• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Research on asphalt concrete pavement deicing technology

    2014-09-06 10:49:48MaHuiYangRuochongQianShunzhi
    關(guān)鍵詞:冰層有機(jī)硅冰雪

    Ma Hui Yang Ruochong Qian Shunzhi

    (School of Transportation, Southeast University, Nanjing 210096, China)

    ?

    Research on asphalt concrete pavement deicing technology

    Ma Hui Yang Ruochong Qian Shunzhi

    (School of Transportation, Southeast University, Nanjing 210096, China)

    In order to reduce the cohesive force between pavement and ice, the approach of pavement surface coating with hydrophobic admixtures is investigated. The deicing effect of this approach is examined by the contact angle test and the shear test. The durability of the approach is examined by the accelerated abrasion test, and the skid resistance of the pavement with surface coating is examined by the British pendulum test and the surface texture depth test. In the contact angle test, the contact angle between hydrophobic admixture and water is 100.2°. In the shear test, the maximum shear stress is 0.06 MPa for the specimen coated with hydrophobic admixture, which is much lower than that of the specimen without hydrophobic admixture coating, 3.5 MPa. Furth-ermore, the ice and asphalt surface are completely separated for the coated specimen while not for the uncoated specimen. Based on the accelerated abrasion test, the residual hydro-phobic admixture in the veins of the pavement after abrasion still has a deicing effect. From the skid resistance tests, the British pendulum number (BPN) and the texture depth (TD) of the specimen coated with hydrophobic admixtures are larger than those of the standard requirements. The overall experi-mental observation indicates that the approach can effectively reduce close contact between asphalt pavement and ice; therefore, it can be a promising solution to road icing problems in winter.

    deicing; hydrophobic admixture; surface coating; cohesive force; durability

    With the second largest road network in the world, China is very vulnerable to snow and icy rain in winter which happens to be the high season for road traffic. The snow and ice on the road significantly impact the normal operation of vehicles, which causes heavy disruption to the national economy and people’s daily life. Over the last several decades, a significant amount of research have been conducted to explore convenient and efficient snow melting and deicing techniques to solve this problem. These techniques can be broadly divided into external and internal approaches.

    External approaches include deicing by technologies such as scattering an ice-melting agent, surface coating and cleaning manually or by machinery, etc[1]. Scattering an ice-melting agent is an approach to reduce the melting point of ice; therefore, the ice can melt at a lower temperature. Chlorine salt is the main ice-melting agent due to its low cost. Although this approach has a high deicing efficiency, chlorine salt can also significantly corrode roads and bridges as well as pollute the soil and water in the long term[1-6]. The manual or machinery cleaning approach is commonly used for deicing; however, it has drawbacks such as a low cleanse rate and a high cost. More innovative deicing approaches such as microwave heating deicing have not been popularized because of their low deicing efficiency and immaturity[7-9].

    An internal approach to deicing has functional pavements using different technologies, such as deicing by heating up the pavement, adding salinization material and granulated crumb rubber into the asphalt mixture[10]. Ice melting by heating mainly uses the heat produced by geotherm, gas, electric and solar energy. This method has a high rate of ice melting; nevertheless using this technology is energy intensive, costly and difficult to construct[10-16].Similar to the scattering ice-melting agent approach, ice melting by adding a salinization material into the asphalt mixture is to reduce freezing point of the ice on the pavement. The difficulty of this approach is to guarantee the pavement’s performance, such as high temperature stability, low-temperature crack resistance and water damage resistance[10,17]. The success of the last approach hinges on the uneven deformation characteristics of rubble particles. With the aid of the rubber particles’ larger deformation compared to the asphalt mixture, ice can be easily broken under the vehicle load. This approach can reduce road noise and improve the pavement’s performance including high temperature stability, low-temperature crack resistance and antiskid performance; nevertheless the deicing effect is not ideal and the smoothness of pavement will deteriorate over time[18].

    As can be seen from the above literature reviews, extensive research has been conducted to solve deicing problems, yet various problems still need to be resolved. Therefore, this paper attempts to improve the efficiency of deicing technology via surface coating approach, resulting in safe and durable pavements.

    1 Experimental Program

    1.1 Materials

    Two kinds of hydrophobic admixtures were used in this study, which include SILQUESTRYC-1005G-NT and SILRESRBS290. They are all liquid materials. YC-1005G-NT is a hydrophobic admixture based on organosilicon. It has a good hydrophobic ability, high penetrability and high adhesiveness. BS290 is a solventless silicone concentrate based on a mixture of silane and siloxane. The physical properties of hydrophobic admixtures are shown in Tab.1.

    Tab.1 Physical properties of hydrophobic admixtures

    1.2 Contact angle test

    The contact angle test was used to illustrate the contact relationships of hydrophobic admixtures/water and hydrophobic admixtures/asphalt. First, hydrophobic admixtures and asphalt were coated on the glass boards, respectively. Then, distilled water was dripped onto the glass boards coated with hydrophobic admixtures and hydrophobic admixtures were dripped onto the glass boards coated with asphalt. The contact angles were measured by the admeasuring apparatus-CA-XP150.

    1.3 Shear test

    In order to study the change of cohesive force between the ice and pavement, which is coated and uncoated with hydrophobic admixtures, the shear test was conducted. To greatly simplify the research task, the surface of the Marshall specimen was adopted to represent the surface of the pavement in the experiment. The diameter and length of the Marshall specimen were 100 and 64 mm, respectively. The asphalt content was 5% in the mixture. First, hydrophobic admixtures were coated onto the top surface of Marshall specimens. There were three different dosages for each hydrophobic admixture, i.e., 0.3, 0.5 and 0.7 kg/m2, respectively. Secondly, the coated specimens were cured at room temperature for 10 h so that the hydrophobic admixtures could be absorbed completely by the Marshall specimen surface. The top surface of the Marshall specimen was lapped with a blown-sponge to form a reservoir to retain water, as shown in Fig.1(a). Afterwards, water was poured into the reservoir, which was then put into a refrigerator to form ice on the surface. At the same time, control specimens without coating were made following the same procedure for comparison.

