Recommended high performance telescope system design for the TianQin project

China is planning to construct a new space-borne gravitational-wave (GW) observatory, the TianQin project, in which the spaceborne telescope is an important component in laser interferometry. The telescope is aimed to transmit laser beams between the spacecrafts for the measurement of the displacements between proof-masses in long arms. The telescope should have ultra-small wavefront deviation to minimize noise caused by pointing error, ultra-stable structure to minimize optical path noise caused by temperature jitter, ultra-high stray light suppression ability to eliminate background noise. In this paper, we realize a telescope system design with ultra-stable structure as well as ultra-low wavefront distortion for the space-based GW detection mission. The design requirements demand extreme control of high image quality and extraordinary stray light suppression ability. Based on the primary aberration theory, the initial structure design of the mentioned four-mirror optical system is explored. After optimization, the maximum RMS wavefront error is less than lamda/300 over the full field of view (FOV), which meets the noise budget on the telescope design. The stray light noise caused by the back reflection of the telescope is also analyzed. The noise at the position of optical bench is less than 10-10 of the transmitted power, satisfying the requirements of space gravitational-wave detection. We believe that our design can be a good candidate for TianQin project, and can also be a good guide for the space telescope design in any other similar science project

Realization of multiple charge density waves in NbTe2 at the monolayer limit

Abstract: Layered transition-metal dichalcogenides (TMDCs) down to the monolayer (ML) limit provide a fertile platform for exploring charge-density waves (CDWs). Though bulk NbTe2 is known to harbor a single axis 3*1 CDW coexisting with non-trivial quantum properties, the scenario in the ML limit is still experimentally unknown. In this study, we unveil the richness of the CDW phases in ML NbTe2, where not only the theoretically predicted 4*4 and 4*1 phases, but also two unexpected sqrt(28)*sqrt(28) and sqrt(19)*sqrt(19) phases, can be realized. For such a complex CDW system, we establish an exhaustive growth phase diagram via systematic efforts in the material synthesis and scanning tunneling microscope characterization. Moreover, we report that the energetically stable phase is the larger scale order (sqrt(19)*sqrt(19)), which is surprisingly in contradiction to the prior prediction (4*4). These findings are confirmed using two different kinetic pathways, i.e., direct growth at proper growth temperatures (T), and low-T growth followed by high-T annealing. Our results provide a comprehensive diagram of the "zoo" of CDW orders in ML 1T-NbTe2 for the first time and offer a new material platform for studying novel quantum phases in the 2D limit

Population genetics of the malaria vector Anopheles aconitus in China and Southeast Asia

Anopheles aconitus is a well-known vector of malaria and is broadly distributed in the Oriental Region, yet there is no information on its population genetic characteristics. In this study, the genetic differentiation among populations was examined using 140 mtDNA COII sequences from 21 sites throughout southern China, Myanmar, Vietnam, Thailand, Laos and Sri Lanka. The population in Sri Lanka has characteristic rDNA D3 and ITS2, mtDNA COII and ND5 haplotypes, and may be considered a distinct subspecies. Clear genetic structure was observed with highly significant genetic variation present among population groups in Southeast Asia. The greatest genetic diversity exists in Yunnan and Myanmar population groups. All population groups are significantly different from one another in pairwise Fst values, except northern Thailand with central Thailand. Mismatch distributions and extremely significant F(s) values suggest that the populations passed through a recent demographic expansion. These patterns are discussed in relation to the likely biogeographic history of the region and compared to other Anopheles species

Optimization of Operation Parameters of the Garlic Plant Divider and Lifter Mechanisms

The technology of the divider and lifter mechanisms of a garlic harvester using the depth limit, straw divide, and straw lift modes was studied in Lanling County, Shandong Province, China, according to the characteristics of high hardness, good uprightness and narrow row spacing of garlic planting. A test prototype of the divider and lifter mechanisms of the garlic harvester was designed and manufactured. Single-factor experiments and orthogonal regression experiments were carried out using the experimental factors of working speed, the angle of the divider, the height of the tip of the divider’s tooth from the ground, the ratio of the lifter’s speed to working speed and the length of the lifter’s tooth. The index was the success rate of feed. The results showed that the working speed, the angle of the divider and the length of the lifter’s tooth had a significant influence on the success rate of feed (p < 0.05), but the experimental factors of the height of the tip of the divider’s tooth from the ground and the ratio of the lifter’s speed to working speed did not have a significant influence on the success rate of feed (p > 0.05). The effects of the angle of the divider, the working speed, and the length of the divider’s tooth on the success rate of feed decreased in significance. When the working speed was 0.72 km·h−1, the length of the lifter’s tooth was 343.5 mm and the angle of the divider was 20°, the success rate of feed was the highest (98.18%). The research results are conducive to promoting high-quality and efficient combined harvesting of garlic in Lanling County, Shandong Province, China

