• Informatization Policy
• /
• v.20 no.3
• /
• pp.3-17
• /
• 2013

As electronic marketplaces grow and a large number of consumers exchange their opinions on products and services on the Internet, many studies have been conducted in the area of online consumer reviews. This paper analyzes the research trend of the online consumer reviews by investigating those studies in an attempt to provide future research directions. Many researchers have focused on the effects of online reviews on consumer behaviors as well as the usefulness of the online reviews. In particular, review contents, characteristics of reviewers/consumers and features of products/services have been identified as influencing factors on the effects of the online consumer reviews. For the review contents, the number and the volume of the contents have increasing effects on the online reviews, while the direction (positive vs. negative) of the contents has resulted in conflicting effects of the review. The reputation and trustfulness of reviewers, consumers' prior knowledge on the products, consumers' product involvement, and types of the products were investigated as these factors influence the effectiveness of the online consumer reviews. Social media (such as Facebook and Twitter) nowadays play an important role to disseminate online reviews among consumers. Thus, it is necessary to study how social media influence the effects of online reviews on consumers. Since some firms abuse the online reviews for their own sakes, we recognize the necessity for empirical studies on the side effects of the online reviews.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.6
• /
• pp.578-586
• /
• 2005

Recently, due to the launch of digital broadcasting service, the demand of Flat Panel Display (FPD) is sharply rising. Among them, the PDP is expected to be one of the most promising digital displays of next generation because of its large screen size, high resolution, thinness and board field of view. Meanwhile, the PDP uses ADS (Address Display-period Separation) scheme which divide one subfield into address and sustaining period to express the grey scale of images. Since the output of sustaining power module Is mostly used for sustaining period, the load of the sustaining power module can be considered as a pulsating load. Due to this particular load condition, if the wide ZVS range of the power switches is not guaranteed, the hard switching causes large amount of switching loss and serious thermal problem in power module. In this paper, a high efficiency power conversion circuit for 60' PDP sustaining power module which achieves wide ZVS range with the help of additional ZVS tank is proposed. According to the various gating methods, the different operations of the proposed converter are presented. And, to confirm the properties of the proposed converter, an experimental prototype of 900W power converter is constructed md tested. As a result, more than $92\%$ of high efficiency is obtained at $10\%$ load condition, and the ZVS operation is achieved from full load to $10\%$ load condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.46-47
• /
• 2005

이번 연구는 $BCl_3/CF_4$ 플라즈마를 사용하여 반도체소자 제조 시 널리 이용되는 GaAs 계열반도체 중 대표적인 재료인 GaAs/AlGaAs 및 GaAs/InGaP 구조를 선택적으로 건식 식각한 후 분석한 것이다. 공정변수로는 ICP 소스파워를 0-500W, RIE 파워를 0-50W 그리고 $BCl_3/CF_4$ 가스 혼합비를 중점적으로 변화시켰다. $BCl_3$ 플라즈마만을 사용한 경우 (20$BCl_3$, 20W RIE power, 300W ICP source power, 7.5mTorr) 는 GaAs:AlGaAs의 선택비가 0.5:1 이었으며 이때 GaAs의 식각률은 ~2200${\AA}/min$ 이었으며 AlGaAs의 식각률은 ~4500${\AA}/min$ 이었다. 식각 후 표면의 RMS roughness은 < 2nm로 깨끗한 결과를 보여주었다. 15% $CF_4$ 가스가 혼합된 $17BCl_3/3CF_4$, 20W RIE power, 300W ICP source power, 7.5mTorr의 조건에서 3분 동안 공정한 결과 순수한 $BCl_3$ 플라즈마만을 사용한 경우보다 표면은 다소 거칠었지만 (RMS roughness: ~8.4) GaAs의 식각률 (~980nm/min)과 AlGaAs와 InGaP에 대한 GaAs의 선택도 (GaAs:AlGaAs=16:1, GaAs:InGaP=38:1)는 크게 증가하였다. 그리고 AlGaAs 및 InGaP의 경우 식각 시 나타난 휘발성이 낮은 식각 부산물 ($AlF_3:1300^{\circ}C$, $InF_3:1200^{\circ}C$)로 인하여 50nm/min 이하의 낮은 식각률을 보였고, 62.5%의 $CF_4$가 혼합된 $7.5BCl_3/12.5CF_4$플라즈마의 조건에서는 AlGaAs 및 InGaP에 대한 GaAs의 선택도가 각각 280:1, 250:1을 나타내었다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.2
• /
• pp.165-170
• /
• 2014

