• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.42 no.4
• /
• pp.91-105
• /
• 2019

Discrete-time Queueing models are frequently utilized to analyze the performance of computing and communication systems. The length of busy period is one of important performance measures for such systems. In this paper, we consider the busy period of the Geo/Geo/1/K queue with a single vacation. We derive the moments of the length of the busy (idle) period, the number of customers who arrive and enter the system during the busy (idle) period and the number of customers who arrive but are lost due to no vacancies in the system for both early arrival system (EAS) and late arrival system (LAS). In order to do this, recursive equations for the joint probability generating function of the busy period of the Geo/Geo/1/K queue starting with n, 1 ≤ n ≤ K, customers, the number of customers who arrive and enter the system, and arrive but are lost during that busy period are constructed. Using the result of the busy period analysis, we also numerically study differences of various performance measures between EAS and LAS. This numerical study shows that the performance gap between EAS and LAS increases as the system capacity K decrease, and the arrival rate (probability) approaches the service rate (probability). This performance gap also decreases as the vacation rate (probability) decrease, but it does not shrink to zero.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.12 no.2
• /
• pp.15-23
• /
• 2008

A numerical method based on the prediction of total pressure loss of major components of the engine has been developed for prediction of the windmilling start performance of micro-turbojet engine. The start performance in on/off design region has been analysed by applying this method to predict windmilling start-able regions of the centrifugal-type engine. The results of this analysis have been validated by comparing with the test data. The effect of each design parameters on windmilling start performance has been analysed for the enlargement of start-able regions.

• The Journal of Korean Physical Therapy
• /
• v.11 no.1
• /
• pp.87-93
• /
• 1999

The purpose of this study were to compare the balance performance with 44 children, who aged 6 and 7years old by means of the Pediatric Clinical Test of Sensory Interaction for Balance(PCTSIB), second is to determine whether age and gender-relatad difference were present, third is to found correlation of weight, height with duration of balance performance. All subjects were performed with different foot position that were feet-together, heel-toes. The starting position was that subject placed their hands on the hips. The results of each test were measured by stop watch. These collected data were analyzed by using oneway ANOVA, Sheffe test t-test and correlation. The results of this study were as follows ; 1. There were all significiant difference is all instances except condition 4 with heel-toes(p<0.05). The duration of balance performance of 7-year-olds group was more increased than 6-year-olds group. 2. There was statistically significiant difference in all instances by gender(p<0.05). 3. There was no correlation between weight or height duration of balance performance (p<0.05).

• International Journal of Fluid Machinery and Systems
• /
• v.10 no.3
• /
• pp.218-226
• /
• 2017

Severe radial thrust under off-design operating conditions can be a harmful factor for centrifugal pumps. In the present work, effects of geometry of a double volute casing on the hydrodynamic performance of a centrifugal pump have been investigated focusing on off-design conditions. Three-dimensional steady Reynolds-averaged Navier-Stokes analysis was carried out by using shear stress transport turbulence model. Numerical results for the hydrodynamic performance of the centrifugal pump were validated compared with experimental data. The hydraulic efficiency and radial thrust coefficient were used as performance parameters to evaluate the hydrodynamic characteristics of the centrifugal pump. The cross-sectional area ratio of the volute casing, the expansion coefficient of the rib structure, the distance between the rib starting point and volute entrance, and radius and width of the volute entrance, and length of the rib structure, were selected as geometric parameters. Results of the parametric study show that the performance parameters are significantly affected by the geometric variables and operating conditions. Optimal configurations of the double volute casing based on the design of experiments technique show outstanding performance in terms of the efficiency and radial thrust coefficient.

• The Korean Journal of Health Service Management
• /
• v.5 no.3
• /
• pp.77-88
• /
• 2011

As same time of starting on the Korean Long-term Care Insurance System, the government developed a program to train new qualification of long-term care workers. The number of enrolled long-term care workers are 950,000 persons in 2010. Mostly they are working in home based care work places such as home visit care centers and home visit bathing centers covered insurance. The purpose of this study is to understand the difference of task performance requirement according to long-term care workers' responsibilities which divided into home visiting care and home visiting bathing. The comparison analysis was conducted to task performance requirement in basic management, safety management, administration management, practical services. Key result was found that task performance requirement of long-term care workers whose responsibilities are home visiting care were more higher than the home visiting bathing. Finally, To improve quality of home visiting care and home visiting bathing, it is necessary to provide the fields based continuing education and reflect new reimburse system.

