An investigation on the mechanics of homogeneous expansion in gas-fluidized beds

The Richardson and Zaki (1954, Sedimentation and fluidization. Trans. Inst. Chem. Eng. 32, pp. 35–53.) equation has been used extensively to investigate the expansion profiles of homogeneous gas-fluidized beds. The experimental value of the parameter n appearing in the equation indicates how significantly interparticle forces affect the expansion of these beds, revealing the relative importance of these forces with respect to the fluid dynamic ones. In this work, we modeled the stable expansion of gas-fluidized beds of different diameter, accounting for enduring contacts among particles and wall effects. We solved the model numerically to obtain the bed expansion profiles, back-calculating from them the values of the parameter n. For all the cases considered, we observed that the values of n are higher than those obtained by purely fluid dynamic correlations, such as those advanced by Richardson and Zaki, and Rowe (1987, A convenient empirical equation for estimation of the Richardson and Zaki exponent. Chem. Eng. Sci. 42, pp. 2795.). This effect was more pronounced in beds of smaller diameter. To validate our model, we carried out fluidization and defluidization experiments, analyzing the results by means of the Richardson and Zaki equation. We obtained a reasonable agreement between numerical and experimental findings; this suggests that enduring contacts among particles, which are manifestations of cohesiveness, affect homogeneous bed expansion. This effect is amplified by wall friction

A Case of Bacterial Postpartum Metritis in a 4-Year Old Duroc Sow

The attention of the Animal Health team of Swine Research Unit of Swine and Rabbit Research Programme of National Animal Production Research Institute (NAPRI) was drawn to a farrowing pen with a complaint of pus discharge from the vulva of a Duroc sow which farrowed 9 piglets 10 days earlier. Microbiological survey identified the presence of Escherichia coli, Staphylococcus and Proteus species from the sterile vaginal swab was taken from the sow. Antibiogram revealed the susceptibility of the three identified bacteria to ofloxacin, streptomycin and gentamicin in the order of increasing susceptibility. Staphylococcus species was also found to be susceptible to ciprofloxacin while Proteus species was susceptible to augmentin® and chloramphenicol. All the three species of bacteria were resistant to nitrofuratoin, rocephin® and ampiclox®. The sow was treated with deep intramuscular administration of streptomycin at 20 mg/kg once daily for 5 days and 10 IU of oxytocin once daily for 2 days. There was expulsion of macerated feotus about 24 hours following administration of the last dose of oxytocin and the macerated feotus was properly disposed and the entire pen was cleaned and disinfected. The vulva was noticed to be completely devoid of the mucous discharges after the course of the antibiotic regimen.Key words: Metritis, Postpartum, Duroc, Sow, NAPRI

Fertility Parameters in Crossbred Sows Treated with Cloprostenol Sodium (Synchromate®) in Zaria, Nigeria

This study was carried out to evaluate fertility parameters in crossbred sows in Zaria, following treatment with Cloprostenol sodium (Synchromate®). Ten (n = 10) apparently healthy crossbred sows were randomly assigned to two equal treatment groups based on number of injections of 500μg Synchromate®. Group 1 received two injections on days 0 and 13, while Group 2 received three injections on days 0, 7 and 13. Oestrus was monitored visually for signs of oestrus twice daily from 0700 – 1000h and 1500 – 1800h. The fertility parameters evaluated were: oestrus response rate (ORR), time to onset of oestrus (TOO), duration of oestrus (DOO), conception rate (CR), pregnancy rate (PR), farrowing rate (FR) and litter size (LS). Data on ORR, CR, PR and FR were expressed in percentages while TOO, DOO and LS were expressed as mean ± SEM. Student t-test and Tukey’s post-hoc test were used to compare the percentages and mean values between the groups. The Graphpad Prism® data package was used for statistical analysis and values of P<0.05 were considered significant. Fertility parameters TOO, DOO, LS, ORR, CR, PR, FR for Group 1 (187.20 ± 8.98h, 87.60 ± 4.49h, 7.25 ± 1.44, 100 %, 60 %, 80 % and 100 % respectively) and Group 2 (176.00 ± 40.00h, 86.60 ± 13.36h, 7.50 ± 1.50, 60 %, 100 %, 80 % and 66.67 % respectively). The differences in fertility parameters between the groups were not statistically significant. It is recommended therefore that double injections of cloprostenol sodium (Synchromate®) should be used for oestrus synchronization as it increases fertility parameters in cross bred sows at 13 days apart.Key words: Fertility parameters, crossbred sows, cloprostenol sodium, Zaria

