• Title/Summary/Keyword: helmet

Search Result 261, Processing Time 0.028 seconds

Printed Type Half-wavelength Small Loop Antenna (프린트형 반파장 소형 루프 안테나)

  • Ryu, Hong-Kyun;Woo, Jong-Myung
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2005.11a
    • /
    • pp.245-248
    • /
    • 2005
  • In this paper, small sized half-wavelength circular loop antenna which attached beneath a visor of helmet is designed and fabricated at the resonant frequency of 449MHz. To reduce the size of the antenna, double series-shorted stubs are inserted inside the loop for practical use of a vacant space of loop inside. Also, It is designed for the printed type to install the helmet easily. The size of antenna on helmet is reduced to 87.75%(diameter : 70mm, height :.36mm) compare with general type antenna(diameter : 200mm height 101mm). The return loss, -10dB bandwidth and gain are -13.2dB, 17.6MHz(3.9%), and -1.78dBd. And, radiation pattern is omni-directional pattern at H-plane. Therefore, it can be seen that the half-wavelength circular loop antenna using double series-shorted stubs is proper structure for the miniaturization and the installed antenna of the helmet.

  • PDF

Research for the Wear Status and Encourage the Children to Wear Safety Helmets (어린이용 안전모의 착용실태와 착용성 증대 방안을 위한 연구)

  • Song, Rae Ho;Lee, Kang In
    • Journal of the Korea Safety Management & Science
    • /
    • v.17 no.3
    • /
    • pp.149-162
    • /
    • 2015
  • This study was conducted on young children safety helmet to prevent risk of head injuries from external shock. Young children helmet shall be easy to wear and use comfortably. But the young children helmet market in domestic has imported dependently and widely variations in quality because the euro product of high priced and the east asia product of low priced are selling at the same time. Therefore, this study surveyed children under 13 years of age and Married people and studies their actual state of wearing. Furthermore, this study is going to propese the improving wearing of helmet and the major points of quality of helmet and the problem by comparing and reviewing regulations of domestic and foreign.

Experimental study on the drag reduction of a helmet for paragliding (패러글라이딩 헬멧의 항력 감소에 관한 실험적 연구)

  • Hwang, Jongbin;Park, Jungmok;Song, Jinseok;Kim, Jooha
    • Journal of the Korean Society of Visualization
    • /
    • v.19 no.3
    • /
    • pp.46-53
    • /
    • 2021
  • In the present study, wind tunnel experiments were performed to reduce the drag of a paragliding helmet in the range of Reynolds numbers from 46,000 to 155,000. The drag force of the helmet model with dimples and deflectors installed was measured by varying the dimple depth and the slant angle of the deflector. The dimples were effective in reducing the drag at low Reynolds numbers, but no significant drag reduction was found in the Reynolds number range in which an actual paraglider flight takes place. On the other hand, the deflector installed tangentially to the side outline of the helmet showed an average drag reduction of 7% in the flight Reynolds number range of real paragliding. This was because the deflector shrunk the size of the wake region and moved the wake region downstream of the deflector.

Determination of Relative Output Factors Using PinPoint Ion Chamber and Gafchromic Film in Gamma Knife

  • Seo, Weon-Seop;Shin, Dong-Oh;Lim, Young-Jin;Im, Yong-Seok
    • Proceedings of the Korean Society of Medical Physics Conference
    • /
    • 2002.09a
    • /
    • pp.300-301
    • /
    • 2002
  • Of many modalities for measuring output factor, we measured the outputs of 18mm, 14mm, 8mm and 4mm helmet in Gamma knife using ion chambers and a Gafrcromic MD-55 film and normalized the outputs of four helmets the one of a 18mm helmet. Ion chambers used for this paper were a PR-05P and a PinPoint having a volume of 0.07cc and 0.015cc respectively. The recommended output factors from a manufacture were 1, 0.984, 0.956, and 0.87. For PR-05P, the output factor of 14mm helmet showed a good agreement, but the ones of 8mm and 4mm helmet showed the difference of 4.6% and 47% respectively. For PinPoint, The output factors of 14mm and 8mm helmet showed a good agreement, but the one of a 4mm helmet showed a difference of 18%. The Gafcromic MD-55, however, showed a good agreement for all helmets.

