• 한국유체기계학회 논문집
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• 제3권4호
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• pp.38-43
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• 2000

Recently, KARI(Korea Aerospace Research Institute, Korea) and CIAM(Central Institute of Aviation Motors, Russia) have made an effort in developing a centrifugal compressor for a small gas turbine engine as part of a collaboration program. This compressor has been designed as a sub-component for an axial-centrifugal compression system for a small turbo-shaft engine aiming adiabatic efficiency higher than 0.81. The geometrical design requirement imposes restrictions to have high inlet hub-to-tip ratio and inlet swirl flow. In this study, the compressor has been designed using the generalized experimental data established from those compressors having pressure ratio of 3.7 to 5. From this generalized empirical correlation, desirable values of design parameters could be obtained. Subsequently, quasi-3D and 3D viscous flow analyses have been performed to ensure the adopted methodology. It is expected that the centrifugal compressor provides total pressure ratio of 4.89, corrected mass flow-rate of 1.64kg/sec, and adiabatic efficiency of 0.815 with inlet hub-to-tip ratio of 0.641. These relatively high total pressure ratio and inlet hub-to-tip ratio are the main distinctive features in this design. Besides, one of the main features of this centrifugal compressor is the adoption of a double-row bladed diffuser to effectively decelerate the transonic flow leaving the impeller. The compressor has been manufactured and will be tested in the near future.

• Biomolecules & Therapeutics
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• 제24권5호
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• pp.489-494
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• 2016

Neuropathic pain (NPP) is the main culprit among chronic pains affecting the normal life of patients. Procaine is a frequently-used local anesthesia with multiple efficacies in various diseases. However, its role in modulating NPP has not been reported yet. This study aims at uncovering the role of procaine in NPP. Rats were pretreated with procaine by intrathecal injection. Then NPP rat model was induced by sciatic nerve chronic compression injury (CCI) and behavior tests were performed to analyze the pain behaviors upon mechanical, thermal and cold stimulations. Spinal expression of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) was detected by qRT-PCR and western blot. JAK2 was also overexpressed in procaine treated model rats for behavior tests. Results showed that procaine pretreatment improved the pain behaviors of model rats upon mechanical, thermal and cold stimulations, with the best effect occurring on the $15^{th}$ day post model construction (p<0.05). Procaine also inhibited JAK2 and STAT3 expression in both mRNA (p<0.05) and protein levels. Overexpression of JAK2 increased STAT3 level and reversed the improvement effects of procaine in pain behaviors (p<0.01). These findings indicate that procaine is capable of attenuating NPP, suggesting procaine is a potential therapeutic strategy for treating NPP. Its role may be associated with the inhibition on JAK2/STAT3 signaling.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.221-230
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• 2019

In this paper, shear behavior of non-persistent joint surrounded in concrete and gypsum layers has been investigated using experimental test and numerical simulation. Two types of mixture were prepared for this study. The first type consists of water and gypsum that were mixed with a ratio of water/gypsum of 0.6. The second type of mixture, water, sand and cement were mixed with a ratio of 27%, 33% and 40% by weight. Shear behavior of a non-persistent joint embedded in these specimens is studied. Physical models consisting of two edge concrete layers with dimensions of 160 mm by 130 mm by 60 mm and one internal gypsum layer with the dimension of 16 mm by 13 mm by 6 mm were made. Two horizontal edge joints were embedded in concrete beams and one angled joint was created in gypsum layer. Several analyses with joints with angles of $0^{\circ}$, $30^{\circ}$, and $60^{\circ}$ degree were conducted. The central fault places in 3 different positions. Along the edge joints, 1.5 cm vertically far from the edge joint face and 3 cm vertically far from the edge joint face. All samples were tested in compression using a universal loading machine and the shear load was induced because of the specimen geometry. Concurrent with the experiments, the extended finite element method (XFEM) was employed to analyze the fracture processes occurring in a non-persistent joint embedded in concrete and gypsum layers using Abaqus, a finite element software platform. The failure pattern of non-persistent cracks (faults) was found to be affected mostly by the central crack and its configuration and the shear strength was found to be related to the failure pattern. Comparison between experimental and corresponding numerical results showed a great agreement. XFEM was found as a capable tool for investigating the fracturing mechanism of rock specimens with non-persistent joint.

