Future benefits and applications of intelligent on-board processing to VSAT services

The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified

The Effects of Gas Angular Momentum on the Formation of Magnetically Arrested Disks and the Launching of Powerful Jets

In this letter, we investigate Bondi-like accretion flows with zero or low specific angular momentum by performing 3D general relativistic magnetohydrodynamic simulations. In order to check if relativistic jets can be launched magnetically from such flows, we insert a large-scale poloidal magnetic field into the accretion flow and consider a rapidly spinning black hole. We demonstrate that under such conditions the accretion flow needs to initially have specific angular momentum above a certain threshold to eventually reach and robustly sustain the magnetically arrested disk state. If the flow can reach such a state, it can launch very powerful jets at $\gtrsim 100\%$ energy efficiency. Interestingly, we also find that even when the accretion flow has initial specific angular momentum below the threshold, it can still launch episodic jets with an average energy efficiency of $\sim 10\%$. However, the accretion flow has nontypical behaviors such as having different rotation directions at different inclinations and exhibiting persistent outflows along the midplane even in the inner disk region. Our results give plausible explanations as to why jets can be produced from various astrophysical systems that likely lack large gas specific angular momenta, such as Sgr A*, wind-fed X-ray binaries, tidal disruption events, and long-duration gamma-ray bursts.Comment: 18 pages, 12 figures, 2 tables, published in ApJL, comments welcome

The properties of wind and jet from a super-Eddington accretion flow around a supermassive black hole

Wind and jet are important medium of AGN feedback thus it is crucial to obtain their properties for the feedback study. In this paper we investigate the properties of wind and jet launched from a super-Eddington accretion flow around a supermassive black hole. For this aim, we have performed radiation magnetohydrodynamical simulation of a magnetically arrested super-Eddington accretion flows. We then have analyzed the simulation data by the ``virtual particle trajectory'' approach and obtained the mass flux, poloidal and toroidal velocities, and mass-flux-weighted momentum and energy fluxes of wind and jet. The mass flux is found to be 2-6 times higher than that obtained based on the time-averaged streamline method widely used in literature. Depending on the black hole spin, the momentum flux of wind is found to be at least 2 times larger than that of jet, while the total energy flux of jet is at most 3 times larger than that of wind. These results are similar to the case of hot accretion flows and imply that winds likely play a more important role than jet in AGN feedback. The acceleration mechanism of wind and jet is analyzed and found to be dominated by Lorentz force rather than radiation force.Comment: 13 pages, 13 figures; submitted to MNRA

Microeconomic Foundations of Research and Development

Numerous studies of the economics of technological change have appeared since the seminal work of Abramovitz and Solow. Most are empirical studies that are without a formal theoretical basis. Scherer was the pioneer of theoretical work on the problem of R&#38;D rivalry. This thesis revisits the issues in the literature on R&#38;D. In Chapter I, sources of R&#38;D allocative failures are identified and suggestions to remedy the situation are covered. In Chapter II, a selective critique of theoretical R&#38;D models is provided. This completes Part I of the thesis. Part II constitutes the thesis proper. In Chapter III, I develop a nonsequential R&#38;D search model and examine the economic determinants of R&#38;D decisions. Predictions based on comparative statics results are given. The Reservation Technology concept is introduced. In Chapter IV, welfare implications of market structure on industrial R&#38;D are investigated. It is shown that a monopolist may be less persistent in R&#38;D search than a social decision maker. Sufficient conditions for noncooperative duopolists to be more persistent in R&#38;D search than a monopolist are provided. A discussion on R&#38;D economies of scale and a treatment of product and process innovation are also provided. Chapter V presents a new approach to the theory of R&#38;D. A sequential R&#38;D model with a two dimensional search space is developed and a Reswitching Property of R&#38;D is established.</p

Physical testing of performance characteristics of a novel drag-driven vertical axis tidal stream turbine; with comparisons to a conventional Savonius

An experimental study of the performance and optimisation of a prototype novel drag-driven vertical axis tidal stream turbine is presented. The drag turbine has several unique advantages, including simple blade design, deployable in shallow waters and potential denser array spacing. Performance optimisation was conducted in the hydraulics flume at Cardiff University (CU), where the turbine reached Cpmax/λ=0.132/0.441 for its 90⁰ phase angle configuration. The CU turbine was then tested using the wider and deeper hydraulics flume at IFREMER, France. Testing at IFREMER reduced the blockage factor from 17% at CU down to 1%; into the range of unblocked conditions. Testing in an unblocked environment, under similar flow conditions, reduced the peak efficiency of the CU turbine by 43% to Cpmax/λ=0.067/0.346. Finally the CU turbine was compared to the performance of a Savonius turbine. The design of the Savonius was based on a literature review. The CU turbine showed inferior efficiency values compared to the performance of the Savonius. The Savonius reached Cpmax/λ=0.098/0.692 in unblocked conditions, 46% greater than Cpmax of the drag turbine

Counterposition and negative phase velocity in uniformly moving dissipative materials

