• 국제초고층학회논문집
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• 제11권2호
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• pp.115-124
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• 2022

Welding is a significant part of the construction industry. Since most high-rise building construction structures rely on a robust metal frame welded together, welding defect can damage welded structures and is critical to safety and quality. Despite its importance and heavy usage in construction, the labor shortage of welders has been a continuous challenge to the construction industry. To deal with the labor shortage, the ultimate goal of this study is to design and develop an automated robotic welding system composed of a welding machine, unmanned ground vehicle (UGV), robotic arm, and visual sensors. This paper proposes and focuses on automated weaving using the robotic arm. For automated welding operation, a microcontroller is used to control the switch and is added to a welding torch by physically modifying the hardware. Varying weave patterns are mathematically programmed. The automated weaving is tested using a brush pen and a ballpoint pen to clearly see the patterns and detect any changes in vertical forces by the arm during weaving. The results show that the weave patterns have sufficiently high consistency and precision to be used in the actual welding. Lastly, actual welding was performed, and the results are presented.

• Composites Research
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• 제20권4호
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• pp.18-24
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• 2007

본 연구에서는 전구체의 종류에 따라 PAN계/rayon계, 직물의 형태에 따라 연속사 및 방적사 탄소 직물을 사용하여 하이브리드 복합재료를 제조하여 역학적 특성과 열적 특성을 살펴보았다. 인장, 층간 전단강도 실험을 통해 연속사 PAN계 탄소 직물을 많이 사용한 하이브리드 복합재료에서 우수한 역학적 특성을 보이는 것으로 확인되었다. 토치 테스트에서는 rayon계 탄소 직물 복합재료의 삭마 저항성이 가장 떨어짐을 확인할 수 있었다. 또한, 방적사 PAN계 탄소 직물과 rayon계 탄소 직물을 하이브리드화한 복합재료가 면내 방향과 수직 방향 모두에서 저 열전도도 구현에 유리한 특성을 보여주었다.

• 한국정밀공학회지
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• 제14권5호
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• pp.42-52
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• 1997

Computer aided process planning and Offline programming are decisive factors in successful implementation of automated robotic production. However, conventional offline programming procedure has proven ineffective due to time-consuming teaching process for robot programming and due to inefficient system modeling. The paper presents an efficient procedure to semi-automatically generate robot job programs for ship block welding applications. In the research, the teaching positions are automatically determined by predefined rules which are functions of the type and the dimensions of the given welding section of ship block. And a sequence of robot movements and welding conditions such as welding type, welding current, welding speed, and welding torch orientation, are determined by use of Standard Program which is experimentally proved to work well for the welding wection group. Finally, a robot program for the welding section is generated automatically. Based on the algorithm, a offline automatic teaching software is developed. The paper presents also the algorithm and structure of the software.

• 천문학회보
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• 제46권2호
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• pp.74.2-75
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• 2021

We demonstrate that a deep learning classifier that only uses to gravitational wave (GW) detectors auxiliary channel data can distinguish various types of non-Gaussian noise transients (glitches) with significant accuracy, i.e., ≳ 80%. The classifier is implemented using the multi-scale neural networks (MSNN) with PyTorch. The glitches appearing in the GW strain data have been one of the main obstacles that degrade the sensitivity of the gravitational detectors, consequently hindering the detection and parameterization of the GW signals. Numerous efforts have been devoted to tracking down their origins and to mitigating them. However, there remain many glitches of which origins are not unveiled. We apply the MSNN classifier to the auxiliary channel data corresponding to publicly available GravitySpy glitch samples of LIGO O1 run without using GW strain data. Investigation of the auxiliary channel data of the segments that coincide to the glitches in the GW strain channel is particularly useful for finding the noise sources, because they record physical and environmental conditions and the status of each part of the detector. By only using the auxiliary channel data, this classifier can provide us with the independent view on the data quality and potentially gives us hints to the origins of the glitches, when using the explainable AI technique such as Layer-wise Relevance Propagation or GradCAM.

