• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.535-542
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• 2011

The performance of a plate heat exchanger for using liquid solution in the absorption chiller-heater was analyzed. The model was developed by using the various performance prediction correlations. The performance characteristics of the plate heat exchanger with the mass flow rate ratio was verified by using experimental data. To investigate performance of plate heat exchanger with geometry variables, the chevron angle, corrugated wave length, and corrugation depth were changed. As a result, the capacity of Kim and Martin correlation models was similar with the experimental data, and the capacity difference was less than 2%. Besides, the pressure drop of Marin correlation model showed a similar variation with experimental data, and the difference of pressure drop was less than 1.5 kPa.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.583-591
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• 2012

Plate heat exchangers have been widely used in many industrial applications because of their compactness and high efficiency. Even though plate heat exchangers have been investigated extensively, studies on the effects of geometric parameters other than the chevron angle are very limited in the open literature. In this study, the effects of the chevron angle, corrugation length, corrugation depth, and the number of plates on the heat transfer and pressure drop characteristics of plate heat exchangers were investigated experimentally. Based on the experimental results, empirical correlations were proposed. More than 95% of the predictions made based on the correlations had relative deviations of less than ${\pm}10%$ when compared with the measured data.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.116-120
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• 2003

To study the trafficability on soft and cohesive benthic terrain, a tracked vehicle model($670mm(L){\times}750mm(B_c)$) is designed and tested. The pitch and chevron angle of grouser, weight and center of gravity of vehicle, and drawbar pull force are chosen as experimental variables. Slip, sinkage and inclined angle of vehicle are picked as performance values. Strength of soil is considered as noise factor. A preliminary straight-line motion test is performed. Then, DOE(Design of Experiment) is discussed for further research.

• Animal Systematics, Evolution and Diversity
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• v.38 no.1
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• pp.46-49
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• 2022

This study newly records a deep-sea coral, Flabellum (Ulocyathus) deludens from Korea. The specimens were collected by trawling at a depth of 100 m off Jejudo Island in 2019. The newly recorded species is described and compared with the other similar consubgeneric species in detail based on morphological characteristics, including corallum size, calicular diameter, calicular edge, face angle, edge angle, and septal arrangement. Flabellum(Ulocyathus) deludens is characterized by its solitary, highly compressed, wedge-shaped corallite with a small cylindrical pedicel, radiating inverse chevron-patterned lateral stripes on thecal faces, highly jagged calicular edges, and hexameral septal arrangement in five cycles. As a result of this study, five species in the family Flabellidae have been recorded from Korea.

• Journal of Korean Foot and Ankle Society
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• v.23 no.4
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• pp.166-172
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• 2019

Purpose: This study evaluated the clinical and radiological results after reinforcement of the weakened medial joint capsule using Internal Brace (Arthrex) for treating severe hallux valgus. Materials and Methods: This study reviewed 56 cases of 50 patients that were followed-up postoperatively for at least 12 months, from September 2017 until August 2018. An extended distal chevron osteotomy combined with a distal soft-tissue release was performed by a single surgeon to treat severe hallux valgus. Internal Brace was applied in 12 cases (group A) who had weakened medial joint capsules, and capsulorrhaphy was performed in 44 cases (group B), and these two groups were compared postoperatively for the clinical and radiological results. The postoperative complications were also investigated. Results: No significant differences at 1-year follow-up on the Manchester-Oxford Foot Questionnaire and the patients' satisfaction scores were found between the two groups (p=0.905 and p=0.668, respectively). For the radiology, the changes of the values between before surgery and at 1-year follow-up according to the group showed no significant differences in the hallux valgus angle, intermetatarsal angle, and the hallux interphalangeal angle (p=0.986, p=0.516, p=0.754, respectively). Recurrence of hallux valgus was reported in two cases in group A, and in three cases in group B. Transfer metatarsalgia occurred in 4 cases in group B. Conclusion: Based on these results, we recommend the capsule reinforcing technique using Internal Brace as a successful operative option for treating a weakened medial capsule in patients with severe hallux valgus.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.213-219
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• 2008

Microscale heat transfer and microfluidics have become increasingly important to overcome some very complex engineering challenges. The use of very small passages to gain heat transfer enhancement is a well documented method for achieving high heat flux dissipation. In this study, the performance evaluation of micro-channel plated heat exchangers with straight, V-shaped and Y-shaped channels has been experimentally carried out under the counterflow condition. It is found that the mixing effect in V-shaped and Y-shaped channels enhances the heat transfer but pressure drop does not increase seriously in the range of low Reynolds number.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.5-10
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• 2009

