Measuring Asymmetry and Persistence in Conditional Volatility in Real Output: Evidence from Three East Asian Tigers Using a Multivariate GARCH approach

We search for evidence of conditional volatility in the quarterly real GDP growth rates of three East Asian tigers: Singapore, Hong Kong and Taiwan. The widely accepted exponential GARCH-type model is used to capture the existence of asymmetric volatility and the potential structural break points in the volatility. We find evidence of asymmetry and persistence in the volatility of GDP growth rates. It is noted that the identified structural breakpoints of volatility correspond reasonably well to the historical economic and political events in these economies. Policy implications are discussed.East Asia, Real Output, GARCH, structural changes, asymmetric volatility

Public Policies in Open Economies

Ph.DDOCTOR OF PHILOSOPH

The effect of picking time and postharvest treatments on fruit quality of mango (Mangifera indica L.)

Mango production in Northern Vietnam is mainly in the upland areas. The two locally grown cultivars are ?Tron? and ?Hoi? with limited yearly production due to poor traditional crop management practices by ethnic minorities. Both cultivars possess excellent fruit aroma and taste properties, yet there is a need to further improve fresh fruit quality to meet high domestic demand and consumer expectations in the market place, thereby exploiting more products of preferred quality. Assessment of quality parameter and consumer preference can assist to precisely determine optimum harvest time and suitable storage regime for a given cultivar. Furthermore, specific postharvest treatments such as applications of hot water, 1-MCP or ethrel for manipulating fruit ripening and shelf-life may help to enhance economic returns and thus to make mango production in the long term more profitable. The research work on both cultivars was carried out on farmer orchards near the township of Yen Chau, Son La Province, Vietnam, in 2007, 2008 and 2009. The research objectives were to (1) monitor internal and external fruit quality changes in relation to varying select picks throughout the harvest period and to a range of storage temperatures; (2) investigate the effect of 1-MCP on various fruit ripening parameters for maintaining fruit quality and extending shelf-life; (3) evaluate applications of aqueous ethrel solution in cool storage for accelerating fruit ripening; and (4) assess the responses of several external fruit criteria to hot water treatments and subsequent cool storage. At each select pick, fruit was immediately taken to the laboratories at Hanoi University of Agriculture for fruit quality assessment at harvest, and following various postharvest treatments, ex-store. Chemical analyses of fruit tissue samples were performed at the University of Hohenheim. Various physicochemical quality parameters such as fruit weight, skin disorder, skin and flesh colour, flesh firmness, total soluble solids concentration, titrable acidity, as well as concentrations of soluble sugars, starch, vitamin C and carotenoids were evaluated. The results of the first part indicated that key quality criteria for determining the optimal harvest time of ?Tron? and ?Hoi? were determined. ?Hoi? fruit was at best quality when harvested late, preferably in the 2nd or 3rd pick, whereas 1st pick fruit was relatively immature with less than 8% total soluble solid concentration and did not properly ripen when stored at 12ºC. In contrast, ?Tron? fruit should be picked early in the harvest period since the 3rd pick with tree-ripened fruit was only suitable for direct local marketing without storage time. The results also indicated that ?Tron? fruit of the 1st and 2nd pick and ?Hoi? fruit of 2nd and 3rd pick continued the ripening process to full maturity when stored at 12ºC. Consequently, fruit from these picks were suitable for distant markets when handled within 5-10 days at 20ºC or up to 20 days at 12ºC. Generally, ?Hoi? had a greater postharvest potential than ?Tron? but ex-store fruit quality of both cultivars was best with flesh firmness ranging from 70.5 to 96.1 N, skin hue angle from 71.4º to 85.4º, flesh hue angle from 70.1º to 78.5º and total soluble solid concentration from 16.8 to 19.6%. The results of the second part clearly showed that 1-MCP is a useful tool to delay fruit ripening and in particular softening of both cultivars during the postharvest period. Both cultivars treated with 1000 nL?L-1 1-MCP delayed considerably the decrease in TA, skin and flesh hue angle as well as the loss of flesh firmness in the 1st and 2nd pick for about 10 days of storage at 12ºC compared to control. Both cultivars were more sensitive to 1-MCP applications in 1st rather than the 2nd pick. In addition, 1-MCP applications were more effective on ?Tron? fruit than ?Hoi? fruit. The results of the third part indicate that 0.8% ethrel accelerated fruit ripening on fruit from the 1st pick of both cultivars while stored at 12ºC. Ex-store fruit quality was acceptable and met consumer preference. The efficacy of ethrel application on ?Hoi? fruit was greater than that on ?Tron? fruit. The results of the fourth part showed that the degree of skin disorder was considerably decreased when ?Tron? and ?Hoi? fruit were treated with either 48ºC or 50ºC water for 6 min and stored at 12ºC. This treatment delayed skin colour development of ?Hoi? when compared to other treatments. In conclusion, this study demonstrates that lack of proper whole chain fruit quality management systems is the key factor for the limited production of mangoes in Northern Vietnam. Improved fruit quality management can result in more consistent and higher quality particularly for distant markets. Based