• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.1029-1036
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• 2012

Push-pull-type copolymers - low-band-gap copolymers of electron-rich fused-ring units (such as cyclopentadithiophene; CPDT) and electron-deficient units (such as benzothiadiazole; BT) - are promising donor materials for organic solar cells. Following a design principles proposed in our previous study, we investigate the electronic structure of a series of new CPDTBT derivatives with various electron-withdrawing groups using the time-dependent density functional theory and predict their power conversion efficiency from a newlydeveloped protocol using the Scharber diagram. Significantly improved efficiencies are expected for derivatives with carbonyl [C=O], carbonothioyl [C=S], dicyano [$C(CN)_2$] and dicyanomethylene [C=$C(CN)_2$] groups, but these polymers with no long alkyl side chain attached to them are likely to be insoluble in most organic solvents and inapplicable to low-cost solution processes. We thus devise several approaches to attach alkyl side chains to these polymers while keeping their high efficiencies.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.571-585
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• 2022

As a vital component of power grids, long-span transmission tower-line systems are vulnerable to wind load excitation due to their high flexibility and low structural damping. Therefore, it is essential to reduce wind-induced responses of tower-line coupling systems to ensure their safe and reliable operation. To this end, a shape memory alloy-bidirectional tuned mass damper (SMA-BTMD) is proposed in this study to reduce wind-induced vibrations of long-span transmission tower-line systems. A 1220 m Songhua River long-span transmission system is selected as the primary structure and modeled using ANSYS software. The vibration suppression performance of an optimized SMA-BTMD attached to the transmission tower is evaluated and compared with the effects of a conventional bidirectional tuned mass damper. Furthermore, the impacts of frequency ratios and SMA composition on the vibration reduction performance of the SMA-BTMD are evaluated. The results show that the SMA-BTMD provides superior vibration control of the long-span transmission tower-line system. In addition, changes in frequency ratios and SMA composition have a substantial impact on the vibration suppression effects of the SMA-BTMD. This research can provide a reference for the practical engineering application of the SMA-BTMD developed in this study.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.226-231
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• 2008

The heat transfer characteristics of a solar high-temperature receiver with heat pipes was investigated by numerical simulation. The concentration ratio of the solar receiver ranges 1000 and the concentrated heat is required to be transported to a certain distance for specific applications. This study deals with internal geometry variation of a solar receiver incorporating high-temperature heat pipe. The isothermal characteristics in the receiver section is of major concern. The diameter of the solar thermal receiver was 120 mm and the length was 400 mm. The angle of receiver end wall was varied between $0^{\circ}$ and $45^{\circ}$. The wall thickness of the heat pipe channel was 4mm and 48 axial channels of the same dimensions were attached to the outer wall of the receiver with even spacing in the circumferential direction. The channels are changed to high-temperature sodium heat pipes. Commercial softwares were employed to deal with the radiative heat transfer inside the receiver cavity and the conduction heat transfer along the channels. The numerical results are compared and analyzed from the view Point of high-temperature solar receiver.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.527-537
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• 2004

Consequence-Based Engineering (CBE) is a new paradigm proposed by the Mid-America Earthquake Center (MAE) to guide evaluation and rehabilitation of building structures and networks in areas of low probability - high consequence earthquakes such as the central region of the U.S. The principal objective of CBE is to minimize consequences by prescribing appropriate intervention procedures for a broad range of structures and systems, in consultation with key decision makers. One possible intervention option for rehabilitating unreinforced masonry (URM) buildings, widely used for essential facilities in Mid-America, is passive energy dissipation (PED). After the CBE process is described, its application in the rehabilitation of vulnerable URM building construction in Mid-America is illustrated through the use of PED devices attached to flexible timber floor diaphragms. It is shown that PED's can be applied to URM buildings in situations where floor diaphragm flexibility can be controlled to reduce both out-of-plane and in-plane wall responses and damage. Reductions as high as 48% in roof displacement and acceleration can be achieved as demonstrated in studies reported below.

• Journal of Hydrogen and New Energy
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• v.20 no.4
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• pp.274-282
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• 2009

Diaphragm compressor is widely used for hydrogen compression because it achieves high gas pressure without gas contamination. Diaphragm deflecting in the cavity with high pressure formed by an oil compression is the most important component in the compressor. Therefore, it is necessary to obtain deflection degree of diaphragm to predict the damage point of diaphragm. The objective of this study is to estimate the diaphragm's damage point through diaphragm deflection test by implementing with strain gauges attached on several radial points. Without gas compression, strain sum of each points varied as similarly as the variation of the pressure with respect to time. And while the motor speed was slower than 400rpm, the strain near the rim was larger than that of the center. When motor speed, however, was over 500rpm, strain became similar to that of the center and the rim. With gas compression, it was shown that the variation of the strain sum was delayed against that of the pressure and the strain near the rim was much higher than that of the center.

