• 한국지반공학회논문집
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• 제19권4호
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• pp.145-153
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• 2003

공진주 실험은 탄성파 이론을 이용하여 흙의 동적 물성, 즉 전단변형률의 크기에 따른 전단탄성계수와 재료감쇠비를 측정하는 실험이다. 공진주 실험에 의한 시료의 동적물성의 측정은 공진주 실험 시스템의 동적 거동에 대한 이해를 전제로 한다. 공진주 실험의 시료 및 실험장치의 구성은 고정단-자유단 경계조건을 가지고 있는 연속보로 단순화할 수 있어서, Richart, Hall and Woods는 공진주 실험 시스템에 대한 파동방정식을 유도하였으나, 시료를 단순히 탄성으로 가정하였고 시료의 점성을 고려하지는 않았다. 그리고, Hardin은 파동방정식의 유도에서 시료의 점탄성을 고려하였으나, 시료의 전단탄성계수를 결정하기 위하여 시료의 점탄성을 가정하여야 하는 문제점을 가지고 있었다. 본 연구에서는 기존의 연구자들이 시도했던 공진주 실험 시스템에 대한 파동방정식을 새로운 측면에서 유도하였으며, 새로이 유도된 파동방정식의 해법을 제안하였다. 한편, 일반적으로 시스템에 대한 동적 거동을 이해하는 방법으로, 시스템의 운동방정식을 이용하는 방법이 있으나, 공진주 실험 시스템에 대한 동적 거동의 해석방법으로 이와 같은 운동방정식을 이용하는 해석방법을 연구한 경우는 거의 없었다. 운동방정식에 의한 해법은 시스템의 동적 증폭계수와 동적 응답에 대한 위상각을 구할수 있기 때문에 파동방정식에 대한 해법보다 더 많은 정보를 활용할 수 있는 장점이 있다. 따라서, 본 연구에서는 공진주 실험 시스템에 대한 보다 기본적이고 많은 정보를 도출하기 위하여, 공진주 실험 시스템에 대한 운동방정식을 유도하였으며, 이를 이용하여 공진주 실험자료를 해석하는 새로운 해석기법의 제안을 위한 근간을 마련하였다. 그리고, 공진주 실험 시스템에 대한 유한요소 해석을 수행하여, 본 연구에서 제안한 공진주 실험시스템의 이론적 모델링의 타당성과 합리성을 검증하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제25권6호
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• pp.861-868
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• 2012

During two years, four samples per year were collected in Vietnam from rice bran, cassava residue, brewer's grain, tofu residue, soybean meal, coconut cake, sweet potato vines and water spinach for chemical analysis and assessment of water holding capacity (WHC). The selected feedstuffs represent fibre-rich plant sources and agro-industry co-products commonly used in pig feeding in Vietnam. The content (g/kg DM) of crude protein (CP), ether extract (EE) and non-starch polysaccharides (NSP) varied between feedstuffs and ranged from 21 to 506 for CP, from 14 to 118 for EE and from 197 to 572 for NSP. Cassava residue had a high starch content of 563 g/kg DM, while sweet potato vines, water spinach, coconut cake and soybean meal had a high content of sugars (63-71 g/kg DM). The content of individual neutral sugars varied between feed ingredients, with the highest content of arabinose, galactose and glucose in tofu residue, the highest content of xylose in brewer's grain and the highest content of mannose in coconut cake. The content of uronic acid was high for cassava residue, tofu residue, sweet potato vines and water spinach (57-88 g/kg DM). The content of soluble non-cellulosic polysaccharides (S-NCP) was positively correlated ($r^2$ = 0.82) to the WHC. The content (g/kg DM) of CP, NDF, neutral sugars, total NSP, total NCP, S-NCP and total dietary fibre in tofu residue, water spinach and coconut cake varied (p<0.05) between years. In conclusion, diet formulation to pigs can be improved if the variation in chemical composition of the fibre fraction and in WHC between potential feed ingredients is taken into account.