    After water on the surface of the specimens was frozen, the shear test was conducted with the universal testing machine (UTM), as shown in Fig.1(b). The test was conducted under a displacement control of 5 mm/min. In the test, the load and displacement data were continuously recorded; and the fracture surfaces of specimens were carefully

    (a)

    (b)

    examined after the test. In order to prevent the ice melting, the temperature in the UTM chamber was set at -10 ℃ for one hour before the test. Due to the difficulty in mounting external LVDTs on the specimen, displacement data from the internal LVDT was used for this investigation.

    1.4 Accelerated abrasion test

    In order to study the durability of hydrophobic admixtures, which were coated on the top surface of pavement, an accelerated abrasion test was devised. First, the SMA-13 specimens were prepared with a size of 280 mm×140 mm×50 mm, as shown in Fig.2. Secondly, hydrophobic admixtures were coated onto the top surface of specimens three times with an interval of 15 min. The total dosage of the hydrophobic admixture for a specimen was 0.7 kg/m2. Finally, the coated specimens were cured at a temperature of 15 ℃ for 20 h so that the hydrophobic admixtures could solidify completely.

    Fig.2 The specimen of accelerated abrasion test

    The accelerated abrasion test was conducted on an instrument modified from a rutting tester with friction provided by the additional loading frame, as shown in Fig.3. In order to imitate the interaction between the wheel and the road for two different scenarios, i.e. braking and driving wheel action, the friction stress levels were set to be 0.11 and 0.33 MPa, respectively, which were calculated by

    τ=σnsinθ+kσn

    (1)

    whereσn=0.7 MPa is the pressure between the wheel and the pavement;kis the coefficient of rolling friction, under the condition of driving wheel action,k=0.13 to 0.22, and under the condition of braking wheel action,k=0.5 to 0.6; andθis the pavement profile grade (in this studyθ=3%). After abrasion, the top surface of the specimen was lapped with a blown-sponge to retain water (see Fig.4), which was then frozen in the refrigerator. Afterwards, the ice on the specimen was compressed 10 times by a rut board molding pendulum to simulate the action of wheel loads on an icy road, as shown in Fig.5. The compressive action on the ice-covered specimen was greatly amplified since the pressure of the rut board molding pendulum was 1.11 MPa, which is much larger than the normal pressure exerted by vehicle types. The fracture/damage forms of the ice on the specimens were checked carefully after compressing. Finally, a shear test was also conducted to reveal the deicing effect of residual hydrophobic admixtures after the accelerated abrasion test. The specimens for shear test were drilled from the specimens for the accelerated abrasion test once the test was finished. The diameter and length of shear test specimen were 100 and 50 mm, respectively.

    Fig.3 Accelerated abrasion instrument

    Fig.4 Specimen lapped with blown-sponge

    Fig.5 Ice on surface of specimen compressed by rut board molding pendulum

    1.5 Skid resistance test

    In order to investigate the impact of hydrophobic admixtures on pavement skid resistance, BPN and TD of specimens were measured. First, the SMA-13 specimens were prepared with the size of 300 mm×300 mm×50 mm. Secondly, hydrophobic admixtures were coated onto the top surface of specimens with a dosage of 0.7 kg/m2. Then, BPN and TD were measured after the hydrophobic admixtures solidified completely. At the same time, control specimens without coating were tested for comparison.

    2 Results and Discussion

    2.1 Contact angle test

    The bigger the contact angle, the better the hydrophobic properties of the surface of the specimen. Generally, when the contact angle is greater than 90°, the surface of the specimen has a hydrophobic property. In addition, if the contact angle is larger than 150°, the surface has super-lyophobic properties.

    The contact angle between the hydrophobic admixture YC-1005G-NT and water is shown in Fig.6(a). The contact angle between YC-1005G-NT and water is 100.2°; while the contact angle between BS290 and water is 85.3°. It can be seen that the hydrophobic property of YC-1005G-NT is better than that of BS290. When hydrophobic admixtures are dripped on the surface of asphalt, the contact angles between asphalt and YC-1005G-NT/BS290 are 10.8° and 15.4°, respectively, as shown in Fig.6(b). The small contact angles between hydrophobic admixtures and asphalt suggest that the hydrophobic admixtures could bond with asphalt efficiently. Overall, hydrophobic admixtures have good hydrophilic properties, in particular YC-1005G-NT. Hydrophobic admixtures have small surface tension with asphalt, so they can permeate into asphalt concrete pavements and greatly extend its service life as a deicing material.

    (a)

    (b)

    Fig.6 Contact angles of different interfaces. (a) YC-1005G-NT and water; (b) YC-1005G-NT and asphalt

    2.2 Shear test

    The test results corresponding to different dosage of hydrophobic admixtures are shown in Figs.7 to 9. It has been observed that hydrophobic admixtures are very effective in reducing the bond between the specimen surface and ice. Deicing effect of hydrophobic admixtures increases (shear strength decreases) when dosage increases. When the dosage increases to 0.7 kg/m2, the shear stress is 0.06 MPa for YC-1005G-NT. In all the shear samples coated with hydrophobic admixtures, ice has been completely sheared off along the interface, leaving the surface of specimen clear and intact, which is not the case for the specimens without surface coating. It can be clearly seen from Fig.7(a) that the surface of the specimen is largely bonded with the ice after the shear test.

