• Journal of Advanced Marine Engineering and Technology
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• 제36권2호
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• pp.286-293
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• 2012

본 연구에서는 설계유량 $16m^3/h$에서 설계효율 90%와 설계양정 20m의 성능을 보이며, 3,500rpm 고정회전수로 작동하는 원심펌프 임펠러를 대상으로 단상류 유동해석을 수행하였다. 임펠러는 A.J. Stepanoff 경험식에 근거로 설계되었다. 단상류 해석의 경우, 설계유량에서 88.8%와 19.4m의 효율과 양정 결과를 보여주었고, 그 결과는 설계값과 상당히 일치하였다. 다상류 해석은 다양한 NPSH 조건하에서 수행되었으며, NPSH가 8.79m 일 때, 블레이드 부압면 근처에서 캐비테이션개시가 관찰되었다. 본 연구에서 설계된 임펠러의 필요흡입헤드는 대략 6.5m이며, 이 값 이상의 입구압력조건하에서 원심펌프는 작동되어야 할 것으로 판단된다.

• Earthquakes and Structures
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• 제10권5호
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• pp.1143-1179
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• 2016

Offshore wind turbines are considered as a fundamental part to develop substantial, alternative energy sources. In this highly flexible structures, monopiles are usually used as support foundations. Since the monopiles are large diameter (3.5 to 7 m) deep foundations, they result in extremely stiff short monopiles where the slenderness (length to diameter) may range between 5 and 10. Consequently, their elastic deformation patterns under lateral loading differ from those of small diameter monopiles usually employed for supporting structures in offshore oil and gas industry. For this reason, design recommendations (API and DNV) are not appropriate for designing foundations for offshore wind turbine structures as they have been established on the basis of full-scale load tests on long, slender and flexible piles. Furthermore, as these facilities are very sensitive to rotations and dynamic changes in the soil-pile system, the accurate prediction of monopile head displacement and rotation constitutes a design criterion of paramount importance. In this paper, the Fourier Series Aided Finite Element Method (FSAFEM) is employed for the determination of static impedance functions of monopiles for OWT subjected to horizontal force and/or to an overturning moment, where a non-homogeneous soil profile has been considered. On the basis of an extensive parametric study, and in order to address the problem of head stiffness of short monopiles, approximate analytical formulae are obtained for lateral stiffness $K_L$, rotational stiffness $K_R$ and cross coupling stiffness $K_{LR}$ for both rough and smooth interfaces. Theses expressions which depend only on the values of the monopile slenderness $L/D_p$ rather than the relative soil/monopile rigidity $E_p/E_s$ usually found in the offshore platforms designing codes (DNV code for example) have been incorporated in the expressions of the OWT natural frequency of four wind farm sites. Excellent agreement has been found between the computed and the measured natural frequencies.

• Journal of Trauma and Injury
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• 제22권2호
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• pp.134-141
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• 2009

Purpose: Patients with traumatic brain injury (TBI) were referred from other hospitals for further management. In addition, patients routinely underwent computed tomography examinations of the head (HCT) in the referral hospitals. The purpose of this study was to evaluate retrospectively the utility of routine HCT scans according to the severity of TBI. Methods: Patients with TBI referred to our hospital between December 2005 and July 2008 were included in this study. We investigated HCT findings, indications for repeat HCT examinations (routine versus a neurological change), and neurosurgical interventions. The head injury severity was divided into three categories according to the Glasgow Coma Scale (GCS) score, including mild, moderate, and severe TBI. The use of neurosurgical interventions between patients who underwent routine HCT scans and patients who underwent HCT scans for a neurological change were compared according to the severity of TBI. Results: A total of 81 patients met the entry criteria for this study. Among these patients, 67%(n=54) of the patients underwent HCT scans on a routine basis, whereas 33%(n=27) of the patients underwent HCT scans for a neurological change. A total of 21 patients showed signs of a worsening condition on the HCT scans. Neurosurgical intervention was required for 23(28.4%) patients. For patients who underwent routine HCT examinations, no patient with mild TBI underwent a neurosurgical intervention. However, one patient with moderate TBI and three(13%) patients with severe TBI underwent neurosurgical interventions. The kappa index, the level of agreement for HCT indications of intervention and referral reasons for intervention, was 0.65 for high hierarchy hospitals and 0.06 for low hierarchy hospitals. Conclusion: Routine serial HCT examinations in the referred hospitals would be useful for patients with severe head injury and for patients from low hierarchy hospitals where no emergency physicians or neurosurgeons are available.