Column replacement algorithms and under-determined linear systems

In this dissertation, we look at the under-determined systems of linear equations with sparse solutions. Our motivation comes from a field called compressed sensing that has seen an unprecedented expansion in recent years. A rather wide span of possible applications of compressed sensing has been considered in the literature during the last decade. They include image reconstruction, single-pixel camera design, the decoding of linear codes, channel estimation in wireless communications to machine learning, DNA microarrays, magneto-encephalography, and many others that can be found in, e.g. [1-7]. The field seems to be developing at a fairly fast pace and, as mentioned above, in this dissertation, we look at several interesting problems derived from it. It is by now fairly well known that the core mathematical problem of compressed sensing reduces to solving large under-determined systems of linear equations. Of course, such systems typically would have a large number of solutions and would not really be exactly (uniquely) solvable. If, on other hand, one additionally assumes that the solution vectors are sparse, then matters become completely different. Depending on the systems\u27 dimensions and the underlying sparsity, the systems may in fact be solvable. Not only that, but if elements of the system matrix (typically in the compressed sensing literature called the measurement matrix) are chosen according to some appropriate probability distributions and if the solution vector (signal) is sparse enough, then a certain polynomial technique called ℓ1-minimization can recover it with overwhelming probability (see, e.g. [3, 8, 9]). In fact, [3, 8, 9] established (in a statistical context) that, if the number of measurements is proportional to the length of the signal, then there is a sparsity of the unknown signal also proportional to its length for which the success of ℓ 1-minimization is guaranteed with overwhelming probability. This result singlehandedly skyrocketed the popularity of the compressed sensing and established it as one of the main research arenas in various branches of mathematics and engineering over the last decade. Since the appearance of pioneering work [3, 8, 9], many powerful results have been developed within the compressed sensing arena as well as in various applications outside of it. In addition to the aforementioned linear under-determined systems, their various alternatives eventually emerged as both practically and theoretically important research problems. Some of these alternatives will be the subject of our attention in this thesis as well. As a short preview, we will mention the two probably the most outstanding ones. The first one relates to the so-called noisy systems. Namely, the linear measurements (mathematically, effectively the equations of the system) may be not only incomplete but also imprecise/corrupted. Moreover, the ideal solution sparseness (which is essentially the core idea behind the entire compressed sensing concept) may not be there, either. If the deviations of the noisy systems from the ideal (non-noisy) ones are not substantial, one would expect that small refinements of the standard ℓ1 would produce results comparable to those, one typically obtains when employing the standard ℓ1 itself in the ideal systems. This indeed turns out to be the case and effectively implies what is typically called in the compressed sensing literature the ℓ1\u27s stability (see, e.g. [8, 10]). The second alternative relates to the existence of systems solutions with special structures that go beyond the standard sparsity one. Of course, such existence is typically only useful if one is aware of it before attempting to solve the systems. While at first glance, it may appear artificial, as in numerous applications of compressed sensing, it actually does happen that one is a priori aware of the special structure that goes beyond the sparsity. Typical examples include block and binary structures (see, e.g. [11-16]). As addressed above, one would then expect that appropriate adjustments to the ℓ1 would be possible so that one could conceivably incorporate the a priori available knowledge of the signals structure. This again does turn out to be the case, and given that one has more information about the unknown solution of the system that is a priori available, the recovery abilities of the adapted algorithms substantially supersede the standard ℓ 1 (see, e.g. [14-16]). In this dissertation, we will first consider a couple of algorithms that are conceptually different from the ℓ1 benchmark and make several observations related to their performances when used for solving under-determined linear systems. We will first focus on the ideal scenarios and then switch to noisy systems and systems with structured solutions. We will present a thorough discussion related to the implementations, complexities, and various other features of these algorithms. Possible applications of these algorithms in other areas that are to some extent also related to sparse signal recovery will be discussed as well

Freeform Optics for Achieving Collimated and Uniform Light Distribution in LCD-Type UV-Curable 3D Printing

Ultraviolet light (UV)-curable three dimensional (3D) printing has emerged as a prominent additive manufacturing technology, finding diverse applications in industries such as figurine production, artifact restoration, dentistry, jewelry design, and etc. For liquid crystal display (LCD) type UV-curable 3D printers, achieving a uniform and collimated light distribution of the illumination system holds paramount importance, as it directly influences printing precision. This study proposes a novel light tailoring method employing freeform lenses to attain high efficient illumination system for 3D printers. The proposed illumination system mainly comprises a high-power UV LED, a freeform lens, and a Fresnel lenses. Initially, a ray mapping between the source domain and the target domain is established to design the preliminary freeform lens, assuming a point-like light source. Subsequently, considering the physical dimension of the high-power UV LED, the preliminary lens is further optimized to generate a uniform illuminance distribution in a rectangular shape. Finally, a Fresnel lens is employed to collimate the light. The results demonstrate a full width half maximum of the angular distribution of less than ±5°, indicating a narrow spread of the light beam. The illuminance distribution within the specified domain exhibits an impressive level of uniformity, exceeding 90%

Indexes on edge angle of thick cutter.

(a) Maximum cutting force on number of cut sets, (b) Useful power consumption on number of cut sets, (c) Cut surface quality grade on number of cut sets. Note: other factors were at level 3.</p

Free-body diagram of cutter cutting banana crown.

1. Banana rachis, 2. Banana crown, 3. Banana hand, 4. Cutter.</p