半钢子午线轮胎胎侧白圈外观不良原因分析及改进措施

分析半钢子午线轮胎胎侧白圈外观不良的产生原因,并提出改进措施。通过采取使用白胎侧轮胎专用覆皮胶、合理设计白胶料在胎侧中的位置、控制胎侧生产时白胶料与黑胶料的挤出压力、确保挤出半成品部件表面平整、减小成型时胎侧位置偏歪、接头搭接尺寸按零偏差控制等措施,并严格管控生产过程,有效解决了半钢子午线轮胎胎侧白圈外观不良的问题。

无效的警告少点好

当前社会上警告一类的宣传比比皆是,“不许”“不准”“严禁”“禁止”满天飞,“违者罚款”“违者重罚”更是成了套话。被罚的一个没有,那是假话;可究竟有多少人被罚呢?夸张一点讲,恐怕还不如这类的警告宣传多。若真是“违者”不多,倒是件好事,可实际情况是“违者”并不在少数,而真正能和“违者罚款”兑上现的,几乎寥寥无几。 这类警告宣传究竟能起多大作用,看来很值得怀疑。它的大量出现会引起什么副作用,我没有研究,但就自己的所见所闻我认为起码在某些地方进行这样的警告宣传是大可不必的。

好人也可能貌丑

这次陕西文艺会演,商洛地区的《屠夫壮元》是好节目之一。戏中被歌颂的那位“屠夫官”,两眼之间有一个白圈圈——原来是丑角,动作也很滑稽,确实有悖于编导“常规”,因而给人脑海中留下的刻痕极深。风行于中国戏坛的所谓“英雄必美貌”论,看来是应当有所改善了。 其实,古人早对戏剧上的“英雄必美貌”有所批判。晏婴戏中的“头号英雄”晏婴,就是一个其貌不扬,个子特低的形象,这种形象,和晏婴的辩才与机智,形成了相当强烈的对照。

Travel Motivation of Domestic Tourists to the Changbai Mountain Biosphere Reserve in Northeastern China: A Comparative Study

This article seeks to develop a fuller understanding of the social and attraction motives of domestic tourists who visit the Changbai Mountain Biosphere Reserve(CMBR) in Northeastern China. To do so, ecotourists are compared to general travelers visiting this area. A questionnaire was employed to collect data on visitor characteristics and motivations, responses to which were then analyzed via descriptive statistics, T-tests and principal component factor analysis. Results showed that 16% of the visitors to this area were classified as ecotourists, while the remainder general travelers. Five motivations displayed significant differences(P<0.05) between these two types of tourists. Three social motives – boosting self-confidence, feeling at home away from home and being together with family – and two attraction motives – indoor sports and viewing unique landscapes of the CMBR(crater lake, waterfall, gorge and hot spring) – were significantly more important for general travelers(P<0.05); while two social motives of experiencing the tranquility of the natural setting and the natural beauty of the landscape were relatively more important for ecotourists(P<0.1). Results suggest that ecotourists have distinct and complicated attraction and social motives compared to general travelers visiting the CMBR. Results have useful implications for researchers interested in tourist motivations and behavior, as well as for managers who wish to focus their marketing strategies more effectively. National Park of South Africa. Uysal et al.(1994) assessed the travel motives of Australian tourists to U.S. national parks and nature areas and formed five groupings including ‘relaxation/hobbies', ‘novelty', ‘enhancement of kinship relationship', ‘escape', and ‘prestige'. Tao et al.(2004) analyzed motivations of Asian tourists travelling to Taiwan's Taroko National Park using a self-defined approach and found that the most significant benefits sought by self-defined ecotourists are ‘learning about nature' and ‘participating in recreation activities'. Beh and Bruyere(2007) analyzed visitor motivations in three Kenyan national reserves, identifying the three most prominent kinds of tourists as escapers, learners and spiritualists. Pan and Ryan(2007) used factor analysis to reveal five motivational dimensions –‘relaxation', ‘social needs', ‘a sense of belonging', ‘mastery skills', and ‘intellectual needs' – of visitors to the Pirongia Forest Park in New Zealand. Kruger and Saayman(2010) did a comparative study on travel motivations of tourists to Kruger and Tsitsikamma National Parks in South Africa and found that common motives of tourists were ‘escape and relaxation' as well as ‘knowledge seeking', ‘nostalgia' and ‘park attributes'. Despite these efforts, on an overall basis past literature on why visitors travel to national parks and nature areas is still rather limited. In China, a number of empirical studies on tourist motivations have been conducted since the early 1990s(Chen and Miao 2006; Dong 2011; Huang et al. 2011; Jeffrey and Xie 1994; Lu 1997; Ma et al. 2013; Zhang 2012). Some studies have focused on motivations of visitors to nature reserves(Li 2007), geological parks(Chen and Qiao 2010), world heritage sites(Su et al. 2005), and seismic memorial sites(Tang 2014). However, most previous research findings on tourist motivations are not comparable, reflecting the fact that visitors to different parks have quite different motives due to the attributes of particular destinations, the geographic locations of these parks, types of available activities, marketing strategies, and the complexity of travel motives(Chen and Qiao 2010; Pan and Ryan 2007). While it is true that certain motivations were shared in varying degrees by most tourists to these places – i.e., ‘appreciating natural landscapes', ‘family and education', ‘social needs', and ‘perceived prestige of visit' – most previous research has not focused on natural settings as destinations. Thus travel motivations of tourists to these areas must be further explored and clarified in relation to impacts on particular natural areas and patterns of market segmentation. As one of the earliest and largest natural reserves established in China, the Changbai Mountain Biosphere Reserve(CMBR) has long been a draw not only for domestic tourists but also for international visitors, and tourism to the area has been growing steadily since 1980. With the number of visitors to the reserve having climbed to 2.44 million in 2010(Statistical Communiqué of the Changbai Mountain Protection and Development Zone of Jilin Province 2011), it has become imperative for local government officials and reserve wardens to understand tourists' desires and interests when identifying tourism development opportunities. However, the existing literature still suffers from a lack of empirical studies that investigate why people travel to the CMBR and whether tourist motives differ between groups such as ecotourists and general travelers. The target population for this study consists of domestic visitors to the CMBR. The goals of this research include:(1) to identify the social and attraction motives of domestic tourists that influence decisions to visit the CMBR;(2) to explore whether there are any differences between the motivations of these two types of tourists; and(3) to provide some useful management implications for local government and tourism marketers.

