Comparative Efficiency of Container Ports in Vietnam and Korea

Ly, Pham Thi Hoai,Ahn, Ki-Myung,Ryoo, Dong-Keun Korean Institute of Navigation and Port Research 2018 한국항해항만학회지 Vol.42 No.2

Currently, there are very few papers that have examined the efficiency of Vietnamese ports. Of those that have, some of them take into account only a few container ports in Northern Vietnam. Others focus on comparing all types of ports in Vietnam with regard to the differences in efficiency scores when applying different methods to evaluate efficiency. However, there is no paper that specifically analyzes the efficiency of Vietnamese container ports throughout the country or that compares Vietnamese container ports with those of other countries in terms of efficiency. In order to provide more accurate and interesting information for container port authorities, in this study, 21 major Vietnamese container ports and seven major Korean container ports are selected and examined with regard to their levels of efficiency in 2016 using data envelopment analysis (DEA). This paper applies both constant return to scale (CRS) and variable return to scale (VRS) to explore the differences among overall technical efficiency, pure technical efficiency, and scale efficiency of the selected container ports. This study also indicate slacks and sets projections for inefficient ports.

Comparative Efficiency of Container Ports in Vietnam and Korea

Pham Thi Hoai Ly,Ki-Myung Ahn,Dong-Keun Ryoo 한국항해항만학회 2018 한국항해항만학회지 Vol.42 No.2

Currently, there are very few papers that have examined the efficiency of Vietnamese ports. Of those that have, some of them take into account only a few container ports in Northern Vietnam. Others focus on comparing all types of ports in Vietnam with regard to the differences in efficiency scores when applying different methods to evaluate efficiency. However, there is no paper that specifically analyzes the efficiency of Vietnamese container ports throughout the country or that compares Vietnamese container ports with those of other countries in terms of efficiency. In order to provide more accurate and interesting information for container port authorities, in this study, 21 major Vietnamese container ports and seven major Korean container ports are selected and examined with regard to their levels of efficiency in 2016 using data envelopment analysis (DEA). This paper applies both constant return to scale (CRS) and variable return to scale (VRS) to explore the differences among overall technical efficiency, pure technical efficiency, and scale efficiency of the selected container ports. This study also indicate slacks and sets projections for inefficient ports.

Evaluation of the turbulence models for gas flow and particle transport in URANS and LES of a cyclone separator

Jang, Kwonwoo,Lee, Gwang Goo,Huh, Kang Y. Elsevier 2018 Computers & fluids Vol.172 No.-

<P><B>Abstract</B></P> <P>Gas-solid separators have played an important role for process or emission control of many facilities including fluidized bed reactors. The flow field and collection efficiency were investigated for a Stairmand- type cyclone separator by Reynolds stress transport model (RSTM) and large eddy simulation (LES) in this work. RSTM and LES both showed good agreement with measured mean tangential velocity, whereas LES reproduced unsteady flow in the core with better agreement of the mean axial velocity profile. The particle dispersion model is required to obtain an accurate overall collection efficiency in both RSTM and LES. Anisotropy in velocity fluctuation should be taken into account, whereas its effect is more significant in RSTM than in LES. The continuous random walk (CRW) model gave more accurate results than the discrete random walk (DRW) model in RSTM, whereas there was no significant difference in LES resolving most large scale eddies. LES made better prediction of the overall particle collection efficiency than RSTM, although further investigation may be required for deviation in the maximum inlet flow case of the cyclone separator.</P> <P><B>Highlights</B></P> <P> <UL> <LI> DRW and CRW models are implemented in OpenFOAM for dispersion of particles in a cyclone. </LI> <LI> The dispersion model is essential for accurate prediction of the particle collection efficiency. </LI> <LI> LES performs better than RSTM for the axial velocity of unsteady turbulent flow. </LI> <LI> CRW predicts the overall collection efficiency better than DRW in RSTM. </LI> <LI> LES gives the better prediction of the overall collection efficiency than RSTM. </LI> </UL> </P>

Are Central Government-Affiliated Performing Arts Organizations in South Korea Being Operated Efficiently?