on the results of this work, ?Tron? and ?Hoi? fruit should be harvested using well-defined and recommended harvest quality indices and thereafter undergo appropriate postharvest management systems to attain higher fruit quality. This will help farmers to better manipulate fruit ripening processes, to deliver high quality fruit to the market and to achieve greater returns and thus livelihoods.Der Mangoanbau konzentriert sich in Nordvietnam hauptsächlich auf die Hochlandregion. Die zwei lokal angebauten Sorten ?Hoi? und ?Tron? erzielen aufgrund von wenig produktiven traditionellen Anbaumaßnahmen durch die ethnischen Minderheiten sehr limitierte Erträge. Zwar zeichnen beide Sorten sich durch exzellentes Aroma und Geschmacksattribute aus, dennoch besteht die Notwendigkeit zur Verbesserung der Frischequalität um den nationalen Ansprüchen und den Erwartungen der Konsumenten am Markt zu entsprechen, indem verstärkt die bevorzugten Qualitäten verwendet werden. Die Kontrolle von Qualitätsparametern und Verbraucherpräferenz können helfen den optimalen Erntezeitpunkt und die passenden Lagerbedingungen für eine bestimmte Sorte präzise zu bestimmen. Des Weiteren können spezifische Nacherntebehandlungen wie beispielsweise Behandlungen mit heißem Wasser, 1 MCP oder Ethrel eventuell helfen die wirtschaftlichen Gewinne zu erhöhen und somit den Mangoanbau auf lange Sicht profitabler zu gestalten. Die Versuche an beiden Sorten wurden auf Pflanzungen nahe der Stadt Yen Chau, Son La Provinz, Vietnam, in 2007, 2008 und 2009 durchgeführt. Ziel der Arbeiten war es (1) interne und externe Fruchtqualitätsänderungen im Zusammenhang mit gewählten Probenahmen während der Ernteperiode und unter verschiedenen Lagertemperaturen zu dokumentieren, (2) den Effekt von 1 MCP auf verschiedene Fruchtreifeparameter, zwecks Aufrechterhaltung der Fruchtqualität und Verlängerung der Haltbarkeit, zu untersuchen, (3) die Applikation von wässrigen Ethrel Lösungen unter Kühllagerbedingungen zu evaluieren um eine beschleunigte Fruchtreife zu erzielen und (4) die Reaktion mehrerer externer Fruchtkriterien auf Behandlungen mit heißem Wasser und nach Kühllagerung zu untersuchen. Nach jeder Probenahme wurden die Früchte unverzüglich zu den Laboratorien der Agrarwissenschaftlichen Universität Hanoi transportiert, um dort die Fruchtqualitätsuntersuchungen zur Erntezeit und, nach erfolgten Nacherntebehandlungen, nach Lagerung durchzuführen. Chemische Analysen von Fruchtgewebeproben wurden an der Universität Hohenheim durchgeführt. Verschiedene physiochemische Qualitätsparameter wie Fruchtgewicht, optische Beeinträctigung der Schale, Schalen- und Fruchtfleischfarbe, Fruchtfleischfestigkeit, Konzentration der gesamt löslichen Feststoffe, titrierbare Säuren, so wie die Konzentration löslicher Zucker, Vitamin C und Karotenoiden wurden untersucht. Die Ergebnisse des ersten Teils weisen darauf hin, dass Schlüsselkriterien für die Feststellung des optimalen Erntezeitpunktes für ?Tron? und ?Hoi? gefunden wurden. ?Hoi? Früchte besaßen die höchste Qualität wenn sie spät geerntet wurden, vorzugsweise in der zweiten und dritten Probenahme, wobei die Früchte der ersten Probenahme mit 8% Gesamtgehalt löslicher Stoffe noch relativ unreif waren und auch nicht vollständig nachreiften, wenn sie bei 12°C gelagert wurden. Im Gegensatz dazu sollten ?Tron? Früchte zu einem früheren Zeitpunkt in der Erntezeit geerntet werden, da die zur dritten Probenahme am Baum ausgereiften Früchten nur für den unmittelbar lokalen Markt ohne Lagerzeit nutzbar sind. Die Ergebnisse zeigten auch, dass ?Tron? Früchte der ersten und zweiten sowie ?Hoi? Früchte der zweiten und dritten Probenahme vollständigen Reifeprozess durchliefen, wenn sie bei 12°C gelagert wurden. Folglich waren Früchte dieser Probenahmen für weiter entfernte Märkte geeignet, wenn sie innerhalb von 5 10 Tagen bei 20°C oder bis zu 20 Tagen bei 12°C gehandelt werden. Generell hat ?Hoi? ein größeres Nacherntepotenzial als ?Tron?, und nach Lagerung erzielten beide Sorten für Fruchtqualität die besten Werte für Fruchtfleischfestigkeit mit 70.5 bis 96.1 N, für den Huewinkel der Fruchtschalen von 71.4º bis 85.4º, für den Huewinkel des Fruchtfleisches von 70.1º bis 78.5º und gesamt löslichen Feststoffe von 16.8 bis 19.6%. Die Ergebnisse des dritten Teils zeigten, dass 0.8% Ethrel die Fruchtreife der bei 12°C gelagerten Früchte der ersten Probenahme beider Sorten beschleunigt. Nach der Lagerung war die Fruchtqualität akzeptabel und entsprach den Wünschen der Konsumenten. Der Wirkungsgrad der Ethrelapplikation war bei ?Hoi? Früchten größer als der bei ?Tron? Früchten. Die Ergebnisse des vierten Teils zeigten, dass die optische Beeinträctigung der Schale bei ?Tron? und ?Hoi? Früchten deutlich vermindert sind, wenn sie 6 Minuten mit 48°C oder 50°C heißem Wasser behandelt und bei 12°C gelagert wurden. Diese Behandlung verzögert Farbveränderungen der Schale von ?Hoi? Früchten im Vergleich mit anderen Behandlungen. Folglich demonstrierte diese Studie, dass das Fehlen eines ausreichenden und umfassenden Fruchtqualitätsmanagementsystems der Schlüsselfaktor zur begrenzten Mangoproduktion in Nordvietnam ist. Verbessertes Fruchtqualitätsmanagement kann, im Besonderen für weiter entfernte Märkte, zu einer konsistenteren und höheren Qualität führen. Basierend auf den Ergebnissen dieser Arbeit sollten ?Tron? und ?Hoi? Früchte mithilfe klar definierter und empfohlener Erntequalitätsindices geerntet werden und nachfolgend ein angemessenes Nacherntemanagementsystem durchlaufen, um höhere Fruchtqualität zu erreichen. Dies wird den Mangoanbauern helfen, den Fruchtreifeprozess besser zu manipulieren, Früchte mit hoher Qualität auf den Markt zu bringen und somit höhere Gewinne und einen besseren Lebensstandard zu erreichen

