• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권9호
• /
• pp.4390-4407
• /
• 2019

The paucity of pilot signals in Massive MIMO system is a vital issue. To accommodate substantial number of users, pilot signals are reused. This leads to interference, resulting in pilot contamination and degrades channel estimation at the Base Station (BS). Hence, mitigation of pilot contamination is exigency in Massive MIMO system. The proposed Time Shifted Pilot Signal Transmission with Pilot signal Hopping (TSPTPH), addresses the pilot contamination issue by transmitting pilot signals in non-overlapping time interval with hopping of pilot signals in each transmission slot. Hopping is carried by switching user to new a pilot signal in each transmission slot, resulting in random change of interfering users. This contributes to the change in channel coefficient, which leads to improved channel estimation at the BS and therefore enhances the efficiency of Massive MIMO system. In this system, Uplink Signal Power to Interference plus Noise Power Ratio (SINR) and data-rate are calculated for pilot signal reuse factor 1 and 3, by estimating the channel with Least Square estimation. The proposed system also reduces the uplink Signal power for data transmission of each User Equipment for normalized spectral efficiency with rising number of antennas at the BS and thus improves battery life.

• 해양환경안전학회지
• /
• 제28권1호
• /
• pp.47-53
• /
• 2022

도선사가 되려는 사람은 선장 경력을 갖추고 도선수습생 전형시험과 도선사 시험에 합격한 다음에 해양수산부장관의 면허를 받아야 한다. 우리나라는 정부에서 도선 수요를 감안하여 도선사 면허의 수(數)를 제한하고 있어서 도선사 면허를 위한 도선수습생전형시험은 절대적 평가기준 없이 응시자 시험성적에 따라 상대평가를 실시함에 따라 문제의 소지가 있다. 본 연구의 목적은 도선사 시험제도에 대한 문제점을 도출하여 개선방안을 제시하는데 있다. 본 연구에서는 국내 도선사 시험제도 변천 내역을 조사하였고, 도선사 자격기준에 관한 국제기준을 분석하고 현직 도선사 77명에 대한 설문조사를 실시하였으며, 연구의 결과로써 국내 도선수습생 전형시험의 개선방안과 도선사 자격증명 제도개선의 단계적 실행방안을 제시하였다. 본 연구의 결과가 도선사 자격증명에 관한 정부의 정책 개발뿐만 아니라 관련 학술적 기초자료도 활용될 수 있을 것으로 기대한다.

• 한국자동차공학회논문집
• /
• 제22권4호
• /
• pp.55-64
• /
• 2014

This work was investigated on pilot injection strategy of blended fuels(Diesel-DME) for combustion and emissions in a single cylinder direct injection compression ignition engine. Diesel and DME were blended by the method of weight ratio. Weight ratios for diesel and DME were 95:05 and 90:10 respectively. dSOI between main and pilot injection timing was varied. A total amount of injected fuels(single injection) was adjusted to obtain the fixed BMEP as 4.2 bar in order to compare with the fuel conditions. Also, the amount of pilot injection fuel was varied by 5%, 10% and 20% of total injection fuel. The engine was equipped with common rail and injection pressure is 700 bar at 1200 rpm. As a result, when mixing ratio increase, indicated thermal efficiency was increased in comparison with DD 100 and CO, THC and smoke were lower than DD 100. The influence of reducing NOx by pilot injection was more effective than DD 100. When pilot injection quantity increase, abrupt increase of NOx was occured at pilot injection quantity of 20%.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2022년도 추계학술대회
• /
• pp.57-58
• /
• 2022

도선사는 해상에서 도선사용 사다리나 갱웨이를 통해 선박에 승선하고 있어 예측할 수 없는 해상환경의 위험에 늘 노출되어 있다. 도선사는 항만으로 입항하거나 출항하는 선박의 안전을 확보하는 중요한 역할을 수행하고 있으므로 도선사 부상은 선박 전체 안전에 큰 영향을 미친다. 본 연구의 목적은 도선사 관련 준사고를 분석하고 사고를 예측하는 것이다. 이를 위해 도선사 상해사고 사례를 분석하고 설문조사를 통해 잠재상황을 식별하고자 한다. 그리고 도선사 상해 사고를 예측하였다. 결과는 도선사관련 사고에 예방 기초 자료로 활용할 수 있다.

