• Journal of Distribution Science
• /
• v.13 no.9
• /
• pp.103-112
• /
• 2015

Purpose - This paper aims to provide a step-by-step approach to factor analytic procedures, such as principal component analysis (PCA) and exploratory factor analysis (EFA), and to offer a guideline for factor analysis. Authors have argued that the results of PCA and EFA are substantially similar. Additionally, they assert that PCA is a more appropriate technique for factor analysis because PCA produces easily interpreted results that are likely to be the basis of better decisions. For these reasons, many researchers have used PCA as a technique instead of EFA. However, these techniques are clearly different. PCA should be used for data reduction. On the other hand, EFA has been tailored to identify any underlying factor structure, a set of measured variables that cause the manifest variables to covary. Thus, it is needed for a guideline and for procedures to use in factor analysis. To date, however, these two techniques have been indiscriminately misused. Research design, data, and methodology - This research conducted a literature review. For this, we summarized the meaningful and consistent arguments and drew up guidelines and suggested procedures for rigorous EFA. Results - PCA can be used instead of common factor analysis when all measured variables have high communality. However, common factor analysis is recommended for EFA. First, researchers should evaluate the sample size and check for sampling adequacy before conducting factor analysis. If these conditions are not satisfied, then the next steps cannot be followed. Sample size must be at least 100 with communality above 0.5 and a minimum subject to item ratio of at least 5:1, with a minimum of five items in EFA. Next, Bartlett's sphericity test and the Kaiser-Mayer-Olkin (KMO) measure should be assessed for sampling adequacy. The chi-square value for Bartlett's test should be significant. In addition, a KMO of more than 0.8 is recommended. The next step is to conduct a factor analysis. The analysis is composed of three stages. The first stage determines a rotation technique. Generally, ML or PAF will suggest to researchers the best results. Selection of one of the two techniques heavily hinges on data normality. ML requires normally distributed data; on the other hand, PAF does not. The second step is associated with determining the number of factors to retain in the EFA. The best way to determine the number of factors to retain is to apply three methods including eigenvalues greater than 1.0, the scree plot test, and the variance extracted. The last step is to select one of two rotation methods: orthogonal or oblique. If the research suggests some variables that are correlated to each other, then the oblique method should be selected for factor rotation because the method assumes all factors are correlated in the research. If not, the orthogonal method is possible for factor rotation. Conclusions - Recommendations are offered for the best factor analytic practice for empirical research.

• Journal of Trauma and Injury
• /
• v.28 no.3
• /
• pp.115-122
• /
• 2015

Purpose: To calculate Preventable Trauma Death Rate (PTDR), Trauma and Injury Severity Score (TRISS) is the most utilized evaluation index of the trauma centers in South Korea. However, this method may have greater variation due to the small number of the denominator in each trauma center. Therefore, we would like to develop new indicators that can be used easily on quality improvement activities by increasing the denominator. Methods: The medical records of 1005 major trauma (ISS >15) patients who visited 2 regional trauma center (A center and B center) in 2014 were analyzed retrospectively. PTDR and PARK Index (Preventable Major Trauma Death Rate, PMTDR) were calculated in 731 patients with inclusion criteria. We invented PARK Index to minimize the variation of preventability of trauma death. In PTDR the denominator is all number of deaths, and in PARK Index the denominator is number of all patients who have survival probability (Ps) larger than 0.25. Numerator is the number of deaths from patients who have Ps larger than 0.25. Results: The size of denominator was 40 in A center, 49 in B center, and overall 89 in PTDR. The size of denominator was significantly increased, and 287 (7.2-fold) in A center, 422 (8.6-fold) in B center, and overall 709 (8.0-fold) in PARK Index. PARK Index was 12.9% in A center, 8.3% in B center, and overall 10.2%. Conclusion: PARK Index is calculated as a rate of mortality from all major trauma patients who have Ps larger than 0.25. PARK Index obtain an effect that denominator is increased 8.0-fold than PTDR. Therefore PARK Index is able to compensate for greater disadvantage of PTDR. PARK Index is expected to be helpful in implementing evaluation of mortality outcome and to be a new index that can be applied to a trauma center quality improvement activity.