The Lorentz transformations of electric and magnetic fields were implemented to study (i) the refraction of linearly polarized plane waves into a half-space occupied by a uniformly moving material, and (ii) the traversal of linearly polarized Gaussian beams through a uniformly moving slab. Motion was taken to occur tangentially to the interface(s) and in the plane of incidence. The moving materials were assumed to be isotropic, homogeneous, dissipative dielectric materials from the perspective of a co-moving observer. Two different moving materials were considered: from the perspective of a co-moving observer, material A supports planewave propagation with only positive phase velocity, whereas material B supports planewave propagation with both positive and negative phase velocity, depending on the polarization state. For both materials A and B, the sense of the phase velocity and whether or not counterposition occurred, as perceived by a nonco-moving observer, could be altered by varying the observer's velocity. Furthermore, the lateral position of a beam upon propagating through a uniformly moving slab made of material A, as perceived by a nonco-moving observer, could be controlled by varying the observer's velocity. In particular, at certain velocities, the transmitted beam emerged from the slab laterally displaced in the direction opposite to the direction of incident beam. The transmittances of a uniformly moving slab made of material B were very small and the energy density of the transmitted beam was largely concentrated in the direction normal to the slab, regardless of the observer's velocity

沒有年齡的課室 : 成效評估研究報告

背景 香港人口老齡化的趨勢持續加劇，傳統的家庭照顧模式已難以滿足老年人和幼童在身心發展上的需求，需要探索新的跨代互助模式。因此，和悅社會企業於2023 年夏季舉辦了一項名為「沒有年齡的課室」的計劃（以下簡稱「計劃」/「課程」）。該課程旨在為長者及幼童提供共學的機會，推動跨代連結與互惠。為了更客觀地檢視「沒有年齡的課室」的實施情況與成效，以及探討在香港推行跨代共學的可行性，和悅社會企業委託嶺南大學亞太老年學研究中心對該課程進行了評估研究，並撰寫了此報告以供相關持分者參考。 研究方法 2. 研究採用定量研究及定性研究的數據收集和分析的混合研究法 (Mixed Methods) 進行。除了透過問卷調查和聚焦小組去收集參加者對課程的看法外，同時分析課程的數據、進行實地觀察，以及檢視相關文獻資料，從而更全面地瞭解整個課程的實施情況、對參與者的影響，以及探討計劃未來的發展方向。 研究結果 3. 本研究於2023年6月至9月期間成功對實驗組及對照組參加者進行了兩輪問卷調查，收集參加者的意見。調查結果顯示，長者及幼童的家長讓他們的孩子參與計劃的最主要原因是為了「想學習新知識 」(長者學員：72%；幼童：73%)，其次為「進行跨代接觸交流」 (長者學員：60%；幼童家長：54%)，第三個主要原因是可以「嘗試新事物」(長者學員：40%；幼童：54%)，以及可以「認識新朋友」 (長者學員：36%；幼童家長：50%)。至於計劃對參加者的影響方面，本研究透過比較實驗組 (即參加「沒有年齡的課室」的長者及幼童學員) 與對照組 (即課程無長幼共學成份)參加者在對雙方態度、自尊心及自信、社交技巧等方面的前後變化。從分析結果顯示，長幼學員在修畢本課程後，對彼此的態度 (長者學員對幼童態度：實驗組增長17%，對照組下降1%；幼童學員對長者態度：實驗組增長19%，對照組增長7%) 及幼童學員的社交技巧 (實驗組增長9%，對照組增長1%) 之增長達統計學顯著程度，足見本課程成功透過長幼共學的方式去改善長幼對彼此的觀感和態度。至於對課程的體驗方面，長者學員及幼童學員之家長均給予高度評價和評分，以1-7分為量表去評價，參加者普遍對課程感到十分滿意 (長者學員：平均分為6.07分；幼童學員：6.29分)、並表示若和悅社會企業日後舉行類似課程會再次參加(長者學員：平均分為5.33分；幼童學員：6.41分) 和向別人推薦此類課程 (長者學員：平均分為5.33分；幼童學員：6.29分)。概括而言，從統計結果反映了課程為參加者帶來很多正面影響，特別是長者或幼童態度之改善比沒有跨代共學成份的課程更為顯著。 4. 此外，本研究邀請了參與課程的長者、幼童家長、和推行「沒有年齡的課室」計劃的同工進行了3 場聚焦小組以深化對問卷調查結果，並進一步探討可如何改善計劃之推行及在社區推廣跨代共學的模式。從結果顯示，長幼學員透過參與本課程互相接觸及互動，增加彼此了解，使彼此的觀感及態度亦變得正面，達到促進跨代共融的目標。同時，幼童的社交技巧、接觸長者的動機及幼童的個人成長亦有所提升。長幼學員、課程導師及項目統籌人員均表示參加者能愉快地學習和十分享受參與本課程。 5. 從不同的的數據作綜合分析，促進「沒有年齡的課室」的成功因素包括: (i) 1對1的長幼配對，增加長幼學員之互動機會以便建立互信關係以及日後的情感聯繫； (ii) 課程時間節數安排要配合幼童的學習時間表 (如與暑假活動分開、每堂時數能讓幼童學員專心等) ；及 (iii) 招募適合的參加者，以其年齡、興趣喜好及性別進行配對 (如女性參加者明顯更為適合參與此類以幼童為對象的活動計劃)。 6. 關於課程的未來發展，研究建議推行機構可考慮以下5 個要點：(i) 除以1對1長幼配對外，亦可考慮同時加入1位長者對數名幼童，或1名幼童對數名長者的混合模式，這樣可以增加長幼學員與不同參加者的互動機會，進一步培養社交技巧；(ii) 可增加針對長者學員的課程內容 ，讓長者以學生身份投入各個課程活動；(iii) 讓一些能力比較高的長者參與課程設計及教材 (如讓長者準備自己過去相片與幼童分享過去時代點滴生活)，為長者充權；(iv) 微調課堂時間以配合長者的活動時間表 (如可參考現時日間長者中心的活動時間)；及 (v) 增加人手安排編制至5至8人，以便在推行活動過程中提供適時的支援 (如增設社工以應付課堂上幼童學員突發的情緒問題)。 總結 7. 綜合各種數數據證明「沒有年齡的課室」有效促進跨代共學與互助，為長者建立正面形象、提升他們的生活質素、亦能令幼童認識如何與長者溝通，改善社交技巧以及提升自尊感等。因此，其他長者服務機構、企業及教育團體可以仿傚此活動，在幼稚園 (即幼兒期) 便引入跨代共學的元素，促進代際間情感、知識與文化的傳遞，重塑「老吾老以及人之老，幼吾幼以及人之幼」的價值觀，建立一個強調代間互助和共融的社會

