欧美成人AAA大片,国产一级强片在线观看,一级特黄AA大片欧美,成人性生交大片免费看中文,91成人午夜性A一级毛片,日韩一区二区三区四区,一级一片在线播放在线观看,日本特黄特色AAA大片免费,精品久久久久中文字幕APP,色黄大色黄女片免费看软件

2022

2022

  • Record 421 of

    Title:Optical design of monocentric multiscale three-line array airborne mapping camera
    Author(s):Yan, Aqi(1); Dong, Sen(1); Wu, Dengshan(1)
    Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12166  Issue:   DOI: 10.1117/12.2613976  Published: 2022  
    Abstract:In view of the urgent demand high resolution and large field of view on three-line array airborne mapping camera, the paper proposes a new idea which applies monocentric multiscale principle to three-line array airborne mapping camera with high resolution and large field of view (FOV), and gives the design method and design process of optical system. monocentric multiscale optical system is designed, focal length is 70mm, resolution is 0.1m@2Km, and there are four multispectral bands which are panchromaticRGB band. The Base to Height ratio (B/H) is 0.83. The FOV of monocentric multiscale optical system is 80°, and working FOV is 60° which can be extended to 105°. The optical system has excellent imaging quality and successfully solved contradiction between large FOV and high resolution. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
    Accession Number: 20220911734820
  • Record 422 of

    Title:Research Progress in Chalcogenide Glass Fibers for Infrared Laser Delivery
    Author(s):Zhang, Hao(1,2); Guo, Haitao(1); Xu, Yantao(1,2); Li, Man(3); Ma, Wenchao(3)
    Source: Zhongguo Jiguang/Chinese Journal of Lasers  Volume: 49  Issue: 1  DOI: 10.3788/CJL202249.0101007  Published: January 10, 2022  
    Abstract:Significance: As the performance of mid-infrared lasers continues to improve, there occurs an increasing demand for their applications in laser surgery, military, materials processing, and other fields. Compared with spatial optical systems, the use of infrared fibers for laser transmission can greatly reduce the size of an optical system and improve the compactness and reliability of the whole system. For example, in the medical field, a considerable amount of laser surgery is performed using 2.94 μm Er: YAG lasers. The Er: YAG laser radiation absorption is very strong because this laser wavelength is practically in the center of the maximum absorption band of cellular water. Since biological tissues contain up to 70%~90% water, the Er: YAG laser is extremely efficient for their high precision cutting and vaporization. In addition, in the military field, another important application for 2 μm to 5 μm short-wave mid-infrared lasers is infrared countermeasures (IRCM) or laser tactical systems. Transmitting high power infrared lasers by infrared fibers can deflect or dazzle the infrared target seeking system. This application puts a high demand on the power handling capability of the fiber (typically tens of watts). For 512 μm long-wave mid-infrared lasers, high power CO (5.4 μm) and CO2 (10.6 μm) lasers can be used for laser surgery, industrial cutting, and welding applications. In addition, the transmission of laser power through optical fibers enables remote operation. Due to the characteristics of wide infrared transmission, good physical and chemical stabilities, and easily fiberized performances, chalcogenide glass is one of the best materials for infrared laser power delivery fiber. Therefore, as an important infrared fiber, the fabrication and application of chalcogenide glass fiber have been paid much attention at home and abroad. This review introduces the research progresses of domestic and foreign research groups in the preparation and application of chalcogenide fibers (including the step-index fibers and micro-structured fibers) for infrared laser power delivery. Progress: Step-index chalcogenide glass fibers are the earliest and most mature chalcogenide fibers. For 25 μm short-wave mid-infrared lasers, researchers first studied chalcogenide multi-mode fibers. In 1998, the US Naval Laboratory reported the successful transmission of a 2.94 μm wavelength medical free electron laser (MFEL) using an As40S60 multi-mode fiber. This result showed that laser surgery should be possible using a chalcogenide multi-mode fiber. Both CW and pulsed laser transmissions through chalcogenide multi-mode fibers were then subsequently reported. With the continuous development of mid-infrared lasers, while large-core multi-mode fibers can transmit higher power lasers, laser transmission quality and transmission modes still had to be considered, which require the development of small-core single-mode fibers. In 2018, the University of Central Florida examined the potential of chalcogenide fibers to handle high power mid-infrared lasers. The AR-coated As40S60 single-mode fiber enables the delivery of 10.3 W laser at 2.053 μm (Fig. 1). For 512 μm long-wave mid-infrared lasers, a multi-hundred-watt CO laser has been successfully delivered through chalcogenide glass fibers under gas cooling conditions (Fig. 2). And Te-based chalcogenide fibers can deliver a CO2 laser with tens of watts. The laser transmission of different chalcogenide step-index fibers has been summarized (Tabled 1). It can be seen that chalcogenide step-index fibers have made a great progress in mid-infrared laser transmission. At present, a multi-mode step-index fiber can achieve multi-hundred-watt laser transmission, while a single-mode step-index fiber can basically meet the demand for laser transmission within 10 W, and has been experimentally demonstrated in the fields of laser surgery and laser processing. Although a great progress has been made in chalcogenide step-index fibers, traditional step-index fibers are incapable due to material limitations with the increase in transmission power. In order to achieve a high power laser delivery, increasing the mode field area is the most direct and effective solution, and at the same time to ensure the beam quality, the transmission in fibers is required to be single-mode. A hollow-core micro-structured optical fiber (HC-MOF) and a large-mode-area photonic crystal fiber (LMA PCF) have become effective approaches to enhance the capability of power handling of chalcogenide fibers. Hollow-core micro-structured fibers can be divided into hollow-core Bragg fibers, hollow-core photonic crystal fibers (HC-PCFs) and hollow-core anti-resonant fibers (HC-ARFs). As researchers continue to study the numerical simulation and fabrication of micro-structured optical fibers, HC-ARFs have become the most promising infrared fibers for a high power laser delivery. The development of HC-ARFs is an encouraging advance in the fiber technology which combines the low theoretical loss over a wide bandwidth with a high tolerance to fabrication imperfections. A tolerance to fabrication imperfection is particularly important for chalcogenide fibers. At present, the minimum loss of HC-ARFs is 2.1 dB/m at 10 μm. This result indicates that HC-ARFs have already some practical value. Conclusions and Prospects: Chalcogenide fibers have been used in laser processing, laser surgery, and homeland security. The development of chalcogenide fibers with low loss and high laser damage threshold has great scientific value and application prospects. In particular, hollow-core micro-structured fibers are a technological race for the next generation of infrared fibers and related applications. ? 2022, Chinese Lasers Press. All right reserved.
    Accession Number: 20221211825987
  • Record 423 of

