• Macromolecular Research
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• v.10 no.2
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• pp.85-90
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• 2002

Poly (ethylene oxide)/polylatide/poly(ethylene oxide) (PEO/PL/PEO) tri-block copolymers, which each block is connected by ester bond, were synthesized by coupling reaction of PL with PEO in the presence of pyridine. PL/PEO/PL tri-block copolymer was synthesized by ring opening polymerization of L-lactide initiated by PEO in the presence of stannous octoate. Degradation behavior of the copolymers was investigated in a pH 7.4 phosphate buffer saline (PBS) at 37$\pm$1 $^{\circ}C$. Gel permeation chromatography (GPC) and $^1$H-nuclear magnetic resonance (NMR) were used to monitor the change of mass loss, molecular weight and composition of copolymers. In hydrolytic degradation, the PEO/PL/PEO tri-block copolymer with high PEO contents affected the increase of its mass loss, and resulted in the decrease of its molecular weight as well as PEO composition. However, when PL/PEO/PL and PEO/PL/PEO tri-block copolymers had similar PEO contents, PEO/PL/PEO decreased faster in molecular weight and PEO composition than PL/PEO/PL.

• Journal of Korea Port Economic Association
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• v.18 no.2
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• pp.65-90
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• 2002

Despite the importance and necessity, the 3PL has not been activated to date. Among many views, customers claim that logistics service provider(LSP) are not prepared or capable of offering satisfactory 3PL services, while LSP emphasize the lack of mutual trust, closed corporate culture of the customer and excessive demand for reducing the costs. With this keeping in mind, it surveyed difference of perception between users and providers of 3PL services in terms of the actual status of using 3PL services, the degree of satisfaction and key factors for selecting 3PL provider through the questionnaire. As shown in this study, 43.3％ of the respondents outsourced logistics services. However, Most company outsourced only inland transportation (49.5％) which is a simple and limited scope of 3PL services, but it also indicated that the percentage of users have ranged was less then 10% in outsourcing their whole logistics sector to 3PL provider and employing other logistics functions. Among respondents, a majority of the service provider stated that they offered satisfactory cost-saving to the customers, while users felt that the degree of satisfaction for using 3PL services was evaluated as at an average level and they more highly regarded the strong partnership of their 3PL provider rather than the saving of cost and improvement of customer's services. Moreover, in contrast to the 3PL providers which regard the most important factor for selecting 3PL service provider is the logistics cost quoted, users of 3PL services felt that the quality of services was more significant than the reduction of cost, and this tendency for selecting 3PL providers was shown in more advanced countries. While users of 3PL services indicated that the main reason for not using 3PL services was to avoid disclosing information of their business and it costs much for employing 3PL providers than doing themselves, 3PL providers thought it was due to reluctancy of opening information and resistance from the logistics division engaged in logistics activities concerned. Accordingly, providers and users of 3PL services should trust each other and prepare plan to activate 3PL services under the collaborative relationships as soon as possible.

• Microbiology and Biotechnology Letters
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• v.25 no.6
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• pp.571-579
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• 1997

For the overproduction of pectate lyase (PL), the recombinant plasmid pl2BS fl which has strong promoter from alkali-tolerent Bacillus sp. YA-14 was used. In order to overexpress the pectate lyase by the action of overlapping strong promoter in pl2BS$\Delta$fl, 1.6 kb of PL gene was inserted into pl2BS$\Delta$fl to form pl2BS$\delta$f1-PL and the enzyme was expressed. But decreased expression efficiency of the PL gene was observed and it was due to the presence of the transcription terminator region on the upstream of the PL gene. The transcription terminator of the PL gene in pl2BS$\delta$f1-PL was removed and the resulting plasmid p12BS$\Delta$fl$\Delta$PL was formed. Bacillus subtilis 207-25 harboring the recombinant plasmid, p12BS$\Delta$fl$\Delta$PL, revealed increased expression efficiency with chloramphenicol induction when cat-86 was used as a reporter gene.

• Current Optics and Photonics
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• v.5 no.2
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• pp.173-179
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• 2021

The electroluminescence (EL) intensities of GaN-based light-emitting diodes (LEDs) are estimated based on their photoluminescence (PL) properties. The PL intensity obtained under open-circuit conditions is divided into two parts: the PL intensity under a forward bias lower than the optical turn-on voltage, and the difference between the PL intensities under open-circuit conditions and under forward bias. The luminescence induced by photoexcitation under a constant forward bias lower than the optical turn-on voltage is primarily the PL from the excited area of the LED. In contrast the intensity difference, obtained by subtracting the PL intensity under the forward bias from that under open-circuit conditions, contains the EL induced by the photocarriers generated during photoexcitation. In addition, a reverse photocurrent is generated during photoexcitation under constant forward bias across the LED, and can be correlated with the PL-intensity difference. The relationship between the photocurrent and PL-intensity difference matches well the relationship between the injection current and EL intensity of LEDs. The ratio between the photocurrent generated under a bias and the short-circuit current is related to the ratio between the PL-intensity difference and the PL intensity under open-circuit conditions. A relational expression consisting of the ratios, short-circuit current, and PL under open-circuit conditions is proposed to estimate the EL intensity.