    Compared with YC-1005G-NT, the shear test results of samples coated with BS290 suggest that the deicing effect of BS290 is less effective. As shown in Fig.9, when the dosage is 0.3 kg/m2, the deicing effect is similar to that of YC-1005G-NT. However, when the dosage increases to 0.5 and 0.7 kg/m2, the ice is not sheared off along the interface and there is some ice remaining on the surface of the Marshall specimen, as shown in Figs.8(c) and (d). The shear strength is minimal when the dosage is 0.3 kg/m2. The main reason for the seemingly unlikely increase in the shear load at higher dosage is that it becomes more difficult for the agent to be absorbed by the specimen with increasing dosage. Some hydrophobic admixture still remained in its liquid state on the surface of specimen when adding water on the top surface. Therefore, part of the hydrophobic admixture is diluted in water and has no effect on reducing the cohesive force. When dosages are 0.5 and 0.7 kg/m2, the shear planes are ice interiors, which suggests that their corresponding shear forces (see Fig.9) reflect more or less the shearing strength of ice.

    (a)

    (b)

    (c)

    (d)

    Fig.7 Interface exposed after shear test for coating YC-1005G-NT at different dosages. (a) 0 kg/m2; (b) 0.3 kg/m2; (c) 0.5 kg/m2;(d) 0.7 kg/m2

    (a)

    (b)

    (c)

    (d)

    Fig.8 Interface exposed after shear test for coating BS290 at different dosages. (a) 0 kg/m2; (b) 0.3 kg/m2; (c) 0.5 kg/m2;(d) 0.7 kg/m2

    Fig.9 Relationship of shear force with dosage for coating hydrophobic admixtures

    A brief sum up is made in this part. The shear stress corresponding to the dosage of 0.7 kg/m2is almost minimal for all coating admixtures, as shown in Fig.9. Among them, the shear stresses of the specimens coated with hydrophobic admixtures are much smaller compared with those of uncoated specimens. The shear planes of specimens coated with YC-1005G-NT are clear and intact according to Figs.7(b), (c) and (d). The test results indicate that YC-1005G-NT is better than BS290, and the optimal dosage of YC-1005G-NT is 0.7 kg/m2.

    2.3 Accelerated abrasion test

    The results of the accelerated abrasion test are shown in Figs.10 to 12. The surface situations of specimens after the accelerated abrasion test with friction 0.11 MPa are shown in Fig.10. It can be clearly seen that there is a hydrophobic admixture membrane on the surface of each specimen. The membrane has been gradually abraded with the increase of the grinding times. However, the residual membrane is found in the veins of the specimen surface. Also, the residual hydrophobic admixture membrane has no change when the grinding times increase from 12 600 to 20 160. The abrasion occurs between the wheel and aggregate when the grinding times are more than 12 600, and the residual membrane can deice persistently. Observing the surface situations of the specimens after the accelerated abrasion test with the friction of 0.33 MPa, it is found that there is only a little residual membrane retained in the veins of the specimen surface when the grinding times are over 5 040. Actually, the friction used in this test is much greater than that in the actual situation.

    (a)

    (b)

    (c)

    (d)

    Fig.10 Surface situation of specimen at different grinding times (σ=0.7 MPa,ζ=0.11 MPa). (a)N=0; (b)N=5 040; (c)N=12 600; (d)N=20 160

    It can be seen from Fig.11(a) that ice on specimens without hydrophobic admixture almost suffers no damage after being laminated by the rut board molding instrument. By contrast, ice on specimens coated with the hydrophobic admixture is damaged completely, as shown in Fig.11(b). The hydrophobic admixture membrane decreases with the increase of the grinding times so that less ice is destroyed, as shown in Fig.12. The same trend is observed when the friction is added to 0.33 MPa.

    (a)

    (b)

    Fig.11 Ice laminated by rut board molding instrument. (a) Without coating; (b) With coating

    (b)

    (c)

    The shear test results corresponding to different grinding times are shown in Fig.13 and Fig.14. It is observed that ice has been completely sheared off along the interface, leaving the surface of specimen clear and intact when the grinding times are below 10 080. But when the grinding times are added to 20 160, the ice cannot shear off completely along the interface, and damage occurs internally in the ice, as shown in Fig.13(c). There is some residual ice on the interface after the shear test. From Fig.14, it can be clearly seen that shear stress increases with the increase of the grinding times. The shear stress for the case of YC-1005G-NT is smaller than that of BS290.

    (a)

    (b)

    (c)

    Fig.14 Relationship between shear stress and grinding times (ζ=0.11 MPa)

    It indicates that when the hydrophobic admixture decreases, the deicing effect is reduced gradually. When the friction is 0.33 MPa, the deicing effect decreases rapidly.

    Based on the above discussions, conclusions can be drawn that hydrophobic admixtures are effective at reducing the cohesive force between the pavement and ice, particularly for YC-1005G-NT. The residual hydrophobic admixture in the veins of pavement also still has the ability to deice after 20 160 times accelerated abrasion.

    2.4 Skid resistance test

    The impacts of hydrophobic admixtures on the skid resistance of pavements are shown in Fig.15 and Fig.16. The BPN and TD of highway pavements should be larger than 42 and 0.55 according to that of the standard, respectively. From Fig.15, it can be seen that when coated with hydrophobic admixtures, BPN decreases slightly compared to that of the specimen uncoated with hydrophobic admixtures, but it is still over 42. TDs of specimens with coating YC-1005G-NT and BS290 reduce from 1.00 to 0.83 and 0.74, respectively, which are greater than the required value of 0.55. So the deicing technology, coating hydrophobic admixture, can guarantee the required of skid resistance of pavement.

    Fig.15 Variation of BPN of different hydrophobic admixtures

    Fig.16 Variation of TD of different hydrophobic admixtures

    3 Conclusions

    Experimental results show that surface coating with hydrophobic admixture approach can greatly reduce the cohesive force between the pavement and ice. This method can also guarantee the required skid resistance. The accelerated abrasion test results indicate a certain durability of this deicing technology. Although further research on durability should be done, it certainly provides an alternative solution for the deicing problem faced by many countries. The following conclusions can be drawn:

    1) The contact angles of hydrophobic admixtures/water and hydrophobic admixtures/asphalt are about 100° and 10°, respectively. It indicates that hydrophobic admixtures have good hydrophobic properties and they can soak on the surface of asphalt, so they can bond with asphalt very well.