Densification behavior of spark plasma sintered duplex stainless steel reinforced with TiN nanoparticles

Abstract: Duplex stainless steel (SAF 2205) reinforced with titanium nitride (TiN) nanoparticles ranging from 0 to 8 wt% were fabricated in vacuum via spark plasma sintering (SPS) using optimized SPS process parameter of 1150 oC, 10 min and 100 oC/min. The influence of TiN addition on the densification and shrinkage mechanism of the fabricated duplex stainless steel composite were evaluated. The results indicate even dispersion of the TiN nanoparticles in the steel matrix during tubular mixing. The displacement and shrinkage rates showed three densification stages relating to micro-nano particles rearrangement, plastic deformation of the particles and rapid densification of the composite. The steel composite samples displayed relatively high densities in the range of 96-99 % of the calculated theoretical density but were noted to decrease with TiN content

A correlation between nano and micro-hardness properties of TiN nanoparticles strengthened SAF 2205

Abstract : This work studied the correlation between Vickers and nano-hardness of SAF 2205 reinforced with TiN nanoparticles for the convenience of assessing its mechanical properties. Spark plasma sintering was used to fabricate the composites. Micro and nanoindentations were performed to determine micro and nanohardness values of the fabricated composite. Optical microscope was used to assess the microstructure. The microstructure revealed that the TiN dominated the ferrite/ferrite, ferrite/austenite and austenite/austenite grain boundaries. The micro and nanohardness at the TiN dominated grain boundaries were higher compared to the grain hardness. Hardness also increased considerably as the TiN nanoparticles increases. This is also owed to the strengthening effect played by TiN at the grain boundaries by disrupting dislocation motion in the composite. The determined Vickers hardness was plotted as a function of the corresponding nanohardness, a good linear relation was found between Vickers hardness and nanohardness. A linear relationship (HV = 215.15 + 15.03Hnano) was established which indicates that there is no difference in behavior for the Vickers hardness and nano- hardness

Numerical simulations of lateral solid mixing in gas-fluidized beds

We investigated the influence of design parameters and operational conditions on lateral solid mixing in fluidized beds adopting the Eulerian-Eulerian modeling approach. To quantify the rate at which solids mix laterally, we used a lateral dispersion coefficient (DsrDsr). Following the usual approach employed in the literature, we defined DsrDsr by means of an equation analogous to Fick׳s law of diffusion. To estimate DsrDsr, we fitted the void-free solid volume fraction radial profiles obtained numerically with those obtained analytically by solving Fick׳s law. The profiles match very well. Our results show that DsrDsr increases as superficial gas velocity and bed height increase; furthermore, it initially increases with bed width, but then remains approximately constant. The values of DsrDsr obtained numerically are larger than the experimental ones, within the same order of magnitude. The overestimation has a twofold explanation. On one side, it reflects the different dimensionality of simulations (2D) as compared with real fluidized beds (3D), which affects the degrees of freedom of particle lateral motion. On the other, it is related to the way frictional solid stress was modeled: we employed the kinetic theory of granular flow model for the frictional solid pressure and the model of Schaeffer (1987) for the frictional solid viscosity. To investigate how sensitive the numerical results are on the constitutive model adopted for the frictional stress, we ran the simulations again using different frictional models and changing the solid volume fraction at which the bed is assumed to enter the frictional flow regime (ϕmin)ϕmin). We observed that DsrDsr is quite sensitive to the latter. This is because this threshold value influences the size and behavior of the bubbles in the bed. We obtained the best predictions for ϕmin=0.50ϕmin=0.50. The results show that accurate prediction of lateral solid dispersion depends on adequate understanding of the frictional flow regime, and accurate modeling of the frictional stress which characterizes it

