Equilibrado de mecanismos

Resumen (Castellano): El siguiente documento presenta el desarrollo del proceso de equilibrado de un mecanismo, más concretamente de un cuadrilátero articulado, con el objetivo de reducir o eliminar fuerzas y momentos de inercia indeseados causantes de vibraciones e, incluso, de fallo de la máquina por fatiga. Para ello, se eliminan todos los coeficientes que dependen del tiempo en la trayectoria del centro de gravedad mediante la inclusión de unos contrapesos para que éste se mantenga fijo. Este proceso se ha llevado a cabo haciendo uso de Solid Edge, un programa que ha facilitado la obtención de la posición y magnitud de dichos contrapesos, desde el punto de vista teórico. Finalmente, se ha fabricado el mecanismo en cuestión mediante impresión 3D y se ha comprobado mecánicamente la veracidad de los resultados obtenidos analíticamente.Laburpena (Euskara): Hurrengo agiri honetan, mekanismo baten orekatze prozesua azaltzen da, zehatzago esanda, kuadrilatero artikulatu batena. Helburua bibrazioak eta, kasurik txarrenean, nekearen ondoriozko makinaren hutsegitea eragiten dituzten inertzia indar eta momentuek murriztea edo ezabatzea da. Horretarako, grabitate zentroaren ibilbidean zehar denboraren menpeko koefiziente guztiak desagerrarazten dira kontrapisu batzuk sartuz, grabitate zentro hori finko mantentzeko. Prozesu hau Solid Edge programa erabiliz burutu da, aipatutako kontrapisuen posizio eta magnitudeen lorpena erraztu duelarik. Azkenik, mekanismo hori 3D inprimagailu baten bidez eraiki da eta analitikoki lortutako emaitzak egiaztatu dira mekanikoki.Abstract (English): This report describes the process of the balancing of a mechanism, specifically, of a four-bar linkage. The aim is to reduce or to remove inercial forces and moments which are the cause of vibrations or,even the cause of fatigue-failure. In order to solve this issue, all the coefficients which are reliant on time in the expression of the track of the centre of gravity are eliminated by the addition of counterweights so as to maintain this centre of gravity stationary. This process is carried out using Solid Edge, a software which facilitates the calculation of the position and magnitude of the aforementioned counterweights. Finally, a 3D construction of the mechanism is made to verify the results obtained analitically.

IMEP Interlaboratory Comparisons – A Tool to Establish Confidence in Measurements

The International Measurement Evaluation Programme (IMEP) is owned by the European Commission's Joint Research Centre. IMEP organises interlaboratory comparison (ILC) in support of the policies of the European Union, covering a wide range of measurement tasks from food safety to environmental pollution. IMEP can be considered as a whole metrological process underlining the need for reliability and comparability of measurements. The article describes shortly the history and purpose of IMEP, and furthermore sums up its activities, links and impacts on the European measurement community

Report of the Ninth Interlaboratory Comparison Organised by the European Union Reference Laboratory for Heavy Metals in Feed and Food - IMEP-109: Total Cadmium, Lead, Arsenic and Mercury as well as Methylmercury and Inorganic Arsenic in Seafood

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the European Union Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the ninth proficiency test (PT) of the EU-RL-HM which focused on the determination of total cadmium, lead, arsenic and mercury as well as methylmercury and inorganic arsenic in seafood. The test material used in this exercise was the Certified Reference Material (CRM) DOLT-4, dogfish liver of the National Research Council of Canada (CNRC). The material was relabelled to prevent recognition by the participants and was dispatched the second half of May 2010. Each participant received one bottle containing approximately 20 g of test material. Thirty-eight laboratories from 27 countries registered to the exercise of which 38 reported results for total Cd, 36 for total Pb, 33 for total As, 36 for total Hg, five for methylmercury and 10 for iAs. The assigned values for total Cd, Pb, As, Hg and methylmercury are the certified values taken from the DOLT-4 certificate. An attempt was made to establish an assigned value for inorganic As (iAs) using the results provided by a group of five laboratories expert in the field, following a similar approach to that used in IMEP-1071, a PT on total and inorganic arsenic in rice. Contrary to what was observed in IMEP-107, the results obtained by the expert laboratories for iAs was method dependent, therefore no assigned value could be established. The uncertainties of the assigned values, uref, were taken directly from the CRM certificate as provided by the producer for total Cd, Pb, As, Hg and methylmercury. Participants were invited to report the uncertainty of their measurements. This was done by the majority of the laboratories taking part in this exercise. Laboratory results were rated with z- and ¿-scores (zeta-scores) in accordance with ISO 135282. Since the concentration of iAs seems to be method dependent according to the results obtained by the expert laboratories, no scoring was provided to the laboratories that submitted results for iAs. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15% by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EURL-HM and on the state-of-the-art in this field of analysis. Between 80 and 97.5 % of the laboratories performed satisfactory for total Cd, As, Hg and methylmercury. Regarding total Pb, 70 % of the laboratories scored satisfactory.JRC.DG.D.6-Food Safety and Qualit