    2) Hydrophobic admixtures, in particular YC-1005G-NT, show a high potential for reducing the cohesive force between the pavement and ice. The cohesive stress can be reduced from 0.44 to 0.06 MPa when the dosage of the hydrophobic admixture is 0.7 kg/m2.

    3) Because the residual hydrophobic admixtures in the veins of the pavement after the accelerated abrasion test still have the ability to reduce the cohesive force between the pavement and ice, the hydrophobic admixture coating approach has certain durability.

    4) BPN and TD of specimens coated with hydrophobic admixture are all larger than the demand values of the standard. The deicing technology, coating hydrophobic admixture, can guarantee the required skid resistance of the pavement.

    [1]Liu H Y, Hao P W. Technology and development trend of pavement deicing [J].RoadMachineryandConstructionMechanization, 2008, 25(11): 17-21. (in Chinese)

    [2]Wang K J, Nelsen D E, Nixon W A. Damaging effects of deicing chemicals on concrete materials [J].Cement&ConcreteComposites, 2006, 28(2): 173-188.

    [3]Yuan X Z, Zhu Y L, Li J. Effect of pavement deicing chloride salt on the soil properties [C]//ProceedingsofInternationalWorkshoponEnergyandEnvironmentintheDevelopmentofSustainableAsphaltPavements. Xi’an, China, 2010: 575-579.

    [4]Green S M, Machin R, Cresser M S. Effect of long-term changes in soil chemistry induced by road salt applications on N-transformations in roadside soils [J].EnvironmentalPollution, 2008, 152(1): 20-31.

    [5]Thunqvist E-L. Regional increase of mean chloride concentration in water due to the application of deicing salt [J].ScienceoftheTotalEnvironment, 2004, 325(1/2/3): 29-37.

    [6]Ostendorf D W, Hinlein E S, Rotaru C, et al. Contamination of groundwater by outdoor highway deicing agent storage [J].JournalofHydrology, 2006, 326(1/2/3/4): 109-121.

    [7]Tang X W, Jiao S J, Gao Z Y, et al. Study of 5.8 GHz magnetron in microwave deicing [J].JournalofElectromagneticWavesandApplications, 2008, 22(10): 1352-1360.

    [8]Macelloni G, Ruisi R, Pampaloni P, et al. Microwave radiometry for detecting road ice [C]//ProceedingsofInternationalGeoscienceandRemoteSensingSymposium. Helsinki, Finland, 1999: 891-893.

    [9]Macelloni G, Paloscia S, Pampaloni P, et al. Monitoring of melting refreezing cycles of snow with microwave radiometers: the microwave alpine snow melting experiment (MASMEx 2002—2003) [J].TransactionsonGeoscienceandRemoteSensing, 2005, 43(11): 2431-2442.

    [10]Zhang H W, Han S, Liu H H. A summary of asphalt concrete pavement for deicing and snow melting technology [J].HeilongjiangJiaotongKeji, 2008, 169(3): 8-9. (in Chinese)

    [11]Tang Z Q, Qian J S, Li Z Q, et al. Influential factors on deicing performance of electrically conductive concrete pavement [J].JournalofWuhanUniversityofTechnology:MaterialsScience, 2006, 21(2): 123-127.

    [12]Sullivan C R, Petrenko V F, Mccurdy J D. Breaking the ice: deicing power transmission lines with high-frequency, high-voltage excitation [J].IndustryApplicationsMagazine, 2003, 9(5): 49-54.

    [13]Yehia S, Tuan C Y. Conductive concrete overlay for bridge deck deicing [J].AciStructuralJournal, 1999, 96(3): 382-390.

    [14]Tuan C Y. Roca Spur Bridge: the implementation of an innovative deicing technology [J].JournalofColdRegionsEngineering, 2008, 22(1): 1-15.

    [15]Wang H J. Study of heat and mass transfer of hydronic snow melting process for pavement [D]. Tianjin: College of Mechanical Engineering, Tianjin University, 2007. (in Chinese)

    [16]Wang H J, Zhao J, Chen Z H. Experimental investigation of ice and snow melting process on pavement utilizing geothermal tail water [J].EnergyConversionandManagement, 2008, 49(6): 1538-1546.

    [17]Zhang L J. The study of salt antifreezing asphalt mixtures [D]. Xi’an: School of Materials Science and Engineering, Chang’an University, 2010. (in Chinese)

    [18]Milani F, Takallou H B. De-icing characteristics of rubber concrete pavements [C]//ProceedingsofAsphaltRubber2009Conference. Nanjing, China, 2009: 989-994.

    瀝青路面除冰雪技術(shù)研究

    馬 輝 楊若沖 錢吮智

    (東南大學(xué)交通學(xué)院, 南京 210096)

    為降低路面和冰雪之間的黏結(jié)力,用有機(jī)硅憎水材料作為道路表面涂層.有機(jī)硅憎水涂層技術(shù)的除冰效果用接觸角實(shí)驗(yàn)和剪切實(shí)驗(yàn)來(lái)表征,其耐久性用加速加載磨耗實(shí)驗(yàn)來(lái)評(píng)價(jià),而其抗滑性能則用擺式摩擦法和鋪砂法來(lái)評(píng)價(jià).接觸角實(shí)驗(yàn)結(jié)果表明,有機(jī)硅憎水涂層材料與水的接觸角為100.2°,具有很好的憎水性能.其次, 通過剪切實(shí)驗(yàn)可以得出: 在涂有有機(jī)硅憎水材料的情況下,冰層與試件表面的最大剪切應(yīng)力僅為0.06 MPa,低于沒有進(jìn)行表面涂層處理的最大剪切力3.5 MPa;剪切之后,冰層能夠很完整地從試件表面脫落.加速加載磨耗實(shí)驗(yàn)表明,在經(jīng)過一定時(shí)間的磨耗之后,殘留在瀝青路面構(gòu)造深度里的有機(jī)硅涂層材料仍然具有除冰雪的效果.表面涂層后的道路表面的BPN值和構(gòu)造深度值均有所降低,但是其仍然遠(yuǎn)遠(yuǎn)大于規(guī)范的要求,確保了安全性.研究表明,瀝青道路表面涂層技術(shù)能有效地降低瀝青路面與冰層的黏結(jié),從而解決冬季道路結(jié)冰影響行車安全的問題.