• Geomechanics and Engineering
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• 제16권3호
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• pp.273-284
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• 2018

A detailed understanding of the mechanical behaviors for crushed coal rocks after grouting is a key for construction in the broken zones of mining engineering. In this research, experiments of grouting into the crushed coal rock using independently developed test equipment for solving the problem of sampling of crushed coal rocks have been carried out. The application of uniaxial compression was used to approximately simulate the ground stress in real engineering. In combination with the analysis of crack evolution and failure modes for the grouted specimens, the influences of different crushed degrees of coal rock (CDCR) and solidified grout strength (SGS) on the mechanical behavior of grouted specimens under uniaxial compression were investigated. The research demonstrated that first, the UCS of grouted specimens decreased with the decrease in the CDCR at constant SGS (except for the SGS of 12.3 MPa). However, the UCS of grouted specimens for constant CDCR increased when the SGS increased; optimum solidification strengths for grouts between 19.3 and 23.0 MPa were obtained. The elastic moduli of the grouted specimens with different CDCR generally increased with increasing SGS, and the peak axial strain showed a slightly nonlinear decrease with increasing SGS. The supporting effect of the skeleton structure produced by the solidified grouts was increasingly obvious with increasing CDCR and SGS. The possible evolution of internal cracks for the grouted specimens was classified into three stages: (1) cracks initiating along the interfaces between the coal blocks and solidified grouts; (2) cracks initiating and propagating in coal blocks; and (3) cracks continually propagating successively in the interfaces, the coal blocks, and the solidified grouts near the coal blocks. Finally, after the propagation and coalescence of internal cracks through the entire specimens, there were two main failure modes for the failed grouted specimens. These modes included the inclined shear failure occurring in the more crushed coal rock and the splitting failure occurring in the less crushed coal rock. Both modes were different from the single failure mode along the fissure for the fractured coal rock after grouting solidification. However, compared to the brittle failure of intact coal rock, grouting into the different crushed degree coal rocks resulted in ductile deformation after the peak strength for the grouted specimens was attained.

• 전자공학회논문지CI
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• 제48권5호
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• pp.88-98
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• 2011

최근 대용량의 지리정보시스템(geographic information system, GIS) DB 보안 중요성이 부각됨에 따라 GIS 네트워크 보안 및 데이터 암호화 기법에 대해 많은 연구가 진행되어 왔다. 그러나 이와 같은 기법들은 GIS 벡터맵 데이터에 대한 원천적인 불법 복제 및 유통에 취약하다. 본 논문에서는 GIS 벡터맵 데이터의 불법 복제 방지 및 권한제어를 위하여 GIS 벡터맵 압축영역 상에서 레이어 단위의 선택적 암호화 기법을 제안한다. 제안한 기법에서는 벡터공간 상에서 벡터맵 압축 과정에서 생성되는 최소부호단위(minimum coding attribute, MCA)의 중점좌표와 방향 파라미터들에 대한 선택적 암호화를 각각 수행한다. 첫 번째 선택적 암호화에서는 MCA 레코드의 중점좌표 위치를 임의치환 함으로써 위치 암호화를 수행한다. 두 번째 선택적 암호화에서는 각 레코드 내의 좌표값들에 대한 방향 정보를 암호화함으로써 지형의 형태를 변화시키는 방향성 암호화를 수행한다. 실험 결과로부터 제안한 벡터맵 데이터 암호화 기법이 낮은 계산복잡도와 대용량 벡터맵 데이터를 효과적으로 암호화 할 수 있음을 확인하였으며, 또한 제안 기법이 AES, DES 등의 일반적인 데이터 암호화 기법을 사용하는 콘텐츠 암호화 기술들에서 발생되는 압축효율의 저하를 최소화할 수 있음을 확인하였다.