    Title:Highly linear integrated lithium niobate modulator based on ring-assisted Mach-Zehnder interferometer
    Author(s):Feng, Hanke(1); Zhang, Ke(1); Sun, Wenzhao(1); Ren, Yangming(2,3); Zhang, Yiwen(1); Zhang, Wenfu(2,3); Wang, Cheng(1)
    Source: Optics InfoBase Conference Papers  Volume:   Issue:   DOI:   Published: 2022  
    Abstract:We report an ultra-high-linearity modulator on thin-film lithium niobate platform based on the ring-assisted Mach-Zehnder interferometer (RAMZI) structure, with measured spurious free dynamic range (SFDR) up to 120.04 dB·Hz4/5 at 1GHz. ? Optica Publishing Group 2022, ? 2022 The Author(s)
    Accession Number: 20223512662422
  • Record 424 of

    Title:Fastening torque simulation method of pressure-ring based on finite element simulation analysis and experimental verification
    Author(s):Zhao, Yue(1); Kang, Shifa(1); Fu, Xihong(1); Zhang, Gaopeng(1)
    Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12166  Issue:   DOI: 10.1117/12.2611752  Published: 2022  
    Abstract:Aiming at the problem of abnormal sound of lens caused by incomplete tightening of pressure coil after optical lens installation, this paper presents a method for calculating and verifying the tightening moment of pressure coil. According to the mechanical dimension of the screw thread of the pressing ring, the mechanical properties of the pressing ring of the mirror tube and the optimal number of turning rings were calculated and analyzed. In order to meet the practical application requirements, the tightening moment of the pressure coil obtained by the solution was brought into the 3D model for simulation, and the finite element modeling analysis of the tightening moment of the pressure coil of the optical lens was completed, so as to further solve the displacement variation of the lens group. Finally, the above analysis results were quantified by torque wrenches, and random vibration was carried out at one third of the order of acceptance level vibration test conditions, so as to complete the bottom analysis and verify the tightening torque of the screw ring under different ratios of XM-31 adhesive and vulcanizing agent. The experimental results show that the characteristic sweep curve of the optical lens does not change before and after the vibration, the mode of the optical lens remains stable all the time, and the data modal analysis results are consistent with the actual situation. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
    Accession Number: 20220911734801
  • Record 425 of

    Title:Research on the properties of Ta2O5optical films prepared with APS plasma assisted deposition
    Author(s):Pan, Yong-Gang(1); Liu, Zheng(1); Liu, Wen-Cheng(1); Li, Mian(1); Zhang, Si-Bao(1); Luo, Chang-Xin(1); Zhang, Chun-Juan(1)
    Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12166  Issue:   DOI: 10.1117/12.2604831  Published: 2022  
    Abstract:Ta2O5 thin films are widely used in optical and microelectronic industry because of its superior optical and mechanical properties. In this paper, single-layer Ta2O5 thin films were prepared by APS plasma assisted electron beam evaporation deposition. Based on the theory of ion energy transfer, the selection criteria of APS process parameters were established. By optimizing APS source parameters, Ta2O5 thin films with different characteristics were prepared. The spectral and refractive index dispersion of Ta2O5 thin films were analyzed by Cary7000 spectrophotometer. The stress and surface roughness of Ta2O5 films were analyzed by Zygo interferometer. Experiment and analysis results showed that the characteristics of Ta2O5 thin films are closely related to APS plasma assisted processing parameters. The discharge current and bias voltage of APS source have great influence on the stress and surface roughness of Ta2O5 thin films, but have little influence on the spectral characteristics and refractive index dispersion. The influences of preparation parameters on the properties of Ta2O5 thin films were analyzed and optimization fabrication parameters were obtained. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
    Accession Number: 20220911734999
  • Record 426 of

    Title:Spectroscopic properties of Er3+-doped fluoroindate glasses
    Author(s):Liu, Zhen(1,2); She, Jiangbo(1,3); Peng, Bo(1)
    Source: Journal of Rare Earths  Volume: 40  Issue: 7  DOI: 10.1016/j.jre.2021.05.011  Published: July 2022  
    Abstract:The optical and thermal properties of a new class of fluoroindate glass with different erbium contents were investigated via Raman, transmission, and fluorescence spectroscopies, fluorescence decay curve analysis, and differential scanning calorimetry. The strength parameters of the samples were calculated using the Judd–Ofelt theory. The mid-infrared luminescence properties of erbium-doped fluoroindate glasses were studied, and a strong emission at 2.7 μm was obtained. Compared with the traditional ZBLAN glass, this glass has excellent emission properties, especially a longer fluorescence lifetime (7.09 ms) and larger emission cross-section (6.95 × 10?21 cm2) at 2.7 μm. The results indicate that fluoroindate glass is an attractive host for mid-infrared lasers and as a gain medium for optical amplifier applications. ? 2021
    Accession Number: 20214010987220
  • Record 427 of