    除冰雪;有機(jī)硅憎水劑;表面涂層;黏結(jié)力;耐久性

    U421.4

    :Ma Hui, Yang Ruochong, Qian Shunzhi. Research on asphalt concrete pavement deicing technology[J].Journal of Southeast University (English Edition),2014,30(3):336-342.

    10.3969/j.issn.1003-7985.2014.03.015

    10.3969/j.issn.1003-7985.2014.03.015

    Received 2013-12-19.

    Biographies:Ma Hui (1987—), male, graduate; Qian Shunzhi (corresponding author), male, doctor, professor, zephyor@gmail.com.

    猜你喜歡
    冰層有機(jī)硅冰雪
    有機(jī)硅灌封材料對(duì)計(jì)控電子設(shè)備的保護(hù)應(yīng)用
    山東冶金(2022年4期)2022-09-14 09:00:20
    逐夢(mèng)的“冰雪一代”
    走向世界(2022年3期)2022-04-19 12:39:14
    擁抱冰雪向未來(lái)
    走向世界(2022年3期)2022-04-19 12:39:02
    點(diǎn)燃“冰雪”
    走向世界(2022年3期)2022-04-19 12:39:00
    Reducing ice melting with blankets 冰層融化,毯子救急
    催化劑體系對(duì)有機(jī)硅單體合成的影響
    云南化工(2021年11期)2022-01-12 06:06:06
    為什么南極降水很少卻有很厚的冰層?
    家教世界(2018年16期)2018-06-20 02:22:00
    美國(guó)湖岸冰層奇景
    海外星云(2016年7期)2016-12-01 04:18:04
    危險(xiǎn)的冰層
    織物抗菌劑有機(jī)硅季銨鹽POASC和PFASC的制備及應(yīng)用
    絲綢(2015年11期)2015-02-28 14:56:49
    美女黄网站色视频| 中出人妻视频一区二区| 麻豆一二三区av精品| 网址你懂的国产日韩在线| 精品人妻1区二区| 中文字幕人妻丝袜一区二区| 性色avwww在线观看| 亚洲人成网站在线播| 搡老熟女国产l中国老女人| 成人av一区二区三区在线看| 久久精品综合一区二区三区| 一级黄片播放器| 国产av一区在线观看免费| www日本在线高清视频| 身体一侧抽搐| 久久久久久久午夜电影| 给我免费播放毛片高清在线观看| 99热这里只有精品一区| 国产精品一区二区三区四区免费观看 | 亚洲av二区三区四区| 亚洲自拍偷在线| 九九热线精品视视频播放| 在线观看日韩欧美| 国产激情偷乱视频一区二区| 国内精品美女久久久久久| 免费电影在线观看免费观看| 欧美成狂野欧美在线观看| 天堂影院成人在线观看| 日本黄大片高清| 宅男免费午夜| 99在线视频只有这里精品首页| 一本精品99久久精品77| 精品不卡国产一区二区三区| 99热只有精品国产| 国产亚洲av嫩草精品影院| 亚洲第一电影网av| 亚洲国产高清在线一区二区三| 他把我摸到了高潮在线观看| 青草久久国产| 国产又黄又爽又无遮挡在线| 身体一侧抽搐| 男女床上黄色一级片免费看| 操出白浆在线播放| 91九色精品人成在线观看| 欧美又色又爽又黄视频| 91在线精品国自产拍蜜月 | 精品国产美女av久久久久小说| 亚洲国产精品成人综合色| 99久久综合精品五月天人人| 亚洲专区国产一区二区| 美女黄网站色视频| 午夜免费激情av| 日韩欧美国产在线观看| 悠悠久久av| 国产国拍精品亚洲av在线观看 | 国产精品99久久99久久久不卡| 国产精品香港三级国产av潘金莲| 99riav亚洲国产免费| 国产av一区在线观看免费| 日本成人三级电影网站| 午夜免费观看网址| 在线观看日韩欧美| 丁香六月欧美| 少妇人妻一区二区三区视频| 亚洲精华国产精华精| 内地一区二区视频在线| 精品国产亚洲在线| 丰满乱子伦码专区| 国产97色在线日韩免费| 成人国产综合亚洲| 亚洲av美国av| 99热6这里只有精品| 久久久久久久久中文| 亚洲av成人不卡在线观看播放网| 欧美性猛交黑人性爽| 女警被强在线播放| 一区二区三区国产精品乱码| 成人三级黄色视频| 精品久久久久久久末码| 看免费av毛片| 2021天堂中文幕一二区在线观| 俄罗斯特黄特色一大片| 91麻豆av在线| 亚洲 欧美 日韩 在线 免费| 久久精品综合一区二区三区| 少妇的丰满在线观看| 少妇熟女aⅴ在线视频| 美女免费视频网站| 嫩草影院入口| 看免费av毛片| 