• Steel and Composite Structures
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• 제25권3호
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• pp.271-286
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• 2017

The use of Hollow Structural Sections (HSS) provides an alternative for steel buildings in seismic zones, with the advantage over WF columns that the HSS columns have similar resistance along both axes and enhanced performance under flexure, compression and torsion with respect to other columns sections. The HSS columns have shown satisfactory performance under seismic loads, such as observed in buildings with steel moment frames in the Honshu earthquake (2011). The purpose of this research is to propose a new moment connection, EP-HSS ("End-plate to Hollow Structural Section"), using a wide flange beam and HSS column where the end plate falls outside the range of prequalification established in the ANSI/AISC 358-10 Specification, as an alternative to the traditional configuration of steel moment frames established in current codes. The connection was researched through analytical, numerical (FEM), and experimental studies. The results showed that the EP-HSS allowed the development of inelastic action on the beam only, avoiding stress concentrations in the column and developing significant energy dissipation. The experiments followed the qualification protocols established in the ANSI/AISC 341-10 Specification satisfying the required performance for highly ductile connections in seismic zones, thereby ensuring satisfactory performance under seismic actions without brittle failure mechanisms.

• 대한정형도수물리치료학회지
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• 제1권1호
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• pp.75-83
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• 1995

Traction is the treatment of choice for a small nuclear protrusion. The nucleus is soft and can be influenced by suction. Traction provides a method of improving on recumbency-the only effective treatment before traction was devised. The intention is to achieve rapid reduction by distraction the joint surfaces mechanically-a positive purpose-instead of merely avoiding the compression of the upright posture by putting the patient to bed and leaving him there. Recumbency, usually successful in the end, wastes an endless amount of the patient's time and money. Traction carries the further advantage of enabling the patient to be up and about, attending to his bussiness, during treatment. Traction brings the joint surfaces much farther apart than just lying in bed, a greater centripetal force acts on the protruded part of the nucleus. Traction has three beneficial effects; 1. Suction : a sub-atmospheric pressure induces a centripetal effect on the contents. 2. Distraction : increases the distance between the articular edges. X -rays have shown an increase in width of the joint of 2.5 mm. 3. Ligamentous tightening : the posterior longitudinal ligament tightens which then exerts centipetal force on a central protrusion.

• Steel and Composite Structures
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• 제27권5호
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• pp.555-566
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• 2018

A 1/3 composite cylindrical shell with a central rectangular opening was axially compressed experimentally, and its critical buckling load and displacement, and strains were measured. A finite element model (FEM) of the shell with Hashin failure criteria was established to analyze its buckling and post-buckling behaviors by nonlinear Newton-Raphson method. The geometric imperfection sensitivity and the effect of side supported conditions of the shell were investigated. It was found that the Newton-Raphson method can be used to analyze the buckling and post-buckling behaviors of the shell. The shell is not sensitive to initial geometric imperfection. And the support design of the shell by side stiffeners is a good way to obtain the critical buckling load and simplify the experimental fixture.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.6-9
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• 2013

Korea Superconducting Tokamak Advanced Research (KSTAR) has a helium refrigeration system (HRS) with the cooling capacity of 9 kW at 4.5 K. Main cold components are composed of 300 tons of superconducting (SC) magnets, main cryostat thermal shields, and SC current feeder system. The HRS comprises six gas storage tanks, a liquid nitrogen tank, the room temperature compression sector, the cold box (C/B), the 1st stage helium distribution box (DB#1), the PLC base local control system interconnected to central control tower and so on. Between HRS and cold components, there's another distribution box (DB#2) nearby the KSTAR device. The entire KSTAR device was constructed in 2007 and has been operated since 2008. This paper will present the maintenance result of the KSTAR HRS during the campaign and discuss the operation record and maintenance history of the KSTAR HRS.

• Macromolecular Research
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• 제14권5호
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• pp.499-503
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• 2006

This report presents a new technical approach for evaluating the fiber orientation of composites using small-angle light scattering (SALS). Glass fiber (GF)/polypropylene (PP) composites with different fiber orientations were prepared by drawing compression-molded specimens. The drawn samples were remelted and then annealed at $150^{\circ}C$ in order to induce a crystalline structure on the fiber surface, and then underwent SALS analysis. The samples showed a combination of circular and streak patterns. The model calculations demonstrated that the number of nuclei on the fiber surface and the thickness of the transcrystalline layer affected the sharpness and intensity of the streak pattern. In addition, the azimuthal angle of the streak pattern was found to be dependent on the direction of the transcrystalline layer, which correlated with the fiber direction. This correlation suggests that the fiber orientation in the composites can be easily evaluated using SALS.