• 한국기계가공학회지
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• 제14권2호
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• pp.38-43
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• 2015

Tungsten inert gas (TIG) welding is commonly used in industries that require airtightness, watertightness, oiltightness, and precision. It is a non-consumable welding method that is commonly used for the welding of non-ferrous metals, but it can be used to weld most metals. The methods of TIG welding can be divided into three types. The first, manual welding is done directly on the metal by a welder with a torch. The second, semi-automatic welding, gets help from a material supplying machine, but it is conducted by a welder. Lastly, automated welding is conducted fully by a machine during its process and operation. Depending on the selection of electrode, the amount of heat that is applied to the base material and the electrode rod changes and makes the shape of welded parts different. A direct-current positive electrode was used for this study. Through the change of shielding gas type on a structural steel (SS-400) that is commonly used in industry, the composition and shape changes in welded parts were detected after welding. The heat-affected area, hardness value, and tensile strength were also identified through hardness testing and tensile testing. In this study, it was found that the higher hardness value of the heat-affected is, the weaker the tensile strength becomes.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.1819-1824
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• 2014

건축물 에너지 효율등급제도, 건축물 에너지 소비증명제 등 건축물 에너지 관련 법 제도가 지속적으로 강화되면서, 이에 대응하기 위한 고성능 단열재, 기능성 유리를 적용한 창호의 개발이 활발히 진행되고 있다. 에너지 절약을 위한 기능성 유리의 중요성이 크게 부각되고 있음에 따라 진공유리에 대한 관심이 높아지고 있다. 진공유리의 핵심공정 중 모서리 접합공정은 진공유리의 기밀성, 강도, 형상에 있어 매우 중요한 공정이다. 본 논문에서는 수소혼합가스를 이용하여 전기로 내부에서 두 장의 유리를 접합하였다. 공정변수에 따른 접합유리의 강도와 형상을 측정 및 분석 하였으며, 다구치 실험계획법을 이용하여 접합유리의 강도를 예측하였다. 추가실험을 통해 예측 값과의 오차율을 확인함으로서 실험의 타당성을 검증하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.268-268
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• 2012

Atmospheric pressure microwave induced plasmas are used to excite and ionize chemical species for elemental analysis, for plasma reforming, and for plasma surface treatment. Microwave plasma differs significantly from other plasmas and has several interesting properties. For example, the electron density is higher in microwave plasma than in radio-frequency (RF) or direct current (DC) plasma. Several types of radical species with high density are generated under high electron density, so the reactivity of microwave plasma is expected to be very high [1]. Therefore, useful applications of atmospheric pressure microwave plasmas are expected. The surface characteristics of SUS304 stainless steel are investigated before and after surface modification by microwave plasma under atmospheric pressure conditions. The plasma device was operated by power sources with microwave frequency. We used a device based on a coaxial transmission line resonator (CTLR). The atmospheric pressure plasma jet (APPJ) in the case of microwave frequency (880 MHz) used Ar as plasma gas [2]. Typical microwave Pw was 3-10 W. To determine the optimal processing conditions, the surface treatment experiments were performed using various values of Pw (3-10 W), treatment time (5-120 s), and ratios of mixture gas (hydrogen peroxide). Torch-to-sample distance was fixed at the plasma edge point. Plasma treatment of a stainless steel plate significantly affected the wettability, contact angle (CA), and free energy (mJ/$m^2$) of the SUS304 surface. CA and ${\gamma}$ were analyzed. The optimal surface modification parameters to modify were a power of 10 W, a treatment time of 45 s, and a hydrogen peroxide content of 0.6 wt% [3]. Under these processing conditions, a CA of just $9.8^{\circ}$ was obtained. As CA decreased, wettability increased; i.e. the surface changed from hydrophobic to hydrophilic. From these results, 10 W power and 45 s treatment time are the best values to minimize CA and maximize ${\gamma}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.179-179
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• 2016

