|Een orkestrepetitie met professor Van Uven in 1923.
Munters, Q.J. - \ 1993
Agricultural University Wageningen papers 21 (1993)2. - ISSN 0169-345X - p. 29 - 31.
Het samenvatten van rassenproeven en het toepassen van vruchtbaarheidscorrecties met niet-orthogonale methoden
Hamming, G. - \ 1949
Wageningen University. Promotor(en): M.J. van Uven; W.J. Dewez. - 's-Gravenhage : Staatsdrukkerij - 199
rassen (planten) - cultivars - rassen (taxonomisch) - statistiek - waarschijnlijkheidsanalyse - wiskunde - landbouw - varieties - cultivars - races - statistics - probability analysis - mathematics - agriculture
Although a formula should be adequate, inadequate formulae had often to be used through lack of knowledge. With adequate formulae weighting of data was dependent on error expectation. With inadequate formulae weighting should be focused on representativeness. Some other pitfalls were discussed.
Correlation analysis was contrasted with regression analysis. These two models had in common that items of a universe were stochastically dependent on a functional relationship. Essential for correlation was that both correlated variables obeyed a probability distribution; for regression analysis this did not need to be true. In correlation the principal axis was a sound base for understanding relationships, while the regression line was a sound base for predictions. The contrast between understanding and prediction was discussed at large.
Special problems of pooling experiments were discussed. In principle a transformation of yield data was advisable if the interaction variety x experiment could be thus reduced. Yet the transformed yields remained inadequate. So weighting, if used, had to improve representativeness. A missing-plot technique for pooling was given.
A separate part deals with the reduction of residual error by drawing freehand fertility maps. This may be much more effective than the corrections provided by the design. A criterion was developed for avoiding undue detail in free-hand curves.
Zwavelzure-ammoniak-proeven in de Java-suikerindustrie en een methode tot bepaling van het optimum in deze proeven
Straaten van Nes, C.B. van - \ 1947
Wageningen University. Promotor(en): M.J. van Uven; J.E. van der Stok. - Amsterdam : Scheltema & Holkema - 86
plantenvoeding - kunstmeststoffen - mest - ammoniumsulfaat - saccharum officinarum - suikerriet - java - rapporten - indonesië - nederlands indië - plant nutrition - fertilizers - manures - ammonium sulfate - saccharum officinarum - sugarcane - java - reports - indonesia - netherlands east indies
Orthogonal polynomials were applied for the estimation of optimal dosage instead of, as formerly, considering only significant differences in yield of pure sugar. Polynomials of second degree fitted the observed cane yields satisfactorily. Very large observed values of the regression coefficients indicated serious disturbance; if so, the yield/rate relation was not well represented by a polynomial.
No simple mathematical function was found to represent the regression of sugar content on fertilizer rate. The correlation between cane yield and sugar percentage was a good measure for judging sugar percentage for a given rate, at least for correlation coefficients within the region -0.8 and 0. Other values pointed to serious aberrations. Large negative values of the regression coefficient of the term of the second degree and small values of that of the third degree corresponded to low correlation. If so, correlation coefficients calculated from the data, ignoring those from the lowest rate, were more useful.
If more than 30% of the cane lodged, the mathematical function was not satisfactory.
Wiskundige beschouwingen bij eenige hoofdstukken uit de philosophie der landbouwwetenschap
Sijpkens, J.P. - \ 1945
Landbouwhogeschool Wageningen. Promotor(en): M.J. van Uven; J.E. van der Stok. - Wageningen : [s.n.] - 137
landbouw - filosofie - wiskunde - agriculture - philosophy - mathematics
Because of the many factors involved in agricultural problems experimental methods could not be based on ceteris paribus, as in other natural sciences, but required factorial trials with simultaneous variation of many factors. A complete factorial experiment was unworkable in practice because of the large area required but trial size could be reduced by ignoring interactions of higher order.
Interactions of higher order sometimes cancelled out main effects and interactions of lower order. To avoid this undesirable effect, analogous functions called 'main action' and 'interplay' were introduced. The trial could be reduced to a smaller size by splitting the complete factorial experiment into partexperiments of factorial form for a small number of factors. Various possibilities were studied, including the replication of some treatments in different experiments to adjust results. Replicates were needed also to estimate variances and to compare these with interactions. Thus the estimation of variance from interaction terms could be avoided.
Een mathematisch-statistische studie over de nauwkeurigheid van het organoleptisch onderzoek van boter
Posthumus, G. - \ 1943
Wageningen University. Promotor(en): M.J. van Uven; B. van der Burg. - Zutphen : Thieme - 122
boter - dierlijke producten - geur en smaak - aroma - smaak - statistiek - waarschijnlijkheidsanalyse - wiskunde - cum laude - butter - animal products - flavour - aroma - taste - statistics - probability analysis - mathematics
The quality of butter, produced by the dairies in the Netherlands, is regularly tested by experienced testers after storage for 2 weeks usually at 14_C. Odour, taste and texture are tested. Usually a score is given, running from 1 (bad) to 5 (excellent). An analysis was made of the accuracy of the evaluations.
Differences in and between testers in score, for tests on many or one sample were assessed by the standard deviation of the score of one, or the mean score of 2 or more judges (subjective accuracy). Deviations were normally distributed. Accuracy was expressed as the correlation coefficient (r) between the scores by one or more judges and the 'real' score (the mean score given by many judges): the objective accuracy.
An extensive mathematical treatment was given to show how r depends on the number of judges. Starting from the fact that for 2 judges r = 0.80, the value for 1 judge was found to be r = 0.686 and for 3 judges 0.853. At least 3 judges were necessary. Methods were given of expressing the capability of 1 judge in terms of r. The subjective and objective accuracy of judges can differ much.