  • PDF

A Study on Improvement of Ballistic Testing Method for Combat Helmet (방탄헬멧의 방탄시험방법 개선에 관한 연구)

  • Gu, Seung Hwan;Kim, Kyung Min;Park, Jung Hwa;Song, Seung Hwan
    • Journal of Korean Society for Quality Management
    • /
    • v.47 no.2
    • /
    • pp.283-294
    • /
    • 2019
  • Purpose: Although the development of bulletproof helmets continues to be carried out, little has been improved in testing methods. Therefore, in this study, we studied the improvement of the test method of the domestic bulletproof helmet. Methods: The causes of head damage in the battlefield and the trends of bulletproof helmet development in developed countries were analyzed. In addition, improvements were derived by comparing the test methods of bulletproof helmet in Korea and the United States. Results: The results of the improvement by comparing the test methods of bulletproof helmet in Korea and the United States are as follows First, it is an addition to the scope of environmental treatment. Second, it is an addition to the level of protection. Third, the addition of the level of protection by impact. Conclusion: This study considered testing methods to prevent head injuries to shocks that cannot be identified by conventional methods. In addition, it considered testing methods for various threats by improving protection performance to advanced countries' levels.

A Survey on Regulations of Safety Helmet for Preventing Fall Hazard (추락위험 방지용 보호구로서 안전모 규정에 관한 고찰)

  • Sang Woo, Shim;Yong Su, Sim;Jong Bin, Lee;Seong Rok, Chang
    • Journal of the Korean Society of Safety
    • /
    • v.37 no.6
    • /
    • pp.96-101
    • /
    • 2022
  • The Occupational Safety and Health Act holds that industrial safety helmets can be used as protective equipment to prevent the risk of injury in fall accidents. To better understand the importance given to PPE for the head, we analyzed the relevant regulations and guidelines in developed countries and reviewed the guidelines on testing safety helmets. The PPE regulations in Korea were notably different from those in other countries. First, except in Korea and Japan, safety helmets were used for protection against falling objects, flying objects, impact, or electric shock. However, the regulations did not recognize safety helmets as a PPE against fall hazards. Second, the impact energy applied on the helmet was within the range 50-100 J, and the helmet could protect only the upper part of the head against hazards such as the impact of falling objects, flying objects, etc. Third, in Korean regulations, the term "fall" was used in relation to the parts where the safety helmet was specified as a fall hazard PPE, unlike in other countries. We propose that the term "fall" should be revised to "shock" in Korean regulations for the safety helmet.

Development of a Customized Helmet Design System for Patients with Plagiocephaly (사두증 환자를 위한 맞춤형 헬멧 몰드 디자인 시스템 개발)

  • Kang, Yeonghoon;Park, Hyeryeon;Kim, Sungmin
    • Fashion & Textile Research Journal
    • /
    • v.24 no.4
    • /
    • pp.443-450
    • /
    • 2022
  • This study developed a three-dimensional helmet mold design software that can design helmets for treating the infant plagiocephaly (flat head syndrome) using three-dimensional head scan data. For this, the three-dimensional head data of sixth SizeKorea body measurement project as well as the data produced by a head modeling software were used to prepare the head shape data of plagiocephaly patients. A total of 14 landmarks and 10 dimensions of heads required for helmet mold shape design and plagiocephaly diagnosis were automatically measured using an anthropometric analysis software. Using the software developed in this study, plagiocephaly can be diagnosed not only visually by three-dimensional head data visualization but also quantitatively by calculating the medically defined indices such as cranial index, which measures the proportions of the head, and the cranial vault asymmetry index, which measures the asymmetry of the head. The basic shape of the helmet mold was automatically generated based on the head scan data. Additionally, it is possible to fine tune the shape of the mold to reflect individual characteristics by using a free form deformation technique. Finally, the designed helmet mold was converted into the data that can be printed on a three-dimensional printer for generating the actual prototype.