    Title:High Power Single Crystal Fiber Ultrashort Pulse Amplification Technology (Invited)
    Author(s):Cao, Xue(1,2,3,4); Li, Feng(1); Zhao, Hualong(1); Wang, Yishan(1); Zhou, Wei(4); Shen, Deyuan(4)
    Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 51  Issue: 8  DOI: 10.3788/gzxb20225108.0851513  Published: August 2022  
    Abstract:Femtosecond laser with high repetition rate and high output power can be used as the driving light source of attosecond pulse generation, which can effectively increase photon flux, obtain enough experimental data quickly, and overcome the existing problem of space charge effect. Therefore, it has important application value in high order harmonics and attosecond pulse generation. At the same time, high repetition rate and high output power femtosecond pulses also have important application prospects in ultrafast laser precision micro-machining field, which can solve the technical problems of hard, brittle and soft materials processing with high-precision and high-quality "cold machining" in aviation and aerospace field. With the rapid development of ultra-fast laser processing market, high power femtosecond laser system with higher cost performance has become the major factor of concern in the industry. Compared with traditional solid-state lasers, fiber amplifiers have many characteristics, such as easy operation, all-fiber fusion, easy integration, excellent heat dissipation performance, excellent beam quality, etc., which have attracted much attention in the field of ultra-short pulse amplification. However, limited by the mode field area of ordinary single-mode or nearly single-mode fiber, the output energy of the ultrashort pulse based on the structure of optical fiber amplifier system is limited due to the Raman scattering and stimulated brillouin scattering, the self-phase modulation, cross phase modulation and other nonlinear effect in the process of high power pulse amplification. In order to achieve high energy femtosecond pulse amplification, the current fiber amplification system mainly adopts the structure of CPA system. Before amplification, the pulse is stretched in the time domain and the special fiber with large mode area is used to achieve high energy output in the space domain. Slab, disc and other solid amplifying media can output higher pulse energy,however,they are difficult to package, and the amplification structure is relatively complex, which is not conducive to the mass production of domestic lasers. Single crystal fiber as a new type of amplifier gain medium, it has a slender crystal structure and waveguide transmission characteristics for pump beam, which makes it have the advantages of both crystal and fiber laser amplification media. Its slender crystal structure can effectively dissipate heat, ensuring high beam quality under high-power operation. The waveguide characteristics of pump beam make it have greater energy extraction efficiency and higher amplification gain than traditional crystal rods. Compared with the fiber amplifier, the nonlinear accumulation of the single crystal fiber amplifier is much smaller, which is more conducive to the improvement of pulse energy. Meanwhile, the amplification structure of the single-crystal fiber amplifier mainly focuses on the single-pass or double-pass traveling wave amplification structure. Compared with the high complexity of the slab and thin-disk amplification system, the single-crystal fiber has better integration and stability. The waveguide structure of single-crystal fiber amplifier can match the multi-mode pump beam with the signal beam propagating in free space, which can obtain higher amplification efficiency and better beam quality than the traditional crystal rods. Excellent thermal management performance also enables the structure to achieve hundred-watt level ultra-short pulse output with good optical parameters. The hybrid fiber-single crystal fiber ultrashort pulse amplification system combined the high gain property of fiber laser and high peak power property of crystal gain medium. In order to further improve the average power and pulse energy, it has been less effective by simply stretching the pulse duration in time domain and increasing the optical fiber mode area in the space domain, technologies such as coherent beam combination can obtain much higher power and larger energy. When the output power of the laser is less than 200 W, the single crystal fiber can consitute a simple and reliable amplification setup. For higher power output, it can also be used as a stable, cost-effective seeder with good optical parameters for solid state amplifier, such as thin-disk lasers. In the future development of lasers, the research and development of fiber laser with appropriate wavelength for pump source and the continuous optimization of brightness of fiber coupled laser diode can effectively improve the amplification efficiency of ytterbium-doped single crystal fiber, and achieve a wider application in the field of ultrafast laser. The cladding structure of crystal fiber can increase the ratio of surface area to volume of single crystal fiber, by improving the heat transfer performance of cladding and the thermal management ability of fiber can realize the long distance fundamental mode waveguide, and finally realize the high power laser with higher efficiency, which is also an important direction of future development. Therefore, single crystal fiber as amplification gain medium has been widely used in ultrashort pulse amplification and has important application prospects in scientific research, national defense, industrial processing and other fields. This paper mainly introduces the structure and preparation methods of single crystal fiber, and the main research methods and results of ultrashort pulse amplification technology based on single crystal fiber in 1 μm waveband, including the main progress made by our research group, the prospect and development direction of single crystal fiber amplification technology are also discussed and prospected. ? 2022 Chinese Optical Society. All rights reserved.
    Accession Number: 20223912795058
  • Record 428 of

    Title:Optical vortex array with deformable hybrid Ferris structures
    Author(s):Long, Zixu(1,2); Zhang, Hao(1); Tai, Yuping(3); Tang, Miaomiao(1); Li, Hehe(1); Li, Xinzhong(1,2)
    Source: Optics and Laser Technology  Volume: 145  Issue:   DOI: 10.1016/j.optlastec.2021.107524  Published: January 2022  
    Abstract:We proposed an optical vortex array (OVA) with deformable hybrid Ferris structures (DH-OVA). The DH-OVA was generated via the coaxial coherent superposition of two grafted elliptic perfect optical vortices (OVs) with different topological charges (TCs). The proposed DH-OVA exhibited the capacity of a free transformation from a circle to an ellipse except for the modulation of the number and sign of the unit OVs on the array. The OV distribution obeys the rule of uniform distribution of the area on the upper or lower half. By adjusting the initial phase difference, the orientation factor, and the direction of the grafted axis, a more complex OV motion and the entire hybrid rotation of the DH-OVA can be easily conducted according to the desired application. For instance, for the unidirectional and bidirectional motions of the OVs, regardless of whether they possessed the same or opposite signs, the entire rotation contained the unit OV's motion. During the OV's motion, the number of dark cores was not conserved, whereas the total TCs of the OVs were conserved on the DH-OVA. Results contrasted with the conventional wisdom on OVAs. Furthermore, the bidirectional motion of yeast particles via the DH-OVA was executed experimentally. This work provided a flexible DH-OVA, which will result in new potential applications in particle transfer, polarity particle sorting, and micro-particle manipulation. ? 2021 Elsevier Ltd
    Accession Number: 20213810910150
  • Record 429 of

    Title:Fe3O4 nanoparticle-enabled Q-switched pulse generation in fiber laser
    Author(s):Ban, Xiaoqiang(1,2); Sun, Penghuan(3); Qyyum, Abdul(3); Li, Xiaohui(3); Song, Zhuoying(3); Zhong, Ming(4); Little, Brent E.(1,2); Zhao, Wei(1,2)
    Source: Optical Fiber Technology  Volume: 71  Issue:   DOI: 10.1016/j.yofte.2022.102909  Published: July 2022  
    Abstract:Fe3O4 nanoparticles (Fe3O4-NPs) are outstanding magnetic materials, which have plenty of applications in many fields, such as magnetic detection, ultrafast photonics, optical communication, etc. In this paper, we used co-precipitation method to synthesize Fe3O4-NPs, which formed saturable absorber (SA) in our erbium-doped fiber laser (EDFL). We obtained stable Q-switched pulses with central wavelength of 1530.46 nm and signal-to-noise ratio (SNR) of 54.4 dB when the pump power was 400 mW. When the pump power increased gradually, outline of the spectrum changed little, however, the repetition rate (RPR) increased gradually, meanwhile the pulse duration decreased gradually. In this experiment, when the pump power reached its maximum of 415.4 mW, the RPR reached its maximum of 72 kHz, meanwhile the pulse duration reached its minimum of 2.44 μs. It shows that Fe3O4-NPs-based passively Q-switched EDFLs have many potential applications, such as laser frequency doubling, laser radar, and study of interaction between light and matter, etc. ? 2022 Elsevier Inc.
    Accession Number: 20221812056608
  • Record 430 of