孫輩照顧者面對的挑戰研究報告

背景和目的香港人口老齡化和長期病患者的增加，令到更多老年人需要人照顧。現時社會對孫輩照顧者的認識不足，使到他們缺乏適切支援服務。本研究旨在探索孫輩照顧殘疾或患有慢性疾病的祖父母的情況，並提出政策與服務建議。嶺南大學亞太老年學研究中心聯同救世軍護老者協會及救世軍護老者服務於2024年4月25日舉辦了「孫輩照顧者的需要、實踐及政策」研討會，各方持份者分享他們對支援孫輩照顧者的經驗和看法，共同尋找方案支援這類照顧者。 研究方法本研究於2023年4月至12月期間，採用深度訪談 (in-depth interview) 方式，訪問了共40位年齡介乎13至63歲的孫輩照顧者，瞭解他們成為照顧者的主要原因、提供了甚麼照顧，以及照顧過程中面對的困難。 研究結果 大部分受訪的孫輩照顧者 (67.5%) 為次照顧者，近半受訪者每周提供20小時以上的照顧工作。 共有47位祖父母/外祖父母受到照顧，年齡介乎62至99歲。大部分被照顧者 (91.5%) 行動不便，或患有長期病患 (76.6%)。被照顧祖父母當中過半 (57.4%) 沒有與孫輩同住，8.5%為獨居。 孫輩成為照顧者有數個原因，包括家庭成員無法提供照顧、減輕父母的壓力和回饋祖父母過往照顧之恩。 孫輩照顧者的照顧角色與他們的年齡、生活狀態、能力，以及被照顧者的需要有關。大部分孫輩照顧者和家人分擔照顧工作，並得到他們的協助。孫輩照顧者會主動運用各種輔助設備，以提高照顧成效。 孫輩照顧者除了要面對一般照顧者的困難外 (如支援服務及資訊不足、身心壓力和社交限制)，他們面對的壓力還包括學業及就業、家庭角色的衝突、「夾心」照顧者面對多重壓力，以及缺乏社會的認同。 政策建議研究報告建議政府須加強院校對就學照顧者的支持、提供額外假期予在職照顧者、將照顧者主題納入中學課程、推廣朋輩支援小組、提供線上及晚間照顧技巧課程、開發多元化暫託服務、建立個案管理制度，以及推動樂齡科技之運用

Active zone proteins are dynamically associated with synaptic ribbons in rat pinealocytes

Synaptic ribbons (SRs) are prominent organelles that are abundant in the ribbon synapses of sensory neurons where they represent a specialization of the cytomatrix at the active zone (CAZ). SRs occur not only in neurons, but also in neuroendocrine pinealocytes where their function is still obscure. In this study, we report that pinealocyte SRs are associated with CAZ proteins such as Bassoon, Piccolo, CtBP1, Munc13–1, and the motorprotein KIF3A and, therefore, consist of a protein complex that resembles the ribbon complex of retinal and other sensory ribbon synapses. The pinealocyte ribbon complex is biochemically dynamic. Its protein composition changes in favor of Bassoon, Piccolo, and Munc13–1 at night and in favor of KIF3A during the day, whereas CtBP1 is equally present during the night and day. The diurnal dynamics of the ribbon complex persist under constant darkness and decrease after stimulus deprivation of the pineal gland by constant light. Our findings indicate that neuroendocrine pinealocytes possess a protein complex that resembles the CAZ of ribbon synapses in sensory organs and whose dynamics are under circadian regulation

Hundreds of variants clustered in genomic loci and biological pathways affect human height

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P < 0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.