• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.65-76
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• 2015

Objective : The purpose of this study was to analyse the differences in core stability and muscle balance of the pilates Teaser motion according to the surfaces and skills. Methods : There were 10 subjects in this study with 5 being skilled and 5 that were not skilled. The independent variables were surfaces (high elastic & aluminum) and skills (skilled & unskilled). Dependent variables were core stability and muscle balance. Core stability was measured by Force Platform (9872, Switzerland), 3D Imagery (IBS-2000, EXYMA) was used to understand the muscle balance. In order to do the Teaser movement subjects had to lay flat on their back and then lean forward as much as possible and hold the position for 10 seconds. Afterwards, they would lay back down again. A camera (MHS-PM5K, SONY) was used to make 4 phases (take off, recoil forward, holding, recoil backward) during the teaser exercise to analyze movement. In this study quantitative and qualitative analysis was used. For the statistical analysis, 2X2 ANOVA was used to analyze the differences in movement time, X,Y,Z maximum force, center of pressure and angles according to different phases. 2X3 ANOVA was used to analyze the differences in muscle balance via SPSS 18.0. Results : Soft. Elastic mat had a longer holding time, lower Fx/ Fy/ Fz, shorter Fx trajectory, larger angle and shorter gaps in muscle balance than a hard surface in skilled subjects. This was because the mat can help to recruit and then sustain core fine muscles during holding time in the Teaser movement.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.67-73
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• 2015

This is a basic research for improving soft magnetic property of Fe based nano crystalline alloy powder core. The main study is done around characteristics of permeability, core loss, and DC bias depending on amount of insulation coating agent and particle size. First, $Fe_{73.5}Si_{13.5}B_9Nb_3Cu_1$ amorphous alloy ribbon was fabricated by using the planar flow casting (PFC) device. Then, heat treatment and ball milling were done to obtain alloy powder. The amount of polyether imide (PEI) added to it was varied by 0.5, 1.0, 2.0, 2.5 wt% to have compression molding into $16ton/cm^2$. After going through crystalline heat treatment, the made toroidal nano crystalline powder core ($OD12.7mm^*ID7.62mm^*H4.75mm$) had smaller permeability as amount of insulation coating agent decreases. However, it was found out that core loss and DC bias characteristics have been improved. The reason for this results were expected to be because green density of power core decreases as amorphous alloy powder particles become smaller as amount of alloy powder insulation coating agent increases, it was determined that 1 wt% of insulation coating agent is appropriate. Also, for powder core made based on alloy powder size with amount of insulation coating agent fixed at 1 wt%, effective permeability and core loss were outstanding as particle size became bigger. However, characteristics of DC bias became worse as applied DC field increases. This is expected to be due to insulation effect, residual pores, or molding density of powder core resulting from thickness of coating on surface of alloy powder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.382-385
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• 2003

In this paper, the solenoid for high-voltage circuit breaker which is composed of bobbin, solenoid coil, stationary core and plunger was studied. The solenoid is made of a soft magnetic iron bar with a large number of coil windings. when an electric current passes through this, this stationary core becomes the strong magnet used for hydraulic and pneumatic valve of a solenoid operated valve. For the performance evaluation of the solenoid for high-voltage circuit breaker, electromagnetic characteristics and dynamic characteristics were analyzed. And, the parameters which is related to performance improvement were investigated.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.2
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• pp.88-97
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• 1984

The combustion process and the performance of a diesel engine are considerably affected by the characteristics of fuel spray. It is known that the spray of swirl nozzle for diesel engine injector of small orifice ratio becomes soft spray that has no core, therefore its penetration, one of the characteristics of spray becomes werse inspite of its good dispersion. In this paper, the spray characteristics of variously designed swirl nozzle for diesel injector were investigated by the photographic method. The nozzles, used in this experiment, vary in the diameter of swirl chambers and orifice ratio. From the results of the study, the sprays of this type nozzle of optimum swirl chamber and orifice ratio show that penetration decreased slightly but dispersion and spray volume increased remarcably, compared with unswirled single hole nozzle of the same size. It was suggested as a reason for the results, that the spray of this type swirl nozzle is similar to hard spray, therefore the core of the spray sustains good penetration considerably.

