• 제어로봇시스템학회논문지
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• 제8권2호
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• pp.142-150
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• 2002

This paper presents a systematic method of the zigzag gait planning for quadruped walking robots. When a robot walks with a zigzag gait, its body is allowed to move from side to side, while the body movement is restricted along a moving direction in conventional continuous gaits. The zigzag movement of the body is effective to improve the gait stability margin. To plan a zigzag gait in a systematic way, the relationship between the center of gravity(COG) and the stability margin is firstly investigated. Then, new geometrical method is introduced to plan a sequence of the body movement which guarantees a maximum stability margin as well as monotonicity along a moving direction. Finally, an optimal swing-leg sequence is chosen for a given arbitrary configuration of the robot. To verify the proposed method, computer simulations have been performed for both cases of a periodic gait and a non-periodic gait.

• Advances in nano research
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• 제15권3호
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• pp.263-275
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• 2023

The electron transport properties of Y-type zigzag branched carbon nanotubes (CNTs) are of great significance for micro and nano carbon-based electronic devices and their interconnection. Based on the semi-empirical method combining tight-binding density functional theory and non-equilibrium Green's function, the electron transport properties between the branches of Y-type zigzag branched CNT are studied. The results show that the drain-source current of semiconducting Y-type zigzag branched CNT (8, 0)-(4, 0)-(4, 0) is cut-off and not affected by the gate voltage in a bias voltage range [-0.5 V, 0.5 V]. The current presents a nonlinear change in a bias voltage range [-1.5 V, -0.5 V] and [0.5 V, 1.5 V]. The tangent slope of the current-voltage curve can be changed by the gate voltage to realize the regulation of the current. The regulation effect under negative bias voltage is more significant. For the larger diameter semiconducting Y-type zigzag branched CNT (10, 0)-(5, 0)-(5, 0), only the value of drain-source current increases due to the larger diameter. For metallic Y-type zigzag branched CNT (12, 0)-(6, 0)-(6, 0), the drain-source current presents a linear change in a bias voltage range [-1.5 V, 1.5 V] and is symmetrical about (0, 0). The slope of current-voltage line can be changed by the gate voltage to realize the regulation of the current. For three kinds of Y-type zigzag branched CNT with different diameters and different conductivity, the current-voltage curve trend changes from decline to rise when the branch of drain-source is exchanged. The current regulation effect of semiconducting Y-type zigzag branched CNT under negative bias voltage is also more significant.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.1067-1072
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• 1996

Sensitivity analysis of the cylindrical zigzag cams under acceleration and centrifugal forces is performed. A Lagrangian method is used to determine the mechanism constant of zigzag track, And the equation of motion for cylindrical zigzag cam under rectangular pulse is derived by the governing equations of a single spring mass system. The ratio of the drive force tn resisting force is derived by angular acceleration, centrifugal force and setback force on the operation of the munition. The theoretical sensitivity curves for 3 models are analyzed. And experiments for 3 models are conducted to check safe and functional zone. Zigzag cam types can be satisfied all major design requirements for switch system of munition.

• Advances in nano research
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• 제3권1호
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• pp.29-37
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• 2015

In the current study, the nonlinear vibration properties of an embedded zigzag single-walled carbon nanotube (SWCNT) are investigated. Winkler-type model is used to simulate the interaction of the zigzag SWCNTs with a surrounding elastic medium. The relation between deflection amplitudes and resonant frequencies of the SWCNT is derived through harmonic balance method. The equivalent Young's modulus and shear modulus for zigzag SWCNT are derived using an energy-equivalent model. The amplitude - frequency curves for large-amplitude vibrations are graphically illustrated. The simulation results show that the chirality of zigzag carbon nanolube as well as surrounding elastic medium play more important roles in the nonlinear vibration of the single-walled carbon nanotubes.

• 한국CDE학회논문집
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• 제6권4호
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• pp.215-221
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• 2001

In the zigzag milling of a pocket having islands, tool retraction is one of the primary factors that decrease productivity. Therefore, tool path with minimum number of tool retraction has been needed. Most researches about this topic have been concentrated on obtaining the optimum solution formulated through the geometric reasoning off pocket. Recently, several attempts were made to simplify this problem into region partitioning in order to get the numerically expressed minimum solution. In this research, a method reducing the number of tool retractions extended from existing region partitioning is provided. Applying the segment that is normal to the reference direction of zigzag milling, region partitioning is carried out and structural elements of the region are searched via graphs of islands and characteristic points. Through the processes presented, the number of region partitioned is less than that of existing processes.

