• Composites Research
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• v.31 no.6
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• pp.404-411
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• 2018

As the autoclave process progresses in a given cure cycle, residual stress in the composite product is induced by cure shrinkage of the resin. As a result, It generates the thermal deformation such as spring-in and warpage, and the inaccuracy of the final product increases. It is important to predict thermal deformation in aerospace parts which require precise fabrication. The research has been done on predicting and grasping curing process of composite material. In this study, the cure mechanism of composite materials according to the process is predicted through finite element analysis, and the effect of cure shrinkage on thermal deformation generated by the process is analyzed.

• Journal of environmental and Sanitary engineering
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• v.5 no.2
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• pp.63-80
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• 1990

A sensitive and simple analytical system for the simultaneous determination of residual oxytetracycline, tetracycline, and doxycycline in honey was described, and that the analytical method for determination of residual propionic acid in honey was established. Experimental subjects were purchased four kinds of honey, native kind honey, acaccia honey, mixed floral honey, chestnut honey in Kyung Sang Nam Do. Several microbiological methods are available to determine tetracycline antibiotecs(TCs) in foods but their precision apears to be variable and the specificity is questionable. These methods are considered to be not suitable for analysis of tetracycline antibiotics in honey because honey itself has bacteriostatic action. For determination of tetracycline antibiotics in honey, therefore the High Performance Liquid Chromatography(HPLC) method was applied, and the propionic acid were determined by Gas Chromatography(5.C). Ethylacetate, as an extract solvent, was found to be suitable for seperation of TCs in honey, but methanol and acetone were not. The recoverly rate of Oxytetracycline(OTC), Tetracycline(TC), Doxycycline(DC) from honey spiked at a level of 10 $\mu $g/g were 97%, 89%, and 91%, respectively. The cailbration curve in TCs was linear expression from 2$\mu $g/ml to 10$\mu $g/ml. As the results of analysis, the residual tetracycline antibiotics were not detected in the 100 samples of honey. The recovery rate of propionic acid from honey spiked at level of 10$\mu $g/g was 98.3% , and the calibra lion curves were linear expression from 21$\mu $g/ml to 101$\mu $g/ml. As the results of analysis, the residual propionic acid was not detected in the 100 samples of honey. Retention time(min) of OTC, DC, and TC were 3.35, 4.61, and 5.30 minutes at the conditions of table 2, respectively, and retention time(min) of propionic acid was 3.50 minutes at the conditions of table 3. The residual TCs and propionic acid were not detected in the 100 samples of honey, but there is a possibility that antibiotics or propionic acid will be to remain in honey if they are used during product period in order to prevent putrefaction of honey-bee.

• Korean Journal of Environmental Agriculture
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• v.32 no.2
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• pp.142-147
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• 2013

BACKGROUND: This study was conducted to monitor residual pesticides in domestic agricultural products and to assess their risk to human health. METHODS AND RESULTS: 123 samples containing both general and environment-friendly certified agricultural products were purchased from traditional domestic markets and supermarkets in six provinces of Korea. Multiresidue analyses of one hundred twenty-two pesticides except for herbicides were performed with gas chromatography-electron capture detector, gas chromatography-nitrogen/phosphorus detector, and high-performance liquid chromatography. Sixteen pesticides were detected in 45 agricultural product samples, which were 38 general, 6 low pesticide and 1 of GAP agricultural product samples and the detection rate was 33.6%. Pesticides detected in agricultural product samples were cypermethrin, lufenuron, fenvalerate, bifenthrin, chlorfenapyr and iprodione. Residual concentration of 18 samples were exceeded the recommended maximum residue limit set by Ministry of Food and Drug Safety and two kinds of unregistered pesticides in korea were also detected in two samples. CONCLUSION(S): In order to do risk assessment by agricultural products consumption, estimated daily intake of residual pesticides were determined and compared to acceptable daily intake, referring to %ADI values. The range of %ADI values was from 0.038% to 2.748%. Taken together, it demonstrates the pesticides found in agricultural products samples were below the safety margin, indicating no effect on human health.

• Design & Manufacturing
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• v.1 no.1
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• pp.17-21
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• 2007

In the manufacture and processing of large plastic materials, product quality is tested and verified through several techniques such as injection processing, residual stress through injection molding and shrinkage. With regards to the injection molding process, common problems such as inconsistent density is seen when different points of the product are discovered to have varying thickness levels. Sink marks in product are then evident. This occurs when there is poor molding conditions caused about by poor runner and packaging systems incorporated into the process. We designed the runner system which is possible balanced filling to cavities using CAE program $Moldflow^{TM}$ and then obtained optimal processing conditions by Taguchi's Robust Design technique.

• Polymer(Korea)
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• v.35 no.5
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• pp.467-471
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• 2011

PET bottle is manufactured by blow molding the preform, which is molded by injection molding. The neck part of the preform of PET bottle for juice or grain-based beverage is crystallized before blowing to improve heat resistance at the entrance of the bottle. However, residual stress, developed during injection molding of preform, prevents the crystallization. In order to release the residual stress in the preform, the preform is annealed after the injection molding. If the residual stress is reduced by optimizing the injection molding conditions of preform the annealing time would be shortened. In this study, the optimum conditions for minimizing the residual stress and increasing dimensional accuracy of the injection molded preform are suggested through CAE analysis. In order to optimize the molding conditions, minimizing residual stress and shrinkage, computer simulations have been carried out with help of design of experiment scheduling. Injection temperature, initial packing pressure and filling time were selected for control parameters. Residual stress was affected by injection temperature and filling time. Shrinkage was affected by injection temperature. It was found that maximum residual stress, distribution of residual stress and shrinkage were decreased by 22%, 40% and 25%, respectively at an optimum molding condition compared with the results of previous molding condition.

