Thermal fluctuations and NMR spectra of incommensurate systems

Journal ArticleIn the presence of thermal fluctuations the incommensurate NMR line shape is a convolution of a static inhomogeneous with a dynamic homogeneous line shape which can be determined separately by 2D NMR. The form of the dynamic line shape and its variation over the inhomogeneous NMR spectrum permit a separate determination of the relative sizes of the phason and amplitudon fluctuations, compared to the static part of the order parameter. 8 7Rb 2D spectra of ultrapure Rb2ZnCU agree with the above theory and show the existence of a temperature range where the incommensurate splitting induced by the static part of the order parameter is averaged out by thermal fluctuations

The order parameter-entropy relation in some universal classes: experimental evidence

The asymptotic behaviour near phase transitions can be suitably characterized by the scaling of $\Delta s/Q^2$ with $\epsilon=1-T/T_c$, where $\Delta s$ is the excess entropy and $Q$ is the order parameter. As $\Delta s$ is obtained by integration of the experimental excess specific heat of the transition $\Delta c$, it displays little experimental noise so that the curve $\log(\Delta s/Q^2)$ versus $\log\epsilon$ is better constrained than, say, $\log\Delta c$ versus $\log\epsilon$. The behaviour of $\Delta s/Q^2$ for different universality classes is presented and compared. In all cases, it clearly deviates from being a constant. The determination of this function can then be an effective method to distinguish asymptotic critical behaviour. For comparison, experimental data for three very different systems, Rb2CoF4, Rb2ZnCl4 and SrTiO3, are analysed under this approach. In SrTiO3, the function $\Delta s/Q^2$ does not deviate within experimental resolution from a straight line so that, although Q can be fitted with a non mean-field exponent, the data can be explained by a classical Landau mean-field behaviour. In contrast, the behaviour of $\Delta s/Q^2$ for the antiferromagnetic transition in Rb2CoF4 and the normal-incommensurate phase transition in Rb2ZCl4 is fully consistent with the asymptotic critical behaviour of the universality class corresponding to each case. This analysis supports, therefore, the claim that incommensurate phase transitions in general, and the A$_2$BX$_4$ compounds in particular, in contrast with most structural phase transitions, have critical regions large enough to be observable.Comment: 13 pp. 9 ff. 2 tab. RevTeX. Submitted to J. Phys.: Cond. Matte

RESPONSIBILITY FOR THE COMPUTER CONTROLLED TECHNOLOGY REQUESTS RELIABLE ENGINEERING SOLUTIONS

Projekti vodenja procesov v prehrambeni industriji, posebno v mlekarstvu, so povezani s povečano stopnjo odgovornosti za zdravstveno neoporečnost in trajnost proizvodov. Prikazujemo zahteve za sistematični pristop k projektiranju strojne opreme, višjo stopnjo zanesljivosti nadzornega in krmilnega računalnika, "robustnost" programske opreme ter pravilen izbor kvalitetnih senzorjev za nadzor fizikalnih, kemijskih in bakterioloških parametrov in kriterijev tehnoloških procesov. Industrijski računalniki morajo zadostiti nizu zelo ostrih zahtev, kot so: odpornost na elektromagnetne motnje, povišane temperature okolja, izhodni moduli morajo biti zaščiteni pred kratkimi stiki, itn. Zanesljivost programske opreme pomeni poleg izvršitve zahtevanih funkcij, predvideti tudi možne konfliktne situacije ter način njihove rešitve. Vse to zahteva izkušenega projektanta, ki optimalno izkorišča razvoj in čas projektiranja. Zagon in vzdrževanje nadzorne in krmilne opreme v času njenega "življenskega ciklusa" zahteva odgovoren pristop izvajalca. Slikovni prikaz poteka procesov je pomembna pomoč pri komunikaciji človek - računalnik, kar povečuje varnost vodenja procesov. Bolj ko se ravnamo po omenjenih dejstvih, večja je verjetnost, da se izognemo nezgodam in materialni škodi.Computer controlled processes in food industry and especially in dairy industry with automated platforms are connected with very high responsibility degree because of necessary product durability and human health. This article explains requests for: systematic approach to system engineering, high reliability of computer systems, robustness of all kinds of integrated software, the correct choice of quality sensors for physical, chemical and bacteriological parameters acquisition. Computer systems for all industrial purposes must satisfy many very important demands, such as: insensitivity to electromagnetic disturbances, permanent operation at high temperatures, short circuit protection of output modules etc. Software reliability is demonstrated not only in the way, of recognizing kind of conflict situations and possible predicting of great many of such cases. Years of experience, time and investments in research are needed. Running a process and maintenance of computerized control system during it’s installed period requests a responsible and systematic approach of hardware/software experts. Using more and more reliable visualitization software an operator gets a very important man-machine interface and gives more security in controlling processes in general. The more we follow the mentioned facts, the more chances we establish to prevent accidents and damage