( Intae Choi ) 한국정책학회 2016 International Journal of Policy Studies Vol.7 No.2

This study compares the operation efficiency of South Korean performing arts facilities using the Data Envelopment Analysis (DEA) method. The DEA was conducted through two stages. First, I compared the operation efficiency of all performing arts facilities. As a result, although private facilities relatively had the upper hand, among public facilities, the central government facilities showed the highest efficiency level. Next, I compared the operation efficiency of further classified genres. The results showed that except for the Korean traditional music genre, all other genres of the central government facilities had low operation efficiency levels.

선박 발전기용 연료전지 시스템의 효율에 관한 연구

이정희(Jung-Hee Lee),곽재섭(Jae-Seob Kwak),김광희(Kwang-Heui Kim) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.5

Most current ships have adopted on-board diesel generators to produce electricity, but the overall efficiency of equipment is down to about 50% due to thermal losses from operations such as exhaust gas, jacket water cooler, scavenge air cooler, etc. Recently, fuel cells have been highlighted as a promising technology to reduce the effect on the environment and have a higher efficiency. Therefore, this paper suggested a solid oxide fuel cell (SOFC)-gas turbine (GT) using waste heat from a SOFC and SOFC-GT-steam turbine (ST) with Rankine cycle. To compare both configurations, the fuel flow rate, current density, cell voltage, electrical power, and overall efficiency were evaluated at different operating loads. The overall efficiency of both SOFC hybrid systems was higher than the conventional system.

부산지역 섬유,패션기업의 공간근접성에 따른 효율성 분석

주수현 ( Soo Hyeon Joo ),이선영 ( Sun Young Lee ),김영재 ( Young Jae Kim ) 국제지역학회 2008 국제지역연구 Vol.12 No.3

This paper investigates the properties and relative importance of Apparel Textile industry of Busan in terms of both the number of employees and the value-added, and then analyzes the relative technical efficiencies from the perspectives of space closeness such as consumption market, suppliers, living standards and clustering environments using the DEA model. The main outcomes are as follows. The Apparel Textile industry is still a key industry in Busan with relatively high intensity and high LQ (greater than one) in spite of the recent decrease between 2000 and 2005 both in the number of employees and the value-added. Those firms with consumption market showed higher efficiency in all kinds of efficiencies than the firms without the market, and further relatively higher efficiency than the firms with suppliers. In addition, the firms located in the higher living standards also showed higher values of efficiency compared with the firms in lower living standards. The policy implication from the results is that the strategic and selective investment should be made according to the relative efficiency and thus the traditional industry should be transformed to the high value added one with additional investment to utilize the scale efficiency.

구강암 경부임파절 전이에 대한 술전 평가의 정확성

이재준(Jae-Jun Lee),남웅(Woong Nam),차인호(In-Ho Cha) 대한구강악안면외과학회 2006 대한구강악안면외과학회지 Vol.32 No.2

Purpose : The aim of this study was to determine the accuracy of clinical and radiologic assessments in detecting positive cervical lymph nodes in oral cancer. Materials and Methods : We had reviewed the preoperative clinical, radiologic and postoperative histopathologic reports of 46 patients who had been diagnosed as oral cancer and underwent surgical excision combined with neck dissection (52 sides of neck) in the Department of Oral and Maxillofacial Surgery, College of Dentistry, Yonsei University from the July 1, 1992 to the April 30, 1999. Results : The results were as follows 1. The male to female ratio was 4.38 : 1 and the mean age was 57. 2. Sensitivity values for the preoperative assessment of cervical lymph node metastasis in oral cancer were 62.5 % in clinical examination and 50.0% in radiologic assessments. Specificity values were 77.8 % in clinical examination and 94.4 % in radiologic assessments. 3. False positive values were 44.4 % in clinical examination and 20.0 % in radiologic assessments. False negative values were 17.6 % in clinical and 19.0% in radiologic assessments. 4. Overall efficiency values were 73.1 % in clinical examination and 80.8 % in radiologic assessments. Summary : There were some limits on the accuracy of clinical and radiologic assessments in the preoperative detection of the cervical lymph nodes in oral cancer. To improve the accuracy, it is important to communicate between clinician and radiologist, and adjunctive diagnostic measures, ultrasound and fine needle aspiration cytology, were helpful increasing the overall efficiency. In the high risk sites (oral tongue and floor of the mouth) the false negative value is higher and the overall efficiency in radiologic evaluation is lower than those of the low risk sites (gingiva and alveolar ridge, retromolar trigone and buccal mucosa ). The elective neck dissection should be considered in the high risk sites.