• 대한두경부종양학회지
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• 제17권1호
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• pp.26-31
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• 2001

Background: Primary malignant lymphoma of the parotid gland is a rare disease and defined as any malignant lymphoma that first manifests in the parotid gland, regardless of the subsequent stage of the diseases, whether it arises in the parenchyma or intraglandular lymph nodes. This study was performed to review the clinicopathological characteristics of primary parotid lymphoma and identify its optimal treatment modality. Materials and Methods: Six cases with parotid mass as first presentation of malignant lymphoma between 1988 and 2000, were studied on the basis of clinical features, diagnostic tools, treatment modality, treatment outcomes, and clinical stage by Ann Arbor Criteria. All were microscopically reevaluated and classified by NCI working formulation. Results: All patients were males and mean age was 36.7 years (2-66 years). Rapid growing non-tender mass was presented in all the cases and cervical lymphnodes were palpated in 4 cases. However, there was not any evidence of concurrent autoimmune disease such as Sjogren's syndrom or Rheumatoid arthritis. One case was confirmed by surgical specimen after superficial parotidectomy, 2 by excisional biopsy, and 3 by incisional biopsy. The stage of disease by NCI working formulation was IE in 1 patient, IIE in 4 and IV in 1. All were classified into non-Hodgkin' lymphoma, of which there were 5 cases of B-cell type and 1 case of T-cell type. There were 3 diffuse large cell lymphomas, 1 Burkitt lymphoma, 1 MALT lymphoma and 1 T-lymphoblastic lymphoma. Three cases were treated by chemotherapy only, 2 by radiotherapy only and 1 by chemo-radiotherapy. One case with Burkitt lymphoma was died from the disease and one case was lost to follow-up. The others are alive with no evidence of recurrence. Conclusions: Although primary parotid lymphoma is rare and difficult to diagnose preoperatively, most were detected in early stage and showed a relatively good response to the chemotherapy or radiotherapy like other types of extranodal malignant lymphoma.

• 대한가정학회지
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• 제19권2호
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• pp.123-133
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• 1981

If we are to define that the traditional costume is a comprehensive expression of the culture, thoughts, and arts of a country, it is needless to say that the traditional costume would have always reflected the social and cultural aspects of the times. In order words, the cultural contemplation of a certain people at some point the history is only possible when we observe the distintive features of the costume worn by the people of respective times. Although the Korean people had the native costume of its own from the times of the Ancient Choson to the Three Kingdoms of Koguryo, Paekche, and Silla, the Chinese influence on Korean traditional costume became somewhat pronounced ever since the Silla strenghtened the political ties with the T'ang dynasty in China, and it came to a climax when the dual structure in Korean native costume, being compounded with the Chinese touch, continued to be prevailed from the era of the Unified Silla to the Koryo and throughout the succeeding Yi dynasty, thereby copying the typical aspects of Chinese pattern in clothing and dresses worn by the ruling classes, namely the goverment officials including the Kings. Therefore, it is our aim to study the pattern of Chinese influence on our traditional costume, as well as social and cultural aspects by way of contrasting and comparing our official outfit system, which had been developing in dualism since the era of the Unified Silla, with that of China, and to trace in part the Korean traditional costume. In comparing our traditional official outfit system with that of China, we have basically concentrated on the comparison of the official outfit systems during the periods of the Three Kingdoms, the Koryo, and The Yi dynasty with that of corresponding era of Chinese history, namely the dynasties of T'ang, Sung, and Ming, and followed the documentary records for the comparison. Koreans had fallen into the practice of worshipping the powerful in China and begun to adopt the culture and institutions of the T'ang dynasty since the founding of the Unified Silla. From this time forth, Korean people started to wear the clothes in Chinese style. The style of clothing during the period of the Koryo Kingdom was deeply influenced by that of the T'ang and Sung dynasties in China, and it was also under the influenced of the Yuan dynasty(dynasty established by the Mongols) at one time, because of the Koryo's subordinative position to the Yuan. At the close of the Koryo dynasty, the King Kongmin ordered the stoppage on the use of 'Ji-Joung', the name of an era for the Yuan dynasty, in May of the eighteenth year of his rule in order to have the royal authority recognized by a newly rising power dominating the Chinese continent, the Mind. Kind Kongmin presented a memorial, repaying a kindness to the Emperor T'aejo of the Ming dynasty in celebration of his enthronement and requested that the emperor choose an official outfit, thereby the Chinese influence being converted to that of the Ming. As a matter of course, the Chinese influence deepened all the more during the era of the Yi dynasty coupled with the forces of the toadyic ideology of worshipping the China, dominant current of the times, and the entire costume, from the imperial crown and robe to the official outfit system of government officials, such as official uniforms, ordinary clothes, sacrificial robes, and court dresses followed the Chinese style in their design. Koreans did not have the opportunity of developing the official outfit system on its own and they just wore the official outfit designated on separate occasions by the emperors of China, whenever the changes in dynasty occurred in the continent. Especially, the Chinese influence had greatly affected in leading our consciousness on the traditional costume to the consciousness of the class and authority. Judging from the results, Koreans had been attaching weight to the formulation of the traditional outfit system for the ruling classes in all respective times of the history and the formulation of the system was nothing more than the simple following of the Chinese system.

