| 1. |
- Chen, S., et al.
(författare)
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Coffin-Mansson equation of Sn-4.0Ag-0.5Cu solder joint
- 2009
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Ingår i: Soldering and Surface Mount Technology. - : Emerald. - 1758-6836 .- 0954-0911. ; 21:2, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this paper is to fit Coffin-Manson equation of Sn-4.0Ag-0.5Cu lead free solder joint by using results of solders joint reliability test and finite element analysis. Also to present a novel device for solder joint reliability test. Design/methodology/approach: Two-points bending test of Sn-4.0Ag-0.5Cu lead free solder joint was carried out at three deflection levels by using a special bending tester that can control displacement exactly by a cam system. The failure criterion was defined as resistance of solder joint getting 10 percent increase. The X-section was done for all failure samples to observe crack initiation and propagation in solder joint. Finite element analysis was presented with ANSYS for obtaining shear strain range, analyzing distribution of stress and strain and supporting experimental results. Findings: The experimental results indicate that the fatigue life decreased obviously with the displacement increased. By using optical microscope and SEM photographs, two kinds of failure mode were found in solder joint. The majority failure mode took place at the bottom corner of solder joint under the termination of resistor initially, and propagated into the solder matrix. Another failure mode was delamination. It appeared at the interface between the termination of resistor and its ceramic body. The distribution status of stress and strain in solder joint and the calculation results of shear strain range at different deflection levels were obtained from simulation result. The Coffin-Manson equation of Sn-4.0Ag-0.5Cu lead free solder joint was fitted by combining experimental data with result of finite element analysis. Originality/value: This paper presents Coffin-Manson equation of Sn-4.0Ag-0.5Cu solder joint with two-points bending test. An effective and economical device was designed and applied.
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| 2. |
- Cheng, Q, et al.
(författare)
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Clinical features of patients with multiple sclerosis from a survey in Shanghai, China
- 2008
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Ingår i: Multiple sclerosis (Houndmills, Basingstoke, England). - : SAGE Publications. - 1352-4585 .- 1477-0970. ; 14:5, s. 671-678
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Tidskriftsartikel (refereegranskat)abstract
- Objective To describe clinical features of patients with multiple sclerosis (MS) in Shanghai, China. Methods Prevalent patients with MS were identified and investigated by a network of physicians in 11 districts of Shanghai during the period from 1 September 2004 to 31 August 2005. Admission registries of each hospital in the study area were checked systematically for patients with a diagnosis of MS, neuromyelitis optica or other demyelinating disorders. All patients with collected information were evaluated by four senior neurologists according to the McDonald criteria. Results There were 249 (146 female and 103 male) patients with a confirmed MS diagnosis, at a female-to-male ratio of 1.4. The mean age at onset of MS was 37.4 years for the 249 patients with MS and, on the prevalence day, 42.7 years. The most frequent location of clinical MS lesions in the central nervous system was the spinal cord (61%), followed by the cerebrum (55%) and optic nerves (41%). Nearly all (96%) of the patients with MS had been examined by magnetic resonance imaging, and 226 (94%) patients of those examined were suggestive of MS. No family history of MS was found in any of the patients. Most (86%) of the patients had no or mild disability on the prevalence day (31 December 2004). Almost all (96%) patients with MS had been treated with corticosteroids. Conclusion Clinical features of patients with MS are described based on the information from the largest case series reported among Chinese. Comparisons and discussions are made with findings from the other populations.
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| 3. |
- Cheng, Q, et al.
(författare)
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Multiple sclerosis in China--history and future
- 2009
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Ingår i: Multiple sclerosis (Houndmills, Basingstoke, England). - : SAGE Publications. - 1352-4585 .- 1477-0970. ; 15:6, s. 655-660
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Tidskriftsartikel (refereegranskat)abstract
- Background Multiple sclerosis (MS) is considered rare in China and reports on MS in the English literature are few. Methods A systematic literature search for articles with MS was made, particularly for papers published in the Chinese medical journals from mainland China. Results In China, the first case of MS was described in the medical records from Xiehe hospital in 1926, and the first autopsy case of MS was reported from Huashan hospital in 1957. Although reports on MS based on the information from hospital case-series have been increased gradually in the recent decades, there is no national surveillance on MS frequency in the population and population-based surveys on MS were few in China. Generally for Chinese patients with MS the mean age at onset of MS is around 30 years, with a few cases younger than 20 years; the most frequent site of the lesions in the central nervous system, based on the clinical symptoms or signs, is the spinal cord (usually more than 60%); there are few patients with a family history of MS; almost all patients are treated with corticosteroids. Reported prevalence rates of MS from population surveys in China are rather low (1–2 per 100,000) and higher in females than in males, which are comparable with the results from other populations in Asia. Conclusion The clinical and epidemiological aspects of MS in China are, in general, similar to that from other populations in Asia. Epidemiological studies and national surveillance on MS are required in China.
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| 4. |
- Elsik, Christine G., et al.