Systems thinking and CMM for continuous improvement in the construction industry

Purpose The purpose of this paper is to present a capability maturity model (CMM) developed to implement continuous improvement in small and medium scale construction companies (SMSCC) in Nigeria. Design/methodology/approach A multi-strategy approach involving qualitative studies of SMSCC in Nigeria was conducted. Semi-structured interviews were conducted with purposively selected construction experts in Nigeria to identify variables essential for continuous improvement in SMSCC. Data collected were thematically analysed using NVIVO. Subsequently, a system thinking approach is employed to design and develop the CMM for implementing continuous improvement SMSCC, by exploring possible relationships between the variables established. Findings CMM provided a five-level approach for the inclusion of investigated variables such as team performance; culture; structure; post-project reviews, financial risk management, waste management policy and cost control. These variables are factors leading to continuous improvement in SMSCC, implementable within a six to seven and a half years’ timeline. Practical implications The system thinking model revealed cogent archetypes in the form of reinforcing loops that can be applied in developing the performance of SMSCC. Continuous improvement is feasible. However, it takes time to implement. Further longitudinal studies on the cost of implementing continuous improvement through CMM a knowledge transfer project can be initiated. Originality/value A methodical strategy for enhancing the effectiveness and operations of SMSCC in developing countries can be extracted from the causal loop diagram and the CMM

Nigerian indigenous hens show more discomfort-related behavior with visual separation than physical separation from their chicks: An exploratory study

The Nigerian indigenous hens exhibit their full natural behavior repertoires, including maternal care. The strong maternal bond between the hen and her chicks is established prior to hatching. Maternal care of chickens is essential for both exotic and indigenous chickens. This study compared the behaviors of six hen-chick pairs in a physical (PHY) and visual (VIS) separation test for 10 min. All the six hen-chick pairs were subjected to PHY separation on the 8th day of post-hatch and a VIS separation on the 12th day of post-hatch. The PHY separation involved the use of a wire mesh to separate the hen from her chicks, while the VIS separation involved the use of a trampoline to separate the hen from her chicks. The hen's behavior was recorded during the 10-min separation period. Behaviors recorded included sitting, body shaking, pecking, movements toward the chicks, jumping, pacing, defecation, movements away from the chicks, and preening. We further grouped these nine behaviors into two categories: discomfort-related (pacing, movement toward chicks, body shaking, defecation, and jumping) and comfort-related (sitting, pecking, preening, and movement away from the chicks) behaviors. Before and after each separation, the hens were gently restrained, and a drop of blood was sampled from the wing vein to determine the blood glucose level. Their heart rate and eye temperature were also measured. A two-related samples test (Wilcoxon) was used to compare the behavior of the hens when subjected to the PHY and VIS separation. Eight out of the nine behaviors monitored did not differ between the separation types. However, the frequency of pacing by the hens was greater (z = −2.201, P = 0.028) in the VIS separation than in the PHY separation. Also, discomfort-related behavior was greater (t(5) = −2.717, P = 0.042) during the VIS separation than the PHY separation. Comfort-related behavior did not differ between the separation types. The change in eye temperature, heart rate, and blood glucose was similar in the two separation types. In conclusion, Nigerian indigenous hens displayed more discomfort-related behavior to the VIS separation from their chicks, but this was not associated with physiological responses indicative of stress.Peer Reviewe

The Discovery and Broad-band Follow-up of the Transient Afterglow of GRB 980703

We report on the discovery of the radio, infrared and optical transient coincident with an X-ray transient proposed to be the afterglow of GRB 980703. At later times when the transient has faded below detection, we see an underlying galaxy with R=22.6; this galaxy is the brightest host galaxy (by nearly 2 magnitudes) of any cosmological GRB thus far. In keeping with an established trend, the GRB is not significantly offset from the host galaxy. Interpreting the multi-wavelength data in the framework of the popular fireball model requires that the synchrotron cooling break was between the optical and X-ray bands on July 8.5 UT and that the intrinsic extinction of the transient is Av=0.9. This is somewhat higher than the extinction for the galaxy as a whole, as estimated from spectroscopy.Comment: 5 pages, 3 figures, and 2 tables. Submitted to the Astrophysical Journal Letters on 27 August 199

Themed project case study: Quadruple tanks control with PLCs^†

A themed project based on the control of a quadruple tank rig using PLCs has been successfully carried out as part of the MSc in Advanced Control and Systems Engineering at the University of Manchester. The themed project involves ten students who address a single multivariable control challenge under the supervision of two academics and four PhD students. As every student is required to write their own MSc dissertation, the key point is the possibility of using different control techniques to be implemented on different hardware platforms. </jats:p