Design and Implementation of Real-Time Helmet Pose Tracking System (실시간 헬멧자세 추적시스템의 설계 및 구현)

  • Hwang, Sang-Hyun;Chung, Chul-Ju;Kim, Dong-Sung
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.44 no.2
    • /
    • pp.123-130
    • /
    • 2016
  • This paper describes the design and implementation scheme of HTS(Helmet Tracking System) providing coincident LOS(Line of Sight) between aircraft and HMD(Helmet Mounted Display) which displays flight and mission information on Pilot helmet. The functionality and performance of HMD system depends on the performance of helmet tracking system. The target of HTS system design is to meet real-time performance and reliability by predicting non-periodic latency and high accuracy performance. To prove an availability of a proposed approach, a robust hybrid scheme with a fusion optical and inertial tracking system are tested through a implemented test-bed. Experimental results show real-time and reliable tracking control in spite of external errors.

Comparison of Three Different Helmet Bolus Device for Total Scalp Irradiation (Total Scalp의 방사선 치료 시 Helmet Bolus 제작방법에 관한 연구)

  • Song, Yong-Min;Kim, Jong-Sik;Hong, Chae-Seon;Ju, Sang-Gyu;Park, Ju-Young;Park, Su-Yeon
    • The Journal of Korean Society for Radiation Therapy
    • /
    • v.24 no.1
    • /
    • pp.31-37
    • /
    • 2012
  • Purpose: This study evaluated the usefulness of Helmet bolus device using Bolx-II, paraffin wax, solid thermoplastic material in total scalp irradiation. Materials and Methods: Using Rando phantom, we applied Bolx-II (Action Products, USA), paraffin wax (Densply, USA), solid thermoplastic material (Med-Tec, USA) on the whole scalp to make helmet bolus device. Computed tomography (GE, Ultra Light Speed16) images were acquired at 5 mm thickness. Then, we set up the optimum treatment plan and analyzed the variation in density of each bolus (Philips, Pinnacle). To evaluate the dose distribution, Dose-homogeneity index (DHI, $D_{90}/D_{10}$) and Conformity index (CI, $V_{95}/TV$) of Clinical Target Volume (CTV) using Dose-Volume Histogram (DVH) and $V_{20}$, $V_{30}$ of normal brain tissues. we assessed the efficiency of production process by measuring total time taken to produce. Thermoluminescent dosimeters (TLD) were used to verify the accuracy. Results: Density variation value of Bolx-II, paraffin wax, solid thermoplastic material turned out to be $0.952{\pm}0.13g/cm^3$, $0.842{\pm}0.17g/cm^3$, $0.908{\pm}0.24g/cm^3$, respectively. The DHI and CI of each helmet bolus device which used Bolx-II, paraffin wax, solid thermoplastic material were 0.89, 0.85, 0.77 and 0.86, 0.78, 0.74, respectively. The result of Bolx-II was the best. $V_{20}$ and $V_{30}$ of brain tissues were 11.50%, 10.80%, 10.07% and 7.62%, 7.40%, 7.31%, respectively. It took 30, 120, 90 minutes to produce. The measured TLD results were within ${\pm}7%$ of the planned values. Conclusion: The application of helmet bolus which used Bolx-II during total scalp irradiation not only improves homogeneity and conformity of Clinical Target Volume but also takes short time and the production method is simple. Thus, the helmet bolus which used Bolx-II is considered to be useful for the clinical trials.

  • PDF

Attitude and Position Estimation of a Helmet Using Stereo Vision (스테레오 영상을 이용한 헬멧의 자세 및 위치 추정)

  • Shin, Ok-Shik;Heo, Se-Jong;Park, Chan-Gook
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.38 no.7
    • /
    • pp.693-701
    • /
    • 2010
  • In this paper, it is proposed that an attitude and position estimation algorithm based on a stereo camera system for a helmet tracker. Stereo camera system consists of two CCD camera, a helmet, infrared LEDs and a frame grabber. Fifteen infrared LEDs are feature points which are used to determine the attitude and position of the helmet. These features are arranged in triangle pattern with different distance on the helmet. Vision-based the attitude and position algorithm consists of feature segmentation, projective reconstruction, model indexing and attitude estimation. In this paper, the attitude estimation algorithm using UQ (Unit Quaternion) is proposed. The UQ guarantee that the rotation matrix is a unitary matrix. The performance of presented algorithm is verified by simulation and experiment.