(författare)
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The Genome Sequence of Taurine Cattle : A Window to Ruminant Biology and Evolution
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 324:5926, s. 522-528
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Tidskriftsartikel (refereegranskat)abstract
- To understand the biology and evolution of ruminants, the cattle genome was sequenced to about sevenfold coverage. The cattle genome contains a minimum of 22,000 genes, with a core set of 14,345 orthologs shared among seven mammalian species of which 1217 are absent or undetected in noneutherian (marsupial or monotreme) genomes. Cattle-specific evolutionary breakpoint regions in chromosomes have a higher density of segmental duplications, enrichment of repetitive elements, and species-specific variations in genes associated with lactation and immune responsiveness. Genes involved in metabolism are generally highly conserved, although five metabolic genes are deleted or extensively diverged from their human orthologs. The cattle genome sequence thus provides a resource for understanding mammalian evolution and accelerating livestock genetic improvement for milk and meat production.
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| 5. |
- Hsieh, Yves S-Y, et al.
(författare)
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Structure and bioactivity of the polysaccharides in medicinal plant Dendrobium huoshanense
- 2008
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Ingår i: Bioorganic & Medicinal Chemistry. - : Elsevier. - 0968-0896 .- 1464-3391. ; 16:11, s. 6054-68
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Tidskriftsartikel (refereegranskat)abstract
- Detailed structures of the active polysaccharides extracted from the leaf and stem cell walls and mucilage of Dendrobium huoshanense are determined by using various techniques, including chromatographic, spectroscopic, chemical, and enzymatic methods. The mucilage polysaccharide exhibits specific functions in activating murine splenocytes to produce several cytokines including IFN-gamma, IL-10, IL-6, and IL-1alpha, as well as hematopoietic growth factors GM-CSF and G-CSF. However, the deacetylated mucilage obtained from an alkaline treatment fails to induce cytokine production. The structure and bioactivity of mucilage components are validated by further fractionation. This is the first study that provides clear evidence for the structure and activity relationship of the polysaccharide in D. huoshanense.
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| 6. |
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| 7. |
- Sun, Peng, 1979, et al.
(författare)
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High temperature aging study of intermetallic compound formation of Sn-3,5Ag and Sn-4.0Ag-0,5Cu solders on electroless Ni(P) metallization
- 2006
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 425:1-2, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- The Sn-3.5Ag and Sn-4.0Ag-0.5Cu solders on Au/electroless Ni(P) metallization exhibited different interfacial morphologies after high temperature storage (HTS) at 150 °C. Ni 3 Sn 4 intermetallic compounds (IMCs) were found in the Sn-Ag system, while for the Sn-Ag-Cu system the IMCs consisted of two kinds of interfacial reactions. For the Sn-3.5Ag solder, the Ni 3 Sn 4 IMC particles lost adhesion/contact to the electroless Ni(P) layer and clear gap was observed in the samples after high temperature storage (HTS) aging for 1000 h. In the Sn-4.0Ag-0.5Cu solder joint, both (Cu,Ni) 6 Sn 5 and (Ni,Cu) 3 Sn 4 compounds were observed after HTS aging. Since the difference in nucleation site and growth rate for kinds of IMCs, (Cu,Ni) 6 Sn 5 was observed at top and (Ni,Cu) 3 Sn 4 at bottom when the interfacial compound layer became thicker as a function of thermal aging. Some voids were found between the electroless Ni(P) interface and the Sn-Ag solder after 168 and 500 h of thermal aging, while the clear gap between the solder and the Ni layer existed after 1000 h aging. The formation mechanism for this gap could be the interconnection and growth of the voids. In the Sn-Ag-Cu system, voids were found inside the Sn-Ni-Cu ternary interfacial compounds after 500 and 1000 h. The formation mechanism for these voids was thought to be Kirkendall effect or etching process. The interfacial layer of Sn-Ag-Cu solder on electroless Ni(P) coating showed the better thermal stable than eutectic Sn-Ag solder. © 2006 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
- Agrell, Fredrik, 1971-
(författare)
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Control of HCCI by aid of Variable Valve Timings with Specialization in Usage of a Non-Linear Quasi-Static Compensation
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis is about controlling the combustion timing of the combustion concept Homogeneous Charge Compression Ignition, HCCI, by means of variable valve timings. The HCCI research usually is regarded to have started in Japan during the later part of the 1970´s. The world of HCCI has since grown and HCCI is of today researched worldwide. Of particular interest from a Swedish point of view is that Lund Institute of Technology has emerged as one of the world leading HCCI laboratories. The idea with HCCI is to combine the Otto and Diesel engine. As in an Otto engine the charge is premixed but as in a Diesel engine the operation is unthrottled and the compression heat causes the ignition. The combustion that follows the ignition takes place homogeneously and overall lean. The result is ultra low NOx and particulate emissions combined with high total efficiency. A difficulty with the HCCI-concept is that it only works in a narrow area and that there is no direct way to control the Start Of Combustion, SOC. Out of this follows that timing/phasing of the combustion is one of the main difficulties with HCCI combustion concepts. This is particularly emphasized during transient operation and calls for feedback control of the combustion timing. This work investigates one method, the variable valve timing, to achieve feedback control of the combustion phasing. From the work it can be concluded that the variable valve timing can control the combustion phasing during engine transients. In order to improve the performance a non-linear compensation from ignition delay to valve timings has been suggested, incorporated in a control structure and tested in engine test. The engine test has been performed in a single cylinder engine based on a Scania truck engine. The speed range from 500 to 1750 rpm and the load range 1.26 and 10.5 bar of netIMEP has been covered with fair transient performance.
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| 10. |
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