• 정보처리학회논문지A
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• 제14A권5호
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• pp.317-326
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• 2007

본 논문에서 GOSST(Grade of Services Steiner Minimum Tree) 문제에 대한 개선된 휴리스틱을 제안한다. GOSST 문제는 스타이너 포인트 문제의 한 변형으로 G-Condition을 만족하는 최소비용의 네트워크 구성을 찾는 문제이며, NP-Hard 혹은 NP-Complete 문제로 알려져 있다. 이 문제에 대한 이전의 연구에서 우리는 거리 우선 최소 신장 트리 생성방법과 직접 스타이너 포인트 배치 방법을 결합한 휴리스틱을 제안했었다. 본 논문에서는 스타이너 포인트 배치 방법으로 지그재그 스타이너 포인트 배치방법을 새롭게 제안한다. 이 방법과 거리우선 최소 신장 트리 생성 방법을 결합한 거리 지그재그 GOSST 휴리스틱은 컨트롤인 G-MST에 비해 31.5%의 네트워크 구축 비용의 절감을 얻었고 이전의 가장 좋은 GOSST 휴리스틱인 거리 직접 GOSST 휴리스틱에 비해 2.2%의 비용 개선을 보였다.

• 대한전자공학회논문지TC
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• 제43권4호
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• pp.44-51
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• 2006

본 논문에서는 우선 지그재그 와이어 다이폴 안테나 공진 특성을 모멘트법을 사용하여 분석함으로써, 직선형 와이어 안테나의 공간 점유 길이를 단축시킬 수 있음을 보였다. 이 단축 효과를 고려하여, 간소화된 마이크로스트립 급전부를 갖는 집적화된 지그재그 다이폴 안테나를 설계하였다. 집적화시 안테나 라인 폭의 급격한 구부림 각도에 의해 불연속이 존재하므로 chamfer를 적용함으로써 보상시키고, 유전체 기판의 영향을 고려하여 기판 양면에 기생소자 역할을 하는 지그재그 라인을 부가함으로써 공진특성을 개선시켰다. UHF와 ISM 대역에서 설계된 결과들의 타당성을 실험을 통해 입증하였다.

• Archives of Plastic Surgery
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• 제34권5호
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• pp.667-670
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• 2007

Purpose: Among the materials for cranioplasty, autogenous bone is ideal because it is less susceptible to infection and has lower rates of subsequent exposure. However, the procedure is technically demanding to perform and requires a donor site. Disadvantages further exist when the defect is large and there are attendant limitations in donor site. The authors present their experience with reconstruction of large skull defect using right-angled zigzag osteotomized outer table of autogenous calvarial bone, overcoming the limitation in donor site. Methods: From 2000 to 2006, 9 patients were retrospectively reviewed, who had undergone reconstruction with right angled zigzag osteotomized outer table of autogenous calvarial bone. Results: Aesthetically satisfactory skull shape was achieved. Major complications of infection, hematoma, plate exposure, and donor site complications of dural tear with bleeding, cerebrospinal fluid leak, and meningitis were not seen. One patient had delayed wound healing and was successfully managed conservatively. Conclusion: Autogenous bone is the material of choice for cranioplasty, especially in complicated cases. Right angled zigzag osteotomy is a useful method in reconstruction of large skull defects with less donor site morbidity.

• 대한산업공학회지
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• 제27권1호
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• pp.69-88
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• 2001

In the zigzag milling operation, an important issue is to design a machining strategy which minimizes the cutting time. An important variable for minimization of cutting time is the tool path length. The tool path is divided into cutting path and non-cutting path. Cutting path can be subdivided into tool path segment and step-over, and non-cutting path can be regarded as the tool retraction. We propose a new method to determine the cutting direction which minimizes the length of tool path in a convex or concave polygonal shape including islands. For the minimization of tool path length, we consider two factors such as step-over and tool retraction. Step-over is defined as the tool path length which is parallel to the boundary edges for machining area and the tool retraction is a non-cutting path for machining any remaining regions. In the determination of cutting direction, we propose a mathematical model and an algorithm which minimizes tool retraction length in complex shapes. With the proposed methods, we can generate a tool path for the minimization of cutting time in a convex or concave polygonal shapes including islands.

• 전기학회논문지P
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• 제66권3호
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• pp.99-104
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• 2017

The three-phase four-wire power distribution system can be used to supply power to single-phase and three-phase loads at the same time. There are linear loads and nonlinear loads as single-phase loads connected to each phase. The nonlinear load generates a harmonic current during the power energy conversion process. In particular, the single-phase nonlinear load has a higher proportion of generation of the third harmonic current than the harmonics of the other orders. In a three-phase four-wire system, the third harmonic current flows through the neutral wire to the power supply side, affecting the power supply side and the line. Furthermore, the magnitude of the current flowing in the neutral line can be higher than the current flowing in the individual phase. If the neutral current is higher than the phase current, the breaker may be blocked. Therefore, it is necessary to reduce the amount of current flowing in the neutral line by harmonics. There is a method of zigzag connecting a single phase transformer by a method of reducing 3 harmonic current. In this study, the method of reducing the magnitude of the three harmonic currents flowing through the zigzag wire by comparing the polarity and the negative polarity characteristics of the single phase transformer was compared through measurement and simulation.