国产成人系列免费观看| 免费搜索国产男女视频| 久久久久久久亚洲中文字幕 | 天堂√8在线中文| 亚洲国产色片| 又黄又粗又硬又大视频| 国内揄拍国产精品人妻在线| 亚洲最大成人手机在线| 18+在线观看网站| 国产av在哪里看| 免费观看人在逋| 老司机福利观看| 老司机在亚洲福利影院| 日本精品一区二区三区蜜桃| 97超级碰碰碰精品色视频在线观看| 国产熟女xx| 日韩欧美精品v在线| 亚洲av熟女| 丰满人妻熟妇乱又伦精品不卡| 亚洲成人免费电影在线观看| 露出奶头的视频| 最新在线观看一区二区三区| 欧美最新免费一区二区三区 | 精品久久久久久久毛片微露脸| 欧美3d第一页| 午夜两性在线视频| 淫秽高清视频在线观看| 欧美中文综合在线视频| 91久久精品电影网| 亚洲av第一区精品v没综合| 熟女少妇亚洲综合色aaa.| 欧美日韩综合久久久久久 | 亚洲中文字幕一区二区三区有码在线看| 一二三四社区在线视频社区8| 在线观看免费午夜福利视频| 国产精品亚洲美女久久久| 国产不卡一卡二| 欧美激情在线99| 国产高清videossex| 老汉色∧v一级毛片| 97超视频在线观看视频| 亚洲欧美激情综合另类| 欧美不卡视频在线免费观看| 亚洲av免费在线观看| 久99久视频精品免费| 亚洲国产日韩欧美精品在线观看 | 亚洲av成人精品一区久久| 一区二区三区高清视频在线| 欧美性猛交╳xxx乱大交人| 人妻久久中文字幕网| 国产老妇女一区| 国产成人福利小说| 亚洲av电影不卡..在线观看| 麻豆久久精品国产亚洲av| 露出奶头的视频| 老司机在亚洲福利影院| 亚洲av日韩精品久久久久久密| 最新在线观看一区二区三区| 全区人妻精品视频| 18禁在线播放成人免费| 观看免费一级毛片| 此物有八面人人有两片| 亚洲精华国产精华精| 脱女人内裤的视频| 成人三级黄色视频| 午夜免费激情av| 丁香六月欧美| 日韩 欧美 亚洲 中文字幕| 日本一二三区视频观看| 熟妇人妻久久中文字幕3abv| 久久久久久久久久黄片| 色视频www国产| 欧美日韩精品网址| 亚洲熟妇熟女久久| 无人区码免费观看不卡| 国产精品一区二区三区四区免费观看 | 男人和女人高潮做爰伦理| 制服人妻中文乱码| 狂野欧美激情性xxxx| 久久精品国产99精品国产亚洲性色| 成人精品一区二区免费| 国产午夜福利久久久久久| 亚洲精品成人久久久久久| 国产一区二区三区在线臀色熟女| 国产97色在线日韩免费| 亚洲色图av天堂| 热99在线观看视频| 久久九九热精品免费| 中文在线观看免费www的网站| 国产毛片a区久久久久| 丁香欧美五月| 欧美zozozo另类| 丰满人妻熟妇乱又伦精品不卡| 日韩精品中文字幕看吧| 男人舔女人下体高潮全视频| 一二三四社区在线视频社区8| 国模一区二区三区四区视频| 亚洲人与动物交配视频| 免费观看精品视频网站| 国产精品一区二区三区四区免费观看 | 国产黄片美女视频| 国产不卡一卡二| 国产伦人伦偷精品视频| 夜夜夜夜夜久久久久| 国产伦在线观看视频一区| 国产三级在线视频| 亚洲av日韩精品久久久久久密| 女警被强在线播放| 看黄色毛片网站| 午夜免费成人在线视频| 一个人免费在线观看的高清视频| 熟女人妻精品中文字幕| 国产一区二区三区视频了| 久久精品国产自在天天线| 搡老妇女老女人老熟妇| 桃色一区二区三区在线观看| 亚洲av中文字字幕乱码综合| 不卡一级毛片| 美女黄网站色视频| 嫁个100分男人电影在线观看| 亚洲天堂国产精品一区在线| 黄色日韩在线| www日本黄色视频网| 在线观看美女被高潮喷水网站 | 男插女下体视频免费在线播放| 最新美女视频免费是黄的| 黄色日韩在线| 女警被强在线播放| 中文在线观看免费www的网站| 欧美最新免费一区二区三区 | 身体一侧抽搐| 国产国拍精品亚洲av在线观看 | 中文字幕高清在线视频| 精品人妻偷拍中文字幕| 欧美一区二区国产精品久久精品| 日韩亚洲欧美综合| 亚洲国产精品合色在线| 欧美成人a在线观看| 一a级毛片在线观看| 欧美性猛交╳xxx乱大交人| 亚洲第一欧美日韩一区二区三区| 人妻丰满熟妇av一区二区三区| 12—13女人毛片做爰片一| 精品久久久久久久毛片微露脸| 美女高潮的动态| 国产伦一二天堂av在线观看| 国产真人三级小视频在线观看| 嫁个100分男人电影在线观看| netflix在线观看网站| 国产精品av视频在线免费观看| 免费看十八禁软件| 熟妇人妻久久中文字幕3abv| 国产一区二区在线av高清观看| 久久久久久国产a免费观看| 最新在线观看一区二区三区| 国产极品精品免费视频能看的| 一个人免费在线观看的高清视频| 黑人欧美特级aaaaaa片| 97人妻精品一区二区三区麻豆| 高清毛片免费观看视频网站| 国产毛片a区久久久久| 久久精品国产清高在天天线| 亚洲av不卡在线观看| 久久精品91蜜桃| 18禁在线播放成人免费| 啦啦啦韩国在线观看视频| 欧美在线黄色| 日本撒尿小便嘘嘘汇集6| 欧美日韩综合久久久久久 | 国产真人三级小视频在线观看| av女优亚洲男人天堂| 在线十欧美十亚洲十日本专区| 19禁男女啪啪无遮挡网站| 成人亚洲精品av一区二区| 成人av一区二区三区在线看| 99riav亚洲国产免费| 欧美乱码精品一区二区三区| 国产伦精品一区二区三区视频9 | 精品一区二区三区人妻视频| 母亲3免费完整高清在线观看| 看黄色毛片网站| 国产91精品成人一区二区三区| 两人在一起打扑克的视频| 久久精品91蜜桃| 69av精品久久久久久| 麻豆一二三区av精品| 91麻豆精品激情在线观看国产| 成年免费大片在线观看| 国产三级中文精品| 日韩亚洲欧美综合| 全区人妻精品视频| 老鸭窝网址在线观看| 国产亚洲精品av在线| 亚洲18禁久久av| 熟女少妇亚洲综合色aaa.