Progressive Orthogonal Optimization Design Method for High Efficiency Axial-flow Blower

Chuang Li,Jianrun Zhang,Wenbin Yu 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.4

To solve the problem of excessive design parameters of flow channel during the comprehensive optimization of the axial-flow blower"s total pressure efficiency and flux, a progressive optimization design method which is based on the importance of structural parameters is proposed. The accurate numerical simulation model of flow channel is built, verified and updated by experiment results. According to the model, progressive orthogonal optimization design is developed as following steps: the first is axial fan design, then the orthogonal design of the structure parameters of entire flow channel is further advanced. This approach is applied to the optimization design of an axial-flow blower in this paper, and the results show that the uniformity of the flow field in the flow channel is significantly increased and the vertexes spreading in the flow channel are obviously reduced, the flux is increased from 0.145m3/s to 0.171m³/s, and the efficiency increased from 45.47% to 58.13%, it indicates that the method can meet the design requirements well while being efficient.

Experimental study of the influence of sodium salts as additive to NOxOUT process

Zhaoping Zhong,Xiujin Liang,Baosheng Jin,Xiaolin Chen,Weiling Li,Hongge Wei,Houkun Guo 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.5

An experimental study of the SNCR process with urea as reducing agent and sodium salts as additive has been carried out, and detailed analysis of the reaction mechanism has been given here. In the temperature range of 800-975 oC, NO concentration decreases at first and then increases while the concentration of N2O increases at first and then decreases with the increasing of temperature, and the turning point is 900 oC. With increasing of normalized stoichiometric ratio of reduction nitrogen to NOx (NSR), NO removal efficiency increases, while the concentration of N2O also increases, which decreases overall NOx removal efficiency. With sodium salts as additive, the concentration of N2O decreases with increasing of sodium salts addition at all temperatures, while the concentration of NO decreases at first and then increases at low-temperature side of the temperature window and increases at high-temperature side with additional increasing, whose changing extent is smaller than N2O. Since sodium salts as additive can remove N2O effectively and have no large influence on the removal of NO, the effect of sodium salts as additive is the combined effect of the production of active radicals and the removal of HNCO produced by the decomposition of urea through neutralization reactions, which is more important. To achieve the same effect under each condition, the needed addition of NaOH and CH3COONa is less than that of Na2CO3 counting as Na atom. For the decomposition of CH3COONa can produce CH3COO, its addition can promote the reduction of NO more obviously at the lower temperature than Na2CO3 or NaOH. Overall NOx removal efficiency at 900 oC with NSR=1.5 had been improved from about 30% to 70.45% through the addition of sodium salts. Sodium salts as additive caused the flue gas to become alkaline gas, but it was not serious for sodium salts existing as NaNCO.

Separation performance investigation of packed distillation columns using simple NEQ approach based on packing multicomponent efficiencies and effective mass transfer coefficients

Hadi Poortalari,Javad karimi Sabet,Farshad Varaminian 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.5

A simple non-equilibrium modeling approach is proposed to simulate multicomponent distillation process in packed columns. The real behavior of the column is simply considered by the evaluation of interphase mass transfer rate based on the overall mass transfer coefficient. Two distinct methods are used to calculate this overall coefficient including the effective mass transfer coefficient method and the packing efficiency method. The modelling procedure consists of an iterative segment-wise algorithm implemented in a MATLAB home-code. For verification, the obtained composition profiles from a structured and a random packed column are compared with reported experimental data. Comparisons show that the packing efficiency-based model could acceptably predict the experimental profiles with an average relative deviation of 18% and 25% for structured and random packed columns, respectively. This confirms that our simple non-equilibrium approach is a reliable and robust model for the performance evaluation of packed columns.