    Title:All-optical Ti3C2Tx modulator based on a sandwich structure
    Author(s):Li, Erkang(1); Jiang, Man(1); Li, Duidui(1); Wang, Ruiduo(2,3); Kang, Xin(1); Wang, Tianqi(1); Yan, Xiaoxin(1); Liu, Beibei(1); Ren, Zhaoyu(1)
    Source: Applied Optics  Volume: 61  Issue: 4  DOI: 10.1364/AO.445975  Published: February 1, 2022  
    Abstract:All-optical modulators based on MXene-Ti3C2Tx have recently garnered much attention due to their broadband light-matter interactions and its ultrafast carrier dynamics. To investigate the modulation characteristics of pump intensity and pump light modulation frequency, we establish an all-optical modulator with a sandwich structure based on MXene-Ti3C2Tx=PVA (polyvinyl alcohol) film. The result shows that this modulator can achieve a high modulation depth of 12.55 dB and a modulation frequency of 50 kHz corresponding to a response time at the microsecond scale. The successful preparation of the modulator is attributed to the saturable absorption characteristics of the MXene-Ti3C2Tx. This modulator has great potential in all-optical communications and ultrafast optical signal processing. ? 2022 Optica Publishing Group.
    Accession Number: 20220511555197
  • Record 431 of

    Title:Theoretical and experimental study on Noise Equivalent Power of X-ray semiconductor ultra-fast response material based on the rad-optic effect
    Author(s):Yan, Xin(1,2); Wang, Tao(2); Wang, Gang(2); Yao, Dong(1,2); Liu, Yiheng(2); Gao, Guilong(2); Xin, Liwei(1,2); Yin, Fei(2); Tian, Jinshou(2); Chang, Xinlong(1); He, Kai(2)
    Source: arXiv  Volume:   Issue:   DOI: 10.48550/arXiv.2206.10890  Published: June 22, 2022  
    Abstract:Semiconductor material based on the rad-optic effect enables ultra-fast detection of X-rays and plays an important role in fusion diagnostics. Obtaining the accurate noise equivalent power (NEP) of the semiconductor ultrafast response material is the key to detecting X-rays. In this paper, the refractive index change mechanism of the semiconductor under X-ray irradiation was analyzed, and the quantitative relationship between the diffraction efficiency and the X-ray photon energy was established through the LT-AlGaAs diffraction imaging experiments. The impulse responses of LT-AlGaAs under 1 KeV-10 KeV X-ray radiation were calculated, revealing the variation of NEP density with radiated photon energy. In the case of bombarding the Al target to generate 1.5 KeV X-rays, the imaging experiments of LT-AlGaAs were performed. The diffraction image of LT-AlGaAs has a linear relationship with the radiation intensity, and the NEP density of LT-AlGaAs reaches 4.80×105W/cm2. This study has reference significance for the development of ultra-fast X-ray imaging systems based on the rad-optic effect. ? 2022, CC BY.
    Accession Number: 20220214035
  • Record 432 of