| 日韩人妻高清精品专区| 久久性视频一级片| 亚洲专区国产一区二区| 丝袜美腿在线中文| 一个人看视频在线观看www免费 | 波野结衣二区三区在线 | 国产激情偷乱视频一区二区| 在线免费观看的www视频| 欧美3d第一页| 两个人的视频大全免费| 青草久久国产| 三级男女做爰猛烈吃奶摸视频| 在线观看美女被高潮喷水网站 | 国产探花极品一区二区| 精品久久久久久久毛片微露脸| 亚洲在线观看片| 亚洲片人在线观看| 精品午夜福利视频在线观看一区| 国产乱人视频| 好男人在线观看高清免费视频| 欧美日韩精品网址| 精品免费久久久久久久清纯| 中文资源天堂在线| 成年女人永久免费观看视频| 看免费av毛片| 色吧在线观看| 亚洲第一电影网av| 久久亚洲精品不卡| 成熟少妇高潮喷水视频| 亚洲国产精品sss在线观看| bbb黄色大片| 成人特级黄色片久久久久久久| 亚洲aⅴ乱码一区二区在线播放| netflix在线观看网站| 国产成人福利小说| 亚洲av成人精品一区久久| 久久精品夜夜夜夜夜久久蜜豆| 亚洲成a人片在线一区二区| 国产免费一级a男人的天堂| 成人无遮挡网站| 国产午夜精品论理片| 国产一区二区亚洲精品在线观看| 真实男女啪啪啪动态图| 宅男免费午夜| 国产久久久一区二区三区| 欧美av亚洲av综合av国产av| 国产97色在线日韩免费| 欧美又色又爽又黄视频| 精品无人区乱码1区二区| 国产一区二区三区视频了| 18美女黄网站色大片免费观看| 色老头精品视频在线观看| 叶爱在线成人免费视频播放| 亚洲成av人片在线播放无| 久久精品综合一区二区三区| 免费一级毛片在线播放高清视频| 亚洲内射少妇av| 国产 一区 欧美 日韩| 在线观看一区二区三区| 精品午夜福利视频在线观看一区| 亚洲国产精品sss在线观看| 午夜激情福利司机影院| 日本五十路高清| 亚洲成人久久爱视频| 国产极品精品免费视频能看的| 久久精品91无色码中文字幕| 老司机在亚洲福利影院| 99久久无色码亚洲精品果冻| 亚洲国产精品合色在线| 两个人视频免费观看高清| 国产成+人综合+亚洲专区| 中文字幕熟女人妻在线| 亚洲午夜理论影院| 噜噜噜噜噜久久久久久91| 免费人成在线观看视频色| 深夜精品福利| 淫妇啪啪啪对白视频| 一进一出好大好爽视频| xxx96com| 久久久久久久久大av| 黄色丝袜av网址大全| 日本 av在线| 熟女少妇亚洲综合色aaa.| 美女免费视频网站| 欧美中文综合在线视频| 草草在线视频免费看| 成熟少妇高潮喷水视频| 国产高清激情床上av| 校园春色视频在线观看| av欧美777| 欧美日韩亚洲国产一区二区在线观看| 色噜噜av男人的天堂激情| 国产单亲对白刺激| 国产不卡一卡二| 蜜桃亚洲精品一区二区三区| 色噜噜av男人的天堂激情| 欧美成人免费av一区二区三区| 欧美av亚洲av综合av国产av| 色综合欧美亚洲国产小说| 丁香欧美五月| 老司机福利观看| 亚洲国产精品sss在线观看| 欧美3d第一页| eeuss影院久久| 少妇的丰满在线观看| 无遮挡黄片免费观看| 国产亚洲欧美98| 最好的美女福利视频网| 国产成人欧美在线观看| 色噜噜av男人的天堂激情| 一卡2卡三卡四卡精品乱码亚洲| 国产不卡一卡二| 亚洲男人的天堂狠狠| eeuss影院久久| 99热这里只有精品一区| avwww免费| 法律面前人人平等表现在哪些方面| 色噜噜av男人的天堂激情| 法律面前人人平等表现在哪些方面| 精品国产三级普通话版| 亚洲天堂国产精品一区在线| 天堂动漫精品| 波多野结衣巨乳人妻| 久久久久久大精品| 国产成+人综合+亚洲专区| 国产伦人伦偷精品视频| 成人国产综合亚洲| 中国美女看黄片| 日韩中文字幕欧美一区二区| 精品一区二区三区视频在线 | 色av中文字幕| 久久99热这里只有精品18| tocl精华| 精品电影一区二区在线| 97超级碰碰碰精品色视频在线观看| 免费看a级黄色片| 国产97色在线日韩免费| 精品国产三级普通话版| 国产 一区 欧美 日韩| 天堂动漫精品| av专区在线播放| 久久久久久久午夜电影| 国产午夜精品论理片| 精品免费久久久久久久清纯| 欧美最新免费一区二区三区 | 美女 人体艺术 gogo| 国产三级中文精品| 成年女人毛片免费观看观看9| www日本黄色视频网| 亚洲avbb在线观看| 香蕉av资源在线| 国内精品久久久久精免费| 