• Korean Journal of Construction Engineering and Management
• /
• v.17 no.5
• /
• pp.97-107
• /
• 2016

CM services have been focused on the advancement of the CM industry and expansion to overseas market based on CM capabilities. However, there has been lack of quantitative and comprehensive research to investigate current CM trends and prospects for improving competitiveness. In this sense, the purpose of this study is to statistically analyze total of 3,453 CM service contracts over the past 18 years (between 1997 and 2014) in term of market type, contract size, owner's type, commodity type. Finding of this research reveal that 1) compared to 2005, CM market size in 2015 increased as much as 2.5 times, and that 2) domestic CM projects count for 87.5%, architectural project 88.4%, less than 1 billion won small contracts 75%, respectively. Also, recently as CM company are developing capability and competitiveness, 1) overseas CM market share has grown up to 20% among total CM contract amount, and 2) CM contracts by private owners has increased 3 times demanding the total management services based on high technical capability. Additionally, the result of this paper supports the growth path model proposed by Jung et al. (2014), where a path from Domestic Public (DP3) and Domestic Private (DC2) CM projects towards the expansion to International Private (IC5) contracts was quantitatively analyzed. Implications for other practical issues are also briefly discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.29 no.11
• /
• pp.580-591
• /
• 2017

In accordance with 2015 Paris agreement, each individual country around the world should voluntarily propose not only its (individual) reduction target, but also actively develop and present expansion targets of its scope and concrete reduction goals exceeding the previous ones. Accordingly, it is necessary to prepare a macroscopic, long-range strategy for reducing energy consumption and greenhouse gas emissions, which can cover a single building, town, city and eventually even a province. The purpose of this research is to gather and compile government-acquired data from various sources and (in accordance with contents and specificity), combine building data by stages by using multi-variable matrix and then analyze the significance of combined data for each stage. The first order data presents the probability and the cost effectiveness of energy saving on the scale of a city or a province, based only upon general information, size and power consumption of buildings. The second order data can identify a pattern of energy consumption for a building of a specific purpose and which tends to consume a larger amount of energy during one particular season (than others). Finally, the third order data can derive influential factors (base load, humidity) from the energy consumption pattern of a building, and thus propose an informed and practical energy-saving method to be applied in real time.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.35.1-35.1
• /
• 2015

We present the results of extinction measurements toward the main ejecta shell of the Cassiopeia A supernova (SN) remnant using the flux ratios between the two near-infrared (NIR) [Fe II] lines at 1.26 and $1.64{\mu}m$. We find a clear correlation between the NIR extinction (E(J-H)) and the radial velocity of ejecta knots, showing that redshifted knots are systematically more obscured than blueshifted ones. This internal "self-extinction" strongly indicates that a large amount of SN dust resides inside and around the main ejecta shell. At one location in the southern part of the shell, we measure E(J-H) by the SN dust of $0.23{\pm}0.05mag$. By analyzing the spectral energy distribution of thermal dust emission at that location, we show that there are warm (~100K) and cool (~40K) SN dust components and that the latter is responsible for the observed E(J-H). We investigate the possible grain species and size of each component and find that the warm SN dust needs to be silicate grains such as $MgSiO_3$, $Mg_2SiO_4$, and $SiO_2$, whereas the cool dust could be either small (${\leq}0.01{\mu}m$) Fe or large (${\geq}0.01{\mu}m$) Si grains. We suggest that the warm and cool dust components in Cassiopeia A represent grain species produced in diffuse SN ejecta and in dense ejecta clumps, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.3D
• /
• pp.239-245
• /
• 2012

The necessity of professional construction management has been increased as a construction project is getting larger, more complex and specialized. Thus, the CM market has steadily expanded since 1996 in Korea. Despite the external expanding of the CM market, experts claim that domestic CM regulations and infrastructures should be revised. Therefore, this paper developed a causal map which consists of elements vitalizing CM market. Then, the simulation model using NUMBER (Normalized Unit Modeling by Elementary Relationships) to predict the size of the CM market is established. As a result, in the case of more regulation related CM, the quantity of CM projects could not reach of construction supervision until 2020. This paper can be used as a baseline providing a prospection of the change of CM market according to causal relation between the improvement as well as the base of revitalization research of CM market based on non-institutional factors change.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.54 no.3
• /
• pp.224-230
• /
• 2018