• Current Optics and Photonics
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• v.3 no.2
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• pp.164-171
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• 2019

Photoluminescence (PL) properties of GaN-based light-emitting diodes (LEDs) were analyzed to study the effects of carrier leakage on the luminescence properties at room temperature. The electrical leakage and PL properties were compared for LEDs showing leakages at forward bias and an LED with an intentional leakage path formed by connecting a parallel resistance of various values. The leakages at the forward bias, which could be observed from the current-voltage characteristics, resulted in an increase in the excitation laser power density for the maximum PL efficiency (ratio of PL intensity to excitation power) as well as a reduction in the PL intensity. The effect of carrier leakages on PL properties was similar to the change in PL properties owing to a reduction of the photovoltage by a reverse current since the direction of the carrier movement under photoexcitation is identical to that of the reverse current. Valid relations between PL properties and electrical properties were observed as the PL properties deteriorated with an increase in the carrier leakage. The results imply that the PL properties of LED chips can be an indicator of the electrical properties of LEDs.

• Journal of the Korea Safety Management & Science
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• v.9 no.5
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• pp.87-95
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• 2007

Logistics creates a boom in accordance with the recent new technique's development along with the recent RFID/USN of ubiquitous computing technique. The wave of 4PL(Fourth Party Logistics) that added the strategic consulting based on new IT techniques to logistics outsourcing through existing 3PL service with is a great issue. Moreover, the customer enterprises which contained manufacturers and distributors need the one stop service, therefore a method for effectively dealing with global logistics' environment changes is needed. Above all, a development of the 4PL system with RFID is very urgent. We developed the RFID u-4PL system progressed more than the present system, in which we applied many international standards. Finally, we constructed the web service based on Web 2.0 because of important condition of 4PL.

• Journal of Korea Port Economic Association
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• v.21 no.3
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• pp.259-270
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• 2005

This study applies the Analytic Hierarchy Process (AHP) to evaluate service quality of Third-Party Logistics (3PL) providers. For this, 3PL service quality is conceptualized and measured using SERVQUAL's five dimensions such as tangibles, reliability, responsiveness, assurance and empathy. Then, the AHP method is applied to determining the relative importance of five service quality dimensions and eventually selecting the best 3PL provider. Finally, this study conducts an empirical case study on four companies providing 3PL services in Korea to demonstrate the basic idea suggested in this paper. The results obtained in the present study indicate that responsiveness to customers is the most important factor perceived by 3PL customers and 3PL C is the best 3PL provider according to the overall service quality scores. In contrast to some previous researches, this study examined issues of service quality from the perspective of 3PL customers as opposed to the perspective of 3PL providers. In order for this study to be more complete, future research is needed in establishing a set of metrics to quantify each dimension of 3PL service quality proposed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.309-312
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• 2008

In this paper, we investigated electric safety manager's PL recognition and accident occurrence of electric power facilities(power cable, transformer, circuit breaker) in electric installation for private use. The target of questionnaire survey is 450 electric installations for private use, 154 responded the questionnaire among these and it occupied 35.8%. Most of receiving voltage were 22.900kV. The questionnaire survey says that 58% of electric safety manager knew well about PL contents and 42% of them did not recognize about PL contents, About the PL application of electrical facility accidents, 82.4% of them must applied PL law, 5.8% of them did not need the PL law. Reason of PL application occupied 64% for stability of electrical facility and product, 19% for prevention of same accident. The accident of transformer occupied most and the power cable accident were much next. The questionnaire survey results, electric safety managers are interested in PL content. thev expected necessity of PL application about electrical accident strongly.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
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• 2002.05a
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• pp.31-36
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• 2002

Product Liability(PL) is a legal policy to deal with global competition by improving domestic industrial competitive power and to reduce the cost of defect products. The purpose of this paper is to address the state of the art solutions to dispute on PL, in reality of a frequent occurrence of global product exchange focussing on product safety that is one of the most important functions of PL and to improve solution of the product safety and reliability responsive to PL. To minimize PL exposure, manufacturers should reflect comprehensive product safety and reliability concepts in establishing PL prevention policies. PL prevention policies are composed of administration system, product safety management system, and total quality management system in respect of prevention, safety, and defence.

• Proceedings of the Safety Management and Science Conference
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• 2008.11a
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• pp.579-582
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• 2008

The wave of 4PL added to strategic consulting based on new IT techniques, for example RFID, with logistics outsourcing through existing 3PL service is a great issue. It is also worthy of notice that EPCglobal network strengthen the role of 4PL. In conclusion, the 4PL system based on EPCglobal network will result in a good success, so it will raise a prestige of air cargo in Korea to a higher position. This study deals with the new logistics system, air cargo logistics system based on u-4PL system, RFID and EPCglobal network, that will bring many advantages.