国产精品三级大全| 内射极品少妇av片p| av视频在线观看入口| 手机成人av网站| www.www免费av| 欧美三级亚洲精品| 国产成人aa在线观看| 亚洲精品在线观看二区| 91麻豆av在线| 一进一出好大好爽视频| 日日摸夜夜添夜夜添小说| 天堂√8在线中文| 国产色婷婷99| 天天添夜夜摸| 天天一区二区日本电影三级| 久久精品91无色码中文字幕| 日韩欧美 国产精品| 18禁黄网站禁片午夜丰满| 日本与韩国留学比较| 国产成人aa在线观看| 亚洲专区中文字幕在线| 国产亚洲欧美98| 热99在线观看视频| 久久久久久久亚洲中文字幕 | 国产美女午夜福利| 国产午夜精品久久久久久一区二区三区 | 黄片大片在线免费观看| 日韩人妻高清精品专区| 91麻豆av在线| 九九久久精品国产亚洲av麻豆| 国产aⅴ精品一区二区三区波| 亚洲精品美女久久久久99蜜臀| 色综合婷婷激情| 观看美女的网站| 国产精品98久久久久久宅男小说| 欧美乱妇无乱码| 久久欧美精品欧美久久欧美| 亚洲av电影不卡..在线观看| 岛国视频午夜一区免费看| 一级毛片高清免费大全| 亚洲七黄色美女视频| 黄色日韩在线| 99精品久久久久人妻精品| 日本与韩国留学比较| 内地一区二区视频在线| 男女床上黄色一级片免费看| 一本综合久久免费| 十八禁人妻一区二区| 欧美一区二区精品小视频在线| 性欧美人与动物交配| 久久亚洲精品不卡| av专区在线播放| 天美传媒精品一区二区| 日本成人三级电影网站| 在线观看免费午夜福利视频| 亚洲自拍偷在线| 国产精品 欧美亚洲| 19禁男女啪啪无遮挡网站| 国产成+人综合+亚洲专区| 日韩高清综合在线| 久久精品人妻少妇| 精品99又大又爽又粗少妇毛片 | 国产不卡一卡二| 国产在线精品亚洲第一网站| 黄色视频,在线免费观看| 黄色成人免费大全| 久99久视频精品免费| www日本黄色视频网| 国产高清三级在线| 国内毛片毛片毛片毛片毛片| 日韩中文字幕欧美一区二区| aaaaa片日本免费| 亚洲美女视频黄频| 啦啦啦韩国在线观看视频| 亚洲av第一区精品v没综合| 亚洲人成网站在线播放欧美日韩| 精品无人区乱码1区二区| 国产精品av视频在线免费观看| 美女被艹到高潮喷水动态| 狠狠狠狠99中文字幕| 国产极品精品免费视频能看的| 日本黄色片子视频| 99热只有精品国产| 国产免费男女视频| 久久九九热精品免费| 99国产极品粉嫩在线观看| 精品久久久久久成人av| 亚洲熟妇熟女久久| 色老头精品视频在线观看| 一级作爱视频免费观看| 男女下面进入的视频免费午夜| 成人一区二区视频在线观看| av视频在线观看入口| 12—13女人毛片做爰片一| 亚洲欧美精品综合久久99| 亚洲av免费在线观看| 国产午夜精品论理片| 久久久久九九精品影院| 日本与韩国留学比较| 真实男女啪啪啪动态图| 青青草视频在线视频观看| 插逼视频在线观看| 国产视频内射| 久久久久久伊人网av| 久久久久免费精品人妻一区二区| 美女内射精品一级片tv| 日韩人妻高清精品专区| 精品亚洲乱码少妇综合久久| 久久精品综合一区二区三区| av天堂中文字幕网| 少妇人妻精品综合一区二区| 日韩制服骚丝袜av| 免费av观看视频| 久久午夜福利片| 国产亚洲5aaaaa淫片| av黄色大香蕉| 成人漫画全彩无遮挡| 最近中文字幕2019免费版| 免费在线观看成人毛片| 亚洲伊人久久精品综合| 久久久久免费精品人妻一区二区| 亚洲最大成人手机在线| 91aial.com中文字幕在线观看| 精品久久久噜噜| 欧美性感艳星| 国产一级毛片七仙女欲春2| 欧美3d第一页| 高清av免费在线| 成年版毛片免费区| 韩国av在线不卡| 免费电影在线观看免费观看| 亚洲在久久综合| 日韩亚洲欧美综合| 男人舔女人下体高潮全视频| 欧美变态另类bdsm刘玥| 18禁在线无遮挡免费观看视频| 神马国产精品三级电影在线观看| 国产在视频线在精品| 欧美性猛交╳xxx乱大交人| 天堂中文最新版在线下载 | 在线观看人妻少妇| 一级二级三级毛片免费看| 全区人妻精品视频| 18禁动态无遮挡网站| 午夜激情久久久久久久| 白带黄色成豆腐渣| 久久人人爽人人片av| 国产 亚洲一区二区三区 | 看黄色毛片网站| 精品久久久精品久久久| 日本色播在线视频| 日韩一区二区视频免费看| 好男人视频免费观看在线| 国产亚洲5aaaaa淫片| 欧美一级a爱片免费观看看| 国产黄片视频在线免费观看| 国产乱人视频| 国产色爽女视频免费观看| av在线播放精品| 久久精品人妻少妇| 国产综合懂色| 亚洲精品久久午夜乱码| 22中文网久久字幕| 中文在线观看免费www的网站| 久久99热这里只频精品6学生| 1000部很黄的大片| 久久精品国产亚洲av天美| 亚洲av一区综合| ponron亚洲| 国产亚洲av片在线观看秒播厂 | 亚洲精品一二三| 2021少妇久久久久久久久久久| 久久久久精品久久久久真实原创| 国产亚洲精品av在线| 好男人在线观看高清免费视频| 国内揄拍国产精品人妻在线| 在线播放无遮挡| 2021少妇久久久久久久久久久|