Biosynthetic approach to modeling and understanding metalloproteins using unnatural amino acids

Metalloproteins have inspired chemists for many years to synthesize artificial catalysts that mimic native enzymes.As a complementary approach to studying native enzymes or making synthetic models,biosynthetic approach using small and stable proteins to model native enzymes has offered advantages of incorporating non-covalent secondary sphere interactions under physiological conditions.However,most biosynthetic models are restricted to natural amino acids.To overcome this limitation,incorporating unnatural amino acids into the biosynthetic models has shown promises.In this review,we summarize first synthetic,semisynthetic and biological methods of incorporates unnatural amino acids(UAAs)into proteins,followed by progress made in incorporating UAAs into both native metalloproteins and their biosynthetic models to fine-tune functional properties beyond native enzymes or their variants containing natural amino acids,such as reduction potentials of azurin,O_2 reduction rates and percentages of product formation of HCO models in Mb,the rate of radical transport in ribonucleotide reductase(RNR)and the proton and electron transfer pathways in photosystemⅡ(PSⅡ).We also discuss how this endeavour has allowed systematic investigations of precise roles of conserved residues in metalloproteins,such as Metl21 in azurin,Tyr244 that is cross-linked to one of the three His ligands to CuB in HCO,Tyr122,356,730 and 731 in RNR and TyrZ in PSⅡ.These examples have demonstrated that incorporating UAAs has provided a new dimension in our efforts to mimic native enzymes and in providing deeper insights into structural features responsible high enzymatic activity and reaction mechanisms,making it possible to design highly efficient artificial catalysts with similar or even higher activity than native enzymes.

Modification of the lithospheric mantle by melt derived from recycled continental crust evidenced by wehrlite xenoliths in Early Cretaceous high-Mg diorites from western Shandong, China