Shear horizontal (SH) waves propagate as a type of plate wave in a thin sheet. The dispersion characteristics of SH waves can be used for signal analysis. Therefore, SH-waves are useful for monitoring the structural health of a thin-sheet-structure. An electromagnetic acoustic transducer (EMAT), which is a non-contact ultrasonic transducer, can generate SH-waves easily by varying the shape and array of magnets and coils. Therefore, an EMAT can be applied to an automated ultrasonic testing system for structural health monitoring. When used as a sensor, however, the EMAT has a weakness in that electromagnetic interference (EMI) noise can occur easily in the automated system because of motors and electric devices. Alternatively, a fiber optic sensor works well in the same environment with EMI noise because it uses a light signal instead of an electric signal. In this paper, a fiber Fabry-P$\acute{e}$rot interferometer (FFPI) was proposed as a sensor to receive the SH-waves generated by an EMAT. A simple test was performed to verify the performance of the FFPI sensor. It is thus shown that the FFPI can receive SH-wave signals clearly.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.8-15
• /
• 2020

In the present paper, as a way of reducing heavyweight impact sounds, in particular, among floor impact sounds which have come to the forefront as a social issue recently, a floor joist slab is proposed that is expected to bring an effect of reducing heavyweight impact sounds through a shift in the natural frequency by installing a floor joist on a flat-type slab to increase the rigidity of the floor slab, differently from the existing method that increases the thickness of floor slab, and the heavyweight impact sound characteristics depending on the floor joist height and interval are interpretively analyzed. As a result of the analysis, though a trend is shown where the sound pressure level decreases as the slab thickness of floor joist increases, and as no difference is shown when thickness is above a certain value, it is thought that there is a threshold for the effect of an increase in floor thickness on blockage of heavyweight impact sounds. Also, as an increase in floor rigidity resulting from an increase in the floor joist height and a decrease in the interval does not lead to a consistent increase in the performance of blocking heavyweight impact sounds, it is thought that a different floor joist height and interval should be applied to each type of house to expect optimum performance of blocking heavyweight impact sounds, and an increase of 100mm in the floor joist height or a decrease of about 100mm in the interval is expected to bring an effect of reducing heavyweight impact sounds by about 1dB to 2dB.

• Journal of Korea Port Economic Association
• /
• v.34 no.4
• /
• pp.17-38
• /
• 2018

The purpose of this study is to establish shipping companies' selection factors related to a classification society and to explore the relative importance of each factor using the analytical hierarchy process(AHP) technique. Insufficient research exists on the hierarchial structure of shipping companies' factors of selecting a classification society. The factors are identified and classified into two tiers of major and detailed factors, by referring to the related industrial linkages, prior research related to the determinants, and the process and service delivery of the classification society's activities. The empirical analysis of this study is based on the relative importance of determinants when selecting a classification society, and experts engaged with shipping companies were surveyed using questionnaires. The results of the AHP methodology on the main factors of shipping companies in selecting a classification society are as follows. The relative importance of the main factors was 0.373 for technical and survey services, 0.284 for recognized organizations(RO) functions, 0.177 for cost and 0.167 for market(related industry) expectations. The relative importance of the detailed factors is 0.144 for the ability to respond to a port state control(PSC) inspection, 0.143 for technical services, 0.090 for the requirements of financial institutions/ shippers/shipyards, 0.087 for class maintenance costs, 0.086 for the survey network, 0.085 for surveyor competency, 0.072 for cooperation with IMO and government authorities, 0.067 for recognition for RO, 0.058 for the business power of the classification society, 0.052 for the initial inspection costs, 0.040 for reputation and trustworthiness, 0.038 for the costs related to the class, and 0.037 for connections to related industries.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.1
• /
• pp.37-44
• /
• 2019