• Child Health Nursing Research
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• v.8 no.3
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• pp.334-343
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• 2002

This study was aimed at primarily to develop a tool to evaluate sexuality education and secondarily to test effectiveness through application of developed evaluation tools in elementary school. The results from this study were summarized below: 1. On the basis of targeting the lower grades (1st- 3th year) and the higher grades (4th-6th year) elementary school students' sexuality education guidebooks published by Korea Ministry of Education & Human Resources Development, 71 preliminary items targeting the lower grades, 90 preliminary items targeting the higher grades were developed. 2. Through the validity test about the contents of the preliminary items three times, the items were regulated to 65 items targeting the lower grads and 57 items targeting the higher grades. And then, the preliminary items were re-regulated to 40 items separately. Then, pre-test which targeting each 30 students was enforced. 3.Finally, the evaluation tools for sexuality education that consisted of 40 items targeting the lower grades and the higher grades were developed. 4. eliability test of the developed tools, sexuality education evaluation tools showed alpha coefficient of internal consistency were 0.8355 (for the use of the lower grades) and 0.8881 (for the use of the higher grades). 5. o apply the developed sexuality education evaluation tools, 10-times sexuality education were carried out class unit and pre-post test were done using same questionnaire, which contains developed tool, there were significant difference in low grade (t=16.548, p=0.000), high grade (t=14.773, p=0.000). The results of this study suggest that the evaluation tool for sexuality education in elementary school may be a useful tool with a high degree of reliability and validity. In this sense, the evaluation tool for sexuality education developed by this study can be effectively utilized in Korea elementary schools.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.69-74
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• 2016

A new wave-piercing-type high-speed planing boat without a chine was developed, and its basic performance was investigated in a model test, including the resistance, trim, and sinkage. The maximum speed of the developed ship was 35 knots. The hull form was developed by combining a VSV (very slender vessel) and TH (transonic hull), which have large deadrise angles at the bow. The main dimensions were estimated by a statistical approach using actual ship data. The effect of a side fin attached at the stern near the water line was investigated from a resistance point of view. It was found that the developed hull form showed the possibility of a new concept for a high-speed planing hull without a chine, and the side fin played an important role in increasing the resistance performance by controlling the trim and sinkage in the high-speed range.

• Journal of Sensor Science and Technology
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• v.33 no.5
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• pp.384-390
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• 2024

Conventional vibration-measurement methods used for vibration testing typically employ accelerometers, which offer the significant advantage of accurately measuring vibrations at specific positions. However, they can only measure one point at a time as simultaneously measurements of multiple points can be economically disadvantageous. This study aims to overcome these limitations by analyzing the vibration outputs of accelerometers attached to a product and those obtained through image processing. The analysis involved assessing the measurement uncertainties and verifying the low-frequency vibration testing according to KS standards. The results validated and confirmed the reliability of the proposed camera-based image-processing vibration-measurement method, which exhibited a notable vibration-detection performance and measurement errors within 5% compared to accelerometers for low-frequency vibrations. This method has the potential for application across various vibration-response and durability evaluations. Future research should focus on expanding it to high-frequency vibration testing using high-speed cameras and further enhancing image-based vibration-analysis techniques.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.9 no.2
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• pp.103-106
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• 2013

The lower labial frenum attached to the free gingival margin can promote local tension, resulting in tissue ischemia, promoting the development of gingival recession, as well as complicating oral hygiene, resulting in chronic inflammation. In this case, early diagnosis and surgical treatment is recommended. This is the case about surgical treatment of heavy mandibular labial frenum in pre-school child with a history of syndactyly surgery. A 5-year-old girl visited the clinic with the chief complaint of high labial frenum of the mandible. Hyperplastic lower labial frenum was attached to the free gingival margin on the primary mandibular lateral incisor area. After fifteen month follow-up, right after the eruption of the permanent lower right lateral incisor, 6 years old patient received lower labial frenectomy to prevent periodontal diseases in permanent teeth and to reestablish normal anatomic characteristics. After 2 years of follow-ups, there were no marked complications.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.2
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• pp.132-141
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• 2019

Foreign body (FB) ingestion of children is a common pediatric emergency requiring medical attention. Pediatric emergency physicians and gastroenterologists often encounter nervous and distressed situations, because of children presenting with this condition in the common clinical practice. When determining the appropriate timing and indications for intervention, physicians should consider multiple patient- and FB-related factors. The utilization of a flexible endoscopy is considered safe and effective to use in these cases, with a high success rate, for the effective extraction of FBs from the gastrointestinal tract of a child. Additionally, a Foley catheter and a magnet-attached Levin tube have been used for decades in the case of FB removal. Although their use has decreased significantly in recent times, these instruments continue to be used for several indications. Using a Foley catheter for this purpose does not require special training and does not necessarily require sedation of the patient or fluoroscopy, which serve as advantages of utilizing this method for foreign object retrieval. An ingested magnet or iron-containing FB can be retrieved using a magnet-attached tube, and can be effective to retrieve an object from any section of the upper gastrointestinal tract that can be reached. Simple and inexpensive devices such as Foley catheters and magnetattached tubes can be used in emergencies such as with the esophageal impaction of disk batteries if endoscopy cannot be performed immediately (e.g., in rural areas and/or in patients presenting at midnight in a facility, especially in those without access to endoscopes or emergency services, or in any situation that warrants urgent removal of a foreign object).