• Korean Journal of Anesthesiology
• /
• 제71권6호
• /
• pp.476-482
• /
• 2018

Background: Several types of receptors are found at neuromuscular presynaptic membranes. Presynaptic inhibitory $A_1$ and facilitatory $A_{2A}$ receptors mediate different modulatory functions on acetylcholine release. This study investigated whether adenosine $A_1$ receptor agonist contributes to the first twitch tension (T1) of train-of-four (TOF) stimulation depression and TOF fade during rocuronium-induced neuromuscular blockade, and sugammadex-induced recovery. Methods: Phrenic nerve-diaphragm tissues were obtained from 30 adult Sprague-Dawley rats. Each tissue specimen was randomly allocated to either control group or 2-chloroadenosine (CADO, $10{\mu}M$) group. One hour of reaction time was allowed before initiating main experimental data collection. Loading and boost doses of rocuronium were sequentially administered until > 95% depression of the T1 was achieved. After confirming that there was no T1 twitch tension response, 15 min of resting time was allowed, after which sugammadex was administered. Recovery profiles (T1, TOF ratio [TOFR], and recovery index) were collected for 1 h and compared between groups. Results: There were statistically significant differences on amount of rocuronium (actually used during experiment), TOFR changes during concentration-response of rocuronium (P = 0.04), and recovery profiles (P < 0.01) of CADO group comparing with the control group. However, at the initial phase of this experiment, dose-response of rocuronium in each group demonstrated no statistically significant differences (P = 0.12). Conclusions: The adenosine $A_1$ receptor agonist (CADO) influenced the TOFR and the recovery profile. After activating adenosine receptor, sugammadex-induced recovery from rocuronium-induced neuromuscular block was delayed.

• 자동차안전학회지
• /
• 제7권3호
• /
• pp.19-24
• /
• 2015

Brake pads are a component of disc brake system of automobile and consist of steel backing plates and friction material facing the disk brake rotor. Due to the repeated sliding forces and torque in vehicle braking, friction performance of brake pads are ensured. Futhermore, the brake pad is one of major tuning components in aftermarket, mechanical characteristics of the brake pad are necessary to evaluate for establishing the certification standards of tuning components. This study had performed the five specimen tests for friction coefficients and wear loss rates according to the SAE test specification. Using the instrumented indentation method, yield strength and tensile strength were measured. Friction coefficients, 0.386 - 0.489, and wear loss rates, 1.0% - 3.7% are obtained. The range of yield strength and tensile strength are 21.4 MPa - 105.3 MPa and 39.5 MPa - 176.4 MPa respectively.

• 자동차안전학회지
• /
• 제8권3호
• /
• pp.28-32
• /
• 2016

Braking system is directly related to the safety of a vehicle and the brake discs are essential part of the braking system. Due to the repeated frictional forces and torque during braking, brake discs are always works at high temperature and high pressure. Furthermore, the brake disc is one of major tuning components in aftermarket, the braking performance of the brake disc should be evaluated for establishing the certification standards of tuning components. This paper proposes the test method to evaluate the performance of tuning brake discs.

• 한국결정성장학회지
• /
• 제29권6호
• /
• pp.329-337
• /
• 2019

스플린터(splinter) 및 판상(plate shape) 형상을 가지는 티탄산칼륨염(K₂O·nTiO₂, PT)을 합성하고 브레이크 마찰재의 보강재로 이용하여 마찰 특성을 평가하였다. 스플린터형 티탄산칼륨염을 합성하기 위하여 먼저 판상 형상을 가지는 사티탄산칼륨염(K₂O·4TiO₂, PT4)을 합성하고 칼륨 이온(K⁺)을 일부 산침출(acid leaching)하여 육티탄산칼륨염(K₂O·6TiO₂, PT6)으로 변환시킨 후, 800℃에서 열처리하여 스플린터 형상의 입자를 얻었다. 판상형 티탄산칼륨염을 합성하기 위해서 염화칼륨을 융제로 사용하고 마그네슘(Mg)을 일부 첨가하여 판상의 형상을 가지는 마그네슘티탄산칼륨염(K_0.8Mg_0.4Ti_1.6O₄, PMT)을 합성하였다. 얻어진 육티탄산칼륨염 및 마그네슘티탄산칼륨염 입자를 보강재로 이용하여 브레이크 패드 마찰재를 제작하고 1/ 5-스케일 다이나모미터(scale dynamometer)를 이용하여 마찰 마모 특성을 평가하였다. 평가 결과, 두 종류의 보강재가 유사한 마찰계수 및 Fade & recovery 특성을 보였으며 판상형 마그네슘티탄산칼륨염의 경우, 스플린터형 육티탄산칼륨염보다 우수한 내마모성을 보이는 것을 알 수 있었다.