IMEP-30: Total Arsenic, Cadmium, Lead, and Mercury, as well as Methylmercury and Inorganic Arsenic in Seafood - Interlaboratory Comparison Report

This report presents the results of an ILC which focussed on the determination of total As, Cd, Pb , and Hg, as well as methylmercury and inorganic arsenic in seafood. The test material used in this exercise was the Certified Reference Material (CRM) DOLT-4, dogfish liver of the National Research Council of Canada (NRC). Each participant received one bottle containing approximately 20 g of test material. Fifty-seven laboratories from 29 countries registered to the exercise and all of them reported results. The assigned values and their associate uncertainties for total As, Cd, Pb, Hg and Methylmercury are the certified values taken from the DOLT-4 certificate. An attempt was made to establish an assigned value for inorganic As (iAs) using the results provided by a group of five laboratories expert in the field. Unfortunately, contrary to what was expected, the results obtained by the expert laboratories for iAs showed a large spread and no assigned value could be established.JRC.DG.D.6-Food Safety and Qualit

Report of the Third Interlaboratory Comparison Organised by the Community Reference Laboratory for Heavy Metals in Feed and Food - Total Cd, Pb and Hg and Extractable Cd and Pb in Feed

The Institute for Reference Materials and Measurements (IRMM) of the European Commission's Directorate-General Joint Research Centre holds the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the third ILC of the CRL-HM which focused on the determination of total Cd, Pb and Hg and extractable Cd and Pb in feed according to Directive 2002/32/EC of the European Parliament and of the Council on undesirable substances in animal feed. The test material used in this exercise was a commercial compound feed for fish provided by the Centro di Referenza Nazionale per la Sorveglianza e il Controllo degli Alimenti per Animali, Istituto Zooprofilattico del Piemonte. The material, naturally contaminated, was processed, bottled, labelled and dispatched by the Reference Materials Unit of the IRMM. The samples were dispatched on the second half of October 2007. Each participant received one bottle containing approximately 20 g of test material. Thirty-one participants from 25 countries registered to the exercise of which 31 submitted results for total Cd and total Pb, 28 for total Hg, 26 for extractable Cd and 24 for extractable Pb. The assigned values (Xref) were provided by IRMM using isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS). The analytical uncertainty of Xref, uchar, was calculated according to the ISO Guide to the Expression of Uncertainty in Measurement (GUM)2. Homogeneity and stability studies were subcontracted to Bundesanstalt für Materialforschung und ¿Prüfung (BAM). The uncertainties of the respective assigned values, uref, were calculated combining the analytical uncertainty, uchar, with a contribution for the between-bottle homogeneity, ubb, and for the short term stability of the test material, usts. Participants were invited to report the uncertainty on their measurements. This was done by 29 laboratories for total Cd, 23 for total Pb, 25 for total Hg, 18 for extractable Cd and 13 for extractable Pb. Laboratory results were rated with z and zeta scores in accordance with ISO 135283. Standard deviation for proficiency assessment (also called target standard deviation) were calculated using the modified Horwitz equation and were 22 % of the assigned value for total Pb and Hg and for extractable Pb and 16 % of the assigned value for total and extractable Cd.JRC.D.4-Isotope measurement

Report of the Second Interlaboratory Comparison Organised by the Community Reference Laboratory for Heavy Metals in Feed and Food: Total Cd, Pb and Hg in Mineral Water

The Institute for Reference Materials and Measurements (IRMM) of the European Commission's Directorate-General Joint Research Centre holds the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM). One of the core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the second ILC of the CRL-HM which focused on the determination of the total Cd, Pb and Hg content in mineral water. The test material used in this exercise was a commercial mineral water purchased in Belgium at a local supermarket. The material was spiked with Cd, Pb and Hg, rebottled and dispatched by the Reference Material Unit of the IRMM. The samples were dispatched on the first half of May 2007. Each participant received two sets of samples containing one bottle per set. Each bottle contained approximately 100 mL of test material. Twenty participants from 17 countries registered to the exercise of which 20 submitted results for Cd and Pb and 19 for Hg. The assigned values were those obtained from the gravimetric measurements used to spike the material. The homogeneity and stability studies were subcontracted to the University of Natural Resources and Applied Life Sciences (BOKU) in Vienna. The uncertainty of the assigned values was calculated combining the uncertainty of the spiking procedure with a contribution for the between-bottle homogeneity and for long-term stability of the test material. Participants were invited to report the uncertainty on their measurements. This was done by all them. Laboratory results were rated with z and zeta scores in accordance with ISO 135281. Standard deviation for proficiency assessment (also called target standard deviation) for Cd, Pb and Hg was 10% of the assigned value.JRC.D.4-Isotope measurement

