjamin,Gayat Etienne,Mebazaa Alexandre,Chousterman Benjamin G. 대한중환자의학회 2023 Acute and Critical Care Vol.38 No.2

Background The role of positive pressure ventilation, central venous pressure (CVP) and inflammation on the occurrence of acute kidney injury (AKI) have been poorly described in mechanically ventilated patient secondary to coronavirus disease 2019 (COVID-19). Methods This was a monocenter retrospective cohort study of consecutive ventilated COVID-19 patients admitted in a French surgical intensive care unit between March 2020 and July 2020. Worsening renal function (WRF) was defined as development of a new AKI or a persistent AKI during the 5 days after mechanical ventilation initiation. We studied the association between WRF and ventilatory parameters including positive end-expiratory pressure (PEEP), CVP, and leukocytes count. Results Fifty-seven patients were included, 12 (21%) presented WRF. Daily PEEP, 5 days mean PEEP and daily CVP values were not associated with occurrence of WRF. 5 days mean CVP was higher in the WRF group compared to patients without WRF (median [IQR], 12 mm Hg [11-13] vs. 10 mm Hg [9–12]; P=0.03). Multivariate models with adjustment on leukocytes and Simplified Acute Physiology Score (SAPS) II confirmed the association between CVP value and risk of WRF (odd ratio, 1.97; 95% confidence interval, 1.12–4.33). Leukocytes count was also associated with occurrence of WRF in the WRF group (14 G/L [11–18]) and the no-WRF group (9 G/L [8–11]) (P=0.002). Conclusions In mechanically ventilated COVID-19 patients, PEEP levels did not appear to influence occurrence of WRF. High CVP levels and leukocytes count are associated with risk of WRF.

Features of a Market Model for Russian Economy

( Alexandr G. Khoodohormov ) 연세대학교 동서문제연구원 1993 East and West Studies Series Vol.25 No.-

Sustainable integration of airports into urban planning – a review

Alexandre G. de Barros 서울시립대학교 도시과학연구원 2013 도시과학국제저널 Vol.17 No.2

Traditional airport planning and design considers the airport as an isolated entity accessed by aircraft and passengers. However, airports are rarely the final destination of air passengers – these have a need to access the airport from a widely distributed set of origins/destinations. The surface portion of air trips has a significant impact on the urban transportation system. In addition, airports also affect the land use in their vicinities due both to the noise generated by low-flying aircraft and the need to protect the airspace used by those some aircraft from obstacles protruding from the ground. This article reviews the most important issues associated with integrating airports into the urban environment in a sustainable manner.

Effect of Forage Feeding on Goat Meat Production: Carcass Characteristics and Composition of Creole Kids Reared Either at Pasture or Indoors in the Humid Tropics

Alexandre, G.,Limea, L.,Fanchonne, A.,Coppry, O.,Mandonnet, N.,Boval, M. Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.8

Forage diets provide good quality carcasses in sheep but very little is known in tropical goats. An experiment was designed with Creole male goats using grass-based systems to assess carcass yield, scores, cuts and composition. After weaning (84 d, 9.2 kg LW) two modes of forage feeding were compared with two replicates of each. Feeding groups were: PF for animals reared at pasture (n = 62) and IF when reared indoors (n = 60). Given that forage finishing will result in low ADG it appeared necessary to study different fattening lengths. The kids were equally divided into 4 groups: group A (n = 32), 4mo after weaning; group B (n = 32), 4mo after A; group C (n = 30), 3mo after B and group D (n = 28), 2mo after C. The animals grazed (in two sub-flocks) on irrigated tropical pastures managed in a rotational system (28 d of re-growth) at a mean stocking rate of 1,200 kg/ha/yr LW. The IF groups were reared in collective pens on a slatted floor (2 replicates of 7 or 8 kids each). They were fed the same stand of tropical grass (25% DM, 12% CP) as that of pasture that was cut daily and provided ad libitum. The ADG (-10%), the weights of omental fat (-60%) and fat in shoulder (-18%), the ultimate pH of carcass (-12%), the meat colour score (-24%), the ""parameter accounting for redness (12%) and the DM and lipid contents (-4%) were significantly lower (p<0.05) in PF than in IF, while the liver was heavier (+23%, p<0.05). Feeding conditions seemed to be similar, thus, differences could be related to gastrointestinal parasitism in the PF system and hypotheses are discussed. Increasing the fattening duration, resulted in significant difference (p<0.01) in many traits: the weights at slaughter and of carcass increased by 40% and 60% from groups A to D and consequently the weights of body compartments and carcass cuts (1.5 to 2.0 fold more). When the results were presented as percentage of empty body weight and carcass weight, these preliminary results (carcass weight 9kg and yield 53%, muscle proportion 70%) and qualitative parameters (low fat score 2/5, fat proportion 5%), seem to be a good incentive for the sector to develop a niche market to meet consumer lean meat expectations. The indoors system could be implemented where there was low availability of grazing areas or problems of dog attacks.