Wiskundige waardeering van arbeidspraestaties
Campo, E.J. a - \ 1936
Wageningen University. Promotor(en): M.J. van Uven; J.E. van der Stok. - Wageningen : Veenman - 48
werk - analyse - arbeid (werk) - arbeidskunde - wiskunde - arbeidsproductiviteit - work - analysis - labour - work study - mathematics - labour productivity
The greater part of the cost price of palm oil was spent on harvesting the ripe bunches. To harvest at the moment of best ripeness, the bunches had to be collected every 5 to 8 days.
An oilpalm estate was divided in 8 divisions of approximately 2000 acres, under supervision of an assistant manager. Topografical differences in the divisions gave rise to very variable harvesting costs. Judging the cost price depended usually on common sense.
On flat terrain the oil palms were planted in rows perpendicular to a railway line; on sloping terrain in widely divergent directions. The following labour analysis was drawn up: the labour effort of the harvesters to detect the ripe bunches; the labour effort to climb into the palm trees to cut off the bunches; the labour effort to carry the bunches to the railway; the labour effort to load the bunches into trucks. A formula was derived for the production per labourer. It represented a hyperbola for production per acre from 0 to∞and contained variables mainly dependent on topographic influences. Weather conditions and other influences explained the deviations from the most probable straight lines (reciprocals) and hyperbolae.
Stamvorm en inhoud van den djati in plantsoenen (Tectona grandis L.F.; Verbenaceae)
Wolff von Wuelfing, H.E. - \ 1933
Wageningen University. Promotor(en): H.A.J.M. Beekman; M.J. van Uven. - Wageningen : Veenman - 253
bosbouw - bomen - volume - tectona grandis - bosopstanden - nederlands indië - cum laude - forestry - trees - volume - tectona grandis - forest stands - netherlands east indies
The author's procedures and methods were described for compiling General Volume Tables for teak, from which Local Tables can be derived. Only easily and rather accurately measurable characteristics should be used: tree height, length of trunk free of branches and timber-yielding length of trunk and trunk girth at 1.30 metre. Girthes at 1.50 metre and 1.70 metre were also necessary, to avoid abnormal trunk bases. The Table should also contain estimated volumes of whole tree and its parts with bark, and diameter, girths and volumes of the tree without bark at different heights.
But more data were needed to construct the Table, primarily the mathematical expression of the trunk form. Two true form quotients are required to represent the trunk form of teak with satisfactory accuracy in a simple equation. Estimation of the form class of an individual tree was only possible by direct measurements, so average form classes were used. These classes for the various trees and stands of one single kind of wood usually varied so little that for any one Table practically only one form class was required. The slight variation in form class of teak can easily be incorporated in the Volume Tables.
Het proefveldonderzoek bij de rijstcultuur op Java
Ossewaarde, J.G. - \ 1931
Wageningen University. Promotor(en): J.E. van der Stok; M.J. van Uven. - Wageningen : Veenman - 180
rijst - oryza sativa - proefvelden - indonesië - java - voorzieningen - nederlands indië - rice - oryza sativa - experimental plots - indonesia - java - facilities - netherlands east indies
A historical review was given of the development of rice cultivation in Java, of the influence of the Netherlands colonial government on the agricultural methods by advice before and after local research, and of the development of field trial techniques and the organization of systematic research. The principle of randomization was not applied at that time. Tests of significance were made by comparing a given difference with three times its estimated standard deviation. To reduce standard deviation the elimination of a linear trend in fertility for different places was discussed in detail. From the results of field experiments between 1911 and 1926 the relation between expected yield and the standard deviation was studied for different soil types and only the data were used of trials, where fertility of the area was even enough to be chosen as the place for a trial. This relation seemed to be reasonably linear. Attention was paid to the power of a test in relation to standard deviation. In the period considered investigators were more concerned with lack of bias in estimators than their efficiency. In this thesis the importance of efficiency is stressed and more insight is given into the possibilities offered by field experiments.
Beoordeling van het verschil tusschen twee variëteiten op grond van een waargenomen opbrengstverschil
Uven, M.J. van - \ 1927
Wageningen : Veenman (Mededelingen van de Landbouwhogeschool te Wageningen dl. 31, verh. 7) - 6
Het studiejaar 1921-1922
Uven, M.J. van - \ 1922
Wageningen : Veenman - 11
Uven, M.J. van - \ 1922
Wageningen : Veenman - 16
Eere-promotie Prof. L. Broekema : rede van den Rector-Magnificus der Landbouwhoogeschool bij het verleenen van het doctoraat in de landbouwkunde, honoris causa, aan Prof. L. Broekema L.I. en toespraak van Prof. Dr. L. Broekema bij het aanvaarden van het doctoraat
Uven, M.J. van; Broekema, L. - \ 1921
Wageningen : Landbouwhogeschool - 15
voedergranen - rassen (planten) - feed grains - varieties
Rede Landbouwhoogeschool Wageningen
Uven, M.J. van - \ 1918
Wageningen : Veenman (Mededeelingen van de Rijks Hoogere Land-, Tuin- en Boschbouwschool en van de daaraan verbonden instituten dl. 13, [verh. 6])
relativiteitstheorie - relativity theory
Openbare voordracht gehouden ter opening van de lessen in de wiskunde aan de Rijks Hoogere Land-, Tuin- en Boschbouwschool te Wageningen, den 29sten April 1913
Uven, M.J. van - \ 1913
Wageningen : Veenman (Mededeelingen van de Rijks Hoogere Land-, Tuin- en Boschbouwschool en van de daaraan verbonden instituten dl. 6 , [verh. 3])
wiskunde - mathematics