Economic Instruments and the Pollution Impact of the 2006-2010 Vietnam Socio-Economic Development Plan

The current study derives optimal growth paths for pollution emission charges, in order to control future water pollution emissions in the Vietnamese manufacturing sector. The study builds on a prior study, which estimated the manufacturing sector pollution impact of the 2006- 2010 SEDP development plan for Vietnam (Jensen et al.; 2008). The current study demonstrates that effective implementation and moderate expansion of optimal emission charges, under certain conditions, could have been used, as part of the 2006-2010 SEDP development plan, to control pollution emissions at 2005 levels. Moreover, such a scenario would have been accompanied by a moderate expansion in fiscal revenues and a relatively minor economy-wide efficiency loss. The current study, therefore, suggests that effective implementation and gradual expansion of pollution emission charges should be incorporated into future SEDP development plans, in order to control pollution emissions as development progresses in Vietnam.Vietnam, manufacturing, CGE

Study of Self-diffusion in GaAs Crystal: Temperature Dependence

The self-diffusion of Ga and As atoms in GaAs crystal with the zince-blende structure (ZnS) is investigated by using the statistical moment method (SMM). The activation energy $(Q)$, diffusion coefficient $(D)$, and pre-exponential factor ($D_0$) are expressed by analytical closed expressions. The present analytical formulas are including the anharmonic effects of the lattice vibrations. The obtained results  are applied to GaAs crystal and the SMM calculations of $Q, D$ and $D_0$  are in agreement with the experimental data

