Detection of incoherent broadband terahertz light using antenna-coupled high-electron-mobility field-effect transistors

The sensitivity of direct terahertz detectors based on self-mixing of terahertz electromagnetic wave in field-effect transistors is being improved with noise-equivalent power close to that of Schottky-barrier-diode detectors. Here we report such detectors based on AlGaN/GaN two-dimensional electron gas at 77~K are able to sense broadband and incoherent terahertz radiation. The measured photocurrent as a function of the gate voltage agrees well with the self-mixing model and the spectral response is mainly determined by the antenna. A Fourier-transform spectrometer equipped with detectors designed for 340, 650 and 900~GHz bands allows for terahertz spectroscopy in a frequency range from 0.1 to 2.0~THz. The 900~GHz detector at 77~K offers an optical sensitivity about $1~\mathrm{pW/\sqrt{Hz}}$ being comparable to a commercial silicon bolometer at 4.2~K. By further improving the sensitivity, room-temperature detectors would find applications in active/passive terahertz imaging and terahertz spectroscopy.Comment: 4.5 pages, 5 figure

Responses of upper layer of northern South China Sea to two locally-generated tropical cyclones

应用Topex/Poseidon卫星高度计海面高度距平(SSHA)资料以及TMI的逐日海表温度数据,对两个局地生成的热带气旋(1999年台风LEO和2000年台风WUKONG)引起的南海北部海洋响应过程进行研究。结果表明,在热带气旋影响下,海面高度显著降低,SSHA平均减少30cm,流场上出现气旋型环流,海表温度显著降低,降低幅度为2℃左右,在其尾迹上出现冷涡;相对于降温过程,海表温度的恢复过程非常缓慢;热带气旋强度突变或移行较缓时易引起海洋的强烈响应,这种响应的空间和时间尺度都较大,持续时间至少1周,发生响应的海域范围也很广,甚至可以跨越3个纬度的距离。Responses of upper layer of the northern South China Sea to two locally-generated tropical cyclones have been studied by using the data derived from Topex/Poseidon altimeter and SST data from TRMM Microwave Imager(TMI).The two tropical cyclones are typhoon LEO from April 27th to May 2nd in 1999 and typhoon WUKONG from September 5th to September 10th in 2000.The following results are obtained.The sea surface height decreased and a geostrophic current appeared under the influence of the tropical cyclones.SST decreased apparently and there were cold eddies in the wakes of the tropical cyclones.Compared with the process of SST decreasing,it took longer time,about one week,for SST to recover.The sea surface height tended to show an intense response when there were abrupt changes in the intensity of the tropical cyclones or when they moved slowly.These responses appeared to have large spacial and temporal scales.国家自然科学基金资助项目(40576015,40576015);; 中国海洋大学物理海洋学教育部重点实验室开放课题(200304

Three new diatom species from coastal sandy environment

摘要 本论文利用光学显微镜和扫描电子显微镜对来自福建省漳州市南太武沙滩和辽宁省大连市海洋岛沙滩两个不同生境的潮间带沙生硅藻样本进行了研究，发现了3个硅藻新种厦门舟形藻、沙生蹄状藻和大连半月藻，其中半月藻属是中国境内的新纪录属，厦门舟形藻作为一个新种已经发表于世界最大的植物系统学杂志《Phytotaxa》。 厦门舟形藻发现于福建省漳州市南太武沙滩，厦门舟形藻的主要特征是端壳缝比较简单并且略微弯曲向同一侧，壳面两端有明显的无纹区，而且壳端环绕有两排相互垂直的孔纹等，这种简单的壳缝系统与壳端特征和蹄状藻属种类极为相似，但是厦门舟形藻的内壳面存在明显的硅质壁加厚，而蹄状藻属种类则没有明显的硅质壁加...Abstract Three new diatom species, Navicula amoyensis, Hippodonta arenaria, Lunella dalianensis, were described from the sandy environments in Nantaiwu, Fujian Province and Haiyang Island, Liaoning Province, China, using light microscopy and scanning electron microscopy. Lunella genera was firstly recorded in China, and Navicula amoyensis was decribed as a new species which have been published in...学位：理学硕士院系专业：生命科学学院_水生生物学学号：2162014115243

OPTIMAL PROCESS of A CLASS of JUMPING STATESDIFPERENTIAL INCLUSION SYSTEMS

本文讨论状态可跳跃的微分包含系统.在较一般的假设下，得到一个关于跳变微分包含系统的最佳过程的POnTryAgIn型的最大值原理，其横截条件表为一统一形式.本文的主要结果包含一些重要的已知结果作为其特例.In this paper, we consider the diFFerential inclusion systems where thestates can jump.Under mild hypothesies, a Pontryagin's type maximum principle Forthe optimal process is obtained.The transversity conditions are expressed in a unitedForm.The main therem includes some well-known results as its special cases

Mapping an on-chip terahertz antenna by a scanning near-field probe and a fixed field-effect transistor

In the terahertz (THz) regime, the active region for a solid-state detector usually needs to be implemented accurately in the near-field region of an on-chip antenna. Mapping of the near-field strength could allow for rapid verification and optimization of new antenna/detector designs. Here, we report a proof-of-concept experiment in which the field mapping is realized by a scanning metallic probe and a fixed AlGaN/GaN field-effect transistor. Experiment results agree well with the electromagnetic-wave simulations. The results also suggest a field-effect THz detector combined with a probe tip could serve as a high sensitivity THz near-field sensor

基于张拉整体结构仿生足式机构的设计与分析

传统足式机器人在复杂地形上自适应行走方面存在着机构柔性不足。基于张拉整体结构与人体肌肉骨骼系统相似性，提出了一种仿生张拉足式机构，用于提升传统足式机器人自适应地形和稳定锁紧性能。通过张拉单元匹配建立了类似人体足部的张拉整体结构等效映射模型；采用仿生设计方法实现了机构构型设计；制作了物理样件并搭建了实验平台。结果表明，提出的仿生足式机构具有较好的柔性和稳定性，提升了传统足式机器人斜坡地形的自适应稳定行走能力