• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1983-1989
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• 2005

Industrial robots are powerful, extremely accurate multi-jointed systems, but they are heavy and highly rigid because of their mechanical structure and motorization. Therefore, sharing the robot working space with its environment is problematic. A novel pneumatic artificial muscle actuator (PAM actuator) has been regarded during the recent decades as an interesting alternative to hydraulic and electric actuators. Its main advantages are high strength and high power/weight ratio, low cost, compactness, ease of maintenance, cleanliness, readily available and cheap power source, inherent safety and mobility assistance to humans performing tasks. The PAM is undoubtedly the most promising artificial muscle for the actuation of new types of industrial robots such as Rubber Actuator and PAM manipulators. However, some limitations still exist, such as the air compressibility and the lack of damping ability of the actuator bring the dynamic delay of the pressure response and cause the oscillatory motion. In addition, the nonlinearities in the PAM manipulator still limit the controllability. Therefore, it is not easy to realize motion with high accuracy and high speed and with respect to various external inertia loads in order to realize a human-friendly therapy robot To overcome these problems a novel controller, which harmonizes a phase plane switching control method with conventional PID controller and the adaptabilities of neural network, is newly proposed. In order to realize satisfactory control performance a variable damper - Magneto-Rheological Brake (MRB) is equipped to the joint of the manipulator. Superb mixture of conventional PID controller and a phase plane switching control using neural network brings us a novel controller. This proposed controller is appropriate for a kind of plants with nonlinearity uncertainties and disturbances. The experiments were carried out in practical PAM manipulator and the effectiveness of the proposed control algorithm was demonstrated through experiments, which had proved that the stability of the manipulator can be improved greatly in a high gain control by using MRB with phase plane switching control using neural network and without regard for the changes of external inertia loads.

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.277-291
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• 2012

Aquaculture is challenged by a number of constraints with future efforts towards sustainable production. Global climate change has a potential damage to the sustainability by changing environmental surroundings unfavorably. The damaging parameters identified are water temperature, sea level, surface physical energy, precipitation, solar radiation, ocean acidification, and so on. Of them, temperature, mostly temperature elevation, occupies significant concern among marine ecologists and aquaculturists. Ocean acidification particularly draws shellfish aquaculturists' attention as it alters the marine chemistry, shifting the equilibrium towards more dissolved CO2 and hydrogen ions ($H^+$) and thus influencing signaling pathways on shell formation, immune system, and other biological processes. Temperature elevation by climate change is of double-sidedness: it can be an opportunistic parameter besides being a generally known damaging parameter in aquaculture. It can provide better environments for faster and longer growth for aquaculture species. It is also somehow advantageous for alleviation of aquaculture expansion pressure in a given location by opening a gate for new species and aquaculture zone expansion northward in the northern hemisphere, otherwise unavailable due to temperature limit. But in the science of climate change, the ways of influence on aquaculture are complex and ambiguous, and hence are still hard to identify and quantify. At the same time considerable parts of our knowledge on climate change effects on aquaculture are from the estimates from data of fisheries and agriculture. The consequences may be different from what they really are, particularly in the temperature region. In reality, bivalves and tunicates hung or caged in the longline system are often exposed to temperatures higher than those they encounter in nature, locally driving the farmed shellfish into an upper tolerable temperature extreme. We review recent climate change and following environment changes which can be factors or potential factors affecting shellfish aquaculture production in the temperate region.

• Korean Journal of Clinical Pharmacy
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• v.26 no.3
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• pp.254-263
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• 2016