IMEP-26: Determination of Brominated Flame Retardants in Plastic

This report presents the results of an interlaboratory comparison (ILC) which focussed on the determination of total bromine, total sum of polybrominated biphenyls (PBB), total sum of polybrominated diphenylethers (PBDE), brominated diphenylethers (BDE-47, BDE-99, BDE-183 and BDE-209) and decabrominated biphenyl (BB-209) in plastic. The test material used in this exercise was the Quality Control material (IRMM-310) from the Institute for Reference Materials and Measurements (IRMM) a poly(ethyleneterephthalate) (PET) granulated that has been fortified with commercially available technical mixtures of polybrominated diphenylethers and polybrominated biphenyls. The material was relabelled to avoid its recognition. Twenty-five laboratories from 15 countries registered to the exercise, from which 23 reported results. The informative values provided by the IRMM-310 material information sheet were taken as the assigned values and their associated uncertainties for all measurands. Studies to asses the adequacy of the selected test material regarding its homogeneity for all the selected measurands were undertaken Participants were invited to report the uncertainty of their measurements. Laboratory results were rated with z- and ζ-scores (zeta-scores) in accordance with ISO 13528. The standard deviation for proficiency assessment was fixed to 25 % of the respective assigned value by the advisory board of this ILC. The outcome of the exercise was illustrating quite well the difficulties laboratories do have to provide consistent values for the investigated measurands; the share of satisfactory z-scores ranged between 61 and 88 %. There was a clear tendency to underestimate most of the measurands. The most influencing variables, leading to the observed variability and lack of trueness, were investigated.JRC.DG.D.6-Food Safety and Qualit

Report of the Seventh Interlaboratory Comparison organized by the European Union - Reference Laboratory for Heavy Metals in Feed and Food. IMEP-107: Total and Inorganic As in Rice.

The Institute for Reference Materials and Measurands (IRMM) of the Joint Research Centre (JRC), a Directorate-General of the European Commission, operates the European Union-Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM). Two of its core tasks are to provide advice to the Directorate General for Health and Consumers (DG Sanco) on scientific matters and to organise interlaboratory comparisons (ILC) among appointed National Reference Laboratories (NRLs). This report represents the results of the seventh ILC of the EU-RL-HM (former CRL-HM) which focused on the determination of total and inorganic As in rice. The test item used in this exercise is rice purchased in a local supermarket and was provided by the University of Aberdeen. The test item was processed, bottled and labelled at IRMM and dispatched to the participants the first half of December 2009. Each participant received one bottle containing approximately 20 g of test item. Participation in this exercise was not limited to the NRLs but was open to laboratories from all around the world, to be able to judge the state-of-the-art of the determination of total and, exercise, of which 98 reported results for total As and 30 for inorganic As. Twenty-nine of the participants were NRLs of the EU-RL-HM network, 8 out of which reported values for inorganic As. The assigned values for IMEP-107 were provided by a group of laboratories expert in the field: seven for total As and six for inorganic As. The uncertainties of the respective assigned values, uref, were derived from the standard deviation of the means provided by the experts, propagated with a contribution for homogeneity, ubb, and stability, ust. Laboratory results were rated with z-and ¿-scores (zeta-scores) in accordance with ISO 13528. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15% by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EU-RL-HL and on the state-of-the-art in this field of analysis. Around 75% of the participants performed satisfactory for total and inorganic As.JRC.DDG.D.6-Food Safety and Qualit

Report of the Tenth Interlaboratory Comparison Organised by the European Union Reference Laboratory for Heavy Metals in Feed and Food - IMEP-110: Total Arsenic, Cadmium, Mercury and Lead in Vegetable Food

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC) a Directorate-General of the European Commission operates the European Union Reference Laboratory for Heavy Metals in Feed and Food (EU-RL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the tenth ILC of the EU-RL-HM which focused on the determination of total arsenic, cadmium, mercury and lead in vegetable food. The test material used in this exercise was the Standard Reference Material SRM 1570a, spinach leaves of the National Institute of Standards and Technology (NIST). The material was rebottled and relabelled to prevent recognition by the participants and was dispatched at the beginning of June. Each participant received one bottle containing approximately 15 g of test material. Thirty-five laboratories from 24 countries registered to the exercise of which 35 reported results for total Cd and total Pb, 32 for total As and 31 for total Hg. The assigned values for total As, Cd and Hg are the certified values taken from the SRM 1570a certificate. For total Pb, the "information value" provided by NIST in the SRM certificate was used as assigned value. The uncertainties of the assigned values (uref) for total As, Cd and Hg, were taken directly from the CRM certificate as provided by the producer. No uref is provided by NIST for the total Pb concentration because the total Pb content is only provided as "information value". Participants were invited to report the uncertainty of their measurements. This was done by the majority of the laboratories taking part in this exercise. Laboratories' results were rated with z- and zeta-scores for total As, Cd, and Hg in accordance to ISO 13528. No zeta-scores were given for total Pb because uref was not known for that measurand. The standard deviation for proficiency assessment (also called target standard deviation) was fixed to 15 % for all the measurands by the advisory board of this ILC, on the basis of the outcome of previous ILCs organised by the EU-RL-HM and on the state-of-the-art in this field of analysis. More than 80 % of the participants performed satisfactory for total Cd and Hg. Around 70 % of the participants obtained a satisfactory z-score for total arsenic with a relatively high number (8 laboratories) of participants having overestimated the total content of arsenic in the test material. When looking at the zeta-scores, 60 to 65 % of the reported results were satisfactory when the associated uncertainties are taken into account.JRC.DG.D.6-Food Safety and Qualit