A bond-based peridynamic model has been reported dynamic fracture characteristic of brittle materials through a simple constitutive model. In the model, each bond is assumed to be a simple spring operating independently. As a result, this simple bond interaction modeling restricts the material behavior having a fixed Poisson's ratio of 1/4 and not being capable of expressing shear deformation. We consider a state-based peridynamics as a generalized peridynamic model. Constitutive models in the state-based peridynamics are corresponding to those in continuum theory. In state-based peridynamics, thus, the response of a material particle depends collectively on deformation of all bonds connected to other particles. So, a state-based peridynamic theory can represent the volume and shear changes of the material. In this paper, the perfect plasticity is considered to express plastic deformation of material by the state-based peridynamic constitutive model with perfect plastic flow rule. The elastic-plastic behavior of the material is verified through the stress-strain curves of the flat plate example. Furthermore, we simulate the high-speed impact on 3D granite model with a nonlocal contact modeling. It is observed that the damage patterns obtained by peridynamics are similar to experimental observations.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.1
• /
• pp.91-101
• /
• 2019

Recently, small-scale excavation like ground cavity restoration and buried pipe replacement works are being carried out in urban area, in order to improve living convenience. This paper describes experiment results on the ground reinforcement method that can reduce the buried pipe damage, when the differential settlement occurred due to poor compaction of ground below the buried pipe. Plate load tests were conducted to evaluate a reinforcement effect of ground using concrete mat and expansion mat in the ground below the buried pipe. The results showed that the stress reduction ratio by concrete mat and expansion mat according to the surcharge load was about 46%~48% and 39%~42%, respectively. Therefore, the differential settlement of the buried pipe and the ground deformation below the buried pipes were reduced by the reinforcement effect of the concrete mat and expansion mat. This means that it is possible to prevent a buried pipe damage due to underground cavity and ground subsidence, if concrete mat and expansion mat are reinforced in the ground below the buried pipe or on the ground between the buried pipes.

• Journal of Food Hygiene and Safety
• /
• v.34 no.2
• /
• pp.178-182
• /
• 2019

This study investigated the antibacterial effects of BioZone atmospheric plasma (AP) against Bacillus cereus (F4810/72) and Staphylococcus aureus (ATCC 6538) as the major foodborne bacteria on the surface of dried filefish (Stephanolepis cirrhifer) fillets. The fillets were experimentally contaminated with 7-8 log CFU/mL of B. cereus or S. aureus using a spot inoculation method. Bacterial counts were measured by standard plate method on tryptic soy agar, and were significantly reduced with the increase in the treatment time (1, 3, 5 or 20 min) of AP on the fillets (p < 0.05). The reductions of the pathogens by AP treatment ranged from 0.9 to 2.93 logCFU/g for B. cereus and from 1.04 to 2.55 logCFU/g for S. aureus. A reduction of >1-logCFU/g for B. cereus and S. aureus was observed on the fillets treated with AP for >3 min. The differences in color on the Hunter scale (L=light vs. dark, a=red vs. green, b=yellow vs. blue) of the fillets were not significantly different between the nontreated (control) and AP-treated fillets (p>0.05). This study suggested that 3 min of AP could be effective in reducing >90% of the bacteria without causing any concomitant changes in the color of the fillets.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.40 no.5
• /
• pp.421-428
• /
• 2022

The earthwork is a core process of all constructions, and compaction measurement of earthwork play an important role in improving productivity. The analog tests such as Plate Bearing Test and Sand-cone occupy current compaction measurement techniques. Due to advanced 4th Industrial Revolution, research on analog tests combined smart construction technology are actively conducted. DCPT (Dynamic Cone penetration Test), simpler and faster than conventional tests, has recently on rise. However, it is also an analog that measures data manually and has several disadvantages such as history management and data verification. The IoT-based DCPT system developed in this study combines digital wire sensors, mobile phones, and Bluetooth with conventional DCPT. Compare to conventional test methods, IoT-based DCPT has advantages such as performance time, single-person measurement, low cost, mobile-based management, and real-time data verification. In addition, a test bed was built to verify IoT-based DCPT. The test bed was built under similar conditions to the actual earthworks site through roller equipment. DCPT data obtained from 322 stations. As a result, IoT-based DCPT showed good performance, and the test bed was also showed stable results as the compaction was carried out.