• 한국항공운항학회지
• /
• 제28권3호
• /
• pp.74-83
• /
• 2020

Securing excellent pilots is not only directly linked to the military's improved combat capabilities, but also a way to minimize human and property losses from aircraft accidents. Therefore, a scientific method is needed to diagnose pilot aptitude from the pilot selection process and select those with high accident potential, those who are dropped out of the flight training process, and those who are not suitable for pilot life in advance. Developed countries have implemented pilot aptitude tests to solve these problems early on, but so far, the Korean Army has not introduced a pilot aptitude test system that uses diagnostic tools in the helicopter pilot selection process. Therefore, in this study, scientific diagnostic tools are developed for selecting helicopter pilots, and through this, it is predicted that the number of people who are likely to be dropped out of the training course and who have the potential for accidents will be selected in advance and eliminated in the selection process. In this context, prior research examined the key factors involved in the pilot aptitude test. Through this, the aptitude test items were developed and aptitude tests were conducted on student pilots currently in flight training, and the results of flight training were analyzed.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2022년도 춘계학술대회
• /
• pp.415-416
• /
• 2022

Marine pilot occupational accidents during transfer to/from the ship are at the top of the agenda after several safety campaigns by IMPA and individual attemptsThere is multiple transfer method for the marine pilot, but a most common way is to use the pilot cutter. This paper aims to predict marine pilot occupational accidents before it occurs by using historical data. Since the problem depends on several variables, this paper develops a model by using the random forest method to predict marine pilot accidents before happening with the random forest method by using RStudio software

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.3007-3012
• /
• 2008

Multidimensional simulation has been carried out to be clear the role of initial combustion in a marine diesel engines on reduction of NOx and soot emissions by different pilot injection condition. Pilot injection can shorten the ignition delay, thus it reduces the premixed combustion phase. Since most NOx is formed during premixed combustion, pilot injections is one of reliable strategies to reduce the NOx. The formation of NOx consists of that formed by pilot injection and that formed by main injection. The result explains that 25-3-75 among the pilot injection conditions is effective to reduce the NOx, due to optimal combination pilot injection with main injection. The purpose of this study is to explain the characteristics of combustion with pilot injection of the marine diesel engine on reduction of exhaust emissions by examining the combustion process in a cylinder and to explore the formation mechanism of NOx between pilot injection and main injection.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제8권2호
• /
• pp.75-85
• /
• 2008

In this paper, we compared domestic with foreign pilot lamps installed on the instrument board or electronic modules (car audio, air-conditional system, etc.) of an automotive vehicle by an accelerated life test in order to estimate the life of domestic pilot lamps. An accelerated life test method was developed and the relation of the life and voltage stress was analyzed. The main results are as follows; i) $B_{10}$ life of pilot lamp is above 5,000 hours, vehicle travel time for 10 years. ii) the life of domestic pilot lamp is longer than that of foreign thing. iii) the life distribution of domestic pilot lamp is wider than that of foreign thing. iv) it is possible to promote import replacement of automobile pilot lamp.

• Restorative Dentistry and Endodontics
• /
• 제43권4호
• /
• pp.41.1-41.7
• /
• 2018

Objectives: The purpose of the present study was to compare the mean preparation times and frequency with which Reciproc and Reciproc Blue instruments reached the full working length in mandibular molars, with or without glide path preparation. Materials and Methods: Previously untreated mesiobuccal and mesiolingual canals with completely formed apices were randomly divided into 6 groups (n = 50) depending on the usage of Reciproc (RC; VDW), Reciproc Blue (RC Blue; VDW), C-Pilot (CP; VDW), and R-Pilot (RP; VDW) files: RC, RC Blue, RC + C-Pilot (RC-CP), RC-Blue + C-Pilot (RC Blue-CP), RC+R-Pilot (RC-RP), and RC Blue + R-Pilot (RC Blue-RP). A glide path was prepared using the hand-operated C-Pilot or the machine-operated R-Pilot instruments, respectively. The ${\chi}^2$ test, analysis of variance, and the Tukey post hoc test were used for statistical comparisons. Results: No statistically significant differences were observed in the distribution of the frequency of reaching the full working length in the RC (94%), RC Blue (88%), RC-CP (94%), RC Blue-CP (90%), RC-RP (96%), and RC Blue-RP (92%) groups (p > 0.05). Conclusions: Preparation of a glide path did not have a significant effect on reaching the full working length using these systems.

• 한국자동차공학회논문집
• /
• 제20권3호
• /
• pp.141-147
• /
• 2012

A direct injection diesel engine with large amount of exhaust gas recirculation was used to investigate low temperature diesel combustion. Pilot injection strategy was adopted in low temperature diesel combustion to reduce high carbon monoxide and hydrocarbon emissions. Combustion characteristics and exhaust emissions of low temperature diesel combustion under different pilot injection timings, pilot injection quantities and injection pressures were analyzed. Retarding pilot injection timing, increasing pilot injection quantity and higher injection pressure advanced main combustion timing and increased peak heat release rate of main combustion. As a result of these strategies, carbon monoxide and hydrocarbon emissions were reduced. Soot emission was slightly increased with retarded pilot injection timing while the effect of pilot injection on nitrogen oxides emission was negligible under low combustion temperature condition. Spatial distribution of fuel from the spray targeting visualization was also investigated to provide more insight into the reason for the reduction in carbon monoxide and hydrocarbon emissions.