Squid is one of the important fisheries resources in Korea. Therefore, squid has been designated and managed as a target species of total allowable catch (TAC) since 2007, but the catch amount is gradually decreasing. The analysis was conducted to identify the change of relative fishing power index to develop the vessel and gear technology that may have improved the fishing efficiency of the offshore squid jigging fishery from 1960s to 2010s. Gross tonnage per fishing vessel increased with the increase in size until 1990, but then gradually decreased to 41.0 tons in 2000 and 37.1 tons in 2010. The illuminating power (energy consumption) by fishing lamps increased to 180 kW in 2005 and stabilized to 120 kW in 2015. Jigging machine started to be supplied to fishing vessels from the early 1970s, and fish finders began to be supplied in the early 1980s and gradually increased. Therefore, the relative fishing power index in the offshore squid jigging fishery increased from 1.0 in 1980 to 1.1 in 1990, to 3.5 in 2000 and to 2.5 in 2010, but the increment rate slowed down gradually. The results are expected to contribute to reasonable fisheries stock management.

• Current Photovoltaic Research
• /
• v.2 no.4
• /
• pp.182-188
• /
• 2014

For the dissemination of new and renewable energy, Korean government introduced a renewable portfolio standard (RPS) scheme in 2012 after terminating feed-in tariff (FIT) scheme that was introduced in 2004. With the RPS scheme, 64.7% of its own goal (95.7% in PV and 63.3% in non-PV) was achieved in 2012 and 67.2% of that (94.9% in PV, 65% in non-PV) was achieved in 2013. The deployment of PV systems met the goal very well and that of non-PV did not. Recently, Korean government revised the target year of supplying 10% electricity from new and renewable energy from 2022 to 2024 and released a couple of measures on PV area. Recent studies showed that the bankability of a project plays a key role for PV dissemination. Therefore, the dissemination should be assessed from the point of bankability under the RPS scheme and a little adjustment is necessary to achieve the goal. Especially, installing a small size PV (<100 kwp) system needs a minimum REC price or a FIT scheme. In non-PV area, permission process is a common bottleneck and the related regulation should be eased. In addition, to achieve the long term goal, an implementing scenario has to be prepared. Currently, the portion of the waste-gas energy originated from fossil fuel is too large among the new and renewable energy sources and the portion should be lowered or eliminated in the 10% of electricity supply goal. Seoul Metropolitan Government (SMG) has its own FIT scheme for PV dissemination from 2014 SMG and revised the PV tariff from 50 to 100 won/kwh in effective of 2015. It is worth to spread the other provinces.

• Journal of Satellite, Information and Communications
• /
• v.10 no.3
• /
• pp.26-31
• /
• 2015

This paper deals with a size-reduced Ku-band waveguide limiter. Basically, it passes the signal from 16.125 GHz through 16.375 GHz, but when excessively high power is injected to the input port, it should change to a bandstop filter. Furthermore, it is required to change to bring attenuation by more than 20 dB and 50 dB over a narrow band and the entire passband, respectively. Therefore, in order to meet this requirement, a limiting device is implemented with multiple PIN-diode posts that enable the limiter to be the bandpass filter and stopband one at the off and on states of the PIN-diode switch, respectively. So, the design goes through the equivalent circuit modelling and the geometry is realized in the accurate electromagnetic analysis CAD tool. Finally, the result is discussed to shed light on whether it complies with the aforementioned requirement.

• Journal of Satellite, Information and Communications
• /
• v.10 no.3
• /
• pp.1-5
• /
• 2015

Recently, RF energy harvesting technology is a promising technology for small-size IoT(Internet of Things) devices such as sensor to resolve battery scarcity problem. When applied to existing cognitive radio networks, this technology can be expected to increase network throughput through the increase of cognitive user's operating time. This paper proposes a optimal channel-selection policy for RF energy harvesting CR networks model where cognitive users in harvesting zone harvest ambient RF energy from transmission by nearby active primary users and the others in non-harvesting zone choose the channel and communicate with their receiver. We consider that primary users and secondary users are distributed as Poisson point processes and contact with their intended receivers at fixed distances. Finally we can derive the optimal frame duration, transmission power and density of secondary user from the proposed model that can maximize the secondary users's throughput under the given several conditions and suggest future directions of research.