http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
The sensitivity of respondent‐driven sampling
Lu, Xin,Bengtsson, Linus,Britton, Tom,Camitz, Martin,Kim, Beom Jun,Thorson, Anna,Liljeros, Fredrik Blackwell Publishing Ltd 2012 JOURNAL OF THE ROYAL STATISTICAL SOCIETY SERIES A- Vol.175 No.1
<P><B>Summary. </B> Researchers in many scientific fields make inferences from individuals to larger groups. For many groups, however, there is no list of members from which to draw a random sample. Respondent‐driven sampling (RDS) is a relatively new sampling methodology that circumvents this difficulty by using the social networks of the groups under study. The RDS method has been shown to provide unbiased estimates of population proportions given certain conditions. The method is now widely used in human immunodeficiency virus related studies among high risk populations globally. We test the RDS methodology by simulating RDS studies on the social networks of a large Lesbian, gay, bisexual and transgender Web community. The robustness of the RDS method is tested by violating, one by one, the conditions under which the method provides unbiased estimates. Simulations indicate that the bias is large if networks are directed or respondents choose to invite people on the basis of characteristics that are correlated with the study outcomes. The bias and variance increase if participants invite close as opposed to more distant friends whereas sampling in denser networks sharply reduces variance. However, the RDS method shows strong resistance to sampling without replacement, low response rates and certain errors in the participants’ reporting of their network sizes, as well as the selection criteria of seeds. The effects of network structure and the number of seeds and coupons are also discussed.</P>
교육기회의 공평성을 위한 전략 : 순환교육과 산업민주주의
TOM SCHULLER,JARL BENGTSSON 木浦大學敎育硏究所 1989 교육연구 Vol.3 No.-
우리는 이 논문에서 순환교육에 대한 정책을 논의한다. 이러한 논의는, 계층과 지위 그리고 교육구조 사이의 조화를 수용함으로써 경제(생산 관계의 구조)와 교육(사회적 관계의 재생산)간의 관계에 관한 이론을 따른다. 이러한 관계는 교육의 변화를 통한 생산관계의 수정과, 동시에 일의 특성을 변화시키는 교육제도에 대한 대응책을 받아들이는 의미에서 상호작용적인 것으로 파악된다. 교육 변화는 사려깊은 계획의 결과와 자유로운 토론의 산물, 그리고 민주정치에 대한 의지의 활동으로서 가능하게된다. 이런 종류의 이론적인 틀안에서 교육개혁을 위한 분석과 처방은 그러한 논의에 공헌하였다.
Bergmark Anders,Dizdar Senad,Bengtsson Sven,Luk Sydney 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
A comparative study is made on root bending fatigue performance of spur gears and plane bending fatigue performance of notched test bars. R = 0 root bending fatigue tests are made on small spur gears with critical root radius 1.0 mm. The results are compared to plane bending fatigue tests of 0.9 mm radius notched specimens. Results are presented for tests on 4%Ni/2%Cu/1.5%Mo prealloyed PM steel with addition of about 0.6% graphite. Predicted values from the test bars coincide well with the results obtained from the gear root fatigue tests.
Practical Aspects of Instantaneous Magnetization Power Functions of Silicon Iron Laminations
Pfützner Helmut,Shilyashki Georgi,Bengtsson Claes,Huber Emanuel 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.2
Magnetic energy loss P of SiFe steel represents a key factor for the efficiency of soft magnetic machine cores. Traditionally, they are operated with 50 Hz (or 60 Hz), a frequency value that yields rather balanced portions of hysteresis loss and eddy current loss. In equivalent circuits of transformers, P tends to be represented by a magnetic power resistance RM, as a constant. For the most important case of sinusoidal induction B of 50 Hz, this would correspond to an instantaneous magnetization power function p(t) that is sinusoidal as well, however, with 100 Hz (or 120 Hz). On the other hand, from complex, non-linear mechanisms of hysteresis, it is obvious that p(t) should be strongly non-sinusoidal, even for exactly sinusoidal B(t). So far, almost all corresponding instantaneous investigations were restricted to calculated modelling of loss portions and transient modelling. On the other hand, for the first time, the present study was focussed on functions p(t) as measured at IEC-standardized samples of industrially relevant steel. Practical evaluations are discussed with respect to the revealed “history” of magnetization processes, as well as for product characterization. For these tasks, a novel digitized “Low-mass Single Sheet Tester” was developed that was applied for both non-oriented steel (NO) and grain-oriented steel (GO), for 50 Hz. Interpretations proved to be favoured by relating p(t) to total P, according to an instantaneous power ratio. As a result, both steel types revealed strongly non-sinusoidal power functions, with short durations of negative p. Negative p proved to be most pronounced for NO steel, as a measure for the onset of reversible turns of atomic moments. As a consequence, p(t) comprises strong upper harmonics of 200 Hz and even 300 Hz. Based on theoretical considerations, we split p(t) in a dissipative loss power function pL(t) and in a potential energy power function pP(t). Finally, we used p(t) to determine the corresponding power resistance RM(t) that proves to be a distinctly nonlinear function as well. It resembles a rectified co-sinus, also exhibiting short negative spikes that reflect the crystallographic dis-orientation of the polycrystalline material.