• Wind and Structures
• /
• v.22 no.5
• /
• pp.595-616
• /
• 2016

Providing high starting torque and efficiency simultaneously is a significant challenge for vertical axis wind turbines (VAWTs). In this paper, a new approach is studied in order to modify VAWTs performance and cogging torque. In this approach, J-shaped profiles are exploited in the structure of blades by means of eliminating the pressure side of airfoil from the maximum thickness toward the trailing edge. This new profile is a new type of VAWT airfoil using the lift and drag forces, thereby yielding a better performance at low TSRs. To simulate the fluid flow of the VAWT along with J-shaped profiles originated from NACA0018 and NACA0030, a two-dimensional computational analysis is conducted. The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the two-equation Shear Stress Transport (SST) turbulence model. The main objective of the study is to investigate the effects of J-shaped straight blade thickness on the performance characteristics of VAWT. The results obtained indicate that opting for the higher thickness in J-shaped profiles for the blade sections leads the performance and cogging torque of VAWT to enhance dramatically.

• Journal of Korea Technology Innovation Society
• /
• v.21 no.4
• /
• pp.1493-1507
• /
• 2018

In this study, based on the results that cooperation increases innovation or increases innovation performance in the same region, the result is that the effects of cooperation in the same region will be more effective, thus starting with the assumption that the innovation performance will be higher. The analysis results showed that the collaborative experience in the same region greatly increases the results of innovation, indicating that the location of cooperative targets in cooperation could be an important decision factor. The implications of this result are that it could have a significant impact on a company's innovation performance. This means that the country's industrial policy should be established in the direction of cluster formation.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.6
• /
• pp.297-302
• /
• 2022

The current study examines the relationship between inventory management efficiency and financial performance in Saudi Arabian companies. The study collected data from the companies listed on Tadawul (a Saudi Arabian stock exchange) during the period starting from 2016 and ending in 2020. The study uses pooled regression model by incorporating Return on Assets (ROA) and Inventory Turnover Ratio (ITR) as a performance measurement variable and inventory conversion period as an inventory management variable to report the results. The results show a positive and significant association between inventory management and firms' financial growth measured in terms of Return on Assets (ROA). Further, the study reports a positive and significant association between the inventory conversion period and inventory turnover (ITR). This shows that managing inventory efficiently shall positively impact the firm's performance. The other variables, such as debt ratio and gross profit, are positively related to ROA and negatively correlated with ITR. The firm growth is positively associated with both the dependent variables. The results suggest that the management of inventory in Saudi Arabian firms is efficient. Further, the firm size is positively associated with ROA and ITR. This shows a nexus between inventory management efficiency and firms' financial growth in Saudi Arabian companies.

• Asia pacific journal of information systems
• /
• v.32 no.4
• /
• pp.707-727
• /
• 2022

Industrial revolution 4.0 makes business competition more challenging and will impact the instability of the company's financial performance. Dynamic environmental conditions make it difficult for companies to make predictions in making decisions. Investing in information technology (IT) is one way for companies to maintain financial stability and competitive advantage in dynamic competition. Resource-Based Theory (RBT) explains that information technology (IT) is a resource that can create a competitive advantage for the company. This study aims to examine the moderating role of dynamic industrial environments and IT strategic emphasis on the relationship between a lag effect of IT investment and firm's financial performance volatility. Using the data of companies listed on the Indonesia Stock Exchange (IDX) for five years starting from 2013-2017, the method used to estimate the research model's parameters is the generalized method of moments (GMM) approach. The results show that the industrial environment and the emphasis on IT strategy have a role in moderating and strengthening the relationship between the time lag in IT investment in reducing the firm's financial performance volatility.

• Journal of the Korean Ceramic Society
• /
• v.53 no.1
• /
• pp.116-121
• /
• 2016

The amount of carbon dioxide ($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical methods of reducing $CO_2$ in building materials is the addition of slag and fly ash, like pozzolan material another method is to reduce $CO_2$ production by developing carbon negative cement. MgO-based cement from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements can improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, basic research on magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as the main starting materials, as well as blast furnace slag for the mineral admixture, was carried out for industrial waste material recycling. In order to increase the overall hydration activity, $MgCl_2$ was also added. In the case of the addition of $MgCl_2$as accelerating admixture, there was a promoting effect on the compressive strength. This was found to be due to the production of needle-like dense Mg-Cl hydrates. Mgnesia cement has a high viscosity due to its high specific surface area therefore, when the PC-based dispersing agent was added at a level of more than 1.0%, it had the effect of improving fluidity. In particular, the addition of $MgCl_2$ in magnesia cement using $MgCO_3$and magnesium silicate ore (serpentine) as main starting materials led to a lower expansion ratio and an increase in the freeze-thaw resistance finally, the addition of $MgCl_2$ as accelerating admixture led to good overall durability.