Optimization of wear loss in silicon nitride (Si3N4)–hexagonal boron nitride (hBN) composite using DoE–Taguchi method

Introduction The contacting surfaces subjected to progressive loss of material known as ‘wear,’ which is unavoidable between contacting surfaces. Similar kind of phenomenon observed in the human body in various joints where sliding/rolling contact takes place in contacting parts, leading to loss of material. This is a serious issue related to replaced joint or artificial joint. Case description Out of the various material combinations proposed for artificial joint or joint replacement Si3N4 against Al2O3 is one of in ceramic on ceramic category. Minimizing the wear loss of Si3N4 is a prime requirement to avoid aseptic loosening of artificial joint and extending life of joint. Discussion and evaluation In this paper, an attempt has been made to investigate the wear loss behavior of Si3N4–hBN composite and evaluate the effect of hBN addition in Si3N4 to minimize the wear loss. DoE–Taguchi technique is used to plan and analyze experiments. Conclusion Analysis of experimental results proposes 15 N load and 8 % of hBN addition in Si3N4 is optimum to minimize wear loss against alumina

The efficacy of flubendazole against Trichinella spiralis in swine

A trial was undertaken to assess the efficacy of flubendazole against experimentally induced trichinellosis in pigs when given mixed with food at different dose rates. At the start of the experiment, 48 pigs were infected with approximately 35,000 larvae of Trichinella spiralis, afterwhat the animals were distributed in six groups. The first three groups were used to test the activity of the drug against adult stages. Other three groups served to define the efficacy against muscle larvae. The dose rate of flubendazole varied according to the purpose of the experiment (from 8 mg/kg up to 62 mg/kg). At the end of the trial, the pigs were necropsied and the number of adults and larvae in predilection muscles were determined. At a dose rate of 8 mg/kg flubendazole supplied with food during eight days was 100 % effective against adults. At a dose rate of 31 mg/kg flubendazole administered for 14 days was 72.35 % effective. Treatment with higher dosages of flubendazole (62 mg/kg) resulted in increased efficacy (87.77 %) against the parasites. The biological assay performed with larvae from the muscle samples originating from the pigs treated with 62 mg/kg showed that at least half of the larvae were not infective

The efficacy of flubendazole against

A trial was undertaken to assess the efficacy of flubendazole against experimentally induced trichinellosis in pigs when given mixed with food at different dose rates. At the start of the experiment, 48 pigs were infected with approximately 35,000 larvae of Trichinella spiralis, afterwhat the animals were distributed in six groups. The first three groups were used to test the activity of the drug against adult stages. Other three groups served to define the efficacy against muscle larvae. The dose rate of flubendazole varied according to the purpose of the experiment (from 8 mg/kg up to 62 mg/kg). At the end of the trial, the pigs were necropsied and the number of adults and larvae in predilection muscles were determined. At a dose rate of 8 mg/kg flubendazole supplied with food during eight days was 100 % effective against adults. At a dose rate of 31 mg/kg flubendazole administered for 14 days was 72.35 % effective. Treatment with higher dosages of flubendazole (62 mg/kg) resulted in increased efficacy (87.77 %) against the parasites. The biological assay performed with larvae from the muscle samples originating from the pigs treated with 62 mg/kg showed that at least half of the larvae were not infective