    Title:Analysis and Design of Fault Prediction and Health Assessment System for the optoelectronic Equipment
    Author(s):Zhang, Chuming(1); Wei, Guojun(1); Wang, Xuan(2); Cao, Yu(2); Xie, Meilin(2)
    Source: IMCEC 2022 - IEEE 5th Advanced Information Management, Communicates, Electronic and Automation Control Conference  Volume:   Issue:   DOI: 10.1109/IMCEC55388.2022.10019826  Published: 2022  
    Abstract:In recent years, due to the rise of emerging technologies such as integrated circuits, artificial intelligence and big data, Optical measurement equipment performance is also constantly improving, more and more new technology, new processes, new materials continue to appear. Therefore, the maintenance of the optoelectronic equipment is also much more difficult. Based on these problems, this paper investigates the application of fault prediction and health management in optoelectronic devices. The main analysis and design of the system failure prediction and health assessment, and in response to the needs of optoelectronic devices for the life analysis, health status determination, fault prediction alarms, etc, designed a failure prediction and health assessment system for optoelectronic devices. ? 2022 IEEE.
    Accession Number: 20230713575048
日本无码专区| 91国自产精品中文字幕亚洲 | 亚洲AV高清无码| 亚洲无码自拍| 99在线视频观看| 三级片网站视频| 内射在线| 亚洲精品久久国产高清情趣图文| 操逼好视频| 91高清视频| 国产精品久久久久久亚洲影视内衣| 国产精品一区二区在线观看| 欧美一级特黄aaaaa片| 欧美日韩精品一区二区在线播放| 娇妻被交换粗又大又硬影视 | 欧美88| 秋霞AV影院| 天天干夜夜爽| 国产日韩视频在线| 亚洲精品自拍| 欧美日韩精品| 五月婷婷啪啪| 国产精品视频一| 黄色精品| 综合色区| 中文熟妇人妻又伦精品| 日韩欧美三级| 欧美视频精品| 秋霞无码在线| 欧美人与物videos另类| 91一区| 四季AV一区二区夜夜嗨| 国产亚洲| 日韩免费在线观看视频| 爆乳熟妇一区二区三区霸乳| 鲁啊鲁视频| 亚洲午夜久久| 天天摸夜夜操| 日韩国产欧美| 青青草原在线视频| 一级特黄60分钟高清免费观看| 99精品人妻一二三区| 91人妻中文字幕在线精品| 午夜激情福利视频| 先锋影音AV资源网| 亚洲欧洲一区二区三区| 天天日夜夜骑| 久久伊人精品| 国内精品国产成人国产三级| 亚洲特黄| 一级a一级a爰片免费免免中国人| 中出无码| 丁香五月天在线观看| 无码精品黑人一区二区三区| 秋霞视频在线观看| 亚洲第一网站| 成人精品一区二区三区| 无码入口| 久久亚洲网站| 国产一区二区三区电影| 强奸91| 国产伦精品一区二区三毛| 日韩毛片无码| 久久久综合色| aV在线无码| 欧美日韩操逼| 久久精品国产亚洲A| 亚洲第一中文字幕| 久久久久久久91| 专约老熟女丰满探花| 成人区精品一区二区婷婷| 亚洲视频一区二区三区| 免费AV观看| 九九热在线观看| 一级免费视频| 精品久久一区二区三区| 一级a毛片免费观看久久精品| 午夜精品美女久久久久av福利| 先锋资源av| 日日夜夜天天干| 国产伦亲子伦亲子视频观看| 亚洲激情在线视频| 亚洲黄色网页| 91在线无码高潮喷水观看99久| 亚洲熟妇XXXXX| 日韩精品在线一区二区| 亚洲精品白浆高清久久久久久 | 国产精品视频观看| 久久久熟妇熟女| 成人免费毛片| 一级操逼毛片| 草草影院ccyy国产日本第一页| 亚洲综合社区| 九九热无码| 亚洲AV无码片一区二区三区| 色色视频网站| 高清无码一区二区三区| 亚洲图片第一页| 色裕3区| 久久综合99| 国产夫妻性爱自拍| 国产亚洲欧美一区二区三区| 日本熟女网站| 精品九九| 欧美一区二区无码三区有限公司 | a v最新天堂| 91国内产香蕉| 国产精品国产三级国产a| 日韩欧美中文字幕在线观看| 玩弄孕妇人妻系列| 欧美日韩中文在线| 友田真希一区| 99自拍视频| 国产欧美精品| 国产精品久久久久永久免费看| 无码精品一区二区| 四季AV一区二区夜夜嗨| 成人妇女免费播放久久久| 国产二级片| 色一情一乱一乱一区91Av| 国产探花av| 亚洲天堂三级片| 91麻豆精品91久久久久同性| 精品无码一区二区| 成人无码毛片| 日韩精品专区| 人妻一区二区三区四区| 啪啪视频免费观看| 琪琪av| 国产无码在线视频| 欧美人伦| 国产精品久久久久久爽爽爽麻豆色哟哟| 热久久免费视频| 岛国一级片视频在线免费观看 | 免费看日本伦人伦A片| mm1313亚洲国产精品无码试看| 91无码高清视频| 男人午夜天堂| 婷婷激情久久| 91色在线观看| 