A Stochastic model of multi-stage pull production systems

The pull multi-stage production scheduling and inventory control system is a way of implementing the just-in-time doctrine. In the pull system the production schedule of the final stage is transmitted back to all the upstream stages. This is achieved by keeping a certain amount of parts at each stage, with succeeding stages withdrawing parts from preceding ones only to the extent that they are needed;A stochastic model for the pull multi-stage production system is developed for two situations. The first situation is that a single machine (server) with non-zero inventory. The second situation is that of several machines with zero inventory;The model is studied and analyzed in the light of several measures of system performance and effectiveness. Allocation of parts among stages, and the effect of processing rates are investigated;A stochastic model for the push multi-stage production system is also developed and compared to the pull model. A new method, which reduced the number of Markovian states, is developed to model the blocking phenomenon in push system. A duality phenomenon between the pull and a specially defined push model is presented and discussed;The confluent system, with made parts processed in house into subassemblies, and then into final assemblies, is also modeled under the pull system. WIP allocation is studied as for the series system, and the possibility is explored of analyzing a process through its sub-process ;Although processing and demand are assumed exponential, the limitation imposed by stage capacity will cause the output process not to be poisson. For this reason, closed form solution for equilibrium probabilities of the system are not available and approximation and numerical methods were investigated, and compared;The proposed model can be applied to flexible manufacturing systems, assembly lines, and flow shops

Critical Pedagogy, Discourse Tensions, and the Basic Writing Classroom: A Critical Action Research Study

This paper discusses a critical action research study in a basic writing classroom, which made use of critical pedagogy as its theoretical framework, as it relates to one of the findings in relation to fostering writing competency and critical consciousness

Faculty Usage of Social Media and Mobile Devices: Analysis of Advantages and Concerns

This study seeks to understand the perceptions of professors using social media (also called Web 2.0 tools) in the classroom, what kinds of mobile devices are used to access the social media used, and what drives individuals to use them. In addition, it seeks to identify the advantages and concerns faculty has with the use of social media for classroom instruction. Two-Way Multivariate Analysis of Variance (MANOVA) procedure was used to ascertain whether differences existed between two dependent variables and (a) gender, (b) different academic ranks, and (c) gender *rank to determine if there are any interaction effects between genders regarding the magnitude of their perceptions of advantages and concerns about social media use for classroom instruction as they migrate through the ranks. Professors, regardless of sex or rank, held statistically the same views of the advantages as well as the concerns related to social media usage in the classroom

csa2sls: A complete subset approach for many instruments using Stata

We develop a Stata command $\texttt{csa2sls}$ that implements the complete subset averaging two-stage least squares (CSA2SLS) estimator in Lee and Shin (2021). The CSA2SLS estimator is an alternative to the two-stage least squares estimator that remedies the bias issue caused by many correlated instruments. We conduct Monte Carlo simulations and confirm that the CSA2SLS estimator reduces both the mean squared error and the estimation bias substantially when instruments are correlated. We illustrate the usage of $\texttt{csa2sls}$ in Stata by an empirical application.Comment: 10 pages, 1 figure, under review by the Stata Journa

Isolation of Salmonella in Commercial Chicken Feeds in Ilala District

Salmonella is one of important hazardous pathogens causing salmonellosis in both humans and animals. In Tanzania, commercial chicken farming is a rapidly growing industry and salmonellosis is a serious problem. A study on Salmonella was conducted in commercially produced chicken feeds from feed mills in Ilala, Dar es Salaam, Tanzania between October 2015 and January 2016. The objective of the study was to estimate the prevalence of Salmonella contamination in commercial chicken feeds. Feed samples were collected from a total of 197 randomly selected feed bags of different types from 3 feed mills to estimate the contamination prevalence. Cultural and biochemical tests were performed for the presence of Salmonella in the samples. The overall prevalence of Salmonella in the study was 29.4%. The prevalence of Salmonella in broiler starter mash, broiler grower mash, broiler finisher mash and layers mash were confirmed to be 30.8%, 38.1%, 33.3% and 21.1 respectively and prevalence of Salmonella in batches 1 and 2 were 27.8% and 30.5% respectively. Prevalence of Salmonella contamination in feed mills A, B and C, was 22.2%, 48.1% and 14.7% respectively. Significantly higher (p = 0.001) prevalence of Salmonella contamination was seen in feed mill B when compared to the other two. The presence of Salmonella in commercial chicken feeds in Ilala presents a contamination hazard for both humans and Salmonella-free flocks, and therefore, calls for improvement of hygienic processing and handling of feeds for effective control measures

ANCIENT KEDAH IRON SMELTING EXPERIMENT IN PREPARATION FOR OFFERING ARCHAEOLOGICAL TOURISM HERITAGE PACKAGES AT SUNGAI BATU ARCHAEOLOGICAL COMPLEX (SBAC), BUJANG VALLEY, KEDAH, MALAYSIA

In order to obtain primary data related to the iron smelting activities, the experimental process of furnaces, tuyere and air pumps making is carried out. The experiment has conducted since 2013 through the Knowledge Transfer Program (KTP) in Sungai Batu Archaeological Complex (SBAC). Through the experiment, the clay in this complex has been used as a raw material for furnaces and tuyere making while the bellows is made of wood, plywood and fabric. In order to complete the experiment regarding the raw material that use for iron smelting, iron ore was taken through survey activities in the area of Kampung Batu 5, UiTM Merbok and Bukit Tupah while charcoal was used from rubber wood in the rubber plantation near the Sungai Batu Archaeological Complex. After the experiment was conducted, the results recorded were different from the findings of the iron ingot excavation at the iron smelting site which is likely to occur due to the difference in technique and ratio of materials used during smelting activities. Although the results obtained during the experiment are different, the smelting process can be used as the main reference for offering tourism full packages related to the demonstration of iron smelting in this complex to foreign tourists

A Stochastic model of multi-stage pull production systems

The pull multi-stage production scheduling and inventory control system is a way of implementing the just-in-time doctrine. In the pull system the production schedule of the final stage is transmitted back to all the upstream stages. This is achieved by keeping a certain amount of parts at each stage, with succeeding stages withdrawing parts from preceding ones only to the extent that they are needed;A stochastic model for the pull multi-stage production system is developed for two situations. The first situation is that a single machine (server) with non-zero inventory. The second situation is that of several machines with zero inventory;The model is studied and analyzed in the light of several measures of system performance and effectiveness. Allocation of parts among stages, and the effect of processing rates are investigated;A stochastic model for the push multi-stage production system is also developed and compared to the pull model. A new method, which reduced the number of Markovian states, is developed to model the blocking phenomenon in push system. A duality phenomenon between the pull and a specially defined push model is presented and discussed;The confluent system, with "made" parts processed in house into subassemblies, and then into final assemblies, is also modeled under the pull system. WIP allocation is studied as for the series system, and the possibility is explored of analyzing a process through its "sub-process";Although processing and demand are assumed exponential, the limitation imposed by stage capacity will cause the output process not to be poisson. For this reason, closed form solution for equilibrium probabilities of the system are not available and approximation and numerical methods were investigated, and compared;The proposed model can be applied to flexible manufacturing systems, assembly lines, and flow shops.</p