Bergman Ola,Lindqvist Bjorn,Bengtsson Sven 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range , due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density , after sintering at followed by cooling at and tempering.
Jiaxin Chen,Fredrik Lindberg,Daniel Wells,Bernt Bengtsson 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.4
Experimental verification of boron species in fuel CRUD (Chalk River Unidentified Deposit) would provideessential and important information about the root cause of CRUD-induced power shifts (CIPS). Todate, only bonaccordite and elemental boron were reported to exist in fuel CRUD in CIPS-troubledpressurized water reactor (PWR) cores and lithium tetraborate to exist in simulated PWR fuel CRUDfrom some autoclave tests. We have reevaluated previous analysis of similar threadlike crystals alongwith examining some similar threadlike crystals from CRUD samples collected from a PWR cycle that hadno indications of CIPS. These threadlike crystals have a typical [Ni]/[Fe] atomic ratio of ~2 and similarcrystal morphology as the one (bonaccordite) reported previously. In addition to electron diffractionstudy, we have applied electron energy loss spectroscopy to determine boron content in such a crystaland found a good agreement with that of bonaccordite. Surprisingly, such crystals seem to appear also oncorroded surfaces of Alloy 600 that was exposed to simulated PWR primary water with a dissolvedhydrogen level of 5 mL H2/kg H2O, but absent when exposed under 75 mL H2/kg H2O condition. It remainsto be verified as to what extent and in which chemical environment this phase would be formed inPWR primary systems.
Annelie Shami,Andreas Edsfeldt,Eva Bengtsson,Jan Nilsson,Angela C. Shore,Andrea Natali,Faisel Khan,Esther Lutgens,Isabel Gonçalves 대한뇌졸중학회 2021 Journal of stroke Vol.23 No.3
Background and Purpose CD40 and CD40 ligand (CD40L) are costimulatory molecules of the tumor necrosis factor receptor superfamily and well known for their involvement in inflammatory diseases: atherosclerotic mouse models with disrupted CD40 signalling develop lesions of reduced size with a more stable plaque profile. This study investigated the potential of plasma and intraplaque levels of CD40 and CD40L as markers for cardiovascular disease (CVD) in humans and their association with plaque stability. Methods Soluble CD40 and CD40L (sCD40L) were measured in plasma in 1,437 subjects from The SUrrogate markers for Micro- and Macro-vascular hard endpoints for Innovative diabetes Tools (SUMMIT) cohort. Intra-plaque levels of sCD40 and sCD40L were measured in atherosclerotic plaque homogenates from 199 subjects of the Carotid Plaque Imaging Project (CPIP) cohort. Results Both plasma sCD40 and sCD40L levels were elevated in individuals with prevalent stroke, while sCD40 levels also were higher in individuals with a prior acute myocardial infarction. Plasma levels of sCD40 correlated with carotid intima-media thickness and total carotid plaque area and were associated with risk of cardiovascular events over a 3-year follow-up period. Intra-plaque levels of sCD40 and sCD40L were associated with plaque components characteristic for plaque vulnerability and extracellular matrix remodelling. Conclusions Higher plasma sCD40 and sCD40L levels are associated with prevalent CVD. Plasma sCD40 levels also correlate with the severity of carotid atherosclerosis and predict future cardiovascular events, while intra-plaque levels correlate with a vulnerable plaque phenotype. Our findings thus demonstrate that elevated levels of sCD40 and sCD40L are markers of CVD.