MECHANICAL STRUCTURE DESIGN TO AVOID FRICTION-INDUCED INSTABILITIES: IN-PLANE ANISOTROPY AND IN-PLANE ASYMMETRY

The stability of a two-degree-of-freedom (2DOF) sliding system with the velocity-weakening friction was examined by the eigenvalue analysis, where the in-plane anisotropy and the in-plane asymmetry were considered. The obtained eigenvalues were organized by using the minimum modal damping ratio as the stability maps. Selecting a stable point in the stability map corresponds automatically to embedding the Yaw-Angle-Misalignment (YAM) method in the mechanical structure design to avoid the instability. If we accept the mechanical structure design of sliding systems with the in-plane anisotropy and the in-plane asymmetry, we can find new stable conditions spread widely in the two-dimensional space, which are invisible from the conventional point of view

Macroscopic tribological properties of thick concentrated polymer brush on rough steel under lubrication with ionic liquid

Concentrated polymer brush (CPB) is the polymer film with a structure that possesses greatly extended polymer chains densely grafted to substrate. CPB is known to swell in good solvents, which have high affinity for the polymer. Swollen CPB by a good solvent shows excellent micro-tribological properties such as super lubrication with the extremely low friction coefficient (μ~10-4). However, macro-tribological properties of CPB surface on steel have not been explored sufficiently. In this study, macroscopic tribological properties of a CPB on rough steel were evaluated using a block-on-ring type tribo-tester under lubrication with an ionic liquid. The CPB showed a significant friction reduction effect with the low friction coefficient of 0.005 on macroscale

チイキ ホウカツ イリョウ ジッシュウ ノ ジュコウセイ ノ トクセイ ト ソノ キョウイク コウカ ニ カンスル ケンキュウ

全国的に地域枠入学者による医学部定員増加が行われている.それに伴い医学部では,より良い地域医療教育の導入が求められている.そこで本研究は,地域医療を目指す学生の特性を知るとともに地域医療教育の効果を学生の自己評価点とSOC (Sense of Coherence) 得点の地域教育導入前後比較により検討することを目的とした.調査対象は,獨協医科大学医学部第1学年おける地域包括医療実習受講生の16名( 男子9名,女子7名:平均年齢18.9±1.0歳) と非受講生の1年生98名( 男子66名,女子32名:平均年齢19.9±1.7歳) である.平成22 年7 月15 日に対象者全員に対して研究の説明を行い,文書による研究参加への同意を得た後,行動規範26項目の自己評価 (7 点満点) とSense of Coherence (SOC) 29 項目及び生活習慣に関する質問12 項目に回答する自記式アンケート調査を行った.さらに,平成22 年12 月11 日に,受講生のみを対象に7 月15 日に施行したものと同一のアンケート調査を行った.地域包括医療実習I 受講生は,非受講生に比較して,家族と同居しているもの,現在運動をしていないものが多かった.また,学習態度の自己評価点とSOC 処理可能感の得点が有意に高かった.地域包括医療実習I の実習前後の変化を検討したところ,生活態度の自己評価が終了時には有意に上昇していた.しかしSOC 把握可能感の得点が有意に低下していた.地域医療教育導入前後でほとんどの項目で大きな変化はなかったが,生活態度の行動変容に良い効果が得られた.また,把握可能感が低下していたため,面接などで適切な支援が必要である.The quotas of students who wish to be involved in communitymedicine have increased in medical schools in Japan.Accordingly, programs focused on community medicineare required in medical education. In this study weaimed to identify the characteristics of medical studentswho pursue community medicine. We also aimed to evaluatethe effects of the local community medical educationcourse for medical students by examining changes in thescores of self-evaluation of standards of conduct and in thescores of sense of coherence (SOC) before and after thecourse.Participants were 16 first-year students (9 men, 7 women;mean age, 18.9±1.0 years) at Dokkyo Medical Universitywho took the comprehensive community medicinepractice course( community medicine course students) and98 students (66 men, 32 women;mean age, 19.9±1.7years) who did not take the course( non-community medicinecourse students).Information on the study was provided on July 15, 2010,and written informed consent was obtained from all participants.A self-evaluation questionnaire comprising 26 itemsregarding standards of conduct, each to be rated on a seven-point scale, and a questionnaire comprising 29 items ofSOC and 12 items of lifestyle were used. Both questionnaireswere completed by all participants on July 15, 2010and by the community medicine course students on DecemberThe percentage of students who lived with their familiesand the percentage of students who did not regularly exerciseat the time of the questionnaire survey were higher inthe community medicine course students than in the noncommunitymedicine course students. In addition, the selfevaluationscore for attitude toward leaning and the SOCscore for sense of manageability were significantly higher inthe community medicine course students than in the noncommunitymedicine course students. In the communitymedicine course students, the self-evaluation score for attitudetoward life was significantly increased, while the SOCscore for sense of comprehensibility significantly decreasedby the end of the course.The comprehensive community medicine practice coursehad a positive effect on student attitude toward life, andpreferable behavioral modifications were observed, althoughscores for most items remained unchanged by the end ofthe course. Our findings revealed a decrease in sense ofcomprehensibility, indicating that appropriate student support,such as consultation, is necessary