亚洲图片中文字幕| 欧美极品少妇×XXXBBB| 国产精品操逼| 国产精品三级在线| 日逼视频免费看| 亚洲中文字幕在线观看| 成人久久大片91含羞草| 熟妇性爱视频| 国产第8页| 一区二区三区成人| 日韩欧美一级片| 无码国产精品一区二区| 婷婷五月天基地| 欧美伊人| 婷婷性爱视频| 久草资源| 怡红院色| 久久国产综合| 国产乱叫456在线| 中文字幕在线无码| 精品人妻伦一二三区久久斗罗| 久精品视频| 国产视频久久久| 一级黄色电影在线观看| 动漫精品一区二区| 特黄AAAAAAA片免费视频| 国产亲子伦视频一区二区三区| 四虎毛片| 欧美乱码精品一区二区三| 一区二区自拍| 狼友视频网站| 日韩逼逼| 免费麻豆国产一区二区三区四区| 99热免费观看| 蜜桃av在线| 在线不卡视频| 色秘密综合网| 思思热在线| 无码少妇一区二区三区| 国产精品久久欧美久久一区| 成人欧美一区二区三区黑人免费| 国产成人精品无码一区二区蜜柚| 天天爽夜夜爽夜夜爽精品视频| 亚洲天堂无码一区| 五月丁香五月婷婷| 91九色视频| 久操视频在线| 天天搞天天色天天干| 安徽妇搡bbbb搡bbbb按摩 | 涩涩屋黄| 中文字字幕在线中文| 国产无码性爱| 色综合色| 岛国黄色网| 亚洲精品在线视频| 麻豆乱伦| 少妇伦子伦精品无吗| 国产黄色电影院| 一本大道无码| 天天射影院| 精品久久ai| 99久久久无码国产精品怎么下载| 日本视频一区二区三区| 中文字幕在线观看第一页| 国产精品裸体一区二区三区| 无码黄色片免费| 国产亚洲一区二区三区| 欧美精品区| 久久国产精品一区二区| 日本不卡久久| 激情久久五月天| 黄片免费下载| 夜夜操天天干| 艳妇臀荡乳欲伦交换在线播放| 国产AV视屏| 今晚国产乱伦av网站| 国产乡下妇女做爰| 一级毛片aaa| 亚洲AV中文无码乱人伦在线视色| 在线日韩视频| 日韩午夜| 成年免费视频黄网站在线观看| 国产伦精品一区二区三区免费肉| 91肉色超薄丝袜一区二区| 色一情一乱一乱一区91Av| 国产精品久久久久久婷婷天堂| 色婷婷一区二区| 欧美日韩国产中文| 麻豆视频一区二区三区| 五月社区| 77777av| 欧美V性爱| 人人操99| 强奸乱伦1区2区3区| 黄色国产在线| c逼网站| 日韩av毛片| 女女百合av大片在线观看免费| 国产又粗又猛又大爽| 99精品在线观看| 天天草夜夜草| 一级a一级a爰片免费免免软件ww| 欧美高清视频| 欧美日韩电影在线观看| 精品久久久久久| 免费在线视频| 欧美日韩精品一区| 一级片免费视频| 色色99| 天天综合天天做天天综合| 青青在线| 免费a视频| 国产精品视频观看| 亚洲精品无码一区二区电影 | 色噜噜综合| 91肉色超薄丝袜一区二区| αⅴ天堂αⅴ| 精品一区二区三区免费观看| 免费一级a| 天天操夜夜操| 97视频| 日韩无码一区二区三区| 天天操天天干天天插| 中出无码| 搞黄无遮挡| 久久精品人妻一区二区三区| 亚洲无码少妇| 精品久久久久久久久久| 欧美日精品| 9999在线视频| 熟妇人妻一区二区三区四区| 国产视频久久久| 日韩免费视频一区二区| 国产熟女视频| 一区无码在线| 我把护士日出水| 国产成人精品视频| 日韩黄片观看| 久热精品在线| 视频一区在线| 久一在线| 久久一区二区三区视频| 男人天堂东京热| 影音先锋男人的天堂| 日韩一区二区在线观看视频| 人人爱人人摸| 在线免费看黄网站| 国产黄色免费观看| 国产V综合V亚洲欧美久久| 国产精品666| 亚洲图片中文字幕| 一级a一级a爰片免费免水l软件| 国产第一页屁屁影院| 国产又大又粗| 亚洲图片欧美另类| 污视频下载| 欧美群妇大交群| 欧美日韩操逼| 国产日韩一区| 天天色天天插| 免费A级黄片| 淫荡网站在线观看| 日韩www| 在线视频一区二区三区| 国产熟女一区二区三区浪潮97| 超碰100| 久久久人妻精品| 日韩一区二区视频| 日韩欧美亚洲| 中日韩美一级毛片天天爽| 国产高清无码视频在线观看| 豪妇荡乳1一5潘金莲| 国产高清无码毛片| 亚洲制服丝袜在线观看| 国产免费一区| 久久久内射| 日本黄a三级三级三级| 日韩久久精品| 欧洲另类类一二三四区| 欧美日精品| 中文字幕在线观看网站| 色老头久久综合网| 中文字幕人妻在线| 天堂久久精品| 国产精品久久久久久久免费看| 翔田千里av一区二区| 亚洲第一网站| 9999在线视频| 日韩精品极品视频在线观看免费 | 一级片免费视频| 日韩中文亚洲第一| 尤物AV在线| 日韩视频精品| 欧美日韩亚| 夜夜福利| 国产亚洲中文字幕| 国产精品无码电影| 国产自慰网站| 日韩在线一区二区| 精品一区二区久久久久久无码| 高清无码专区| 乱伦熟女肉妇| 久久久999| 久久精品国产亚洲AV麻豆图片| 思思热在线观看| 国产精品91在线| 国产一区二区三区四区视频| 福利一区二区视频| 中文有码| 超碰在线免费| 偷拍区图片区小说区| jazzjazz国产精品麻豆| 亚洲A级片| 亚洲乱强伦乂 乄乄乄乄9| 久久水蜜桃| 在线亚洲精品| 91视频免费观看| 老熟女伦一区二区三区| 精品在线免费观看| 精品无码人妻一区二区三区 | 亚州人妻| 影音先锋亚洲AV少妇熟女| 国产一级特黄录像片| 国产精品一级av| 91麻豆精品视频| 少妇放荡的呻吟干柴烈火| 久久精品网| 亚洲高清视频一区二区| 国产一区二区三区四区五区加勒比| 黄色在线网站| 国产精品无码久久久久一区二区| 国产精品一区视频| 97精品国产| 国产伦精品一区二区三区视频不卡| 国产在线视频第一页| 国产精品666| 久久精品2019中文字幕| 思思热视频在线观看| 一级全黄60分钟免费网站| 亚洲天堂AV在线播放| 青青草原国产| 久久这里有精品| 天天射影院| 欧美精品一二三四区| 五月综合在线| 久久99日韩| 伊人五月| 国产一区二区视频在线| 91精品久久久久久久蜜月| 99视频精品| 天天爽夜夜爽夜夜爽精品视频| 无码人妻精品一区二区三区蜜桃91| 亚洲乱妇老熟女爽到高潮的片 | 黄色18禁| 看一级黄色片| 无码A片在线看www不卡福利姬| 国产精品igao视频网网址| 国产日韩欧美一区二区东京热| 中文字幕日韩一区| 91精品久久人人妻人人做人人爱| 96超碰在线| 亚洲性在线| 伊人久久亚洲| 国产精品久久久久三级无码| 狠狠做六月爱婷婷综合aⅴ | 久久av一区二区三区| 