• 대한수학회논문집
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• 제39권1호
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• pp.187-199
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• 2024

In the present paper, following the pullback approach to Finsler geometry, we study intrinsically the C^v-reducible and generalized C^v-reducible Finsler spaces. Precisely, we introduce a coordinate-free formulation of these manifolds. Then, we prove that a Finsler manifold is C^v-reducible if and only if it is C-reducible and satisfies the 𝕋-condition. We study the generalized C^v-reducible Finsler manifold with a scalar π-form 𝔸. We show that a Finsler manifold (M, L) is generalized C^v-reducible with 𝔸 if and only if it is C-reducible and 𝕋 = 𝔸. Moreover, we prove that a Landsberg generalized C^v-reducible Finsler manifold with a scalar π-form 𝔸 is Berwaldian. Finally, we consider a special C^v-reducible Finsler manifold and conclude that a Finsler manifold is a special C^v-reducible if and only if it is special semi-C-reducible with vanishing 𝕋-tensor.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.65-69
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• 2018

Due to large in-field current carrying capacity and strong mechanical strength, a REBCO wire has been regarded as a viable high temperature superconductor (HTS) option for high field MRI and > 1 GHz (>23.5 T) NMR magnets. However, a REBCO magnet is well known to have an inherent problem of field inhomogeneity, so-called 'Screening Current induced magnetic Field (SCF)'. Recently, 'field shaking' and 'current overshoot operation' techniques have been successfully demonstrated to mitigate the SCF and enhance the field homogeneity by experiments. To investigate the effectiveness of current overshooting operation technique, a numerical simulation is conducted for a test REBCO magnet composed of a stack of double pancake coils using '2D edge-element magnetic field formulation' combined with 'domain homogenization' scheme. The simulation result demonstrates that an appropriate amount of current overshoot can negate the SCF. To verify the simulation results, current overshoot experiments are conducted for the REBCO magnet in liquid nitrogen. Experimental results also demonstrate the possible application of current overshoot technique to mitigate the SCF and enhance the field homogeneity.

• 대한본초학회지
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• 제38권2호
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• pp.9-16
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• 2023

Objectives : Many people use natural soap instead of commercially available bar type general soap for skin care. They tend to prefer cp (cold process) type soaps that go through a sufficient maturation process in formulation. The purpose of this study was to investigate the efficacy of PCPS (placenta cp soap). Methods : The researcher selected 36 subjects, 28 as the experimental group and 8 as the control group. I asked participants to wash their face twice a day in the morning and evening, and the period was set for 6 weeks. The researcher had the people who were selected as the control group use a commercially available foam cleanser, meanwhile the experimental group use PCPS. They performed a skin test before the start of the test, and the change status was continuously investigated after 2 weeks, 4 weeks, and 6 weeks after using the soap. Results : In the case of U zone oil and pores, there was a significant decrease and in the case of skin tone, there was a significant increase in the group of using PCPS. In T zone oil change, there was no significant effect in both the experimental group and the control group. Conclusion : In the case of PCPS, it is recommended to use it in the effect of reducing the size of pores and increasing skin tone, but it can reduce u-zone oil content.