• 대한두경부종양학회지
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• 제24권1호
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• pp.9-14
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• 2008

The most important concern to do parotidectomy is correct identification of the facial nerve and preservation of the nerve function. Many descriptions for the localization and branching types of the facial nerve trunk have existed. During the parotid surgery, it is necessary to have knowledges about the incidence and prognostic aspect of a invasion of the facial nerve by the parotid tumors. The method of the dissection and the surgical extent of the parotid gland would be decided not only by the anatomic variation of the facial nerve. but also the size and location of the tumor. Invasion of the facial nerve in parotid malignancies is the most significant factors affecting the prognosis, so radical parotidectomy which consists of the total extirpation of the parotid gland in conjunction with resection of the facial nerve is often required for proper management. Radical parotidectomy is advocated for the surgical treatment of high grade malignancies and in selective recurrent benign tumors intimately involving the facial nerve. Unfortunately, the morphologic and functional deficits created by sacrificing the facial nerve can be emotionally and physically traumatizing to the patient. Therefore, when the facial nerve is sacrificed, immediate reconstruction of the facial nerve should be necessary. Immediate nerve repair with direct anastomosis of the resected nerve ends or placement of a cable nerve graft provides the better cosmetic and functional results. Surgical resection remains the mainstay of treatment for cancer of the parotid gland, and there is general agreement that facial nerve should not be sacrificed unless the tumor is adherent to, or surrounds the nerve. The following statement is described general principles of troublesome management of the facial nerve during surgery for parotid tumor.

• Clinical and Experimental Reproductive Medicine
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• 제46권2호
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• pp.60-66
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• 2019

Objective: To compare black rice (Oryza sativa L) extract with three different staining methods for human sperm head assessment. Methods: Semen samples were collected from 34 volunteers. Four smears of each ejaculate were prepared for staining using the rapid Papanicolaou (PAP) stain, SpermBlue, DipQuick, and black rice extract. The percentage of defective sperm heads (mean${\pm}$standard deviation) was compared. Results: Black glutinous rice extract, a natural dye, was used instead of hematoxylin to stain the nuclei of the sperm heads. The percentage of defective sperm heads showed a significant difference between black rice extract and DipQuick (p= 0.000). In contrast, black rice extract and rapid PAP showed no statistically significant difference (p= 0.974). A strong correlation (r = 0.761) was found between the findings obtained using rapid PAP and black rice extract. In contrast, a weak correlation (r = 0.248) was obtained between DipQuick and black rice extract for the percentage of defective sperm heads. Conclusion: The results showed good agreement and a strong correlation between the rapid PAP and black rice extract stains. The advantages of black rice extract as a novel substitute for hematoxylin for nuclear staining include ease of preparation, local availability, and favorable nuclear staining properties. Further studies could also focus on comparing staining techniques in clinical samples.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.137-144
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• 2021