国产精品久久久久久久久久免费看| 亚洲欧美精品SUV| 亚洲av无码一区二区二三区 | 黄色电影在线免费观看| 国产香蕉视频| 91免费在线视频| 一区二区三区在线看| 秋霞影院在线观看| 欧美一级视频| 久久久影院| 久一在线| 奶大灬好大灬好硬灬好爽在线播放| 国内熟女乱伦视频| 日韩精品视频在线免费观看| 亚洲日本三级| 日韩精品在线观看视频| 国产片91| 狠狠操天天操| AV一二三区| 狠狠爽狠狠操| 碰碰人人| 成人日本A片无码| 农村毛片| 天堂AV一区| 亚洲精品日韩激情在线电影| 日韩免费一区二区三区| 九九热在线视频| 99人妻| 国产成人精品久久二区二区| 亚洲精品无码久久久久av | 国产av看片| 国产乱伦小说| 成人精品国产| 思思网站| 中文字幕在线视频网站| 91www| 视频一区二区在线| 热久久久久久久| 综合成人| 久久久成人网站| 在线无码视频| 秋霞一级片| 亚洲av免费在线| 顶级嫩模被啪到呻吟不断| 久久人妻人人爽| 99国产在线拍91揄自揄视| 最好看的中文视频最好的中文| 午夜成人视频| 成人爱爱视频| 天堂中文在线视频| 成人黄色电影在线观看| 日本少妇高潮日出水了| a一片一免费| 午夜精品久久| 色婷婷综合久久| 日本中文字幕有码| 婷婷一区二区| 新啪啪视频| 97人人爽人人爽人人爽人人爽| 污网站免费观看| 91手机操逼视频| 99re在线| 日本55丰满熟妇厨房伦| 日韩一级无码毛片| 日本一区视频| 亚洲欧美小说| 无遮挡无掩盖的网站| 色欲无码精品一区二区三区99满 | 麻豆精品国产| 婷婷一区二区| 欧美性爱一区二区社区| 99在线观看视频| 精品无码av一区二区鲁一鲁| 欧美三日本三级三级在线播放| 欧美电影一区二区| 日韩av在线免费观看| 欧美一二| 91久久精品国产| 成人在线网站| 国产黄色小视频| 国产AV一级片| 综合网久久| 中文无码二区| 人人操免费| 久久久久毛片无码| 午夜精品久久久久久久| 亚洲综合图片区| 一区二区在线免费视频| 91日韩视频| 亚洲三级片在线| 岛国大片在线一区二区三区在线免费观看| 国产无码免费视频| 性爱视频A| 天天激情| 九九香蕉视频| 丁香五月综合| 香蕉久久久| 鲁鲁狠狠狠7777一区二区| 一本色道久久综合亚洲精品小说 | 久久内射| 国产精品久久一区| 苍井空久久| 国产三级网站| 免费看黄色一级片| 欧美国产日韩视频| 精品伊人久久大香线蕉| 哪里可以看毛片| 日本黄色不卡视频| 亚洲毛片免费看| 天天夜夜操| 人人操人人看人人摸| 毛多色婷婷| 亚洲激情网站| 久久毛片视频| 亚洲一级黄色录像| 亚洲AV无码牛牛影视| 成人乱人乱一区二区三区| caoprom人人| A级黄片免费看| 亚洲欧洲在线观看| 天天日天天爱天天操| 失眠是什么原因引起的| 久久精品一区二区| 五月婷婷六月丁香综合| 成人免费毛片足控| 91精品国产91久久久久游泳池| 国产成人精品一区二三区熟女在线| 国产色区| 欧洲精品一区| 丁香五月天色| 久久久人妻精品| 欧美性爱综合| 西西444WWW无码大胆| 欧美一区二区精品| 在线中文无码| 国内精品视频| 国产又大又黄| 性一交一黄一片一区二区男女| 国产一级毛片视频| 手机在线看黄色片| 91精品国产日韩91久久久久久| 欧美XXXBBB| 亚洲高清毛片一区二区| 亚洲一区二区三区四区在线| 国产无码久久久| 人妇视频一区二区| 中文字幕在线观看av| 国产精品久久久久久一级毛片探花| 久久久亚洲熟妇熟女| 色橹橹欧美在线观看视频高清| 国产高清一级A片免费看少妃 | 午夜一二三| 思思久久主页| 秋霞AV影院| 91黄色片| 一本一道久久a久久精品蜜桃| 亚洲成人无码在线| 免费看成人网站| jazzjazz国产精品麻豆| 国产精品久久久久久亚洲影视内衣| 草莓视频在线| 尤物视频网站在线观看| 国产一级做a爰片久久毛片男 | 国产无码精品一区二区| 国产一级做a爰片久久毛片男 | 99精品国产91久久久久久无码| 成人无码片免费178www| 无码专区视频| 亚洲天堂男人天堂| 波多野结衣二区| 免费看一级高潮毛片| 欧美性爱中文字幕| 国产a一区| 国产乱伦一区二区| 国产SUV精品一区二区883| 国产又粗又爽又黄的视频| 91爽爽| 国产精品2| 韩国久久| 狠狠干狠狠操天天爽| 午夜在线无码| 国产在线第二页| 久久动态图| 国产永久免费| 一级免费黄色片| 午夜影院在线观看| 亚洲中文字幕一区二区| 成人精品影院| 国产精品Av久久| 日韩久久久久久久| 亚洲国产精品久久久| 蜜桃久久久| 熟妇人妻中文字幕无码老熟妇| 一级黄色电影在线观看| 午夜精品一区二区三区在线视频| 白洁性荡生活第90章| 九七操逼啊| 青青草精品视频| 国产精品国产三级国产a| 秋霞无码| 日韩高清免费无专码区| 亚洲精品国产精品乱码不卡| 一牛影视无码| 亚洲自拍小说| 国产乱伦小说| 亚洲天堂av无码| 国产在线拍揄自揄拍无码福利| 婷婷综合五月天| 成全视频观看免费高清第6季| 欧美日韩精品在线观看| 欧美一级视频| 91无码人妻精品一区二区三区四| 国产嫩草一区二区三区在线观看| 亚洲成av人片在线观看| 久久中文视频| 日日狠狠久久| 国产性色视频| 黄色91视频| 亚洲制服丝袜在线观看| 亚洲熟妇在线| 国产大片免费看| 色情无码免费视频网站在线观看| 人妻无码内射| 亚洲熟女一区二区三区| 精品视频一区二区| 美女裸体久久久久久久久| 亚洲国产网址| 日韩色视频| 91黄色在线观看| 精品无码区| 波多野42部无码喷潮在线| 日韩精品一区二区三区中文字幕| 亚洲日本三级| 狠狠操av| 久久精品一区二区三区四区| 国产裸体永久免费视频网站| 亚洲av一二区| 香蕉久久夜色精品国产更新时间 | 日韩无码| 成人国产色情无码视频网站代码 | 欧洲精品视频在线观看| 亚洲无码在线播放| 黄色免费看网站| 躁躁躁日日躁网站| 国产精品久久久久久久久久三级 | 国产无码精品一区二区| 国产一级a毛一级a做免费视频| 一区二区www| 风间由美久久久无码人妻| 亚洲无码TV| 97人人爽人人爽人人爽人人爽| 欧美熟妇另类久久久久久牛牛影视| 日本三级电影中文字幕| 成人午夜福利在线观看| 91Av导航| 国产成人精品久久二区二区| 羞羞久久久久久久| 国产高清不卡| 国产视频精品一区二区三区| 欧美少妇性爱| 