• Advances in Computational Design
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• v.4 no.1
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• pp.43-52
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• 2019

Variation Analysis (VA) is used to simulate final product variation, taking into consideration part manufacturing and assembly variations. In VA, all the manufacturing and assembly processes are defined at the product design stage. Process Capability Data Bases (PCDB) provide information about measured variation from previous products and processes and allow the designer to apply this to the new product. A new challenge to this traditional approach is posed by the Industry 4.0 (I4.0) revolution, where Smart Manufacturing (SM) is applied. The manufacturing intelligence and adaptability characteristics of SM make present PCDBs obsolete. Current tolerance analysis methods, which are made for discrete assembly products, are also challenged. This paper discusses the differences expected in future factories relevant to VA, and the approaches required to meet this challenge. Current processes are mapped using I4.0 philosophy and gaps are analysed for potential approaches for tolerance analysis tools. Matching points of simulation capability and I4.0 intents are identified as opportunities. Applying conditional variations, incorporating levels of adjustability, and the un-suitability of present Monte Carlo simulation due to changed mass production characteristics, are considered as major challenges. Opportunities including predicting residual stresses in the final product and linking them to product deterioration, calculating non-dimensional performances and extending simulations for process manufactured products, such as drugs, food products etc. are additional winning aspects for next generation VA tools.

• Polymer(Korea)
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• v.36 no.6
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• pp.685-692
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• 2012

Injection molding operation consists of phases of filling, packing, and cooling. The highest cavity pressure is involved in the packing phase among the operation phases. Thus the cavity pressure largely depends upon velocity to pressure (v/p) switchover timing and magnitude of packing pressure. Developed cavity pressure is directly related to stress concentration in the cavity of mold and it may cause a crack in the mold. Consequently control of cavity pressure is considered very important. In this study, cavity pressure was analyzed in terms of v/p switchover timing and packing pressure through computer simulation and experiment. Cavity pressure was increased as the v/p switchover timing was delayed. Residual pressure after cooling phase was observed when the v/p switchover timing was late, which was due to increased pressurizing time for long filling phase. Cavity pressure was increased proportionally with the packing pressure. Residual pressure after cooling phase was also observed, and it was increased with increasing packing pressure. High cavity pressure and residual pressure have been observed at late v/p switchover and high packing pressure. Compared with simulation and experimental results, the profiles of pressures were very similar however simulation could not predict residual pressure. Packing condition was important for the control of cavity pressure and the optimum condition could be set up using CAE analysis.

• Korean Journal of Environmental Agriculture
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• v.36 no.3
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• pp.217-221
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• 2017

BACKGROUND: For the food safety of cultivated mushroom, information on the safety of agricultural by-products imported as medium substrates for mushroom cultivation is urgently needed. Therefore, this study was performed to detect the presence of heavy metals, residual pesticides, and nutrient component in the imported medium substrates. METHODS AND RESULTS: Six kinds of medium substrates imported from nine countries from 2015 to 2017 were investigated. A mercury analyzer MA-2000 and an inductively coupled plasma spectrometer OPTIMA 7000DV were used to analyze mercury, lead, arsenic, copper, nickel and cadmium. All of these heavy metals were detected at lower level than heavy metal tolerance standard level of by-product fertilizer in Korea. When 246 kinds of residual pesticides were examined by GC and HPLC, imidacloprid, thiamethoxam and carbendazim were detected from Egyptian beet pulp, Indian cottonseed meal and cottonseed hull, respectively. The content of nutrient components (water, crude ash, crude fat, crude protein and crude fiber) varied among imported countries and the medium substrates. CONCLUSION:The presence of heavy metals and residual pesticides in imported medium substrates for mushroom cultivation was confirmed. For the safe production of mushroom, this study shows that imported medium materials for mushroom cultivation need to be managed through continuous monitoring.

• Polymer(Korea)
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• v.38 no.5
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• pp.645-649
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• 2014

The causes of residual stress in an injection molded part are high temperature variation and shear stress during molding process. Chemical cracking test is one of the methods of measuring residual stress and cracks are developed according to the degree of residual stress. In this study, the relationship between chemical cracking and exerted stress have been investigated. Deformation jig was designed and used to give a stress through deformation in a specimen. Specimens were molded by a hot press using polycarbonate (PC) and annealed to remove residual stresses in the specimens. Specimens were fixed in the deformation jig and immersed into the solvent to create cracks in the specimens. Solvents were prepared by using tetrahydrofuran and methyl alcohol. As stress accordance with the deformation in the specimen increased, the frequency and density of cracks in the specimen also increased. The results of this study can be used for the measurement of residual stress quantitatively in an injection molded PC product using a chemical cracking method.

• Journal of Nutrition and Health
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• v.15 no.3
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• pp.186-193
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• 1982

Dry hams and sausages we re processed manually under the environmental conditions in Seoul, Korea, by addition with $NaNO_2$ - equivalent of 264ppm and 185ppm, respectively. The residual nitrites levels throughout the processing and storage periods were 32-67 ppm which are below the maximum legal allowance of 70ppm . The nitrites showed the highest levels at 2- weeks processing of dry sausages and at 5-weeks processing of dry hams, and the levels were gradually decreased thereafter. The residual nitrites in sausages dried in intestinal cases were lower and dropped below 10ppm after 3-weeks processing. The dry hams processed in summer also contained lower levels of nitrites, below 10ppm after 4-weeks processing. The levels of residual nitrates, however, showed highest when that of nitrites were lowest and were increased gradually with the duration of storage.