• Steel and Composite Structures
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• 제47권5호
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• pp.569-585
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• 2023

This paper proposes an efficient approach for the structural topology optimization of bi-directional functionally graded structures by incorporating popular radial basis functions (RBFs) into an implicit level set (ILS) method. Compared to traditional element density-based methods, a level set (LS) description of material boundaries produces a smoother boundary description of the design. The paper develops RBF implicit modeling with multiquadric (MQ) splines, thin-plate spline (TPS), exponential spline (ES), and Gaussians (GS) to define the ILS function with high accuracy and smoothness. The optimization problem is formulated by considering RBF-based nodal densities as design variables and minimizing the compliance objective function. A LS-RBF optimization method is proposed to transform a Hamilton-Jacobi partial differential equation (PDE) into a system of coupled non-linear ordinary differential equations (ODEs) over the entire design domain using a collocation formulation of the method of lines design variables. The paper presents detailed mathematical expressions for BiDFG beams topology optimization with two different material models: continuum functionally graded (CFG) and mechanical functionally graded (MFG). Several numerical examples are presented to verify the method's efficiency, reliability, and success in accuracy, convergence speed, and insensitivity to initial designs in the topology optimization of two-dimensional (2D) structures. Overall, the paper presents a novel and efficient approach to topology optimization that can handle bi-directional functionally graded structures with complex geometries.

• Earthquakes and Structures
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• 제26권5호
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• pp.349-361
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• 2024

Excessive torsional behaviour is one of the major reasons for failure of buildings, as inferred from past earthquakes. Numerous seismic codes across the world specify a displacement-based or drift-based criterion for classifying buildings as torsionally irregular. In recent years, quite a few researchers have pointed out some of the inherent deficiencies associated with the current codal guidelines on torsional irregularity. This short communication paper aims to envisage the need for a revision of the displacement-based guidelines on torsional irregularity, and further highlight the appropriateness of a rotation-based criterion. A set of 6 reinforced concrete building models with asymmetric shear walls are analysed using ETABS v18.0.2, by varying the number of stories from 1 to 9, and the torsional irregularity coefficient of various stories is calculated using the displacement-based formula. Since rotation about the vertical axis is a direct indication of the twist experienced by a building, the calculated torsional irregularity coefficients of all stories are compared with the corresponding floor rotations. The conflicting results obtained for the torsional irregularity coefficients are projected through five categories, namely mismatch with floor rotations, inconsistency in trend, lack of clarity in incorporation of negative values, sensitivity to low values of displacement and error conceived in the mathematical formulation. The findings indicate that the irregularity coefficient does not accurately represent the torsional behaviour of buildings in a realistic sense. The Indian seismic code-based values of 1.2 and 1.4, which are used to characterize buildings as torsionally irregular are observed to be highly sensitive to the numerical values of displacements, rather than the actual degree of rotation. The study thus emphasizes the revision of current guidelines based on a more relevant rotation-based or eccentricity-based approach.

• Tribology and Lubricants
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• 제16권1호
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• pp.39-45
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• 2000

In this paper, the effects of shaft and bearing flexibilities are investigated for the accurate modeling of a shaft-bearing system supported by ball bearings. Generally, rolling bearings are modeled by simple rigid pin-joint in the mechanical design. However, they can no longer be modeled by ideal boundary conditions in the advanced applications because the rigid pin-joint model cannot satisfy the current trends of mechanical design decreasing mass and reducing volume. Consequently the flexible support model of ball bearing is investigated using the static analysis module developed by A .B. Jones and T. A. Harris. A simple two-bearing system, supported by two deep groove ball bearings and radially loaded on the shaft midway between the bearings, is utilized to validate the coupled model of shaft-bearing system. Numerical computations using the model indicate that the shaft span length, locating/floating bearing arrangements and applied bearing size are significant factors in determining the mechanical behaviors. The flexible support model of ball bearing can be escaped to over-estimate in the bearing fatigue life. The proposed simple design formulation obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft span length/shaft diameter (L/d).