MỘT SỐ KẾT QUẢ NGHIÊN CỨU BƯỚC ĐẦU VỀ ĐỘNG LỰC TRẦM TÍCH LƠ LỬNG TRONG MÙA LŨ TẠI VÙNG BIỂN VEN BỜ CỬA SÔNG HẬU

Land-ocean interactions in the coastal zone are severely influenced by tidal processces. In regions of high sediment discharge like the coast of Hau river estuary, these processes are even more significant when we analyse data in flood season (September) - which belongs to Agreement of Cooperation in Science and Technology between Vietnam and US (2013-2015) and project VAST-DLT.06/15-16 (2015-2016). Our goal is to investigate the sedimentation  processes. Additionally, we investigated the influence of the tidal currents in relation to the suspended sediment. Salinity (PSU - Practical salinity unit), suspended sediment concentration (NTU - Nephelometric Turbidity Units) were measured by Compac-CTD (Depth temperature conductivity chlorophyll turbidity) and OBS-3A (Turbidity and Temperature Monitoring System) instruments. The results show that the suspended sediment concentration (SSC) correlate with tidal current velocities. The tidal current velocities are up to 60 cm/s near the surface and 40 cm/s near the bottom, increasing SSC in the water column at bottom layer (24 NTU) and decreasing SSC at surface layer (8 NTU). Processes of sediment transport and deposition in flood tide in flood season are influenced by tidal currents more significantly than those in dry season. This leads to an asymmetry of the tidal ellipses and the different deposition between seasons. The analytical results imply the influence of tide and tidal currents on SSC in the coast of Hau river estuary, hence, the spread, sea water and fresh water mixing processes have difference during tidal phases and seasons.Các mối tương tác biển - đất liền trong vùng ven bờ bị chi phối chủ yếu bởi các quá trình thủy động lực như sóng, dòng chảy, lưu lượng nước sông, thủy triều trong đó thủy triều đóng vai trò quan trọng. Tại các khu vực có lưu lượng phù sa lớn như vùng ven biển sông Hậu, các quá trình này càng trở nên rõ rệt khi phân tích từ số liệu khảo sát trong thời kỳ mùa lũ (tháng 9) thuộc chương trình hợp tác khoa học và công nghệ giữa Việt Nam và Hoa Kỳ (2013 - 2015) và đề tài độc lập mã số VAST-ĐLT.06/15-16 (2015 - 2016). Trong chuyến khảo sát này, mục đích là điều tra sự lắng đọng và phân bố theo không gian, thời gian của hàm lượng trầm tích lơ lửng. Ngoài ra, chúng tôi còn khảo sát ảnh hưởng của dòng triều trong mối tương quan với hàm lượng trầm tích lơ lửng. Độ muối (đơn vị PSU - Practical Salinity Unit), hàm lượng trầm tích lơ lửng (đơn vị đo NTU - Nephelometric Turbidity Units) được đo bằng thiết bị Compac-CTD (Depth temperature conductivity chlorophyll turbidity), và thiết bị đo độ đục OBS-3A (Turbidity and Temperature Monitoring System). Kết quả nghiên cứu cho thấy hàm lượng trầm tích lơ lửng tương quan với vận tốc dòng chảy. Tốc độ dòng chảy khi triều lên đến 60 cm/s ở lớp mặt và 40 cm/s ở đáy tạo nên sự tăng nồng độ trầm tích lơ lửng trong cột nước ở tầng đáy 24 NTU và 8 NTU tại tầng mặt. Trong pha triều lên, quá trình vận chuyển và lắng đọng trầm tích lơ lửng bị chi phối bởi dòng triều dài hơn so với mùa khô. Điều này cho thấy sự bất đối xứng của elip thủy triều và dẫn đến sự lắng đọng trầm tích lơ lửng trong các mùa là khác nhau. Từ kết quả phân tích có thể thấy vùng biển ven bờ cửa sông Hậu, hàm lượng trầm tích lơ lửng chịu sự chi phối bởi dòng chảy triều và thủy triều là rất lớn, do đó quá trình lan truyền, xáo trộn nước sông và biển có sự khác biệt đáng kể trong các điều kiện triều và điều kiện mùa

Study of Melting Temperature of Metals: Pressure Dependence

The melting temperature of metals are studied using the statistical moment method, going the quasi-harmonic appromations. The melting temperature of metals are calculated as a function of the pressure. We discuss the pressure dependence of melting temperatures of Ce, Fe metals and compare the present results with those of the experimental results

Study of Oxygen Vacancy Diffusion in Yttria-doped Ceria and Yttria-stabilized Zirconia by Statistical Moment Method

Oxygen vacancy diffusion in yttria-doped ceria (YDC) and yttria-stabilized zirconia(YSZ) are investigated using statistical moment method, including the anharmonicity effects of thermal lattice vibrations. The expressions of oxygen vacancy-dopant association energy and oxygen vacancy migration energy are derived in an explicit form. Calculation of the vacancy migration energy enable us to evaluate the important role of dopant cation on the oxygen vacancydiffusion. The dependences of the vacancy activation energies and diffusion coefficients in YDC and YSZ systems on dopant concentration are also discussed in detail. The calculated results are in good agreement with the other theoretical and experimental results