Influence of Ink Composition on Tribological Properties of Ballpoint Pen

In this work, the influence of ink composition on the tribological properties of ballpoint pens has been examined with a view to improve writing smoothness and pen lifetime. Friction experiments were performed using a ball on plate tribometer in order to simulate the sliding contact of a ballpoint pen. Ballpoint pen ink is composed of various solvents, resins, friction modifiers, colorants. To determine the basic tribological properties of ballpoint pen ink, this study focuses on the investigating the influence of different ink compositions: solvents, resins, and phosphate on the tribological behavior. The worn surfaces of specimens from tribological tests using different ink compositions were analyzed by using Fourier-transform infrared spectroscopy. Tribological tests were performed on eight different lubricant compositions including: i) the solvents without additives ii) the solvents with the resins and iii) the solvents with the friction modifiers. The results showed that for Oil A the tribological properties were affected by the molecular weight of the resin and the addition of phosphate reduced the coefficients of friction. Similar results were not observed for Oil B. In addition, it was found that the ratio of the components of the base oil affects the tribological properties of ballpoint pen ink

Ultralow Friction of a Tetrahedral Amorphous Carbon Film Lubricated with an Environmentally Friendly Ester-Based Oil

The tribological properties of diamond-like carbon (DLC) films that were lubricated with an environmentally friendly ester-based oil were investigated. Sliding tests were performed on two types of DLC films, hydrogenated amorphous carbon (a-C:H) and tetrahedral amorphous carbon (ta-C) films, using a steel cylinder that was in contact with a steel disk coated with either a-C:H or ta-C under boundary lubrication. To compare the tribological properties of ester-based oils and other based oils, Trimethylolpropane (TMP) ester, polypropylene glycol (PPG), and poly-alpha olefin (PAO) were used as the test lubricants. The ta-C film that was lubricated with TMP ester exhibited the ultralow friction coefficient of 0.015; however, the a-C:H film that was lubricated with TMP ester did not exhibit the ultralow friction. On the other hand, results obtained by a quartz-crystal microbalance with dissipation indicated that the adsorption properties of based oils depended on the type of sensor material (carbon or iron) and the type of based oil used in the measurements. Moreover, the frequency change of based oils increased with decreases in the average frictional coefficients of the steel-steel tribopair and the DLC-steel tribopair. Results of surface analysis indicated that TMP ester formed tribofilms on the ta-C surfaces, which exhibited high viscosity and low friction. All these results suggest that the combination of the ta-C film and TMP ester is the new ultra-low-friction and environmentally friendly sliding system