Objective: Written information could be helpful for senior population to adhere to complex medication therapies, but must be well prepared and empirically assessed to achieve such end. We purposed to develop a drug information leaflet for senior citizens by applying 'performance-based user-testing.' Methods: We employed a user-testing, a mixed method to figure difficulties out with patients' leaflets from the user perspective. The cycle made of test and revision can be repeated as necessary. We recruited senior citizens with age of 65 or above who were taking antihypertensive medications at the point of participating and excluded the elderly who suffered illiteracy. We firstly rectified a drug information leaflet of antihypertensive medications for the general public distributed by the Korean authority based on focus group interviews (9 participants). The revised leaflets were tested four times with 8~12 participants in each round (40 seniors in total). We targeted to develop a leaflet which more than 80% of participants understood 10 key information. Main outcomes measures were to be able to find information and be able to understand information. This study was approved by the Yeungnam University Research Ethics Committee. Results: Focus group interviews identified difficulties with small font of words, professional language, long information, and a poor structure. The leaflet was revised and in the first round questionnaire found problems with 4/10 information points; interviews disclosed all but one (normal blood pressure range) were ill-understood. The second round questionnaire and interview found fewer problems but the comprehensiveness of participants was still poor in several points. For the third and fourth rounds we revised the leaflets in the individual-targeted manner. Finally, the fourth round showed all key information found and understood by at least 80% of participants except one question about drug name. Conclusion: The drug leaflets need to be developed in a personalized mode for the seniors. There was a limit for Korean seniors to understand nonproprietary name of their drugs because they used to producers' trade names which the Korean health system predominantly works with.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3637-3641
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• 2014

In this study, we analyzed the toxicity of mixtures of dimethylformamide (DMF) and methyl ethyl ketone (MEK) or DMF and toluene (TOL) and predicted their toxicity using quantitative structure-activity relationships (QSAR). A QSAR model for single substances and mixtures was analyzed using multiple linear regression (MLR) by taking into account the statistical parameters between the observed and predicted $EC_{50}$. After preprocessing, the best subsets of descriptors in the learning methods were determined using a 5-fold cross-validation method. Significant differences in physico-chemical properties such as boiling point (BP), specific gravity (SG), Reid vapor pressure (rVP), flash point (FP), low explosion limit (LEL), and octanol/water partition coefficient (Pow) were observed between the single substances and the mixtures. The $EC_{50}$ of the mixture of DMF and TOL was significantly lower than that of DMF. The mixture toxicity was directly related to the mixing ratio of TOL and MEK (MLR $EC_{50}$ equation = $1.76997-1.12249{\times}TOL+1.21045{\times}MEK$), as well as to SG, VP, and LEL (MLR equation $EC_{50}=15.44388-19.84549{\times}SG+0.05091{\times}VP+1.85846{\times}LEL$). These results show that QSAR-based models can be used to quantitatively predict the toxicity of mixtures used in manufacturing industries.

• Journal of the Ergonomics Society of Korea
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• v.29 no.4
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• pp.465-471
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• 2010

Work-related musculoskeletal disorders (WMSDs) have been the most common health problem covered by worker's accident compensation insurance for several years in Korea. Korean government has strengthened related regulations since 2003. People looked forward to decreasing the incidence and prevalence of WMSDs. At first, the expectation could be realized. However, we were bumped against to limit at present. The authors think it is due to the negligence of psychosocial factors for WMSDs. Many researchers reported that the various psychosocial factors were associated with WMSDs or symptoms. Job demand, social support, job satisfaction and decision latitude are the major risk factors in job stress aspect. Work pressure, lack of rest, qualified workload, workload variability and monotonous job are the significant risk factors in work context of work organization. Employment flexibility, downsizing, lean production, contingent work and pay for by the piece are also the risk factors in an organizational context. Furthermore, these risk factors are associated with each other across different dimensions of work organization. Suggestive possible pathways between these risks and WMSDs have been taken note of increasing muscle strain or ergonomic stress and of a cognitive aspect. The authors suggest these risk factors could explain the limitation of the regulation system for WMSDs. In conclusion, the strategy to manage psychosocial factors is the one of the essential approach to prevent WMSDs.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.19-26
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• 1988

The low leakage leading pattern has features as the placement of some fresh fuel assemblies in the core interior to reduce the neutron fluence on the pressure vessel and to enhance the neutron economics. But as fresh fuel assemblies are loaded in the core interior, the local power tends to exceed safety limit due to the high reactivity of the fresh assemblies. Therefore, a large number of burnable poisons must be utilized in a low leakage scheme to suppress the high assembly power as well as the excess reactivity. In this study the effects of burnable poisons are treated as a perturbation on the power distribution, and the 'Power Sensitivity Coefficient' concept is adopted. An application study is performed for cycle 1 of the Korea Nuclear Unit-7 (KNU-7) to justify the usefulness of the reverse depletion method coupled with the above concept. To obtain the optimal burnable poision distribution at the given burnup step, the linear programming technique is adopted. The result shows maximum 4.5% error in the amount of burnable poisons between the calculated and the reference values. It is concluded that the design methodology which consists of the reverse depletion, the power sensitivity coefficient concept, and the linear programming technique can be used to find the optimal turnable poison distribution.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.240-245
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• 2000