• The korean journal of orthodontics
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• v.45 no.5
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• pp.268-272
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• 2015

Clear thermoplastic retainers have been widely used in daily orthodontics; however, they have inherent limitations associated with thermoplastic polymer materials such as dimensional instability, low strength, and poor wear resistance. To solve these problems, we developed a new type of clear orthodontic retainer that incorporates multi-layer hybrid materials. It consists of three layers; an outer polyethylenterephthalate glycol modified (PETG) hard-type polymer, a middle thermoplastic polyurethane (TPU) soft-type polymer, and an inner reinforced resin core. The resin core improves wear resistance and mechanical strength, which prevent unwanted distortion of the bucco-palatal wall of the retainer. The TPU layer absorbs impact and the PETG layer has good formability, optical qualities, fatigue resistance, and dimensional stability, which contributes to increased support from the mandibular dentition, and helps maintain the archform. This new type of vacuum-formed retainer showed improved mechanical strength and rate of water absorption.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1167-1168
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• 2006

In this study, the pure iron powder was treated with aqueous phosphoric acid to produce phosphate insulating layer on the surface. After drying the powder, it was compacted in a mold with a diameter of 20mm at 800MPa. The powder compacts were then heat treated at $500^{\circ}C$ for 1 hour. The results showed that insulated iron powder was obtained with uniform phosphate layer by chemical reaction. With increased amount of phosphate layer, the core loss and density of compacts were decreased. It was also found that the addition of ethyl alcohol during insulating reaction resulted in improved core loss value.

• Journal of Powder Materials
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• v.12 no.1
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• pp.24-29
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• 2005

Nano Fe-6.5wt%Si powders have been synthesized by mechano-chemical process (MCP) for an application of soft magnetic core. Owing to hard and brittle characteristics of Fe-6.5Si nano powders having large surface area, it is very difficult to reach high density more than 70% of theoretical density (~7.4 g/$cm_3$) by cold compaction. To overcome such problem a magnetic pulsed compaction (MPC), which is one of dynamic compaction techniques, was applied. The green density was achieved about 78% (~5.8 g/$cm_3$) by MPC at room temperature.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1442-1443
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• 2006

본 논문에서는 분말 연자성체에 플라즈마를 이용하였을 때 특성 개선에 관한 연구이다. 기존의 압분 방식은 낮은 강도를 갖는 단점 때문에 신뢰성에 문제가 있어서, 직접적인 모터분야에 연자성체(SMC)를 적용하는데 큰 문제점 이였다. 그러나 본 논문에서 제안하는 SPS(Spark Plasma sintering)공법을 적용한 모터 코어 제조 방법은 플라즈마를 이용하여 분말의 표면에서만 접촉이 일어나게 하는 소결 방식으로, 내부재질의 특성변화 없이 표면의 절연층끼리만 접촉되게 하여 자기적 특성의 손상없이 기계적인 강도를 높일 수 있었다. 실제적으로 기존의 압분체(Hoganass550+윤활제(KE))의 경우 파단강도가 700Mpa정도였으나 SPS를 적용시 1200Mpa까지 증가 되었다. 이러한 SPS 공법을 통해 연자성체(SMC)재질의 모터 Core 분야 적용하는 데 생기는 문제점을 해결하고자 하였다.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.139.1-139.1
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• 2008

• Educational Technology International
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• v.10 no.1
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• pp.107-135
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• 2009

The purpose of this paper is to review a variety of challenges facing the Human Performance Technology (HPT) in supporting knowledge workers' performance, and to explore possible HPT models for knowledge workers. The first section of this paper investigates the core attributes and major models of HPT as a foundation. While HPT has a lot of strengths in terms of systemic, systematic, methodologically eclectic, evidence based, and results oriented approaches, some pitfalls - which could be detected if these principles were mindlessly applied to problem areas - are explored. The second section presents some considerations such as analysis, intervention design, and leadership that HP technologists need to take in order to make HPT a better field of practice for knowledge workers. The author also suggests a tentative diagnostic model and a process model for knowledge workers, core principles of which are based on systems thinking, in particular Senge's the fifth discipline and Checkland's soft systems methodology. The importance of formative evaluations to improve these models is noted as a conclusion.