A radio-frequency (RF) Inductively Coupled Plasma (ICP) torch system was used for boron-nitride nano-tube (BNNT) synthesis. Because of electrodeless plasma generation, no electrode pollution and effective heating transfer during nano-material synthesis can be realized. For stable plasma generation, argon and nitrogen gases were injected with 60 kW grid power in the difference pressure from 200 Torr to 630 Torr. Varying hydrogen gas flow rate from 0 to 20 slpm, the electrical and optical plasma properties were investigated. Through the spectroscopic analysis of atomic argon line, hydrogen line and nitrogen molecular band, we investigated the plasma electron excitation temperature, gas temperature and electron density. Based on the plasma characterization, we performed the synthesis of BNNT by inserting 0.5~1 um hexagonal-boron nitride (h-BN) powder into the plasma. We analysis the structure characterization of BNNT by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy), also grasp the ingredient of BNNT by EELS (Electron Energy Loss Spectroscopy) and Raman spectroscopy. We treated bundles of BNNT with the atmospheric pressure plasma, so that we grow the surface morphology in the water attachment of BNNT. We reduce the advancing contact angle to purity bundles of BNNT.

• 대한치과보철학회지
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• 제34권1호
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• pp.143-150
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• 1996

The purpose of this study was to evaluate the tensile strength of solder joint between gold alloy and nickel-chromium alloy. The specimens were made with type III gold alloys and Ni-Cr-Be alloy and Degular Lot 2 solder. Eighteen paired specimens were made, and subdivided into three groups. Group I specimens were gold alloy-gold alloy combination, Group II specimens were gold alloy-Ni-Cr alloy combination, Group III specimens were Ni-Cr alloy-Ni-Cr alloy combination. Solder block were made with solder investment(Degussa A,G, Germany) and stored in room temperature for 24 hours. To reduce the formation of metallic oxide and increase wetting properties, flux was used before preheating and soldering procedure. The specimens were preheated at $650^{\circ}C$ and flux were applied again and gas-oxygen torch was used to solder the specimen. All soldered specimens were subjected to a tensile force in the Instron universal testing machine : the crosshead speed was 1 mm/mim. Tensile strength values of three soldered joint groups were 1. Gold alloy-Gold alloy solder joint : $$48.8kg/mm^2$$ 2. Gold alloy-Ni-Cr alloy solder joint : $$30.9kg/mm^2$$ 3. Ni-Cr alloy-Ni-Cr alloy solder joint : $$31.8kg/mm^2$$ The microscopic examination of fracture site showed cohesive and combination fracture modes in gold alloy specimens, but showed all adhesive fracture modes in Ni-Cr alloy containing specimens.

• Korean Journal of Acupuncture
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• 제27권4호
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• pp.1-4
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• 2010

Objectives : The purpose of this study is to summarize the historical aspects of parabolic reflector moxa and to suggest the applications of light moxibustion in Korean medicine. Results : Getting a fire by parabolic reflector(concave mirror) is well known because of the Olympic torch lighted with a solar reflector in Greece. From anecdotes or myths for Diocles and Archimedes(third century B.C.) a long history has been chronicled in books and films in western culture. However, it has another history in Asian countries since 2,000 years ago. Some reflectors had a tiny size with 6.5 to 10 cm in diameter, 4 mm to 1 cm thickness, and these mobile handheld devices could make us guess that they have been used for multiple purposes. Bronze reflectors were described in Dongeui-bogam, and excavated from the ancient remains of the Shilla and Koryo dynasties. This common firing device was used as a moxibustion device, one of the acupuncture and moxibustion modalities in traditional Korean medicine. Conclusions : Reflector moxa has been used as a light moxibustion to deliver heat energy to acupuncture points, muscles, and skin along meridians. We present a plausible proposal to improve other phototherapy modalities including reflector moxa in Korean medicine practice.