Fatigue crack propagation rates and characteristics of the SA516-60 steel which is used for the low temperature pressure vessels, were studied in the room temperature of $25^{\circ}C$ and low temperature ranges of $10^{\circ}C,\; -10^{\circ}C,\; -30^{\circ}C,\; -50^{\circ}C, \;and\; -70^{\circ}C4 with stress ratio of R=0.05. The obtained experimental results are as follows; 1) In the logarithmic relationship between the fatigue crack propagation rate(da/dN) and stress intensity factor K, the linear relationship was obtained up to da/dN 〉$8\times10^{-3}$/mm/cycle in the same of room temperature, but in low temperature case, the relationship was extended to the range of crack propagation rate. 2) The lower limit stress intensity factor of SA516-60 $\DeltaK_{th}$ was 15.8MPa and in the case of low temperature $-50^{\circ}C\; and\; -70^{\circ}C$, the crack propagation rate da/dN which showed a linear relation, reached rapidly to the $\DeltaK_{th}$/. As the results, the crack propagation rates of $-50^{\circ}C\; and\; -70^{\circ}C$ were lower than that of room temperature and according to the testing temperature the rates were decreased rapidly to the $\DeltaK_{th}$/. 3) On the relationship between the stress intensity factor $\DeltaK$ and the crack propagation cycle, the stress intensity factors of low cycle region was rapidly increased at low temperature, but $\DeltaK$ was increased rapidly at room temperature of high cycle. 4) On the relationship between the fatigue crack propagation rate and cycle, the fatigue crack propagation rate showed higher gradient in the room temperature than the low temperature due to the increment in ductility at low temperature.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.308-313
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• 2005

In this study the electrical conductivity of excess BaO in $BaTiO_3$ was measured to investigate the relationship between defects and solubility in the temperature range of $900^{\circ}C$ to $1300^{\circ}C$ under various oxygen partial pressure. First of all, quenched $BaTiO_3$ powders of various Ba/Ti ratios were analysed by X-ray diffraction to confirm whether second phase is formed or not. As the results, we observed the solubility of BaO in the temperature range of $1200^{\circ}C$ to $1400^{\circ}C$, and it was also found that the conductivity minima move to lower $PO_2$ with increasing excess BaO within solubility limit.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.47-56
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• 2017

Aseismic designs of pile-supported wharves are commonly performed utilizing simplified dynamic analyses, such as multi-mode spectral analyses. Simplified analyses can be useful for evaluating the limit state of structures. However, several pile-supported wharves, that have been damaged during past earthquakes, have shown that soil deformation and soil-pile dynamic interaction significantly affect the entire behavior of structures. Such behavior can be captured by performing nonlinear effective stress analyses, which can properly consider the dynamic interactions among the soil-pile-structure. The present study attempts to investigate the earthquake performance of a pile-supported wharf utilizing a three-dimensional numerical method. The damaged pile-supported wharf at the Kobe Port during the Hyogo-ken Nambu earthquake (1995) is selected to verify the applicability of the numerical modeling. Analysis results showed a suitable agreement with the observations on the damaged wharf, and the significant effect of excess pore pressure development and pile-soil dynamic interaction on the seismic performance of the wharf.

• Journal of the Korean Institute of Gas
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• v.17 no.2
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• pp.9-20
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• 2013

Depleted gas reservoir has been already explored and its geologic data, along with its reservoir properties, are already known through seismic exploration and drilling. Therefore it would be less difficult to develope a gas storage from depleted gas reservoir. Cushion gas which remains in the reservoir to maintain pressure affects withdrawal rate of working gas in underground gas storage. In this study, we attempted to investigate the relationship between cushion gas and withdrawal rate using a commercial simulator. From the analyses of the results, it is found that the minimum limit for a cycle of 5-month injection and 5-month withdrawal is 10 wells with 50% cushion gas, and 12 wells with 60% cushion gas for a cycle of 7-month injection and 3-month withdrawal.