This paper reports petrographic, mineral chemical, olivine oxygen isotopic, and whole-rock geochemical data for wehrlite xenoliths from the Early Cretaceous Tietonggou high-Mg diorites in western Shandong Province, in the eastern part of the North China Craton (NCC), and describes the origin of these wehrlites and the processes that affected the deep lithospheric mantle in this area.Wehrlite xenoliths are rounded and vary in size between 3 cm × 4 cm 5 cm and 3 cm 2 cm 1 cm.Olivine within these xenoliths occurs as an isolated residual phase within clinopyroxene, has Fo contents between 89 and 91, and contains between 1414 and 3629 ppm Ni, similar to the values of olivine from peridotite xenoliths in the Cenozoic basalts of eastern China, but lower than the values of olivine from harzburgite xenoliths in the Early Cretaceous high-Mg diorites in western Shandong.In situ oxygen isotope analysis yielded 18 O values of olivine from (6.03±0.33)‰ to (6.82±0.35)‰, averaging (6.5±0.4)‰; this is higher than typical mantle-derived olivine ((5.2±0.3)‰).Compared with clinopyroxenes from peridotite xenoliths in the Late Cretaceous and Cenozoic basalts, clinopyroxenes in the wehrlites contain relatively low concentrations of Na 2 O, TiO 2 , and Al 2 O 3 , high concentrations of CaO, and higher Mg # (91.2-94.1) and Ti/Eu ratios (2082-2845), being similar in composition to clinopyroxenes within harzburgite xenoliths in the Early Cretaceous high-Mg diorites.Clinopyroxenes from wehrlite xenoliths are characterized by low total REE abundance, enrichment in light REEs, and depletion in high field strength elements such as Nb, Ta, Zr, and Hf.Moreover, the 87 Sr/ 86 Sr, 143 Nd/ 144 Nd, and 187 Os/ 188 Os (125 Ma) ratios of these wehrlites vary from 0.70596 to 0.70737, 0.512181 to 0.512416, and 0.12661 to 0.57650, respectively.These data suggest that these wehrlite xenoliths were formed by modification of the lithospheric mantle by melts derived from recycled continental crust.

Decratonic gold deposits

The North China Craton(NCC) hosts numerous gold deposits and is known as the most gold-productive region of China. The gold deposits were mostly formed within a few million years in the Early Cretaceous(130–120 Ma), coeval with widespread occurrences of bimodal magmatism, rift basins and metamorphic core complexes that marked the peak of lithospheric thinning and destruction of the NCC. Stable isotope data and geological evidence indicate that ore-forming fluids and other components were largely exsolved from cooling magma and/or derived from mantle degassing during the period of lithospheric extension. Gold mineralization in the NCC contrasts strikingly with that of other cratons where gold ore-forming fluids were sourced mostly from metamorphic devolatization in compressional or transpressional regimes. In this paper, we present a summary and discussion on time-space distribution and ore genesis of gold deposits in the NCC in the context of the timing, spatial variation, and decratonic processes. Compared with orogenic gold deposits in other cratonic blocks, the Early Cretaceous gold deposits in the NCC are quite distinct in that they were deposited from magma-derived fluids under extensional settings and associated closely with destruction of cratonic lithosphere. We argue that Early Cretaceous gold deposits in the NCC cannot be classified as orogenic gold deposits as previously suggested, rather, they are a new type of gold deposits, termed as "decratonic gold deposits" in this study. The westward subduction of the paleo-West Pacific plate(the Izanagi plate) beneath the eastern China continent gave rise to an optimal tectonic setting for large-scale gold mineralization in the Early Cretaceous. Dehydration of the subducted and stagnant slab in the mantle transition zone led to continuous hydration and considerable metasomatism of the mantle wedge beneath the NCC. As a consequence, the refractory mantle became oxidized and highly enriched in large ion lithophile elements and chalcophile elements(e.g., Cu, Au, Ag and Te). Partial melting of such a mantle would have produced voluminous hydrous, Au- and S-bearing basaltic magma, which, together with crust-derived melts induced by underplating of basaltic magma, served as an important source for ore-forming fluids. It is suggested that the Eocene Carlin-type gold deposits in Nevada, occurring geologically in the deformed western margin of the North America Craton, are comparable with the Early Cretaceous gold deposits of the NCC because they share similar tectonic settings and auriferous fluids. The NCC gold deposits are characterized by gold-bearing quartz veins in the Archean amphibolite facies rocks, whereas the Nevada gold deposits are featured by fine-grained sulfide dissemination in Paleozoic marine sedimentary rocks. Their main differences in gold mineralization are the different host rocks, ore-controlling structures, and ore-forming depth. The similar tectonic setting and ore-forming fluid source, however, indicate that the Carlin-type gold deposits in Nevada are actually analogous to decratonic gold deposits in the NCC. Gold deposits in both the NCC and Nevada were formed in a relatively short time interval(<10 Myr) and become progressively younger toward the subduction zone. Younging of gold mineralization toward subduction zone might have been attributed to retreat of subduction zone and rollback of subducted slab. According to the ages of gold deposits on inland and marginal zones, the retreat rates of the Izanagi plate in the western Pacific in the Early Cretaceous and the Farallon plate of the eastern Pacific in the Eocene are estimated at 8.8 cm/yr and 3.3 cm/yr, respectively.