• Tribology and Lubricants
• /
• 제23권6호
• /
• pp.266-271
• /
• 2007

The brake performance of sintered friction materials for the high speed train was studied. In this study, newly developed sintered materials based on copper were compared with the commercial products for high speed trains. They were tested on a 1/5 scale dynamometer using low carbon steel disks. Effectiveness, fade, and recovery tests were carried out to examine friction performance and the change of disk thickness variation (DTV) during brake applications and noise propensity were also evaluated. Results showed that the two sintered friction materials exhibit similar friction coefficients and braking performance, whereas the newly developed friction material was superior in terms of DTV generation and noise propensity to the commercial friction material. The improvement of the newly developed friction material was attributed to the high graphite content which reduced the stick-slip phenomena and prevented uneven disk wear by producing friction films on the counter disk.

• 전력전자학회논문지
• /
• 제21권5호
• /
• pp.396-403
• /
• 2016

Usually, large-sized buses and trucks have a very high load. In addition, frequent braking during downhill or long-distance driving, causes the conventional method using the brake friction to have a problem in safety because of brake fade and brake burst phenomenon. Auxiliary brakes dividing the braking load is essential. Hence, environment-friendly auxiliary brakes, such as contactless brake rather than the engine auxiliary brake system are needed. A study aimed at improving the energy efficiency by recharging electric energy with changing mechanical to electrical energy that occurs when braking is actively in progress. In this paper, the voltage control method is utilized to recover the electric energy generated in the electromagnetic retarder instead of the eddy current. To regenerate the braking energy into the electrical energy, the resonant L-C circuit is configured in the retarder. The voltage generated in the retarder is simply modeled as a transformer. However, retarder voltage control in this paper is simulated by modeling the induction generator because this induction generator modeling is more practical than transformer modeling. The changes in the voltage of the resonance circuit, which depends on the switch pulse duration of the control device, were analyzed. A PI controller algorithm to control this voltage is proposed. The feasibility of modeling retarder and voltage controller are shown by using MATLAB Simulink in this paper.

• Journal of Advanced Marine Engineering and Technology
• /
• 제22권1호
• /
• pp.67-76
• /
• 1998

Friction materials for brake linings and clutches have severe performance requirements. The principal function of such frictional elements is to convert kinetic energy to heat, and then either to absorb or to dissipate heat. In order to achieve these objectives, the coefficient of friction must be as high as possible, independent of variations in operating conditions, and the necessary energy conversion must be accomplished with a minimum of wear on the contacting parts. In this study, Al powder, Al bronze powder and Mo powder used in general for automobile brake was sprayed on automobile brake disc to restrain rust and to maintain friction performance. Dynamo and corrosion tests have been carried out. It is concluded that the sprayed disc with Al bronze powder has the most improved frictional performance and anti-corrosive characteristics. The main results obtained can be summarized as follows; 1. From the corrosion current density test for gray cast iron and sprayed disc with powders of Al, Al bronze and Mo, it was cleared that the spray treatment with Al bronze powder showed the most superior anti-corrosive characteristics than other powders. 2. By anode polarization toward the noble direction from corrosion potential, corrosion current density with sprayed brake disc by Al-bronze powder was the lowest. 3. Mean frictional coefficients obtained from dynamo test are as follows : the sprayed disc with Al(99.99%) powder was 0.190 ; the sprayed disc with Al-bronze powder was 0.312 ; the sprayed disc with Mo powder was 0.257 ; the non-sprayed disc of gray cast iron was 0.331. In the case of the sprayed disc Al-bronze powder showed the most excellent frictional characteristics . 4. Amount of burnish quantity obtained from burnish test by dynamometer is as follows : the sprayed disc with Al-powder was 1.079 mm : the sprayed disc with Al-bronze powder was 0.155 mm : the sprayed disc with Mo powder was 0.253 mm : the non-sprayed disc of gray cast iron was 0.241 mm. Al-bronze powder also showed the most excellent burnish characteristics.