본 연구에서는 판형열교환기를 적용한 청수제조장치의 성능에 대하여 연구를 수행하였다. 판형열교환기는 자체의 높은 열전달 성능과 컴펙트한 장점으로 하여 산업에서 점차 널리 사용되고 있다. 또한 사용, 유지보수가 다른 종류의 열교환기에 비하여 편리하여 유연성 있게 사용할 수 있다. 본 실험에서는 세브론 각도가 60도인 전열판을 사용하였으며 이젝터의 작동으로 열교환기를 장착하고 있는 탱크내부에 진공압력을 유지함으로서 내부유체가 $51^{\circ}C{\sim}57^{\circ}C$에서 증발현상이 발생하는 것을 확인하였다. 또한 수치해석적 방법을 통하여 복잡하며 좁은 세브론전열판으로 이루어진 유로내의 유동특성을 파악할 수 있었다.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.229-234
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• 2007

Microscale heat transfer and microfluidics have become increasingly important to overcome some very complex engineering challenges. The use of very small passages to gain heat transfer enhancement is a well documented method for achieving high heat flux dissipation. As the passage size is decreased, the heat transfer performance increases but the pressure drop increases sharply when the passage size is reduced. In this study, the performance evaluation of micro plated heat exchangers under the counter flows with straight, V-shaped and Y-shaped channel are carried out.

• Journal of Korean Foot and Ankle Society
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• v.21 no.4
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• pp.135-138
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• 2017

Purpose: The purpose of this study is to determine the correlation between the correction loss of hallux valgus angle and the severity of valgus angle of the second toe. Materials and Methods: We selected 312 cases from 268 surgical patients with hallux valgus deformity receiving distal chevron osteotomy. For a radiological evaluation, we analyzed the changes in the hallux valgus angles, first to second intermetatarsal angles, and valgus angle of the second toe post index operations. All patients were women; the mean age was 46 years. The mean follow-up period was 17 months. Results: The mean hallux valgus angle was $33.6^{\circ}$ preoperatively (range, $25.7^{\circ}{\sim}44.8^{\circ}$), $13.1^{\circ}$ (range, $8.4^{\circ}{\sim}16.4^{\circ}$) after 4 weeks of postoperative period, and $17.1^{\circ}$ (range, $9.4^{\circ}{\sim}28.5^{\circ}$) at their final follow-up. The mean valgus angle of the second toe was $8.4^{\circ}$ preoperatively (range, $2.0^{\circ}{\sim}25.8^{\circ}$) and $8.3^{\circ}$ (range, $1.7^{\circ}{\sim}24.9^{\circ}$) at the final follow-up. Preoperatively, there was a positive correlation between the valgus angle of the second toe and hallux valgus angle (r=0.747, p=0.001). The correction loss of hallux valgus angle had a significant correlation with the severity of valgus angle of the second toe (r=0.802, p=0.001). Conclusion: The existence of the second toe valgus deformity may present itself as a cause of correction loss of hallux valgus angle. The preoperative measurement of the second toe valgus angle may be a good predictor of correction loss; therefore, thorough preoperative warning on the possibility of correction loss should be conducted to maximize patient satisfaction after the procedure.

• Journal of Korean Foot and Ankle Society
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• v.25 no.4
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• pp.157-164
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• 2021

Purpose: This study aimed to report the current trends in the management of the hallux valgus (HV) deformity over the last few decades through a survey of the Korean Foot and Ankle Society (KFAS) members. Materials and Methods: A web-based questionnaire containing 34 questions was sent to all KFAS members in September 2021. The questions were mainly related to the preferred techniques and clinical experience in correction in patients with an HV deformity. Answers with a prevalence of ≥50% of respondents were considered a tendency. Results: One hundred and nine (19.8%) of the 550 members responded to the survey. The most common symptom for determining surgical treatment was bunion pain (68.8%), and different surgical techniques were selected according to the following radiological parameters: HV angle 30 to 40 degrees and intermetatarsal angle 15 to 20 degrees. The two procedures most preferred by the respondents were distal chevron osteotomy (55.0%), and proximal chevron osteotomy (21.1%). In an average of 71.6% of respondents, Arkin osteotomy was performed simultaneously during HV surgery. HV accompanied by an overriding deformity of the second toe was most often addressed with a combination of second metatarsal osteotomy and soft tissue rebalancing procedure (35.8%). After HV surgery, the recurrence rate of HV deformity was found to be 12.2% on average and the surgeons who had performed minimally invasive surgery (MIS) for HV comprised 34.9% of the total respondents. Conclusion: This study provides updated information on the current trends in the management of the HV deformity in Korea. Both consensus and variation in the approach to patients with HV were identified by this survey study. Although MIS for HV has increased, it appears the consensus for selecting this method has not yet been established.