Purpose: This study aimed to investigate the accuracy of head scatter factor (S_c) by applying a developed multi-leaf collimator (MLC) scatter source model for an unflattened photon beam. Methods: Sets of S_c values were measured for various jaw-defined square and rectangular fields and MLC-defined square fields for developing dual-source model (DSM) and MLC scatter model. A 6 MV unflattened photon beam has been used. Measurements were performed using a 0.125 cm³ cylindrical ionization chamber and a mini phantom. Then, the parameters of both models have been optimized, and S_c has been calculated. The DSM and MLC scatter models have been verified by comparing the calculated values to the three S_c set measurement values of the jaw-defined field and the two S_c set measurement values of MLC-defined fields used in the existing modeling, respectively. Results: For jaw-defined fields, the calculated S_c using the DSM was consistent with the measured S_c value. This demonstrates that the DSM was properly optimized and modeled for the measured values. For the MLC-defined fields, the accuracy between the calculated and measured S_c values with the addition of the MLC scatter source appeared to be high, but the only use of the DSM resulted in a significantly bigger differences. Conclusions: Both the DSM and MLC models could also be applied to an unflattened beam. When considering scattered radiation from the MLC by adding an MLC scatter source model, it showed a higher degree of agreement with the actual measured S_c value than when using only DSM in the same way as in previous studies.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1247-1254
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• 2004

In momentum exchange theory the loss models for the circulatory flow is critically important. But because of lack of loss model on the circulatory flow, analysis model on regenerative turbomachines is not available in the open literature. In the present study circulatory loss is evaluated by combining bend's losses. Through the comparison with the previous experimental data on linear pressure gradient, a combination factor is suggested in terms of the aspect ratio of a channel. Applying this factor to two kinds of regenerative blowers the predicted results are found to be in good agreement with the experimental data of the overall performance and the head distribution along the rotational direction. Especially, the comparison with the head distribution demonstrates the accuracy of hydraulic model and loss model suggested in the present study. And the comparison with the overall performance confirms the validness of physical models as well as loss models suggested in the present study.

• 한국음향학회지
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• 제24권2호
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• pp.111-116
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• 2005

본 연구는 주관적 음향평가를 통하여 콘서트 홀에서 선호되는 음향특성과 중요한 음향지표 조사에 그 목적이 있다. 호주의 두 콘서트 홀 (이하 Hall A와 Hall B로 가칭함)에서 더미헤드 (Dummy Head)로 녹음된 음악을 이용하여 음향평가를 위한 청감실험을 통해 실시하였다. 평가된 두 콘서트 홀의 음향선호도는 측정된 음향지표와의 상관도를 분석하여 실제 홀에서의 음향평가에 기여하는 음향지표를 조사하였다. 청감실험에서 피험자들은 Hall B가 Hall A에 비해 음향적으로 우수하다는 결과를 보여주었으며, Hall A의 낮은 음향선호도는 전문음악가와의 인터뷰조사결과와 유사하였다. 두 콘서트 홀의 음향평가에 가장 중요한 음향지표는 음압레벨로 밝혀졌다.

• 한국유체기계학회 논문집
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• 제14권5호
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• pp.12-17
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• 2011

The seawater lift pump system is responsible for maintaining the open canal level to provide the suction flow of circulating water pump at the set point. The objective of this paper is to design a 2-stage mixed flow pump (for seawater lifting) by inverse design method and to evaluate the overall performance and the local flow fields of the pump by using a commercial CFD code. Rotating speed of the impeller is 1,750 rpm with the flow rate of 2,700 $m^3$/h. Finite volume method with structured mesh and realized k-${\varepsilon}$ turbulent model is used to guaranty more accurate prediction of turbulent flow in the pump impeller. The numerical results such as static head, brake horse power and efficiency of the mixed flow pump are compared with the design data. The simulated results are good agreement with the design data less 3% error.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.162-169
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• 2009

This paper describes a study on dynamic characteristics analysis and dynamic compliance evaluation of a 5-axis multi-tasking machine tool of ram-head type. Structural dynamics analysis and evaluation are necessary to machine tool design and development to secure good machine tool performance against tough and harsh machining conditions. In this study, natural frequencies and corresponding vibration modes of the machine tool structure were analyzed by using both F.E.M. modal analysis and impulse hammer test. Furthermore, dynamic compliance of the machine tool was analyzed by using F.E.M. and also measured by using a hydraulic exciter test. Both the theoretical analysis and experimental test results showed good agreement with each other.