Reconstruction of post-burn anterior neck contractures using a butterfly design free anterolateral thigh perforator flap

Lellouch, Alexandre G.,Ng, Zhi Yang,Pozzo, Victor,Suffee, Tabrez,Lantieri, Laurent A. Korean Society of Plastic and Reconstructive Surge 2020 Archives of Plastic Surgery Vol.47 No.2

Anterior neck burns represent a major reconstructive challenge due to severe sequalae including restriction in movement and poor aesthetic outcomes. Common treatment options include skin grafting with/without dermal matrices, and loco-regional and distant free flap transfers with/without prior tissue expansion. Such variation in technique is largely influenced by the extent of burn injury requiring resurfacing. In order to optimize like-for-like reconstruction of the anterior neck, use of wide, thin and long flaps such as the anterolateral thigh (ALT) perforator flap have been reported with promising results. Of note, some patients have a tendency towards severe scar contractures, which may be contributed by the greater extent of inflammation during wound healing. We report our experience at 4 years' followup after secondary reconstruction of severe, anterior neck burn contractures in two patients by harvesting the ALT flap with a butterfly design. This technique provides adequate wound resurfacing of the burned neck and surrounding areas, and provides good neck extensibility by addressing both anterior and lateral aspects of the scar defect simultaneously. Such a flap design reduces tension on wound edges and thus, the risk of contracture recurrence in what remains a particularly challenging type of burn reconstruction.

Numerical simulation by the finite element method of the constructive steps of a precast prestressed segmental bridge

Gabriela G. Machado,Américo Campos Filho,Paula M. Lazzari,Bruna M. Lazzari,Alexandre R. Pacheco 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.2

The design of segmental bridges, a structure that typically employs precast prestressed concrete elements and the balanced cantilever construction method for the deck, may demand a highly complex structural analysis for increased precision of the results. This work presents a comprehensive numerical analysis of a 3D finite element model using the software ANSYS, version 21.2, to simulate the constructive deck stages of the New Guaiba Bridge, a structure located in Porto Alegre city, southern Brazil. The materials concrete and steel were considered viscoelastic. The concrete used a Generalized Kelvin model, with subroutines written in FORTRAN and added to the main model through the customization tool UPF (User Programmable Features). The steel prestressing tendons used a Generalized Maxwell model available in ANSYS. The balanced cantilever constructive steps of a span of the New Guaiba Bridge were then numerically simulated to follow the actual constructive sequence of the bridge. A comparison between the results obtained with the numerical model and the actual vertical displacement data monitored during the bridge's construction was carried out, showing a good correlation.

Effects on Performance of Sulla and/or Maize Silages Supplements for Grazing Dairy Cows

Chaves, Alexandre V.,Woodward, S.L.,Waghorn, G.C.,Brookes, I.M.,Burke, J.L. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.9

The objective of this study was to investigate the effects of either maize or sulla silage supplementation to grazing dairy cows in summer. Forage mixtures used in the four week trial were based on previous experimental results but inclusion of rumen fistulated cows in five treatments enabled rumen sampling and use of in sacco incubations to determine the diet effects on digestion kinetics. Sulla and maize silages were used to supplement pasture and to meet minimum requirements for dietary protein concentration. Five groups of ten cows were grazed on a restricted daily allowance of 18 kg dry matter (DM) pasture/cow to simulate a summer pasture deficit, and four of these five groups received an additional 6 kg DM $cow^{-1}d^{-1}$ of silage (sulla, maize, or sulla and maize silages). A sixth group was given a relatively unrestricted (38 kg DM $cow^{-1}d^{-1}$) pasture allowance. The silage mixtures and pasture were incubated in sacco during the final week of the trial. The pasture was of high nutritive value and not typical of usual summer conditions, which favoured a response to quantity rather than quality of silage supplements. There was no difference in cow performance with the four silage supplements and the low milk solids (MS) production (about 1.0 kg $MS\;d^{-1}$) relative to full pasture (1.3 kg $MS\;d^{-1}$) showed the principal limitation to performance was dry matter intake. Milk composition was not affected by silage type and the low level of pasture substitution (0.29) suggested metabolizable energy (ME) was the principal limitation to performance. Samples of rumen liquor and in sacco data demonstrated significant effects of supplement; DM degradation rates (k) was highest ($0.084h^{-1}$) when cows were fed 6 kg sulla silage whereas diets with a high proportion of maize silage were slowly degraded (p<0.01).

Fe-Co 분말이 분산된 CFRP의 전자파차폐 특성

홍창기(C. G. Hong),고선호(S. H. Go),투기루무바노 알렉산드레(T. Alexandre),김정근(J. K. Kim),이재준(J. J. Lee),최선호(S. H. Choi),임윤지(Y. J. Yim),신희재(H. J. Shin),곽이구(L. K. Kwac) 한국기계가공학회 2019 한국기계가공학회 춘추계학술대회 논문집 Vol.2019 No.4

Public Transportation and Sustainability: A Review

Patrick Miller,Alexandre G. de Barros,Lina Kattan,S.C.Wirasinghe 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.3

Public transportation is often framed as a key component of building sustainable cities. Conversely, the social, economic, and environmental impacts of transport are framed as critical issues that can challenge the sustainability of cities and regions. This paper presents a critical literature review of the relationship between public transportation and sustainability. First the paper offers a review of key sustainable transportation concepts and how public transport contributes to sustainability goals. Second, the paper reviews past studies that analyse sustainable transportation in order to develop recommendations for planning, engineering, and researching sustainable public transport. Finally, the paper concludes by offering suggestions for future research into the sustainability performance of public transit.