国产美女内射| 欧美不卡一区| 亚洲国内自拍| 91丝袜精品久久久久久无码人妻| AV天堂无码| 国产成人无码精品亚洲| 国产日韩欧美一区二区东京热| 亚洲精品久久久久久中文传媒| 欧美大成色www永久网站婷| 娇妻被交换粗又大又硬影视| 男人的天堂无码| 国产在线视频第一页| 无码人妻精品一区二区蜜桃网站| 亚洲成人精品一区二区三区| 亚洲一级二级三级| 手机在线看黄色片| 国产成人精品亚洲日本在线观看| 国产精品人妻无码一区二区三区牛牛| 色综合色综合网色综合| 国产一级片在线播放| 中文字幕精品无码| 国产欧美黄片| www91com| 无码精品一区二区三区潘金莲 | 久久久黄色| 一起草无码在线| 91久久婷婷| 91新网址| 亚洲卡一卡二| 香蕉视频国产| 精品视频免费| 国产a毛片一级二级真人| 黄色网在线看| 五月天丁香网| 爱爱视频网址| 无码人妻束缚av又粗又大| 午夜操逼逼| 午夜精品在线观看| 亚洲国产电影| 亚洲色久悠悠| 91AV视频在线播放| 无码内射视频| 国产精品9999| 国产性爱大片| 妖精视频黄色| 国产免费小视频| 伊人999| 欧美一区二区三区成人片在线| 国产精品99久久久久久白浆小说| av大香蕉| 91视频入口| 欧美日韩三级视频| 色www91| 91久久免费视频| 国产精品久久久久久久久免费看| 亚洲精品一区二区三区在线观看 | 污污网站在线观看| 免费看黄色大片| 免费无码国产| 人人妻人人摸| 久久性生活视频| 久久综合视频国产| 国产一级片免费观看| 成人网站在线看| 亚洲综合一区二区三区| 久久精品国产AV一区二区三区| 国产一级aa| 无码不卡在线| 日本大香蕉在线| jizz欧美大全| 熟妇人妻videos| 狼人综合网| 天堂网在线视频| 久久久国产一区二区三区渔网袜| 91久久久久久久久| 视频国产精品| 综合久久亚洲| 国产又粗又长又硬| 一级无码在线| 污网站在线免费观看| 国洲 一区二区| 一级av在线| 婷婷色在线视频| 亚洲视频在线一区二区| 欧美日韩视频在线播放| 亚洲美女高潮久久久| 国产高清在线| 日本中文字幕在线看| 自拍偷拍一区| 五月婷婷综合| 国产视频一区二区在线观看| 欧美午夜精品久久久久免费视| 天天色影院| 中文字幕免费视频| 午夜成人亚洲理伦片在线观看| 国产色播| 亚州AV一区二区三区| 国产乱伦一区| AV性天堂网| 丰满欧美大爆乳性猛交| 高清无码精品视频| 久久免费小视频| 凹凸久久99精品久久久久久琪琪| 五月婷婷色色午夜| 欧洲操逼视频| www夜夜操| 久久综合久| 九一免费视频| 天天干天天干天天| 国产亲子乱露脸一区二区 | 欧美精品一区二区在线| 中日韩无码精品| 91人人操人人摸| 免费黄色网站| 日本性爱视频在线观看| 小黄片在线播放| 日韩免费在线视频| 久久久久久亚洲av| 日本无码在线观看| 国产真人真事一级A片| 国产原创精品| 男人亚洲天堂| 日韩成人在线播放| 一区两区小视频| 岛国天堂av在线| 超碰在线观看91| 日韩免费在线观看| 天天日夜夜爽| 国产亚洲色婷婷久久99精品91| 久久日本无码中文字幕三级伦| 国产深夜视频| 欧美精品亚洲精品日韩精品| 精品无人区一区二区三区软件下载| 三上悠亚一区二区| 色无码视频| 超碰在线人妻| 中文无码在线| 一区二区三区亚洲| 国产精品av久久久| 亚欧高清无码| 特黄视频| 91久久精品国产91性色tv| 国产一区二区免费| 黄色网址免费观看| 蜜芽在线| 亚洲第一黄色网址| 国产性爱在线视频| 欧美特级| 日韩影院黄片| 亚洲熟女乱综合一区二区| 道日本一本草久| 91黄色在线观看| 久草中文在线| 精品国产91久久久久久久黄无码| 男人的天堂电影院| 乱伦熟妇| 国产一区二区三区在线| 岛国大片在线一区二区三区在线免费观看| 天天干天天曰| AV在线天堂| 蜜桃91丨九色丨蝌蚪91桃色| 成人网站免费观看完整版入口| 久久久18禁一区二区三区精品| 美国式禁忌| 一区二区三区性爱视频| 午夜精品A片一二三区蜜臀| 色欲无码精品一区二区三区99满| 北条麻妃满足邻居的美人妻| 日韩成人在线观看| 欧美三级在线看| 黄色免费av| 秋霞三级伦电影| 成年免费视频黄网站在线观看 | 九色影院| 国产精品久久一区二区三区| 亚洲天堂手机版| 精品亚洲一区二区| 中国农村毛片免费播放| 色悠悠在线| 国产av成人| FREEZEFRAME丰满少妇| 久久久久久精品无码一区二区三区| 无码午夜精品一区二区三区视频| 国产精品免费看| 亚洲91色图| 在线无码视频| 无码在线免费视频| 国产精品无码久久久久一区二区| 啪啪视频com| 亚洲东京热| 一本色道久久综合狠狠躁篇的优点| 国产人妻一区二区三区四区五区六| 色色毛片的网站| av网站在线播放| 国产二区在线播放| 日韩欧美综合| 自拍偷拍第二页| 91色综合| 国产精品九九| 国产伦精品一区二区三区视频不卡| 97超碰人妻| 美女网站免费黄| 91精品视频网| 一级亚洲| 凹凸久久99精品久久久久久琪琪 | 国产无码高清视频在线观看| 国产真人无遮挡作爱免费视频| 色秘密综合网| 国产一国产一级毛片日本导航 | 91麻豆精品国产91久久久久久| 欧美精品福利视频| 嫩草在线视频| 欧美亚洲免费| 国产69精品久久久久孕妇大杂乱| 亚洲精品一| 久久1热| 国产一区二区无码| 亚洲av免费在线| 日韩午夜影院| 一级片中文字幕| 国产一区二区精品| 欧美日韩国产乱伦| 日韩精品在线视频| 伊人成人电影| 精品无码少妇| 伊人五月天综合| 欧美一区二区在线| 久久精品99| 亚洲黄片在线播放| 五月婷婷综合视频| 亚洲综合社区| 高清无码操逼| 欧美一级内射美妇网站| 91丨国产丨精品白丝| 九九色视频| 少妇人妻偷人精品无码视频新浪| 久久午夜免费视频| 久久久久久久一区| 日日夜夜天天| 亚洲AV无码成人精品国产丁香| 露脸对白| 精品欧美久久| 女人高潮天天躁夜夜躁| 美国一级黄片| 91色在线| 亚洲制服丝袜| 秋霞无码视频| 久久久久久久国产精品| 91无码人妻精品一区二区蜜桃| av无码在线播放| 伊人久操| 日韩无码导航| 日韩欧美亚洲国产| 国产成人三区| 欧美一级片内射| 国产熟妇久久777777| 国产精品精品| A级免费视频| 一级片在线免费观看| 久久午夜夜伦鲁鲁片无码免费| 久久亚洲综合| 精彩视频一区二区|